ARMY MEDICAL LIBRARY WASHINGTON Founded 1836 1NNE* Section \ Form 113c, W. D., S. G. O. po 3—10543 (Reviaed June 13, 1936) I ELEMENTS OF PHYSIOLOGY. BY A. RICHERAND, if* PROFESSOR OF THE FACULTY OB MEDICINE OF PAKIS, MEMBER OF THE ACADEMIES OB VIENNA, PETERSBURGH, MADRID, TURIN, &C TRANSLATED FROM THE FRENCH BY G. J. M. DE LYS, M.D. jFrom tije fLast H-otftou IStrition, WITH NOTES AND A COPIOUS APPENDIX BY JAMES COPLAND, M D. LECTURER ON PHYSIOLOGY, PATHOLOGY, AND THERAPEUTICS ", CONBtTLTING PHYSICIAN O.UEEN CHARLOTTE'S LYING-IN HOSPITAL ; PHYSICIAN TO THE ROYAL UNIVERSAL INFIRMARY FOR CHILDREN; AND MEMBER OF THE ROYAL COLLEGE OF PHYSICIANS, LONDON, &C. &C. A6 NEW-YOBS. FRINTEDJFOR THE TRADE, BY W. E< DEAN, No. 36 Stone-Street. MDCOCXXV. A.rYA-natomy, as may be re- quired to illustrate the doctrine he hears ; he wih then be qualified to turn his private studies to account, and will pursue them with interest. Haller, who may justly be termed the Fathe'r of Physiology, was him- self a distinguished lecturer, and his mode of instruction may be safely followed He was a pupil of the celebrated Boerhaave, and when he himself became a public teacher, the doctrines of that great man had pos- session of the schools ; these doctrines, he tells us, in his preface to the Primae Lineae Physiologiae, he continued to teach, for twenty-four years, using the work of his illustrious teacher, as he calls him, for his text book ; but finding that since the time of Boerhaave, many improvements and discoveries had been ma " visions and subdivisions,because they are perplexing; and repetitions, " because they are oppressive. What has been once said, and in its " proper place, is clearer, than if several times repeated elsewhere*." In following these precepts, and they cannot be too much attended to, one may, it is true, incur the risk of being thought superficial, by superficial readers, who form their opinion of a work from the perusal of a single chapter, but a most ample compensation will be found in the opinion of those who choose to be thoroughly acquainted with a work, before they pass on it their final judgment. After having stated in what spirit this work has been written, I may say something of the motives which have led to its publication. I would mention, in the first place, the advantage which, it might be ex- pected, would accrue to the science, and to those who are engaged in its pursuit; and, in the next place, the satisfaction which study has in store for him, who bestows on it the time he can snatch from the laborious practice of our art. In his short intervals of leisure from pub- lic instruction, and from professional duty, left to himself and his own thoughts, in the silence of study, and in the calm of meditation, he looks down, with an eye of pity, on those who drag on, through the lowest in- trigues a despicable existence, and finds his consolidation against the end- less vexations, that are prepared for him by supercilious ignorance and jealous mediocrity. * Condillac Essaisur I'Origine des Connoissances humanes, seconde partie, sect, ii chap. iv. .fto % :^ •*< ANALYTICAL. TABLE OF CONTENTS. Preface—Preliminary discourse. 'Physiology—the Science of life, Definition of life, 1. § 1. Of Natural beings. They are inorganic or organized - The former are simple or complex ; the latter always complex, and distinguished into vegetable and animal. Reciprocal dependance of all these beings, 1. § II. Of the elements of bodies. The elements of bodies. Their number forty-four ; but it is probable that several appear to us simple, from the imperfection of our means of analysis, 2. § III. Differences between organized and inorganized bodies. Differences between organized and inorganized bodies, 3. Homoge* neousness of the latter ; complex nature of the former ; necessary co- existence of fluids and solids in all organized and living beings ; simplicity of inanimate matter ; complex nature and tendency to decomposition of organized bodies, 4. «- § IV. Differences between animals and plants. Differences between animals and plants, 5. The great distance be- tween the mineral and vegetable kingdom. A considerable approxima- tion, on the contrary, between animals and plants, 6. Of all the charac- ters which mark the differences between these substances, the most re- markable is the presence of an alimentary tube, which is found in every animal from man down to the polypus, 7. In all animals, nutrition is performed by two surfaces, especially by the internal ; the alimentary canal is the most essential part of their body, 7. It retains life longer than any other part.—Experiments disproving Haller's opinion on this subject, 7. § V. Of life. Consists of a number of phenomena proportioned to the complication of the organization, 8. Simple in plants, in which its actions are limited to nutrition and reproduction, 8. Of life in the polypus ; this animal, consisting merely of a sentient and contractile pulp, shaped into an ali- mentary cavity, 9- Of life in worms, 9.—in crustaceous animals, its ap- paratus more perfect, 10. Of life in cold-blooded animals, 10. In warm- blooded animals, and in man, 11. General view of the human organiza- tion, 11. Of the elementary fibre, 12. Dependance of life on the ox- ydation of the blood in the lungs, and on the distribution of this vivified blood throughout the organs, 14. § VI. Of the vital properties;. sensibility and contractility. Those two properties not possessed in an equal degree by all living bodies, 14. Modifications of sensibility in different organs, 17. Obser- vations on the contractility of serous membranes, 18. Caloricity, 19. Laws of sensibility, 20. Influence of sleep, of climate, of the seasons, of the age, &c. on the vital properties, 22—24, rivi CUNXfcN'If. § VII. Of sympathies. Of sympathy■, 24. Diseases arising from association ; Synergies, 2<... § VIII. Of habit. Of habit, 27. It uniformly lessens physical sensibility—A curious fact showing the effects of habit, 29. Habit impairs the sensitive power, but improves the judgment. § IX. Of the vital principle. The vital principle, not a being existing oy itself, and independently of the actions by which it manifests itself, ^1. A perpetual struggle in or- ganized bodies/between the laws of the vital principle and those of uni- versal nature, 3£. The vital principle resists the laws of chemistry, of physics and mechanics, 32. These take place, however, in the animal economy, chemical, physical, and mechanical phenomena, but they are always modified by the vital principle, 33. Influence of the stature on the energy of the vital powers and even on longevity, 33. Vis medica- trix naturae, 34. Theory of inflammation, 36. Analogy between the tumescence of an inflamed part, and of one in a state of erection, as the penis, &c. 36. Indirectly tonic influence of cold, 37. § X. Of the system of the great sympathetic nerves. These nerves are to be considered as connecting the organs of the functions of assimilation, as the cerebral nerves unite that of the external functions, 37. They are the only nerves found in several animals with- out vertebra?. They arise from all the vertebral nerves, from which they receive filaments, as well as from the fifth and sixth cerebral pairs, 38. Ganglions of the sympathetic nerves ; the semi lunar ganglion, the principal 38. The great sympathetics render the internal organs inde- pendent of the will, 39. § XI. Of the relations of physiology to several other sciences. The relation of physiology to physics, chemistry, and mechanics, 42. Connexion of physiology with human and comparative anatomy, 44, 45. Its connexion with medicine, 46. § XII. Classification of the vital functions. The best division of the vital functions is that which was first pointed out by Aristotle, adopted by Buffon. and completely developed by Gri- maud, 47. Modifications of which this division is susceptible ; preser- vative functions of the individual or of the species, 48. These two great divisions further divided into two orders, 49. Why man is subject to more diseases than animals, 51. Of the arrangement of this work, 53. The voice is a natural connex- ion between the preservative functions of the individual and those of the species, 54. The history of the ages and temperaments, and of the va- rieties of the human species ; the account of death and putrefaction forms a separate appendix, 54. FIRST CLASS. Functions subservient to the preservation of the individual. ORDER j'lRST. Functions of assimilation. CHAPTER I. On digestion. Definition of this function, 57. General considerations on the diges- tive apparatus, 57. Connexion between the nature of the aliment and 0 0 NTEKTS. xvu die extent of the digestive tube, 58. Of aliments, 53. The nutrient principle obtained from the aliment, by our organs, is always the same, 59. Of the nature of the alimentary principle, 59. Differences of re- gimen, according to the climate, 60. Hunger and thirst, 62—64. Mastica- tion, 65. Action of the lips, of the cheeks, of the tongue, of the teeth, of the jaws, 65, 66, 67. The salivary solution, 68. Deglutition, its mecha- nism, 70. Deglutition of fluids and of gaseous substances, 71. Of the ab» domen, 71. Ofdigestion in the stomach, 72. Different systems of digestion; of concoction, fermentation, 74. Of putrefaction, 75. Of trituration ; of digestion in granivorous fowls, 75. Of maceration, 76. Phenomena of rumination, 77. Of the gastric juice, 77. Its source, its quantity, and solvent qualities, 78. Digestion chiefly consists in the solution of the aliment in this fluid, 79. Singular case of a fistula of the stomach, 82. Action of the stomach, 84. Functions of the pylorus, 84. Of vomiting, 86. Digestion in the duodenum, 87. Of the bile and its secretory or- gans, 88. Circulation of the blood in the liver, 89. Uses of the spleen, 90. Of the pancreas and pancreatic juice, 91. Separation of the ali- mentary matter into two substances, the one chylous the other excremen- titious, 92. Of the action in the small intestines, 92. The uses of their curvatures and valvular conniventes ; of the peristaltic motion, 93. Of digestion in the great intestines, 94. Uses of the appendicula vermi- formis of the coecum, 94. Of the evacuation of the faeces, 95. Intesti« nal gases, 97. Of the secretion and excretion of the urine, 97. Of the calibre of the venal arteries, structure of the kidneys, 98. Action of the kidneys and ureters, 101. Accumulation of the urine within the bladder, 101. In what manner is it expelled, 102. Physical qualities of the urine, 104, Chemical analysis of this fluid, urea, 105. Its retention produces uri- nous fever, 106. Experiments on the effects attending retention of urine by tying the ureters, in living animals, 106. Urinary calculi, why most frequent in cold and damp climates, 109. CHAPTER II. Of absorption. Absorption takes place, in every part of the body, both on its surface, and in its internal parts, 110. Absorption more or less active in different circumstances, 111. Its activity is very slight on the external surface, except where the skin is thin and the epidermis moist, 112. Absorbing mouths, 113. Their mode of action, in absorption, US. Of the lymphatics, 113. Their innumerable anastomoses, from the union of which there is formed a mesh work enveloping the whole body, 116» Pathological inferences, 115. Of the conglobate glands, 116. Their action, H6. Circulation of the lymph, 117. Observations on cancer, 118. Of the thoracic duct, 119. Of the physical and chemical properties of the lymph, 120. CHAPTER III. Of the circulation. Definition and general idea of this function, 121. Of the action of the heart; uses of the pericardium, 121, 122. Connexion between the bulk of the heart, and strength, and courage, 122. Singular case of communis cation between the two ventricles, 124. Structure of the heart, 125. Action of the heart, in circulation, 126. Decurtation and pulsation of the C XVlll CONTENTS. heart, every time the ventricles contract, 128. The quantity of blood which these cavities send out, along the arteries, 128. Action of the arteries, 129; their arrangement and anastomoses, 130. Of the structure of the arteries, the force and contractility of their dif- ferent coats, 130. Dilatation of the arteries, 130. Of the pulse and its varietes, 134. Velocity of the circulation along the arteries, 136. Of the capillary vessels, 136. Those which convey a colourless fluid, 137. Of the manner in which the blood flows along these vessels, 138. Terminations of the arterial system, 140. Of the action of the veins, 140. Proportion of the arterial to the ve- nous blood ; difference of arrangement and structure between the arteries and veins, 141. Of the use of the valves of the veins, 141. Gradual increase of velocity in the venous circulation, 142. Of the use of the vena azygos, 143. Reflux of the blood in the great venous trunks, 143. The- ory of the circulation, 144. Partial circulations in the midst of the ge- neral circulation, 145. Of the two divisions, venous and arterial, of the circle of circulation, 146. Organs situated on the two points of inter- section of this great circle, 146. CHAPTER IV. Of respiration. Of all the changes which the blood undergoes in penetrating through the organs placed in the course of the circulation, the most remarkable are those it receives from respiration, 147. Differences of arterial and venous blood, 147. Of the atmosphere, 147. Action by which respi- ration is performed, 149. Motions of the ribs, 151. Difficult respira- tion, 153. Structure of the lungs, 154. Use of the bronchial arteries, 154. Pulmonary inflammations, 155. Changes on the air and on the blood by respiration, 156. Vitality of the lungs, 159. Respiration of certain animals, 159. Division or ligature of the eighth pair of nerves, 160. Of animal heat, 161. Animal heat is independent of the media in which animated beings live, 161. The heat of the animal body thirty- , two degrees, 163. The lungs not the only parts in which caloric is dis- engaged, 164. Caloric evolved, to a certain degree, in all organs re- ceiving arterial blood, 164. Cutaneous evaporation, the most powerful means of lowering the temperature, 165. It does not explain, however, why the animal temperature remains the same, in a medium hotter than the body ; case of a man said to be incombustible, 166. Effects of cold, 167. Phenomena of the circulation of the blood through the lungs, 168. Pulmonary exhalation, 169. Of asphyxia, from drowning and from stran- gulation, 170. From noxious gases and from intoxication, 171. From obstruction of the glottis ; of the asphyxia of new-born children, 171. Of several phenomena of respiration, as sighing, yawning, sneezing, coughing, hiccup, and laughter, 171. Cutaneous perspiration, 173. Its connection with the other functions, 174. Its quantity, 174. Of the sweat; of the formation of carbonic acid gas on the surface of the skin, 175. Of the uses of the cutaneous perspiration, 175. CHAPTER V. Of the secretions. Classification of the animal .fluids, 176. Chemical classification of the *n»4s by Fourcroy, the best. 176. Of the blood. Of its physical, ch^ uOSTE»i£. XiX mical, and vital properties, 177. Of sanguification 179. Of the effects of regimen on the blood, 180. The transfusion of blood, 181. Of the secretory apparatus, 182. Serous transudation, 183. Secre- tion in the mucous follicles, 184. In the conglomerate glands, 184. Of accidental secretions, 185. Influence of the nervous energy on the se- cretions. 186. Influence of the imagination on the secretions, 188. Quantity of fluids secreted, 190. Secretion of adeps within the cellular tissue, 190. Difference of quantity and quality of this fluid, in the different parts of the body, 191. Of the use of adeps, 192. Circumstances which increase or lessen its secretion, 5 93. Analogy of the marrow of the bones to adeps, 193. Of the insensibility of the medullary membrane, 193, CHAPTER VL Of nutrition. Nutrition is the compliment of assimilation, 194. Period of the com- plete renovation of the body, 194. Mechanism of nutrition ; from arte- rial blood only, 195. Difference of vegetable and animal substances, 196. New products, 197. Of the emunctories, 198. General view of the/unctions of nutrition, 198. CHAPTER VII. Of sensations. Functions that are subservient to the preservation of the individual by connecting him with surrounding beings, 201. Of sensations, 201. Na= tural succession of the phenomena of sense, 201. Of light and of colours, 201. Organ of sight, 203. Formed of three distinct parts, 203. Use of the eyelids, eyelashes, and lacrymal ducts, 203. Eye-ball, its structure, 206. Mechanism and phenomena of vision, 209. Motions of the iris, 210. Refraction of the rays of light by the membranes, 212, and by the fluids of the eye ; inversion of object on the retina; point of distinct vision, 213 Defects of vision, 213. Deve- lopment of the eyes and their motions, 214. Errors of vision, 215, Its difference in different animals, 215. Organ of hearing, 216. Of sound, 216. Structure of the ear, and mechanism of hearing, 217. Differences in animals, 219. Defects of hearing, 220. Of odours, 221. Organ of smell, 222. Sensation of smell, 222. Of taste, 223. Of the tastes of different substances, organ of taste, 224. ^ In different animals. 224. Uses of the nerves of the tongue, 225. Galvanic experiments on this subject, 225. Of touch, 226. Its certainty and errors, 2i'6. Of the integuments, 227. Of the nails, 230. Of the hair, 231. Of the hand, 233. Touch in different animals, 235. Of the nerves, 235. Of their origin in sensible parts, 236. Of their structure, 236. Opinion of Reil on this subject, 237. Of the manner they arise from each other, 237. Of their termination in the brain, 237. Of their comparative size, in different animals, and in man at different ages, 237. Of the spinal chord and its functions, 238—240. Of the coverings of the brain, 240. Mechanism of the bones of the 9kull and face, 240. Uses of the sphenoid, 241. Rounded form of the skull, 241. Uses of the dura mater, of the arachnoid, and the pia mater. IX CONTENTS. 243. Size of the brain, 244. Form of the head 244. Connexion with the intellectual powers, 245. Structure of the brain, 246. Nerves crossing, 246. Divergent and convergent fibres, 246. Cerebral circu- lation, 248. Arterial blood retarded, 248. Jugular veins, 249. Con- nexion ofthe action of the brain and heart, 249. Theory of syncope, 250. Motion of the brain, 253. Experiments, 254. Actions ofthe nerves and brain, 259. Principle of motion and sensation, 261. Diffe- rent intellectual functions of different parts of the brain, 261. Not yet perfectly understood, 261. Analysis of the understanding, 262. Perception, 262. Reasoning and instinct, 263. Generation of the faculties, 265. Sensation, per- ception, attention, memory, imagination, association of ideas, comparison, judgment, reasoning, 265. Influence of signs on the faculties of thought, 266. Analyses of ideas, by Tracey, 268. Derangements of the mind. 268. Mania, 268. Idiotcy, 269. Ofthe passions, 271. State of the intellectual powers connected with them, 272. Effects on the animal economy, 273. Of sleep and waking, 273. Repose of the functions which connect us with surrounding objects ; condition of the functions of assimilation, during sleep, 274. Proximate causes of sleep, 276. Of dreams and somnambulism, 277. Animals are also subject to dreams, 278. CHAPTER VHI. Of motions. This chapter treats only of voluntary motions, whose organs may be distinguished into active and passive (the bones and the muscles.) 279. Structure and properties of muscular fibres, 280. Of the tendons and aponeuroses, 281. Phenomena of muscular contraction determined by an act ofthe will, 282. A sound state of the nerves, arteries, and veins belonging to a muscle, is necessary to its action, 282. Theory of this action, 283. Preponderance of the flexor muscles over the extensors, 284. This preponderance varies, according to the age, the state of health or disease, 285. Ofthe power of the muscles, it bears a proportion to the number of their fibres, 287. The degree of decurtatation of which they are capable is proportioned to the length of their fibres, 289. Direction ofthe motions performed by the action of the muscles, 289. Of muscular flesh, 290. Galvanism, 291. Volta's apparatus or galvanic pile, 294. Effects of galvanism, in the treatment of disease, 297. General view of the osseous system, 298. Ofthe vertebral column, it forms the most es- sential part of the skeleton. 298. Difference of the stature at different times ofthe day, 299. Ofthe lower limbs, 300. Structure ofthe bones, 300. Uses ofthe periosteum, and of the marrow, 302. Theory of ne- crosis, 303. Of the articulations, 304. Of the articulating cartilages, 304. Of the synovia, 305. Theory of anchyloses, 305. Of animal mechanics ; of standing, 307. Of the centre of gravity, 307. Tendency ofthe body to fall, 308. Standing is performed by an effort ofthe extensor muscles, 308. Reasons why it is impossible for a new-born child to stand, 309. Man is the only animal that can stand up- right, 311. Of falls, 313. Of standing on one foot, 315. A degree of separation of the feet necessary in standing, 315. Of kneeling ; of sitting ; of the recumbent posture, 315. Of lying on the sides, 316. Of the prone and supine postures, 317. The different modes of the re- rumbent posture have a reference to the degrees of facility of respira- CUN TEN TS. XX J (ion and to the period of life, 317. Recumbent posture, on an inclined plane, necessary, especially to old people, 318. Of motions of progres- sion ; of walking, 318. Of walking up or down an inclined surface, 319. Mechanism of the articulation between the leg and foot, 320. Of run- ning, 322. Of leaping, 313. Leaping is performed by the sudden ex- tension ofthe lower extremities, previously in a state of flexion, 323. Of the vertical and oblique leap, 324. Of swimming ; man swims with difficulty, 325. Swimming natural and easy to fishes ; its mechanism, 326. Of flying, 326. The structure of the body in birds is favourable to this action, how performed, 327. Of crawling, 328. All the phe- nomena of animal mechanics may be referred to the theory of the lever of the third kind, 328. Partial motions performed by the upper extremi- ties, 330. Of climbing ; of pushing, 330. Of throwing a projectile, 331. Partial motions, as signs expressive of ideas, 332. Of gestures and attitudes, 332. CHAPTER IX. Of voice and speech. * Definition of the voice and of speech ; circumstances necessary to the formation of the voice; its organs, 333. Opinions of Ferrein and Dodart, on the uses of the glottis, 333. The larynx is, at once, a wind and a stringed instrument, 335. Ofthe power of the voice ; of speech, man alone is capable of speech, 335. Of the vowels and consonants, 336. Of song and music, 336. Of stammering, burr, and dumbness; 337. Instruction of the deaf and dumb, 338. Ventriloquism, 339. SECOND CLASS. Functions subservient to the preservation ofthe species. Differences ofthe sexes, 343. *Case in which the sexual organs did not exist, 344. Hermaphrodism is never met with in the human species 345. Man, in the exercise of the functions of generation, not under the con- trol of the seasons, 345. Of the organs of generation, in man, 346, Of the female organs of generation, 348. Ofthe signs of virginity, 349. Of erection, 349. Of the human semen, 350, Of the ovaria, 352. Of the impregnation of the ovum, 353. On barrenness, 354. bystems of generation, 355. Gestation. 356. Of the foetus and its coverings, 357. Ofthe development of its organs, 359. Ofthe circulation ofthe blood, in the foetus, 360. Of the placenta, 361. The umbilical cord, 361. Mode of existence of the foetus, 363. Morbid affections to which it is subject while in the womb, 364. Of monsters, 365- Their different kinds, and the causes which produced them, 365. History of a remarkable case, 366. Of tha chorion: of the amnion and liquor amnii, 367. Ofthe al- lantois and urachus, 368. Of the natural term of gestation, 368. Of parturition, 368. Ofthe mechanism of parturition, 369. Of twins, 371. The number of male children born exceeds that of female, 371. Of superfoetations, 372. Of suckling, 372. Sympathy between the uterus and mammae ; structure of the latter, 373. The milk appears not to be brought to the breasts by the lymphatics, 375. Chemical qualities of the milk, 376. Connexion between the new-born child and the mo- ther, 376. Imperfect development ofthe foetal lungs, 377. CHAPTER XI. Containing the history of the ages, the temperaments, and the varieties of the human species; of death and putrefaction. Of infancy: of dentition, 378. Ossification. 380. Phenomena of po- xxn C O N T E N 'I S betfy, 380. Connexion between the development of the sexual or- gans and the voice, 381. Of menstruation, 381. Of the cause of nien- struation, 382. Of the cessation of this evacuation, 383. Of manhood, 384. Of temperaments and idiosyncrasies, 384. Of the sanguine tem- perament, 384. Ofthe muscular or athletic temperament, 386. Of^ the bilious temperament, produced by an increased energy of the hepatic system, joined to considerable activity of the sanguineous system, 387. Ofthe melancholic temperament, 389. Lymphatic temperament, 391. Nervous, 391. Mixed and acquired temperaments, 392. Influence of climate on temperaments, 392. Varieties ofthe human species, 394. European Arab race. 394. Ne- gro, 395. Mogul, 395. Hyperborean, 395. Moral characteristics of the different races, 396. Giants and dwarfs, 397. Of old age and decrepitude, 397. Decay, 398. Death, 399 Gradual extinction of bodily and mental powers, in the reversed order of their production, 400. Period of death, 401. Probabilities of human life, 402. Putrefaction, 405. APPENDIX. CHAPTER I.—P. 1. Of life, I Of the nervous system of the lower animals, 2. Of the elementary solids of the body, 3. Of the compound solids of the body, 4. Classification of the animal textures, 5. Of sensibility, 6. Of or- ganic sensibility, 7. Of contractility, 8. Of sympathy, 8. Of habit, 10. Of inflammation, 11. Of uneasy sensation and pain, 11. Of red- ness and the injection of the capillaries, 12. Of the ganglial system of nerves, 14. Of the function of the ganglial system, 15. Of long protracted abstinence, 19. Of digestion in the sto- mach, 21. Of vomiting, 21. Of human rumination, 22. Action ofthe stomach in digestion, 24. Of the influence of the pneumogastric nerves in digestion, 24. Of the intimate structure of the liver, 25. Of the functions of the liver, 26. Of the uses of the bile, 27. Ofthe struc- ture of the spleen, 29. Of ihe office of the spleen, 29. Of the mu- cous coat of the digestive canal, 31. Functions of the mucous coat, 31. Of the digestive process in the intestines, 31. Of the functions of the kidnies, 32. Of absorption in the digestive organs, 33. Of absorption from the lungs, 34. Mode in which absorption is performed, 34. Of imbibition and exhalation, 35. Absorption, experiments and observations on, 36. Of the action ofthe heart and arteries, 39. Ofthe active dilatation of the heart, 40. Of the action of the arteries, 40. Of the functions ofthe capillaries, 41. Of subordinate capillaries, 42. Of the veins and their functions, 42. Of the mechanism of the respiratory organs, 43. Of the structure of the lungs, 43. Of the actions of the glottis, 44. Ofthe effects of re- spiration on the circulation of the blood, 44. Of the state of the lungs during respiration, 44. Of suspended respiration. 45. Of the changes produced on the air and the blood by respiration, 45. Of the production of carbonic acid by respiration, 45. Of the absorp- CONTENTS. XXI11 tion and exhalation of azote during respiration, 47. Of the assimilat- ing function of the lungs, 47. Of pulmonary transpiration, 47. Of the production of animal heat, 48. Of cutaneous exhalation, 48. Of the respiratory function of the skin, 49. Of the fluids, 50. Classification of the fluids, 50. Of the blood, 51. Ofthe colourless globules of the blood, 51. Of the red globules, 52. Of the coagulation of the blood, 52. Of transfusion of blood, 54. Of secretion and exhalation, 54. Of nutrition, 55. Of the decussation of the optic nerves, 57. Of the motions of the eye, 58. Of the formation of the spinal marrow, 58. Of the formation of the brain, 60. Of the functions of the cerebro-spinal system of nerves, 61. Gene- ral view of the nervous system, 61. Of the functions of distinct parts of the cerebro-spinal system, 63. Of the functions of the spinal mar- row, 66. Of the respiratory order of nerves, 67. Classification ofthe manifestations of mind, 68. Of dreaming, 68 Of the development ofthe muscular tissue, 69. Of irritability, 69. Of galvanic electricity, 70. Its relations, with inorganized matter, 71. Its influence on the animal textures, 73. Of ossification, 75. Of the voice, 76. Of ventriloquism, 76. Of the male organs of generation, 77. Of the female organs of generation, 77. Of impregnation, 78. Of superfcetation, 79. Of the development of the textures and organs of the foetus, 80. Of the circulation ofthe foetus, 81 Of the respiration of the foetus, 83. Of the varieties of the human species, 83. Of the mortality of females at the change of life, 84. APPENDIX. CHAPTER II. Chemical constitution of the solids and fluids of the human body, 85, Simple bodies composing the animal textures and fluids, 85. Animal principles or constituents, 85. Composition of the individual textures and fluids, 86. Of the bones, 86. Of the synovia, 87. Of the membranes and integuments, 88. Of the hair, 88. Of muscles, 88. Of brain and nerves, 88. Of saliva, &c. 89. Of gastric juice, lymph, chyle, &c. 89. Of the blood, 89. Of milk, 91. Of bile, cerumen, &c 92. Of urine, sweat, &c. 92. Of pus, &c. 93. Of the faeces, 93. Of the intestinal gases, 93. ERRATA. P. 68, for Steward read Stewart. for Pritchard read Prichard, PRELIMINARY DISCOURSE. Physiology* is the science of life. The term life is applied to an aggre- gate of phenomena, which manifest themselves in succession, for a limited time in organized bodies. Combustion is likewise only a combination of phenomena ; oxygen unites with the substance which is burning, caloric is disengaged from it; affinity is the cause of these chemical phenomena, as at- traction is the cause ofthe phenomena of Astronomy, and in the same man- ner as the sensibility and contractility of living and organized bodies are the primary causes of all the phenomena which such bodies exhibit—phenome- na, which in their union and aggregate succession constitute life. The false notions which have been entertained on the subject of life, and the vague definitions which have been given of it, are to be accounted for, by considering that physiologists, instead of regarding life as a simple result, have mistaken it for the properties of life. These last are causes ; the first is merely an effect, more or less complex : and, as the spring of a watch, or rather the elasticity of that spring, determines by the mere action of the wheels, the motion of the hands, and all the phenomena of which the ma- chine is capable ; so the vital properties acting by the organs produce all those effects, which in their combination constitute life t- These effects are more or less numerous, according to the number of the organs ; they become more rapid too in their succession and life more active, with the in- crease of energy in the vital properties ; precisely as the motions of a watch become more complicated, stronger or quicker, according to the greater ten- sion ofthe spring, or the increased number of the wheels. Sensibility and contractility, are to be ranked among primary causes, of whose existence and laws we acquire a knowledge from observation, but whose essence eludes our investigation]:, and will probably remain for ever beyond its reach. § I. OF NATURAL BEINGS. The vast domain of nature is divided between two classes of beirigs. In- organic beings, possessing merely the common properties of matter ; orga- nic and living beings, obeying particular laws, though subjected to the gene- ral laws which regulate the universe. Each of these two grand divisions h naturally divided into two classes ; we meet with inorganic bodies under tie form of elementary substances, simple and not capable of analysis ; or else * Anatomy is the science of organization. t See Appendix, Note, A. 4 t It would be wrong to infer, from our ignorance of the nature of the vital properties, that physiology is an uncertain Science. Its certainty in that point of view, is equal to that of other parts of natural philosophy. The chemist, who explains all his combinations by referring them to the principle of affinity, and the astronomer, who finds in attraction I he cause that rules the universe. are absolutely ignorant of the nature of tho^e properties h.ifhor's Note. ! 2 under the form of mixed substances, compound, and admitting of decomposi- tion. Thus, too, organized beings exist under two very different forms of life, which distinguish them into vegetables and animals. The first general conception with which we ought to enter upon this comprehensive study of nature, is the mutual dependence of those beings, which, in their co-ordinate whole, compose the system of nature; a de- pendence which requires for each the simultaneous existence of all. Thus a vegetable derives its nourishment from inorganic bodies *, and alters their inert substance, which is unfit for the food of animals, unless it has previous- ly undergone the influence of vegetable life. § II. OF THE ELEMENTS OF BODIES. Another consideration, of equal importance with the former, is the con- vertibility of all those substances so different from one another, and their capacity of being reduced to a small number of simple substances, called elements. The ancient doctrine of Aristotle, relative to the four elements, still prevailed in the schools, with a few modifications, which it bad receiv- ed from the chemists, when the " Pneumatistsf demonstrated by their beautiful experiments, that three, at least, of these pretended principles of bodies, air, water, and earth, far from being simple substances, were evi- dently formed by the union and combination of several others ; that atmos- pherical air, for example, far from being an homogeneous fluid, was com- posed of many different gazes, and that in its purest state, it contains at least two very distinct principles, oxygen and azote ; that water is a com- pound of oxygen and hydrogen, and that earth contains clay, lime, silex, &c. We have seen added in the present day, to the number of the elements or simple substances, several which were not considered as such, at the time when natural philosophers, misled by erroneous metaphysical doctrines, had created out of their imaginations, beings of the existence of which they could find no proof. There is every reason to believe, that the number of substances not admitting of decomposition, limited at present to forty-four, may hereafter be increased or diminished, by the discovery of new princi- ples in simple substances, or of new elements in compound bodies, which have hitherto eluded the investigation of chemists. Whatever may be the success of their inquiries, of which it is impossible to foresee the results, or to fix the limits, there is reason to believe, that it will ever be denied us, to arrive at a knowledge of the true elements of bodies, and that many of * Mirbel, in his treatise on Vegetable Anatomy and Physiology, observes, " that plants have the power of deriving nourishment from inorganic matter, which is not the case with animals, who feed on animals and vegetables, or on both ; but are never nourished on earths, salts and airs." Richerand has adopted the plausible opinion of Mirbel. Farther inquiry might, however, have shewn them that " earths and salts" furnish as little direct nourishment to plants as to animals. Indeed it may be observed, that the vegetable king- dom derives the chief part of its food from dead animal and vegetable matters'—which, al- though they contain both "earths and salts," cannot be either ranked under these sub- stances, nor even classed with them. t This is the name given to the school of modern chemistry, because it originated from the discoveries made relative to the nature of air and elastic fluids. It must be acknow- ledged, to the credit of metaphysics, that the old errors were forsaken, only at the period when chemists were thoroughly convinced of this truth,that every idea is obtainedthrough the medium ofthe senses, and that nothing is to be admittedbeyond what they demonstrate in actual experiment- Authors Note. 3 those substances, which the imperfection of our means of decomposition or analysis obliges us to consider as such, are frequently compound substances, and subject to their laws. After what-has been stated on the elements or constituent principles of substances, let 119 now see in what manner the combination ef these elements gives existence to all beings, and what are the general differences existing among the great classes into which they are divided. § III. DIFFERENCES BETWEEN ORGANIZED AND INORGANIZED BODIES. Much attention has been bestowed of late on the difference which exists between organized and inorganized bodies. The latter have been observed to be very different from those which are endowed with life, in the homo- geneous nature of their substance, in the complete independence of their molecules, each of which, according to the observation of Kant, has in itself causes to account for its peculiar mode of existence, in that power of resisting dtcomposition which they owe to the simplicity of their structure, and in the absence of those peculiar powers which free organic bodies from the absolute dominion of physical laws. The multiplicity, the volatility of their elements, the necessary union of fluids and solids, the nutrition and develop- ment from the diffusive combination, while the growth of inanimate bodies takes place from the mere juxta position of particles, the origin of living bodies in generation, their destruction in death, such are the characters which distinguish organized beings from inorganized substances. We are about to enter into a detail of those characters, to appreciate all their differ- ences, for knowledge is to be acquired only by comparison ; and the greater our accuracy in comparing, the more precise and extensive will be the knowledge we obtain. Several modern authors have proved, that it is im- possible to obtain an accurate idea of life, except by comparing those bodies which are endowed with it, with those in which life have never existed, or has ceased to exist. This comparison, I hope, will be fruitful in interesting results, and will furnish several useful considerations, immediately applica- ble to the knowledge of man. The first remarkable difference between organized and inorganized bodies, is to be found in the homogeneousness of the latter, and the compound nature of the former. Let a block of marble be broken, each piece will be perfectly similar to the rest, there will be no differences among them, but such as relate to size or shape. Break down the fragments, each grain will contain particles of carbonate of lime, which will be throughout the same. On the other hand, the division of a vegetable or an animal, shows parts heterogeneous or dissimilar. Indifferent parts there will be found muscles, bones, arteries, blossoms, leaves, bark, pith, &c. Organized beings cannot live or exist in their natural .jcpndition, unless solids and liquids enter at once into their composition. ThcCo-existence of these two elements is necessary ; and living bodies always Contain a liquid mass more or less considerable, and incessantly agitated by"Uhe 'motion of the solid and living parts. It is in fact impossible to conceive life existing, without a complicated combination of solids and fluids ; and without admit- ting in the former, the faculty ofbeing affected by impressions from the latter, and the power of acting in consequence of those impressions. The water which penetrates into mineral substances, does not form a necessary part of them, and one cannot adduce in proof of the existence of liquids in that 4 class of substances the water of crystallization, though intimately combined, and rendered solid in the crystallized substances. These inorganic and homogeneous substances, formed of particle* similar to one another, when resolved by decomposition into their last elements, possess a great implicity of inward nature. Among them are rank d all the substances which do not admit of analysis ; the mineral compounds are often binary, as the greater part of saline substances ; sometimes they are ternary, but seldom quaternary ; while the most simple vegetable contains at least three constituent principles, oxygen, hydrogen, and carbon, and no being possessed of life, consists of less than four, oxygen, hydrogen, car- bon and azote. In the degree of composition, nature appears therefore to rise in gradations, from the mineral to the vegetable, and from the latter to the animal kingdom. The complicated nature of the latter, the multiplicity of their elements account for their tendency to alteration. Minerals are not subject to change, unless they are acted upon by external causes. Endow- ed with a vis-inertia?, they contiuue in one condition without change.' The state of organized bodies is incessantly varying. Their internal parts con- tain an active laboratory, in which a number of instruments are constantly transforming into their own substance, nutritious particles. Besides that tendency to alteration in living animals and vegetables, when deprived of life, they become decomposed, by a process of fermentation, which begins in their internal parts, and by which their nature is changed in proportion to the complication of their structure, and the greater number and volatility of their constituent principles. All the part9 of a living body, whether of an animal or a vegetable, have a natural tendency to a common object, the preservation of the individual and of the species : each of the organs, though provided for a peculiar ac- tion, concurs in this object; and life in general, or life properly so called, is the result of that series of concurring and harmonic actions. On the con- trary, each part of an inorganic mass is independent of the other parts, to which it is utiited, only by the force or affinity of aggregation. When such a part is separated from the rest, it maintains all its characteristic proper- ties, and differs only by its size from the mass to which it no longer belongs. Among animals and vegetables, all the individuals of the same class ap- pear to have been formed after the same model ; their parts are equal in number, and resemble each other in colour ; their differences are slight and evanescent. The forms peculiar to organized beings are therefore in- variably determined, and when nature departs from them, she never does so, to such a degree, as in the shapes of minerals. The veins of mines are never precisely alike, as the leaves of vegetables or the limbs of animals. Crystals formed from similar substances, assume very different shapes, equally distinct and precise. Carbonate of lime, for example, assumes ac- cording to circumstances the shape of a rhomboid, that of a six-sided re- gular prism, that of a solid, terminated by twelve scaleni triangles, that of a different dodecahedron with pentagonal faces, &c. as may be seen at large in the writings of Haiiy. A powerful inward cause seems to arrange the constituent parts of ani- mal and vegetable bodies, by a determinate rule, in such a manner that they present a surface, more or less completely rounded. Minerals often take their form from external bodies, and when an especial force assigns it to them, as in crystals, their surfaces are flat and angular. When the crystallization is disturbed, and the molecules ofthe crystals are driven tu- ij multuously together, the geometrical form is impaired, the parts are round- ed which would have been terminated by angles, if a slow and tranquil crystallization had allowed of regular aggregation ; and as M. Haiiy has re- marked, these waving outlines, these roundings, so frequent in vegetables and plants, where they belong to beauty of form, are, in minerals, indication of defects. True beauty, in these beings, is characterized by the straight line, and it is on good grounds that Rome de Lisle* has said of this sort of line, that it seems to have an especial determination to the mineral king- dom. Amongst all the characteristics which distinguish the two great divisions of natural bodies, the most absolute, and the most palpable, is that which is drawn from the manner of growth and of nourishment. Inorganic bodies grow only by accretion, that is, by the accession of new layers to their sur- face, whilst the organic, in virtue of its vital powers, receives into in- timate combination, and is penetrated and pervaded, by the substance it as- similates to itself. In animals and plants, nutrition is the effect of an inter- nal mechanism : their growth is a developement from within. In miner- als, on the contrary, growth cannot claim the name of developement: it goes on externally, by successive addition of new layers ; it is the same being, as- suming other dimensions, whilst the organic body is renewed in its growth. Living bodies spring from a germ, which at first, was part of another be- ing, from which it detaches itself, for the sake of its own developement and growth. From the first, they are already aggregates. Inorganic bodies have no germ : they are made up of distinct parts brought together ; they have no birth, but a multitude of molecules, collecting into one, compose masses of various bulk and figure. Organized bodies alone can die ; all have a duration, determined by their own nature ; and this duration is not like that of minerals, proportioned to the bulk and density : for if man has not the life of the oak, whose sub- stance much exceeds his in density, neither does he equal the life of many animals, such as fishes, whose flesh is cf inferior consistence to his own : and he lives longer than the large quadrupeds, though his bulk is less. Finally, inorganic are essentially distinguished from organic bodies, by the want of these peculiar powers or properties of living nature ; powers, which uphold the equilibrium ofthe whole system of nature, as I shall ex- plain more at large, when I have considered the differences that mark the two divisions ofthe organic kingdom, vegetables and animals. § IV. DIFFERENCES BETWEEN VEGETABLES AND ANIMALS. These are much fewer, less absolute, and therefore more difficult to es- tablish. There is, in fact, very little difference between a zoophyte, and a plant, and there is a much wider distance in their internal oeconomy, be- tween man, who stands at the height ofthe animal scale, and the polypus on its lowest line, than between the polypus and a plant. There lies be- tween organized and inorganic bodies, a space, which is not to be filled up by figured stones, nor by lithophytes, nor by crystals, in which some naturalists have thought they saw a* beginning of organization. Whilst, at the extremity of the animal chain, are found beings, fixed, like plants, on the spot of their birth, sensitive and contractile, like the sen- sitive and some other plants, and reproduced like them from,slips. Yet we ''* Christ allographie- Tom. I. p. °4. are able to state some differences, sufficiently marked, to assign to the ve- getable kind a character of their own, which will not suit the individuals of either ofthe other kingdoms. Their nature, more complex than that of minerals, is less so than that of animals : the proportion of the solids to the liquids, is greater than in these last: accordingly they retain, long after death, their form and bulk, only that they grow lighter. The solids are, in man, nearly a sixth of the whole body : his carcase, decomposed by putrefaction, remains a little earth, and a lio-ht skeleton, when the ground and the air have drawn from it all its juices. A tree, on the contrary, is more than three parts of its substance, solid wood. It has been dead for ages, and yet in our buildings, it pre- serves its form and size, though by drying it has lost a little of its weight. Their constituent principles, as they are less in number, are also less dif- fusable. In fact, azote, which is predominant in animal substances, is a ga- seous and volatile principle, whilst carbon, the base of vegetable substance, is fixed and solid. This circumstance, added to the smaller quantity of their liquids, explains the long duration after death, of vegetable substances. But of all the characteristics which have been employed in establishing the limits of animal and vegetable nature, there is one quite sufficient to dis- tinguish these two great classes of beings, but which has not been allowed the weight it deserves. The zoophyte, who, fixed in his rocky habitation, cannot change his place, confined to partial movements, which certain plants are possessed of, who besides, has not that sensitive unity, so remarked in man, and in the animals who nearest resemble him in their organization : the zoophyte, whose name indicates an animal-plant, is totally separated from all beings ofthe vegeta- ble kingdom, by the existence of a cavity, in which alimentary digestion is carried on, a cavity by. the surface of which is an absorption, an imbibition, far more active than that which takes place by the external surface ofthe body. From this shapeless animal, up to man, nutrition is effected by two surfaces, and especially the internal, whilst in the plant, nutrition, or rather the absorption of nutritive principles, is only by the external surface *. Every animal may be considered, in extreme abstraction, as a nutritive tube, open at the extremities |; the whole existence ofthe polypus seems reduced to the act of nutrition, as its whole substance is employed in the formation of an alimentary tube, of which the soft parietes, extremely sensi- ble and contractile, are busied in appropriating to themselves, by a sort of absorption, the substances which are brought into it. From the worm up to man, the alimentary canal is a long tube, open at the extremities ; at first, only ofthe length ofthe body of the animal, not bent at all in passing from the head to the tail, and carried on towards the mouth, and towards the anus, with the external covering ofthe body, but soon returning upon itself, aod stretching out into length, far beyond that ofthe body which contains it. It is in the thickness ofthe parietes of this animated tube, betwixtthe mu- cous membrane that lines it inwardly, and the skin with which this niem- * This most prominent characteristic of animal organization was first pointed out by Boerhaave, and afterwards insisted on by Dr. Alston of Edinburgh, and recently by Mr. A. T. Thomson, in his excellent work on the Elements of Botany. t Lacipide, Histoire Naturelle des Poissons, torn. 1. There may be brought against this principle, the instance of some zoophytes, such as sponges, &c.; but do these bodies really belong to the animal kingdom ? and should not we be warranted in rejecting them by the want of the alimentary cavity, the essential characteristic of animal existence ? \y. thorns Note. 1 brane is continuous, that all the organs are placed, which serve for the trans- mission and elaboration of fluids, together with the nerves, the muscles, in short, all that serves for the carrying on of life. As we rise, from the white-blooded animals, to the red and cold-blooded, from these to the warm- blooded, and from these to man, we see a progressive multiplication ofthe organs that are contained within the thickness ofthe parietes ofthe canal: —If we follow, on the other hand, the descending scale, we see this struc- ture gradually simplified, till we arrive at last at the polypus, and find in it only the essential part of animal existence. The simplicity of its organiza- tion is such, that it may be turned inside out, and the external be made the internal surface ; the phenomena of nutrition, which are the whole life of the animal, goon, from the cl is^ analogy between the two surfaces ; unlike to man and the greater part of animals, in whom the skin and the mucous membranes, though growing into each other, though linked by close sympathies, are far from possessing a complete analogy of structure, or a capacity for the interchange of functions. Man, then, and the whole animal kind, carry about within themselves, the supply of their subsistence ; and absorption, by an inward surface, is their distinguishing characteristic. It is inaccurate to ascribe to Boerhaave the comparison ofthe digestive system of animals, to the soil in which plants suck up the juices that feed them, and the chylous vessels, to real internal roots. I find the same thought well expressed in the work on humours, which, justly or falsely, bears the name of Hippocrates. Qjiemadmodum terra arboribus, ita animalibus ventriculus. The digestive tube, that essential part of every animal, is the part of which the existence and action are the most independent ofthe concur- rence of the other organs, and to which the properties of life seem to adhere, if one may say so, with most force. Haller*, who has made so many and such interesting inquiries into the contractile power of the mus- cular organs, examining them under the two-fold relation of their irritability, as it is more or less lively, or more or less lasting, looks on the heart, as the one in which these two conditions are found in the highest combination. He gives the second place to the intestines, the stomach, the bladder, the uterus, and the diaphragm, and, after these, all the muscles under the com- mand ofthe will. I had at first admitted, with every other writer, this classification ofthe contractile parts ; but more than a hundred experiments on living animals have satisfied me, that the intestines are always the last part in which the traces of life may be discovered. Whatever may be the sort of death by which they are destroyed, peristaltic motions, undulations, are still continued in this canal, while the heart has already ceased to beat, and the rest of the body is all an inanimate mass. M. Jurine had already ob- served on the pulex monoculus, that, of all the parts of the body of this lit- tle white-blooded animal, the intestines were the last to die. If the intestinal tube be the ultimum moriens, if it be the last organ in which life lingers and goes out, it is to it we ought to direct, in preference, the stimulants that are capable of recalling it in case of asphyxia. I think that, after the blowing of pure air into the lungs, the means that ought next to be attended to is the injection of acrid and irritating clysters, thrown in with force. The large intestines are connected with the diaphragm by a close sympathy, as is proved by the phenomena of fecal evacuation ; the * Opera minora, 3 vols. 4to. .3 irritation of them is the surest means of accelerating it; and this "'^tation is the easier, as the alimentary canal is the last part that is forsaken by life. §V. OF LIFE*. After having thus laid down, between organic bodies and organized living bemgs and again between animal and vegetable nature, a line of demarcation Sfa^otbe'mistaken.letusendeavourtoexah ourselves to the concep- tion of Life; and for accuracy of thought let us, i n some sor iw^ *, by studying it in all the beings of nature that are endowed with it. In this studv, of which I may be allowed to state, in advance, the results, we shall see life composed at first of a small number of phenomena, simple as the ap- paratus to which it is given in charge ; but soon extending itself as its or- gans or instruments are multiplied, and as the whole organic machine be- comes more complex ; the properties which characterize it and bear wit- ness of its presence, at first abscure, becoming more and more manifest, in- creasing in number as in developement and energy ; the field ot existence enlarging, as from the lower beings we re-ascend to man, who, ot all, is the most perfect ; and observe, that by this time of perfection, it is simply meant that the living beings to which we apply it, possessed of more means, present also more numerous results and multiply the acts of their existence; for in this wonderful order ofthe universe, every being is perfect in itself each being is constructed most favourably for the purpose it is to fulfil ; and all is equally admirable, in living and animated nature, from the lowest vegetation to the sublimity of thought. What does this plant present to us that springs up, and grows, and dies every year ? A being whose existence is limited to the phenomena ot nu- trition and reproduction ; a machine constructed of a multitude of vessels straight or winding, capillary tubes, through which the sap is filtrated and other mices necessary to vegetation ; these vegetable liquors ascend, gene- rally, from the roots, where their materials are taken in, to the summit, where what remains from nutrition is evaporated by the leaves, and what the plant could not assimilate to itself is thrown off in transudation. Two properties direct the action of this small number of functions : a latent and faint sensibility, in virtue of which, each vessel, every part of the plant, is affected in its own way by the fluids with which it is in contract; a contrac- tility as little apparent, though the results prove irrefragably its existence ; a contractility, in virtue of which, the vessels, sensible to the impression of liquids, close or dilate themselves, to effect their transmission and elabora- tion. The organs allotted to reproduction, animate, for a moment, this ex- hibition : more sensible, more irritable, they are visibly in action ; the sta- mina, or male organs, bow themselves over the female organ, the pistils, shake on the stigma their fertilizing dust, then straighten, retire from it, and die with the flower, which is succeded by the seed or fruit. This plant, divided into many parts, which are set in the earth with suita- ble precautions, is reproduced and multiplied by slips, which proves that these parts are little enough dependent on each other ; that each of them contains the set of organs necessary to life, and can exist alone. The differ- - ent parts of a plant can live separately, because life, its simpler organs and properties are diffused more equably, more uniformly, than in animals like man, and its phenomena are connected in a less strict and absolute depend- ■^p Appendix, rs'otp V 9 ance. I myself have witnessed a very curious fact, which confirms what I have said*. A vine, trained against the eastern wall of a forge, shot into the building a few branches. These branches, which entered by straight enough passages, were covered with leaves in the middle of the hardest winters ; and this premature but partial vegetation went through all its periods, and was already in flower when the part remained without was beginning to bud with the spring. If we pass from the plant to the polypus, which forms the last link ofthe animal chain, we find a tube of soft substance, sensible and contractile in all its parts, a life and organization at least as simple as that ofthe plant. The vessels which carry the liquids, the contractile fibres, the trachea, which give access to the atmospheric air, are no longer distinctly to be traced in this almost homogeneous substance. There is no organ especially allotted to the reproduction of the kind. Moisture oozes from the internal surface ofthe tube, softens and digests the aliments which it finds there ; the whole mass draws in nourishment from it; the tube then spontaneously contracts, and casts out the residue of digestion. The mutual independence of parts is absolute and perfect: cut the creature into many pieces, it is reproduced in every piece ; for each becomes a new polypus, organized and living, like that to which it originally belonged. These gemmiparous animals enjoy, in a higher degree than plants, the faculties of feeling and of self-motion ; their substance dilates and lengthens, and contracts, according to the impressions they receive. Nevertheless, these spontaneous movements do not suppose, any more than those of the mimosa, the existence of reflection and will; like those of a muscle detached from the thigh of a frog and exposed to gal- vanic excitation, they spring from an impression which does not extend be- yond the part that feels it, and in which sensibility and contractility are blend- ed and lost in each other. From this first degree ofthe animal scale, let us now ascend to worms. We have no longer a mere animated pulp shaped into an alimentary tube ; parcels of contractile or muscular fibres, a vessel divided by several con- strictions into a series of vesicles, which empty themselves one into another, by a movement of contraction that begins from the head, or the entrance of the alimentary canal, and proceeds towards the tail, which answers to the anus, a vessel from which, in all probability, are sent out lateral ramifica- * Vegetable life, compared in its means and in its results, to the life of animals, would throw the greatest light on many phenomena which it is still difficult for us to conceive and to explain. The treatment of disease in plants, for which as much would be gained by these enquiries, is almost entirely surgical. When, to make vegetation more fruitful, the gardener prunes a luxuriant branch; when the peasants of the Cervennes, as M. Chap- tal has observed, burn the inside of their chesnut trees to stop the progress of a destructive caries; when the actual cautery is applied to the really ichorous and foul ulcers of many trees, &c it is to the organs of inward life, (or that which carries on the process of assimi- lation,) the only life of vegetables, that surgery is applied; while on the contraiy, in man and animals, it is to the derangement of the external organs that the remedy is directed. I shall conclude this note with an observation on the wounds of plants. Like those of the human body, they are much less dangerous when their surface is smooth, than when their edges are hacked, torn, or bruised. Trees felled with the saw will hardly shoot up from the stool, which always furnishes a better growth when an axe has been employed. The saw lacerates the vegetable texture, and its violent and distressing action on the fibres extending towards the roots, affects, more or less, the organization. The uneven surface of a tree felled in this manner, holds wet, as injurious to the trunk, which it rots, as a too great quantity of pus, which bathes constantly the surface of a wound, checks the process of granulation, and resists cicatrization. Author's note. t This class of animals cannot be considered to possess a spinal marrow. The series of ganglions which they exhibit* is merely the vertebral ganglia of the sympathetic nerve o 10 tions, a spinal marrowj equally knotted, or composed of a chain ot gang- lions* , stigmas, and tracheae, analogous to the respiratory organs of plants, and in some, even gills : all shows clearly an organization further advanced, and more perfect: sensibility and contractility are more distinct; the motions are no longer absolutely autom die . there are some which seem to suppose a choice. The worm, too. may be divided imo many pieces ; each will become a separate and perfect worm ; a head and tail growing to each t ; but this division has its term, beyond which there is no longer complete re- generation. It cannot, therefore, be pushed so far as in the polypi. The substance ofthe worm being formed of elements more dissimilar, it may be that f oo small a portion does not contain all that is necessary to constitute the animal. The crustaceous tribes, and among them the lobster, discovers a more complex apparatu» of organization. Here you will find distinct muscles, an external articulated skeleton, of which the separate parts are moveable upon each other, distinct nerves, a spinal marrow with bulgings, but, above all, a brain and a heart. These two organs, though imperfect, assign the animal to an order much above that of worms. The first becomes the seat of a sort of intelligence ; and the lobster acts evidently under impulses of will, when attracted by a smell, it pursues a distant prey, or when it flies a danger dis- covered to it by its eyes. There are viscera accompanying the intestinal tube, which give out to it liquids that concur in alimentary digestion. Sen- sibility and contractility present each two shades : in fact, the parts ofthe animal are obedient to the internal stimuli, feel the impression of fluids, and contract to impel them ; on the other hand, by its nerves and locomotive j muscles, the lobster places itselfin connexion with the objects that surround it. The phenomena of life are linked together by a strict necessity : it is no longer possible to separate the creature into two parts, of which each may continue to live ; there are but few parts you may cut off without inju- ry, while you spare the central foci of life. So, if you take off a claw, you observe soon a little granulation, whi^h swells and is developed, and which, soft at first, is soon clothed in a calcareous covering like that which encloses the rest of its body. This partial regeneration is frequently to be seen. If from white-blooded animals we go on to the red and cold-blooded, such as fishes and reptiles, we see this power of reproduction becoming more and more limited, and life more involved in organization. In fact, if you cut off a part of the body of a fish, the tail of a serpent, or the foot of a frog, the separated parts are either not supplied at all. or very imperfectly repro- duced. All these creatures maintain, with the medium in which they live, relations of more strict dependence. Gills in these, lungs in others, are added to a heart, nor are less essential to life. However, the action of these j chief organs is not so frequent, nor of momentary necessity for the continu- j anceoflife. The serpent passes long winters, torpid with cold, in holes where he has no air, without breathing, without any motion of life, and in all appearance dead. These creatures, like all reptiles, are able to breathe only at long intervals, and to suspend, for a time, the admission of air, without risking their existence. Here the vital powers are distinct and strong, and differ from those ofthe more perfect animals and of man, by very slight shades : the'heart and the vessels ofthe fish feel and act with him, with- out his consciousness. Further, he has senses, nerves, and a brain, from * Appendix, Note B. t This may be observed in several of the intestinal worms. It ought to be kept in re- collection during pur endeavours to remove them from the body. il which he has intimation of whatever can affect him ; muscles and hard parts, by the action of which he moves, and changes his place, adapting himself to the relations that subsist between the substances around him and his own peculiar mode of existence. We are come, at last, to the red and warm blooded animals, at the head of which are the mammiferae and man. They are entirely alike, save some slight differences in the less essential organs. There is none that has not the vertebral column, four limbs, a brain which fills, exactly, the cavity of the skull, a spinal marrow, nerves of two sorts, five senses, muscles, partly obeident to the will, partly independent in their action ; add to these a long digestive tube coiled upon itself, furnished at its mouth with agents of saliva and mastication : vessels and lymphatic glands, arteries and veins, a heart with two auricles, and two ventricles, lobular lungs, which must act incessantly in impregnating the blood, that passes through them, with the vi- tal part ofthe atmosphere*, which if it fail, life is suspended, or gone. None of their organs live, but while they partake in the general action of system, and while they are under the influence of the heart. All die, irrecovera- bly, when they are parted from the body of the animal, and are in no way replaced ; whatever some physiologists may have said on pretended regen- eration of the nerves and some other parts. Every thing that is impoitar.t to life, is to be found in these animals ; and as the most essential organs are within, and concealed in deep cavities, a celebrated naturalist was correct in saying, that all animals are essentially the same, and that their differences are in their external parts, and chiefly to be observed in their coverings and in their extremities. The human body, consisting of a collection of liquids and solids, contains of the former, about five-sixths of its weight. This proportion of the liquids to the solids, may, at first sight, appear to you beyond the truth ; but consider the excessive decrease of size of a dried limb ; theglutaeus maximus, for ex- ample, becomes, by drying, no thicker than a sheet of paper. The liquids which constitute the greatest weight of the body, exist before the solids ; for the embryo, which is at first in a gelatinous state, may be considered as fluid ; besides, it is from a liquid that all the organs receive their nourish- ment and repair their wastes. The solids, formed from the liquids, return to their former state, when, having for a sufficient length of time, formed a part ofthe animal, they become decomposed by the nutritive process. Even from this slight view of the subject, fluidity is seen to be essential to living matter, since the solids are uniformly formed from the fluids, and eventual- ly return to their former state. Solidity is then only a transient condition and an accidental state of organized and living matter, and this circumstance affords to the humoral pathologists ample opportunities of embarrassing their opponents with many objections not easily answered. Water forms the principal part and the principal vehicle of all the animal fluids, it con- tains saline substances in a state of solution, and even animal matter itself is found in it fluid, and that in three different conditions, under the form of gelatine, of albumine, or fihrine. The first of these substances, solidified, forms the basis of all the organs of a white colour, to which the ancients gave thename of spermatic organs, such as the tendons, the aponeurosis, the cellular tissue, and the membranes. Albumine exists in abundance in sal- most all the humours ; the fibrine ofthe blood is the cement which is em- Late experiments have shewn that a different process takes place in the lungs. Sjeb Chapter of Respiration 12 ployed in repairing the waste of a system of organs, which, in point of bulk hold the first rank among the constituent parts of the human body—I mean the muscular system. The chemists suspect, and not without reason, that the animal matter passes successively through the different states of gelatine, albumine, and fibrine ; that these different changes depend upon the progressive animalization of the animal matter, which is at first gelati- nous, a bydro-carbonous oxyde, containing no azote, and acidifiable by fermentation, becomes more closely combined with oxygen, takes up azote, so as to become albumen, subject to putrefaction, and finally fibrine, by a super-addition ofthe same principles. The solid parts are formed into different systems, to each of which is in- trusted the exercise of a function of a certain degree of importance. Li- miting the term organic apparatus, or system, to a combination of parts which concur in the same uses, we reckon ten, viz.—the digestive appara- tus, consisting essentially ofthe canal which extends from the mouth to the fy anus ; the absorbent, or lymphatic system, which is formed ofthe vessels or gtands of that name : the circulatory system, which consists of an union of the heart, the veins, the arteries, and the capillary vessels ; the respiratory, or pulmonary system ; the glandular, or secretory system ; the sensitive sys- tem, including the organs of sense, the brain, and spinal marrow ; the mus- cular system, or that of motion, including not only the muscles, but their tendons and aponeuroses ; the osseous system, including the appendages of the bones, the cartilages, the ligaments, and the synovial capsules ; the vocal system, and the sexual, or generative system, different in the two sexes. Each of these organic systems contains in its structure several sim- ple tissues, or" similar parts," as the ancients called them ;—these tissues in man may be enumerated as follows ; cellular tissue, nervous tissue, muscular tissue, besides that horny substance which constitutes the basis of the epi- dermis, the nails and the hair*. These four substances may be considered as real organic elements, since with our means of analysis, we never can succeed in converting any of these substances into another. The cerebral pulp is not convertible into a horny substance, into cellular substance, or into muscular fibre, neither can any one * One of the oldest divisions ofthe primary textures of the body, and one which nearly coincides with that given by the author, acknowledges three tissues only, viz. the cellular, nervous, and muscular. This arrangement has been adopted by the majority of physiolo- gists since the time of Haller. It may be shown that all the textures and organs of the body result either from the various distribution of these primary tissues; or from the cellular only, in consequence of a greater condensation of its substance, or approxima- tion of the molecules of matter entering into its constitution, and owing to a deposition of earthy substance between its interstices, as in the bones. It may, however, be a matter of doubt whether the muscular texture does not arise from the union ofthe cellular tissue with the nervous substance; the former combining with the fibrillar of the organic or ganglial nerves to form the muscular fibre generally, whether involuntary or voluntary, while the latter class of muscles derives its peculiar characters and functions from the ac- cession of the fibrillse of voluntary nerves to the ganglial and cellular textures. If this position be allowed, the involuntary fibres will appear to result from the combination of the cellular substance with the ganglial nerves only, the voluntary from the union of the .cellular with both the ganglial and cerebral matters composing the extremities of their r&>,niifications; the muscular fibre varying its character and phenomena according as more or h'ess of either kind of nervous substance enter into its composition. An intimate view of the mode of distribution which characterizes both class of nerves, as well as various other considerations, support this opinion, which is calculated to form the basis of some plausi- ble explanations of many of the most important appearances and functions of the different muscular textures. Ill jf these tissues ever be converted into cerebral pulp. The bones, the car- tilages, the ligaments, the tendons, the aponeuroses, may, by long maceration, be converted into cellular substance. Muscular fibres are not subject to that alteration, nor is the nervous or cerebral pulp : the horny substance also resists that change. Every thing, therefore, leads us to acknowledge these four constituent principles in our organs. The primitive or simple tissues, variously modified, and combined in dif- ferent quantities and in various proportions, constitute the substance of our organs. Their number is much more considerable, according to Bichat, whose happiest conception was the analysis of the human organization. This physiologist reckoned in the human oeconomy, no fewer than twenty- one general or generating tissues*. But it is evident, that this analysis is car- ried too far; that the tissues of which the skin and the hair are formed, are exactly of the same nature, are analagous in their properties, and are nou- rished in a similar manner ; that the cellular tissue is the common basis of the osseous, cartilaginous, mucous, serous, synovial, dermoid, &.c. It must be confessed, that this separate consideration of each organic tissue has furnished him with new ideas, ingenious analogies, and useful results, and that his " Anatomie generale," in which those researches are contained, is his chief title to glory. That glory would be complete, if in that book, and yet more, in his other works, he had done his predecessors, as well as his contemporaries, the justice they had a right to expect from him. The simple, or elementary fibre, about which so much has been written, may be considered as the philosopher's stone of physiologists t- In vain has Haller himself in his pursuit of his chimera, told us, that the elementary * The following classification of the primary and compound textures nearly coincides with that recommended by Dupuytren and Magendie: (I. Cellular. *•»«—.................|SS. '■"".................lEEET l Arterial, 4. Vascular................/ Veinous, x { I Lymphatic. 5. Osseous. C Fibrous, 6. Fibrous.................1 Fibro-Cartilaginous, I Dermoid. 7. Erectile. 8 Mucous. 9. Serous. 10. Synovial. 11. Glandular. 12. Epidermous, or Corneous. t Almost every physiologist who has written on Animal Organization has proposed a new arrangement of the primary textures. We will only take notice of the two follow- ing:—Walther considered the different organs and compound textures to result from the cellular or membranous, the vascular or fibrous, and from the nervous. J. F. Meckel founds his classification of organic substances on microscopic researches. He is of opin- ion that the solids and fluids of the human body can be reduced to two elementary substan- ces, the one formed by globules, the other by a coagulable matter which, either alone or united to the former, constitutes the livingfluids, if it be in the liquid state, and gives rise to the solid tissues, when it assumes the concrete form. See APPENDIX, Note C. for a more detailed account ofthe opinion of this eminent Anatomist. 11 fibre is to the physiologist what the line is to the geometer, and, that as all figures are formed from the latter, so are all the tissues formed from this fibre : Fibra enim physiologo id est quod linea geometrce, ex qua nempe figurct omnes oriuntur. The mathematical line is imaginary, and a mere abstraction of the mind, while the elementary fibre is allowed a material or physical existence. Nothing, therefore, can mak«' us admit the existence of a simple, elementary, or primitive fibre, since our senses show us in the human or- ganization, four very distinct materials. Among the organs, whether single or combined in systems, which enter into the human organization, there are some whose action is so essential to life, that with the cessation of that action, life at once becomes extinct. These primary systems, whose action regulates that of all secondary sys- tems, are as numerous in man as in the other warm-blooded animals. None of them can act unless the heart sends into the brain a certain quantity of blood, vivified by the contact of atmospherical air in the pulmonary tissue. Every serious wound ofthe brain or heart, every lasting interruption to the access of blood into the former of these organs, is invariably attended with death. The oxydation ofthe blood, and its distribution into all the organs, is consequently the principal phenomenon on which the life of man and of the most perfect beings depend. § VI. OF THE VITAL PROPERTIES ; SENSIBILITY AND CON- TRACTILITY*. By sensibility is meant that faculty of living organs, which renders them capable of receiving from the contact of other bodies, an impression strong- er, or fainter, that alters the order of their motions, increases or diminishes their activity, suspends, or directs th mi. Contractility is that other proper- ty by which parts excited, that is, in which sensibility has been called into action, contract or dilate, in a word, act, and execute motions. In the same manner, as we h;>ve not always a consciousness ofthe impressions received by our organs, and as, for example, no sensation informs us ofthe stimulat- ing impression by which the blood calls the heart into action, so it is by re- flexion only, that we are induced to admit the existence of certain motions ; of those, for instance, by which the humours, when they have reached the smallest vessels, become incorporated into the tissue of our organs t- These motions, to make use of an ingenious comparison, resemble those of the hour-hand, compared with the second-hand of a watch. The hour-hand appears motionless, and yet in twelve hours it describes the whole circum- ference ofthe dial-plate, round which the other hand moves in one minute, with a motion that is visible. In considering life through the great series of beings that possess it, we have seen that those in which it is most limited, or rather in which it con- sists of the least number of actions, and phenomena, vegetables, for instance, and animals like the polypus, which have no brain, no distinct nervous sys- tem, are at once endowed with sensibility and contractility in all their parts. All living beings, all the organs which enter into their composition, are im- pregnated, if we may be allowed the expression, with these two faculties, * See APPENDIX, Note D. t If the suggestions offered, in the Note at p 12, respecting the constitution of the dif- ferent kinds of muscular fibres, were adopted, the explanation of the properties, sensibility and contractility, and the relatiouswhich they hold with the circle of vital functions, would. be more apparent and better understood. 15 necessarily co-existing, and which shew themselves by internal and nutritire motions, obscure, indeed, and to be distinguished only by their effects. These two faculties appear to exist in the degree absolutely required for enabling the fluids that pervade all the parts of a living body, to induce the action by which these parts are to assimilate such fluids. It is clear, that the two properties of feeling and of motion are indispensable to all parts of the body. They are properties universally diffused through organized and living matter, but they exist without possessing any peculiar organ or instru- ment of action. Were it not for these two faculties, how would the different parts act on the blood, or on the fluid which supplies its place, so as to ob- tain from it the materials subservient to nutrition and the different secre- tions ? These faculties are therefore given to every thing that has life—to animals, to vegetables, to man in his waking hours, or in his most profound sleep, to the foetus, to the child that is born, to the organs ofthe assimilating functions, and to those which connect us with surrounding beings. Both these faculties, obscure, and inseparable, preside over the circulation of the blood, of the fluids, and, in short, over all the phenomena of nutri- tion. Though this kind of sensibility is always latent or concealed, it is other- wise with regard to contractility, which may be sensible or otherwise. The bone, which takes up the phosphate of lime, to which it owes its solidity, exerts that action without our being aware of its taking place, except by its effect: but the heart which feels the presence of the blood, without any consciousness, on our part, of such sensation, exerts motions that are easily perceptible, but over which we have no controul, either to suspend or ac- celerate them. Vital properties in so weak a degree, would not have been sufficient to the existence of man and ofthe animals which resemble him, obliged to keep up multifarious intercourse with every thing that surrounds them ; thus they enjoy a very superior kind of sensibility, by means of which the impressions which affect some of their organs are perceived, judged, and compared. This mode of sensibility might be more properly called perceptibility, or the fa- culty of accounting to oneself for the emotions which are experienced. It requires a centre to which the impressions may be referred, and therefore it exists only in the animals which, like man, have a brain or some organ in its stead ; so that the zoophytes and vegetables, wanting that organ, are equally destitute of this faculty. The polypi, and some plants, as the sen- sitive, perform nevertheless certain spontaneous motions, which seem to in- dicate the existence of volition, and consequently of perceptibility. But these motions are the result of an impression, which does not extend beyond the part in which it is experienced, and in which sensibility and contractili- ty are blended. The almost latent sensibility of certain parts of the body, cannot be ab- solutely compared to that of vegetable ; since those organs whose sensibili- ty is so imperfect, manifest in disease a percipient sensibility, which shows itself by acute pain, and it is even sufficient to change the stimulus to which they are accustomed, to determine the occurrence of that phenomena. Thus the stomach, on the parietes of which, the food does not in health produce any perceptible impression, becomes the seat of very distinct sensation and of dreadful pain, when a small quantity of poisonous matter is introduced in- to it. In like manner, we are not conscious of the impressions excited in the parietes of the bladder or rectum, by the collection of urine or faecal substances, except when their contents have become sufficiently irritating 10 by their presence, to excite in a certain degree, those irritable and sentient cavities, and to transform their obscure, into a very distinct sensibility. Is there not reason to suspect, that our unconsciousness, in health, ofthe im- pressions made on our organs by the fluids which they contain, depends on our being accustomed to the sensations which they incessantly excite ? so that there remains but a confused perception, which in time disappears, and may we not, under that point of view, compare all these organs to those of sight, hearing, smelling, tasting, and touching, that are no longer irritable by stimu- lants, to which they have long been habituated ? Two systems of organs, very different in their uses and in their qualities, enter into the composition of the human body ; they are as two living and united machines, the one, formed by the organs of sense, the nerves, the brain, the muscles, and the bones, serves to maintain its connexion with ex- ternal objects ; the other, destined to internal life, consists in the digestive tube, and the organs of absorption, circulation, respiration, and secretion. The organs of generation in the two sexes form a separate class, which, as far as relates to the vital properties, partakes of the nature of the other two. By the organs of sense, and the nerves which form a communication be- tween these organs and the brain, we are enabled to perceive or to feel the impressions made on us by external objects : the brain, the true seat of that relative sensibility, which might very justly be termed perceptibility or the perceptive power, (Pott) when excited by these impressions, is able to irra- diate into the muscles the principle of motion, and to induce the exertion of their contractility. This property, which is under the direction ofthe will, manifests itself by the sudden decurtation of a muscle, which swells, hardens, and determines the motion of those parts of the skeleton to which it is at- tached. The nerves and the brain are essentially the organs of these two properties, a division ofthe former is attended with a loss of sentiment and voluntary motion in the parts to which they are distributed. The other kind of sensibility is, on the contrary, quite independent ofthe presence of nerves ; it exists in all organs, although all do not receive nervous filaments. It might even be asserted, that the cerebral nerves are not at all essential to the life of nutrition ; the bones, the arteries, the cartilages, and several other tissues, in which no nerves are seen to enter, are nourished equally well with the organs in which they exist in considerable number; the muscles themselves will carry on their own internal oeconomy, notwithstanding the division of their nerves ; only, deprived of those means of communication with the brain, they can no longer receive from it the principle of volunta- ry contraction ; instead of that sudden, energetic, and lasting decurtation, which the will determines in them, they become merely capable of those quiverings called palpitations. The anatomist who studies the nerves with a view to ascertain their ter- mination, finds them all arising from the brain and spinal marrow, and pro- ceeding by a longer or shorter course, to the organs of motion or of sensa- tion: let him take his scalpel and dissect one of our limbs, the thigh, for in- stance, he will see the cords parting into numerous threads, most of which disappear in the thickness ofthe muscles, whilst others, after creeping for a time about the cellular tissue, which joins the skin to the aponeurosis, end on the inward surface ofthe skin, of which they compose the texture, and expand into santient papillae on its surface. The bones, the cartilages, the ligaments, the arteries, and the veins, all those parts whose action is not un IT der the controul of the will, are without them*. Nevertheless, ". far as relates to the sensibility of perception, and the voluntary motion which is entirely subservient to it, but that the existence of nerves is not at all necessary to the exercise of the sensibility and contractility which arc- indispensable to the assimilation of nutrition. * Are destitute, or at least nearly so, of voluntary nerves. t All these parts may be considered to possess ganglial nerves; for as these nerves may be demonstrated on the more considerable trunks of arteries, even in the extremities, they may be supposed to accompany these vessels to their most minute ramifications and termi- nations, and to bestow on them the manifestations which these parts ofthe vascular system evince. Such, then, being the constitution and connexion ofthe arterial and capillary vessels, no texture which possesses these vessels can be considered to be destitute of this plass of nerves. Those nerves that belong to the other class, or the cerebral, may be infer- red to exist, in an organ, more or less abundantly, or to be entirely absent from it, accord* ing to the nature of the phenomena which that organ presents. See Chapters on the Circulation, Sensation, and Motion- tlf the constitution of the muscular fibre, as formerly alluded to, be consk'efed, the source of irritability and its various degrees of intensity, with the relation which it holds to sensibility and the other modes of action which the animal texim*?? evin-c?, will V veneered.more apparent. 18 No part of the living body is absolutely insensible, but that sensibility of every organ is so modified, that it is not affected by the same stimuli. Thus, the eye is insensible to sound, and the ear to light. A solution oi tartar emetic, causes no disagreeable impression to the conjunctiva ; taKen into the stomach, it excites convulsive motions, while an acid from which tne stomach does not suffer, proves a cause of irritation to the conjunctiva, ana brings on a violent inflammation ofthe eye. In the same manner, purgatives pass along the stomach, without producing any effect on that vi*cus, hut they stimulate the alimentary canal. Cantharides have a specific action on the bladder ; and mercury on the salivary glands. Each part feels, lives, moves, after its own way ; in each, the vital properties appear under such shades and modifications, that they may be looked upon as so many separate members of the same family, concurring in one endeavour, working tor a common end, consentientia omnia. (Hipp.) . The faculty of assigning a cause to the sensation, and that of moving by volition, which man possesses in common with all animals formed with a distinct nervous centre, are essentially bound together. For suppose a living being, furnished with locomotive organs, but without sensation, placed in the midst of bodies, that every moment endanger its existence, without any means of distinguishing them, it will hasten its own destruction. If perceptibility could, on the other hand, exist independently of motion, how dreadful would be the fate of such sentient being, similar to the fabulous Hamadryads, who, immoveably fixed in the trees of our forests, received, without any power to shun them, all the blows inflicted on their rustic abode. Dreams place us sometimes in situations which give us a just idea of their condition. A certain danger threatens our existence ; an enor- mous rock seems to detach itself, to roll and precipitate itself on our frail machine ; a frightful monster seems to pursue us, and opens a yawning mouth to ingulf us. We struggle to escape this imaginary danger, to avoid or to repel it, but an irresistible and unknown power, a mighty hand para- lyses our efforts, and keeps us rooted to the spot ; it is a situation of horror and despair, and we awaken overwhelmed with the uneasiness which we have suffered. As there is no part that does not feel, in a manner peculiar to itself, so there is no one that does not act, move, or contract, in a manner peculiar to itself; and the parts which have been found without a power of motion analogous to muscular contractility, have remained in that state of immo- bility, only for want of a stimulus fitted to their peculiar nature. Some physiologists say they have excited a distinct quivering, in the mesentery of a frog and of a cat, by touching them after they had been previously moist- ened with alcohol, or muriatic acid. In the operation for sarcoele*, I have often perceived that while with my left hand I supported the tumour, and with a scalpel in the right, divided the spermatic chord, the tunica vaginalis shewed oscillatory contractions. It visibly contracts in the operation for hydrocele. The injection of an ir- ritating fluid determines evident motions in the tunica vaginalis. The os- * The contraction ofthe membrane, formfd by the expansion of the cremaster muscle, has doubtless assisted in rendering more distinct the appearance in question. This effect must be particularly distinct, a the moment of dividing the spermatic chord. The con- tractions of the same muscle corrugate the skin ofthe scrotum, when this part is exposed to cold, and draw up the testicles towards the inguinal rings. The contractility ofthe skin of the scrotum, has but little influence in producing this effect-—■AvMmr's Note. 19 seous tissue, notwithstanding the phosphate of lime with which it is incrust- ed, is susceptible of a contraction, whose effects, though slow, are never- theless undeniable. After teeth have been shed or extracted, the edges of the alveolar process become thinned from contraction and the alveolar cavi- ties disappear. These facts appear to me to prove, still better than all the experiments performed on living animals, (experiments of which, by the bye, the results ought not too confidently to be applied to the ceconomy of man) what one should think of the assertions of Haller and his followers, on the insensibility and inirritability of the serous membranes, and ofthe organs of a structure analogous to their's. We will/jat present, say nothing ofthe porosity, ofthe divisibility, ofthe elasticity, and other properties which are common to living bodies and inani- mate substances. These properties are never possessed in their whole extent, and in all their purity, if that expression may be allowed. Their results are always influenced by the vital power, which constantly modifies the effects which seem to depend most immediately upon a physical, che- mical, or mechanical cause, or upon any other agent whatsoever. Not so with the truly vital extensibility, which is so manifest in certain organs, as the penis and the clitoris. When excited, they become turgid and dilated by the afflux of humours, but that effect does not depend on a peculiar pro- perty, distinct from sensibility and contractility. These parts dilate, their tissue stretches under the action of these two properties, which would oc- casion the same phenomenon in all other parts, if their structure were similar. , The same applies to caloricity, or that power inherent in all living beings, of maintaining the same degree of heat, in varying temperatures*. Incon- sequence of which property, the human body preserves its temperature, of from thirty to forty degrees (Reaumur's scale) under the frozen climate of the polar regions, as well as in the burning atmosphere of the torrid zone. It is by the exercise of sensibility and of contractility, that is, by the exercise of the functions over which these vital powers preside, that the body resists the equally destructive influence of excessive heat and cold. If one were to admit caloricity as one of the vital properties, because, according to Professor Chaussier that power of preserving a uniform warmth is a very remarkable phenomenon; one might be led to suppose, a distinct cause or a peculiar property to operate in producing other pheno- mena of no less importance. Barthez and Professor Dumas have fallen into the same error, the former, in wishing to establish the existence of a power of permanent situation in the molecules of muscular fibres ; the latter, in adding to sensibility and con- tractility a third property, which he terms the power of vital resistance. Living muscles are torn vnth much more difficulty than when dead, because the contractility which, nese organs possess in the highest degree, is inces- santly tending to preserve the contact ofthe molecules, the series of which forms the muscular fibre, and even to draw them into closer connexion. This fact, which is brought forward as a proof of the existence of a peculiar power, is easily explained, on the principle of contractility. Organized and living bodies resist putrefaction, from the very circum- stance of their being endowed with life. The continual motion ofthe fluids, the re-action ofthe solids on the fluids, the successive and continual renova- * See the notes on the subject of animal heat contained in the Chafer ow PtKSPIRATIOtf. ■20 .«u or the latter, by the reception of new chyle, their constant purification by means ofthe secretions, through which the products animalized in excess are. parted with, such are the causes which prevent the putrefactive action from taking place in bodies endowed with life, notwithstanding the multipli- city and the volatility of their elements. Their preservation is therefore a secondary effect, and depending on the exercise of the functions regulated by sensibility and contractility. Nature is distinguished fur deriving a mul- titude of effects from a very small number of causes, it therefore shows a very imperfect acquaintance with her laws to assign a separate cause to each fact. The separation ofthe chyle, which takes place in the duodenum, from the admixture of the bile with the alimentary substance, the vivification of the blood by respiration, the secretion of the fluids in the conglobate glands, /nutrition in the organs, are so many acts of the living oeconomy, to which one might feel disposed to assign distinct causes ; but these chemico-vital processes, are so subordinate to sensibility and contractility, that they are met with only in organs endowed with these two properties, and they take place, in a degree more or less perfect, according to the condition of these properties in the organs in which they occur. We have stated that there exists two great modifications of sensibility and Contractility ; that sensibility is divided into percipient sensibility and latent sensibility, that contractility is at times voluntary, at others involuntary, and that the latter may be perceivable or insensible. ' Perceiving, (cerebral, nervous, animal, sensibility, per- ceptibility.) With consciousness of impressions or perceptibility ; it requires a peculiar apparatus. sf?:sibiuty. •{ Latent, (nutritive, organic sensibility.) Without consciousness of impressions ; or, general sen- sibility, common to every thing that has life ; it has no peculiar organ, and is found universally diffused in living L parts, animal or vegetable.* f Voluntary and sentient, subordinate to perceptibility. "ONTRAcxiUTy. ! Involuntary and insensible, corresponding to latent sensi- ( bility. Tonicity. t Involuntary and sentient. The cause of this last modification of contractility, appears to depend on the peculiar organization of the system of the great sympathetic nerves. From these nerves, the heart, the digestive canal, &c. seem to receive the power of exerting sensible contraction, an effect produced by the direct ap- plication of a stimulus, and over which volition has no controul, as will be stated in speaking of those nerves. Sensibility and contractility offer a vast number of differences, the prin- cipal of which depend on the age, the sex, the regimen, the climate, the state of waking or of sleep, health or of sickness, on the relative develope- ment of the lymphatic, cellular, or adipose systems, on the proportions which exist between the nervous and muscular systems. In the first place, the principle of sensibility and of contractility mav in its action, be likened to a fluid flowing from any source whatsoever which is consumed, repaired, and drained by use, re supplied, or exhausted equally distributed, or, occasionally concentrated on certain organs. * Pee. Not* at P. 17. ■21 secondly. Sensibility, like contractility, is very considerable at the instant of birth, and seems to diminish more or less rapidly till death. Thirdly. The liveliness and frequency of impressions wear it out very early. It, in a manner, repairs itself, that is, recovers its original delicacy, when the sentient organs have been long at rest. Thus, an epicure, whose taste has grown dull with high living, will recover all its accuracy, if during several months, instead of spiced ragouts and spiritous liquors, he lives on dry bread and plain water. In like manner, contractility becomes exhausted in the muscles which are too long employed, and it is recovered during the repose of sleep. Fourthly, the following is an instance ofthe manner in which sensibility becomes concentrated on one organ, and appears to forsake the others : when the venereal excitement is in its highest degree, animals under its in- fluence receive blows and stings without pain. Domestic animals in that condition, are often ill treated, without appearing to feel what is done to them. If the hind legs ofthe toad are cut off, at the time that he is holding the female firmly embraced, and is pouring his prolific seminal fluid on the ova which are issuing at her anus, he does not lose his hold, he seems insen- sible to every other sensation ; as a man who is taken up with one thought, and absorbed in reflection, is scarcely diverted from it by any means that can be employed. When during the influence of satyriasis, the vital power is carried to excess in the penis, patients have been known, (as we are told by Aetius) to cut off both their testicles, without suffering the pain usually attending so severe an operation. It is by this law of sensibility, that we are to explain the observation of Hippocrates, that two parts of the body cannot be in pain at the same time. If two pains come on at once, the more violent prevents the slighter from being felt; Ambo partes non possunt dolore simul. Duobus doloribus, sirnul orientibus, vehementior obscurat allerum. (Hipp.) Incases of scrophulous swellings, the parts are observed to in- flame, to become painful, and suppuration occurs but rarely in every part at once, if the case is serious and attended with acute pain. The germ of a disease or of a slighter affection, may sometimes remain dormant under a greater pain. I was once overturned in a carriage, from the awkwardness ofthe coachman, the windows were broken and my wrists sprained. The right wrist which had suffered most, swelled first; I employed the proper treatment, and when at the end of a week, the swelling and pain had almost completely ceased, and the right band was beginning to recover its suppleness and flexibility, the left wrist swelled and in its turn became pained ; two complaints, if they may be called such, appeared in succession, and separate- ly went through their regular course*. * John Hunter maintains from theory, the position that no two different fevers can take place at the same time in the constitution, but that if the two causes of disease exist toge- ther, the diseases themselves must be vicarious. And he verifies his reasonings from expe- rience. " On Thursday, the 16th of May, 1775,1 inoculated a gentleman's child, and it was ob- served that I made pretty large punctures. On the Sunday following, viz. the nineteenth, he appeared to have received the infection, a small inflammation or redness appearing round each puncture, and a small tumour. On the twentieth and twenty-first, the child was feverish, but I declared that it was not the variolous fever, as the inflammation had not at all advanced since the nineteenth. On the twenty-second, a considerable eruption ap- peared, which was evidently the measles, and the sores on the arms appeared to go back, becoming less inflamed. '"' Onitu; twenty-third he was very full of the measles; but the puncture on the arm5; were 'u>Ttto same state as on the preceding day. i l>.) The perfection of one sense is never obtained but at the expense ot an- other ; the blind who bestow more attention on the sensations communicated by the sense of touch and of hearing, often astonish us by the delicacy of these organs, so that, as has been observed, those who, to improve the hu- man voice, have dared to mutilate their fellow-creatures, by depriving them of the organs of generation, might have bethought themselves of putting out their eyes, to render them more sensible to the sweet impressions of harmony. Fifthly. During sound sleep, the exercise ofthe percipient faculty, and that of voluntary contractility, are entirely suspended. During that state, it seems as if some covering were thrown over the sentient extremities. We know how hard the hearing becomes, how dull the senses of smell and of taste become, how dim the sight, a cloud spreading before the eyes, the moment we are fallen asleep. Fir quidam exquisitissima sensibilitate prtedi- tus, semi consopitus coibat; huic, ut si velamento levi glans obductus fuisset, sensus voluptatis referebatur. Sixthly. Sensibility is more lively, and more easily excited in the inha- bitants of warm climates than in those of northern regions. What a prodi- gious difference there is, in that respect, between the native of Germany and ofthe southern provinces of France. Travellers tell us, that there are in the neighbourhood of the poles, natives, so little endowed with sensibility, that they feel no pain from the deepest wounds. The inhabitants ofthe coast of North America, if we may believe the testimony of Dixon and Vancouver, thrust into the soles of their feet, sharp nails and pieces of glass, withoutfeel- ing the slightest uneasiness. On the contrary, the slightest prick from a thorn, for instance, in the foot, is in the strongest African, frequently followed by convulsions and locked jaw. The impression of the air is alone sufficient to produce the same accident in the negro children in the colonies, the great- er number of whom die of locked jaw, a few days after birth. Montesquieu* very justly observed this difference which exists in the sensibility ofthe southern and northern nations, and he says of the latter, that" if you would tickle you must flay them." Now, as the imagination is always proportioned to the sensibility, all the arts that are cultivated and brought to perfection, only by the exercise of that faculty, will flourish with difficulty near the icy polar regions, unless the powerful influence of climate be counteracted by well directed moral and physical causes. Man is of all beings, the one that most powerfully resists the influence of external causes : and although the influence of climate is sufficient to modify " On the twenty-fifth, the measles began to disappear, on the twenty-sixth and twenty- seventh, the punctures began again to look a little red. On the twenty-ninth, the inflam- mation increased, and there was a little matter formed. On the thirtieth, he was seized with fever. The small-pox appeared at the regular time, went through its usual course, and terminated favourably." Hunter on Inflammation, page 5.--Author's Note. * This philosopher has borrowed from the father of physic, one of his most brilliant and paradoxical opinions. In his conception, warm climates are the seat of despotism, and the cold, the seat of liberty. This error is completely refuted in the profound and philo- sophical work of Volney on Egypt and Syria. He shews, that what Montesquieu has said of cold climates applies to mountainous regions, while a champaign is more favourable to the establishment of tyranny. Hippocrates had said of the Asiatics, that their being less warlike than the Europeans, depended on the differences of climate, and likewise on the despotic form of their government. And he observes, that men who do not enjoy their na- tural rights, but whose affections are controuled by masters, cannot feel the bold passion of war. See Chap. XI. on the Varieties ofthe Human Species.—Author's Note. 23 « his external appearance, so as to lead to a division of the species into seve- ral distinct varieties or kinds, this superficial impression is very different from the great alterations to which other beings are exposed, from the mere change of climate. Man is every where indigenous, and exists in all cli- mates ; while the plants and animals of the equator languish and die when conveyed to the polar regions. From the flexibility of his nature, man en- joys the power of adapting himself to the most opposite situations, of es- tablishing, between them and himself, relations compatible with the preser- vation of life. Nevertheless, it is not without difficulty that man undergoes these changes, and accustoms himself to new impressions. The periodical return ofthe season determines that of certain derangements, to which the animal ceconomy is subject. The same diseases manifest themselves under the influence ofthe same temperature, and to use an ingenious comparison, resemble those birds of passage which visit us at stated seasons of the year. Thus, hemorrhages and eruptive affections come on with the return of the spring, summer comes attended by bilious fevers, autumn brings on a return of dysenteric affections, and winter abounds in inflammation ofthe lungs and other parts. The influence of climate on t he human body, does not show itself merely in occasioning epidemic diseases, the consideration of which led to the establishing what physicians call medical constitutions. This in- fluence operates on man in health, as well as in sickness ; and to say nothing of the alterations which our moral nature experiences from the tendency to love, rendered more impetuous with the return of spring, or of the me- lancholy to which nervous people are often subject towards the end of autumn, when the trees are shedding their leaves, the increase of growth is particularly remarkable at the time ofthe first growth of plants, as was ob- served again and again, by a friend of mine, physician to a large seminary. Seventhly. Sensibility is greater in women and children ; their nerves* are likewise larger and softer, in proportion to the other parts of the body. In general, the principle of sensibility seems to decrease, in proportion as it has contributed to the developement of the acts of life ; and the power of being impressed by external objects, diminishes gradually with age, so that there is a period of decrepid old age, at which death appears a necessary consequence ofthe complete exhaustion of that principle. In short, as I have said in describing the progress of death, at its approach, sensibility shows increase of activity and liveliness, as if its quantity required to be completely exhausted, before the termination of existence, or as if the or- gans made a last effort to cling to life. The developement of the cellular and adipose substance, diminishes the en- ergy of sensibility, the extremities ofthe nerves being more covered, and therefore not so immediately applied to the objects, the impressions which are felt, are more obscure. The fat operates on the nerves, as wool would do on vibrating chords, if wrapped round them, to fix them, to prevent their quiverings, and stop their vibrations. Very nervous women are very thin ; persons of much sensibility have seldom much embonpoint. Swine, in which the nerves are covered by a thick layer of fat, are the most insensible of all animals. The susceptibility ofthe nerves may be diminished, and their sensibility blunted by pressure. The application of a bandage firmly rolled round the body and limbs of an hysterical woman, will diminish the violence of her fits. In dressing wounds * Their voluntary nerves. 24 affected with what is called the hospital gangrene, I have often relieved the pain, by desiring an assistant to apply firm pressure above the sore. Ninthly. There exists between the force of the muscles, and the sen- sibility ofthe nerves, between the sensible energy and the force of contrac- tion, a constant opposition, so that the most vigorous athlets, whose muscles are capable of the most prodigious efforts, and ofthe most powerful contrac- tions, are but slightly affected by impressions, and are with difficulty roused into action, as we have explained in giving a history ofthe nervous and mus- cular temperaments, which are characterized by this difference. Hence, man has more sensibility than the quadrupeds, although his nerves are smaller than theirs, which seem destined to set the muscles in action, and to serve as nerves of motion, rather than that of sensation. There is no muscular fibre, however minute, in which we are not oblig- ed to admit the existence of a small nervous flament, to which it probably owes the power of contracting ; contractility, at least voluntary contractility, does not appear to be inherent in the muscular fibre, nor independent ofthe nerves, through the medium of which, the will determines the action ofthe muscles ; and if these last organs were insulated, contract on the direct ap- plication of a stimulus, is there not reason to suspect, that this stimulus acts on that portion of nerves which remains in the muscle, after it has been insulated, and which is intimately united to its fibres ? The animals which have no distinct nervous system, possess at once in all their parts, sen- sibility and contractility ; these two properties become blended in the or- gans, as well as in the phenomena of life, and can be perceived separate, only by a pure abstraction of the mind, which considers in succession the impression produced on these beings, and the motion of their substance, which is an immediate consequence of that impression. We will not enter any farther into a consideration of the laws and pheno- mena of the vital properties, for fe.«r of being led into useless repetitions, when we come to the history of the functions over which they preside. We willponclude what relates to them, by presenting the two most impor- tantfeatures of their history, 1 mean, sympathy and habit. § VII. OF SYMPATHY. There exist among all the parts of the living body, intimate relations ; all correspond to each other, and carry on a reciprocal intercourse of sensations and affections. These links which unite together all the organs, by estab- lishing a wonderful concurrence, and a perfect harmony among all the ac- tions that take place in the animal ceconomy, are known under the name of Sympathies. The nature of this phenomenon is yet unknown; we know not why, when a part is irritated, another very distant part partakes in that irritation, or even contracts : we do not even understand what are the in- struments of sympathy, that is, what are the organs which connect two parts, in such a manner, that when one feels or acts, the other is affected. But though beyond explanation, sympathy is not the less important in the cecono- my of living beings ; and these connexions between remote parts, constitute one ofthe most remarkable differences between those beings and inorganic bodies. Nothing similar is observable in dead or inanimate nature, in which all things are connected together, only by palpable and material links ; here the chain is invisible, the connexion evident, the cause occult, and the ef- fect apparent, 25 Whytt has clearly shown, that the nerves cannot be considered as the ex* elusive instruments of sympathy*, since several muscles of a limb which receive filaments from the same nerve, do not sympathize together, while there may be a close and manifest relation between two parts, of which the nerves have no immediate connexion, since each nervous filament hav- ing one of its extremities terminating in the brain, the other, in the part to which it is sent, remains distinct from those ofthe same trunk, and does not communicate with them. Sympathies may be distinguished into different kinds. In the first place, two organs, which execute similar functions ;—the kidnies may supply each other's office. When the uterus is in a state of pregnancy, the breasts par- ticipate in its condition, and there is determined into them a flow of humours necessary to the secretion which is to take place. Secondly. The con- tinuity of membranes is a powerful source of sympathy. The presence of worms in the bowels, determines an uneasy pruritus around the nostrils. When there is a stone in the bladder, a certain degree of itching is felt at the extremity of the glands. The secretion of several fluids is determined in the same manner : thus, the presence of food in the mouth, brings at the extremity of the parotid duct, an irritation which extends to the parotid glands, calls them into action, and increases their secretion. Thirdly. If the pituitary membrane is irritated, the diaphragm with which it has no im- mediate organic connexion, nervous, vascular, or membranous, contracts and occasions sneezing. Is not this sympathy one of those which Haller ascribed to a re-action of the sensorium commune? If the impression produced on the olfactory nerves by snuff, is too powerful, the uneasy sensation is trans- mitted to the brain, which determines towards the diaphragm, a quantity of the principle of motion sufficient to enable that muscle suddenly to contract the dimensions of the chest, so as to expel a column of air, that may detach from the pituitary membrane, the substances that are a cause of uneasiness to it. Fourthly. Does not the principle of life seem to controul at plea- sure the phenomena of sympathy ? The rectum, when irritated by the presence of the excrements, contracts ; what cause determines the acces- sory and simultaneous action of the diaphragm and abdominal muscles 1 Does this connexion depend on organic communications ? Why, then, is not the sympathy reciprocal, and why does not the rectum contract, when the diaphragm is irritated ? Fifthly. Can the repeated habit of the same mo- tions explain the harmony which is observed in the symmetrical organs ? Why, when our sight is directed to an object, placed laterally, does the rectus externus of the eye on that side, act at the same time as the rectus internus ofthe other eye ? The indispensable utility of this phenomenon, in keeping a parallelism ofthe axis of vision is very obvious, but who can assign the cause ? Why are rotatory motions, in different directions, per- formed with so much difficulty by the arm and leg of the same side of the body. Can it be called a just idea of the innumerable varieties of this phenomenon, and of its frequent anomalies, to say, with Rega, that there are sympathies of action or of contractility (consensus actionum) sympathies of sensibility (consensus passionurn). *' The nerves of voluntary motion certainly can be but seldom supposed to be the instra- ments of sympathy, but no valid argument can be adduced, against the opinion which re- fers the sympathies chiefly to the distribution and connections of the ganglial class of nerves. See the Notes on the Chapter which treats of " thf, System of the grevj ^ywpathftfc Nerves.'" 4 All these difficulties render it pardonable in Whytl, to have considered the soul as the sole cause of sympathy ; which was, in fact, a modest avowal 01 the difficulty of explaining the subject. We are not justified in considering sympathy as an anomalous action, as an aberration ofthe vital power . oan 11 be said, that the natural order of sensibility and irritability is inverted, in the sympathetic erection ofthe clitoris and ofthe nipple, or in the turgessence ofthe breasts, determined by the gravif! state of the uteius ? It is by means of sympathy that all the organs concur in the same end, and yield each other mutual assistance, h affords us the means of explain- ing how an affection, at first local or limited in its extent spreads and extends to all the systems ; it is thus that every morbid process is carried on. The diseases termed general, always originate, through the medium of association, in the insulated affection of an organ or a system of organs. . , In fact, the affections which appear to us most complex, in the number, the variety, and the dissimilarity of their symptoms, consist of only one, or of a small number of primitive or essential elements, all the rest are acces- sory, and depend on numerous sympathies of the affected organ, with the other organs ofthe animal ceconomy. Thus, if the stomach is the seat of irritation, from foulness of its contents, pains of all kinds come on, but espe- cially in the head and limbs, with a burning heat, nausea, loss of appetite, anxiety, and these symptoms constitute a disease, which appears to affect the whole system. To go on with the same illustration, the stomach, when oppressed by ir- ritating substances, contracts spontaneously to get rid of them. The uni- versal disturbance which their presence occasions, seems directed towards the same end, as if the suffering organ called upon all the others to assist in relieving it. These synergies, or aggregate motions, tending to one end, and arising outx ofthe laws of sympathy, constitute the diseases termed general, as well as the greater part of those which are called local. It is by means of them, and through these kinds of organic insurrections, if we may be permitted to use that expression, which perfectly expresses our meaning, that nature struggles with advantage, and rids herself of the morbific principle, or ofthe cause ofthe disease ; and the art of exciting and directing these actions, fur- oishes the materials ofthe most important doctrines ofthe practice of medi- cine. I have used the terms excite and direct : for it is necessary at times to increase, at others to diminish their intensity and force, and on some oc- casions to excite them, when nature, overwhelmed under disease, is almost incapable of re-action. This last circumstance belongs to the diseases of the most dangerous kind, if we include those in which the efforts of nature, * Sympathy may be considered to be that state which an organ or texture presents, which holds a certain relation to the condition which characterizes another organ or tex- ture, in health or in disease: or it may be viewed as a certain relative state of the vital power as it exists in separate organs or textures ; as when one part is excited an- other participates in the change and evinces a similar feeling, motion, or function. Sympathies may be classed into the reflex and direct. The former may be chiefly 4 referred to the cerebral nerves and to the reaction of the sensorium, as when the Schneiderian membrane is irritated the diaphragm is affected in consequence of the excitement conveyed to the brain, and thence to this muscle by means of its volun- tary nerves. The latter class takes place independently of the sensorium, and arises. •'{ from the ramification and distribution of the ganglial nerves, especially those which .are sent to the vascular system. For the elucidation of this subject, see APPENDIX. NatfcE. 27 though marked by a certain degree of energy, are without connection, or consent, and frustrated by their want of coherence. The character of these affections was first well expressed by Selle, who substituted, for the term malignant, which used to be applied to them without any precise meaning, that of ataxic, which points out very correctly, the want of order, and the irregular succession of their symptoms*. A knowledge of sympathies is of the highest importance in the practice of medicine j. When we wish to avert an irritation fixed in a diseased or- gan, experience and observation prove, that it is on the organ which bears to it the closest sympathetic connexions, that it is useful to apply medicines intended to excite counter-irritation. This might perhaps be the fittest place to inquire into the nature of those concealed relations which draw men together, and of those aversions which prevent their union ; to discover the causes of those secret impulses which lead two beings towards each other, and force them to yield to an irresisti- ble propensity. We might inquire into the reason of antipathy, and in a word, establish the complete theory of moral sentiments and affections. Such an undertaking is greatly above our strength, and besides, does not absolute- ly belong to our subject. It would require a considerable time, and who- ever should undertake it, would be in considerable danger of losing his way at every step, in the extensive field of conjectures. § VII. OF HABIT. It is easier to feel the meaning of this term than to define it. Habit, how- ever, may be said to consist in the frequent repetition of certain acts, of cer- tain motions, in which the whole body participates, or only some of its parts. The • most remarkable effect of habit, is to weaken after a time the sensi- bility of organsJ. Thus, a catheter introduced along the urethra, and allow- ed to remain there, causes during the first day, rather sharp pain, on the second day, it feels less uneasy ; on the third day, it i3 only troublesome ; and on the fourth, the patient scarcely feels it. The use of snuff at first in- creases the secretion of mucus in the nose, but if continued a certain time, it ceases to affect the pituitary membrane, and the secretion would diminish considerably but for the practice of increasing daily the quantity of that acrid powder ; the presence of a canula in the nasal duct, after the opera- tion for fistula lachrymalis, increases at first the mucous secretion of that ca- nal ; but in proportion as it becomes accustomed to the extraneous body, the secretion returns to its natural condition. It is only by our sensations that we are aware of our existence. Life, to -make use ofthe figurative language of system, of a modern writer, consists * Symptomata nervosa, nee inter se, neque causis manifestis respondentia. Ordo. tert. atactae, €. G. Selle. Rudimenta pyretologiae methodicte. f This information may be obtained by consulting the works of the ancients, and especially of Hippocrates, who appears to have felt all the importance ot this subject. Among the moderns, Vanhelmont, Baglivi, Rega, Whytt, Hunter Barthez, and Bichat, have collected on this subject, a great number of facts obtained from experiments on animals, and especially from observations on diseases.—Author slSote. X The influence of habit is chiefly perceptible on the organs ot sense and voluntary motion. . . . Habit produces verv different effects upon separate parts of the animal ceconomy ac- cording as they are altogether removed from the influence of the will, or as they are more or lessor entirely subjected to it; the effects of habit, for instance, on our voluntary organs, differ very much from those which result from its operation on the viscera or or- ganic life. See APPENDIX, Note F. 28 in the action of stimuli on the vital powers. (Tota vita, quanta est, consisiit in stimulo, et vi vitali. Brown.) Sentient beings feel a continual necessity ot renewed emotions ; all their actions tend to the obtaining agreeable or dis- agreeable sensations ; for in the absence of other sensations, pain is some- times attended wtth enjoyment. Those who have exhausted every kind of enjoyment, and who have had no pleasures ungratffied, are led to suicide from a weariness of life ; who can live, when all power of feeling is gone 1 The following is the most extraordinary and remarkable instance known, ofthe manner in which habit and a frequent repetition ofthe same impres- sions, wear out by degrees the sensibility of organs. A shepherd, about the age of fifteen, became addicted to onanism, and to such a degree, as to prac- tise it seven or eight times in a day. Emission became at last so difficult, that he would strive for an hour, and then discharge only a few drops of blood. At the age of six and twenty his hand became insufficient, all he Could do, was to keep the penis in a continual state of priapism. He then bethought himself of tickling the internal part of his urethra, by means of a bit of wood six inches long, and he would spend in that occupation several hours, while tending his flock in the solitude ofthe mountains'. By a con- tinuation of this titillation for sixteen years, the canal ofthe urethra became hard, callous, and insensible. The piece of wood then became as ineffectual as his hand ; at last, after much fruitless effort, G, one day, in despair, drew from his pocket a blunt knife, and made an incision into his glands, along the course ofthe urethra ; this operation, which would have been painful to any one else, was in him attended with a sensation of pleasure, followed by a co- pious emission. He had recourse to his new discovery, every time his de- sires returned. When after an incision into the cavernous bodies the blood flowed profusely, he stopped the hemorrhage, by applying around the penis a pretty tight ligature. At last, after repeating the same process perhaps a thousand times, he ended in splitting his penis into two equal parts, from the meatus urinarius to the scrotum, very near to the symphysis pubis. When he had got so far, unable to carry his incision any farther, and again reduced to new privations, he had recourse to a piece of wood, shorter than the for- mer : he introduced it into what remained of the urethra, and exciting at pleasure the extremities of the ejaculatory ducts, he provoked easily the discharge of semen. He continued this about ten years, after that long space of time, he one day introduced his bit of wood so carelessly that it slipped from his fingers and dropped into the bladder. Excruciating pain and serious symptoms came on. The patient was conveyed to the Hospital at Narbonne. The surgeon, surprised at the sight of two penes of ordinary size, both capable of erection, and in that stage diverging on both sides, and seeing besides from the scars and from the callous edges ofthe division, that this conformation was not congenital, obliged the patient to gi«e-him an ac- count of his life, which he did, with the details which have been related. This wretch was cut as for the stone, recovered ofthe operation, but died three months after, of an abscess in the right side ofthe chest, his phthisical state having been evidently brought on by the practice of onanism carried on nearly forty years*. The habit of suffering, renders us in the end insensible to pain ; but every thing in this world is balanced, and if habit lightens our evils, l-y blunting sensibility, it on the other hand drains the source of our sweetest enjoyments. Pleasure and pain, these two extremes of sensation, in a man- Chopart, maladies des vole's urinaires. Tome II. lit» nep, approximate to each other, and become indifferent to him who is ac- customed to them. Hence arises inconstancy, or rather that insatiable de- sire of varying the objects of our inclinations, that imperious want of new emotions ; hence we possess with indifference what we pursued with the utmost ardour and perseverance, and even cease to be impressed by those charms which once held us captivated. A striking instance ofthe powerful influence of habit on the action of or- gans, is afforded by that criminal, who, we are told by Sanctorius, was taken ill on being removed from a noisome dungeon, and did not recover till he was replaced in the impure air to which he had been long accustomed. Mi- thridates, that formidable rival of the Roman power, dreading to be taken alive by his enemies, tried in vain to put an end to his life, by taking large doses ofthe most subtle poisons, because he had long inured himself to their action*. It has, therefore, been justly said of habit, that it is a second na- ture, whose laws ought to be respected. The organs of generation in women, in consequence of their lively sensi- bility, are in an especial manner submitted to the powerful influence of habit. The womb, after a miscarriage, has a tendency to a renewal of the same occurrence, when the same period of pregnancy recurs, so that the greatest precautions are necessary to prevent abortion in women, who are subject to it, when they have reached the month in which they before mis- carried. May not death be considered as a natural consequence of the laws of sen- sibility ? Life, depending on the continual excitement of the living solids by the fluids which moisten them, ceases, because the parts endowed with sen- sibility and contractility, after long habitude ofthe impressions of those fluids, lose their capacity of feeling them. Their action gradually extinguished, would perhaps revive, if the energy ofthe stimulating power were increased. A knowledge of the power of habit, is a useful guide in the application of remedies, the greatest part of which operate in the cure of diseases, only by modifying sensibility. A wound in which lint has kept up the degree of in- flammation necessary to cicatrization, becomes insensible to that applica- tion, the parts become spungy and soft, and the cure is protracted. J he lint should then be covered with an irritating powder, and the pledgits soak- ed in an active fluid : one may safely increase the doses of a medicine which has been long employed. Thus, in the treatment ofthe venereal disease by mercurials, the dose is to be gradually increased ; with the same view, Frederic Hoffman recommended in the treatment of chronic diseases, that the remedies should be suspended for a time and then resumed, lest the sys- tem should get accustomed to them, and their influence be lost. The same motive should lead one to vary the treatment, and to employ, in succession, those medicines to which nearly the same qualities are assigned, for, each of them call forth the sensibility in a peculiar manner. The nervous sys- tem may be compared to an earth abounding in various juices, and tor a full display of whose fecundity, it is necessary that the husbandman commit to it the germs of various plants. It is very remarkable that habit, or the frequent repetition of the same act, which uniformly, under all circumstances, and in all organs, blunts * In some very rare cases, habit produces a quite contrary effect Cullen states that heknew persons so accustomed to excite vomiting in themselves, that the twentieth^part of a Ri-ain of tartar emetic was sufficient to excite a convulsive action ofthe stomach.- Aalhor'it Note. 30 physical sensibility, should improve the intellect*, and increase the facility, and activity of execution of all the operations ofthe understanding, or ofthe actions which depend on them. '• Habit impairs the sensitive power, and improves the judgment." Bichat was therefore incorrect, when in his dis- tinction ofthe organs which are subservient to the functions of assimilation, from those which serve to keep up our relation with the surrounding objects : he maintained, that the sensibility of the latter becomes more exquisite, while tbe sensibility ofthe former becomes impaired from habit. But can a painter, because he judges more correctly than the ignorant, of the beauties of a picture, be said to see it better ? Surely not, for, he may with a sight far iess penetratiug, and more infirm, form a more accurate analysis, from the habit which he has acquired, and judge with a great deal more promptitude and certainty, of the several parts of the whole ; just as the practised ear ofthe musician seizes, in a piece of music, and during the most rapid execution, the expression and the value of all the notes and tones. The error has arisen, from its being forgotten, that, correctly speaking, it is not the eyes that see, or the ears that hear ; that the impressions produced by the sounds on these organs, are but the occasional cause ofthe sensation, or of the perception of which the brain is the exclusive seat. Which has the more delicate sense of hearing, the North American savage, who hears the noise of the step of his enemies, at distances that astonish us, or the artist who does not hear a person speaking at the distance of fifty paces from him, but who directs with judgment, all the operations of a great or- chestra, and who distinguishes skilfully, the effect of each part ? Bringdown to a frugal Pythagorean regimen, one of our modern epicures : his palate, exhausted of its sensibility by the most savoury dishes, by ardent liquors, and the most exquisite ragouts, will discover no taste in dry bread. Let him, however, live on bread, if he can, for some time, it will soon ap- pear to bim to have a grateful taste, as it does to those who make it their principal article of food, or who take it only with substances which have not a very distinct taste Although with the sense of smell, that of taste furnishes us only with ideas the most directly connected with our preservation, those which most turn upon the wants of our animal nature : although we retain, with difficulty, the impressions of these senses, and that, to enable us to re- tain them, they must be often repeated ; the epicure had so carefully ana- lyzed them, that he had attained to the discernment ofthe faintest differences of taste, all those delicacies of sensation, which, as Montesquieu said, are lost to us vulgar eaters. The motions, under the direction ofthe will, acquire by the precision of the determinations, the same aptness, facility, and readiness, and the dancer, who surprises us with his agility, has reflected, more than might be imagined, on the very complicated steps of which a ballet is composed. Morbid sensibility, is equally under the influence of habit. I have always observed, that discharges from the urethra become less painful from their frequency. There is nothing down to disease itself, that is not made ligther by habit, as has been well observed by the old man of Cos. It remains then demonstrated, even as a general thesis, that habit, or the frequent repetition ofthe same acts, whilst it regularly reduces physical sen- sibility, improves intelligence, and gives facility and promptness to all the motions that are under the direction ofthe will. * As soon as an act fails to excite our sensations, in an inordinate degree, at least, the reasoning powers proceed to analyse its nature: as sensation ceases, reflection com- mences ; an exquisite state ofthe former is seldom compatible with a sound judgment. 31 § IX. OF THE VITAL PRINCIPLE *. The words vital principle, vital force, &c. do not express a being existing by itself, and independently ofthe actions by which it is manifested : it must be used only as an abridged formula, which serves to mark the total of the powers that animate living bodies, and distinguishes them from inert matter. So that, whenever, in the course of this section, I shall use these terms, or any equivalent, it is to be taken as if I had said, the aggregate ofthe proper- ties and laws that regulate the animal oeconomy. This explanation is be- come indispensable, now that several writers, realizing a mere abstraction, have spoken of the vital principle, as of something very distinct from the body, as of a being altogether separable, which they have invested withfeel- ing, and thought, and even deliberate intentions From the furthest antiquity, the many and striking differences of living, and inorganic bodies, have led some philosophers to conceive in the former, a principle of particular actions, a force which maintains the harmony of their functions, and directs them all to a common end. the preservation of individuals and of the species. This simple and luminous doctrine, has re- mained, even to our own days, only modified in its passage through many years : and, no one now disputes the existence of a principle of life, which subjects the beings, that enjoy it, to a system of laws different from those which inanimate beings obey ; a force which might be characterized, as withdrawing the bodies it animates, from the absolute dominion of chemical affinities, which would else, from the multiplicity of their elements, act on them with great power ; and as maintaining them in a nearly equal tempera- ture, whatever may be that ofthe atmosphere. Its essence is not in pre- serving the aggregation of constituent molecules, but in drawing to it other molecules, which, by assimilation to the organs it pervades, replace those that are carried off in daily waste, and serve for their nourishment and growth. All the phenomena that are to be observed in the living human body,* might be brought as proofs of the principle which animates it.—The actions of the digestive organs on its food ; the absorption, by the chylous vessels, of its nutritious parts ; the circulation of these nutritious juices through the san- guineous system ; the changes they undergo in their passage through the lungs, and the secretory glands ; the impressibility by outward objects ; the power of approaching or avoiding them ; in a word, all the functions that are carried on throughout the animal ceconomy, proclaim its existence. But it is customary to take a proof of it yet more direct, from the properties with which the organs of these functions are endowed. We have examined these properties, and we have seen that each of them presents us with, at least, two great modifications ; that the last discovers three, which are, voluntary contractility, contractility involuntary and insensible, Stahl's tonic motion ; and lastly, contractility involuntary and sensible, as that of the heart and the intestines. If it is useful to analyse, in order to know, it is of equal importance not to multiply causes, from misconceiving the nature of effects. And, if, on the one hand, the multitude ofthe phenomena of life, inclines us to the be- lief of many causes to produce them ; the unfailing harmony that pervades all the actions, their mutual connexions, and reciprocal dependencies, point * See APPENDIX, Note A much more decisively to a sole agent, as causing, directing, and controuling* these phenomena. , The hypothesis ofthe vital principle, is to the philosophy of living beings, what attraction is to astronomy. To calculate the revolutions of the planets, this science is compelled to recognize a force, which draws them constantly towards the sun, and constrains their tendency to fly from it, within the measured distance of those ellipses, which they describe around that common centre of light and heat, which dispenses to them, as they roll, the precious germs of life and of fertility. We are about to speak of this force, to which all the powers that animate each separate organ, join them- selves, and in which all the vital powers are blended, but under the declara- tion, for the second time, of using the term only in a metaphorical sense. Without this precaution, I might lead you into all the false reasonings, which those have fallen into, who have assigned to it a real and separate ex- istence. The vital power is in perpetual strife with the powers that govern inani- mate bodies. The laws of individual nature are, according to the saying of antiquity, for ever struggling against those of universal nature ; and life, which is only this contest prolonged, in favour, altogether, ofthe vital pow- ers, during health, but with uncertain issue in disease, is at an end, the mo- ment in which the bodies endowed with it, fall again into the system of life- less being This constant opposition of vital to physical laws, both me- chanical and chemical, does not withdraw, altogether, living bodies from the controul of these laws. There are effects always going on in the liv- ing being, chemical, physical, and mechanical : only these effects are con- stantly influenced, modified, and altered by the powers of life*. Why, when we stand up, are not all the humours carried down to the lower parts, by the force of gravitation ? The vital power resists the com- pletion of this hydrostatic phenomenon, and neutralizes this tendency ofthe , fluids, the more successfully as the individual is more robust and vigorous. If it is one enfeebled by previous disease, the propensity will be but imper- fectly repressed : the feet, after a certain time, swell ; and this oedematous swelling can be ascribed only to the insufficient energy ofthe vital powers, which determine the distribution ofthe fluids, &c. When a tumbler throws himself backwards, the blood does not flow alto- gether to his head, though this is become the lowest part; yet the natural tendency of fluids downwards is not altogether overcome ; it is only dimi- nished ; for if he preserve long the same attitude, the struggle ofthe hydrau- lic and vital powers becomes unequal : the former prevail; they accumulate the blood upon the brain ; and the man dies. The following experiment proves incontestably, what has just been said ofthe power of resistance, which, in the human body, more or less, effec- tually counterbalances the force of physical laws. 1 applied bags filled with very hot sand, along the leg and foot of a man whose artery had been tied by two ligatures, in the hollow of the ham, for popliteal aneurism. Not only the limb was not chilled, which is what happens when the course of the blood is intercepted, but the extremity thus covered, acquired a heat much above the ordinary temperature ofthe body. The same apparatus applied * In proof of this may be adduced the observation long since made by Dr Alexan- der, that the range of temperature most favourable to the putrefaction of dead animal matter, being between 86° and 100« of Fahrenheit, includes the usual standard of human heat. 33 to the sound leg, did not produce this excess of heat, certainly, because the fulness of life, in that limb, resisted the physical action. The vital principle seems to act with the greater energy, as the sphere of its activity is narrowed ; which has led Pliny to say, that it was chiefly in the smallest things that Nature has shown the fulness of her power*. The circulation is quicker, the pulse more frequent, the determinations more prompt, in men of short stature. Such was the great Alexander: never did man of colossal make display great activity of imagination: none of them have glowed with the fire of genius. Slow in their actions, moderate in their desires, they obey without murmuring the will that governs them, and seem made for slavery. Agrippa (says Omilius Probus, in his History of Augustus) advised that they should disband the Spanish guard, and that in its room, Caesar should choose one of German, "wotting well, that in these " large bodies, there was little of coverte malice, and yet lesse of subtiltie, " and that it was a people more minded to be ruled than to rule." To judge soundly ofthe remarkable difference which inequality of stature brings into the character, compare extremes ; set against a Colossus, a little man of diminutive stature ; granting, nevertheless, to this last, full and vigor- ous health. You may guess that he is talkative, stirring, always in action, always changing his place ; one would say that he is labouring to recover in time, what he has lost in space. The probable reason of this difference in the vital activity, following the difference of stature, arises from the relative bulk ofthe primary organs of life. The heart, the viscera of digestion, &c. are of nearly the same bulk in all men: in all, the great cavities are nearly ofthe same extent, and it is principally in the length of the lower limbs that the difference of stature will be found to lie. It is easily conceivable, that the viscera supplying the same quantity of nutritious juices to a smaller bulk, that the heart giving the same impulse to blood which is to traverse a shorter course, all the functions will be executed with greater rapidity and energy. By an obvious consequence, the diseases of little men have a more acute character ; they are more vehement, and tend more rapidly to their crisisf. They have in them something of the velocity, I would even say the insta- bility of morbid re-action during infancy. There is nothing even to the duration of life, on which the differences of stature have not some influence. With this suspicion, and some curiosity to ascertain its justness, I have made inquiries in the hospitals, when people in advanced life are taken in, and I found them, for the most part, occupied by old men above the middle size; so that reasoning and observation concur in showing that all things else being equal, those of superior stature have a grounded hope of prolonging their life beyond the ordinary term. I have observed with many others, that the whole body unfailingly re- ceives an increase of vigour, from the amputation of a limb. Frequently, after the loss of a part of the body, you will see a manifest change take place in the temperament; those that were weak, even before the disease which brings on the necessity ofthe operation, becoming robust: affections, chronic from debility, such as scrophula, tabes mesenterica, dissipated ; glandular swellings resolved ; which indicates a very remarkable increase in the actions of all the organsj. * Nusquam mugis quam in minimis est. tola Naiura. Hist. Nat. lib. II. cap. 2. tThe acute diseases of tropical countries, especially fever, prove more iatal to short men, or those of middle size, than to the tall. X The extraordinary developement of an organ never takes place but at the expense ot those about it, of which it draws off the juices. Aristotle observes, that the lower ex- 34 The parts most remote from the centre of circulation are, in general, less alive than those which are nearer. Wounds ofthe legs and feet, are more liable to ulcerate, because, besides the circulation of the fluids, which the slightest weakness greatly retards in them, their life is too feeble for their wounds to go quickly through their periods, and readily cicatrize. 1 he toes freeze first, when we remain too long exposed to severe cold ; it is in them too that the mortification begins, which sometimes attacks a limb after the ligature of its vessels. Thus, although we may say, that the principle of life is not seated in any part of our being, that it animates every system of organs, every separate organ, every living molecule, that it endows them with different properties, and assigns to them, in some sort specific characters, it mast be confessed, that there are in the lving body some parts more alive, from which all the others seem to derive motion and life. We have already seen that these central organs, these foci of vitality, in whose life that of the whole body is involved, diminish gradually in number in the animal kinds, as they are more removed from man, whilst the fewer they are, the more they are spread out over the body ; so that life is more generally diffused, and its pheno- mena less rigorously and strictly connected, as we descend in the scale of being, fronTthe red and warm-blooded, to the red and cold-blooded ani- mals, from these to the mollusca, the Crustacea, worms and insects, to the polypus, who forms the extreme link ofthe animal chain, and lastly, to plants, of which not a few, like the zoophytes, so similar to them in many respects, are endowed with the remarkable property of reproduction by slips ; which implies, that each part contains the aggregate of organs neces- ary to life, and can exist alone. The vital principle has by some been confounded with the rational soul; but others have distinguished it from that emanation of divinity, to which, as much as to the perfection of his organization, man owes his superiority to all the animal kinds. What bond unites the material principle, which re- ceives impressions and transmits them, to the intelligence which feels, per- ceives, examines, compares, judges, and reasons on them ? Were man one, says Hippocrates, did his material principle make up his whole nature, plea- sure and pain would be as nothing to him ; he would be without sensation : for, how could he account to himself for impressions ? Si unus esset homo, non doleret, quia nen sciret unde doleret. Here we stand on the confines of physiology and metaphysics ; let us beware of setting foot in the dim paths that are before us : the torch of observation would yield but ineffectual light, too fiiint to dispel the thick darkness that lies over them. The vital power is merely the vis medicatrix naturce, more powerful than the physician, in the cure of many diseases ; the art of the physician consisting, in most cases, in awakening or directing the action of that power. When a thorn is thrust into a part endowed with sensibility, a sharp pain is felt, the fluids rush in abundance to the part, it becomes red and swollen ; tremities are most always dry, and wasted in those who are of urgent temperament, or in habits of frequent venery. Hippocrates relates in his work (De are, locis, et aquis, Foes : fol. 293.) that the Scythian women seared their right breast, that the arm on that side might grow in size and strength. Galen speaks of Athletes, who, in his time, kept the sexual organs in the most entire inaction, that withered, shrunk, and perished, in some sort, by this absolute repose, they might not draw off the nutritious juices, fromthe sole nourishment ofthe muscular organs. A young man, who has several times carried off the prize by running at the public fetes, abstains from venery for some months before entering the lists, in perfect certainty of victory, after this privation. Avthor.i note 3;j all the vital powers are excited, the sensibility becomes more acute, lh^ contractility greater, and the temperature rises. Does not this increase of vital energy in the injured part, this process which takes place, around the substance that is the cause ofthe disorder ; those means which are provided to expel it, indicate the existence of a preserving principle, incessantly watching over the harmony ofthe functions, and struggling against all the powers that may tend to interrupt its exercise, or to annihilate the vital motion ? Theory of inflammation*. Inflammation may, I believe, be defined ; the increase of vital properties in the part, which it affects. Sensibility becomes more acute in the part so affected, its contractility greater ; and from that increase of sensibility and action, arise all the symptoms characteristic of inflammation. Thus the pain, the swelling, the redness, the heat, and the difference in the state ofthe secretions, denote in the part a more energetic and active vitality. Those who have objected to the definition which I have given of inflamma- tion, have evidently mistaken the functions of the organs for their proper- ties. It is very true, that inflammation ofthe eye is attended with loss of sight, but that circumstance depends on the opacity ofthe transparent parts which should transmit the luminous rays to the retina. The sight is pre vented by a mechanical obstacle, but the sensibility ofthe organ is augment- ed to such a degree, that the faintest light reaching the bottom ofthe eye, through the transparent cornea dimmed by the congestion of the vessels, causes in it intolerable pain. On this principle, darkness is universally re- commended to patients affected with ophthalmia In like manner, when a muscle is inflamed, the action of the fibre, its decurtation, is prevented by the congestion in the cellular membrane, which covers it and fills its interstices. The cause preventing contraction, or the exercise of contractility, is me- chanical, and may be compared to that, which, in an inflamed lung, opposes the admission of air, and the passage ofthe blood, from the right to the left side of the heart. Can any one call in question the increase of vital action in peripneumony ? I am therefore of opinion, that the above definition is bet- ter than that proposed by Bichat, in his " Anatomie generale," a work of later date than the first edition of these elements of physiology, and in which he makes inflammation to consist in the increase of those vital properties which he terms insensible. All the parts of the human body, with the exception of the epidermis and its different productions, as the nails and the hair, appear capable of inflam- mation. One might include among these " epidermoid" parts, certain dry and slender tendons, as those of the flexors of the fingers, which, when pricked, lacerated and irritated in a thousand ways, are insensible to pain, and remain uninjured in the midst of a whitlow, though attended with sup- puration of all the neighbouring soft parts; and when exposed to the air, they exfoliate instead of granulating. Organization is so indistinct in all these parts, life so feeble and languid, that they remain insensible to the impression of all those causes which might tend to increase its activity. The degree of sensibility in a part, the number and size ofthe nerves and vessels which are sent into it, determine the degree of ii'i aptitude to in- flammation ; thus the bones and cartilages inflame with considerable diffi- culty. When one of these parts is laid bare, the first effect of the irritation See APPENDIX. Note G 3ti to whfch it is exposed, is a softening of its substance. W hen a bone is laid bare, it becomes cartilaginous and softens, in consequence of the absorp- tion ofthe phosphate of lime which fills up the interstices of its tissue ; and it is only after this kind of incarnation, that fleshy granulations begin to spout, as may be observed on the extremities of bones after amputation. The difficulty with which inflammation is set up in the harder parts ofthe body, explains why, before the twelfth or fifteenth day after a fracture, it is of little consequence towards union of the bone, that the fractured ends should be placed in opposition : not that it is right to wait so long, before applying the proper bandages, which are indispensable from the first, to prevent the pain and laceration occasioned by the displaced bone 1 he blood is determined, from all quarters, towards the irritated and painful part, which swells and assumes a red colour, from the presence of that fluid. The swelling would be unlimited, if, at the same time that the arteries increase in power and calibre, to occasion that determination, the veins and lymphatics did not acquire a corresponding energy, to enable them to re- lieve the part, of the fluids which have accumulated in it. and which irrita- tion is constantly determining to it. The power of irritability and contrac- tility increases with sensibility ; the circulation is more rapid in the in- flamed part ; the pulsations of the capillary vessels are manifest. The part is likewise hotter, because, in a given time, there passes through its tissue more arterial blood, from which a larger quantity of caloric is disengaged, and the continued effects ofthe pulmonary respiration are better marked in it than in any other organ. It forms no part of our intention to treat of the varieties of inflammation : they depend principally on the structure of the organ which is affected, on the violence and rapidity ofthe symptoms, and on its effects. Is not the turgescence of an inflamed part occasioned in the same man- ner, as in parts subject to erection, as the corpora cavernosa of the penis and of the clitoris, the nipples, the iris, &.c? In erection of the penis, as in inflammation, there is an irritation, a determination of fluids to the part, an increase of sensibility and contractility ; yet its condition is not that of inflammation. Nature has so disposed the organization of these parts, that they can sustain, without injury, those instantaneous augmentations of vital energy, necessary to the exercise ofthe functions performed by the organs to which they belong. As in inflammation, these congestions disappear, when the cause of irritation has ceased to act ; thus, the pupil dilates, be- cause the iris recedes, when the eye is no longer exposed to the rays of a vivid light. The penis returns to its naturally flaccid and soft state, when no irritation operates to determine to it the fluids, whose presence, as long as the erection lasts, is easily explained by the continuance ofthe ir- ritation, without its being necessary to have recourse to mechanical expla- nations, to account for that phenomenon. When the irritation, which pro- duces the vital turgescence of the penis or iris, is carried too far, or con- tinues too long, the natural congestion becomes morbid. It is well known, that priapism is frequently attended with mortification of the penis, and that the too long continued action of light on the eye, brings on inflammation of that organ. The preceding observations on inflammation show, that an acquaintance with its phenomena is useful, even in a physiological point of view. The vital processes, which in some organs take place in so obscure a manner that they are imperceptible, acquire in inflammation a character of rapidity 37 and intensity, which renders it much easier to observe and recognize them. Considered in a general and abstract point of view, amd merely with a refer- ence to its object, inflammation may be considered as a means employed by nature, to repel the influence of noxious agents, which, when introduced within the body, or on its surface, she has no power of resisting, but by a more active developement ofthe powers which animate it. During the severe winter of 1793, the chemist Pelletier repeated the ce- lebrated experiment of freezing mercury, and obtained a solid ball in the bulb of a barometer, which he had for a long while kept immersed in the midst of a quantity of ice, continually moistened with nitric acid When the metal had attained a completely solid state, he drew the ball from the bulb, and placed it on his hand. The heat ot the part, joined to that ofthe at- mosphere, soon restored the quicksilver to its fluid state : at the same instant, he experienced in his hand so intolerable a degree of cold, that he was obliged to drop the quicksilver instantly. There soon came on, in the pain- ful and chilled part, a phlegmonous inflammation, which was cured by reso- lution. Quicksilver, in a solid state, is one ofthe coldest bodies in nature : how very rapidly the caloric must have been carried off in this case, and how deep the impression must have been in the palm ofthe hand, doubly affect- ed by the cold, and by the vital re-action, which terminated in inflammation ! I have produced a similar effect, by endeavouring to melt a piece of ice in my hand, during the heat of summer. In this experiment, the impression of cold is soon succeeded by a sensation of acute pain and extraordinary throb- bings, in the hand and fore arm. When the two hands are afterwards com- pared, that which held the piece of ice is extremely red, from the congestion of blood in the cutaneous capillary tissue, and is very different in its appear- ance, from that which was not the subject of experiment. Analogous facts, if seriously considered, should induce the followers of Brown to apply to the effects of cold, the distinction which he applied to debility, of direct and indirect. They would have no difficulty in ascertain- ing, that in its medical application, that negative state of caloric, which is di- rectly debilitating, may, nevertheless, by the re-action which it excites, be considered as an indirect tonic. § X. OF THE SYSTEM OF THE GREAT SYMPATHETIC NERVES*. The great sympathetic nerves are to be considered as the bond destined to unite the organs ofthe nutritive functions, by whose action man grows, is evolved, and incessantly repairs the continual waste attending the vital mo- tions. They form a nervous system, very distinct from the system of the cerebral nerves ; and, as the latter are the instruments ofthe functions by which we hold intercourse with external objects, the great sympathetic nerves supply motion and life to the organs of the inward, assimilating, or nutritive functions. In animals, without vertebra?, may not the nervous system, which floats in the great cavities with the viscera which they contain, be considered as consisting entirely of the great sympathetics | ? These nerves are princi- * See APPENDIX, Note H. f Treviranus, in his Biologic, considers the knotted cord found in the abdomen cf insects and worms to be the vertebral ganglia of the sympathetic nerve. That it cannot be considered a spinal cord is evident: its situation sufficiently shows the difference. The mollusca, and many animals removed a little above this class in the scale of crea- tion, possess merely single ganglia, from which proceed fibrillar to the different organs. 3» pally distributed to the organs of inward life, whose activity* in those ani- mals, seems to grow, in proportion as their external senses, and their faculty of locomotion, are imperfect. If the great sympathies exist in all the ani- mals which have a distinct nervous system, do they not, in an especial manner, contain the principle of vegetable life, essential to the existence of every organized body possessing the power of digestion, absorption, circu- lation, secretion, and nutrition ? Finally, is it not probable, that m man, the system ofthe great sympathetic nerves, has a very great share in occa- sioning a number of diseases, and that the impressions with which patients are affected, are referred to their numerous ganglions, while the brain is ex- clusively the seat of intellect and thought* ? These suggestions will, doubtless, be answered in the affirmative, if one considers the origin, the distribution, and the peculiar structure of these nerves, the acute sensibility of their branches, as well as the disorders at- tending their injury. Extended along the vertebral column, from the base of the skull to the lower part of the sacrum, these great nerves, in some measure parasitic, do not arise from the branches supplied them by the fifth and sixth pairs aris- ing from each side of the brain ; they live and are nourished, as it were, at the expence of all the nerves ofthe spinal marrow, from which they re- ceive branches, so that there is not one of them, from which one can say, that the great sympathies arise exclusively. 1 he numerous ganglions which are distributed along their course, divide them into se many small systems, from which arise the nerves ofthe organs nearest to them. Amid these bulg- ings, considered by several physiologists, as so many little brains, in which is performed the elaboration ofthe fluid which they transmit to the nerves, no one is of more importance than the semi-lunar ganglion, situate behind the organs which occupy the epigaitric region, and from which those nerves originate, which are distributed to the greater part of the viscera of the abdomen. It is to the region occupied by that gapglion, in which the great sympathetic nerves unite, and which may be considered as the centre ofthe system formed by their union, that we refer all our agreeable sensations ; there it is that we feel in sadness, a construction which is commonly referred to the heart. Thence, in the sad emotions of the soul, seem to originate those painful irradiations which trouble and disorder the exercise of all the functions |. The numerous filaments ofthe great sympathetic nerves are finer, they are The great sympathetic nerve is " the most general and the most original of all the nerves." Its characters are. however, modified in different classes. " In worms and insects there are merely vertebral ganglia, without the cceliac ganglia of mammalia and birds : in the acephalous mollusca there are the latter, without the former ; in the cuttle-fish and snails there are single ganglia of both kinds." All these animals have no spinal marrow; fishes and reptiles have one, and also vertebral ganglia, but the cceliac is not fully developed in them (see the Observations of Serres and Weber) as in birds and mammalia. These remarks convey the sum ofthe observations made by those who have inquired into the subject. How, therefore, can the ganglial class of nerves be considered to arise from the cerebral and vertebral masses ? * These opinions on the uses of the great sympathetic nerves, are explained in my Essay on the connexion of life with the circulation. This essay was published before any thing that has appeared on the same subject.—Consult the " Memoires de la Societe Mcdicale pour Pan VII." Author's Note. | Consult on the subject of the epigastric centre, Van Helmont, who calls it the archeus; Buffon, Bordeu, Barthez, and Lacaze, who give it the name of the phrenic centre, because they ascribe to the diaphragm what belongs to the nervous ganglion* placed in front of its crura. Author's Note. :;<•) not of the same whitish colour, nor ofthe same consistence as the filaments of the cerebral nerves. Qn that account, they are less easily dissected*, the nervous fibrillar are less distinct, their reddish chords are moister, and they appear formed of a more homogeneous substance ; their membranous co- verings are less considerable. They are likewise endowed with a more acute and more delicate sensibility. Every one knows the danger attend- ing wounds ofthe mesentery, a membranous duplicature, in itself insensible, but containing such numerous nerves destined to the intestinal tube, that the most pointed instrument can scarcely wound the mesentery, without injuring some of their branches. The pain attending affections of the great sympathetic nerves, is of a peculiar kind ; it leads directly to the extinction ofthe vital power. It is a well known fact, that a bruise of the testicles overpowers, in a moment, the strongest man. Every one knows that pa- tients who die of a strangulated hernia, of volvulus, or of every other affec- tion ofthe same kind, die in the most distressing anguish, their heart feels oppressed, and they are tormented with constant vomiting. Intestinal and nephritic colics are attended with the same sort of pain ; that attending in- jection ofthe tunica vaginalis in hydrocele, is of the same kind. And one expects a favourable event of the operation, only in those cases in which the patient has felt pain along the spermatic chord, in the course of the spermatic nerves, which arise, as it is well known, from the renal plexus. In the case of wounds ofthe abdomen, I was led, by the nature ofthe pain which the patients suffered, to prognosticate that the wounds had penetrat- ed ; the event justified my prognostic. In all these affections of the great sympathetic nerves, the pulse is frequent and hard, the face is covered with a cold sweat, the features are sunk ; all the symptoms are alarming, and soon terminate fatally. The use ofthe system ofthe great sympathetic nerves is, not merely to establish a closer connexion and a greater union between all the organs which perform the functions of assimilation, but likewise to free those parts from the influence of the will. A power ofthe mind so fickle and so vary- ing, that life would be in constant danger, if we had it in our power to stop or suspend the exercise of functions with which life is essentially con- nected. If we consider what are the organs to which the functions of assimilation are entrusted, and which receive their nervous influence from the great sympathetic nerves, we shall find that the action of the greater number is wholly independent of the controul ofthe will \. The heart, the stomach, the intestinal canal, &c. do not obey the will, and seem to possess a more in- sulated and more independent existence, and to act and rest, without any in- * One of the best modes of dissecting them is to macerate the part, in which we wish to trace their ramifications, during two or three days in water ; then place it for a short time in a very dilute acid, or warm spirits, or in oil of turpentine. The filaments of these nerves may be then traced more distinctly. Other processes, which are more complex, are requisite to the dissection of the minuter ramifications, especially those which supply the blood-vessels. t All these parts which receive their nerves from ganglions, are equally independent. Professor Chaussier thinks that the upper filaments of the great sympathetic nerves ascend along the internal carotid, and join the sphenopalatine and lenticular ganglions. M. Ribes thinks he has ascertained by dissection, that several very long and slender filaments follow the course ofthe branches of the internal carotid, and like them are sent to the base of the brain, beyond which they cannot be traced. I have myself ob- served, in dissection, these filaments around the branches of the internal carotid artery. but I had always considered them to be formed of cellular substance. Author's Nnff. ' 1U fluence on our part. Some of these organs, as the bladder, the rectum, and the muscles of respiration, which do not receive their nerves exclusively from the great sympathetics, are obedient to the will, and receive from the brain the principle of motion, the former, from the branches which the sacral nerves send to the hypogastric plexuses : the diaphragm, from the nerves which it receives from the fifth and sixth cervical pairs. The great sympathetic nerves supply the diaphragm, the rectum, and bladder, only with nerves of sensation. This provision was a very neces- sary one, for, if, as is the case with the heart, and the intestines, these parts had received their nerves of motion from the great sympathetics, their ac- tion would have been independent of the will, as is the case with all the parts which these nerves supply with motion. The bladder and rectum, placed at the extremities ofthe digestive apparatus, and destined to serve as reservoirs to the excrementitious residue of our solid and liquid aliments, would have been constantly evacuating their contents, as fast as the sub- stances which are destined to be retained within them forsome time, reach- ed their cavity. On the other hand, if the diaphragm had received its nerves of motion fiom the great sympathetics, respiration would have ceased to be a volunta- ry function, of which we might at pleasure accelerate, slacken, or even completely suspend the action. To prove that the act of respiration is un- der thecontroul of the will, we may have recourse to analogy, and adduce the instance of reptiles, as lizards, frogs, serpents, salamanders, and toads, which are cold-blooded animals, and in which this function is manifestly voluntary. We may further mention those slaves, who, we are told by Galen, put them- selves to death, when summoned before their executioners or judges. Ac- cording to that physiologist, and others, they choked themselves by swal- lowing their tongue. But it is sufficient to know how the muscles that bind down the tongue are situated, and the degree of motion which they allow, to see how little ground there is for that opinion. The action of the brain would, in that case, have been no longer necessary to the maintenance of life ; in an animal without a brain, respiration would have continued, and the circulation would not have been interrupted. The death of that viscus would not have been attended with the sudden death of all the rest. The nerves which arise from the spinal marrow, and which give to the diaphragm the power of contraction, a power which that muscle loses sud- denly, if these nerves be tied, appear to me the chief links which unite the internal assimilating or nutritive functions, to those which keep up the rela- tion of the animal with external objects. Without this bond of union, the series of vital phenomena would have been less close, and their dependence less necessary. Had it not been for the uecessity that the diaphragm should receive from the brain, by means ofthe phrenic nerves, the principle which determines its contractions, acephalous animals, which are born without that organ, might continue to live as they did before birth, when the organs of nutritive life received blood, which had undergone, in the lungs ofthe mo- ther, the changes necessary to life. But where the bond which united them to the mother is destroyed, obliged themselves to produce in their fluids, the necessary changes, by the inhalation ofthe vivifying principle contained in the atmosphere, they no longer can obey that necessity ; the organs of respiration are deficient in the principle which should excite them. -11 When an internal inflammation is of small extent*, and is seated in a part in which there are not many nerves, and whose tissue yields easily to the humours which irritation determines into it, the whole morbid action takes place in the affected part, and the general order of the functions is not sensi- bly deranged. But when inflammation takes place in a part endowed with much sensibility, or of a close texture, as the fingers and toes, then fever comes on, because a sympathy in the morbid action takes place, between the diseased part and the rest ofthe system. This diffusion ofthe local action almost infallibly takes place, when inflammation occurs in one ofthe organs of the assimilating functions. This effect may be considered as uniform, though Morgagni mentions several instances of inflammation Of the liver, marked by no peculiar symptoms. A knowledge ofthe great sympathetic nerves accounts for this difference. When an external part is affected with inflammation, the irritation which it suffers, is by means of its nerves propagated to the brain, which by a re-ac- tionj, called by Vicq-d'Azyr (who on this subject has only developed the opinions of Vanhelmont) internal nervous action, transmits that irritation to the heart, to the organs of respiration, of digestion, and of secretion, in which the phenomena, denoting a febrile state, are principally evolved. When, on the contrary, the heart, the lungs, or any other internal organ is affected with acute inflammation, all the viscera partake in the derangement with which any one of them is affected, and without the intervention ofthe brain. They are all intimately connected by the filaments which they re- ceive from the great sympathetic nerves ; and, by means of that nervous system, which is in an especial manner appropriated to them, they carry on a more iutimate intercourse of sensations and affections. Besides, the de- rangement ofthe important functions entrusted to the diseased organs, is ne- cessarily attended with appropriate changes in all the acts ofthe animal ceco- nomy, in the same manner, no doubt, as the defect of one wheel interrupts or disturbs the mechanism ofthe whole machine. There exists in the stomach an union of the cerebral and sympathetic nerves„which explains the manifest dependency, in which that one ofthe three supports of life is found with the brain : a dependency so marked, that every strong affection ofthe soul, every violent agitation ofthe mind, weakens el- even totally suspends the action of digestion in the stomach.—This combi- nation of cerebral and sympathetic nerves likewise accounts tor a pheno- menon, which was mentioned in speaking of the influence of habit on the action ofthe organs. The stomach differs essentially from the intestinal canal; for, far from getting accustomed to the impression of emetics, so as * A thousand pustules in the small-pox occasion only a moderate degree of fever, it they are at a distance from each other ; but if the disease is confluent, that is, if the pustules are close together, and run into each other, the fever becomes considerable, and the patient's life endangered. The fleshy granulations which sprout in abundance from an ulcerated surface, are so many small phlegmons unaccompanied by a febrile state, but if brought close to each other by irritation, that condition will not fail to ensue. Vaccination is not, in the greater number of cases, attended by the slightest febrile ac- tion, if, as 1 always have done, the punctures are made at a certain distance from each other, so that the'inflammatory areolae may not run into each other.—Author's Note. t The cerebral re-action appears to be in no measure necessary to the induction of symptomatic fever: it may, however, contribute to its continuance. The irritation aj> pears to be propagated to the heart in consequence of the numerous connexions which this organ holds, by means ofthe ganglial nerves, with the other viscera ; and owing to the continuous reticulation of these nerves upon the blood-vessel? trr.ru H)p hcavi i0 the '••ruiillarv terminations. <• 12 to become by degrees less sensible to their action, as the intestines to the action of purgatives, though three grains of tartar emetic could, at first, scarcely excite it, half a grain only of that salt is able to bring on vomiting, when by frequent use, it has acquired the habit of the motions excited by its action. It is not in that case with the stomach, as with a limb, whose muscles perform motions with the greater ease and facility when they have been often practised. $ XI. OF THE RELATIONS OF PHYSIOLOGY TO SEVERAL OTHER SCIENCES. It would be entertaining a very incorrect notion of the science of living man, to imagine with some authors, that it solely consists in the application ofthe laws of Natural Philosophy, to the explanation of the phenomena of the animahceconomy. Physiology is an independent science ; resting upon truths of its own, which it draws from the observation of those actions, which, in their aggregate succession and connexion, constitute life. k It is enriched, it is true,'with facts furnished to it by Natural Philosophy, Che- mistry, and Mathematics ; but what it has borrowed from these, is accesso- ry merely, and does not form an essential part ofthe edifice ofthe science. Thus, the better to understand the mechanism of hearing and vision, phy- siology borrows from acoustics and optics, elementary notions on sound and light ; and, in order to obtain a more correct knowledge of the nature of our solids and fluids, and ofthe manner in which animal substances are con- stantly passing from the one to the other of these two conditions, physiology calls in the aid of chemistry. Thus, geometry and mechanism furnish it with the means of better understanding the advantageous form ofthe organs, and the perfection of their structure*. No study carries along with it a more lively interest, than that ofthe ad- mirable relations existing between the conformation of our parts and the ex- ternal objects, to which they are applied. These relations are calculated with such precision, and laid down with such accuracy, that the organs of sense and of motion, considered in this point of view, may be regarded as the model ofthe most ingenious productions of art. So true it is, in the words ofthe great physician of Pergamus, that nature did every thing before art, and better!. At the beginning of the last century, geometrical physicians, deceived by an appearance of rigid precision, attempted to explain every thing by the calibre of vessels, their length, their curvatures, the compound ratio of the action of solids and the impulse of fluids. Hence were formed theories so very imperfect, that, as we shall see, in treating of several points of physi- ology, and especially ofthe force with which the heart acts, not one of those * A knowledge of mathematics, and of the whole circle of natural philosophy, in- cluding more especially chemistry and natural history, and, in a more particular man- ner, human and comparative anatomy, is requisite to the successful study of physiology. This branch of knowledge, although independent of some of these, is yet more easily acquired, and its difficulties are better explained, by a previous acquaintance with all of them. Pathology and the treatment of diseases, also, reflect a light upon physiology which they first derived from this productive source. t Quandoquidem natura, ut arbitror, et prior tempore sit, et in operibus magis sapiens quamars. Galenus, de usu partium, lib. VII. cap. 13. It was from observing the manner in which nature prevents the diffusion of light in the globe of the eye, that Euler was led to the improvement of his astronomical tele- trope?.—Author's Note- 43 who proposed them, coincides with those who have since followed their track. However, it does not admit of a doubt, that there occur in the ani- mal machine, effects which are referable to the laws of hydraulics. The brain, for example, required a large and constant supply of arterial blood, vivified by recent circulation through the lungs ; but the too rapid and abrupt access of that fluid in the brain, might have disordered its structure. Nature, therefore, has, as we shall mention in the article of the cerebral circulation, employed all the hydraulic resources in her power, to break the force with which the blood enters the brain, and to slacken its course. Has man ever applied the laws of hydraulics in a more felicitous manner than nature, in the rete mirable formed at the base ofthe brain by the caro- tids of quadrupeds ? An arrangement truly remarkable, without which, the blood conveyed to the brain by those arteries, impelled by a force superior to that ofthe human heart, and not having to overcome the resistance of its own gravity, would infallibly have occasioned a disorganization of that organ, whose consistence is so soft. As to the application which is allowable of mathematical sciences, it may be said, that, as in physiology, but little is absolutely certain*, and much merely probable, we can reckon only on probabilities, and seek our ele- ments in facts deduced from observation or experience ; facts which when collected and multiplied to a certain degree, lead to results of equal value with truths absolutely demonstrated. The phenomena presented by living bodies vary incessantly, in their ac- tivity, their intensity, and their velocity. How can mathematical formulae apply to such variable elements ? As well might you inclose in a frail vessel, hermetically sealed, a fluid subject to expansion, and of variable bulk. The motions of progression in man and in the animals, afford, nevertheless, suffi- ciently correct applications of calculation. Calculation may likewise be applied with advantage, to the measurement ofthe results of our different secretions to ascertain the quantity of air, or of aliment, introduced into our organs, &c. Among the principal causes which have retarded, in a considerable de- gree, the progress of physiology, may be enumerated the mistake of those who have endeavoured to explain all the phenomena of living bodies, by a single science, as chemistry, hydraulics, &c. while the union of all these sciences, will not account for the sum of these phenomena. The abuse, however, of these sciences, should not be a reason for setting them aside altogether. The facts obtained from natural philosophy, chemistry, me- chanics, and geometry, are so many means applicable to the solution of the great problem of the vital ceconomy ; a solution which, though as yet un- discovered, should not be considered as unattainable, and to which we shall approach the nearer, as we attempt it with a greater number of data. But it cannot be too often repeated, that he alone can hope for that honour, who, in the application ofthe laws of natural philosophy to living bodies, will take into account the powers inherent, in organized nature, which controul, with supreme influence, all the acts of life, and modify the results that ap- pear most to depend on the laws by which inorganic bodies are governed. Anatomy and physiology are united by such close relations, that it has * This is to be understood, as applying only to the causes of the phenomena, and not to tlfe phenomena themselves ; for physiology is perphaps richer than anyother sci- ence, in facts unquestionable, and easily ascertained by observation.— \«!horsNote. 44 been an opinion with some, that they are absolutely inseparable. If physi- ology, say they, has for its object, a knowledge ofthe functions carried on by our organs, how is one to understand their mechanism, without knowing the instruments by which they are performed ? One might as well attempt to explain the manner in which the hand of a watch performs the circle of its diur- nal revolution, without understanding thesprings and numerous wheels which set it in motion. Haller is the first who established the connexion between, anatomy and physiology, and who illustrated it in hi« great work. Since Haller, a great number of anatomists, and among them Soemmering*, in a work recently published, have combined, as much as possible, these two sciences ; the latter, in treating separately of each system of organs, ex- plains what is best known of their uses and properties. However close the connexion between anatomy and physiology, they have, nevertheless, appeared perfectly distinct to the greater number of authors, and we have several valuable works on anatomy, of which physiology occu- pies but a small part.—This manner of embracing the two sciences appears to me attended with the greatest advantage ; in fact, if the insulated descrip- tion of organs suffices to the physiologist who wishes tostudy their functions, that method is attended with the disadvantage of furnishing few truly useful views, in the practice of operative surgery. To render the knowledge of the human body more especially applicable to the practice of surgery, it is necessary, not only to consider separately the different parts, but likewise to view them in their connexion, and to determine precisely their relations. The anatomist, who knows that the principal artery ofthe thigh is the cru- ral,—that, continued under the name of popliteal, it passes behind the knee inits way to the leg,— that, in its course, it supplies with branches different parts of the limb,—even though he knew perfectly the name, the number of these branches, the varieties to which they are subject, the parts to which they are distributed, would nevertheless possess a knowledge of that branch ofthe system, almost useless in the treatment of the diseases with which it may be affected. The situation ofthe artery, its direction, the parts which Surround it, its precise relations to each of them, its superficial or deep seated course, &c. are the only circumstances from which he can derive any advantage. He who, in this point of view, cultivates anatomy, may be compared to the chemist; in the same manner as the latter is never better acquainted with a substance, than when he is able to decompose it, and to reproduce it from a combination of its parts, so the anatomist is well acquainted with the body of man, only, when having studied separately, and with the greatest care, each of his organs and each of the systems, formed by the collection of a certain number of similar organs, he is able to assign to each of them its place, to determine its relations, and the proportions which it bears in the structure of any one of our limbs. The study of the latter is much more difficult and extensive than that of the former ; for, the chemist who de- composes and recompounds a well-known substance, phosphate of lime, for instance, attains only to the knowledge of its constituent principles, and re- spective proportions : the phenomena of situation altogether escape him. The anatomist, on the other hand, who knows that such a part is composed of bones, of muscles, of nerves, of vessels, must know, not only every one of these parts, their relative bulk, but the exact place in which they are to ?