m i*£ itVJI-.V.'.i^i —,:.£*AK ',r..-»'U.v« ££a3SgS£ UNITED STATES OF AMERICA ^ . , FOUNDED 1836 WASHINGTON, D. C. SPO 16—67244-1 HUMAN PHYSIOLOGY. BY ROBLEY DUNGLISON, M. D., PROFESSOR OF THE INSTITUTES OF MEDICINE IN JEFFERSON MEDICAL COLLEGE, PHILADELPHIA, VICE-PRESIDENT OF THE SYDENHAM SOCIETY OF LONDON | SECRETARY TO THE AMERICAN PHILOSOPHICAL SOCIETY, ETC. ETC. " Vastissimi studii primas quasi lineas circumscripsi."—Haller. WITH NEARLY FIVE HUNDRED ILLUSTRATIONS. SEVENTH EDITION, THOROUGHLY REVISED, AND EXTENSIVELY MODIFIED AND ENLARGED. IN TWO VOLUMES. VOL. II. PHILADELPHIA: LEA AND BLANCHARD. 1850. :D9l£ri 1950 v. c2 Entered according to the Act of Congress, in the year 1841, By RoBLET DUNGLISON, In the Clerk's OfBce of the District Court for the Eastern District of Pennsylvania. PHILADELPHIA : T. K. AND P. G. COLLINS, PRINTERS. CONTENTS OP VOL. II. BOOK II. Chap. III. Respiration ....... 1. Anatomy of the Respiratory Organs 2. Atmospheric Air ..... 3. Physiology of Respiration .... a. Mechanical Phenomena of Respiration 1. Inspiration ..... 2. Expiration ...... 3. Respiratory Phenomena concerned in certain Functions 4. Respiratory Phenomena connected with Expression b. Chemical Phenomena of Respiration c. Cutaneous Respiration, &c. .... d. Effects of Section of the Cerebral Nerves on Respiration e. Respiration of Animals .... Chap. IV. Circulation ...... 1. Anatomy of the Circulatory Organs a. Heart ...... 6. Arteries ...... c. Intermediate Peripheral or Capillary System d. Veins ....... 2. Blood 3. Physiology of the Circulation a. Circulation in the Heart b. Circulation in the Arteries c. Circulation through the Capillaries d. Circulation in the Veins e. Forces that Propel the Blood /. Accelerating and Retarding Forces g. The Pulse . h. Uses of the Circulation i. Transfusion and Infusion 4. Circulatory apparatus in animals Chap. V. Nutrition . . VI. Calorification .... VII. Secretion .... 1. Anatomy of the Secretory Apparatus 2. Physiology of Secretion IV CONTENTS. I. Exhalations .... a. Internal Exhalations 1. Exhalation of the Areolar Membrane 2. Exhalation of the Serous Membranes 3. Exhalation of the Synovial Membrane 4. Exhalation of the Adipous Membrane a. Fat . b. Marrow 5. Exhalation of the Pigment Membrane 6. Exhalation of Areolar Capsules . 7. Vascular Exhalation'. b. External Exhalations 1. Exhalation of Mucous Membranes general and pulmonary 2. Menstrual Exhalation 3. Gaseous Exhalation . II. Follicular Secretions .... 1. Follicular Secretion of Mucous Membranes a. Secretion of Peyerian Glands b. Secretion of the Ovaria 2. Follicular Secretion of the Skin III. Glandular Secretions 1. The Transpiratory Secretion 2. The Lachrymal Secretion 3. The Salivary Secretion 4. The Pancreatic Secretion 5. The Biliary Secretion 6. The Urinary Secretion Connexion between the Stomach and the Kidneys 7. The Spermatic Secretion 8. The Lacteal Secretion Glandiform Ganglions a. The Spleen PAGE 261 262 262 263 265 266 266 272 272 274 274 274 274 277 278 278 278 281 281 281 283 283 296 296 300 302 325 346 349 349 349 349 BOOK III. REPRODUCTIVE FUNCTIONS ' Chap. I. Generation 1. Generative Apparatus . a. Genital Organs of the Male 1. Sperm b. Genital Organs of the Femal 1. Menstruation . c. Sexual Ambiguity 2. Physiology of Generation a. Copulation 6. Fecundation . c. Theories of Generation d. Conception . e. Superfoetation /. Pregnancy . 359 369 . 369 378 !e . . 386 .400 . 414 419 . 420 • • • 424 • .450 470 . 480 * 4S2 CONTENTS. V g. Signs of Pregnancy h. Duration of Pregnancy t. Parturition j. Lactation .... Chap. II. Fatal Existence.—Embryology 1. Anatomy and Histology of the Foetus a. Foetal Developement . b. Foetal Dependencies c. Foetal Peculiarities 2. Physiology of the Foetus a. Animal Functions b. Functions of Nutrition c. Reproduction . PAGE 493 500 504 510 521 521 521 541 555 564 564 565 590 BOOK IV. Chap. I. Ages ..... 1. Infancy ..... a. First period of Infancy 6. Second period of Infancy or first Dentition c. Third period of Infancy 2. Childhood . 3. Adolescence 4. Virility or Manhood 5. Old Age Chap. II. Sleep . 1. Dreams 2.'Waking Dreams . 3. Revery Chap.' III. Correlation of Functions 1. Mechanical Correlations . 2. Functional Correlations .... 3. Sympathy ...... a. Sympathy of Continuity b. Sympathy of Contiguity . c. Remote Sympathies .... d. Imagination . . . . . e. Superstitions connected with Sympathy /. Agents by which Sympathy is accomplished Chap. IV. Individual Differences amongst Mankind 1. Temperaments . . . . . a. Sanguine Temperament b. Bilious or Choleric Temperament . c. Melancholic or Atrabilious Temperament d. Phlegmatic, Lymphatic or Pituitous Temperament e. Nervous Temperament 2. Idiosyncrasy ...... 3. Natural and Acquired Differences a. Natural Differences . . . . Peculiarities of the Female 1* 591 591 591 596 602 602 606 608 610 614 620 627 633 634 635 635 640 640 641 642 643 644 646 648 649 650 651 651 651 652 653 655 655 656 VI CONTENTS. b. Acquired Differences 1. Habit .... 2. Association 3. Imitation 4. Varieties of Mankind 1. Division of the Races a. Caucasian Race b. Ethiopian Race c. Mongolian Race d. American Race e. Malay Race 2. Origin of the Different Races Chap. V. Life . 1. Instinct .... 2. Vital Properties Chap. VI. Death .... 1. Death from Old Age . 2. Accidental Death a. Death beginning in the Heart b. Death beginning in the nervous centres c. Death beginning in the Lungs PAGE 659 659 663 664 665 667 668 670 672 673 674 675 684 689 697 707 708 711 712 712 713 725 LIST OF ILLUSTRATIONS VOL. II. FIG. PAGE 262. Anterior view of thorax, ...... 17 263. Anterior view of the thoracic viscera in situ, as shown by the removal of the anterior parietes of the thorax, .... 19 264. Posterior view of the thoracic viscera, showing their relative positions by the removal of the posterior portion of the parietes of the thorax, 20 265. A shaded diagram, representing the heart and great vessels, injected and in connexion with the lungs: the pericardium is removed, after Quain, ......... 21 266. Arrangement of the capillaries of the air-cells of the human lung, after Carpenter, ........ 22 267. Air-cells from an emphysematous lung, after Leidy, ... 24 268. Transverse section of a portion of the pulmonary parenchyma, after Leidy, ......... 25 269. Longitudinal section of the termination of a bronchus, after Leidy, . 25 270. Outline of a transverse section of the chest, showing the relative posi- tion of the pleurae to the thorax and its contents, ... 27 271. The changes of the thoracic and abdominal walls of the male during respiration, after Hutchinson, ..... 34 272. The respiratory movements in the female, after Hutchinson, . . 34 273. Thoracic and abdominal viscera of the ostrich, ... 75 274. Heart of the dugong, ....... 76 275. Heart placed with its anterior surface upwards, and its apex turned to the right hand of the spectator. The right auricle and right ventricle are both opened, after Quain, ...... 78 276. Semilunar valves closed, . . . . . .78 277. Part of the left ventricle, and commencement of the aorta laid open to show the sigmoid valves, after Quain. . . . .79 278. Heart seen from behind, and having the left auricle and ventricle opened, after Quain, ....... 80 .279. Anterior view of external muscular layer of the heart after removal of its serous coat, &c, ....... 82 280. Posterior view of the same, ...... 82 281. View of the heart in situ, after Pennock, .... 83 282. Circulation in the web of the frog's foot, after Wagner, . . 89 283. Portion of the web of the frog's foot, after Wagner, T 90 284. Circulation in the under surface of the tongue of the frog, after Donn6, 90 285. Capillaries of the web of the frog's foot, after Wagner, . . 92 viii LIST OF ILLUSTRATIONS. FIG. 286 287 288 289 290, 291. 292. 293. 294. 295. 296. 297. 298. 299. 300. 301. 302. 303. 304. 305. 306. 307. 308. 309. 310. 311. 312. 313. 314. 315. 316. 317. 318. 319. 320. 321. 322. Bloodvessels of the lung of a live newt, after "Wagner, Splenic vein with its branches and ramifications, Diagrams showing valves of veins, after Quain, Roots, trunk, and divisions of the vena portae, Portal system, after Wilson, . . . • Red corpuscles of human blood, after Donne1, . Blood corpuscles of rana esculenta, after Wagner, White corpuscles of the blood, after Paget, Developement of human lymph and chyle corpuscles into red corpuscles of blood, after Paget, Aggregation of corpuscles in healthy and in inflamed blood, after T. W. Jones, Hydraulic apparatus, after Venturi, Hsemadynamometer, after Poiseuille, Section of a forcing pump, Small venous branch, from the web of a frog's foot, magnified 350 di- ameters, after Wagner, ..... Large vein of frog's foot, magnified 600 diameters, after "Wagner, Diagram illustrating the circulation, . . Vena contracta, . Do. do. . Circulation in the frog, Circulation in fishes, Interior of the leech, Areolar tissue, after Edwards, . Muscular tissue, after Edwards, Nervous tissue, after Edwards, Cellules of brain, after Dutrochet, Primary organic cell, showing the germinal cell, nucleus, and nucleo lus, after Todd and Bowman, Plan representing the formation of a nucleus, and of a cell on the nu- cleus, according to Schleiden's view, Endogenous cell-growth in cells of a meliceritous tumour, after Goodsir, Tattooed head of a New Zealand chief, Secreting arteries, and nerves of intestines, Plan of a secreting membrane, after Sharpey and Quain, Plan to show augmentation of surface by formation of processes, after Sharpey and Quain, .... Plans of extension of secreting membrane by inversion or recession form of cavities, after Sharpey and Quain, . Portion of areolar tissue inflated and dried, showing the general charac- ter of its larger meshes; magnified twenty diameters, after Todd and Bowman, .... Arrangement of fibres in areolar tissue, magnified 135 diameters, after Carpenter, ..... White fibrous tissue, from ligament, magnified 65 diameters, after Car- penter, ..... Yellow fibrous tissue, from ligamentum nuchae of calf, magnified 65 diameters, after Carpenter, . . 251 262 262 263 263 LIST OF ILLUSTRATIONS. ix FIG. 323. A small cluster of fat-cells, magnified 150 diameters, 324. Bloodvessels of fat vesicles, after Todd and Bowman, 325. Fat vesicles from an emaciated subject, after Todd and Bowman 326. Sebaceous or oil glands and ceruminous glands, after Wagner, 327. Cutaneous follicles or glands of the axilla, magnified one-third, after Horner, ........ 328. Entozoa from the sebaceous follicles, after Todd and Bowman, 329. Vertical section of the sole, after Todd and Bowman, . 330. Lobules of the parotid gland, in the embryo of the sheep, in a more advanced condition, after Miiller, ..... 331. Distribution of capillaries around the follicles of parotid gland, after Berres, . . . 332. Figure, altered from Tiedemann, in which the liver and stomach are turned up to show the duodenum, the pancreas, and the spleen, after Quain, ........ 333. Liver in situ, together with the parts adjoining, in a new-born infant, 334. Inferior or concave surface of liver, showing its subdivisions into lobes, ........ 335. Lobules of liver, after Kiernan, .... 336. Connexion of lobules of liver with hepatic vein, after Kiernan, 337. Transverse section of lobules of the liver, after Kiernan, 338. Horizontal section of three superficial lobules, showing the two prin- cipal systems of bloodvessels, after Kiernan, 339. Horizontal section of two superficial lobules, showing interlobular plexus of biliary ducts, after Kiernan, 340. A small portion of a lobule highly magnified, after Leidy, 341. Portion of a biliary tube, from a fresh human liver, very highly maj nified, after Leidy, ...... 342. Hepatic cells gorged with fat, after Bowman, . 343. Minute portal and hepatic veins and capillaries, after Budd, . 344. Lobules of the liver magnified, after Budd, 345. First stage of hepatic venous congestion, after Kiernan, 346. Second stage of hepatic venous congestion, after Kiernan, 347. Portal venous congestion, after Kiernan, 348. The three coats of gall-bladder separated from each other, 349. Gall-bladder distended with air, and with its vessels injected, 350. Right kidney with its renal capsule, .... 351. Plan of a longitudinal section of the kidney and upper part of the ure- ter, through the hilus, copied from an enlarged model, 352. Portion of kidney of new-born infant, after Wagner, . 353. Small portion of kidney magnified 60 diameters, after "Wagner, 354. Tubuli uriniferi, after Baly, * 355. Plan of the renal circulation, after Bowman, . 356. Lateral view of the viscera of the male pelvis, after Quain, . 357. Part of the ossa pubis and ischia, with the root of the penis attached, after Kobelt, . . • 358. Section of the spleen, ...... 359. Male organs, after Sir C. Bell, ..... 360. Human testis injected with mercury, after Lauth, PAGE 266 267 268 281 282 283 285 297 298 300 302 303 304 305 305 305 306 306 306 307 307 308 309 309 309 310 310 326 326 327 328 329 329 331 334 351 370 371 X LIST OF ILLUSTRATIONS. PAGE FIG. 361. Plan of the structure of the testis and epididymis, after Lauth, • 371 362. Vertical section of the union of vas deferens and vesiculse seminales 374 so as to show their cavities, . 37fi 363. Section of the penis, . . . . • • ' 364. Glans penis injected, . . . • • • ' 365. Portion of the erectile tissue of the corpus cavernosum magnified, to show the areolar structure and the distribution of the arteries, after Miiller,...... . • . . 377 366. A single tuft or helicine artery projecting into a vein, highly magnified, after Miiller, . . . • • • • .377 367. Spermatozoa from man, and their developement, after "Wagner, . 382 368. Developing vesicles of spermatozoids from the testicle of the dog, after Wagner and Leuckardt, ...... 383 369. Spermatozoid of the dog in the interior of the vesicle of developement, after Wagner and Leuckardt, ..... 383 370. External organs of generation in the unmarried female—the vulva being partially opened, ...... 387 371. Side view of viscera of female pelvis, ..... 388 372. Lateral view of the erectile structures of the external organs of gene- ration in the female, the skin and mucous membrane being removed, after Kobelt......... 389 373. Front view of the erectile structures of the external organs of genera- tion in the female, after Kobelt, ..... 390 374. Anterior view of the uterus and appendages, after Quain and Sharpey, 390 375. Posterior view of the uterus and its appendages: the cavity of the ute- rus being shown by the removal of its posterior wall; and the vagina being laid open, after Quain and Sharpey, .... 391 376. Vaginal mucus containing trichomonads, magnified 400 diameters, . 391 377. Section of Uterus, . . . . . . .392 378. Section of the paries of the uterus, magnified three diameters, after Coste, ......... 393 379. Nerves of the uterus, after R. Lee, ..... 395 380. Fallopian tube, ........ 395 381. Section of ovary, ....... 396 382. New-laid egg with its molecule, &c, after Sir E. Home, . . 397 383. Section of the Graafian vesicle of a mammal, after Von Baer, . 398 384. Ovum of the sow, after Barry, ...... 398 385. Diagram of a Graafian vesicle, containing an ovum, after Warner, . 398 386. Ovarium laid open, with Graafian vesicles in various stages of evolu- tion, after Coste, ...... 399 387. Ovarium of the living hen, natural size. The ova at different stages of evolution, after Sir E. Home, ..... 400 388. Ovary of a female dying during menstruation, . . 406 389. Tubal pregnancy. ..... 427 390. Corpora lutea of different periods, .... 442 391. Corpus luteum in the third month, after Montgomery, . 443 392. Corpus luteum at the end of the ninth month, after Montgomery, . 443 393, 394. Corpora lutea, after Sir E. Home, . . . . 444 395, 396. Corpora lutea, after Sir E. Home, .... 445 LIST OF ILLUSTRATIONS. xi FIG. 397. Decidua uteri, after Von Baer, ...... 398. Section of the uterus about eight days after impregnation, after "Wag- ner, ......... 399. Section of the uterus when the ovum is entering its cavity, after Wag- ner, ......... 400. Section of the uterus with the Ovum somewhat advanced, after Wag- ner, ......... 401. Extra-uterine pregnancy, ...... 402. Two thin segments of human decidua, after recent impregnation, viewed on a dark ground; they show the openings on the surface of the membrane, after Sharpey, ..... 403. Section of the lining membrane of a human uterus at the period of commencing pregnancy, after E. H. "Weber, 404. Natural labour, . 405. Rotation of the head in its exit, 406. Breech presentation, 407. Arm presentation, 408. Twin case, 409. Milk ducts in human mamma, after Sir Astley Cooper, 410. Commencement of milk ducts as exhibited in a mercurial injection, after Sir Astley Cooper, 411. Ultimate follicles of mammary gland, after Lebert, 412. Section of bird's egg, .... 413. Duplication of cells, .... 414. Cleaving of the yolk after fecundation, 415. Membrana granulosa of an ovum from the ovary, after Bischoff, 416. Ova from the Fallopian tube and uterus, .... 417. Portion of the germinal membrane of a bitch's ovum, with the area pel- lucida and rudiments of the embryo, magnified ten diameters, 418. Portion of the germinal membrane, with rudiments of the embryo from the ovum of a bitch, after Bischoff, ..... 419. Vascular area in the chick thirty-six hours after incubation, after Wagner, ........ 420. Egg thirty-six hours after incubation, after Sir E. Home, 421. Egg opened three days after incubation, after Sir E. Home, . 422. Embryo of the chick at the commencement of the third day, as seen from the abdominal aspect, after Wagner, .... 423. Embryo from a bitch at the 23d or 24th day, magnified ten diameters, after Bischoff, ......•• 424. Plan of early uterine ovum, after Wagner, . 425. The amnion in process of formation, by the arching over of the serous lamina, after Wagner, . . 426. Diagram representing a human ovum in the second month, after Wag- ner, ....••••• 427. Egg five days after incubation, after Sir E. Home, 428. Egg ten days after incubation, after Sir E. Home, 429. The umbilical vesicle, allantois, &c, ..... 430. Diagram of part of the decidua and ovum separated, to show their mu- tual relation, after Sharpey, ...... PAGE 483 484 484 485 488 489 489 505 506 507 508 509 511 511 511 523 524 524 525 525 526 527 528 528 529 529 529 530 531 531 531. 531 532 532 xii LIST OF ILLUSTRATIONS. FIG. 431. 432. 433. 434. 435. 436. 437. 438. 439. 440. 441. 442. 443. 444. 445. 446. 447. 448. 449, 451. 452. 453. 454. 455, 457. 458. 459. 460. 461. 462. 463. 464. 465. 466. 467. 468. 469. 470. 471. 472. Ovum fourteen days old, . Ovum and embryo fifteen days old, after Maygrier, Ovum and embryo twenty-one days old, after Maygrier, Foetus at forty-five days, . Foetus at two months, ...••' Corpora Wolffiana, with kidney and testes, from embryo of birds, Foetus at three months, in its membranes, Full period of utero-gestation, . The extremity of a villus magnified 200 diameters, after Weber, Transverse section of the uterus and placenta, after J. Reid, Connexion between the maternal and foetal vessels, after J. Reid, Extremity of a placental villus, after Goodsir, . Uterine surface of the placenta, . Foetal surface of the placenta, . Knotted umbilical cord, ..... Section of thymus gland at the eighth month, after Sir Astley Cooper, Circulatory organs of the foetus, after Wilson, Descent of the testicle, after Curling, . 450. Diagrams illustrating the descent of the testis, . Schemes of sections of the lower jaw of the foetus at different periods, to show the stages of developement of the sac of a temporary incisor and of the succeeding permanent tooth from the mucous membrane of the jaw, after Goodsir. ...... Front view of the temporary teeth, ..... The separate temporary teeth of each jaw, .... Vertical section of an adult bicuspis, cut from without inwards ; greatly magnified, after Retzius, ...... 456. View of an incisor and of a molar tooth, given by a longitudinal section, showing that the enamel is striated and that the striae are all turned to the centre. The internal structure is also seen, a. Permanent rudiment given off from the temporary in an incisor, b. Permanent rudiment given off from the temporary in a molaris, Temporary tooth and permanent rudiment, after T. Bell, Temporary teeth and permanent rudiments, after T.. Bell, Do. do. do. Side view of upper and lower jaw, showing the teeth in their sockets. The outer plate of the alveolar processes has been taken off, Upper and lower teeth, ..... Skull of the aged, after Sir C. Bell, Physiognomy of the aged, after Sir C. Bell, Curves indicating the developement of the height and weight of male and female at different ages, after Quetelet, . Caucasian variety, after Blumenbach, . Oval skull of a European, after Prichard, Negro skull, after Prichard, .... Ethiopian variety, after Blumenbach . Mongolian variety, after Blumenbach, American variety, after Godman, Curves indicating the viability or existibility of male and female at dif- ferent ages, after Quetelet, ..... PAGE 533 533 533 534 534 534 535 539 547 548 548 549 550 550 552 557 559 562 563 598 599 599 600 601 602 603 603 604 604 605 610 611 612 668 668 670 672 672 673 716 HUMAN PHYSIOLOGY. BOOK II. CHAPTER III. RESPIRATION. The consideration of the function of absorption has shown how the different products of nutritive ab- sorption reach the venous blood. Fig. 262. By simple admixture with this fluid they do not become converted into a substance, capable of supplying the losses sustained by the frame from the different excretions. No- thing is better established than the fact, that no being, and no part of any being, can continue its func- tions unless supplied with blood, that has become arterial by expo- sure to air. It is in the lungs, that the absorbed matters undergo their final conversion into that fluid,—by a function, which has been termed hsematosis, the great object of that which we have now to investigate— Respiration. This conversion is occasioned by the venous blood of the pulmonary vessels coming in „ftn;„„i -antli air in +np nir-^pll<5 rvf 1- Superior piece of sternum. 2. Middle piece. contact witn air in tne air-ceiis 01 3 Infer*;or pie£e> or ensiform cartilage. 4. First the lunSTS, during which the blood dorsal vertebra. 5. Last dorsal vertebra. 6. . & ' . b ,. . . First rib. 7. Its head. 8. Its neck, resting gives tO the air SOme 01 ltS COnStltU- against transverse process of first dorsal verte- . . ... hr. Q Tfo hihftrnaitv 10 Spvpn^h nr last frrni* Anterior View of Thorax. j. „ 4-T,~ „;». ^«^<-c bra. 9. Its tuberosity. 10. Seventh or last true ents, and, in return, the air parts rib- n Costal cartilages of true ribs. 12. ■nn'rri ita plpmpnt<5 to thp blood Tw0 last false ribs — floating ribs. 13. The Wltn ltS elements tO lUC U1UOU. ^ groove along lower border of rib for lodgment To Comprehend this mysteriOUS of intercostal vessels and nerve. process, we must be acquainted with the pulmonary apparatus, as well as with the properties of atmospheric air, and the mode in which the contact between it and the blood is effected. vol. II.—2 18 RESPIRATION. 1. ANATOMY OF THE RESPIRATORY ORGANS. The thorax or chest contains the lungs,—the great agents of respira- ■ tion. It is of a conical shape, the apex of the cone being formed by the neck, and the base by a muscle, which has already been referred to more than once,—the diaphragm. The osseous framework, Fig. 262, is formed, posteriorly, of twelve dorsal vertebrae; anteriorly, of the sternum, originally composed of eight or nine pieces; and laterally, of twelve ribs on each side, passing from the vertebrae to, or towards, the sternum .^ Of these, the seven uppermost extend the whole distance from the spine to the breast-bone, and are called true or sternal, and at times, vertebrosternal ribs. They become larger as they descend, and are situate more obliquely in re- gard to the spine. The other five, called false or asternal, do not pro- ceed as far as the sternum; the cartilages of three of them join that of the seventh true rib, whilst the two lowest have no union with those above them, and are, therefore, called floating ribs. These false ribs become shorter and shorter as we descend; so that the seventh true rib may be regarded as the common base of two cones, formed by the true and false ribs respectively. The different bones constituting the thorax are so articulated as to admit of motion, and thus of dilatation and contraction of the cavity. The motion of the vertebrae on each other has been described under another head. It is not materially concerned in the respiratory move- ments. The articulation of the ribs with the spine and sternum de- mands attention. They are articulated with the spine in two places, —at the capitulum or head, and at the tubercle. In the former of these, the extremity of the ribs, encrusted with cartilage, is received into a depression, similarly encrusted, at the side of the spine. One half of this depression is in the body of the upper vertebra; the other half in the one beneath it; and, consequently, partly in the interver- tebral fibro-cartilage between the two. The joint is rendered secure by various ligaments; but it can move readily up and down on the spine. In the first, eleventh, and twelfth ribs, the articulations are with single vertebrae respectively. In the second articulation, the tubercle of the rib, also encrusted with cartilage, is received into a cavity in the transverse process of each corresponding vertebra; and the joint is rendered strong by three distinct ligaments. In the eleventh and twelfth ribs, this articulation is wanting. The articulation of the ribs with the sternum is effected by an intermediate cartilage, which becomes gradually longer, from the first to the tenth ribs, as seen in Fig. 262. The end of the cartilage is received into a cavity at the side of the sternum; and the junction is strengthened by an anterior and a posterior ligament. This articulation does not admit of much motion; but the existence of a synovial membrane shows, that it is destined for some. The cavity of the thorax is completed by muscles. In the intervals between the ribs are two planes, whose fibres pass in inverse directions, and cross each other. These are the intercostals. The diaphragm forms the septum between the thorax and abdomen. Above, the cavity RESPIRATORY ORGANS. 19 is open; and through the opening numerous vessels and nerves enter. The muscles, concerned in the respiratory function, are numerous. The most important of them is the diaphragm. It is attached, by its circumference, around the base of the chest; but its centre rises into the thorax; and, during its state of relaxation, forms an arch, the middle of which is opposite the inferior extremity of the sternum. It is tendinous in its centre, and is attached by two fasciculi, called pillars, to the spine,—to the bodies of the first two lumbar vertebrae. It has three apertures; one before for the passage of the vena cava inferior; and two behind, between the pillars, for the passage of the oesophagus and aorta. The other great muscles of respiration are the serratus posticus inferior, serra- tus posticus superior, Fig. 263. levatores costarum, in- tercostal muscles, in- fra-costales, and trian- gularis sterni or sterno- costal; but, in an excited condition of respiration, all the mus- cles, that raise and de- press the ribs, directly or indirectly, partici- pate—as the scaleni, sterno-mastoidei, pec- toralis, (major and minor,) serratus major anticus, abdominalmus- cles, &c. In the structure of the lungs, as M. Ma- gendie1 has remarked, nature has resolved a mechanical problem of extreme difficulty. The problem was,—to es- tablish an immense sur- face of contact between the blood and air, in the small space occu- pied by the lungs. The admirable arrangement adopted consists in this, —that each of the mi- nute vessels, in which the pulmonary artery terminates and the pul- monary veins originate, Anterior View of the Thoracic Viscera in situ, as shown by the removal of the Anterior Parietes of the Thorax. 1. Superior lobe of right lung. 2. Its middle lobe. 3. Its in- ferior lobe. 4, 4. Lobular fissures. 5, 5. Internal layer of costal pleura forming the right side of the anterior mediastinum. 6, 6. Right diaphragmatic portion of pleura costalis. 7,7. Right pleura costalis on the ribs. 8. Superior lobe of left lung. 9. Its inferior lobe. 10,10. Interlobular fissures. 11. Portion of pleura costalis which forms the left side of the anterior mediastinum. 12. Left diaphragmatic portion of pleura costalis. 13. Left pleura costalis. 14, 14. The middle space between the pleurae, known as the ante- rior mediastinum. 15. Pericardium. 16. Fibrous partition over which the pleurae are reflected. 17. Trachea. 18 Thyroid gland. 19. Anterior portion of thyroid cartilage. 20. Primitive carotid artery. 21. Subclavian vein. -2'i. Internal jugular vein. 23. Bra- chio-cephalic vein. 24. Abdominal aorta. 25. Xiphoid cartilage. 1 Precis, &c, ii. 307. 20 RESPIRATION. Fir. 26-1. Posterior View of the Thoracic Viscera, showing their rela- is surrounded on every side by air. The lungs are two organs of con- siderable size, situate in the lateral parts of the chest, and subdivided into lobes and lobules, the shape and number of which cannot be rea- dily determined. They are termed right and left, respectively, ac- cording to the side of the cavity of the chest which they occupy. The former consists of three lobes ; the latter of two. Each of these exactly fills the corre- sponding cavity of the pleura; and they are separated from each other by a duplicature of the pleura—(the se- rous membrane that lines the chest, and is reflected over the lungs) ^^^i^Tb^^0'^^^^^^^-^ by the heart. the Parietes of the Thorax. 1,2. Upper and lower lobes of right lung. 3. Interlobular fis- sures. 4. Internal portion of pleura costalis, forming one of the sides of posterior mediastinum. 5. Twelfth rib and lesser dia- phragm. 6. Reflection of the pleura over the greater muscle of the diaphragm on the right side. 7, 7. Right pleura costalis adherin" to the ribs. 8. 9 The two lobes of the left lung. 10,10. Interlobu* lar fissures. 11, 11. Left pleura, forming the parietes of the poste- rior mediastinum. 12,13. Its reflections over the diaphragm on this side. 14, 14. Left pleura costalis on the parietes of the chest 15 Trachea. 16. Larynx. 17. Opening of the larynx and the epiglot- tic cartilage in situ. 18. Root and top of the tongue. 19, 19 Rkjht and left bronchia. 20. The heart enclosed in pericardium 21 Up- per portion of diaphragm on which it rests. 22. Section of oeso- phagus. 23. Section of aorta. 24. Arteria innominata. 25 Primi- tive carotid arteries. 26. Subclavian arteries. 27. Internal jugu- lar veins. 28. Second cervical vertebra. 29. Fourth lumbar ° The colour of-the lungs is generally of a marble blue; and the exterior is furrowed by figures of hexagonal shape.' The appearance is not, however, the same at all ages, and under all circumstances. In in- fancy, they are of a pale red; in youth, of a darker colour ; and in old age, of a livid blue. The elements that compose them are ;—the ramifications of the tra- chea ; those of the pulmonary artery and pulmonary veins, besides the organic elements, that appertain to every living structure,—arteries, veins, lymphatics, nerves, and areolar tissue. The ramifications of the windpipe form the cavity of the organ of respiration. The trachea is continuous with the larynx, from which it receives the external air conveyed to it by the mouth and nose. It passes down to the thorax at the anterior part of the neck, and bifurcates opposite the second dorsal vertebra, forming two large canals called bronchi or bron- chia. One of these goes to each lung; and, after numerous subdi- RESPIRATORY ORGANS. 21 visions, becomes impercepti- Fi§ 265- ble; hence, the multitudinous speculations that have been indulged regarding the mode in which the bronchial rami- fications terminate. Mal- pighi1 believed, that they form vesicles, at the inner surface of which the pulmonary ar- tery ramifies. Reisseisen2 describes the vesicles as of a cylindrical, and somewhat rounded figure; and states, that they do not communi- cate with each other. Hel- vetius,3 on the other hand, affirmed, that they end in . -,. c 7 , , i j-/v A shaded Diagram, representing the Heart and Great Cells, formed by the different Vessels, injected and in connexion with the Lungs; Constituent elements of the the Pericardium is removed. lung ___the Cells havin0" no *• Right auricle. 2. Vena cava superior. 3. Vena cava - &' 1 *5 inferior. 4. Right ventricle. 5. Pulmonary artery, divid- determmate Shape, Or regU- ing into two branches a, a, one for the right, the other for the 1 'JL l_ a.T. left lung. 6. Point of the left auricle. 7. Part of left ventri- lar Connexion With each Other; cle. 8. Aorta. 9, 10. Two lobes of the left lung. 11,12,13. wliil«f M Mfio-onrJin4 aaaovra Three lobes of the right lung, a, a. Right and left pulmo- Wllllfel in. lVldgeilUlC dbbertb, nery arteries- 6> b Right and left bronchi. v,v. Right that the minute bronchial and left pulmonary veins. The relative position of these ,. . . 1 • 1 • three vessels is seen to differ on the two sides. division, which arrives at a lobe, does not enter it, but terminates suddenly as soon as it has reached the parenchyma ; and, he remarks, that as the bronchus does not pene- trate the spongy tissue of the lung, it is not probable, that the surface of the cells, with which the air comes in contact, is lined by a prolonga- tion of the mucous coat, which forms the inner membrane of the air- passages. Mr. Hassall,5 however, contrary to the opinion of most observers, and—as will be seen—to that of Mr. Rainey, one of the most recent of them, affirms, that in sections of recent lungs "it is a very easy matter not merely to determine the existence of epithelium in the air-cells, but also the fact of its cylinder and ciliated form and charac- ter," and this "fact" of the epithelium extending from the bronchial tubes into them—he adds—would seem in itself to imply that the mu- cous membrane also lines them. The ramifications of the pulmonary artery are another constituent element of the lung. This vessel arises from the right ventricle of the heart, and, at a short distance from that organ, divides into two branches; one passing to each lung. Each branch accompanies the correspond- ing bronchus in all its divisions; and, at length, becomes capillary and imperceptible. Its termination, also, has given rise to conjecture. Mal- pighi conceived it to end at the mucous surface of the bronchi, in an 1 Epist. de Pnlmon., i. 133. 2 Ueber den Bau der Lungen, u. s. w., Berlin, 1822 ; also, in Latin, Bjrl., 1822. 3 Memoires de l'Academ. pour 1718, p. 18. 4 Preciis, &c, ii. 309. 5 The Microscopic Anatomy of the Human Body in Health and Disease, part xii. p. 381, London, 1848. 22 RESPIRATION. Fig. 266. Arrangement of the Capillaries of the Air-cells of the Human Lung. extremely delicate network, which he called rete mirabile; and this was, likewise, the opinion of Reisseisen. Bichat1 admitted at the extre- mities of the pulmonary artery, and between that artery and the veins of the same name, vessels of a more delicate character, which he conceived to be the agents of haematosis, and called the capil- lary system of the lungs. This, however, is nothing more than the fine dense capillary network, formed by the distribution of the artery on the air-cells, from which the pulmonary veins arise. Their radicles communicate freely with those of the pulmonary artery. When we observe them distinctly, they are found uniting to consti- tute larger and larger veins, until they ultimately end in four large trunks, which open into the left auri- cle of the heart. The pulmonary arteries do not anastomose in their course ; and according to Dr. Cammann,2 the capillaries of one lobule do not communicate with those of another : the interstitial areolar membrane even of the most minute lobules was seen entirely free from colour when a coloured injection was thrown into the vessels. In addition to these organic constituents, the lung, like other organs, receives arteries, veins, lymphatics, and nerves. It is not nourished by the blood of the pulmonary artery, which is not adapted for the pur- pose, seeing that it is venous. The bronchial arteries are its nutritive vessels. They arise from the aorta, and are distributed to the bronchi. Around the bronchi, and near where they dip into the tissue of the lung, lymphatic glands—bronchial glands—exist, the colour of which is almost black, and with which the few lymphatic vessels, that arise from the superficial and deep-seated parts of the lung, communicate. Hal- ler3 has traced the efferent vessels of these glands into the thoracic duct. The nerves, distributed to the lungs, proceed chiefly from the eighth pair or pneumogastric. A few filaments of the great sympathetic are also sent to them. The eighth pair—after having given off the superior laryngeal nerves, and some twigs to the heart—interlaces with nume- rous branches of the great sympathetic, and forms an extensive nervous network, called anterior pulmonary plexus. After this, the nerve gives off the recurrents, and interlaces a second time with branches of the great sympathetic, forming another network, called posterior pulmo- nary plexus. It then proceeds to the stomach, where it terminates. (See Figs. 198 and 225.) From these two plexuses the nerves proceed, that are distributed to the lungs. These accompany the bronchi, and 1 Anatomie Generate, edit, de MM. Beclard, Blandin, and Magendie, ii. 381-386, Paris, 1832 2 New York Journal of Medicine, Jan., 1848. 3 Elem. Physiologic, viii. 2, § 15, Lausann. 1764. RESPIRATORY ORGANS. 23 are spread chiefly on the mucous membrane of the air-tubes. The lung likewise receives some nerves directly from the three cervical ganglions of the great sympathetic, and from the first thoracic ganglion. In addition to these, a distinct system of nerves—the respiratory system, described in the first volume of this work (p. 89)—is supposed by Sir Charles Bell to be distributed to the multitude of muscles, that are asso- ciated in the respiratory function, in a voluntary or involuntary man- ner. This system includes one of the nerves just referred to—the eighth pair—and the phrenic nerves, which are distributed to the dia- phragm. The various nerves composing it are intimately connected, so that, in forced or hurried respiration, in coughing, sneezing, &c, they are always associated in action. We have seen, however, that few phy- siologists now admit the respiratory system of Sir Charles. Lastly; the lungs are constituted also of areolar tissue, which has been termed interlobular tissue; but it does not differ from areolar tissue in other parts of the body. Such are the constituent elements of the pulmonary tissue; but, with regard to the mode in which they are combined to form the intimate texture of the lung we are not wholly instructed. We find, that the lobes are divided into lobules, and these, again, seem to be subdivided almost indefinitely, forming an extremely delicate spongy tissue, the areolae of which can only be seen by the aid of the microscope.1 It is generally thought, that the areolae communicate with each other, and that they are enveloped by the areolar tissue which separates the lobules. M. Magendie2 inflated a portion of lung, dried and cut it in slices, in order that he might examine the deep-seated cells. These appeared to him to be irregular, and to be formed by the final ramifications of the pulmonary artery, and the primary ramifications of the pulmonary veins; the cells of one lobule communicating with each other, but not with those of another lobule. Professor Horner,3 of the University of Pennsylvania, has attempted to exhibit that this communication between the cells is lateral. After filling the pulmonary arteries and pulmonary veins with minute injection, the ramifications of the bronchi, with the air-cells, were distended to their natural size by an injection of melted tallow. The latter, being permitted to cool, the lung was cut into slices and dried. The slices were subsequently immersed in spirit of turpentine, and digested at a moderate heat for several days. By this process, all the tallow was removed, and the parts, on being dried, ap- peared to exhibit the air-cells empty, and, seemingly, of their natural size and shape. Preparations, thus made, appear to show the air-cells to be generally about the twelfth of a line in diameter, and of a spheri- cal form, the cells of each lobule communicating freely, like the cells of fine sponge, by lateral apertures. The lobules, however, only com- municate by branches of the bronchi, and not by contiguous cells. This would seem to negative the presumption of some anatomists and physi- ologists,—as Reisseisen, Blumenbach, Cuvier, &c,—that each air-cell is insulated, communicating only with the minute bronchus that opens 1 Ha6sall, op. cit. * Precis, &c, ii. 309. * American Journal of the Medical Sciences for Feb., 1832, p. 538, and op. cit. 24 RESPIRATION. into it; whilst it confirms the views of Ilaller, Monro (Secundus), Boyer, Sprengel, Magendie, Carpenter, and others;—but it is not easy to^decide positively, where all is so minute. The observations of Vr. Addison led him to maintain, that the views of Reisseisen and others are cer- tainly true as regards the foetal lung, in which the ultimate subdivisions of the bronchial tubes terminate in closed extremities. But when an animal has respired, the terminations are said to experience a great change. The membrane composing them offers but slight resistance to the pressure of the air, and is pushed forwards, and distended laterally into rounded inflations, forming a series of cells, which are moulded by mutual pressure into various angular forms, and which communicate freely with each other by large oval apertures. The passages, thus formed, do not communicate otherwise than by their connexion with the same bronchial tube, and the bloodvessels lie between the contiguous walls of each two of them, so that the blood in the capillaries is exposed to air on both sides. It would appear, also, from the researches of M. Bourgery,2 that the developement of the air-cells,—and, consequently, the capacity for forcible inspiration,—continues in man to the age of thirty, at which time the capacity is greatest. Subsequently, it de- creases, especially in those who suffer from cough,—the violence of the respiratory effort often causing rupture of the air-cells, and thus gra- dually producing the emphysematous state of the lungs so common in old people. After thirty, the capacity for forcible inspiration diminishes one-fifth in the first twenty years; one-fifth more in the next ten; and nearly one-half in the next twenty; and this gradual decrease of capa- city for forcible inspiration is true of all persons, although one may have a greater general capacity of respiration than another of the same age. Hence the young person possesses a greater capacity of respira- tion, as it were, in reserve. The aged have little, and are, therefore, unfit for great exertion. The observations of Mr. Rainey,3 which have been adopted by many histologists, lead to the belief, that when the bronchia have attained the diameter of from ^th to -g^th of an inch, they gradually lose their cylindrical form, and appear more like irregular passages—termed by Mr. Rainey intercellular passages-*-through the substance of the lung. Fig. 267. Air-cells from an Emphysematous Lung. (Leidy.) 1. A group of air-cells laid open and exhibiting the fact that there is no lateral intercommunication. 2. Two air-cells; the one to the left exhibits its bronchiolar orifice. 3. Another group ; to the left are represented two cells freely communi- cating from the partition being ruptured by over-distension; and between the two cells to the right are observed some in- flated areola? of areolar tissue. These passages are clustered with air-cells, which have the appearance of polyhedral alveolar cavities separated by exceedingly thin septa, and do not open into one another by anastomosis or lateral communication, 1 Proceedings of the Royal Society, March 17, 1842; and Philos. Transact, for 1842. 2 Gazette Medicale, 16 Juillet, 1842, and Archives Generates de Med., Mars, 1843. 3 Medico-Chirurgical Transactions, vol. xxviii., London, 1845. RESPIRATORY ORGANS. 25 but communicate freely through the medium of the common air passage to which they belong. The marginal figure (Fig. 267) represents several groups of air-cells from an emphysematous lung, drawn the size of nature from a preparation by Dr. Goddard. The diagrams, Figs. 268 and 269, Fig. 268. Fig. 269. Transverse Section of a portion of the Pulmonary Longitudinal Section of the termina- Parenchyma. tion of a Bronchus. 1. The orifices of bronchioles. 2. The air-cells arranged 1. The bronchiole, in which are seen around the bronchioles, and opening into them, but not com- the orifices (3) of the air-cells (2) ar- municating laterally. 3. Interspaces filled with areolar tis- ranged around itandat its termination. sue, which, when inflated, is liable to be mistaken for the true air-cells. are given by Dr. Leidy to facilitate the understanding of the relative arrangement of the air-cells to the minute bronchial tubes' in this view of the subject. Mr. Rainey affirms, as the result of actual observation, that the mucous lining of the bronchial tube is not continued along the intercellular passages and into the air-cells, a circumstance, which, as he suggests, explains the different effects of inflammation of the tubes and of the air-cells;—the latter, which are lined by fibro-areolar tissue, being accompanied by the exudation of fibrin instead of mucus. Ana- tomists, consequently, who, by the term "air-cell," meant simply the ultimate termination of a bronchial tube; and pathologists, who regarded bronchitis of the terminal extremities of those tubes and pneumonia as essentially alike, were nearer the truth than was generally admitted. It is proper to remark, that the researches of Mr. Rainey led him to conclude—in opposition to Dr. Addison,—that the foetus, prior to the act of respiration, possesses fully formed air-cells, which are also sur- rounded by capillary plexuses. The surface afforded by the air-cells is immense. Hales2 supposed them to be polyhedral, and about one-hundredth part of an inch in diameter. The surface of the bronchi he estimated at 1635 square 1 Quain's Human Anatomy, by Quain and Sharpey, Amer. edit, by Dr. Leidy, ii. 119, Philad., 1849. « Statical Essays, i. 242. 26 RESPIRATION. inches; and that of the air-cells at 40,000, making the surface of the whole lungs 41,635 square inches or 289 square feet,—equal to 19 times the surface of the body, which, at a medium, he computes to be 15 square feet. Keill1 estimated the number of cells to be 1,744,186,015; and the surface 21,906 square inches; and Lieberkiihn has valued it at the enormous amount of 1500 square feet.2 M. Rochoux3 estimates the number of cells at 600,000,000, and that these are about 17,790 grouped around each terminal bronchus. All that we can derive from these mathematical conjectures is, that the extent of surface is surprising, when we consider the small size of the lungs themselves. Professor Horner4 has published an account of various experiments, which exhibit the ready communication between the pulmonary air- vesicles and veins. By fixing a pipe into the human trachea, and per- mitting a column of water to pass gently, he found that the air-cells became distended with water; and that the left side of the heart filled, and the aorta discharged water freely from its cut branches. This ex- periment he repeated on human lungs on different occasions, and with like results. Very little water flowed from the pulmonary artery. In the sheep and the calf, however, when the experiment was practised upon them after they had been pretty thoroughly evacuated of blood, the water passed freely through both the pulmonary veins and the pul- monary arteries. Dr. Horner is disposed to infer, that his experiments exhibit a communication of the pulmonary air-vesicles by a direct route with the pulmonary bloodvessels, especially the veins; but this may well be questioned. It is possible, that such a communication may really have been made by the force of the column of water ; and if not so, the passage of the fluid from air-cells to bloodvessels might have been effected through the pores, as in ordinary imbibition, which, we have elsewhere seen, is readily accomplished in the lungs, but not more readily perhaps than in the case of serous and other tissues under favourable circumstances. Hemorrhage by transudation occurs, we know, most rapidly at times through the coats of vessels; and a thinner fluid would of course transude more easily. It can scarcely be doubted, from Dr. Horner's experiments, that a certain arrangement exists be- tween the air-vesicles and the pulmonary veins in man, which allows a more ready imbibition and transudation; but what that arrangement is admits of question. Each lung is covered by the pleura,—a, serous membrane analogous to the peritoneum,—and, in birds, a prolongation of the latter. This membrane is reflected from the adjacent surface of the lung to the peri- cardium which covers the heart, and is then spread over the interior paries of the half of the thorax to which it belongs; lining the ribs and intercostal muscles, and covering the convex or upper surface of the diaphragm. There are, consequently, two pleurae, each of which is confined to its own half of the thorax, lining its cavity and covering 1 Tentam. Med. Phys., p. 80. * Blumenbach, in Elliotson's Physiology, p. 197, Lond., 1835. » Gazette M£dicale, 4 Janv., 1845. * Amer. Journ. of the Medical Sciences, April, 1843, p. 332; and Special Anatomy and Histology, 6th edit., ii. 163. RESPIRATORY ORGANS. 27 the lung. Behind the sternum, however, they are contiguous to each other, and form the partition called mediastinum, which extends be- tween the sternum and spine. Fig. 270 exhibits the boundaries of the two cavities of the pleura. The middle space between is the mediasti- num. Within this septum, the heart, enveloped by the pericardium, is situate, and separates the pleurae considerably from each other. Ana- tomists generally subdivide the mediastinum into two rigions; one passing from the front of the pericardium to the sternum, called anterior mediastinum; the other, from the posterior surface of the pericardium to the dorsal vertebras,—posterior mediastinum; and, by some, the part which is within the circuit of the first ribs, is termed supe- rior mediastinum. The second of these contains the most im- portant organs,—the lower end of the trachea, oesophagus, aorta, vena azygos, thoracic duct, and pneumogastric nerves. The portion of the pleura cover- ing each lung, is called pleura pulmonalis; that which lines the thorax, pleura costalis. It is obvious that, as in the case of the abdomen, the viscera are not in the cavity of the pleura, but external to it; and that there is no communication between the serous sac of one side and that of the other. The use of the pleura is to attach the lungs by their roots to their respective cavities, and to facilitate their movements. To aid this, the membrane is always lubricated by a fluid, exhaled from its surface. The other surface is attached to the lung in such a manner, that air cannot get between it and the parietes of the thorax. Dr. Stokes1 admits a proper fibrous tunic of the lungs. In a healthy state, this capsule, although possessing great strength, is transparent, a circumstance in which it differs from the fibrous capsule of the pericardium, and which, Dr. Stokes thinks, has probably led to its being overlooked. It invests the whole of both lungs; covers a por- 1 On Diseases of the Chest, Part i. p. 460, Dublin, 1837; or Dunglison's American Medical Library edition, p. 301, Philad., 1837. Fig. 270. Outline of a Transverse Section of the Chest, show- ing the relative position of the Pleurse to the Thorax and its Contents. 1. Skin on the front of the chest drawn up by a hook. 2. Skin on the sides of the chest. 3. That on the back. i. Subcutaneous fat and muscles on the outside of the thorax. 5. Section of the muscles in the vertebral gutter. 6. Section of fifth dorsal vertebra. 7. Spinal canal. 8. Spinous process. 9, 9, 10, 10. Sections of ribs and intercostal muscles. 11. Their cartilages. 12. Sternum. 13. Division of the pulmonary artery. 14. Exterior surface of lungs. 15. Posterior face of lungs. 16. Anterior face of lungs. 17. Inner face of lungs. 18. Anterior face of heart covered by pericardium. 19. Pul- monary artery. 20, 21. Its division into right and left branches. 22. Portion of right auricle. 23. Descending cava cut off at right auricle. 24. Section of left bron- chus. 25. Section of right bronchus. 26. Section of oesophagus. 27. Section of thoracic aorta. The space between figures 12 and 18 and the two 16s is the an- terior mediastinum, and the space which contains 26 and 27 is the posterior mediastinum. These spaces are formed by the reflections of the pleura?. 28 RESPIRATION. tion of the great vessels; and the pericardium seems to be but its con- tinuation,—endowed, in that particular situation, with a greater degree of strength, for purposes that are obvious. It covers tne diaphragm where it is more opaque: in connexion with the pleura, it lines the ribs; and, turning, forms the mediastina, which are thus shown to consist of four layers,—two serous and two fibrous. It seems, that Dr. Hart, of Dublin, had, for years, demonstrated this tunic to his class. It was, at one time, the prevalent belief, that air always exists in the cavity of the chest. Galen supported the opinion by the fact, that, having applied a bladder, filled with air, to a wound, which had pene- trated the chest, the air was drawn out of the bladder at the time of inspiration. This was also maintained by Hamberger, Hales,1 and numerous others. The case, alluded to by Galen, is insufficient to esta- blish the position, inasmuch as we have no evidence, that the wound did not also implicate the pulmonary tissue. Since the time of Haller, who opposed the prevalent doctrine by observation and reasoning, the fact of the absence of air in the cavity of the pleura has been generally considered established. It is obvious, that its presence there would materially interfere with the dilatation of the lungs, and thus be produc- tive of fatal consequences; besides, anatomy instructs us, that the lungs lie in pretty close contact with the pleura costalis. When the inter- costal muscles are dissected off, and the pleura costalis is exposed, the surface of the lungs is seen in contact with that transparent membrane; and when the pleura is punctured, the air rushes in, and the lungs re- tire, in proportion as the air is admitted. This occurs in cases of injuries inflicted upon the chest of the living animal. Moreover, if a dead or living body be placed under water, and the pleura be punctured, so as not to implicate the lungs, it has been found by the experiments of Brunn, Sprbgel, Caldani, Sir John Floyer, Haller,2 and others, that not a bubble of air escapes,—which would necessarily be the case, if air were in the cavity of the pleura. 2. ATMOSPHERIC AIR. The globe is surrounded everywhere, to the height of fifteen or six- teen leagues, by a rare and transparent fluid called air; the total mass of which constitutes the atmosphere. Atmospheric air, although invisi- ble, can be proved to possess the ordinary properties of matter; and, amongst these, weight. It also partakes of the character of a fluid, adapting itself to the form of the vessel in which it is contained, and pressing equally in all directions. As^ air is possessed of weight, it results, that every body on the earth's surface must be subjected to its pressure; and as it is elastic or capable of yielding to pressure, the part of the atmosphere near the surface must be denser than that above it. As a body, therefore, ascends, the pressure will be diminished; and this accounts for the dif- ferent feelings experienced by those who ascend lofty mountains or voyage in balloons, into the higher strata of the atmosphere. M. Ed- 1 Statical Essays, ii. 81. 2 Element. Physiol., viii. 2, § 3, Lausann., 1764. ATMOSPHERIC AIR. 29 wards1 ascribes part, at least, of the effect produced upon the breathing, at great elevations, to the increased evaporation which takes place from the skin and lungs; and in many aerial voyages great inconvenience has certainly been sustained from this cause. The pressure of the atmosphere at the level of the sea is the result of the whole weight of the atmosphere, and is capable of sustaining a column of water thirty-four feet high, or one of mercury of the height of thirty inches, as in the common barometer. This is equal to about fifteen pounds avoirdupois on every square inch of surface; so that the body of a man of ordinary stature, the surface of which Haller esti- mates to be fifteen square feet, sustains a pressure of 32,400 pounds. Yet, as the elasticity of the air within the body exactly balances or counteracts the pressure from without, he is not sensible of it. The experiments of Davy, Dalton, Gay Lussac, Humboldt, Despretz, and others, have shown, that pure atmospheric air is composed essen- tially of two gases, oxygen and nitrogen or azote, which exist in it in the proportion of 21 of the former to 79 of the latter: according to MM. Dumas and Boussingault,2 20*81 of the former to 79-19 of the latter: Dr. T. Thomson says 20 of oxygen to 80 of nitrogen; and these proportions have generally been found to prevail in the air whencesoever taken;—whether from the summit of Mont Blanc, the top of Chimborazo, the sandy plains of Egypt, or from an altitude of 23,000 feet in the air.3 It has been affirmed, indeed, that the propor- tion of the gases is subject to a variation of two or three parts in the thousand, in situations where the oxygen is much exposed to absorption, as over the sea, when there is no wind.4 Chemical analysis has not been able to detect the presence of any emanation from the soil of the most insalubrious regions, or from the bodies of those labouring under the most contagious diseases,—malignant and material as such emanations unquestionably must be. The great uniformity in the pro- portion of the oxygen to the nitrogen in the atmosphere has led to the conclusion, that as there are many processes, which consume the oxygen, there must be some natural agency, by which a quantity of oxygen is produced equal to that consumed. The only source, however, by which oxygen is known to be supplied, is the process of vegetation. A healthy plant absorbs carbonic acid during the day; appropriates the carbon to its own necessities, and gives off the oxygen with which it was com- bined. This is a nutritive or digestive process; but at the same time the plant is respiring, or consuming oxygen, and giving off carbonic acid. In bright light, however, the former function is so active as to prepon- derate over, and mask the latter. During the night an opposite effect is produced. Digestion is almost suspended; and respiration is pre- ponderant. Oxygen is then taken from the air, and carbonic acid given off; but the experiments of Davy and Priestley show, that plants, during 1 De l'lnfluence des Agens Physiques, &c, p. 493, Paris, 1824. 2 Annates de Chimie et de Physique, iii. 257, Paris, 1S41. 3 Art. Atmosphere, (Physical and Chemical History,) by Dr. R. M. Patterson, in Amer. Cyclopedia of Practical Medicine and Surgery, vol. ii. p. 526, Philad., 1836. 4 Lewy, Comptes Rendus, 1842; also, Morren, Annates de Chimie et de Physique, xii. 5, Paris, IS 11. 30 RESPIRATION. the twenty-four hours, yield more oxygen than they consume. It seems impossible, however, to look to this as the great cause of equilibrium between the oxygen and the nitrogen. Its influence can extend to a small distance only; yet the uniformity has been found to prevail, as we have seen, in the most elevated regions, and in countries whose and sands never admit of vegetation. In addition to the oxygen and nitrogen,—the principal constituents of atmospheric air,—another gas exists in very small proportion, but is always present. This is carbonic acid. It was found by De Saussure on Mont Blanc, and by Humboldt in air brought down by Garnenn, the aeronaut, from the height of several thousand feet. The proportion is estimated by Dalton not to exceed the toW*1 or t^th of its bulk. In one of the wards of La Pitie, in Paris, which had been kept shut during the night, M. Felix Leblanc1 found a larger portion of carbonic acid, nearly TT3ffTjths. and in a dormitory of La Salpe'triere, the air yielded Tf ^ths; the largest proportion found by him in hospitals. In the lecture room of the Sorbonne, which is capable of containing 1000^ cubic inches of air, after a lecture an hour and a half long, and at which 900 persons were present, the oxygen was found to have lost 1 in every hundred, although two doors were open; whilst the carbonic acid was increased in rather a greater ratio. In a ward in an institution for children, although the door was half open, and there was an open space in the roof, the air was found to contain TT)30Tjths of carbonic acid, and there was a proportional diminution of oxygen. Dr. Dalton analyzed the air of a room in which 50 candles had been kept burning, and 500 people had been collected for two hours, and found it to contain one per cent. of carbonic acid.2 M. Boussingault3 has made 142 analyses of large quantities of the air of Paris, whence he has drawn the generally admitted conclusion, that the quantity of carbonic acid contained in the air of large towns is not above the average. The average quantity found by him was 3-97 volumes in 10,000. Although largely produced where combustion is extensively going on, and where numbers of per- sons are congregated together, as in large cities, it becomes so speedily diffused in the atmosphere as not to excite any marked difference be- tween the air in them and in rural dstricts.4 These, then, may be looked upon as the constituents of atmospheric air. There are certain substances, however, which are adventitiously present in variable proportions; and which, with the constitution of the atmosphere as to density and temperature, are the causes of gene- ral or local solubrity, or the contrary. Water is one of these. The quantity, according to M. de Saussure, in a cubic foot of air, charged with moisture, at 65° Fahr., is 11 grains. Its amount in the atmo- sphere is very variable, owing to the continual change of temperature to which the air is subject; and even when the temperature is the same, 1 Gazette Med. de Paris, 11 Juin, 1842. 2 London and Edinb. Philos. Magazine, xii. 405, 1838. 3 Annales de Chimie et de Physique, Mars, 1844. See, also, M. Lewy, loc. cit. 4 See Dr. John Reid, article Respiration, in Cyclopaedia of Anat. and Physiol., Pt. xxxii. p. 326, London, April, 1848. ATMOSPHERIC AIR. 31 the quantity of vapour is found to vary, as the air is rarely in a state of saturation. The varying condition as to moisture is indicated by the hygrometer. From a comparison of numerous observations, Gay Lussac affirms, that the mean hygrometric state of the atmosphere is such, that the air holds just one-half the moisture necessary for its satu- ration. In his celebrated aerial voyage, he found it to contain but one- eighth. This is, perhaps, the greatest degree of dryness ever noticed. It has been presumed, that the hygrometric condition of the air has more agency in the production of disease than either the barometric or thermometric. It is not easy to say, which exerts the greatest influence : probably all are concerned; and when we have a union of particular barometric, thermometric, hygrometric, electric, and other conditions, we have certain epidemics existing, which do not prevail under any other combination. When the air is dry, we feel a degree of elasticity and buoyancy; whilst, if it be saturated with moisture,—especially during the heat of summer,—languor, lassitude, and indisposition to mental or corporeal exertion are experienced. In addition to aqueous vapour, numerous emanations from animal and vegetable substances are generally present, especially in the lower strata of the atmosphere; by which the salubrity of the air may be more or less affected. All living bodies, when crowded together, de- teriorate the air so much as to render it unfit for the maintenance of the healthy function. If animals be kept crowded together in ill-ven- tilated apartments, they speedily sicken. The horse becomes attacked with glanders; fowls with pep, and sheep with a disease peculiar to them if they be too closely folded. This is probably a principal cause of the insalubrity of cities compared with the country. In them, the air must necessarily be deteriorated by the impracticability of due ven- tilation ; and this, with the want of due exercise, is a fruitful cause of cachexia—and of tuberculous cachexia; hence, also, it is, that in work- houses and manufactories, diseases dependent on this condition of constitution are prevalent. One of the greatest evidences we possess of the positive insalubrity of towns is in the case of the young. In London, the proportion of those that die annually under five years of age to the whole number of deaths is as much as thirty-eight per cent., and under two years, twenty-eight per cent.; in Paris, under two years of age twenty-five per cent.; and in Philadelphia and Baltimore, rather less than a third. These estimates maybe considered approximations; the proportions varying somewhat, according to the precise year in which they have been taken. Manifest, however, as is the existence of some deleterious principle, in these cases, it has always escaped the researches of the chemist. Lastly. Air is indispensable to organic* existence. No being— animal or vegetable,—can continue to live without a due supply of it; nor can any other gas be substituted for it. This is proved by the fact, that all organized bodies cease to exist, if placed in vacuo. They require, likewise, renovation of the air, otherwise they die; and if the residual air be examined, it is found diminished in quantity, and to have received a gas, which is totally unfit for life,—carbonic acid. The experiments of Hales prove this as regards vegetables; whilst Spallan- 32 RESPIRATION. zani and Vauquelin have confirmed it in the case of the lower animals. The necessity for the presence of air, and its due renewal,—as regards man and the upper classes of animals,—is sufficiently obvious. JNot less necessary is a due supply of it to aquatic animals. I hey can be readily drowned, when the air in the water is consumed, if prevented from coming to the surface. If the fluid be put under the receiver of an air-pump, and the air be withdrawn, or if the vessel be placed so that the air cannot be renewed, the same changes are found to have been produced in it. Hence the necessity for making holes through the ice, where small fish-ponds are frozen over, if we are desirous of preserving the fish alive. The necessity for the renewal of air is not, however, alike imperative in all animals. Whilst the mammalia, birds, fishes, &c, speedily expire, when placed under the receiver of an air- pump, if the receiver be exhausted; the frog is but slightly incommoded. It swells up almost to bursting, but retains its position, and when the air is admitted seems to have sustained no injury. The exception, afforded by the amphibious animal to the ordinary effects of destructive agents, we have already had occasion to refer to more than once; and it is exemplified in the fact, now indisputable, that the toad has been found alive in the substance of trees and rocks, where no access of air appeared practicable. The influence of air on mankind is interesting and important in its hygienic relations, and has accordingly been a topic of study since the days of Hippocrates. In other works, it has been investigated, at considerable length, by the author.1 3. PHYSIOLOGY OF RESPIRATION. a. Mechanical Phenomena of Respiration.—Within certain limits, the function of respiration is under the influence of volition. The muscles, belonging to it, have consequently been termed mixed, as we can at pleasure increase or diminish their action, but cannot arrest it altogether, or for any great length of time. If, by a forced' inspira- tion, we take air into the chest in large quantity, we find it impossible to keep the chest in this condition beyond a certain period. Expira- tion irresistibly succeeds, and the chest resumes its pristine situation. The same occurs if we expel the air as much as possible from the lungs. The expiratory effort cannot be prolonged indefinitely, and the chest expands in spite of the effort of the will. The most expert divers do not appear capable of suspending the respiratory movements longer than 95 or 100 seconds. Dr. Lef^vre2 found the average period of the Turkish divers to be 76 seconds for each man. These facts have given rise to two curious and deeply interesting topics of inquiry;—the cause of the first inspiration in the new-born infant; and of the regu- lar alternation of inspiration and expiration during the remainder of existence? The first of these will fall under consideration when we investigate the physiology of infancy; the latter will claim some atten- 1 Human Health, Philad., 1844; and American Cyclopaedia of Practical Medicine and Surgery, art. Atmosphere, p. 527, Philad., 1836. 2 Loudon's Magazine of Nat. Hist., p. 617, Dec, 1836; and Dunglison's Amer. Med. In- telligencer, p. 30, April 15, 1837. MECHANICAL PHENOMENA—INSPIRATION. 33 tion at present. Haller1 attempted to account for the phenomenon by the passage of the blood through the lungs being impeded during ex- piration,—a reflux of blood into the veins, and a degree of pressure upon the brain, being thus induced; hence a painful sensation of suffo- cation in consequence of which the muscles of inspiration are called into action by the will, for the purpose of enlarging the chest, and, in this way, removing the impediment. The same uneasy feelings, how- ever, ensue from inspiration, if too long protracted: the muscles cease to act, and, by their relaxation, the opposite state of the chest is in- duced. Whytt2 conceived, that the passage of the blood through the pulmonary vessels is impeded by expiration, and a sense of anxiety is thus produced. The unpleasant sensation acts as a stimulus upon the nerves of the lungs and the parts connected with them, which arouses the energy of the sentient principle; and this, by acting in a reflex manner, causes contraction of the diaphragm, enlarges the chest, and removes the painful feeling. The muscles then cease to act, in conse- quence of the stimulus no longer existing. These, and all other me- thods of accounting for the phenomena, are, however, too pathological. From the first moment of respiration the process appears to be accom- plished without the slightest difficulty, and to be as much a part of the instinctive extra-uterine actions of the frame, as circulation, digestion, or absorption. It is obviously an internal sensation, after respiration has been once established; and, like all internal sensations, is inexpli- cable in our existing state of knowledge. The part which developes the impression is probably the lung, through its ganglionic nerves ; and the pneumogastric nerves convey the impression to the brain or spinal marrow, which calls into action the muscles of inspiration. We say, that the action of impression arises in the lungs, and this, from some internal cause, connected with the office to be filled in the economy: but in so saying we sufficiently exhibit our total want of acquaintance with its nature. The movements of inspiration and expiration, which, together, con- stitute the function of respiration, are entirely accomplished by the dilatation and contraction of the thorax. Air enters the chest when the latter is expanded; and is driven out when the chest is restored to its ordinary dimensions;—the thorax thus seeming to act like an ordi- nary pair of bellows with the valve stopped : when the sides are sepa- rated, the air enters at the nozzle, and when they are brought together, it is forced out. (1.) INSPIRATION. The augmentation of the capacity of the thorax, which constitutes inspiration, may be effected to a greater or less extent, according to the number of muscles that are thrown into action. The chest may, for example, be dilated by the diaphragm alone. This muscle, as we have seen, in its ordinary relaxed condition, is convex towards the chest. When, however, it contracts, it becomes more horizontal; in 1 Elementa Physiologise, viii. 4, 17, Lausann., 1764.1 2 An Essay on the Vital and other Involuntary Motions of Animals, sect, viii., Edinb., 1751. VOL. II.—3 34 RESPIRATION. this manner augmenting the cavity of the chest in a vertical direction. The sides or lateral portions of the diaphragm, which are fleshy and correspond to the lungs, descend more, in this movement, than the central, tendinous portion, which is moreover kept immovable by its attachment to the sternum, and its union with the pericardium. In the gentlest of all breathing, the diaphragm appears to be the sole agent of inspiration; and in cases of inflammation of the pleura cos- talis, or of fractured rib, our endeavours are directed to the prevention of any elevation of the ribs by which the diseased part might be put upon the stretch. Generally, however, as the diaphragm descends, the viscera of the abdomen are compressed; the abdominal muscles relaxed; the abdomen is rendered more prominent, and the ribs and the breast bone are raised so that the latter is protruded. When the diaphragm acts, and, in addition, the ribs and sternum are raised, the cavity of the chest is still farther augmented. Fig. 271. Fig. 272. The Changes of the Thoracic and Ab- dominal Walls of the Male during Respiration. The back is supposed to be fixed in or- der to throw forward the respiratory move- ment as much as possible. The outer black continuous line in front represents the ordinary breathing movement: the an- terior margin of it being the boundary of inspiration, the posterior margin the limit of expiration. The line is thicker over the abdomen, since the ordinary respiratory movement is chiefly abdominal: thin over the chest, for there is less movement over that region. The dotted line indicates the movement on deep inspiration, during which the sternum advances while the ab- domen recedes. The Respiratory Movements in the Female. The lines indicate the same changes as in the last figure. The thickness of the continuous line over the sternum shows the larger extent of the ordinary breathing movement over that region in the female than in the male. In young children inspiration is effected almost wholly by the dia- phragm; and as in diaphragmatic breathing the movement of the MECHANICAL PHENOMENA—INSPIRATION. 35 parietes of the abdomen is more marked than that of any other part, this has been termed the abdominal mode or type of respiration. In adult men, the lower part of the chest and sternum move more largely than in women; who, owing to greater mobility of the first rib, have a more extensive movement of the upper than of the lower part of the chest,—an arrangement which, it has been suggested, may have for its object the providing of sufficient space for respiration when the lower part of the chest is encroached upon by the pregnant uterus. The former is called by MM. Beau and Maissiat the costo-inferior or inferior costal; the latter the costo-superior or superior costal type of respiration.1 From the admeasurements of Mr. Sibson2 it appears, that in health the inspiratory movement of the walls of the chest, during tranquil breathing, is only from two to six-hundredths of an inch; whilst that of the abdomen is about three-tenths of an inch. During a deep in- spiration, the expansive motion of the walls of the chest is, in front, about one inch; and at the sides about two-thirds of an inch; and that of the abdomen about one inch. The expansion of the two sides of the chest is nearly equal; the left side does not, however, expand quite so much as the right over the lower two-thirds, owing to the position of the heart. The mechanism, by which the ribs are elevated, has been productive of more controversy than the subject merits. Haller3 asserted, that the first rib is immovable, or at least admits of but trifling motion when compared with the others; and he denied that the thorax, as a whole, makes any movement of either elevation or depression; affirming that the ribs are raised successively towards the top of the cavity; and this to a greater extent as they are more distant from the first. M. Magendie,4 on the other hand, denies that they are elevated in this manner; and endeavours to show that they are all raised at the same time; that the first rib, instead of being the least movable, is the most so; and that the disadvantage, which the lower ribs possess in the movement, by their admitting of less motion in their posterior articu- lations, is compensated by the greater length of those ribs. This com- pensation he considers to have its advantages; for as the true ribs, with their cartilages and the sternum, usually move together, and the motion of one of these parts almost always induces that of the rest, it would follow, that if the lower ribs were more movable, they could not execute a more extensive movement than they do; whilst the solidity of the thorax would be diminished. By the elevation, then, of the ribs, and the depression of the dia- phragm, the chest is augmented, and a deeper inspiration effected than when the diaphragm acts singly. In this elevation of the ribs, we see the advantage of their obliquity as regards the spine. Had they been horizontal, or inclined obliquely upwards, any elevation would neces- 1 Archives Generates de Medecine, iii. 263, Paris, 1843 j also, Kirkes and Paget, Manual of Physiology, Amer. edit., p. 127, Philad., 1849. 1 Provincial Medical and Surgical Journal, Sept. 5, 1849. 3 Elementa Physiologia>, viii. 4, Lausann., 1764. 4 Precis, &c., 2de edit., ii. 316. 36 RESPIRATION. sarily have contracted the thoracic cavity, and thus favoured expiration instead of inspiration. The muscles chiefly concerned in inspiration are the intercostals, and those that arise, either directly or indirectly from the spine, head, or upper extremities, and that can, in any manner, elevate the thorax. Amongst these are the scaleni antici and postici, levatores costarurn, the muscles of the neck, which are attached to the sternum, &c. The elasticity of the cartilages, and the weight of the osseous portions of the parietes of the chest, must afford considerable resistance to the action of the inspiratory muscles in dilating it. It is probable, how- ever, that the estimates of Dr. Hutchinson1 are far above the reality. He calculates, that the force which the muscles of inspiration have to overcome in ordinary breathing from these sources is probably at least equal to about 100 lbs.; and in deep inspiration to about 300 lbs.; and yet, in these calculations, the additional resistance from the elasticity of the lungs is not taken into the account. As no air exists in the cavity of the pleura, it necessarily happens, that when the capacity of the chest is augmented, the residuary air, contained in the air-cells of the lungs after expiration, is rarefied; and, in consequence, the denser air without enters the larynx by the mouth and nose, until the air within the lungs has attained the density, which the residuary air had, prior to inspiration,—not that of the external air, as has been affirmed.2 At the time of inspiration, the glottis opens by the relaxation of the arytenoidei muscles, as M. Legallois3 proved by experiments performed at the Ecole de Medecine of Paris. On expos- ing the glottis of a living animal, the aperture is found to dilate dis- tinctly at each inspiration, and contract at each expiration. If, according to M. Magendie, the eighth pair of nerves be divided low down in the neck, and the dilator muscles of the glottis, which receive their nerves from the recurrents—branches of the eighth pair—be thus paralysed, the aperture is no longer enlarged during inspiration, whilst the con- strictors—the arytenoidei muscles, which receive their nerves from the superior laryngeal,—given off above the point of section, preserve their action, and close the glottis more or less completely. When air is inspired through the mouth, the velum is raised, so as to allow it to pass freely to the glottis; and, in forced inspiration, it is so horizontal as to completely expose the pharynx to view. The physi- cian takes advantage of this in examining morbid affections of those parts, and can often succeed much better in this way than by pressing down the tongue. On the other hand, when inspiration is effected entirely through the nose, the velum palati is depressed until it becomes vertical, and there are no obstacles to the free entrance of the air into the larynx. In such case, where difficulty of breathing exists, the small muscles of the alae nasi are frequently thrown into violent action, al- ternately dilating and contracting the apertures of the nostrils: hence this is a common symptom in pulmonary affections. 1 Medico-Chirurgical Transactions, xxix. 205, London, 1846. 2 Animal Physiology, Library of Useful Knowledge, p. 100, Lord., 1829 3 (Euvres, p. 177, Paris, 1824. MECHANICAL PHENOMENA—INSPIRATION. 37 Mayow1 conceived, that air enters the lungs in inspiration as it would a bladder put into a pair of bellows, and communicating with the ex- ternal air by the pipe of the instrument. The lungs, however, are not probably so passive as this view would indicate. In cases of pulmonary hernia, the extruded portion has been observed to dilate and contract in inspiration and expiration. Reisseisen believed this to be owing to muscular fibres, which Meckel and himself conceived to make the whole circuit of the bronchial ramifications. They are not, however, gene- rally admitted by anatomists; and the phenomenon is usually ascribed to the bronchi having in their composition the highly elastic tissue, which is an important constituent of arteries. Laennec2 affirms, that he has endeavoured, without success, to verify the observations of Reisseisen; but that the manifest existence of circular fibres in branches of a mo- derate size, and the phenomena presented by many kinds of asthma, induce him to consider the temporary constriction and occlusion of the minute bronchial ramifications as a thing established. The muscular action of the lungs may, indeed, be demonstrated by galvanizing them shortly after they have been taken from the body; when they con- tract so as to lift up water placed in a tube introduced into the trachea;3 and it is affirmed by M. Longet4 and by Volkmann,5 that they may be made to contract by stimulating their nerves. The latter physiologist tied a glass tube, drawn fine at one end, into the trachea of a decapitated animal; and when the small end was turned to the flame of a candle, he galvanized the trunk of the pneumogastric nerve. On each appli- cation, the flame was blown upon; and once it was extinguished. In the trachea, an obvious muscular structure exists in the posterior third, where the cartilages are wanting. There it consists of a thin muscular plane, the fibres of which pass transversely between the inter- rupted extremities of the cartilaginous rings of the trachea and bronchi, to which a layer of longitudinal fibres may at times be seen superadded.6 The use of the transverse muscular tissue, as suggested by Dr. Physick,7 and after him by M. Cruveilhier and Sir Charles Bell,8 is to diminish the calibre of the air-tubes in expectoration; so that the air having to pass through the contracted portion with greater velocity, its momentum may remove the secretions that are adherent to the mucous membrane. The explanation is ingenious and probably just. M. Magendie9 asserts, that the lung has a constant tendency to return upon itself, and to occupy a smaller space than it fills ; and that it con- sequently exerts a degree of traction on every part of the parietes of the thorax. This traction has but little effect upon the ribs, which cannot ' Tractatus Quinque, p. 271, Oxon., 1674. 2 On the Diseases of the Chest, &c, 4th edit., Lond., 1834: reprinted in this country, Philad., 1835. 3 C. J. B. Williams, Report of the Meeting of the British Association, in Athenaeum for 1840, p. 802. 4 Traite de Physiologic, ii. 328, Paris, 1850. 5 Art. Nervenphysiologie, in Wagner's Handworterbuch der Physiologie, lOte Lieferung, s. 586, Braunschweig, 1845. 6 Goddard, in Wilson's Anatomist's Vade-Mecum, Amer. edit., p. 404, note, Philad., 1843. i Horner's Lessons in Practical Anat., p. 179, Philad., 1836. 8 Philos. Transact, for 1832, p. 301. » Precis, &c, ii. 325. 38 RESPIRATION. yield; but upon the diaphragm it is considerable. It is, in his opinion, the cause why that muscle is always tense, and drawn so as to be vaulted upwards; when the muscle is depressed during contraction, it is compelled to draw down the lungs towards the base ot the cnest, so that they are stretched, and by virtue of their elasticity have a powerful tendency to return upon themselves, and draw the diaphragm upwards. If a puncture be made into the chest in one of the intercos- tal spaces, the air will enter the chest through the aperture, and the lung will shrink. By this experiment, the atmospheric pressure is equalized on both surfaces of the lung, and the organ assumes a bulk determined by its elasticity and weight. Owing to this resiliency of the lungs, and to their consequent tendency to recede from the pleura costalis, there is less pressure upon all the parts against which the lungs are applied; and, accordingly, the heart is not exposed-to the same degree of pressure as the parts external to the chest; and the degree of pressure is still farther reduced, when the chest is fully dilated, the lungs farther expanded, and their elastic resiliency increased. Dr. Carson1 states, that in his experiments on calves, sheep, and large dogs, the resiliency of the lungs was found to be balanced by a column of water, varying in height from a foot to a foot and a half; and in rabbits and cats by a column varying in height from six to ten inches. Many physiologists have pointed out three degrees of inspiration, but it is manifest that there may be innumerable shades between them: —1. Ordinary gentle inspiration, owing simply to the action of the dia- phragm ; or, in addition, to a slight elevation of the ehest. 2. Deep inspiration, when, with the depression or contraction of the diaphragm, there is evident elevation of the thorax ; and, lastly, forced inspiration, when the air is strongly drawn in by the rapid dilatation produced by the action of all the respiratory muscles that elevate the chest directly or indirectly. Trials have been instituted for determining the quantity of air taken into the lungs at an inspiration ; and considerable diversity, as might be expected, exists in the evaluations of different experimenters.2 We have just remarked, that, in the same individual, the inspiration may be gentle, deep, or forced; and, in each case, the quantity of air in- spired will necessarily differ. There is, likewise, considerable diver- sity in individuals; so that an approximation can alone be attained. The following table sufficiently exhibits the discordance on this point. Many, however, of the estimates, which seem so discrepant, may pro- bably be referred to imperfection in the mode of conducting the expe- riment, as well as to the causes .above mentioned:— 1 Philosophical Transactions, for 1820, p. 42. 2 Dr. Marshall Hall has devised a pneumatometer for this purpose. See art. Irritability,in Cyclop, of Anat. and Physiol., July, 1840. MECHANICAL PHENOMENA—EXPIRATION. 39 ' Cubic inches at each Inspiration. Cubic inches at each Inspiration. Reil, ...... 42 to 100 40 35 to 38 35 30 to 40 Jeffreys,..... Herholdt, .... Jurine and Coathupe, Allen and Pepys, . . T. Thomson, . . . J. Borelli, .... Goodwin, .... Sir H. Davy, . . . Abernethy and Mojon, 30 26 24 to 30 20 to 29 20 16£ 16 15 to 40 14 13 to 17 12 6 to 12 Menzies, Sanvages, Hales, Haller, Ellis, Sprengel, Sommering, Thomson, Bostock, > . . Richerand, .... In passing through the mouth, nasal fossae, pharynx, larynx, tra- chea, and bronchi, the inspired air acquires nearly the temperature of the body; and, if it be cool, the same quantity by weight occupies a much larger space in the lungs, owing to its rarefaction in those organs. According to Valentin, the temperature of the expired air is 99°*5 Fahr., when breathing an atmosphere of moderate temperature. In its passage, too, it becomes mixed with the halitus, that is constantly ex- haled from the mucous membrane of the air-passages : in this condition, it enters the air-cells, and becomes mixed, by diffusion, with the residu- ary air. It is obvious, that if we knew the exact capacity of the lungs in an individual in health, we might be able to determine the extent of solidi- fication in pulmonary affections by the diminution in their capacity. Owing, however, to our want of this requisite preliminary knowledge, the test is not of much' avail. (2.) EXPIRATION. An interval, scarcely appreciable, elapses after the accomplishment of inspiration, before the reverse movements of expiration succeeds; and the air is expelled from the chest. The great cause of this expul- sion is the restoration of the chest to its former dimensions; and the elasticity of the yellow tissue composing the bronchial ramifications, which has been put upon the stretch by the air rushing into them during inspiration. The restoration of the chest to its dimensions may be effected simply by the cessation of the contraction of the muscles, that have raised it, and the elasticity of the cartilages, that connect the bony portions of the ribs with the sternum or breast-bone. In active expiration, however, the ribs are depressed by the contraction of appropriate muscles, and the chest is still farther contracted. The chief expiratory muscles are the triangularis sterni, the broad muscles of the abdomen, rectus abdominis, sacro-lumbalis, longissimus dorsi, serratus posticus inferior, &c. Haller1 conceived that the ribs, in expiration, are successively depressed towards the last rib ; which is first fixed by the abdominal muscles and quadratus lumborum. The intercostal mus- ' Element. Physiol., viii. 4, Lausann., 1764. 40 RESPIRATION. cles then act, and draw the ribs successively downwards. M. Magen- die1 contests the explanation of Haller; and the truth would seem to be, that the muscles just mentioned, participate with the intercostals in every expiratory movement. By this action, the capacity of the chest is diminished ; the lungs are correspondently pressed upon, and the air issues by the glottis. It has been already remarked, that, during expi- ration, the arytenoidei muscles contract, and the glottis appears to close. Still, space sufficient is left to permit the exit of the air. It has been asked:—Is the air expired precisely that which has been taken in by the previous inspiration? It is impossible to empty the lungs wholly by the most forced expiration. A portion still remains; and hence it has been assumed, that the use of inspiration is to con- stantly renew the air remaining in the air-cells. On this subject we are not well-informed; but it is probable, that the lighter and more rarefied air mixes, by diffusion, with the newly-arrived and denser. Many experiments have been made to determine the change of bulk which air experiences by being respired. According to Sir Humphry Davy,2 it is diminished, by a single inspiration, from ^th to T^o*Q part of it's bulk. Cuvier makes it about g^th; Allen and Pepys a little more than one-half per cent. Berthollet from 0*69 to 3*70 per cent.; and Bostock ^th,—as the average diminution. Assuming this last estimate to be correct, and forty cubic inches to be the quantity drawn into the lungs at each inspiration, it would follow, that half a cubic inch disappears each time we respire. This, in a day, would amount to 14,400 cubic inches, or to rather more than eight cubic feet. The experiments of MM. Dulong and Despretz make the diminution con- siderable. The latter gentleman placed six small rabbits in forty-nine quarts of air for two hours, at the expiration of which time the air had diminished one quart. A portion of the inspired air must, conse- quently, be absorbed. In the ordinary respiration of men from seventeen to thirty-three years old, Valentin3 has calculated, from the watery vapour contained in the saturated expired air, that the average quantity of air expired in a minute is 400 cubic inches,—the extremes under varying circum- stances being 234 and 686 cubic inches, and the average quantity of one ordinary expiration 31-1 cubic inches; the extremes in very tran- quil and somewhat hurried respiration 11-4 and 74 cubic inches. Mr. Paget,4 however, thinks that Mr. CoathupeV estimate of 20 to 25 cubic inches is probably better, inasmuch as it was drawn from the results of respiration continued during a longer period and with less restraint than in the experiments of Valentin. Of late, some interesting experiments have been made by Dr. Hutchinson,6 with an instrument somewhat unhappily termed by him a spirometer, by which he measures: the quantity of air expired in a full 1 Precis, &c, ii. 324. 2 Researches, Chemical and Philosophical, p. 431, Lond., 1800. 3 Lehrbuch der Physiologie des Mensehen, i. 542, Braunschweig, 1844. < Kirkes and Paget, Manual of Physiology, Amer. edit., p. 128, Philad., 1849. 6 Philos. Magazine, June, 1839. 6 Medico-Chirurgical Review, xxix. p. 237, Lond., 1846. MECHANICAL PHENOMENA—EXPIRATION. 41 and forcible expiration, and which he esteems an index of the vital capacity, as it expresses the power which a person has of breathing in the exigencies of active exercise, violence, and disease. From the results of 1923 observations made on males, he has inferred, that for every inch of height—from five feet to six—eight additional cubic inches of air at 60° Fahr. are given out by a forced expiration; so that, he believes, from the height alone of an adult male, he can pronounce what quantity of air he should breathe when healthy. Dr. Hutchinson gives the following table of the quantity. of air, expelled by the strongest expiration after the deepest inspiration, for every inch of height between five and six feet, as ascertained by actual observation with the spirometer, and as calculated by the rule of pro- gression referred to above. Height. Ft. in. Ft. in 5 0 to 5 1 5 1 " 5 2 5 2 " 5 3 5 3 " 5 4- 5 4 " 5 5 5 5 " 5 6 5 6 " 5 7 5 7 " 5 8 5 8 " 5 9 5 9 " 5, 10 5 10 " 5 11 5 11 " 6 0 From Observation. Regular Progression Cub. in. Cub. in. 174 174 177 182 189 190 193 198 201 206 214 214 229 222 228 230 237 238 246 246 247 254 259 262 Dr. Hutchinson found, that two other conditions influence the quan- tity of air that passes to and from the lungs in forced voluntary respi- ration,—weight, and age. The former does not affect the respiratory power of an individual of any height between five feet one inch and five feet eleven inches, until it has increased seven per cent, above the average weight of the body in persons of that height; but, beyond this, it diminishes in the ratio of one cubic inch per pound for the next 35 pounds,—the limit of his calculations. In males of the same height the respiratory power is increased from 15 to 35 years of age; but from 35 to 65 years it decreases nearly 1J cubic inch for each year;1 and the results of the examinations are so nearly uniform, that it has been inferred, disease may be suspected in any man wno cannot blow out nearly as many cubic inches as the average of those of the same height, even when by external measurement his chest appears to be of full size. The size of the chest is, indeed, stated to afford no good indication of the capacity of expiration. The only exceptions among the healthy to the general rule of the direct propor- tion between the height of the body and the capacity of expiration, are in the cases of fat persons, whose capacity is always low. It was the observation—made by M. Bourgery2—that thin men have the greatest capacity of respiration, which first led Dr. Hutchinson to the experiments, that furnished the law given above. He found, that the 1 For the quantity of air inspired and expired in forced respiration, see Hales, Statical Essays, i. 242, and Bostock, System of Physiology, p. 316, Lond., 183U. 2 Archiv. Generates de Medecine, Mars, 1843. 42 RESPIRATION. full expiratory force of a healthy man is commonly about one-third greater than his inspiratory force; and he states, that whenever the expiratory are not stronger than the inspiratory muscles, some Qjseue is present. In examining the results of all his experiments—1500 in number—he found the power of the inspiratory muscles was greatest m men of five feet nine inches in height,—their inspiratory powers being equal, on an average, to a column of 2*75; and their expiratory power to one of 3-97 inches of mercury; whilst in four of the classes, composed generally of active, efficient and healthy individuals, namely Firemen, Metropolitan Police, Thames Police, and Royal Horse Guards, the inspiratory power of the men of five feet seven inches was the greatest, being equal to 3-07 inches of mercury; and those of five feet eight inches to 2-96, or nearly three inches. The average power of the five feet seven inches and five feet eight inches men of all classes examined was only 2*65 inches of mercury. He infers, from all his experiments, that a healthy man of the height of five feet seven inches or five feet eight inches ought to elevate by inspiration a column of mercury of three inches. The experiments of Valentin1 and Mendelssohn,2 as far as they go, confirm those of Dr. Hutchinson. Attempts have been made to estimate the quantity of air remaining in the lungs after respiration; but the sources of discrepancy are here as numerous as in the cases of inspiration or expiration. Goodwyn3 estimated it at 109 cubic inches: Menzies4 at 179; Jurin5 at 220; Fontana6 at 40; and Cuvier, after a forced inspiration, at from 100 to 60. Davy7 concluded, that his lungs, after a forced expiration, still retained 41 cubic inches of air; and after a natural expiration 118 cubic inches; after a natural inspiration, 135 ; and after a forced inspiration, 254. Vierordt8 supposes that the residual air after the deepest expira- tion is about 36.600 cubic inches. By a full forced expiration after a forced inspiration, he expelled 190 cubic inches; after a natural inspira- tion, 78-5; and after a natural expiration, 67'5. Mr. Julius Jeffreys9 divides the air of respiration into four quantities—First, the residual air, or that which cannot be expelled from the lungs, but remains after a full and forcible expiration; which he estimates at 120 cubic inches— Secondly, the supplementary air,—reserve air of Dr. Hutchinson—or that which can be expelled by a forcible expiration, after an ordinary outbreaking, valued at 130 cubic inches— Thirdly, the breath, or tidal air,—breathing air of Dr. Hutchinson—valued at 26 cubic inches; and Fourthly, the complementary or complemental air, or that which can be inhaled after an ordinary inspiration, which amounts to 100 cubic inches. 1 Lehrbuch der Physiologie des Menschen, i. 524, Braunschweig, 1844. 2 Der Mechanismus der Respiration und Circulation, Berlin, 1845: cited by Dr. John Reid, op. cit., p. 336. 3 3 Op. citat., p. 36. 4 Op. citat., p. 31. * Philosoph. Trans., vol. xxx. p. 758. e Phiios. Trans, for 1799, p. 355. 7 Op. citat., p. 411. 8 Art. Respiration, in Wagner's Handworterbuch der Physiologie, u. s. w. 12teLieferung, Braunschweig, 1845. » Views upon the Statics of the Human Chest, &c, London, 1843. MECHANICAL PHENOMENA—EXPIRATION. 43 This estimate gives 250 cubic inches as the average volume which the chest contains after an ordinary expiration. It is impossible, from such variable data as the above, to deduce any thing like a satisfactory conclusion; but if we assume with Dr. Bostock, and Dr. Thomson1 is disposed to adopt the estimate, 170 cubic inches as the quantity that may be forcibly expelled, and that 120 cubic inches will be left in the lungs, we shall have 290 cubic inches as the measure of the lungs in their natural or quiescent state; to this quantity 40 cubic inches are added by each ordinary inspiration, giving 330 cubic inches as the measure of the, lungs in their distended state. Hence it would seem, that about one-eighth of the whole contents of the lungs is changed by each respiration; and that rather more than two-thirds can be expelled by a forcible expiration. Supposing that each act of respiration occupies three seconds, or that we respire twenty times in a minute, a quantity of air, rather more than 2f times the whole contents of the lungs, will be expelled in a minute, or about four thousand times their bulk in twenty-four hours. The quantity of air respired during this period will be 1,152,000 cubic inches, about 666J cubic feet. Such is Dr. Bostock's estimate. It is the residuary air, that gives to the lungs the property of floating on the surface of water, after they have once received the breath of life; and no pressure can force out the air, so as to make them sink. Hence, the chief proofs, whether a child has been born alive or dead, are deduced from the lungs. These constitute docimasia pulmonum, Lungenprobe or A them probe, ("Lung-proof or Respiration- proof,") of the Germans. Expiration, like inspiration, has been divided into three grades; ordinary, free, and forced; but it must necessarily admit of multitu- dinous shades of difference. In ordinary passive respiration, expiration is effected solely by the relaxation of the diaphragm. In free active respiration, the muscles that raise the ribs are likewise - relaxed, and there is a slight action of the direct expiratory muscles. In forced expiration, all the respiratory muscles are thrown into action. In this manner, the air makes its way along the air passages through the mouth or nostrils, or both; carrying with it a fresh portion of the halitus from the mucous membrane. This it deposits when the atmosphere is colder than the temperature acquired by the respired air, and if the atmosphere be sufficiently cold, as in winter, the vapour becomes condensed as it passes out, and renders expiration visible. Dr. Hutchinson2 measured the costal movement during ordinary respiration in healthy males, and found it not to exceed from two to four-tenths of a line. He states, that the difference between the cir- cumference of an ordinary man's chest measured over the nipples in the two states of a deep inspiration and a deep expiration amounts to three inches; and Valentin,3 under the same circumstances, found the average difference in the circumference of the chest, measured over the 1 System of Chemistry, vol. iv. 2 Medico-Chirurgical Transactions, xxix. 187, Lond., 1846. 3 Lehrbuch der Physiologie des Menschen, i. 541, Braunschweig, 1844. 44 RESPIRATION. scrobiculus cordis, in seven individuals of the male sex between 17-g and 33 years of age, to be as 1 : 8-29 of the whole circumference. If the whole time occupied by a respiratory act,—that is, from the beginning of one inspiration to the beginning of the next,—be repre- sented by 10, the time occupied by the inspiratory movement has been estimated approximately at 5; that of the expiratory at 4; and the pause between the expiratory and succeeding inspiratory movement at 1. The number of respirations in a given time differs considerably in different individuals. Dr. Hales,1 Dr. Dalton,2 Mr. Coathupe3 and Dr. Bostock4 reckon them at twenty. Laennec from 12 to 15. A man, on whom Menzies made experiments, breathed only fourteen times in a minute. Sir Humphry Davy5 made between twenty-six and twenty- seven in a minute. Dr. Thomson,6 and Allen and Pepys, about nine- teen; and Magendie,7 fifteen. In 1714 adults of the male sex considered to be in a state of health Dr. Hutchinson8 found, that the majority, in the sitting posture, breathed between 16 and 24 in the minute; and of these a great number 20 per minute. Vierordt9 found the number in his own person to be, on an average, ll/^ths when sitting and the mind disengaged; whilst the maximum was 15, and the minimum 9. Our own average is about sixteen; and this is the average, in the adult, assumed by Giinther10 and Berthold.11 That, deduced from the few observers, whojiave recorded their observations,—twenty per minute,— has generally been taken; but we are satisfied it is above the truth; eighteen Avould be nearer the general average, and it has accordingly been admitted by many. Eighteen in a minute give twenty-five thou- sand nine hundred and twenty in the twenty-four hours. The number is influenced, however, by various circumstances. The child and the female, and perhaps also the aged, breathe more rapidly than the adult male. MM. Hourmann and Dechambre12 examined two hundred and fifty-five women between the ages of sixty and ninety-six, the average number of whose respirations was 21-79 per minute. We find as much variety in men as we do in horses: whilst some are short, others are long-winded; and this last condition may be improved by appropriate training, to which the pedestrian and the prize-fighter, equally with the horse, are subjected for some time before they are called upon to test their powers. In sleep, the respiration is generally deeper, less frequent, and appears to be performed greatly by the intercostals and diaphragm.13 Motion has also a sensible effect in hurrying the respiration, as well as 1 Statical Essays, 3d edit., i. 243. 2 Memoirs of the Literary and Philosophical Society of Manchester, 2d series, ii. 26, Manchester, 1813. 3 Lond. and Edinb. Philos. Magaz., xiv. 401, 1839. 4 System of Physiology, p. 321, Lond., 1836. 5 Researches chiefly concerning Nitrous Oxide, p. 434, Lond., 1800. 6 System of Chemistry, iv. 604, Glasgow, 1820. "> Precis de Physiologie, 2de edit.. Paris, 1825. « Op. cit., p. 226. 9 Wagner's Handworterbuch derPhvsiologie.art. Respiration, ii. 834, Braunschweig, 1845. ■° Lehrbuch der Physiologie des Menschen, 2 Band., 1 Abtheil., s. 217, Leipzig, 1848. 11 Lehrbuch der Physiologie, dritte Auflage, 2ter Theile, s. 227, Gotting., 1848. 12 Archiv. Genev. de Medecine, Nov., 1835. 13 Adelon, Physiologie de l'Homme, iii. 185. MECHANICAL PHENOMENA—STRAINING. 45 distension of the stomach by food, certain mental emotions, &c.: its condition during disease becomes also a subject of interesting study to the physician, and one that has been much facilitated by the acoustic method introduced by Laennec. To his instrument—the stethoscope— allusion has already been made. By it, or by the ear applied to the chest% we are able to hear distinctly the respiratory murmur and its modifications; and thus to judge of the nature of*"pulmonary affections. But this is a topic that appertains more especially to pathology. (3.) RESPIRATORY PHENOMENA CONCERNED IN CERTAIN FUNCTIONS. There are certain respiratory movements, concerned in effecting other functions, that require consideration. Some of these have already been discussed. M. Adelon1 has classed them into: First. Those employed in the sense of smell, either for the purpose of conveying the odorous molecules into the nasal fossae; or to repel them and prevent their in- gress. Secondly. The inspiratory actions employed in the digestive func- tion, as in sucking. Thirdly. Those connected with muscular motion when forcibly exerted; and particularly with straining or the employ- ment of violent effort. Fourthly. Those concerned in the various ex- cretions, either voluntary,—as in defecation and spitting; or involun- tary,—as in coughing, sneezing, vomiting; accouchement, &c; and lastly, those that constitute phenomena of expression,—as sighing, yawning, laughing, crying, sobbing, &c. Some of these, that have already en- gaged attention, do not demand comment; others are topics of considera- ble interest, and require investigation. 1. Straining.—The state of respiration is much affected during the more active voluntary movements. Muscular exertion of whatever kind, when considerable, is preceded by a long and deep inspiration; the glottis is closed; the diaphragm and respiratory muscles of the chest are contracted, as well as the abdominal muscles which press upon the contents of the abdomen in all directions. Whilst the proper respira- tory muscles are exerted, those of the face participate, owing to their association through the medium of particular nerves. By this series of actions, the chest is rendered capacious; and the force that can be de- veloped is augmented, in consequence of the trunk being rendered immovable as regards its individual parts,—thus serving as a fixed point for the muscles that arise from it, so that they are enabled to employ their full effort.2 The physiological state of muscular action, as con- nected with the mechanical function of respiration, is happily described by Shakspeare, when he makes the fifth Harry encourage his soldiers at the siege of Harfleur. "Stiffen the sinews, summon up the blood; Now set the teeth, and stretch the nostrils wide; Hold hard the breath and bend up every spirit To its full height." King Henkt V. Hi. 1, In the effort required for effecting the various excretions, a similar action of the respiratory muscles takes place. The organs, from which 1 Op. cit., p. 188. 2 Ibid., p. 190; and art. Effort, in Diet, de MeU, 2de edit., xi. 197, Paris, 1835. 46 RESPIRATION. these excretions have to be removed, are either in the thorax or abdo- men; and in all cases have to be compressed by the parietes of those cavities. A full inspiration is first made; the expiratory muscles, with those that close the glottis, are then forcibly and simultaneously con- tracted, and by this means the thoracic and abdominal viscera are compressed. Some difference, however, exists, according as the viscua to be emptied is seated in the abdomen or thorax. In the evacuation of the feces, the lungs are first filled with air; and whilst the muscles of the larynx contract to close the glottis, those of the abdomen con- tract also; and as the lung, in consequence of the included air, resists the ascent of the diaphragm, the compression bears upon the large in- testine. The same happens in the excretion of the urine, and in ac- couchement. 2. Coughing and Sneezing.—When the organs that have to be cleared are the air-passages,—as in coughing to remove mucus from them,—- the same action of the muscles of the abdomen is invoked; but the glottis is open to allow the exit of the mucus. In this case, the expi- ratory muscles contract convulsively and forcibly, so that the air ia driven violently from the lungs; and, in its passage, sweeps off the irritating matter, and conveys it out of the body. To aid this, the muscular fibres, at the posterior part of the trachea and larger bron- chial tubes, contract, so as to diminish the calibre of these canals; and in this way expectoration is facilitated. The action differs, however, according as the expired air is sent through the nose or mouth; in the former case, constituting sneezing; in the latter, coughing. The former is more violent than the latter, and is involuntary; whilst the latter ia not necessarily so. In both cases the movement is excited by some external irritant, applied directly to the mucous membrane of the wind- pipe or nose; or by some modified action in the very tissue of the part, which acts as an irritating cause. In both cases the air is driven forci- bly forwards; and both are accompanied by sounds that cannot be mistaken. In these actions, we have striking exemplifications of the extensive association of muscles, through the medium of nerves, to which we have so often alluded. The pathologist, too, has repeated opportunities for observing the extensive sympathy between distant parts of the frame, as indicated by the actions of sneezing and cough- ing, especially of the former. If a person be exposed for a short period to the partial and irregular application of cold, so that the capillary action of a part of the body is modified, as where we get the feet wet, or sit in a draught of air, a few minutes is frequently sufficient to ex- hibit sympathetic irritation in the Schneiderian membrane of the nose, and sneezing. Nor is it necessary, that the capillary action of a distant part shall be modified by the application of cold. We have had the most positive evidence, that if the capillary circulation be irregularly excited, even by the application of heat, whilst the rest of the body is receiving none, inflammation of the mucous membrane of the nasal fossae and fauces may supervene with no less certainty. 3. Blowing the Nose.—The substance that has to be excreted by this operation is composed of the nasal mucus, the tears sent down the ductus ad nasum, and the particles deposited on the membrane by the MECHANICAL PHENOMENA—SIGHING. 47 air in its passage through the nasal fossse. Commonly, these secretions are only present in quantity sufficient to keep the membrane moist, the remainder being evaporated or absorbed. Frequently, however, they exist in such quantity as to fall by their own gravity into the pharynx, where they are sent down into the stomach by deglutition, are thrown out at the mouth, or make their exit at the anterior nares. To prevent this last effect more especially, we have recourse to blowing the nose. This is accomplished by taking in air, and driving it out suddenly and forcibly, closing the mouth at the same time, so that the air may issue by the nasal fossse and clear them; the nose being compressed so as to make the velocity of the air greater, as well as to express all the mucus that may be forced forwards. 4. Spitting differs somewhat according to the part in which the mucus or matter to be ejected is seated. At times, it is exclusively in the mouth; at others, in the back part of the nose, pharynx, or larynx. When the mucus or saliva of the mouth has to be excreted, the muscular parietes of the cavity, as well as the tongue, contract so as to eject it from the mouth; the lips being at times approximated, so as to render the passage narrow, and impel the sputa more strongly forward. The air of expiration may be, at the same time, driven forcibly through the mouth, so as to send, the matter to a considerable distance. The prac- tised spitter sometimes astonishes us with the accuracy and power of propulsion of which he is capable. % When the matter to be evacuated is in the nose, pharynx, or larynx, it requires to be brought, first of all, into the mouth. If in the posterior nares, the mouth is closed, and the air is drawn in forcibly through the nose, the pharynx being at the same time constricted so as to prevent the substances from passing down into the oesophagus. The pharynx now contracts from below to above, in an inverse direction to that required in deglutition; and the farther excretion from the mouth is effected in the manner just described. Where the matters are situate in the air passages, the action may consist in coughing; or, if higher up, simply in hawking. A forcible expiration, unaccompanied by cough, is, indeed, in many cases, suffi- cient to detach the superfluous mucous secretion from even the bronchial tubes. In hawking, the expired air is sent forcibly forwards, and the parts about the fauces are suddenly contracted so as to diminish the capacity of the tube, and propel the matter onwards. The noise is produced by their discordant vibrations. Both these modes bear the general name of expectoration. When these secretions are swallowed, they are subjected to the digestive process ; a part is taken up, and the remainder rejected; so that they belong to the division of recremento-excrementitial fluids of some physiologists. (4.) RESPIRATORY PHENOMENA CONNECTED WITH EXPRESSION. It remains to speak of the expiratory phenomena that strictly form part of the function of expression, and depict the moral feeling of the individual who gives them utterance. 1. Sighing consists of a deep inspiration, by which a large quantity of air is received slowly and gradually into the lungs, to compensate 48 RESPIRATION. for the deficiency in the due aeration of the blood which precedes it. The most common cause of sighing is mental uneasiness; it also occurs at the approach of sleep, or immediately after waking. In all these cases, the respiratory efforts are executed more imperfectly than under ordinary circumstances; the blood, consequently, does not circulate through the lungs in due quantity, but accumulates more or less in these organs, and in the right side of the heart; and it is to restore the due balance, that a deep inspiration is now and then established. 