■* ! 1 & 111 Mik **''** Surgeon General's Office ---♦ -£-= ^ ^ Sio^tm, ■■'■■■■■ -''Mp......'........ ® N< &f£..(?... PRESENI£D BY J JC.--' g^s*j^ U4J u^J L J u 0 u nr ■' " ' Y" '> :W, JOSHUA GREEN, Jun. CARPE DIEM. ZOONOMIA; OR THE IL^WS ®W ®M«@ MSR& IN THREE PARTS. BY ERASMUS DARWIN, M.D. F.R.S. AUTHOR OF THE BOTANIC GARDEN, &C. Principle ccelum, ac terras, camposque liquentes, Lucentemque globum lunae, titaniaque astra, Spiritus inius alit, totamque infusa per anus Mens agitat moleui, et roagno se corpore miscct. Virg. A£n. vi. Earth, on whose lap a thousand nations tread, And Ocean, brooding his prolific bed, Night's changeful orb, blue pole, and silvery zones, Where other worlds encircle other suns, One Mind inhabits, one diffusive Soul Wields the large limbs, and mingles with the whole. COMPLETE IN TWO VOLUMES. VOL. I. FOURTH AMERICAN EDITION. PHILADELPHIA: PUBLISHED BY EDWARD EARLE, CORNER OF FOURTH AND LIBRARY STREET. William Brown, Printer. 1818. Id! ■W'ST-IUiF TO the candid and ingenious Members of t\\e College of PYv^sicians, of tne BAYjal P¥A\o- sop\vica\ Society, of t\\e two Universities, and to a\\ those, who study, the operations of the mind as a science, or w\io practise medicine as a profession, the subsequent work is, with great respect, inscribed by TYve Autbor. Derby, May l, 1794. DIRECTIONS TO THE BINDER. 1. Please to place the Plate consisting of one red spot at Sect. III. 1. page 9. 2. ---- Consisting of one black spot, at Sect. III. 3. 3. page 12. 3 ____ Consisting of five concentric coloured circles, at Sect. IH. 3. 6. page 13. 4. ____ Consisting of one yellow circle surrounded by one blue one, at Sect. XL. 4. 2. page 451. 5 ____ Consisting of one yellow circle and two blue ones, at Sect. XL. 10. 3. page 462. 6. .____ Consisting of the word BANKS in blue on a yellow ground, at Sect. XL. 10. 5. page 465. TO ERASMUS DARWIN, OX HIS WORK ENT1TLSD a®®^r®MHA3 BY DEWHURST BILLSBORROW Hail to toe Bard ! who sung, from Chaos hurl'd How suns and planets form'd the whirling world ; How sphere on sphere Earth's hidden strata bend, And caves of rock her central fires defend; Where gems new-born their twinkling eyes unfold, 5 And young ores shoot in arborescent gold. How the fair Flower, by Zephyr woo'd, unfurls Its panting leaves, and waves its azure curls ; Or spreads in gay undress its lucid form To meet the sun, and shuts it to the storm ; 10 While in green veins impassion'd eddies move, And Beauty kindles into life and love. How the first embryon fibre, sphere, or cube, Lives in new forms,—a line,—a ring,—a tube ; Clos'd in the womb with limbs unfinish'd laves, 15 Sips with rude mouth the salutary waves; Seeks round its cell the sanguine streams, that pass, And drinks with crimson gills the vital gas; Weaves with soft threads the blue meandering vein, The heart's red concave, and the silver brain; 30 Leads the long nerve, expands the impatient sense, And clothes in silken skin the nascent Ens. Erewhile, emerging from its liquid bed, It lifts in gelid air its nodding head; The light's first dawn with trembling eyelid hails, 23 With lungs untaught arrests the balmy gales; Tries its new tongue in tones unknown, and hears The strange vibrations with unpractised ears ; Seeks with spread hands the bosom's velvet orbs, With closing lips the milky fount absorbs ; 30 And, as compress'd the dulcet streams distil, Drinks warmth and fragrance from the living rill; Eyes with mute rapture every waving line, Prints with adoring kiss the Paphian shrine, And learns ere long, the perfect form confess'd, -55 Ideal Beauty from its mother's breast. TO ERASMUS DARWIN. Now in strong lines, with bolder tints design'd, You sketch ideas, and portray the mind ; Teach how fine atoms of impinging light To ceaseless change the visual sense excite : While the bright lens collects the rays, that swerve, And bends their focus on the moving nerve. How thoughts to thoughts are link'd with viewless chains, Tribes leading tribes, and trains pursuing trains; With shadowy trident how Volition guides, Surge after surge, his intellectual tides; Or, Queen of Sleep, Imagination roves With frantic Sorrows, or delirious Loves. Go on, O friend ! explore with eagle eye, Where wrapp'd in night retiring Causes lie : Trace their slight bands, their secret haunts betray, And give new wonders to the beam of day; Till, link by link, with step aspiring trod, You climb from Nature to the throne of God. ---So saw the Patriarch with admiring eyes, From earth to heaven a golden ladder rise : Involv'd in clouds the mystic scale ascends, And brutes and angels crowd the distant ends. Triw. Col. Cambridge, Jan. 1, 1794. 40 45 50 REFERENCES. Botanic Garelen, Part I. Line 1. Canto I. 1. 105 ----3. ---- IV. 1. 402 ----4. ---- I. 1. 140 ----5. ---- III. 1. 401 ----8. ---- IV. 1. 452 ----9. ---- I. 1. 14 Zoonomiei. 12. Sect XIII. 13. ---- XXXIX. 4. 1. Sect. X\l. 2. and XXXVHI ---- XVI 4. ---- XVI. 4. ---- XVI. 6. ---- III. and VII. ---- X. ---- XVIII. 17. ---- XVII. 3. 7. ---- XVIII 8. --- XXXIX. 4. 8. ---XXXIX. the Motto --- XXXIX. 8. PREFACE. TFIE purport of the following pages is an endea- vour to reduce the facts belonging to Animal Life into classes, orders, genera, and species; and, by comparing them with each other, to unravel the theory of diseases. It happened, perhaps unfortunately for the inquirers in- to the knowledge of diseases, that other sciences had received improvement previous to their own; whence, instead of comparing the properties belonging to ani- mated nature with each other, they, idly ingenious, bu- sied themselves in attempting to explain the laws of life by those of mechanism and chemistry; they considered the body as an hydraulic machine, and the fluids as pass- ing through a series of chemical changes, forgetting that animation was its essential characteristic. The great Creator of all things has infinitely diver- sified the works of his hands, but has at the same time stamped a certain similitude on the features of nature, that demonstrates to us, that the whole is one family of one parent. On this similitude is founded all rational analogy; which, so long as it is concerned in compar- ing the essential properties of bodies, leads us to many and important discoveries; but when with licentious ac- tivity it links together objects, otherwise discordant, by some fanciful similitude, it may indeed collect orna- VI11 PREFACE. ments for wit and poetry, but philosophy and truth re- coil from its combinations. The want of a theory, deduced from such strict ana- logy, to conduct the practice of medicine, is lamented by its professors; for, as a great number of unconnected facts are difficult to be acquired, and to be reasoned from, the art of medicine is in many instances less effi- cacious under the direction of its wisest practitioners; arid by that busy crowd, who either boldly wade in dark- ness, or are led into endless error by the glare of false theory, it is daily practised to the destruction of thou- sands; add to this the unceasing injury which accrues to the public by the perpetual advertisements of pretend- ed nostrums; the minds of the indolent become super- stitiously fearful of diseases, which they do not labour under; and thus become the daily prey of some crafty empyric. A theory founded upon nature, that should bind to- gether the scattered facts of medical knowledge, and converge into one point of view, the laws of organic life, would thus on many accounts contribute to the interest of society. It would capacitate men of moderate abili- ties to practise the art of healing with real advantage to the public; it would enable every one of literary ac- quirements to distinguish the genuine disciples of medi- cine from those of boastful effrontery, or of wily ad- dress; and would teach mankind in some important situations the knowledge of themselves. There are some modern practitioners, who declaim against medical theory in general, not considering that to think is to theorize; and that no one can direct a me- thod of cure to a person labouring under disease with- out thinking, that is, without theorizing; and happy therefore is the patient, whose physician possesses the best theory. PREFACE. IX The words idea, perception, sensation, recollection, suggestion, and association, are each of them used in this treatise in a more limited sense than in the writers of metaphysic. The author was in doubt, whether he should rather have substituted new words instead of them; but was at length of opinion, that new definitions of words already in use would be less burthensome to the memory of the reader. A great part of this work has lain by the writer above twenty years, as some of his friends can testify: he had hoped by frequent revision to have made it more worthy the acceptance of the public; this, however, his other perpetual occupations have in part prevented, and may continue to prevent, as long as he may be capable of re- vising it; he therefore begs of the candid reader to ac- cept of it in its present state, and to excuse any inaccu- racies of expression, or of conclusion, into which the intricacy of his subject, the general imperfection of language, or the frailty he has in common with other men, may have betrayed him; and from which he has not the vanity to believe this treatise to be exempt. VOL. I. b PREFACE TO THE THIRD LONDON EDITION. THE reader should be apprized, that many new pages are interspersed in this edition, which consist of practical and theoretical observations, as the whole arti- cles on hemicrania idiopathica, retroversio uteri, aneu- risma, and the appendix to the section on generation, beginning at No. 8. as well as the distinction between philosophy and sophistry in Sect. XV. 1. 5. and the ratiocinatio verbosa, verbal reasoning, in Class III. 1. 2. 3. and some others. Derby, Jan. 1, 1801. & In the former editions of this work the Materia Medica [which forms Part III.] was placed after the second part, or the classes of diseases; but to preserve the more equal size of the volumes in this octavo edi- tion, the publisher has placed it, with the assent of the author, after the first part. CONTENTS 21 PART I. Page Seot. 1. Of Motion.......l II. Explanations and Definitions ... 3 III. The Motions of the Retina demonstrated by Experiments......8 IV. Laws of Animal Causation .... 20 V. Of the four Faculties or Motions of the Sen- sorium ....••• VI. Of the four Classes of Fibrous Motions . 23 VII. Of Irritative Motions .... 25 VIII. Of Sensitive Motions.....29 IX. Of Voluntary Motions . . • • 31 X. Of Associate Motions . . • • -34 XI. Additional Observations on the Sensorial Powers.......37 XII. Of Stimulus, Sensorial Exertion, and Fibrous Contraction......43 XIII. Of Vegetable Animation • • • .73 XIV. Of the Production of Ideas ... 79 XV. Of the Classes of Ideas . . . -95 XVI. Of Instinct......101 XVII. The Catenation of Animal Motions . . 143 XVIII. Of Sleep......153 XIX. Of Reverie......170 XX. Of Vertigo......175 XXI. Of Drunkenness.....191 XXII. Of Propensity to Motion. Repetition. Imi- tation .......198 XXIII. Of the Circulatory System ... 206 XXIV. Of the Secretion of Saliva, and of Tears. And of the Lachrymal Sack . . .212 XXV. Of the Stomach and intestines . . 217 XXVI. Of the Capillary Glands, and of the Mem- branes .......226 XXVII. Of Haemorrhages.....229 XXVIII. The Paralysis of the Lacteals . . 234 XIV CONTENTS. Page Sect. XXIX. The Retrograde Motions of the Absorbent Vessels . • • • • • 238 XXX. The paralysis of the Liver and Kidneys . 272 XXXI. Of temperaments .... 277 XXXII. Diseases of Irritation .... 282 XXXIII. ----- of Sensation .... 305 XXXIV. ----- of Volition .... 324 XXXV. ----- of Association ...• 343 XXXVI. The Periods of Diseases . • • 352 XXXVII. Of Digestion, Secretion, Nutrition . . 360 XXXVIII. Of the Oxygenation of the Blood in the Lungs and Placenta .... 366 XXXIX. Of Generation.....373 XL. Of Ocular Spectra . . .443 [Part II. forms the Second Volume.] PART III. ARTICLES OF THE MATERIA MEDIC A. Art. I. Nutrientia .......5 II. Incitantia.......19 III. Secernentia . . • • . • .31 IV. Sorbentia.......42 V. Invertentia........65 VI. Revertentia.......70 VII. Torpentia .......73 INTRODUCTION TO THE AMERICAN EDITION. CONTENTS OP THE INTRODUCTION. Object of the first part of the Zoonomia. Arrangement of living mo- tions. Functions referable to each of these. Classification of animat- ed action under four heads. Influence of stimuli in sustaining life. Comparison of Dr. Darwin's doctrine of stimulus and exertion with the Brunonian Elements. Great resemblance acknowledged by the former. Which of them was indebted to the other ? The two authors espouse similar fundamental principles. Examinat Hon of the slander that Brown's doctrine ivas but a revival of the opinions of the ancient Methodic Sect. History of that sect. A branch of the Epicureans. Sketch of the Epicurean philoso- phy. Application of this to medicine. Reasoning wholly me- chanical. History of the opinions concerning life superadded to mechanism, from Hippocrates to Cullen. How far the lat- ter had proceeded. Merits of Brown. Abstract of the first edition of his Elementa, published in 1780, and now very rare. Review of his second edition, in 1784. The English work a mere translation of this. Epitome of the Brunonian Doctrine. Very different from the notions of Themison and Thessalus. Defects in Brown's system. Room for improvements. Great amendments made by various persons. Introduction of chemical principles and modes of reasoning. Insufficient to explain the phenomena of life. Laudable attempt of Dr. Darwin to inves- tigate those laics which neither mechanism nor chemistry can ex- plain. Object of the second part to form a nosology, or cata- logue of diseases, by a natural classification, founded on their proximate causes. AN attempt has been made in the first part of this work to in- vestigate the complex laws of animal causation. These are de- duced from the contractions and relaxations performed by the living fibres, which constitute the muscles and organs of sense. Fibrous contractions seem to constitute all the functions of ani- mated bodies, and indeed all we know both physiologically and XVI INTRODUCTION TO THE medically concerning life and its functions. They are arrang- ed into four classes of motions which form the foundation of all just nosology and practice, as detailed in the second great division of the Zoonomia. Vital motions are thus called irrita- tive, sensitive, voluntary, and associated, according as the parts of the body in which they exist are endowed with irritability, sensation, volition, or symfiathy. This guadrufile allotment of functions form a strong and peculiar character of the following work. And the distribution of the almost endless variety of animated phenomena into this fourfold and lucid argument, is a clear proof of the discriminating and generalizing mind of the author. But in all these conditions of the system, whether influenced by the vis insita or the vis nervea* by voluntary or sympathetic energy, the sensorial powers are sustained by the unceasing operation of stimulants. The theory of these is contained in the twelfth chapter of the first part, and exhibits very advan- tageously the doctrine of stimulus and exertion, or as it has been more generally called, excitement. There is a striking analogy between these fundamental doc- trines of Dr. Darwin and those contained in Dr. Brown's Ele- ments of Medicine. Our author was aware of this, and to guard himself against the imputation of having borrowed Brown's ideas without acknowledgment, or of being merely his imitator, he observes that " the coincidence of some parts of this work " with correspondent deductions in the Brunonian Elementa " Medicinae, a work (with some exceptions) of great genius, " must be considered as confirmations of the truth of the theory, " as they were probably arrived at by different trains of rea- " soning." In respect to originality there is great difficulty in settling claims. In this case however, there is not even a suspicion that Brown derived any thing from Darwin. Both might indeed have come to similar conclusions., by the independent exercise of their 1 eason, without any communication or intercourse. And yet, an impartial observer, prone neither to obloquy nor flattery, would not forfeit his candour in suspecting that a writer of Dar- wii.'s acutenessmight have gathered something from Brown, who published fourteen years before him. Considering the Brunonian and Darwinian systems as resting upon the same pillars, it appears to me there maybe both use- fulness and curiosity in searching and digging about the ground on which they stand. In performing this task, it has been ex- pected there should be a statement shewing how far these doc- trines of the Scottish and English physicians are themselves novel or modern, or whether they are both of the old school, and derived from remote and ancient sources. By deciding in favour of their modernity, it will be likewise eicpected that a view should be given of the Brunonian system, AMERICAN EDITION. XV11 that it may be compared with the contemporary doctrines of Cullen and Darwin. In this comparison it will be found, that Brown's merit is very conspicuous. The three distinguished authors have finished their earthly career, and they and their writings may now be considered without envy or partiality. To those who are curious to trace the progress of these opinions, which exert such extensive dominion over the mind, these intro- ductory remarks may perhaps afford some gratification. Others, who possess not the taste or leisure for such inquiries, may pass them over, and in the progress of observation and experiment in physics, within a few years, such a number of new and impor- tant facts have been brought to light, that many philosophers have believed the people of the present day were possessed of a great deal more knowledge than the moderns of the three last centuries, or their ancient predecessors. This opinion, in particular, has been deemed well founded, and true in its respect to medicine, which, at this time, is not only considered susceptible of new expositions and interpreta- tions, but of being greatly improved and enlarged, both in theory and practice. And although among those who think thus are reckoned most of the original and clear-sighted geniuses of our time, yet there are not wanting some, and those men of talents and reputation too, who are in the habit of thinking, if the ancients knew not quite as much as ourselves, yet their writings contain the leading hints, or great outlines of almost every thing dis- coverable, either directly expressed, or signified in allegorical terms. This literary superstition has been carried a great way ; and if it had stopped at declaring the Iliad the best of possible poems, or the Philififiics the most finished of the rhetorical pro- ductions, I should not at this time have troubled myself to con- tradict it. But when these enthusiastic admirers of antiquity declare, that, in matters of science as well as of letters, the sub- jects of enquiry have been exhausted two thousand years ago, and that no idea can be started which is not an imitation of some- thing that a Greek or a Roman, or some body else, had thought before, I own I am a little disposed to believe their assertions are grounded neither in truth nor in the nature of things. For why must we resort to the Platonists, Stoics, and Peripate- tics, for doctrines which the Academy, the Porch, and the Ly- ceum never knew ? These remarks are made in consequence of an opinion, pro- pagated and believed by some, that a certain method of reason- ing upon medical subjects, and of medical practice, introduced now of late, as many believe, which are already pretty well esta- blished, and acquiring rapidly more and more adherents, are in fact but a revival and new-modelling of the opinions and proce- dure of the Methodic Sect, founded by Asc-lepiades, the eotemporary of Mithridates and Crassus. VOL. I. c X,V1H INTRODUCTION TO THE In order to know whether this opinion is well founded, I shall enquire what the philosophy of the Methodic Sect was. Its founder, Asclepiades, adopted that philosophy,whose foun- dation had been laid by Anaxagoras, Empedocles, and Hera- cnTus,and which was afterwards wrought up into the Atomic Sys- tem, by LEucipPus,and Democritus, of the Eleatic Sect ; who, rejecting all metaphysical explanations of the causes of things, undertook the interpreting nature, from the laws of matter and motion. This was afterwards commented upon, enlarged and adorned by Epicurus, so as to form, what was afterwards called the Efiicurean Philosofihy. What the details of this are, may be seen in Diogenes Laertius, in Brucker, and his translator Enfield, as well as in the poem of Lucretius, who has con- fessedly attempted a poetical display of these very doctrines. A general view, comprising a mere sketch of the system of this At»7^ifcECT. III. 5. 9. THE RETINA. 17 sion or the organs of sense, and that our ideas are the motions of these organs: the subsequent cases will illustrate this obser- vation. Miss G-----, a fair young lady, with light eyes and hair, was seized with most violent convulsions of her limbs, with outrageous hiccough, and most vehement efforts to vomit: after near an hour was elapsed this tragedy ceased, and a calm talkative delirium supervened for about another hour; and these relieved each other at intervals during the greatest part of three or four days. After having carefully considered this disease, I thought the convulsions of her ideas less dangerous than those of her muscles; and having in vain attempted to make any opiate continue in her stomach, an ounce of laudanum was rubbed along the spine of her back, and a dram of it was used as an enema; by this medicine a kind of drunken delirium was continued many hours; and when it ceased the convulsions did not return; and the lady continued well many years, except some slighter relapses, which were re- lieved in the same manner. Miss H-----, an accomplished young lady, with light eyes and hair, was seized with convulsions of her limbs, with hiccough, and efforts to vomit more violent than words can express; these continued near an hour, and were succeeded with a cataleptic spasm of one arm, with the hand applied to her head; and after about twenty minutes these spasms ceased, and a. talkative reve- rie supervened for near an hour, from which no violence, which it was proper to use, could awaken her. These periods of con- vulsions, first of the muscles, and then of the ideas, returned twice a day for several weeks; arid were at length removed by great doses of opium, after a great variety of other medicines and appli- cations had been in vain experienced. This lady was subject to frequent relapses, once or twice a year for many years, and was as frequently relieved by the same method. Miss W-----, an elegant young lady, with black eyes and hair, had sometimes a violent pain of her side, at other times a most painful strangury, which were every day succeeded by delirium; which gave a temporary relief to the painful spasms. After the vain exhibition of variety of medicines and applications by dif- ferent physicians, for more than a twelvemonth, she was directed to take some doses of opium, which were gradually increased, by which a drunken delirium was kept up for a day or two, and the pains prevented from returning. A flesh diet, with a little wine or beer, instead of the low regimen she had previously used, in a few weeks completely established her health; which, except a few relapses, has continued for many years. 9. Lastly, as we advance in life ail the parts of the body be- VOL. i. i> IS MOTIONS OF Sect. III. 6. 1. Come more rigid, are rendered less susceptible of new habits of motion, though they retain those that were before established. This is sensibly observed by those who apply themselves late in life to music, fencing, or any of the mechanic arts. In the same manner many elderly people retain the ideas they had learned early in life, but find great difficulty in acquiring new trains of memory; insomuch that in extreme old age we frequently see a forgetfulness of the business of yesterday, and at the same time a circumstantial remembrance of the amusements of their youth; till at length the ideas of recollection and activity of the body gradually cease together,—such is the condition of humanity!— and nothing remains but the vital motions and sensations. VI. 1. In opposition to this doctrine of the production of our ideas, it may be asked, if some of our ideas, like other animal motions, are voluntary, why can we not invent new ones, that have not been received by perception? The answer will be better understood after having perused the succeeding section, where it will be explained, that the muscular motions likewise are origi- nally excited by the stimulus of bodies external to the moving organ; and that the will has only the power of repeating the mo- tions thus excited. 2. Another objector may ask, Can the motion of an organ of sense resemble an odour or a colour? To which I can only an- swer, that it has not been demonstrated that any of our ideas re- semble the objects that excite them; it has generally been believed that they do not; but this shall be discussed at large in Sect. XIV. 3. There is another objection that at first view would seem less easy to surmount. After the amputation of a foot or a finger, it has frequently happened, that an injury being offered to the stump of the amputated limb, whether from cold air, too great pressure, or other accidents, the patient has complained of a sen- sation of pain in the foot or finger, that was cut off. Does not this evince that all our ideas are excited in the brain, and not in the organs of sense? This objection is answered, by observing that our ideas of the shape, place, and solidity of our limbs, are acquired by our organs of touch and of sight,* which are situated in our fingers and eyes, and not by any sensations in the limb it- self. In this case the pain or sensation, which formerly has arisen in the foot or toes, and been propagated along the nerves to the central part of the sensorium, was at the same time accompanied with a visible idea of the shape and place, and with a tangible idea of the solidity of the affected limb: now when these nerves are afterwards affected by any injury done to the remaining Sect III. 6. 4. THE RETINA. 19 stump with a similar degree or kind of pain, the ideas of the shape, place, or solidity of the lost limb, return by association; as these ideas belong to the organs of sight and touch, on which they were first excited. 4. If you wonder what organs of sense can be excited into motion, when you call up the ideas of wisdom or benevolence, which Mr. Locke has termed abstracted ideas; I ask you, by what organs of sense you first became acquainted with these ideas? And the answer will be reciprocal; for it is certain that all our ideas were originally acquired by our organs of sense; for whatever excites our perception must be external to the organ that perceives it, and we have no other inlets to knowledge but by our perceptions: as will be further explained in Section XIV. and XV. on the Productions and Classes of ideas. VII. If our recollection or imagination be not a repetition of animal movements, I ask, in my turn, What is it? You tell me it consists of images or pictures of things. Where is this extensive canvass hung up? or where are the numerous receptacles in which those are deposited ? or to what else in the animal system have they any similitude? That pleasing picture of objects, represented in miniature,on the retina of the eye, seems to have given rise to this illusive ora- tory! It was forgot that this representation belongs rather to the laws of light, than to those of life; and may with equal elegance be seen in the camera obscura, as in the eye; and that the picture vanishes for ever, when the object is withdrawn. 20 ANIMAL CAUSATION. Sect. IV. SECT. IV. LAWS OF ANIMAL CAUSATION. I. The fibres, which constitute the muscles and organs of sense, possess a power of contraction. The circumstances at- tending the exertion of this power of contraction constitute the laws of animal motion, as the circumstances attending the exer- tion of the power of attraction constitute the laws of motion of inanimate matter. II. The spirit of animation is the immediate cause of the con- traction of animal fibres, it resides in the brain and nerves, and is liable to general or partial diminution or accumulation. III. The stimulus of bodies external to the moving organ is the remote cause of the original contractions of animal fibres. IV. A certain quantity of stimulus produces irritation, which is an exertion of the spirit of animation exciting the fibres into contraction. V. A certain quantity of contraction of animal fibres, if it be perceived at all, produces pleasure; a greater or less quantity of contraction, if it be perceived at all, produces pain; these constitute sensation. VI. A certain quantity of sensation produces desire or aver- sion; these constitute volition. VII. All animal motions which have occurred at the same time, or in immediate succession, become so connected, that when one of them is reproduced, the other has a tendency to accompany or succeed it. When fibrous contractions succeed or accompany other fibrous contractions, the connection is termed association; when fibrous contractions succeed sensorial motions, the connection is termed causation; when fibrous and sensorial motions reciprocally introduce each other, it is termed catenation of animal motions. All these connections are said to be produced by habit, that is, by frequent repetition. These laws of animal causation will be evinced by numerous facts, tvhich occur in our daily exertions: and will afterwards be employed to explain the more recondite phenomena of the production, growth, diseases, and decay of the animal system. Sf.ct.V. 1. SENSORIAL FACULTIES. 21 SECT. V. OF THE FOUR FACULTIES OR MOTIONS OF THE SENSORIUM. 1. Four sensorial powers. 2. Irritation, sensation, volition, as- sociation, defined. 3. Sensorial motions distinguished from fibrous motions. 1. The spirit of animation has four different modes of action, or in other words the animal sensorium possesses four different faculties, which are occasionally exerted, and cause all the con- tractions of the fibrous parts of the body. These are the faculty of causing fibrous contractions in consequence of the irritations excited by external bodies, in consequence of the sensations of pleasure or pain, in consequence of volition, and in consequence of the associations of fibrous contractions, with other fibrous con- tractions, which precede or accompany them. These four faculties of the sensorium during their inactive state are termed irritability, sensibility, voluntarity, and associa- bility; in their active state they are termed as above, irritation, sensation, volition, association. 2 Irritation is an exertion or change of some extreme part of the sensorium residing in the muscles or organs of sense, in consequence of the appulses of external bodies. Sensation is an exertion or change of the central parts of the sensorium, or of the whole of it, beginning at some of those ex- treme parts of it, which reside in the muscles or organs of sense. Volition is an exertion or change of the central parts of the sensorium, or of the whole of it, terminating in some of those ex- treme parts of it, which reside in the muscles or organs of sense. Association is an exertion or change of some extreme part of the sensorium residing in the muscles or organs of sense, in consequence of some antecedent or attendant fibrous contrac- tions. 3. These four faculties of the animal sensorium may at the time of their exertions be termed motions without impropriety of language; for we cannot pass from a state of insensibility or inaction to a state of sensibility or of exertion without some change of the sensorium, and every change includes motion. We shall therefore sometimes term the above described facul- ties sensorial motions to distinguish them from fibrous motions; which latter expression includes the motions of the muscles and organs of sense. The active motions of the fibres, whether those of the muscles 22 SENSORIAL FACULTIES. Sect. V. 3. or organs of sense, are probably simple contractions; the fibres being again elongated by antagonist muscles, by circulating fluids, or sometimes by elastic ligaments, as in the necks of quadrupeds. The sensorial motions, which constitute the sen- sations of pleasure or pain, and which constitute volition, and which cause the fibrous contractions in consequence of irritation or of association, are not here supposed to be fluctuations or re- fluctuations of the spirit of animation; nor are they supposed to be vibrations or revibrations, nor condensations or equilibrations of it; but to be changes or motions of it peculiar to life. Sect. VI. 1.1. FIBROUS CONTRACTIONS. 23 SECT. VI. OF THE FOUR CLASSF.S OF FIBROUS MOTIONS. I. Origin of fibrous contractions. II. Distribution of them into four classes, irritative motions, sensitive motions, voluntary mo- tions, and associate motions, defined. I. All the fibrous contractions of animal bodies originate from the sensorium, and resolve themselves into four classes, corres- pondent with the four powers or motions of the sensorium above described, and from which they have their causation. 1. These fibrous contractions were originally caused by the irritations excited by objects, which are external to the moving organ. As the pulsations of the heart are owing to the irritations excited by the stimulus of the blood; and the ideas of perception are owing to the irritations excited by external bodies. 2. But as painful or pleasurable sensations frequently accom- panied those irritations, by habit these fibrous contractions be- came causable by the sensations, and the irritations ceased to be necessary to their production. As the secretion of tears in grief is caused by the sensation of pain; and the ideas of imagination, as in dreams or delirium, are excited by the pleasure or pain, with which they were formerly accompanied. 3. But as the efforts of the will frequently accompanied these painful or pleasurable sensations, by habit the fibrous contractions became causable by volition; and both the irritations and sensa- tions ceased to be necessary to their production. As the delibe- rate locomotions of the body, and the ideas of recollection, as when we will to repeat the alphabet backwards. 4. But as many of these fibrous contractions frequently accom- panied other fibrous contractions, by habit they became causable by their associations with them; and the irritations, sensations, and volition, ceased to be necessary to their production. As the actions of the muscles of the lower limbs in fencing are associated with those of the arms; and the ideas of suggestion are associated with other ideas, which precede or accompany them; as in re- peating carelessly the alphabet in its usual order after having began it. II. We shall give the following names to these four classes of fibrous motions, and subjoin their definitions. 1. Irritative motions. That exertion or change of the senso- rium, which is caused by the appulses of external bodies, either simply subsides, or is succeeded by sensation, or it produces 24 FIBROUS CONTRACTIONS. Sect. VI. 2.2. fibrous motions; it is termed irritation, and irritative motions are those contractions of the muscular fibres, or of the organs of sense, that are immediately consequent to this exertion or change of the sensorium. 2. Sensitive motions. That exertion or change of the senso- rium, which constitutes pleasure or pain, either simply subsides, or is succeeded by volition, or it produces fibrous motions; it is termed sensation, and the sensitive motions are those contractions of the muscular fibres, or of the organs of sense, that are imme- diately consequent to this exertion or change of the sensorium. 3. Voluntary motions. That exertion or change of the senso- rium, which constitutes desire or aversion, either simply subsides, oris succeeded by fibrous motions; it is then termed volition, and voluntary motions are those contractions of the muscular fibres, or of the organs of sense, that are immediately consequent to this exertion or change of the sensorium. 4. Associate motions. That exertion or change of the senso- rium, which accompanies fibrous motions, either simply subsides, or is succeeded by sensation or volition, or it produces other fibrous motions; it is then termed association, and the associate motions are those contractions of the muscular fibres, or of the organs of sense, that are immediately consequent to this exertion or change of the sensorium. S,.;-r. VII. 1.1. IRRITATIVE MOTIONS :s SECT. VII. OF IRRITATIVE MOTIONS. I. 1. Some muscular motions are excited by perpetual irritations. 2. Others more frequently by sensations. 3. Others by volition. Case of involuntary stretchings in paralytic limbs. 4. Some sensual motions are excited by perpetual irritations. 5. Others more frequently by sensation or volition —II. 1. Muscular mo- tions excited by perpetual irritations occasionally become obedient to sensation and to volition. 2. And the sensual motions.—III. 1. Other muscular motions are associated with the irritative ones. 2. And other ideas with irritative ones. Of letters, language, hiero- glyphics. Irritative ideas exist without our attention to them. I. 1. Many of our muscular motions are excited by perpetual irritations, as those of the heart and arterial system by the cir- cumfluent blood. Many other of them are excited by intermitted irritations, as those of the stomach and bowels by the aliment we swallow; of the bile-ducts by the bile; of the kidneys, pancreas, and many other glands, by the peculiar fluids they separate from the blood; and those of the lacteal and other absorbent vessels by the chyle, lymph, and moisture of the atmosphere. These mo- tions are accelerated or retarded, as their correspondent irrita- tions are increased or diminished, without our attention or con- sciousness, in the same manner as the various secretions of fruit, gum, resin, wax, and honey, are produced in the vegetable world, and as the juices of the earth and the moisture of the atmosphere are absorbed by their roots and foliage. 2. Other muscular motions, that are most frequently connect- ed with our sensations, as those of the sphincters of the bladder and anus, and the musculi erectores penis, were originally excit- ed into motion by irritation, for young children make water, and have other evacuations without attention to these circumstances; " et primis etiam ab incunabulus tenduntur saepius puerorum penes, amore nundum expergefacto." So the nipples of young women are liable to become turgid by irritation, long before they are in a situation to be excited by the pleasure of giving milk to the lips of a child. 3. The contractions of the larger muscles of our bodies, that are most frequently connected with volition, were originally ex- cited into action by internal irritations: as appears from the stretching or yawning of all animals after long sleep. In the VOL. I. F. 2G IRRITATIVE .MOTIONS. Sect. VII. 1. 4 beginning of some fevers this irritation of the muscles produces perpetual stretching and yawning; in other periods of fever an universal restlessness arises from the same cause, the patient changing the altitude of his body every minute. The repeated struggles of the foetus in the uterus must be owing to this inter- nal irritation: for the foetus can have no other inducement to move hs limbs but the tacdium or irksomeness of a continued posture. The following case evinces, that the motions of stretching the limbs after a continued attitude are not always owing to the power of the will. Mr. Dean, a mason, of Austry, in Leicestershire, had the spine of the third vertebra of the back enlarged; in some weeks his lower extremities became feeble, and at length quite paralytic: neither the pain of blisters, the heat of fomentations, nor the utmost efforts of the will could produce the least motion in these limbs; yet twice or thrice a day for many months his feet, legs, and thighs, were affected for many minutes with forci- ble stretchings, attended with the sensation of fatigue; and he at length recovered the use of his limbs, though the spine continued protuberant. The same circumstance is frequently seen in a less degree in the common hemiplegia; and when this happens, I have believed repeated and strong shocks of electricity to have been of great advantage. 4. In like manner the various organs of sense are originally excited into motion by various external stimuli adapted to this purpose, which motions are termed perceptions or ideas; and many of these motions during our waking hours are excited by perpetual irritation, as those of the organs of hearing and of touch. The former by the constant low indistinct noises that murmur around us, and the latter by the weight of our bodies on the parts which support them; and by the unceasing variations of the heat, moisture, and pressure of the atmosphere; and these sensual mo- tions, precisely as the muscular one above mentioned, obey their correspondent irritations without our attention or conscious- ness. 5. Other classes of our ideas are more frequently excited by our sensations of pleasure or pain, and others by volition: but that these have all been originally excited by stimuli from exter- nal objects, and only vary in their combinations or separations, has been fully evinced by Mr. Locke: and are by him termed the ideas of perception in contradiction to those, which he calls the ideas of reflection. II. 1. These muscular motions, that are excited by perpetual irritation, are nevertheless occasionally excitable by the sensations of pleasure or pain, or by volition; as appears by the palpita- Sect. VII. 2. 2. IRRITATIVE MOTIONS. 27 tion of the heart from fear, the increased secretion of saliva at the sight of agreeable food, and the glow on the skin of those who areashamed. There is an instance told in the Philosophi- cal Transactions of a man, who could for a time stop the motion of his heart when he pleased; and Mr. D. has often told me, he could so far increase the peristaltic motion of his bowels by voluntary efforts, as to produce an evacuation by stool at any time in half an hour. 2. In like manner the sensual motions, or ideas, that are ex- cited by perpetual irritation, are nevertheless occasionally excit- ed by sensation or volition; as in the night when we listen under the influence of fear, or from voluntary attention, the motions excited in the organ of hearing by the whispering of the air in our room, the pulsation of our own arteries, or the faint beating of a distant watch, become objects of perception. III. 1. Innumerable trains or tribes of other motions are as- sociated with these muscular motions which are excited by irri- tation; as by the stimulus of the blood in the right chamber of the heart, the lungs are induced to expand themselves; and the pectoral, and intercostal muscles, and the diaphragm, act at the same time by their associations with them. And when the pha- rinx is irritated by agreeable food, the muscles of deglutition are brought into action by association. Thus when a greater light falls on the eye, the iris is brought into action without our atten- tion, and the cilinary process, when the focus is formed before or behind the retina, by their associations of the increased irri- tative motions of the organ of vision. Many common actions of life are produced in a similar manner. If a fly settle on my fore- head, whilst I am intent on my present occupation, I dislodge it with my finger, without exciting my attention or breaking the train of my ideas. 2. In like manner the irritative ideas suggest to us many other trains or tribes of ideas that are associated with them. On this kind of connexion, language, letters, hieroglyphics, and every kind of symbol, depend. The symbols themselves produce irri- tative ideas, or sensual motions, which we do not attend to; and other ideas, that are succeeded by sensation, are excited by their association with them. And as these irritative ideas make up a part of the chain of our waking thoughts, introducing other ideas that engage our attention, though themselves are unattended to, we find it very difficult to investigate by what steps many of our hourly trains of ideas gain their admittance. It may appear paradoxical, that ideas can exist, and not be at- l< nded to; but all our perceptions are ideas excited by irrita- tion, and succeeded by sensation. Now when these ideas excit- 2d IRRITATIVE MOTIONS. Sect. VII. 3. 2. ed by irritation give us neither pleasure nor pain, we cease to attend to them. Thus whilst I am walking through that grove before my window, I do not run against the trees or the benches, though my thoughts are strenuously exerted on some other ob- ject. This leads us to a distinct knowledge of irritative ideas, for the idea of the. tree or bench which I avoid, exists on my re- tina, and induces by association the action of certain locomotive muscles; though neither itself nor the actions of those muscles en- gage my attention. Thus whilst we are conversing on this subject, the tone, note, and articulation of every individual word forms its correspondent irritative idea on the organ of hearing; but we only attend to the associated ideas, that are attached by habit to these irritative ones, and are succeeded by sensation; thus when we read the words " printing-press" we do not attend to the shape, size, or existence of the letters which compose these words, though each of them excites a correspondent irritative motion of our organ of vision, but they introduce by association our idea of the most useful of modern inventions^ the capacious reservoir of human knowledge, whose branching streams diffuse sciences, arts, and morality, through all nations and all ages. Sect. VIII. 1.1. SENSITIVE MOTIONS. 29 SECT. VIII. OF SENSITIVE MOTIONS. I. 1. Sensitive muscular motions were originally excited into action by irritation. 2. And sensitive sensual motions, ideas of ima- gination, dreams.—II. 1. Sensitive muscular motions are oc- casionally obedient to volition. 2. And sensitive sensual motions. —III. 1. Other muscular motions are associated with the sen- sitive ones. 2. And other sensual motions. I. 1. Many of the motions of our muscles, that are excited into action by irritation, are at the same time accompanied with painful or pleasurable sensations; and at length become by habit causable by the sensations. Thus the motions of the sphincters of the bladder and anus were originally excited into action "by irritation; for young children give no attention to these evacuations; but as soon as they become sensible of the inconvenience of obeying these irritations, they suffer the water or excrement to accumulate, till it disagreeably affects them; and the action of those sphinctures is then in consequence of this disagreeable sensation. So the secretion of saliva, which in young children is copiously produced by irritation, and drops from their mouths, is frequently attended with the agreeable sensation produced by the mastication of tasteful food; till at length the sight of such food to a hungry person excites into action these salival glands; as is seen in the slavering of hungry dogs. The motions of those muscles, which are affected by lascivi- ous ideas, and those which are exerted in smiling, weeping, starting from fear, and winking at the approach of danger to the eye, and at times the actions of every large muscle of the body become causable by our sensations. And all these motions are performed with strength and velocity in proportion to the energy of the sensation that excites them, and the quantity of sensorial power. 2. Many of the motions of our organs of sense, or ideas, that were originally excited into action by irritation, become in like manner more frequently causable by our sensations of pleasure or pain. These motions are then termed the ideas of imagina- tion, and make up all the scenery and transactions of our dreams. Thus when any painful or pleasurable sensations pos- sess us, as of love, anger, fear; whether in our sleep or waking hours, the ideas that have been formerly excited by the objects 30 SENSITIVE MOTIONS. Sect. VIII. 2. 1. of these sensations, now vividly recur before us by their con- nexion with these sensations themselves. So the fair smiling virgin, that excited your love by her presence, whenever that Sensation recurs, rises before you in imagination; and that with all the pleasing circumstances that had before engaged your at- tention. And in sleep, when you dream under the influence of fear, all the robbers, fires, and precipices, that you formerly have seen or heard of, arise before you with terrible vivacity. All these sensual motions, like the muscular ones above men- tioned, are performed with strength and velocity in proportion to the energy of the sensation of pleasure or pain, which excites them, and the quantity of sensorial power. II. 1. Many of these muscular motions above described, that are most frequently excited by our sensations, are nevertheless occasionally causable by volition; for we can smile or frown spontaneously, can make water before the quantity or acrimony of the urine produces a disagreeable sensation, and can volun- tarily masticate a nauseous drug, or swallow a bitter draught, though our sensation would strongly dissuade us. 2. In like manner the sensual motions, or ideas, that are most frequently excited by our sensations, are nevertheless occasion- ally causable by volition, as we can spontaneously call up our last night's dream before us, tracing it industriously step by step through all its variety of scenery and transactions; or can volun- tarily examine or repeat the ideas, that have been excited by our disgust or admiration. III. 1. Innumerable trains or tribes of motions are associated with these sensitive muscular motions above mentioned; as when a drop of water falling into the wind-pipe disagreeably affects the air-vessels of the lungs, they are excited into violent action; and with these sensitive motions are associated the actions of the pec- toral and intercostal muscles, and the diaphragm; till by their united and repeated successions the drop is returned through the larinx. The same occurs when any thing disagreeably affects the nostrils, or the stomach, or the uterus; variety of muscles are excited by association into forcible action, not to be sup- pressed by the utmost efforts of the will; as in sneezing, vomit- ing, and parturition. 