>e found. * J Ch. Soemmering d* corporis humnnit'ahrim. fivols. Svo. 180! 43 Anatomy, pursued in this spirit, offers a field of wide extent: it is the art which Leibnitz called the analysis of situation, analysis situs; and the know- ledge of it is too important not to require a separate place among the de- parfnents of medical knowledge. I will not pass over the motives that are alleged for combining anatomy and physiology in one course of instruction. Anatomy, confined to the mere description of the organs, is too dry and fatiguing ; physiology throws over it interest and variety ; it helps to ensure the attention of the hearers, who will retain more permanently, what they have listened to with pleasure. Would not one think that physiological de- tails were, for an audience, what is contrived for a sick and froward child, in the honey that is rubbed on the edge ofthe cup, to disguise the bitterness ofthe draught that is to recall him to life? In combining two objects, of which one has no interest but that of usefulness, whilst the other is engaging as well, the attention will be not merely divided, but altogether distracted, and the mind of those who read or listen, will skim over dry details, to seize with avidity what furnishes more to its activity of intelligence. Anatomy is to physiology what geography is to history. General considerations on the situation, the size, the form, the relations, the structure of the organ, are an indispensable preparation to the perfect understanding of its functions : ac- cordingly, you shall find much anatomy in physiological treatises, as you find much geographical detail in faithful historians. I have said enough, I trust, to escape the reproach of not having filled my book with anatomical descriptions, from the multitude of excellent works we possess on the anatomy of the human body. Let us now inquire what relation physiology bears to Comparative Anatomy. If a machine can be perfectly known, only after taking it to pieces, down to its simplest elements ; if the mechanism ofthe whole action is conceived, only by separately studying the action of each different part, Comparative Anatomy, by aid of which we can study, in the great chain which the animal kinds compose, the separate action of each organ, appreciate its absolute or relative importance, consider it, at first, insulated and reduced, so to speak, to its own powers, in order to determine what part it bears in the carrying on of a function ; Comparative Anatomy is of absolute necessity to him who would make great progress in the knowledge of man ; it may be looked upon as a sort of analytic method, by means of which we more completely attain 1o the knowledge of ourselves In order to conceive rightly the operations of the human intellect, and explain the generation of the faculties of the soul, metaphysicians have imagined a statue, into which they have infused a gradual animation, by in- vesting it, one by one, with our organs of sensation Now, Nature has re- alized in some sort this dream of philosophy. There are animals to which she has entirely denied the organs of sight and hearing ; in some, taste and smell seem to have no separate existence from touch ; in others, she has exercised a sort of analysis on a system of parts which all concur in one function It is thus, that in some anim-.ds, divesting the organ of hearing of the accessories allotted to collect, transmit, and modify the rays of sound, she has reduced it to a simple cavity, filled with a gelatinous fluid, in which float the extremities of the acoustic nerve, alone fitted to receive the im- pression of sound ; a fact which overthrows all the hypotheses that had ascribed this sensation to other parts ofthe auditory apparatus. Of all the physical sciences, Comparative Anatomy is that which furnishes 46 the most useful facts to physiology.* Like physiology, it is concerned with organized living beings : there is, therefore, no need of watching against the false applications, so often made from the sciences, whose objects are mat- ter inorganic and dead, or which study, in living beings, only the general properties of matter. Haller was so well aware ofthe utility of introduc- ing this science into physiology, that he has brought together the greater part ofthe ficts known in his time, on the anatomy of animals, at the head of each chapter of his immortal work. This general consideration of living and animated beings, so well adapt- ed to unveiling the secret of our organization, has this further advantage, that it enlarges the sphere of ideas of him who applies to it. Let him who aspires to that largeness of conception, so requisite in medicine, where facts are so multiplied and various, explanations so contradictory, and rules of conduct so unfixed, cast a genera! glance on this great division of organized beings, of which many, in their physical structure, so nearly resemble man :~-he will see the sovereign Architect ofthe world distributing to all, the element of life and activity, giving to some a less power of motion, to others more ; so that, formed all on one model, they seem only the infi- nitely varied, but gradual shades ofthe same form, if forms have shades like colours ; never passing abruptly from one to another, but rising or falling by gentle and due degrees ; covering the interval that separates two differ- ent beings, with many species that serve as a transition! from one to the other, and which pre-ent a continuous series of advancement or degradation; organization being constantly simplified, in descending from man to the in- ferior creatures ; but rising in complexity, in re-ascending from those ani- mds to man, who is the most complex being in nature, and was justly con- sidered, by ancient philosophy, as the master-piece ofthe Creator. If the intimate structure of our organs totally eludes our investigation, it is, that the finest and most delicate of their constituent parts are of such minute dimensions, that our senses have no hold on them. It is then well to have recourse to analogy, and to study the organization of ani- mals that exhibit the same organs on a larger scale. Thus, the cellular * " The extensive examination of various structures," Mr. Lawrence very justly ob- serves, " is not only a necessary ground-work for the edifice of general physiology, but it has thrown great light on the organization and functions of the human frame. Whoever will reflect on our present knowledge of the digestive, respiratory, generative, or other processes of man, and will review the successive stages of its progress, will find . that comparative anatomy has rendered us the most essential assistance." t The conception is noble and interesting of a scale of being, which, as was said by C. Bonnet, connecting all the worlds, embracing all the spheres, should extend from the atom to the most exalted of cherubim. Without carrying it so high or so low, if we confine it to the natural beings with which we are well acquainted, and which can be brought under observation, it will be seen, that the idea is not so chimerical as some writers of most respectable authority have supposed it. The plan traced by C. Bonnet is evidently defective; we find in it beings set beside each other, that have but faint lines of resemblance, or altogether illusive. The present state of the natural sciences would al- low of its being better done : one might try at least for all bodies what Jussieu has exe- cuted with regard to vegetable productions; and if this undertaking, in the hands of men the most able to bring it to a successful termination, left anything defective, would not that imperfection be an indication of the existence of other worlds, or of lands yet un- known on the globe we inhabit; undiscovered regions where those animals, and plants and minerals would be found which were wanting to fill up the gaps in the immense se- ries of co-ordinate existence ? Demonstratumfuit et hoc, nullam rem contrarias, vel omnino multum differentes, qualitates recipere posse, nisiper media privs iter fecerif. Galf.nus de Usu par Hum, lib. iv. cab. 12.— Author's Note. 47 texture ofthe lungs, which cannot be distinctly shewn in man, on account of the extreme minuteness of the smallest bronchia?, maybe satisfactorily seen in the vesicular lungs of salamanders and frogs. In like manner, the scales which cover the bodies of fishes and reptiles, or the legs of birds, give us a just idea of the structure of the epidermis, and of the arrangement of its small scales, which lie over each other, in a part of their surface. '1 he human structure being more complicated, must produce effects more numerous, and results more varied, and more difficult to understand. In commencing the study ofthe animal organization by that of man, we do not therefore, follow the analytic method, we do not proceed from what is simple, to what is more complex. It would perhaps be an easier and a more natural way of arriving at a solution of the grand and difficult problem ofthe animal ceconomy, to begin by explaining its most simple terms ; to rise by degrees from planets to vegetating animals, as polypi ; from these to white-blooded animals, then to fishes and reptiles ; from the latter to warm- blooded animals, and lastly to man himself, placed at the head of that long series of beings whose existence becomes complicated, in proportion as they approach him. The study of every part of natural history, and especially of Comparative Anatomy, cannot fail, therefore, to prove of infinite advantage to the physi- ologist; a truth well expressed by the eloquentM.de Buffon*, who says, that if there existed no animals, the nature of man would be still more in- comprehensible. I shall say nothing ofthe well-known relations of physiology to medical science, of which it is justly considered as the base or support. Medicine, called by some the art of healing, by others more properly, the art of treat- ing diseases, may be defined the art of preserving health, of curing diseases, or of rendering them more supportable ; medicine, in all its parts, is en- lightened by physiology, and cannot have a surer guide. Owing to a neg- lect of this auspicious guide, therapeutics and materia medica long remained involved in a mist of conjectures and hypotheses. Physicians should never for a moment forget, that as a great number t of diseases consist in a de- rangement of the vital function, all their efforts should tend to bring back sensibility and contractility to their natural condition that the best classifi- cation of diseases and of medicines, is that which is founded on a judi- cious distinction of the vital powers. With this view it is that M. Alibert, in his elements of materia medica, clashes medicines according to their ef- fects on sensibility or contractility, and according to the organs on which their action is particularly exerted. § XII. CLASSIFICATION OF THE VITAL FUNCTIONS. After having treated separately ofthe vital powers of faculties, nothing is easier than to arrange, in a clear and methodical order, the functions carried on by the organs which these powers call into action The term function might be defined, means of existence. This definition would be the more just as life is only the exercise of these functions, and as in cases, when any one ofthe more important cannolonger be carried on. From not distinguish- *' Histoire Nat. torn. V. 12mo. p. 241. Discours sur la nature des animaux. t All diseases consist in physical derangements, as solutions of continuity, displace- ments, organic alterations, as polypi, aneurisms, and other affections resulting from or- ganic affection and alteration of structure; vital lesions, as fevers, ataxia, adynamic- vesania?, fcc see \osographia Chiru^irale.—Author's Note. 48 ing the faculties from the functions which are merely the acts ot the facul- ties or powers, several modern divisions, though far preferable to the old classification of the functions into vital, animal, and natural, are, nevertheless, deficient in accuracy and simplicity. Thus Vicq-d'Azyr, in the classifica- tion ofthe phenomena of physiology inserted in the discourse which he has prefixed to his work on anatomy, mistakes the cause for the effect, and places sensibility and irritability among the functions, and commits another mistake, by ranking among the latter, ossification, which is but a peculiar mode of nutrition, belonging to parts of a hard structure. The best method of classing the actions which are performed in the living human body is, doubtless, that by which they are distributed and arranged according to the object which they fulfil. Aristotle, Buffon, and especially Grimaud, have laid on that base the foundation of a method which we shall adopt, with the modifications which we are about to mention. Aristotle and Buffon had observed that among the acts of the living cecono- my, some were common to all beings that have life, to plants and animals during sleep and in waking, while others seemed to belong exclusively to man, and to the animals which more or less resemble him. Of these two modes of existence, the one vegetative, the other animal, the former ap- peared to them the more essential, as being mote diffused, and consisting merely in assimilation of nutritive molecules, in the nutrition absolutely ne- cessary to the preservation of the living being*, who, as his substance is in- cessantly wasting, would soon cease to exist, if these continual losses were not always repaired by the act of nutrition. Grimaud, Professor of Physiology at Montpellier, too soon lost to the sci- ence which he cultivated as a philosopher, truly deserving that name, adopt- ed this simple and luminous division, developed it better than had been done before him. and uniformly followed in his lectures and in his workst. This division ofthe functions into internal, which he likewise calls digestive, and into external or loco-motive, lately brought forward under the name of organic and animal, the former of which terms is quite inaccurate and de- fective, since it leads to a belief, that the animal life, or of relation is not confined to organs, and that their vital instruments are solely employed on internal life or of nutrition (Motu, assimilationis, Bacon ; Bias alterativum, Vanhelmont.) This distinction does not comprehend the whole of the phenomena, and does not embrace the sum of the functions which are per- formed in the animal ceconomy. In fact, there are not found in the two great classes which it establishes, the acts by which animals and vegetables * Nam anima nutriva etiam alHs inest, et prima et maxima, communis facultus animus, secundum quam omnibus viverc inest. Ahistot. de anim. lib. ii. cap. 4. t In his MS. lectures on physiology, he seems to feel a complacency in that division which he had in a manner appropriated to himself, by his happy illustrations of it, and by the changes which he had introduced into it. In every lecture, I might almost say in every page, he returns to this division, explains it, dilates, and comments upon it. " The functions," says he, " maybe divided into two great classes ; some are formed in the interior ofthe body, and exclusively belong to it; others take place outwardly, and belong to external objects," k.c. The digestive power presides, in his opinion, over the internal functions, whose object is nutrition ; the loco-motive power directs the external functions. " It is by means of the organs of the sense that the animal enlarges his ex- istence, that he applies and distributes it on the surrounding objects, that he takes cog- nizance of the qualities in those objects which concern him ; it is by means of the mus- cles essentially obedient to the organs of sense, that he adapts himself to those objects, that he places him?elf in a manner suited to the mode of their activity," kc—Au- thor's Note. *? reproduce and perpetuate themselves, and immortalize the duration of their species. All the functions destined to the preservation of the species are not included ; they merely relate to the functions subservient to the pre- servation of individuals. I have, therefore, thought it right to include under two general classes, in the first place, the functions which belong to the preservation ofthe spe- cies, functions without which man might exist, as we see in eunuchs, but without which the human species would soon perish, from a loss of the power of reproduction. Inlaying down these two great divisions, 1 have merely considered the object and end which each function has to fulfil. Among the functions which are employed in the preservation of the in- dividual, some fulfil this office by assimilating to his own substance the food tvith which he is nourished ; the others, by establishing, in a manner suited to his existence, his relations with the beings which surround him. The functions destined to the preservation of the species, may likewise be divided into two classes. Those ofthe first class require the concourse of two sexes ; they constitute generation, properly so called ; those ofthe second order, exclusively belong to the female, who, after conception, is alone destined to bear, to nourish, to bring into the world, and suckle the new being, the result of conception*. The internal, assimilating, or nutritive functions concur in the same end, and all serve to the elaboration of the nutritive matter. The aliment once admitted into the body, is subjected to the action of the digestive organsa which separate its nutritive parts ; the absorbents take it up, and convey it into the mass of fluids ; the circulatory system conveys it to all the parts of the body, makes it flow towards .the organs ; the lungs and the secretory glands supply it with certain elements, and deprive it of others, alter, modi- fy, and annualize it; in fine, nutrition, which may be considered as the complement of assimilating functions, whose object it is to provide for the maintenance and growth ofthe organs, applies to them this animalized sub- stance, assimilated by successive acts, when it has become quite similar to them. Several,however, of these functions, serve at once to preserve and to destroy. Absorption, which takes up extraneous molecules to be employed in the growth of the organs, takes up equally the organic molecules which are detached by motion, friction, heat, and all the other physical, chemical, and vital causes. The action of the heart and of the blood-vessels sends these fragments, together with the parts truly recrementitious, towards the lungs, which, at the same time that they bring about a combination ofthe nutritive parts with the oxygen of the atmosphere, separate from the blood the materials which can no longer be employed in nourishing the organs ; the same power sends them towards the secretory glands, which not only purify what is liquid, by separating from it that which cannot without danger re- main in the animal ceconomy, but which likewise elaborate or prepare pe- culiar fluids, some of which are results ofthe act of nutrition, are employed in that act, and impart to the substances on which it is performed a certain * The classification ofthe functions which Richerand adopted, with a slight modifi- cation from Gsymaud, nearly agrees with the one more generally followed by the best modern physiologists. Sperengel arranges them into the vegetative, the sensiferous, and the generative. M ygendie divides them into functions of relation, functions of nutrition, and functions of generation. Lenhossek, professor of anatomy and physiology in the. university of Vienna, the latest writer on physiology, classes the functions into those of irzavic life, of sensiferous or animal life, and those belonging to generation. ,'">« degree of animalization, (as to the bile and saliva) while the others seem to be intermediate states, which the nutritive particles ofthe food are obliged to Undergo, before the complete animalization ; such are the serous fluids and the fat. It might perhaps seem more in conformity to the order of nature, to have combined the account of respiration with that of the cirdulation by treating ofthe course ofthe venous blood, after the action of the absorbent vessels, with which the veins have so much analogy. - Then to have treat- ed of the phenomena of respiration, or ofthe conversion of the venous blood into arterial, and of the course ofthe latter into all the parts ofthe body, by the action of the heart and arteries ; but the advantage which would be obtained from a method so contrary to the common practice, which is to consider separately the functions of circulation and respiration, appeared to me too unimportant to justify its adoption. The external or relative functions equally connected by their common destination, connect the individual to every thing that surrounds him : the sensations, by warning him ofthe presence of objects which may be useful or injurious to him ; motion, by enabling him to approach, or avoid such objects, according as he perceives relations of advantage or disadvantage, according as the opposite sensations of pain or pleasure result from his action on them, or from theirs on him. In fine, voice and speech give him communication with beings enjoying the same means of communication, and that without a necessity of motion. 1 he brain is the principal organ of these functions, as the system of circulation is the centre of the assimi- ~ lating functions. All the impressions received by the organs of sense are transmitted to the brain, and from the brain, determinations arise, as well as the voluntary motions and the voice. The sanguineous system receives the molecules destined to nutrition, and those which are to be thrown out of the body. The sensitive and circulatory systems are the only systems provided with a centre, (the brain and the heart)which extend to all parts of the body, by emanations originating from that organ, or terminating in it (the nerves, the arteries, and veins): and, as the motions and the voice depend on sensation, and are immediately connected with it as necessary consequences, so, respiration, secretion, and nutrition, are, in a manner, but consequences ofthe circulation which distributes the blood to all the organs, in order that these may produce on it various changes which constitute res- piration, secretion, and nutrition. They are, to anticipate what is to come hereafter, only different kinds of secretion that take place at the expense ofthe different principles contained in.the blood. The circulation which holds the functions of nutrition in a kind of de-\ pendence, subjects the brain, which is the principal organ of the external functions, to an influence still more immediate and indispensable. The muscular motions are not less under its influence. It is the first function that is apparent in the embryo, whose evolution it brings about; in natural death, of all the functions, it is the last to cease. There are many reasons which justify Haller, for having placed it in the first order, and for having begun by its history, his great work on physiology. I enter into this di- ' gression, only to expose the absurdity of the claims of some authors, who, | because they have varied the methodical order ofthe functions, broken the series, or made the slightest changes, for example, by placing the history of the function of smell and taste before the account ofthe internal or nutri- tive functions, think they have totally changed the aspect ofthe science: pitiful sophists,, who accumulate subtleties instead of facts and idea* <>1 in warm and red-blooded animals, the nutritive functions, digestion, ab- sorption, circulation, respiration, the secretions and digestion are performed as in a man, and in that respect there exist between them very slight dif- ferences ; nay, in some animals, these functions are performed with much more energy.—Thus several animals digest substances, on which our own organs produce no effect, and others (birds) have a more rapid circulation, a more active nutrition, and evolve more heat. But not one of them is as well provided with organs to keep up intercourse, as a living being, with the surrounding objects. In no one animdl. are the senses possessed ofthe same degree of perfection ; the eagle, whose sight is so piercing, has a very dull sense of touch, taste, and smell. The dog, whose smell is exquisite. has a very ordinary extent of sight: in him, the taste and touch are equal- ly imperfect.—His touch, in the perfection of which no animal comes up to man, has not been improved in delicacy at the expense ofthe other senses. The sight, the hearing, the taste, and smell, preserve a great delicacy, when their sensibility has not been impaired by injudicious br too frequent im- pressions. The sensitive centre is in no one better developed, and fitter to di- rect safely the use ofthe organs of motion. No other animal can articulate vocal sounds, so as to acquire speech. This greater extension of life in man, from the number and perfection of his organs, makes him liable to many more diseases than the other animals. It is with the human body, as with those machines which become more lia- ble to be deranged, by increa-ing the number of their wheels, with a view of obtaining more extensive or more varied effects. All organized bodies are possessed of assimilating functions ; but as as- similation requires means varying in number and power, according to the nature ofthe bein^ which performs it, the. series of assimilating phenomena commences in the plant by absorption, since it draws immediately from the earth, the juices which it is to appropriate to itself. Its absorbing system, at the same time, performs the functions of a circulatory organ, or rather, the circulation does not exist in plants, and the direct and progressive motion of the sap which ascends from the root towards the branches, and sometimes in a retrograde course, from the branches, towards the roots, cannot be com- pared to the circulation ofthe fluids which takes place in man, and in the ani- mals which most resemble him, by means of a system of vessels which every moment bring back the fluids to the same spot, and convey them over the whole body, by making them desciibe a complete circle, frequently, even, a double rotation (animals with a single or double circulation, that is, whose heart has one or two ventricles.) Plants breathe after their own manner, and produce a change in the atmospherical air, by depriving it of its carbo- nic acid gas, the result of combustion and of animal respiration, so that by a truly admirable reciprocity, plants, which decompose carbonic acid, and allow oxygen to exhale, continually purify the air, which combustion and ani- mal respiration are incessantly contaminating*. " This opinion originated with Priestley, and was generally adopted, in opposition in the experience of his cotemporary, the celebrated Scheele. Subsequent physiologists, especially Ellis, Gilby, and T. i»e Saussure, have shown, by well conducted experi- ments, that all plants, whether growing in absolute darkness, in the shade, or when not exposed to the direct rays of the sun, " are constantly removing a quantity of oxygen from the atmosphere, and substituting an equal volume of carbonic acid." Thus far Miese philosophers nearly agre^. They differ, however, very widely respecting; the man- o2 The functions preservative of the species are common to animals and plants. The organs by which these functions are performed, when com- pared in these two kingdoms of nature, offer a resemblance which has struck all naturalists, and has led them to observe, that of all these acts of vegeta- ble life, no one is more analogous to the animal ceconomy, than that by which fecundation is effected. We shall not here explain the general characters of the two orders of functions which are subservient to the preservation ofthe species : the dif- ferences which belong to them are pointed out in several parts of this work*. I shall merely observe with the authors who have considered them gene- rally, that they are in an inverse ratio to each other, so that in proportion as the activity of the assimilating functions increases, that of the external functions is abated. Grimaud has, in the most complete manner, illustrated this idea ofthe constant opposition which exists between these two series of actions, over which, in the opinion of that physician, th^re preside two powers which he calls loco-motive a ad digestive. It is in no kind of animals more distinct than in the carnivorous, which possess organs of sense of the greatest delicacy, together with muscles capable of prodigious efforts, and yet powers of assimilation so feeble that their food cannot be digested, unless it be composed cf materials analogous in composition to their own organs|. Too much importance should not be attached to this classification like all other divisions, it is purely hypothetical. All is connected together, all is co-ordinate in the animal ceconomy ; the function? are linked together, and depend on one another, and are performed simultaneously ; all represents circle of which it is not possible to mark the beginning or the end. In c»V- culum abeunt (Hippocrates ) In man, while awake, digestion, absorption, circulation, respiration, secretion, nutrition, sensation, motion, voice, and even generation may be performed at the same time ; but, whoever in the study ofthe animal ceconomy should bestow hi» attention on this simultaneous exertion of the functions, would acquire but a very confused knowledge of them J. ner in which this change is effected. Ellis supposes that the leaves, flowers, fruits, stems, and roots of plants, emit, carbonaceous matter, which combines with the oxygen of the surrounding air. Gilb v and Sausswp.e are of opinion, that the oxygen is absorbed by the respiratory organs, and that .he carbonic acid is formed within the plant. Although vegetables, undei the ordinary circumstances of their growth, consume oxy- gen during respiration, and disengage carbonic acid, yet, according as their situation and particular condition may require, they partially absorb the carbonic acid from the air, convert it to their use, decompose it, and emit the oxygen which results from the decom- position, especially when they are exposed to the sun's rays. The illustration of this 6ubject belongs to vegetable physiology. * Especially in the account of living beings, § V. of the preliminary discourse; articles sleep and fetus. It is impossible at present to go over alf these distinctions, without en- tering into useless and disagreeable repetitions__Author's Note. tin carnivorous animals, the power of digestion is exceedingly weak; but their mus cles are very powerful. This relative force of the muscles was necessary in carnivorous animals, as they live by depredations and slaughter, as their instinct, in unison with their organization, sets them constantly at war with everything that has life, and as their subsistence depends on their being victorious in the battles to which Nature incessantly calls them. Grimaud, first Memoir on Nutrition.—Author's Note. X The division which I lay down, is not to be strictly adopted, and as being; absolutely true. It is a mere hypothesis to be attended to, only in so far as it assists in arranging one's ideas in a more orderly manner. For, every arrangement, even when arbitraryi h useful in laying before uss» great number of ideas, and in thereby facilitating the com- ^3 By becoming familiar with these abstractions, one might soon mistake them for realities ; one might even go the length of seeing two distinct lives in the same individual ; one would be apt to assign as the character of in- ternal life, that it is carried on by organs independent of the will. Although this faculty ofthe soul presides over the phenomena of respiration, of mas- tication, of the expulsion ofthe urine and fasces, one might consider life as intrusted to unsymmetrical organs, although the heart, the lungs, and the kidneys, are evidently symmetrical; one migbt fancy it to exist in the foetus, which neither breathes, nor digests, &c. Nothing in the animal economy, said Galen, is ruled by invariable laws, or can be subject to the same accu- rate results and calculations, as an inanimate machine (Nil est in corpore vi- venti plane sincerum. Galen.) Thus, respiration, which connects the ex- ternal and assimilating function, furnishes the blood with the principle which is to keep up the action of the brain, and to excite muscular contractions. On the other hand, the motion ofthe muscles is of use in the distribution of the humours, and concurs in the phenomena of assimilation. The brain, by means ofthe eighth pair of nerves, holds influence over the stomach. The sensations of taste and smell s^em to preside, in an especial manner, over the choice of food and of air, and to belong rather to the digestive and respira- tory functions, than to those ofthe intellect, or of thought. We have seen in this kind of general introduction ofthe study of physio- logy, what idea is to be formed of that science as well as of life, the study of which is its object; into how many classes the beings in nature may be di- vided, and into how many elements they are resolvable ; what differences exist, between inorganized, and organized and living bodies, between plants and animals ; how life is complicated, modified, and extended, in the im- mense series of beings which are endowed with it, from the plant to man; and in further particularizing the object under our consideration, we have examined, what are the organs which, by their union, form the human ma- chine ; what powers govern the exercise of their functions : then, we have laid down the fundamental laws of sensibility and contractility, we have spoken of sympathies and habits, ofthe internal nervous apparatus, which unites, collects, and systematizes the organs ofthe assimilating function ; we have endeavoured to determine from facts, the existence ofthe cause which subjects living beings to a set of laws very different from those which inor- ganic matter obeys. The knowledge of these laws is the light which is to guide us in the application to physiology ofthe accessory sciences. Finally, in the arrangement ofthe objects which this science considers, 1 have adopt- ed a more simple and natural division than any hitherto employed. I shall close this preliminary discourse, by saying a few words on the order adopted in the distribution of the chapters. I might have begun by a view ofthe external functions, as well as of those of assimilation or nutrition, of sensation, or of digestion. I have given preference to the functions of assi- milation, because of all others, they are the most essential to existence, and their exercise is never interrupted, from the instant in which the embryo parison that is to be instituted among them. All the acts of Nature are so connected, and are linked together in so close an union, and she passes from the one to the other, by such uniform motions, and by gradations so insensible and so adjusted, as to leave no space for us to lay down the lines of separation, or demarcation, which we may choose to draw. All our methods of classing and arranging the productions of nature, are mere abstractions oi the mind, which does not consider things as they really are, but which attends to certain qualities, and neglects or rejects all the rest. Grimacp. Lectures on Physiology.'—Author's Note. i4 begins to live, till death. In beginning with an account of them we imitate nature therefore, who imparts to man this mode of existence, before she has connected him with outward objects, and who does not deprive him of it, until the organs of sense, of motion, and of the voice, have completely ceased to act. As to the course which has been followed in the arrangement of the functions that belong to the s*me order, or which concur in tbe same end, it was too w ell laid down by nature, to allow us to depart from it. I have thought it right that the consideration ofthe voice should immediately precede that of generation, in order that the arrangement might, at a glance, show the connexion which exists between their phenomena. Several animals use their voice only during the season of love ; the birds which sing at all times have, during that period, a more powerful and sonorous voice. When man becomes capable of reproduction, his vocal organs suddenly become evolved, as though nature had wished to inform him, that it is through them he is to express his desires to the gentle being who may sympathize in them. The voice, therefore, serves as a natural connexion between the external func- tions, and those which are employed in the preservation of the human species. The voice, which leads so naturally from the functions which establish our external relations, to those whose end is the preservation ofthe species, is still more intimately connected with motion. It is, in a manner, the comple- ment ofthe phenomena of locomotion ; by means of it, our communication with external objects is rendered easier, more prompt, and more extensive: it depends on muscular action, and is the result of voluntary motion. Fi- nally, these motions sometimes supply the place of speech, in pantomime, for example, and in the greater number of cases, the language of action concurs in adding to its effect. Every thing, therefore, justifies me in placing this function after motion, in separating it from respiration, with which every other author has joined it, without considering that the rela- tion between the voice and respiration is purely anatomical, and can, there- fore, in no wise apply to physiology. I have placed after generation, an abridged account of life and death, in which will be found, whatever did not belong to any ofthe preceding divi- sions. The necessity of this appendix, containing the history ofthe differ- ent periods of life, that of the temperaments and varieties of the human species, that of death and putrefaction, arises from the impossibility of intro ducing into the particular history ofthe functions, these general phenomena in which they all participate. FIRST CLASS LIFE OF THE INDIVIDUAL. FIRST ORDER t#/w^^>^^^A^ FUNCTIONS OF ASSIMILATION, Or, Functions which are subservient to the Preservation of the Individual, by assimilating to his Substance the Food by which he is nourished. II fa Si.. NEW ELEMENTS OF PHYSIOLOGY. CHAPTER I OF DIGESTION. I. Digestion is a function common to all animals, by which substances extraneous to them, are introduced into their body, and subjected to the action of a peculiar system of organs, their qualities altered, and a new com- pound formed, fitted to their nourishment and growth. II. General considerations on the Digestive organs. Animals alone are provided with organs of digestion ; all of them, from man down to the poly- pus, contain an alimentary cavity, variously shaped. The existence of a digestive apparatus may, therefore, be taken as the essential characteristic ofthe animal kind. In man, this apparatus consists of a long tube extend- ing from-the mouth to the anus ; within this canal, there empty themselves the excretory ducts of several neighbouring glands, that secrete fluids fit for changing, for liquefying, and animalizing the alimentary substance. The different parts of this digestive tube are not of equal capacity ; at first, en- larged in the part which forms the mouth and pharynx, it becomes narrower in the oesophagus ; this last, dilating considerably, forms the stomach, which again contracting, is continued down under the name of intestine. The tube itself varies in size in different parts of its extent; and it is by the consideration of these differences of size, that anatomists have principally been guided in their divisions. The length ofthe digestive tube is from five to six times the length ofthe whole body, in an adult : it is greater in proportion in a child. At this age, likewise, digestion is more active, and proportioned to the necessities of growth in the individual. The digestive cavity is in man open at both ex- tremities ; in some animals, in the zoophyte for example, one opening serves the purpose of mouth and of anus, receives the food, and ejects the excrementitious remains. The extent of the digestive canal is according to the nature of the ali- ments on which the animals feed : the less those aliments are analogous in their nature to the substance ofthe animal which they are to nourish, the longer must they remain in his body to undergo the necessary changes. Therefore, it is observed, that the intestine of gramnivorous animals is very long, their stomach very capacious, and often complex, while carnivorous animals have their intestinal canal short and strait, and so arranged, that the animal substances which are most nourishing, in least bulk, of easy and rapid digestion, which, by too long a stay in the intestines, might become putrid, pass readily through it. In this respect, man holds a middle station between those animals which feed on vegetables, and those which feed on animal substances. He is. therefore, equally fitted for these two kinds of food : .jtf be is neither exclusively herbivorous, nor carnivorous, but omnivorous or polyphagous. This question, of such easy solution, has long employed phy- sicians, naturalists, and philosophers ; each bringing, in favour of his opinion, very plausible arguments, drawn from the form and number of the teeth, from the length ofthe intestinal canal, from the force of its parietes, &c. The parietes of the digestive tube are essentially muscular ; a mucous membrane lines its inside, forming within it various folds ; lastly, a third coat is accidentally placed over the other two ; and is furnished by the pleu- ra to the oesophagus, by the peritoneum to the stomach, as well as to the intestinal canal. The characteristic of this third coat is, that it does not cover the whole surface of the parts ofthe tube to which it is applied. The muscular coat may be considered as a long hollow muscle, extending from the mouth to the anus, andTormed throughout almost all the whole of its length, by two lay- ers of fibres, the one set longitudinal, the other circular. The will directs the motions ofthe two extremities, while the rest of its course is not under its controul. In the cells ofthe tissue which unites its surfaces to the other coats, fat never accumulates, which might have impeded its contractions, and straitened and even obliterate the tube along which the food was to pass.* III. Of food, solid and liquid. The aliments which nourish man are obtained from vegetables, or from animals. The mineral kingdom furnishes only condiments, medical substances, or poisonst. By aliment is meant whatever substance affords nutrition, or whatever is capable of being acted upon by the organs of digestion. Substances which resist the digestive action, those which the gastric juice cannot sheathe, whose asperities it cannot soften down, whose nature it cannot change, possess to a certain degree the power of disturbing the action ofthe digestive tube, which revolts from whatever it cannot overcome : there is no essential dif- ference between a medical substance and a poison. Our most active reme- dies are obtained from among the poisonous substances ; tartar emetic, cor- rosive sublimate, opium, all of them remedies of so much efficacy in skilful hands, when administered unseasonably, or in too strong doses, act as most violent poisons ; they forcibly resist the digestive powers, and furnish them nothing to be acted upon, while mild and inert substances yield to these powers, and come under the class of aliments. What then is to be thought of our ptisans, of chicken and veal broth, and other such remedies 1 That they are employed to deceive the hunger and thirst of the patient, to * The digestive tube comprehends, 1. the mouth ; 2. the pharynx; 3. the oesophagus, 4. the stomach ; 5. the small intestines; 6. the large intestines; and 7. the anus. The commencement and termination of this apparatus are subjected, but not completely, to the influence ofthe will. Volition and sensation are distinctly evinced in the moiitli and pharynx; in the oesophagus and stomach the influence of the will gradually disap- pears, and sensation becomes imperfect and peculiar. It is in consequence ofthe distri- bution of voluntary nerves, in greater or less number, to certain parts of the digestive canal, and of the accession thus brought to the ganglial system of nerves with which It is chiefly supplied, that many of the sensations and operations which belong to its upper portion, as the pharynx, oesophagus, and the stomach, are so peculiar, and so difficult of explanation. + Magendie arranges the aliments which nourish man according to the immediate principle which predominates in their composition. After this manner he distinguishes nine classes; namely, farinaceous, mucelaginous, saccharine, acidulated, oleaginous, milky or cheesy, gelatinous, albuminous, and fibrinous aliment? 59 pi event his receiving into his stomach, substances whose laborious digestion would take up the strength required for the cure ofthe disease ; that they are mere precautions of regimen, that he who most varies this kind of re- source, can only be said to adopt a treatment of expectation, leaving to na- ture alone, the care of exciting those salutary motions which are to bring about a cure. Why do certain vegetable purgatives, as manna and tama- rinds, produce so little effect, even though given in large doses ? Because these substances contain many nutritious particles capable of being assimi- lated, so that'strong constitutions digest them, and completely neutralize their irritating or purgative qualities.. An animal or vegetable substance, though essentially nutritious, may act as a medicine, or even as a poison, when, in consequence of the extreme debility of the digestive tube, or because it has not been sufficiently divided by the organs of mastication, it resists the digestive action. Thus surfeits are brought on because the stomach is de- bilitated, because it is oppressed by too great a mass of substances, or be- cause, having been imperfectly triturated, they are insoluble. It is in con- siderations of this kind, that the true foundations of materia medica are laid. Mineral substances are of a nature too heterogeneous to our own, to ad- mit of being converted into our substance. It appears that their elements require the elaboration of vegetable life; hence, it has been justly ob- served, that plants are laboratories'in which nature prepares the food of animals. Aliments obtained from plants are less nutritious than those furnished by the animal kingdom, because in a given bulk, they contain fewer parts that can be assimilated to our own substance. Of all the parts of vegetables, the most nourishing is their amylaceous fecula, but it yields the more readily to the action of the digestive organs, from having already experienced an incipient fermentation ; on that account, leavened bread is the best of vegetable aliments. The flesh of young animals is less nourishing than that of the full-grown, although, at an early age, the flesh of the former abounds more in gelatinous juices ; for, this abundant gelatine wants the ne- cessary degree of consistence. However various our aliments may be, the action of our organs always separates from them the same nutritious principles ; in fact, whether we live exclusively on animal or vegetable substances, the internal composi- tion of our organs does not alter; an evident proof that the substance which we obtain from aliments, to incorporate with our own, is always the same, and this affords an explanation of the snying of the father of physic, " There is but one food, but there exist several forms of food." Attempts have been made to ascertain the nature of this alimentary prin- ciple, common to all nutritive substances, and it is conjectured, with some probability, that it must be analogous to gummy, mucilaginous, or saccha- rine substances ; they are all formed from hydrogen and carbon, are well known to differ chemically only in the different proportions of oxygen which they contain. Thus, sugar is a kind of gum, containing a considera- ble quantity of oxygen ; and which is reduced, in a certain degree, to the state of starch, when brought to a fine powder by means of a rasp, for, the friction disengaging a portion of its oxygen, deprives it in part of its flavour, and leaves it an insipid taste, similar to that of farinaceous substances. Nothing, in fact, nourishes better, more quickly, and from a similar bulk, 'han substances of this kind. The Arab crosses the vast plains of the G(J desert, and supports himself by swallowing a small quantity of gum arable. The nourishing quality of animal and vegetable jellies is well known ; saccharine substances soon cloy the appetite of those who are fondest of them. In decrepid old age, some persons live exclusively on sugar ; I know several in that condition, who spend the day in chewing this substance, which is a laborious employment for their feeble and toothless jaws . Lastly, milk, the sole nourishment ofthe early periods of life, contains a great pro- portion of gelatinous and saccharine matter. Though man, destined to live in all latitudes, is formed to subsist on all "kinds of food, it has been observed, that the inhabitants of warm climates generally prefer a vegetable dietf. The Bramins in India, the inhabitants ofthe Canary Islands, and ofthe Brazils, &c who live almost exclusively on herbs, grain, and roots, inhabit a climate, against the excessive heat of which they have to seek means of protection ; now, the digestion of vegeta- bles is attended with less heat and irritation. The philosophical or reli- gious sects, by which the abstinence from animal food was considered as a meritorious act, were all instituted in warm climates. The school of Py- thagoras flourished in Greece, and the anchorets, who, in the beginning of * Magkndie concluded from his experiments, that no animal seems capable of deriv- ing nutriment from any substance that does not contain some portion of azote. There are, however, many circumstances which*prove the contrary.—Adanson asserts, that the Nomadic Moors have scarcely any other food than gum senega. HASSELauiST re- lates, that a caravan of Abyssinians, consisting of 1000 persons, subsisted for two months on a stock of gum arabic alone, which they found among their merchandize ; and it is well known, that negroes, and individuals otherwise imperfectly fed, soon become fat from the mastication of the sugar-cane. A case lately came under our observation, which fully exemplifies the nutritious quality of sugar, in a lady, about the middle age, who consulted us respecting great and increasing corpulency. Her countenance was full, clear, and florid; her pulse strong; her health excellent; and her strength very considerable. She partook of animal food only once in a day, and then in a small quan- tity. She never took suppers, and was very moderate in the use of fluids. She had al- ways taken considerable exercise on foot, and even up to the period at which we saw her, she resorted to it as much as the great bulk of her body could permit. The secret, how- ever, of her increasing obesity was disclosed, when she mentioned her insatiable desire for refined sugar, which she almost hourly made use of, frequently to the extent of one pound weight daily. She considered it her chief article of diet. She reckoned the average quantity which she used at about three-fourths of a pound in the day. Tea or coffee was taken by her sweetened in the usual way. She ate the sugar in the solid state, and unaccompanied with any other article of diet: the finest sort only wa3 relished. Her digestive functions were in a perfect condition; neither cardialgia, acidity, nor flatu- lence, were complained of. Her teeth were sound. She found her. corpulence super- vene to a spare habit some time after the habit of eating sugar was acquired. She thought that the obesity increased with the increase in the quantity of sugar she consum- ed. The habit had become so confirmed, at the time which we saw her, that she con- ceived it to be quite impossible to relinquish it. t These inhabitants of warm climates, who are subjected, in consequence of the na- ture ofthe situation in which they live, to a moist and miasmatous atmosphere, generally adapt their vegetable diet, as much as may be in their power, to the circumstances in which they are placed. They endeavour, by adding a large proportion of the stimulant and tonic seeds of plants to their aliments, to counteract the debilitating and septic influ- ence of the air which they breathe, and to other causes to which they are more or less opposed. To them the hot spices are the chief condiment, and even prophylactic ; with- out the use of these, their very aliments would become a source of disease ; the various kinds of parasitical animals, which prey on man, would abound to the most loathsome degree, and they would be continually the subject of dysentery, and the other diseases which imperfect or improper nourishment and an unwholesome climate induce. The hot spicies are, to individuals so circumstanced, more requisite than salt is to the inhabit- ant* of temperate or cold climates, who live chiefly on animal food 61 the Christian religion, peopled the solitudes of Thebais, could not have en- dured such long fastings, or supported themselves on dates and water, in a more severe/climate. So that the monks that removed into different parts of Europe, were obliged to relax from the excessive severity of such a regi- men, and yielded to the irresistible influence ofthe climate ; the most aus- tere came to add to vegetables, which formed the base of their food, eggs, butter, fish, and even water-fowl. In books of casuistry, it may be seen, on what ridiculous grounds there was granted a dispensation in favour of plovers, of water hens, wild ducks, snipes, scoters, birds whose brown flesh, more animalized. and more heating, ought to have been proscribed from the kitchen of monasteries, much more strictly than that of common poultry. Consider what is the alimentary regimen of the different nations on the face ofthe earth, and you will see, that a vegetable diet is preferred by the inhabitants of warm countries : to them, sobriety is an easy virtue ; it is a happy consequence of the climate. Northern nations, on the contrary, are voracious from instinct and necessity. They swallow enormous quantities of food, and prefer those substances which in digestion produce the most 'heat.—Obliged to struggle incessantly against the action of cold, which tends to benumb the vital powers, to suspend every organic motion, their life is but a continual act of resistance to external influences. Let us not reproach them with their voracity, and t'.eir avidity for ardent spirits and fermented liquors. Those nations that inhabit the confines of the habitable world, in which man is scarcely able to withstand the severity ofthe cli- mate, the inhabitants of Kamtschatka, the Samoiedes, live on fish, that in the heaps in which they are piled up, have already undergone a certain degree of putrefactive fermentation. Does not the use of a food so acrid and heat- ing, that in our climate it would inevitably be attended with a febrile action, prove plainly the necessity of balancing, by a vigorous inward excitement, the debilitating influence of powers that are operating from without 1 The abuse of spirituous liquors is fatal to the European transported to the burning climate ofthe West Indies. The Russian drinks spirituous liquors with a sort of impunity, and lives on to an advanced age, amidst excesses under which an inhabitant of the south of Europe would sink. This influence of climate affects alike the regimen of man in health, and that of man in sickness, and, it has been justly observed of medicine, that it ought to vary according to the places in which it is practised. Barley, ptis m, honey, and afew other substances, the greater part obtained from the vege- table kingdom, sufficed to Hippocrates in the treatment of diseases, his the- rapeutic treatment was, in almost every case, soothing and refreshing. Phy- sicians, who practise in a climate such as that of Greece, may imitate this simplicity ofthe father of physic. Opium, bark, wine, spirits, aromatic*, and the most active cordials, are, on the other hand, the medicines suited to the inhabitants ofthe North. The English physicians use. freely and with- out risk, these medicines, which elsewhere would be attended with the ut- most danger. Simple aqueous drinks promote digestion*, by facilitating the solution of the solids ; by serving as a vehicle to their divided parts ; and when ren- dered active by saline or other substances, as spirituous liquors are by alco- * Simple fluids promote this process only when they are taken in small quantity. If they are used so largely as to dilute in too great a degree the gastric juice, and to over- distend the stomach, especially during meals, they evidently retard digestion &2 hoi, they are further useful in stimulating the organs, and exciting their action. The least compound drinks are possessed, in different degrees, of this double property of dissolving solid aliments, and of stimulating the digestive organs. The purest water is rendered stimulating by the air, and by the salts which it contains, in different proportions ; and, to the want of that stimulating quality is to be attributed the difficult digestion of distilled water. The drinks best suited to the wants of the animal economy, are those in which the stimulating principles are blended, in due proportions, with the water which holds them in solution. But almost all the fluids which we drink, contain a certain proportion of nutritious particles. Wine, for exam- ple, contains these nutritive particles in greater quantity, as it is the produce ofa warmer climate, and as saccharine matter predominates in its composi- tion. Thus, Spanish wines are in themselves nourishing, and are perhaps fit- ter to satisfy hunger than to allay thirst, while the acidulous Rhenish wines. which are merely thirst allaying, scarcely contain any cordial quality. Be- tween the two extremes are the French wines, which possess, in a nearly equal degree, the treble advantage of diluting the fluids, of stimulating the organs, and of furnishing to the animal economy materials of nutrition. IV. Of hunger and thirst. By the words hunger and thirst are meant two sensations, which warn us ofthe necessity of repairing the loss which our body is continually undergoing from the action of the vital principle. Their nature, as is well observed by M. Gall, is not better known than that of thought. Let us endeavour to explain the phenomena by which they are attended. The effects ofa protracted abstinence are, a diminution of the weight of the body, a diminution which becomes sensible in the course of twenty-four hours ; a wasting ofthe body from the loss of fat, discoloration ofthe fluids, especially the blood, loss of strength, excessive sensibility, sleeplessness, with painful sensations in the epigastric region.* Death from inanition is most easily brought on, in those who are young and robust. Thus, the unfortunate father, whose horrible story has been related by Dante, condemned to die of hunger, and shut up with his children in a dark dungeon, died the last, on the eighth day, after having witnessed, in the convulsions of rage and despair, the death of his four sons, unhappy victims of the most execrable vengeance ever recorded in the history of man. Haller has related, in his great work on physiology, several instances of prolonged abstinence : if we are to give credit to these accounts, some of which are deficient in the degree of authenticity required to warrant belief, persons have been known to pass eighteen months, two, three, four, five, six, seven, and even ten years, without taking any nourishment. In the memoirs of the Edinburgh Society is found the history of a woman who lived on whey only for fifty years. The subjects of these cases are mostly weak, infirm women, living in obscurity and inaction, and in whom life, nearly extinct, just shewed itself, in an almost insensible pulse, an unfre- quent and indistinct respiration. It is a fact well worthy of observation, that the muscles and viscera of some of them, when examined after death, shone with a light evidently phosphoric.t Can it be that phosphorus is the - See APPENDIX, Note 1. t Nitidis*ima viscera sunt animaliumfame cnecloruw, et argeniti ij.b r arum fasciculi.— Hatj.jsr. FJem Phys. *om. VI, page i^3. result ofthe lowest degree of animalization ? It may be easily conceived that living in a manner, on their own substance, the fluids in such persong have been frequently subjected to the causes which produce assimilation and animalization, and have undergone the greatest alteration of which they are capable. The proximate cause of hunger has by some been conceived to depend on the friction of the nervous papillae of the empty stomach on each other ; by others, it has been imputed to the irritation produced on its parietes, by the accumulation ofthe gastric juice. It has been thought to depend on the lassitude attending the permanent contraction of the muscular fibres of the stomach ; and on the compression and creasing of the nerves, during that permanent constriction ; on the dragging down of the diaphragm by the liver and spleen, when the stomach and intestines being empty, cease to support those viscera: a dragging which is the greater, as a new mode of circulation takes place in the viscera, which are supplied with blood by the caeliac artery, and while the stomach receives less blood, the spleen and liver increase in weight and size, because their supply is increased*. Those who maintain that hunger depends on the friction of the parietes of the stomach against each other, when brought together in an empty state, adduce the example of serpents, whose stomach is purely membranous, and who endure hunger a long time, while fowls, whose powerful and muscular stomach is able to contract strongly on itself, endure it with difficulty. But to say nothing of the great difference of vitality, in the organs of a bird and ofa reptile, the stomach which continues closing on itself as it is emptied, may contract to such a degree as scarcely to equal in size a small intestine, without its following, as a necessary consequence, that the parietes which are in contact should exert on each other any friction, on which the sensa- tion of hunger may depend. In fact, the presence of food is necessary to determine an action ofthe parietes of the stomach, and as long as it is empty, there is nothing to call forth such action. Those who think that hunger is mechanically produced by the weight of the spleen and liver that keeps pulling down the diaphragm, which the empty stomach no longer bears up, observe, that it may be appeased, for a time, by * The most prevalent opinions respecting the proximate causes of hunger are, that it is owing to the action of the gastric juice on the stomach, or that it is a sensation connected with the contracted state of this organ and the corrugation of its internal membrane. It is not unlikely that both causes may contribute to the production of this sensation, in con- sequence of the impression which they may make on the sentient extremities of these cere- bral nerves which reinforce the vital operations of the stomach. The state of the absorb- ent vessels, and the irritation which the gastric fluid induces on the extremities of these vessels, during an empty state of this viscus, ought also to be taken into consideration in our speculations respecting the origin of this sensation. The following experiment of Dr. W. Philip, detailed in his excellent work on indi- gestion, appears to confirm the opinion that the influence of the gastric juice on the stomach is, in some way or other, productive ofthe sense of hunger. " A person in good health was prevailed upon to abstain from eating for more than twenty hours, and further to increase the appetite by more exercise than usual, At the end of this time he was very hungry; but, instead of eating, excited vomiting by drinking warm water, and irritating the fauces. The water returned mixed only with a ropy fluid, such as the gastric fluid is described to be by Spallanzani, or as I have myself obtained it from the stomach of a crow. After this operation, not only all desire to eat was removed, but a degree of disgust was excited by seeing others eat. He, however, was prevailed upon to take a little milk and bread, which in a very short time ran into the acetous fer* mentation, indicated by flatulence and acid eructations.'' 64 supporting the abdominal viscera by means ofa white girdle ; that hunger ceases as soon as the stomach is full, before the food can have yielded to it any materials of nutrition. On this hypothesis, which is purely mechanical, as that which explains hunger by the irritation ofthe gastric juice, by the lassitude ofthe contracted muscles, by the compression ofthe nerves, how shall we explain the fact, that when the hour ofa meal is over, hunger ceases for a time ? Ought not hunger, on the contrary, to be considered as a nervous sensation which exists in the stomach, is communicated by sympa- thy to all the other parts, and keeping up an active and continuous excite- ment in the organ in which it is principally seated, determines into it the fluids from all parts ? This phenomenon, like all those which depend on nervous influence, is governed by the laws of habit, by the influence of sleep, and ofthe passions ofthe mind, whose power is so great, that literary men, absorbed in meditation and thought, have been known entirely to for- get that they required food. Every thing which awakens the sensibility of the stomach, in a direct or sympathetic manner, increases the appetite, and occasions hunger. Thus, bulimia depends, sometimes, on the irritation ofa tape-worm in the organs of digestion. The application of cold to the skin, by increasing, from sympathy, the action ofthe stomach, has been known to occasion fames canina, of which several instances are related by Plutarch (Life of Brutus.) Ardent spirits and highly-seasoned food, excite the appe- tite, even when the stomach is overfilled. Whatever, on the contrary, blunts or renders less acute the sensibility ofthe stomach, renders more en- durable or suspends the sensation of hunger. Thus, we are told by travel- lers, that the Turkish dervises and the Indian faquirs, endure long fasts, be- cause they are in the habit of using opium, and lull, in a manner, by this narcotic, the sensibility ofthe stomach. Tepid and relaxing drinks impair the appetite ; the use of opiates suspends suddenly the action ofthe stomach. V. Of Thirst. The blood deprived of its serosity, by insensible perspira- tion and by internal exhalation, requires incessant dilution, by the admix- ture of aqueous parts, to lessen its acrimony ; and as the serosity is inces- santly exhausting itself, the necessity for repairing that loss is ever urgent.* * As hunger seems to depend upon a certain condition of, or impression made upon, these cerebral nerves distributed to the stomach, so thirst appears to arise from an altered state ofthe fluids, which state modifies the functions of the vessels, diminishes or other- wise alters the condition ofthe fluids secreted in the mouth and fauces, and impresses the nerves of sensation, in these situations, in such a manner as to give rise to the phenome- non under consideration. As the sense of thirst is induced by a state of the circulating fluids, which would be- come hurtful to the system were it to continue for any considerable period, so this sen- sation is to be regarded in the light of a watchful guardian, which both points out that state, and the only way in which it can be removed. The super-abundance of saline or stimulating substances in the blood, is readily indi- «ated by the sensation induced in the mouth and fauces, which are the first parts to evince the deleterious effects of these substances upon the animal economy : hence the state of these organs is an important index to the condition ofthe circulating fluids, and ofthe whole system, in a number of diseases. Those physiologists who refer the operations ofthe living body to a galvanic process, carried on by the nervous system on the fluids contained in the vascular, especially in the capillaries, assign, as the proximate cause of thirst, a deficiency of oxygen and an abundance of the inflammable materials amongst these elements which constitute the fluids circulating at the time \n which the sensatioi. is induced, (" Oxygenii autem defectum et phlogisticorum abummntium sitim adducere.") This, or a similar opinion, is enter- tained by Sprengel, Prochaska. Burbacii, and Lenhosseck. The arguments which these systematic writers on physiology adduce, a? well as the experiments of h:i The calls of thirst are still more absolute than those of hunger, and it is much less patiently endured. If it be not satisfied, the blood, and the fluids which are formed from it, become more and more stimulating, from the con- centration ofthe saline and other substances which they contain. The gene- ral irritation gives rise to an acute fever, with heat and parching ofthe fau- ces, which inflame, and may even become gangrenous, as happens iD some cases of hydrophobia. English sailors, who were becalmed, had exhausted all their stock of fresh water, and were at a distance from land ; not a drop of rain had for a long while cooled the atmosphere : after having borne, for some time, the agonies of thirst, further increased by the use of salt provi- sions, they resolved to drink their own urine. This fluid, though very dis- gusting, allayed their thirst; but at the end ofa few days, it became so thick and acrid, that they were incapable of swallowing a mouthful of it. Reduced to despair, they expected a speedy death, when they fell in with a ship which restored them to hope and life. Thirst is increased every time that the aqueous secretions are increased ; ihus, it becomes distressing to a dropsical patient, in whom the fluids are determined towards the seat of effusion. It is excessive in diabetes, and in proportion to the increased quantity of urine. In fever, it is increased, from the effect of perspiration, or because in some of these affections, for example, in bilious fevers, the blood seems to become more acrid. Hence the advantage of cooling, diluting, and refreshing drinks, administered copiously, with a view to correct the temporary acrimony oc- casioned by the absence ofa great quantity ofthe serous parts ofthe blood, and to lessen the over excitement of a fluid become too stimulating. The use of aqueous drink is not the most effectual method of allaying thirst. A traveller, exposed to the scorching heat of summer, finds it ad- vantageous to mix spirits to plain water, which alone does not stimulate suffi- ciently the mucous and salivary glands, whose secretion moistens the inside ofthe mouth and pharynx, and covers these surfaces with the substance best calculated to suspend, at least for a time, the erethism on which thirst appears to depend. VI. On mastication* The organs employed in the mastication ofthe food, are the lips, the jaws, and the teeth ; with these are furnished, the muscles by which they are moved, and those which form the parietes of the mouth. The motions of the lips are extremely varied, and depend on the single or combined action of their muscles, by which the greater part ofthe face is covered, and which may be enumerated as follows :—Elevators of the upper lip (caninus, incisivus. levatores communes labiorum et myrtiformes.) De- pressors ofthe under lip (triangularis labiorum, quadratus gen the stomach is di- vided into two parts by a circular contraction. The food which is re- ceived into the great fundus of the stomach, may remain longer in that viscus, as this part of its cavity lies out of the course of the aliment. XX. Of the gastric juice. Of all the organs, the stomach probably re- ceives, in proportion to its bulk, the greatest number of blood-vessels ; in its membrano-muscular parietes, which are little more than the twelfth part of an inch in thickness, there is distributed the coronary artery of the stomach, entirely destined to that organ ; the pyloric, the right gastro-epiploic, given off by the hepatic artery. The greater part of the blood, therefore, which passes from the aorta to the casliac artery goes to the stomach, for though of the arteries into which that trunk is divided, the coronary of the stomach is the least, the arteries of the liver and spleen send to the stomach several pretty considerable branches, before entering the viscera to which they are more particularly allotted. One need only observe the great disproportion between the stomach and the quantity of blood which it receives, to conclude, that this fluid is not merely subservient to its nutrition, but is destined to furnish the materials of some secretion. The secretion in question, is that of the gastric juice, which is most abundantly supplied by arterial exhalation, from the internal surface of fhe stomach ; it is most active at the instant when the food received with- *See AfPFNOIX, Note K. 78 in its cavity, excites irritation, transforms it into a centre of fluxion, towards which the fluids flow from all directions. The state of fulness of the stomach, favours the afflux of the fluids into the vessels, as, in conse- quence of the extension of its parietes previously collapsed, the vessels are no longer bent and creased. The arteries of the stomach, of the spleen and liver, arising from a common trunk, it may be easily under- stood how, when the stomach is empty, little blood enters into it, in that state of contraction ; how at the same time, the spleen which is less compressed, and the liver, must receive a larger supply of blood, and again a smaller quantity, when the stomach is full. The gastric juicenthe result of arterial exhalation, mixes with the mu- cus poured out by thfe mucous follicles ofthe internal membrane of the stomach. This mixture renders it viscous and ropy, like the saliva, to which, in man, the gastric juice bears a great analogy. It is very difficult to obtain it pure, so as to analyze it, and even if by long fasting, the sto- mach should be deprived ofthe alimentary residue, which might affect its purity, one could not prevent it being mixed with a certain quantity of liquid bile, which always flows back through the pyloric orifice, turns yellow the inner surface of the stomach, in the neighbourhood of that orifice, and even imparts a certain degree of bitterness to the gastric juice. The passage ofthe bile from the duodenum into the stomach, can- not be looked upon as morbid ; it occurs in the most perfect health, which has led to a well founded opinion, that a small quantity ofthe bilia- ry fluid is a useful stimulus to the stomach. This opinion is confirmed by an observation of Vesalius, who relates, that he found the ductus communis choledochus, opening into the stomach, in the body of a con- vict noted for his voracious appetite. It is further confirmed by what is observed in birds of prey, in the pike, &.c. who digest easily and with great rapidity, because the termination into the duodenum of the ductus communis choledochus, being very near to the pylorus, the bile easily ascends into the stomach, and is always found there in considerable quan- tity- To obtain some of this gastric juice, it is necessary, either to open a liv- ing animal under the influence of hunger, or to oblige a night bird of prey, as an owl, to swallow small spunges fastened to a long thread. When the spunge has remained for a short time in the stomach, it is withdrawn soaked with gastric juice, of which the secretion has been promoted by its presence in the stomach. The gastric juice, in its natural state, is neither acid nor alkaline : it does not turn red or green, vegetable blue colours. Its most remarkable quality is. its singularly powerful solvent faculty, the hardest bones can- not withstand its action ; it acts on those on which the dog feeds ; it com- bines with all their organized and gelatinous parts, reduced them to a calcareous residue, forming those excrementitious substances so absurd- ly called album gr cecum, by the older chemists. The solvent energy of the gastric juice, is in inverse ratio of the muscular strength of the pari- etes ofthe stomach, and in those animals in which the parietes of that viscus are very thin, and almost entirely membranous, it has most power and activity. In the numerous class of zoophytes, it alone suffices to ef- fect decomposition ofthe food, always more prompt, when accompanied by warmth of the atmosphere, as was observed by du Trembly, in the polypi, which in summer, dissolve in twelve hours, what in colder wea- 79 the* it would take three days to digest. In the actinia, in the holothuna, the gastric juice destroys even the shells ofthe muscles which they swal- low. Are we not all acquainted with the peculiar flavour of oysters, how much they tend to whet the appetite ? this sensation depends less on the salt water contained in the shell, than on the gastric juice which acts on the tongue, which softens its tissue, and quickens its sensibility. This mucous substance, when received into the stomach, promotes the diges- tion ofthe food which is afterwards taken into it, for the oyster itself is very little nutritious, and is used rather as a condiment, than as affording nourishment. The gastric juice not only pervades and dissolves the food received in- to the stomach, but it unites and intimately combines with it, completely alters its nature, and changes its composition. The gastric juice acts, in a manner peculiar to itself, on the food exposed to its action, and far from inducing a beginning of putrefaction, suspends on the contrary, and cor- rects putrescency. This antiseptic quality of the gastric juice, suggested the practice of moistening ulcers with it to accelerate their cure, and the experiments made at Geneva and in Italy, have, it is said, been fully suc- cessful. I have made similar experiments with saliva, which, there is every reason to consider, is very similar to the gastric juice, and i have seen old and foul ulcers assume a better appearance, the granulations be- come healthy, and the affection rapidly advance towards a cure, from the use of that irritating fluid. I had under my care an obstinate sore on the inner ankle of the left leg of an adult; notwithstanding the external ap- plication of powdered bark, and of compresses soaked in the most deter- gent fluids, this sore was improving very slowly, when 1 bethought my- self of moistening it every morning with my saliva, the secretion of which was increased by the hideous aspect of the sore. From that time, the patient evidently mended, and his wound contracting daily, at last became completely cicatrized. However powerful the efficacy ofthe gastric juice, to dissolve the ali- mentary substances, it does not direct against the coats ofthe stomach its active solvent faculty. These parietes endowed with life, powerfully resist solution. The lumbrici so tender and delicate, for the same rea- son, can exist within it, without being in the least affected by it. and such is this power of vital resistance, that the polypus rejects unhurt its arms, when it happens to swallow them among its food.* But when the stomach and the other organs have lost their vitality, its parietes yield to the sol- vent power of the juices which it may contain, they become softened, and even in part destroyed, if we may believe Hunter, who found its inner membrane destroyed in several points in the body ofa criminal, who for some time before his execution, had been prevailed upon, in considera- tion ofa sum of money, to abstain from food.j * It had been thought, that no animal could live on the flesh of its own kind, and this circumstance was explained on the same principle; but to refute it, we need only quote the instance of cannibals, and of several tribes of carmverous animals, who, in the absence of other prey, devour one another.—Author's Note. t The following case of solution ofthe stomach after death came under the obser- vation of Professor Haviland. The subject was a young man whose body was opened twelve hours after death, and the stomach, on being examined alter its removal from the body, presented the following appearances :—The mucous membrane seemed more red and vascular than usual throughout its whole extent, and here and there wer* 80 The gastric juice is capable, even after death, of dissolving food intro- duced into the stomach, by a wound made into it, provided the animal still preserves some degree of animal heat. It acts on vegetable and animal substances triturated and put into a small vessel, such as those under which Spallanzani, in his experiments on artificial digestion, kept up a moderate heat. Let us not, however, consider as the same, this solution ofthe food in the gastric juice, out ofthe stomach, and that which occurs in digestion within the organ. Every thing tends to shew, that the sto- mach ought not to be considered as a chemical vessel, in which there takes place a mixture giving rise to new combinations. The tying the nerves of the eighth pair, the use of narcotic and of opium, intense thought, every powerful affection of the mind, trouble or even gaiety, entirely suspend digestion in the stomach, which cannot take place iade- small spots of what seemed to be extravasated blood, lying beneath the mucous coat, as they could not be washed off, nor removed by the edge of the scalpel. There were two holes in the stomach ; the larger very near to the cardiac end ofthe small curva- ture, and on the posterior surface; this was more than an inch in length, and about half an inch in breadth. The other, not far from the former, and likewise upon the posterior surface, was about the size ofa sixpence. The edges of these holes were smooth, well denned, and slightly elevated. The coats of the stomach were thin in many other spots, and in one part nothing was left but the peritoneum, the mucous and muscular coats being entirely destroyed. There was a hole in the diaphragm through the muscular portion, where it is of considerable thickness, large enough to admit the end of the finger. There was no appearance of ulceration or of pus ad- hering to the edges of this perforation of the diaphragm. Dr. Haviland concludes, that, owing to the activity of the solvent power of the gastric juice, it sometimes not only corrodes the parietes of the stomach, but even the thick muscle ofthe diaphragm, and that within the space of twelve hours after death, as was exemplified in this case.— Transactions ofthe Cambridge Philosophical Society, Vol. 1. Part. II. 1822. Hunter's view of this subject has been disputed, to the present day, by several emi- nent pathologists; but Dr. Philip's observations are qualified to prove it in a very satis- factory manner to those who yet required more convincing arguments. On opening the abdomen of rabbits which had been killed immediately after having eaten, and which were allowed to lie undisturbed for some time before the examination, he has found ''the great end of the stomach soft, eaten through, sometimes altogether con- sumed, the food being only covered by the peritoneum, or lying quite bare for the space of an inch and a half in diameter ; and part ofthe contiguous intestines, in the last case, also consumed, while the cabbage, which the animal had just taken, lay in the centre of the stomach unchanged, if we except the alteration which had taken place in the external parts ofthe mass it had formed, in consequence of imbibing gas- tric fluid from the half-digested food in contact with it." The following are Dr. Philip's observations:—" We sometimes found the great end ofthe stomach dissolved within an hour and a half after death. It was more fre- quently found so when the animal had lain dead for many hours. This effect does not always ensue, however long it has lain dead. It seems only to take place when there happens to be a greater than usual supply of gastric fluid ; for we always ob- served it most apt to happen when the animal had eaten voraciously. " Why it should take place without the food being digested, is evident from what has been said. Soon after death, the motions of the stomach, which are constantly carrying on towards the pylorus the most digested food, cease. Thus, the food which lies next to the surface of the stomach, becoming fully saturated with gastric fluid, neutralizes no more, and no new food being presented to it, it necessarily acts on the stomach itself, now deprived of life, and, on this.account, as Mr. Hunter justly ob- serves, equally subject to its action with other dead animal matter. It is remarkable that the gastric fluid of the rabbit, which in its natural state refuses animal food, should so completely digest its own stomach as not to leave a trace of the parts acted oa. I never saw the stomach eaten through except in the large end ; in. other parts, its internal membrane is sometimes injured." BI pendently of nervous influence. Yet this nervous influence may possi- bly not concur directly, and of itself, to stomachic digestion ; it is perhaps merely relative to the secretion ofthe gastric juice, which the ligature of the nerves, the action of narcotics or of other substances may impede, alter, or even completely suspend. It is now pretty generally admitted, that digestion in the stomach con- sists in the solution of the food in the gastric juice. This powerful sol- vent penetrates, in every direction, the alimentary mass, removes from one another, or divides its molecules, combines with it. alters its inward composition, and imparts to it qualities very different from those which it possessed before the mixture. If, in fact, a mouthful of wine or of food is rejected, a few minutes after being swallowed, the smell, the fla- vour, all the sensible and chemical qualities of such substances, are so completely altered, that they can scarcely be recognized ; the vinous substances turned, to a certain degree, sour, are no longer capable ofthe acetous fermentation. The energy of the solvent power of the gastric juice, perhaps over-rated by some physiologists, is sufficient to dissolve and reduce into a pulp, the hardest bones on which some animals feed. It is highly probable, that its chemical composition varies at different times ; that it is acid, alkaline or saponaceous, according to the nature of the food. Although the gastric juice be the most powerful agent of di- gestion, its solvent power requires to be aided by several secondary causes, as warmth, which seems to increase, and, in a manner, to concen- trate itself in the epigastric region, as long as the stomach is engaged in digestion ; a sort of inward fermentation which cannot be, strictly speak- ing, compared to the decomposition which substauces, subject to putre- faction and acescency undergo. The gentle and peristaltic action of the muscular fibres of the stomach, which press in every direction, on the alimentary substance, performs on it a slight trituration, while the mois- ture of the stomach softens and macerates the food, before it is dissolved ; one might therefore say, that the process of digestion is at once chemical, mechanical, and vital ; in that case, the authors of the theories that have been broached, have been wrong, only in ascribing to one cause, such as heat, fermentation, putrefaction, trituration, maceration, and the action of the gastric juice, a process which is the result of a concurrence of these causes united. The food remains in the stomach, during a longer or shorter space of time, according as by its nature, it yields more or less readily to the changes which it has to undergo. Gosse of Geneva, ascertained, by ex- periments performed on himself, that the animal and vegetable fibre, con- crete albumen, white and tendinous parts, paste containing fat or butter, substances which have either not undergone fermentation, or which do not readily undergo that process, remain longer in the stomach, offer more resistance to the gastric juice, than the gelatinous parts of animals Sr vegetables, fermented bread, &c. ; that the latter required but an hour for their complete solution, while the former were scarcely dissolved, at the end of several hours. XXI. The following case throws, methinks, some light on the mechan- ism and importance of the action of the stomach in digestion. The pa- tient was a woman whom I had frequent opportunities of examining at the "hopi* >! de la charite'," at Paris, in the clinical wards of Professor 11 82 Corvisart, in which she died on the 9th nivose of the year X. after six months' stay in the hospital. A fistulous opening, of an oval form, an inch and a half in length, and upwards of an inch in breadth, situated at the lower part of the chest, at the upper and left side of the epigastric region, afforded an opportunity of viewing the inner part of the stomach, which, when empty of food, appeared of a vermilion colour, was covered with mucus, its surface wrinkled over with folds about half an inch deep, and enabled one to dis- tinguish the vermicular undulations of these folds, and of all the parts which were in sight. The patient, who was then forty seven years of age, had had this fistula since she was in her thirty-eighth year. Eigh- teen years before, she had fallen on the threshold of a door, the blow had struck against her epigastric region. The place remained affected with pain, and she became incapable of walking or of sitting, otherwise than bent forward and to the left side. At the end of this long interval a phlegmonous and oblong tumour appeared on the injured spot: during the nausea and vomiting which came afterwards, the tumour broke, and there escaped at the wound, which was left by this rupture, two pints of a fluid which the patient had just swallowed to obtain relief. From that time, the fistula, which at first, would scarcely have admitted the tip of the little finger, increased daily ; at first it allowed only the fluids to pass, but, on the eighth day, the solid food came away freely, and continued to do so till she died. When admitted into the hospital, she ate as much as three women of her age, she voided about a pint of urine, and went to stool only once in three days. Her faeces were yellowish, dry, rounded, and weighed more than a pound. Her pulse was very feeble and ex- tremely slow, its pulsation scarcely exceeding forty-five or forty-six beats in a minute. Three or four hours after a meal, an irresistible desire obliged her to take off the lint and compresses with which she* covered the fistulous opening, and to give vent to the food which her stomach might happen to contain ; it came out rapidly, and there escaped at the same time, and with a noise, a certain quantity of gases. The food thus evacuated, exhaled an insipid smell, was neither acid nor alkaline, for, the chymous and greyish coloured pulp into which they were reduced, when suspended in a certain quantity of distilled water, did not affect vegetable blues. The digestion of the food was far from being always complete; sometimes, however, the smell of wine could not be recognized, and the bread formed a viscid, thick, and soft substance pretty similar to fibrine newly precipitated by the acetous acid, and it floated in a tenaceous liquid of the colour of common broth.* * Dr. Prout has made several experiments in order to ascertain the chemical com- position of the chyme, from which he obtained tne following results:— No. 1. Chyme of a dog fed on vegetable food. Composed ofa semifluid, opake, yel- lowish white part, containing another portion of similar colour, but of firmer consis- tence mixed with it. Spec. grav. 1.056. It showed no traces of a free acid, or alka- li, but coagulated milk completely, when assisted by a gentle heat. No. 2. Chyme of a dog fed on animal food. This was more thick and viscid than No. 1. and its colour was more inclining to red. Spec. Grav. i.022. It showed no traces of a free acid, or alkali, nor did it coagulate milk, even when assisted by the most favourable circumstances. On being subjected to analysis, these two specimens of chyme were found to consist •f 83 It follows, from the experiments performed at the Ecole de Medicine, on these half digested substances, and on the same before their admission into the stomach, that the changes which they undergo, consist in the in- crease of gelatine, in the formation ofa substance which has the appear- ance of fibrine, without having all its qualities, in a greater proportion of muriate and phosphate of soda, as well as of phosphate of lime. This patient was unable to sleep, till she had emptied her stomach, which she cleared by swallowing a pint of infusion of chamomile. In the morning, there was seen in the empty stomach a small quantity ofa ropy frothy fluid, like saliva. It did not turn vegetable blues to a green or red colour, was not homogeneous, but exhibited particles, of some degree of consistence, among the more fluid parts, and even albuminous flakes completely opaque. The experiments performed on this fluid, shewed that it bore a considerable analogy to saliva, which, however, is rather more liable to putrefaction. The vermicular motion by which the stomach cleared itself of its con- tents, took place in two different, but not in opposite directions, the one pressing the food towards the fistulous opening, the other towards the pylorus, through which the smaller quantity was allowed to pass. On opening the body, it was found, that the fistula extended from the cartilage ofthe seventh left rib, as high as the osseous termination ofthe sixth ; its edges were rounded, and from three to four lines in thickness ; they were covered with a thin moist skin, of a red colour, and similar to that of the lips. The peritoneal coat of the stomach adhered so firmly to the peritoneum lining the fore part ofthe abdomen, around the open- ing, that the line of adhesion would not be observed. The opening was in the anterior part ofthe stomach, at the union of the two-thirds on the left side, with the third on the right of that viscus ; that is, about eight fingers' breadth from its greater extremity, and only four from the pylorus. It extended from the greater to the lesser curvature. In other respects, it was the only organic affection of that viscus. It should be stated, that for several years, the patient had been thin and emaciated, and had led a languid life, which was terminated by a col- liquative diarrhcea. She seemed to be supported only by the small quan- tity of food which passed through the pylorus, into the duodenum, where it received the influence ofthe bile, whose action on the chyme, is, as we shall presently state, absolutely essential to the separation of the nu- tritious parts. Not that there was any thing to prevent the absorbents of A. Water....................................... B. Gastric principle, or mucus united with ali- mentary matters, and apparently constituting the chyme, properly so called, mixed with ex- crementitious matter.......................... C. Albuminous matter, chiefly fibrin............. D. Biliary principle............................. E. Vegetable gluten.............................. F. Saline matters................................ G. Insoluble residuum.............................■ F. The saline matters were obtained by incineration, and consisted chiefly of the muriates, sulphates, and phosphates. l. Vsiiyiuu lrum Vegetable Food. 86-5 1-6 5- 100- Animal Food. 80- 15-S 1-3 1-7 -% •S 100- 84 the stomach from taking up a certain quantity oi nutritious particles, bu; that small quantity of food in an imperfect condition, was of very little service in imparting nourishment, and, in that respect, she was in similar circumstances to patients who are affected with obstruction ofthe pylorus, and reject the greater part of their food, when, digestion being over, this contracted opening can no longer allow any food to pass. XXII. While the alimentary solution is going on, the two openings of the stomach remain perfectly closed ; no gas disengaged from the food, escapes along the oesophagus, except when digestion is imperfect. A slight shivering is felt, the pulse becomes quicker, and more contracted, the vital power seems to forsake the other organs, to concentrate itself on that which is the seat of the digestive process. The parietes of the Stomach are soon called into action ; its circular fibres contract in different points ; these peristaltic oscillations, at first irregular and uncertain, ac- quire more regularity, and act from above downwards, and from the left to the right, that is to say, from the cardiac to the pyloric orifice. Be- sides, its longitudinal fibres shorten it, in the direction of its greatest dia- meter, and bring nearer to each other its two orifices. In these different motions, the stomach rises over the pylorus, so that the angle which it forms with the duodenum, almost entirely ceases, and this facilitates the escape of the food. It has been observed, that during sleep, digestion takes place much more readily, when we lie on the right, than on the leftside, and this circumstance has been ascribed to the compression of the liver on the stomach. It is much more, likely to depend on the cir- cumstance, that when we lie on the right side, the passage ofthe food is facilitated by its own weight, the natural obliquity of the stomach, from left to right, being increased by the changes attending the presence ofthe food. XXIII. On the uses of the Pylorus. The pyloric orifice is furnished with a muscular ring, covered over by a fold ofthe mucous membrane ofthe stomach. This kind of sphincter keeps it perfectly clused, while digestion is going on in the stomach, and will not allow a free passage to the food which has not yet undergone a sufficient change. The pylorus, which is endowed with a peculiar and delicate sensibility, may be con- sidered as a vigilant guard, which prevents any thing from passing into the intestinal canal, till it has undergone the necessary changes. Seve- ral authors quoted by Haller, have, very justly, observed, that the ali- mentary substances do not leave the stomach in the same order that they were received into it, but that they are evacuated according to their de- grees of digestibility. One may say, that there really takes place in the stomach, a sorting of the different substances which it contains. Those that are most readily dissolved, get near to the pylorus, which admits them, rejecting those which, not yet sufficiently digested, cannot produce on it the necessary affection. To this delicacy of tact, which I ascribe to the pylorus, will be objected, perhaps, the passage it allows to pieces of money and other foreign indigestible substances. But these bodies, which have always lain some time in the stomach, before they make their way into the in- testines, repeatedly attempt the orifice ofthe pylorus, and pass through, only when they have at last accustomed it to their contact. The gastric system is under the laws of a secretory gland ; and as the roots ofthe excretory ducts, being endued with a sort of elective sensibility, will not receive the secreted fluid, until it has undergone the necessary prepara* tion in the glandular parenchyma, in the same manner, the pylorus ad- mits aliments, and gives them passage into the intestines, which may be regarded as the excretory ducts ofthe stomach, only when they have been sufficiently elaborated by the action of this organ. XXIV. As the stomach empties itself, the spasm ofthe skin goes off ; the shivering is followed by a gentle warmth ; the pulse increases in ful- ness and frequency ; the insensible perspiration is augmented. Diges- tion brings on, therefore, a general action analogous to a febrile parox- ysm ; and this fever of digestion, noticed already by the ancients, is par- ticularly observable in women of great sensibility. Nothing positive can be said on the duration of stomachic digestion ; food passes sooner or slower from the stomach, according as its nature is such as to resist, more or less, the actions which tend to dissolve it; according too to the strength and vigour ofthe stomach at the time, and to the activity of the gastric juices. Yet we may state from three to four hours as the mean time of their remaining there. It is of consequence to know the time required for digestion in the stomach, that we may not disturb it by baths, bleed- ings, &c. which would call off towards other organs, those powers which ought, at that time, to be concentrated upon the stomach. If, as is indisputable, the stomach carries with it, into its action, all the other organs ofthe economy ; if it summons to its aid, so to say, the whole system ofthe vital powers ; if this sort of derivation is the more conspicuous, as the organization is more delicate, the sensibility more lively, the susceptibility greater, the importance is apparent of enforcing a strict diet in acute diseases, and in all cases where Nature is engaged in an organic operation, which a little increase of irritation could not fail to disorder, or to break off. Those who have practised in great hospi- tals, know to how many patients indigestions are fatal. I have seen some with large ulcers ; suppuration was copious and healthy ; the granula- tions florid, and all promising a happy issue, when ignorant friends bring them by stealth indigestible food, with which they cram themselves, in spite ofthe utmost watchfulness. The stomach, used to mild and mode- rate regimen, at once overloaded with food, is changed into a centre of fluxion, towards which the juices and humours all tend, an irritation is produced beyond that on the ulcerated surface ; which, in a little time, ceases to secrete pus, the fleshy granulation become flabby, extreme op- pression is felt ; with a difficulty of breathing comes on a pungent pain in the side, the pain sympathetically felt in the lungs, makes this organ the seat of an inflammatory and purulent congestion, a rattle ensues, and the patients die of suffocation, at the end of two or three days, sometimes in twenty-four hours ; and this fatal termination is especially accelerated, when, as I have often witnessed, a blister is applied to the seat ofthe pain, instead ofthe ulcerated surface. It will seem surprising, perhaps, that in the case of which 1 have just been speaking, it should be in the lungs, and not the stomach itself, that the congestion and the pain take place ; but besides that the most perme- able organ ofthe body, is the lungs, as well as the weakest, and the most easily yielding to fluctionary motion*, a host of instances prove, what a * Of all the organs it is that in which we most meet with organic injury ; and those who have opened many bodies, may have observed, how rare it is to find the lungs 'jompletely sound in adults and in eld men.—Author's Note. 86 close sympathy unites it to the stomach. Let us but call to mind pleuri- sies and bilious peripneumonies, those acute pains of the side, which, since Stahl, physicians have so successfully treated with vomits. 1 he rapidity with which their symptoms go off, on the evacuation of thesordes which oppress the stomach, shows clearly that the sympathetic diseases are not owing to the metastasis of bile upon the lungs, and that they do not consist in the simultaneous existence of a gastric affection, and of an inflammatory state ofthe pleura or ofthe lungs, but that they are simple gastric affections, in which the lungs are, at the same time, the seat ofa sympathetic pain. The action of the parietes ofthe stomach ceases, only when this viscus is completely cleared of the food it contained, the gastric juice, no longer secreted, ceases to be poured so freely by its arteries, and the parietes, which close upon each other, are chiefly lubricated by the mucus so plentifully secreted by the inner coat. At times, the action ofthe muscular fibres ofthe stomach is altogether inverted, they contract from the pylorus, towards the cardia, and this anti-peristaltic motion, in which the contractions are effected with more force, more rapidly, and in a manner really convulsive, produces vomiting. Then, the action ofthe abdominal muscles is added to that ofthe stomach; the viscera are driven upwards and backwards, by the contraction ofthe larger muscles ofthe abdomen ; the diaphragm rises up towards the chest. If it sunk as it contracted, the oesophagus, which passes in the interval of its two crura, would be compressed, and the passage ofthe alimentary substances by the cardiac orifice, could uot take place. Accordingly it is observed, that it is only during expiration, that any thing passes from the stomach into the oesophagus. Vomiting may depend upon the obstruction of the pylorus*, on the too irritating impression of any substance on the coats of the stomach ; it may be produced by the irritation of some other organ with which the s-tomach is in sympathy, &c. Digestion in the stomach is essentially assisted by nervous influence. Many physiologists, since Brunner, have found that the tying of the eighth pair of nerves (the pneumo-gastriques) provoked vomiting and retarded the work of digestion \. As it is impossible to make this experiment with- out effecting respiration, a function of very different importance, it be- comes difficult to know, whether the derangement of digestion did not proceed from the general disturbance brought upon all the functions: however, the brain does appear to be in more immediate sympathy with the stomach, than with any other part of the digestive tube. Disgust from the recollection of loathed food excites vomiting. A more than ordinary exertion ofthe brain relaxes, disorders, and will even suspend, altogether, the functions of the stomach : an unexpected piece of news, a violent emotion, are attended with a cessation ofthe strongest sensation * The best description of the pylorus is given by Blumenbach from Levelling, who designates it an annular fold, " consisting not, like the other rugae of the stomach, of merely the mucous, but also of fibres derived from the nervous and muscular coats. All these, united, form a couoidal opening at the termination of the stomach, project- ing into the duodenum, as the uterus does into the vaginia, and, in a manner, embrac- ed by it.' t Dr. Haighton has proved, in the most satisfactory manner, that a ligature on the eighth puir of nerves, far from inducing vomiting, renders the stomach incapable of rejecting its contents, even though excited by the most powerful emetics.— See Me- moirs ofthe London Medical Society Trans, vol. II. page 512. 87 of hunger. It would be useless to bring together, in this place, proofs of the intimate connexion subsisting between the brain and the stomach, through the intervention ofthe pneumogastric nerves, for the connexion is questioned by no one*. XXV. Of digestion in the duodenum. The food, on quitting the sto- mach, enteis the duodenum, and there experiences new changes, as es- sential as those which were produced upon it, by digestion in the sto- mach It might even be said, that as the essence of digestion and its prin- cipal object is the separation of the food into two parts, the one recre- mentitious and the other chylous or nutritious, the duodenum, in which that separation is performed, is its principal organ. In fact, however carefully one may examine the greyish chyme which is sent out of the stomach, it will be discovered to be a mere slimy homogeneous pulp; and in more than a hundred animals which I have opened during the pro- cess of digestion, I never observed the absorbents of the stomach filled with real chyle, like those ofthe intestines. The duodenum may be considered as a second stomach, very distinct from the other small intestines, by its situation exterior to the perito- neum, by its size, and by its readiness of dilatation, the size and regu- larity of its curvatures, the great number of valvulae conniventes with which its inner part is furnished, the prodigious quantity of chylous ves- sels which arise from it, and especially by its receiving, within its cavity, the biliary and pancreatic fluids. If the situation of the duodenum and the peculiarities of its structure are attended to, it will be readily observ- ed, that every thing in that intestine, tends to slacken the course of the alimentary substance, and to prolong its stay Within it, that it may remain the longer exposed to the action of these fluids. The duodenum is, in fact, almost entirely uncovered by the peritoneum, a serous membrane, which like all those that line the inside ofthe great cavities, and reflect themselves over the viscera which they contain, by furnishing them external coverings, admits but of little extension, and seems to stretch, when these viscera become dilated, only by the unfold- ing of its numerous duplicatures. Fixed by a rather loose cellular tissue to the posterior side ofthe abdomen, the duodenum is susceptible of such dilatation, as to equal the stomach in size, as is sometimes seen in opening dead bodies. Its curvatures depend on the neighbouring organs, and seem almost invariably fixed ; lastly, numerous valvulae line its inner surface, so as to add to the friction, and to increase the extent of surface, and there- by the number of absorbents destined to take up the chyle separated in the duodenum, from the excrementitious part ofthe food, by the action ofthe fluids poured into it, from the united ducts ofthe liver and pancreas.! * See APPENDIX, Note L. t The muscular coat of the duodenum is thicker than that of the small intestines, the base ofthe villi ofthe mucous tunic is more thickly set with glandular follicles, and the whole duodenum presents a more vascular appearance than any other por- tion ofthe intestines. The experiments of Dr. Prout od chyme, taken from the duodenum, exhibit the following results:— 1. Vegetable Food. Composed of a semifluid, opake, yellowish white part, having mixed with it an- other portion of similar colour, but of firmer consistence. It coagulated mdk com- pletely. 38 XXVI. Ofthe bile and ofthe organs which serve for its secretion. I he bile is a viscous, bitter, and yellowish fluid, containing a great quantity of water, of albumen to which it owes its viscid condition, and oil to which the colouring and bitter principle is united. Soda to which the bile owes the property of turning vegetable blues to a green colour, phosphates, carbonates, and muriates of soda, phosphates of lime, and ot ammonia ; and, lastly, as some say, oxide of iron, and a saccharine substance re- sembling the sugar of milk. This fluid, which the ancients looked upon as animal soap, fitted for effecting a more intimate mixture ofthe alimen- tary matter, by combining its watery with its fat and oily, parts, is, there- fore, extremely compound : it is at once watery, albuminous, oily, alka- line, and saline*. The liver which secretes it, is a very bulky viscus, situated in the upper part ofthe abdomen, and kept in its place, chiefly by its attachment to the diaphragm, of which it follows all the motion. The hepatic artery, which the cceliac sends off to the liver, supplies it only with the blood requisite for its nutrition : the materials of its secre- tion are brought by the blood ofthe vena portae. This opinion on the uses of the hepatic artery, which I take up with Haller, cannot rest upon the experiments of those who pretend to have seen the secretion of the bile going on, after it was tied. Besides that Water . . . . 86-5 Chyme, &c. . . . 6- Biliary principle . . 1-6 Vegetable gluten . 5- Saline matter •7 Insoluble residuum .0 100 2. Animal Food. More thick and viscid than chyme from vegetable food, and its colour more inclio* iag to red. Did not coagulate milk- Water .....80- Chyme, &c. . 15-8 Albuminous matter 13 Biliary principle . 1.7 Saline matters ■ 7 Insoluble residuum '5 100 * " Human bile differs considerably from that of all other animals. Its colour is sometimes green, sometimes yellowish brown, and sometimes it is nearly colourless. Its taste is not very bitter. It is seldom completely liquid, but usually contains some yellow matter suspended in it. When evaporated to dryness, it leaves a brown mat- ter amounting to about 1-1 lth of the original weight. When this matter is calcin- ed, it yields all the salts which are to be found in the bile. All the acids decompose human bile, and throw down a copious precipitate, consisting of albumen and resin." -"Thomson's Chemistry, &c. The following is the analysis of human bile according to Berzelius :— Water . . . . . 908-4 Picromel . . . . • 80- Albumen ..... 3' Soda.....4-1 Phosphate of lime . . A Common salt . . ■ y • 3*4 Phosphate of secla with some lime 1- ; flOf) 89 the position of this vessel makes the operation almost impossible, which gives me reason to doubt if ever it was practised ; and if it were, by in- tercepting the course of the arterial blood carried to the liver, this viscus, even under the received hypothesis,would remain deprived of nourishment and of action : and the vena portae would supply it, in vain, with a blood on which it could exert no influence. When this vein is tied, which it is far more easily done than the artery, the secretion of bile is seen to stop ; but the experiment which suspends the abdominal venous circulation, is too speedily fatal, to justify any conclusive inference. It is on analogical proofs, that the received hypothesis rests, touching the manner ofthe bi- liary secretion. The hepatic artery, remarkably lessened by the branch- es it has sent off in its way towards the liver, is to that organ what the bronchial arteries are to the lungs ; and in the same manner, the branch- es of the vena portae, spread through its substance, may be compared to the system of pulmonary vessels. It is still to be confessed, however, that the enormous bulk ofthe liver, its being found in almost all animals, and the quantity of blood carried into it by the vena portae, compared to the small secretion there is of bile, lead to the belief that the blood sent to it from all the other organs of digestion, undergoes changes there, on which science possesses, as yet, no certain data, though the chemists maintain, that the liver is, in some sort, the supplementary organ of the lun^s, and assists in clearing the blood of its hydrogen and car- bon. This name of vena portce is given to a peculiar venous system, enclos» ed in the abdominal cavity, and formed as follows : the veins which bring back the blood ofthe 9pleeo, and the pancreas, of the stomach and intes- tinal canal, are united in a verj' large trunk, which ascends towards the concave face of the liver, and there divides into two branches.* These lie in a deep fissure in the substance of this viscus ; they send out, through all its thickness, a multitude of branches, which divide like ar- terial vessels, and end, in part, by opening into the biliary ducts or pores, and, in part, by producing the simple hepatic veins. These veins, situ- ated chiefly towards the convex or upper surface ofthe liver, bring back, into the course of the circulation, the blood which has not been employ- ed in the formation of bile, and that which has not served to nourish the substance of the liver: for, they arise equally from the extremities of the vena portae, and from the extremities of the ramifications of the he- patic artery.f The liver differs from all organs of secretion, in this, that the materi- als of the fluid it elaborates, are not supplied to it by its arteries. It should seem that the bile, a fat and oily fluid, in which hydrogen and car- bon predominate, could be drawn only from venous blood, in which, as is known, these two principles are in superabundance. The blood acquires the venous qualities, as it passes along; the circuitous course ofthe circu- lation, and is supplied with hydrogen and carbon the more fully, the slow- er it flows. Now, it is easy to see, that all is naturally disposed for * In two instances the vena portse has been found running, not to the liver but di- rectly to the vena cava inferior. One of these is described by^r. Aberwetht, in Vol. LXXXIII. of the Philosophical . Transactions, and the other by Mr. Law- rence, in Vol. IV. of the Medico-Chirurgical Transactions. t For some observations on the structure and actions ofthe liver, see APPENDIX, 90 slackening the circulation of the hepatic blood, and to give it, eminently, the distinguishing properties of venous blood. The arteries which fur- nish blood to the organs, in which the vena portae rises, are either very flexuous as the splenic, or frequently anastomose, like the arteries of the intestinal tube, which of all that are in the body, abound most in vi- sible divisions and anastomoses. It will be seen in the chapter on circu- lation, how well these dispositions are adapted for retarding the course of the arterial blood. Once carried into the organs of digestion, the blood stays there, whether it be that the coats of the hollow viscera being col- lapsed or closed upon themselves, hardly yield it passage, or that the organization of some one of these viscera is favourable to its stagna- tion. The spleen seems to serve this purpose. Does this dingy and soft vis- cus, lodged in the left hypocondrium, and attached to the great fundus of the stomach, receive the blood into the minute cells of its spungy paren- chyma, or does this fluid merely traverse, very slowly, the delicate and tortuous ramifications of the splenic vessels ? In other respects, there is no organ that exhibits more variety of number, of bulk, of figure, of colour, and of consistence. Sometimes manifold, often divided into several lobes by deep clefts ; its bulk varies, not only in different individuals, but even in the same, at different times of the day, as the stomach, full or empty, admits or rejects the arterial blood, and compresses the spleen between its large extremity, and the ribs under which it is situated, or leaves it free. The blood which fills the tissue ofthe spleen, blacker, more fluid, rich- er in oily principles, owes all these qualities, which led the ancients to consider it as a peculiar substance, called by them the atra bilis, or black bile, to its long protracted continuance within that viscus. The branch- es, which by their union form the vena portae, have thinner parietes than the other veins ofthe body, they are not furnished with valves, and they do not readily free themselves ofthe blood which fills them. The action of these veins is, in fact, so feeble, that it would not suffice to en- able them to carry the blood onward, if the gentle and alternate compres- sion of the diaphragm and abdominal muscles on the viscera ofthe abdo- men, did not favour its circulation. On reaching the liver, the blood, which is highly venous, is further slackened in its circulation, by the in- creased dimensions ofthe space in which it is contained, the united cali- bre ofthe branches of the hepatic vena portae, exceeding considerably that ofthe principal trunk. Besides, these vessels are enveloped in the parenchymatous substance of the liver, and can act but feebly. It, there- fore, circulates slowly through that organ, and, with difficulty, returns into the course of circulation. The hepati<: veins, which are of pretty considerable calibre, and without valves, remain constantly open, their parietes cannot close and contract on the blood which fills them, on ac- count of their adhesion to the parenchymatous substance of the liver. They open into the vena cava, very near the place at which that vein terminates into the right auricle. The regurgitation of the blood, during the contraction of that cavity of the heart, is felt in the veins, and the blood forced back towards the liver, is exposed for a longer time to its action. The spleen, therefore, performs only preparatory functions, and may 91 be considered as the auxiliary ofthe liver, in the secretion ofthe bile*. It is observed, that the quantity ofthe latter increases, after the spleen has been extirpated, and that it is less yellow, less bitter, and always im- perfect. The blood which circulates in the omentum, is very similar to that of the spleen ; I would even say, that it contains oily particles, if the drops which I have clearly noticed on its surface, might not have come from the adipose tissue of the omentum, which allows the fluid contained in its cells to flow, when a small puncture is made into it, in . examining the blood contained in its veins. The bile secreted in the tissue ofthe liver t is absorbed by the biliary ducts, the union of which forms the hepatic duct. The latter issues from the concave surface of the liver, and conveys the bile, either immediately into the duodenum, by means ofthe ductus communis choledochus, or into the gall bladder. This small membranous pouch, which adheres by means of cellular tissue to the lower surface ofthe liver, is in some ani- mals entirely distinct from that organ, and connected to it, only by the in- sertion of its duct, into that which comes from the liver. Its inner mem- brane is soft, fungous, plicated, and always covered with the mucus, se- creted by the glandular criptae which it contains. This mucus defends the gall bladder against the action ofthe bile which it contains. The al- most parallel course ofthe hepatic and cystic ducts, the acute angle at which they meet, renders it difficult to account for the passage ofthe bile into the gall bladder. It appears, that when the duodenum is empty, the % bile regurgitates, in part, from the hepatic duct into the gall bladder, col- lects within it, becomes thicker and yellower, and requires a greater de- gree of bitterness. Consequently, the use ofthe gall bladder, is to serve as a reservoir to a portion of the bile, which, by remaining within it, is improved in quality, acquires consistence and bitterness, and is heighten- ed in colour, by the absorption of its fluid parts. XXVII. The irritation produced on the parietes ofthe duodenum, when distended by the chyme, is propagated to the gall bladder, by the cystic and common ducts. Its pari >tes then contract, and oblige the bile to flow, along this cystic duct into the ductus communis choledochus. The pres- sure of the distended intestines on the gall bladder, favours the excretion of bile. The hepatic bile is also more abundantly poured into the duo" denum during digestion, from being secreted in greater quantity by the liver, which participates in the irritation affecting the organs of digestion, and secretes a greater quantity. The cystic and hepatic bile, mixed in the ductus communis choledochus, undergoes a change before entering the duodenum, by uniting with the fluid ofthe pancreas. The excreto- ry duct ofthe pan.reas, a glandular organ, which, in structure, bears so great an analogy to the parotid glands, that some physiologists, assuming an identity of functions, have called it the abdominal salivary gland, joins the biliary duct, before the latter opens in the duodenum, after having in- sinuated itself obliquely between the coats of that intestine. It arises within the pancreas, from a great number of radicles which join it, like the feathers ofa quill to a common trunk. Its calibre increases in size as it approaches the large end ofthe pancreas, situated on the right, in the concavity ofthe second curvature of the duodenum. ^Nothing pre- * See APPENDIX. Note N, for an account ofthe latest observations and opinion* respecting the structure and functions of the spleen. t See. in the chapter on secretion, the laws which that function obeys. [\2 cise is known, with regard to the nature of the pancreatic fluid ; the striking resemblance ofthe pancreas to the salivary glands leads to a pre- sumption, that this fluid bears considerable analogy to the saliva. The quantity of fluid secreted by the pancreas is likewise unknown, but it must be considerable, if one may judge from the great number of nerves and vessels which pervade its glandular tis*ue, and its quantity is, most probably, increased by the irritation ofthe food in the duodenum*. This combination ofthe united pancreatic and biliary fluids poured on the chyme, penetrates it, renders it fluid, animalizes it, separates the chylous from the excrementitious part, and precipitates whatever ft not nutritious. In bringing about this separation, the bile itself seems to be divided into two parts, its oily, coloured, and bitter portion passes along with the excrements, sheathes them, and imparts to them the stimulating qualities necessary to excite the action of the digestive tube. Its albu. minous and saline particles combine with the chyle, become incorporated to it, are absorbed along with it, and return into the circulation. There may, in fact, be noticed in the alimentary mass, after it has undergone this combination, two very distinct parts, the one is a whitish milky sub- stance, which swims to the surface, and is the least in quantity ; the other is a yellowish pulp, in which, when digestion is healthy, it is not easy to recognize the nature ofthe food. When the liver is obstructed, and the bile does not flow in sufficient quantity, the faeces are dry and discolour- ed ; the patients are troubled with obstinate costiveness, the excrement, uncombined with the bitter and colouring matter of the bile, not proving sufficiently irritating to the intestinal canal. We have just mentioned how the separation ofthe chyle is performed; hut the mechanism of that separation and the process of chylification are absolutely unknown. How does the union of the bile to the chyme ope- rate, in extracting from the latter the recrementitious part, and in making it swim above the rest ? Is there any connexion between that process and the nature of the constituent principles of the bile ? The knowledge of the composition of the bile, affords as little assistance in the explanation as does the knowledge ofthe chemical properties ofthe semen, in under- standing the admirable function of generation. All these acts ofthe ani- mal economy, areas mysterious and inexplicable, as the action of the brain in producing thought, a phenomenon which so many physiologists have considered as exceeding the power of matter, and for which they seem to have reserved all their admiration, though nil mirari, which I would translate by wondering at nothing, ought to be the motto of any one who has made some progress in the study of the laws of life. XXVIII. Of the action of the small intestines. After remaining a cer* * Opinions are various respecting the quantity of the secreted fluid which the pan- creas yields. Autenrieth reckoned the quantity at nine ounces the twenty-four hours. It has been generally supposed that this secretion is considerably augmented at the time that the chyme flows into the duodenum; and the intimate connexion existing between the ganglial nerves, supplying these viscera, favours the conclusion. Magendie, however, rejects this inference, and inserts, without stating the grounds of his opinion, that the flow ofthe pancreatic juice is least abundant during digestion. The disordered functions of this organ appear to be very essentially concerned in the production ^some diseases which are too often referred entirely to the stomach and small intestines, which, no doubt, become consecutively deranged from this cause; or,if the actions of the pancreas be not primarily diseased, a co-existeut dis- order may be present in the?e allied viscera, and be equally the result of onecausp. 9;> tain lime within the duodenum, the alimentary mass decomposed by th* bile, or rather by the pancreatico-biliary fluid, separated into two parts, the one chylous, the other excrementitious, passes into the jejunum and ileum which are not easily distinguished from each other, and which dif- fer id their relative length, according to the elements on which anatomists ground the distinction*. The jejunum and the ileum alone occupy nearly three-fourths of the whole length ofthe digestive canal ; they are straiter than the duodenum, and do not dilate so readily, because the peritoneum, which forms their outer covering, ties over their whole surface, with the exception of the posterior border at which their vessels and nerves enter It is along that border, that they are fixed to the mesentery, a membranous band formed by adupl,cature ofthe peritoneum, which contains the vessels and nerves going to the jejunumand ileum, which prevents knots from forming in the intestines, and is a security against the occurrence ofintus-susceptio It is well known, however, that in some rare cases, intus-susceptio does take place, with utmost danger of the patient's life, who generally dies in the agonies of insufferable cholic pains, which nothing can alleviate The progress ofthe food, along the small intestines, is retarded by its nume- rous curvatures, very aptly compared by some physiologists to the wind- ings ot a meandering stream which fertilizes the soil it waters. These numerous convolutions of the intestinal canal favour the long continued presence of the food within its cavity, so that the chyle expressed from the excrementitious part by the peristaltic contractions of the intestine, may present itself to the inhaling mouths ofthe lacteals, by which it is to be absorbed These chylous absorbents are in greatest number on the surface of the valvule conmventes, which are circular folds ofthe inner membrane, and these are at a greater-distance from each other, the nearer they are to the termination of the ileum. The valvule conniventes not only slacken the progress ofthe food, but by their projections, they sink during the contraction of the bowels, into the alimentary mass, and the lacteals on their surface take up, from its inmost part, the chyle which they are destined to absorb!. The number of the valvulae conniventes diminishes with that of the lymphatics. The progress ofthe alimentary substance is gradually ac- celerated, as it parts with its nutritive and recrementitious particles. A * The redness of the parietes of the jejunum, the empty condition of that intestine, its situation m the umbilical region, the great number of its valvulae conniventes, do not distinguish it from the ileum, for, the colour ofthe intestinal canal varies in differ- ent parts of its extent, and the substances whieh fill it are found in different parts of the canal, according to the progress of digestion at the time the parts are examined : ac- cording as the convolutions are situated within the cavity ofthe pelvis, or rise towards the epigastric region; according to the full or empty state ofthe bladder and stomach; and the number of circular folds, called valvulae conniventes, diminishes, as one -eta near to the termination of the ileum. Winslow got over the difficulty, by considering the upper two-fifths of the small intestines as jejunum, and the remaining three-fifths as ileum. This last division, from measurement, is wholly arbitrarv, and is besides useless^for there is not, perhaps, above one occasion in which it would be iwtere«iin» to distinguish the jejunum from the ileum. In operating for hernia, when the intes° tine is mortified, one would decide the more readily to leave an artificial anus if one could be sure that the gangrenous portion belonged to the latter intestine • but'of this it is absolutely impossible to be certain.—Author's Note. t See APPENDIX, Note O, for some remarks respecting the mucous coat of thf ttigesttve canal, and the functions ofthe small and large intestines. 94 quantity of mucus, secreted by the internal membrane ofthe small intes* tines, envelopes the chymous mass and promotes its progress, by lubricat- ing it: this intestinal mucus thrown out by the exhalant arteries, imbues it, renders it liquid, and adds to its bulk. This fluid which seems to par- take ofthe nature of albiimen and gelatine, and to hold several saline sub- stances in s —Au* thor's Nnif- 97 that hydrogen is more abundant in the great than in the small intestines, that it is less in quantity in these than in the stomach*. Do the oxygen and azote form a part ofthe atmospherical air which is taken in with the food and with the saliva, ar»d which is disengaged by the heat ofthe intestinal ca- nal ? Or are these ^ases the result of the decomposition of the food and of the intestinal fluids '.' Bt-ides, may not the gas contained in the intestines of a dead body, have been formed at the moment of death ? We know that in several instances, at the moment contractility is forsaking our organs, the intestines become distended by gas which hastens the approach of death, by impeding the descent ofthe diaphragm. Digestion, when healthy, is unaccompanied by the production of gases. In indigestion, there almost always escapes carbonated or sulphureted hydrogen gas, which-produces the offensive smell of the air which es- capes at the anus : this smell is different from that ofthe flatus which are brought upwards, these contain pure hydrogen or carbonic acid ga3. The latter is, likewise, sometimes voided by the rectum, but less frequently than hydrogen combined with carbon, sulphur, or even phosphorus. Is not ammonia itself extricated, and does it not accompany the evacuation of the faeces in certain putrid diarrhoeas, as in dysentery combined with low fever ? Though the formation of this gas implies a putrefactive motion opposed to the vital principle, may not this decomposition commence in substances lying in the great intestines, when these are become almost inert from the impaired condition of the vital power. This would not be the only instance of a chemical process taking place in the intestinal cai.al, notwithstanding the counteracting influence of vitality. Thus, on some occasions, grapes eaten in too great quantity, ferment and produce carbo- nic acid gas, in such abundance, that this elastic fluid overcomes the re- sistance of the intestines. This is the kind of distension from flatulence which is cured by drinking plentifully of cold water, which dissolves the gas naturally soluble in that fluid. XXXI. Of the secretion and excretion of the urine. The fluids absorb- ed with the chyle, and taken up by the lymphatics ofthe intestinal tube, dilute the nutritive part extracted from the solid aliment, and serve it as a vehicle. When they have reached the mass ofthe blood, they increase its quantity, diminish its vicidity, and render it more fluid ; going along with it throughout the whole course of the circulation, they supply moist- ure to all the parts of the body, and become loaded with the molecules detached from them by the vital motion. Then, conveyed to the urinary organs, they become disengaged from the rest of the fluid-., carrying along with them a number of products of every kind, which by a longer stay in the animal economy, would not fail to occasion a manifest disturbance in the exercise.of the functions. XXXII. The rapidity with which we void, with the urine, certain diu- retics, has induced several physiologists to think, that there exists a di- rect communication between the stomach and bladder : no one, however, has ever succeeded in pointing out those peculiar ducts, which might serve to convey the urine from the stomach to the urinary organs, without taking the circuitous course of absorption and ofthe circulation, and, be- sides, the learned Haller has proved, by accurate calculations, that the size of the renal arteries, whose calibre amounts to an eighth of that of * See APPENDIX, Note O. 1?- 98 the aorta, and the quickness with which the blood flows, sufficed to account for the shortness of the time in which certain fluids reach the urinary organs.* A thousand ounces of blood pass through the renal tissue in the space of an hour : supposing that this fluid contains only a tenth of the mate- rials fit for supplying urine, a hundred ounces, or seven pounds and a quarter, may be given out in this short time ; and never, with the most copious and diuretic drinks, does more of it pass in an hour. We shall see, however, in treating of absorption, that it is not absolutely impossi- ble, that by means of the numerous anastomoses of the lymphatics, this set of vessels may carry a liquid, directly from the stomach into the blad- der. It would be superfluous to mention, in this place, the varieties ob- servable in the kidnies, in point of number, size, and situation. These two lobular viscera, composed ofthe union from twelve to fifteen glandular bodies, divided in the feetus, and in some quadrupeds, attached to the pos- terior part ofthe abdomen, behind the peritoneum, are surrounded with a cellular covering of different thickness, and particularly remarkable by the consistence, approaching to that of tallow, of the fat which fills its cells. If ever the art of man shall penetrate into the mystery ofthe intimate Structure of our organs, it seems probable that the kidnies will furnish the first solution of the problem.* Even coarse injections pass readily * The experiments of Darwin with the nitrate of potash, and of Branbe with the prussiate of potash, have led several, in modern times, and amongst these, Sir Everard Home, to support the opinion alluded to above. Magendie made experiments in order to ascertain this matter, and deduced from them the following inferences:— 1. Whenever the prussiate of potash is injected into the veins, or absorbed from the intestinal canal, or from a serous surface, it passes quickly into the bladder, where it may be easily recognized in the urine. 2. Whenever a very considerable quantity ofthe prussiate is injected, it can be detected in the blood by means of re-agents; but when the quantity is small, it is impossible to discover its presence by any ofthe usual tests. 3. That the same thing takes place if the prussiate be mixed with blood in a vessel, 4. That this salt may be detected in the urine in any proportion, and therefore it is by no means extraordinary, that Darwin and Brands could not find in the blood a sub- stance which they easily perceived in the urine. Meg- Phys. Vol. II p.. 380. The existence of absorbent vessels which open into veins along their smaller ramifi- cations, and even towards their terminations, and the frequent anastomoses of the form- er set of vessels with the latter, all which appears to be satisfactorily shown, (see Ap- pendix, Note Q.) sufficiently explain the rapid transit of liquids, or other substances, from the stomach and other parts ofthe body into the circulating fluid, and their quick, but subsequent, appearance in the secretions. Inconsequence ofthe activity of those secreting organs whose chief function it is to remove substances from the blood, which would become deleterious from their accu- mulation in it, and owing to the stimulus which such substances give theie organs when conveyed to them in the course ofthe circulation, they are eliminated from the blood as fast as they enter it, so that they seldom can^be present in sufficient quantity to be detected by the usual chemical agents. * One of the latest and most minute dissections of the kidney, has been made by Etsenharbt, of Berlin, (De structura renum Observationes Anatomicae, Ber. 1818, 4to.) His observations were made on very thin slices of the kidney cut longitudinally! and also in the short diameter: these were wetted with diluted alcohol, and examined in the microscope. " The experiments were originally made to discover the peculi- arity, if any, of a diabetic kidney;" but no perceptible difference was found to exist be- tween the diabetic and healthy state of this organ. " The naked eye discovered small points on these slices, which the microscope re- presented as oval and sometimes round granulations, situated at different distances from each other, and varying in size, both in the same kidney and in the kidneys of c'/ftrrent sexes. After maceration, these grains could be detached with their adher- 99 from the renal arteries into the ureters, or excretory ducts of the kid- neys ; a convincing proof of immediate communication among the minute arteries, which exceedingly tortuous, form, with the minute veins, the cortical or outward substance of the kidneys, and the straight urinary tubes, which distributed in conic d fasciculi, in the interior of these or- gans, constitute what has been called its tubuli and papillae. The passage of injections from the arteries into the renal veins, is as easy ; and I have often seen the coarsest liquids flowing at once by the ureters and by the emulgent veins. This free communication between the arteries, the veins, and excretory ducts of the kidneys, gives an idea of the ra- pidity with which the blood must flow through these organs, whose firm consistence allows a very moderate dilatation to the vessels : 'and suggests the possibility of a sort of filtration of the urinary fluid, the se- cretion of which would be only succession of chemical or mechanical se- parations, from the blood, in its passage along very minute ducts, ofa bore progressively decreasing. This was the opinion, at least, of Ruysch, whose system on the intimate composition of our organs, and on the immediate continuation of the blood-vessels with the excretory dmts is chiefly founded on the facts of structure, discovered to him by his beautiful in- jections of the renal arteries. The kidnies are of duller sensibility, and less energetic action than the other glands. The force of life has less to do in their secretion, and their functions may be more readily explained on the principles of che- mistry or hydraulics. XXXIII. If we attempt, indeed, to apply to the urinary organs the fundamental laws on the mechanism of secretions*, it is not seen, that these organs are not under their absolute controul. Of all the animal ing vessels, and a void was left. They were composed of knotty vessels, surrounded by an ash-grey substance, and united, not so much by frequent anastomoses, as by numerous meetings with each other. The ash-coloured substance was not granular; it appeared as if traced with a pencil. Injection by the renal artery made these cor- puscules wholly red; but still, some deeper and other clearer points could be perceiv- ed in them. Dr. E. considered these corpuscules to be the glandules and glomerules of Malfighi and of Schumlansky. He could not trace the veins arising from these glandules ; but he refers to an observation of Prochascka, in which a success- ful injection ofthe renal vein showed, under the microscope, a very loose, vascular little net, surrounding the isolated corpuscules of the cortical substance." Dr. Map- pes, of Frankfort on the Maine, says, that he has seen exactly this structure from injec- tions of the hepatic vein, and therefore he infers that the anatomy of the liver and kidney may be similar in other respects. From these glandules, Eysenhardt says, " that the greyish and transparent uni- feroii3 vessels, which seem to be articulated, arise. These vessels form a net-work, which every where unites the glandules with each other. He therefore thinks Schum- lansky was deceived, in supposing that each glandule had an excretory duct, which, after making numerous curves, ran straight into the medullary substance. " Little precise information is given by Eysenhardt respecting the medullary part. The excretory ducts, however, which become straight when they pass out of the cor- tical substance, pass along in fasciculi of about twenty in each fasciculus. " In a foetus, the cortical substance was smaller in proportion, and the glandules were of scarcely half the size. Each vascular vessel of the medullary substance was com- posed of granulations; some of them being voluminous, and others much smaller, and all strongly pressed against each other, so that the vessels could no longer be distin* guished from each other, but their passage only marked by striae. The granules were not produced by putrefaction, although putrefaction gives a globular appearance to these parts." * See the Chapter on Secretion. 100 fluids, uriue is the one most complex in its elements, and most variable in its qualities. Not only do foreign substances sometimes appear in it, af- fect, and even change its composition ; other fluids may, at tunes, mix with it, and disguise it altogether. Thus credible observers tells us ofthe appearance of urine, of bile, fat, milk, blood, pus, of which many facts may be found collected in Haller's great work on physiology. The kid- nies, then, have less sensibility than the other secretory organs : they reason less, if I may venture on the expression, on the sensation produc. ed by the various substances in the blood : their action is also less pow- erful ; it does not so intimately affect the fluid subjected to it. It does not change the heterogeneous qualities of those that are mixed with it, and allows them to pass in a pure state*. This multitude of elements in the composition of urine, had surely been understood by the ancients, before it was demonstrated by modern chemistry : for they considered it as a sort of extract of animal substance, as a real lixivium, carrying off all that is impure ia the economy, and gave it the name of lotium, which indicates that destination. Finally, the secretion of urine is more uniformly carried on : it is con- tinual, or at least, does not exhibit so prominently those alterations of ac- tion and repose, so apparent in the work of the other secretory organs. When, in a case of retention of urine, we introduce a catheter into the urinary bladder, and leave it there, the urine keeps dropping continually, and would wet the patient's bed, if the orifice of the catheter were not kept closed. In the memoirs of the Academy of Sciences for the year 1761, there is related a case of singular conformation ofthe urinary bladder. This musculo-membranous viscus protruded through an open- ing at the lower part of the linea alba, and was turned inside out, so as to present externally, its mucuous membrane. This case afforded an op- portunity of observing the continual flow of the urine through the orifices of the ureters, and of ascertaining the different circumstances attending this process, either with regard to the qualities of this fluid, or to the quantity which might be voided, in a certain space of time ; and in this respect, there was a good deal of difference, according to the state of sleep and waking, to the quantity, and to the diuretic qualities of the drink. * This opinion is very different from that entertained by Dr. Thomson. He con- ceives that it is not merely the abstraction of a quantity of water and of salts accu- mulated in the blood which the kidnies perform, but that a chemical change is pro- duced by them, either upon the whole blood, or at least upon some important part of it. In proof of this additional function, he adduces the formation of nephrin and uric acid, as he supposes, in the kidnies. " These two substances,'1 he says," are formed in the kidnies, and as they are thrown out, after being formed, wthout being applied to any useful purpose, they are certainly not formed in the kidnies for their own sake. Some part of the blood then must be decomposed in the kindney, and a new substance, or substances, must be formed ; and the urea and uric acid must be formed at the same time, in consequence of the combined action of the affinities which produce the change on the blood ; and being useless, they are thrown out together with a quanti- ty of water and salts, which in all probability were useful in bringing about the changes which take place in the arteries and in the kidnies, but which are no longer of any service after these changes are brought about. Thorn. Vol. IV. p. 62. This reasoning rests entirely on the assumption that these substances are actually formed in the kidnies; it is quite as probable that they are produced in other parts of the body, and are, with other substances, removed from the blood by the action of these organs. See APPENDIX, Note P, for some experiments and further observa- tions in support of the latter opinion. 101 The urine contained in the ureters is turbid a.id imperfect; its consti- tuent parts are not thoroughly blended together, as may be observed, if made to flow, by compressing the kidnies in a dead body. It improves by passing alone those ducts, acquires the characteristic qualities of urine, oozes at the surface of the papillae, and flows into the membranous calices which embrace the rounded terminations of the tubuli unniferi. The union of the calices forms the pelvis, or ijhe expanded portion of the ureters, or membranous ducts, along which the urine is incessantly flow- ing into the bladder. 1 ne urine flows into the bladder by its own weight, and especially by the action of tbe parietes of the ureters, which possess a certain degree of contractility. To the above causes, may be added tbe concussions excited by the pulsations of the renal arteries, behind which the pelvis of the kidney is situated, and by the pulsations of the iliac ar- teries, in front of which the ureter passes, before entering the cavity of the pelvis ; the alternate compression from the viscera of the abdomen, during the motions of respiration ; the concussion attending bodily exer- cise, as riding on horseback, walking, running, &c. ; the pressure of the column of urine from the kidneys, and the want of resistance towards the bladder. XXXIV. The urine is continually passing, in drops, into the bladder, it separates its parietes, without, however, exciting in them any percepti- ble impression, as they are accustomed to its stimulus. The urine cannot accumulate in the musculo-membranous cavity of the bladder*, which is situated, exterior to the peritoneum, in the cavity ofthe pelvis, behind the pubis, above which, in the adult, it never rises, except when excessively distended, unless it is prevented from flowing along the urethra, or from returning by the ureters. This retrograde flow is prevented by the ob- lique insertion of these ducts, which pass, for some distance, between the muscular and mucous coats of the bladder, before opening within it, to- wards the posterior angles ofthe trigone vesical!, by openings of smaller dimensions than their cavity. The inner coat ofthe bladder, raised over these apertures, gives them the appearance of being provided with valves, which fit the better these orifices, according as the urine contained in the bladder, by separating its parietes, presses against each other the coats by which they are formed, and between which the ureters pass, along a space of from seven to eight lines. The urine which flows into the bladder, requires a certain degree of force, to separate its parietes on which the weight ofthe intestines press- * In the numerous tribe of birds, the bladder is wanting. In them, the ureters open into the cloaca, a musculo-membranous bag, which supplies the place ofthe rectum, bladder, and uterus, and which serves as a reservoir to the solid excrements, to the urine, and to the eggs detached from the ovaria. The urine of birds dilutes the faeces, and furnishes the carbonate of lime which forms the basis of the egg-shell. It has such a tendency to concretion, that I have alwayi observed, in dissecting various fowls of different kinds, an earthy, saline, or crystallized substance, forming white striae easily seen in the fluid of the ureters, through their skin and transparent coats. Hence one may readily conceive, how frequently calculi would form in these animals, if their urine accumulated and remained, for any length of time, stationary in a cavity destin- ed to contain it.—Authors Note. t The French anatomists give the name of trigone vesicle, to that portion of the bladder, included between the openings of the ureters and the neck of the bladder, and forming a triangle, whose base is represented by a line drawn from the opening of one ureter to the other, and whose apex is situated at the insertion of the urethra into be neck of the bladder. Trans 102 os. This is effected by no other power, than by that which causes the flow of the urine along the ureters, and though inconsiderable, it will ap- pear sufficient, if it be considered that the fluids which pass from a strait channel into a larger cavity, act on every superficial portion of its parietes equal to the area of the channel, with a power equal to that which de- termines their flow into the latter ; so that if tie urine descends along the ureters, with a degree of^orce equal to one, and if the inner surface of the bladder is a thousand times more extensive than the area of the ureters, the power will be multiplied a thousand fold. This purely mathematical proposition is expressed by saying, that the force with which the urine passes along the ureters, is to that by which the parietes of the bladder are distended, as the calibre of the ureters is to the superficies of the bladder. The pressure which the urine, accumulated within the bladder, exerts on the lower part ofthe ureters, does not prevent the force which deter- mines its descent along the ureters, from carrying it into the, bladder : - for, the column which descends along the ureters, being higher than that contained in the bladder, these two organs represent an inverted syphon, the longer branch of which is represented by the ureter. The following are the causes which enable the bladder to retain the Urine : the contraction of its sphincter, a muscular ring surrounding the termination of the urethra into the bladder : the angle formed by that canal, after it leaves the bladder ; and lastly, the action of the anterior fibres ofthe levator ani, which surround the neck of that organ, surround- ed besides and supported by the prostate gland. These fibres, which are calculated to compress the prostate oyer the neck of the bladder, and to raise the latter against the pubis, have been called by Morgagni, pseudo sphincteres vesica. The urino, deposited by drops into the bladder, gradually separates its parietes. This musculo-membranous organ rises, and at the same time, carries upwards the convolutions ofthe ileum, and the peritoneum before which it lies, behind the pubis and the recti muscles with which it is in immediate contact. These relations of the peritoneum to the distended bladder, account for the possibility of puncturing it above the pubis, so as to let out an accumulation of urine, without penetrating into the cavity ofthe peritoneum. The urine remains a certain time in the bladder, ac- cording to the capacity of the latter, to the irritability and extensibility of its parietes, and according to the acrid or stimulating qualities of the fluid itself. Thus in old men, in whom the bladder has but a small de- gree of irritability and contractility, the urine is voided less frequently ; it accumulates in greater quantity, and is, at times, evacuated with difficulty. The use of diuretics, especially of cantharides, renders the urine more stimulating, it excites powerfully the parietes of the bladder, and inces- santly stimulates it to contraction. Every cause of irritation seated with- in the bladder itself, or in its vicinity, renders more frequent the calls to void urine. This is observed in cases of stone in the bladder, of piles, gonorrhma, &c. The urine, while in the bladder, becomes thicker from the absorption of its more fluid parts, its elements become more intimate- ly blended, sometimes even, it appears to undergo a certain degree of de- composition. XXXV. When, either by the extension which the urine occasions in the muscular fibres ofthe bladder, or by the irritation which it excites ids in the nerves distributed on its inner membrane, we experience in the pelvis a sensation of weight, together with a kind of tenesmus, which, as it extends along the urethra, warns us to void urine ; then we bring on a contraction ofthe bladder, and joining to its action, that ofthe abdominal muscles and ofthe diaphragm, we expel the urine by a process very si- milar to that ofthe excretion ofthe faeces (XXIX.) It should be observ- ed however, that in a healthy state ofthe parts, this assistance is requir- ed, only to overcome the equilibrium between the contractions of the bladder, and the resistance which the cause of retention opposes to the evacuation ofthe urine. After the simultaneous contraction ofthe dia- phragm and abdominal muscles, to press down the intestines on the blad- der, and to determine the first flow ofthe urine, we cease that effort, and the bladder alone, still supported t>y the weight ofthe surrounding vis- cera, which compress it as it empties itself, completes the evacuation. We repeat the first effort, only in case we wish to accelerate the flow of the urine. In the evacuation ofthe faeces, on the contrary, the muscular coat ofthe rectum requires the incessant co-operation ofthe respiratory powers, as these solid substances are evacuated with more effort than the urine. To prove, beyond a doubt, that the urine is evacuated, chiefly by the action ofthe bladder, one need but observe the violent, but useless straining of patients affected with retention of urine, from paralysis ofthe bladder*. The urine is projected along the urethra with the greater force, as it passes from a spacious cavity, into a straight canal, and it is expelled with a force proportioned to that ofthe muscular coat ofthe bladder : we know, that in old men this is so weak, that the jet of urine is not projected more than a few inches beyond the urethra. The urethra is not to be con- sidered as inert in the evacuation ofthe urine, it closes upon it and accele- rates its flow, aided in that action, by the buibo-cavernous muscles to which several anatomists have given a name taken from their functions, (acceleratores urines) The action of these muscles expels the last drops of urine which remain within the urethra, when the bladder is completely emptied. The con- tractile and tonic action of the urethra is so distinctly marked, that its spasmodic contraction may be enumerated, among the causes which fre- quently occasion a difficulty in introducing the catheter. If we attempt to inject fluids along the urethra the moment we remove the pipe ofthe syringe which closes its external orifice, that instant, the parietes ofthe canal contract on the fluid, and expel it with a rapid jet. The bladder and the canal of the urethra are lined internally with a membrane, whose mucous follicles secrete a viscid humour calculated to protect the parietes of these organs, against the action ofthe urine, and to facilitate the evacuation of that fluid. This membrane, whose surface is more extensive than the cavities which it lines, forms a great number of folds, which disappear when the bladder is distended with urine. This mucus is secreted, in an unusual quantity, in catarrhal affections ofthe bladder, and becomes, likewise, more ropy and more albuminous. The * It is scarcely credible that some physiologists should have considered this organ as inert and absolutely passive, in the evacuation of urine, which, in their opinion, is per- formed by the immediate pressure ofthe abdominal muscles and diaphragm on that cavity. Amid this variety of opinions, if you wish to come at tbe truth, you must take a medium. Iliacos intra mures peecatur, et extra. 104 mucous secretion of the glands of the urethra is altered in its quality, and becomes more abundant, from the action ofthe venereal poison d gives rise to the discharge ofgonorrhaea ; the orifices of these lacun . ay stop the end ofa catheter, so as to add to the difficulty of introducing that in- strument*. The urine cannot be voided at the same time as the fasces, when these, by their hardness, compress the prostatic and the membranous part ofthe urethra, situated before the lower extremity of the rectum. It is diffi- cult, and often impossible, to void urine during a violent erection, as the parietes of the canal are then closely applied to each other, by the tur- gescence ofthe corpus spungiosum and ofthe corpora cavernosa ofthe pe- nis. The mode of sensibility ofthe urethra, is besides changed in such a manner, that it is calculated to permit only the emission of the seminal fluid. When tbe bladder is completely emptied, it sinks behind the pubis; the tumour which it formed above these bones, while in a state of dis- tension, collapses, the abdomen becomes less prominent, respiration more free, and there is a general feeling of lightness. The bladder cannot be completely evacuated, unless the pelvis is gently inclined forward ; its basfond, which is on a lower level than its neck, would, in any other posture, retain a certain quantity of urine. XXXVI. Of the physical properties of urine As this fluid varies in quantity in a healthy man, according to the quantity and diuretic qua- lities of the drink, the state of sleep or waking, the condition of the se- cretions, and especially of the perspiration, it is very difficult to deter- mine, accurately, its proportions. Nothing varies more than its quantity, as may be ascertained, by comparing the different calculations on that subject, of a great number of physiologists. At times the urine is less in quantity than the drink that has been taken in, at others, more. It may be affirmed, however, that the quantity of urine voided in twenty- four hours, is equal to that of the insensible perspiration in the same time, and it may, therefore, be estimated at between three and four pounds, in a healthy adult. Its colour varies, from a light lemon yellow, to an orange, approaching to red. Its smell and flavour are peculiar, and distinguish it from every other animal fluid Its colour is, in gene- ral, darker, its imell and flavour stronger and more pungent, as it is less in quantity, as the circulatory system is more active and powerful, and as the substances of our food are more annualized. We all know how fetid and how scanty is the urine of carnivorous animals ; how offensive to the smell is that of the cat! The specific gravity of urine is greater than that of distilled water, and varies, according to the quantity of saline and other substances, which it holds in solution : it is, likewise, slightly * When this operation is performed in a case of simple paralysis ofthe bladder, it is better to employ a very large catheter, which may stretch the parietes of the urethra, and prevent their forming into wrinkles, and whose rounded beak may not get en- gaged in the lacunae of that canal. When in a case of retention of urine, the bladder rises above the pubis, its basfond is carried upwards, and there is a period of excessive distension, at which, like the uterus in an advanced state of pregnancy, it seems to make an effort to rise above the brim ofthe pelvis: under such circumstances in women, it is impossible to introduce the catheter, except by increasing the ".urve ofthe instrument. —Author's Not'- 105 viscid, but not ropy like the serum ofthe blood, the bile, the saliva, and other albuminous fluids. XXXVII. Ofthe chemical properties of urine* The peculiar qualities of urine are always more marked in a powerful and adult male, than in children, women, and weakly persons. By chemical analysis, the urine is found to contain eleven substances, dissolved in a consider- able quantity of water, viz. urea, a gelatinous animal matter, muriates and phosphates of soda and ammonia, in separate or in triple salts, phosphate of lime, phosphate of magnesia, phosphorus, uric and benzoic acids. Besides these substances which are constantly found in human urine, this fluid may contain a great number of others ; and if it be true that the urinary system is to be considered as the emunctory of the whole economy, one would expect to find in it, in certain proportions and under different circumstances, the whole of the constituent principles which analysis has hitherto discovered in our solids and liquids. Hence, doubtless, the dif- ference in the results obtained by the chemists who have investigated the nature ofthe urine, by allowing it to run into decomposition, or by apply- ing to it various re-agents. As the urine is, of all our fluids, that which has the greatest tendency to putrefaction, it should be examined shortly after being voided ; it is then distinctly acid, but in a very short time, and especially if the heat of the atmosphere promotes and accelerates these changes, it becomes turbid, its component parts separate and form various precipitates. Urea and gelatine, which alone of its constituent principles are capable offer- mentation and decomposition, give out ammonia, acetous and carbonic acids, and from the chemical attraction between these newly formed sub- stances, and from the primitive elements, there are produced new com- pounds, the knowledge of which is of the department of chemistry. Of all the constituent parts of urine, the most essential is a substance of the consistence of syrup, deliquescent, susceptible of crystallization, to which M. Fourcroy has given the name of urea. This substance to which the urine owes its characteristic properties, its peculiar colour, smell, and flavour, which was imperfectly known to several chemists who had sketched some of its features, giving it different names, according to the notions they entertained of its nature, was never well understood till the late investigations of this celebrated professorf. It is a compound in which azote prevails, as is shown by the immense quantity of carbo- nate of ammonia, which it gives out in distillation ; it may be considered as the most animalized product, having such a tendency to the putrid fer- mentation, that, even while in the animal economy, it is liable to that de- composition, and might overcome the antiseptic influence of the vital power, if nature did not get rid of it by the evacuation of the urine. Sufficient attention has not hitherto been paid to the symptoms of uri- nary fever, an affection occasioned by the protracted retention of the urine within the bladder, I have observed, on several occasions, that no kind of fever is attended with more marked signs of what physicians term putridity. The urinous and ammoaiacal smell exhaled from the * For some observations on the physical and chemical properties of urine, see AP- PENDIX, Note P. t See his work entitled, Systeme des connoissances cliimiqucs: 8vo. torn. X. pijgft 153. U ioc? oody ofthe patients, tbe yellowish and oily moisture of their skin, the parching thirst with which they are tormented, the dryness and redness of their tongue and throat, their frequent and irritable pulse, combined with a flaccid and doughy feel ofthe cellular tissue, every thing indicates that the animal frame is threatened with, the most speedy and dangerous decomposition. I observed similar appearances in a cat and in a rabbit, in which I tied the ureters. Nothing is easier th«n to find the ureters, and to perform this experiment. After a crucial incision ofthe parietes of the abdomen, on the left side, the intestines are pushed aside to the left, so as to applya ligature on the right ureter, they are then pushed to the right, while the left ureter is tied. Both ureters are seen through the peritoneum, situated behind that membrane, in the lumber region. When the ligatures have been applied to the ureters about their middle, the di- vided edges ofthe abdomen are brought together and united by sutures, and the body ofthe animal is wrapped round with a cloak soaked in some emollient decoction. At the end of six and thirty hours, the animals be- came exceedingly thirsty and restless, their eyes glistening ; their saliva, which flowed copiously, exhaled a smell evidently urinous : on the third day, the cat was seized with vomiting of a slimy substance, remarkable by its having the same smell. This convulsive agitation was followed by an excessive prostration of strength ; it died on the fifth day; the intes- tines were not inflamed, the bladder quite empty, the ureters distended with urine between the ligatures and the kidneys, and as large as the ring finger. The kidnies themselves, gorged with urine, were turgid, softened, and as if macerated. All the organs, all the fluids, the blood itself, par- took of this urinous diathesis ; putrefaction came on immediately after death, and at the end ofa few days, an almost complete decomposition of the body had taken place. In the rabbit the symptoms were less violent and rapid ; it did not die till the seventh day ; the smell ef its whole bo- dy, though evidently urinous, was less offensive, and the putrefaction which succeeded was less rapid. These two experiments confirm, in the first instance, what some au- thors have said ofthe absence of urine in the bladder, when the ureters have been tied, an undeniable proof that these are the only channels which convey the urine into the bladder ; they likewise concur in afford- ing the most convincing proof, that the kidnies are the emunctories by means of which the blood clears itself of that part of it which is animalized in excess ; finally, they prove, that the retention of this fluid is the more dangerous to the animal economy, as the urine is itself more animalized. Has nature the means of supplying the evacuation of urine by other excretions ? might this highly recrementitious fluid be, without danger, evacuated by other emunctories ? With a view to answer this interest- ing question, the kidnies have been extirpated in dogs. The removal of one kidney, did not prevent the secretion from being carried on ; in eve- ry case in which both kidnies were removed at once, the animal died in a few days, and on opening the body, there was uniformly found, a con« siderable quantity of bile in the gall-bladder, in the small intestines, and even in the stomach, as if the urea had endeavoured to make its escape in that direction, by combining with the bile. These experiments were performed at the Hopital Saint Louis, in the course ofthe year XI. Urea, combined with a certain quantity of oxygen, appears to form an 10? •acid peculiar to human urine, and which is the substance of the greater numbers of urinary calculi. It resembles urea, in this, that its crystals, exposed to heat, give out carbonate of ammonia ; but it differs essentially from it, by its ready concrescibility. It, in fact, crystallizes, every time the urine grows cold, and forms the greatest part ofthe urinary sedi- ment. This acid, so weak that several chemists have considered it to be a mere oxide, has been called by M. M. Fourcroy and Vauquelin, the uric acid. Among its distinguishing characters, may be mentioned its be- ing insoluble in cold water; it is so fixed, that several thousand times its own weight of boiling water is required to dissolve it, hence it may be easy to account for its so frequently giving rise to urinary calculi: we may, indeed, wonder that this complaint is not of more frequent occur- rence, since a slight cooling ofthe urine is sufficient to cause a precipita- tion and crystallization of the urine. Thus, every time an extraneous substance drops into the bladder, it becomes the nucleus of a calculus, formed by the uric acid becoming concrete on the surface of this body, which is ofa colder temperature. Quadrupeds are less frequently affect- ed with urinary calculi, from the absence of the uric acid in their urine, and because carbonate of lime, of which, in those animals, such concre- tions are formed, is a salt decomposed with effervescence by the weaker acids, and several such acids are found in the urine. Phosphorus, which may be considered as the result ofa high degree of animalization, enters, in considerable proportions, into human urine. Besides the phosphoric salts which it contains, there is always found a certain quantity of disengaged phosphoric acid, which holds in solution the calcareous phosphate, and gives to the urine its manifest acidity, when examined fresh, or shortly after it has been voided. It was from urine, that phosphorus was first obtained by those who originally discovered it4 and from that fluid, it has long been procured for the purposes of com- merce. But it is seldom obtained from urine, since the discovery of the phosphoric acid in the earth of bones, has rendered the manufacture of phosphorus easier and less expensive. In the urine of frugivorous mnm- miferous animals, phosphoric salts have their place supplied by calcareous carbonate. Certain substances impregnate the urine with a peculiar odour. It is well known that if one remain a few minutes in a room newly painted with oil of turpentine, the urine, for some time afterwards gives out a smell of violets ; asparagus gives to the urine a very remarkable fetor. XXXVIII. Besides the accidental varieties observed in the urine, vari- eties which cannot be determined, since the urine is never uniformly the same in its composition, and does not contain the same ingredients in the same person, at different times of the day, according to the quantity and quality of the food and drink, the exercise which has been taken, the affections of the mind which have been experienced, &c; it constantly varies, according to the time which has elapsed since a meal, the age of the subject, and the diseases under which he may labour. Physiologists have for a long while, admitted two and.even three differ* ent kinds of urine, according to the time at which it is voided ; they are distinguished by the names of urine of the drink, urine of the chyle, and urine of the blood. The first is a limpid and nearly colourless fluid, which frequently retains, in a remarkable manner* the qualities ofthe drink, arid 108 is voided shortly after drinking, and has scarely one of the characters ot perfect urine. *The urine of tbe chyle or of digestion, voided two or three hours after a meal, is more formed, still it is not perfect, and does not contain all the component parts of this fluid. Lastly the urine ofthe blood which is voided seven or eight hours after a meal, and in the morning after the night's rest, contains, in an eminent degree, all the qualities of urine, hence it is that whr,h chemists prefer using in their analysis. The imperfect state of the two former kinds of urine, would prove better than the rapidity of their secretion, the disputed existence ofa peculiar communication from the stomach and intestines into the bladder. The urine of children and that of nurses contains very little phosphate of lime and phosphoric acid ; it is only after the process of ossification is completed, that these elements abound in the urine. That of old men, on the other hand, contains a considerable quantity of these substances; their osseous system already containing phosphate of lime in excess, and incapable of receiving more, this saline substance would ossify all the tis- sues, as it sometimes does that of the arteries, the ligaments, the cartilages and membranes, if the urine did not carry off the greater part. In the rickets, it is by the urine that the phosphate of lime is carried out ofthe system, and the absence of that substance is the cause of molli- fies ossium ; on the approach of fits ofthe gout, the phosphoric ingredients of the urine diminish, and seem to be carried to the joints, to produce in their vicinity arthritic concretions. The great quantity of saline and crystallizable elements which enter into human urine, accounts for the frequency of the concretions which form in that fluid. Urinary calculi were long considered as formed of a single substance, which the ancients thought analogous to the earth ofthe hones, and which Scheele took for uric acid. The late investigations of M. M. Fourcroy and Vauquelin have shown, that the component parts of urine are too numerous and too complex to produce uniformly calculi of one kind : that urinary concretions, most frequently formed from uric acid, contain urate of ammonia, phosphate of lime, phosphate of ammonia and magnesia, oxalate of lime, silex, and that these substances, singly, or in binary and ternary combinations, form tbe materials of nearly six hundred calculi which they analysed. Notwithstanding the extent of these re- searches, there is reason to believe, that when carried further by the same chemists, they will be attended with results still more varied. For, as there is no integral molecule in the body which may not be voided with the urine, and be found in the urine, so it is conceivable, that under certain circumstances, which it is impossible to assign or to forsee, every thing in the human body that is capable of concretion, might supply the materials of urinary concretions. This variety of elements in the composition of urinary calculi, the ab- sence of signs, by which to ascertain their nature, the sensibility of the parietes ofthe bladder which would be irritated by agents capable of dis- solving the concretions so frequently formed in its cavity, must render it very difficult, not to say impossible, to discover a lithontriptic which should supersede the necessity of a surgical operation, whose difficulties and dan- ger have been much over-rated. XXXIX. The energy of the urinary system in the inhabitants of tem- perate climates, has been considered as the cause ofthe frequency of cal- 109 culous affections in Holland, England, and France, while they are very rare in more southern countries, in which the cutaneous perspiration seems to be substituted, in great measure, for the urinary secretion. There is no part of the world in which cases of stone in the bladder are more frequent than in England, and especially in Holland, in which a cold and damp atmosphere is unfavourable to perspiration, which is, at any rate, but scanty in persons of a leucophlegmatic temperament like that of the Dutch. In no other country, could a lithotomist (Raw) have operated on more than fifteen hundred patients, it is said, sucessfully. Diabetes, or an immoderate discharge of urine, a disease which appears to depend on an excessive relaxation ofthe renal tissue, is of frequent occurrence only in cold and damp countries, as Holland, England, and Scotland ; it is more rare in France and Germany, and is unknown in warm climates. This re- laxation of the renal tissue in diabetes, depends on the exhaustion of the urinary organs called into too frequent action, as is proved by the efficacy of tonics and astringents in the treatment of that complaint. Cutaneous affections, on the contrary, seem to belong to the inhabitants of southern countries.* Lepra originated in Judea; the elephantiasis rubra of Cayenne, the framboesia of Java, the yaws, elephantiasis, herpetic and psoric eruptions, are more frequent among the inhabitants of southern latitudes than among those who live under the temperate zones. In countries near to the equator, the surface ofthe body, habitually exposed to an ardent atmosphere, is powerfully excited : the skin is irritated, and its secretion increased ; perspiration becomes so profuse, that it weak- ens, in a short time, those who, coming from distant countries, are not accustomed to so intense a heat. The activity of the cutaneous system exceeds that ofthe urinary system, whose action decreases in proportion. These differences in the energy of the two systems, account readily for the difference of their diseases : for, it is a law of Nature, that the more an organ, or system of organs, is called into action, the more it is liable to disease,(which is but a derangement of its action. Calculous affections are more frequent in children and old people than in adults. In old age, the proportionate quantity of the urine exceeds that of the perspiration. Phosphoric salts, the base of a great number of urinary calculi, are more abundant in old men, as is proved in them by the ossification of the arteries, ofthe ligaments, of the cartilages, of the membranes, the solidification, and the almost universal induration of the different parts. In children the activity of the urinary system is propor- tionate to that of the digestive organs. Destined to throw out the resi- due of nutrition, which, at that period, is very active, the organs by which the urine is secreted are likewise endowed with considerable ener- gy. Lastly, it is observed, that the greatest number of calculous patients received into the hospitals of large towns, come from low and damp streets near to rivers ; every thing, therefore, tends evidently to esta- blish, that the frequency of urinary calculi, depends on an increase of activity, in the organs destined to the secretion and excretion of urine. * It would be more correct to say that Cutaneous affections are more frequent among; the inhabitants of southern climates. 110 CHAPTER II. OF ABSORPTION. XL. In the history of the phenomena of life, a statement of the func- tions of the absorbent system, ought immediately to follow that of the functions of the digestive organs. The vessels, which take up the chyle separated from the food, by the action of the organs of digestion, form a considerable part of the absorbent system, bear a perfect resem- blance to the other lymphatics, and differ from them only in their origin. When digestion is not going on, those vessels convey lymph absorbed in the intestinal canal, the inner part of which, even when in a state of emptiness, is always bedewed by an abundant quantity of serous mu- cus. There exists in all the parts of the human body, in the interior, as well as on the surface of our organs, vessels whose office it is to absorb, and to carry into the mass of the blood, those substances by which our machine is maintained and kept in repair, as well as what comes off in the continual destruction of our parts ; for, it must not be forgotten, that the organized and living machine, inwardly acted upon by a double im- pulse, is perpetually undergoing decay and renovation. XLI. Absorption is effected on substances introduced from without; such is the absorption from the skin, and the absorption of the chyle, &c. At other times, absorption takes place in fluids effused by arterial transudation ; such is the serosity which moistens the serous membranes, the fat, the marrow of the bones, and this absorption, almost always, bears a proportion to transudation, so that the serosity, absorbed as fast as it is effused on the surface of the membranes which lie in close con- tact, except in cases of dropsy, never accumulates so as to separate those membranes. Finally, there is a kind of absorption, which may be termed nutritive or molecular, because it exerts its influence on mole- cules, which, in the process of nutrition, are separated from the organs, and replaced by others. It is this absorption which brings about the de- composition of organs, and to which John Hunter gave the name of inter- stitial absorption. By means of it, the thymus, so voluminous in the foetus, disappears entirely in the adult. This absorption seems to be in- cessantly going on, and to carry on decomposition, with a force that can- not be resisted. It explains, in a satisfactory manner, the spontaneous erosions of the living solids, of which ulceration* is the consequence. M. Dumas has endeavoured to explain in this way, tbe sensation of hun- ger, which, in the opinion of that physician, is felt when the absorbents exert on the solid coats of the stomach, their activity previously employed in taking up liquids. But to give even a degree of probability to that Supposition which is entirely gratuitous, it would be necessary to show, :" Nosographie Chirugicale, tome J. art. Ulceres Aloniqur?< ill that the parietes of the stomach have been found destroyed or thinned, ia persons who have died of hunger. The parietes of the stomach of such persons, have, on the contrary, been found thickened and in a state of contraction. This inward absorption is promoted by inflammation, hence the advantage of applying heat to indolent tumours, and of exciting a slight inflammation in swollen glands, in order to bring about resolution. It is on that account, that in swelling and induration of the testicle, unat- tended by cancer of the part, the operation for hydrocele by injection, may be safely employed.—Of this I had a convincing proof, a few years ago ; a gardener, born deaf and dumb, had had for some years an hydro- cele, which he was in the habit of getting tapped every six months. When I last tapped it, I found the testicles swollen and hard, and three times larger than in its natural state ; the patient, however, was free from pain. A considerable quantity of a reddish serous fluid was dis- charged ; at the end of two days, inflammation of the tunica vaginalis came on, the scrotum became enlarged, and was covered with emollient poultices. At the end of twenty days, the testicle was a good deal lessen- ed in size, and adhered to the inside of the tunica vaginalis : the cure was considered radical, and proved such ; for,'though it is now ten years since the operation was performed, the water has not collected, and the patient continues in the laborious employment of his business. I fre- quently meet him, and he never fails, by inarticulate sounds and signs'of satisfaction, to express to me his gratitude. The process of absorption is very active in children, in women, during sleep, in the morning, when the body is refreshed by the night's rest. Is a state of weakness favourable or unfavourable to that process ? it is well known, that there are robust men who have intercourse with women infected with the venereal virus, and who escape the contagion, unless they expose themselves to it, when debilitated by excesses. A mind free of fear and anxiety, has ever been considered in the Eastern countries, a safe-guard against the plague. A dog. caeteris paribus, is in much less danger from the bite ofa viper, when suddenly bitten, than when he has been sometime gazing at the reptile, and, more or less terrified by the sight. But in all these cases, does debility favour the introduction ofthe contagious matter, by increasing the force of absorption ;• or is it not more probable, that by affecting the nervous system, it renders it more suscep- tible of deleterious impressions ? XLII. Absorption is much less active, on the external surface ofthe body, than on the surface of its internal cavities, and in the very substance of our organs. Cutaneous absorption, under certain circumstances, has even so little activity, as to have led some physiologists to doubt its exis- tence. The absorbing orifices of vessels which arise on the surface of the body, are covered by the epidermis. This covering, which is insen- sible, and, as it were, inorganic, forms a sort of separation between the external and internal part of our being, and opposes, or renders more dif- ficult, the absorption of substances in immediate contact with our body, and if it be considered, that we are frequently immersed in the midst of gases and other substances, to a certain degree, deleterious, it will be un- derstood, how essential it was, that the absorbing surface of the skin, should not be entirely exposed, and that cutaneous absorption should not be easily carried on. The increased weight of the body, after exercise in wet weather ; the J1-2 abundant secretion of urine, after remaining long in the bath ; the mani- fest enlargement ofthe glans ofthe groin, after keeping the feet immersed, for a considerable time, in water, an experiment often performed by Mas- cagni on himself; the effects of mercurial frictions, &c. show, however, in an unquestionable manner, that absorption takes place through the skin, with more or less rapidity, according to circumstances. It must be taken into account, that the means which promote cutaneous absorption, ope- rate, at least as much, by altering the structure ofthe epidermis, as by increasing the action ofthe absorbing orifices. In this manner the bath appears to operate, by softening the texture ofthe epidermis ; and fric- tions, by displacing and raising its scales. It is by means of frictions, that we succeed in introducing into the lym- phatic system, medicines possessing purgative, febrifuge, sedative, or diu- retic qualities, combined with the gastric juice, or diluted in any other liquids, for, as has been shown by the experiments performed at the Sal- petriere, by M. M. Dumeril and Alibert, in the name of the Philoraatic Society, the mixture with saliva or gastric juice, ofthe medicines which are to be administered by friction, is not necessary to insure their absorp- tion Extract of opium has soothed pain, bark has checked fits of inter- mittent fever, rhubarb has procured alvine evacuations : squills have stimulated powerfully the action ofthe urinary organs, nor has the pre- viola's mixture, with gastric juice, of these substances reduced into powder, seemed to increase or diminish their efficacy. Absorption takes place quickly and readily, wherever the epidermis is «thin, habitually moist, and the skin delicate, so as to leave almost bare of covering, the subjacent parts, as on the lips, in the inside ofthe mouth, on the surface ofthe glands, &c. The complete removal ofthe epider- mis, favours absorption from all parts ofthe skin which it covered. Hence the least scratch on the fingers of an accoucheur touching women infected with the venereal virus, exposes him to this peculiar infection, which, in such ca.