2. Yawning, oscitancy, oscitation, or gaping, is a full, deep, and protracted inspiration, accompanied by a wide separation of the jaws, and followed by a prolonged and sometimes sonorous expiration. It is excited by many of the same causes as sighing. It is not, however, the expression of a depressing passion, but is occasioned by any circum- stance that impedes the necessary aeration of the blood ; whether it be retardation of the action of the respiratory muscles, or the air being less rich in oxygen. Hence we yawn at the approach of sleep, and immediately after waking. The inspiratory muscles, fatigued from any cause, experience some difficulty in dilating the chest; the lungs are, consequently, not properly traversed by the blood from the right side of the heart; oxygenation is, therefore, not duly effected and an uneasy sensation is induced; this is put an end to by the action of yawning, which allows the admission of a considerable quantity of air. We yawn at the approach of sleep, because the agents of respiration, be- coming gradually more debilitated,, require to be now and then excited to fresh activity, and the blood needs the requisite aeration. Yawning on waking seems to be partly for the purpose of arousing the respira- tory muscles to greater activity, the respiration being always slower and deeper during sleep. It is, of course, impossible to explain why the respiratory nerves should be chiefly concerned in these respiratory movements of an expressive character. The fact, however, is certain; and it is remarkably proved by the circumstance, that yawning can be excited by even looking at another affected in this manner; nay, by simply looking at a sketch, and even thinking of the action. The same also applies to sighing and laughing, and especially to the latter. 3. Pandiculation or stretching is a frequent concomitant of yawning, and appears to be established instinctively to arouse the extensor mus- cles to a balance of power, when the action of the flexors has been predominant. In sleep, the flexor muscles exercise that preponderance which, in the waking state, is exerted by the extensors. This, in time, is productive of some uneasiness; and, hence, occasionally during sleep, but still more at the moment of waking, the extensor muscles are roused to action to restore the equipoise; or, perhaps, as the muscles of the upper extremities, and those engaged directly or indirectly in respiration, are chiefly concerned in the action, it is exerted for the purpose of exciting the respiratory muscles to increased activity. By Dr. Good,1 yawning and stretching have been regarded as morbid affections and amongst the signs of debility and lassitude:—"Every one," he remarks, " who resigns himself ingloriously to a life of lassi- Study of Medicine, class 4, ord. 3, gen. 2, sp. 6. LAUGHING—WEEPING. 49 tude and indolence, will be sure to catch these motions as a part of that general idleness which he covets ; and, in this manner, a natural and useful action is converted into a morbid habit; and there are loungers to be found in the world, who, though in the prime of life, spend their days as well as their nights in a perpetual routine of these convulsive movements, over which they have no power; who cannot rise from the sofa without stretching their limbs, nor open their mouths to answer a plain question without gaping in one's face. The disease is here idiopathic and chronic; it may perhaps be cured by a perma- nent exertion of the will, and ridicule or hard labour will generally be found the best remedies for calling the will into action." 4. Laughing is a convulsive action of the muscles of respiration and voice, accompanied by a facial expression, which has been ex- plained elsewhere. It consists of -a succession of short, sonorous ex- pirations. Air is first inspired so as to fill the lungs. To this succeed short, interrupted expirations, with simultaneous contractions of the muscles of the glottis, so that the aperture is slightly contracted, and the lips assume the tension necessary for the production of sound. The interrupted character of the expirations is caused by convulsive con- tractions of the diaphragm, which constitute the greater part of the action. In very violent laughter, the respiratory muscles are thrown into such forcible contractions, that the hands are applied to the sides to support them. The convulsive action of the thorax likewise inter- feres with the circulation through the lungs; the blood, consequently, stagnates in the upper part of the body; the face becomes flushed; the sweat trickles down the forehead, and the eyes are suffused with tears; but this is apparently,owing in part to mechanical causes; not to the lachrymal gland being excited to unusual action, as in weeping. At times, however, we find the latter cause in operation, also. 5. Weeping. The action of weeping is very similar to that of laugh- ing ; although the1 causes are so dissimilar. It consists in an inspira- tion, followed by a succession of short, sonorous expirations. The facial expression, so diametrically opposite to that of laughter, has been depicted in another' place. Laughter and weeping appear to be characteristic of humanity. Animals shed tears, but the act does not seem to be accompanied by the mental emotion that characterizes crying in the sense in which we employ the term. It has, indeed, been affirmed by Steller,1 that the phoca ursina or ursine seal; by Pallas,2 that the camel; and by Von Humboldt,3 that a small American monkey, shed tears when labour- ing under distressing emotions. The last scientific traveller states, that "the countenance of the titi of the Orinoco,—simia seiurea of Linnaeus,—is that of a child; the same expression of innocence; the same smile; the same rapidity in the transition from joy to sorrow. The Indians affirm, that it weeps like man, when it experiences chagrin; and the remark is accurate. The large eyes, of the ape are suffused 1 Nov. Coram. Academ. Scient. Petropol., ii. 353. 2 Sammlungen Historisch. Nachricht. iiber die Mongolischen Volkerschaften, Th. i. 177. 3 Recueil d'Observations de Zoologie, &c, i. 333. VOL. II.—4 50 RESPIRATION. with tears, when it experiences fear or any acute suffering." Shaks- peare's description of the weeping of the stag,— " That from the hunter's aim had ta'en a hurt," is doubtless familiar to most of our readers. " The wretched animal heaved forth such groans, That their discharge did stretch his leathern coat Almost to bursting ; and the big, round tears Coursed one another down his innocent nose1 In piteous chase; and thus the hairy fool, Much marked of the melancholy Jaques, i Stood on th' extremest verge of the swift brook, Augmenting it with tears." As Yor Like It, ii. 1. We have less evidence in favour of the laughter of animals. Le Cat,2 indeed, asserts, that he saw the chimpanzee both laugh and weep. The orang, carried to Great Britain from Batavia by Dr. Clarke Abel, never laughed; but he was seen occasionally to weep.3 6. Sobbing still more resembles laughing, except that, like weeping, it is usually indicative of the depressing passions ; and generally ac- companies weeping. It consists of a convulsive action of the dia- phragm ; which is alternately raised and depressed, ,but to a greater extent than in laughing, and with less rapidity. It is susceptible of various degrees, and has the same physical effects upon the circulation as weeping. Dr. Wardrop4 considers laughter, crying, weeping, sob- bing, sighing, &c, as efforts made with a view to effect certain altera- tions, in the quantity of blood in the lungs and heart, when the circula- tion has been disturbed by mental emotions. 7. Panting or anhelation consists in a succession of alternate, quick, and short inspirations and expirations. Its physiology, how- ever, does not differ from that of ordinary respiration. The object is, to produce a frequent renewal of air in the lungs, in cases where the circulation is unusually rapid; or where, owing to disease of the tho- racic viscera, a more than ordinary supply of fresh air is demanded. We can, hence, understand why dyspnoea should be one of the con- comitants of most of the severe diseases of the chest; and why it should occur whenever the air we breathe does not contain a sufficient quantity of oxygen. The panting, produced by running, is owing to the necessity for keeping the chest as immovable as possible, that the whole effort may be exerted on the muscles of locomotion; and thus suspending, for a time, the respiration, or admitting only of its imper- fect accomplishment. This induces an accumulation of blood in the lungs and right side of the heart; and panting is the consequence of the augmented action necessary for transmitting it through the vessels. » " The alleged 'big round tears,' which ' course one another down the innocent nose' of the deer the hare, and other animals, when hotly pursued, are in fact only sebaceous mat- ter, which, under these circumstances, flows in profusion from a collection of follicles in the hollow of the cheek."_Fletcher's Rudiments of Physiology, part ii. b. p. 50, Edinb., 1836. 2 1 raite de 1 Existence du Fluide des Nerfs, p. 35. 3 Lawrence, Lectures on Physiology, Zoology, and the Natural History of Man rj 236 Lond., 1814. ' *' ' 4 On the Nature and Treatment of Diseases of the Heart, part i. p. 62, Lond. 1837. H.EMAT0SIS. 51 b. Chemical Phenomena of Respiration. Having studied the mode in which air is received into, and expelled from, the lungs, we have now to inquire into the changes produced on the venous blood—containing the products of the various absorptions —in the lungs; as well as on the air itself. These changes are effected by the function of sanguification, hsematosis, respiration in the restricted sense in which it is employed by some, arterialization, decarbonization, aeration, atmospherization, &c, of the blood. With the ancients this process was but little understood. It was generally believed to be the means of cooling the body; and, in modern times, Helvetius revived the notion, attributing to it the office of refrigerating the blood,—heated by its passage through the long and narrow channels of the circulation, —by the cool air constantly received into the lungs. The reasons, which led to this opinion, were:—that the air, which enters the lungs in a cool state, issues warm; and that the pulmonary veins, which con- vey the blood from the lungs, are of less dimension than the pulmonary artery, which conveys it to them. From this it was concluded, that the blood, during its progress through the lungs, must lose somewhat of its volume, or be condensed by refrigeration. The warmth of the expired air can, however, be readily accounted for; and it is not true that the pulmonary veins are smaller than the pulmonary artery. The reverse is the fact; and it is obvious, that the doctrine of Helvetius does not explain how we can exist in a temperature superior to our own; which, in his hypothesis, ought to be impracticable.1 Another theory, which prevailed for some time, was;—that during in- spiration the vessels of the lungs are deployed or unfolded, as it were, and that thus the passage of the blood from the right side of the heart to the left, through the lungs, is facilitated. Its progress was, indeed, conceived to be impossible during expiration, in consequence of the considerable flexures of the pulmonary vessels. The discovery of the circulation of the blood gave rise to this theory; and Haller2 attaches importance to it, when taken in connexion with the changes effected upon the blood in the vessels. It is incorrect, however, to suppose, that the circulation of the blood through the lungs is mechanically interrupted, when respiration is arrested. The experiments of Drs. Williams3 and Kay4 would seem to show, that the interruption is ascribable to the non-con- version of venous into arterial blood, and to the non-adaptation of the radicles of the pulmonary veins for any thing but arterial blood, owing to which causes stagnation of blood supervenes in the pulmonary radicles. Numerous other objections might be made to this view. In the first place, it supposes, that the lungs are emptied at each expira- tion; and, again, if a simple deploying or unfolding of the vessels were all that is required, any gas ought to be sufficient for respiration— which is not the fact. 1 Adelon, Physiologie de l'Homme, edit, cit., iii. 201. 8 Element. Physiol., lib. viii. sect, iv., Lausann., 1766. 3 Edinburgh Medical and Surgical Journal, vol. lxxvii., 1823, * Edinburgh Med. and Surg. Journal, vol. xxix.; and Physiology and Pathology, &c, of Asphyxia, Lond., 1834. 52 RESPIRATION. In these different theories, the principal object of respiration is over- looked—the conversion of the venous blood, conveyed to the lungs by the pulmonary artery, into arterial blood. This is effected by the contact of the inspired air with the venous blood; in which they both lose certain elements, and gain others. Most physiologists have con- sidered that the whole function of haematosis is effected in the lungs. M. Chaussier,1 however, has presumed, that some kind of elaboration ia effected on the air, in passing through the cavities of the nose and mouth, and the different bronchial ramifications, by being agitated with the bronchial mucus; similar to what he conceives is effected by the mucus on the aliment in its passage from the mouth to the stomach; but his view is conjectural in both one case and the other. M. Legallois,2 again, thought, that haematosis commences at the part, where the chyle and lymph are mixed with the venous blood, or in the subclavian vein. This admixture, he conceives, occurs more or less immediately; is aided in the heart, and the conversion is completed in the lungs. To this belief he was led by the circumstance, that when the blood quits the lungs it is manifestly arterial; and he thought, that what the products of absorption lose or gain in the lungs is too inconsiderable to account for the important and extensive change; and that therefore it must have commenced previously. Facts, however, are not exactly in accordance with the view of Legallois. They seem to show, that the blood of the pulmonary artery is analogous to that of the subclavian vein; and hence it is probable, that there is no other action exerted upon the fluid in this part of the venous system, than a more intimate admixture of the venous blood with the chyle and lymph in their passage through the heart. The changes, wrought on the air by respiration, are considerable. It is immediately deprived of a portion of both of its main constituents— oxygen and nitrogen; and it always contains, when expired, a quantity of carbonic acid greater than it had when received into the lungs, along with an aqueous and albuminous exhalation to a considerable amount. Oxygen is consumed in the respiration of all animals, from the largest quadruped to the most insignificant insect; and if we examine the expired air, the deficiency is manifest. Many attempts have been made to estimate the precise quantity consumed during respiration; but the results vary essentially from each other; partly owing to the fact, that the amount consumed by the same animal differs in different circumstances. Menzies3 was probably the first that attempted to as- certain the quantity consumed by man in a day. According to him, 36 cubic inches are expended in a minute; consequently, 51,840 in the twenty-four hours, equal to 17,496 grains. Lavoisier4 makes it 46,048 cubic inches, or 15,541 grains. This was the result of his earlier experiments; and, in his last, which he was executing at the time when he fell a victim to the tyranny of Robespierre, he made it 15592-5 grains; corresponding greatly with the results of his earlier observa- 1 Adelon, Physiologie de l'Homme, iii. 205. 2 Annales de Chimie, iv. 115. 3 Dissertation on Respiration, p. 21, Edin., 1796. 4 Memoir de l'Academ. des Sciences, 1789, 1790. H.EMAT0SIS. 53 tions. The experiments of Sir Humphry Davy1 coincide greatly with those of Lavoisier. He found the quantity consumed in a minute tc be 31*6 cubic inches; making 45,504 cubic inches, or 15,337 grains in twenty-four hours. The results obtained by Messrs. Allen and Pepys2 make it much less. They consider the average consumption to be, in the twenty-four hours, under ordinary circumstances, 39,534 cubic inches, equal to 13,343 grains. If we regard the experiments of Lavoisier and Davy, between which there is the greatest coincidence, to be an approximation to the truth, it will follow, that, in a day, a man consumes rather more than 25 cubic feet of oxygen; and as the oxygen amounts to only about one-fifth of the respired air, he must render 125 cubic feet of air unfit for support- ing combustion and respiration. The experiments of Crawford, Jurine, Lavoisier and S^guin, Prout, Fyfe, and Edwards,3 have proved, that the quantity of oxygen con- sumed varies according to the condition of the functions and the system generally. Se'guin4 found, that muscular exertion increases it nearly fourfold. Dr. Prout,5 who gave much attention to the subject, was induced to conclude, from his experiments, that moderate exercise increases it; but if the exercise be continued so as to induce fatigue, a diminished consumption takes place. The exhilarating passions ap- peared to increase the quantity ; whilst the depressing passions and sleep, the use of alcohol and tea, diminished it. He discovered, that the quantity of oxygen consumed is not uniformly the same during the twenty-four hours. Its maximum occurred between 10 a. m. and 2 P. M., or generally between 11 a. M. and 1 P. M.: its minimum commenced about 8J P. m., and it continued nearly uniform till about 3£ A. M. Dr. Fyfe6 found, that the quantity was diminished by a course of nitric acid, by a vegetable diet, and by affecting the system with mercury. Temperature has an influence. Dr. Crawford7 found, that a Guinea-pig, confined in air at the temperature of 55°, consumed double the quantity which it did in air at 104°. He also observed, in such cases, that venous blood, when the body was exposed to a high temperature, had not its usual dark colour; but, by its florid hue, indicated that the full change had not taken place in its constitution in the course of circulation. The same fact is mentioned by a recent observer, who affirms, that if, when an animal is near dying from the effect of heat, an artery be opened, its blood is as black as that of a vein, and does not become bright by exposure. We may thus understand the great lassitude and yawning, induced by the hot weather of summer; and the languor and listlessness which are so characteristic of those who have long resided in torrid climes. Dr. Prout conceives, that the presence or absence of the sun alone regu- lates the variation in the consumption of oxygen which he has described; 1 Researches, &c, p. 431. 2 Philos. Transact, for 1808. 3 De l'lnfluence des Agens Physiques sur la Vie, p. 410, Paris, 1824; or Hodgkin and Fisher's translation. 4 Mem. de TAcadem. des Sciences, 1789 and 1790. 5 Annals of Philos., ii. 330, iv. 331, and xiii. 269. 6 Annals of Philos., iv. 334, and Rostock's Physiol., i. 350. i Op. cit., p. 387. 54 RESPIRATION. but the deduction of Dr. Fleming1 appears to be more legitimate,— that it keeps pace with the degree of muscular action, and is dependent upon it. Consequently, a state of increased consumption is always fol- lowed by an equally great decrease, in the same manner as activity is followed by fatigue. The disagreement of experimenters, as respects the removal of nitro- gen or azote from the air, during respiration, is still greater than in the case of oxygen. Priestley, Davy, Humboldt, Henderson, Cuvier, and Pfaff, found a less quantity exhaled than was inspired. Spallanzani, Lavoisier and Se'guin, Vauquelin, Allen and Pepys, Ellis, Thomson, Va- lentin and Brunner, and Dalton, inferred that neither absorption nor exhalation takes place,—the quantity of that gas, in their opinion, undergoing no change during its passage through the air-cells of the lungs ; whilst Jurine, Nysten, Berthollet, and Dulong and Despretz, on the contrary, found an increase in the bulk of the nitrogen. In this uncertainty, most physiologists have been of opinion that the nitrogen is entirely passive in the function. The facts, ascertained by M. W. F. Edwards,2 of Paris, shed considerable light on the causes of this dis- crepancy amongst observers. He has satisfactorily shown that, in the respiration of the same animal, the quantity of nitrogen may be, at one time, augmented; at another, diminished; and, at a third, wholly un- changed. These phenomena he has traced to the influence of the sea- sons, and he suspects that other causes have a share in their produc- tion. In nearly all the lower animals that were the subjects of expe- riment, an augmentation of nitrogen was observable during summer. Sometimes, it was so slight that it might be disregarded; but, in numerous instances, it was so great as to place the fact beyond the possibility of doubt; and, on some occasions, it almost equalled the whole bulk of the animal. Such were the results of his observations until the close of October, when he noticed a sensible diminution in the nitrogen of the inspired air, and the same continued throughout the whole of winter and beginning of spring. M. Edwards considers it probable, that, in all cases, both exhalation and absorption of nitrogen are going on ; that they are frequently accurately balanced, so as to exhibit neither excess nor deficiency of nitrogen in the expired air; whilst, in other cases, depending, as it would appear, chiefly upon tem- perature, either the absorption or the exhalation is in excess, producing a corresponding effect upon the composition of the air of expiration. MM. Regnault and Reiset,3 in their experiments on animals, always ob- served an exhalation of nitrogen; the proportion of which varied—as in thecase of carbonic acid formed—with the nature of the food. Whilst the respired air has lost its oxygenous portion, it has received, as we have remarked, an accession of carbonic acid, and, likewise, a quantity of serous vapour. If we breathe through a tube, one end of which is inserted into a vessel of lime-water, the fluid soon becomes milky, owing to the formation of carbonate of lime, which is insoluble m water. Carbonic acid must, consequently, have been given off from 1 Philosophy of Zoology, i. 355, Edinburgh, 1S22. 2 0p it 4fi2 3 Comptes Rendus, Paris, 1848. *' v' H.EMAT0SIS. 55 the lungs. In the case of this gas, again, it has been attempted to compute the quantity formed in the day. Jurine conceived, that the amount, in air once respired in natural respiration, is in the large proportion of j'flth or y^th; Menzies, that it is 2^th; and, from his estimate of the total quantity of air respired in the twenty-four hours, he deduced the amount of carbonic acid formed to be 51,840 cubic inches, equal to 24105-6 grains. MM. Lavoisier and Seguin,1 in their first experiments, valued it at 17720*89 grains; but in the next year they reduced their estimate more than one-half;—to 8450-20 grains; and, in Lavoisier's last experiment, it was farther reduced to 7550*4 grains. Sir Hum- phry Davy's estimate nearly corresponds with that of the first experi- ment of MM. Lavoisier and Seguin,—17811-36 grains; and Messrs. Allen and Pepys accord pretty nearly with, him. These gentlemen found, that air, when inspired, issued, on the succeeding expiration, charged with from 8 to 6 per cent, of carbonic acid; but this estimate greatly exceeds that of Dr. Apjohn,2 of Dublin, who, in his experiments, found the expired air to contain only 3*6 per cent. The experiments and observations of Messrs. Crawford, Prout, Edwards, and others, to which we have referred—as regards the consumption of oxygen, under various circumstances—apply equally to the quantity of carbonic acid formed, which always bears a pretty close proportion to the oxygen consumed. These experiments also account, in some degree, for the discrepancy in the statements of individuals on this subject. The experiments of Mr. Coathupe,3 which were carefully conducted, make the amount of carbonic acid, generated in the 24 hours, about 17*856 cubic inches, that is, 2*616 grains or 5J ounces of solid carbon. Liebig found the proportion of carbon expired by himself to be 8J ounces daily; by a soldier, 13| ounces; by prisoners in close confine- ment, 7 ounces; and by a boy who took considerable exercise, 9 ounces.4 More recently, farther experiments have been made on the subject by competent observers. Professor Scharling,5 of Copenhagen, found, that, at the age of 35, he exhaled 7*7 ounces avoirdupois of car- bon in the twenty-four hours—seven of which were passed in sleep. A soldier, 28 years of age, exhaled 8*15 ounces; a lad, of 16, 7*9 ounces; a young woman, aged 19, 5-83 ounces; a boy, 9\ years old, 3*069 ounces; and a girl, 10 years old, 4-42 ounces. In the last two, the time spent in sleep was 9 hours. These amounts, however, were exhaled both from the lungs and cutaneous surface. He constructed an air-tight chamber, of dimensions sufficient to permit him to remain in it for some time without inconvenience. This was connected with an apparatus by which the air was constantly renewed, and the air removed was carefully analyzed, in order to determine the quantity of carbonic acid contained in it. Of the 7*7 ounces exhaled by himself in the twenty-four hours, we may perhaps estimate the amount from 1 Memoir, de l'Academ. des Sciences, p. 609, Paris, 1790. 2 Edinb. Med. and Surg. Journal, Jan., 1831. 8 Philos. Magazine, June, 1839. 4 Graham's Elements of Chemistry, Amer. edit., p. 686, Philad., 1843. 5 Annates des Sciences Naturelles, Fevrier, 1843 j cited in Brit, and For. Med. Rev. for July, 1843, p. 285. 56 RESPIRATION. the lungs at 5*5 ounces. He infers from all his experiments, that males exhale more carbonic acid than females; and children compara- tively more than adults. MM. Andral and Gavarret undertook a series of interesting experi- ments on the subject. Their first object was to ascertain the modilying influence of age, sex, and constitution on the quantity of carbonic acid exhaled from the lungs. To determine this, their observations were made under circumstances as uniform as possible; and each experi- ment was repeated several times on the same subject. The apparatus employed was so devised as to enable the respirations to be freely per- formed; no portion of the expired air was again inspired; and the greatest care was taken to analyze the expired air with accuracy. The general results obtained by these observers were as follows.:—1. The quantity of carbonic acid exhaled by the lungs in a given time varies according to age, sex, and constitution. 2. In, both male and fe- male, the quantity undergoes modification, according to the ages of the individuals experimented upon,, quite independently of their weights. 3. In all periods of life, there is a difference between the male and female in the amount of carbonic acid exhaled in a given time: cseteris paribus, man exhales a much larger quantity than woman. Between the ages of 16 and 40, the former exhales nearly twice as much as the latter. 4. In man, the quantity exhaled goes on regularly increasing from 8 to 30 years of age; and a remarkable augmentation takes place at puberty. After 30, it begins to decrease; and the decrease con- tinues becoming more and more marked as the individual approaches nearer and nearer extreme old age; so that, at this last period, it re- turns to the standard at which it was about the age of 10. 5. In woman the exhalation augments up to the period of puberty, according to the same law as in man; the increase then suddenly ceases, and the quantity continues at this low standard, with little variation so long as the cata- menia appear regularly; but as soon as they cease, the exhalation of carbonic acid from the lungs undergoes a considerable augmentation, after which it decreases as in man, according to the advance of age. 6. During pregnancy, the amount of carbonic acid exhaled is raised tem- porarily to the standard which it attains after the cessation of the catamenia. 7. In both sexes, and at all ages, the quantity of carbonic acid exhaled by the lungs is greater in proportion to the strength of the constitution, and the developement of the muscular system. The following table exhibits the amount of solid carbon calculated to be exhaled in one hour at different ages;—the gramme is equal to about 15^ grains. Male. Female. 8 years. 5 grammes. 15.....8-7 16.....10-8 18-20 .... 11-4 20-30 --.. 12-2 30-40 .... 12-2 40-60 .... 10-1 60-80 -.-- 9-2 102 .... 5-9 8 years. 5 grammes. 12-38 .... 64 38-50 .... 8-4 50-60 .... 7-3 60-80 .... 6-8 82 .... 6-0 The same standard con-tinues in women during the whole of the menstrual pe-riod : but if the catamenia be temporarily suppressed, or pregnancy occur, it rises to the standard it attains after their entire cessation, name-ly, 84 grammes. H^MATOSIS. 57 These numbers express the averages,—the maximum amount being often considerably greater. In a young man of athletic system, and sound constitution, the quantity of carbonic acid exhaled in an hour was 14-1 grammes; in a man of 60, equally vigorous for his age, 13*6 grammes; and in one of 63, 12-4 grammes. An old man, of 92, of a remarkable degree of energy, and who had possessed unusual vigour in his youth, was found to exhale 8-8 grammes per hour ; whilst the same amount appeared to be the ordinary standard in a man of 45; who, unlike the last, had a feeble system, although in equally good health. How far these variations were connected with differences in the capa- city of the chest, and with the number of the respiratory movements, MM. Andral and Gavarret proposed to investigate subsequently. This they have not done. The following table, by Dr. John Reid,1 of the quantity of carbonic acid gas in 100 parts of the expired air estimated by volume gives the result obtained by recent experimenters. Difference between Average. Maximum. Minimum. Maximum and Minimum. Prout .... 3-45 4-10 3-30 •80 Coathupe t 4-02 7-98 1-91 6.07 Brunner and Valentin - 4-380 5495 3.299 2-196 Vierordt ... 4-334 6-220 3-358 2.86 Thomson ... 416 7-16 1-71 5.45 It has been a question amongst physiologists, whether the quantity of carbonic acid given out is equal in bulk to the oxygen taken in. In Dr. Priestley's experiments,2 the latter had the preponderance. Men- zies and Crawford found them to be equal. MM. Lavoisier and Se'- guin supposed the oxygen, consumed in the twenty-four hours, to be 15661-66 grains; whilst the oxygen, required for the formation of the carbonic acid given out, was no more than 12,924 grains; and Sir Humphry Davy found the oxygen consumed in the same time to be 15,337 grains, whilst the carbonic acid produced was 17811-36 grains; which would contain 12824-18 grains of oxygen. The experiments of Messrs. Allen and Pepys seem, however, to show that the oxygen which disappears is replaced by an equal volume of carbonic acid ; and hence it was supposed that the whole of it must have been employed in the formation of this acid. They, consequently, accord with Menzies and Crawford; and the view is embraced by Dalton, Prout, Ellis, Henry, and other distinguished individuals. On the other hand, the view of those, who consider that the quantity of carbonic acid produced is less than that of the oxygen which has disappeared, is embraced by Dr. Thomson, and by MM. Dulong and Despretz. In the carnivorous animal, they found the difference as much as one-third; in the herbi- vorous, on the average, only one-tenth. The experiments of M. Ed- wards have shown, that here, also, the discordance has not depended so much upon the different methods and skill of the operators, as upon 1 Art. Respiration, Cyclopaedia of Anat. and Physiol., Pt. xxxii. p. 345, Lond., Aug., 1848. 2 Experiments, &c, on Different Kinds of Air, vol. iii., 3d edit., Lond., 1781. 58 RESPIRATION. a variation in the results arising from other causes; and he concludes, that the proportion of oxygen consumed, to that employed in the pro- duction of carbonic acid varies from more than one-third of the volume of carbonic acid, to almost nothing; that the variation depends upon the particular animal species subjected to experiment, its age, or some peculiarity of constitution, and that it differs considerably in the same individual at different times. . . . According to the law of diffusion of gases, the carbonic acid given off from the blood will, of itself, independently of the movements of respiration, have a tendency to quit the lungs by diffusing itself in the external air in which it is in less proportion; and the oxygen of the bronchial tubes and external air will have a tendency to pass towards the air-cells in which its proportion is less than in the air of the tubea and the external air. Were this not the case, the air in the air-cells would be highly charged with carbonic acid, and could not fail to act injuriously, inasmuch as the respiratory movements, even when aided by the resiliency of the pulmonary tissue, can never empty the air-cells; and hence there is always—as has been shown—a quantity of reserve and residual air in the cells.1 Interesting experiments by Valentin2 and Brunner, made on a large scale, seemed to demonstrate, that the chemical changes in respiration are a good deal owing to the simple diffusion of gases taking place be- tween those of the atmosphere and of the blood. The volumes of oxygen absorbed and of carbonic acid exhaled from the blood may be, according to them, determined by the established laws of the diffusion of gases, so that, for one volume of carbonic acid exhaled, 1-17421 volume of oxygen is absorbed,—these numbers representing the pro- portionate diffusion-volumes of the two gases, calculated according to the law that they are inversely as the square roots of their specific gravities,—or, according to weight, one part of carbonic acid to 0-85163 of oxygen. One part by weight of carbonic acid contains 0*72727 of oxygen; consequently for each part of carbonic acid discharged in respiration, there is an excess of 0.12436 of oxygen, which is disposed of otherwise than in forming the carbonic acid thrown off from the lungs,—or, by volumes, for each one of carbonic acid there is an excess of 0-17421 of oxygen. Hence if it be known how much carbonic acid has been exhaled from the lungs in a given time, we can calculate the amount of oxygen absorbed in the same time. Valentin and Brunner satisfied themselves, that in a medium temperature and atmospheric pressure, each of them, on an average of six experiments, breathed 562-929 litres of air in the hour, and, in the same time, expired 635*8565 grains of carbonic acid, containing 173-414 grains of carbon. From this and their respective diffusion-volumes, the hourly consump- tion of oxygen was calculated at 541*5 grains;—the results obtained by these gentlemen according greatly with those of MM. Andral and Gavarret. More recently, a series of apparently carefully conducted experi- 1 Kirkes and Paget, Manual of Physiology, Amer. edit., p. 131. 2 Lehrbuch der Physiologie des Menschen, i. 547. HJ3MAT0SIS. 59 ments in regard to the changes produced in the air by respiration has been performed by MM. Regnault and Reiset.1 The following are the results of one on a young dog, which was confined in an appropriate apparatus for twenty-four hours and a half. Oxygen consumed, ...... 182-288 grammes. Carbonic acid produced, ..... 185-961 " Oxygen contained in the carbonic acid, ... 135:244 " Nitrogen given off, - - - - - - 0-1820 " Representing the quantity of oxygen consumed at 100, the results would be as follows:— Oxygen consumed, ...... 100 Oxygen in the carbonic acid, .... 74-191 Oxygen otherwise disposed of, - - - - 25809 Nitrogen disengaged, ..... 0-0549 Average quantity of oxygen consumed in an hour, - 7-44 These experiments are not confirmatory, however, of the views of Valentin and Brunner, in regard to the exchanged oxygen and carbonic acid in respiration, being in the proportion to each other as their dif- fusion-volumes. Fresh observations are, indeed, needed on this subject. In the meantime it has been well remarked by Messrs. Kirkes and Paget,2 that the conditions of the gases, engaged in respiration, are not those in which the law of diffusion would exactly hold. The law re- quires, that both gases should be free and under equal pressure; whilst in the actual case, the gas in the blood is dissolved under pressure, and separated by a membrane from that with which it has to be diffused. In their experiments on animals, MM. Regnault and Reiset found that the nature of the diet influences the relative amount of oxygen absorbed, and of carbonic acid given out. When animals were fed on flesh, they absorbed much more oxygen in proportion. In the case of a dog, confined exclusively to this kind of aliment, the proportion of oxygen absorbed to 100 parts of carbonic acid exhaled was 134*3, much more than that which the law of diffusion of gases would indi- cate ; whilst in that of a rabbit, fed wholly on vegetable food, the pro- portion was as 100 to 109*34, or less. The difference between the relative proportions of surplus oxygen in the same animal, under these different circumstances, was as high as 62 to 104. The same experi- menters found that, when an animal was kept fasting, the relation be- tween the quantity of oxygen absorbed, and of carbonic acid exhaled, is nearly the same as when it is fed on flesh;—" the reason evidently being," observes a recent writer,3 " that in the former case the animal's respiration is kept up at the expense of the constituents of its own body, which correspond with animal food in their composition." It must be borne in mind, however, that in such circumstances the fat would probably be most largely taken up; and it corresponds in com- position with vegetable food. It would appear, then, that the whole of the oxygen, which respira- 1 Comptes Rendus, Paris, 1848. 2 Op. cit.. p. 137. 3 Carpenter's Principles of Physiology, 4th Amer. edit., p. 572, Philad., 1850. 60 RESPIRATION. tion abstracts from the air, is by no means accounted for by the quart- tity of carbonic acid formed; and that, consequently, a portion of it disappears altogether. It has been supposed by some, that a,part of the watery vapour, given off during expiration is occasioned by the union of a portion of the oxygen of the air with hydrogen from the blood in the lungs; but the view is conjectural. This subject, with the quantity of vapour combined with the expired air, will be a matter of inquiry under the head of Secretion.1 The air likewise loses, during inspiration, certain foreign matters diffused in it. In this way, it has been attempted to convey medicines into the system. If air, charged with odorous particles,—as with those of turpentine,—be breathed for a short time, their presence^ in the urine can be detected; and it is probably in this manner, that miasmata produce their effects on the frame. Anaesthetic agents act in the same manner; and all pass immediately through the coats of the pulmonary veins by imbibition, and, in this way, speedily affect the system. The changes, produced in the air during respiration, are easily shown, by placing an animal under a bell-glass, until it dies. On examining the air, it will be found to have lost a portion of its oxygen and nitrogen, and to contain carbonic acid and aqueous vapour. The expired air has always, even in greatly varying temperatures of the atmosphere, a tem- perature of from 97°*25 to 99°-5 Fahr.,—most commonly the latter. Let us now inquire whether the changes produced in the respired air be connected with those effected on the blood in the lungs. In its pro- gress through the lungs, this fluid has been changed from venous into arterial. It has become of a florid red colour; of a stronger odour; of a higher temperature by from one to four degrees, according to some,2 but others have perceived no difference, whilst others, again, have found it of lower temperature;3 of less specific gravity, in the ratio of 1053 to 1050 on the average, according to Dr. John Davy ;4 and it coagulates more speedily, according to most observers; but Mr. Thackrah5 observed the contrary. That this conversion is owing to the contact of air in the lungs we have many proofs. Lower6 was one of the first, who clearly pointed out, that the change of colour occurs in the capillaries of the lungs. Prior to his time, the most confused notions had prevailed on the subject, and the most visionary hypotheses been indulged. On opening the thorax of a living animal, he observed the precise point of the circulation at which the change of colour takes place; and showed, that it is not in the heart, since the blood, when it leaves the right ven- 1 See on the whole of this subject, Dr. John Reid, art. Respiration, Cyclop, of Anat. and Physiol., pt. xxxii. p. 346, Lond., Aug., 1848; and Vieiordt, art. Respiration, Wagner's Handworterbuch der Physiologie, 12te Lieferung,s. 828, Braunschweig, 1845. 2 Magendie, Precis de Physiologie, ii. 343; Dr. J. Davy, in Philos. Transact, for 1814; Metcalfe on Caloric.ii. 548, Lond., 1843; and Becquerel and Breschet, Annales des Sciences Naturelles, 2de serie, vii. 94, Paris, 1837. 3 Wagner's Elements of Physiology, by R. Willis, § 180, Lond., 1842; and Simon's Ani- mal Chemistry, vol. i. p. 193, Lond., 1845. 4 Physiological and Anatomical Researches, American Med. Library edit., p. 16, Philad., 1840. 5 Inquiry into the Nature and Properties of the Blood, p. 42, Lond., 1819. 6 Tractatus de Corde, &c, c. iii., Amstelod., 1761. HiEMATOSIS. 61 tricle, continues to be purple. He then kept the lungs artificially dis- tended, first with a regular supply of fresh air, and afterwards with the same portion of air without renewing it. In the former case, the blood experienced the usual change of colour. In the latter, it was returned to the left side of the heart unaltered. Experiments, more or less resembling those of Lower, have been per- formed by Goodwyn,1 Cigna, Bichat,2 Wilson Philip, and numerous others, and with similar results. The direct experiments of Dr. Priestley3 more clearly showed, that the change effected on the blood was to be ascribed to the air. He found, that a clot of venous blood, confined in a small quantity of air, assumed a scarlet colour, and that the air experienced the same change as from respiration. He afterwards examined the effects produced on the blood by the gaseous elements of the atmosphere separately, as well as by the other gaseous fluids that had been discovered in his time. The clot was reddened more rapidly by oxygen than by the air of the atmosphere, whilst it was reduced to a dark purple by nitrogen, hydro- gen, and carbonic acid. Since Dr. Priestley's time, the effect of different gases on the colour of venous blood has been investigated by numerous observers. The following is the result of their observations, as given by M. The'nard.4 It must be remarked, however, that all the experiments were made on blood out of the body; and it by no means follows, that precisely the same changes would be accomplished if it were circulating in the vessels. Gas. Colour. Remarks. Oxygen .... Rose red. The blood employed had Atmospheric air Do. been beaten, and, conse- Ammonia .... Cherry red. quently, deprived of its Gaseous oxide of carbon Slightly violet red. fibrin. Deutoxide of azote Do. Carburetted hydrogen Do. Azote .... Brown red. Carbonic acid Do. Hydrogen .... Do.5 Protoxide of azote Do. Arseniuretted hydrogen Sulphuretted hydrogen C Deep violet, passing 1 gradually to a greenish ( brown. Chlorohydric acid gas Maroon brown. "] Sulphurous acid gas . Black brown. j These three gases coa- C Blackish brown, pass- J> gulated the blood at the Chlorine .... < ing by degrees to a ( yellowish white. J same time. It is sufficiently manifest, then, from the disappearance of a part of the oxygen from the inspired air, and from the effects of that gas on 1 The Connexion of Life with Respiration, &c, Lond., 1788. 2 Recherches Physiol, sur la Vie et la Mort, 3eme edit., p. 238, Paris, 1805. 3 Experiments, &c, on Different Kinds of Air, &c, Lond., 1781. « Traite de Chimie, &c, 5e edit., Paris, 1827. 5 Miiller says he agitated blood with hydrogen, but could perceive no change of colour. Handbucb, u. s. w., Baly's translation, p. 322, Lond., 1838. 62 RESPIRATION. venous blood out of the body, that it plays an essential_ part in the function of sanguification. But we have seen, that the expired air con- tains an unusual proportion of carbonic acid. Hence carbon, either in its simple state or united with oxygen, must have been given off from the blood in the vessels of the lungs. To account for these changes on chemical principles has been a great object with chemical physiologists at all times. At an early period, the conversion of venous into arterial blood was supposed to be a kind of combustion; and, according to the Stahlian notion of combustion then prevalent, it was presumed to consist in the_ disengagement of phlogiston; in other words, the abstraction or addition of a portion of phlogiston made the blood, it was conceived, arterial or venous; and its removal was looked upon as the principal use of respiration. This hypothesis was modified by Lavoisier, who proposed one of the chemical views to be now mentioned. Two chief chemical theories have been framed to explain the mode in which carbon is given off. The first is that of Black,1 Priestley,2 Lavoisier,3 Crawford ;4 and others ;5—that the oxygen of the inspired air attracts carbon from venous blood, and the carbonic acid is gene- rated by their union. The second, which has been supported by La Grange,6 Hassenfratz,7 Edwards,8 Miiller,9 Bischoff, Magnus and others, —that the carbonic acid is generated in the course of the circulation, and is given off from the venous blood in the lungs, whilst oxygen gas is absorbed. The former of these views is still maintained by many che- mical physiologists. It is conceived, that the oxygen, derived from the air unites with certain parts of the venous blood,—the carbon and hydro- gen,—owing to which union, carbonic acid and water are found in the expired air ; the venous blood, thus depurated of its carbon and hydro- gen, becomes arterialized; and, in consequence of these various com- binations, heat enough is disengaged to keep the body always at the due temperature. According to this theory, respiration is assimilated to combustion. The resemblance, indeed, between the two processes is striking. The presence of air is absolutely necessary for respira- tion ; in every variety the air is robbed of a portion of its oxygen; hence a fresh supply is continually needed; and respiration is always arrested before the whole of the oxygen of the air is exhausted, and this partly on account of the residuary nitrogen and carbonic acid gas given off during expiration. Lastly, it can be continued much longer when an animal is confined in pure oxygen than in atmospheric air. All these circumstances likewise occur in combustion. Every kind requires the presence of air. A part of the oxygen is consumed ; and, unless the air is renewed, combustion is impossible. It is arrested, too, before the whole of the oxygen is consumed, owing to the residuary 1 Lectures on the Elements of Chemistry, by Robison,~ii. 87, Edinb., 1803. 2 Philosoph.Transact, for 1776, p. 147. 3 Mem. de l'Acad. des Sciences, pour 1777, p. 185. 4 On Animal Heat, 2d edit., Lond., 1788. s Metcalfe, op. cit. 6 Annales de Chimie, ix. 269. 7 Ibid., ix. 265. » De l'lnfluence des Agens Physiques, &c, p. 411, Paris, 1823; or Hodgkin and Fisher's translation. 9 Physiology, by Baly, p. 537. H.EMAT0SIS. 63 nitrogen, and carbonic acid formed; and it can be longer maintained in pure oxygen than in atmospheric air. Moreover, when air has been respired, it becomes unfit for combustion. Again, the oxygen of the air, in which combustion is taking place, combines with the carbon and hydrogen of the burning body; hence the formation of carbonic acid and water; and, as in this combination, the oxygen passes from the state of a rare gas, or one containing a considerable quantity of caloric between its molecules, to that of a much denser, and even of a liquid, the whole of the caloric, which the oxygen contained in its former state, can no longer be held in the latter, and is accordingly disengaged; hence the increased temperature. In like manner, in respiration, the oxygen of the inspired air, it is conceived, combines with the carbon and hydrogen of the venous blood, giving rise to the formation of car- bonic acid and water; and, as in these combinations, the oxygen passes from the state of a rare to that of a denser gas, or of a liquid, there is a considerable disengagement of caloric, which becomes the source of the high temperature maintained by the human body. M. Thdnard1 admits a modification of this view,—sanguification being owing, he con- ceives, to the combustion of the carbonaceous parts of the venous blood, and probably of its colouring matter, by the oxygen of the air. This chemical theory, which originated chiefly with Lavoisier, and La Place and Seguin, was adopted by many physiologists with but little modification. Mr. Ellis, indeed, imagined, that the carbon is separated from the venous blood by a secretory process; and that then, coming into direct contact with oxygen, it is converted into carbonic acid. The circumstance that led him to this opinion was his disbelief in the pos- sibility of oxygen being able to act upon the blood through the animal membrane or coat of the vessel in which it is confined. It is obvious, however, that to reach the blood circulating in the lungs, the oxygen must, in all cases, pass through the coats of the pulmonary vessels. These coats, indeed, offer little or no obstacle, and, consequently, there is no necessity for the vital or secretory action suggested by Mr. Ellis. Besides, Priestley and Hassenfratz exposed venous blood to atmospheric air and oxygen in a bladder, and in all cases, the parts of the blood, in contact with the gases, became of a florid colour. The experiments of Drs. Faust, Mitchell, and others (vol. i. p. 65), are, in this respect, pregnant with interest. They prove the great facility with which the tissues are penetrated by gases, and confirm the facts developed by the experiments of Priestley, Hassenfratz, and others. The second theory,—that the carbonic acid is generated in the course of the circulation,—was proposed by M. La Grange, in conse- quence of the objection he saw to the former hypothesis—that the lung ought to be consumed by the perpetual disengagement of caloric within it; or, if not so, that its temperature ought to be much superior to that of other parts. He accordingly suggested, that, in the lungs, the oxy- gen is simply absorbed, passes into the venous blood, circulates with it, and unites, in its course, with the carbon and hydrogen, so as to form carbonic acid and water, which circulate with the blood, and are finally exhaled from the lungs. 1 Trait6 de Chimie, edit, citat. 64 RESPIRATION. The ingenious and apparently accurate experiments of M. Edwards proved convincingly, not only that oxygen is absorbed by the Pulmo- nary vessels, but that carbonic acid is exhaled from them; YVhen he confined a small animal in a large quantity of air, and continued the experiment sufficiently long, he found, that the rate of absorption was greater at the commencement than towards the termination of the expe- riment ; and that, at the former period, there was an excess of oxygen, and at the latter an excess of carbonic acid. This proved to him, that the diminution was dependent upon the absorption of oxygen, not of carbonic acid. His experiments, in proof of the exhalation of car- bonic acid, ready formed, by the lungs, are decisive. Spallanzani had asserted, that when certain of the lower animals are confined in gases containing no oxygen, the production of carbonic acid is uninterrupted. Upon the strength of this assertion, M. Edwards confined hogs in pure hydrogen for a length of time. The result indicated, that carbonic acid was produced, and in such quantity, that it could not have been derived from the residuary air in the lungs ; as in some cases it was equal to the bulk of the animal. The same results, although to a less degree, were obtained with fishes and snails,—the animals on which Spallanzani's observations were made. The experiments of Edwards were extended to the mammalia. Kittens, two or three days old, were immersed in hydrogen ; they remained in this situation for nearly twenty minutes without dying, and on examining the air of the vessel after death, it was found, that they had given off a quantity of carbonic acid greater than could possibly have been contained in their lungs at the com- mencement of the experiment. The conclusion of Dr. Edwards, from his various experiments, is, " that the carbonic acid expired is an exha- lation proceeding wholly or in part from the carbonic acid contained in the mass of blood." Several experiments were subsequently made by M. Collard de Martigny,2 who substituted nitrogen for hydrogen; and, in all cases, carbonic acid gas was given out in considerable quantity. These and other experiments would seem, then, to show, that in the lungs, carbonic acid is exhaled, and oxygen and nitrogen are absorbed. They would also seem to prove the existence of carbonic acid in venous blood, respecting which so much dissidence has existed amongst chemists. Allusion has already been made to the fact, that gelatin is not met with in the blood, and to the idea of Dr. Prout,3 that its formation from albumen must be a reducing process. This process he considers to be one great source of the carbonic acid that exists in venous blood. Gelatin contains three or four per cent, less carbon than albumen; it enters into the structure of every part of the animal frame, and espe- cially of the skin; the skin, indeed, contains little else than it. He considers it, therefore, most probable, that a large part of the carbonic acid of venous blood is formed in the skin, and analogous textures. "Indeed," he adds, "we know that the skin of many animals gives off carbonic acid, and absorbs oxygen;—in other words, performs all the offices of the lungs;—a function of the skin perfectly intelligible, on 1 Op. citat., p. 437, and Messrs. Allen and Pepys, in Philos. Transactions for 1829. 2 Journal de Physiologie, x. 111. 3 Bridgewater Treatise, Amer. edit., p. 280, Philad., 1834. ILEMATOSIS. 65 the supposition, that near the surface of the body, the albuminous por- tions of the blood are always converted into gelatin." Gmelin and Tiedemann, Mitscherlich,1 and Stromeyer,2 affirm, on the strength of experiments, that the blood does not contain free carbonic acid, but that it holds a certain quantity in a state of combination, which is set free in the lungs, and commingles with the expired air. The views of Gmelin and Tiedemann, and Mitscherlich on this subject are as follows. It may be laid down as a_ truth, that the greater part, if not all, of the pro- perties of secreted fluids are not dependent upon any act of the secreting organs, but are derived from the blood, which again, must either owe them to the food, or to changes effected on it within the body. These changes are probably accomplished, in part, during the process of di- gestion, but are doubtless mainly effected in the lungs by the contact of the blood with the air. Now, most of the animal fluids, when ex- posed to the air, generate, by the absorption of oxygen, acetic or lactic acid, and this is aided by an elevated temperature, like that of the lungs. In their theory of respiration, the nitrogen of the inspired air is but sparingly absorbed,—by far the greater proportion remaining in the air-cells. The oxygen, on the other hand, penetrates the membranes freely; mingles with the blood; combines partly with the carbon and hydrogen of that fluid, and generates carbonic acid and water, which are thrown off with the expired air; the remainder combines with the organic particles of the blood, forming new compounds, of which the acetic and lactic acids are two; these unite with the carbonated alkaline salts of the blood, and set free the carbonic acid, so that it can be thrown off by the lungs. The acetate of soda—thus formed during the passage of the blood through the lungs—is deprived of its acetic acid by the several secretions, especially by those of the skin and kidneys, and the soda again combines with the carbonic acid, formed during, the circula- tion of the blood through the body, by the decomposition of its organic elements. Carbonate of soda is thus regenerated, and conveyed to the lungs, to be again decomposed by the fresh formation of acids in those organs. Almost the same view is entertained by MM. Dumas and Boussingault, and it is esteemed by Professor Graham3 to be highly probable. Another view, in many respects similar, is held by Professor Arnold.4 As it is more than probable, he remarks, that the carbonic acid occurs in the venous blood, united with some substance from which it is separated with greater or less rapidity by the contact of atmospheric air; and as, further, the carbonate of protoxide of iron greedily with- draws oxygen from the atmosphere, at the same time parting with its carbonic acid and becoming changed into a peroxide, it may be reason- ably supposed, that the carbonic acid of venous blood is united with the iron of the red colouring matter, and is set free during the act of re- spiration, by the reciprocal action of the blood and air. The protoxide, by absorption of oxygen, becomes a peroxide, which, during the circu- lation of the blood through the capillaries, again parts with its oxygen. 1 Tiedemann und Treviranus, Zeitschrift fur Physiol., B. v. H. i. 2 Schweigger's Journal fiir Chimie, u. s. w., lxiv. 105. 3 Elements of Chemistry, Amer. edit., by Dr. Bridges, p. 687, Philad., 1843. * Lehrbuch der Physiologie des Menschen, Zurich, 1836-7. VOL. II.—5 66 RESPIRATION. Carbon is at the same time eliminated from the blood, and unites with- the liberated oxygen to form carbonic acid, which is thrown out by the lungs, whilst oxygen is again absorbed. This is the view embraced by Liebig,1 who has affirmed, that the amount of iron present m the blood, if in the state of protoxide, is sufficient to furnish the means of transport- ing twice as much carbonic acid as can possibly be formed by the oxygen absorbed in the lungs. MM. Chaussier and Adelon,2 again, regard the whole process of haematosis to be essentially organic and vital. They are of opinion, that an action of selection and elaboration is exerted both as regards the reception of oxygen and the elimination of carbonic acid. But their arguments on this point are unsatisfactory, and are negatived by the facility with which oxygen can be imbibed, and carbonic acid trans- udes through animal membranes. In their view, the whole process it- effected in the lungs, as soon as the air comes in contact with the vessels containing venous blood. Imbibition of oxygen they look upon as a case of ordinary absorption; transudation of carbonic acid as one of exhalation; both of which they conceive to be, in all cases, vital actions, and not to be likened to any physical or chemical process. Admitting that oxygen and a portion of nitrogen absolutely enter the pulmonary vessels, of which we have direct proof, are they, it has been asked, separated from the air in the air-cells, and then absorbed; or does the air enter undecomposed into the vessels, and then furnish the proportion of each of its constituents needed by the wants of the system,—the excess being rejected ? Could it be shown, that such a decomposition is actually effected at the point of contact between the pulmonary vessels and the air in the lungs, it would seem, at first, to prove the notion of Mr. Ellis,3 and of Chaussier and Adelon, that a vital action of selection is exerted; but the knowledge we have attained concerning the transmission of gases through animal membranes would suggest another explanation. The rate of transmission of carbonic acid is greater than that of oxygen; of oxygen greater than that of nitrogen (see vol. i. p. 68). We can hence understand, that more oxygen than nitrogen may pass through the coats of the pulmonary bloodvessels5 and can comprehend the facility with which the carbonic acid, formed in the course of the circulation, may permeate the same vessels, and mix with the air in the lungs. Sir Humphry Davy is of opinion, that the whole of the air is absorbed, and that the surplus quantity of each of the constituents is subsequently discharged. In favour of this view, he remarks that air has the power of acting upon the blood through a stratum of serum, and he thinks that the undecomposed air must be absorbed before it can arrive at the blood in the vessels. It is probable, however, from the different penetrating powers of the gases—oxygen and nitrogen, that the proportion of those constituents cannot be the same in the interior as at the exterior of the pulmonary vessels. Pro- 1 Animal Chemistry, Webster's Amer. edit., p. 26l, Cambridge, 1843. 2 Physiologie de 1'Homme, edit, cit., iii. 254. 3 An Enquiry into the Changes induced on Atmospheric Air, &c, Edinb., 1807; and Fur- ther Enquiries, Edinb., 1816. HAEMATOSIS. 67 fessor Muller,1 however, accords with Sir Humphry, and supposes that the air, on entering the lungs, is decomposed in consequence of the affinity of oxygen for the red particles of the blood; carbonic acid being formed, which is exhaled in the gaseous form, along with the greater part of the nitrogen.2 It has been remarked, that when oxygen is applied to venous blood out of the body, the latter assumes a florid colour. On what part of the blood, then, does the oxygen act? Doubtless, upon the red cor- puscles. Facts, hereafter stated in the description of venous blood, have appeared to some to show that these corpuscles are devoid of colour, whilst they exist in chyle and lymph; but in the lungs, the contact of air changes them to a florid, red. The coloration of the blood is, con- sequently, effected in the lungs; but whether this change be of any importance in haematosis is doubtful. In many animals, the red colour does not exist; and, in all,vit can perhaps only be esteemed an evidence, that the other important changes have been accomplished in those organs. Of late, the opinion has been revived, that the oxygen of the air acts upon the iron, which Engelhart and Rose3 had detected in the colouring matter,—but how we are not instructed. It has been asserted, that if the iron be separated, the rest of the colouring matter, which is of a venous red colour, loses the property of becoming scarlet by the contact of oxygen; but this, again, has been denied. Another view of arterialization has been advanced by Dr. Stevens.4 According to him, the colouring matter is naturally very dark; is rendered still darker by acids, and acquires a florid hue from the addi- tion of chloride of sodium, and from the neutral salts of the alkalies generally. The colour of arterial blood is ascribed by him to hematosin reddened by the salts contained in the serum; the characters of venous blood to the presumed presence of carbonic acid, which, like other acids, darkens hematosin; and the conversion of venous into arterial blcod to the influence of the saline matter in the serum being restored by the separation of carbonic acid. If we take a firm clot of venous blood, cut off a thin slice, and soak it for an hour or two in repeatedly renewed portions of distilled water; in proportion as the serum is washed away, the colour of the clot deepens; and, when scarcely any serum remains, the colour, by reflected light, is quite black. In this state, it may be exposed to the atmosphere, or a current of air may be blown upon it without any change of tint whatever; whence it would follow, that when a clot of venous blood, moistened with serum,, is made florid by the air, the presence of serum is essential to the-phenomenon. The serum is believed, by Dr. Stevens, to contribute to this change by means of its saline matter; for when a dark clot of blood, which oxygen fails to redden, is immersed in a pure solution of salt, it quickly acquires 1 Handbuch, u. s. w., Baly's translation, p. 334, Lond., 1838. 2 See, on this subject, Dr. John Reid, art. Respiration, Cyclop, of Anat. and Physiol., Pt. xxxii. p. 365, Lond., Aug., 1848. 3 Edinb. Med. and Surg. Journal for Jan., 1827. * Observations on the Healthy and Diseased Properties of the Blood, Lond., 1832; and Proceedings of the Royal Society for 1834-5, p. 334. 68 RESPIRATION. the crimson tint of arterial blood; and loses it again when the salt M abstracted by soaking in distilled water. The facts, detailed^ by Dr. Stevens, were confirmed by Mr. Prater,1 and by Dr. lurner, ot the London University. The latter gentleman, assisted by Professor Cjuain, of the same institution, performed the following satisfactory experiment. He collected some perfectly florid blood from the femoral artery ot a dog; and on the following day, when a firm coagulum had formed, several thin slices were cut from the clot with a sharp penknife, and the serum was removed from them by distilled water, which had just before been briskly boiled, and allowed to cool in a well-corked bottle. The water was gently poured on these slices, so that while the serum was dissolving, as little as possible of the colouring matter should be lost. After the water had been poured off, and renewed four or five times, occupying in all about an hour, the moist slices were placed in a saucer at the side of the original clot, and both portions were shown to several medical friends, all of whom unhesitatingly pronounced the unwashed clot to have the perfect appearance of arterial blood, and the washed slices to be as perfectly venous. On restoring one of the slices to the serum it shortly recovered its florid colour; and another slice, placed in a solution of bicarbonate of soda, instantly acquired a similar hue ;—yet, as we have seen, carbonate of soda is considered by Messrs. Gmelin, Tiedemann, and Mitscherlich, to exist in venous or black blood! In brightening, in this way, a dark clot by a solution of salt or a bicarbonate, Dr. Turner found the colour to be often still more florid than that of arterial blood; but the colours were exactly alike when the salt was duly diluted. Dr. Turner remarks, that he is at a loss to draw any other inference from this experiment, than that the florid colour of arterial blood is not due to oxygen; but, as Dr. Stevens sug- gests, to the saline matter of the serum. The arterial blood, which was used, had been duly oxygenized within the body of the animal, and should not in that state have lost its tint by the mere removal of its serum; and he adds,—the change from venous to arterial blood appears, contrary to the received doctrine, to- consist of two parts essentially distinct; one a chemical change, essential to life, accompanied by ab- sorption of oxygen, and evolution of Carbonic acid; the other depend- ant on the saline matter of the blood, which gives a florid tint to the colouring matter after it has been modified by the action of oxygen. "Such," says Dr. Turner, "appears to be a fair inference from the facts above stated; but being drawn from very limited observation, it is offered with diffidence, and requires to be confirmed or modified by future researches." But we are perhaps scarcely justified in inferring, from the experiments of Stevens, Turner, and others, more than the fact, that a florid hue is communicated to blood by sea-salt, and by the neutral salts of the>alkalies in general, and indeed by admixture with sugars; whilst acids render it still darker. The precise changes that occur during the arterialization of the blood in the lungs are still unknown; 1 Experim. Inquiries in Chemical Physiology, Part i., on the Blood, Lond., 1832. . 2 Elements of Chemistry, 5th edit., by Dr. Bache, p. 609, Philad., 1835. HiEMATOSIS. 69 and if we rely on the recent experiments of Gmelin, Tiedemann, and Mitscherlich, venous blood cannot owe its colour to free carbonic acid, because none is to be met with in it; whilst the presence of the carbon- ates of alkalies ought to communicate the florid hue to it. Since Dr. Stevens first published his views, the subject has been far- ther investigated by Dr. William Gregory, and Mr. Irvine. They intro- duced portions of clot, freed by washing from serum, into vessels contain- ing pure hydrogen, nitrogen, and carbonic acid, placed over mercury. As soon as the strong saline solution came in contact with them, the colour of the clot, in all the true g-ases, changed from black to bright red; and the same change was found to take place in the Torricellian vacuum. On repeating these experiments with the serum of blood, and a solution of salt in water of equal strength with the serum, no change took place until atmospheric air, or oxygen gas, was admitted. Whence it appears—as properly inferred by the late Mr. Egerton A. Jennings, who published an interesting "Report on the Chemistry of the Blood as Illustrative of Pathology,"1—that though saline matter may be ne- cessary to effect the change of colour of venous to that of arterial blood, with so dilute a saline solution as that which exists in serum, the pre- sence of oxygen is likewise necessary. Dr. Davy2 dissents, however, from these conclusions, and is disposed to infer, from all the facts with which he is acquainted, that the Colour of the blood, whether venous or arterial,—that is, dark or florid,—is independent of the saline matter in the serum, considered in relation to agency; and that, according to the commonly received view, oxygen is the cause of the bright hue of the arterial fluid, and its consumption and conversion into carbonic acid the cause of the dark hue of the venous,—the saline matter being negative in regard to colour; and its chief use, in his opinion, being "to preserve the red globules from injury, prevent the solution of their colouring matter, retain their forms unchanged, and to bear them in their course through the circulation." An idea has been entertained, that the change from arterial to venous blood, and conversely, as regards colour, is dependent in a great mea- sure on a difference in the shape of the blood corpuscles; and is there- fore owing rather to physical than to chemical changes in them. Such is the opinion Of Kaltenbrunner, Schultz, Reuter, Gulliver, Harless, Kirkes and Paget,3 Nasse, Mulder, and others. It is of course opposed to that of Liebig, already stated. Mulder4 explains the difference be- tween the colour of arterial and venous blood as follows. Two oxides of protein are formed in the act of respiration, which have a strong plastic tendency, and solidify around each corpuscle, making the cap- sule thicker, and better qualified to reflect light. Each corpuscle of arterialized blood is then, in reality, invested with a complete envelope 1 Transactions of the Provincial Medical and Surgical Association, vol. ifi., Worcester and London, 1835. 2 Researches, Physiological and Anatomical, Dunglison's Amer. Med. Lib. edit., p. 96, Philad., 1840. 3 Manual of Physiology, Amer. edit., p. 59, Philad., 1849. 4 Versueh einer Allgemeinen Physiologischen Chemie, cited by Mr. Day in Simon, Animal Chemistry, Sydenham edit., p. 193, Lond., 1845; and Chemistry of Vegetable and Animal Physiology, translated by Fromberg, p. 342, Lond. and Edinb., 1849. 70 RESPIRATION. of buffy coat, which gradually contracts, and speedily forms cupped or bi-concave surfaces, which are favourable to the reflection ot hgnt. Un reaching the capillaries, the coating of the oxides of protein is removed, and the corpuscles, losing their opaque investment, and cupped form, no longer reflect light, and the blood assumes the venous tint. Dr. G. 0. Rees,1 however, considers this explanation to be entirely hypothetical and erroneous. He rejects the idea of a layer of plastic oxy-protein being deposited on the blood corpuscles during respiration; and.mstead of considering the hematosin as undergoing no change, and maintaining the same condition in arterial and venous blood, he looks upon it as the cause of the change of colour in the blood by virtue of some chemical altera- tion, which takes place in it, but whose nature—if there be any such alteration—remains a mystery. Recently, indeed, he has himself ad- vanced the following ingenious theory.2 He found by analyses, that the corpuscles of venous blood contain fatty matter in combination with phosphorus. This does not exist in arterial blood, or, at most, is met with in it in very small quantity. During respiration the oxygen of the inspired air unites with the phosphorus and fatty matter, and com- bustion takes place; of which the products are water and carbonic acid from the union of the oxygen with the elements of the fatty matter; and phosphoric acid from the union of the oxygen with the phosphorus. The carbonic acid and water are exhaled, and appear in the expired air; the phosphoric acid attracts the soda of the liquor sanguinis from its combination with albumen and lactic acid, and forms a tribasic phosphate of soda,—a salt, which possesses in a marked degree the property of communicating a bright colour to hematosin. It is proper to add, that Burdach, Miiller, Bruch, Marchand, Scherer, and others, have failed to detect by the microscope any difference in the external form of the corpuscles in arterial and in venous blood. Still, Dr. John Reid3 is disposed to conclude, that the change in the blood from the venous to the arterial hue in the lungs is a physical and not a chemi- cal action; and "that though there is pretty strong evidence in favour of the opinion, that this physical change consists in an alteration of the form of the red corpuscles, yet it is not free from doubt." The slight diminution, if it exist, in .the specific gravity of arterial blood has been considered, but we know not on what grounds, to depend on the transpiration, which takes place into the air-cells, and was formerly thought to be owing to the combustion of oxygen and hydrogen. This will engage us in another place;—as well as the changes produced in its capacity for heat, on which several ingenious speculations have been founded to account for animal temperature. The other*changes are at present inexplicable ; and can only be understood by minute chemi- cal analysis, and by an accurate comparison of the two kinds of blood, —venous and arterial. This has been carefully done by Simon, who 1 Lond. Med. Gazette, 1844-5, p. 840, and Mulder, op. cit., p. 341. 2 Proceedings of the Royal Society, June 3, 1847, and Lond., Edinb., and Dublin Philos. Magazine for July, 1848. 3 Art. Respiration, Cyclop, of Anat. and Physiology, Pt. xxxii. p. 361, London, August, 1848. CUTANEOUS RESPIRATION. 71 infers, from his analyses, that arterial blood generally contains less solid residue than venous blood; and less fat, albumen, hematin, extractive matter, and salts ; but further experiments are demanded. The blood corpuscles of arterial blood contain less colouring matter than those of venous blood.1 It is manifest, from the preceding detail, that our knowledge regard- ing the precise changes effected on the air and the blood by respiration is by no means definite. We may, however, consider the following points established. In the first place :—-the air loses a part of its oxy- gen and nitrogen; but this loss varies according to numerous circum- stances. 2dly. It is found to have acquired carbonic acid, the quan- tity of which is also variable. 3dly. The bulk of the air is diminished; but the extent of this likewise differs. 4thly. The blood, when it attains the left side of the heart, has a more florid colour. 5thly. This change appears to be caused by the contact of oxygen. 6thly. The blood in the lungs gets rid of a quantity of carbonic acid. 7thly. The oxygen taken in is more than necessary for the carbonic acid formed. 8thly. The constituents of the air pass directly through the coats of the pulmonary vessels, and certain portions of each are discharged or retained, according to circumstances. 9thly. A quantity of aqueous vapour is discharged from the lungs ; the expired air is indeed saturated with it. lOthly. The expired air has always a temperature at or near 99°; and, lastly, it would appear, from the facts stated elsewhere, that the red corpuscles are not the only constituent of the blood that under- goes a change in the respiratory process ; and that the fibrin of venous blood most nearly resembles albumen, whilst that of arterial blood con- tains more oxygen, and is more highly annualized. c. Cutaneous Respiration, Sfc. A question has arisen, whether any absorption and exhalation of air, and conversion of blood from venous to arterial, take place in any other part of the body than the lungs. The reasons, urged in favour of the affirmative of this question, are ;—that, in the lower classes of animals, the skin is manifestly the organ for the reception of air; that the mucous membrane of the lungs evidently absorbs air, and is simply a.prolongation of the skin, resembling it in texture ; and, lastly, that when a limited quantity of air has been placed in contact Avith the skin of a living animal, it has been absorbed, and found to have experienced the same changes as are effected in the lungs. Mr. Cruikshank2 and Mr. Abernethy3 analyzed air, in which the hand or foot had been con- fined for a time ; and detected in it a considerable quantity of carbonic acid. Jurine, having placed his arm in a cylinder hermetically closed, found, after it had remained there two hours, that oxygen had disap- peared, and 0*08 of carbonic acid had been formed. These results were confirmed by Gattoni ;4 and from experiments by Professor 1 For various analyses of the two kinds of blood, see Simon, op. cit., p. 194. 2 Experiments on the Insensible Perspiration, &c, Lond., 1795. 3 Surgical and Physiological Essays, Part ii. p. 115, Lond., 1793. 4 Diet, dee Sciences Medicales, art. Peau. 72 RESPIRATION. Scharling, referred to before, the amount of carbon exhaled by the skin in the twenty-four hours, has been estimated at two ounces; but this is probably beyond the real amount. On the other hand, Drs. Priestley,1 Klapp,2 and Gordon" could never perceive the least change in the air under such circumstances. Perhaps in these, as in all cases where the respectability of testimony is equal, the positive ought to be adopted rather than the negative. It is probable, however, that absorption >is effected with difficulty; and that the cuticle, as we have elsewhere shown, is placed on the outer surface to obviate the bad effects that would be induced by heterogeneous gaseous, miasmatic, or other absorp- tion. We have seen that some of the deleterious gases, as sulphuretted hydrogen, are most powerfully penetrant, and, if they could enter the surface of the body with readiness, unfortunate results might super- vene. In those parts where the cuticle is extremely delicate, as in the lips, some conversion of venous into arterial blood may be effected, and this may be a great cause of their florid colour. According to this view, the arterialization of the blood occurs in the lungs chiefly, owing to their formation being sO, admirably adapted to the purpose; and it is not effected in other parts, because their arrange- ment is unfavourable for such a result. d. Effects of the Section of certain Nerves on Respiration. It remains for us to inquire into the effect produced on the lungs by the cerebro-spinal nerves distributed to them,—or rather, into what is the effect of depriving the respiratory organs of their nervous influence from the brain and spinal marrow. The only encephalic nerves, dis- tributed to them, are the pneumogastric or eighth pair of Willis, which, we have seen, are sent, as their name imports, to both the lungs and stomach. The section of these nerves early suggested itself to phy- siologists, but it is only in recent times that the phenomena resulting from it have been clearly comprehended. The operation appears to have been performed as long ago as the time of Rufus of Ephesus, and was afterwards repeated by Chirac, Bohn, Duverney, Vieussens, Schra- der, Valsalva, Morgagni, Haller, and numerous other distinguished physiologists. It is chiefly, however, in recent times, and especially from the labours of Dupuytren, Dumas, De Blainville, Provencal, Legallois, Magendie, Breschet, Hastings, Broughton, Brodie, Wilson Philip, Longet, John Reid, and others, that the precise effects upon the respiratory and digestive functions have been appreciated. When these nerves are divided in a living animal, on both sides at once, the animal dies more or less promptly; at times immediately after their division, but it sometimes lives for a few days;—M. Magendie says never beyond three or four. The effects produced upon the voice, by their division above the origin of the recurrents, have been referred to under another head (vol. i. p. 593). Such division, however, does not simply implicate the larynx; it necessarily affects the lungs, as well as the stomach. As regards the larynx, the same results, aecord- 1 Experiments and Observations on Different Kinds of Air, ii. 193, and v. 100, Lond., 1774. 2 Inaugural Essay on Cuticular Absorption, p. 24, Philad., 180.5. 3 Ellis's Inquiry into the Changes of Atmospheric Air,&c, p. 355, Edinb., 1837. EFFECTS OF DIVIDING CERTAIN NERVES. 73 ing to M. Magendie,1 are produced by dividing the trunk of the pneu- mogastric above the origin of the recurrents as by the division of the recurrents themselves: the muscles, whose function it is to dilate the glottis, are paralysed; and consequently, during inspiration, no dilata- tion takes place ; whilst the constrictors, which receive their nerves from the superior laryngeal, preserve all their action, and close the glottis, at times so completely, that the animal dies at once from suffo- cation. But if the division of these nerves should not induce instant death in this manner, phenomena follow, considerably alike in all cases, which go on until the death of the animal. These are the fol- lowing:—respiration is, at first, difficult; the inspiratory movements are more extensive and rapid, and the animal's attention appears to be particularly directed to them; the locomotive movements are less frequent, and evidently fatigue; frequently, the animal remains en- tirely at rest; the formation of arterial blood is not prevented at first, but soon, on the second day, for instance, the difficulty of breathing augments, and the inspiratory efforts become gradually greater. The arterial blood has now no longer the vermilion hue proper to it. It is darker thah it ought to be: its temperature falls; respiration requires the exertion of all the respiratory powers; the body gradually becomes cold, and the animal dies. On opening the chest, the air-cells, bronchi, and frequently the trachea, are found filled by a frothy fluid, which is sometimes bloody; the substance of the lung is tumid; the divisions and even the trunk of the pulmonary artery are greatly distended with dark, almost black, blood; and extensive effusions of serum and even of blood are found in the parenchyma of the lungs. Experiments have, like- wise, shown that, in proportion as these phenomena appeared, the animal consumed less and less oxygen, and gave off a progressively diminishing amount of carbonic acid. From the phenomena that occur after the section of the nerves on both sides, it would seem to follow, that the first effect is exerted upon the tissues of the lungs, which, being deprived of nervous influence from the brain, are no longer capable of exerting their ordinary tonicity and muscularity. Respiration, consequently, becomes difficult; the blood no longer circulates freely through the capillary vessels of the lungs; the consequence is, that transudation of its serous portions, and occa- sionally effusion of blood, owing to rupture of small vessels, takes place, filling the air-cells more or less; until, ultimately, all communication is prevented between the inspired air and the bloodvessels, and the con- version of venous into arterial blood is completely precluded. Death is then the inevitable and immediate consequence. The division of the nerve on one side affects merely the lung of the corresponding side. Life can be continued by the action of one lung only: it is, indeed, a matter of astonishment how long some individuals have lived when the lungs have been almost wholly obstructed. Every morbid anatomist has had repeated opportunities of observing, that, for a length of time prior to dissolution, in cases of pulmonary consumption, the process of respiration must have been carried on by a very small portion of lung. 1 Precis, &c, 2de edit, ii. 355. 74 RESPIRATION. From his experiments on this subject, Sir Astley Cooper infers, that the pneumogastric nerve is most important;—1st, in assisting in the maintenance of the function of the lungs, by contributing to the change of venous into arterial blood; 2dly, in being necessary to .the act of swallowing; and 3dly, in being essential to the digestive process. Dr. John Reid is of opinion, that the pulmonary branches would seem to be nerves concerned chiefly in transmitting to the medulla oblongata the impressions that excite respiratory movements, and are thus prin- cipally afferent nerves; but it is possible, he thinks, that they contain motor filaments also.1 The experiments of Dr. Wilson Philip2 and others show, moreover,- what has been more than once inculcated,—the great similarity between the nervous and galvanic fluids. The state of dyspnoea induced by the division of the pneumogastric nerves was, in numerous cases, entirely removed by the galvanic current passed from one divided extremity to the other. The results of these experiments induced him to try gal- vanism in cases of asthma. By transmitting its influence from the nape of the neck to the pit of the stomach, he gave decided relief in every one of twenty-two cases; four of which occurred in private prac- tice, and eighteen in the Worcester Infirmary. Sir A. Cooper3 instituted similar experiments on the phrenic nerves. As soon as they were tied, the most determined asthma was produced; breathing went on by means of the intercostal muscles; £he chest was elevated to the utmost by them; and in expiration the chest was as remarkably drawn in. The animals did not live an hour; but they did not die suddenly, as they do from pressure on the carotid and vertebral arteries. The lungs appeared healthy, but the chest contained more than its natural exhalation. He also tied the great sympathetic; which produced little effect; the heart appeared to beat more quickly and feebly than usual. The animal was kept seven days, when one nerve was found ulcerated through; the other nearly so at the situation of the ligatures. On examination, no particular alteration of any organ was observed. Lastly, Sir Astley tied all three nerves on each side, the pneumogastric, phrenic, and great sympathetic: the animal lived little more than a quarter of an hour, and died of dyspnoea. From these experiments, he infers, that the sudden death, which he found to follow pressure on the sides of the neck, cannot be attributed to any injury of the nerves, but to an impediment to the due supply of blood to the great centres of nervous influence. The nervous centre of the respiratory movements is the vesicular neurine in the upper part of the medulla oblongata. Into it the pneu- mogastric nerves, which appear to be the chief excitors of respiration, may be traced; ,and from it the different motor or efferent nerves pro- ceed either directly or indirectly. Of these, the most important is the phrenic. The vesicular neurine of the medulla receives the impression 1 Edinb. Med. and Surg. Journ., April, 1839; and art. Par Vagum in Cyclop, of Anat. and Physiol., Part xxvii. p. 896, March, 1846. 2 Experimental Inquiry into the Laws of the Vital Functions, &c, 2d edit., p. 223, Lond., 1818; also, Journal of Science and Arts, viii. 72. 3 Op. cit., p. 475. OF ANIMALS. 75 of the besoin de respirer or necessity of breathing; and thence it is reflected along the appropriate nerves to the muscles concerned in inspiration. e. Respiration of Animals. In concluding the subject of respiration, we may briefly advert to the different modes in which the process is effected in the classes of animals, and especially in birds,—the respiratory organs of which con- stitute one of the most singular structures of the animal economy. The lungs themselves,—as in the marginal figure of those of the ostrich, (Fig. 273,)—are comparatively small, and adherent to the chest,— where they seem to be placed in the intervals of the ribs. They are covered by the pleura on their under surface only, so that they are, in fact, on the outside of the cavity of the chest. A great part of the tho- rax, as well as of the abdomen, is occupied by membranous air-cells, into which the lungs open by con- siderable apertures. Besides these cells, a considerable portion of the skeleton in many birds forms recep- tacles for air, and if we break a long bone of a bird of flight, and blow into it when the body of the animal is immersed in water, bubbles of air will escape from the bill. The ob- ject, of course, of all this arrange- ment is to render the body light, and thus to facilitate its motions. Hence, the largest and most numerous bony cells are found in such birds as have the highest and most rapid flight, as the eagle. The barrels of the quills are likewise hollow, and t;an be filled with air, or emptied at pleasure. In addition to the uses just mentioned, these air receptacles diminish the necessity for breathing so frequently in the rapid and long-continued mo- tions of certain birds, and in the great vocal exertions of those that sing. In fishes, in the place of lungs we find branchiae or gills, which are placed behind the head on each side, and have a movable gill-cover. By the throat, which is connected with the gills, the water is conveyed to, and distributed through them: in this way, the air, contained in the water, which, according to Biot, Von Humboldt1 and Provencal, Con- Thoracic and Abdominal Viscera of the Os- trich. o. Heart, lodged in one great air-cell, b. The stomach, c. The intestines, surrounded by large air-cells, d. The trachea dividing into bronchi. e,e. The lungs. 1,2,3, f,f. Other great air- cells, communicating with other cells and with the lungs, g, g. The openings by which such communication is made. Memoires de la Societe d'Arcueil, i. 252, and ii. 400. 76 CIRCULATION. figliachi, and Thomson,1 is richer in oxygen than that of the atmo- sphere, having from 29 to 32 parts in the 100, instead ot M or 21, comes in contact with the blood circulating through the gills. ±ne water is afterwards discharged through the branchial openings— aper- turse branchiales— and, consequently, they do not expire along the same channel as they inspire. . „ Lastly, in the insect tribe—in the white-blooded animal—we find the function of respiration effected altogether by the surface ot the body; at least, so far as regards the reception of air, which enters through apertures termed stigmata, the external terminations ot tra- chese or air tubes, whose office it is to convey air to different parts of the system. In all these cases, we find precisely the same changes effected upon the inspired air;—and especially, that oxygen and nitrogen have disap- peared; and that carbonic acid of a bulk nearly equal to that of the organ is met with in the residuary air. CHAPTER IV. 274. CIRCULATION. The next function to be considered is that by which the products of the various absorptions, converted into arterial blood in the lungs, are distributed to every part of the body,—a function most important to the physiologist and the pathologist, and without a know- ledge of which it. is impossible for the latter to comprehend the doctrine of disease. Assuming the heart to be the great organ of the function, the circulatory fluid must set out from it, be distribut- ed through the lungs, undergo aeration there, be sent to the opposite side of the heart, whence it is distributed to every part of the system by efferent vessels, and be returned by veins or afferent vessels to the right side, from which it set out,— thus performing a complete circuit. The lower class of animals differ essen- k Left auhcie. l. Left ventricle, f. tially, as we shall find hereafter, in their Pulmonary artery. A. Aorta. n • • • V, organs of circulation: whilst in some, the apparatus appears to be confounded with the digestive; in others, the blood is propelled without any great central organ; and in others, again, the heart is but a single organ. In man, and in the upper classes of ani- mals, the heart is double;—consisting of two sides, or really two hearts, 1 Dr. Thomson found that 100 cubic inches of the water of the river Clyde contained 3-113 inches of air; and that the air contained 29 per cent, of oxygen. Edinb. New Philo- soph. Journal, xxi. 370, Edinb., 1836. Heart of the Dugong D. Right auricle. E. Right ventricle. CIRCULATORY APPARATUS. 77 separated from each other by a septum. In the dugong, the two ven- tricles are almost entirely detached from each other. As all the blood of the body has to be emptied into this central organ, and to be subsequently sent from it; and as its flow is continuous, two cavities are required in each heart,—the one to receive the blood, the other topropcl it. The latter distinctly contracts and dilates alternately. The cavity or chamber of each heart, that receives the blood, is called auricle, and the vessels that transport it thither are veins; the cavity by which the blood is projected forwards is called ventricle, and the vessels, along which the blood is sent, are arteries. One of these hearts is entirely appropriated to the circulation of venous blood, and hence has been called venous heart,—also right or anterior heart, from its situation,—and pulmonary from the pulmonary artery arising from it. The other is for the circulation of arterial blood, and is hence called arterial heart, also left or posterior, from its situation,—aortic heart, because the aorta arises from it; and systemic, because the blood is sent from it to the general system. The whole of the vessels communicating with the right heart contain venous blood; those of the left side arterial blood. If we consider the heart, to be the centre, two circulations must be accomplished, before the blood, setting out from one side of the heart, performs the whole circuit. One of these consists in the transmission of the blood from the right side of the heart, through the lungs, to the left; the other, in its transmission from the left side, along the arte- ries, and by means of,the veins, back to the right. The former is called the lesser or pulmonic, the latter the greater or systemic circulation. The organs, by which these are effected, will require a more detailed examination. 1. ANATOMY OF THE CIRCULATORY ORGANS. The circulatory apparatus is composed of organs by which the blood is put in motion, and along which it passes during its circuit. a. Heart. To simplify the consideration of the subject, we shall consider the heart double; and that each system of circulation is composed of a heart; of arteries, through which the blood is sent from the heart; and of veins, by which the blood is returned to it. At the minute termi- nation of each of these is a capillary system. We shall first describe the central organ as forming two distinct hearts; and afterwards the two united. The pulmonic, right or anterior heart, called also heart of black blood, is composed of an auricle and a ventricle. The auricle, so termed from some resemblance to a small ear, is situate at the base of the organ, and receives the whole of the blood returned from various parts of the body by three veins;—the two vense cavas, and the coronary. The vena cava descendens terminates in the auricle in the direction of the aper- ture by which the auricle communicates with the ventricle. The vena cava ascendens, the termination of which is directed more backwards, has the remains of. a valve which is^much larger in the foetus, called 78 CIRCULATION. Fig. 275. valve of Eustachius. The third vein is the cardiac or coronary fit returns the blood from the heart which has been carried thither by the coronary artery. In the septum between the right and left auricle, there is a superficial de- pression, about the size of thepointof the finger, which is the vestige of the foramen ovale,—an important part of the circulatory apparatus of the foetus. The opening, through which the auri- cle projects its blood into the ventricle, is situate downwards and forwards, as seen in Fig. 275. The inner surface of the proper auricle, or that which more particu- larly resembles the ear of a quadruped, — the remainder being some- times called sinus ve- nosus or sinus venarum cavarum, — is distin- guished by having a number of fleshy pillars in it, which, from their supposed resemblance to the teeth of a comb, are called musculi pectinati. They are mere varieties, however, of the columnse carneee of the ventricles. The right ventricle or pulmonary ventricle is situate in the anterior part of the heart; the base and apex corresponding to those of the heart. Its cavity is generally greater than that of the left side, and its parietes not so thick, owing to its having merely to force the blood through the lungs. ^ It communicates with the auricle by the auriculo-ventricular opening— ostium venosum; and the only other opening into it is that which communicates with the interior of the pulmonary artery. The open- ing between the auricle and ventricle is fur- nished with a tripartite valve, called tricuspid or triglochin; and the Heart placed with its Anterior Surface upwards, and its Apex turned to the right hand of the spectator. The Right Auricle and Right Ventricle are both opened. Parts in right auricle:—h. Entrance of vena cava superior, which is itself marked, d. Inferior cava, marked r, has a probe passed through it into the auricle, m. The smooth part of the auricle, o. MusCuli pectinati; seen in the auricular appendix which is cut open. n. Eustachian valve placed over the mouth of the inferior cava. i. Fossa ovalis, or vestige of the foramen ovale. s. Annulus ovalis. The probe leading from s into the right ven- tricle passes through the auriculo-ventricular opening, v'. Mouth of the coronary vein. Parts in the right ventricle, in which the other end of the probe, from s, appears :—tt. Cavity of conus arteriosus, leading to the pulmonary artery, k. I. Convex septum between the ventricles, c. Anterior segment of the tricuspid valve connected by slender cords, the chordae tendineae, to the musculi papillares, e. f. The aorta. Fig. 276. Semilunar Valves closed. CIRCULATORY APPARATUS. 79 pulmonary artery has three others, the sigmoid or semilunar. From the edge of the tricuspid valve, next the apex of the heart, small, round, tendinous cords, called chordse tendinese, are sent off, which are fixed, as represented in Fig. 275, to the extremities of a few strong columnse carnese—called muscidipapillares. These tendinous cords are of such a length as to allow the valve to be laid against the sides of the Fig. 277. ventricle, In the dilated state of that organ, and to admit of its being pushed back by the blood, until a nearly complete septum is formed during the contraction of the ven- tricle. The semilunar or sigmoid valves are three in number, situate around the artery. When these fall together, there must necessarily be a space left between them. To ob- viate the inconvenience that would result from the existence of such a free space, a small granular body is attached tO the middle Of the margin Part of the Left Ventricle, and commencement of each valve; and_ these, coming ^J^Aorta laid open to show the Sigmoid a. Portion of the aorta, v. Muscular wall of left ventricle. 1, 2, 3. Semilunar or sigmoid valves, c. Corpus Arantii in one of them. e. Thin lunated marginal portion or lunula, s, t, t. Sinuses of Valsalva, t, t. Mouths of the two coronary arteries of the heart, m. Anterior seg- ment of the mitral valve, the fibrous structure of which is continuous above with the aortic tendi- nous zone, opposite the attached margin of the sigmoid valve, marked 1. Opposite the valves, 2 and 3, the tendinous zone receives below the muscular substance of the ventricle, v. h. Larger chordae tendineae. o,o. Musculi papillares. together, as at A, Fig. 276, when the valves are shut down, complete the diaphragm, and prevent any blood from passing back to the heart. These small bodies are termed, from their reputed discoverer, corpuscula Arantii and also corpuscula Mor- gagnii; or, from their resemblance to the seed of the sesamum, corpuscula sesamoidea. The valves, when shut, are concave towards the lungs, and convex towards the ventricle. Immediately above them the artery bulges out, forming three sacculi or sinuses, called sinuses of Valsalva. These are often said to be partly formed by the pressure of the blood upon the sides of the vessel. The structure is doubtless ordained, and is admirably adapted for a specific purpose,—namely, to allow the free edges of the valves to be readily caught by the refluent blood, and thus facilitate their closure. Within the right ventricle, and especially to- wards the apex oPfhe heart, many strong eminences are seen, columnse carnese (Fig. 275). These run in different directions, but the strongest of them longitudinally with respect to the ventricle. They are of various sizes, and form a beautifully reticulated texture. Their chief use probably is, to strengthen the ventricle, and prevent it from being over-distended; in addition to which they may tend to mix the different products of absorption. The corporeal, left, aortic or systemic heart,—called also heart of red blood,—has likewise an auricle and a ventricle. The left auricle is con- siderably thicker and stronger but smaller than the right; and it is likewise divided into sinus venosus and proper auricle, which'form a 80 CIRCULATION. 278. common cavity. The columns in the latter.are like those of the right, but less distinct. From the under part of the auricle, a circular passage, termed ostium arteriosum or " auricu- lar orifice," leads to the posterior part of the base of the cavity of the left ventricle. The left auricle re- ceives the blood from the pulmonary veins. The left or aortic ventricle is situate at the posterior and left part of the heart. Its sides are three times thicker and stronger than those of the right ventricle, to adapt it for the much greater force it has to exert; for, whilst the right ventricle merely sends its blood to the lungs, the left Heart seen from behind, and having the Left ventricle transmits it to every part of the body. Its muscular force has been estimated at twice that of the right.1 It is narrower and rounder, but considerably longer, than the right ventricle, and forms the apex of the heart. The internal surface of this ventricle has the same general appearance as the other; but differs which may be compared with that of the walls frnrrl it jn La vino- "hvo-pr rnnrp nnmp- of the right ventricle, Fig. 275. r. Entrance lrorn- ll ln naVNlg larger, more nUHie- of inferior cava. rous, firmer, and stronger columnsecar- neae. In the aperture of communica- tion with the corresponding auricle, there is here, as in the opposite side of the heart, a ring or zone, from which a valve, essentially like the tri- cuspid, goes off. It is stronger, however, and divided into two princi- pal portions only; the chordae tendinese and musculi papillares, are also stronger and more numerous. This valve has been termed mitral, from some supposed resemblance to a bishop's mitre. At the fore and right side of the valve, and behind the commencement of the pulmonary artery, a round opening exists, which is the mouth of the aorta. Here are three semilunar valves, with their corpuscula Arantii; like those of the pulmonary artery, but a little stronger; and, on the outer side of the semilunar valves, are the sinuses of Valsalva, a little more promi- nent than those of the pulmonary artery. The structure of the two hearts is the same. A serous membrane covers both. It is an extension of the inner membrane of the pericar- dium. The substance of the heart is essentially muscular. The fibres run in different directions, longitudinally and transversely, but most of them obliquely. Many pass over the point, from one heart to the other, and all are so involved as to render it difficult to'unravel them. The cavi- Auricle and Ventricle opened Parts in left auricle:—a. Smooth wall of auricular septum c, c, c. Openings of the four pulmonary veins, d. Left auricular ap- pendage, e. Slight depression in the septum, corresponding to the fossa ovalis on the right side. A probe is seen which passes down into the ventricle through the auriculo-ventricular orifice. Parts in left ventricle :—i. Posterior segment of the mitral valve, behind which is the probe passed from the left auricle, n, n. The two groups of musculi papillares. o. Section of the thick walls of this ventricle, 1 Valentin, Lehrbuch der Physiologie des Menschen, i. 415, Braunschweig 1844 CIRCULATORY APPARATUS. 81 ties are lined by a thin membrane, endocardium, which differs some- what in the two hearts ;—being in one a prolongation of the inner coat of the aorta, and in the other, of the venre cavse. On this account, the inner coat of the left heart is but slightly extensible, more easily rup- tured, and considerably disposed to ossify; that of the right heart, on the other hand, is very extensible, not readily ruptured, and but little liable to ossify. M. Deschamps1 has described a membrane, which is situate between the endocardium and the areolar tissue that lines the mus- cular structure at its inner surface, and belongs essentially to the elas- tic fibrous tissue. The tissue of the heart is supplied with blood by the cardiac or coronary arteries—the first division of the aorta ; and their blood is conveyed back to the right auricle by the coronary veins. The nerves, which follow the ramifications of the coronary arteries, proceed chiefly from a plexus, formed by the spinal nerves and great sympathetic. Besides the large .ganglia on the cardiac plexuses at the base of the organ, the nerves present minute ganglia along their course in its sub- stance ; and Dr. Robert Lee2 has affirmed, that it can be clearly de- monstrated, that every artery distributed throughout the walls of the heart, and every muscular fasciculus of the organ, is supplied with nerves upon which ganglia are formed. The results of Dr. Lee's obser- vations are not, however, considered by all to be established.3 In both hearts, the auricles are much thinner and more capacious than the ventricles; but they are. themselves much alike in structure and size. The, observation, that the right ventricle is larger than the left, is as old as Hippocrates, and,has been attempted to be accounted for in various ways. Some have ascribed, it to original conformation; others to the blood being cooled in its passage through the lung, and therefore occupying a smaller space when it reaches the left side of the heart. Haller4 and Meckel5 assert, that it is dependent upon the kind of death; that if the right ventricle be usually more capacious, it is owing to the lung being one of the organs that yields first, thus occa- sioning accumulation of blood in the right cavities of the heart; and they state that they succeeded, in their experiments, in.rendering either one or the other of the ventricles more capacious, according as the cause of death arrested first the circulation in the lung or in the aorta; but the experiments of Legallois6 and Seiler,7 especially of the former, upon dogs, cats, Guinea pigs, rabbits, in the adult, the child, and the still- born foetus, with mercury poured into the cavities, have shown that, except in the foetus, the right ventricle is more capacious, whether death has been produced by suffocation, in which the blood is accumulated in the right side of the heart, or by hemorrhage ; and Legallois8 thinks, that the difference is owing to the left ventricle being more muscular, 1 Gazette Medicate de Paris, No. 10, and Encyclographie des Sciences Medicales, Avril, 1840, p. 281. 2 Philosophical Transactions, Part i. for 1849. 3 British and Foreign Medico-Chirurgical Review, p. 5,50, Oct., 1849. 4 Element. Physiol., iv. 3, 3. 6 Handbuch der Menschlichen Anatomie, Halle, 1817, s. 46; or the translation from the French version, by Dr. Doane, Philad., 1 832. 6 Diet, des Sciences Medicales, v. 440. 7 Art. Herz. in Pierers Anat. Physiol. Real Worterb., iv. 32, Leipz., 1821, 8 CEuvres, Paris, 1824. VOL. II.—6 82 CIRCULATION. Posterior View of the same. 1. Right auricle. 2. Descending vena cava. X Right posterior pulmonary vein. 4. Muscular fibres of left auricle. 5. Left posterior pulmonary vein. 6, 7. Arrangementof muscular fibres at the end of left'auricie. 8. Orifice of great coronary vein. 9. Band of fibres between the two venae cava. 10. Orifice of the ascending vena cava; Eustachian valve is at the end of the line. 11,12. Muscular fibres at the base of aurieie. 13, 14. Muscular fibres in the ventricles. Anterior View of External Muscular Layer of the Heart after removal of its Serous Coat, Sec. 1. Right auricle. 2. Descending vena cava. a. Right anterior pulmonary vein. 4. Horizontal band of fibres passing across the base of the auri- cles. 5. Left anterior pulmonary vein. 6. Mus- cular fibres between auricles. 7. Fringed or ring-shaped bands of fibres at the extremity of left auricle. 8. Muscular fibres at the base of right auricle. 9. Section of pulmonary artery, show-. ing semilunar valves. 10, 11. Anterior bis-ven- tricular muscular fibres. 12,13. Their continua- tion on to left ventricle. and, therefore, returning more upon itself. The capacity of each of the ventricles in the full-sized heart has been estimated at about two fluid ounces;1 but by Valentin at more than double that amount.3 The two hearts, united together by a median septum, form, then, one organ, which is situate in the middle of the chest, (see Fig. 265,) between the lungs, and, consequently, in the most fixed part of the thorax. Figure 281 is modified from one carefully made from nature by Dr. Pennock.3 It represents the normal position of the heart and great vessels. According to Carus,4 the weight of the heart compared with that of the body is as 1 to 160. M. J. Weber* found the proportion, in one case, to be 1 to 150; Dr. Clendinning6 that of the male to be 1 to 160; that of the female 1 to 150; and Laennec considered the organ to be of a healthy size when equal to the fist of the individual. M. Cruveilhier estimates the mean weight at six or seven ounces. M. Bouilland7 weighed the hearts of thirteen subjects, in whom, from the general habit, pre- vious state of health, and mode of death, there was every reason to believe that they were in the natural state. The mean was eight ounces and three drachms. From all his data he is led to fix the ave- rage weight of the heart, in the adult, from the 25th to the 60th year, 1 Quain and Sharpey's edit, of Quain's Human Anatomy, Amer. edit., by Leidy, ii. 487, Philad., 1849. 2 Lehrbuch der Physiologie des Menschen, i. 415. 3 Medical Examiner, April 4, 1840. 4 Introduction to Comp. Anat., translated by R. T. Gore, Lond., 1827. 6 Hildebrandt's Handbuch der Anatomie, von E. H. Weber, Braunschweig, 1831, Band. iii. s. 125. 6 Journal of the Statistical Society of London, July, 1838. t Traite Clinique des Maladies du Cceur,&c., Paris, 1835. CIRCULATORY APPARATUS. 83 at from 8 to 9 ounces. Dr. Clendinning carefully examined nearly four hundred hearts of persons of both sexes, and of all ages above Fig. 281. S. Outline of sternum. C, C. Clavicles. 1, 2, 3, 4, 5, 6, &c. Ribs. 1', 2', 3', 4', 5', 6', &c. Carti- lages of ribs. 4". Right and left nipples, a. Right ventricle. 6-. Left ventricle, c. Septum between ventricles, d. Right auricle, e. Left auricle. /.Aorta, f. Needle passing through aortic valves. g-. Pulmonary artery, g'. Needle passing through valves of pulmonary artery, h. Vena cava de- scendens. i. Line of direction of mitral valve; dotted portion posterior to the right ventricle, i'. Needle passed into mitral valve at its extreme left. lc. Line of tricuspid valve, o. Trachea. puberty. The average weight was about nine ounces avoirdupois,— much less than that observed by Dr. John Reid,1 who found the ave- rage weight of the male heart—of 89 weighed—to be 11 oz. and 1 dr.; and of the female heart—of 53 weighed—to be 9 oz. and J dr. The weight and dimensions of the organ, according to Lobstein and Bouil- laud, are as follows:—Weight, 9 to 10 ounces; length from base to apex, 5 inches 6 lines; breadth at the base, 3 inches; thickness of walls of left ventricle, 7 lines; do. at a finger's breadth above the apex, 4 lines; thickness of walls of right ventricle, 2\ lines; do. at apex, J a line; thickness of right auricle, 1 line; do. of left auricle, J a line. M. Bizot2 has given the following measurements, taking the average of males from 16 to 89 years. 1 Lond. and Edinb. Monthly Journal of Med. Science, April, 1843, p. 322. 2 For the results of M. Bizot's researches, to ascertain the dimensions of the heart and arteries, see Memoires de la Societe Medicate d'Observation, Paris, 1837; and Hope on the Diseases of the Heart, Amer. edit., by Dr. Pennock, p. 234, Philad., 1842. 84 CIRCULATION. Base. Middle. Apex. Left ventricle.....4£ lines 5£ H Right ventricle ...... 1}! l§ 3ff In the female, the average thickness is something less. Dr. Ranking1 has published the results of measurements, evidently made with accu- racy, of upwards of 100 hearts,—care being taken to exclude all those that exhibited any trace of organic change. The following are the mean admeasurements. Of 15 male hearts, the mean circumference was 9f|ths inches; of 17 female hearts, 8{fths inches. The mean length of the male heart was 4|£ths inches; of the female, 4f|ths. The mean thickness of the left ventricle, in the male, was f|tha of an inch; in the female, f |ths; of the right ventricle, in the male, /gths; in the female, /gths. The septum ventriculorum has, in the male, a mean thickness of ffths of an inch; in the female, ^fths. The aortic orifice, in the male, had a mean circumference of 2||ths inches; the right auriculo-ventricular orifice, 4|fths inches; the left auriculo-ven- tricular orifice, 3ffths inches. The corresponding parts of the female were relatively less. Dr. Ranking infers, that the heart of the male is larger than that of the female,—that the length of the healthy heart is to its circumference rather less than 1 to 2,—that the thickness of the parietes of the right ventricle to the left is as 1 to 3 nearly:—that the pulmonary artery is slightly wider than the aorta; and, lastly, that the right auriculo-ventricular opening is considerably larger than the left. It need scarcely be said, that the weight and dimensions of the organ must vary according to the age, sex, &c, of the individual. M. Bizofc2 found, that the influence of stature on its size was slight; and not such as might have been expected d priori; for, in individuals of the male sex above sixty inches, and in females above fifty-five inches, in height, the mean dimensions of the organ, especially its breadth, were less than in persons of a lower stature. He found the width of the shoulders furnish a better proportionate standard of its measurement,—the dis- tance between the acromial point of the clavicles, and the length and breadth of the heart increasing in a tolerably regular ratio. Numerous measurements of the organ have been made on children by MM. Rilliet and Barthez ;3 whence it results: First. That its circumference does not augment in proportion to age. It is nearly the same from 15 months to five years and a half; and from the latter age it goes on increasing irregularly until puberty. Secondly. The distance from the base to the apex is nearly one-half the total circumference at the base of the ven- tricles. Thirdly. The maximum thickness of the parietes of the right ventricle varies but little according to age. It is generally 0-078 Eng. inch to the age of six years; and after this from 0*118 to 0-157. Fourthly. The maximum thickness of the left ventricle remains below 0*393 Eng. inch, until six years of age. Later, it is habitually 0*393, or a little more. Fifthly. The proportion between the thickness of the two ventricles is generally, as stated by M. Guersant, as 3 to 1, or 4 to 1, 1 London Medical Gazette, No. xxiv., 1842. * Memoires de la Societe Medicale dObservation de Paris, torn, lere, Paris, 1836. 3 Traite Clinique et Pratique des Maladies des Enfants, iii. 662, Paris, 1843. CIRCULATORY APPARATUS. 