2. In like manner with these sensitive sensual motions, or ideas of imagination; are associated many other trains or tribes of ideas, which by some writers of metaphysics have been class- ed under the terms of resemblance, causation and contiguity; and will be more fully treated of hereafter. Skct. IX. 1. 1. VOLUNTARY MOTIONS. 31 SECT. IX. OF VOLUNTARY MOTIONS. I. 1. Voluntary muscular motions are originally excited by irrita- tions. 2. And voluntary ideas. Of reason.—II. 1. Voluntary muscular motions are occasionally causable by sensations. 2. And voluntary ideas.—III. 1. Voluntary muscular motions are occasionally obedient to irritations. 2. And voluntary ideas.—IV. 1. Voluntary muscular motions are associated with other muscular motions. 2- And voluntary ideas. When pleasure or pain affect the animal system, many of its motions both muscular and sensual are brought into action; as was shewn in the preceding section, and were called sensitive motions. The general tendency of these motions is to arrest and to possess the pleasure, or to dislodge or avoid the pain: but if this cannot immediately be accomplished, desire or aversion is pro- duced, and the motions in consequence of this new faculty of the sensorium are called voluntary. I. 1. Those muscles of the body that are attached to bones, have in general their principal connexions with volition, as I move my pen or raise my body. These motions were originally ex- cited by irritation, as was explained in the section on that sub- ject, afterwards the sensations of pleasure or pain, that accom- panied the motions thus excited, induced a repetition of them; and at length many of them were voluntarily practised in suc- cession or in combination for the common purposes of life, as in learning to walk, or to speak; and are performed with strength and velocity in proportion to the energy of the volition, that ex- cites them, and the quantity of sensorial power. 2. Another great class of voluntary motions consists of the ideas of recollection. We will to repeat a certain train of ideas, as of the alphabet backwards; and if any ideas that do not be- long to this intended train, intrude themselves by other con- nexions, we will to reject them, and voluntarily persist in the de- termined train. So at my approach to a house which I have but once visited, and that at the distance of many months, I will to recollect the names of the numerous famih I expect to see there, and I do recollect them. On this voluntary recollection of ideas our faculty of reason depends, as it enables us to acquire an idea of the dissimilitude of any two ideas. Thus if you voluntarily produce the idea of a right-angled triangle, and then of a square; and after having 32 VOLUNTARY MOTIONS. Sect. IX 2. 1. excited these ideas repeatedly, you excite the idea of their differ- ence, which is that of another right angled triangle inverted over the former; you are said to reason upon this subject, or to com- pare your ideas. These ideas of recollection, like the muscular motions above mentioned, were originally excited by the irritation of external bodies, and were termed ideas of perception; afterwards the pleasure or pain, that accompanied these motions, induced a repe- tition of them in the absence of the external body, by which they were first excited: and then they were termed ideas of imagina- tion. At length they become voluntarily practised in succession or in combination for the common purposes of life; as when we make ourselves masters of the history of mankind, or of the sciences they have investigated; and are then called ideas of re- collection; and are performed with strength and velocity in pro- portion to the energy of the volition that excites them, and the quantity of sensorial power. II. 1. The muscular motions above described, that are most frequently obedient to the will, are nevertheless occasionally causable by painful or pleasurable sensation, as in the starting from fear, and the contraction of the calf of the leg in the cramp. 2. In like manner the sensual motions, or ideas, that are most frequently connected with volition, are nevertheless occasionally causable by painful or pleasurable sensation. As the histories of men, or the description of places, which we have voluntarily taken pains to remember, sometimes occur to us in our dreams. III. 1. The muscular motions that are generally subservient to volition, are also occasionally causable by irritation, as in stretching the limbs after sleep, and yawning. In this manner a contraction of the arm is produced by passing the electric fluid from the Leyden phial along its muscles; and that even though the limb is paralytic. The sudden motion of the arm produces a disagreeable sensation in the joint, but the muscles seem to be brought into action simply by irritation. 2. The ideas, that are generally subservient to the will, are in like manner occasionally excited by irritation; as when we view again an object, we have before well studied, and often recollected. IV. 1. Innumerable trains or tribes of motions are associated with these voluntary muscular motions above mentioned; as when I will to extend my arm to a distant object, some other muscles are brought into action, and preserve the balance of my body. And when I wish to perform any steady exertion, as in Sect. IX. 4. 2. VOLUNTARY MOTIONS. 33 threading a needle, or chopping with an ax, the pectoral muscles are at the same time brought into action to preserve the trunk of the body motionless, and we cease to respire for a time. 2. In like manner the voluntary sensual motions, or ideas of recollection, are associated with many other trains or tribes of ideas. As when I voluntarily recollect a Gothic window, that I saw some time ago, the whole fronts of the cathedral occurs to me at the same time. vol. r 31 ASSOCIATE MOTIONS. Sect. X. 1. 1 SECT. X. OF ASSOCIATE MOTIONS. I. 1. Many muscular motions excited by irritations in trains or tribes become associated. 2. And many ideas.—II. 1. Many sensitive muscular motions become associated. 2. And many sen- sitive ideas.—HI. 1. Many voluntary muscular motions become associated. 2. And then become obedient to sensation or irrita- tion. 3. And many voluntary ideas become associated. All the fibrous motions, whether muscular or sensual, which are frequently brought into action together, either in combined tribes, or in successive trains, become so connected by habit, that when one of them is reproduced the others have a tendency to succeed or accompany it. I. 1. Many of our muscular motions were originally excited in successive trains, as the contractions of the auricles and of the ventricles of the heart; and others in combined tribes, as the various divisions of the muscles which compose the calf of the leg, which were originally irritated into synchronous action by the taedium or irksomeness of a continued posture. By frequent re- petitions these motions acquire associations, which continue dur- ing our lives, and even after the destruction of the greatest part of the sensorium; for the heart of a viper or frog wili continue to pulsate long after it is taken from the body; and when it has entirely ceased to move, if any part of it is goaded with a pin, the whole heart will again renew its pulsations. This kind of connexion we shall term irritative association, to distinguish it from sensitive and voluntary associations. 2. In like manner, many of our ideas are originally excited in tribes; as all the objects of sight, after we become so well ac- quainted with the laws of vision, as to distinguish figure and dis- tance as well as colour; or in trains, as while we pass along the objects that surround us. The tribes thus received by irritation become associated by habit, and have been termed complex ideas by the writers of metaphysics, as this book, or that orange. The trains have received no particular name, but these are alike as- sociations of ideas, and frequently continue during our lives. So the taste of a pine-apple, though we eat it blindfold, recals the colour and shape of it; and we can scarcely think on solidity without figure. II. 1. By the various efforts of our sensations to acquire or avoid their objects, many muscles are daily brought into succes- sect. X. 2.2. ASSOCIATE MOTIONS. 35 sive or synchronous actions; these become associated by habit, and are then excited together with great facility, and in many instances gain indissoluble connexions. So the play of puppies and kittens is a representation of their mode of fighting or of taking their prey; and the motions of the muscles necessary for those purposes, become associated by habit, and gain a great adroitness of action by these early repetitions; so the motions of the abdominal muscles, which were originally brought into concurrent action with the protusive motion of the rectum or bladder by sensation, become so conjoined with them by habit, that they not only easily obey these sensations, occasioned by the stimulus of the excrement and urine, but are brought into violent and unrestrainable action in the strangury and tenesmus. This kind of connexion we shall term sensitive association. 2. So many of our ideas, that have been excited together or in succession by our sensations, gain synchronous or successive associations, that are sometimes indissoluble but with life. Hence the idea of an inhuman or dishonourable action perpetually calls up before us the idea of the wretch that was guilty of it. And hence those unconquerable antipathies are formed, which some people have to the sight of peculiar kinds of food, of which in their infancy they have eaten to excess, or by constraint. III. 1. In learning any mechanic art, as music, dancing, or the use of the sword, we teach many of our muscles to act to- gether or in succession by repeated voluntary efforts: which by habit become formed into tribes or trains of association, and serve all our purposes with great facility, and in some instances acquire an indissoluble union. These motions are gradually formed into a habit of acting together by a multitude of repeti- tions, whilst they are yet separately causable by the will, as is evident from the long time that is taken up by children in learn- ing to walk and to speak; and is experienced by every one, when he first attempts to skate upon the ice or to swim: these we shall term voluntary associations. 2. All these muscular movements, when they are thus associ- ated into tribes or trains, become afterwards not only obedient to volition, but to the sensations and irritations; and the same movement composes a part of many different tribes or trains of motion. Thus a single muscle, when it acts in consort with its neighbours on one side, assists to move the limb in one direction; and in another, when it acts with those in its neighbourhood on the other side; and in other directions, when it acts separately or jointly with those that lie immediately under or above it; and all these with equal facility after their associations have been well established. 36 ASSOCIATE MOTIONS. Sect. X. 3. J. The facility, with which each muscle changes from one asso- ciated tribe to another, and that either backwards or forwards, is well observable in the muscles of the arm in moving the wind- lass of an air-pump; and the slowness of those muscular move- ments, that have not been associated by habit, may be experi- rienced by anyone who shall attempt to saw the air quick perpen- dicularly with one hand, and horizontally with the other at the same time. 3. In learning every kind of science we voluntarily associate many tribes and trains of ideas, which afterwards are ready for all the purposes either of volition, sensation, or irritation; and in some instances acquire indissoluble habits of acting together, so as to affect our reasoning, and influence our actions. Hence the necessity of a good education. These associate ideas are gradually formed into habits of act- ing together, by frequent repetition, while they are yet separate- ly obedient to the will; as is evident from the"difficulty we expe- rience in gaining so exact an idea of the frontof St. Paul's church, as to be able to delineate it with accuracy, or in recollecting a poem of a few pages. And these ideas, thus associated into tribes, not only make up the parts of the trains of volition, sensation, and irritation; but the same idea composes a part of many different tribes and trains of ideas. So the simple idea of whiteness composes a part of the complex idea of snow, milk, ivory; and the complex idea of the letter A composes a part of the several associated trains of ideas that make up the variety of words, into which this letter enters. The numerous trains of these associated ideas are divided by Mr. Hume into three classes, which he has termed contiguity, causation, and resemblance. Nor should we wonder to find them thus connected together, since it is the business of our lives to dispose them into these three classes; and we become valuable to ourselves and our friends, as we succeed in it. Those who have combined an extensive class of ideas by the contiguity of time or place, are men learned in the history of mankind, and of the sciences they have cultivated. Those who have connect- ed a great class of ideas of resemblance, possess the source of the ornaments of poetry and oratory, and of all rational analo- gy. While those who have connected great classes of ideas of causation, are furnished with the powers of producing effects. These are the men of active wisdom, who lead armies to victory, and kingdoms to prosperity; or discover and improve the sci- ences, which meliorate and adorn the condition of humanity. Sect XI. 1. SENSORIAL ACTIONS. 37 SECT. XI. ADDITIONAL OBSERVATIONS ON THE SENSORIAL POWERS. I. Stimulation is of various kinds, adapted to the organs of sense, to the muscles, to hollow membranes and glands. Some objects irritate our senses by repeated impulses.—II. 1. Sensation and volition frequently affect the whole sensorium. 2. Emotions, pas- sions, appetites. 3. Origin of desire and aversion. Criterion of voluntary actions, difference of brutes and men. 4. Sensibility and voluntarily.—III. Associations formed before nativity, irri- tative motions mistaken for associated ones. Imtation. I. The various organs of sense require various kinds of stim- ulation to excite them into action; the particles of light pene- trate the cornea and humours of. the eye, and then irritate the naked retina; sapid particles, dissolved or diffused in water or saliva, and odorous ones, mixed or combined with the air, irri- tate the extremities of the nerves of taste and smell; which ei- ther penetrate, or are expanded on the membranes of the tongue and nostrils; the auditory nerves are stimulated by the vibra- tions of the atmosphere communicated by means of the tympa- num and of the fluid, whether of air or of water, behind it; and the nerves of touch by the hardness of surrounding bodies, though the cuticle is interposed between these bodies and the medulla of the nerve. As the nerves of the senses have each their appropriated ob- jects, which stimulate them into activity; so the muscular fibres, which are the terminations of other sets of nerves, have their pe- culiar objects, which excite them into action; the longitudinal muscles are stimulated into contraction by extension, whence the stretching or pandiculation after a long continued posture, during which they have been kept in a state of extension; and the hollow muscles are excited into action by distention, as those of the rectum and bladder are induced to protrude their contents from their sense of the distention rather than of the acrimony of those contents. There are other objects adapted to stimulate the nerves, which terminate in variety of membranes, and those especially which form the terminations of canals; thus the preparations of mercury particularly affect the salivary glands, ipecacuanha the stomach, aloe the sphincter of the anus, cantharides that of 38 SENSORIAL ACTIONS. Sect. XI. 2. I the bladder, and lastly every gland of the body appears to be in- dued with a kind of taste, by which it selects or forms each its peculiar fluid from the blood; and by which it is irritated into activity. Many of these external properties of bodies, which stimulate our organs of sense, do not seem to affect this by a single im- pulse, buf by repeated impulses; as the nerve of the ear is pro- bably not excitable by a single vibration of air, nor the optic nerve by a single particle of light; which circumstance produces some analogy between those two senses, at the same time the solidity of bodies is perceived by a single application of a solid body to the nerves of touch, and that even through the cuticle; and we are probably possessed of a peculiar sense to distinguish the nice degrees of heat and cold. The senses of touch and of hearing acquaint us with the me- chanical impact and vibration of bodies, those of smell and taste seem to acquaint us with some of their chemical properties, while the senses of vision and of heat acquaint us with the exist- ence of their peculiar fluids. Sensation and Volition. II. Many motions are produced by pleasure or pain, and that even in contradiction to the power of volition, as in laughing, or in the stranguary; but as no name has been given to pleasure or pain, at the time it is exerted so as to cause fibrous motions, we have used the term sensation for this purpose; and mean it to bear the same analogy to pleasure and pain, that the word vo- lition does to desire and aversion. 1. It was mentioned in the fifth Section, that, what we have termed sensation is a motion of the central parts, or of the whole sensorium, beginning at some of the extremities of it. This ap- pears first, because our pains and pleasures are always caused by our ideas or muscular motions, which are the motions of the ex- tremities of the sensorium. And, secondly, because the sensation of pleasure or pain frequently continues some time after the ideas or muscular motions which excited it have ceased: for we often feel a glow of pleasure from an agreeable reverie, for many mi- nutes after the ideas, that were the subject of it, have escaped our memory; and frequently experience a dejection of spirits without being able to assign the cause of it but by much recol- lection. When the sensorial faculty of desire or aversion is excited so as to cause fibrous motions, it is termed volition; which is said in Sect. V. to be a motion of the central parts; or of the whole Sect. XI. 2. 2. SENSORIAL ACTIONS. 39 sensorium, terminating in some of the extremities of it. This appears, first, because our desires and aversions always termi- nate in recollecting and comparing our ideas, or in exerting our muscles; which are the motions of the extremities of the senso- rium. And, secondly, because desire or aversion begins, and frequently continues for a time in the central parts of the sensor riurn, before it is peculiarly exerted at the extremities of it; for we sometimes feel desire or aversion without immediately know- ing their objects, and in consequence without immediately exert- ing any of our muscular or sensual motions to attain them: as in the beginning of the passion of love, and perhaps of hunger, or, in the ennui of indolent people. Though sensation and volition begin to terminate at the ex- tremities or central parts of the sensorium, yet the whole of it is frequently influenced by the exertion of these faculties, as ap- pears from their effects on the external habit: for the whole skin is reddened by shame, and an universal trembling is produced by fear: and every muscle of the body is agitated in angry people by the desire of revenge. There is another very curious circumstanee, which shews that sensation and volition are movements of the sensorium in con- trary directions; that is, that volition begins at the central parts of it; and proceeds to the extremities: and that sensation begins at the extremities and proceeds to the central parts: I mean that these two sensorial faculties cannot be strongly exerted at the same time; for when we exert our volition strongly, we do not attend to pleasure or pain; and conversely, when we are strongly affected with the sensation of pleasure or pain, we use no volition. As will be further explained in Section XVIII. on sleep, and Section XXXIV. on volition. 2. All our emotions and passions seem to arise out of the ex- ertions of these two faculties of the animal sensorium. Pride, hope, joy, are the names of particular pleasures: shame, despair, sorrow, are the names of peculiar pains: and love, ambition, avarice, of particular desires: hatred, disgust, fear, anxiety, of particular aversions. Whilst the passion of anger includes the pain from a recent injury, and the aversion to the adversary that occasioned it. And compassion is the pain we experience at the sight of misery, and the desire of relieving it. There is another tribe of desires, which is commonly term- ed appetites, and are the immediate consequences of the absence of some irritative motions. Those, which arise from defect of internal irritations, have proper names conferred upon them, as hunger, thirst, lust, and the desire of air, when our respiration is impaired by noxious vapours; and of warmth,, when we are 40 SENSORIAL ACTIONS. Sect. XI. 2. s. exposed to too great a degree of cold. But those, whose stimu- li are external to the body, are named from the objects, which are by nature constituted to excite them; these desires originate from our past experience of the pleasurable sensations they oc- casion, as the smell of a hyacinth, or the taste of a pine apple. Whence it appears that our pleasures and pains are at least as various and as numerous as our irritations; and that our desires and aversions must be as numerous as our pleasures and pains. And that as sensation is here used as a general term for our nu- merous pleasures and pains, when they produce the contractions of our fibres; so volition is the general name for our desires and aversions, when they produce fibrous contractions. Thus, when a motion of the central parts, or of the whole sensorium, ter- minates in the exertion of our muscles, it is generally called vo- luntary action; when it terminates in the exertion of our ideas, it is termed recollection, reasoning, determining. 3. As the sensations of pleasure and pain are originally intro- duced by the irritations of external objects; so our desires and aversions are originally introduced by those sensations; for when the objects of our pleasures or pains are at a distance, and we cannot instantaneously possess the one, nor avoid the other, then desire or aversion is produced, and a voluntary exertion of our ideas or muscles succeeds. The pain of hunger excites you to look out for food, the tree that shades you presents its odoriferous fruit before your eves, you approach, pluck, and eat. The various movements of walking to the tree, gathering the fruit, and masticating it, are associated motions introduced by their connexion with sensation; but if from the uncommon height of the tree, the fruit be inaccessible, and you are prevented from quickly possessing the intended pleasure, desire is produ- ced. The consequence of this desire is, first, a deliberation about the means to gain the object of pleasure in process of time, as it cannot be produced immediately; and, secondly, the mus- cular action necessary for this purpose. You voluntarily call up all your ideas of causation, that are related to the effect you desire, and voluntarily examine and compare them, and at length determine whether to ascend the tree, or to gather stones from the neighbouring brook, is easier to practise, or more promising of success; and, finally, you gather the stones, and repeatedly sling them to dislodge the fruit. Hence then we gain a criterion to distinguish voluntary acts or thoughts from those caused by sensation. As the former are always employed about the means to acquire pleasurable objects, or the means to avoid painful ones; while the latter are em- Sect. XI 2.4. SENSORIAL ACTIONS. 41 ployed in the possession of those, which are already in our power. Hence the activity of this power of volition produces the great difference between the human and the brute creation. The ideas and the actions of brutes are almost perpetually employed about their present pleasures, or their present pains; and, except in the few instances which are mentioned in Section XVI. on instinct, they seldom busy themselves about the means of procuring future bliss, or of avoiding future misery; so that the acquiring of lan- guages, the making of tools, and labouring for money, which are all only the means to procure pleasures; and the praying to the Deity, as another means to procure happiness, are characteristic of human nature. 4. As there are many diseases produced by the quantity of the sensation of pain or pleasure being too great or too little; so are there diseases produced by the susceptibility of the constitution to motions causable by these sensations being too dull or too vivid. This susceptibility of the system to sensitive motions is termed sensibility, to distinguish it from sensation, which is the actual existence or exertion of pain or pleasure. Other classes of diseases are owing to the excessive prompti- tude, or sluggishness of the constitution to voluntary exertions, as well as to the quantity of desire or of aversion. This suscepti- bility of the system to voluntary motions is termed voluntarity, to distinguish it from volition, which is the exertion of desire or aversion; these diseases will be treated of at length in the pro- gress of the work. Association. III. 1. It is not easy to assign a cause, why those animal move- ments, that have once occurred in succession, or in combination, should afterwards have a tendency to succeed or accompany each other. It is a property of animation, and distinguishes this order of being from the other productions of nature. When a child first wrote the word man, it was distinguished in his mind into three letters, and those letters into many parts of letters; but by repeated use the word man becomes to his hand in writing it, as to his organs of speech in pronouncing it, but one movement without any deliberation, or sensation, or irritation, in- terposed between the parts of it. And as many separate motions of our muscles thus become united, and form, as it were, one motion; so each separate motion before such union may be con- ceived to consist of many parts or spaces moved through; and perhaps even the individual fibres of our muscles have thus gra- VOL. I. R 42 SENSORIAL ACTIONS. Sf.ct. XI. 3.2, dually been brought to act in concert, which habits began to be acquired as early as the very formation of the moving organs, long before the nativity of the animal; as explained in the Sect. XVI. 2. on instinct. 2. There are many motions of the body, belonging to the irri- tative class, which might, by a hasty observer, be mistaken for as- sociated ones; as the peristaltic motion of the stomach and intes- tines, and the contractions of the heart and arteries, might be sup- posed to be associated with the irritative motions of their nerves of sense, rather than to be excited by the irritation of their muscular fibres by the distension, acrimony, or momentum of the blood. So the distension or elongation of muscles by objects external to them irritates them into contraction, though the cuticle or other parts may intervene between the stimulating body and the con- tracting muscle. Thus a horse voids his excrement when its weight or bulk irritates the rectum or sphincter ani. These muscles act from the irritation of distension, when he excludes his excrement, but the muscles of the abdomen and diaphragm are brought into motion by association with those of the sphincter and rectum. SifT XH. OF STIMULUS, &c. 43 SECT. XII. OF STIMULUS, SENSORIAL EXERTION, AND FIBROUS CONTRACTION. I. Of fibrous contraction. 1. Two particles of a fibre cannot ap- proach without the intervention of something, as in magnetism, electricity, elasticity. Spirit of life is not electric ether. Galva- nVs experiments. 2. Contraction of a fibre. 3. Relaxation suc- ceeds. 4. Successive contractions, with intervals. Quick pulse from debility, from paucity of blood. Weak contractions per- formed in less time, and with shorter intervals. 5. Last situa- tion of tlie fibres continues after contraction. 6. Contraction greater than usual induces pleasure or pain. 7. Mobility of the fibres uniform. Quantity of sensorial power fluctuates. Consti- tutes excitability.—II. Of sensorial exertion. 1. Animalmotion includes stimulus, sensorial power, and contractile fibres. The sensorial faculties act separately or conjointly. Stimulus of four kinds. Strength and weakness defined. Sensorial power perpe- tually exhausted and renewed. Weakness from defect of stimulus. From defect of sensorial power, the direct and indirect debility of Dr. Brown. Why we become warm in Buxton bath after a time, and see well after a time in a darkish room. Fibres may act vio- lently, or with their whole force, amd yet feebly. Great exertion in inflammation explained. Great muscular force of some insane people. 2. Occasional accumulation of sensorial power in muscles subject to constant stimulus. In animals sleeping in winter. In eggs, seeds, schirrhous tumours, tendons, bones. 3. Great exer- tion introduces pleasure or pain. Inflammation. Libration of the system between torpor and activity. Fever fits. 4. Desire and aversion introduced. Excess of volition cures fevers.—III. Of repeated stimulus. 1. A stimulus repeated too frequently loses effect. As opium, wine, grief. Hence old age. Opium and aloes in small doses. 2. A stimulus not repeated too frequently docs not lose effect. Perpetual movement of the vital organs. 3. A stimulus repeated at uniform times produces greater effect. Ir- ritation combined with association. 4. A stimulus repeated fre- quently and uniformly may be withdrawn, and the action of the organ will continue. Hence the bark cures agues, and strengthens weak constitutions. 5. Defect of stimulus repeated at certain intervals causes fever-fits. 6. Stimulus long applied ceases to act a second time. 7. If a stimulus excites sensation in an organ not usually excited into sensation, inflammation is produced.— IV. Of stimulus greater than natural. 1. A stimulus greater than natural diminishes the quantity of sensorial power ingeneral. 41 OF STIMULUS Sect. XII. 1. 1. 2. In particular organs. 3. Induces the organ into spasmodic aetions. 4. Induces the antagonist fibres into action. 5. Induces the organ into convulsive or fixed spasms. 6. Produces paralysis of the organ.—V. Of stimulus less than natural. 1. Stimulus less than natural occasions accumulation of sensorial power in general. 2. In particular organs, flushing of the face in a frosty morning. In fibres subject to perpetual stimulus only. Quantity of sensorial power inversely as the stimulus. 3. Induces pain. As of cold, hunger, head-ache. 4. Induces more feeble and frequent contractions. As in low fevers. Which are frequently owing to deficiency of sensorial power, rather than to deficiency of stimulus. 5. Inverts successive trains of motion. Inverts ideas. 6. Induces paralysis and death.—VI. Cure of increased exer- tion. 1. Natural cure of exhaustion of sensorial power. 2. Decrease the irritations. Venesection. Cold. Abstinence. 3. Prevent the previous cold fit. Opium. Bark. Warmth. Anger. Surprise. 4. Excite some other part of the system. Opium and warm bath relieve pains both from defect and from excess of stimulus. 5. First increase the stimulus above, and then de- crease it beneath the natural quantity.—VII. Cure of decreased exertion. 1. Natural cure by accumulation of sensorial power. Ague-fits. Syncope. 2. Increase the stimulation, by wine, opium, given so as not to intoxicate. Cheerful ideas. 3. Change the kinds of stimulus. 4. Stimulate the associated organs. Blis- ters of use in heart-burn, and cold extremities. 5. Decrease the stimulation for a time, cold bath. 6. Decrease the stimulation below natural, and then increase it above natural. Bark after emetics.^ Opium after venesection. Practice of Sydenham in cldorosis. 7. Prevent unnecessary expenditure of sensorial pow- er. Decumbent posture, silence, darkness. Pulse quickened by rising out of bed. 8. To the greatest degree of quiescence apply the least stimulus. Otherwise paralysis or inflammation of the organ ensues. Gin, wine, blisters, destroy by too great stimula- tion in fevers with debility. Intoxicatian in the slightest degree succeeded by debility. Golden rule for determining the best de- gree of stimulus in low fevers. Another golden ride for determin- ing the quantity of spirit which those, who are debilitated by drinking it, may safely omit.—VIII. Conclusion. Some stimuli increase the production of sensorial power. I. Of fibrous contractions. 1. If two particles of iron lie near each other without motion and afterwards approach each other; it is reasonable to con- clude that something besides the iron particles is the cause of Sect. XII 1. 1. AND EXERTION. 45 their approximation; this invisible something is termed magne- tism. In the same manner, if the particles, which compose an animal muscle, do not touch each other in the relaxed state of the muscle, and are brought into contact during the contraction of the muscle, it is reasonable to conclude, that some other agent is the cause of this new approximation. For nothing can act, where it does not exist; for to act includes to exist; and there- fore the particles of the muscular fibre (which in its state of re- laxation are supposed not to touch) cannot effect each other without the influence of some intermediate agent; this agent is here termed the spirit of animation, or sensorial power, but may with equal propriety be termed the power, which causes con- traction; or may be called by any other name, which the reader may choose to affix to it. The contraction of a muscular fibre may be compared to the following electric experiment, which is here mentioned not as a philosophical analogy, but as an illustration or simile to facilitate the conception of a difficult subject. Let twenty very small Leyden phials, properly coated, be hung in a row by fine silk threads, at a small distance from each other; let the internal charge of one phial be positive, and of the other negative alter- nately, if a communication be made from the internal surface of the first to the external surface of the last in the row, they will all of them instantly approach each other, and thus shorten a line that might connect them like a muscular fibre. See Botanic Garden, P. I. Canto I. 1. 202. note on Gymnotus. The attractions of electricity or of magnetism do not apply philosophically to the illustration of the contraction of animal fibres, since the force of those attractions increases in some pro- portion inversely as the distance, but in muscular motion there appears no difference in velocity or strength during the begin- ning or end of the contraction, but what may be clearly ascribed to the varying mechanic advantage in the approximation of one bone to another. Nor can muscular motion be assimilated with greater plausibility to the attraction of cohesion or elasticity; for in bending a steel spring, as a small sword, a less force is re- quired to bend it the first inch than the second; and the second than the third; the particles of steel on the convex side of the bent spring endeavouring to restore themselves more powerfully the further they are drawn from each other. See Botanic Gar- den, P. I. addit. Note XVIII. I am aware that this may be explained another way, by sup- posing the elasticity of the spring to depend more on the com- pression of the particles on the concave side than on the exten- sion of them on the convex side; and by supposing the elasticity 4t> OF STIMULUS Sect. XII. 1. 2. of the elastic gum to depend more on the resistance to the lateral compression of its particles than to the longitudinal extension ol them. Nevertheless in muscular contraction, as above observ- ed, there appears no difference in the velocity or force of it at its commencement or at its termination; from whence we must conclude that animal contraction is governed by laws of its own, and not by those of mechanics, chemistry, magnetism, or elec- tricity. On these accounts I do not think the experiments conclusive, which were lately published by Galvani, Volta, and others, to shew a similitude between the spirit of animation, which con- tracts the muscular fibres, and the electric fluid. Since the electric fluid may act only as a more potent stimulus exciting the muscular fibres into action, and not by supplying them with a new quantity of the spirit of life. Thus in a recent hemiplegia I have frequently observed, when the patient yawned and stretch- ed himself, that the paralytic limbs moved also, though they were totally disobedient to the will. And when he was electrified by passing shocks from the affected hand to the affected foot, a mo- tion of the paralytic limbs was also produced. Now as in the act of yawning the muscles of the paralytic limbs were excited into action by the stimulus of the irksomeness of a continued pos- ture, and not by any additional quantity of the spirit of life; so we may conclude, that the passage of the electric fluid, which produced a similar effect, acted only as a stimulus, and not by supplying any addition of sensorial power. If nevertheless this theory should ever become established, a stimulus must be called an eductor of vital ether; which stimulus may consist of sensation or volition, as in the electric eel, as well as in the appulses of external bodies; and by drawing off the charges of vital fluid, may occasion the contraction or motions of the muscular fibres, and organs of sense. 2. The immediate efforts of the action of the spirit of anima- tion or sensorial power on the fibrous parts of the body, whether it acts in the mode of irritation, sensation, volition, or associa- tion, is a contraction of the animal fibre, according to the second law of animal causation. Sect. IV. Thus the stimulus of the blood induces the contraction of the heart; the agreeable taste of a strawberry produces the contraction of the muscles of de- glutition; the effort of the will contracts the muscles, which move the limbs in walking; and by association other muscles of the trunk are brought into contraction to preserve the balance of the body. The fibrous extremities of the organs of sense have been shewn, by the ocular spectra in Sect. III. to suffer Sect. XII. 1. 3. AND EXERTION. 47 similar contraction by each of the above modes of excitation; and by their configurations to constitute our ideas. 3. After animal fibres have for some time been excited into contraction, a relaxation succeeds, even though the exciting cause continues to act. In respect to the irritative motions this is ex- emplified in the peristaltic contractions of the bowels; which cease and are renewed alternately, though the stimulus of the aliment continues to be uniformly applied; in the sensitive mo- tions, as in strangury, tenesmus, and parturition, the alternate contractions and relaxations of the muscles exist, though the sti- mulus is perpetual. In our voluntary exertions it is experienced, as no one can hang long by the hands, however vehemently he wills so to do; and in the associate motions the constant change of our attitudes evinces the necessity of relaxation to those mus- cles, which have been long in action. This relaxation of a muscle after its contraction, even though the stimulus continues to be applied, appears to arise from tbe expenditure or diminution of the spirit of animation previously resident in the muscle, according to the second law of animal causation in Sect. IV. In those constitutions, which are termed weak, the spirit of animation becomes sooner exhausted, and tremulous motions are produced, as in the hands of infirm peo- f)le, when they lift a cup to their mouths. This quicker ex- laustion of the spirit of animation is probably owing to a less quantity of it residing in the acting fibres, which therefore more frequently require a supply from the nerves, which belong to them. 4. If the sensorial power continues to act, whether it acts in the mode of irritation, sensation, volition, or association, a new contraction of the animal fibre succeeds after a certain interval; which interval is of shorter continuance in weak people than in strong ones. This is exemplified in the shaking of the hands of weak people, when they attempt to write. In a manuscript epistle of one of my correspondents, which is written in a small hand, I observe from four to six zigzags in the perpendicular stroke of every letter, which shews that both the contractions of the fingers, and intervals between them, must have been performed in very short periods of time. The times of contraction of the muscles of enfeebled people being less, and the intervals between those contractions being less also, accounts for the quick pulse in fevers with debility, and in dying animals. The shortness of the intervals between one contraction and another in weak constitutions, is probably owing to the general deficiency of the quantity of the spirit of animation, and that therefore there is a less quantity of it to be 48 OF STIMULUS S;.ct. XII. 1. 4. received at each interval of the activity of the fibres. Hence in repeated motions, as of the fingers in performing on the harpsi- chord, it would at first sight appear, that swiftness and strength were incompatible: nevertheless the single contraction of a mus- cle is performed with greater velocity, as well as with greater force by vigorous constitutions, as in throwing a javelin. There is however another circumstance, which may often contribute to cause the quickness of the pulse in nervous fevers, as in animals bleeding to death in the slaughter-house; which is the deficient quantity of blood; whence the heart is but half distended, and in consequence sooner contracts. See Sect. XXXII. 2.1. For we must not confound frequency of repetition with quickness of motion, or the number of pulsations with the ve- locity, with which the fibres, which constitute the coats of the arteries, contract themselves. For where the frequency of the pulsations is but seventy-five in a minute, as in health; the con- tracting fibres, which constitute the sides of the arteries, may move through a greater space in a given time, than where the frequency of pulsation is one hundred and fifty in a minute, as in some fevers with great debility. For if in those fevers the arteries do not expand themselves in their disastole to more than half the usual diameter of their diastole in health, the fibres which constitute their coats, will move through a less space in a minute than in health, though they make two pulsations for one. Suppose the diameter of the artery during its systole to be one line, and that the diameter of the same artery during its di- astole is in health four lines, and in a fever with great debility only two lines. It follows that the arterial fibres contract in health from a circle of twelve lines in circumference to a circle of three lines in circumference, that is, they move through a space of nine lines in length. While the arterial fibres in the fever with debility would twice contract from a circle of six lines to a circle of three lines; that is, while they move through a space equal to six lines. Hence though the frequency of pulsation in fever be greater as two to one, yet the velocity of contraction in health is greater as nine'to six, or as three to two. On the contrary, in inflammatory diseases with strength, as in the pleurisy, the velocity of the contracting sides of the arteries is much greater than in health: for if we suppose the number of pulsations in a pleurisy to be half as much more than in health, that is, as one hundred and twenty to eighty, (which is about what generally happens in inflammatory diseases) and if the di- ameter of the artery in diastole be one-third greater than in Sect. XII. 1. 5. AND EXERTION. 49 health, which I believe is near the truth, the result will be, that the velocity of the contractile sides of the arteries will be in a pleurisy as two and a half to one, compared to the velocity of their contraction in a state of health; for if the circumference of the systole of the artery be three lines, and the diastole in health be twelve lines in circumference, and in a pleurisy eighteen lines; and secondly, if the artery pulsates thrice in the diseased state for twice in the healthy one, it follows, that the velocity of contraction in the diseased state to that in the healthy state will be forty-five to eighteen, or as two and a half to one. From hence it would appear, that if we had a criterion to de- termine the velocity of the arterial contractions, it would at the same time give us their strength, and thus be of more service in distinguishing diseases, than the knowledge of their frequency. As such a criterion cannot be had, the frequency of pulsation, the age of the patient being allowed for, will in some measure assist us to distinguish arterial strength from arterial debility, since in inflammatory diseases with strength the frequency sel- dom exceeds one hundred and eighteen or one hundred and twenty pulsations in a minute; unless under some peculiar cir- cumstance, as the great additional stimuli of wine or of exter- nal heat. 5. After a muscle or organ of sense has been excited into contraction, and the sensorial power ceases to act, the last situ- ation or configuration of it continues; unless it be disturbed by the action of some antagonist fibres, or other extraneous power. Thus in weak or languid people, wherever they throw their limbs on their bed or sofa, there they lie, till another exertion changes their attitude; hence one kind of ocular spectra seems to be produced after looking at bright objects; thus when a fire-stick is whirled round in the night, there appears in the eye a complete circle of fire; the action or configuration of one part of the retina not ceasing before the return of the whirling fire. Thus if any one looks at the setting sun for a short time, and then covers his closed eyes with his hand, he will for many se- conds of time perceive the image of the sun on his retina. A similar image of all other bodies would remain some time in the eye, but is effaced by the external chauge of the motions of the extremity of this nerve in our attention to other objects. See Sect. XVlI. 1.3. on Sleep. Hence the dark spots and other ocular spectra, are more frequently attended to, and remain longer in the eyes of weak people, as after violent exercise, in- toxication, or want of sleep. 6. A contraction of the fibres somewhat greater than usual vol. i. n 50 OF STIMULUS Sect. XII. 1. 7. introduces pleasurable sensation into the system; according to the fourth law of animal causation. Hence the pleasure in the be- ginning of drunkenness is owing to the increased action of the system from the stimulus of vinous spirit or of opium. If the contractions be still greater in energy or duration, painful sen- sations are introduced, as in consequence of great heat, or caus- tic applications or fatigue. If any part of the system, which is used to perpetual activity, as the stomach, or heart, or the fine vessels of the skin, acts for a time with less energy, another kind of painful sensation ensues, which is called hunger, or faintness, or cold. This occurs in a less degree in the locomotive muscles, and is called wearisome- ness. In the two former kinds of sensation there is an expendi- ture of sensorial power, in the latter there is an accumulation of it. 7. We have used the words exertion of sensorial power as a general term to express either irritation, sensation, volition, or association; that is, to express the activity or motion of the spirit of animation, at the time it produces the contractions of the fibrous parts of the system. It may be supposed that there may exist a greater or less mobility of the fibrous parts of our system, or a propensity to be stimulated into contraction by the greater or less quantity or energy of the spirit of animation; and that hence if the exertion of the sensorial power be in its natural state, and the mobility of the fibres be increased, the same quan- tity of fibrous contraction will be caused as if the mobility of the fibres continues in its natural state, and the sensorial exertion be increased. Thus it may be conceived, that in diseases accompanied with strength, as in inflammatory fevers with arterial strength, that the cause of greater fibrous contraction may exist in the increas- ed mobility of the fibres, whose contractions are thence both more forcible and more frequent. And that in diseases attended with debility, as in nervous fevers, where the fibrous contrac- tions are weaker, and more frequent, it may be conceived that the cause consists in a decrease of mobility of the fibres; and that those weak constitutions, which are attended with cold extremi- ties and large pupils of the eyes, may possess less mobility of the contractile fibres, as well as less quantity of exertion of the spirit of animation. In answer to this mode of reasoning it may be sufficient to ob- serve, that the contractile fibres consist of inert matter, and when the sensorial power is withdrawn, as in death, they possess no power of motion at all, but remain in their last state,* whethei of contraction or relaxation, and must thence derive the whole Sect. XII. 1. 