-es, is the more to be dreaded, from tbe admission ofthe virus by an unusual course. The inoculation of variolus and vaccine matter, equally furnishes proofs ofthe obstacle which the epidermis presents to cutaneous absorption, and ofthe facility with which that function takes place, from surfaces denuded of that covering. Absorption goes on, like- wise, with great activity, from the surfaces of internal parts, but it no where is so considerable, as in the intestinal canal, and it would perhaps be the most favourable part for introducing medicinal substances into the animal economy, if when swallowed, they did not undergo changes, by mixing with the gastric juices, or with the intestinal fluids and faecal sub- stances, when injected by the rectum. From the evacuation by urine of clysters of warm water, soon after they have been administered, it is to be presumed, that trie great intestines absorb, almost as powerfully as the rest ofthe digestive canal. A pint of warm water injected into the abdomen ofa large dog or sheep, is often absorbed in less than an hour, and the ef- fusions which take place in those cavities, would possibly not require an operation to let them out, if such fluids were not subject to coagulation, and if the absorbing surfaces were not diseased. Besides absorption from surfaces, there exists, as we have already stat- ed, another which takes place in the living solid, and in the internal sub- stance ofthe organs. It is by this kind of absorption, that the nutritive decomposition is effected ; by means of it, the living matter is incessantly 113 renovated. Its vitiated action accounts for the spontaneous formation of ulcers, the disappearing ofthe thymus, the atrophy of parts in which nutrition is carried on, in a sluggish manner; the resolution of certain tumours, and many other phenomena, are dependent on the same cause. I do not think, however, that it is possible to admit the explanation ofthe sensation of hunger, adopted by Professor Dumas, who believes that it depends on the action ofthe absorbing orifices directed against the or- ganized substance ofthe stomach, in the absence of aliment on which to act. The sensation of hunger is felt only in the stomach, although its effects extend to all parts ofthe body : it begins in a circumscribed spot, its seat is limited, yet absorption takes place every where, so that if the hypothesis in question had any foundation, the sensation of hunger ought to be felt at the heel, as well as at the pit ofthe stomach*. The radicles from which the lymphatics arise, have orifices 60 very minute, that they are imperceptible to the naked eye ; a tolerably accu- rate notion may be formed of them, by comparing them to the puncta la- chrymalia, which are larger and more easily discovered. Each orifice endowed with sensibility, and with a peculiar power of contraction, di- lates or contracts, absorbs or rejects, according as it is affected by the substances which are applied to it. The variations ofthe absorbing pow- er, according to the age. the sex, the constitution, and different periods ofthe day, show that it cannot be compared, as several physiologists have done, to that principle which makes fluids ascend, contrary to the laws of gravitation, in capillary tubes. If absorption were a process merely mechanical, it would, in no case, be accelerated or retarded, and would proceed with a regularity never observed in the vital functions. The mouth of every lymphatic, when about to absorb, erects itself, draws to- wards itself, and raises the surrounding membranous parts, and thus forms a small tubercle similar to the puncta lachrymalia. These little bulgings deceived Lieberkuhn, and led him to think, that the absorbents ofthe in- testines, originated from small ampullalae, or vesicular enlargements, which, as so many exhausted receivers, pumped up the fluid extracted from the food. This physiologist may, further, have been led into error, by the nervous papilla? of tbe inner membrane of the canal, swollen by tbe determination of blood attending irritation, the natural cnsequence ofthe friction ofthe alimentary substances. The inhaling faculty belongs, not only to the orifices at the extremity of each radicle, but, likewise, to the lateral pores, which are infinitely numerous, in the parietes of the vesselsj. XLI1I. After arising on the surface, and in the interior of the body, by radicles in close contact, the lympathetics creep and coil themselves, * It does not fall to the lot of everyone, to err like M. Dumas, whose talents and in- genuity I have much pleasure in acknowledging. Me imagines ricket9 to consist, is a deficient influence ofthe nervous system on the bones ; which would constitute a kind of paralysis. Anatomy shows the presence of no nerves in the tissue of the bones, and veins and arteries are alone seen te enter the foramina, and no nerves ap- pear to be transmitted through them. The functions ofthe bones made it unneces- sary that they should be endowed with that peculiar sensibility which requires the existence of nerves. The bones are active by being subject to the process of nutri» tion, but in every other respect, they are absolutely passive. In the opinion of some people, such doctrines are real discoveries. Credal judozus Abella, non ego.—'Au" thorns Note. t S*e APPENDIX, Note Q 114 describe numerous curves, unite, then divide, and presently^ unite again and from these numerous inosculations, there results a net"worK'fw"" close meshes, forming, with that of the blood-vessels, the texture oi tne cellular tissue and of the membranes. nfttr.inse workmen in a large manufactory in which various kinds of goods are made, who are employed in carrying the materials to those who are to work them ; and as among the latter, some finish the work, while others prepare the materials, so the lungs and the secretory glands are continually occupied in separating from the blood whatever is too heterogeneous to our nature to become assimilated to our organs, or to afford them nourishment. To understand, thoroughly, the mechanism of this function, it is neces- sary to study separately the action ofthe heart, that ofthe arteries which arise from it, and, lastly, that ofthe veins which enter it. The union of these three classes of organs, forms the circle ofthe circulation. LI. Of the action of the heart. In man, and in all warm-blooded ani- mals, the heart is a hollow muscle, the inner part of which is divided in- to four large cavities which communicate with one another ; from these, vessels arise which convey the blood to all parts ofthe body, and the ve's- * See APPENDIX, Note Q. 16 122 sels which bring it back from all those parts, likewise terminate in these CRVltlPS The heart is placed in the chest, between the lungs, above the dia- phragm, whose motions it follows ; it is surrounded by the pericardium, a dense and fibrous membrane admitting of very slight extension, closely united to the substance of the diaphragm, coveiing the heart and great vessels, without containing them in its cavity, furnishing an external co- vering to the heart, and bedewing its surf ice with a serous fluid, which never accumulating, except in disease, facilitates its motion, and prevents its adhering to the neighbouring parts. The principal use of the peri- cardium, is to fix the heart in its place, to prevent its being displaced in- to other parts of the chest, which could not happen, without occasioning a fatal disorder in the circulation. If, after having laid open the chest ofa living animal, by raising the sternum, an incision is made into the pericardium, the heart protrudes through the opening, and moves to the right and left by bending itself on the origin of the large vessels ; the course of the blood is then intercepted, and the animal threatened with immediate suffocation. In man, the heart is placed nearly towards the union of the upper third ofthe body, with the lower two-thirds ; it is, therefore, nearer to the upper parts ; it holds them under a more immediate controul, and as that organ keeps up the action of all the rest, by the blood which it sends into them, the parts above the diaphragm have much more vitality than the parts beneath. The skin of the upper part of the body, and espe- cially of the face, has more colour, and is warmer than that of the lower parts ; the phenomena of diseases come on more rapidly in the upper parts ; they are, however, less liable to put on a chronic character. The bulk ofthe heart, compared to that of other parts, is larger in the foetus, than in the child that has breathed, in short men, than in those of high stature. The heart is likewise larger, the stronger, and more pow- erful in courageous animals than in weak and timid creatures. This is the first instance ofa moral quality depending on a physical dis- position of parts ; it is one ofthe most striking proofs ofthe influence of the moral character of man on his physical nature. Courage arises out of the consciousness of strength, and the latter is in proportion to the activity with which the heart propels the blood towards all the organs. The inward sensation occasioned by the afflux ofthe blood, is the more lively, and^ the better felt, when the heart is powerful. It is on that ac- count that ^ome passions, for example, anger, by increasing the action of the heart, increase a hundred fold both the strength and courage, while fear producekan opposite effect. Every being that is feeble, is timorous, shuns danger, because an inward feeling warns him, that he does not possess sufficient strength to resi*t it. It may perhaps be objected, that some animals, as the turkey cock and the ostrich, possess less courage than the least bird of prey, that the ox has less than the lion and other carnivorous animals. What has been said does not apply to the absolute, but to the relative size ofthe heart. Now, though the heart of a hawk be absolutely smaller than that of a turkey cock, it is nevertheless larger, in proportion to the other parts of the animal. Besides, the bird of prey, like the other carnivorous animals, in part owes his courage to the strength of his weapons of offence. Another objection, more specious, but not better founded, is drawn 123 from the courage manifested, on certain occasions, by the most timid animals, for example, by the hen in protecting her young ; from the courage with which other animals pressed by hunger or lust, surmount all obstacles, but particularly from the heroic valour of men ofthe most fee- ble bodies. All these facts, however, are only proofs ofthe influence of the mind on the body. In civilized man, the prejudices of honour, inte- rested considerations, and a thousand other circumstances, degrade the natural inclinations of man, so as to make a coward of one whose strength is such as would induce him to brave all kinds of danaers, while on the other hand, men whose organization should render them most timid, are inspir- ed to perform the most daring actions. But all these passions, all these moral affections, operate only by increasing the action ofthe heart, by increasing the frequency and the force of its pulsations, so that it excites the brain or the muscular system, by a more abundant supply of blood. The heart is not quite ovoid in man as it is in several animals, nor is it parallel to the vertebral column, but it lies obliquely, and is flattened to- wards the side next the diaphragm on which it rests. Ofthe four cavities which form the heart, two are, in a measure, acces- sary, viz. the auricles ; they are small musculo-membranous bags oppos- ed to each other, receiving the blood of all the veins, and pouring that fluid into the ventricles at the base of which the auricles are, as it were, applied. The ventricles are two muscular bags separated by a partition ofthe same nature, and belonging equally to both : they form the great- est part ofthe heart, and give origin to the arteries. The auricle and ventricle on the right side, are larger than those on the left. But that difference of size depends as much on the manner in which the blood circulates, at the approach of death, as on the original conformation of the lungs. On the point of death, the lungs expand with difficulty, and the blood sent into them, by the contractions ofthe right ventricle, being no longer able to circulate through them, collects in that cavity, flows back into tbe right auricle, in which the veins continue to deposit blood, stretches their parietes, and increases considerably the di- mensions of those cavities. The capacity ofthe right cavities is, however, originally greater than that of the left, and is proportioned to that of the venous system which opens into it. The right cavities of the heart, which might be called its venous cavities, have likewise thinner parietes than the left or arterial, and, in this respect, the same difference is ob- served, as in the parietes of the arteries and veins. The right ventricle having to send the blood destined to the lungs, to a very short distance, and through a tissue easily penetrated, requires but a moderate impelling force. As will be shown, in speaking of respiration, a function of which the physiological history is not easily separated from that ofthe circulation, the heart may further be considered as formed of two parts in contact, the one right or venous, the other left or arterial. Notwithstanding the juxta position of these two parts ofthe same organ, they are perfectly distinct, and the blood in each cavity is very different from that in the other. The blood, in the adult, can never pass immediately from the one to the other ; the right side of the heart receives the blood of the whole body, and transmits it to the lungs ; the left side of the heart re- ceives the blood of the lungs, and distributes it over the whole body, so that, in a physiological point of view, the lungs form a part ofthe circle 124 ofthe circulation, and serve as an indispensable medium between the two divisions ofthe heart, and as will be seen hereafter, their part of the circle is, by no means, the least important. If there existed, between the ventricles, a direct communication, the venous blood would mix with the arterial, and the union of these two fluids would mutually impair the qualities of each, liecent observations have furnished an opportunity of judging of the effects of such a commu- nication between the ventricles, which had been imagined by the ancients, but of which no case had yet been met with. A man, forty one years of age, came to the Hopital de la Charite, to undergo the operation of litho- tomy. He was remarkable for the lividity of hi- complexion, the turges- cence of the vessels of the conjunctiva, and the thickness of his lips, which, like the rest of his face, were of a dark colour, his respiration was laborious, bis pulse irregular, he could not utter two words in succes- sion without taking breath ; was obliged to sleep in a sitting posture, and was particularly remarkable for his indolence. This indolence, joined to great simplicity of nature, was such, that he had never been able to main- tain himself without the assistance of his wife. A very small quantity of blood was taken from his arm, in consequence of which his pains were diminished, but his difficulty of breathing increased, was followed by syn- cope, and he died from suffocation. On opening his body, his heart was found filled with blood, and especially the right auricle, which was con- siderably distended ; the pulmonary artery was aneunsmal, and uniform- ly distended from the right ventricle, to its division ; none of its coats had yet given way. The two ventricles of the heart were of nearly the same capacity, and the relative thickness of their parietes did not vary so much as in health. The partition between them, contained an opening of com- munication of an oblong shape, about half an inch in extent, and directed obliquely from below upwards, from before backward, and from left to right, so that, not only the direction of the opening, but likewise a kind of valve formed in the right ventricle, by a fleshy column, so placed as to prevent the return ofthe blood into the left ventricle ; clearly showed, that the blood flowed from the left into the right ventricle, and thence into the pulmonary artery. The ductus arteriosus, an inch in length, and large enough to admit a goose quili, allowed, as in the foetus, a free pas- sage to the blood, from the pulmonary artery into the aorta. The fora> men ovale was closed. This singular conformation explains, in the most satisfactory manner, the phenomena observed during the life ofthe patient, and the organic affection of the pulmonary artery. There was necessarily, in this ves- sel, a mixture of venous and arterial blood, and this blood was sent into it, in part by the action ofthe left ventricle, with an increased impetus, which accounts for the aneurism. The blood which reached the lungs was already vivified, and required less action from that organ, to com- plete its oxydation ; on the other hand, the right auricle emptied itself, with difficulty, into the right ventricle, in part filled with the blood which the left ventricle sent into it with greater force : hence the extreme diffi- culty in the venous circulation, the lividity of the complexion, the colour and the puffiness ofthe face, the habitual and general torpor. This state of languor and inactivity might, likewise, depend on the flow ofthe venous blood into the aorta, along the ductus arteriosus, it is worthy of obser- vation, however, that this impure blood was not transmitted to the brain, who.se vital excitement it would not have been able to maintain. The 126 lower extremities bore no proportion to the upper, and this inequality analogous to what is observed in the foetus, depended on a similar cause. This morbid preparation was deposited by M. Deschamps, in the museum ofthe Kcole de Medicine of Paris, and was, by their desire, modelled in wax. M. Beauchene, junior, presented the same museum with a similar preparation, which he procured from a subject in the dissecting room. Several anatomists have paid attention to the structure of the heart ; much has been said on the subject of the peculiar arrangement of the muscular fibres which form its parietes, yet, the only result that can be obtained from all these researches is, that it is absolutely impossible to unravel the intricacy of these fibres*. Fibres ofthe ordinary structure, * On this point the author is by no means correct. The structure ofthe heart may be demonstrated with tolerable accuracy. The latest and best description of it has been furnished by J. F. Vacss, teacher of anatomy in the University of Lieges. As an accurate view ofthe distribution of its fibres is requisite to enable us to know the nature of the actions of this viscus, the following account by this anatomist is here introduced:— " The heart is a conical hollow muscle, covered by the serous membrane, the peri- cardium—lined by a membrane, which is ofa different nature in each ventricle, and composed of three layers of muscular fibres : the superficial one common to both ven- tricles—the middle one at least four times as large as the preceding, and like it, com- mon to the two great cavities ofthe heart—and the lower one, divided into two parts, the right and the left, each belonging to the corresponding ventricle; both of them forming the septum by their junction, and giving birth to the carnoae columnae. " The other layer is very fine ; its bundles of fibres which become more oblique as they get lower, are directed, the anterior ones from the right to the left, and the pos- terior ones from left to right, from the base to the apex of the heart, where they are confounded with the fibres ofthe middle layer. " The fibres ofthe middle layer are much more numerous, and follow the same di- rection ; only they are more oblique, and are not all of them carried to the apex of the heart. The inferior fibres only reach the apex, and are there confounded with the fibres ofthe outer layers. Whilst the others, according as they become more superfi- cial, reach the posterior furrow, where the layer untwists itself, to form the two une- qual portions which compose the lower layer of each ventricle. "The lower layer of the right ventricle, which is much thinner than that ofthe left, separates itself from the latter on a level with the posterior furrow, and is carried backwards, on the outside, before, and then within the ventricle which it immediate- ly envelopes. All its bundles bend from below upwards, and, crossing the direction of those ofthe middle layer, are fixed, the upper ones, which are almost transverse, to the circumference ofthe auriculo-ventricular opening, and to the anterior part of the mouth ofthe pulmonary artery—the others, which are longer and more oblique, and which form the right side of the septum, successively to the part of that orifice which is between the two ventricles, and to its posterior part. "The lower layer ofthe left ventricle, which is much thicker than that of the right, arises like it from the middle layer, on a level with the posterior furrow. Its bundles run from behind to before, between the two cavities, thus forming the left side of the septum, reach the anterior furrow, then, running from right to left, and and from below upwards, they surround the ventricles; and. crossing the line of the bundles of the middle layer, are fixed successively, one by the side ofthe other, to the origin of the aorta, and to the opening of communication between the ventricle and auricle, all the way to the upper extremity of the posterior furrow. " The lowest bundles on each side alone follow a different direction. These bun- dles, after separating from the others, approach the centre of the corresponding ven- tricle, and form the earner columns ofthe heart. " Thus all the fibres of the superficial layer take the form ofa lengthened spiral, which takes a direction from the base towards the apex of the heart, where the fibres are confounded with those ofthe middle layer, after having made a turn or a turn and a half. Those ofthe middle layer have the same form, the same general direction, and the same origin; but they are more oblique, and are so arranged, that one part only of them reach the apex of the heart, whilst the greater part terminate at its posterior 12ti and crossing each other, in various directions, form the two auricles ; other and more numerous fibres form the parietes of the ventricles, reach from the apex to the base, extend into the septum which divides them, pass from the one to the other, and are lost into each other, in several points. They are exceedingly red, short, close, and united by a cellular tissue, in which fat scarcely ever accumulates. These fibres forcibly pressed against each other, form a tissue similar to the fleshy part of the tongue, endowed with but little sensibility, but contractile in the highest degree. Vessels and nerves, in considerable number, if compared to the bulk ofthe heart, pervade this muscular tissue, whose contraction., whatever in other re-pects may be the direction of its fibres, tends to draw towards the centre ofthe cavities, every point of their parietes. Lastly, a very fine membrane lines the inner part of these cavities, facilitates the flow of blood, and prevents the infiltration of that fluid. L1I. If we suppose, for a moment, that all tbe ravtties ofthe heart are perfectly emptied of blood, and that they fill in succession, the following may be considered as the mechanism ofthe circulation through the heart. The blood brought back from every part ofthe body, and deposited into the right auricle, by the two venae cava?, and by the coronary vein, sepa- rates its parietes and dilates it, in every direction. The irritation attend- ing the presence of the blood, stimulates the auricle to contraction : this fluid, which is incompressible, flows back, in part, into the veins, but it chiefly passes into the pulmonary ventricle, through a large aperture, by means of which it communicates with the right auricle. The auricle, after freeing itself of the blood with which it is filled, relaxes and again dilates by the accesion of a new supply of this fluid, continually brought by the veins which open into it. However the right ventricle, filled with the blood which it has received from the auricle, contracts in its turn on the fluid whose presence excites its parietes, and tends, in part, to return it into the right auricle, and to send it along the pulmonary artery Regurgitation from the ventricle into the auricle, is prevented by the tricuspid valve, a membranous ring sur- rounding the edge ofthe opening of communication, and the free edge of which is divided into three divisions, to which are attached small tendons terminating into the columnae carnae ofthe heart. Three valves laid against the parietes of the ventricle, the instant the blood passes into its cavity, recede from them when it contracts, and rise towards the auricular open- ing. They cannot be forced into the auricle, as their free and loose edge is kept in its situation by the columnae carnae;, which are like so many little muscles whose tendons inserted into loose edges ofthe valves, bind them furrow. Those of the last layer of each ventricle have still a spiral form, but the screw takes the inverse direction, for the fibres stretch from the posterior furrow to the base ofthe heart; and they do not reach that part until they have surrounded the corresponding ventricle from right to left, crossing the line of the fibres of the two other layers. The septum is formed by the junction ofthe two lower layers with the addition ofa few bundles, which run from the apex ot the heart, and appertain to the middle and superficial layers, which are mixed together at that part. " The structure of the auricles is less regular. In general, the fleshy fibres pass from the circumference ofthe mouths ofthe veins, and from the auriculo-ventricular opening, to be distributed over the parietes, and especially on the septum ; where, in the situation ofthe fossa ovalis, they form two crescents, the concave parts of which are opposed to each other." For remarks on the functions of the heart, see APPENDIX, Note R 127 down, when the stream of blood tends to force those membranous folds towards the auricles. The three divisions, however, of the tricuspid valve, by rising towards the auricular aperture, return into the auricle, all the blood contained in the inverted cone which they form, immediately before rising. Besides, these three portions ofthe tricuspid valve do not close completely the aperture, around which they are placed, they are per- forated by a number of small holes : a part of the blood, therefore, re- turns mto the auricle, but the greatest portion is sent into the pulmonary artery. 1 he action of this vessel begins, when the parietes of the ventri- cal are in a state of relaxation, and the blood would be forced back into the ventricle if the sy-moid valves, by risin, suddenly, did not prevent it. Supported on a kind of floor formed by three valves, which lie across the calibre ofthe vessel, the blood pervades the tissue ofthe lungs, and flows along the divisions of the pulmonary vessels ; from the arteries it passes into the veins, and these, four in number, deposit it into the left auricle. This auricle, stimulated by the presence of the blood, contracts in the same manner as the right, part of the blood flows back into the lungs, but the greatest part enters the last ventricle, which sends it along the aorta, to every part of the body, whence it returns to the heart by the veins! The return of the blood into the left auricle, is prevented by the mitral valve which is similar to the tricuspid, except that its loose edge is divid- ed only into two divisions. As soon as the blood has reached the aorta, this vessel contracts, its sygmoid valves fall, and the blood is sent to every part ofthe body which is supplied by some of the innumerable branches of that great artery. In a natural state, the circulation is not carried on as has been just stat- ed ; and, we have supposed this successive action of the four cavities of the heart, only to render more intelligiide the mechanism of the circula- tion in that organ, if we lay bare the heart in a living animal, we ob- serve, that the two auricle* contract at the same time, that the contrac- tion of the ventricles is likewise simultaneous, so that while the auricles are contracting, to expel the blood which fills them, the ventricles are dilating to receive it. This successive contraction of the auricles and ventricles is readily explained, by the alternate, application of the stimu- lus which determines the action of these cavities. The blood which the veins bring into the auricles, does not excite their contraction, till a suf- ficient quantity has been collected. While this accumulation is taking place, they yield, and the resistance which is felt on touching them, dur- ing their diastole, depends, almost entirely, on the presence of the blood which separates and supports their parietes. The same applies to the ventricles; they cannot contract, until a sufficient quantity of blood 19 collected within them ; that there remains some blood in these ca- vities, for they are never completely emptied, is no objection to the theory, since this small quantity is not sufficient to bring on contrac- tion of the heart, and is not worth taking into account. If I am asked, why the four cavities of the heart do not all contract at once, I answer that it is easier to assign the final than the proximate cause. If the contraction of these cavities had been simultaneous, in- stead of being successive, it is evident, that the auricles could not have emptied themselves into the ventricles, i'he alternate action is more- over absolutely necessary, as the heart any more than the other organs, is umable to keep up a perpetual action; the principle of its motion, which is soon exhausted, being incapable of restoring itself, except dur- 128 frig rest. But, as was observed at the beginning of this work, in speaking of the vital power and functions, the alternations of action and repose in organs which, like the heart, perform functions essential to life, must be extremely short in their duration, and at very close intervals. The cavities of the heart, however, are not entirely passive during dilatation, ind the action of that organ does not wholly depend on the ex- citement of the blood on its parietes, since the heart alter it has been torn from the body ofa living animal, palpitates, its cavities contract and dilate, though quite emptied of blood, and appear agitated by alternate motions, which become fainter as the part gets cold. If you attempt to check the diastole of the heart, this organ resists the hand which com- presses it, and its cavities appear endowed with a power which Galen termed pulsive; in virtue of which they dilate to receive the blood, and not because they receive it. In that respect, the heart differs essentially from the arteries, whose dilatation is occasioned by the presence of the blood, whatever some physiologists may have said to the contrary. I have repeated, but unsuccessfully, the famous experiment by which it is attempted to be proved, that these vessels have tbe power of moving in- dependently of the presence of the blood. An artery tied and emptied of blood, contracts between the two ligatures, and is no longer seen to move in alternate contractions. LIII. The heart manifestly shortens itself, and the base approaches towards the apex, during the systole or contraction ofthe ventricles. U it became elongated, as some anatomists have thought, the tricuspid and mital valves would be incapable of fulfilling the functions to which they are destined, since the columnae carnas, whose tendons are inserted in the edges of these valves, would keep them applied to the parietes of the ventricles. The pulsations which are felt, in the interval between the cartilages of the fifth and sixth true ribs, are occasioned by the apex of the heart which strikes against the parietes of the chest. In the expla- nation of this phenomenon, it is not necessary to admit the elongation of the heart during its systole ; it is sufficient to consider, that the base of the heart, in which the auricles are situated, rests against the vertebral column, that these two cavities, by dilating at the same time, and by their inability to move the vertebrae, before which they are situated, displace the heart, and thrust it downwards and forwards. This motion depends, likewise, on the effort which the blood sent into the aorta makes, to bring to a straight line the curvature of that artery, which re-acts and carries downwards and forwards the whole mass ofthe heart, as it were, suspend- ed to it. The quantity of blood which each contraction of the ventricles sends into the aorta and pulmonary artery, most probably, does not exceed two ounces in each of these vessels I be force with which the heart acts on the blood which it «ends into them, is but imperfectly known, however numerous the calculations by winch it has been endeavoured to solve this physiological problem. In fact, from Keil, who estimates at a few ounces only, the force of the heart, to Borelli, who makes it amount to one hun- dred and eighty thousand pounds, we have the calculation of Michelot, Jurine, Robinson, Morgan, Hales. Sauvages. Cheselden, &c. ; but as Vicq-d' Azyr observes, not one of these calculations is without some error, either anatomical or arithmetical : hence we may conclude with Haller, that the force of the heart is great, but that it is, perhaps, impossible to estimate it with mathematical precision. If we open the chest of a living 129 animal, and make a puncture in his heart, and introduce a finger into the wound, pretty considerable pressure is felt, during the contraction of the ventricles. Those who admit, to its full extent, Harvey's opinion on the circula- tion of the blood, and who think with him, that the heart is the sole agent of the circulation, over-rate the power of that organ, so as to proportion it to the extent of the course which the blood is to take, and to the num- ber of the obstacles which it is to meet in its way. But, as I am about to state, the blood-vessels should not be considered as inert tubes, in which the blood flows from the mere impulse which it has received from the heart. LIV. Of the action of the arteries. There is no part of the body to which the heart does not send blood by the arteries, for, it is impossible to make a puucture, with the finest needle, into any of our organs, with- out wounding several of these vessels, and causing an effusion of blood. The aortic arterial system may be compared to a tree, whose trunk, re- presented by the aorta, having its root in the left ventricle ofthe heart, extends afar its branches, and throws out, on every side, its numerous ra- mifications. The size of the arteries decreases, the farther they are from the trunk by which they are given off. Their form, however, is not that of a cone, they are rather cylinders arising from one another, and decreasing successively in size. As the branches given off by a trunks taken collectively, have a greater diameter than that of the trunk itself, the capacity of the arterial system increases with the distance from the heart, hence it follows, that as the blood is continually flowing from a straiter to a wider channel, its course must slacken. The direction of the arteries is often tortuous, and it is observed, that the arteries which are sent to hollow viscera, as the stomach, the uterus, and the bladder, or other parts capable of contracting, of stretching, and of changing their dimensions every moment, as the lips, are much the most curved, no doubt, that they may by unfolding, give-way to the extension of the tissues into which they are distributed. Lastly, the arteries arise from one another, and form with the trunk or branch from which they are given off, an angle varying in size, but which is always obtuse, and more or less acute towards the branch. As the arteries recede from their origin, they communicate together, and these anastomoses form arches, two branches bending towards each other, and joining at their extremities, as we see in the vessels of the mesentery ; sometimes two parallel branches meet at an acute angle, and unite into one trunk, thus the two vertebrals join to form the basilary artery : some communicate by transverse branches, which pass from the one to the other, as is seen within the skull. In the anastomoses of the first kind, the columns of blood flowing, in contrary directions, along the two branches, meet at the point of union, and mutually repel each other, their particles mingle, and lose much of their motion in that reciprocal shock. The blood then follows a middle direction, and enters the branches which arise from the convexity of these anastomotic arches. When two branches unite to produce a new artery, of a greater calibre than each taken separately, but not so large as both together, the motion ofthe blood becomes accelerated, because it passes from a more capacious into a straiter channel, and the forces which determined its progression. \r 130 are concentrated into one. Lastly, the transverse anastomoses are well calculated to promote the passage of the blood from the one branch into the other, and to prevent congestion in the parts. LV. The arteries are inbedded in a certain quantity of cellular tissue, are almost universally accompanied by corresponding veins, by lympha- tics and nerves, and their coats are thicker in proportion as their calibre is smaller. The experiments of Clifton Whittringham prove, that the parietis are stronger in the small than in the large arteries, hence it is observed, that aneurism are much less frequent in the former. Their parietes have sufficient firmness not to collapse, when the tube of the ar- tery is empty. They are formed of three coats ; the external or cellular admits of considerable extension, and appears to be formed by the con- densation of the lamina? of the cellular tissue, which surrounds the arte- ry, and unites it to the neighbouring parts. The second coat is thicker and firmer, of a yellow colour, and fibrous, and is by some considered as muscular * and contractile, while other physiologists merely allow it to possess a considerable degree of elasticity. The longitudinal fibres, ad- mitted by some authors in the texture of this second coat cannot be dis- tinguished, and their existence is not necessary to account for the longitu- dinal retraction of arteries. In fact, this retraction might depend on elasticity, it might likewise be occasioned by the contraction of fibres not absolutely circular nor longitudinal, but spiral and imperfectly surround- ing the vessel, and crossing each other, in various directions. This yel- low coat, thicker in proportion, in the smaller arterial twigs, than in the larger branches, and thicker in these than in the trunks, is dry, hard, not capable of much extension, and is ruptured by an effort to which the ex- ternal coat yields by stretching. Lastly, a third, thin, and epidermoid coat lines the inside of these vessels, and seems less calculated to give strength to the parietes of the arteries, than to facilitate the flow of the blood, by presenting to it a smooth, even, and slippery surface, continu- ally moistened by a serous exudation, from the minute arteries, or vasa va- sorum, which are distributed between these coats t- Besides these three coats, the great arteries receive a fourth from the membranes lining the great cavities ; thus, the pericardium and the pleu- ra in the chest, the peritoneum in the abdomen, furnish to the different parts of the aorta, an adventitious coat which does not completely sur- round the vessel. Ofthe three coats which form the parietes of the arteries, the fibrous, though thicker than the other two, offers, however, the least resistance. If you take the carotid artery, which for a considerable space, does not send off any branches, and forcibly inject into it a fluid, the internal and middle coat will be torn, before dilatation has increased, by one half, the calibre ofthe vessel. The external coat resists the cause of rupture, by dilating, and forms a tumour, and it is only by applying a pretty con- siderable force, that it can be ruptured. The experiment is attended with the same success, if performed with air or any other gas. In aneu- * If in man and the greater number ef animals, the yellow fibres which form this coat, differ greatly from muscular fibres, they in the elephant resemble that texture very completely, as I had an opportunity of observing, when I witnessed the dissec- tion of the elephant that died in the year X at the Museum of Natural History. Let men of judgment decide, whether the analogy is sufficient to warrant our admitting, in the arteries of the human body, the existence of muscular fibres.—Author's Note. * See APPENDIX. Note R: for remarks on the structure and action of the arteries. 131 nsm, the internal and fibrous coats ofthe arteries, but more particularly the fibrous, are ruptured at an early stage of the disease, which at that period increases suddenly, in a very rapid manner, and on opening the tumour, it is observed, that the sac is entirely formed bv the dilated cellu- lar coat. Take an artery ofa certain calibre, for example, the carotid or humeral, apply a ligature around it, and tighten it with some degree of force. Dissect and take out the vessel, then cut the thread, and examine the place to which it was applied, you will observe, that the parietes of the artery are in that part thinner, and formed merely by the cellular coat which alone has withstood the constriction. Take hold of the two ends of an insulated arterial sube, and stretch it, then examine its inner coat, and you will find it torn and cracked in several places, and the pa- rietes ofthe artery evidently weakened. LVI. This want of extensibility in the coats of arteries, is the princi- pal cause of aneurism ; hence the popliteal artery is so liable to that af- fection, from its situation behind the knee, whose extension is limited, merely by the resistance ofthe posterior tendons and ligaments : this ar- tery is affected by the jar which takes place through all the soft parts, when the leg is violently extended ; and being less extensible than the other parts, its inner coat is ruptured, or at least weakened, so as to occasion an aneurism, always rapid in its progress. Of ten popliteal aneurisms which 1 have seen in different hospitals, eight were ascribed to a violent extension of the ham. In looking over the cases that have been recorded, it will be seen, that a considerable number of aneurisms ofthe aorta, have been occasioned by too forcible and too sudden an ex- tension of the trunk in raising a heavy burthen. From the dryness, the frailty ofthe yellow or fibrous coat of arteries, the application of ligatures to these vessels is attended with a speedy la- ceration of their tissue ; a moderate degree of compression is sufficient to rupture that coat, the external and internal remaining, at the same time, uninjured, provided the constriction be not excessive. Why is the arterial tissue, almost the only one on which ligatures require to be ap- plied, the least fitted of all the organic tissuesto bear them ? This incon- venience attending the ligature of arteries, led Pouteau to prefer tying arteries so as to include the surrounding soft parts within the ligature, though this process is, in other respects, less eligible. The objections will be obviated, by employing flat ligatures, which, by acting on a great- er surface ofthe artery, are less likely to divide the coats ofthe vessel, which will become obliterated at the spot to which the ligature is applied, the more rapidly as the patient is younger and stronger. I once saw, in a man whose thigh was amputated, on account of caries ofthe knee joint combined with a scorbutic affection, hemorrhage attend the fall ofthe ligatures, which did not come away till nineteen days after the operation ; as if the fibrous coat of these arteries, partaking in the debility ofthe muscular organs, had not preserved a sufficient degree of contractile power to close the cavity ofthe vessel. LVII. The contractile power of the arteries is in their middle coat, it is greater, as this coat is thicker in proportion to the calibre of the ar- tery. ' Hence, as Hunter observes in his work on the blood and inflam- mation, the larger arteries are endowed with elasticity, merely, while on the other hand, contractility is very apparent in those ofa smaller ca- libre, and is found complete in tbe capillary vessels ; hence, in the trunks near the heart, the progression of the blood is effected, chiefly by the 132 impulse which it receives from the heart, and as Lazarus Riviere ob- served, the circulation of the blood in the large vessels, is more an hy- draulic than a vital phenomenon. The action ofthe main arterial trunks, near the heart, has so little influence on the motion ofthe blood sent in- to them by that organ, that the aorta is frequently ossified, without af- fecting the circulation. The aorta is naturally bony in the sturgeon. J. L. Petit, in the case of a bookseller, whose leg he had taken off, found all the arteries ofa certain calibre in a state of ossification ; they were indu- rated, and. of course, incapable of acting, in the slightest degree, on the column of blood which flowed along them. All these facts seem conclu- sive arguments in favour of those physiologists, who explain, on the prin- ciple of elasticity, the contraction of arteries. But however correct this explanation may be, with regard to the vessels near the heart, it does not apply to the capillaries ; the influence of that organ does not operate on these vessels. One may easily conceive, that the column of blood which by the impulse it has received, in the first instance, has been sent along the whole length of tubes whose sides are ossified, inflexible, and conse- quently inert, on reaching the extremity of these canals, is, in a manner, again taken up by the vital power residing in the capillary vessels, and circulates from the influence ofthe action belonging to these vessels. Be- sides, elasticity, however considerable, merely restores those tissues that have been stretched, to the condition in which they were before exten- sion.' Elasticity is a kind of re-action, proportionate or relative to the action which precedes it. Why do arteries in the living body contract, to such a degree, that when empty, their canal becomes obliterated,. while in the dead body, however perfect the depletion of the arterial system may have been, the cavity ofthe arteries remains perfectly open. Several physiologists, however, and those among the most modern, con- sider elasticity as the principal cause ofthe progression of the blood along the arteries. As the distance from the centre increases the circulation slackens, from several causes, and the blood could not reach all the parts ofthe body, if the arteries, whose vitality increases with their distance from the heart, and as they become smaller, did not propel it to all the organs. The causes which retard the circulation ofthe arterial blood, are, the increased dimensions ofthe space in which it is contained ;—the resistance from the curves of the vessels;—the friction which it undergoes, and which in- creases, as, at a distance from the heart, the canals along which it circu- lates, increase in number; and lastly, the deviations which the blood meets with in its course, from the trunks into the branches which, coming off sometimes, almost at right angles, divert it from its original direction. Several physiologists have called in question this progressive slacken- ing ofthe flow of arterial blood, and several among them, who reject en- tirely the appli ation ofthe physical sciences to that ofthe animal econo- my, have, nevertheless, supported their opinion by a fact taken from hy- draulics. I ogive any certainty to these calculations, respecting the im- pediments to the circulation ofthe blood in the arteries, it would, they say, be necessary, that the arteries should be empty at the instant when they receive the jet of blood sent into them by the contraction ofthe ventricals. This, however, is not the case ; the arteries are always full, the blood flows along all of them with the same degree of velocity. This system of vessels may be compared to a syringe, from which a number of straight aad tortuous tubes should arise ; each of these would throw out 133 -lie fluid with an equal degree of velocity, on applying pressure to the In refuting this doctrine, I must take notice of the manifest contradic- tion of pretending to exclide, absolutely, HU application ofthe principles o mechanics to physiology, aud the complete application of these princi- ples to the phenomena ofthe animal economy. This contradiction, how- ever, is not more surprising than that of authors who exclaim against the abuse of modern nomenclatures, and who, nevertheless, eagerly embrace every opportunity of adding to it. by assigning new names to such parts as may have escaped the attention ofthe new nomenclators. What resem- blance is there, between a forcing pump, whose sides are unyielding, as well as those ofthe tubes which might arise from it, and the aorta which dilates every time the blood is sent into it; and again, what resemblance is there, between tubes which decrease towards their open extremities while the space contained in the arterial tube constantly enlarges, from the innumerable divisions ofthe vessels Since it is admitted, that the course ofthe blood is slower in the capillary vessels, must not this re- sistance, opposed to the blood which fills the series of vessels from the capillaries to the heart, be felt more at a greater distance from that organ, &c? Without this progressive increase of resistance, as the arterial blood is at a greater distance from the heart, this fluid would flow along the arteries, as it does along the veins without any pulsations ; for, this resistance, which causes the lateral effort of dilatation effected by the blood on the parietes ofthe arteries, is the principal cause of the pulse, which belongs only to that set of vessels. , A very remarkable difference is observable, between the blood which is sent to the toes, and that which goes to the mammas, as I have several times noticed in removing the cu- rious bones ofthe toes, or in extirpating cancerous breasts : the small ar- teries of these parts are nearly of the same size, but the jet of blood is much more rapid, the blood is sent to a much greater distance, when one of the mammary arteries is divided. The re-action ofthe arteries on the blood which dilates them, depends not only on the great elasticity of their parietes, but likewise on the con- tractility ofthe muscular coat. Elasticity has a considerable share in the action of the larger trunks, while contractility is almost the sole agent, in producing the action of the minute arteries. If a finger is introduced into the artery of a living animal, its parietes compress it in every direc- tion ; if the blood is prevented from flowing in it, the canal becomes obliterated by the adhesion of its parietes, and the vessel is converted into a ligamentous cord, such as that formed in the adult, by the remains of the umbilical arteries and veins. This contractility which, during life, is always in action, keeps the arteries, distended by the blood which fills them, of a smaller calibre, than after death. In performing capital operations, especially in the amputation of limbs, I have always found the arteries, whether filled with blood or empty, much smaller than I should have expected from their appearance in the dead body. It happens, however, sometimes, that the quantity of blood sent to an organ increases, in consequence of some cause of irritation ; the calibre ofthe arteries of the part, then becomes remarkably enlarged. Thus, the arteries of the uterus, which are very small in its unimpregnated state, acquire, towards the end of pregnancy, a calibre equal to that of the radial artery : the small arteries which are sent to the mamma?, are not. in the same condition, as I have had the opportunity of ascertaining 134 in a woman who had been sucking a child for two months before her death ; they retained their almost capillary minuteness, which would seem to prove, that the lymphatics are alone concerned in bringing to these glands the materials of their secretion. The mammary arteries evidently enlarged in an open cancer of the breast; in cancer ofthe pe- nis, the blood-vessels likewise become enlarged ; hence in removing the penis for that affection, it is absolutely necessary to secure the arteries with ligatures, a precaution which need not be attended to in a case of gangrene. Gangrene is attended with this peculiarity, that the arteries of the mortified parts contract, so as to become obliterated, when their calibre is inconsiderable. As the arteries are the canals which convey to all our organs the ma- terials of growth and reparation, they are larger, in proportion, in child- ren, in whom nutrition is more active, and their calibre is always propor- tionate to the natural or morbid developement of organs : hence the des- cending aorta and the iliac arteries are larger in women than in men; hence the right subclavian artery, which conveys blood to the larger and more powerful ofthe two upper extremities, because the more employ- I ed, is larger than the left subclavian. But the effect should not be mis- taken for the cause, and it should not be imagined, that the right upper extremity owes its superiority to the greater calibre of its artery. In the new-born child, this vessel is not larger than the left subclavian : but the right arm being more frequently employed, the distribution ofthe fluids takes place more favourably, nutrition is carried on with more energy, it acquires more bulk and -strength, and therefore the right subclavian arte- ry conveys blood to it by a wider channel. If the left upper extremity were employed in the same manner, and if the right were kept in a state ( of inaction, the left subclavian would, no doubt, exceed the right. I am warranted by two facts in forming this conjecture. In dissecting the bo- dies of two men that were left-handed, I observed in the left subclavian i arteries, the same proportionate enlargement which is usually met with in the same vessels on the right side. LVIII. As the arteries are always full during life, and as the blood ilows along them with less velocity, the greater their distance from the heart, the blood which the contractions ofthe left ventricle send into the aorta, meeting the column of blood already in that vessel, communicates to it the impulse which it has received ; but retarded in its direct progres- sion, by the resistance of that column, it acts against the parietes of the vessels, and removes them to a greater distance from their axis. This lateral action which dilates the arteries, depends, therefore, on the resist- ance of the parietes of these cavities, always filled with blood, to that which the heart sends into them. This dilatation, which is more consi- derable in the large arteries than in the smaller ones, manifests itself by a , beat, known under the name of pulse*. The experiments of Lamure would lead one to believe, that another cause of this phenomenon is a slight displacement of the arteries, every time they dilate. These dis- placements are most easily observed at their curvatures, and where they adhere to surrounding parts, by a loose and yielding cellular tis- sue. The pulse is more frequent in women, in children, in persons of small * See APPENDIX, Note S, for a different explanation of this phenomenon from that a:iven by M. Richerand. 136 stature, during the influence of the passions, and under violent bodily exercise, than in an adult man, of high stature and of a calm, physical, and moral nature. At an early period of life, the pulse beats as often as a hundred and forty times in a minute. But as the child get older, the motion of the circulation slackens, and at two years old, the pulse beats only a hundred times, in the same space of time. At the age of puberty, the beats of the pulse are about eighty in a minute; in manhood, seven- ty-five ; aud lastly, in old men of sixty, the pulse is not above sixty. It is slower in the inhabitants of cold, than in those of warm climates. Since the time of Galen, the pulse has furnished physicians with one of their principal sources of diagnosis. Tbe force, the regularity, the equality of its pulsations, opposed to their weakness, inequality, irregu- larity, and intermittence, afford the means of judging of the nature and danger of a disease, of the power of nature in bringing about a cure, of the organ that is most affected, of the time or period of the complaint, &c. No one has been more successful than Bordeu, in the consideration of the pulse, under these different points of view. Its modifications in- dicative of the periods of diseases, establish, according to that celebrated physician, as may be seen in his Recherches sur le pouts par rapport aux crises, the pulse of crudity, of irritation, and of concoction. Certain ge- neral characters indicate, whether the affection is situated above or be- low the diaphragm, hence the distinction of superior and inferior pulse. Lastly, peculiar characters denote the lesion of peculiar organs ; which constitutes the nasal, guttural, pectoral, stomachic, hepatic, intestinal, renal, uterine, &c. Besides these sensible beats, which constitute the phenomenon ofthe pulse in the arteries, there is an inward and obscure pulsatory motion, by which all the parts of the body are agitated, every time that the ventri- cles of the heart contract. There is a kind of antagonism between the heart and the other organs, they yield to the impulse which it gives to the blood, dilate en receiving this fluid, and collapse when the effort of contraction is over. Every part vibrates, trembles, and palpitates within the body, the motions of the heart shake its whole mass, and these qui- verings, which may he observed externally, are most manifest when the circulation is carried on with rapidity and force. In some head-aches, the internal carotid arteries pulsate with such violence, that not only the ear is sensible to the noise made by the column of blood striking against the curvature of the osseus canal, but the head is evidently moved and raised, as it were, at each pulsation. If you look at your hand or foot, when the upper or lower extremity is quiescent and pendulous, you will observe in it, a slight motion corresponding to the beats of the heart. This motion increases, and even makes the hand shake, when, from the influence of the passions, or from violent exercise, the circulation is ac- celerated ; in every violent emotion, we feel, within ourselves, the effort by which the blood, at each beat of the pulse, penetrates into our organs, and fills every tissue. And it is, in a great measure, from this inward tact, that we are conscious of existence. A consciousness the more lively and distinct, as the effect of which we are speaking is more marked. It is, likewise, from observing this phenomenon, that several physiologists have been led to conceive the idea of a double motion, which dilates or con- denses, which contracts or expands, alternately, all organs endowed with 136 life ; they have observed, that dilatation prevails in youth, in inflamma- tion and erection, conditions of which all parts are capable, according to their difference of structure. LIX. At the moment when the left ventricle contracts, to send the blood into the aorta the sigmoid valves of that artery ruse, and apply them- selves to its parietes, without, nevertheless, closing the orifices of the Coronary arteries, which lie above the loose edges of the valves ; so that the blood is received into these vessels, at the same time as into the others. When the contraction of the ventricle is over, the aorto acts on the blood which it contains, and would send it back into the ventricle, if the valves, by suddenly descending, did not present an insuperable obstacle to the return of blood, and did not yield a point of resistance to the ac- tion of the whole arterial system ; only the small quantity of blood be- low the valves, at the moment of their descending, flows backs towards the heart, and returns into the ventricle. Though the rate at which the blood flows along the aorta, has been estimated at only about eight inches in a second, a pulsation is felt in all the arteries ofa certain calibre, at the instant the ventricles are contract- ing. The reason that the pulsations ofthe heart appear to take place, at the same time as those ofthe arteries, is, that the columns of blood, in these vessels, receive an impulse from that which is issuing from the ven- tricles, and this concussion is felt in an instant of time, too short to be measured, such as that which is felt by the hand applied to the end of a piece of timber struck at the other end, with a hammer. The blood which fills the main trunk, supplies to each ofthe branches which arise from it, columns proportionate to their calibre. This division ofthe principal column is effected by a kind of projection at the mouth of each artery. These internal projections detach from the main stream, the lesser ones, and these flow the more readily into the branches, according as these arise from the trunk, at a more acute angle, as the projection is more prominent, and the deviation ofthe fluid less considerable. If the branches are given off, at an almost right angle, the orifices ofthe arteries scarcely project at all, and nothing but the effort of lateral pressure de- termines the flow ofthe blood into them. The flow of the blood into the arteries which are distributed to muscles, is not interrupted, nhen these muscles contract, for, whenever arteries, of a certain calibre, penetrate into muscles, they are surrounded by a tendinous ring, which, during the contraction of the muscle, becomes en- larged, from the extension in every direction, eflected by the fibres which are attached to it, around its circumference. The existence of this truly admirable conformation, may be readily ascertained, by observing the aorta, in its passage through the crura ofthe diaphragm ; the perforating arteries ofthe thigh, where they enter it the back part ofthe limb into the adductor muscles, the popliteal, as it passes through the upper ex- tremity ofthe soleus muscle. LX. Ofthe capillary vessels. The arteries, after dividing into branches, these branches into lesser ones, and these into progressively smaller ramifications, terminate in the tissue of our organs, by becoming continu- ous with the veins. The venous system arises, therefore, from the arte- rial system, the origins of the veins being merely the more minute ex- tremities ofthe arteries, which becoming capillary from the great number 137 e.i divisions* they have undergone, bend in an opposite direction, and become altered in their structure. These minute capillary arteries form with the minute veins, with which they are continuous, and with the lymphatics, wonderful meshes in the tissue of our organs. Several physiologists consider the capillary blood-vessels as an inter- mediate system between the arteries and veins, in which the blood, en- tirely out ofthe influence ofthe action ofthe heart, flows slowly, with an oscillatory and sometimes retrograde motion, is no longer red, because its globules are strained, as it were, and, in a manner, lost in a colourless serum, which serves them as a vehicle. It is, in fact, necessary, that bodies should be ofa certain bulk, to re- flect the rays of light at an angle sufficiently obtuse, that the eye may discover their colour. We know, that grains of sand reduced to a very fine dust, appear colourless, when examined separately, and are seen to possess colour, only when in a state of aggregation : further, very thin laminae of a horny substance, appear transparent, though the part from which they have been detached be ofa red or blue colour. But if seve- ral of these transparent laminae be laid on one another, the red colour becomes darker, in proportion as a greater number are brought together. Let irritation, from whatever cause, determine the blood to flow into the serous capillary vessels, in greater quantity, and with more force, these vessels will become apparent, the organs in whose structure they circulate, will acquire a red colour, more or less deep ; thus the con- junctiva, the pleura, the peritoneum, the cartilages, the ligaments, &c. which naturally, are whitish or transparent, become red, when affected with inflammation, whether from the increased impetus of the circulation, which forces and accumulates into the capillary vessels, a greater num- ber of red globules, or that the sensibility of these small vessels is im- paired by inflammation, so that they admit globules which they formerly rejected. Some capillary vessels transmit blood at all times, and uniformly ex- hibit a red colour : this is the case with the capillary vessels ofthe spleen, ofthe corpora cavernosa ofthe penis, ofthe bulb and corpus spongiosum ofthe urethra : the same applies to the capillaries ofthe muscles of the mucous membranes : there are, however, very few of those organs, in which the whole portion ofthe capillary tube, between the termination of the artery and the origin ofthe vein, is filled with red blood. There is, almost always, a division in the tortuous line described by the capillary, and within this space, tbe blood cannot be detected of its usual colour.! The number of the capillary vessels, as well as that ofthe arteries, to which the former are as auxiliaries, is much more considerable in the secretory organs, than in those in which life carries on only the process * The arterial divisions which may be discerned by the aid of anatomy, do not ex- reed ei-hteen or twentv : nevertheless, they divide still further, when they are become&so minute as not to be discernible without the help of the most powerful mi- Cr+SThere is every reason for concluding that capillary vessels exist, which, running between some ofthe terminations ofthe arteries and the commencement of veins, ad- S only T. -reus portion ofthe blood, when performing the.rhc.Hl.y functions; but which may, in :i Uate of inflammation, admit also the red rnr*— 01 'ms umdto flow along them- p 138 of nutrition. It is on that account, that the bones, the tendons, the liga- ments, the cartilages, contain so much smaller a quantity of blood, than the mucous and serous membranes, and the skiu. The capillary vessels are, however, very numerous, in the muscles, which owe that colour to the great quantity of blood they contain, but as we shall point out, when we come to speak of motion, this fluid appears to form an essential ele- ment in muscular contraction ; it is, therefore, not to be wondered, that these organs should have a greater number of capillary vessels sent to them : since these vessels do not supply them merely with molecules to carry on nutrition, and to repair the waste ofthe part, but impart to them the principle of their frequent contraction ; the quantity of them is so con- siderable, in all these parts, employed in the two-fold offices of nutrition and secretion, that Ruysch penetrated, with his injections, the whole thickness of their substance, to such a degree, that the organs which lie had prepared, were dnly a wonderful and inextricable network of capil- lary vessels extremely minute. On these anatomical preparations, made with an art hitherto unrivalled, Ruysh grounded his hypothesis relative to the intimate structure ofthe body, in which, he imagined, all was capil- lary tubes, an hypothesis which has obtained tbe most favourable recep- tion, and has reigned, during more than a century, in the schools. It is enough to reflect a moment on their uses, to conceive that the number of tbem must be really prodigious. As long as the blood is enclosed within the arteries, and flows under the controul ofthe heart, it fulfils no pur- pose either of nutrition or secretion. To make it subservient to these great functions, it must be diffused through the very tissue ofthe organs, by means ofthe capillary divisions ; these little vessels exist then, in every part, where any organized molecules are found united ; since the parti- cle formed by their assemblage, must, at least, find, in the juices which they bring to it, the materials of its reparation. Entering, in greater or less proportion, into the organization of all tbe tissues, the capillaries re- ceive certain modifications from the organs of which they are an integral part ; modifications which enable them to deposit the serous part of the blood on the surface ofthe serous membranes, admit the transudation of the fat into the cells ofthe cellular tissue, furnish the urine to the kid- nies, and the liver with the materials ofthe bile : in a word, suffer to es- cape, through the porosities with which their parietes are pierced, the principles which the blood has to furnish to every organ. It is by these lateral porosities, and not by extremities open on all the surfaces, and in all the points ofthe organs, that the capillaries transpire, in some sort, the elements of nutrition, and of the various secretions*. Mascagni was aware, that Nature, skilful in deducing many effects from few causes, has not deviated, in the construction ofthe system of circulation, from the invariable laws of her ordinary simplicity ; but the lateral pores ofthe capillaries, which are sufficient for the explanation of all the phe- nomena ascribed to the exhaling mouths ofthe arteries, and to the pre- tended continuity of these vessels with the excretory ducts ofthe organs, &e. are not openings like the pores common to all matter ; each of them may be considered as an orifice, sensible, and, especially, contractile, of differing size, according to the state of the strength, or of the vital powers. The size then of these capillary pores is subject to frequent variations ; # See APPENDIX, note S, for observations on the functions ofthe capillary system ; and on nutrition. 13fi and this is the explanation given ofthe formation of scorbutic ecchymoses, of petechias, of passive or relaxed hemorrhages. In all these affections] contractility being really diminished, the pores of the capillaries enlarge, and sufler the red blood to transude through their relaxed mouths. Thia phenomenon takes place, not only under the skin and on the various mu- cous surfaces, it is observed also in the very tissue ofthe organs. It is thus, that I have often seen, on opening the bodies of those that had died of the scurvy, in its last stage, the muscles of the leg filled with blood. This sort of interior hemorrhage, converts the muscles into a kind of pulp ; and the extravasated blood itself undergoes a beginning of decomposition. 'I he bones themselves are liable to these scorbutic bloody infiltrations. I had an opportunity of ascertaining this in the Hospital of St. Louis, at tbe same time that I learnt the difficulty of procuring a durable skeleton from such bodies. The greatest number die, in a very advanced stage of the disease, and the bones dissolve in maceration, or rot in a very little time. The capillary vessels, whether the blood flow through them red, or colourless, are not a system of vessels distinct from that ofthe arteries, and from that of the veins ; they belong essentially to these two orders df vessels. Those which, ramifying in the tissue ofthe skin, or ofthe se- rous membranes, suffer the serum ofthe blood to transude, are not more entitled to the name of exhalant system, which some authors have given them. To consider as distinct and insulated systems, separate parts ofa system of organs, is to incumber science with a crowd of divisions, as false as they are useless. LXI. The sanguineous capillaries anastomose, and form, like the lym- phatic capillaries, a net-work that envelopes all the organs. Their frequent communications do not allow obstructions to take place, and to produce inflammation, as Boerhaave thought, and as was long taught, on the au- thority of that celebrated physician. Haller, Sp.dlanzani, all the micros- copic observers, have perceived threads of blood flowing in the capillaries, offering themselves at the various inosculations of these vessels, and have seen them flow back, when they were not admitted, to seek other easier entrances. 1 will not heap up, in this place, superfluous arguments against the theory ofthe Leyden professor, rejected at its birth by the physicians of Montpellier, absolutely refuted, and now universally given up. Irritation alone keeps the blood in the inflamed part ; for, when death, which puts an end to all irritations, and relaxes all spasms, (mors spasmos, solvit. Hipp.) when I say, death comes on, all slight inflammations are dissipat- ed, and whenever they have not been sufficiently intense, to induce tran- sudation of tbe blood through the parietes of the capillaries, into the areola: of the organic tissues, the blood flows back into the large vessels, and there is no trace of it left. It is thus, that erysipelas of the skin disap- pears, that the pleura preserves its transparency, in individuals affected, before death, with sharp pains in the side. If to this, we add our igno- rance on the real organization of the nervous system, on the conditions absolutely required of the brain and nerves, for the maintenance of life, we shall cease to be surprised, that the opening of bodies has taught us no more on the real seat of disease, and we shall confess with Morgagni, who however employed, with great success, this means of improving the art of healing, that there are numberless diseases, of which, after death, Mi) ii.o trace is left, and for the fatal termination of which, we are unable to account. Contractility and sensibility exist, in a much higher degree, in the ca- pillary and serous vessels, than in the veins and arteries. Life must needs be more active in the former, for, the motion given to the blood by the contractions of the heart, being exhausted, this fluid, no longer in the sphere of action of that organ, can circulate, but from the influence of the action ofthe vessels themselves. The termination ofthe arteries into veins, is the only well ascertained termination of those vessels; it may be seen by the help ofthe microscope, in cold-blooded animals, in frogs and salamanders. In some fish, we may, even with the naked eye, observe frequent and considerable inosculations, between the arteries and veins. In man, however, and in other warm- blooded animals, these communications take place, only at the extremities ofthe two systems of vessels. In this case, the arteries terminate, some- times, in capillary vessels carrying serous fluid, such as the vessels ofthe sclerotic coat; these vessels become small veins whose calibre gradually increases, until they admit red globules in sufficient number to reflect that colour. At other times, the artery and vein are continuous, without the intervention of that extremely minute subdivision : the red blood then passes readily and immediately from the artery into the vein. It will be shown, in speaking of secretion, that the continuation ofthe arteries into the excretory ducts of the conglomerate glands, and their termination in exhaling orifices, cannot be admitted, and that the presence of small pores, in the sides ofthe minute arteries and veins, would afford an explanation of the phenomena on which the belief of this termination of the arteries rests. There exists no parenchyma, no spungy tissue, be- tween the extremities of the arteries and the origin of the veins, with, perhaps, the exception of the substance of the cavernous bodies of the penis and of the clitoris, ofthe bulb and spungy part of the urethra*, the retiform plexus, which surrounds the orifice of the vagina, and perhaps also the tissue ofthe spleen, though the experiments of anatomists (Mas- cagni and Lobstein) seem to prove, that in these organs, the arteries and veins are immediately continuous!. LXII. Of the action ofthe veins\. These vessels, whose function it is to carry back to the heart, the blood which the arteries have sent to all the organs, are much more nnmerous than tbe arteries themselves. It is observed, in fact, that arteries of a middle size, as those ofthe leg and fore-arm, have each two corresponding veins, whose calibre, at least, equals theirs, and that there is besides, a set of superficial veins, lying between the skin which covers the limbs and the aponeuroses which en- velope the muscles : these have no corresponding arteries. The space which the venous blood occupies is, therefore, much greater than that ta- ken up by the blood in the arteries. Hence also, it is estimated, that of twenty-eight or thirty pounds of this fluid, making about a fifth part ofthe whole weight of the body in an adult man, nine parts are present in the veins, and only four in the arteries. In this calculation, one should con- aider as arterial, the blood contained in the pulmonary veins and in the Heft cavities of the heart, while that which fills the cavities in the right * See the chapter on the Organs of Generation. t See APPENDIX, Note N. f See APPENDIX. Note T 111 side ofthe heart and the pulmonary artery, is truly venous, and has every character of such blood. Although the veins generally accompany the arteries, and are united to them, by a common sheath of cellular membrane, this disposition of parts is not without exceptions. The veins which bring back the blood from the liver, do not. in any respect, follow the course of the branches ofthe hepatic artery : the sinuses ofthe brain are very different, in their arrangement, from the cerebral arteries ; the veins of the bones, which are particularly numerous, and of a much greater calibre than the arte- ries of the same parts, from the slow circulation of the blood along them, do not generally follow the direction ofthe arteries, and arise singlyfrom the substance of the bone, with the exception of those in the middle ca- nal, and which pass through the nutritious foramen of the bone. The veins are not only more numerous than the arteries, but they are like- wise more capacious, and dilate more readily ; this structure was neces- sary, on account ofthe slowness with which the blood circulates, and of the readiness with which it stagnates, when the slightest obstacle impedes its circulation.* The force which carries on the circulation ofthe blood, along the arteries, is so great, that Nature seems not to have availed her- self of the mechanical advantages which might have facilitated its flow. On the other hand, the power which determines the progression ofthe venous blood is so feeble, that she has sedulously retnoved.every obstacle which might have impeded its course. And as the relation of the minute to the larger branches, of these to the trunk, is the same as in the arteries, two branches unite to form a vein of greater calibre than each separate ves- sel, but smaller than the two taken together, the blood flows along a space which becomes narrower, the nearer it approaches the heart; the rapi- dity of its course must, therefore, be progressively increased. The veins are almost straight in their course ; ;t least, they are much less tortuous than the arteries. The force which makes the blood flow along them, is consequently not taken up in straightening these curves ; the anastomoses are, likewise, more frequent, and as the flow of the blood might have been intercepted in the deep seated veins of the limbs, when the muscles, among which these vessels lie, during contraction, compress them by their enlargement and induration, they communicate freely with the superficial veins, towards which the blood is carried, and flows the more readily, as they are not liable to be compressed. It is to be observed, and is to be accounted for on the same principle, that the superficial veins are very large and distinct among the lower orders who are employed in laborious occupations, requiring an almost continual ex- ertion of their limbs. Lastly, the internal part of the veins, like that ofthe lymphatics, is furnished with valvular folds, formed by the dupli- cature of their epidermoid coat. These valves, which are seldom single, and almost always in pairs, are not found in the minute veins, nor in the * The arteries contain, at all times, nearly the same quantity of blood. The veins are always the seat of plethora, because the blood stagnates in them more readily ; and this condition brings on imfianunatory fever (consisting merely in an increased action of the vascular system, as is expressed by the term angeiotenique applied to it by Professor Pinel) only when the venous congestion becoming excessive, the blood passes with difficulty from the arteries into the veins. The heart and the arteries then struggle, with considerable effort, to rid themselves of the fluid which oppresses them, &c°— Author's Note. 142 great trunks, nor in the veins which bring back the blood from the visce- ra in the great cavities. These valves, in falling, close completely the canal of the vessel, de- stroy the continuity ofthe column of blood returning to the heart, divide it into smaller columns, as numerous as the intervals between the valves, and the height of which is determined by the distance between these folds. So that the power which carries onward the venous blood, and which would be incapable of propelling the whole mass, acts advantage- ously on each of the small portions into which it is divided. LXIII. It has been thought, that the principal cause which makes the blood flow into the veins, is the combined action ofthe heart and arteries ; but the impulse from those organs, is lost in the system of capillary ves- sels, and does not extend to the veins. The specific action of their own parietes, aided by auxiliary means, such as the motion of the neighbour- ing arteries, is sufficient to carry the blood on to the heart. These parietes, which are much thinner than those ofthe arteries, are contained, like theirs, in a sheath common to all the vessels. Three coats, likewise, enter into their structure ; the middle or fibrous coat is not very distinct, and consist merely ofa few longitudinal reddish fibres, which can be distinguished only in the larger veins, near the heart. In some ofthe larger quadrupeds, as in the ox, these fibres form distinct fasciculi, and their muscularity is much more manifest. The internal coat, which is more extensible than that of the arteries, and equally thin, adheres more closely to the other coats. The cellular coat, which connects it to the middle one, is less abundant, hence phos- phate of lime is seldom deposited into it, as happens to the arteries which frequently become ossified, as we advance in years. This internal coat is merely a continuation of that which lines the cavities ofthe heart; and as the origin ofthe inner coat ofthe arteries is the same, there exists a non- interrupted continuity in tbe membrane which lines all the canals of the circulation. The inner coat forms the only essential part of the venous system ; it alone constitutes the veins within the bones, the sinuses ofthe dura mater, the hepatic veins, in a word, all the veins which are so firmly attached externally to the neighbouring parts, that the blood flows along them, as along inert tubes, their parietes being, almost completely, inca- pable of contracting. The veins, in their passage through muscles, are, like the arteries, guarded by aponeurotic rings, than which is more remarkable than that which belongs to the aperture in the diaphragm, which transmits the as- cending cava from the abdomen into the thorax. This vessel is, therefore, not compressed by the contraction of that muscle in inspiration. LXIV. As the inferior cava passes through the lower edge ofthe liver, whether along a deep fissure, or in a real canal in the parenchymatous substance of that viscus, the course ofthe blood must be impeded, when, from congestion of the parenchyma, the vessel is, in some sort strangu- lated. Obstruction of the liver, which is of such frequent occurrence, would have been attended with fatal consequences, by preventing the return of the blood from the inferior parts, along the ascending cava, if this great venous trunk did not keep up, by means ofthe vena azygos, an open and * It would perhaps be more just to assign the cause ofthe flow of blood in the veins to the action of their own parietes, and to the active dilatation of the heart. 113 free communication with the descending or superior cava. The use of this anastomosis of the two great veins is, evidently, to facilitate the pas- sage of the blood from the one of these vessels into the other, when either, especially the lower, does not readily evacuate its contents into the right auricle. Un this account, the vena azygos is capable of considerable dila- tation, and is entirely without valves. In the body of a man opened, this day, in my presence, and whose liver was twice as large as in health, I observed that the vena azygos, which was distended with blood, was of the size of the little finger ; the termination downward of this vessel, in the right renal vein, and above in the superior cava, were most distinct, and by compressing it from above downward, or from below upward, the blood flowed into one or the other of these vessels. As tbe causes which determine the circulation of the venous blood, communicate to it an impulse which is far from rapid, and as this fluid meets with only trifling obstacles, and such as are easily overcome, the pressure against the parietes ofthe veins is very inconsiderable, and these vessels do not pulsate, as the arteries. There is observed, however, near the heart, an undulatory motion, which the blood communicates to the parietes ofthe vessels. These kinds of alternate pulsations depend on the rapidity with which the blood, whose course is progressively accele- rated, flows towards the heart, and on the reflux ofthe blood, during the contraction of the right auricle. The contraction of this cavity, forces back the blood into the veins which open into it; this retrograde course is manifest in the superior cava, and is the more readily occasioned, as the orifice of this vein is not furnished with any valve that might prevent it. It does not, however, extend very far towards the brain, the blood having to ascend against its own weight, and the jugulars admitting of considera- ble dilatation. This regurgitation is still more marked in the inferior cava, the orifice of which is but imperfectly closed by the valve of Eustachius ; it is felt in the abdominal veins, and extends even to the external iliacs, ac- cording to the testimony of Haller. LXV. The orifice ofthe great coronary being exactly covered over by its valve, the blood does not return into the tissue of the heart, which being a contractile organ, would have had its irritability impaired by the presence of venous blood. It is of consequence to observe, that this re- flux never extends to the veins which bring back the blood from the mus- cles, and that it is never felt in the veins ofthe limbs which are furnished internally with valvular folds. The case is very different, between our organs of motion and these secretory glands : towards these the blood re- quired to be sent back, so as to be the longer exposed to their action : ve- nous blood diminishes and even destroys muscular irritability, and is truly oppressive, as may be ascertained by injecting some, in the arteries of a living animal, or else by tying the veins, so as to prevent its return, or by observing what happens, when the course of the blood is interrupted, either by applying firm ligatures round the limbs, or by wearing confined clothes. I am satisfied, that it was from observing the oscillatory undulations of the venous blood, in the great vessels, that the ancients were led to the opinions they entertained on the course of the blood, which they com- pared to the Euripus, whose waves are represented by the poets, as un- certain in their course, and in currents running in contrary directions. The internal veins in which this reflux is observed, show this motion of the blood most distinctly of any ; their sides which are thin arid semi- 144 transparent, not being, as in other parts, surrounded by an adipose cellu- lar tissue. To give a complete notion ofthe doctrine ofthe ancients, on the subject of the circulation, it will merely be necessary to add to the above idea, the opinion which they entertained, that the chyle taken up by the meseraic veins, was carried to the liver, in which its signification was effected ; and lastly, that the arteries were filled with vital spirit, and contained only a few drops of blood which passed through small holes, which, Galen says, perforate the septum of the ventricles. The blood, however, continually urged on by the columns which fol- low each other in succession, by the action of the veins whose parietes become gradually stronger, and by the compression which these vessels experience from the viscera, during the motions of respiration, reaches the heart, and enters the auricles with the greater facility, as the orifices of the cava? not being directly opposed to each other, the co- lumns of blood which they convey, do not meet, and do not oppose each other. LXVI. Tbe blood continually carried to all parts of the body by the arteries, returns, therefore, to the heart, by a motion which can never be interrupted, without considerable danger of life. We know that the cir- culation is thus effected, from the direction of the valves ofthe heart, of the arteries and veins ; by what happens, when these vessels are open- ed, compressed, or tied, or when a fluid is injected into them. When an artery is wounded, the blood comes from the part of the vessel near- est the heart: it comes, on the contrary, from towards the extremities, if it is a vein that has been opened. By compressing or tying an artery, the course of the blood is suspended below the ligature, and the vessel swells above. The veins, on the contrary, when tied or compressed, di- . late below. Lastly, when an acid fluid is injected into a vein, the blood > is seen to coagulate in the direction ofthe heart. By the help ofthe mi- croscope, we may see in the semi-transparent vessels of frogs and other cold-blooded animals, the blood flowing from the heart into the arteries, and from these into the veins which return it to the heart. It was on the strength of these convincing proofs, that William Harvey established, to- wards the middle of the seventeenth century, the theory ofthe circula- tion of the blood, its mechanism had rather been guessed at, than un- derstood, by several authors. Servetus and Cesalpine appear to have' * been acquainted with it;. but no one has more clearly explained it than the English physiologist, who is justly considered the author of that im- mortal discovery. LXVH. The theory of Harvey, such as it is laid down in his work, entitled, De sanguinis circuitu, cxercitationes anutomicce, does not appear to me entirely admissible. He considers the heart as the only agent which set the blood in motion, and does not take into account the action ofthe veins and arteries, which he considers as completely inert tubes, while every thing tends to prove that the arteries and veins assist the mo- tion of the blood by an action peculiar to themselves*. He admits, that the blood flows in every part of the circulatory system, with an uniform degree of speed ; an opinion so manifestly contradicted by reasoning and experience, which prove that the velocity of its course diminishes, the greater its distance from the heart, from the influence ofa great number of circumstances, which it would be useless to repeat (LVII.) This * See APPENDIX. Notes A, B, S. T H5 doctnne has yet, however, several abettors, and among the moderns, spallanzani has endeavoured to support it, by a number of experiments ^ contradictory that one is surprised, that so judicious a physiologist hould have collected them to establish a theory completely refuted by everal of them. Nothing, for example, contradicts it more fully, than he continuation ofthe flow of the blood, in the vessels of frogs and sa- lamanders, after the heart of these reptiles have been torn out: there are besides, animals which, not possessed of that central organ, have ne- ver heless vessels along which the blood flows, and which contract and dilate, by alternate motions. If the mere force ofthe heart propelled the blood to every part, the course of this fluid ought, at intervals, to be suspended, its circulation, at least, ought to be slackened, when the ventricles cease to contract; but as the contraction ofthe arteries corresponds to the relaxation ofthe ventricles, these two powers, whose action alternates, are continually em- ployed in propelling the blood along its innumerable channels. Besides* the general circulation of which the laws aud phenomena have just been mentioned, each part may be said to have its peculiar mode of circulation, more or less rapid, according to the arrangement and structure of its vessels. Each of these individual circulations forms a part of the machinery included in the great circle of the general circu- lation, and in which the course of the blood takes place in a different manner, may be accelerated or retarded, without affecting the general circulation. Thus, in a whitlow of a finger, the radial artery pulsates a hundred times in a minute, while on the sound side, its beats are only seventy in number, and perfectly isochronous with the pulsations of the heart. In the same manner, the blood of the intestines, which is des- tined to furnish the materials of bile, flows much more slowly than that of other parts. These modifications affecting the velocity of the circulatory motion of the blood, account for the difference of its qualities in different organs ; all these differences form a part ofthe plan of nature, and it is not difficult to understand their utility. LXVIII. In what has been said ofthe circulation, no separate mention has been maele ofthe course of the blood through the lungs, called by authors the lesser or pulmonary circulation. The vascular system ofthe lungs, with the addition even ofthe cavities ofthe heart which belong to it, does not represent a complete circle, it is only a segment, or rather an arch ofthe great circle of general circulation. The blood, in going along that great circle, meets with the organs, si- tuated like so many points of intersection in the course ofthe vessel which form that circle. To render still more simple, the idea which is to be entertained on the subject, one may reduce these intersections to two principal ones ; the one corresponding to the lungs, the other to the rest of the body ; the veins, the right cavities of the heart, and the pulmonary artery with its divisions, forming one half of the circle ; the pulmonary veins, the left cavities of the heart, tbe aorta with all its branches representing the other half. The capillary vessels of the lungs form one ofthe points of inter- section, and the capillaries of all the other organs, represent the other point of intersection, by uniting together the arteries and veins of the 146 whole body, in the same manner as those of the lungs establish a com- munication between the veins and arteries of these organs. This division ofthe system of circulation into two parts, in one of which there circulates a dark or venous blood, while the other contains red or ansrial blood, is at once more simple and more accurate. As was alrea- dy stated, in the history ofthe circulation, that its organs are, in an espe- cial manner destined to the mechanical act of conveying the fluids : the changes, the alterations which the blood undergoes in passing through tbe orgms, are affected, only at the moment when in penetrating into their tissue, it passes into the capillary vessels which are distributed into them. The columns of blood are then sufficiently minute, to be operated upon by the vital action ; till then, the column* "of blood are too large, and re- sist, by their bulk, if one may so speak, any decomposition. It is, therefore, in the capillary vessels, that the blood receives its essential principles ; and to understand how the nutritious lymph which is deposited by the thoracic duct into the left subclavian vein, experiences, in its course along the sanguiferous system, the changes which are to assimilate it to our own substance, it is necessary to follow it, along the venous blood with which it unites, into the heart, through the right half of which it passes in its way to the lungs, there to combine with the atmospherical air, from which we are perpetually deriving another aliment indispensa- ble to life; then to examine, how, when modified and conveyed with the red blood, from the lungs to the whole body, it serves to the secretions, and supplies nourishment to the whole body. In considering, in this manner, the circulation of the blood, with a re- ference to the changes which it undergoes in the organs through which it passes, in describing that circle, we shall find, that this fluid, already com- bined with the lymph and chyle, parts, in the lungs, with some of its prin- ciples, at the same time that it becomes impregnated with the vital por- tion ofthe atmosphere, which suddenly changes its colour and other qua- lities. The blood will then be seen to flow into all the parts which it stimulates, to keep up their energy, to awaken their action, and furnish them the materials of the fluids which they secrete, or the molecules by which they grow or are repaired ; so that in supplying thus the different Organs, the blood loses all the qualities which it had acquired by the union of the chyle and of the vital air, parts with the principles to which it owed its colour, and again becomes dark, to be repaired anew by com- bining with the lymph, and by the absorption of the vital part ofthe at- mospherical air* : this constitutes the principal phenomenon ofthe func- tion, which will be considered in the fourth chapter. * See tke Netes or Respir*ti«n, in the APPENDIX, for a different opinion. 147 CHAPTER IV. OF RESPIRATION. ^X1X- 0f the different changes which the blood undergoes in the different organs, none are more essential or more remarkable than those it receives from the air, which, during respiration, is alternately received into the lungs, and expelled from them. The blood which the veins con- vey to the heart, and which the right ventricle transmits to the lungs, is ofa dark colour, and heavy; its temperature is only thirty degrees (Reaumur's thermometer ;) if laid by, it coagulates slowly, and there is separated from it a considerable quantity of serum. The blood which is brought by the pulmonary veins to the left side ofthe heart, and which is conveyed to all parts ofthe body, by means ofthe arteries, is, on the contrary, ofa florid red colour; it is spumous, lighter, and warmer by two degrees. It likewise coagulates more readily, and contains a smaller quantity of serum. All these differences, which are so easily distinguish- ed, depend on the changes which it has undergone, by being in contact with the atmospherical air LXX. Of the atmosphere. The mass of air which surrounds the globe, and to which we give the name of atmosphere, bears on all bodies with a pressure proportioned to their surface. That Of man* bears a weight of air amounting to about thirty-six thousand pounds. Moreover, one of its constituent principles is absolutely necessary to the keeping up of life, of which i,t is a principal agent. The variations in the weight ofthe atmosphere have, in general, but little influence on the exercise of the functions ; nevertheless, when by ascending the tops of very high mountains, man rises several thousand fathoms above the level of the sea, the very remarkable diminution of the weight of the air, produces a very sensible effect. Respiration be- comes laborious and panting, the pulse is quickened, and there is felt an universal uneasiness, joined to excessive weakness, and haemorrhages come on ; these symptoms are occasioned both by the diminished pres- sure of the air, and by the smaller quantity of oxygen contained in a rarer atmosphere.—(Saussure, Voyage au Mont-Blanc.) The human body resists, without any effort, the atmospherical pres- sure, because it is applied, at all times, and in every direction. But if a part of its surface ceases, for a moment, to be under its influence, it swells, the fluids are determined to it, in considerable quantity, the Inte- guments become excessively distended, so as to be in danger of bursting; such are the phenomena which attend the application of cupping glasses. The pressure of the air, on the surface of the globe is necessary to the existence of bodies in the condition in which we see them. Several very volatile fluids, as alcohol and ether, would become gaseous, under a less pressure of the atmosphere ; water would boil, under eighty de- * The surface of the body is estimated at fifteen or sixteen square feet, in a man of *ruddte sizp 148 grees of temperature (Reaumur's scale ;) solid bodies themselves might become fluid. In a word, a considerable diminution in the weight ofthe atmosphere would have absolutely the same effect, as raising its tempera- ture to a very great height, which, changing the face of the universe, would convert all liquids into elastic fluids, and would, doubtless, melt all solid bodies. The variations in the weight ofthe atmosphere, distinguishable by the barometer, are of very little importance to the physiologist, and, I might even add, to the physician, notwithstanding the minute attention with which some writers note the state ofthe barometer, of the thermome- ter, and hygrometer, and of the electrical state of the atmosphere, in giving an account ofa disease, or of an experiment, on which the above circumstances have no apparent or certain influence. The atmosphere, like every other fluid, has a perpetual tendency to a state of equilibrium, hence the rush of air into the lungs, or into other situations in which its quantity is diminished, by the combinations which it forms, or by the ef- fects of heat which renders it lighter by rarefaction : the same principle explains the formation ofthe trade and other winds. The atmospherical air combines with water and dissolves it, as the lat- ter dissolves saline substances. In this consists the process of evapora- tion The air becomes saturated with water, in the same manner as wa- ter becomes saturated with salt, to such a degree, as to be incapable of holding a greater quantity in solution. As its temperature rises, its solv- ent power increases, and the latter diminishes, as it grows cold ; variations of temperature produce the same effect on solutions of salts in liquids. The formation of all the aqueous meteors, depends on the different condi- tions of the solvent powers of the atmosphere ; when considerable, the atmosphere is warm and dry, and the air serene ; clouds form, when it is saturated ; dews, fogs, and rain, are the consequence of a diminution of its solvent power, as snow and hail, ofa degree of cold which precipi- tates the fluid. The different degrees of dryness or moisture, marked by the hygrometer, only sensibly affect the human body, when it has been exposed for a considerable time to its influence. Chemically considered, the atmospherical air, which was long regarded as a simple body, is composed of about 0,27 of oxygen, 0,73 of azote, and of 0,01 or 0,02 of carbonic acid The proportions of oxygen, according to Humboldt, vary from 0,23 to 0,29 ; that of azote, is almost always the same ; carbonic acid is the more abundant, as the air is less pure. This part of natural philosophy, which is called eudiometry, or the measure- ment ofthe purity ofthe air, is far from accomplishing what its name in- dicates, and has disappointed the hopes which had been entertained on the subject. Eudiometrical instruments can inform us,-only of the propor- tion of oxygen contained in the atmosphere ; now. its salubrity, its fitness for respiration, is not in proportion to the quantity of oxygen. The vola- tilized remains of putrid animal or vegetable substances, various mephitic gases, combine with it, and affect its purity. In the comparative analysis of air procured on the Alps and in the marshes of Lombardy, there was found in each the same quantity of oxygen ; and yet, those who breathe the former, enjoy robust health, while the inhabitants ofthe marshy plains of Lombardy are carried off by epidemic diseases, are pale, ema- ciated, and habitually lead a languid existence. Though, at least, 0,20 of oxygen are necessary to render the air fit for respiration, the proportion may be diminished to seven or eight parts in 149 the hundred ; but in such cases, the breathing is laborious, panting, and attended with a sense of suffocation, in short, asphyxia comes on, even while the air still contains a certain quantity of oxygen, of which the lungs cannot entirely deprive it. Whenever a number of persons are collected in a confined place, in which the air cannot be easily renewed, the quan- tity of oxygen diminishes rapidly, that of carbonic acid increases. The latter, m consequence of its specific gravity, sinks to the lowest part, and strikes with death every living being which it envelopes. When two lighted candles, of different lengths, are placed under the same bell, the shorter candle goes out first, because the carbonic acid formed during combustion, sinks to the most depending part. For the same reason, the pit is the most unhealthy part of a play-house, when a great number of people, after remaining in it for several hours, have deprived the air ofa considerable portion of its oxygen. Persons collected together, and enclosed in a small space, injure each other, not only by depriving the atmosphere of its respirable element, but particularly by altering its composition, by the combination of all the sub- stances exhaled from their bodies These volatilized animal emanations, become putrid, while in the atmosphere, and conveyed to the lungs du- ring respiration, become the germ ofthe most fatal diseases. It is in this manner, that the jail and hospital fever, so fatal to almost all. whom it at- tacks, arises and spreads. A dry and temperate air, containing G,27 of oxygen and 0,7.5 of azote, and free of other gases, or other volatilized substances, is the fittest for respiration. In certain cases of disease, how- ever, this function is most freely performed in a less pure air. Thus, patients labouring under pulmonary consumption, prefer the thick and damp air of low situations, to the sharp and dry air of mountains ; nervous women prefer that in which horn, feathers, or other animal substances are burning. An atmosphere highly electrical, at the approach of a storm, renders respiration very laborious, in some cases of asthma. In short, the qualities ofthe air must be suited to the condition ofthe vital power in the lungs, as those ofthe food, to the sensibility ofthe stomach. Being obliged, on this subject, to content myself with the ungracious office of compiler, 1 hasten to bring this article to a close, and to refer the reader for a fuller account of the air. considered in its physical and chemical relations, to the works of M. M. Fourcroy, Hauy, Brisson, &c. to that of M. Guyton Morveau. on the method of purifying the air, when from different combinations it is become unfit for respiration. LXXI. In man and in all warm-blooded animals, with a heart contain- ing two auricles and two ventricles, the blood which has been conveyed to all the organs by the arteries, and which has been brought back, by the veins, to the heart, cannot return to it, without having previously passed through the lungs, which are viscera destined to the transmission of air ; of a spungy texture, and through which the blood must, of necessity, circulate to »et from the right to the left cavities ofthe heart. This course ofthe blood constitutes the pulmonary or lesser circulation : it does not exist in some cold blooded animals In reptiles, for instance, the heart has but one auricle and one ventricle ; the pulmonary artery, in them, arises from the aorta, and conveys but a small proportion of the blood ; hence the habitual temperature of these animals is much lower than that of man. For the same reason too, there exists so small a difference, be- tween their venous and arterial blood; the quantity of fluid vivified by 150 exposure to the air, in the pulmonary tissue, being too small to effect, by its union with the general mass, a material change on its qualities. Mayow has given the most accurate notion of the respiratory organ, by comparing it to a pair of bellows, containing an empty bladder, the neck of which by being adapted to that of the bellows, should admit air on drawing asunder its sides. The air, in fact, enters the lungs, only when the chest dilates and enlarges, by the separation of its parietes. agents of respiration are, therefore, the muscles which move the parie- tes of the chest, these are formed of osseus and soft parts, in such a man- ner, as to possess a solidity proportioned to the importance of the organs which the chest contains, besides a capacity of motion required to carry on the functions intrusted to them.* To carry on respiration which may be defined the alternate ingress of air into the lungs, and its egress from those organs, it is necessary that the dimensions 0f the chest should be enlarged (this active dilatation of the cavity of the chest is called inspiration,) and that it should contract to expel the air which it had received during the first process. This se- cond action is called expiration, it is always of shorter duration than the former, its agents are more mechanical, and the muscles have much less influence upon it The parietes of the chest are formed, at the back part, by the verte- bral column, at the fore part by the sternum, and on the sides by the ribs, which are osseo cartilaginous arches, situated obliquely between the vertebral column, which is fixed and becomes the point of support of their motions, and the sternum which is somewhat moveable—the spaces between the ribs are filled by muscular planes of inconsiderable thick- ness, the internal and external intercostal muscles, the fibres of which lie in opposite directions.—Besides, several muscles cover the outer part of the thorax, and pass from the ribs to the neighbouring bones ; as the subclavian muscles, the great and lesser pectorals, the serrati, the latissi- mai dorsi, the scaleni, the longissinai dorsi, the sacro lumbales, and the serrati minores, posterior, superior, and inferior. But of all the mus- cles which form the anterior, posterior, and lateral parietes ofthe chest, the most important is the diaphragm, a fleshy and tendinous partition, ly- ing horizontally between the chest and the abdomen, which it divides from each other; it is attached to the cartilages of the false ribs, and to the lumber vertebrae, and has three openings to transmit the oesophagus and the vessels which pass from the abdomen to the chest, or from the latter into the abdomen. In health the chest dilates only by the descent ofthe diaphragm. The curved fibres of that muscle, straightened in contraction, descend towards the abdomen, and compress the viscera. The descent of the viscera thrusts forward the interior parietes of that cavity, and these recede, when on expiration taking place after inspiration, the diaphragm now re- laxed., rises, pressed upward by the abdominal viscera, compressed them selves by the large muscles of the abdomen. But when it is necessary to take into the chest a great quantity of air, it is not sufficient that it should be enlarged merely by the descent ofthe diaphragm—it is required be- sides, that its dimensions should be increased in every direction. The inter- costal muscles then contract, and tend to bring together the ribs between * See APPENDIX, Noto U, for remarks on the mechanism of the respiratory rv- 2fanr. ii)l which they are situated. The intercostal spaces, however, become wider, especially at their anterior part, for, whenever lines falling obliquely on a vertical line, change their direction, approaching to a right angle, the inter- mediate spaces receive the greater in, rease, as the lines, more oblique at tint, become at last more nearly horizontal. Besides, as the libs are curv- ed m the course of their length, in two directions, and both in the direction ot their faces, and edgewise, the convexity of the first curvature is out- wards, the ribs recede to a distance from the axis ofthe chest, whose ca- vity is enlarged transversely, while the second curvature (in the direction of their edge) being increased by a real twisting of these bones, and which reaches to the cartilaginous pm-ts, the sternum is heaved forward and upward, so that the posterior extremity of the ribs is removed from their sternal end. But as the ribs are not all equally moveable, as the first is most always invariably fixed, and as the others are moveable in proportion to their length, the sternum is tilted in such a way that the lowermost extremity is thrust forward The diameter of the chest from the fore to the back part increases, therefore, as well as the transverse diameter. This increase of dimensions has been estimated at two inches, to each of these diameters ; the dimensions ofthe vertical diame- ter, which are regulated by the depression of tbe diaphragm, are much greater. LXXII. Professor Sabatier, in his memoir on the motion of the ribs, and on the action of the intercostal muscles, maintains that during the action of inspiration, the upper ribs alone rise, that the lower ribs descend and slightly close on the chest, while the middle ribs project outwardly, and that in expiration, the former set of ribs descend, that the latter start a little outwardly, and that the middle set encroach on the cavity of the chest. The learned Professor adds, that the cartilaginous articulating surfaces, by which the ribs are connected to the transverse processes of the vertebrae, appear to him to favour these different motions, as the di- rection of the articulations of upper ribs, is upward, and that ofthe low- er downward ; but on considering the subject with attention, it will be seen, that the surfaces by which the transverse processes of tbe verte- brae are articulated to the tuberosities of the ribs, are turned directly for- ward in the greatest number, some of the lower ribs are, at the same time, directed slightly upward. If we examine the action of the bones of the chest, during inspiration, in a very thin person, for example, in phthisical patients, whose bones are covered with little else th-m skin, we shall find, that all the ribs rise, and are carried somewhat outwardly. It is not easy to conceive how the intercostal muscles, which Professor Sa- batier considers as the agents of respiration should elevate the upper ribs and depress the lower. The diaphragm, whose circumference is in- serted in the latter, might, by its contraction, produce this effect ; but as the intercostals have their fixed point of action in the upper ribs, they oppose and neutralize this effort, and all the ribs are elevated at once. If this were not the case, the ribs ought to be depressed, whenever the intercostals contract, since the lowermost, fixed by the diaphragm, would become the fixed point on which all others should move. As the fibres ofthe external and internal intercostal muscles, are in di- rect opposition to each other, those ofthe former set of muscles having an oblique direction, from above downward, and from behind forward, and crossing the fibres ofthe other set whose obliquity is in a different direc- tion ; several physiologists have thought, that these muscles were oppos- 152 ed to each other, that the internal intercostal muscles brought together the ribs, after they had been separated by the external intercostals, the one set being muscles of expiration, while the other set contracted during in- spiration. It is well known with what pertinacy, Hamberger, in other respects, a physiologist of considerable merit, defended this erroneous opinion, in his dispute with Haller ; it is now, however, ascertained, that all the intercos- tal muscles concur in dilating the chest, and that they ought to be ranked among the agents of inspiration, because the unequal capacity of motion in the ribs, prevents the internal intercostals, the lower insertion of which is nearer to the articulation of these bones to the vertebra;, from depress- ing the upper ribs. Of the very conclusive experiments, by which Haller undertook to refute the arguments of his adversary, I shall relate only that which is performed by stripping the parietes of the chest, in a living animal, of
;ayow, at the expence of a certain quantity of air contained in a bladder, or by breathing into a vessel connected with a pneumatic apparatus the air taken in, by drawing a deep inspiration. Or else one may inflate the lungs of a dead body, by adapting to the trachea, a stop-cock connected with a curved tube to receive the air under_ a vessel of the same apparatus. Various means have been employed to mea- sure the capacity of the chest. Boerhaave placed a man in a tub containing water »bove his shoulders, he then made him take a deep inspiration, and measured the tteigM: at which the fluid rose from the dilatation of the chest. Keill injected water S£,^hl i0h*,dea? b°dy' La,tljr'St has beea Pr°P°sed t0 inJect tne ^onchial tabes and th. lob.lar tissue into which they terminate, with fusible metal consisting of eight parts of pewter, five of lead, three of bismuth, to which may be added one of mercury.—Author's Note. &niSee^r^FNPLX' N°te ^' for observations on the changes induced on the air. en* on the blood, by respiratien. % 157 with its hydrogen and carbon, its capacity for caloric increases in the pro- portion of 10 : 11.5. In parting with its carbon which, by uniting with oxygen, forms the carbonic acid that is thrown out during expiration, the blood loses its- dark and nearly purple colour, and becomes ofa florid red, and its con- sistence increases, from the escape of its hydrogen and of its aqueous parts. Besides, as it absorbs a certain quantity of oxygen, it becomes spumous and light ; its concrescibility and plasticity increase, ana^ on coagulating, there is separated from it, a smaller quantity of serum. After parting with its hydrogen and carbon, and combining with oxy- gen and caloric, in its passage through the lungs, the blood, which is be- come arterial, parts with these two principles, in proportion as ia reced- ing from the heart, it forms new combinations, and is converted into ox- ides of hydrogen and carbon, which, on receiving an additional quantity o£ oxygen, are changed into water and carbonic acid, when on being carried along with the venous blood, into the pulmpnary tissue, they are exposed to the inflaence of the atmospherical air. The arterial blood becomes venous, by yielding its oxygen, when any cause whatever suspends or slackens its course, as is proved by the fol- lowing experiment of John Hunter. He tied the carotic artery ofa dog, with ligatures placed at the distance of about four inches from each other : the blood contained in the portion of artery included between the two li- gatures, on laying open this part ofthe vessel, at the end ofa few hours, was found coagulated and as dark as that in the veins. The blood con- tained in an aneurismal, sac and which is frequently found in a fluid state, when the internal coats of the artery are but lately ruptured, becomes venous after remaining in it some time. The changes, however, which the blood undergoes in its course through the arterial system, are not very remarkable, owing to the rapidity with which it flows along those vessels ; there is less difference between the blood contained in an arte- ry near the heart, and that contained in an artery at a distance from that organ, than in the blood taken from the veins near their extremi- ties, and from the great trunks which deposit it into the right auricle. The blood in the small veins resembles arterial blood, and frequently in a very copious bleeding, the colour of the blood, which at first, is very dark, gradually becomes less dark, till towards tbe end ofthe bleeding, it shows nearly the same qualities as if arterial ; a phenomenon which, as is well ob-erved by the English writer already quoted, depends on the more easy and rapid flow ofthe blood ofthe arteries into the vems, in consequence of the evacuation ofthe venous system. This observation is a complete refutation ofthe assertion of Bellini, who maintains, that when a vein is wounded, the blood which comes from it, forms a double current which flows out at the wound. The above opinion is maintained by highly distinguished physiologi.-ts, as Haller and Spallanzani, who sup- port it by experiments performed on the vessels of cold-blooded animals, or on veins without valves. In bleeding at the bend ofthe arm, the blood cannot come from that part of the vessel which is above the wounds : the valves oppose insuperable obstacles to its retrograde flow, hence it is very easy to distinguish the red blood which comes from the lower extre- mity of the vein; from that which flows from the upper end, and which is poured into the vessel by the veins which open into it, between the punc- ture and the nearest valve. In its course to the parts among which the arteries are distributed, the blood, vivified in its passage through the lungs, and fitted, as M. Four- Ib8 tr»y says, f»r a new life, loses its oxygen and caloric Its capacity for the latter, diminishes, in proportion as the oxygen, by combining with hy- drogen and carbon, restores it to the venous state. This theory of the process by which the blood parts with its oxygen, in its progress along the blood-vessels, is rendered still more probable, by recent discoveries on the nature of the diamond This substance is the only pure carbon, and that which is called so by chemists, is an oxyde of carbon which owes its dark colour to the oxygen with which it is com- bined. Before these experiments, it was not easy to determine the parti- cular condition ofthe carbon which exists so plentifully in venous blood. No precise calculation has yet been made, ofthe quantity ofthe oxygen absorbed by the venous blood, nor of the quantity employed in the com- bustion of hydrogen and carbon in the lungs, so as to form water and car- bonic acid*. Is the carbon, in venous blood, merely combined with oxygen, or is it united with hydrogen, so as to form carburated hydrogen ? It appears to me more probable, that the oxygen which is absorbed, by combining with hydrogen, in every part of the body, produces the water which dilutes the venous blood, renders it more fluid, and richer in serum than arterial blood ; while, by its union with carbon, it forms an oxide that gives to the blood the dark colour, which is one of its most remarkable characters. On reaching the lungs, which are real secretory organs, the water is ex- haled, dissolved in the air, and forms the pulmonary transpiration ; the oxide of carbon, completely decomposed by an additional quantity of oxy- gen, constitutes carbonic acid, which gives to the air that is expired, the power of forming a precipitate in lime water. The absorption of oxygen by tbe venous blood, explains how the phe- nomena of respiration are continued into every part ofthe body, and pro- duce the warmth uniformly diffused over all our organs. In proportion 1 as the blood parts with its caloric, for which its affinity diminishes as it be- comes venous, the parts which give out their hydrogen and carbon, com- bine with it. If the lungs were the only organs in which caloric might be disengaged, the temperature of those viscera ought considerably to exceed that of other parts : experience, however, shows that the temperature of the lungs is not sensibly more elevated. This theory of respiration, for which we are entirely indebted to mo- dern chemistry, is contradicted by no one phenomenon. The greater the extent and capacity of the lungs, the more frequent is respiration, and the greater the warmth and vivacity of animals. Birds, whose lungs extend into the abdomen, by various membranous sacs, and whose bones are hollow, and communicate with the lungs, consume a great deal of oxygen either on account ofthe magnitude of this respiratory apparatus, or from their frequent, and, at times, hurried respiration. On that account, the habitual temperature of their body, exceeds that of man and mammiferous animals. In reptiles, on the contrary, whose vesicular lungs admit but a very small quantity of blood, and present to the atmosphere a surface of very limited extent, and in which respiration is performed with intervals of longer duration, the body is at a temperature which, naturally, never rises above seven or eight degrees. « * Instead of saying that the venous blood absorbs oacygen, it will approach nearer the state of our knowledge to believe that the venous blood gives off its earbon, which combines, in the lungs, with the oxygen of the inspired air. For a full vi*w of the latest opinions on this subject) see APPENDIX- Note W lirii LXXVII. 1 hough the temperature or warmth ofthe body is generally proportioned to the extent of respiration, to the quantity of blood exposed, in a given time, to the action ofthe atmospherical air, it may be higher or lower, according to the degree of the vital energy of the lungs. .1 nese organs should not be considered as mere chemical receivers ; tney act on the air, digest it, as the ancient said, and combine it with the mood, by a power which is peculiar to ihein.* If it were otherwise, there would be nothing to prevent a dead body from being restored to life, by inflating with oxygen its pulmonary tissue. The ancients alluded to this action ot the lungs on the air we breathe, by calling that air the pabulum vitas. Its digestion was, they thought, effected in the lungs, in the same manner as the digestion in the stomach, of other aliments less essential to lite, and whose privation may be borne for a certain time, while life is endangered, when the aeriform nutriment ceases to be furnished to the lungs, for the short space of a few minutes. In proof ofthe vitality ofthe lungs, and ofthe share which they have m producing the changes which the blood undergoes in passing through them, I may mention the experiment which proves that an animal placed under a vessel tilled with oxygen, and breathing that gas in a pure state, consumes no more of it, than if it was received into the chest, mixed with other gases unfit for respiration. A guinea pig, placed under a vessel lull ot vital air and of known capacity, will live four times longer than if the vessel contained atmospherical air. No remarkable difference is at first perceived in the aUof respiration, but if the animal remains long im- mersed m the oxygen, his respiration becomes more frequent, his circu- lation more rapid, all the vital functions are executed with more energy. The lungs separate, by a power inherent in themselves, the two atmo- spherical gases, and this process is effected by a pretty considerable pow- er, for oxygen, in its combination with the blood, is, with difficulty, sepa- rated from azote. In fact, the blood, though in thin layers, becomes dark, when exposed to the atmospherical air. It is observed, that the purity ofthe air contained in the receiver, is the more readily affected, as the animal placed under it is younger, more robust, and his lungs are more capacious. Hence birds, whose lungs are very large, contaminate a considerable quantity of air, and consume more quickly its respirable part. A frog, on the contrary, will remain a con- siderable time, in the same quantity of air, without depriving it of its oxy- gen. The vesicular lungs of that reptile, as well as of all oviparous quadru- peds, are much more irritable than those of warm-blooded animals ; they appear to contract, at the will of the animal. The frog is without a dia- phragm, attracts the air into its lungs, by swallowing it by a real process of deglutition, as was proved by Professor Rafu, of Copenhagen, who killed those animals by holding their jaws asunder for a certain time. They reject the air by a contraction ofthe lungs, in the same manner as in man, the bladder empties itself of urine. In birds, whose diaphragm is equally membranous and contains seve- ral openings to transmit the air into the pulmonary appendices, the pari- etes of the thorax are likewise more moveable than in man and quadru- peds. Their pectoral muscles are more powerful, their ribs contain a joint situated in the middle of those arches which are completely ossified •n that class of animals j and those two portions move on each other, See APPENDIX, Note W 160 forming, at their point of union, angles more or less acme, according to the distance ofthe sternum from the vertebral column. A numerous class of cold red-blooded animals, viz. fishes, have no lungs ; the gills, which supply their place, are small penniform laminae, generally four in number, situated on each side, at the posterior and late- ral part ofthe head, covered over by a moveable lid, to which naturalists give the name of operculum- The water which the animal swallows, passes, when he chooses, through the parietes of the pharynx, which contain several pretty considerable openings, is spread over tbe gills and the pulmonary vessels which are distributed in them, then escapes at the auricular apertures, when the animal closes his mouth, and raises the opercula. It is not known, whether the water is decomposed and yields its oxygen to the blood which circulates in the gills, or whether the small quantity of air that is dissolved in the water, alone serves to vivify the pulmonary blood. The latter opinion seems the most probable, if it be considered that a fish may be suffocated, by closing accurately the vessel of water in which it is enclosed. The same result might, I con- ceive be obtained, by placing the vessel under the receiver of an air- pump, so as to exhaust it completely. Respiration, which is completely under the influence of the brain, as as far as relates to its mechanism, is less dependent upon it, in regard to the action of the lungs on the blood, and the combination of that fluid with oxygen, which is the essential object of that function. The nerves, however, have some influence on that function, as well as on the various secretions, in which, according to Bordeu, they are of the first rate im- portance. M. Dupuytren ascertained by his experiments, that the divi- sion of the cervical portion of the eighth pair of nerves, did not sensi- bly affect respiration ; but the animal died with all the symptoms of as- phyxia, when this nerve was divided on both sides. Death took place,' 4 in the course of a few minutes, when the ex eriment was performed on horses. Other animals did not die so soon after ; dogs, for instance, have been known to live several days after the experiment. By interrupting thecommunicationbetweenthelungs and the brain, we paralyze theformer of these organs, and it ceases to convert the venous into arterial blood. This fluid, conveyed by the pulmonary artery, continues ofa dark colour, when brought to the left cavities of the heart, the arteries convey the blood without its having received its vivifying principle, in passing through the lungs which are paralyzed, by having their nerves tied or divided. It is easy to conceive that all organs, for want of the stimulus which de- termines their action,carry on their functions imperfectly, and at last cease to act. The animal heat i* likewise lowered a few degrees, as was as- certained by the above-mentioned physician, who thinks he has establish- ed as a fact, that the ligature of the nerves of the lunjj;s does not destroy, but weakens the vital power, which enables them to take up the oxygen, and to give out the carbonic acid. The brain, therefore, possesses a dou- ble influence over the function of respiration ; on the one hand, it directs its mechanism, by means of the nerves which it sends to the diaphragm, and to the intercostal muscles, and on the other hand, it is through the J nerves which arise from the brain, that the lungs have the power of • converting dark blood into arterial blood, which is the principal pheno- | menon of respiration. Experiments performed on the same subject, by Dr. Gallois, subse- quent to those I just related, tend to throw some degree of uncertainty on their results. Dr. Gallois repeated these experiments publicly, in mv 161 presence, and at the society of the Ecole de Medecine of Paris. After dividing the two nerves ofthe eighth pair, in a guinea-pig, and after hav- ing, by that process, brought on a state of asphyxia, he restored life and motion to the animal, by opening the trachea at its interior part. The blood of the carotids, which from red had become dark the moment the nerves were divided, respiration is restored, and the animal lives seve- ral days after the experiment. Whence does this difference arise l does the division of the eighth pair bring on asphyxia, by occasioning a spas- modic constriction of the glottis, and by impeding, or even completely obstructing the admission of the atmospherical air* ? LXXVllI. Of animal heat. The human body, which is habitually of a temperature of between thirty-two and thirty-four degrees of Reau- mur's thermometer!, preserves the same degree of warmth under the frozen climate of the polar region, as well as under the burning atmos- phere of the torrid zone, during the most severe winters and the hottest summers. Nay, further, the experiments of Blagden and Fordyce in England, and of Duhamel and Tillet in France, shew, that the human bo- dy is capable of enduring a degree of heat sufficient to bake animal sub- stances. The fellows of the Academy of Sciences, saw two girls enter r_ into an oven, in which fruits and animal substances were being baked ; | Reaumur's thermometer, which they took in with them, stood at 150 de- grees ; they remained several minutes in the oven, without suffering any S inconvenience. All living bodies have a temperature peculiar to themselves, and inde- pendent of that of the atmosphere. The sap of plants does not freeze, | when the thermometer stands only at a few degrees above zero ; on placing R; the bulb of a thermometer in a hole in the trunk ofa tree, during winter, i j the fluid sensibly rises. Now, three circumstances remain to be inves- ' tigated : in the first place, what produces in living bodies, this inherent and independent temperature ? In the second place, how do these bodies i resist the admission of a greater degree of heat, than that which is natu- % ral to them ? What prevents caloric, which has a perpetual tendency to a w state of equilibrium, from passing into a body surrounded by a burning W atmosphere ? Lastly, how does a body which resists the influence of heat, £ withstand equally, the destructive influence of an excessive degree of | coldj? I LXXIX. Caloric, in a latent state, or in combination with bodies, is disengaged from them, whenever they assume a different state ; when, from a gaseous form they become liquid ; or, when from being liquid, they become solid. Now, living bodies are a kind of laboratories in which all these changes are perpetually going on ; the blood which cir- ? culates in every part of the human frame, is constantly receiving supplies 1 of fresh materials ; from the thoracic duct which pours into it the chyle, ' abounding in nutritious particles ; from respiration which imparts to it an aeriform principle obtained from the atmosphere; and even, in some u cases, from cutaneous absorption, through which different elements are - received into it. All these different substances carry along with them ii4- into the blood, a certain quantity of caloric, which is combined with :hem, and which is disengaged during the changes which they undergo, * See APPENDIX, Note W. | + Between 96 and 98 of Fahrenheit. L t Seethe remarks, in ArrEwrux, Note Y, on the production of Animal Ueiti. f 21 162 from the influence of the action of the organs, and gives out its calorie to the parts among which it is disengaged. Of all the principles in the blood, which have the power of communicating heat to the organs, none furnishes a greater quantity than oxygen, which during respiration, com- bines with the blood in the lungs. Gaseous substances, it is well known, contain most combined caloric ; their state of elastic fluidity, is entirely owing to the accumulation of that principle and they part with it, when from any cause whatever, they become liquid. It is on that account, that the heat of the bodies is greater, the more they have the power of im- pregnating their fluids with a considerable quantity of oxygen from the atmosphere. For the same reason, as was already observed, in animals that have cellular lungs, and a heart with two ventricles, the blood is of the same temperature as in man ; and such animals befohg, as well as man, to the great class of warm red-blooded animals; a class in which birds occupy the first place, from the vast extent of their lungs, which reach into the abdomen and communicate with the principal bones ofthe skeleton. The capacity of the pulmonary organ of birds, is not the only cause why their temperature is ei^ht or ten degrees higher than that of man : this increase of temperature depends, likewise, on the greater frequency of their respiration, and on the velocity of their pulse ; on the quickness and multiplicity of their motions, and on the vital activity which animates them. In reptiles which have visicular lungs, and a heart with a single ventricle, whose respiration is slow, and performed at distant intervals, the blood, though red, is of very inferior tempera- ture to that of man. They have, from that circumstance, been called cold red-blooded animals : this numerous class include fishes, which pos- sess an organ supplying but imperfectly the office of lungs. In fishes, the heart which has but a single ventricle, sends, it is true, to the gills (the organ supplying the place of lungs is so called) the whole ofthe blood; that fluid, however, is but imperfectly vivified in the gills, on account of the small quantity of air which can be taken in during the act of respiration. Lastly, in white-blooded animals and in plants, the combinations with the air being more difficult, the vital ener- gy less, marked, the temperature differs only by a few degrees, from that of the atmosphere, and they do not endure heat or cold, so well as the more perfect animals. . The lungs, jis was before observed, consuming only a certain quantity of air, there is no increase of temperature, however great the quantity of oxygen contained in the atmosphere that is breathed ; as a man who should take a double quantity of aliment, could not receive more nourish- ment, than if he contented himself with the quantity of food proportion- ed to his wants ; for, as the digestive organs can extract only a certain quantity of chyle, the quantity of recrementitious matter would only be greater, if more than the due quantity of food were received into the stomach. Hence the common saying, that nourishment comes from what we digest, and not from what we eat. The pulmonary organ may, however act on the air, with different de- grees of power, in robbing it of its oxygen ; and when the body becomes of an icy coldness, in certain nervous and convulsive affections, this cold may depend as much on the atony of the lungs, and on the spasmodic condition of the chest, which, dilating with difficulty, does not admit the air readily, as on the spasm and general insensibility ofthe organs, which allow the blood to pass without affecting its component parts. It would be curious to ascertain, whether the air expired from the lungs ofa cata- 163 leptic, contains more oxygen, is less impaired, and contains a smaller quantity of carbonic acid than the breath of a sound active adult. Per- haps it would be found, that in catalepsy and other similar affections, the blood does not part with its hydrogen and carbon, that it retains its co- louring principles, and the different materials ofthe urine, which is void- ed in a colourless and limpid state, insipid and without smell, and in the condition of a mere serosity. The temperature of the body is produced, not only by the pulmonary and circulatory combinations ; it is besides developt-d in several organs, in which fluid or gaseous substances become solid by parting with a por- tion of their caloric. Thus digestion, particularly of certain kinds of tood, is an abundant source of caloric ; the skin which is habitually in contact with the atmosphere, decomposes it. and deprives it of its caloric. --Lastly, caloric is produced and evolved in all parts, whose molecules affected by a double motion, in consequence of which they are incessant- ly being formed and decomposed, by changing their condition and consist- ence, absorb or disengage more or less caloric. The great activity ofthe power of assimilation in children, is, no doubt, the cause of the habitually high temperature, at that period of life * The temperature ofthe body is not only one or two degrees higher at that period of life ; but young peo- ple, after death, preserve for a longer period, the remains of vital heat; or rather, as tonicity does not so soon forsake the capillary vessels, life de- parting reluctantly, the combinations from which caloric is evolved, con- tinue some time, even after it is extinct For the ^ame reason the bodies of persons that have died suddenly, retain their warmth long, while an icy coldness seizes the bodies of those who have died of lingering dis- ease, from the slow, gradual, and total abolition of the powers of life Calorification, or the disengaging of animal heat, like nutrition, takes place at all times, and may be considered as belonging to all organs. It was of the utmost consequence, that the internal temperature of the human body should be nearly the same at all times. For, let us, for one moment, suppose that the temperature of the blood should rise to fifty de- grees of Reaumur's thermometer, its albuminous parts would suddenly coagulate, obstruct all the vessels, interrupt the circulation, and destroy life. When, therefore, from an increased activity of the nutritive com- binations, a greater quantity of heat is disengaged, the animal economy parts with it, and it is taken up, in greater quantity by the surrounding bodies. This accounts for the equality of the temperature of the inter- nal parts of the body, in old people, and in children, notwithstanding the difference of their temperature externally. The difference consists in this, that where most caloric is produced, most is given out, and though the blood and urine in old people, as well as in the young, are at thirty- two degrees, what a difference is there not, between the hot and pene- trating perspiration which is poured in abundance, from the child, and the dryness and coldness of the skin in old people ; between the sweet and warm breath of the former, and the frozen breath of the latter ! Hence the opinion so generally received and of such antiquity, that old people * Considering the temperature of the body to be under the influence .of that part of the nervous system which is distributed to the blood-vessels, as pointed out in the note on this subject in the Appendix, the reason will appear evident, why animal warmth is greater in young and robust subjects, than in the old and debilitated. In- deed the temperature holds a close relation with the other changes which take place in the different textures of the body; and it as well as these seem equally to result from the influence of these ner^rs upon the vessels to which they are distributed. i 61 are benefited by cohabiting with the young. Thus wo are told, tna;. David had a young virgin brought to him, that he might lie with her, and get heat in his limbs that were stiffened with years*. If it be true, that in the very act of nutrition, which converts our fluids into solids, there is disengaged a considerable quantity of caloric; the motion of nutritive decomposition, by which our solids are converted into liquids, must cause an equal quantity of heat to be absorbed. The objec- tion is a very strong one, and not easily got over ; it may be answered, by observing, that all living bodies, from the instant of their formation, con- tain a certain quantity of caloric which they retain, so that this double process of acquiring beat and parting with it, the unavoidable result of nu- tritive composition, and decomposition, merely keeps up an equilibrium, and maintains the same degree of temperature. The blood which becomes saturated with oxygen, in the capillaries of the lungs, parts with that principle, and disengages its caloric, throughout the capillary vessels of the whole body, of which each organ must set free a greater quantity, in proportion to the activity of the living princi- ple, and to the rapidity of the circulation The parts through which the greatest number of vessels circulate, perhaps give out most caloric, and communicate a portion of it to the organs, which receive but a small quantity of blood, as the bones, the cartilages. &c. It is easy to under- stand, why an inflamed part, through which the blood circulates with more rapidity, and whose sensibility and contractility are much increased, is manifestly hotter to the feel of the patient and of the physician, though, as was observed by John Hunter, a thermometer applied to the inflamed part, shews a scarcely perceptible increase of temperature. He injected into the rectum of a dog, and into the vagina of an ass, a strong solution of oxymuriate of mercury. Acute inflammation came on, the swollen mu- cous membrane formed, externally, a considerable projection. Blood flowed from the torn capillaries, yet the thermometer rose very slightly, only one degree of Fahrenheit's. But however slight that increase of heat in the inflamed part, it is very sensibly felt, on account of the extreme sensibility of the organ, whose vital properties are all increased. The liveliness of impressions being proportionate to the degree of the power of sensation, one need not wonder that the patient should experience a sensation of burning heat, in a part in which the thermometer indicates no increase of temperature, in which it cannot be perceived even by the touch. I have just felt ayoung man's hand, that is swollen from chilblains ; though the pain which he feels in it, seems to him to be occasioned by an accumulation of caloric; his hand is colder than mine, which is of the same degree of warmth as the rest of my body, and in which I have no peculiar sensation. It may, therefore, be laid down as an axiom, that the real or thermometrical increase of heat is inconsiderable in inflamma- tion, but that it is intensely felt, in consequence of the increase of sensi- bility. What is the reason, that during the cold fit of a febrile paroxysm, a sen- sation of excessive cold is felt in a part in which no diminution of heat can be discovered by the touch? Whence comes the burning heat which attends inflammatory fever (causos ?) What is the cause of the difference ofthe sensations attending the heat of erysipelas, bilious fevers, and * The ancients appeared to have seme idea of what the moderns would do well t© attend to more than they have done, if, indeed, they have attended to it at all, namely tha beneficial influence ofthe application of animal warmth to the system when its vi- tal influence is either languid or sinking. 16o phlegmon, &.c. These various sensations are owing to the different mo- difications of sensibility in these different diseases. Should this explana- tion appear unsatisfactory, let it be recollected, that however accurate the calculations may be, that have been made on the subject of caloric, or of the matter of heat, the existence of caloric itself is hypothetical, and that it is not known, whether caloric is a body, or whether heat is mere- ly a property of matter. LXXX. If we now enquire into the causes which enable the body to resist the admission of a degree of heat superior to that which habitual- ly belongs to it, we shall be compelled to admit, in all living bodies, a power by means of which they repel an excess of heat, and retain the same temperature. Cutaneous perspiration, it is true, acts very power- fully in lowering the temperature, and as this evaporation increases with the temperature, it should seem as if this function sufficed to moderate the head of the body, and to restore the equilibrium. It is a fact known since the time of Cullen *, that the evaporation ot fluids, or their solution in the air, is the most powerful means of cooling bodies, and that the mercury in the bulb of a thermometer, may be frozen merely by moistening it with aether, spirits of wine, or any other volatile substance, and then exposing it to a dry and warm air. This method is equally successful in its application to the human body, and the hands may- be cooled to such a degree, as to feel benumbed, by being frequently wetted with a spiritous fluid, and by being moved in a dry and renewed air. But though cutaneous perspiration operates in a somewhat similar manner, and though it may be ranked among the means which nature em- ploys to preserve the animal temperature in a nearly uniform state, it must however be confessed, that it is not the only way in which this ob- ject is accomplished, and that it does not satisfactorily account for this phenomenon, for. the evaporation of the fluids contained in dead animal substances, does not prevent their being roasted on tne application ot heat, and besides, fishes and frogs have been known to live and retain their temperature in mineral waters, nearly of a boiling heatt. I thought it right to repeat these experiments, and with ihis view, 4 placed living frogs in a vessel containing water at titty degrees ot tempe- rature, and on taking them out, at the end often minutes, I ascertained that they were not so hot as the liquid, nor as pieces of flesh which had been put into it at the same time. We cannot admit the opinion of Grimaud, that living bodies have the power of producing cold ; for, as cold is merely the absence of heat, one cannot allow a positive existence to a negative being. Habit has a remarkable influence on the faculty which the body pos- sesses of bearing a degree of heat, much exceeding that which is natu- ral to It Cooks handle burning coals with impunity ; workmen employ- ed in forces leave the mark of their feet on the burning and liquid metal, at the moment when it becomes solid by cooling. Many, no doubt recol- lect the too famous instance ofa Spaniard, who became so general a sub- ject of conversation in Paris : this young man, in making His way through * This celebrated physician made this discovery about forty years ago which has ♦u L!6 hb"ht o several physico chemical phenomena, and he published it in a SSSStSfi0 - Of S cold produced by evaporating fluids, and of some other means of producing cold," by Dr. W. CMen.-Authors Note. t See » Sonnerat's Voyage to tbe East Indies. I6G a house on fire, perceived that the heat was less inconvenient to bun than he had imagined. He applied himself to bear with impunity, the action of fire, and was enabled to apply to his tongue a spatula heated red hot, and to apply the soles of his feet and the palms of his hands on a red hot iron, or on the surface of boiling oil. Nothing can equal the absui- dity and the exaggeration ofthe stories that were told of this man, except the ignorance and the want of veracity of those who invented them. 1 he following is a correct statement ofthe feats of tnis man who was repre- sented as incombustiok- and insen-ible. He passes rapidly along the sur- face of his tongue, which is covered with saliva, a red hot spatula, the ac- tion of which seems merely to dry it. by bringing on an evaporation ot the fluids with which it is covered. After carrying the spatula, from tne base to the tip of ins tongue, he brings it back again into his mouth, and applies it to his palate, to which it communicates a part of its heat, at the same time that it becomes moistened with saliva. This man, having, in a public exhibition, carried on too long, the application ofthe spatula, the caustic effects of its heat showed themselves, the epidermis was detached, and found coiled, like the outer covering of an onion, in the cloth which he used to wipe his mouth. He does not dip his hands and feet in boiling oil, he merely applies to the surface ofthe fluid, bis palms and his soles, and he repeats this frequently with only a short interval between each application. When the experiment is carried on, for a certain length of time, there is emitted a smell of burnt horn. No one has yet observed, that though this man's hand* are not callous, the palms of these, and the soles of his feet are cushioned with fat A thick layer of fat, which is a bad conductor of heat, separates the skin from the subjacent aponeuroses and nerves : this circumstance, to a certain degree, accounts for his im- perfect sensibility. His pulse daring those experiments, was about a hundred and twenty ; the perspiration evidently increased, and sometimes copious. Every part of his body possesses the ordinary degree of sensibility may be destroyed by the protracted application of caustic substances, and would be consum- ed by fire, if applied for a sufficient length of time, and nitric acid would infallibly destroy his tongue, if he took any into his mouth, as it has been said he did. This man, therefore, in no one respect departs from the known laws of the animal economy, but on the contrary, affords an addi- tional proof of the influence of habit on our organs*. LXXXI. Before bringing to a conclusion this article on animal heat, it remains forme to explain how the body resists cold, and preserves its tem- perature, in the midst of a frozen atmosphere. This cannot be accom- plished without an increase of activity in the organs, it is only by augment- ing the sum of the combinations by which caloric is disengaged, that we cannot succeed in making up for the loss of that principle so necessary to our existence. What i* the reason that in cold weather digestion is more active, (Hieme verb ventres sunt calidwres. Hipp.) the pulse stronger and more frequent, and the vital energy greater ? It is because heat comes from the same source, and is produced by the same mechanism as the nu- trition of the organs; and that its evolution may go on increasing, it is ne- cessary that the secretions, nutrition, in a word all the vital functions, should increase in the same proportion. Observe, for a moment, a man who is exposed to a moderate degree of :;: There is every reason to believe that these feats are performed by means of a com- position previously applied to the parts abeut to be exposed to the high temperature. 167 cold, he feels more activity, more strength, and is more nimble, he walks and exerts himself, the most violent exertions do not appear to him labori- ous, he struggles against the disadvantages of the debilitating influence ; and provided the cold is not excessive, and the body tolerable vigorou-, there i* disengaged, within himself, a sufficient quantity of caloric to make up for the loss of that which is carried off by the air and the surrounding bodies. These general effects of cold are not disproved by what happens, when only a part ofthe body is exposed to it. Supposing the temperature a few degrees below zero, there is felt, at first, a sensation of cold much more inconvenient, caeieris paribus, than if it acted on a more extensive surface. The spot on which the cold air acts, becomes affected with a painful sense of pricking, reddens, then inflames ; and in this case, inflam- mation is evidently the result of a salutary effort of nature which deter- mines into the inflamed part, an excess of the vital principle, so that the quantity of heat that is disengaged may correspond to that which has been abstracted. The effort of this conservatory principle is more marked, than if the whole surface of the body were at once exposed to cold, be- cause, acting wholly on a limited point, of small extent, it operates with more intensity. Beyond a certain degree, however, nature in vain struggles against cold ; if severe, and if the creature exposed to it, have not the power of suffi- cient re-action, the part becomes purple and benumed from the loss of its caloric, vitality ceases, and it mortifies ; and if the whole body is equal- ly exposed to the influence of cold, the per-on is benumed, feels a stiff- ening of his limbs, stammers, and overpowered by an irresistable propen- sity, yields to a sleep which inevitably ends in death. By yielding thus to the illusive sweets of a perfidous sleep, many travellers have perished af- ter losing their way, in the mountains of the old and of the new world. I jThus, two thousand soldiers of Charles the Twelfth's army perished, dur- hling a siege, in the severe winter of 1709. *■* To resist the effects of cold, a certain degree of strength and vigour is therefore necessary ; it is consequently very injudicious to recommend ■the cold bath to very young children, to delicate and nervous women, to » 'persons whose constitution is not capable of a sufficient re-action. The I 'evil attending the injudicious use of this remedy in the cases that havejust ||jbeen enumerated, justifies the apparently singular terms in which Galen expressed himself: " Let the Germans, (says this first of physiologists) let fM.the Sarmatians, those northern nations as barbarous as bears and lions, . plunge their children in frozen water ; what I write is not intended for ;• them." On the other hand, if it be recollected, that there is within us a power | of re-action, which increases with use, that motion strengthens our organs, it will be readily understood, that cold acts as a tonic, whenever it is not applied to such a degree, as to extinguish the vital power. The manner in which enlightened phvsicians have, at all times, pres- h Scribed thecold bath, shews that they were acquainted with this tonic effect * depending, not on the application of cold, which in itself is debilitating, but on the re-action which it occasions. Hence along with the cold bath, they are in tbe habit of recommending exercise, a generous wine, bark, nutritious food, and an analeptic regiment, calculated to excite a salutary re-action. H LXXXII. Animal heat is, therefore, produced by the combination of || our fluids and solids in the process of nutrition ; it is a function common I to all the organs, for, as they all nourish themselves, so they all disen- 168 gage, more or less, the caloric combined with the substances which they apply to their nutrition. Though we are without precise information respecting the manner in which a living body resists the admission of a decree of heat exceeding that which is natural to it, one may consider cutaneous exhalation, which is increased by the use of heating substances, as the most powerful means employed by nature to get rid ofthe excess of heat, and to restore the equilibrium. Lastly, the body resists cold, because the organs being rendered more active by cold, t: ere is disengaged a quantity of caloric equal to that which is carried off by the air, or by the other substances with which the body happens to be in contact * LXXXIII. The rapidity of the circulation of the blood through, the lungs, is equal to the velocity with which it flows in the other organs. For, if on the one hand, the parietes of the right ventricle and of the pulmonary artery, are weaker and thinner than those of the left ventri- cle and aorta, the lungs, from their soft, easily dilated and spungy tex- ture, are the most easily penetrated by fluids of all our organs. The right ventricle sends into the lungs a quantity of blood, equal to that which each contraction of the left ventricle propels into the aorta, and it is not necessary to adopt the opinion of M. Kruger, that each con- traction ofthe heart sends into the lungs, and into the rest ofthe body an equal quantity of blood, for, in that case, the circulation would have been much slower, the length ofthe lungs being much shorter than the whole body. Nor need we say, with Boerhaave, that this circulation is much more rapid, because the same quantity of blood returns by tbe extremi- ties ofthe pulmonary artery, and of all the other arteries ofthe body. The extension ofthe pulmonary tissue, the straightening of its vessels are, no doubt, favourable to the circulation ofthe blood, but if the admis- sion of air did not answer a different purpose, the circulation would not be indispensably necessary. The blood flows from the right into the left cavities of the heart, notwithstanding the collapse of the lungs and the creases of their vessels. The air which penetrates, at all times, into the lungs, supports their tissue and the vessels which are distributed to it, so that even during expiration, the vessels are much less creased, than has been imagined by several physiologists. But the changes produced by the contact of the atmosphere, renovate this fluid, and fit it to re-excite and keep up the action of all the organs, which require to be stimulated by arterial blood. If you make a living animal breathe de-oxygenated air, the blood undergoes no change by its pulmonary circulation; the left cavities ofthe heart are no longer duly irritated by this fluid, which preserves all its venous qualities ; their action becomes languid, and with it that of all the organs ; and in a little while, it ceases altogether. It is revived by introducing pure air, through a tube fitted to the trachea ; all the parts seem to awake out of a sort of lethongic sleep ; in which they are again immersed, by depriving the lungs anew ofthe vital air. * The animal economy resists a moderate degree of cold, and is even strengthened by it, owing to the re-action of the vital influence. If, however, the degree of cold be either absolutely or relatively great, the energy of the system is entirely over- whelmed by its sedative operation. The effects of cold differ not only according to its degree, but also according to the duration of exposure to it—to the state of the nervous system previous to, or during the exposure—and to the general condition of the body at the time. 169 The chyle, mixed in great quantity with the venous blood,undergoes, in its passage through the heart and the sanguineous system, a more vio- lent agitation ; its molecules are struck together, break on each other, and, thus attenuated, become more perfectly intermingled : in its passage through the lungs, a great part of this recrementitious fluid is deposited by a sort of internal perspiration, in the parenchymatous substance of these viscera. Oxydated by the contact of the air, re-absorbed by a mul- titude of inhalent vessels, it is carried into the bronchial glands, which are found blackened by what it there deposites of carbonic and fuliginous matter. Purified by this elaboration, it returns into the thoracic duct, which pours it into the subclavian vein, whence it soon returns to the lungs, to be there anew subjected to the action of the atmosphere ; so that there is effected, through these organs, a real lymphatic circulation, of which the object is to bring on the chyle to a higher degree of ani- malization. LXXXIV. Of pulmonary exhalation. It will be remembered, that one ofthe great differences between the blood ofthe arteries, and that ofthe veins, consists in the great quantity of serum found in this last. It is in the lungs that the separation of this aqueous part takes place, and that its proportion is reduced, whether it be, that oxygen gives albumen and ge- latine a greater tendency to concrete, or that the serum, formed by the fixation of oxygen throughout the whole extent ofthe circulatory system, exhales from the arteries, and thus furnishes the matter of pulmonary exhalation. It is scarcely possible to admit the combination of oxygen with the hydrogen of the venous blood, and that water is thus formed from its elements, as happens when storms are gathering in the high regions ofthe atmosphere. If a similar process can be carried on in the lungs, without producing deflagration and the various phenomena attend- ing the production of aqueous meteors, it is probable, that it furnishes but a small part ofthe exhalation ; and that this humour, analogous to the serum ofthe blood, exhales, completely formed, from the arterial capil- laries ramified in the bronchia? and the lobular tissue of the lungs. It is believed, that the quantity of the pulmonary exhalation is equal to that of the cutaneous exhalation (four pounds in twenty-four hours.) These two secretions are supplemental to one another : when much water passes off by the pulmonary exhalation, the cutaneous is less, and vice versa. The surface, from which the pulmonary exhalation is given out, is equal, if not superior in extent, to that ofthe skin ; exhalation and ab- sorption are at once carried on from that surface, many nerves are dis- tributed to it, and are almost exposed in the tissue ofthe membranes which are extremely thin. Are the miasmata with which the atmosphere is sometimes loaded, absorbed by the lymphatics, which, it is well known, have the power of taking up gaseous substances ; or do they merely pro- duce on the nervous and sensible membranes of tbe bronchiae, and ofthe lobular tissue, the impression whence the diseases of which they are the germ arise ? A part ofthe caloric which is disengaged in the combinations which oxygen undergoes in the lungs, is taken up in dissolving and reducing into vapour, the pulmonary exhalation which is the more abundant, according as resoiration is more complete. Pulmonary exhalation should be care- fully distinguished from the mucous matter secreted within the bronchiae and trachea, and which is thrown up by a forcible expiration, and forms *he matter of what ^cspit. Q9 17tt LXXXV. Of asphyxia*. The term asphyxia, though merely indicat- ing a want of pulse, is applied to any kind of apparent death occasioned by an external cause and suspending respiration, as submersion, strangu- lation, the diminution of oxygen in the air inhaled, &c. The only diffe- rence between real death and asphyxia, is, that in this last state, the prin- ciple of life may yet be re animated, whilst, in the other, it is completely extinct. . Asphyxia takes place in drowning, because the lungs, deprived of air, no longer impart to the blood which passes through them, the qualities essential to the support of life. The water does not find its way into these viscera ; the spasmodic closing ofthe glottis, prevents its getting into the trachea and its branches. Yet there is found a small quantity in the bronchiae, after drowning, always frothy, because air has mixed with it, in the struggles which precede asphyxia. If the body remain long under water, the spasmodic state of the glottis ceases, water passes into the trachea, and fills the lungs. The anatomical examination ofa drowned body, shews the lungs collapsed, and in the state of expiration ; the right cavities ofthe heart, the venous trunks which terminate in them, and ge- nerally, all the veins, are gorged with blood*, whilst the left cavities and the arteries are almost entirely empty. Life ceases in this kind of as- phyxia, because the heart has sent to the different organs, and especially to the lungs, no blood that is not deficient in the qualities necessary to their action ; and perhaps also, because the venous blood that is accu- mulated in the tissues, affects them by its oppressive and deadly influence. On that account, the best way of restoring the drowned to life, is to blow pure air into their lungs. This is done by means of bellows adapted to a canula introduced into the nostril ; if a proper apparatus cannot be pro- cured, one might blow with one's mouth into that of tbe drowned person, or into his nostrils, by means of a tube ; but air so expired, having alrea- dy undergone the process of respiration, contains a much smaller quanti- ty of oxygen, and is much less fitted to excite the action of the heart. There remain several other less efficacious remedies, such as friction, bronchotomy glysters, fumigations and suppositories, stimulating errhines, and especially ammonia. Stimulants taken into the mouth and stomach, the application of fire, bleeding, the bath, electricity, and galvanism. The redness and lividity of the face, in persons who are hanged, had led to the opinion that death, in such cases, was from apoplexy ; but it appears that in the asphyxia from strangulation, as in that from drowning death is caused by the interception ofthe air. To prove this, Gregory performed the following experiment : he opened the trachea ofa dog, and passed a noose round his neck, above the wound. The animal, though hanged, continued to live and to breathe ; the air entered and came out al- ternately, at the small opening. He died, when the constriction was ap- plied below the wound. A respectable surgeon, who served in the Aus- trian army, assured me, that he had saved the life ofa soldier, by per- forming upon him the operation of laryngotomy, a few hours before his execution. Persons who are hanged may die, however, from dislocation ofthe cer- vical vertebras, and from tbe injury done, at the same time, to the spinal marrow. Louis, it is well known, ascertained, that of the two executioners iu Lyons and Paris, the one dispatched the criminals he executed, by dis- f See APPENDIX, Note W. * Hence the dark and livid colour of the skin and conjunctiva. This last mem- brane is frequently injected with dark blood ; the very delicate veins ofthe brain are considerably dilated, and this viscus is distended with venous blood 171 locating the head at its articulation with the neck, while the other execu- tioner destroyed them, by inducing asphyxia. Of the different mephitic gases unfit for respiration, some appear to bring on asphyxia, merely by depriving the lungs ofthe vital air necessary to the support of life, while others evidently affect the organs and the blood which fills them, by their poisonous and deleterious influence. One may mention amo'.g the former, carbonic acid ; in the asphyxia occasioned by this gas, and which of all others, is the most frequent, the blood preserves its fluidity, the limbs their suppleness, and the body its natural warmth, or even a greater degree of warmth, for some hours after death ; for, this kind of asphyxia occurring always in a very hot situation, the body deprived of life, admits an excess of caloric, such as would have been resisted, if the vital power had not been suspended. However, in this asphyxia, as in the preceding, the lungs remain uninjured ; the right cavities of the heart and the venous system, are gorged with a dark but fluid blood. In the asphyxia, on the other hand, that is occasioned by sulphureted or phosphureted hydrogen, &c. or by certain vapours whose nature is not well understood, and which escape from privies, or from vaults in which a number of dead bodies undergo putrefaction ; there are frequently found in the lungs, dark and gangrenous marks, and death seems the effect ofa poigon which is the more active, as its particles, exceeding- ly divided and in a gaseous state, are more insinuating, and affect through- out its whole extent, the nervous and sensible surface ofthe lungs. Inebriation seldom goes the length of bringing on asphyxia, it most com- monly produces a stupor readily distinguished from the affection treated of in this article, by the perceptible, though obscure pulse, and by the motions of respiration, though these are rare and indistinct. On this ac- count, M. Pinel, in his JVosographic Philosophique, has placed inebriation and the different kinds of asphyxia, in two separate genera of the class neuroses. It is conceivable, however, that the muscular irritability may- be so far impaired by the use of spiritous liquors, that the heart and dia- phragm might lose the power of contraction, which would bring on com- plete asphyxia. The glottis, through which the atmospherical air passes in its way to the lungs, is so small, that it may be readily obstructed, when the epiglot- tis rising at the moment of deglutition, the substance that is swallowed stops at the orifice of the larynx ; a grape seed may produce this effect, and it was in this manner, we are told, that Anacreon, that lovely poet of the graces and of voluptuousness, came by his death. Gilbert, the poet, died in the same way, after a long and painful agony. A great eater, in the midst ofa feast, went into an adjoining room, and did not return, to the great surprise of all the guests. He was found stretched on the floor, without any sign of life. Help, given by ignorant people, was of no use. On opening the body, a piece of mutton was found fixed in the larynx, and completely stopping tbe passage ofthe air. Sometimes a child is born, md shows no signs of life. When it is pro- bable from the circumstances ofthe delivery, that there has been no or- ganic'injury decidedly mortal, it must be considered as a case of asphyxia, from weakness ; and all means employed that are recommended in such cases especially blowing in air into the lungs, by means oi a tube intro- duced into the mouth or nostrils. It is thus, that the Prophet Elisha re- stored to life the son ofthe Shunamite, as we are informed, in the second lbook of Kings, Chapter the fourth. LXXXV1. Of certain phenomena of respiration, as sighing, sobbings yawning, sneezing, coughing, hiccup, laughing, <$rc. When the imagination is strongly impressed with any object, when the vital luuctiuns are languid, the vital principle seems to forsake all the organs, to concentrate itself on those which partake most in the affection ofthe mind. When a lover, in the midst of an agreeable reverie, sighs deeply, and at intervals, a physi- ologist perceives in that expression of desire, nothing but a long and deep inspiration, which, by fully distending the lungs, enables the blood, col- lected in the right cavities of the heart, to flow readily into the left cavi- ties of that organ. This deep inspiration which is frequently accompa- nied by groans, becomes necessary, as the motions of respiration rendered progressively slower, are no longer sufficient to dilate the pulmonary tissue. Sobbing differs from sighing, merely in thi j, that though the expiration is long, it is interrupted, that is, divided into distinct periods. Yawning is effected in the same manner ; it is the certain sign of ennui, adisagreeable affection, which, to use the expression of Brown, may be considered as debilitating or asthenic. Tbe fatigued inspiratory muscles have some difficulty in dilating the chest, the contracted lungs are not easily penetrated by the blood which stagnates in the right cavities ofthe heart, and produces an uneasy sensation, which is put an end to by a long and deep inspiration ; the admission of a considerable quantity of air is facilitated by opening the mouth widely, by the separation of both jaws. One yawns at the approach of sleep, because the agents of inspiration. being gradually debilitated, require to be roused at intervals. One is, likewise, apt to yawn on waking, that the muscles of the chest may be set for respiration, vvhich is always slower and deeper, during sleep. It is for the same reason, that all animals yawn on waking, that the muscles may be prepared for the contractions which the motions of respiration require. The crowing ofthe cock and the flapping of his wings seem to answer, the same purpose. It is in consequence ofthe same necessity, that the numerous tribes of birds in our groves, on the rising ofthe sun, warble, and till the air with harmonious sounds. A poet then fancies he hears the joyous hymn, by.which the feathered throngs greet the return of the God of light. While gaping lasts, the perception of sounds is less distinct, the air, as it enters the mouth, rushes along the eustachian tubes into the tympanum, and the membrane is acted upon in a different direction. The recollec- tion ofthe relief attending the deep inspiration which constitutes gaping, the recollection ofthe grateful sensation vvhich follows the oppression that was felt before, involuntarily leads us to repeat this act, whenever we see any one yawning. Sneezing consists in a violent and forcible expiration, during which the air, expelled with considerable rapidity, strikes against the tortuous nasal passages, and occasions a remarkable noise. The irritation ofthe pitui- tary membrane determines, by sympathy, this truly ronvulsive effort of the pectoral muscles, and particularly ofthe diaphragm. Coughing bears a considerable resemblance to sneezing, and differs from it, only in the shorter period of duration and the greater frequency of the expirations ; and as in sneezing, the air sweeps along the surface of the pituitary membrane, and clears it ofthe mucus vvhich may be ly- ing upon it, so the air, when we cough, carries along with it the mucus contained in the bronchia?, in the trachea and which we spit up. The violent cough, at the beginning of a pulmonary catarrh, the sneezing which attends coryza, show that the functions of the animal economy arenot directed by an intelligent principle, for such an archasus could not mistake, in such a manner, the means of putting a stop to the disease, 173 and would not call forth actions which, instead of removing the irritatio;*, and inflammation already existing, can only aggravate them. Laughing is but a succession of very short and very frequent expira- tions. In hiccup, the air is forcibly inspired, enters the larynx with dif- ficulty, on account ofthe spasmodic constriction of the glottis ; it is then expelled rapidly, and striking against the sides of that aperture, occasions the particular noise attending it. I shall, on another occasion, explain the mechanism of sucking, of panting, and ofthe efforts by which the muscles ofthe thorax fix the pa- rietes of that cavity, so that it may serve as a fixed point of the other muscles of the trunk and of the limbs. Respiration is besides employed in the formation of the voice, but the voice and the different modifications of which it is capable, will form the subject of a separate chapter.* LXXXVII. Of cutaneous perspiration. An abundant vapour is contin- ually exhaling from the whole surface ofthe body, and is called the insen- sible perspiration, when in a state of gas in the air which holds it in sana- tion, it then eludes our sight ; it is called sweat, when in greater quantity and in a liquid form. Sweat differs, therefore, from insensible perspira- tion, only by the condition in which it appears, and it is sufficient for its production, that the air should be incapable of reducing it into vapour, whether from an increased secretion by the skin, or from the dampness and consequent diminished solvent powers ofthe atmosphere, The insen- sible perspiration is constantly escaping through the innumerable pores in the parietes of the minute arteries of the integuments ; it oozes in the in- terstices of the scales of the skin ; the air which immediately surrounds our body, becomes saturated with it, and carries it off, as soon as it is re- newed. There is the greatest resemblance between the cutaneous pers- piration and the plumonarv exhalation ; both are mere arterial exhalations, and the mucous membrane, which lines the canals along which the air is transmitted, is a mere prolongation of the skin into those organs and into * The author has neglected to notice the state of respiration during the more active voluntary motions. Muscular exertion, especially when considerable, is preceded by a long and deep inspiration, the glottis is closed, the diaphragm and respiratory mus- cles of the chest are contracted, and the reaction of the abdominal muscles cause the contents of the abdomen to be pressed upon in all directions. At the same time that the respiratory muscles are exerted, those ofthe face are associated, in the increased action, in consequence of the latter receiving some nerves from the same class, (see the notes in the APPENDIX on the different orders and functions of the 'voluntary system of nerves) and the jaws are forcibly pressed together. By this action of the muscles engaged in respiration, the chest is rendered capacious, and the strength is greatly increased, because the trunk of the body is thus rendered immovable in re- spect to its individual parts, the muscles arise from fixed points, and, consequent- ly, wield the members of the body with their full energy. Haller appears to be correct in concluding that, under a state of increased action of the muscles, the flow of blood becomes greater towards the head, and thus the nervous energy is in- creased, and amply generated, by means of this augmented flow, so as to keep up the muscular action for a longer period than otherwise would be the case. During vio- lent exertions, also, the return of blood from the brain is in some degree impeded. The physiological state of muscular actions, as they are related to the mechanical function of respiration, is very happily described by Shakspeare, where he makes the fifth Henry encourage his soldiers at the siege of Harfleur:— Stiffen the sinews, summon up the blood, ft * a- ■* * tf- -r * * * * * Now set the teeth, and stretch the nostrils wide ; Hold hard the breath, and bend up every spirit, To his full height. In vomiting also, and in the action of expelling the faeces and contents ofthe blad- der, the thoracic and abdominal muscles of respiration are breught into action. 174 the digestive tube. The surface from which the cutaneous perspiratioo is exhaled, is not quite so considerable as that from which the pulmonary exhalation arises, since it is reckoned at only fifteen square feet, in a man of middle size These two secretions are supplementary to each other; the increase ofthe one is generally attended with a sensible diminution of the other ; lastly, the mucous membrane of the intestinal canal, besides secreting mucus, exhales likewise a fluid which increases much in quanti- ty, when the cutaneous perspiration is languid, as is proved by the serous diarrhoeas so frequently occasioned by a suppressed perspiration. It must be owned, however, that notwithstanding those analogies of structure and function, in the skin and mucous membranes, there exists perhaps a still more intimate connexion between its action and that of the organs which secrete the urine ; it has always been observed, that when this last fluid is scanty, there is a greater cutaneous perspiration, and vice versd. If we examine, with a microscope, the naked body, exposed during summer to the rays of a burning sun, it appears surrounded with a cloud of steam, which becomes invisible, at a little distance from the surface. And if the body is placed before a white wall, it is easy to distinguish the shadow of that emanation We may, likewise, satisfy ourselves of the existence of the cutaneous perspiration, by the following experiment : hold the tip of the finger, at the distance of the twelfth part of an inch from a looking-glass, or any other highly polished surface, its surface will soon be dimmed by a vapour condensed in very small drops, which disap- pear on removing the finger. One may, in this man ier, ascertain that the cutaneous perspiration varies in quantity, in different parts of the surface of the body, for, on placing the back of the hand before a looking-glass, the latter will be covered by no vapour. No function of the animal economy has been the subject of more in- vestigation, nor has any excited the attention of more accurate and inde- fatigable physicians, than the secretion now under consideration. From the time of Sanctorius, who, in the beginning of the seventeenth century, published in his immortal work, " Medicina statica," the result of experi- ments carried on, for thirty years, with a patience which very few will imitate, to that of Lavoisier, whojointly with Seguin, aided by the resour- ces ofthe improved state of chemistry, instituted an examination ofthe in- sensible perspiration, we find engaged in this enquiry, Dodart, who in 1668 communicated to the Academy of Sciences, which had been founded but a short time, the resultofhis observations at Paris, under a climate dif- ferent from that of Venice, where Sanctorius lived :—Keill, Robinson, and Rye, who repeated the same experiments in England and Ireland :—Linnings, who performed his in South Carolina ; and several physiologists of no less merit, as Gorter, Hartmann, Arbuthnot, Takenius, Winslow, Haller, &c. who all aimed at ascertaining, with more precision than had been done by Sanctorius, the variations in the cutaneous perspiration, accord- ing to the climate, the season of the year, the age, the sex, the state of health, or disease, the hour ofthe day, and the quantity of other secretions. According to Sanctorius, of eight pounds of solid and liquid aliments taken in twenty four hours, five were carried off by the perspiration, and only three in excrement and urine. Haller conceives this calculation to be exaggerated ; Dodart. however, carried it still further, and maintained that the relation of the perspiration to the solid excrements, was as seven to one. In France and in temperate climates, the quantity ofthe cutaneous per- spiration, and ofthe urine, is nearly the same ; it may be estimated at be- tween two anil four pounds in the twenty-four hours. We perspire most 175 m summer, and void most urine in winter. The perspiration/hke every other secretion, is u smaller quantity during sleep, than while we are awake ; in old age than during infancy, in weak persons, and in damp weather, than under the opposite circumstances. The perspiration may be said to be in a compound ratio of the force with whicn the heart propels the blood into the minute capillarv arteries, ot the vital energy of the cutaneous or-an, and of the solvent'powers of the atmosphere. The strongest and most robust men perspire most; some parts of the skin perspire more than others, as the palms of the hands, the soles of the feet, the arm-pits, &c. When the air is warm, dry, and frequently renewed, cutaneous perspiration is greater, and the necessity of taking liquid aliment is more urgent, and more frequently ex- perienced ; in summer, as every body knows, a profuse perspiration is brought on by passing from the heat of the sun into the shade ; and, on no occasion, is a copious sweat more easily brought on, than by taking exercise in summer, when on the approach of a storm, the atmosphere containing a small quantity of vapours, and^varm from the rays ofthe sun' which shows itself, now and then, surrounded by the clouds, is little capa- ble of dissolving the insensible perspiration. The skin may be covered with sweat, without any increase ofthe cuta- neous perspiration , this may happen from dampness in the air, or from its being imperfectly renewed. It must be owned, however, that sweat- ing is more frequently occasioned by an increase of the insensible perspi- ration, and that the warmth ofthe bed which excites it, acts by increasing the power of the organs of circulation and the energy of the cutaneous system. The body is weakened by sweating, which is seldom the case with the insensible perspiration. A profuse sweat is attended with a very speedy exhaustion ; thus, in hectic fever, in the suelte (sudor angli- cus) and other affections, equally dangerous, it is the cause of a wasting almost universally fatal. The matter ofthe insensible perspiration and ofthe sweat, is, in great measure, aqueous. Like the urine, it holds in solution several salts, also the volatilized recrementitious matter of animal substances, sometimes even acids, as in the case in which Berthollet detected the phosphoric acid in children affected with worms, in pregnant women, in nurses, from whom there exhales an odour manifestly acid. It may contain ammonia, and, on certain occasions, the smell enables us to discover that alkali, in the sweat or perspiration. The air which constantly surrounds our body, does not merely dissolve the aqueous vapour which arises from it, but several physiologists very reasonably conjecture, that the oxygen of the atmosphere may combine with the carbon ofthe blood brought to the skin by the numerous vessels which are sent to it, and likewise with the gelatine forming the substance ofthe rete mucosum ofMalpighi. The experiments of Jurine, ofTingry, and of several other naturalists, show that carbonic acid is constantly formed on the surfice ofthe skin, so that the skin may be considered as a supplementary organ to that of respi- ration *, and in that point of view, one may compare to it, the mucous membranes which are in contact with the atmospherical air in the nasal fossae, and in the intestinal canal which they line. The cutaneous perspiration is, likewise, as was before mentioned, a powerful means of cooling the body, and of keeping it while living, in an uniform temperature. The water which is exhaled from the whole sur- face of the body, carries off from it, in passing into vapour, a considera- ble quantity of caloric ; and it is observed that every thing which increase? 176 the production of caloric, gives rise to a proportionate increase ofthe cu- taneous perspiration and of the pulmonary exhalation, so that a constant equilibrium being kept up between its production and escape, the animal warmth always remains nearly the same*. To conclude, the extremities of the nerves of our organs of sensation, are all moistened by a fluid varying in quantity, and which maintains them in a softened state, favourable to the exercise of their functions. It was likewise necessary, that the membrane in which the sense of touch resides should be habitually kept moist by a fluid that should penetrate it through- out : this use ofthe insensible perspiration is not less important than the preceding, on which physiologists have bestowed most attention. CHAPTER V. OF THE SECRETIONS. LXXXVUI. Of the animal fluids. The animal fluids were formerly divided into recremeniitioxis, excrementitious, and excremento-recrementi- lious ; this division, founded on the uses to which the fluids are subser- vient, is preferable to any that has since been adopted, and in which they are ranked according to their nature. The first class remain in the body, and are employed in its nutrition and growth ; such as the chyle, the blood, the serosity which lubricates the surface ofthe pleura, ofthe peritoneum, and of the other membranes ofthe same kind. The second kind are ejected from our body, and can- not remain long within it, without danger ; such as tbe urine, the matter of insensible perspiration and of sweat. Lastly, those of the third class partake of the nature of the two preceding, and are, in part, rejected, ■while another part is retained and employed in the support and growth ofthe organ ; this is the case with the saliva, the bile, the mucus of the intestines, &c. If one affected to be very minutely scrupulous, one might consider all the animal fluids as recremento-excrementitious. The chyle and the blood, which are so very nutritious, contain an abundance of heterogeneous and excrementitious parts ; the urine, which of all our fluids is that which may, with most propriety, be termed such, contains, likewise, aqwebus parts, which, while it remains in the bladder, the lymphatics absorb and carry into the mass ofthe fluids. Of all the modern divisions, Fourcroy's is the best; Vicq-d'Azir ac- knowledged its superiority over that proposed by Haller, in his Physiolo- gy. Fourcroy admits six classes of fluids : 1st, those which hold salts in solution, as the sweat and urine ; he gives the name saline to such fluids : 2nd, inflammable oily fluids, all possessing a certain degree of consistence * If transpiration be restrained or slopped, and if the causes productive of Jieat act with intensity, it would appear that the temperature of the surface of the body rises some degrees; hence the reason that the heat is so distressing in those diseases which are characterized by diminished transpiration, and in which the dryness of the skin is i so remarkable, as erysipelas, erythema, &c. M. M. Berger and Delaroche have sup- posed that they have seen, when the air ofa room is saturated with humidity and ren- dered very warm, that the human body exposed to this atmosphere acquires a higher temperature than is natural to it, the cutaneous and pulmonary transpiration either being altogether arrested or imperfectly performed For farther observation.? on thi" subject, see APPFNDIX, Note Z. 177 aud concrescibility, as fat, and the cerumen of the ears, fcc; 3d, the sa- ponaceous fluids, as the bile and milk ; 4th, the mucous fluids, as those which lubricate the internal coat ofthe intestinal canal ; 5th, the albu- minous fluids, among which one may rank the serum of the blood ; 6th, the^&rmows fluids, containing fibrina, as the fluid last mentioned.