85 rather more than less. Sixthly. The maximum thickness of the septum is nearly the same as that of the left ventricle, a little more rather than less. Seventhly. The seat of the maximum thickness of the right ven- tricle is at the base, and near the auriculo-ventricular orifice; that of the left ventricle one or two centimetres (in. 0-393 or 0-796) from the base; and that of the septum from two to three centimetres (in. 0*796 to 1-171). Eighthly. The size of the right auriculo-ventricular orifice remains nearly the same until the age of 5 years; it scarcely increases in size up to the age of 10; but then augments more, manifestly. Ninthly. The left auriculo-ventricular orifice, which is always smaller than the right, increases a little more regularly than it with age, and frequently has the same dimensions as the distance from the base of the heart to its apex. Tenthly. The aortic orifice presents but a slight augmentation from 15 months to 13 years of age. Eleventhly. The pulmonary artery, on the other hand, increases notably from the age of six years to eight, so that although before this period it is equal to or scarcely greater than the aortic orifice, afterwards it is commonly much larger. They did not find any marked difference between the male and female heart in children. The heart is surrounded by its proper capsule, called pericardium,— a fibro-serous membrane, composed of two layers. The outermost of these is fibrous, semi-transparent, and inelastic; strongly resembling the dura mater in its texture. Its thickness is greater at the sides than below, where it rests upon the diaphragm; or than above, where it passes along the great vessels which communicate with the heart. The inner layer is of a serous character, and lines the' outer, giving the polish to its cardiac surface; it is then reflected over the heart, and adheres to it by areolar substance. Like other serous membranes, it secretes a fluid, termed liquor pericardii, to lubricate the surface of the heart. This fluid is always found in greater or less quantity after death; and a question has arisen as to the amount that should be considered morbid. This must obviously vary according to circumstances. In the healthy condition, it is seldom above a tea-spoonful. When its quantity is aug- mented, the disease hydropericardium exists. Its great use probably is to keep the heart constantly moist by the exhalation effected from it; and, also, to restrain the movements of the organ, which, under the influence of the emotions, sometimes leaps inordinately. If the peri- cardium be divided in a living animal, the heart is found to bound, as it were, from its ordinary position; and hence the expression,—"leaping of the heart,"—during emotion, is physiologically accurate. b. Arteries. Arteries are solid, elastic tubes, which arise, by a single trunk, from the ventricle of each heart, and gradually divide and subdivide, until they are lost in the capillary system. The large artery, which arises from the left ventricle, and conducts the blood to every part of the body,—even to the lungs, so far as regards their nutrition,—is the aorta; and that, which arises from the right ventricle and conveys venous blood to the lungs for aeration, is the pulmonary artery. Neither the one nor the other is the continuation of the proper tissue 86 CIRCULATION. of the ventricles; the inner membrane is alone continuous—the mus- cular structure of the heart being united to the fibrous coat of the arteries by means of an intermediate fibrous tissue. The aorta, as soon as it quits the left ventricle, passes beneath the pulmonary artery, is entirely concealed by it, and ascends to form a curvature with the con- vexity upwards, the summit of which rises to within three quarters of an inch or an inch of the superior edge of the sternum. This great curvature is called the cross or arch of the aorta. .The vessel then passes downwards, from the top of the thorax to nearly as far as the sacrum, where it divides into two trunks, one of which proceeds to each lower extremity. In the whole of this course, it lies dose to the spine, and gives off the various branches that convey arterial blood to the different parts of the body. Of the immense multitude of these ramifications an idea may be formed, when we reflect, that the finest pointed needle cannot be run into any part of the surface of the body, without blood,—probably both arterial and venous,—flowing. The larger arteries are situate deeply, and are thus remote from external injury. They communicate freely with each other, and their anasto- moses are more frequent as the arteries become smaller and farther from the heart. At their final terminations, they communicate with the veins and lymphatics. *Tt has been a common, but erroneous belief, that the branches'of the aorta, when taken collectively, are of much greater capacity than the parent trunk, and that this'excess goes on augmenting; so that the- ultimate divisions of an artery are of much greater capacity than the parent trunk. Hence, the arterial system has been considered to represent, in the aggregate, a cone, whose apex is at the heart, and base in the organs; but as all the minute arterial ramifications are not visible, it is obviously impracticable to discover the ratio between their united capacity and that of the aorta at its origin: yet the problem has been attempted. Keill, by experiments made on an injected subject, considered it to be as 44,507 to 1: J. C. A. Helvetius and Sylva as 500 to 1. Sdnac estimated, not their capacities but their diameters, and conceived the ratio of these to be as 118,490 to 90,000; and George Martine affirmed, that the calibre of a parent arterial trunk is equal to the cube root of the united diameters of the branches.5 It will be shown, however, hereafter, from the observations of M. Poiseuille and Mr. Ferneley, that the notion of the much greater capacity of the branches than of the parent trunk is a fallacy.K This subject will be referred to hereafter. The pulmonary artery strongly resembles the aorta. Its distribution has been already described as a part of the respiratory organs. The arteries are composed of different coats in superposition, respect- ing the number of which anatomists have not been entirely of accord. Some have admitted six; others five; others four; but at the present day, three only are perhaps generally received;—first, an external, areolar or cellular, called also nervous, and cartilaginous by Vesalius, and tendin- ous by Heister, which is formed of condensed areolar substance, and 1 Haller, Element Physiolog., lib. ii., sect. 1, § 18, Lausan., 1757. CIRCULATORY APPARATUS. 87 has considerable strength and elasticity, so that if a ligature be applied tightly round the vessel, the middle and internal coats may be com- pletely cut through, whilst the outer coat may remain entire. Scarpa is not disposed to admit this as one of the coats. He considers it only an exterior envelope, to retain the vessel in situ. The next coat is the middle, muscular or proper coat, the character of which has been the subject of much discussion. It was, at one time, almost universally believed to be muscular. Such was the opinion of Mr. Hunter.1 Henle2 advances the opinion, that its structure is intermediate between areolar and muscular tissue; its microscopic elements being broad, and very flat, slightly granulated fibres or bands, which lie in rings around the inter- nal membrane, and are about 0-003 lines in diameter. These with a system or network of dark streaks constitute the middle coat. In the large arteries, as the aorta and its main branches, nearly the whole thickness of this coat is composed of yellow elastic tissue—the tissu jaune of the French anatomists: few muscular fibres are perceptible; but in the smaller arteries the proportionate thickness of the elastic coat gradually diminishes; whilst, as a general rule, the muscular fibres increase in number, and form a layer within the elastic coat. -The mus- cular fibres resemble those of the intestinal tube, being of the nonstriped or nonstriated variety. v They are arranged areolarly; are pale and flat, and mingled with filaments of fine elastic tissue. Nysten,3 Magendie,4 and Miiller5 applied the galvanic stimulus to the middle coat, which is the most sensible test of irritability, but without effect. It is proper, however, to remark, that the heart seems equally unsusceptible of the galvanic stimulus; or at least is not affected by it like the voluntary muscles. In the cases of two executed criminals, which the author^ had an opportunity of observing, although all degrees of galvanism were applied half an hour after the drop fell, no motion whatever was perceptible; yet the voluntary muscles contracted, and continued to do so for an hour and a half after execution. The same fact is recorded in the galvanic experiments of Dr. Ure, detailed in another part of this work, (vol. i. p4 408,) and is attested by Bichat, Treviranus and others. Humboldt, Pfaff, J. F. Meckel, Wedemeyer, and J. Miiller, however, affirm the contrary. The last observer states,6 that with a single pair of plates he excited con- tractions not only in a frog's heart, which had ceased to beat, but also in that of a dog, under similar circumstances. Into the subject of the cause of the heart's action, we shall, however, inquire presently. Miiller7 suggests, that in the capability to contract under the influence of cold, as exhibited in the experiments of Schwann, referred to here- 1 On the Blood, Inflammation and Gunshot Wounds; by Palmer, Amer. edit., p. 156, Philad, 1840. 2 Casper's Wochenschrift, May 23, 1840, cited in Brit, and For. Med. Rev., Oct., 1840, p. 551. 3 Recherches de Physiologie, &c,p. 325, Paris, 1811. 4 Precis, 2de edit., ii. 387, Paris, 1825. 6 Handbuch der Physiologie, Baly's translation, p. 205, Lond., 1838. 6 Loc. cit. ' Archiv. fur 1836, in Lond. Med. Gaz., May, 1S37. 88 CIRCULATION. after, the contractile tissue of the arteries resembles that of the dartos, and that found in many parts of the skin, as about the nipple an(* follicles, although the physical characters of the latter are so different from elastic tissue. The third or inner coat is smooth and polished, and a continuation of the membrane that lines the ventricles. It has an epithelial lining, resembles the serous membranes, and is lubricated by a form of serous exhalation.1 The arteries receive the constituents that belong to every living part, —arteries, veins, lymphatics, and nerves. These arteries do not pro- ceed from the vessels they nourish, but from adjacent trunks, as we have remarked of the vasa vasorum, to which class they really belong. The nerves proceed from the great sympathetic; form plexuses around the vessels, and accompany them through all their ramifications. By some anatomists, the arteries of the head, neck, thorax, and abdomen, are conceived to be supplied from the great sympathetic, whilst those of the extremities are supplied from the nerves of the spinal marrow. It is probable, however, that more accurate discrimination might trace the dispersion of twigs of the nerves of involuntary motion on all these vessels. The organization of the arteries renders them tough and ex- tremely elastic, both of which qualities are necessary to enable them to withstand the impulse of the blood sent from the heart, and to react upon the fluid so as to influence its course. It is by virtue of this structure, that the parietes retain their form in the dead body,—one of the points that distinguish them from the veins. The vitality of the arteries is inconsiderable. Hence their diseases are by no means numerous or frequent,—an important fact, seeing that their functions are essential, and their activity incessant. c. Intermediate, Peripheral or Capillary System. The capillary or intermediate vessels are of extreme minuteness, and are by some considered to be formed by the terminations of arteries and the commencement of veins; by others to be a distinct set of ves- sels. This system forms a plexus which is distributed over every part of the body, and constitutes, in the aggregate, what is meant by the capillary system. It admits of two great divisions, one situate at the termination of the branches given off from the aorta, and called the general capillary system; the other at the termination of the branches of the pulmonary artery,—the pulmonic capillary system. Although the capillary system of man does not admit^of detection by the unaided sight, its existence is evidenced by the microscope; by injections, which develope it artificially in almost every organ; by the application of excitants, and by inflammation. The parietes frequently cannot be distinguished from the substance of the tissues;—the colour of the blood, or the matter of the injection alone indicating their course. In some parts, as in the white textures, these vessels do not seem to admit the red particles of the blood, whilst others admit them always. This 1 For some speculations as to the agency of this secretion in the production of the buffy state of the blood, &c, see M. Romain Gerardin, in Journal des Connaissances Medico- Chirurgicales, Mars, 1836. CIRCULATORY APPARATUS. 89 diversity gave rise to a distinction of the capillaries into red and white; but there are probably none of the latter. It is difficult, indeed, to conceive how the red particles could be arrested at the mouths of the white arteries—if such existed—without their preventing altogether the entrance of blood into them. The true cause of the whiteness appears to be the small quantity of blood they receive; and it is only when the network is very close, and the quantity of blood passing through them great, that a perceptible colour is produced. If a plate of red glass be reduced to a very thin pellicle, and be placed between the eye and light, its colour will be scarcely sensible. To perceive it, several of these pellicles must be placed over each other, and they must be examined not by their transparency, but by causing the light to fall on their surface, or by reflection. There are certain textures, again, which receive no bloodvessels,— the corneous and epidermic, for example. They are probably nou- rished by transudation of nutritive matter from the vessels of the sur- rounding tissue. The ancients were of opinion, that arteries and veins are separated by an intermediate substance, consisting of a fluid effused from the blood, which they called, in consequence, parenchyma.1 The notion is, indeed, still entertained; and is considered to be supported by micro- scopical observations. In the examination of delicate and transparent tissues, currents of moving globules are seen with many spaces of ap- parently solid substances, resembling small islets, surrounded by an agitated fluid. If the tissue be irritated by thrusting a fine needle into Fig. 282. Circulation in the Web of the Frog's Foot. (Wagner.) 1, 1. Veins. 2, 2. Arteries. it, the motion of the globules becomes more rapid; new currents arise where none were previously perceptible, and the whole becomes a mass 1 Galen. Administrat. Anatom.,vi. 2. 90 CIRCULATION. «f& of moving particles, the general direction of which tends towards the points of irri- tation. But although a part of the appa- ratus of intermediate circulation may be arranged, in this manner, there are reasons for the belief, that a more direct commu- nication between the arteries and veins exists also. The substance of an injection passes from one set of vessels into the other, without any evidence of intermediate extravasation. The blood has been seen, too, passing in living animals, directly from the arteries into the veins. Leeuen- hoek1 and Malpighi,2 on examining the Portion of the Web|of the Frog's Foot. swim-bladderS, gills, and tails of fishes, a. A deeper lying venous trunk, with {ne nieSenterV of frogS, &C.---which are which two smaller capillary veins, b b, * 1 P. .... -•• ,. ,■. communicate, c, c. The angularunnu- transparent,—observed this distinctly; cleatedcellsof the parenchyma. (Wag- ^ ^ ^ j^ been ^^ hj ^ ^^ vations of Cow- Fig. 284. per, Cheselden, Hales, Spallan- zani, Thomson, Cuvier, Config- liachi, Ru^coni, Dollinger, Ga- rus, and others. The artery and vein termi- nate in two dif- ferent ways;— at times, af- ter the former has become extremely mi- nute, by send- ing off nu- merous lateral branches, as Haller stateshe noticed in the swim bladders of fishes; at others, by pro- ceeding paral- x, x. Venous branches uniting to form a principal vein, y z, z. Follicles lpl +n oa^Vi into which a small artery enters, which becomes convoluted before issuing eaCU from them. A beautiful capillary rete, and some muscular fibres, are also seen", other and COU1- 1 Select Works, containing his Microscopical Discoveries, by Samuel Hooke p 90 Lond 1778. ' ' "' 2 Epist. de Pulmonibus, 1661, and Haller, Element. Physiol., lib. iii. sect. 3 § 20 Lau- sana, 1757. Circulation in the Under Surface of the Tongue of the Frog-. (Donne.) Follicles CIRCULATORY APPARATUS. 91 municating by a multitude of transverse branches. Fig. 282 exhibits a microscopic view of the membrane between two of the toes of the hindfoot of the frog, Rana eseulenta, magnified three diameters. Fig. 283 shows a portion of the web of a frog's foot magnified 45 diameters. The superficial network of capillaries is seen admitting but a single series of blood particles. All the vessels, here figured, are, according to Wagner,1 furnished with distinct parietes. Fig. 284 is a beautiful representation of the circulation in the under . surface of the tongue. Along the larger vessels the blood can be seen rushing with excessive velocity. It is proper,, however, to state that the more the parts are magnified, the greater will be the apparent velocity. The mean real velocity, Valentin2 thinks, is one-eighth less in the capilla- ries than in the veins and arteries.3 These larger vessels have distinct coats; but single files of globules are seen proceeding slowly through channels to which the author has not been able to satisfy himself that there were distinct parietes. The tongue of the frog offers by far the most satisfactory opportunity for distinctly witnessing the circulation; a fact for the knowledge of which the author is indebted to M. Donne'.4 The capillary vessels have'been esteemed by some* to belong chiefly to the arteries, the venous radicles not arising almost imperceptibly from the capillary system, as the arteries terminate in it, but having a marked size at the part where they quit this system, which strikingly contrasts with the excessive tenuity of the capillary arterial vessels; whilst between the capillary system and the arteries there is no distinct line of demarcation. The opinion Of Bichat5 was, that this system is entirely independent of both arteries and veins; and Autenrieth6 imagined, that the minute arteries unite to form trunks, which again divide before communicating with the veins, so as to represent a system analogous to that of the vena portse. The experiments of Dr. Marshall Hall7 on the batrachia, which were performed with signal care, led him to the following conclusions, which agree with those of Bichat, so far as regards the independent existence of a capillary system. The minute vessels, he says, may be considered as arterial, so long as they continue to divide and subdivide into smaller and smaller branches. The minute veins are the vessels that gradually enlarge from the suc- cessive addition of small roots. The true capillary vessels are distinct from these. They do not become smaller by subdivision, or larger by conjunction, but are characterized by continual and successive union and division or anastomoses, whilst they retain a nearly uniform diame- ter. The last branches of the arterial system, and the first root of the venous, Dr. Hall remarks, may be denominated minute, but the term "capillary" must be reserved for, and appropriated to, vessels of a dis- 1 Elements of Physiology, by R. Willis, Lond., 1842. 2 Lehrbuch der Physiologie des Menschen, i. 467, Braunschweig, 1844. 3 See also Lebert, Physiologie Pathologique, i. 7, Paris, 1845. 4 Cours de Microscopie, p. 109, Paris, 1844; and Atlas, planche vi., Paris, 1845. 5 Anatomie Generate, &c, edit, de MM. Blandin et Magendie, ii. 299, Paris, 1832. 6 Physiologie, ii. 138. 7 A Critical and Experimental Essay on the Circulation, &c, Lond., 1830; Amer. edit, Philad., 1836. 92 CIRCULATION. tinct character and order, and of an intermediate station, carrying red globules, and perfectly visible by means of the microscope. Recently, M. Bourgery1 has maintained, that besides the intermediate vessels, which form the direct communication between the arteries and veins, there is a special capillary arrangement in every tissue by which the functions of nutrition and secretion are accomplished. The diameter of these capillaries, according to M, Bourgery, is not more than one-half, one-third or even one-fourth of that of the blood corpuscles; and they can, consequently, convey only liquor sanguinis. But the existence of these vessels is not considered to be demonstrated; whilst their absence in tissues—as cartilage—which they were formerly supposed to penetrate, has been established.2 The capillary arteries are distinct in structure—as they are in office—from the larger arteries. All. the coats diminish in thickness and strength, as the tubes lessen in size; but this is more especially the case with the middle coat, which, according to, Wedemeyer, may still be distinguished by its colour in the transverse section of any vessel whose calibre is not less than the tenth of a line; but entirely disap- pears in vessels too small to receive the wave of blood in a manifest jet. Fig. 285. Capillaries of the Web of the Frog's Foot. sm1al?ervPes"e^^tWUangkneTP08ed ^^ PrlnCiPal b'anches> Wi «* covered with a rete ot While the coats diminish, the nervous filaments, distributed to them increase; the smaller and thinner the capillary, the greater the propor- 1 Comptes Rendus, &c, 1848, and Gazette Medicale, No. 37, 1848 2 British and Foreign Medico-Chirurgical Review, p. 527 Oct. 1848. CIRCULATORY APPARATUS. 93 tionate quantity of its nervous matter. The coats of the capillaries become successively thinner and thinner, and at length disappear alto- gether; and the vessels—many of them at least—seem to terminate in membraneless canals or interstitial passages, formed in the substance of the tissues. The blood is contained—according to Wedemeyer, Gruithuisen, Dollinger, Cams,, and others—in the different tissues in channels, which it forms in them: even under the microscope, the stream is seen to work out for itself, easily and rapidly, a new pas- sage in the tissues, and it is esteemed certain, that in the figura venosa of the egg, the blood is not' surrounded by vascular parietes. Most histologists of the day are disposed, however, to believe, that the capillaries are provided with distinct coats. Such, as has been seen, appeared to Wagner to be the case in the frog's foot, when magnified 45 diameters: and it has even been announced, that they are composed of a fibrous structure, analogous to the muscular. Fig. 285, from Wagner, exhibits the vascular rete and circulation of the web of the hind foot of a frog—-Rana temporaria—magnified 110 times: here the parietes are very distinct. In Fig. 286y also from Wagner, which represents a portion of a live newt, magnified 150 Fig. 286. •. Bloodvessels of the Lung of a Live Newt. b, a. Pulmonary vein receiving blood from anothef vein, c; itself made up of two ^ranches, d. Pulmonary artery anastomosing with the pulmonary veins by means of capillary vessels. (Wagner.) diameters, the capillaries are exceedingly delicate, and their walls by no means as distinct. The arterial and venous trunks and the capillaries 94 CIRCULATION. that form the medium of communication between them are well seen, as well as the islets of the substance of the lung, in which a granular or areolar texture is indistinctly perceptible. Dr. Carpenter1 is of opinion, that the mode of origin of the capillaries refutes the supposition, that they are mere passages channeled out of the tissues through whieh they convey the blood. He thinks there can be no doubt, that they are pro- duced, in any newly forming tissue, not by the retirement of the cells, one from the Other, so as to leave passages between them, but by the formation of communications among certain cells, whose cavities become connected with each other, so as to constitute a plexus of tubes, of which the original,cell-walls become the parietes. Of the minute capillaries,—the diameter of which, in parts finely injected, varies from the TTfoiFtn to the ^'eth, and the g^th of an inch and even more,—some, according to Wedemeyer, communicate with veins; in others, there are no visible openings or pores in the sides or ends, by which the blood can be extravasated preparatory to its being imbibed by the veins. There is nowhere apparent a sudden pas- sage of the arterial into the venous stream ; no abrupt boundary between the division of the two systems. The arterial streamlet winds through long routes before it assumes the nature, and takes the direction, of a venous streamlet. The ultimate capillary rarely passes from a large arterial into a large venous branch. Many speculations have been indulged regarding the mode in which the vascular extremities of the capillary system are arranged. Bichat regarded it as a vast reservoir, whence originate, besides veins, vessels of a particular order, whose office it is to pour out, by their free extremity, the materials of nutri- tion,—vessels, which had been previously imagined by Boerhaave, and are commonly known under the appellation of exhalants. Mascagni3 supposed that the final arterial terminations are pierced, towards their point of junction with thei veins, by lateral pores, through which the secreted matters transude ;—but these points will farther engage atten- tion under Nutrition and Secretion. d. Veins. The origin of the veins, like that of all capillary vessels, is imper- ceptible. By some they are regarded as continuous with the capillary arteries; Malpighi3 and Leeuenhoek4 state this as the result of their microscopic observations on living animals; and it has been inferred, from the facility with which an injection passes from the arteries into the veins. According to others, cells exist between the arterial and the venous capillaries, in which the former deposit their fluid contents, and whence the latter obtain it; Others, again, substitute a spongy tissue for the cells. It has also been asked,—whether there may not be more delicate vessels, communicating with their radicles, similar to the exhalants which are presumed to exist at the extremities of the arte- ' Human Physiology, § 477, Lond., 1842. 2 Vasor. Lymph. Corpor. Human. Histor., Sen. 1817; and Prodromo della Grande Anato- mie, Firenz., 1819. 3 Secunda Epistola de Pulmonibus, Opera., Lond., 1687. * Epistol. 59, Opera., Lugd. Bat., 1722. CIRCULATORY APPARATUS. 95 Fig. 287. ries, and which are regarded as the agents of exhalation. All this is, however, conjectural. It has already been observed, that the mesen- teric veins have been supposed by some to terminate by open mouths in the villi of the intestines; and the same arrangement has been con- ceived to prevail with regard to other veins; but there is no evidence of this. M. Ribes concludes, from the results of injecting the veins, that some of the venous capillaries are immediately continuous with the minute arteries, whilst others open into the cells of the areolar tissue, and into the substance of different organs. When the veins become visible, they appear as an infinite number of extremely small tubes communicating very freely with each other; so as to form a very fine network. These vessels gradually become larger and less numerous, but still preserve their reticular arrangement; Until, ulti- mately, all the veins of the body empty themselves into the heart by three trunks—the vena cava inferior, vena cava superior, and coronary vein. The first- of these receives the veins from the lower part of the body, and extends from the fourth lumbar vertebra to the right auricle; the second receives all those of the upper part of the body. It extends from the cartilage of the first rib to the right auricle. The coronary vein be- longs to the heart exclusively: be- tween the superior and inferior cava a communication is formed by means of the vena azygos. Certain organs, as the spleen, ap- pear to be almost wholly composed of venous radicles. Fig. 287,represents the ramifications of the splenic vein, in the substance of that organ; and if we consider, that the splenic artery has corresponding ramifications, the viscus would seem to be almost wholly formed of bloodvessels. The same may be said of the corpus cavernosum of the penis and clitoris, nipple, urethra, glans penis, &c. If an injection be thrown into one of the veins that issue from these different tissues, they are filled by the injection : this rarely occurs, if the injection be forced into the artery. M. Magendie1 affirms, that the communication of the cavernous tissue of the penis with the veins occurs through apertures two or three millimetres—in. 0*117— in diameter. In their course towards the heart, particularly in the extremities, the veins are divided into two planes;—one subcutaneous or superficial; the other deep-seated, and accompanying the deep-seated arteries. Splenic Vein with its Branches and Rami- fications. 1. Trunk of the vein. 2. Gastric branch of this vein coming from the stomach. 3. Branch- es coming from the substance of the spleen. 4. Small mesenteric vein cut off. 5. Branches coming from external coat' of the spleen. 6. Branches of lymphatic vessels of spleen. 1 Precis, &c, ii. 238. 96 CIRCULATION. Numerous anastomoses occur between these, especially when the veins become small, or are more distant from the heart. We find, that their disposition differs according to the organ. In the brain, they con- stitute, in great part, the pia mater; and enter the ventricles, where they contribute to the formation of the plexus choroides and tela cho- roidea. On leaving the organ we^find them situate between the laminae of the dura mater; when they take the name of sinuses. In the spermatic cord, they are extremely tortuous; anastomose repeatedly, and form the corpus pampiniforme; around the vagina, they constitute the corpus retiforme; in the uterus, the uterine sinuses. They have three coats in superposition, according to most anatomists: but many modern anatomists are disposed to assign them six. The outer coat is areolar; dense, and very difficult to rupture. The middle coat has been termed the proper membrane of the veins. The generality of anatomists describe it as composed of longitudinal fibres, which are more distinct in the vena cava inferior than in the vena cava superior; in the superficial veins than in the "deep-seated; an the branches than in the trunks. M. Magendie1 states, that he has never been able to observe the fibres of the middle coat; but has always seen a multitude of filaments interlacipg in all directions; and assuming the appearance of longitudinal fibres, when the vein is folded or wrinkled longitudi- nally, which is frequently the case in the large veins. It exhibits no signs of muscularity; even when the galvanic stimulus is applied; yet M. Magendie suspects its chemical nature' to be fibrinous. It was re- marked, in an early part of this work (vol. i. p. 58), that the bases of the areolar and muscular tissue are, respectively, gelatin, and fibrin; and that the various resisting solids may all be brought to one or other of those tissues. The middle coat of the veins doubtless belongs essen- tially to the former, and is a variety of the tissu jaune of the French anatomists. M. Magendie merely states its fibrinous nature to be a suspicion; and, like numerous suspicions, this may be devoid of founda- tion. Yet we have reason to believe, that it is contractile; and, of late,2 it has been described as formed of one or two or even more layers between the external and internal coats; these layers consisting of fibres, which agree, in all respects, with the white areolar tissue; and are either quite pure, or mixed in one or other of the layers with a greater or less amount of fibres, resembling those of the middle coat of the arteries in having the anatomical characters of the nonstriated or unstriped muscular fibres. M. Broussais3 affirms, that its contrac- tion is one of the principal causes of the return of the blood to the heart. He conceives, that the alternate movements of contraction and relaxation are altogether similar to those of the heart; but that they are so slight as not to have been rendered perceptible in the majority of the veins, although they are very visible in the vena cava of frogs, where it joins the right auricle. In some experiments by M. Sarlandiere 1 Op. cit., ii. 242. See, on the researches of recent histologrsts, Mr. Paget, Brit, and For. Med. Review, July, 1842, ii. p. 242. 2 Quain's Human Anatomy, by Quain and Sharpey, Amer. edit., by Leidy, i. 51$, Philad., 1849. 3 Op. citat., American translation, p. 391. CIRCULATORY APPARATUS. 97 Fig. 288. on the circulation, he observed these movements to be independent of those of the heart. After the organ was removed, and even after blood had ceased to flow,1 the contraction and relaxation of the vein continued for many minutes in the cut extremity. The inner coat is extremely thin and smooth at its.inner surface, and has an epithelial lining. It is very extensible, and yet presents con- siderable resistance; bearing a very tight ligature without being rup- tured. In many of the veins, parabolic folds of the inner coat exist, like those in the lymphatics, which are inservient to a similar purpose; the free edge of these valves is directed towards the centre of the circulation, showing that their office is to permit the blood to flow in that direction, and prevent its retrogression. They do not seem, how- ever, in many cases, well adapted for the purpose; inasmuch as their size is insufficient to obliterate the cavity of the vein. By most anato- mists, this arrangement is considered to depend upon primary organization; but Bichat conceives it to be wholly owing to the state of contraction, or dilatation of the veins, at the moment of death. M. Magendie affirms, that he has never seen the distension of the veins exert any influence on the size of the valves ; but that their shape is somewhat modified by the state of contraction or dilatation ; and this he thinks probably misled Bi- chat.2 Moreover, they are covered by the epithelial coat and consist of tissue like that of fibrous membrane, which, as Mr. Hunter3 observed, shows, that they are not duplicatures of the lining mem- „11t'Ji^^aJfrinofaidIopenaBdTspread mi • ... out, with two pairs of valves. B. Longi- brane. Their number varies in different tudinai section of a vein, showing the ap- . i i , 1 position of the edges of the valves in their veins. As a general rule, they are more closed state, c. Portion of a distended numerous, where the blood proceeds J&o^S^ h™*}*** in the situa" against its gravity, or where the veins are very extensible, and receive but a feeble support from the circum- ambient parts, as in the extremities. They are entirely wanting in the veins of the deep-seated viscera; in those of the brain and spinal marrow, and of the lungs; in the vena portae, and in the veins of the kidneys, bladder, and uterus. They exist, however, in the spermatic veins; and, sometimes, in the internal mammary, and in the branches of the vena azygos. On the cardiac side of these valves, cavities or sinuses exist, which appear externally in the form of varices. These dilatations enable the refluent blood to catch the free edges of the valves, and thus depress them, so as to close the cavity of the vessel; serving, in this respect, precisely the same functions as the sinuses of the pulmonary artery and aorta serve in regard to the semilunar valves. The valves exist in veins of less than a line in diameter. Diagrams showing Valves of Veins. 1 See, on this subject, the remarks on the Circulation in the veins. 2 Precis, &c, ii. 241. 3 Treatise on the Blood, &c, by Palmer, Amer. edit., p. 216, Philad., 1840. VOL. II.—7 CIRCULATION. The three coats united form a solid vessel,—which, according to Bichat, is devoid of elasticity, but in the opinion of M. Magendie elas- tic in an eminent degree. The elasticity is certainly much less than in the arteries. The veins are nourished by vasa vasorum, or by small arteries, that have their accompanying veins. Every vessel, indeed, in the body, if we may judge from analogy, draws its nutriment, not from the blood circulating in it, but from small arterial vessels, hence termed vasa vasorum. This applies not only to the veins, but to the arteries. The heart, for example, is not nourished by the fluid con- stantly passing through it; but by vessels, which arise from the aorta, and are distributed over its surface, and in its intimate texture. The coronary arteries and their corresponding veins are, consequently, the vasa vasorum of the heart. In like manner, the aorta and all its branches, as well as the veins, receive their vasa vasorum.^ There must, however, be a term to this; and if our powers of observation were sufficient we ought to be able to discover a vessel, that must derive its support or nourishment exclusively from its own stores. The nerves that have been detected on the veins are branches of the great sympathetic. The capacity of the venous system is generally esteemed to be double that of the arterial. It is obvious, however, that we can only arrive at an approximation, and that not a very close one. The size and number of the veins are generally so much greater than those of the corresponding arteries, that when the ves- sels of a membranous part are injected, the veins are observed to form a plexus, and, in a great measure, to conceal the ar- teries: in the intestines, the number is more nearly equal. The difficulty of ar- riving at any exact conclusion regarding the relative capacities of the two systems is forcibly indicated by the fact, that whilst Borelli conceived the preponderance in favour of the veins to be as four to one, Sauvages estimated it at nine to four; Haller at sixteen to nine; and Keill at twenty-five to nine.2 The ratio between the capacity of individual arteries and veins, is very different in different parts. Between the carotid and internal jugular it is as 196 to 441; the subclavian artery and vein, 3844 to 7396; the aorta and venae cavse, 9 to 16; and between the Roots, Trunk, and Divisions of the SP^ic «*ery and vein, 136 to 676. Vena Porta?. There is one portion of the venous sys- 1,1. veins coming from intestines, tern, to which allusion has already been aisTXtefrnKvel: 3'3-Branchea made, that is peculiar:-the abdominal 1 Precis, &c, ii. 243. 2 Elementa Physiologiae, lib. ii., sect. 2, § 10, Lausann., 1757. Fig. 289. BLOOD. 99 venous or portal system. All the veins, that return from the digestive organs situate in the abdomen unite into a large trunk called vena porta\ This, instead of passing into a larger vein—into the vena cava, for example—proceeds to the liver, and ramifies, like an artery, in its substance. From the liver other veins, called supra-hepatic, arise, which empty themselves into the vena cavae; and correspond to the branches of the hepatic artery as well as to those of the vena portae. The portal system is concerned only with the veins of the digestive organs situate in the abdomen; as the spleen, pancreas, stomach, intes- tines, and omenta. The veins of all the other abdominal organs,—of the kidney, suprarenal capsules, &c, are not connected with it. The first part of the vena portae is called, by some authors, vena portse abdominalis seu ventralis to distinguish it from the hepatic portion, which is of great size, and has been called sinus of the vena portae. 2. BLOOD. It is not easy to ascertain the total quantity of blood circulating in both arteries and veins. Many attempts have been instituted for this purpose, but the statements are most diversified, partly owing to the erroneous direction fol- lowed by experimenters, Fig. 290. but, still more, to the vari- ation that must be perpetu- ally occurring in the amount of fluid, according to age, sex, temperament, activity of secretion, &c. Harvey and the earlier experi- menters formed their esti- mates by opening the veins and arteries freely on a living animal, collecting the blood that flowed, and com- paring this with the weight of the body. The plan is, however, objectionable, as the whole of the blood can never be obtained in this manner, and the proportion discharged varies in dif- ferent animals and circum- stances. By this method, Moulins found the propor- tion in a sheep to be o^d; King, in a lamb, -^-th; in a duck, J^th; and in a rab- From these and Portal System. 1. Inferior mesenteric vein : traced by means of dotted lines behind the pancreas (2) to terminate in splenic vein (3). 4. Spleen. 5. Gastric veins, opening into splenic vein. 0. Su- perior mesenteric vein. 7. Descending portion of duodenum. 8. Its transverse portion which is crossed by superior mesen- Other Observations, Harvey teric vein and by a part of trunk of superior mesenteric arte- ' . ,•' ry. 9. Portal vein. 10. Hepatic artery. 11. Ductus com- COncluded, that the Weight munis choledochus. 12. Divisions of duct and vessels at n . 1 1 , in • i transverse fissure of liver. 13. Cystic duct leading to <*all- of the blood of an animal bladder. (Wilson.) s ° bit ^th. 100 CIRCULATION. is to that of the whole animal as 1 to 20. DreTincourt, however, found the proportion in a hog to be nearly -ityih; and Moor, Jjth.1 Sir George Lefevre2 cites from Wrisberg, that from a plethoric young woman, who was beheaded, 25 pounds[?] of blood were collected; and some recent experiments by Mr. Wanner led to the following results: A bullock, weighing 1659 pounds imperial, yielded 69 pounds of blood, or in the ratio of 1 to 23*81; another weighing 1640 pounds, yielded 65 pounds, or in the ratio of 1 to 23*73; a cow, weighing 1293 pounds, yielded 59 pounds, or as 1 to 21*77; a sheep, weighing 110 pounds, yielded 5J pounds, or in the proportion of 1 to 22*72; another weigh- ing 88 pounds, yielded 4*4 pounds, or as 1 to 20; and in a rabbit, the proportion was as 1 to 25 exactly. An animal, according to Sir Astley Cooper,4 generally expires, as soon as blood, equal to about Jgth of the weight of the body, is abstracted. Thus, if it weighs sixteen ounces, the loss of an ounce of blood will be sufficient to destroy it; and, on examining the body, blood will still be found—in the small vessels especially—even although every facility may have been afforded for draining them. Experiments have, how- ever, shown that no fixed proportion of the circulating fluid can be'indi- cated as necessary for the maintenance of life. In the experiments of Rosa, asphyxia occurred in young calves when from three to six pounds, or from J^d to o^th of their weight, had been abstracted; but in older ones not until they had lost from twelve to sixteen pounds, or from jTth to ^th of their weight. In a lamb, asphyxia supervened on a loss of twenty-eight ounces, or ^gth of its weight; and in a wether, on a loss of sixty-one ounces, or ^d of its weight. Dr. BlundelP found that some dogs died after losing nine ounces, or ^th of their weight; whilst others withstood the abstraction of a pound, or y^th of their weight; and M. Piorry affirms, that dogs can bear the loss of 3]5th of their weight, but if a few ounces more be drawn they succumb. From all the experiments and observations, Burdach6 concludes, that, on the average, death occurs when f ths, or gths, of the mass of blood is lost, although he has observed it in many cases, as in haemoptysis, on the loss of ^th, and even of ^th. The following table exhibits the computations of different physiolo- gists regarding the weight of the circulating fluid—arterial and venous. lbs. Harvey, ~) Lister, 1 ... 8 Moulins, | Abildguard, J Blumenbach, ) Lobb, > - 10 Lower, ) Sprengel, - - - - 10 to 15 Giinther, - - - - 15 to 20 Miiller and Burdach, Wagner, - Quesnai, F. Hoffmann, Haller, Young, Hatnberger, Keill, lbs. - 20 20 to 25 - 27 - 28 28 to 30 - 40 - 80 - 100 Although the absolute estimate of Hoffmann has been regarded as 1 Haller, op. cit., lib. v. sect. 1, § 2. 2 An Apology for the Nerves, p. 30, London, 1844. 3 Edinburgh Med. and Surg. Journ., July, 1845. 4 Principles and Practice of Surgery, p. 33, Lee's edition, Lond. 1836. 6 Researches, Physiological and Pathological, pp. 66 and 94 Lond. ] 825 6 Die Physiologie als Erfahrungswissenschaft, iv. 101 and 334, Leipzig 1832. BLOOD—QUANTITY. 101 below the truth, the proportion has seemed to be nearly accurate. He conceives, that the weight of the blood is to that of the whole body as 1 to 5. Accordingly, an individual weighing one hundred and fifty pounds, will have about thirty pounds of blood ; one of two hundred pounds, forty ; and so on. Of this, one-third is supposed to be con- tained in the arteries, and two-thirds in the veins. The estimate of Haller1 is, perhaps, near the truth; the arterial blood being, he con- ceives, to the venous, as 4 to 9. Were we, therefore, to assume that the whole quantity of the blood is thirty pounds in a man weighing one hundred and fifty pounds, which is perhaps allowing too much,—nine pounds, at least, may be contained in the arteries, and the remainder in the veins. # An ingenious plan, proposed by Valentin2 for estimating the quan- tity of blood in the body, affords an approximation to the truth, and is confirmatory of the estimate made from other data. Having weighed an animal, and determined the proportion of solid matter in a portion of its blood, he injects into its Vessels a given quantity of distilled water, which soon becomes mixed with the blood. He then takes away a fresh portion of blood, and ascertains the proportion of solid matter in it. The relation between the amount of solid matter in the blood first taken, and that in the blood diluted with the given quantity of water, enables him to calculate the quantity of blood in the body of the animal. The following question and solution are given, in order to show, how the quantity of blood may be estimated in the manner proposed by Valentin. A portion of blood, (=1190 grains,) drawn from a dog, yielded 24*54 per cent, of solid matter. After injecting 10,905 grains of water into the bloodvessels, a portion of blood drawn yielded 21*86 (or, by another trial, 21*89) per cent, of solid matter. What was the amount of blood in the body at the commencement of the experiment? Let x be the amount of blood after the first experiment. Then, since it contained 24*54 per cent, of solid residue, the amount of solid mat- ter in it was *2454 x. After injecting the water the whole amount of the diluted blood was a* 4- 10905; and, (by the experiment,) the solid matter which it con- tained was =-2186 (x + 10905). But the solid matter was of the same amount in both cases. Therefore we have, •2454 x = -2186 (z+10905) or, (-2454 — -2186) a* = -2186x10905 2383*8330 or, x= —^gg— = 88945 grs. Add for the blood first drawn - 1190 And we get...... - - 90135 grs. the weight of blood in the body, at the commencement of the experi- ment. The ratio 21:89 per cent, gives - - - 91269 grs. And the mean of the two is 90702 " 1 Op. cit., lib. v. sect. 1, §3. * Lehrbuch der Physiologie des Menschen, i. 490, Braunschweig, 1844. 102 CIRCULATION. In this manner, Valentin found the ratio of blood to the yeight of the body to be in the dog as 1 to 4*36 in the male sex, and 1 to 4*93 in the female; and adapting these proportions to M. Quetelet s table of the weight of the human subject at different ages, he infers, that the mean quantity of blood in the male adult, at the time when the weight of the body may be presumed to be greatest, namely, at 30 years, should be about 34J pounds; and that of the female at 50, when the weight is generally greatest, at about 26 pounds. It is difficult, however, to believe, that there is not some fallacy in these calculations. The proportion of blood to the rest of the body, judging from the quan- tity that has usually flowed from animals bled to death, and the appa- rent quantity remaining in the vessels, seems to be excessive; and such is the view, of Professor Blake of Saint Louis. In a recent letter to the author, he refers to experiments instituted by him, which consisted in injecting a weighed quantity of sulphate of alumina into the veins, and analyzing a weighed portion of the blood. As the salt had time to be well mixed with the blood before the animal died, such an analy- sis, he conceived, would enable the whole quantity of blood with which the salt had been mixed to be determined. The only error which—it appeared to him—might arise would be from a portion of the salt having combined with some of the tissues, or having been rapidly ex- creted, which could only affect the result in one direction, viz. in.fur- nishing a greater quantity of blood than really exists. The results led Dr. Blake to infer, that there was no such source of error, as he found by this method, that the weight of blood in the body of a dog does not amount to more than between one-eighth . or one-ninth part o-f the weight of the animal, a ratio much lower—as has been shown—than is generally conceived. "That this, however, is nearer the truth is pro- bable from the consideration of the velocity of the circulation and the capacity of the heart, as, on the generally received opinion of the quan- tity of the blood, it is difficult to imagine how it can circulate so rapidly."1 This estimate would give the quantity of blood in a man weighing 150 pounds from 16J lbs. to 18f—'not very far from the recent estimate of Giinther2—which is from 15 to 20 pounds. The blood strongly resembles the chyle in properties;—the great difference consisting in the colour. The venous blood, the chyle, and the lymph become equally converted into the same fluid—arterial blood— in the lungs: both the chyle and lymph may, indeed, be regarded as rudimental blood. Venous blood, which chiefly concerns us at present, is contained in all the veins, in the right side of the heart, and in the pulmonary ar- tery;—organs which constitute the apparatus of venous circulation. As drawn from the arm its appearance is familiar1 to every one. At first, it seems to be entirely homogeneous; but, after resting for some time, separates into different portions. The colour of venous blood is much darker than that of arterial; so dark, indeed, as to have led to the epithet black blood applied to it. Its smell is faint and peculiar; by 1 Medical Examiner, August, 1849, p. 459. 2 Lehrbuch der Physiologie des Menschen, ii.Band. 1 Abtheilung. s. 122, Leipzig, 1848. BLOOD—SPECIFIC GRAVITY. 103 some compared to a fragrant garlic odour, but sui generis; its taste is slightly saline, and also peculiar. It is viscid to the touch; coagulable; and its temperature has been estimated at 96° Fahrenheit; simply, we believe, on the authority of'the inventor of the thermometric scale, who marked 96° as blood heat. This is too low by at least three or four degrees. Rudolphi,1 and the German writers in general, estimate it at 29° of Re'aumur, or "from 98° to 100° of Fahrenheit;" whilst, by the French writers in general, its mean temperature is stated at 31° of Re'aumur, or 102° of Fahrenheit; M. Magendie,2 who is usually very accurate, fixes the temperature of venous blood at 31° of Re'aumur, or 102° of Fahrenheit; and that of arterial blood at 32° of Re'aumur, or 104° of Fahrenheit. 100° may perhaps be taken as the average. This was the natural temperature of the stomach in the case related by Dr. Beaumont,3 which has been so often referred to in these pages. In many animals, the temperature is considerably higher. In the sheep it is 102° or 103°; but it is most elevated in birds. In the duck, it is 107°. On this subject, however, • further information will be given under the head of Calorification. The specific gravity of blood is differently estimated by different observers. Hence it is probable, that it varies in individuals, and in the same individual at different periods. Compared with water, the mean has been estimated, by some, to be as 1*0527; by others, as 1*0800, to 1*0000. It is stated, however, to have been found as high as 1*126; and, in disease, as low as 1*022. It has, moreover, been conceived, that the effect of disease is, invariably, to make it lighter; and that the more healthy the individual, the greater is its specific gravity; but our information on this point is vague. That it is not always the same in health, is proved by the discrepancy of observers. Boyle estimated it to be 1*041; Martine, 1*045; Jurin, 1*054; Mus- chenbroek, 1*056; Denis, 1*059; Senac, 1*082; Berzelius, from 1*052 to 1*126; J. Miiller, from 1*0527 to 1*0570; Mandl, from 1*050 to 1*059; and Dr. G. O. Rees, from 1*057 to 1*060. In a large number of experiments made upon the blood of man, the ox, and horse, M. Simon4 found it to be between 1*051 and 1*058. The average was 1*042, which, he says, corresponds very nearly with the statement of Berzelius. The average may perhaps be 1*050. Nasse says 1*055; Zimmerman, 1*056. A part of the discrepancy may be owing to the specific gravity not having been always taken at the same temperature. Dr. B. Babington found experimentally, that four degrees of tempera- ture corresponded with a difference of *001 of specific weight; conse- quently, if one author states the specific gravity of blood at about its circulating temperature—say 98° of Fahr.—while another states it at 60° Fahr.—the usual standard—the former will make it *0095 lighter than the latter. The blood of man is thicker, and at least one-thousandth heavier than that of woman. 1 Grundriss der Physiologie, i. 143, Berlin, 1821. 1 Precis, &c, ii. 229. 3 Experiments, &c, on the Gastric Juice, &c, p. 274, Plattsburg, 1833. 4 Animal Chemistry, Sydenham edition, p. 100, Lond., 1845. 104 CIRCULATION. Fig. 291. When blood is examined with a microscope of high magnifying power, it appears to be composed of numerous, minute, red particles or cor- puscles,—commonly called red globules, blood corpuscles, and blood disks,—suspended in the serum. These corpuscles have a different shape and dimension, according to the nature of the animal. In the mammalia, they are circular; and, in birds and cold-blooded animals, elliptical. In all animals, they are affirmed, by some observers, to be flattened, and marked in the centre with a luminous point, of a shape analogous to the general shape of the corpuscle. Professor Giacomoni,1 of Padua, has, however, affirmed, that the red corpuscles swimming in serum,—which have been described, by so many writers, in the circu- lating fluid,—exist only in the imagination. As in everycase that rests on microscopic observation, the greatest discrepancy prevails, not only as regards the shape, but the size of the corpuscles. These were first noticed by Malpighi;2 and afterwards more minutely examined by Leeuenhoek, who at first described them correctly enough in general terms; but subsequently became hypothetical; and advanced the fan- tasy, that the red corpuscles are composed of a series of globular bodies, descending in regular gradations; each of the red corpuscles being com- posed of six particles of serum ; a par- ticle of serum of six particles of lymph, &c. Totally devoid of foundation as the whole notion was, it was believed for a considerable period, even until the time when Haller wrote. Mr. Hewson3 described the corpuscles as consisting of a solid centre, surrounded by a vesi- cle, filled with a fluid; and to be "as flat as a guinea." Mr. Hunter,4 on the other hand, did not regard them as solid bodies, but as liquids possessing a central attraction that determines their shape. Delia Torre5 supposed them to be a kind of disk or ring, pierced in the centre; whilst Dr. Monro conceived them to be cir- cular, flattened bodies, like coins, with a dark spot in the centre, which he thought was not owing to a perforation, as Delia Torre had imagined, but to a depression. Cavallo,6 again, conceived, that all these appear- ances are deceptive, depending upon the peculiar modification of the rays of light, as affected by the form of the particle; and he concluded, that they are simple spheres. Amici found them of two kinds; both with angular margins; but, in the one, the centre was depressed on both sides; whilst, in the other, it was elevated. The observations of Dr. i Encyclogr. des Sciences Medicales, Avril, 1840, p. 529. 2 Opera, Lond., 1687. 3 Experimental Inquiries, part. iii. p. 16, Lond., 1777, or Hewson's Works, by Gulliver, Sydenham Society's edit., p. 215, Lond., 1846. * On the Blood, &c, by Palmer, Amer. edit., p. 63, Philad., 1840. 5 Philos. Trans, for 1765, p. 252. 6 An Essay on the Medicinal Properties of Factitious Air, &c, p. 237, Lond., 1798. m w Red Corpuscles of Human Blood. Represented at a, as they are seen when rather beyond the focus of the microscope; and at b as they appear when within the focus. Magnified 400 diameters. (Donnfe.) BLOOD—RED CORPUSCLES. 105 Young,1 of Sir Everard Home and Mr. Bauer,2 and of MM. Provost and Dumas,3 accord chiefly with those of Mr. Hewson. All these gen- tlemen consider the red corpuscles to be composed of a central globule, which is transparent and whitish; and of a red envelope, which is less transparent. Dr. Hodgkin and Mr. Lister4 have denied that they are spherical, and consist of a central nucleus enclosed in a vesicle. They affirm, on the authority of a microscope, which, on comparison, was found equal to a celebrated one, taken a few years ago to Great Britain by Fis- 292- Professor Amici,5 that the particles of human blood appear to consist of circular, flattened, transparent cakes, their thickness being about 45th part of their diameter. These, when seen singly, appear to be nearly or quite colourless. Their edges are rounded, and being the thickest part, occasion a depression in the middle, which Blood Corpuscles of Rana Esculenta. exists On both Surfaces. The View Of 1, 1, 1, 2. Blood corpuscles. 2. Seen edge- ■ 1____ •__,1 __ ,i wise. -3. Lymph corpuscle. 4. Altered by dilute these gentlemen, consequently, ap- acetic acid! (Wagner.) • pears to resemble that of Dr. Monro. Mr. Gulliver/ however, thinks that the ratio of 1 to 45, given by Dr. Hodgkin and Mr. Lister, must be a misprint. From measurements of the thickness, at the circumference of the corpuscles of several mam- malia, he found it to be generally one-third and one-fourth the diameter: the average thickness of the human bjood corpuscle he estimates at yo^^th of an English inch, and the diameter at g^^th. Amidst this discordance, it is difficult to know which view to adopt. The belief in their consisting of circular, flattened, transparent bodies, with a depression in the centre, and of an external envelope and a cen- tral nucleus, the former of which is red and gives colour to the blood, has had, perhaps, the greatest weight of authority in its favour. The nucleus has appeared to be devoid of colour, and to be independent of the envelope; as, when the latter is destroyed, the central portion pre- serves its original shape. The nucleus is much smaller than the enve- lope, being, according to Dr. Young, only about one-third the length, and one-half the breadth of the entire corpuscle. According to Sir Everard Home,7 the corpuscles, enveloped in the colouring matter, are Y^^th part of an inch in diameter, requiring 2,890,000 to a square inch; but deprived of their colouring matter they appear to be ^^th part of an inch in diameter, requiring 4,000,000 corpuscles to a square inch. From these measurements, the corpuscles, when devoid of colour- ing matter, are not quite one-fifth smaller. The views of MM. Prevost and Dumas, who have investigated the subject with extreme care and 1 Introduct. to Med. Literature, p. 545. 2 Philosoph. Transact, for 1811-1818; and Lectures on Comp. Anat., iii. 4, Lond., 1823. * Annales de Chimie, &c, xxiii. 50, 90 ; and Journal of Science and Arts, xvi. 115. 4 Philosoph. Magazine and Annals of Philosophy, ii. 130, Lond,, 1827. 5 Edinb. Medical and Surgical Journal, xvi. 120. 6 Hewson's Works, Sydenham Society's edit., note to page 215, Lond., 1846. ' Lectures on Comparative Anatomy, iii. 4, and v. 100, Lond., 1828. 106 CIRCULATION. signal ingenuity, are deserving of great attention. They conceive the blood to consist essentially of serum, in which a quantity of red cor- puscles is suspended; that each of these corpuscles consists of an ex- ternal red vesicle, which encloses, in its centre, a colourless globule; that during the progress of coagulation, the vesicle bursts, and permits the central globule to escape ; that, on losing their envelope, the central globules are attracted together; that they are disposed to arrange them- selves in lines and fibres ; that these fibres form a network, in the meshes of which they mechanically entangle a quantity of both the serum and the colouring matter ; that these latter substances may be removed by draining, and by ablution in water; that, when this is done, there remains only pure fibrin; and that, consequently, fibrin consists of an aggregation of the central globules of the red corpuscles, while the general mass, that constitutes the crassamentum or clot, is composed of the entire particle. So far this seems satisfactory; but, we have seen, Dr. Hodgkin does not recognise the existence of external vesicle, or central nucleus; and he affirms, contrary to the notion of Sir Eve- rard Home and others, that the particles are disposed to coalesce in their entire state. - This is best seen when the blood is viewed between two slips of glass. Under such circumstances, the following appear- ances are distinctly perceptible. When human blood, or that of any other animal which has circular corpuscles, is examined in this manner, considerable agitation is, at first, seen to take place among the cor- puscles ; but, as this subsides, they apply themselves to each other by their broad surfaces, and form piles or rouleaux, sometimes of consider- able length. These rouleaux often again combine,—the end of one being attached to the side of another,—so as to produce, at times, very curious ramifications. (See Fig. 295, b.) The belief in the corpuscles being flattened disks is now generally admitted ;—but the form of the disk is found to be altered by various substances. Its external envelope readily admits the endosmose of fluids ; so that, if placed in water, it may assume a truly globular shape. In examining the blood, consequently, it is advisable to dilute it with a fluid of as nearly as possible the same character as the serum. In the particles of the blood of the frog—as represented in Fig. 292—a nu- cleus is observed projecting somewhat from the central portion : this is rendered extremely distinct by the action of acetic acid, which dissolves the rest of the particle, and renders the nucleus more opaque. It then appears to consist of a granular substance. The vesicular character of the red corpuscles has been clearly shown by Dr. G. 0. Rees,1 by the readiness with which they become collapsed or distended by increasing or diminishing the specific gravity of the medium in which they float. In order to collapse the corpuscles, a solution of sp. gr. 1*060 is sufficient, but a solution of 1*070 or more is required to produce a decided effect. Solutions cease to distend the corpuscles when of sp. gr. 1*050 to 1*055, and to distend them well a solution of 1*015 or 1*010 is desirable. He has, moreover, established, 1 Ranking's Half-Yearly Abstract of the Medical Sciences, vol. i, Jan to June 1845) p. 250. BLOOD—RED CORPUSCLES. 107 that the red colouring matter of the corpuscle is seated, not in the envelope, but in the fluid within the vesicle, and that the envelopes themselves are white and colourless membranes. This is shown by in- creasing the specific gravity of the liquid in which the corpuscles float, the result of which is the escape by exosmose of the red coloured fluid from within the corpuscles ; and, again, by applying water to the cor- puscles, and inducing endosmose, the vesicles become distended and burst; their colouring matter mixes with the water, and the envelopes subside to the bottom of the vessel, forming a white layer. The red corpuscles of man have no nuclei, and their contents are probably homo- geneous. They appear so at least when their surfaces are flat or slightly convex; but when concave the unequal refraction of transmitted light gives the appearance of a central spot, which is brighter or darker than the border according as it is viewed in or out of focus.1 (See Fig. 291.) Microscopical discordances are no less evidenced by the estimates, which have been made of the size of the red corpuscles; yet all are adduced on the faith of positive admeasurements. Leaving out of view the older, and, consequently, it might be presumed, less accurate obser- vations, the following table-shows their diameter in human blood, on the authority of some of the most eminent microscopic observers of modern times. Sir E. Home and Mr. Bauer, with colouring"I , ,, x» • i matter, - - - - S } Wo o^ part of an inch. Eller, .... Sir E. Home and Mr. Bauer, without colour- ing matter, 1^3 (5 WoiS Miiller, - - - ss'otj to -ifa Mandl, - - - - 35>25 to , J^ Hodgkin, Lister, and Rudolphi, - -g^1^ Sprengel, - 3^ to ,^ Cavallo, - hp t0 4W Donne*, " - "3T5 0 t0 SZET) Jurin and Gulliver, Blumenbach and Senac, Tabor, Milne Edwards^ Wagner, 324 u _i_ s? s 3 ■■ 5 Phil. Trans, for 1823, p. 506; and Edinb. Med. and Surg. Journ, xxix. 253. Since that time, however, Dr. Davy has succeeded in extricating it both from venous and arterial blood. See his Researches, Physiological and Anatomical, Amer. Med. Lib edit p 82 Philad, 1840, '' ' 6 Elements of Chemistry, 5th edit, by Dr. Bache, p. 607, Philad, 1835. 7 Schweigger's Journal fur Chemie, u. s. w. lxiv., 105. 8 Tiedemann und Treviranus, Zeitschrift fur Physiologie, B. v. H. i.; cited in British and Foreign Med. Review, No, 9, p. 590, April, 1836. 9 Op. cit, p. 329. 10 Annales de Chimie et de Physique, Nov., 1837. 112 CIRCULATION. from venous blood by the air-pump, to the air in the receiver not hav- ing been sufficiently rarefied. Prof. C. A. Schultz, of Berlin—who believes, that the vesicles of the blood, in a perfect state, are composed of a membranous covering, whose interior is filled with an aeriform fluid in the midst of which is found the nucleus1—succeeded in so evident a manner by the following simple method in extracting air from the blood, " that it is impossible to doubt there exists a great quantity of air in the vesicles." He completely filled a bottle with warm blood flowing immediately from the vein of a horse, and her- metically sealed the bottle so that the cork was plunged into the blood, thus absolutely preventing the contact of air. The blood, on cooling, diminished in volume, and thus produced a perfect vacuum in the upper part of the bottle; and in proportion as this took place, bubbles of air arose from the blood and filled the vacuum. Chemical analysis of this air demonstrated that it was carbonic acid. In arterial blood, he found oxygen mixed with more or less carbonic acid.2 The experiments of Dr. Stevens,3 and of Dr. Robert E. Rogers,4 also show, that carbonic acid is contained in the blood. The latter observer found, when a portion of venous blood was placed in a bag of some membrane, and the bag was immersed in an atmosphere of gas—as of oxygen, hydrogen, or nitrogen—that carbonic acid was pretty freely evolved.5 Whilst the blood is circulating in the vessels, it consists of liquor sanguinis and red corpuscles; but during coagulation it separates into two distinct portions;—a yellowish liquid, called serum; and a red solid, known by the name of clot, cruor, crassamentum, coagulum, pla- centa, insula and hepar sanguinis. The proportion of the serum to the crassamentum varies greatly in different animals, and in the same animal at different times, according to the state of the system. The latter is more abundant in healthy, vigorous animals, than in those that have been impoverished by depletion, low living, or disease. Sir Charles Scudamore found, by taking the mean of twelve experiments, that the crassamentum amounted to 53*307 per cent, in healthy blood. The difference between living and coagulated blood may be expressed in a tabular form as follows:— Liquor Sanguinis, c Red Corpuscles, ' Water, Various salts, Fatty matters, | Extractive do. | Albumen, L Fibrin, >■ Serum, Crassamentum, 1 Q td J The serum is viscous, transparent, of a slightly yellowish hue and alkaline owing to the presence of a little free soda. Its smell and taste resemble those of the blood. Its average specific gravity has been estimated at about 1*027 ; but on this point, also, observers differ. Dr. 1 London Lancet, August 10, 1839, p. 713. 2 Ibid p 714 3 Philos. Transact, for 1834-5, p. 334. ' ■ 4 American Journal of the Med. Sciences, August, 1836, p. 283. 5 See, on all this subject, Dr. John Reid, art. Respiration, Cyclop, of Anat and Phvsiol Pt. xxxii. p. 359, Lond, August, 1848. ' 3 '' BLOOD—SERUM. 113 John Davy1 found it to vary from 1*020 to 1*031. Martine, Muschen- broek, Jurin, and Haller, from 1*022 to 1*037 ; Berzelius and Wagner,2 from 1*027 to 1*029; Dr. Christison,3 from 1*029 to 1*031; Lauer,4 from 1*009 to 1*011; whilst Mr. Thackrah5 found the extremes to be 1*004 and 1*080. At 158° of Fahrenheit, it coagulates; forming at the same time, numerous cells, containing a fluid, which oozes out from the coagulum of the serum, and is called serosity. It contains, accord- ing to Dr. Bostock, about ^th of its weight of animal matter, to- gether with a little chloride of sodium. Of this animal matter, a portion is albumen, which may be readily coagulated by means of galvanism; but a small quantity of some other principle is present, which differs from albumen and gelatin, and to which Dr. Marcet6 gave the name muco- extractive matter, and Dr. Bostock,7 uncoagulable matter of thehlood—as a term expressive of its most characteristic property. Serum preserves its property of coagulating, even when largely diluted with water. Ac- cording to Mr. Brande,8 it is almost pure liquid albumen, united with soda which keeps it fluid. Consequently, he affirms, any reagent, that takes away the soda, produces coagulation; and by the agency of caloric, the soda may transform a part of the albumen into mucus. The action of the galvanic pile coagulates the serum, and forms globules in it analogous to those of the blood. From the analysis of serum, by Berzelius,9 it appears to consist, in 1000 parts;—of water, 903; albumen, 80; substances soluble in alco- hol,—as lactate of soda and extractive matter, chlorides of sodium and potassium, 10; substances soluble in water,—as soda and animal matter, and phosphate of soda, 4; loss, 3. Dr. Marcet assigns it the following composition:—water, 900 parts; albumen, 86*8; chlorides of potassium and sodium, 6*6 ; muco-extractive matter, 4; carbonate of soda, 1*65; sulphate of potassa, 0*35, and earthy phosphates, 0*60;— a result, which closely corresponds with that of Berzelius, who states that the extractive matter of Dr. Marcet is lactate of soda, united with animal matter. According to M. Lecanu,10 1000 parts contain,—water, 906 parts; albumen, 78; animal matter, soluble in water and alcohol, 1*69;, albumen combined with soda, 2*10; crystallizable fatty matter, 1*20; oily matter, serolin, 1; chlorides of sodium and potassium, 6; subcarbonate and phosphate of soda, and sulphate of potassa, 2*10; phosphate of lime, magnesia and iron, with subcarbonate of lime and magnesia, 0*91; loss, 1. A very recent analysis by Scherer,11 gives the following constituents:— 1 Researches, Physiological and Anatomical, Amer. Med. Lib. edit, p. 11, Philad, 1840. 2 Elements of Physiology, by R. Willis, § 103, Lond, 1842. 3 On Granular Degeneration of the Kidneys, p. 61, Lond, 1839; or American Medical Library edition, Philad,' 1839. 4 Hecker's Annalen, xyiii. 393. s Inquiry into the Nature and Properties of the Blood, &c, Lond, 1819. 6 MedicoChirurg. Transact., ii. 364. t Op. cit, p. 292. 8 Philosoph. Transact, for 1809, p. 373. 9 Medico-Chirurg. Transactions, iii. 231. 10 Journal de Pharmacie, xvii.; and Annales de Chimie, &c, xlviii. 308. 11 Canstatt und Eisenmann's Jahresbericht iiber die Fortsshritte in der Biologie im Jahre, 1848, s. 65, Erlangen, 1849. VOL. II.—8 114 CIRCULATION. Water, ... - - 910-45 Fixed parts, ... - - 8?'55 1000- Albumen, .... - 74-15 - Extractive matters, - - • ' ' i. Salts soluble in water, Occasionally, the serum presents a whitish hue, which has given rise to the opinion that it contains chyle; but it would seem that this is fatty matter, and is always present. In the serum of the blood of spirit-drinkers, Dr. Traill found a considerable portion, which has been considered to favour the notion, that the human body may, by intem- perance, become ^preternaturally combustible; and has been used to account for some of the strange cases of spontaneous combustion, or rather of preternatural combustibility, which are on record. Dr. Christi- son has likewise met with fat mechanically diffused through the serum, like oil in an emulsion. On one occasion, he procured five per cent. of fat from milky serum, and one per cent, from serum which had the aspect of whey.1 The crassamentum or clot is a solid mass, of a reddish-brown colour, which, when gently washed for some time under a small stream of water, separates into two portions,—colouring matter and fibrin. As soon as the blood is drawn from a vessel, the colouring matter of the red corpuscles leaves the central nucleus free; these then unite, as we have seen, and form a network, containing some of the colouring mat- ter, and many whole corpuscles. By washing the clot in oold water, the free colouring matter and the globules can be removed, and. the fibrin will alone remain. When' freed from the colouring matter, the fibrin is solid, whitish, insipid, inodorous, heavier than water, and with- out action on vegetable colours; elastic when moist, and becoming brittle by desiccation. It yields, on distillation, much carbonate of ammonia, and a bulky coal, the ashes of which contain a considerable quantity of phosphate of lime, a little phosphate of magnesia, carbonate of lime, and carbonate of soda. One hundred parts of fibrin, according to Ber- zelius, consist of carbon, 53*360; oxygen, 19*685; hydrogen, 7*021; nitrogen, 19*934. Fibrin has been designated by various names : it is the gluten, coagulable lymph, and fibre of the blood, of different writers. Its specific gravity is said to be greater than that of serum ; but the difference has not been accurately estimated, and cannot be great. The red corpuscles are manifestly, however, heavier than either, as we find them subsiding during coagulation to the lower surface of the clot, when the blood has flowed freely from the orifice in the vein. Fibrin appears to be the most important constituent of the blood. It exists in animals in which the red corpuscles are absent, and is the basis of muscular tissue. The colouring matter of the blood, called, by some, cruorin, hematin, hematosin, zoo-hematin, hemachroin, globulin (of Lecanu), and rubrin, has been the subject of anxious investigation with the analytical che- mist. It has been already remarked, that it resides in distinct parti- cles or corpuscles, and in the fluid within the enveloping membrane. 1 Edinb. Med. and Surg. Journal, xvii. 235, and xxxiii. 274. BLOOD—COLOURING MATTER. 115 Formerly, however, the opinion was universal, that the vesicular enve- lope is the seat of colour. The colouring principle is dissolved, by pure water, acids, alkalies, and alcohol. M. Raspail1 asserts, that the corpuscles are entirely soluble in pure water, but MM. Donne' and Boudet, who repeated his experiments, declare that they are wholly insoluble, and Miiller2 is of the same opinion. Great uncertainty has always existed regarding the cause of the colour of the corpuscles. As soon as the blood was found to contain iron, the peroxide of which has a red hue, their colour was ascribed to the presence of that metal. MM. Fourcroy and'Vauquelin3held this opinion, conceiving the iron to be in the state of subphosphate; and they affirmed, that if this salt be dis- solved in serum by means of an alkali, the colour of the solution is exactly like that of the blood. Berzelius,4 however, showed, that the subphosphate of iron cannot be dissolved in serum by means of an alkali, except in very minute quantity; and that this salt, even when rendered soluble by phosphoric acid, communicates a tint quite different from that of the red corpuscles. lie found, that the ashes of the colouring matter always yield oxide of iron in the proportion of 5uo*n of the original mass ; whence it was inferred, that iron is somehow or other concerned in.the production of the colour; but the experiments of Berzelius did not indicate the state in which that metal exists in the blood. He could not detect it by any of the liquid tests. The views of Berzelius, and the experiments on which they were founded, were not supported by the researches of Mr. Brande.5 He endeavoured to show, that the colour of the blood does not depend upon iron ; for he found the indications of the presence of that metal as con- siderable in the parts of the blood that are devoid of colour, as in the corpuscles themselves; and in each it was present in such small quan- tity, that no effect, as a colouring agent, could be expected from it. He supposed that the tint of the red corpuscles is produced by a peculiar, animal colouring principle, capable of combining with metallic oxides. He succeeded in obtaining a compound of the colouring matter of the blood with the oxide of tin : but its best precipitants are the nitrate of mercury and corrosive sublimate. Woollen cloths, impregnated with either of these compounds, and dipped in an aqueous solution of the colouring matter, acquire a permanent red dye, unchangeable by wash- ing with soap. The conclusions of Mr. Brande have been supported by M. Vauquelin,6 but the fact of the presence of iron seems to have been decided by many observers. Engelhart7 demonstrated, that the fibrin and albumen of the blood, when carefully separated from colouring par- ticles, do not contain a trace of iron ; whilst he procured it from the red corpuscles by incineration. He also succeeded in proving the pre- sence of iron in the colouring matter by liquid tests ; for on transmit- ting a current of chlorine gas through a solution of red corpuscles, the 1 Chimie Organique, p. 368, Paris, 1833. 2 Handbuch der Physiologie, Baly's translation, p. 105, Lond, 1838. 3 System. Chyrn., ix. 207. . 4 Med. Chir. Trans, iii. 213. 6 Philosophical Transactions for 1812, p. 90. 6 Annates de Chimie et de Physique, torn. i. p. 9. 7 Edinb. Med. and Surg. Journal, Jan, 1827 ; and Turner's Chemistry, 5th Amer. edit., p. 605, Philad, 1835. 116 CIRCULATION. colour entirely disappeared ; white flocks were thrown down, and a transparent solution remained, in which peroxide of iron was discovered by the usual reagents. The results, obtained by Engelhart, as regards the quantity of iron, correspond with those of Berzelius. These facta have since been confirmed by Rose,1 of Berlin ;—and Wiirzer,2of Mar- burg, by pursuing Engelhart's method by liquid tests, detected the existence of the protoxide of manganese likewise. The proportion of iron does not appear to be more than one-half per cent. ; yet, as it is contained only in the colouring matter, there is some reason for believ- ing, that it may be concerned in the coloration of the blood, although probably in the form of oxide. Sulphocyanic acid has been detected in the saliva; and this acid, when united with peroxide of iron, forms a colour exactly like that of venous blood; so that it has been presumed that it may be connected with the coloration of the blood; but this is not probable ; for Dr. Stevens found, that venous blood is darkened by sulphocyanic acid. M. Lecanu3 has subjected hematosin or the colour- ing matter to analysis, and found it to be composed of:—loss, repre- senting the weight of the animal matter, 97*742 ; subcarbonate of soda, alkaline chlorides, subcarbonates of lime and magnesia,-and phosphates of lime and magnesia, 1*724; peroxide of iron, 0*534. The result of his researches induces him to conclude, that the colouring matter is a compound of albumen with some colouring substance unknown. This substance yielded on analysis:—loss, 98*26; peroxide of iron, 1*74; and M. Lecanu suggests, that it may result from the combination of some animal matter with certain ferruginous compounds analogous to cyanides. After all, therefore, our ignorance on this subject is still great; and all that we seem to know is, that peroxide of iron is contained in the colouring matter of the blood; but it can scarcely be the cause of the colour, for Scherer found, that the iron may be wholly dissolved by the agency of acids, and yet the animal matter, boiled afterwards in alcohol, colours the spirit deeply red. Dr. G. 0. Rees,4 however, objects to this being received as a conclusive argument against the iron being essential to the formation of the red colour. The redness of the blood is one of its most obvious characteristics; and the change effected in the lungs as regards colour has been esteemed of eminent importance. It is no farther so, however, than as it indi- cates the conversion of venous into arterial blood. There is nothing essential connected with the mere coloration. In the insect, the blood is transparent; in the caterpillar, of a greenish hue; and in the internal vessels of the frog, yellowish. In man, it differs according to numerous circumstances; and the hue of the skin, which is partly dependent upon these differences, thus becomes an index of the state of individual health or disease. In morbus cseruleus, cyanopathy or blue disease, the whole surface is coloured blue, especially in those parts where the skin is deli- 1 Poggendorf's Annalen, vii. 81; and Annales de Chimie, &c, xxxiv. 268. 2 Schweigger's Journal, lviii. 481. 3 Annales de Chimie et de Physique, xlv. 5. * Gulstonian Lecture; see Ranking's Abstract, Jan.to July, 1845, p 251 Amer edit New York, 1845. ' ' '' BLOOD—COAGULATION. 117 cate, as in the lips; and the appearance of the jaundiced is familiar to all. The formation of the clot, and its separation from the serum, are manifestly dependent upon the fibrin, which, by assuming the solid state, gives rise to the coagulation of the blood;—a phenomenon, that has occasioned much fruitless speculation and experiment; yet, if the views of M. Raspail1 were proved to be correct, it would be sufficiently simple. The alkaline character of the blood, and the production of coagulation by a dilute acid leave no doubt, in his mind, that an alkali is the menstruum of the albumen of the blood. The alkaline matter, he thinks, is soda, but more especially ammonia, of which, he says, authors take no account; but whose different salts are evident under the microscope. Now, "the carbonic acid of the atmospheric air, and the carbonic acid, that forms in the blood by its avidity for oxygen, satu- rate the menstruum of the albumen, which is precipitated as a clot. The evaporation of the ammonia, and, above all, the evaporation of the water of the blood, which issues smoking from the vein, likewise set free an additional quantity of dissolved albumen, and,the mass coagulates the more quickly as the blood is less aqueous." The process of coagulation is influenced by exposure to air. Mr. Hewson affirmed, that it is promoted by such exposure, but Mr. Hunter was of an opposite opinion. If the atmospheric air be excluded,—by completely filling a bottle with recently drawn blood, and closing the orifice with a good stopper,—coagulation is retarded. Yet Sir C. Scuda- more affirms, that if blood be confined within the exhausted receiver of an air-pump, coagulation is accelerated; and MM. Gmelin, Tiedemann, and Mitscherlich2 found that, under such circumstances, both venous and arterial blood coagulated as perfectly as usual. The presence of air is certainly not essential to the process. Experiments have also been made on the effect produced by different gases on the process of coagu- lation; but the results have not been such as to afford much information. It is asserted, for example, by some, that it is promoted by carbonic acid; and certain other irrespirable gases; and retarded by oxygen: by others, the reverse is affirmed; whilst Sir Humphry Davy3 and M. Schroder van der Kolk4 inform us, that they could not perceive any difference in the perjod of the coagulation of venous blood, when it was exposed to nitrogen, nitrous gas, oxygen, nitrous oxide, carbonic acid, hydrocarbon, or atmospheric air. The time, necessary for coagulation, is affected by temperature. It is promoted by warmth; retarded, but not prevented, by cold. Mr. Hew- son froze blood newly drawn from a vein, and afterwards thawed it: it first became fluid, and then coagulated as usual. Hunter made a simi- lar experiment with the like result. It is obviously, therefore, not from simple refrigeration that the blood coagulates. Sir C. Scudamore found, that blood, which begins to coagulate in four minutes and a half, in a 1 Chimie Organique, p. 373. 2 Tiedemann und Treviranus, Zeitschrift fiir Physiol, B. v. Heft i. 3 Researches, &c, chiefly concerning nitrous oxide, p. 380,. Lond, 1800; and Dr. John Davy, Researches, Physiological and Anatomical, Amer. Med. Libr.edit, p. 48, Philad, 1840. 4 Dissert, sistens Sang. Coag. Histor., Groning,p. 81,1820; and Burdach, op. citat, iv. 37. 118 CIRCULATION. temperature of 53° Fahr., undergoes the same change in two minutes and a half at 98°; and that, which coagulates in four minutes at 98° Fahr., becomes solid in one minute at 120°. On the contrary, blood, that coagulates firmly in five minutes at 60° Fahr., remains quite fluid for twenty minutes at the temperature of 40° Fahr., and requires up- wards of an hour for complete coagulation. The observations of M. Gendrin1 were similar. As a general rule, it would seem, from those of Hewson,2 Schroder van der Kolk,3 and Thackrah,4 that coagulation takes place most readily at the temperature of the body. During the coagulation, a quantity of caloric is disengaged. M. Fourcroy5 relates an experiment, in which the thermometer rose no less than 11° during the process; but as certain experiments of Mr. Hunter6 appeared to show, that no elevation of temperature occurred, the observation of Fourcroy was disregarded. It was, however, confirmed by experiments of Dr. Gordon,7 of Edinburgh, in which the evolution of caloric during coagulation was rendered more manifest by moving the thermometer during the formation of the clot, first into the coagulated, and after- wards into the fluid part of the blood: he found, that by this means he could detect a difference of 6°, which continued to be manifested for twenty minutes after the process had commenced. In repeating the experiment on blood taken from a person labouring under inflammatory fever, the thermometer was found to rise 12°. Sir C. Scudamore affirms,8 that the rate at which the blood cools is distinctly slower than it would be were no caloric evolved; and that he observed the thermo- meter rise one degree at the commencement of coagulation. On the other hand, Dr. John Davy,9 Mr. Thackrah, and Schroder van der Kolk,10 accord with Mr. Hunter in the belief, that the increase of tem- perature from this cause, is very slight or null, whilst M. Raspail asserts that the temperature falls.11 Again we have to deplore the discordance amongst observers; and it will perhaps have struck the reader more than once, that such discordance applies as much to topics of direct observation as to those of a theoretical character. The discrepancy regarding anatomical and physical facts, is even more glaring than that which prevails amongst physiologists in accounting for the corporeal phenomena; a circumstance, which tends to confirm the notion promul- gated by one of the most distinguished teachers of his day, (Dr. James Gregory,) that "there are more false facts in medicine, (and the remark might be extended to the collateral or accessory sciences,) than false theories." 1 Hist. Anatom. de6 Inflammations, ii. 426, Paris, 1826. 2 Experiment. Inquiries, i. 19, Lond, 1774, or Sydenham Society edit., Lond 1846. 3 Op. cit, p. 48. 4 Inquiry into the Nature, &c, of the Blood, p. 38, Lond, 1819. 5 Annales de Chimie, xii. 147. 6 A Treatise on the Blood, &c, p. 27, Lond, 1794. 7 Annals of Philosophy, vol. iv. 139. s An Essay on the Blood, p. 68, Lond, 1824. 9 Researches, Physiological and Anatomical, Amer. Med. Libr. edit, p. 6 Philad. 1840. 10 Miiller's Physiology, Baly's translation', p. 98, Lond, 1838. u Chimie Organique, p. 361. BLOOD—COAGULATION. 119 There are certain substances, again, which, when added to the blood, prevent or retard its coagulation. Mr. Hewson found, that sulphate of soda, chloride of sodium, and nitrate of potassa were amongst the most powerful salts in this respect. Muriate of ammonia and a solution of potassa have the same effect. On the contrary, coagulation is pro- moted by alum, and by the sulphates of zinc and copper.1 How these salts act on the fibrin, so as to prevent its particles from coming to- gether, it is not easy to explain. But these are not the only inscruta- ble circumstances that concern the coagulation of the blood. Many causes of sudden death have been considered to have this result:— lightning and electricity; a blow upon the stomach; injury of the brain; bites of venomous animals; certain narcotico-acrid vegetable poisons ; excessive exercise, and violent mental emotions, when they suddenly destroy, &c. Many of these affirmations, doubtless, rest on insufficient proof. For example, Sir C. Scudamore asserts that lightning has not this effect. Blood, through which electric discharges were transmitted, coagulated as quickly as that which was not electrified; and in animals killed by the discharge of a powerful galvanic battery, that in the veins was always found in a .solid state. M. Mandl has summed up the results of modern experiments on the subject as follows. First. The alkalies—potassa, soda, and ammonia—completely prevent coagu- lation: lime retards it. Secondly. The soluble alkaline salts—combi- nations of soda, potassa, ammonia, magnesia, baryta and lime with car- bonic, acetic, nitric, phosphoric, tartaric^ citric, boracic, sulphuric and cyano-hydric acid—also the chlorides, in very small quantity—favour coagulation. On the other hand, these substances in concentrated solution retard, and even prevent it entirely. The most active salts are the carbonates; the least so, combinations of chlorine, and sul- phates. 0*007 of carbonate of soda retards coagulation for several hours, whilst the sulphates do not act in the proportion of 14 per 1000. The action of a salt is more marked in proportion as it reddens more the blood; whilst combinations of chrome, chlorine and iodine do not redden it, and do not prevent its coagulation. When water is added to blood thus liquefied by a Salt it coagulates again—the fibrin being precipitated. Thirdly. Metallic salts decompose the blood; some causing coagulation ; others preventing it. Fourthly. Very dilute ve- getable acids favour it; when a little more concentrated, they prevent it; and when highly concentrated, decompose it like the mineral acids. Fifthly. The action of vegetable substances has not been sufficiently studied : some affirm, for instance, that narcotics prevent coagulation ; others that they favour it. The same doubt exists in regard to the action of poisons; it^s generally believed, however, that they—as well as lightning, a violent discharge of electricity, the instantaneous de- struction of the nervous system, &c.—prevent coagulation. Sixthly. Very dilute solutions of gum Arabic, sugar, albumen, milk, &c, appear to act only in a mechanical manner by preventing the approximation of the coagulated particles. 1 Magendie, Lectures on the Blood, in Lond. Lancet, reprinted in Bell's Select Medical Library, Philad, 1839. 120 CIRCULATION. We shall find, hereafter, that the action of some of these agents has been considered evidence that the blood may be killed; and, conse- quently, that it is possessed of life. All the phenomena, indeed, of coagulation, inexplicable in the present state of our knowledge, have been invoked to prove this position. The preservation of the fluid state, whilst circulating in the vessels—although agitation, when it is out of the body, does not prevent its coagulation—has been regarded of itself, sufficient evidence in favour of the doctrine. Dr. Bostock,1 indeed, asserts, that perhaps the most obvious and consistent view of the subject is, that fibrin has a natural disposition to assume the solid form, when no circumstance prevents it from exercising this inherent tendency. As it is gradually added to the blood, particle by particle, whilst that fluid is in a state of agitation in the vessels, it has no oppor- tunity, he conceives, of concreting; but when suffered to remain at rest, either within or without the vessels, it is liable to exercise its natural tendency. It is not our intention, at present, to enter into the subject of the vitality of the blood. The general question will be considered in a subsequent part of this work. We may merely observe, that, by the generality of physiologists, the blood is presumed', either to be endowed with a principle of vitality, or to receive from the organs, with which it comes in contact, a vital impression or influence, which, together with the constant motion, counteracts its tendency to coagula- tion.2 Even M. Magendie,3—who is unusually and properly chary in having recourse to this method of explaining the notum per ignotius,— affirms, that instead of referring the coagulation of the blood to any physical influence, it should be considered as essentially a vital process; or, in other words, as affording a demonstrative proof, that the blood is endowed with life;—a position, which—as will be seen hereafter—is not tenable.4 M. Vauquelin discovered in the blood a considerable quantity of fatty matter, of a soft consistence, which he, at first, regarded as fat; but M. Chevreul,5 after careful investigation, declared it to be identical with the matter of the brain and nerves, and to form the singular compound of an azoted fat. Cholesterin has been detected in it by Gmelin,6 and by Boudet.7 MM. Prevost and Dumas, Sdgalas, and others, have like- wise demonstrated the existence of urea in the blood of animals, whose kidneys had been removed. Chemical analysis is, indeed, adding daily to our stock of information on this matter; and is exhibiting to us, that many of the substances, that compose the tissues, exist in the blood in the very state in which we meet with them there. This is sigaally shown by the following table by Simon8 of the constituents found in the blood of man, and certain mammalia. 1 Physiology, 3d edit, p. 271, Lond, 1836. 2 J. Muller's Handbuch, u. s. w, Baly's translation, p. 97, Lond, 1838. 3 Precis, &c, ii. 234. 4 See vol. ii, chap. 5, on Life. 6 Bostock's Physiology, p. 294. 6 Chimie, iv. 1163. i Journ. de Pharmacie, Paris, 1833, and Annales de Chimie, Iii. 337. 8 Animal Chemistry, Sydenham Society edit., p. 166, Lond, 1845. BLOOD—ANALYSIS. 121 Protein compounds. Colouring matters. Extractive matters. Fats. Water. Fibrin. Albumen. Globulin. Hematin. Hemaphaein. Alcohol-extract. Spirit-extract. Water-extract. Cholesterin. ' Serolin. Red and white solid fats containing phos- phorus. Margaric acid. Oleic acid. Salts. Gases. Iron (peroxide). Albuminate of soda. Phosphates of lime, magnesia, and soda. Sulphate of potassa. Carbonates of lime, magnesia, and soda. Chlorides of sodium and potas- sium. Lactate of soda. Oleate and margarate of soda. Oxygen. Nitrogen. Carbonic acid. Sulphur. Phosphorus. The analyses of M. Lecanu1 are generally regarded as among the best. Blood obtained by him from two stout healthy men was found to be composed as follows:— Water, - - - - - Fibrin, ....... Albumen, ;' - • Colouring matter (globules), - Fatty crystallizable matter, .... Oily matter, -...... Extractive matter soluble in water and alcohol, Albumen combined with soda, ... Chloride of sodium, "1 potassium, { Carbonates } f Phosphates > of potassa and soda J Sulphates ) Carbonates of lime and magnesia, } Phosphates of lime, magnesia, and iron, > - Peroxide of iron, ; Loss, - - - 780-145 785-590 2-100 3 565 65090 69-415 133-000 119626 2430 4-300 1-310 2-270 1-790 1-920 1-265 2-010 8370 2-100 2-400 100-000 7-304 1-414 2-586 100-000 On these analyses, Dr. Prout2 has remarked, that gelatin is never found in the blood, nor any product of glandular secretion; and he adds, that a given weight of gelatin contains at least three or four per cent. less carbon than an equal weight of albumen. Hence, the production of gelatin from albumen, he conceives, must be a reducing process. We have seen, under "the head of Respiration, what application he makes of these considerations.3 Researches on the ashes of the blood by Enderlin,4 in the laboratory of Giessen, give the following as the quantitative analysis in 100 parts from human blood:— Tri-basic phosphate of soda, Chloride of sodium, - - potassium, - Sulphate of soda, - Phosphate of lime, - ■- magnesia, - Oxide of iron, with some phosphate of iron, 221 54-769 4-416 2461 3-636 0-769 1077 1 Annales de Chimie et de Physique, xlviii. 308, and Journal de Pharmacie, Sept, 1831. 2 Bridgewater Treatise, Amer edit, p. 280, Philad, 1834. 3 For the methods of analyzing the blood, see Simon, op. cit, p. 166. 4 Annalen der Chemie und Pharmacie, Marz und April, 1844, cited by Mr. Paget, in Brit. and For. Med. Rev, Jan, 1845, p. 255. 122 CIRCULATION. It has been inferred, from these analyses, that the albumen of the blood is not in the form of an albuminate of soda, nor of a combina- tion with carbonate or bicarbonate of soda, but in combination with the alkaline tribasic phosphate, and chloride of sodium,—the former salt possessing, in a high degree, the power of dissolving protein compounds and phosphates of lime, and probably being the solvent of those con- stituents in the blood. Dr. John Davy,1 however, thinks, that even admitting the accuracy of Enderlin's results, the propriety of applying them to the condition of the alkali in liquid blood may be questioned. Carbonate of soda, he observes, is decomposed when heated, with phos- phate of lime; and when added in small quantity to blood is not to be detected in its ashes. This may account for its not. having been found there. Were the opinion, referred to, correct, an acid added to blood or its serum, after the action of the air-pump, ought not on re-exhaustion to occasion a farther disengagement of air; but Dr. Davy finds that it does. This and other results induce him to give the preference to the conclusion, that blood contains sesquicarbonate of soda. M. Dutrochet believed, that he had formed muscular fibres from albumen by the agency of galvanism; and supposed, that the red cor- puscles of the blood formed each a pair of plates, the nucleus being negative, the envelope positive; but Miiller2 has shown, that all the appearances, which he attributed to different electric properties of the blood, are explicable by the precipitation of the albumen and fibrin in consequence of the decomposition of the salts of the serum and of the oxidation of the copper wire used in the experiments,—both the decom- position of the salts and the oxidation of the copper being the usual effects of galvanic action. With the galvanometer he was unable to discover any electric current in the blood; and he perceived no variation in the needle of the multiplicator, when he inserted one wire into an artery of a living animal, and the other into a vein. Lastly :—Interesting,experiments and observations on the blood were published several years ago by Dr. Benjamin G. Babington.3 The principal experiment was the following. He drew blood in a full stream into a glass vessel filled to the brim, from the vein of a person labour- ing under acute rheumatism. On close inspection, a colourless fluid was immediately perceived around the edge of the surface, and after a rest of four or five minutes, a bluish appearance was observed forming an upper layer on the blood, which was owing to the subsidence of the red corpuscles to a certain distance below the surface, and the conse- quent existence of a clear liquor between the plane of the corpuscles and the eye. A spoon, previously moistened with water, was now im- mersed into the upper layer of liquid, by a gentle depression of one border. The liquid was thus collected quite free from red corpuscles, and was found to be an opalescent, and somewhat viscid solution, per- fectly homogeneous in appearance. By repeating the immersion, it was collected in quantity, and transferred to another vessel. That 1 Proceedings of the Royal Society of Edinburgh, vol. ii. No. 26, for 1845. 2 Handbuch, u. s. w, Baly's translation, p. 133. 3 Med-Chirurg. Transact, vol. xvi. Part 2, Lond, 1831; and art. Blood (Morbid Conditions of the) in Cyclop. Anat.and Physiol, Lond, 1836. BLOOD—BUFFY COAT. 123 which Dr. Babington employed was a bottle holding about 180 grains, of globular form, with a narrow neck and perforated glass stopper. The solution with which the globular bottle was filled, though quite homo- geneous at the time it was thus collected, was found, after a time, to separate into two parts, viz., into a clot of fibrin, which had the precise form of the bottle into which it was received, and a clear serum, pos- sessing all the usual characters of the fluid. From this experiment, Dr. Babington inferred, that buffed blood, to which we shall have to refer under another head, consists of only two constituents, red corpuscles, and a liquid to which he gives the name liquor sanguinis—plasma of Schultz—so called by him, because he esteems it to be the true nutri- tive and plastic portion of the blood, from which all the organs of the body are formed and nourished. It has long been observed, that the blood of inflammation is longer in coagulating than the blood- of health, and that the last portion of blood drawn from an animal coagulates quickest. The immediate cause of the buffy coat is thus explained by Dr. Babington. The blood, con- sisting of liquor sanguinis and insoluble red corpuscles, preserves its fluidity long enough to permit the corpuscles, which are of greater specific gravity, to subside through the liquor sanguinis. At length, the liquor sanguinis separates, by a general coagulation and contrac- tion, into two parts; and this phenomenon takes place uniformly through- out the liquor. That part of it, through which the red corpuscles had time to fall, furnishes a pure fibrin or buffed crust, whilst the portion into which the red corpuscles had descended furnishes the coloured clot. This, in extreme cases, may be very loose at the bottom, from the great number of red corpuscles collected there, each of which has supplanted its bulk of fibrin, and consequently diminished its firmness in that part. There is, however, with this limitation, no more fibrin in one part of the blood than another. Researches by Mr. Gulliver1 would seem to show, that the rate at which the red corpuscles sink in a fluid may give a very incorrect measure of its tenuity,, since they sub- side much slower in serum, or in liquor sanguinis made thinner and lighter by weak saline solutions, than in the same animal fluids made thicker and heavier by gum. The blood, too, may have its coagulation retarded, whilst it is thinned and reduced in specific gravity; and yet no buffy coat appear. The greater aggregation of the corpuscles, ob- served by Mr. T. Wharton Jones,2 and subsequently in his experiments, seemed to him to be connected with the accelerated rate of subsiding; as it was prevented or reversed by salts, which dispersed the corpus- cles, and increased by viscid matters, which increased the aggrega- tion. It is a well-known fact, that the shape of the vessel into which the blood is received influences the depth of the buff. The space, left by the gravitation of the red corpuscles, bears a proportion to the whole perpendicular depth of the blood, so that in a shallow vessel scarcely any buff may appear, whilst the same blood in a deep vessel would have furnished a crust of considerable thickness ; but Dr. Babington asserts, • 1 Dublin Med. Press, Dec. 11, 1844. * Edinburgh Med. and Surg. Journal, Oct, 1S43, p. 309. 124 CIRCULATION. that even the quantity of the crassamentum is dependent, within cer- tain limits, on the form of the vessel. If this be shallow, the crassa- mentum will be abundant; if approaching the cube or sphere in form, it will be scanty. The difference is owing to the greater or less dis- tance of the coagulating particles of fibrin from a common centre, which causes a more or less powerful adhesion and contraction of those particles. This is a matter of practical moment, inasmuch as blood is conceived to be thick or thin, rich or poor, in reference to the quantity of crassamentum; and pathological views are entertained in conse- quence of conditions, which, after all, may depend not perhaps on the blood itself, but on the vessel into which it is received. To remove an objection, that might be urged against a general con- clusion deduced from the experiment cited,—that it was made upon blood in a diseased state,—Dr. Babington received healthy blood into a tall glass vessel half filled with oil, which enabled the red corpuscles to subside more quickly than would otherwise have been the case. This blood was found to have a layer of liquor sanguinis, which formed a buffy coat, whilst a portion of the same blood, received into a similar vessel, in which there was no oil, had no buff. Hence, it appeared, that healthy blood is similarly constituted as blood disposed to form a buffy coat, the only difference being, that the former coagulates more quickly than the latter. Dr. J. Davy,1 however, has observed, that inflammatory blood, in some instances, does not coagulate more slowly than healthy blood, and as from the experiments of Professor Miiller2 it would appear that the presence of fibrin in the blood favours the sub- sidence of the red particles, Miiller was led to infer, that the formation of the buffy coat may arise from the blood containing a larger quantity of fibrin, which the blood of inflammation is known to do. So that the principal causes, he thinks, of the subsidence of the red particles and the formation of the buffy coat in inflammatory blood, appear to be— the slow coagulation of the blood, and the increased quantity of fibrin. The most correct view, however, is, perhaps, that of M. Andral,3 that the essential condition of the buffy coat is an increase in the quan- tity of fibrin in proportion to the red corpuscles. Hence, if there be an absolute increase of fibrin, the red corpuscles remaining the same, as in inflammation; or, if there be a diminution in the proportion of the red corpuscles, the fibrin remaining the same, as in chlorosis, the buffy coat may result; provided only there be—as there probably always is under such circumstances—a greater aggregation of the cor- puscles. An interesting fact connected with this subject has been noticed by Mr. T. Wharton Jones.4 If a single drop of inflammatory blood be examined by the microscope, it will be seen that the red corpuscles have an unusual attraction for each other, which occasions them to coalesce in piles and masses, as in the second marginal illustration, leaving wide interspaces for the fibrin, lymph-corpuscles, and serum. It is probable, too, that there is an increased attraction between the 1 Philosophical Transactions, for 1822. 2 Qp. citat, p. 117. 3 Hematologic Pathologique, p. 75, Paris, 73, or Meigs's and Stille's translation, Philad, 1844. * Edinburgh Medical and Surgical Journal, Oct., 1843, p. 309. BLOOD—OF DIFFERENT VEINS. 125 particles of the fibrin, which will account for Fis- 295. the firmer clot of the blood of inflammation. ^ The fact of a single drop of blood being suf- a ficient to indicate the character of the whole mass may be important in cases where a doubt exists as to the propriety of bleeding to any extent. It is proper to remark, that recent researches by Mulder1 have led him to infer, that the buffy coat does not consist of true fibrin, but fr is a compound of a binoxide of protein, which Sj is insoluble in boiling water, and a tritoxide, "W. which is soluble. These oxides Mulder com- ^ prehends under the name oxyprotein. It may, also, be remarked, that in all expe- Aggregation of Corpuscles in , Aui, i ii_ -li a Healthy and in Inflamed Blood. nments on the horse, whenever the blood flows from an opened vein in a continuous bio0dHealthy bl°°d- *' Inflamed stream, with a sufficiently strong jet, and is received into a vessel that is neither too shallow nor too wide, the upper part of the clot is instantly found occupied by a white mass, which perfectly resembles the buff of the blood of man. Such was the result of the observations of MM. Andral, Gavarret, and Delafond.2 It need scarcely be said, that venous blood, composed as it is in part of the products of heterogeneous absorption, must differ in its charac- ter in the different veins. In its passage through the capillary or intermediate circulation, the arterial blood is deprived of several of its elements, but this deprivation is different in different parts of the body. That, for example, which returns from the salivary glands, must vary from that which returns from the kidneys. In the blood of the abdo- minal venous system, the greatest variation is observed. Professor Schultz3 has inquired into the chemical and physiological differences between that of the vena portae and of the arteries and other veins. He found, that it is not reddened by the neutral salts, or by exposure to the atmosphere, or to oxygen; that it does not generally coagulate; contains less fibrin; proportionably more cruor, and less albumen; and has twice as much fat in its solid parts as that of the arteries and other veins ; the proportions being as follows :— Blood of the vena porta? ...... 166 per cent. of the arteries....... 0-92 of the other veins......0-83 Simon,4 in his researches, also found a much less proportion of fibrin, and a larger of fat and of colouring matter. The fat he ascribes to the fluids produced during the act of digestion, which are conveyed into the portal vein. The subject of the changes produced on the portal 1 Annalen der Chemie, u. s. w, Bd. xlviii, Heidelb, 1843; cited by Mr. T. Wharton Jones, in Brit, and For. Med. Rev, July, 1844, p. 259. 2 Essai d'Hematologie Pathologique, p. 27, Paris, 1843. 3 Rust, Magazin flir die gesammt. Heilkund. Bde. 44, H. i, and Lond. Lancet, Aug 10 1839, p. 717. 4 Animal Chemistry, Sydenham Society edition, p. 208, Lond, 1845. 126 CIRCULATION. blood, more especially as regards the quantity of red corpuscles, will be referred to when considering the functions of the Spleen. The character and quantity of the different constituents of the blood, as well as its coagulation, vary greatly in disease; and the investigation is one of the most important in the domain of pathology. It is^ one that has attracted the attention of modern pathologists, and especially of MM. Andral and Gavarret, and of Simon, and MM. Becquerel and Rodier, who have endeavoured to detect the changes that occur in dis- ease in the amount of the organic elements of the fluid. These the author has referred to in their appropriate places in another work.1 The usual proportions of each element, in 1000 parts of healthy blood, according to M. Lecanu, adopted by MM. Andral and Gavarret, are as follows:— Fibrin, Red corpuscles, Solid matter of serum, Water, The average of analyses of the blood of nine healthy individuals- four females and five males, by Dr. Ch. Frick, of Baltimore,2 corre- sponds nearly with the above. According to Simon,3 the proportions are somewhat different,—a dif- ference resulting in a great measure from a different method of analy- sis. The mean of his observations gave— Water, - Solid residue, Fibrin, - Fat, Albumen, Globulin, Hematin, Extractive matter and salts, The following table exhibits the mean composition of the blood, in eleven cases, as observed by MM. Becquerel and Rodier.5 Density of the defibrinated blood, .... 1060-2 " of the serum, ' - - - - . 1028 Water, - - - - - - . 779 Corpuscles, - - - - - . 141.1 Albumen, ----._ 59.4 Fibrin, ....... 2-2 Extractive matters and free salts, - g.g Fatty matters, Serolin, .... Fatty phosphuretted matter, Cholesterin, ... Soapy matter, ... 1 Practice of Medicine, 3d edit, Philad, 1848. 2 American Journal of the Medical Sciences, Jan., 1848, p. 27. 3 Animal Chemistry, p. 245. < It is proper to remark, with Simon, that the sum of the hematin and globulin, in his analysis, can never represent the absolute quantity of blood corpuscles. In his method the nuclei and capsules of the blood corpuscles are estimated as albumen ; in that of Berzelius as fibrin; and in that of MM. Andral and Gavarret, as appertaining to the corpuscles. * Gazette Medicale de Paris, Nos. 47,48,49, 50, and 51, for 1844. 3 127 80 790 795-278 204-022 2-104 2-346 76-600 103 022 6209 12 0124 0-02 0-488 0088 BLOOD—CONSTITUENTS. 127 One thousand parts of calcined blood contained— Chloride of sodium, Soluble salts, Phosphates, - Iron, 3-1 2-5 0-334 0-565 From these numbers they draw the following deductions. First. The limits within which the composition of healthy blood varies are restrict- ed, and probably dependent on constitution, age, and diet. Secondly. The number for the corpuscles exceeds 127, which has been regarded as expressing the healthy mean. Thirdly. The number for the fibrin, 2*2, is below that usually admitted as the mean of that element, 3. The following tables have been constructed chiefly from the analyses of Denis, Lecanu, Simon, Nasse, Lehmann, Becquerel and Rodier, and Gavarret; and "are designed to combine, as far as possible, the ad- vantage of accuracy in numbers with the convenience of presenting at one view a list of all the constituents of the blood."1 Average proportions of the chief constituents in 1000 parts:— Water, - - - Red corpuscles, Albumen of serum, Saline matters, Extractive, fatty and other matters, Fibrin, - - 784 131 70 6-03 6-77 2-2 1000- Average proportion of all the constituents of the blood in 1000 parts:— Water, .... • 784 Albumen, - 70 Fibrin, .... - 2-2 Red corpuscles, - . globulin, ... - 123-5 hematin, ... - 7-5 Fatty matters: Cholesterin, 0-08^ Cerebrin, 0-40 Serolin, 002 ! Oleic and margaric acids, J - 1*3 Volatile and odorous fatty acid, Fat containing phosphorus, J Inorganic salts : Chloride of sodium, - - 36 Chloride of potassium, . 0-36 Tribasic phosphate of soda, - . 0-2 Carbonate of soda, - - 0-84 Sulphate of soda, ... . 0-28 Phosphates of lime and magnesia, - . 025 Oxide and phosphate of iron, • 0-5 Extractive matter, with salivary matter, urea, bil- ) iary colouring matter, gases and accidental sub- J> 5-47 stances, 1000- The mode in which the ratio of the various elements of the blood is estimated is detailed by MM. Andral and Gavarret, Simon, and Bec- 1 Kirkes and Paget, Manual of Physiology, Amer. edit, p. 54, Philad, 1849. 128 CIRCULATION. querel and Rodier, in the works referred to. A simpler method has, however, been given by M. Figuier,1 founded on the fact made known by Berzelius, that after the addition of a solution of a neutral salt to defibrinated blood, the corpuscles do not pass through bibulous paper. On the addition of two parts of a solution of sulphate of soda, of speci- fic gravity 1*130, to one of blood, M. Figuier found, that the whole of the corpuscles remained on the surface of the filter. The following is his procedure. The fibrin is removed in the usual way by whipping; and dried, and weighed. The weight of the corpuscles is then ascer- tained, and that of the albumen by coagulating the filtered solution by means of heat. The proportion of water is determined by evaporating a small known weight of the blood. The advantage of this plan con- sists in the facility with which the most important constituents may be determined without any difficult manipulations. The proportion of fibrin, according to MM. Andral and Gavarret, may vary perhaps within the limits of health, from 2J to 3J parts in a thousand. The amount of red corpuscles appears to be subject to greater variation within the limits of health than that of the fibrin. The maximum is about 140, but this is connected with a plethoric con- dition: the minimum about 110. Strength of constitution contributes most to raise the corpuscles towards the maximum; whilst debility, con- genital or acquired, diminishes them towards the minimum proportion. The solid matter of the serum likewise varies, but there is a certain point of diminution in health below which they do not pass.2 The analyses of MM. Becquerel and Rodier exhibit a marked differ- ence in the proportion of the constituents of the blood of the two sexes. So great is this, that in order to attain correct conclusions in regard to morbid blood, it is indispensable to contrast it with the male or female blood in health. The average differences between the two are seen in the following table:— Density of defibrinated blood, Density of serum, - Water, Fibrin, Sum of fatty matters, Serolin, Phosphorized fat, Cholesterin, - Saponified fat, Albumen, Blood corpuscles, Extractive matters and salts, Chloride of sodium, Other soluble salts, - Earthy phosphates, - Iron, The main difference, consequently, between male and female blood is in the amount of water and blood corpuscles.3 1 Annales de Chimie et de Physique, ii. 503, cited in Ranking's Abstract i 299 Amer edit. New York, 1845. ' ' 9 Andral, Hematologic Pathologique, p. 29, Paris, 1843. 3 For the differences of blood, according to constitution, temperament, &c. see Simon Ani- mal Chemistry, Sydenham Society edition, p. 2"b, /-ond, 1845, or Amer. edit, Philad. 1846. Male. Female. 1060-0 1057-5 1028-0 1027-4 779-0 791-1 2-2 2-2 1-60 1-62 0-02 0-02 0-488 ' 0-464 0-088 0-090 1-004 1046 694 70-5 141-1 127-2 6-8 7-4 31 3-9 2-5 2-9 0-334 0-354 0566 0-541 BLOOD—ORGANIC CONSTITUENTS. 129 The following table by Henle,1 gives the results of the analyses of different observers as regards the proportion of the organic constituents of human blood, and the corresponding specific gravities of blood and serum. S.G. S. G. Blood Cor- Residue of of Blood. of Serum. Water. puscles. Serum. Fibrin. Observer. Remarks. 1 1062 1031 772 128 97 2 Popp. 2 1061 781 121 86 10 do. Many colourless corpuscles. 3 1057 773 142 82 3 Few do. 4 1055 1028 799 130 75 3 Becquerel and Rodier. 5 1055 1027 793 126 78 2 do. 6 1053 771 146 78 4 Popp. 7 1053 781 140 76 2 do. 8 1051 802 117 76 5 do. 9 1050 790 114 90 5 do. Many do. 10 1049 803 120 71 5 do. do. 11 1049 806 92 96 5 do. do. 12 1048 791 128 76 2 do. 13 1048 814 104 76 5 do. Few do. 14 1048 806 124 66 4 do. 15 1048 801 107 86 5 do. Many do. 16 1048 811 95 86 8 do. A moderate num-ber of do. 17 1047 811 118 65 6 do. 18 1047 794 121 81 4 do. 19 104G 790 129 78 2 do. 20 1046 1023 831 105 .54 2 Becquerel and Rodier. 21 1045 1024 78 3 do. 22 1044 827 91 71 11 Popp. 23 1044 801 100 86 12 do. 24 1044 790 115 83 11 do. A strong buffy coat. 25 1043 826 93 72 9 do. Few1 colourless corpuscles. 