7. AND EXERTION. 51 of this property from the spirit of animation. At the same time it is not improbable, that the moving fibres of strong people may possess a capability of receiving or containing a greater quantity of the spirit of animation than those of weak people. In every contraction of a fibre there is an expenditure of the sensorial power, or spirit of animation; and where the exertion of this sensorial power has been for some time increased, and the muscles or organs of sense have in consequence acted with greater energy, its propensity to activity is proportionally lessen- ed; which is to be ascribed to the exhaustion or diminution of its quantity. On the contrary, where there has been less fibrous contraction than usual for a certain time, the sensorial power or spirit of animation becomes accumulated in the inactive part of the system. Hence vigour succeeds rest, and hence the propen- sity to action of all our organs of sense and muscles is in a state of perpetual fluctuation. The irritability for instance of the retina, that is, its quantity of sensorial power, varies every mo- ment according to the brightness or obscurity of the object last beheld compared with the present one. The same occurs to our sense of heat, and to every part of our system, which is capable of being excited into action. When this variation of the exertion of the sensorial power be- comes much and permanently above or beneath the natural quantity, it becomes a disease. If the irritative motions be too great or too little, it shews that the stimulus of external things affects this sensorial power too violently or too inertly If the sensitive motions be too greater too little, the cause arises from the deficient or exuberant quantity of sensation produced in consequence of the motions of the muscular fibres or Organs of sense; if the voluntary actions are diseased the cause is to be looked for in the quantity of volition produced in consequence ol the desire or aversion occasioned by the painful or pleasurable sensations above mentioned. And the diseases of association probably depend on the greater or less quantity of the other three sensorial powers by which they were formed. From whence it appears that the propensity to action wheth- er it be called irritability, sensibility, voluntarily, or associability is only another mode of expression for the quantity of sensorial power residing in the organ to be excited. And that on the con- trary the words inirritability and insensibility, together with in- aptitude to voluntary and associate motions, are synonimous with deficiency of the quantity of sensorial power, or of the spirit of animation, residing in the organs to be excited. 52 OF STIMULUS Sect. XII. 2. i II. Of Sensorial Exertion. 1. There are three circumstances to be attended to in the pro- duction of animal motions. 1st. The stimulus. 2d. The sen- sorial power. 3d. The contractile fibre. 1st. A stimulus, ex- ternal to the organ, originally induces into action the sensorial faculty termed irritation; this produces the contraction of the fibres, which, if it be perceived at all, introduces pleasure or pain; which in their active state are termed sensation; which is another sensorial faculty, and occasionally produces contrac- tion of the fibres; this pleasure or pain is therefore to be con- sidered as another stimulus, which may either act alone or in conjunction with the former faculty of the sensorium termed irri- tation. This new stimulus, of pleasure or pain, either inducts into action the sensorial faculty termed sensation, which then produces the contraction of the fibres; or it introduces desire or aversion, which excite into action another sensorial faculty, termed volition, and may therefore be considered as another stimulus, which either alone or in conjunction with one or both of the two former faculties of the sensorium produces the contrac- tion of animal fibres. There is another sensorial power, that of an association, which perpetually, in conjunction with one or more of the above, and frequently singly, produces the contrac- tion of animal fibres, and which is itself excited into action by the previous motions of contracting fibres. Now as the sensorial power, termed irritation, residing in any particular fibres, is excited into exertion by the stimulus of ex- ternal bodies acting on those fibres; the sensorial power, termed sensation, residing in any particular fibres is excited into exertion by the stimulus of pleasure or pain acting on those fibres; the sensorial power, termed volition, residing in any particular fibres is excited into exertion by the stimulus of desire or aversion; and the sensorial power, termed association, residing in any particu- lar fibres, is excited into action by the stimulus of other fibrous motions, which had frequently preceded them. The word sti- mulus may therefore be used without impropriety of language, for any of these four causes, which excite the four sensorial powers into exertion. For though the immediate cause of voli- tion has generally been termed a motive; and that, of irritation only has generally obtained the name of stimulus; yet, as the im- mediate cause, which excites the sensorial powers of sensation, or of association, into exertion, have obtained no general name, we shall use the word stimulus for them all. Hence the quantity of motion produced in any particular part of the animal system will be as the quantity of stimulus, Sect. XII. 2.1. AND EXERTION. 53 and the quantity of sensorial power, or spirit of animation, resid- ing in the contracting fibres. Where both these quantities are great strength is produced, when that word is applied to the mo- tions of animal bodies. Where either of them is deficient, weak- ness is procured, as applied to the motions of animal bodies. Now as the sensorial power, or spirit of animation, is perpe- tually exhausted by the expenditure of it in fibrous contractions, and is perpetually renewed by the secretion or production of it in the brain and spinal marrow, the quantity of animal strength must be in a perpetual state of fluctuation on this account; and if to this be added the unceasing variation of all the four kinds of sti- mulus above described, which produce the exertions of the sen- sorial powers, the ceaseless vicissitude of animal strength becomes easily comprehended. If the quantity of sensorial power remains the same, and tfce quantity of stimulus be lessened, a weakness of the fibrous con- traction ensues, which may be denominated debility from defect of stimulus. If the quantity of stimulus remains the same, and the quantity of sensorial power be lessened, another kind of weakness ensues, which may be termed debility from defect of sensorial power; the former of these is called by Dr. Brown, in his Ele- ments of Medicine, direct debility, and the latter indirect debility. The coincidence of some parts of this work with correspondent deductions in the Brunonian Elementa Medicinae; a work (with some exceptions) of great genius, must be considered as confir- mations of the truth of the theory, as they were probably arrived at by different trains of reasoning. Thus in those who have been exposed to cold and hunger there is a deficiency of stimulus. While in nervous fever there is a deficiency of sensorial power. And in habitual drunkards, in a morning before their usual potation, there is a deficiency both of stimulus and of sensorial power. While, on the other hand, in the beginning of intoxication there is an excess of stimulus; in the hot-ache, after the hands have been immersed in snow there is a redundancy of sensorial power; and in inflammatory diseases with arterial strength, there is an excess of both. Hence if the sensorial power be lessened, while the quantity of stimulus remains the same, as in nervous fever, the frequency of repetition of the arterial contractions may continue, but their force in respect to removing obstacles, as in promoting the circu- lation of the blood, or the velocity of each contraction, will be diminished, that is, the animal strength will be lessened. And secondly, if the quantity of sensorial power be lessened, and the stimulus be increased to a certain degree, as in giving opium in 54 OF STIMULI'S Sect. XII. 2- 1. nervous fevers, the arterial contractions may be performed more frequently than natural, yet with less strength. And thirdly, if the sensorial power continues the same in re- spect to quantity, and the stimulus be somewhat diminished, as in going into a darkish room, or into a coldish bath, suppose of about eighty degrees of heat, as Buxton-bath, a temporary weakness of the affected fibres is induced, till an accumulation of sensorial power gradually succeeds, and counterbalances the deficiency of stimulus, and then the bath ceases to feel cold, and the room ceases to appear dark; because the fibres of the subcutaneous vessels, or of the organs of sense, act with their usual energy. A set of muscular fibres may thus be stimulated into violent exertion, that is, they may act frequently, and with their whole sensorial power, but may nevertheless not act strongly; because the quantity of their sensorial power was originally small, or was previously exhausted. Hence a stimulus may be great, and the irritation in consequence act with its full force, as in the hot pa- roxysms of nervous fever; but if the sensorial power, termed irri- tation, be small in quantity, the force of the fibrous contractions, and the times of their continuance in their contracted state, will be proportionally small. In the same manner in the hot paroxysm of putrid fevers, which are shewn in Sect. XXXIII. to be inflammatory fevers with arte- rial debility, the sensorial power termed sensation is exerted with great activity, yet the fibrous contractions, which produce the cir- culation of the blood, are performed without strength, because the quantity of sensorial power then residing in that part of the sys- tem is small. Thus in irritative fever with arterial strength, that is, with excess of spirit of animation, the quantity of exertion during the hot part of the paroxysm is to be estimated from the quantity of stimulus, and the quantity of sensorial power, while in sen- sitive (or inflammatory) fever with arterial strength, that is, with excess of spirit of animation, the violent and forcible ac- tions of the vascular system during the hot part of the paroxysm are induced by the exertions of two sensorial powers, which are excited by two kinds of stimulus. These are the sensorial pow- er of irritation excited by the stimulus of bodies external to the moving fibres, and the sensorial power of sensation excited by the pain in consequence of the increased contractions of those moving fibres. And in insane people in some cases the force of their muscular actions will be in proportion to the quantity of sensorial power, which they possess, and the quantity of the stimulus of desire or Sr.CT.XII. 2.2. AND EXERTION. 55 aversion, which excites their volition into action. At the same time in other cases the stimulus of pain or pleasure, and the sti- mulus of external bodies, may excite into action the sensorial powers of sensation and irritation, and thus add greater force to their muscular actions. 2. The application of the stimulus, whether that stimulus be some quality of external bodies, or pleasure or pain, or desire or aversion, or a link of association, excites the correspondent sen- sorial power into action, and this causes the contraction of the fibre. On the contraction of the fibre a part of the spirit of ani- mation becomes expended, and the fibre ceases to contract, though the stimulus continues to be applied; till in a certain time the fibre having received a supply of sensorial power is ready to contract again if the stimulus continues to be applied. If the stimulus on the contrary be withdrawn, the same quantity of quiescent sensorial power becomes resident in the fibre as before its contraction; as appears from the readiness for action of the large locomotive muscles of the body in a short time after com- mon exertion. But in those muscular fibres, which are subject to constant stimulus, as the arteries, glands, and capillary vessels, another phenomenon occurs, if their accustomed stimulus be withdrawn; which is, that the sensorial power becomes accumulated in the contractile fibres, owing to the want of its being perpetually expended, or carried away, by their usual unremitted contrac- tions. And on this account those muscular fibres become af- terwards excitable into their natural actions by a much weaker stimulus; or into unnatural violence of action by their accus- tomed stimulus, as is seen in the hot fits of intermittent fevers, which are in consequence of the previous cold ones. Thus the minute vessels of the skin are constantly stimulated by the fluid matter of heat; if the quantity of this stimulus of heat be a while diminished, as in covering the hands with snow, the ves- sels cease to act, as appears from the paleness of the skin; if this cold application of snow be continued but a short time, the sensorial power, which had habitually been supplied to the fibres, becomes now accumulated in them, owing to the want of its being expended by their accustomed contractions. And thence a less stimulus of heat will now excite them into violent contractions. If the quiescence of fibres, which had previously been subject to perpetual stimulus, continues a longer time; or their accustomed stimulus be more completely withdrawn; the accumulation of sensorial power becomes still greater, as in those exposed to cold and hunger; pain is produced, and the organ gradually dies from 56' OF STIMULUS Sj:ct. XII. 2. J. the chemical changes, which take place in it; or it is at a great distance of time restored to action by stimulus applied with great caution in small quantity, as happens to some larger animals and to many insects, which during the winter months lie benumbed with cold, and are said to sleep, and to persons apparently drowned, or apparently frozen to death. Snails have been said to revive by throwing them into water after having been many years shut up in the cabinets of the curious; and eggs and seeds in general are restored to life after many months of torpor by the stimulus of warmth and moisture. The inflammation of schirrous tumours, which have long ex- isted in a state of inaction, is a process of this kind; as well as the sensibility acquired by inflamed tendons and bones, which had at their formation a similar sensibility, which had so long lain dormant in their uninflamed state. 3. If after long quiescence from defect of stimulus the fibres, which had previously been habituated to perpetual stimulus, are again exposed to but their usual quantity of it; as in those who have suffered the extremes of cold or hunger; a violent exertion of the affected organ commences, owing, as above explained, to the great accumulation of sensorial power. This violent exer- tion not only diminishes the accumulated spirit of animation, but at the same time induces pleasure or pain into the system, which, whether it be succeeded by inflammation or not, becomes an ad- ditional stimulus, and acting along with the former one, produces still greater exertions; and thus reduces the sensorial power in the contracting fibres beneath its natural quantity. When the spirit of animation thus exhausted by useless exer- tions, the organ becomes torpid or unexcitable into action, and a second fit of quiescence succeeds that of abundant activity. Dur- ing this second fit of quiescence the sensorial power becomes again accumulated, and another fit of exertion follows in train. These vicissitudes of exertion and inertion of the arterial system constitute the paroxysms of remittent fevers; or intermittent ones, when there is an interval of the natural action of the arteries be- tween the exacerbations. In these paroxysms of fevers, which consist of the libration of the arterial system between the extremes of exertion and qui- escence, either the fits become less and less violent from the contractile fibres becoming less excitable to the stimulus by habit, that is by becoming accustomed to it, as explained below, XII. 3.1. or the whole sensorial power becomes exhausted, and the arteries cease to beat, and the patient dies in the cold part of the paroxysm. Or secondly, so much pain is introduced into Sect. XII. 2.4. AND EXERTION. 'f, the system by the violent contractions of the fibres, that inflam- mation arises, which prevents future cold fits by expending a part of the sensorial power in the extension of old vessels or the production of new ones; and thus preventing the too great ac- cumulation or exertion of it in other parts of the system; or which by the great increase of stimulus excites into great action the whole glandular system as well as the arterial, and thence a greater quantity of sensorial power is produced in the brain, and thus its exhaustion in any peculiar part of the system ceases to be effected. 4. Or thirdly, in consequence of the painful or pleasurable sensation above mentioned, desire and aversion are introduced, and inordinate volition succeeds; which by its own exertions expends so much of the spirit of animation, that the two other sensorial faculties, or irritation and sensation, act so much more feebly; that the paroxysms of fever, or that libration between the extremes of exertion and inactivity of the arterial system, gradually subsides. On this account a temporary insanity is a favourable sign in fevers, as I have had some opportunities of observing. III. Of repeated Stimulus. 1. When a stimulus is repeated more frequently than the ex- penditure of sensorial power can be renewed in the acting or gan, the effect of the stimulus becomes gradually diminished. Thus if two grains of opium be swallowed by a person unused to so strong a stimulus, all the vascular systems in the body act with great energy, all the secretions and the absorption from those secreted fluids are increased in quantity; and pleasure or pain are introduced into the system, which adds an additional stimulus to that already too great. After some hours the senso- rial power becomes diminished in quantity, expended by the great activity of the system; and thence, when the stimulus of the opium is withdrawn, the fibres will not obey their usual de- gree of natural stimulus, and a consequent torpor or quiescence succeeds, as is experienced by drunkards, who on the day after a great excess of spirituous potation, feel indigestion, head-ach, and general debility. In this fit of torpor or quiescence of a part or of the whole of the system, an accumulation of the sensorial power in the af- fected fibres is formed, and occasions a second paroxysm of ex- ertion, by the application only of the natural stimulus, and thus a libration of the sensorial exertion between one excess and the other continues for two or three days, where the stimulus was VOL. i. i 58 OF STIMULUS Sect. XII. 3. 1. violent in degree; and for weeks in some fevers, from the stimu- lus of contagious matter. But if a second dose of opium be exhibited before the fibres have regained their natural quantity of sensorial power, its ef- fect will be much less than the former, because the spirit of ani- mation or sensorial power is in part exhausted by the previous excess of exertion. Hence all medicines repeated too frequent- ly gradually lose their effect, as opium and wine. Many things of disagreeable taste at first cease to be disagreeable by frequent repetition, as tobacco; grief and pain gradually diminish, and at length cease altogether; and hence life itself becomes toler- able. Besides the temporary diminution of the spirit of animation or sensorial power, which is naturally stationary or resident in every living fibre, by a single exhibition of a powerful stimulus, the con- tractile fibres themselves, by the perpetual application of a new quantity of stimulus, before they have regained their natural quan- tity of sensorial power, appear to suffer in their capability of re- ceiving so much as the natural quantity of sensorial power; and hence a permanent deficiency of spirit of animation takes place, however long the stimulus may have been withdrawn. On this case depends the permanent debility of those, who have been ad- dicted to intoxication, the general weakness of old age, and the natural debility or inirritability of those, who have pale skins and large pupils of their eyes. There is a curious phenomenon belongs to this place, which has always appeared difficult of solution; and that is, that opium or aloes may be exhibited in small doses at first, and gradu- ally increased to very large ones without producing a stupor or diarrhoea. In this case, though the opium and aloes are given in such small doses as not to produce intoxication or catharsis, yet they are exhibited in quantities sufficient in some degree to exhaust the sensorial power, and hence a stronger and a stronger dose is required; otherwise the medicine would soon cease to act at all. On the contrary if the opium or aloes be exhibited in a large dose at first, so as to produce intoxication or diarrhcea; after a few repetitions the quantity of either of them may be diminish- ed, and they will still produce this effect. For the more pow- erful stimulus dissevers the progressive catenations of animal mo- tions, described in Sect. XVII. and introduces a new link be- tween them; whence every repetition strengthens this new as- sociation or catenation, and the stimulus may be gradually de- creased, or be nearly withdrawn, and yet the effect shall*con- tinue; because the sensorial power of association or catenation Sect. XU. 3.2. AND EXERTION. 59 being united with the stimulus, increases in energy with every repetition of the catenated circle; and it is by these means that all the irritative associations of motions are originally produced. Thus if the Peruvian bark be given in the intervals between the fits of intermittent fever in such small doses, as not to pre- vent the returns of fever, the constitution ceases to obey its stimulus, and the disease cannot be cured even by the largest doses of bark, unless the patient ceases to take any for a few days previous to the exhibition of larger doses. But if large doses be at first exhibited so as to prevent the return of fever, small ones taken afterwards will continue to prevent the return of it. 2. When a stimulus is repeated at such distant intervals of time, that the natural quantity of sensorial power becomes com- pletely restored in the acting fibres it will act with the same en- ergy as when first applied. Hence those who have lately accus- tomed themselves to large doses of opium by beginning with small ones, and gradually increasing them, and repeating them fre- quently as mentioned in the preceding paragraphs; if they inter- mit the use of it for a few days only, must begin again with as small doses as they took at first, otherwise, they will experience the inconveniences of intoxication. On this circumstance depend the constant unfailing effects of the various kinds of stimulus, which excite into action all the vascular systems in the body; the arterial, venous, absorbent, and glandular vessels, are brought into perpetual unwearied ac- tion by the fluids, which are adapted to stimulate them; but these have the sensorial power of association added to that of irri- tation, and even in some degree that of sensation, and even of volition, as will be spoken of in their places; and life itself is thus carried on by the production of sensorial power being equal to its waste or expenditure in the perpetual movement of the vascular organization. 3. When a stimulus is repeated at uniform intervals of time with such distances between them, that the expenditure of sen- sorial power in the acting fibres becomes completely renewed, the effect is produced with greater facility or energy. For the sensorial power of association is combined with the sensorial power of irritation, or, in common language, the acquired habit assists the power of the stimulus. This circumstance not only obtains in the annual and diur- nal catenations of animal motions explained in Sect. XXXVI. but in every less circle of actions or ideas, as in the burthen of a song, or the iterations of a dance; and constitutes the pleas* 60 OF STIMULUS. Sect. XII. 3.4. sure we receive from repetition and imitation; as treated of in Sect. XXII. 2. 4. When a stimulus has been many times repeated at uniform intervals, so as to produce the complete action of the organ, it may then be gradually diminished, or totally withdrawn, and the action of the organ will continue. For the sensorial power of association becomes united with that of irritation, and by fre- quent repetition becomes at length of sufficient energy to carry on the new link in the circle of actions, without the irritation which at first introduced it. Hence, when the bark is given at stated intervals for the cure of intermittent fevers, if sixty grains of it be given every three hours for the twenty-four hours preceding the expected paroxysm, so as to stimulate the defective part of the system into action, and by that means to prevent the torpor or quiescence of the fibres, which constitutes the cold fit; much less than half the quantity, given before the time at which another paroxysm of quiescence would have taken place, will be sufficient to prevent it; because now the sensorial power, termed association, acts in a twofold manner. First, in respect to the period of the catenation in which the cold fit was produced, which is now dissevered by the stronger stimulus of the first doses of the bark; and, secondly, because each dose of bark being repeated at periodical times, has its effect increased by the sensorial faculty of association being combined with that of irritation. Now, when sixty grains of Peruvian bark are taken twice a day, suppose at ten o'clock and at six, for a fortnight, the irrita- tion excited by this additional stimulus becomes a part of the diurnal circle of actions, and will at length carry on the increas- ed action of the system without the assistance of the stimulus of the bark. On this theory the bitter medicines, chalybeates, and opiates in appropriated doses, exhibited for a fortnight, give permanent strength to pale feeble children, and other weak con- stitutions. 5. When a defect of stimulus, as of heat, recurs at certain diurnal intervals, which induces some torpor or quiescence of a part of the system, the diurnal catenation of actions becomes disordered, and a new association with this link of torpid action is formed; on the next period the quantity of quiescence will be increased, suppose the same defect of stimulus to recur, because now the new association conspires with the defective irritation in introducing the torpid action of this part of the diurnal cate- nation. In this manner many fever-fits commence, where the patient is for some days indisposed at certain hours, before the Ski t. XII. 3. 6. AND EXERTION. 61 cold paroxysm of fever is completely formed. See Sect. XVII. 3. 3. on Catenation of Animal Motions. 6. If a stimulus, which at first excited the affected organ into so great exertion as to produce sensation, be continued for a cer- tain time, it will cease to produce sensation both then and when repeated, though the irritative motions in consequence of it may continue to be re-excited. Many catenations of irritative motions were at first succeeded by sensation, as the apparent motions of objects when we walk past them, and probably the vital motions themselves in the early state of our existence. But as those sensations were fol- lowed by no movements of the system in consequence of them, they gradually ceased to be produced, not being joined to any succeeding link of catenation. Hence contagious matter, which has for some weeks stimulated the system into great and perma- nent sensation, ceases afterwards to produce general sensation, or inflammation, though it may still induce topical irritations. See Sect. XXXIII. 2. 8. XIX. 10. Our absorbent system then seems to receive those contagious matters, which it has before experienced, in the same manner as it imbibes common moisture or other fluids; that is, without be- ing thrown into so violent action as to produce sensation; the consequence of which is an increase of daily energy or activity, till inflammation and its consequences succeed. 7. If a stimulus excites an organ into such violent contractions as to produce sensation, the motions of which organ had not usually produced sensation, this nsw sensorial power, added to the irritation occasioned by the stimulus, increases the activity of the organ. And if this activity be catenated with the diurnal circle of actions, an increasing inflammation is produced; as in the evening paroxysms of small-pox, and other fevers with in- flammation. And hence schirrous tumours, tendons and mem- branes, and probably the arteries themselves become inflamed, when they are strongly stimulated. IV. Of Stimulus greater than natural. 1. A quantity of stimulus greater than natural, producing an increased exertion of sensorial power, whether that exertion be in the mode of irritation, sensation, volition, or association, di- minishes the general quantity of it. This fact is observable in the progress of intoxication, as the increased quantity or energy of the irritative motions; owing to the stimulus of vinous spirit, in- troduces much pleasurable sensation into the system, and much exertion of muscular or sensual motions in consequence of this 62 OF STIMULUS Sect. XII. 4. 2. increased sensation; the voluntary motions, and even the asso- ciate ones, become much impaired or diminished; and delirium and staggering succeed. See Sect. XXI. on Drunkenness. And hence the great prostration of the strength of the locomotive muscles in some fevers is owing to the exhaustion of sensorial power by the increased action of the arterial system. In like manner a stimulus greater than natural, applied to a part of the system, increases the exertion of sensorial power in that part, and diminishes it in some other part. As in the com- mencement of scarlet fever, it is usual to see great redness and heat on the faces and breasts of children, while at the same time their feet are colder than natural: partial heats are observable in other fevers with debility, and are generally attended with torpor or quiescence of some other part of the system. But these partial exertions of sensorial power are sometimes attended with increased partial exertions in other parts of the system, which sympathize with them, as the flushing of the face after a full meal. Both these therefore are to be ascribed to sympathetic associations, explained in Sect. XXXV. and not to general ex- haustion or accumulation of sensorial power. 2. A quantity of stimulus greater than natural, producing an increased exertion of sensorial power in any particular organ, diminishes the quantity of it in that organ. This appears from the contractions of animal fibres being not so easily excited by a less stimulus after the organ has been subjected to a greater. Thus after looking at any luminous object of a small size, as at the setting sun, for a short time, so as not much to fatigue the eye, this part of the retina becomes less sensible to smaller quan- tities of light; hence when the eyes are turned on other less lu- minous parts of the sky, a dark spot is seen resembling the shape of the sun, or other luminous object which we last behold. See Sect. XL. No. 2. Thus we are some time before we can distinguish objects in an obscure room after coming from bright day-light, though the iris presently contracts itself. We are not able to hear weak sounds after loud ones. And the stomachs of those who have been much habituated to the stronger stimulus of fermented or spirituous liquors are not excited into due action by weaker ones. 3. A quantity of stimulus something greater than the last mentioned, or longer continued, induces the organ into spas- modic action, which ceases and recurs alternately. Thus on looking for a time on the setting sun, so as not greatly to fatigue the sight, a yellow spectrum is seen when the eyes are closed and covered, which continues for a time, and then disappears and recurs repeatedly before it entirely vanishes. See Sect. XI. Sect. XII. 4. 4. AND EXERTION. 63 No. 5. Thus the action of vomiting ceases and is renewed by intervals, although the emetic drug is thrown up with the first effort. A tenesmus continues by intervals some time after the exclusion of acrid excrement; and the pulsations of the heart of a viper are said to continue some time after it is cleared from its blood. In these cases the violent contractions of the fibres produce pain according to law 4; and this pain constitutes an additional kind or quantity of excitement, which again induces the fibres into contraction, and which painful excitement is again renew- ed, and again induces contractions of the fibres with gradually diminishing effect. 4. A quantity of stimulus greater than that last mentioned, or longer continued, induces the antagonist muscles into spasmodic acnon. This is beautifully illustrated by the ocular spectra de- scribed in Sect. XL. No. 6. to which the reader is referred. From those experiments there is reason to conclude that the fa- tigued part of the retina throws itself into a contrary mode of action like oscitation or pandiculation, as soon as the stimulus, which has fatigued it, is withdrawn; but that it still remains li- able to be excited into action by any other colours except the colour with which it has been fatigued. Thus the yawning and stretching the limbs after a continued action or attitude seems occasioned by the antagonist muscles being stimulated by their extension during the contractions of those in action or in the situ- ation in which that action last left them. 5. A quantity of stimulus greater than the last, or longer con- tinued, induces variety of convulsions or fixed spasms either of the affected organ or of the moving fibres in the other parts of the body. In respect to the spectra in the eye this is well illus- trated in No. 7 and 8, of Sect. XI. Epileptic convulsions, as the emprosthotonos and opisthotonos, with a cramp of the calf of the leg, locked jaw, and other cataleptic fits, appear to origi- nate from pain, as some of these patients scream aloud before the convulsion takes place, which seems at first to be an effort to relieve painful sensation, and afterwards an effort to prevent it. In these cases the violent contractions of the fibres produce so much pain, as to constitute a perpetual excitement; and that in so great a degree as to allow but small intervals of relaxation of the contracting fibres as in convulsions, or no intervals at all as in fixed spasms. 6. A quantity of stimulus greater than the last, or longer con- tinued, produces a paralysis of the organ. In many cases this paralysis is only a temporary effect, as on looking long on a small area of bright red silk placed on a sheet of white paper on the 64 OF STIMULUS Skit. XII 5. 1 floor in a strong light, the red silk gradually becomes paler, and at length disappears; which evinces that a part of the retina, by being violently excited, becomes for a time unaffected by the stimulus of that colour. Thus cathartic medicines, opiates, poi- sons, contagious matter, cease to influence our system after it has been habituated to the use of them, except by the exhibition of increased quantities of them; our fibres not only become unaf- fected by stimuli, by which they have previously been violently irritated, as by the matter of the small-pox or measles; but they also become unaffected by sensation, where the violent exertions, which disabled them, were in consequence of too great quantity of sensation. And lastly, the fibres which become disobedient to volition, are probably disabled by their too violent exertions in consequence of too great a quantity of volition. After every exertion of our fibres a temporary paralysis suc- ceeds, whence the intervals of all muscular contractions, as men- tioned in No. 3 and 4 of this Section; the immediate cause of these more permanent kinds of paralysis is probably owing in the same manner to the too great exhaustion of the spirit of anima- tion in the affected part; so that a stronger stimulus is required, or one of a different kind from that, which occasioned those too violent contractions, to again excite the affected organ into ac- tivity; and if a stronger stimulus could be applied, it must again induce paralysis. For these powerful stimuli excite pain at the same time, that they produce irritation; and this pain not only excites fibrous motions by its stimulus, but it also produces volition; and thus all these stimuli acting at the same time, and sometimes with the addition of their associations, produce so great exertion as to expend the whole of the sensorial power in the affected fibres. V. Of Stimulus less than natural. 1. A quantity of stimulus less than natural, producing a de- creased exertion of sensorial power, occasions an accumulation of the general quantity of it. This circumstance is observable in the haemiplegia, in which the patients are perpetually moving the muscles, which are unaffected. On this account we awake with greater vigour after sleep, because during so many hours, the great usual expenditure of sensorial power in the perform- ance of voluntary actions, and in the exertions of our organs of sense, in consequence of the irritations occasioned by external objects had been suspended, and a consequent accumulation had taken place. In like manner the exertion of the sensorial power less than Sect. XII. 5. 2. AND EXERTION. 65 natural in one part of the system, is liable to produce an increase of the exertion of it in some other part. Thus by the action of vomiting, in which the natural exertion of the motions of the stomach are destroyed or diminished, an increased absorption of the pulmonary and cellular lymphatics is produced, as is known by the increased absorption of the fluid deposited in them in dropsical cases. But these partial quiescences of sensorial power are also sometimes attended with other partial quiescences, which sympathize with them, as cold and pale extremities from hunger. These therefore are to be ascribed to the associations of sympathy explained in Sect. XXXV. and not to the general accumulation of sensorial power. 2. A quantity of stimulus less than natural, applied to fibres previously accustomed to perpetual stimulus, is succeeded by ac- cumulation of sensorial power in the affected organ. The truth of this proposition is evinced, because a stimulus less than na- tural, if it be somewhat greater than that above mentioned, will excite the organ so circumstanced into violent activity. Thus on a frosty day with wind, the face of a person exposed to the wind is at first pale and shrunk; but on turning the face from the wind, it becomes soon of a glow with warmth and flushing. The glow of the skin in emerging from the cold-bath is owing to the same cause. It does not appear, that an accumulation of sensorial power above the natural quantity is acquired by those muscles, which are not subject to perpetual stimulus, as the locomotive muscles; these, after the greatest fatigue, only acquire by rest their usual aptitude to motion; whereas the vascular system, as the heart and arteries, after a short quiescence are thrown into a violent action by their natural quantity of stimulus. Nevertheless by this accumulation of sensorial power during the application of decreased stimulus, and by the exhaustion of it during the action of increased stimulus, it is wisely provided, that the actions of the vascular muscles and organs of sense are not much deranged by small variations of stimulus; as the quantity of sensorial power becomes in some measure inversely as the quan- tity of stimulus. 3. A quantity of stimulus less than that mentioned above, and continued for some time, induces pain in the affected organ, as the pain of cold in the hands, when they are immersed in snow, is owing to a deficiency of the stimulation of heat. Hunger is a pain from the deficiency of the stimulation of food. Pain in the back at the commencement of ague-fits, and the head- achs which attend feeble people, are pains from defect of stimu- lus, and are hence relieved by opium essential oils, spirit of wine. vol. i. k 66 OF STIMULUS Sect. XII. 5.4 As the pains, which originate from defect of stimulus, only occur in those parts of ihe system, which have been previously subjected to perpetual stimulus; and as an accumulation of sen- sorial power is produced in the quiescent organ along with the pain, as in cold or hunger, there is reason to believe, that the pain is owing to the accumulation of sensorial power. For, in the locomotive muscles, in the retina of the eye, and other organs of sense, no pain occurs from the absence of stimulus, nor any great accumulation of sensorial power beyond their natural quan- tity, since these organs have not been used to a perpetual supply of it. There is indeed a greater accumulation occurs in the organ of vision after its quiescence, because it is subject to more con- stant stimulus. 4. A certain quantity of stimulus less than natural induces the moving organ into feebler and more frequent contractions, as men- tioned in No. I. 4. of this Section. For each contraction moving through a less space, or with less force, that is, with less expendi- ture of the spirit of animation, is sooner relaxed, and the spirit of animation derived at each interval into the acting fibres being less, these intervals likewise become shorter. Hence the tremors of the hands of people accustomed to vinous spirit, till they take their usual stimulus; hence the quick pulse in fevers attended with debility, which is greater than in fevers attended with strength; in the latter the pulse seldom beats above 120 times in a minute, in the former it frequently exceeds 140. It must be observed that in this and the two following articles the decreased action of the system is probably more frequently occasioned by deficiency in the quantity of sensorial power, than in the quantity of stimulus. Thus those feeble constitu- tions which have large pupils of their eyes, and all who labour under nervous fevers, seem to owe their want of natural quantity of activity in the system to the deficiency of sensorial power; since, as far as can be seen, they frequently possess the natural quantity of stimulus. 5. A certain quantity of stimulus less than that above mention- ed, inverts the order of successive fibrous contractions; as in vomiting the vermicular motions of the stomach and duodenum are inverted, and their contents ejected, which is probably owing to the exhaustion of the spirit of animation in the acting muscles by a previous excessive stimulus, as by the root of ipecacuanha, and the consequent defect of sensorial power. The same re- trograde motions affect the whole intestinal canal in ileus* and the oesophagus in globus hystericus. See this further explained in Sect. XXIX. No. 11. on Retrograde Motions. I must observe, also, that something similar happens in the Sect. XII. 5. 6. AND EXERTION. 67 production of our ideas, or sensual motions, when they are too weakly excited; when any one is thinking intensely about one thing, and carelessly conversing about another, he is liable to use the word of a contrary meaning to that which he designed, as cold weather for hot weather, summer for winter. 6. A certain quantity of stimulus, less than that above men- tioned, is succeeded by paralysis, first of the voluntary and sensi- tive motions, and afterwards of those of irritation and of associa- tion, which constitutes death. VI. Cure of increased Exertion. 1. The cure, which nature has provided for the increased exer- tion of any part of the system, consists in the consequent expen- diture of the sensorial power. But as a greater torpor follows this exhaustion of sensorial power, as explained in the next para- graph, and a greater exertion succeeds this torpor, the constitu- tion frequently sinks under these increasing librations between exertion and quiescence; till at length complete quiescence, that is, death, closes the scene. For, during the great exertion of the system in the hot fit of fever, an increase of stimulus is produced from the greater mo- mentum of the blood, the greater distention of the heart and ar- teries, and the increased production of heat, by the violent actions of the system occasioned by this augmentation of stimulus, the sensorial power becomes diminished in a few hours much beneath its natural quantity, the vessels at length, cease to obey even these great degrees of stimulus, as shewn in Sect. XL. 9. 1. and a tor- por of the whole or of a part of the system ensues. Now as this second cold fit commences with a greater defi- ciency of sensorial power, it is also attended with a greater defi- ciency of stimulus than in the preceding cold fit, that is, with less momentum of blood, less distention of the heart. On this ac- count the second cold fit becomes more violent and of longer duration than the first; and as a greater accumulation of senso- rial power must be produced before the system of vessels will again obey the diminished stimulus, it follows, that the second hot fit of fever will be more violent than the former one. And that unless some other causes counteract either the violent exer- tions in the hot fit, or the great torpor in the cold fit, life will at length be extinguished by the expenditure of the whole of the sensorial power. And from hence it appears, that the true means of curing fevers must be such as decrease the action of the system in the hot fit, and increase it in the cold fit; that is, 68 OF STIMULUS Skct. XII. 6. 2. such as prevent the too great diminution of sensorial power in the hot fit, and the too great accumulation of it in the cold one. 2. Where the exertion of the sensorial power is much in- creased, as in the hot fits of fever or inflammation, the follow- ing are the usual means of relieving it. Decrease the irritations by blood-letting, and other evacuations; by cold water taken into the stomach, or injected as an enema, or used externally; by cold air breathed into the lungs, and diffused over the skin; with food of less stimulus than the patient has been accustom- ed to. 3. As a cold fit, or paroxysm of inactivity of some parts of the system, generally precedes the hot fit, or paroxysm of exertion, by which the sensorial power becomes accumulated, this cold pa- roxysm should be prevented by stimulant medicines and diet, as wine, opium, bark, warmth, cheerfulness, anger, surprise. 4. Excite into greater action some other part of the system, by which means the spirit of animation may be in part expended, and thence the inordinate actions of the diseased part may be les- sened. Hence when a part of the skin acts violently, as of the face in the eruption of the small-pox if the feet be cold they should be covered. Hence the use of a blister applied near a topical in- flammation. Hence opium and warm bath relieve pains both from excess and defect of stimulus. 5. First increase the general stimulation above its natural quantity, which may in some degree exhaust the spirit of ani- mation, and then decrease the stimulation beneath its natural quantity. Hence after sudorific medicines and warm air, the application of refrigerents may have greater effect, if they could be administered without danger of producing too great torpor of some part of the system; as frequently happens to people in health from coming out of a warm room into the cold air, by which a topical inflammation in consequence of torpor of the mucous membrane of the nostril is produced, and is termed a cold in the head. VII. Cure of decreased Exertion. 1. Where the exertion of the sensorial powers is much de- creased, as in the cold fits of fever, a gradual accumulation of the spirit of animation takes place; as occurs in all cases where inactivity or torpor of a part of the system exists; this accumu- lation of sensorial power increases, till stimuli less than natural are sufficient to throw it into action, then the cold fit ceases; and from the action of the natural stimuli a hot one succeeds with in- creased activity of the whole system. Sect. XII. 7.2. AND EXERTION. 