* In proportion as we advance in our knowledge of animal chemistry, the defects of these divisions become more and more evident. In short, the animal fluids are so compound, that there is not one which does not, at once, belong to several of these classes, and whose prevailing element is not sometimes exceeded in quantity, by materials which commonly form but a small part of them. LXXXIX. The blood is the reservoir and the common source ofthe fluids ; these do not exist in the blood, with the qualities which characte- rize them, unless, after having been previously formed by^he secretory organs, they have been absorbed by the lymphatics, and conveyed, with the chyle and lymph, into the circulatory system. Let us shortly attend to its nature, although this belongs more especially to the department of chemistry. The blood is red in nun, and in all warm-blooded animals, and even in some whose temperature i« not very different from that ofthe atmosphere as in fishes and reptiles. This colour, of a deeper or light- er shade, according as the blood is drawn from an artery or a vein, varies in its degree of intensity, according to the state of health or weak- ness. It is of a deep red in strong and active persons, pale and colour- less in dropsical patients, and whenever the health is weak. By its co- lour one may judge of all its other qualities. Its viscidity is greater, its sa- line taste more marked, its peculiar smell stronger, when its colour is deep. This colour is produced by a prodigious number of globular molecules, which move and fluat in an aqueous and very liquid fluid. When the blood is. pale, the number of these molecules diminishes, they seem to be dissolved in cachexias. The microscope, which affords the only method of perceiving them, does not enable one to determine their bulk and their figure. Leeu- wenhoek, who brought forward the idea of their being so minute, by his calculation that they were one millionth part of an inch in size, thought them spherical. Hewson says they are annular, and have an opening in their centre, Others compare them to a flattened lentil, with a dark spot in the middle. They are solid, and formed by a nucleus or red point, covered over by a membranous vesicle, which appears to be rea- dily formed and destroyed. XC. The blood, when no longer in the course of the circulation, and on bein<* received into a vessel, parts with its caloric, and exhales, at the same time, a powerful smell, a gas to which according to some physio- logists (Moscati. Rosa &c), it owes its vital properties, and the absence of which is attended with a loss of its vitality ; so that its analysis cannot furnish facts applicable to the explanation of the phenomena of health and disease. This odour, extremely strong in carnivorous animals, is ve- * Berzelius distinguishe* the fluids formed from the blood into secretions proper- ly so called, and excretions, or those wh.ch are directly discharged fro« the body. The former class of fluids is destined to perform a farther office in the animal econo- my-all of these arealcaline; they are the bile, the sal.va, and the fluid which is secreted on the mucous and serous surfaces. In the latter division, acids predominate, the excretory fluids embrace the urine, the cutaneous and pulmonary transpiration, and the milk. Magkjtdie divides the secretions into exhalations, follicular teere- tions, and glandular secretions. See APPENDIX, Note A A, for farther observations oa this subject. I7U ry distinguishable in man, especially in arterial blood. 1 remember re- taining it, a whole day in my throat, after removing the dressings, and -suppressing a hemorrhage, occasioned by a relaxation of the ligatures, a week after the operation for popliteal aneurism. Uuless by agitation it is prevented from coagulating, as it cools, its consistence increases, and, on being laid by, it separates into two very different parts, the one aque- ous, more or less red, heavier than common water, and evidently saltish ; this is called the serum, consisting of water, in which are dissolved albu- men, gelatine, soda, phosphates, and muriates of soda ; nitrate of potash, and muriate of lime. Serum, though bearing some analogy to the albumen of egg, differs from it, in forming, on coagulating, a less solid and less homogeneous mass. The albumen is evidently mixed with a portion of transparent gelantine, not coagulable by heat. Albumen has so great an attraction for oxygen, that it is fair to presume, that the serum absorbs oxygen and combines with it, through the very thin parietes of the air cells of the lungs, and that it gives to the arterial blood that spumous appearance which is one of its distinguishing characters. This oxidizement, and the fixation ofthe caloric which accompanies it, equally increase its consistence. It does not, however, coagulate ; because it is.kept in perpetual motion by the circulatory action, and is diluted by a sufficient quantity of water ; be- cause the animal temperature, which never exceeds thirty-two or thirty- four degrees, cannot give a solid form to albumen, which coagulates only at fifty degrees of Rea timer's thermometer ; and lastly, because as serum contains a certain quantity of uncombined soda, which enables it to turn green vegetable blues, this alkali concurs in keeping the albumen in a dissolved state, which it renders fluid, when it has been coagulated by the acids, by heat, or by alcohol. Amid the serum, and on its surface, there floats a red cake, spungy, and solid, (insula rubra which, by repeated washing, may be separated into two very distinct parts. The one is the cruor or the colouring mat- ter which mixes with the water ; it is a more highly oxygenated and more concrescible albumen than that of the serum ; it holds in solution soda, as well as phosphate of iron, with an excess of iron.* The other is a solid and fibrous substance, which, after being repeat- edly washed, has the appearance of felt, the filaments of which cross each other, are extensible and very elastic. This third part ofthe blood is called fibrina, it is very similar in its nature to muscular fibre, and like it, gives out, on distillation, a considerable quantity of carbonate of am- monia. Fibrina does not exist in the blood in a solid form, but in a state * It is a more oxygenated and a more coagulable albumen than that of the se- rum. The colouring part of the blood, when incinerated, after giving off a consider- able quantity of ammonia during the combustion, leaves ashes which, according to Berzelius, are only a hundredth part of its weight, and which contains 55 parts ofthe oxide of iron, 8£ ofthe phosphate of lime, a little of magoesia, 17£ parts of lime, and 16£ of carbonic acid. The oxide of iron is neither found in the ashes of the coagulable part of the serum, nor of those of the fibrine. Berzelius, however, farther informs us, that the serum, although able to dissolve a small portion of the oxides of iron, but not of its phosphates, does not acquire a red colour by this weak solution, and that he has neither detected iron nor lime in the entire blood, although both are so abundant in its ashes. He therefore concludes, that the blood contains the elements only of the phosphate of iran, and of lime and magnesia, and of the carbonate of lime, united very differently from their combination of these salts. Nor is it unlikely that these salts are formed during incineration, from the presence of the elements of their res- pective bases in the blood, either in an' uncombined, or in a differently combined form, the other elements being partly furnished by this fluid also, and partly by the atmos- phere, during the incineration. 179 of solution, and combined with the other constituent parts of the fluid, as is indicated by the appropriate expression of liquid flesh (chair cou~ lante) first used by Bordeu. in speaking of the blood. XCI. If the blood be exposed to the action of fire, if it be calcined and reduced to powder, and if this pulverized substance be exposed to a magnet, the presence of iron will be manifestly seen by the magnetic at- traction. Authors do not agree in their accounts of the quantity of iron contained in the blood. Menghini says, there is one part in the hundred ; others that it is in the proportion of 1 to 303 ; so that it is probable, that this constituent principle of the blood, like all the materials of our fluids, may vary in quantity, according to different circumstances. Blumenbach justly observes that iron is fouud only in calcined blood ; that none is to be found if it be slowly dried. This peculiarity is no long- er surprising, since M. Fourcroy has shown that iron existed in the blood, in combination with the phosphoric acid, and formed with that acid a phosphate of iron, with an excess of its base. This salt becomes decom- posed by calcination, the iron is set free, and is acted upon by the magnet. Physiologists attribute the colour of the blood to the presence ofthe ox- ide of iron in that fluid. It has been the received opinion, that the red colour of the blood is owing to the presence of phosphate of iron, which, being conveyed, ofa white colour into the blood, along with the chyle, meets with the pure soda, by which it is dissolved, and from which it receives its colour ; the colour ofthe blood is, likewise owing to the oxidizement ofthe metallic portion, which is in very considerable quantity in that salt. This solu- tion of the phosphate of iron by soda, the oxidizement of the excess of the recess of iron, and the absorption of oxygen by albumen, constitute, in an especial manner, hematosis or sanguification, which is principally carried on in the lungs.* The respective proportion ofthe three parts into which the blood se- parates spontaneously, varies considerably. The serum constitutes about one half or three fourths of the fluid ; the colouring matter and fibrina are in inverse ratio of the serum, and it is observed, that the more bril- liant and red the colour of the blood the greater tbe proportion of the fibrous part. The pale, aqueous, and colourless blood of a dropsical patient contains very little fibrina. In putrid or adynamic fever, in which bleeding, as is universally known, is improper, I have sometime- seen the blood containing but a small portion of fibrina, and very slow of co- agulating ; its texture seemed to suffer from the affection under which the muscular organs were evidently labouring. In infl immatory diseases, on the contrary, the plastic power ofthe blood is augmented ; the fibrina is in greater quantity, even the albumen coagulates spontaneously, and forms a crust above the serum, which is always in smaller quantity!. XCII. Of the changes on the blood. The fluids not only undergo changes in their composition, in their qualities and nature, when the action ofthe * This opinion of Fourcroy respecting the source whence the blood acquires its red colour, has, since his time, been adopted by some, and combated by other physio- loffists It is now entirely abandoned, because it is known that the colouring part oi this fluid may be obtained separately, and entirely exempt from iron. This colour- ing portion of the blood, according to M. VAtrawELiN, does not change its colour when triated with gallic acid-a farther proof that it contains no iron t According to Mr. Brande and Sir E. Home, both venous and arterial blood con^ tains carbonic acid in the proportion of two cubic inches of the gas for each ounce of blood. This acid disengages itself immediately when a portion of the warm blood is placed in an air-pump. See APPENDIX, Note B B, for farther remarks respecting the blood. 180 solids is itself altered, but even the absorbent system may introduce, into the mass of our fluids, heterogeneous principles, evidently the cause of several diseases. In this manner, all contagions spread, the virus of small-pox. of syphilis, of the plague, &c. Thus, in time, the habitual use of the same aliment produces in our fluids a crasis or peculiar con- stitution which has, on organized solids, an influence acting even on the mind. A purely vegetable diet conveys into the blood, according to Pythago- ras, bland and mild principles : this fluid excites the organs, in a moder- ate degree, and this check over the physical excitement, facilitates the observance ofthe laws of temperance, the original source of all virtue. These observations of ancient philosophy, on the influence of regimen, have, doub'less, led their authors to exaggerated inferences, but they should not be considered as altogether unsupported. The carnivorous species are marked by their strength, their courage, and their ferocity ; savages who live by hunting, and who feed on raw, bloody, and palpitating flesh, are the most ferocious of men ; and, in our country, in the midst of those scenes of horror which we have witnessed, and from which we have suffered, it was observed, that butchers were foremost in the massa- cres, and in all the acts of atrocity and barbarity. I know that this fact, which was uniformly noticed has been explained by saying, that the habit of slaying animals, had familiarized them to shed human blood. But though 1 do not deny the existence of this moral cause, which cer- tainly operates, I think i may add to it, as a physical cause, the daily and plentiful use of animal food, the breathing an air filled with emanations of the same kind, which they inhale, and which contribute to their em- bonpoint, which is sometimes excessive. As the plasticity and concrescibility of tbe blood are diminished in as- thenic diseases, or of debility, as putrid fevers and scurvy, two causes may be assigned for the hemorrhages which come on in those diseases, viz. the relaxed state of the vessels and the dissolution ofthe blood. In scurvy, the tissue of the capillaries is relaxed, its meshes enlarged, red blood passes intothem, transude* through their parietes, and forms scorbutic spots. I have sometimes seen those ecchymoses or sanguineous cutaneous transudations, extend under the skin of the whole of one lower extre- mity. Petechiae, in putrid fever, are formed in the same manner, and depend, likewise, on the relaxation of the minute vessels, and on the greater fluidity of the blood, whose molecules are less coherent, and more readily separated from each other. In the summer ofthe year i8Ul, I amputated the arm of an old man of sixty, on account of a corroding and varicose ulcer, which for thirty years had occupied a part of the fore arm, and extended to the elbow. all who were present at this operation, observed that the blood which flowed from the arteries, was not nearly so red as that from the arteries of a young man, whose thigh had just been taken off, on account of a scrophulous caries of the leg; that the venous blood was entirely dis- solved, purple, and similar to a weak dye of logwood. This blood did not coagulate, like that of the young man, it became fluid, and was con- verted into a serum containing a few colourless clots. Those who have endeavoured to find, in the changes undergone by the blood and tbe other fluids, the cause of all diseases, have fallen into as serious blunders as the determined solidists, who maintain that all diseases arise from a deranged condition of the solids, and that every change in the condition of the fluids is a consequence of that derange- ment. The believers in the humoral pathology, have certainly gone too 181 far ; they have admitted that the animal fluids might be acid, alkalescent, acrimonious, while we have no proof whatever that they ever do under- go such changes. The sohdists have, likewise, gone much beyond the truth, in saying, that every primitive change in the condition of the fluids is imaginary, and that the doctrine of humeral pathology i* without foun- dation. Stahl relates* that the blood of a young woman, who was bled during a fit of epilepsy, was absolutely coagulated, as if that fluid had partaken in the rigidity affecting the muscular organs. Some authors say they have met with the same appearance ; I have, however, never been able to discover any sensible difference between the blood of an epilep- tic patient and of any other person of the same constitution, of the same age, and living on the same regimen ; and it should be considered, that to make a just comparison of our fluids, it is necessary that every thing should be alike in the persons from whom they are taken, with the ex- ception of the difference of which we are to judge. In fact, the blood has not the same appearance, and does not coagulate, in the same manner, when taken from a child, a woman, or an old man ; from a man who lives abstemiously, or from one who lives on a full diet. After enumerating the changes which the blood undergoes, one might speak of those which affect the fluids that are formed from it, one might attend to the greenish, leek colour, and sometimes even darkish appear- ance of the bile, which is not always of the same degree of bitterness ; the liquid state ofthe urine, which is voided colourless, without smell or flavour, after a fright, or during the convulsive fits of hysterical women ; the foetid smell and the viscidity of the saliva, when the salivary glands are under mercurial influence ; the milky state ofthe serum which lubri- cates the parietes of the abdomen and of the viscera which it contains, after inflammation of the peritoneum ; changes which almost universally depend on a derangement of action in the secretory organ, and sometimes, likewise, on the general condition of the fluids ; for, a gland cannot se- crete a fluid endowed with the qualities which peculiarly belong to it, unless the blood furnish it with the materials of secretion, and unless it be in a state to bring about a due combination of their particles. When we come to the article of accidental secretions, we shall speak of some of those disorders of the fluids, depending on a depraved condition of the secretory organs!• XCIII. On the transfusion of blood. In the midst of the disputes to which the discovery ofthe circulation gave rise, some physicians conceiv- ed the idea of renovating completely the whole mass o! the fluids, in per- sons in whom they might be vitiated ; by filling their vessels with the blood of an animal, or a person in good health. Richard Lower, known by his work on the heart, first practised it on dogs, in lt>b"6. > wo years afterwards, transfusion wa» performed at Paris on men : it excited the greatest expectations : it was thought, that by this process, called trans- fusing surgery (chirurge transfuse ore,) all remedies would be superseded, that henceforth, to cure the most serious and inveterate diseases, it would be necessary merely to transfuse the blood of a strong and healthy man into the veins ofthe diseased ; nay, they went so far as actually to imagine they might realize the fabulous fountain of Jouvtnce; they expected no less, than to restore youthful vigour to the old, by infusing into them the blood of the young, and thus to perpetuate life. All these brilliant chime- * Theoria medica vera, page 678. T For additional remarks on the changes observed, under various influences and cir- cumstances, in the condition of the Hood, and on its transfusion, see APPENDIX, Note R B. 182 ras soon vanished, some underwent the experiment, without any remark^ able effects from it, others were affected with the most violent delirium ; a lad of fifteen lost his senses, after suffering two months from the most violent fever. The legislative authority at last interfered, and prohibited those dangerous experiments. The experiments on the subject ofthe transfusion of blood were repeat- ed, hut without success, at the Academy of Sciences. Perault opposed this new method, and showed that it was very difficult for one animal to exist on the blood of another, that this fluid, though apparently tbe same in animals ofthe same age, was as different from it as the features of their face, their temper, &c. that an extraneous fluid was thus introduced, which conveying to the organs an irritation to which they were not accustomed, must disorder their action, in various ways ; that if, as an objection to what he had said, they should bring forward what takes place in graft- ing, in which the sap of one tree nourishes another ot a different kind, he would answer, that vegetation does not depend on so complicated, nor on so delicate a mechmism, as the nutrition of animals ; that a hut may be formed of all kinds of stones taken at random ; but that to build a palace, stones must be designedly shaped for the purpose, so that a stone destined for an arch, will not do for a wall, nor even for another arch*. It would be easy, by means of a curved tube, to transfuse the arterial blood of an animal, from a wound in its carotid artery, into the saphena vein of a man, into the internal jugular, or into some ofthe cutaneous veins of the fore arm ; but it is to be presumed from experiments on living animals, that it would be very difficult to transfuse blood into the arteries, as these vessels, tilled with blood, during life, do not yield to a greater distension. The capillaries, in which the arteries terminate, be- come corrugated, and refuse to transmit a fluid which does not act upon them, according to their wonted sensibility. Such was the result of the experiments of Professor Buniva: he observed, in a living calf, that the vessels did not transmit freely the fluid which was forced into them, till the instant when the animal was killed, by dividing the upper part of the spinal marrow. Attempts have been made to turn to useful purposes these experiments on transfusion, by limiting the process to the injecting of medicinal substances into the veins. It is singular, that the moment a fluid is injected into the veins of an animal.it endeavours to perform mo- tions of deglutition, as if the substance had been taken in at the mouth. All these attempts have been too few in number, and are not sufficiently authenticated to justify their application to the human subject. But there is every reason to believe, that, even with the utmost care, the life of those who should submit to them, would be endangered ; so that it is at once humane and prudent to abstain from them !• XCIV. Of the secretions. It has been said, in too general a way, that the organs receive from the blood conveyed to them by the arteries, the materials ofthe fluids which they separate from it. We have seen, that the liver is a remarkable exception to this general rule ; the same obser- vation seems, likewise, applicable to the mammae ; they appear to receive the elements of their milky secretion, from the lymphatics, which are so very numerous in their structure \. One is, therefore, justified in saying, that the elements of our fluids may be furnished by vessels of every kind, to the organs in which such * Academie Royale des Sciences, 1667, page 37. t See APPENDIX, Note B B. % This opinion respecting the source of the secretion of milk, is now relinquished by M. Picherend ia:j tluids may be elaborated. The term secretion, whatever its etymology may be, denotes that function by which an organ separates from the blood, the materials of a substance which does not exist in that fluid, with its characteristic qualities. By the term secretion, one should not, there- fore, understand the mere separation ofa fluid existing, before the action of the organ by which it is piepared. XCV. The difference between the secreted fluids, are evidently con- nected with those, of the organs employed in their iormation. Thus, the arterial exhalation which takes place, throughout the whole extent ofthe internal surfaces, maintains their confguity, throws out an albuminous serosity which is merely the serum of the blood, slightly changed, by the feeble action of a very simple organization. The analysis of the fluid of dropsy, which is merely the serosity constantly transuding from the surface of the serous membranes, as the pleura and peritoneum shows, that it bears the strongest resemblance to the serum ofthe blood and that it differs from it only in the varying proportions of albumen and of the different salts which it holds in solution. This first kind of secretion, this perspiratory transudition, would seem to be a mere filtration, through the pores ofthe arteries, of a fluid already formed in the blood. There is, however, besides, an inherent action in the membranes whose surface it continually lubricates. If it were not for this action, the serum would remain united to the other constituent parts ofthe fluid, which is in too much motion, and at too high a temperature, to allow of a spontaneous separation. The term exhalation, which is applied to this secretion, gives an incorrect idea of it, for, exhalation, which is a purely physical phenomenon, and requiring the presence of air to dissolve the fluid that is exhaling, cannot take place from surfaces that are in absolute contact, and between which there is no interval. The character of this mode of secretion, is the absence of any intermediate substance, between the vasa afferentia and the excretory ducts ; the mi- nute arteries and veins which enter into the structure of the membranes being, at once, vasa afferentia and excretory ducts. The fluid secreted by the serous membranes, though bearing a considerable analogy to the serum ofthe blood, differs from it, however, by being animalized in a greater degree. The most important function of these organs is, there- fore, that they concur in the common process of assimilation ; the office which has long been assigned to them of facilitating the motion ofthe or- gans which they envelope, by lubricating their surface, will appear to be of very secondary importance, if it be considered, that respiration is not impeded by adhesions between the lungs and the pleura, and that, be- sides, the brain, vvhich, when the cranium is whole, is completely motion- less, is entirely surrounded by a serous membrane. XCVI. Next in order to the serous transudition, which requires a very simple organization, comes the secretion which takes place in the cryptae, in the glandular follicles, and in the mucous lacunas. Each of these small glands, contained within the membranes lining the digestive canal, air tubes, and the urinary passages, and the collection of which forms the amygdala?, the arytenoid glands, kc. may be compared to a small bottle with a round bottom, and a very short neck ; the membranous parietes of these vesicular cryptae receive a considerable number of vessels and nerves. The peculiar action ofthe parietes of these different parts, de- termines the secretion of the mucus furnished by those glands. These mucous fluids, less liquid and more viscid than the serosity which is the product ofthe first mode of secretion, contain more albumen and a great- er number of salts, differ still more from the serum of the blood, are more animali?iprt. and are-e£**Hre excrementitious nature. 184 The bottom of these utricular glandulae, is turned towards the parts to which the mucous membranes adhere ; their mouth, or neck, opens on the surface at which tho->e membranes are in contact. These kinds of excretory ducts, wider, or narrower, and always very short, sometimes unite, run into each other, and open within the cavities. These common orifices, at which several mucous glands empty themselves, are easily seen on the amygdalae, towards the mucous lacunas of the rectum and of the urethra, at tbe base ofthe totgue, &c. The albuminous fluid, which is poured within those glandular cryptae, remains some time within the cavity, becomes thicker from the absorption of its more fluid parts ; for, there are, likewise, lymphatics within the texture of their parietes. When the surfaces, on which they are situated, require to be moistened, this small pouch contracts, and throws up the fluid with which it is filled. The secretion and excretion are promoted by the irritation which the presence of the air. of the aliment, or of the urine occasions, by the compression exerted by those substances, and lastly, by the peristaltic contractions ofthe muscular planes to which the mucous membranes ad- here, throughout the whole extent ofthe digestive tube. XCVTl Those fluids which differ much from the blood, require for their secretion, organs of a more complicated nature; such organs are called conglomerate glands, to distinguish them from the lymphatic glands, which have been termed conglobate. Those glands constitute the viscera, and are formed by a number of nerves and vessels of all kinds, arranged in fasciculi, and united by cellular membrane. A membrane peculiar to the organs, or supplied by those which line the cavities in which they are contained, covers their outer part, and insulates them from the neighbouring organs. The intimate arrangement of the different parts which form the secre- tory glands, the disposition of the arteries, ofthe veins and nerves, and the manner in which the lymphatic and excretory ducts arise from them, has given rise to endless discussions, and formed the basis of former physiological theories. What follows may be considered as a correct abstract of what is known on the subject. The respective arrangement of the similar parts (parties similaires*) which enter into the structure of the gl tnds, and which form their proper substance, or parenchyma t, is different in each of them : this explains their differences, in the double relation of their properties and their uses. The arteries are not as Kuysch thought immediately continuous with the excretory ducts nor are there immediate glands between those vessels, as Malpighi conceived. It seems more probable that each gland has its own peculiar cidlular or parenchymatous tissue, in the areolae of which, the arteries pour the materials of the fluid which the gland pre- pares, in virtue ofa power vvhich is inherent to it, ai.d which is its distin- guishing character. The lymphatics and the excretory ducts arise from the parietes of those cells ; and these two kinds of vessels absorb ; the one set, the secreted fluid which they carry to the reservoirs in which * By parties similaires, the author means the simple elementary tissues.—See the preliminary discourse, p. 12. + Do the different appearances of the substance of glandular bodies depend on the different manner in which the similar parts cross each other, and on the different proportions in every gland ; or do these differences of colour, of density, by means of which we so readily distinguish the substance of the liver from that ofthe salivary glands, depend on the existence of a peculiar tissue in each organ ? This question cannot be answered, in the present state of anatomy. The opinion, however, which supposes the differeut nature of the glands to depend on the different proportions of those constituent part*, in each of them appears the most probable.—Author's Note. 185 it accumulates, while the other set take up that part of the fluid, on which the organ has not completed its action ; in other words, the residue of se- cretion. XCVII1. Of accidental secretions. If one wished to extend the idea attached to the term secretion, one might say, that every thing, in the living economy, is performed by means of the secretions. What is di- gestion, but the separation or secretion of the chylous or nutritive parts of aliments, from their faecal or excrementitious portion ? Do not the absor- bents concur in this secretion ; may they not be considered as the excre- tory ducts of the digestive organs which acts on the aliment, in the same manner as a secretory gland acts on the blood that contains the materials ofthe fluid to be elaborated ? Respiration as we have alreadv seen, is but a double secretion which the lungs perform, on the one hand, of the oxy- gen contained in the atmospherical air, and on the other hand, of the hy- drogen and carbon, ofthe water, and ofthe other heterogeneous principles contained in venous blood ; and, as will be shown in the ensuing chapter, nutrition is but a peculiar mode of secretion which is different in every or- gan. It is, therefore, only a series of very delicate and very complicated separations and analyses, that the organs are enabled to make extraneous substances undergo such a change of composition, as to render them fit for their growth and reparation. There is every reason to believe, that the phenomena of sensation and of motion, by means of which man keeps up, with surrounding objects, the relations necessary to his existence, are the result of the secretions of which the blood furnishes the materials prepared by the brain, by the nerves, by the muscles, &c. A plant separates from the earth, in which its roots are buried, th juices which it requires ; these juices constitute the sap. which, after being filtered through a multitude of ca- nals, supplies the different secretions, whose products are leaves, blos- soms, and fruits, with gums, essential oils, and acids. All organized bo- dies are, therefore, so many laboratories, in which numerous instruments spontaneously perform various compositions, decompositions, syntheses. analyses, which may be considered as so many secretions from the com- mon fluid. If we confine ourselves in our view of the subject, and limit our atten- tion to man, Ihe principal and almost the sole object of our study, we shall see that the different secretions that may take place in him, are extremely numerous and varied, and that a change in the condition of one of his organs, is sufficient to enable it to secrete a new fluid. Hence inflammation in any gland, is sufficient to alter the secretion of the organ that is affected. A portion of adipose tissue, on being affected, with in- flammation, shall secrete, instead of fat, a whitish fluid known by the name of pus. The pituitary membrane, when inflamed, furnishes a mu- cus more fluid and more abundant, and which, by degrees, returns to its natural state, in proportion as the coryza goes off; the serous mem- branes, as the pleura and the peritoneum, will allow a greater quantity of serum of a more albuminous quality, sometimes even coagulable lymph, to exude ; at other times, inflammation causes an adhesion of their contiguous surfaces, and as the inflammatory state varies in intensity, the accidental secretion will likewise vary as to its qualities ; thus, the phlegmonous inflammation which should furnish, on terminating in sup- puration, a whitish fluid, thick, consistent, and almost without smell, will give out, if the process is not sufficiently active, a serous pus, colourless, and without consistence, &c. For the- same reason, the blood-vessels 24 18U of the uterus pour out in some women, a dark coloured blood, wu|'£ in others, they give out a mere serosity, very slightly, if at all, tinged with blood. f The menstrual discharge, in women, is the product ofa real secretion ot the arterial capillaries ofthe uterus, in the same manner as those vessels in the pituitary membrane, the membrane which lines the bronchiae, the sto- mach, the intestine*, the bladder, &c. pour out blood abundantly, or allow its transudation, when irritation is determined to those parts; in hemorrhage from the nose, in bleeding from the lungs, or from the stomach, when the vessels are not ruptured by external violence. Apoplexy itself, whether sanguineous or serous, may, in several instances, be ranked among those se- cretory evacuations, the quality of which varies, according to the energy of the capillaries which produce it. On opening dead bodies, one frequently meets with a collection of blood in the ventricles of the brain, in persons who have died from apoplexy, yet the most careful examination does not enable one to detect the slightest laceration or rupture in the veins, or in the arteries within the skull. The nerves, of which there is always a certain number in the structure ofthe secretory organs, and which are principally branches^ of the great sympathetic* nerves, terminating in various ways, in their substance, give to each of them a peculiar sensibility, by means of which they discover in the blood which the vessels bring to them, the materials of the fluid which they are destined to secrete, and these they appropriate to themselves by a real selection. Besides, the nerves communicate to them a peculiar mode of activity, the exercise of which makes those separated elements undergo a peculiar composition, and bestows on the fluid which is the product of it, specific qualities always bearing a certain relation to the mode of action of which it is the result. Thus, the liver seizes the materials ofthe bile con- tained in the blood of the vena portae, elaborates, combines those materials, and converts them into bile, an animal fluid, distinguishable by peculiar cha- racteristic properties, subject to certain variations, according as the blood contains, in different proportions, the elements of which it is formed; ac- cording as the gland is more or less disposed to retain them, and to blend them together. The qualities ofthe bile depending on a concurrence of all these circumstances, must present as many differences as the blood which contains its elements, and the liver may present varieties, with regard to the composition ofthe former, and to the activity of the latter. Hence the many changes in the qualities of the fluid, the slightest of which, not affect- ing the health, escape observation, while those changes which are greater, and which disorder the natural order of the functions, show themselves in diseases of which they may be considered as the effect and at other times, as the cause. These changes in the condition ofthe bile (and what is now said applies to almost all the secretions of the animal economy), these changes are never carried so far as to make the bile lose all its distinguishing characters, it never takes on the qualities belonging to another fluid, it ne- ver resembles semen, urine, or saliva. The secretory glands do not carry on an uninterrupted action ; almost all of them are subject to alternate action and repose ; all as Bordeu observed, sleep or waken, when irritation affects them, or their neighbouring parts, and determines their immediate and sympathetic action. Thus, the saliva is more plentifully secreted during mastication ; the gastric juice is poured * They are likewise given off, in great numbers, from the cerebral nerves; thus, the salivary glands receive from the seventh pair, from the maxillary nerve, from the fifth pair, and from the cervical nerves, a number of nerves that will appear very great, if the balk of those glands is considered. within the stomach, only while digestion is going on ; when the stomach is emptied of food, the secretion ceases, and is renewed, when the presence of food again excites a sufficient degree of irritation. The bile flows more abundantly, and the gall bladder frees itself of that which it contains, while the duodenum is filled by thechymous mass. When a secretory organ is in action, it determines the motion ofthe parts m its vicinity, or, as Bordeu expresses it, within its atmosphere. A part is said to belong to the department of a certain gland, when it partakes m the motion affecting the latter, during the process of secretion, or when it is employed in functions subservient to that of the gland ; these depart- ments are of different extent, according to the importance of the action of tk giand' Thus' one may say that the spleen and most of tb^e viscera of the abdomen are of the department ofthe liver, since they receive from it, the blood on which they are to act. 1 he liver is also comprised in the sphere of activity ofthe duodenum, since the distension of that intestine ir- ritates it, determines a more copious flow of its fluids, and a more abundant secretion of bile. C. The blood which is sent to a secretory gland, before reaching it, un- dergoes preparatory changes, which dispose it to furnish the materials of the fluid which is to be separated from it. We have seen, in treating of digestion, how the blood which the vena porta? sends to the liver, is fit for the secretion of bile There can be no doubt, that the portion of blood which it carries to the testicles, by the long, slender, and tortuous sperma- tic arteries, undergoes changes which bring it nearer to the seminal fluid. The rapidity with which the blood flows into an organ, the length, the diameter, the direction, the angles of its vessels, the arrangement of their extreme ramifications, which may be stellated, as in the liver, in fisciculi, as in the spleen, convoluted, as in the testicles, &c. are circumstances which should be taken into account in the study of each secretion, since all have some influence on the nature of the fluid secreted, and on the manner in which the secretion is effected. The fluid which lubricates the whole extent of the moveable surfaces by which the bones of the skeleton are articulated together, is not exclu- sively prepared by the membranous capsules which envelope the articula- tions. A number of reddish coloured cellular substances, placed in their vicinity, co-operate in the secretion. Though these parts, which were long considered as synovial glands, do not completely resemble the conglomerate glands, and although no glandular bodies, nor excretory ducts, can be de- monstrated in them, they cannot, however, but be considered as fulfilling, to a certain degree, the same functions, and one must admit that they are of some utility, in the secretion of the synovia. They are always met with ; their extent and bulk are always proportioned to the extent of the auricular surfaces, and to the frequenc}' of motion in the joints near which they are situated. They are found in all animals ; pale and light coloured in those which have been long at rest ; red, highly vascular, and bearing the marks of. a kind of inflammatory diathesis, in those which have been compelled to violent exercise, as the oxen which are brought to Paris from distant provinces, and the wild animals which have been hunted. In an- chylosis, they are less red and of greater consistence, than in a healthy state. When, from the irritation attending friction, the fluids are determined towards an articulation which is in motion, do they not then, by passing through those glandulo-cellular bodies, undergo a peculiar modification which renders them fitter for the secretion of synovia. This would not be the only instance, in the human bodv, of parts whose action is but se 188 condary and connected with that of other organs principally engaged in a secretion whose materials are contained in the blood which passes through them. It will be urged, no doubt, that this preparatory apparatus is not met with in the neighbourhood of the great cavities ; but it should be re- collected, that the chemical composition and the uses of the synovia, are not precisely the same as those of the fluids secreted by the pleura or the peritoneum ; and that, besides, the analogy between two objects, does not constitute their identity. The human mind being naturally indolent, loves to discover analogies that support it in its weakness, and that may save it the trouble of seeking points of difference. I am aware, that to prove that the mechanism of the synovial secretion, which exactly resembles that of the fluid vvhich moistens the inside of the great cavities, requires like it but a simple membranous apparatus, it is customary to repeat, in every possible way, that Nature is scanty in her means, and lavish in her results ; that she produces from the same cause, a variety of different effects, &c. but without pointing out the manifest absurdity of admitting metaphysical arguments in the natural sciences, is it not much more reasonable to acknow- ledge with philosophers,"that the primitive cause may vary in many ways, and that its innumerable modifications, whence arise the difference in the effects, exceed the limited powers of our understanding ? CI. When a gland is irritated, it becomes a centre of fluxion, towards which the fluids are determined from every part; it swells, hardens, con- tracts, is in a kind of state of erection, bends on itself, and acts on the blood conveyed by its vessels. Secretion, depending on the peculiar and inherent power of the glandular organ, is promoted by the slight motion which it re- ceives from the neighbouring muscles. The gentle pressure of those parts on the glandular organ, is sufficient to keep up their excitement, and to as- sist in the separation and excretion of the fluid. Bordeu, in his excellent work on the glands and on their action, has shown that it is not in conse- quence of the compression which is produced on them by the neighbouring muscles, that they part with the fluid they have prepared, that physiologists were therefore very much in the wrong, in saying, that the excretion of a fluid consisted merely in its expression, and in comparing, under that point of view, the glands to spunges soaked with a fluid which they give out, on being squeezed. The excretory ducts of organs absorb or reject the secreted fluid, accord- ing as it affects their inhalant mouths : these canals partake in the convul- sive state of the gland, undergo a degree of erection, and contract on the fluid to expel it. Thus, the saliva starts from the parotid duct, at the sight, or on the recollection of food that has been longed for : thus, the vesiculae seminales and the urethra (for the reservoirs in which the fluids he some time before being expelled, may be considered as forming a part of the ex- cretory ducts), contract, become straighter, and lengthen themselves to force to a distance the spermadic fluid. The thin and transparent ureters of fowls have been seen to contract on the urine, which, in these animals, concretes on the slightest stagnation. After remaining a certain length of time, in that state of excitement, the glands relax, their tissue collapses, the juices cease to be conveyed to it as plentifully, they fall into a state of repose or sleep, which restores their sen- sibility, exhausted by too much action. It is well known, that a gland over- stimulated, becomes, like any other part, insensible to the stimulus, the con- tinued application of which parches and exhausts it. From what has just been said relative to the mechanism of the secretions, it will be seen that this function may be divided into three very distinct pe- riods ; 1st. that of irritation, characterised on the growth of the vital pro- 189 perties, and by the more copious accession of the fluids, the necessary con- sequence of that excitement ; 2nd. the action of the gland ; that is, its secre- tion, properly so called ; 3d. lastly, the action by which the organ parts with the fluid which it has prepared : this is the last process, it is called excre- tion, and is promoted by the action of the neighbouring parts. The deter- mination of fluids to the part, the secretion and excretion succeed each other ; they are preceded by the excitement which is the primary cause of all the subsequent phenomena. The circulation is, at first, excited, more blood is sent into the part, and penetrates into the tissue of the gland. Dr. Murat has had occasion to open a considerable number of old men, who died at the Bicetre, and who were known to be great smoakers of tobacco. He uniformly observed, that their parotid glands, continually called into action by that habit, were larger than in those who were not given to it, and that they were remarkably red, in consequence of the blood with which they were constantly injected. What is the office of the nerves in the act of secretion ? what share has the nervous influence in the elaboration of the fluids furnished by the glandular organs ? All the glands which receive their nerves from the sys- tem of animal life, sucb as the lachrymal and salivary glands, appear, in certain cases, to receive, from the brain, the secretory excitation. The in- fluence of the imagination is sufficient to determine it; thus, we shed in- voluntary tears, when the mind is taken up with painful thoughts ; and the mouth fills with saliva, on the recollection of a grateful meal*. In such cases, the influence of the nerves, on the process of secretion, is indispu- table ; it is not so, however, with the conglomerate glands that receive their nerves from the great sympathetics. The secretion of the kidneys, of the liver, and of the pancreas, appears less influenced by affections of the mind ; the brain, besides, has no immediate connection with these glands ; their nerves are, almost entirely, given off by the great sympathetics ; the kidneys in particular, receive no nerves from the brain, or from the spinal marrow, hence the secretion of urine seems, more than any other, to be in- dependent of the nervous influence |. * These glands, viz. the lachrymal and salivary, receive nerves both from the near- est ganglions, and from the nerves of voluntary motion : the former set of nerves most probably enables them to perform their ordinary functions, the latter excites or reinforces these functions whenever the mind is under certain impressions. t Although these organs are not directly influenced by tbe cerebral and spinal nerves, it cannot be satisfactorily denied that the ganglial nerves which are so abundantly distri- buted to the blood-vessels supplying these organs, bestow on these vessels that peculiar influence which determines the nature and quantity of the secretion; for how can we suppose the capillary tubes, through which the blood flows, to be able to secrete a pecu- liar fluid of the'iselves, withouta resorting to the position that the nerves, which so abundantly supply the ramifications of the blood-vessels, and the substance of the se- creting organs, actually influence, and, through the medium of tho°e vessels, even pro- duce the secretions in question ? Are not these nerves requisite to the vital actions of the viscera which they supply ? Do we know an animal that does not possess them as a most essential part of its organization ? And can we suppose that they are distributed in so abundant a manner to the vessels of a secreting organ, without performing a most re- quisite part in the production of the fluids which that organ secretes ? A close investiga- tion of the structure of the secreting viscera and surfaces shows that their blood-vessels, which bear in their number and size, a close relation to the extent of function which such viscera individually perform, are more amply supplied with this class of nerves than the vessels of any other of the animal textures : indeed every important secreting gland has a distinct ganglion, or plexus of these nerves surrounding the blood-vessels which belong to it, but more especially the arteries, and some of these organs havo loth a large plexus of nerves and a ganglion, whence their nerves are exclusively derived, and which appear to be entirely devoted to the functions of the viscus whose bipod-ves- sels they so plentifully supply. See, on this subject, the APPENDIX, Notes H, A A, and those on Digestion, &c. 190 This great number of secretory organs, constantly engaged in separating various secretions from the mass of the fluids, would soon exhaust it. if the calculations of physiologists of tbe amount of what a gland, is capable, of se- creting, were not manifestly exaggerated. In fact, if we admit, with Haller* that the mucous glands ofthe intestinal canal secrete, in twenty-four hours, eight pounds of mucus ; that, in the same space of time, the kidnies secrete four pounds of urine ; that the same quantity is lost by the insensible per- spiration ; and again, as much by the pulmonary exhalation; there will be lost, daily, twenty pounds of fluids, almost entirely excrementitious ; for we do not include in th-.t calculation the bile, the tears, nor the saliva and pancreatic fluid, which, in part, returns into the blood after being separated from it; nor the serum which moistens the internal surface, and which is purely recrementitious. This exaggeration, in the calculation ofthe fluids which are daily poured out by the different emunctories, is to be attributed to the circumstance of having taken the maximum of each secretion, without considering that they mutually supply each other ; so that, when less urine is voided, the quantity of perspiration is greater, and vice versa. It is very well known, that a violent diarrhea is frequently the consequence of sudden cold applied to the skin ; the fluids at once repelled towards the intestinal canal, having to pass through the mucous glands whose action is greatly increased*. CII It has been customary to enumerate, among the glands, certain bo- dies which have truly a glandular appearance ; but the uses of which are yet unknown. Thus, the thyroid and thymus glands, which are parenchy- matous organs destitute of excretory ducts, though receiving many vessels and some nerves, do not appear to secrete any fluid. But may not the blood, which is conveyed so plentifully to the thyroid gland, undergo never- theless certain changes, though we may not be able to discover what they are ? Besides, may not the lymphatics perform the office of excretory ducts, and convey back again immediately into the mass of the blood, the fluid which has undergone changes in the glandular body ? The capsular renales are in the same condition : they have, however, in addition, an in- ternal reservoir, a kind of lucana, whose parietes are smeared with a viscid and brown coloured substance secreted by the capsule, and which doubtless is conveyed into the mass of the blood by the lymphatics arising from the parietes of its internal cavity. CHI. Of the secretion of adeps within the cellular tissue. This soft tissue which is diffused over the whole body, and affords a covering to all our or- gans, is of use not merely in separating them from one another, and con- necting together the different parts ; it is besides, the secretory organ of the adipose substance, a semi-concrete oily animal substance, which is found, in almost every part of the body, deposited in its innumerable cells .The mem- branous parietes of these small cellular cavities* re supplied by numerous mi- nute arteries, in which the adeps is separated ; it is conveyed by its specific light weight to the circumference of the column of blood in the vessels, and transudes through the pores in their parietes. Its quantity and consistence , vary, in different parts ofthe body, and in different persons : there is situated below the skin a thick layer of cellular substance (pannicuh grassieux ;) it is found, in considerable quantity, between the interstices ofthe muscles, along the blood-vessels, near the articulations, and in the vicinity of certain organs as the eyes, the kidnies, and the breasts. That which fills the bottom of the orbit, and which surrounds the.eye-ball, is softish and almost fluid ; that * An increased flow of urine takes place in most persons during the first cold of autumn, and cold suddenly applied to the surface of the body, by checking the perspiration, often increases exhalation into the cellular textures, and on the serous membranes, thereby in d.uqing dropsies 191 which envelopes the kidnies and the great joint is, on the contrary, of the consistence of suet. Between these two extremes, there are many grada- tions, and it may be said, that the animal in question, is not exactly the same in any two different parts ofthe body. The high temperature of the human body maintains it in a state of sem£fluidity, as may be observed in surgical operations. In some parts, it is even absolutely fluid, but its nature is then observed to be greatly changed, it no longer contains any oily substance, and differs, but little, from a mere aqueous gelatine. Thus, the fluid in the cellular tis- sue of the eye-hds, of the scrotum, &c. has been considered by several physiologists, as absolutely different from fat. It may not be amiss to ob- serve, that the lamina? of the cellular tissue, in such circumstances, yield more readily to extension, present a greater surface, form membranous ex- pansions, and circumscribe cells of a considerable size, so that the differ- ences in the secretion, perfectly coincide with the difference of structure. It may further be observed, that the functions of the eyelids and ofthe penis required that they should not contain any fat. Considerable deformity, when the person grew fat, would have been the consequence ofthe increas- ed bulk of these parts, and besides, the folds ofthe skin would not have that free motion which their functions require. No real adeps is ever found within the skull, and the utility of this condition is very obvious. To how many dangers would not life have been exposed, if a fluid, so varying in quantity, and the amount of which may be trebled, in a very shorfspace of time, had been deposited into a cavity accurately filled by anorgan which is affected by the slightest compression ? In an adult male, of moderate embonpoint, the proportion of adeps is about one twentieth of the weight of the whole body ; it is greater, in proportion, in children and in females ; for, its quantity is always relative to the energy of the functions of assimilation. When digestion and absorption are per- formed with great activity, fat accumulates within the cellular substance : and if it be considered that it is but imperfectly animalized, that it bears the most striking analogy to the oils extracted from plants ; that it contains very little azote, and much hydrogen and carbon, like all other oily sub- stances, since on distillation it is decomposed, and yields water and carbonic acid, with a very small quantity of ammonia ; that its proportions are very variable, and may be considerably increased or diminished, without manifest- ly impairing the order of the functions ; that animals that spend a great part of their life without eating, seem to exist during their torpid state, on the fat which they have previously accumulated in certain parts of their body* ; one will be led to think, that the state of fat is, to a portion of the nutritive matter extracted from the food, a kind of intermediate state, through which it has to pass before it can be assimilated to the animal whose waste it is destined to repair. Animals which live on grain and ve- getables are always fatter than those which live exclusively on flesh. Their fat is consistent and firm, while that of carnivorous animals is almost com- pletely fluid. A corpulent man, on having his diet suddenly reduced, sensibly becomes thinner, in a very short time : the bulk and weight of his body diminishes, from the absorption ofthe fat which supplies the deficient quantity of blood. Adeps may, therefore, be considered as a substance in reserve, by means of ■- Marmots and dormice become prodigiously fat during the autumn, they then take to their holes and live in them, during the six winter months, on the fat which is accu- mulated in all their organs. There is most fat collected in the abdomen, in which the epiploon forms masses of a considerable size. When, in the spring, their tupor ceases, and they awaken from their sleep, they are for the most part, exceedingly emaciated. 192 which, notwithstanding the small quantity of food and its want of nutritious qualities, Nature finds wherewith to repair the daily waste. CIV. The use of adeps is not, as has been stated, on the authority of Macquer, to absorb the acids that are formed in the animal economy ; that which is obtained from it, by distillation, (the sebaceous acid) is a new pro- duct former! by the combination of the atmosphere with the hydrogen, the carbon, and the small quantity of azote which it contains. The small quantity of this last substance nearly constitutes it into a vegetable acid. Fat has a considerable affinity for oxygen, and by combining with it, turns rancid, after remaining some time exposed to the air. It deprives metallic oxides of a part of their oxygen, and likewise, on being triturated with me- tallic substances, promotes their oxidizement In proportion as it absorbs oxygen, its indensity increases ; thus oils become concrete by combining with oxygen, and fat acquires a consistence almost equal to that oi wax, which is itself a fatty substance highly oxidized. Besides the principal use which we have assigned to adeps, and accord- ing to which, the cellular system imy be looked upon as a vast reservoir, in which there is deposited a considerable quantity of nutritive and semi-ani- malized matter, this fluid answers several purposes of secondary utility. It preserves the body in its natural temperature, being, as well as the tissue ofthe cells in which it is contained, a very bad conductor of heat. Persons who are excessively corpulent, scarcely feel the most severe cold ; the ani- mals which inhabit northern climates, besides being clothed in a thick fur, are likewise provided with a considerable quantity of fat. The fishes of the frozen seas, the cetaceous animals which seldom go far from the polar regions, all kinds of whales, are covered with fat, and have likewise a con- siderable quantity within their body. By its unctuous qualities, fat promotes muscular contraction, the motion ofthe different organs, the free motion on each other of the different surfaces ; it stretches and supports the skin, fills vacuities, and gives to our limbs those rounded outlines, those elegant and graceful forms peculiar to the female body. Lastly, it envelopes and covers over the extremities of the nerves, diminishes their susceptibility, which is always in an inverse ratio of the embonpoint, which induced a physician of merit to say, that the nervous tree, planted in the adipose and cellular substance, suffers, when from the collapse and the removal of that tissue, its branches are exposed, in an unprotected state, to the action of ex- ternal causes, as injurious to ihem as the rays ofthe sun to a plant torn from its native soil. It is in fact, observed that nervous people are exceed- ingly thin, and have an excessive degree of sensibility. Too much fat, how- ever, is as injurious as too small a quantity of it. I have seen several per- sons whuse obesity was such, that besides being completely incapable of taking the slightest exercise, they were in great danger of suffocation. Re- spiration in such persons is, at times interrupted by deep sighs, and their heart, probably overloaded with fat, expels with difficulty the blood within its cavities. CV. According to modern chemists, the use of fat is to take from the sys- tem a part of its hydrogen. When the lungs or liver are diseased, when respiration or the biliary secretion do not carry out of the system, a suffi- cient quantity of that oily and inflammable principle, fat forms in a greater proportion. They appeal to the result of the experiment of shutting up a goose, whose liver is to be fattened, in a confined cage, placed in a hot and dark situation, and in gorging it with paste, of which it eats the more gree- dily, as being unable to stir, it gratifies its inclination to action, by exerting the organs of digestion. Notwithstanding this quantity of food, the bird be- 193 ^omes emaciated, is affected with a kind of marasmus, its liver softens, grows fatter, more oily, and attains an enormous size. This experiment, and many other facts, prove, that the secretions from which analogous products are formed, may mutually supply each other ; but can we admit the chemical theory ofthe use of fat when we recollect that frequently, in the most corpulent persons, respiration and the secretion of bile are performed with great freedom and with no difficulty ; while the difficult respiration attending pulmonary consumption, and the difficult flow of the bile from an obstruction of the liver, are always accompanied with complete marasmus. Whatever moderates the activity ofthe circulatory system, tends to bring on adipose plethora. Thus an inactive state ofthe mind and body, profuse bleedings, castration, sometimes induce obesity, an affection in which the cellular tissue appears affected with atony, and undergoes an actual adipose infiltration, which may be compared to that which gives rise to tumours called steatomatous. If the energy of the heart and arteries is too great, emaciation is always the consequence ; when, on the contrary, the sanguine- ous system is languid, there is formed a merely gelatinous fat, and the em- bonpoint is a mere state of bloatedness. This incompletely formed fluid, which distends the parts in persons of a leucophlegmatic habit, is but an imperfect kind of fat; it resembles the mar- row or the medullary juice, which is merely a very liquid fat, whose con- sistence diminishes when animals become lean. Inclosed within the cells of the osseous tissue, in cavities whose sides cannot collapse, and whose dimensions must always remain the same, the marrow of which they are never free, is of different degrees of density ; and what authors say of its diminished quantity, must be understood as applying to the diminution of its consistence. CVI. The secretion ofthe marrow is, like that ofthe fat, a mere arterial transudation ; it is performed by the medullary membrane, which is thin, transparent, and cellular, which lines the inside of the central cavity ofthe long bones, and extends over all the cells of their spungy substance. The medullary membrane, when in a healthy state, does not give any marks of relative sensibility. In all the amputations I have performed, and they have not been few, in all the operations ofthe same kind at which I hare been present, whatever the bone was, whether it was divided near a joint or in the middle of its body, I never knew the patient complain of pain, provided the limb was well supported by the assistants, and provided no jerk was given by the operator himself. In that operation, the pain occa- sioned by the division ofthe skin and ofthe nerves, overcomes every other pain, and I have always seen patients impressed with the popular preju- dice, and expecting anxiously the division of the bone, feel quite free from pain, as soon as the saw had begun to work. Nay, several, after express- ing, by their cries, the most acute pain, taking advantage of the kind of ease which follows the division ofthe flesh, raise their head, and look on, while the bone is being sawn through ; at once actors and spectators in thh) last part ofa painful and bloody operation. Yet the medullary membrane, the injury of which is attended with no pain, while in a healthy state, becomes the seat ofthe most exquisite sensi- bility in the pains in the bones which mark the last stages of the venereal disease ; in the kind of conversion into flesh, of the solid bone, known by the name of spina ventosa, as will be mentioned, in speaking of the uses of the marrow, in the chapter on the organs of motion and on their action. 194 CHAPTER VI OF NUTRITION. CVII. All the functions which we have hitherto made the object of oui study ; digestion, by which the alimentary substances received within the body, are deprived of their nutritive parts ; absorption, which conveys that recrementitious extract into the mass ofthe fluids ; the circulation, by which it is carried to the parts wherein it is to undergo different changes ; diges- tion, circulation, absorption, respiration, and the secretions, are but prelimi- nary acts, preparatory to the more essential function treated of in this chap- ter, and the consideration of which terminates the history ofthe phenomena of assimilation. Nutrition may be considered as the complement ofthe functions of assimi- lation. The aliment, altered in its qualities, by a series of decompositions, animalized and rendered similar to the substance ofthe being which it is to nourish, is applied to the organs whose waste it is to repair ; and this iden- tification of the nutritive matter to our organs which take it up and appro- priate it to themselves, constitutes nutrition. Thus, there is accomplished a real conversion ofthe aliment into our own substance. There is incessantly going on a waste of the integrant particles of the living body, which a multiplicity of circumstances tend to carry away from it; several of its organs are constantly engaged in separating from it the fluids containing the recrementitious materials of its substance worn by the com- bined action ofthe air and of caloric, by inward friction, and by a pulsatory motion that detaches its particles. Alike, therefore, to the vessel of the Argonauts, so often repaired in the course ofa long and perilous navigation, that on her return, no part of her former materials remained ; an animal is incessantly undergoing decay, and if examined at two different periods of its duration, does not contain one of the same molecules. The experiment performed with madder, which dyes red the bones of animals among whose food it is mixed, proves, most unques- tionably, this incessant decomposition of animated and living matter. One has only to interrupt, for a sufficient length of time, the use of that plant, to make the uniformly red colour assumed by the bones completely disappear. Now, if the hardest and most solid parts, most calculated to resist decay, are undergoing a perpetual motion of decomposition and of regeneration; there can be no doubt, that this motion must be far more rapid in those whose power of cohesion is much inferior ; for example, in the fluids. Attempts have been made to determine the period at which the body is completely renovated ; it has been said, that an interval of seven years was required for one set of molecules to disappear and be replaced by others; but this change must go on more rapidly in childhood and in youth. It must be slower at a mature age, and must require a considerable time, at a very advanced period of life, when all the parts ofthe body become, in a remarka- ble degree, fixed and firm in their consistence while the vital powers become more languid. There can be no doubt, that the sex, the habit, the climate in wbich we live, the profession we follow, our mode of life, and a variety of other circumtances, accelerate or retard it; so that it is absolutely impos- sible to fix, with any degree of certainty, its absolute duration. CVIII. The parts of our body, in proportion as they undergo decay, are repaired only by means of homogeneous particles exactly like themselves : were it otherwise, their nature, which always remains the same, would be undergoing perpetual changes. When, in consequence ofthe successive changes vvhich it has. undergone 19j trom the action of the organs of digestion, of absorption, ofthe circulation, of respiration, and of secretion, the nutritive matter is animalized or as- similated to the body, which it is to nourish, the parts which it moistens, retain it and incorporate it to their own substance. This nutritive identi- fication is not performed alike in the brain, in the muscles, in the bones, &c. Each of them appropriates to itself, by a real process of secretion, whatever it meets with fitted for its nature, in the fluids conveyed to it by the different kinds of vessels, but especially by the arteries ; it leaves un- affected, the remaining heterogeneous particles. A bone is a secretory or- gan, around which phosphate of lime is deposited ; the lymphatic vessels * which, in the process of nutrition, perform the office of excretory ducts, remove that salme substance, when it has lain sufficiently long in the cells of its tissue. The same happens to the muscles, with regard to fibrina, and to albumen with regard to the brain ; every part appropriates to itself, and converts into a solid form, those fluids which are ofthe same nature, in vir- tue ofa power of vvhich the term affinity of aggregation, used in chemistry, gives an idea, and of which it is perhaps the emblem.* The nutrition of apart requires that it should be possessed of sensibility and motion ; by tying the arteries and nerves of a part, it cannot be nou- rished, nor can it live. The blood which flows along the veins, the fluid conveyed by the absorbents, contain, in a smaller proportion than arterial blood, vivifying and reparatory particles. It is even commonly thought, that the lymph and venous blood contain no directly nutritive particles. As to the share which the nerves take in the process of nutrition, that is not yet completely determined. A limb that is paralized, by the division or ty- ing of its nerves, or by any other affection, sometimes retains its original size and plumpness ;| most frequently, however, though perhaps for want of motion, it becomes parched, emaciated, and shrinks in a remarkable degree. C1X. We should be enabled to understand the process of nutrition, if af- ter having accurately determined the difference of composition between our food, and the substance itself of our organs, we could see Jiow each function robs the aliments of their qualities, to assimilate them to our own bodies ; and what share each function takes in the transmutation ofthe nu- tritive particles into our own substance. To illustrate this point, suppose a man to live exclusively on vegetable substances, vvhich, in fact, form the basis of our food ; on whatever part of the plant he may live, whether on the stem, on the leaves, on the blossoms, on the seeds, or on the root ; carbon, hydrogen, and oxygen enter into the composition of these vegetable substauces, which, by a complete analysis, may all be resolved into water and carbonic acid. To these three constituent principles, there is fre- quently united a small quantity of azote, of salts, and of other materials, in different proportions. If then, we examine the nature of the organs in this man whose food is entirely vegetable, it will be found that they are differ- rent in their composition, and far more animalized than that kind of food ; that azote predominates, though the vegetable substance contains none or only a very sm ill quantity, that new products, (indistinguishable in the ali- ments, exist, in considerable quantity, in the body which is fed on them, and appear produced by the very act of nutrition. The essence ofthis function is, therefore, to make the nutritive matter undergo a more advanced state of composition, to deprive it ofa portion of * Assimilation takes place in the most perfect manner when the vital influence is complete in all its relations. See APPENDIX, Note C C. + This and various other considerations evince that nutrition is not essentially de- pendent upon the voluntary nerves, but upon that class of nerves which are ramified on the blood-vessels. See the above note in the APPENDIX. 196 its carbon and of its hydrogen, to make azote predominate, and U produce several substances, which did not exist in it before. All living bodies seem to possess the faculty of composing and decomposing the sub- stances by means of which they are maintained, and to form new products . but they possess it, in various degrees of energy. The sea-weed, from tne ashes of which soda is obtained, on being sown in a box of soil, in whicn there is not a single particle of that alkali, and watered with distilled water, will no longer contain it, as if it had grown on the sea-shore, m the midst oi marshes constantly inundated by salt and brackish water.* . Living bodies then, are real laboratories, in which there are carried on combinations and decompositions which art cannot imitate ; bodies that^ap- pear to us simple, as soda and silex, seem to be formed by the union ot tneir constituent particles ; while other bodies, whose composition we do not un- derstand, undergo an irresistible decomposition : hence, methinks, one may infer, that tbe power of Nature in the composition and decomposition ot bodies, far exceeds that of chemistry. Straw and cereal plants contain an enormous quantity of silex, even when the earth in which they grow has been carefully deprived of its siliceous particles. Oats, particularly, contain a considerable quantity of that vitriti- able earth ; the ashes obtained by burningits seed, on being analyzed by means ofthe nitric acid, were found by M. Vauquelin, to contain T%%\ ot pure silex indissoluble in that acid, and 0,393 of phosphate of lime dissolved in it. The excrements of a hen, fed, for ten days, on oats only, on being cal- cined and analyzed by the same chemist, produced twice as much phosphate and carbonate of lime as was coutained in the oats, with a small deficiency in the quantity of silex, which might have been employed in furnishing the excess of calcareous matter; a transmutation depending on the absorption ot an unknown principle, to the amount of nearly five times its own weight T. CX. A substance to be fit for our nourishment, should be capable of de- composition and fermentation ; that is, capable of undergoing an inward and spontaneous change, so that its elements and relations may be altered. This spontaneous susceptibility of decomposition, excludes from the class of aliments, whatever is not organized and is not a part of'a living body ; thus, mineral substances absolutely resist the action of our organs, and are not convertible into their own substance. The common principle extracted from alimentary substances, however varied they may be, the aliment, as Hippocrates terms it, is most probably, a compound highly subject to de- composition and fermentation ; this is likewise, the opinion of all those who have endeavoured to determine its nature. Lorry thinks it a mucous sub- stance ; Cullen says it is saccharine ; Professor Halle considers it as an hy- dro-carbonous oxide, which differs from the oxalic acid, only in containing a smaller quantity of oxygen. It is evident, that these three opinions are very much alike, since oxygen, carbon, and hydrogen, combined in differ- * I am unacquainted with the details of the experiment referred lo by the author ; he quotes it, I conceive, to show that the power which, he says, is common to all living bo- dies, of producing a substance not supplied to them from without, is not possessed, in the same degree, by all bodies endowed with life ; since the sea-weed here alluded to, does not possess it, in an equal degree, wheu watered with distilled as with sea-water. This, I apprehend, is the author's meaning, though the text is somewhat obscure, and would almost lead one to believe he meant, that no alkali whatever can be obtained from the sea plant under the circumstances he states, " L'algue marine dont les cendres fournis- •• sent lasoude, semee dans une caisse pleine d'un terreau qui ne contient pas un seul "atomede cet alkali, arrosee avec leau distillee, ne le fournit plus comme si elle avoit "pris sacroissance au milieu des marais toujour inondes par leurs eaux saumatres et " muriatiques."—Trans. t See the Annates de Chimie, and the Syslcmedes Connaissances Chimiques de Four- croy, Tome X. page 1% 197 ent proportions, form the mucous saccharine substances and the base ofthe oxalic acid. On analyzing the animal substance, by means ofthe nitric acid, it is reduced to this last base, by depriving it of a considerable quantity of azote which constitutes its most remarkable character. But whence comes this enormous quantity of azote ? How happens it, that the flesh of a man living exclusively on vegetables, contains as much azote and ammonia, and is as putrescent, as that ofa man living on animal food ? Respiration does not introduce a single particle of azote in our fluids ; this gas comes out ofthe lungs as it entered ; the oxygen alone is diminished in quantity *. Might not one suspect that this element of animal substances is a product of the vital action, and that instead of receiving it from our aliments, we form it within ourselves, by an act that is hyper-chemi- cal; that is, which chemistry cannot imitate t ? CXI. It has been maintained, that the hydro-carbonous oxide, combines, in the stomach and intestinal canal with oxygen, whether this last principle has entered, with the aliments, into the digestive tube, or whether it is fur- nished by the decomposition of the fluids within that cavity. The intestinal fluids extricate azote which combines with the alimentary mass, and occu- pies the place of the carbon which the oxygen has taken from it, to form carbonic acid. On reaching the lungs, and being again exposed to the ac- tion of the oxygen ofthe atmosphere, this gas robs it ofa portion of its car- bon, and as it disengages the azote of the venous blood it brings about a new combination of that principle with the chyle : Lastly, propelled with the blood to the surface ofthe skin, the atmospherical oxygen disengages its carbon, and completes its azotisation. The cutaneous organ is perhaps to the ly mphatic system, what the pulmonary organ is to the sanguineous system. The animalization of the animal substance is therefore effected, princi- pally by the loss of its carbon, which is replaced by the excess of azote in the animal fluids. These maintain themselves, in this manner, in a due tem- perament ; for, continually parting with the carbonous principle in the in- testinal, pulmonary, and cutaneous combinations, they would be over ani- malized, if an additional quantity of chyle did not seize the azote, which is in excess. Still, this theory does not account for the formation of the phosphoric salts, of the adipocere, and a variety of other products ; but without adopting it, to the full, one may presume, from the experiments and facts on which it rests, that the oxygen ofthe atmospherical air is one of the most powerful agents employed by Nature, in the transformation ofthe aliments we live upon, into our substance. How are those animals nourished which live solely on mere animalized flesh, that is, containing a greater quantity of azote, and a greater proportion of ammonia than their own substance. In such a case, the assimilation of the aliments, consist in their desanimalization either, by the co-operation of all the organs, or by the sole action ofthe digestive organs, by the combina- tion ofthe gastric juice with the other fluids. The constituent elements entering into the composition of our organs, whether coming from the exterior, or formed by the vital power itself, are thrown out of our body, by the different emunctories, and cease to form a part of it, after remaining within it, for a limited time. The urine carries along with if, an enormous quantity of azote, the lungs and the liver rid us ofthe carbon and of the hydrogen ; the oxygen which contains eighty-five parts in the hundred, in the composition of water, is evacuated by means of * See APPENDIX, Notes W andC C. t The late experiments of Messrs. Allen and Pepys prove that when an animal is made to breathe pure oxygen, the blood disengages a certain quantity of azote, and absorbs an equal quantity of oxygen. Philosophical Transactions, 1809. 198 the aqueous secretions which carry off, in a state of solution, the saline and other soluble principles. Among those salts there is one, but little soluble, and which, nevertheless, is of primary consequence among the constituent principles of the animal economy. Phosphate of lime, in fact, forms the base of several organs, it almost entirely, forms the osseous system, at an advanced period of life ; all the white organs, all our fluids contain a remarkable quantity of that sub- stance, of which the economy rids itself by a kind of dry secretion. The outer covering is, in all animals, the emunctory destined for that purpose ; the annual moulting of birds, the fall of the hair of quadrupeds, the renova- tion of tne scales of fishes and reptiles, carry off, every year, a considerable quantity of calcareous phosphate. Man is subject to the same laws, with this difference, that the annual desquamation ofthe epidermis, is not under the absolute influence ofthe seasons, as in the brute creation. The human epidermis is renewed annually, as well as the hair on the head and on the body ; but this change is brought about gradually, and is not completed in a season : it does not take place in the spring, as in most animals, nor in au- tumn with the fall ofthe leaf, though at these two periods, the hair falls off in greatest quantity, and the desquamation of the cuticle is more active. These two phenomena last throughout the whole year, as in southern cli- mates, the fall ofthe leaves and the renovation of vegetation are continually going on. As will be mentioned, in speaking ofthe functions of generation, man living in a state of society, and enjoying all the advantages of civilization, is not as much under the influence of the seasons as the inferior animals. One cannot, however, but observe, that the successive shedding and renew- ing ofthe epidermoid parts, as the cuticle, the nails, and the hair, are among the most effective means which nature possesses of parting with the phos- phate of lime, so abundant in all animals, and which, nevertheless, is so in- soluble, and consequently so unfit to be carried out ofthe system, along with the excrementitious fluids. This effect is very remarkable, on the termina- tion of several diseases, in the salutary renovation of the solids and fluids which takes place during convalesence. The hair ceases to grow on the bald head of an old man ; his perspiration diminishes ; may not this be the cause of the great quantity of calcareous salts, ofthe ossification ofthe ves- sels, ofthe induration ofthe membranes ? CXI I. What is the ultimate results presented to us, by this series of func- tions, linked together, growing out of one another, and all acting on the mat- ter of nutrition, from the moment it is received within the body, till it is ap- plied to the growth and reparation of its organs*? It shows us man living within himself, unremittingly employed in converting, into his own substance, heterogeneous substances, and reduced to an existence purely vegetative, in- ferior even to the greater part of organized beings, in his powers of assimi- lation. But how high is he not placed above them all, in the exercise of those functions we are now about to contemplate, functions, which raise him above bis own nature, which enlarge the sphere of his existence, which serve him to provide for all his wants, and to keep up, with all Nature, those manifold relations which subject her to his empiref ! * Intimately connected with the consideration of nutrition is that of reproduction. This phenomena takes place to a very limited extent, indeed, in the more perfect animals ; but as we descend in the scale of creation, we find that the destruction of a member or part ofthe body of an animal is, after a time, followed by a partial, or entire reproduction ofthe part destroyed ; and amongst the lowest class of animals, even a portion only ofthe body becomes a perfect animal, and presents the specific characters of the parent. In this respect, the phenomena of animal life, as we descend through its gradations, approach those of vegetable existence. i For further observations on Nutrition, see APPENDIX,Notes S and C C. FIRST CLASS. SECOND ORDER. Functions which tend to the Preservation of the Individual, by establishing his Relations with the Beings that surround him. CHAPTER VII. OF SENSATIONS. CXIII. We have already seen, how the human body, esbentially change- able and perishable, maintains itself in its natural economy, carries on °its growth, and supplies its decay, by assimilating to its own substance, prin- ciples that are yielded to it by the food it digests, and by the air it breathes. We shall now proceed to examine, by what organs man is enabled to keep up, with all nature, the relations on which his existence depends; by what means he is made aware of the presence of objects which concern him, what means he possesses to fit his connexion with them to his welfare, to draw them towards him or to repel them, to approach or to avoid and escape them, as he perceives in them danger, or the promise of enjoyment. Man possesses, in all its plenitude, this new mode of existence, which is denied to vegetable Nature. Of all the animals it is he that receives im- pressions the most crowded and various, that is most filled with sensations, and that employs them, with the most powerful combination, as the mate- rials of thought, and the sources of intelligence: he is the best organized for feeling the action of all beings around him, and re-acting on them in his turn. In the study which we are about to undertake, we shall see many instruments placed on the limits of existence, on the surface of the living being ready to receive every impression ; conductors, stretching from these instruments to one common centre, to which all is carried; conductors through which this central organ regulates the actions, which now transport the whole body from one place to another (locomotion) ; now merely change the relative situation of its parts (partial motion); and, at other times, pro- duce, in the organs, certain dispositions, of which speech and language, in their various forms, are the result. CXIV. If we are thoroughly to understand the mechanism of this action of outward objects on our body, we must follow the natural succession of the phenomena of sensation ; sudying first, the bodies which produce the sensitive impression, examining next, the organs that receive it, and next the conductors which transmit it to a particular centre, whose office is percep- tion. To take the sense of sight, for instance, we can never understand how jt is that light procures us the knowledge of certain qualities of bodies, if we have not learnt The laws to which that fluid is subjected, if we know nothing ofthe conformation of the eyes, of the nerves by which those or- gans communicate with the brain, and of the brain itself, whither all sensa- tions, or rather the motions in which they consist, are ultimately carried. CXV. Of light. At this day, the greater part of Natural Philosopher? consider it as a fluid impalpable from its exceeding tenuity. Many believe it to be only a modification of caloric, or of the matter of heat; and this last opinion has received much plausibility from the late observations of Her- schel.* I shall not examine whether, as Descartes and his followers imagine, * This celebrated Astronomer has published, in the Philosophical Transactions of the Royal Society for J800, a series of experiments, which shew* that the d^rnrf ^'ourcd 26 202 light, consisting of globular molecules, exist of itself, uniformly diffused through space, or as Newton has taught us to believe, it be but an emanation ofthe sun and fixed stars, which throw off, from their whole surface, a part of their subsistence, without ever exhausting themselves by this continual efflux: It is enough for us to know, 1st, that the rays of this fluid move with such velocity, that light passes, in a second, through a distance of seventy- two thousand leagues, since, according to the calculation of Roemer and the tables of Cassini, it traverses in something less than eight minutes, the thirty- three millions of leagues that separate us from the sun; 2dly, that light is called direct, when it passes from the luminous body to the eye, without meeting any obstacle; reflected, when it is thrown back to that organ, by an opake body; refracted, when its direction has been changed, by pass- ing from one transparent medium to another of different density ; 3dly,that the rays of light are reflected at an angle equal to that of incidence ; that a ray, passing through a transparent body, is more strongly refracted, as the body is more convex on the surface, denser, or of more combustible ele- ments. It was from this last observation, that Newton conjectured the combustibility of the diamond, and the existence of a combustible principle in water, since placed beyond doubt, by the beautiful experiments of modern chemistry ; 4thly, that a ray of light refracted by a glass prism is decom- posed into seven rays, red, orange, yellow, green, blue, indigo, and violet. Each of these rays is less refrangible, as it is nearer to the red. This ray is of all, that which strikes the eye with the greatest force, and produces on the retina the liveliest impressions. The eagerness of savages for stuffs of this colour is well known*. Among almost all nations it has dyed the mantle of Kings: it is the most brilliant and splendid of all: there are animals whose eyes seem scarcely to sustain it: I have seen maniacs whose madness, after a long suspension, never failed to break out, at the sight of a red cloth, or of one cloathed in that colour. Green is, on the contrary, the softest of colours ; the most permanently grateful ; that which least fatigues the eyes; and on which they will longest and most willingly repose. Accordingly, Nature has been profuse of green, in the colouring of all plants; she has dyed, in some sort, of this colour, the greater part ofthe surface of the globe. When the eyes bear uneasily the glare of too strong a light, glasses of this colour are used to soften the impression, which slightly tinge, with their own hue, all the objects seen through them. Lastly, the violet ray, last in the scale, of which the middle place is filled by the green, is of all the weakest, the most-refrangible. Of all colours, violet has the least lustre; forms shew to less advantage under it; their prominences are lost; painters accordingly make but little use of it. When an enlightened body reflects all the rays, the sensations they might separately produce, blend into the sensation of white; if it reflects a few, it appears differently coloured, according to the rays it repels ; finally, if all be absorbed, the sensation of black is produced, which is merely the negation of all colour. A black body is wrapped in utter dark- ness, and is visible only by the lustre of those that surround it; 5thly, that from every point in the surface of a luminous or enlightened body, there issue a multitude of rays, diverging according to their distance, with a proportion- rays, heat, in different degrees, the bodies on which they fall, and that the red ray, which is the least refrangible, gives also the greatest heat. The thermometer placed out of the spectrum and towards the red ray, so that it would receive any rayj yet less refrangible, rises higher than when it is placed in that colour. From which Herschel concludes that rays are given out by the sun, too little refrangible to produce the sensation of light, and of colours-, but which produce the stnsatlon of heat*— Author's Note* 203 ate diminution of their effect; so that the rays from each visible point ofthe body, form a cone, of which the summit is at that point, and the base, the surface ofthe eye on which they fall. CXVI. Sense of sight. The eyes, the seat of this sense, are so placed, as to command a great extent of objects at once, and enclosed in two osseous cavities, known by the name of orbits. The base of these cavities, is for- wards, and shaped obliquely outwards ; so that their outward side not being so long as the others, the ball of the eye supported, on that side, only by soft parts, may be directed outwards and take cognizance of objects placed to a side^ without it being necessary, at the same time, to turn the head. In pro- portion as we descend from man in the scale of animated beings, the shape of the base of tbe orbits becomes more and more oblique ; the eyes cease to be directed forward, in short, the external side ofthe socket disappears, and the sight is entirely directed outward, and as the physiognomy derives its prin- cipal character from the eyes, its expression is absolutely changed. In cer- tain animals very fleet in running, such as the hare, the lateral situation of the organs of vision, prevents the animals from seeing small objects, placed directly before them, hence those animals, when closely pursued, are so easily caught in the snares which are laid for them. The organ of sight consists of three essentially distinct parts. The one set intended to protect the eye-ball, to screen it, at times, from the influence of light, and to maintain it in the conditions necessary to the exercise of its functions : these parts are the eye-brows, the eye-lids, and the lachrymal apparatus, and they serve as appendages of the organ. The eye-ball itself contains two parts, answering very different purposes ; the one, formed by nearly the whole globe, is a real optical instrument, placed immediately in front of the retina, and destined to produce on the luminous rays those changes which are indispensable, in the mechanism of vision; the other, formed by the medullary expansion of the optic nerve, is the immediate or- gan of that function. It is the retina, which alone is affected by the impres- sion of light, and set in motion by the contact of that very subtle fluid. This impression, this motion, this sensation is transmitted* to the cerebral organ; by the optic nerve, the expansion of which forms the retina. CXVII. Of the eye-brows, the eye-lids, and the lachrymal apparatus ( Tutamina oculi, Haller.) The more or less dark colour of the hairs ofthe eye-brows, renders that projection very well adapted to diminish the effect of too vivid a light, by absorbing a part of its rays. The eye-brows answer this purpose, the more completely, from being more projecting, and from the darker colours of the hairs which eover them: hence we depress the eye- brows, by knitting them transversely, in passing from the dark, into a place strongly illuminated, which causes an uneasy sensation to the organ of sight. Hence, likewise, the custom that prevails with some southern nations, whose eye-brows are shaded by thicker and darker hairs, to blacken them, that they may still better answer the purpose for which they are intended. The eye-lids are two moveable curtains, placed before the eyes which they alternately cover and uncover. It was requisite that they should be on the stretch, and yet capable of free motion ; now, both these ends are obtained by the tarsal cartilages, which are situated along the whole of their free edges, and of the muscles which enter into their structure. The cel- lular tissue, which unites the thin and delicate skin of the eye-lids to the muscular fibres, contains, instead of a consistent fat, which would have im- peded its motion, a gelatinous lymph, which, when in excess, constitutes oedema of the eye-lids. The tissue of the eye-lids is not absolutely opaque, 204 >inoe, even when strongly drawn together, and completely covering tin- globe ofthe eye, one may still discern through their texture, light from darkness. On that account, light may be considered as one of the causes of awakening, and it is of consequence to keep in the dark, patients fatigued by want of sleep. The principal use of the eye-lids is to shade the eyes from the continual impression of light. Like all the other organs, the eyes require to recruit themselves by repose ; and they had not been able to c.\joy it, if the inces- sant impression ofthe luminous rays had continually e\e'f.ed their sensibi- lity. The removal of the eye-lids* is attended with loss of sleep. The fluids arc determined to the affected organ which suffers from incessant irritation. The eyes inflame, the inflammation spreads towards the brain, and the pa- tient expires in the most dreadful agony. Thanks to an advanced state of civilization, these barbarous tortures have long been abolished ; but what happens, when from ectropium of one or other of the eye- lids, a small por- tion of the sclerotic coat or cornea remains uncovered, proves the indis- pensable necessity of those parts. The spot exposed to the continued action of the air and of the light, becomes irritated and inflamed, and there comes on an ophthalmia, which can be cured only, by bringing together, by means ofa surgical operation, the divided edges ofthe opening which is the cause of the affection. From the moveable edges of both eye-lids, there arise short curved hairs, of the same colour as those of the eye-brows; they are called eye-lashes, and are intended to prevent insects, or other very light substances, floating in the atmosphere, from getting between the eye-ball and the eye-lids.t The anterior part of the eye, thus defended against external injuries, is continually moistened by the tears. The organ which secretes this fluid, is a small gland situate in a depression at the anterior and external part of the arch of the orbit, imbedded in fat, and supplied with pretty considerable vessels and nerves in proportion to its bulk, and pouring the fluid it secretes, by means of seven or eight ducts which open on the internal surface of the upper eye-lid, by capillary orifices directed down- ward and inward. The tears are a muco-serous fluid, rather heavier than distilled water, saltish, changing to a green colour, vegetable blues, and containing soda, muriate, and carbonate of soda, and a very small quan- tity of phosphate of soda and of lime.f In ophthalmia, the irritation of the conjunctiva, transmitted by sympa- thy, to the lachrymal gland, not only augments the quantity of its secretion, but appears, likewise, to alter the qualities of the fluid that is secreted. The tears which, in those cases, flow in such profusion, bring on a sense of burning heat in the inflamed part; do they not, perhaps, contain a greater quantity of the fixed alkali than in the ordinary state of the parts, and may not the painful sensation depend as much on the increased pro- portion of soda in the tears, as on the greater sensibility of the conjunctiva? This last membrane is merely a fold of the skin, which is exceedingly *A mode of punishment adopted by the ancients, especially the Carthaginians. t They also absorb and intercept some of the luminous rays, and thus diminish the hurtful effects of too strong a light. }" The saline parts amount only to about 0- 01 ofthe whole. The mucus contained in the tears has the property of absorbing oxygen from the atmosphere, and of becom- ing thick and viscid, and of a yellow colour. This property of acquiring new properties from t.ie absorption of oxygen explains the changes which take place in tears in some diseases of the eye." See the Chapter, at the end of the Appendix, on the Chemical Constitution of the Textures and Secretions. 205 thin,*covers the posterior surface of the eye-lids, and is then reflected over the anterior surface of the eye, which it thus unites to the eye-lids. From the whole extent of this surface, there oozes an albuminous serosity, which mingles with the tears, and adds to their quantity.* The tears are equably diffused over the globe of the eye, by the alternate motions of the palpebrse ; they prevent the effects of friction, and save the organ of sight from being dried, at that part which is exposed to the air. The air dissolves and carries off, by evaporation, a part of the lachrymal fluid. This evaporation of the tears is proved by the weeping to which those in whom that secretion is very profuse, are subject, whenever the atmospherical air, from being damp, does not carry off a sufficient quantity of the fluid. The unctuous and oily fluid, secreted by the meibonian glands, smears the loose edge of the palpebrse, prevents the tears from falling on the cheek, and answers the same purpose as the greasy substance with which one anoints the edges of a vessel, filled above its level, to pre- vent the overflowing of the contained fluid. The greatest part of the tears, however, flow from without inward and towards the inner canthus of the eye ; they take that direction in conse- quence of the natural slope of the moveable edge of the palpebrae, of the triangular groove, which is formed behind the line of union of their edges whose round and convex surfaces touch each other only in a point, and this course of the tears is likewise promoted by the action of the palpebral portions of the orbicularis palpebrarum, whose fibres, having their fixed point at the inner angle of the orbit, where the tendon is inserted, always draw inward their external commissure. On reaching the internal angle of the palpebrae, the tears accumulate in the lacus lachrymalis, a small space formed between the edges of the pal- pebral kept separated from each other by the caruncula lachrymalis. This last substance, long considered by the ancients as the secretory organ of the tears, is merely a collection of mucous cryptae covered over by a loose fold of the conjunctiva. These follicles, alike in nature to the mei- bomian glands, secrete like them, an unctuous substance which smears the moveable edges of the palpebrae, near the internal commissure. The edges of the eye-lids, in this situation, require a thicker coating, as the tears accumulated in that spot have no where a greater tendency to flow on the chee!,.. Near the union of the inner sixth of the free edge of the palpebrae with the remaining five-sixths, at the outer part, where their internal, straight, or horizontal portion unites with the curved part, there are situ- ated two small tubercles, at the top of each of vvhich there is a minute orifice. These are the puncta lachrymalia, and they are called superior and inferior, according to the palpebrae to which they belong. In the dead body, the puncta do not appear to be tubercular, the small bulgings produced, doubtless, by a state of orgasm and of vital erection, collapse at the approach of death. These small apertures, directed inward and back- * There is no opening in the skin at the part which corresponds to the globe of the eye; it is exceedingly thin, and is continued, under the name of conjunctiva, over the transparent cornea, to which it adheres so "firmly, that it is not easily separated from it. In some animals that have no palpebrae, the skin is continued, of the same thickness, over the fore part of the eye. The conjunctiva (if, however, this portion of skin de- serves that name) when opaque, renders the globe of the eye, iu other respects imperfect, absolutely useless. This is observed in the kind of eel called, in books of natural history, murena cazcilia: the gastrobranchus catcus is blind from the same circumstance.—(Richk- rano.) M. Biefc Js of opinion that it terminates af the circumference of die cornea. 206 ward, are incessantly immersed in the accumulated tears, absorb them and convey them into the lachrymal sac, by means of the lachrymal ducts of which they are the external orifices. The absorption of the tears, and their flow into a membranous reservoir lodged in the groove formed by the os unguis, do not depend on the capillary attraction of the lachrymal ducts; each of them, endowed with a peculiar vital action, takes up, by a real process of suction, the tears accumulated in the lacus lachrymalis, and determines their flow into the sac. The weight of the fluid, the effort of the columns which succeed each other, co-operate with the action of the parietes of the duct. The flow of the tears is further facilitated by the compression and slight concussions attending the contractions of the palpebral fibres of the orbicularis, behind which the lachrymal ducts are situated. This vitality of the puncta lachrymalia and of the ducts is rea- dily discovered, when we attempt to introduce into them Anel's syringe or Mejean's stylet, to remove slight obstructions of the lachrymal passages. In a child now under my care, for a mucous obstruction of the nasal duct, I can see the puncta lachrymalia contract, when the extremity of the syphon does not, at once, enter the canal. One is then obliged to wait, before it can be introduced, for a cessation of the spasmodic contraction, sac, which lasts but a few moments. The tears which flow into the lachrymal by the common orifice of the united puncta lachrymalia, never accumulate within it, except in case of morbid obstruction ; they, in that case, at once enter into the nasal duct, which is a continuation of it, and fall into the nasal fossse, below the anterior part of the inferior turbinated bones of these cavities. There, they unite with the mucous of the nose, increase its quantity, render it more fluid, and change its composition. The use of the tears is to protect the eye-ball against the irritating impression of the immediate contact of the atmosphere. They, at the same time, favour the sliding of the palpebrae, lessen the friction in those parts and in the eye- ball, and thus promote their motion. CXVIII. Of the globe of the eye. The eye-ball, as was already ob- served, may be considered as a dioptrical instrument placed before the retina; whose office it is to refract the luminous rays, and to collect them into one fasciculus, that may strike a single point of the nervous membrane exclusively calculated to feel its impression. An outer, membranous, hard, and consistent covering supports all its parts. Within the first mem- brane called the sclerotic, lies the choroid, a darkish coat, which lines the inside of the sclerotic, and forms the eye into a real camera obscura.* At the anterior part of the globe, there is a circular opening in the sclerotic in which the transparent cornea is inserted. At about the distance of the twelfth part of an inch from this convex segment, received in the anterior aperture of the sclerotica, lies the iris, a membranous partition placed per- pendicularly, and containing a round opening, (the pupil) which dilates or contracts, according to the state of dilatation or contraction of the iris. * Gmelin (Schweigger's Joum. x 507.) made an interesting set of experiments, in order to determine the composition of the black pigment which lines the choroid coat of the eye. "Its colour," he informs us, "is blackish brown, is tasteless, and adheres to the tongue like clay; is insoluble in water, alcohol, ether, oils, lime-water, and distilled vinegar. It dissolves in potash and ammonia when assisted by heat, and is again precipitated by acids. Sulphuric acid dissolves it, and changes its colour to reddish-brown. When dis- tilled, it yields water, a brown oil, and carbonate of ammonia. It gives out, at the same time, carburelted hydrogen, carbonic oxide, azotic and oxygen gasses. The coal re- maining in the retort, consists almost entirely of charcoal." 207 0 At the distance of about half a line from the hack part of the iris, to- wards the union of the anterior fourth of the globe of the eye with the posterior three fourths, opposite to the opening of the pupil, there is situa- ted a lenticular body, inclosed in a membranous capsule, immoveably fixed in its situation by adhering to the capsule of the vitreous humour. Behind the crystalline lens, the posterior three fourths of the cavity of the eye contain a viscid transparent humour, enclosed in the cells of a re- markably fine capsule, called hyaloid. This vitreous humour forms about two-thirds of a sphere from which the anterior segment had been taken out; the pulpous expansion of the optic nerve, the retina, is spread out on its surface, so as to be concentrical to the choroid and sclerotic coats. The eye-ball being nearly spherical, the length of its different diameters differs but little. The diameter of the eye, from the fore to the back part, is between ten and eleven lines ; the transverse and vertical diameters are somewhat shorter. Within the space measured by the diameter from the fore to the back part, there are situated, taking them in their order from the fore part, the cornea, the aqueous humour contained in the anterior chamber, the iris and its central opening or pupil; the aqueous humour of the posterior chamber; the crystalline lens, surrounded by the ciliary pro- cesses ; then, the vitreous humour in its capsule, and behind those transpa- rent parts of,the eye, through which tbe luminous rays pass, in approaching to a perpendicular, are the retina which receive the impression, the choroid whose black point absorbs the rays that pass through the thin and transpa- rent retina, and the sclerotic in which there is an opening for the passage of the optic nerve to the globe of the eye. The cornea, contained in the anterior aperture of the sclerotica, like the glass of a watch case within its frame, is about the third of a line in thick- ness ; it forms, at the fore-part of the eye, the segment of a smaller sphere: behind it lies the aqueous humour which fills what are called the chambers of the eye ; these form spaces divided into anterior and posterior, the former, which is the larger of the. two, bounded by the cornea at the fore part, and by the iris at the back part; the latter, which is smaller, and separates the crystalline humour from the iris, the posterior part of which, covered by a black pigment, is called the uvea.* The specific gravity of the aqueous humour does not much exceed that of distilled water; some have even thought it less ; it is albuminous, and holds in solution several * Some anatomists have doubted the existence of the posterior chamber of the eye; but to be convinced of its existence, one need but freeze an eye, when there will be found a piece of ice between the crystalline lens and the uvea. The formation of this isicle is not owing to the admission, through the opening of the pupil, of the aqueous humour which, like all other fluids, expands considerably on freezing, for, the expan- sion of fluid* on their freezing, being proportioned to their bulk, the vitreous humour which freezes at the same time as the aqueous, must prevent its retrogade flow through the pupil. Lastly, the uvea or posterior part of the iris is covered with a black point which is easily detached from it; now, if the anterior part of the crystalline lens had been in immediate contact with it, it would have been soiled by some of this colouring matter which would have tarnished its natural transparency, indispensable to perfect vision. It is, therefore, undeniable that there does exist a posterior chamber, which is to the anterior in the proportion of two to five, and containing about two-fifths of the aqueous humour, the whole of which is estimated at five grains, and that the iris forms a loose partition between tbe two portions of the aqueous humour in which the dark pigment of the uvea is insoluble. The aqueous humour appears to be the product of arterial exhalation ; it is soon reproduced, as we see after the operation for cataract. Author's Note, 208 saline substances.* The crystalline, inclosed in its membranous ami transparent capsule, is a lenticular body rather solid than fluid ; its consist- ence is particularly great towards its centre ; it there forms a kind of nucleus, on which are laid several concentric layers, whose density dimi- nishes as they approach the surface, where the external layers, truly fluid, form what Morgagni considered, as a particular liquid on which the lens might be nourished by a kind of imbibition. This body, composed of two segments of unequal convexity, about two lines in thickness, at its centre, consists of an albuminous substance coagulable by heat and alkohol. Ex- tremely minute arteries given off by the central artery of Zinn, pass through the vitreous humour, and bring to it the materials of its growth and reparation.t The vitreous humour, so called from its resemblance to melted glass, is less dense than the crystalline, and more so than the vitreous, and is in considerable quantity in the human eye ; it appears to be secreted by the minute arteries which are distributed to the parietes of the membrane of the vitreous humour ; it is heavier than common water, somewhat albumi- nous and saltish.^ The sclerotica is a fibrous membrane to which the tendons which move the globe of the eye are attached; it supports all the parts of that organ, and these collapse and decay, whenever the continuity of its external covering * The Aqueous Humour. Specific gravity 1090 at a temperature of 60. From various recent experiments, it appears to be water slightly impregnated with—1st. Albumen; 2d. Gelatin; 3d. Muriate of soda. Its constituents, according to the analyses of Ber- zelius, are:— Water.........98 10 Albumen........a trace Muriates and lactates......1*15 Soda, with animal matter soluble only in water 75 10000 t The Chrystalline Lens. Its specific gravity is 1100. When fresh it has little taste. It putrifies very rapidly. It is almost completely soluble in water. The solution is partly coagulated by heat, and gives a copious precipitate with tannin both before and after the coagulation. Its composition, according to the analysis of Berzelius, is as follows :— Water ,..........580 Peculiar matter.........3* 9 Muriates, lactates, and animal matter soluble in alcohol . 2 4 Animal matter soluble only in water with some phosphates 13 Portions of the remaining insoluble cellular membrane . 2-4 100-0 The peculiar matter of the lens possesses all (he chemical characters of the colouring matter ofthe blood, except colour. When burnt it leaves a little ash, containing a very small portion of iron. When its solution in water is coagulated by boiling, the liquid in which the -oagulum was formed reddens iumus, containing free lactic acid. (Ann. Phil. 11-386.) I The Vitreous Humour possesses the same properties as the aqueous, even its spec. grav is the same, or only a very little greater. Its constituents, according to the analy- sis of Berzelius, are :— Water........• 98-40 Albumen........© 16 Muriates and lactates......1.42 Soda, with animal matter soluble only in water 0*02 10000 203 u» destroyed. The use of the choroid, is not so much to afford a covering to the other parts, as to present a dark surface, destined to absorb the luminous rays, when they have produced on the retina a sufficient impression. If it were not for the choroid, the light would be reflected, after having impin- ged on the nervous membrane, its rays would cross, and produce only indistinct sensations. Mariotte thought that the choroid was the immedi- ate seat of vision, and that the retina was only its epidermis. This hypo- thesis would never have obtained so much celebrity, if, besides the objections that analogy might have furnished against it, there had been adduced, in opposition to it, the fact observed in fishes, in which the cho- roid is separated from the retina, by a glandular body, opaque and incapable of transmitting the luminous rays. The retina loses its form, as soon as it is separated from the vitreous humour, or from the choroid coat, between which it is spread out as a very thin capsule, so soft as to be almost fluid. A number of blood-vessels, from the central artery of Zinn, are distributed on the nervous substance of the retina, and give it a slight pink colour. Ought we, with Boerhaave, to attribute to the aneurismal or varicose en- largements of those small vessels, the spots which are seen in objects, in the disease to which Maitre Jean gave the name of imaginations? In order to form the retina, the optic nerve which penetrates into the globe of the eye, by piercing the sclerotica, to wbich the covering given to that nerve by the dura mater is connected ; the optic nerve, penetrates through a very thin membrane perforated by a number of small holes and closing the opening left by the nerve, and which belongs as much to the choroid as to the sclerotic coats, it then spreads out to furnish the expansion which lines the concavity of the choroid, and covers over the convex surface of the vitreous humour.* The whole extent of the retina, which is equally ner- vous and sentient, may receive the impression of the luminous rays, though this faculty has, by several philosophers, been exclusively assigned to its central part, called the optical axis or porus opticus. This central part is easily recognized, in man, by a yellow spot discovered by Soemmering; in the middle of this spot, situated at the outer side of the entrance of the optic nerve into the globe of the eye, there is seen a dark spot and a slight depression, the use of which is not understood. This peculiar structure, recently discovered, is met with only in the eye of man and of monkeys. CX1X. Mechanism and phenomena of vision. The rays of light pass- ing from any point of an enlightened object, form a cone of which the * The optic nerves differ very remarkably from the other cerebral pairs, both in their thickness, and in the delicacy of their substance which appears to be an immediate continuation of medullary fibres of the brain, to which the meninges furnish one com- mon envelope, and not a distinct iriembranous canal for each fibre. The nerves of vision cross each other before the cella turcica, in a manner similar to the primitive crossing, which their roots, as well as those of the other nerves, undergo in the substance of the brain. These double decussations may be said to neutralize each other, and, consequently, each optic nerve may be considered to arise primarily from the hemisphere corresponding to the eye which it supplies. In hemiplegia, the affected eye is not on that side of the body struck with the paralysis—it is on the opposite side that the pupil is dilated, and this pathological phenomenon, which is easily proved in persons who have experienced a paralytic seizure, seems to be one of the best proofs which can be opposed to those who suppose that the optic nerves, where they approach each other, experience an approximation of their fibres only. It may be farther argued, in support of the actual decussation of these nerves, that the wasted optic nerve of an eye that has been for some time in a slate of atrophy can be traced towards the opposite lobe of the brain ; and that an evident crossing of the optic nerves may be observed in many of the class of fishes. 27 210 apex answers to the point of the object, and of which the base covers the anterior part of the cornea. All the rays, more diverging, which fall without the area of the cornea on the eye-brows, the eye-lids, and the sclerotica are lost to vision. Those which strike the mirror of the eye pass through it, under a refraction proportioned to the density of the cor- nea, which much exceeds that of the atmosphere, and to the convexity of that membrane, approaching the perpendicular, they now pass through the aqueous humour, less dense, and fall upon the membrane called the iris. All those that fall upon this membrane are reflected, and show its colour, different in different persons, and apparently depending on the organic texture, and on the particular and very diversified arrangement of the nerves, of the vessels, and cellular tissue, vvhich enter into its structure. None but the most central traverse the pupil and serve to sight. These will pass that opening, in greater or less number, as it is more or less dilated. Now, the pupil is enlarged or diminished, by the eoniraction or expansion of the iris. The motions of this membrane depend entirely on the manner in which light affects the retina. The iris itself is insensible to the impression of the rays of light, as Fontana has proved, who always found it immoveable, when he directed on it alone the luminous rays. When the retina is disagreeably affected, by the lustre of too strong a light, the pupil contracts, to give passage only to a smaller number of rays : it dilates, on the contrary, in gloom, to admit enough to make the requisite impression on the retina. To explain the motions of the iris, it is not necessary to admit that mus- cular fibres enter into its structure ;* it is enough to know its vascular, * Some anatomists contend, and we think justly, that two sets of muscular fibres enter into the structure of the iris, the one radiant, and the other orbicular. Amongst those who have lately argued in support of this position, we may mention M. Maunoir, of Geneva. It appears to us, that those who deny muscularity 1o this part, do so in conse- quence of a mistaken idea, which seems to be too generally adopted, viz. that no part is really muscular but that which possesses fibres of a similar appearance to those which perform the function of voluntary motion. It should, however, be kept in recollection that involuntary muscles—those fibrous textures which receive only nerves proceeding, from the ganglia, which are not supplied with voluntary nerves, and which are, conse- quently, not directly influenced by the will—differ very essentially from voluntary muscles in their structure Indeed muscular textures vary not only in their functions, but even in their external characters, according as they are more or less plentifully sup- plied with either class 6f nerves—the cerebral or ganglial. The structnre also of mus- cular parts, especially those which are removed from the influence of volition, has some relation to the kinds of irritants by which they are designed by nature to be influenced. Thus the eye being formed with an intimate relation to the functions which it has to perform, and to the external influences which act on it, possesses, in the structore of its iris, a muscular texture of peculiar delicacy, and hence it is more sensible to the irritations which accompany, and are subservient to, the right performance of this impor- tant animal function. If the structure of the iris, the number of the soft and delicate nervous fibrils which proceed to it from the lenticular ganglion, and the connexion vvhich they form with the retina in their course, be kept in view, we shall readily be able to comprehend the procession of phenomena which lead to the motions of the iris. It is not improbable that the nervoas fibrils proceeding from the ganglion to the iris form, with the capillary arteries which supply its cellular texture, that particular organization which may be considered as muscular; or, in other words, that these ganglial nerves terminating conjunctly with eapillary ramifications in the delicate cellular substance of the iris constitute, by such a disposition, its particular structure, and enable it to perform its peculiar functions. Hence it will be seen that impressions made upon the retina, (in the sensible state of that nervous expansion, and in proportion to the extent of its sensibility) and transmitted to the iris, by means of the connexion which exists between the retina and the nerves supplying the iris, cause a contraction of its circular fibres: as soon as such impressions cease, these fibres relax,and the'comparative action, in the ctrciltar arm" 211 spungy and nervous texture; the irritation of the retina sympathetically transmitted to the iris, determines a more copious afflux of humours; its tissue dilates and stretches, the circumference of the pupil is puhed to- wards the axis of this opening, which becomes contracted by this vital expansion of the membranous tissue. When the irritating cause ceases to act, by our passing from light into darkness, the humours flow back into the neighbouring vessels, the membrane of the iris returns upon itself, and the pupil enlarges, the more as the darkness is greater. The rays, admitted by the pupil, pass through the aqueous humour of the posterior chamber, and soon meet tbe crystalline, which powerfully refracts them, both from its density and its lenticular form. Brought towards the perpendicular by this body, they pass on towards the retina through the vi- treous humour, less dense, and which preserves, without increasing it, the refraction produced by the crystalline lens. The rays, gathered into one, strike on a single point ofthe retina, and produce the impression which gives us the idea of certain properties of the body which reflects them. As the retina embraces the vitreous humour, it presents a very extensive surface to the contact of the rays, vvhich enables us to behold, at once, a great diversi- ty of objects, variously situated towards us, even when we or these objects .change our relative situation.* The luminous rays, refracted by the trans- parent parts ofthe eye, form therefore, in the interior ofthe organ, a cone, of which the base covers the cornea, and applies to that of the external lu- minous cone, whilst its apex is on some point of the retina. It is-conceived, generally, that the luminous cones issuing from all points of the object be- radiated fibres, giving rise to certain states of pupil, is relative to the extent, to which the irritation proceeds along the axis of the nerves and vessels, and affects either set of fibres. According to this view of the subject, compression of the brain, or an insensible state of the optic nerve, is followed by expansion of the pupil, because the first impression requisite to contraction ofthe orbicular fibres cannot be made, unless occasionally to a small extent, owing to the loss of sensibility, and consequently the greater tonic power of the antagonist (the radiated) fibres predominates in preserving a permanent stale of dilatation of the pupil. The pupil is also dilated in weak children, and in those afflicted with worms, conformably to what is generally observed in the animal economy, name- ly, that all orbicular muscles, when no adjoining irritation exists, exhibit a greater or less degree of relaxation as the vital energies are more or less diminished. It would appear, in a debilitated state ofthe system, that the nervous influence proceeding from the lenticular ganglion is insufficient to the purpose of exciting fully the orbicular fibres ofthe iris, and, al the same time, the retina perhaps, possesses that low degree of sensi- bility to the irritation of light which is followed by an inadequate effect upon the nerves supplying the iris. Indeed it seems, under the circumstances just referred to, where irritation is generally present in the abdominal viscera, that nervous influence is secreted in the brain and parts adjoining in an insufficient manner, and consequently the dimi- nished activity of the cerebral and ganglial nerves supplying the various structures of the eye is the result. When, however, irritation exists in the brain, or when an increase ofthe circulation occurs in that organ, without overwhelming its powers, accompanied with, or preceded by debility, the pupil contracts, or even remains contracted, because, in eonsequence of such irritation or increase of circulation in the brain and connected parts, the sensibility and nervous activity are heightened. * The rays of light may be said to penetrate or traverse the demi-transparent tissue of the retina, and, as it were, to search through the nervous pulp, when they arrive at the choroid coat, which is designed, in a great measure, to absorb these rays. Does any in- timate combination take place between the nervous pulp and the light, which may give rise to that sensation which follows a violent compression of the globe of the eye in an obscure situation ? The spots which are observable after having had the eye fixed, for a considerable time, on certain coloured objects, do they arise from this sort of impregna- tion of the retina, oi rather ofa portion of it, with the rays of light, or, as is more gene- rally believed, has the sensibility of the retina, become partially increased or diminished jv tbe circumstance of inaction, or of exercise ? 212 held, cross in their passage through the eye, so that the object is imaged on the retina reversed. Admitting this opinion, established on a physical ex- periment, we have to inquire, why we see objects upright, whilst their image is reversed on the retina. The best explanation we possess of this phenomena, we owe to the philosopher Berkeley, who proposed it in his English work, entitled Theory of Vision, &c. In his opinion, there is no need ofthe touch to correct this error into which sight ought to betray us. As we refer all our sensations to ourselves, the uprightness of the object is only relative, and its inversion really exists at the bottom of the eye. By the point of distinct vision, is understood the distance at which we can read a book of which the characters are of middling size, or distinguish any other object equally small. This distance is not confined within very narrow limits, since we can read the same book at six inches from the eye, or at five or six times the distance. This faculty of the eyes to adapt them- selves to the distance and the smallness of objects, cannot depend, as has been fondly repeated, on the lengthening or shortening of the globe of the eye by the muscles that move it. Its four recti muscles are not, in any case, capable of compressing it on its sides, nor of lengthening it by altering its spherical form; their simultaneous action can only sink the ball in its socket, flatten it from the fore to the back part, diminish its depth, and make there- fraction, consequently, less powerful, when objects are very distant or very small: this last effect, even, might be disputed. The eye which moves and rests on the adipose cushion which fills the bottom of the socket, is never strongly enough pressed to lose its spherical figure, which of all the forms in which bodies can be invested, is that which, by its especial nature, best resists alteration. The extremities of the ciliary processes, which surround the circumference of the crystalline lens, cannot act on this transparent lens, compress nor move it: for, these little membranous folds, of which the ag- gregate composes the irradiated disk, known under the name of corpus ciliare, possessing no sort of contractile power, are incapable of moving the crystalline lens with which their extremities lying in simple contiguity have no adherence, and which, besides, is immoveably fixed in the depression which it occupies, by the adhesions of its capsule with the membrane ofthe vitreous humour. The various degrees of contraction or dilatation of which the eye-ball is susceptible, afford a much more satisfactory explanation of this physiological problem. The rays of light which come from a very near object, are very diver- gent : the eye would want the refracting power necessary to collect them into one, if the pupil, contracting by the enlargement of the iris, did not throw off the more divergent rays, or those which form the circumference of the luminous cone. Then, those, which form the centre of the cone, and which need but a much smaller refraction for their re-union on a single point of the retina, are alone admitted by the straitened opening. When, on the contrary, we look at a distant object from which rays are given out, already very convergent, and which need but a small refraction to bring them towards the perpendicular, we dilate the pupil, in order to admit the mere diverging rays, which, when collected, will give the image of the ob- ject. In this respect, very small bodies are on the same footing as those at a great distance. Though the image of every object is traced at the same time in both pur eyes, we have but one sensation, because the two sensations are in harmony and are blended, and serve only, one aiding the other, to make the impres- sion stronger and more durable. It has long been observed, that sight i9 213 more precise and correct when we use only one eye, and Junne thinks that the power of the two eyes united exceeds only by one thirteenth, that ofa single eye. The correspondence of affection requires the direction of the optical axes on the same objects, and be that direction ever so little dis- turbed, we see really double, which is what happens in squinting. If the eyes are too powerfully refractive, either by the too great convex- ity ofthe cornea and the crystalline, the greater density ofthe humours, or the excessive depth ofthe ball, the rays of light, too soon re-united, diverge anew, fall scattering on the retina, and yield only a confused sensation. In this defect of sight, called myopia, the eye distinguishes only very near ob- jects, giving out rays of such extreme divergence as to require a very pow- erful refractor. In presbytia, on the other hand, the cornea too much flat- tened, the crystalline little convex, or set too deeply, the humours too scanty, are the cause that the rays are not yet collected when they fall upon the re- tina, so that none but very distant objects are distinctly seen, because the very* convergent rays they give out, have no need of much refraction. Myopia is sometimes the effect of the habit which some children get, of looking very close at objects which catch their attention. The pupil then becomes accustomed to great constriction, and dilates afterwards with diffi- culty. It is obvious, that, to correct this vicious disposition, you must show the child distant objects which will strongly engage his curiosity, and keep v him at some distance from every thing he looks at. The sensibility ofthe retina, on some occasions, rises to such excess, that the eye can scarcely bear the impression of the faintest light. Nyctaclopes, such is the name given to those affected with this disorder, distinguish ob- jects amidst the deepest darkness; a few rays are sufficient to impress their organ. . It is related that an English gentleman, shut up in a dark dungeon, came gradually to distinguish all it contained: when he returned to the light of day, of which he had in some sort lost the habit, he could not endure its splen- dour, the edges of the pupil, before extremely dilated, became contracted to such a degree as entirely to efface the opening. When, on the other hand, the retina has little sensibility, strong daylight is requisite to sight. This injury of vision, known by the name of hemera- lopia^ may be considered as the first step of total paralysis of the optic nerve, or gutta serena. It may arise from any thing that can impair the sensibility of the retina. Saint-Yves relates, in his work on diseases ofthe eyes, many cases of hemeralopia. The subjects were chiefly workmen, employed at the Hotel des Monnoies, in melting the metals- The inhabit ants of the northern regions, where the earth is covered with snow great part ofthe year, become at an early age hemeralopes. Both contract this weakness, from their eyes being habitually fatigued by the splendour of too strong a light. . . Finally, in order to the completion ofthe mechanism of vision, it is re- quisite that all parts of the eye be under certain conditions, the want of which is more or less troublesome. It is especially necessary, that the mem- * The author means " scarcely divergent."— Trans. . f I give to the words nyctalopia and hemeralopia the same meaning as all other writers down to Scarpa, who has published the latest Treatise on diseases of the eyes. This ac- ceptation is, however, a grammatical error, since of the two terms, nyctalopia, in its Greek roots, signifies an affection which takes away sight during the night, and hemeralopia,one in which it is lost during the day. It is accordingly in this sense that they are used by the father of physic. I owe this remark to Dr. Roussille Chamseru, who has carefully verified tb<- text of Hippocrates in the MSS. ofthe Imperial Library.—Author's Nofr 2M branes and the humours which the rays of light are to pass through, should be perfectly transparent. Thus, specks of the cornea, the closing of the pupil by the preservation of the membrane vvhich stops that opening during the first months of the life of the foetus; cataract, an affection which consists in the opacity of the crystalline lens or its capsule ; the glaucoma, or defect of transparency in the vitreous humour, weaken or altogether destroy sight, by impeding the passage of the rays to the retina. This membrane itself must be of tempered sensibility to be suitably affected by their contact. The choroid, the concavity of which it fills, must present a coating black enough to absorb the rays that pass through it. It is to the sensible decay of the dye of the choroid in advancing years, as much as to the collapsing induration, and discolouring of different parts of the eye, and the impaired sensibility of the retina from long use, that we ascribe the confusion and weakness of sight in old people. The extreme delicacy of the eyes of the Albinos proves equally the necessity of the absorption of light, by the black coating which covers the choroid. The eyes are, of all the organs of sense, those which are the most deve- loped in a new-born child.—They have then nearly the bulk which they are to retain during life. Hence it happens, that the countenance of chil- dren, whose eyes are proportionably larger, is seldom disagreeable, because it is chiefly in these organs that physiognomy seeks expression. Might we not say, that if Nature sooner completes the organ of sight, it is because the changes vvhich it produces on the rays of light, arising purely from a phy- sical necessity, the perfection of the instrument was required for the exer- cise of the sense ? The eyes are not immoveable in the place they occupy. Drawn into very various motions, by four recti muscles, and two oblique, they direct themselves towards all objects of which we wish to take cognizance; and it is observed, that there is, between the muscles which move the two oyes, sueh a correspondence of action, that these organs turn at once the same way, and are directed, at once, towards the same object, in such a manner, that the visual axes are exactly parallel. It sometimes happens, that this harmony of motion is disturbed; and thence squinting; an affection, vvhich depending, almost always, on the unequal force ofthe muscles ofthe eye, may be distinguished into as many species as there are muscles which can draw the globe of the eye into their direction, when from any cause, they become possessed of a predominating power. Buffon has further as- signed as a cause of squinting, the different aptitude of the eyes to be affect- ed by light. According to this celebrated naturalist, it may happen, that one of the eyes being originally of greater sensibility, the child will close the weaker to use the stronger, which is yet strengthened by exercise, whilst repose still weakens the one which remains in inaction. The exami- nation of a great many young people, who had fallen under military con- scription, and claimed exemption, on the score of infirmities, has shown me that squinting is constantly connected with the unequal power of the eyes. Constantly, the inactive eye is the weakest, almost useless, and it was quite a matter of necessity that the diverging globe should be thus neutralized, else the image it would have sent to the brain, different from that which the sound eye gives, would have introduced confusion into the visual functions. The squinting eye, being inactive, falls by degrees into that state of debili- ty, from default of exercise, which Brown has so well called indirect debility. The sense of sight appears to me, much rather to deserve the name which J. J. Rousseau has given to that of smell, of sense of the imagination. Like 215 that brilliant faculty ofthe soul, the sight, which furnishes us with ideas sju rich and varied, is liable to betray us into many errors. It may be doubted, Whether it gives the notion of distance, since the boy couched by Chesel- den, conceived every thing he saw to touch his eye. It exposes us to false judgments on the form and size of objects; since, agreeably to the laws of optics, a square tower seen at a distance, appears to us round; and very lofty trees seen also very far off, seem no taller than the shrubs near us. A body, moving with great rapidity, appears to us motionless, &c. It is from the touch, that we gain the correction of these errors, vvhich Condillac, in his Treatise on Sensation, has perhaps exaggerated. CXX. The organ of sight, in different animals, varies according to the medium in vvhich they live ; thus, in birds which fly in the higher regions of the air, there is an additional and very remarkable eye-lid : this is particu- larly the case with the eagle, which is thus enabled to look at the sun, and with night birds, whose very delicate eye it seems to protect from the effects of too strong a light. In birds, likewise, there is a copious secretion of tears, the medium in which they live causing a considerable evaporation. The greater part of fishes, on the contrary, have no moveable eye-lid, and their eyes are not moistened by tears, as the water in vvhich they are immersed, answers the same purpose. In some fishes, however, the eyes are smeared with an unctuous substance calculated to prevent the action of the water on the organ. The globe of the eye in birds, is remarkable by the convexity of the cor- nea, which is, sometimes, a complete hemisphere, hence it possesses a con- siderable power of refraction. This power of refraction, appears to be very weak in fishes, the fore part of their eyes being very much flattened; but the water in which they live made it unnecessary, that they should have an aqueous humour, for, the density of this fluid being nearly the same as that of water, it would not have produced any refraction: besides, being, in sea- fish, of inferior density to that of salt water, it would have broken the rays of light, by making them diverge from the perpendicular. In fact, the re- fractive power of a medium is never but a relative quantity ; the degree of refraction is not determined by the density of the medium, but by the dif- ference of density between it and the medium that is next to it. To make up for the flatness ofthe cornea occasioned by the small quantity, or even by the absence, of aqueous humour, fishes have a very dense and spherical crystalline humour, the spherical part of which forms a part of a small sphere. The eyes of birds, whose cornea is thrust out by a very copious aqueous humour, possess, in consequence of the presence of this fluid, a very consi- derable power of refraction ; the air, in the higher regions of the air, owing to its extreme rarefaction, being but little calculated to approximate the rays of light. The pupil admits of greater dilatation in the cat, in the owl, in night birds, and in general in all animals that see in the dark. The sensibility of the retina appears, likewise, greater in those animals ; several of them appear incommoded by the light of day, and never pursue their prey, but in the most obscure darkness. The crystalline humour of several aquatic fowls, as the cormorant's, is spherical like that of fishes, and this is not, as will be mentioned hereafter, the only peculiarity of structure in these kind of amphibious animals. Last- ly, the choroid of some animals, more easily separated into two distinct lami- nae, than that of man, presents, at the bottom of the eye, instead of a dark* 2lii isii, uniformly diffused coating, a pretty extensive spot ol various colours, and in some, most beautiful and brilliant. It is not easy to say what is the use of this coloured spot, known by the name of tapetum. The rays of light, reflected by this opaque substance, must, in passing through the eye, cross those which are entering at the same time ; they must, consequently, prevent distinct vision, or at least impair the impres- sion, in a manner which it is impossible to determine. It has been said, that the lower animals, provided with less perfect and often less numerous senses than those of man, must have different ideas ofthe universe : is it not, likewise, probable, that in consequence of the indistinct vision occasioned by the reflection from the tapetum, they may entertain erroneous and ex- aggerated notions of the power of man ? And notwithstanding the power granted to man by the Creator over the lower animals, as we are told in the book of Genesis, is it probable that those which Nature has gifted with prodigious strength, or with offensive weapons, would obey the lord of the creation, if they saw him in his feeble and destitute condition, in a word. such as he is ? The heads of insects With numerous eyes, are joined to their body, and move along with it: their existence is, besides, so frail, that it was requisite that Nature should furnish them abundantly with the means of seeing those objects which may be injurious to them. We shall not enter, any farther, into these remarks relative to the differences in the organ of sight, in the various kinds of animals. More ample details on this subject belong, in an especial manner, to Comparative Anatomy. CXXI. Ofthe organ of hearing. Of sound. Sound is not, like light, a body having a distinct existence: we give the name of sound to a sensa- tion which we experience, whenever the vibrations of an elastic body strike our ears. All bodies are capable of producing it, provided their molecules are susceptible of a certain degree of re-action and resistance. When a so- norous body is struck, its integrant particles experience a sudden concussion, are displaced and oscillate with more or less rapidity. This tremulous mo- tion is communicated to the bodies applied to its surface ; if we lay our hand on a bell that has been struck by its clapper, we feel a certain degree of this trembling. The air, which envelopes the sonorous body, receives and trans- mits its vibrations with the more effect from being more elastic. Hence, it is observed that, caeteris paribus, the voice is heard at a greater distance in winter, when the air is dry and condensed by the cold. The sonorous rays are merely series of particles of air along which the vibration is transmitted, from the sonorous body, to the ear which perceives the noise occasioned by its percussion. These molecules participate in the vibrations vvhich are communicated to them ; they change their form and situation, in proportion as they are nearer to the body that is struck, and vice versa; for, sound becomes weaker, in proportion to the increase of dis- tance. But this oscillatory motion of the aerial molecules, should be well distinguished from that by which the atmosphere, agitated by the winds, is transported and changes its situation. And in the same manner as the balance of a pendulum moves incessantly within the same limits, so, this oscillatory motion affects the molecules of the air within the space which they occupy, so that they move to and fro during the presence or the absence ofthe vibra- tion. The atmospherical air, when set in motion, in a considerable mass at a time, produces no sound, unless in its course, it meets with a body which vibrates from the percussion vvhich it experiences. The force of sound depends, entirely on the extent ofthe vibrations ex- 217 peiienced by the molecules of the sonorous body. In a large bell struck violently, the agitation ofthe molecules is such, that they are transmitted to considerable distances, and that the form of the body is evidently changed by it. Acute or grave sounds are produced by the greater or smaller number of vibrations, in a given time, and the vibrations will be more numerous, the smaller the length and diameter of the body. Two catgut strings, ofthe same length and thickness, and with an equal degree of tension, will vibrate an equal number of times, in a given time, and produce the same sound. This, in music, is called unison. If one of the strings is shortened by one half, it vibrates as often again as the other, and gives out a sound more acute, or higher by one octave. The same result may be obtained by reducing the string one half of its original thickness, without taking from its length. The vibrations will, in the same manner, be accelerated, by giving a greater de- gree of tension to the sonorous cord. The difference ofthe sounds produced by a bass, a harp, or any other stringed instrument, depends on the unequal tension, length, and size of the strings. This division of the elementary sound is an act of the understanding, which distinguishes, in a noise apparently monotonous, innumerable varie- ties, and shades expressed by signs of convention. But in the same manner as light, refracted by a prism, presents innumerable intermediate shades, between the seven primitive colours, and as the transition is gradual, from the one to the other of these colours : so the division ofthe primitive sound into seven tones expressed by notes, is not absolute, and there are a number of intermediate sounds which augment or diminish their value, &c. Sound has, therefore, been analysed as well as light; the use of the ear, with regard to sound, corresponds to that of the prism with regard to light, ' and the modifications of which sound is capable, are as numerous and as various, as the shades between the primitive colours. Sound is propagated with less velocity than light. The report of a cannon fired at a distance, is heard only a moment after the eye has perceived the flash of the explosion. Its rays diverge and are reflected, like those of light, when they meet with an obstacle at an angle equal to that of incidence. The force of sound, like that of light, may be increased by collecting and concentrating its rays. The sonorous rays which strike a hard and elastic body, when reflected by it, impart to it a vibratory motion, giving rise to a secondary sound, which increases the force ofthe primitive sound. When these secondary sounds, produced by the percussion ofa body at a certain distance, reach the ear, they give rise to what is called an echo. Who is unacquainted with the ingenious allegory, by which its nature is ex- pressed in ancient mythology, in which echo was called, daughter of the air and of the earth ? CXXII. Ofthe organ and mechanism of hearing. The organ of hearing in man, consists of three very distinct parts ; the one placed externally, is intended to collect and to transmit the sonorous rays which are modified in passing along an intermediate cavity, between the external and internal ear. It is within the cavities of this third part ofthe organ, excavated in the sub- stance of the petrous portion ofthe bone, that the nerve destined to the per- ception of sound, exclusively resides. The external ear and the meatus auditorius externus may be compared to an acoustic trumpet, the broad part of which, represented by the concha, collects the sonorous rays which are afterwards transmitted along the contracted part, represented by the meatus externus. The concha contains several prominences separated by corres- ponding depressions; its concave part is not wholly turned outward, in 28 218 Uiose who have not laid their ears flat against the side ofthe head, by tight bandages, it is turned slightly forward, and this arrangement, favourable to the collecting of sound, is particularly remarkable in savages, whose hearing, it is well known, is remarkably delicate. The base of the concha consists of a fibro cartilaginous substance, thin, elastic, calculated to reflect sounds and to increase their strength and intensity, by the vibrations to which it is liable. This cartilage is covered by a very thin skin, under which no fat is collected that could impair its elasticity; these prominences are connected together by small muscles ; these may relax it, by drawing the projections together, and thus place it in unison with the acute or grave sounds. These small muscles within the external ear, as the musculi helicis major and minor; the tragicus and anti-tragicus and the transversus auris, are like the muscles on the outer part of the ear, stronger and more marked in timid animals with long ears. In the hare, the fibres of these muscles are most distinctly marked, iheir action is most apparent in this feeble and fearful animal which has no resource but in flight, against the dangers which incessantly threaten his existence, and which required that he should receive early intimation ofthe approach of danger; hence hares have the power of making their ears assume various forms, of shaping them into more advantageous trumpets, of moving them in every direction, of directing them towards the quarter from which the noise proceeds, so as to meet the sounds and collect the slightest. The form of the external ear, is not sufficiently advantageous in man, whatever Boerhaave may have said to the contrary, to enable all the sono- rous rays, which in striking against it, are reflected at an angle equal to that of their incidence, to be directed towards the meatus auditorius externus. United, for the most part into a single fasciculus, and directed towards the concha, they penetrate into the meatus auditorius externus, and the tremu- lous motions which they excite in its osso cartilaginous parietes contribute to increase their force. On reaching the bottom of the meatus, they strike against the membrana tympani, a thin and transparent septum stretched be- tween the bottom of the meatus and the cavity in which the small bones of the ear are lodged. These small bones form a chain of bone which crosses the tympanum from without inward, and which extends from the membrana tympani to that which connects the base of the stapes to the edge of the fenestra ovalis. An elastic air, continually renewed by the Eustachian tube, fills the cavity of the tympanum; small muscles attached to the malleus and stapes move these bones or relax the membranes to which they are attached, and thus institute a due relation between the Organ of hearing and the sounds which strike it. It will be easily conceived, that the relaxation ofthe membrana tympani, effected by the action ofthe anterior muscle ofthe malleus, must weaken acute sounds, while the tension ofthe same membrane, by the inter- nal muscles of the same bone, must increase the force of the grave sounds. In the same manner, as the eye by the contraction or dilatation ofthe pupil, accommodates itself to the light, so as to admit a greater or smaller number ( of its rays, according to the impression which they produce, so by the relaxa- tion or tension ofthe membrane of the tympanum, or ofthe fenestra ovalis, the ear reduces or increases the strength of sounds whose violence would affect its sensibility, in a painful manner, or whose impression would be in- sufficient. The iris and the muscles of the stapes and of the malleus are, therefore, the regulators of the auditory and visual impression; there is as close a sympathetic connexion between these muscles and the auditory nerve, as between the iris and the retina. The air which fills the tympanum 219 is the true vehicle of sound ; this air diffuses itself over the mastoid cells, the use of which is to augment the dimensions of the tympanum, and the force and extent of the vibrations vvhich the air experiences within it. These vibrations transmitted by the membrana tympani, are communica- ted to those membranes which cover the fenestra ovalis and the fenestra rotunda, then, by means of these, to the fluid which fills the different cavi- ties of the internal ear, and in vvhich lie the soft and delicate filaments of the auditory nerve or of the portio mollis of the seventh pair. The agitation of the fluid affects these nerves and determines the sensa- tion of grave or acute sounds, according as they are slower or more rapid. It appears that the diversity of sounds should rather be attributed to the more or less rapid oscillations, and to the undulations of the lymph of Co- tunni, than to the impressions on filaments of different lengths, of the audi- tory nerve. These nervous filaments are too soft and too slender to be traced to their extreme terminations. It is, however, probable, that the various forms of the internal ear (the semi-circular canals, the vestibule, and the cochlea), have something to do with the diversity of sounds. It must also be observed, that the cavities of the ear are contained in a bony part, harder than any other substance of the same kind, and well fitted to main- tain, or even to augment by the reaction of vvhich it is capable, the force of the sonorous rays.* The essential part ofthe organ of hearing, that vvhich appears exclusively- employed in receiving the sensations of sounds is, doubtless, that which ex- ists in all animals endowed with the faculty of hearing. This part is the soft pulp of the auditory nerve, floating in the midst of a gelatinous fluid, con- tained in a thin and elastic membranous cavity. It is found in all animals, from man to the sepiae. In no animal lower in the scale of animation, has an organ of hearing been met with, although some of these inferior animals do not seem to be absolutely destitute of that organ. This gelatinous pulp is, in the lobster, contained in a hard and horny covering. In animals ofa higher order, its internal part is divided into various bony cavities. In birds there is interposed a cavity between that which contains the nerve of hear- ing and the outer part of the head; in man and in quadrupeds, the organ of hearing is very complicated; it is enclosed in an osseous cavity, ex- tremely hard, situated at a considerable depth, and separated from the outer part of the head, by a cavity and a canal along which the sonorous rays are transmitted, after having been collected into fasciculi by trumpets situated on the outside. This kind of natural analysis ofthe organ of hearing, is well calculated to give accurate notions on the nature and importance ofthe functions fulfilled by each of its parts. But in the investigation ofthe uses and of the relative importance of the auditory apparatus, morbid anatomy furnishes data of an equal value with those obtained from comparative anatomy. CXXIII. The external ear may be removed, with impunity, in man, and even in animals in which its form is more advantageous; the bearing is, at first impaired, but at the end of a few days, recovers its wonted delicacy. The complete obliteration of the meatus auditorius externus, is attended with complete deafness. It is not essentially necessary for the mechanism * If the cavities ofthe internal ear were hermetically sealed, it maybe conceived that the violent undulations of the lymph of Cotunni would injure the nervous pulp; but the most violent agitation of this fluid does not proceed to such a height; for it may flow towards the internal surfaces ofthe cranium by mean* of the two small conduits namH HOMfdurff 220 of hearing, that the membrana tympani should be whole; persons in whom it has been accidentally ruptured, can force out smoke at their cars, vyithout losing the power of hearing ; it may be conceived, however, that if instead of having merely a small opening that would not prevent its receiving the impression of the sonorous rays, nor its being acted upon by the handle ot the malleus, the membrana tympani were almost entirely destroyed, deafness would be the almost unavoidable consequence.* If, in consequence of the obstruction ofthe Eustachian tube, the air in the tympanum is not renewed, it loses its elasticity and combines with the mucus within the tympanum. , The cavity of the tympanum is then, in the same condition as an ex- hausted receiver, in which the sonorous rays are transmitted with difficulty. It has been thought, that the use of the Eustachian tube was, not only to renew the air contained in the tympanum, but also transmit the sonorous rays into that cavity. In listening attentively, we slightly open our mouth; in order, it is said, that the sound may pass from this cavity into the pharynx and thence reach the organ of hearing. This explanation is far from satis- factory, forthe obliteration ofthe meatus auditorius externus is attended with complete deafness, which would not happen, if the Eustachian tubes trans- mitted the sonorous rays. When a man listens attentively, and with his mouth open, the condyles ofthe lower jaw, situated in front ofthe external auditory meatus, being depressed and brought forward, the openings are evidently enlarged, as may be ascertained by putting the little finger into one's ears, at the moment of depressing the lower jaw.t The luxation of the small bones of the ear, or even their complete destruction, does not oc- casion deafness, the only consequence is a confusion in the perception of sounds. When, however, the stapes, the has of which rests on the greatest part of the fenestra ovalis, or when the thin membrane which closes the fenestra ovalis, or when that vvhich closes the fenestra rotunda is destroyed, deafness takes place in consequence of the escape ofthe fluid which fills the cavities in which the auditory nerve is distributed. The existence of this fluid appears essential to the mechanism of hearing, either from its keeping the nerves in the soft and moist state required for the purpose of sensation, or from its transmitting to them, the undulatory motion with vvhich it is agitated. The deafness of old people, which, according to authors, depends on the impaired sensibility of the nerves, whose excitability has been exhausted by impressions too frequently repeated, appears sometimes to be occasioned by a deficiency of this humour, and by the want of moisture in the internal cavities of the ear. During the severe winter of 1798, Professor Pinel opened, at the Hospital of Saltpetriere, the skulls of several women who died at a very advanced age, and who had been deaf for several years. The cavities of the internal ear were found quite empty; they contained an icicle in younger subjects who had possessed the power of hearing. * We find that a temporary obstruction of the Eustachian tube in guttural angina is sufficient to occasion a considerable degree of deafness. In such a case, the inflamma- tion ofthe mucous membrane of the pharynx extends itself to lhat which lines the tube, of which it is a continuation ; and the effects that the inflammation produces on the function ofthe organ are proportionate to the extent to which it advances in the differ- ent compartments ofthe internal ear. t The open state ofthe mouth in an attentive listener by no means proves that tbe sonorous rays are introduced along the Eustachian tube. Indeed, if such were the case, the aerial pulsations arriving by this direction would strike the tympanum in an opposite direction to those that are admitted by the external passage, and thus render the hearing confused. The purpose, therefore, which the Eustachian tube performs is nothing more fh«n to allow the renewal ofthe airwithin the tympanum 221 Deafness may, likewise, be produced by a palsy of the portio mollis of the seventh pair, or by a morbid condition of the part of the brain from which this nerve arises. The mechanical explanation applied by Willis to the anomalous affections of the organ of hearing, is inadmissible, those in which that organ is sensible only to the impression of weak or strong sounds aeting together or separately. This author relates the case of a woman who could not hear, unless a great noise was made near her, either by beating a drum or by ringing a bell, because, says he, under such circumstances, these loud noises determine in the membrana tympani, which he supposes in a state of relaxation, the degree of tension required to enable it to vibrate uuder the impression of weaker sounds. This membrane, to prevent greater resistance, must be put on the stretch by the internal muscle of the malleus, or by its own con- traction. The total absence of muscular fibres in the membrana tympani, in man, renders very doubtful this spontaneous contraction. Mr. Home, however, has just ascertained that the membrana tympani of the elephant is muscular and contractile. Admitting all these suppositions, we only sub- stitute one difficulty for another, and it remains to be shown, why the more powerful sounds merely increase the tone of membrana tympani; why they do not become objects of perception of the organ of hearing, though they might be expected to render us insensible to the perception of weaker sounds. jq CXXIV. Of odours. Chemists have long thought that the odoriferous part of bodies formed a peculiar principle, distinct from all the other sub- stances entering into their composition ; they gave it the name of aroma ; M. Fourcroy, however, has clearly shown, that this pretended element con- sisted merely of minute particles of bodies, detached by heat and dissolved in the atmosphere, which becomes loaded with them and conveys them to the olfactory organs. According to this theory, all bodies are odoriferous, since caloric may sublimate some of the particles of those which are least volatile. Linnaeus and Lorry had endeavoured to class odours, according to the sensations which they produce ;* M. Fourcroy has been guided by the chemical nature of substances; but however advantageous this last clas- sification may be, it is difficult to include in it, the infinited odours which ex- hale from substances of all kinds, and it is perhaps as difficult to arrange them in classes, as the bodies from vvhich they are produced. This being laid down on the nature of odours, it is next explained, why the atmosphere becomes loaded with the greater quantity, the warmer and the more moist it is. We know, that in a flower-garden, ihe air is at no time more loaded with fragrant odours, and the smell is never the source of greater enjoyment, than in the morning, when the dew is evaporating by the rays of the sun. It is likewise, easily understood, why the most pungent smells, generally evaporate very readily, as ether, alcohol, the spirituous tinctures and essential volatile oils. * Linnaeus admits seven classes of odours; 1st class, ambrosiac odours, those of the rose and of musk belong to this class, they are characterised by their tenacity; 2nd,fragrant; for example, the lily, the saffron,and jasmine; they fly off readily; 3rd, aromatic, as the smell of the laurel; 4th, aliaceous, approaching to that of garlic ; 5ih,fetid, as that of va- lerian and fungi; 6th, virous, as of poppies and opium; 7th, nauseous, as that of gourds, melons, cucumbers, and, in general, all cucurbitaceous plants. Lorry admits only five kinds of colours, camphorated, narcotic, ethereal, volatile acid, and alkaline. M. Fourcroy admits the mucous aroma, belonging to plants improperly termed inodo- rous. City and fugacious, oily and volatile, acid and hydro-sulphureous.—Author's Note. 222 CXXV. Of the organ of smell. The nasal fossa?, within which this organ is situated, are two cavities in the depth of the face and extending back- ward into other cavities, called frontal, ethmoideal, sphenoidal, palatine, and maxillary sinuses. A pretty thick mucous membrane, always moist, and in the tissue of which, the olfactory nerves and a considerable number of other nerves and vessels are distributed, lines the nostrils and extends into the sinuses which communicate with them and covers their parietes, throughout their wind- ings and prominences. This membrane, called pituitary, is soft and fungous, and is the organ which secretes the mucus ofthe nose; it is thicker over the turbinated bones which lie within the olfactory cavities ; it grows thinner and firmer, in the different sinuses. The smell appears more delicate in proportion to the nasal fossae being more capacious, the pituitary membrane covers a greater space. The soft and moist condition of this membrane is, likewise essentially necessary to the perfection of this sense. In the dog, and in all animals which have a very exquisite sense of smell, the frontal, ethmoideal, sphenoidal, palatine, and maxillary sinuses, are prodigiously capacious, and the parietes of the skull are in great measure, hollowed by these different parts ofthe olfactory apparatus; the turbinated bones are, likewise, very prominent in them, and the grooves between them very deep ; lastly, the nerves ofthe first pair are large in proportion. Among the animals possessed of great delicacy of smell, few are more remarkable than the hog * This impure animal, accus- tomed to live in the most offensive smells, and in the most disgusting filth, has, however, so very nice a smell, that it can detect certain roots, though buried in the earth at a considerable depth. In some countries, this quality is turned to advantage, and swine are employed in looking for trufles. The animal is taken to those places where they are suspected to be, turns up the earth in which they are buried, and would feed on them greedily, if the herdsmen, satisfied with this indication, did not drive them away from this substance intended for more delicate palates. CXXVI. Of the sensation of odours. Do the nerves of the first pair alone give to the pituitary membrane, the power of receiving the impression of smell, and do the numerous filaments of the fifth pair, merely impart to it the general sensibility belonging to other parts? This question appears to require an answer in the affirmative. This pituitary membrane, in fact, possesses two modes of sensibility, perfectly distinct, since the one of the two may be almost completely destroyed, and the other considerably in- creased. Thus, in violent catarrh, the sensibility ofthe part, as far as relates to the touch, is very acute, since the pituitary membrane is affected with pain, while the patient is insensible to the strongest smells. It seems probable, that the olfactory nerves do not extend into the sinuses, and that these improve the sense of smell, merely by retaining, for a longer space of time, a considerable mass of air loaded with odorife- rous particles. I have known detergent injections, strongly scented, thrown into the antrum highmorianum by a fistula in the alveolar processes, pro- duce no sensation of smell. A phial filled with spirituous liquor having been applied to a fistula in the frontal sinuses, gave no impression to the patient. The true seat of the sense of smell is at the most elevated part of the nostrils, which the nose covers over in the form of a capital. There the pituitary membrane is moister, receives into its tissue the numerous filaments of the first pair of nerves, which arising by two roots from the interior lobe of the brain, and from the fissure which separatos it from the 223 posterior lobe, passes from the cranium, through the openings of the cri- briform plate of the ethmoid bone, and terminates forming, by the expan- sion of its filaments, a kind of parenchymatous tissue not easily distin- guished from that of the membrane. The olfactory papillae would soon be destroyed by the contact of the atmospherical air, if they were hot covered over by the mucus of the nose. The use of this mucus is, not merely to preserve the extremities of the nerves, in a sentient state, by preventing them from becoming dry, but, likewise, to lessen the too strong impression that would arise from the immediate contact of the odoriferous particles. It perhaps even combines with the odours, and these affect the olfactory organs, only when dissolved in mucus, as the food in saliva. As the air is the vehicle of odours, these affect the pituitary membrane, only when we inhale it into the nostrils. Hence, when any odour is grateful to us, we take in short and frequent inspirations, that the whole of the air, which is received into the lungs, may pass through the nasal fossae. We, on the contrary, breathe through the mouth, or we suspend respiration altogether, when smells are disagreeable to us. The sense of smell, like all the other senses, is readily impressed in children, though the nasal fossae are, in them, much contracted, and though the sinuses are not yet formed. The general increase of sensibility, at this period of life, makes up for the imperfect state of the organization, and it is, in this respect, with the nasal fossae, as with the auditory appara- tus, of which an important part, the meatus externus, is then not com- pletely evolved. The sense of smell is perfected by the loss of some of the other senses ; every body, for example, knows the history of the blind man whom that organ enabled to judge of the continence of his daughter; it becomes blunted by the application of strong and pungent odours. Thus, snuff changes the quality of the mucus secreted by the membrane of the nose, alters its tissue, dries its nerves, and, in the course of time, impairs their sensibility. The shortness of the distance between the origin of the olfactory nerves, in the brain, and their termination in the nasal fossae, render very prompt and easy the transmission of the impressions which they experience. This vicinity to the brain, induces us to apply to those nerves, stimulants calcu- lated to rouse the sensibility, when life is suspended, as in fainting and asphyxia. The sympathetic connexions, between the pituitary membrane and the diaphragm, account for the good effects of sternutatories, in cases of apparent death. CXXVII. Of flavours. Flavours are no less varied and no less nu- merous than odours; and it is as difficult to reduce them to general classes connected by analogies and including the whole.* Besides, there exists no element of flavour, any more than an odoriferous principle. The fla- vour of fruits alters, as they ripen, and appears to depend on the in- ward composition of bodies, on their peculiar nature, rather than on the form of their molecules, since crystals of the same figure, but belonging to different salts, do not produce similar sensations. To affect the organ of taste, a body should be soluble at the ordinary * This has been attempted, though with indifferent success, by Boerhaave, Haller, and Linnaeus. Ac id, sweet, bitter, acrid, saltish, alkaline, vinous, spirituous, aromatic, and acerb, were the terms employed by those physicians, to express the general characters of flavours. The flavour of any substance appears chiefly to arise from the odoriferous particles which escape from it, during the process of mastication and deglutition, through the posterior nares, and affect the olfactory nerve* in that situation. 2124 temperature of the saliva; all insoluble substances are insipid, and one might apply to the organ of taste, this celebrated axiom in chemistry, cor- pora non agunt nisi soluta. If there is a complete absence of saliva, and if the body that is chewed is altogether without moisture, it will affect the parched tongue, only by its tactile, and not at all by its gustatory qualities. The substances which have most flavour, are those which yield most readily to chemical combinations and decompositions, as acids, alkalies and neu- tral salts. When, in affections of the digestive organs, the tongue is covered with a mucus or whitish fur, or of yellowish or bilious colour, we have only incorrect ideas of flavours ; the thinner or thicker coating prevents the immediate contact of the sapid particles ; when they act, besides, on the nervous papillae, the impression which they produce is lost in that occasioned by the morbid contents of the stomach ; hence every aliment appears bitter, while the bilious disposition exists, and insipid, in those diseases in which the mucous elements prevail. CXXVIII. Of the sense of taste. No sense is so much akin to that of the touch, or resembles it more. The surface of the organ of taste differs from the common integuments, only in this respect, that the chorion, the mucous body, and the epidermis which envelope the fleshy part of the tongue are softer, thinner, and receive a greater quantity of nerves and vessels, and are habitually moistened by the saliva and by the mucus, secreted by the mucous glands contained in their substances. These mucous cryptae, and the nerves of the cutaneous covering of the tongue, raise the very thin epidermis which covers its upper surface, and form a number of papillae distinguished, by their form, into fungous, co- nical, and villous. With the exception of the first kind, these small prominences are formed by the extremities of nerves, surrounded by blood- vessels which give to these papillae the power of becoming turgid and prominent, and of being affected with a kind of erection, when we eat highly-seasoned food, or when we long for a savoury dish. The fungous papillae are mostly situated at the remotest part of the upper surface of the tongue, towards its root, and where it forms a part of the isthmus faucium. The pressure with which they are affected by the alimentary bolus, in its passage from the mouth into the pharynx, squeezes out the mucus which lubricates the edges of the aperture, and serves to promote its passage : these mucous follicles, fulfil, in this respect, the same office, as the amygdale. The upper surface of the tongue is the seat of taste : it is undeniable, however, that the lips, the gums, the membrane lining the arch ofthe palate, and the velum palati,* may be affected by the impression of certain flavours. It is observed, in the different animals, that the organ of taste is more per- fect, according as the nerves of the tongue are larger, its skin thinner and moister, its tissue more flexible, its surface more extensive, its motions easier and more varied. Hence, the bone in the tongue of birds, by diminishing its flexibility, the osseous scales ofthe swan's tongue, by reducing the extent ofthe sentient surface ; the adhesion ofthe tongue to the jaws, in frogs, in the salamander, and in the crocodile, by preventing freedom of motion, ren- der in these animals, the sense of taste duller and less calculated to feel the * Especially the anterior part of the palatine membrane. The naso-palatine nerve, discovered by Scarpa, after arising from the ganglion of Meckel, and going for a pretty considerable distance into the nasal fossa-, terminates in that thick and rugous portion ofthe palatine membrane, situated behind the upper incisors, and with which the tip of the tongue Is in such frequent contact. 225 impression of sapid bodies, than in man, and the other mammiferous ani- mals. Man would, probably, excel all the other animals, in delicacy of taste, if he did not, at an early period, impair its sensibility, by strong drinks, and by the use of spices, and of all the luxuries that are daily brought to our tables. The quadrupeds, whose tongue is covered by a rougher skin, discover better than we can, by the sense of taste, poisonous, or noxious substances. We know, that in the variety of plants which cover the face of the earth, herbivorous animals select a certain number of plants suited to their nature, and uniformly reject those which would be injurious to them. CXXIX. Is the lingual branch of the fifth pair of nerves, alone subser- vient to the sense of taste ? Are not the ninth pair (almost wholly distribu- ted in the tissue of the tongue,) and the glosso pharyngeal branch of the eighth, likewise subservient to this function ? Most anatomists, since Ga- len, have thought that the eighth and ninth pair supplied the tongue with its nerves of motion, and that it received from the fifth, its nerves of sensation. Several filaments, however, of the great hypoglossal nerve, may be traced into the nervous papillae of tbe tongue. This nerve is larger than the lin- gual, and is more exclusively distributed to this organ than the fifth pair, to which the other nerve belongs. Havermann states, that he knew a case, in Which the sense of taste was lost from the division of the nerve of the ninth pair, in removing a schirrous gland. This case, however, appears to me a very suspicious one. The patient might still have tasted, by means of the lingual nerve, and the sense would only have been weakened. The division of One ofthe nerves of the ninth pair could render insensible, only that half of the tongue to which it is distributed, the other half would continue fully to possess the faculty of taste. The application of metals to the different nervous filaments distributed to the tongue, ought to inform us of their different uses, if, as Humboldt sus- pects, the galvanic excitement of the nerves of motion, alone produces con- tractions. To ascertain the truth of this conjecture, I placed a plate of zinc within the skull, under the trunk of the nerve of the fifth pair, in a dog that had been killed a few minutes before, and that still retained its warmth; the muscles of the tongue, under which a piece of silver was placed, quivered very slightly ; those of the forehead and temples in contact with the same metal, experienced very sensible contractions, whenever a communication was made by means of an iron rod. This experiment showed, that the lin- gual branch of this nerve was, almost solely, subservient to the sensation of taste, which agrees with the opinion of most physiologists, and the same in- ference may be drawn from the anatomical knowledge of the situation of this nerve, which, almost entirely, terminates in the papillae of the membrane of the tongue, and sends very few filaments to the muscles of that organ. But though the galvanic irritation applied to the hypoglossal nerve affected the whole tongue, in a convulsive manner, I did not think myself justified to in- fer, that this nerve was solely destined to perform its motions ; as this ner- vous trunk might, in this part of the body, as it does in others, contain fila- ments both of sensation and motion. The tongue, though an azygous organ, is formed of parts completely sym- metrical ; there are, on each side, four muscles (stylo, hyo, genio, glosso, and lingual;) three nerves (lingual, glossopharyngeal, and hypoglossal;) a ranine artery and vein ; and a set of lymphatic vessels precisely alike. All these parts, by their union, form a fleshy body of a close texture, and not easily unravelled, similar to that of the ventricles of the heart, endowed with a. considerable degree of mobility, in consequence of the numerous 22(5 vessels and nerves entering into its substance.* If we compare their num- ber and size with the small bulk of the organ, it will be readily understood, that, as no part of the body can execute more frequent, more extensive, and more varied motions, so no one receives more vessels and nerves. A mid- dle line separates and marks the limits of the two halves of the tongue, which anatomically and physiologically considered, appears formed of two distinct organs in juxta-position. This independence of the two parts of the tongue is confirmed by the phenomena of disease ; in hemiplegia, the side of the tongue corresponding to the half of the body that is paralyzed, loses, likewise, the power of mo- tion ; the other retains its mobility, and draws the tongue towards that side. In carcinoma of the tongue, one side remains unaffected by the affection vvhich destroys the other half; lastly, the arteries and nerves of the left side rarely anastomose with those on the right; injections forced along one ofthe ranine arteries, fill only the corresponding half of the organ, &c. CXXX. Of the touch. No part of the surface of our body is exposed to receive the touch of a foreign body, without our being speedily informed of it. If the organs of sight, of hearing, of smell, and of taste, occupied only limited spaces, touch resides in all the other parts, and effectually watches over our preservation. The touch, distributed over the whole sur- face, appears to be the elementary sense, and all the others are only modi- fications of it, accommodated to certain properties of bodies. All that is not light, sound, smell, or flavour, is appreciated by the touch, which thus in- structs us in the greater part of the qualities of bodies which it concerns us to know, as their temperature, their consistence, their state of dryness, or humidity, their figure, their size, their distance, &c. It corrects the errors of the sight and of all the other senses, of which it may justly be called the regulator, and it furnishes us with the most exact and distinct ideas. The touch, of which some authors have sought to consecrate the excel- lence, by giving it the name of the geometrical sense, is not, however, safe from all mistake. Whilst it is employed on the geometrical properties, de- rived from space, and that it appreciates the length, the breadth, the thick- ness, the form of bodies, it transmits to the intellect, rigorous and mathe- matical results; but the ideas we acquire, by its means, on the temperature of bodies, are far from being equally precise. For, if you have just touched ice, another body colder than yours, will appear warm. It is for this reason, that subterraneous places appear warm to us during winter. They have * Haller concluded that the tongue possesses irritability. Blumenbach has lately de- termined the point by direct experiment. He caused the tongue of a four-year-old ox, which had been killed in the usual way, to be cut out while the animal was yet warm, and at the same time, the heart, in order that he might compare the oscillatory motions of both viscera; and when both were excited at the same time by mechanical stimuli, the tongue appeared to survive the heart by more than seven minutes, and so vivid were its movements, when cut across after its separation, that its motions might be compared to those of the tail of a mutilated snake. The same phenomena were remarkable in the divided tongue of other animals, on the application of mechanical or chemical stimuli j and also in that of a boy which had been bit off during a fit of violent epilepsy. From this it would appear that the account which Ovid gives ofthe croel deed of Tt> reus is nearly correct:— ------------" Compressam forcipe linquam, Abstulit ense fero. Radix micat ultima linqua', Ipsa jacet, terraeque tremens immurmuratatr», Utque salire solet mutilatae cauda colubraj, Palpitat, et moriens dominae vestigia queerit." Metamor. VI. 22T kept their temperature whilst all things else have changed theirs ; and as we judge of the heat of an object by its relation not only to our own, but also to that of other bodies and of the air about us, we find the same places warm, which had appeared cold to us, in the middle of summer. The densest bodies being the best conductors of heat,* marble, metals, &c. appear colder to us than they really are, because they carry it off so rapidly. Marble and metals, when polished, appear still colder, because, as they touch the skin in many more points at once, they effect this abstraction more effectually. Every one knows the experiment of placing a little ball between the two fingers crossed, and producing the sensation of two dif- ferent balls. CXXXI. Of the integuments. The general covering of the whole body is the organ of touch, vvhich resides in the skin properly so called. The cel- lular tissue vvhich connects together all our parts, forms over the whole body, a layer varying in thickness, vvhich covers it, in every part; it is called panniculus adiposus. As it approaches the surface, its laminae are more condensed, are in more immediate contact with each other, and are no longer separated by adeps. It is by the closer juxta-position of the laminae of the cellular tissue, that the skin or dermis is formed, a dense and elastic mem- brane, into which numerous vessels, of all kinds, are distributed, and into whieh so*great a quantity of nerves terminate, that the ancients did not hesi- tate to consider the skin as purely nervous. In certain parts of the body, a very thin muscular plane separates the skin from the panniculus adiposus. This kind of panniculus carnosus en- velopes, almost entirely, the body of some animals ; its contractions wrinkle their skin covered with hairs, these rise, vibrate, and thus are cleared of the dust and dirt which may have gathered on them. It is by means of a cuta- neous muscle, of very complex structure, that the hedge-hog is enabled to coil himself up, and to present to his enemy a surface studded with sharp points: only a few scattered rudiments of an analogous structure, are to be met with in the human body; the occipito frontalis, the corrugator super- cilii, several muscles of the face, the platysma myoides, the palmaris cuta- neous may be considered as forming part of this muscle. We may even include the cremaster, whose expanded fibres, surrounded by the dartos, have misled some anatomists to such a degree, that they have admitted the existence of a muscular texture in the latter. These fibres of the cremas- ter, produce distinct motions, in the skin of the scrotum, wrinkle it, in a transverse direction, and, at the same time, bt ing up the testicles. The platysma myoides acts, likewise, on the skin of the neck; lastly, the occi- pito-frontalis, in some men, performs so distinct a motion of the hairy scalp, as to throw off a hat, a cap, or any other covering that may be on the head. One may compare to the panniculus carnosus, the muscular coat of the digestive tube situated, throughout its whole length, below the mucous mem- brane, vvhich is merely a prolongation of the skin modified and softened. But if, in man, the subcutaneous muscle, from its imperfect state, answers * Woolly substances, &c. all felts, of which the crossing hairs confine, in some sort, a great quantity of air, a fluid which from its gaseous state, is a very bad conductor of heat, retain heat well;—and, of equal thickness, a stuff of fine wool, of which the hairs are more separated, the tissue softer, will be warmer than a stuff of coarse wool, of which the threads, too close, form a dense body, through which cold, as well as heat, will pass with ease. It is by thus confining a certain mass of air, that snow keeps the soil it covers, in a mild temperature, aud preserves plants from the injury of excessive cold; a physical truth which is found figuratively expressed, in the words of the Psalmist, " El dedit illi nivem tanquam vestimenfrm"—Author's Not*. 