26 1043 812 112 66 10 do. A moderate buffy coat. 27 1042 812 105 77 6 do. Few colourless corpuscles. 28 1042 821 91 84 4 do. 29 1042 828 95 74 3 do. Many colourless corpuscles. 30 1042 1022 92 - 2 Becquerel and Rodier. 31 1041 816 77 94 13 Popp. Strong buffy coat. 32 1041 , 817 99 76 8 do. 33 1040 ' 831 92 68 9 do. 34 1040 827 92 76 4 do. 35 1039 855 68 72 6 do. Few colourless corpuscles. 36 1039 845 96 80 5 do. 37 1030 792 126 81 2 do. 38 1026 788 124 82 6 Heller. 39 1025 773 146 77 4 do. 40 1025 834 78 83 5 do. 41 1024 820 87 85 8 do. 42 1023 782 147 65 6 do. 4 3 1011 58 Popp. Serum rich in fat. 1 Handbuch der Rationellen Pathologie, 2er Band. s. 18, Braunschweig, 1847. VOL. II.—9 130 CIRCULATION. There is considerable difference, however, amongst observers in re- gard to the ratio of the different organic constituents of healthy blood, and this is dependent upon the different modes of evaluation adopted by them. It is advisable, therefore, in observations made on diseased blood, to follow the method employed by some one of them; and that of MM. Andral and Gavarret is generally chosen. To exhibit this difference the following table drawn up by Henle1 may be introduced:— 1000 parts of healthy venous blood contain According to Le Canu, " Becquerel and Rodier, of men, of women, " Popp, " Zimmerman, " Simon, of "men, of women, " Christison, of men, of women, " Hittorf, of women, Corpuscles. Water. Fibrin. 127 790 3 141.1 779 2-2 127-2 791-1 2-2 120 790 2-5 127 3 112-2 791-9 20 106-0 798-6 22 153-5 756-2 5-2 120-7 795-2 25 126-4 7930 1:4 Albumen. Extractive matters. 72 Salts, 69-4 70-5 8-4 9 88 80 75/6 77-6 16-6 12-6 85-3 81-6 67-4 11-5 I. II. III. 78318 769-64 7757 21682 230-36 2243 2-30 2-03 2-63 63-34 68-45 7008 139-92 146-22 138-71 5 16 5 34 3-84 8-85 8-86 904 1-70 A very recent analysis of healthy human blood by Scherer2 gives the following proportion of the various constituents:— Water, ... Fixed parts, Fibrin, ... Albumen, ... Blood corpuscles, Extractive matters, Soluble salts, - Fat, ..... It may be added, that a peculiar entozoon,—polystoma venarum, hexathyridium venarum,—has been found in human venous blood especially in that of persons affected with haemoptysis; Treutler found one in the tibial vein of a .young man, who had lacerated it whilst bathing. Vogel, however, suggests, that it may have been a planaria, which had entered the vein from without;3 and Valentin several times observed minute entozoa—anguillulse intestinales—in the circulating blood of frogs. MM. Gruby and Delafond4 communicated to the AcadSmie Roy ale des Sciences, of Paris, the discovery of filarige in the circulating fluid of a living dog. 1 Op. cit, s. 73. 2 Jahresbericht iiber die Fortschritte in der Biologie im Jahre, 1848, s. 65 Erlaniren 1849. 8 Tbe Pathological Anatomy of the Human Body, English translation bv Dav o 467^ Lond, 1847. ' '' v' * Philad. Med,. Examiner, Jan. 13, 1844, from Comptes Rendus. PHYSIOLOGY OF THE CIRCULATION. 131 3. PHYSIOLOGY OF THE CIRCULATION". The blood, contained in the circulatory apparatus, is in constant motion. The venous blood, brought from every part of the body, is emptied into the right auricle; from the right auricle it passes into the corresponding ventricle; and the latter projects it into the pulmonary artery, by which it is conveyed to the lungs, passing through the capil- lary system into the pulmonary veins; these convey it to the left auri- cle ; from the left auricle it enters the corresponding ventricle ; and the left ventricle sends it into the aorta, along which it passes to the different organs and tissues of the body, through the general inter- mediate or capillary system, which communicates with the veins; these return it to the part whence it set out. This entire circuit includes both the lesser and the greater circulation. It was not until the commencement of the seventeenth century, that any precise ideas were entertained regarding the general circulation. In antiquity, the most erroneous notions prevailed; the arteries being generally looked upon as tubes for the conveyance of some aerial fluid to, and from, the heart; whilst the veins conducted the blood, whither or for what precise purpose was not understood. The names, given to the principal arterial vessel—aorta—and to the arteries, sufficiently show the functions originally ascribed to them,—both being derived from the Greek, a^p, "air" and t^tiv, "to kee£;" and this is farther con- firmed by the fact, that the trachea or windpipe was originally termed an artery,—the apr^pta fpa^fca of the Greek,—aspera arteria of the Latin writers. In the time of Galen, however, the arteries were known to contain blood; and he seems to have had some notions of a circulation. He remarks, that the chyle, the product of digestion, is collected by the meseraic veins and carried to the liver, where it is converted into blood; the supra-hepatic veins then carry it to the pulmonary heart; whence a part proceeds to the lungs, and the remainder to the rest of the body, passing through the median septum of the auricles and ven- tricles. This limited knowledge of the circulation continued through the whole of the middle ages,—the functions of the veins being univer- sally misapprehended; and the general notion being, that they also convey blood from the heart to the organs; from the centre to the circumference. It was not until after the middle of the sixteenth century, that the lesser circulation or that through the lungs was comprehended by Michael Servetus,—who fell a victim to the persecution and intolerance of Calvin,—and of Andrew Csesalpinus and Realdus Columbus. It has been imagined, that they possessed some notion of the greater circulation. Howsoever this may have been, all nations unite in awarding to Harvey the merit, if not of entire originality of at least having first clearly described it. The honour of the discovery is, there- fore, his; and by it his name has been rendered immortal,—for its importance to the knowledge of the physiology and pathology of the animal fabric is overwhelming. How vague and inaccurate must have been the notions of the early pathologists regarding the doctrine of acute diseases, in which the circulation is always largely affected,—dis- 132 CIRCULATION eases, which, according to the estimate of some writers, constitute two- thirds of the morbid states to which mankind are liable ! It was in the year 1619, that Harvey attained a full knowledge of the circulation; but his discovery was not promulgated until the year 1628, in a tract, to which the merit of clearness, perspicuity, and demonstration has been awarded by all.1 Yet so strong is the force of prejudice, and so difficult is it to discard preconceived notions, that according to Hume,2 it was remarked, that no physician in Europe, who had reached forty years of age, ever, to the end of his existence, adopted Harvey's doctrine of the circulation; and Harvey's practice in London diminished extremely for a time from the reproach drawn upon him by that great and signal discovery. Of the truth of the course of the blood, as discovered hj Harvey, we have numerous and incontestable evidences, which it is almost a work of supererogation to adduce. Of these the following are some of the most striking. First. If we open the chest of a living animal, we find the heart alternately dilating and contracting so as manifestly to receive and expel the blood in reciprocal succession. Secondly. The valves of the heart, and of the great arteries that arise from the ven- tricles, are so arranged as to allow the blood to flow in one direction, and not in another; and the same may be said of the veins, which are directed towards the heart. The tricuspid valve permits the blood to flow only from the right auricle into the corresponding ventricle; the sigmoid valves admit it to enter the pulmonary artery, but not to return; and, as there is, in the adult, no immediate communication between the right and left sides of the heart, the blood must pass along the pulmonary artery and the pulmonary veins to the left auricle. The mitral valve, again, is so situate, that the blood can only pass in one direction from auricle to ventricle ; and, at the mouth of the aorta, the same valvular arrangement exists as in the pulmonary artery, which per- mits the blood to proceed along the artery, but prevents its reflux. Thirdly. If an artery and vein be wounded, the blood will be observed to flow from the part of the vessel nearest the heart in the case of the artery ; from the other extremity in that of a vein. The ordinary ope- ration of bloodletting at the flexure of the arm affords an elucidation of this. The bandage is applied above the elbow, for the purpose of com- pressing the superficial veins, but not so tightly as to compress the deep-seated artery also. The blood passes along the artery to the ex- tremity of the fingers, and returns by the veins ; but its progress back to the heart by the subcutaneous veins being prevented by the ligature, they become turgid ; and, if a puncture be made, it flows freely. If, however, the ligature be applied so forcibly as to compress the main artery, the blood no longer flows to the extremity of the fingers; there is none, consequently, to be returned by the veins; they do not rise properly; and if a puncture be made no blood flows. This is not an unfrequent cause of the failure of an inexperienced phlebotomist. If the bandage, under such circumstances, be slackened, the blood resumes 1 Exercitat. Anatom. de Motu Cordis et Sanguinis, Francof., 1628, Glasgure, 1751. 2 History of England, vol. vii. chap. lxii. p. 347, London, 1782. IN THE HEART. 133 its course along the artery, and a copious stream issues from the orifice, which did not previously transmit a drop. This operation, then, exhibits the fact of the flow of blood along the arteries from the heart, and of its return by the veins. From what has been said, too, it will be obvious, that if a ligature be applied to both vessels, the artery will become turgid above the ligature, the vein below it. Fourthly. The microscopical experiments of Leeuenhoek, Malpighi, Spallanzani, and others have exhibited to the eye the passage of the blood in suc- cessive waves by the arteries towards the veins, and its return by the latter. Lastly. The fact is farther demonstrated by the effect of trans- fusion of blood, and of the injection of substances into the vessels; both of which operations will be alluded to in another place. In tracing the physiological action of the different parts of the cir- culatory apparatus, we shall follow the order observed in the anatomi- cal sketch; and describe, in succession, the circulation in the heart, arteries, capillary vessels, and veins ; on all of which points there has been interesting diversity of opinion, and much room for ingenious speculation, and farther improvement. a. Circulation in the Heart. It has been already observed, that when the heart of a living animal is exposed, it is remarked to undergo alternate contraction and dilata- tion. The mode, in which the circulation through the organ is accom- plished is generally considered to be as follows : The blood is received into the two auricles at the same time, and is transmitted into the two great arteries synchronously. In order that the heart shall receive blood, it is necessary that the auricle should be dilated. This move- ment is partly effected by virtue of the elasticity which it possesses in its structure. Let us suppose it to be once filled ; the stimulus of the blood excites it to contraction, and the blood is sent into the corre- sponding ventricle. As soon, however, as it has emptied itself, the stimulus is withdrawn; and, by virtue of its elasticity the muscular structure returns to the state in which it was prior to its contraction. An approach to a vacuum is thus formed in the cavity, and the blood from the veins is solicited towards it, until it is again filled, and its contraction renewed. When the right auricle contracts there are four channels by which the blood might be presumed to pass from it,—the two termina- tions of the venae cavae ; the coronary vein, and the auriculo-ventricular opening. The constant flow of blood from every part of the body pre- vents it from readily returning by the venae cavae, whilst the small quan- tity, which, under other circumstances, might have entered the coronary vein, is prevented by its valve. To the flow of the blood through the aperture into the ventricle, which is in a state of dilatation, there is no obstacle, and accordingly it takes this course, raising the tricuspid valves. It may be remarked, that physiologists are not entirely of accord regarding the reflux of blood into the venae cavae. Some think, that this always occurs to a slight extent; others, never in the healthy state. Its existence is unequivocal, where an obstacle occurs to the due dis- charge of the blood into the ventricle. For example, if there is any 134 CIRCULATION impediment to the flow of blood along the pulmonary artery, either owing to mechanical obstruction or to diminished force of the ventri- cle, the reflux is manifested by a kind of pulsation in the veins, which Haller has called venous pulse. The blood having attained the right ventricle by the effort exerted by the contraction of the auricle, and by the aspiration exerted by the dilatation of the cavity through the agency of its elastic structure, the ventricle contracts. Into it there are but two apertures, the auriculo- ventricular, and the mouth of the pulmonary artery. By the former, much of the blood cannot escape, owing to the tricuspid valve, which acts like the sail of a ship,—the blood distending it as the wind does a sail, and the chordae tendineae retaining it in position, so that the greater part of the blood is precluded from reflowing into the auricle. This auriculo-ventricular valve is not, however, as perfect as that of the left heart. The observations of Mr. T. W. King1 show, that whilst the structure of the mitral valve is adapted to close completely all commu- nication between the left auricle and left ventricle during the contrac- tion of the latter, that of the tricuspid valve is designedly calculated to permit, when closed, the flow of a certain quantity of blood into the auricle. The comparatively imperfect valvular function of the tricus- pid was shown by various experiments on recent hearts, in which it was found, that fluids, injected through the aorta into the left ventricle, were perfectly retained in that cavity by the closing of the mitral valve; but when the right ventricle was similarly injected through the pulmo- nary artery, the tricuspid valves generally allowed the escape of the fluid in streams more or less copious, in consequence of the incomplete apposition of their margins. This peculiarity of. structure in the tri- cuspid, Mr. King regards as an express provision against the mischiefs, that might result from an excessive afflux of blood to the lungs,—thus acting as a safety valve, and being more especially advantageous in incipient morbid enlargements of the right ventricle. The only other way the blood can escape from the right ventricle is by the pulmonary artery, the sigmoid valves of which it raises. These had been closed like flood-gates, during the dilatation of the ventricle ; but they are rea- dily pushed outwards, by the columns transmitted from the ventricle. Such is the circulation through one heart,—the pulmonic. The same explanation is applicable to the other,—the systemic; and hence it is, that the structure, as well as the functions of the heart, is so much better comprehended, by conceiving it to be constituted of two essen- tially similar organs. The above description is that which is usually given of the circula- tion through the heart. There is great reason, however, for the belief, that too much importance has been assigned to the distinct contraction of the auricles. If we examine their anatomical arrangement we dis- cover, that there are no valves at the mouths of the great veins which open into them, and that although in the proper auricle or dog's ear portion muscular fibres and columns exist,—somewhat analogous to those of the columnse carneae of the ventricles, and probably destined for 1 Guy's Hospital Reports, No. iv. for April, 1837. IN THE HEART. 135 similar uses,—the parietes of the main portions of the auricles,—those that constitute the venous sinuses are but little adapted for energetic contraction. In experiments on living animals observation shows, that the rhythmic acts of dilatation and contraction are more signally,ex- hibited by the ventricle, and, moreover, in some monsters the auricles are wanting, and in birds very small. M. d'Espine considers the auricles, in receiving or transmitting blood, to have only a vermicular motion, not one of contraction; and in a case of monstrosity, described by Br. T. Robinson,1 of Petersburg, Virginia, no distinct systole and diastole of the auricles could be detected. Besides, if we admit both an active power of dilatation and contraction in the ventricles, any similar action of the auricles would seem to be superfluous. In the state of active dilatation of the ventricles, the blood is drawn into their cavities; and as soon as they enter into contraction, the auriculo- ventricular valves prevent the farther entrance into them of blood arriving in the auricles by the large veins; and give occasion to the distension of the auricles; in this way, the dilatation of the auricles, synchronous with the contraction of the ventricles, is accounted for. As soon as the ventricle has emptied itself of its blood, it dilates actively; the blood then passes suddenly from the auricle into its cavity through the auriculo-ventricular opening. From careful experiments instituted by Drs. Pennock and Moore,8 they drew the following conclusions, which have been confirmed by the observations of others, and merit universal assent. The ventricles contract and the auricles dilate at the same time, occupying about one- half of the whole time required for contraction, diastole, and repose. Immediately at the termination of the systole of the ventricle, its diastole occurs, occupying about one-fourth of the whole time, syn- chronously with which the auricle diminishes, by emptying a portion of its blood into the ventricle, but without muscular contraction. The remaining fourth is devoted to the repose of the ventricles, near the termination of which the auricle contracts actively, with a short, quick motion, thus distending the ventricles with an additional quantity of blood: this motion is propagated immediately to the ventricles, and their systole follows so rapidly as to make the contraction of auricle and ventricle almost continuous. From the termination of their dias- tole to the commencement of the systole, the ventricles are in a state of perfect repose; their cavities remaining full but not distended; whilst those of the auricles are partially so, during the whole time. It appears probable, that the great use of the auricles—in which we include the sinuses—is to act as true gulfs for the reception of the blood proceed- ing from every part of the body;—and that little effect is produced on the circulation by their varying condition.3 The state of the heart in which the ventricles are dilated is termed Diastole ; that, in which they are contracted, Systole. 1 American Journal of the Medical Sciences, No. xxii. for February, 1833. 2 Medical Examiner, Nov. 2, 1839, and American Medical Intelligencer. Dec. 16, 1S39, p. 277. 3 See, on this subject, Elliotson's Human Physiology, p. 174, Lond., 1840. 136 CIRCULATION Since the valuable improvement, introduced by M. Laennec in the discrimination of diseases of the chest by audible evidences, it has been discovered, that the heart is not in a state of incessant activity, but has, like other muscles, its intervals of repose. If we apply the ear or the stethoscope to the praecordial region, we hear, first, a dull, length- ened sound, which, according to Laennec,1 is synchronous with the arterial pulse, and is produced by the contraction of the ventricles. This is instantly succeeded by a sharp, quick sound, like that of the valve of a bellows or the lapping of a dog. To convey a notion of these sounds, Dr. C. J. B. Williams employs the word lubb-dup or lubb- tub;—the first word of the compound expressing the protracted first sound—and the latter the short second sound. The latter sound corre- sponds to the interval between two pulsations, and, according to Laen- nec, is owing to the contraction of the auricles. The space of time, that elapses between this and the sound of the contraction of the ventricles, is the period of repose. The relative duration of these periods is as follows:—one-half, or somewhat less, for the contraction of the ventricles; a quarter, or somewhat more, for the contraction of the auricles; and the remaining quarter for the period of total cessa- tion from labour. So that in the twenty-four hours the ventricles work twelve hours, and rest twelve; and the auricles work six, and rest eighteen. Such is the view of Laennec; but it is manifestly erroneous. Ocular observation on living animals, as Dr. Alison2 has remarked, shows that the emptying of the auricle precedes that of the ventricle, and that the interval of rest is between the contraction of the ventricle and the next contraction or emptying of the auricle: between the contraction of the auricle and that of the ventricle, there is no appreciable interval. Puchelt3 thinks it most probable, that the first sound is caused by the impulse of the blood against the walls of the ventricle during the con- traction of the auricles, and the second by the impulse of the blood against the commencement of the arteries during the contraction of the ventricles. In regard to the first sound, M. Beau4—and M. Valleix5 accords with him—agrees pretty nearly with Puchelt. He ascribes it to the wave of blood striking against the parietes of the ventricles during the ventricular diastole. The second sound he ascribes, how- ever, to the shock of the column of blood arriving by the veins against the parietes of the auricles. M. d'Espine thinks, that the first sound is produced by the contraction of the ventricles, and that the second is owing to their dilatation.6 The following table by Messrs. Kirkes and Paget7 exhibits the differ- ent actions of the heart, and their coincidence with the sounds and impulse of the organ. It presumes, that the period from the com- mencement of one pulsation to that of another—or that occupied by a 1 A Treatise on the Diseases of the Chest, translated by Dr. Forbes, 4th edit., Lond., 1834. 2 Outlines of Physiology, Lond., 1831. 3 System der Medicin., th. i. Auflage 2te, s. 149, Heidelb., 1835. 4 Archiv. General de Med., Dec, 1835, Janvier, 1839, Juillet, 1841. 8 Guide du Medecin Praticien, torn. iii. p. 34, Paris, 1843. 6 Revue Medicale, Oct., 1831. 7 Manual of Physiology, Amer. edit., p. 75, Lond., 1849. IN THE HEART—SOUNDS. 137 complete set of the heart's actions—is divided into eight parts; and if the case of a person, whose pulse beats sixty times in a minute, be assumed, each of these parts will represent the eighth part of a second. EIGHTHS OF A SECOND. Last part of the pause, • 1. Auricles contracting: Ventricles distended. First sound and impulse, - 4. Ventricles contracting : Auricles dilating. Second sound, - - - 2. Ventricles dilating: Auricles dilating. Pause, -. - - 1. Ventricles dilating: Auricles distended. Our knowledge of the cause of the sounds of the heart is sufficiently imprecise; as is farther proved by the circumstance, that M. Magendie ascribed the first sound to the shock or impulsion of the apex of the heart during its diastole, and the second to the impulsion of the base of the heart during its systole; but the results of more recent experiments'* have led him to infer, that the first sound is owing to the contraction of the ventricles, and the impulse of the apex of the heart against the ribs; and the second to a similar impulse of the anterior part of the heart, produced by their dilatation. M. Rouanet2 ascribes the first or dull sound to the shock or impulse of the tricuspid and mitral valves against the auriculo-ventricular orifices; and the second or clear sound to the succussion of the blood in the distended aorta and pulmonary artery backwards against the semilunar valves, during the dilatation of the ventricles; and a similar opinion is entertained by Dr. Hope and by Messrs. Mayo3 and Bouillaud.4 In evidence that the first sound is due to the tension of the auriculo-ventricular valves, M. Valentin5 states, that if a portion of a horse's intestine tied at one end be moderately filled with water, without any admixture of air, and have a syringe con- taining water adapted to the other end, the first sound of the heart will be exactly represented by forcing more water in. It may be distinctly heard with the stethoscope applied near the tied extremity of the in- testine, at the instant the water from the syringe renders it tense. Mr. Carlisle6 and Dr. Williams7 refer the first sound, with Laennec, to the systole of the ventricles, and the second to the obstacle presented by the semilunar valves to the return of the blood from the arteries into the heart,—and Messrs. Corrigan,8 Pige'aux,9 Stokes,10 and Mack- intosh,11 think the first sound is owing to the systole of the venous sinuses, and the second to the systole of the ventricles—an opinion, which Burdach12 thinks is best founded, but which, as we have seen, is manifestly erroneous. 1 Annales des Sciences Naturelles, 1834. 2 Ibid. No. xcvii. 3 Outlines of Human Pathology, p. 465, Lond., 1836. 4 Journal Hebdomad. No. ix., 1834. 6 Lehrbuch der Physiologie des Menschen, i. 427, Braunschweig, 1844. 6 Report of the Third Meeting of the British Association for the Advancement of Science; and Amer. Journal of Med. Sciences, p. 477, for Feb., 1835. 7 A Rational Exposition of the Physical Signs of Diseases of the Lungs arid Pleura, Amer. edit., Philad., 1830. 8 Dublin Med. Trans., vol. i., New Series. 9 Bulletin des Sciences Medicales, par Ferussac, xxv. 272. 10 Edinb. Med. and Surg. Journal, vol. xxxiv. 11 Principles of Pathology, &c, 2d Amer. edit., ii. 6, Philad., 1837. 12 Die Physiologie als Erfahrungswissenschaft, iv. 219, Leipz., 1832. 138 CIRCULATION In a case of ectopia cordis, described by M. Cruveilhier,1 a distinct vibratory thrill was perceived, by applying the finger to the origin of the pulmonary artery, which corresponded with the ventricular systole; but no such thrill could be felt when the finger was applied to any part of the base of the ventricles. He inferred, therefore, that the first sound cannot be dependent upon the action of the auriculo-ventricular valves. The greatest intensity of the first sound was, indeed, in the same situ- ation as the greatest intensity of the second, that is, at the origin of the large arteries. Dr. Carpenter2 thinks the results of these observations of Cruveilhier clearly establish, that the principal cause of the first sound exists at the entrances to the arterial trunks; and it does not seem to him, that any other reason can be assigned for it than the pro- longed rush of blood through their orifices, and the throwing back of the semilunar valves, which, in suddenly flapping down again, produce the second sound. M. Cruveilhier states it, in his opinion, to be a uni- form occurrence, that disease of the semilunar valves modifies both sounds;—a fact, which the author has long noticed. Without expressing an opinion as to the validity of M. Cruveilhier's conclusion regarding the two sounds of the heart, Dr. Forbes evidently regards it with favour, under the view long maintained by him, that although characteristically different, the two sounds have so great a similarity, and are so allied in time and place, that he could not readily bring his mind to believe, that they do not both depend upon one and the same cause slightly modi- fied ; or at least on the different play of the same parts.3 Drs. Pennock and Moore,4 who agree in the main with Dr. Hope, found the first sound, the impulse, and the systole of the ventricles to be synchronous; and the second sound to be synchronous with the diastole of the ventricles. The first sound, they suggest, may be a combination of that caused by the contraction of the auricles, the flap- ping of the auriculo-ventricular valves, the rush of blood from the ven- tricles, and the sound of muscular contraction. In four of their expe- riments, when the heart was removed from the body, the ventricles cut open and emptied of their contents, and the auriculo-ventricular valves , elevated, a sound resembling the first was still heard, which they attri- buted chiefly to muscular contraction. The second sound they referred exclusively to the closure of the semilunar valves by the refluent blood from the aorta and pulmonary artery. "This," they remark, "is proved by the greater intensity of this sound over the aorta than else- where, the blood having a strong tendency to return through the val- vular opening; by the greater feebleness of the sound over the pulmo- nary artery, which is short, and soon distributes its blood through the lungs, thus producing but slight impulse upon the valves in the attempt to regurgitate; by the disappearance of the sound when the heart becomes congested and contracts feebly; and finally, on account of its entire extinction when the valve of the aorta was elevated." The main results of the experiments of Drs. Pennock and Moore 1 Gazette Med. de Paris, 7 Aoilt, 1841, p. 535; or Brit, and For. Med. Review, Oct., 1S41, p. 535. 2 Human Physiology, § 486, Lond., 1842. 3 Translation of Laennec, 4th edit.; and Brit, and For. Med. Review, loc. cit. * Op. citat. IN THE HEART—SOUNDS. 139 accord closely with what the author has entertained and taught on this subject; but the views of M. Cruveilhier are well worthy of attention. The whole matter is still open for further investigation. A case of thoracic ectopia has been published by M. Monod,1 in which the maximum intensity of the first sound did not occur at the base of the ventricles, but at the middle of their fleshy walls ; and M. Monod thinks, that it was caused by the shock of the walls of the ventricles against the internal fleshy columns at the moment of contraction. As to the second sound, he is of opinion, that it was owing to the return of the wave of blood against the semilunar valves. More recently, the mechanism by which the valves of the heart are closed, and its sounds produced has been subjected to a fresh investigation by Baumgarten, and subsequently by Hamernjk,2 and others. According to them, there is, during the systole of the auricles, very little regurgitation- into the venous trunks, owing, in part, to an arrangement of circular muscular fibres surrounding their openings into the auricles, as well as to the other causes generally admitted. The auriculo-ventricular valves—they conceive—are closed by the counterpressure of the ventricular blood, such counterpressure being suddenly developed by the contraction of the auricles. The cavities of the auricles and ventricles, during the diastole of the heart, are dis- tended by the continuous current from the veins; and at this period the valves are floating in the blood in the form of a funnel. The object of the auriculo-ventricular systole is to induce such a degree of tension in the contents of the ventricles, and of necessity in the blood surround- ing the funnel-shaped arrangement of the valves, as to cause their rapid closure and prevent regurgitation. Such closure is not due to the contraction of the musculi papillares, but is much facilitated by the small specific gravity of the valves, which enables them to float on the surface of the blood. The mechanism, by which the valves of the arte- ries are closed, is similar to that of the auriculo-ventricular valves. Immediately on the contraction of the ventricles, the pressure of the blood, contained in the large arterial trunks, acting equally in all directions, produces the closure of the semilunar valves,—their com- plete closure occurring synchronously with the end of the ventricular systole. When the diastole of the ventricle commences, the arterial retraction begins, and the refluent blood from the large arteries falls on the valves already closed, and causes the second sound; but there is no regurgitation, as there necessarily would be—M. Hamernjk main- tains—were the valve shut out by the returning wave of blood. The first sound, according to this view, is occasioned by the vibration of the tense auriculo-ventricular valves, caused by the blood forced against them in the systole of the ventricles, and the vibration of the chordae tendineae. In like manner, the second sound is produced by the 1 Bullet, del. Acad^m. Royale de Med., 7 Fevrier, 1843; cited in Edinb. Med. and Surg. Journal, July, 1843. 2 Edinburgh Monthly Journal for Jan., 1849, cited from Prager Vierteljahrschrift, 1847 and 1848; see. also, Schmidt's Jahrbucher, No. 1, s. 10, Jahrgang, 1848, and No. 5, s. 151 Jahrgang, 1849. 140 CIRCULATION impulse of the blood on the semilunar valves already shut, and not by their closure, as usually supposed. The following table, compiled in part by MM. Barth and Roger,1— to which additions have been made by the author—affords at a glance the discordant opinions entertained by observers in regard to this important topic of physiology,—an accurate^ knowledge of which is essential to the correct understanding of cardiac diseases. Laennec, Turner, Corrigan, D'Espine, PlGEAUX, 1832, PlGEAUX, 1839, Hope, 1831, Hope, 1839, RorjANET, PlORRT, Carlisle, Magendie, Burdach, Bouillaud, Gendrin, Cruveilhier, FIRST SOUND CAUSED BY Ventricular contraction. Do. Shock of the blood against the ventricular parietes during the diastole. Ventricular contraction. Shock of the blood against the ventricular parietes at the mo- ment of the diastole. Friction of the blood against the parietes of the ventricles, the orifices and parietes of the < great vessels at the moment of the systole. Molecular collision of the blood in the systole. Sound of tension of the valves, sound of muscular extension, rotatory sound in the systole. Clacking of the auriculo-ventricu- lar valves in the systole. Friction of the molecules of the blood against each other, and against the parietes of the ven- tricles, the orifices, and the valves, during the systole of the left ventricle. Irruption of the blood into the arteries during the systole. Shock of the apex of the heart against the thorax at the mo- ment of the systole. Irruption of the blood into the ventricles containing air (?) at the moment of the contraction of the auricles. Sudden tension (redressemenf) and shock of the opposed surfaces of the auriculo-ventricular valves, and sudden depression of the semilunar valves during the systole. Vibrations resulting from the collision of the blood in the sys- tole. Sudden tension (redressemenf) of the semilunar valves by the systole. SECOND SOUND CAUSED BX Auricular contraction. Shock of the heart falling back upon the pericardium during the diastole. Rebiprocal shock of the internal surface of the opposite parietes of the ventricles during the sys- tole. Ventricular dilatation. Shock of the blood against the parietes of the aorta and pul- monary artery at the moment of the systole. Friction of the blood against the parietes of the auricles, the au- riculo-ventricular orifices, and the cavity of the ventricles at the moment of the diastole. Molecular collision of the blood in the diastole. Clacking of the semilunar valves in the diastole. Do. Passage of the blood into the right ■ • cavities. Into what parts'? At what moment? Clacking of the semilunar valves in the diastole. Shock of the anterior' surface of the heart at the moment of the diastole. Projection of the blood into the arteries containing air(?) at the moment of the systole. Tension (redressemenf) of the semilunar valves, and shock of their opposed surfaces, and sud- den depression of the auriculo- ventricular valves at the mo- ment of the diastole. Percussion of the blood against the parietes of the ventricles at the moment of the diastole. Depression of these valves at the moment of the diastole. ' Traite Pratique d:Auscultation, &c, 2de edit., p. 359, Paris, 1844. IN THE HEART—SOUNDS. 141 Skoda, Dublin Committee, London Committee, Pennock and Mooke, Barth and Rogeii, Baumgarten AND Hamernjk. fihst sound caused bt First ventricular sound. Shock of the blood against the auriculo- ventricular valves ; impulsion of the apex of the heart against the thorax. .First arterial sound. Shock of the blood against the parietes of the aorta, artd of the pulmonary ar- tery in the systole. ^ Shock of the wave of blood against C •the parietes of the ventricles in < the ventricular diastole. ( Muscular contraction of the ven- \ tricles during the systole. J Friction of the blood against the f parietes of the ventricles, and J muscular contraction during the j systole. t Sudden muscular tension of the "^ ventricles in the systole, and I shock of the heart against the ; thorax. J Muscular contraction of the ven- **] tricles and clacking of the auri- ' culoventricular valves during the systole. Contraction of the ventricles: shock at the inferior surface of the semilunar valves, and at the bf+se of the aortic and pulmonary columns of blood; f " clacking of the auriculo-ven- tricular valves; and impulse of the heart against the chest. The vibration of the tense auricu- ^ lo ventricular valves acted on | by the blood sent against them ! during the systole of the ven- | tricles, and the vibration of the j chorda? tendineae. J SECOND SOUND CAUSED BT Second ventricular sound. Shock of the columns of the blood against the parietes of the ven- tricles in the diastole. Second arterial sound. Retro- grade shock of the column of blood upon the semilunar valves. Shock of the column of blood, ar- riving by the veins against the parietes of the auricles. Return shock of the columns of blood against the semilunar valves during the diastole. Tension of the semilunar valves, and return shock of the co- lumns of blood during the dia- stole. Sudden occlusion of the semilu- nar valves by the arterial co- lumns of blood. Occlusion of the semilunar valves by the return shock of the arte- rial columns of blood. Tension of the semilunar valves; and return shock of the blood on their concave surfacs. The impulse of the blood on the semilunar valves already shut, not by their closure. It has been a question with physiologists, whether the cavities of the heart completely empty themselves at each contraction. Senac,1 and Thomas Bartholine,2 from their experiments, were long ago led to an- swer the question negatively. On the other hand, Haller3 entertained an opposite opinion,—suggested, he remarks, by his experiments ; but, perhaps, notwithstanding all his candour, connected, in some manner, with his doctrine of irritability, which could not easily admit the pre- sence of an irritant in a cavity that had ceased to contract. It has been remarked by M. Magendie,4 that if we notice the heart of a living animal, whilst it is in a state of action, it is obvious, that the extent of the contractions cannot have the effect of completely emptying the ventricles; but it must, at the same time, be admitted, that such expe- riments are inconclusive, inasmuch as they exhibit to us the action of the organ under powerfully deranging influences, and such as could be 1 Traite de la Structure du Coenr, &c, 2de edit., Paris, 1774. 2 Dissertat. de Corde, Ham., 1648. 3 Element. Physiol., lib. iv. sect. 4, § 7, Lausann., 1757. 4 Precis, &c, torn. ii. 142 CIRCULATION readily conceived to modify materially the extent of the contractions. The same may be said of a case of monstrous foetus observed by Dr. Thomas R. Mitchell.1 After each contraction of the ventricle he waa able to make blood pass into the aorta. If the heart of a frog be exam- ined by cutting out the lower portion of the sternum, owing to the transparency of. the parietes of the heart, it can be observed that the ventricle completely empties itself at each contraction ; but Dr. Mitchell is decidedly of opinion, that the frog is not a fit subject from which to draw a conclusion, and agrees with Mr. Carlisle, that the cavities empty themselves more completely in the lower order of animals than in the higher. These observations, however, are insufficient to prove, that whilst an animal is in a normal condition, the auricles and ventri- cles are not emptied of their contents by their contraction. The objection urged against the opposite view, that there would always be stagnant blood in the cavities of the heart, is not valid.. The experiments of Venturi2 have shown, that even in an ordinary hydraulic apparatus, the mo- Fig. 296. tion of a stream passing through a vessel of water ia communicated to the fluid at rest in the vessel, so that an incessant change is produced. Let us suppose a stream of water to enter the vessel DEFB, Fig. 296, which is full of fluid, by the pipe A C, and that oppo- site to this pipe ia the tube S M B R. The stream will pass up this tube higher than the vessel, and discharge itself at B V. At the same time, the fluid in the vessel will be observed to be in motion, and, in a few seconds, the level in the vessel will fall from D B to H M. During the systole of the heart, the organ is suddenly carried for- ward ; and although it appears to be rendered shorter, its point or apex is generally considered to strike the left side of the chest opposite the interval between the fifth and seventh true ribs; producing what is called the " beating of the heart." The cause of this phenomenon was, at one period, a topic of warm controversy. Borelli,3 Winslow, and others, affirmed, that it was owing to the organ being elongated during con- traction ; but to this it was replied by Bassuel,4 that if such elongation took place, the tricuspid and mitral valves, kept down by the columnse carneae, could not possibly close the openings between the correspond- 1 Dublin Journal of Medical Science, Nov., 1844, p. 275. 2 Sur la Communication Late>ale du Mouvement dans les Fluides, Paris, 1798; and Sit C.Bell, in Animal Mechanics, p. 35, Library of Useful Knowledge, Lond., 1829. 3 De Motu Animalium, Lugd.Bat., 1710. 4 Magendie, Precis, &c, ii. 395. IN THE HEART—IMPULSE. 143 ing auricles and ventricles. Experiments by Drs. Pennock and Moore1 exhibited to them, that the expulsion of the blood from the ventricles was effected by an approximation of the sides of the heart, and not by a contraction of the apex towards the base ; and that, during the sys- tole, the heart performs a spiral movement, and becomes elongated. Se"nac2 ascribed the beating of the heart to three causes, and his views have been adopted by most physiologists :—1, to the dilatation of the auricles, which occurs during the contraction of the ventricles; 2, to the dilatation of the aorta and pulmonary artery by the introduction of blood sent into them by the ventricles ; and 3, to the straightening of the arch of the aorta, owing to the blood being forced against it by the contraction of the left ventricle. Dr. William Hunter3 considered the last cause quite sufficient to explain the phenomenon, and many physiologists have assented to his view. Sir David Barry4 instituted some experiments upon this subject. He opened the thorax of a living animal, and by passing his hand into the cavity, endeavoured to ascertain the actual Condition of the heart and great vessels, as to distension and relative position. He performed seven experiments of this kind, from which he concluded, that the vena cava is considerably increased in size during inspiration, which he ascribes, as will be better understood hereafter, to the partial vacuum formed in the chest. He supposes that the force exerted by the venous blood on entering the heart, in consequence of the expansion of the chest and the great vessels behind the heart, pushes the organ forwards, and thus causes it to strike against the ribs. Dr. Corrigan thinks, that the apex of the heart has nothing to do with the impulse. He ia of opinion that the heart acts like any other muscle,—that as soon as the ventricles contract, it is shortened from below upwards, and by this shortening becomes thickened in the middle, in a similar manner to the thickening of the belly of the biceps muscle, which, when it contracts, gives rise to an evident impulse, plainly perceptible to the hand applied to it; and that in like manner the heart's impulse is owing to the body of the ventricles, and not to the apex, striking against the ribs. Dr. Corrigan's view is considered by Dr. T. R. Mitchell,5 to be confirmed by the phenomena observed by him on a foetus born with the left side of the thorax wanting; and in which the action of the heart could be closely observed. Drs. Pennock and Moore,6 however, in their experi- ments, found that the impulse was synchronous with and caused by the contraction of the ventricles, and, when felt externally, arose from the striking of the apex against the thorax. To show, however, that this) apparently simple matter cannot be considered settled, Professor Miil- ler7 thinks that great uncertainty rests as to whether the impulse be produced during the contraction or the dilatation of the ventricles. In proof, however, that the impulse of the heart is dependent on the contraction of the muscular fibres of the ventricles, the experiments of 1 Med. Examiner, Nov. 2,1839. 2 Traite de la Structure du Coeur, &c, Paris, 1749. 3 John Hunter, Treatise on the Blood, p. 146, Lond., 1794. * Exper. Researches on the Influence of Atmospheric Pressure upon the Circulation, Lond., 1826. 5 Dublin Journal of Med. Science, Nov., 1844, p. 271. 6 Op. citat. 7 Handbuch, u. s. w., Baly's translation, p. 175, Lond., 1838. 144 CIRCULATION Valentin1 may be cited. He cut off the apex of the heart in several cases, so that the resistance of the blood and the great vessels, and the supposed consequent recoil, were prevented ; yet the tilting movement was observed as much as when the heart was entire. It has even been supposed that the impulse is produced by the blood sent into the ven- tricles by the contraction of the auricles, but it must be borne in mind, in the inquiry, that there is no appreciable interval between the contrac- tion of the auricles, and that of the ventricles. The systole of the heart is admitted by all to be active. Some are disposed to'think the diastole passive,—that is, the effect of relaxation of the fibres or the cessation of contraction. Pechlin, Perrault, Ham- berger, d'Espine, Alison, and numerous others, have supported an oppo- site view;—affirming that direct experiment on living animals shows, that positive effort is exerted at the time of the dilatation of the cavi- ties;—a view confirmed by the case of monstrosity related by Dr. Robinson.2 His opinion is, that the force of the diastole was in that case equal to, if not greater than, that of the systole. In the case, too, observed by M. Cruveilhier, the diastole had the rapidity and energy of a very active movement, overcoming pressure made upon the heart, so that the hand closed upon it when it was contracted was opened with violence. It has been suggested, that if the course of all the fibres composing the muscular parietes of the organ were better known, this apparent anomaly might, perhaps, be as easily explained as in the ordinary case of antagonist muscles. It is probable, however, that the active force exerted in the dilatation of these cavities is that of elasti- city ; and when the contraction of the muscular fibres has ceased, this is aroused to action, and promptly restores the organ to its pre- viously dilated condition. According to this view, the natural state would be that of dilatation. We shall see, hereafter, that elasticity is probably one of the agents of the circulation of the blood along the vessels. The cause of the heart's action has been a deeply interesting ques- tion to the physiologist, and, in the obscurity of the subject, has given rise to many and warm controversies. From the first moment of foetal existence, at which the organ becomes perceptible, till the cessation of vitality it continues to move. By many of the ancients this was sup- posed to be owing to an inherent pulsific virtue,3 which enabled it to contract and dilate alternately,—a mode of expression, which, in the infancy of physical science, was frequently employed to cover ignorance, and has been properly and severely castigated by Moliere:— " Mihi a docto doctore Domandatur causam et rationem quare Opium facit dorm ire. A quoi respondeo; Quia est in eo Virtus dormitiva, Cujus est natura Sensus assoupire." Le Malade Imaginaihe, Intermede iii. 1 Lehrbuch der Physiologie des Menschens, i. 427. 2 Amer. Journal of the Medical Sciences, No. xxii., Feb., 1833. 3 Haller, Elementa Physiologise, lib. iv. 6ect. v. § 1. IN THE HEART. 145 It was in ridicule of the same failing that Swift represented the action of a smokejack to be depending on a meat-roasting power.1 Descartes2 imagined that an explosion took place in the ventricles as sudden as that of gunpowder. With equal nescience, the phenomenon was ascribed by Van Helmont3 to his imaginary archaeus; and by Stahl,4 and the rest of the animists, to the anima, soul or intelligent principle, which he supposed to preside over all the mental and corporeal phenomena. Stahl was one of. the first that attempted any rational explanation of the heart's action. Its muscular tissue; the similarity of its contrac- tions to those of ordinary muscles, with the exception of their not being voluntary; the fact of its action being modified by the passions, &c, led him to liken its movements-to those of muscles. He admitted, that, generally, we possess neither perception of, nor power over, its motions; but he affirmed, that habit alone had rendered them involuntary; in the same manner as certain muscular twitchings or tics, which are at first voluntary, may become irresistible by habit. A strong confirmation of this opinion was drawn from the celebrated case of the honourable Colonel Townshend, (called by M. Adelon5 and other French writers, Captain Towson,) who was able, (not all his life, as Adelon asserts, but a short time before his death,) to suspend the movements of his heart at pleasure. This case is of so singular a character, in a physiological as well as pathological point of view, that we shall give it in the words of Dr. George Cheyne,6 one of the physicians who attended him, and whose character for veracity is beyond suspicion. " Colonel Townshend, a gentleman of excellent natural parts, and of great honour and integrity, had, for many years, been afflicted with constant vomitings, which had made his life painful and miserable. During the whole time of his ill- ness he had observed the strictest regimen, living on the softest vege- tables and lightest animal food; drinking asses' milk daily, even in the camp; and for common drink Bristol water, which, the summer before his death, he had drunk on the spot. But his illness increasing, and his strength decaying, he came from Bristol to Bath in a litter, in autumn, and lay at the Bell Inn. Dr. Baynard, who is since dead, and I were called to him, and attended twice a day for about the space of a week: but, his vomitings continuing still incessant, and obstinate against all remedies, we despaired of his recovery. While he was in this condition, he sent for us early one morning ; we waited on him with Mr. Skrine, his apothecary (since dead also); we found his senses clear, and his mind calm; his nurse and several servants were about him. He had made his will and settled his affairs. He told us he had sent for us to give him some account of an odd sensation he had for some time observed and felt in himself, which was that, composing himself, he could die or expire when he pleased, and yet by an effort, or some- how, he could come to life -again; which it seems he had sometimes tried before he had sent for us. We heard this with surprise; but as it was not to be accounted for from tried common principles, we could . ' Fletcher's Rudiments of Physiology, P. ii. a., p. 52, Edinb., 1836. 2 Tract, de Homine, p. 167, Amst., 1677. 3 Onus Medicin. &c, Amstel., 1648. * Theoria vera Medica, Hal., 1737. 5 Physiol, de 1'Hoinme, edit, cit, iii. 302. * Treatise on Nervous Diseases, p. 307. VOL. II.—10 146 CIRCULATION hardly believe the fact as he related it, much less give any account of it; unless he should please to make the experiment before us, which we were unwilling he should do, lest, in his weak condition, he might carry it too far. He continued to talk very distinctly and sensibly above a quarter of an hour, about this (to him) surprising sensation, and insisted so much on our seeing the trial made, that we were at last forced to comply. We all three felt his pulse first; it was distinct, though small and thready; and his heart had its usual beating. He composed him- self on his back, and lay in a still posture some time. While I held his right hand, Dr. B. laid his hand on his heart, and Mr. S. held a clean looking-glass to his mouth. I found his pulse sink gradually, till at last I could not feel any, by the most exact and nice touch. Dr. Baynard could not feel the least motion in his heart, nor Mr. Skrine the least soil of breath on the bright mirror he held to his mouth. Then each of us, by turn, examined his arm, heart and breath, but could not by the nicest scrutiny discover the least symptom of life in him. We reasoned a long time about this odd appearance as well as we could; and all of us judging it inexplicable and unaccountable; and finding he still continued in that condition, we began to conclude in- deed that he had carried the experiment too far, and at last were satis- fied that he was actually dead, and were just ready to leave him. This continued about half an hour, by nine o'clock in the morning, in autumn. As were going away, we observed some motion about the body, and upon examination found his pulse and the motion of his heart gradually returning; he began to breathe gently, and speak softly; we were all astonished, to the last degree, at this unexpected change, and after some further conversation with him, and among ourselves, went away fully satisfied as to all the particulars of this fact, but confounded and puzzled, and not able to form any rational scheme, that might account for it. He afterwards called for his attorney, added a codicil to his will, settled legacies on his servants, received the sacrament, and calmly and composedly expired about five or six o'clock that evening." It is manifest that this case—unaccountable as it is, in many respects —can add no weight to the views of the Stahlians... It is as strange, as it is inexplicable. The opinion, with them, that the heart's action is a muscular function was accurate. The error lay in placing it amongst the voluntary functions. It belongs to the involuntary class, equally with many of the muscles concerned in deglutition, and those of the stomach and intestines; and how well is it for us, as Sir Charles Bell has remarked, that its action as well as that of other organs directly instrumental to the organic functions is placed out of our control! " A doubt—a mo- ment's pause of irresolution—a forgetfulness of a single action at its • appointed time—would otherwise have terminated our existence." In an oriental journal, Mr. H. M. Twedel1 published a case even more extraordinary than that of Col. Townshend,—of a Hindoo, thirty years of age, who " is said, by long practice, to have acquired the art of holding his breath, by shutting the mouth, and stopping the interior opening of the nostrils with the tongue." This man submitted to ba 1 India Journal of Medical and Physical Sciences ; cited in Amer. Journ. of the Medical Sciences, p. 250, Nov., 1837. IN THE HEART. 147 buried for a month, and was dug out alive at the expiration of that period. " He was taken out in a perfectly senseless state—his eyes closed; his hands cramped and powerless; his stomach shrunk very much, and his teeth jammed so fast together, that they were forced to open his mouth with an iron instrument to pour a little water down his throat. He gradually recovered his senses, and the use of his limbs, and was restored to perfect health" ! The doctrine of Haller1 on the heart's action rested upon the vis insita or irritability to which he referred all muscular contractions, voluntary and involuntary. This property, as stated in another place, he conceived to be possessed by muscles as muscles, independently of all nervous influence. The heart, being a muscle, enjoyed it of neces- sity ; and the irritant, that incessantly developed it, was the blood. In evidence of this, he observes, that its contractions are always more forcible and rapid, when the blood is more abundant; and that they occur successively in the cavities of the heart as the blood reaches them. So wholly did Haller assign the heart's action to this irritability, that he denied the nerves any influence over it; resting his belief on the admitted facts,—that it will continue to beat after decapitation; after the division of the spinal marrow in the neck; and of the nerves dis- tributed to the organ; and, even after it has been entirely removed from the body. How far the opinions of this great man are correct, re- specting the power of contraction residing in the heart, as he conceived it to do in other muscles, we shall inquire presently. It is, however, doubtless, indirectly, under the nervous influence. We see it affected in the various emotions; sometimes augmenting violently, at others, retarding its action. These Circumstances have led some to adopt a kind of intermediate opinion, and to regard the nervous influence as one of the conditions necessary for all muscular contraction, just as the due circulation of blood is; and to admit, at the same time, the separate existence of a vis insita. Sommering2 and Behrends3 have, indeed, asserted that the cardiac nerves are not distributed to the tissue of the heart, but merely to the ramifications of the coronary arteries; and hence, that these nerves are not concerned in the motions of the organ, but only in its nutrition: but this special distribution is denied by Scarpa,4 and the generality of anatomists. Although the emotions manifestly affect the heart, direct experiments exhibit but little influence over it on the part of the nerves. This, indeed, we have seen, is one of the grounds for the doctrine of Haller. Willis5 divided the eighth pair of nerves; yet the action of the heart persisted for days. Similar results followed the section of the great sympathetic. M. Magendie6 states, that he removed, on several occa- sions, the cervical ganglions, and the first thoracic; but was unable to determine anything satisfactory from the operation, in consequence of the immediate death of the animal from such extensive injury. He observed, however, no direct influence on the heart. 1 Op. citat. 2 Corpor. Human. Fabric, iii. § 32. 3 Dissert, qua Demonstrat. Cor. Nervis Carere, Mogunt., 1792; and in Ludwigii Script. Neurol. Min., i. 1. 4 Tabulae Neurologicae, &c, Ticin., 1794. 6 Cerebri Anat., cap. xxiv. in Oper., Genev., 1776. • 6 Precis, &rj., ii. 401. 148 CIRCULATION We have numerous examples of the comparative independence of the organ, as regards the encephalon. Decapitated reptiles have lived for months; and anencephalous infants, or those born with part of the brain only, have vegetated during the whole period of pregnancy, and for some days after birth. M. Legallois1 kept several decapitated mam- malia alive; and maintained the heart in action, (having taken the precaution to tie the vessels of the neck for the purpose of preventing hemorrhage,) by employing artificial respiration, so as to keep up the conversion of venous into arterial blood, and thus insure to the heart a supply of its appropriate fluid. We find, too, that in fracture of the skull, in apoplexy, and congenerous affections, the functions of the heart are the last to be arrested. The result of his own experiments led Legallois to infer, that the power of the heart is altogether derived from the spinal marrow; and he conceived, that through the cardiac nerves it is influenced by that portion of the cerebro-spinal axis, and is liable to be affected by the passions because the spinal marrow is itself influenced by the brain. Dr. Wilson Philip2 has, however, shown, that the facts do not warrant the conclusions; and has exhibited, by direct experiment, that the brain has as much influence as the spinal marrow over the motions of the heart, when the circumstances of the experiment are precisely the same. The removal of the spinal marrow, like that of the brain, if the, experiment be performed cautiously and slowly, does not sensibly affect the motion of the organ,—the animal having been previously deprived of sensibility. In these experiments, the circulation ceased quite as soon without, as with, the destruction of the spinal marrow. Loss of blood appeared to be the chief cause of its cessation; and pain would have contributed to the same effect, if the animal had been operated on, without having been previously rendered insensible. Mr. Gift,3 the former conservator of the Museum of the Royal College of Surgeons of London, made a series of experiments to ascertain the influence of the spinal marrow on the action of the heart in fishes, and found, that its action continues long after the brain and spinal marrow are destroyed, and still longer when the brain is removed without injury to its substance. Similar results were obtained by Tre- viranus on the frog, and by Saviole on the chick in ovo. Zinn and Ent, too, found, that after the destruction of the cerebellum, to which Willis ascribed its action, it continued to beat. All these facts plainly exhibit, that, although the heart is indirectly influenced by the brain or spinal marrow, it is not directly acted upon by either one or the other, and that its action can be maintained for some time after the destruction of one or both, provided artificial re- spiration be kept up; and even this is unnecessary: it will continue to beat after it has been removed from the body. Dr. Dowler, of New Orleans,4 saw the heart of the alligator beat for seven hours when its "annexing vessels" had been separated, In the case of the rattlesnake, Dr. Har- 1 Sur le Principe de la Vie, p. 138. * An Experimental Inquiry into the Laws of the Vital Functions, &c, p. 62, Lond., 1817. 3 Philosoph. Transact, for 1815. * Contributions to Physiology, p*». 17, New Orleans, 1849. IN THE HEART. 149 Ian1 observed it, torn from the body, continue its contractions for ten or twelve hours; and in the monstrous foetus, described by Dr. T. Robin- son,2 its motion continued for some time after the auricles and ventricles had been laid open; the organ roughly handled, and thrown into a basin of cold water. We are compelled, then, if we do not admit the whole of the Hallerian doctrine of irritability, to presume, that there is some- thing inherent in the structure of the heart, which enables it to contract and dilate, when appropriately stimulated; and it is not even necessary that this should be by the fluid to which it is habituated. It is certain, that the organ, when separated from the body, may be stimulated to contraction, by being immersed in warm water, or pricked with a sharp- pointed instrument. In some experiments by Sir B. Brodie,3 the heart was emptied of its blood, and still contracted and relaxed alternately. Similar experiments were instituted by Mr. Mayo,4 and with like results, —from which he concludes, that the alternations of contraction and re- laxation of the heart depend upon something in its structure. The con- clusion seems, indeed, irrefutable, if we add to these evidences the results of certain experiments of Dr. J. Wiltbank,5 and of Dr. J. K. Mitchell. After the brain and medulla spinalis of the Testudo serpentaria, snap- ping-turtle or snapper had been destroyed, the heart continued to beat for thirty-two hours and upwards. In 1823, Dr. Mitchell,6 being en- gaged in dissecting a sturgeon—Acipenser brevirostrum?—took out its heart and laid it on the ground. After a time, it ceased to beat and was inflated with the breath, for the purpose of being dried. Hung up in this state, it began again to move, and continued for ten hours to pulsate regularly, though more and more slowly; and when last observed in motion, the auricles had become so dry as to rustle when they con- tracted and dilated. He subsequently repeated the experiment with the heart of a Testudo serpentaria, and found it to beat well under the influence of oxygen, hydrogen, carbonic.acid, and nitrogen, thrown into it in succession. Water also stimulated it,—perhaps more strongly,— but made its substance look pale and hydropic, and, in one minute, destroyed action beyond reoovery. A few years ago, (1845,) Dr. Mitchell repeated the experiment with the sturgeon, with the like results; and soon afterwards, Dr. F. G. Smith, junior,7 experimented on the hearts of the sturgeoq, frog, and snapping-turtle. The heart of one sturgeon contracted for twenty-two hours after its removal from the body; of another twelve hours; of the frog thirteen hours; and of the snapping-turtle for 25f hours. The contractions of the last were arrested by putting the organ in warm water with the hope of increasing them. The heart of a sturgeon inflated by Dr. Smith, and kindly sent by him to the author, hung up in his library and kept moist, contracted and dilated for upwards of twenty hours. 1 Medical and Physical Researches, p. 103, Philad., 1835. 2 Amer. Journ. of the Med. Sciences, No. xxii., Feb., 1833. 3 Cooke's Treatise on Nervous Diseases, Introd. p. 61, Lond., 1820-23, Amer. edit., Boston, 1S24. . 4 Outlines of Human Physiology, 4th edit., p. 46, Lond., 1837. 5 The Philadelphia Journal of the Medical and Physical Sciences, ix. 361, Philad., 1824. 6 American Journal of the Medical Sciences, vii. 58, Philad., 1830. " Letter to the author, in Philadelphia Medical Examiner, for July, 1845, p. 393. 150 CIRCULATION It has been supposed, that when the heart was empty of blood, the contact of air with its cavities is the stimulus by which its irritability is excited, but Dr. John Reid1 found, as Caldani, Wernlein and Kiirschner had already done, when he .placed a frog's heart in a state of activity under the receiver of an air-pump, that its action still continued after the receiver had been exhausted. More recent experiments, however, by F. Tiedemann2do not accord, in their results, with those of Dr. Reid; but confirm those of Fontana. He placed the heart, immediately after it was removedfrom a living'frog, under the receiver of an air-pump, from which he exhausted the air: the pulsations of the heart became weaker and slower, and in thirty seconds ceased. After five minutes, the air was readmitted, and the pulsations were resumed; and this alter- nation was repeated several times; whilst another heart, suspended in air, continued in uninterrupted action for an hour. These experi- ments were repeated at the request of the author during the winter of 1849-50, by Drs. S.Weir Mitchell, and T. H. Bache; with analogous results. When the density of the air was augmented under the re- ceiver, M. Tiedemann found, that the pulsations became quicker and stronger. The heart is the generator of one of the forces that move the blood. This force has been the subject of much calculation, but the results have been so discordant as to throw discredit upon all mathematical investigations on living organs; a circumstance, which renders it un- necessary to state the different plans that have been pursued in these estimations. Many of them are given in the elaborate work of Haller,3 to which the reader, who may be desirous of examining them, is referred. Borelli4 conceived the force exerted by the left ventricle to be equiva- lent to 180,000 pounds; Senac5 to 40; Hales6 to 51*5 pounds; Jurin7 to 15 pounds 4 ounces; whilst Keill8 conceived it not to exceed from 5 to 8 ounces! The mode adopted by Hales has always been regarded the most satisfactory. By inserting a glass tube into the carotid of various animals, he noticed how high the blood rose in the tube. This he found to be, in the dog, 6 feet 8 inches; in the ram, 6 feet 5J inches; in the horse, 9 feet 8 inches; and he estimated that,in man it would rise as high as 7-| feet. Now, a tube, whose area is one inch square and two feet long, holds nearly a pound of water. We may therefore reckon the weight, pressing on each square inch of the ven- tricle, to be, on a rough estimate, three pounds and three-quarters, or four pounds; and if we consider, with Michelotti, the surface of the left ventricle to be fifteen square inches, it will exert a force, during its contraction, capable of raising sixty pounds. Its extent is more fre- quently, however, "estimated at 10 square inches, and the force developed 1 Cyclop, of Anat. and Physiol., ii. 611, Lond, 1S39. 2 Miillers Archiv. fur Anatomie, u. s. w., s. 490, Berlin, 1847. 3 Elementa Physiologias, lib. i. sect. iv. § 42, Lansann., 1757. 4 De Motu Animalium, pars ii., Lugd. Bat., 1710. 5 Traite de la Structure du Caeur, Paris, 1749. 6 Statical Essays, &c, ii. 40, Lond, 1733. 7 Philosophical Transactions for 1718 and 1719, 8 ^fentamina Medico-Physica, &c, Lond., 1718. IN THE HEART. 151 would therefore, be forty pounds ;x but this is, of course, a rude approxi- mation. In such a deranging experiment, the force of the heart cannot fail to be modified; and it is so much affected by age, sex, tempera- ment, idiosyncrasy, &c, that the attainment of accurate knowledge on the subject is impracticable. The indefinite character of our informa- tion on this matter is indeed sufficiently shown by the investigations of M. Poiseuille,2 which led him to suppose, that the force with which the organ propels the blood into the human aorta is about 4 pounds, 3 ounces, and 43 grains, and if Valentin's estimate of the muscular force of the right ventricle being one-half that of the left be taken, it must propel the blood into the lungs with a force only equal to about two pounds, two ounces. By means of an instrument, which, from its use, he terms hsema- dynamometer, M. Poiseuille has endeavoured to show, that the blood is urged forward with as great a momentum in a small artery, far from the heart, as in any important branch near it. In other words, that there is a uniform amount of pressure exerted by the blood upon the coats of the arteries Fis- 297- in every part of the body;—those in the im- mediate vicinity of the heart being distended by an equal force with those most remote from it. M. Poiseuille3 made the experiment on the carotid, and muscular branch of the thigh of the horse, and notwithstanding the very great dissimilarity in the diameter of the two tubes, and in their distance from.the heart, the displacement of the mercury was exactly the same in both. This inference, if correct, —and the experiments have been repeated by M. Magendie4 and others with corresponding e 1 M results,—is important in a therapeutical point of view, as it leads to the belief, that if it be desirable to lessen the quantity of the circulating fluid, it is of little consequence what vessel is opened. The haemadynamo- meter employed by M. Poiseuille, consists of a bent glass tube, of the form represented in the marginal figure, filled with mercury in the lower bent part, a, d, e. The horizontal part b, provided with a brass head, is fitted into the artery, and a small quantity of a Hamiadynamometer. solution of carbonate of soda is interposed between the mercury and the blood, which is allowed to enter the tube with the view of preventing coagulation. When the blood is allowed to press upon the fluid in the horizontal limb, the rise of the mercury 1 Arnott's Elements of Physics, Amer. edit., pp. 447 and 461, Philad., 1841. 2 Magendie's Journal de Physiologie, x. 241. 3 Ibid., ix. 46. 4 Lecons sur le Sang, &c, or translation in Lond. Lancet, Sept. 1838 to March, 1839: and in Bell's Select xMedical Library, p.'57, Philad., 1839. 152 CIRCULATION towards e, measured from the level to which it has fallen towards d, gives the pressure under- which the blood moves. Estimates by Valentin1 as to the force of the heart make it even less than those of M. Poiseuille. He states, that in man and the higher mammalia, the absolute force exerted by the left ventricle is equal to ^th of the weight of the body; and that by the right ventricle equal to T^oth of the same. During the diastole of the ventricles, the pressure, as indicated by the instrument, is somewhat diminished. It was observed by Hales,2 that the column of blood in a tube inserted into an artery fell after each pulsation. The pressure must obviously be augmented or dimin- ished by anything that adds to or detracts frdm the heart's action; and it will be seen afterwards, that it is materially modified by the respira- tory movements.3 * b. Circulation in the Arteries. The blood, propelled from the heart by the series of actions we have described, enters the two great bloodvessels;—the pulmonary artery from the right ventricle, and the aorta from the left; the former of which sends it to the lungs, the latter to every part of the system; and, in both vessels, it is prevented from returning into the corresponding ventricles by the depression of the semilunar valves. We have now to inquire into the circumstances, that act upon it in the arteries, and whether it be the contraction of the ventricle, which is alone concerned in its progression. Harvey4 and all the mechanical physiologists regarded the arteries as entirely passive in the circulation, and as acting like so many lifeless tubes; the heart being, in their view, the sole agent. We have, how- ever, numerous reasons for believing that the arteries are concerned to a certain degree in the progression of the blood. If we open a large artery in a living.animal, the blood flows in distinct pulses; but this effect gradually diminishes^ as the artery recedes from the heart, and ultimately ceases in the smallest ramifications;—seeming to show, that the force, exerted by the heart, is not the only one concerned. It is manifest, too, that if such was the case, the blood ought to flow out of the aperture, when the artery is opened, at intervals coinciding with the contractions of the organ; and that during the diastole of the artery no blood ought to issue. This, however, is not the case, not- withstanding the authority of Bichat and some others is in its favour. The flow is uninterrupted; but in jets or pulses, coinciding with the contractions of the ventricles. Again, if two ligatures be put round an arterial trunk, at some distance from each other, and a puncture be made between the ligatures, the blood flows with a jet,—indicating that compression is exerted upon it; and if the diameter of the artery be measured with a pair of compasses, before and after puncturing the vessel, it will be found manifestly smaller in the latter case;—an ex- 1 Lehrbuch der Physiologie des Menschen, i. 415, Braunschweig, 1844. 2 Op. cit., ii. 2. 3 Ludwig, in M tiller's Archiv. fur Anatomie, u. s. w., Heft iv. s. 242, Berlin 1847. * Exercitatio Anat. De Motu Cordis et Sanguinis, &c, Rotterd., 1648. IN THE ARTERIES. 153 periment which shows the fallacy of a remark of Bichat,—that the force with which the arteries return upon themselves is insufficient to expel the blood they contain. An experiment of M. Magendie1 exhibits this more clearly. He exposed the crural artery and vein in a dog, and passed a ligature behind the vessels, tying it strongly at the posterior part of the thigh, so that the blood could only pass to the limb by the artery, and return by the vein. He then measured, with a pair of compasses, the diameter of the artery; and on pressing the vessel be- tween his fingers, to intercept the course of blood, it was observed to diminish perceptibly in size below the part compressed, and to empty itself of its blood. On readmitting the blood, by removing the fingers, the artery became gradually distended at each contraction of the heart, and resumed its previous dimensions. These facts prove, that the arteries contract; but the kind of con- traction has given occasion to discussion.' Under the idea that their middle coat is muscular, it was conceived formerly, that they exert a similar action on the blood to that of the heart; dilating to receive it from that organ, and contracting to propel it forwards;—their systole being synchronous with that of the auricles and the diastole of the ventricles, and their diastole with that of the auricles and the systole of the ventricles. The principal reasons urged in favour of this view are;—the fact of the circulation being effected solely by the arteries in acardiac foetuses, and in animals that have no heart;—the assertion of MM. Lamure and Lafosse, that they noticed, in an experiment on the carotid artery, similar to that described above, that the vessel continued to beat between the ligatures;—the affirmations of Verschuir,2 Bikker, (xiulio, and Rossi,3 Thomson,4 Parry,5 Hastings,6 Wedemeyer, and nu- merous others, that when they irritated arteries with the point of a scalpel, or subjected them to the electrical and galvanic influences, they exhibited manifest contractility; and lastly, the fact, that the pulse is not perfectly synchronous in different parts of the body, which ought to be the case, were the arteries not possessed of distinct action. The chief objection to the views founded on the muscularity of the middle coat was the want of evidence of the fact. In the anatomical proem to the function of the circulation it was stated, that this coat had not seemed to anatomists to consist of fibrous or muscular tissue; and that the experiments of MM. Magendie, Nysten, and others, had not been able to exhibit any contraction, on the application to it of the ordinary excitants of muscular irritability. The chemical analyses of Berzelius7 and Young8 also appeared to show, that the transverse fibres differ essentially from those of proper muscles. It has been suggested, however, that the older analyses may have been made on the largest 1 Journal de Physiologie, i. Ill; and Precis, &c, ii. 386. 2 De Arteriar. et Venar. Vi Irritabili, &c, Groning., 1766. 3 Elemens de Medec. Operat., Turin, 1806. 4 Lectures on Inflammation, p. 83, Edinb., 1813; also, 2d Amer. edit., Philad., 1831. 5 On the Arterial Pulse, p. 52, Bath, 1816. 8 On Inflammation of the Mucous Membrane of the Lungs, p. 20, Lond., 1820. t View of the Progress of Animal Chemistry, p. 25, Lond., 1813. 8 An Introduction to Medical Literature, p. 501, Lond., 1813. 154 CIRCULATION arteries in which muscular fibres scarcely exist ;J for histologists—as elsewhere shown—are now agreed, that, in the smaller arteries, more especially, the middle coat is partly composed of nonstriated or un- striped muscular tissue. Moreover, if any doubt existed in regard to the contractile action of the smaller arteries, it ought to be removed by the experiments of MM. E. and E. H. Weber,2 accurate observers, which were made with the rotating magneto-electric apparatus upon the arte- ries of the mesentery of frogs between }th and TVth of a Paris line in diameter. When vessels between these dimensions were exposed to the electric stream they did not immediately respond to the irritation; but in a few seconds they began to contract, so that in froin five to ten seconds their diameter was diminished one-third. If the stimulus was continued, the diminution of size went on until the diameter was re- duced to one-third or even one-sixth of what it was originally, so that only a single row of blood corpuscles could pass along the vessel, and at last became completely closed unless the stimulus was removed. They found, however, no change produced in the capillaries when the mag- neto-electric current was applied to them; but it appeared to cause an unusual adhesion of the corpuscles to each other, and to the parietes of the vessels, and a consequent stagnation of the circulating fluid in them. Nor did the larger arteries exhibit any signs of contraction when the stream was directed to them. If an artery be exposed in a living animal, we observe none of that contraction and dilatation which is perceptible in the heart; although a manifest pulsation is communicated to the finger placed over it. The phenomena of the pulse will engage attention speedily. We may merely remark, at present, that the pulsations are manifestly more dependent upon the action of the heart than upon that of the arteries. In syncope, they entirely cease; and whilst they continue beneath an aneurismal tumour, because the continuity of the vessel is not destroyed, they completely cease beneath a ligature so applied around an artery as to cut off the flow of blood. Bichat attached an inert tube to the carotid artery of a living animal, so that the blood could flow through it: the same kind of pulsation was observed in it as in the artery. To this he adapted a bag of gummed taffeta, so as to simulate an aneurismal tumour: the pulsations were evidenced in the bag. If, again, arterial blood be passed into a vein, the latter vessel, which has ordinarily no pulsation, begins to beat; whilst, if blood from a vein be directed into an artery, the latter ceases to beat.3 Another class of physiologists have reduced the whole of the arterial action to simple elasticity; a property, which the yellow tissue that composes the proper membrane of the artery seems to possess in an unusual degree. Such is the opinion of M. Magendie.4 " Admitting it to be certain," he remarks, "that contraction and dilatation occur in arteries, I am far from thinking, with some authors of the last century, 1 Kirkes and Paget, Manual of Physiology, p. 91, Amer. edit., Philad, 1849. 2 Miiller's Archiv. fur Anatomie, u. s. w., H. ii. s. 282, Jahrgang, 1847. 3 Adelon, art. Circulation, in Diet, de Medecine, lere edit., v. 321, Paris, 1822, and Phy- siol, de 1'Hotnme, edit, cit., iii. 380. * Precis, &c, edit, cit., ii. 387 IN THE ARTERIES. 155 Fig. 298. that they dilate of themselves, and contract in the manner of muscular fibres. On the contrary, I" am certain, that they are passive in both cases,—that is, that their dilatation and contraction are the simple effect of the elasticity of their parietes, put in action by the blood, which the heart sends incessantly into their cavity,"—and he farther remarks, that there is no difference, in this respect, between the large and small arteries. As regards the larger arteries, it is probable that this elasticity is the principal but not the only action exerted; and that it is the cause why the blood flows in a continuous, though pulsatory, stream, when an opening is made into them; thus acting like the reservoir of air in certain pumps. In the pump A B, re- presented in the marginal figure, were there no air-vessel C, the water would flow through the pipe E at each stroke of the piston, but the stream would be interrupted. By means of the air-ves- sel this is remedied. The water, at each stroke, is sent into the vessel; the air contained in'the air-vessel is thus com- pressed, and its elasticity thereby aug- mented; so that it keeps up a constant pressure on the surface of the water, and forces it out of the vessel through the pipe D in a nearly uniform stream.— Now, in the heart,' the contraction of the ventricle acts like the depression of the piston; the blood is propelled into the artery in an interrupted manner, but the elasticity of the blood- vessel presses upon the blood, in the same manner as the air in the air-vessel presses upon the water within it; and the blood flows along the vessel in an uninterrupted, although pulsatory, stream.' There are many difficulties, however, in the way of admitting the whole of the action of the arteries in the circulation to be dependent upon simple elasticity. The heart of a salamander was opened by Spallanzani;1 the blood continued to flow through the vessels for twelve minutes after the operation. The heart of a tadpole was cut out; the circulation was maintained for some time in several of the vascular ramifications of the tail. The heart of the chick in ovo was destroyed immediately after contraction; the arterial blood took a retrograde direction, and the momentum of tire venous blood was redoubled. The circulation continued in this manner for eighteen minutes. Dr. Wilson Philip2 states, that he distinctly saw the circulation in the smaller vessels, for some time after the heart had been removed from the body? and a simi- lar observation was made by Dr. Hastings.3 The latter gentleman states, that in the large arterial trunks, and even in the veins, he has 1 Experiments on the Circulation, &c, translated by R. Hall, Lond., 1801. 2 An Experimental Inquiry into the Laws of the Vital Functions, Lond., 1817; and Lend. Med. Gazette, for March 25th, 1837, p. 952. 3 Op. citat., p. 51. Section of a Forcing Pump. 156 CIRCULATIO" noticed, in the clearest manner, their contraction on the application of various stimulants, both chemical and mechanical. It is, moreover, well known, that if a small living artery be cut across, it soon contracts so as to arrest the hemorrhage;—that whilst an animal is bleeding to death the arteries will accommodate themselves to the decreasing quantity of blood in the vessels, and contract beyond the degree to which their elasticity could be presumed to carry them; and that after death they will again relax. Dr. Parry found, that an artery of a living animal, if exposed to the air, sometimes contracts in a few minutes to a great extent; in such case, only a single fibre of the artery may be affected, narrowing the channel in the same way as if a thread were tied round it. The experiments that have been instituted for the purpose of disco- vering the dependence of the arterial action on the nervous system have likewise afforded evidences of their capability of assuming a con- tractile action, and have led to a better comprehension of cases of what have been called local determinations of blood. Dr. Philip found, that the motion of the blood in the capillaries is influenced by stimulants applied to the central parts of the nervous system, which must be owing to these vessels, possessing a power of contractility, capable of being aroused to action by the nervous influence. The experiihents of Sir Everard Home1 are, however, more applicable, as they were directed to the larger arteries, respecting which the greatest doubts have been en- tertained. The carotid artery of a dog was laid bare ; the par vagum and great sympathetic, which, in that animal, form one bundle, were separated from it by a flattened probe for one-tenth of an inch in length; the head and neck of the dog were then placed in an easy position, and the pulsations of the carotid artery were attended to by all present for two minutes, in order that the eye might be accustomed to their force in a natural state. The nerve passing over the probe was then slightly touched with caustic potassa. In a minute and a half, the pulsations of the exposed artery became more distinct. In two minutes, the beats were stronger; in four minutes, their violence was lessened; and in five minutes the action was restored to its natural state. The experiment was repeated with analogous results upon a rabbit. The par vagum was separated from the intercostal nerve ; and when the former nerve alone was irritated no increase took place in the force of the action of the artery. " The carotid artery," says Sir Eve- rard, " was chosen as the only artery in the body of sufficient size, that can be readily exposed, to which the nervous branches, supplying it, can be traced from their trunk. This experiment was repeated three different times, so as to leave no doubts respecting the result." These experiments demonstrate, that, under the nervous influence, an increase or a diminution may take place in the contraction of an artery; and they aid*us in the explanation of cases, in which the circulation has been accomplished where the heart has been altogether wanting or completely defective in structure. Sir Everard instituted farther expe- riments, with the view of determining whether heat or cold has the Lectures on Comparative Anatomy, iii. 57, Lond., 1823. IN THE CAPILLARIES. 157 greater agency in stimulating the nerves to produce this effect upon the artery. The wrist of one arm was surrounded by bladders filled with ice ; and after it had remained in that state for five minutes, the pulse of the two wrists was felt at the same time. The beats in that which had been cooled were found to be manifestly stronger. A simi- lar experiment was now. made with water, heated to from 120° to 130° of Fahrenheit. The pulse was found to be softer and feebler in the heated arm. When one wrist was cooled and the other heated, the stroke of the pulse of the cooled arm had much greater force than that of the heated one. These experiments were repeated upon the wrists of several young men and young women of different ages, with uniform results. Lastly, we have remarked, and shall have occasion to refer to the matter again, that certain animals, that have no heart, have circulating vessels in which contraction and dilatation are perceptible. This is the case with the class vermes of Cuvier, and distinctly so in the lum- bricus marinus or lug, the leech, &c. The fact has been invoked both by the believers in the muscular contractility of arteries, and by those who conceive the contractility to be peculiar; but our acquaintance with the intimate structure of the coats of the vessels in those animals is too imperfect for us to assert more than that they are manifestly con- tractile. In an interesting case of a cardiac foetus examined by Dr. Houston, of Dublin, it seemed impossible that the heart of a twin foetus could have occasioned the movement of blood in the acardiac one ; and hence that there must have been some power in the vessels of the latter— general, or capillary, or both—to effect the circulation through it. In most or all of these cases, however, a perfect twin foetus exists, whose placenta is in some degree united with that of the imperfect one ; and the circulation in the latter has usually been attributed to the influence of the heart of the former propagated through the placental vessels. From these and other considerations, the majority of physiologists have admitted a contractile action, in perhaps all except the larger arterial trunks; and, at the present day, the most general and satis- factory opinion appears to be, that, in addition to the highly elastic property possessed by the middle coat, it is capable of being thrown into contraction by the organic muscular fibres, which exist in larger quantities in the smaller arteries than in the larger; that, consequently in the larger vessels this contraction is little evidenced, the action of the artery being mainly produced by its elasticity; but tliat, in the smaller arterial ramifications, the contractility is more manifest; its great object being to regulate the quantity of blood to be distributed to a part; or to adjust the vessel to the amount of fluid circulating in it. To this contractility, necessarily connected with the life of the vessel, and which he considered to differ from both muscular contractility and simple elasticity, Dr. Parry1 gave the name tonicity. c. Circulation through the Capillaries. The agency of the capillary vessels in the circulation has been a 1 On the Arterial Pulse, p. 52, Bath, 1816. 158 CIRCULATION subject of contention. The opinion of Harvey, embraced by J. Miiller,1 was, that the action of the heart alone is sufficient to send the blood through the whole circuit; but we have seen, that, even when aided by the elasticity and contractility of the arterial trunks, the pulsations of that organ become imperceptible in the smaller arteries ; and, hence, there is some show of reason for the belief, that in the capillary vessels the force may be entirely spent. Were we, indeed, to admit that the force of the heart is sufficient to send the blood through a single capil- lary circulation, it would be difficult to admit that it could send it through two—as in the portal circulation. Still, we can by no means accord with Professor Draper,2 of New York, that "it is now on all hands conceded," that this powerful muscular organ—the heart—dis- charges "a very subsidiary duty." Bichat regarded the capillaries as organs of propulsion, and alone concerned in returning the blood to the heart through the veins. Dr. Marshall Hall,3 on the other hand, denies, that we have any proof of irritability in the true capillaries; and Magendie4 conceives the con- traction of the heart to be the principal cause of the passage of the blood through those vessels. In support of this view he adduces the following experiment. Having passed a ligature round the thigh of a dog, so as not to compress the crural artery or vein, he tied the latter near the groin, and made a small opening into the vessel. The blood immediately issued with a considerable jet. He then pressed the ar- tery between the fingers, so as to prevent the arterial blood from pass- ing to the limb. The jet of venous blood did not, however, stop. It continued for some moments, but went on diminishing, and the flow was arrested, although the vein was filled through its whole extent. When the artery was examined during these occurrences, it was ob- served to contract gradually, and at length became completely empty when the course of the blood in the vein ceased. At this stage of the experiment, the compression was removed from the artery; the blood immediately passed into the vessel, and, as soon as it had reached the final divisions, began to flow again through the opening in the vein, and the jet was gradually restored. On compressing the artery again until it was emptied, and afterwards allowing the arterial blood to pass slowly along the vessel, the discharge from the vein took place, but without any jet: the jet was resumed, however, as soon as the artery was entirely free. This experiment is not so convincing to us as it appears to have been to M. Magendie. The chief fact, which it exhibits, is the elastic, and probably contractile, power of the arteries. It might have been expected, a priori, under any hypothesis, that the quantity of blood discharged from the vein would hold a ratio to that sent by the artery; and, consequently, the experiment appears to us to bear but little on the question regarding the separate contractile action of the capillaries. 1 Handbuch, u. s. w., Baly's translation, p. 220, Lond., 1838. 2 A Text-Book on Chemistry, p. 392, New York, 1846. 3 A Critical and Experimental Essay on the Circulation, &c, p. 78, Lond., 1831, reprinted in this country, Philad., 1835. 4 Precis, &c, ii. 390. IN THE CAPILLARIES. 159 It is difficult, indeed, to believe that such an action does not exist. In addition to the circumstance, already mentioned, of the absence of pul- sation in the smaller arteries, almost every writer on the theory of inflammation considers the fact of a distinct action of the capillaries established, and leaves to the physiologist the by no means easy task of proving it. Dr. Wilson Philip1 placed the web of a frog's foot under the microscope, and distinctly saw the capillaries contract on the appli- cation of those stimulants that produce contraction of the muscular fibre. The results of Dr. Thomson's2 experiments in investigating inflammation, as well as those of Dr. Hastings,3 were the same. The facts, already referred to, regarding the continuance of the circulation in the minute vessels after'the heart has been removed, as well as the observation of Dr. Philip, that the blood in the capillaries is influenced by stimulants applied to the central parts of the nervous system, are confirmatory of the same point. The experiments of Drs. Thomson, Philip, and Hastings, were repeated by Wedemeyer,4 with great care. The circulation in the mesentery of the frog, and in the web of its foot, being observed through the microscope, it was evident, that no change occurred in the diameter of the small arteries, or in that of the capil- laries, so long as the circulation was allowed to go on in its natural state; but as soon as excitants were applied to them, an alteration of their calibre was perceptible. Alcohol arrested the flow of blood with- out inducing much apparent .contraction of the vessels. Chloride of sodium, in the course of three or four minutes, caused them to contract one-fifth of their calibre, which was followed by their dilatation, and a gradual retardation and stoppage of the blood. In a space of time varying from ten to thirty seconds, and sometimes immediately after the application of the galvanic circle, they contracted, some one-fourth, others one-half, and others three-fourths of their calibre. The con- traction at times continued for a considerable period, occasionally for seveVal hours; in other instances it ceased in ten minutes, and the ves- sels resumed their natural diameter. . A second application of galva- nism to the same capillaries seldom caused any material contraction. Schwann5 likewise found, that when cold water was poured on the ves- sels of a frog, which had been previously in a warm atmosphere, the capillaries immediately contracted, but after a time regained their diameter. Farther, Mr. Hunter6 found, on exposing arteries to the air, that they contracted so much as to occasion obliteration of their cavities, and it is well known, that when arteries—as the temporal—are divided, the hemorrhage is arrested by the spontaneous contraction of the divided vessel,—a contraction, which, as remarked by Dr. Carpenter, is much greater than could be accounted for by simple elasticity of tissue, and is more marked in small than in large vessels.7 1 A Treatise on Febrile Diseases, 3d edit., ii. 17, London, 1813; and Medico-Chirur. Transact., vol. xii. p. 401. 2 Lectures on Inflammation, p. 83, Edinb., 1813. 3 Op. citat. 4 Untersuch, iiber die Krieslauf, u. s. w., Hannover, 1828; cited in Edinb. Med. and Surg. Jnurn , vol. xxxii. 5 Aliiiler's Archiv, 1836, and Lond. Med. Gazette, May, 1837. •« 6 A Treatise on the Blood, Inflammation, and Gunshot Wounds, Amer. edit., ii. 156, Philad., 1840. t Human Physiology, § 502, Lond., 1842. 160 CIRCULATION All these facts prove the existence of a vital power in the capillaries, capable of modifying, to a considerable extent, the flow of blood through them. Again :—of this independent action of the capillary vessels we have, every day, proofs in local inflammation; in which there maybe in- creased redness of a part, without the general circulation exhibiting the slightest evidences of augmented action or excitement. In the natural state, the vessels of the tunica conjunctiva covering the white of the eye receive little blood; but if any cause of irritation exists, as a grain of sand entering between the eyelids, we find blood rapidly sent into them, giving the appearance that has been not inappropriately termed "blood-shot."1 In the experiments of Kaltenbrunner,2 which were fully confirmed on repetition, the blood in inflammation was at first observed streaming to the irritated part, in consequence of. which the capillary vessels became distended; afterwards irregularity of circula- tion occurred in the gorged capillary system ; and subsequently com- plete arrest of the flow, and disorganisation. These phenomena are of themselves sufficient to prove the existence of a separate action of the capillaries, and, taken in conjunction with other facts, are overwhelming. The blush of modesty, and the paleness of guilt, the hectic glow, and the translucency of congelation are circumstances that go to establish the same point. The contractile power of the capillaries is doubtless modified by the condition of the nerves distributed to them, which, as we have seen, are observed to increase as the size of the vessels and the thickness of their coats diminish. Their influence is strikingly evinced in actions, that are altogether nervous, as in the flushed countenance occasioned by sudden mental emotion. By some, however, the whole capillary circulation has been ascribed to a motive faculty inherent in the cor- puscles of the blood; whilst others, again, have asserted, that the "electro-galvanic power,"—or in other words—the nervous power, generated in the nervous system, and acting on the blood corpuscles through the parietes of the capillaries, is the immediate agent that directs the circulation in the capillaries. All this, however, enters into the inscrutable question,—what is the cause of life in the fluids or tissues,—a question to be agitated, but not solved, in a subsequent part of this volume. But, not only has a vital power of contraction been conceded to the capillaries; it has been imagined, that they possess what the Germans call a Lebensturgor (turgor vitalis) or vital property of expansi- bility or turgescence. Such is the opinion of Hebenstreit3 and of Prus;4 and it has been embraced, in this country, by Professor Smith of Yale College; by his son, Professor N. R. Smith of Baltimore, in his excellent work on the "Arteries,"5 and by Professor Hodge,6 of 1 Thomson's Lectures on Inflammation, Edinb., 1813. 2 Experiments circa Statum Sanguinis et Vasorum in Inflammatione, p. 23, Monaco., 1826. 3 Dissert, de Tnrgore Vitali, Lips., 1795; Hildebrandt's Physiologie, Auflag. 5, § 84; and Tiedemann's Physiologie, trad, par Jourdan, p. 625, Paris, 1831. * De l'lrritation, &c, Paris, 1825. 6 Surgical Anatomy of the Arteries, 2d edit, Baltimore, 1835. 6 North Amer. Med. and Surg. Journal, June, 1828. , IN THE CAPILLARIES. 161 Philadelphia. The idea has been esteemed to be confirmed by the fact of excitants having been seen under the microscope, by Hastings, Wede- meyer, and others, to occasion not only contraction but dilatation of the capillaries. The phenomena observed in the erectile tissues have likewise been considered to favour the hypothesis ; but in answer .to these arguments it may be replied, that the irregular excitation, pro- duced in the parts by the application of powerful stimulants, might readily give occasion to an appearance of expansibility under the mi- croscope, without our being justified in inferring, that these vessels pos- sess an innate vital property of expansibility; and, in many of the cases, in which ammonia and galvanism were applied by Thomson, Hastings, Wedemeyer, and others, the action of contraction ought rather to be esteemed physical or chemical than vital. The results of the applica- tion of such excitants, as diluted alcohol, dilute solutions of ammonia and chloride of sodium, can alone be adduced as evidences of vital action on the part of those vessels. The dilatation of the capillary system and of the smaller arteries, which has been remarked on the contact of those agents, is not, as Oesterreicher1 has remarked, the primary effect: it is the consequence of the afflux of blood to the irri- tated part, as was demonstrated, also, in the experiments of Kalten- brunner on inflammation, to which allusion has been made. Lastly, attentive observation of the phenomena presented by the erectile tissues must lead to the conclusion, that turgescence of vessels is not the first link in the chain of phenomena; excitation is first induced in the nerves of the part—generally through the influence of the brain, and thence, perhaps, through the sympathetic nerve,—and the afflux of fluid supervenes on this. The vital expansibility of the capillaries can- not, we think, be regarded as proved, 6r probable. Professor Draper, of New York, maintains, that the great agency in the circulation of the blood is of a physical character; and is dependent upon the chemical relations of that fluid to the tissues with which it is brought in contact. On the principles of capillary attraction—he says —a liquid will readily flow through a porous body for which it has a chemical affinity; but it will refuse to flow through it, if it has no affinity for it. On this principle he explains why the arterial blood presses the venous before it in the systemic circulation, and why the reverse takes place in the pulmonic. " The systemic circulation takes place because arterial blood has a high affinity for the tissues, and venous blood little or none. The pulmonary circulation takes place because venous blood has a high affinity for atmospheric oxygen, which it finds on the air cells of the lungs; and arterial blood little or none.) On the same principle we may explain the rise of sap in trees, the cir- culatory movements in the different animal tribes, and the minor circulations of the human system."2 Dr. Dowler,3 of New Orleans, whilst he earnestly combats the views of Professor Draper, is a strong 1 Versuch einer Darstellung der Lehre vom Kreislauf des Blutes, Numberg, 1826. 2 A Text-Book of Chemistry, p. 392, New York, 1846; and On the Forces which Produce the Organization of Plants, chap. iii. 3 Researches, Critical and Experimental, on the Capillary Circulation. (Reprinted from the New Orleans Medical and Surgical Journal.) January, 1849. VOL. II.—11 162 CIRCULATION Fig. 299. advocate for the distinct action of the capillary vessels, and he adduces a number of striking experiments to establish his position. In perhaps one-fourth of the dissections which he records, the bodies were carried to the dissecting-room a few minutes after death. The external veins, chiefly those of the arms and neck, sometimes became distended; and when they were opened, the blood often flowed in a good stream, and was, at times, projected to the distance of a foot or more. In some cases, by putting a ligature around the arm, or by grasping it above the elbow, the blood was made to flow more freely, and by moving the muscles, as is done in ordinary bloodletting, the blood- shot forth for some distance. Punctures in the middle of the subclavian discharged blood, which arose in a full stream, against gravity, two or three inches; sometimes forming an arch as it fell. The coronary veins discharged blood rapidly and "with surprising force." The dissections are con- sidered by Dr. Dowler to show conclusively the independent action of the capillaries; " which in yellow fever, and other acute fevers, probably survives respiration and the heart's action; and when it ceases cada- veric hypersemia takes place." Such is doubtless the fact; but it may still be questioned, whether anything more than the physical capillarity invoked by Professor Draper is concerned in the phenomenon. In a case observed by the author, and referred to elsewhere, blood flowed freely from the vessels of the brain, and coagulated fifteen hours after the cessation of respiration and circulation; and many similar cases are on record. The circulation through the capil- laries has long been an interesting topic of microscopic research. Accord- ing to Wagner,1 a magnifying power of from two to three hundred diameters is required to make out the particular details. The blood in mass, or in the larger channels, he says, is seen to flow more rapidly than in the smaller. Here the blood corpuscles advance with great rapidity, especially in the arteries, and with a whirling mo- Small Venous Branch, from the Web of a ^on an(j f r>ln«olxr ^ynwrlnrl Frog's Foot, magnified 350 diameters. - , ' . J°rm a cl°Sely Crowded b,b. Cells of pavement epithelium, contain- St.™am ln the middle of the V^SSel, ing nuclei. In the space between the current Without ever tOUchinfi" its DarieteS. of oval blood corpuscles, and the walls of the Ti7.'i.r. i-++1 ,, ,.& " vessel, the round transparent lymph globules. VY 11U a little attention, anarrOWer (?) are seen. (Wagner.) . an(J clearer) but always Very distinct space is seen to remain between the great middle current of blood corpuscles and the walls of the vessel, in which a few white corpuscles, or what Wagner considers to be lymph corpuscles, are moved onwards, but at a much slower rate. These white corpuscles swim in smaller numbers in the transparent liquor sanguinis, 1 Elements of Physiology, translated by R. Willis, § 122, Lond., 1842. IN THE CAPILLARIES. 163 and glide slowly, and in general smoothly, though they sometimes advance by fits and starts more rapidly, but with intervening pauses; and, as a general rule, at least ten or twelve times more slowly than the corpuscles of the central stream. The clear space, filled with liquor sanguinis and white corpuscles, is obvious in all the larger capil- laries, whether arterial or venous, but ceases to be apparent in the smaller intermediate vessels which admit but one or two rows of blood corpuscles (Fig. 283). In these vessels, two sets of corpuscles pro- ceed pari passu; but, according to Wagner, it is easy to see, that the blood corpuscles glide more readily onwards,—the white corpuscles seeming often to be detained at ■ the bendings of vessels, and at . Fig. 300. the angles, where anastomosing branches are given off: here they remain adherent for an instant, and then suddenly pro- ceed onwards. These pheno- mena are observed in every part of the peripheral systemic circulation; but an exception appears to exist in the pulmo- nic circulation; the capillaries there being filled with both kinds of corpuscles to their very walls. It is in this—the intermediate —part of the sanguiferous sys- tem, that most important func- tions take place. In the small- est artery we find arterial blood; and in the smallest vein com- municating with it blood always possessing venous properties. Between those points, a change must have occurred, the reverse of that which happens in the lungs. It is here, too, that nutrition, secretion, and calorification are effected. In the explanation of these functions, we shall find it impossible not to suppose a distinct and elective agency in the tissues concerned; and as it is by such agency, that the varying activity of the different functions is regulated, we are constrained to believe, that the capillary vessels may be able to exert a controlling influence over the quantity and velo- city of the blood circulating in them. In disease, the agency of this system of vessels is an object of attentive study with the pathologist. To its influence in inflammation we have already alluded; but it is no less exemplified in the more general diseases of the frame,—as in the cold, hot, and sweating stages of an intermittent. Local, irregular capillary action is, indeed, one of the most common causes or effects of acute diseases, and this generally occurs in some organ at a distance from the seat of the deranging influence. It is a common and just ob- servation, that getting the feet wet, and sitting in a draught of air, are Large Vein of Frog's Foot, magnified 600 diameters. b, c. Blood corpuscles, a, a. Lymph corpuscles (?) principally conspicuous in the clear space near the parietes of the vessel. (Wagner.) • 164 CIRCULATION more certain causes of catarrh than sudden atmospheric vicissitudes, that apply to the whole body; and so extensive is the sympathy between the various portions of this system of vessels, that the most diversified effects are produced in different individuals exposed to the same com- mon cause; one may have inflammatory sore throat; another, ordinary catarrh; another, inflammation of the bowels;—according to the pre- cise predisposition, existing in the individual at the time, to have one structure morbidly affected rather than another;—but these are in- teresting topics, which belong more strictly to the pathologist. ^ By the united action, then, of the heart, arteries, and capillary or intermediate system of vessels, the blood attains the veins. We have now to consider the circulation in these vessels. - d. Circulation in the Veins. * It has been already observed, that Harvey considered the force of the heart to be of itself sufficient to return the blood, sent from the left ventricle, to the heart; whilst Bichat conceived the whole propulsory effort to be lost in the capilla- Fig. 301. ries, and the transmission of the blood along the veins to be en- tirely effected by the agency of the capillary system. It is singular, that an individual of such distinguished powers of discrimination should have been led into an error of this mag- nitude. It is a well-known principle in hydrostatics, that although water, when uncon- fined, can never rise above its level at any point, and can never move upwards ; yet, by being confined in pipes or close channels of any kind, it will rise to the height from which it came. Hence the water or blood in the vessel A, Fig. 301, which may be considered to represent the right auricle, would stand at the same height as that in the vessel B, which we may look upon as the left ventricle,—were they inanimate tubes. We heed be at no loss, therefore, in understanding how the blood might attain the right auricle, when the body is erect, by this hydrostatic principle alone; but we have seen, that the force exerted by the heart, arteries, and capillary system is superadded to this, so that the blood would rise much higher than the right- auricle, and consequently exert a manifest effort to enter it. It may be re- marked, also, that the left ventricle is not the true height of the source, but the top of the arch of the aorta, which is more elevated by several inches than the right auricle. A similar view is embraced by Dr. Bil- ling ;l but Dr. -Carpenter2—in commenting on the author's observa- tions on this subject—suggests, that the influence of this hydrostatic 1 First Principles of Medicine, Amer. edit., p. 36, Philad., 1842. 1 Human Physiology, § 516, Lond., 1842. IN THE VEINS. 165 force would scarcely be felt through the plexus of capillary vessels; " for the interposition of a system of tubes even of much larger calibre would be, by the friction created between the fluid and their walls, an effectual obstacle to the rapid ascent of a current, which had so slight an-impetus as that derived from its previous fall." The author did not mean, however, to say more than that the blood " might attain" the right auricle by the hydrostatic force alone: he did not wish to convey the idea, that the circulation could be carried on without the aid of an additional force ; but that a slight effort only on the part of the heart and arteries might be needed to enable the blood to perform its entire circuit. It is proper to add, that in the last editions of his valuable work, Dr. Carpenter has omitted those comments on the observations of the author. Are we then to regard the veins as simple elastic tubes ? This is the prevalent belief. Their elasticity is, however, much less than that of the arteries. Some physiologists have conceived them to possess con- tractile properties also. Such is the opinion of M. Broussais,1 who founds it, in part, upon certain experiments by M. Sarlandiere, already referred to, in which contraction and relaxation of the venae cavae of the frog were seen for many minutes after the heart was removed from the body. These pulsations of the venae cavae, and of the pulmonary veins in their natural state, have been seen by numerous observers—by Steno, Lower, Wepfer, Borrachius, Whytt, Haller, Lancisi, Miiller, Marshall Hall, Flourens, J. J. Allison, and others.2 The experiments of Dr. Allison, in reference to the venae cavae and pulmonary veins, appeared to him to prove ;—that they pulsate near the heart in the four classes of the vertebrata ;—that in dying animals they pulsate long after the auricle and ventricle have ceased ;—that they also beat even in quadrupeds, for hours after they have been separated from the heart and from the body ;—and that they can be stimulated to contract, either in or out of the body, by mechanical and galvanic agency, especially By the latter, after all motion has ceased for some time. It has been deemed doubtful, whether the veins generally possess any contraction like that of the venae cavae and the pulmonary veins near the heart, for although irritated by galvanic and mechanical stimuli by Hal- ler, Nysten, Miiller, J. J. Allison, and others, no motion whatever could be detected in them. It has been before shown, however, that non- striated muscular fibres enter into their composition, and Gerber affirms, that the fibres of their middle coat bear a stronger resemblance to those of muscular tissue than do those of the corresponding coat of the arteries, which more resemble ordinary elastic fibres ; but Dr. Carpen- ter3 thinks it not improbable, that his observations were made on por- tions of the veins near the heart, which partake of its contractility. In the experiments of Dr. Marshall Hall4 on the circulation in the 1 Traite" de Physiol., &c, Drs. Bell's and La Roche's translat., p. 391, Philad:, 1832. 2 See the experiments of the last named gentleman, proving the existence of a venous pulse independent of the Heart and Nervous System, in Amer. Journal of the Medical Sci- ences, Feb., 1839, p. 306. 3 Human Physiology, § 514, note, Lond., 1S42. < Essay on the Circulation, ch. i., Lond., 1831, and Philad., 1835. 