69 So in fainting fits, or syncope, there is a temporary deficiency of sensorial exertion, and a consequent quiescence of a great part of the system. This quiescence continues, till the sensorial power becomes again accumulated in the torpid organs; and then the usual diurnal stimuli excite the revivescent parts again into action; but as this kind of quiescence continues but a short time compared to the cold paroxysm of an ague, and less affects the circulatory system, a less superabundancy of exertion succeeds in the organs previously torpid, and a less excess of arterial ac- tivity. See Sect. XXXIV. 1.6. 2. In the diseases occasioned by a defect of sensorial exertion, as in cold fits of ague, hysteric complaint, and nervous fever, the following means are those commonly used. 1. Increase the stimulation above its natural quantity for some weeks, till a new habit of more energetic contraction of the fibres is established. This is to be done by wine, opium, bark, steel, given at exact periods, and in appropriate quantities; for if these medicines be given in such quantity, as to induce the least degree of intoxica- tion, a debility succeeds from the useless exhaustion of spirit of animation in consequence of too great exertion of the muscles or organs of sense. To these irritative stimuli should be added the sensitive ones of cheerful ideas, hope, affection. 3. Change the kinds of stimulus. The habits acquired by the constitution depend on such nice circumstances, that when one kind of stimulus ceases to excite the sensorial power into the quantity of exertion necessary to health, it is often sufficient to change the stimulus for another apparently similar in quantity and quality. Thus when wine ceases to stimulate the constitu- tion, opium in appropriate doses supplies the defect; and the contrary. This is also observed in the effects of cathartic medicines, when one loses its power, another, apparently less efficacious, will succeed. Hence a change of diet, drink, and stimulating medicines, is often advantageous in diseases of de- bility. 4. Stimulate the organs, whose motions are associated with the torpid parts of the system. The actions of the minute ves- sels of the various parts of the external skin are not only associat- ed with each other, but are strongly associated with those of some of the internal membranes, and particularly of the stomach. Hence when the exertion of the stomach is less than natural, and indigestion and heartburn succeed, nothing so certainly removes these symptoms as the stimulus of a blister on the back. The coldness of the extremities, as of the nose, ears, or fingers, are hence the best indication for the successful application of blisters. 5. Decrease the stimulus for a time. By lessening the quan- 70 OF STIMULUS :->ect. XII. 7. 6. tity of heat for a minute or two by going into the cold bath, a great accumulation of sensorial power is produced; for not on- ly the minute vessels of the whole external skin for a time be- come inactive, as appears by their paleness; but the minute vessels of the lungs lose mucli of their activity also by concert with those of the skin, as appears from the difficulty of breathing at first going into cold water. On emerging from the bath the sensorial power is thrown into great exertion by the stimulus ot the common degree of the warmth of the atmosphere, and a great production of animal heat is the consequence. The longer a person continues in the cold bath the greater must be the pre- sent inertion of a great part of the system, and in consequence a greater accumulation of sensorial power. Whence M. Pome re- commends some melancholy patients to be kept from two to six hours in spring-water and in baths still colder. 6. Decrease the stimulus for a time below the natural, and then increase it above natural. The effect of this process, im- properly used, is seen in giving much food, or applying much warmth, to those who have been previously exposed to great hunger, or to great cold. The accumulated sensorial power is thrown into so violent exertion, that inflammations and mortifi- cations supervene, and death closes the catastrophe. In many diseases this method is the most successful; hence the bark in agues produces more certain effect after the previous exhibition of emetics. In diseases attended with violent pain, opium has double the effect, if venesection and a cathartic have been pre- viously used. On this seems to have been founded the successful practice of Sydenham, who used venesection and a cathartic in chlorosis before the exhibition of the bark, steel, and opiates. 7. Prevent any unnecessary expenditure of sensorial power. Hence in fevers with debility, a decumbent posture is preferred, with silence, little light, and such a quantity of heat as may pre- vent any chill sensation, or any coldness of the extremities. The pulse of patients in fevers with debility increases in frequency about ten pulsations in a minute on their rising out of bed. For the expenditure of sensorial power to preserve an erect posture of the body adds to the general deficiency of it, and thus affects the circulation. 8. The longer in time and the greater in degree the quiescence or inertion of an organ has been, so that it still retains life of excitability, the less stimulus should at first be applied to it. The quantity of stimulation is a matter of great nicety to de- termine, where the torpor or quiescence of the fibres has been experienced in a great degree, or for a considerable time, as in cold fits of the ague, in continued fevers with great debility, or Sect. XII. 7. 8. AND EXERTION. 71 in people famished at sea, or perishing with cold. In the two last cases, very minute quantities of food should be first suppli- ed, and very few additional degrees of heat. In the two former cases, but little stimulus of wine or medicine, above what they had been lately accustomed to, should be exhibited, and this at frequent and stated intervals, so that the effect of one quantity may be observed before the exhibition of another. If these circumstances are not attended to, as the sensorial power becomes accumulated in the quiescent fibres, an inordi- nate exertion takes place by the increase of stimulus acting on accumulated quantity of sensorial power, and either the para- lysis, or death of the contractile fibres ensues, from the total ex- penditure of the sensorial power in the affected organ, owing to this increase of exertion, like the debility after intoxication. Or, secondly, the violent exertions above mentioned produce painful sensation, which becomes a new stimulus, and by thus producing inflammation, and increasing the activity of the fibres already too great, sooner exhausts the whole of the sensorial power in the acting organ, and mortification, that is, the death of the part, supervenes. Hence there have been many instances of people, whose limbs have been long benumbed by exposure to cold, who have lost them by mortification on their being too hastily brought to the fire; and of others, who were nearly famished at sea, who have died soon after having taken not more than an usual meal of food. 1 have heard of two well-attested instances of patients in the cold fit of ague, who have died from the exhibition of gin and vinegar, by the inflammation which ensued. And in many fevers attended with debility, the unlimited use of wine, and the wanton application of blisters, I believe, has destroyed num- bers by the debility consequent to too great stimulation, that is, by the exhaustion of the sensorial power by its inordinate ex- eriion. Wherever the least degree of intoxication exists, a proportion- al debility is the consequence; but there is a golden rule by which the necessary and useful quantity of stimulus in fevers with debility may be ascertained. When wine or beer is ex- hibited either alone or diluted with water, if the pulse becomes slower the stimulus is of a proper quantity; and should be re- peated every two or three hours, or when the pulse again be- comes quicker. In the chronical debility brought on by drinking spirituous or fermented liquors, there is another golden rule by which I have successfully directed the quantity of spirit which they may safe- ly lessen, for there is no other means by which they can recover 72 OF STIMULUS, &c. Sect. XII. 8. their health. It should be premised that where the power of di- gestion in these patients is totally destroyed, there is not much reason to expect a return to healthful vigour. I have directed several of these patients to omit one-fourth part of the quantity of vinous spirit they have been lately accustomed to, and if in a fortnight their appetite increases, they are advised to omit another fourth part; but if they perceive that their di- gestion becomes impaired from the want of this quantity of spiri- tuous potation, they are advised to continue as they are, and rather bear the ills they have, than risk the encounter of greater. At the same time flesh-meat with or without spice is recommend- ed, with Peruvian bark and steel in small quantities between their meals, and a half a grain of opium, or a grain, with five or eight grains of rhubarb at night. VIII. Conclusion. It may be asked, if stimulus exhausts the sensorial power, can an increase of it ever be used with advantage, if where the sen- sorial power is already in too small quantity? We must recol- lect, that the sensorial power is produced in the brain and spinal marrow by the fibrous actions of those glands like other secre- tions: and that hence an increased action of these glands by an adapted stimulus,, or by association of motions may increase the quantity of sensorial power, which increased actions of the system may be continued by habit, after the stimulus is with- drawn. Thus some kinds of stimuli affect particular parts of the system, blisters affect the skin, and the stomach by its asso- ciation with the skin; emetics affect the stomach, cathartics the intestines; and sea-salt the perspirable glands or capillaries: but it is probable, that wine and opium affect the whole system; and, when given in small repeated quantities, that they increase the secretion of sensorial power, either by their immediate stimulus or by association, and that the strength of convalescents is re- cruited, as they are thus enabled to digest more food, and that of a somewhat more stimulating quality. The Peruvian bark, and arsenic, in the curve of agues, probably act in a similar manner on the stomach, and on the parts associated with it, so as to in- crease their powers of action; but not on the whole system, as general heat is not produced by them. Sect. XIII. 1. 1 OF VEGETABLE, &c. 73 SECT. XIII. OF VEGETABLE ANIMATION. I. 1. Vegetables are irritable, mimosa, dioncea muscipula. Vegeta- ble secretions. 2. Vegetable buds are inferior animals, are liable to greater or less irritability. II. Stamens and pistils of plants sheic marks of sensibility. III. Vegetables possess some degree of volition. IV. Motions of plants are associated like those of ani- mals. V. 1. Vegetable structure like that of animals, their an- thers and stigmas are living creatures. Male flowers of Vallis- neria. 2. JVhether vegetables possess ideas? They have organs of sense, as of touch and smell, and ideas of external things? I. 1. The fibres of the vegetable world, as well as those of the animal, are excitable into a variety of motions by irritations of external objects. This appears particularly in the mimosa or sensitive plant, whose leaves contract on the slightest injury; the dionaea muscipula, which was lately brought over from the marshes of America, presents us with another curious instance of vegetable irritability; its leaves are armed with spines on their upper edge, and are spread on the ground around the stem; when an insect creeps on any of them in its passage to the flower or seed, the leaf shuts up like a steel rat-trap, and destroys its ene- my. See Botanic Garden, Part II. note on Silene. The various secretions of vegetables, as of odour, fruit, gum, resin, wax, honey, seem brought about in the same manner as in the glands of animals: the tasteless moisture of the earth is con- verted by the hop plant into a bitter juice; as by the caterpillar in the nutshell the sweet kernel is converted into a bitter powder. While the power of absorption in the roots and barks of vegeta- bles is excited into action by the fluids applied to their mouths like the lacteals and lymphatics of animals. 2. The individuals of the vegetable world may be considered as inferior or less perfect animals; -a tree is a congeries of many living buds, and in this respect resembles the branches of coral- line, which are a congeries of a multitude of animals. Each of these buds of a tree has its proper leaves or petals for lungs, produces its viviparous or its oviparous offspring in buds or seeds; has its own roots, which extending down the stem" of the tree are interwoven with the roots of the other buds, and form the bark, which is the only living part of the stem, is an- nually renewed, and is superinduced upon the former bark, which then dies, and with its stagnated juices gradually harden- VOL. i. L 74 OF VEGETABLE Sect. XIII. 2. ing into wood forms the concentric circles, which we see in blocks of timber. The following circumstances evince the individuality of the buds of trees. First, there are many trees, whose whole internal wood is perished, and yet the branches are vegete and healthy. Secondly, the fibres of the barks of trees are chiefly longitudinal, resembling roots, as is beautifully seen in those prepared barks, that were lately brought from Otaheite. Thirdly, in horizontal wounds of the bark of trees, the fibres of the upper lip are al- ways elongated downwards like roots, but those of the lower lip do not approach to meet them. Fourthly, if you wrap wet moss around any joint of a vine, or cover it with moist earth, roots will shoot out from it. Fifthly, by the inoculation or ingrafting of trees many fruits are produced from one stem. Sixthly, a new tree is produced from a branch plucked from an old one, and set in the ground. Whence it appears that the buds of deciduous trees are so many annual plants, that the bark is a contexture of the caudexes of each individual bud; which consists of a leaf or plumula at top, of a radicle below, and of a caudex, which joins these together, and constitutes the bark of the tree, and that the internal wood is of no other use but to support them in the air, and that thus they resemble the animal world in their in- dividuality. The irritability of plants, like that of animals, appears liable to be increased or decreased by habit; for those trees or shrubs, which are brought from a colder climate to a warmer, put out their leaves and blossoms a fortnight sooner than the indigenous ones. Professor Kalm, in his Travels in New York, observes that the apple-trees brought from England blossom a fortnight sooner than the native ones. In our country the shrubs, that are brought a degree or two from the north, are observed to flourish better than those which come from the south. The Siberian barley and cabbage are said to grow larger in this climate than the similar more southern vegetables. And our hoards of roots, as of potatoes and onions, germinate with less heat in spring after they have been accustomed to the winter's cold, than in autumn after the summer's heat. II. The stamens and pistils of flowers shew evident marks of sensibility, not only from many of the stamens and some pistils approaching towards each other at the season of impregnation, but from many of them closing their petals and calyxes during the cold parts of the day. For this cannot be ascribed to irri- tation, because cold means a defect of the stimulus of heat- but as the want of accustomed stimuli produces pain, as in cold- Sect. XIII. 3. ANIMATION. 75 ness, hunger, and thirst of animals, these motions of vegetables in closing up their flowers must be ascribed to the disagreeable sen- sation, and not to the irritation of cold. Others close up their leaves during darkness, which, like the former, cannot be owing to irritation, as the irritating material is withdrawn. It may be objected, that, when the petals and calyxes of flowers, and the leaves of some vegetables, close in the night, this may be their natural state, like the closing of the eyelids in the sleep of animals; and that it should thence be ascribed to the suspension of volition, rather than to disagreeable sensation. It may be an- swered, that in the sleep of animals the closing of the eyelids may not be the natural state of the part, since in the great inirritability and insensibility attending some fevers the patients sleep with their eyes half-open, and in actual death the eyes do not close spontaneously, and that hence the closing of the eyelids in sleep seems to be in consequence of our increased internal sensibility to light, or dust, or dryness. And it is certain, that the absence of the accustomed quantity of heat decreases the action of animal fibres, as is evinced by the paleness of the skin, when it is exposed to great cold; and the in- creased action of the subcutaneous muscles, as in shuddering from cold, is certainly owing to the diagreeable sensation consequent to the diminution of the accustomed irritative motions, as in Sect. XXXII. 10. and Sect. IV. 5. An excess of moisture on some parts of flowers and leaves may occasion a disagreeable sensation, as when a drop of water gets down the windpipe into the lungs of animals, and may thus oc- casion them to close. The approach of the anthers in many flowers to the stigmas, and of the pistils of some flowers to the anthers, must be ascrib- ed to the passion of love, and hence belongs to sensation, not to irritation. III. That the vegetable world possesses some degree of volun- tary powers, appears from their necessity to sleep, which we have shewn in Sect. XVIII. to consist in the temporary abolition of voluntary power. This voluntary power seems to be exerted in the circular movement of the tendrils of vines, and other climb- ing vegetables; or in the efforts to turn the upper surface of their leaves, or their flowers to the light. IV. The associations of fibrous motions are observable in the vegetable world, as well as in the animal. The divisions of the leaves of the sensitive plant have been accustomed to contract at the same time from the absence of light; hence if by any other circumstance, as a slight stroke or injury, one division is irrita- ted into contraction, the neighbouring ones contract also, from 76 OF VEGETABLE Sect. XIII. 5. 1. their motions being associated with those of the irritated part. So the various stamina of the class of syngenesia have been accus- tomed to contract together in the evening, and thence if you stimulate one of them with a pin, according to the experiment of M. Colvolo, they all contract from their acquired association. Which also shows, that the number of male or female organs existing in one flower does not destroy the individuality of it; any more than the number of paps of a bitch or sow, or the double organ of a barn-door cock; which is further evinced by the anthers and stigmas of some hermaphrodite flowers proba- bly receiving their nutriment from the same honey-gland or nectary, and having their blood oxygenated by the same corol, while in the plants of the classes of monecia and diecia the male and female organs of reproduction belong to different vegetable beings. To evince that the collapsing of the sensitive plant is not ow- ing to any mechanical vibrations propagated along the whole branch, when a single leaf is struck with the finger, a leaf of it was slit with sharp scissars, and some seconds of time passed be- fore the plant seemed sensible of the injury; and then the whole branch collapsed as far as the principal stem: this experiment was repeated several times with the least possible impulse to the plant. V. 1. For the numerous circumstances in which vegetable buds are analogous to animals, the reader is referred to the ad- ditional notes at the end of the Botanic Garden, Part I. It is there shewn, that the roots of vegetables resemble the lacteal sys- tem of animals: the sap-vessels in the early spring, before their leaves expand, are analogous to the placental vessels of the foetus; that the leaves of land-plants resemble lungs, and those of aquatic plants the gills of fish; that there are other systems of vessels resembling the vena portarum of quadrupeds, or the aorta of fish; that the digestive power of vegetables is similar to that of animals, converting the fluids, which they absorb, into sugar; that their seeds resemble the eggs of animals, and their buds, and bulbs their viviparous offspring. And lastly, that the anthers and stigmas are real animals, attached indeed to their parent tree like polypi or coral insects, but capable of spon- taneous motion; that they are affected with the passion of love, and furnished with powers of reproducing their species, and are fed with honey like the moths and butterflies, which plunder their nectaries. See Botanic Garden, Part I. add. note XXXIX. The male flowers of vallisneria approach still nearer to appar- ent animality, as they detach themselves from the parent plant. Skct. XIII. 5. 2. ANIMATION. 77 and float on the surface of the water to the female ones. Botanic Garden, Part II. Art. Vallisneria. Other flowers of the classes ofmonecia and diecia, and polygamia, discharge the fecundating farina, which floating in the air is carried to the stigma of the female flowers, and that at considerable distances. Can this be effected by any specific attraction? or, like the diffusion of the odorous particles of flowers, is it left to the currents of winds, and the accidental miscarriages of it counteracted by the quantity of its production ? 2. This leads us to a curious inquiry, whether vegetables have ideas of external things? As all our ideas are originally received by our senses the question may be changed to, whether vege- tables possess any organs of sense? Certain it is, that they pos- sess a sense of heat and cold, another of moisture and dryness, and another of light and darkness; for they close their petals oc- casionally from the presence of cold, moisture, or darkness. And it has been already shewn, that these actions cannot be perform- ed simply from irritation, because cold and darkness are nega- tive quantities, and on that account sensation or volition are im- plied, and in consequence a sensorium or union of their nerves. So when we go into the light, we contract the iris; not from any stimulus of the light on the fine muscles of the iris, but from its motions being associated with the sensation of too much light on the retina: which could not take place without a sensorium or centre of union of the nerves of the iris with those of vision. See Botanic Garden, Part I. Canto 3. 1. 440 note. Besides these organs of sense, which distinguish cold, moisture, and darkness, the leaves of mimosa, and of dionaea, and of dro- sera, and the stamens of many flowers, as of the berberry, and the numerous class of syngenesia, are sensible to mechanic im- pact, that is, they possess a sense of touch, as well as a common sensorium; by the medium of which their muscles are excited into action. Lastly, in many flowers the anthers, when mature, approach the stigma, in others the female organ approaches to the male. In a plant of collinsonia, a branch of which is now before me, the two yellow stamens are about three-eighths of an inch high, and diverge from each other at an angle of about fif- teen degrees, the purple style is half an inch high, and in some flowers is now applied to the stamen on the right hand, and in others to that of the left; and will, I suppose, change place to- morrow in those, where the anthers have not yet effused their powder. I ask, by what means are the anthers in many flowers, and stigmas in other flowers, directed to find their paramours? How do either of them know, that the other exists in their vicinity? 78 OF VEGETABLE, &c. Sect. XIII. 6. 2. Is this curious kind of storage produced by mechanic attraction, or by the sensation of love? The latter opinion is supported by the strongest analogy, because a reproduction of the species is the consequence; and then another organ of sense must be wranted to direct these vegetable amourettes to find each other, one pro- bably analogous to our sense of smell, which in the animal world directs the new-born infant to its source of nourishment, and they may thus possess a faculty of perceiving, as well as of pro- ducing odours. Thus, besides a kind of taste at the extremities of their roots, similar to that of the extremities of our lacteal vessels, for the purpose of selecting their proper food: and besides different kinds of irritability residing in the various glands, which separate honey, wax, resin, and other juices from their blood; vegetable life seems to possess an organ of sense to distinguish the vari- ations of heat, another to distinguish the varying degrees of moisture, another of light, another of touch, and probably ano- ther analogous to our sense of smell. To these must be added the indubitable evidence of their passion of love, and I think we may truly conclude that they are furnished with a common sen- sorium belonging to each bud, and that they must occasionally repeat those perceptions either in their dreams or waking hours, and consequently possess ideas of so many of the properties of the external world, and of their own existence. Sect. XIV. 1. PRODUCTION, &c. 79 SECT. XIV. OF THE PRODUCTION OF IDEAS. I. Of material and immaterial beings. Doctrine of St. Paul. II. 1. Of the sense -of touch Of solidity. 2. Of figure. Motion. Time. Place. Space. Number. 3. Of the penetrability of matter. 4. Spirit of animation possesses solidity, figure, visi- bility, fyc. Of spirits and angels. 5. The existence of external things. III. Of vision. IV. Of hearing. V. Of smell and taste. VI. Of the organ of sense by which we perceive heat and cold, not by the sense of touch. VII. Of the sense of extension, the whole of the locomotive muscles may be considered as one organ of sense. VIII. Of the senses of hunger, thirst, want of fresh air, suckling children, and lust. IX. Of many other organs of sense belonging to the glands. Of painful sensations from the excess of light, pressure, heat, itching, caustics, and electricity. I. Philosophers have been much perplexed to understand, in what manner we become acquainted with the external world; insomuch that Dr. Berkley even doubted its existence, from hav- ing observed (as he thought) that none of our ideas resemble their correspondent objects. Mr. Hume asserts, that our belief de- pends on the greater distinctness or energy of our ideas from perception; and Mr. Read has lately contended, that our belief of external objects is an innate principle necessarily joined with our perceptions. So true is the observation of the famous Malbranch, " that our senses are not given us to discover the essences of things, but to acquaint us with the means of preserving our existence," (L. I. ch. v.) a melancholy reflection to philosophers! Some philosophers have divided all created beings into material and immaterial; the former including all that part of being, which obeys the mechanic laws of action and reaction, but which can begin no motion of itself; the other is the cause of all mo- tion and is either termed the power of gravity, or of specific at- traction, or the spirit of animation. This immaterial agent is supposed to exist in or with matter, but to be quite distinct from it; and to be equally capable of existence, after the matter, which now possesses it, is decomposed. Nor is this theory ill supported by analogy, since heat, elec- tricity, and magnetism can be given to or taken from a piece of iron; and must therefore exist, whether separated from the metal, or combined with it. From a parity of reasoning, the 80 PRODUCTION OF IDEAS. Sect. XIV. 2. 1. spirit of animation would appear to be capable.of existing as well separately from the body as with it. I beg to be understood, that I do not wish to dispute about words, and am ready to allow, that the powers of gravity, spe- cific attraction, electricity, magnetism, and even the spirit of animation, may consist of matter of a finer kind; and to believe, with St. Paul and Malbranch, that the ultimate cause only of,all motion is immaterial, that is God. St. Paul says, " in him we live and move, and have our being;" and, in the 15th chapter to the Corinthians, distinguishes between the psyche or living spirit, and the pneuma or reviving spirit. By the words spirit of animation or sensorial power, I mean only that animal life which mankind possess in common with brutes, and in some degree even with vegetables, and leave the consideration of the immortal part of us, which is the object of religion, to those who treat of revelation. II. 1. Of the Sense of Touch. The first ideas wre become acquainted with are those of the sense of touch; for the foetus must experience some varieties of agitation, and exert some muscular action, in the womb; and may with great probability be supposed thus to gain some ideas of its own figure, of that of the uterus, and of the tenacity of the fluid, that surrounds it, (as appears from the facts mentioned in the succeeding Section upon Instinct.) Many of the organs of sense are confined to a small part of the body, as the nostrils, ear or eye, whilst the sense of touch is dif- fused over the whole skin, but exists with a more exquisite de- gree of delicacy at the extremities of the fingers and thumbs, and in the lips. The sense of touch is thus very commodiously dis- posed for the purpose of encompassing smaller bodies, and for adapting itself to the inequalities of larger ones. The figure of small bodies seems to be learnt by children by their lips as much as by their fingers; on which account they put every new object to their mouths, when they are satisfied 'with food, as well as when they are hungry. And puppies seem to learn their ideas of figure principally by the lips in their mode of play. We acquire our tangible ideas of objects either by the simple pressure of this organ of touch against a solid body, or by moving our organ of touch along the surface of it. In the former case we learn the length and breadth of the object by the quantity of our organ of touch, that is impressed by it: in the latter case we learn the length and breadth of objects by the continuance of their pressure on our moving organ of touch. Sect. XIV. 2.2. PRODUCTION OF IDEAS. m SI It is hence, that we are very slow in acquiring our tangible ideas, and very slow in recollecting them; for if I now think of the tangible idea of a cube, that is, if I think of its figure, and of the solidity of every part of that figure, I must conceive myself as passing my fingers over it, and seem in some measure to feel the idea, as I formerly did the impression, at the ends of them, and am thus very slow in distinctly recollecting it. When a body compresses any part of our sense of touch, what happens? First, this part of our sensorium undergoes a mechan- ical compression, which is termed a stimulus; secondly, an idea, or contraction of a part of the organ of sense is excited; thirdly, a motion of the central parts, or of the whole sensorium, which is termed sensation, is produced; and these three constitute the perception of solidity. 2. Of Figure, Motion, Time, Place, Space, Number. No one will deny, that the medulla of the brain and nerves has a certain figure; which, as it is diffused through nearly the whole of the body, must have nearly the figure of that body. Now it follows, that the spirit of animation, or living principle, as it oc- cupies this medulla, and no other part, (which is evinced by a great variety of cruel experiments on living animals,) it follows, that this spirit of animation has also the same figure as the me- dulla above described. I appeal to common sense! the spirit of animation acts, Where does it act? It acts wherever there is the medulla above mentioned; and that whether the limb is yet join- ed to a living animal, or whether it be recently detached from it; as the heart of a viper or frog will renew its contractions, when pricked with a pin, for many minutes of time after its exsection from the body.—Does it act any where else?—No; then it cer- tainly exists in this part of space, and no where else; that is, it hath figure; namely, the figure of the nervous system, which is nearly the figure of the body. When the idea of solidity is ex* cited, as above explained, a part of the extensive organ of touch is compressed by some external body, and this part of the sen- sorium so compressed exactly resembles in figure the figure of the body that compressed it. Hence, when we acquire the idea of solidity, we acquire at the same time the idea of figure; and this idea of figure, or motion of a part of the organ of touch, ex- actly resembles in its figure the figure of the body that occasions it; and thus exactly acquaints us with this property of the ex- ternal world. Now, as the whole universe with all its parts possesses a cer- tain form or figure, if any part of it moves, that form or figure of VOL. I. M 82 PRODUCTION OF IDEAS. Sect. XIV. 2.2. the whole is varied: hence, as motion is no other than a perpe- tual variation of figure, our idea of motion is also a real resem- blance of the motion that produced it. It may be said in objection to this definition of motion, that an ivory globe may revolve on its axis, and that here will be a mo- tion without change of figure. But the figure of the particle a: on one side of this globe is not the same figure as the figure of y on the other side, any more than the particles themselves are the same, though they are similar figures; and hence they cannot change place with each other without disturbing or changing the figure of the whole. Our idea of time is from the same source, but is more ab- stracted, as it includes only the comparative velocities of these variations of figure; hence if it be asked, How long was this book in printing? it may be answered, Whilst the sun was passing through Aries. Our idea of place includes only th~ figure of a group of bodies, not the figures of the bodies themselves. If it be asked where is Nottinghamshire, the answer is, it is surrounded by Derbyshire, Lincolnshire, and Leicestershire; hence place is our idea of the figure of one body surrounded by the figures of other bodies. The idea of space is a more abstracted idea of place excluding the group of bodies. The idea of number includes only the particular arrangements or distributions of a group of bodies, and is therefore only amore abstracted idea of the parts of the figure of the group of bodies; thus when I say England is divided into forty counties, I only speak of certain divisions of its figure. Hence arises the certainty of the mathematical sciences, as they explain these properties of bodies, which are exactly resem- bled by our ideas of them, whilst we are obliged to collect al- most all our other knowledge from experiment; that is, by ob- serving the effects exerted by one body upon another. I feel myself much obliged by the accurate attention given to the first volume of Zoonomia, and by the ingenious criticisms bestowed on it, by the learned writers of that article both in the Analytical and English Reviews. Some circumstances, in which their sentiments do not accord with those expressed in the work, I intend to reconsider, and to explain further at some future time. One thing, in which both these gentlemen seem to dissent from me, I shall now mention, it is concerning the manner, in which we acquire the idea of figure; a circumstance of great importance in the knowledge of our intellect, as it shews the cause of the accuracy of our ideas of motion, time, space, number, and of the S/ct. XIV. 2.2. PRODUCTION OF IDEAS. 83 mathematical sciences, which are concerned in the mensurations or proportions of figure. This I imagine may have in part arisen from the prepossession, which has almost universally prevailed, that ideas are immaterial beings, and therefore possess no properties in common with solid matter. Which I supposed to be a fanciful hypothesis, like the stories of ghosts and apparitions, which have so long amused, and still amuse the credulous without any foundation in nature. The existence of our own bodies, and of their solidity, and of their figure, and of their motions, is taken for granted in my ac- count of ideas; because the ideas themselves are believed to con- sist of motions or configurations of solid fibres; and the question now proposed is, how we become acquainted with the figures of bodies external to our organs of sense? Which I can only repeat from what is mentioned in Sect. XIV. 2. 2. that if part of an organ of sense be stimulated into action, as of the sense of touch, that part so stimulated into action must possess figure, which must be similar to the figure of the body, which stimulates it. Another previous prepossession of the mind, which may have rendered the manner of our acquiring the knowledge of figure less intelligible, may have arisen from the common opinion of the perceiving faculty residing in the head; whereas our daily expe- rience shews, that our perception (which consists of an idea, and of the pleasure or pain it occasions) exists principally in the or- gan of sense, which is stimulated into action; as every one, who burns his finger in the candle, must be bold to deny. When an ivory triangle is pressed on the palm of the hand, the figure of the surface of the part of the organ of touch thus com- pressed is a triangle, resembling in figure the figure of the exter- nal body which compresses it. The action of the stimulated fibres, which constitute the idea of hardness and of figure, re- mains in this part of the sensorium, which forms the sense of touch; but the sensorial motion, which constitutes pleasure or pain, and which is excited in consequence of these fibrous motions of the organ of sense, is propagated to the central parts of the sensorium, or to the whole of it; though this generally occurs in less degree of energy, than exists in the stimulated organ of sense; as in the instance above mentioned of burning a finger in the candle. Some, who have espoused the doctrine of the immateriality of ideas, have seriously doubted the existence of a material world, with which only our senses acquaint us; and yet have assented to the existence of spirit, with which our senses cannot acquaint us; and have finally allowed, that all our knowledge is derived through 84 PRODUCTION OF IDEAS. Sect. XIV. 2. 3. the medium of our senses! They forget, that if the spirit of ani- mation had no properties in common with matter, it could neither affect nor be affected by the material body. But the knowledge of our own material existence being granted, which I suspect few rational persons will seriously deny, the existence of a material external world follows in course; as our perceptions, when we are awake and not insane, are distinguished from those excited by sensation, as in our dreams, and from those excited by volition or by association, as in insanity and reverie, by the power we have of comparing the present perceptions of one sense with those of another, as explained in Sect. XIV. 2. 5. And also by com- paring the tribes of ideas, which the symbols of pictures, or of languages, suggest to us by intuitive analogy with our previous experience, that is, with the common course of nature. See Class III. 2. 2. 3. on Credulity. 3. Of the Penetrability of Matter. The impossibility of two bodies existing together in the same space cannot be deduced from our idea of solidity, or of figure. As soon as we perceive the motions of objects that surround us, and learn that we possess a power to move our own bodies, we experience, that those objects, which excite in us the idea of soli- dity and of figure, oppose this voluntary movement of our own organs; as whilst I endeavour to compress between my hands an ivory ball into a spheriod. And we are hence taught by expe- rience, that our own body, and those which we touch, cannot ex- ist in the same part of space. But this by no means demonstrates, that no two bodies can exist together in the same part of space. Galilaeo, in the pre- face to his works, seems to be of opinion, that matter is not impe- netrable: Mr. Mitchel, and Mr. Boscowich, in his Theoria Phi- los. Natur. have espoused this hypothesis: which has been lately published by Dr. Priestley, to whom the world is much indebted for so many important discoveries in science. (Hist, of Light and Colours, p. 391.) The uninterrupted passage of light through transparent bodies, of the electric aether through me- tallic and aqueous bodies, and of the magnetic effluvia through all bodies, would seem to give some probability to this opinion. Hence it appears, that beings may exist without possessing the property of solidity, as well as they can exist without possessing the properties, which excite our smell or taste, and can thence occupy space without detruding other bodies from it; but we cannot become acquainted with such beings by our sense of Sect. XIV. 2. 4. PRODUCTION OF IDEAS. 85 touch, any more than we can with odours or flavours without our senses of smell and taste. But that any being can exist without existing in space, is, to my ideas utterly incomprehensible. My appeal is to common sense. To be implies a when and a where; the one is compar- ing it with the motions of other beings, and the other with their situations. If there was but one object, as the whole creation may be con- sidered as one object, then I cannot ask where it exists? for there are no other objects to compare its situation With. Hence if any one denies, that a being exists in space, he denies, that there are any other beings but that one; for to answer the question, "Where does it exist?" is only to mention the situation of the objects that surround it. In the same manner if it be asked—" When does a being exist?" The answer only specifies the successive motions either of itself, or of other bodies; hence to say, a body exists not in time, is to say, that there is, or was, no motion in the world. 4. Of tlie Spirit of Animation. But though there may exist beings in the universe, that have not the property of solidity; that is, which can possess any part of space, at the same time that it is occupied by other bodies; yet there may be other beings, that can assume this property of soli- dity, or disrobe themselves of it occasionally, as we are taught of spirits, and of angels; and it would seem, that the spirit of animation must be endued with this property, otherwise how could it occasionally give motion to the limbs of animals?—or be itself stimulated into motion by the obtrusions of surrounding bodies, as of light, or odour? If the spirit of animation was always necessarily penetrable, it could not influence or be influenced by the solidity of com- mon matter; they would exist together, but could not detrude each other from the part of space, where they exist; that is, they could not communicate motion to each other. No (wo things can influence or affect each other, which have not some pro- perty common to both of them; for to influence or affect another body is to give or communicate some property to it, that it had not before; but how can one body give that to another, which it Joes not possess itself?—The words imply, that they must agree in having the power or faculty of possessing some common property. Thus if one body removes another from the part of space, that it possesses, it must have the power of occupying that space itself: and if one body communicates heat or motion 86 PRODUCTION OF IDEAS. Sect. XIV. 2. 5. to another, it follows, that they have alike the property of pos- sessing heat or motion. Hence the spirit of animation, at the time it communicates or receives motion from solid bodies, must itself possess some property of solidity. And in consequence at the time it re- ceives other kinds of motion from light, it must possess that property, which light possesses, to communicate that kind of motion; and for which no language has a name, unless it may be termed Visibility. And at the time it is stimulated into other kinds of animal motion by the particles of sapid and odorous bodies affecting the senses of taste and smell, it must resemble these particles of flavour, and of odour, in possessing some simi- lar or correspondent property; and for which language has no name, unless we may use the words Saporosity and Odorosity for those common properties, which are possessed by our organs of taste and smell, and by the particles of sapid and odorous bodies; as the wrords Tangibility and Audibility may express the common property possessed by our organs of touch, and of hearing, and by the solid bodies, or their vibrations, which af- fect those organs. 5. Finally, though the figures of bodies are in truth resembled by the figure of the part of the organ of touch, which is stimulated into motion; and that organ resembles the solid body, which stimulates it, in its property of solidity; and though the sense of hearing resembles the vibrations of external bodies in its capa- bility of being stimulated into motion by those vibrations; and though our other organs of sense resemble the bodies that stimu- late them, in their capability of being stimulated by them; and we hence become acquainted with these properties of the ex- ternal world; yet as we can repeat all these motions of our organs of sense by the efforts of volition, or in consequence of the sen- sation of pleasure or pain, or by their association with other fibrous motions, as happens in our reveries or in sleep, there would still appear to be some difficulty in demonstrating the ex- istence of any thing external to us. In our dreams we cannot determine this circumstance, be- cause our power of volition is suspended, and the stimuli of ex- ternal objects are excluded; but in our waking hours we can compare our ideas belonging to one sense with those belonging to another, and can thus distinguish the ideas occasioned by irrita- tion from those excited by sensation, volition or association. Thus if the idea of the sweetness of sugar should be excited in our dreams, the whiteness and hardness of it occurs at the same time be association; and we believe a material lump of sugar present before us. But if, in our waking hours, the idea of the Sect. XIV. 5. PRODUCTION OF IDEAS. 87 sweetness of sugar occurs to us, the stimuli of surrounding ob- jects, as the edge of the table, on which we press, or green colour of the grass, on which we tread, prevent the other ideas of the hardness and whiteness of the sugar from being excited by association. Or if they should occur, we voluntarily com- pare them with the irritative i leas, of the table or grass above mentioned, and detect their fallacy. We can thus distinguish the ideas caused by the stimuli of external objects from those, which are introduced by association, sensation, or volition; and during our waking hours can thus acquire a knowledge of the external world. Which nevertheless we cannot do in our dreams, because we have neither perceptions of external bodies, nor the power of volition to enable us to compare them with the ideas of imagination. HI. Of Vision. Our eyes observe a difference of colour, or of shade, in the prominences and depressions of objects, and that those shades uniformly vary, when the sense of touch observes any variation. Hence when the retina becomes stimulated by colours or shades of light in a certain form, as in a circular spot; we know by ex- perience, that this is a sign, that a tangible body is before us; and that its figure is resembled by the miniature figure of the part of the organ of vision, that is thus stimulated. Here whilst the stimulated part of the retina resembles exact- ly the visible figure of the whole in miniature, the various kinds of stimuli from different colours make the visible figures of the minuter parts; and by habit we instantly recall the tangible figures. Thus when a tree is the object of sight, a part of the retina resembling a flat branching figure is stimulated by various shades of colours; but it is by suggestion, that the gibbosity of the tree, and the moss, that fringes its trunk, appear before us. These are ideas of suggestion, which we feel or attend to, associated with the motions of the retina, or irritative ideas, which we do not attend to. So that though our visible ideas resemble in miniature the out- line of the figure of coloured bodies in other respects they serve only as a language, which by acquired associations introduce the tangible ideas of bodies. Hence it is, that this sense is so readily deceived by the art of the painter to our amusement and instruction. The reader will find much very curious knowledge on this subject in Bishop Berkeley's Essay on Vision, a work of great ingenuity. 