228 purposes only of secondary importance, the layer of cellular adipose sub- stance, extended under the skin, gives to the latter its tension, its white- ness, its polish, its suppleness, favours its applying itself to tangible objects, and thus renders the touch more delicate. Too hard or wrinkled a skin, would have applied itself in a very incomplete manner, to bodies of a small size, and would not readily have accommodated itself to the small irregu- larities of those of inconsiderable bulk. Hence the pulp of the fingers, which is the seat of a more delicate touch, is furnished with a kind of adi- pose cushion supported by the nails, ready to be applied to polished sur- faces, and to discover the slightest asperities. I have observed the sense of touch to be very imperfect, in men wasted by marasmus, and whose hard, dry, and wrinkled skin adheres, in certain situations, to the subjacent parts. The chemical analysis of the cutaneous tissue shows, that it does not exactly resemble that of the cellular and membranous tissue ; it is gelatino- fibrous, and, with regard to its structure and to its share of contractility, it occupies a medium, between the cellular tissues and the muscular flesh.* There arise, from the surface ofthe skin, innumerable small papillae, fun- gous, conical, pointed, obtuse and variously shaped, in the different parts of the body. These papillae are merely the pulpous extremities of the nerves which terminate into them, and around which there are distributed vascular tissues of the utmost minuteness. The papillae of the skin, which are more distinct in the fingers and lips than elsewhere, swell, when irritated, elevate, in a manner, the epidermis, and this kind of erection, which is useful when we wish to touch a substance with great precision, may be excited by fric- tion or by moderate heat. The nervous or sentient surface of the skin is covered with a mucous coating, colourless in Europeans, of dark colour, from the effects of light, among the natives of southern climates ; of a gelatinous nature, destined to maintain the papillae in that state of moisture and softness favourable to the touch. This mucilaginous layer, known under the name of rete muco- sum of Malpighi, seems to contain the principle which causes the variety of colour in the skin of different nations, as will be observed, in speaking of the varieties of the human species. The reticular state of the rete mucosum may be explained in two ways ; a thin and gelatinous layer, extending on the papillar surface of the skin, is perforated, at each nervous papilla; and if it were possible to coagulate or to detach this coating, we should have a real sieve, or reticulated mesh work, with a perforation at every point, corresponding to a cutaneous pa- pillae. The sanguineous and lymphatic capillaries, which surround the ner- vous papillae, form, besides, by their connexions, a net-work, the meshes of which are very minute and adhere to the epidermis, by a multitude of small vascular filaments that insinuate themselves between the scales of this last envelope.t The skin would be unable to perform its functions, if an outer, thin, and transparent membrane, the epidermis, did not prevent it from being over dried. This superficial covering is quite insensible, no nerves and no ves- * See the Chapter in the Appkndix, on the chemical constitution ofthe animal textures and secretions. t......And terminate in exhaling or absorbing pores, according as they belong to to the arterial capillaries, or to the lymphatic absorbents. It is sufficient, indeed, to to remove gently the scales ofthe epidermis, in order to bare their orifices and procure the absorption of any virus. It is the net-work of Malpighi, or rather this assemblage of interlaced capillary vessels below the epidermis, which appears to be the seat of the primary phenomena in the majority of cutaneous inflaranratrons and eruptive diseases 229 seis, of any kind, are found in it, and even in the present state of science, we do not understand how it is formed, how it repairs and reproduces itself when destroyed. The most minute researches on its structure, merely show the existence of an infinite number of lamellae, lying over each other, and overlapping each other, like the tiles of a roof. This embrication of the epidormoid lamellae, is very obvious in fishes and reptiles, the scaly skin of which is merely an epidermis whose parts are much more coarsely shaped. It was observed (XLII.) in the account of absorption, how much friction facilitates the absorption of substances applied to the surface of the skin, by raising the scales of the epidermis, so as to expose the orifices of the absorbents, whose activity, it in other respects, increases. Haller conceives, that the epidermis is formed by the drying up of the outer layers of the rete mucosum. Morgagni thinks it is formed by the induration of the skin in consequence of the pressure of the atmosphere. In objection to these hypotheses, one may inquire, how it happens, that by the time the foetus, immersed in the liquor amnii,has attained its third month, it is covered with such an envelope.* Pressure renders the skin hard and callous, increases considerably its thickness, as we see in the soles of the feet and in the palms of the hands of persons engaged in laborious employments. The epidermis reproduces itself with an incredible rapidity, after falling off in scales, after erysipelas or herpetic eruptions, or, when removed, in large flakes, by blistering, it is renewed in the course of a very few days. The cuticle, together with the hairs and the nails, vvhich may be considered as productions of the same substance, are the only parts, in man, that are capable of reproducing themselves. The hairs and the horns of quadru- peds, the feathers of birds, the calcareous matter of the lobster and of several molusca, the shell of the turtle, the solid sheaths of a number of insects, possess, as well as the epidermis, this singular property. In other respects, the chemical structure of all these parts is the same ; they all contain a considerable portion of phosphate of lime, withstand decompo- sition, and give out a considerable quantity of ammonia, on being exposed to heat. The use of the epidermis is to cover the nervous papillae, in vvhich the faculty of the touch essentially resides, to moderate the too vivid impression that would have been produced by an immediate con- tact, and to prevent the air from drying the skin, or from impairing its sensibility. The dessication of the cutaneous tissue is further prevented, and its suppleness maintained, by an oily substance, which exudes through its pores, and is apparently secreted by the cutaneous exhalants. This unc- tuous liniment should not be mistaken for that which is furnished by the sebaceous glands, in certain situations, as around the nostrils, in the hollow of the arm-pits, and in the groins. This adipose substance, with which the skin is anointed, is abundant and fetid in some persons, especially in those of a bilious temperament, with red hair. It is, likewise, more copious in the African negroes, as if Nature had been anxious to guard against the too rapid dessication, by the burning atmosphere of tropical *The epidermis seems to be formed from a certain dry secretion of which the skin is the organ. The exhalants, with which the dermaltissue is abundantly supplied, allow a viscous and albuminous fluid to escape, which contaius a great proportion of phosphate of lime; thus an envelope is formed analagous to the shell which covers the egg. The epidermis may, therefore, be considered as a kind of excrementitious tissue—as a residue or product of nutrition thrown on the surface of the body, and forming a useful and requisite protection to the economy of organized beings. 230 climates. This use of the oil of the skin, is, likewise, answered by the tallow, the fat, and the disgusting substances with which the Caffres and the Hottentots anoint their body, in the manner described under the name of tattooing, by the travellers* who have penetrated into the interior of the burning regions of Africa. The ancients had a somewhat similar practice, and the anointing with oil, so frequently used in Ancient Rome, answered the same purpose, of softening the skin, of preventing its becoming dry, or chapped.t The pomatums employed at the present day at the toilet, possess the same ad- vantages. The continual transudation of this animal oil renders it necessary, occasionally, to clean the skin by bathing; the water removes the dust and the other impurities which may be attached to its surface by the fluid which lucubrates it. It is this humour which soils our linen, and obliges us so frequently to renew that in immediate contact with the skin, and which makes the water collect in drops when we come out of the bath, &c. Though the parts in which there is found the greatest quantity of subcu- taneous fat, are not always the most oily, and though one cannot consider this secretion as a mere filtration of this adeps through the tissue of the skin, corpulence has, however, a manifest influence on its quantity. I know several very corpulent persons in whom it appears to be evacuated by perspiration, on their being heated by the slightest exertion. They all grease their linen in less than twenty-four hours. An excess of the oily matter of perspiration is injurious, by preventing the evacuation of the perspiration and its solution in the atmosphere. We all know, how, after the epidermis has been removed, the slightest con- tact is painful: that of the air is sufficient to bring on a painful inflamma- tion of the skin exposed by the application of a blister. The epidermis, as was likewise mentioned in speaking of the absorption, placed on the limits of the animal economy, and in a manner inorganic, serves to prevent heterogeneous substances from being too readily admitted into the body, and, at the same time, it lessens the too vivid action of external objects on our organs. All organized and living bodies are furnished with this covering, and, in all, in the seed of a plant, in its stem and on the surface of the body, in man and animals, it bears to the skin the greatest analogy of function and nature. Incorruptibility is, in a manner, its essence, and is its peculiar character ; and in tombs which contain merely the dust of the skeleton, it is not uncommon to find the whole, and in a state to be readily distinguish- ed, the thickened epidermis that forms the sole of the foot, and especially the heel. However, this incorruptibility is possessed, as well as others of the qualities of the skin, by the hairs and the nails, which may be consider- ed as its appendages. CXXXII. Of the nails. The nails are, in fact, only a part of the epidermis : they are continuous with it, and, after death, fall off along with it. They are thicker and harder; like it they are inorganic and lamellated; they grow rapidly from their root towards their free extremity; they reproduce themselves rapidly and acquire several inches in length, when the part beyond the ends of the fingers and toes has not been re- * Among others Kolben, Description du Cap de Bonne-Esperance. Sparmann, Voyage aw Cap de Bonne-Esperance et Chez les Hottentots. Vaillant, Voyage dans I'Interieur de I'Afriquc. t The reply ofHhe old soldier is Well known, who, on being asked by Augustus, how he came to live so long, said he owed his long life to the use of wine inwardly, and to *bat of oil outwardly; inlusvino, extus oleo. 231 moved; as is the case with the Indian fakirs. In this state of develope- ment, they bend over the tips of the fingers and toes, and impair the sense of touch, whose free enjoyment is preferable to any advantages which savages can derive from their long and crooked nails, in defending them- selves, or in attacking animals, or tearing to pieces those which they have killed in hunting. The nails are quite insensible, and the reason that so much pain is felt, when the nails run into the flesh, and that the operation of tearing them out, which is sometimes necessary, is so painful, is, that the nerves, over which the nail grows, are more or less injured when it grows in a wrong direction. The pain from the growing of the nails into the quick, is no proof of their being sentient, any more than the growth of corns proves the sensibility of the epidermis, of which they are but thick- ened parts, become hard and callous by pressure, and which, confined in tight shoes, press painfully on the nerves below. The nail itself may ac- quire a considerable degree of thickness ; I have seen that of a great toe nearly half an inch thick. The use of the nails is to support the tips^of the fingers, when they are applied to unyielding substances; they likewise concur in improving the mechanism of the touch.* CXXXIII. Of the hair on the head and on other parts of the body. These parts are treated of, in the present instance, only in consequence of their connexion with the epidermis ; as, far from improving the touch, they interfere with it, or at least render it less delicate. The skin, in man, is more bare than that of other animals ; it is, likewise, least covered with insensible parts that might blunt the sense of touch. In almost all mammiferous animals, the whole body is covered with hair, only a small part of the human body has any hair on it, and that in too small a quantity, and of too delicate a texture, to interfere with the touch. Some men, however, have a very hairy skin, and I have seen several who, when naked, looked as if covered over with the skin of an animal, so great was the quantity of hair over the whole body, of which no part was bare, but a small portion of the face, the palms of the hands, and the soles of the feet. This extraordinary growth of hair, is, in general, a sure sign of vigour and strength. In childhood, there is no hair except on the head, the rest of the body is covered with down. Women have no beard, and there is in them, a smaller quantity of hair in the arm-pits and on the parts of generation, and scarcely any on the limbs and trunk. But as though the matter which should provide for the growth of the hair, were wholly applied to the hairy scalp, it is observed, that their hair is longer and in greater quantity. The colour of the hair varies from white to jet black; and, as will be mentioned, in speaking of the temperaments and of the varieties of the hu- man species, this difference of colour is a test by which we judge of those varieties. The colour of the hairs enables us to judge of their thickness: Withof, who, with a truly German patience, was at the pains to count how *The toe-nails are favourable to the laying the foot to the surface on which the body is supported; they, likewise, improve the sense of touch in this part. The use of the feet is not merely to support the weight of the body, they are also intended to guide us in feeling for tbe plane on which we are to rest them, to enable us to judge of the solid- ity, of the temperature, and of the inequalities of the ground on vvhich we tread. They, therefore, required rather a delicate sense of touch. The division of the fore part of the foot, into several distinct and separate parts, serves to enable us to stand more firmly, and facilitates the action of walking. I have seen several soldiers who lost, from severe cold, the extremities of their feet, in crossing the Alps which separates France from Italy. Those who had lost only their toes, did not walk so stendily, and frequently fell in treading on uneven ground. Those who had lost one half of their feet, were obliged •»* use crutches.—Author's N*>tf 232 many hairs were contained in the space of a square inch, states, in his dis- sertation on the human hair, that there are five hundred and seventy-two black hairs, six hundred and eight chesnut, and seven hundred and ninety light coloured, so that the diameter of a hair, which is between the three and seven hundredth part of an inch, is least in light hair, and these are finer the lighter their shade. It is, likewise, observed, that men of a bilious con- stitution, with dark hair, and inhabiting warm climates, have more hair, in other parts of the body, and that it is coarser and more greasy. In whatever part of the body hairs may grow, they are, every where, of tie same structure, they all arise from a vesicular bulb in the adipose cel- lular tissue ; from this bulb containing a gelatinous lymph, on which the hair seems to be nourished, the latter, at first divided into two or three filaments which constitute a kind of root, comes out in a single trunk, passes through the skin and epidermis, receiving from the latter a sheath that covers it to its extremity, which terminates in a point. A hair may, therefore, be considered as an epidermoid tube filled with a peculiar kind of marrow. This spungy stem, which forms the centre ofa hair, is a more essential part of it, than the sheath supplied by the epidermis. Along this spungy and cellular fijament, the animal oil of the hair and the juices on which it is repaired flow. Though we see, in some animals, vas- cular branches and very small nervous filaments directed towards the root of certain kinds of hair, and lost in it, as is the case with the long and stiff whis- kers of some of the quadrupeds, it is impossible to say, whether in man, the hair or its bulbs receives vessels and nerves. Is the human hair nourished by the imbibtion of the gelatinous fluid contained in its bulb, or is it nour- ished on the fat in which the latter is imbedded ? Are vessels distributed along their axis, from the root to the extremity ? In favour of this opinion, it was usual to mention the bleeding from the hair when cut, in the disease called plica polonica. But this disease, lately observed in Poland, by the French physicians, appeared to them a mere entangling of hair, in conse- quence of the filth of the Poles, and of their habit of keeping their head constantly covered with a woollen cap. The hairy scalp remains perfectly sound beneath the entangled hair, and the only way to cure the complaint is to cut off the hair. Fourcroy* thinks that each hair has several short branches that stand off from it, vvhich, according to the explanation given by Monge, favour the matting of the hairs that are to be converted into tis- sues, by the process called felting. CXXXIV. Among the most remarkable qualities of the hair one may take notice of the manner in which it is affected by damp air, which, by re- laxing its substance, increases its length. It is on that account, that hairs are used for the construction of the best hygrometers. Nor must we omit either the readiness with which they grow and are reproduced, even after being plucked out by the roots, as I have often seen after the cure of tinea by a painful method : nor their insulating property, with respect to the elec- tric fluid, of which they are very bad conductors; a remarkable property, viewed with reference to the conjectured nature of the nervous fluid. The hairs possess no power of spontaneous motion by vvhich they can rise on the head, when the soul shudders with horror or fear ; but they do bris- tle at those times, by the contraction of the occipito-frontales, which, inti- mately adhering to the hairy scalp, carries it along in all its motions. They appear totally without sensibility; nevertheless, the passions have over them such influence, that the heads of young people have turned white * Bystcme des connoissvncz chimiqwes, tome IX. p. 263. 233 the night before execution. The Revolution, which produced, in abundance, the extremes of human suffering, furnished many authentic instances of per- sons that grew hoary, in the space of a few days. In this premature hoari- ness, is the hair dried up, as in old people, when it seems to die for want of moisture and its natural juices ? The following fact seems to show, that they are the excretory organ of some principle, the retention of which might be of very injurious conse- quence. A chartreux, who, every month, had his head shaved, according to the rule of his order, quitting it at its destruction, went into the army, and let his hair grow. After a few months, he was attacked with excruciating head aches, which nothing relieved. At last, some one advised him to re- sume his old habit, and to have his head frequently shaved ; the head aches went off, and never returned. We know, says Grimaud,* that there are nervous head aches, which give way to frequent cropping the hair:—when it is kept close cut, the more ac- tive growth that takes place sets in motion stagnating juices. A friend of Valsalva, as Morgagnit relates, dispelled a maniacal affection, by having the head of the patient shaved ; Casimir Medicus cured obstinate gonorrhea, by the frequent shaving of the parts of generation. The hairs partake ofthe inalterability, the almost indestructibility of the epidermis. Like it, they burn with a fizzing, and give out, in abundance, a fetid ammoniacal oil. The ashes, that remain from burning them, contain much phosphate of lime.J The horns of mammiferae, the feathers of birds, give out the same smell in burning and yield the same products as the hair on the head and other parts; which has led to the saying that these last were a sort of horny substance drawn out like wire. Acids, but especially alkalies, dissolve them : accordingly, all nations that cut the beard, first soften it, by rubbing it with alkaline and soapy solutions. Is the use of the hair to evacuate the superabundant nutritious matter ? The epoch of puberty and of the termination of growth, is that in which it first springs, in many parts of the body, which were before without it. They are, at the same time, the emunctory by which nature gets rid of the phos- phate of lime, which is the residue of the work of nutrition. The hairs of quadrupeds, whose urine abounds less in phosphoric salts than that of man, seem especially to fulfil this destination. The hairs have some analogy with the fat, which has not yet been ascertained. They are often found accidentally developed in the fatty tumours known under the name of stea- tomas. Finally, they have uses relative to the parts on which they grow. CXXXV. The faculty of taking cognizance of tangible qualities, belongs to all parts of the cutaneous organ. We have only to apply a substance to any part of the surface of our body, to acquire the idea of its temperature, of its dryness or moisture, of its weight, its consistence, and even its par- ticular figure. But no part is better fitted to acquire exact notions, on all these properties, than the hand, which has ever been considered as the especial organ of touch. The great number of bones that form its struc- ture, make it susceptible of very various motion, by which it changes its form, adapts itself to the inequalities of the surfaces of bodies, and exactly embraces them: this apt conformation is particularly manifest at the extre- mities of the fingers. Their anterior part, which is endued with the most delicate feeling, receives, from the medium and cubital nerves, branches of * Second Memoir on Nutrition, p. 49. t De Sedibus et Causis, Epist. 8. No. 7. | See the Chapter in the Appendix, on the chemical constifntkm ofthe textures, && 30 2M name size, which end in rounded extremities, close, and surrounded with d cellular tissue. The part of the fingers, which is called their pulp, is sup- ported by the nails; vessels in great number are spread through this nervo- cellular tissue, and moisten it with abundant juices, that keep up its sup- pleness. When perspiration is increased, it breaks out, in small drops, over this extremity of the fingers, along the hollow of the concentric lines with which the epidermis is furrowed. It has been attempted to explain the pleasure we feel in touching round- ed and smooth surfaces, by showing that the reciprocal configuration of the hand and of the body to which it is applied, is such, that they touch in the greatest number of points possible. The delicacy of the touch is kept up by the fineness of the epidermis: it increases by education, which has more power over this sense than over any of the others. It is known with what eagerness a child, allowed the free use of his limbs, stretches his little hands to all the objects within his reach, what pleasure he seems to take in touching them, in all their parts, and running over all their surfaces. Blind men have been known to distinguish, by touch, the different colours, and even their different shades. As the difference of colour depends on the disposition, the arrangement, and the number of the little inequalities, which roughen the surface of bodies that appear the most polished, and fit them to reflect such, or such a ray of light, absorbing all the others, one does not refuse to believe facts of this kind, related by Boyle, and other Natural Philosophers. Some parts appear endowed with a peculiar touch ; such are the lips, whose tissue swells, and spreads out under a voluptuous contact; a vital turgescence, explicable without the supposition of a spungy tissue in their structure :—such are those organs which Buffon considers as the seat of a sixth sense. In most animals, the lips, and especially the lower one, without feathers, scales, or hair, are the organ of a sort of touch, imperfect at best. When the domestic quadrupeds, such as the horse, the dog, the ox, &c. want to judge of the tangible qualities of bodies, you will see them apply to it the end of their nose, the only part where the external covering is without hair; the fleshy appendages of certain birds, and many fish, the antennae of butterflies, always set near the opening of the mouth, an- swer the same purpose. The tail of the heaves, the trunk of the elephant, are, in like manner, the parts of their body where the touch is most delicate. Observe that the pefection of the organ of touch, ensures to these two animals a degree of intelligence allotted to no other quadruped, and becomes perhaps the principle of their sociability. The books of travellers and naturalists swarm with facts, attesting the wonderful sagacity of the elephant. Some Indian philosophers have gone the length of allowing him an immor- tal soul. If birds, notwithstanding the prodigious activity of their life of nutrition, are yet of such confined intelligence, so little susceptible of durable attachment, so restive to education, is not the cause to be assigned to their imperfection of touch ? In vain the heart sends towards all their organs, with more force and velocity than in any other animal, a warmer blood, and endued, more remarkably, with all the qualities which charac- terize arterial blood. In vain is their digestion rapid, their muscular power lively, and capable of long continued motion ; certain of their senses, as those of sight and hearing, happily disposed; touch being almost nothing with them, as also the greater number of impressions belonging to this sense, which informs us of the greater part of the properties of bodies ; \the circle of their ideas must be extremely narrow, and their habits, and 23Si manners, much more remote than those of quadrupeds, from the habits and manners of man. CXXXVI. Of all the senses, the touch is the most generally diffused among animals. All possess it, from man, who, in the perfection of this sense, excels all the vertebral animals, to the polypus, who, confined to the sense of touch only, has it, in such delicacy, that he appears, to use a happy expression of M. Dumeril, to feel even light. The skin of man is more delicate, fuller of nerves than that of the other mammiferae: its surface is covered only by the epidermis, insensible indeed, but so thin that it does not intercept sensation, whilst the hairs which cover so thickly the body of quadrupeds, the feathers which clothe that of birds, quite deaden it. The hand of man, that admirable instrument of his intelligence, of which the structure has appeared to some philosophers* to explain suffi- ciently his superiority over all living species ; the hand of man, naked, and divided into many moveable parts, capable of changing, every moment, its form, of exactly embracing the sarface of bodies, is much fitter for ascer- taining their tangible qualities, than the foot of the quadruped enclosed in a horny substance, or than that of the bird, covered with scales too thick not to blunt all sensation. CXXXVII. Of the nerves. These whitish cords which arise from the base of the brain, and from the medulla oblongata, are distributed to all parts of the body, and give them, at once, the power of moving and feel- ing. In this analysis of the functions of the nervous system, the most natural order is to consider them merely as conductors of the power of sensation. We shall then see, in what manner, they transmit the principle of motion to the organs by which it is performed. Tho nerves arise,t from the sentient parts, by the extremities that are, in general, soft and pulpy,^ but not alike in all, in consistence and form, and it is to these varieties oil" arrangement and structure, that the varieties of sensation is the different organs are to be referred. One may say that there exists, in the organs of sense, a certain relation, between the softness of the nervous extremity, and the nature of the bodies which produce an impression upon it. Thus, the almost fluid state of the retina, bears an evident relation to the subtilty of light. The contact of this fluid could not produce a sufficient impression, unless the sentient part were capable of being set in motion by the slightest impression. Tha portio mollis of the seventh pair, wholly deprived of its solid covering, and reduced to its medullary pulp, readily partakes in the sonorous motions transmitted to it by the fluid, in the midst of which its filaments are im- mersed. The nerves of smell and of taste are more exposed, than the nervous papillae of the skin employed in receiving the impressions produ- ced by the coarser properties of bodies, &c. * See the work of Galen, de usu partium, cap. 4, 5, 6, and Buffon, Histoire Nalurelte, torn IV. et V. 12mo. t In considering the nerves as conductors of sensation, it is correct to say, that they' arise from sentient parts, since it is the extremity most distant from the brain, which experiences the sensitive impression, that it is propagated to the organ itself, along the course of the nerve. In attending, on the contrary, to the phenomena of motion, the nerves are considered to arise from the brain, for, it 19 from the centre ofthe circumfe- rence, that the principle of motion is transmitted to the muscles called, by Cullen, moving extremities of the nerves. Some anatomists have considered it as a doubtful point, whe^ ther the nerves arise from the brain and spinal marrow, or whether these parts are former by the union of the newts—>Authpr's Notg, 236 From their origin, the nerves ascend towards the medulla oblongata and the spinal marrow, in a line nearly straight, and seldom tortuous, as most of the vessels. When they have reached these parts, they terminate in them, and are lost, in their substance, as will be mentioned, in speaking of the structure of these nervous cOrds. CXXXVIII. Every nerve is formed of a great number of filaments, extremely delicate, and which have two extremities, the one in the brain and the other from the part into which they terminate, or from which they originate. Each of these nervous fibres, however minute, is composed of a membranous tube which is a production of the pia mater. Within the parietes of this tube, there are distributed innumerable vessels of extreme minuteness; it is filled within, with a whitish marrow, a kind of pulp, which Reil states he insulated from the small canal containing it, by concreting it, by means of the nitric acid, which dissolves the membranous Bheath, and leaves uncovered the medullary pulp forming the essential part or basis of the nervous filament. The same physiologist discovered, by a different process, the internal structure of each nervous fibrilla ; he dissolved the whitish or pulpy part, by a long continued solution in an alkaline ley, and he succeeded thus in separating it from the membranous tube which enclosed it and which was emptied. The membranous sheath is of cellular struc- ture, and is remarkable only by its consistence and by the very considera- ble number of vessels of all kinds that are distributed to its parietes ; it ceases to cover the nerves, near their two extremities, and protects them, only along their eourse. Each nervous fibre, thus formed of two very distinct parts, joins other fibres of a perfectly similar structure, to form a nervous filament enveloped in a common sheath of cellular tissue. These filaments by their union, form small ramifications, and these progressively larger branches, and last- ly, trunks wrapped in a common covering of cellular tissue ; then other envelopes to each fasciculus of filaments, and lastly, a sheath to each indi- vidual filament. When nervous cords are of a certain size, veins and arteries of a pretty considerable calibre, may be seen to insinuate them- selves between the bundles of fibres of which they are composed ; these vessels then divide, after penetrating among them, and furnish the capillary ramifications which are distributed to the parietes of the sheath common to each filament. These small vessels, according to Reil, allow the nervous substance to exhale into each membranous tube ; this, likewise, becomes the secretory organ of the medulla with vvhich it is filled. CXXXIX. The nervous filaments unite, or are separated from one another, but do not run into each other. The divisions of the nerves are different from those of the arteries, and their mode of junction does not admit of being compared to that of the veins. It is, in the first instance, a mere separation ; in the second, an approximation of filaments which had been separated, and which, though united in common sheaths, have, nevertheless, each a proper covering, are merely in juxta-position and perfectly distinct. If that were not the case, one could not say, that each fibre has one extremity in the brain, and the other in some one point of the body; nor could one conceive how the impressions which several sentient extremities receive at once, reach the brain without running into each other ; nor, in what manner, the principle of motion could be directed towards a single muscle receiving its nerves from the same trunk as the other muscles of The limb. 237 In general, the nerves divide from each other and unite at an angle more or less acute, and equally favourable to the circulation of a fluid, from the circumference to the centre, and from the centre to the circumference. The structure of the nerves is different according to their situation.— Thus, the medullary fibres ofthe optic nerve, are not furnished with mem- branous coverings, the pia mater alone furnishing a sheath to the cord formed by the union of these filaments ; the dura mater adds a second coat to it, on its leaving the skull. This coat, belonging, likewise, to the whole nerve, is not continued over it, after it has entered the eye-ball, and is lost in the sclerotica. A minute artery passes through the centre of the optic nerve, and then dividing, forms a rete mirabile which supports the medullary pulp of the retina. The nerves which pass along osseous canals, as the Vidian nerve of the fifth pair, are not provided with a cellular covering, and their consistence is always greater than that of the nerves which are surrounded by soft parts. CXL. On reaching the brain, the medulla oblongata, or the spinal mar- row, every nervous filament, as was already mentioned, parts with its mem- branous covering, which is lost in the pia mater, or immediate covering of these central parts ofthe brain. The medullary or white part ofthe brain is continued into their substance, which may be considered as principally formed by the assemblage of these nervous extremities which it is difficult to distinguish in its tissue, from its want of consistence. It has long been known, that the origin of the nerves is not fhe spot at which they are de- tached from the brain, that they sink into the substance of this viscus, in Which their.fibres r.roKs each other so that those on the right pass to the left, and vice versa. Soemmering thought, that the roots of the nerves, especially of the nerves of the organs of sense, reached to the prominences in the parietes of the ventricles of the brain, and that their furthest ex- tremity was moistened by the serosity which keeps these inward surfaces in contact. It has likewise long been thought, that the cerebral extremi- ties of the nerves all joined in a fixed point of the brain, and that to this central point, all sensations were carried, and that from it, all the determi- nations producing voluntary motion arose. But the inquiries of Gall on the structure of the brain and nervous system, have completely overset these various hypotheses. The spinal marrow and the nerves, in the different animals furnished with them, are larger in proportion to the brain, according as the animal is more distant from man in the scale of animation. In carnivorous ani- mals, the prodigious developement of the muscles required nerves of motion of a proportionate size; hence, in them, the cerebral mass, compared to the nerves and spinal marrow, is very inconsiderable. It is observed, that there exists the same relation, in men of an athletic disposition; the whole nervous power seems employed in moving their large muscles, and the nerves, though very small, in proportion to the rest of the body, are how- ever, very large, if compared to the cerebral organ. In children, in women, and in individuals possessed of much sensibility, the nerves are very large, in proportion to the other parts ofthe body, they decrease in size and shrink, in persons advanced in years; the cellular tissue which surrounds them, becomes more consistent, adheres to them more closely, and there exists a certain analogy between the nerves of old men, enveloped by that yellowish tissue, which makes their dissection laborious, and the branches of an old tree covered over by a destructive moss. 238 As the uses of the nerves cannot be explained independently of those of the brain, I shall now go on to consider this important viscus. CXLI. Of the spinal cord and its functions.* This part of the nerv- ous system ought no more to be called the spinal prolongation of the en- cephalon, as it has been by some writers, than it ought to be named the spinal marrow : both designations are equally erroneous. It is independent ofthe encephalic organ. As the central portion ofthe nervous system, it is to be found in many animals which possess no brain, and its volume is not proportionate to that of this organ. The ox, horse, and sheep, for ex- ample, which have smaller brains than man, have a much larger spinal cord. It is found in acephalous foetuses, where the brain never existed. This latter organ appears to be superadded to it, and that only in the perfect animals, its proportionate size being always in an inverse ratio to the spinal cord. This part of the nervous system cannot, therefore, be considered as a production from the brain, and as formed by a collection of nerves which successively detach themselves from it. Its volume does not gradually diminish, owing to the nerves which it sends off; and instead of presenting the characters of a cord which gradually decreases in thickness as it ad- vances from the brain, it consists of a set of knots, bulbs, or separate pro- minences, equal in number to the pairs of nerves which arise from it.— Finally, the spinal marrow is formed in the foetus before either cerebellum or cerebrum, these organs proceeding from it, and not it from them. About the second month of the foetal existence, the first epoch at which the brain can be rendered apparent by the action of alcohol, this organ is uncom- monly small in proportion to the siy.e of th<» spinal mawow, and arises evi- dently from a prolongation of the pyramidal eminences and the corpora olivaria. The different parts of the encephalic mass are gradually formed by the successive developement of the corpora pyramidaha, and it is only towards the end of gestation that the hemispheres are fully formed.t The special functions that may be assigned to the spinal cord, are different from those performed by the brain. In the spinal marrow resides the source of all the movements, both voluntary and involuntary, that are performed by the animal economy : it presides over those ofthe heart, of all the mus- cles of the interior life, as well as over those of the locomotive apparatus; and while the brain, reserved for the most noble and most important func- tions, seems exclusively charged with the operations of intelligence and thought, the spinal marrow holds under its control all the contractile or- gans, and it is by its influence that all their contractions are executed.! Thomas Bartholin had already acknowledged that the brain was more particularly the organ of sensation, and the spinal marrow that of motion.^ He was equally sensible that the best way of proceeding in the dissection of the brain, was to advance from the base to the vertex, and not from the summit to the base, as was the custom until our own times. If we take a view of the graduated scale of the animal creation, says Dr. Gall, in his Researches on the Nervous System, &c. the sensible substance, * The whole of this Section has been translated from the last French edition of this work. f See APPENDIX, Note D D. X See the above Note in the Appendix. § " Et id quidem manifestos fit inspicientibus anatomen piscium ; ibi enim medullae caput et cauda insignis est magnitudinis; processus vero medulla? ad cerebrum admo- dum exiguum, cujus rei causa est, quod pisces motu magis quam sensu utantur, ac sic ad sensum plus conferat cerebrum vel cortex, ad motum plus medulla ipsa."—AuatmnUt, 239 which is merely a gelatinous pulp in the polypus, gradually becomes dis- posed into nervous filaments and cords in the more perfect animals. In order to establish a more extended intercourse with the external world, Nature has added more complex organs, according as the relations of the species with the surrounding creation become more numerous : it is thus that, by the successive addition of new organs, and the perfection of others, the animal creation is elevated to man himself. The brain, a simple tubercle added to the anterior extremity ofthe spinal marrow, of which it seems to be nothing else than an accessory part, an appendix, in the insects, because amongst them it is but little larger than one of their numerous ganglions, becomes more complex and more perfect in the higher animals: in the fishes it but little exceeds the spinal cord; whilst in the mammalia it possesses the same parts as in man, and is dis- posed nearly in the same form; but, in no animal is the double appearance of diverging and converging fibres better developed than in him; in no other animal is the brain properly so called, that is to say, the superior part of the encephalon, or the hemispheres, possessed of a greater volume in proportion to the size of the animal.* The brain proper seems to be the seat ofthe nobler functions of intelligence, whilst in the cerebellum the medulla oblongata, and the spinal cord, those faculties and manifestations that are common to us and the lower animals, appear to reside. The nervous system ought not, therefore, to be compared to a tree, the trunk of which, represented by the spinal marrow, has its roots in the brain, and expands its branches through all parts of the body ; but ought rather to be considered as a net-work whose threads communicate with each other, separate, re-unite, and join several masses or dilatations of greater or less size: these masses or ganglions ought to be viewed as being the centres of communication. The brain should not be considered as a ganglion, or even as a collection of ganglions, as the common ganglion of the nerves of the cranium, as some physiologists have done : the nerves which detach themselves from its base, or from the medulla oblongata, have their origins distinct from its substance. Their volume has no relation to its bulk, but are proportionate to the perfection of the different senses, in the various species of animals; thus, the olfactory nerve, which is very large in the mole, is small in the eagle, while the optic nerve is on the contrary largely developed in the latter. The spinal marrow may be considered as a series of ganglions, commu- nicating with each other and with the brain.t These ganglions are of a size proportionate to that of the nerves which originate from them. It is owing to this that the spinal marrow is thicker towards the inferior part of the cervical and dorsal regions, than in other portions of its length. Can, therefore, the vertebral column be compared to a Galvanic pile, of which the spinal cord is the conductor, of which the brain and the parts of gene- ration form the two extremities, and constitute, in a manner, the two poles of this kind of electro-motive apparatus? Observation establishes, it may be said, a sort of antagonism between these two organs. Is there any analogouf opposition existing between the cerebral nervous system and that which forms the grand sympathetic nerves ? We have formerly remarked more than once, how ill founded this attempt at identifying the vital pheno- mena with those of electricity, appears to us* * See APPENDIX, Note D D. ♦ Ibid. 240 The communication of the spinal marrow with the brain is established by the medium of a double bundle of fibres which, crossing each other, form the corpora pyramidalia, and direct themselves towards the brain, where we shall find them again when the structure of this viscus comes under consideration. CXLII. Of the coverings of the brain. If it be true, that one may judge of the importance of an organ, by the care which Nature has taken to protect it from external injury, no organ will appear of greater import- ance than the brain, for, no one appears to have been protected with greater care. The substance of this viscus has so little consistence, that the slightest injury would have altered its structure, and deranged its action; hence it is powerfully guarded by several envelopes, the most solid of which, is the bony case, in which it is contained. No part of anatomy is better understood, than that of the many bones which, by their union, form the different parts of the human head. Every thing that relates to the place they occupy, to their respective size, to their projections and depressions to the cavities whose parietes they form, every thing that relates to their internal structure, to the different proportions of their component parts, to the aggregation of some of these substances, in certain points of their extent, has been described by several modern ana- tomists, with an accuracy which it would not be easy to surpass. Several, however, have not sufficiently appreciated the direct influence of their mode of union on the purposes which they are destined to fulfil; no one has insisted sufficiently on the manner in which they all concur to a princi- pal object; the preservation of the organs enclosed within the skull. Hunauld, in a memoir inserted among those of the Academy of Sciences, for the year 1730, was the first that endeavoured to account for the ar- rangement of the articulating surfaces of the bones of the skull. After laying down a few principles on the theory of arches, and after showing, that the difference of extent of their concave and convex surfaces, renders it necessary that the parts of which they are formed, should be shaped obliquely, he explains the advantages of the squamous articulation between the temporal and parietal bones. When the arch of the cranium is loaded with a very heavy burthen, the temporary bones prevent the parietals on which the effort is immediately applied, from being forced inwardly, or from being separated outwardly. Hunauld very aptly compares them to buttresses which are to the parietal bones of the same use as walls to the arches which they support. Bordeu* endeavoured to apply to the bones of the face, the principles by which Hunauld has been guided in his investigation with regard to those of the skull. According to Bordeu, the greater part of the bones of the upper jaw, but particularly the superior maxillary bones, resist the effort of the lower jaw, which, by acting on the upper dental arch, has a perpe- tual tendency to force upward, or to separate outwardly, the bones in which the teeth of that jaw are inserted. As the greatest stress of the effort determines them upward, it is, likewise, in that direction, that the bones of the upper jaw rest most powerfully on those of the skull. The author concludes this very ingenious memoir, by proposing to physiologists, the solution of the following problem, " When a man supports a great weight on his head, and holds at the same time any thing very firmly between :' Academic des Sciences, Memoires presentes par les savoms circmgers. Tome III, 241 his teeth, which is the bono of the head that is most acted upon $ which supports the weight of the whole machine ?" The body of the sphenoid, and especially the posterior half, appears to me to be the central point on vvhich the united efforts of the bones of the skull and of the face act, in the case supposed by Bordeu. The sphenoid is connected with all the other bones of the skull; it is immediately connected with several of the bones of the face, as with the malar bones, with the palatine bones, with the vomer, and sometimes, with the superior maxillary bones. These bones ofthe face, in the case in ques* tion, alone support the lower jaw against the upper. The ethmoid bone, the ossa unguis, and the inferior turbinated bones, are thin and frail, and serve merely to form the nasal fossae, of which they increase the windings, and do not deserve to be attended to in this investigation. The vomer may, it is true, communicate to the ethmoid, in an inferior degree, a part of the effort; for, the anterior part of its upper edge is articulated with the per- pendicular lamella of that bone; but this quantity is very small, as the vomer is thin and transmits it almost wholly, to the body of the sphenoid, with the lower face of which it is articulated. The effort exerted on the bones of the upper jaw, is transmitted, by means of the nasal processes of the upper maxillary bones, by the orbitar and zygomatic processes of the malar bones, and by the upper edge of the palate bones and ofthe vomer, to the frontal, to the temporal, and sphenoi- dal bones. If we wish to determine what becomes of the greater part of the effort transmitted to the frontal bones by the maxillary and malar bones, we may observe, in the first place, that it is articulated with the sphenoid bone, by the whole of its lower edge which is bevelled at its inner part, so that it is covered by the alas minores of the os sphenoides, which is shaped obliquely at the outer part of the bone. The frontal bone is articulated, besides, with the latter and inferior parts of its upper edge. The remainder of this upper part is united to the anterior edge of the parietal bones, which, by means of a slope, in a different direction, rest on the middle part of this edge, while the frontal bone is applied to them laterally. This bone, which the effort tends to force upward and backward, cannot yield to this double impulse, for, on the one hand, its mode of articulation with the anterior edge of the alae minores of the sphenoidal bone, and the internal part of the anterior edge ofthe parietal bones, resist this tendency upward, while the resistance from the latter, prevents them from being forced backward. That share of the effort which affects the parietal bones, follows the curved lines described by these bones, and extends along that formed by the occipital, and thus reaches the posterior face of the body of the sphenoid bone. The portion directly transmitted by the anterior and inferior face of this bone, by the ossa palati and by the vomer, is considerable, and proportioned to their thinness. The anterior half of the body of the sphenoid bone, hollowed by the sphenoidal sinus, would have been incapable of supporting greater pressure. Lastly, the situation of the body, placed between the dental arches, in front of the place occupied by the ossa palati, explains why this transmission is chiefly effected by the upper maxillary bones. The above is the manner in vvhich the effort exerted from below upward, by the lower on the upper jaw, is carried to the anterior, posterior, and inferior faces of the body of the sphenoid bone. The temporal bones which are affected by it, in a very slight degree, by 31 242 means of the zygomatic processes of the malar bones, support tbe greater weight of the effort acting from above downward, or from the arch of the skull towards its base. The weight laid on the head, tends to depress or to separate the parietal bones, which resist the pressure, in consequence oi the support afforded them by the temporals. These transmit the effort to the lateral and posterior parts of the body of the sphenoid, by means of alae majores of that bone, vvhich are articulated, along the whole extent of their external edge, and along the posterior fourth of their internal edge, with the temporals. Besides, the upper extremity of the alae majores is sloped, on the inner part of the bone, that it may be articulated with the anterior and inferior angles of the parietal bones, and answer the same purpose to them as the squamous portion of the temporals. The lateial and posterior parts of the body of the sphenoid support, therefore, almost the whole effort of the pressure applied to the parietal bones. It is communicated to them by the alae majores, which receive it themselves, either direetly at the anterior and inferior angles of this bone, or through the medium of the temporals. The small portion of the effort transmitted by the latter to the occipital, follows the curved line of this bone, and is felt on the posterior face of the body of the sphenoid. To the effort resulting from the pressure exerted by the body on the summit of the head, one should add that occasioned by the contraction of the muscles which elevate the lower jaw. These tend to depress the temporal, the malar and the sphenoid bones, and in this action, they employ a power equal to that by which they raise the lower jaw, and press it firmly against the upper. The effort exerted from the arch to the base of the skull depends, there- fore, on two very different causes : the portion resulting from the action of the elevators of the lower jaw, is equal to the effort exerted from below upward, by this bone. After what has been stated, it would be useless to say any thing further of the manner in which the effort is transmitted: we may merely observe, that the least powerful of these muscles, the internal pterygoid, tends to draw the sphenoid downward, and prevents this bone, fixed like a wedge with its base turned upward, from being disengaged by the effort applied to it, by the bones between which it is situated. The posterior, anterior, inferior and lateral faces of the sphenoid bone, support, therefore, 'the whole effort of the bones of the skull and face, on one another, when the top of the head being loaded with a heavy burthen, one presses, at the same time, something very firmly between the dental arches. The anterior part of the body of the bone, containing the sphenoidal sinus, is thin and very frail; the posterior part, corresponding to the cella turcica, is alone capable of resisting the effort which, I believe, it is destined to sustain :* hence, it is at this point, that ossification begins, and this con- firms the observation of Kerkingius that the spot at which bones begin to ossify, is that on which they have to bear the greatest effort; hence the alae majores, by means of which the greatest part of the efforts which the * The sphenoidal sinus is prolonged, it is true, into this posterior part of the body of the bone, in persons considerably advanced in years; but the parietes of this portion of its cavity are of considerable thickness. The anterior part of the basilary process of the occipital bone, is then firmly united to the sphenoid, and may be considered as forming a part of that bone, from which it cannot be detached. The cranium of an old man, in this respect, resembles that of several quadrupeds, in which tbe union of the sphenoid to the occipital bone takes place so early, that these two bones might well be considered as forming but one. 243 body of the sphenoid has to support, arise from the lateral part or us posterior half, by an organ of considerable size, and which is further increased by the base of the pterygoid processes which arise from its lower part. I have, in this inquiry, purposely avoided mentioning the support which the head receives from the vertebral column, and which, in the case under consideration, is of use merely in preventing it from yielding to the law of gravitation. If the bones of the skull and of the face had passed, during the effort which they sustain, on the circumference of the foramen magnum; this aperture would have been incapable of increasing its dimensions, and this would have been attended with the most serious inconveniences. The name given by the ancients to the bone whose principal use has just been explained, is composed of sphenos, which means a wedge, and eidos, which signifies resemblance, and would lead one to think, that they were not ignorant of its uses. From its situation, at the middle and inferior part ofthe skull, and from its various connexions with the bones which form this osseous case, it is to them of the same use as the key-stone of arches, with regard to the different parts of which they are formed. The numerous con- nexions required for this puspose, account for its strange and irregular form and for the different shapes of its articular surfaces and the great number of its projections, which render the demonstration of this bone so complicated, and a knowledge of it so difficult. It is more advantageous, with regard to the brain, that the skull should be formed of several bones, than if it had consisted of a single bone. It resists, more effectually, the blows it receives, their effect being lessened, in passing from one bone to the other, and being interrupted, in the obscure motions which they may experience at their sutures; its rounded form in- creases, likewise, its power of resistance. This force would be equal, in every point of the parietes of the cranium, if the form of that cavity were completely spherical, and if the thickness of its parietes were, in every part of it, the same. In that case, no fractures by contre coup could occur, a kind of lesson occasioned by the unequal resistance ofthe bones ofthe head, to the force applied to their surface. The pericranium, the hairy scalp, the muscles which cover it, and the great quantity of hair on its surface, serve, besides, to defend the brain, and are well calculated to break the force of blows applied to the cranium. In addition to this hard and unyielding case, there lies over the brain, a treble membranous covering, formed by the dura mater, vvhich owes its names to the erroneous opinion according to which it was supposed to form all the other membranes of the body ; it is further covered by the tunica arachnoidea, so called from the extreme minuteness of its tissue, and by the pia mater which adheres firmly to the substance of the brain. The dura mater lines, not only the inside of the skull and of the verte- bral canal, which may be considered as a prolongation of it, but, likewise, penetrates between the different parts of the cerebral mass, supports them in the different positions of the head, and prevents mutual compression. Thus, the greatest of its folds, the falx, stretched between the crysta galli of the ethmoid bone, and the inner protuberance of the occipital bone, prevents the two hemispheres of the brain, between vvhich it lies, from compressing each other, when the body is on the side, and maintains, on the other hand, the tentorium cerebelli in the state of tension necessary to enable it to support the weight of the posterior lobes of the brain. This fold of dura mater is of a semi-circular form, separates the portion of the 244 skull which contains the brain, from that in which the cerebellum is situated. It is kept in a state of tension by the falx cerebri, on which it also exerts the same action: it does not present a horizontal plane to the portion of brain which lies upon it, but one that slopes, in every direction, towards the parietes of the skull, to which it transmits most of the weight which it has to support. The tentorium cerebelli, which thus divides the internal cavity of the skull into two parts of unequal dimensions, is bony in some animals that move by bounding and with rapid aetion; this is the case with the cat, which can, without being stunned, take leaps from a consi- derable height. By means of this complete partition, the two portions of the brain are prevented from passing on each other, in the violent con- cussions whieh the\ r>. **«/'Jnee. The tunica arachnoides, according to Bonn*, who was thoroughly ac- quainted with its structure, and who has given a very beautiful plate of it, is the secretory organ of the serum which moistens the internal surface of the dura mater, a fibrous membrane which serves as a periosteum to the bones it lines.t CXLIII. Of the size of the brain. Of all animals, man has tbe most capacious skull, in proportion to his face, and, as the bulk of the brain is always of a size proportioned to that of the osseous case which contains it, the brain is also most bulky in man. This difference of size between the cranium and face, may be taken as the measure of the human understand- ing and of the instinet of the lower animals ; the stupidity and ferocity of the latter are greater, according as the proportions of these two parts of their skull, vary from those of the human head. To express this difference of size, Camper imagined a vertical line drawn from the forehead to the chin, and perpendicular to another drawn in the direction of the base of the skull. He has called the first of these lines facial, the second, palatine or mental. It is easy to understand, that, as the projection of the forehead is determined by the size of the skull, the larger it is, the more ihe angle at which the facial line meets that from the base of the skull must be obtuse. In a well-formed European head, the facial line meets the palatine at an angle nearly straight (of between 80 and 90 degrees.) When the angle is quite straight, and the line which measures the height of the face is completely vertical, the head is of the most beautiful form possible, it approaches most to that conventional degree of perfection which is termed ideal beauty. If the facial line slopes backward, it forms with the palatine line, an angle more or less acute, and projecting forward, the inclination increases, and the sinus of the angle is shorter ; if, from man, we pass to monkeys, then to quadrupeds, to birds, reptiles, and fishes, we find this line slope more and more, and, at last, become almost parallel to the mental, as in reptiles and in fishes, with flat heads. If, on the contrary, we ascend from man to the Gods, whose images have been transmitted to us by the ancients, we find the facial line to incline in a different direction, the angle then enlarges and becomes more 4 Dissertatio de continuationibus membranarum. Lagdun. 4° Bat. 1763. t Analagous to the serous membranes vvhich line the cavities of the body, tho arachnoid is a shut sac, whose internal surface is every where in contact with itself, while its external surface adheres to the two other meninges. Tbe serosity which exudes from the internal surface of the arachnoid differs from that which escapes from the other serous membranes, owing to the almost entire absence of albumen from the former. The exhalation that takes place from this membrane appears to be the source ofa more limpid and dilute effusion, even in disease, than that vvhich is observed fn 'ho cMier 'Brsi? "ari'^3. 245 or less obtuse. From this inclination forward of the facial line, there results an air of grandeur and majesty, a projecting forehead, indicating a voluminous brain and a divine intellect. To obtain with precision, by this means, the respective dimensions of the skull and face, one must measure, not only the outside, but, likewise, draw the tangents on^the internal surfaces, after dividing the head verti- cally. There are, in fact, animals, in which the sinuses ofthe frontal bone are so large, that a considerable portion of the parietes of the skull is pro- truded by their cells. Thus, in the dog, in the elephant, in the owl, &c. the apparent size of the skull exceeds much its real capacity.* The relative size of the head, and consequently the proportionate bulk of the brain, is inconsiderable in very tall and muscular subjects: this fact will be confirmed by observing the proportions of antique statues. In all those which represent heroes or athlets gifted with a prodigious bodily power, the head is very small, in proportion to the rest of the body. In the statues of Hercules, the head scarcely equals in size the top ofthe shoulder. The statues alone of the King of the Gods, present the singular combi- nation of an enormous head, resting on limbs of a proportionate size, but the Greek artists have transgressed the laws of Nature, only in favour of the God that rules over her, as if a vast brain had been necessary to one whose intellect carries him, at a glance, over the universe. The relative small dimensions ofthe head, in athlets, depend oh this circumstance, that in such men, the excessive developement ofthe organs of motion, gives to" the body, and especially to the limbs, an enormous size, while the head covered by few muscles, remains very small. Soemmering has stated, that the head in women is larger than in men, and that their brain is heavier ; but it must be recollected, that this great anatomist obtained this result, by examining two bodies, male and female, of the same length. Now, the absolute size being the same, the proportionate magnitude was not so, and he was wrong in comparing the head, the skull, and brain ofa very tall woman, to that of a very short man. It has long been thought, that there exists a connexion between the bulk of the cerebral mass and the energy of the intellectual faculties. It has been thought, that, in general, men whose mind is most capacious, whose genius is most capable of bold conceptions, had a large head supported on a short neck. The exceptions to this general rule have been so numerous, that many have doubted its truth ; should it then be absolutely rejected, and will it be allowed to be wholly without foundation, when we consider that man, the only rational being out of so great a number, and some of which bear to him a considerable resemblance both of organization and structure, is, likewise, the only animal in which the brain, properly so called, is largest in proportion to the cerebellum, to the spinal marrow, to the nerves, and to the other parts of the body ? Why may it not be with the brain, as with the other organs, which fulfil their functions the better, from being more completely developed? It should be recollected, in this comparison of the brain and of the intellectual powers, that several causes may give to this viscus an unnatural degree of enlargement. Thus, in subjects of a leucophlegmatic temperament, the tardy ossification of the bones of the skull, causes the brain, gorged with aqueous fluids, to acquire a considerable size, without its containing a greater quantity of real me- dullary substance. Hence it is observed, that men of this temperament * See APPENDIX, No* DD 24tf are, most frequently, unfit for mental exertion, and rarely succeed in un- dertakings that require activity and perseverance.* CXLIV. Structure of the cerebral mass. What we know of the brain, serves only to show us that we are ignorant of much more. All that we know of it consists of notions tolerably exact of its external conformation, its colour, its density, and of the different substances that enter into its com- position ; but the knowledge of its intimate structure is yet a mystery, which will not be so soon unveiled to us. The brain, properly called, is divided by a longitudinal furrow, into two lobes of equal bulk. Gunzius, however, imagined that he found the right lobe, or hemisphere, a little larger than the left; but even were this fact as certain as it is doubtful, we could not thereby explain the predominant force of the right side of the body, since the nerves whieh are distributed to this side, rise from the left lobe of the brain, in the substance of which all the roots of these cords cross. This fact of the crossing of the nerves, at their origin, is proved by a multitude of pathological observations, in which the injury of a lobe is always found to bring on paralysis, convulsion, or any other symptomatic affection, on the opposite side of the body. Unless you choose to explain this phenomena by admitting a necessary equilibrium in the action of the two lobes ; an equlibrium, the disturbance of which is the occasion that the sound lobe, acting with more force, compresses the origin of the nerves on its side, and determines paralysis. Might the want of judgment, the unevenness of humour and character, depend on the want of harmony between the two corresponding halves of the cerebral mass? In order to disclose, better than had been before done, the structure of the brain, M. Gall begins his dissection at the lower part, examining, in the first place, the anterior part of the prolongation, known under the name of the cauda of the medulla oblongata, he finds the two pyramidical emi- nences. If you part the two edges of the median line, below the furrow which separates the two pyramids, you see distinctly the crossing of three or four cords or fasciculi of nerves, which, consisting of many fila- ments, tend obliquely from right to left, and vice versa. This crossing of nervous fibres, which is not found in any other part of the brain, had been observed by several anatomists. It is not known how it came to be for- gotten, so that the most exact and latest among them, Boyer, for instance, says that the crossing of the nerves cannot be proved by anatomy. These nervous cords, traced upward, enlarge, strengthen, and forming pyramidi- cal eminences, ascend towards the tuber annulare. Having reached the ganglion, the fibres strike into it, and are lost in a mass of pulpy or greyish substance, of the same nature as that, which, under the name of cortical substance, covers the two lobes of the brain. This greyish pulp, distributed in various parts, may be considered, agreeably to the views of M. Gall, who calls it the matrix of the nerves, as the source from which the medul- lary fibres take their origin. These ascending fibres cross other transverse fibres, which, on either side, proceed from the crura of the cerebellum ; enlarged and multiplied by means of their passage through the grey sub- stance which is found in the tuber annulare; they rise from it, at its upper part, in two fasciculi which compose nearly tbe whole of the crura cerebri. The interior of these crura, contains a certain quantity of grey substance, which is what nourishes the nervous fibre. On reaching the ventricles, these peduncles, or rather the two fasciculi which form them, meet with * See, in the article on Temperaments, an account of the influence ofthe physical organization on the moral disposition and on the intellectual faculties, 247 large ganglions, full of grey substance ; they have long been called thalanii optici, though they do not give origin to the optic nerves. There the fibres are sensibly enlarged; and they pass from the thalami optici into new ganglions. These are the corpora striata, and the striae which are apparent on cutting these pyriform masses of grey substance, are only the same fibres, which, enlarged, multiplied, and radiated, spread out in the manner of a fan, towards the lobes of the brain, where, after forming by their expansion, a whitish and fibrous substance, they terminate at the outer part of that viscus, forming its convolutions, all covered with the substance in which are terminated, in like manner, the extremities of the diverging fibres. From this grey substance, proceed converging fibres, tending from all parts of the periphery to the centre of the brain, where they unite to form the different commissures, the corpus callosum, and other produc- tions, destined to facilitate the communication of the two hemispheres.* The exterior of the brain may, therefore, be considered as a vast nervous membrane, formed by the grey substance. To form a due conception of its extent, it must be understood, that the convolutions of the brain, are a sort of duplicatures, susceptible of extension by the unfolding of two contiguous medullary laminae, which form its base. The exterior surface of the brain, by means of this unfolding, offers them some relation to the skin, a vast nervous expanse every where covered by a sort of pulpy substance, known by the name of the rete mucosum of Malphigi. M. Gall compares this cutaneous pulp, to the cineritious substance which forms the outer part of the brain, and, I must confess, it is not every one that will admit the ana- logy. However, true it is, that the brain consists, principally, of a mass of ganglions, that it produces neither the elongated medulla, nor the spinal marrow, that this last may be considered as a series of ganglions, united together, that the vertebral nerves arise from the greyish pulp of which the spinal marrow is full, as is best seen in animals without a brain, but not the less provided with a spinal marrow, or series of ganglions, from which the nerves arise. The ganglions, or rather the grey substance which they always show, produce the nervous fibres, and thicken the nervous cords that pass through them. That is the only use that can be assigned to these parts of the nervous system ; for, if they were meant to withdraw from the dominion of the will, the parts in which they are found, why do not the ganglions of the vertebral nerves fulfil the same function ? All these nerves communicate by the reciprocal anastomoses. These communications, in man, are equivalent to a real continuity. In truth, the brain acts upon the nerves that proceed from the spinal marrow, as if this were one of its productions, and all the nervous fibres, spread through the different organs, had an ex- tremity terminating in this viscus. One thing well worthy of attention, and on which no anatomist has dwelt, is that the brain of the foetus, and of the child just born, appears to consist, almost entirely, of a cineritious pulp, to such a degree that the medullary substance is difficult to perceive in it. Would it be absurd to believe, that the medullary part of the brain does not take its perfect or- ganization till after birth, by the developement of the fasciculi of medul- lary fibres, in the midst of these masses of cineritious substance, which must be considered as the common source from which the nerves have their origin, or, to use the language of Gall, as the uterus which gives them * See APPENDIX, Note D P 248 birth. The almost total inactivity, the passive state of the brain, in the foetus, makes unnecessary there the existence of the medullary apparatus, to which the most important operations of intelligence seem entrusted. Its first rudiments are found in the foetus at its full time. That fibro-medullary apparatus will be strengthened by the exercise of thought, as the muscles are seen to enlarge and perfect their growth, by the effect of muscular action. CXLV. Circulation of the brain. I have said that the blood, in its circular course, does not traverse the different parts of the body with uni- form velocity ; that there are partial circulations in the midst of the gene- ral circulation. In no organ are the laws, to which this function is subjected, more remarkably modified than in the brain. There is none which receives, in proportion to its bulk, larger arteries and more in num- ber. The internal carotid and vertebral arteries, as we may satisfy our- selves from the calculations of Haller, carry thither a great portion of the whole quantity of blood that flows along the aorta ; (from a third to the half.) The blood which goes to the brain, said Boerhaave, is more aerated than that which is distributed to the other parts : the observation is not without foundation. Though the blood which the contractions of the left ventricle send into the vessels, arising from the arch of the aorta, does not undergo, at the place of this curvature, a mechanical separation carrying its lighter parts towards the head; it is not less true, that this blood, just passing from the contact of the air in the lungs, possesses, in the highest degree, all the peculiar qualities of arterial blood. So great a quantity of light, red, frothy blood, impregnated with caloric and oxygen, coming upon the brain, with all the force it has received from the action of the heart, would unavoidably have deranged its soft and delicate structure, if nature had not multiplied precautions to weaken its impulse. The fluid, compelled to ascend against its own weight, loses, from that alone, a part of its motion. The vertical column must strike against the angular curvature vvhich the internal carotid takes in its passage along the osseous canal of the petrous portion ofthe temporal bone, and as this curva- ture, supported by hard parts, cannot straighten itself, the column of blood is violently broken and turned out of its first direction, with considerable loss of velocity. The artery immersed in the blood of the cavernous sinus, as it comes out from the carotid canal, is very easily dilated. Finally, the branches into which it parts, on reaching the base of the brain, have coats exceed- ingly thin, and so weak that they collapse, when they are empty, like those of the veins. This weakness of the cerebral arteries, explains their fre- quent ruptures, when the heart sends the blood into them too violently ; and it is thus, that the most part of sanguineous apoplexies are occasioned, many of which, however, take effect without rupture, and by the mere transudation of blood through the coats of the arteries. These vessels, like the branches arising from their divisions, are lodged in the depressions with which the base ofthe brain is furrowed, and do not enter its substance, till they are reduced to a state of extreme tenuity, by the further divisions they undergo, in the tissue of the pia mater. Notwithstanding the proximity of the brain to the heart, the blood reaches it, then, with an exceedingly slackened motion: it returns, on the contrary, with a motion progressively accelerated. The position of the veins at the upper part of the brain, between its convex surface and the hollow of the skull, causes these vessels, gently compressed by the 249 alternate motions of rising and falling of the cerebral mass, to disgorge their contents readily into the membranous reservoirs of the dura mater, known by the name of sinuses. These, all communicating together, offer to this fluid a sufficiently large receptacle, from which it passes into the- great jugular vein, which is to carry it again into the general course of the circulation. Not only is the calibre of this vein considerable, but its coats too, of little thickness, are extensible: so much so, that it acquires by injection, a calibre superior to that ofthe venae cava. The flowing ofthe blood is favoured by its own weight, which mikes a retrograde course very difficult.*—Thus, to sum up all that is peculiar in the cerebral circulation, the brain receives, in great quantity, a blood abounding in oxygen; the fluid finds, in its course thither, many obstacles which impede and slacken its impulse, whilst all, on the contrary, favours its return, and prevents venous congestion/!" Let me observe, to conclude what I have to say on the circulation of the brain, that of the eye is nearly allied to it, since the ophthalmic artery is given out by the internal carotid, and the ophthalmic vein empties itself into the cavernous sinus of the dura mater. Accord- ingly, the redness of the conjunctiva, the prominence, the brightness, the rnoistness of the eyes, indicate a stronger determination of tbe blood to- wards the brain. Thus the eyes are animated at the approach of apoplexyys in the transport of a burning fever, during delirium, a dangerous symptom of malignant or ataxic fevers. On this connexion of the vessels of the eye and brain, depends the lividity of the conjunctiva, whose veins, injected with a dark coloured blood, indicate the fulness of the brain in the gene- rality of cases of suffocation. CXLVI. Of the connexion between the action of the brain and that of the heart. It is possible, as was done by Galen, to tie both carotids, in a living animal, without his appearing sensibly affected by it; but if, as has never yet been done, both the vertebral arteries are tied, the animal drops instantly and dies, at the end of a few seconds. To perform this experi- ment, it is necessary, after tying the carotid arteries of a dog, to remove the soft parts which cover the side of the neck, then with needles, bent in a semi-circular form, passed into the flesh along the sides of the articular tion of the cervical vertebrae, to apply ligatures to the arteries which as* cend along their transverse processes. The same effect, viz. the speedy death of the animal is produced by tying the ascending aorta in an herbi- vorous quadruped. These experiments, which have been repeated a number of times, de- cidedly prove the necessity of the action of the heart on the brain, in preserving life. But how does this action operate ? Is it merely me- chanical ? Does it consist solely in the gentle pressure which the arteries of the brain exert on the substance of this viscus, or is it merely, to the intercepted arterial blood which the contractions of the heart determine towards the brain, that death is to be attributed ? The latter opinion seems to me the most probable, for, if, the moment the vertebrals have been tied, the carotids are laid open, and the pipe of a syringe adapted to them, and any fluid whatever is then injected with a moderate degree of force, * In preventing this reflux, there is no use of vales, which the jugular vein i? entirely without. It is sufficiently prevented, by the direction in which the blood flows, and the extensibility of its coats. This great size which the vein can acquire, would have made useless the valvular folds, insufficient to stop the canal, in that great augmentation of its dimensions.—Author's Note. f The transvere anastomoses of the arteries, at the base ofthe braiu, are very proper r?v distributing the blood, in efpial quantity, to all parts of this v5?r!u? 25U aud at nearly the same intervals as those of the circulation, the animal will not be restored to life. . The heart and brain are, therefore, united to each other by the strictest connexion, the continual access of the blood flowing along the arteries ot the head, is, therefore, absolutely necessary to the preservation of life ; it intercepted, for one moment, the animal is infallibly destroyed. The energy of the brain appears, in general, to bear a relation to the quantity of arterial blood which it receives. I know a literary man, who, in the ardour of composition, exhibits all the symptoms of a kind of brain fever. His face becomes red and animated, his eyes sparkling; the caro- tids pulsate violently ; the jugular veins are swollen, every thing indicates that the blood is carried to the brain with an impetus, and in a quantity proportioned to its degree of excitement. It is, indeed, only during this kind of erection of the cerebral organ, that his ideas flow without effort, and that his fruitful imagination traces, at pleasure, the most beautiful de. scriptions. Nothing is so favourable to this condition as remaining long m a recumbent posture: in this horizontal posture, the determination of the fluids towards the head is the more easy, as the limbs, which are perfectly quiescent, do not divert its course. He can bring on this state by fixing his attention steadfastly on one object. May not the brain, which is the seat of the intellectual action, be considered as a centre of fluxion ; and may not the stimulus ofthe mind be compared, as to its effects, to any other stimulus, chemical or mechanical ? . A young man of a sanguineous temperament, subject to mflamatory te- vers which always terminate by a profuse bleeding at the nose, expe- riences, during the febrile paroxysms, a remarkable increase of his intellec- tual powers and of the activity of his imagination. Authors had already observed, that in certain febrile affections, patients of very ordinary pow- ers of mind, would sometimes rise to ideas which, in a state of health, would have exceeded the limits of their conception. May we not adduce these facts in opposition to the theory of a celebrated physician, who con- siders a diminution of the energy of the brain to be the essential character of fever? It is well known that the difference of the length of the neck, and, con- sequently, the greater or lesser degree of vicinity of the heart and brain, give a tolerable just measure ofthe intellect of man, and ofthe instinct of the lower animals ; the disproportionate length of the neck has ever been considered as the emblem of stupidity. In the actual state of our knowledge, is it possible to determine in what manner arterial blood acts on the brain ? Are oxygen or caloric, of which it is the vehicle, separated from it by this viscus, so as to become the prin* ciple of sensation and emotion, or do they merely preserve it in the degree of consistence necessary to the exercise of its functions ? What is to be thought ofthe opinion of those chemists who consider the brain, as a mere albuminous mass, concreted by oxygen, and of a consistence varying in different persons, according to the age, the sex, or the state of health or disease ? Any answer that one might give to these premature questions, would be but a simple conjecture to which it would be difficult to give any degree of probability.* . . , CXLVII. Of the theory of syncope. If we consider the action ot the heart on the brain, we are naturally led to admit its necessity to the mam- * The connexion which exists between the functions of the heart and those of the b-*in. are not only manifest in their healthy relations, but also m their disordered *c, 2.V1 Umande of life, and to deduce from its momentary suspension, the theory- of syncope. Several authors have attempted to explain the manner in which their proximate cause operates, but as not one of them has gone upon facts ascertained by experience, their explanations do not at all agree with what is learnt from observing the phenomena of these diseases. To satisfy one's self, that the momentary cessation of the action of the heart and the brain, is the immediate cause of syncope, one need but read, with attention, the chapter which Cullen, in his work on the practice of physic, has devoted to the consideration of this kind of affection. It will be readily understood, that their occasional causes, the varieties of which determine their different kinds, exist in the heart or great blood-vessels, or act on the epigastric centre, and affect the brain only in a secondary man- ner. Thus the kinds of syncope occasioned by aneurismal dilatations of the heart and great vessels, by polypous concretions formed in these pas- sages, by ossification of their parietes or of their valves, evidently depend on the extreme debility, or on the entire cessation ofthe action ofthe heart and arteries. Their parietes, ossified, dilated, adhering to the neighbour- ing parts, or compressed by any fluid whatever, no longer act on the blood with sufficient force, or else this fluid is interrupted, in its progress, by some obstacle within its canal, as a polypous-concretion, an ossified and immoveable valve. Cullen, very justly, termed these, idiophatic or cardiac syncopes. To the above may be added plethoric syncope, depending on a conges- tion of blood in the cavities of the heart: the contractions of this organ become more frequent, it struggles to part with this excess of blood, which is injurious to the performance of its functions; but to this unusual excite- ment by which the contractility of its fibres is exhausted, there succeeds a kind of paralysis necessarily accompanied by syncope. One may, likewise, include the fainting attending copious blood-letting; the rapid detraction of a certain quantity ofthe vivifying principle, deprives the heart of the stimulus necessary to keep up its action. The same effect is produced by drawing off the water contained in tbe abdomen, in ascites: a considerable number of vessels cease to be compressed ; the blood which they before refused to transmit, is sent to them in profusion; the quantity tions. Portal, Bricheteau and Testa had pointed out this connexion in the diseases of these organs, and more recently Dr. Craigie has contended for its importance, al- though some contemporary pathologists have denied its existence. This pathologist.; after stating his experience on the subject, draws the following inferences from it:— "1st. It is quite obvious, that several maladies ofthe heart, such as ossification of the left side, or of the artery connected with it; ossification of the neutral varve; of the semilunar valves; aretation of the apertures either auriculo-ventricular, or aortic, have a tendency fo terminate in extravation within the cranium, producing apoplexy, paralysis, or a comatose state terminating in death. "2d. Is it by no means difficult to see how these effects in the cerebral organ result from an irregular and disordered action of the heart. The difficulty which the blood experiences in passing either, 1st. through the auriculo-ventricular opening; 2d. the aortic orifice; 3d. along the aorta, necessarily produces a stagnation and congestion; 1st. in the pulmonary veins; >d. in the pulmonary artery; 3d. in the right side of the heart. The effect of this is to retard or impede very remarkably the return of the blood from the cerebral veins, and consecutively either to distend them, to ruplure them, or to occasion an effusion of the serous part of the blood, as we find in other examples of obstructed venous circulation."—(Edin. Med. Journ.No. 74)- Dr. Craigie has, however, omitted to mention the influence of active enlargement of the left side of the heart in causing apoplexy, owing to the increased impulse or determination of blood which is thus produced, and to which the brain is most obnoxious. This and every other form of connexion of disease of the heart with apoplexy can only be viewed as occasional oc- curr^nre?. the former states beio? by no means necessarily followed by the latter, 2.)2 sent to the brain b} the heart is lessened, in the same proportion, and In- comes insufficient for its excitement. Among the syncopes, called idiopha- tic, one may enumerate those occurring in the last stage of the scurvy, the principal character of which is, an excessive debility of the muscles em- ployed in the vital functions, and in voluntary motion ; lastly, we may add asphyxia from strangulation, from drowning, and from the gases unfit for respiration; affections in vvhich the blood being deprived ofthe principle which enables it to determine the contractions of the heart, the circulation becomes interrupted. If the blood loses, by slow degrees, its stimulating qualities, the action of the heart gradually weakened, impels towards the brain a bloood which, by its qualities, partakes of the nature of venous blood, and which, like it, cannot preserve the natural economy of the brain. It was thought, that by injecting a few bubbles of air into the jugu- lar vein of a dog, one might occasion in the animal, immediate syncope, and that it was even sufficient to deprive it of life; but the late experi- ments of M. Nysten have proved, that the atmospherical air produces these bad effects, only when injected in a quantity sufficient to distend, in ex- cess, the cavities of the heart, or when by being injected into the arteries, it compresses the brain. When injected only in a small quantity, the gas dissolved in the venous blood, is conveyed along with it, to the lungs, and is thence exhaled in respiration. A second class of occasional causes consists of those which, by acting on the epigastric centre, determine, by sympathy, a cessation of the pulsations of the heart and the syncope necessarily attending this cessation. Such ■are the violent emotions of the soul, terror, an excess of joy, an irresistible aversion to certain kinds of food, the dread which is felt on the unexpected sight of an object, the disagreeable impression occasioned by certain odours, &c. In all these cases, there is felt, in the region of the diaphragm, an inward sensation of a certain degree of emotion. From the solar plexus ofthe great sympathetic nerve, which, according to the general opinion, is considered as the seat of this sensation, its effects extend to the other abdo- minal and thoracic plexuses. The heart, the greater part of whose nerves arise from the great sympathetic, is particularly affected by this sen- sation. Its action is, at times, merely disturbed by it, and at others wholly suspended. The pulse becomes insensible, the countenance pale, the ex- tremities cold, and syncope ensues. This is the course of things, when a narcotic or poisonous substance has been taken into the stomach; when this viscus is much debilitated, in consequence of long fasting, or when it contains indigestible substances ; in colic, and in hysterical affections. The last class of occasional causes do not act directly, and produce syn- cope only at a distant period; but the result is always the same. It hap- pens, in all the cases, that as the arteries of the head no longer receive as much blood, as in health, the brain fells into a kind of collapse, which occa- sions a momentary cessation of the intellectual faculties, of the vital func- tions, and of voluntary motion. Morgagni, in treating of deseases, according to their anatomical order. ranks lypothymia among the affections of the chest, because the viscera contained in that cavity, shew marks of organic affection, in persons who during life, where subject to frequent fainting. The compression of the brain, by a fluid effused on the dura mater, in wounds of the head, does not produce real syncope, but rather a state of stupor. All causes acting, in this manner, on the brain, produce comatose and even apoplectic affections. When a man, on being exasperated, falls 2 >:j nito a violent and sudden fit of passon, his face becomes flushed, and he i* affected with vertigo and fainting. There is no loss of colour, no loss of pulse, the latter, on the contrary, generally beats with more force. This is not syncope, but the first stage of apoplexy, occasioned by the mechani- cal pressure on the brain, towards which the blood is carried suddenly and in too great a quantity. I might support this theory of syncope, by additional proofs drawn from the circumstances which favour the action of the causes giving rise to affections of this kind. For instance, syncope comes on, almost always, when we are in an erect posture, and in such a case, it is right to lay the patient in a horizontal posture. Patients debilitated by long diseases, faint the moment they attempt to rise, and recover on returning to the recum- bent posture. Now, how are we to explain this effect of standing, in per- sons in whom the mass of humors is much impoverished, and whose organic action is extremely languid, unless by the greater difficulty to the return of the blood, from the more depending parts, and on the difficulty in ascending, of that which the contractions of the heart send towards the head ? The phenomena of the circulation, are, under such circumstances, more subject to the laws of hydraulics, than when the body is in a state of health; the living solid yields more easily to the laws of physics and me- chanics, and, according the sublime idea of the father of physic, our indi- vidual nature approaches the more to universal nature. CXLVIH. Of the motions of the brain. Are the alternate motions of elevation and depression seen, when the brain is exposed, exclusively iso- chronous to the pulsations of the heart and arteries, or do they correspond, at the same time, to those of respiration ? Such is the physiological problem, of which I am about to attempt the solution. Those authors who admit the existence of motions in the dura mater, do not agree as to the cause which produces them. Some, and among others, Willis and Baglivi, thought they had discovered muscular fibres, and ascri- bed these motions to their action : others, as Fallopius and Bauhinus, attri- buted these motions to the pulsations of the arteries of that membrane. The dura mater possesses no contractile power; its firm adhesion to the inside of the skull, would, besides, prevent any such motion. The motion observed in this membrane is not occasioned by the action of its vessels, for, as Lorry observes, the arteries of the stomach, of the intestines, and of the bladder, do not communicate any motion to the parietes of these hollow viscera, and yet, in number and size, they, at least, equal the me- nyngeal arteries. The motion observed in the dura mater is communicated to it by the cerebral mass which this membrane covers; and this opinion of Galen, adopted by the greater number of anatomists, has been placed beyond a doubt, by the experiments of Schlitting, of Lamure, Haller, and Vicq-d'Azyr. They have all observed, that on removing the dura mater, the brain continued to rise and fall, and with the exception of Schlitting, they agreed that the brain, absolutely passive, received from its vessels, the motions in which the dura mater partook : but are these motions communicated by the arteries or by the cerebral veins, and by the sinuses in which these terminate, or, in other words, are they isochronous, to the beats of the pulse, or to the contraction and successive dilatation of the chest, during respiration. _ . Galen, in his treatise on this function, says, that the air admitted into the pulmonary organ distends the diaphragm., and is conveyed,, along the 254 ■-■ertebral canal, into the skull. According to this writer, the brain risiis during the enlargement of the chest, and it sinks, on the contrary, when the parietes of this cavity are brought nearer to its axis. Schlitting, in a me- moir presented to the Academy of Sciences, towards the middle of the last century, maintains that these motions take place, in a different order, the elevation of the brain corresponding to expiration, and its depression to inspiration. Conceiving that he has determined this fact, by a sufficient number of experiments, he does not enter into any explanation, and con- cludes his inquiry, by asking whether the motions of the brain are occa- sioned by the afflux of air, or of blood, towards that organ. Haller and Lamure attempted to answer this difficulty. They both performed a number of experiments on living animals, acknowledged the fact observed by Schlitting, and explained it in the following manner: as well as this last anatomist, Lamure believed that there is a vacuum between the dm-a and pia mater, by means of which, the motions of the brain might always be performed. The existence of such vacuum is disproved by the close contact of the membranes between which it is supposed to exist. During expiration, continues Lamure, the parietes of the chest close on themselves, and lessen the extent of this cavity. The lungs, pressed in every direction, collapse ; the curvature of their vessels increases, and the blood flows, along them, with difficulty. The heart and great vessels thus compressed, the blood carried off by the upper vena cava to the right auri- cle, cannot be freely poured into this cavity which empties itself, with difficulty, into the right ventricle, whose blood is unable to penetrate through the pulmonary tissue. On the other hand, as the lungs compress the vena cava, a regurgitation takes place of the blood which it was con- veying to the heart; forced back along the jugulars and vertebrals, it dis>- tends these vessels, the sinus of the dura mater which empty themselves into them, and the veins of the brain which terminate into these sinuses. Their distension accounts for the elevation of the cerebral mass soon fol- lowed by depression, when, on inspiration succeeding expiration, and on the lungs dilating, the blood which fills the right cavities of the heart, can freely penetrate into the pulmonary substance, and make way for that which the vena cava is bringing from thes uperpr parts of the body. Haller considered this reflux as very difficult, the blood having to rise against its own gravity, and he admitted Lamure's explanation, only in the forcible acts of respiration, as in coughing, laughing, and sneezing. He maintained that, in a state of health, there is to be observed, during expi- ration, a mere stagnation of the blood, in the vessels which bring it from the internal parts of the skull. He further admits, on the testimony of a great number of authors, another order of motions depending on the pulsa- tions of its arteries ; so that, according to Haller, the cerebral mass is inces-. santly affected by motions, some of which depend on respiration, while others are quite independent of it. Lastly, according to Vicq-d'Azyr, the brain, on being exposed, presents a double motion, or rather two kinds of motion, from without; the one from the arteries, and which is least remarkable, the other from the alter nate motions of respiration. CXLIX. This opposition between authors of reputation, and whose theories have, in general, been adopted, induced me to repeat the experi- ments which each of them brings in support of his own opinion, and to perform further experiments on this subject. My investigation soon con- vinced me, that these authors had given a statement of their opinions, and 255 not of the fact itself. In fact, the alternate motions of elevation and depression observed in the brain, are isochronous to the systole and diastole of the arteries at its base. The elevation of the brain corresponds to the dilatation of these vessels, its depression to their contractions. The process of respiration has nothing to do with this phenomenon, and, even admitting the stagnation of the regurgitation of the blood in the jugular veins, the arrangement of the veins, within the skull, is such, that this stagnation or reflux could not produce alternate motions of the cerebral mass. The brain receives its arteries from the carotids and vertebrals, after they have entered the skull, the former along the carotid canals, the latter through the foramen magnum of the occipital bone. It would be useless to describe their numerous divisions, their frequent anastomoses, the arterial circle, or rather polygon formed by these anastomoses, and by means of which, the carotid and vertebral arteries communicate together, by the side of the sella turcica. Haller has given a very correct view and an excellent description of this part.* The account of the internal carotid artery published by that great anatomist is, according to Vicq-d'Azyr, a chief- d'eeuvre of learning and precision ; the same encomium might be bestow- ed on the latter who gave a superb drawing of the same part. I shall content myself with observing, that the principal arterial trunks going to the brain, are situated at the base of this viscus ; that the branches into which these trunks divide, and the subdivisions of these branches, are, likewise, lodged at its base in a number of depressions, and that, in the last place, the arteries of the brain do not penetrate into its substance, till after they have undergone in the tissue of the pia mater, which appears com- pletely vascular, very minute subdivisions. The vessels which return the portion of blood which has not been em- ployed in the nutrition and growth of the brain, are, on the contrary, situated towards its upper part, between its convex surface, and the arch of the cranium, each convolution contains a great vein which opens into the superior longitudinal sinus. The vena Galeni which deposits into the sinus, the blood brought from the choroid plexus ; small veins which open into the cavernous sinuses ; others, likewise very minute, which passing through the foramina in the, alae majores of the sphenoid bone, contribute to form the venous plexus of the zygomatic fossa, are the only exceptions to this general rule. This being laid down on the arrangement of the arteries and veins, let us examine what will be the effect of their action, with regard to this viscus. \ The contractions of the heart propel the blood into the arterial tubes, which experience especially at the place of their curvatures, a manifest displacement, at the time of their dilatation. All the arteries situated at the base of the brain, experience both these effects at once. Their united efforts, communicate to it a motion of elevation succeeded by depression when, by their contraction, they re-act on the blood which fills them. These motions take place, only as long as the skull remains entire; this cavity is too accurately filled, and there is no void space between the mem- branes of the brain. Lorry who, with good reason, denied the existence of such a space, committed an equally serious anatomical mistake in asserting, that as no motion could take place, on account of the state of fulness of the skull, it was effected in the ventricles, which he considers * Fasciculi Anatomici, P. 7 tab, ?• 256 as real cavities, but which, as Haller has shewn, are, when in a natural state, merely surfaces in contact. No motion actually takes place, except in those eases in which there is a loss of substance in the parietes of the skull. It is easy to conceive, however, that the brain which is soft and of weak consistence, yields to the gentle pressure of its arterial vessels. Does not this continued action of the heart on the brain, explain in a satisfactory manner, the remarkable sympathy between those two organs, linked by such close connections ? It is, besides, of very manifest utility, and con- nected with the return of the blood distributed to the cerebral mass and to its envelopes. The veins which bring it back, alternately compressed against the arch ofthe skull, empty themselves more easily into fh*3 sinuses of the dura mater, towards which their course is tetrograde, and unfavoura- ble to the circulation of the blood which they pour into them. When any thiug impedes the free passage of the blood through the lungs, it stagnates in the right cavities of the heart; the superior vena cava, the internal jugulars, and consequently the sinuses of the dura mater, and the veins ofthe brain which terminate in them, are gradually distended; and if this dilatation were carried to a certain degree, the veins of the brain, placed between it and the arch of the skull, would tend to depress it towards the base of that cavity. If this dilatation, at first sight, were carried beyond the extensibility of these vessels, their rupture would occa- sion fatal effusions. It is in this manner, that some authors have explained sanguineous apoplexy. It will be objected perhaps, that many of the sinuses of the dura mater are at the base of the skull, and that, consequently, their dilatation must tend to raise the cerebral mass. But the greater part of these sinuses are connected only with the cere- bellum and the medulla oblongata, of which it has not yet been possible to ascertain the motions. These sinuses are almost all lodged in the edges of the falx and of the tentorium cerebelli. The cavernous sinus inwhich the ophthalmic vein disgorges itself, the communicating sinuses, which allow the blood of one of these sinuses to pass into the other, are too insignificant to produce a raising of the cerebral mass. Lastly, the resistance of their parietes, formed chiefly by the dura mater, must set strait bounds to their dilatation; the spungy tissue which fills the interior of the cavernous sinuses, still makes this dilatation and the reflux of the blood more difficult. CL. It is enough to prove, by reasons drawn from the disposition of parts, that the motions of the brain are communicated to it, by the collec- tion of arteries at its base; the fact must yet be established upon observa- tion, and placed beyond doubt, by positive experiments. The following are what I have attempted for this purpose: A. I have first repeated the observation of some authors, and ascertained, as they did, that the pulsations felt on placing the finger on the fontanels ofthe skulls of new-born infants, correspond perfectly to the beatings of the heart and arteries. B. A patient, trepanned for fracture, with effusion on the dura mater, enabled me to see the brain, alternately rising and falling. The rising corresponded with the diastole, the falling with the systole of the arteries. C. Two dogs, trepanned, exhibited the same phenomenon, in the same relation, to the dilatation and contraction of the arteries. D. I removed, carefully, the arch of the skull, on the body of an aduk. The dura mater* disengaged from its adhesion^ to the bones which it lines. 257 was preserved, perfectly untouched. I afterwards laid bare the maiu caro- tids, and injected them with water. At every stroke of the piston, the brain showed a very sensible motion of rising, especially when the injection, was forced at once along the two carotids. E. I have injected the internal jugular veins. The cerebral mass re- mained motionless. Only the veins of the brain, the sinuses of the dura mater dilated. The injection having been kept up for some time, there resulted from it a slight swelling of the brain : when driven with more force, some of the veins burst, and the liquor flowed out. The same in- jection being made with water strongly reddened, the surface of the brain became coloured with an intense red. To see clearly this effect, you ought, after removing the arch of the skull, to divide, on each side, the dura mater, on a level with the circular incision of the skull, then turn back the flaps towards the upper longitudinal sinus. F. The internal jugular veins having been laid open, while the injection was forced along the main carotids, each time the piston was pushed for- ward, the venous blood flowed with the greatest impetus ; a clear proof of the manifest influence of the motions of the brain, on the course of the blood in its veins, and in the sinuses of the dura mater. This experiment had been already performed by other anatomists, and amongst others, by Ruasch, with a view of proving the immediate communication between the arteries and veins. This communication, which is, at present, universally acknowledged, may be proved by other facts. This one is evidently any thing but conclusive. G. In a trepanned dog, I tied successively the two carotids. The mo- tions of the brain abated, but did not cease. The anastomoses- of the vertebrals, with the branches of the carotids, account for this phenomenon. H. I took a rabbit, a gentle creature, easy to confine, and very well adapted for difficult experiments : after laying bare the brain, and observ- ing that its motions were simultaneous to the beats of the heart, I tied the trunk of the ascending aorta: the moment the blood ceased rising to the head, the brain ceased moving, and the animal died. I. The tying of the internal jugular veins, did not stop the motions of the brain ; but its veins dilated, and its surface, bared by the removal of a flap of the dura mater, was sensibly redder than in the natural state.— The dog became affected with stupor, and expired in convulsions. The opening of these veins did not hinder the continuance of the mo- tions; they grew fainter only when the animal was weakened by loss of blood. K. The opening of the superior longitudinal sinus, the only one that could easily be opened, did not weaken the motions of the brain. It is observed that the blood flows out more freely from it, during the elevation. L. The compression of the thorax, on human bodies, produces but a slight reflux in the jugular veins, especially, if, during this compression, the trunk is kept raised. The reflux is greater, when the trunk is laid flat. These experiments might be varied and multiplied ; if, for instance, the injection were thrown, at once, along the vertebral arteries, and the in- ternal carotids ; but those T have stated are sufficient for my purpose. Since the first publication of this inquiry, in the Memoirs ofthe Medical Society,* I have had many opportunities of repeating the observations and experiments, which serve as a foundation to the theory there detailed. * Memoires de la Societe Medicale de Paris, an VII. (1799.) troi?icme anne'ensee W, et sui". 258 Among the facts which confirm this theory, there is one that appears to mo Worth stating : it would be sufficient by itself, if it were possible to establish a theory on the observation of a single fact. . A woman, about fifty years of age, had an extensive carious affection of the skull ; ihe left parietal bone was destroyed, in the greatest part of its extent, and left uncovered a pretty considerable portion ofthe dura mater. Nothing was easier than to ascertain the existence of a complete correspondence, between the motions of the brain and the beats of the pulse. I desired the patient to cough, to suspend her respiration suddenly, tbe motions continued in the same relation to each other; when she coughed, the head was shaken, and the general concussion, in which the brain partook, might have been mistaken by a prejudiced observer, for the proper motions of that organ, and depending on the reflux of blood in the veins. In experiments on dogs, the same motion takes place, when the animal barks, but it is easy to perceive, that the concussion affecting the brain is experienced by the whole body, and that the effort of expiration, in barking, causes a concussion more or less violent. The patient, mentioned in the preceding observation, died about a month after I came to the Hospital of St. Louis, in which she had been for a considerable length of time. On opening the body, the left lobe of the brain was found softened and in a kind of putrid state ; the ichor vvhich was formed, in considerable quantity, flowed outwardly, by a fistulous opening in tbe dura mater whose tissue was rather thickened. CLI. The slight consistence of the brain, which Lorry considers as favourable to the communication of the motion which its arteries impart to it, appears.to me to be against this transmission. In fact, the dilated vessels not being able to depress the base of the skull on which they rest, make their effort against the cerebral mass, and raise it the more easily (the arch of the skull being removed) from its presenting a certain re- sistance. If the brain were too soft, the artery would merely swell into it, and would not lift it. To satisfy one's-self of this truth, one need only observe what happens when the posterior part of the knee rests on a pillow, or on any thing of the same sort; then, the motions which the popliteal artery impresses on the limb, are but little apparent; but they become very visible, if the ham rests on any thing that resists the action on the other knee, for instance :—then the artery, which cannot depress it, exerts its whole action in raising the lower extremity : which it does, the more easily, from acting against a bony, resisting, and hard part. This experi- ment completely invalidates the opinion of Lorry. The want of analogy will not be objected : it will not be said that the brain is heavier than the lower extremity, nor that the sum of the calibres of the internal carotid and the vertebral arteries, is not greater than that of the popliteal artery. This continual tendency of the brain to rise, produces in the end, on the bones of the skull which resist this motion, very marked effects. Thus, the interior surface of these bones, smooth, in early life, becomes furrowed with depressions, the deeper as we advance in age. The digital depres- sions and the mammillary processes, corresponding to the convolutions and windings of the brain, are very evidently the result of its action on the enclosing parietes. Sometimes it happens, that, at a very advanced age, the bones of the skull are so thinned by this internal action, that the pul- sations of the brain become perceptible through the hairy scalp. No doubt, the same cause hastens the destruction of the skull by the fungous tp'.flours of the dura mater. The effort from expansion of the 259 lOiuoni; which developes itself, is further added, and makes the waste of the bones more rapid. At the end of a few mouths, the tumour projects outwardly, with pulsations plainly simultaneous to the beatings of the pulse, as Louis observes in a Memoir inserted among those of the Academy of Surgery. I have shown (CXLIX.) that the disposition of the veins of the brain and of the sinuses of the dura mater was adverse to the action ascribed to them, on this viscus. Experiment (E. L.) shows that the stagnation of the blood, or even its regurgitation, could produce only a slow and gradual distension of the sinuses of the dura mater, and veins terminating in it, with a slight turgescence of the cerebral mass, if the cause, producing the stagnation of the blood or its reflux, prolonged its action to a partial de- struction of the skull. Lastly, the alternate motions of the brain, said to correspond to those of respiration, ought to be to the beats of the pulse, in the ordinary ratio of 1 to 5. On the contrary, it is easy to satisfy one's self that these motions are in an inverse ratio, and perfectly simultaneous to the pulsations of the heart and arteries. The results of the experiments I have stated in that Memoir, compared to those obtained by justly celebrated inquirers, are too remarkably differ- ent not to have induced me to make some attempt at investigating the cause of our disagreement. For that purpose^ 1 thought it necessary to examine scrupulously all the circumstances The work of Lamure contains anatomical errors, which throw suspicious upon his accuracy. Haller did not himself make the experiments of which he speaks, in treating of the influence of respiration on the circulation of venous blood. This article is drawn from a thesis defended at Gottingen by one of his disciples. Lastly, Vicq-d'Azyr attempted no confirming experiment, and seems to have had in view only the reconciling all opinions. No one of these anatomists has distinguished the motions of elevation impressed on the cerebral mass by the influence of its arteries, from the swelling of the sinuses of the dura mater, of the veins distributed to it, and from the tumefaction of the brain which may be caused by difficult respi- ration. This mistake would be the more easy, as animals tortured by the knife of the anatomist, breathe painfully, convulsively, and at shorter inter- vals than in their natural state. Schlitting, the first author of these experi- ments, appears especially to have confounded the motion of rising, the real displacement of the brain, with the turgescence of this viscus. At every expiration, he says, J have seen the brain rise, that is to say, swell, and and at every inspiration I have seen it fall, that is to say, collapse. " Toties animadverti perspicue—in omni expiratione, cerebrum universim ascendere, id est itumescere; atque in quavis inspirationa illud daccndcrc, id est dctumescereP We may, therefore, consider as a truth strictly demonstrated by obser- vation, experiment, and reasoning, the following proposition :— The motions observable in the brain, when laid bare, are imparted to it solely by the pulsations of the arteries at its base, and are perfectly sinml- taneous to the pulsations of these vessels : further, the reflux and stagna- tion of the venous blood, are able to swell its substance. CLII. Action of-the nerves and brain. It is undoubtedly, as Vicq- d'Azyr has said, by a motion of some sort that the nerves act. Setting out from this simple idea, one may admit sevc-ral kinds of nervous motions. 260 the one operating from the circumference to the centre, it is die motion oi sensation which we are about more particularly to study in this paragraph ; the other, acting from the centre to the circumference, and this motion. produced by the will, determines the action of the muscular organs, &c. In what manner are the impressions produced on the senses by the bodies which surround us, transmitted, along the nerves, to the brain ? Is it through the intervention of a very subtle fluid, or can the nerves, as has been stated by some physiologists, be considered as vibrating cords ? This last idea is so absurd, that one cannot help wondering it should so long have been in vogue. A cord that it must vibrate, must be in a state of tension, along the whole of its length, and fixed at both extremities. The nerves are not in a state of tension, their extremities, in no degree fixed, approach towards each other, or recede according to the difference of posi- tion, the tension, the turgescence, the fulness or collapse of the parts, and vary constantly in their distance from each other. Besides, the nervous cords, situated between pulps, at their origin, and at their termination, cannot be extended between these two points. The nervous fibre is the softest, the least elastic of all the animal libres ; when a nerve is divided, its two extremities, far from receding by contracting, project, on the con- trary, beyond each other; the point of section shows a number of small granulations of medullary and nervous substance, which flows'through its minute membranous canals. Surrounded by parts to which they are, to a certain degree, united, the nerves could not vibrate ; lastly, admitting the possibility of their being capable of vibrating, the vibration of a single filament ought to bring on that of all the rest, and carry confusion and disorder in every motion and sensation. It is much more probable that the nerves act by means of subtle, invisi- ble, and impalpable fluid, to which the ancients gave the name of animal spirits: this fluid, unknown in its nature, and to be judged of only by its effects, must be wonderfully minute, since it eludes all our means of investigation. Does it entirely proceed from the brain, or is it equally secreted, by the membranous envelopes of each nervous filament ? (Neurilemes, Reil.) To say the truth, one can bring no other proof of the existence of a nervous fluid, but the facility with which, by means of it, we are enabled to ex- plain the various phenomena of sensation, and its utility in explaining these phenomena. These proofs, however, may not appear completely satisfactory to those who are very strict, and who do not consider as proved what is merely probable. Among the constituent principles of the atmosphere, there are generally diffused several fluids, such as the magnetic and electric fluids. Might not these fluids, on entering with the air into the lungs, combine with the arte- rial blood, and be conveyed, by means of it, to the brain, or to the other organs ? Does not the vital action impart to them new qualities, by making them undergo unknown combinations ? Do caloric and oxygen enter into these combinations which endow fluids with a certain vitality, and produce on them important changes, and which are not understood ?* Have not these conjectures acquired a certain degree of probability, since the analogy of galvanism to electricity, at first supposed by the author of this discovery, has been confirmed, by the very curious experiments of Volta, repeated, * Were it not for these changes, electricity, magnetism, and galvanism, would suffice to restore life to an animal recently dead. 261 • .lamented, and explained, by all the natural philosophers of the present day, in Europe ?* ^ The action of the nervous fluid takes place, from the extremity of the nerves towards the brain, so as to produce the phenomena of sensation for, when the nerves are tied, the parts below the ligature lose the power of sensation, while, as will be seen in the proper p.ace, this action is pro- pagated from the brain towards the nervous extremities, and from the cen- tre to the circumference, in producing motions of every kind. This double current, in contrary directions, may take place in the same nerves, and it is not necessary to arrange the nerves into two classes of sensation and of motion. All the impressions received by the organs of sense, and by the sentient extremities of nerves, are transmitted to the cerebral mass. The brain is therefore, the centre of animal life ; all sensations are carried to it; it is the spring of all voluntary motion ; this centre is to the functions of relation as the heart to the functions of nutrition. One may say of the brain as of the heart, omnibus dat et ab omnibus accipit. It receives from all and gives to all.t The existence of a centre, to which all the sensations are carried, and from vvhich all motions spring, is necessary to the unity of a thinking being, and to the harmony of the intellectual functions. But is this seat of the' principle of motion and of sensation, circumscribed within the narrow limits of a mathematical point, or rather should it not be considered as diffused over nearly the whole brain ? The latter appears to me the more probable opinion ; were it otherwise, what could be the use of those divi- sions of the organ into several internal cavities ; what could be the use of those prominences all varying in their form ; and of the arrangement of the two substances which enter into their structure ? We may conjecture and with considerable probability, that each perception, each class of ideas' each faculty, is assigned to some peculiar part of the brain. It is, indeed, impossible to determine the peculiar functions of each part of the organ • to say what purpose is served by the ventricles, what is the use of the commissures, what takes place in the peduncles ; but it is impossible to study an arrangement of such combination, and to believe that it is without design, and that this division of the cerebral mass, into so many parts, so distinct, and of such various forms, is not relative to the different function, which each has to fill in the process of thought. That ingenious compari- son, mentioned m the panegyric of Mery, by Fontenelle, is very applicable to the brain. « We anatomists," he once said to me, " are like the porters in Paris, who are acquainted with the narrowest and most distant streets, but who know nothing of what takes place in the houses." What then are we to think of the system of Gall, and of his division of the outside of the skull into several compartments, which, according to the depression or projection of the osseous case, indicate the absence or the presence of certain faculties, moral or intellectual ? I cannot help thinking, that this physiological doctrine of the functions of the brain, resting on too few well observed facts, is frivolous ; while his anatomical discoveries on the anato- my of this organ, and on the nervous system, are of the highest importance, and well founded. * Galvanism, as yet, has not realized the expectations of physiologists Chemistry has derived the greatest advantages from it. It is, at present, with M. M Davy, Thenard, and Gay-Lussac, the most powerful agent in the analysis of certain bodies. * See APPENDIX, Note F. E. 262 CLIII. Analysis of the Understanding. In vain were the organs ol sense laid open to all impressions of surrounding objects; in vain were their nerves fitted for their transmission: these impressions were to us as if they had never been, were there not provided a seat of consciousness in the brain. For it is there, that every sensation is felt; light and sound, and odour, and taste, are not felt in the organs the}' impress ; it is the sensitive centre that sees, and hears, and smells, and tastes. You have only to interrupt, by compression of the nerves, the communication be- tween the organs and the brain, and all consciousness of the impressions of objects, all sensation is suspended. The torturing pains of a whitlow cease, if you bind the arm so strongly as to compress the nerve which carries the sensation to the brain. A living animal, under experiments, suffers nothing from the most cruel laceration, if you have first cut the nerves of the parts on which you are operating. To conclude, the organs of sense, and the nerves vvhich communicate between them and the brain, shall have suffered no injury, shall be in perfect state for receiving and transmitting the sensitive im- pression, yet no phenomena of sensation can take place, if the brain be deceased : when it is compressed, for instance, by a collection of fluid, or by a splinter from the skull in a wound of the head. This organ is, therefore, the immediate instrument of sensations, of which impressions made on the others are only the occasional causes. This modification of sensibility, vvhich serves to establish the relations of the living being, with objects without, would be correctly denominated cerebral sensibility ; but that even in animals without brain, or distinct nervous system, it is very manifest. The sensibility, in virtue of which the polypus dilates his cavity, for the admission of his prey, and contracts itself to retain it, is in fact, quite distinct from that sensibility of nutrition, by which its substance is enabled to take to itself nutritious juices. The brain, as Cabanis has well expressed it, acts upon the impression transmitted by the nerves, as the stomach upon the aliments it receives by the oesophagus : it does, in its own way, digest them : set in motion by the impulse it receives, it begins to re-act; and that re-action is the per- ceptive sensation, or perception. From that moment, the impression becomes an idea, it enters as an element into thought; and becomes subject to the various combinations that are necessary to the phenomena of understanding.* CLIV. Our sensations are nothing but modifications of our being ; they are not qualities of the objects : no body has colour to the blind from birth: the rose has lost its most precious quality to him who has lost his smell: he knows it from the anemone, only by its colour, its figure, &c. We perceive nothing but within ourselves. It is only by habit, only by applying different senses to the examination of the same object, that we are at last able to separate it from our own existence ; to conceive of it as distinct from ourselves, and from the other bodies with which we are acquainted ; in a word, to refer to outward objects the sensations that take place within ourselves. Our ideas come to us, only by the senses; there are none innate as was imagined till the time of Locke, who has allotted to the refutation of this error a large part of his valuable work on the Human Understanding. The child that opens its eyes to the light, is * I ought to observe, that the lerms thought and understanding are, in my opinion, synonymous; both are alike, an abridged expression of the whole of the operations of the sensitive centre. 265 prepared for the acquisition of ideas, by this merely that it has senses; that is, that it is susceptible of impressions from the objects that surround it. It is inaccurate, however, to compare, as some philosophers have done, the brain of a child new born to a blank tablet, on which are to be figured all the future acts of his intelligence. If sensation came only from without, if the external'senses were the only organs that could send impressions to the cerebial centre, the understanding, at the moment of birth, had indeed been nothing, and the comparison of its organ to a sheet of white paper, or to a slab of Parian marble, on which not a character were drawn, had been perfectly correct. But we are compelled to acknowledge with Cabanis, two sources of ideas quite distinct from each other, the external senses, and the internal organs. These inward sensations, springing from functions that are carrying on with us, are the cause of those instinctive determinations by which the new-born child seizes the nipple of its mother, and sucks the milk by a very complicated process, which directs the young of animals the moment after birth, and sometimes in the very act of birth, while the limbs are yet engaged in the vagina, to seize upon the dug of their dam. Instinct, as the author just quoted, has very justly observed, springs from impressions received by the interior organs, whilst reasoning is the produce of external sensations; and the etymology of the word instinct, composed of two Greek words, signifying " to prick," &e. " within," agrees with the meaning we assign to it. These two parts of the understanding, reason and instinct, unite and blend together, to produce the intellectual system, and the various determi- nations of mental action. But the part that each bears in the generation of ideas, is very different in animals, whose grosser external senses allow instinct to predominate; and in man, in whom the perfection of these senses, and the art of signs, vvhich perpetrate the transient thought, aug- ment the power of reason, while they enfeeble instinct. It is easy to conceive, that the brain, assailed by a crowd of impressions from without, will regard less attentively, and therefore suffer to escape the greater part of those that result from internal excitation. Instinct is more vigorous in savage man, and its relative perfection is his compensation for the ad- vantages which superior reason brings to man in civilization. The moral and intellectual system of the individual, considered at different periods of life, owes more to internal sensation, the less it is advanced; for, instinct declines as reason is strengthened and enlarged. Thus, though all the phenomena of understanding have their source in physical sensibility, this sensibility being set in action by two sorts of impressions, the brain of an infant just born, has already the consciousness of those which spring from the internal motion, and it is from these impresions that it executes certain spontaneous movements, of which Locke and his followers could find no explanation : accordingly, the par- tizans of innate ideas, looked upon them as the strongest confirmation of their system; but these ideas, anterior to all action of outward objects on the senses, are simple, few, and extending to a very small number of wants : the child is but a few hours old, and already it expresses a multitude of sensations, that throng upon it from the instant of its birth, sensations, which have passed to the brain, combined themselves there, and entered into the action of the will, with a velocity which equals, if it does not sur- pass, that of light. It is only, after laying down between ihe sources of our knowledge, a very exact line of demarcation, after scrupulously distinguishing the v<>- 264 tional from the instinctive determinations, acknowledging that age, sex, temperament, health, disease, climate, and habit, which modify our physical organization, must, by a secondary effect, modify these last, that we can possibly understand the diversity of humours, of opinions, of characters, and of genius. He who has well appreciated the effect, on the judgment and reason, of the sensations that spring from the habitual state of the internal organs, sees easily the origin of those everlasting disputes on the distinction between the sensitive and the rational soul; why some philoso- phers have believed man solicited for ever by a good or an evil genius ; spirits which they have personified under the names of Oromazes, and Arimanes, betwixt whom they imagined eternal war; the contest of the soul with the senses, of the spirit with the flesh, of the concupiscent and irascible with the intellectual principle, that contradiction which St. Paul laboured under, when he said in his Epistle to the Romans, that his mem- bers were in open war with his reason. These phenomena which suggest the conception of a two-fold being (Homo duplex, Buffon,) are nothing but a necessary strife betwixt the determinations of instinct and the de- terminations of reason; between the often times imperious wants of the organic nature, and the judgment which keeps them under, or deliberates on the means of satisfying them, without offending received ideas of fitness, of duty, of religion, &c. CLV. A being, absolutely destitute of sensitive organs, would possess only the existence of vegetation : if one sense were added, he would not yet possess understanding, because, as Condillac has shown, the impres- sions produced on this only sense, would not admit of comparison ; it would end in an inward feeling, a perception of existence, and he would believe the things which affected him to be a part of his being. The fundamental truth, so completely made out by modern metaphysicians, is found distinctly stated in the writings of Aristotle ;* and there is room for surprise that that father of philosophy should have merely recognised it, without conforming to its doctrines; but, still more that it should have been for so many ages disregarded by his successors. So absolutely is sensation the source of all our knowledge, that even the measure of un- derstanding is according to the number and perfection of the organs of sense ; and that by successively depriving them of the intelligent being, we should lower, at each step, his intellectual nature; whilst the addition of a new sense to those we now possess, might lead us to a multitude of unknown sensations and ideas, would disclose to us in the beings we are concerned with, a vast variety of new relations, and would greatly enlarge the sphere of our intelligence. The impression, produced on any organ, by the action of an outward body, does not constitute sensation ; it is further requisite, that the impres- sion be transmitted to the brain, that it be there perceived, that is, felt by that organ ; the sensation then becomes perception, and this first modifica- tion supposes, as is apparent, a central organ, to which the impressions on the organs may be carried. The cerebral fibres are, more or less disturbed, by the sensations sent to them, at once, from all tbe organs of sense; and we should acquire but confused notions of the bodies from which they proceed, if one stronger perception did not silence, as it were, the rest, and fix the attention. In this concentration of the soul upon a single object, the brain is feebly stirred by many sensations that leave no trace ; * Nil est in intellectu, quod non priues fucrif in sensu:—Nisi intellectus ipse, as Leibniff has very justly added. Seo Appenmx -.Not'? F, E • 265 it is thus, that after the attentive perusal of a book, we have lost the sensations that were produced by the different colour of the paper and the letters. When a sensation is of short duration, our knowledge of it is so light, that soon there remains no remembrance of it. It is thus, that we do not perceive, every time we wink, that we pass from light to darkness, and from darkness to light. If we fix our attention on this sensation, it affects us more permanently. After occupying one's self, for a given time, with a num her of things, with but moderate attention to each; after reading, for in- stance, a novel, full of events, each of which in its turn has interested us, we finish it without being tired of it, and are surprised at the time it has taken up. It is because successive and light impressions have effaced one another, till we have forgotten all but some of the principal actions. Time ought then to appear to us to have passed rapidly ; for, as Locke has well said, in his Essay on the Human Understanding, " We conceive the suc- cession of times only by that of our thoughts." This faculty of occupying oneself long and exclusively with the same idea, of concentrating all the intellectual facilities on one object, of bestow- ing on the contemplation of it alone, a lively and well supported attention, is found in greater or less strength in different minds ; and some philosophers appear to me to have explained, very plausibly, the different capacity of dif- ferent minds, the various degrees of instruction of which we are capable, by the degree of attention we are able to give to the objects of our studies. Who, niore than the man of genius, pauses on the examination of a single idea, considers it with more profound reflection, under more aspects and relations, bestows on it, in short, more entire attention ? Attention is to be considered as an act of the will, which keeps the organ to one sensation, or prepares if for that sensation, so as to receive it more deeply. To look, is to see with attention ; to listen, is to hear attentively: the smell, the taste, in the same way, are fixed upon an odour, or a flavour, 60 as to receive from them the fullest impression. In all these cases, the sensation may be involuntary, but the attention by which it is heightened, is an act of the will. This distinction has already been well laid down with regard to the feeling, which is only the touch exerted under the di- rection of the will. According to the strength or faintness ofthe impression that a sensation^ or an idea (which is but a sensation operated upon by the cerebral organ,) has produced on the fibres of that organ, will be the liveliness and per- manence of the recollection. Thus, we may have reminiscence of it, or recall faintly that we have been so affected ; or memory, which is a repre- sentation of the object, with some of its characteristic attributes, as colour, bulk, &c. The pains that appear to be felt in limbs which we have lost, have not their place in the part which is left; the brain is not deceived, when it refers to the foot, the sufferings of which the cause is in the stump, after the amputation of the leg or thigh. I have at this moment before me, the case of a woman and of a young man, whose leg and thigh I took off for scrophulous caries, of many years standing, and incurable by any other n'eans. The wound, from the operation, is completely cicatrised. The stump* has not more sensibility than any other part covered by integuments, lince it may be handled without pain. And yet, both at intervals, and especially when the atmosphere is highly electrified, complain of pains in 2£1 Iuiq and difficult, that, as Condillac observed, it is not surprising, that hav- ing begun with a method so inconvenient, they have not beon able to ad- vance any farther. " Deny, (says this writer) to a superior mind, the use of letters, how much of knowledge you put out of his reach, which an ordinary capacity will attain to without difficulty. Go on, and take from him the use of speech, the lot of the dumb will show you, how narrow are the limits within which you confine him. Finally, take from him the use of all sorts of signs, let him be unable to find the least sign for the most ordinary thought, and you have an idiot."* We are made acquainted by travellers with certain tribes, so backward in the art of expressing their ideas by signs, that they seem to serve as a link between civilized nations and certain species of animals, whose in- stinct has been perfected by education. One might even assert, that there is less distance, in respect to intelligence, from a man in that extreme abasement, to the higher animals, than there is to a man of superior genius, such as Bacon, Newton, or Voltaire. In another part of the same work, after having demonstrated, that Ian* guages are real analytic methods, that the sciences may be reduced to well constructed languages, he shows how powerful is their influence in the cultivation of the mind. But he shall speak himself with that clearness of expression, which is the characteristic and the charm of his writings. " Languages are like the cyphers of the geometricians ; they present new views to the mind, and expand it as they are brought nearer to perfection. The discoveries of Newton had been prepared for him, by the signs that had been already contrived, and the methods of calculations that had been in- vented. If he had arisen sooner, he might have been a great man to his own age; but he would not have been the admiration of ours. It is the same in other departments." The most scanty languages have been formed in the most barren coun- tries. The savage who strays along the desert shores of New Zealand, needs but few signs to distinguish the small number of objects that habitu- ally impress his senses : the sky, the earth, the sea, fire, shells, the fish that form his chief food, the quadrupeds, and the vegetable, which are but few in number, under this severe climate, are all that he has to name and to know: accordingly his vocabulary is very small; it has been given to us by travellers in the compass of a few pages. A copious language, one capable of expressing a great variety of objects, of sensations, and of ideas, supposes high civilization in the people among whom it is spoken. You hear complaints of the perpetual recurrence of the same expressions, the same thoughts, the same images, in the poetry of Ossian: but living amidst the barren rocks of Scotland, the bards could not speak of things, of which nothing, on the soil they inhabited, could supply them with the idea. The monotony of their languages was involved in that of their im- pressions, always produced by rocks, mists, winds, the billows of the ireful ocean, the gloomy heath, and the 6ilent pine, &c. The repetition of the same expressions, in the Scriptures, shows that civilization had not made the same progress among the Hebrews, as among the Greeks and Romans. The connexion there is between the genius of a language and the charactei of the people that speak it; the influence of climate, of government, and of manners on language, the reason why the great writers, in every depart- ment, appear together, at the very time in which a language reaches its " Essai sur I'Origjne des Connoissances Humaines, sec. 4, •168 perfection and maturity,&c'. these are problems thai suggest themselves, and would well merit our endeavours to obtain solution, did not the investiga- tion manifestly lead beyond the limits of our inquiry. Though Condillac has said, repeatedly, in his works, that all the opera- tions of the soul, are merely sensation, variously transformed, that all its faculties are included in the single one of sense; his analysis of thought leaves still much doubt and uncertainty on the real character and relative importance of each of her faculties. The merit of dispersing the mist which covered this part of metaphysics remained for M. de Tracy. His Elements of Ideology,* leave nothing to be wished for on this subject. I shall extract some of its main results, referring the reader for the rest to the work. To think is only to feel; and to feel is, for us, the same as to exist; for, it is by sensation we know of our existence. Ideas, or perceptions, are either sensations, properly so called, or recollections, or relations which we perceive, or, lastly, the desire that is occasioned in us by these relations. The faculty of thought, therefore, fails into the natural subdivision of sensibility, properly termed memory, judgment and will. To feel, properly speaking, is to be conscious of an impression ; to remember, is to be sensi- ble of the remembrance of a past impression; to judge is to feel relations among our perceptions : lastly, to will is to desire something. Of these four elements, sensations, recollections^ judgments, and desires, are formed all compound ideas. Attention is but an act of the will: comparison cannot be separated from judgment, since we cannot compare two objects without judging them : reasoning is only a repetition ofthe act of judging: to reflect, to imagine, is to compose ideas, analyzable into sensations, re- collections, judgments, and desires. This sort of imagination which is only certain and faithful memory, ought not to be distinguished from it. Finally, want, uneasiness, inquietude, desire, passions, &c. are either sensations or desires. There is room, therefore, to reproach Condillac with having divided the human mind into understanding and will only : because the first term includes actions too unlike, such as sensation, me- mory, judgment; and with having run into the opposite extreme, in the too great multiplication of secondary divisions. CLVII. Disorders of thought. Philosophers would undoubtedly attain to a much profounder knowledge of the intellectual faculties of man, if they joined to the study of their regular and tranquil action, that of the many disordered actions to which they are liable. It is not enough, if we would understand Ihem aright, to watch their operation when the soul is undisturbed and at ease: we must follow it in its perturbations and wan- derings : we must see its powers, now separating themselves from those with which they ought to act; now combining with them under false per- ceptions : sometimes, altogether drooping, and sometimes starting into an extreme violence of action, of which we can neither mistake the impor- tance nor the nature ; and, as the greater part of our ideas are derived from the analogies we are able to discern among the objects that supply them, amidst these troubles of human passion and human reason, we learn to conceive more profoundly of their nature, than if we had been satisfied with observing them in the calm of their natural condition. The observation of mania is yet tOo imperfect in the number; variety, and precision of its facts, to fix the classification of the species of mental * Elemens d'ldeologie, par M. Destutt Tracy, senateur, Membre de l'lnstitut 269 alienation, according to the intellectual faculty that is disordered in eacL Professor Pinel has, nevertheless, ventured to ground his distinctions oi the species of mania on the labours of modern psychologists, and shown that all might be referred to five kinds, which he marks by the names of melancholy, of mania without delirium, mania with delirium, dementia, and idiotcy.* In the first four kinds, there is perversion ofthe mental faculties, which are in lagguid or excessive action. We are not to look for the cause of these derangements in vice of original conformation ; for, melancholy. mania with or%ithout delirium, and madness, scarcely ever appear before puberty. It is agreed, among observers, that almost all maniacs have become so, between twenty and forty years old : that very few have lost their reason either before or after this stormy period of life, wherein men, yielding, by turns, to the torments of love and of ambition, of fear and of hope, to the sweet illusions of happiness, and the realities of suffering, consumed with passions for ever reviving, often repressed, and rarely satis- fied, feel their intellectual powers impaired, annihilated, or abused by that tempest of the moral nature, which has well been compared to the storms which, in their violence, lay desolate the flourishing earth. We are compelled to grant, that our acquaintance with the structure of the brain and of the nerves is too imperfect, that dissections of the bodies of maniacs have been too few, and those often by physicians! too little familiar with the minute structure of the sensitive organ, to warrant us in asserting or denying, that derangement of intellect depends constantly on organic injury ; though it is highly probable, many facts, at least, collected by observers, who, like Morgagni, deserve the utmost confidence, authorize the belief, that the consistence of the brain is increased in some maniacs who are distinguished by the most obstinate and unvarying adherence to their ruling ideas ; that it is, on the other hand, soft, watery, and in a kind of incipient dissolution, in some others, whose incoherent ideas after their aptitude for association, and for transformation into judgments is gone, succeed one another rapidly, and seem to pass away without a trace, &c. If, in the multitude of maniacs, the organ of the understanding suffer only imperceptible injury, it is very remarkably changed in idiots. The almost entire obliteration of the intellectual faculties, which constitutes idiotcy, when it is not brought on by some strong and sudden shock, some unexpected and overwhelming emotion breaking down at once all the springs of thought, when it is an original defect, is always connected with mal-conformation of the skull, with the constraint of the organs it encloses. These defects of organization lie, as M. Pinel observes, in the excessive smallness of the head, to the whole stature, or to the want of proportion among the different parts of the skull. Thus in the idiot, whose head is given in the work on mania (pi. 2. fig. 6.) it is only the tenth of the whole height, whilst it should be something more than a seventh, if we take the Apollo of Belvidere as the type of the ideal perfection of the human figure. An idiot, whom I occasionally see, has the occipital extremity of the head so much contracted, that the large extremity of the oval formed by the upper face, instead of being placed at the back, as in other men, is, on the contrary, turned forwards and answers to the forehead, which itself slopes towards the sinciput. The vertical diameter ofthe skull is inconsiderable. The head, thus shortened from above downwards, is much flattened on the * For more ample explanation I must refer to the work. Traite medico-philosophiqut ■uir VAlienation menlaleou la Manie, par P. Pinel Paris, 1800. f This censure is especially applicable to the researches of Dr Grading. 270 sides. The bauds and ieet are $ery small, aud often void; the gjEUJitius, on the contrary, are extremeby large. In two other children, equally idiots, and now m the hospital of St. Lours, the skull,, very large behind, ends in a very contracted extremity, and the forehead is very short, and not more than two inches and a half wide, mea- suring from the semi-circular process, which terminates, at the upper part, the temporal fossa, to the commencement of the same process on the other side. The excessive growth of the genitals is not le6» conspicuous ; they are, in these two children, one ten, the other twelve years^old, as well as in the first of whom I spoke, who is fourteen, of larger size than is corn* monly seen after the appearance of puberty. There is nothing to indicate that this season is attained by these three idiots. The same excess of growth is found, more conspicuously among tbe cretins of tho Valais, idiots who (in consequence of a weak and degraded organization) are prone to lasciviousness and the most frequent onanism. This sort of opposition in the relative energy of the intellectual organ, and of the system of reproduction, in the developement of the brain, and that of the parts of generation, is a phenomenon which must strongly interest the curiosity and engage the attention of physiologists. Who is there unacquainted with that enervation of the understanding, that in- tellectual and physical debility, which indulgence in the pleasures of love brings on, if we exceed ever so little the bounds of scrupulous moderation ? Castration modifies the moral character of men and animals, at least a's. powerfully as their physical organization, as M. Cabanis has shewn, in treating of the influence of the «exes on the origin and growth of the moral and intellectual powers. CLVIII. Our physical, therefore, holds our moral nature under a 6trict and necessary dependence ; our vices and our virtues, sometimes produced and often modified by social education, are frequently, too, results of orga- nization. To the conclusivo proofs which the philosopher I have jnst named, who is an honour to his profession, brings forward of the influence of the physical on the moral bumaa being, I will only add a single obser- vation. It is not, certainly, the first that has been made of the kind ; but none such, I believe, has yet been published. The reader recollects, I have no doubt, the old woman of whom I have spoken in treating of the motions of tho brain, which an enormous caries of the bones of the skull gave an opportunity of observing in her. I wiped off the sanious matter which covered the dura mater, and I, at the same time, questioned the patient on her situation : as she felt no pain from the compression of the cerebral mass, I pressed down lightly the pledget of lint, and on a sudden the patient, who was answering my questions rationally, stopped in the midst of a sentence, but she went on breathing, and her pulse continued to beat: I withdrew the pledget; she said nothing: I asked her if she re* membered my last question: she said not. Seeing that the experiment was without pain or danger, I repeated it three times, and thrice I suspend- ed all feeling and all intellect. A man trepanned for a fracture of the skull, with effusion of blood and pas on the dura mater, perceived his intellectual faculties going, the con- sciousness of existence growing benumbed and threatening to cease, in the interval of each dressing, in proportion as the fluid collected. There are surgical observations on wounds of the head containing seve- ral facts that may be connected with the preceding observations. There is no one who has had syncope of more or k$s continuance, but knows {ifat 271 the state is without pain or uneasiness, and leaves no consciousness of what passed while it lasted. It is tbe same after an apoplexy, a fit of epilep- sy, &c. The history of temperament supplies us with too many examples ofthe strict connexion which there is between the physical organization and the intellectual and moral faculties, to leave any necessity for dwelling longer on this truth, which no one questions, but which no philosopher has yet followed into all its consequences. CLIX. An English writer, in a work on the history of mental aliena- tion* has traced, better than had before been done, the physiological history of the passions, which he looks upon as mere results of organization, ranking them among the phenomena of animal economy, and with abstrac- tion of any moral notion that might attach to them. All passion is directed to the preservation of the individual or the re- production of tho species. They may he distinguished, therefore, like tbe functions into two classes.f In the second, we should find parental love, and all the affections that protect our kind through the helplessness of itg °¥utnCrichton, with the greater part of metaphysicians and physiologists, appears to me not to have settled correctly the meaning that should belong to the word passion. When he gives this name to hunger, an inward pain- ful sensation; the source of many determinations of many kinds, a powerful mover of savage and civilized man,—to the anxiety which attends the breathing an air deficient in oxygen,—to the impressions of excessive heat and cold —to the troublesome sensations produced by tho accumulation oi mine and fecal matter,—to the feeling of weariness and fatigue that is loft by violent exertions,—he confounds sensation with the passions or desires which may spring from it. ...,,., • c It is to avoid extreme wants, of which a vigilant foresight perceives afar off the possibility—it is to satisfy all the factitious wants which society and civilization have ereated, that men condemn themselves to those agitations, of which honour, reputation, wealth, and power, are the uncertain aim. Our passions have not yet been analyzed with the same care as our ideas : no one has yet duly stated the differences there are, in respect to their number and energy, betwixt savage man, and roan in the midst of civilized and enlightened society. As the habitual state of the stomach, of tbe lungs, of the liver and in- ternal organs, is connected with certain sets of ideas;—as every vivid sen- sation of joy or distress, of pleasure or pain, brings on a feeling of anxiety io the pra3cordia,—the ancients placed in tbe viscera the seat of the pas- sions of the soul: they placed courage in the heart, anger in the liver, joy in the spleen, &c. Bacon and Van Helmont seated them in the stomach ; Lecat in the nervous plexuses; other physiologists in the ganglions ot the great sympathetic, &c. But have they not confounded the effect with the cause ? the appetite with the passion to which it disposes ? The appetites, out of which the passions spring, reside in the organs, they suppose only instinctive determinations, whilst passion carries with it the idea of intel- lectual exertion. Thus, the accumulation of semen in the yesieulae which serve for its reservoirs, excites the venereal appetite, quite distinct from the * An Inquiry into the Nature and Origin omental Derangement—London, 1793, 2 vols 8vo. i 9tee APPENDIX, Note E E am I m. passion of love, though often its determining cause. Animals have scarcely more than appetite, which differs as much from passion as instinct from intelligence. However, the brain is not to be considered as the primitive seat ofthe passions,* as is done by the greater number of philosophers. Of all the feelings of man, the most lasting, the most sacred, the most passion- ate, the least susceptible of injury from all the prejudices of the social state, maternal love, is surely not the result of any intellectual combination, of any cerebral action : it is in the bowels (entrailles) its source lies; thence it springs, and all the efforts of imagination cannot attain it for those who have not been blessed with a mother's name. All passion springs from desire, and supposes a certain degree of exalt- ation of the intellectual faculties. The shades of the passions are infinite : they might be all arranged by a systematic scale; of which indifference would be the lowest gradation, and maniacal rage the highest. A. man, without passion, is as impossible to imagine, as a man without desires; yet we distinguish, as passionate, those whose will rises powerfully towards one object earnestly longed for. In the delirium of the passions, we are for ever making, unconsciously, false judgments, of which the error is exaggeration. A man recovering from a seizure of fear, laughs at the object of his terror. Look at the lover whose passion is extinct! freed, at last, from the spell that enthralled him, all the perfections with which his love had invested its object are vanished : the illusion has passed away ; and he can almost believe that it is she who is no longer the same, while himself alone is changed : like those maniacs who, on their return to reason, wonder at the excesses of their delirium, and listen, incredulously, to the relation of their own actions. The ambitious man feeds on imaginations of wealth and power. He who hates, exaggerates the defects of the object of his hatred, and sees crimes in his slightest faults. The affections of the soul, or the passions, whether they come by the senses, or some disposition of the vital organs favour their birth and growth, may be ranged in two classes, according to their effects on their economy. Some heighten organic activity ; such are joy, courage, hope, and love ; whilst others slacken the motions of life, as fear, grief, and ha- tred. And others there are, that produce the two effects alternately, or together. So ambition, anger, despair, pity, assuming, like the other pas- sions, an infinite variety of shades, according to the intensity of their causes, individual constitution, age, sex, &c. at times increase, at times abate, depress or exalt the vital action, and exalt or depress the power of the organs. The instances which establish the powerful influence of the passions on the animal economy are too frequent to need reciting. Writers, in every department, furnish such as show that excess of pleasure, like excess of pain, joy too lively or too sudden, as grief too deep and too unexpected, may bring on the most fatal accidents and even death. Without collecting, in this place, all the observations of the sort with which books swarm, I shall content myself with referring to those who have brought together the greatest number of facts under one point of view ; as Haller, in his Phy- siology ; Tissot, in his Treatise on Diseases of the Nerves ;' Lecamus, in * If we analyzed the passions carefully, it would be right to distinguish those which are common to all men, which appertain to our physical wants and to our nature, from certain caprices of tbe mind which have been honoured with the name of passiom, as avarice, ambition, &c. which should be referred to kinds of mental derangement., at>4 Massed as species of monomania. 2?;J his work on diseases of the Mind ; Bonnefoy, in a paper on the Passions of the Soul; inserted in the fifth volume of the Collection of Prizes ad- judged by the Academy of Surgery. } The effects of the passions are not, for their uniformity, the less inex- plicable. How, and why does anger give rise to madness, to suppression. of urine, to sudden death ? How does fear determine paralysis, convulsions, epilepsy, &c? Why does excessive joy, a sense of pleasure carried to extremity, produce effects as fatal as sad and afflicting impressions ? In what way can violence of laughter lead to death ? Excess of laughter killed the painter Zeuxis and the philosopher Chrysippus, according to the relation of Pliny. The conversion of the reformed of the Cevennes under Louis XIV. was effected by binding them on a bench, and tickling the soles of their feet, till, overpowered by this torture, they abjured their creed : many died in the convulsions and immoderate laughter which the Tickling excited.* A hundred volumes would be insufficient to detail all the effects of the passions on physical man ; how many would it take to tell their history, in moral man, from their dark origin, through all their stages of growth, in the infinite variety of their characters, and in all their evanescent shades! The inquiries of Physiology are directed to the functions that are carried: on in physical man, to the functions of life : the study of the nobler part? of ourselves, of those wonderful faculties which place our kind above all that have motion or life ; in a word, the knowledge of moral and intellectual man belongs to the science known by the name of metaphysics, or psycho- logy? °f analysis of the understanding, but better described by that applied to it by the writers of our days, ideology. On this science, you may con- sult, with advantage, the philosophical works of Plato and Aristotle, among the ancients ; of Bacon, Hobbes, Locke, Condillac, Bonnet, Smith, Eeid, Dugald, Stewart, Brown, Cabanis, and Tracy, among the moderns. CLX. Of sleep and waking. The causes of excitation to which our organs are exposed during waking, tend to increase progressively their action ; the pulsations of the heart, for instance, are much more frequent in the evening than in the morning, and this motion, gradually accelerated, would soon be carried to a degree of activity incompatible with the con- tinuance of life, did not sleep daily temper this energy, and bring it down to its due measure. Fever is occasioned by long continued want of sleep, and in all acute diseases, the exacerbation comes on towards evening, the- night's sleep abates again the high excitation of power : but this state of tho animal economy, so salutary and so desirable in all sthenic affections, ia more injurious than useful in diseases, consisting chiefly in extreme de> bility. Adynamy shows itself, almost always, in the morning, in putrid fevers ; and petechiae, a symptom of extreme weakness, break out during sleep. This state is, likewise, favourable to the coming on and to tho progress of gangrene, and this is a pathological fact well ascertained. In all the cases I have mentioned, sleep does not improve the condition of the patients ; a thing easy to conceive, since it only adds to accidental debility* the essential characteristic ofthe disease, weakness-, which is also its princi- pal characteristic. * This instance, however, does not illustraie the influence of the passions on the vital functions. It shows merely the effects of irritation of the extremities of nerves upon the functions of other nerves either of the same, or of a different order, which effects are either produced by a direct medium of communication with the nerves first a8e.ctgd,'or then by means of the nervous centres. 2*4 Sleep, that momentary interruption in the coinmunicatiou of the sensii-j with outward objects, may be defined the repose of the organs of sense, and of voluntary motion. During sleep, the inward or assimilating func- tions are going on : digestion, absorption, circulation, respiration, secretion, nutrition, are carried on; some as absorption and nutrition* with more energy than during waking, whilst others are evidently slackened. During sleep, the pulse is slower and weaker, inspiration is less frequent, insensi- ble perspiration, urine, and all other humours derived from the blood, are separated in smaller quantity. Absorption is, on the contrary, very active: hence the danger of falling asleep in the midst of a noxious air. It is known that the marshy effluvia, which make the Compagna di Roma so unhealthy, bring on, almost inevitably, intermittent fevers, when the night is passed there, whilst travellers, who go through without stopping, are not affected by it.f The human body is a tolerable representation of the centripetal and centrifugal powers of ancient physics. The motion of many of the systems which enter into its structure is directed from the centre to the circum- ference : it is a real exhalation that carries out the result of the perpetual destruction of the organs ; such is the action of the heart, of the arteries, and of all the secretory glands. Other actions, on the contrary, take their direction from the circumference to the centre; and it is by their means that we are incessantly deriving from the food we take into the digestive passages, from the air which penetrates the interior of the lungs, and covers the surface of the body, the elements of its growth, and repair. These two motions, in opposite directions, continually balance each other^ prevailing by turns, according to the age, the sex, the state of sleep or waking. During sleep, the motions tend from the periphery to the centre, (Hipp.) and if the organs that connect us with outward objects are in re- * Nutrition is evidently more active during 9leep, in early life, especially in childhood; and, in many constitutions and habits of body, it appears equally active, during this state, through the middle stages of life: but as soon as the period of decay approaches, absorp- tion appears to predominate, while, on the contrary, nutrition gradually languishes more and more, during sleep, as age advances. In the middle periods of existence it is difficult to determine whether absorption or nutrition is augmented during this state: the difference fannot always be correctly appreciated; but we generally find that when the one is increased tho other is generally diminished, both functions being seldom augmented op impaired at the same timo. t This is quite as much the result of the low state of the nervous and vital energies ofthe system during sleep. The vital powers at that time are not under the impression of the excitements communicated through the medium of the nerves of sensation and motion; the operations, indeed, of this part of the nervous system are for a time sus- pended, and consequently the vital functions lose part of their energy, and are open to the influence of such causes of disease as generally invade them duiing states of debility and exhaustion, or when they are not otherwise acted on either by external or internal stimuli. It may be justly asserted that the operations ofthe system languish in a degree pro- portionate to that in vvhich they are deprived of their natural excitements, whetnerthese excitements are food, air, exercise, amusement, &c.—whether they are corporeal or mental— or whether they are external or internal with respect to their modes of existence, and to their manner of operation on the body. When, therefore, the system is deprived of a part of these excitements,—of the influences of the mental operations, and of the excitements of sensation and voluntary motion, as it is during sleep, its operations are necessarily more languid and weak, and consequently it is more ready impressed by many ofthe causes of disease, especially by those which are usually productive Of fever, than daring the waking state. The condition of the night air, in respect to temperature, and the concentration ofthe moisture and of the terrestrial exhalations in the lower regions of the atmosphere, especially in particular 04 cartilages of the joints, and mix with the synovia to increase its quantity 3 and to lessen the friction of the articulating surfaces ? If this transuda- tion may take place after death, why might it not take place, when all the parts are in a state of vital warmth and expansion ?* CLXXVIII. Of the articulations, the articulating cartilages and liga- ments, and the sinovial fluid. The articulations of the different parts of the skeleton are not all intended to allow of motion, several, as the serrated and squamous sutures, and the gomphosys, are entirely without motion, and are, on that account, termed synarthrosis. All the other articulations, whether the bones are in immediate contact (diarthrosis of contiguity,) whether they are united by a substance interposed between them (diarthro- sis of continuity or amphiarthrosis,) are endowed with a certain degree of mobility. I shall speak merely of the moveable articulations; whether they allow of extensive motions and in every direction (diarthrosis orbi- cularis,) or whether the bones move only in two opposite directions (alternate diarthrosis or ginglymus,) by forming an angle (angular ginglymus,) or by executing, on each other, motions of rotation (lateral ginglymus.) In all the articulations, the osseous surfaces are covered by laminae of a substance less hard than that of the bone. These are the articulating eartilages which answer the two purposes of giving to the ends of the bones, the degree of polish necessary to their slipping freely, and to facili- tate motion, by the considerable degree of elasticity which they possess. Morgagni has shown, that of all animal substances, cartilages possess most elasticity; their structure is very different from that of the bones, even when these are yet cartilaginous ; for, these articulating cartilages do not become ossified, even in persons greatly advanced in years.t They are * The marrow of the bonies is contained in the medullary membrane. This latter su b- stance may be easily detached from the bone. It resembles, in some respects, a cobweb, being pierced by a number of holes. It is formed of cellular tissue, and of vessels. The former is very delicate and rare ; and evidently performs the function of furnishing a fiurface for the ramification of the vessels. Some of these vessels are ramified ex- ternally, proceeding directly from the medullary membrane to the osseous textnre surrounding it, and thus performing the office of an internal periosteum to the bone ;— others are distributed internally, and in the direction ofjfhe axis of the bone, to the medullary membrane itself, and to the spongy extremities of the bones. The principal artery ofthe medullary canal is surrounded by absorbent vessels at its entrance into this canal. A plexus of nerves may be also observed to surround the artery, in the same situation, and to dip into the bone at the place nearest to the arterial trunk. The adipose vesicles, which contain the marrow and occupy the interior of the medol- lary membrane, are the same in kind as those ofthe cellular texture, although less distinct. Authors have long since considered that those adipose vesicles are united engrappe, and may believe that they communicate with each other. M. Beclard considers the marrow to consist of seven parts out of eight of an oleagin- ous matter, in fat subjects, which inference accords with the opinion oiGrutzmacuer ; while this substance, in a phthisical patient, was found to consist of only a fourth part of fatty matter, the rest being a serous, or albuminous-like fluid. The marrow does not exist in the foetus, and even the medullary membrane itself cannot be recognised previous to ossification. As this process advances, the medullary canal begins to be formed ; and at first the nutritious artery nearly fills it. At a later period this artery is seen ramified on the parietes of this cavity, and in the situation of the medullary membrane. The marrow becomes abundant- as age advances, owing to the enlargement ofthe medullary cavity. •* The sensibility of the marrow, which was contended for by Durvernev, but since denied, is considered by M. Beclard really to exist, and to be satisfactorily shown, when some time is allowed to elapse between the pain of the operation necessary to expos© the marrow, and the experiment to which it is to be subjected. See Appendix, Note H H, for additional remarks on this subject. t Sometimes, however, these cartilages are destroyed, the denuded bone then becomes polished by friction, and as hard as ivory. JOj formed of very short fibres disposed according to the length of the bone, strongly compressed against each other, and united by other transverse fibres. This vertical direction of the greatest part of cartilaginous fibres, demonstrated by Lassone, is very favourable to their elastic re-action. The capsular ligament is reflected over them, becomes very thin, and is lost in their perichondrium, according to Bonn, Nesbith, and other anatomists. Besides the cartilages which surround the extremities of bones, there are found, in certain articulations, fibro-cartilaginous lamina? lying between the articulating surfaces. These connecting ligaments may be observed in the articulation of the lower jaw to the temporal bones, of the femur with the tibia, and of the sternum with the clavicle ; and all such articulations perform a great number of motions, as is the case with the jaw, or suffer considerable pressure, as the joints of the knee and sternum. The latter, which has a very slight degree of motion, being the point in which termi- nate all the efforts ofthe upper extremity, required this apparatus to lessen the effect on the trunk, the motion that is given being, in part, lost, in the action of the articulating cartilage.* I shall not repeat what has been already said of the secretion of the fluid that lubricates the articulating surfaces, that facilitates their motion, and keeps them in contact. Its quantity is in direct ratio to the extent of these surfaces, and of the membranous capsule in which they are contained; it is, likewise, proportioned to the frequency of motion which each articulation allows. Synovia is the name that is given to the fluid prepared by the glandulo- cellular bodies in the vicinity of the articulations, and secreted by the membranous capsules which surround them, and are reflected over the articulating extremities of the bones whose cartilages they cover; so that, as was shown by Bonn, about the middle of the last century, these extre- mities cannot be said to be contained within the cavity of the capsule, which is closed, in every direction, any more than the abdominal viscera within that of the peritoneum. The synovia is heavier than common water, quite colourless, and more viscid than any other animal fluid. It contains a considerable quantity of albumine, which, according to Margueron, who first gave a tolerably accurate analysis of synovia, it is found in a particular state, and much disposed to concrete into filaments, on the addition of acids. Besides, it contains muriate and carbonate and phosphate of lime, the whole dissolved in water, which forms about three-fourths of its weight.t CLXXIX. Theory of Anchylosis. Motion may be considered as the proper stimulus of the synovial secretion ; and a moveable joint, as is justly observed by Grimaud, is as a centre of fluxion towards vvhich the fluids rush, in every direction, in consequence of the irritation which friction determines. If the joint remains long without motion, the synovia is secreted in smaller quantity, and this lessens gradually: it may even happen that the articulating surfaces, remaining long and absolutely motion- less, lose their moisture, and from the want of the fluid which should lubri- * The most certain proof of the organic nature of the cartilages is the serous exudation which appears in the course of a few seconds after a clean division of them by the knife. Cellular texture forms the mould or basis in which the cartilaginous substance is deposited. The vessels of this texture carry only the colourless part ofthe blood into it, during its ordinarv state of health ; yet it is remarkable that other colouring substances, as bile and madder, give this substance their respective colours. t See the Chapter on the Chemical Constitution of the Secretions, Sic", at the exiu c': •^ Arrrrmx, 30 30(3 cate them, bring on irritation and adhesive inflammation in each other, either from increased action of the vessels of the perichondrium, or as is believed by Nesbith, Bonn, and others, from an inflammatory state of the fold, which is reflected from the capsule of the joint over the ligament. This is the manner in which the disease, termed anchylosis, comes on, a disease improperly ascribed to the congestion of the soft parts, and espe- cially of the ligaments surrounding the articulations. In fact, when in a fracture of the thigh or leg, about the middle of the length of one of these bones, and consequently, at the greatest possible distance from the kneo joint, the circumstances of the case require that the bandages should he kept on the limb, a considerable time, the joint loses its power of motion, recovers it with difficulty, and sometimes not at all. I have^at present befoie me, the case ofa man in whom a scorbutic affection has delayed, to such a degree, the union of the bone, after a simple fracture of the femur, about the middle of the bone, that it has been found necessary to continue, for seven months, the use of splints. In the course of so long a state of inaction, the soft parts have lost the habit of moving, and the knee is, almost completely, ancholysed. Whenever, on account of any complaint, one has been confined to bed, the first attempts to walk are painful, difficult, and attended by a marked crepitus in the knee, denoting clearly the want of synovia. On the other hand, if the joint is examined in a person who before death has been long without motion, the articulating surfaces will be found rough and dry, with evident marks of inflammation. Flajani mentions the case of a patient who died, after having been three months in bed, in an almost motionless state. Externally, the knees did not appear to have been injured, and yet he could not bend his knee joint. On opening the joint, it was found that the articulating surfaces had grown together; the posterior part of the patella adhered to the condyles of the femur, and it was necessary to use a scalpel to detach these parts from each other. I have frequently observed the same appearance in dissecting the knee joint of persons who died while labouring under white swelling, with or without ulceration. The anchylosis which invariably attends this affection, evidently arises from the absolute rest of the diseased joint. Anchylosis from want of motion, and consequently from want of synovia, is not always a partial affection limited to one or two joints; sometimes, it affects several at once, as in the case of the patient whose skeleton was presented by M. Larrey to the museum of the School of Medicine at Pans. One of the most remarkable cases of universal anchylosis of the joints, is that lately communicated to the National Institute by M. Percy: the patient was an old cavalry officer, who was subject to fits of the gout, and whose articulations, even that of the lower jaw, became stiff and completely lost all power of motion, so that, towards the latter end of his wretched exist- ence, he could not be moved without feeling severe pain in his ancholysed joints. From this explanation may be conceived the advantage of moving the lower extremity, when, after a fracture of the leg, the ends of the bone have become sufficiently united to prevent their being displaced. These motions, which are of indispensable necessity in all fractures of the femur, of the tibia, and especially of the patella, are much better calculated to prevent anchylosis, than the various resolvent remedies which are com- monly employed, as plasters of soap, vigo, cicuta, diabotanura, diachylon, pumping, bathing, and fumigations, which, however, should be used in 307 rcmibination with a moderate exercise of the limb, in order to obtain the most complete success. The gout affects those joints which are most subject to motion, and on which there is the greatest pressure. The first attacks, as Sydenham ob- serves, come on in the joint of the great toe with tho first metatarsal bone, an articulation which bears the weight of the whole body, and which is most called into action, in the various motions of progression. The muscles which pass over the joints give them much greater security than the lateral ligaments. In fact, if the muscles become palsied, the mere weight of the limb stretches the ligaments, which give way, become elongated, and allow the head of the bone to escape from its glenoid cavity. It is, in this manner, that a loss of motion, and atrophy of the deltoid mus- cle, are attended with a luxation of the humerus : tbe orbicular ligament of the articulation of this bone with the scapula, being incapable of retaining its head within the glenoid cavity. The spinal column, when dissected and deprived of all but its ligamentous attachments, gives way under a weight much smaller than that which it would have supported, before being strip- ped of the muscles vvhich are connected with it. CLXXX. Of standing. This is the name given to the action by which man holds himself upright on a solid plane. In this erect position of all our parts, the perpendicular line, passing through the centre of gravity* of the body, must fall on some point of the space measured by their soles of the feet. Standing is most firm when, on prolonging the line of the centre of gravity of the body, it falls on the base of sustentation (I call thus the space defined by the feet, whether close or apart;) but this line may tend to exceed it, without our necessarily falling, the muscular action soon restoring the equilibrium which is deranged by the altered direction of this line. But if the lower extremity of the line, by being prolonged, should fall without the limits of the base of sustentation, a fall is unavoidable on the side towards which this line inclines.t If the body is inclined backwards, so that there is a danger of a fall on the occiput, the extensor muscles of the leg contract powerfully, to prevent the thigh from bending, while other powers bring forward the upper parts, and give to the prolonged line ofthe centre of gravity a different direction; and if, in proportion as the extensors of the leg are brought into action, its inclination be increased to such a degree that nothing is capable of keeping up the body, which its own weight tends to bring to the ground, these muscles, by amotion proportioned to the quickness ofthe fall, will increase their efforts to prevent it, and may be able, in that violent contraction, to snap asunder the patella, as I have explained in a Memoir on the fractures of that bone. I think it useful to insist, more than has been done hitherto, on the me- chanism by which the human body is supported in the erect posture ; for, a knowledge of that mechanism facilitates the explanation of the motions of progression. To walk, or to run, the body must be upright; now, when * The centre of gravity, in the adult, is situated between the sacrum and pubis. t« Quotiescumquelineapropennonis corporis humanicadit extra unius pedis innixi plardam, cut extra quadrilaterum, comprehensum a duabus plant is pedum, impediri ruina, a quocumque musculorum conatu, non potest." Borelli. Prop. 140. The firmness of the attitude^ in standing, depends, therefore, in part, on the breadth ofthe feet and on their distance; hence, it is much more tottering when we stand on one foot, and we are, under such circumstances, obliged to be perpetually struggling, to prevent the centre of gravity from falling out of the narrow limits of the base of sus- tentation.—Author's Not?.. ;;o;; u is known by what power the centre of gravity of the body is maintained perpendicular on the plane which support- it, it will be easy to understand the different ways in vvhich it changes its place, in the course of locomotion. Let us first inquire into the question so long agitated, whether man is intended to support himself and to walk on his four limbs, in the early period of his existence after birth ? CLXXXI. An upright position would be to man a state of rest, if his head were in a perfect equilibrum on the vertebral column, and if the latter, forming the axis of the body and supporting equally, in every direc- tion, the weight ofthe abdominal and thoracic viscera, fell perpendicularly on the pelvis placed horizontally, and, in short, if the bones of the lower extremities formed columns set perpendicularly under their superincumbent weight; but not one of these circumstances is to be observed in the human body : the articulation of the head does not correspond to its centre of gravity; the weight of the thoracic and abdominal viscera, and of the parietes of the cavities in which they are contained, rests, almost entirely, on the anterior part of the vertebral column. The vertebral column is supported on an inclined base, and the bones of the inferior extremities, which are connected to each other by convex and slippery surfaces, are, more or less, inclined towards one another. It is therefore necessary, that an active power* watch incessantly, to prevent the fall which would be the natural consequences of their weight and direction. This power resides in the extensor muscles which keep the parts of our body in a state of extension, the more perfect, and which render our erect posture the firmer, as they are endowed with a more considerable power of antagonism, and as our parts are naturally less disposed to flexion; and, besides, as we have seen, (CLXVI.) these powers are not sufficient to balance those whose action is directly opposed to theirs. The relative weakness of the extensor muscles is not the only obstacle which renders impossible an erect posture, at an early period of life. Other causes, into which we are about to enter, concur in unfitting the new born child for the exercise of that faculty. The articulation of the head to the vertebral column being nearer the occiput than the chin, and not corresponding to its centre of gravity, its own weight is sufficient to make it fall on the upper part of the chest. It is the more disposed to fall forward, from its greater bulk, and, as in a new born child the head is much larger in proportion than the other parts of the body, and as its extensor muscles partake of the greater weakness of that set of muscles, it falls on the fore part of the chest, and its fall draws the body after it. The weight of the thoracic and abdominal viscera tends to produce the same effect. * An upright posture is not, in all animals, as it is in man, the consequence of an effort. This is proved by the following fact, observed by M. Dumeril. The sea fowl, and es- pecially the waders (Grallae, Lin.) as the herons and storks, forced to live in the midst of marshes and muddy waters, in which they find the fishes and reptiles, on which they feed, have long since afforded matter of surprise to Naturalists, by the length of time they can remain motionless in an erect posture. This singular power, so necessary to animals obliged to expect their prey, more from change than from industry, they owe to a peculiar conformation of the articulation between the leg and the thigh. The articu- lating surface of the thigh bone, as M. Dumeril had an opportunity of observing in a stork (Ardea ciconia, Linn.) contains, in its centre, a depression, into which there is re ceived a projection of the tibia. To enable the animal to bend its leg, that projection must be disengaged from the depression into which it is lodged, and this is resisted by several ligaments which keep the leg extended in standing, in flying, and other progres- sive motions,, without the assistance ofthe extensor muscle?. 