166 CIRCULATION. web of the frog's foot, he was almost invariably able to detect, with a good microscope, a degree of pulsatory acceleration of the blood in the arteries at each contraction of the heart; and he is disposed to con- clude, that the natural circulation is rapid, and entirely pulsatory in the minute arteries, and slow and equable in the capillary and venous systems. But whenever the circulation was in the slightest degree im- peded, the pulsatory movement became very manifest at each systole of: the heart, and it was seen in all the three systems—arterial, capillary, and venous. He observed, that in the arteries there was generally an alter- nate, more or less rapid flow of the corpuscles at each systole and dias- tole of the ventricle; and that in the capillaries and veins the blood was often completely arrested during the diastole, and again propelled by a pulsatory movement during the systole ;—all which he esteems conclu-1 sive proof, that the power and influence of the heart extend through the arteries to the capillaries, and through these to the veins, even in the extreme parts of the body. The experiments of Valentin1 would seem, however, to show, that but little of the force of the. left ventricle remains to propel the blood in the veins. He found, that the pressure of the blood in the jugular vein of a dog, as estimated by the haemadynamometer of Poiseuille, was not more than ^th or y^th of that in the carotid artery. In the upper part of the vena cava inferior, he- could scarcely detect any pressure ; almost the whole force of the heart having been appa- rently consumed during the passage of the blood through the. capilla- ries:2 still—as Messrs. Kirkes and Paget3 suggest—slight as this rema- nent force might be, it would be enough to complete the circulation, inasmuch as although the spontaneous dilatation of the auricles and ven- tricles may not be forcible enough to assist the movement of blood in them, it is adapted to present no obstacle to the movement. That the veins are possessed of elasticity is proved by the operation of bloodletting, in which a part of the jet, on puncturing the vein, is owing to the over-distended vessel returning upon itself; but that this" property exists to a trifling extent only is shown by the varicose state of the vessels, which is so frequently seen in the lower extremities. e. Forces that propel the Blood. From the inquiry into the agency of the different circulatory organs in propelling the blood, it is manifest, that the action of the heart, the elasticity of the arteries, and a certain degree of contractile action in the smaller vessels more especially, a distinct action of the capillary vessels, and a slight elastic and perhaps contractile action on the part of the veins, may be esteemed the efficient motors. Of these, the action of the heart and capillaries^ and the contraction of the arteries and veins, can alone be regarded as sources of motion, the elasticity of the vessels being simple directors, not generators of force. But there is another agency, which is probably more efficient than has been gene- rally conceived. This is the suction power of the heart, or derivation 1 Lehrbuch, der Physiologie des Menschen, j. 477, Braunschweig, 1844. 2 Magendie. Lecons sur les phenomenes physiques de la^vie, iii. 152, Paris, 1837. 3 Manual of Physiology, Amer. edit., p. 113, Philad., 1849. FORCES THAT PROPEL THE BLOOD—SUCTION POWER. 167 as it has been termed, to which attention has been chiefly directed by Haller,1 Wilson,2 Carson,3 Zugenbiihler, Schubarth, Platner, Blumen- batfi,4 and others; but which is not assented to by Oesterreicher,5 Miil- ler,6 and some others.7 It is presumed,"that the muscular fibres of the heart are mixed up with a large quantity of areolar tissue; and that whilst the contraction of the cavities is effected by the action of the muscular fibres, dilatation is produced by the relaxation of the con- tracted fibres, and the elasticity of the areolar tissue; so that when the heart has contracted, and sentits blood onwards, its elasticity instantly restores it to its dilated condition; a vacuum is formed, and the blood rushes in to fill it. This action has been compared by Dr. Bostock,8 and by Dr. Southwood Smith,9 Prof. Turner,10 and others, to that of an elastic gum bottle, which, when filled with water, and compressed by the hand, allows the fluid to be driven from its mouth with a velocity proportionate to the compressing force; but the instant the pressure is removed, elasticity begins to operate, and if the mouth of the bottle be now immersed in water, a considerable quantity of that fluid will be drawn up into the bottle, in consequence of the vacuum formed within it. The existence of this force is .confirmed by Dollinger,11—who, when examining the embryos of birds, saw the blood advance along the veins, and the venous trunks pour it into the auricles at the moment they dilated to-receive it: as well as by Dr. T. Robinson,12 and M. Cruveil- hier,13 who were forcibly struck with the activity with which the diastole was effected, in the cases of monstrosity more than once referred to. Dr. Carpenter14 thinks it very doubtful "how far the auricles have such a power of active dilatation as would berequired for this purpose;" but the question need not regard the auricles. It is but necessary to suppose, that an action or power of dilatation exists in the ventricles; and this is now generally admitted. He farther remarks, that it has been shown experimentally by Dr. Arnott and others, that no suction power exerted at the farther end of a long tube, whose walls are as deficient in firmness as those of the veins are, can occasion any. accele- ration in a current of fluid transmitted through it; for the effect of the suction is destroyed at no great distance from the point at which it is applied by the flapping together of the sides of the vessel; but in answer to this it may be observed, that it remains to be shown, that 1 Elem. Physiol., ii. lib. vi. 2 Enquiry into the Moving Powers employed in the Circulation of the Blood., Lond., 1784. 3 Inquiry into the Causes of the Motion of the Blood, 2d edit., Lond., 1833. 4 Institutiones Physiologies, § 126, Getting., 1798. 5 Lehre vom Kreislauf des Blutes, Nurnberg, 1826. 6 Handbuch, u s. w., Baly's translation, p. 173. 1 Burdach, Physiologie als Erfahrungswissenschaft, iv. 270, Leipz., 1832. 8 Physiology, 3d edit., p. 251, Lond., 1836. » Animal Physiology, (Library of Useful Knowledge,) p. 83, Lond., 1829. 10 Edinb. Medico-Chirurg. Transact, iii. 225. 11 DenkschriftenderKonigl. Akademie der Wissenschaft. zu Munchen, vii. 217; and Bur- dach, op. citat., p. 272. .,2 American Journal of the Medical Sciences, No. xxii. '3 Gazette Medicate de Paris, 7 Aout, 1841, p. 535,; cited in Brit, and Foreign Medical Re- view, Oct. 1841, p. 535. 14 Human Physiology, § 515, Lond., 1842. I 168 CIRCULATION. such flapping of the sides would necessarily occur in the veins, which are living vessels, and constantly receiving blood from the capillaries under the action of vital forces. Another accessory force, that has been invoked, is the suction power of the chest or inspiration of venous blood, as it has been termed. This is conceived to be effected by the same mechanism as that which draws air into the chest. The chest is dilated during inspiration; an approach to a vacuum occurs in it; and the blood, as well as the air, is forcibly drawn towards that cavity. On the other hand, during ex- piration, all the thoracic viscera are compressed; the venous blood is repelled from the chest, and the arterial blood reaches its destination with greater celerity, owing to the action of the expiratory muscles being added to that of the left ventricle. Haller,1 Lamure,2 and Lorry,3 had observed, that the blood in the external jugular vein moves under manifestly different influences during inspiration and expiration. Generally, when the chest is dilated in inspiration, the vein empties itself briskly ; becomes flat, and its sides are occasionally accurately applied against each .other;—but during expiration it rises, and be- comes filled with blood;—effects, which are more evident, when the respiratory movements are extensive. The explanation of this pheno- menon by Haller and Lorry is the one given above. To discover whether the same thing happens to the venae cavae, M. Magendie introduced a gum elastic catheter into the jugular vein, so as to penetrate the vena cava and even the right auricle:—the blood was observed to flow from the extremity of the tube at the time of expira-, tion only. During inspiration, air was rapidly drawn into the heart, giving rise to the symptoms to be mentioned hereafter, which attend the reception of air into that organ. Similar results were obtained, when the tube was introduced into the crural vein in the direction of the abdomen. So far as regards the larger venous trunks, therefore, the influence of respiration on the circulation is sufficiently evidenced.4 It can be easily shown, by opening an artery of the limbs, that expira- tion—especially forced expiration, and violent efforts—manifestly acce- lerate the motion of arterial blood. In animals subjected to experiment, it is impracticable to excite either the forced expiration or violent effort at pleasure; but we can, as a substitute, compress the sides of the chest with the hands, according to the plan recommended by Lamure; when the blood will be found to flow more or less copiously in proportion to the pressure exerted. It occurred to M. Magendie, that this effect of respiration on the course of the blood in the arteries might influence the flow along the veins. To prove this, he passed a ligature around one of the jugular veins of a dog. The vessel emptied itself beneath the ligature, and became turgid above it. He then made a slight punc- ture with the lancet in the distended portion; and in this way obtained a jet of blood, which was not sensibly modified by the ordinary respira- tory movements, but became of triple or quadruple the size, when the animal struggled. As it might be objected to this experiment, that 1 Elementa Physiologias, torn. ii. lib. vi. sect. iv. § 8, Lausann., 1760. 2 Mem. de l'Acad. des Sciences, pour 1749. a Magendie, Precis, &c., ii. 416. 4 Poiseuille, in Magendie's Journal de Physiologie, viii. 272. FORCES THAT PROPEL THE BLOOD—EFFECT OF RESPIRATION. 169 the effect of respiration was not transmitted by the arteries to the open vein, but rather by the veins that had remained free, which might have conveyed the blood repelled from the vena cava towards the tied vein by means of anastomoses, the experiment was varied. The dog has not, like man, large internal jugular veins, which receive the blood from the interior of the head. The circulation from the head and neck is, in it, almost wholly confined to the external jugular veins, which are extremely large; the internal jugulars being-little more than vestiges. By tying both of these veins at once, M. Magendie made sure of obvi- ating, in great part, the reflux in question; but, instead of this double ligature diminishing the phenomenon under consideration, the jet be- came more closely connected with the respiratory movement; for it was manifestly modified even by ordinary respiration, which was not the case when a single ligature was employed. From these and other ex- periments, he properly concluded that the turgescence of the veins must not be ascribed, with Haller, Lamure, and Lorry, simply to the reflux of the blood of the venae cavae into the branches opening directly or indirectly into them; but partly to the blood being sent in larger quan- tity into the veins from the arteries.1 In the same manner are ex- plained,—the rising and sinking of the brain, which, as was observed in an early part of this work, (vol. i. p. 108,) are synchronous with expiration and inspiration. During expiration, the thoracic and abdominal viscera are compressed: the blood is driven more into the branches of the ascending aorta, and is, at the same time, prevented from returning by the veins: owing to the combination of these causes, the brain is raised during expiration. In inspiration, all this pressure is removed; the blood is free to pass equally by the descending and ascending aorta; the return by the veins is ready, and the brain there- fore sinks.2 We can thus, also, explain why the face is red and swollen during crying, running, straining, and the violent emotions; and why pain is augmented in local inflammations of an extremity,—as in cases of whitlow; and when respiration is hurried or impeded by running, crying, &c. The blood accumulates in the part, owing to the compound effect of increased flow by the arteries, and impeded return by the veins. The same explanation applies to the production of hemorrhage by any violent exertion; and M. Bourdon3 affirms, that he has always seen hemorrhage from the nose largely augmented during expiration; dimin- ished at the time of inspiration; and arrested by prolonged inspiration; —a therapeutical fact of some interest. Experiments with the haemadynamometer by Poiseuille, and Ludwig,4 confirm those mentioned above:—the column of mercury having been found to rise somewhat at each expiration, and to sink during inspira- tion. It is manifest, then, that the circulation is modified by the move- 1 Precis, &c, ii. 421. 2 This motion of the brain must not be confounded with that which is synchronous with the contraction of the left ventricle; and is owing to the pulsation of the arteries at the base of the brain. 3 Recherches sur la Mechanisme de la Respiration et sur la Circulation du Sang, Paris, 1820; see, also, Longet, Anatomie et Physiologie du Systeme Nerveux, pp. 777 and 779. 4 M tiller's Archiv. fur Anatomie, u. s. w., Heft. iv. s. 242, Berlin, 1847. 170 CIRCULATION. ments of inspiration and expiration,1—the former facilitating the flow of blood to the heart by the veins, and the latter encouraging the flow by the arteries; and we shall see hereafter, that the dilatation of the chest,—which constitutes the first inspiration of the new-born child,— is the cause of the establishment of the new circulation; the same dila- tation, which causes the entrance of air into the air-cells, soliciting the flow of blood, or the "inspiration of venous blood," as M. Magendie2 has termed it. In a paper read before the Royal Society of London, in June, 1835, Dr. Wardrop,3—after remarking, that he considers in- spiration as an auxiliary to the venous; and expiration to the arterial circulation,—-attempts, on this principle, to explain the influence everted on the circulation, and on the action of the heart, by various modes of respiration, whether voluntary or involuntary, under different circum- stances. Laughing, crying, weeping, sobbing, and sighing, he regards as efforts made with a view to effect certain alterations in the quantity of blood, in the lungs and heart, when the circulation has been dis- turbed by mental emotions. The influence of ordinary respiration can, however, be trifling; yet it has been brought forward by Sir David Barry4 as the efficient cause of venous circulation. His reasons for this belief are,—the facts just mentioned, regarding the influence of in- spiration on the flow of blood towards the heart; and certain ingeni- ously modified experiments, tending to the elucidation of the same result. He introduced one end of a spirally convoluted tube into the jugular vein of an animal,—the vein being tied above the point where the tube was inserted,—and plunged the other into a vessel filled with a coloured fluid. During inspiration, the fluid passed from the vessel into the vein: during expiration, it remained stationary in the tube, or was repelled into the vessel. Dr. Bostock5 remarks, that he .was pre- sent at some experiments, which were performed by Sir David at the Veterinary College in London, and it appeared sufficiently obvious, that when one end of a glass tube was inserted either into the large veins, into the cavity of the thorax, or into the pericardium,—the other end being plunged into a vessel of coloured water,—the water was seen to rise up the tube during inspiration, and descend during expiration. The conclusion of Sir David from these experiments is most compre- hensive ;—that " the circulation in the great veins depends upon atmo- spheric pressure in all animals possessing the power of contracting and dilating a cavity around that point, to which the centripetal cur- rent of their circulation is directed;" and he conceives, that as, during inspiration, a vacuum is formed around the heart, the equilibrium of pressure is destroyed, and the atmosphere acts upon the superficial veins, propelling their contents onwards to supply the vacuum; but in- dependently of other objections, there are a few that appear convincing 1 Dr. Clendinning's Report to the Brit. Association, 1839-40, in Lond. Med. Gazette, Nov. 13, 1840, p. 270. 2 Precis, &c, ii. 416. 3 On the Nature and Treatment of the Diseases of the Heart; with some new views of the Physiology of the Circulation, Lond., 1837. 4 Experimental Researches on the Influence of Atmospheric Pressure upon the Circulation of the Blood, &c, Lond., 1826. 6 Physiology, 3d edit., p. 330, note, Lond., 1836. FORCES THAT PROPEL THE BLOOD—VENA CONTRACTA. 171 against the sole agency of ordinary respiration in effecting venous cir- culation. According to Sir David's hypothesis, blood ought to arrive at the heart at the time of inspiration only; and as there are, on the average, seventy-two contractions of the heart for every eighteen in- spirations; or four contractions, or—what is the same thing—four dilatations of the auricle for each respiration; one of these only ought to be concerned in the propulsion of blood, whilst the rest should be bloodless ; yet we feel no difference in the strength of the four pulsations. It is clear, too, if we adopt Sir David's reasoning, that, of the four pulsations, two, and consequently two dilatations must occur during expiration, at which time the capacity of the chest is actually dimin- ished : moreover, holding the breath ought to suspend the circulation; and the respiratory influence, cannot be invoked to explain the circula- tion in the foetus or in aquatic animals. At the most, therefore, respira- tion can only be regarded as a feeble auxiliary in the circulation. In favour of his opinion of the efficiency of atmospheric pressure in causing the return of the blood by the veins, Sir David adduces the fa,ct,— already referred to, under the head of Absorption,—that the applica- tion of an exhausted vessel over a poisoned wound prevents the absorp- tion of the poison; but this, as we have seen, appears to be a physical effect, which would apply equally to any view of the subject^ In all these cases, the elastic resilience of the lungs, by contributing to diminish' the atmospheric pressure from the outer surface of the auricles, may, likewise, as suggested by Dr. Carson,1 have some agency in soliciting the blood into these cavities; but the agency cannot be great. It has recently been suggested by Liebig,2 that the fluids of the body, in consequence of the cutaneous and pulmonary transpiration, acquire a motion towards the skin and lungs; but it is not easy to see that this could have any important effect on the circulation. There is another circumstance of a purely physical nature, which may Fig. 302. exert some influence upon the flow of the blood along the veins; the ex- panded termination of the venae cavae in the right auricle. To explain this, it is necessary to premise a detail of a few hydraulic facts. If an aperture A, Fig. 302, exist in a cistern X, the water will not issue at the aperture by a stream of uniform size; but, at a short distance from the reservoir, it will be contracted as at B, constituting what has been termed the vena contracta. Now, it has been found, that if a tube technically called an adjutage be attached to this Vena Contracta. 1 Philosoph. Transact, for 1820, and An Inquiry into the Causes of Respiration, &c, 3d edit., Liverpool, 1833. 2 Researches on the Motion of the Juices in the Animal Body, by W. Gregory, M. D., p. 74, London, 1848. 172 CIRCULATION. aperture, so as to accurately fit the stream, as at A B, Fig. 303, as much fluid will flow from the reservoir as if the aperture alone existed. Again, if the pipe B C be attached to the adjutage A B, the expanded extremity at A will Fig. 303. occasion the flow of ~°^ "~ ^ I , to the tube B C, a Vena Contracta. truncated conical tube C D be at- tached, the length of which is nearly nine times the diameter of C; and the diameter of C to that of D be as 1 to 8; the flow of water will be augmented in the proportion of 24 to 12*1; so that, by the two adjutages A B and C D, the expenditure through the pipe B C is increased in the ratio of 24 to 10. This, fact,—the result of direct experiment, and so important to those who contract to supply water by means of pipes,— was known to the Romans. Private persons, according to Frontinus,1 were in the habit of purchasing the right of delivering water in their houses from the public reservoirs, but the law prohibited them from making the conducting pipe larger than the opening allowed them in the reservoir, within the distance of fifty feet. The Roman legislature must, therefore, have "been aware of the fact, that an adjutage with an expanded orifice, would increase the flow of "water; but they were ignorant that the same effect would be induced beyond the fifty feet. A case—" The Schuylkill Navigation Company against Moore"—was tried in March term 1837, before the Supreme Court in Pennsylvania, in which these hydraulic principles were involved. The defendant had conveyed to him by the plaintiffs a certain lot of ground together with the privilege of drawing from the Schuylkill canal as much water as would pass through two metallic apertures of a size mentioned. He applied, however, to the aperture a conical tube or adjutage by which the flow of water was proved to have been greatly augmented. It was decided, that he had no right to increase the flow by such agency.2 Let us apply this law of hydraulics to the circulation. In the first place, at the origin of the pulmonary artery and aorta, there is a manifest narrowness, formed by the ring at the base of the semilunar valves: this might be conceived unfavourable to the flow of the blood along those vessels during the systole of the ventricles; but from the law, which has been laid down, the narrowness would occupy the natural situation of the vena contracta, and, therefore, little or 1 De Aquseductibus; Oudendorp,,Lugd. Bat., 1731. 2 Reports of Cases adjudged in the Supreme Court of Pennsylvania in the Eastern Dis- trict. By Thomas I. Wharton, vol. ii. p. 477: Philadelphia, 1837. FORCES THAT PROPEL THE BLOOD—AUTOMATIC POWER. 173 no effect would be induced. The discharge would be the same as if no such narrowness existed. We have seen, again, that the vena cava becomes of larger calibre as it approaches the right auricle, and finally terminates in that cavity by an expanded aperture. This may have a similar effect with the expanded tube C D, Fig. 303, which doubles the expenditure.1 In making these conjectures,—some of which have been adduced by Sir Charles Bell,—it is proper to observe, that, in the opinion of some natural philosophers, the effect of the adjutage is entirely due to atmo- spheric pressure, and that no such acceleration occurs, provided the experiment be repeated in vacuo. Sir Charles Bell2 conceives, that " the weight of the descending column in the reservoir being the force, and this operating as a vis a tergo, it is like the water propelled from the jet d'eau, and the gradual expansion of the tube permits the stream from behind to force itself between the filaments, and disperses them, without producing that pressure on the sides of the tube, which must take place, where it is of uniform calibre." It is on this latter view only, that these hydrostatic facts can be applied to the doctrine of the circulation. In addition to the movements impressed on the blood by the parietes of the cavities in which it moves, it has been considered by many phy- siologists,—as by Harvey, Glisson, Bohn, Albinus, Rosa, Tiedemann, Gr. R. Treviranus,3 Rogerson,4 Alison,5 and others,—to possess a power of automatic or self-motion. M. Broussais6 asserts, that he has seen experiments,—originally performed by M. P. A. Fabre, which showed, that the blood, in the capillary system, frequently moves in an opposite direction to that given it by the heart,—repeated by M. Sarlandiere on the mesentery of the frog. In these, the blood was seen to rush for some moments towards the point irritated; and, when a congestion had taken'place there, they remarked, that the corpuscles took a different direction, and traversed vessels which conveyed them in an opposite course; and, a few seconds afterwards, they were again observed to return with equal rapidity to the point from which they had been repelled. Tiedemann7 has collected the testimonies of various indi- viduals on this point. Haller,8 Spallanzani,9 Wilson Philip,10 G. R. Treviranus,11 and others, have remarked, by the aid of the microscope, that the blood continued to move in the vessels of different animals, but chiefly of frogs, for some time after the great vessels had been tied, or the heart itself removed;—a fact which Tiedemann, also, often wit- 1 Venturi, Sur la Communication Laterale du Mouvement dans les Fluides, Paris, 1798. 2 Animal Mechanics, p. 40, in Library of Useful Knowledge, Lond., 1829. 3 Tiedemann, Traite Complet de Physiologie de l'Homme, traduit par Jourdan, i. 348, Paris, 1831. 4 A Treatise on Inflammation, &c, Lond., 1832. 5 Edinburgh Med. and Surg. Journal for Jan., 1836. 6 Traite de Physiologie, &c, translated by Drs. Bell and La Roche, 3d edit., p. 374, Philad., 1832. i Op. citat. 8 Oper. Minor., i. 115, sect, 8. 9 Exper. on the Circulation, &c, in Eng. by R. Hall, Lond., 1801. 10 Philos. Transact, 1815; and Medico-Chirurg. Trans., vol. xii. 11 Vermischte Schriften, i. 102. 174 CIRCULATION. nessed. C. F. Wolff,1 Rolando,2 Dbllinger and Pander,3 Pre'vost and Dumas,4 Von Baer,5 and others,6 saw blood corpuscles in motion in the incubated egg, before the formation of either vessels or heart; and Hunter, Gruithuisen, and Kaltenbrunner observed,—in the midst of the areolar tissue of inflamed parts, in tissues undergoing regeneration, and during the cicatrization of wounds,—bloody points placed suc- cessively in contact with each other, forming small currents, which represented new vessels, and united to those already existing. The fact, indeed, that the embryo forms its own vessels, and that blood in motion can be detected before vessels are in esse, is a sufficient proof,— were there no other,—that the corpuscles of the blood possess the faculty of motion, either in themselves, or by virtue of an attraction exerted upon them by the solid parietes in which they move. Miiller7 thinks the idea of spontaneous motion in a fluid, independently of attraction or repulsion from the sides of another object, is inconceiva- ble ; and as Tiedemann8 has remarked, if ive admit this faculty in animals provided with a heart, the progression of the blood must be mainly owing to that viscus; for, after the heart ceases to act, the cir- culation is soon arrested. The blood, too, only remains fluid, and possesses the faculty of motion, whilst it is in connexion with the living body. When taken from the vessel in which it circulates, it soon coagulates, and loses its motive power. This motion has, by some,— and, according to Brandt,9 not without grounds,—been presumed to be owing to electro-chemical agency. Burdach10 has properly observed, that the old but perfectly correct saying, "ubi stimulus ibi affluxus," means nothing more than that where the vital activity of an organ is augmented, more blood will be drawn to it; whence it naturally follows, that the progression of blood in the capillaries must be, in some measure, dependent on the activity of the vital manifestations in the tissue. It has been already shown, that if the capillary action be excited by stimulants, a greater flow of blood takes place into that system of vessels ; and as the functions of nutrition and secretion are accomplished by that system, it is obvious, that any increase in the activity of those functions must attract a larger afflux of fluids, and, in this manner, modify the circulation independ- ently of the heart and larger vessels. But this, again, can have but a subordinate influence on the general circulation. Lastly, M. Raspail11 resolves the whole of the circulation, as he does other functions, into a double action of aspiration and expiration by the tissues concerned. As the blood is the bearer of life to every 1 Theoria Generationis, Hal., 1759. 2 Dizionario Periodico di Medicina, Torino, 1^22-1823. 3 Dissert, sist. Hist. Metamorphoseos quam Ovum Incubatum prioribus quinque Diebus subit, Wirceb., 1817. 4 Annales des Sciences Naturelles, torn. xii. p. 415, Dec, 1827. 6 Ueber die Entwickelungsgeschichte der Thiere, u. s. w., Th. i. Konigsberg, 1828. 6 Allen Thomson, On the Formation of New Bloodvessels, Edinb., 1832; and art. Cir- culation, in Cyclopaedia of Anat. and Physiology, p. 7, Lond., 1836. 7 Handbuch, u. s. w., Bal'y's translation, p. 224, Lond., 1838. 8 Op. cit., p. 349. 9 Art. Blut, in Encyclopad. Wiirterb. der.Medicinisch. Wissenschaft. v. 596, Berlin, 1830. 10 Die Physiologie als Erfahrungswissenschaft, &c., Band, iv., Leipz., 1832. 11 Chimie Organique, p. 364, Paris, 1833. ACCELERATING AND RETARDING FORCES—FRICTION. 175 part of the organism, and of nourishment and reparation to the organs, —to prevent its destination being annulled, a part of the fluid, he says, must be absorbed by the surfaces, which it bathes: these surfaces must attract nutritive juices from the blood, and they must return to the blood the refuse of their elaboration,—in other words, they must aspire and expire. Now, this double function cannot take place without the fluid being set in motion, and this motion must be the more constant and uniform as the double function is inherent in every molecule of the sur- face of the vessels. In this way he accounts for the mercury, placed in a tube communicating with an artery, being kept at the same height near to, or at a distance from, the heart; because, he says, it is not the action of the heart which supports it, but the action of the parietes of the vessels. Every surface, which aspires, provided it is flexible, must be, in its turn, he conceives, attracted by the substance aspired, and, consequently, by the act of aspiration alone, the motions of systole and diastole of the heart and arteries.may be explained. When their inner parietes aspire—or assimilate the fluid,—the heart will contract; when, on the contrary, they expire,—owing to the mutual repulsion between the heart and the fluid, the former dilates; and, as the movements of the heart are energetic on account of its size, its movements will add to the velocity of the circulation'in the arteries, which will, therefore, besides their proper actions of aspiration and expiration, present movements isochronous with the pulsations of the heart. "Add to this accessory cause of arterial pulsations, the movements impressed by the aerial aspiration, which takes place in the lungs, and the circulation of the blood will no longer present insurmountable problems." All this, it need scarcely be said, is ingenious; but nothing more. f. Accelerating and Retarding Forces. The above are the chief accelerating causes of the circulation. There are others, that at times accelerate, and at times retard; and others, again, that must always be regarded as impeding influences. All these are of a physical character, and applicable as well to inert hydraulic machines as to the pipes of the human body. 1. Friction always acts as a retarding force. That, which occurs between a solid and the surface on which it moves, can be subjected to calculation, but not so with a fluid, inasmuch as all its particles do not move equally: whilst one part is moving rapidly, another may be sta- tionary, moving slowly, or even in a contrary direction, as is seen in rivers, where the middle of the stream always flows with greater velocity than the sides. The same thing happens to water flowing through pipes; the water, which is in contact with the sides of the pipe, moves more slowly than that at the centre. This retarding force is much diminished by the polished state of the inner surface of the bloodvessels, as is proved by the circumstance, that if we introduce an inert tube into an artery, the blood will not flow through it for any length of time. M. Poiseuille1 infers, from his investigations, that a still layer of serum lines the interior of the capillary vessels, which may have some effect 1 Biblioth. Universelle, Novemb., 1835, 176 CIRCULATION. in retarding the blood globules in their progress through the interme- diate system. Yet the viscosity of the blood, within certain limits, would seem to be important to enable it to pass through the capillary system. M. Magendie, indeed, pronounces it to be an indispensable condition for its free circulation through the capillaries.1 2. Gravity may either be an active or retarding force, and is always exerting itself, in both ways, on different sets of vessels. If, for example, the flow of blood to the lower extremity by the arteries is aided in the erect attitude by the force of gravity, its return by the veins is retarded by the same cause. Every observer must have noticed, that the pulse of a person in health beats slower when he is in the recumbent, than in the erect, attitude. This is owing to there being no necessity.for the heart to make use of unusual exertions for the purpose of forcing the blood, against gravity, towards the upper part of the body. In thera- peutics, the physician finds great advantage from bearing this influence in mind; and, hence, in diseases of the hea,^,—as in inflammation of the brain, in apoplectic tendency, ophthalmia, &c,—he directs the pa- tient's head to be kept raised; whilst in uterine affections the horizontal posture, or one in which the lower part of the body is raised even higher than the head, is inculcated; and in ulcers or inflammatory diseases of the lower extremities, the leg is recommended to be kept elevated. Every one, who has had the misfortune to suffer from whitlow, has experienced the essential difference in the degree of pain produced by position. If the finger be held down, gravity aids the flow of blood by the arteries, and retards its return by the veins: the consequence is turgescence and painful distension; but if it be held higher than the centre of the circulation, the flow by the arteries is impeded/whilst its . return by the veins is accelerated, and hence the marked relief afforded. 3. Curvatures.—Besides friction, the existence of curvatures has considerable effect on the velocity and quantity of the fluid passing through pipes. A jet does not rise as high from the pipe or adjutage of a reservoir, if there be an angular turn in it, as if the bend were a gradual curve or sweep. The expense of force, produced by such cur- vatures in arteries, is seen at each contraction of the ventricle,—the tendency in the artery to become straight producing an evident move- ment, which has been called locomotion of the artery, and has been looked upon, by some, as the principal cause of the pulse. This motion is, of course, more perceptible the nearer to the heart, and the greater the vessel; hence it is more obvious at the arch of the aorta; and we can now understand why this arch should be so gradual. There is a striking example of the force used in this effort at straightening the artery, in the case of the popliteal artery, when the legs are crossed, and a curvature thus produced. The force is sufficient to raise a weight of upwards of fifty pounds at each contraction of the ventricle, not- withstanding it acts at the extremity of so long a lever. This fact is sufficient to exhibit the inaccuracy of the notion of MM. Bichat and Bricheteau,2 that the curvatures in the arteries can have no effect in 1 Lectures on the Blood, edit, cit., p. 102, Philad., 1839. 2 Clinique Medicale, p. 145, Paris, 1835; or the author's translation in his American Medical Library, Philad., 1837. ACCELERATING AND RETARDING FORCES—ANASTOMOSES. 177 retarding the flow of blood. Such could only be the case, Bichat thinks, if the vessels were empty at each systole. " 3. Anastomoses.—The anastomoses of vessels have, doubtless, also some influence on the course of the blood ; but it is impossible to appre- ciate it. The superficial veins are especially liable to have the circu- lation impeded by compression in the different postures of the body; but, by means of the numerous anastomoses if the blood cannot pass by one channel, it is diverged into others. Although, however, a forcible compression may arrest or retard the flow by those vessels, a slight degree of support prevents the vein from being dilated by the force of the blood passing into it, and thus favours its motion. The constant pressure of the skin hence facilitates the circulation through the sub- cutaneous veins, and if, by any means, the pressure be diminished, especially in those parts in which the blood has to make its way against gravity—as in the lower extremities—varices or dilatations of the ves- sels supervene, which are remedied by the mechanical compression of an appropriate bandage. Attempts have been made to calculate the velocity with which the blood proceeds in its course; and how long it would take for a blood corpuscle, setting out from the left side of the heart, to attain the right side. It is clear, that the data are, in the first place, totally insuffi- cient for any approximation. We know not the exact quantity of blood contained in the vessels;—the amount sent into the artery at each contraction of the ventricle; the relative velocity of the arterial, venous, and capillary circulations;—and, if we knew them at any one moment, they are liable to incessant fluctuations, which would preclude any accurate average from being deduced. Were these circumstances insufficient to exhibit the inanity of such researches, the varying esti- mates of different observers would establish it. These assign the time occupied in the circulation from two minutes to fifteen or twenty hours! Moreover, the distances which the corpuscles have to traverse must be various. In the heart, the passage from one side to the other by the coronary vessels is very short; whilst if the blood have to proceed to a remote part of the body, the distance is considerable. Were we to regard the vascular system as forming a single tube;— by knowing the weight of the blood and the quantity which the left ventricle is capable of sending forward at each contraction, we could calculate with facility the period that must elapse before an amount equal to the whole mass is distributed. Thus, if we estimate, with many physiologists, the quantity propelled forward at each contraction of the ventricle to be two ounces; and the whole mass of blood to be 30 pounds, it will require, on an average, about 240 beats of the heart to send it onwards; which can be accomplished in little more than 3 minutes, yet, notwithstanding the absence of the requisite data, a modern writer has gone so far as to affirm the average velocity of the blood in the aorta to be about eight inches per second; whilst "the velocity in the extreme capillaries is found to be often less than one inch per minute"! A similar estimate was made by Dr. Young:1 Hales,2 too, 1 An Introduction to Med. Literature, p. 609, Lond., 1813. 2 Statical Essays, vol. ii. p. 40, Lond., 1733. VOL. II.—12 178 CIRCULATION. estimated the velocity of the blood, leaving the heart at 149*2 feet per minute, and the quantity of blood passing through the organ every hour at twenty times the weight of the blood in the body; but the judi- cious physiologist knows well, that in all operations, which are, in part, of a vital character, the results of every kind of calculation must be received with caution. In the larger animals, as the whale, the quan- tity of the fluid circulating in the aorta must be prodigious. Dr. Hun- ter, in his account of the dissection of a whale, states that the aorta was a foot in diameter, and that ten or fifteen gallons of blood were probably thrown out of the heart at each stroke; so that this vessel is, in the whale, actually larger than the main pipe of the old water-works at London Bridge; and the water, rushing through the pipe, it has been conceived, had less impetus and velocity than that gushing from the heart of this leviathan.1 But the highest of these estimates, as to the velocity of the circula- tory current, is probably far beneath the truth, inasmuch as experi- ments have shown, that substances introduced into the venous circula- tion may be detected in the remotest parts of the arterial circulation in animals larger even than man in less than thirty seconds. Ten seconds after having injected a solution of ni-trate of baryta into the jugular vein of a horse, Dr. Blake,2 now of Saint Louis, drew blood from the carotid of the opposite side:, after allowing this to flow for five seconds, he received the blood that flowed during the next five seconds into another vessel; and that which flowed after the twentieth second, by which time the action of the heart had stopped, was received into a third vessel. No trace of baryta could be detected in the blood that flowed between the tenth and fifteenth seconds ; but it was discovered in that which flowed between the fifteenth and twentieth. In a dog, the poisonous effects of strychnia on the nervous system appeared in twelve seconds after injection into the jugular vein; in a fowl in six and a half seconds; and in a rabbit in four and a half seconds,—the interval being in an inverse ratio to the velocity of their respective circula- tions. From the results of these and other experiments, Dr. Carpenter thinks it difficult to resist the conclusion, that some other force than the contractions of the heart must have a share in producing the move- ment of the blood through the vessels.3 If, however, we adopt the estimate of the average quantity of blood discharged by the left ven- tricle at each contraction, as given by Valentin,4 a part of the difficulty is removed. He gives it at five ounces; so that thirty pounds of blood would require on an average, 96 contractions of the ventricle, which would be accomplished on an average in about a minute and a third. Mr. Paget says in from 43f to 62f seconds—the discordance being owing to the varying estimates as to the quantity of blood in the body. If we take the recent estimate of the amount of blood by Dr. Blake 1 Paley's Natural Theology; and Animal Physiology, p. 75, Library of Useful Knowledge, Lond., 1829. a Edinb. Med. and Surg. Journal, Oct., 1841; St. Louis Medical and Surgical Journal, Nov. and Dec, 1848; and American Journal of the Medical Sciences, p. 100, July, 1849. 3 Human Physiology, § 491, Lond., 1842. 4 Lehrbuch der Physiologie des Menschen, i. 415, Braunschweig, 1844. VELOCITY OF THE CIRCULATION. 179 (page 102), it could be accomplished in from 53 to 60 contractions of the ventricle, or in from 44 to 50 seconds. Valentin's estimate of the quantity sent out at each contraction is probably, however, too high: —three ounces may be nearer the mark. With this velocity of the general circulation, it seems at first difficult to comprehend its slowness of progression in the capillary vessels, which in the frog, according to Valentin,1 from many careful micrometric examinations, is from 0*938 to 1*4 English inch per minute. In the small veins, he says, it is about |th faster. These velocities, as Mr. Paget2 remarks, agree nearly with those of Hales,3 who estimated the velocity at an inch in a minute and a half; and more nearly still with those of Weber, who found it 1£ inch per minute. On examining the circulation in the tongue of the frog, the blood is observed streaming with immense velocity through the larger vessels, whilst in those that admit but a single file of red corpuscles, the motion is as slow as de- scribed by those observers. It has been well remarked by Messrs. Kirkes and Paget,4 that the speed at which the -blood may be seen moving in transparent parts is not opposed to the calculations of Valentin and others; inasmuch as, although the movement through certain capillaries may be very slow, the length of capillary through which any portion of blood has to pass is very small. " If we estimate that length at the tenth of an inch, and suppose the velocity of the blood therein to be only one inch per minute, then each portion of blood may traverse its own distance of the capil- lary system in about six seconds. There would thus be plenty of time left for the blood to travel through its circuit in the larger vessels, in which the greatest length of tube that it can have to traverse in the human subject does not exceed ten feet." The velocity of the circulating fluid in the smaller vessels is generally thought to be less than in the larger; and their united calibres to be much greater than that of the trunk with which they communicate. Were this the case, the diminution of velocity would be in accordance with a law of hydrodynamics;—that when a liquid flows through a full pipe, the quantity which traverses the different sections of the pipe in a given time must be every where the same; so that where the pipe is wider the velocity diminishes: and, on the contrary, where it is nar- rower the velocity increases. This would not seem, however, to be consistent with the calculations of Dr. T. Young, and Weber, and the experiments of M. Poiseuille, already referred to, in which Drs. Spengler5 and Valentin6 concur, which show, that the pressure exerted on the blood in different parts of the body—as measured by the column of mercury, which the blood in different, arteries will sustain—is almost exactly the same. The cause of error in the common belief,—that the capacity of the arterial tubes increases in proportion to thejr distance from the heart,— has been explained by Mr. Ferneley7 and others. It is true, he observes, 1 Op. cit. 2 Loc. cit. 3 Op. citat., ii. 68. * Manual of Physiology, Amer. edit., p. 118, Philad., 1849. 6 Miillers Archiv., 1844, Heft i. 6 Op. cit., p. 456. i London Medical Gazette, Dec. 7, 1839. 180 CIRCULATION. that the sum of the diameters of the branches is considerably greater than that of the trunk. Thus a trunk, 7 lines across, may divide into two branches of 5 lines each; or a trunk of 17 into threebranches of 10, 10, and 9|; but when their areas are compared, which is the only mode of arriving at their calibres, the correspondence is as close as can be reasonably expected, when the nature of the measurement is taken into account. In the first case, the area of the trunk is represented by the square of 7—that is 49; whilst the area of each branch will be 25, and the sum of the two will be 50. In the second instance, the area of the trunk will be 17 squared, or 289; whilst that of the branches is the sum of 100,-100, and 90|, making 290£. This will be more strikingly seen from the following table:— Trunks. Diameter. Square of Diameter I. 9 81 II. 7-2 51-64 III. 3-5 12-25 IV. 7-0 49 V. 17 289 VI. 10 100 VII. 4-5 20-25 VIII. 8 64 , Branches. Diameter. Sum of Squares of Diameter. 7-5+5 81-25 6 + 4 52 3+2 13 5+5 50 10+10 + 9-5 290-25 7+7 + 2 102 3-5+3 21-25 4 + 7 65 It will be observed, that the sum of the squares of the diameters of the branches is in every case slightly more than the square of the diameter of the trunk. The discrepancy was found to be somewhat greater in subsequent experiments made by Mr. Paget.1 The follow- ing table gives the ratio of the area of each arterial trunk to the joint area of its branches, as observed by him:— Arch of the aorta .... Innominata . . • •. Common carotid . . . External do...... Subclavian...... Abdominal aorta to the last lumbar arteries ._________------- just before dividing . Common iliac ..... External iliac . . runk. Branches 1 1-055 1 1-147 1 1-013 1 1-19 1 1-055 1 1-183 1 •893 1 •982 1 1-15 Analogous experiments by actual admeasurement made bj Mr. Erskine Hazard,2 of Philadelphia, lead to. a similar conclusion. It would appear, that where the aorta divides into the common iliacs, or at the division next lower down, the stream is always contracted; the effect of which must necessarily be to accelerate the circulation not only in the iliacs themselves, but in the arteries given off from the trunk above them,—as the mesenteric and the renal. From what has been said regarding the curvatures and angles of vessels, it will be understood, that the blood must proceed to different organs with different velocities. The renal artery is extremely short, straight, and large, and must transmit the blood very differently to the ' London Medical Gazette, July 8, 1842. 2 Horner, Special Anatomy and Histology, 7th edit., u. 184, Philad., 1846. VELOCITY OF THE CIRCULATION—DIVERTICULA. 181 kidney, from what the tortuous carotid does to the brain; or the spermatic artery to the testicle. A different impulse must, conse- quently, be made on the corresponding organs by these different vessels. A great portion, however, of the impulse of the heart must fail to reach the kidney, short as the renal artery is, owing to its passing off from the aorta at a right angle; and, hence, the impulse of the blood on that organ may not be as great as might be imagined at first. The tortuosity of the carotid arteries is such as to greatly destroy the impetus of the blood; so that but trifling hemorrhage takes place when the brain is sliced away on a living animal, although it is pre- sumed, that one-eighth of the whole quantity of blood is sent to the encephalon. Dr. Rush supposed, that the use of the thyroid body is to break the afflux of blood to the brain ; for which its situation between the heart and head appeared to him to adapt it; and he adduced, as farther arguments,—first, the number of arteries it receives, although effecting no secretion; secondly, the effect on the brain, which he con- ceived to be caused by disease, and extirpation, of the thyroid; the operation having actually occasioned, in his opinion, in one case, inflam- mation of the brain, rapidly terminating fatally; and, thirdly, the fact that goitre is often, accompanied by idiotism. The opinion, however, is so entirely conjectural, and some of the facts, on which it rests, so questionable, that it does not demand serious examination. This leads us to remark, that the thyroid body as well as other organs, with whose precise functions we are totally unacquainted,—as the thymus, spleen, and supra-renal capsules,—have been conceived to serve as diverticula or temporary reservoirs to the blood, when, owing to specia.1 circumstances, that fluid cannot circulate properly in other parts of the frame. M. Lieutaud having observed, that the spleen is always larger when the stomach is empty than when full, considered that the blood, when digestion is not going on, reflows into the spleen, and that thus this organ becomes a diverticulum to the stomach. The opinion has been indulged by many, with more or less modification. Dr. Rush's view was more comprehensive. He regarded the organ as a diverticulum, not simply to the stomach, but to the whole system, when the circulation is greatly excited, as in passion, or in violent muscular efforts, at which times there is danger of sanguineous conges- tion in different organs; and in support of this view, he invoked its spongy nature; the frequency of its distension; the large quantity of blood distributed to it; its vicinity to the centre of the circulation; and the sensation referred to it, in running, laughing, &c. M. Broussais1 has still farther extended the notion of diverticula. He affirms, that they always exist in the vicinity of organs, whose functions are mani- festly intermittent. In the foetus, the blood does not circulate through the lungs as when respiration has been established: hence, diverticula are necessary: these are the thymus and thyroid glands. The kid- neys do not act in utero; hence the use of the supra-renal capsules as diverticula. At birth, these organs are either wholly obliterated, if 1 Commentaires des Propositions de Pathologie, &c, Paris, 1829; or, translation, p. 214, Philad., 1832. 182 CIRCULATION. the organs to which they previously served as diverticula have continu- ous functions; or they are partly obliterated, if the functions be inter- mittent. Thus, the spleen continues as a diverticulum to the stomach, because its functions are intermittent through life; and the thymus dis- appears when respiration is established: the liver and the portal system he regards as a reservoir for the reception of blood in cases of impedi- ment to the circulation in different parts of the body. These notions are entirely hypothetical. We shall see, hereafter, that our ignorance of the offices of the spleen, thymus, &c, is great; and we have already shown, that much more probable uses can be assigned to the portal system. The insufficiency of M. Broussais's doc- trine of diverticula is strikingly evidenced by the fact, that whilst the thymus gland disappears gradually in the progress of age, the thyroid remains, as well as the supra-renal capsules.1 The nature of the circulation in the brain, as well as the advantages of the tortuous arrangement of the carotids, which convey a great por- tion of the blood to it, has been referred to before.2 From the mode in which its vessels—arterial and venous—are distributed to it, a uniform supply of blood is secured; and it has been presumed, that this uni- formity exists to such a degree, that no augmented quantity of blood can exist in it so as to exert undue pressure on the cerebral neurine. Resting chiefly on the recorded results of certain experiments by Dr. Kellie,3 of Leith, many modern physiologists and therapeutists have maintained, that the quantity of blood in the cranium never varies; and that the brain is incompressible. Under this notion, Dr. Clutter- buck4 affirmed, that no additional quantity of blood can be admitted into the vessels of the brain, the cavity of the skull being already filled by its contents. "A plethoric state or overfulness of the cerebral ves- sels altogether, though often talked of, canliave no real existence; nor on the other hand can the quantity of blood within the vessels of the brain be diminished; no abstraction of blood, therefore, whether it be from the arm, or other part of the general system, or from the jugular veins (and still less from the temporal arteries) can have any effect on the bloodvessels of the brain, so as to lessen the absolute quantity of blood contained in them." Similar views were maintained by Monro Secundus,5 and Dr. Abercrombie,6 and they seemed to be supported by the experiments of Dr. Kellie, who inferred that, "in animals bled to death, whilst all the other organs of the body are nearly emptied of blood, the vessels of the brain contain the usual quantity; but that if, previous to bleeding an animal, a hole be made in its cranium, and the brain be thus exposed, equally with other organs, to atmospheric pres- sure, its vessels, like those of other parts of the body, will be emptied as the animal bleeds to death." It was important to establish the truth or inaccuracy of those views—influencing, as they were calculated to do, 1 Adelon, Physiologie de l'Homme, torn. iii. 328, 2de edit., Paris, 1829. 2 Vol. i. p. 107. 3 Medico-Chirurgical Transactions of Edinburgh, i. 2. * Art. Apoplexy, Cyclopaedia of Practical Medicine, Amer. edit., by the author, Philad., 1844. 5 Observations on the Structure and Functions of the Nervous System, Edinb., 1783. 6 Pathological and Practical Researches on Diseases of the Brain and the Spinal Cord, Amer. edit., Philad. PULSE. 183 and have done, in so essential a manner, the therapeutics of encephalic affections; and this has been conclusively accomplishd by Dr. Burrows.1 The experiments of Dr. Kellie were repeated by him, but with opposite results; and he concludes, that it is not a fallacy, as some suppose, that bleeding diminishes the actual quantity of blood in the cerebral vessels; —that by it we not only diminish the momentum of the blood in the cerebral arteries and the quantity supplied to the brain in a given time, but actually diminished the amount of blood in these vessels. "Whether,"—he remarks—"the vacated place is replaced by serum or resiliency of the cerebral substance under diminished pressure, is a question into which I will not enter." Dr. Burrows farther investigated, whether position can affect the quantity of blood in the vessels of the encephalon,—the opinion of Dr. Kellie from the results of his experiments having been in the negative. Two full grown rabbits were killed by hydrocyanic acid, and whilst their hearts still pulsated, one was suspended by the ears; the other by the hind legs. In this manner, they were left for twenty-four hours; and before they were taken down for examination, a tight ligature was placed around the throat of each, to prevent, as effectually as possible, any farther flow of blood to or from the head, after they were removed from their respective positions. The contrast in the appearance of the two animals was striking. The one presented a most complete state of anaemia of the internal as well as the external parts of the cranium ; the other a most intense hyperaemia or congestion of the same parts; and these opposite conditions induced solely by posture, and the gravitation of the blood. The erectile tissues offer a variety in the circulation, which requires some comment. Examples of these occur in the corpora cavernosa of the penis and clitoris; and in the nipple. They appear, according to Gerber,2 to consist of a plexus or rete of varicose veins enclosed in a fibrous envelope, with relatively minute interspaces, which are occupied and traversed in all directions by arteries, nerVes, contractile fibres, and by elastic, fibrous and areolar tissue. Of the particular arrangement of vessels in the corpora cavernosa, mention will be made hereafter: the mode of termination of the arteries in the erectile tissues has not been sufficiently studied, nor are views uniform in regard to their mode of action; some being of opinion, that they afford examples of vital ex- pansibility; but as before remarked (page 161), excitation is first induced in the nerves of the part—generally through the influence of the brain—and the turgescence of vessels is a consequence. The arrangement of the portal system of the liver is also peculiar, and has been given already (p. 99). g. The Pulse. We have had occasion, more than once, to refer to the subject of the pulse, or to the beat felt by the finger when applied over any of the larger arteries. Opinions have varied essentially regarding its cause. ' On Disorders of the Cerebral Circulation, Amer. edit., Philad., 1848. 2 Elements of General Anatomy, by Gulliver, p. 298, Lond., 1842. 184 CIRCULATION. Whilst most physiologists have believed it to be owing to distension of the arteries, caused by each contraction of the left ventricle; some have admitted a systole and diastole of the vessel itself; others, as Bichat and Weitbrecht,1 have thought that it is owing to the locomotion of the artery; others, that the impulse of the heart's contraction is transmitted through the fluid blood, as through a solid body; and others, as Dr. Young2 and Dr. Parry,3 that it is owing to the sudden rush forward of the blood in the artery without distension. Bichat was one of the first, who was disposed to doubt, whether the dilatation of the artery, which was almost universally admitted, really existed; or if it did, whether it was sufficient to explain the phenomenon; and, since his time, numerous experiments have been made by Dr. Parry, the result of which satisfied him, that not the smallest dilatation can be detected in the larger arteries, when they are laid'bare during life; nor does he believe, that there is such a degree of locomotion of the vessel as can account for the effect produced upon the finger. He ascribes the pulse to " impulse of distension from the systole of the left ventricle, given by the blood, as it passes through any part of an artery con- tracted within its natural diameter." Dr. Bostock4 appears to coincide with Dr. Parry, if we understand* him rightly, or at all. " According to this doctrine," he remarks, " we-must regard the artery as an elastic and distensible tube, which is at all times filled, although with the con- tained fluid not in an equally condensed state, and that the effect pro- duced upon the finger depends upon the amount of this condensation, or upon the pressure which it exercises upon the vessel, as determined by the degree in which it is capable of being compressed. Where there is no resistance to the flow of the blood along the arteries, there is no variation, it is conceived, in their diameter, and it is only the pressure of the finger or some other substance against the side of an artery that produces its pulse." Most of the theories of the pulse take the contractility of the artery too little into account. In pathology, where we have an opportunity for observing the pulse in various phases, we meet with sensations, com- municated to the finger, which it is difficult to explain upon any theory, except that of the compound action of the heart and arteries. The impulse is obviously that of the heart, and although the fact of disten- sion escaped the observation of Bichat, Parry, Weitbrecht, Lamure, Dbllinger, Rudolphi,5 Jager,6 and others, we ought not to conclude, that it does not occur. It is, indeed, difficult for us to believe, that such an impulse can be communicated to a fluid filling an elastic vessel with-; out pulsatory distension supervening. In opposition, too, to the nega- tive observations of Bichat and Parry, we have the positive averment 1 Comment. Acad. Imper. Scient. Petropol. ad An. 1734 and 1735, Petrop., 1740. * Croonian Lectures, in Philos. Transact, for 1809, part i. 3 An Experimental Inquiry into the Nature, Causes, and Varieties of the Arterial Pulse, by Caleb Hillier Parry, London, 1816; also, Additional Experiments on the Arteries of Warm-blooded Animals, &c, by Charles Henry Parry, M.D., &c, London, 1819. 4 Physiology, 3d edit., p. 246, Lond., 1836. 5 Grundriss der Physiologie, 2ter Band. 2te Abtjieil, s. 301, Berlin, 1828. 6 Tractatus Anatomico-physiologicus de Arteriarura Pulsu., Virceb., 1S30. PULSE. 185 of Dr. Hastings, and of Poiseuille,1 Oesterreicher, Segalas, and Wede- meyer, that the alternate contraction and dilatation of the larger arteries were clearly seen.2 The pulsations of the different arteries are pretty nearly synchronous with that of the left ventricle. Those of the vessels near the heart may be regarded as almost wholly so; but an appreciable interval exists in the pulsations of the more remote. We have remarked, that the arterial system is manifestly more or less affected by the nerves distributed to it; that it may be stimulated by irritants, applied to the great nervous centres, or to the nerves pass- ing to it; and this is, doubtless, the cause of many of the modifications of arterial tension, noticed in disease. Inflammation cannot affect a part of the system, for any length of time, without both heart and arteries participating, and affording unequivocal evidence of it. This, however, is a subject that belongs more especially to pathology. The ordinary number of pulsations, per minute, in the healthy adult male, is from seventy to seventy-five; but this varies greatly according to temperament, habit of life, position,—whether lying, sitting, or stand- ing, &c. Dr. Guy,3 from numerous observations, found the pulse, in healthy males, of the mean age of 27 years, in a state of rest, 79 when standing; 70, sitting, and 67, lying; the difference between standing and sitting being 9 beats; between sitting and lying, 3 beats; and be- tween standing and lying, 12 beats. When all exceptions to the general rule were excluded, the numbers were;—standing, 81; sitting, 71; lying, QQ;—the difference between standing and sitting being 10 beats ; be- tween sitting and lying, 5 beats; and between standing and lying, 15 beats. The effect, produced upon the pulse by change of posture, Dr. Guy ascribes to muscular contraction, whether employed to change the position of the body, or to maintain it in the same position. In chil- dren, the difference between the pulse in the sitting and lying posture is often very marked. In a boy, six years of age, observed by the author, it amounted to fifteen beats; and Dr. Evanson4 states, that he has often found the pulse—which at night (during sleep) was 80, full and steady—up to 100 or even 120 during the day, small and hurried,—■ and this in children six or seven years of age, and in perfect health. In some individuals in health, the number of beats is singularly few. The pulse of a person known to the author was on the average thirty- six per minute; and Lizzari5 affirms, that he knew a person in whom it was not more than ten. It is not improbable, however, that in these cases, obscure beats may have taken place intermediately, and yet not 1 Repertoire gen£rale d'Anatomie, &c, par Breschet, 1829, torn. vi. and vii, and Magendie's Journal de Physiol., viii. and ix. 2 For a mode of estimating the arterial distension, see Poiseuille, in Magendie's Journal de Physiologie, ix. 44, and Jules Herison's description of an instrument—Sphygmometer— which makes the action of the arteries apparent to the eye. 3 Guy's Hospital Reports, No. vi., April, 1838, p. 92. 4 Practical Treatise on the Management and Diseases of Children, by Messrs. Evanson and Maunsell: Amer. edit., by Dr. Condie, p. 19, Philad., 1843. 5 Raccolta D'Opusculi Scientifica, p. 265; and Good's Study of Medicine, Physiological Proem to class iii. Ha?matica. See Cases of Slowness of Pulse, by Mr. Mayo, Lond. Med. Gaz., May 5, 1838, p, 232. 186 CIRCULATION. have been detected. In a case of pericarditis, in which the author felt great interest, the pulse exhibited a decided intermission every few beats, yet the heart beat its due number of times; the intermission of the pulse at the wrist consisting in the loss of one of the beats of the heart. It was not improbable but that in this case the contractility of the aorta was unusually developed by the inflammatory condition of the heart; and that the flow of blood from the ventricle was thus occasionally spasmodically diminished or entirely impeded. The quickest pulse, which Dr. Elliotson1 ever felt, was 208, counted easily, he says, at the heart; though not at the wrist. The pulse of the adult female is usually from ten to fourteen beats in a minute quicker than that of the male. In infancy, it is generally irregular, intermitting, and always rapid, and it gradually becomes slower in the progress of age. It is, of course, impossible to arrive at any accurate estimate of its comparative frequency at different periods of life, but the average of the following numbers, on the authority of Heberden,2 Sommering, and Miiller,3 may, on the whole, be regarded as approximations. Ages. Number of beats per minute, according to Heberden. Sommering. Mailer. In the embryo, .... One month, -Three years, .... Seven years, .... Twelve years, .... Adult,..... Old age,..... 130 to 140 120 120 to 108 108 to 90 90 to 80 72 70 Do. 120 110 90 80 70 60 150 Do. 115 to 130 , 100 to 115 90 to 100 ' 85 to 90 80 to 85 70 to 75 50 to 65 Dr. Guy4 lays down the following as a near approximation to the average numbers at the several leading periods of life. It must be borne in mind, that, as in all similar cases, such averages can never apply to special examples. At birth, - - - - - 140 In infancy, ..... 120 Childhood,.....100 Youth,......90 Adult age, - - - • - 75 Old age,.....70 Decrepitude, - - - 75—80 Researches by MM. Hourmann aftd Dechambre,5 do not accord with these estimates in respect to the smaller number of pulsations in the aged. MM. Leuret and Mitivie had suspected an error in this matter from an examination of 71 of the aged inmates of the Bicetre and La Salpe'triere. MM. Hourmann and Dechambre examined 255 women 1 Human Physiology, p. 215, London, 1840. 2 Med. Transact., ii. 21. 3 Handbuch der Physiologie, Baly's translation, p. 171, London, 1838. < Art. Pulse, Cyclop, of Anat. and Physiol., Pt. xxxi. p. 183, Lond., May, 1848. 8 Archiv. Gen&rales de Med. pour 1835. PULSE—ACCORDING TO AGE AND SEX. 187 between the ages of 60 and 96, and found the average number of the pulse to be 82*29. M. Rochoux,1 however, still believes—from the results of his own observations as well as those of others—that, as a general rule, the frequency of the pulse diminishes in the progress of age. The attention of Dr. Pennock,2 of Philadelphia, has more recently been directed to the subject; and the author has great confidence in the authenticity of results recorded by him. In 170 males, and 203 females, of the average age of about 67, the average frequency of the pulse was 75. The difference between the pulse of the male and female continues to be well marked in advanced life. MM. Leuret and Mitivie found the average frequency in 27 aged men, 73; and in 34 aged women, 79. The average obtained by Dr. Pennock was 72 for the former; 78 for the latter: Dr. Gorham3 assigns 130 as the mean number of the pulse from five months to two years old; and 107*63 from two to four years of age, whence the number continues almost the same up to the tenth year. His estimates, however, are much higher than those of M. Valleix.4 M. Trousseau,5 from repeated observations, infers, that but little stress ought to be laid on the pulse in the diagnosis of disease in infants. He found, that during the first two weeks, it may vary from 78 to 150 ; during the second fortnight, from 120 to 164 ; from one to two months, from 96 to 132; two to six months, 100 to 162; six to twelve months, 100 to 160 ; and from twelve to twenty-one months, 96 to 140. From the observations of MM. Billard, Valleix, and others, it would seem, that the pulse of the foetus at the moment it is expelled from the uterus often falls to 83 in the minute, and, in some minutes afterwards, rises to 160. In the course of the first day, it falls again to 127, and con- tinues to diminish during the first ten days, the average being then from 87 to 90. These are, however, only averages: the variations are very great. Sex appeared to have some influence. In infants, from eight days to six months old, the average number of pulsations for boys was 131; for girls, 134; from six to twenty-one months, the average for boys was 113; for girls, 126. The state of sleeping or waking had a greater influence. In infants from fifteen days to six months old, the average of the pulse was 140 during waking.; 121 during sleep. He has known it rise from 112 to 160 and 180, when the child cried or struggled. On the whole, M. Trousseau concludes, that the pulse of children at the breast varies from 100 to 150. After the first two months, it is a little more frequent in females than in males; and is about 20 higher in the waking than in the sleeping state. Strange to say, it may be wholly absent, without the health seeming to be interfered with. A case of the kind is referred to by Prof. S. Jackson,6 as having occurred in the mother of a physician of Philadel- 1 Art. Pulse, in Diet. de'Med., 2d edit., xxv. 619, Paris, 1842. 2 Amer. Journ. of the Medical Sciences, July, 1847, p. 68. 3 Lond. Med.Gaz., Nov. 25,1837. « Memoires de la Societe Medicale d'Observation de Paris, torn, ii., Paris, 1844. ft Journ. des Connaiss. Med. Chir., Juillet & Aout, 1841; cited in Amer. Journ. Med. Sciences, Oct., 1841, p. 458, and Jan., 1842, p. 199. 6 The Principles of Medicine, founded on the Structure and Functions of the Animal Or- ganism, p. 492, Philad., 1832. A case of complete disappearance of the beating of the heart 188 CIRCULATION. phia. The pulse disappeared during an attack of acute rheumatism, and could never again be observed. Yet she was active in body and mind,.and possessed unusual health. In no part of the body could a pulse be detected. Dr. Jackson attended her during a part of her last illness—inflammation of the intestines; no pulse existed. She died whilst he was absent from the city, and no examination of the body was made. Between the number of pulsations and respirations there would not appear to be any fixed relation. In many persons the ratio in health is 4 to l,1 but in disease it varies greatly. Dr. Elliotson2 alludes to a case of nervous disease in a female at the time in no danger whose respiration was 106, and pulse 104. Dr. Knox3 has made some observations on the pulsations of the heart, and on its diurnal revolution and excitability, from which he infers: 1. The velocity of the heart's action is in a direct ratio with the age of the individual,—being quickest in young persons, slowest in the aged. There may be exceptions to this, but. they do not affect the general law. 2. There are no data to determine the question of an average pulse for all ages. 3. There is a morning acceleration and an evening retardation in the number of the pulsations independently of any stimulation by food, &c. 4. The excitability of the heart under- goes a daily revolution;—that is, food and exercise affect its action most in the morning and during the forenoon; less in the afternoon, and least of all in the evening. Hence it might be inferred, that the pernicious use of spirituous liquors must be greatly aggravated in those who drink before dinner. 5. Sleep does not farther affect the heart's action than through the cessation of all voluntary motion, and a re- cumbent position. 6. In weak persons, muscular action excites that of the heart more powerfully than in the strong and healthy; but this does not apply to other stimulants,—wine and spirituous liquors, for example. 7. The effect of the position of the body in increasing or diminishing the number of pulsations is solely attributable to the mus- cular exertion required to maintain the body in the sitting or erect posture; the debility may be measured by altering the position of the person from a recumbent to a sitting or erect one. 8. The most pow- erful stimulant to the heart's'action is muscular exertion. The febrile pulse never equals this.4 h. Uses of the Circulation. The chief uses of the circulation are,—to transmit to the lungs the products of absorption, in order that they may be.converted into arte- rial blood; and to convey to the different organs arterial blood, which is in Gazette Medicate, Nov. 21, 1836; and analogous cases are given in Parry on the Pulse, Bath, 1816, and in Medico-Chirurg. Review, xix. 285, and April, 1836. 1 Quetelet, Sur LHomme, p. 87; also, Guy, Pennock, &c, in Art. Pulse, op. cit., and Dr. John Reid, art. Respiration, ibid., pt. xxxii. p. 338, Lond., 1848. 2 Human Physiology, p. 215, Lond., 1835. See, also, Dr. Ch. Hooker, of New Haven, Conn., in Boston Medical and Surgical Journal, for May 16, 23, &c, 1838. 3 Edinburgh Medical and Surgical Journal, April, 1837. 4 The article on the Pulse, by Dr. Guy, in Cyclop, of Anat. and Physiology, is an excellent resume of the whole subject. USES. 189 is not only necessary for their vitality, but is the fluid by which the different processes of nutrition, calorification, and secretion are effected. These functions will engage us next. We may remark, in conclusion, that the agency of the blood, as the cause of health or disease, has had greater importance assigned to it than it merits; and that although the blood may be the medium, by which the source of disease is conveyed to other organs, we cannot look to it as the seat of those taints that are commonly referred to it. " Upon the whole," says Dr. Good,1 " we cannot but regard the blood as, in many respects, the most im- portant fluid of the animal machine; from it all the solids are derived and nourished, and all the other fluids are secreted; and it is hence the basis or common pabulum of every part. And as it is the source of general health, so is it also of general disease. In inflammation, it takes a considerable share, and evinces a peculiar appearance. The miasms of fevers and exanthems are harmless to every part of the sys- tem, and only become mischievous when they reach the blood; and emetic tartar, when introduced into the jugular vein, will vomit in one or two minutes, although it might require perhaps half an hour if thrown into the stomach, and in fact it does not vomit till it has reached the circulation. And the same is true of opium, jalap, and most of the poisons, animal, mineral, and vegetable. If imperfectly elaborated, or with a disproportion of some of its constituent principles to the rest, the whole system partakes of the evil, and a dysthesis or morbid habit is the certain consequence; whence tabes, atrophy, scurvy, and various species of gangrene. And if it becomes once impregnated with a pecu- liar taint, it is wonderful to remark the tenacity with which it retains it, though often in a state of dormancy and inactivity for years, or even entire generations. For as every germ and fibre of every other part is formed and regenerated from the blood, there is no other part of the system that we can so well look to as the seat of such taints, or the predisposing cause of the disorders I am now alluding to; often corporeal, as gout, struma, phthisis: sometimes mental, as madness; and occasionally both, as cretinism." This picture is largely overdrawn. Setting aside the erroneous pathological notions that assign to the blood what properly belongs to cell life in the system of nutrition, how can we suppose a taint to con- tinue for years, or even entire generations, in a fluid which is perpetu- ally undergoing mutation; and, at any distant interval, cannot be presumed to have one of its quondam particles remaining? Were all hereditary diseases derived from the mother, we could better compre- hend this doctrine of taints; inasmuch as, during the whole of foetal existence, she transmits the pabulum for the support of her offspring: the child is, however, equally liable to receive the taint from the father, who supplies no pabulum, but merely a secretion from the blood at a fecundating copulation, and from that moment can exert no influence on the character of the progeny. The impulse to this or that organi- zation or conformation must be given from the moment of union of the particles, furnished by each parent at a fecundating intercourse; and 1 Op. cit. 1 190 CIRCULATION. it is probable, that no material influence is exerted subsequently even by the mother, except through the pabulum she furnishes. The em- bryo accomplishes its own construction, as independently of the parents as the chick in ovo. i. Transfusion and Infusion. The operation of Transfusion,—as well as of Infusion of medicinal agents,—was referred to in an early part of this chapter, to prove the course of the circulation to be from the arteries into the veins. Both these operations were suggested by the discovery of Harvey. The former, more especially, was looked upon as a means of curing all dis- eases, and of renovating the aged ad libitum. The cause of every disease and decay was presumed to reside in the blood, and, conse- quently, all that was necessary was to remove the faulty fluid, and substitute pure blood obtained from a healthy animal in its place. As a therapeutical agency, the history of this operation does not belong to physiology. The detail of the fluctuation of opinions regard- ing it, and its total disuse, are given at some length in the Histories of Medicine, to which we must refer the reader.1 It appears to have been first performed on man in France by Denis and Emmerez in 1666; and in the following year it was practised in England by Drs. Lower and King.2 Before this, however, many experiments had been made on animals. In his "Diary" under the date of the 14th of November, 1666, Pepys3 has the following entry:—"Dr. Croone told me, that at the meeting of Gresham College to-night, which, it seems, they now have every Wednesday again, there was a pretty experiment of the blood of one dog let out, till he died, into the body of another on one side, while all his own run out on the other side. The first died upon the place, and the other very well, and likely to do well. This did give occasion to many pretty wishes, as of the blood of a Quaker to be let into an Archbishop, and such like; but, as Dr. Croone says, may, if it takes, be of mighty use to man's health, for the amending of bad blood by borrowing from a better body." There are some interesting physiological facts, connected with trans- fusion, that cannot be passed over. MM. Provost and Dumas found that the vivifying power of the blood does not reside so much in the serum as in the red particles. An animal bled to syncope was not revived by the injection of water or of pure serum at a proper temperature; but if blood of one of the same species was used, the animal seemed to acquire fresh life, at every stroke of the piston, and was at length restored. The operation was revived by Dr. Blundell,4 and by MM. PreVost and Dumas;5 the first of whom employed it with safety, and he thinks with happy effects, in exhausting uterine hemorrhage. All these gen- 1 Sprengel, K., Histoire de Medecine, par Jourdan, iv. 120, Paris, 1815. 2 J. P. Kay, art. Transfusion, Cyclopaedia of Practical Medicine, Amer. edit., by the author, iv., 468, Philad., 1845; and The Physiology, &c. of Asphyxia, p. 254, Lond., 1834. 3 Diary and Correspondence of Samuel Pepys, F. R. S., by Lord Braybrooke, 3d edit., iii. 336, London, 1848. 4 Medico-Chirurgical Transactions, ix. 56; and x. 296 ; and Researches physiological and pathological, p. 63, London, 1825. 6 Bibliotheque Universelle, xvii. 215. TRANSFUSION AND INFUSION. 191 tlemen remark, that it can only be adopted with perfect safety in ani- mals of like kinds, or in those the corpuscles of whose blood are of similar configuration. MM. PreVost and Dumas, Dieffenbach,1 and Bischoff,2 all agree as to the deadly influence of the blood of the mam- malia when injected into the veins of birds. This influence, according to Miiller, is in some way connected with the fibrin of the blood, and experiments have certainly shown, that blood deprived of fibrin acts most injuriously when injected into the vessels.3 The introduction of the practice of infusing medicinal agents into the blood was coeval with that of transfusion. It appears to have been first subjected to a philosophical examination by Sir Christopher Wren, who practised it on a malefactor in 1656.4 It is a singular fact, that in cases of infusion, medicinal substances are found to exert their specific actions upon certain parts of the body, precisely in the same manner as if they had been received into the stomach. Tartar emetic, for example, vomits, and castor oil purges, not only as certainly, but with much greater speed; for, whilst the former, as before remarked, requires to be in the stomach for fifteen or twenty minutes, before vomiting is excited, it produces its effect in one or two minutes, when thrown into the veins. Dr. E. Hale, of Boston, has published an interesting pamphlet on this subject.5 In it he traces the history of the operation, detailing several interesting- experiments upon animals; and one upon himself, which consisted in the introduc- tion of a quantity of castor oil into the veins. In this experiment, he did not feel much inconvenience immediately after the injection; but very speedily experienced an oily taste, which continued for a length of time, and the medicine occasioned much gastric and intesti- nal disturbance, but did not act as a cathartic. Considerable difficulty was experienced in the introduction of the oil, to which circumstance M. Magendie6 ascribes Dr. Hale's safety; for it is found, by experi- ments on animals, that viscid fluids, such as oil, are unable to pass through the pulmonary capillaries, in consequence of which the circu- lation is arrested, and death follows. Such, also, appears to have been the result of the experiments of Dr. Hale with powdered substances. The injection of medicines into the veins has been largely practised at the Veterinary School of Copenhagen, and with complete success— the action of the medicine being incomparably more speedy, and the dose required much less. It is rarely employed by the physician, except in experiments on animals; but it is obvious, that it might be had recourse to with happy effects, where narcotic and other poisons have been taken, and where the mechanical means for their removal are not at hand. 1 Die Transfusion des Blutes, Berlin, 1828. 2 Miiller's Archiv., 1835; cited in Baly's translation of J. Miiller's Handbnch, u. s. w. 3 See, on the different effects of transfusion of arterial and venous blood on animals, Bis- choff in Muller's Archiv., Heft iv. 1838, cited in Brit, and For. Med. Rev., April, 1839, p. 548. 4 Chelius, System of Surgery, translated by South, Amer. edit., iii. 626, Philad., 1847. 5 Boylston Medical Prize Dissertations, for the years 1819 and 1821, p. 100, Boston, 182*1. 6 Pr4cis, &c, ii. 430. 192 CIRCULATION. 4. CIRCULATORY APPARATUS IN ANIMALS. .In concluding this subject, a brief allusion to the circulatory appa- ratus of other parts of the animal kingdom may be interesting and instructive. In the mammalia in general, the inner structure of the heart is the same as in man; but its situation differs materially ; and in some of them, as in the stag and pig, two small flat bones, called bones of the heart, exist, where the aorta arises from the left ventricle. In the amphibious mammalia and the cetacea, it has been supposed, that the foramen ovale in the septum between the auricles is open as in the human foetus, to allow them to pass a considerable time under water without breathing; but the observations of Blumenbach, Cuvier, and others seem to show, that it is almost always closed. Sir Everard Home found it open in the sea otter, in two instances; but these are regarded by naturalists as exceptions to the general rule. In several of the web-footed mammalia and cetacea, as in the common otter, sea otter, and dolphin, particular vessels are always greatly enlarged and tortuous;—a structure which has been chiefly noticed in the vena cava inferior, and is supposed to serve the purpose of a diverticulum, whilst the animal is under water; or to receive a part of the returning blood, and retain it until respiration can be resumed. In birds, the structure of the heart universally possesses a singular peculiarity. Instead of the right ventricle having a membranous valve, as in the left, and as in all the mammalia, it is provided with a strong, tense, and nearly triangular muscle, which aids in the propulsion of the blood from the right side of the heart into the lungs. This is pre- sumed to be necessary, in consequence of their lungs not admitting of expansion like those of the mammalia, and of their being connected with numerous air-cells. The heart of reptiles or amphibia in general consists either of only one ventricle, or of two, which freely communicate, so as to constitute essentially but one. The number of auricles always corresponds with that of the ventricles. That the cavities—auricular and ventricular- are, however, single, although apparently double, is confirmed by the fact, that, in all, there is only a single artery proceeding from the heart, which serves both for the pulmonic and systemic circulations. After this vessel has left the heart, it divides into two branches, by one of which a part only of the blood is conveyed to the lungs, whilst the other proceeds to different parts of the body. These two portions are united in the heart, and after being mixed together "are sent again through the great artery. In these animals, therefore, aeration is less extensive than in the higher; and we can thus understand many of their peculiarities;—how, for example, the circulation may continue, when the animal is so situate as to be incapable, for a time, of respi- ration; as well as the great resistance to ordinary deranging influences, by which they are characterized. Fig. 304 represents the circulatory apparatus of the frog; in which E is the ventricle and D the auricle. From the former arises the aorta F, which soon divides into two trunks. These, after sending branches to the head and neck, turn IN ANIMALS. 193 Circulation in the Froar. Circulation in Fishes. Fig. 306. downwards, (0 and P,) Fis- 304 and unite in the single trunk A. This vessel sends arteries to the body and limbs, which ultimately terminate in veins, and unite to form the vena cava C. From each of the trunks into which the aorta bifur- cates at its origin arise the arteries F. These are distributed to the lungs, and communicate with the pulmonary veins, which return' the blood to the auricle, D, where it becomes mixed with the blood of the systemic circulation. In the tadpole state, the circulation is branchial, as in fishes. The heart then sends the whole of its blood to the branchise or gills, and it is returned by veins fol- lowing the course of the dotted lines M and N, (Fig. 304,) which unite to form the descending aorta. As the lungs undergo their developement, small arterial branches arise from the aorta and are distributed to those organs; and in proportion as these arteries enlarge, the original branchial arteries diminish, until ultimately they are ob- literated, and the blood flows wholly through the enlarged lateral trunks, 0 and P, which, by their union, form the descending aorta. In fishes, the heart is extremely small, in pro- portion to the body; and its structure is simple; consisting of a single auricle and ventricle D and E (Fig. 305). From the ventricle E an arterial trunk arises, which, in most fishes, is expanded into a kind of bulb, F, as it leaves the heart, and proceeds straight forward to the branchise or gills, G and H. From these, the blood passes into a large artery, A, analogous to the aorta, which pro- ceeds along the spine, and conveys the blood to the various parts of the system; and, by the vena cava, C, the blood is returned to the auricle. This is, consequently, a case of single circulation. Insects appear to be devoid of bloodvessels. Cuvier examined all the organs in them, which, in tS^f^iti\n red-blooded animals, are most vascular, without •£ p^j^ g.'uterus, (sir discovering the least appearance of a bloodvessel, although extremely minute ramifications of the trachea were obvious in vol. n.—13 [Interior of the Leech. a, a. Respiratory cells. b, b. Two large arteries. c. Mucous glands, d, d. 194 NUTRITION. every part. Insects, however, both in their perfect and larve state, have a membranous tube running along the back, in which alternate dilatations and contractions are perceptible, and which has been con- sidered as their heart; but it is closed at both ends, and no vessels can be perceived originating from it. To this the innumerable ramifications of the trachea convey the air, and thus, as Cuvier has remarked, " le sang ne pouvant aller chercher l'air, c'est Fair qui va chercher le sang;" ("the blood not being able to go in search of the air—the air seeks the blood.") Carus, however, discovered a continuous circulation through arteries and veins in a few of the perfect insects, and especially in some larves. Lastly: in many genera of the class vermes, particularly amongst molluscous animals, there is a manifest heart, which is sometimes of a singular structure. Some of the bivalves—it is affirmed—have as many as four auricles; whilst many animals, as the leech and Lum- bricus marinus, have no heart; but circulating vessels exist, in which contraction and dilatation are perceptible. The marginal figure, (Fig. 306,) of the interior of a leech, given by Sir Everard Home, exhibits the mode of circulation and respiration in that animal. There is no heart, but a large vessel exists on each side. The water is received, through openings in the belly, into the cells or respiratory organs, and passes out through the same. CHAPTER. V. NUTRITION. The investigation of the phenomena of the circulation has exhibited the mode in which arterial blood is distributed over the body in minute vessels, not appreciable by the naked eye, and often not even with the microscope, and so numerous, that it is impossible for the finest-pointed instrument to be forced through the skin without penetrating one, and perhaps several. It has been seen, likewise, that, in the capillary system of vessels, this arterial blood is changed into venous; and it was observed, that in the same system, parts are deposited or separated from the blood, and certain phenomena occur, into the nature of which we have now to inquire; beginning with those of nutrition, which com- prise the incessant changes that are taking place in the body, both of absorption and deposition for the decomposition and renovation of each organ. Nutrition is well defined by M. Adelon1 as the action, by which every part of the body, on the one hand, appropriates or assimilates to itself a portion of the blood distributed to it; and, on the other, yields to the absorbing vessels a portion of the materials that previously com- posed it. The precise character of the apparatus,, by which this im- portant function is accomplished, we have no exact means of knowing. All admit that the old matter must be taken up by absorbents, and the new be deposited by arteries, or by vessels continuous with them. As the precise arrangement of these, minute vessels is not perceptible by 1 Physiologie de l'Hornme, torn. iii. p. 359, 2de edit., Paris, 1829. NUTRITION. 195 the eye, even when aided by powerful instruments, their arrangement has given rise to controversy. Whilst some have imagined lateral pores in the capillaries, for the transudation of nutritive deposits; others have presumed, that inconceivably small vessels are given off from the capil- lary system, which constitute a distinct order, and whose function is to exhale the nutritive substance,—an idea, which, as has been said else- where, has been revived by M. Bourgery.1 Hence, they have been termed exhalants or nutritive exhalants; but the anatomical and phy- siological student must bear in mind, that whenever the term is used by writers, they do not always pledge themselves to the existence of any distinct set of vessels, but merely mean the minute vessel, whatever may be its nature, which is the agent of nutrition, and conveys the pabulum to the different tissues. In investigating the physiology of nutrition, two antagonistic pro- cesses demand attention; 1st. Decomposition, by which the tissue yields to the absorbing vessels a portion of its constituents; and 2dly. Com- position, by which it assimilates a part of the arterial blood that enters it, and supplies the loss it had sustained by the previous act of decom- position. The former of these actions obviously belongs to the function of absorption; but its consideration was deferred, in consequence of its close application to the function we are about to investigate. It comprises what is meant by interstitial, organic, or decomposing absorption, and does not require many comments, after the long investigation of the general phenomena of absorption into which we entered. The conclu- sion, then arrived at, was,—that the chyliferous and lymphatic vessels form only chyle and lymph respectively, refusing the admission of all other substances;—that the veins admit every liquid which possesses the necessary tenuity; and that whilst all the absorptions,—which re- quire the substance acted upon to be decomposed and transformed,— are effected by the chyliferous and lymphatic vessels, those that demand no alteration are accomplished through the coats of the veins by imbi- bition. It is easy, then, to deduce the agents to which we refer the absorption of decomposition. As it is exerted on solids, ano) as these cannot pass through the coats of the vessel in their solid condition, it follows that other agents than the veins must accomplish the process; and, again, as we never find in the lymphatic vessels any thing but lymph, and have every reason to believe, that an action of selection is exerted at their extremities, similar to that of the chyliferous vessels on the heterogeneous substances exposed to them, we naturally look to the lymphatics as the main, if not the sole, organs concerned in the absorption of solids. It has been maintained, by some physiologists, that the different tis- sues are endowed with a vital attractive and elective force, which they exert upon the blood;—^that each tissue attracts only those materials of which it is itself composed; and thus, that the whole function of nutrition is an affair of elective affinity; but this, obviously, cannot be the force that presides over the original formation of the tissues in the embryo. An attraction cannot be exerted by parts not yet in existence. 1 See page 92 of this volume. 196 NUTRITION. To account for this, it has been imagined, that a peculiar force is destined to preside over formation and nutrition, and various names have been assigned to it. By most of the ancients it was termed facul- tas formatrix, nutrix, auctrix; by Van Helmont,1 Bias alterativum; and by Bacon,2 motus assimilationis. It is the facultas vegetativa of Harvey;3 the anima vegetativa of Stahl;4 the puissance du moule in- terieur of Buffon ;5 the vis essentialis of C. F. Wolff;6 and theBildungs- trieb or nisus formativus of Blumenbach and most German writers.7 This force is meant, when writers speak of germ force, plastic force, force of nutrition, force of formation, and force of vegetation. Whatever dif- ference there may be in the terms selected, all appear to regard it as charged with maintaining, for a certain length of time, living bodies and all their parts, in the possession of their due composition, organization, and vital properties; and of putting them in a condition, during a cer- tain period of their existence, to produce beings of the same kind as themselves. It is obvious, however, that none of these terms elucidate the intricate phenomena of nutrition, and none express more than— that living bodies possess a vital force, under the action of which, formation and nutrition are accomplished. The important—indispensable actions—that constitute nutrition occur in the tissues "supplied by the intermediate or capillary system of ves- sels; but not in those vessels themselves. Their function is to convey to the system of nutrition the pabulum or material from which the tissues are formed; but the formation of the tissues takes place on the outside of the vessel; and the organic cells are the immediate agents. It is not, however, the whole of the circulating fluid that constitutes such pabulum. The blood corpuscles—excepting in a single case, men- struation—are not found outside the vessels in the exercise of the healthy functions. The liquor sanguinis alone transudes, and is the material on which the nucleated cell exerts its plastic power.8 Under the idea that all the vessels of the capillary system are possessed of coats, it is not so easy to comprehend how either nutrition or secretion can be accomplished. Were we to adopt the opinion, before referred to, that many of the vessels of the capillary system consist of membraneless or coatless tubes, it would be more readily understood, that by the elective and attractive forces possessed by the tissues and exerted by them on the blood, materials may be obtained from that fluid as it passes through the intermediate system of vessels, which may be inservient to the nutrition of the tissues bathed by it. The mode in which the blood is distributed through the tissues may be likened to the distribution of the water of a river through a marsh, which conveys to the animal and vegetable bodies that flourish in it the materials for their nutrition. To adopt the language of an 1 Opera, pars i. 2 Novum Organum, lib. ii., aphor. 48. 3 De Generatione Animalium, Lond., 1651, p. 170. 4 Theoria Medica Vera. Hal., 1708. 5 Histoire Naturelle, torn. ii. e De Generatione, Hal., 1759. ' Comment. Societ. Gotting., torn, viii.; and Institutiones Physiologies?, § 31, Gotting., 1798. s Mulder, The-Chemistry of Vegetable and Animal Physiology, translated by Fromberg, p. 597, Edinburgh and London, 1849. AGENTS OF NUTRITION. 197 intelligent and philosophical writer,1 "In every part of the body, in the brain, the heart, the lung, the muscle, the membrane, the bone, each tissue attracts only those constituents of which it is itself com- posed. Thus the common current, rich in all the proximate constituents of the tissues, flows out to each. As the current approaches the tissue, the particles appropriate to the tissue feel its attractive force, obey it, quit the stream, mingle with the substance of the tissue, become identified with it, and are changed into its own true and proper nature. Mean- time, the particles which are not appropriate to that particular tissue, not being attracted by it, do not quit the current, but, passing on, are borne by other capillaries to other tissues, to which they are appropri- ate, and by which they are apprehended and assimilated. When it has given to the tissues the constituents with which it abounded, and received from them particles no longer useful, and which would become noxious, the blood flows into the veins, to be returned by the pulmonic heart to the lung, where, parting with the useless and noxious matter it has accumulated, and replenished with new proximate principles, it returns to the systemic heart, by which it is again sent back to the tissues." Particles of blood are seen to quit the current and mingle with the tissues; particles are seen to quit the tissues, and mingle with the cur- rent ; but all that we can see, as Dr. Smith has remarked, with the best aid we can get, does but bring us to the confines of grand operations, of which we are altogether ignorant. It would not seem, however, to be necessary for the nutrition of certain parts, that they should receive capillary vessels. There are tissues, commonly termed extra-vascular, in the substance of which neither injection nor the microscope has exhi- bited the existence of bloodvessels, and which would seem to derive their nourishment by imbibition from blood flowing in the vessels of adjacent tissues. To these belong the crystalline body, epidermis and epithelium, hair, nails, enamel of the teeth, &c, &c. We have said that the main, if not the sole, agents of the absorption of solids are the lymphatics. > Almost all admit, that they receive the products of the absorption of solids; but all do not admit, that the action of taking up solid parts is accomplished immediately by the absorbents. They who think, that a kind of spongy tissue or "paren- chyma" exists at the radicles of the absorbent vessels, believe that this sponge possesses a vital action of absorption, when bodies, possess- ing the requisite constitution and consistence, are, put in contact with it; but they maintain, that the solid parts are broken down by the same agents—the extreme arteries—which secreted them, and that, when reduced to the proper fluid condition, they are imbibed by the paren- chyma, and conveyed into the lymphatics. But if the existence of this sponge were demonstrated, the above explanation would scarcely be admissible, for the sponge could not be conceived to do more than imbibe; it Could not break down solids, and reduce them to lymph—the only fluid which, as we have seen, is ever met with in lymphatics. Its existence is, however, altogether supposititious. Besides, the arrangement has not been invoked in favour of the chyliferous vessels, which are so analogous in their organization and functions to the lymphatics. It has not been 1 The Philosophy of Health, by Dr. Southwood Smith, vol. i._p. 405, London, 1835. 1 198 NUTRITION. contended, that the arteries of the intestinal canal form the chyle from the alimentary matters in the small intestine, and that the office of the chyliferous vessels is restricted to the reception of this chyle, imbibed and brought in contact with their radicles by the ideal sponge or parenchyma. We have before shown, that there is every reason for the belief, that a vital action of selection and elaboration exists at the very origin of the chyliferous vessels; and the same may be inferred of the lymphatics. The great difficulty has been to understand how either exhaling artery or absorbing lymphatic can reduce the solid matter—of bone, for ex- ample—to the constitution and consistence requisite for entering the lymphatics; but we might conceive, that the latter as readily as the former, by virtue of its vital properties—for the operation must be admitted by all to be vital—and by means of its contained fluid, might soften the solid so as to admit of its.being received into the vessel. We should still, however, have to explain the mysterious operation by which those absorbents are enabled to reduce to their elements, bone, muscle, tendon, &c, and to recompose them into the form of lymph. Dr. Bostock1 fancifully suggests, that the first step in this series of operations is the death of the part; by which expression he means, that it is no longer under the influence of arterial action. "It therefore ceases to receive the supply of matter which is essential to the support of all vital parts, and the process of decomposition necessarily com- mences." The whole of his remarks on this subject are eminently gratuitous, and appear to" be suggested by an extreme unwillingness to ascribe the process to any thing but physical causes. If there be, how- ever, any one phenomenon of the animal economy, which is more mani- festly referable to vital action than another, it is the function of nutrition, both as regards the absorption of parts already deposited, and the exha- lation of new. We know that the blood contains most of the principles that are necessary for the nutrition of organs, and that it must contain the elements of all. Fibrin, albumen, fat, osmazome, salts, &c, exist in it, and these are deposited, as the blood traverses the tissues; but why one of these should be selected by one set of vessels, and another by another set, and in what manner the elements of .those, not already formed in the blood, are brought together, is unknown to us. Blood has been designated as "liquid flesh,"—chair coulante,—but something more than simple transudation through vessels is necessary to form it into flesh, and to give it the compound organization of fibrin, gelatin, osmazome, &c.—in the form of muscular fibre and areolar membrane— as we observe in the muscle. Nothing, perhaps, has more clearly exhi- bited the want of knowledge on this subject than the following vague attempt at solving the mystery by one of the most distinguished physi- ologists of the age. " Some immediate principles, that enter into the composition of the organs or of the fluids, are not found in the blood,— such as gelatin, uric acid, &c. They are consequently formed at the expense of other principles, in the parenchyma of the organs, and by a chemical action, the nature of, which is unknown to us, but which is 1 System of Physiology, edit, cit., p. 625. AGENTS OF NUTRITION. 199 not the less real, and must necessarily have the effect of developing heat and electricity." The views of recent histologists have approximated us more to a true knowledge of this mysterious action. They have not been content with endeavouring to reduce the different organized textures to primary fibres and filaments, but, by the aid of the microscope, have attempted to discover the particular arrangement and mode of formation of the constituent corpuscles. The discovery of that valuable instrument gave the impulse; and very soon the scientific world was presented with the results obtained by numerous observers. These observations have been, from time to time, continued until the present day. It is, however, to be regretted, that, until recently, our information, derived from this source, was not as accurate as was desirable. From different quarters, the most discordant statements were presented, exhibiting clearly, either that the narrators employed instruments of very different powers, or that they were blinded, or had the vision depraved, by preconceived theories or hypotheses. One of the very first effects of the discovery of the microscope was the detection by Leeuenhoek,1 of a globular structure of the primitive tissues of the body, an announcement which gave rise to much controversy, and has engaged the attention particu- larly of Prochaska,2 Fontana,3 Sir Everard Home, Mr. Bauer, the bro- thers Wenzel,4 M. Milne Edwards, MM. PreVost and Dumas,5 Dutro- chet, Hodgkin,6 Raspail, and others.7 The observations and experiments of Dr. Edwards, more especially, occasioned at the time much interest- ing speculation and inquiry. They may perhaps be taken as the foundation on which the believers in the globular structure of later years rested their opinions. His views were first published in 1823, in a com- munication, entitled "Memoire sur la Structure Slementaire des princi- paux Tissues Organiques des Animaux ;" and in a second article in the Annales des Sciences Naturelles, for December, 1826, entitled "Re- cherches microscopiques sur la Structure intime des Tissues Organiques des Animaux." He ex- Fig. 307. amined all the principal textures of the body, the areolar tissue, membranes, tendons, muscular fibre, nervous tissue, skin, coats of the blood- vessels, &c. When the areolar tissue was viewed through a powerful lens, it seemed to consist of cylinders; but, by using still higher magnifying powers, these cylinders were found to be formed of rows of globules of the same size, that is, about the ^^th or g^^th of an inch in dia- meter (Fig. 307); separated from each other, and lying in various directions; crossing and interlac- P ., , • i , .i i i Areolar Tissue ing; some ot the rows straight; others bent, and wards.) 1 Opera^ Omnia, Lugdun. Batav., 1722. 2 De Structura Nervorum, Vind., 1779. 3 Sur les Poisons, ii. 18. * De Structura Cerebri, Tubing., 1812. 5 Bibliotheque Universelle des Sciences et Arts, t. xvii. 6 In Drs. Hodgkin's and Fisher's translation of W. Edwards, Sur les Agens Physiques Lond., 1832. ' i Klencke, Ueber das Physiologische und Pathologische Leben der Mikropischenzellen Jena, 1844. 200 NUTRITION. 308. some twisted, forming irregular layers united by a kind of network. The membranes, which consist of areolar tissue, were found to present exactly the same kind of arrangement. The muscular fibre, when examined in like manner, was found to be formed of globules also g^o^th part of an inch in diameter. Here, however, the rows of globules are always parallel. The fibres never intersect each other like those of areolar tissue, and this is the only discernible difference,— the form and size of the globules being alike. The size of the glob- ules, and the linear arrangement they assume, seemed to be the same in all animals that possess a muscular structure. (Fig. 308.) The nervous structure has, by almost all observers, been esteemed globular—and a recent observer1 has satisfied himself that this is cer- tainly the most uniform appearance. The examination of M. Edwards yielded similar results. It seemed to be composed of lines of globules of the same size as those that form the areolar membrane and muscles; but holding an intermediate place as to the regularity of their arrange- ment, and having a fatty matter interposed between the rows. In regard to the size of the globules, however, M. Edwards differed materially from an accurate and experienced microscopic observer, Mr. Bauer, w ho asserted that the cerebral globules are of various sizes. (Fig. 309.) From the results of his own diversified observations, M. Edwards concluded, that " spherical corpuscles, of the diameter of -s£cth of a millimetre, constitute by their aggregation all the organic textures, whatever may be the properties, in other respects, of those parts, and the functions for which they are des- tined." The harmony and simplicity, which would thus seem to reign through the structures of the animal body, attracted great attention to the labours of M. Edwards. The vegetable king- dom was subjected to equal scrutiny; and—what seemed still more astounding—it was affirmed, that the microscope proved it also to be consti- tuted of globules precisely like those of the animal, and of the same magnitude, 5555th of an inch in diameter; hence, it was assumed, that all organized bodies possess the same elementary structure, and of necessity, that the animal and the vegetable are readily convertible into each other under favourable circumstances, and differ only in the greater or less complexity of their Nervous Tissue. (Edwards.) organization. Independently of all other objec- tions, however, the animal differs, as we have seen, from the vegetable, in composition; and this difference must exist not only in the whole, but in its parts; so that, even were it demon- 1 Calori, in Bulletino dello Scienze Medich. di Bologna, Sett., 1836, p. 152. 2 Philosoph. Transact, for 1S18; Sir E. Home, Lectures on Comparative Anatomy, vol. iii. lect. 3, Lond., 1823. Muscular Tissue. (Edwards.) Fig. 309. AGENTS OF NUTRITION. 201 strated that the globules of the beings of the two kingdoms are alike in size, it would by no means follow that they should be identical in intimate composition. The discordance, which we have deplored, is strikingly applicable to the case before us. The appearance of the memoir of Dr. Edwards excited the attention of M. Dutrochet, and in the following year his " Recherches" on the subject were published, in which he asserts, that the globules, which compose the different structures of invertebrated animals, are considerably larger than those of the vertebrated; that the former appear to consist of cells, containing other globules still smaller; and hence he infers, that the globules of vertebrated animals are likewise cellular, and contain series of still smaller globules. Dr. Edwards, in his experiments, found, that the globules of the nervous tissue, whether examined in the brain, in the spinal cord, ganglia, or nerves, have the same shape and diameter, and that no difference in them can be distinguished from whatever animal the tissue is taken. M. Dutrochet, on the other hand, considers, with Sir Everard Home, and the brothers Wenzel, that the globules of the brain are cellules of extreme minuteness, containing a medullary or nervous substance, which is capable of becoming concrete by the action of heat and acids. This structure, he remarks, is strikingly evidenced in certain molluscous animals; and he, instances the small Fig. 310. pulpy nucleus, which forms the cerebral hemisphere of Umax rufus, and helix pomatia, and is composed of glob- ular, agglomerated cellules, on the parietes of which a considerable number of globular or pvoid corpuscles are perceptible. (Fig. 310.) M. Dutrochet, again, did not find the structure of the CeSrs0chenin' nerves to correspond with that of the brain. < He asserts, ( that the elementary fibres, which enter into their composition, do not con- sist simply of rows of globules, according to the opinion of M. Edwards and others, but that they are cylinders of a diaphanous substance, the surface of which is studded with globular corpuscles; and that, as these cover the whole surface of the cylinder, we are led to believe that they are in the interior also. After detailing this difference of structure between the brain and the nerves, the former consisting chiefly of nerv- ous corpuscles, the latter chiefly of cylinders or fibres, M. Dutrochet announces the hypothesis, which exhibits too many indications of hav- ing been formed prior to his microscopic investigations,—that these cerebral corpuscles are destined for the production of the nervous power, and that the nervous fibres are tubes, filled with a peculiar fluid, by the agency of which nervimotion is effected. For further developements of the views of M. Dutrochet, the reader is referred to the work itself, which exhibits all the author's ingenuity and enthusiasm, but can scarcely be considered historical. The beautiful superstructure of M. Edwards, and the ingenuity of M. Dutrochet, were, however, most fatally assailed by subsequent ex- periments of Dr. Hodgkin with a microscope of unusual power. The globular structure of the animal tissues, so often asserted, and appa- rently so clearly and satisfactorily established by M. Edwards, is, as § 202 NUTRITION. we are told by Dr. Hodgkin,1 a mere deception; and the most minute parts of the areolar membrane, muscles, and nerves, were again referred to the striated or fibrous arrangement. A part of the discrepancy between MM. Edwards and Dutrochet may be explained by the fact of the former using an instrument of greater magnifying power than the latter, who employed the simple microscope only; and it was observed, that when the former used an ordinary lens, the arrangement of a tissue appeared cylindrical, which, with the compound microscope, was distinctly globular. The discordance between Messrs. Edwards and Hodgkin was reconcilable with more difficulty. On the whole subject, indeed, minds were kept in a state of doubt, and the rational physiolo- gist waited for ulterior developements. MM. Prevost and Dumas, and M. Edwards, farther affirmed, that all the proximate principles—albu- men, fibrin, gelatin, &c.,—assume a globular form, whenever they change from the fluid to the solid state, whatever may be the cause producing such conversion. M. Raspail2—a wayward genius, who has quitted the sober pursuit of science, for the uncertainty and turmoil of politics, from which he has suffered greatly—ranged himself among those who considered, that the ultimate structure of all organic textures is vesicu- lar, and that the organic molecule, in its simplest form, is an imperforate vesicle, endowed with the faculty of inspiring gaseous and liquid sub- stances, and of expiring again such of their elements as it cannot assi- milate ;—properties, which he conceived it to possess under the influence of vitality. His views contain, perhaps, the germ of those that follow, and that now occupy the minds of observers. The microscopical researches of Schwann and Schleiden3ledthemto af- firm, that the new-forming tissues of vegetables originate from a liquid gum or vegetable mucus, and those of animals probably Fig. 311. from the liquor sanguinis—which consists essentially of fibrin—after transudation from the capillary ves- sels. This matrix, in a state fully prepared for the formation of the tissue, is termed by them intercel- lular substance and cytoblastema. In the first in- stance, it exhibits minute granular points, which grow and become more regular and defined from the ag- glomeration of minuter granules around the larger, Primary Organic Cei1' constituting nuclei or cytoblasts or cell-germs, and showing the germina1 having, when fully formed, and in fact formed before NucieoSr'rToddand tnem' one or more well-defined bodies within, called Bowman.) nucleoli. From the cytoblasts, cells—primordial or germinal cells—are formed. A transparent vesicle grows over each, and becomes filled with fluid; this gradually extends and becomes so large that the cytoblast appears like a small body within its walls, and hence the cell is said to be nucleated. The form of the cells is at first irregular, then more regular, and they are alternately flattened 1 Op. citat., p. 466. 