88 PRODUCTION OF IDEAS. Sect. XIV. 4. The immediate object however of the sense of vision is light; this fluid, though its velocity is so great, appears to have no per- ceptible mechanical impulse, as was mentioned in the third sec- tion, but seems to stimulate the retina into animal motion by its transmission through this part of the sensorium: for though the eyes of cats or other animals appear luminous in obscure places; yet it is probable, that none of the light, which falls on the retina, is reflected from it, but adheres to or enters into combination with the choroide coat behind it. The combination of the particles of light with opaque bodies, and therefore with the choroide coat of the eye, is evinced from the heat which is given out, as in other chemical combinations. For the sun-beams communicate no heat in their passage through transparent bodies, with which they do not combine, as the air continues cool even in the focus of the largest burning-glasses, which in a moment vetrifies a particle of opaque matter. IV. Of the Organ of Hearing. It is generally believed, that the tympanum of the ear vi- brates mechanically, when exposed to audible sounds, like the strings of one musical instrument, when the same notes are struck upon another. Nor is this opinion improbable, as the muscles and cartilages of the larinx are employed in producing variety of tones by mechanical vibrations: so the muscles and bones of the ear seem adapted to increase or diminish the ten- sion of the tympanum for the purposes of similar mechanical vibrations. But it appears from dissection, that the tympanum is not the immediate organ of hearing, but that, like the humours and cor- nea of the eye, it is only of use to prepare the object for the im- mediate organ. For the portio mollis of the auditory nerve is not spread upon the tympanum, but upon the vistibulum, and cochlea, and semi-circular canals of the ear; while between the tympanum and the expansion of the auditory nerve the cavity is said by Dr. Cotunnus and Dr. Mechel to be filled with water; as they had frequently observed by freezing the heads of dead animals before they dissected them; and water being a more dense fluid than air is much better adapted to the propagation of vibration. We may add, that even the external opening of the ear is not ab- solutely necessary for the perception of sound: for some people, who from these defects would have been completely deaf, have distinguished acute or grave sounds by the tremours of a stick held between the teeth propagated along the bones of the head, (Haller. Phys. T. V. p. 295.) Six*. XIV 5. PRODUCTION OF IDEAS 89 Hence it appears, that the immediate organ of hearing is not affected by the particles of the air themselves, but is stimulated into animal motion by the vibrations of them. And it is "probable from the loose bones, which are found in the heads of some fishes, that the vibrations of water are sensible to the inhabitants of that element by a similar organ. The motions of the atmosphere, which we become acquainted with by the sense of touch, are combined with its solidity, weight, or vis inertiae; whereas those, that are perceived by this organ, depend alone on its elasticity, But though the vibration of the air is the immediate object of the sense of hearing, yet the ideas, we receive by this sense, like those received from light, are only as a language, which by acquired associations acquaints us with those motions of tangible bodies, which depend on their elasticity; and which we had before learned by our sense of touch* V. Of Smell and of Taste. The objects of smell are dissolved in the fluid atmosphere, and those of taste in the saliva, or other aqueous fluid, for the better diffusing them on their respective organs, which seem to be stimulated into animal motion perhaps by the chemical af- finities of these particles, which constitute the sapidity and odo- rosity of bodies, with the nerves of sense, which perceive them. Mr. Volta has lately observed a curious circumstance relative to our sense of taste. If a bit of clean lead, and a bit of clean silver be separately applied to the tongue and palate no taste is perceived; but by applying them in contact in respect to the parts out of the mouth, and nearly so in respect to the parts, which are immediately applied to the tongue and palate, a saline or acidu- ous taste is perceived, as of a fluid like a stream of electricity passing from one of them to the other. This new application of the sense of taste deserves further investigation, as it may ac- quaint us with new properties of matter. From the experiments above mentioned of Galvani, Volta, Fowler, and others, it appears that a plate of zinc and a plate of silver have greater effect than lead and silver. If one edge of a plate of silver about the size of half a crown-piece he placed up- on the tongue, and one edge of a plate of zinc about the same size beneath the tongue, and if their opposite edges are then brought into contact before the point of the tongue, a taste is perceived at the moment of their coming into contact; second- ly, if one of the above plates be put between the upper lip and the gum of the fore-teeth, and the other be placed under the VOL. I N 90 PRODUCTION OF IDEAS. Sect. XIV. 6 tongue, and their exterior edges be then brought into contact in a darkish room, a flash of light is perceived in the eyes. These effects I imagine only shew the sensibility of our nerves of sense to very small quantities of the electric fluid, as it passes through them, for I suppose these sensations are occasioned by slight electric shocks produced in the following manner. By the experiments published by Mr. Bennet, with his ingenious doubler of electricity, which is the greatest discovery made in that science since the coated jar, and the eduction of lightning from the skies, it appears that zinc was always found minus, and silver was always found plus, when both of them were in their separate state. Hence, when they are placed in the manner above described, as soon as their exterior edges come nearly into contact, so near as to have an extremely thin plate of air between them, that plate of air becomes charged in the same manner as a plate of coated glass; and is at the same instant discharged through the nerves of taste or of sight, and gives the sensations, as above described, of light or of saporositv; and only shews the great sensibility of these organs of sense to the stimulus of tbr electric fluid in suddenly passing through them. VI. Of the Sense of Heat. There are many experiments in chemical writers, that evinct the existence of heat as a fluid element, which covers and per- vades all bodies, and is attracted by the solutions of some of them, and is detruded from the combination of others. Thus from the combinations of metals with acids, and from those combinations of animal fluids, which are termed secretions, this fluid matter of heat is given out amongst the neighbouring bodies; and in the solutions of salts in water, or of water in air, it is absorbed from the bodies, that surround them; whilst in its faci- lity in passing through metallic bodies, and its difficulty in per- vading resins and glass, it resembles the properties of the electric aura; and is like that excited by friction, and seems like that to gravitate amongst other bodies in its uncombined state, and to find its equilibrium. There is no circumstance of more consequence in the animal economy, than a due proportion of this fluid of heat; for the digestion of our nutriment in the stomach and bowels, and the proper qualities of all our secreted fluids, as they are produced or prepared partly by animal and partly by chemical processes, depend much on the quantity of heat; the excess of which, or its deficiency, alike gives us pain, and induces us to avoid the circumstances that occasion them. And in this the perception SECT XIV. 6. PRODUCTION OF IDEAS. 91 of heat essentially differs from the perceptions of the sense of touch, as we receive pain from too great pressure of solid bodies, but none from the absence of it. It is hence probable, that na- ture has provided us with a set of nerves for the perception of this fluid, which anatomists have not yet attended to. There may be some difficulty in the proof of this assertion; if we look at a hot fire, we experience no pain of the optic nerve, though ihe heat along with the light must be concentrated upon it. Nor does warm water or warm oil poured into the ear give pain to the organ of hearing; and hence as these organs of sense do not perceive small excesses or deficiencies of heat; and as heat has no greater analogy to the solidity or to the figures of bodies, than it has to their colours or vibrations; there seems no sufficient reason for our ascribing the perception of heat and cold to the sense of touch; to which it has generally been attributed, either because it is diffused beneath the whole skin like the sense of touch, or owing to the inaccuracy of our observations, or the defect of our languages. There is another circumstance would induce us to believe, that the perceptions of heat and cold do not belong to the organ of touch; since the teeth, which are the least adapted for the perceptions of solidity of figure, are the most sensible to heat or cold; whence we are forewarned from swallowing those mate- rials, whose degree of coldness or of heat would injure our stomachs. The following is an extract from a letter of Dr. R. W. Dar- win, of Shrewsbury, when he was a student at Edinburgh. " I made an experiment yesterday in our hospital, which much fa- vours your opinion, that the sensations of heat and of touch de- depend on different sets of nerves. A man who had lately re- covered from a fever, and was still weak, was seized with vio- lent cramps in his legs and feet; which were removed by opiates, except thai one of his feet remained insensible. Mr. Ewart pricked him with a pin in five or six places, and the patient de- clared he did not feel it in the least, nor was he sensible of a very smart pinch. I then held a red-hot poker at some distance, and brought it gradually nearer till it came within three inches, when he asserted that he felt it quite distinctly. I suppose some violent irritation on the nerves of touch had caused the cramps, and had left them paralytic; while the nerves of heat, having suffered no increased stimulus, retained their irritability." Add to this, that the lungs, though easily stimulated into in- flammation, are not sensible to heat. See Class III. 1. 1. 10. 92 PRODUCTION OP IDEAS. Sect. XIV. 7. VII. Of the Sense of Extension. The organ of touch is properly the sense of pressure, but the muscular fibres themselves constitute the organ of sense, that feels extension. The sense of pressure is always attended with the ideas of the figure and solidity of the object, neither of which accompany our perception of extension. The whole set of muscles, whether they are hollow ones, as the heart, arteries, and intestines, or longitudinal ones attached to bones, contract themselves, whenever they are stimulated by forcible elonga- tions; and it is observable, that the white muscles, which con- stitute the arterial system, seem to be excited into contraction from no other kinds of stimulus, according to the experiments of Haller. And hence the violent pain in some inflammations, as in the paronychia, obtains immediate relief by cutting the mem- brane, that was stretched by the tumour of the subjacent parts. Hence the whole muscular system may be considered as one organ of sense, and the various attitudes of the body, as ideas be- longing to this organ, of many of which we are hourly consci- ous, while many others, like the irritative ideas of the other senses, are performed without our attention. When the muscles of the heart cease to act, the refluent blood again distends or elongates them; and thus irritated they con- tract as before. The same happens to the arterial system, and I suppose to the capillaries, intestines, and various glands of the body. When the quantity of urine, or of excrement, distends the bladder, or rectum, those parts contract, and exclude their con- tents, and many other muscles by association act along with them; but if these evacuations are not soon complied with, pain is produced by a little further extension of the muscular fibres: a similar pain is caused in the muscles, when a limb is much ex- tended for the reduction of dislocated bones; and in the punish- ment of the rack: and in the painful cramps of the calf of the leg, or of other muscles, for a greater degree of contraction of a muscle, than the movement of the two bones, to which its ends are affixed, will admit of, must give similar pain to that, which is produced by extending it beyond its due length. And the pain from punctures or incisions arises from the distention of the fibres, as the knife passes through them; for it nearly ceases as soon as the division is completed. All these motions of the muscles, that are thus naturally ex-. cited by the stimulus of distending bodies, are also liable to be called into strong action by their catenation with the irritations Sect. XIV. 8. PRODUCTION OF IDEAS. 93 or sensations produced by the momentum of (he progressive par- ticles of blood in the arteries, as in inflammatory fevers, or by acrid substances on other sensible organs, as in the strangury, or tenesmus, or cholera. We shall conclude this account of the sense of extension by observing, that the want of its object is attended with a disagree- able sensation, as well as the excess of it. In those hollow mus- cles, which have been accustomed to it, this disagreeable sensa- tion is called faintness, emptiness, and sinking; and, when it arises to a certain degree, is attended with syncope, or a total quiescence of all motions, but the internal irritative ones, as hap- pens from sudden loss of blood, or in the operation of tapping in the dropsy. VIII. Of the Appetites of Hunger, Thirst, Heat, Extension, the want of Fresh Air, Animal Love, and the Suckling of Children. Hunger is most probably perceived by those numerous rami- fications of nerves that are seen about the upper opening of the stomach; and thirst by the nerves about the fauces, and the top of the gula. The ideas of these senses are few in the generality of mankind, but are more numerous in those, who by disease, or in- dulgence, desire particular kinds of foods or liquids. A sense of heat has already been spoken of, which may with. propriety be called an appetite, as we painfully desire it, when it is deficient in quantity. The sense of exiension may be ranked amongst these appetites, since the deficiency of its object gives disagreeable sensations; when this happens in the arterial system, it is called faintness, and seems to bear some analogy to hunger and to cold; which like it are attended with emptiness of a part of the vascular system. The sense of want of fresh air has not been attended to, but is as distinct as the others, and the first perhaps thst we experience after our nativity; from the want of the object of this sense many diseases are produced, as the jail-fever, plague, and other epi- demic maladies. Animal love is another appetite, which occurs later in life, and the females of lactiferous animals have another natural inlet of pleasure or pain from the suckling their offspring. The want of which, either owing to the death of their progeny, or to the fashion of their country, has been fatal to many of the sex. The males have also pectoral glands which are frequently turgid with a thin milk at their nativity, and are furnished with nipples, which erect on titillation like* those of the female; but which seem now to be of no further use, owing perhaps to some 94 PRODUCTION OF IDEAS. Sect. XIV. 9. change which these animals have undergone in the gradual pro. gression of the formation of the earth, and of all that it inhabit. These seven last mentioned senses may properly be termed appetites, as they differ from those of touch, sight, hearing, taste, and smell, in this respect; that they are affected with pain as well by the defect of their objects as by the excess of them, which is not so in the later. Thus cold and hunger give us pain, as well as an excess of heat or satiety; but it is not so with dark- ness and silence. IX. Before we conclude this Section on the organs of sense, we must observe, that, as far as we know, there are many more senses than have been here mentioned, as every gland seems to be influenced to separate from the blood, or to absorb from the cavities of the body, or from the atmosphere, its appropriated fluid, by the stimulus of that fluid on the living gland; and not by mechanical capillary absorption, nor by chemical affinity. Hence it appears, that each of these glands must have a peculiar organ to receive these irritations, but as these irritations are not succeeded by sensation, they have not acquired the names of senses. However, when these glands are excited into motions stronger than usual, either by the acrimony of their fluids, or by their own irritability being much increased, thtn the sensation of pain is produced in them as in all the other senses of the body; and tlrse pains are all of different kinds, and heuce the glands at this time really become each a different organ of sense, though these differ- ent kinds of pain have acquired no names. Thus a great excess of light does not give the idea of light but of pain; as in forcibly opening the eye when it is much inflamed. The great excess of pressure or distention, as when the point of a pin is pressed upon our skin, produces pain, (and when this pain of the sense of distention is slighter, it is termed itching, or tick- ling), without any idea of solidity or of figure: an excess of heat Produces smarting, of cold another kind of pain; it is probable y this sense of heat the pain produced by caustic bodies is per- ceived, and of electricity, as all these are fluids, that permeate, distend or decompose the parts that feel them. Sect. XV. 1.1. CLASSES OF IDEAS. 95 SECT. XV. OF THE CLASSES OF IDEAS. I. 1. Ideas received in tribes. 2. We combine them further, or ab- stract from these tribes. 3. Complex ideas. 4. Compounded ideas. 5. Simple ideas, modes, substances, relations, general ideas. 6. Ideas of reflexion. 7. Memory and imagination imper- fectly defined. Ideal presence. Memorandum-rings. II. l.Irri* lative ideas. Perception. 2. Sensitive ideas, imagination. 3. Voluntary ideas, recollection. 4. Associated ideas, suggestion. III. I. Definitions of perception, memory. 2. Reasoning,judg- ment, doubting, distinguishing, comparing. 3. Invention. 4. Consciousness. 5. Identity. 6. Lapse of time. 7. Freewill. I. 1. As the constituted elements of the material world are only perceptible to our organs of sense in a state of combination: it follows that the ideas or sensual motions excited by them, are never received singly, but ever with a greater or less degree of combination. So the colours of bodies or their hardnesses occur with their figures: every smell and taste has its degree of pun- gency as well as its peculiar flavour: and each note in music is combined with the tone of some instrument. It appears from hence, that we can be sensible of a number of ideas at the same time, such as the whiteness, hardness, and coldness of a snow- ball, and can experience at the same time many irritative ideas of surrounding bodies, which we do not attend to, as mentioned in Section VII. 3. 2. But those ideas which belong to the same sense, seem to be more easily combined into synchronous tribes, than those which were not received by the same sense, as we can more easily think of the whiteness and figure of a lump of sugar at the same time, than the whiteness and sweetness of it. 2. As these ideas, or sensual motions, are thus excited with greater or less degrees of combination; so we have a power, when We repeat them either by our volition or sensation, to increase or diminish this degree of combination, that is, to form compounded ideas from those, which were more simple; and abstract ones from those, which were more complex, when they were first ex- cited; that is, we can repeat a part or the whole of those sensual motions, which did constitute our ideas of perception: and the repetition of which now constitutes our ideas of recollection, or of imagination. 3. Those ideas, which we repeat without change of the quan- tity of that combination, with which we first received them, are 96 CLASSES OF IDEAS. Sect. XV. 1.4. called complex ideas, a^ when you recollect Westminster Abbey, or the planet Saturn: but it must be observed, that these com- plex ideas, thus re-excited by volition, sensation, or association, are seldom perfect copies of their correspondent perceptions, ex- cept in our dreams, where other external objects do not detract our attention. 4. Those ideas, which are more complex than the natural ob- jects that first excited them, have been called compounded ideas, as when we think of a sphinx, or griffin. 5. And those that are less complex than the correspondent na- tural objects, have been termed abstracted ideas: thus sweetness, and whiteness, and solidity, are received at the same time from a lump of sugar, yet I can recollect any of these qualities without thinking of the others, that were excited along with them. See Sect. XVI. 17. When ideas are so far abstracted as in the above example, they have been termed simple by the writers of metaphysics, and seem indeed to be more complete repetitions of the ideas or sen- sual motions, originally excited by external objects. Other classes of these ideas, where the abstraction has not been so great, have been termed, by Mr. Locke, modes, substances, and relations, but they seem only to differ in their degree of ab- straction from the complex ideas that were at first excised; for as these complex or natural ideas are themselves imperfect copies of their correspondent perceptions, so these abstract or general ideas are only still more imperfect copies of the same percep- tions. Thus when I have seen an object but once, as a rhino- ceros, my abstract idea of this animal is the same as my complex one. I may think more or less distinctly of a rhinoceros, but it is the very rhinoceros that I saw, or some part or property of him, which recurs to my mind. But when any class of complex objects becomes the subject of conversation, of which I have seen many individuals, as a castle or an army, some property, or circumstance belonging to it is peculiarly alluded to; and then I feel in my own mind, that my abstract idea of this complex object is only an idea of that part, property, or attitude of it, that employs the present conversation, and varies with every sentence that is spoken concerning it. So if any one should say, "one may sit upon a horse safer than on a camel," my abstract idea of the two animals includes only an outline of the level back of the one, and the gibbosity on the back of the other. What noise is that in the street?—Some horses trotting over the pavement. Here my idea of the horses includes principally the shape and motion of their legs. So al>o die abstract ideas, of goodness and courage are still uioreim- Sect. XV. 1.6. CLASSES OF IDEAS. 97 perfect representations of the objects they were received from; for here we abstract the material parts, and recollect only the qualities. Thus we abstract so much from some of our complex ideas, that at length it becomes difficult to determine of what percep- tion they partake; and in many instances our idea seems to be no other than of the sound or letters of the word, that stands for the collective tribe, of which we are said to have an abstracted idea, as noun, verb, chimaera, apparition. Mr. Home Tooke, also, in his Diversions of Purley, has very in- geniously shewn,that whatwerecalled general ideas, are in reality only general terms; or words which signify any parts of a com- plex object. Whence arises much error in our verbal reasoning, as the same word has different significations. And hence those, who can think without words, reason more accurately than those, who only compare the ideas suggested by words; a rare faculty, which distinguishes the writers of philosophy from those of sophistry. See Class III. 2. 2. 3. 6. Ideas have been divided into those of perception and those of reflection, but as whatever is perceived must be external to the organ that perceives it, all our ideas must originally be ideas of perception. 7. Others have divided our ideas into those of memory and those of imagination; they have said that a recollection of ideas in the order they were received constitutes memory, and without that order imagination; but all the ideas of imagination, excepting the few that are termed simple ideas, are parts of trains or tribes in the order they were received; as if I think of a sphinx, or a griffin, the fair face, bosom, wings, claws, tail, are all complex ideas in the order they were received: and it behoves the writers, who adhere to this definition, to determine, how small the trains must be, that shall be called imagination; and how great those, tfiat shall be called memory. Others have thought that the ideas of memory have a greater vivacity than those of imagination: but the ideas of a person in sleep, or in a waking reverie, where the trains connected with sensation are uninterrupted, are more vivid and distinct than those of memory, so that they cannot be distinguished by this criterion. The very ingenious author of the Elements of Criticism has described what he conceives to be a species of memory, and calls it ideal presence; but the instances he produces are the reveries of sensation, and are therefore in truth connexions of the imagina- tion, though they are recalled in the order they were received. The ideas connected by association are in common discourse vol. i. o 93 CLAboES OF IDEAS. Sect. XV. 2. 1. attributed to memory, as we talk of memorandum-rings, and tie a knot on our handkerchiefs to bring something into our minds at a distance of time. And a school-boy who can repeat a thousand unmeaning lines in Lilly's Grammar, is said to have a good me- mory. But these have been already shewn to belong to the class of association; and are termed ideas of suggestion. II. Lastly, the method already explained of classing ideas into those excited by irritation, sensation, volition, or association, we hope will be found more convenient both for explaining the opera- tions of the mind, and for comparing them with those of the body; 'and for the illustration and the cure of the diseases of both, and which we shall here recapitulate. 1. Irritative ideas are those, which are preceded by irritation, which is excited by objects external to the organs of sense: as the idea of that tree, which either I attend to, or which I shun in walking near it without attention. In the former case it is term- ed perception, in the latter it is termed simply an irritative idea. 2. Sensitive ideas are those, which are preceded by the sensa- tion of pleasure or pain; as the ideas, which constitute our dreams or reveries; this is called imagination. 3. Voluntary ideas are those, which are preceded by voluntary exertion, as when I repeat the alphabet backwards: this is called recollection. 4. Associate ideas are those, which are preceded by other ideas or muscular motions, as when we think over or repeat the alpha- bet by rote in its usual order; or sing a tune we are accustomed to: this is called suggestion. III. 1. Perceptions signify those ideas, which are preceded by irritation and succeeded by the sensation of pleasure or pain, for whatever excites our attention interests us; that is, it is accom- panied with pleasure or pain; however slight may be the degree or quantity of either of them. The word memory includes two classes of ideas, either those which are preceded by voluntary exertion, or those which are suggested by their associations with others ideas. 2. Reasoning is that operation of the sensorium, by which we excite two or many tribes of ideas: and then re-excite the ideas, in which they differ, or correspond. If we determine this differ- ence, it is called judgment: if we in vain endeavour to deter- mine it, it is called doubting. If we re-excite the ideas in which they differ, it is called dis- tinguishing. If we re-excite those in which they correspond, it is called comparing. 3. Iqvention is $n operation of the sensorium, by which we voluntarily continue to excite one train of ideas, suppose the de- Sect. XV. 3, 4. CLASSES OF IDEAS. 99 sign of raising water by a machine; and at the same time attend to all other ideas, which are connected with this by every kind of catenation; and combine or separate them voluntarily for the pur- pose of obtaining some end. For we can create nothing new, we can only combine or sepa- rate the ideas, which we have already received by our percep- tions: thus if I wish to represent a monster, I call to my mind the ideas of every thing disagreeable and horrible, and combine the nastiness and gluttony of a hog, the stupidity and obstinacy of an ass, with the fur and awkwardness of a bear, and call the new combination Caliban. Yet such a monster may exist in nature, as all his attributes are parts of nature. So when I wish to represent every thing that is excellent and amiable; when I combine benevolence with cheerfulness, wisdom, knowledge, taste, wit, beauty of person, and elegance of manners, and asso- ciate them in one lady as a pattern to the world, it is called in- vention; yet such a person may exist,—such a person does ex- ist!—It is----------, who is as much a monster as Caliban. 4. In respect to consciousness, we are only conscious of our existence, when we think about it; as we only perceive the lapse of time, when we attend to it; when we are busied about other objects, neither the lapse of time nor the consciousness of our own existence can occupy our attention. Hence, when we think of our own existence, we only excite abstracted or reflex ideas, (as they are termed,) of our principal pleasures or pains, of our desires or aversions, or of the figure, solidity, colour, or other properties of our bodies, and call that act of the sensorium a con- sciousness of our existence. Some philosopher, I believe it is Des Cartes, has said " I think, therefore, I exist." But this is not right reasoning, because thinking is a mode of existence; and and it is thence only saying, " I exist, therefore I exist." For there are three modes of existence, or in the language of gram- marians three kinds of verbs. First, simply I am, or exist. Secondly, I am acting, or exist in a state of activity, as I move. Thirdly, I am suffering, or exist in a state of being acted upon, as 1 am moved. The when, and the where, as applicable to this existence, depends on the successive motions of our own or of Other bodies; and on their respective situations, as spoken of, Sect. XIV. 2. 5. 5. Our identity is known by our acquired habits or catenated trains of ideas and muscular motions; and perhaps, when we compare infancy with old age, in those alone can our identity be supposed to exist. For what else is there of similitude between the first speck of living entity and the mature man?—every de- duction of reasoning, every sentiment or passion, with every fibre IQO CLASSES OF IDEAS. Sect. XV. 3. 6. of the corporeal part of our system, has been subject almost to annual mutation; while some catenations alone of our ideas and muscular actions have continued in part unchanged. By the facility with which we can in our waking hours volun- tarily produce certain successive trains of ideas, we know by ex- perience, that we have before reproduced them; that is, we are conscious of a time of our existence previous to the present time; that is, of our idcnlitv now and heretofore. It is these habits of action, these catenations of ideas and muscular motions, which begin with life, and only terminate with it; and which we can in some measure deliver to our posterity; as explained in Sect. XXXIX. 6. When the progressive motions of external bodies make a part of our present catentalion of ideas, we attend to the lapse of time: which appears the longer, the more frequently we thus at- tend to it; as when we expect something at a certain hour, which much interests us, whether it be an agreeable or disagreeable event; or when we count the passing seconds on a stopwatch. When an idea of our own person, or a reflex idea of our plea- sures and pains, desires and aversions, makes a part of this catena- tion, it is termed consciousness; and if this idea of consciousness makes a part of a catenation, which we excite by recollection, and know by the facility with which we excite it, that we have before experienced it, it is called identity, as explained above. 7. In respect to freewill, it is certain, that we cannot will to think of a new train of ideas, without previously thinking of the first link of it; as I cannot will to think of a black swan, without previously thinking of a black swan. But if I now think of a tail, I can voluntarily recollect all animals, which have tails; my will is so far free, that I can pursue the ideas linked to this idea of tail, as far as my knowledge of the subject extends; but to will without motive is to will without desire or aversion; which is as absurd as to feel without pleasure or pain; they are both solecisms in the terms. So far are we governed by the catenations of mo- tions, which affect both the body and the mind of man, and which begin with our irritability, and end with it. Sect. XVI. 1. OF INSTINCT. 101 SECT. XVI. OF INSTINCT. Hand equidem credo, quia sit divinitus illia Ingenium, aut rerum fiito prudentia major. Virg. Georg. 1. L. 415. I. Instinctive actions defined. Of connate passions. II Of the sen- sations and motions ofthefcetus in the womb. III. Some animals are more perfectly formed than others before nativity. Of learn- ing to walk. IV. Of the swallowing, breathing, sucking, pecking, and lapping of young animals. V. Of the sense of smell, and its uses to animals. Why cats do not eat their kittens. VI. Of the accuracy of sight in mankind, and their sense of beauty. Of the sense of touch in elephants, monkies, beavers, men. VII. Of na- tural language. VIII. The origin of natural language; 1. the language of fear; 2. of grief; 3 of tender pleasure; 4. of se- rene pleasure; 5. of anger; 6. of attention. IX. Artificial lan- guage ofturkies, hens, ducklings, wagtails, cuckoos, rabbits, dogs, and nightingales. X. Of music; of tooth-edge; of a good ear; of architecture XI. Of acquired knowledge; of foxes, rooks, fieldfares, lapwings, dogs, cats, horses, crows, pelicans, the tiger, and rattlesnake. XII. Of birds of passage, dormice, snakes, bats, swallows, quails,ring-doves, the stare, chaffinch, hoopoe, chatterer, haufinch, cross-bill, rails and cranes. XIII. Of bird-nests; of the cuckoo; of swallow—nests; of the taylor bird. XIV. Of the old soldier; of haddocks, cods, and dog-fish; oftheremora; of crabs, herrings, and salmon. XV. Of spiders, caterpillars, ants, and the ichneumon. XVI. 1. Of locusts, gnats; 2. bees; 3.' dormice, flies, worms, ants, and wasps. XVII. Of the faculty that distinguishes man from the brutes. I. All those internal motions of animal bodies, which contri- bute to digest their aliment, produce their secretions, repair their injuries, or increase their growth, are performed without our at- tention or consciousness. They exist as well in our sleep, as in our waking hours, as well in the foetus during the time of gesta- tion, as in the infant after nativitv, and proceed with equal regu- larity in the vegetable as in the animal system. These motions have been shewn in a former part of this work to depend on the irritations of peculiar fluids; and as they have never been classed amongst the instinctive actions of animals, are precluded from our present disquisition. 102 OF INST1NQT. Skct. X\ I. J. But all those actions of men or animals, that are attended with consciousness, and seem neither to have been directed by their appetites, taught by their experience, nor deduced from observa- tion or tradition, have been referred to the power of instinct. And this power has been explained to be a divine something, a kind of inspiration; whilst the poor animal, that possesses it, has been thought little better than a machine! The irksomeness, that attends a continued attitude of the body, or the pains, that we receive from heat, cold, hunger, or other injurious circumstances, excite us to general locomotion; and our senses are so formed and constituted by the hand of nature, that certain objects present us writh pleasure, others with pain, and we are induced to approach and embrace these, to avoid and ab- hor those, as such sensations direct us. Thus the palates of some animals are gratefully affected by the mastication of fruits, others of grains, and others of flesh; and they are thence instigated to attain and consume those materials; and are furnished with powers of muscular motion, and of diges- tion proper for such purposes. These sensations and desires constitute a part of our system, as our muscles and bones constitute another part: and hence they may alike be termed natural or connate; but neither of them can properly be termed instinctive; as the word instinct, in its usual acceptation, refers only to the actions of animals, as above ex- plained; the origin of these actions is the subject of our present inquiry. The reader is entreated carefully to attend to this definition of instinctive actions, lest by using the word instinct without adjoin- ing any accurate idea to it, he may not only include the natural desires of love and hunger, and the natural sensations of pain or pleasure, but the figure and contexture of the body, and the fa- culty of reason itself, under this general term. II. We experience some sensation, and perform some actions before our nativity; the sensations of cold and warmth, agitation and rest, fulness and inanition, are instances of the former; and the repeated struggles of the limbs of the foetus, which begin about the middle of gestation, and those motions by which it fre- quently wraps the umbilical cord around its neck or body, and even sometimes ties it in a knot; are instances of the latter. (Smellie's Midwifery, Vol. I. p. 182.) By a due attention to these circumstances, many of the actions of young animals, which at first sight seemed only referable to an inexplicable instinct, will appear to have been acquired like all other animal actions, that are attended with consciousness by tlie Skct. XVI. J. OF INSTINCT. 103 repeated efforts of our muscles under the conduct of our sensations or desires. The chick in the shell begins to move its feet and legs on the sixth day of incubation (Mattreican, p. 138); or on the seventh day, (Langley); afterwards it is seen to move itself gently in the liquid that surrounds it, and to open and shut its mouth, (Harvei, de Generat. p. 62, and 197. Form, de Poulet. ii. p. 129). Puppies before the membranes are broken, that involve them, are seen to move themselves, to put out their tongues, and to open and shut their mouths, (Harvey, Gipson, Riolan, Haller). And calves lick themselves, and swallow many of their hairs, before their nativity, which however puppies do not, (Swammerdam, p. J19. Flemyng Phil. Trans. Ann. 1755. 42). And towards the end of gestation, the foetuses of all animals are proved to drink part of the liquid in which they swim, (Haller. Physiol. T. 8. 204). The white of egg is found in the mouth and gizzard of the chick, and is nearly or quite consumed before it is hatched, (Harvei de Generat. 58). And the liquor amnii is found in the mouth and stomach of the human foetus, and of calves; and how c!se should that excrement be produced in the intestines of all animals, which is voided in great quantity soon after their birth; (Gipson Med. Essays, Edinb. V. i. 13. Halleri Physiolog. T. 3. p. 318. and T. 8). In the stomach of a calf the quantity of this liquid amounted to about three pints, and the hairs amongst it were of the same colour with those on its skin, (Blasii Anat. Animal, p. m. 122). These facts are attested by many other writers of credit, besides those above mentioned. III. It has been deemed a surprising instance of instinct, that calves and chickens should be able to walk by a few efforts al- most immediately after their nativity: whilst the human infant in those countries where he is not encumbered with clothes, as in India, is five or six months, and in our climate almost a twelve- month, before he can safely stand upon his feet. The struggles of all animals in the womb must resemble their mode of swimming, as by this kind of motion they can best change their attitude in water. But the swimming of the calf and chicken resembles their manner of walking, which they have thus in part acquired before their nativity, and hence accomplish it afterwards with very few efforts, whilst the swimming of the human creature resembles that of the frog, and totally differs from his mode of walking. There is another circumstance to be attended to in this affair, that not only the growth of those peculiar parts of animals, which are first wanted to secure their subsistence, are in general 104 OF INSTLNLI'. Sect. XVI. 4. furthest advanced before their nativity: but some animals come into the world more completely formed throughout their whole system than others; and are thence much forwarder in all their habits of motion. Thus the colt, and the lamb, are much more perfect animals than the blind puppy, and the naked rabbit; and the chick of the pheasant, and the partridge, has more perfect plumage, and more perfect eyes, as well as greater aptitude to locomotion, than the callow nestlings of the dove, and of the wren. The parents of the former only find it necessary to shew them their food, and teach them to take it up; whilst those of the latter are obliged for many days to obtrude it into their gaping mouths. IV. From the facts mentioned in No. 2. of this Section, it is evinced that the foetus learns to swallow before its nativity; for it is seen to open its mouth, and its stomach is found filled with the liquid that surrounds it. It opens its mouth, either instigated by hunger, or by the irksomeness of a continued attitude of the muscles of its face; the liquor amnii, in which it swims, is agree- able to its palate, as it consists of a nourishing material, (Haller. Phys. T. 8. p. 204). It is tempted to experience its taste fur- ther in the mouth, and by a few efforts learns to swallow, in the same manner as we learn all other animal actions, which are at- tended with consciousness, by the repealed efforts of our muscles under the conduct of our sensations or volitions. The inspiration of air into the lungs is so totally different from that of swallowing a fluid in which we are immersed, that it cannot be acquired before our nativity. But at this time, when the circulation of the blood is no longer continued through the placenta, that suffocating sensation, which Ave feel about the precordia, when we are in want of fresh air, disagreeably af- fects the infant: and all the muscles of the body are excited into action to relieve this oppression; those of the breast, ribs, and diaphragm are found to answer this purpose, and thus res- piration is discovered, and is continued throughout our lives, as often as the oppression begins to recur. Many infants, both of the human creature, and of quadrupeds, struggle for a minute after they are born before they begin to breathe, (Haller Phys. T. 8. p. 400. ib. pt. 2. p. 1). Mr. Buffon thinks the action "of the dry air upon the nerves of smell of new-born animals, by producing an endeavour to sneeze, may contribute to induce this first inspiration, and that the rarefaction of the air by the warmth of the lungs contributes to induce expiration, (Hist. Nat. Tom. 4. p. 174). Which latter it may effect by produ- cing a disagreeable sensation by its delay, and a consequent ef- Sfxt. XVI. 5. 1. OF INSTINCT. 105 fort to relieve it. Many children sneeze before they respire, but not all, as far as I have observed, or can learn from others. At length by the direction of its sense of smell, or by the offi- cious care of its mother, the young animal approaches the odo- riferous rill of its future nourishment, already experienced to swallow. But in the act of swallowing, it is necessary nearly to close the mouth, whether the creature be immersed in the fluid it is about to drink, or not; hence, when the child first attempts to suck, it does not slightly compress the nipple between the lips, and suck as an adult person would do, by absorbing the milk; but it takes the whole nipple into its mouth for this purpose, compresses it between its gums, and thus repeatedly chewing (as it were) the nipple, presses out the milk; exactly in the same manner as it is drawn from the teats of cows by the hands of the milkmaid. The celebrated Harvey observes, that the foetus in the womb must have sucked in a part of its nourishment, because it knows how to suck the minute it is born, as any one may ex- perience by putting a finger between its lips, and because in a few days it forgets this art of sucking, and cannot without some difficulty again acquire it, (Exercit. de Gener. Anim. 48.) The same observation is made by Hippocrates. A little further experience teaches the young animal to suck by absorption, as well as by compression; that is, to open the chest as in the beginning of respiration, and thus to rarefy the air in the mouth, that the pressure of the denser external atmosphere may contribute to force out the milk. The chick yet in the shell has learnt to drink by swallowing a part of the white of the egg for its food; but not having expe- rienced how to take up and swallow solid seeds, or grains, is either taught by the solicitous industry of its mother; or by many repeated attempts is enabled at length to distinguish and to swal- low this kind of nutriment. And puppies, though they know how to suck like other ani- mals from their previous experience in swallowing, and in re- spiration; yet are they long in acquiring the art of lapping with their tongues, which from the flaccidity of their cheeks, and length of their mouths, is afterwards a more convenient way for them to take in water. V. The senses of smell and taste in many other animals greatly excel those of mankind, for in civilized society, as our victuals are generally prepared by others, and are adulterated with salt, spice, oil, and empyreuma, we do not hesitate about eating whatever is set before us, and neglect to cultivate these senses: whereas other animals try every morsel by the smell, be- fore they take it into their mouths, and by the taste before they VOL. I. p 106 OF INSTINCT. Sect. XVI. 6. 1. swallow it; and are led not only each to his proper nourishment by this organ of sense, but it also at a maturer age directs them in the gratification of their appetite of love. Which may be further understood by considering the sympathies of these parts described in Class IV. 2. 1.7. While the human animal is di- rected to the object of his love by his sense of beauty, as men- tioned in No. VI. of this Section. Thus Virgil Georg. III. 250. Nonne vides, ut tota tremor pertentat equorum Corpora, si tantum notas odor attulit auras ? Nonne canis nidum veneris nasutus odore Quxrit, et erranti trahitur sublamfaere lingaua ? Respuit at gustum cupidus, labiisque retractis Elevat os, trepidansque novis impellitur aestris Inserit et vivum felici vomere semen.— Quam tenui filo caccos adnectit amores Docta Venus, vitxque monetrtnovare favillam ! Anox. The following curious experiment is related by Galen. " On dissecting a goat great with young, I found a brisk embryon, and having detached it from the matrix, and snatching it away be- fore it saw its dam, I brought it into a certain room, where there were many vessels, some filled with wine, others with oil, some with honey, others with milk, or some other liquor; and in others were grains and fruits; we first observed the young animal get upon its feet, and walk; then it shook itself, and af- terwards scratched its side with one of its feet ; then we saw it smelling to every one of these things, that were set in the room; and when it had smelt to them all, it drank up the milk." L. 6. de locis. cap. 6. Parturient quadrupeds, as cats, and bitches, and sows, are led by their sense of smell to eat the placenta as other common food; why then do they not devour their whole progeny, as is repre- sented in an ancient emblem of Time? This is said sometimes to happen in the unnatural state in which we confine sows; and indeed nature would seem to have endangered her offspring in this nice circumstance! but at this time the stimulus of the milk in the tumid teats of the mother excites her to look out for, and to desire some unknown circumstance to relieve her. At the same time the smell of the milk attracts the exertions of the young animals towards its source, and thus the delighted mother discovers a new appetite, as mentioned in Sect. XIV. 8. and her little progeny are led to receive and to communicate pleasure by this most beautiful contrivance. VI. But though the human species in some of their sensa- tions are much inferior to other animals, yet the accuracy of the Sf.ct. XVI. 6. 1. OF INSTINCT. 