309 Growth always proceeds from the upper to the lower parts, and this law, vvhieh operates uniformly, completely eludes every kind of mechanical explanation. It is otherwise, with regard to the effects which result from this unequal growth in respect to the erect posture. The inferior limbs, which serve as a base to the whole edifice being imperfectly evolved at the period of birth, the upper parts placed on these unsteady foundations, must necessarily fall and bring them down with them. The relative weight of the head, of tbe thoracic and abdominal viscera, tends, therefore, to bring forwards the line in the direction of vvhich all the parts of the body press on the plane which supports it, and this line should be exactly perpendicular to that plane to enable the body to be perfectly erect: the following fact proves this assertion: I have observed, that children, whose head is very large, whose belly projects^ and whose viscera are loaded with fat, have much difficulty in learning to stand; it is only about the end of their second year, that they dare trust to their own strength, and then they meet with frequent falls, and have a continual ten- dency to go on all fours. The vertebral column, in the child, does not describe, as in the adult, three curves alternately placed, in opposite directions. It is almost straight, and yet presents in the direction of its length a slight curvature, the con- cavity of which looks forwards. This incurvation, which depends solely on the flexion of the trunk while in the womb, is accordingly more marked, the nearer the child is to the time of its birth. It is well known that the curvatures, in opposite directions to the verte- bral column, add to the firmness of the erect posture, by increasing the extent of the space within which the centre of gravity may move, without being carried beyond its limits. With regard to that use, the vertebral column may be considered, as defined by two lines drawn from the anterior and posterior part of the first cervical vertebra, to the sacro lumbari symphysis. These two lines, very near to each other at their upper part, and, below, at a distance from each other, would be the chords of arcs and the tangents of the curves, formed by the vertebral column. So that this column may be considered as having a fictitious thickness greatly exceeding its real bulk. In the new born child the want of alternate curvatures not only contracts the boundaries within which the centre of gravity may be varied, but the direction of the only curvature which exists favours the flexion of the trunk, and consequently the inclination forward of the centre of gravity, and tbe tendency to fall in that direction. This inflexion of the vertebral column in the foetus and in the young child, resembles that observed in several quadrupeds.* The disadvantages resulting from the want of alternate curvatures in the vertebral column of the child, is further increased, by tbe total absence of spinous processes. It is well known, that the principal use of these pro- jections, is to place the power at a distance from the centre of motion of the vertebras, to increase the length of the lever by which it acts in straightening the trunk, and thereby to render its action more efficacious. * This curvature is very distinctly marked in swine. The back of these animals is remarkably prominent, and this form, necessary to enable the vertebral column to support the immense weight of their abdominal viscera, has a considerable influence on the me- chanism of their motions of progression. When frightened by any noise, they spring in bounds, and it is easy to perceive that, at each spring, the spine becomes arched and then straightens itself, and that their motion when rapid is effected by the alternate ten- sion and relaxation of their spinal arch.—Author's N»ic. 310 At the period of birth, the vertebra? have no spinous processes, they uitci- wards grow from the place at which the laminee of those bones are uuited, by means of a cartilaginous substance, which completes the posterior part of the vertebral canal. The muscles destined to keep the trunk erect, weakened by its constant flexion during gestation, lose, besides, a great deal of their power, from the unfavourable manner in which they are applied to the part on which they are to act. The flexion of the head does not depend merely on its very considerable Weight, but, likewise, on the want of spinous processes in the cervical ver- tebras, since the principal motions of the neck are performed, not so much by articulation with the atlas, as by union of the other cervical vertebra?. The pelvis of the child is but imperfectly evolved, and its upper outlet very oblique. The viscera, which are afterwards to be contained within its cavity, are, for the greater part, situated above it. This obliquity of the pelvis would require a perpetual straightening of the vertebral column to prevent the direction of the centre of gravity from obeying its natural tendency forward. On the other hand, the vertebral column, resting on a narrow pelvis, is less firmly fixed, and may more readily be drawn beyond the limits of the base of sustentation. Lastly, the limited extent of the pelvis, together with its obliquity, causes the ill supported abdominal viscera to fall on the anterior and interior part of the parietes of the abdomen, aud favours the fall of the body in the same direction. The patella, which answers the double purpose of giving firmness to the knee joint, in front of which it is placed, and of increasing the power of the muscles of the leg, by placing them at a distance from the centre of motion in that articulation, and by increasing the angle at which they are inserted into the tibia, as yet does not exist in new born children. The tendinous portion of the leg, where the patella is hereafter to be formed, is merely of a more condensed tissue, and of a cartilaginous hardness. The want of a fulcrum is attended with a continual disposition in the leg to bend upon the thigh, and the parallel direction of its extensor muscles, occasions a complete loss of their effective power. Then their antago- nizing muscles induce a flexion of that limb, which is the more considera- ble, as it is but imperfectly limited by the tendon which is situated at the fore part of the knee. The length of tho os calcis, the extent of its projection beyond the inferior extremity of the bones of the leg, tend to give firmness to the erect posture, by increasing the length of tho lever, by which the extensors of the foot act on the heel, and, as, in the new born child, this bone is shorter and less projecting, the power of these muscles, whose insertion is very near the centre of motion of the articulation of the foot, is greatly diminished. The feet, in man, are broader than those of any other animal, and to this breadth of the surface of the base on which he rests, he, in great measure, owes the advantage of being able to support, on one leg or on both, the weight of his body, in standing and in the different motions of progression; while the other mammalia cannot support themselves, at least only for a very limited time, without resting on three of their extremities. When I say that from the extent of the feet, the body of man does, of all animals, rest on the broadest surface, I do not take into account the space which those parts include between them when apart from each other. In fact, the space which is measured by the feet, is much greater in quadrupeds than in man. Nature has made up for the disadvantage arising out of the sma.lloess of their feet, by the distance at which they are placed : and if 311 that form disables them from standing on two feet, it gives firmness to their peculiar mode of standing. The feet of the ourang outang, which, in the general structure of his organs, bears so striking an analogy to the human species, resemble a coarsely formed hand, better fitted to climb the trees on which that animal seeks his food, than to the purposes to which man applies his hands. Thus the erect posture which he, at times, assumes, is neither the most convenient nor the most natural to him. And, according to a philosopher who speaks on the authority of several travellers, if a sudden danger obliges him to make his escape, or to leap, he drops on all fours, and discovers his real origin • he is reduced to his own condition, when he quits that unnatural attitude, and discovers in himself an animal, which, like many a man, has no better quality to recommend him than a specious disguise. The feet are the parts least developed in the new born child ; his body is insecure on that narrow basis ; the prolongation of the line of his centre of gravity, which so many other causes tend to carry beyond that base, will be the more inclined to fall beyond it, from its small extent. The greater number of the differences which have just been examined, depend on the mode of nutrition in the foetus. The umbilical arteries bring to the mother the blood which the aorta carries towards the lower parts, and only a few small branches are sent to the pelvis and to the lower extremities. Thus, the developement, which almost uniformly bears a proportion to the quanti- ty of blood sent into organs, is but imperfect in those parts at the time of birth, while the head of the trunk and upper extremities are enveloped much more considerably. # . The new born child, therefore, resembles quadrupeds in the physical arrangement of his organs. This analogy is the more marked, the nearer the foetus is to the period of its formation, and it might be laid down as a general proposition, that organized beings resemble one another more closely, the nearer to the period of incipient existence, they are examined. The differences which characterize them become apparent, in proportion to tbe progress of evolution, and they are more and more distinct, as the acts of life are repeated in the organs whieh it animates. The unequal distribution of power in the muscles, and the unfavourable disposition of the parts to which these powers are applied, render it impossi- ble for the infant to stand upright, that is, to keep the mean line of direction of bis body nearly perpendicular to the plane which supports it. But in proportion as he advances in age, the preponderance of the flexors over the extensors ceases to be in excess. The proportionate size of the head and ofthe thoracic abdominal viscera diminishes. The curvatures ofthe vertebral column begin to be distinguishable, the spinous processes of the vertebrae are evolved ; the breadth of the pelvis is increased, and its ob- liquity lessened; the patella becomes ossified, the os calcis jutsoutback- wards, the relative smallness ofthe feet ceases. By degrees the child learns to stand, resting on both or only on one of his feet; his eyes naturally directed towards heaven, a noble prerogative, which, if one might believe Ovid,* is possessed by man alone of all the animals. Man is of all animals the only one that can stand upright and walk m * Os homivi sublime dedit, ccelumquc tueri Jussitf et ereclos ad sidera tollere vultus. These verses may be much more justly applied to the fish, called by naturalists Urmioscn; put. Its eyes are tamed upwards, and constantly look towards the ueavens.-tftrfAor s Note. 312 that attitude, when his organs are sufficiently evolved. Let us now point out some of the principal causes to which that privilege is to be ascribed. CLXXXII. Though the articulation of the head to the cervical column does not correspond either to its centre of magnitude, or to its centre of gravity, and though it is nearer to the occiput than to the chin, its distance from the latter is much smaller in man, than in the monkey and other animals, whose foramen magnum is, according to Daubenton, placed nearest to the posterior extremity of the head, when they resemble man the least. The head, therefore, is very nearly in equilibrio on the column which supports it; at least to keep it in that position, a very slight power is re- quired, while the head of a quadruped, which has a constant tendency towards the ground, requires to be supported by a part capable of a great and continued resistance. This purpose is answered by the posterior cervical ligament, so remarkable in those animals, attached to the spinous processes of the vertebrae and to the protuberance of the occipital bone, which projects much more in them than in the human species, in whom instead of posterior cervical ligament, there is found a mere line of cellular substance, dividing the nape of the neck into two equal parts. The alternate curvatures ofthe vertebral column, the breadth ofthe pel- vis and of the feet, the great power ofthe extensors ofthe foot and thigh,* all these favouable conditions, observable in man, are wanting in animals; but as, in the latter, every thing concurs to prevent their being capable of standing on two feet, in man every thing is so disposed, as to render it very difficult for him to rest on his four extremities. In fact, independently of the great inequality which there is between his upper and lower limbs, a difference of length which, being less sensible in early life, makes it less uneasy for a child to walk on his hands and feet, those four limbs are far from affording the body an equally solid support. The eyes being natural- ly forwards, are, in that attitude, directed towards the earth, and do not embrace a sufficient space. We cannot, therefore, agree with Barthez, that man, during infancy, is naturally a quadruped, since he is then but an imperfect biped ; (CLXXXI.) nor can we admit that man might walk on all fours all his life, if he were not broken of the bad habit vvhich he learns in infancy. CLXXXIII. Very little has been added to what Galen has said In his ad- mirable work ofthe structure of parts, relative to the respective advantages at- tending the peculiar conformation and structure ofthe upper and lower limbs. It is easy to see, that in combining, as much as possible, strength and facili- ty of motion, Nature has made the former predominate in the structure of the inferior extremities, while she has sacrificed strength to facility, to precision, to extent, and rapidity of motion, in the upper extremities. To convince one's self ofthe truth of what has been stated, it is sufficient to compare, under the two relationst ofthe resistance of which they are capable, and ofthe motions which they allow, the pelvis to the shoulder, the thigh to the humerus, the leg to the fore arm, and the foot to the hand. The inferior extremities, if examined when the bones are covered with the soft parts, will present the appearance of an inverted cone or pyramid, H These masses form the calf of the leg and the buttocks; in no animal are these muscles more prominent than in man. t See the anatamical observations on the neck ofthe thigh bone, vvhich I have prefix^ ed to a memoir which bears the title of Dissertation anatomico-chirurgicalo sur Itafrazlurt* d" co! defemvr. Paris, an VII. SIJ which, at first sight, appears contrary to the object which Nature had in view; but if the bones be stripped of their fleshy coverings, these solid supports will be seen to represent a pyramid, whose base is at the lowest part, and formed by the foot, and which decreases in breadth upward from the leg, foimed by the union of two bones, towards the thigh, consisting of only one bone. If it be asked why the inferior exrtemities are formed of several pieces, detached and placed one above the other, it will be found that they are thereby much more solid, than if formed of one bone, since, according to a theorem, demonstrated by Euler* two columns containing the same quanti- ty of matter, and of equal diameter, have each a solidity in inverse ratio of the squares of their height; in other words, of two columns, containing the same materials, of equal diameter, and of unequal height, the smaller is the stronger. The long bones, which by their union form the inferior extremity, con- tain a cavity which adds to their strength, for, according to another theorem, explained by Galileo, two hollow columns ofthe same quantity of matter, of the same weight and length, bear to each other a proportion of strength measured by the diameter of their internal excavations. The breadth of surface ofthe articulations of the inferior extremities, assists, materially, in giving them additional strength, when in standing, these bones are in a vertical direction. No articulation has a broader surface than that of the thigh with the leg and knee-pan. Among the orbicular articulations, no one has more points of contact than the joint ofthe thigh bone to those ofthe pelvis. Professor Barthez says, that when the body is erect, the head ofthe thigh bone and the acetabulum ofthe os innominatum, which receives that bone, come in contact in a surface of small extent. lam, on the contrary, of opinion, that in no possible case can the cnotact of two bones be more complete. The middle line of direction ofthe upper part the thigh bone, is then exactly perpendicular to the surface ofthe condyloid cavity, which embraces and touches, in nearly every point, the almost spherical head of that bone. The cervix on which the head ofthe bone is placed, by keeping the thigh bone at a distance from the cavity of the pelvis, increases the extent of the space, in which the centre of gravity may vary without being carried beyond its limits. CLXXXIV. The erect posture does not imply a perfect absence of motion. / It is on the contrary, accompanied by a staggering, vvhich is the more marked in proportion as the person has less strength and vigour.— These perpetual oscillations, though but slightly distinct, in a man who stands upright, depend on the incapacity of the extensors to keep up a constant state of contraction, so that they become relaxed for a short time, and the intervals of rest in the extensors are frequent, in proportion to the weaker state ofthe subject. • Methodus inveniendi lineas curvas. Nature has, therefore, increased the number of these columns in the extremities of quadrupeds, by raising their heel and the different parts ofthe foot, whose bones she has lengthened, to make of them so many secondary legs. These numerous columns placed above one another, are alternately inclined, and in a state of habitual flexion, in the quad- rupeds remarkable for swiftness in running, or for their power in leaping, as in the hare and squirrel, while in the ox, and especially in the elephant, they are all placed vertically, so that the enormous mass of the latter rests on four pillars, the different pieces of which are short and so slightly moveable on one another, that, as Barthez observes, Saint Basil bus adopted tbe error of Pliny, /Elian, and several other writers of antiquity, that there are no articulations in the legs of that monstrous animal—Author's Pc'i. 40 314 Sonic physiologists have given a very inaccurate idea of standing, by making that attitude depend on a general effort of the muscles ; the exten- sors onlv arc truly active. The flexors, far from assisting, tend, on the contrary, to disturb the relation between the bones, necessary to render that state permanent. This explains, why standing is so much more fa- tiguing than walking, in which, the extensors and flexors ofthe limbs, are in alternate action and rest. It may bo said, nevertheless, that to give the greater firmness to the attitude, we sometimes contract, in a moderate degree, the flexors them- selves ; then, that great part of the real force of the muscles, which acts according to the direction of the levers which they are to set in motion (CLXVI.) and which is completely lost in the different motions which they produce, is usefully employed in drawing together tho articular extremities, in keeping their surfaces firmly applied to each other, and in maintaining their exact superposition which is necessary to the erect posture of the body. No one that I know of, had taken notice of this employment of the greater portion of our muscular power, vvhich was thought completely lost by the unfavourable arrangement of our organs of motion. The line, according to vvhich all the parts of the body bear on the plane which sup- ports them, has much more tendency to fall forwards than backwards ;* and falls forward are the most common and the easiest. Thus, nature has directed, in the same direction, the motion ofthe hands, which we carry forward to break the force of our falls, to prevent too violent shocks, and to lessen their effect. At the same time, she has provided means of pro- tection towards the sides which the hands could not guard. She has given more thickness to the back part of the skull; the skin which covers the neck and back, is much denser than that which covers the fore part of the body. The scapula, in addition to the ribs, protects the posterior part of the chest. The spinal column lies along the whole length of the back; the bones ofthe pelvis have their whole breadth turned backward. Falls are the more serious, as they occur in a more perfect state of extension of the articulations ; the falls of a child whose limbs arc in an habitual state of flexion, are much less dangerous than those of a strong and powerful adult, whose body falls in one piece, if I may be allowed that expression. The falls which skaiters meet with, on the ice, are often fatal from fracture of the skull, which, placed at the extremity of a long lever formed by the whole body, whose articulations are on the stretch, strikes the slippery and solid ice, with a momentum increased by the quick- ness of the fall. We have already seen, that wading fowls remain a long while standing, without effort, by means of a peculiar contrivance in the articulation of the tibia to the thigh bone, but all other birds are obliged to employ mus- cular action when standing, except during sleep. The greater part, it is well known, roost on a branch which they grasp firmly with their claws. Now, this constriction, by which they cling to their support, is a necessary result of the manner in which the tendons of the flexors of their feet descend along their legs. These tendons pass behind the articulation of the heel; a muscle which arises from the pubis joins them, as it passes in * This tendency is much less distinct in tall slender men. It is observed, that they, for the most part, stoop in walking, less from the habit of bending forward, than to pre- vent the centre of gravity from falling behind. Pregnant women, dropsical patients, all persons who have much ehbonpolnt, throw their body back, from an opposite and easily imc^rstood reason. 315 front of the knee, so that the bird has but to give way to ins weight, and the joints, becoming salient on the side along which the tendons run, stretch and pull them, and make them act upon the feet, so as to draw in the claws to clasp tightly the branch on which he is perched. Borelli was the first who understood distinctly and explained satisfactorily this pheno- menon.* CLXXXV. Although standing on both feet is most natural to man, he is able to stand on one ; but the posture is fatiguing, from the forced incli- nation of the body to the side of the leg which supports him, and the effort of contraction required to keep up this lateral inflexion. The difficulty increases, if, instead of resting on the entire sole, we choose to stand on the heel or on the toe : the base of support is then so small, that no effort is sufficient to keep the centre of gravity, long together, in the requisite situa- tion. As to the degree of separation of the feet, which gives the firmest possi- ble stand, it depends upon their length. When they enclose a perfect square, that is, when taking their length at nine inches, each side of the quadrilateral figure is of that measure, the stand is the firmest that can be conceived. Nevertheless, we are far from keeping or taking this posture to prevent falls. The wrestler who wants to throw his antagonist, strides much more ; but then, he loses on one side what he gains on another ; and if he stride thirty-six inches, on the transversal line, it will need much greater force to overthrow him on that side; but it will take much less to throw him forwards, or on his back. Whereforo, one of the great princi- ples of this gymnastic art, is to bring back the feet to a moderate stride^ in the line of the effort which is foreseen to require resistance. There is some resemblance to standing, in the attitudes of kneeling and sitting. In the first, the weight of the body bears upon the knees, and we must bring back the body, to throw the centre of gravity over the middle of the legs. Accordingly, if we have nothing before us to lean on, this posture is extremely distressing, and we cannot long keep it on. I have said, in another work, that genuflexion rendered monks very liable to hernia ; the abdominal viscera being pushed against the anterior and lower part of the abdomen, by the throwing back of the body. In sitting, the weight of the body bearing on the tuberosities of the ischia, there is much less effort required than in standing on the feet. The base of support is much larger; and when the back leans, almost all the extensor muscles employed in standing, are in action. CLXXXVI. Of the recumbent posture. Decubitus. All the authors who, like Borelli, have treated professedly of the animal mechanism; all the physiologists, who, like Haller, have set forth, in some detail, the mechanism of standing, and of progression, have completely passed over the considera- tion of the human body in repose, left to its own weight, in lying on an horizontal plane. The intention of the following observations is to fill up this gap. ,Let us consider, at setting out, that lying on an horizontal plane, is the only posture in which all the locomotive muscles recover the princi- ple of their contractility, exhausted by exertion. Standing without motion, has only the appearance of repose, and the unremitted contractions it requires, fatigue the muscular organs, more than the alternate contractions, by which the various motions of progression are carried into effect. * De rnotu animalium. Prop. 150. Quantur quare aves stando, ramis arborvm compre- hensis, quiescunt et dormiunt absque ruina. Tab. II. fig. 7. 310 The human body, stretched on an horizontal plane, reports in four posi- tions ; as it lies on the back, the belly, or one or other of the sides. The Latin tongue expresses the first two situations, by the terms supine and prone.* Jt has no particular word for lying upon the side.t Lying upon the right side is the most ordinary posture of sleep, in which we rest most pleasantly, and longest together. There are very few, except under constraint of some faulty organization, who lie on the other side. This depends on two causes; when the body lies on the left side, the liver, a bulky viscus, very heavy, and ill steadied in the right hypochondrium, presses with all its weight on the stomach, and draws down the diaphragm : thence ensues an uneasiness, which hinders long continuance of sleep, or disturbs it with distressing dreams : then the human stomach presents a canal in which the course of its contents is obliquely directed from above downwards, and from left to right: the right or pyloric orifice of the sto- mach is much less raised than its left or cardiac orifice; lying on the right side favours, therefore, the descent of aliments, which, to pass into the intestines, are not obliged to ascend against their own weight, as they must, in lying on the left side. These two anatomical causes exert their influ- ence on the generality of men, and if there are any who fall into the habit of lying on the left, one may safely conjecture some vicious organization, or some accidental cause, that determines them, as by instinct, to this posture. Let us suppose an effusion of blood, water, or pus, in the sac of the pleura of the right side. The patient lies on this side, that the weight of his body may not oppose the dilatation of the sound side of the chest. The parietes of this cavity are not equally distant from its axis ; the pressure of the body on the plane of support, prevents the separation of the ribs, whether as a mechanical hindrance to the displacement of these bones, or in numbing the contractility of the muscles of inspiration, all more or less com- pressed : Now, as the healthy lung must supply the place of the diseased, nothing could be more in the way than to produce, on that side, by a bad posture, a constraint equal to that occasioned by disease, on the other. It has long been imagined, and it is taught still, that, in thoracic effusions, patients lie on the side of the effusion, to hinder the effused fluid from pressing on the mediastinum, and pushing it against the opposite lung, of which it will constrain tbe developement. The following experiments show clearly enough the error of such a supposition : I had several times produced artificial hydrothorax, by injecting with water, the chest of several bodies, through a wound in one of the sides. This experiment can be made, only on bodies in which the lungs are free from adhesion to the parietes of the chest, and the number is smaller than might be imagined: you may introduce in this way from three to four pints of water. 1 afterwards opened carefully the opposite side of the chest: the ribs removed and the lung displaced, gave room to see distinctly the septum of the mediastinum stretched from the vertebral column to the sternum, and supporting without yielding, the weight of the liquid, what- ever might be the posture given to the body. It is for the sake then, evidently, of not preventing the dilatation of the sound part of the respiratory apparatus, already condemned in one part to inaction, that patients, in thoracic effusion, lie constantly on the side of * Cubitus supinus, Plin. Cubitus pronus. Cicer. Cubare in faciem, Juven. Supinos vel pronus jacere. i Dextro vel laevo latere cnbare; cubitus in latus. Pliny. Of* viie effusion. It is for the same motive, to which we may add that of not increasing the pain by dragging downward the inflamed pleura, that patients in pleurisy lie on the affected side. The same thing happens in peripneu- monies; in a word, in all diseased affections of the lungs and parietes of the chest.* Lying on the back, which is unusual in health, is natural in many diseases. It commonly indicates more or less weakness of the muscles of inspiratiou. The contractile powers which perform the dilatation of the chest, when affected with adynamia, in fevers of a bad character, or after extreme fatigue, carry very imperfectly into effect this dilatation. Nevertheless, a determinate quantity of atmospherical air must be admitted, every moment, into the lungs, and the general weakness would be increased, if respiration did not impregnate the blood with a sufficiency of oxygen: patients choose, therefore, the posture which makes the dilatation of the lungs easiest for their weakened muscles. The posterior parietes of the chest, on which the body reposes, lying upon the back, is almost useless in the expansion of the cavity. The ribs, which have the centre of their motions in their articulations with the vertebral column, are almost immoveable backwards, and the moveableness of these bones increases with the length of the lever which they represent. So that, no where is it greater than at the anterior extremity terminating in the sternum. Thus, lying on the back has the double advantage of not constraining any of the muscles of inspiration, and of not opposing the motion of the ribs, except at that part where these bones have the least play : lying on the back is one of the characteristic symptoms of putrid or adynamic fever, of scurvy, and of all the diseases of which debility of the contractile parts forms the principal characteristic. After Jthe fatigue of a long march, or of any other continued exertion, we take this position in lying, and change it, only when sleep has sufficiently replaced the loss of contractility. Lying on the belly has effects directly the reverse. The expansion of the chest is hindered, exactly where the bony structure is formed for the greatest play of motion : the abdominal viscera are besides pushed up on the diaphragm, of which they resist the depression, and the posture is accordingly unusual. The continuance of it. during sleep is possible only to the robust; others, even when they do fall asleep in this posture, soon awake from troubled and distressing dreams, under the agony known by the name of the night-mare. We sometimes seek this posture to constrain respiration, and so abate inward excitation, in the ardour, for instance, of a febrile paroxysm. The different postures of lying having reference to the degrees of facility of respiration, very young children, and persons advanced in years, prefer lying on the back, this posture being, as was already observed, the most favourable to the motions of respiration. Respiration, like all the other functions of the animal economy, with the exception of the circulation and of the phenomena which immediately depend on it, requires a kind of cultivation : it is but feebly performed at an early period of life. It is only after a certain number of years, and when the muscles of respiration, at first small and weak, acquire strength from the very circumstance of being called into frequent action, that the chest dilates with facility, and that the lungs enjoy the full exercise of their faculties. Until that period the enlargement of the chest and the dilatation of the lungs took place, in * This is not the case until after adhesions ofthe pleura? have taken place, :;ltf an imperfect manner, the child was unable, even by spitting, to free itsfch of the mucus with which its bronchia are apt to get filled, and which render the pulmonary catarrh, called the hooping cougb, so dangerous at an early period of life. In like manner, in an old man, the muscles, debili- tated, and returned to the relative weakness of infancy, in vain strive to clear the air cells of the mucus with which they become obstructed in the suffocating catarrh. The mechanical process of respiration is, therefore, equally difficult in the child, from the weakness of the muscles which have remained in a long continued state of inactivity; in the old man, from the debility ofthe same organs and from the induration ofthe cartilages. Thus, at those two distant periods of life, it is most natural to lie on one's back, but there is a sufficiently remarkable difference in that respect, and which may now be inquired into. In the foregoing observations, I have always spoken of the human body as stretched on a perfectly horizontal plane. It is seldom, however, that we rest on such a surface; almost every one, and especially person's advanced in life, require that the plane should be inclined, and that the head should be raised, to a certain degree, else the brain would become affected with a fatal congestion of blood. Children, on the other hand, suffer no inconvenience from a neglect of this precaution, whether it is that, in them, the vital power has more energy, and thus balances better the laws of mechanics, by opposing more powerfully the effects of gravitation, or whether it is, that in very young children, the parietes of the arteries within the skull, have a proportionate thickness, and consequently greater power. The extreme disproportion observable in adults, in the thickness of the parietes, between the cerebral arteries and those of other parts of the body, is but trifling in children ; and may not this difference of structure, which I have several times observed in the coarse of dissection, be con- sidered as one ofthe principal causes which, in old age, bring on apopolexy, a disease to vvhich the child is not liable ? It is well known, that as the enlargement of the chest is produced by the depression of the diaphragm, persons who have taken a plentiful meal, dropsical patients, pregnant women, cannot rest, without lying on a very inclined plane, so that the chest being considerably raised, and the patient, as it were, seated, the weight of the abdominal viscera draws them towards tho most depending part, that their bulk may not interfere with tho depres- sion of the diaphragm. We might now inquire what is the posture in which the body rests with least fatigue : this investigation, unimportant to the physician, would be of the highest value to the arts which have for their object the imitation of Nature. In consequence of ignorance on this subject, we often see, in the Works of several of our sculptors, figures in attitudes of repose so incorrect and uneasy, that they could not maintain them, without considerable effort and fatigue. CLXXXVII. Of the motions of progression. Of walking. Walking, ruuning, and leaping, are so closely connected, that it is difficult to distin- guish them. There is, in fact, very little difference between walking, in a certain manner, or running ; and running is most frequently produced, by the complicated mechanism of running and leaping. In the most natural way of walking, we, in the first instance, poise the body on one foot, then, bending the opposite foot on the leg, the latter on the thigh, and the thigh on the pelvis, we shorten that extremity ; we, at the same time, carry it forward, extend its articulations which are bent, and when firmly applied to the ground, 319 we bend the body forward, and carry back the centre of gravity in that direo tion ; and performing the same motions with the limb which remained be- hind, we measure the space the more rapidly, caeteris paribus, as the levers on which the centre of gravity alternately bears, are longer. The weight of the body, compared to that of the lower extromities, is as that of a car- riage which moves, in succession, on the different spokes of its wheels. The centre of gravity does not move along a straight line, but between two parallels, in which space it describes oblique lines from the one parallel to the other, and forms zig zags. The oblique direction of the neck of the thigh bones, accounts for the lateral oscillations ofthe body, when we walk ; the arms which move, in a different direction, from that of the lower extremities, serve to balance us, preserve the equilibrium, and correct the staggering, which would be much greater, if the neck of the thigh bone, instead of being oblique, had been horizontal. The impulses communicated to the trunk, are reciprocally balanced, and the latter moves in the diagonal ofa parallelogram, whose sides are represented by the line of these impul- ses. We constantly deviate from the straight line, in walking, and if the sight did not enable as to see, at a distance, the object towards which we are moving, we should go to a considerable distance from it. If you place a man, with his eyes blind-folded, in the middle of a square field, he will, in his attempt to get out, and thinking that he is moving in a straight line, make for one of the corners. It is, almost always, towards the left that we deviate, the right lower extremity, whieh is tbe stronger, inclining the body towards the opposite side. Those who are lame depart much more from a straight line, and deviate towards the side of the shorter leg. The motions which they are obliged to use, and which render their gait so remarkable, are occasioned by the necessity of incessant and powerful efforts, to prevent the body from giving way to its own weight, and to the greater power of the sound extremity, which inclines it towards the affected side. The breadth af the feet, and a moderate separation of these parts, give a much firmer support to the centre of gravity. Thus, in walking on a moving and insecure surface, we hold apart our feet, so as to include a greater base of sustentatio*. Those who have been long at sea, acquire such a habit of holding their feet asunder, in the way they are obliged to do during the rolling of a ship, that they cannot lose the habit, even when on shore, and are easily recognized by their gait. A sailor is unfit for active service, till he has acquired what is called, by sea-faring people, a seaman's foot, that is, till he is capable of stepping firmly on the deck of a vessel tossed by the tempest. The gait of a woman, from her having smaller feet, is less firm ; but ought we, from that circumstance, to infer, with the most eloquent writer of the eighteenth eentury, that this diminutive size of the foot, is connected with the necessity of her being overtaken in flight ? The concave form of the sole of the feet, by enabling them better to adapt themselves to the unevenness of the soil, concurs in giving a firmer footing in walking, and in other motions of progression. There is, in walking, an intermediate mo- ment, between the beginning and the end of a step, during which the cen- tre of gravity is in the air: this lasts from the moment when the centre of gravity is no longer in tbe foot which remains behind, till it returns into the other foot which is carried forward. Walking is modified, according as it takes place on an horizontal or an inclined plane ; in tho latter case, we ascend, or descend, and the exertion 320 is much more fatiguing. To explain the action of ascending, let us suppose a man at the bottom of a flight of stairs, which he wishes to go up ; he begins by bending the articulations of the limb which he is desirous of carrying forward ; he raises it thus, and shortens it to advance ; and when the foot, which is in a state of semi-extension, rests on the ground, he extends the articulations of the other extremity, carries thus the body upward, in a vertical direction, and completes this first step, by contracting the extensors of the leg that were first in action, so that they may bring forward and restore to it the centre of gravity, to which the posterior leg, whose foot is extended, has given a vertical motion of elevation. Hence, in ascending, the calves of the legs and knees, especially the latter, are so much fatigued ; for, the effort with which the extensors of the foremost leg, bring back again upon it the centre of gravity, is more powerful than that by which the gemelli and the soleus impart to it, by extending the hind- most foot, a motion of vertical elevation. To relieve the extensors of the leg, we bend the body forward, as much as possible; we lean back, on the contrary, in descending a flight of stairs, or a rapid slope, in order to slacken the motion, by which the body, yield- ing to its own weight, falls on the leg that is carried forward. At the moment when the centre of gravity is no longer within the base of sustentation, all the powers unite in action, that it may fall, as little as possible, from a vertical direction. The glutcei steady the pelvis, and straighten the thigh, the lumbar muscles extend the trunk on the pelvis; hence, in going down a slope, the loins get so much fatigued. We are less fatigued in going down hill, when the slope is moderate, than in going up hill; as the force of gravitation, or the weight of the body, assists con- siderably the descending vertical motion. The motion of walking, when we take very long steps, resembles that of going up hill, as the body being lowered, every time the legs are much apart, requires to be elevated, at each step, towards the foremost leg. At every step we take, the articulation of the leg with the foot is the principal seat of an effort, to which physiologists have not paid any atten- tion. The whole weight of the body is supported by the action ofthe levator muscles of the heel, and the astralagus supports this weight, which varies according to the corpulence of the person, and the burthen with which he is loaded. The weight of an adult, of common stature and of moderate size, may be estimated at about one hundred and fifty pounds; but which sometimes, in corpulent people, amounts to between four and five hundred pounds. If, then, to the weight of the body, there be added that ofthe burthens which it may support, it will be conceived how immense tbe efforts must be, which are, as it were unconsciously, carried on, in the articulation of the foot with the leg. But how numerous the resources which nature has provided to overcome this great resistance ; how many the circumstances she has happily combined to accomplish this without fatigue! In the first place, the foot in this action, represents a lever ofthe second class, and this lever, it is well known, is the most advantageous, the resistance being always nearer to the fulcrum than the power, and the arm, by which the latter aets, consisting of the whole length of the lever. If you attend to the mechanism of the different parts of the skeleton, you will no where find so powerful a lever applied in so favourable a manner. The os calcis, by carrying the foot beyond its articulation with the leg, adds likewise to the length of the lever by which the power acts. Its ':ngth has considerable influence on our strength, on our power of talkiDg, 321 ^.VihuM tatrfue^lorjg &<>. ~. . or engaging in exertions requiring considerable ■^ . ••■•iiaKlorcc m the 'ov* 3r extremities. The negroes, who excel in W.-iAng, is* dii:>cing: and •. all gymnastic exercises, have a longer and .£;e ;>;';- jct-iig ik'^I tha^ Europeans. They dance best, whose tendo r^'chiilis j£.raoit detacher];, that is to say, projecting, and at the greatest . «Ks.?.!v o from the axis of tb: leg; vvhich implies, that its lower attachment is'carted backj of th.3 pj ongation ofthe os calcis. Thc?o wji'f'Hve h short ..Del, have a long and flat foot: this conformation, '.vhicK, v. hen'taarked, ;s fau.ty, is not only unfavourable to beauty of form, but in, besides-romerkobly mjurious to the strength ofthe limb, as well as ■■'-': freedom, of raotiorn ^len with flat feet, are always bad walkers, hence, this flati* .vd loim, wit n very considerable, is considered as unfitting a -i)sn\^,rmlMtary service lastly, the term denoting this physical imper- *e• 'V2 ;'^:V ii^ptats-,) is accounted insulting in the French language, as •Wi'i; as in'severe* others. Jut let us go on with our inquiry into the advan- tageous disposition ofthe articulation of the foot with the leg, for facility in walking, and in tne different motions of progression. We have seen that the tendons are generally inserted at a very acute angle, into the bones on which they act; in the present instance, however. the insertion takes place at a right angle, the common tendon of the mus- cles ofthe calf ofthe leg joining the os calcis, at the angle most favourable to their freedom of action. With the exception of the muscles which move the head and lower jaw, no others are so evidently disposed with this purpose. Nature has not been contented with forming the foot in such a manner as to afford the most advantageous lever, to vvhich the moving powers are applied, at the greatest possible distance from the fulcrum, and at the angle most favourable to their action ; she has further increased the efficacy of this action, by adding extraordinarily to the num- ber of muscular fibres. There is not, in the body, a stronger muscle than the soleus, whose short and oblique fibres between the two wide aponeuroses which cover its anterior and posterior surfaces, are more numerous than in any other muscle, as may be conceived, by considering the extensive surfaces to which they are attached. Besides, the tendo Achillis is kept in -a due degree of straightness, by the aponeurosis of the leg behind it. Every thing in the powers, as well as in the levers, is formed so as to overcome the resistance, without difficulty ; that is, so as to raise the weight of the body, by the extension of the foot, the end of which rests on the ground, in every motion of progression. This immense power with vvhich the muscles of the calf of the leg act to raise the heel, and to support the whole weight of the body resting on the astralagus, accounts for the possibility of transverse fractures of the os ■calcis, and for the rupture of the tendo Achillis, notwithstanding its great thickness ; and should lead one not to allow patients, after such accidents, to walk freely, for several months; the substance which unites the parts being liable to rupture, as is known to have been the case, in several in- stances. This same arrangement of parts likewise accounts for an acci- dent, which physiologists have long endeavoured to explain by a very unsatisfactory theory. It not unfrequently happens, that the mere effort of walking occasions a rupture of some of the fibres of the gemelli and of the soleus, in conse- quence of which there comes on pain, attended with induration of the muscles, and with a certain degree of ecchymosis, occasioned by the ex- travasation of blood. Pathologists suppose these symptoms to depend on / 41 .i'2'2 :» rupture oi the plantaris muscle: this nipt has never been proved by experience to exi are altogether idle and fallacious. I could, if it were not out of place, briiv affection: in all the cases vvhich have com« the use of the bath, of emollient and slight] ■ all, continued rest, while the symptoms last most appropriate remedies. CLXXXVIII. Of running. In runni » ■ being raised before that which is foreim ; % . ground, the centre of gravity is, for a mon the air, impelled by the force of projection, :- ■••> ■ •■ constitutes leaping. The mechanism of running is a compound ! •■< ■ <': . i »• ing, but resembling most the latter ; hence . > .l u. h> ■,.•• '. • ■ ■ ■. '■ < <■'>' '--:; • The i_. of gravity is transferred, with more rapidity, from one leg to the other, and falls are much more apt to take place. The quick repetition of the same motions, in running, requires a very lively contractility in the muscles which move the extremities, and as the energy of this vital property is proportioned to the extent of respiration, to the quantity of air which the blood acquires in passing through the lungs; in running, we pant and breathe frequently, and at short intervals, without any particular enlarge- ment of the chest, at each aet of respiration. It was necessary that the parietes of this cavity should, in running, be remarkably fixed; for, it becomes the point on which those muscles are inserted which steady the pelvis and loins, and prevent their yielding an unsteady basis to the lower extremities. The best runners are those who have the strongest lungs, that is, who can give to the chest tbe greatest degree of permanent dilatation. In contending for the prize in running, you may see them throw back their head and shoulders, not only to obviate the propensity which there is in the line of the centre of gravity to fall towards the anterior plane, but, likewise, that the cervical column, the scapulae, the clavicles, and the hu- merus, being fixed, may furnish a firm attachment to the auxiliary muscles of respiration. We should run with much less speed, if we applied to the ground the whole sole of the foot; partly from the time which would be taken up in thus applying the foot to the ground, and partly by the friction which would necessarily take place. Hence, in running, we generally touch the ground, only with the end of the foot. We run with most speed, when the foot is in a state of extension, the leg being moved rapidly by the extensors ofthe knee. This accounts for the tendency which there is to fall while we run, the centre of gravity obeying the impulses which follow each other in rapid succession, and never resting but on a basis of very limited extent. Another reason why the slightest unevenness of the ground is apt to occa- sion falls in running, is, that the rapid motion communicated to the body by the sudden and perpetually recurring extensions of the posterior extre- mity, increases at every step, so that it is impossible to stop suddenly, and without having previously slackened one's pace, and moderated the impulse to which the body is subjected. As it is mostly forward that falls are apt to take place, in running we always throw back the head, and make use of our arms to balance the 323 body, so that they may be in constant opposition to the legs, that is, that: ;;>•, ]>:■ , ;" ' . -.tremity, for example, being carried forward, the left arm ■\, , . < backward. ■■■ .■!• e better formed than man to inn with speed, his lower 1 equal to one half of the whole length of the body, and ■.-.:.•;• move them are very powerful; hence, savages, who are ;.i; -abit of running, overtake the animals which they make ■■U ■ ..■'.. even in Europe, there are professed runners who equal in .,w;-. i'-'. test horses. This animal, like every other swift quadru- p' •;. much more slowly than man, on account of the number '>>' iV.'-, >mich he rests, if he had not the power of moving them in pan'--, '<:■■ 'ducing his legs to two, as in what is called full gallop. C\.!'■ ■'■ - \ Of leaping. Leaping, in man, is performed, principally by the ■>•.- . . tension of the lower limbs, whose articulations were in a pr"vi< .-•. •; ■ flexion. The alternate angles of the foot, of the knee ''-■ i , ' ar, and the extensors contract in almost a convulsive : ..•i.e.'. Tni; ^raightening is not limited to the lower limbs, in violent leaping: it, likewise, affects the vertebral column, which acts as a bow in unbending. Professor Barthez, who has the merit of having suggested this explanation, which Borelli and Mayow had very imperfectly understood, perhaps goes too far, in considering as imaginary, a power of repulsion in the ground. This re-action, admitted by Hamberger and by Haller, clearly operates, when we leap on an elastic floor; it enables tumblers to rise, without much effort, on the rope vvhich bears them. But though all physio- logists do not admit that, in leaping, there is a re-action from the ground; it is universally admitted, that there must be a certain resistance, from the ground on which we tread. In fact, a moving sand,yielding to the pressure of the body, would, by giving way to a considerable degree, render it impossible to leap. The instantaneous contraction of the extensor muscles is so powerful, in extending the lower extremities, and in communicating to the body a power of projection, so as to raise it, that frequently, during this effort, the tendons of these muscles, or even the bones into which they are inserted, break across. It is on this account that dancers are very apt to fracture their patella. This accident happens, at the moment when their body, in rising from the ground, is powerfully elevated to a certain height: If leaping consists merely in the sudden straightening of the lower ex- tremities, whose articulations are bent in alternate directions, it must be more considerable, according as these are longer, more bent on one another, and as the muscles which straighten them contract more powerfully.— Hence, animals that move by leaps, as the haro, the squirrel, and the jer- boa, have posterior. extremities of considerable length, in proportion to their fore legs. Their different parts are, besides, capable of considerable flexion. All these animals, strictly speaking, are incapable of walking or running, and they move by leaps or bounds succeeding each other with different degrees of rapidity. Some, however, as the rabbit and the haro, are capable of running, when climbing up a steep place, as the slope, in this case, lessens the effect ofthe impulse communicated by the extension of the posterior limbs; an impulse which, from the strength and len^ili of these extremities, throws the whole weight of the body on the fore Jogs, which are weaker and shorter, with such a degree of force, that the animal is obliged to stiffen these and to keep them straightened, and in a state of extension, to avoid striking the ground with his head, while leaping on an ho- rizontal plane. Frogs, but especially grasshoppers and fleas, between rvliose 324 hind extremities and the rest of the body, there is tbe gre? > ■ astonish us by the very considerable space vvhich they c but the wonder ceases, when we consider that powers r>< masses equal degrees of velocity, when proportionate to the space gone over, depending entirely on the veloc > that leaps, loses, by a gradation which nothing can 1> had acquired: these motions must"be nearly alike in- animate. Swammerdam says, that the height to which grasshmv >•-'-> ■/'■■■, , ing, is to the length of .their body as 200 to 1. A fl< - '■' 3; : : and more swiftly.* The larva, called the cheese maggot, forms itself . ,->. -;... ,y tracting, as much as possible, its abdominal muscular ibr-r : M'un ii.-;vi in this manner, brought near to each other its head ..-,..) rnil, it s amonStho CCXIII. Of monsters. As it is useful to study Nature, even in her irregularities, I shall say a few words on the subject of monsters, adopting he arrangement proposed by Buffon, of dividing them into three classes : tne nrst including monsters from excess; the second, monsters from aetect; the third including those in which there is a misplacement of organs. In the first, are included those which have supernumerary limbs or fingers, or even two bodies joined in various ways. In the second, children born with a hare-lip, or who are deficient in some one part. In the last place, those monsters belong to the third class, in which there is a general transposition of organs ; when, for example, the heart, the spleen, and the sigmoid flexure of the colon are on the right side, and the liver and caecum on the left; those born with hernia- of different kinds, likewise belong to this class. One may reckon among these monstrous conforma- tions, spots in the skin, the colour of which always resembles that of some oi our fluids, but whose various forms are purely accidental, though, from pre- judice, one is apt to imagine some likeness to objects longed for by- pregnant women accustomed to those fantastic appetites and longings, so frequent during pregnancy. Various attempts have been made to account for these .unnatural forma- tions : some, as Mallebranche, attributed them to the influence of the mother's imagination on the fcetus in the womb; others, as Maupertuis, thought that her passions communicated to her humours irregular motions, which, acting with violence on the delicate body of the embryo, disturbed its structure. Disease, while the child is in utero, is a much more probable cause of such affections. If the two foetuses, contained in one ovum, lie back to back, and if the surfaces at which they are in contact, become affected with inflammation, it is easy to conceive that adhesion may take place between them. By placing, in a confined vessel, the fecundated ova of a tench or any other fish, the numerous young ones, which are formed, not having space sufficient for their growth, adhere to each other, and fishes truly monstrous in their formation are produced. When, from disease, or from an original malformation, the body of the foetus is deficient in some of its parts, the others are better nourished and grow to a large size. Hence, in acephalous monsters, as there is no brain, the blood which should be sent to that viscus, going to the face, it acquires a remarkable enlargement. #« One of the most curious of all the cases of montrosities, depending on an original defect in the organization of the germ% is-, that, which was sent, a few years ago, by the Minister of the Interior;, -to 'the-School » See the APPENDIX, Note I* I. V ;>tiO of Medicine at Paris. I' shall give an abstract of it, from a mora detailed account, drawn up with much accuracy and sagacity by M. Dupuytrun. A young man, thirteen years of age, had complained, from his earliest infancy, of pain, in the left side and lower part of the abdomen. ' This side had been prominent and contained a tumour, from the earliest period of life. At the age of thirteen, he was seized with fever, the tumour increased in bulk, and became very painful. Some days after, he voided, by stool, purulent and fetid matters; at the end of three months, he became wasted by marasmus, he passed, by stool, a ball of hairs, and in the course of a few weeks, died of consumption. On opening his body, there was found, in a cavity in contact with the transverse arch of the colon, and communicating with it, some balls of hairs and an organized mass. The cyst, situated in the transverse meso- colon, near the colon, and externally to the digestive canal, communicated with the intestine. But this communication was recent and accidental, and one could plainly see the remains of the septum between these cavities. The organized mass presented, in its forms, a great number of features of resemblance with the human foetus, and, on dissection, no doubt could be entertained of its nature. There was discovered in it, the trace of some of the organs of sense, a brain, a spinal marrow, very large nerves, muscles converted into a sort of fibrous matter, a skeleton consisting of a vertebral column, a head and pelvis, and limbs in an imperfect state; lastly, a very short umbilical cord attached to the transverse mesocolon, at the outer part of the intestine, an artery and vein, ramifying at each of their extre- mities, where they were in contact with the foetus and with the individual which contained it. This much is sufficient to establish the distinct exist- ence, as an individual, of this organized mass, though, in other respects, destitute of organs of digestion, of respiration, of the secretion of urine, and of generation. The absence, however, of a great number of the organs necessary to the maintenance of life, should make it be considered as one of those monstrous foetuses, not destined to live beyond the moment of birth. This foetus was evidently contemporary with the boy to whose body it was attached. Similar to the product of extra uterine conceptions, it received its nourishment from that which may be considered as its brother, and whose germ had originally inclosed its own. During the thirteen years of the life of Bissieu, (this was the name of the subject of this singular case) the organized mass obtained from the mesocolon, by means of vessels of its own, the blood necessary for its existence; this blood, propelled by the organs of circulation into the body of the fcetus, returned afterwards to the mesocolon of the boy who had so long been to him as a mother. At last, the period fixed by Nature for expulsion being arrived, and this expul- sion being impracticable, the cyst became inflamed; the inflammation ex- tended to the intestine, the part which separated these two cavities was destroyed, and the cyst opened into the colon; pus and hair were voided by stool, and the patient died of marasmus. The drawings of different parts of the body of this foetus, taken by M. Cuvier and M. Jadelot, render this interesting case most complete. They will be published in the first volume of the transactions of the Academical Society, near the Faculty of Medicine at Paris.* * Mr. Young, of London, has communicated a case of the same kind, in a valuable t.pnper inserted in the first voluroe ofthe Medico-Chirrtrsrical Transactions. In Mr.Tonng'a 3 sometimes, though rarely, at a third. In all countries ot the world. poK- gamy is, therefore, in direct opposition to the intentions of Nature, and to the multiplication of the species: this is proved, in a most undeniable manner, by the loss of population in those countries in which this practice exists. The boys, more numerous than the girls, during the early part of life, exposed afterwards, to the dangers of war, of navigation, and occupied in laborious occupations, lead a more laborious and anxious life, and die in greater numbers, so that the equilibrium is soon restored, and the least numerous portion of the human species, at the cradle, forms about two- thirds of it, in old age, since we always see more women than men reach a very advanced age. CCXIX. Of superf&tations. The cases of foetuses born with unequal degrees of developement, are not to be considered as superfoetations, but as twin cases. Thus, if in a case of twins, one foetus is of its full size, while the other is an embryo whose size does not exceed that of a fcetus in the first month; it does not follow that their conception look place at different and distinct periods, but merely that for some reason or other, one of the germs has been incapable of growth and developement. To settle the question of superfcetations, one should know whether a woman, with a single uterus, is capable of conceiving two months after \ effective copulation. Haller is of opinion, that the cervix of the uterus is always open to the semen; but how is the latter to reach the ovaria, through the adhesions of the chorion to the uterus ? It appears easier, where the two conceptions are separated by a short interval; thus, the , American woman mentioned by Buffon, who, in the course of one morning, had connexion with her husband and with a negro slave, bore two children of different colours. Hence, likewise, it sometimes happens, that one of two twins is, by its features, a living testimony of adultery. Two children, born with an interval of some months between their births, cannot be considered as twins, though they may have existed some time together within the mother's womb The possibility of such superfoeta- tions is well proved; they are ascribed to septa, dividing the uterus, some- times, into two cavities, merely because such an arrangement would explain^ to a certain degree, how two conceptions might take place, at some interval from one another; for it has never been ascertained, by actual dissection, that any woman, in whom such superfcetations took place, had a double uterus. CCXX. Of suckling. Nothing is more generally known, in physio- logy, than the strict sympathy which subsists between the uterus and mam- mae; a connexion, in consequence of which, these two organs are called into action at the same period of life, are evolved, and cease to perform their functions at the same time, when woman becomes incapable of co-ope- rating in the reproduction of the species. I shall not endeavour to account for this sympathy, by ascribing it to the influence of the nervous system, or to the anastomosis of the epigastric with the internal mammary arteries; an anastomosis which is not uniform, for, instead of inosculating with each other, these vessels frequently terminate in the recti muscles of the abdo- men. But even though this anastomosis should exist, as distinctly, as it is often met with in some subjects, it would not account for this sympathy, since the uterus and the mammae often receive no branches from the 3*3 -epigrasiic and manimary arteries, and when they do they are exceedingly small. The new born child, on being brought in contact with the breasts, applies his mouth to the nipple, and withdrawing his tongue, while, with his lips, he compresses the edges of the nipple, he draws in the fluid, whose flow is facilitated hy the erection of the lactiferous tubes. These ducts, from twelve to fifteen in number, not only become enlarged, when the nipple, which almost entirely consists of them, is elongated by being drawn out by the child, but, besides, being excited by his touch, they become affected with a certain degree of erection, and emit their fluid. This excretion, like that of other glands, is excited by the touch and the motion of the hands of the child on his nurse's breasts. The use of these gentle compressions, is not so much to express the milk mechanically, as to excite the organ to excretion. The irritation produced by the child on the nipple, is the most powerful exciting cause of the determination of milk into the breasts ; this irritation, or any other of the same kind, is sufficient to excite the secretion of milk, even under circumstances not provided for by Nature. It is thus that virgins have been enabled to suckle another mother's child; that young girls, under the age of puberty, have had so complete a secretion of milk, as to furnish a pretty considerable quantity of this fluid. There have been known men, in whom a long continued titillation of the breasts had deter- mined so considerable an afflux ofthe humours, that there oozed from them a whitish, milky, and saccharine fluid, not unlike the milk of a woman. The sucking of the new-born child, is necessary to keep up the secretion of milk in the mammae. It ceases to be formed in them, when the child is committed to the care ofa different nurse ; tbe mammae, at first turgid^ soon collapse, especially if care have been taken to determine the fluids downwards, by exhibiting gentle laxatives. The erection of the breasts, by titillation on the nipple, the spasmodic, and almost convulsive, action which follows this kind of excitement, may be carried so far as to produce an emission of the fluid to some distance. While its excretion lasts, women experience, in their breasts, an agreeable sensation ; these parts are tense and swollen ; they feel, as they express it the milk rising ; several feel a sensation of extension reaching to the axilla to the arms and chest. The whole mass of cellular substance, surrounding the breasts and extending to the neighbouring parts, partakes in their activity. The breasts, themselves, consist, in great measure, of cellular substance ; an adipose and lymphatic layer, of a certain thickness, covers the gland, which is divided into several lobes, and incloses it within its substances. They receive a number of nerves, but very few blood-vessels for their Their structure appears almost wholly lymphatic ; the vessels of this kind, after being distributed to the neighbouring glands, and especially to those of the axilla, penetrate into the breasts, in which their proportion, compared to that of the sanguineous vessels, is as eight to one. These lymphatic vessels, which enter in considerable, numbers into the compo- sition ofthe breasts, increase greatly in size in nurses ; and when injected in this condition, it has been ascertained, that several of them joined to form larger trunks, which, going towards the nipple, contributed in forming 37d what are called the lactiferous tubes. If the lympliutit vessels be 1mmp* diately continuous with the excretory ducts of the breasts, there is reason to believe, that it is these vessels which convey the materials of tbe fluid which they separate, especially if it be considered, how small the number of minute arteries which are distributed into their tissue, and what a disproportion there is between the calibre of these small vessels, and the quantity of blood which the breasts supply. The opinion that the lym- phatic vessels bring to the breasts the materials of the secretion of milk, is not in opposition to the laws of the circulation in the lymphatics ; all who are acquainted with these laws, know that the course of the lymph, though, in general, from the circumference to the centre, is naturally liable to a number of aberrations or deviations, facilitated by the number- less anastomoses of these vessels. CCXXI. The granulated structure is not as apparent in the breasts, as in the other glandular organs, hence they bear a greater resemblance to the lymphatic, than to the conglomerate glands. The milk which they secrete, has always been considered as very like the chyle, which it resembles in its white colour, its smell, and its saccharine taste. Like the chyle, it is the least animalized fluid, the sweetest, that on which the action of the organs produces the least effect, and that which preserves most the characteristic qualities of the food taken by the nurse. It is well known, that instead of giving medicines to infants at the breast, we most frequently administer the medicine to the nurse ; thus, the milk acquires purgative qualities, and acts on the boweis of the child., when the nurse has been purged.* The chyle is white and opaque, only in those animals which suckle their 3'oung ; in the others, it is as trans- parent as lymph. (Cuvier.) In the last place, if the arteries carried to the breasts the materials of their secretion, these vessels ought to increase in size, when these organs become twice, or even three or four times larger than natural; in the" same manner that, in open cancer, and in other similar affections, in which the determination of blood being increased, the calibre of the vessels is proportioned to them. Nothing, however, of the same kind occurs, what- ever size the breasts may acquire from the presence of milk ; their arteries preserve their almost capillary minuteness, as I had an oppor- tunity of ascertaining, by injecting the mamma? of a woman twenty-nine years of age, who died in the second month of suckling, and whose breasts were remarkable by their size, and by the quantity of milk they were able to secrete. Notwithstanding all these reasons, which have long made me adopt the opinion of the celebrated Haller, who considers the milk as immediately extracted from the chyle, I own that it must be considered as hypothetical, and resting solely on probability. The impossibility of demonstrating, anatomically, the branches going from the mesentery to the breasts, without communicating with the thoracic duct, gives still greater probability to the generally received opinion, which makes the milk, like all the other secreted fluids, with the exception of the bile, to be supplied by arterial blood.t * Tliis only takes place when such purgatives are used as are readily absorbed into the circulation. * The passage of injections from tbe arteries into the lactiferous tubes-., and tne cm The milk doe's not resemble chyle, in every respect, though it may be- considered as extracted from the food,* changed in its way to the mammae-, by the glands through which it has passed, and especially by the action of the organs themselves. This action is so evident, that, as Bordeu observes, <{ There are women who seem to have no milk in their breasts, which are flaccid and empty; but as soon as the child excites them, they become distended, and the milk comes spontaneously." It is well known, and the same author has pointed it out, that women, cows, and the females of other animals, allow themselves more willingly to be sucked by a suckling that knows how to excite their sensibility, and to apply due irritation to the nipple ; and that, on the contrary, they retain their milk, when the suckling does not excite the sensation in which they feel pleasure. It is thought, in some countries, that serpents know how to tickle the teats of cows, and that these animals enjoy this excitement, and allow themselves to be sucked "by these reptiles. CCXXII. Of the physical properties of milk, and of the oJiemical nature of this fluid. The quantity of milk is, in general, proportioned to that of the aliments, to the degree of their nutritious qualities, to their moist and farinaceous nature. Though it equals, in weight, about one- third of the quantity of food taken by the nurse, it may exceed that pro- portion, or may not come up to it. Its specific gravity, even when the milk is lightest, is greater than that of distilled water, and is always pro- portioned to its consistency. The latter quality is in an inferior degree, in woman, but is greater in the cow, the goat, the ass, and the ewe. Its fluidity is intermediate between that of aqueous and oily liquids, its colour, its smell and flavour have something very peculiar, and by which it is easily recognized ; in the last place, it is not exactly alike, at different periods of the same milking. This is proved by the work of .MM. Deyeux and Parmentier on milk, a work abounding in valuable observa- tions, and which may be considered as the complete history of this animal fluid. They observed, that the milk first drawn from the cow is serous, that its consistency gradually increases, and that the richest milk is that wbieh is obtained towards the end of milking, as if the fluid contained in the udder were affected by the laws of gravitation.! The milk, when exposed to the open air, in a vessel, beeomes de- composed, like the blood, and separates into three parts; the serum, the curd or cheesy part, and the fatty part or cream. The latter, which is lighter than the others, is always, on the surface, and its quantity depends, not only on the richness of the milk, but also on the extent ofthe surfaces by which it is in contact with the air; and this proves, as was first ob- served, by Fourcroy, that the oxygen of the atmosphere has some influence on its separation. The caseous part, which coagulates spontaneously, cumstance of blood having been drawn from an exhausted breast, when the child has been allowed to suck too long; and, lastly, analogy, leave no doubt of the true source of the fluid secreted by the mammae. * "Lac utilis alimenti est snperfluum." Gal. De Usu part. Lib. VII. Cap. XXII. t The author seems to forget that he is speaking ofthe cow, and that her udder hangs in a situation unfavourable to flits hypothesis.— 7'*™.'-. 37() appears albuminous, and abounds in oxygen. MM. Parmentier and Deyeu.1; consider it as the colouring matter of milk, and as giving to it its most characteristic properties. Lastly, the serum or whey, which alone con- stitutes the greatest part of this fluid, contains, besides a peculiar acid, (the lactic acid) which is formed when this substance is allowed to remain for some time, a saccharine matter, which may be obtained by evaporation, and which, when chrystallized in rhomboidal parallepipeds, constitutes the sugar of milk, whose purity depends on the degree of care with which the process has been carried on. This sugar of milk contains, as Scheie first ascertained, while endeavouring, by means ofthe nitric acid, to convert it into the oxalic, a peculiar acid, in the form of a powder, difficult of solu- tion, and to which he gave the name of saclactie acid. Milk may be con- sidered as one of the most compound of the animal fluids, whose qualities are very valuable, and whose parts have but an imperfect affiinity to each other. So that it is liable to spontaneous decomposition, and this takes place very easily. This kind of emulsion contains but a small quantity of azote, so that it retains its vegetable character. Hydrogen, carbon, and oxygen, predominate in milk ; in the last place, it contains several salts, amongst others, muriate of soda, muriate of potash, and phosphate of lime.* The presence of the two last of these substances leads to the following considerations. Muriate of potash, as is observed by Rouelle, does not exist in the blood; the probability is, therefore, that it is not the blood which supplies the mammae with the materials whence the milk is secreted, muri- ate of potash being found in greater quantity in milk than muriate of soda. These salts of potash, on the contrary, are found in considerable proportions in the chyle, formed from vegetable substances; which would lead one to think, that milk is furnished by the absorbent system. The phosphate of lime, which is found in smaller quantity in the urine of nurses, and which is wholly determined towards the mammae, was absolutely necessary in a fluid which supplies nourishment to the new being, while the bones become indurated, and all the parts acquire solidity. If we now wish to inquire into the causes which render suction neces- sary, and which subject the new born child to this peculiar mode of nutri- tion, these causes will be found in the general weakness of its organs. The organs of digestion would have been incapable of extracting, from the aliments, their nutritive parts,these substances not having undergone the due degree of trituration, from the want of teeth and from the imperfect state of the other organs of mastication. It was of consequence, therefore, that the mother should perform the preliminary function, and that she should transmit the aliment ready digested.! It is not, however, to be imagined, that the milk passes, without undergoing any change, into the vessels of the child; the child digests the milk, and obtains from it, in a short space of time, and without effort, a considerable quantity of nutritious particles, necessary to the rapidity of its growth. The connexion between the mother and child is far from being broken, at the period of birth; the relations between them, though not so close, are * See the Chapter, at the end of the Appendix, on the Chemical Constitution of the Secretions. ; Lac Ml tibus exactcconfecfut. Galenus De Usu partium Lib. VII, cap. XXU 377 not less indispensable. Before birth, the vital power was so limited in the child, that it was necessary it should receive a fluid already animalized, aad in a. state to yield to the function of assimilation and nutrition. When the child has breathed, when its strength is increased, it may be entrusted with a greater share of the process; it is then sufficient that the aliment should have undergone the first degree of elaboration, within the digestive canal. But it is not merely to assist in preparing its food, that tbe new born child requires the aid of the mother ; its lungs, which are delicate and imperfectly evolved, do not supply a due quantity of oxygen to tho blood which circulates through them ; the animal heat would be under what is required by the wants of life, if the mother did not make up for this defi- ciency, by transmitting some of her own warmth. She folds her infant gently to her bosom, warms it with her breath, and by this kind of maternal incubation continues to cherish it with that calorific influence to which it was fully exposed, while forming a part of herself. Besides, she feels for it, keeps it from danger, foresees its wants, and understands its language; and this very interesting intercourse takes place after the bonds of their physical communication are loosened, but it does not tear them asunder. The infantis, therefore, detached from the mother, only by degrees, since it is only in proportion as it grows older, that it acquires the means of living independent. Tbe seeretion of milk, in the breasts, may be prevented by irritation in the uterus. If the labour have been difficult, if the woman have suffered a certain degree of injury, the irritation in the parts so affected prevents the determination of the fluids towards the mammae. Hence these organs collapse, during the puerperal fever, not that the milk flows back into the humours and becomes the cause of the complaint, but that the inflamma- tion of the uterus prevents the fluids from flowing in their natural direction. During the first few days after delivery, the parietes of the uterus dis- charge a fluid, at first bloody,then of a reddish colour, and, in the last place, mucous and whitish, termed the lochia. CCXXIII. All the parts of the lungs arc not distended with air; in the first inspirations of the child, after birth. Some of the lobes, which are harder and more compact, take some time to admit this fluid, and even sometimes altogether reject it. A child died, twenty-one days after birth; the body was opened by Professor Boyer. On examining the lungs, he found that the posterior part of these organs was as hard and compact, as in the foetal state. Tbe anterior part alone was distended, contained air, could be felt to crepitate, and floated in water. The heart was examined, to ascertain whether its structure was connected with this condition of the lungs, which depended on the want of power in the respiratory functions. The foramen ovale was found pervious, so that the blood could pass from the right into the left cavities of the heart, without flowing through tho lungs. The child had been exceedingly languid during the whole of its Short life ; its skin was at times pale, at others livid. It was very difficult to keep it warm. The child of Madame L**** died nine days after birth, with the same appearances. I opened the chest, and found the upper part of both lungs indurated and compact; the foramen ovale was quite pervious. This aperture is often closed very imperfectly, so that there remains, at ths 48 378 upper patt of it, an opening, varying in size, which would enable a small quantity of venous blood to pass from the right into the left auricle, it these cavities did not contract at the same moment, and if the fluid which they contain did not present equal resistance on both sides. There are cases of persons in whom the foramen ovale remained pervious, and who, nevertheless, lived to a pretty advanced age. Their skin was purple and livid, all their moral and physical faculties feeble and torpid. It would be interesting to ascertain, by dissection, whether in good divers, who can remain a long while" under water, without breathing, the foramen ovale is not imperfectly closed. CHAPTER XL Containing the History of the Ages, the Temperaments, and the 1/arieties ofthe Human Species ; of Death, and Putrefaction. CCXXIV. Of infancy. The epidermis of the new-born babe thickens. the redness of the skin grows paler, the wrinkles are effaced, the soft down which covered the face, falls and disappears, the buttocks swell out and soon conceal the opening of the rectum. During the first months of life, it seems to need nothing but nourishment and sleep. In the mean while, the understanding is beginning to form, it looks fixedly at objects, and seeks to take cognizance of all the bodies that surround it. Confined, at first, to the uneasy sensations, which it expresses by almost continual tears, its existence becomes less painful, as it grows accustomed to the impressions of outward things upon its delicate organs. Towards the middle of the second month, it becomes, capable of agreeable sensations. If it feels them before that time, at least it is only then that it begins to express them by laughing.* CCXXV. Dentition. Towards the end of the seventh month,t the middle incisor teeth of the upper jaw, cut through the substance of the * At Hercules risus praecox ille et celerrimus, ante quadragesimum diem nulii datur. Kin. Hist. Nat. Praef. ad lib. VIII. t It would be very difficult to say, why a tertian fever often terminates of itself, when it has reached its seventh paroxysm, whilst a continued fever is judged of by critica' evaouations, in seven, fourteen, or twenty-one days; why delivery happens at the enn 6T nine months; why the first teething begins at seven months old,the second, at seven 379 gums i a litde while after, the corresponding incisors of the lower jaw show themselves: next, the lateral incisors of the upper jaw, those of the lower, then the cuspidati, in the same order. At the age between eighteen months and two years, the small molar teeth appear, but in reversed order, those of the lower preceding those of the upper jaw. When these molar teeth have come through, the first dentition is complete; the life of the child is more secure: it was before very uncertain, since the calculations of the probable-duration of human life show, that a third of the children born at any given time, die before the age of twenty-three months. Con- vulsions and diarrheas are the most fatal accidents attending difficult dentition. To these twenty teeth are added two new grinders in each jaw, when the child has reached the end of his fourth year. These last will afterwards bocome the first large grinders. They differ from those that precede them in this, that they are to remain all life long, whilst the primitive or milk teeth are lost at seven years old, in the same order in which they appeared, and are replaced by new teeth, better formed, and larger, excepting the small grinders, and with longer and more perfect roots. Towards the ninth year, two new large grinders appear beyond the others. The child has then twenty-eight teeth, and dentition is complete ; though between eighteen and thirty, and sometimes much later, the dentes sapientiae, two to each jaw, show themselves at the extremi- ties of the alveolar processes. The order observed in the successive cutting of the teeth is not so invariable, but it is frequently inverted. A child ten years old, now under my care, cut the four first small grinders before the canine teeth. Den- tition is, in this respect, like all other acts of the living economy : insta- bility is its principal character. An attentive examination soon shows how irregularly those phenomena proceed, whether physiological or patho- logical, which appear the most to be subjected to calculable and deter- minate periods.* This double range of successive teeth existed in the jaws of the fcetus. Each alveolar process, at that age of life, contains two membranous follicles, lying one over the other. That which is to form the primitive tooth swells the first, a calcareous matter covers its surface and forms the body of the tooth, which invades also the follicle by vvhich the osseous part is secreted, so that the growth of the little bone being completed, the membranous vesicle, in the parietes of which the dental vessels and nerves branch out, is found in the centre of its body, and adheres to the parietes of its internal cavity. It is difficult to say, why the growth of the dental germs is successive ; why, in the seventh year, the primitive teeth are years; why puberty shows itself, towards the fourteenth year, and menstruation is repeated at determinate periods. Nature appears to subject herself, in all her acts, to certain periods, which observation may ascertain, without any possibility of arriving at a knowledge of the causes of these phenomena so easy to establish. Because then: manifestation is correlative to certain numerical terms, we are not to put faith, like Pythagoras, in the power of numbers, and believe that the number 3 and the numbers 7 and 9 enslave all nature to their supreme influence. We find traces of this ancient error in all sciences, in all religions, even in those of enlightened nations.—>Author's Note. * See Erreurspopnlaire's, sec: edit: Chap. 4.chs Artnres ctimnttriqnes,et.des Jourscri' tildes dans les maladtes. 380 detached, and aie replaced by others which have remained so long buried within the alveolar processes. Dentition is like all the other phenomena of the living economy; it is subject to endless varieties in its period and duration, &c. Thus, teeth of a third set have been known to be cut in very old people. There are instances, but they are very scarce, of children that have come into the world with two incisors in the upper jaw*; there are often supernumerary teeth, &c. CCXXVI. Ossification. The process which goes on in the osseous system, is not confined to the cutting and growth of the little bones which are attached to the two jaws. All other parts of the skeleton harden; osseous nuclei are formed in the centre of the cartilages, which hold the place of the short bones of the carpus and tarsus ; the thickness of the cartilaginous substances, which separate the epiphyses of the bodies of the long bones, is diminished; the large bones grow, and acquire solidity, from the centre to the circumference. Those of the skull meet at their edges, their fibres cross and form the sutures ; the cartilaginous spaces, (fontanels) which were situated at the meeting of their edges and angles, disappear. The urine contains exceedingly little phosphate of lime, that salt being entirely taken up in the solidification of the bones. About the middle of the second year, these have already acquired substance and solidity enough to support the weight of the body ; the child can stand and walk. Before this time, it would be dangerous for him to try it: the pillars of support, yet too flexible, would yield under the burthen, and bend permanently in different directions. It is towards the head, that the vital motions tend in infancy : accordingly, this part is the principal seat of the affections peculiar to this age, affections in which it is often of use to procure local evacuations. The organs ofthe senses, open to all sorts of impressions, receive them with ease ; but if, in early infancy, sensation is easy, it is very transient: no doubt from the want of consistence in the cerebral organ. As it grows older, the mobility of the child is lessened, without diminution of suscep- tibility : and it is during the years that precede the boisterous season of puberty, that he enjoys, in the highest degree, the faculty of recalling things that have affected him, that his memory is most distinct and extended; but soon overpowered by imagination, roused up by the powerful re- action of the sexual organs on the brain, it ceases to have the same exactness, CCXXVII. Of puberty. Sex, climate, manner of life, have great in- fluence onthe earlier or later manifestation ofthe phenomena of puberty. Women reach it one or two years before men : the inhabitants of southern, long before those of northern countries. Thus, in the hottest climates of Africa, Asia, and America, girls arrive at puberty at ten, even at nine years old, but in France, not till twelve, fourteen, or fifteen: whilst in Sweden, Russia, and Denmark, the menstrual discharge, the most characteristic mark of puberty, is from two to three years later. • Louis XIV. was born in this condition. Baudexocque observes, that the evolution of some teeth, before birth, is not always connected with an extraordinary growth of the infant; nor is it always a presage of a stronger constitution. He endeavours to (•rove this by several examples: these, however, may be regarded as exceptions only rom the general, and, we think, correct opinion on the subject. For some remarks o"n the production of fhe teeth, sjjb Appendix, Note K. K. 381 The male is known to be capable of generation, and that he begins to live the life of the species, by the emission of prolific semen, and the change of voice, which becomes fuller, more grave, and sonorous: the chin becomes covered with beard, the genitals with hair, and they attain- rapidly their full size. The whole body grows: the general characters which distinguish the two sexes, and which are so obscure, before puberty, that they may often be mistaken, become very decided, and can no longer be confounded. By all these signs of strength and virility, woman, urged by desires which may be termed wants, recognizes the being capable of gratifying them. The change of voice is the most certain of the indications of male puberty. It depends, as tbe following observations show, on the develope- ment of the vocal organs, which constantly accompanies that of the sexual parts. CCXXVTII. A boy, aged fourteen, died in 1799 at the Hospital of la Charite. On opening the larynx, I was surprised to see it so small; and especially the glottis, which was not above five lines in its antero-posterior diameter, and about a line and a half in its transverse diameter, where its dimensions are greatest; an observation that must not be omitted, is, that he was very tall; but that the developement of the genital organs was as backward as of the vocal. I have repeated the same observation on sub- jects further from the age of puberty; I have extended my researches to those who had passed it, and I have obtained, as a general result, that between the larynx and the glottis of a child of three or of twelve, the difference of size is very inconsiderable, and cannot be estimated by the height of the figure :— That, at the epoch of puberty, the organ of the voice enlarges rapidly, and that, in less than a year, the opening of the glottis increases, in the proportion of five to ten, that its extent is thus doubled both in length and breadth. That these changes are less remarkable in women, whose glottis in* creases, in the proportion only of about five to seven: that in this respect they still resemble children, as the tone of their voices would Jead us to suppose. These differences, in the size of the glottis, account for tbe danger which, in children, accompanies the croup. For, suppose an opening of a line and a half in width, of which the edges are covered with a membrane of coagulaDle lymph, the opening will be entirely stopped: it would be only narrowed, if its width were double : a sufficient space would remain free from the passage of the air. This supposition, wbich I have employed to make myself understood, is only the expression of the truth, since anato- mical inspection shows that the glottis, in adults, is double the size it is before puberty. CCXXIX. Menstruation. The symptoms by which puberty is known, in women, are not less remarkable. The swelling of the genital organs straitens the opening of the canals that make part of them. The breasts become enlarged, and form, at the fore part of the thorax, marked projec- tions. Further, there comes on a discharge of blood, which takes place every month, from the vessels of the womb, and which is known by the name of the menstrual discharge, or menses. This periodical evacuation declares itself, in most women, by all the symptoms that indicate fulness of 332 blood, as spontaneous lassitude, heat, and flushings in the face; and by- others, which show the direction of the humours towards the uterus, and a local plethora of that organ, as pains in the kidneys, and a certain itching of the parts. The first eruption puts an end to this state; which, in many, may be considered as real disease. A pure red blood flows, in more or less abundance, for some days, the general heaviness goes off, and the woman feels herself relieved. I shall not now speak of the many deviations incident to the menstrual discharge, and which must be considered as real diseases. Thus, the uterine discharge has been known to be supplied, by bleeding from the nose, haemoptysis, melaena, and sometimes by unusual evacuations of blood from the eyes, ears, the fore-finger, from ulcerated surfaces over different parts of the body. It is easily conceived, that the different parts of the sanguineous system may supply each other's place, and that the bloody secretion, in which menstruation consists, failing on the internal surface of the uterus, may be carried on by another part equally provided with capillary vessels; but that similar deviations may take place for the fluids secreted by the conglome- rate glands, as urine, bile, saliva, is difficult to believe, notwithstanding the many testimonies and authorities that may be brought in support of this opinion. The fluids are not in existence, before the work of secretion; the urine, retained in the bladder and in the uterus, the bile stopped in the gall bladder and the hepatic ducts, after it has been prepared by the peculiar action of the liver, may, it is true, from absorption, by the lymphatic ves* sels, be carried into the blood, and produce there a diseased urinary or bilious diathesis; occasion an irritation and derangement, after which, the humour of the cutaneous perspiration, and of the sweat, and the saliva itself, will exhibit some of the qualities of the humour retained, and introdu- ced by the absorbents, into the circulation. The blood, contaminated by the admixture of a certain quantity of urine, may purify itself by various emunc- tories, by urinous vomitings and sweats; but that urine may, like the men- strual blood, come out at the eyes, the ears or the navel, except in case of urinary umbilical fistula; that one whose urinary discharge, by the urethra, is not interrupted, may spontaneously vomit it, is what no man, who has an}' sound notions of physiology, will believe; and yet it is related, with full details, in a late work, where these errors are found, in the midst of many interesting researches, on various points of physiological chemistry. I have seen myself the woman, whose urine has been so well analyzed by Dr. Nysten, when the clinical professor of medicine, at Paris, obliged ber to submit to a severe but necessary examination, and I am astonished that well informed men should so long have given credit to such gross impos- tures. The reader will, I hope, excuse this long digression, for the sake of its importance. Literary criticism is now carried on with such partial- ity, that no journalist, in praising justly what is praise-worthy in the valu- able work of Dr. Nysten, has pointed out the imposture of which he was the dupe. At first irregular, the menstrual discharge assumes regularity, is repeated every month, and lasts from two days to a week, with evacuation of from three ounces to a pound of blood, every time. Women of sanguine temperament, robust and libidinous, are those whose menses last longest, 383 and flow most copiously. The blood is arterial, red, and has not, in a healthy vVoman, any of the pernicious qualities which have been ascribed to it. During the whole time of menstruation, women are weaker, more delicate, more susceptible of impressions ; all their organs partake, more or less, in the affection of the uterus ; and it is not difficult to an observer, of any practice, to discern the state, not merely by the state of the pulse, but by the change of countenance and tone of the voice. Women then require very careful management. An improper blood-letting, a purge, or any other remedy untimely administered, may suppress the discharge, and occasion the most serious affections. Climate evidently influences the duration and quantity of the discharge, since in Africa, it flows almost continually, whilst in Lapland, it takes place only two or three times a year. I shall not dwell upon the different explanations thut have been given of this phenomenon. Some have ascribed it to the oblique position of the uterus, without considering, that upon their principle, menstruation should take place from the soles of the feet. Richard Mead believed that it depended on the influence of the moon over the female system; but why is it not then subjected to the lunar phases ? Those who have found the cause of it in plethora, general or local, if we admit their explanation, only changed the difficulty; for then, we must ask, what are the causes of this plethora? But, if this opinion had any ground, nervous women, with a small quantity of blood in their system, ought not to men- struate ; and yet they do so plentifully. Must we ascribe menstruation to an acquired habit ? Is the problem resolved, by saying that all the secretory organs of women are too weak to evacuate the superfluity of humours, which would require for them a new emunctory ? But is not this taking the effect for the cause ? Does not this smaller quantity of fluids, proceeding from the blood, arise from the purification which the blood undergoes in the uterus? Let it be remarked, in the mean time, that this periodical discharge seems to exempt the sex from many inconveniences, from which our's suffers ; such as gout, stone and gravel, so unfrequent with them, and so common with us. Nor can we avoid recognizing, in this discharge, a utility relative to con- ception ; does it not seem to dispose the uterus to that function ?* (CCIV.) Was it not requisite that this organ should be accustomed to receive a great quantity of blood, that pregnancy, which calls for this afflux, might not be injured, by bringing on a sudden change in the system, and the whole of the vital functions. Menstruation is suspended during pregnancy: it is so during the first month of suckling; though this rule admits of many exceptions. Its cessation, in our climate, is from the fortieth to the fiftieth year; some- times before, seldom later ; though I have now before me the instance of a woman of seventy, who has not yet ceased to menstruate; a fact, which, after all, is nothing more surprising, than that of menstruation beginning at an early period of life. When menstruation ceases, the breasts collapse, plumpness goes off, and the skin shrivels, and loses its softness, colour, * The greater part of the female quadropedshave the parts of generation bathed Jn a reddish lymph, during the time of being in heat. 384 and suppleness. This cessation is the cause of a great many diseases which break out, at this season of life, called the turn of life, and are fatal to many women ; but then, it is observed, that when this period is past, their life is more secure, with more hope of prolonging it than a man has, at the same age. CCXXX. Of manhood. To youth succeeds manhood : which may- be considered as beginning from the twenty-first to the twenty-fifth year. Then, all increase of the body, in height, is at an end. The processes are completely united to the body of the bones; but still, growth goes on in other dimensions. All the organs acquire remarkable hardness, solidity, and consistency. It is the same with the intellectual and moral faculties. To the empire of imagination, succeeds that of judgment. Man is capable of fulfilling all the duties of family and society. This period of life, to which we give the name of mature age, extends to the fiftieth or fifty-fifth year for men : it scarcely goes beyond the forty-fifth for women, with whom it begins also a little sooner. During this long interval, men enjoy the whole plentitude of their existence. Although, in general, it is not difficult to distinguish, at first sight, a man of twenty-five, from one of fifty, the differences which mark them, depending on the quantity and colour of their hair, and on their muscular strength, are neither many nor very essential. Let us avail ourselves of this age, during which the characters of the human speeies, merely sketched, in childhood and youth, take a more defined and lasting form, to trace the features of individuals and of races. CCXXXI. Of temperaments and idiosyncrasies. We give the name of temperaments to certain moral and physical differences in men, which depend on the various proportions and relations among tho parts that ma'ke up their organization, as well as upon different degrees, in the relative energy of certain organs. There is, besides, in each individual, a mode of existence which distinguishes his temperament from that of any other, to whom, however, he may bear great resemblance. We express by the term idiosyncrasy, these individual temperaments, the knowledge of which is of no small importance in the practice of medicine. The predominance of any particular system of organs, modifies the whole economy, impresses striking differences on the results or the organi- zation, and has no less influence on the moral and intellectual, than on the physical faculties. This predominance establishes the temperament; it is the cause, and constitutes its essence. If the heart and the vessels which carry the blood through every part, are of predominant activity, the pulse will be sharp, frequent, regular, the complexion ruddy, the countenance animated, the shape good, the forms softened though distinct, the flesh of tolerable consistence, moderate plump- ness, the hair fair and inclining to chesnut; the nervous susceptibility will be lively, and attended with rapid successibility, that is to say, that being easily affected by the impressions of outward objects, men of this temper- ament will pass rapidly from one idea to another; conception will be quick, memory prompt, the imagination lively; they will be addicted to the pleasures ofthe table and of love ; will enjoy a health seldom interrupted by disease; and all their diseases, and these slight, modified by the temper- ament, will have their seat principally in the circulatory system, (wflprn. 3&i matary fever, or angeiotejtique ; phlegmasia ; adite hemorrhage) and wjll terminate, when moderate, by the mere force of nature, and require the use of the remedies, called antiphlogistic, among which, bleeding is the chief. The aneients applied the name of sanguine to this disposition of body; they considered it as produced by the combination of warmth and moisture, and had very correctly perceived that it existed in the young of both sexes, was heightened by the spring, the season which has been justly compared to yonth, calling that age the spring time of life. That the specific characters of the temperament I have" just described. may show themselves, in all their truth, it is requisite that, the moderated developement of the lymphatic system, coincide with the energy of tbe sanguineous system, so that these two sets of vascular organs may he in true equipoise. The physical traits of this temperament are to be found in the statues of Antinous and the Apollo of Belvidere. Its moral phy- siognomy is drawn in the lives of Mark Antony and Aicibiades. In Bacchus are found both the forms and tbe character. But why seek amongst the illustrious men of antiquity, or among its gods, the model of the tempera> ment I have been describing, whilst it is so easy to find it among the moderns ? No one, in my opinion, exhibits a more perfect type of it than the Marshal Duke of Richelieu, that man, so amiable, fortunate and brave in war, light and inconstant, to the end of his long and brilliant career.* Inconstancy and levity are, in fact, the chief attribute of men of this temperament: excessive variety appears to be, to them, a necessity as much as an enjoyment; good, generous, feeling, quick, impassioned, deli- cate in love, but fickle, disgust in them follows close upon enjoyment: meditating desertion, in the midst of the most intoxicating caresses, they make their escape from beauty, at the very moment she thought to have bound them by indissoluble chains.t In vain he whom nature has endowed with a sanguine temperament, will think to renounce the pleasures of the senses, to take fixed and lasting likings, to attain, by profound meditation, to the most abstract truths; mastered by physical dispositions, he will be for ever driven back to the pleasures from which he flies, to the inconstancy which is bis lot; more fitted to the brilliant productions of wit, than the sublime conceptions of geuins.l His blood, which a vast lung impreg- * See his Memoirs, 6 vols. 8vo. Voltaire ha^s painted his character, with superior ability, in many vejsqs addressed to him. Rival da conqnerant de l'lnde, Tu bois, tu plais, tu combats, &a?. t The history of Henry IV. of Louis XIV. of ftegnerd, and of Mirabeau, prove? that, to the extreme love of pleasure, sangnine men join, when circumstances require it, gre&t elevation oMhought and character; and can bring into action the highest talents in every department. flhave just met, in a gazette, with an assertion, at least singular. All the world knows, says the journalist, that Newton was sanguine, and this proves clearly, he adds, that temperaments havo no influence on the intellectual powers. I wonld ask tbe journalist, where he has discovered that Newton was sanguine. The few details which biographers have preserved on the physical temperament of this illustrious philosopher, lead us to believe that his temperament was the melancholic, which is very frequently met with in England. I will not djre to pronounce absolutely, on subjects on which we can 38$ nates, plentifully, with atmospherical oxygen, flows freely in very dilatable canals, and this facility in the distribution and course of the humour is, at once, the cause and the image of the happy disposition of his mind. CCXXXII. If men of this temperament apply themselves, from circum- stances, to labours which greatly exert the organs of motion, the muscles, plentifully supplied with nourishment, and disposed to acquire a develope- ment proportioned to that of the sanguineous system, increases in bulk: the sanguineous temperament undergoes a great modification; and there results from it, the muscular or athletic temperament, conspicuous by all the outward signs of vigour and strength. The head is very small, the ueck sunk, especially backward, the shoulders broad, the chest large, the haunches solid, the intervals of the muscles deeply marked. The hands, the feet, the knees, all the articulations not covered by muscles, seem very small, the tendons are marked through the skin which covers them : the susceptibility is not great: feeling dull and difficult to rouse, the athletic surmounts all resistance, when he has broken from hii habitual tranquillity. The Farnese Hercules exhibits the model of the physical attributes of this particular constitution of body; and what fabu- lous antiquity relates of the exploits of this demi-god, gives us the idea of the moral dispositions that accompany it. In the history of his twelve labours, without calculation, without reflection, and as by instinct, we see bira courageous, because he is strong, seeking obstacles to conquer them, certain of overwhelming whatever resists him ; but joining to such strength so little subtlety, that he is cheated by all the kings he serves, and all the women he loves. It would be difficult to find, in history, the example of a man who has combined, with the physical powers which this tempera- ment implies, distinguished strength of the intellectual faculties. For excelling in the fine arts, and in the sciences, there is need of exquisite sensibility, a condition absolutely at variance with much developement of the muscular masses. CCXXXHI. If sensibility, which is vivid and easily excited, can dwell long upon one object: if the pulse is strong, hard, and frequent, the sub- cutaneous veins prominent, the skin of a brown, inclining towards yellow, the hair black, moderate fulness of flesh, but firm, the muscles marked, the forms harshly expressed ; the passions will be violent, the movements of the soul often abrupt and impetuous, the character firm and inflexible. Bold in the conception of a project, constant and indefatigable in its exe- cution, it is among men of this temperament we find those who in different ages have governed the destinies ofthe world : full of courage, of boldness, and activity, all have signalized themselves by great virtues or great crimes, have been the terror or admiration of the universe. Such were Alexander and Julius Caesar, Brutus, Mahomet, Charles XII. the Czar Peter, Cromwell, Sixtus V. Cardinal Richelieu. As love in the sanguine, ambition is in the bilious the governing passion. Observe a roan, who, born of an obscure family, long vegetates in the lower ranks: great shocks agitate and overthrow empires : at first a attain only a certain degree of probability; but, if Newton had been sanguine, he would not have carried his maidenhead with him to the grave at the age of fourscore as it is affirmed he did.—Author's Note. 387 secondary actor in these great revolutions which are to change his destiny the ambitious man hides his designs from all, and by degrees, raises himself to the sovereign power, employing, to preserve it, the same address with which he possessed himself of it. This is, in two words, the history of Cromwell, and of all usurpers.* To attain to results of such importance, the profoundest dissimulation, and the most obstinate constancy, are equally necessary; these are, further, the most eminent qualities of the bilious. No one ever combined them in higher perfection, than that famous Pope, who slowly travelling on towards the pontificate, went, for twenty years, stooping, and talking, for ever, of his approaching death, and who, at once, proudly rearing himself, cries out, " I am Pope !"t petrifying with astonishment and mortification, those whom his artifice had deceived into his party. Such too was Cardinal Richelieu, who raised himself to a rank so near to the highest, and was able to maintain himself in it: feared by a King whose authority he established, hated by the great, whose power he de- stroyed, haughty and implacable towards his enemies, ambitious of every sort of glory, &c.| The historians of the time inform us, that this celebrated minister showed all the customary signs of the bilious temperament. Gourville tells us that he was, all his life subject to a very troublesome haemorrhoidal discharge.^ This temperament is further characterized by the premature develope- ment of the moral faculties. Scarcely past their youth, the men I have named projected and carried into execution enterprizes which would have been sufficient for their fame. An excessive developement of the liver, a remarkable superabundance of the biliary juices, most commonly accompanying this constitution of body, in which the vascular sanguineous system enjoys the greatest energy, to the prejudice of the cellular and lymphatic system, the ancients gave it the name of bilious. The diseases to which those distinguished by it are subject, involve, in fact, either as their principal characteristic, or as accessary circumstances, or as com- plication, the derangement of the action of the hepatic organs, joined to changes of composition in the bile. Among the remedies directed against these sort of diseases, evacuants, and especially emetics, are the best. If all the characteristics assigned to the bilious temperament are carried to the highest degree of intensity, and to this state is added great susceptibility, men are irascible, impetuous, violent, on the slightest occasions. Such Homer describes Achilles, and some others of his heroes. ,■,,.. CCXXXIV. When, to the bilious temperament, is added disease*, ' Vie d'Olivier Cromwell, par Jeudy Dugour, 2 toIs. 18m which took place towards the thirty-second year of his age, on the ev© of a triumphal pomp which was prepared for him in the capitol. The author of the Provincial Letters, and of the Thoughts, enjoying, like Tass°j a premature celebrity, almost on quitting childhood, was led to melancholy, not like him by the crosses-- of unhappy love, but by a 3£9 violent and overpowering terror, which left, in his imagination, the sight of a galph for ever open at his side ; an illusion which left him only at hte death, eight years after the accident.* No one perhaps, has ever shown the melancholic temperament, in a higher degree of energy, than the philosopher of Geneva. To be con- vinced of it, it is enough to read, with attention, certain passages of his immortal works, and especially the two last parts of his confessions, and the Reveries in the solitary walker: tormented with continual distrusts and fears, his fruitful imagination represents to him all men as enemies. If you believe him, the whole human race is in league to do him mischief, " kings and nations have conspired together against the son of a poor watch-maker ;" children and invalids are brought in to execute these dread- ful plots. But let us leave him to speak for himself, the most eloquent and most unfortunate man of .the eighteenth century: " Here then I am, alone upon the earth, without brother, neighbour, friend, without society but myself; the most socfable and the most loving of men has been pro- scribed by them with unanimous consent." Further on he adds, " Could I believe that I should be held, without the smallest doubt, for a monster, a prisoner, an assassin, that I should become the horror of the human race, and the game of the rabble ; that all the salutation of those that passed -by me, would be to spit upon me; that a whole generation would amuse itself, with unanimous consent, in burying me alive?" It is idle to multiply quotations, in speaking of the works of a philosopher, who, in spite of his errors, will ever be the delight of all those who love to read and to think.t The history of J. J. Rousseau, like that of all the melancholies who have distinguished themselves in literature, shows us genius struggling with mis- fortune-; a strong soul lodged in a feeble body, at first gentle, affectionate, open and tender, soured by the sense of an unhappy condition, and of the injustice of men. Till the time when, impelled by the desire of fame, Rousseau sprang forward in the career of letters, we see him endowed with a sanguine temperament, acting with all the qualities belonging to it, gentle, loving, generous, feeling, though inconstant: his fertile imagination shows him nothing but gay images, and, in this illusion of happiness, he lives on agreeable chimeras; but gradually undeceived by the hard lessons of experience, afflicted, in the depth of his heart, with his own wretched- ness and the wrongs of his fellow-creatures, his bodily vigour wastes and decays, with it his moral nature changes, and he may be referred to as the most striking proof of the reciprocal influence of the moral on the physical, and the physical on the moral part of our being.f His history is a proof, * Blaise Pascal died at 39. See his life by Condorcet. t Consult the Studies of Nature, by Bernardin de Saint-Pierre; and the Letters on J. J. Rousseau, by Madame de Stael. t I have no doubt that the influence of the physical organization on the intellectual faculties is so decided, that we may regard as possible the solution of the following problem, analogous to that with which Condillac concludes his work on the origin of Ttelhyslcatman being given, to determ** the character ^^ g ** "V"**', r*-nvir-t'K. 39W beyond reply, that the melancholic temperament is less a peculiui constitution of the body than a real disease, of which the degrees may infinitely vary, from a mere originality of character, to the most decided mania. Gilbert arrived at Paris, with the germs of talents fitted for that great theatre. Poor and rebuffed by those on whom he had built his hopes, he mixed in the ranks of their detractors, and soon signalized himself, among the most formidable, by a vigour worthy of a better cause. Persecuted, without respite, by want; the mortifying sight ofthe happiness which his enemies enjoyed, and to which he believed himself called, led him into a state of perfect madness. He believed himself persecuted by the philoso- phers, who wanted to rob him of his papers: to save them from the ima- gined rapacity, he locked his manuscripts in a press, and swallowed the key. It stuck at the entrance of the larynx, stopped the passage of the air, and suffocated the patient, who died, at the Hotel-Dieu, after three days of the most cruel sufferings.* Zimmerman, early exhausted by study, already a physician of celebrity, at an early age, lived in solitude, with an ardent imagination joined to the highest susceptibility: abandoned to himself, devoured with the thirst of glory, he gave himself up to labour in excess, published his treatise on Experience, and the work on Solitude, so deeply imbued with the colour- ing of his soul. Forced from the solitude he loved, he carried, into the courts to which his reputation called him, an inexhaustible store of bitter- ness and sadness, which political events supervening brought to greater excess : arrived, at length, gradually at the last term of hypochondria, he died beset with pusillanimous fears, worthy of all eulogium and all regret.t The profound meditation ofthe work of Galen (quod animi mores corporis temperament* sequantur;) the perusal of Plutarch's Lives of Illustrious men, and ofthe other biogra- phers and historians of ancient and modern times; of the Eulogies of Fontenelle, Thomas, d'Alembert, Condorcet, Vicq-d'Ayzr, &.c. and tbe study ofthe medico-philoso- phical works of Haller, Cullen, Cabanis, Pinel, Halle who have modified and enriched the ancient doctrine of temperaments, will be of great avail in the search of this solution. «« Philosophy," cries an eloquent writer, in the noble enthusiasm which seizes him at the sight of the riches accumulated by Fontana, in the Anatomical Museum in Florence, " Philosophy has been in the wrong, not to descend more deeply into physical man; there it is that the moral man lies concealed ; the outward man is only the shell of the man within."—fDupaty, 33d Letter on Italy.—Author's Note. * His life would have been preserved, if the cause of his illness had been understood, which he indicated himself by repeating for ever " the key chokes me." His state of madness made this pass for the woids of a madman; but on opening the body, the key was found, of which the ward was fixed at the entrance of the larynx: it would have been easy to draw it out, by putting a finger down the throat. This unfortunate young man expressed, a few days before his death, the melancholy state of his soul, in stanzas most touchingly mournful: this is one, full of interest and simplicity: Au banquet de la vie infortune convive, Je apparus un jour, et je meurs ; Je meurs et sur ma tombe ou lentement j'arrive Nul ne viendra verser des pleurs. t See his Eulogium by Tissot; it is at the beginning of the last edition of the Trea- tise on Experience in viedicine. It there appears how deeply he was affected by the French revolution, of which he foresaw, with a sort of prophetic spirit, the disastrous con- sequences to hiso v»n country. 391 CCXXXV. If the proportion of the fluids to the solids is too great, this superabundance of the humours, which is constantly in favour of the lymphatic system, gives to the whole body considerable bulk, determined by the developement and repletion ofthe cellular tissue. The flesh is soft, the countenance pale, the hair fair, the pulse weak, slow, and soft, the forms rounded and without expression, all the vital actions more or less languid, the memory treacherous the attention not continuous. Men of this temperament, to which the ancients gave the name of pituitous, and which we should call lymphatic, because it depends really on the excessive developement of this system, have, in general, an insurmountable incli- nation to sloth, averse alike to labours of the mind and body : accordingly, we are not to wonder, if we find none of them among Plutarch's Illustrious Men. Little fitted for business, they have never exercised great empire over their fellow-creatures, they have never changed the face of the globe, by their negociations or their conquests. One of the friends of Cicero, Pomponius Atticus, whose history Cornelius Nepos has left us, conciliating to himself all the factions which tore the Roman republic to pieces, in the civil wars of Caesar and Pompey, may be given as the model of it.__ Among the moderns, the easy Michel Montaigne, all whose passions were so moderate, who reasoned on every thing, even on feeling, was truly pituitous. iiut, in him, the predominance of the lymphatic system was not carried so far, but that he joined to it a good deal of nervous suscepti- bility. In the pituitous, from the excess of watery particles in the fluid which should, carry every where heat and life, the circulation goes on slowly, the imagination is weak, the passions languid ; and, from this moderation of the desires, spring, on many occasions, those virtues of tem- perament, which, to say it, by the bye, should not supply their possessors with matter of quite so much self-complacency. CCXXXVI. This property by which we are, more or less, sensible to impressions on our organs, weak in the pituitous, almost nothing in athletes, moderate in those of sanguine temperament, rather quick in the i bilious, constitutes, by its excess, nervous temperament;—seldom natural or primitive, but commonly acquired, and depending on a sedentary and too inactive life, on habitual indulgence in sensuality, on the morbid action of the brain promoted by reading works of imagination, &c. This tem- perament shows itself in the emaciation, in the smallness of the muscles, soft, and, as it were, in an atrophy, in the vivacity of the sensations, in the suddenness and mutability of tbe determinations and judgments.__■ Nervous women, whose wills are absolute but changeable, with excess of sensibility, frequently exhibit it with all these characteristics. Often,, however, tbey have something of good looks, the extreme preponderance of the nervous system still allowing a moderate developement of the lymphatic. Spasmodic affections are not uncommon among them ; and when it is observed that, on the other hand, the athletic constitution. directly opposite to the nervous temperament, predisposes to tetanus, may we not say, that the two extremes meet, or produce the same effects ? Anti-spasmodics are employed, with success, in the treatment of their diseases, which partake always, more or less, of the temperament. Stimu- lants, on the contrary, are very suitable to those of a pituitous or lymphatic temperament. The nervous temperament, like the melancholic, i» not so much a natural constitution of the body, as the first, stage of a disease. 392 This temperament, like the nervous affections which are the result of it, has never shown itself but among societies brought to that state of civili- zation, in which man is the farthest possible from nature. The Roman ladies became subject to nervous affections, only in consequence of those depraved manners which marked the decline ofthe Empire. These affec- tions were extremely common in France, during the eighteenth century, and in the times preceding the fall of the monarchy. Of that epoch, are the works of Wytt, Raulin, Lorry, Pomme, &c. on nervous affections.— Tronchin, a Genevese physician, acquired great wealth and reputation by the treatment of these diseases. His whole secret consisted in exercising to fatigue, women habitually inactive, keeping up their strength, at the same time, by simple, healthy, and plentiful food. The two most remark- able men of the eighteenth century, Voltaire and the great Frederick, may be given as instances of the nervous temperament; and the history of their brilliant and agitated life, shows, sufficiently, how much the cir- cumstances in which they lived, contributed to develope their native dispositions. I shall finish this article on temperaments by observing, that in truth, we bring with us into the world these particular dispositions of body: but that from education, manner of life, climate, acquired habits, they are altered, or altogether changed. Further, it is exceedingly rare to find individuals, who show, in their purity, the characters assigned to tbe diffe- rent temperaments : the descriptions given are drawn from an assemblage of individuals, much resembling one another. Their characters are pure abstractions, which it is difficult to realize, because all men are at once sanguine and bilious, sanguine and lymphatic, &c. In this instance, phy- siologists have imitated the artist, who united in the image of the goddess of beauty, a thousand perfections which he saw separate in the most beau- tiful women of Greece.* It is an observation that the sanguine constitution is directly opposed to the melancholic, and never combines with it; that it is the same with the bilious and lymphatic: though it may happen that a man sanguine in youth, shall become melancholic after a lapse of time; for, as I have said before, man never remains such as he came from the hands of Nature; fashioned by all that surrounds him, his physical qualities, at different periods of his life, are as much changed as his character. Of all the causes that can modify the nature of man, and which will even change completely the nature of his native dispositions, there is none more powerful than the long continued action of air, water, and residence, as the father of medicine has said. Climate, in fact, exerts upon the tempe- rament the most marked influence. Thus, the bilious temperament is that of the greater part of the inhabitants of southern countries ; the sanguine* that of the north; the lymphatic constitution reigns, on the contrary, in cold and moist countries, like Holland. We have seen in what manner the athletic, melancholic, and nervous temperament grows out of our habits of life: let us now endeavour to appreciate the power of climate over the constitution of the greater part of mankind. It is known, that the influence of beat, in the production of bilious ^ * Itis thus that, in the arts of imitation, the ideal grows up; now, from the exaggera- tion of features, now? from the union of qi&litres which Nature has produced EcnarSjp. 393 disease's, is such, that after having been extremely prevalent, during the summer, they disappear, or at least becomo much less frequent, in the autumn. A notable increase of perspiration never takes place, without a proportional diminution in the quantity of the liquids with which the alimentary surfaces- are moistened. Now, when the gas- tric juice is less abundant, the bile, being mixed with a smaller quan- tity of serosities, irritates more the intestinal surfaces', the diges- tive powers languish, and there is an appro idling disposition to meningo- gastric fevers. The same influences, continued during the whole year in hot countries, must necessarily increase, with the activity of the biliary system, its power over the other parts of the economy, and thus establish a predominance of the bilious constitution, through both health and disease. As for the sanguine temperament, so generally met with among north- ern nations, it is the necessary consequence of the continual and very energetic re-action of the powers of circulation, against the effects of external cold. It is only by the constant activity of the heart and ves- sels, that calorification can he effected with the necessary vigour. Now, the effects of this redoubled action are the same to the organs of circu- lation, as to the muscles under the influence of volition: in both, exertion increases the power of the organs exerted. The diseases of the nations of the north, analagous to their temperament, have, for the most part, their seat in the system of sanguineous vessels: their character is eminently inflammatory. Lastly, the lymphatic state of nations, living under a moist climate, is nothing more surprising than the aqueous nature of plants, and small density of the wood, in trees growing under the influence of a foggy air. Animal bodies, like plants, absorb by their surfaces, and become gorged with humours, the excess of which always produces a remarkable Slackening of activity in the organic motions. The temperament of which the character is the predominance of one organ or system of organs, departs from that ideal state, where all the powers are reciprocally balanced, so as to exhibit in the living economy a perfect equilibrium. This state, which has perhaps never been found but in the imaginations of physiologists, and which was called by the ancients the temperate temperament, temperamentum- temperatum, being taken as the type of health, it follows that this temperament is already a step made towards disease. Yet the action of the predominant sj'stem is not in such excess as to destroy all equi- librium, and impede the action of life; but let the constitutional dis- „ positions be much increased, the disease is begun, and this transition takes place in the conversion of the lymphatic temperament into scro- phula.* In the scrophulous constitution, there is, at once, activity of the absorbing mouths, great facility of absorption, inertness of the vessels and lymphatic glands, weakness of the absorbents, and consequently * See Nosographie Chirurgicale, tome I. for the history of scrophulous ulcers* from which this paragraph is taken entire. The author, in that wOrk, has aimed at introducing physiology into surgery, till then esclusively abandoned to explanations ofthe grossest mechanism, 50 3i*f a thickening and stagnation of the liquids absorbed. The same thing is seen in the lymphatic temperament, characterized by the activity of the inhaling mouths, and the debility of the lymphatic system, as Pro- fessor Cabanis was aware,* when he refuted the opinion of those who ascribe the lymphatic temperament to the excess of activity in the absorbent system, though the only part of this system really quickened, is that which immediately performs absorption, whilst the rest is in a state of perfect atony. CCXXXVH. Varieties of the human species. The power of pro- ducing, by copulation, individuals which are alike, is considered by na- turalists as the most certain test for fixing the species in red and warm-blooded animals. This power of self-perpetuation, by a con- stant succession of similar beings, is found in all the races composing the human species, however different in colour, structure, and manner of life. Men, then, are but one species, and the difference that appears in them, according to the region of the globe they inhabit, can only constitute varieties or races. I admit, with M. Lacepede, the worthy continuator of Buffon, four principal races of the human species, which I shall call, like him, the European Arab, the Mogul, the Negro, and the Hyperborean. We might add a fifth, ofthe American, were it not most probable, that the new Continent is peopled by inhabitants, who, coming from the old, either by land in the austral hemisphere, or along the immense Archipelago of the Pacific Ocean, have been altered by the influence of that climate, and the yet virgin soil, so that they are to be regarded less as a distinct race than a simple variety.t There is, in truth, this difference between varieties and races, that, in these last, there are implied modifications more profound, more essential differences, changes not confined to the surface, but extending to the very structure of the body ; whereas, to make a variety, nothing more is needed, than the superficial influence of climate on the integuments which it colours, and on the hairs which it makes longer or shorter, lank or curled, hard or soft. An Abyssinian, scorched by the heat of an almost tropical sky, is as black as the negro under the equator ; yet they are by no means of one race, since the Abyssinian, a negro only in colour, resembles the European in the cast of his face, and the proportions of all his parts. The characteristics of the European Arab race, which takes in the inhabitants, not of Europe only, but of Egypt also, Arabia, Syria, Barbary, and Ethiopia, are an oval, or almost oval face, in the vertical direction, a long nose, a prominent skull, long and commonly lank hair, a skin more or less white. These fundamental characteristics are no where more decided than in the north of Europe. The inha- bitants of Sweden, Finland, and Poland, give the prototype of the race : their stature is tall, their skin of perfect whiteness, their hair long, lank, and of a light colour ; the colour of the iris generally bluish. * Of the relations of the physical and moral man, by G. Cabanis, Senator, Professor in the School of Medicine in Paris, &c. J See APPENDIX, Note L L 39/] The Russians, the English, the Danes, the Germans, are already 1 -n- moved somewhat from this primordial type : the colour of their skin is of less pure white, their hair of a deeper hue. The French seem to stand midway betwixt the nations of the north, and those of the south of Europe. Their skin is shaded with a deeper dye, their hair less straight, and more ofa chesnut and brown colour. The Spaniards, the Italians, the Greeks, the European Turks, and the Portuguese, are browner, their hair in general black. Lastly, the Arabs, the Moors, and the Abyssinians have hair, in some measure, black and crisp, the skin tawny, and might serve for the step from the European Arab to the Negro race; which is, however, distinguished from them by the flattening of the forehead, the smallness of the skull, the slope of the line measuring the heigtht of the face, the thickness of the lips, the projection of the malar bones, and further, by a darker skin, thicker, greasy, and, as it were, oily, as well as by shorter, finer, curly, and woolly hair. The Mogul race has the forehead flat, the skull jutting but little, the eyes looking rather obliquely outwards; the cheeks are prominent, and the oval of the face, instead of extending from the forehead to the chin, is drawn between the two malar bones. The Chinese, the Tartars, the inhabitants of the Peninsula, of the Ganges, and of the other countries of India, of Tonquin, Cochin-china, Japan, of the kingdom of Siam, &c. compose this race, which is more numerous than all the others, and apparently more ancient also, which is spread over a greater extent of surface than the European Arab race, and yet greater than the Negro race, since it reaches from the fortieth to the sixtieth parallel of latitude, occupying an arc of the meridian of nearly 75", whilst that which measures the countries of the European race is only of 50°, and the Negro race lying under the equator, be- tween the tropics of Cancer and of Capricorn, is bounded within the limits of an arc of from 30° to 35°.* The Hyperborean race, situated in the north of the two continents, in the neighbourhood of the polar circles, composed of the Laplanders. the Ostiaks, the Samoiedes, and the Greenlanders, is characterized by a flat face, a squat body, and a very short stature. This degraded portion of the human species derives, evidently, from the climate, its distinctive characteristics. Striving for ever with the inclemency of a severe climate, the destructive action of an icy temperature, Na- ture, fettered in her motions, shrunk in her dimensions, can produce only beings whose physical imperfections explain their almost bar- barous condition. The small progress of the negroes in the study of the sciences, and in civilization, their decided taste, and singular aptitude for all the arts which require more taste and dexterity than understanding and re- flection, as dancing, music, fencing, &c. the figure of the head, which is midway between that of the European and the ourangoutang.t * Lacepede, Geographic Zoologique. f The black colour ofthe skin in the negroes seems owing, as I have already said, 396 tbe existence of the intermaxillary bones, at an age when, with us. *he traces of their separation are completely effaced ; the high situ- ation and small developement of the c;ilf of the leg, have been arguments more specious than solid to those who have endeavoured to abase this portion of the human species, in order to justify an ini- quitous traffic, and a cruel tyranny; reproaches of civilized men, which they must wipe off by ether means than a presumptuous assertion of their own dignity, or a pround insult on the native character of those whom they themselves have cast into degradation. ^ Without admitting this belief, which owes its origin to a thirst of riches, we cannot help acknowledging that the differences of organi- zation draw after them a striking inequality in the developement of the moral and intellectual faculties. This truth would appear in its full light, if, after summarily indicating, as I have just done,the phy- sical characteristics of the races of men, I could unfold their moral differences as real, and not less marked : opposing the activity, the ver- satility, the restlessness of the European, to the indolence, the phlegm, the patience of the Asiatic, examining what is the power, or the character of nations, the fertility of soil, serenity of sky, mildness of climate ; showing by what catenation of physical and moral causes, the empire of custom is so powerful over the people of the east, that we find in India and China the same laws, manners, and religion, which prevailed there long before our era; inquiring by what singularity, well worthy the meditation of philosophers and politicians, these laws, this worship, and these manners have undergone no change, amidst the revolutions which have so often taken place among those nations many times conquered by the warlike Tartars ; showing how, by the irresistible ascendency of wisdom and knowledge, ignorant and fero- cious conquerors have adopted the usages of the nations they have subjugated; and proving that the stationary condition of the sciences and arts among those who, so long before ourselves, were in posses- sion of the advantages of civilized society, is derived not so much from the imperfection of their organization, as from the degrading yoke of a religion loaded with absurd practices, and which makes knowledge the exclusive birthright of a privileged cast.* But such an under- to (he scorching of tbe gelatine, which is the base ofthe rete mucosum of Malpighi. This colour, acquired in a long succession of ages, perpetuated and transmitted by generation, is become one of the characteristic features of the Negro race. M. Volney, in a work which should be a model to all travellers, grounds on the face of the blacks, a conjecture as ingenious as it is probable. He observes, that it exhibits precisely that state of contraction which our face takes when it is struck by light, and a strong reverberation of beat; then, says this philosophical traveller, the brow contracts, the cheek-bones rise, the eye-lids contract, and the lips project. Must not this contraction of the moveable part have influenced, in course of time, the hard parts, and even moulded the structure of the bones? Voyage en Syrie ct en Egypt, torn. I. p. 70. Sieme Edition.—Author's Note. * We must assign further as a main cause of the want of progress of the Indians and Chinese,in the arts and sciences,spmng from civilization, the imperfection of their alphabet, which, being composed of a multitude of characters, which do not, like ours, represent sounds, but ideas. It belongs not to our subject to show, how much sjgns 90 defective must confine the sphere, and fetter the combinations of the mind. AT, raking, besides exceeding the limits I have prescribed myself, does not belong directly to my subject. The Albinocs of Africa, the Cagots of the Pyrenees, and the Cre- tins of the Valais, cannot but be given as varieties of the human species. They are infirm, feeble, degraded beings, incapable of re- producing an existence, which has fallen to them, in the midst of a healthy, vigorous, and robust population. We are not to believe what some travellers have written on the ex- istence of tribes of giants, that have appeared on the Magellanic coast. The Patagonians, concerning whose stature there is so little agreement in relations, are men very well formed, and whose stature does not ex- ceed ours more than nine or ten inches. The Laplanders, whose stature is the smallest, are as much below, as the Patagonians are above; it does not exceed from four feet to four and a half. In the midst of ourselves, individuals reach from time to time, a stature suffi- cient to entitle them to the name of giants, whilst others, shrunk in all their proportions, are a renewal of the pygmies. Such was Bebe, the dwarf of Stanislaus, king of Poland ; Goliah, spoken of in the book of Kings, chap. xvii. v. 4 ; the king Og, Deut. chap. iii. v. 2 ; and many others, whose stature varies from six to ten feet high. CCXXXVIII. Of old age and decrepitude. The human body, which, from the twentieth year of life, ceases to grow in height, in- creases in every dimension during the twenty succeeding years. After this period, far from growing, it begins to decay, and loses daily a part of its strength. The decay proceeds at the same rate as the growth, and is not more rapid, since man requires from thirty to forty years in reaching to his full growth, and takes about the same time in his progress to the grave, provided no accident hurries him to an un- timely end.* The whole bulk of the body diminishes,t the cellular See, concerning the religion of the Bramins, and the Indian customs, Raynal's Philosophical History, the Asiatic Researches; Institutes of Menu; Edin. Review, I xxxii.; Ward's View of the History of the Hindoos: Halked's Code of Gentoo Laws; Colebrook's Digest of Hindoo Law. * The duration of life may be estimated by that of the growth. A dog ceases to grow at the end of two or three years, and lives only ten or twelve; man, whose growth requires a space of from twenty to thirty years, attains to the age of ninety or a hundred. Fishes live several centuries, theii developement requiring a conside- rable number of years—Author's Note. t The diminution ofthe entire bulk of the body of aged persons frequently gives place to an augmentation of size, espee)ally of the trunk of the body. This is en. tirely owing to the increased deposit of fat, which often supervenes at this age, and which appears to depend on the energy of the system being insufficient to the com- plete assimilation of the nutritive materials, and on the slow circulation of the blood in the capillary vessels, which state of the circulation seems to give rise to the predominance of hydrogen and carbon in the blood which these vessels and the veins contain. The abundance of these elements in the extreme vessels being the sonrce whence the fat is so largely formed, the combination of them into that parti- cular substance is the result of the same state of the vital energies which favours their predomin&fece. 'JElie increase of bulk, owing to this augmentation of the se- cretion of fat, in person! advanced in life, is far from being favourable to the free exercise of the various functions; for certain organs being incommoded with the weight and bulk which thev thus acqnire, are still farther embarrassed in their ox- 398 {issue becomes collapsed, and the skin wrinkled, especially thai of the forehead and face. The hairs of the head and over the rest of the body turns grey, then white; the organic action becomes languid; the fluids become more disposed to putrefaction (Hunter;) hence, at this period of life, all diseases of debility' are more frequent, and attended with greater danger. Decay succeeds old age. The sensibility of the organs is blunted ; the physical and intellectual faculties undergo a gradual decay; man ceases to be impressed, in the same manner, by surrounding bodies. His judgments are incorrect, because self-love preventing him from being aware of the changes which he has undergone, he is more dis- posed to ascribe to an universal degeneracy, the difference which exists between the sensations which he now experiences, and those which he experienced in his youth, (laudator temporis acti.) The di- gestion is bad, the pulse weak and slow ; the absorption difficult, from the almost complete obliteration of the lymphatics and the induration of the conglobate glands; the languid secretion and imperfect nutri- tion. The old man is slow in all his actions, and stiff in all his mo- tions; his hair falls off, his teeth drop from their sockets; the cartilages ossify; the bones grow irregularly and become anchylosed, their in- ternal cavity enlarges; all the organs become indurated, and the fibres dried and shrivelled. The bones become heavier, from the gradual accumulation of phosphate of lime, and if those of the skull, as is justly observed by Soemmering, on the contrary, become lighter, it is that they arc, in a manner, worn out by the continued motions of the brain on their internal surface. The ossification of some of the cartilages, for example, those of the ribs and vertebrae, is productive of remarkable effects. The ribs be- coming soldered, in a manner, to the sternum, perform very imper- fectly their natural motion of elevation and twisting, (LXXI.) which produces the enlargement of the chest. This cavity dilating less fully, the pulmonary combinations, which are the abundant sources of animal heat, take place in a less effectual manner, which, joined to a want of tone and energy in the lungs, and in all the organs, lowers the tempe- rature of old people, as was observed by the father of physic,* a circumstance, however, which has been denied by Dehaen. Those fibro-cartilaginous laminae, with oblique fibres crossing each other, which unite so firmly the bodies of the vertebrae, become indu* rated, dried, and shrivelled, sink under the weight of the body, and do not recover their former thickness, so that the stature is really reduced ; besides, the weakened condition of the muscles which raise the trunk, makes the weight of the viscera bend forward the vertebral column, whose different parts may remain fixed in this attitude, so that the whole ganic movements, the circulation in the extreme vessels is rendered still slower, and thus the cause ofthe increased secretion of fat goes on increasing. This sufficiently accounts for the fact, that, in general, leanness is at an advanced age more favoura- ble to long life, than the opposite state. j«l # i» IP * Senibus autem modicus est calor * * * * frigidum est enim ipsornm corpus. Hippocr. Aph. 14. beet. 2. 399 column, consisting of twenty-four vertebrae, may come to consist of only seven or eight distinct bones. It should not be imagined, how- ever, that all the soft parts become more compact, for several, as Haller observes, the muscles, for instance, become softer,* and seem, in losing a part of their vital properties, to draw towards a speedy dissolution ; not that death is entirely owing to the accumulation of phosphate of lime, which enters into the composition of all the organs, converts into ossific matter the whole osseous system, and interrupts the action of the animal machine. If this ossific matter invade every part of the animal system, it is because the digestive powers, gradually weak- ened, cease to affect, in a suitable manner, the alimentary substances. The exuberance of calcareous salts, is, therefore, not so much the cause as the effect of the successive destruction of the vital powers. The slowness, the rigidity, and the difficulty of moving, do not depend so much as is thought, on the induration of the ligaments and other fibrous organs: these ligaments become softened and relaxed to a considerable degree, so that laxation is more easily performed, after death, in old people. In them likewise, organs, which, in youth, have a degree of consistency, become flaccid and soft: this is the case with the heart, which becomes collapsed in old people, its cavities remaining entire, while in young persons, and in adults, their parietes are not in close contact. The brain becomes harder and firmer, less soluble in alkalies : its albumen appears more completely oxydized than in younger subjects: impressions are less easily made, and the motions necessary to the operations of the understanding are performed with difficulty. Hence, in decrepitude, man returns, as far as relates to his intellectual faculties, to a state of second childhood, limited to certain recollections, which are at first confused, and, in the end, completely lost, incapable of judgment or will, or of new impressions ; sleep resumes its influence; reduced to a mere vegetative existence, he sleeps the greatest part of the day, and wakens only to satisfy his physical wants, and to take food, which he digests very imperfectly; for, in the first place, the want of teeth prevents his being able to divide sufficiently the different substances, and in the next place, the supply of saliva, of gastric and intestinal juices, is almost interrupted ; the bile and other fluids are less active, and the intestinal tube is without energy. Universal rigidity will be admitted as one of the principal causes of death, if it be consi- dered that women, in whom the organs are naturally softer, are longer in reaching that state, are more retentive of life than men, and generally live to a greater age. The body, therefore, dies slowly, and by degrees, says the eloquent M. De Buffon ; life gradually becomes extinguished, and death is but the last term of this series of degrees, the last shade (nuance) of life. CCXXXIX. Of death. Long, in fact, before the close of life, * Non ergo in sola rigiditate causam senii mortis oportet ponere; nam ex defectu irritabilitatis, plurimi in senibus musculi languent, mollesque pendent Elementa Physiol, torn. VIII, 4to. lib. 30 4UU man loses the power of reproduction; and, in the course of thcf agony which serves as a passage between life and death, the organs of sense first become insensible to all sorts of impressions ; the eyes grow dim, the cornea fades, the eye-lids close, the voice becomes extinct, the limbs and the trunk motionless ; yet the circulation and respiration continue to be carried on, but at last cease, first in the vessels farthest from the heart, and then gradually in the vessels nearest that organ. Respiration, gradually slackened, being entirely suspended after a strong expiration,* the lungs no longer transmit the blood which the veins bring from every quarter to the heart. This fluid stagnates in the right cavities of the heart, and these die last, (ultimum moriens) and dis- tended by the blood which collects within them, they attain a capacity- exceeding greatly that ofthe left cavities, which are, to a certain degree, emptied. Such is the course of natural death ; the brain ceases to receive from the weakened heart, a sufficient quantity of blood to keep up sensibility; there remains still some degree of contractility in the respiratory mus- cles ; it is soon exhausted, however, and the circulatory motion of the blood ceases with the life of all the organs, of which this fluid is one of the principal movers. As to accidental death, it is always determined by the cessation of the action of the heart and brain ; for, the death of the lungs occa- sions that of the whole body, only by preventing the action of the heart, by interrupting its influence on the encephalic organ. In natural death, therefore, life becomes extinguished, from the circumference to the centre; in accidental death, on the contrary, the centre is affected before the extremities. Bichat, in his work entitled, Rccherches sur la vie et la mort, has given a very complete account of the manner in which the organs of the animal economy cease to act in articulo mortis; but like all the authors who went before him, he has limited his inquiries to certain functions. No one has attempted to extend them to the phenomena of the aetion of the brain, nor has any one traced the order in which the various faculties of thought and of sensation vanish. I shall endea- vour faithfully to mention the results of several hundred observations of my own on this subject. The close of life is marked by phenomena similar to those with which it began. The circulation first manifested itself, and ceases last. The right auricle is the part first seen to pulsate in the embryo, and in death is the last to retain its motion. The phenomena of nu- trition, to which the foetal existence is almost entirely limited, continue, even when the organs destined to establish a relation with the beings that surround us, have long been sunk into a slumber from which they are never to be roused. The following is the order in which the intellectual faculties cease * Does this last and powerful expiration, often attended by sighing, depend on the spasmodic contraction ofthe muscles of expiration ; or rather does it not depend on the re-action ofthe elastic parts which form the chest, a re-action which suddenly ceases to be counterbalanced by the vital properties * 401 and are decomposed.* Reason, the exclusive attribute of man, firs? forsakes him. He begins by losing the faculty of associating judg- ments, and then of comparing, of bringing together, and of connecting, a number of ideas, so as to judge of their relations. The patient fs then said to have lost his consciousness, or to be delirious. This de- lirium has generally for its subject the ideas that are most familiar to the patient, and his prevailing passion is easily recognized. The raiser talks, in the most indiscreet manner, of his hidden treasures, the un- believer dies haunted by religious apprehensions. Sweet recollections of a distant native land, then it is that ye return with your all powerful energy and delight! ! After reasoning and judgment, the faculty of associating ideas is next completely destroyed. The same occurs in fainting, as I once experienced in myself: I was conversing with one of my friends, when I experienced an insuperable difficulty in associating two ideas, frpm the comparison of which I wished to form a judgment. Yet syn- cope was not complete, I still preserved memory and the faculty of feeling. I could distinctly hear those about me say, he is fainting, and exert themselves to relieve me from this condition, which was not without enjoyment. The memory then fails. The patient who, during the early part of his delirium, recognized the persons about him, no longer knows his nearest and most intimate friends. At last, he ceases to feel, but his senses vanish in succession and in a determinate order; the taste and smell cease to give any sign of existence; the eyes become obscured by a dark and gloomy cloud ; the ear is yet sensible to sound and noise, and no doubt it was, on this account, that the ancients, to ascertain that death had really taken place, were in the habit of calling loudly to the deceased. A dying man, though no longer capable ©f smelling, tasting, hearing, and seeing, still retains the sense of touch : he tosses about in his bed, moves his arms in various directions, and is perpetually changing his posture : he performs, as was already said, motions similar to those of the fcetus, within the mother's womb. CCXL. Of the period of death. This period is nearly the same with all men, whether they live near the poles, or under the equator, whethe r they live exclusively on animal or vegetable substances, whe- ther they lead an aetive life, or consume their existence in disgraceful sloth, few live beyond a hundred years. There are, however, eases of men who have lived far beyond that period, as, for example, those mentioned in the Philosophical Transactions, one of whom lived to a hundred and sixty-five. Few men, however, attain a hundred years, and death even when natural, overtakes us from the age of seventy-five to a hundred. Difference of climate, though producing no difference in the duration * I need not inform the reader, that I am not here speaking of the immortal sOul, of that divine emanation which outlives matter, and which, freed from our perisha- ble part, returns to the Almighty. I am speaking merely of the intellectual faculties common to man, and to those animals which, like him, are provided with a br?jn.-™- tiutfmr's Note. 51 402 of* life, has, however,, a remarkable influence on rapidity of growth*, Puberty, manhood, and old age, come on much sooner in warm climates than in northern countries, but this premature developement, which shortens the duration of the periods of life, augments, in tho samo proportion, that of old age. It is, however, difficult to say, at what precise period old age begins. Is it towards the fortieth year, when the body begins to decrease and to decay? Can the change of the colour of the hair be considered as the certain sign of old age ? We daily seo young men with grey hair. May we determine its accession by the cessation of the func- tions of generation and the incapacity of reproduction ? Fecundity, whose term is so easily determined in women, by the cessation of the menses, is in man very equivocal; the emission of the seminal fluid is an uncertain sign, from the difficulty of distinguishing the mucus of the vesiculae- seminales and of the prostate, from the truly prolific scmem Erection is likewise a sign not to be relied upon: this state may be occasioned by sympathetic irritation, by the compression of the bladder, distended with urine, on the vesiculae seminales. It is more difficult than is imagined, to determine, from observation, the period at which, in the human species, the male is entirely deprived of tho power of generation ; and it may be said that, in establishing the period of from forty-five to fifty-five, as the beginning of old age in our climate, there will be found men arrived at that state before having reached that age ; as, on the other hand, others will be found after the age of fifty-five with all the characters of manhood. The climaeterical period of sixty-three is the decided and confirmed period of old age. Whatever regimen may have been followed, man at that age is truly old, and cannot but be aware of it. CCLXI. Of the probabilities of human life. Man dies at all ages 5 and if the duration of his life surpass that of the lower animals, the great number of diseases to which he is liable, renders it much more uncertain, and is the cause why a much smaller number arrive at the natural term of existence. It has been attempted to discover what are* the probabilities of life, that is, to ascertain, from observation, how long a man may expect to live, who has already reached a, determi- nate age. From late accurate observations of the age at which a number of persons have died, and from a comparison of the deaths' with the births, it has been ascertained, that about one-fourth of the children that are born, die within the first eleven months of life ; one-third between twenty-three months ; and one-half before they reach the eighth year. Two-thirds of mankind die before the thirty- ninth year, and three-fourths before the fifty-first; so that, as Buffon observes, of nine children that are born, only one arrives at the age of seventy-three; of thirty, only one lives to the age of eighty; while out of two hundred and ninety-one, one only lives to the age of ninety ; and in the last place, out of eleven thousand nine hundred and ninety-six, only one drags on a languid existence to the age of a hundred years. The mean term of life is, according to the same author, eight years, an a new-horn child. As the child grows older, his existence becomes 103 snore secure, and after the first year, he may reasonably be expected To live to the age of thirty-three. Life becomes gradually firmer up to the age of seven, when tbe child, after going through the dangers of dentition, will probably live forty-two years and three months. After this period, the sum of probabilities, which had gradually in- creased, undergoes a progressive decrease ; so that a child of fourteen cannot expect to live beyond thirty-seven years and five months ; a man of thirty, twenty-eight years more ; and, in the last place, a man of eighty-four, one year only. From the eighty-fifth to the ninetieth year, probabilities remain stationary, but after this period, existence is most precarious, and is painfully carried on to the end. Such is the result of observation, and of calculations on the different degrees of probability of human life, by Halley, Graunt, Kersboom, Wargentin, Simson, Deparcieux, Dupre de St. Maur, Buffon, d'Alembert, Barthez, and M. Mourgues, who has just published his observations, collected at Montpelier, in the course of a great number of years, and with the most scrupulous accuracy.* I should enter more fully into this subject, but that it belongs more to the department of political economy than to that of physiology. Do the calculations on the probabilities of human life present results applicable to the generality of cases, and is the mean duration of ex- istence nearly the same with all men, in all countries and climates ? The shepherd of the Pyrenees, who lives happy in the innocence of a pastoral life, breathing the pure air of his mountains, is. he, in this respect, subject to the same laws as the inhabitant of populous cities, exposed to the inconveniences attending numerous collections of men; inconveniences which, viewed in a philosophical point of view, or which greatly over-rated, have so often furnished a text to the meditations of philosophy, and to the idle declamations of oratory.! * From tbe observations made during more recent periods, it would appear that the mean duration of human life has experienced an increase of nearly five years in the greater number of European countries. This may be in some measure owing to the introduction of vaccination, but perhaps the chief causes may be found in the progress of science and civilization, giving rise to a general improve- ment in the habits of life, particularly with regard to ventilation and cleanliness; to better habitations; a more ample supply of food, clothing, and fuel; greater sobriety; a more general cultivation of the soil, and consequent removal of the sources of several diseases: to improved management of children ; and to the ad- vanced state of medical knowledge. The same causes that conduce to longevity must, of course, increase the popu- lation of a country. The suppression of monastic celibacy, and tbe more equal distribution of landed property, consequent on the revolution in France, have tended to increase the population of that country, notwithstanding the destructive Wars in which she has been engaged. t In order to answer these questions in a satisfactory manner, it would be neces- sary to have tables of mortality kept with care in the different countries and climate? ef the globe. Tbe religions and superstitions of the East, of all Africa, and of a great part of America, oppose invincible obstacles to these researches, indepen- dently of those resulting from the state of civilization, and the policy of the va- rious governments of these countries. Judging, however, from the results already before us, the northern kingdoms of Europe appear to be those in which mankind ■enjoys the loDgest term of existence. The tables of mortality of the empire of 404 Does life experience a progressive diminution, iti proportion to the duration of the world, and to say nothing of the time preceding the flood, when, according to the Book of Genesis, men lived several hundred years, did the men of former times live longer than those oi our own ? This is very improbable: among the Egyptians, the He- brews, the Greeks, and Romans, there were very few instances of persons living to the age of a hundred years, and instances of longevity are perhaps more frequent among the moderns. The art of providing for the wants of life, making daily progress, it is very probable, that far from being shortened, the term of human life may be lengthened a certain number of years beyond its ordinary duration. This idea is, it is true, contrary to the commonly received opinion of the progressive depravity of mankind in all ages; but the golden age never existed but in the imagination of poets, and the daily complaints of morose old age have their origin in motives easily under- stood by the physiologist. He whose sentiment is blunted by a long Russia, for the year 1811, gave, in 828,561 individuals deceased belonging to the Greek church, 947 who had reached an hundred years and upwards ; amongst whom were 83 of 115 years of age, 51 of 120, 21 of 125, 7 of 130, 1 of 135, and another who had reached 140. According to the abstract of the population returns of Great Britain in 1821, the number of individuals in England, aged from 90 to 100 years, was 9.90 in every 20,000; and, of those aged 100 and upwards, 34 : the general mortality was 1 in 57. In Scotland, those aged from 90 to 100 was 14.13, and 100 and upwards 1.03, in every 20,000. In Wales, the number of persons aged from 90 to 100 was 17.97, and of those aged 100 and upwards, .50 in 20,000: the mortality was 1 in 69. The maximum longevity was found to be in Scotland in the shire of Boss and Cromarty. Here the proportion of individuals aged from 90 to 100 was 34.39 to the 20,000, and of those aged 100 and upwards 9,22. In the shires of Inverness and Argyle, the proportion of persons aged from 90 to 100 were 32.4t and 29.84, re- spectively, to 20,000. In 1811, the population of Scotland was 1,865,900; in 1821 it Was 2,135,300. The first actual enumeration of the inhabitants of England and Wales was made in 1801, and gave a population ef 9,168,000, and a mortality of 1 in 44.8 The second was made in 18Ui and gave a population of 10,502,900, and a mortality of 1 in 50. The third and last, which took place in 1821, has given an enumeration of 12,218,500, and a mortality of 1 in 58. It appears from these returns, that the healthiest counties in England and Wales are Pembroke, Sussex, Cornwall, Cardigan, and Monmouth, the mortality in these being 1 in about 71 ; and that the least salubrious are Middlesex, Kent, Surry, and Warwick, the mortality being in these 1 in about 50. It is not easy to explain alto- gether the difference in salubrity in the different countries. Locality is, doubt- less, an important agent. Cities and large manufacturing towns modify greatly the ratio of mortality in a particular district. This is well illustrated with respect to London. In 1700, the annual mortality of this city was 1 in 25 ; in 1750, 1 in 21; in 1821, and the four preceding years, 1 in 35; in 1810, 1 in 38; and in 1821, 1 in 40. It must be evident that the increase or diminution of the population of a dis- trict, as well as the mean term of life in it, must depend upon the nature of the cli- mate and soil, its mean elevation and temperature, the state of its civilization and cultivation, pursuits of its inhabitants, and means of subsistence. The government and religion of a country also exert no inconsiderable control on the mean duration of human life, and increase of its population. Together with these already men- tioned, many other causes of a moral and physical nature may be adduced, as influ- encing, in no slight degree, the extent of population, and the salubrity of a district or country. 40j course of years, is affected, in a very different manner, by surround- ing objects. As to the old man, flowers have lost their scent and beauty, fruits no longer retain their flavour. The whole of nature seems dull and colourless. But the cause of all these changes is within himself, every thing else remains as it was. Always equally fruitful, Nature exposes every thing to the action of her inexhaustible crucible; maintains every thing in a state of everlasting youth, and preserves a freshness ever renewed. Individuals die, species are renovated: life every where arises in the midst of death. The materials of organized bodies enter into new combinations, and serve in forming new beings, when life ceasing to animate those to which they belonged, putre- faction seizes upon them, and effects their destruction. CCXLII. Of putrefaction. Here the history of life ought to termi- nate ; if, however, it be considered that the changes which bodies expe- rience, after death, throw a considerable light on its means, its ends, and its nature, there will be an obvious necessity for shortly inquiring into the different phenomena which accompany the decomposition of animal substances. And this investigation appears to me to belong to the department of physiology, until the aspect of the body ceases to recall the idea of its former state, and until the last lineaments of organization are completely effaced. As soon as life forsakes our or- gans, they become subject to the laws of physic, operating upon sub- stances that are not organized. An inward motion takes place within their substance, and their molecules have the greater tendency to be- come separated from one another, as their composition is more ad- vanced. Chemistry informs us that the tendency to decomposition of bodies is in direct ratio to the number of their elements, and that a dead animal body is capable of remaining unchanged, in proportion as its composition is more simple, and its constituent principles less nu- merous and less volatile. Before putrefaction can come on in the human body, it must be en- tirely deprived of life, for the vital powers are most powerfully anti- septic, and one might say that life is a continual struggle against the laws of phvsics and chemistry. This vital resistance, alluded to by the ancients when they said, that the laws of microcosm were in perpetual opposition to those of the universal world, and that these, in the end, prevailed ; this power, which is in a state of perpetual re-action, manifests itself in life: the latter, considering only the results, might, therefore, be defined as follows: the resistance opposed by organic bodies to the causes incessantly tending to their destruction. By at- tending to all these phenomena, it will be seen that all of them tend to one end, the preservation of the body, and that they obtain it, by keeping up a perpetual struggle with the laws which govern inor- ganic substances. It might appear singular, that death should afford a just idea of life, did we not know that it is by comparing, that we are enabled to distin- guish, to judge, and to arrive at knowledge.* Putrefaction takes place and is completed, only in substances de- * See Aw?ndis. Note M M. for some remarks on the signs of death. 406 jirived of life. A mortified limb loses its vitality, before putrefaction comes on; and if nature preserve sufficient energy to resist this de- structive process, she draws, by a line of inflammation, the separation between the dead and the living part. Life and putrefaction are, therefore, two absolutely contradictory ideas; and when, in some diseases, there is observed a tendency in solids and fluids to spontaneous decomposition, this tendency to putrefaction should not be mistaken for putrefaction itself. Several conditions are required to enable putrefaction to affect the buman body after death. In the first place, a mild temperature, that is, above ten degrees of Reaumur's-thermometer ; in the next place, a certain degree of moisture; and lastly, the presence of air. This last condition, however, is not so necessary as the two former, since substances undergo putrefaction in a vacuum, though more slowly. The air consequently promotes a decomposition, only by carrying off the element which rises in vapours. On the other hand, an icy cold, or a degree of heat approaching to boiling, prevents it; the former, by condensing the parts; the second, by depriving them of moisture, the complete absence of which, accounts for the preservation of the Egyp- tian mummies. The phenomena of putrefaction, resulting from a series of peculiar attractions, are modified in various ways, according to the nature of the animal substances which are subjected to it, to the media in which it takes place, to the different degrees of moisture and temperature, and even according to its different periods. Notwithstanding these innumerable varieties, one may say, that all exhale a certain cada- verous smell, are softened, increase in bulk, acquire heat, change colour, assume a greenish, then a livid and dark brown colour; there are, at the same time, disengaged a great number of gaseous substances, of which ammonia is the most remarkable, either from its quantity, or from being given out by animal substances, from the moment when decomposition begins, to the period of tbe most complete dissolution. This gas produces the pungent and putrid smell wbich exhales from dead bodies. Towards the termination of putrefaction, there is disengaged car- bonic acid gas, which, combining with ammonia, forms a fixed and crystallizable salt. Besides these products, there are given out sul- phuretted and phosphoretted hydrogen, or combined with azote, car- bonic acid, and all the substances which may be produced by their re- spective combinations. In the last place, animal substances, when re- duced to a residue containing oils and salts of different kinds, form a mould, from which plants draw the principles of a luxuriant and vi- gorous vegetation. The bones, those least alterable parts of the or- ganized machine, in time, become dried by the slow combustion of their fibrous part, and by the evaporation of their medullary juices. At last, reduced to an earthly skeleton, they crumble into dust, and this dust is dissipated, on opening the tombs in which they were laid. Thus, in the course of time, is effaced all that could recall the idea of our physical existence Putrefaction, Considered in a philosophical point of view, is but a 407 means employed by nature, to Festore our organs, deprived of life, toe. more simple composition, in order that their elements may be applied to new creations, (circulus aterni motus.*) Nothing, therefore, is better proved, than the metempsychosis of matter ;t which warrants the belief that this religious dogma, like most of the fabulous worships and imaginations of antiquity, is but a veil ingeniously thrown by Phi- losophy, between nature and the ignorant. * Beccher, physica subterranea. t Matter is eternal, in this sense, that the molecules of bodies merely pas&from (he one into the other; they survive the destruction, or rtTther the dissolution of organic and inorganic beings, when the former, ceasing to live, restore to the inex- haustible fund of Nature, those elements which sha lends without ever parting with them. * Mancipio nulli datar, omnibus usu. Lucre!, lib. HI. APPENDIX- CHAPTER I. Of Life. Note A. Physiologists are divided into those admitting a principle of life, and those attributing the vital phenomena to organization solely—the latter class contending that life pre-sup- poses organization, the former that organization pre-supposes the presence of life. An at- tentive consideration ofthe phenomena presented by the whole range of organized bodies, and a fair contrast instituted between these and the changes which inanimate matter exhi- bits, will readily convince the mind unbiassed by preconceived notions, which of the two doctrines to prefer. Those who contend that life is the result of organization, ought to explain in what man- ner the organization itself took place; they should show the means employed to produce the disposition of parts, which they conceive requisite to give rise to vital phenomena. It they deny the primary influence of a vital power, associated with the particles of matter, let them explain by what other agency the different atoms can assume organic actions. All effects must have a cause, and it is better to assign one according to which difficulties may be accounted for, than to contend for the efficiency of properties or powers, ofthe existence of which we have no evidence, and which, even granting them to exist, can only be consid- ered as inferior agents, or certain manifestations ofa vital principle. With respect to this class of Physiologists, it may be remarked generally ;—1st. That ex- planations of organization, which admit not ofthe primary and controlling influence of vi- tality, however applicable they may seem to those who look only at the gross relations of things, cannot satisfactorily account for the origin and nature ofthe phenomena to which they relate;.for,however terms may be substituted, or illustrations multiplied, the changes vvhich continually take place in living bodies cannot be explained by means of the laws and affinities which characterize the combinations of inorganized matter. 2d. In order to explain the phenomena, which are more justly ascribed to a vital princi- ple, the supporters ofthe doctrine of organism have recourse to the substitution of proper- ties, occult qualities, impulses, and motions ; and when required to show wherein these qua- lities, impulses and properties are different from those which we observe in inorganized mat- ter, and are there subjected to our experience, they endeavour to get rid ofthe difficulty by denominating them vital, thus tacitly admitting the very principle, in the place of which such insufficient properties are attempted to be substituted ; and after all, without the smallest success in preventing a recurrence to this principle, of .which all these properties, admitting their existence, are nothing else than the results; for, however we may denominate them, we merely substitute expressions which, (if they convey any meaning) imply only the ex- istence of certain effects or operations, which are inferior agents or instruments, under the control of vitality in the production ofthe organic phenomena. From this view, therefore, of tbe subject, it appears that the argument used against the existence of a vital principle is more verbal than real. The organists cannot even prove the basis of their doctrine, for they cannot show that organization came into existence be- fore the effects which they impute to it; and while they bestow properties and qualities on organized matter similar to those imputed to a vital principle, and different from those which characterize inorganized matter, although lhey cunnot point out the difference other- wise than by calling them vital, they virtually admit the existence ofthe principle against which they contend ; for what principle in nature, we would ask, can be shown to exist, or how can its existence be rationally inferred, but by certain properties and qualities, which are peculiar to itself, and which, moreover, as respects this principle, are dissimilar and greatly superior to, and indeed hold a controlling influence over all the other properties of matter with which we are acquainted ? • ..,.,. ...... Such therefore bein« the case, we are justified in recurring to the belief in a vital principle which allied to matter, controls i:s changes and forms, and to vvhich principle the laws and affinities of matter are entirely subject whenever they are embraced within its sphere of ac- - first setof organs is a continuation, in his opinion, of the vascular system ; while the second, on the contrary, is far- ther removed from such a connexion. Foreign substances introduced into the circulation, pass immediately, and with rapidity, into the former textures, while they either fail alto- gether in penetrating, or insinuate themselves much more slowly, and after quite a different manner, into the parenchyma of the latter organs. The one class seems to appertain in general to the system of secretion ; the other class of textures neither secrete from their in- dividual influence, nor can they of themselves add to their nutrition The first appears to be nourished by the immediate, rapid, and continual access into the fluid part ofthe blood; the second by a slo» and periodic deposition, and conversion into their proper substance, of the sanguineous globules of the blood, by means of the influence of the vascular extrem- ities upon the blood which they contain. The primary solids, or rather, the elementary fibres* ofthe human body, and ofthe higher classes of animals, cannot be considered with propriety, to be more than three—the cellular or laminar, the muscular, and the nervous. 1st. The cellular fibre is the most essential to animal existence, and is found in every individual of this kingdom. It consists of an assemblage of minute lamina? and delicate fila- ments. It is neither sensible nor irritable, and is chiefly composed of a nearly complete gelatine. 2d. The muscular fibre is not so generally distributed throughout the animal kingdom as the former, for it is not found in the Zoophites. 3d. The nervous or medullary fibre. The nature of this tissue has been the subject of much investigation. M. de Blainville thinks that it originates in the muscular fibre, as this latter takes its origin in the cellular substance. To these fibres Professor Ohaussier has added a fourth, namely, the albugineous fibre, vvhich is satiny, white, and very strong; and is neither sensible nor irritable. The majority of anatomists, however, consider it as merely a very condensed variety ofthe cellu- lar fibre. These fibres may be called the first order of solids, as they serve to form all the other tis- sues and organs ofthe body. The cellular substance, for instance, is spread our, and con- densed into membranes, or rolled up in the form of vessels ; muscular fibres also assume the form of membranes, concur to the formation of vessels, and constitute muscles; nervous fibres produce the nerves, &c. Finally, those primary solids associate in various forms, and give rise to the compound solids, as the bones, the glands, &c.; and even to those ofa more complex nature, as several of the thoracic and abdominal viscera. Indeed, every species of solid has for its base cellular substance, which is penetrated by nerves and vessels. The viscera, for example, are of this nature, having moreover membranous envelopes. The bones also consist of a similar texture, and ofa deposition of phosphate of lime in their cel- lular substance. (See Adelon's Physiol, vol. i. p. 108.) Those primary solids, or most simple anatomical constituents which we have just now particularized, associate in various forms, giving rise to compound solids or tissues, which are characterized not only by their form and nature, but also by the functions which they perform. These animal textures or compound solids were first arranged with any degree of accuracy by Bichat; and, however successful future researches into their ultimate nature may be,or whatever classifications may be proposed by future inquirers, he is still entited to the honor * It should be kept in recollection ti\&t fibre is used as signifying an elementary animal substance;—tissue indicates a certain arrangement of the former—a peculiar structure of parts;—and organ signifies a compound or complex part vvhich performs functions peculiai to itself. OF THE COMPOUND SOLlDs. O o having introduced a philosophical analysis into anatomical and physiological science. A a/Tan°ement of tile tissues which this great man adopted, is as follows :—the exhalant, aosorbenl, cellular, arterial, venous, nervous of animal life, nervous of organic life, osseous, meau/lary cartilaginous, fibro-carlilaginous, fibrous, muscular of animal life, muscular of organic life, mucous, serous, synovial, glandular, dermoid, epidermoid, and corneus or pilous, systems. M Adelon has lately proposed another classification, possessing some advantages over that of Bichat. He has reduced the number of textures or systems to twelve, viz.—the cellular, vascular, nervous, osseous, cartilaginous, fibrous, muscular, erectile, mucous, serous, corneus or epidermoid, and parenchymatous. Professor Mayer has recently adopted a classification ofthe animal textures, or compound solids, founded on his views respecting the elementary fibres, or primary solids. He recog- nises only seven systems, viz.—1st, the lamellated tissue ; 2d, the cellulo-fibrous tissue ; 3d, thefibrous system ; 4th, the cartilaginous tissue; 5th, the osseous tissue; 6th, the muscular fibre; and 7th, the nervous tissue. (Bibliotheque Germanique. No. 8. T.II.) The arrangement of this class of solids, which we would propose, is nearly the same as that given at another place. (London Medical Repository for July, 1823.) Employing the term tissue generically, we would divide the compound solids ol the body into two classes, viz. general systems, and particular textures. I. General Systems. Under this class we would arrange, 1st, the cellular system; 2d, the nervous system, which comprehends two orders, viz. A, the involuntary or ganglial order of nerves, or the system of the great sympathetic—and B, the voluntary order of nerves; 3d, the muscular system, which also embraces two orders—A, the involuntary or- der of muscular fibres, and B, the voluntary order of muscular fibres; 4th, the vascular system : this system has four orders, viz. A, the arterial order of vessels ; B, the capillary order; C, the venous order ; D, the absorbent vessels, including a, the lymphatics, and b, the lacteals. II. Particular Textures. This class includes, 1st, the mucous textures; 3d, serous textures; 3d, tbe fibrous textures, embracing the fibrous, the fibrocartilaginous, and the dermoid ; 4th, the cartilaginous textures ; 5th, the osseous textures; 6th, the erectile tex- tures ; 7tb, the glandular textures, including the parenchyma ofthe viscera; 8th, the cor- neous textures, embracing A, the pilous, aad D, the epidermoid textures. Proceeding synthetically, we may arrange all the solids of which the animal body is com- posed after the following manner. CLASS I. OR ELEMENTARY ANIMAL SOLIDS. The cellular fibre. The nervous fibre. The muscular fibre. CLASS II. SECONDARY OR COMPOUND ANIMAL SOLID>. Order I. General Systems. The cellular system. TJie nervous system. Including the adipose tissue. A. The involuntary or ganglial order of nerves, or system ofthe great sym- pathetic. B. The voluntary order of nerves. The muscular system. The vascular system. A. Involuntary muscles. A. Arterial vessels. B. Voluntary muscles. B. Venous vessels. C. Absorbents. a. Lymphatic absorbents. b. Lacteal absorbents. Order II. Particular Textures Mucous textures. Serous textures. Erectile tertvrrs. Fibrous textures. A. The fibrous. B. Fibro-cartilaginous textures. C. The dermoid textures. APPENDIX. Glandular textures. Corneous texture. Cartilaginous textures. A. The epidermoid. Osseous textures. B. The Pilous. CLASS. III. ASSOCIATED OR COMPLEX ANIMAL SOLIDS. Order I. Organs of Nutrition. Digestive organs. Organs of absorption and circulation. Organs of respiration and assimilation. Organs of secretion and animal hcaL Order II. Organs of Relation. Organs of sensation. Organs of voluntary motion. Order III. Organs of Reproduction. Organs of generation in both sexes. Of Sensibility and Contractility. Note D. Sensibility.