2 Op. citat., § 126. 3 Mikroskopische Untersuchungen iiber die Uebereinstimmung in der Struktur und dem Wachstum der Thiere und Pflanzen, von Dr. Th. Schwann und Schleiden, in Miiller's Archiv., p. 137, 1838; and Microscopical Researches into the Accordance and Growth of Animals and Plants, translated by Henry Smith, Sydenham Society edition, London, 1847. AGENCY OF CELLS IN NUTRITION. 203 Fig. 312. • "■© £) Q Plan representing the formation of a Nu- cleus, and of a Cell on the Nucleus, ac- cording to Schleiden's view. by pressure against each other, so as to assume different forms in different tis- sues. Such is their description of the vegetable cells from which all the tissues of plants take their origin. In like man- ner, the tissues of animals are formed from a fluid, in which nucleoli, nuclei or cytoblasts—and cells, are successively developed. The globules of lymph, pus, and mucus, are cells with their walls distinct and isolated from each other; horny tissues are cells with distinct walls, but united into coherent, tissues; bone, car- tilage, &c, are formed of cells whose walls have coalesced; areolar tis- sue, tendon, &c, are cells which have split into fibres, and muscles, nerves, and capillary vessels are cells whose walls and cavities have coalesced. These cells seem to possess an independent and limited life, which has no immediate connexion with that of the organism; the decomposi- tion constantly taking place in the living body being connected with the death of the cells of which the several parts are constructed; and for the reintroduction of which into the circulating fluid, the lymphatic system appears to be specially destined. By virtue of this vital power, they not only attract but change the substances brought in contact with them, or have a power of self-nutrition; and that this is probably independent of the nervous system is shown by an experiment of Dr. Sharpey, in which the reproduc- tion of a portion of the tail of a salamander took place, although it was cut off, after the organ had been completely paralysed by dis- secting out at its root a portion of the spinal cord, together with the arches of the vertebrae. To the doctrine of cell formation, Pro- fessor Goodsir,1 of Edinburgh, has, of late years, made several import- ant additions. Amongst other ob- servations, he states, that besides all organs and tissues having their • origin in and consisting essentially of simple or developed cells pos- sessed of a special independent vitality, the component cells are divided into numerous depart- ments, each of which consists of several cells arranged round one central or capital cell, which latter is the source whence all the other cells in its own department de- Fig. 313. Endogenous Cell-growth in Cells of a Melice- ritous Tumour. a. Cells presenting nuclei in various stages of developement into a new generation, b. Parent-cell filled with a new generation of young cells, which have originated from the granules of the nucleus. 1 Anatomical and Pathological Observations, p. 1, Edinb., 1845. 204 NUTRITION. rived their origin. To each of these several central nucleated cells he gives the name nutritive centre or germinal spot. Each nutritive centre possesses the power of absorbing materials of nourishment from the surrounding vessels, and of generating, by means of its nucleus, successive broods of young endogenous cells, which from time to time fill the cavity of the parent cell, and, carrying with them its cell-wall, pass off in certain directions, and under various forms, according to the texture or organ of which the parent forms a part. There are two kinds of nutritive centres,—those peculiar to the textures, and those belonging to organs. The former are in general permanent; the latter peculiar mostly to the embryonic state, and ultimately disappearing; but there is one form in which the nutritive centres are arranged both in healthy and morbid parts, which constitutes what Mr. Goodsir calls a germinal membrane. It is only met with on the free surface of organs or parts. It is a fine transparent membrane, consisting of cells arranged at equal and variable distances within it. The centres of these component cells are flattened, so that their walls form the mem- brane by cohering at their edges, and their nuclei remain in its sub- stance as germinal centres. One surface of the membrane is attached to that of the organ or part, and is, therefore, applied upon a more or less richly vascular tissue; the other is free, and it is to it only that the developed or secondary cells of its germinal spots are attached. These secondary cells, whilst forming, are contained between the two layers of the germinal membrane; but as they become developed, they carry forward the anterior layer, and become attached to the free sur- face, whilst the nuclei are left in the substance of the posterior layer in close contact with the bloodvessels, from which they derive the mate- rials for the formation of new cells. The doctrine of the developement of all the organic tissues from cells is now embraced by almost all histological inquirers; yet there are some who doubt it; and others, who by no means regard it as applicable to all the tissues. Thus M. Mandl1 objects to the term cytoblastema as applicable to the matrix or organizing material of the tissues, because it necessarily involves the supposition that it gives origin to cells. According to him, the elements, that are developed in the blastema—as he prefers to call it—do not generally deserve the name of cells, inasmuch as they may either liquefy as in the glands; consolidate as in the amorphous membranes; or become transformed directly into fibres, as in the areolar tissue. Mr. Gulliver,2 too, has inferred from his observations, that the mere extension of the parietes of cells is not essential to the formation of all tissues, since fine fibres or fibrils are found in fibrin that has coagulated even out of the body. He has given several figures to exhibit the analogy of structure between false membranes and fibrin coagulated after death, or after the removal of the blood from the body. Schwann, on the other hand, lays down the rule, which he considers of universal application, that all organic tissues, however different they may be, have one common principle of 1 Manuel d'Anatomie Generale, p. 549, Paris, 1843. 2 Appendix to Gerber's Anatomy, Atlas, p. 60, and Figs. 244-6, Lond., 1842. AGENCY OF CELLS IN NUTRITION. 205 developement as their basis, the formation of cells;—that is to say, nature never unites molecules immediately into a fibre, tube, &c.; but, always, in the first instance, forms a round cell; or changes, when it is requisite, the cells into the various primary tissues, as they present themselves in the adult state; but "how," says Mr. Gulliver,1 "is the origin of the fibrils, which I have depicted in so many varieties of fibrin, to be reconciled with this doctrine? and what is the proof that these, fibrils may not be the primordial fibres of animal textures? I could never see any satisfactory evidence, that the fibrils of fibrin are changed cells; and indeed, in many cases, the fibrils are formed so quickly after coagulation, that their production, according to the views of the eminent physiologist just quoted [Schwann], would hardly seem possible. Nor have I been able to see, that these fibrils arise from the interior of the blood-disks, like certain fibres delineated in the last interesting researches of Dr. Barry." Mr. T. Wharton Jones,2 also, has considered the notion entertained by Dr. Barry,3 that a fibre exists in the interior of the blood corpuscles, and that these fibres, after their escape from them, constitute the fibres which are formed by the con- solidation of the fibrin of the liquor sanguinis, to be erroneous. He regards the appearance as altogether illusive. Dr. Carpenter,4 in remarking on Mr. Gulliver's figures, all of which, as he properly observes, clearly show, that a small portion of coagulated fibrin contains a far larger number of fibres than we can imagine to be contained in the number of blood-disks that would fill the same space, states, that he has discovered a very interesting example of a membrane composed almost entirely of matted fibres, which so strongly resembles the deline- ations of fibrous coagula given by Mr. Gulliver, that he cannot but believe in the identity of the process by which they are produced. This is the membrane enclosing the white of the egg, and forming the animal basis of the shell. If the shell be treated with dilute acid, a tough membrane remains, exactly resembling that which lines it; and if the hen has not been supplied with lime, there is no difference between the two membranes even without the action of acid on the outer one. Each of them consists of numerous laminae of most beauti- fully matted fibres intermixed with round bodies exactly resembling exudation cells. It is in the interstices of these fibres, that the calcare- ous particles are deposited, which give density to the shell. These membranes, according to Dr. Carpenter, are formed around the albu- men, which is deposited on the surface of the ovary during its passage alonjj the oviduct, from the interior of which the fibrinous exudation must take place. It is clear, then, that this doctrine of the origin of all the tissues from cells cannot be considered established. We believe, indeed, with a recent writer,5 that most physiologists, who are not prejudiced by the seductive simplicity of Schwann's generalization as to the derivation of 1 Lond. and Edinburgh Philosoph. Magazine, Oct., 1842. 2 Proceedings of the Royal Society, No. 56. 3 Philosophical Transactions for 1842. * Origin and Functions of Cells, in Brit, and For. Med Rev. for Jan., 1843, p. 277. 5 Brit, and For. Med. Review, July, 1844, p. 95. 206 NUTRITION. all the tissues from cells, have arrived at the conclusion, that as regards the areolar and other simple fibrous tissues, no other explanation of their production need be looked for than the known tendency of the particles of fibrin to arrange themselves in a linear manner so as to form fibres,—a tendency which "manifests itself much more decidedly, when the consolidation takes place upon a living surface than upon a dead one." Nor can ideas be esteemed more fixed in regard to the character of the matrix or blastema. M. Mandl1 affirms that we know not whether it is the albumen or fibrin of the blood. Others, and per- haps the majority of the present day, ascribe it to fibrin, between which, as we have elsewhere seen, and albumen, there is, according to Mulder, Liebig, and others, an almost identity of chemical composition., Fibrin, however, is considered to possess much higher vital properties; and the change of albumen into fibrin has been esteemed the first important step in the process of assimilation. In the chyliferous ves- sels, the proportion of fibrin increases as the chyle and lymph proceed onwards in the vessels; whilst that of the albumen diminishes. Such, however, is not rigorously the fact, for on referring to the table slightly modified from that of Gerber, which has been given elsewhere (vol. i. p. 653), it will be seen, that in the afferent lacteals between the intes- tines and mesenteric glands, the albumen has been found in minimum quantity; in the efferent or central lacteals, from the mesenteric glands to the thoracic duct, in maximum quantity; and in the thoracic duct in medium quantity; whilst the fibrin goes on progressively increasing as the chyle and lymph proceed onwards. On the other hand, the fat was found to diminish progressively; so that there appears to be more probability that the fibrin is formed from the fat, directly or indirectly, than from the albumen. It would seem not improbable, that some nitrogenized material like pepsin, or diastase in plants, is secreted from the parietes of the chyliferous vessels, which occasions a change in the elements of the constituents of the chyle, and is the earliest step in animalization: and the view is somewhat confirmed by the fact to which attention has been drawn by Mr. G. Ross,2 that the constituents of fatty matter, added to those of uric acid, would very nearly give the atomic constituents of albumen; whence, as Dr. Carpenter3 has re- marked, it might be surmised, that when there is a demand for pro- teinaceous compounds in the system, nitrogenized matter, which would otherwise be thrown out of the system, may be united with non-nitro- genized compounds taken as food, in order to supply its wants. That there is an essential physiological difference, however, between fibrin and albumen, notwithstanding their affirmed similarity in chemical composition, is shown by the fact, that effused fibrin has a tendency to spontaneous coagulation, whilst albumen requires the agency of heat; and that, as we have seen, there is an appearance of distinct organiza- tion in coagulated fibrin. This difference in properties would necessa- rily induce the belief, that the two substances differ more perhaps in chemical composition than the results of the analyses of Mulder, Liebig, 1 Op. cit., p. 548. 2 Lancet, 1842-3, vol. i. 3 Op. cit., p. 492. NUTRITION—GROWTH. 207 and others, would seem to indicate; and such appears to be proved by those of MM. Dumas and Cahours, which have been conducted on a very extensive scale; and show, that the proportion of carbon is seven per cent, less in fibrin than in albumen; whilst that of azote is from eight to nine per cent. more. A correct idea, these gentlemen think, may be formed of the elementary composition of fibrin by considering it a compound of casein, albumen, and ammonia.1 A view is entertained by many, that nothing but proteinaceous com- pounds can serve for the nutrition of the tissues; and that, as before remarked, gelatin is not adapted for this purpose. Liebig suggests, that it may be inservient to the nutrition of the gelatinous tissues; and Dr. Carpenter2 says, there is no doubt, that it is incapable of being applied to the reconstruction of any but the gelatinous tissues; and that it seems questionable, whether, even in these, it exists in a condi- tion that can rightly be termed organized: yet it appears to the author, that great doubt may be entertained on this subject. The inconclusive- ness of the experiments made on gelatin as an article of food has been animadverted on elsewhere (vol. i. p. 547). Although not a protein- aceous compound, it is one that is highly nitrogenized. When used as an aliment, it is not capable of being detected in the chyle or blood, and hence must have undergone a metamorphosis, probably into an albuminous compound; and it is certainly as difficult to comprehend how, under such circumstances, gelatin can be inservient to the nutri- tion of gelatinous tissues when no gelatin is present in the blood, as to comprehend that it may be converted first into albumen, and afterwards into fibrin. How gelatinous aliment, in other words, is formed into chyle and blood in which gelatin is not discoverable, and from these again gelatinous tissues are re-formed, is as incomprehensible as that any of the proteinaceous tissues should be constituted from the same pabulum; or that oleaginous aliments—as is admitted by some, who deny the same power to the gelatinous—should be convertible into pro- teinaceous compounds. Such is the state of uncertainty in which we are compelled to rest in regard to this important function. None of the views can be esteemed established. They are in a state of transition; and all, perhaps, that we are justified in deducing is, that the vital property, which exists in organizable matters—in the fibrinous portion of the blood, and in the blastema furnished by the parents at a fecundating union—gives occa- sion to the formation of cells, in some cases—of fibres in others; and that the tissues are farther developed through the agency of cell-life ox fibre-life, so as to constitute all the textures of which the body is composed. It is the action of nutrition, that occasions the constant fluctuations in the weight and size of the body, from the earliest embryo condition till advanced life. The cause of the developement or growth of organs and of the body generally, as well as of the limit accurately assigned to such developement, according to the animal or vegetable species, is dependent upon vital laws that are unfathomable. Nor are we able to 1 Med. Examiner, October 14, 1843, p. 232. 1 Principles of Human Physiology, 2d edit., p. 476, London, 1844. 208 NUTRITION. detect the precise mode in which the growth of parts is effected. It cannot be simple extension, for the obvious reason that the body and its various compartments augment in weight as well as in dimension. The rapidity with which certain growths are effected is astonishing. The Bovista giganteum has been known to increase, in a single night from a mere point to the size of a large gourd, estimated to contain 48,000,000,000 of cellules; and supposing twelve hours to have been necessary for its growth, the cells in it must have been produced at the rate of 4,000,000,000 an hour, or more than 66,000,000 a minute,— the greater part of the elements necessary for this astonishing forma- tion being obtained from the air.1 But these rapid growths possess little vitality, and their decay is almost as rapid as their production. Analogous growths—but not to the like extent—occur in the human body, and the same remark applies to them. In the large trees of our forests we find a fresh layer or ring added each year to the stem, until the full period of developement; and it has been supposed that the growth of the animal body may be effected in a similar manner, both as regards its soft and harder materials,— that is, by layers deposited externally. That the long bones lengthen at their extremities is proved by an experiment of Mr. Hunter.2 Having exposed the tibia of a pig, he bored a hole into each extremity of the shaft, and inserted a shot. The distance between the shots was then accurately taken. Some months afterwards, the same bone was examined, and the shots were found at precisely their original distance from each other; but the extremities of the bone had extended much beyond their first distance from them. The flat bones also increase by a deposition at their margins; and the long bones by a similar de- position at their periphery,—additional circumstances strongly ex- hibiting the analogy between the successive developement of animals and vegetables. Exercise or rest; freedom from, or the existence of, pressure, produces augmentation of the size of organs, or the contrary; and there are certain medicines, as iodine, which are said to occasion emaciation of particular organs only—as of the female mammae. The effect of disease is likewise, in this respect, familiar and striking.3 The ancients had noticed the changes effected upon the body by the function we are considering, and attempted to estimate the period at which a thorough conversion might be accomplished, so that not one of its quondam constituents should be present. By some, this was held to be seven years; by others, three. It is hardly necessary to say, that in such a calculation we have nothing but conjecture to guide us. The nutrition of the body and its parts varies, indeed, according to numerous circumstances. It is not the same during the period of growth as subsequently, when absorption and deposition are balanced, —so far at least as concerns the augmentation of the body in one direction. Particular organs have, likewise, their period of develope- ment, at which time the nutrition of such parts must necessarily be 1 Truman, Food and its Influence on Health and Disease, &c, p. 229, Lond., 1842. 2 Observations on Certain Parts of the Animal Economy, with notes, by Prof Owen, Amer. edit., p. 321, Philad., 1840. 3 The author's General Therapeutics and Mat. Med., 4th edit., ii. 285, Philad., 1850- and his Practice of Medicine, 3d edit., Philad., 1848. NUTRITION. 209 more active,—the organs of generation, for example, at the period of puberty; the enlargement of the mammae in the female; the appear- ance of the beard and the amplification of the larynx in the male, &c. All these changes occur after a determinate plan. The activity of nutrition appears to be increased by exercise, at least in muscular organs; hence the well-marked muscles of the arm in the prize-fighter, of the legs in the dancer, &c. The muscles of the male are, in general, much more clearly defined; but the difference between those of the hard-working female and the inactive male may not be very apparent. The most active parts in their nutrition are the glands, muscles, and skin, which alter their character—as to size, colour, and consistence— with great rapidity; whilst the tendons, fibrous membranes, bones, &c, are much less so, and are altered more slowly by the effect of disease. A practice, which prevails amongst certain professions and people, would seem, at first sight, to show that the nutrition of the skin cannot be energetic. Sailors are in the habit of forcing gunpowder through the cuticle with a pointed instrument, and of figuring the initials of their names upon the arm in this manner: the particles of the gunpowder are thus driven into the cutis vera, and remain for life. The operation of tattooing, or of puncturing and staining the skin, prevails in many parts of the globe, and especially in Polynesia, where it is looked upon as greatly ornamental. The art is said to be carried to its greatest perfection in the Washington or New Marquesas Islands ;l where Fis- 314- the wealthy are often covered with various designs from head to foot; subjecting themselves, to a most painful operation for this strange kind of personal decoration. The operation consists in puncturing the skin with some rude instru- ment, according to figures pre- viously traced upon it, and rubbing into the punctures a thick dye, frequently composed of the ashes of the plant that furnishes the colouring matter. The marks, thus made, are indelible. M. Magendie2 asks: — "How can we reconcile this phenomenon with the renova- tion, which, according to authors," (and he might have added, accord- ing to himself,) "happens to the skin?" It does not seem to us to be in any manner connected with the nutrition of the skin. The colouring matter is an extraneous sub- Tattooed Head of a New Zealand Chief. VOL. 1 Lawrence, Lectures on Physiology, &c, p. 411, Lond., 1819. 2 Precis, &c, edit. cit.. ii. 483. II.—14 210 CALORIFICATION. stance, which takes no part in the changes constantly going on in the tissue in which it is embedded; and the circumstance seems to afford a negative argument in favour of venous absorption. Had the substance possessed the necessary tenuity, it would have entered the veins like other colouring matters; but the particles are too gross for this, and hence remain free from all absorbing influence. CHAPTER VI. CALORIFICATION. The function we have now to consider is one of the most important to organized existence, and one of the most curious in its causes and results. It has, consequently, been an object of interesting examina- tion with the physiologist, both in animals and plants; and as it has been presumed to be greatly owing to respiration, it has been a fa- vourite topic with the chemist also. Most of the hypotheses, devised for its explanation, have, indeed, been of a chemical character ; and hence it will be advisable to premise a few observations regarding the physi- cal relations of caloric or the matter of heat,—an imponderable body, according to common belief, which is generally distributed throughout nature. It is this that constitutes the temperature of bodies,—by which is meant, the sensation of heat or cold we experience when they are touched by us; or the height at which the mercury is raised or de- pressed by them, in the instrument called the thermometer;—the eleva- tion of the mercury being caused by the caloric entering between its particles, and thus adding to its bulk ; and the depression produced by the abstraction of caloric. Caloric exists in bodies in two states ;—in the free, uncombined or sensible ; and in the latent or combined. In the latter case, it is inti- mately united with the other elementary constituents of bodies, and is neither indicated by the feelings nor thermometer. It has, conse- quently, no agency in the temperature of bodies ; but, by its proportion to the force of cohesion, it determines their condition ;—whether solid, liquid or gaseous. In the former case, caloric is simply interposed be- tween the molecules; and is incessantly disengaged, or abstracted from surrounding bodies ; and, by impressing the surface of the body or by acting upon the thermometer, indicates to us their temperature. Equal weights of the same body, at the same temperature,'contain the same quantities of caloric; but equal weights of different bodies at the same temperature have by no means the same. The quantity, which one body contains, compared with another, is called its specific caloric, or specific heat; and the power or property, which enables bodies to retain different quantities of caloric, is called capacity for caloric. If a pound of water heated to 156° be mixed with a pound of quicksilver at 40°, the resulting temperature is 152°,—instead of 98°, the exact mean. The water, consequently, must have lost four degrees of temperature, and the quicksilver gained one hundred and twelve; from which we deduce, that the quantity of caloric, capable of raising one pound of TEMPERATURE OF ANIMALS. 211 mercury from 40° to 152° is the same as that required to raise one pound of water from 152° to 156°: in other words, that the same quan- tity of heat, which raises the temperature of a pound of water four degrees, raises the same weight of mercury one hundred and twelve degrees. Accordingly, it is said, that the capacity of water for heat is to that of mercury, as 28 to 1; and that the specific heat is twenty- eight times greater. All bodies are capable of giving and taking free caloric; and conse- quently, all have a temperature. If the quantity given off be great, the temperature of the body is elevated. If it takes heat from the ther- mometer, it is cooler than the instrument. In inorganic bodies, the disengagement of caloric is induced by various causes,—such as elec- tricity, friction, percussion, compression, the change of condition from a fluid to a solid state ; and by chemical changes, giving rise to new compounds, so that the caloric, which was previously latent, becomes free. If, for example, two substances, each containing a certain amount of specific heat, unite, so as to form a compound whose specific heat is less, a portion of caloric must be set free, and this will be indicated by a rise in the temperature. It is this principle, which is chiefly con- cerned in some of the theories of calorification. The subject of the equilibrium and conduction of caloric has already been treated of under the sense of Touch (vol. i. p. 136); where other topics were discussed, that bear more or less upon the present inquiry. It was there stated, that inorganic bodies speedily attain the same tem- perature, either by radiation or conduction ; so that the different objects in an apartment exhibit the same degree of heat by the thermometer; but the temperature of animals being the result of a vital operation, they retain the degree of heat peculiar to them with but little modifica- tion from external temperature. There is a difference, however, in this respect, sufficient to cause the partition of animals into two great divi- sions—the warm-blooded and cold-blooded ; the former comprising those whose temperature is high, and but little influenced by that of external objects;—the latter those whose temperature is greatly modified by external influences. The range of the temperature of the warm-blooded —amongst which are all the higher animals—is limited; but of the cold-blooded extensive. The following table exhibits the temperature of various animals in round numbers ;—that of man being 98° or 100°, when taken under the tongue. The temperature in the axilla is some- thing less. In the latter situation, M. Edwards1 found it vary, in twenty adults, from 96° to 99° Fahrenheit, the mean being 97*5°. It would appear, however, to vary at different periods of the day. Hallmann, from his own observations and those of Gierse,2 found that the tempera- ture of healthy individuals under the tongue was on the average 37° Cent., or 98-66° Fahr. ; late in the morning and evening from 36*7° to 36-8° Cent.,—from 98-06° to 98-24° Fahr.; in the forenoon, at 37*3° Cent.—99-14° Fahr.; and in the afternoon,at 37'5° Cent.—99-5° Fahr. 1 De l'lnfluence des Agens Physiques, &c, Paris, 1824; or Hodgkin'sand Fisher's transla- tion, Lond., 1832. 2 Henle, Handbuch der rationellen Pathologie, 1 Band. s. 301, Braunschweig, 1846. 212 CALORIFICATION. JLSIMA.IS. Active young horse, four years old, Arctic fox, ... Arctic wolf, Squirrel, - Hare, .... Whale, .... Arctomys citillus, zizil,—in summer, Do. when torpid, Goat, .... She goat, three months old, Mother of the same, old, and in poor condition Bat, in summer, .... Musk, - - - - Marmota bobac,—Bobac, - House mouse, - Arctomys marmota, marmot—in summer, Do. when torpid, - Rabbit, --... Tame young rabbit, two months old, Polar bear, .... Dog,..... Cat, ..... Swine, ----- Sheep, ..... Ox,..... A fine active kitten, two months old, A vigorous cat, nearly full grown, Mother of the kitten, three years old, A very old cat, said to be in its 19th year, An active cur dog, three months old, Guinea-pig, Arctomys glis, Shrew, ... Young wolf, Fringilla arctica, Arctic finch, Rubecola, redbreast, Fringilla linaria, lesser red poll Falco palumbarius, goshawk, Caprimulgus Europaus, European goat-sucker, Emberiza nivalis, snow-bunting, Falco lanarius, lanner, Fringilla carduelis, goldfinch, Corvus cor ax, raven, Turdus, thrush, (of Ceylon.) Tetrao perdrix, partridge, Anas clypeata, shoveler, - Tringa pugnax, ruffe, Scolopax limosa, lesser god wit, Tetrao telrix, grouse, Fringilla brumalis, winterfinch, Loxia pyrrhula, - Falco nisus, sparrowhawk, Vultur barbatus, - OBSERVERS. Metcalfe.' Capt. Lyon.2 Do. Pallas/* Do. Scoresby.4 Pallas. Pallas. Prevost and Dumas.5 *• Metcalfe. Do. Prevost and Dumas. Do. Do. Do. Do. Do. Delaroche. Metcalfe. Capt. Lyon. Martine.6 Do. Do. Do. Do. Metcalfe. Do. Do. Do. Do. Delaroche. Pallas. Do. Do. Braun.7 Pallas. Do. Do. Do. Do. Do. Do. Despretz.8 J. Davy.9 Pallas. Do. Do. Do. Do. Do. Do. Do Do. TEMPERATURI. 104° 107 105 104 103 80 to 84 103 107 104 . 102 101 or 102 101 101 or 102 43 100 to 104 108 100 f- 100 to 103 J 105-5 104 103-5 102 106 100 to 102 99 98 96 I '» 110 or 111 I 110 109 to 110 1 I J. 109 108 1 Caloric, its Mechanical, Chemical, and Vital Agencies in the Phenomena of Nature, iL 567, Lond., 1843. 2 Parry's Second Voyage to the Arctic Regions. 3 Nov. Species Quadruped, de Glirium Ordine, Erlang., 1774. 4 An Account of the Arctic Regions, Edinb., 1820. 6 Bibliotheque Univers., xvii. 294. 6 Med. and Philos. Essays, Lond., 1740; and De Similibus Animalibus et Animal. Calore, &c, Lond., 1740. 7 Nov. Comment. Acad. Petropol., xiii. 419. s Annales de Chimie, xxvi. 337, Amst., 1824. 9 Edinb. Philos. Journal, Jan., 1826. TEMPERATURE OF ANIMALS. 213 OBSERVERS. TEMPERATURE Do. 1 Do. Do. [ I 107° Do. J Do. 107 to 111 Do. 1 Do. 1 Do. 106 Do. 1 Do. J Pallas. Do. \ 105 Do. ) Do. Do. I 104 Martine. ] Do. Do. 103 to 107 Do. j Pallas. Do. \ 103 Do. ) Schultze. 89 to 91 J. Davy. 83 Rudolphi.1 74 ANIMALS. Anter pulchricollis, Colymbus auritus, dusky grebe, - Tringa vanellus, lapwing, (wounded,) Tetrao lagopus, ptarmigan, Fringilla domestica, house-sparrow, Strix passerina, little owl, Hcematopus estralagus, sea-pie, Anas penelope, wigeon, - Anas strepera, gadwall, - Pelecanus carbo, ... Falco ossifragus, sea-eagle, Fulica atra, coot, Anas acuta, pintail-duck, Falco milvus, kite, (wounded,) - Merops apiaster, bee-eater, Goose, .... Hen, - . . . Dove, .... Duck, - Ardea stellaris, Falco albicollis, - Picus major, Cossus ligniperda, Shark, - Torpedo Marmorata, It will be observed, that according to this table the inhabitants of the Arctic regions—whether belonging to the class of mammalia or birds—are among those whose temperature is highest. That of the Arctic fox is probably higher than given in the table, as it was taken after death, when the temperature of the air was as low as —14° of Fah- renheit, and when loss of heat may be supposed to have occurred rapidly. It is, of course, impracticable to mark the temperature of the smaller insects, but we can arrive at an approximation in those that congre- gate in masses, as the bee and the ant; for it is difficult to suppose with Miraldi, that the augmented temperature is dependent upon the motion and friction of the wings and bodies of the busy multitudes. Juch2 found, when the temperature of the atmosphere was —18° of Fahren- heit, that of a hive of bees 44°: in an ant-hill, the thermometer stood at 68° or 70°, when the temperature of the air was 55°; and at 75°, when that of the air was 66°; and Hausmann3 and Rengger4 saw the thermometer rise when put into narrow glasses in which they had placed scarabsei and other insects.5 Berthold detected the elevation of heat only when several insects were collected together, never in one isolated from the rest. This, according to Mr. Newport,6 must have arisen from his having ascertained the temperature only whilst the insect was in a state of rest; for Mr. Newport found, that although during such a state, the temperature of the insect was very nearly or exactly that of the surrounding medium; yet when it was excited or disturbed, or in a state of great activity from any cause, the thermome- 1 Grundriss der Physiol., &c, Band. i. 106. 2 Ideen zu einer Zoochemie, i. 90. 3 De Animal. Exsanguium Respiratione, p. 65. 4 Physiologische Untersuchung. uber die Insecten,p. 40, Tubing., 1817. 6 Tiedemann, op. citat, p. 511. 6 Philosoph. Transact, for 1837, part ii. p. 259. 214 CALORIFICATION. ter rose, in some instances, even to 20° Fahr. above the temperature of the atmosphere,—for instance, to 91°, when the heat of the air was 71°. The power of preserving their temperature within certain limits is not, however, possessed exclusively by animals. The heat of a tree, examined by Mr. Hunter,1 was found to be always several degrees higher than that of the atmosphere, when the latter was below 56° of Fahr.; but it was always several degrees below it when the weather was warmer. Some plants develope a great degree of heat during the period of blooming. This was first noticed by De Lamarck2 in Arum Italicum. In Arum cordifolium, of the Isle of Bourbon, M. Hubert found, when the temperature of the air was 80°, that of the spathe or sheath was as high as 134°; and M. Bory de St. Vincent3 observed a similar elevation, although to a less degree, in Arum esculentum, escu- lent arum or Indian kale. The most exact and elaborate investiga- tions appear to have been made by MM. Vrolik and De Vriese.4 Ac- cording to them, the temperature has a regular periodicity within the twenty-four hours, and attains its maximum in the afternoon between the hours of two and five. The difference between the temperature of the atmosphere and that of the root is sometimes as much as from 20° to 30° of Re'aumur. According to M. De Saussure, the root of an arum maculatum converted thirty times its volume of oxygen into carbonic acid in twenty-four hours. In all cases, the absolute temperature appeared to depend on the intensity of the vital processes, and was higher in proportion to the vigour of the vegetation in plants, or to the absorption of the sap and the activity of its chemical processes.5 The temperature of the animal body is so far influenced by external heat as to rise or fall with it; but the range, as already remarked, is limited in the warm-blooded animal,—more extensive in the cold- blooded. Dr. Currie found the temperature of a man plunged into sea- water at 44° sink, in the course of a minute and a half after immersion, from 98° to 87°: in other experiments, it descended as low as 85°, and even to 83°.6 It was always found, however, that, in a few minutes, the heat approached its previous elevation; and in no instance could it be depressed lower than 83°, or 15° below the temperature at the com- mencement of the operation. Similar experiments have been performed on other warm-blooded animals. Mr. Hunter found the temperature of a common mouse to be 99°, that of the atmosphere being 60°: when the same animal was exposed, for an hour, to an atmosphere of 15°, its heat had sunk to 83° ;7 but the depression could be carried no farther. He found, also, that a dormouse,—whose heat in an atmosphere at 64 , was 81 J°,—when put into air, at 20°, had its temperature raised in the course of half an hour to 93°; an hour after, the air being at 30°, it was still 93°; another hour after, the air being at 19°, the heat of the 1 Philos. Transact., 1775 and 1778. 2 Encyclop. Method., iii. 9. 3 Voyage dans les Quatre Principals lies des Mers d'Afrique, ii. 66. 4 Annales de Chimie et de Physique, xxi. 279. 5 Schleiden, Principles of Scientific Botany, by Dr. Lankester, p. 541, London, 1849. 6 Philos. Transact, for 1792, p. 199.. 7 Ibid., 1778, p. 21. TEMPERATURE IN ARCTIC REGIONS. 215 pelvis was as low as 83°,—an experiment which strongly proves the great counteracting influence exerted, when animals are exposed to an unusually low temperature. In this experiment, the dormouse had maintained its temperature about 70° higher than that of the surround- ing medium, and for the space of two hours and a half. In the hiber- nating torpid quadruped the reduction of temperature, during their torpidity, is considerable. Jenner1 found the temperature of a hedge- hog, in the cavity of the abdomen, towards the pelvis, to be 95°, and that of the diaphragm 97° of Fahrenheit, in summer, when the ther- mometer in the shade stood at 78°; whilst in winter, the temperature of the air being 44°, and the animal torpid, the heat in the pelvis was 45°, and that of the diaphragm 48|-°. When the temperature of the atmosphere was 26°, the heat of the animal in the cavity of the abdomen, where an incision was made, was reduced as low as 30°; but —what singularly exhibits the power possessed by the system of regu- lating its temperature,—when the same animal was exposed to a cold atmosphere of 26° for two days, the heat, in the rectum, marked 93°, or 67° above that of the atmosphere. At this time, however, it was lively and active, and the bed on which it lay felt warm. In the cold- blooded animal, we have equal evidence of the generation of heat. Hunter found the heat of a viper, placed in a vessel at 10°, reduced, in ten minutes, to 37°; in the next ten minutes, the temperature of the vessel being 13°, it fell to 35°; and in the next ten, that of the ves- sel being 20 , to 31°.2 In frogs, he was able to lower the temperature to 31°; but beyond this point it was not possible to depress it, without destroying the animal. In the Arctic regions, animal temperature appears to be steadily maintained notwithstanding the intense cold that prevails; and we have already seen, that the animals of those hyperborean latitudes possess a more elevated temperature than those of more genial climes. In the enterprising voyages, undertaken by the British government for the discovery of a northwest passage, the crews of the ships were'fre- quently exposed to the temperature of —40° or —50° of Fahrenheit's scale; and the same thing happened during the disastrous campaign of Russia in 1812, in which so many of the French army perished from cold. The lowest temperature noticed by Captain Parry3 was —55° of Fahrenheit. Captain Franklin,4 on the northern part of this con- tinent, observed the thermometer on one occasion—Feb. 7, 1827,—as low as —58° of Fahrenheit. Von Wrangel5 states that, in January, on the north coast of Siberia, it reaches —59° of Fahrenheit. Cap- tain Back,6 in his expedition to the Arctic regions of this continent on 1 Hunter, On the Animal Economy, with Professor Owen's notes, p. 165, Philad., 1840. 2 Op. citat. 3 Journal of a Voyage for the Discovery of a Northwest Passage, American edition, p. 130, Philadelphia, 1821. 4 Narrative of a Second Expedition to the Shores of the Polar Sea, &c, American edition, p. 245, Philadelphia. 1835. s Reise des kaiserlich Russischen Flotten Lieutenants Ferdinand Von Wrangel, liings der Nordkiiste von Siberien, u. s. w., Berlin, 1839, translated in Harper's Family Library. 6 Narrative of the Arctic Land Expedition to the mouth of the Great Fish River, &c, in the years 1833, 1834, and 1835, London, 1836. 216 CALORIFICATION. the 17th of January, 1834, noticed the thermometer at —70° of Fah- renheit. Mr. Erman1 states, that at Yakutsk it was at —72-5 of Fahrenheit; and Sir George Simpson2 affirms, that it has fallen in Siberia to —83°, or 115° below the freezing point,—which may be re- garded as the greatest depression observed in any climate. During the second voyage of Captain Parry,3 the following tempera- tures of animals, immediately after death, were taken principally by Captain Lyon. Temperature of the 1821. Animal. Atmosphere. Nov. 15. An Arctic fox . - - - 106J° - — 14° Dec. 3. Do. . - - - 101$ - — 5 Do. . - - - 100 - — 3 11. Do. . - . . 101} . — 21 15. Do. . . - . 99| . — 15 17. Do. . - - ■ 98 ■ — 10 19. Do. - - - . 99f - — 14 1822. Jan. 3. Do. - - - - 104^ - — 23 9. A white hare - - - . - 101 - — 21 10. An Arctic fox • - - - - 100 - — 15 17. Do. . - - - 106 - — 32 24. Do. . - - . 103 - — 27 Do. - . - - 103 - — 27 Do. - - - - 102 . — 25 27. Do. - - - - 101 - — 32 Feb. 2. A wolf - . • - 105 - — 27 These animals must, therefore, have to maintain a temperature at least 100° higher than that of the atmosphere throughout the whole of winter; and it would seem as if the counteracting energy becomes proportionately greater as the temperature is more depressed. It is, however, a part of their nature to be constantly eliciting this unusual quantity of caloric, and therefore they do not suffer. Where animals, not so accustomed, are placed in an unusually cold medium, the efforts of the system rapidly exhaust the nervous energy; and when this is so far depressed as to interfere materially with the function of calorifica- tion, the temperature sinks, and the sufferer dies lethargic—or, as if struck with apoplexy. The ship Endeavour, being on the coast of Terra del Fuego, on the 21st of December, 1769, Messrs. Banks, Solander, and others were desirous of making a botanical excursion on the hills on the coast, which did not appear to be far distant. The party, con- sisting of eleven persons, were overtaken by night, during extreme cold. Dr. Solander, who had crossed the mountains which divide Sweden from Norway, knowing the almost irresistible desire for sleep produced by exposure to great cold, more especially when united with fatigue, enjoined his companions to keep moving, whatever pains it might cost them, and whatever might be the relief promised by an indulgence in rest. " Whoever sits down," said he, " will sleep, and whoever sleeps will wake no more." Thus admonished, they set forward, but whilst 1 Travels in Siberia, translated from the German, by W. D. Cooley, ii. 369, London, 1848. 2 An Overland Journey round the World, Amer. edit., part ii. p. 134, Philad., 1847. 3 Op. citat., p. 157. EFFECTS OF DEPRESSED TEMPERATURE. 217 still upon the bare rock, and before they had got among the bushes, the cold suddenly became so severe as to produce the effects that had been dreaded. Dr. Solander himself was the first who found the desire irresistible, and insisted on being suffered to lie down. Mr. Banks (afterwards Sir Joseph) entreated and remonstrated in vain. The doctor lay down upon the ground, although it was covered with snow; and it was with the greatest difficulty that his friend could keep him from sleeping. Richmond, one of the black servants, began to linger and to suffer from the cold, in the same manner as Dr. Solander. Mr. Banks, therefore, sent five of the company forward to get a fire ready at the first convenient place they came to; and himself, with four others, remained with the Doctor and Richmond, whom, partly by persuasion and partly by force, they carried forward; but when they had got through the birch and swamp, they both declared they could go no far- ther. Mr. Banks had again recourse to entreaty and expostulation, but without effect. When Richmond was told, that if he did not go on, he would, in a short time, be frozen to death, he answered, that he desired nothing but to lie down and die. Dr. Solander was not so obstinate, but was willing to go on, if they would first allow him to take some sleep, although he had before observed, that to sleep was to perish. Mr. Banks and the rest of the party found it impossible to carry them, and they were consequently suffered to sit down, being partly supported by the bushes, and, in a few minutes, they fell into a profound sleep. Soon after, some of the people, who had been sent forward, returned with the welcome intelligence, that a fire had been kindled about a quarter of a mile farther on the way. Mr. Banks then endeavoured to rouse Dr. Solander, and happily succeeded; but, although he had not slept five minutes, he had almost lost the use of his limbs, and the soft parts were so shrunk, that his shoes fell from his feet. He consented to go forward with such assistance as could be given him; but no at- tempts to relieve Richmond were successful. He, with another black left with him, died. Several others began to lose their sensibility, having been exposed to the cold near an hour and a half, but the fire recovered them. The preceding history is interesting in another point of view besides the one for which it was more especially narrated. Both the individuals, who perished, were blacks; and it has been a common observation, that they bear exposure to great heat with more impunity, and suffer more from intense cold, than the white variety of the species. As regards inorganic bodies, it has been satisfactorily shown, that the phenomena of the radiation of caloric are connected with the nature of the radiat- ing surface; and that those surfaces, which radiate most, possess, in the highest degree, the absorbing power; in other words, bodies that have their temperatures most readily raised by radiant heat are those that are most easily cooled by their own radiation. In the experiments of Professor Leslie1 it was found, that a clean metallic surface produced an effect upon the thermometer equal to 12; but when covered with a thin coat of glue its radiating power was so far increased as to produce 1 On Heat, Lond., 1788; and Dr. Stark, in Philosoph. Transact., part ii. for 1833. 218 CALORIFICATION. one equal to 80; and, on covering it with lampblack, it became equal to 100. We can thus understand why, in the negro, there should be a greater expense of caloric than in the white, owing to the greater radi- ation ; not because as much caloric may not have been elicited as in the white. In the same manner we can comprehend, that, owing to the greater absorbing power of his skin, he may suffer less from excessive heat. To ascertain, whether such be the fact, the following experiments were instituted by Sir Everard Home.1 He exposed the back of his hand to the sun at twelve o'clock, Avith a thermometer attached to it, another being placed upon a table with the same exposure. The tem- perature, indicated by that on his hand, was 90°; by the other, 102°. In forty-five minutes, blisters arose, and coagulable lymph was thrown out. The pain was very severe. In a second experiment, he exposed his face, eyelids, and the back of his hand to water heated to 120°; in a few minutes they became painful; and, when the heat was farther increased, he was unable to bear it; but no blisters were produced. In a third experiment, he exposed the backs of both hands, with a ther- mometer upon each, to the sun's rays. The one hand was uncovered; the other had a covering of black cloth, under which the ball of the thermometer Avas placed. After ten minutes, the degree of heat of each thermometer was marked, and the appearance of the skin ex- amined. This was repeated at three different times. The first time, the thermometer under the cloth stood at 91°; the other at 85°; the second time, they indicated respectively 94° and 91°; and the third time, 106° and 98°. In every one of these trials, the skin that was uncovered was scorched; whilst the other had not suffered in the slightest degree. From all his experiments, Sir Everard concludes, that the power of the sun's rays to scorch the skin of animals is destroyed, when applied to a black surface; although the absolute heat, in consequence of the absorption of the rays, is greater. When cold is applied to particular parts of the body, their heat sinks lower than the minimum of depressed temperature. Although Mr. Hun- ter was unable to heat the urethra one degree above the maximum of elevated temperature of the body, he succeeded in cooling it 29° lower than the minimum of depressed temperature, or to 58°. He cooled down the ears of rabbits until they froze; and when thawed they reco- vered their natural heat and circulation. The same experiment was performed on the comb and wattles of a cock. Resuscitation was, however, in no instance practicable where the whole body had been frozen.2 The same distinguished observer found, that the power of generating heat, when exposed to a cooling influence, was possessed even by the egg. One, that had been frozen and thaAved, was put into a cold mixture along with one newly laid. The latter was seven minutes and a half longer in freezing than the former. In another experiment, a fresh-laid egg, and one that had been frozen and thawed, were put into a cold mixture at 15°; the thawed one soon rose to 32°, and began to swell and congeal; the fresh one sank to 29}°, and in twenty-five 1 Lect. on Comp. Anat., iii. 217, London, 1823. 2 Sir E. Home's Lect., &c, iii. 438. EFFECTS OF DEPRESSED TEMPERATURE. 219 minutes after the dead one, rose to 32°, and began to swell and freeze. All these facts prove, that when the living body is exposed to a lower temperature than usual, a counteracting power of calorification exists; but that, in the human species, such exposure to cold is incapable of depressing the temperature of the system lower than about 15° beneath the natural standard. In fish, the vital principle can survive the action even of frost. Captain Franklin found, that those which they caught in Winter Lake, froze as they were taken out of the net; but if, in this completely frozen condition, they were thawed before the fire, they recovered their animation. This was especially the case Avith a carp, which recovered so far as to leap about with some vigour after it had been frozen for thirty-six hours. On the other hand, when the living body is exposed to a temperature greatly above the natural standard, an action of refrigeration is exerted; so that the animal heat cannot rise beyond a certain number of degrees; —to a much smaller extent in fact than it is capable of being depressed by the opposite influence. Boerhaave1 maintained the strange opinion, that no warm-blooded animal could exist in a temperature higher than that of its own body. In some parts of Virginia, there are days in every summer, in which the thermometer reaches 98° of Fahrenheit; and in other parts of this country it is occasionally much higher. The meteorological registers shoAv it to be, at times, at 108° at Council Bluffs, in Missouri; at 104° in New York; and at 100° in Michigan;2 whilst in most of the states, in some days of summer, it reaches 96° or 98°. At Sierra Leone, Messrs. Watt and Winterbottom3 saw it frequently at 100°, and even as high as 102° and 103°, at some distance from the coast. Adanson observed it at Senegal as high as 108|°. Sir John BarroAv,4 at the village of Graaff Reynet, in South Africa, noted it on the 24th of November, at 108° in the shade and open air. Brydone affirms, that when the sirocco blows in Sicily the heat rises to 112°.5 Dr. Chalmers observed a heat of 115°6 in South Carolina; Humboldt7 of 110° to 115° in the Llanos or Plains near the Orinoco; and Captain Tuckey asserts, that on the Red Sea he never saw the thermometer at midnight under 94°; at sunrise under 104°; or at midday under 112°. In British India it has been seen as high as 130°.8 So long ago as 1758, Governor Ellis9 of Georgia had noticed how little the heat of the body is influenced by that of the external atmo- sphere. "I have frequently," he remarks, "walked an hundred yards under an umbrella with a thermometer suspended from it by a thread, to the height of my nostrils, when the mercury has rose to 105°, which 1 "Observatio docet nullum animal quod pulmones habet, posse in aere vivere, cujus eadem est temperies cum suo sanguine." Element. Chemise, i. 275, Lug. Bat., 1732. 2 Meteorological Register, for the years 1822, 1823, 1824, and 1825, from observations made by the surgeons at the military posts of the United States. See, also, a similar register for the years 1826, 1827, 1828, 1829, and 1830, Philad., 1840. • Account of the Native Africans, vol. i. pp. 32 and 33. 4 Auto-biographical Memoir, p. 193, London, 1847. 6 Lawrence's Lectures on Comparative Anatomy, Physiology, &c., p. 306, London, 1819. 6 Account of the Weather and Diseases of South Carolina, London, 1776. 7 Tableau Physique des Regions Equatoriales. 6 Prof. Jameson, British India, Amer. edit., iii. 170, New York, 1832. » Philosophical Transactions, 1758, p. 755. 220 CALORIFICATION. is prodigious. At the same time I have confined this instrument close to the hottest part of my body, and have been astonished to observe, that it has subsided several degrees. Indeed I could never raise the mercury above 97° with the heat of my body." Two years after the date of this communication, the power of resisting a much higher atmospheric temperature was discovered by accident. MM. Duhamel and Tillet,1 in some experiments for destroying an insect, that infested the grain of the neighbourhood,—having occasion to use a large public oven, on the same day in which bread had been baked in it,—were desirous of ascertaining its temperature. This they endeavoured to accomplish by introducing a thermometer into the oven at the end of a shovel. On being Avithdrawn, the thermometer indicated a degree of heat considerably above that of boiling water; but M. Tillet, feeling satisfied, that the thermometer had fallen several degrees in approach- ing the mouth of the oven, and seeming to be at a loss how to rectify the error, a girl,—one of the servants of the baker, and an attendant on the OAren,—offered to enter and mark with a pencil the height at which the thermometer stood within. She smiled at M. Tillet's hesita- tion in accepting her proposition; entered the oven, and noted the temperature to be 260° of Fahrenheit. M. Tillet, anxious for her safety, called upon her to come out; but she assured him she felt no inconvenience, and remained ten minutes longer, when tlfe thermometer had risen to 280° and upwards. She then came out of the oven, with her face considerably flushed, but her respiration by no means quick or laborious. These facts excited considerable interest; but no farther experiments appear to have been instituted, until, in the year 1774, Dr. Geo. Fordyce, and Sir Charles Blagden2 made their celebrated trials with heated air. The rooms, in which these were made, were heated by flues in the floor. Having taken off his coat, Avaistcoat, and shirt, and being provided with wooden shoes tied on with list, Dr. Fordyce went into one of the rooms, as soon as the thermometer indicated a degree of heat above that of boiling water. The first impression of the heated air upon his body was exceedingly disagreeable; but in a few minutes all uneasiness was removed by copious perspiration. At the end of twelve minutes he left the room very much fatigued; but not otherwise disordered. The thermometer had risen to 220°. In other experi- ments, it was found, that a heat even of 260° could be borne with tolerable ease. At this temperature, every piece of metal was intolera- bly hot; small quantities of water, in metallic vessels, quickly boiled; and streams of moisture poured down over the whole surface of his body. That this was merely the vapour of the room, condensed by the cooler skin, was proved by the fact, that when a Florence flask, filled with water of the same temperature as the body, was placed in the room, the vapour condensed in like manner upon its surface, and ran down in streams. Whenever the thermometer was breathed upon, the mercury sank several degrees. Every expiration—especially if made 1 Memoir, de l'Academie des Sciences, p. 186, Paris, 1762. 2 Philosophical Transactions for 1775, p. 111. EFFECTS OF ELEVATED TEMPERATURE. 221 with any degree of violence—communicated a pleasant impression of coolness to the nostrils, scorched immediately before by the hot air rushing against them when they inspired. In the same manner, their comparatively cool breath cooled the fingers, whenever it reached them. "To prove," says Sir Charles Blagden, "that there was no fallacy in the degree of heat shown by the thermometer, but that the air which we breathed was capable of producing all the well-known effects oY such an heat on inanimate matter, we put some eggs and beef-steak upon a tin frame, placed near the standard thermometer, and farther distant from the cockle than from the wall of the room. In about twenty minutes the eggs were taken out roasted quite hard; and in forty-seven minutes, the steak was not only dressed, but almost dry. Another beef- steak was rather overdone in thirty-three minutes. In the evening, when the heat was still greater, we laid a third beef-steak in the same place; and as it had now been observed, that the effect of the heated air was much increased by putting it in motion, we blew upon the steak with a pair of bellows, which produced a visible change on its surface, and seemed to hasten the dressing: the greatest part of it Avas found pretty well done in thirteen minutes." In all these experiments, and others of a like kind were made in the following year, by Dr. Dobson,1 of Liverpool, the heat of the body, in air of a high temperature, speedily reached 100°; but exposure to 212° and more did not carry it higher. These results are not exactly in accordance with those of MM. Ber- ger and Delaroche,2 from experiments performed in 1806. Having exposed themselves, for some time, to a stove,—the temperature of which was 39° of Re'aumur, or 120° of Fahrenheit—their temperature was raised 3° of Re'aumur, or 6f ° of Fahrenheit; and M. Delaroche found, that his rose to 4° of Re'aumur, or 9° of Fahrenheit, when he had remained sixteen minutes in a stove heated to 176° of Fahrenheit. According to Sir David Brewster,3—the distinguished sculptor, Chantry, exposed himself to a temperature yet higher. The furnace which he employed for drying his moulds, was about 14 feet long, 12 high, and 12 broad. When raised to its highest temperature, with the doors closed, the thermometer stood at 350°, and the iron floor Avas red-hot. The workmen often entered it at a temperature of 340°, walking over the floor with wooden clogs, which were, of course, charred on the surface. On one occasion, Sir Francis, accompanied by five or six of his friends, entered the furnace, and after remaining two minutes, brought out a thermometer, which stood at 320°. Some of the party experienced sharp pains in the tips of their ears, and in the septum of the nose, whilst others felt a pain in the eyes. In certain experiments of Cha- bert, who exhibited his powers as a "Fire King," in this country as well as in Europe, he is said to have entered an oven with impunity, the heat of which was1 from 400° to 600° of Fahrenheit. Experiments have shown, that the same power of resisting excessive 1 Philosophical Transactions for 1775, p. 463. 2 Exper. snr les Effets qu'une forte Chaleur produit sur l'Economie, Paris, 1805- and Journal de Physique, lxiii. 207, lxxi. 289, and Ixxvii. 1. 3 Letters on Natural .Magic, p. 281, Amer. edit., New York, 1832. 222 CALORIFICATION. heat is possessed by animals. Drs. Fordyce and Blagden shut up a dog, for half an hour, in a room, the temperature of which was be- tween 220° and 236°; at the end of this time a thermometer was applied betAveen the thigh and flank of the animal; and in about a minute the mercury sank to 110°; but the real heat of the body was certainly less than this, as the ball of the thermometer could not be kept a sufficient time in proper contact; and the hair, which felt sen- sibly hotter than the bare skin, could not be prevented from touching the instrument. The temperature of this animal, in the natural state, is 101°. We find in organized bodies astonishing cases of adaptation to the medium in which they live. Sonnerat saw, in India, vitex agnus castus flourishing near a spring, whose temperature was 144°; and Foster found it at the foot of a volcano in the Island of Tanna, the temperature of the ground being 176°. Adanson affirms, that different plants vegetate arid preserve their verdure in Senegal, although their roots are plunged in sand at a temperature at times as high as 142°; and M. Desfontaines found several plants surrounding the springs at Bonne in Barbary, the heat of which was as high as 1710.1 Although man is capable of breathing with impunity air, heated to above the boiling point of water, we have seen, that he cannot bear the contact of Avater much below that temperature. Yet we find certain of the lower animals—as fish—living in water at a temperature which would be sufficient to boil them if dead. In the thermal springs of Bahia, in Brazil, many small fishes are seen swimming in a rivulet, which raises the thermometer to 88°, when the temperature of the air is only 77J°. Sonnerat found fishes existing in a hot spring at the Manillas, at 158° Fahr.; and MM. Humboldt and Bonpland, in travel- ling through the province of Quito, in South America, percei\red them thrown up alive, and apparently in health, from the bottom of a vol- cano, in the course of its explosions, along with water and heated vapour, Avhich raised the thermometer to 210°, or only two degrees short of the boiling point.2 Dr. Reeve found living larvae in a spring, whose temperature Avas 208°; Lord Bute saAV confervse and beetles in the boiling springs of Albano, which died when plunged into cold water; and Dr. Elliotson kneAV a gentleman, who boiled some honey-comb, two years old, and, after extracting all the sweet matter, threw the refuse into a stable, which was soon filled with bees.3 When the heating influence is applied to a part of the body only, as to the urethra, the temperature of the part, it has been affirmed, is not increased beyond the degree towhich the whole body may be raised. From all these facts, then, it may be concluded, that when the body is exposed to a temperature greatly above the ordinary standard of the animal, a frigorific influence is exerted: but this is effected at a great expense of vital energy; and hence is followed by considerable ex- haustion, if the effort be prolonged. In the cold-blooded animal, the power of resisting heat is not great; so that it expires in water not 1 Girou de Buzareingues, Precis Elementaire de Physiologie Agricole, p. 126, Paris, 1849. 2 Animal Physiology, Library of Useful Knowledge, p. 3. 3 Physiology, p. 247, Lond., 1840. DIFFERS ACCORDING TO SEX, ETC. 223 hotter than the human blood occasionally is. M. Edwards found that a frog, which can live eight hours in water at 32°, is destroyed in a few seconds in water at 105°: this appears to be the highest temperature that cold-blooded animals can bear. Warm-blooded animals, when exposed to a high temperature, have their temperature increased to a certain extent; but whenever it passes this they perish. M. James1 took two rabbits, whose normal temperature was about 102-2°, and placed them in two stoves, one at 212°, the other at 140°. The first died sooner than the second; but the temperature of each at the moment of death was the same, 111#2°. The same experiment, over and over again repeated, shoAved, that whatever might be the degree at which the heat was applied, the animal died when an increase of nine degrees was attained. In birds, whose normal temperature was 111'2°, the same at which the rabbits died, death ensued on the same increase of nine degrees, or Avhen their blood reached 120'2°. Observation has shown, that although the average temperature of an animal is such as we have stated in the table, particular circum- stances may give occasion to some fluctuation. A slight difference exists, according to sex, temperament, idiosyncrasy, &c. MM. Edwards and Gentil found the temperature of a young female half a degree less than that of two boys of the same age. Edwards2 tried the tempera- ture of twenty sexagenarians, thirty-seven septuagenarians, fifteen octogenarians, and five centenarians, at the large establishment of Bicetre, and observed a slight difference in each class. Dr. John Davy3 found, that the temperature^of a lamb was a degree higher than that of its mother; and in five new-born children, the heat was about half a degree higher than that of the mother, and it rose half a degree more in the first twelve hours after birth. He subsequently examined the temperature of the aged.4 In eight old men and Avomen, all, with one exception, between eighty-seven and ninety-five years of age, the temperature under the tongue was 98°, or 98-5°; therefore little, if at all, below the average of adult persons in like circumstances. Two observations, however, showed, that on exposure to external cold, the temperature was more reduced than in young persons. In one case it fell to 95°; in the other to 96'5°. A few observations were also made on persons working in rooms at a temperature of 92°: in one case, the temperature Avas 100°, in another 100*5°; and in a third, the external temperature being 73°, it Avas 99°. The same slight variations of the temperature of superficial parts in accordance with changes of external temperature were shown by repeated observations on a healthy man in the different seasons, at Constantinople. By moderate exercise, the temperature on the surface of the extremities Avas raised—but not above the general average—and was not affected in the internal parts. Dr. G. C. Holland5 found that the mean temperature of forty infants exceeded that of the same number of adults by If ° : twelve of the 1 Gazette Medicale de Paris. 27 Avril, 1844. 2 De l'lnfluence des Agens, &c, p. 436, Paris, 1826. s Philosoph. Transact., p. 602, for 1814. 4 Philosophical Transactions for 1844, p. 57. 6 An Inquiry into the Laws of Life, &c, Edinb., 1829. 224 CALORIFICATION. children had a temperature of from 100° to 103J°. M. Edwards, on the other hand, found, that, in the warm-blooded animal, the faculty of producing heat is less, the nearer to birth; and that, in many cases as soon as the young dropped from the mother, the temperature fell to Avithin a degree or two of that of the circumambient air; and he more- over affirms, that the faculty of producing heat is at its minimum at birth, and increases successively to the adult age. His trials on chil- dren at the large Hbpital des Enfans of Paris, and on the aged at Bicetre, showed, that the temperature of infants, one or two days old was from 93° to 95° of Fahrenheit; of the sexagenarian from 95° to 97°; of the octogenarian, 94° or 95°; and that, as a general rule, it varied according to age. In his experiments connected with this sub- ject, he discovered a striking analogy betAveen Avarm-blooded animals in general. Some of these are born Avith the eyes closed; others with them open: the former, until the eyes are opened, he found to resem- ble the cold-blooded animal; the latter—or those born with the eyes open—the Avarm-blooded. Thus, he remarks, the state of the eyes, although having no immediate connexion with the production of heat, may coincide Avith an internal structure which influences' that function, and it certainly furnishes signs, which indicate a remarkable change in this respect; for, at the period of the opening of their eyes, all young mammalia have nearly the same temperature as adults. Now, in ac- cordance with analogy, a new-born infant at the full period, having its eyes open, should have the power of maintaining a pretty uniform tem- perature during the Avarm seasons; but if birth should take place at the fifth or sixth month, the case is altered; the pupil is generally covered with the membrana pupillaris, which places it in a condition similar to that of closure of the eyelids in animals. Analogy, then, would induce us to conclude, that, in such an infant, the power of pro- ducing heat should be inconsiderable, and observation confirms the con- clusion ; although we obviously have not the same facilities, as in the case of animals, of exposing the infant to a depressed temperature. The temperature of a seven months' child, though well swathed, and near a good fire, was, within tAvo or three hours after birth, no more than 89-6° Fahrenheit. Before the period at which this infant was born, the membrana pupillaris disappears; and it is probable, as M. Edwards has suggested, if it had been born prior to the disappearance of the membrane, its power of producing heat might have been so feeble, that it would scarcely have differed frgm that of mammalia born with the eyes closed.1 An extensive series of experiments has been instituted by M. Roger,1 in regard to the temperature of children in health and various diseases. In nine examinations from one to twenty minutes after birth, the tem- perature observed in the axilla was from 99*95° to 95*45.° Immedi- ately after birth it was at the highest, but quickly fell to near the low- est point stated above. By the next day, however, it was entirely, or nearly, Avhat it was before. The rapidity of the pulse and respiration appeared to have no certain relation to the temperature. In thirty- 1 Op. cit. 2 Archiv. General, de Medecine, Juillet, Aout, 1844. CIRCUMSTANCES INFLUENCING. 225 three infants, from one to seven days old, the most frequent tempera- ture was 98*6°; the average 98*75°; the maximum—one case only— was 102*2° ; the minimum—also one case—96*8°. All the infants were healthy. The frequency of respiration had no evident or constant relation to the temperature. A few of the infants were of a weakly habit; their average temperature was 97*7° : the others Avere strong, and their average temperature 99*534°. The age, at this period, had no influence on its temperature; nor had its sex, state of sleeping or waking, nor the period after suckling. In twenty-four children, chiefly boys, from four months to fourteen years old, the most frequent temperature was above 98*6° ; the average 98*978°; the minimum 98*15° ; the maximum 99*95°. The average of those six years old, or under, was 98*798° ; of those above six years, 99*158°. The average number of pulsations in the minute was, in those under six years, 102; above that age, 77 ; yet the temperature of the latter was higher than that of the former and of younger infants. There wae no evident relation between the temperature and frequency of respiration; nor, in a few examinations, was the temperature affected in a regular way, by active exercise for a short time, or by the stage of digestion. The state of the system, as to health or disease, also influences the evolution of heat. Dr. Francis Home,1 of Edinburgh, took the heat of various patients at different periods of their indispositions. He found that of two persons labouring under the cold stage of an inter- mittent to be 104°; whilst, during the sweat and afterwards, it fell to 101°, and to 99°. The highest, which he noticed in fever, was 107°. The author has Avitnessed it at 106° in scarlatina and in typhus, but it probably rarely exceeds this, although it is stated to have been as high as 112°;2 and this is the point designated as "fever heat" on Fahren- heit's scale. M. Edwards alludes to a case of tetanus, in a child, the particulars of which were communicated to him by M. PreVost, of Geneva, in which the temperature rose to 110*75° Fahrenheit.3 Mr. Hunter4 found the interior of a hydrocele, on the day of operation, to be 92°; on the following day, when inflammation had commenced, it rose to 99°. The fluid obtained from the abdomen of an individual tapped for the seventh time for ascites indicated a temperature of 101°. Twelve days thereafter, when the operation was repeated for the eighth time, it was 104°. Dr. Granville5 has asserted that the temperature of the uterus sometimes rises as high as 120°—the elevation seeming to bear some ratio to the amount of action in the organ. The author has frequently been struck with the seemingly elevated temperature of the vagina under those circumstances ; but cannot help suspecting inac- curacy in the observations of Dr. Granville, the temperature which he indicates being so much higher than has ever been noticed in any con- dition of the system. Under this feeling, several experiments were 1 Medical Facts and Experim., Lond., 1759. 2 G. T. Morgan's First Principles of Surgery, p. 80. Lond., 1837. 3 Edwards, op. citat., p. 490. 4 On the Blood, &c, p. 296, Lond., 1794. s Philos. Transact., p. 202, for 1825; and Sir E. Home, in Lect. on Comp. Anat.,v. 201, Lond., 1828. VOL. II.—15 226 CALORIFICATION, made, at the author's request, by Dr. Barnes,1 at the time one of the resident physicians of the Philadelphia Hospital, which exhibit only a slight difference between the temperature of the vagina and that of the uterus during parturition. In two cases, that of the labia was 100°, and in a third 105°; whilst that of the uterus was 100°, 102°, and 106°, respectively. Dr. James Currie had himself bled; and during the operation, the mercury of a thermometer, held in his hand, sank, at first slowly, and afterwards rapidly, nearly 10°; and when he fainted, the assistant found that it had sunk 8° farther. In diseased states, M. Roger2 found, that the temperature of the skin may descend in children to 74*3°, and rise as high as 108*5°. Its range is, conse- quently, greater than in adults, in whom M. Andral found it not to vary, in different diseases, more than from 95° to 107*6°. His esti- mates are, however, much too limited; as in Asiatic cholera the tem- perature has been marked as low as 67°, whilst in disease it has cer- tainly risen as high as nearly 111°, Fahrenheit. M. Chevallier3 has investigated the temperature of the urine on issuing from the bladder. This he found was affected by rest, fatigue, change of regimen, remain- ing in bed, &c. The lowest temperature, which was observed on rising in the morning, was about 92°; the highest, after dinner, and when fatigued, 99°. In the case of another person, the temperature of the urine was never loAver than 101°, and occasionally, when fatigued, upwards of 102°. MM. Edwards and Gentil assert, that they have likewise observed diurnal variations in the temperature, and these produced, apparently, by the particular succession in the exercise of the different organs; as where intellectual meditation was followed by digestion. The varia- tions, they affirm, frequently amounted to two or three degrees, be- tween morning and evening. Such are the prominent facts connected with the subject of animal heat. It is obvious, that it is disengaged by an action of the system, which enables it to counteract, within certain limits, the extremes of atmospheric heat and cold. The animal body, like all other substances, is subjected to the laws affecting the equilibrium, conduction, and radi- ation of caloric; but, by virtue of the important function we are now considering, its own temperature is neither elevated nor depressed by those influences to any great extent. Into the seat and nature of this mysterious process, and the various ingenious theories that have been indulged in regard to it, we shall now inquire. Physiologists have been by no means agreed as to the organs or apparatus of calorification. Some, indeed, have affirmed that there is not, strictly speaking, any such; and that it is a result of all the other vital operations. Amongst those, too, who admit the existence of such an apparatus, a difference of sentiment prevails; some thinking that it is local, or effected in a special part of the organism; others, that it is general, or disseminated through the whole economy. Under the name caloricite, M. Chaussier admitted a primary vital property, by virtue 1 American Medical Intelligencer, Feb. 15,1839, p. 346. 2 Op. cit. 3 Essai sur la Dissolution de la Gravelle, &c, p. 120, Paris, 1837. THEORIES OF CALORIFICATION. 227 of which living beings disengage the caloric on which their proper tem- perature is dependent, in the same manner as they accomplish their other vital operations by distinct vital properties; and in support of the views, he adduced the circumstance, that each living body has its own proper temperature;—which is coexistent only Avith the living state; is common to every living part; ceases at death; and augments by every cause that excites the vital activity. It has been properly objected, however, to this view, that the same arguments would equally apply to many other vital operations,—and that it would be obviously improper to admit, for each of these functions, a special vital property. The notion has not experienced favour from the physiologist, and is, we believe, confined to the individual from Avhom it emanated. So striking a phenomenon as animal temperature could not fail to attract early attention; and accordingly, we find amongst the ancients various speculations on the subject. The most prevalent was,—that its seat is in the heart; that the heat is communicated to the blood in that viscus, and is afterwards sent to every part of the system; and that the great use of respiration is to cool the heart. This hypothesis is liable to all the objections that apply to the notion of any organ of the body acting as a furnace,—that such organ ought to be calcined; and it has the additional objection, applicable to all speculations regarding the ebullition and effervescence of the blood as a cause of heat, that it is purely conjectural, without the slightest fact or plausible argument in its favour. It was not, indeed, until the chemical doctrines pre- vailed, that any thing like argument was adduced in support of the local disengagement of heat: the opinions*of physiologists then settled almost universally upon the lungs; and this, chiefly, in consequence of its being observed, that animals, which do not breathe, have a tempera- ture but little superior to the medium in which they live; whilst man and animals that breathe have a temperature considerably higher than the medium heat of the climate in which they exist, and one which is but little affected by changes in the thermal condition of that medium; and, moreover, that birds, which breathe, in proportion, a greater quan- tity of air than man, have a still higher temperature than he. Mayow,1 whose theory of animal heat was, in other respects, sufficiently unmean- ing, affirmed, that the effect of respiration is not to cool the blood, as had been previously maintained, but to generate heat, which it does by an operation analogous to combustion. It was not, however, until the promulgation of Dr. Black's doctrine of latent heat, that any plausible explanation of the phenomenon appeared. According to that distin- guished philosopher, a part of the latent heat of the inspired air be- comes sensible; consequently, the temperature of the lungs, and of the blood passing through them, must be elevated; and, as the blood is dis- tributed to the whole system, it must communicate its heat to the parts as it proceeds on its course. But this view was liable to an obvious objection, which was, indeed, fatal to it, and so Dr. Black himself appears to have thought, from his silence on the subject. If the whole of the caloric were disengaged in the lungs, as in a furnace, and were 1 Tract, quinque, Oxon., 1674. 228 CALORIFICATION. distributed through the bloodvessels, as heated air is transmitted along conducting pipes, the temperature of the lungs ought to be much greater than that of the parts more distant from the heart; and so con- siderable as to consume that important organ in a short space of time. The doctrine, maintained by MM. Lavoisier1 and Se'guin, AYas;—that the oxygen of the inspired air combines with the carbon and hydrogen of the venous blood, and produces combustion. The caloric given off is then taken up by the bloodvessels, and is distributed over the body. The arguments, Avhich they urged in favour of this view, were:—the great resemblance between respiration and combustion, so that if the latter gives off heat, the former ought to do so likewise;—the generally admitted fact, that arterial blood is somewhat warmer than venous;— and certain experiments of Lavoisier and La Place,2 which consisted in placing animals in the calorimeter, and comparing the quantity of ice which they melted, and, consequently, the quantity of heat, which they gave off, with the quantity of carbonic acid produced; and finding, that the quantity of caloric, which would result from the carbonic acid formed, was exactly that disengaged by those animals. Independently, how- ever, of other objections, this hypothesis is liable to those already urged against that of Black, which it closely resembles. The objection, that the lungs ought to be much hotter than they really are—both absolutely and relatively—was attempted to be obviated by Dr. Crawford3 in a most ingenious and apparently logical manner. The oxygen of the inspired air, according to him, combines vwith the carbon given out by the blood, so as to form carbonic acid. But the specific heat of this is less than that of oxygen; and accordingly, a quantity of latent caloric is set free; and this caloric is not only sufficient to support the tem- perature of the body, but also to carry off the water—which was sup- posed to be formed by the union of the hydrogen of the blood and the oxygen of the air—in the state of vapour, and to raise the temperature of the inspired air. So far the theory of Crawford was liable to the same objections as those of Black, and Lavoisier and Seguin. He affirmed, however, that the same process by which the oxygen of the inspired air is converted into carbonic acid, converts the venous into arterial blood; and as he assumed from his experiments, that the capa- city of arterial blood for caloric is greater than that of venous, in the proportion of 1*0300 to 0*8928; he conceived, that the caloric, set free in the formation of the carbonic acid, in place of raising the tempera- ture of the arterial blood, is employed in saturating its increased capa- city, and maintaining its temperature at the same degree with the venous. According to this view, therefore, the heat is not absolutely set free in the lungs, although arterial blood contains a greater quantity of caloric than venous; but when, in the capillaries, the arterial becomes converted into venous blood, or into blood of a less capacity for caloric, the heat is disengaged, and this occasions the temperature of the body. Were the facts, which served as a foundation for this beautiful theory 1 Mem. de l'Acad. des Sciences pour 1777, 1780, and 1790. 2 Memoir, de l'Acad. des Sciences pour 1780. 3 Experiments and Observations on Animal Heat, &c, 2d edit., London, 1788; and Flem- ing, Philosophy of Zoology, i. 387, Edinb., 1822. i THEORIES OF CALORIFICATION. 229 true, the deductions would be irresistible: and, accordingly, it was at one time almost universally received, especially by those who consider, that all vital operations can be assimilated to chemical processes; and it is still favoured by many. "The animal heat," observes a recent writer,1 "has been accounted for in different ways by several ingenious physiologists: from the aggregate of their opinions and experiments, I deduce, that heat is extricated all over the frame, in the capillaries, by the action of the nerves, during the change of the blood, from scarlet arterial to purple venous; and also whilst it is changing in the lungs from purple to scarlet. There is a perpetual deposition by the capillary system of new matter, and decomposition of the old all over the frame, influenced by the nerves ; in this decomposition there is a continual dis- engagement of carbon, which mixes with the blood returning to the heart, at the time it changes from scarlet to purple; this decomposition, being effected by the electric agency of the nerves, produces a constant extrication of caloric ; again, in the lungs that carbon is thrown off and united with oxygen, during which caloric is again set free, so that-we have in the lungs a charcoal fire constantly burning, and in the other parts a wood fire, the one producing carbonic acid gas, the other carbon, the food supplying through the circulation the vegetable (or what answers the same end, animal) fuel, from which the charcoal is prepared which is burned in the lung." Numerous objections have, however, been made against the view of Crawford. In the first place, it A^as objected, that our know- ledge is limited to the fact, that oxygen is taken into the pulmonary vessels, and carbonic acid given off, but that we have no means of knowing whether-the one goes immediately to the formation of the other. Dr. Crawford had inferred from his experiments, that the specific heat of oxygen is 4*7490; of carbonic acid, 1*0454; of nitrogen, 0*7936; and of atmospheric air, 1*7900 ; but the more recent experiments of MM. Delaroche and Bdrard make that of oxygen, 0*2361; carbonic acid, 0*2210; of nitrogen, 0*2754; and of atmospheric air, 0*2669 ; a difference of such trifling amount, that it has been conceived the quan- tity of caloric, given out by oxygen during its conversion into carbonic acid, would be insufficient to heat the residual air in the lungs to its ordinary elevation. Secondly. The elevation of temperature of one or two degrees, which appears to take place in the conversion of venous into arterial blood, although generally believed, is not assented to by all (see page 60). The experiments instituted on this point have been few and imprecise; and those of MM. Becquerel and Breschet,2 made by introducing delicate thermometers into the auricles of the heart of dogs, invariably gave the temperature of arterial, only a few fractions of a degree higher than that of venous, blood. Thirdly. M. Dulong,3— on repeating the experiments of Lavoisier and La Place, for comparing the quantities of caloric given off by animals in the calorimeter with that which Avould result from the carbonic acid formed during the same time in their respiration—did not attain a like result. The quantity of caloric disengaged by the animal was always superior to that which 1 Billing, First Principles of Medicine, 2d edit., p. 19, London, 1837. 2 Comptes Rendus, Oct., 1841. * Magendie, Journal de Physiologie, iii. 45. 230 CALORIFICATION. would result from the carbonic acid formed. Fourthly. The estimate of Crawford regarding the specific heat of venous and arterial blood has been contested. He made that of the former, we have seen, 0*8928; of the latter, 1*0300. The result of the experiments of Dr. John Davy1 give 0*903 to the former, and 0*913 to the latter; and in another case, the result of which has been adopted by M. Magendie, the specific heat of venous was greater than that of arterial blood, in the proportion of •852 to *839. Granting, however, the case to be as stated by Craw- ford, it is insufficient to explain the phenomena. It has, indeed, been attempted to show, that if the whole of the caloric, set free in the manner mentioned, were immediately absorbed, it would be insufficient for the constitution of the arterial blood; and that, instead of the lung running the risk of being calcined, it would be threatened with con- gelation. The theory of combustion is still, however, maintained by many physiologists,2 and an able writer of this country, Dr. Metcalfe,3 from a consideration of the various facts observed by himself and others, thinks we are authorized to, conclude;—first, that during the passage of dark venous blood through the lungs, it gives off variable proportions of carbon and hydrogen, which unite chemically with atmospheric oxy- gen to form carbonic acid and water as in ordinary combustion, by which it acquires an addition of caloric, and a bright florid hue; and secondly, that during its circulation through the systemic capillaries, the caloric obtained from the atmosphere is transferred to the solids, by which their temperature and vitality are maintained; and the blood returns to the heart of a dark modena hue, having lost its power of stimulating the organs, until it acquires an additional quantity of caloric from the lungs. Dr. Spencer,4 formerly of Geneva College, N. Y., who regards the great end and function of respiration to be, to aid, both directly and indirectly, in the office of the generation and diffusion of animal heat, maintains, that the substance thrown off from the venous blood in respira- tion is hydrate of carbon:—that the carbon, on coming in contact with atmospheric oxygen combines with it, forming carbonic acid, which is exhaled from the lungs and skin by expiration and perspiration;—that the amount of latent heat of the oxygen employed is much greater than that of the carbonic acid formed in the lungs, and hence caloric is set free, which imparts heat to the blood and surface; that this free heat also combines with the water of the hydrate of carbon and converts it into vapour;—that the lungs and cutaneous surface aid in regulating animal temperature by the conversion of water into vapour, thus con- veying off any excess of free caloric in the system, by combining with it in the form of latent heat;—that the water of the hydrate of carbon is converted into vapour in the lungs, and upon the surface, precisely as when wood is burned, and hence assumes the form of insensible respiratory and perspiratory transpiration;—and that the systemic red 1 Philos. Transactions for 1814. 2 Nasse, Art. Thierische Warme, in Wagner's Handworterbuch der Physiologie; 23ste Lieferung, s. 1, Braunschweig, 1849. 3 Caloric, its Mechanical, Chemical, and Vital Agencies, &c, ii. 555, London, 1843. 4 Lectures on Animal Heat, Geneva, N. Y., 1845. THEORIES OF CALORIFICATION. 231 capillaries are the antagonists of the pulmonary; and are constantly decomposing carbonic acid, and forming, with water, hydrate of car- bon,—or, in other words, carbonizing the blood; from which union water and carbonic acid are transformed into a solid substance, and hence latent becomes free heat, at every point where red blood circu- lates. The views of Dr. Spencer are ingenious, but far from convinc- ing; and are presented by him, although aphoristically, in some detail. He objects to the view, Avhich holds that hydro-carbon is thrown off from the blood in the lungs by its union with oxygen, because hydro-carbon is an imaginary compound. The same objection, howeA'er, applies to his hydrate of carbon, which, he thinks, exists in the blood in the solid state, and is analogous to, if not identical with, the lignin of vegetables. In regard to his opinion, that the systemic red capillaries are the antago- nists of the pulmonary capillaries, it must not be forgotten, that there are also red capillaries in the lungs; and that in the system of nutrition every where arterial is converted into venous blood; and doubtless with the same phenomena. The combustion theory has received the powerful support of Liebig, and many elucidations and expansions from that distinguished chemist. According to him, the carbon and hydrogen of the food, in being con- verted, through the agency of oxygen, into carbonic acid and water, must give out as much heat as if these gases were burned in the open air. The temperature of the human body is essentially the same in the torrid as in the frigid zone; but as the body may be regarded in the light of a heated vessel, which cools with the greater rapidity the colder the surrounding medium, the fuel, necessary to maintain its heat, must vary in different climates. How unequal must be the loss of heat at Palermo, where the external temperature is nearly equal to that of the body, and in the polar regions, where the external temperature is from 70° to 90° lower. In the animal body, food is fuel, and with a proper supply of oxygen we obtain the heat during its oxidation or combustion. In winter, when we take exercise in a cold atmosphere, and the amount of inspired oxygen consequently increases, the neces- sity for food containing carbon and hydrogen increases in the like ratio, and, by gratifying the appetite thus excited, we obtain the most efficient protection against piercing cold. A starving man is soon frozen to death; and every one, says Liebig, knows, that the animals of prey in the Arctic regions far exceed those of the torrid zone in voracity. Our clothing is merely an equivalent for a certain amount of food. Were we to go naked, like certain savage tribes, or exposed in hunting or fishing to the same degree of cold as the Samoyedes, we should be able to consume with ease sixteen pounds of flesh, and perhaps a dozen tallow candles, as travellers have related of those people. We should, also, be able to take the same quantity of brandy or train-oil without bad effects, because the carbon and hydrogen of these substances would only suffice to keep up the equilibrium between the external tempera- ture and that of our bodies. The whole process of respiration, he thinks, is clearly exhibited when we view the condition of man or ani- mals under abstinence from food. Oxygen is abstracted from the air, and carbonic acid and water expired, because the number of respirations 232 CALORIFICATION. remains unaltered. With the continuance of the abstinence the carbon and hydrogen of the body diminish. The first effect of abstinence is the disappearance of the fat, Avhich can be detected neither in the scanty faeces nor urine; its carbon and hydrogen are thrown off by the skin and lungs, in the form of a compound with oxygen. These constituents, then, have served for the purposes of respiration. Every day, 32J ounces of oxygen are inspired; and these must remove their equivalents of carbon to form carbonic acid. When this combination ceases to go on, respiration terminates: death has ensued. The time required for starving an animal to death depends on its fatness, state of activity, the temperature of the air, and the presence or absence of water. That the quantity of heat evolved by the combustion of 13*9 ounces of carbon is amply sufficient to account for the temperature of the human body, may be estimated by figures. An ounce of carbon burned, according to the experiments of Despretz, would evolve 14067 degrees of heat; and 13-9 oz. would, therefore, give out 195531*3 degrees of heat. This would suffice to boil 67*9 pounds Of water at 32°, or to convert 11*4 pounds of water at 98*3° into vapour. If we consider the quantity of water vaporized through the skin to be, in twenty-four hours, 48 ounces or 3 pounds, there will then remain, after deducting the necessary amount of heat, 144137*7 degrees of heat, which are dissipated by radiation in heating the expired air, and in excrementi- tious matters.1 These views of Liebig necessarily attracted the devout attention of the chemical physiologist, and whilst they have met with unqualified support from some, they have been as much condemned by others, who appear to have a horror at the introduction of chemical explanations to account for vital phenomena. Yet it cannot be contested, that the function of calorification is an act of vital chemistry; and, consequently, although the views of Liebig may fail to convince, they certainly have taken the proper direction, and, all must admit, have been plausibly and ably supported. It has been objected, that if even his theory were allowed to be applicable to mammalia, birds, and reptiles, it by no means follows, that it should be so to animals that respire by means of branchiae or gills, all of which consume little oxygen, comparatively speaking; yet many of them devour enormous quantities of food. Even the largest and most voracious of the reptiles, as alligators, crocodiles, &c, under a burning climate too, breathe feebly with their vesicular lungs, and consume but little oxygen. Fishes, too, whose blood is but imperfectly oxygenized by their branchial apparatus, are perhaps amongst the most voracious of animals; yet, according to this theory, they ought to eat little, because they consume little oxygen. These and other facts were eagerly urged by M. Virey,2 as objections to the views of the Professor of Giessen. It may be replied, however, that in such cases, a large portion of the carbon must pass off in the excre- ments. There is no country in the world, according to Madame Cal- deron de la Barca,3 where so much animal food is consumed as in 1 Animal Chemistry, Amer. edit, by Webster, p. 33, Cambridge, 1842. 2 Journal de Pharmacie, Mai, 1842. 3 Life in Mexico, vol. i. p. 152, Boston, 1842. THEORIES OF CALORIFICATION. 233 Mexico, "and there is no country in which so little is required." To this and to want of exercise she ascribes the early fading of beauty in the higher classes, the decay of teeth, and the over-corpulency so com- mon amongst them; and in regard to the last she is, doubtless, correct. To the statement of Liebig respecting the greater voraciousness of the animals of prey of the Arctic regions, it has been replied,1 that a Bengal tiger or Cape hyena requires, in proportion to its size, quite as much aliment as any of the Arctic carnivora; and that the vultures of Hindostan and Persia exceed, perhaps, all other animals in gluttony. The voraciousness of the shark, too, even Avithin the tropics, is pro- verbial. " Those who ride over the Pampas in South America," says Dr. Graves, " at the rate of one hundred miles a-day, exposed to a burning sun, subsist entirely on boiled beef and Avater, without a par- 0 tide of vegetable food of any kind, and yet they attain to an extraor- dinary condition, and capability of enduring violent and long-continued exertion. Liebig's theory must be very ductile, if it can explain how it happens, that an exclusively animal diet agrees with man quite as well at the equator as within the Arctic circle."2 Numerous facts, indeed, can be brought forward of an opposite tendency to those of Liebig, which render it impracticable for us, in the present state of our knowledge, to embrace all his positions. Under Respiration, the theory, supported by him, that the blood corpuscles are the carriers of oxygen from the lungs to the tissues, and the conveyers of carbonic acid back from the tissues to the lungs, Avas mentioned. Were this view tenable it would seem, that if the amount of blood corpuscles should become diminished from any cause, the function of calorification ought to be impaired to a like extent. To discover what effect would be produced on the temperature of the living body by a diminution in the quantity of blood corpuscles, M. Andral instituted some experiments, which showed, that the temperature remained normal, even in cases in Avhich the corpuscles had experienced the greatest diminution in number. In the axilla, the temperature was 98° or 99° of Fahrenheit in persons, the proportion of whose blood corpuscles was not higher than 50, 40, 30, and even 21 parts in the 1000; the healthy ratio being 127. In- deed, notwithstanding the great depression in ansemic patients, the heat rose, as usual, when they were attacked with fever, to which they are as subject as other individuals.3 But the combustion theories of calorification were most seriously assailed by experiments, tending to show, that the function of calorifi- cation is derived from the great nervous centres. When an animal is decapitated, or the spinal marrow, or the brain, or both, are destroyed, the action of the heart may still be kept up, provided the lungs be arti- ficially inflated. In such case, it is found, that the usual change in the blood, from venous to arterial, is produced; and that oxygen is ab- sorbed and carbonic acid exhaled as usual. Sir Benjamin Brodie,4 in performing this experiment, directed his attention to the point—whe- 1 R. J. Graves, a System of Clinical Medicine, p. 57, Dublin, 1843. a See, on all this subject, Metcalfe on Caloric, vol. ii. chap. 2, London, 1843. 3 Andral, Hematologic Pathologique, p. 60, Paris, 1843. 4 Philos. Trans, for 1811 and 1812. 234 CALORIFICATION. ther animal heat be evolved under such circumstances, and the tem- perature maintained, as where the brain and spinal marrow are entire— and he found, that although the blood appeared to undergo its Ordinary changes, the generation of animal heat seemed to be suspended; and consequently, if the inspired air happened to be colder than the body, the effect of respiration was to cool the body; so that an animal, on which artificial respiration had been kept up, became sooner cold than one killed and left undisturbed. The inference from these experiments, was, that instead of circulation and respiration maintaining heat, they dissipate it; and that as the heat is diminished by the destruction of the nervous centres, its disengagement must be ascribed to the action of those centres, and especially to that of the encephalon. Thirty years ago, M. Chossat1 endeavoured to discover the precise part of the nervous system that is engaged in calorification; but the results of his experiments were not such as to induce him to refer it exclusively, with Sir B. Brodie, to the encephalon. He divided the brain, anterior to the pons Varolii, in a living animal, so that the eighth nerve was uninjured. Respiration, consequently, continued, and inflation of the lungs was unnecessary. Notwithstanding this serious mutilation, the circulation went on ; and M. Chossat observed distinctly, that arterial blood circulated in the arteries. Yet the temperature of the animal gradually sank, from 104° Fahr.,—its elevation at the com- mencement of the experiment,—to 76°, in twelve hours, when the ani- mal died. It seemed manifest to M. Chossat, that, from the time the brain was divided, heat was no longer given off, and the body gradually cooled, as it would have done after death. He, moreover, noticed, that the time, at which the refrigeration occurred most rapidly was that in which the circulation was most active,—at the commencement of the experiment. In other experiments, M. Chossat paralysed the action of the brain by violent concussion, and injected a strong decoction of opium into the jugular vein,—keeping up artificial respiration. The results were the same. From these experiments, he drew the conclu- sion, that the brain has a direct influence over the production of heat. His next experiments were directed to the discovery of the medium through which the brain acts,—the eighth pair of nerves, or spinal mar- row. He divided the eighth pair in a dog, and kept up artificial respi- ration. The temperature sank gradually; and, at the expiration of sixty hours, when the animal died, it was reduced to 68° of Fahrenheit. Yet death did not occur from asphyxia or suspension of the phenomena of respiration ; for the lungs crepitated ; exhibited no signs of infiltra- tion, and were partly filled with arterial blood. The animal appeared to M. Chossat to expire from cold. As, hoAvever, the mean depression of heat Avas less than in the preceding experiments, he inferred that a slight degree of heat is still disengaged after the section of the eighth pair; whilst, after injury done to the brain directly, heat is no longer given off. Again, he divided the spinal marrow beneath the occiput, and although artificial respiration was maintained, as in the experi- ments of Sir B. Brodie, the temperature gradually fell, and the animal 1 Sur la Chaleur Animale, Paris, 1820, and Adelon, op. cit., iii. 416. THEORIES OF CALORIFICATION. 235 died ten hours afterwards, its heat being 79°; and as death occurred in this case so much more speedily than in the last, he inferred, that the influence of the brain over the production of heat is transmitted rather by the spinal marrow than by the eighth pair. In his farther experiments, M. Chossat discovered, when the spinal marrow was divided between each of the twelve dorsal vertebrae, that the depression of tem- perature occurred less and less rapidly, the lower the intervertebral section; and at the lowest was imperceptible: he, therefore, con- cluded, that the spinal marrow does not act directly in the function, but indirectly through the trisplanchnic nerve. To satisfy himself on this point, he opened the left side of a living animal, beneath the twelfth rib, and removed the left supra-renal capsule, dividing the trisplanch- nic where it joins the semilunar plexus. The animal lost its heat gra- dually, and died ten hours afterwards in the same condition, as regarded temperature, as when the spinal marrow was divided beneath the occi- put. Desiring to obtain more satisfactory results,—the last experi- ment applying to only one of the trisplanchnic nerves,—he tied the aorta, which supplies both, beneath the place where it passes through the arch of the diaphragm, at the same time preventing asphyxia by inflating the lungs. The animal lost its heat much more rapidly; and died in five hours. In all these cases, according to M. Chossat, death occurred from cold; the - function, by which the caloric, constantly abstracted from the organism by the surrounding medium, is generated having been rendered impracticable. To obtain a medium of compari- son, he killed several animals by protracted immersion in cold water, and found, that the lowest temperature to which the warm-blooded could be reduced, and life persist, was 79° of Fahrenheit. He also alludes to cases of natural death by congelation, which, he conceives, destroy in the manner before suggested,—that is, by impairing the nervous energy, as indicated by progressive stupor, and debility of the chief functions of the economy. Lastly:—on killing animals suddenly, and attending to the progress of refrigeration after death, he found it to be identical with that which follows direct injury of the brain, or the division of the spinal marrow beneath the occiput. A view somewhat analogous to this of M. Chossat, was embraced by Sir Everard Home.1 He considered, that the phenomenon is restricted to the ganglionic part of the nervous system; resting his opinion chiefly on the circumstance, that there are animals, which have a brain, or some part equivalent to one, and whose temperature is not higher than that of the surrounding medium; whilst all the animals that evolve heat are provided with nervous ganglia. The doctrines of Brodie, Chossat, and Home have been considered by the generality of the chemists—by Brande,2 Thomson,3 and Paris,4 —to be completely subversive of the chemical view, which refers the production of animal heat to respiration; and their position,—that it is a nervous function,—has seemed to be confirmed by the facts at- 1 Philos. Trans., p. 257, for 1825; Journal of Science and Arts, xx. 307; and Lect. on Comparative Anat., v. 121 and 194, Lond., 1828. 2 Manual of Chemistry, vol. iii. 3 System of Chemistry, vol. iv. 4 Medical Chemistry, p. 327, Lond., 1825. 236 CALORIFICATION. tendant upon injury done to the nerves of parts, and by what is wit- nessed in paralytic limbs, the heat of which is generally and markedly inferior to that of the sound. But there are many difficulties in the way of admitting, that the nervous system is the special organ for the production of animal temperature. Dr. Wilson Philip,1 from a repeti- tion of the experiments of Sir Benjamin Brodie, was led to conclude, that the cause of the temperature of the body diminishing more rapidly, when artificial inflation was practised, than when the animal was left undisturbed, was—too large a quantity of air having been sent into the lungs; for he found, when a less quantity was used, that the cooling process was sensibly retarded by the inflation. The experiments of Legallois,2 Hastings,3 and Williams,4 although differing from each other in certain particulars, corroborate the conclusion of Dr. Philip; and, what is singular, appear to show, that the temperature occasionally rises during the experiment; a circumstance which tends rather to con- firm the view, that respiration is concerned materially in the evolution of heat. Many of the facts detailed by M. Chossat are curious, and exhibit the indirect agency of the nervous system; but his conclusion, that the trisplanchnic is the great organ for its developement, is liable to the objections already brought against the theory, which looks upon the heart, or the lung, as a furnace for the disengagement of caloric,—that they ought to be consumed in a short space of time. All the facts, however, clearly show, that, in the upper classes of animals, the three great acts of innervation, respiration, and circulation are indirectly concerned in the function; but not that any one of them is the special seat. M. Edwards has maintained, that it is more connected with the second of these than with either of the others. Thus, animals, he argues, whose temperature is highest, bear privation of air least: cold- blooded animals suffer comparatively little ; and young animals are less affected than the adult. Now, the greater the temperature of the ani- mal, and the nearer the adult age, the greater is the consumption of oxygen. He farther observed, that whilst season modifies calorification, it affects also respiration; and if, in summer, less heat be elicited, and in winter more, it is found that respiration consumes less oxygen in the former than in the latter season. The experiments of M. Legallois, as well as those instituted by M. Edwards, led the latter to infer, that there is a certain ratio between heat and respiration in both cold-blooded and warm-blooded animals, and in hibernating animals both in the periods of torpidity and full activity. When the eighth pair of nerves is divided in the young of the mam- malia, a considerable diminution is produced in the opening of the glottis; so that, in puppies recently born, or one or two days old, so little air enters the lungs, that when the experiment is made under ordinary circumstances the animal perishes as quickly as if it were 1 An Experimental Inquiry into the Laws of the Vital Functions, 3d edit., p. 180. 2 Annales de Chimie, iv. 5. Paris, 1817. 3 Wilson Philip, op. cit.; and Journal of Science, &c, xiv. 96. 4 Edinb. Medico-Chirurgical Transact., ii. 192. THEORIES OF CALORIFICATION. 237 entirely deprived of air. It lives about half an hour. But, if the same operation be performed upon puppies of the same age benumbed with cold, they live a Avhole day. In the first case M. Edwards thinks, and plausibly, the small quantity of air is insufficient to counteract the effect of the heat, whilst, in the other, it is sufficient to prolong life considerably; and he draAvs the following practical inferences applica- ble to the adult age, and particularly to man. A person is asphyxied by an excessive quantity of carbonic acid in the air he breathes; the pulse is no longer perceptible; the respiratory movements cannot be discerned, but his temperature is still elevated. How should we pro- ceed to recall life ? Although the action of the respiratory organs is no longer perceptible, all communication with the air is not cut off. It is in contact with the skin, on which it exerts a vivifying influence: it is also in contact Avith the lungs, in which it is renewed by the agitation constantly taking place in the atmosphere, and by the heat of the body, which rarefies it. The heart continues to beat, and a certain degree of circulation is kept up, although not perceptible by the pulse. The temperature of the body is too high to allow the feeble respiration to produce upon the system all the effect of Avhich it is capable. The temperature must, therefore, be reduced; the patient withdrawn from the deleterious atmosphere; be stripped of his clothes, in order that the air may have a more extended action upon his skin; be exposed to the cold, although it be winter, and cold water be thrown upon his face until.the respiratory movements reappear. This is precisely the treat- ment adopted to revive an individual from a state of asphyxia. If, instead of cold, continued warmth were to be applied, it would be one of the most effectual means of extinguishing life,—a consequence, which like the former, is confirmed by experience. In sudden faintings, when the pulse is weak or imperceptible, the action of the respiratory organs diminished, and sensation and voluntary motion suspended, persons, the most ignorant of medicine, are aware, that means of refrigeration must be employed,—such as exposure to air, ventilation, and sprinkling with cold water. In violent attacks of asthma, also, when the extent of respiration is so limited that the patient experiences a sense of suffoca- tion, he courts the cold air even in the severest weather; opens the windows; breathes a frosty air, and finds himself relieved. As a general rule, an eleA'ated temperature accelerates the respira- tory moArements, but the degree of temperature requisite to produce this effect is not the same in all persons. The object of the accelerated respiration is, that more air may come in contact Avith the lungs in a given time, so as to reanimate what the heat depresses. It is proper to remark, however, that we meet with many exceptions to the rule en- deavoured to be laid down by M. Edwards, as regards the constant ratio between heat and respiration. Experiments on the lower ani- mals, and pathological cases in man, have shown, that lesions of the upper part of the spinal marrow give occasion, at times, to an extra- ordinary developement of heat. In the case of a man at St. George's Hospital, London, labouring under a lesion of the cervical vertebrae, Sir B. Brodie observed the temperature to rise to 111°, at a time Avhen 238 CALORIFICATION. the respirations were not more than five or six in a minute.1 Drs. Graves and Stokes2 give the case of a patient who laboured under very extensive developement of tubercles, had tubercular abscesses in the upper portions of both lungs, and general bronchitis. In this case, at a period when the skin was hotter than usual, and the pulse 126, the respirations were only 14 in a minute. Besides, as Dr. Alison* has remarked, the temperature of the body is not raised by voluntarily in- creasing or quickening the acts of respiration, but by voluntary exer- tions of other muscles, Avhich accelerate the circulation, and thus necessitate an increased frequency of respiration;—a fact, Avhich would seem to show that calorification is dependent not simply on the appli- cation of oxygen to the blood, but on the changes that take place during the circulation, and to the maintenance of which its oxygena- tion is one essential condition. Moreover, in the foetus in utero, there is, of course, no respiration; yet its temperature equals, and indeed is said to even exceed, that of the mother; and we know that its circula- tion is more rapid, and its nutrition more active.4 That innervation is indirectly concerned in the phenomenon is proved by the various facts, which have been referred to; and Legallois, al- though he does not accord with Sir B. Brodie, conceives that the tem- perature of the body is greatly under the influence of the nervous system, and that whatever weakens the nervous power, proportionally diminishes the capability of producing heat. Dr. Philip, too, concluded from his experiments, that the nervous influence is so intimately con- nected with the power of evolving heat, that it must be looked upon as a necessary medium between the different steps of the operation. He found, that if the galvanic influence be applied to fresh-drawn arterial blood, an evolution of heat, amounting to three or four de- grees, takes place; at the same time, the blood assumes the venous hue, and becomes partly coagulated. He regards the process of calorifica- tion as a secretion; and explains it upon his general principle of the identity of the nervous and galvanic influences, and the necessity for the exercise of such influence in the function of secretion. Mr. H. Earle5 found the temperature of paralysed limbs slightly lower than that of sound limbs, and the same effect is observed to supervene on traumatic injuries of the nerves. In a case of hemiplegia, of five months' duration, under the author's care at the Blockley Hospital, the thermometer in the right—the sound—axilla of the man stood at 96J°; in the axilla of the paralysed side, at 96°. The difference in temperature of the hands was more marked—that of the right being 87°, whilst that of the left was only 79|°. In another case—that of a female—of two weeks' duration, accompanied with signs of cerebral 1 London Medical Gazette for June, 1836. 