107 sense of touch, which they possess in so eminent a degree, gives them a great superiority of understanding; as is well observed by the ingenious Mr. Buffon. The extremities of other animals terminate in horns, and hoofs, and claws, very unfit for the sen- sation of touch; whilst the human hand is finely adapted to en- compass its object with this organ of sense. The elephant is indeed endued with a fine sense of feeling at the extremity of his proboscis, and hence has acquired much more accurate ideas of touch and of sight than most other crea- tures. The two following instances of the sagacity of these ani- mals may entertain the reader, as they were told me by some gentlemen of distinct observation, and undoubted veracity, who had been much conversant with our eastern settlements. First, the elephants, that are used to carry the baggage of our armies, are put each under the care of one of the natives of Indostan, and whilst himself and his wife go into the woods to collect leaves and branches of trees for his food, they fix him to the ground by a length of chain, and frequently leave a child yet unable to walk, under his protection: and the intelligent animal not only defends it, but as it creeps about, when it arrives near the ex- tremity of his chain, he wraps his trunk gently round its body, and brings it again into the centre of his circle. Secondly, the traitor elephants are taught to walk on a narrow path between two pit-falls, which are covered with turf, and then to go into the woods, and to seduce the wild elephants to come that way, who fall into these wells, whilst he passes safe between them: and it is universally observed, that those wild elephants that escape the snare, pursue the traitor with the utmost vehemence, and if they can overtake him, which sometimes happens, they always beat him to death. The monkey has a hand well enough adapted for the sense of touch, which contributes to his great facility of imitation; but in taking objects with his hands, as a stick or an apple, he puts his thumb on the same side of them with his fingers, instead of counteracting the pressure of his fingers with it: from this ne- glect he is much slower in acquiring the figures of objects, as he is less able to determine the distances or diameters of their parts, or to distinguish their vis inertiae from their hardness. Helve- tius adds, that the shortness of his life, his being fugitive be- fore mankind, and his not inhabiting all climates, combine to prevent his improvement. (De 1'Esprit. T. 1. p.) There is however, at this time an old monkey shewn in Exeter Change, London, who having lost his teeth, when nuts are given him, takes a stone into his hand, and cracks them with it one by one; thus using tools to effect his purpose like maukind. 10S OF INSTINCT. Sect. XVI. 6. 1. The beaver is another animal that makes much use of his hands, and if we may credit the reports of travellers, is possessed of amazing ingenuity. This, however, M. Buffon affirms, is only where they exist in large numbers, and in countries thinly peo- pled with men; while in France in their solitary state they show no uncommon ingenuity. Indeed all the quadrupeds that have collar-bones, (claviculae) use their fore-limbs in some measure as we use our hands, as the cat, squirrel, tyger, bear and lion; and as they exercise the sense of touch more universally than other animals, so are they more sagacious in watching and surprising their prey. All those birds, that use their claws for hands, as the hawk, parrot and cuckoo, appear to be more docile and intelligent; though the gregarious tribes of birds have more acquired knowledge. Now as the images, that are painted on the retina of the eye, are no other than signs, which recal to our imaginations the ob- jects we had before examined by the organ of touch, as is fully demonstrated by Dr. Berkeley in his treatise on vision; it follows that the human creature has greatly more accurate and distinct sense of vision than that of any other animal Whence as he advances to maturity he gradually acquires a sense of female beauty, which at this time directs him to the object of his new passion. Sentimental love, as distinguished from the animal passion of that name; with which it is frequently accompanied, consists in the desire or sensation of beholding, embracing, and saluting a beautiful object. The characteristic of beauty therefore is that it is the object of love: and though many other objects are in common language called beautiful, yet they are only called so metaphorically, and ought to be termed agreeable. A Grecian temple may give us the pleasurable idea of sublimity, a Gothic temple may give us the pleasurable idea of variety, and a modern house the pleasur- able idea of utility; music and poetry may inspire our love by association of ideas; but none of these, except metaphorically, can be termed beautiful; as we have no wish to embrace or sa- lute them. Our perception of beauty consists in our recognition by the sense of vision of those objects, first, which have before inspired our love by the pleasure, which they have afforded to many of our senses: as to our sense of warmth*, of touch, of smell, of taste, hunger and thirst; and, secondly, which bear any analogy of form to such objects. When the babe, soon after it is born into this cold world, is applied to its mother's bosom; its sense of perceiving warmth Sect. XVI. 7. 1. OF INSTINCT. 109 is first agreeably affected; next its sense of smell is delighted with the odour of her milk; then its taste is gratified by the fla- vour of it; afterwards the appetites of hunger and of thirst afford pleasure by the possession of their objects, and by the subsequent digestion of the aliment; and, lastly, the sense of touch is de- lighted by the softness and smoothness of the milky fountain, the source of such variety of happiness. All these various kinds of pleasure at length become associated with the form of the mother's breast; which the infant embraces with its hands, presses with its lips, and watches with its eyes; and thus acquires more accurate ideas of the form of its mother's bosom, than of the odour and flavour or warmth, which it per- ceives by its other senses. And hence at our maturer years, when any object of vision is presented to us, which by its wav- ing or spiral lines bears any similitude to the form of the female bosom, whether it be found in a landscape with soft gradations of rising and descending surface, or in the forms of some an- tique vases, or in other works of the pencil or the chissel, we feel a general glow of delight, which seems to influence all our senses; and, if the object be not too large, we experience an attraction to embrace it with our arms, and to salute it with our lips, as we did in our early infancy the bosom of our mother. And thus we find, according to the ingenious idea of Hogarth, that the waving lines of beauty were originally taken from the temple of Venus. This animal attraction is love; which is a sensation, when the object is present; and a desire, when it is absent. Which constitutes the purest source of human felicity, the cordial drop in the otherwise vapid cup of life, and which overpays mankind for the care and labour, which are attached to the pre-eminence of his situation above other animals. It should have been observed, that colour as well as form sometimes enters into our idea of a beautiful object, as a good complexion for instance, because a fine or fair colour is in gene- ral a sign of health, and conveys to us an idea of the warmth of the object; and a pale countenance on the contrary gives an idea of its being cold to the touch. It was before remarked, that young animals use their lips to distinguish the forms of things, as well as their fingers, and hence we learn the origin of our inclination to salute beautiful objects with our lips. For a definition of Grace, see Class III. 1.2.4. VII. There are two ways by which we become acquainted with the passions of others: first, by having observed the effects of them, as of fear or anger, on our own bodies, we know at HO OF INSTINCT. Sect. XVI. 8. 1. sight when others are under the influence of these affections. So when two cocks are preparing to fight, each feels the feath- ers rise round his own neck, and knows from the same sign the disposition of his adversary: and children long before they can speak, or understand the language of their parents, may be frightened by an angry countenance, or soothed by smiles and blandishments. Secondly, when we put ourselves into the attitude that any passion naturally occasions, we soon in some degree acquire that passion; hence when those that scold indulge themselves in loud oaths, and violent actions of the arms, they increase their anger by the mode of expressing themselves: and on the contrary the counterfeited smile of pleasure in disagreeable company soon brings along with it a portion of the reality, as is well illustrated by Mr. Burke, (Essay on the Sublime and Beautiful.) This latter method of entering into the passions of others is rendered of every extensive use by the pleasure we take in imi- tation, which is every day presented before our eyes, in the ac- tions of children, and indeed in all the customs and fashions of the world. From this our aptitude to imitation, arises what is generally understood by the word sympathy, so well explained by Dr. Smith of Glasgow. Thus the appearance of a cheerful countenance gives us pleasure, and of a melancholy one makes us sorrowful. Yawning and sometimes vomiting are thus propa- gated by sympathy, and some people of delicate fibres, at the presence of a spectacle of misery, have felt pain in the same parts of their own bodies, that were diseased or mangled in the other. Amongst the writers of antiquity Aristotle thought this aptitude to imitation an essential property of the human species, and calls man an imitative animal. To £««» fnfttay.-voi. These then are the natural signs by which we understand each other, and on this slender basis is built all human language. For without some natural signs, no artificial ones could have been invented or understood, as is very ingeniously observed by Dr. Reid, (Inquiry into the Human Mind.) VIII. The origin of this universal language is a subject of the highest curiosity, the knowledge of which has always been thought utterly inaccessible. A part of which we shall however here attempt. Light, sound, and odours, are unknown to the foetus in the womb, which, except the few sensations and motions already mentioned, sleeps away its time insensible of the busy world. But the moment it arrives into day, it begins to experience many vivid pains and pleasures; these are at the same time at- tended with certain muscular motions, and from this their Skct. XVI. 8. 1. OF INSTINCT. Ill early, and individual association, they acquire habits of occur- ring together, that are afterwards indissoluble. 1. Of Fear. As soon as the young animal is born, the first important sensa- tions, that occur to him, are occasioned by the oppression about his precordia for want of respiration, and by bis sudden transition from ninety-eight degrees of heat into so cold a climate.—He trembles, that is, he exerts alternately all the muscles of his body, to enfranchise himself from the oppression about his bosom, and begins to breathe with frequent and short respirations; at the same time the cold contracts his red skin, gradually turning it pale; the contents of the bladder and of the bowels are evacu- ated: and from the experience of these first disagreeable sensa- tions the passion of fear is excited, which is no other than the expectation of disagreeable sensations. This early association of motions and sensations persists throughout life; the passion of fear produces a cold and pale skin, with tremblings, quick re- spiration, and an evacuation of the bladder and bowels, and thus constitutes the natural or universal language of this passion. On observing a canary bird this morning, January 28, 1772, at the house of Mr. Harvey, near Tutbury, in Derbyshire,- I was told it always fainted away, when its cage was cleaned, and de- sired to see the experiment. The cage being taken from the ceiling, and its bottom drawn out, the bird began to tremble and turned quite white about the root of his bill: he then open- ed his mouth as if for breath, and respired quick, stood straighter up on his perch, hung his wings, spread his tail, closed his eves, and appeared quite stiff and cataleptic for near half an hour, and at length with much trembling and deep respirations came gradually to himself. * 2. Of Grief. That the internal membrane of the nostrils may be kept al- an,T ' Vhc bftter PercePtion of odours, there are two ni mo * n a™? thC tCarS after they have done their office cTh Tg f^ C,T"S the baI1 of the e?e int0 a sapk, ^hich called the lacrymal sack; and from which there is a duct of eE,,nt° thKe,n0Stri,s: the ap^" of this duct is formed liclIS'11' 3nd when h is stimu,atcd Porous frac i£i? 7A dfyneSS °r C0ldness of the air> the *ack con- m of mill aniPT m°re °f Us contained moisture °" the or- 3.m ol smell. By tins contrivance the organ is rendered more 112 OF INSTINCT. Skct. XV I. 8. 2. fit for perceiving such colours, and is preserved from being in- jured by those that are more strong or corrosive. Many other receptacles of peculiar fluids disgorge their contents, when the ends of their ducts are stimulated; as the gall bladder, when the contents of the duodenum stimulate the extremity of the com- mon bile duct; and the salivary glands, when the termination of their ducts in the mouth are excited by the stimulus of the food we masticate. Atque vesiculae seminales suum exprimunt flu- idum glande penis fricata. The coldness and dryness of the atmosphere, compared with the warmth and moisture, which the new-born infant had just before experienced, disagreeably affect the aperture of this lacry- mal sack; the tears, that are contained in this sack, are poured into the nostrils, and a further supply is secreted by the lacry- mal glands, and diffused upon the eye-balls; as is very visible in the eyes and nostrils of children soon after their nativity. The same happens to us at our maturer age, for in severe frosty weather, snivelling and tears are produced by the coldness and dryness of the air. But the lacrymal glands, which separate the tears from the blood, are situated on the upper external part of the globes of each eye; and, when a greater quantity of tears arc wanted, we contract the forehead, and bring down the eye-brows, and use many other distortions of the face, to compress these glands. Now as the suffocating sensation, that produces respiration, is removed almost as soon as perceived, and does not recur again: this disagreeable irritation of the lacrymal ducts, as it must fre- quently recur, till the tender organ becomes used to variety of odours, is one of the first pains that is repeatedly attended to: and hence throughout our infancy, and in many people through- out their lives, all disagreeable sensations are attended with sni- velling at the nose, a profusion of tears, and some peculiar dis- tortions of countenance: according to the laws of early associ- ation before mentioned, which constitutes the natural or universal language of grief. You may assure yourself of-the truth of this observation, if you will attend to what passes, when you read a distressful tale alone; before the tears overflow your eyes, you will invariably feel a titillation at that extremity of the lacrymal duct, which termi- nates in the nostril, then the compression of the eyes succeeds, and the profusion of tears. Linnaeus asserts, that the female bear sheds tears in grief; the same has been said of the hind, and some other animals. Sect. XVI. 8. 3. OF INSTINCT. 113 3. Of Tender Pleasure. The first most' lively impression of pleasure, that the infant enjoys after its nativity, is excited by the odour of its mother's milk. The organ of smell is irritated by this perfume, and the lacrymal sack empties itself into the nostrils, as before explain- ed, and an increase of tears is poured into the eyes. Any one may observe this, when very young infants are about to suck; for at those early periods of life, the sensation affects the organ of smell much more powerfully, than after the repeated habit of smelling has inured it to odours of common strength: and in our adult years, the stronger smells, though they are at the same time agreeable to us, as of volatile spirits, continue to produce an in- creased secretion of tears. The pleasing sensation of smell is followed by the early affec- tion of the infant to the mother that suckles it, and hence the ten- der feelings of gratitude and love, as well as of hopeless grief, are ever after joined with the titillation of the extremity of the lacrymal ducts, and a profusion of tears. Nor is it singular, that the lacrymal sack should be influenced by pleasing ideas, as the sight of agreeable food produces the same effect on the salivary glands. Ac dum vidimus in somniis las- civae puellae simulacrum tenditur penis. Lambs shake or wriggle their tails, at the time when they first suck, to get free of the hard excrement, which had been long lodged in their bowels. Hence this becomes afterwards a mark of pleasure in them, and in dogs and other tailed animals. But cats gently extend and contract their paws when they are pleased, and purr by drawing in their breath, both which resemble their manner of sucking, and thus become their language of pleasure, for these animals, having collar-bones, use their paws like hands when they suck, which dogs and sheep do not. 2. Of Serene Pleasure. In the action of sucking, the lips of the infant are closed around the nipple of his mother, till he has filled his stomach, and the pleasure occasioned by the stimulus of this grateful food succeeds. Then the sphincter of the mouth, fatigued by the continued action of sucking, is relaxed; and the antagonist mus- cles of the face gently acting, produce the smile of pleasure; as cannot but be seen by all who are conversant with children. Hence this smile during our lives is associated with gentle pleasure; it is visible in kittens, and puppies, when they are played with, and tickled; but more particularly marks the VOL. I. q 114 OF INSTINCT. Sj.cr. XVI 8. 5. human features. For in children this expression of pleasure is much encouraged, by their imitation of their parents, or friends; who generally address them with a smiling countenance: and hence some nations are more remarkable for the gaiety, and others for the gravity of their looks. 5. Of Anger. The actions that constitute the mode of fighting, are the im- mediate language of anger in all animals; and a preparation for these actions is the natural language of threatening. Hence the human creature clenches his fist, and sternly surveys his adver- sary, as if meditating where to make the attack; the ram, and the bull, draws himself some steps backwards, and levels his horns; and the horse, as he most frequently fights by striking with his hinder feet, turns his heels to his foe, and bends back his ears, to listen out the place of his adversary, that the threatened blow may not be ineffectual. 6. Of Attention. The eye takes in at once but half our horizon, and that only in the day, and our smell informs us of no very distant objects, hence we confide principally in the organ of hearing to apprize us of danger; when we hear any the smallest sound, that we cannot immediately account for, our fears are alarmed, we sus- pend our steps, hold every muscle still, open our mouths a little, erect our ears, and listen to gain further information: and this by habit becomes the general language of attention to objects of sight as well as of hearing; and even to the successive trains of our ideas. The natural language of violent pain, which is expressed by writhing the body, grinning and screaming; and that of tumultu- ous pleasure, expressed in loud laughter; belong to Section XXXIV. on Diseases from Volition. IX. It must have already appeared to the reader, that all other animals, as well as men, are possessed of this natural language of the passions, expressed in signs or tones; and we shall endeavour to evince, that those animals, which have preserved themselves from being enslaved by mankind, and are associated in flocks, are also possessed of some artificial language, and of some traditional knowledge. The mother turkey, when she eyes a kite hovering high in air, has either seen her own parents thrown into fear at his pre- sence, or has by observation been acquainted with his dangerous Sect. XVI. 9. 1. OF INSTINCT. 115 designs upon her young. She becomes agitated with fear, and uses the natural language of that passion, her young ones catch the fear by imitation, and in an instant conceal themselves in the grass. At the same time that she shews her fears by her gesture and deportment, she uses a certain exclamation, Koe-ut, Koe-ut, and the young ones afterwards know, when they hear this note, though they do not see their dam, that the presence of their ad- versary is announced, and hide themselves as before. The wild tribes of birds have very frequent opportunities of knowing their enemies, by observing the destruction they make among their progeny, of which every year but a small part escapes to maturity: but to our domestic birds these opportuni- ties so rarely occur, that their knowledge of their distant enemies must frequently be delivered by tradition in the manner above explained, through many generations. This note of danger, as well as the other notes of the mother- turkey, when she calls her flock to their food, or to sleep under her wings, appears to be an artificial language, both as expressed by the mother, and as understood by the progeny. For a hen teaches this language with equal ease to the ducklings she has hatched from supposititious eggs, and educates as her own off- spring: and the wagtails, or hedge-sparrows, learn it from the young cuckoo their foster nursling, and supply him with food long after he can fly about, whenever they hear his cuckooing, which Linnaeus tells us, is his call of hunger, (Syst. Nat.) And all our domestic animals are readily taught to" come to us for food, when we use one tone of voice, and to fly from our anger when we use another. Rabbits, as they cannot easily articulate sounds, and are form- ed into societies, that live under ground, have a very different method of giving alarm. When danger is threatened, they thump on the ground, with one of their hinder feet, and produce a sound, that can be heard a great way by animals near the sur- face of the earth, which would seem to be an artificial sign both from its singularity and its aptness to the situation of the animal Hie rabbits on the island of Sor, near Senegal, have white hesh, and are well tasted, but do not burrow in the earth, so that we may suspect their digging themselves houses in this cold cli- mate is an acquired art, as well as their note of alarm. (Adan- son's Voyage to Senegal.) v The barking of dogs is another curious note of alarm and would seem to be an acquired language, rather than a natural «gn: for < ,„ the island of Juan Fernandes, the dogs did no attempt to bark, till some European dogs were put among them 116 OF INSTINCT Sect. XVI. 10. 1. and then they gradually began to imitate them, but in a strange manner at first, as if they were learning a thing that was not natural to them." (Vovage to South America by Don G. Juan, and Don Ant. de Ulboa. B. 2. c. 4.) Linnaeus also observes, that the dogs of South America do not bark at strangers, (Syst. Nat.) And the European dogs, that have been carried to Guinea, are said in three or four generations to cease to bark, and only howl, like the dogs that are natives of that coast, (World Displayed, Vol. XVII. p. 26.) A circumstance not dissimilar to this, and equally curious, is mentioned by Kircherus de Musurgia, in his Chapter de Lus- ciniis. " That the young nightingales that are hatched under other birds, never sing till they are instructed by the company of other nightingales." And Johnston affirms, that the nightingales that visit Scotland, have not the same harmony as those of Italy, (Pennant's Zoology, octavo, p. 255); which would lead us to suspect that the singing of birds, like human music, is an arti- ficial language, rather than a natural expression of passion. X. Our music, like our language, is perhaps entirely consti- tuted of artificial tones, which by habit suggest certain agreeable passions. For the same combination of notes and tones do not excite devotion, love, or poetic melancholy in a native of Indos- tan and of Europe. And " the Highlander has the same war- like ideas annexed to the sound of a bagpipe (an instrument which an Englishman derides) as the Englishman has to that of a trumpet or fife." (Dr. Brown's Union of Poetry and Music, p. 58.) So " the music of the Turks is very different from the Italian, and the people of Fez and Morocco have again a differ- ent kind, which to us appears very rough and horrid, but is high- ly pleasing to them," (L'Arte Armonica a Giorgio Antoniotto.) Hence we see why the Italian opera does not delight an un- tutored Englishman; and why those who are unaccustomed to music are more pleased with a tune the second or third time they hear it than the first. For then the same melodious train of sounds excites the melancholy, they had learned from the song; or the same vivid combination of them recalls all the mirthful ideas of the dance and company. Even the sounds, that were once disagreeable to us, may by habit be associated with other ideas, so as to become agreeable. Father Lafitau, in his account of the Iroquois, says " the music and dance of those Americans have something in them extremely barbarous, which at first disgusts. We grow reconciled to them by degrees, and in the end partake of them with pleasure: the savages themselves are fond of them to distraction." (Mceurs des Sauvages, torn, ii.) Sect. XVI. 10. 1. OF INSTINCT. 117 There are indeed a few sounds, that we very generally associate with agreeable ideas, as the whistling of birds, or purring of animals, that are delighted; and some others, that we as generally associate with disagreeable ideas, as the cries of animals in pain, the hiss of some of them in anger, and the midnight howl of beasts of prey. Yet we receive no terrible or sublime ideas from the lowing of a cow, or the braying of an ass; which evinces that these emotions are owing to previous associations. So if the rumbling of a carriage in the street be for a moment mistaken for thunder, we receive a sublime sensation, which ceases as soon as we know it is the noise of a coach and six. There are other disagreeable sounds, that are said to set the teeth on edge; which, as they have always been thought a neces- sary effect of certain discordant notes, becomes a proper subject of our inquiry. Every one in his childhood has repeatedly bit a part of the glass or earthen vessel, in which his food has been given him, and has thence had a very disagreeable sensation in the teeth, which sensation was designed by nature to prevent us from exerting them on objects harder than themselves. The jarring sound produced between the cup and the teeth is always attendant on this disagreeable sensation: and ever after, when such a sound is accidentally produced by the conflict of two hard bodies, we feel by association of ideas the concomitant disagree- able sensation in our teeth. Others have in their infancy frequently held the corner of a silk handkerchief in their mouth, or the end of the velvet cape of their coat, whilst their companions in play have plucked it from them, and have given another disagreeable sensation to their teeth, which has afterwards recurred on touching those materials. And the sight of a knife drawn along a china plate, (hough no sound is excited by it, and even the imagination of such a knife and plate so scraped together, I know by repeated experience will produce the same disagreeable sensation of the teeth. These circumstances indisputably prove, that this sensation of the tooth-edge is owing to associated ideas; as it is equally ex- citable by sight, touch, hearing, or imagination. In respect to the artificial proportions of sound excited by mu- sical instruments, those, who have early in life associated'them with agreeable ideas, and have nicely attended to distinguish them from each other, are said to have a good ear, in that country where such proportions are in fashion: and not from any superior perfection in the organ of hearing, or any instinctive sympathy between certain sounds and passions. I have observed a child to be exquisitely delighted with music, 118 OF INSTINCT. tscT.XVI. 11. 1. and who could with great facility learn to sing any tune that he heard distinctly, and yet whose organ of hearing was so imper- fect, that it was necessary to speak louder to him in common con- versation than to others. Our music, like our architecture, seems to have no founda- tion in nature, they are both arts purely of human creation, as they imitate nothing. And the professors of them have only classed those circumstances, that are most agreeable to the acci- dental taste of their age, or country, and have called it Propor- tion. But this proportion must always fluctuate, as it rests on the caprices that are introduced into our minds by our various modes of education. And these fluctuations of taste must be- come more frequent in the present age, where mankind have enfranchised themselves from the blind obedience of the rules of antiquity in perhaps every science, but that of architecture. See Sect. XII. 7. 3. XI. There are many articles of knowledge, which the ani- mals in cultivated countries seem to learn very early in their lives, either from each other, or from experience, or observa- tion: one of the most general of these is to avoid mankind. There is so great a resemblance in the natural language of the passions of all animals, that we generally know, when they are in a pacific, or in a malevolent humour; they have the same knowledge of us; and hence we can scold them from us by some tones and gestures, and could possibly attract them to us by others, if they were not already apprized of our general ma- levolence towards them. Mr. Gmelin, Professor at Petersburg, assures us, that in his journey into Siberia, undertaken by order of the empress of Russia, he saw foxes that expressed no fear of himself or companions, but permitted him to come quite near them, having never seen the human creature before. And Mr. Bougainville relates, that at his arrival at the Maloune, or Falk- land's Islands, which were not inhabited by men, all the ani- mals came about himself and his people; the fowls settling upon their heads and shoulders, and the quadrupeds running about their feet. From the difficulty of acquiring the confidence of old ani- mals, and the ease of taming young ones, it appears that the fear, they all conceive at the sight of mankind, is an acquired article of knowledge. This knowledge is more nicely understood by rooks, who are formed into societies, and build, as it were, cities over our heads; thev evidently distinguish, that the danger is greater when a man is armed with a gun. Every one has seen this, who in the spring of the vear has walked under a rookery with a gun in his hand: the inhabitants of the trees rise on their wings, and Sict. XVI. 11. 1. OF INSTINCT. 119 scream to the unfledged young to shrink into their nests from the sight of the enemy. The vulgar observing this circum- stance so uniformly to occur, assert that rooks can smell gun- powder. The fieldfares, (turdus pilaris,) which breed in Norway, and come hither in the cold season for our winter berries; as they are associated in flocks, and are in a foreign country, have evi- dent marks of keeping a kind of watch, to remark and announce the appearance of danger. On approaching a tree, that js cover- ed with them, they continue fearless till one at the extremity of the bush rising on his wings gives a loud and peculiar note of alarm, when they all immedjately fly, except one other, who continues till you approach still nearer, to certify as it were the reality of the danger, and then he also flies off, repeating the note of alarm. And in the woods about Senegal there is a bird called uett- uett by the negroes, and squallcrs by the French, which, as soon as they see a man, set up a loud scream, and keep flying round him, as if their intent was to warn other birds, which upon hear- ing the cry immediately take wing. These birds are the bane of sportsmen, and frequently put me into a passion, and obliged me to shoot them, (Adanson's Voyage to Senegal, 78.) For the same intent the lesser birds of our climate seem to fly after a hawk, cuckoo, or owl, and scream to prevent their companions from being surprised by the general enemies of themselves, or of their eggs and progeny. But the lapwing, (charadrius pluvialis, Lin.) when her unfledg- ed offspring run about the marshes, where they were hatched, not only gives the note of alarm at the approach of men or dogs, that her young may conceal themselves; but flying and screaming near the adversary, she appears more solicitous and impatient, as he recedes from her family, and thus endeavours to mislead him, and frequently succeeds in her design. These last instances are so apposite to the situation, rather than to the natures of the creatures, that use them; and are so similar to the actions of men in the same circumstances, that we cannot but believe that they proceed from a similar principle. Miss M. E. Jackson acquainted me, that she witnessed this autumn an agreeable instance of sagacity in a little bird, which seemed to use the means to obtain an end; the bird repeatedly hopped upon a poppy-siem, and shook the head with its bill, till many seeds were scattered, then it settled on the ground, and eat the seeds, and again repeated the same management. Sept. 1, 1794. On the northern coast of Ireland a friend of mine saw above 120 OF INSTINCT Skit. XVI. 11. 1. a hundred crows at once preying upon muscles; each crow took a muscle up into the air twenty or forty yards high, and let it fall on the stones, and thus by breaking the shell, got pos- session of the animal.—A certain philosopher (I think it was Ana\.igoras) walking along the sea-shore to gather shells, one of these unlucky birds mistaking his bald head for a stone, drop- ped a shell fish upon it, and killed at once a philosopher and an oyster. The martin (hirundo urbica) is said by Linnaeus to dwell on the outside of houses in Europe under the caves, and to return with the early foliage. And that, when it has built, the sparrow, fringilla domestica, frequently occupies the finished nest; but that the martin convoking its companions, while some guard the captive enemy, others bring clay, exactly close up the entrance, and fly away, leaving the intruder to be suffocated. Syst. Natur. Pass. Hirundo. A similar relation was printed many years ago in the Gentleman's Magazine. Our domestic animals, that have some liberty, are also possess- ed of some peculiar traditional knowledge: dogs and cats have been forced into each other's society, though naturally animals of a very different kind, and have hence learned from each other to eat dog's grass (agrostis canina) when they are sick, to pro- mote vomiting. I have seen a cat mistake the blade of barley for this grass, which evinces it is an acquired knowledge. They have also learnt of each other to cover their excrement and urine;—about a spoonful of water was spilt upon my hearth from the tea-kettle, and I observed a kitten cover it with ashes. Hence this must also be an acquired art, as the creature mistook the ap- plication of it. To preserve their fur clean, and especially their whiskers, cats wash their faces, and generally quite behind their ears, every time they eat. As they canrot lick those places with their tongues, they first wet the inside of the leg with saliva, and then repeatedly wash their faces with it, which must originally be an effect of reasoning, because a means is used to produce an effect; and seems afterwards to be taught or acquired by imitation, like the greatest part of human arts. These animals seem to possess something like an additional sense by means of their whiskers; which have perhaps some analogy to the antennae of moths and butterflies. The whiskers of cats consist not only of the long hairs on their upper lips, but they have also four or five long hairs standing up from each eye- brow, and also two or three on each cheek; all which, when the animal erects them, make with their points so many parts of the periphery of a circle, of an extent at least equal to the Strj. XVI. 11. 1. OF INSTINCT. 121 circumference of any part of their own bodies. With this in- strument, I conceive,' by a little experience, they can at once de- termine, whether any aperture amongst hedges or shrubs, in which animals of this genus live in their wild state, is large enough to admit their bodies; which to them is a matter of the greatest consequence, whether pursuing or pursued. They have likewise a power of erecting and bringing forward the whiskers on their lips; which probably is for the purpose of feeling, whe- ther a dark hole be further permeable. The antenna?, or horns of butterflies and moths, who have awkward wings, the minute feathers of which are very liable to injury, serve, I suppose, a similar purpose of measuring, as they fly or creep amongst the leaves of plants and trees, whether their wings can pass without touching them. I this morning saw a terrier bitch repeatedly lick her paws, and wash her face on both sides, and over her eyes, exactly as cats do; from whom I suppose she had acquired this art, as she lived in the parlour with two of them. Mr. Leonard, a very intelligent friend of mine, saw a cat catch a trout by darting upon it in a deep clear water at the mill at Weaford, near Litchfield. The cat belonged to Mr. Stanley, who had often seen her catch fish in the same manner in summer, when the mill-pool was drawn so low that the fish could be seen. I have heard of other cats taking fish in shallow water, as they stood on the bank. This seems a natural art of taking their prey in cats, which their acquired delicacy by domestication has in general prevented them from using, though their desire of eating fish continues in its original strength. Mr. White, in his ingenious History of Selbourne, was witness to a cat's suckling a young hare, which followed her about the garden, and came jumping to her call of affection. At Elford, near Litchfield, the Rev. Mr. Sawley had taken the young ones out of a hare, which was shot; they were alive, and the cat, who had just lost her own kittens, carried them away, as it was sup- posed, to eat them; but it presently appeared, that it was affec- tion, not hunger, which incited her, as she suckled them, and brought them up as their mother. Other instances of the mistaken application of what has been termed instinct may be observed in flies in the night, who, mis- taking a candle for day-light, approach and perish in the flame. So the putrid smell of the stapelia, or carrion-flower, allures the large flesh fly to deposite its young worms on its beautiful petals, which perish there for want of nourishment. This therefore cannot be a necessary instinct, because the creature mistakes, the application of it. VOL. I. R 122 OF INSTINCT. Sixt. XVI. 11.1 Though in this country horses shew little vestiges of policy, yet in the deserts of Tartary and Siberia, when hunted by the Tartars, they are seen to form a kind of community, set watches to prevent their being surprised, and have commanders, who di- rect, and hasten their flight. Origin of Language, Vol. I. p. 212. In this country where four or five horses travel in a line, the first always points his ears forward, and the last points his backward, while the intermediate ones seem quite careless in this respect; which seems a part of policy to prevent surprise. As all ani- mals depend most on the ear to apprize them of the approach of danger, the eye taking in only half the horizon at once, and horses possess a great nicety of this sense; as appears from their mode of fighting, mentioned No. 8. 5. of this Section, as well as by common observation. There are some parts of a horse which he cannot conveniently rub, when they itch, as about the shoulder, which he can neither bite with his teeth, nor scratch with his hind foot; when this part itches, he goes to another horse, and gently bites him in the part which he wishes to be bitten, which is immediately done by his intelligent friend. I once observed a young foal thus bite its large mother, who did not choose to drop the grass she had in her mouth, and rubbed her nose against the foal's neck instead of biting it: which evinces that she knew the design of her progeny, and was not governed by a necessary instinct to bite where she was bitten. Many of our shrubs, which would otherwise afford an agree- able food to horses, are armed with thorns or prickles, which se- cure them from those animals; as the holly, hawthorn, goose- berry, gorse. In the extensive moorlands of Staffordshire, the horses have learnt to stamp upon a gorse-bush with one -of their fore feet for a minute together, and when the points are broken, they eat it without injury. The horses in the new forest in Hampshire are affirmed to do the same by Mr. Gilpin. Forest Scenery, II. 251, and 1J 2. Which is an art other horses in the fertile parts of the country do not possess, and prick their mouths till they bleed, if they are induced by hunger or caprice to at- tempt eating gorse. Swine have a sense of touch as well as of smell at the end of their nose, which they use as a hand, both to root up the soil, and to turn over and examine objects of food, somewhat like the proboscis of an elephant. As they require shelter from the cold in this climate, they have learnt to collect straw in their mouths to make their nest, when the wind blows cold; and to call their companions by repeated cries to assist in the work, and add to their warmth by their numerous bed-fellows. Hence these ani- S£CT. \VI. H. 1. OF INSTINCT. 123 mals, which arc esteemed so unclean, have also learned never to befoul their dens, where they have liberty, with their own excre- ment; an art, which cows and horses, which have open hovels to run into, have never acquired. I have observed great sagacity in swine; but the short lives we allow them, and their general confinement, prevents their improvement, which might probably be otherwise greater than that of dogs. Instances of the sagacity and knowledge of animals are very numerous to every observer, and their docility in learning various arts from mankind, evinces that they may learn similar arts from their own species, and thus be possessed of much acquired and traditional knowledge. A dog whose natural prey is sheep, is taught by mankind, not only to leave them unmolested, but to guard them; and to hunt, to set, or to destroy other kinds of animals, as birds, or vermin; and in some countries to catch fish, in others to find truffles, and to practise a great vaii^'y of tricks; is it more surprising that the (rows should teach each other, that the hawk can catch less birds, by the superior swiftness of his wing, and if two of them follow him, till he succeeds in his design, that they can by force share a part of the capture? this I have formerly observed with attention and astonishment. There is one kind of pelican mentioned by Mr. Osbeck, one of Linnacus's travelling pupils, (the pelicanus aquilus,) whose food is fish; and which it takes from other birds, because it is not formed to catch them itself; hence it is called by the English a Man-of-war-bird, Voyage to China, p. 88. There are many other interesting anecdotes of the pelican and cormorant, collect- ed from authors of the best authority, in a well-managed Natural History for Children, published by Mr. Galton. Johnson. Lon- don. And the following narration from the very accurate Mons. Adanson, in his voyage to Senegal, may gain credit with the reader, as his employment in this country was solely to make ob- servations in natural history. On the river Niger, in his road to the island Griel, he saw a great number of pelicans, or wide throats. " They moved with great state like swans upon the water, and are the largest bird next to the ostrich; the bill of the one 1 killed was upwards of a foot and a half long, and the bag fastened underneath it held two and twenty pints of water. They swim in flocks, and form a large circle, which they contract af- terwards, driving the fish before them with their legs; when they see the fish in sufficient number confined in this space, they plunge their bill wide open into the water, and shut it again with 1^4 OF INSTINCT. Sect. XVI. 12. 1. great quickness. They thus get fish into their throat-bag, which they eat afterwards on shore at their leisure." P. 247. Another curious effort of design, or use of means in animals, is related by Abbe Grosier, in his Description of China, Vol. I. p. 562. A kind of tiger is seen in China, which has a body like a dog, but no tail, and is remarkably swift and ferocious. If any one meets this animal, and to escape from his fury climbs up a tree, the tiger immediately sends forth a loud yell, and several other tigers arrive; which all together dig up the earth round the roots of the tree, and overturning it, seize their prey. > The rattlesnake and black serpent of America also should here be mentioned, which are supposed to possess an instinctive power of fascinating birds; as many birds have been seen repeatedly to run to them and to retreat from them with piteous screams, till the snake has seized and devoured them. I formerly suspected, that this serpent had hid himself in the bushes, and had secretly wounded the bird, and followed it with his steady eye, till the poison instilled into the wound had time to take effect; and that the bird then fell from the tree into his mouth. But from an in- genious paper, which Dr. B. S. B?rton, Professor of Natural History, in Pennsylvania, has favoured me with, and which will be published in their Philosophical Transactions, it is clearly shewn, that this piteous cry, and approach, and retreat, of the bird supposed to be fascinated, is simply an attack made by the female bird on the serpent in defence of her young; which credu- lity and the love of admiration has converted into a prodigy of fascination, which is still credited by the multitude in America. This circumstance of the mother bird daring to defend her young from a serpent, till she was devoured by him, and her screaming around him, is described by that great observer of nature, the im- mortal Homer, above 2000 years ago. Iliad. Lib. 2. 1. 310. XII. The knowledge and language of those birds, that fre- quently change their climate with the seasons, is still more ex- tensive; as they perform these migrations in large societies, and are less subject to the power of man, than the resident tribes of birds. They are said to follow a leader during the day, who is occasionally changed, and to keep a continual cry during the night to keep themselves together. It is probable that these emigra- tions were at first undertaken as accident directed, by the more adventurous of their species, and learned from one another like the discoveries of mankind in navigation. The following cir- cumstances strongly support this opinion. 1. Nature has provided these animals, in the climates where they are produced, with another resource, when the season be- Sect. XVI. 12. 2. OF INSTINCT. 125 comes too cold for their constitutions, or the food they were sup- ported with ceases to be supplied: I mean that of sleeping. Dormice, snakes, and bats, have not the means of changing their country; the two former from the want of wings, and the lat- ter from his being not able to bear the light of the day. Hence these animals are obliged to make use of this resource, and sleep during the winter. And those swallows that have been hatched too late in the year to acquire their full strength of pin ion, or that have been maimed by accident or disease, have been frequently found in the hollows of rocks on the sea coasts, and even under water, in this torpid state, from which they have been revived by the warmth of a fire. This torpid state of swallows is testi- fied by innumerable evidences both of ancient and modern names. Aristotle, speaking of the swallows, says, " They pass into warmer climates in winter, if such places are at no great distance; if they are, they bury themselves in the climates where they dwell," (8. Hist. c. 16. * See also Derham's Phys. Theol. v. ii. p. 177.) The hybernation of animals is mentioned by M. Fabricius, who supposes it only to happen to animals, which originally be- longed to a warmer climate, and adds, that when these animals are carried back to a warmer climate, and supplied plentifully with food, they cease to hybernate. Hence their emigrations cannot depend on a necessary instinct, as the emigrations themselves are not necessary. 2 When the weather becomes cold, the swallows in the neighbourhood assemble in large flocks; that is, the unexperi- enced attend those that have before experienced the journey they are about to undertake: they are then seen some time to hover on the coast, till there is calm weather, or a wind that suits the direction of their flight. Other birds of passage have been drowned by thousands in the sea, or have settled on ships quite exhausted with fatigue. And others, either by mistaking their course, or by distress of weather, have arrived in countries where they were never seen before: and thus are evidently subject to the same hazards that the human species undergo, in the execu- tion of their artificial purposes. 3. The same birds are emigrant from some countries and not so from others: the swallows were seen at Goree in January by an ingenious philosopher of my acquaintance, and he was told that they continued there all the year; as the warmth of the cli- mate was at all seasons sufficient for their own constitutions, and for the production of the flies that supply them with nourishment. Herodotus says, that in Lybia, about the springs of the Nile, the swallows continue all the year. (L. 2.) 126 OF INSTINCT Sect. XVI. 12. 