—The phenomena classed by the author under this property of Animal Lile, at p. 19 and 20, are evidently referrible only to organic contractility, with which all classes of animals are endowed, and which, in the lowest orders and in some vegetables, assumes the appearance of sensibility. In ihese, however, we have no reason to infer the presence of sensibility, merely because they contract under the influence of a stimulus; for the contraction may take place without the existence of this property, from the effect produced by the stimulus upon the organization of the contracting part. Indeed we cannot suppose that sensibility is present where the parts generally observed to be instrumental in its pro- duction are not found to exist;—a sensation cannot be supposed to be produced where there neither is an organization suitable to receive, a channel to convey, or an organ to perceive an impression. We should, therefore, limit this term to those phenomena, which the author arranges under that of perceptibility. With this limitation, sensibility may be called the function of sensation, and a property peculiar to the animal kingdom. The sensations are derived through the medium of the senses, and of the nerves, whiqh are distributed to certain parts of the body, and which communicate with the encephalic centre. On this centre the existence of sensibility chiefly depends; the ramifications of its nerves, or the subordinate portions of it, being also parts ofthe apparatus requisite, but not giving rise to this property. As we ascend in the scnle of creation, and as we perceive the seuses, and the organs of volition in more intimate re- lation with this nervous mass—the encephalon—so we find sensibility becoming more per- fect, until, in man, it reaches an extent greatly surpassing that in which we observe it in any qther animal. In man, and perhaps, in the more perfect animals, the modes of sensibility seem to vary. These modes may, however, be divided into two conditions, as they are more or less ac- tive ; namely, conscious or active sensibility, and inconscious or passive sensibility: the former relates to these impressions, either from within or from without, which give rise to perceptions or ideas, the latter to those that are frequently produced upon the senses and upon the ramifications of the cerebral nerves, and, owing either to habit or the want of due attention to theai, are not pe.ceived by the mind In this latter mode of sensibility, the organ receiving, and the channel conveying, the impression, perform their offices, but the mind either is not, at the time when the impression is made, in a state to receive it, or re- ceives it so imperfectly, from its weakness or its transient nature, as not to give rise to con- sciousness. This mode does not necessarily imply a difference in the degree of sensibility, but a condition in which it exists, owing either to its being excited by other impressions, or to its enjoying repose from being exhausted at the time when the impression is made : it is a state to which the highest manifestations of sensibility, as well as the lowest, may be occasionally subject. It is, however, merely a relative mode of this property, and the rela- tion subsists entirely between the state ofthe cerebral organ which perceives, and the force and duration of the impression made upon the organ of sense. Thus when the sensibility OF SENSIBILITY. if J* actively occupied with a particular object, and an impression is made at the same time upon a different organ from that through which the perception, with which the mind is en- gaged, was conveyed ; the second impression may affect the senses in an evident manner, and even so as to influence volition, yet we may be inconscious of its operation, and no active perception may result from it. If however, the second impression be stronger or more vivid than the first, or if, from various circumstances besides, it should excite the cerebral functions, active sensibility or consciousness is the result. As sensibility, according to this view of the subject, is, in its active state, a term merely expressive of consciousness in the entire range of this very generally diffused faculty of ihe nervous system ; and as this faculty is evidently dependent upoTi this system, especially on that more complex part of it which holds relation with surrounding objects; and also as we have no reason to attribute the possession of this part ofthe nervous system, to the very lowest orders of animals, particularly to the class Radialce, so we must conclude, that, although a property of animal life, its higher grades are not possessed by all animals. It may be also stated, that active sensibility, being considered as expressive of the conscious- ness ofthe whole class of sensations, and all the intellectual and moral operations, varies in its extent throughout the animal kingdom, according as those manifestations are more or less numerous and perfect. How far the passive mode of sensibility, or that unattended by consciousness, may be a property of the lowest orders of animals, is difficult to say. We may, however infer that, as this condition of sensibility may take place without an active exertion of this property in the highest animals, so it may result from a less perfect endow- ment of sensibility in the lower ; and as this mode may require a less complex apparatus for its production, inasmuch as its relations are more simple, so it may be possessed by ani- mals, whose organization and manifestations do not permit us to conclude that they are capable of evincing sensibility in its more perfect and active conditions. The relations which this form or mode of sensibility hold with the numerous instincts of animals, must be evident to all who consider the subject. The relations, however, which evidently subsist between that form of sensibility, called organic sensibility by Bichat, and the animal instincts, are much more numerous, distinct, and intimate Organic Sensibility refers to those sensations which are produced in different degrees of intensity, owing to the existence of certain conditions of those viscera which are immediate- ly subservient to the preservation of the individual and the species—to nutrition and repro- duction, and vvhich are not immediately subjected to the influence of volition. The condi- tions of the parts exciting sensibility are very various, and are the result of irritations arising from the presence of a stimulus, of unnatural actions supervening in particular systems or textures, and ofthe deficiency of that stimulus or influence to which particular viscera have become accustomed. Many of the changes preceding this class of sensa- tions, seem to interest, in the first instance, the ganglial class of nerves ; but, owing to the intimate relation existing between this part of the nervous system and the voluntary or sentient part, the impression or change is propagated to the brain. This is the only essen- tial difference which subsists between this and the other forms of sensibility. It is the brain which perceives in them all; and, although stimuli, or the defect of stimuli, may give rise to certain phenomena possessing the characters of the higher manifestations of this property, in the organs appropriated to the preservation of the organic system, inde- pendently of tbe sensorium, consciousness or the more perfect form of sensibility, cannot form part ofthe results. Organic sensibility may be active or passive—it may, or it may not, be attended with consciousness; and even the inconscious mode of it may indirectly impel to action, or give rise to many of the manifestations or instincts which characterize the lower ani- mals, owing to the ganglial centres, either from their organization or connexions, or from both, performing a greater extent of functions than generally falls to their share. If, there- fore, the passive form of organic sensibility may propel to action without consciousness or the sensorial sensibility being excited in these animals, we may also account in the same manner, for many ofthe instinctive functions being performed when we cannot trace them to the influence of a cerebral organ. Of all the conditions of seusibilityits active organic form is the least under the control of the mental energies of the individual in which this form of sensibility is developed. It also, in all its modes of existence, more intimately in- terests the existence ofthe individual than the other forms of sensibility,—it involves a f'eelhi" instinctive of life or death in all its active manifestations. From this it wili be readily seen, how close a connexion exists between organic sensibili- ty and the animal instincts : it does not belong to our plan to trace the connexion in all its relations. . ... . , , Of sensibility, generally, we may observe that, in tht* human species, it is very variable ; in some persons it is very much exalted, in others very obtuse. It is vivid in early life and in vouth ; after the age of manhood, it gradually diminishes; as old age advances, it de- creases rapidly ; and, in persons who have attained a great a^e, it is present in the lowest ovacV in which we li;i'l il in the species. 8 APPENDIX Contractility is essentially a vital phenomenon, and it is the result of a change in the il- lative position of the molecules composing the solids of a living body. This property may be divided into the following grades, commencing with the lowest, it being the most generally diffused throughout nature :— 1. Insensible Organic Contractility, or, that usually denominated lone or tonicity. This grade of contractility is not confined to the animal kingdom ; it is a property of vegetables, and of animals not possessed oi a heart. It is diffused throughout the tissues. The vascu- lar system possesses it in the most eminent degree ; and it may be viewed as the result oi the vital influence with which the structures are endowed—it is more or less perfect as the vital energy is perfect, and it disappears with the extinction of this principle. It is a pro- perty ofthe tissues and of the vessels, which is more or less exerted in all the vital opera- tions—in the circulation, the secretions, nutrition, and absorption. The ganglial or or- ganic class of nerves seem to be instrumental in its production and preservation, in the animal kingdom. 2. Sensible organic contractility, or irritability, is that inherent property of contraction which exists in all muscular, and in some other textures. It is excited by the application of a variety of irritants. It seems to depend upon the ultimate distribution of the nervous sub- stance to these parts, and chiefly upon the nerves proceeding from the ganglia. Both these species of organic contractility seem to result from one species of influence with which animal bodies are endowed—they are the proximate result of vitality, and merely differ from each other owing to the intimate structure ofthe parts in which they are seated, and to the extent to which each ofthe parts evincing their presence is supplied with ganglial ramifications1. 3. Cerebral Contractility is the contraction occasioned by the will in voluntary muscles. It takes place only in such muscular parts as have nerves proceeding from encephalon, or ra- ther from the medulla oblongata and spinal chord, terminating in their structure, and is the result of this conformation and connexion with these large nervous masses. The first and second species of contractility result from the ganglial distributions and in- fluence, the third from the superaddition of the nerves of voluntary motion. Whilst, therefore, sensibility, in its more perfect grades, is the function ofthe sensations, is chiefly confined to certain parts and textures ofthe body, and is dependent upon the part of the nervous system of which the encephalon is the centre, contractility exists throughout the whole animal structures, although in different grades, and is, with the exception of the third species, or grade of its existence, entirely independent of sensibility and volition ;— contractility is a general expression of life, sensibility of the higher functions only of this principle. Of Sympathy. Note E. . Bag'ivi attributed the sympathies to membranous connexion; Bordeu to the cellulat tissue ; Willis and Vieusens to the agency ofthe nerves ; and Whitt and Broussais chiefly io the brain. Rega divided the sympathies into those of sensibility and those of contracti- lity—a division which has much to recommend it. Bichat offered some very excellent ob- servations on the relations subsisting between them and the different parts ofthe nervous system ; but, although these observations were calculated to lead to a more correct arrange- ment ofthe sympathies than had been formerly offered, it has not come to our knowledge that any has appeared founded on a better basis than that indicated in the observations of Bichat. In a preceding note, we suggested that the sympathies should be arranged into the reflex and the direct—the former arising through the instrumentality of the sensorium, the latter taking place indepsndently of it, through the means of the ganglial nerves, and chiefly oi those which are distributed to the blood-vessels and which form communicating chords be- tween the viscera. With a view to the illustration ofthe latter class of sympathies, viz. those which are di- rect, and chiefly consist of the sympathetic actions of organic life, we shall offer a few re- marks. When it is considered that the ganglial nerves alone supplied the blood-vessels and the secreting organs and surfaces ; that they accompany these vessels to the utmost limits n! their ramifications; that they coinnuinicate very freely with each other, and with their chief centre—the semilunar gar-el'ioii; that they give i'isr to numerous plexu&es which render thp OF ORGANIC SYMPATHY. 9 ^onnexion between them still more intimate; and that they hold fl close relation" with the rest of the nervous system through means of communicating nerves,—the mutual depen^ dence of action between the chief organs ofthe body, in health and in disease, may be ea- sily explained : If, moreover, it be granted that the most important vital phenomena, as di- gestion, assimiiation,'circulation, secretion, animal heat, generation, &c. (see the note on the functions ofthe ganglial system,) in short, that life itself with all those manifestations of it now particularised, and which have been usually called organic, lesult from the influ- ence exerted by this part ofthe nervous system, through the instrumentality ofthe vessels, upon the fluid they contain, and in some measure reciprocally by this fluid upon these nerves ramified in the parietes of the vessels, and upon the ganglia themselves through vvhich it must of course circulate, the agency of this system in the production ofthe class of sympa- thies under consideration must be evident. From this view of the subject and from taking into account the modifying operation of similar textures, the related action of various or- gans, and, under certain circumstances, the combined influence and re-action ofthe senso- rium, the numerous relations and connexions of healthy function and of disordered action may be more satisfactorily traced. When one organ or system of parts is excited to increased action, or when its operations are diminished or obstructed, we perceive all the other parts ofthe system which communi- cate with it, through the medium ofthe ganglial system, experiencing a modification of their functions,—the action of one or more organs having always an evident relation with the kind and degree of action going on in the other. In these cases the relation is sufficiently manifest; but the kind and degree of it may vary very greatly between different organs. And the relations may be ofthe following sorts, as the vital energies distributed throughout the system are affected in degree or in kind, or in both ways at the same time. I. Organic sympathies in which the vital energy of the system evinces various modifica- tions in degree and distribution ; but in which it is not changed in kind. 1. Related actions may be characterised by a due proportion or a healthy degree of the vital forces ofthe whole system ; but, owing to the application of an exciting cause to one organ or part, or to two or three organs, these forces may be greatly increased in them; as, however, the healthy or medium quantity ofthe vital forces ofthe body is not supposed to be exceeded, there consequently must be a proportionate diminution of these forces through- out the other parts of the system.* * When the natural functions of one organ is simply excited without being diseased, the functions of the other organs with vvhich it holds communication, by means of the ganglial nerves, undergoes a relative degree of change, for the excitement of a viscus is merely an exaltation of its vitality ; and as we exalt the vital actions in one or more departments of the entire series, we diminish them throughout the rest in an equal proportion ; the excite- ment being frequently greater or less in some parts, and the diminution more or less confin- ed to others. If, for the sake of illustration, we suppose the vital energies of the system to be equal to 50; and, through means of the organic or ganglial nerves to be distributed as follows ;—to the stomach and intestines—7 ; to the heart, vascular system and lungs—8 ; to the brain and voluntary nerves—7; to the liver, spleen and pancreas—6; to the generative organs __3; to the urinary apparatus—4; to the surface of the body—3; to the rest ofthe body __H ; We may consider that it is duly proportioned. But if, owing to the application of certain excitants to one or more organs, as to the stomach and intestines, we exalt the pro- portion bestowed on these to 13, we shall consequently find the brain and voluntary nerves possessing only 5 ;—the heart, vessels and lungs 7 ;~the urinary organs 3;—the surface of the body 2; and the rest of the body experiencing the loss of the remaining one. If, again, we excite the vital forces distributed to the heart and vascular system, until they amount to 16, we shall have a febrile condition of the system in its simplest form, and all the other organs will suffer a diminution in proportion : the stomach will only equal 4, and so on in proportion. But the vital forces of the heart and blood-vessels may equal 1G ; and, owitig to the arteries of the brain experiencing an undue proportion of this increase, this organ may at the same time equal 10; or, instead of this increase falling to the lot of the cerebral vessels, those of the viscera may be similarly augmented whilst those of the re- maining organs may be proportionally diminished : in such cases we have a less simple result • but nevertheless, the increase of the circulating functions is followed by an equal diminution 'of the secreting. Viewing the sympathetic connexion of function in another direction, we shall suppose that the excited state of vital action takes place in secreting organs • in this case the nutritive and other animal operations are diminished in an equal degree ' Or we shall suppose that the excitement commences in the capillaries of an organ, from the presence of an irritating cause, that, owing to these vessels being supplied with ramifictionsof the same order of nerves which supply the heart and vascular system eenera'ly the excitement extends more or less throughout this system ; and that, in con- sequence of the continuity of this order of nerves, and their very frequent reticulations and " B 10 APPENDIX. In this order of sympathies there are three relations to be observed, which actually more or less obtain and constitute the essence of the subject, or the actual condition of- the ani- mal functions under consideration : 1st, the relation may respect the increased actions subsisting in two or more organs ; 2d, it may be viewed between the increased functions of one part and the diminished functions of another; and 3rd, it may regard the diminished functions observed in those parts which do not participate in the excitement; the relation being most immediate in the first, and least so in the third of these forms. 2. The sympathetic or related actions may be attended with a diminution of the sum of the vital energies throughout the system. In this case the different relations pointed out above, may nevertheless exist, or one or two of them may only be remarkable ; the chief difference here being that the sympathies of this order are generally induced by agents, which, while they diminish the entire sum of vital energy, act more decidedly upon particu- lar organs or systems of parts. 3. The sympathetic operations may be characterized by a somewhat greater amount of the vital energies ofthe whole body. In this order of sympathies the three relations par- ticularized above also subsist; for although the entire sum of vital actions may be greater than what is usually bestowed on the system, it may be so much increased in some organs as to be greatly diminished in others. This condition of functional sympathy seldom con- tinues long until it subsides to the first, or, from exhaustion of the vital energies, to the second order just now particularized. II. Organic sympathies in which, in addition to various modifications in degree and distribution, the vital energy of the system suffers a change in Us kind. 1.—Sympathetic actions in which the general amount of the vital forces is natural in degree but vitiated or modified in kind, the relation being evident—1st, mutually between these functions which are increased ; 2nd, between the actions which are augmented and these which are diminished ; and 3rd, between those only which are diminished. 2.—Sympathies in which the entire sum of vital energy is both reduced in degree and modified in kind ; the relation between its distribution in the various organs being the same as just now pointed out. 3.—Sympathies in which the amount of the whole vital energy is both heightened in de- gree and modified in kind, In this order the distribution and the relations to which such distribution gives rise, are the same as already adduced. The application of this classification, and of the views which it embraces to medicinp. must appear evident. Of Habit. Note F. We have before said that the effects of habit upon our voluntary organs are veay different from those which result from its influence on the viscera of organic life. This difference is, however, chiefly in degree ; for, as sensibility, there is every reason to sup- pose, from its most vivid state of existence until it merges in contractility, and in its various jnodes of manifestation, differs chiefly in degree, and as it is bestowed in some one mode and degree to all the organs ofthe body, although it be more particularly limited to one of theiruissues, and also as the influence of habit is chiefly exerted upon the sensibility ofthe inosculations, not only do the heart and arteries experience the excitement produced at a part ofthe extreme circumference, but the whole body suffers a relative degree of derange- ment, and hence evinces all the phenomena of sympathetic fever. Thus the capillaries of a particular organ are excited ; the excitement extends more or less generally throughout the vascular series, and the nutritive and secreting functions are diminished in proportion as the actions ofthe heart and arteries are increased. Many collateral views of this sub- ject may be adduced, and many of its connexions traced, as well as various modifying influences, both in and out ofthe body, appreciated,—all tending to establish the positions that it is chiefly to the ganglial nerves we ought to attribute the manifold phenomena of related action which we observe in the animal economy. At this place we hiive only con- sidered one ofthe genera belonging to this class of sympathies, namely, that which compre- hends the most simple of the related actions—those which supervene in the system without an increase or diminution ofthe whole amount ofthe vital energies with which the body is endowed. The other kinds of related function have been pointed out in the above arrange- ment of this class of sympathies; and we cannot farther allude to them here ; indeed it would be much beyond our limits to consider fully the different kinds of sympathy in their manifold relations; we have illustrated one more particularly, because of its importance, ?!id of its having been very generally overlooked. OF INFLAMMATION. 11 system; so it follows that it modifies more or less, all the animal and organic functions, although it acts in the most manifest manner on those organs which are in the closest rela- tion with the sensorium or functions of the brain. Thus the stimulus which excites the ac- tion of the sensorium produces a much less intense effect by repetition, but the repeated employment of the same food, or of the same purgative, does-not materially less excite the action of the viscera, to which they are respectively applied. As the influence of habit, therefore, is chiefly on the sensibility of the system, so it follows, that, when the organic sensibility of the involuntary organs is repeatedly excited, it is then that the diminished effects ofthe excitant upon them are most manifest—that the more the sensibility of our organ is called forth, the more is the influence of habit remarkable. Those stimuli, however, which act chiefly and the most exclusively on the contractility of the textures, and those or- gans whose actions principally consist in the exertion of this principle of life, have their operations the least impaired by repeated employment; indeed, in many instances those organs have their functions increased and rendered more perfect by frequent exertion. Hence, independently of degree, is the chief difference in the influence of habit on the volun- tary organs ofthe body. Of Inflammation.. Note G. As the author has taken occasion to give his opinion respecting the proximate cause of in- flammation, we shall follow his example, and briefly illustrate the view which we entertained of it, and published in a thesis on rheumatism, in 1815, and more recently in a paper on the functions of the ganglionic nerves, contained in the London Medical Repository for May 1822. On these occasions we defined active inflammation to be the result of a morbidly ex- cited state ofthe ganglial nerves supplying the capillaries ofthe affected part, or a derange- ment arising from the unnaturally exalted condition of these nerves on which the functions of the capillaries depend. One of the chief inquiries respecting its nature, and physiological relations, is whether this exalted or excited state of thes* nervous fibrillae is one of simple excitement or no,— whether the natural functions of these fibrillse be merely increased above their healthy o* ordinary pitch, or whether or no they are also otherwise changed. In the definition, we said morbidly or unnaturally excited, thereby indicating that the functions or influence of these nerves are not only simply increased, but also increased differently from what we observe in a healthy part, from the application of a stimulus, both as respects duration and kind of action. 1. As respects the duration of this exalted state. In the vascular phenomena displayed by blushing, or by the application ofa gentle stimulus, the effects soon subside after the re- moval of the exciting cause ; because the nervous influence exerted on the capillaries is sim- ply increased without the mode or habitude of operation being changed. But before we can farther explain the duration of excitement we must secondly inquire into its kind. 2. When a stimulus or irritant is applied to a part, its action seems to be first upon the ganglial fibrillar supplying the capillaries. The vital influence of these fibrillae being excited, the actions ofthe capillaries which they supply are consequently increased. There is, how- ever, every reason to suppose, that the increase of this influence is not simple, that it is not only'changed in degree, but also modified in kind. The irritant seems to impress the nerv- ous fibrillar ofthe part, or of the system more generally, in such a manner as to prevent it from returning to its natural state for a very considerable time, or even at all;—the excited action is induced, it continues, and the longer it continues the less it is disposed to return to its healthy condition. But wherefore doe., the excitement continue ? To this we may an- swer either because the irritating or exciting cause continues to operate by its actual pre- sence or more frequently because the impression made by it, while it changed the degree of nervous influence, also modified its state of existence, and kind of operation on the vessels themselves and the fluids vdiich they contain. It is, therefore, owing to the impression of causes or changes thereby produced in the kind as well as degree of influence exerted by the nervous fibrillse, that we are to impute, 1st, the duration of the excitement; and, 2dly, the different phenomena which capillary derangements or inflammations present. A few of these phenomena we shall particularize. 1 Uneasy sensations from ils'loivest degree until it amounts to acute pain. Uneasy sen- sation alone may be considered one of the primary phenomena following the operation of the exc.itine cause ; or rather one of the manifestations characteristic of that kind or state of excitement or deranged influence of tho nervous fibrillae, forming the first series of the change" induced in the affected part; and it may be farther kept up by the subsequent chan- 12 APPENDIX. ges induced in the capillaries by the disordered state ofthe nervous influence, of which state it is itself one ofthe manifestations. When the uneasy sensation amounts to pain, it may be owing cither to the degree of change with which the influence ofthe nervous fibrillae, and through it the action ofthe capillaries are imbued, or it may arise in consequence of the ganglial system of nerves communicating their disordered excitement, which has com- menced in them to these cerebral nerves, with which they are associated in the textures: for, as we have already stated, the ganglial nerves being plentifully distributed to the capillary vessels in every part and tissue of the body, must consequently communicate freely, and come closely in contact with the sentient or voluntary class of nerves, especially in those textures which are abundantly supplied with them. By means of this connexion the excited functions ofthe former class is very probably communicated to the sentient extremities of the other class, and the sensibility of the latter being thus excited, is still farther promoted by the derangement of the capillaries which the former nerves induce. But this phenomenon of inflammation may not result exclusively in the one manner or in the other. It may take place in both ways in the same part, or in the one or the other more or less partially. In those viscera which are imperfectly supplied with the cerebro-spinal nerves, the first alter- native may be adopted. Indeed, in these textures very considerable inflammation may exist without any other modification of pain than uneasy sensations being felt; whereas, in the other organs, whose supply of sentient nerves is considerable, the 6econd explanation may be entertained ; whilst in some viscera both modes of accounting for this morbid manifestation may be resorted to. But whatever manner of explanation should be adopted, according to the distinction just now stated, it «ught not to be forgotten that this particular manifestation of disease is modified, throughout its manifold grades, by the texture of the part affected, and by the exciting and other causes to which it is indebted for its existence and progress. According to this view of the subject it will be observed, that we consider the pain of in- flammation as originating in, or caused by, the condition ofthe particular influence or func- tion performed by the fibrillae or the ganglial system of nerves,—as a state of these nerves producing deranged action ofthe capillaries to which they are distributed, and exciting or otherwise disturbing the sensibility and functions of the other class of nerves with which they become associated in many ofthe textures; whereas the most acute pains, those which are not necessarily attended with inflammation, and very seldom give rise to it, as those ac- companying tic douloureux, trismus, the various forms of spasmodic diseases, and some other painful disorders which it is unnecessary to designate, originate exclusively in the fibrilhe of the cerebro-spinal nerves. This appears to be an important and fundamental dis- tinction in pathology, and one which we have adopted, not without much reflection and pa- thological research. It accounts for a very frequent phenomenon, namely, the presence of the most violent pain when there are no appearances of inflammation either during its exist- ence or after its subsidence. It shows also that, with the exception of the countenance, and one or two other parts, excitement commencing in tbe cerebro-spinal or sentient nerves, has but little immediate influence upon the capillary circulation; and it also points out, that whatever influence these nerves may possess over the circulation and the vital phenomena allied to it, it is only by means of exciting the ganglial nerves distributed to the structure of tbe part, and to the blood-vessels ramifying in it, that any such influences can be exerted. This, it may be shown, were it necessary to speculate respecting final causes, is a provision requisite to the preservation of the textures, and consequently of the animal body; for if the circulation throughout the different textures and organs were immediately under the do- minion of the sentient nerves, and removed from that of the ganglial, we should have not only all the phenomena which more strictly belong to it, but all the vital manifestations of nutrition, secretion, animal heat, &c. which are under the influence of the ganglionic sys- tem, subjected to continual derangement from the various impulses ofthe will and the pas- sions. As these functions, on which the preservation of the individual depends, are under the dominion of another and less fluctuating influence, they are less endangered by the nu- merous causes of change by which thc-y are constantly surrounded, and with which they hold frequent communication. But, although the functions which are immediately vital are those which belong to the province of this system, they may be acted upon either generally or partially through the medium ofthe nervous system of relation, or of animal life, which system has its own particular functions to perform, and these occasionally exert no mean influence over those ofthe former class. 2. Redness, or the injection ofthe capillaries with red blood. This phenomenon has cre- ated much discussion. It would be foreign to our plan to enter at this place upon the dif- ferent arguments which have been entertained lespecting it. We shall merely state our own opinion as to its nature. The vital influence ofthe ganglial class of nerves is, as we have just now stated, morbidly increased in the affected part, especially as respects these nerves distributed more directly to the capillaries. We observe, on every occasion in the animal economy, that when the v^ldl actions of capillary vessels are increased, the vessels themselves become larger, more fully injected, and circulate a linger quantity of blood. Nov.'. if we allow that an increase OF INFLAMMATION. 13 in degree forms one part ofthe change in the vital influence bestowed on the capillaries by the ganglial nerves, it therefore follows that a proportionate change in the calibre ofthe mi- nuter vessels should result from such increase as usually does on those occasions when it supervenes in a natural manner. In short, that one ofthe changes constituting the acute stage of inflammation is an ex- alted state ofthe vital influence distributed by the ganglial nerves to the capillaries ofthe part; an exalted state of this influence always increases the action and calibre ofthe ca- pillaries, therefore both must be increased whenever this conditiou of vital influences con- stitutes a part ofthe primary derangement. But it has been argued, that when an inflamed capillary is viewed in a microscope, the current of blood in it is slower, instead of bei-g quicker, than natural. This, however, arises, as we have stated on another occasion, from the inflamed capillary vessel admitting a great- er number of red globules, and thus giving rise to the optical illusion of their slower motion, when in fact they actually move much quicker than when the vessel admits a single globule at a time, and when the entire space between each globule moving in the vessel can be seen. Another objection has been urged in support of the hypothesis of relaxation or debili- ty of the vessels, namely, that the exposed capillaries contract upon the application of an irritant ; but so do all irritable parts, and so do all parts, to a greater or less extent, which are supplied with the vital influence. In these experiments it has not been considered, be- cause jt was unfavourable to the hypothesis, that the irritant acts in a two-fold capacity; it excites irritable fibres to contraction, and it constringes the structure of the part. These experiments also appear generally to have been performed under circumstances of disorder, and at a period when the inflammation was passing into that stage which is constituted by a greater or less exhaustion of the increased influence which formerly actuated the capilla- ries. 3.—Increase pf the animal heat in an actively inflamed part.—We have contended in an- other place that animal heat is the result ofthe vital influence of the ganglial nerves upon the vessels and the fluid circulating through them, and that the heat of the whole body or of a single part has an intimate relation with the degree of influence which this system of nerves exerts, especially that part of it supplying the vessels, either as respects the body ge- nerally, or as regards the part more particularly affected. If this position be gianted, it cannot be denied that the augmented heat in inflammation is derived from the same source, namely, the increased influence, on the vessels of the affected part, of that particular system of nerves on which the production of animal heat chiefly depends. (See the Note on the functions of the ganglionic system of nerves.) From this it will be seen that we consider inflammation, in its various forms and stages to originate in, and to depend upon, the altered kind and degree of influence which the gan- glial system of nerves exerts on the capillaries of the part ;—that whenever this influence is greater than natural, the action of tlie capillaries is greater than natural, and whenever it is below the healthy condition, these vessels are equally deficient in a requisite degree of action;—that the kind oi influence is changed as well as the degree of influence ; and that, as inflammation originates in this class of nerves, it may be considered as a lesion of the functions of these nerves, and therefore occurring more frequently in those tissues which are the least supplied with an additional and a compensating influence from the other parts ofthe nervous system : hence the reason that inflammation is very seldom seen in the mus- cular fibre, to which the cerebral nerves are so plentifully distributed, and hence the pro- bable cause that it so frequently attacks cellular parts, or those which are essentially cel- lular in their nature. At this place we have merely considered a few of the physiological relations of acute in- flammation, in a brief and an imperfect manner. Tne other points connected with this sub- ject which might be discussed, but which are more strictly pathological, are—1st, the differ- ent characters of acute inflammation, according to the textuies in which it is seated ; 2d, the stages of inflammation, in relation to the individual tissues, down through their numer- ous grades until they reach the lowest; 3d, inflammations in which the influence bestowed on the vessels by the ganglial nerves are more or less exhausted or destroyed ; 4th, the state. ofthe venous capillaries and absorbents in the different stages and grades of inflammation ; 5th, the varying phenomena which this species of derangement presents according as it is modified by constitutional peculiarities; 6th, the different manifestations of inflammation arising from the nature of its exciting causes, &•:. These and other relations of this funda- mental, and most important part of pathology, will be considered in an extended manner on another occasion., 14 APPENDIX. Ofthe Ganglial or Great Sympathetic System qfj\'erves. Note H. ' It would be incompatible with the limits of these notes to point out the anatomical pecu- larities and connexions of this important system, or even to enter upon a lengthened dis- cussion of their functions. We shall therefore confine ourselves to the statement of the ge- neral propositions, at which we arrived on the latter part ofthe subject, and which were contained in a paper on the functions of the ganglionic system of nerves, read at the Medi- ca] Society of London in 1820. It may be proper to remark, that these inferences were deduced from numerous dissec- tions of individual subjects belonging to the different classes of animals, and from several experiments made in order to ascertain the extent of function which this system of nerves performs. The observations made on these occasions we will soon have an opportunity of describing in a particular manner. 1. The ganglial class of nerves is to be found throughout every order ofthe animal crea- tion, commencing with the lowest, the Radiata, and ascending to the highest. 2. The ganglial nerves is the only part ofthe nervous system with which the lowest or- ders of animals are provided. 3. As we ascend the scale of creation another class of nerves is superadded, namely, the en- cephalic, with vvhich the ganglial nerves are connected. In the higher animals possessing only the ganglial nerves, we perceive the ganglion placed on or near the oesophagus gradual- ly assuming more and more the characters ofa brain, and becoming more evidently connect- ed with organs of sense. We also observe the nervous chords between the ganglia arrang- ing themselves more and more in the manner ofa spinal marrow, as the locomotive organs become more distinct from those of nutrition ; thus rendering the steps of gradation between the animals provided only with the lowest or simplest form of nervous ganglia, and those possessed both of ganglia and of an animal or voluntary system of nerves, almost imper- ceptible. 4. The nerves which are given off from the encephalic mass and from the spinal marrow evince different characters as soon as these parts of the nervous system become distinct from the ganglia; and even in progress towards the fullest distinction which they ultimately at- tain, the difference between both the classes of nerves becomes still more manifest. 5. In all the more perfect animals, the ganglia and their various distributions, as far as they can be traced by the senses, even when aided by powerful glasses and minute dissec- tion, are entirely different from the nerves derived from the brain and spinal chord, in thei* texture, colour, consistence, mode of ramification and distribution ; and they supply very different organs and textures from those to which the cerebral and spinal nerves are distri- buted. 6. Not only in the lowest order of animals may the ganglial nerves be traced before the voluutary or sentient class of nerves come into existence, but also in the embryos ofthe higher animals the ganglia may be distinguished before any traces of a spinal marrow or of a brain can be perceived. 7. The ganglial nerves cannot be supposed to originate in either the brain or spinal mar- row—1st, because they are observed in the lowest animals, who possess neither brain nor spinal chord ; 2dly, because they may be distinguished in embryos before either the one or the other nervous mass can be traced; and 3d)y, because they are never wanting in the foe- tal state, whereas not only have the brain and spinal marrow been individually wanting, but the came fcetus has been found entirely without both. 8. The difference between this class of nerves and those of animal life is not evinced on- ly by their respective appearances, by the general distribution ofthe former throughout the animal creation, by the history ofthe embryal foetus, and by the phenomena exhibited by monsters, but it is also apparent from the very different effects which are observed in them, as respects both the living and dead subject, on the application of various excitants and re- agents.* * The difference between these nerves is very remarkable on the application of galvan- ism ; for, whilst we found that the voluntary nerves could be excited with a few plates, two hundred could produce only a slightly perceptible effect upon the parts more immediately supplied with tibrillae from the semilunar ganglion. When galvanism was applied to this ganglion itself in the recently killed animal, but little appreciable effect was produced either on the vessels with which it is intimately connected, or upon the stomach and upper portion of the small intestines. In the majority of instances, however, these parts seemed to be in a more contracted state while under the galvanic influence. When the influence of the battery (of two hundred plates) was directed upon the semilunar ganglion of a young cat, j? evinced symptoms of pain and distres-s. and several irregular contractions of the dia- OF THE FUNCTIONS OF THE GANGLIAL SYSTEM. 15 tW m™«n!?«tSH?^ ^8Bi.mHa"ty just now instanced evidently show that the ganglia and as on? thinJ I V'k Ut'°.nS f0im an inil«Pendent system in the animal economy ; and that ferent o he «„„l T^0 f°rm a Part of another thinS from which il is essentially dif-. v^Js m?em ff a6„ m»|n 1vheir ra"llfications can"°* be supposed to form a part of the ner- funcS l 1,fe' °r lhat which Presid«s °ver the intellectual and locomotive lower Jnhima1lsePanndden,;i; °f the g™P',al SyStem may be farther demonstrated in many of the anTJnf^ »10st perfect animals ; for in these both the brain tit at t destroyed gradually ; and, provided the function of respiration be 11 ThJftR* J' ' f *ullctions of circulation and secretion will still he continued. exerts in the anS / Syutem' and the esteilt of the peculiar influence in which it dtea e noon the h-i "°Ty ' ^ proven 5" the ",osl Per,ect animals, by the effects of a Zt nd, a'ld Spmal ma»™, either of which may be destroyed to a very fhose vfscera SnVh T °-'&?u °"ly Th,C.h ^ SU^ be deP'ived of their functions, while fo^mtbeS ,he 6a"K'ia{ ^em will continue to per- whfchacuatesTh*,th0utf?v,nc»ng"luch.d^^er, unless that part of the nervous mass 12 The «n* f» COnt!act10!1 °f*T respiratory muscles becomes involved in the disease. and secreuJn. g PP * W ^^ aU U,e °'ganS of digestion, assimilation, circulation 14 Thes^ne! „ °fiefly T^f Whl? "V™ COminS directly from this class °f nerves. andabdomen InH , /tK°Se,y ret,culated enveloPe around the.a.teries of the throat a teries L tl e ex^e T ,? Tu S^T = ^ "lay be tfaced ,n the ,a'ge' bl™^s °f arteries in the extremities, and ol the head, until they reach the brain itself. 15 I he arteries throughout the body, and indeed all the other parts of the vascular svs- tem receive nerves directly from no other source than from the ganglia Y lb. ine same system supplies, in a demonstrable manner, all the involuntary muscles, and ,t seems to send fibrill* to several ofthe voluntary muscles, especially to thoS ^bout face" y' II iS alS° libemUy dist"buted t0 all the seaeting^lands and sur- hrl?' fT thC m-anT 'n Whifh the ganSlial "erves invest the arteries proceeding into the ihTJ^i teaS?Tg anal°Sy' we infer that they accompany the arteries throughout he substance of this viscus, as in other organs of the body, and that they influence its vascu- lar functions in a similar manner. 18. The chief origin or centre of the ganglial system is generally situated, in all the higher orders of animals especially, about the middle of the body, and, under the name of the semilunar gapglion, ,t sends off branches, which form plexuses ; these present modified characters, as respects their external appearance and confirmation, in their course to the different organs which they supply. This central ganglion more immediately supplies the organs of digestion, chylifaction and circulation, where the expenditure ofthe vital influence is greatest, and sends commu- nicating branches to the subordinate ganglia and plexusus 19. The external characters ofthe ganglia and of their plexuses and ramifications vary phragm supervened. The effects of galvanism wg-o also tried on some ofthe other ganglia but they evinced no appearance of being oppressed by it in the dead subject, and, in the living, the result was equivocal. On th^se occasions we experienced great difficulty from the want of proper assistance. We propose however, to repeat and to extend these ex- periments; and we expect eminent coadjutorship in their performance, and the assistance of a very powerful galvanic battery. * If, therefore, the existence of these nerves is every where demonstrable in the centre of the system, and even throughout its radius, until we arrive at the superficies or extreme parts ofthe body, where it may be supposed that they must elude, from the nature of their organization, the detection of the senses, it cannot be contrary to the uniform operations of nature, and to the many analogies she presents, to infer, that they are distributed to the ex- treme ramifications ofthe arteiies, upon whose more considerable branches they are rea- dily demonstrable. And if they are also shown to exist in some voluntary muscles may they not be considered to be present in all, bestowing upon these muscles their peculiar energies, the nerves of animal life producing only the functions which usually result from this class of nerves, in addition to those arising from the involuntary influence or vital en- ergy which these muscles derive from the ganglia and their distributions. It may be mentioned, that consistently with the opinions we entertained respecting the independence of, and extent of the functions performed by, the ganglia and their distribu- tions, that we assign the terms—ganglial system, organic system of nerves, vital system of nerves, synonymously ; and we use the terms—cerebrospinal system of nerves, voluntarv nerves, and sentient system, also synonymously. To this there may be some objection* • hut as we did so in the original paper, we wish not to alter it. 1*3 APPENDIX. considerably in different situations, both as respects their colour, their external form, and internal structure. 20. The subordinate ganglia, while they seem to receive a reinforcement of vital influ- ence from the centre ganglion, modify that influence, and generate an accession to it, suita- ble both in kind and degree to the functions of the organs which they are destined to actu- ate. 21. This class of nerves send off, and receive chords of communication between the brain and its subordinate organs, and between the spinal marrow and its distributions : this seems to give rise to a reciprocal communication of influence between the organs of nutri- tion, &c. and those of relation, and a mutual dependence of function, which is more inti- mate and apparent as we rise in the scale of creation,—the independence of toe former class of functions becoming more evident as we descend, and the younger the animal is as we ascend the scale. 22 The extent and mode of communication between different parts of the voluntary nerves, and the ganglia and their distributions, vary very considerably. 23. As this class of nerves a>e so entirely different in their appearance, structure, pro- perties, and mode of distribution, and as they supply very different organs from those which receive the encephalic class of nerves ; so it may be inferred that they perform essentially different functions, although tiiese functions, in the higher animals more particularly, aie in close relation with those ofthe rest ofthe body. 24. As it is demonstrated, that the ganglial or vital nerves supply the heart, that they surround and are ramified in the arteries throughout their distribution ; that no part of the vascular system receives, in a direct manner, any voluntary nerves ; and as it is reason- able to suppose that this p ovision does not exist without accomplishing important purposes in the animal economy, and as the fibres of involuntary muscles are evidently supplied from the same source : and, farther, as we cannot suppose, conformably to the laws of na- ture, that the bare coats ofthe vessels, and particularly ofthe arteries, without such a pro- vision, could be possessed of any vital properties—so we infer tbat all the vital phenomena, which the vascular system exhibits throughout the body, are under the direct influence of this class of nerves. 25. The distribution of these nerves around the arteries, and the manner in which their fibrillae penetrate the coats of these vessels, seem to evince that they not only impart to them whatever vital properties they may possess, but that they moreover produce those changes on the blood to which it is subject, whilst flowing in the vessels, and many of those phenomena which this fluid presents soon after it has been Uken from the body. 26. It is also reasonable to suppose that the influence exerted by this system on the ca- pillaries, and the additional infliience which its ramifications bestow on the substance of the viscera, combine to produce the secretions, in secreting organs and surfaces, and nutri- tion throughout the textures of the body. Hence, that the varied phenomena displayed by the blood itself, by the functions of digestion, secretion*, assimilation, &c. result from the condition of the influence which this system, in its centre and distributions, is instrumental in generating in the vessels and fluids which they contain. May not a vital influence or atmosphere, as it were, be produced from the extreme fibrillae of this system, or between * No experiment instituted with the intention of showing the influence of the nerves given off from the brain and spinal chord upon secretion, can prove the reality of such in- fluence. Because these orders of nerves are not ramified upon the vascular system, nor do they even supply the capillary vessels. This is a wise provision : for if the heart rod blood-vessels were directly under the influence of the voluntary nerves, in any of its di- visions, this system would be const.intly deranged by it, and vascular disease be incompara- tively more frequent and fatal. Such experiments, were they instituted with the utmost precautions, could prove no more than has been shown by those of Dr. Phillips and Legallois, vvhich at most evince that the vital functions resulting from the ganglial or vital class of nerves may be influenced, in the more perfect animals, by the destruction of a part of the nervous system with which they have held, and with which they always hold, a more or less intimate relation; and that the same nerves, which, during health, have conveyed a natural stimulus to the vital activity of particular organs, may convey an artificial one ; and when the natural stimulus or excitant is removed, or the subordinate function annihila- ted, the operations to which it is requisite, in the highest animals, must languish and ulti- mately decay. Indeed, it is only reasonable to suppose, that the involuntary nerves, as they communi- cate with the organic or vital nerves, convey a natural stimulus, or influence to the latter, which, if they were deprived of it, after its continued and uninterrupted influx, the vital functions of the organs enjoying this additional influence, would necessarily languish, or even be overturned if the privation took place suddenly and completely. If, hower, it were brought about gradually, it might be produced to a great extent, and in many animal? comnletelv. OF THE FUNCTIONS OF THE GANGLIAL NERVES. 1 / them and the coats of the capillary vessels, which influence, whatever may be its state of existence, Impresses the fluid circulating in these vessels in a manner which produces differ- ent ettects, according to its excess or defect, or according to other modifications to which it may De subject—in health and disease, owing to the numerous causes of change to which it »s exposed r * »..5J' Tne.seParation fr°m the blood of the materials which supply the waste of the tex- ,„ J5' ? glVC "S.t0 .e,r Srowth» is the office of this system, which imparts its influence %T T?P6ra ? thr°Ugh the mediutn of the vascular system. „„1 n • T,Lal ma,n,festations of the veins and absorbents (with the exception of the vena E^n!?- *"£ 'r°m *• d,stributlon of the system of nerves to the minute arterial capillaries supply.ng their parietes, and to the adjoining textures; and, probably, from the distribution oi minute fibrilla to their tunics—an organization which, although it cannot be demonstra- ted, may nevertheless exist, and thus the vital manifestations of the venous system may more readily be explained. r „29\Jhe SanSlialJnerves sheathe the vena porta throughout its course in the liver: and, ™fV",f abundant manner in which they supply this particular vein, from the confor- mation ot the vein itself both as respects its coats and connexions with the texture ofthe liver, and with the other vessels, and from the character ofthe blood conveyed to and from it, we conclude,—that it is through the vital influence bestowed on the vena porta by the ganglial nerves, assisted with that belonging to the other vessels and the texture of this vis- cus, that the changes induced in the blood returned from the digestive canal and its allied viscera, and containing a large proportion of absorbed materials, are produced ; and that tne secretion of the bile results from the same influence, partly as a consequence of these previous changes, and partly as its independent act exerted both upon the extreme ramifica- tions of the vena portae, and ofthe hepatic artery, this secretion consequently proceeding Jrom both the kinds of blood contained by these vessels. 30. That this system of nerves, by means ofthe influence derived from its principal and subordinate sources, and numerous distributions, and exerted upon the vascular system, ge- nerates animal heat throughout the body ; and that the production of animal heat takes place tn a manner analogous to the process of nutrition and secretion.* ,.?1' The state of animal heat, like other secretions, will be greatly modified by the con- dition, both as respects kind and degree, of the vital influence of the ganglial system, and by the state ofthe blood on which this influence is exerted, which state will have a double ope- ration in modifying the result. (See the note on animal heat.) 32. It appears probable, from the effects of several agents upon tbe voluntary and other muscular parts, when applied immediately to the ganglial or vital system of nerves, from the general distribution of this system to the capillary arteries, and from the circumstance of its supplying and actuating the involuntary muscles, that it also bestows its proper influence upon those which are voluntary, and that thus it gives rise, in both, to the phenomenon of muscular parts usually called irritability ; the different manifestations of this property, as it is displayed in voluntary and involuntary muscles, resulting from the accessory supply of the cerebro-spinal nerves which the former class of muscles receives. (See Note F. F.) 33. That the ganglial system appears to be productive of certain obscure sensations or in- stinctive impulses (organic sensibility) which are, by means ofthe communicating branches of nerves between this system and the cerebro-spinal masses, propagated to the latter, and from the influence they there excite, become the cause of several manifestations, which more immediately proceed from this latter part ofthe nervous system. 34. This operation of the ganglial system on the functions of the cerebro-spinal system is more remarkable when the former is influenced by disease or by a stimulus which is unna- tural either in kind or degree; or even when a natural excitant, to which this system has been accustomed, is withheld, whether such excitant operates either directly or indirectly* or in both ways, as the supply of food, &c. 35. The communicating branches of nerves between the chief ganglia of the abdominal and thoracic cavities, whilst they are the medium of communication between the ganglial and cerebro-spinal systems, intercept or moderate, by means of the subordinate ganglia placed in their course, the influences proceeding from the one system to the other. Thus it is that the ganglia in the neck and chest moderate the influences of the functions of the brain on the heart, and that no impulse of the former can reach the latter but through the medium of the ganglia ; and so little are the ganglia influenced by the operations and excitements of the brain, that organic sensibility is only slightly produced by them. If, therefore, the im- * The experiments of insulating a limb by dividing all the voluntary nerves and arteries. excepting one arterial trunk, performed by Mr. Brodie, in order to ascertain the effects pro- duced upon the generation of heat in the limb, prove this proposition, and could not fail of giving rise to what was actually observed. For tbe ganglial or vital nerves supply in» that vessel could not be completely detached as long as any ofthe coat? ofthe artery remained vndivided. C 18 APPENDIX. pulses of passion and volition produce but an obscure effect upon the ganglia and their chief "ntre» II 's not to be wondered at, that the galvanic influence—vvhich must be very con- siderable to equal the impulses of volition—should act comparatively in a very slight and almost insensible manner upon this system. 36.The ganglia on the communicating branches between the internal ganglia and the spinal chord, intercept the impulses proceeding through this latter channel; and while they thus moderate the operations of both the brain and spinal marrow upon the internal ganglial, they seem to generate an influence suited to the intermediate place which they hold. 37. Irritations ofthe ganglial system appear to act in a slight and obscure manner upon the voluntary organs, through the medium ofthe communicating or conducting branches be- tween this system and the spinal chord ; and, but for the ganglia on their course, the irrita- tions of the former, and the impulses of the latter and of the brain, would reciprocally act in a manner that would be much more marked, and even in a way that would be injurious to the whole body. 38. The influence of the ganglial on the cerebro- spinal system, is more marked as the de- velopement and functions of the former system predominate, as in the lower animals and in the fcetus of those which belong to the highest orders.* * The following outline exhibits a view of the extent of influence which we have attributed to the ganglionic system : it formed a part of the contents of a treatise on the anatomy, physiology, and pathology of the ganglionic class of nerves, &c. the publication of which was commenced in the London Medical Repository, but was discontinued in order that it might appear in a separate and extended form. u Part I. comprehends the following sections :—1. A description ofthe organs general- ly called nervous ganglia.—2. An examination into the distribution of their ramifications, or fibrillae, as far as that has been determined, either by my own, or by the observations of others.—3. Reasons against the usually received opinion, that they constitute a part of the cerebral and spinal nerves; and proofs of their forming a distinct system from the brain, spinal chord, and nerves proceeding from these sources.—4. An account ofthe connexion existing between the ganglia or their ramifications, and the nervous system, properly so called ; and the mode by which that connexion is effected.—5.An inquiry respecting what vis- cera and textures they supply.—6. Proofs from the history ofthe species, and from compa- rative anatomy, that they form the first effort of organization, and are instrumental in the production of the other textures.—7. Remarks respecting their state during the formation, progress, and decline of the animal.—8. Inferences from the preceding inquiries. " Part If. The functions ofthe ganglia considered.—1. As they regard the vascular sys- tem, on which they are chiefly ramified.—A. Proofs that the ganglia are the primary and chief source of the heart's action.—C. Their power over the arterial and capillary systems inquired into, and the irritability of the latter class of vessels contended for, and shown to be derived from this cause.—D. Evidences of their influence over the secreting viscera and textures, a. On the gastric secretions and functions, b. Their control over the secretions from mucous and other surfaces, and from follicular glands, c. Over the biliary and pan- creatic secretions, d. Over the secretions and functions of the urinary organs.—E. Their influence on the mass of blood circulating through the heart and blood-vessels, a. As re- gards the changes induced in this fluid during respiration, b. As respects the phenomena which it displays, after having been drawn from an artery and vein in the general circula- tion, during various states of the system, c. The power of these organs in the production of animal heat. "2. The functions of these organs, viewed in connexion with the muscular fibies of invo- luntary motion.—3. The probability of their being the chief source of irritability contended for, and the varying characters of this principle explained, as it is displayed in the different muscular textures and capillary vessels—4. The influence of the brain and spinal chord, upon the operations ofthe organs under consideration, viewed, a In respect to the man- ner and extent in which the former affect the contractions of the heart, b. As they (the voluntary nerves) may affect the capillary circulation ofa part, and proofs of their limited influence over the vascular ramifications, c. With regard to the small extent of power which the brain and spinal chord can exert over the functions of digestion, unless through the me- dium of the ganglions.—5. A general view of the phenomena to which the ganglial ramifica- tions give rise, when reinforced by the nerves properly so called.—6. The manifestations to which they give rise in the inferior classes of the animal creation.—7. The functions ofthe ganglions, as they regard the generative process, a. In the male. b. In the female.—8. Their influence in the formation and nutrition ofthe textures; and in the progress and de- cay of the animal, considered.—9. The effects produced on different animals, by the ap- plication of certain substances to the expansion of these organs.—10. The consideration, that the manifestations essentially vital are the result of these organs, entertained, argued for, and explained from the inferences deduced from the foregoing sections.—11. A general view of the doctrines contained in this part of the treatise.—(Lond. Med. Repos.for May, 1822.) EFFECTS OF LONG PROTRACTED ABSTINENCE. 19 39. As the ganglia ofthe great sympathetic form an independent system presiding over certain functions which are essentially vital, consequently they may be viewed as the sys- tem and seat of organic life, and may, therefore, be denominated the vital system of nerves, whose centre is the semilunar ganglion.* 40. It seems probable, from the circumstance of a separate ganglion or plexus, or both, being generally assigned to each important secreting or animalizing organ, that the centre or source of vital influence does not supply the whole vitality distributed by the ganglial ramifications to the individual organs and textures ; but that the vital influence proceeding from this centre is reinforced by that which is produced by the subordinate ganglia, and is not only reinforced, but modified by them, and by their distributions in the various organs, so as to give rise to the specific difference of function vvhich each performs; and that the vital manifestations of particular ganglia are still farther modified by the communicating branches between them and the cerebro-spinal system, the extent of modification being rela- tive to the extent to which the nerves of this latter system either communicate with, or con- tribute to supply, or to form, the individual subordinate ganglia. Lastly. The vital influence, being thus produced from the centre of the body, and rein- forced and modified by the subordinate ganglia, allotted to the individual organs, according to their functions, is propagated along the distributions of the system, on which it depends and is inherent, throughout the whole body. The Effects of long protracted Abstinence. Note I. The effects of protracted abstinence on the human subject are well illustrated by the fol- lowing facts :—During the famine which desolated certain parts of France, in the year 1817, especially during the months of April, May, and June, when the miserable inhabitants had exhausted their stock of provisions, and when they were reduced to live on herbaceous vege- tables only, as wild sorrel, nettles, patience, succory, thistles, the tops of beans, the sprigs of young trees, &c, M. Gaspard, (Journ. de Physiol. Eper. No. 3.) observed that a general serous diathesis prevailed, or universal anasarca ofthe cellular membrane, without ascites, jaundice, or any organic lesion of the liver, or of any ofthe abdominal viscera. Many wo- men experienced an interruption ofthe catamenia ; and a reference to the register of births subsequently in the communes which suffered from the famine, showed that the number of conceptions was less by more than one half, during the three calamitous months of that year, than during the same months of the preceding and following years. During these months many assuaged their hunger by eating snails, of which an incredi- ble number was destroyed; but those who largely partook of them experienced a state of stupor, analagous to that produced by belladonna. A tradesman, impelled by a succession of misfortunes, retired to a sequestered spot in a forest in Germany, and there resolved to starve himself to death. He put his determination in force on the 15th of Sep. 1818; and was found 18 days afterwards still living, although speechless, insensible, and reduced to the last stage of debility. A small quantity of liquid was given him, after which he expired. By his side was found a pocket-book and pencil ; the former containing a daily journal of his state and sufferings up to the 29th of Sept., four days before his death. He had constructed a little hut of bushes and leaves. On the 17th of Sept. (the second day) he complained of suffering from cold ; on the 18th he mentioned having suffered from intolerable thirst, to appease which he licked the dew from the sur- rounding vegetables. On the 20th he found a small coin, and with difficulty reached an inn, where he purchased a bottle of beer; the beer failed to quench his thirst, and his strength was so reduced, that he took three hours to accomplish the distance, which was about two miles On the 22d he discovered a spring of water, but though tormented with thirst, the agony which the cold water produced on his stomach excited vomiting and convulsions. * Violent blows or contusions on the epigastric region, when they do not immediately destroy the individual subjected to them, depress in a very remarkable manner the vital en- ergies of the system. The animal heat is uncommonly diminished ; the surface is cold and nale • the pulse slow, and scarcely perceptible; and the breathing feeble and very slow. An analogous effect in some respects, is produced by concussion ofthe semilunar ganglion, as that which follows concussion ofthe brain : in the former the vital or organic actions are either exhausted or destroyed, in the other the animal or voluntary operations only «u- suspended. 20 APPENDIX. The 25th made ten days since he had taken any food but beer and a little water. During that time he had not slept at all. On the 26th he complained of his feet being dead, and of being distracted by thirst; he was too weak to crawl to the spring, and yet dreadfully sus- ceptible of suffering. The 29th of September was the last day on which he made a memo- randum. No dissection of his body was made.—Journal derpraetisch: Heilkunde, &c. C. TV. Hufeland, Mars. 1819. A criminal, called Viterbi, determined on the 2d of December, to starve himself to death, in the prison of Bastia, where he was confined. During the first three days of the attempt, he felt himself progressively tormented by hunger. He manifested no debility during these three days, nor any irregular muscular movement; his ideas continued sound, and he wrote with his usual facility. From the 5th to the 6th of Dec. the much more grievous suffering of thirst succeeded insensibly to hunger. Thirst became so acute on the 6th, that without tver deviating from his resolution, he began to moisten his lips and mouth occasionally, and to gargle with a few drops of water, to relieve the burning pain in his throat; but He let no- thing pass the organs of deglutition, being desirous not to assuage the most insupportable cravings, but to mitigate a pain which might have shaken his resolution. On the 6th his physical powers were a little weakened ; his voice was, nevertheless, still sonorous, pulsa- tion regular, and a natural heat equally extended over his whole frame. From the 3d to the 6th he had continued to write; at night several hours of tranquil sleep seemed to sus- pend the progress of his sufferings: no change was remarkable in his mental faculties, and he complained of no local pain. Until the 10th the thirst had become more and more insupportable: Viterbi, however, merely continued to gargle, without once swallowing a single drop of water; but in the course ofthe 10th, overcome by excess of pain, he seized the jug of water, which was near him, and drank immoderately. Duiing the last three days, debility had made sensible pro- gress, his voice became feeble, pulsation had declined, and the extremities were cold. He, however, continued to write; and sleep, each night, afforded him a few hours ease. From the 20th to the 12th the symptoms mads a slight progress. His constancy never yielded an instant: he dictated his journal, and afterwards approved and signed what had been written agreeable to his dictation. Duriug the night ofthe 12th the symptoms assumed a more decided character; debility was extreme, pulsation scarcely sensible, his voice ex- traordinarily feeble, the cold had extended itself all over his body, and the pangs of thirst were more acute than ever. On the 13th the unhappy man, thinking himself at the point of death, again seized the jug of water and drank twice, after which the cold became more se- vere ; and, congratulating himself at the approach of death, he stretched himself on the bed, and said to the gendarmes who were guarding him, " Look how well I have laid myself out.'' At the expiration ofa quarter of an hour, he asked for some brandy : the keeper not having any, he called for some wine, of which he took four spoonsful. When he had swal- lowed these the cold suddenly ceased, heat returned, and he enjoyed a sleep of four hours. On awaking (on the morning of the 12th) and finding his powers restored, he fell into a rage with the keeper. During the two following days, he resisted his inclination to drink, but continued to gargle occasionally with water. Duiing the nights he suffered a little from exhaustion, but in the morning found himself rather relieved. It was then he composed some stanzas. On the. 16th in the morning his powers were nearly annihilated, pulsation could hardly be felt, and his voice was almost wholly inaudible ; his body was benumbed with cold, and it was thought that he was upon the point of expiring. At ten o'clock he began to feel better, pulsation was more sensible, his voice strengthened, and heat again extended over his frame ; and in this state he continued during the whole ofthe l?th. From that day until the 20th he only became more inexorable in his resolution to die. During the 19th the pangs of hunger and thirst appeared more grievous than ever; so in- sufferable indeed were they, that, for the first time, Viterbi let a few tears escape him ; but his invincible mind instantly spurned the human tribute. For a moment he seemed to have resumed his wonted energy, and said in the presence of his guards, " I will persist, my mind shall be stronger than my body, my strength of mind does not vary, that of my body daily becomes weaker" A little after this energetic expression, which showed the powerful in- fluence of his moral faculties over his physical necessities, an icy coldness again assailed his body, the shiverings were frequent and dreadful, and his loins, in particular, were seized with a stone coldness, which extended itself down his thighs. During the 19th, a slight pain at intervals affected his heart, and for the first time he felt a ringing sensation in his ears. At noon, on this day, his head became heavy; his sight, however, was perfect, and he conversed almost as usual, making some signs with his hands. On the 20th he declared to the gaolc and physicians that he would not again moisten his mouth, and, feeling the approach of death, he stretched himself on the bed, and said, "I am prepared to leave this world." Death did not this time betray his hopes: on the 21st ho was no more. Until the day of his death this man regularly kept his journal. The delivery if it to his friends was refused. (From the Corsican Gazette.) OF DIGESTION. •21 Of Digestion. Note K. I. Of Digestion in the Stomach. M. Lallemand has drawn the following inferences from his observations and experiments on digestion : its two constituent parts of coagulum and whey, the former of which is afterwards' APPENDIX. redissolved, an:, v.c whole converted into a fluid substance, with very minute portions oi coagulum floating in it. Under the ordinary circumstances, the chyme, as soon as it has entered the duodenum, assumes the character of chyle. The latter is seen mixed with ex- crementitious matter in the intestine ; and in its pure state ascending the lacteal vessels. Nothing like chyle is ever found in the stomach ; and Dr. Prout, whose attention has been much directed to the chemical examination of these fluids, has ascertained, that, albumen, which is the principal component part of chyle, is never to be discovered higher than the pylorus. Now, in my experiments, which were made chiefly on young cats, where a ligatuii; had been applied so as to obstruct the choledoch duct, the first of these processes, namely, the production of chyme in the stomach, took place as usual; but the second, namely, the conversion ofthe chyme into chyle, was invariably and completely interrupted. Not the smallest trace of chyle was perceptible either in the intestines or in the lacteals. The former contained n semi-fluid substance, resembling the chyme found in the stomach, with this difference, however, that it became ofa thicker consistence in proportion as it was at a greater distance from the stomach : and that, as it approached tbe termination of the ileum in the caecum, the fluid part of it had altogether disappeared, and there remained only a solid substance, differing in appearance from ordinary faeces. The lacteals con- tained a transparent fluid,Which I suppose to have consisted partly of lymph, partly of the more fluid part ol, the chyme, which had become absorbed. "I conceive that these experiments are sufficient to prove that the office of the bile is to change the nutritious part of the chyme into chyle, and to separate from it the excremen- titious matter. An observation will here occur to the physiologist. If the bile be of so much importance in the animal economy, how is it that persons occasionally live for a cen- siderable time, in whom the flow of bile into the duodenum is interrupted? On this point it may be remarked, 1st, That it seldom happens that the obstruction ofthe choledoch duct from disease is so complete as to prevent the passage of the bile altogether; and the circumstances ofthe evacuations being of a white colour may prove the deficiency, but does not prove the total absence of bile. 2dly, That in the very few authenticated cases vvhich have occurred, of total obliteration ofthe choledoch duct in the human subject, there has been, I believe, always extreme emaciation, showing that the iunciion of nutrition was not properly performed. 3dly. That the fact of individuals having occasionally lived for a few weeks or months under these circumstances only proves that nutrition may take place to some extent without chyle being formed. In my experiments I found that the more fluid parts of the chyme had been absorbed, and probably this would have been sufficient to maintain life during a limited period of time."—(Journal of Science and the Arts, No. 28.) Dr. Stearns of New York, is of opinion that the gall-bladder is not passive in the recep- tion of the bile, and that it is not a mere receptacle for this fluid. He supposes that the cystic duct acts as an absorbent, selecting from the bile in the hepatic duct, its more active ingredients, vvhich are carried into the gall-bladder, where they remain until "some pecu- liar irritation" of the mouth of the common duct, by the passing chyme or by some other stimulating cause, solicits its discharge, in a gradual manner, for the purpose of purging the intestines. In support of this opinion he refers to the experiments of Dr. Douglass, of the same city, who found that the bile which passed directly from the hepatic duct into the intestines was bland and harmless, and was mixed with the chyme, and thus seemed to aid, as shown by the very conclusive experiments of Mr. Brodie,, in the formation of the chyle, and of the new materials for the nourishment of the body ; whilst the bile found in the gall- bladder was always bitter, pungent, and viscid. These properties, however, of the cystic bile may supervene without any election being exerted by the cystic duct in the process; for if we suppose, what is most probable, that during the empty state of the duodenum the bile flows into the gall-bladder, where its more bland and fluid portions are removed by the numerous absorbent vessels with which the gall-bladder and its ducts are provided, and where, during its retention, its elements com- bine in such a manner as to modify the characters of the secretion, and to render them very different from those which it evinced immediately after its formation, we have a sufficient reason for the more pungent qualities, of cystic bile. It seems by no means unlikely, therefore, that the change takes place in the bile itself within me gall-bladder, and that it is promoted by the temperature and vital influence of the system. With respect to Dr. Stearns's opinion, that the gradual flow ofthe cystic bile into the in- testines serves the purpose ofa gentle purge or stimulus to their functions, it is by no means new ; but we have no more proof that it acts the part of a purge, than that it performs the office of an astringent. How is it, if this opinion be correct, that diarrhoea, or a lax state of the bowels, is so often observed during the interruptions of the biliary secretion, and especially of the cystic bile ? After the full detail of the results of Mr. Brodie's conclusive experiments we need state at greater length modern views upon the subject. In the note upon the function of respiration, we will briefly notice some peculiarities connected with the. functions of the liver and con- ditions ofthe bile. OF THE STRUCTURE AND FUNCTIONS OF THE SPLEEN. 29 Ofthe Structure and Functions ofthe Spleen. Note N. Although considerable attention has been paid to the physiology of the spleen, yet its iuncttons are but imperfectly understood. They have, indeed, been variously explained by philosophers, but all have erred, chiefly in endeavouring to assign to it one definite function only, which they consider it to perform under all the circumstances which influence the body. Thus, Malpighi, Haller, Blumenbach, Richerand and Fodere, imagine this organ to be subservient in its functions to those of the liver. Hewson believed it to be destined to the elaboration ofthe globules of the blood. Tiedemann, and Gmelin are of opinion, that it . is intimately connected with the absorbent system, and that it assists the process of sangui- faction. Haighton and Moreschi, consider that it is subordinate to the stomach in the process of digestion ; and many pathologists believe that it permits, in consequence of its peculiar texture, accumulations of blood to take place within it duing certain stages of disease, and that it thus prevents more vital organs from suffermj; injury to which they would otherwise be liable. To us, however, it appears more rational, and certainly more consistent with the operations wbich characterize the economy ofthe more perfect animals, to view the functions of this organ as ultimately relating to those which the absorbent, cir- culating, and secreting systems perform, and as including several of the operations} just specified, to a greater or less extent, according to the influences to which the body is sub- jected. In order to learn the nature of the offices which the spleen performs in the animal econo- my, it ought to be our first object to ascertain correctly its structure ; that is, however, a matter of great difficulty. The attention of anatomists has lately been particularly direct- ed to the subject, and Home, Heusinger, and Hopfengaertner, have been assiduous in that investigation, without, however, determining the much disputed point, whether or no this viscus possesses a proper or glandular structure, or is it simply a minute and infinite inter- lacement of arteries, veins, and lymphatics. Sir Everard Home concludes from his research- es, that, '• it consists of blood vessels, between which there is no cellular membrane, and the interstices are filled with serum, and the colouring matter ofthe bloed from the lateral ori- fices in the veins, when these vessels are in a distended state ; which serum is afterwards re- moved by the numberless absorbents belonging to the organ, and carried into the theoracic duct by a very large absorbent." Sir Everard considers "the spleen, from this mechanism, to be a reservoir fo/ the superabundant serum, lymph globules, soluble mucus and colouring matter, carried into the circulation immediately after the process of digestion is completed. M. Beclard, (udditions to the anat. general of Bichat.) has given an opinion respecting the structure of this viscus, which appears to be the most coirectyet offered. He considers that it belongs to the class of erectile tissues, and that its structure results from a peculiar arrangement of arteries and veins similar to that which is found in the penis, the clitoris, and female nipple. M. B. thinks, that the spleen very nearly resembles the cavernous body ofthe penis, both in structure and in its phenomena ; and he considers it not only to consist of erectile tissue, but to be also the seat of a species of erection more or less similar to that of the cavernous body. This viscus, he argues, presents an actual motion of expan- sion and contraction, and he adduces the three following circumstances under which this takes place. 1st, In experiments; when the course of blood in the splenic vein is ar- rested in living animals, the spleen swells, but returns to its former dimensions as soon as the circulation through the vein is restored. 2d, In diseases; the paroxysms of intertmit- tents are accompanied with an obvious enlargement of this viscus, which subsides as soon as the paroxysm is over. 3d,?A similar phenomenon takes place|during digestion. The lateral openings of the veins, noticed by Sir Everard Home, seem to confirm the views of M. Beclard respecting the dilation and frequent inosculation ofthe venous radicles in this vis- cus which are comino?. to it and the other erectile tissues. (See the note in the appendix on the organs ofGeneraiio.i.) With respect to tbe functions ofthe spleen we will only adduce those views which possess claims to a favourable notice. C. H. Schmidt, (Comment, de Pathol. Lienis.) considers that its vasa brevia contribute to nourish and strengthen the stomach; and that, as the blood of dogs deprived of the spleen is found to run speedily to putrefaction, it is concerned in the preparation and as- similation of the, elements of the blood, and that it performs an office to the liver analogous to that which the lungs fulfil with respect to the heart. Professors Tiedemann and Gmelin (Ve.rsuc.he uber die Verrichlung der Mils, Sic.) con- clude from their investigations on this subject. 1st. That the spleen is an organ closnlv 30 APPENDIX. connected with the lymphatic system. This is shown by its being restricted to those annnal3 which possess a separate absorbent system, by the number of its lymphatic vessels, and by the circumstance ofthe spleen ofthe turtle being similar to a mesenteric gland. 2nd. That a coagulating fluid is secreted in it from the arterial blood, is taken up by the absorbents, and carried into the theoracic duct. This fluid or lymph, they remark, was seen not only by them, but by Hewson ; and they conclude, that the formatien of it is the only means by which it is possible to account for the use of the great quantity of arterial blood which flows into the spleen. In answer to the question,—by what means this coagulable lymph passes into the absorbents? they reply, —either there are, in the substance of this organ, particu- lar gland like bodies, and small spaces or cells, which several anatomists say they have remarked, in which the fluid is secreted and taken up by the absorbents, or the finest branches of the arteries in the spleen pass immediately into the absorbents, and by this means some parts of the arterial blood reach the absorbents. From a consideration of all the facts obtained by theinselve? and former investigators, they infer that a connexion sub- sists between the splenic arteries and absorbents, either directly, or indirectly, by means of cells. The secretion of this reddish coagulating lymph from the arterial blood takes place, in their opinion, from the nerves being excited, particularly during digestion ; and conse- quently, by the plentiful secretion, the course of the blood is carried forward in the spleen, which by this means is reduced in size. 3d That this secreted coagulable lymph, when conveyed into the theoracic duct is intended to render the chyle similar to the blood. They consider this inference to be proved by at least two circumstances: 1st. That this change actually takes place, for the chyle ofthe theoracic duct differs from the chyle ofthe mesen- teric vessels, by a closer resemblance to perfect blood : 2d. That when this coagulable mat- ter was by any means prevented from reaching the theoracic duct, this change did not take place. Amongst other proofs which Professors Tiedemann and Gmelin adduce in support of these circumstances, they show that the chyle taken from the absorbents of the intestinal canal, before they had passed through the mesenteric glands, is always white and has no tinge of red, and either undergoes no coagulation, or does so very feebly and slowly. The same fact had been previously shown by various anatomists, and similar appearances to those vvhich are now to be noticed have been remarked by Dr Prout. Professor Tiedemann and Gmelin always observed that this fluid, when it is taken from the absorbents which had pas- sed out ofthe mesentric glands, is redder, and coagulates more easily and more firmly than the other :. and that the chyle in the theoracic duct, above the entrance ofthe splenic absorb- ents, and after being mixed with the reddish coagulable lymph, appears the reddest, and coagulates very rapidly. The gradual change of the chyle into blood, they argue, 6eems, therefore, to be, a consequence of its passage through the mesenteric glands, and ofthe ad- mixture ofthe reddish coagulable lymph supplied by the absorbents ofthe spleen. " The properties of the. spleen in the foetus, and in old age, support this view. In the foetus the spleen is known 10 be very small, and no chyle is formed in the intestinal canal in this stage of existence ; the spleen, accordingly, intended to assimilate the alimentary mat- ter derived from the intestinal canal, is of no importance. After birth, when the formation ofthe chyle begins, this organ shows itself full of blood, and increases in size rapidly. In old persons, the spleen is commonly diminished : it appears, therefore, like the lymphatic glands, to decrease in size with age." In order to establish the second circumstance which supports their third conclusion, Pro- fessors'Tiedemann and Gmelin had recourse to direct experiment, which fully proved its ac- curacy They conclune by observing, that pathology furnishes many confirmations of their opinion ; and they adduce the instances of scrofula, diseases of the chylopoietic viscera in general, intermittent fever, and abdominal dropsy.* * The nerves of the spleen are chiefly from the cceliac plexus, and form a reticulum around the splenic artery, accompanying this vessel in all its distributions ; a very few mi- nute nerves also come from the par vagum and inosculate with those of the coeliac plexus. M. Defermon recently found, in his experiments on the abdominal circulation, that the spleen is susceptible of contraction under the influence of various substances which act directly on the nervous system, such as strychnine, camphor, acetate of morphine, &c. In dogs to which he had given strychnine, the spleen, which is usually flat, rolled itself into a spiral form when absorption commenced, and presented very energetic contractions. The action of camphor was different ; the spleen under its influence became rugous, and its sur- face assumed a granulated appearance, producing a degree of motion in the whole organ. The influence of these agents on a viscus, whose nerves are nearly exclusively belonging to the ganglial system, confirms our views respecting the extent of function which we have tttributed to this system. OF THE INTESTINAL CANAL, ETC. 31 Ofthe Mucous Coat of the Digestive Canal, and the Functions ofthe small and large Intestines. Note O. The Mucous membrane of the Digestive Tube has an amphorous and spongy structure, more or less soft, and of variable thickness. The free surface of this membrane presents,— 1st. Valvules formed of folds of tins membrane, ofthe submucous tissue, and of muscular fibres contained within these folds ; 2d, more or less evident depressions, which are general- ly infundibuliform, cellular, or alveolar ; the follicles differ but little from tbe alveolar de- pressions ; they have a narrow neck, more or less lengthened, and a dilated body lodged in the submucous tissue. They aie formed of this membrane turned back upon itself, and ex- teriorly surrounded by dense cellular tissue supplied with numerous-capillaries. They vary greatly in number in different situations ; 3d, small eminences called papillae, and villosities which are situated on the unattached surface of the membrane. These assume various forms, but in general, those in the pyloric extremity ofthe stomach and in the duodenum, being more broad than long, present a laminated appearance; those of the jejunum are long and straight, and are correctly called villosities, whilst towards the end of the ileum, and in the colon, they reassume the laminated character. The villosities are semi-diapha- nous, their surface is smooth, without any appearance of a cellular or vascular texture, both of which have been imputed to them. Professor Meckel, whilst he doubts whether oi not they possess either the one species of structure or the other, is inclined to believe, from analogy with certain parts of some vegetables, that they consist of a continuous series of cells. The villosities ofthe mucous membrane of the intestinal canal appear to be a mode of structure which, as well as that of folds, gives an increase ofthe extent of surf ace exposed to the influence of external agents. "Villosities are only more minute forms of membranous folds, differing somewhat from the latter in the greater proportion ofthe extent of their sur- face to that of their base, and thus presenting where they exist,—which is chiefly in the small intestines,—the means by which the above-mentioned purpose may be most perfectly fulfilled." The epidermis, or epithelium, is very manifest at the openings into the digestive canal, but soon becomes much less so, as we advance into the cavities, until it becomes entirely .indemonstrable. The blood vessels and absorbents of this membrane are abundant. Its nerves are chiefly ofthe ganglial system, but at its natural openings they come also from the cerebre-spinal system. The functions of the mucous membrane of the digestive tube may be enumerated under the following heads. 1. Absorption, of which the villosities are the most active agents, although not the only agents. . • 2. Secretion, which is perspiratory and follicular; and of which the products, differing much according to the situation when they issue, are generally known under the term mu- cosity. 3. Tonic contraction, which is promoted by the action ofthe muscular fibres. 8. Sensibility, varying in all its grades, and modes of manifestations. The mucous membrane of the intestinal canal is next to the first, if not the first of the structures ofthe body which comes into existence. Its characters are but little modified by age or sex. (See the Note in the Appendix, on the Developement ofthe Textures of the Foztus.) , . , . ,.... Ofthe Digestive process in the Intestines.—It is not necessary to say much in addition to what is contained in the text. This process, as it respects the whole apparatus destined for its performance, may be divided into three stages,—namely, Chymifacuo»,Chyliiaction, and Fecation ; the first is performed in the stomach, the serond in the small intestines, and the third in the large intestines. The first has already come before us, and the second was the materials of the new product; this process is altogether a vital one, and the result is early alike under every circumstance. Chyhfaction chiefly takes place in the duodenum and jejunum from the admixture of the juices just now mentioned with the chyme The experiments of Professor Vlondini confirm the inierence, that the duodenum is distended with the chyme when the bile is passing into it. The absorption of the chyle commences about the end of the duodenum, and goes on 82 APPENDIX. throughout the jejunum, and the first half of the ilium, and is completed at the termination of this intestine ; this function takes place with greatest activity in the jejunum. To the function ofthe larger intestines may be given the term Fecation ; because it is in this situation ofthe digestive canal that the foccal matter is formed. In its couise through the small intestines the alimentary matters are deprived of their chyle, and of a portion of 'their more aqueous parts: the residue is poured into the colon, where its course is more slow, and wheie it assumes new characters. The foecal mass, according to the properties vvhich it presents at the commencement of the colon, is evidently composed—1st, of ^the residue of the aliments ■ and 2d, of the excrementitial parts of the secretions poured into the superior part of the digestive tube. The faeces, when they arrive in the rectum, or at the time of their expulsion from the body, me greatly increased by the moie solid parts of the secretions poured out upon the internal surface of the colon, their more fluid parts having been absorbed. It is, in some measure, owing 10 the quantity and progenies ofthe excrenventitial parts of these latter secretions, which principally proceed from the follicular apparatus of this intestine, that the faeces present distinctive characters. Gaseous substances generally are found in greater or less abundance in the small intes- tines. This gas may come from more than one source : it may arise from the change vvhich the alimentary substances undergo in their course ; or it may be secreted by the mucous membrane of the intestines themselves. While we would not altogether deny a share in its production to the former, we contend for the latter. We believe that the mucous membrane of the digestive canal may both secrete gaseous substances and absorb them; and we found our belief upon the following circumstances1—1st, We have proofs derived from experiment and observation that gaseous substances are absorbed and given off from the mucous membrane ofthe respiratory apparatus. 2d, Pathological facts intimately con- nected with the functions and properties of this membrane in different parts of the body, support the position. We"have, however, no doubt that the changes which the alimentary substances undergo in the stomach occasionally j^ives rise to gaseous products; and we believe that a similar result follows the remora of the excrementitial matters in the colon and rectum. As to the chemical characters of the gaseous substances found in different parts of the intestinal tube, see Chapter II. Of the Functions of the Kidnies. Note P. The latest, and, we think, the most correct examination of the intimate structure of the kidnies was given in the text. We now add the latest experiments which have been made, in order to ascertain the extent of their functions. MM Dumas and Prevost, of Geneva, and afterwards M. Segalas, of Paris, found on examining the blood of living animals, whose kidnies had been extirpated, that it contained urea*, the quantity of vvhich was increased in proportion to the duration of life after the operation; whilst this substance could not be detected in the blood of those animals in which the urinary secretion was uninterrupted. The last mentioned physiologist, moreover, having injected an aqueous solution of urea into the veins of an animal, observed the secretion of urine rapidly increased by it, and this substance so quickly eliminated in the process that, after twenty-four hours, it could not be detected in the blood. It seems, therefore, not improbable that the debris of the textures, being carried into the circulation, is converted by the influence of the organs and vessels through which it flows into the substance called urea, aud that the function of the kidnies is to eliminate it, with other materials which would be hurtful to the system. These experiments show that the urea is not formed in the kidnies by their appropriate functions, as was believed by some physiologists, but that it, and, probably other materials which are removed from the, blood by these organs, are derived from other sources. The following facts more closely relate to pathology, than to physiology. In inflammatory fever the urine is red or deep coloured, or even a deep brown, and per- fectly transparent until the disease tends to a termination; it then deposits the laterititious sediment, which is of a reddish colour, and consists of animal matter, phosphate of lime, lithic acid, and sojnetimes lithate of ammonia. According to Dr. Prout lithate of soda, and purpurates of ammonia and soda, are also present. In intermittents the appearance of the urine varies according to the stage of the disease ; but when a paroxysm of ague is over, what is then avoided deposits a peculiarly red powder, which has been examined by Dr. Prout, and found to be a distinct acid, which he has named rosacic acid, from its colour. H Five ounre« of blood contain one scruple of urea. OF ABSORPTION. 33 in typhus levers, the urine is loaded with gelatin and urea. It deposits in gouty disorders, as it cools, a large quantity of lithic acid, in the form of red crystals. The urine in hvsteria is oi a very pale colour; it contains abundance of saline ingredients, but is very deficient arlm-e1 fK-i inaUer* In Jaund'ce it is usually ofa brown colour, arising from an tinn fA V various other disorders, especially those affecting the secreting func- tion oi tne liver, more particularly when that function is imperfectly performed, the urine Inm-S6 / Prfsents a brown and muddy appearance, owing to the kidnies having as- ™T« oa" " J" S^me degree vica»°us of that of the liver, and thus removed much ofthe carbonaceous and effcete materials from the blood usually eliminated by that viscus. A similar appearance of the urine is often met with in those fevers wherein the functions ofthe liyer are much embarrassed, especially in those fevers called bilious, and in those which are met with in warm climates. In ascites this fluid frequently assumes a yellowish green colour, and is extremely viscid. It deposits a copious sediment of rosacic acid mixed with mmc acid, phosphate of lime, and animal matter; and is often loaded with albumen to sucn a degree, as to deposit it when healed, or on the addition of concentrated sulphuric acid. ji nose appearances, however, are not constant, they are more generally met with in the acute forms oi dropsy. In some cases of rickets, the urine has been found saturated to a high ctegree with phosphate of lime. Its character in diabetes is well known. Blood is frequently in the urine ; it gives this secretion more or less of a dark colour and muddy sedi- ment. Mucus is also met with in this fluid, during diseases affecting either the kidnies, the mucous membrane of the bladder, or the prostate gland. Of Absorption, Note Q. I. Of Absorption from the Digestive Canal. It appears, from the experiments of Tiede= mann and Gmelin on absorption, that the lacteals take up the digested and dissolved por- tions of alimentary substances, and convey them as a chyle through the thoracic duct to the blood-vessels; but as odoriferous, colouring, and some saline substances, are not ab- sorbed by them, and yet are fouud in the blood of the vena portae, and in secreted fluids, it must necessarily follow, that there must be some other way, than the thoracic duct, by which they pass into the blood. : The following are the chief suppositions which have been offered in explanation of the facts :—" Either all the lacteals do not enter the thoracic duct, and part of them join the veins which form the vena portae, and thus transmit their contents into the blood of the vena portae ; or substances pass directly from the stomach and intestinal canal into the veins ; or finally, both of these suppositions may be true.'' These physiologists found, that quicksilver injected into the absorbents of the intestinal canal easily reached the mesenteric veins and the vena portae, and this communication was found to take place in the mesenteric glands. By means of this communication they explain the appearance of streaks of a substance like chyle, which is perceived in the blood of the vena porta? after taking food—a fact which has been frequently observed by other anatomists. Though the passage of chyle into the vena portae, may be explained by this connec- tion of the absorbents with the veins of the intestines, it would appear from the experi- ments, that the passage of odorous colouring and saline substances, does not take place in the same way. The presence of alcohol, gamboge, indigo, could never be detected in the lacteals, or thoracic duct, though it was abundantly manifest in the blood ofthe mesenteric veins, and in the vena portae. They therefore conclude, that the passage of these substan- ces must be effected through other channels, and that these channels must be the radicles of the veins of the intestines. It was found, on examining blood taken from a branch of the mesenteric vein of a dog, to which sulphuro-prussiate of potass had been given, that no streaks of chyle were present, but the saline matter was perceived. From this, and other experiments, they conclude that the veins of the intestines appear particularly to absorb heterogeneous substances, such as those already particularized, whilst the lacteals take up nutritious matter; and consequently, that substances taken into the digestive canal may pass into the mass of blood—1°, through the absorbents, and the thoracic duct; 2°, through absorbents, which are united with veins in the mesenteric glands; 3°, through the radicles or the commencement ofthe mesenteric veins which ultimately form the vena portae. And it seems established by tbe experiments, that the vena portae receives chyie from the absorbents, and other substances which are taken up from the intestinal canal by the veins themselves, and as the blood of the vena portae, into which these materials are conveyed, passes through the liver, this viscus must be regarded as an organ of assimilation as well as of secretion. See the Note on the Functions ofthe Liver, App. p. 23. E 34 APPENDIX. II. Of Absorption in the Lungs.—Professor Mayer, of Bonne, infers, from experiments instituted in order to ascertain to what extent absorption takes place from the lungs— 1°. That animals support a considerable quantity of liquid injected into the lungs, with- out experiencing mortal symptoms from them ; but these injections should be performed by an opening made in the trachea. 2Q. The symptoms of suffocation which arise from injections are not serious when we inject pure water; but they become so when thick fluids, for example, oil which ob- tructs the aerial passages, or some chemical solutions, which inflame the bronchial sur- faces, are employed in this manner. 3"*. The fluids and solutions injected into the lungs are absorbed more or less quickly, according to their nature, and their degree of concentration. 4 but n,any wbkh may be Dhenomena TT^ y .exP,ainin6 abs°'Pti°n," he observes, " we solve a number of other iwSTron,iP,» T lyStCr otberwise '"explicable: for example, the principle on Utina IT »« cured, the relief from congestion and inflammation produced by blood- IhJ fl 1 Want ° ?fecacy m ,ned,cines during those febrile states ofthe system in which wLh i 7t ' SySiem'S-greatly distended.- the'propriety of that practice which institutes 1 «*'• I ,ug a,,d.Pur8,nS Prior l° the administration of other active medicinals, the ration- £•..». .u Partialra,nd general dropsies, under circumstances of cardiac or plumonary diseases ; the use of ligatures upon limbs after the bite of venomous animals, in order to prevent the consequences of such accidents," &c. That absorption takes place exclusively through the medium ofthe veins cannot, in our opinion, be granted to any part of the body or to any organ, excepting to the brain. As respects this organ, we believe that sufficient proofs exist of this function being performed entirely by this set of vessels. (See the Note on the Structure and Functions ofthe Brain.) Ihis very interesting subject has been further investigated by MM. Seaalas and Fode'ra. (Journ.de Physiol. April 1822, and Jan. 1823.) The latter physiologist entered upon a series ol experiments, which, although they appear not to us fully to substantiate the opinion of M. Magendie that venous absorption takes place by capillary attraction, seem nevertheless to show that this process, or one similar to it, actually exists to a certain ex- tent in the living body, and that though it may be subordinate to more energetic influences, it should not be altogether overlooked in our inquiries into the operations of the animal economy. M. Fodera's end, in his experiments, has been to demonstrate that exhalation, which he calls transudation ; and absorption, which he names imbibitiori, are similar phenomena, owing to the capillary attraction of the parietes of the different vessels, owing to their porosity, operating, in the first case, from the interior of the vessels to the exterior, and in the second from the exterior to the interior. M. Magendie conceived he had already proved that venous absorption takes place by imbibition, and came to the conclusions which we have now stated. One of his experi- ments consisted in completely isolating a portion of vein, and placing its surface in con- tact with an active poison : its presence was soon discovered at the internal surface of the vessel. M. Fodera then inversed the experiment. He injected a poisonous substance, with every proper precaution, into the interior of a portion of artery comprised between two ligatures, and isolated from its cellular tissue, its lymphatics, and its vasa vasorum : poisoning took place. He obtained the same result by filling with poison a portion of an artery, vein, or of intestine, removing and placing them either at the surface of a wound made in another animal, or in the abdominal cavity. In these different experiments, the rapidity of the poisoning appeared to vary according to the age and kind of animal; the thickness and length ofthe portion of vessel or intestine, its greater or less distention: the more or less perfect solution of the injected matter, &c. M. Fodera has also seen gases absorbed in the same manner. He placed on the perito- neal cavity of a rabbit sulphuretted hydrogen, enclosed in a portion of intestine removed from another animal; and at the end of some time, symptoms of poisoning manifested themselves, and the sulphuretted hydrogen was no longer found in the intestine. If, in a living animal, an artery or vein is exposed, an oozing is observed to take place through its parietes. This oozing augments, if a ligature be applied to the vessel: differ- ent dropsies may likewise be produced by the ligature of the great venous trunks. M. Fodera concludes, from these facts, that exhalation is only a phenomenon of transu- dation through the parietes ofthe vessels, as many physicians had thought, before the ex- halent vessels were imagined. The following experiments prove that, at least, on the dead body, transudation of liquids may take place at the same time from the interior to the exterior, and vice versa through the vascular or intestinal parietes. M. FodeVa filled a portion ofa rabbit's intes- tine with a solution of prussiate of notass, and plunged it into a solution of hydrochlorate 36 APPENDIX. of lime: he introduced into another portion some hydrochloric acid, and surrounded i' with sulphuric acid : finally, he placed a bladder, filled with tincture of turnsol, in a solution of gall nuts. Sometime afterwards he found in the interior of these portions of the intestine and of the bladder, hydrochlorate of lime, sulphuric acid, and gallic acid, by the tests of nitrate of silver, hydrochlorate of barytes, and sulphate of iron; and in the liquids in which they had been immersed, prussiate of potass, hydrochloric acid, and tinc- ture of turnsol, by the tests of sulphate of copper, the nitrate of silver, and by the reddish Colour ofthe solution of galls being rendered bluish by the potass. On injecting at the same time into the pulmonary vein of a sheep, a solution of hydro- chlorate of barytes, and one ofthe hydrocyanate of potass into the trachea, M. Fodera also found hydrocyanate of potass in the pulmonary artery, and hydrochlorate of baryte6 in the bronchiae. Similar phenomena may be produced upon a living animal. M. Fodera has found, for example, in the bladder or in the thorax, substances which had been injected into the perito- neum ; and in the abdominal cavity, substances which had been introduced into the thorax or bladder. In these experiments he employed the solution of gall and sulphate of iron, or rather, the latter salt and prussiate of potass. The black or blue colour, announcing that transudation has taken place, is frequently not observed until tbe end of more than an hour : it may be rendered almost instantaneous by putting in action the galvanic influence. For this purpose, this ingenious experimenter injects into the bladder, or into a portion of the intestine of a living rabbit, a solution of prussiate of potass, communicating with a copper wire ; externally, he places a cloth wet with a solution of the sulphate, communicating with an iron wire : these wires are put in contact with those of the pile. If the galvanic stream be directed from the exterior to the interior, by making a communication between the iron wire and the positive pole, and between that of copper and the negative, the tissues of the organs imbibe the Prussian blue : if the stream be changed, the colour appears on the cloth. M. Fodera injected into the left cavity of the thorax of a rabbit a solution of hydrocy- anate of potass, and into the peritoneum a solution of sulphate of iron; he afterwards kept the animal placed on its left side for three quarters of an hour. At the end of this pe- riod the animal was opened, when he found that the whole of the tendinous part of the diaphragm had imbibed the blue matter: the muscular part was much less tinged, and only in isolated points. The substernal lymphatic glands were likewise blue. The thoracic duct contained a bluish liquid : the peritoneal membrane of the stomach and duodenum was coloured with spots ofthe same colour : they were observable, but in less number, on the rest ofthe digestive canal and on the arteries. The lymphatic glands ofthe mesentery, the suspensory ligament ofthe liver, the epiploon, were also tinged blue. Some small sub- peritoneal veins presented a slight blue coloration of the liquid contained in their interior. Twelve hours afterwards, the blue tint of these different parts was much more intense. The progress ofthe coloration may be traced, and the phenomenon in some measure be seen in its different phases, by injecting a ferruretted solution of prussiate of potass into a portion of the intestine of a living animal; tying both ends, and plunging it into a bath containing sulphate of iron. At first a slight coloration, only, is observable in the parts, which gradually becomes deeper : afterwards the liquids of the lymphatics and of the blood- vessels become coloured in its turn. In the latter, the coloration begins by small ramifica- tions, and afterwards extends to the branches, which are observed to be filled with intervals of blood and a blue liquid. In these experiments M. Fodera discovered the presence ofthe prussiate of iron in the lymphatic vessels, in the thoracic duct, and, finally, in the portion Ofthe inferior vena cava contained in the chest. M. Fodera concludes, from these different experiments, 1st, that exhalation and absorption take place by transudation and imbibition, and depend on the capillarity of the tissues; Sdly, that this double phenomenon may take place in every part, and that the liquids imbibed may be conveyed equally well, either by the lymphatic vessels, or by the arterial or venous. But (the author very wisely adds) the phenomena of exhalation and absorption ought not to be considered as connected alone with imbibition and transudation: the modifications which they experience from the action of surrounding agents, from the nervous influence, the state of rest and motion, the energy of the circulation, the affinities of the substances with the tissues, the derangements produced by disease, and the elaboration which the fluids undergo whilst absorption and exhalation are taking place, ought likewise to be studied. M. Fodera endeavours to explain the increase of exhalation in the phlegmasia by the dilatation which the parietes of the capillary vessels experience; the interstices of the fibres which form these parietes become at such times increased, and, consequently, permit a more ready issue to the fluids: the serosity and the white globules, which are smaller than the red, are first effused; at last the red globules themselves occasionally escape. It will be seen that this mode of conceiving the phenomenon does not explain the infinite modifications which the liquids exhaled into the inflamed parts undergo. M. Fodera notices cases in which the lymphatics or thoracic duct have been said to con- OF ABSORPTION. 37 tain different substances, which had been introduced either into the digestive canal, the serous cavities, or into the cellular tissue. If the effects of absorption are not manifested, in the experiments, where a portion of intestine, containing poison, has no longer any com- munication with the rest ofthe body, except by a lymphatic vessel, we must seek for a cause in the extreme slowness of the circulation ofthe lymph. M. Fodeia inserted some liquid prussiate of potass in the subcutaneous cellular tissue of the thigh and abdomen of two young rabbits. In the first animal, at the expiration of a few minutes, and in the second, at the end of half an hour, he found it in the lymph of the thoracic duct, in the urine, the mucous of the intestines, the synovia, the serum of the blood, the serosity of the pericardi- um, ofthe pleura, and of the peritoneum, as well as in all the solid parts, except in the crystalline lens, the cerebral substance, the interior of the nerves, and the osseous tissue. In another experiment the interior ofthe nerves presented traces of it. Would not these experiments tend to prove that absorption in these cases had taken place at the same time, both by the lymphatics and blood-vessels? While the German physiologists have ascribed absorption to the absorbents and veins only, MM. Magendie and Fodera have extended this function to the arteries also. In this, however, we think that they have been misled by fallacies which had crept into their ex- periments, and especially by the unnatural position and deranged actions which the opera- tions and agents required by the experiments induce in the animal and in the parts experi- mented on. From every consideration we are led to infer, that the inferences at which Tiedemann, Gmelin, and ;V|ayer have arrived,'approach the nearest to truth. The experiments performed by Darwin, and more recently by \\ ollaston, Brande, and Marcet, tend to prove that different substances introduced into the stomach are found mixed with the urine, without having passed by the lymphatic or blood-vessels. M. Fodera has repeated these experiments, and made them undergo an ingenious modifi- cation, which has discovered to him phenomena unobserved by former physiologists. He introduced into the bladder a plugged catheter, after having tied the penis in order to pre- vent the urine from flowing along the sides of the sound. He laid bare the oesophagus at the anterior part of the neck, and injected into the stomach a solution containing some grains ofthe ferruretted hydrocyanate of potass. This being done, he frequently removed the plug, and received on filtering paper the urine which escaped. On this paper he dropped a solution of sulphate of iron, and added to it a little hydrochloric acid in order to destroy the colour. In one experiment the prussiate was detected in the urine ten minutes after its injection into the stomach, and in another five minutes afterwards. The animals were opened immediately. The salt was found in the serum of the blood taken from the thoracic portion of the vena cava inferior, in the right and left cavities of the heart, in the aorta, the thoracic duct, the mesenteric glands, the kidnies, the joints, and the mucous membrane ofthe bronchiae. This important experiment proves the extreme rapidity of absorption ; it shows also that the prussiate of potass found in the urine, is conveyed thither by the ordinary circulating ways. The following experiment demostrates the rapidity of pulmonary absorption in particular. M. Fodera opened the thorax of a rabbit, and removed the heart, immediately after some prussiate of potass had been injected into the trachea. This operation was performed in twenty seconds : the interior of the left auricle, however, presented a bluish green colour, which was more deep at the mitral valve and less apparent in the aorta. The absorption, therefore, seems to take place at the very instant when the injection has penetrated into the subdivisions of the bronchiae. We are of opinion, that to limit the process of absorption in every part ofthe body, and under every combination of circumstances to which it is subject, to one particular process, or to one particular conformation or property which the vessels, whether blood-vessels or others may possess, would, in the present state of our knowledge, be to draw an inference not justified by many important facts. On the contrary, it seems more probable that not only the vital properties, but those of a physical nature, are requisite to the production of the phenomena in question ; and that the latter set of properties are under the control of Instead of attempting to show that those physical properties for which MM. Magendie and Fodera have contended, are not to a certain degree efficient in the production of the process in question, we would only argue for their subordinate character, which may be nroved by evidence still more uncontrovertible than that which M. Magendie has adduced in support of his purely physical properties : but, although the vital properties are chiefly nredominant in the operation, yet those for which they contend may have still a place to a certainexte.it, which extent is modified by a superior influence. Investigations into the process of absorption have also ,been entered upon in America. :M APPENDIX. the vena portae, the oesophageal veins and the thoracic duct, and if all these are closed, the absorbed matters are no longer conveyed to the circulation or to the urine. With regard to the quantity conveyed by each, they had no accurate means of judging. As the quantity of fluid, however, contained in the vena portarum, is so much greater than in the thoracic duct, it follows, that to produce a colour of equal intensity, a much larger amount of the colouring matter is requisite, and, as the serum of the blood of the vena portae gave an equally deep colour, the greater proportion of the materials must have been absorbed through the veins contributing to this system of vessels. In consequence of reading the experiments of professor Mayer of Gottingen, upon ab- sorption in the lungs, Doctors Lawrence and Coates made a few with that reference. The animals generally died in about a minute after the injection, from suffocation, by the ligatures which they placed on the tracheas of most of them. These experiments, we think, go to favour the idea that absorption from the'mucous membrane of the lungs, is per- formed principally by the pulmonary veins. They lay particular stress upon experiments 5th and 6th. In the first, the blood from the left side of the heart indicated the agent in much larger proportion than that from the right side, both being examined about the same time : viz, seven minutes. In the second, where the examination was made in a much shorter period, viz., three minutes and a half, and four minutes and a half, the article was distinctly found in the left side of the heart before it had arrived in any other part of the system. The effect, of infiltration was also remarkable in these experiments. The results of five trials ofthe prussiate in the cavity of the abdomen are here arranged / for inspection. Animals. Quantity. Thoracic Duct. Carotid and Jugular. Urine. Kitten. ioz. of solu-tion. 12 & 13 m. distinct blue. 6 m. distinct blue. 19 m. no blue. Idem. Idem. 4 m. blue. 2 m. no blue. 10 or 15 m. no blue. 29 m. distinct blue. Idem. Idem, nearly. 3| m. blue. 2 m. no blue. 5 m. blue, not strongly. Idem. ioz\ 3 m. blue. 4 rn. strongly blue. More than 4 in. doubtful. Cat. Uncertain. 9£ m.blue. 6 m. no blue. More than 9J m. no blue. The short time in which the prussiate reached the upper part of the thoracic duct in the above cases, induced them to make four other trials in order to ascertain the earliest period at which that took place. Half an ounce of solution was employed in each case. In the first animal, a kitten, the salt first arrived at the spot of observation in four min- utes, and the quantity gradually increased till seven or eight minutes. In the second kitten, it appeared in two minutes. The serum of this animal gave a blue tinge. In the third kit- ten, in three minutes and a half. Serum of blood also blue. In the cat, it §rst appeared in thirteen minutes. In these cases, the thoracic duct was cut off near its insertion ; and the test applied there. In consequence of this interruption, previously to the prussiate arriving at the upper ex- tremity ofthe duct, the discovery ofthe salt in the serum ofthe blood clearly evinces that it was conveyed there by other channels. It is mentioned by Magendie, that he has seen, on pressing the lacteal branches so as to discharge their contents in the direction ofthe trunks, that those branches would again fill themselves after the animal's death. They have also witnessed these appearances; but they do not know of any similar observations to the following made on the lymphatics, or of any evidence ofthe actual chemical presence of an article conveyed after death into either of these systems from without. OF THE ACTIONS OF THE HEART AND ARTERIES. 39 Four kittens were bled to what is commonly considered death. The blood ceased to flow rom the divided carotid, and voluntary motion was extinct. Prus ussiate of potass in solution w *u *u — •----- vuiumaij uiuiiou was exunci. rvussiaie oi potass in solution was men thrown into the abdomen. It appeared at the thoracic duct in five and a half, five, lourteen, and twelve minutes respectively. In the two last, the great vessels originating at fectlyedistincte ^ b/ * Common liSat«^. The blue colour was in every instance per- In reasoning on the subject of absorption, the question has frequently arisen, whether the articles foundI in the living fluids exist there as chemical substances, or have their chemical nature altered and animalized by the action ofthe vessels through which they have entered ine system. It was, however, deemed a curious subject of inquiry, whether artificial chemi- cal changes can take place in the fluids while they continue to circulate in living vessels, and the ordinary actions of life go on. With a view of ascertaining this point, they com- menced by throwing prussiate of potass into the abdomen, and green sulphate of iron into the cellular tissue, in order to try whether the well known result of their admixture, the Prussian blue, would be produced in the vessels. This, however, did not take place ; and they resolved to repeat it, by throwing the sulphate, as the article of more difficult absorp- tion, into the abdomen, where this process went on with more facility, and the prussiate into tlie cellular substance. On performing this, they were gratified by the striking result of a distinct and beautiful blue in the thoracic trunk, and its contents, and in nearly the whole substance and surface of the lungs. These viscera were preserved in spirits, and are now in their possession. The blood threw up a coagulum of a strong blue colour, and the lvmuh and chyle from the thoracic duct, threw down a blue deposit. Thus not only a foreign but a pulverulent substance could present its unnatural stimulus and circulate through the ves- sels, and accumulate in the lungs, without preventing the actions of life from considerable exertion, and without occasioning coagulation of blood. The animal manifested some diffi- culty of respiration before she was killed, but walked about without the least difficulty and uttered no cries, nor other signs of disturbance of its powers. In another case, the urine and lungs were noted as exhibiting a blue colour. The other parts similar to those above enu- merated, are not described as being found coloured. In a third, the fluid in the thoracic duct was blue, but not the other fluids examined, nor the lungs. Two unsuccessful trials were also made. In another case the thoracic duct was tied, and the same process lepeat- ed. A divided bluish green was here found in the urine ; but neither the serum of the arte- rial blood, nor the lymph of the ductus thoracicus, manifested the blue or green. Ofthe Actions ofthe Heart and Arteries. Note R. I. Of the Heart—The muscular fibres of the heart are more apparent in the foetus than in the adult; it only participates in the general paleness of muscular textures at that epoch, although it is deeper coloured than they. It also is entirely without fat at this peri- od. In old age the texture ofthe heart becomes softer and more flaccid than in the young subject, and its parietes thinner : its cavities enlarge, especially the right, and its surface is more charged with fat. The nerves ofthe heart have been a subject of interest with physiologists. Since thev were investigated by Scarpa opinions have been tolerably uniform respecting them ; and numerous observers have proved the general accuracy of his researches. The cardiac nerves are chiefly derived from the ganglia ofthe great sympathetic : a few also come from the pneumo-gastric; but these seem rather to inosculate with the former, than to po direct- ly to the texture of the organ. The cardiac ganglion, situated behind this organ, seems more particularly to preside over its movements, or to reinforce with additional energy whatever it may receive from other sources, especially from the centre of the ganglial sys- tem and the other ganglial in the neck and chest. These nerves, according to our own ob- servations, supply the substance of the heart in two ways:—1st, There are numerous branches which proceed from the different plexuses directly to its muscular texture, and which, dipping between the fibres, give off minute fibrillae to these fibres next to them in the course of their descent into the substance of the heart. 2d, A large portion also ofthe nerves ofthe heart form an envelope ofthe coronary arteries. A part of these seem to fol- low the arteries throughout their distributions ; but, before the coronary arteries have rami- fied to a great extent, a part of the nerves surrounding them is detached to the adjoining parts, so that all the nerves vvhich surround these arteries, like a reticulum or sheath, do not accompany the ramifications of the latter to their ultimate subdivisions and terminations in the veins, a portion of them appealing to be detached in numerous and minute fibrillae to ■;;e immediately adjoining fibres. T';ms it will be perreived t'lat. the muscular ip.vnne n« 40 APPENDIX. the heart receives directly and mediately a very considerable portion of ganglial nerves; whilst, it may be presumed, that it also receives an accession in those fibriles which termi- nate with the nutritious capillaries in this particular structure. The functions of the heart, it may reasonably be supposed, are chiefly the result of the influence which this disposition of the ganglial system of nerves bestows on its structure, In addition to the support which this inference derives from the conformation of the viscus and its relation with trie rest of this particular system of nerves, both in man and the lower animals, experiments which have been performed by different physiologists, prove its accu- racy* ; and prove it the more conclusively, inasmuch as they were performed with a view of establishing a different proposition. But, although the heart derives its chief influence from the ganglial system, it is acted on through the medium of the nerves wdiich communicate between this system and the cerebro-spinal, and which seem to convey an additional influence from the latter, to the ganglia and plexuses which immediately supply the heart. And as this communication is more intimate in the more perfect animals, and the functions of the cerebro-spinal system are more energetic in them, so it appears to follow that the heart's action is more readily influenced either by the increase or diminution of these functions in them, than in the lowest order of animals. Another point to which it is necessary to advert, is the question as to the active dila- tion ofthe heart—a function of this viscus much insisted on by Hamberger, and more re- cently by Carson and others. We doubt not that it actually exists to some extent, in all animals provided with a perfect heart, but we do not believe that it takes place with great energy. If the dilation, however,of the heart, were a mere result ofa relaxation of its fibres, its cavities could not be so quickly and perfectly filled by the mechanical pressure ofthe blood directed towards them, as we observe that they are; and dilatation would be only the consequence of this pressure, and be proportionate to it. But this is not the case ; for, as far as we could judge from observing the circulation in fishes, the dilation seems to pre- cede the flow of blood, the latter appearing as a consequence of the former. Allowing, therefore, that the dilation ofthe cavities ofthe heart takes place to a certain extent—an extent which it is difficult fully to determine, but which we consider much less than that contended for by Hamberger and Carson, one ofthe causes of the flow of blood in tbe large veins will be apparent. The heart is perfectly insensible in its natural state. This was satisfactorily shown in an operation performed by M Richerand, in 1813, wherein he divided the ribs and removed a portion of scirrhous pleura, thus allowing the pericardium to be exposed. The patient was perfectly insensible of any impression, when M. Richerand touched this organ, although the pericardium, the part through which it was bandied, is evidently the most sensible part of it during disease : in a state of disease its organic sensibly becomes indistinctly-and ob- scurely developed. II. Of the Arteries.—The arteries throughout the body are surrounded by the gan- glial nerves. These nerves form a reticulum around them, from which reticulum very mi- nute fibrillae are given off and dip into their fibrous or muscular tunic. This particular disposition ofthe ganglial nerves on the arteries ought to be kept in re- collection when we inquire into the functions of the latter. How far it tends, not only to the discharge of the more manifest actions vvhich the arterial system performs, but also to those insensible changes which the blood undergoes in health and in disease, and to the as- similation ofthe chyle and other absorbed materials conveyed into this fluid, we have ven- tured to state at another place. We shall here merely take notice of an opinion relative to the operations of this class of vessels in the circulation of the blood, lately contended for by M. Magendie. This physiologist has inferred from his researches on the circulation,— u 1. That neither the larger nor the smaller arteries present any trace of irritability. " 2. That they are dilated during the heart's systole. * Willis divided the eignth pan oi nerves in the neck with a view of paralyzing the ac- tion of the heart, but death did not supervene until some hours, and, in some cas s. not until several days, after the operation. In the experiments of Legallois and Dr. Phillips, destruction ofthe brain and spinal marrow did not necessarily and immediately put a stop to the action of this viscus although, as should be expected, it was greatly influenced by the privation of a necessary and an accustomed influence. In experiments which were per- formed on several species of fishes, the actions ofthe heart continued long after the destruc- tion of the cerebro-spinal masses, and frequently for a short time after it was removed from the body. Lastly, foetuses have been born, in which the action ofthe heart and circulation were perfect, although they wanted both brain and spinal chord; and many of the lower classes of animals have continued tol ive for a very considerable time after decapitation. OF THE FUNCTIONS OF THE CAPILLARIES. 41 ■3. That they are capable of contracting themselves with sufficient force on the blood tiiey contain, so as to propel it into the veins. 4. That the blood in the arteries is not alternately at rest and in motion ; but that it is, on the contrary, in a continued succedaneous (by little jets) motion in the trunks and ramifications—and uniform in the smallest ramifications and divisions. 5. That the contraction of the left venticle of the heart, and the elasticity of the larger ti cm^ller arteries» furnishes a satisfactory mechanical reason for these phenomena. 6. That the contraction ofthe heart and arteries has a considerable influence on the course ofthe blood through the veins." M^iv/r cannot,concur in these conclusions, especially in the sweeping inference which forms M. Magendie's fifth proposition : and we might, were it consistent with our limits, point out various fallacies in his experiments, to some of which, indeed, all experiments on living subjects are more or less liable, viz. the unnatural position of the animal during their per- formance, and more particularly as respects the operations of the part immediately its sub- ject. IfM. Magendie limits the process to the mechanical means indicated above, wo would ask, how he accounts for the influence of mental emotions in determining the action of the'vessels in particular parts ofthe body ? How the diversified influences of numerous external agents on the circulation can be explained ? Wherefore so very opposite effects are produced upon the arteries, when one extremity is placed in a pail of ice, and another in a pail of warm water? How can he reconcile his conclusions with the very satisfactory ex- periments performed by Sir Everard Home, Dr. Hastings, and others? and how he can ac- count for the determinations of blood to particular parts, whilst a diminishing quantity is sent to other situations ?—if he discard the predominating or vital power which the vessel9 themselves, and especially their smaller ramifications possess in virtue of the particular struc- ture already noticed. We readily grant that the larger branches of arteries evince little or no contractile action, particularly in their natural state ; but we contend that it increases as we advance towards the extreme capillaries, the action of which derives the blood to them in larger proportion, and thus increases both the mechanical and vital properties ofthe lar- ger branches supplying them. We allow that the properties for which M. Magendie contends have an actual place in the process of arterial circulation ; but they are not the only ones ; they are insufficient of themselves to accomplish the purposes which he assigns to them; and, moreover, they are secondary to, and controlled by, a superior influence. From these observations it maybe perceived that the arteries act in the process ofthe circulation, not by means of a contractile action similar to what is performed by the heart; nor yet by means of elasticity only ; but by an organic or vital operation, whicii is nearly imperceptible in the larger arterial branches, but which increases as we advance to the ex- treme capillaries ; whilst, on the contrary, the elastic or mechanical properties augment as we proceed in the opposite direction. Of the Functions ofthe Capillaries. Note S. This class of vessels may be divided into two orders, performing distinct functions :—* 1st, those capillary vessels between the terminations of the aortic arteries and the com- mencement of the veins of the body ; and 2d, those between the termination of the pulmo- nary arteries and veins ofthe same name. The first of these orders is disposed, in different proportions, to the compound solids ofthe body ; the second is distributed on the surface of the aircells of tbe lungs only. In the one are performed changes which render the blood unfit for the purposes of the animal economy ; in the other takes place an elaborative pro- cess of an opposite nature. In the first are produced those organic functions which relate more directly to the nourishment of the frame, as digestion, secretion, and nutrition ; in the second those preparatory operations on the blood which enable the sensible and contractile texture's of the body to perform their offices. Without the accomplishment of the latter, the former could not be performed : for, as the former depends upon the vital influence distri- buted to the ratnl'a X s and to their respective organs, as well as upon its state in the sources whence it is derived, so does this influence itself depend upon the operations which take place in the latter order of capillaries. The importance, therefore of these operations m the animal economy must be manifest, as well as the intimate bond which unites them throughout the frame : without the performance of the one class of functions, the other could " Thisdoarhtaof the circulation-the most interesting, perhaps, of any to the physiologist and nathologSt,-withoiit bein<< independent »f the heart's action, is the least under us control; 1 42 APPENDIX. the functions of the capillary vessels continuing to a certain extent, even after the heart has ceased to contract. And, as have been shown by some experiments performed in this coun- try, in France, and in America, these actions are not limited, even then, to the mere circu- lation of the fluid which they contain; for under this particular circumstance, they may also perform, for a short time, the functions of absorption and secretion. These phenomena may be readily explained when we consider two circumstances ;—1st, the source whence the capillaries derive their functions; and 2d, the kind of death which the animal experiences, and the order in which the different organs cease to act. We can- not enter here further into this topic; we have pointed out the way: those who are inter- ested in it will be able to pursue it; those who are not, would profit little from a lengthened explanation. Before we leave this subject we may notice an opinion which has been entertained amongst the most eminent physiologists. This relates to the existence of subordinate sets of minute and colourless arterial capillaries, each devoted to a particular function ; namely, one to nutrition, another to secretion, and a third and principal set, to the transmission of the red blood, which, in consequence of the functions ofthe former two, have become pos- sessed of venous properties. The first and second of these sets are considered to be pellu- cid in their natural state, and, although they cannot be satisfactorily demonstrated, in this state, their existence seems to be rendered probable, if not proved, by many of the pheno- mena of disease and by artificial injections. Dr. Alard has lately contended for the existence of a similar set of colourless vessels connected in the same manner with the veins; and that whilst those of the arteries carry the fluids intended for the nutrition of the textures, for the secretions, and exhalation; these belonging to the veins perform the functions of absorption. Some of these latter ves- sels, whose open mouths are present every where, in the most intimate textures of the organ.-, as well as on the surfaces of the great cavities, are supposed by Dr. Alard to terminate in the parietes of the adjacent veins ; whilst others unite and form the trunks which are generally known by the name of absorbents. The discovery of Dr Fohmann, of Heidelberg, of a communication of the lymphatics of the intestine with the mesenteric veins, in some ani- mals, concuis to support the proposition of Dr. Alard. On this subject Dr. Hutchinson, whose physiological knowledge is of the first order, has justly observed,—the view ef Alard __that supposing the existence of minute pellucid vessels, springing from the parietes ofthe small arteries; distributed to every part of the body ; conveying different fluids, and pro- ducing different effects, according as their vital properties are modified : having correspond- ing vessels, which spring from the most intimate texture of the organs and surfaces of the great cavities, and unite in larger tubes, forming in some instances long continuous canals, denominated absorbents, in others running to be inserted into veins,—is one whicii is quali- fied to explain, more plausibly than any other the mechanism of the distribution of the fluids for the purposes of the organic functions; and is, besides, capable of obviating the diffi- culties which have been presented by the diversity of the results of the experiments of Hunter, Majendie, Brodie and others, relative to the mechanism of absorption.'* (See the Note on Absorption.) Of the Veins. Note T. 1. As to the precise way in which the veins commence, opinions have been various. At the place where the capillaries change from arteries into veins, there appears to be no rea- son to suppose the existence of either interspace, or vesicular or spongy structure. The in-, fleeted canal of the artery seems to be continuous with the vein. Whilst, however, this con- formation is allowed by nearly all, some consider, with M. Ribes, that the veins have anoth- * Admitting fully the justness of Dr. Hutchinson's remarks, we must observe that, the existence of the sets of capillaries here contended for by Dr. Alard, is not proved demon- stratively. Indeed, we possess this species of proof in favour only of one set of capilla- ries—namely, those whicii constitute the termination of the arteries and commencement of veins. We know that secretion, nutrition, and adsorption, are functions of capillary vessels. This has always been granted from the time of Hippocrates; but there have been various instiuments allotted to the process, some physiologists insist, with Dr. Alard, upon the existence of subordinate sets of capillaries allotted to each function, whilst others con- tend, with M. Richerand, that they take place through the medium of lateral pores in those capillaries which communicate directly between the arteries and veins. These veins will come under consideration in the notes in this Ar-nf/idir on Secretion 'tritinv. OF THE MECHANISM OF THE RESPIRATORY ORGANS. 43 er commencement in addition to this; and that a certain proportion of their roots com- mence in open mouths or in tbe pores or areolae of the laminous tissues, and in the sub- stance ofthe organs. Others also suppose with M. Alard, (See the preceding note,) that some of their roots commence in pellucid lymphatic absorbents. The structure of the erectile tissues, as the penis, the clitoris, the spleen, &c. seems to support the opinion of M. Ribes, (which is also that of M. Meckel,) who farther supposes t.iat one cause of the difference of the appearance and functions of organs may be ascribed to the extent to vvhich the veins originate in the particular manner for which he contends. The views of M. Alard derive their chief support from the phenomena connected with absorption, but, although they appear probable, they cannot be fully demonstrated. The veins receive but a small proportion of nerves, and these are chiefly from the ganglia. The nerves supplying the pulmonary veins come principally from the anterior pulmonary plexus. 2. Thef unctions of the veins are— 1st, to bring back the blood from the capillaries to the heart; 2d, to receive and assist in the assimilation of the fluids, which are absorbed by the lacteals and absorbents; and 3d,in certain situations, and under certain circumstances, to co-operate in the function of absorption. The first of these operations is performed by means nf the vital action with which the veins are endowed, assisted by the vis a targo proceeding from the vital action of the capil- laries,—by the contraction of the surrounding muscles viewed in connexion with the direc- tion of the valves, with which they are provided,—and by the active dilation ofthe cavities of the heart whicii derives the blood from the venous trunks. The third action ofthe veins, or absorption, seems to be proved by the researches already detailed. (See Absorption in the Appendix.) The venous radicles, either immediately or mediately, seize the absorbed materials, and convey them into the current of the circula- tion. This seems to be a vital or organic action, which is probably assisted, in some parts of the body, and under certain circumstances, by the physical property of imbibition or capillary attraction, which all animal textures evince in a greater or less degree. It should, however, be recollected, that this property is a very subordinate one to vitality, is entirely under its control, and takes place very impeifectly when this influence is in full vigour. The second function of this class of vessels, is the admixture of the absorbed materials, and the assimilation of them. The former, or mechanical part of this function is performerl generally throughout the body, although it takes place to a greater extent in some instances than in others, as in those viscera in which the blood circulates more immediately after it has received the chyle and lymph from the lacteal absorbents and thoracic duct. Hence it chiefly takes place in the heart itself, and in the liver and lungs. The latter part of this function is essentially a vital one, and appears to us to result from the vital influence de- rived from the nerves with which the blood-vessels are provided. Supposing this position to be correct, we should expect that the vessels in which this process takes place would be most abundantly supplied with those nerves, whence we consider the assimilating influence to proceed. Now this is actually the case, the blood which is carried into the portal veins contains a larger proportion of absorbed and imperfectly assimilated materials than the blood in any other organ ; and this particular order of veins, whose office it is to assimilate them, and to eliminate the effcete elements from the circulating fluid, is provided with a much greater number of ganglial nerves than any other part of the venous system ; and, indeed, even more than the arteries iu some situations. This particular set of veins, there- fore, performs a double function, viz. of assimilation, and of secretion ; in the latter, how- ever, it may participate with the hepatic artery ; for, as the hepatic vein returns the blood of both the vena portse and the artery, the biliary secretion may, probably, not take place until the terminating capillaries of both have given rise to the radicles of the vein. Assimilation goes on, in the next degree of activity, in the lungs, and more or less par- tially in other organs of the body. Of the Mechanism ofthe Respiratory Organs. Note U. I. Of the Structure of the Lungs.—According to the observations of M. Magendie, the cellules of the lungs do not appear to be arranged in a methodical manner, nor to have membranous parietes. With respect to the non-existence of the latter, we think that he was betrayed into error by the method of investigation which he adopted.* These cellules * He partially filled the lungs by insufflation after their removal from the subject, and o1 lowed them to dry. When quite dry he found this sort of preparation to be nearly trans, parent, and readily cut into thin slices with a knife. 44 APPENDIX. seemed to him to be formed solely by the minutest and last ramifications of the pulmonary artery ; by the radicules of the veins of the same name, which are a continuation of the former, and lastly, by the numerous anastamoses of all these vessels. These cellules are separated into many district lobules, in each of which the cellules communicate among themselves ; while between the lobules there is no communication. " The number of cellules is in an inverse ratio to the age of the subject; consequently the older the person, the larger is each cellula, or what comes to the same thing, the fewer are the cellulse. "It follows, therefore, that the lungs become specifically lighter as we advance in life; and in support of the correctness of this inference M. M. states that he found, by actual experiment, that in equal volumes, a portion of the lungs of a man at seventy was fourteen times specifically lighter than that of a child a few days old." II. Of the Actions of the Glottis.—M. Bourdon (Reeherches sur le mechanisme de let respiration, &c. Paris, 1820,) considers that the glottis performs the following functions, in addition to those which are requisite to the formation of the voice. 1. "That is the glottis which suspends respiration during considerable efforts, in opposing, by its closure, the escape of the air contained in the lungs. 2. " Without the glottis, the action ofthe abdominal muscles would be cqpstantly em- ployed in producing respiration: neither compression ofthe viscera, nor flexure ofthe trunk could be produced. 3. " There exists a real consensus of action between the glottis and the abdominal muscles, and through this medium, between the glottis and the different reservoirs, the bladder, the rectum, the stomach, and the uterus. 4. "The glottis does not confine its action to the production of the voice ; but, by the aid of the sympathetic connexions which unite it to the abdominal muscles, charged to concur in, if not to preside over important functions, ii excites the greatest influence on those func- tions themselves. 6. " Lastly, in the different efforts there is a tendency to expiration, to the production of which the closure of the glottis is an obstacle." III. Of the Effects of Respiration on the Circulation of the Blood.—The experiments of Haller, Lamure, and Lorry, and subsequently those of Cloquet and Bourdon, have shown, 1. That, during inspiration, the blood of the vena cava, superior and inferior, is drawn tewards the heart. 2. That, during expiration, the blood is, on the contrary, driven in the same veins, to- VirRrds the viscera. 3. That the arterial blood is also driven towards the viscera at the time of expiration. 4. That the alternate motions ofthe brain is owing to the changes caused by respiration in the flow of blood. 5. That all these charges are but little marked in ordinary respiration ; but that they be- come very evident in full respirations, and particularly so during great efforts. 6. Lastly, that, during great efforts the glottis is firmly closed, the air contained in the lungs is compressed, as well as all the pectoral and abdominal viscera. In order to ascertain the precise effects produced by respiration on the venous circulation, M. Magendie instituted a set of experiments from which he draws the inferences, that res- piration modifies the venous circulation ;—1° by the influence which it exerts on the course ofthe arterial blood;—2" by its direct action on the current of blood in the veins. That in profound respirations and violent efforts, the circulation appears nearly suspended. IV. Ofthe Stale of the Lungs during Respiration.—The experiments of Dr. Carson have directed the attention of physiologists to the state ofthe lungs themselves during respiration, and under the various influences to which they are usually subjected either by accident, by operations, or by disease. Dr. Carson had inferred from his experiments, that it is possible to collapse one ofthe lungs, and to retain it in that state, ad libitum, by keeping open the communication between the cavity ofthe chest and the external air; and further, that upon allowing the opening to close, the lung, in a given time, will recover its wonted function, thereby rendering it practicable, when conceived necessary, to place the opposite lung un- der the like discipline. In order to examine the stability of these inferences. Dr. David "Williams, of Liverpool, instituted several experiments, in the presence of Dr. Trail ar ' V OF THE FUNCTIONS OF THE LUNGS. 45 others, which contradict some of the chief positions held by Dr. Carson. After detailing his experiments, Dr. Williams draws the following conclusions from them. " 1. That a lung will not collapse from exposure to the atmosphere as long as respiration is carried on by the opposite one, and the auxiliary respiratory powers are not restrained. "2. That a lung possesses for a time, independently of the influence of the diaphragm and intercostal muscles, if respiration is carried on by the opposite lung, a peculiar motive power, the source of which I do not pretend to explain. " 3. That a sound lung soon regains its full power of expansion, when the pressure of the exterior air is iemoved. "4. That air freely and uninterruptedly admitted into both cavities ofthe chest simulta- neously, through tubes of a certain calibre, will not collapse the lungs, if the auxiliary res- piratory organs are unrestrained. u>. That air admitted into both the cavities ofthe chest (of a middle sized dog) simulta- neously through appe.tures of an inch and better in length in the intercostal spaces, will not collapse the lungs, provided t,he animal is allowed unconfined the use of his respiratory organs. " 6. That a sound lung never fills the bag of the plura".'' V. Of the Effects of Suspended Respiration on the Circulation.—From the experiments which were made by Dr. Williams, of Liverpool, on this subject, he deduces the following corollaries: 1. The blood is obstructed in its passage through the lungs, on suspension of respiration, while its circulation through the other parts ofthe body continues. 2. The obstruction of the blood in the lungs, on suspension of respiration, is not occasion- ed by a mechanical cause. This is proved by the flow of blood through the lungs being suddenly arrested, without any subsidence of this organ, while the circulation was carried on vigorously through the other parts of the body, in the experiments detailed by the author. 3. The observation of blood in the lungs, on suspension of respiration, arises from the de- privation of pure atmospheric air. 4. The blood, which is found post mortem in the left auricle and ventricle, is the remnant after the last systole, and the subsequent draining of the pulmonary veins. 5. The obstruction of blood in the lungs, on suspension of respiration, is one of the prin- cipal causes ofthe vacuity after death ofthe system circulating arterial blood. 6. The immediate cause ofthe cessation of the action of the heart is a privation of its natural stimulus, arising from the obstruction ofthe blood in the lungs.—(Annals of Philos. Sept. 1823.) Of the Changes induced o?i the Air and the Blood by Respiration. Note W. 1. Of the Production of Carbonic Acid during Respiration.—The experiments of Mr. Ellis and others have led physiologists to conclude, that oxygen is not absorbed by the blood in the lungs from the air, during respiration, but that the blood gives off its superabundant carbon from the surface ofthe air-cells and the carbonic acid is thus formed in the lungs themselves. This mode of accounting for the changes induced upon the air and upon the blood during respiration, has been very generally adopted in this country, while the former mode of ex- plaining the process (that which is given in the text) has still been received, with various modifications, on the Continent. It appears to us that the production of carbonic acid gas by the respiratory function has been ascribed too exclusively to one of the above processes; and that it has been too generally viewed as altogether a chemical phenomenon. When the theory of the absorption of oxygen was dismissed in favour of that which contended for the discharge of carbon from the blood, either in its pure state or in that of an hydrate, no participation in the pro- cess by which the carbonic acid is formed, was allowed to the previously received opinion : however, it still appears a matter of doubt how far either function predominates ; for we are inclined to think that both operations go on simultaneously, and that, whilst a portion of the carbonic acid gas is given out from the blood, already formed, it is accompanied with another portion of free carbon, or an oxide of carbon, or even with an hydrate ofthe same substance, which combines with an additional quantity of oxygen in the lungs, and thus Vorms the whole ofthe carbonic acid in question; and that, at the same time, a portion m 4b APPENDIX. oxygen is absorbed, which combines with the carbon ofthe biood, and there generates this carbonic acid gas, or the oxide of carbon, which forms a part of the matters discharged from the blood in the lungs. These processes may vary, and either may predominate ac- cording to the state of the vital influence at the time, under whose control they are immedi- ately and completely placed. This view of the phenomenon in question seems to be fully supported by the experiments of Dr. Edwards of Paris. They prove that the carbonic acid gas does not form instan- taneously in the lungs through the action of the respired air, but that it appears to be se- creted to a considerable extent, from the blood in the respiratory organs. As to the quantity of this gas which is formed during respiration, different physiologists have estimated it differently. Godwin considered that lor every 100 cubic inches of atmos- phere respired, there were given off 10 or 11 of carbonic acid. Menzies, from experiments made with much accuracy, found the quantity of carbonic acid to be about 5 in the 100. Dr. Murray considered it to vary from 6 to 6.5. Sir H. Davy from 3.95 to 4.5. Messrs. Allan and Pepys from 3.5 to 9.5 They estimated the mean at about 8. Dr. Prout found it to be about 3.45. Dr. Fyfe about 8.5. The discrepancies which are remarkable in these results of the experiments performed by these physiologists doubtless arose, in a great measure, from the different proportions of this gas, produced by different individuals accor- ding to the state and developement of the lungs, and according to the particular circum- stances of the individual at the time of the experiment. The influence wbich the state of the individual exerts upon the function was first shown by the experiments of Dr. Prout and Dr. Fyfe. They proved that the carbonic acid gas formed during respiration is liable to be very materially affected in its quantity in the same individual, by various circumstances. It was formed in a minimum quantity during the night; and the maximum quantity, which was generally produced about noon, exceeded the minimum about one-fifth of the whole. The passions of the mind were found to have a great influence over its production ; the depressing passions diminishing its quantity, and ft those of an opposite nature the reverse; exercise, when moderate, appeared to increase in some measure the quantity, but fatigue diminished it. The greatest decrease experienced was from the use of alcohol and vinous liquors, especially when they were taken upon an empty stomach. In short, whatever diminished the powers of life, as low diet, mercurial irritation, &c. appeared from the experiments of Dr. Prout and Dr. Fyfe to have the effect of diminishing the quantity ofthe carbonic acid. Dr. Crawford found the quantity of this gas was much diminished when respiration was performed in a high temperature ; and Lavoisier and Seguin confirmed his observation. Nearly similar results to theirs were obtained from some experiments which we performed in 1815 : and from the data thus obtained we endeavoured * to account for several ofthe most important diseases to which the inhabitants of warm countries are liable. Similar experi- ments were afterwards performed in an intertropical climate, where we found the diminu- tion ofthe quantity of carbonic acid to be considerably greater than that which our experi- ments, in an artificial temperature of equal elevation had furnished. This seems to be ac- counted for by the depressing influence upon the nervous system which the atmosphere, loaded with moisture and malaria, may be reasonably expected to produce. We also at- tribute a share of this discrepancy to the increased function of the skin, which evidently co- operates, in hot climates with the lungs, and performs a subordinate respiratory function. We shall not pursue this particular topic farther at this place, as we propose considering it more at length on a future occasion. Reverting to the question whether the carbonic acid is formed within the vessels, or without them; we must remark, that the evidence on the subject is very contradictory. The experiments of Dr Edwards, already referred to, show that the former process exists, at least to some extent; and it is farther supported by the fact established by Berzelius, tiiat blood, especially its colouring part, not only absorbs oxygen very quickly, but it also retains some part of the carbonic acid thereby produced; but whether or no this absorption will take place through the parietes of the capillaries, is the point at issue. The evidence for the absorption of oxygen through the capillary parietes is, however, nearly on a par with that for the excretion of the carbon ; if the vessels will permit the transmission of the one, they may allow the transit ofthe other. Those who contend for the passage ofthe carbon from the vessels, and who, consequently consider that the carbonic acid is formed externally as respects the vessels, support their opinion by the experiments of Mr. Ellis, who first promulgated the doctrine. His experi- ments, were, however, performed out of the body, and under circumstances which entirely excluded the operation of the vital influence of the lungs and of the system generally. The most conclusive experiments in favour of this opinion are those performed by MM. Magendie and Orfila. They found that phosphorus, dissolved in oil, and injected into the jugular vein ofa dog, was expelled by the mouth and nostrils in the form of copious vapours * These views were contained in a Latin Theses written at Edinburgh. OF THE FUNCTIONS OF THE LUNGS 47 at phosphorus acid, which could hardly have been the case if the phosphorus acid had been formed within the vessels, as in this case, it would have remained in solution in the blood, it not being a volatile substance. It might therefore be supposed that the phosphorus was excreted in a state of minute division, from the vessels of the lungs, and meeting, in this state, with the oxygen of the atmosphere, formed the phosphorus acid in question. If this reason- ing be admitted with respect to the phosphorus, it may be extended to the carbon contained in the venous blood. From the contradictory evidence on the subject; from the nature of that evidence; from the experiments of Dr Edwards; from varies analogies that might be adduced, could our limits permit, from the conformation of the lungs, and the extent of their exerting and ab- sorbing functions as evinced by experiments; and lastly,.from the consideration that, although respiration takes place frequently, yet a very large portion of air remains for a considerable time in the chest, thereby allowing the vitality of the lungs themselves to be exerted upon the air received into them,—we conclude that this organ may act in both the ways contended for ; and that, whether it act in one manner or the other, more or less par- tially, the process is a vital one, and whatever chemical laws may be employed in it, are under the control ofthe vital influence ofthe organ, and modified by the ever-varying con- dition of this influence. II. Of Absorption and Exhalation of Azote during Respiration.—Another subject of much interest connected with the respiratory function, is that which immediately relates to the absorption in the lungs of a portion of the azote contained in the respired air. On this point also, the results of experiments have been various, and opinions respecting them equally so. Dr. Edwards, of Paris, who is well known as a very intelligent physiologist, concludes, from different experiments, and from the circumstance of the opposite results which they give, some indicating a diminution of the azote of the air, others an increase of it during respiration, that this gas is absorbed into the circulation, and afterwards dis- charged from it; and that each of these actions is regulated by the constitution, habit, and circumstances of the individual, and by the influences to which he may be subjected, the absorption being to a small extent, while the exhalation is considerable, and nee versa. Independently of the satisfactory nature of the experiments whence Dr. Edwards has drawn his inferences, there are many collateral proofs that may be brought to their support, derived from the manifestations of the animal economy in health and disease ; and we have little doubt that not only is azote, but that other gases, even those whose presence in the respired air are accidental, may be also absorbed into, and discharged from the circulation, in a greater or less quantity, according to the varying state or the vital energies of the svstem. III. Ofthe Assimilating Function of the Lungs.—The extent ofthe function ofthe lungs has been a matter of doubt. Their principal office, namely, that of changing venous into arterial blood, has always been admitted, although the nature of the process has been disputed. Many physiologists have, in addition to this, attributed to them an assimilating influence which is exerted chiefly upon the absorbed chyle and lymph whicii the venous blood contains. This opinion appears correct. But the process is purely a vital one. If the opinion of Dr. Edwards, respecting the absorption and exhalation of azote be correct, this substance may be instrumental in the process. A third function has been referred to this organ, viz. the formation of animal heat. But however intimately related it may be with the respiratory process, it cannot be considered a function of the lungs. It must, nevertheless, be allowed that the changes induced upon the blood during respiration, are preparatory to the evolution of animal heat; and, although we contend that this heat is immediately the result ofa manifestation of the vital influence ofthe ganglial system of nerves, exerted upon the blood contained in the vessels to which these nerves are distributed, yet it must be admitted, that the respiratory pro- cesses are requisite to its production, inasmuch as they produce on the blood a change of properties which are requisite to excite this system, and as this fluid, when thus changed, contains the materials necessary to,or is otherwise in a suitable condition for, the manifes- tation ofthe influence which that part of this system of nerves which is distributed to the blood-vessels exert. IV. Of Pulmonary Transpiration.—The mucus membrane of the lungs gives off a con- siderable portion ofthe watery secretion, which is carried out of the lungs, in the form of vapour, by the respired air. This perspiration equally takes place when the animal breathes a gas containing neither oxygen, hydrogen, nor azote ; it, therefore, does not result from the combining in the lungs of the hydrogen contained in the blood with the 48 APPENDIX. respired air, but is strictly an aqueous vapour slightly charged with animal matter—and i« the production ofa vital transpiration or secretion. It has not been determined whether or no it be produced from the bronchial, or from the pulmonary arteries. The question is difficult to decide, as an injection thrown into either set of arteries arrives on the surface of the air-cells. Pulmonary transpiration may con- tain, like secretions, foreign matters which have been conveyed into the circulation; the lungs acting as an organ eliminating them from the system. This has been shown by some experiments cf M. Magendie, and also in an experiment which we performed, in which ten drachms of the oil of turpentine were chiefly discharged by the lungs, from the circulation in the state of vapour, within twenty-four hours The large quantity of the turpentine vapour evolved from the lungs on that occasion, leads us to suppose that transpiration takes place principally from the venous blood about the time when the changes are effected in it by respiration. This experiment, also seems to support the doctrine ofthe evolution of carbon from the blood. Of the Production of Animal Heat. Note Y. It is not necessary to add at this place, much to what is contained in the text. We then attributed the production of animal heat to the vital influence exerted by that part of the ganglial system distributed to the arteries on the blood which they circulate. Preparatory changes, however, take place in the lungs which are necessary to the exer- tion of this influence, and to the evolution of heat; but, as it was contended that those changes are more of a vital than of a chemical nature, so it is considered, that the produc- tion of heat is more the result of the influence which the nerves of the vessels exert upon the blood than of the change in the capacity for caloric which the blood itself experiences in its passage into the venous state. The difference of capacity which actually exists be- tween venous and arterial blood is not sufficient, according to the experiments of Dr. Davy, to form the basis of the chemical theory formerly received, but the difference which actually does exist may be concerned in a subordinate manner in the process. Conformably with the opinion, as was first maintained on an occasion already alluded to, we infer that the various causes which modify the production of animal heat, act, 1st, immediately upon the organic system of nerves themselves, changing the condition of their influence ; 2d, upon the blood, altering the nature and composition of this fluid, and thereby rendering it unfit for producing the requisite excitement of this system of nerves, and in- capable of the changes which the influence of these nerves produces upon its constituent parts; 3d, immediately through the cerebro-spinal system, modifying the influence which this system imparts to the ganglial. These different ways in which the vital influence, exerted by this system of nerves in the production of animal heat, is modified, might have been illustrated by experiments, and by reference to facts in comparative physiology and in pathology, if our limits could have ad- mitted of so great an extension of them. From what we have said it will be perceived, that we view the production of animal heat more in the light of a vital secretion than of a chemical phenomenon; and that, like the other secretions and nutrition, it proceeds from «nd is controlled by the vital influence of trie ganglial system of nerves. Of the Cutaneous Function. Note Z. I. Cutaneous Exhalation, or Insensible Transpiration.—In transpiration there appears to be two actions, a physical one consisting of the evaporation in the air of the fluid parts of the body; and a vital action, giving rise to an excrementitial exhalation, of which the skin is the organ. This view of the subject is much contended for by Dr. Edwards; but we think he has refilled in an unnecessary manner in explaining it. The cutaneous exhala- tion is doubtless an organic function of which the skin is the organ ; but, vve conceive, that the skin must first perform its office before the physical action can take place to any considerable extent: in short, that as transpiration is performed, the physical law operates, and that both go on, the latter as a consequence ofthe former, paripassu, until an increase of tbe transpiration on the one hand, and an uncommonly dry state of the atmosphere, on OF THE RESPIRATORY ORGANS, &C. 49 tiie other, give us different results. When the former takes place we perceive the formation of sweat, or the transpiration becomes sensible : when the latter exists, then the pheno- menon, for which Dr. Edwards and some others have argued, as constituting one of the actions into which this function may be divided, really supervenes to some extent. Thus we have witnessed, duiing the Harmattan wind, which occasionally blows on the West coast of Africa, and which is remarkabre fonts dryness, evaporation going on so rapidly as to give rise to very inconvenient sensations, and even to serious disorders of the parts whicii are usually exposed to the air. In this case the e vapc ation exceeds the mere solution of the transpired fluid in the surrounding atmosphere: and the parts of the body which are sub- jected to its operation, have a portion of the fluids sent to the surface carried off by it, in addition to what is exhaled by the natural and organic action of the vessels of the skin. The cutaneous exhalation contains a portion of the carbonic and lactic acids. II. Of the Sweat or Sensible Exhalation.—When we said, that, if the production of the halitus or insensible transpiration from the skin exceed the evaporation of it in the atmos- phere, sweat is formed, we stated the source of this fluid. It is, therefore, produced from the same vessels as the insensible perspiration. But although this is the case, with respect to their source, there is some difference between the nature or chemical constitution of the sensible and insensible cutaneous exhalations. The former is generally less charged with carbonic acid than the former, but it abounds more with the salts usually excreted from the system. A careful view of the functions of the skin throughout the different classes of animals, leads us to conclude that it performs operations which hold an intermediate place between those of respiration and elimination,— that it partakes of the character of a respiratory and of an eliminating organ. 1. // is a Respiratory Organ.—This is shown by the circumstance of this function being performed in the lower orders of animals by the surface only ; and by the gradation ob- served from these up to the higher orders, and by the gradual perfection at which the respi- ratory organ arrives in ascending the scale of anjma) creation. In the higher animals the respiratory apparatus becomes more and more distinct, and the function depending upon it more and more/limited to appropriate organs ; however, the same type which characterizes the lower orders, and is most remarkable in them, is still preserved throughout the whole series of the animal scale, although it becomes gradually, and nearly, but not altogether lost. Thus in man, the lungs perform the chief respiratory process; but, even in him, the respiratory function of the skin is remarkable. Carbonic acid gas is produced from the cutaneous surface, transpiration also takes place there ; and this respiratory act of the skin becomes more and more remarkable under circumstances which diminish or partially ob- struct the respiratory process of the lungs. Thus we found that the quantity of carbonic acid gas, formed in the lungs, in a given time and in the same individual, was about one- third less in a hot climate than in a cold one ; this was about the average result of our ex- periments : whilst we observed that the respiratory function of the skin, both as respects the quantity of the insensible transpiration and the formation of carbonic gas, was very re- markably increased.* In a Negro, as far as we could infer from experiments performed on a single limb, the respiratory function of the external surface of the body was much greater, and the quantity of carbonic acid formed in his lungs much less than in our own case al- though our size and weight were equal. Mence we were led to infer that, in this race of the human species, the skin performs a much greater supplementary function to that of the lungs, than in the inhabitants of cold or temperate climates. In two cases which came, under our observation, in whicii the lungs were partly destroy- ed from an imposthume, and the side of the chest was consequently contracted, the cutane- ous functions were afterwards very remarkably increased. Were it consistent with the limits of these notes, many facts illustrative of this particular function of the skin, as it respects the inhabitants of cold, temperate, and hot climates, might be adduced. 2. The Skin is an Eliminating Organ.—M. Richerand has so fully illustrated this func- tion of the skin, and contrasted it with that performed by the kidnies, that it is unnecessary to say any thing respecting it. at this place. The chemical analysis of the perspired fluid, given in the next chapter of the Appendix, will show to what extent it performs an elimin- ating office. * The experiments wbich were made in order to ascertain this from the want of the means and proper facilities were not performed upon the whole body, they were made only upon a single limb ; but the results were very decisive and remarkable- JO APPENDIX. Of the Fluids. Note AA. In addition to tiie classifications of the fluids, we may mention that adopted by M. CiiauS' sier. He divides the fluids into five classes: those produced by the digestive process—the chvme and the chyle; the circulating fluids—the lymph and the blood ; the exhaled ov perspired humours; the follicular humours, and the glandular humours. M. Adelon, the able and eminent pupil of M. Chaussier, has proposed another classifica- tion, vvhich possesses some advantages over those which have preceded it. It is also simp- ler and more natural. He divides the organic fluids into those of Absorption, the fluid specially Nutritive, and the Secreted Humours. 1° The Absorbed Fluids are the chyle, the lymph, and the venous blood. These are taken up and conveyed by the lymphatic and venous class of vessels, and ultimately become assimilated with, and, indeed, concur to form the fluid specifically nutritive. Thus the chyle, after a longer or shorter course, mingles with the lymph, both aie poured into the venous blood, and when they arrive at the organs of respiration, they become perfectly united, being converted into the nutritive fluid by the functions of those organs 2° 77ie Fluid especially Nutritive.—The three fluids constituting the first class being changed in the respiratory organs into that which can alone nourish the body, thus consti- tute the second class, which, in its turn, furnishes the materials of all those embraced by the third. The second class is, therefore, the arterial blood only, which, being fully per- fected in the lungs by the action of the atmospheric air, and circulated throughout the body, furnishes the materials of nutrition and secretion, and stimulates, and contributes to pre- serve the functions of the living solids, and, in conjunction with these solids,* produces the calorification of the animal system. 3° The Secreted Humours.—This class may be divided into three orders, according to the forms of the secreting organs which produce them; namely, into Exhaled or Perspired Fluids, Follicular Humours, and Glandular Humours. A. Exhaled or Perspired Humours.—These are numerous, are produced in the form of vapour, and they differ from one another in their physical and chemical properties, and in the purposes which they fulfil in the animal economy. They are, moreover, distinguished into those whicii are taken up by lymphatic or venous absorption, and carried back into the torrent of the circulation, and into these which are entirely thrown out of the body ; the former being usually denominated recrementilial, the latter excrementitial, from these circumstances. The recrementitial fluids are all produced in cavities or in situations that have no exter- nal outlet. The following enumeration includes all the fluids appertaining to this genus :— 1° Serous fluids, as those which are exhaled on the surface ofthe arachnoid, ofthe pleura, of the pericardium, the peritoneum and the tunica vaginalis.—2° The Synovia. 3° The serosity of luminous tissues.—4° The fat formed in the adipose tissue.—5° The marrow, or medullary juice.—6Q The colouring humour of the skin, placed under the epidermis.—7Q The colouring humours of the iris, of the uvea, and of the choroid.—8° The three humours of the eye—the aqueous, crystalline, and vitreous.—9° The lymph of Colugno.—10° The hutnour ofthe lymphatic glands, a gelatino-albuminous fluid, existing in the spongy tissue of their organs.—11" and lastly, the fluid perspired on the internal surface of all the vessels, the existence of which may be doubted, as it is next to impossible to demonstrate its exist- ence. In addition to the perspired recrementitial fluids may be added those which exist in tbe human ovum, viz. the amniotic fluid; the water of the chorion, which exists between the chorion and amnios, only during the early months of pregnancy ; and the water of the umbilical vesicle, vvhich may be compared to the yolk of an egg, and which some Physiolo- gists believe destined to nourish the embryo before the developement ofthe placenta. The excrementitial perspired fluids are all thrown off from the external surface of the body, and from the mucous membranes which have a communication externally by means ofthe natural outlets, and which may therefore be considered as merely forming parts of the ex- ternal surface.—1° Those fluids which perspire from the skin, as the cutaneous insensible perspiration, and the humour constituting the sweat.—2° The fluids perspired from the respiratory apparatus ; these differ somewhat in different situations, as in the nasal cavities, in the trachea, and bronchiae.—3° The humours exhaled on the surface of the digestive canal.__4° Those humours exhaled on the internal surface of the urinary apparatus, viz. on * By living solids is here meant all sensitive and irritable parts—all those which are in- fluenced by an irritating cans?, CLASSIFICATION OF THE FLUIDS. 61 the internal surface of the ureters, the bladder, and urethra.—5° The fluids exhaled from the genital organs, namely from the internal surface ofthe vesiculae seminales and ejacula- tory conduits, in tke male, and from the uterus and vagina in females (the menstrual flux and the lochia?.) B. The Secreted Follicular Fluids are those formed by a particular secreting organ called follicular. They are all excrementitial, and consequently are formed on, and elim- inated from, the two external surfaces of the body—the skin, and mucous membranes. They consist of—lo The sebaceous humour ofthe skin.—2° The cerumen; tne humours of Meibomius.—3° The humour of the caruncula lachrymalis.—4* The humour secreted at the base of the glans penis in the male, and on the surface of the vulva in the female. The humours secreted by the follicles in the mucous surfaces are generally characterized by the generic term mucous. They are distinguished into the mucus ofthe respiratory organs, the mucous ofthe digestive apparatus, of the urinary apparatus, and of the genital organs. The humours formed by the prostate, and by the glands of Cowper—compound and glandiform follicles—are usually referred to the last mentioned in this enumeration. The fluid secreted by the tonsilsis generally classed with those ofthe digestive organs. C Lastly. The Secreted Glandular Humours are the production of glandular organs. They are—1° The lachrymal fluid.—2° The salivary fluid.—3° The pancreatic humours. —4° The bile.—5° The urine.