2 Dublin Hospital Reports, vol. v.; and Dr. Graves, Clinical Lectures, American Med. Lib. edit., p. 126, Philad., 1838. 3 Outlines of Physiology, Lond., 1831. 4 On the connexion of respiration with calorification, see P. H. Berard, art. Chaleur Animale, in Diet, de Med., 2de edit., vii. 175, Paris, 1834 ; and Mr. Newport on the Tem- perature of Insects, and its Connexion with the Functions of Respiration and Circulation in this Class of Invertebrated Animals, Philos. Transact., part ii. 4to. p. 77, Lond., 1837. 5 Medico Chirurgical Transactions, vii. 173, Lond., 1819. THEORIES OF CALORIFICATION. 239 turgescence, the temperature in the axilla of the sound side was 100°• in that of the paralysed 98*25°: of the hand of the sound side, 94°\ of the other, 90°. It is a general fact, that the temperature of the paralysed side in hemiplegia is less than that of the sound; yet the irregularity of nervous action is so great, and the power of resistance to excitant or depressing agents so much diminished, that the author has not unfrequently found it more elevated.1 In such cases, more- over, the nutrition of the limb will fall off, in consequence of the want of exercise; and this circumstance would sufficiently account for any diminution of temperature that might be manifested. Lastly, that the circulation is necessary to calorification, we have evidence in the circumstance, that if the vessels proceeding to a part be tied, animal heat is no longer disengaged from it. It has been seen, however, that there is no certain ratio between the heat and frequency of the pulse. It is manifest, then, that in animals, and especially in the warm- blooded, the three great vital operations are necessary for the disen- gagement of the due temperature, but we have no sufficient evidence of the direct agency of any one; whilst we see heat elicited in the vegetable, in which these functions are at all events rudimental; and the existence of one of them—innervation—more than doubtful. The views of those who consider, that the disengagement of caloric occurs in the intermediate system or system of nutrition of the whole body, appear to be most consistent with observed phenomena. These have varied according to the physical circumstances, that have been looked upon as producing heat. By some, it was regarded as the pro- duct of an effervescence of the blood and humours; by others, as owing to the disengagement of an igneous matter or spirit from the blood; by others ascribed to an agitation of the sulphureous parts of the blood; whilst Boerhaave2 and Douglas3 ascribed it to the friction of the blood against the parietes of the vessels, and of the corpuscles against each other. In favour of the last hypothesis, it was urged, that animal heat is in a direct ratio with the velocity of the circulation, the circumference of the vessels, and the extent of their surface; and that we are thus able to explain, why the heat of parts decreases in a direct ratio with their distance from the heart; whilst the greater heat of the arterial blood in the lungs was accounted for by the supposition, that the pulmonary circulation is far more rapid. Most of these notions—it need scarcely be said—were entirely hypothetical. The data were generally incorrect, and the deductions characteristic of the faulty physics of the period in which they were hazarded. The correct view, it appears to us, is, that caloric is disengaged in every part, by a special chemico-vital action, which, in animals, is greatly under the nervous influence. In this manner, calorification becomes a function executed in the whole system of nutrition; and, therefore, appropriately 1 American Med. Intelligencer, Oct. 15, 1838, p. 252. 2 Van Swieten, Comment, in Boerhaav. Aphorism., &c, §§ 382, 675, Lugd. Bat., 1742- 3 On Animal Heat, p. 47, Lond., 1747. 240 CALORIFICATION. considered in this place. It has been remarked by Tiedemann,1 that the intussusception of alimentary matters, and their assimilation by digestion and respiration ; the circulation of the humours; nutrition and secretion; the renewal of materials accompanying the exercise of life, and the constant changes of composition in the solid and liquid parts of the organism,—all of which are influenced by the nervous sys- tem,—participate in the evolution of heat, and we deceive ourselves, when we look for the cause in one of those acts only. In certain ex- periments by Dr. Robert E. Rogers,2 of the University of Virginia, he found that when recently drawn venous blood contained in a freshly removed pig's bladder was immersed in oxygen gas, there was a re- markable elevation of temperature. Dr. Davy3 performed experiments which led to the same results. In one of these, he took a very thin vial, of the capacity of eight fluidounces, and carefully enveloped it in badly conducting substances,—for example, in several folds of flannel, fine oiled paper, and oiled cloth. Thus prepared, and a perforated cork being provided holding a delicate thermometer, two cubic inches of mercury were introduced, and immediately after it was filled with venous blood kept liquid by agitation. The vial was then corked, and shaken. The thermometer included was stationary at 45°. After five minutes, during which it remained so, it was withdrawn; the vial, closed by another cork, was transferred inverted to a mercurial bath, and 1J cubic inch of oxygen introduced. The common cork was re- turned, and the vial was well agitated for about a minute; the ther- mometer was now introduced; it rose immediately to 46°, and by con- tinuing the agitation, to 46*5°, and very nearly 47°. This experiment was made on the blood of the sheep. These, and other experiments of a similar character, Dr. Davy thinks, appear to favour the idea, that animal heat is owing, first, to the fixation or condensation of oxygen in the blood of the lungs in its conversion from venous to arterial; and secondly, to the combinations into which it enters in the circulation in connexion with the different secretions and changes essential to animal life. More recent experiments by M. Chossat,4 confirm the view of the great dependence of calorification on the proper supply of materials on which changes have to be effected in the system of nutrition. He found, that birds, totally deprived of food and drink, experienced a gradual, although slight daily diminution of temperature. This was not shown so much by a fall of their maximum heat, as by an increase in the diurnal variation which existed in the healthy state. The amount of this variation in birds properly supplied with food is 1 J° of Fahrenheit daily—the maximum being about noon, and the minimum at midnight. In the state of inanition, however, the average variation was about 6°, and it increased as the animal became weaker. The 1 Traite de Physiologie, &c, trad. par. Jourdan, p. 514, Paris, 1831. 2 Amer. Journal of the Med. Sciences, p. 297, for Aug., 1836. 3 Proceedings of the Royal Society for 1837-8, No. 34, and Researches Physiological and Anatomical, American Med. Lib. edit., p. 89, Philad., 1840. 4 Recherches Experimentales sur l'lnanition, Paris, 1843; noticed in Brit, and For. Med. Rev., April, 1844. THEORIES OF CALORIFICATION. 241 gradual rise of temperature, too, which should have taken place be- tween midnight and noon, was retarded; whilst the fall subsequent to noon commenced much earlier than in the healthy state; so that the average of the whole day was lowered by about 4J° between the first and last day but one of this condition. On the last day, the diminu- tion took place very rapidly, and the thermometer fell from hour to hour, until death supervened—the Avhole loss on that day being about 25° Fahrenheit, making the total depression about 29J°. On examin- ing the amount of loss sustained by the different organs of the body, it was found that 93 per cent, of the fat had disappeared,—all, in fact, that could be removed; whilst the nervous centres exhibited scarcely any diminution in weight. The loss in the weight of the whole body averaged about 40 per cent. This preservation of weight on the part of the nervous centres has been regarded, but Avith little plausibility, to favour the idea, that they may be formed from fatty matter,1—a por- tion of the fat absorbed being appropriated for their nutrition ; yet it would be strange, if proteinaceous compounds should be required for other organized structures, and the highest of all in importance should originate from a non-nitrogenized material, or what Liebig terms an "element of respiration." Dr. Carpenter,—in commenting on the experi- ments of Chossat—remarks, that from the constant coincidence between the entire consumption of the fat, and the depression of temperature, joined to the fact that the duration of life under the inanitiating process evidently varied cseteris paribus with the amount of fat previously accu- mulated in the body, the inference seems irresistible, that the calorify- ing power depended chiefly—if not wholly—on the materials supplied by this substance; and he adds—whenever the store of combustible matter in the system was exhausted, whether by the respiratory process alone, or by this in conjunction with the conversion of adipous matter into the materials for the nervous or other tissues, the inanitiated ani- mals died by the cooling of their bodies consequent upon the loss of calorifying power. This is plausible; yet it can be readily imagined, that the loss of the accustomed supply of aliment may so interfere with changes perpetually taking place in the system of nutrition, as to give occasion to the functional changes, Avhich eventuate in the loss of life, and that the system cannot exist for any length of time on the mate- rials that are taken up from itself. The use of the fat as a nutriment deposited for special occasions is generally admitted by physiologists. Its use as an element of respiration has only been suggested of late years; and it must be admitted, that the view Avhich has been em- braced by Dr. Carpenter is confirmed by the experiments of M. Chossat, who found that if inanitiated animals, when death is impending, were subjected to artificial heat, they were almost uniformly restored from a state of insensibility and Avant of muscular power to a condition of comparative activity; their temperature rose; muscular power re- turned; they flew about the room and took food Avhen it was presented to them; and if the artificial assistance Avas sufficiently prolonged, and they Avere not again subjected to the starving process, most of 1 Carpenter, Principles of Human Physiology, 2d edit., p. 673, London, 1844. VOL. II.—16 242 CALORIFICATION. them recovered. In other words, it might be said, that the applica- tion of artificial warmth prevented the farther consumption of the fuel —fat—and exerted a most salutary agency on the organic as well as the animal functions. The experiments of M. Chossat are the more worthy of attention and of careful repetition, from their seeming to lead to a conclusion, which, Dr. Carpenter thinks, can scarcely be questioned, from the similarity of the phenomena,—that inanitiation with its consequent depression of temperature is the immediate cause of death in various diseases of ex- haustion. Hence it has been suggested, that in those forms of febrile maladies in which no decided lesion is discoverable after death, a judi- cious and timely application of artificial heat might prolong life until the malignant influence—as in cases of narcotic poisoning—had passed away. It has been suggested, too, that the beneficial result of alcohol in pro- tracted cases of such fevers, and the large amount in which it may be given with impunity, may probably be accounted for on this principle. " We cannot support the system in fever by aliment, for this would not be digested, even if it were taken into the stomach. But we well know the beneficial effects of alcohol in its advanced stages; and the large quantity of this stimulus that may be administered in many cases of fever is a matter of familiar experience. Noav, admitting that its bene- ficial operation is partly due to its specific effect upon the nervous sys- tem, we cannot help thinking, that Ave are to regard it as also resulting from the new supply of combustible material, Avhich is thus introduced in the only form in which it can be taken up by the vascular system. If we turn our attention for a moment to the state of the digestive apparatus at this period, we shall at once see-why no other substance should answer the same purpose. In the advanced stage of fever, the secretion of gastric fluid, and the special absorbent process which take3 place through the villi and lacteals, seem to be in complete abeyance. Still, however, simple imbibition may go on through the walls of the bloodvessels, provided that the circumstances are favourable to the pro- duction of endosmose ; that is, provided the fluid in the alimentary canal is less dense than the blood. Now, the substances on which we ordi- narily depend for the support of the respiratory process are either of an oily, a saccharine, or a mucilaginous character. Oily substances cannot be taken in by imbibition, since they completely check the endos- motic current. Saccharine and mucilaginous substances can only be taken in, when their solution is so dilute as to be of a density much inferior to that of the blood ; hence they must be given in a large bulk of fluid; a practice of which experience has shown the benefit. But alcohol, being already of a density far inferior to that of the blood, is easily absorbed; and, from deficiency of other materials, it is rapidly consumed, so that a very large quantity may be thus ingested, without its stimulating effects being perceptible; just as we see that, in a very cold atmosphere, large quantities of spirituous liquors may be taken Avith impunity, on account of the rapid combustion they undergo."1 It is by the theory of the general evolution of caloric in the capillary 1 Brit, and For. Med. Rev., April, 1844, p. 356. THEORIES OF CALORIFICATION. 243 system, or in the system of nutrition, that we are able to account for the increased heat that occurs in certain local affections, in which the temperature greatly exceeds that of the same parts in health. By some, it has been doubted, whether, in local^ inflammation, any such augmentation of temperature exists ; but the error seems to have arisen from the temperature of the part in health having been generally ranked at blood heat; whereas it differs essentially in different parts. Dr. Thomson found, that a small inflamed spot in his right groin gave out, in the course of four days, a quantity of heat sufficient to have heated seven wine-pints of water from 40° to 212°; yet the temperature was not sensibly less than that of the rest of the body at the end of the experiment, when the inflammation had ceased.1 By supposing, too, that calorification is effected in every part of the body, we can under- stand why different portions should have different temperatures ; as the activity of the function may vary, in this respect, according to the organ. MM. Chopart and Dessault found the heat of the rectum 100° ; of the axilla and groin, when covered with clothes, 96° ; and of the chest, 92°. Dr. Davy2 found the temperature of a naked man, just risen from bed, to be 90° in the middle of the sole of the foot; 93° between the inner ankle and tendo achillis; 91*5° in the middle of the shin; 93° in the calf; 95° in the ham; 91° in the middle of the thigh; 96*5° in the fold of the groin ; 95° at three lines beneath the umbilicus ; 94° on the sixth rib of the left side ; 93° on the same rib of the right side; and 98° in the axilla. MM. Edwards and Gentil found the temperature of a strong adult male in the rectum and mouth, 102°; in the hands, 100° ; in the axilla and groins, 98° ; on the cheeks, 97°; on the pre- puce and feet, 96° ; and on the chest and abdomen, 95°. It is %ob- vious, however, that all these experiments concern only the temperature of parts, which can be readily modified by the circumambient medium. To judge of the comparative temperature of the internal organs, Dr. Davy killed a calf, and noted that of different parts, both external and internal. The blood of the jugular vein raised the thermometer to 105*5°; that of the carotid artery to 107°. The heat of the rectum was 105*5° ; of the metatarsus, 97° ; of the tarsus, 90° ; of the knee, 102° ; of the head of the femur, 103°; of the groin, 104° ; of the under part of the liver, 106°; of the substance of that organ, 106° ; of the lung, 106*5° ; of the left ventricle, 107°; of the right, 106° ; and of the substance of the brain, 104°. In the case of fistulous opening into the stomach, observed by Dr. Beaumont,3 the thermometer indicated a difference of three-fourths of a degree between the heat of the splenic and pyloric orifices of the stomach ; the temperature of the latter being more elevated. It is not easy to account for these differences, without supposing, that each part has the power of disengaging its own heat, and that the communication of caloric from one part to another, is not sufficiently ready to prevent the difference from being perceptible. Of the mode in which heat is evolved in the system of nutrition, it is impossible for us to arrive at any satisfactory information. The ' Annals of Philosophy, ii. 27. 2 Philosoph. Transact, for 1814. 3 Exp. and Observations on the Gastric Juice, p. 274, Plattsburg, 1833. 244 CALORIFICATION. result alone indicates, that the process has been accomplished. In the present state of our knowledge, we are compelled to refer it to some chemico-vital action, of the nature of which we are ignorant; but which seems to be possessed by all organized bodies,—vegetable as well as animal. We know that wherever carbon unites with oxygen to form carbonic acid; oxygen with hydrogen to form water; or with phospho- rus or sulphur to form phosphoric acid, and sulphuric acid, as is con- stantly the case in organized bodies, heat must be disengaged. We shall have to refer hereafter, when treating of the phenomena of death, to interesting observations of Dr. Dowler of New Orleans, and others, showing, that the heat of the body may rise after somatic death,—that is, after the cessation of circulation and respiration; and that the ele- vation of temperature varies materially in different parts of the body. The disengagement of caloric, which takes place until the supervention of the putrefactive process, must manifestly be of a physical character, and of course in no respect connected with respiration. Still, it may admit of a question, whether it be identical with that which takes place in the living body, and constitutes the function now under consideration. This much, however, the observations establish, that physical changes in the recently dead may give occasion to the evolution of heat in a manner strikingly analogous to what takes place during life. It was stated early in this section, that man possesses the power of resisting cold as well as heat within certain limits, and of preserving his temperature greatly unmodified. A few remarks are needed in regard to the direct and indirect agents of these counteracting in- fluences. As the mean temperature of the warmest regions does not exqeed 85° of Fahrenheit, it is obvious that he must be constantly giving off caloric to the surrounding medium;—still, his temperature remains the same. This is effected by the mysterious agency which we have been considering, materially aided, however, by several circum- stances, both intrinsic and extrinsic. The external envelope of the body is a bad conductor of caloric, and therefore protects the internal organs, to a certain extent, from the sudden influence of excessive heat or cold. But the cutaneous system of man is a much less efficient protection than that of animals. In the warm-blooded in general, the bodies are covered with hair or feathers. The whale is destitute of hair; but, besides the protection, which is afforded by the extraordinary thickness of the skin, and the stratum of fat—a bad conductor of caloric—with which the skin is lined, as the animal constantly resides in the water, it is not subjected to the same vicissitudes of temperature as land animals. Seals, bears, and walruses, which seek their food in the colder seas, sleep on land. They have a coating of hair to protect them. In the case of certain of the birds of the genus Anas, of northern regions, we meet with a singular anomaly,—the whole of the circumference of the anus being devoid of feathers; but, to make amends for this deficiency, the animal has the poAver of secreting an oleaginous substance, with Avhich the surface is kept constantly smeared. It may be remarked, that we do not find the quantity of feathers on the bodies of birds to be pro- portionate to the cold of the climates in which they reside, as is pretty universally the case regarding the quantity of hair on the mammalia. THEORIES OF CALORIFICATION. 245 Man is compelled to have recourse to clothing for the purpose of preventing the sudden abstraction or reception of heat. This he does by covering himself with substances that are bad conductors of caloric, and retain an atmosphere next to the surface, which is warmed by the caloric of the body. He is compelled, also, in the colder seasons, to have recourse to artificial temperature; and it will be obvious, from what has been said, that the greater the degree of actiA'ity of any organ or set of organs, the greater will be the heat developed: and in this way muscular exertion and digestion must influence its production. By an attention to all these points, and by his acquaintance with the physical laws relative to the developement and propagation of caloric, man is enabled to live amongst the Arctic snows, as well as in climates where the temperature is frequently, for a length of time, upAvards of 150° lower than that of his own body. The contrivances adopted in the polar voyages, under the direction of Captain Parry and others, are monuments of ingenuity directed to obviate one of the greatest obstacles to prolonged existence in cold inhospitable regions, for which man is naturally incapacitated, and for which he attains the capability solely by the exercise of that superior intellect with which he has been vested by the Author of his being. In periods of intense cold, the extreme parts of the body, unless carefully protected, do not possess the neces- sary degree of vital action to resist congelation. In the disastrous expedition of Napoleon to Russia, the loss of the nose and ears was a common casualty; and, in Arctic voyages, frost-bites occur in spite of every care.1 When the temperature of the whole body sinks to about 78° or 79°, death takes place, preceded by the symptoms of nerv- ous depression, which have been previously detailed. The counteracting influence exerted, when the body is exposed to a temperature greatly above the ordinary standard of the animal, is as difficult of appreciation as that by which calorification is effected. The probability is, that in such case the disengagement of heat is suspended; and that the body receives it from without by direct, but not by rapid, communication, owing to its being an imperfect conductor of caloric. Through the agency of this extraneons heat, the tempera- ture rises a limited number of degrees; but its elevation is generally considered to be checked by the evaporation constantly taking place through the cutaneous and pulmonary transpirations. For this last idea we are indebted to Dr. Franklin*,2 and its correctness and truth have been maintained by most -observers. MM. Berger and Delaroche put into an oven, heated to from 120° to 140°, a frog, and one of those porous vessels called alcarazas—which permit the transudation of the fluid, within them, through their sides—filled with water at the tem- perature of the animal, and two sponges, imbibed with the same water. The temperature of the frog at the expiration of two hours, was 99°; and the other bodies continued at the same. Having substituted a rab- bit for the frog, the result was identical. On the other hand, having placed animals in a warm atmosphere, so saturated Avith humidity that • Larrey, Memoires de Chirurgie Militaire et Campagnes, torn. iv. p. 91, 106, and 123, Paris, 1817. * Works, iii. 294, Philad., 1809; or Sparks's edit., vi. 213, Boston, 1S38. 246 CALORIFICATION. no evaporation could occur, they received the caloric by communica- tion, and their temperature rose; whilst inert, evaporable bodies, put into a dry stove, became but slightly warmed;—much less so, indeed, than the warm-blooded animals in the moist stove. Hence, they con- cluded, that evaporation is a great refrigerative agent when the body is exposed to excessive heat; and that such evaporation is considera- ble is shown by the loss in weight which animals sustain by the experi- ment. It has been contested, however, that the cutaneous evaporation has any effect in tempering the heat of the body; whilst it is admit- ted that the elimination from the system of a certain quantity of aqueous matter is all important, and that whatever arrests it is the source of morbid phenomena. MM. Becquerel and Breschet1 found, when the hair of rabbits had been shaved off, and the skin covered with an impermeable coating of strong glue, suet, and resin, that the ani- mals died soon afterwards ; and, they thought, by a process of asphyxia in consequence of the transpiration from the skin being prevented. In these experiments, to their surprise, the temperature of the animals, instead of rising, fell considerably. Thus, the temperature of the first rabbit, before it was shaAred and covered with the impermeable coating, was 38° Centigrade; but immediately after the coating was dry, the temperature of the muscles of the thigh and breast had fallen to 24*5° Centigrade. In another rabbit, on which the coating was put on with more care,—as soon as it was dried, the temperature was found to have fallen so much that it was only three degrees above that of the sur- rounding atmosphere, which was, on that day, 17° Centigrade. An hour after the animal died. These experiments—and they have been repeated with like results by M. Magendie2—clearly exhibit the im- portance of the functions executed by the skin. Dr. Carpenter3 thinks they place in a very striking point of view the importance of the cuta- neous surface as a respiratory organ, and enable us to understand how, when the aerating power of the lungs is nearly destroyed by disease, the heat of the body is kept up to its natural standard by the action of the skin. "A valuable therapeutical indication, also;" he adds, "is derivable from the knowledge which we thus gain of the importance of the cutaneous respiration; for it leads us to perceive the desirableness ■ of keeping the skin moist in those febrile diseases in which there is great heat and dryness of the surface, since aeration cannot properly take place through a dry membrane." M. Edwards, in his experiments on the influence of physical agent3 on life, observed, that warm-blooded animals have less power of pro- ducing heat, after they have been exposed for some time to an elevated temperature, as in summer; whilst the opposite effect occurs in winter. He instituted a series of experiments, which consisted in exposing birds to the influence of a freezing mixture, first in February, and afterwards in July and August; and observing in what degree they were cooled by remaining in this situation for equal lengths of time; the result was, that the same kind of animal was cooled six or eight times as much in 1 Comptes Rendus, Oct., 1841. 2 Gazette Medicale de Paris, 6 Dec., 1843. 3 Human Physiology, § 726, Lond., 1842. SECRETION. 247 the summer as in the winter months. This principle he presumes to be of great importance in maintaining the regularity of the tempera- ture at different seasons; even more so than evaporation, the effect of , which, in this respect, he thinks, has been greatly exaggerated. From several experiments on yellow-hammers, made at different periods in the course of the. year, it would result, that the averages of their tem- perature ranged progressively upwards from the depth of winter to the height of summer, within the limits of five or six degrees of Fahrenheit; and the contrary was observed in the fall of the year. Hence, M. Edwards infers, and with probability, that the temperature of man experiences a similar fluctuation.1 When exposed to high atmospheric temperature, the ingenuity of man has to be as much exerted as under opposite circumstances. The clothing must be duly regulated according to physical principles,2 and perfect quietude be observed, so that undue activity of any of the organs, that materially influence the disengagement of animal heat, may be prevented. It is only Avithin limits, that this refrigerating action is sufficient. At a certain degree, the transpiration is inade- quate ; the temperature of the animal rises, and death supervenes. CHAPTER VII. SECRETION. We haAre next to describe an important and multiple function, which also takes place in the intermediate system—in the very tissue of our organs—and separates from the blood the various humours. This is the function of secretion,—a term literally signifying separation—and which has been applied both to operation and product. Thus, the liver is said to separate the bile from the blood by an action of secretion, and the bile is said to be a secretion. The organs that execute the various secretory operations differ greatly from each other. They have, however, been grouped by ana- tomists into three classes, each of which will require a general notice. 1. anatomy; op the secretory apparatus. The secretory organs have been divided into the exhalant, follicular, and glandular. The remarks made respecting the exhalant vessels under the head of Nutrition will render it unnecessary to allude, in this place, to any of the apocryphal descriptions of them, especially as their very existence is supposititious. Many, indeed, imagine them to be nothing more than the minute radicles of ordinary arteries. The follicle or crypt has the form of an ampulla or vesicle, and is situate in the substance of the skin and mucous membranes; secreting a fluid for the purpose of lubricating them. In the exhalant vessel, 1 De l'lnfluence des Agens Physiques, p. 489; and Hodgkin's and Fisher's translation, Lond., 1832. * See the chapter on Clothing in the author's Human Health, p. 340, Philadelphia, 1S44. 248 SECRETION. the secreted fluid passes immediately from the bloodvessel, without being received into any excretory duct; and, in the simplest follicle, there is essentially no duct specially destined for the excretion of the humour. It is membranous and vascular, having an internal cavity into which the secretion is poured; and the product is excreted upon the surface beneath which it is situate, either by a central aperture, or by a very short duct—if duct it can be called—generally termed a lacuna. Many of the so called follicles are, however, more compli- cated, and consist, like the Meibomian, of various cul-de-sacs, with sepa- rate ducts which open into one; so that the distinction between a compound follicle and a gland is not easily made; and physiologically no difference can be considered to exist. The gland is of a more complex structure than the last. It consists of an artery which conveys blood to it; of an intermediate body,—the gland, properly so called,—and of an excretory duct to carry off the secreted fluid, and to pour it on the surface of the skin or mucous membrane. The bloodvessel, that conveys to the gland the material from which the secretion has to be effected, enters the organ,—at times, Fig. 315. Secreting Arteries, and Nerves of Intestines. ~ a, a. A portion of intestine. 6, b. Part of aorta, c, c, c. Nerves following branches of aorta to supply intestine. by various branches; at others, by a single trunk; and ramifies in the tissue of the gland; communicating at its extremities with the origins of the veins and excretory ducts. These ducts arise by fine radicles at the part where the arterial ramifications terminate; and they unite to form larger and less numerous canals, until they end in one large duct, as in the pancreas; or in several, as in the lachrymal gland,— the duct generally leaving the gland at the part where the bloodvessel enters. Of this we have a good exemplification in the kidney. SECRETORY APPARATUS. 249 The pavement and the cylinder epithelium, as well as all the inter- mediate forms, are met with in the different glands. These are not necessarily a continuation of the epithelium of the cutaneous system; on the contrary, that of the latter is often seen changing its form at its entrance into the gland. Besides the vessels above mentioned, veins exist, which communicate with the bloodvessels that convey blood to the gland, both for the for- mation of the humour and the nutrition of the organ; and which return the residuary blood to the heart. Lymphatic vessels are likewise there; and nerves,—proceeding from the ganglionic system,—form a net-work around the secreting arteries, as in Fig. 315, accompany them into the interior of the organ, and terminate, like them, invisibly. Bordeu1 was of opinion, that the glands, judging from the parotid, are largely supplied with nerves. They do not, however, all belong to it, some merely crossing it in their course to other parts. Bichat,2 from the small number sent to the liver, was induced to draw opposite conclu- sions to those of Bordeu. These may be looked upon as the great components of the glandular structure. They are bound together by areolar tissue, and have gene- rally an outer envelope. The intimate texture of these organs has been a topic of much speculation. It is generally considered, that the final ramifications of the arterial vessels, with the radicles of the veins and excretory ducts, and the final ramifications of the lymphatic vessels and nerves, form so many small lobules, composed of minute, granular masses. Such, indeed is the appearance the texture presents when examined by the naked eye. Each lobule is conceived to contain a final ramification of the vessel or vessels that convey blood to the organ, a nerve, a vein, a lymphatic, and an excretory duct,—with areolar tissue binding them together. When the organ has an external membrane, it usually forms a sheath to the various vessels. The lobated structure is not equally apparent in all the glands. It is well seen in the pan- creas, salivary and lachrymal. The precise mode in which the vessel, from the blood of which the secretion is effected, communicates with the excretory duct, does not admit of detection. Professor Miiller3 maintains, that the glandular structure consists essentially of a duct with a blind extremity, on whose parietes plexuses of bloodvessels ramify, from which the secretions are immediately made,—a view which was confirmed by the pathological appearances, in a case of disease of the portal system that fell under the author's observation, and is referred to hereafter. The opinion of Malpighi4 was similar. He affirmed that such glands as the liver are composed of very minute bodies, called acini from their resemblance to the stones of grapes ;—that these acini are hollow internally, and covered externally by a network of blood- vessels ; and that these minute bloodvessels pour into the ca\-ities of the acini the secreted fluid, from which it is subsequently taken up by 1 Sur les Glandes,in ffiuvres Completes, par M. Richerand, Paris, 1818. 2 Anat. G£n6ral., torn. ii. 8 De Glandular. Secernent. Structura Penitiori, &c, Lips., 1830; or the English edit, by Mr. Solly, Lond., 1839. 4 Opera Omnia, &c, p. 300, Lugd. Batav., 1687. 250 SECRETION. the excretory ducts. Ruysch,1 however, held, that the acini of Mal- pighi are merely convoluted vessels, continuous with the excretory ducts. In Malpighi's view, the secretory organ is a mere collection of follicles; in Ruysch's, simply an exhalant membrane, variously convoluted. " The chief, if not the only difference," says a popular writer,2 "between the secreting structure of glands and that of simple surfaces, appears to consist in the different number and the different arrangement of their capillary vessels. The actual secreting organ is in both cases the same,—capillary bloodvessel; and it is uncertain whether either its peculiar arrangement, or greater extent in glandular texture, be pro- ductive of any other effect than that of furnishing the largest quantity of bloodvessels within the smallest space. Thus convoluted and packed up, secreting organ may be procured to any amount that may be re- quired, without the inconvenience of bulk and weight." It is manifest, that the simplest form of the secretory apparatus con- sists of simple capillary vessel, and animal membrane; and that the follicles and glands are structures of a more complex organization, but still essentially identical;—all perhaps—as will be seen presently—exe- cuting their functions by means of cell agency. Or, to use the views and language of the day, every secreting organ possesses as essential parts of its structure, a simple and apparently anhistous or textureless membrane, called primary or basement membrane; cells and bloodvessels: and by some, all the various modes in which these three structural ele- ments are arranged havebeen Fis- 316. classed under one or other of two principal divisions— membranes, and glands.3 Some of the glands, as the lacteal and salivary, are gra- nular in their arrangement; others, as the spermatic and urinary, consist of convo- luted tubes; but all may be regarded as a prolongation of the skin; and the essential difference between the various secretory organs is in the extent occasionally of ever- sion but generally of inver- sion and convolution of the secretory membrane. This is Avell represented in the marginal figures.4 The mor- Plan of a Secreting Membrane. a. Membrana propria or basement membrane. thelium, composed of secreting nucleated cells. of capillary bloodvessels. Fig. 317. 6. Epi- c. Layer Plan to show augmentation of Surface by formation of Processes. a, b, c. As in preceding figure. branched or subdivided processes. d. Simple, and e, f, 1 Epist. Anatom. qua respondet Viro Clarissimo Hermann. Boerhaav., p. 45, Lugd. Batav., 1722. 2 Southwood Smith, in Animal Physiology, p. 115; Library of Useful Knowledge, Lond., 1829. 3 Kirkes and Paget, Manual of Physiology, Amer. edit., p. 238, Philad., 1849. 4 Quain's Human Anatomy by Quain and Sharpey, Amer. edit, by Leidy, ii. 99, Philad., PHYSIOLOGY OF SECRETION. 251 phology of the secretory ap- paratus has been carefully investigated; but here—as elsewhere—we remain igno- rant of the vital processes concerned. " We must not" —saysLiebig1—"forget that anatomy alone, from the days of Aristotle to Leeuenhoek's time, has thrown but a par- tial light upon the laws of the phenomena of life, as the knowledge of the apparatus of distillation does not in- struct us alone concerning its uses: so in many pro- cesses, as in distillation, he who understands the nature of fire, the laws of the diffu- sion of heat, and of evapora- tion, the construction of the still, and the products of dis- tillation,—knows infinitely more of the process of dis- tillation than the smith him- self who made the apparatus. Each new discovery in ana- tomy has added acuteness, exactitude, and extent to its descriptions; unwearied in- vestigation has almost pene- trated to the inmost cell, from whence a new road of inquiry must be opened." h .....B I Plans of extension of Secreting Membrane, by inversion or recession in form of cavities. a. Simple glands, viz., g, straight tube, h, sac, i, coiled tube. b. Multilocular crypts, k, of tubular form, I, saccu- lar, c. "Racemose or vesicular compound glands, m. Entire gland, showing branched duct and lobular structure, n. A lobule, detached with o, branch of duct proceeding from it. D. Compound tubular gland. 2. PHYSIOLOGY OF SECRETION. The uncertainty which has rested on the intimate structure of secret- ing organs, and on the mode in which the different bloodvessels com- municate Avith the commencement of the excretory duct, has enveloped the function, executed by those parts, in obscurity. We see the pan- creatic artery pass to the pancreas; ramify in its tissues; become capillary, and escape detection; and other vessels becoming larger and larger, and emptying themselves into vessels of greater magnitude, until, ultimately, all the secreted humour is contained in one large duct, Avhich passes onwards, and discharges its fluid into the small intestine. Yet if we folloAV the pancreatic artery as far back as the eye can carry Chemistry and Physics in relation to Physiology and Pathology, p. 105, Lond., 1846. 252 SECRETION. us, even when aided by glasses of considerable magnifying power, or if we trace back the pancreatic duct, we find, in the former vessel, always arterial blood, and in the latter, always pancreatic fluid. It must, con- sequently, be between the part at which the artery ceases to be visible, and at which the pancreatic duct becomes so, that secretion is effected; and we infer, that it occurs in the \*ery tissue, parenchyma, or capillary system of the secreting organ. Conjecture, in the absence of positive knowledge, has been busy, at all times, in attempting to explain the mysterious agency by which such various humours are separated from the same fluid; and, according as chemical, or mechanical, or exclusively vital doctrines have prevailed in physiology, the function has been referred to one or other of those agencies. The general belief amongst the physiologists of the sixteenth and seventeenth centuries was, that each gland possesses a peculiar kind of fermentation, which assimilates to its own nature the blood passing through it. The notion of fermentation was, indeed, applied to most of the vital phenomena. It is now totally abandoned, owing to its being purely imaginary, and inconsistent with all our ideas of the vital operations. When this notion had passed away, and the fashion of accounting for physiological phenomena on mechanical principles took its place, the opinion prevailed, that the secretions are effected through the glands as through filters. To admit of this mechanical result, it was maintained, that all the secreted fluids exist ready formed in the blood, and that, when they arrive at the different secretory organs, they pass through, and are received by the excretory ducts. Des Cartes1 and Leibnitz2 were warm supporters of this mechanical doc- trine, although their views differed materially with regard to the precise nature of the operation. Des Cartes supposed, that the particles of the various humours are of different shapes, and that the pores of the glands have a corresponding figure; so that each gland permits those particles only to pass through it which have the shape of its pores. Leibnitz, on the other hand, likened the glands to filters, which had their pores saturated with their own peculiar substance, so that they admitted it to pass through them, and excluded all others,—as paper, saturated with oil, prevents the filtration of water. The mechanical doctrine of secretion Avas taught by Malpighi and Boerhaave,3 and continued to prevail until the time of Haller. All the secretions were conceived to be ready formed in the blood, and the glands were looked upon as sieves or strainers to convey off the appropriate fluids or humours. In this view of the subject, all secretion was a transudation through the coats of the vessels,—particles of various sizes passing through pores respect- ively adapted for them.4 The mechanical doctrine of transudation, in this shape, is founded upon supposititious data; and the whole facts and arguments are so manifestly defective, that it is now abandoned. MM. Magendie and Foddra have, however, revived the mechanical view of late years; but under an essentially different form, and one especially applicable to the 1 De Homine, p. 11, Lugd. Bat., 1664. 2 Haller, Element. Physiol., vii. 3. 3 Praelectiones Academicse, &c, edit. A. Haller, § 253, Gotting., 1740-1743. 4 Mascagni, Nova per Poros Inorganicos Secretionem Theoria., Rom., 1793, torn. ii. PHYSIOLOGY OF SECRETION. 253 exhalations. The former gentleman,1 believing that many of these exist ready formed in the blood, thinks that the character of the ex- haled fluid is dependent upon the physical arrangement of the small vessels, and his vieAvs repose upon the following experiments. If, in the dead body, we inject warm water into an artery passing to a serous membrane, as soon as the current is established from the artery to the vein, a multitude of minute drops may be observed oozing through the membrane, which speedily evaporate. If, again, a solution of gelatin, coloured with vermilion, be injected into the vessels, it will often hap- pen, that the gelatin is deposited around the cerebral convolutions, and in the anfractuosities, Avithout the colouring matter escaping from the vessels, whilst the latter is spread over the external and internal sur- faces of the choroid. If, again, linseed oil, also coloured with vermi- lion, form the matter of the injection, the oil, devoid of colouring matter, is deposited in the articulations that are furnished with large synovial capsules; and no transudation takes place at the surface of the brain, or in the interior of the eye. M. Magendie asks, if these be not instances of true secretion taking place post mortem, and evidently dependent upon the physical arrangement of the small vessels; and whether it be not highly probable, that the same arrangement must, in part at least, preside over exhalation during life. M. Fode'ra,2 to whose experiments on the imbibition of tissues we had occasion to allude under the head of Absorption, embraces the views of M. Magendie, and so does Valentin.3 If the vessels of a dead body, M. Fode'ra re- marks, be injected, the substance of the injection is seen oozing through them; and if an artery and a vein be exposed on a living animal, a similar oozing through the parietes is observable. This is more mani- fest if the trunk, whence the artery originates, be tied,—the fluid being occasionally bloody. If the jugular veins be tied, not only does oedema occur in the parts above the ligatures, but there is an increase of the salivary secretion. It is not necessary to refer to the various experi- ments of Fodera relating to this topic, or those of Harlan, Lawrence and Coates, Dutrochet, Faust, Mitchell, and others. They are of the same character as those previously alluded to when treating of the im- bibition of tissues; for transudation is only imbibition or soaking from within to without: MM. Magendie and Fode'ra, indeed, conclude, that imbibition is a primary physical cause of exhalation as it is of absorp- tion. Another physical cause, adduced by M. Magendie, is the pressure experienced by the blood in the circulatory system, which, he thinks, contributes powerfully to cause the more aqueous part to pass through the coats of the vessels. If water be forcibly injected through a syringe into an artery, all the surfaces, to which the vessel is distributed, as well as the larger branches and the trunk itself, exhibit the injected fluid oozing in greater abundance according to the force exerted in the in- jection. He farther remarks, that if Avater be injected into the veins 1 Precis, &c, edit. cit.. ii. HI. 2 Magendie's Journal de Physiologie, iii. 35; and Recherches, &c, sur l'Absorption et TExhalation, Paris, 1&.'4. 3 Lehrbuch der i hysiolugie des Menschen, Bd. 1, s. 001, Braunschweig, 1844. 254 SECRETION. of an animal, in sufficient quantity to double or treble the natural amount of circulating fluid, a considerable distension of the circulatory organs is produced, and the pressure is largely augmented. If any serous membrane be now examined,—as the peritoneum,—a watery fluid is observed issuing rapidly from it, Avhich accumulates in the cavity, and produces a true dropsy under the eye of the experimenter; and occasionally, the colouring part of the blood transudes at the surface of certain organs, as the liver, spleen, &c. Hamberger, again, broached the untenable physical hypothesis, that each secreted humour is de- posited in its proper secretory organ by virtue of its specific gravity,1— but it is obvious, that all these speculations proceed upon the belief that the exhalations exist ready formed in the blood; and that, conse- quently, the act of secretion, so far as concerns them, is one of separa- tion or secerning,—not of fresh formation. That this is the case with the more aqueous secretions is probable, and not impossible with regard to the rest. Organic chemistry is subject to more difficulties in the way of analysis than inorganic; and it can be understood, that in a fluid so heterogeneous as the blood the discovery of any distinct humour may be impracticable. Of course, the elements of every fluid, as well as solid, must be contained in it; and we have already seen, that not merely the inorganic elements, but the organic or compounds of organi- zation have been detected in it by the labours of Chevreul and others. There are indeed, some singular facts connected with this subject. MM. Pre'vost and Dumas,2 having removed the kidneys in cats and dogs, and afterwards analyzed the blood, found urea in it—the charac- teristic element of urine. This principle was contained in greater quantity, the longer the period that had elapsed after the operation; whilst it could not be detected in the blood, when the kidneys were pre- sent. The experiment was soon afterwards repeated by MM. Vauquelin and Segalas3 with the same results. The latter introduced urea into the veins of an animal whose kidneys were untouched; he was unable to detect the principle in the blood; but the urinary secretion was largely augmented after the injection; whence he concludes, that urea is an excellent diuretic. Subsequently, MM. Gmelin and Tiedemann, in association with M. Mitscherlich,4 arrived, experimentally, at the same conclusions as MM. Pre'vost and Dumas. The existence of urea in the fluid ejected from the stomach of the animal was rendered pro- bable, but there were no traces of it in the faeces or the bile. The animal died the day after the extirpation of the second kidney. They were totally unable to detect either urea or sugar of milk in the healthy blood of the cow. ^ These circumstances would favour the idea, that certain of the secre- tions may be formed in the blood, and may simply require the inter- vention of a secreting organ to separate them;5 but the mode in which such separation is effected is entirely inexplicable under the doctrine of 1 Adelon, Physiologie de l'Humme, 2de e\dit., iii. 455, Paris, 1829. 2 Annales de Chimie, torn. xxii. and xxxiii. 90. 3 Magendie, Precis, &c, ii. 478. 4 Tiedemann und Treviranus, Zeitschrift fur Physiol., B. v. Heft i.; cited in Brit, and Foreign Med. Review, p. 592, for April, 1836. * Dr. W. Philip, in Lond. Med. Gazette for March 25th, 1837, p. 952. THEORIES. 255 simple mechanical filtration or transudation. It is unlike any physi- cal process that can be imagined. The doctrine of filtration and trans- udation can apply only to those exhalations in which the humour has undergone no apparent change; and it is obviously impossible to spe- cify these, in the imperfect state of our means of analysis. In the ordinary aqueous secretions, simple transudation may embrace the whole process; and, therefore, it is unnecessary to have recourse to any other explanation; especially after the experiments instituted by M. Magendie, supported by pathological observations in which there has been partial oedema of the legs, accompanied by more or less complete obliteration of the veins of the infiltrated part,—the vessels being obstructed by fibrinous coagula, or compressed by circumjacent tumours. It is obvious, that ascites or dropsy of the peritoneum may be occa- sioned by obstruction of the portal circulation in the liver, and that in this way we may account for the frequency with which we find a union of hydropic and hepatic affections in the same individual. The same pathological doctrine, founded on direct observation, has been extended to phlegmasia dolens or swelled leg; an affection occurring in the puer- peral state, and often found connected with obstruction in the great veins that convey the blood back from the lower extremity. It may not, consequently, be wide of the truth—if not wholly accurate—to consider certain of the secretions, with Dr. Billing,1 to be "vital transudations from the capillaries into the excretory ducts of the glands, by pores invisible to our senses, even when aided by the most perfect optical instruments." The generality of physiologists have regarded the more complex secretions—the follicular and glandular—as the results of chemical action; and under the view, that these secretions do not exist ready formed in the blood, and that their elements alone are contained in that fluid, it is impossible not to admit that chemical agency must be exerted. In support of the chemical hypothesis, which has appeared under various forms,—some, as Keill,2 presuming that the secretions are formed in the blood, before they arrive at the place appointed for secretion; others, that the change is effected in the glands themselves, —the fact of the formation of a number of substances from a very few elements, provided these be united in different proportions, has been urged. Take, for example, the elementary bodies, oxygen and nitro- gen. These, in one proportion, form atmospheric air; in another, nitrous oxide; in another, nitric oxide; in a fourth, hyponitrous acid; in a fifth, nitrous acid; in a sixth, nitric acid, &c, compounds which differ as much as the various secretions differ from each other and from the blood. Many of the compounds of organization likewise exhibit, by their elementary constitution, that but a slight change is necessary, in order that they may be converted into each other. Dr. Prout3 has exhibited the close alliance between three substances—urea, lithic acid, and sugar,—and has shown how they may be converted into each other, by the addition or subtraction of single elements of their con- 1 First Principles of Medicine, Amer. edit, p. 55, Philad., 1842. 2 Tentamina Medico-Physica, iv.; and Haller, Element. Physiol., &c, lib. vii. sect. 3. 3 Medico-Chirurg. Transact., viii. 540. 256 SECRETION. Stituents. Urea is composed of two atoms of hydrogen, and one of carbon, oxygen, and nitrogen respectively; by removing one of the atoms of hydrogen and the atom of nitrogen, it is converted into sugar; by adding to it an additional atom of carbon, into, lithic or uric acid. Dr. Bostock,1—who is disposed to push the application of chemistry to the explanation of the functions as far as possible,—to aid us in con- ceiving how a variety of substances may be produced from a single compound, by the intervention of physical causes alone, supposes the case of a quantity of materials adapted for the vinous fermentation being allowed to flow from a reservoir through tubes of various dia- meters, and with various degrees of velocity. " If we were to draw off portions of this fluid in different parts of its course, or from tubes, which differed in their capacity, we should, in the first instance, obtain a portion of unfermented syrup; in the next, we should have a fluid in a state of incipient fermentation; in a third, the complete vinous liquor; while, in a fourth, we might have acetous acid." Any ex- planation, however, founded upon this loose analogy, is manifestly too physical. Dr. Bostock admits this, for he subsequently remarks, that " if we adopt the chemical theory of secretion, we must conceive of it as originating in the vital action of the vessels, which enables them to transmit the blood, or certain parts of it, to the various organs or struc- tures of the body, where it is subjected to the action of those reagents which are necessary to the production of these changes." The admis- sion of such vital agency, in some shape, seems indispensable. Attempts have been made to establish secretion as a nervous action, and numerous arguments and experiments have been brought forward in support of the position. That many of the secretions are affected by the condition of the mind is known to all. The act of crying, in evidence of joy or sorrow; the augmented secretion of the salivary glands at the sigfit of pleasant food; of the kidney during fear or anxiety; and the experimental confirmation, by Mr. Hunter, of the truth of the common assertion—that the she-ass gives milk no longer than the impression of the foal is on her mind,—the skin of the foal, thrown over the back of another, and frequently brought near her, being sufficient to renew the secretion,—sufficiently indicate, that the organs of secretion can be influenced through the nervous system in the same manner as the functions of nutrition and calorification.2 The discovery of galvanism naturally suggested it as an important agent in the process,—or rather suggested, that the nervous fluid strongly resembles the galvanic. This conjecture seems to have been first hazarded by Berzelius, and Sir Everard Home ;3 and, about the same time, an experiment was made by Dr. Wollaston,4 Avhich, he con- ceived, threw light on the process. He took a glass tube, two inches high, and three-quarters of an inch in diameter; and closed it at one 1 Physiol., 3d edit, p. 519, Lond., 1836. 2 For examples of the same kind, see Fletcher's Rudiments of Physiology, partii. b, p. 10, Edinb., 1836; Burdach, Physiologie, u. s. w., § 522; and Dr. A. Combe, on Infancy, Amer. edit, chap, v.,' Philad., 1840. 3 Lectures on Comp. Anat, iii. 16, London, 1810; and v. 154, London, 18:28. * Philosoph. Mag. xxxiii. 438. THEORIES OF SECRETION. 257 extremity with a piece of bladder. He then poured into the tube a little water, containing s^th of its weight of chloride of sodium, moist- ened the bladder on the outside, and placed it upon a piece of silver. On curving a zinc wire so that one of its extremities touched the piece of metal, and the other dipped into the liquid to the depth of an inch, the outer surface of the bladder immediately indicated the presence of pure soda; so that, under this feeble electric influence, the chloride of sodium was decomposed, and the oxide of sodium—soda—passed through the bladder. M. Fode'ra1 performed a similar experiment, and found, that whilst ordinary transudation frequently required an hour before it was evidenced, it was instantaneously exhibited under the galvanic influence. On putting a solution of cyanuret of potassium into the bladder of a rabbit, forming a communication with the solution by means of a copper wire; and placing on the outside a cloth1 soaked in a solution of sulphate of iron, to which an iron wire was attached ; he found, by bringing these wires into communication with the galvanic pile, that the bladder or the cloth was suddenly coloured blue, accord- ing as the galvanic current set from without to within, or from within to without;—that is, according as the iron wire was made to communi- cate with the positive pole, and the copper wire with the negative, or conversely. But it is not necessary, that there should be communica- tion with the galvanic pile. If an animal membrane, as a bladder, containing iron filings, be immersed in a solution of sulphate of copper, the sulphuric acid will penetrate the membrane to reach the iron, with which it forms a sulphate, and the metallic copper will be deposited on the lower surface of the membrane; the animal membrane, in such case, offering no obstacle to the action of the ordinary chemical affinities. With some of the chemical physiologists, there has been a disposition to resolve secretion into a mere play of electric affinities. Thus, M. Donne'2 affirms, that from the whole cutaneous surface an acid humour is secreted, whilst the digestive tube, except in the stomach, secretes an alkaline mucus: hence, he infers, th'at the external acid, and the internal alkaline membranes of the human body represent the two poles of a pile, the electrical effects of which are appreciable by the gal- vanometer. On placing one of the conductors of the instrument in contact with the mucous membrane of the mouth, and the other with the skin, the magnetic needle deviated fifteen, twenty, and even thirty degrees, according to its sensibility; and its direction indicated, that the mucous or alkaline membrane took negative, and the cutaneous membrane, positive electricity. He further asserts, that, between the acid stomach and the alkaline liver, extremely powerful electrical cur- rents are formed. These experiments do not, however, aid us mate- rially in our solution of the phenomena of secretion. They exhibit merely electrical phenomena dependent upon difference of chemical com- position. This is, indeed, corroborated by the experiments of M. Donne himself on the secretions of vegetables. He observed electrical phenomena of the same kind in them; but, he says, electrical currents 1 Magendie's Journal de Physiologie, iii. 35; and Recherches, &c., sur l'Absorption et l'Ex- halation, Paris, 1824. 2 Annales de Chimie, &c, lvii. 400; and Journal Hebdomad., Fev., 1834. VOL. II.—17 258 SECRETION. in vegetables are not produced by the acid or alkaline conditions of the parts as in animals, the juice of fruits being always more or less acid. Experiments of M. Biot, however, show, that the juices, which arrive by the pedicle, are modified in some part of the fruit, and M. Donne thinks it is perhaps to this difference in the chemical composition of the juices of the two extremities, that the electrical phenomena are to be attributed. The effects of the section of the pneumogastric nerves on the func- tions of digestion and respiration have been given elsewhere, at some length. It was then stated, that when digestion was suspended by their division, Dr. Wilson Philip1 was led to ascribe it to the secretion of the gastric juice having been arrested; an opinion, which Sir B. Brodie had been induced to form previously, from the results of experi- ments, which showed, that the secretion of urine is suspended by the removal or destruction of the brain; and that when an animal is de- stroyed by arsenic, after the division of the pneumogastric nerves, all the usual symptoms are produced, except the peculiar secretion from the stomach. Sir B. Brodie did not draw the conclusion, that the nervous influence is absolutely necessary to secretion, but that it is a step in the process; and the experiments of M. Magendie2 on the effect of division of the nerve of the fifth pair on the nutritive secretion of the cornea, confirm the position. We have, indeed, numerous evidences, that the nervous system cannot be indispensable to secretion. In all animals, this power must exist; yet there are some in which no nervous system is apparent. Dr. Bostock3 has given references to cases of monstrous or deformed foetuses, born with many of their organs fully developed, yet in which there was apparently no nervous system. It may be said, however, that, in all these cases, a rudimental nervous system may and must have existed; but setting aside the case of ani- mals, secretion is equally effected in the vegetable, in which there is no nervous system; yet the function is accomplished as perfectly, and perhaps in as multiple a manner, as in animals. It is manifest, there- fore, that this is one of the vital actions occurring in the very tissue of organs, of which we have no more knowledge than we have of the nutritive actions in general. All that we know is, that in special organs various humours are secreted from the blood, some of which can be detected in that fluid; others not. The doctrine of developement by cells was an important step in the inquiry. It has been elsewhere shown how cells are considered to effect the work of absorption; and secretion is probably accomplished in a similar manner. It is essentially a function of nucleated cells,— such cells possessing a peculiar organic power by virtue of which they can draw into their interior certain kinds of materials varying according to the nature of the fluid they are destined to secrete.4 Some cells have merely to separate certain ingredients from the surrounding medium; others have to elaborate within themselves matters that do not exist as • London Medical Gazette, March 18, and March 25, 1837. 2 Precis, &c, ii. 489. 3 Physiology, edit, cit, p. 525, Lond., 1836. 4 Professor Goodsir. Transactions of the Royal Society of Edinburgh, 1842, and Ana- tomical and Pathological Observations, Edinb., 1845. I THEORIES. 259 such in the nutritive medium. Although secreting cells thus differ in the nature of the fluid which they secrete, their structure seems to be nearly the same in all cases,—each consisting, like other primitive cells, of a nucleus, cell-wall, and cavity. The nucleus appears to be both the reproductive organ by which new cells are generated, and the agent for separating and preparing the secreted material. The cell-cavity seems chiefly destined to contain the secreted fluid until ready to be dis- charged ; at which time the cell, then matured, bursts and discharges its contents into the outer cellular space on which it is situate, or upon a free surface, as the case may be. The mode of secretion in glands, of which Professor Goodsir takes the testicle of the squalus cornubicus as a type, appeared to him to be as follows. Around the extremities of the minute ducts of the glands are developed acini or primary nucleated cells, each of which, as it increases in size, has generated* within it, secondary cells—the product of its nucleus. The cavity of the parent cell does not communicate with the duct on which it is situate until its contents are fully matured, at which time the cell-wall bursts or dissolves away, and its contents are discharged into the duct. From this constant succession of growth and solution of cells it results, that the whole parenchyma of a gland is continually passing through stages of developement, maturity, and atrophy,—the rapidity of the process being in proportion to the activity of the secretion. There seems, consequently, in this view of the sub- ject, to be no essential difference between the process of secretion, and the growth of a gland: the same cells are the agents by which both are effected. The parenchyma of glands is chiefly made up of a mass of cells in all stages of developement: as these cells individually increase in size, and so constitute their own growth as well as that of the com- mon glandular mass, they are at the same time elaborating within themselves the material of secretion, which, when matured, they dis- charge by dissolving away. There are numerous germinal spots or centres in a gland, from which acini or primary cells are developed. The true fluid of secretion, in Mr. Goodsir's opinion, is not the product of the parent cell of the acinus, but of its included mass of secondary cells, which themselves become primary secreting cells, and form the material of secretion in their cavities. In some cases, these secondary cells pass out entire from the parent cell, constituting a form of secre- tion in which the cells possess the power of becoming more fully de- veloped after being discharged and cast into the duct or cavity of the gland. He considers growth and secretion to be identical—the same process under different circumstances,—a view which had indeed been already embraced by others, and which ought to be universally. It must be recollected, that bloodvessels, like absorbents, are shut sacs; and, therefore, the materials for nutrition and secretion must pass either through them in the manner suggested by Mr. Goodsir, or by transuda- tion. Transudation, however, would seem to be mainly, if not wholly, applicable to tenuous fluids only'; whilst every solid in the body must be nourished by materials obtained from the blood. The agency of cells in nutrition and secretion may, therefore, be regarded as established. 260 SECRETION. Mr. Addison1 has suggested, that these cells are not developed in the organs of nutrition and secretion at the expense of materials supplied by the blood; that they are neither more nor less than the colourless cor- puscles of the blood, which elaborate those products whilst still floating in its current, and then escape from the vessels. It is not easy, however, to comprehend, that corpuscles, apparently identical, should exist in the blood charged with the different properties of separating bile, urine, saliva, &c, from the fluid; or that they could escape through the parietes of the containing bloodvessels, and then penetrate the parietes of the excretory ducts to take their place—it has been supposed—as epithelium cells on the lining membrane of these outlets. Moreover, as has been shown elsewhere, there is reason to believe, that the office of the white corpuscles of the blood is of a different character.2 In cases of vicarious secretion, we have the singular phenomenon of organs assuming an action for which they were not destined. If the secretion from the kidney, for example, be arrested, urine is occasion- ally found in the ventricles of the brain, and, at other times, a urinous fluid has been discharged by vomiting or by cutaneous transpiration: the secreting cells of those parts must, consequently, have assumed the functions of the kidney, and to this they were excited by the pre- sence of urea, or the elements of the urinary secretion in the blood,—a fact, which exhibits the important influence that the condition of the blood must exert on the secretions, and, indeed, on nutrition in general. It is thus that many of our remedial agents, alkalies, the preparations of iodine, &c,—produce their effects. They first enter the mass of blood, and, by circulating in the capillary system, induce a modification of the function of nutrition. There are other cases, again, in Avhich the condition of the blood being natural, the cells of nutrition may assume morbid action. Of this we have examples in the ossification of organs, which, in the healthy condition, have no bony constituent; in the deposition of fat in cases of diseased ovaria; and in the altered secretions produced by any source of irritation in a secreting organ. In describing the physiology of the different secretions, one of three arrangements has usually been adopted; either according to the nature of the secreting organ, the function of the secreted fluid, or its chemi- cal character. The first of these has been followed by MM. Bichat and Magendie,3 who have adopted a division into exhaled, follicular, and glandular secretions. It is the one followed by M. Lepelletier, except that he substitutes the term perspiratory for exhaled. Accord- ing to the second, embraced by MM. Boyer,4 Sabatier,5 and Adelon,6 they are divided into recrementitial, or such as are taken up by internal absorption and re-enter the circulation; and excrementitial, or such as are evacuated from the body, and constitute the excretions. Some physiologists add a third—the recremento-excrementitial,—in which a 1 The Actual Process of Nutrition- on the Living Structure demonstrated by the Micro- scope, &c.. Lond., 1844. 2 See p. 109 of this volume. 3 Precis de Physiologie, 2de edit, ii. 243, Paris, 1825. 4 Anatomie, 2de£dit, i. 8, Paris, 1803. 5 Traite Complet d'Anatomie, Paris, 1791. 6 Physiologie de l'Homme, edit, cit, iii. 438. EXHALATIONS. 261 I. Exhalations. b. External IL Follicular Secretioss. part of the humour is absorbed and the remainder ejected. Lastly, the division according to chemical character has been followed, with more or less modification, by Plenck,1 Richerand,2 Blumenbach,3 Young,4 and Bostock ;5 the last of whom has eight classes; the aqueous, albu- minous, mucous, gelatinous, fibrinous, oleaginous, resinous, and saline. To all of these classifications cogent objections might be made. The one we shall follow is the anatomical,—not because it is the most per- fect, but because it is the course that has been usually adopted through- out this work. Defective, too, as it is, it will enable us to take a survey of every one of the numerous secretions classified in the following TABLE OF THE SECRETIONS. T 1. Of the areolar membrane. 2. Of the serous membranes. 3. Of the synovial membrane. I ' i 4. Of the adipous membrane. < ,' ,, ( b. Marrow. I 5. Of the pigment membrane. l_ 6. Of areolar capsules. f . r\C i. ^ General and 1. Of mucous membranes. < . J ( pulmonary. j 2. Menstrual. (^ 3. Gaseous. f , „. , C Gastro-pulmonary, genito- L Of mucous membranes. £ utixairy, &c. a. Of the Peyerian glands. b. Of the ovaria. 2. Of the skin. a. Sebaceous. 6. Meibomian. c. Ceruminous. d. Preputial. e. Odoriferous. 1. The transpiratory. 2. The lachrymal. 3. The salivary. 4. The pancreatic. 5. The biliary. 6. The urinary. I 7. The spermatic. L 8. The lacteal. I. EXHALATIONS. All the exhalations take place into the areolae and internal cavities of the body, or from the skin and mucous membranes;—hence their divi- sion into internal and external. The former are recrementitial, the latter recremento-excrementitial. To the class of internal exhalations belong: 1. The areolar exhalation. 2. The serous exhalation. 3. The synovial exhalation. 4. The adipous exhalation. 5. The pig- mental exhalation. 6. The exhalation of the areolar capsules. To 1 The Chemico-Physiological Doctrine of the Fluids, &c, translated by Dr. Hooper, Lond., 1797. 2 Elemens de Physiologie, 13eme edit, chap, vi., Bruxelles, 1837. 3 Physiology, by Elliotson, 4th edit, Lond., 1828. 4 Introduction to Medical Literature, p. 104, Lond., 1813. 5 Physiology, 3d edit, p. 48, Lond., 1836. III. Glandular Secretions 262 SECRETION. the class of external exhalations belong: 1. The exhalation of the mucous membranes. 2. The menstrual exhalation; and 3. Gaseous ex- halations. A. INTERNAL EXHALATIONS. 1. Exhalation of the Areolar Membrane. A brief view of the nature of the primary areolar^ cellular or fibro- cellular membrane was given in an early part of this work (vol. i. p. 58). As we observe it, it is not properly cellular, but is composed of a network of fibres, and lamellae formed by the adhesion of fibres laid Fig. 319. Fig. 320. Portion of Areolar Tissue inflated and Arrangement of Fibres in Areolar dried, showing the general charac- Tissue.—Magnified 135 diameters. ter of its larger meshes ; magnified twenty diameters. (Todd and Bowman.) side by side; and these interwoven so as to leave numerous interstices and areolae amongst them, which have a tolerably free communication with each other.1 Two kinds of fibrous tissue—the white and the yellow—may be de- tected in it,—the white presenting itself in the form of inelastic bands, the largest ^o^h °f an ^ncn in breadth, somewhat wavy in their direc- tion, and marked longitudinally by numerous streaks ; and the yellow existing in the form of long, single, elastic, branched filaments, with a dark decided border, and disposed to curl when not put upon the stretch. These interlace with the others, but seem to have no con- tinuity of substance with them. They are, for the most part, between the s^otn and io^ootn °f an incn m thickness; but are often met with both larger and smaller. The interstices in the areolar membrane, wherever existing, are kept 1 For the histology of the areolar and serous membranes, see Todd and Bowman, Phy- siological Anatomy and Physiology of Man, London, 1842; and Dr. Brinton, art. Serous and Synovial Membranes, Pt. xxxiv. p. 512, Lond., Jan., 1849. EXHALATION OF THE SEROUS MEMBRANES. 263 moist by a serous fluid, analogous to that exhaled from serous mem- branes, and which appears to have the same uses,—that of facilitating the motion of the lamellae, or fibres on each other, and, consequently, Fig. 321. Fig. 322. White Fibrous Tissue, from Liga- Yellow Fibrous Tissue, from Ligamentum ment.—Magnified 65 diameters. Nucha? of Calf.—Magnified 65 diameters. of the organs between which the areolar tissue is placed. When this secretion collects, from the causes mentioned in the last section, the disease called oedema or anasarca is induced. 2. Exhalation of the Serous Membranes. This is the fluid secreted by the serous membranes that line the various cavities of the body;—as the pleura, pericardium, peritoneum, arachnoid coat of the brain, tunica vaginalis testis, and the lining membrane of the vessels. Rudolphi1 asserts, that serous membranes are incapable of inflammation, are not vascular, and do not secrete; and that the secretions of shut sacs take place from the subjacent parts, and transude through the serous membrane, which, consequently, in his view, is a kind of cuticle. In a physiological consideration, it is not of moment whether they resemble the cuticle or not; and ana- tomically the question only concerns the layer that covers the surface. Serous membranes, as elsewhere remarked, form shut sacs, and in- vest viscera, whose free surfaces come in contact, or which lie in cavi- ties unattached to surrounding parts. To the law, that they form close or shut sacs, there is but one exception in the human subject; in the opening of the Fallopian tubes into the cavity of the abdomen. They are constituted of fibro-areolar tissue so interwoven as to con- stitute a membrane,—the free surface covered with a layer of flattened cells forming, in most cases, a tesselated epithelium.2 Between the epithelium and subserous areolar tissue is the primary or basement membrane.3 The basement membrane and epithelium are concerned in the secretion of the fluid by which the free surface of the membrane 1 Grundriss der Physiologie, § 113, Berlin, 1821. 2 See vol. i.p. 132. , 3 Bowman, art. Mucous Membrane, Cyclopaedia of Anatomy and Physiology, p. 484, April, 1842. 264 SECRETION. is moistened. The general arrangement of serous membranes has been well described by Professor Goodsir.1 A portion of the human pleura or peritoneum, according to him, consists, from its free surface inwards, of a single layer of nucleated scales; of a germinal mem- brane, and of a subserous areolar texture intermixed with occasional elastic fibres. The bloodvessels of the serous membrane ramify in the areolar texture. The germinal membrane seldom shows the lines of junction of its component flattened cells. These appear elongated in the form of ribands,—their nuclei or the germinal spots of the mem- brane being elongated, expanded at one extremity, pointed at the other, and somewhat bent upon themselves; they are bright and crystalline, and may or may not contain smaller cells in their interior. If these germinal centres be the sources of all the scales of the superficial layer, each centre being the source of the scales of its own compartment, then the matter necessary for the formation of these during their de- velopement must pass, he conceives, from the capillary vessels to each of the centres, acted on by forces whose centres of action are the ger- minal spots;—each of the scales, after being detached from its parent centre, deriving its nourishment by its own inherent powers. From these membranes a fluid is exhaled, which is of an albuminous character, resembling greatly the serum of the blood, except in con- taining less albumen. M. Donne'2 says it is always alkaline in the healthy state. This is owing to the presence of carbonate or albumi- nate of soda. It contains 7 or 8 per cent, of albumen, and salts. In health, this fluid never accumulates in the cavities,—the absorbents taking it up in proportion as it is deposited; but if, from any cause, the exhalants should pour out a larger quantity than usual, whilst the absorbents are not proportionably excited, accumulation may take place; or the same effect may ensue if the exhalants pour out no more than their usual quantity, whilst the absorbents do not possess their due activity. Under either circumstance, we have an accumulation— a dropsy. The exhaled fluid probably transudes through the parietes of the arteries, and re-enters the circulation by imbibition through the coats of the veins. If we kill an animal and open it immediately afterwards, this exhalation appears in the form of a halitus or vapour, and the fluid is seen lubricating the free surface of the membrane. This, indeed, appears to be its principal office; by which it favours the motion of the organs upon each other. The serous exhalations probably differ somewhat in each cavity, or according to the precise structure of the membrane. The difference between the chemical character of the fluid of the dropsy of different cavities would lead to this belief. As a general rule, according to Dr. Bostock,3 the fluid from the cavity of the abdomen contains the greatest proportion of albumen, and that from the brain the least; but many exceptions occur to this. 1 Anatomical and Pathological Observations, Edinb., 1845. 2 Journal Hebdomad., Fevrier, 1834. 3 Op. citat, p. 485. EXHALATION OF THE SYNOVIAL MEMBRANE. 265 3. Exhalation of the Synovial Membrane. Within the articular capsules, and bursae mucosae,—which have been described under Muscular Motion,—a fluid is secreted, which is spread over the articular surfaces of bones, and facilitates their movements. Dr. Clopton Havers1 considered this fluid to be secreted by synovial glands,—for such he conceived the reddish cellular masses to be, that are found in certain articulations. Haller2 strangely regarded the synovia as the marrow, which had transuded through the spongy ex- tremities of the bones; but, since the time of Bichat, every anatomist and physiologist has ascribed it to the exhalant action of the synovial membrane, which strongly resembles the serous membranes in form, structure, and functions, whose folds constitute the projections that Havers mistook—it was conceived—for glands. The opinion of Havers has, however, been lately confirmed by Mr. Rainey.3 It had been believed by many, that the folds of synovial membrane, which form fringes, contain merely globules of fat, and are only inservient to the mechanical office of filling up spaces that would otherwise be left vacant during the movements of the joints. By a careful examination of their structure, with the aid of the microscope, Mr. Rainey found a peculiar arrangement of vessels not at all resembling those that secrete fat, and an epithelium of remarkable form and disposition, and characteristic of organs whose function it is to effect a special secretion. These fringes he traced not only in the joints but in the sheaths of tendons, and in the bursae—wherever, indeed, synovia is secreted. When well injected they are seen under the microscope to consist of a convolution of blood- vessels and an investing epithelium, which, besides enclosing separately each packet of convoluted vessels, sends off from each tubular sheath secondary processes of various shapes into which no bloodvessels enter. The lamina itself forming these folds and processes consists of a very thin membrane studded with flattish oval cells, a little larger than blood corpuscles, but destitute of nucleus or nucleolus,—presenting none of the characters of tesselated epithelium, but corresponding more to what Mr. Goodsir has termed "germinal membrane." From this morpholo- gical arrangement, Mr. Rainey accords with Havers in the view, that the proper office of the structure is to secrete synovia. The synovial membrane exists in all the movable articulations, and in the channels and sheaths in which the tendons play. The gene- rality of anatomists regard the articular capsules as shut sacs; the membranes being reflected over the incrusting cartilages. M. Magen- die, however, affirms, that he has several times satisfied himself, that they do not pass beyond the circumference of the cartilages. From the inner surface of these membranes the synovia is exhaled in the same manner as in other serous cavities. M. Margueron4 analyzed synovia obtained from a posterior extremity of the ox, and found it consist of fibrous matter, 11*86 ; albumen, 4*52; 1 De Ossibus, serm. iv. c. 1; and Oste.ologia Nova, London, 1691. 2 Element. Physiol., iv. 11. 3 Proceedings of the Royal Society of London, No. 65, 1847. * Annales de Chimie, xiv. 123. 266 SECRETION. chloride of sodium, 1*75; soda, 0*71; phosphate of lime, 0*70; and water, 80*46. M. Donne*1 says it is always alkaline in health; but in certain diseases sometimes becomes acid. The synovia of a stall fed ax was found by Frerichs2 to consist of Water,...........96990 Solid constituents,.........30-10 Mucous matter with epithelium,......2-40 Fat,............062 Albumen and extractive matter,......15-76 Salts,............11*32 That of an ox, which had been pasture-fed all the summer, contained Water,...........948-54 Solid constituents,.........51-46 Mucous matter and epithelium, ------- 5-00 Fat,............0-76 Albumen and extractive matter, ...... 35-12 Salts,........... 9-98 4. Areolar Exhalation of the Adipous Membrane. a. Fat. Considerable diversity of opinion has prevailed regarding the precise organ for the secretion of fat. Haller supposed, that the substance exists ready formed in the blood, and simply transudes through the pores of the arteries ; and Chevreul and others have given some coun- tenance to the opinion, by Fis-323- the circumstance of their /r>—y^^v^-v^^. having met with fatty mat- ter in that fluid. Anato- mists have, likewise, been divided upon the subject of the precise tissue into which the fat is deposited; some believing it to be the ordi- ^^••Nj^ t*)il^^lVI!l^^^^^^^^ nary areolar tissue, into which it is dropped by the agency of appropriate ves- sels ; others, as Malpighi3 A small cluster of Fat-Cells magnified 150 diameters. and Dr. William Hunter,4 be- lieving in the existence of a peculiar adipous tissue, consisting, according to M. Be'clard,5 of small bursae or membranous vesicles, which enclose the fat, and are found in the areolae of the tissue. These vesicles are said to vary greatly in size : generally, they are round and globular; and, in certain subjects, receive very apparent vessels. They form so many small sacs without apertures, in the interior of which are filaments arranged like septa. In fatty subjects, these adipous vesicles are very perceptible, being 1 Journal Hebdomad., Fevrier, 1834. 2 Art Synovia, in Wagner's Handworterbuch der Physiologie, 18te Lieferung, s. 467, Braunschweig, 1848. 3 De Omento, Pinguedine, et Adiposis Ductibus, in Oper., London, 1687. 4 Medical Observations and Inquiries, vol. ii., London, 1577. 5 ArtAdipeux, in Dictionnaire de Medecine, torn, i.; and Elements of General Anatomy, translated by Togno, p. 128, Philad., 1830. .... ..13. )1 AREOLAR EXHALATION OF THE ADIPOUS MEMBRANE. 267 Fig. 324. attached to the areolar tissue and neighbouring parts by a vascular pedicle. The fat originates from fat-cells, which are usually of a spherical or spheroidal shape, but sometimes, when closely pressed together without the intervention of any intercellular substance, they become polyhedral. The adipous tissue is a membrane of extreme tenuity, which forms the vesicle that includes the fat. The mem- brane is homogeneous and transparent, about the o^^th of an inch thick, and is moistened by a watery fluid, for which it has a greater attraction than the fat it contains. Each vesicle is from the -g^th to the Bloodvessels of Fat Vesicles. 1. Minute flattened fat-lobule, in which the vessels only are represented. 3. Terminal artery. 4. Primitive vein. 5. Fat vesicle, of one border of the lobule, separately represented. Mag- nified 100 diameters.—2. Plan of the arrangement of capillaries on the exterior of the vesicles, more highly magnified. g^th of an inch in dia- meter. When the fat vesicles exist in any num- ber, their arrangement is generally lobular, with an investment of areo- lar tissue, which favours motion, and the distribution of the bloodvessels. These enter the interlobular clefts, ramify through their interior as a solid capillary network, occupy the angles formed by contiguous sides of the vesicles, and anastomose with one another at the points where these angles meet. M. Raspail1 affirms, that there is the most striking analogy between the nature of the adipous granules and that of the amylaceous grains. As in the case of fecula, each adipous granule is composed of at least one integument, and an enclosed substance, both of which are as slightly nitrogenized as fecula ; and both fecula and fat are equally inservient to the nutrition of the organs of developement: whenever there is excess of life and activity, the fat is seen to disappear, and whenever there is rest, it accumulates in its reservoirs. If a portion of fat be examined, it is found to consist of an outer vesicle with strong membranous pari- etes, containing small adipous masses readily separable from each other, each invested with a similar, but slighter, vesicular membrane; and these, again, contain others still more minute, until ultimately we come to the vesicles that invest the adipous granules themselves. Each of these masses adheres, at some point of its surface, to the inner surface of the vesicle that encloses it, by a hilum in the same manner as the grain of fecula. All the vesicles, but especially the outermost and 1 Chimie Organique, p. 183, Paris, 1833. 268 SECRETION. strongest, have a reddish vascular network on their surface, the vessels of which augment in size as they approach the part where the vesicle is adherent, and there open into one of the vessels of the larger vesicle that encloses them. The arrangement of this tissue, as well as the quantity of fat, varies in different parts of the body. It is always found in the orbit, on the sole of the foot, and at the pulps of the fingers and toes. The subcuta- neous areolar tissue, and that covering the heart, kidneys, &c, also generally contain it; but it is never met with in the eyelids, scrotum, or within the cranium. Fat is exhaled by the secretory vessels in a fluid state ; but after it is deposited, it becomes more or less solid. According to the researches of MM. Chevreul1 and Braconnot, human fat is almost always of a yel- low colour ; inodorous, and composed of two portions ;—the one fluid, and the other concrete, which are themselves composed, but in different proportions, of two immediate principles, to which the former chemist gave the names elain or olein, and stearin. Subsequently, the organic elements of fat were considered to be stearin, margarin, and olein; the two former, which are solid when separate, being dissolved in the latter at the ordinary temperature of the body. Chemistry has, however, shown, that the fat contained in the cells of the adipous tissue is com- posed of a base of a sweetish taste, thence termed glycerin, itself an oxide of glyceryl with stearic, margaric, and oleic acids,—stearin being esteemed a bi-stearate of glycerin ; and olein or elain an Fig. 325. oleate of glycerin. These proximate, principles ^^>s. are sometimes seen spontaneously separated (CaJlliiJfer"'a w^hin the human fat vesicle. The stearin col- ^>5^^^p\.....2 lects in the form of a small star on the inner sur- f^^S^JjSJSm *"ace °*? tne membrane, as in the marginal figure 2 ^iLJir^^^ a* ^' ^' ^' ^e e^n occupying the remainder of ^gFJ- <«• the vesicle, except where there is an unusually Fat Vesicles from an Emaci- small quantity of fat, when a little aqueous fluid ated Subject. ig geen interpose(j between the elain and the 1, 1. Cell-membrane. 2, 2, _ ii „„„],.,..„ 2. Solid portion collected as a cen-memDrane. star-like mass, with the elain It is probable, that chemical analysis would in connexion with it, but not . f . •> „ , fining the cell. exhibit the fat to vary m different parts ot tne body, as its sensible properties are different. Sir Everard Home,2 on loose analogies and inconclusive arguments, has advanced the opinion, that it is more than probable, that fat is formed in the lower portion of the intestines; and thence is carried, through the medium of the circulating blood, to be deposited in almost every part of the body. " When there is a great demand for it, as in youth, for carrying on growth, it is laid immediately under the skin, or in the neighbourhood of the abdomen. When not likely to be wanted, as in old age, it is deposited in the interstices of muscular fibres, to make up in bulk for the wasting of these organs." M. de Blainville3 held the opinion, that fat is derived from venous blood, and that it is exhaled 1 Recherches Chimiques sur les Corps Gras, &c, Paris, 1823. 2 Lect on Comp. Anat, i. 468, Lond., 1814, and vol. vi. Lond., 1828; and Philos. Transact, 1821 p. 34. 3 De l'Organisation des Animaux, &c, Paris, 1825. EXHALATION OF THE ADIPOUS MEMBRANE. 269 through the coats of the vessels. This opinion he founds on the mode in which the fat is distributed in the omenta along the course of the veins ; and he affirms, that he has seen it flow out of the jugular vein in a dead elephant. But this last fact, as M. Lepelletier1 has judi- ciously remarked, proves nothing more than that fat—taken up by the absorbents from the vesicles in which it had been deposited by the exha- lants—had been conveyed into the venous blood with other absorbed matters. It in no wise shows, that the venous blood is the pabulum of the secretion, or that the veins accomplish it. The purposes served by the fat are both general and local. The great general use is, by some physiologists, conceived to be,—to serve as a provision in cases of wasting indisposition; when the digestive function is incapacitated for performing its due office, and emaciation is the con- sequence. In favour of this view, the rapidity with which fat disap- pears after slight abstinence has been urged, as well as the facts, connected with the torpidity of animals, which are always found to diminish in weight during this state. Professor Mangili, of Pavia, procured two marmots from the Alps, on the 1st of December. The larger weighed 25 Milanese ounces; the smaller only 22|th; on the 3d of January, the larger had lost fths of an ounce, and the smaller £fths. On the 5th of February, the larger weighed only 22|; the smaller 21. Dr. Monro kept a hedgehog from the month of November to the month of March following, which lost, in the meanwhile, a considerable por- tion of its weight. On the 25th of December, it weighed 13 ounces and 3 drachms; on the 6th of February, 11 ounces and 7 drachms; and on the 8th of March, 11 ounces and 3 drachms. The loss was 13 grains daily.2 The local uses of fat are chiefly of a physical character. On the sole of the foot it diminishes .the effects of pressure, and serves the same office on the nates; in the orbit it forms a kind of cushion, on which the eyeball moves with facility; and when in certain limits, it gives that rotundity to the frame, which we are accustomed to regard as symmetry. Dr. Fletcher,3 indeed, considers its principal use to be, to fill up interstices, and thus to give a pleasing contour to the body. In another place, it was observed, that fatty substances are bad conductors of caloric; and hence may tend to preserve the temperature of the body in cold seasons; a view which is favoured by the fact, that many of the Arctic animals are largely supplied with fat beneath the common in- teguments; and it has been affirmed, that fat people generally suffer less than lean from the cold of winter. It is obviously impracticable to estimate accurately the total quantity of fat in the body. It has been supposed that, in an adult male of moderate size, it forms ^th of the whole weight; but it is doubtful whether we ought to regard this as even an approximation,—the data being so inadequate. In some cases of polysarcia or obesity, the bulk of the body has been enormous. That of a girl is detailed, who weighed 1 Physiologie Medicale et Philosophique, ii. 496, Paris, 1832. 1 Fleming, Philosophy of Zoology, ii. 59, Edinb., 1822. » Rudiments of Physiology, part iii., by Dr. Lewins, p. 71, Edinb., 1837. 270 SECRETION. 256 pounds, when only four years old.1 A girl, said to be only ten years old, called the " Ohio giantess," was exhibited in Philadelphia, in the year 1844, who was said to weigh 265 pounds; and in March, 1847 an Ohio girl, twelve years of age—perhaps the same—was ex- hibited, who weighed 330 pounds. The Lowell Advertiser, of Septem- ber 1844, states, that a coloured girl, aged fourteen, a native of Nassau, New York, died in that city, weighing 500 pounds. A man of the name of Bright, at Maiden, England, weighed 728 pounds; and the celebrated Daniel Lambert, of Leicester, England, weighed 739 pounds a little before his death, which occurred in the fortieth year of his age.2 The circumference of his body was three yards and four inches; and of his leg one yard and one inch. His coffin was six feet four inches long; four feet four inches wide; and two feet four inches deep. A Ken.tuckian, of the name of Pritchard, who exhibited himself in Cincinnati, in 1834, weighed five hundred and fifty pounds. The "Canadian giant,"—as he was called—whom Dr. Gross3 saw in Philadelphia, in 1829, weighed six hundred and eighteen pounds. He was six feet four inches in height, and the circumference of each leg around the calf was nearly three feet. The deposition of fat was confined chiefly to the abdomen and lower limbs,—the thorax, shoulders, and arms being little larger than in other persons. The public Journals of this country4 have also recorded the death of a Mr. Cornelius, who weighed 720 pounds. Dr. Elliotson5 says he saw a female child, but a year old, which weighed sixty pounds. She had begun to grow fat at the end of the third month. In these cases, the specific gravity of the body may be much less than that of water. It is said, that some time ago there was a fat lighterman, on the river Thames, " who had fallen overboard repeatedly, without any farther inconvenience than that of a good ducking; since though he knew nothing whatever of the art of swimming, he always continued to flounder about like a firkin of butter, till he was picked up."6 In some of the varieties of the human family we meet with singular adipous deposits. In the Bosjesman female vast masses of fat accu- mulate on the buttocks, which give them the most extravagant appear- ance. The projection of the posterior part of the body, in one subject, according to Sir John Barrow,7 measured five inches and a half from a line touching the spine. " This protuberance," he remarks, " consisted of fat, and when the woman walked, had the most ridiculous appear- ance imaginable, every step being accompanied with a quivering and tremulous motion, as if two masses of jelly were attached behind. The "Hottentot Venus," who had several projections, measured more than nineteen inches around the haunches; and the projection of the hips exceeded 6 J inches. Dr. Somerville8 found on dissection, that the 1 Philos. Transact, No. 185. 2 Good's Study of Medicine, Class vi. Ord 1, Gen 1, Jap. 1. 3 Elements of Pathological Anatomy, 2d edit., p. 202, Philad., 184o. 4 Philadelphia Public Ledger, October 4, 1841. 5 Human Physiology, London, 1841, P. i. 301. 6 Fletcher, Rudiments of Physiology, by Dr. Lewins, pt. 3, p. 71, Edinb, 1837 i Travels, p. 281. .. s Medico-Chirurgical Transactions, va. 1D7. EXHALATION OF THE ADIPOUS MEMBRANE. 271 size of the buttocks arose from a vast mass of fat, interposed between the integuments and muscles, which equalled four fingers' breadth in thickness. It is singular, that, according to the statement of this female, which is corroborated by the testimony of Sir John Barrow, the deposition does not take place till the first pregnancy. Pallas1 ha& described a variety of sheep—ovis steatopyga or " fat buttocked"—which is reared in immense flocks by the pastoral tribes of Asia. In it, a large mass of fat covers the nates and occupies the place of the tail. The protuberance is smooth beneath, and resembles a double hemisphere, when viewed behind,—the os coccygis or rump-bone being perceptible to the touch in the notch between the two. They consist merely of fat; and, when very large, shake in walking like the buttocks of the female Bosjesman. Mr. Lawrence2 remarks, that there are herds of sheep in Persia, Syria, Palestine, and some parts of Africa, in which the tail is not wanting as in ovis steatopyga, but retains its usual length, and becomes loaded with fat. In the view of Liebig,3 the abnormous condition, which causes an undue deposition of fat in the animal body, depends on a disproportion between the quantity of carbon in the food, and that of the oxygen absorbed by the skin and lungs. In the normal condition, the quantity of carbon given out is exactly equal to that which is taken in the food, and the body experiences no increase of weight from the accumulation of substances containing much carbon and no nitrogen; but if the sup- ply of highly carbonized food be increased, then the normal state can only be preserved, by exercise and labour, through which the waste of the body is increased, and the supply of oxygen accumulated in the same proportion. The production of fat, Liebig maintains, is always a consequence of a deficient supply of oxygen; for oxygen is absolutely indispensable for the dissipation of the excess of carbon in the food. " This excess of carbon, deposited in the form of fat, is never seen in the Bedouin or in the Arab of the desert, who exhibits with pride to the traveller his lean, muscular, sinewy limbs, altogether free from fat; but in prisons and jails it appears as a puffiness in the inmates, fed, as they are, on a poor and scanty diet: it appears in the sedentary females of oriental countries; and is produced under the well-known conditions of fattening of domestic animals." In accordance, too, with his views of animal temperature, already referred to, Liebig considers that in the formation of fat there is a new source of heat. The oxygen set free in the action is given out in combination with carbon and hydrogen; and whether this carbon and hydrogen proceed from the substance that yields the oxygen, or from other compounds, still there must have been generated by the formation of carbonic acid or water as much heat as if an equal weight of carbon or hydrogen had been burned in air or in oxygen gas. Whether the view of Liebig be admitted or not, it is certain that the circumstances, which favour obesity, are absence of activity and excite- 1 Spicilegia Zoologica, fasc. xi. p. 63. Also, Erman, Travels in Siberia, Amer. edit, Philad., 1850. 2 Lectures on Physiology, Zoology, &c, p. 427, London, 1819. 3 Animal Chemistry, Webster's edit, p. 85, Cambridge, Mass, 1S42. 272 SECRETION. ment of all kinds; hence, for the purpose of fattening animals in rural economy, they are kept in entire darkness, to deprive them of the stimulus of light, and encourage sleep and muscular inactivity. Cas- tration—by abolishing one kind of excitability—and the time of life at which the generative Functions cease to be exerted, especially in the female, are favourable to the same result. b. Marrow. A fluid, essentially resembling fat, is found in the cavity of long bones, in the spongy tissue of short bones, and in the areolae of bones of every kind. This is the marrow—medulla ossium. The secretory organ is the very delicate membrane, which is perceptible in the interior of the long bones, lining the medullary cavity, and sending prolonga- tions into the compact substance, and others internally, which form septa and spaces for the reception of the marrow. The cells, thus formed, are distinct from each other. From the observations of Mr. Howship,1 it would seem probable, that the oil of bones is deposited in longitudinal canals, that pass through the solid substance of the bone, and through which its vessels are transmitted. This oil of bones is the marrow of the compact structure, the latter term being generally re- stricted to the secretion when contained in the cavities of long bones; that which exists in the spongy substance being termed, by some writers, the medullary juice. The medullary membrane, called also the internal periosteum, consists chiefly of bloodvessels ramifying on an extremely delicate areolar tissue, in which nerves may likewise be traced. Berzelius examined marrow obtained from the thigh-bone of an ox, and found it consist of the following constituents:—pure adipous mat- ter, 96; skins and bloodvessels, 1; albumen, gelatin, extractive, pecu- liar matter, and water, 3. The marrow is one of the corporeal components, of whose use we can scarcely offer a plausible conjecture. It has been supposed to render the bones less brittle; but this is not correct, as those of the foetus, which contain little or no marrow, are less so than those of the adult; whilst those of old persons, in whom the medullary cavity is large, are more brittle than those of the adult. It is possible that it may be placed in the cavities of bones,—which would otherwise be so many vacant spaces,—to serve the general purposes of fat, when required by the system. The other hypotheses that have been enter- tained on the subject are not deserving of notice. 5. Exhalation of the Pigment Membrane. The nature of the exhalation, which constitutes the colouring matter of the rete mucosum, has already engaged attention, when treating of the skin under the Sense of Touch. It is presumed to be exhaled by the vessels of the skin, and to be deposited beneath the cuticle, so as to communicate the colours that characterize the different races. Such are regarded as the secretory organs by most anatomists and physiolo- 1 MedicoChirurg. Trans, vii. 393. EXHALATION OF THE PIGMENT MEMBRANE. 273 gists; but M. Gaultier,1 whose researches into the intimate constitution of the skin have gained him much celebrity, is of opinion, that it is furnished by the bulbs of the hair; and he assigns, as reasons for this belief, that the negro, in whom it is abundant, has short hair; that the female, whose hair is more beautiful and abundant than that of the male, has the fairest skin ; and that when he applied blisters to the skin of the negro, he saw the colouring matter oozing from the bulbs and deposited at the surface of the rete mucosum. But the views of modern anatomists on the corpus mucosum have been given already.2 The composition of this pigment cannot be determined with precision, owing to its quantity being too small to admit of examination. Chlo- rine deprives it of its black hue, and renders it yellow. A negro, by keeping his foot for some time in water impregnated with this gas, deprived it of its colour, and rendered it nearly white; but in a few days the black colour returned with its former intensity. The experi- ment was made with similar results on the fingers. Blumenbach3 thought, that the mucous pigment was formed chiefly of carbon; and the notion has received favour with many. The colour, according to Henle and others,.is owing to pigment cells, of which the pigmentum nigrum of the eye is wholly composed. They are considered to exhibit, usually, the original form of the cell with little alteration. On the choroid coat they form a kind of pavement, and have somewhat of a polyhedral shape. In the human skin, they are scattered through the ordinary epidermic cells, and the colour of the skin is determined by that of their contents. Krause,4 however, denies that the colour of the cuticle of the Ethiopian depends on pig- ment cells, like those of the pigmentum nigrum. It is owing chiefly, he says, to the colour of the proper nuclei and cells of the epidermis. There are, indeed, some few pigment cells mingled with the proper cells of the middle and superficial layers of the epidermis; but they are dis- tinguishable from those of the pigmentum nigrum by containing far fewer pigment granules, and by having always a dark, not a clear, nucleus. The colour depends especially on the dark or almost black- brown colour of the nuclei, whether free in the deep layers of epider- mis or surrounded by cells. They have dark nucleoli; sharp outlines; appear only very obscurely granular, and cannot be broken into smaller pigment granules. The cells surrounding them may be seen in the deeper layers: they, also, are uniformly dark, although less so than the nuclei. In the middle and superficial layers, the nuclei, as long as they can be seen, are still dark; the cells are much paler, but brownish and darker than in the corresponding layers in uncoloured persons. Pigment granules are amongst the most minute structures of the body, being not more than ^fo^th of an inch in their largest dia- meter, and about one-fourth as much in thickness. 1 Recherches sur l'Organisation de la Peau de 1'Homme, &c,,Paris, 1809 and 1811. 2 See Vol. i. p. 124. 3 Instit Physiol., § 274; and Elliotson's translation, 4th edit, Lond, 1S28. 4 Art. Haut, in Wagner's Handworterbuch der Physiologie, 7 Lief, s. 108, Braunschweig, 1844. VOL. II.—18 274 SECRETION. The uses of the pigment of the skin—as well as of that which lines the choroid coat of the eye, the posterior surface of the iris, and the ciliary processes—are detailed in other places. 6. Exhalation of Areolar Capsules. Under this term, M. Adelon1 has included different recrementitial se- cretions effected within the organs of sense, or in parenchymatous struc- tures,—as the aqueous, crystalline, and vitreous humours of the eye, and the liquor of Cutugno, all of which have already engaged attention; the exhalation of a kind of albuminous, reddish, or whitish fluid into the interior of the lymphatic ganglions, and into the organs, called by M. Chaussier, glandiform ganglions, and by M. Be'clard, sanguineous ganglions;—namely, the thymus, thyroid, supra-renal capsules, and spleen. We know but little, however, of the fluids formed in these parts: they have never been analyzed, and their uses are unknown. 7. Vascular Exhalation. A fluid is exhaled from the inner or serous coat of the arterial, venous, and lymphatic vessels. It must be serous, and its use doubtless is to lubricate the interior of the vessel, and prevent adhesion between it and the fluid circulating within it. B. EXTERNAL EXHALATIONS. 1. Exhalation of Mucous Membranes—General and Pulmonary. The mucous membranes, like the skin, which they so strongly resem- ble in their structure, functions, and diseases, exhale a similar tran- spiratory fluid. This has not been subjected to chemical examination. It is, indeed, almost impracticable to separate it from the follicular secretions of the same membrane; and from the extraneous substances almost always in contact with it. It is probably, however, similar to the fluid of the cutaneous and pulmonary depurations, both in character and use. The pulmonary transpiration, to which allusion has so often been made, bears a striking analogy to the cutaneous. Sir B. Brodie and M. Magendie, from the examination of cases of fistulous opening into the trachea, deny that it comes from the lungs, believing it to be formed by the moist mucous lining of the nose, throat, &c.; but this view has been disproved by Paoli and Regnoli, in the case of a young female, whose trachea had been opened, and in whom, at the temperature of 39° Fahr., watery vapour was distinctly expired through the canula. Mojon2 strangely supposes the vapour of the breath to be a watery fluid secreted by the thyroid gland, and suspended in the respired air, its volatility being caused by the presence of caloric. At one time, it was universally believed to be owing to the combustion of the hydrogen and carbon given off from the lungs; but we have elsewhere shown, that no such combustion occurs there; and besides, the exhalation takes place when gases containing no oxygen are respired by animals. It is 1 Physiologie de l'Homme, 2de &lit, torn. iii. 483. Paris, 1829. 2 Leggi Fisiologiche, &c, translated by Skene, p. 76, Lond, 1827. I EXHALATION OF MUCOUS MEMBRANES—PULMONARY. 275 now almost universally admitted to be exhaled into the air-cells of the lungs from the pulmonary artery chiefly; but partly from the bronchial arteries distributed to the mucous membrane of the air-passages. Much of the vapour, Dr. Prout conceives, is derived from the chyle in its passage through the lungs; and thus, he considers, the weak and delicate albumen of the chyle is converted into the strong and perfect albumen of the blood. The air of expiration, according to Valentin1 and Brunner, appears saturated with it, so that, as they have remarked, the quantity of vapour exhaled may be estimated by subtracting the quantity contained in the atmospheric air expired from the quantity, which, at the same barometric pressure, would saturate the same atmospheric air at the temperature of 99*5°—the general temperature of the air of expiration. On the other hand, if the quantity of watery vapour in the expired air be esti- mated, the quantity of the air itself may thence be accurately deter- mined—being as much as that quantity of watery vapour would satu- rate at the ascertained temperature and barometric pressure. It has not been established, however, that the expired air is saturated with moisture. Sundry interesting experiments have been made on this exhalation by Magendie, Milne Edwards, Breschet, and others. If water be injected into the pulmonary artery, it passes into the air-cells in myriads of almost imperceptible drops, and mixes with the air contained in them. M. Magendie3 found, that its quantity might be augmented at pleasure on living animals, by injecting distilled water, at a temperature ap- proaching that of the body, into the venous system. He injected into the veins of a small dog a considerable amount of water. The animal was at first in a state of real plethora—the vessels being so much dis- tended that it could scarcely move; but in a few minutes the respira- tion became manifestly hurried, and a large quantity of fluid was discharged from the mouth, the source of which appeared evidently to be the pulmonary transpiration greatly augmented. But not only is the aqueous portion of the blood exhaled in this man- ner, experiment shows, that many substances introduced into the veins by absorption, or by direct injection, issue from the lungs. Weak alcohol, a solution of camphor, ether, and other odorous substances, when thrown into the cavity of the peritoneum or elsewhere, were found, by M. Magendie, to be speedily absorbed by the veins, and con- veyed to the lungs, where they transuded into the bronchial cells, and were recognised in the expired air by their smell. Phosphorus, when injected, exhibited this transmission in a singular and evident manner. M. Magendie,4 on the suggestion of M. Armand de Montgarny, "a young physician," he remarks, "of much merit," now no more, in- jected into the crural vein of a dog, half an ounce of oil, in which phosphorus had been dissolved: scarcely had he finished the injection, before the animal sent through the nostrils clouds of a thick white 1 Lehrbuch der Physiologie des Menschen, i. 547, Braunschweig, 1844. 2 Dr. John Reid, art. Respiration, Cyclop, of Anat. and Pins., pt. xxxii. p. 345, Lond, Aug., 1848. 3 Precis, &c, ii. 346. * Ibid, ii. 348. I 276 SECRETION. vapour, which was phosphoric acid. When the experiment was made in the dark, these clouds were luminous. M. Tiedemann1 injected a drachm of the expressed juice of garlic into a vein of the thigh of a middle-sized dog: in the space of three seconds the breath smelt strongly of garlic. When spirit of wine was injected, the exhaled vapour was recognised when the injection was scarcely over. MM. Breschet and Milne Edwards2 made several experiments for the purpose of discovering why the pulmonary transpiration expels so promptly the different gases and liquid substances received into the blood. Considering properly, that exhalation differs only from absorp- tion in taking place in an inverse direction, these gentlemen conjec- tured, that it ought to be accelerated by every force, that would attract the fluids from within to without; and such a force they conceive inspi- ration to be, which, in their view, solicits the fluids of the economy to the lungs, in the same mechanical manner as it occasions the entrance of air into the air-cells. In support of this, view they adduce the fol- lowing experiments. To the trachea of a dog a pipe, communicating with a bellows, was adapted, and the thorax was largely opened. Natural respiration was immediately suspended; but artificial respira- tion was kept up by means of the bellows. The surface of the air-cells was, in this way, constantly subjected to the same pressure, there being no longer diminished pressure during inspiration, as when the thorax is sound, and the animal breathing naturally. Six grains of camphorated spirit were now injected into the peritoneum; and, at the same time, a similar quantity in another dog, whose respiration was natural. In the course of from three to six minutes, the odorous sub- stance was detected in the pulmonary transpiration of the latter; but in the other it was never manifested. They now exposed in the first animal a part of the muscles of the abdomen, and applied a cupping- glass to it; when the smell of the camphor speedily appeared at the cupped surface. Their conclusion was, that the pulmonary surface, having ceased to be subjected to the suction force of the chest during inspiration, exhalation was arrested, whilst that of the skin was deve- loped as soon as an action of aspiration was exerted upon it by the cupping-glass. Into the crural veins of two dogs,—one of which breathed naturally, and the other was circumstanced as in the last experiment, they injected essential oil of turpentine. In the first of these, the substance was soon apparent in the pulmonary transpiration; and, on opening the body, it was discovered, that the turpentine had impregnated the lung and pleura much more strongly than the other tissues. In the other animal, on the contrary, the odour of the turpentine was scarcely apparent in the vapour of the lungs; and on dissection, it was not found in greater quantity in the lungs than in other tissues;—in the pleura, for instance, than in the peritoneum. From the results of these experiments, MM. Breschet and Edwards conclude, that each inspiratory movement constitutes a kind of suction, 1 Tiedemann und Treviranus, Zeitschrift fur Physiologie, Band. v. H. ii.; cited in British and Foreign Medical Review, i. 241, Lond., 1836. 