3. Quails (tetrao coturnix, Lin.) are birds of passage from the coast of Barbary to Italy, and have frequently settled in large shoals on ships, fatigued with their flight. (Ray, Wisdom of God, p. 129. Derham, Physic. Theol. v. ii. p. 178.) Dr. fiusscl, in his history of Aleppo, observes, that the swallows visit that country about the end of February, and having hatched their young disappear about the end of July; and returning again about the beginning of October, continue about a fortnight, and then again disappear. (P. 70.) When my late friend Dr. Chambers of Derby was on the island of Caprea in the bay of Naples, he was informed that great flights of quails annually settle on that island about the begin- ning of May, in their passage from Africa to Europe. And that they always come when the south-east wind blows, are fatigued when they rest on this island, and are taken in such amazing quantities, and sold to the continent, that the inhabitants pay the bishop his stipend out of the profits arising from the sale of them. The flights of these birds across the Mediterranean are record- ed near three thousand years ago. " There went forth a wind from the Lord and brought quails from the sea, and let them fall upon the camp, a day's journey round about it, and they were two cubits above the earth," (Numbers, chap. ii. ver. 31.) In our country, Mr. Pennant informs us, that some quails migrate, and others only remove from the internal parts of the island to the coasts, (Zoology, octavo, 210.) some of the ring- doves and stares breed here, others migrate, (ibid. 510, 511.) And the slender billed small birds do not all quit these kingdoms in the winter, though the difficulty of procuring the worms and insects, that they feed on, supplies the same reason for migration to them all, (ibid. 511.) Linnaeus has observed, that in Sweden the female chaffinches quit that country in September, migrating into Holland, and leave their mates behind till their return in spring. Hence he has called them Fringilla c?elebs, (Amaen. Acad. ii. 42. iv. 595.) Now in our climate both sexes of them are perennial birds. And Mr. Pennant observes that the hoopoe, chatterer, hawfinch, and cross-bill, migrate into England so rarely, and at such uncertain times, as not to deserve to be ranked among our birds of passage, num, like that of the cuckoo, and supposes that many other birds may be organized in the same manner. And, as the fern-owl in- cubates and hatches her own eggs, he rationally concludes, that this structure of the bird cannot be the cause of her want of ma- ternal storge. Hist, of Selbourn, p. 208. As the Rev. Mr. Stafford was walking in Glosop Dale, in the Peak of Derbyshire, he saw a cuckoo rise from its nest. The nest was on the stump of a tree, that had been some time felled, among some chips that were in part turned grey, so as much to resemble the colour of the bird; in this nest were two young cuckoos; tying a string about the leg of one of them, he peg- ged the other end of it to the ground, and very frequently for many days beheld the old cuckoo feed these young, as he stood very near them. The following extract of a Letter from the Rev. Mr. Wilmot, of Morley, near Derby, strengthens the truth of the fact above mentioned, of the cuckoo sometimes making a nest, and hatching her own young. "In the beginning of July 1792, I was attending some la- bourers on my farm, when one of them said to me, ' There is a bird's nest upon one of the Coal-slack Hills; the bird is now sitting, and is exactly like a cuckoo. They say that cuckoos never hatch their own eggs, otherwise I should have sworn it was one.' He took me to the spot, it was in an open fallow ground; the bird was upon the nest, I stood and observed her some time, and was perfectly satisfied it was a cuckoo; I then put my hand towards her, and she almost let me touch her be- fore she rose from the nest, which she appeared to quit with great uneasiness, skimming over the ground in the manner that a hen partridge does when disturbed from a new hatched brood, and went only to a thicket about forty or fifty yards from the nest; and continued there as long as I stayed to observe her, which was not many minutes. In the nest, which was barely a hole scratch- ed out of the coal-slack in the manner of a plover's nest, I ob- served three eggs, but did not touch them. As I had labourers constantly at work in that field, I went thither every day, and al- ways looked to see if the bird was there, but did not disturb her for seven or eight days, when I was tempted to drive her from the nest, and found tioo young ones, that appeared to have been hatched some days, but there was no appearance of the third egg. I then mentioned this extraordinary circumstance (for such I thought it) to Mr. and Mrs. Holyoak of Bidford Grange, War- wickshire, and to Miss M. Willes, who were on a visit at my house, and who all went to see it. Very lately I reminded Mr. Holyoak of it, who told me he had a perfect recollection of Sect. XVI. 14. 1. OF INSTINCT 133 the whole, and that, considering it a curiosity, he walked to look at it several times, was perfectly satisfied as to its being a cuckoo, and thought her more attentive to her young, than any other bird he ever observed, having always found her brooding her young. In about a week after I first saw the young ones, one of them was missing, and I rather suspected my plough-boys having taken it; though it might possibly have been taken by a hawk, some time when the old one was seeking food. I never found her off her nest but once, and that was the last time I saw the remaining young one, when it was almost full feathered. I then went from home for two or three days, and when I return- ed, the young one was gone, which I take for granted had flown. Though during this time I frequently saw cuckoos in the thicket I mention, I never observed any one, that I supposed to be the cock-bird, paired with this hen." Nor is this a new observation, though it is entirely overlooked by the modern naturalists, for Aristotle, speaking of the cuckoo, asserts that she sometimes builds her nest among broken rocks, and on high mountains, (L. 6. H. c. 1.) but adds in another place that she generally possesses the nest of another bird, (L. 6, II. c. 7.) And Niphus says that cuckoos rarely build for them- selves, most frequently laying their eggs in the nests of other birds, (Gesner, L. 3. de Cucuio.) The philosopher who is acquainted with these facts concern- ing the cuckoo, would seem to have very little reason himself, if he could imagine this neglect of her young to be a necessary instinct! XIV. The deep recesses of the ocean are inaccessible to man- kind, which prevents us from having much knowledge of the arts and government of its inhabitants. 1. One of the baits used by the fisherman is an animal called an Old Soldier; his size and form are somewhat like the craw- fish, with this difference, that his tail is covered with a tough membrane instead of a shell; and to obviate this defect, he seeks out the uninhabited shell of some dead fish, that is large enough to receive his tail, and carries it about with him as part of his clothing or armour. 2. On the coasts about Scarborough, where the haddocks, cods, and dog-fish, are in great abundance, the fishermen uni- versally believe that the dog-fish make a line, or semicircle, to encompass a shoal of haddocks and cod, confining them within certain limits near the shore, and eating them as occasion re- quires. For the haddocks and cod are always found near the shore without any dog-fish among them, and the dog-fish further off without anv haddocks or cod; and vet the former are know, 134 OF INSTINCT. Sect XVI. 11 J. to prey upon the latter, and in some years devour such immense quantities as to render this fishery more expensive than pro- fitable. 3. The remora, when he wishes to remove his situation, as he is a very slow swimmer, is content to take an outside place on whatever conveyance is going his way; nor can the cunning animal be tempted to quit his hold of a ship when she is sailing, not even for the lucre of a piece of pork, lest it should endanger the loss of his passage: at other times he is easily caught with the hook. 4. The crab-fish, like many other testaceous animals, annual- ly changes its shell; it is then in a soft state, covered only with a mucous membrane, and conceals itself in holes in the sand or under weeds; at this place a hard shelled crab always stands centinel, to prevent the sea insects from injuring the other in its defenceless state; and the fishermen from his appearance know where to find the soft ones, which they use for baits in catching other fish. And though the hard shelled crab, when he is on this duty, advances boldly to meet the foe, and will with difficulty quit the field; yet at other times he shews great timidity, and has a won- derful speed in attempting his escape; and, if often interrupted, will pretend death like the spider, and watch an opportunity to sink himself into the sand, keeping only his eyes above. My in- genious friend Mr. Burdett, who favoured me with these accounts at the time he was surveying the coasts, thinks the commerce between the sexes takes place at this time, and inspires the courage of the creature. 5. The shoals of herrings, cods, haddocks, and other fish, which approach our shores at certain seasons, and quit them at other seasons without leaving one behind; and the salmon, that periodically frequent our rivers, evince, that there are vagrant tribes of fish, that perform as regular migrations as the birds of passage already mentioned. 6. There is a cataract on the river Liffey in Ireland, about nineteen feet high: here in the salmon season many of the inha- bitants amuse themselves in observing these fish leap up the tor- rent. They dart themselves quite out of the water as they ascend, and frequently fall back many times before they surmount it, and baskets made of twigs are placed near the edge of the stream to catch them in their fall. I have observed, as I have sat by a spout of water, which de- scends from a stone trough about two feet into a stream below, at particular seasons of the year, a great number of little fish called miliums, or pinks, throw themselves about twenty times bixT. XVI. 15.1. OF INSTINCT. 135 their own length out of the water, expecting to get into the trough above. This evinces that the storge, or attention of the dam to pro- vide for the offspring, is strongly exerted amongst the nations of fish, where it would seem to be the most neglected; as these salmon cannot be supposed to attempt so difficult and dangerous a task without being conscious of the purpose or end of their en- deavours. It is further remarkable, that most of the old salmon return to the sea before it is proper for the young shoals to attend them, yet that a few old ones continue in the rivers so late, that they become perfectly emaciated by the inconvenience of their situ- ation, and this apparently to guide or to protect the unexperi- enced brood. Of the smaller water animals we have still less knowledge, who nevertheless probably possess many superior arts; some of these are mentioned in Botanic Garden, P. I. Add. Note XXVII. and XXVIII. The nymph a) of the water-moths of our rivers, which cover themselves with cases of straw, gravel, and shell, contrive to make their habitations nearly in equilibrium with the water; when too heavy, they add a bit of wood or straw; when too light, a bit of gravel. Edinb. Trans. All these circumstances bear a near resemblance to the delibe- rate actions of human reason. XV. We have a very imperfect acquaintance with the vari- ous tribes of insects: their occupations, manner of life, and even the number of their senses, differ from our own, and from each other; but there is reason to imagine, tint those which possess the sense of touch in the most exquisite degree, and whose oc- cupations require the most constant exertion of their powers. are endued with a greater proportion of knowledge and inge- nuity. The spiders of this country manufacture nets of various forms, adapted to various situations, to arrest the flies that are their fond; and some of them have a house or lodging-place in the middle of the net, well contrived for warmth, security, or concealment. There is a large spider in South America, which constructs nets of so strong a texture as to entangle small birds, particularly the humming bird. And in Jamaica there is an- other spider, who digs a hole in the earth obliquely downwards, about three inches in length, and one inch in diameter, this cavity she lines with a tough thick web, which when taken out resembles a leathern purse; but what is most curious, this house has a door with hinges, like the operculum of some sea shells; and herself and family, who tenant this nest, open and shut the 136 OF INSTINCT. Skit. XVI. 15. 1. door, whenever they pass or repass. This history was told me, and the nest with its operculum shewn me by the late Dr. Butt of Bath, who was some years physician in Jamaica. The production of these nets is indeed a part of the nature or conformation of the animal, and their natural use is to sup- ply the place of wings, when she wishes to remove to another situation. $ut when she employs them to entangle her prey, there are marks of evident design, for she adapts the form of each net to its situation, and strengthens those lines, that require it, by joining others to the middle of them, and attaching those others to distant objects, with the same individual art, that is used by mankind in supporting the masts and extending the sails of ships. This work is executed with more mathematical exactness and ingenuity by the field spiders, than by those in our houses, as their constructions are more subjected to the injuries of dews and tempests. Besides the ingenuity shewn by these little creatures in tiking their prey, the circumstance of their counterfeiting.de >'h, when they are put into terror, is truly wonderful; and as soon ;is the object of terror is removed, they recover and runaway. Some beetles are also said to possess this piece of hypocrisy. The curious webs, or cords, constructed by some young cater- pillars to defend themselves from cold, or from insects of prey, and by silk-worms and some other caterpillars, when they trans- migrate into aureliajor larvae, have deservedly excited the admi- ration of the inquisitive. But our ignorance of their manner of life, and even of the number of their senses, totally precludes ns from understanding the means by which they acquire this knowledge. The care of the salmon in choosing a proper situation for her spawn, the structure of the nests of birds, their patient incuba- tion, and the art of the cuckoo in depositing her egg in her neigh- bour's nursery, are instances of great sagacity in those creatures: and yet they are much inferior to the arts exerted by many of the insect tribes on similar occasions. The hairy excrescences on briars, the oak apples, the blasted leaves of trees, and the lumps on the backs of cows, are situations that are rather produced than chosen by the mother insect for the convenience of htr offspring. The cells of bees, wasps, spiders, and of the various coralline insects, equally astonish us, whether we attend to the materials or to the architecture. But the conduct of the ant, and of some species of the ich- neumon fly in the incubation of their eggs, is equal to any exer- tion of human science. The ants many times in a day move their eggs nearer the surface of their habitation, or deeper be- Sect. XVI. 16. 1. OF INSTINCT. 137 low it, as the heat of the weather varies; and in colder days lie upon them in heaps for the purpose of incubation: if their man- sion is too dry, they carry them to places where there is moisture; and you may distinctly see the little worms move and suck up the water. When too much moisture approaches their nest, they convey their eggs deeper in the earth, or to some other place of safety. (Swammerd. Epil. ad Hist. Insect, p. 153. Phil. Trans. No. 23. Lowthorp. V. 2. p. 7.) There is one species of ichneumon-fly, that digs a hole in the earth, and carrying into it two or three living caterpillars, depo- sites her eggs, and nicely closing up the nest, leaves them there; partly, doubtless, to assist the incubation, and partly to supply food to her future voung. (Derham. B. 4. c. 13. Aristotle, Hist. Animal. L. 5. c. 20.) A friend of mine put about fifty large caterpillars, collected from cabbages, on some bran and a few leaves into a box, and covered it with gauze to prevent their escape. After a few days we saw, from more than three-fourths of them, about eight or ten little caterpillars of the ichneumon-fly come out of their backs, and spin each a small cocoon of silk, and in a few days the large caterpillars died. This small fly it seems lays its egg in the back of the cabbage caterpillar, which, when hatched, preys upon the material, which is produced there for the purpose of making silk for the future nest of the cabbage caterpillar; of which being de- prived, the creature wanders about till it dies, and thus our gar- dens are preserved by the ingenuity of this cruel fly. This curious property of producing a silk thread, which is common to some sea animals, see Botanic Garden, Part I. Note XXY1I. and is designed for the purpose of their transformation, as in the silk-worm, is used for conveying themselves from higher branches to lower ones of trees by some caterpillars, and to make themselves temporary nests or tents, and by the spider for en- tangling his prey. Nor i3 it strange that so much knowledge should be acquired by such small animals; since there is reason to imagine, that these insects have the sense of touch, either in their proboscis, or their antenna?, to a great degree of perfection; and thence may possess, as far as their sphere extends, as accu- rate knowledge, and as subtle invention, as the discoverers of hu- man arts. XVI. I. If we were better acquainted with the histories of those insects that are formed into societies, as the bees, wasps, and ants, I make no doubt but we should find, that their arts and improvements are not so similar and uniform as they now appear to us, but that they rose in the same manner from experience VOL. I. t 138 OF INSTINCT. Sect. XVI. 16.2. and tradition, as the arts of our own species; though their reason- ing is from fewer ideas, is busied about fewer objects, and is ex- erted with less energy. There are some kinds of insects that migrate like the birds be- fore mentioned. The locust of warmer climates has sometimes come over to England; it is shaped like a grasshopper, with very large wings, and a body above an inch in length. It is mention- ed as coming into Egypt with an east wind, " The Lord brought an east wind upon the land all that day and night, and in the morning the east wind brought the locusts, and covered the face of the earth, so that the land was dark," Exod. x. 13. The mi- grations of these insects are mentioned in another part of the scripture, "The locusts have no king, yet go they forth all of them in bands," Prov. xxx. 27. The accurate Mr. Adanson, near the river Gambia, in Africa, was witness to the migration of these insects. " About eight in the morning, in the month of February, there suddenly arose over our heads a thick cloud, which darkened the air, and deprived us of the rays of the sun. We found it was a cloud of locusts, raised about twenty or thirty fathoms from the ground, and cover- ing an extent of several leagues; at length a shower of these in- sects descended, and after devouring every green herb, while they rested, again resumed their flight. This cloud was brought by a strong east wind, and was all the morning in passing over the adjacent country." (Voyage to Senegal, 158.) In this country the gnats are sometimes seen to migrate in clouds, like the musketoes of warmer climates, and our swarms of bees frequently travel many miles, and are said in North Ame- rica always to fly towards the south. The prophet Isaiah has a beautiful allusion to these migrations, u The Lord shall call the fly from the rivers of Egypt, and shall hiss for the bee that is in the land of Assyria," Isa. vii. 18. which has been lately explained by Mr. Bruce, in his Travels to discover the Source of the Nile. 2. I am well informed that the bees that were carried into Barbadoes, and other western islands, ceased to lay up any honey after the first year, as they found it not useful to them; and are now become very troublesome to the inhabitants of those islands by infesting their sugar-houses; but those in Jamaica continue to make honey, as the cold north winds, or rainy seasons of that island, confine them at home for several weeks together. And the bees of Senegal, which differ from those of Europe only in size, make their honey not only superior to ours in delicacy of flavour, but it has this singularity, that it never concretes, but remains liquid as syrup, (Adanson). From some observations of Sect. XVI. 16. 3. OF INSTINCT. 139 Mr. Wildman, and of other people of veracity, it appears, that during the severe part of the winter season, for weeks together, the bees are quite benumbed and torpid from the cold, and do not consume any of their provision. This state of sleep, like that of swallows and bats, seems to be the natural resource of those creatures in cold climates, and the making of honey to be an arti- ficial improvement. As the death of our hives of bees appears to be owing to their being kept so warm, as to require food, when their stock is ex- hausted; a very observing gentleman at my request put two hives for many weeks into a dry cellar, and observed during all that time, they did not consume any of their provision, for their weight did not decrease as it had done when they were kept in the open air. The same observation is made in the Annual Register for 1768, p. 113. And the Rev. Mr. White, in his Method of Preserving Bees, adds, that those on the north side of his house consumed less honey in the winter than those on the south side. There is another observation on bees well ascertained, that they at various times, when the season begins to be cold, by a general motion of their legs as they hang in clusters, produce a degree of warmth, which is easily perceptible by the hand. Hence by this ingenious exertion, they for a long time prevent the torpid state they would naturally fall into. According to the late observations of Mr. Hunter, it appears that the bees'-wax is not made from the dust of the anthers of flowers, which they bring home on their thighs, but that this makes what is termed bee-bread, and is used for the purpose of feeding the bee maggots; in the same manner butterflies live on honey, but the previous caterpillar lives on vegetable leaves, while the maggots of large flies require flesh for their food, and those of the ichneumon fly require insects for their food. What induces the bee, who lives on honey, to lay up vegetable powder for its young? What induces the butterfly to lay its eggs on leaves, when itself feeds on honey? What induces the other flies to seek a food for their progeny different from what they consume them- selves? If these are not deductions from their own previous ex- perience or observation, all the actions of mankind must be re- solved into instinct. 3. " The dormouse consumes but little of its food during the rigour of the season, for they roll themselves up, or sleep, or lie torpid the greatest part of the time; but on warm sunny days experience a short revival, and take a little food, and then re- lapse into their former state." (Pennant, Zoolog. p. 67.) Other animals that sleep in winter without laying up any provender, 140 OF 1NS1INCT Sect. XVI. 16 4. are observed to go into their winter beds fat and strong, but re- turn to day light in the spring season very lean and feeble. The common flies sleep during the winter without any provision for their nourishment, and are daily revived by the warmth of the sun, or of our fires. These whenever they see light endeavour to approach it, having observed, that by its greater vicinity they get free from the degree of torpor that the cold produces; and are hence induced perpetually to burn themselves in our candles: de- ceived, like mankind, by the misapplication of their knowledge. Whilst many of the subterraneous insects, as the common worms, seem to retreat so deep into the earth as not to be enlivened or awakened by the difference of our winter days; and stop up their holes with leaves or straws, to prevent the frosts from injuring them, or the centipes from devouring them. The habits of peace, or the stratagems of war, of these subterranean nations are cover- ed from our view; but a friend of mine prevailed on a distressed worm to enter the hole of another worm on a bowling-green, and he presently returned much wounded about his head. And I once saw a worm rise hastily out of the earth into the sun-shine, and observed a centipes hanging at its tail: the centipes nimbly quitted the tail, and seizing the worm about its middle, cut it in half with its forceps, and preyed upon one part, while the other escaped. Which evinces they have design in stopping the mouths of their habitations. 4. The wasp of this country fixes his habitation under ground, that he may not be affected with the various changes of our climate; but in Jamaica he hangs it on the bough of a tree, where the seasons are less severe. He weaves a very curious paper of vegetable fibres to cover his nest, which is constructed on the same principle with that of the bee, but with a different material; but as his prey consists of flesh, fruits, and insects, which are perishable commodities, he can lay up no provender for the winter. M. de la Loubiere, in his relation of Siam, says, " That in a part of that kingdom, which lies open to great inundations, all the ants make their settlements upon trees; no ants' nests are to be seen any where else." Whereas in our country the ground is their only situation. From the scriptural account of these in- sects, one might be led to suspect, that in some climates they lay up a provision for the winter, (Prov. vi. 6. xxx. 25.) Origen af- firms the same, (Cont. Cels. L. 4.) But it is generally believed that in this country they do not. The white ants of the coast of Africa make themselves pyramids eight or ten feet high, on a base of about the same width, with a smooth surface of rich clay, excessively hard and well built, which appear at a distance Sei t. XVI. 17. 1. OF INSTINCT. 141 like an assemblage of the huts of the negroes, (Adanson.) The history of these has been lately well described in the Philosoph. Transactions, under the name of termes, or termites. These differ very much from the nest of our large ant; but the real his- tory of this creature, as well as of the wasp, is yet very imperfect- ly known. Wasps are said to catch large spiders, and to cut off their legs, and carrv their mutilated bodies to their young, Diet. Raison. Tom. I. p. 152. One circumstance I shall relate which fell under my own eye, and showed the power of reason in a wasp, as it is exercised among men. A wasp, on a gravel walk, had caught a fly nearly as large as himself; kneeling on the ground I observed him sepa- rate the tail and the head from the body part, to which the wings were attached. He then took the body part in his paws, and rose about two feet from the ground with it; but a gentle breeze wafting the wings of the fly turned him round in the air, and he settled again with his prey upon the gravel. I then dis- tinctly observed him cut off with Lis mouth, first one of the wings, and then the other, after which he flew away with it unmolested by the wind. Go, thou sluggard, learn arts and industry from the bee, and from the ant! Uo, proud reasoner, and call the worm thy sister! XVII. Conclusion. It was before observed how much the superior accuracy of our sense of touch contributes to increase our knowledge; but it is the greater energy and activity of the power of volition (as explained in the former Sections of this wrork) that marks man, and has given him the empire of the world. There is a criterion by which we may distinguish our volun- tary acts or thoughts from those that are excited by our sensa- tions: " The former are always employed about the means to ac- quire pleasurable objects, or to avoid painful ones: while the lat- ter are employed about the possession of those that are already in our power." If we turn our eyes upon the fabric of our fellow animals, we find they are supported with bones, covered with skins, moved by muscles; that they possess the same senses, acknowledge the same appetites, and are nourished by the same aliment with our- selves; and we should hence conclude, from the strongest analogy, that their internal faculties were also in some measure similar to our own. 142 OF INSTINCT. Sect. XVI. 17. 1. Mr. Locke indeed published an opinion, that other animals possessed no abstract or general ideas, and thought this circum- stance was the barrier between the brute and the human world. But these abstracted ideas have been since demonstrated by bishop Berkeley, and allowed by Mr. Hume, to have no existence in na- ture, not even in the mind of their inventor, and we are hence necessitated to look for some other mark of distinction. The ideas and actions of brutes, like those of children, are al most perpetually produced by their present pleasures, or their present pains; and, except in the few instances that have been mentioned in this Section, they seldom busy themselves about the means of procuring future bliss, or avoiding future misery. Whilst the acquiring of languages, the making of tools, and the labouring for money; which are all only the means of procur- ing pleasure; and the praying to the Deity, as another means to procure happiness, are characteristic of human nature. Sict. XVII. 1.1. CATF.NATION, &c. 143 SECT. XVII. THE CATENATION OF MOTIONS. I. 1. Catenations of animal motion. 2. Are produced by irrita- tions, by sensations, by volitions. 3. They continue some time after they have been excited. Cause of catenation. 4. We can then exert our attention on other objects. 5. Many catenations of motions go on together. 6. Some links of the catenations of motions may be left without disuniting the chain. 7. Interrupt- ed circles of motion continue confusedly till they come to the part of tlie circle, where they were disturbed. 8. Weaker catenations are dissevered by stronger. 9. Tlien new catenations take place. 10. Much effort prevents their re-uniting. Impediment of speech. 11. Trains more easily dissevered than circles. 12. Sleep destroys volition and external stimulus. II. Instances of various catenations in a young lady playing on a harpsichord. III. 1. What catenations are the strongest. 2. Irritations joined with associations form strongest connexions. Vital motions. 3. New links with increased force, cold fits of fever produced. 4. New links with decreased force. Cold bath. 5. Irritation joined with sensation. Inflammatory fever. Why children can- not tickle tliemselves. 6. Volition joined with sensation. Irri- tative ideas of sound become sensible. 7. Ideas of imagination diddered by irritations, by volition, production of surprise. I. 1. To investigate with precision the catenations of animal motions, it would be well to attend to the manner of their pro- duction; but we cannot begin this disquisition early enough for this purpose, as the catenations of motion seem to begin with life, and are only extinguishable with it. We have spoken of the power of irritation, of sensation, of volition, and of associ- ation, as preceding the fibrous motions; we now step forwards, and consider, that conversely they are in their turn preceded by those motions; and that all the successive trains or circles of our actions are composed of this twofold concatenation. Those we shall call trains of action, which continue to proceed without any stated repetitions; and those circles of action, when the parts of them return at certain periods, though the trains, of which they consist, are not exactly similar. The reading an epic poem is a train of actions; the reading a song with a chorus at equal distances in the measure constitutes so many circles of action. 2. Some catenations of animal motion are produced by reiter- lit CATENATION Sect XVII 1.3. ated successive irritations, as when we learn to repeat the alpha- bet in its order by frequently reading the letters of it. Thus the vermicular motions of the bowels were originally produced by the successive irritations of the passing aliment; and the succession of actions of the auricles and ventricles of the heart was origin- ally formed by successive stimulus of the blood, these afterwards become part of the diurnal circles of animal actions, as appears by the periodical returns of hunger, and the quickened pulse of weak people in the evening. Other catenations of animal motions are gradually acquired by successive agreeable sensations, as in learning a favourite song or dance: others by disagreeable sensations, as in coughing or nictitation; these become associated by frequent repetition; and afterwards compose parts of greater circles of action like those above mentioned. Other catenations of motions are gradually acquired by fre- quent voluntary repetitions; as when we deliberately learn to march, read, fence, or any mechanic art, the motions of many of our muscles become gradually linked together in trains, tribes, or circles of action. Thus when any one at first begins t* use the tools in turning wood or metals in a lathe, he wills the mo- tions of his hand or fingers, till at length these actions become so connected with the effect, that he seems only to will the point of the chissel. These are caused by volition, connected by associa- tion like those above described, and afterwards become parts of our diurnal trains or circles of action. 3. All these catenations of animal motions are liable to pro- ceed some time after they are excited, unless they are disturbed or impeded by other irritations, sensations, or volitions; and in many instances in spite of our endeavours to stop them; and this property of animal motions is probably the cause of their cate- nation.. Thus when a child revolves some minutes on one foot, the spectra of the ambient objects appear to circulate round him some time after he falls upon the ground. Thus the palpitation of the heart continues some time after the object of fear, which occasioned it, is removed. The blush of shame, which is an ex- cess of sensation, and the glow of anger, which is an excess of volition, continue some time, though the affected person finds that those emotions were caused by mistaken facts, and endea- vours to extinguish their appearance. See Sect. XII. 1. 5. 4. When a circle of motions becomes connected by frequent repetitions as above, we can exert our attention strongly on other objects, and the concatenated circle of motions will neverthe- less proceed in due order; as whilst you are thinking on this Sect. XVII. 1. 5. OF MOTIONS. 145 subject, you use variety of muscles in walking about your par- lour, or in sitting at your writing table. 5. Innumerable catenations of motions may proceed at the same time, without incommoding each other. Of these are the motions of the heart and arteries; those of digestion and glandu- lar secretion; of the ideas, or sensual motions; those of progres- sion, and of speaking; the great annual circle of actions so appa- rent in birds in their times of breeding and moulting; the month- ly circles of many female animals; and the diurnal circles of sleeping and waking, of fulness and inanition. 6. Some links of successive trains or of synchronous tribes of action may be left out without disjoining the whole. Such are our usual trains of recollection: after having travelled through an entertaining country, and viewed many delightful lawns, rolling rivers, and echoing rocks; in the recollection of our journey we leave out the many districts that we crossed, which were mark- ed with no peculiar pleasure. Such also are our complex ideas, they are catenated tribes of ideas, which do not perfectly resem- ble their correspondent perceptions, because some of the parts are omitted. 7. If an interrupted circle of actions is not entirely dissevered, it will continue to proceed confusedly, till it comes to the part of the circle where it was interrupted. The vital motions in a fever from drunkenness, and in other periodical diseases, are instances of this circumstance. The ac- cidental inebriate does not recover himself perfectly till about the same hour on the succeeding day. The accustomed drunk- ard is disordered if he has not bis usual potation of fermented liquor. So if a considerable part of a connected tribe of ac- tion be disturbed, that whole tribe goes on with confusion, till the part of the tribe affected regains its accustomed catenations. So vertigo produces vomiting, and a great secretion of bile, as in sea-sickness, all these being parts of the tribe of irritative ca- tenations. 8. Weaker catenated trains may be dissevered by the sudden exertion of the stronger. When a child first attempts to walk across a room, call to him, and he instantly falls upon the ground. So while I am thinking over the virtues of my friend, if the tea- kettle spurt out some hot water on my stocking, the sudden pain breaks the weaker chain of ideas, and introduces a new group of figures of its own. This circumstance is extended to some un- natural trains of action, which have not been confirmed by long habit; as the hiccough, or an ague-fit, which are frequently curable by surprise. A young lady about eleven years old had for five days had a contraction of one muscle in her fore arm, VOL. I. U 146 CATENATION Sect. XVII. 1. 9. and another in her arm, which occurred four or five times every minute; the muscles were seen to leap, but without bending the arm. To counteract this new morbid habit, an issue was placed over the convulsed muscle of her arm, and an adhesive plaster wrapped tight like a bandage over the whole fore arm, by which the new motions were immediately destroyed, but the means were continued some weeks to prevent a return. 9. If any circle of actions is dissevered, either by omission of some of the links, as in sleep, or by insertion of other links, as in surprise, new catenations take place in a greater or less degree. The last link of the broken chain of actions becomes connected with the new motion which has broken it, or with that which was nearest the link omitted; and these new catenations proceed instead of the old ones. Hence the periodic returns of ague-fits, and the chimeras of our dreams. 10. If a train of actions is dissevered, much effort of volition or sensation will prevent its being restored. Thus in the com- mon impediment of speech, when the association of the motions of the muscles of enunciation with the idea of the word to be spoken is disordered, the great voluntary efforts, which distort the countenance, prevent the rejoining of the broken associations. See No. II. 10. of this Section. It is thus likewise observable in some inflammations of the bowels, the too strong efforts made by the muscles to carry forwards the offending material fixes it more firmly in its place, and prevents the cure. So in endea- vouring to recall to our memory some particular word of a sen- tence, if we exert ourselves too strongly about it, we are less like- ly to regain it. 11. Catenated trains or tribes of action are easier dissevered than catenated circles of action. Hence in epileptic fits the synchronous connected tribes of action, which keep the body erect, are dissevered, but the circle of vital motions continues undisturbed. 12. Sleep destroys the power of volition, and precludes the stimuli of external objects, and thence dissevers the trains, of which these are a part; which confirms the other catenations, as those of the vital motions, secretions, and absorptions; and pro- duces the new trains of ideas, which constitute our dreams. II. 1. All the preceding circumstances of the catenations of animal motions will be more clearly understood by the follow- ing example of a person learning music: and when we recollect the variety of mechanic arts, which are performed by associated trains of muscular actions catenated with the effects they pro- duce, as in knitting, netting, weaving; and the greater variety of associated trains of ideas caused, or catenated by volitions, or Skt. XVII. 2. 2. OF MOTIONS. 147 sensations, as in our hourly modes of reasoning, or imagining, or recollecting, we shall gain some idea of the innumerable catenat- ed trains aud circles of action, which form the tenor of our lives, and which began, and will only cease entirely with them. 2. When a young lady begins to learn music, she voluntarily applies herself to the characters of her music-book, and by many repetitions endeavours to catenate them with the proportions of sound, of which they are symbols. The ideas excited by the musical characters are slowly connected with the keys of the harpsichord, and much effort is necessary to produce every note with the proper finger, and in its due place and time; till at length a train of voluntary exertions becomes catenated with certain irritations. As the various notes by frequent repetitions become connected in the order, in which they are produced, a new catenation of sensitive exertions becomes mixed with the voluntary ones above described; and not only the musical sym- bols of crotchets and quavers, but the auditory notes and tones at the same time, become so many successive or synchronous links in this circle of catenated actions. At length the motions of her fingers become catenated with the musical characters; and these no sooner strike the eye, than the finger presses down the key without any voluntary attention be- tween them; the activity of the hand being connected with the irritation of the figure or place of the musical symbol on the re- tina; till at length by frequent repetitions of the same tune the movements of her fingers in playing, and the muscles of the larynx in singing, become associated with each other, and form part of those intricate trains and circles of catenated motions, according with the second article of the preceding propositions in No. 1. of this Section. 3. Besides the facility, which by habit attends the execution of this musical performance, a curious circumstance occurs, which is, that when our young musician has begun a tune, she finds her- self inclined to continue it; and that even when she is carelessly singing alone without attending to her own song; according with the third preceding article. 4. At the same time that our young performer continues to play with great exactness this accustomed tune, she can bend her mind, and that intensely, on some other object, according with the fourth article of the preceding propositions. The manuscript copy of this work was lent to many of my friends at different times for the purpose of gaining their opinions and criticisms on many parts of it, and I found the following anecdote written with a pencil opposite to this page, but am not certain my whom. " I remember seeing the pretty young 148 CATENATION Sect. XVII. 2. 5. actress who succeeded Mr9. Arne in the performance of the ce- lebrated Padlock, rehearse the musical parts at her harpsichord under the eye of her master with great taste and accuracy; though I observed her countenance full of emotion, which I could not account for; at last she suddenly burst into tears; for she had all this time been eyeing a beloved canary bird, suffering great agonies, which at that instant fell dead from its perch." 5. At the same time many other catenated circles of action are going on in the person of our fair musician, as well as the mo- tions of her fingers, such as the vital motions, respiration, the movements of her eyes and eyelids, and of the intricate muscles ofvocality, according with the fifth preceding article. 6. If by any strong impression on the mind of our fair musi- cian she should be interrupted for a very inconsiderable time, she can still continue her performance, according to the sixth article. 7. If, however, this interruption be greater, though the chain of actions be not dissevered, it proceeds confusedly, and our young performer continues indeed to play, but in a hurry, without accu- racy and elegance, till she begins the tune again, according to the seventh of the preceding articles. 8. But if this interruption be still greater, the circle of ac- tions becomes entirely dissevered, and she finds herself immedi- ately under the necessity to begin over again to recover the lost catenation, according to the eighth preceding article. 9. Or in trying to recover it she will sing some dissonant notes, or strike some improper keys, according to the ninth pre- ceding article. 10. A very remarkable thing attends this breach of catenation, if the performer has forgotten some word of her song, the more energy of mind she uses about it, the more distant is she from re- gaining it; and artfully employs her mind in part on some other object, or endeavours to dull its perceptions, continuing to repeat, as it were inconsciously, the former part of the song, that she re- members, in hopes to regain the lost connexion. For if the activity of the mind itself be more energetic, or takes its attention more than the connecting word, which is wanted; it will not perceive the slighter link of this lost word; as who listens to a feeble sound, must be very silent and motionless; so that in this case the very vigour of the mind itself seems to pre- vent it from regaining the lost catenation, as well as the too great exertion in endeavouring to regain it, according to the tenth pre- ceding article. We frequently experience, when we are doubtful about the spelling of a word, that the greater voluntary exertion we use, that is, the more intensely we think about it, the further are we Sbct. XVII. 2.11- OF MOTIONS. 149 from regaining the lost association between the letters of it, but which readily recurs when we have become careless about it. In the same manner, after having for an hour laboured to recollect the name of some absent person, it shall seem, particularly after sleep, to come into the mind as it were spontaneously; that is, the word we are in search of, was joined to the preceding one by association; this association being dissevered, we endeavour to re- cover it by volition; this very action of the mind strikes our atten- tion more than the faint link of association, and we find it impos- sible by this means to retrieve the lost word. After sleep, when volition is entirely suspended, the mind becomes capable of per- ceiving the fainter link of association, and the word is regained. On this circumstance depends the impediment of speech be- fore mentioned; the first syllable of a word is causable by voli- tion, but the remainder of it is in common conversation intro- duced by Us associations with this first syllable, acquired by long habit. Hence when the mind of the stammerer is vehemently employed on some idea of ambition of shining, or fear of not suc- ceeding, the associations of the motions of the muscles of articu- lation with each other become dissevered by this greater exer- tion, and he endeavours in vain by voluntary efforts to rejoin the broken association. For this purpose he continues to repeat the first syllable, which is causable by volition, and strives in vain, by various distortions of countenance, to produce the next links, which are subject to association. See Class IV. 3. 1. 1. 11. After our accomplished musician has acquired great va- riety of tunes and songs, so that some of them begin to cease to be easily recollected, she finds progressive trains of musical notes more frequently forgotten, than those which are composed of re- iterated circles, according with the eleventh preceding article. 12. To finish our example with the preceding articles wc must at length suppose, that our fair performer falls asleep over her harpsichord; and thus by suspension of volition, and the exclusion of external stimuli, she dissevers the trains and circles of her mu- sical exertions. III. 1. Many of these circumstances of catenations of motions receive an easy explanation from the four following consequences to the seventh law of animal causation in Sect. IV. These are, first, that those successions or combinations of animal motions, whether they were united by causation, association, or catenation, which have been most frequently repeated, acquire the strongest connexion. Secondly, that of these, those which have been less frequently mixed with other trains or tribes of motion, have the strongest connexion. Thirdly, that of these, those which were 150 CATENATION Sect. XVII. 3. 2. first formed, have the strongest connexion. Fourthly, that if an animal motion be excited by more than one causation, association, or catenation, at the same time, it will be performed with greater energy. 2. Hence also we understand, why the catenations of irrita- tive motions are more strongly connected than those of the other classes, where the quantity of unmixed repetition has been equal; because they were first formed. Such are those of the secerning and absorbent systems of vessels, where the action of the gland produces a fluid, which stimulates the mouths of its corresponded absorbents. The associated motions seem to be the next most strongly united, from their frequent repetition; and where both these circumstances unite, as in the vital motions, their catena- tions are indissoluble but by the destruction of the animal. 