—6° The semen ; and 7° the milk. It may be remarked generally with respect to the humours, that the degrees of fluidity which belonging to them, vary greatly from a state of gas or of vapour, to that of semi- fluidity ;—they have, moreover, all the physical conditions constituting a fluid body. Their fluidity, however, does not result from the general forces of matter, but from those of life. Indeed the vital influence modifies their physical form of existence, in a more or less marked manner, as long as they continue subjected to its operation. From this source also they are imbued with a certain influence, the presence of which is indicated by the continuance, for a time, of the specific characters of each. This influence, being no longer renewed when they are removed from the body, soon becomes dissipated, and the secretion which, while within the sphere ofthe animal system and for a short time afterwards, possessed an emanation of the vital influence sufficient to give it certain characters, and to preserve it from the chemical changes to which its constituents are naturally pione, at last falls into a state of dissolution, as unequivocal as that evinced by the textures of the body. In con- firmation of this view, we need only refer the Physiologist and Pathologist to the compara- tive condition ofthe more perfectly elaborated secretions immediately after their formation and excretion, and after periods of various duration have elapsed from the time of their discharge from the body. Finally, we may remark that the fluids, being composed of molecules moving with facility on each other, cannot, as the solids, be traced to constituents of an elementary nature. They can only become the subject of miscroscopic research in our endeavours to trace the nature of their constitution ; by this means we can merely learn that they are generally ' composed of globules, swimming in a fluid substance, and whatever be the fluid employed, we perceive only globules suspended in an amorphous liquid. It should, however, be remarked that, as we find in some solids merely a concreted amorphous substance containing no globules, as in the cellular tissue for example, so we perceive some fluids destitute of globulee and formed only of an amorphous substance, which is perfectly fluid. In other solids and fluids, on the contrary, we find both globules and an amorphous matter which is concrete in the former and liquid in the other But these globules vary greatly, both in in solids and in fluids, and even in the same part, according to age : those of the blood, for instance, are composed of a solid central part, and of an exte rnal envelope which is coloured ; those ofthe chyle appear to be the same as the central part ofthe former with- out its coloured envelope; those ofthe muscular fibre seem to be the same as those of the blood; those ofthe brain and nerves are smaller than the foregoing; and those of the kidnies are smaller than those of the spleen.—During the first epoch of conception, the globules are not visible ; they, however, soon form, and become more and more distinct. See on this subject Physiologic de rHomme,parN. P. Adelon. Vol. I. p. 116. Of the Blood. Note BB. I. Ofthe small colourless Globules of the Blood.—The researches of Sir Everard Home- and Mr. Bauer, (Phil. Trans, for 1820.) seem to lead to the following conclusions respect- ing these globules. 52 APPENDIX. 1. That the milk-like fluid, the produce of digestion (chyle) which is found in the laclcui vessels and glands, contains an infinite number of white globules, chiefly of a minute size. 2. These newly discovered minute globules are ^^Vo Part °f an 'ncn in diameter. 3. That the chyle contains also some white globules ofthe size ofthe red globules of the blood. 4. Mr. Bauer supposes that the full sized globules acquire their form in the lacteal glands. 5. Sir Everard Home considers that the globules ofthe blood receive their red hue in the vessels of the lungs. 6. That lymph or fibrile, whether taken from an inflamed surface, from tbe buff of what is commonly called inflamed blood, or from the s'owly formed layers of aneurismal tumours, consists of innumerable white globules, much smaller than those which constitute the red globules ofthe blood, and similai to those minute elobules already described. 7. That these small globules constitute the substance thiown out in inflammation. 8. That they are held in solution in the serum, and consequently are only brought into view in the act of coagulation* 9. That these globules, as well as those which subsequently receive the red colour, are the produce of digestion, and are formed in the pyloric portion of the stomach, and in the duodenum, surrounded by a glairy mucous, which is met with in these parts. MM. Prevost and Dumas * agree with Sir Edward Home, as to the form and structure of the globules of the blood ; but they do not admit with him that the red globules undergo a rapid change after they escape from the 'vessel, or that the colouring matter which envelopes the central spherical body separates as soon from the globule, as thirty seconds after the blood has issued from the vein. They, however, agree with him in saying, that these cen- tral spheres (the smaller globules) unite themselves in filaments, which differ in no respect from the muscular fibre. They observed also small globules in the milk, in pus, and in the chyle ; and they consider that those of the former fluids have been, and these of the latter are to be, surrounded by the colouring matter of the blood. MM. Prevost and Dumas found the globules of the blood to be circular in all the mam- malia ; and in their size to vary in different animals; they are smallest in the goat. The globules are elliptical in birds, and they vary considerably in size in this class of animals. This variation is chiefly in the great axis of the globules. They are elliptical also in all cold-blooded animals. II. Ofthe Coagulation of the Blood.—On this part of the subject before us, we cannot enter minutely. We will merely state, as briefly as we can, those inferences at vvhich vvc * The microscopic observation of the blood satisfied these gentlemen that this liquid during life, was nothing else than the serum, holding in suspension small, regular, and insoluble corpuscles. These are uniformly composed of a central colourless spheroid, and ofa species of membranous bag, ofa red colour, surrounding this spheroid, from which it is easily separable after death. The central body is white, transparent, of a spherical form in animals with circular particles; of an ovoid form, in those with elliptical particles. Its diameter is constant in the first, but it varies very perceptibly in the second. It manifests also a great disposition to form aggregates or ranges, in the form of a string of beads. The coloured portion appears to be a kind of jelly, easily divisible, but insoluble in water, from which it may always be separated by repose. It is likewise transparent, but much less so than the central corpuscle; and the fragments arising from its division are not suscepti- ble of regular aggregation. As the attraction, which keeps the red substance fixed round the white globules, ceases at the same time with the movement ofthe liquid, these globules can then obey the force which tends to unite them, and to form a net-work, in whose meshes the liberated red colouring matter gets enclosed ; and thus to produce the phenome- non of coagulation. If the coagulum be exposed to a stream of water, the colouring mat- ter is washed away, while the aggregate formed by the white globules remains in the form of filaments, in which may be recognised, by means of the miscroscope, the aspect ami structure ofthe muscular fibre. D Three animal substances ought, therefore, to fix our attention : these are, the albumen of the blood, the white globule, and the colouring matter which envelopes this. Witk respect to the colouring particles of the blood, these chemists suppose that it is formed of an animal substance, in combination with a peroxide of iron. The colourless globules they consider to be coagulated albumen. They have examined the proportion vvhich the white corpuscles and red matter together bear to the rest of the blood, in a great variety of animal's; and they find them most abundant in birds, next in the mammalia, especially the carnivorous mammalia ; and they are least plentiful in cold-blooded animals. In man they constitute about one hundred and twenty-nine parts by weight, per thousand. They are more abundant in arterial than in venous blood ; one"thousand parts ofthe arterial blood of the sheep, dog, and cat, contain ten parts more of these particles than blood taken from the veins. The serum is identical in both. OF THE COAGULATION OF THE BLOOD. 03 have arrived, after a careful examination of the phenomenon itself, under various circum- stances, and ofthe different opinions entertained respecting it. 1. According to the observations of Treviranus and Kolk, those observations on this sub- ject have been extended and faithful, the particles or globules of the blood possess a rota- tory motion during life, and this motion continues until the phenomenon of coagulation takes place. 2. That this motion ofthe globules is the cause of the blood's fluidity. 3. That the motion of the globules is the consequence of the vital influence emanating from the ganglial nerves distributed in the parietes of the vessels in which they circulate. 4. That the cause ofthe coagulation ofthe blood is not to be fouud in external agencies but in the loss of that emanation, (proceeding from the organic nerves distributed to the coats ofthe vessels,) ofthe vital influence with which the globules are endowed. 5. That the presence ofthe air, especially ofthe oxygenous portion of it, promotes this phenomenon. 6. That when coagulation commences at any point of a mass of blood it is rapidly propa- gated throughout the whole : this may arise from the cause being co-ordinate, or nearly so, throughout the whole. 7. Neither the heat of the body, nor the strength of the circulation, are causes of the blood's fluidity, they are both results of one cause, viz. the vital energy ofthe vessels ; both are co-ordinate, and both as well as the phenomena of coagulation itself, are dependent on this one source. 8. That coagulation occurs sooner in venous than in arterial blood . and that coagulation of arterial blood is still longer delayed if it be prevented from leaving the arteries. 9. That coagulation takes place the sooner after the blood is removed from the vital sphere of the system, the weaker the vital energy to which it was subjected whilst circula- ting in the system. 10. That the weaker the vital energy, and, consequently, the quicker the coagulation, the more lax is the coagulum which is formed. 11. That, on the same principle, coagulation is more slow, and the coagulum more firm, according as the vital influence of the vessels is more energetic. 12. That the quantity of globules modifies these results; a large proportion also of these globules indicates great energy, and vice versa. 13. That as the central globules retain their coloured envelopes, during their circulation in the blood-vessels, and lose them soon after removal beyond the sphere ofthe vital influ- ence of these vessels, and as this is a part, and indeed the first part of the act of coagula- tion, so we consider, that it is in consequence ofthe vitality emanating from the interior of the vessels into the blood, that the coloured envelopes of the central globules continue to surround them; and, consequently, that the separation of the envelope from the central globule is the result of the loss ofthe chief portion of that vitality vvhich proceeds from the containing blood vessels ; and, as this loss of vitality may be reasonably supposed to be quickest where it has been originally the least, therefore the suparation of the envelopes and the coagulation will be the quicker the weaker the vital energy, and vice versa ; and the coagulum will be the more lax. 14. That the loss of the vitality, emanating from the vessels, and, consequently, the loss of their envelopes, disposes the central globules to attract each other ; and that in the ex- ertion of this contraction they dispose themselves into reticulated fibres, which entangle the colouring matter and a portion of the serum ; and thus the clot is formed. 15. It would appear that the central globules continue to retain, in the fibres which they form, in the act of coagulation, a small portion ofthe vital emanation with wbich they were endowed ; in as much as the fibrous part of the coagulum evinces phenomena approaching to those denominated irritable ; and that it is the loss of the chief part of the vitality, and not the whole of it, which occasions the separation of the coloured envelopes from the central globules. 16. That the firmness of the coagulum and the irritable phenomena evinced by its fibrous part are proportionate in degree to the vital energies with which the vessels are endowed by the ganglial nerves distributed in them, and to the emanation which the globules them- selves derive from this source. 17. That the vital emanation, proceeding from the ganglial nerves distributed in the vessels affecting the globules in this manner, and »iving rise to these phenomena, has been the cause of, and has countenanced, the hypoth* sis of the vitality of the blood—a vitality vvhich does not originally belong to it, which it possesses in a diminished degree, and whicii is an emanation from a different source, which source is efficient in the formation of the blood itself and bestows on it, through the medium of the vessels containing it, the chief properties whicii this fluid evinces in health and in disease. 18. That when the vitality of the blood-vessels is greatly diminished, as in purpura haemorrhagica, scurvy, and in other diseases,coagulation either does not at all take place, ;-»r it takes place very quickly, and the coagulum is weak, lax. and resembling cruor. Un- *1 APPENDIX. der such circumstances, the envelopes separate rapidly from the central globules, because the,vitality of the vessels is scarcely sufficient to continue them in connexion even when circulating through the vessels themselves; coagulation takes place quickly, because the motion impressed upon the globules by the vital energy of the vessels, owing to the defect of this energy, is soon lost, and because the separation of the envelopes from the globules takes place almost instantly ; and the coagulum which is formed is weak, or it does not form at all, because the vitality of the globules is insufficient to dispose to an energetic at- traction, or even to any attraction between the central globules. 19 and lastly. Opposite phenomena result from the increased energy of the vital func- tions of the ganglial nerves distributed to the blood-vessels. III. Of Transfusion of Blood.—MM. Prevost and Dumas found that, after bleeding an animal until all organic actions ceased, and injecting, ivithin a few minutes afterwards, the warm blbod taken from another of the same species, until a quantity equal to that taken away was restored, the animal gradually revived and took nourishment, and perfectly recovered, if the operation was perfectly performed. If, however, the blood injected was taken from an animal ofa different species, possess- ing globules of the same form, but different in dimensions, the animal was veiy imperfectly revived, and could be rarely preserved beyond six dstys. The pulse became in these fre- quent, the temporature fell remarkably, if not artificially preserved, while the respiration retained its natural frequency. Immediately after the operation, the dejections became mucous and bloody, and preserved that character until death. If blood with circular globules, was injected into the veins of a bird, the animal generally died before the operation was completed, in very violent and rapid nervous convulsions. Transfusion of blood from the cow or sheep into the veins of the cat or rabbit, was fol- lowed by the recovery of the animal in a number of cases. The blood of the sheep excited in the mallard duck the most violent and rapid convul- sions, which were immediately followed by death, as was observed to follow the injection of the first syringeful in land-birde. (Bibliotheque Univers. Juillel, 1821.) Of Secretion and Exhalation. Note CC. Opinions have been various respecting tbe mechanism provided for tbe performance ot exhalation and secretion. One class of physioligists contends for a separate order of very minute capillaries proceeding from those carrying red blood, vvhich they call exhalent or secretory capillaries, and devote to these functions. Belonging to this class we may reckon Haller, Hewson, Soemmering, Bichat, Chaussiei, Alard, &c. As these vessels cannot be de- monstrated, their existence is denied by Mascagni, Prochaska, Richerand, Magendie, and others, who argue, that these functions take place in the sanguineous capillaries through the medium of organic lateral pores. The fact appears to be that the evidence for a sepa- rate set of capillaries is equal to that for the existence of organic pores in the capillaries carrying red blood : it is not easy to dembnstrate the presence of either; whilst both the one and the other may prove a sufficient medium through vvhich the processes will go on under the influence with which the capillary vessels are endowed. The existence and effi- cacy of this influence is sufficiently manifest, although the more minute instruments by means of which it operates, cannot be satisfactorily demonstrated to our senses. With respect to secretion, the state of opinions and of our knowledge as to the manner in which it takes place, or rather the mechanism provided for its performance, is similar to what we have shown to exist on the subject of absorption and on that of the minute capil- laries. In stating the opinions on these subjects, and those lately espoused by M. Alard, we gave the views of those who contend for the existence of minute lymphatics running into the venous capillaries, in a similar manner to that in which exhalent vessels are supposed, as stated above, to proceed from the arterial capillaries. But the latter set of vessels has been as little seen as the former. This however, in a matter of this nature, is not a suffi- cient proof against their existence. Other physiologists, on the other hand, contend that exhalation and secretion take place through means of pores analogous to those whicii are supposed to be instrumental in the phenomena of absorption ; and that the process is en- tirely one of transudation. But the same objection may be offered against the existence of pores as to that, of the exhalents or secreting capillaries in question. OF NUTRITION Hit h? be*ieve tnat tlic Precise way in which exhalation and secretion take place cannot be readily demonstrated to the senses,—that the one apparatus may explain the process as well as the other,—that secretion as well as absorption, are not mechanical processes, although there are apparatuses, or subordinate instruments, provided for their performance, and that they are essentially vital operations, and under the control of the vital influence with which the capillaries themselves, and the organs to which they belong, are endowed. As to the question of pores, it must be granted that the solids of the body, and the parietes ot the vessels, are all porous; it is only with respect to the extent and magnitude of the pores that the question can be entertained. Those who contend for the existence of sepa- rate and subordinate sets of capillary vessels cannot deny the existence of pores, for if they do not exist both on the surfaces and in the textures whence these capillaries are sup- posed to originate, how could they obtain the fluids circulating in them ? On the other band, those who contend for the existence and functions of pores cannot deny the existence of minute absorbents or lymphatics, for they can be demonstrated, to a certain extent, as respects the minuter ramifications, and, in a satisfactory manner, as regards the more con- siderable branches. It appears to us that both species of organization exist to a greater or less extent in different textures, and secreting organs. Each secreting viscus, is supplied with a distinct ganglion, plexu9, or both ; these preside over the secreting function, and the functions of some of these ganglia are influenced by the operations of the cerebro-spinal system ; as, for example, the secretion of the lachrymal gland is increased by the influence which the nerves of this latter system convey to the ganglion which supplies it, and is the chief source of its functions. Of Nutrition. Note C. C. and ;?. As we have already seen, in the notes on the capillary system and on secretion, the func- tion of nutrition has been explained, by one class of Physiologists, by supposing the exis- tence of nutritive capillaries, and by another, by means ot organic pores, with which they endow the capillary vessels circulating red blood, and to which they commit the exhalent, secreting, and nutritive functions. The first of these hypotheses supposes that nutrition takes place in minute colourless vessels, whicii proceed in a more or less tortuous direction from the arterial capillaries, absorption proceeding through the medium of a similar set of colourless vessels continuous with the former, which run into the venous capillaries, and thus the nutritions molecules are always circulating within colourless capillaries, which, with the nerves and larger capillaries, constitute the basis of the different textures. Mascagni supposes that the arterial capillaries, at the point where they change into veins, are provided with exhalent pores both for the pin poses of secretion and nutrition ; and that there every where exists the orifices of minute absorbent vessels, commencing in the latter description of pores, in order to take up the nutritive molecules. The elementary tissues consist, in his opinion, of this particular class of absorbent vessels, which contain the mole- cules as long as they are a part of the textures, and whicii by their union, form the most simple membranes. These hypotheses do not differ very materially. Both contend for the existence of very fine capillaries which attract the nutritive molecules, and contain them in a state of pro- gressive circulation, as long as they form constituents of the textures : these molecules be- ing afterwards carried onward in succession iDto the branches of the absorbent lymphatics and into the veins. In the first of these hypotheses, the nutritious particles are supposed to circulate in the finest of the vessels proceeding from the arterial capillaries; in the second, the process is ascribed to the most minute radicles of the absorbents; but both agree in considering the molecules constituting the mass ofthe textures to be contained in colourless vessels, and to be in a state of continual circulation. The opinion of Bichat on this subject is somewhat different. According to him, each molecule of these constituting the textures of the body is placed between the orifices of two vessels : one, a nutritive exhalent orifice, which has deposited the molecule, the other a nutritive absorbent orifice about to absorb it. Prochaska, who conceives that the arterial capillaries are continued directly into veins, considers that nutrition takes place, in consequence of the porosity of the capillaries, and of the genera! permeability of the substances constituting the mass of the structures. M. Richerand espouses a similar opinion, but he seems to allow an organic property to the pores which he ascribes to the capillary vessels. Opinions respecting the mechanism of nutrition, or the manner in which it takes place, .an on|v iJe theoretical. We have not the means of demonstrating the existence or non- Ob APPENDIX. existence of either the one or the other mode of organization contended lor: each may of itself be sufficient to explain the phenomenon, as far as respects the apparatus required for the process, but it is only the apparatus. The function itself is purely a vital one. re- presents us with a continual motion of a double nature—a continual attraction and de- composition ef material molecules. In the most simple animals, as the polypus, these pro- cesses go forward without any previous preparatory function : the animal imbibes, in a di- rect manner, similar molcules of matter to those of which it is itself formed from the sur- rounding medium, and again exhales them in a manner equally direct. In these there are no vessels destined for the purpose of circulation and nutrition, yet they present the phe- nomenon of irritability; and on examination, with a microscope, their structure appears almost homogeneous, with the exception of globules entbely similar to those which aie ob- served in the ganglial nerves of the higher animals. As these are the chief marks of inter- nal organization vvhich can be detected in the very lowest of the animal kingdom, and as we must conceive that the organization must be instrumental in the nutrition and opera- tions of animal bodies; and as, moreover, we perceive that the perfection of the organiza- tion or material apparatus is commensurate with, and has an evident relation to the extent ofthe vital operations which it performs, so it seems reasonable to suppose that this organi- zation, which is the only one which is detected in the very lowest of animals, is the chief and indeed only instrument of the limited function which these animals perform; and that, as a similar, but more perfect organization presides over the nutritive function of the highest animals, so this presides over that of the lowest, without the assistance of the more complicated capillary apparatus assigned by some physiologists to the former ; and if a dis- tinct set of subordinate capillary vessels be not requisite to the nutritive function in the one, we may allow that it takes place in the other, under the dominion of the more perfect nervous organization to which we have assigned it, without the existence of the more complicated capillary apparatus for which some contend. Concluding, therefore, that as the nervous globules demonstrable in the very lowest animals are the only organization which they evince, that organization must have a deter- minate object or function which it performs under the control of the vitality with which it is allied, and which all animals possess ; and that nutrition and irratibility are the only organic actions which these animals perform, so it must inevitably follow that these actions result from the vital influence allied to the particular organization in question, and that the nervous globules, constituting the only marks of interna] organization possessed by these animals, attract from the surrounding medium, in consequence of the vitality with which they are allied, these molecules of matter corresponding to those forming the structure of the animal, which come within the sphere of their influence, and retain them for an indefi- nite time, without either the medium of exhalent or absorbent vessels. Now, as the same type, especially as respects the nutritive functions, may be observed throughout the whole animal creation, and-as we can trace nervous chords, formed of globules similar to those already ascribed to the lower, and indeed to all animals, throughout almost the whole of their bodies, is it not reasonable to suppose that similar globules exist in all the simple textures in a more diffused form—that the globules constituting the organic or ganglial Fvstem of nerves become more disseminated amongst the molecules of the textures in the course of their distribution with the capillary vessels, or of their more direct ramifications and terminations in the textures themselves? If this be granted—and it scarcely can be denied, for it has been demonstrated in different orders of animals,—and as it has been shown that these nervous globules are present, in a more or less organized form, throughout the whole animal creation, it may consequently be inferred that the same function which we have ascribed to them in the lowest animals should be extended to them in the highest. This is conformable to the laws characterizing the animal economy. As we have contended in another place, conformably with this opinion, that the ganglial nerves in some one or other of their forms of existence, are present throughout every pait of the body, that they preside over digestion, nutrition, secretion, &c. and are more nearly allied than any other texture with the vital influence which the body exhibits, so we now conclude that the globules constituting the ganglial system, being allied with vitality, and being distributed in different forms of connexion to the various textures of the body, exert, inconsequence ofthe vital influence with vvhich they are endowed, a vital attraction on those molecules of matter vvhich come within the sphere of their influence; that the force of this attraction, and the manner in vvhich the material molecules are arranged in order to form the different textures of the body, result in a great measure from the influence pro- ceeding from the form, the number, or the condition of these globules in the textures which it is their office to perpetuate; and that the chief office of the digestive, the respiratory, the anamalizing, and the circulating processes, is to present the materials, whence the different textures are preserved, in a fit state for the exertion of this vital attraction; and that the principal operation performed by the capillary vessels is to convey these materials within the sphere of this attraction ; and, so that this is performed, it matters but little whether o? no theso vessels accomplish it by means of subordinate nuti'tivo capillaries destined to tu? ON THE OPTIC NERVES. J% circulation or deposition of the nutritious molecules, or by means of organic pores, with, which the parietes may be provided. But, whilst we suppose that the function of nutrition mRy thus take place in consequence ofa vital attraction, resulting in the manner vvhich we have explained, and exerted exte- rior to and independently ofthe vessels, and whilst we consider this explanation to be sup- ported by the nutritive actions of the lowest animals, yet we would by no means exclude the influence of that part of the ganglial nerves distributed to the capillaries, from a part in the operation, more especially in the higher classes of animals. Indeed it seems difficult to suppose whicii of those in the higher animals—namely, whether the nervous globules distributed to the simple textures, and placed beyond the capillaries, or those constituting the nervous fibrillae which surround them,—are most efficient in the nutritive process. An nitimate view ofthe subject would suggest, that in man and the more perfect animals, the latter organization is the more active of the two in the opeiation in question ; and that the capillary vessels, in consequence ofthe ultimate nervous structure vvhich surrounds them, and of the vital influence which this structure exerts, secrete from the fluid circulating in them certain materials in a similar manner to that in which they perform the other secre- tions in secreting organs, and by means either of appropriate vessels or pores. As it has been shown that the blood consists of minute globules, or corpuscles surrounded by a coloured envelope circulating in a mass of fluid, and that the simple solids of the body are constituted of similar corpuscles, in a state of intimate or vital attraction, as those ofthe blood, when they are separated from the envelopes, so it may be inferred, that a part of the function vvhich the ultimate distribution ef the ganglial nerves perform on the capilla- ry vessels, is to secrete similar corpuscles, from the blood circulating in them, to that whicii the texture possesses in which the operation takes place ; and that this having been accom- plished, the vital attraction is preserved either by means of the influence with vvhich these corpuscles are endowed, as a consequence ofthe previous process of animalization which they have undergone, or of the influence exerted upon them after they leave the vessels by the nervous globules and fibrillae disseminated in the textures, or perhaps by both species of vital action, either the one or the other acting more or less partially according to the nature of the particular texture in whicii the process takes place, and according to inappreciable and fortuitous causes. Hence it will be perceived that nutrition is essentially a vital operation, that it is placed under the control of the extreme ramifications of a particular system, to which we have referred all the vegetative or organic operations vvhich characterize the animal kingdom ; that it is performed in all animals except the very lowest, through the medium of circulating organs, and in the highest, as a consequence of certain preparatory processes; that it re- quires in man and in the higher animals a capillary circulation for its performance, but that neither of the capillary apparatuses vvhich have been contended for is sufficient of themselves to accomplish it, although the most simple of them under the dominion of ths vital influence of that particular structure whicii we find every where disseminated where there is life, is all that is requisite as the material instrument of the process; and lastly, and as a consequence of the foregoing position, that nutrition is modified, controlled, in- creased, or even annihilated, either generally orin particular parts of the body, by the state of the vital influence allied to the material organization, to vvhich we have already imputed it, according as this parlicular organization in its centres and ramifications throughout the animal frame is generally or locally affected. Of the Decussation of the Optic Nerves, Vicq D'Azyr, found, on examining with the microscope, an horizontal section of the opti- nerves of the human subject, after it had been hardened in alcohol, that the medullary fibres occupying the exterior side of the optic nerve, proceed in a direct manner from the optic thalamus to the eye of the same side ; and that the place of union presents a homoge- neous tissue. The Wenzels came nearly to the same conclusion from their observations, hut remarked, in addition, that while the fibres of the exterior side of the nerve go imme- diately to the eye of the same side, those fibres, placed in its interior side, are directed obliquely towards the other nerve, without, however, any crossing of fibres being manifest at the point where the junction of both nerves takes place. M. Treviranus has, in a great measure, confirmed these observations, on the male simm augula. The nerves and brain were left during some months in alcohol, and afterwards kept some time in caustic potash to soften them. Having thus prepared them, he submitted them to a careful dissection, when he made out, with the aid of a microscope, that the ex- •nnal fibres of the upper side of each were continued from their cerebral extremity to that .■> the €■"■'<■. without uniting themselves tc those of the other side ; whilst, on the contrary, H M APPENDIX. the internal and inferior fibres of one nerve went to the other side, and united with the fibres of the opposite nerve. It was difficult to determine whether any of the fibres actually passed from one side to the other. He thought, however, that some ofthe fibres did so. The internal fibres, thus interlacing together, were evidently more numerous than the external fibres which ran to the eye without uniting with those of the opposite nerve.—Journal Complementaire, Oct. 1823. On the Motions of the Eye. Mr. Charles Bell has lately examined the motions of the eye, in illustration of the uses of the muscles of the orbit; and has shown, in the first place, that there are motions per- formed by this organ not hitherto noticed. Every time the eyelids descend to cover the transparent part of the eye, the eyeball ascends, or suffers a revolving motion. If this were noyt the case, the surface of the eye would not be moistened, nor freed from offensive parti- cles. He has proved, in the next place, that during sleep the eyeball is turned up, and the cornea lodges secure and moistened by the tears, under cover of the upper eyelid. He con- siders that these motions are rapid and insensible, and that they are provided for tbe safe- guard of the eye. The other motions are voluntary, and for the purpose of directing the eye to objects. Mr. Bell next examined the actions of the muscles of the eyeball, and distinguished them, as usual, into the straight and oblique muscles. It has been supposed, hitherto, that both these classes of muscles were voluntary ; some describing the oblique as coadjutors of the recti muscles, and others as opponents to the recti; but Mr. Bell has viewed the oblique as provided for the insensible motions of the eyeball, and the recti for those motions which are directed by the will, and of which we are conscious. Mr. B. has also proceeded to show, that the consciousness of the action of the recti muscles gives us the conception of the place or relation of objects ; and has'endeavoureii to prove, by observation and experiment, that the actions of the straight muscles are in- seperably connected with the activity of the retina ; that is, with the enjoyment of vision: but that the moment the vision is unexercised, the eyeball is given up to the operation of the oblique muscles, and the pupil is consequently drawn up under the eyelid. "Hence the eyes are elevated in sleep, in faintness, and on the approach of death ; and that distor- tion vvhich we compassionate as the expression of agony, is the consequence merely of ap- proaching insensibility." Annals of Philosophy, May 1323. Ofthe Formation ofthe Spinal Marrow and Brum. Note D. D. 1. Of the Formation ofthe Spinal Marrow.—The researches of M. Tiedemann, the Wenzels, Doelliuger, Carus, and Desmoulins, have furnished us with much interesting in- formation on this subject. The soft and gelatinous state ofthe embryo at the earliest pe- riods of its existence, the rapidity of its metamorphoses, and the difficulty of demonstrating, owing to its colo.ur and consistency, that part of the nervous system, which from the cir- cumstance of its supplying those parts ofthe embryo that are first formed, as well as from other considerations, we are led to consider as the first vvhich assumes an organized ap- pearance, combine to render the exact origin of the spinal marrow difficult, if not impossi- ble of demonstration. Reasoning from the condition ofthe nervous system throughout the scale of the animal kingdom, from the manner in which tbe different organs seem to be form- ed, from the organization of some monstrous foetuses, and from other considerations on which we cannot enter at this place, we are disposed to conclude, that the spinal marrow is itself produced from the ramifications ofthe sympathetic ganglia; that the semilunar gan- glion is the first part ofthe nervous system to assume an organized state ; and that the sub- ordinate ganglia, the spinal marrow, and lastly the brain, come successively into existence, und gradually arrive at their full development. It is not until about the third in fourth week that a greyish-white fluid may be detected in the cavities of the head and spine. From the fourth to the fifth week the medulla oblon- gata may be distinctly seen. It is then about twice as thick as the medulla spinalis, which. ■nOne the development ofthe limbs, is of an equal thickness throughout its whole length. OF THE CEREBRO-SPINAL SYSTEM. M ami presents a slight curvature near the commencement of the medulla oblongata, owing to the flexion of the head upon the chest. The spinal marrow at this time consists of two white strips of medullary matter, whicii offers a manifest decussation at the place where it curves forwards at the margin of the inferior extremity ofthe pyramids. It is not, however, the whole of the two chords of the marrow that cross, but the middle or pyramidal fasciculi of each. The spinal marrow descends from this point through the whole extent of the ca- nal to the interior ofthe caudal prolongation. At the fifth week these strips or chords form, by the junction of their interior and ante- rior margins, a longitudinal gutter : their external and posterior margins are then full and prominent. At the seventh week the spinal marrow is open throughout its whole length. On each side ofthe fourth ventricle, a straight thin lamina is put forth, which inclines from without in- wards, applying itself to that of the opposite side, without, however, uniting with it: these are the rudiments ofthe cerebellum, springing from the restiforni bodies. The cervical en- largement begins to appear, particularly its cephalic extremity. The formation of the limbs coincides with that ofthe corresponding enlargements of the chord. The longitudinal raphe, formed by the approach ofthe interior margins ofthe two chords constituting the marrow, is continued upwards, and separates the tubercles, that is, the laminae vvhich represent them: the optic thalami are developed. At the commencement ofthe third month, the marrow is still open at its superior half, and extends to the extremity ofthe sacrum. The tubercula quadrigemina are voluminous, hol- low, and separated by the median furrow : the optic thalami are full. The two cervical and lumbar prominences are a third of a line thicker than the body of the marrow : M. Tie- demann has not observed the junctions of its exterior margins until the end of the third month. M. Serres has seen it a fortnight earlier. This junction takes place from beneath upwards. At twelve weeks the marrow extends only to the middle of the sacrum. The tubercula quadrigemina are united and form a canal; at this period the mammillary eminence's and the corpora striata may be 6een. The internal canal, which is now formed by the junction ofthe margins of the marrow communicates with the fourth ventricle. According to M. Desmoulins, this canal results from a sinus, formed by the fold of the pia mater as it dips in- to the interior ofthe marrow, or rather between both the chords of which the marrow is then formed. The precise period at which this canal is completely obliterated, has not been as- certained. M. Carus conceives that the pectoral portion of the marrow is the first to close, and that the canal is obliterated along its whole extent, owing to the formation ofthe gray substance. At the fourth month, the spinal marrow reaches only to the base of the sacrum ; the cer- vical eminence is larger than the lumbar The two contiguous chords of the marrow di- vide, in the medulla oblongata, each into three others much smaller. The internal or py- ramidal forms a tolerably broad surface, as in fishes and reptiles, and evidently crosses, as was already noticed, with that ofthe other side about the fourth or fifth week ofthe foetal life. The middle chord, or the corpus oblivare, is placed above the former; some of its fi- bres ascend to the tubercula quadrigemina, and unite with those proceeding from the oppo- site side, in order to form the vault ofthe aqueduct of Sylvius. The external or restiforni chord, proceeding from the lateral and posterior portion of the marrow, forms the prominent paries ofthe fourth ventricle, and advances into the cerebellum. At this period the annular protuberance is perceptible. The interior canal of the marrow is now very narrow, and s.till communicates with the fourth ventricle. It is not until towards the end ofthe fourth month that the lumbar and sacral nerves become elongated, and form what has been impro- perly called the cauda equina, which at first does not exist. The pia mater which penetrates by the posterior median furrow, is observable in the centre ofthe marrow. At the fifth month the pyramidal eminences are evident: there still exists a communica- tion between the fourth ventricle and the canal of the marrow. The two swellings of the chord are well marked. The annular protuberance becomes more distinct, and the corpora striata, are large. The increased thickness of the tubercles has narrowed considerably the cavity which they formed by their approach. The marrow extends at this period no farther than the margin of the fifth lumbar vertebra. The human embryo possesses a caudal prolongation until the fourth month of uterine life. At this period it disappears, and its disappearance coincides with the ascension of the'spinal marrow in the vertebral canal. If the ascension ofthe marrow is arrested, the human foetus is born with a tail, as has been observed in several cases. The circumstance ofthe spinal marrow descending lower in the vettebral canal the younger the fcetus has at- tracted the particular notice of those physiologists, to whose researches we are indebted for our knowledge ofthe subject under consideration. M. Tiedemann, who offers the most ra- tional explanation of this phenomenon, supposes that the marrow descends not so far in the canal of the full-grown foetus, as in that ofthe early embryo, because the vertebral column grows more rapidly in length, than the nervous chord which it is destined to protect. 60 APPEiNDlA. Towards the end of tlic sixth month, the corpora olivaria form a well-marked lateral pro- jection. At this epoch may be seen the internal and middle chords, forming the peduncles ofthe brain, plunging into the optic thalami which they formed by their enlargement. The fibres composing them may be perceived on scraping away a thick pulpy layer from their in- terior and superior aspect. A few fibrous portions detach themselves from their internal side, and proceed outwards to the mammillary eminence. All the other fibres continue to advance from behind forwards, and from within outwards, beneath the corpora striata, and proceed, in a diverging form, to the cerebral lobes. A few fibres may be seen entering them. In the course ofthe sixth month the transverse furrow separating the eminenlia quadrigemi^ v.a begins to appear, or rather, each of these prominences becomes more developed. At the seventh month, the length of the marrow is nearly the same. The transverse fibres which compose the annular protuberance are now distinct, and they may be seen interlac- ing with those of the pyramids. This part results from the following disposition : the fibres of one lateral hemisphere ofthe. cerebellum are continued beneath the spinal marrow with the fibres of the opposite hemisphere, by layers which alternate with the planes of fibres pro- ceeding obliquely from the pyramids to the optic thalami. At the eighth month the marrow reaches only to the fourth lumbar vertebra, and at the ninth month it is at the margin ofthe third. The interior canal ofthe marrow still exists, and remains until from six months to a year after birth. It is at the last months of gesta- tion that the disposition of the medullary fibres of the marrow may be most distinctly traced, and the mode of formation of the mesocephalon ot pons Varolii, which is only a continua- tion of the marrow, becomes most evident. All the white or medullary parts whicii are seen at the base of the brain, manifestly arise from the superior part ofthe spinal marrow. (Olmvieb, sur le Devcloppcment de la Moclle Opinitre.y. II. bfthe Formation ofthe Brain.—The interesting results of Dr. Tiedemamvs research- es on this subject may be reduced to the following heads: " 1. In the commencement of pregnancy, especially about the second month, the earliest period at which the brain can be rendered perceptible by the action of alcohol, this organ is very small in proportion to the spinal marrow. In fact, it results from the prolongation upward and forward, of the two principal chords, the olivary and pyramidal. All its supe- rior part is open, or, more properly speaking, forms a broad gutter, whicii at once compre- hends the third ventricle, the aqueductus sylvii, the fourth ventricle, and calamus scriptorius. This gutter is uninterruptedly continuous with the canal, which traverses the whole length ofthe marrow. "2. The cerebellum evidently originates from the spinal marrow; from the lateral parts of vvhich arises, on each side, a small flattened chord. These two, at first so distinct and separate that they may be readily parted without laceration, afterwards unite so as to form the roof ofthe fourth ventricle* Then only the brain, viewed from above, ceases to repre- sent a guttsr; and the laminae and branches of the cerebellum are formed at a much later period. ''3. The mass which supports the tubercula quadrigemina equally shows itself in its ori- gin, under the form of two small thin membranes, which arise from the olivary chords of tho spinal marrow, and which, when they cease to be distinct, represent a vault covering a large ventricle, who.se successive contraction gives rise to the aqueductus sylvii. "4. The pyramidal chords ofthe spinal marrow, which take a direction below upward. and from behind forward, after having produced two swellings, or ganglia, the optic thala- mi, and corpora striata, each terminate by a lamina, which bent from before backward, and from the side towards the superior and internal part, forms the commencement of the hemis- phere of the brain. These membranes and thin hemispheres are so small at the second month, that they scarcely cover the corpora striata. In proportion as they increase they extend backward, and cover, at the third month, the optic thalami; at the fourth, the tu- bercula quadrigemina ; and, at the sixth or seventh, the cerebellum. The lateral ventri- cles result from their inversion. ''5. The medullary fibres of the pyramidal chords, previously to the formation ofthe tu- ber-annulare, are immediately continuous with those of the crura cerebri: from whence the i/ye may readily trace them in the optic thalami, and corpora striata, and see them after- wards spreading and radiating in the hemispheres. " 6. The parietes ofthe hemispheres gradually increase in thickness in proportion as new .-irata of cerebral substance are deposited on their surface ; and convolutions are not de- cidedly seen till towards the close of pregnane}'. " All these combined facts clearly demonstrate, in the opinion of Dr. Tiedemann, that the brain and cerebellum proceed from the spinal marrow : or that, to employ a modern expres- sion, they are an efflorescence "fit. In nuiniur? through the stiIr of animals, amnio com- OF THE CEREBRO-SPINAL SYSTEM. (31 brmation may be found ofthe assertions here advanced. The structure of the encephalon and spinal marrow becomes complicated in proportion as we ascend from fishes to reptiles, !/irds and mammalia. If the contrary opinion were correct—if the spinal marrow were derived from the brain, the cerebrum and cerebellum must necessarily be found the first formed in the fcetus, which is not the case. It is equally necessary that, in the animal scale, where it is impossible to mistake a gradation in the figure and development of the organs, that a complete brain should exist previously to any trace of a spinal marrow ; but this is never observed. Comparative anatomy, on the contrary, shows that the spinal mar- row is very large in the inferior classes of animals, while the brain forms but a small and delicate prolongation of it; and in ascending from reptiles to birds and mammalia, it is seen gradually to increase in volume and complication, as absolutelv takes place in the fcetal encephalon.* Ofthe Functions ofthe Cerebro-spinal System of Nerves. I. General view of the Nervous System.—At a former part of these notes we divided the nervous system into two principal orders, viz. the ganglial or vita), and the cerebro-spinal. * Prochaska and the Wenzels conclude from, their microscopic observations, that the brain is composed ofa number of small globules ofa tolerably firm consistence contained in a flocculent pulp. The researches of Mr. Bauer into the ultimate structure of this organ are more precise. He considers that the brain and nerves consist of extremely delicate fi- bres, formed of minute globules, connected together by a transparent gelatinous fluid, or viscid mucus, vvhich is soluble in water. These globules vary in dimensions, from -jg-g-g1 to 4jjQ parts of an inch. " The principal difference," he states, " in the appearance of the different parts ofthe brain, consists in the proportions which the quantity of mucus and fluid bear to the quantity of globular tissue, and in some measure, in the size of the glo- bules. The cortical substance of the cerebrum and cerebellum is made up by the small globules, the gelatinous fluid and mucus being very abundant. The medullary substance in tbe cerebrum and cerebellum differs from the above, in the large globules prevailing, the mucus being more tenacious and less abundant. The crura cerebri and cerebelli resemble the medullary substance, only that the mucus and fluids are more abundant, and in greater proportion than the globules The medulla oblongata, the corpora pyramydalia, and olivaria, have nearly the same structure as tbe medullary substance, but the mucus is very abundant. In the medulla spi- nalis, the mucus and fluid are less tenacious, but in greater quantity than in any part of the brain. Every part ofthe brain is pervaded by innumerable blood vessels, which are of consider- able size towards the centre, but branch out to an extreme degree of minuteness; but even then carry red blood. The arteries in the brain never anastomose, and are accompanied by veins still smaller, which are supp'ied with valves. This view ofthe structure ofthe cerebrum and cerebellum is calculated, in the opinion of Sir Everard Home, to throw considerable light on the functions ofthe brain. He thinks that the cortical substance is one ofthe most essential parts of this organ, and considers it rhe seat of memory, from having observed that that faculty is destroyed or materially dimi- nished by any undue pressure upon the upper anterior part of the brain, as in that requiring the operation of trepan. In hydrocephalus, on the other hand, where the fluid is in large nuantity, and there only remain the cortical part of the brain, and pons Varolii, all the functions goon, and the memory can retain passages of poetry. In one case, slight pres- sure upon the sinciput produced complete derangement, and violent excesses ofthe passion of lust, vvhich went off by removing, by the trepan, the depressed bone. The veins being so minute, and being supplied with valves, perform in the opinion of this physiologist, the office of absorbents—which have never been observed in the brain—and Larry the absorbed matter into the superior longitudinal sinus, which appears more a re- servoir than a vein. The transparent mucus being not only one ofthe most abundant materials of vvhich the brain itself is composed, but also the medium by which the globules are kept together, and serving the same purpose in the nerves, Sir E. H. thinks that the communication of sensa- tion and volition depends upon it. He concludes from all his experiments and observations, that this fluid, as well as the principal materials of which tho body is comnosed. are met, "•■♦h in the ''i'"^5 (52 APPENDIX. Of the former we remarked, that the globules of which it is constituted are disseminated in the structure ofthe Zoophyta, are organized into a homogeneous ganglion, but imperfectly developed in many of the orders of the Echinodermata, and are arranged into ganglia com- municating by means of intermediate chords in the Annelides, Cirrhipedes, &c. The ho- mogeneous nature ofthe ganglions disappears as the animal is provided with separate or- gans, especially with those devoted to the senses: and, with the development of separate organs, accessary or subordinate, ganglions make their appearance, which latter, in the progressive rise in the scale ofthe animal kingdom, assume in the anterior part ofthe body ofthe animal the character oi the rudiments of an encephalon. So long as there exists on- ly simple ganglia without any spinal chord, the ganglion .epresenting the rudiments of an encephalon, surrounds the oesophagus in the manner of a ring. This encephalic ganglion is intimately connected with the ganglial functions, and presides over those imperfect ope- rations of sense with which the animal is endowed, and which are those more immediately subordinate to its functions of nutrition, and to its immediate preservation. In all animals possessing no other rudiments ofa cerebro-spinal system, than an acces- sary ganglion disposed around the oesophagus, the manifestation of volition is by no means distinct: their movements appear to be'the result neither of reflection nor of choice. An obscure instinct seems to be the actuating principle of those operations, which may assume in them the nearest resemblance to those of volition. As we rise in the scale ofthe animal creation, and as we perceive the relation between the exterior world and the animal, to be more extended and intimate, owing to the exten- sion and perfection ofthe organs of sense and volition, so. we perceive the cerebro-spinal system more perfectly organized, more fully developed, and more complicated in its struct- ure. With the formation of the spinal chord, in the class of fishes,* the accessary encepha- lic ring or ganglion disappears, and the encephalon is surrounded by a protecting case^ which is continued over the chord itself. The diversity and complication of he parts constituting the encephalon increase as we rise through the four superior classes of animals. In the Hymenoptercs, especially in the bees, each sensorial nerve possesses an enlargement in the encephalon appropriated to it- self, from which it takes its origin; but all these enlargements coalesce in a central mass composed of two symmetrical hemispheres, the prototype ofthe cerebral hemispheres of all the superior classes. In another part of these notes we gave a full detail ofthe progressive development ofthe cerebro-spinal system of nerves in the human foetus. It will readily appear from what we there advanced, that a similar gradation, (from the simplest to the most complicated and perfect state ofthe nervous structure,) to that which we observe in ascending the scale of the animal creation, may be remarked in the changes which the nervous system undergoes in the progressive evolution of the human embryo. In the lowest of all the animal king- dom the nervous matter is not organized in a manner distinct from the tissue constituting the animal: the nervous globules are disseminated through an amorphous and pulpy mass. As we ascend the scale we perceive this particular structure arranged in succession into ganglia; then into ganglia and a spinal marrow ; and lastly into ganglia, a spinal marrow and a brain,—each becoming more perfect as we ascend the scale, and the gradation from the one to the other being nearly unappreciable in the species or genera, but sufficiently re- markable in thejorders. A development of the nervous system, in which a similar progres- sion to this is observed, takes place in the formation ofthe human fcetus, and in that of the most perfect animals; and a similar type to that, in which this system exists in the lower orders, is adopted at first in the highest, and preserved,—every successive state of organi- zation which this system assumes in its progressive development being additions to that previously adopted, whilst in the process of formation as respects the entire animal, each intermediate series from the lowest, which is its first state of existence in the embryo, is successively passed through, until the foetus arrives at that specific condition and stage of organization bestowed on the species to which it belongs. Thus the human fcetus, in the progress of its formation, as respects both its nervous system and other organs and textures, runs through the different grades of organization from the lowest, to that at the head of which it is itself placed.! (See the Note on the Development ofthe Fcetus.) * M. Desmoulins has lately shown that many reptiles and several fishes offer not a trace of grey substance in their spinal chords, and that on the contrary, this part is entirely coin- posed of white substance. He has also found that the sturgeon is entirely without a cere- bellum ; and that its fourth ventricle possesses a considerable extent. He concludes that the dimensions and extreme development of the fourth ventricle always coincides with the extreme development ofthe eighth pair of nerves. The circumstance of the grey substance being wanting in the spinal chord of some fishes militates against tho opinion of M. Ollivier stated at a subsequent page. t Sir Everard Home, MM. Geoffroy Saint Hillaire and Blainville and Dr. Schultze,con- sider that the skeleton of animals was intended more to prevent the nervous and vascnla-.- OF THE CEREBRO-SPINAL SYSTEM. «3 II. Of the Functions of distinct parts of the Cerebro-Spinal Order of the Nervous Sys- tem.—The researches of M.«Flourens into the functions of the cerebro-spinal order of nerves, have lately added greatly to our knowledge as to actions in which distinct parts of this part of the nervous system are more particularly concerned. But before we can give any account ofthe conclusions at which he has arrived, we must briefly notice the meaning he has attached to some ofthe terms which he employs. The term contractility he very propeily limits to the property inherent in the muscular fibre only, of undergoing brisk contractions under the application of stimuli: and the term sensibility, to imply the property of experiencing sensations. The word irritability, he applies to the property of exciting sensation and motion, without evincing or experiencing them. This application of the word'is by no means judicious; it must, however, be allowed, that it is not easy to find a term which can convey the meaning wished to be attached to it. The questions proposed by M. Flourens, and which he has endeavoured to ascertain by experiment, are:—1st, from what points of the nervous system artificial irritation may set off to arrive at a muscle ; 2d, to what points of this system an impression must be propa- gated to produce sensation ; 3d, from what points voluntary irritation descends, and what parts of this system must be influenced to produce it regularly. M. Flourens commenced with the nerves, and fully confirmed the views usually entertained respecting their functions. He has shown, in a satisfactory manner, "that, in order to effect contraction, a free and continued communication is requisite between the nerve and mus- cle ; and that to produce sensation, a similar communication with the brain is equally ne- cessary. Hence he concludes, that neither contraction nor sensation belong to the nerve ■ that these two effects are distinct; that they may take place independently of each other ' and that these propositions hold good, at whatever part, and in whatever branch ofa nerve the communication is interrupted. " Employing the same method with regard to the' final marrow, he arrived at similar conclusions. When it is irritated in any given point, contractions are excited in all the muscles which derive their nerves from below this point, if the communication remains free ; but not if the communication be intercepted. Exactly the reverse obtains with regard to sensation; and, as in the nerves, the government of the will requires the same freedom of communication as sensation, the muscles beneath the intercepted part no longer obey the animal, and he has no feeling in them: in fine, if the spinal marrow be intercepted at two points, the muscles whicii receive their nerves from this interval experience contractions alone ; but the animal does not command them, nor receive from them any sensation." M. F. farther inferred, from his experiments respecting the functions ofthe spinal marrow, that sensation and contraction belong no more to it than to the nerves. He next directed his researches to the brain, in order to ascertain the point whence irrita- tion departed, and the point where sensation arrives, and to determine their respective co- operation in acts of volition. Advancing from the medulla oblongata towards the hemi- spheres, M. Flourens first examined how far it was possible to go, and still produce suffi- cient irritation on the muscular system, when he arrived at a point where these irritations disappeared : "then, taking the brain at the opposite part, he irritated it at points deeper and deeper, as long as he did not act upon the muscles; and when he did begin to act upon them, he found himself at the same point where the action had ceased in ascending. This part is also that where the sensation of irritation applied to the nervous system likewise systems from being compressed or suffering any other injury, than to give form and the pow- er of motion to the body. The last named physiologist (Al/gemeine Encyclopadie fur Practische Arzteund Wundarzte, 1 theil, 1 band Leip. 1820.) concludes: 1° " That the spinal marrow and vertebral column at all times exist together, even only the slightest vestiges ofthe osseous system can yet be found. 2° " That the osseous and nervous systems have between them numerous intimate rela? lions, both physiological and pathological. 38 " That the more the exterior hard envelopment penetrates the interior ofthe body, and approaches towards the nervous system, the more also are the phenomena of sensibility de- veloped, and vice versa. 40 "• That the organs possess more or less importance according as they are more or less protected from external influence by bones." The blood proceeding from the mass of muscles, spine and spinal marrow, is emptied into the great spinal veins, as into a reservoir; when it passes into the veins placed on the sides and anterior surface ofthe spine, and thence into the superior and inferior cava?. By what power, it has been asked, ioth influences combined. u APPENDIX. r eases : above this, punctures and wounds do not excite pain. Thus M. Flourens pricKed the hemispheres without producing contraction of the muscle*, nor the appearance of pain in the animal; he removed them in successive slices: he did the same with regard to tho cerebellum; he removed at once the hemispheres and cerebellum. The animal remained passive. The corpora striata and the optic thalami were attacked, and removed without any other effect: the iris was not contracted, nor even paralysed. But when he pricked the tuburcula quadrigemina, trembling and convulsions began, and these increased in pro- portion as he penetrated into the medulla oblongata. Pricking the tubercles, as well as the optic nerve, produced quick and continued contraction of the »iris. These experiments agree with those of Lorry, published in third volume of the ' Memoires des Savans Gran- gers.' * Neither the irritation of the brain, nor of the corpus callosum itself produce con- vulsions : it may even be removed with impunity. The only part among those contained in the brain which has appeared uniformly and universally capable of exciting convulsions, is the medulla oblongata: it is this part which produces them to the exclusion of every other.' They contradict the experiments of Haller and Zinn with regard to the cerebellum; but, from what M. Flourens has seen and pointed out, it appears that these physiologists had touched the medulla without being aware of it. He concludes that the medulla ob- longata and the tubercles are ( in his language) irritable ; which means that they are con- ductors of irritation, like the spinal marrow and nerves, but that neither the cerebrum nor cerebellum possess this property. The author hence concludes, likewise, that these tuber- cles form the continuation and superior termination of the spinal cord and medulla oblon- gata; and this opinion is in conformity with their situation and anatomical connexions. Wounds of the brain and cerebellum do not excite pain any more than convulsions. Hence M. Flourens infers that to them the impression received by sensible organs must be conveyed, in order that the animal may experience a sensation. He appears to have esta- blished this proposition in a satisfactory manner, with regard to the senses of sight and hearing; for when both lobes of the cerebrum are removed, the animal becomes both blind and deaf. " Instead of saying, with M. Flourens, that the cerebral lobes are the only or- gans of sensation, we should restrict ourselves to ascertain facts, and content ourselves with saying that these lobes are the sole receptacle where the senses of sight and hearing can be perfected, and become perceptible to the animal. If we wished to add to this, we should say that they are likewise those where all the sensations take a distinct form, and leave durable traces on the memory,—that they serve, in a word, as the seat of memory ; a pro- perty, by means of whicii they furnish the animal with materials for judgment. This con- clusion, thus reduced to proper terms, becomes the more probable, in that, besides the veri- similitude whicrrit receives from the structure of these lobes and their connexion with the rest of the system, comparative anatomy offers another confirmation in the constant rela- tion of the volume of these lobes with the degree of intelligence of the animal." M. Flourens next examined the effects which follow the extirpation of the tubercula quadrigemina. " The removal of one of them, after a convulsive movement, which soon ceases, produces, as a permanent result, blindness of the opposite eye and involuntary stag- gering; that of both tubercles renders the blindness complete, and the staggering more violent and long-continued. The animal, however, retains all its faculties, and the iris continues contractile. The deep extirpation of the tubercle, or the section of the optic nerve only, paralyses the iris: from which the author infers, that the removal of the tubercle only acts as the division of the nerve would do; that this tubercle is only a conductor with regard to vision; and that the cerebral lobe alone is the seat of the sensation, the point where it is consummated, and passes into perception."'' M. F. next investigated the functions of the cerebellum, and found that, during the re- moval of the first layers, " there appeared only a slight weakness and want of harmony among the movements. At the middle layers, a disturbance nearly general was manifested. The animal, in continuing to see and hear, only executed quick and irregular movements : the faculty of flying, walking, and keeping itself standing, were lost by degrees. When the brain was cut off, this facility of performing regulated motion had entirely disappeared. Placed upon the back, he did not rise ; but continued to see the blow which menaced him; he heard sounds, and endeavoured to shun the danger which was threatened : in a word, feeling and voliiion were retained, but the power over the muscles was lost; scarcely could he support himself with the assistance of the wings and tail. In depriving the animal of the brain, it was thrown into a state resembling sleep : in removing the cerebellum, it was brought to a state resembling intoxication." The reporters to the Institute on tbe inquiries of M. Flourens, have drawn the following conclusions "from a rigorous examination of the facts which he has established :—the in- tegrity of the cerebral lobes is necessary to the exercise of sight and hearing: when they are removed, the will no longer manifests itself by voluntary acts. However, when the animal is immediately excited, he performs regular movements, as if endeavouring to avoid pain or inconvenience; but these movements do not effect his purpose, most probably be- cause the memory, vvhich has beon removed along with the lobes which constituted its se^t. wF THE CEREBRO-SPINAL SYSTEM. 6*' no longer affords grounds or elements of judgment: these movements have no consistency, for the same reason, that the impulse which caused them neither leaves any remembrance nor permanent volition. The integrity of the cerebellum is necessary to the regularity of locomotion : let the brain remain, the animal will see, hear, and have evident and powerful volition; but, if the cerebellum be removed, he will never find the balance necessary to locomotion. As to the rest, irritability remains in parts without the brain or cerebellum being necessary. Every irritation of a nerve brings it into play, in muscles to which it IS distributed : every irritation of the spinal marrow excites it in all the members beneath the point of its application. It is quite at the top of the medulla oblongata, at the point where the tuburcula quadrigemina join it, that this faculty of receiving and propagating irritation on the one hand, and pain on the other, ceases. It is this point at which sensation must arrive in order to be perceived : it is from hence that the mandates of the will must ema- nate. Thus, the continuity ofthe nervous organ from this point to the different parts of the body is requisite for voluntary motion, and for the perception of impressions whether exter- nal or internal." Thus, then, the property of nervous irritability or of receiving and conducting sensation and irritation is limited to the nerves, spinal chord, medulla oblongata, and corpora quad- rigemina, «' the integrity of the optic thalami is not essential to the contractility of the iris; the sensations of light and of sound reside in the cerebral lobes, and there also all other sensations acquire distinctness and durability ; the spinal chord combines the muscu- lar contractions so as to produce motion in the joints; and the cerebellum regulates these movements, and unites them so as to constitute the actions of standing and locomotion :— such are the discoveries of M. Flourens*." * Experiments, similar to those of M. Flourens were instituted, in 180£, by professor Rolando, of Turin, from which he deduced inferences in some respects the same as those at which M. Flourens has arrived. The experiments of the latter physiologist were, however, more varied, were, apparently, more carefully performed, and therefore were more conclu- sive, than those of his predecessor. They were repeated, moreover, before a commission of the institute of France, composed of some of the most eminent of that body, who ap- proved of the conclusions which are given above. The following are the inferences which M. Flourens considers that his experiments justify. 1. "No movement proceeds immediately from the will. The will is the exciting and de=^ termining cause of certain movements; but it is never the efficient or effective cause of any. 2. "It has been shown that the immediate cause of muscular contraction, particularly resides in the spinal marrow and nerves, and that the regulating cause of these contractions is placed in the cerebellum. 3. " There are, therefore, three phenomena essentially distinct in a movement proceeding from volition : 1, the volition of movement, a volition which seems to reside in the cerebral hemispheres : 2, the appropriate regulation of the different muscular contractions product- ive of motion, which resides in the cerebellum ; and 3, the excitation of these contractions, which has its efficient seat in the spinal marrow and its nerves. # 4. " As these three phenomena, essentially distinct, reside in three organs also distinct, the possibility of abolishing any one of them, and leaving the others uninjured, seems appa- rent ; thus the will may be destroyed, and the legulation of contraction itself will remain ; or both volition and the regulating cause of contraction may be abolished, and contraction will alone be produced, Sic. 5. " There exists, therefore, in the nervous system, (cerebro-spinal system,) three pro- perties essentially different: one, the exciter of motion ; the other the regulator; and the third, the wilier and pcrceiver. 6. " The spinal marrow, the medulla oblongata, the tubercula quadrigemina, alone pos- sess the property of directly exciting muscular contraction ; the cerebral lobes and cerebel- lum do not possess it. 7. " There are two ways of destroying vision without going beyond the cerebral mass : cue by the removal ofthe tubercula quadrigemina—producing loss of the sense of sight, the other, by the removal of the cerebral lobes,—causing the loss ofthe sensation of sight. 8. " There is, therefore, in the cerebral mass, distinct organs for the senses, for the sen- salions, for the movements. , , 9. " Not only all the sensations, all the perceptions, all the volitions, all trie intellectual! and'sensitive faculties reside exclusively in the cerebral lobes, but all these faculties occu- py jointly the same seat in these organs; for if one of them disappear, all disappear; and if one return, all return. The power of feeling, willing, and perceiving, constitute therefore but one faculty, residing but in one organ. 10. " The cerebial lobes, the cerebellum, the tubercula quadrigemina, may lose a consi- derable, but limited, portion of their substance, without losing the exercise of their func« ••.-hs • and thov may re-acquiie them after being totally deprived of them- 66 APPENDIX. TIL Ofthedistinct Funcliohs ofthe anterior and posterior Columns ofthe Spinal Marrow. It is certain that the spinal marrow sends off nerves engaged in the performance of two dis- tinct functions, viz. that of feeling and that of motion. From what part—we are led to ask—of this organ, do the nerves allotted to each of these functions proceed ? It is well known that the spinal marrow is formed of two substances—a white substance, which is exterior, and a grey substance, occupying the interior ofthe chord. The continuity of the fibres composing the roots ofthe spinal nerves with the latter, as established by Kcuffel and Ollivier, naturally leads us to suppose that it is particularly concerned in the production of these functions. It may be also observed, that the fibres of the anterior roots are much Smaller than those ofthe posterior,—a circumstance which, when viewed in connexion with What has been advanced on the subject of Mr. Charles Bell* and M. Magendie shows that each set of fibres (posterior and anterior) is more immediately allotted to the performance of a distinct function,—that the posterior roots are devotedrto the sensibility of the parts which these nerves supply, and the anterior to the muscular contractions. But it appears, from the experiments of M. Magendie, that one of these functions does not exclusively be- long to one order of these roots ; for, when the posterior roots, or those which more particu- larly belong to sensibility, are irritated, contractions are occasioned in the muscles to which their nerves are distributed, although the contractions are much more strong and tnuch more* complete when the irritation is directly applied to the anterior roots of the Yierves. Slight appearances of sensibility are also occasioned when irritation is made on the anterior roots. It must therefore be concluded, that sensibility, although chiefly, is not exclusively, in the posterior roots, nor motion in the anterior. This defect of complete isolation of these two functions may arise, as M. Ollivier sup- poses, from the grey matter of each lateral half of the marrow, which seems to be concern- ed in their production, being entirely confounded at their central points of contact; and from the intimate union vvhich takes place between both the roots, below the spinal enlarge- ments (intervertebral ganglions,) and which must contribute still farther to combine these functions so as to prevent their perfect separation. It should be recollected that the functions ought not to be attributed to the roots of the nerves themselves. M. Magendie found, that when these nerves were divided close to the mariow, and irritation then made on their roots.no sensible effect followed: whereas, while their connection with the marrow was preserved, the slightest irritation was productive of effect; and the nearer that it was made to the spinal chord, the more intense was the in- fluence occasioned by it. Hence it follows that the grey substance of the chord, whence arise the roots ofthe spinal nerves, is much more intimately concerned in the production of the operation^ in question than the roots of the nerves themselves ; but this substance it- self seems to depend more upon the different parts composing the encephalic mass, for what- ever influence it may exert in the production ofthe phenomena undor consideration, than M. Ollivier appears to allow. He attributes them both almost exclusively to the grey sub- stance of the centre of the chord, which lie considers to be voluminous in proportion as these faculties are developed. This part ofthe chord, although altogether necessary to, and in- strumental in, their production, can only be viewed as one of three distinct classes of struc- ture, each of which, as M. Flourens has stated, perforins distinct actions, which by their combination, constitute but an individual function, that could not result from any one or 11. "The spinal marrow and the medulla oblongata, are the only parts which directly affect the same side of the body, with that in which they are themselves affected. The tu- bercula quadrigemina, the cerebral lobes, and the cerebellum alone produce their effects upon the opposite side to that in which they are influenced :—the former act in a direct course, the latter in a cross direction." * Mr. Bell's attention was attracted by " the difference in the distribution ofthe nerve?; ofthe head from those ofthe body, and the fact that all the spinal nerves arise by double roots. Observing that this form of origin was the same in all animals possessing a spinal cord, and considering that the anterior column of the spinal marrow was continuous with the crura ofthe cerebrum, and the posterior with the crura ofthe cerebellum,—he conceiv- ed that by experiments on the roots of these nerves, he might discover the functions of the two columns, and, perhaps, through them, arrive at a more accurate knowledge of the re- lations and individual uses ofthe cerebrum and cerebellum." Previously, however, to these experiments, Mr. Bell entertained the opinion that the anterior column of the spinal cord was different in function from the posterior ; and that, through the former, the simple vo- luntary power of moving particular parts was conveyed. He deduced this from observing, that the two nerves, vvhich are generally supposed to be purely motors, arise from the an- terior fasciculus. The experiments which these opinions suggested, although they were not conclusive, yet encouraged the view he had taken, and gave results in some degree similar *o those which Magendie aubsequently obtained from his experiments. To Mr. Bell, there- fore, the honour of hav'ny originated tbe-se views clearly belongs. OF THE RESPIRATORY ORDER OF NERVES. 67 two only of the actions composing it, but is the consequence of a more or le.s.s perfect co- operation of the wholes* IV. Of the Respiratory Order of Nerves___All animals that possess a perfect cerebro- spinal system have an intermediate order of nerves which connect the vegetative functions oi the ganglial system with the functions of the encephalon. This order of nerves has late- / if,?" VJ:,ry sat,sfact""ly examined into, both as respects their distribution and functions, by Mr. Charles Bell. On investigating the minute structure ofthe nerves which, both in man and in the lower animals, arise from the spinal marrow by double roots, and those which proceed from the medulla oblongata, by single origins, to the organs of respiration and those parts of the face and trunk which evince an intimate relation with this important function, Mr. Bell perceiv- ed that their texture and mode of distribution were very different. This circumstance led rum to consider that two distinct orders of nerves must exist independently ofthe sympathe- tic, the one simple and uniform, the other irregular and complex in proportion to the com- plexity of the organization. The former he has called original or symmetrical, the latter superadded or irregular. In the superadded class of nerves, vvhich are chiefly devoted to liie function of respiration, Mr. Bell arranges, 1st, the par vagum; 2d, the portio dura; 3d, the spinal accessory ; 4th, the phrenic; 5th, the external respiratory nerves, &c. "The nerves, this Physiologist states, " on which the associated actions of respiration depend^ and whicii have been proved to belong tp this system, by direct experiment, and the induc- tion from anatomy, arise very nearly together. Their origins are not in a bundle, or fasci- culus, but in a line or series, and from a distinct column ofthe spinal marrow. Behind the corpus olivare, and anterior to that process which descends from the cerebellum, the corpus retiforme, a convex slip of medullary matter, may be observed ; and this convexity, ox fas- ciculus, or virga, may be traced down the spinal marrow, betwixt the sulci, whicii give rise to the anterior and posterior roots ofthe spinal nerves. This portion of medullary matter is narrow above where the pons varolii overhangs it. It expands as it descends; opposite to the lower part of the corpus olivare it has reached its utmost convexity, after whicii it contracts a little, and is continued down the lateral part of tbe spinal marrow." From this track of medullary matter on the side of the medulla oblongata, arise in suc- cession from above downwards the portio dura, the glosso-pharyngeus, the par vagum, the nervus accessorious, the phrenic, and the external respiratory. These superadded nerves are comparatively but little sensible; they do not arise by double roots, as the symmetri- cal do : they have no ganglia on their origins, and while the other voluntary nerves have large, free, and round filaments, they have a close, loose texture, resembling a minute plex- us. "These are the nerves which give the appearance of confusion to the dissection, be- cause they cross the others, and go to parts already plentifully supplied from the symme- trical system." From these anatomical investigations, and from experiments made in order to ascertain the exact functions of this order of nerves, Mr. C. Bell and Mr. Shaw have drawn some im- portant inferences:—1st, They consider that the portio dura ofthe seventh pair " produces all those motions of the nostrils, lips, or face generally, which accord wiih the motions of the chest in respiration. When cut, the face is deprived of its consent with the lungs, and all expression of emotion. 2d, The par vagum associates the larynx, the lungs, the heart, and the stomach with the muscular apparatus of respiration. 3d. The spinal accessory con- trols and directs the operations of the muscles ofthe neck and shoulder, in the offices of re- spiration. 4th, The phrenic nerve has its functions sufficiently characterized in the name of internal respiratory, vvhich Mr. Bell has assigned it. 5th, The glossopharyngeal nerve, &c.; and, 6th, the external respiratory nerve, perform the functions which those parts, tq which they are distributed, have in connexion with the operations of respiration." * Of the distinct functions ofthe cerebellum, numerous opinions have been lately enter- tained. Dr. Gall considers it to be the seat of physical love. M. Rolando, who adopts the opinion of a nervous fluid, which he regards as analogous to the galvanic fluid, places the source and seat ofthe principle of muscular contraction in the cerebellum, which, ow- ing to the disposition of its laminated convolutions, he considers to act in the manner of a voltaic pile, and to transmit, under the direction of the brain, and through the channel of the spinal chord and nerves, the moving principle to the muscles. M. Flourens, as we have shown, views this organ as the regulator and balancer of the muscular contractions. M. Magendie regards it as requisite to the production of motion forwards: and Mr. C. Bell, MM. Fodera, Foville, and Pinel-Grandchamp, are of opinion that it is the seat of sensibj- 68 APPENDIX. Of the Faculties of the Mind, as evinced through the instmmenlality of a perfect JVer-- ■vous System. Note EE. This very extensive subject can only receive a very cursory notice from us at this place. We shall merely offer an arrangement ofthe ppwers ofthe mind, commencing with its low- est manifestations, or those most extensively disseminated throughout the animal kingdom, and proceeding to the highest or most perfect faculties. CLASS I. Instinctive Powers.—(Strong and immediate incentives to Action.) Order I. Instinctive Powers which tend to preserve the Individual. 1, The appetite for food and drink. 2, The desire of preserv- ing the animal warmth. 3, The desire of repose. 4, De-» sire of place. Order II. Instinctive Powers which tend to perpetuate the species. 1, The appetite for procreation. 2, Parental and filial after. tion. 3, Desire of society. 4, Social affection, giving risa to mutual support. 5, Sympathy. f'LASS II. Intellectual Powers. Order I. Powers of Consciousness, or the simpler Manifestations of Mind. 1, Perception. 2, Attention. 3, Memory. 4, Conception. Order II. Powers of Intellection, or the more Active Poivers of Mind. 1, Association of Ideas. 2, Abstraction. 3, Imagination. 4, Judgment or Reasoning. Order III. Ideas of Reflection, springing from the Exercise of the formes Orders of Powers. (Rational incentives to Action.) 1, Personality. 2, Time. 3, Power. 4, Truth, Causation. 5, Existence of a Deity. 6, Duty, Moral and Religious Ob- ligations, Rectitude, Merit and Demerit, &c. It will be perceived that the third order of ideas, into which we have here arranged the intellectual powers, are chiefly derived from reflection, or from the mind itself.—(See on this subject the writings of Dugald Steward; of Doctor Brown; Dr. Barclay, on Life and Organization; Dr. Pritchard, on the Nervous System; and the London Medical Reposi- tory, volumes xvii. and xviii-) Of Dreaming.--Mr. A. Carmichael has lately adopted and illustrated the theory of dreaming proposed by Dr. Spurzheim, that dreams are caused by certain isolated portions or organs of the brain continuing awake, while the remainder of it is in a temporary para- lysis frem sleep. " According to this view the particular dream will be fashioned by the part or parts which are not under the dominion of sleep; and the irrationality of our sleeping thoughts is accounted for by one or more parts or organs, thus acting without co- operation or correction from the other parts of the encephalon." M. C. enumerates no less than seven different states of sleeping and waking :—When the entire brain and nervous system are buried in sleep, then there is a total exemption from dreaming. 2, When some of the mental organs are awake, and all the senses are asleep ; then dreams occur, and seem to be realities. 3. When the above condition exists, and the nerves of voluntary motion are also in a state of wakefulness; then may occur the rare phenomenon of somnambulism. 4, When 07ie of the senses is awake, with some of the men- tal organs; then we may be conscious, during our dream, of its illusory nature. 5, When some of the menial organs are asleep, and two or more senses awake; then we can attend to external impressions, and notice the gradual departure of our slumbers. 6, When we are totally awake, and in full possession of our faculties and powers. 7, When, under these circumstances, we are so occupied with mental operations, as not to attend to theimpres sions of external objects; and then our reye.ry deludes us like a dream, OF THE MUSCULAR STRUCTURE. 69 Of the Formation and Development of the Muscular Structure, and of the Source of Irritability. Note F.F. etJ." th*TIe-y l0W"^ °rderS of an"!mals a muscular structure does not exist in a distinct siate. Iheir partial movements are performed by means of the cellular tissue of which riiey are composed. In the lowest of the series possessing a muscular texture, it moves only the integuments to which it is attached, and of vvhich it even forms a part. In all animals possessed ot a heart, the muscular tissue constitutes an important part. In all the verte- fo tu t"ima a ? Sma Dumber only of lhe muscles are attached to the mucous surfaces, ton Z .un an "S aPPendaSes ; whilst the greatest proportion is connected with the skele- ton lor the purposes of progression. ^oA"0/d|DStothe1 "searches of Dr. Isenflamm, of Dorpat, into the progressive develop- ment of the muscular structure in the human foetus, this tissue is formed from the mucous and gelatinous fluid of vvhich the embryo is at first composed. trom this mucous fluid the involuntary muscles are at first developed, and afterwards ue voluntary. During the first three months the voluntary muscles present the appearance ot viscous layers, with a slight yellowish tint. At the end of the third month the tendons make their appearance. During the fourth and fifth months the muscles become redder, more fibrous, and more easily to be distinguished from their tendons. In the sixth month, although very soft, they are still more perfect. At the full term ot utero-gestation the mus- cles are formed, but they are pale, yet vascular; they are soft, and their bulk much greater in proportion to the tendinous and aponeurotic substances than in the adult. As age advances, the voluntary muscles become redder and more fully developed, and towards the decline of life, more rigid, less capable of quick and extensive contraction, and comparatively of less bulk than their aponeurotic and tendinous connexions The microscopic observations of M. Bauer, Sir Everard Home, MM. Prevost, Dumas, and Beclard, seem to prove that the ultimate muscular fibre is composed of corpuscles (ar- ranged like a string of beads) in every respect similar to those in the centre of the red glo- bules of the blood. However, to obtain a correct idea of the ultimate conformation of the muscular fibre, researches ought to be made with this view on the raw and unprepared mus- cle ; for the action of heat, of alcohol and acids, evidently produces changes in the fibre, and coagulates the albumen, whicii enters into its composition. The voluntary nerves dip into the texture of the voluntary muscles at different points, and divide into numerous minute fibriles, which abruptly escape demonstration. This sudden manner of disappearing is owing to the extreme fibriles having become soft and diaphanous, and deprived of their proper envelopes, so that their medullary substance is diffused, as it were, into the mucous tissue, connecting the muscular fibres. The cerebro-spinal nerves, although they are numerous and large in the voluntary mus- cles, disappear in the manner just pointed out, long before their divisions become sufficiently numerous to be distributed to each muscular fibre. This being the case, how can the ac- tion of these nerves on all the fibres be explained? They cannot be the direct cause of the muscular contraction, but must act in producing it through the medium of another and a more general conformation. What this formation appears to us to be, we will now endea- vour briefly to shew. It has been stated that all the involuntary muscles are supplied with the ganglial or soft nerves only;—that they surround the arteries throughout their ramifications, and conse- quently are thus present in the voluntary muscles and in all vascular parts;__that the volun- tary nerves themselves, whether we trace the process of their formation in the human em* bryo, or observe them in the lower orders of animals, seem to originate from the ganglial the cerebro-spinal masses being the perfection of the nervous conformation, and the last part of it which becomes completely developed,—and that the cerebro-spinal nerves are destined to the performance of functions distinct from those to which the other and more generally diffused class is allotted. As irritability is present in parts which do not receive voluntary nerves, and in animals vvhich do not possess this part of the nervous system this property cannot be attributed to it. To what other species of organization can we refer this property? We find it, in the more perfect animals, chiefly displayed by the muscular structure. Is it from this circumstance, an attribute of muscular parts, and the pure result '.f their conformation? One class of physiologists answer this nuestion in the affirmative 70 APPENDIX. But irritability has been displayed by the lowest orders of the animal creation, wherein a muscular structure could not be detected, even in the parts themselves whicii furnished the phenomenon, therefore, although a property of the muscular fibre it is neither altogether restricted to it, nor is it strictly the result of the organization ofthe fibre itself. We must, consequently, refer this property to a conformation still more general than the muscular tissue, both as respects the whole scale of the animal creation and the organization of in- dividual species; allowing, at the same time, that a particular structure is requisite to the full and perfect development of this property, but that this structure depends upon a differ- ent source from itself for the property which it displays. Having arrived at the conclusion that irritability, although a property of muscular parts, is not the result of muscular organization, but is derived from a different, and more general system, supplying the muscular structure as well as other structures, we must next inquire what this system is. It has been already inferred, from various considerations, that the ganglial class of nerves is distributed in different proportions, to the various textures and organs of the body; that these nerves are similarly distributed throughout all the individuals composing the animal kingdom; that in some of its orders they constitute the only nervous system which the animal possesses : it has also been demonstrated that this class of nerves, in a more or less perfect state of organization, is present wherever irritability is manifested ; that these nerves are the most generally diffused of any ofthe animal tissues; that no othes structure exists but this vvhich can be shown to be present in every species of irritable parts, in all orders of animals ; and, consequently, that to no other source but this can the pro- perty of irritability be assigned. Having inferred that the muscular fibre is only the instrument of contraction, in its more perfect condition,—that it performs this function, in consequence of a certain conformation, and owing to that conformation being endowed by means of another still more generally diffused than itself,—and that this property is derived from the ganglial or soft nerves which proceed, either directly or as an envelope to the arteries, to all the tissues of the body—we are led farther to infer that the cerebro-spinal nerves are distributed to muscular parts for specific purposes, but that these parts do not derive their innate properties from these latter nerves—these nerves merely excite them, or rather are conductors of a stimulus acting on properties which proceed from a different source. We have contended that these proper- ties are not innate, or the consequence of the conformation ofthe muscular fibre itself; but are derived from a conformation still more general, which surrounds, or is otherwise con- nected with, the muscular fibriles, and that this more general conformation is the ramifica- tions of the ganglial class of nerves. Conceiving, therefore, that these nerves in their state of ultimate distribution and dissemination in the texture of the muscle, whether in the form of unarranged globules, or of minute and variously arranged fibriles resulting from the regu- lar distribution of these globules, are the chief source of the property evinced by muscular parts of every denomination, we further conclude that the voluntary or cerebro-spinal nerves do not produce their specific effects on the muscular fibres, owing to a nervous fibrile being ramified to each muscular fibrile, for this does not take place; nor do these effects 'proceed from the direct influence of these nerves upon the muscular fibrile, for the muscular fibre derives its property or faculty of contraction from a source different from itself, and from the voluntary nerves which occasionally excite its contractions ; but that these nerves seem to act directly upon the ultimate distribution of the ganglial nerves of the muscle, which latter nerves bestow on it the faculty of, or the disposition to active contraction, on the application of a stimulus, which faculty all muscular parts possess,—the former class of nerves conveying to some of these parts only the natural stimulus which induces contrac- tion, or which excites the active exertion of this faculty bestowed on these parts from a different source, namely, from the ganglial system. The mode of termination which the voluntary nerves observe in muscular parts, also favours the opinion which we have now given. These nerves terminate, as we have already noticed, in such a manner as leads us to infer, that they become, in a manner gradually identified or amalgamated, in the textures which they supply, with the ultimate distributions of the ganglial nerves : and the history of the embryo, and the progressive nervous development of the lower animals, would dispose us to believe that the voluntary nerves originate in the textures to which they are ramified, from the ganglial system, and that the larger branches of these nerves, the spinal marrow^ and encephalon are successively formed. Of Galvanic Electricity. Note GG. The phenomena of electricity have been long known to philosophers: but science has been chiefly indebted} in out own times, to the researches of Davy, Wollaston, Biot, Con- OF GALVANIC ELECTRICITY", 71 tomb, PoisSon, Oersted, and Becquerel, for a knowledge of the laws by which it is charac- terized. The observations and experiments of these successful inquirers appear fully to warrant the conclusion, that this vory active agent of nature results from two distinct fluids universally diffused through every species of matter. During their circulation, in their electro-motive capacity, through the corpuscles of matter forming the crust of this planet, they accumulate in their free and uncombined state upon its external surface, in consequence of the imperfectly conducting property of the enveloping atmosphere. The electricities '< are thus confined on the superficies of the globe, and indeed of all bodies placed on its exterior, not merely by the non-conducting faculty of the air, but also by a species of mechanical pressure which the air exercises." Hence arise the electrical phenomena which so frequently become the objects of observation. In elevated situations, in experiments where the density of the air is exhausted, and the aerial particles rendered fewer in number, and in other favorable circumstances of the at- mosphere, as in its humid state, the electric power emanates with rapidity from the electrized ball. Such is the mode of existence of this fluid upon the surface of the earth. But there also exists a continual condensation of the electrical agencies in the substance of the different matters composing the crust of this planet; and the galvanic, chemical, and other phenome- na, clearly shew that although such condensation ofthe electricities takes place under par- ticular circumstances of matter, yet a continuous circulation of it is also evident under other relations. This, indeed, is observed to occur during every manifestation of the gal- vanic influence. Such then being the case, and as it is now generally believed that the circulation of the electricities through the atoms of matter, or the electro-motive state, as it has with pro- priety been called, gives rise to the phenomena of galvanism*, which, within these few years, has led to the most splendid discoveries in the physical world, is it not reasonable to suppose that similar operations to those with which galvanic experiments make us acquaint- ed, are continually taking place in the elements of nature ? As it has been shewn that every species of matter possesses a certain proportion of the electricities, may it not be allowed that under circumstances similar to those with which experiment and observation make us acquainted, a continuous current of the different electricities are produced, the rapidity and sensible effects of which vary according to the accidental disposition and situation of the different material bodies, and their natural states of electricity. This opinion is calculated to account for many of the changes which are continually taking place on the face of our globe, and although many may not feel inclined to consider these fluids as the chief agents, no one can deny them a share in producing the effects which are so frequently observed upon its surface. The laws of electricity, whether they have been observed in connection with its free and uncombined state, or in its form of continuous circulation, as displayed in the various gal- vanic processes, have been lately, very closely marked and reduced even to precise calcula- tion. From among these we may adopt the following general law, which has been clearly established by M. Biot, namely ; that " each of the two electrical principles is a fluid, whose particles, perfectly moveable, mutually repel each other, and attract those of the other principle, with forces reciprocal as the square of the distance. Also at equal distances the attractive power is equal to the repulsive." This, therefore, being an established law vvhich characterizes the actions of these fluids, is it not reasonable to explain the material phenomena of the universe by its assistance, especially when such an explanation may be conducted in accordance with the known laws of matter, and supported by the conviction that the atoms of every material substance pos- sess certain electrical states ? Another very important law which regards the electric fluids, chiefly with respect to the atoms of matter with which they are associated, must not be overlooked : viz. " that a mu- tual attraction exists between the electric fluid and all material substances, when they are * The galvanic, or electro-motive apparatus may be considered, " as producing, by the mutual contact of the heterogeneous bodies which compose it, a development of electricity, which is propagated and distributed through its interior, by means of the conductors inter- posed betweenlts metallic elements (plates). If we form a communication between its two poles, the discharge which follows, overturning the state of electrical equilibrium, in the series' of bodies super-imposed on each other," (and forming the voltaic pile,) "causes them to be recharged according to the conditions of this equilibrium, either at the expence of the ground, or by the decomposition of their natural electricities. The repetition then of such discharges, or rather their continuation, must occasion in the apparatus a continued electric current the energy and the quantity of which depend as well on the magnitude and the nature 'of the metallic elements, in contact with each other, as on the greater or less facility, which the conducting parts of the apparatus present to the transmission of electricity."-- Biot. IT.) APPENDIX. in their natural state oi electricity." But this is a mere extension of the former law as re- gards the connexion of these fluids with the atoms of matter, and is entirely the result oi the electrical influence with which these atoms are endowed, as we can have no idea oi matter devoid of its natural electricity. Proceeding, therefore, upon the established laws of electricity, and upon these which, it is presumed, the particles of matter obey, it may be concluded that the cohesion which ex- ists between the atoms of unorganized substances, results from the attraction existing be- tween the opposite electricities. Whether we conceive the particles of matter to exist in- nately endowed with certain electrical states,or surrounded with one or other of these fluids, according to their reciprocal affinity, still the attraction between the atoms of matter must be equally the result of opposite states of this universally diffused agent. But it may be contended, that as the particles of matter mutually repel each other, they, therefore, are either altogether devoid of any kind of electrical influence, or are endowed with the property of mutual repulsion, whicii they exert notwithstanding the electrical agency. But this objection is by no means valid, for it may be shewn that, even granting them to possess the property of mutual repulsion, the supposition is favourable to the theory, and serves, moreover, to account for the varied phenomena to which the different particles of matter and the electrical fluids give rise. As, however, we have just supposed that the attraction of matter results from the atoms being endowed with the opposite state of electricity, it is as reasonable to suppose, that an op- posite condition to attraction must take place when homogeneous particles, or those possess- ing the same kind of electrical energy, are brought within the sphere of action. From this consideration we are led to the conclusion that attraction and repulsion be- tween the particles of matter arise as a necessary consequence of the electrical states of these particles. The various anomalies or peculiar conditions of material substances can be easily supposed to result from certain degrees of electrical saturation, or neutralization to which these substances are subjected. From the consideration of corpuscular attraction and repulsion, the transition to chemical affinity becomes evident. It may be shewn by direct experiment, that repulsion can be produced between two bo- dies, by giving one of them an electrical state different from that which it «aturally pos- sesses ; that is, by bringing it artificially into a condition similar to the other ; so chemical attraction between two bodies may be increased by exalting the energy of the electrical states which they naturally possess. As chemical affinities are the result of attraction or repulsion between the particles of matter, owing to their electrical conditions, so these affinities will be simple or compound, according to the electric states of the different materials which are brought into mutual ac- tion, and according to the various energies of these states. Having endeavoured to establish the proposition of different material atoms possessing different electrical states, both as regards its negative or positive modes of existence, and as respects the energy of each, and having considered such relations sufficient to account for the phenomena of repulsion and gravitation, it becomes unnecessary to point the applica- tion of the doctrine to the various chemical changes which take place. However, that such changes actually do occur, after the manner which a priori reasoning would lead us to expect, is a general inference vvhich presents but very few exceptions. But our knowledge respecting the abstract state of these substances which present the presumed exceptions are, as yet so very imperfect, that no conclusive argument can be adduced that their chemical combination is not the result of the electrical states of their atoms, or of these fluids during their continuous circulation through them. The excitement of electricity by means of friction, by compression, bjr the fusion of in- flammable bodies, by evaporation, by the disengagement of gas, by the disruption ofa solid body, by the contact of dissimilar substances, and lastly by chemical decomposition—all combine in establishing the intimate connexion tor which we contend. Whenever bodies, brought by artificial means into high states of opposite electricity, are allowed to.restore the electricity ; heat and light are the consequences. [Davy.] These effects take place in the same manner if performed in a vacuum. The light pro- duced isi this manner appears from the experiments which have been related, to be ofthe same nature wiih the solar beam, and to be divisible into the prismatic colours. The light exhibited by phosphorescent bodies, and by matter under its various conditions, gives simi- lar results. Therefore, from taking a survey ofthe electrical phenomena, of those display- ed by chemical combinations, and of other manifestations of nature, we are inclined to adopt the belief that light and caloric (as they exist in the solar rays, and as they are other- wise produced) are the result of the combination and neutralization ofthe opposite electri- cities, whether taking place in a dirct manner, and in their free state of existence, or through the medium of the particles of matter which they endow ; light being more or less perfect according as the neutralization is more or loss cc-in^cte, ;uid the caloric resulting from the intensity cf their actior. OF GALVANIC ELECTRICITY'. 73 Before leaving the consideration ofthe action ofthe electric fluids upon each other, and upon the molecules of matter, it is necessary to remark respecting a property which the mo- lecules of matter appear to possess under certain circumstances, of arranging themselves in definite ditections ;—this has generally been called the polarization of matter—a phenome- non observed in the crystallization of numerous substances, and in different chemical ac- tions. The polarization of the atoms of matter seems to result from the electrical states which they acquire from the electricities circulating around them, and to arise from a pro- perty with which the electricities are themselves endowed, or from their mutual action in- dependently of their connexion with the molecules of matter. According to this view ofthe subject, we should be led to expect, that the electricities, as they exist in the solar beam, unconnected with matter, would give rise to the phenomenon of polarization, in a similar manner as when their action is exerted through the medium of the atoms of matter; this conclusion is supported by the experiments of Dr. Brewster, Biot, and others, on the polari- zation of light. The intimate connexion which exists between the electrical agencies and the magnetical attractions, is a subject vvhich has lately interested scientific inquirers throughout Europe. It would almost seem, from their observations, that manifestations of the magnetic power result from the electrized state ofthe atoms of the magnet, and their consequent polariza- tion ; and, from the continuous circulation of the electric fluids either through its substance o. upon its surface.* Since the discovery of Galvani, several physiologists have attempted to explain the phe- nomena ofthe animal world, by imputing the functions of the nervous system to the elec- iro-motive energy, generated or developed by the cerebro-spinal masses. Amongst those who have espoused this opinion we may mention Sprengel, Reil, Prochaska, Wilson Philip, Lenhossek, &c. There can be no doubt that the electricities circulate through animal bo- dies in different conditions, and give rise to subordinate offices in the animal economy, un- der the superior dominion ofa vital influence ; and moreover, that they (or one of them at least) are a stimulus to this influence. The experiments of tne physiologists just named, especially those of Dr. Philip show this, but nothing more than this. They refer to the electrical apparatus which certain fishes possess, and the power they have of giving electri- cal shocks in fartherproof of the justness of their inference; but it may be asked, ifthe ner- vous influence be the same as electricity, why should these animals possess an apparatus distinct from the nervous system, and under its control, fox the production ofthe electrical phenomena? The existence of this apparatus confirms the proposition we havejust now stated ; and its office is evidently that of accumulating within itself, in consequence of the vital function with whicii it is endowed, the electricities circulating in the body, so that they may be discharged according to the wants of the animal; but the electricities which the ani- mal thus accumulates and discharges cannot be said, from the evidence which we as yet possess on the subject, to be identical with its nervous influence, nor with the vitality of its system more than oxygen, nitrogen, hydrogen, or any other fluid constantly present in, cir- culating through, and combining with the constituents ofthe body, may be considered to be the source of its numerous manifestations. The one fluid may accumulate in the system as well as the other, by means ofthe vital operations ofthe organ in which the accumulation takes place, and it may be again discharged in consequence either of an operation deter- mined by the nervous influence, or of some other process, and, in fact, we find such a phe- nomenon actually taking place; but, are we to infer, on that account, that either the one or the other of these fluids constitute the vitality of tbe system, or even that they are the source of vitality, when it can only be shown to be a single function from amongst the many whicii the animal exhibits? We find that electricity is accumulated in, and discharged from, the electrical apparatus of some fishes ; and we also perceive that oxygen and nitro- gen are, in like manner, accumulated in, and discharged from, tho swimming bladders of other fishes ; but these circumstances do not warrant us to infer that electricity is the nerv- ous influence ofthe former, more than that oxygen is the nervous influence ofthe latter ; or, that the vitality ofthe one is electricity, ofthe other it is oxygen. But, although the agency ofthe electricities have been extended, farther as respects the animal kingdom, by some physiologists, than well ascertained facts can warrant, it must be allowed, from the evidence which has been adduced, that they give rise to very important phenomena when they are brought to operate on some of the animal textures. It is these effects, or rather the stimulus which electricity imparts to the sensible and contractile parts ofthe body, that constitute the chief physiological relations of electricity, and give a degree * In the annual oration delivered to the Medical Society of London in 1822, we endea- voured to show that the phenomena of attraction or gravitation, chemical affinity, combus- t on crystallization, magnetism, light and heat, (both as they exist iu the solar rays, and as uiev are otherwise produced,) in short, that all the phenomena of the inorganized world and ofthe solar systems may be explained by means of the a^ncy of two universally diffused electricities, _„ 74 APPENDIX. of plausibility to the doctrines of those who consider that all the animal functions are dis- charged by the electricities in their electro motive condition. These circumstances require that we should notice at farther length the effects of this agent on the animal system.* "According to Ritter, the electricity ofthe positive pole augments while the negative di- minishes the actions of life. Tumefaction of parts is produced by the former, depression by the latter. The pulse ofthe hand, he says, held a few minutes in contact with the positive pole, is strengthened; that ofthe one in contact with the negative is enfeebled ; the former is accompanied with a sense of heat, the latter with a feeling of coldness. Objects appear to a positively electrified eye, larger, brighter, and red ; while to one negatively electrified they seem smaller, less distinct, and bluish,—colours indicating opposite extremes of the pris- matic spectrum." An electrical practitioner referred toby Dr. Ure, from whom the above paragraph is quot- ed, considers that his experience in the application of this agent in disease warrants him in referring its operation to three distinct heads: " first, the form of radii, when projected from a point positively electrified; secondly, that ofa star, or the negative fire concentrated on a brass ball; thirdly, the Leyden explosion." The first acts, he considers, as a sedative ; the second as a stimulant; and the last has a deobstruent operation. Dr. Ure has found that the negative pole ofa voltaic battery, gives more poignant sensations than the positive. The experiments of Dr. Philip with voltaic electricity have led him to infer that the ner- vous influence is nothing else than this agent. This proposition has already been noticed, and it will be again referred to; we shall only observe at this place, that his experiments appear to show the extent to which the electro-motive agency, transmitted through their voluntary nerves, may prove a stimulus to particular organs, and enable them to perform their functions when these functions have been impeded by tbe removal of a natural and re- quisite stimulus. We have at another place endeavoured to show that the functions vvhich Dr. Philip has imputed to the cerebro-spinal nerves are actually derived from another source; that the operations of these nerves (with the exception ofthe nerves of sense) are chiefly confined to the transmission ofthe cerebro-spinal influence, which is the natural sti- mulus to the vital endowment that the organs receive from a different system—the gan- glial; but that this stimulus cannot be considered to be galvanism, merely because galvan- ism is a stimulus, and acts in a manner which we have every reason to suppose other sti- muli would act, if they were capable of being transmitted through, and be present in, every part ofthe body, on which they are disposed to operate. It is the particular constitution of this agent, its properties, and its relations with the solids and fluids ofthe body, that give rise to its active operation, and to phenomena liable to be confounded with those ofthe ner- vous system, or even with tfaose of life itself. What we have just now adduced has a stricter reference to the opinions of those who consider that the nervous influence and galvanism are the same, we shall now refer mote particularly to the notion of the identity of this agent and life itself; and here we cannot do better than quote the very acute, conclusive, and unanswerable observations of Dr. Pringf (Principles of Pathology) on this subject. "We observe that electricity is related with life, and acts upon it; this is no proof of idenity. We observe also that electricity will sub- stitute in some instances the properties derived from a. nervous centre ; in this respect there is an identical property common to it and life, which is also possessed by many other sub- stances. We observe, also, that the formation of heat, and the faculty of generating elec- tricity, belong to animals, and are dependent upon their life. The faculty of generating electricity, in animals, does, not prove that electricity is even a constituent part of their life: it proves that it is a phenomenon of their life ; but that it is a part of it, is no more to be concluded on this account, than that urine, or mucus, &c. is a part of life, because these are also products of it. " We have made out then only one point of resemblance between life and electricity, which is, that electricity will in some cases substitute a property otherwise derived from a * Amongst the living tissues, the nervous is the best conductor of electricity; therefore, when an electrical current is established through the body, it is transmitted by this tex- ture. If the electrical current consists only of one of the electricities, the molecules com- posing the nervous texture tend to propel each other, or to disunite; and, if the electrical action is very intense, they are actually decomposed, and confounded with the fatty matter whicii isolate the nervous fibres ; all the functions ofthe nerves are instantly destroyed, the irritability ofthe muscles dissipated, and life is immediately terminated. These effects are frequently witnessed from lightning. They are not confined, however, to the nervous and muscular systems, all the soft parts are more or less affected ; the blood does not coagulate, owing to thVdissipation ofthe vital influence giving rise to the phenomenon of coagulation (See p. 633;) and all the tissues fall quickly into a state of putrefaction. t We recommend the physiologist to study closely the physiological and pathology :.~. -flyings of this most acute and philosophical writer. OF OSSIFICATION. 75 nervous centre; whicii property, applied to the stomach, will aid digestion, in which res- pect, it has not yet been found that more common stimuli resemble it: applied to the vo- untary muscles, it will produce their contraction, and in this respect the property is a com- mon one to many other substances, which no one ever thought of identifying with life. out even the properties which are said to depend upon a nervous centre, are not all of them substituted by electricity, which will stimulate muscular contraction, like many other substances, but like those substances also, it is incapable of conferring sensibility ; or if elec- trical influence ever excites sensation in paralytic limbs, it is only because their sensibility is not totally extinct, and will therefore admit of sensation under the application of this, or of any other stimulus, of a powerful kind. " We have seen that electricity can do a very little which is also done by life ; there is then analogy in one property, but to be the same identity, there must be analogy in all; or to approach to such identity there must be at least a general analogy. The living principle maintains itself by assimilation from exposure to its elements ; electricity is not capable of maintaining itself from its elements, but must be produced from them. Muscular power in the animal system is related with mind, and directed by volition ; wo have no evidence that mind, or volition, independently of the properties which distinguish the living state, can so ally itself with electricity. Animal life confers sensibility on structures; electricity can merely excite sensation in common with chemical and mechanical stimuli. The or- ganic life produces from a common material, arranges, and renovates, in the muscular sys- tem, the particles which compose muscle ; in the tendons, those of tendon ; in the mem- branes, those of membrane : in the bones, the constituents of these structures ; and of all others, with all their circumstances, however diversified. Now if electricity were capable of doing all this, there would then be established only a general resemblance with life ; an- alogies would afterwards be sought for, corresponding with those powers exhibited by the relation of properties of life in different seats, and more especially among the phenomena of disease. But until the pretensions of electricity to an identity with life shall be established by rather a more extensive analogy, it is superfluous to inquire how far the phenomena of electricity resemble those of dyspepsia, diarrhoea, consumption, abscess, or gout. If, per- chance, electricity should be endowed with the properties engaged in these phenomena, it will be greatly indebted to its friends, for bestowing upon it attributes which it has never displayed. In the mean time, it is to be wished that experimentalists will go on multiply- ing their facts, and that they will abstain from reasoning upon them: they will not, how- ever, err to any great extent in this way, if they will take the trouble to remember that so far as things are proved to be alike, they are alike ; and where they are not proved to be alike, it is possible that they may be different. " The identity of life and electricity, or galvanism, has been inferred, as appears from the preceding account, from very slender premises : but the arguments just considered are among the best that have been proposed in favour of the sameness of the two principles, or substances, if they are substances." Of Ossification. Note HH. The bones are at first ofa mucous or gelatinous consistence in the embryo. They next become cartilaginous, and some of them fibro-cartilaginous : they are lastly perfectly ossifi- ed. At the early period of tbe embryal state the bones gradually increase, without any apparent division, into separate parts. The cartilaginous bones, or the temporary cartila- ges, do not appear before two months have elapsed from the period of conception, and then this process towards ossification only commences in those bones, or in the parts of bones which are ossified at a later period. It appears doubtful whether or no those bones which) .ossify the first, or those parts of bones in which the process takes place at an early period, pass through an intermediate or cartilaginious state. It seems most probable from the ob- servations of MM Beclard and Serres, that in them the ossific deposit is made in the first or mucous state of their existence ; whilst, in those bones which are perfected at a remoter period the cartilaginous or intermediate state which they assume is rather a provisional function, than a stage of ossification—a temporary conditiou of structure for the purpose of performing the offices of bone, and not a requisite antecedent to the ossific process. Ossification commences successively in the different bones, from about a month after im- pregnation, in those which are the first formed, until ten or twelve years after birth, in those which ossify at a later period ; and in certain suberdinate parts of bones, the ossific p-ocess does not commence until the fifteenth or eighteenth year. The clavicle and maxillary bones are amongst the first developed ; the sternum, tb.e bones of the pelvis, 76 APPENDIX. and those of the extremities ore the latest. It may be considered as a general proposition that those bones which are nearest tbe nervous and sanguineous centres are the first to be formed, as if their more immediate developement were required to protect these important systems; hence we perceive that the vertebrae and ribs ossify at an early period. At the end ofthe first month ossification commences in the clavicle, and successively in the inferior maxilla, in the femur, tibia, humerus, superior maxilla, and bones of the fore- arm, where it begins about the thirty-fifth day. About the fortieth day this process com- mences in the fibula, scapuluin, the palatine bones; and during the following days, in the occipital and frontal bones, in the arches of the first vetebrae, and in their sides, in the sphenoid, the zygomatic apophysis, the phalanges of the fingers, the bodies ofthe vetebrse, the nasal and zygomatic bones, the ilium, the metacarpal hones, the condyles of the occi- pital bones, in the squamous portion ofthe temporal bone, the parietal, and in the vomer • in all these ossification begins about the middle of the seventh week. In the course ofthe same week it commences also in the arbitar process of the sphenoid ; and, about the end ofthe week, in the metatarsal bones and phalanges of the fingers and toes. During the ten following days it begins in the first sacral vertebise, and around the tympanum. During the subsequent weeks and months it commences in the bones of the ear, in the pubis, in th': processes of many ofthe already mentioned bones, in the small bones of the extremities, &c. (Beclard). Ossification does not result, as we have already noticed, from the transformation of cartilage into bone. The diaphysis of the long bones, and the centre of the large bones, which are amongst those first formed, pass immediately from a mucous to an osseous state. The other parts of this structure have an intermediate cartilaginous condition ; and it is in these parts that the successive stages of ossification may be best observed. The cartilage which, for a longer or shorter period, supplies the place of bone, becomes at first hollowed into irregular cavities, afterwards into canals lined with a vascular mem- brane and filled by a mucilaginous and viscid liquid ; these canals become red, the cartilage now assumes an opaque appearance, and ossification commeuces towards its centre. The first point of ossification is always in the centre of the cartilage, and never at its surface. This point is surrounded by n reddish cartilage, and that part witch is nearest it is opaque and pierced with canals still farther than opacity reaches. The osseous point augments progressively by means of additions on its surface, as well as by an interstitial deposit in its substance. The cartilage gradually becomes hollowed by cavities, and canals, lined by a vascular sheath, diminishes as the ossification extends, and disappears altogether when the process is completed. With respect to the state in vvhich the osseous matter is formed, we are inclined to agree with M. Beclard, in the opinion that the earthy matter is deposited, in a fluid condition, and at the same time with animal matter, in the organized tissue whicii secretes it. Its subse- quent solidification arises either from the deposition of a larger proportion of earthy mat- ter, or from the absorption of the vehicle which gives it the flu!'1, condition ; or from the joint operation of both these causes. Of Voice. Note H.H.* The cricoid cartilage, which supports the two arytenoid cartilages, is not immoveable at the inferior part of the larynx. The trachea to vvhich it is attached by its inferior margin, yields and allongates itself in order to allow it motion. The muscles of the larynx do not contribute to the production of the voice solely by means of the. action which they exercise on the sides of the glottis; several of them, and particularly the thyro-arytenoids, may he considered as forming part of the parietes of this opening. These small muscles give rise to acute sounds by drawing closer the two arj'tenoid cartilages, and vvher. in a state of con- traction they also seem susceptible of it vibratory motion, varj'ing in degree according to the degree of contraction : by the assistance, therefore, of the muscular fibres covering its sides, the glottis is susceptible of vibrations analagous to that ofthe lips applied to the opening of a French-horn. The production of sound is owing to the action of the muscles of the larynx on its cartilages, during expiration ; and whatever impedes the functions of the nerves actuating these muscles, puts a stop to the utterance of sound. Of Ventriloquism-—Various attempts have been made to explain the manner in which the ventriloquist is enabled to modifv his articulations into th? semblance of distinc' OF THE GENERATIVE ORGANS, ETC 77 voices. Dr. Good considers ventriloquism " to be an imitative art, founded in a close at- tention to the almost infinite variety of tones, articulations, and inflexions, which the glottis is capable of producing in its own region alone, when long and dexterously practised upon ; and a skilful modification of these vocal sounds, Ihus limited to the glottis, into mimic :-peech, passed for the most part, and whenever necessary, through the cavity of the nostrils, instead of through the mouth." He farther supposes that" some peculiarity in the structure of the glottis, and particularly in respect to its muscles and cartilages," is requisite to carry this art to perfection. The explanation which Magendie offers on this subject, appears to us to be more correct, although perhaps not sufficiently so. This physiologist asserts, that ventriloquism consists in certain modifications of 6ounds or speech, produced by a larynx of the common formation, with a strict attention to the different effects of sound thrown at dif- ferent distances, and through different modes of conveyance. We cannot agree with Dr. Good, that the ventriloquist performs articulation by means of the larynx only, although we may concede some share in the process to this organ ; nor can it be granted that any «' addition to the muscular organism of the glottis" is enjoyed by those who have perfectly acquired this imitative an. Of the Generative Organs arid (heir Functions. Note I.I. I. Of the Male Organs of Generation.—The cellular structure ofthe corpora cavernosa penis, according to the microscopic examinations of M. Bauer, appears to be made up of an infinite number of thin membranous plates, exceedingly elastic, so connected together as to form a trellis work, the edge of whicii is firmly attached to the strong elastic ligamen- tous substance which surrounds the whole, and also forms the septum peclini-formt. This substance has an admixture of muscular fibres. The cells are generally larger, or rather the trellis work is more loose in the middle portion of each corpus cavernosum. Arterial ramifications are supported by this reticular structure, and they are distributed every where throughout the cavernous part of this organ. In the usual state of the penis, the blood is not poured into the cells, but returns by the veins, and it remains flaccid ; but when a person is under the influence of particular impressions, the minute arterial branches which before had their orifices closed, now have their action suddenly increased, and pour from their open mouths the blood into these cells, so as to overcome tbe elastic power that under ordinary circumstances keeps them collapsed. The corpus spongiosum penis appears, from the observations of the same physiologist, to consist of the same kind of structure as that observed in the corpora cavernosa, but on a less scale. Its structure is also more regular throughout; without, however, having any muscular fibres mixed with the trellis work, these being confined to the outer surface of the inner membrane of the urethra. The erection of this part is supposed to take place after the same manner as that of the corpora cavernosa, namely, from a vital expansion taking place in the extremities of the arterial capillaries, and thus allowing the blood to flow from them into the cells of both structures. We may state, moreover, that the arteries of the penis are surrounded by a larger pro- portion of nerves than in most ofthe other tissues ofthe body. The veins form very nume- rous anastomoses. It is the division, on dissection, of these numerous veins, and of their t.umerous roots, anastomoses, and plexuses, which, in the opinion of M. Beclard, gives the appearance of cells, the existence of which he denies. Erection of this texture is the result of the influence of the nerves upon the arteries and veins belonging to it. By this influence the action of the arteries is increased, whilst the diameter of the veins returning, the blood is diminished by the tonic contractility which these nerves exert on the coats ofthe veins. MM. Prevost and Dumas have both examined the spermatic animalculee. They seem to vary in form indifferent animals, and to be the product ofa real secretion. These physiolo- gists conclude " 1st, that spermatic animalculae have nothing in common with infusory ones, except in their microscopic size; 2d, that they are produced in the testes alone, but do not appear in these organs till the age of puberty ; and 3d, that they seem to be the active prin- ciple or agent of the semen." The vesiculae seminales may, under particular circumstances, more likely to occur in the '^urnan species than in the lower animals, be employed as reservoirs; although their ordina- ry use may be to secrete a fluid which, mixing with the semen in coitu, may render the act r:ore perfect, and more likely, therefore, to produce foecundation. II. Ofthe Female Organs of Generation.—The uterus, the ovaria, and the fallopian tubes -"•ei've their Merves f>-orn the a'x'mninal portion of the trisnlanchnic nerves, branches of 78 APPENDIX. wbich unite variously with each other, and form six plexuses. The first, which JVT. Tiede- mann calls spermatic, or the plexus common to the ovaria and tubes, is situated on the ante- rior surface ofthe abdominal aorta, and on the origin of tbe internal spermatic artery. It is formed of a number of branches, whicii come from the renal ganglia. Its filaments descend, surrounding the arteries of the ovaria, between the membranes which form the broad liga- ments ofthe uterus, and arrive at the ovaria and tubes, in whicii they are ramified : a few filaments reaches the fundus of the uterus. The second plexus, vvhich is the largest, M. Tiedemann calls the superior lumbar plexus, or' common uterine. It is formed of branches, which proceed from the superior lumbar and renal ganglions ; and is placed on the body of the fifth lumbar vertebra, and on the promon- tory of the sacrum, between the iliac arteries. On its entrance into the pelvic basin, it di- vides itself into two considerable plexuses, which M. T. calls the hypogastric or lateral ute- rine plexuses. These are placed on the trunks of the iliac arteries, and anastomose with the first and second sacral ganglions. A great many filaments proceed from these plexuses, form- ing a reticulum around the arteries of the uterus, with the ramifications of which they pe- netrate into the texture ofthe organ, chiefly its posterior and lateral aspects. Several branches proceed from the superior lateral or hypogastric plexus to the vagina, at the point of its union with the neck of the uterus, and there unite with the anterior branches of the third and fourth sacral nerves, and form a large plexus, which M. Tiede- mann calls the inferior lateral hypogastric, and which interweaves with and embraces small ganglia. This g&ngliform plexus gives origin to a great many branches, chiefly to the va- gina, to the ut?tus, and also to the bladder and rectum. These nerves, as well as those be- longing to the other plexuses, always closely embrace the arteries in the form ofa network. It appears, therefore, that the womb and its appendages are surrounded by important ner- vous plexuses. These nerves are soft, small, reddish-gray, and in every respect similar to the other portions ofthe great sympathetic nerves. Of their appearance and character we have had several opportunities of satisfying ourselves, when making researches respecting this grand organic system, and we can bear testimony to the correctness ofthe observations of M. Tiedemann. M. Tiedemann states that the number and size of the uterine nerves vary according to the age ofthe female ; that they are small and apparently few in girls—large and numerous in adults—and very small in old women. He has observed another fact, confirmatory of their functions, which indeed was previously noticed by Dr. W. Hunter and Professor Chaussierj that these nerves become larger and more numerous during gestation. III. Of Impregnation.—Several opinions have been entertained respecting the impregna- ting process. Some physiologists suppose that the actual contact of the ovum and semen are requisite ; others that the aura seminaiis is all that is requisite. Ofthe former class of physiologists some suppose that the semen is absorbed into the uterus, where the ovum, hav- ing descended through the fallopian tubes, meets it; others consider that the semen is con- veyed by a paristaltic-like action ofthe vagina, uterus, and tubes, to the ovarium ; and they adduce, in support of their opinion, the occurrence of extra-uterine foetation; a third party, belonging to this class, conceives that the semen is conveyed to the ovum itself, in its situa- tion in the ovarium, by means of absorption through a set of vessels allotted to this specific purpose. Dr. Dewees, of Philadelphia, has argued strenuously for this last doctrine : it has also been adopted by other physiologists, and it seems to have received support from the la- bours of Dr. Gartner, of Copenhagen, who has discovered in some animals a duct leading from the ovary to the vagina. The occurrence of ovarian fcetation, wherein the foetus is lodged within the enveloping membrane ofthe ovarium, can be most satisfactorily explain- ed by means of this doctrine. Two cases of this description have lately been detailed by Dr. Granville and Mr. Painter. It must, however, be allowed that the latter class of physi- ologists, or those who contend for the impregnating influence ofthe aura seminaiis, have it in their power to adduce strong arguments in behalf of their opinion. It has even been as- serted very recently, by some continental pli3rsiologists, that the impregnating power of the aura seminaiis may be proved by experiment performed on rabbits,in the following manner : Let the semen be received in a cup, over which is to be immediately placed an inverted fun- nel ; and let the apex of this funnel be introduced into the vagina. If this experiment be performed immediately after the seminal emission, they say that impregnation will be the result. It has been argued that the venereal desire is present in neither sex before the development ofthe testes and ovaria. This, however, is not the case. The venereal appetite makes its appearance in both girls and boys long before the generative organs are developed. It has been frequently observed in them both, in temperate climates, as early as the sixth or se- venth year. It has also been supposed that the venereal appetite disappears soon after t>e menses have ceased to flow : this also is not the case. ON THE GENERATIVE ORGAiNS. ETC. 79 With respect to the assertion that the venereal orgasm on the part ofthe female is neces- sary to impregnation, we may observe that although it may be requisite in some females, it is by no means so in others ; for many women conceive who are indifferent during the Vene- real congress; there are others who conceive, notwithstanding their successful endeavours to suppress their orgasm; and some are impregnated, when owing to disease, as procidentia uteri, &c. they cannot be supposed to enjoy much pleasure from the act.* Dr. Blundell found in his experiments that when only one ofthe uteri ofa rabbit was di- vided, or rendered impervious at its neck, or when the passage to both was obstructed by ty- ing the vagina, and afterwards freely admitted to the male, that the obstructed uterus, or uteri, did not become impregnated ; but he found, in those whose vagina was tied, that, not- withstanding, the ovaries, fallopian tubes, and womb were excited by coition; and in those who admitted the male frequently, the abdomen acquired a large size, and in some cases ex- ceeded the bu'k of mature gestation. These enlargements arose from an accumulation ofa humour in the womb, which, at a temperature below boiling, formed albuminous concretions. In its appearance it was various, but generally fluid, pale, and turbid. In those who had on- ly one uterus obstructed, the sound one became filled with foetuses, and the barren one with the humour described. The formation of the lutea, the development ofthe womb, and the repeated accumulations of fluid in consequence of coition, in these experiments seem to in- dicate the descent ofthe rudimental material. Thus although the passage to the uterus was completely interrupted, the tubes were ex-* cited by the venereal orgasm, they really conveyed the rudiments to the,.womb, and these rudiments engendered the watery accumulations there, in the abortive attempts at g«nera-. tion. This appears to confirm the supposition, and indeed to establish it, that even in vi- viparous animals, generation may be carried to a certain extent, although the access ofthe semen to the rudiments is interrupted ; under these circumstances the young animal cannot be formed, it is true, but corpora lutea may be generated,the womb may be developed ; and the rudiments may be transferred to the uterine cavity by the play of the fallopian tubes. This opinion receives countenance from the generation of oviparous animals, in most of whom the rudiments may be discharged independently of preceding impregnation.—(Med. Chirug. Trans. Vol. 10.) Dr. Blundell supposes that the vagina and womb perform a peristaltic motion from the stimulus of the semen, both in the human subject and lower animals ; and that this motion conveys the semen to the rudiments. From these experiments it would appear that the presence of corpora lutea cannot be re- lied upon as a proof that impregnation had taken place. There is even evidence that they may be produced, even independently ofthe sexual intercourse, from the mere excitement of desire in a high degree. Dr. Blundell has in his possession a preparation of the ovaria of a young woman who died of chorea under seventeen years of age, in which the hymen was unbroken, and nearly closed the entrance of the vagina. In these ovaries the corpora lutea are no fewer than four—two rather obscure, the other two perfectly distinct. As Dr. Blundell's experiments go to prove that impregnation cannot take place without the semen coming in contact with the rudiments, he therefore supposes, that when the ovary lodges either in the tubes, the peritoneal cavity, or in the ovary itself, and there impregnated, that the semen must be-conveyed to those situations. Or, that the rudiments in its descent meet the semen in its ascent, and that the transfer of the semen beyond the womb may be the cause of extra uterine pregnancy. IV. Of Superfcetation.—M. de Bouillon (Bullet, de la Facul. et de laSociete de Medecine, No. 3,) has adduced an instance of superfcetation in a Negress. At the end of her preg- * Sir Everard Home (Philosoph. Trans. 1818) states that corpora lutea are never met with before puberty. They are formed in the loose structure ofthe ovarium previous to, and in- dependent of, sexual intercourse; and when they have fulfilled their office of forming ova, . hey are afterwards removed by absorption, whether the ova be impregnated or not. It seems that the ovum too, with its amnion and chorion, is formed in the virgin after puberty. This was found to be the case in a woman of 20 years of age, who had a perfect hymen. " The •allopian tube of that side was fuller than the opposite. The fimbriae were spread out, and unusually vascular." We know that animals part with their eggs whether there be sexual intercourse or not; and this is done with such force during coition that the cavity ofthe cor- pus luteum is absolutely inverted, so that the ovum is exposed completely to the emission of the male. Extravasation of blood follows the rupture ofthe ovum frequently to so great a degree that blood occasionally passes out through the vagina. In nine months after impreg- nation, the corpus luteum is nearly absorbed, but a new one is usually found in a state of forwardness in the other ovarium. All preparations of corpora lutea, which are made from women who have died in child-bed, belong, in Sir E.'s opinion, to ova which were to suc- ked, net to the ovum of the child which had been born. 80 APPENDIX. nancy she was delivered of two male children, full-grown, and of the same proportions., but the one a Negro and the other a Mulatto. The mother, after a long resistance, con- fessed that she had connexion the same evening with a white and a negro. Similar instan- ces have lately been detailed in the American journals, of which we shall only instance the following :—A white woman, near Philadelphia, is said by Dr. Dewees, to have been deli- vered of twins, one of whom was perfectly white, the other black. The latter of these had all the characteristics of the African, whilst the former was delicate, lair-skinned, light- baiied, and blue-eyed. Similar cases have been detailed by Dr. Elliotson, and Drs. Nor- ton and Stearns, of New-York.' Superfcetation, in our opinion, can only take place under circumstances similar to those which produced it in the foregoing instances :—in them, it would seem, that there had be*i: connexion with different individuals within a short space of time. We conceive that, when the decidua is thrown out and the ovum ha6 formed its connexions, superlactation is then impossible, unless in the case of a double uterus. Of the Development of the Textures and Organs of the Fcetus, Note K.K. It was our intention to have illustrated this subject at considerable length; but we have so far exceeded Our limits that we must now be brief. At first the embryo appears to be only a semi-liquid vesicle, and to consist of minute glo- bules disseminated through a more fluid medium, which presents an oval or spheroid form*. As the embryo advances, the proportion of solid matter increases, and continues to increase to the termination of the life of the individual. The first stage of its existence resembles that of the polypus ; and the globules which may be observed in its otherwise homogeneous texture, closely resembles those which are observed in the nervous system. At first the embryo is colourless; it afterwards presents a gradual development of colour, and at last, a coloured fluid may be discerned. From a state of organization, consisting merely of disseminated globules, fibres, membranes, and vessels, come successively into existence. The organs, as we have already said, are not formed at once : they are gradually developed. Even par- ticular systems do not assume at once their form of organization, but are developed by de- grees, and run through the same stages of organization as may be remarked in the animai scale. This is particularly remarkable, as respects the development of the nervous system!. (See the note on this subject.) The exterior form of the foetus seems to be assumed before its tissues attain any conside- rable degree of consistence. The glandular viscera are at first formed in isolated parts. The globules of the nervous system first appear ; these become united into chords and gan- glia^. The vessels commence in isolated vesicles, vvhich become elongated and connected * Mr. Bauer says that he has detected the human ovum on the eighth day from coition. It consisted of two membranes; the external one open throughout its length, but with its edges turned inwards, like the shells of the genus voluta; the internal membrane pointed at one end and obtuse at the other, slightly contracted in the middle, and containing a slimy fluid and two vesicles. t It would appear that in the process of the growth of the embryo, even of man, that, during the first days of its existence, the nervous system can only be traced as it exists in the polypi; its globules seem dispersed through the e.mbryal structure : as the ovum advan- ces the ganglial branches, and the ganglia themselves make their appearance. ^ Viewing the nervous system throughout the numerous classes of animals, and tracing the process of its formation from the embryo up to the period of perfect foetal existence in the perfect animals, especially in man, we are led to infer that this system is not originally formed from the centre towards the circumference, but that the origin of its ramifications commences in the mucous or cellular tissue,when the embryo is yet but in an apparently ho- mogeneous state ; and that as the textures become, in the process of frutnl growth, more ami more developed, so the globules composing the nervous system, and chiefly those of the gan- glial system of nerves are arranged into chords of communication, chiefly in the course of the vessels, for the purpose of preserving a communication between the organs, and rein- forcing each of the textures with the influence which they generate in their perfect state or development. As the process of funal growth proceeds, the nervous ramifications advance towards centres, vvhich vary in their characters, according to the species of the animal; in those which are more perfect those centres are numerous, and almost each differs in a more or less sensible manner from the ether, both as to appearance and function. ON THE DEVELOPMENT OF THE FtETUS. 81 tn regular series. The intestinal tube seems to be the viscus, which first presents a definite conformation. It is at first straight, and afterwards it curves forwards, and is embraced by wh- JJ. chord: it thus forms an angle and descends into the abdominal cavity, f !i jS °T j1 Its anteri°r aspect, and apparently continuous with the short and imper- iectiy developed chord. This turn of the intestinal canal, and its retention in the chord, seems to form the umbilical vesicle, and the subsequent strangulation of the intestine by the constriction and elongation of the chord first gives rise to an isolated appearance of this vesicle, subsequently, to its entire disappearance, and lastly, to the separation of the intes- tines ; the vermiform appendix remaining as a type of the original conformation. M ^°Ut SSme time that the intestinal tube curves into the umbilical chord, the urinary Diadcler seems to be also prolonged into the chord, between the chorion and amnion, forming tne allantois and urachus, the former of which disappears as the foetus is developed and the Chord lengthened, the urachus only remaining at the time of birth, showing the nature and type of the original conformation, and the communication formerly existing between the allantois and bladder. . We *lave al.feady said that all the phases, through which the human embryo passes until its conformation is perfected, correspond with the different stages of permanent organiza- tion which characterize the animal scale. Since these observations were made, we perceive that a similar opinion has been lately entertained by J. F. Meckel, and adopted by M. Be- clard, in his recent and excellent work on General Anatomy. Many proofs may be addu- ced in support of this doctrine : so evident indeed is the analogy that a very close parallel may be drawn between the stages of development through whicii the human foetus passes, and the degrees of animal organization. The human embryo is at first an imperfectly formed vesicle; such are the polypi and others of the Zoophytce. At a remoter period it consists of a small vermiform body without a distinct head, or limbs ; such are the Echinodermata, and the Annelides. At a still later period its limbs are equally developed, and its tail is prominent: such are the Quadruped's. As respects the nervous system, the ganglial or vital nerves first appear with their gan- glions : such is the nervous structure of the invertebrated animals. As the embryo advan- ces, the ganglial nerves give rise to two thin strips of medullary matter in the situation of the spinal canal, these increase, coalesce, form the spinal and cervical marrow, (medulla oblongata) and the tubercles of the latter, whence are produced the brain and cerebellum : we observe the same conformation in reptiles, fishes, &c. The human fcetus is remarkable for the rapidity with which it runs through the early grades of the scale of organization. It is this circumstance that renders the early changes vvhich it experiences so difficult to be recognised. II. Of the circulation of the Fozlus.—There are abundant facts to prove that the circu- lation of the fcetus is independent of that of the mother; that the blood of the former flows from the umbilical arteries into the vein ofthe same name, and not from the uterine arteries into that vein* that the foetal blood is fabricated by tbe foetus itself, from the juices fur- nished by the mother to the placenta, and, consequently, that the foetus does not receive one drop ready formed from this organ by the umbilical vein*. In proof of the correctness of this opinion, we may refer to the experiments performed by M. Gaspard, (Journ. de Physiol. Experiment, No. 3,) in order to ascertain this point, and to the formation of blood in the impregnated egg on the second or third day after incuba- tion, and to the fact that, in the numerous tribe of oviparous animals, the foetuses are insu- lated from the mother, and are the real manufacturers of their own blood. At an early period of foetal life the ganglial ramifications and centres are first formed. and afterwards the ramifications and centres of the voluntary nerves. In the more perfect animals, even that part of the nervous system which is general throughout the animal crea- tion, and which the lowest orders of it possess, is the first formed, and that part which is destined to perform the highest functions, and which the perfect animals only possess, is produced the last. * D. F. Lavagna concludes that the menstrual blood differs from common blood, only in containing no fibrin; also, that the blood in the umbilical arteries of the funis contains scarcely any fibrin, whilst that in the umbilical vein forms a tenacious jelly ; hence, he in- fers, that the blood acquires fibrin in the circulation in the placenta, which it parts with in irs passage through the fcetus.—Annali di Medicina di Milano, No. 17. L 82 APPENDIX. Other peculiarities of the frxtus are adduced in the subjoined notes:— Of the Development of the Heart and Lungs.—J. F. Meckel has concluded from his ob- servations, 1st, The heart is relatively larger the younger the embryo. For in his observa- tions he found, at the first period, at which the heart could be distinguished, that it filled Completely the thoracic cavity. 2d, The heart is more symmetrical with respect to situation and form, soon after its for- mation, than at a more remote period. 3d, The form of the heart undeigoes various changes during the growth ef the foetus. A. The proportion between the arterial and venous portions of the heart is not always the same. The auricles surpass the ventricles in capacity, in proportion as the embryo is younger. B. The relative volume of the two sides of the heart is not always the same at all pe- riods. In the adult the right side always more or less exceeds the left; but in very young embryos the two ventricles are equally capacious, but that of the right side increases ra- pidly. The right auricle surpasses the left in size in the foetus, and it is only by degrees that the left becomes equal to the right. C. The right ventricle is unquestionably smaller than the left at first. D. The thickness of the parietes of the heart is much more considerable at first. The two halves of the heart equally present this difference, but the right ventricle always ap- pears a little thicker than the left. This is, however less, the younger the foetus. E. The two ventricles communicate with each other at an early period, and, according to all appearances, continue to do so until the end of the second month, by means of an opening in their interior aspects, situated at their base, and immediately beneath the origin of the great vessels. F. The interior disposition of the auricles with respect to their communication, either with one another, or with the venous trunks, undergoes considerable changes. These turn chiefly on the form and size of the oval hole, the situation of the orifice of the vena cava inferior, the situation, the form, the extent and relations of the valve of Eustachius and that of the foramen ovale. Here M. Meckel's researches confirm those of Sebatier and Wolff. 4th, The disposition of the aorta and of the pulmonary artery offers several considerable Changes, in succession, of which the following are the chief. A. At first there exists only an aorta. A pulmonary artery is formed at a remoter pe- riod. It is not until after the seventh week that the pulmonary artery begins to appear, and then it is only a second aortic trunk, as yet without branches—a right aorta, proceeding in the direction of the lungs, which are very distant, and extremely small. The disposition of the large arteries at this period (seventh week) nearly resembles what it continues to be, in reptiles, during tbe whole life of the animal. B. It is in the course of the eighth week only, in which the branches of tbe pulmonary artery can be discovered. ' They are then much smaller, when compared to the trunk of the artery and to the arterial canal, the younger the embryo. At five months they become equal to this canal, and afterwards they surpass it, frequently so far that when the foetus has completed the ninth month, each principal branch of the pulmonary artery is as large as it is, or even larger. The venous canal presents similar appearances. It is during the first periods of the ex- istence of the foetus when it offers, proportionally, the greatest amplitude. All the obser- vations which M. Meckel has made, confirm this law, which is the more important as it throws considerable light on the functions of this canal. Indeed, it is probable that this conformation is only the remains of a disposition vvhich may be seen at the epoch when the liver has not come into existence, when the vena porta and the vena cava inferior form but one trunk, as the pulmonary artery forms, at the early stage of its existence, only one with the aorta. This conjecture respecting the origin of the venous canal is confirmed by the or- ganization of the acephalous class of animals, in whicii the veins of the intestinal canal, and consequently the vena porta, also, open immediately into the vena cava inferior. 5th, The lungs are not formed until a more advanced period. In man, manifest traces of them cannot be seen before the sixth or seventh week. Then they advance beneath the heart, at the two sides of the inferior extremity of the pectoral portion ofthe aorta. At the period of their appearance, and even for some time afterwards, they are so small, in proportion to the heart and the other organs, that it requires the great- est attention in following their progressive development, to be convinced that they are in reality the rudiments ofthe respiratory organ. At first the lungs closely approach one another : they are flat and ofa whitish colour. Their surface is perfectly united ; bat, on their external border, may be observed, at an early period, indentations, which are the traces ofthe approaching separation ofthe lobe^, notwithstanding that these lobes are not yet in existence. At a farther advanced period the lobes appear to be composed of lobules. These latter are at first larger and much less numerous, rin proportion, than at subsetnient periods, but they separate by degrees int~> OF THE DEVELOPMEiNT OF THE FCETL'S. &3 Of the Varieties of the Human Species. Note L. L. Buffon, Blumenbach, Prichard, Gavoty and Touluzan, Cuvier, and others, have propos- ed classifications of the varieties ofthe human species: of these we prefer that of Cuvier. The following is an outline of it:— 1st, The fair, or Caucasian variety ; 2d, the yellow, or Mongolian ; 3d, the negro, or Ethiopian. others much smaller. At the period when they are first observed, they are as much more apparent, and as much less intimately united, by cellular tissue, as the embryo itself is 3'ounger. 6th, As the lungs become developed, in the reptiles and leeches, in the form of an empty sac, it is natural to suppose that their production, in animals ofa higher order, takes place according to the same manner and law. M. Meckel endeavoured to ascertain whether or no this was actually the case. But, under whatever aspect he viewed the lungs at the ear- ly stages of their formation, even with the assistance of the microscope, he always found the slices which were removed from them completely solid ; if they are really so during this epoch, it would seem as if they had some analogy of structure with the Branchiae of fishes. 7th, The branches ofthe pulmonary artery, vvhich proceed from the right or pulmonary aorta, are at first certainly wanting. It must therefore be admitted that at this epoch, their places are supplied by the bronchial arteries, especially by the inferior, since the lungs are at first placed low in the inferior part ofthe chest. Moreover, this depending situation ofthe respiratory organ, at the commencement of its development, is remarkable under two points of view : A. Since, amongst reptiles, and many of the mammiferi, the lungs are placed much lower than in man, and below the heart, in every respect like the fishes, the swimming bladder is placed below this organ. B. Because it seems that the lungs and the thymus gland correspond in their functions, the development ofthe one being in direct proportion to the decrease ofthe other. I. F. Meckel concludes from the researches of whicii we have given an abridged outline, that the general results confirm it to be a grand law of the animal economy, that the em- bryo, from the instant of its formation until that of its maturity, rises successively through many inferior grades of organization, and that the principal monstrosities of the heart and large blood-vessels depend upon these organs being arrested at some one grade or degree of organization, instead of following the progress of the others towards perfection. Respiration of the Fcetus.—The thymus gland appears to assist the placenta, the liver, and the secretion of fat, in the respiration of the foetus, or rather in purifying the blood of the foetus. It seems to form a nidus for the reception of those elements of the blood—car- bon and hydrogen, which are secreted in a state approaching to fat, and vvhich if too abun- dant in this fluid, would endanger the existence of the foetus. These materials on the com- mencement of active respiration are again absorbed, to be discharged from the economy by the lungs, liver, or intestinal canal. The thymus gland in the human foetus, in the ninth month,°generally weighs from 160 to 180 grains ; at 28 years of age only 90 grains. In the calf it weighs 16 ounces, in the cow 9 ounces. "Etenim placanta, hepar, adipis aucla secretio respiration!, sed aliud alio modo, inservi- unt. Quas naturae institutio, ut in foetu organon alterum alterius vices obtinere possit, pul- cherrima et prsestantissima ; quo fit, ut foetus vita nondum autonomica, a noxiis quibus- cunque momentis, qua? vim in ipsum habere possunt, tueatur conserveturque, donee ex asy- lo matris in lucem aeremque editus vim innatam exerceat. * * * Vena umbilicalis illo principio (oxygenio) gravida partim in hepar, partim in venam ca- vam inferiorem sanguinem reducit a partibus phlogisticis liberatuim Itaque vena cava in- ferior postquam sanguinis partem ex vena umbilicali et venis hepaticis excepit, praeter san- guinem oxydatum, venosumquoque sanguinem ex corporis partibus reducem continet, cujus tamen pars satis magna, sanguis lienalis ac meseraicus, in hepate jam carbone relicto, mera existit. Quoniam vero vena cava inferior prima vitas foetalis parte magis in sinistrum quam in dex'trum cordis atrium aperitur, sanguis autem venae cava? superioris, nil minus quam oxyeenium ducens ex dextro cordis atrio per arteriam pulmonalem, nine per ductum Botal- licuni demum, postquam jam arterise supenorum partium ex aorta excreverunt, in ipsam nerfunditur ;—sequitur caput atque extremitates superiores sanguinem magis oxydatum, seu si mavis, dephlogisticatum, in atrio sinistro ventriculoque congestum, accipere;—aor- tamvero descendentem sanguinem ex vena cava superiori phlogisticum nee oxydatum in r>odomen atque extremitates inferinves perducere, quo fit, ut superiores corporis partes, ex- 84 APPENDIX. 1st, Caucasian. Characters. The beautiful form of the head, the variable snades of complexion, and colour ofthe hair. Principal Branches. 1, The Syrian, whence have proceeded the Assyrians, the Chal- deans, the Arabs, Phoenicians, Jews, the Abyssinians, Arabian colonies, and ancient Egyp- tians. 2, The Indian, German, or Pelasgic branch was early subdivided into the Sanscrit, the Pelasgi, the Teutonic, and Sclavonian. 3, The Scythian, or Tartarian^branch. 2d, Mongolian. Characters. Prominent cheek-bones; flat visage ; narrow and oblique eyes ; straight and black hair ; scanty beard, and olive complexion. Its civilization has al- ways remained stationary. 3d, The Negro. Characters. Black complexion; woolly hair; compressed cranium, and flatfish nose. " It is very difficult to refer the Malays, or the Papuas, to any one of the three great va- rieties of mankind already described. It is a question, however, whether the former people can be accurately distinguished from their neighbours on either side : the Caucasian Hin- doos on the one, and the Mongolian Chinese on the other. (i The Americans themselves have not yet been properly referred to either of the other races, nor have they characters precise and constant enough to constitute a fourth variety. Their copper-coloured complexion is not sufficient. The black lank hair, and scanty beard, would seem to approximate them to the Mongoles, if their well defined features, and pro- minent noses, did not oppose such a classification ; their languages are likewise as innume- rable as their tribes, and no mutual analogy has yet been ascertained.between them, nor any affinity with the dialects ofthe ancient world." (Griffith's Trans, of the RegneAni- mate.) We are inclined to infer that America was peopled by the Mongoles from Asia ; and that, subsequently, it had been visited by Phoenician navigators: the greater part of whom set- tled in it, particularly in Mexico ; and that the imperfect navigation of that era prevented many of the adventurers, if not all of them, from returning. Ofthe Mortality of Females at the Change of Life. From the bills of mortality of both sexes, collected in Provence, Switzerland, Paris, Ber- lin, Sweden, and Petersburgh, it would seem, 1st, that from 30 to 70, no other increase takes place in the mortality of females, than what naturally results from the progress of age ; 2d, that at all periods of the life of man, from 30 to 70, a greater mortality occurs than in wo- men, but especially from 40 to 50. (M. Benoision de Chateauneuf on the Mortality of Fe- nmlesfrom 40 to 50 Years of Age. Paris, 1822.) Ofthe Signs of Death. Note M. M. This subject has been so fully and ably discussed in the very excellent works of Dr. Gor- don Smith, and of Dr. Paris and Mr. Foublanque, on Medical Jurisprudence, that we pre- fer recommending the reader to consult them on this subject, to entering imperfectly upon the topic at this place, our limits not allowing the satisfactory discussion of it. ceptis pulmonibus, qui sanguinem ex vena cava superiori venientem venosum accipiunt, primo graviditatis tempore magis vigeant polleantque. p. 215. " Placenta oxygenium afferente, hepate carbonium submovente, quae functiones in adulto in uno pulmone conjunctae sunt."p.216. (JoannisMueller de Respiratione Fcetus Commen- tatio Physiologica, in Academia Borussica Rhenana Pramio Ornata. Lipsic. 1823. p. 159. M. Geoffory-Saint-Hillaire, proceeding on the principle, that there cannot be organiza- tion without the combination of a nutritious fluid, nor yet assimilation without oxygenation or previous respiration, endeavours to show >—1st, That a respirable gas is present in the amniotic fluid, as shewn by the experiments of MM. Chevreuil and Lassaigne ; 2d, That the foetus, by means of its pores, as by so many tracheas, in the same manner as aquatic insects, is enabled to consume the air contained in the surrounding fluid, owing to the air being thus brought in contact with the venous blood which fills the capillaries ofthe skin ; 3d, That the contraction of the womb and of the abdominal muscles keeps up a certain de- gree of pressure, which is as requisite to the perfect performance of this process as to tbr. ordinary act of respiration.—Rev. Mid. Dec. 1G23. 8iJ CHAPTER II. Chemical constitution of the Solids and Fluids of the Human Body. I. Simple substances entering into the Constitution of the different Animal Principles or Constituents of the Human Body. The following simple substances are variously combined, in order to produce the consli- iv.tnt parts of the body : 1. Azote, 6. Lime, 11. Magnesia, (Magnesium,) 2. Carbon, 7. Sulphur, 12. Silica, 3. Hydrogen, 8. Soda, (Sodium,) 13. Iron, 4. Oxygen, 9. Potass, (Potassium,) 14. Manganese, 5. Phosphorus, 10. Muriatic Acid. Of these, magnesia and silica may be considered as foreign bodies; they being seldom found, and in exceeding small quantities. The principal elementary ingredients are the first six: animal substances may be considered as chiefly composed of them. The first four con- stitute almost entirely the soft parts; and the other two form the basis of the hard parts. II. Animal Constituents or Principles. I. Gelatin consists of Carbon, 47.88 ; Hydrogen, 27.20; Oxygen, 27.20 ; .Azote, 17.00; or of 15, 14, 6, 2, atoms respectively. Contained in skin, bone, tendons, &c. Test, Tannim. II. Albumen,—Corrosive sublimate detects -joVcT Part 'be weight ofthe water contain- ed in it. Comp.—Carbon, 52.883; oxygen, 23.872; hydrogen, 7 540; azote, 15.705, in 100 parts. Dr. Prout found it to consist of 15 atoms of carbon, 6 of oxygen, 14 hydrogen, 2 azote, according to the analysis quoted. III. Fibrine varies in its species in the different classes of animals. Comp.—Carbon, 53.360; oxygen, 19.685; hydrogen, 7.021; azote, 19.934. Consists of carb. 18 atoms, oxyg. 5, hydrag. 14, azote 3. IV. Colouring Matter of the Blood.—Berzelius found it possessed of nearly the same properties as fibrin. It is soluble in water at a low temperature; and in all the acids, except the muriatic, contains iron. (Berzelius, vol. 3. Med. Chirurg. Trans.) V. Urea, or Nephrin, soluble in water and in alcohol. Precipitated in pearly crystals by nitric acid and oxalic acid. Dissolved by a solution of potass or soda. Oxygen, . . . 39.5 \ 2 atoms Hydrogen,. . 0.25 . . . 6.66 Azote, . . . 32.5 f 1---~- Carbon, . . 0.75 . . . 20.00 Carbon,. . .14.7(1-----Oxygen, . .1.00. . .26.66 Hydrogen, . . 13.3) 1-----Azote, . . . 1.75 . . . 46.66 100. 3.75 100. (Dr. Prout.) Gelatin is insoluble in cold water, albumen is insoluble in hot, and fibrine is insoluble in both cold and hot. The constituents of these three bodies, and of nephrin, according to the best analysis of hem hitherto made, are as follow: Carbon. Oxygen. Hydrogen. Azote. Gelatin, atoms 15 .... 6* .... 14 .... 2 Albumen,-----17 .... 6 .... 13 .... 2 Fibrine, —---18 . . . . 5 . . . . 14 . . . .3 Nephrin, ----- 1....1....2....1 The colouring matter of the blood approaches albumen in many of its properties; but it seems entirely destitute of azote. VI. Mucus.—Insoluble in water, transparent when evaporated to dryness,and, like gum, soluble in the acids. Not soluble in alcohol or ether—does not coagulate by heat—nor is precipitated by corrosive sublimate, or by galls. Is precipitated by the acetates of lead, and by nit. argenti. Found in the epidermis, in nails, feathers, &c. Bostock, in Nicholson'; JoUTTl* **■*■• 251 »J VII. Osmazome is, probably, only an altered state of fibrine. Soluble in water and al- cohol—does not gelatinize. Precipitated by nit. argenti, nit. bydrarg. and acet. and nit. of eVlII. Pi«Romel—found principally in bile; resembles inspissated bile in its appearance soluble in water and in alcohol : uti '■> atoms Carbon, . . 3.75 . . . 64.5o 1-----Hydrogen, . 1.25. . . 1.82 3-----Oxygen, . . 3.000 . . . 43.65 (Dr. Thomson, An. Ph. 14. 69.) IX. Sugar oe Milk, according to.Berzelius, consists of oxygen, 53.359; carbon, 39.471 hydrogen, 7.167. (Annals of Philos. 5. 266.) Dr. Thomson gives the table of the atomic analysis as follows: 4 atoms Oxygen, . . 4 ... 48.4 5-----Carbon, . . 3.75 . . . 45.4 4-----Hydrogen, . . 0.50 ... 6.2 8.25 100.0 X. OlL3 are fixed.—Fat—Cholesterine.—The former is composed of oxygen, hydrogen, and carbon. The latter, according to Saussure, consists of 84.068 of carbon ; 12.672 of hy- drogen ; and 3.914 of oxygen; and differs little from the other fixed animal oils, excepting that it contains more carbon and less oxygen than they. XI. Acids.—The acids found constituting and ready formed in animal bodies are the fol- lowing : 1. Phosphoric, 2. Sulphuric, 3. Muriatic, 4. Carbonic, 5. Benzoic, 6. Uric, *7. Rosacic, 8. Amniotic, 9. Oxalic, 10. Formic, 11. Acetic, 12. Malic, 13. Lactic, 14. Silica. It maybe remarked that the whole ofthe soft parts of animals consist chiefly of albumen, fibrine, and oils; and the hard parts of phosphate of lime. The other animal principles are only in small quantities, and in particular textures. The oils seldom enter into the struc- ture of the organs of animals, they serve rather to lubricate the different parts, and to fill up interstices. III. Individual Textures and Fluids of the Human Body (formed of two or more of the foregoing Constituents.) The Constituents of the Bones and Teeth of some of the Mammalia, according t6 the Analyses cf Berzelius and other Chemists. Substances analyzed. Cartilage, with the water of crystalli-zation ofthe earthy salts and gelatine. — 0 £ 3 « S 0 .3 WJ S3 0 a a a 0 c U a 0 a a. 0 a c e" a 73 0 "S CD « 3 E O M » a J3 O. O — I Pi Human bones recently dried, . . 33.3 1.2 11.3 51.4 2.0 1.16 j Bullock's bones recently dried, . 33.3 2.45 3.85 55.45 2.9 2.05 Osseous parts of human teeth, . 28.0 1.4 5.3 61.95 2.1 1.25 Osseous parts of bullock's teeth, 31.0 2.4 1.38 57.46 5.69 2.07 The enamel of human teeth, . . •2.0 — 8.0 85.3 3.2 1.5 The enamel of bullock's teeth, 3.56 1.4 7.1 810 4.2 3.0 | The compact and cellular substances of human bones are, according to Berzelius, of the same composition. Forms the lateritious sediment in fevers, &■•- 87 Substances submitted to ana-lysis. bO U ho I "3 « la a. o x: Ph oi .§ o CB !§■ a o "s "E. o ja Pi .9 o The human milk differs from cow's milk. 1st, in containing a much smaller quantity ot curd. 2d, Its oil is so intimately combined with its curd, that it does not yield butter. 3d, It contains rather more sugar of milk. Parmentier and Deyeux ascertained, that the quantity of curd in woman's milk increases in proportion to the time after delivery. (Journ. de Phys. 38. 422.) None of the methods by which cow's milk is coagulated, succeed in producing the coagu- lation of the human milk. (Clarke Irish Trans, vol. ii. p. 175.) Bile (human). The following is the analysis of bile, according to Berzelius :—water, 908.4; picromel, 80.0; albumen, 3.0: soda, 4.1; phosphate of lime, 0.1; common salt, 3.4 ; phosphate of soda, with some lime, 1.0.—1000. Biliary calculi are formed either entirely of cholesterine; or they also contain a yellow i concrete mucous, picromel, and rarely phosphate of lime or carbonate of lime. These lat- ter ingredients frequently almost entirely replace the cholesterine. (Gren. Orfila.) Cerumen of the Ear. Vauquelin considers it composed of the following substances. 1st, Albumen. 2/1, An inspissated oil. 3d, A colouring matter. 4th, Soda. 5th, Phos- phate of lime. (Fourcroy, ix. 373.) Tears. According to the analysis of Fourcroy and Vauquelin (Journ. de Phys. vol. xxxix. p. 236,) they are composed of the following ingredients :—1st, Water. 2d, Mucus. 3d, Muriate of soda. 4th, Soda. 5th, Phosphate of lime. 6th, Phosphate of soda. " The saline parts amount only to about 0.01 ofthe whole. The mucus contained in the tears has the property of absorbing oxygen gradually from the atmosphere, and of becoming thick and viscid, and of a yellow colour. This property of acquiring new qualities from the absorption of oxygen, explains the changes which take place in tears in some diseases of the eye." Sweat contains salivary mucus; osmazome ; lactic acid ; lactate of soda ; and hydro- chlorate of potass and soda. (Berzelius.) Thenard found it composed of an animal substance analagous to gelatine ; acetic acid ; hydrochlorate of soda; phosphate of lime ; phosphate of iron, and water. Urine. The human urine, in a state of health, has a specific gravity of 1.02. It con- tains urea, 3.01; a matter analagous to saliva, osmazome, lactic acid, lactate of ammonia, and a little urea, 1.724; mucus, 0.032; uric acid, 0.10; phosphate of ammonia, 0.150; sulphate of potassa, 0.371; sulphate of soda, 0.316 ; hydrochlorate of soda, 0.445 i phos- phate of soda, 0.294; phosphate of lime, with a little phosphate of magnesia, and a trace of the fluate of calcium, 0.1 ; silica, 0.003; water, 93.3. (Berzelius.) Besides the constituents of healthy urine, as determined by Berzelius, the following have been occasionally detected in it: albumen ; resin with ulmine ; acetic acid ; benzoic acid (in infants) ; carbonic acid ; sulphur ; chloruret of potassium ; and iron. Urine which is excreted in the morning, generally contains more of the saline and solid ingredients. Uric acid abounds most in the urine of individuals who live on animal diet; Urine absorbs oxygen from the atmosphere, and passes into a state of putrid fermentation. This is more or less rapid according to the elevation of the temperature; and the quantity of mucus and albumen present in the urine is considerable. The urine in diabttes mellitus has a specific gravity of from 1.026 to 1.05. It generally contains no urea—sometimes a minute quantity of it. It is remarkable for its quantity, and for the saccharine matter which it holds in solution ; the saline ingredients are gene- rally present, but in smaller proportions. As the quantity of sugar diminishes, that of al- bumen increases, and this latter is replaced, as the disease disappears, by urea and uric acid. The chief difference between this urine and that secreted in diabetes insipidus, consists in the absence of saccharine matter from the latter. Icteric urine is frequently yellow and bitter, and contains the principles of bile. In acute dropsy the urine is generally charged with albumen. When dropsy results from disease of the liver, the urine is brown, and deposits a brown sediment. Semen, when ejected, is the product of two different glands, the one fluid and milky, supposed to be secreted by the prostate gland ; the other a thick mucilaginous substance, considered to be secreted by the testes, and in which numerous white shining filaments may be discovered: it has a slightly disagreeable odour, an acrid irritating taste, and is of a greater specific gravity than water. As this liquid cools, the mucilaginous parts become transparent, and acquire a greater consistency ; but in about twenty minutes after its emis- sion, the whole becomes perfectly liquid. This change supervenes without any absorption of moisture from the air, and without its action, taking place equally in close vessels. Semen is insoluble in water before this spon- taneous liquefaction, but readily so afterwards. (Vauquelin, Ann. de Chim. ix. 70.) When semen is kept in a moist air, at about 77*, it acquires a yellow colour, like the yolk of an egg; it exhales the odour of putrid fish, and its surface is covered by the byssus septica. According to Vauquelin, semen is composed of water, 90 ; mucilage, 6; phosphate of lime, ?• soda, 1.= 10O. 93 The ova from the ovaria of the human subject: gelatine, albumen, phosphate, with an alkaline base in excess. (John's Chemical Writings, vi. 158.) Amniotic fluid, which surrounds the fcetus, in the human species is of a slightly milky colour, owing to a curdy matter suspended in it, of a weak pleasant odour, and saltish taste; specific gravity 1.005; is composed of about water, 93.8; albumen, muriate of soda, 60 ■•'• V-°SpilateN of lime' lime> 12 = 100°- (Vauquelin and Buniva, Ann. de Chim. xxxm. 270. 274.) A curdy-like matter is deposited on the surface of the foetus, evidently Jrom the liquor of the amnios. Vauquelin and Buniva have shewn that it is different from any thing contained in this fluid ; that it has in its chemical relations a great resemblance to lat. They conjecture that it is formed from the albumen of this liquid, which has under- gone some unknown changes. It appears to be of service in preserving the skin ofthe fcetus lrom being acted on by the liquor of the amnios, and to facilitate its passage in parturition. Pus. Its taste is insipid, and it has no smell when cold. Before the microscope it exhi- bits the appearance of white globules swimming in a transparent fluid, specific gravity from \vcf\ t0r1,033, When ir)cinerated, the ashes give traces of iron. (Gren's Handbuck, ii. 4<56.) It produces no change on vegetable blues. Alcohol thickens pus, but does not dis- solve it; nor does it unite with oils. Soluble in sulphuric acid, but separated on the addi- tion of water. The same is the case with nitric acid. Muriatic acid also dissolves it when heated, and it is again separated by water. The fixed alkaline leys form with it a whitish ropy fluid, which is decomposed by water, the pus being precipitated. Corrosive sublimate, nitrate of mercury, and nitrate of silver, give a whitish precipitate from its solution, indicating an analogy with albumen. Expectorated matter yields traces of sulphur, and perhaps also of phosphorus ; and it con- tains the following saline substances:—1st, Muriate of soda, varying from 1£ to 2£ in the 1000 of expectorated matter. 2d, Phosphate of lime, half a part in the 1000. 3d, Ammo- nia united probably to phosphoric acid. 4th, A phosphate probably of magnesia. 5th, Car- bonate of lime. 6th, A sulphate. 7th, Vitrifiable matter, ;probably silica. 8th, Oxide of iron. The whole of these last six substances scarcely amount to one part in the 1000 of expectorated matter. The proportion of saline matter of albumen present in expectorated matter varies much in different circumstances. The thicker it is, in general the smaller is the quantity of the saline matter : whereas, when very thin, it is often impregnated with salts, especially with the muriate of soda to a great degree, and tastes distinctly salt and hot. Liquor of the pericardium. Dr. Bostock (Nicholson's Journ. xiv. 147.) considers it to be composed of—water, 92.0; albumen, 5.5; mucus, 20; muriate of soda, 0.5—100.0. Liquor vf dropsy. Dr. Bostock found the liquid formed in "spina bifida," to be composed as follows:—water, 97.8 ; muriate of soda, 1.0; albumen, 0.5; mucus, 0.5. gelatin, 0.2; lime, a trace. (Nichol. Journ. xiv. 145.) The same kind of fluid obtained from the head of a child often years was examined by Dr. Prout. It faintly reddened litmus paper. Its constituents were as follow :—water, 987. 18 ; albumen, precipitated by nitric acid and heat, 1.66 ; substances soluble in alcohol (fatty adipocirous matter, lactate of soda,) 1.65 ; substances soluble in water—9.51. viz. muriates of potash and soda, 6.80; sulphate of soda, and some animal matter not coagulated by beat, 2.71—1000.00. (Ann. of Phil. xvi. 151.) Liquor of blisters. The analysis of Macqueron (Ann. deChim. xiv. 225.) gives it nearly the same constituents as the serum of the blood ; from 200 parts he obtained—albumen, 36 ; muriate of soda, 4; carbonate of soda, 2; phosphate of lime, 2; water, 156—200. Human FjECES. Their colour seems to depend »ipon the bile mixed with the food in the digestive canal; when too light it is supposed to denote a deficiency of bile; when too dark, there is supposed to be a redundancy of that secretion. The following table shews the an- alysis of Berzelius. (Gehlin's Journ. vi. 536.) Water......73.3, Vegetable and animal remains - - 7.0 Bile - - • - - - - 0.9 Albumen - - - - - - 0.91 * The Salts, their relative proportions. Peculiar and extractive matter sup-) I Carbonate of soda 3J posed to be formed from picro-> 2.71 Muriate of soda ... 4 rnel. J } Sulphate of soda - 2 Salts* - ----- 1.21 Amm. phosphate of magnesia, - - 2 Slimy matter, consisting of picromel, 1 I Phosphate of lime. - 4 peculiar animal matter, and inso- > 14.0 * luble residue ) 100.0' Gases Existing in the intestinal canal. These may be ascribed to three sources : —1st, from the common air swallowed with the food; 2d, from the decomposition of the intestinal contents ; and 3d, from the occasional secretion of gas from the mucus surface of t?:e tub?. 94 The gases from the first source are found chiefly in the superior portions of the can at , those from the second source in the lower part, and those from the third, are by no means iimited in their situation. It is reasonable to suppose that a large proportion of the azote and carbonic acid is derived from this last source. From the experiments of Magendie and Chevreul, who examined very soon after deatii the gaseous contents ofthe stomach and intestines of four criminals executed at Paris, the following appear to be the proportions and the relative quantities in the different portions ofthe canal. 1. Gases in the Stomach. Oxygen* - - - Carbonic acid - - - Hydrogen - Azote - ' 11.00 14.00 3.55 71.45 100.00 2. Gases in the small Inteslines.% Oxvgen 00.00 - - 00.00 - - 00.0 Carbonic acid 24.39 - - 40.00 - • 25.0 Hydrogen 55.53 - - 51.15 - - 8.4 Azote 20.08 - - 8.85 - - 66.6 100.00 100.00 100.0 Carbonic acid Hydrogen and carburretted hydrogen Azote ------ 4. Gases in the Ccecum. Carbonic acid - l2.5 Hydrogen - - 7.5 Carburetted hydrogen - - - 12.5 Azote......67.5 3. Gases in the large Intestines. 43.50 - - - 70.0 54.7 - - - 11.6 51.03 = 100.00 18.4 = 100.0 5. Gases in the Rectum. Carbonic acid - - - - Carburetted hydrogen .- Azote - 100.0 42.86 11.18 45.96 100.00 (Ann. de Chim. et Phys. ii. 492.) ■ The oxygen seems to be absorbed by the blood before it reaches the small intestines t Results in the different individuals. >'JNI*.