2 Recherches Experimentales 6ur l'Exhalation Pulmonaire, Paris, 1826. MENSTRUAL EXHALATION. 277 which attracts the blood to the lungs; and causes the ejection of the liquid and gaseous substances which are mingled with that fluid, through the pulmonary surface, more than through the other exhalant surfaces of the body. In their experiments, these gentlemen did not find, that exhalation was effected with equal readiness in every part of the sur- face, when the cupping-glass was applied in the mode that has been mentioned. The skin of the thigh, for example, did not indicate the odour of camphorated alcohol as did that of the region of the stomach. The chemical composition of the pulmonary transpiration is proba- bly nearly identical with that of the sweat; appearing to consist of water, holding in solution, perhaps, some saline and albuminous matter; but our information on this matter, derived from the chemist, is not precise. M. Collard de Martigny's1 experiments make it consist, in 1000 parts,—of water 907, carbonic acid 90; animal matter—the nature of which he was unable to determine—3. M. Chaussier found, that by keeping a portion of it in a close vessel exposed to an elevated temperature, a very evident putrid odour was exhaled on opening the vessel. This could only have arisen from the existence of nitrogenized matter in it. The pulmonary transpiration being liable to all the modifications which affect the cutaneous, it is not surprising, that we should meet with so much discordance in the estimates of different individuals, regarding its quantity in a given time. Hales2 valued it at 20 ounces in the twenty-four hours: Sanctorius,3 Menzies,4 and Dr. William Wood,5 at 6 ounces; Mr. Abernethy6 at 9 ounces; MM. Lavoisier and Se'guin7 at 17£ ounces poids de marc; Dr. Thomson8 at 19 ounces, Dr. Dalton at from 1 pound 8f ounces,9 to 20J ounces avoirdupois,10 and Dr. Car- penter11 at from 16 to 20 ounces, and Kirkes and Paget12 at from 6 to 27 ounces. The uses it serves in the animal economy are identical with those of the cutaneous transpiration. It is essentially depura- tory. Experiments, some of which have been detailed, have sufficiently shown, that volatile substances introduced in any way into the circula- tory system, if not adapted for the formation of arterial blood, are rapidly exhaled into the bronchial tubes. Independently, therefore, of the lungs being the great organs of respiration, they play a most important part in the economy, by throwing off those substances, that might be injurious, if retained. 2. Menstrual Exhalation. The secretion of the menstrual fluid, which is a true sanguineous exhalation from the vessels of the uterus, will fall more appropriately under consideration when treating of the functions of reproduction. 1 Magendie's Journal de Physiologie, x. 111. 2 Statical Essays, ii. 322, Lond, 1767. 3 Medicina Statica, Aphor. v. 4 Dissertation on Respiration, p. 54, Edinb., 1796. s Essay on the Structure, &c, of the Skin, Edinb., 1832. 6 Surgical and Physiol. Essays, p. 141, Lond, 1793. 7 Mem. de la Societe Royale de Medecine, pour 1782-3; Annal. de Chimie, v. 264 ; and Mem. de l'Acad. des Sciences, pour 1789. 8 System of Chemislry, vol. iv. 9 Manchester Memoirs, 2d series, ii. 29. 10 Ibid, vol. v. " Human Physiology, § 549, Lond, 1842. 12 Manual of Physiology, Amer. edit, p. 139, Philad, 1849. 278 SECRETION. 3. Gaseous Exhalation. The secretion of air from the bloodvessels is not so manifest as in the case of the exhalations thus far considered; but if we regard, with many, the separation of carbonic acid from the blood as a secretion, it is one of the most extensive and important in the animal economy. Gases are perpetually received into the vessels of the lungs, and to a certain degree elsewhere, whilst carbonic acid—as we have seen, under the function of Respiration—is constantly exhaled. Moreover, in the swim-bladders of fishes an unequivocal case of gaseous secre- tion is presented; for many of these have no communication whatever by duct or otherwise with any outlet of the body. In the order Pharyngognathi of Miiller, which includes the family of the saury- pike and others—in Anacanthini, including the cod and plaice; in Acanthopteri, including the perch, gurnard, mullet, mackerel, and others; in the Plectognathi of Cuvier, including the globe fish; and in Lophobranchii of the same naturalist, which includes the sea horse and pipe fish,—a characteristic is the possession of a swim bladder with- out an air duct. In these cases,there can be no question of the secretion of air; and accordingly such a secretion has been admitted by physio- logists.1 It may account for the copious developement of air in the intestinal canal, as has been suggested elsewhere;2 and for the produc- tion of many of the pneumatoses, which are so difficult of explanation under any other view. The last subject has, however, received the author's attention in another work.3 II. FOLLICULAR SECRETIONS. The follicular secretions must, of necessity, be effected from the skin or the mucous membranes, inasmuch as follicles or crypts are met with there only. They may, therefore, be divided into two classes;—1st, the follicular secretions of mucous membranes ; and 2dly, the follicular secretions of the skin. 1. Follicular Secretion of Mucous Membranes. The whole extent of the mucous membranes lining the alimentary canal, air-passages, and urinary and genital organs, is the seat of a secretion, the product of which has received, in the abstract, the name of mucus; although it differs somewhat according to the situation and cha- racter of the particular follicles whence it proceeds. Still, essentially, the structure, functions, and products of all mucous membranes are the same (see vol. i. p. 131). Such is the general sentiment. M. Donne*,4 however, ranges the different mucous membranes in three great divi- sions—according to their microscopical characters, the chemical reaction of their mucus, and the structure of the epithelium. His first division comprises those membranes that are analogous to the skin,—in other words, that secrete an acid fluid, which contain, under the form of pelli- 1 John Hunter, Observations on Certain Parts of the Animal Economy, with Notes by Prof. Owen, Amer. edit, p. 127, Philad, 1840. J. Vogel, The Pathological Anatomy of the Human Body, by Dr. Day, p. 31, London, 1847; and Prof. Owen, Lectures on the Compara- tive Anatomy and Physiology of the Vertebrate Animals, p. 272, Lond, 1846. 2 Vol. i. p. 615. 8 Practice of Medicine, 3d edit, i. 172, Philad, 1848. 4 Cours de Microscopie, p. 143, Paris, 1844. FOLLICULAR—OF MUCOUS MEMBRANES. 279 cles, or scales, the product of the desquamation of the epidermis. They are, in reality, reflections of the outer skin, and in no respect deserve the name of mucous membranes. The vaginal mucous membrane is one of these, being a mere reflection of the outer skin, and possessing its prin- cipal properties. It secretes a mucus, which is always acid; strongly reddening litmus paper, and filled with soft, flattened lamellae, or rather cells, like the epidermic vesicles of the skin. In regard to its physio- logical properties, this membrane, like the skin, is endowed with ex- quisite sensibility; it is scarcely ever the seat of hemorrhage, and ulcerates less readily than mucous membranes properly so called. The membranes with acid mucus and epidermic vesicles never, he says, exhibit any epidermic cells. The second division comprises the "true mucous membranes." They differ from the skin in every respect,— both by the nature of their epithelium, and the chemical reaction of their secretion, which is always alkaline. It is viscid, and, instead of exhibiting under the microscope the epidermic lamellae or cellules, men- tioned above, it presents only mucous globules, whose structure, pro- perties, and origin are entirely different. These membranes, of which the bronchial mucous membrane may be taken as the type, ulcerate readily; are the seat of hemorrhages, and do not possess tactile sensi- bility like the skin. To these belong the vibratile organs or cilia. These two orders of membranes, according to M. Donne*, are found approximated, and almost confounded, although still preserving their distinct characters, in the vagina and neck of the uterus,—the one secreting a creamy, not ropy, always acid mucus; and presenting, under the microscope, large epidermic cellules; the other furnishing a glairy, ropy mucus, constantly alkaline, and containing mucous globules much smaller than epidermic cells, and of a structure and composition wholly different. The third division comprises a class intermediate between the two others, constituted by parts which participate in the organization of skin and mucous membranes, through surfaces which have not yet entirely lost the qualities of the external membrane, and already possess some of those of the internal or true mucous membranes. Such are the orifices where the skin does not terminate suddenly, but becomes gradually transformed into mucous membrane, as at the mouth, nose, anus, &c. These parts secrete a mucus, which M. Donne" terms mixed; in this are found combined the characters of the two already mentioned, with a predominance of the one or the other, according as the properties of the skin, or those of the mucous membranes, prevail. The mucus of the mouth he regards as an example of the intermediate species.1 In the history of the different functions, in which certain of the mucous membranes are concerned, the uses of the secretion have been detailed; and in those functions, that will hereafter have to engage attention, in which other mucous membranes are concerned, its uses will fall more conveniently under notice. But few points will, there- fore, require explanation at present. The mucus secreted by the nasal follicles seems alone to have been 1 See, on the structure, relations, and offices of the Mucous Membranes, Mr. Bowman, art. Mucous Membrane, in Cyclop, of Anat. and Physiol., Parts xxiii. and xxiv, Lond., 1842. 280 SECRETION. subjected to chemical analysis. I.xM. Fourcroy and Vauquelin1 found it composed of the same ingredients as tears. According to the analysis of Berzelius,2 its contents are as follows:—water, 933*7; mucus, 53*3; chlorides of potassium and sodium, 5*6; lactate of soda with animal matter, 3*0; soda, 0*9; albumen and animal matter, soluble in water, but insoluble in alcohol, with a trace of phosphate of soda, 3*5. Dr. G. 0. Rees3 considers mucus to be a compound of albumen in a state of close combination with alkaline salts, and probably free alkali; and he affirms, that the artificial compound formed by the addition of alkalies and neutral salts to albuminous matter is essentially the same as mucus. According to M. Raspail,4 mucus is the product of the healthy and daily disorganization or wear and tear of mucous membranes. Every mucous membrane, he affirms, exfoliates in organized layers, and is thrown off, more or less, in this form; but the serous membranes either do not exfoliate, or their exfoliation (excoriation) is reduced to a liquid state to be again absorbed by the organs. This, however—like many of M. Raspail's speculations—is a generalization that does not appear to be warranted by facts: the slightest examination, indeed, exhibits^ that the general physical character of mucus is very different from that of the membranes which form it: still, when examined by a micro- scope of high magnifying power, it presents here and there, appear- ances of shreds similar to those described by M. Raspail. These have been considered by recent histologists detached epithelium cells, with granulated globular particles, which are esteemed to be characteristic of the secretion from the surface of mucous membranes.5 Although mucus is classed as a follicular secretion, it would seem to be formed in mucous membranes in which no follicles can be detected, as in those lining the frontal and other sinuses of the cranium. M. Mandl,6—who first stated the belief in the identity in structure of the globules of mucus and pus and the red corpuscles of the blood,— describes mucus as composed of a viscid liquid in which are swimming, besides lamellge of epithelium, special elements, which he calls globules of mucus. These are of two kinds,—the one consisting of mammillated corpuscles, 0*005 to 0*006 of a millimetre in diameter; the other, from 0*01 to 0*02 of a millimetre in diameter,—the latter being true cells, composed of an envelope and a nucleus. The great use of mucus, wherever met with, is to lubricate the sur- face on which it is poured. Experiments, however, by Oesterlen7 have proved the influence of the layer of mucus, which lines the digestive canal, in retarding both the imbibition of fluids inclosed within the canal, and the permeation of fluids by endosmose. The passage of fluid into, or through, the mucous membrane of the intestines was, in 1 Journal de Physique, xxxix. 359. 2 Medico-Chirurg. Transactions, torn, iii.; also, Thomson, Chemistry of Animal Bodies, p. 507, Edinb, 1843. 3 Cyclop, of Anat and Physiol, P. xxiii. p. 484, April, 1842. 4 Chimie Organique, p. 246, and p. 504, Paris, 1832. 5 For the different forms of mucus, see Donne, op. cit, p. 145. 6 Manuel d'Anatomie Generate, p. 478, Paris. 1843. i Beitrage zur Physiologie des Gesunden und Kranken Organismus, s. 245, Jena, 1843. FOLLICULAR—OF XHE SKIN. 281 many cases, more than twice as raj/id when the mucus had be^n ?&■ moved as when still adherent. a. Secretion of the Peyerian Glands. The morphology and functions of the Peyerian follicles or glands have been investigated elsewhere.1 They are peculiar in having no outlets; the fluid elaborated by them from the blood being poured, by the bursting of the formative cells, on the mucous surface of the intesti- nal canal. b. Secretion of the Ovaria. In many respects the secretion of the ovaria—the formation of ova —is accomplished like that of the Peyerian glands. Like them, the follicles of De Graaf are devoid of outlet; and the secretion has to make its way to the surface of the ovary and be discharged,—the Fallopian tube receiving it, and acting as an excretory duct. The mode' in which this is accomplished will fall more appropriately under con- sideration, when the functions of Reproduction are investigated. 2. Follicular Secretion of the Skin. This is the sebaceous and micaceous humour, observed in the skin of the cranium, and in that of the pavilion of the ear. It is, also, the humour, which occasionally presents the appearance of small worms beneath the skin of the face, when it is forced through the external aperture of the follicle; and when exposed to the air Fis- 32(3- causes the black spots sometimes observable on the face. The following were found by Esenbeck2tobeits constituents: salt, 24*2; osmazome, with traces of oil, 12*6; watery ex- tracts, 11*6; al- bumen and casein, 24*2;carbonate of lime, 2*1; phos- phateof lime 20*0; carbonate of mag- nesia, 1*6; acetate of soda, and chlo- ride Ot SOdlUm, i. Section of Bkin, magnified three diameters. 2, 2. Hairs. 3, 3. Su- traCeS. perficial sebaceous glands. 1, 1. Larger and deeper-seated glands by _. which the cerumen appears to be secreted. 3. A ceruminous gland more 1 llC CUtaneOUS Or largely magnified, formed of convoluted tube 1, forming excretory duct 2. m'V f 11" 1 3. A small vessel, and its branches. 2. A hair from meatus auditorius, miliary IOlllCleS Or perforating epidermis at 3, and at 4, contained within its double follicle glands Were refer- 5'5' *' *' Sebaceous folllcles of nair witn their excretory ducts. (Wag- 1 Vol. i. p. 532. 2 V. Bruns, Lehrbuch der Physiologie des Menschen, s. 353, Braunschweig, 1841. Sehaceous or Oil Glands and Ceruminous Glands. 282 SECRETION. jr-fc-a to in describing/ihe anatomy of the common integument.1 At times, they are simple c/rvpts, formed merely by an inversion of the common inte- gument; at others, more complicated but still a like in- version ; and they commonly open into channels by which the hairs issue. (Figs. 44 and 326, 2.) In certain parts of the skin, they are more numer- ous than in others. Mr. Rainey — as hereafter remark- ed2— was unable to detect them in the palms of the hands and soles of the feet. Their appearance in the axilla of the ne- gro has been de- scribed by Professor Horner.3 Their granular or composite character in the axilla, he thinks, is sufficiently evident; but the point is yet to be settled, whether their excretory ducts have the tortuous arrange- ment of those of the ceruminous glands, or whether they be branched and racemose, like those of the salivary. Mr. Hassall4 affirms, that they are similar in organization to the sudoriparous glands, but much larger. The secretion from the different cutaneous follicles differs, probably, according to the different character and arrangement of animal mem- brane from which the cells that form it are developed. There is, certainly, a marked difference between the fluids secreted in the axilla, groin, prepuce, feet, &c, each appearing to have its characteristic odour; although a part of this may be owing to changes occurring in the mat- ter of secretion by retention in parts to which the free access of air is prevented. The cutaneous or miliary glands, depicted by Dr. Horner, are considered by him to be the glandulse odorjferse of the axilla. In many animals odorous secretions of a similar character are formed by special organs; but whether the scent peculiar to animals and to races is thus secreted is canvassed elsewhere,5 and must be regarded as some- what unsettled. The cerumen is, likewise, a follicular secretion, as well as the whitish, 1 Vol. i. p. 126. 2 Page 292. 3 American Journal of the Medical Sciences, for January, 1846, p. 13. 4 The Microscopic Anatomy of the Human Body, Part xiii. p. 426, Lond, 1848. * P. 294. Fig. 327. Cutaneous Follicles or Glands of the Axilla, magnified one-third. (Horner.) TRANSPIRATORY. 283 odorous and fatty matter—smegma—which forms under the prepuce of the male, and in the external parts of the female, where cleanliness is disregarded. The humour of Meibomius is also follicular, as well as that of the caruncula lachryma- lis of the crypts around the v Fis- 328- base of the nipple, &c. The use of these secretions is to favour the functions of the parts over which they are dis- tributed. That which is se- creted from the skin is spread over the epidermis, hair, &c, giving suppleness and elasticity to the parts; rendering the sur- face smooth and polished, and thus obviating the evils of abra- sion that might otherwise arise. It is also conceived, that its unctuous nature may render the parts less permeable to humid- ity. In the ducts of the sebaceous follicles, a parasite was dis- covered by M. Simon, of Ber- lin;1 which has been minutely described by Mr. Erasmus Wilson,2 Pro- fessor Vogel,3 Messrs. Todd and Bowman,4 and Professor Owen.s It is the Acarus folliculorum of Simon, Demodex folliculorum of Owen, and Steatozoon folliculorum of Mr. Wilson. By him two chief varieties of the adult animal are depicted. These are mainly distin- guished by their length—the one measuring from the y-J^th to thes ^gth, the other from the y^th to the y^gth of an inch. The marginal figure represents them as found by Messrs. Todd and Bowman in a sebaceous follicle of the scalp. They do not appear to be of any physiological or pathological importance. Entozoa from the Sebaceous Follicles. a. Two seen in their ordinary position in the orifice of one of the sebaceous follicles of the scalp, b. Short variety, c. Long variety. III. GLANDULAR SECRETIONS. The glandular secretions are seven in number; the transpiration, tears, saliva, pancreatic juice, bile, urine, sperm, and milk. 1. The Transpiratory Secretion. A transparent fluid is constantly exhaled from the skin, which is generally invisible in consequence of its being converted into vapour as soon as it reaches the surface; but, at other times, owing to augmenta- • Miiller's Archiv., s. 218, 1842. 2 On Diseases of the Skin, 2d Amer. edit, p. 424, Philad, 1847; and in Philosophical Transactions for 1844. 3 The Pathological Anatomy of the Human Body; translated by Dr. Day, p. 453,Lond, 1847. 4 The Physiological Anatomy and Physiology of Man, p. 425, Lond, 1845. 6 Lectures on the Comparative Anatomy and Physiology of the Invertebrate Animals, p. 251, Lond, 1S43. 284 SECRETION. tion of the secretion, or to the air being loaded with humidity, it is apparent on the surface of the body. When invisible, it is called in- sensible transpiration or perspiration; when perceptible, siveat. In the state of health, according to M. Thenard,1 this fluid reddens litmus paper; yet the taste is rather saline—resembling that of common salt —than acid. Wagner,2 indeed, affirms that it generally shows alkaline reaction; and, at other times, does not affect vegetable blues; but the sweat of many parts of the body,—the armpits for example,—is said always to react like an alkali. Allusion has already been made to the views of M. Donne",3 who considers, that the external, and the internal alkaline membranes of the human body represent the two poles of a pile, the electrical effects of which are appreciable by the galvano- meter. The smell of the perspiration is peculiar, and when concentrated, and especially when subjected to distillation, becomes almost insup- portable. The fluid is composed, according to M. The'nard, of much water, a small quantity of acetic acid, chloride of sodium, and perhaps of potassium, a very little earthy phosphate, a trace of oxide of iron, and an inappreciable quantity of animal matter. Berzelius4 regards it as water holding in solution chlorides of potassium and sodium, lactic acid, lactate of soda, and a little animal matter; Anselmino,5 as con- sisting of a solution of osmazome, chlorides of sodium and calcium, acetic acid, and an alkaline acetate, salivary matter, sulphates of soda and potassa, and calcareous salts, with mucus, albumen, sebaceous humour, and gelatin in variable proportions; and M. Raspail6 looks upon it as an acid product of the disorganization of the skin. The solid con- stituents, according to Simon,7 are a mixture of salts and extractive matters, of which the latter preponderate: the principal ingredient of the salts is chloride of sodium. From what he admits to be super- ficial and merely qualitative investigations, he considers he has estab- lished the existence in normal sweat, of—First. Substances soluble in ether; traces of fat, sometimes including butyric acid. Secondly. Substances soluble in alcohol; alcohol extract; free lactic or acetic acid ; chloride of sodium; lactates and acetates of potassa and soda; lactate or chlorohydrate of ammonia. Thirdly. Substances soluble in water; water—extract; phosphate of lime, and occasionally an alka- line sulphate; and, fourthly. Substances insoluble in water; desquama- ted epithelium; and—after the removal of the free lactic acid by alcohol —phosphate of lime with a little peroxide of iron. In the solid matter urea was detected by Landerer.8 After evaporation upon a clean glass plate, fragments of epidermic cells are generally observed in it, and crystals are left behind, which 1 Traite de Chimie, torn. iii. 2 Elements of Physiology, by R. Willis, § 204, Lond, 1842. 3 Journal Hebdomad, Fevrier, 1834. 4 Medico-Chir. Trans, iii. 256. 5 Lepelletier, Physiologie Medicale et Philosophique, ii. 452, Paris, 1832. 6 Chimie Organique, p. 505, Paris, 1832. ' Animal Chemistry, Sydenham Society edit, ii. 101, Lond., 1846. . 8 G. O. Rees, art. Sweat, Cyclopaedia of Anatomy and Physiology, pt. xxxvii. p. 844, Lond, October, 1849. TRANS PIRAT0RY. 285 Fig. 329. are those of its contained salts. With great care to avoid admixture, Krause1 collected a small quantity of pure cutaneous perspiration from the palm of the hand, where there are no sebaceous follicles. The fluid yielded, with boiling ether, some small globules of oil and crystals of margarin. It was acid, but after twenty-four hours became alkaline, by the developement of ammonia. In another experiment, he found, that the tissue of the epidermis contains a fatty substance independ- ently of the fatty matter secreted on its surface. In a memoir presented to the Academic Royale des Sciences of Paris, MM. Breschet and Roussel de Vauzeme first clearly showed, that there exists in the skin an apparatus for the secretion of the sweat, consisting of a glan- dular parenchyma, which secretes the liquid, and of ducts, which pour it on the surface of the body. These ducts are arranged spirally, and open very obliquely under the scale of the epidermis. To this apparatus they applied the epithet "diapnogenous:" and called the ducts "sudoriferous or hidrophorous."2 Each sudoriparous gland consists of a coil or excretory duct surrounded by bloodvessels, and imbedded in fat vesicles. Thence the duct passes in the manner represented in the mar- ginal figure, towards the surface, and opens on the epidermis by an oblique valve-like aperture. The excretory duct is lined by epithelium, which is a prolongation of the epidermis. These glands are numerously distributed: but especially so in the palms of the hand, and soles of the foot. In the former situation they amount, according to Professor Krause,3 to 2736 in every square inch; and in the latter, to 2685. Mr. E. Wilson4 counted the per- spiratory pores on the palm of the hand, and found 3528 in a square inch; and each of these pores being the aperture of a little tube of about a quarter of an inch long, it follows, that in a square inch of skin, on the palm of the hand, there exists a length of tube equal to 882 inches, or 73J feet. To obtain an estimate of the length of tube of the perspiratory system of the whole surface ]&£nt£^£i'&Sst«£ of the body, he thinks that 2800 might be globules of fat. its duct is seen . i i. . p ,, -, W passing to the surface. Magnified taken as a fair average ot the number ot pores 40diameters. (ToddandBowman.) Vertical Section of the Sole. a. Cuticle ; the deep layers (rete mucosum) more coloured than the upper, and their particles rounded ; the superficial layers more and more scaly, b. Papillary struc- ture, e. Cutis, d. Sweat-gland, 1 Art. Haut, in Wagner's Handworterbuch der Physiologie, 7te Lieferung, s. 108 2 Op. cit, s. 131. 3 Breschet, Nouvelles Recherches sur la Structure de la Peau, Paris, 1835. * A Practical Treatise on Healthy Skin, p. 42, Lond, 1S45. 286 SECRETION. in the square inch ; and 700, consequently, of the number of inches in length. " Now the number of square inches of surface in a man of ordinary height and bulk is 2500 ; the number of pores, therefore, 7,000,000, and the number of inches of perspiratory tube, 1,750,000; that is, 145,833 feet or 48,600 yards, or nearly 28 miles!" The marginal figure (Fig. 329) exhibits the transpiratory apparatus magnified. Numerous experiments have been instituted for the purpose of dis- covering the quantity of transpiration in a given time. Of these, the earliest were by Sanctorius,—for which he is more celebrated than for any of his other labours,—after whom the cutaneous transpiration was called Perspirabile Sanctorianum.1 For thirty years, this indefatigable expe- rimentalist weighed daily, with the greatest care, his solid and liquid ingesta and egesta, and his body, with the view of deducing the loss sustained by the cutaneous and pulmonary exhalations. He found, that every twenty-four hours his body returned to the same weight, and that he lost the whole of the ingesta ;—five-eighths by transpira- tion, and three-eighths by the ordinary excretions. For eight pounds of ingesta, there were only three pounds of sensible egesta, which con- sisted of forty-four ounces of urine, and four of faeces. It is lamenta- ble to reflect, that so much time was occupied in the attainment of such insignificant results. The self-devotion of Sanctorius gave occasion, however, to the institution of numerous experiments of the same kind; as well as to discover the variations in the exhalation, according to age, climate, &c. The results of these have been collected by Haller,2 but they afford little instruction ; especially as they were directed to the transpiration in general, without affording any data from which to cal- culate the proportion exhaled from the lungs compared with that con- stantly given off by the cutaneous surface. Rye,3 who dwelt in Cork, lat. 51° 54', found, in the three winter months—December, January, and February—that the quantity of urine was 3937 ounces; of perspi- ration, 4797 ;—in the spring months—March, April, and May—the urine amounted to 3558; the perspiration to 5405 ; in the summer months—June, July, and August—the former amounted to 3352 ; the latter to 5719; and in the three autumnal months—September, Octo- ber, and November—the quantity of urine was 3369 ; of perspiration 4471. The daily average estimate in ounces was as follows :— Urine. Perspiration. Winter,......42-^ 53 Spring, ..... 40 60 Summer, ...... 37 63 Autumn, ..... 37 50 thus making the average daily excretion of urine, throughout the year, to be a little more than 39 ounces ; and of the transpiration, 56 ounces. Keill,4 on the other hand, makes the average daily perspiration, 31 1 Ars Sanctorii de Statica Medicina, cum Comment. Martini Lister, Lugd. Bat, 1711. 2 Elem. Physiol., xii. 2, 10. s Rogers on Epidem. Diseases, Appendix, Dub!, 1734. * Tentamina Medico-Phys.—Appendix, Lond, 1718. TRANSPIRATORY. 287 ounces ; that of the urine 38 ; the weight of the fasces being 5 ounces, and of the solid and liquid ingesta, 75. His experiments were made at Northampton, England, lat. 52° 11'. Bryan Robinson1 found, as the result of his observations in Ireland, that the ratio of the perspiration to urine was, in summer, 5 to 3 ; in winter, 2 to 3; whilst in April, May, October, November and December, they were nearly equal. In youth, the ratio of the perspiration to urine was 1340 to 1000 ; in the aged, 967 to 1000. Hartmann, when the solid and liquid ingesta amounted to 80 ounces, found the urine discharged 28 ounces; the faeces, 6 or 7 ounces; and the perspirable matter, 45 or 46 ounces. De Gorter,2 in Holland, when the ingesta were 91 ounces, found the perspiration amount to 49 ounces ; the urine to 36 ; and the fasces to 8. Dodart3 asserts, that in France, the ratio of the perspiration to the faeces is as 7 to 1 ; and to the whole egesta 15 to 12 or 10. The average perspiration in the twenty-four hours, he estimates at 33 ounces and two drachms ; and Sauvages, in the south of France, found, that when the ingesta were 60 ounces in the day, the transpiration amounted to 33 ounces ; the urine to 22; and the fasces to 5. But most of these estimates were obtained in the cooler climates,—the " regiones boreales,"—as Haller4 has, not very happily, termed them. According to Lining,5 whose experiments were made in South Caro- lina, lat. 32° 47', the perspiration exceeded the urine in the warm months; but in the cold, the latter had the preponderance. The fol- lowing table, quoted by Haller, gives the average daily proportion of urine and perspiration, for each month of the year, in ounces. December, January, February, March, April, May, June, July, August, September, October, November, Urine. Perspiration 70-81 42-55 72-43 39-97 77-86 37-45 70-59 43-23 5917 47-72 56-15 5811 52-90 71-39 43-77 86-41 55-41 70-91 40-60 77-09 47-67 40-78 63-16 4097 After the period at which Haller wrote, no experiments of any mo- ment were adopted for appreciating the transpiration. Whenever trials were instituted, the exhalation from both the skin and lungs was included in the result, and no satisfactory means were adopted for separating them, until MM. Lavoisier and Seguin6 made their cele- brated experiments. M. Se'guin enclosed himself in a bag of gummed taffeta, which was tied above the head, and had an aperture the edges of which were fixed around the mouth by a mixture of turpentine and pitch. By means of this arrangement, the pulmonary transpiration 1 Dissertation on the Food and Discharges of Human Bodies, Dublin, 1748. 2 De Perspiratione Insensibili, Lugd. Bat, 1736. 3 Memoir, de l'Acad. des Sciences, ii. 276. 4 Op. cit. 6 Philos. Trailer, lor 1743 and 1745. 6 Memoir, de l'Acadein. des Sciences de Paris, Paris, 1777 and 1790. 288 SECRETION. alone escaped into the air. To estimate its quantity, it was merely necessary for M. Se'guin to weigh himself in the sac by a very delicate balance, at the commencement and termination of the experiment. By repeating it out of the sac, he determined the total quantity of transpired fluid; so that by deducting from this the quantity of fluid exhaled from the lungs, he obtained the amount of cutaneous transpira- tion. He, moreover, kept an account of the food which he took; of the solid and liquid egesta; and, as far as he was able, of every circum- stance that could influence the transpiration. The results—as applicable to Paris, at which MM. Lavoisier and Seguin arrived, by a series of well-devised and well-conducted experi- ments—were the following -.—First. Whatever may be the quantity of food taken, or the variations in the state of the atmosphere, the same individual, after having increased in weight by the whole quantity of nourishment taken, returns daily, after the lapse of twenty-four hours, to nearly the same weight as the day before;—provided he is in good health: his digestion perfect; not fattening nor growing; and avoids all kind of excess. Secondly. If, when all other circumstances are identical, the amount of food varies; or if—the amount of food being the same—the effects of transpiration differ, the quantity of the excre- ments augments or diminishes, so that every day at the same hour, we return nearly to the same weight; proving, that when digestion goes on well, the causes, that concur in the loss or excretion of the food taken in, afford each other mutual assistance,—in the state of health one charging itself with what the other is unable to accomplish. Thirdly. Defective digestion is one of the most direct causes of dimi- nution of transpiration. Fourthly. When digestion goes on well, and the other causes are equal, the quantity of food has but little effect on the transpiration. M. Se'guin affirms, that he has very frequently taken at dinner two pounds and a half of solid and liquid food; and at other times four pounds; yet the results in the two cases differed but little,—provided only, the quantity of fluid did not vary materially in the two cases. Fifthly. Immediately after dinner, the transpiration is at its minimum. Sixthly. When all other circumstances are equal, the loss of weight induced by insensible transpiration is at its maxi- mum during digestion. The increase of transpiration during digestion compared with the loss sustained when fasting, is, on an average, 2T35 grains per minute. Seventhly. When circumstances are most favour- able the greatest loss of weight caused by insensible transpiration was, according to their observations, 32 grains per minute; conse- quently 3 ounces, 2 drachms and 48 grains poids de marc, per hour; and 5 pounds in twenty-four hours, under the calculation, that the loss is alike at all hours of the day, which is not, however, the tact. Eighthly. When all the accessory circumstances are least favourable, provided only that digestion is properly accomplished, the smallest loss of weight is 11 grains per minute; consequently, 1 ounce, 1 drachm and 12 grains per hour; and 1 pound, 11 ounces and 4 drachms in the twenty-four hours. Ninthly. Immediately after eating, the loss ot weight caused by the insensible perspiration is 10£ grains per minute during the time at which all the extraneous causes are most unfavour- TRANSPIRATORY. 289 able to transpiration; and 19T-ff grains per minute when these causes are most favourable, and the internal causes are alike. " These differ- ences," says M. Se'guin, "in the transpiration after a meal, according as the causes influencing it are more or less favourable, are not in the same ratio with the differences observed at any other time when the other circumstances are equal; but we know not how to account for the phenomenon." Tenthly. The cutaneous transpiration is immedi- ately dependent both on the solvent virtue of the circumambient air, and the power possessed by the exhalants of conveying the perspirable fluid as far as the surface of the skin. Eleventhly. From the average of all the experiments it seems, that the loss of weight caused by the insensible transpiration is 18 grains per minute; and that, of these 18 grains, 11, on the average, belong to the cutaneous transpiration, 7 to the pulmonary. Twelfthly. The pulmonary transpiration, compared with the volume of the lungs, is much more considerable than the cuta- neous, compared with that of the surface of the skin. Thirteenthly. When all other circumstances are equal, the pulmonary transpiration is nearly the same before and immediately after a meal; and if, on an average, it is 17£ grains per minute before dinner, it is 17T7s grains after dinner. Lastly. All intrinsic circumstances being equal, the weight of the solid excrements is least during winter. Although these results are probably fairly deduced from the experi- ments; and the experiments themselves almost as well conceived as the subject admits of, we cannot regard the estimates as more than approxi- mations. Independently of the fact, that the envelope of taffeta must necessarily have retarded the exhalation, by shutting off the air, and causing more to pass off by pulmonary transpiration, the perspiration must incessantly vary, according to circumstances within and without the system: some individuals, too, perspire more readily than others; and the amount exhaled is dependent, as we have seen, upon climate and season,—and likewise upon the quantity of fluid received into the digestive organs. From all these and other causes, Bichat is led to observe, that the endeavour to determine the quantity of the cutaneous transpiration is as vain as to endeavour to specify what quantity of water is evaporated every hour on a fire, the intensity of which is vary- ing every instant. To attempt, however, the solution of the problem, experiments were undertaken by Cruikshank,1 and by Abernethy. Their plan consisted in confining the hand, for an hour, in an air-tight glass jar, and collecting the transpired moisture. Mr. Abernethy, having weighed the fluid collected in the glass, multiplied its quantity by 38 J, the number of times he conceived the surface of the hand and wrist to be contained in the whole cutaneous surface. This gave 2J pounds, as the amount exhaled from the skin in the twenty-four hours, on the sup- position, that the whole surface perspires to an equal extent. These experiments have been repeated by Dr. William Wood,2 of Newport, England, with some modifications. He pasted around the mouth of a jar one extremity of a bladder the ends of which were cut away, and 1 Experiments on the Insensible Perspiration, p. 5, Lond, 1795. 2 An Essay on the Structure and Functions of the Skin, &c, Edinb, 1832. VOL. II.—19 290 SECRETION. the hand being passed through the bladder into the jar, the other extremity was bound to the wrist with a ligature, not so tight, however, as to interfere, in any degree, with the circulation. The exact weight of the jar and bladder had previously been ascertained. During the experiment, cold water was applied to the outer surface of the jar, to cause the deposition of the fluid accumulated within. The result of his experiments was as follows:— cp. Time of day. Temperature in Pulse per Fluid collected in apartment. minute. an hour. 1 Noon. 66° 84 32 grs. 2 Do. 66 78 32 3 Do. 66 78 26 4 Do. 61 84 32 5 9 P.M. 62 80 26 6 Do. 62 75 23 Mean 63-8 79-8 28-5 The next thing was to estimate the proportion, which the surface of the hand and wrist bears to the whole surface of the body. Mr. Aber- nethy reckoned it as 1 to 38\, and Mr. Cruikshank as 1 to 60! Dr. Wood does not adopt the estimate of either. He thinks, however, that the estimate of the former as regards the surface of the hand and wrist, which he makes seventy square inches, is near the truth, having found it correspond both with his own measurements and the reports of glovers. Mr. Abernethy's estimate of the superficial area of the whole body— 2700 square inches, or above eighteen square feet, he regards as too high. Perhaps the most general opinion is, that it amounts to sixteen square feet, or 2304 square inches; but Haller did not think it exceeded thirteen square feet, or 2160 square inches. Dr. Wood adopts the former of these estimates, and is disposed to think, that the proportion of the surface of the hand and fingers, taken to the extremity of the bone of the arm, does not fall short of 1 to 2, which if we adopt the ratio of the quantity, he found transpired per hour, gives, for the whole body, about forty-five ounces, or nearly four pounds troy in the twenty- four hours. This is considerably above the result of the experiments of either Se'guin or Abernethy; yet, on reviewing the experiments, Dr. Wood is not disposed to think it far from the truth. Upwards of fifty years ago, Dr. Dalton, of Manchester, undertook a series of experiments similar to those of Sanctorius, Keill, Hartmann and Dodart.1 The first he made upon himself in the month of March, for fourteen days in succession. The aggregate of the articles of food consumed in this time was as follows,—bread, 163 ounces avoirdupois; oaten cake, 79 ounces; oatmeal, 12 ounces; butcher's meat 54J ounces; potatoes, 130 ounces; pastry, 55 ounces; cheese, 32 ounces;—Total of solid food, 525J ounces; averaging 38 ounces daily;—of milk, 435| ounces; beer, 230 ounces; tea, 76 ounces;—Total of liquid food, 741J, averaging 53 ounces of fluid daily. The daily consumption was, con- sequently, 91 ounces; or nearly six pounds. During the same period, the total quantity of urine passed was 680 ounces; of faeces, 68 ounces— the daily average being,—of urine, 48J ounces; of fasces, 5 ounces: 1 Manchester Memoirs, vol. v. TRANSPIRATORY. 291 making 53J ounces. If we subtract these egesta from the ingesta, there will remain 37|- ounces, which must have been exhaled by the cutaneous and pulmonary transpirations, on the supposition that the weight of the body remained stationary. To test the influence of dif- ference of seasons, Dr. Dalton resumed his investigations in the month of June of the same year. The results were as might have been anti- cipated,—a less consumption of solids and a greater of fluids; a dimi- nution in the evacuations and an increase in the insensible perspiration. The average of solids consumed per day was 34 ounces; of fluids, 56 ounces ;—total, 90 ounces; the daily average of the evacuations—urine, 42 ounces; fasces, 4|-,—leaving a balance of nearly 44 ounces for the daily loss by perspiration, or one-sixth more than during the cooler season. He next varied the process, with the view of obtaining the quantity of perspiration, and the circumstances attendant upon it more directly. He procured a weighing beam, that would turn with one ounce. Dividing the day into periods of four hours in the forenoon, four or five in the afternoon, and nine in the night—or from ten o'clock at night to seven in the morning—he endeavoured to findthe perspiration cor- responding to these periods respectively. He weighed himself directly after breakfast, and again before dinner, observing neither to take, nor part, with, any thing in the interval, except what was lost by perspira- tion. The difference in weight indicated such loss. The same course was followed in the afternoon and night. This train of experiments was continued for three weeks in November. The mean hourly losses by transpiration were;—in the morning, 1*8 ounce avoirdupois;—after- noon, 1*67 ounce; night, 1*5. During twelve days of this period he kept an account of urine corresponding in time with perspiration. The ratio was as 46 to 33. From the whole of his investigations on this subject, Dr. Dalton concludes;—that of six pounds of aliment taken in the day, there appears to be nearly one pound of carbon and nitro- gen together; the remaining five pounds are chiefly water, which seems necessary as a vehicle to introduce the other two elements into the cir- culation, and also to supply the lungs and membranes with moisture;— that very nearly the whole quantity of food enters the circulation, for the fasces constitute only Jgth part, and of these a part—bile—must have been secreted;—that one great portion is thrown off by the kid- neys, namely, about half of the whole weight taken, but probably more or less according to climate, season, &c.;—that another great portion is thrown off by means of insensible perspiration, which may be sub- divided into two parts, one of which passes off by the skin—amounting to one-sixth part, and the other five-sixths are discharged from the lungs in the form of carbonic acid, and water or aqueous vapor. Since the time of Lavoisier and Se'guin, M. Edwards1 instituted expe- riments with the view of illustrating the effect produced upon cutaneous transpiration by various circumstances to which the body is subjected. His first trials were made on cold-blooded animals, in which the cuta- neous transpiration can be readily separated from the pulmonary, owing 1 Sur lTnfluencedes Agens Physiques, Paris, 1822 ; or Hodgkin's and Fisher's translation Lond, 1832. 292 SECRETION. to the length of time they are capable of living without respiring. All that was necessary was to weigh the animal before and after the expe- riment, and to make allowance for the ingesta and egesta. In this way he discovered, that the body loses successively less and less in equal portions of time;—that the transpiration proceeds more rapidly in dry than in moist air; in the extreme states nearly in the proportion of 10 to 1;—that temperature has, also, considerable influence,—the transpi- ration at 68° of Fahrenheit, being twice as much; and at 104°, seven times as much as at 32°. He likewise found, that frogs transpire, whilst they are in water, as is shown by the diminution they experience while immersed in that fluid, and by the appearance of the water itself, which becomes perceptibly impregnated with the matter excreted by the skin. In warm-blooded animals, as in the cold-blooded, the transpiration became less and less in proportion to the quantity of fluid evaporated from the body; and he observed the same difference between the effects of moist and dry air, and between a high and a low tempera- ture. The effects of these agents were essentially the same on man as on animals. He found, that the transpiration was more copious during the early than the latter part of the day ; and after taking food ; and, on the whole, it appeared to be increased during sleep. Whenever the fluid, which constitutes the insensible transpiration, does not evaporate, owing to causes referred to at the commencement of this article, it appears on the surface in the form of sensible perspi- ration or sweat. It has been supposed by some physiologists, that the insensible and sensible perspirations are two distinct functions. Such appears to be the opinion of Haller, and of M. Edwards, who regards the former as a physical evaporation,—the latter as a vital transudation or secretion; but no sufficient reason seems to exist, why we should not regard them as different degrees of the same function. Very recently, indeed, it has been maintained by Mr. Rainey,1 as the results of careful histological inquiry, that there are no glands but the sudoriparous on the integument of the hands and feet, and hence it is inferred by him, that these glands furnish the oily or sebaceous matter with which these parts are anointed; and in place of regarding the sweat as an increase of the insensible perspiration, he esteems it an increased secretion of glands, which, in their less active state, secrete sebaceous matter, and, in their more active, the fluid of transpiration. It has been affirmed, that the sweat is generally less charged with carbonic acid than the vapour of transpiration ; and that it is richer in salts, which are deposited on the skin, and are sometimes seen in the form of white flocculi; but our knowledge on this matter is vague. There can be no doubt, however, that a large portion of the transpiration —pulmonary and cutaneous—consists of the fluid of evaporation,—the smaller portion, which is the true matter of perspiration, being the secre- tion of sudoriferous glands. To establish the amount of the fluids of eva- poration and secretion, Krause2 endeavoured both to number and measure these glands. On an average, he says, in each superficial square inch of > Proceedings of the Royal Medical and Chirurgical Society, June 22, 1849, and London Med. Gaz., July 20, 1849. 2 Art. Haut, in Wagner's Handworterbuch der Physiologie, 7te Lieferung, s. 108, Braun- schweig, 1844. TRANSPIRATORY. 293 the body there are 1000 orifices and glands of gth of a line in diame- ter ; the greatest and least numbers in this space being, in the palm, 2736; in the sole, 2685 ; in the cheek, 548; in the neck, back, and nates, 417. The whole number, excluding the axilla, in which they are peculiarly large and thickset, is estimated at about 2,381,248. Adopting these numbers, and supposing each gland to be occupied by a column of fluid presenting at the orifice a hemispherical surface ^'gth of a line in diameter—the size, which Krause found by admeasurement of some drops in a warm and moist, but not sweating skin—the whole of the glands would present an evaporating surface of 7896 square inches. Krause, therefore, considers it probable—according to ascer- tained laws of evaporation, and experiments instituted for the purpose— that only a portion of the fluid discharged by cutaneous transpiration is furnished by these glands; inasmuch as there could not be more than 3365 grains evaporated in the twenty-four hours from such a surface under favourable circumstances, whereas the experiments of MM. La- voisier and Se'guin—as has been shown—gave an average of 11 grains per minute, or 15,840 grains in the twenty-four hours,—leaving 12,475 grains to be accounted for probably by evaporation. But these are, of course, mere approximations to the truth. Careful examinations have been made by Valentin1 on his own person, in regard to the amount of both cutaneous and pulmonary transpira- tion. Taking three days of ordinary life in September, weighing himself naked fifteen times a day, and all his ingesta and sensible ex- cretions, he found the averages of three days to be:—nutritive matter taken, 45325*5 grains; excrement, 2956*3 grains; urine, 22439*3 grains; perspiration, 19327*4 grains. The ingesta being as 1, the excrement was *065, the urine, *503; and the perspiration, *422. There were differences, however, in the days;—in the first, the proportion of the ingesta to the excretions was as 1*097 to 1; in the second, as 1*028 to 1; in the third, as 1 to 1*090. The hourly amount of tran- spiration was occasionally 4J times as much as at others; the greatest difference being caused by whatever excited sweating, or perceptible moisture of the skin. For instance, on the same day, the hourly amount, after taking two cups of coffee, and during gentle perspiration, was 1213*65 grains; in the forenoon, in pretty active exercise and sweating, 1402*75 grains; and in the evening, during copious sweating from exercise, 2056*85 grains; but whilst writing quietly in the fore- noon of the same day it fell to 858*7 grains, and three or four hours after dinner, it was only 509*95 grains. Nothing influenced the transpiration so much as rest and bodily exertion. Even when the latter did not produce manifest sweating, the effect was considerable. After eating, also, transpiration was generally increased, and its mini- mum was observed during fasting, and whilst at rest in a cool tempera- ture. During the night and in sleep, the transpiration was diminished; but not more than in rest during the day. Mental exertion had no obvious influence. Particular parts of the body perspire more freely, and sweat more 1 Lehrbuch der Physiologie des Menschen, B. i. s. 582; and Krause, op. cit, s. 140. 294 SECRETION. readily than others. The forehead, armpits, groins, hands, feet, &c, exhibit evidences of this most frequently; some of them perhaps, owing to the fluid, when exhaled, not evaporating readily,—the contact of air being impeded. It is presumed, likewise, that the sweat has not every 'where the same composition. Its odour certainly varies in- different parts. In the armpits and feet it is generally considered to be more acid; but M. Donnd1 affirms, that there, as well as around the genital organs and between the toes, and wherever it is most odorous, it is alkaline, restoring the blue of litmus paper which had been previously reddened by an acid. He properly suggests, however, that this may be owing to admixture with the secretion of the follicles. In the vio- lent sweats that accompany acute rheumatism, its acidity always attracts attention; and in the groins, its odour is strong and rank. It differs greatly, too, in individuals, and especially in races. In the red-haired, it is said to be unusually strong; and in the negro, during the heat of summer, alliaceous and overwhelming. By cleanliness, the red-haired can obviate the unpleasant effect in a great measure by pre- venting undue accumulation in the axilla, groins, &c.; but no ablution can remove the odour of the negro, although cleanliness detracts from its intensity. Each race appears to have its characteristic odour; and, according to Humboldt, the Peruvian Indian, whose smell is highly developed by education, can distinguish the European, American Indian, and negro, in the middle of the night, by this sense alone. Certain anatomists and physiologists—as has been seen (p. 282)—have doubted, whether this special odorous matter of the skin belongs properly to the perspiration, and have presumed it to be the product of special organs. This is, however, by no means established; and the experiments of M. The'nard, as well as the facts just mentioned, would rather seem to show, that the matter of sweat itself has, within it, the peculiar odour. Simon,2 too, affirms, that on evaporating his own sweat, the peculiar smell of the axilla was observed, and an odour of ammonia was de- veloped: and allusion has been made to the recent view of Mr. Rainey, that the same glands may in one condition of activity furnish the mat- ter of transpiration, and in another the ordinary secretion, of sebaceous follicles. The fact of the dog tracing its master to an immense dis- tance, and discovering him in a crowd, has induced a belief, that the scent may be distinct from the sweat; but the supposition is not neces- sary, if we admit the matter of perspiration to be itself odorous. There can be no doubt, however, that certain odorous secretions are formed by cutaneous follicles. The singular fact has been stated, that by mixing fresh blood with one-third or one-half its bulk of strong sulphuric acid, and stirring the mixture with a glass rod, a peculiar odour is evolved, which differs in the blood of man and animals, and in the blood of the two sexes. This odour resembles that of the cutaneous perspiration of the animal. "They have hereby pretended to determine," says a recent medico- legal writer,3 " whether any given specimen of blood had belonged to 1 Cours de Microscopic p. 207, Paris, 1844. 2 Animal Chemistry, Sydenham Society edition, ii. 102, Lond, 1846. 3 Taylor, Medical Jurisprudence, Amer. edit, by Dr. Griffith, p. 275, Philad, 1845. TRANSPIRATORY. 295 a man, a woman, a horse, sheep, or fish. Others pretend, that they have been able to identify the blood of frogs and fleas!" The first person who directed {attention to this point was M. Barruel;1 who was of opinion that a knowledge of the fact might be important in a medico- legal relation, with the view of determining the source of spots of blood on linen for example; but even admitting the fact, as stated by MM. Barruel, Devergie,2 and others, it is obvious, that so much must depend upon the power of olfactory discrimination of the observer, that the evidence in any doubtful case could scarcely be deserving of much weight. Mr. Taylor, indeed, affirms, that there is probably not one individual among a thousand, whose sense of smell could be so acute as to allow him to state, with undeniable certainty, from what animal the unknown blood had really been taken. Besides the causes before referred to, the quantity of perspiration is greatly augmented by running or violent exertion of any kind; espe- cially if the temperature of the air be elevated. Warm fluids favour it greatly; hence their use, alone or combined with sudorifics, when this class of medicines is indicated. M. Magendie3 conceives, that being readily absorbed they are readily exhaled. This may be true; but the perspiration breaks out too rapidly to admit of this explanation. When ice-cold drinks are taken in hot weather, the cutaneous transpiration is instantaneously excited. The effect, consequently, must be produced by the refrigerant influence of the cold medium on the lining membrane of the stomach,—this influence, being propagated, by sympathy, to every part of the capillary system. The same explanation is applica- ble to warm drinks; but the hot exert a sympathetic effect on the skin by virtue of their stimulant action on the mucous membrane. With regard to the uses of the insensible transpiration, it has been supposed to preserve the surface supple, and thus favour the exercise of touch; and also, by undergoing evaporation, to aid in the refrigeration of the body. It is probable, however, that these are secondary uses under ordinary circumstances; and that the great office performed by it is to remove a certain quantity of fluid from the blood: hence it has been properly termed the cutaneous depuration. In this respect, it bears a striking analogy to the urine, which is the only other depura- tory secretion, with the exception of the pulmonary transpiration, which we shall find essentially resembles the cutaneous. Being depuratory, it has been conceived, that any interruption to transpiration must be followed by serious consequences; accordingly most diseases have, from time to time, been ascribed to this cause. There is, however, so great a compensation existing between the urinary and cutaneous de- purations, that if one be augmented, the other is decreased,—and con- versely. Besides, it is well known, that disease is more apt to be induced by partial and irregular application of cold than by frigorific influences of a more general character. The Russian vapour-bath ex- emplifies this; the bather frequently passing with impunity from a tem- perature of 130° into cold water. The morbific effect—in these cases 1 Annales d'Hygiene, i. 267. 2 Medecine Legale, 2de edit., iii. 761, Paris, 1840. 3 Precis de Physiologie, 2de edit, ii. 455. 296 SECRETION. of fancied check given to perspiration—is derangement of the apparatus engaged in the important functions of nutrition, calorification, and secretion, and the extension of this derangement* to every part of the organism. As the sensible transpiration or sweat is probably only the insensible perspiration in increased quantity, with the addition of saline, and other matters that are not evaporable, its uses demand no special notice. 2. The Lachrymal Secretion. The lachrymal apparatus, being a part of that accessory to vision, was described under another head (vol. i. p. 283). The tears, as we meet with them, are not simply the secretion of the lachrymal gland, but of the conjunctiva, and occasionally of the carun- cula lachrymalis and follicles of Meibomius. It has been presumed, too, by several modern ophthalmologists—by Wardrop, Rosas, Jiingken, for example—that a portion of them—Rognetta1 says the principal portion—consists of the aqueous humour, which passes through the cornea by endosmose; but although such endosmose may exist, it can assuredly furnish but little towards the composition of the tears.2 They have a saline taste; mix freely with water; and, owing to the presence of free soda, communicate a green tint to blue infusion of violets. Their chief salts are chloride of sodium, and phosphate of soda. Ac- cording to M. Fourcroy and Vauquelin,3 the animal matter of the tears is mucus; but it is presumed, by some, to be albumen or an analogous principle—dacryolin. They found them to consist of water, mucus, chloride of sodium, soda, phosphate of lime and phosphate of soda. The following is the result of analyses by Professor Frerichs:4— I. IT. Water,.........99*06 98-70 Solid constituents,.......094 130 Epithelium,........014 032 Albumen,........O-08 0-10 Chloride of Sodium—Alkaline Phosphates, Earthy Phos- phates, Mucus, Fat,......072 088 When tears are examined with the microscope, globules of mucus, and debris of the epidermis are seen in them. This secretion is more influenced by the emotions than any other; and hence it is concerned hi the expressions of lively joy or sorrow, especially the latter. 3. The Salivary Secretion. The salivary apparatus has likewise engaged attention elsewhere. It consists of a parotid gland on each side, situate in front of the ear, and 1 Traite Philosophique et Clinique d'Ophthalmologie, p. 705, Paris, 1844. a Frerichs, Art. Thranensecretion in Wagner's Handworterbuch der Physiologie, 19te Lieferung, s. 621, Braunschweig, 1848. 3 Journal de Physique, xxxix. 256. 4 Op. cit, s. 618. SALIVARY. 297 330. behind the neck and ramus of the jaw; a submaxillary, beneath the body of the bone; a sublingual, situate immediately beneath the tongue;—and an intralingual or lingual, seated at the inferior surface of the tongue; —the parotids and submaxillary glands having each but one excre- tory duct,—the sublingual several.1 The structure of the salivary glands in man greatly resembles that of the mammary glands. The marginal figure exhibits their structure in the sheep. All these glands pour their respective fluids into the mouth, where it collects, and becomes mixed with the exhalation of the mucous membrane of the mouth, and the secretion from its follicles. It is this mixed fluid that has generally been analyzed by the chemist. When collected without the action of sucking, it is of a specific gravity varyingfrom 1*004to 1*009; translucent; slightly opaque; very frothy; and ultimately deposits a nebulous sediment. Even with the purest saliva there are always found mixed a few epithelial cells, de- rived from the mucous lining of the mouth, or from the excretory ducts of the secreting glands. It usually Contains free alkali: in rare cases, during meals, Professor Schultz,2 of Berlin, found it acid; and during fasting, it is occasionally neutral. Mitscher- lich,3 indeed, affirms, that it is acid whilst fasting; but becomes alkaline during eating,—the alkaline charac- ter disappearing, at times, with the first mouthful of food. The average amount of the secretion in the twenty- four hours does not probably exceed four ounces. According to Berze- lius,4 its constituents are—water, 992*2; peculiar animal matter, 2*9; mucus, 1*4; chlorides of potassium and sodium, 1*7; lactate of soda, and animal matter, 0*9; soda, 0*2. Drs. Bostock5 and Thomas Thomson6 think that the " mucus" of Berzelius resem- bles coagulated albumen in its pro- perties. In the tartar of the teeth, which seems to be a sediment from the saliva, Berzelius found 79 parts of earthy phosphate; 12*5 of unde- composed mucus; 1 part of a matter peculiar to the saliva, and 7*8 of an animal matter soluble in chlorohydric acid. This animal matter, ac- cording to the microscopic experiments of M. Raspail,7 is composed of deciduous fragments from the mucous membrane of the cavity of 1 Vol. i. p. 516. 2 Hecker, Wissenschaftliche Annalen, B. ii. H. i. § 32, 1835. 3 Rullier and Raige-Delorme, art. Digestion, Diet de Medecine, 2de £dit, x. 300, Paris, 1835. 4 Medico-Chirurgical Transactions, iii. 242. 6 Physiol, ed. cit, p. 487. 6 System of Chemistry, vol. iv. ' Nouveau Systeme de Chimie Organique, p. 454. Lobules of the Parotid Gland, in the Embryo of the Sheep, in a more advanced condi- tion. (Miiller.) 298 SECRETION. 331. Distribution of Capillaries around the follicles of Parotid Gland. the mouth; and he considers, that the saliva is nothing more than an albuminous solution, mixed with different salts, that are capable of modifying more or less its solubility in water, and of shreds or layers of tissue. MM. Leuret and Las- saigne1 analyzed pure saliva, obtained from an individual labouring under salivary fistula, and found it to contain,—water, mucus, traces of albumen, soda, chloride of potassium, chloride of sodium, carbon- ate and phosphate of lime:—and Messrs. Tiedemann and Gmelin2 affirm,—and their analysis agrees pretty closely with that of Van Setten3—that it.has only one or two hundredths of solid matter, which are composed of a peculiar substance, called salivary matter or ptyalin, osmazome, mucus, perhaps albumen, a little fat containing phosphorus, and the insoluble salts—phosphate and carbonate of lime. Besides these, they detected the following soluble salts;—acetate, carbonate, phosphate, sulphate, sulphocyanate of potassa; and chlo- ride of potassium. Treviranus4 thinks the saliva contains a peculiar acid, to which he gives the name Blausaure, probably combined with an alkali; but its chemical properties resemble the sulpho-cyanic acid so greatly, that according to Kastner5 they may be taken for each other. As the result of numerous analyses, Dr. Wright6 gives the fol- lowing constituents of healthy saliva;—water, 988*1; ptyalin, 1*8; fatty acid, *05; chlorides of sodium and potassium, 1*4; albumen with soda, 0*9; phosphate of lime, 0*6; albuminate of soda, *08; lactates of po- tassa and soda, *07 ; sulphocyanide of potassium, *09; soda, *05; mucus with ptyalin, 2*6. Saliva has also been carefully analyzed by Enderlin,7 who concludes that, like the blood, it contains no lactate, carbonate, or acetate; but its alkaline reaction is owing to the tribasic phosphate of soda, which serves also as a solvent of the mucus and protein compounds. The analysis of the ashes obtained from a very large quantity afforded, in 100 parts:— Tribasic phosphate of soda, Chlorides of sodium and potassium, Sulphate of soda, Phosphate of lime, J " magnesia, > " iron, ) 28-122 61-93 2-315 5-509 Still more recently, human saliva has been analyzed by Jacubowitsch8 and found to be composed as follows:— ' Recherehes, &c, sur la Digestion, p. 33. Paris, 1826. 2 Recherehes, &c, sur la Digestion, par Jourdan, Paris, 1827. 3 De Saliva ejusque Vi et Utilitate, Groning, 1837; cited in Brit, and For. Med. Rev, Jan., 1839, p. 236. * Biologie, Band. iv. § 330. s Ficinus, art. Speichel, in Pierer's Anat Physiol. Real Worterbuch, vii. 634, Altenb., 1827. 6 London Lancet, Mar, 1842. 7 Annalen der Chemie und Pharmacie, Marz, 1844. 8 De Saliva, Dissert, inaugur. Med. Univers. Dorpatens; cited by Scherer, in Canstatt und Eisenmann's Jahresbericht iiber die Forstchritte der Biologie im Jahre 1848, Erlang, 1849. SALIVARY. 299 Water, - Fixed residue, • Epithelium, Organic matters, Sulphocyanide of potassium, Salts, ... 999-16 4-84 1-62 1-34 0-06 1-82 The salts consisted of phosphate of soda, 0*94; lime, 0*03; magnesia, 0*01; chlorides of potassium and sodium, 0*84. Messrs. Tiedemann and Gmelin, and M. Donne',1 found the saliva in- variably alkaline, when the functions of the stomach were well executed. The last gentleman considered acidity of the stomach a diagnostic symp- tom of gastritis; and Dr. Robt. Thomson2 observed the acid reaction in all cases of inflammation of the mucous and serous membranes. With the view of testing these points, Mr. Laycock3 instituted numerous ex- periments, and tabulated the results of no less than 567 observations. His deductions do not accord with those of M. Donne*. They are as follows:—1. The saliva may be acid without apparent disease of the stomach, and when the person is in good health. 2. It is alkaline during different degrees of gastric derangement, as indicated by the tongue. 3. It may be alkaline, acid and neutral, when the gastric phenomena are the same; and, consequently, acidity of the saliva is not a diagnostic mark of gastric derangement; and, lastly—in general it is alkaline in the morning, and acid in the evening. In a more recent work M. Donne4 accounts for the varying testimony of different observers in regard to the chemical reaction of the saliva, by the greater or less proportion of the mucus of the mouth contained in the specimens sub- jected to examination. In the normal state, he affirms, it is alkaline; but the mucus secreted by the mucous membrane of the mouth being acid, the mixed fluid, to which the name saliva is given, must necessarily vary according to the proportion of each. When saliva is examined by the microscope, it presents, besides a considerable number of lamellas of epithelium, globules in variable quantity, which, according to M. Mandl,5 proceed partly from the muciparous glands of the mouth, and partly from the salivary glands. They cannot, however, be distinguished from each other. As the salivary secretion forms a part in the processes preparatory to stomachal digestion, its uses have been detailed in the first volume of this work, to which the reader is referred. The view of MM. Bernard and Barreswil, and of Mialhe, that the saliva contains an active prin- ciple, analogous in its physical and chemical characters to diastase, as well as its action on amylaceous substances, is there described. A soft, whitish or yellowish matter, of greater or less thickness, is constantly deposited on the teeth, which, unless attention is paid, ac- cumulates, and sometimes adheres to them with great force, constituting hard and dry concretions, known—as already remarked—under the 1 Archives Generates, Mai & Juin, 1835; and Histoire Physiologique et Pathologique de la Salive, Paris, 1836. 2 Records of General Science, Dec, 1836. 3 Lond. Med. Gazette, Oct. 7, 1S37. See, for a detailed account of the saliva, Dr. S. Wright, op. cit. 4 Cours de Microscopie, p. 208, Paris, 1844. 6 Manuel d'Anatomie Generate, p. 488, Paris, 1843. 300 SECRETION. name of tartar or tartar of the teeth. Different views have existed in regard to its origin. Some have supposed it to be a secretion, others a deposition from the saliva, which is the most probable opinion; and others that it is an exhalation from the capillary vessels, to which the mucous membrane of diseased gums is liable. It has been affirmed by M. Mandl,1 to be a collection of calcareous skeletons of infusoria, ag- glutinated by means of dried mucus. 4. The Pancreatic Secretion. The pancreas or sweetbread, (Fig. 332, h, t, i,) secretes a juice or hu- mour called succus pancreaticus, pancreatic juice. Its texture resembles that of the salivary Fig. 332. glands; and hence it has been called by some the abdominal salivary gland. It is situate transverse- ly in the abdomen; behind the stomach; towards the conca- vity of the duode- num; is about six inches in length, and between three and four ounces in weight. From the results of six exami- nations, Dr. Gross2 In this figure, which is altered from Tiedemann, the Liver and Sto- gives the following mach are turned up to show the Duodenum, the Pancreas, and ao ;±.a -„»„„ .ro'rrV,+ the Spleen. as ns mean# weigiil I. The under surface of the liver, g. Gall-bladder. /. The common an . dimensions : — bile-duct, formed by the union of a duct from the gall-bladder, called Weight 2A- OUnCCSJ the cystic duct, and of the hepatic duct coming from the liver, o. The , ", *r V. . cardiac end of the stomach, where the oesophagus enters, s. Under length, | incneS J surface of the stomach, p. Pyloric end of stomach, d. Duode- TU1,/.„JtVi ot +I10 bnrlv num. h. Head of pancreas; t, tail : and i, body of that gland. The Dieaam ai lUt) UUUV substance of the pancreas is removed in front, to show the pancreatic arid Solenic extre- duct (e) and its branches, r. The spleen, v. The hilus, at which the . " .. bloodvessels- enter, c. Crura of diaphragm, n. Superior mesenteric mitV, 16i lines J artery, a. Aorta. breadth at the neck, 12 lines; at the head, 2 inches and 3 lines; thickness at the body, neck, and splenic extremity, 4 lines; thickness at the head, 8 lines. M. Be'court found the average length of thirty-two to be 8 inches; and the weight between three and four ounces.3 It is of a reddish-white colour, and firm consistence. Its excretory ducts terminate in one,— called duct of Wirsung,—which opens into the duodenum, at times separately from the ductus communis choledochus, but close to it; at others, confounded with, or opening into, it.4 The amount of fluid secreted by the pancreas does not seem to be 1 Gazette des Hopitaux, 8 Aout, 1843, p. 363. 2 Elements of Pathological Anatomy, ii. 357, Boston, 1839. 3 Recherehes sur le Pancreas, ses Fonctions et ses Alterations Organiques, These, Stras- bourg, 1S30, cited by Mondiere, Archives Generates de Medecine, Mai, 1836. * Magendie, Precis Elementaire, i. 462; and J. P. Mondiere, op. cit. PANCREATIC. 301 considerable. M. Magendie, in his experiments, was struck with the small quantity discharged. Frequently, scarcely a drop issued in half an hour; and, occasionally, a much longer time elapsed. Nor did he find that the flow, according to common opinion, and to probability, was more rapid whilst digestion was going on. It will be readily under- stood, therefore, that it cannot be an easy task to collect it. De Graaf1 affirms, that he succeeded, by introducing into the intestinal end of the excretory duct, a small quill, terminating in a phial fixed under the belly of the animal. M. Magendie2 states, that he tried this plan seve- ral times, but without success; and he believes it to be impracticable. The plan he adopts is to expose the intestinal orifice of the duct; to wipe the surrounding mucous membrane with a fine cloth, and as soon as a drop of the fluid oozes to suck it up by means of a pipette or small glass tube. In this way, he collected a few drops, but never suf- ficient to undertake a satisfactory analysis. Messrs. Tiedemann and Gmelin3 make an incision into the abdomen; draw out the duodenum, and a part of the pancreas; and, opening the excretory duct, insert a tube into it; and a similar plan was adopted successfully on a horse by MM. Leuret and Lassaigne.4 The difficulty experienced in collecting any quantity is a probable cause of some of the discrepancy amongst observers, regarding its sensible and chemical properties. Certain of the older physiologists affirm that it is acidulous and saline; others, that it is alkaline.5 The majority of those of the present day compare it with saliva, and affirm it to be inodorous, insipid, viscid, limpid, and of a bluish-white colour. The latest experimenters by no means accord with each other. According to M. Magendie, it is of a slightly yellow- ish hue, saline taste, devoid of smell, occasionally alkaline, and partly coagulable by heat. MM. Leuret and Lassaigne found that of the horse—of which they obtained three ounces,—to be alkaline, and com- posed of 991 parts of water in 1000; an animal matter, soluble in i alcohol; another, soluble in water; traces of albumen and mucus; free soda; chloride of sodium ; chloride of potassium, and phosphate of lime. In their view, consequently, the pancreatic juice strongly resembles saliva. Messrs. Tiedemann and Gmelin succeeded in obtaining upwards of two drachms of the juice in four hours; and, in 100 parts, found from five to eight of solid parts. These consisted of osmazome; a matter which became red by chlorine; another analogous to casein, and probably associated with salivary matter; much albumen; a little free acid, probably acetic; acetate, phosphate, and sulphate of soda, with a little potassa; chloride of potassium, and carbonate and phosphate of lime:—so that, according to these gentlemen, the pancreatic juice dif- fers from saliva in containing—a little free acid, whilst saliva is alka- line ; much albumen, and matter resembling casein; but little mucus and salivary matter, and no sulpho-cyanate of potassa. In an exami- nation, by M. Blondlot,6 of three or four grammes of fluid, obtained from the duct of a large dog, he found no evidences of albumen, when 1 Tract, de Pancreat., Lugd. Bat., 1761; and Haller, Elem. Physiol., lib. xxii. sect. 8, Bern 1764. 2 I'rev is, &c, ii. 462. 3 Recherehes, &c, i. 41. 4 Recherehes, &c, p. 49. 5 Haller, op. cit; and Seiler, art Pancreas, Pierer's Anat. Physiol. Real Worterb., Band vi. 100, Altenb., 1825. 6 Traite Aualylinue de la Digestion, p. 124, Paris, 1S44. 302 SECRETION. he passed an electric current through it. He, also, holds it to be of the same nature as saliva. The precise use of the pancreatic juice in digestion—as we have previously seen—is not determined. Brunner1 removed almost the whole pancreas from dogs, and tied and cut away portions of the duct; yet they lived apparently as well as ever. The secretion, therefore, cannot be indispensable. Its main uses seem to be to favour the ab- sorption of oleaginous matters.2 5. The Biliary Secretion. The biliary secretion is, also, a digestive fluid, and has been treated of in the appropriate place. The mode, however, in which the process is effected, has not yet been investigated. The apparatus consists of the liver, which accomplishes the formation of the fluid; the hepatic duct—the excretory channel, by which the bile is discharged; the gall- bladder, in which a portion of the bile is retained for a time; the cystic duct—the excretory channel of the gall-bladder; and the ductus com- munis choledochus or eholedoch duet, formed by the union of the he- patic and cystic ducts, which conveys the bile immediately into the duodenum. The liver (Fig. 333) is the largest gland in the body; situate in the abdomen beneath the diaphragm, above the stomach, the arch of the colon, and the duodenum; filling the whole of the right hypochondrium, and more or less of the epigastrium, and fixed in its situation by dupli- catures of the peritoneum, called ligaments of the liver. The weight of the human organ is generally, in the adult, about three or four pounds. Some make the average about five pounds ; but this is a large estimate. Of 60 male livers weighed, Dr. John Reid3 found the average weight to be 52 oz. 12| dr.: and of 45 oz. 3| dr. 25 female, In disease, sometimes Liver in Situ, together with the parts adjoining, in a New- born Infant. 1, 1. Integuments of abdomen turned back. 2,2. Thoracic surface of a section of diaphragm. 3. Anterior face of right lobe of the liver. 4. Left lobe. 5. Suspensory ligament. 6. Round ligament. 7. Point of origin of coronary ligament. 8. Spleen. 9. Section of the stomach. 10. Upper portion of the colon. however, it weighs twenty or twenty- five pounds; and, at other times, not as many ounces. Its shape is irregular, and it is divided into three chief lobes, the right, left, and lobulus Spigelii. Its upper convex surface every where touches the arch of the diaphragm. The lower concave surface corresponds to the sto- mach, colon, and right 1 Experimenta nova circa Pancreas, Amstel., 1683; and J. T. Mondiere, op. cit 2 Vol. i. p. 614. 3 Lond. and Edinb. Monthly Journ. of Med. Sciences, April, 1843, p. 323. BILIARY. 303 kidney. On the latter surface, two fissures are observable,—the one passing from before to behind, and lodging the umbilical vein in the tcetus—called horizontal sulcus or fissure, great fissure or fossa umbili- calis; the other cutting the last at right angles, and running from right to left, by which different nerves and vessels proceed to and from the liver, and called principal fissure, or sulcus transversus. The liver itself is composed of the following anatomical elements: 1. The hepatic artery, a branch of the cceliac which ramifies minutely through the substance of the organ. The minuter branches of this vessel are arranged somewhat like the hairs in a painter's brush, and have hence been called penicilli of the liver. Mr. Kiernan1 believes, that the blood, which enters the liver by the hepatic artery, fulfils three functions:—it nourishes the organ; supplies the excretory ducts with mucus ; and, having fulfilled these objects, becomes venous; enters the branches of the portal veins, and not the radicles of the hepatic, as usually supposed, and contributes to the secretion of bile. 2. The vena porta, which, we have elsewhere seen, is the common trunk of the veins of the digestive organs and spleen. It divides like an artery, its branches accompanying those of the hepatic artery. Where it lies in the transverse fissure, it is of great size, and has hence been called sinus vense portse. The possession of two vascu- lar systems, containing blood, is peculiar, perhaps, to the liver, and has been the cause of difference of opinion, with re- gard to the precise fluid—arte- rial or venous—from which the bile is derived. According to Mr. Kiernan, the portal vein fulfils two functions: it carries the blood from the hepatic ar- tery, and the mixed blood to the coats of the excretory ducts. It has been called vena arte- riosa, because it ramifies like an artery, and conveys blood for secretion: but, as Mr. Kier- nan has observed, it is an arte- Fig. 334. Inferior or Concave Surface of Liver," showing Subdivisions into Lobes. 1. Centre of right lobe. 2. Centre of left lobe. 3. Its anterior, inferior or thin margin. 4. Its posterior, thick or diaphragmatic portion. 5. Right extremity. 6. Left extremity. 7. Notch on the anterior margin. 8. Umbi- lical or longitudinal fissure. 9. Round ligament or re- mains of umbilical vein. 10. Portion of the suspensory ligament in connexion with the round ligament. 11. Pons hepatis, or band of liver across the umbilical fissure. • 7 . . ,- . 12. Posterior end of longitudinal fissure. 13, 14. Attach- riat Vein, in another Sense, aS it ment of obliterated ductus venosus to ascending vena ia a rn,'« 4-~ 4.1».« U„~~4.:____4.____ cava. 15. Transverse fissure. 16. Section of hepatic IS a Vein tO the hepatiC artery, duct. 17. Hepatic artery. 13. Its branches. 19. Vena porta?. 20. Its sinus, or division into right and left branches. 21. Fibrous remains of ductus venosus. 22. Gall-bladder. 23. Its neck. 24. Lobulus quartus. 25 Lobulus Spigelii. 26. Lobulus caudatus. 27. Inferior vena cava. 28. Curvature of liver to fit ascending colon. 29. Depression to fit right kidney. 30. Upper portion of its right concave surface over renal capsule. 31. Portion of liver uncovered by peritoneum. 32. Inferior edge of coronary ligament in the liver. 33. Depression made by vertebral column. and an artery to the hepatic vein. 3. The excretory ducts or biliary ducts. These are presumed to arise from acini, communicating, according to some, with the extremities of 1 Philosophical Transactions for 1833, p. 711. 304 SECRETION. the vena portae; according to others, with radicles of the hepatic artery; whilst others have considered, that the radicles of the hepatic ducts have blind extremities, and that the capillary bloodvessels, which secrete the bile, ramify on them. This last arrangement of the biliary apparatus was well shown in an interesting case, which fell under the care of Professor Hall, in the Baltimore Infirmary, and was examined after death in the author's presence. The particulars have been de- tailed, with some interesting remarks by Professor Geddings.1 In this ease, in consequence of cancerous matter obstructing the ductus com- munis choledochus, the whole excretory apparatus of the liver was enormously distended; the common duct was dilated to the size of the middle finger : at the point where the two branches that form the hepa- tic duct emerge from the gland, they were large enough to receive the tip of the middle finger; and as they were proportionally dilated to their radicles in the intimate tissue of the liver, their termination in a blind extremity was clearly exhibited. These blind extremities were closely clustered together, and the ducts, proceeding from them, were seen to converge, and terminate in the main trunk for the correspond- ing lobe. At their commencement, the excretory ducts are termed pori biliarii. These ultimately form two or three large trunks, which issue from the liver by the transverse fissure, and end in the hepatic duct. 4. Lymphatic vessels. 5. Nerves, in small number, compared with the size of the organ, some proceeding from the eighth pair; but the majority from the solar plexus, which follow the course and divisions of the hepatic artery. 6. Supra-hepatic veins or vense cavse hepaticse, which arise in the liver by imperceptible radicles, communicating, accord- ing to common belief, with the final ramifications of both the hepatic artery and vena portae; according to Mr. Kiernan occupying the centre of the lobules, and hence termed intralobular veins—venulse intralo- bulares seu centrales. They return the superfluous blood, carried to the liver by these vessels, by means of two or three trunks, and six or seven branches, which open into the vena cava inferior. These veins generally pass, in a convergent manner, towards the posterior margin of the liver, and cross the divisions of the vena portae at right angles. 7. The remains of the umbilical vein, which, in the foetus, enters at the horizontal fissure. This vein, after respiration is established, becomes converted into a ligamentous substance, called, from its shape, ligamen- turn rotundum or round ligament. It is difficult to describe the paren- chyma or substance formed by these anatomical elements; and, although the term liver-coloured is used in common Fis- 335- parlance, it is not easy to say what are the ideas attached to it. The views of Mr. Kiernan in regard to the intimate structure of the liver, which have been embraced by so many anatomists, may be understood by the accompanying illustrations, taken from Lobules of Liver. his communications on the subject. The North American Archives of Medical and Surgical Science, for June, 1S35, p. 157. BILIARY. 305 Fig. 336. acini, to which allusion has been made, are termed by him lobules. Fig. 335, 1, exhibits some of the cells of which the lobules are composed, seen under a magnifying power of 200 diameters. 2, represents a longitudinal section of a lobule with ramifications of the hepatic vein: and Fig. 336, the con- nexion of the lobules with the same vein; —the centre of each being occupied by a venous twig—or intralobular vein. Fig. 337 represents the lobules as seen on the surface of the liver when divided transversely. In this, 2, exhibits the interlobular spaces; 3, interlobular fis- sures; 4, intralobular veins occupying the centres of the lobules; and 5, __ -n • ■ ,• ■ ,i j.il. Hepatic vein. 2, 2, 2. Lobules, each Smaller VemS terminating in the Central containing an intralobular or hepatic twig. veins. Fig. 338, is a similar section of three lobules, showing the arrangement of the two principal systems of bloodvessels; 1, 1, intralobular veins; and 2, 2, interlobular plexus Connexion of Lobules of Liver with He- patic Vein. Fig. 337. Fig. 338. Transverse Section of Lobules of the Liver. Horizontal Section of three Superficial Lobules, showing the two principal Systems of Blood- vessels. formed by branches of the vena porta. Fig. 339 represents a horizontal section of two superficial lobules, showing the interlobular plexus of biliary ducts: 1, 1, intralobular veins; 2, 2, trunks of biliary ducts, pro- ceeding from the plexus, which traverses the lobules; 3, interlobular tissue; and 4, parenchyma of the lobules. The interlobular biliary ducts ramify upon the capsular surface of the lobules; and then enter their substance and are supposed to subdivide into minute branches, which by anastomoses with each other form the reticulated plexus depicted in Fig. 339, called by Mr. Kiernan the lobular biliary plexus. It is from this arrangement of the bloodvessels and biliary ducts, that Mr. Kiernan infers that bile must be secreted from the portal vol. n.—20 306 SECRETION. 339. vessels;—the intralobular rami- fications of the hepatic veins conveying back to the heart the blood which has been inser- vient to the secretion. The views of Mr. Kiernan have been generally adopted by anatomists. Wagner, however, whilst he re- gards the beautiful figures and descriptions of Mr. Kiernan as the best he has seen, asserts, that they very certainly also include many mistakes; whilst Krause " combats the views of Kiernan, holding them to be hypothetical;"1 and E. H. Weber2 and Kro- nenberg3 oppose them. The chief point, according to Mr. Paget, in which these gentlemen differ from Mr. Kiernan, is in denying that the compo- nent parts of the liver are arranged in lobules. They, with Henle and Mr. Bowman, describe the capillary networks as solid,—that is as extend- ing uniformly through the liver. They, also, deny the existence of fibre- cellular partitions dividing the liver into lobules as maintained by Mr. Kiernan and J. Miiller;4 and even the existence of more fibro-areolar tissue than serves to invest the larger vessels, &c, of the organ. They Horizontal Section of two Superficial Lobules showing Interlobular Plexus of Biliary Ducts. Fig. 340. Fig. 341. A small portion of a Lobule highly mag- nified. (Leidy.) The secreting cells are seen within the tubes, and in the interspaces of the latter the fibrous tissue is represented. Portion of a Biliary Tube, from a fresh Human Liver, very highly magnified. (Leidy.) The secreting cells may be no- ticed to be polygonal from mutual pressure. likewise deny that there are any such interlobular veins and fissures as Mr. Kiernan describes, and state, that the smaller branches of these veins communicate by branches only just larger, if at all larger, than capillaries.5 1 Wagner, Elements of Physiology, by R. Willis, § 195, Lond., 1842. 2 Miiller's Archiv., 1844, Heft 3. 3 Ibid. * Ibid. 5 See, on all this subject, Professor Theile, art. Leber, Wagner's Handworterbuch der Phy- siologic, 9te Lieferung, s. 308, Braunschweig, 1845. BILIARY. 307 Fig. 342. Histologically considered, the liver may be regarded as consisting of ramifications of excretory ducts, surrounded by bloodvessels, which afford the materials for secretion, and of cells which elaborate it, but as respects the precise arrangement of the cells anatomists are not wholly in accordance. Dr. Leidy" affirms, that they line the inner surface of the tubuli that form the biliary plexus of Kiernan ; that they are irregu- larly angular or of a polygonal shape, owing to their pressing upon each other; and contain a fine granular matter, oil globules, a granular nucleus and transparent nucleolus,—the oil glob- ules, under special circumstances of diet and disease, ex- periencing considerable increase. Dr. C. Handfield Jones3 has, however, recently maintained, that the ramifications of the hepatic ducts do not enter the lobules as main- tained by Mr. Kiernan, but are confined to the inter- lobular spaces,—the substance of the lobules being com- posed of secreting parenchyma and bloodvessels; and that the action of the liver seems to consist in the trans- mission of the bile, as it is formed, from cell to cell, until Fig. 343. Hepatic gorged Fat. a. Atrophied nu- cleus, b. Adipose globules. Minute Portal andHepatic Veins and Capillaries. o, a. Twigs of the portal vein. d. Twig of the hepatic vein. 6. Intermediate capillaries. it arrives in the neighbourhood of the excretory ducts by which it ia absorbed. Perhaps the best mode, according to Br. Budd,3 to get a general 1 American Journal of the Medical Sciences, p. 1, Jan., 1848; and Quain's edition of Quain and Sharpey s Human Anatomy, ii. 487, Philad., 1849. 4 Pliilos-opliic-al Transactions, Pt. i., for 1849. * On Diseases of the Liver, Amer. edit., p. 17, Philad., 1846. 308 SECRETION. idea of the structure of the liver is to examine under the microscope, —first, a thin slice of liver, in which the portal and hepatic veins are thoroughly injected; and secondly,—a small particle taken from the lobular substance of a fresh liver, in which the bloodvessels are empty, as in an animal killed by bleeding. Figure 343, from a specimen by Mr. Bowman, represents, on a magnified scale, a small branch of the hepatic vein, two or three branches of the portal vein, and the intermediate capillaries. The capillaries appear to have nearly the same relation to the branches of the portal vein as they have to those of the hepatic. It is difficult to tell, from this specimen, which branch is portal and which hepatic,—the smaller branches of both being, as it were, hairy with capillaries springing directly from them on every side, and forming a close and continuous network* Dr. Budd thinks, that the injected preparations of Mr. Bowman show clearly, that the opinion of Malpighi, Kiernan, Miiller, and others, that the lobules are isolated from each other, each being invested by a layer of areolar tissue, is erroneous; and that the lobules are not dis- Lobules of the Liver magnified. a, a. a. Minute twigs of the portal vein, b, b, b. Capillaries immediately springing from them, and serving with thein to mark the outline of the lobules, d, d, d. Capillaries in the centre of the lobules, injected through the hepatic vein. e,e. Places at which the size injected into the portal vein has met that injected into the hepatic vein, so that all the intermediate capillaries are coloured and conspicuous. /, I. Centres of lobules into which the injection has not passed through the hepatic vein. tinct, isolated bodies, but merely small masses, tolerably defined by the ultimate twigs of the portal vein, and the injected or uninjected BILIARY. 309 capillaries immediately contiguous to them. The lobules, according to Dr. Budd, appear only as distinct isolated bodies when seen by too low a magnifying power to clearly distinguish the capillaries. The real nature of the lobules, and the manner in which they are formed, will perhaps be better understood, he thinks, by reference to the illustration, (Fig. 344,) for which he expresses his indebtedness to Mr. Bowman. It represents, on a magnified scale, six lobules of the liver, and was made from a drawing under the microscope of a section of the liver of a cat, partially injected through the portal vein, and also through the hepatic. Mr. Kiernan has deduced interesting pathological inferences from the anatomical arrangement of the liver which he conceives to exist; Fig. 345. Fig. 346. First Stage of Hepatic Venous Congestion. (Kiernan.) thus, he considers that the lobules may be congested by accumulation of blood in the hepatic or in the portal venous system ; which may be detected by a minute inspection of the lobules. The precise causes of this are referred to in another work.1 The accompanying illustrations will be sufficient here. Fig. 345 represents the lobules in the first stage of what he terms hepatic venous congestion or congestion of the terminations of the hepatic vein : 2, the interlobular spaces and fissures. In Fig. 346, the lobules are in the second stage of congestion. B and C, the inter- lobular spaces; D, congested intra- Second Stage of Hepatic Venous Congestion. (Kiernan.) x Fig. 347. Portal Venous Congestion. B. Interlobular spaces and fissures. C. Intra- lobular veins. D. Ana?mic portions. E. Con- gested portions. (Kiernan.) • Practice of Medicine, 3d edit., vol. ii. chap. 3, Philad., 1848. 310 SECRETION.* Fig. 348. lobular or hepatic veins; I, congested patches extending to the cir- cumference of the lobules; F, uncongested portions. In Fig. 347, the lobules are in a state of portal venous congestion; not a common occur- rence. It has been seen by Mr. Kiernan in children only. The view of Mr. Kiernan has been held to explain also the diversity of the statement of anato- mists as to the relative posi- tion* of the red and yellow substances, which have been considered to compose the liver: the red is the congested portion of the lobules, whilst the yellow is the non-con- gested portion in which the biliary plexus appears more or less distinctly. The liver has two coats;— the outer, derived from the peritoneum, which is very thin, transparent, easily lace- rable, and vascular, and is the seat of the secretion ef- fected by serous membranes in general. It does not cover the posterior part, or the ex- cavation for the gall-bladder, the vena cava, or the fissures in the concave surface of the liver. The inner coat is the proper membrane of the liver. It is thin, but not easily iorn, and covers not only every part of the surface of the liver, but the large vessels that are proper to the organ. The condensed areolar sub- stance,—which unites the sinus of the vena portse and its two great branches, the hepatic artery, common biliary duct, lymphatic glands, lymphatic vessels, and nerves Fie- 349- in the transverse fossa or fis- sure of the liver,—was de- scribed by Glisson as a cap- sule; and hence has been called capsule of Glisson. It connects the various anatomi- cal elements of the liver to- gether. The gall-bladder (Figs. 300 and 348) is a small mem- Gall-bladder distended with Air, and with its Vessels pranoUS pouch of a pyriform mjected" shape, situate at the inferior 1. Cystic artery. 2. Branches of it which supply the •, „__„„ r,,,„A,„« «£ +V10 peritoneal coat of the liver. 3. Branch of the hepatic ar- and COnCaVe Surface Ot tne tery which goes to gall-bladder. 4. Lymphatics of gall- j-yer to which it is attached I bladder. The three Coats of Gall-bladder separated from each other. 1. External or peritoneal coat. 2. Areolar coat with its vessels injected. 3. Mucous coat covered with wrinkles. 4, 4. Valves, formed by this coat in the neck of gall-bladder. 5, 5. Orifices of mucous follicles at this point. BILIARY. 311 and above the colon and duodenum. A quantity of bile is usually found in it. It is not met with in all animals; is wanting in the elephant, horse, stag, camel, rhinoceros, and goat; in certain of the cetacea; in some birds, as the ostrich, pigeon, and parrot; and is occasionally so in man. No traces of it are met with in the invertebrata. It may be looked upon as a dilatation of the gall-ducts, and adapted for the reception and retention of bile. Its largest part or fundus is turned for- wards; and, when filled, frequently projects beyond the anterior margin of the liver. Its narrowest portion, cervix or neck, is turned back- wards, and terminates in the cystic duct. Externally, it is partly covered by the peritoneum, which attaches it to the liver, and to which it is, moreover, adherent by areolar tissue and vessels. Internally, it is rugous; the folds being reticulated, and appearing somewhat like the cells of a honeycomb. Anatomists have differed with regard to the number of coats proper to the gall-bladder. % Some have described two only;—the peritoneal and mucous; others have added an intermediate areolar coat; whilst others have reckoned four;—a peritoneal,—a thin stratum of muscular fibres passing in different directions, and of a pale colour,—an areolar coat, in which a number of bloodvessels is situate, and an internal mucous coat. The existence of the muscular coat has been denied by perhaps the generality of anatomists ; but there is reason for believing in its existence. Amussat saw muscular fibres distinctly in a gall- bladder dilated by calculi; and Dr. Monro (Tertius),1 Professor of Ana- tomy in the University of Edinburgh, asserts, that he has seen it con- tract, in a living animal, for half an hour, under mechanical irritation, and assume the shape of an hour-glass. The mucous coat forms the rugae to which we have already alluded. In the neck, and beginning of the cystic duct, there are from three to seven—sometimes twelve— semilunar duplicatures, which retard the flow of any fluids inwards or outwards. These are sometimes arranged spirally, so as to form a kind of valve, according to M. Amussat.2 On the inner surface of the gall-bladder, especially near its neck, numerous follicles exist, the secretion from which is said to fill the gall-bladder, when that of the bile has been interrupted by disease, as in yellow-fever, scirrhus of the liver, &c. The hepatic duct is the common trunk of all the excretory vessels of the liver; and makes its exit from that organ by the transverse fissure. It is an inch and a half in length, and about the diameter of an ordinary writing- quill. It is joined, at a very acute angle, by the duct from the gall- bladder—cystic duct—to form the ductus communis choledochus. The cystic duct is about the same length as the hepatic. The ductus communis choledochus is about three, or three and a half inches long. It descends behind the right extremity of the pancreas, through its substance; passes for an inch obliquely between the coats of the duodenum, diminishing in diameter; and ultimately terminates by a yet more contracted orifice on the inner surface of the intestine, at the 1 Elements of the Anatomy of the Human Body, Edinb., 1825. 2 Magendie, Precis, &c, ii. 464. 312 SECRETION. distance of three or four inches from the stomach. The structure of all these ducts is the same. The external coat is thick, dense, strong, and generally supposed to be of an areolar character; the inner is a mucous membrane, like that which lines the gall-bladder. The secretion of bile is probably effected like that of other glandular organs ; modified, of course, by the peculiar structure of the liver. We have seen, that the organ differs from every other secretory apparatus, in having two kinds of blood distributed to it;—arterial by the hepatic artery; and venous by the vena portae. A question has consequently arisen—from which of these is the bile formed? Anatomical inspection does not positively settle the question; and, accordingly, argument is all that can be adduced on one side or the other. The most com- mon and the oldest opinion is, that the bile is separated from the blood of the vena portae; and the chief reasons brought forward in favour of the belief, are the following: First. The blood of the portal system is better adapted than arterial blood for the formation of bile, on account of its having, like all venous blood, more carbon and hydro- gen, which are necessary for the production of a humour as fat and oily as the bile; and, as the experiments of Schultz3 and others have proved, that portal blood contains more fat than that of other veins and arteries, it has been imagined, by some, that the blood, in crossing the omentum, becomes loaded with fat. Secondly. The vena portae rami- fies in the liver after the manner of an artery, and evidently commu- nicates with the secretory vessels of the bile. Thirdly. It is larger than the hepatic artery; and more in proportion to the size of the liver; the hepatic artery seeming to be merely for the nutrition of the liver, as the bronchial artery is for that of the lung. In answer to these positions, it has been argued. First. That there seems to be no more reason why the bile should be formed from venous blood than other fatty and oleaginous humours,—marrow and fat for example,—which are derived from arterial blood. It is asked, too, whether, in point of fact, the blood of the vena portae is more rich in carbon and hydrogen? and whether there be a closer chemical relation between bile and the blood of the vena portae, than between fat and arterial blood? The notion of the absorption of fat from the omentum, it is properly urged, is totally gratuitous. Secondly. The vena portae does not exist in the invertebrated animals; and yet, in a number of them, there is an hepatic apparatus, and a secretion of bile. Thirdly. Admitting that the vena portae is distributed to the liver after the man-, ner of an artery; is it clear, it has been asked, that it is inservient to the biliary secretion ? Fourthly. If the vena portae be more in pro- portion to the size of the liver than the hepatic artery, the latter ap- pears to bear a better ratio to the quantity of bile secreted: and, Lastly. It is probable, as has been shown in another place, that the liver has other functions connected with the portal system, in the ad- mixture of heterogeneous liquids absorbed from the intestinal canal; and, it may be, in depriving the blood of the vena portae of principles 1 Rust's Magazine, B. xliv.; or Gazette Medicale, Aug. 15,1835. BILIARY. 313 which go to the formation of bile and,might be unfit for assimilation, if transported into the blood of the general system. In the absence of accurate knowledge derived from direct experi- ment, physiologists have usually embraced one or other of these exclu- sive views. The generality, as we have remarked, assign the function to the vena portae. Bichat, on the other hand, ascribes it to the hepatic artery. M. Broussais1 thinks it probable, that the blood of the vena portae is not foreign to the formation of bile, since it is confounded with that of the hepatic artery in the parenchyma of the liver; " but to say with the older writers, that the bile can only be formed from venous blood, is, in our opinion," he remarks, "to advance too bold a position, since the hepatic arteries send branches to each of the glandu- lar acini, that compose the liver." M. Magendie likewise concludes, that nothing militates against the idea of both kinds of blood participating in the secretion; and that it is supported by anatomy, as injections prove, that all the vessels of the liver,—arterial, venous, lymphatic, and excretory,—communicate with each other. Mr. Kiernan, as we have seen, considers that the blood of the hepatic artery, after having nourished the liver, is inservient to the secretion, but not until it has become venous, and entered the portal veins. He,—with all those that coincide with him in the morphological arrangement of the liver—de- nies that there is any communication between the ducts and bloodves- sels; and asserts, that if injections pass between them, it is owing to the rupture of the coats of the vessels. Experiments on pigeons, by M. Simon,2 of Metz, showed, that when the hepatic artery was tied, the secretion of bile continued, but that if the portal and hepatic veins were tied, no trace of bile was subsequently found in the liver. It would thence appear, that in these animals the secretion of bile takes place from venous blood. But inferences from the ligature of those vessels have been very discordant. In two cases, in which Mr. Phillips tied the hepatic artery, the secretion of bile was uninterrupted, yet the same thing was observed in three other cases, in which the ligature was applied to the trunk of the vena portae. The view, that ascribes the bile to the hepatic artery, has always appeared to the author the most probable. It has all analogy in its favour. There has been no disputed origin as regards the other secre- tions, excepting, of late, in the case of the urinary. All proceed from arterial blood; and function sufficient, we have seen, can be assigned to the portal system, without conceiving it to be concerned in the forma- tion of bile. We have, moreover, morbid cases, which would seem to show that bile can be formed from the blood of the hepatic artery. Mr. Abernethy3 met with an instance, in which the trunk of the vena portae terminated in the vena cava; yet bile was found in the biliary ducts. A similar case is given by Mr. Lawrence;4 and Professor Monro* details a case communicated to him by the late Mr. 1 Traite de Physiologie, &c, Drs. Bell's and La Roche's translation, 3d edit, p. 456, Philad., 1832. 2 Edinburgh Med. and Surg. Journal, xc. 229. 3 Philosoph. Transact., vol. lxxxiii. 4 Medico-Chirurgical Transact., iv. 174. 6 Elements of Anatomy, Edinb., 1825. 314 SECRETION. Wilson, then of the Windmill Street School, in which there was reason to suppose, that the greater part of the bile had been derived from the hepatic artery. The patient, a female, thirteen years old, died from the effects of an injury of the head. On dissection, Mr. Wilson found a large swelling at the root of the mesentery, consisting of several ab- sorbent glands in a scrofulous state. Upon cutting into the mass, he accidentally observed a large vein passing directly from it into the vena cava inferior, which on dissection, proved to be the vena portae; and on tracing the vessels entering into it, one proved to be the inferior mesenteric vein: and another, which came directly to meet it, from behind the stomach, proved to be a branch of the splenic vein, but somewhat larger, which ran upwards by the side of the vena cava in- ferior, and entered that vein immediately before it passes behind the liver. Mr. Wilson traced the branches of the trunk of the vessel cor- responding to the vena portae sufficiently far in the mesentery and mesocolon to be convinced, that it was the only vessel that returned the blood from the small intestines, and from the caecum and colon of the large intestines. He could trace no vein passing into the liver at the cavity of the porta; but a small one descended from the little epiploon, and soon joined one of the larger branches of the splenic vein. The hepatic artery came off in a distinct trunk from the aorta, and ran directly to the liver. It was much larger than usual. The greater size of the hepatic artery, in this case, would favour the idea, that the arterial blood had to execute some office, that ordinarily be- longs to the vena portae. Was this the formation of bile ? The case seems, too, to show, that bile can be formed from the blood of the hepatic artery. Professor Gintrac1 has published a case in which there was ossifica- tion with obliteration of the vena portae. The patient died of ascites. The liver was pale or whitish, and irregularly wrinkled or mammillated on its surface. The gall-bladder contained a medium quantity of thickish yellow bile. The biliary ducts were normal. The vena portae above the junction of the splenic and superior mesenteric veins was completely filled by an old clot, which adhered to the inner membrane. The clot was solid, and of a deepish black colour. At the same part of the vein several osseous plates were observed many lines in diameter, which were situate between the inner and middle coats of the vein, without having much adherence to either. All the abdominal veins that ended in these vessels were gorged with blood, and varicose. Pro- fessor Gintrac ascribed the ascites to the obliteration and ossification of the vena portae, and he considered the case to prove, that although obliteration of that vessel probably modified the secretion of bile, it did not prevent it altogether; but interfered materially with the nutri- tion of the liver. Hence, he inferred, that the blood of the vena portae contributes to the nutrition of the liver; but is not indispensable to the secretion of bile. In Professor Hall's patient,2 the vena portae and its bifurcation were completely filled with encephaloid matter, so that no blood could pass « Cited in Amer. Journal of the Med. Sciences, Oct., 1844, p. 476. » P. 304. BILIARY. 315 through it to the liver; the secretion of bile could not, consequently, have been effected through its agency. It has been presumed, however, that in such cases, portal blood might still enter the liver through the extensive anastomoses, which Professor Retzius,1 of Stockholm, found to exist between the abdominal veins. That gentleman observed, when he tied the vena portae near the liver, and threw a coloured injection into the portion below the ligature, that branches were filled, some of which, proceeding from the duodenum, terminated in the vena cava; whilst others, arising from the colon, terminated in the left emulgent vein. In subsequent investigations, he observed an extensive plexus of minute veins ramifying in the areolar tissue on the outer surface of the peritoneum, part of which was connected with the vena portae, whilst the other terminated in the system of the vena cava. In a successful injection, these veins were seen anastomosing very freely, in the pos- terior part of the abdomen, with the colic veins, as well as with those of the kidneys, pelvis, and even the vena cava. The arrangement, pointed out by Retzius, accounts for the mode in which the blood of the abdominal venous system reaches the cava, when the vena portae is obliterated from any cause; and it shows the possibility of portal blood reaching the liver so as to be inservient to the biliary secretion, but does not, we think, exhibit the probability. Still more recently, cases of obliteration of the vena portae have been recorded, in which the nutrition of the liver was materially impaired, so that the organ had become atrophied, whilstthe secretion of bile persisted. Such a case is given by M. Raikem,2 of Brussels. In this, the vein was entirely obliterated by clots of blood intimately adherent to its inner sur- face. The liver was smaller than usual; the gall-bladder contained a large quantity of serous bile of a yellowish and orange colour, and the cystic and hepatic ducts were filled with it. The trunk of the hepatic artery was three lines in diameter, and contained no clots of blood; and such was the case with the supra-hepatic veins. Whence M. Raikem concludes, that in the present state of physiological knowledge, there are reasons sufficiently conclusive for the opinion, that the hepatic artery is capable alone of furnishing to the liver the materials necessary for the secretion of bile, when the vena porta is obliterated to so great a degree as not to allow the blood to be conveyed through it to the organ; and, he asks, as the result of observations of numerous pathological cases, whether "it is indeed proved, as is generally believed, that the hepatic artery is alone charged with the function of nourishing the liver to the exclusion of the portal vein," when "we observe that the liver is atrophied in those in whom the portal vein has been entirely obliterated for a long time?" An additional case of the kind has been detailed by Dr. Craigie.3 In this, the vein was found completely filled and distended by firm, yet compressible, elastic matter, as if the vessel had been injected, so that its diameter was fully one inch. Of the 1 Ars Berattelse af Setterblad, 1835, s. 9; cited in Zeitschrift fur die Gesammte Heil- kunde, Feb., 1837, s. 251. 2 Memoires de l'Academie Royale de Medecine deBelgique, torn, i., Bruxelles, 1848; trans- lated in the Edinb. Med. and Surg. Journal, April, 1850, p. 350. 8 Edinb. Med. and Surg. Journal, April, 1850, p. 512. 316 SECRETION. effects of this obliteration, the most remarkable, again, was the atrophy of the liver, which was not more than one-third of its usual size. A small quantity of light coloured bile was found in the gall-bladder, and during life the faeces had the usual colour. "M. Raikem," says Dr. » Craigie, "has adverted to the notion so much favoured by various phy- siological speculators, that the hepatic artery is employed in maintain- ing the nutrition of the liver, while to the portal vein belongs the function of conveying to the gland the materials from which bile is to be prepared; and to show its incompetency, has adduced several con- clusive arguments. It is scarcely possible to conceive a stronger argu- ment against it than is furnished by the facts of this case. The portal vein was completely obstructed, and no blood must for a long time have been conveyed through its branches into the gland. The liver is like- wise very much reduced in size, not, indeed, uniformly and equally in all its parts, but still so much and so generally atrophied, that it is difficult to ascribe the diminution and wasting of parts to any other cause. The two circumstances, therefore, appear to stand in the rela- tion of cause and effect." It is to be regretted that the history of this case is rendered imperfect by the circumstance, that " the state of the hepatic artery was not ascertained." It would seem, then, that the portal system is not absolutely necessary to the formation of bile; yet a modern writer1 considers it "a most puerile question" to ask whether the secretion can be effected from venous blood! " Had not," he adds, "secretion been destined to take place from the blood of the vena portarum, nature would not have been at the pains to distribute it through the liver; the peculiar arrangement is already an answer to the question; the end of it is, as I have said, to economise arterial blood." As before remarked, however, a sufficient function can be assigned to the portal system without supposing that it has any agency in the secretion of bile. Still, there is nothing inconsistent with the idea, that both kinds of blood may be inservient to the secre- tion. Mention has been made elsewhere,2 that MM. Bouchardat and Sandras, having fed herbivorous animals on farinaceous substances, detected more dextrin, grape sugar, and lactic acid in the blood of the vena portae than in that of any other vessel; and that Trommer dis- covered grape sugar in the blood of the portal vein, but not in that of the hepatic veins of animals with whose food that substance had been mixed. Moreover, MM. Blondlot3 and Chossat4 found, that the administra- tion of non-nitrogenous articles of food, especially of sugar, considerably increased the amount of bile secreted. All these circumstances cer- tainly lead to the belief, that nitrogenized aliments, absorbed by the veins of the stomach a