3. Where a new link has been introduced into a circle of ac- tions, by some accidental defect of stimulus; if that defect of stimulus be repeated at the same part of the circle a second or a third time, the defective motions thus produced, both by the re- peated defect of stimulus and by their catenation with the parts of the circle of actions, will be performed with less and less energy. Thus if any person is exposed to cold at a certain hour to-day, so long as to render some part of the system for a time torpid; and is again exposed to it at the same hour to-morrow, and the next day; he will be more and more affected by it, till at length a cold fit of fever is completely formed, as happens at the beginning of many of those fevers, which are called nervous or low fevers. Where the patient has slight periodical shiverings and paleness for many days before the febrile paroxysm is com- pletely formed. 4. On the contrary, if the exposure to cold be for so short a time, as not to induce any considerable degree of torpor or quiescence, and is repeated daily as above mentioned, it loses its effect more and more at every repetition, till the constitution can bear it without inconvenience, or indeed without being conscious of it. As in walking into the cold air in frosty weather. The same rule is applicable to increased stimulus, as of heat, or vinous spi- rit, within certain limits, as is applied in the two last paragraphs to Deficient Stimulus, as is further explained in Sect. XXXVI. on the Periods of Diseases. 5. Where irritation coincides with sensation to produce the same catenations of motion, as in inflammatory fevers, they are excited with still greater energy than by the irritation alone. So when children expect to be tickled in play, by a feather lightly Sect. XVII. 3. 6. OF MOTIONS. 151 passed over the lips, or by gently vellicating the soles of their feet, laughter is most vehemently excited; though they can sti- mulate these parts with their own fingers unmoved. Here the pleasurable idea of playfulness coincides with the vellication; and there is no voluntary exertion used to diminish the sensa- tion, as there would be, if a child should endeavour to tickle himself. See Sect. XXXIV. 1. 4. 6. And lastly the motions excited by the junction of voluntary exertion with irritation are performed with more energy, than those by irritation singly; as when we listen to small noises, as to the ticking of a watch in the night, we perceive the most weak sounds, that are at other times unheeded. So when we attend to the irritative ideas of sound in our ears, which are generally not attended to, we can hear them; and can see the spectra of objects, which remain in the eye, whenever we please to exert our voluntary power in aid of those weak actions of the retina, or of the audilory nerve. 7. The temporary catenations of ideas, which are caused by the sensations of pleasure or pain, are easily dissevered either by irri- tations, as when a sudden noise disturbs a day-dream; or by the power of volition, as when we awake from sleep. Hence in our waking hours, whenever an idea occurs, which is incongruous to our former experience, we instantly dissever the train of ima- gination by the power of volition, and compare the incongruous idea with our previous knowledge of nature, and reject it. This operation of the mind has not yet acquired a specific name, though it is exerted every minute of our waking hours; unless, it may be termed intuitive analogy. It is an act of reason- ing of which we'are unconscious except from its effects in pre- serving the congruity of our ideas, and bears the same relation to the sensorial power of volition, that irritative ideas, of which we are inconscious except by their effects, do to the sensorial power of irritation; as the former is produced by volition with- out our attention to it, and the latter by irritation without our at- tention to them. If on the other hand a train of imagination or of voluntary ideas are excited with great energy, and passing on with great vivacity, and become dissevered by some violent stimulus, as the discharge of a pistol near one's ear, another circumstance takes place, vvhich is termed surprise; vvhich, by exciting violent irritation, and violent sensation, employs for a time the whole sensorial energy, and thus dissevers the passing trains of ideas, before the power of volition has time to compare them with the usual phenomena of nature. In this case fear is generally the companion of surprise, and adds to our embarrassment, as every' J52 CATENATION, &c Si:only those parts of the system, which are always excited by internal stimuli, as the stomach, intestinal canal, bile-ducts, and the various glands, but the or- gans of sense also may be more violently excited into action by the irritation from internal stimuli, or by sensation, during our sleep than in our waking hours; because during the suspension of volition, there is a greater quantity of the spirit of animation to be expended by the other sensorial powers. On this account our irritability to internal stimuli, and our sensibility to pain or pleasure, is not only greater in sleep, but increases as our sleep is prolonged. Whence digestion and secretion are performed better in sleep, than in our waking hours, and our dreams in the morning have greater variety and vivacity, as our sensibility in- creases, than at night when we first lie down. And hence epi- leptic fits, which are always occasioned by some disagreeable sen- sation, so frequently attack those who are subject to them, in their sleep; because at this time the system is more extitable by painful sensation in consequence of internal stimuli; and the power of volition is then suddenly exerted to relieve this pain, as explained Sect. XXXIV. 1. 4. There is a disease, which frequently affects children in the cradle, which is termed ecstasy, and seems to consist in certain exertions to relieve painful sensation, in which the voluntary power is not so far excited as totally to awaken them, and yet is sufficient to remove the disagreeable sensation, which excites it; in this case changing the posture of the child frequently re- lieves it. I have at this time under my care an elegant young man Ski-t. XVHI. 15. OF SLEEP. 163 about twenty-two years of age, who seldom sleeps more than an hour without experiencing a convulsion fit; which ceases in. about half a minute without any subsequent stupor. Large doses of opium only prevented the paroxysm, so long as they pre- vented him from sleeping by the intoxication, which they induc- ed. Other medicines had no effect on him. He was gently awakened every half hour for one night, but without good ef- fect, as he soon slept again, and the fit returned at about the same periods of time, for the accumulated sensorial power, which occasioned the increased sensibility to pain, was not thus exhaust- ed. This case evinces that the sensibility of the system to in- ternal excitation increases, as our sleep is prolonged; till the pain thus occasioned produces voluntary exertion; which, wdien it is in its usual degree, only awakens us; but when it is more violent, it occasions convulsions. The cramp in the calf of the leg is another kind of convulsion, which generally commences in sleep, occasioned by the continual increase of irritability from internal stimuli, or of sensibility, dur- ing that state of our existence. The cramp is a violent exertion to relieve pain, generally either of the skin from cold, or of the bowels, as in some diarrhoeas, or from the muscles having been previously overstretched, as in walking up or down steep hills. But in these convulsions of the muscles, which form the calf of the leg, the contraction is so violent, as to occasion another pain in consequence of their own too violent contraction, as soon as the original pain, which caused the contraction, is removed. And hence the cramp, or spasm, of these muscles is continued without intermission by this new pain, unlike the alternate con- vulsions and remissions in epileptic fits. The reason, that the contraction of these muscles of the calf of the leg is more violent during their convulsion than that of others, depends on the weak- ness of their antagonist muscles; for after these have been con- tracted in their usual action, as at every step in walking, they are again extended, not, as most other muscles are, by their an- tagonists, but by the weight of the whole body on the balls of the toes; and that weight applied to great mechanical advantage on the heel, that is, on the other end of the bone of the foot, which thus acts as a lever. * Another disease, ^,e periods of which generally commence during our sleep, is the asthma. Whatever may be the remote cause of paroxysms of asthma, the immediate cause of the con- vulsive respiration, whether in the common asthma, or in what is termed the convulsive asthma, which are perhaps only differ- ent degrees of the same disease, must be owing to violent volun- tary exertions to relieve pain, as in other convulsions; and the J64 OF SLEEP. Skct. XVII I. 16. increase of irritability to internal stimuli, or of sensibility, during sleep must occasion them to commence at this time. Debilitated people, who have been unfortunately accustomed to great ingurgitation of spirituous potation, frequently part with a great quantity of water during the night, but with not more than usual in the day-time. This is owing to a beginning torpor of the absorbent system, and precedes anasarca, which com- mences in the day, but is cured in the night by the increase of the irritability of the absorbent system during sleep, which thus imbibes from the cellular membrane the fluids, which had been accumulated there during the day; though it is possible the hori- zontal position of the body may contribute something to this pur- pose, and also the greater irritability of some branches of the ab- sorbent vessels, which open their mouths in the cells of the cel- lular membrane, than that of other branches. As soon as a person begins to sleep, the irritability and sensi- bility of the system begin to increase, owing to the suspension of volition and the exclusion of external stimuli. Hence the ac- tions of the vessels in obedience to internal stimulation become stronger and more energetic, though less frequent in respect to number. And as many of the secretions are increased, so the heat of the system is gradually increased, and the extremities of feeble people, which had been cold during the day, become warm. Till towards morning many people become so warm, as to find it ne- cessary to throw off some of their bed-clothes, as soon as they awake; and in others sweats are so liable to occur towards morn- ing during their sleep. Thus those, who are not accustomed to sleep in the open air, are very liable to take cold, if they happen to fall asleep on a garden bench, or in a carriage with the window open. For as the system is warmer during sleep, as above explained, if a cur- rent of cold air affects any part of the body, a torpor of that part is more effectually produced, as when a cold blast of air through a key-hole or casement falls upon a person in a warm room. In those cases the affected part possesses less irritability in respect to heat, from its having previously been exposed Jo a greater stimu- lus of heat, as in the warm room, or during sleep; and hence, when the stimulus of heat is diminished, a torpor is liable to ensue; that is, we take cold. Hence people who sleep in the open air generally feel chiily both -at the approach of sieep, and on their waking; and hence many people are perpetually subject to ca- tarrhs if they sleep in a less warm head-dress, than that which they wear in the day. 16. Not only the sensorial powers of irritation and of sensa- tion, but that of association also appear to act with greater vi- Sect. XVIII. 10 OF SLEEP. 165 gour during the suspension of volition in sleep. It will be shewn in another place, that the gout generally first attacks the liver, and that afterwards an inflammation of the ball of the great toe com- mences by association, and that of the liver ceases. Now as this change or metastasis of the activity of the system generally commences in sleep, it follows, that these associations of motion exist with greater energy at that time; that is, that the sensorial faculty of association, like those of irritation and of sensation, be- comes in some measure accumulated during the suspension of volition. Other associate tribes and trains of motions, as well as the ir- ritative and sensitive ones, appear to be increased in their activi y during the suspension of volition in sleep. As those which con- tribute to circulate the blood, and to perform the various secre- tions as well as the associate tribes and trains of ideas, which contribute to furnish the perpetual streams of our dreaming ima- ginations. In sleep the secretions have generally been supposed to be di- minished, as the expectorated mucus in coughs, the fluids dis- charged in diarrhoeas, and in salivation, except indeed the secre- tion of sweat, which is often visibly increased. This error seems to have arisen from attention to the exertions rather than to the secretions. For the secretions, except that of sweat, are gene- rally received into reservoirs, as the urine into the bladder, and the mucus of the intestines and lungs into their respective cavities; hut these reservoirs do not exclude these fluids immediatelv by their stimulus, but require at the same time some voluntary ef- forts, and therefore permit them to remain during sleep. And as they thus continue longer in those receptacles in our sleeping hours, a greater part is absorbed from them, and the remainder becomes thicker, and sometimes in less quantity, though at the time it was secreted the fluid was in greater quantity than in our waking hours. Thus the urine is higher coloured after long sleep; which shews, that a greater quantity has been secreted, tnd that more of the aqueous and saline part has been re-absorb- ed, ami the earthy part left in the bladder; hence thick urine in fevers shews only a greater action of the vessels which secrete it in the kidneys, and of those which absorb it from the bladder. The same happens to the mucus expectorated in coughs, which is thus thickened by absorption of its aqueous and saline parts; and the same of the faeces of the intestines. From hence it appears, and from what has been said in No. 15 of this Sec- tion, concerning the increase of irritability and of sensibility dur- ing sleep, that the s produced; which being instilled into a wound of another animal stimulates the cutaneous or mucous glands into morbid actions, but which are ineffectual in respect to the production of a similar contagious material; but the sali- vary glands by irritative sympathy are thrown into similar action. 204 REPETITION Sect. XXII. 3.4. and produce an infectious saliva similar to that instilled into the wound. Though in many contagious fevers a material similar to that which produced the disease, is thus generated by imitation; yet there are other infectious materials, vvhich do not thus propagate themselves, but which seem to act like slow poisons. Of this kind was the contagious matter, which produced the jail-fever at the assizes at Oxford about a century ago. Which, though fatal to so many, was not communicated to their nurses or at- tendants. In these cases, the imitations of the fine vessels, as above described, appear to be imperfect, and do not therefore produce a matter similar to that, which stimulates them; in this circumstance resembling the venereal matter in ulcers of the throat or skin, according to the curious discovery of Mr. Hun- ter above related, who found, by repeated inoculations, that it would not infect. Hunter on Venereal Disease, Part. vi. ch. 1. Another example of morbid imitation is in the production of a great quantity of contagious matter, as in the inoculated small- pox, from a small quantity of it inserted into the arm. These particles of contagious matter stimulate the extremities of the fine arteries of the skin, and cause them to imitate the motions by which themselves were produced, and thus to produce a thousand fold of a similar material. As different kinds of light may be supposed to stimulate parts of the retina into different kinds of motion, so the application of different contagious mat- ters may be believed to stimulate the fine terminations of the arteries into different kinds of motion, which may form matters similar to themselves. This is truly difficult to understand, but may be conceived to depend on this circumstance; that those matters, which stimulate other bodies into action, and the bodies thus stimulated, must possess some common properties, as spoken of in Sect. XIV. 4. See Sect. XXXIII. 2. 6. Other instances are mentioned in the Section on Generation, which shew the probability, that the extremities of the seminal glands may imitate certain ideas of the mind, or actions of the organs of sense, and thus occasion the male or female sex of the em- bryon. See Sect. XXXIX. 6. 4. We come now to those imitations, which are not attended with sensation. Of these are all the irritative ideas already ex- plained, as when the retina of the eye imitates by its action or configuration the tree or the bench, which I shun in walking past without attending to them. Other examples of these irritative imitations are daily observable in common life; thus one yawn- ing person shall set a whole company a yawning; and some have Sect. XXII. 3. 5. AND IMITATION. 205 acquired winking of the eyes or impediments of speech by imita- ting their companions without being conscious of it. 5. Besides the three species of imitations above described there may be some associate motions, which may imitate each other in the kind as well as in the quantity of their action; but it is diffi- cult to distinguish them from the associations of motions treated of in Section XXXV. Where the actions of other persons are imitated there can be no doubt, or where we imitate a precon- ceived idea by exertion of our locomotive muscles, as in paint- ing a dragon; all these imitations may aptly be referred to the sources above described of the propensity to activity, and the facility of repetition; at the same time I do not affirm, that all those other apparent sensitive and irritative imitations may not be resolvable into associations of a peculiar kind, in which certain distant parts of similar irritability or sensibility, and which have habitually acted together, may affect each other exactly with the same kinds of motion; as many parts are known to sympathise in the quantity of their motions. And that therefore they may be ultimately resolvable into associations of action as described in Sect. XXXV. 206 CIRCULATORY SYSTEM. Sect. XXI11. 1. 1. SECT. XXIII. OF THE CIRCULATORY SYSTEM. I. The heart and arteries have no antagonist muscles. Veins absorb the blood, propel it forwards, and distend the heart; contraction of the heart distends the arteries. Vena portarum. II. Glands which take their fluids from the blood. Wiih long necks, and short necks. III. Absorbent system. IV. IIcat given out from glandular secretions. Blood changes colour in the lungs and in tlie glands and capillaries. V. Blood is absorbed by veins, as chyle by lacteal vessels, otherwise they could not join timr streams. VI. Two kinds of stimulus, agreeable and disagreeable. Glandular appetency. Glands originally possessed sensation. I. 1. We now step forwards to illustrate some of the pheno- mena of diseases, and to trace out their most efficacious methods of cure; and shall commence the subject with a short description of the circulatory system. As the nerves, whose extremities form our various organs of sense and muscles, are all joined, or communicate, by means of the brain, for the convenience perhaps of the distribution of a subtile ethereal fluid for the purpose of motion; so all those ves- sels of the body, which carry the grosser fluids for the purposes of nutrition, communicate with each other by the heart. The heart and arteries are hollow muscles, and are therefore indued with power of contraction in consequence of stimulus, like all other muscular fibres; but, as they have no antagonist muscles, the cavities of the vessels, which they form, would re- main for ever closed, after they have contracted themselves, un- less some extraneous power be applied to again distend them. This extraneous power in respect to the L- art is the current of blood which is perpetually absorbed by the veins from the various glands and capillaries, and pushed into the heart by a power prob- ably very similar to that, which raises the sap in vegetables in the spring, which, according to Dr. Hale's experiment on the stump of a vine, exerted a force equal to a column of water above twenty feet high. This force of the current of blood in the veins is partly produced by their absorbent power, exert- ed at the beginning of every fine ramification; which may be couceived to be a mouth absorbing blood, as the mouths of the lacteals and lymphatics absorb chyle and lymph. And partly by their intermitted compression by the pulsations of their gene- rally concomitant arteries; by which the blood is perpetually pro- Slct. XXIII. 1. 1. CIRCULATORY SYSTEM. 507 pellcd towards the heart, as the valves in many veins, and the absorbent mouths in them all, will not suffer it to return. The blood, thus forcibly injected into the chambers of the heart, distends this combination of hollow muscles; till by the stimulus of distension they contract themselves; and, pushing forwards the blood into the arteries, exert sufficient force to over- come in less than a second of time the vis inertiae, and perhaps some elasticity, of the very extensive ramifications of the two great systems of the aortal and pulmonary arteries. The power necessary to do this in so short a time must be considerable, and has been variously estimated by different physiologists. The muscular coats of the arterial system are then brought into action by the stimulus of distention, and propel the blood to the mouths, or through the convolutions, which precede the secretory apertures of the various glands and capillaries. Iu the vessels of the liver there is no intervention of the heart; but the vena portarum, which does the office of an artery, is dis- tended by the blood poured into it from the mesenteric veins, and is by this distention stimulated to contract itself, and propel the blood to the mouths of the numerous glands, which compose that viscus. The power of absorption in vegetable roots was shewn by the experiments of Dr. Hales on vine-stumps to be equal to the pres- sure of thirty-eight inches of quicksilver. Veg. Statics, p. 107. and from the experiments of Mr. Cooper, who tied the thoracic ducts of living dogs, it appeared, that the absorbent power of the lacteals and lymphatics always burst the receptaculum chyli. Mr. Cooper adds, " The contractile powers of the absorbents are proved by these experiments to be very strong; for it appears, that their action is sufficient to occasion a rupture of their coats. It is true, that the receptaculum chyli, which was the part brok- en, is thinner and less capable of resistance than the thoracic duct; yet it is able to bear the pressure of a column of quick- sil\ «t more than two feet in height. The force therefore exerted In the absorbents, must be acknowledged to be greater than that of such a column of mercury; more especially when it is remem- bered, that living parts will resist a force vvhich will readily tear them when dead." Medical Researches. London. 1798, p, Dr. Hales made experiments similar to those on the stumps of vines above mentioned, by opening the crural arteries of a horse, a dog, and a fallow deer, by applying mercurial guages to mea- sure the projectile impetus of their blood; and found that of the Mne-stump to be five times greater than the force of the blood 208 CIRCULATORY SYSTEM. Sycr. XXIII. 2. 1. in the great crural artery of a horse, seven times greater than that of a dog, and eight times greater than that of a fallow doe. The power of absorption in the animal system exerts a force superior to that of the heart, though perhaps with less velocity; and thus removes all difficulty of accounting for the circulation in the veins and absorbents; and consequently of the circulation in the aortal arteries of fish, and in the vena portarum, or the bile-secreting artery of the liver of quadrupeds. II. 1. The glandular system of vessels may be divided into those which take some fluid from the circulation, and those which give something to it. Those which take their fluid from the cir- culation, are the various glands by which the tears, bile, urine, perspirations, and many other secretions are produced; these glands probably consist of a mouth to select, a belly to digest, and an excretory aperture to emit their appropriated fluids; the blood is conveyed by the power of the heart and arteries to the mouths of these glands, it is there taken up by the living power of the glands, and carried forwards to its belly, and excretory aperture, where a part is separated, and the remainder absorbed by the veins for further purposes. Some of these glands are furnished with long convoluted necks or tubes, as the seminal ones, which are curiously seen when in- jected with quicksilver. Others seem to consist of shorter tubes, as that great congeries of glands vvhich constitute the liver, and those of the kidneys. Some have their excretory apertures open- ing into reservoirs, as the urinary and gall-bladders. And others on the external body, as those which secrete the tears, and per- spirable matter. Another great system of glands, which have very short necks, are the capillary vessels; by which the insensible perspiration is secreted on the skin; and the mucus of various consistences, which lubricates the interstices of the cellular membrane, of the muscular fibres, and of all the larger cavities of the body. From the want of a long convolution of vessels, some have doubted whether these capillaries should be considered as glands, and have been led to conclude, that the perspirable matter rather ex- uded than was secreted. But the fluid of perspiration is not sim- ple water, though that part of it which exhales into the air may be such; for there is another part of it, which in a state of health is absorbed again; but which, when the absorbents are diseased, remains on the surface of the skin, in the form of scurf, or indu- rated mucus. Another thing, vvhich shews their similitude to other glands, is their sensibility to certain affections of the mind; as is seen in the deeper colour of the skin in the blush of shame, or the greater paleness of it from fear. Sect. XXIII. 3. CIRCULATORY SYSTEM 209 III. Another series of glandular vessels is called the absorbent system; these open their mouths into all the cavities, and upon all those surfaces of the body, where the excretory apertures of the other glands pour out their fluids. The mouths of the ab- sorbent system drink up a part or the whole of these fluids, and carry them forwards by their living power to their respective glands, which are called conglobate glands. There these fluids undergo some change, before they pass on into the circulation; but if they are very acrid, the conglobate glands swell, and some times suppurate, as in inoculation of the small-pox, in the plague, and in venereal absorptions; at other times the fluid may per- haps continue there, till it undergoes some chemical change that renders it less noxious; or, what is more likely, till it is regurgi- tated by the retrograde motion of the gland in spontaneous sweats or diarrhoeas, as disagreeing food is vomited from the stomach. The powers of absorption are shewn in No. I. of this Section, both those of the blood and of the chyle of animals, and of the sap-juice of vegetables, to be much greater than has commonly been conceived. To which may be added, that the moving force of the chyle in the receptaculum chyli and thoracic duct must be equal to the moving force of the blood in the subclavian vein, as otherwise the chyle could not enter into that vein, un- less it be supposed to possess a systole and diastole near the heart; which also affords an argument to shew, that the progress of the blood in the veins, and that of the chyle in the absorbent system, originate from a similar cause, that of their absorptive powers. IV". As all the fluids that pass through these glands, and ca- pillary vessels, undergo a chemical change, acquiring new com- binations, the matter of heat is at the same time given out; this is apparent, since whatever increases insensible perspiration, in- creases the heat of the skin; and when the action of these vessels is much increased but for a moment, as in blushing, a vivid heat on the skin is the immediate consequence. So when great bilious secretions, or those of any other gland, are produced, heat is generated in the part in proportion to the quantity of the se- cretion. The heat produced on the skin by blushing may be thought by some too sudden to be pronounced a chemical effect, as the fermentations or new combinations taking place in a fluid is in general a slower process. Yet are there many chemical mixtures in which heat is given out as instantaneously; as in solutions of metals in acids, or in mixtures of essential oils and acids, as of oil of cloves and acid of nitre. So the bruised parts of an un- ripe apple become almost instantaneously sweet; and if the che- mico-animal process of digestion be stopped for but a moment, as vol. i. Ee 210 CIRCULATORY SYSTEM. Seer. XXIII. 5. by fear, or even by voluntary eructation, a great quantity of air is generated, by the fermentation vvhich instantly succeeds the stop of digestion. By the experiments of Dr. Hales it appears, that an apple during fermentation gave up above six hundred times its bulk of air; and the materials in the stomach are such and in such situation, as immediately to run into fermentation, when digestion is impeded. As the blood passes through the small vessels of the lungs, which connect the pulmonary artery and vein, it undergoes a change of colour from a dark to a light red; which may be term- ed a chemical change, as it is known to be effected by an ad- mixture of oxygene, or vital air; vvhich, according to a discovery of Dr. Priestley, passes through the moist membranes, which constitute the sides of these vessels. As the blood passes through the capillary vessels, and glands, which connect the aorta and its various branches with their correspondent veins in the ex- tremities of the body, it again loses the bright red colour, and undergoes some new combinations in the glands or capillaries, in which the matter of heat is given out from the secreted fluids. This process, therefore, as well as the process of respiration, has some analogy to combustion, as the vital air or oxygene seems to become united to some inflammable base, and the matter of heat escapes from the new acid, which is thus produced. V. After the blood has passed these glands and capillaries, and parted with whatever they chose to take from it, the re- mainder is received by the veins which are a set of blood-absorb- ing vessels, in general corresponding with the ramifications of the arterial system. At the extremity of the fine convolutions of the glands the arterial force ceases; this, in respect to the capillary vessels, which unite the extremities of the arteries with the com- mencement of the veins, is evident to the eye, on viewing the tail of a tadpole by means of a solar, or even by a common mi- croscope, for globules of blood are seen to endeavour to pass, and to return again and again, before they become absorbed by the mouths of the veins; which returning of these globules evinces, that the arterial force behind them has ceased. The veins are furnished with valves like the lymphatic absorbents; and the great trunks of the veins, and of the lacteals and lymphatics, join together before the ingress of their fluids into the left cham- ber of the heart; both which evince, that the blood in the veins, and the lymph and chyle in the lacteals and lymphatics, are car- ried on by a similar force; otherwise the stream, which was pro- pelled with a less power, could not enter the vessels, which con- tained the stream propelled with a greater power. From whence it appears, that the veins are a system of vessels absorbing blood, Sei t. XXIII. 6. CIRCULATORY SYSTEM. 211 as the lacteals and lymphatics are a system of vessels absorbing chyle and lymph. See Sect. XXVII. 1. VI. The movements of their adapted fluids in the various vessels of the body are carried forwards by the actions of those vessels in consequence of two kinds of stimulus, one of which may be compared to a pleasurable sensation or desire inducing the vessel to seize, and, as it were, to swallow the particles thus selected from the blood; as is done by the mouths of the various glands, veins, and other absorbents, vvhich may be called glandular appetency. The other kind of stimulus may be com- pared to disagreeable sensation, or aversion, as when the heart has received the blood, and is stimulated by it to push it forwards into the arteries; the same again stimulates the arteries to con- tract, and carry forwards the blood to their extremities, the glands and capillaries. Thus the mesenteric veins absorb the blood from the intestines by glandular appetency, and carry it forward to the vena portarum; which acting as an artery contracts itself by disagreeable stimulus, and pushes it to its ramified extremi- ties, the various glands, which constitute the liver. It seems probable that, at the beginning of the formation of these vessels in the embryon, an agreeable sensation was in real- ity felt by the glands during secretion, as is now felt in the act of swallowing palatable food; and that a disagreeable sensation was originally felt by the heart from the distention occasioned by the blood, or by its chemical stimulus; but that by habit these are all become irritative motions; that is, such motions as do not affect the whole system, except when the vessels are diseased by inflammation. 212 OF THE SALIVA Sect. XXIV. 1 SECT. XXIV. OF THE SECRETION OF SALIVA, AND OF TEARS, AND OF THE LACRYMAL SACK. I. Secretion of saliva increased by mercury in the blood. 1 .By the food in the mouth. Dryness of the mouth not from a deficiency of saliva. 2. By sensitive ideas 3. By volition. 4. By distaste- ful substances. It is secreted in a dilute and saline state. It then becomes more viscid. 5. By ideas of distasteful substances. 6. By nausea. 7. By aversion. 8. By catenation with stimulating substances in the ear. II. 1. Secretion of tears less in sleep. From stimulation of their excretory duct. 2. Lacrymal sack is a gland. 3. Its uses. 4. Tears are secreted, when the nasal duct is stimulated. 5. Or when it is excited by sensation. 6. Or by volition. 7. The lacrymal sack can regurgitate its contents into the eye. 8. More tears are secreted by association with the irri- tation of the nasal duct of the lacrymal sack, than the puncta la- crymalia can imbibe. Of the gout in the liver and stomach. I. The salival glands drink up a certain fluid from the cir- cumfluent blood, and pour it into the mouth. They are some- times stimulated into action by the blood that surrounds their origin, or by some part of that heterogeneous fluid: for when mercurial salts, or oxydes, are mixed with the blood, they stimu- late these glands into unnatural exertions; and then an unusual quantity of saliva is separated. 1. As the saliva secreted by these glands is most wanted during the mastication of our food, it happens, when the terminations of their ducts in the mouth are stimulated into action, the salival glands themselves are brought into increased action at the same time by association, and separate a greater quantity of their juices from the blood; in the same manner as tears are produced in greater abundance during the stimulus of the vapour of onions, or of any other acrid material, in the eye. The saliva is thus naturally poured into the mouth only dur- ing the stimulus of our food in mastication; for when there is too great an exhalation of the mucilaginous secretion from the membranes, which line the mouth, or too great an absorption of it, the mouth becomes dry, though there is no deficiency in the quantity of saliva; as in those who sleep with their mouths open, and in some fevers. 2. Though during the mastication of our natural food the sa- lival glands are excited into action by the stimulus on their ex- Slct. XXIV. 1 .1. ANO TEARS. 213 crctory ducts, and a due quantity of saliva is separated from the blood, and poured into the mouth; yet as this mastication of our food is always attended with a degree of pleasure; and that plea- surable sensation is also connected with our ideas of certain kinds of aliment; it follows, that when these ideas are reproduced, the pleasurable sensation arises along with them, and the salival glands are excited into action, and fill the mouth with saliva from this sensitive association, as is frequently seen in dogs, who slaver at the sight of food. 3. We have also a voluntary power over the action of these salival glands, for we can at any time produce a flow of saliva into our mouth, and spit out, or swallow it at will. 4. If any very acid material be held in the mouth, as the root of pyretlnum, or the leaves of tobacco, the salival glands are sti- mulated into stronger action than is natural, and thence secrete a much larger quantity of saliva; which is at the same time more viscid than in its natural state; because the lymphatics, that open their mouths into the ducts of the salival glands, and on the mem- branes, which line the mouth, are likewise stimulated into stronger action, and absorb the more liquid parts of the saliva with greater avidity; and the remainder is left both in greater quantity and more viscid. The increased absorption in the mouth by some stimulating substances, which are called astringents, as crab-juice, is evident from the instant dryness produced in the mouth by a*small quan- tity of them. As the extremities of the glands are of exquisite tenuity, as appears by their difficulty of injection, it was necessary for them to secrete their fluids in a very dilute state; and, probably for the purpose of stimulating them into action, a quantity of neutral salt is likewise secreted or formed by the gland. This aqueous and saline part of all secreted fluids is again reabsorbed into the habit. More than half of some secreted fluids is thus imbibed from the reservoirs, into which they are poured; as in the urinary bladder much more than half of what is secreted by the kidneys becomes reabsorbed by the lymphatics, which are thickly dis- persed ai>ound the neck of the bladder. This seems to be the pur- pose of the urinary bladders of fish, as otherwise such a recep- tacle for the urine could have been of no use to an animal im- mersed in water. 5. The idea of substances disagreeably acrid will also produce a quantity of saliva in the mouth; as when we smell very putrid vapours, we are induced to spit out our saliva, as if something disagreeable was actually upon our palates. 0. When disagreeable food in the stomach produces nausea. 214 OF HIE SALIVA S*ct. XXIV. 1. 7. a flow of saliva is excited in the mouth by association; as efforts to vomit are frequently produced by disagreeable drugs in the mouth by the same kind of association. 7. A preternatural flow of saliva is likewise sometimes occa- sioned by a disease of the voluntary power; for if we think about our saliva, and determine not to swallow it, or not to spit it out, an exertion is produced by the will, and more saliva is secreted against our wish; that is, by our aversion, which bears the same analogy to desire, as pain does to pleasure; as they are only mo- difications of the same disposition of the sensorium. See Class IV. 3. 2. 1. 8. The quantity of saliva may also be increased beyond what is natural, by the catenation of the motions of these glands with other motions, or sensations, as by an extraneous body in the ear; of vvhich I have known an instance; or by the application of stizolobium, siliqua hirsuta, cowhage, to the seat of the parotis, as some writers have affirmed. II. 1. The lacrymal gland drinks up a certain fluid from the circumfluent blood, and pours it on the ball of the eye, on the upper part of the external corner of the eyelids. Though it may perhaps be stimulated into the performance of its natural action by the blood, which surrounds its origin, or by some part of that heterogeneous fluid; yet as the tears secreted by this gland are more wanted at some times than at others, its secretion is varia- ble, like that of the saliva above mentioned, and is chiefly pro- duced when its excretory duct is stimulated; for in our common sleep there seems to be little or no secretion of tears; though they are occasionally produced by our sensations in dreams. Thus when any extraneous material on the eye-ball, or the dry- ness of the external covering of it, or the coldness of the air, or the acrimony of some vapours, as of onions, stimulates the excretory duct of the lacrymal gland, it discharges its contents upon the ball; a quicker secretion takes place in the gland, and abundant tears succeed, to moisten, clean, and lubricate the eye. These by frequent nictitation are diffused over the whole ball, and as the external angle of the eye in winking is closed sooner than the internal angle, the tears are gradually driven forwards, and downwards from the lacrymal gland to the puncta lacry- malia. 2. The lacrymal sack, with its puncta lacrymalia, and its nasal duct, is a complete gland; and is singular in this respect, that it neither derives its fluid from, nor disgorges it into the circulation. The simplicity of the structure of this gland, and both the ex- tremities of it being on the surface of the body, makes it well worthy our minuter observation; as the actions of more intricate Sect. XXIV. 2. 3. AND TEARS. 215 and concealed glands may be better understood from their ana- logy to this. 3. This simple gland consists of two absorbing mouths, a bel- ly, and an excretory duct. As the tears are brought to the in- ternal angle of the eye, those two mouths drink them up, being stimulated into action by this fluid, which they absorb. The belly of the gland, or lacrymal sack, is thus filled, in which the saline part of the tears is absorbed, and when the other end of the gland or nasal duct, is stimulated by the dryness, or pained by the coldness of the air, or affected by any acrimonious dust or vapour in the nostrils, it is excited into action together with the sack, and the tears are disgorged upon the membrane, which lines the nostrils; where they serve a second purpose to moisten, clean, and lubricate, the organ of smell. 4. This gland, when its nasal duct is stimulated by any very acrid material, as the powder of tobacco, or volatile spirits, not only disgorges the contents of its belly or receptacle (the lacrymal sack), and absorbs hastily all the fluid, that is ready for it in the corner of the eye; but, by the association of its motions with those of the lacrymal gland, excites that also into increased ac- tion, and a large flow of tears is poured into the eye. 5. This nasal duct is likewise excited into strong action by sensitive ideas, as in grief, or joy, and then also by its associa- tions with the lacrymal gland it produces a great flow of tears without any external stimulus; as is more fully explained in Sect. XVI. 8. on Instinct. 6. There are some, famous in the arts of exciting compassion, who are said to have acquired a voluntary power of producing a flow of tears in the eye; which, from what has been said in the section on Instinct above mentioned, I should suspect, is per- formed by acquiring a. voluntary power over the action of this nasal duct. 7. There is another circumstance well worthy our attention, that when by any accident this nasal duct is obstructed, the lacry- mal sack, which is the belly or receptacle of this gland, by slight pressure of the finger is enabled to disgorge its contents again into the eye; perhaps the bile in the same manner, when the biliary ducts are obstructed, is returned into the blood by vessels which secrete it? 8. A very important though minute occurrence must here be observed, that, though the lacrymal gland is only excited into ac- tion, when we weep at a distressful tale, by its association with this nasal duct, as is more fully explained in Sect. XVI. 8; yet the quantity of tears secreted at once is more than the puncta la- crymalia can readily absorb; which shews that the motions oc- 216 OF THE SALIVA, &c. Sect. XXIV. 2. 8. casioned by associations are frequently more energetic than the ori- ginal motions, by which they were occasioned. Which we shall have occasion to mention hereafter, to illustrate, why pains fre- quently exist in a part distant from the cause of them, as in the other end of the urethra, when a stone stimulates the neck of the bladder. And why inflammations frequently arise in parts distant from their cause, as the gutta rosea of drinking people, from an inflamed liver. The inflammation of a part is generally preceded by a torpor or quiescence of it; if this exists in any larger congeries of glands, as in the liver, or any membranous part, as the stomach, pain is produced and chilliness in consequence of the torpor of the vessels. In this situation sometimes an inflammation of the parts succeeds the torpor; at other times a distant more sensible part becomes inflamed; whose actions have previously been associated with it; and the torpor of the first part ceases. This I appre- hend happens, when the gout of the foot succeeds a pain of the biliary duct, or of the stomach. Lastly, it sometimes happens, that the pain of torpor exists without any consequent inflamma- tion of the affected part, or of any distant part associated with it, as in the memb.anes about the temple and eye-brows in hemi- crania, and in those pains which occasion convulsions; if this happens to gouty people, when it affects the liver, I suppose epi- leptic fits are produced; and, when it affects the stomach, death is the consequence. In these cases the pulse is weak, and the extremities cold, and such medicines as stimulate the quiescent parts into action, or which induce inflammation in them, or in any distant part, which is associated with them, cures the pre- sent pain of torpor, and saves the patient. I have twice seen a gouty inflammation of the liver, attended with jaundice; the patients after a few days were both of them affected with cold fits, like ague fits, and their feet became af- fected with gout, and the inflammation of their livers ceased. It is probable, that the uneasy sensations about the stomach, and indigestion, which precedes gouty paroxysms, are generally ow- ing to torpor or slight inflammation of the liver, and biliary ducts; but where great pain with continued sickness, with feeble pulse, and sensation of cold, affect the stomach in patients debili- tated by the gout, that it is a torpor of the stomach itself, and destroys the patient from the great connexion of that viscus with the vital organs. See Sect. XXV. 17. aiicT. XXV. 1. OF THE STOMACH, &c. 217 SECT. XXV. OF THE STOMACH AND INTESTINES. 1. Of swallowing our food. Ruminating animals. 2. Action of the stomach. 3. Action of the intestines. Irritative motions con- nected with these. 4. Effects of repletion. 5. Stronger action of tlie stomach and intestines from more stimulating food. 6. Their action inverted by still greater stimuli. Or by disgustful ideas. Or by volition. 7. Other glands strengthen or invert their motions by sympathy. 8. Vomiting performed by intervals. 9. Inversion of the cutaneous absorbents. 10. Increased secre- tion of bile and pancreatic juice. 11. Inversion of the lacteals. 12. And of the bile-ducts. 13. Case of a cholera. 14. Far- ther account of the inversion of lacteal. 15. Iliac passion. Valve of the colon. 16. Cure of the iliac passion. 17. Pain of gall-stone distinguished from pain of the stomach. Gout of the stomach from torpor, from inflammation. Intermitting pulse owing to indigestion. To overdose of foxglove. Weak pulse from emetics. Death from a blow on the stomach. From gold of the stomach. 1. The throat, stomach, and intestines, may be considered as one great gland; vvhich, like the lachrymal sack above mention- ed, neither begins nor ends in the circulation. Though the act of masticating our aliment belongs to the sensitive class of mo- tions, for the pleasure of its taste induces the muscles of the jaw into action; yet the deglutition of it when masticated is gene- rally, if not always, an irritative motion, occasioned by the appli- cation of the food already masticated to the origin of the pharinx; in the same manner as we often swallow our spittle without at- tending to it. The ruminating class of animals have the power to invert the motion of their gullet, and of their first stomach, from the stimu- lus of this aliment, when it is a little further prepared; as is their daily practice in chewing the cud: and appears to the eye of any one, who attends to them, whilst they are employed in this se- cond mastication of their food. 2. When our natural aliment arrives into the stomach, this or- gan is stimulated into its proper vermicular action; which, be- ginning at the upper orifice of it, and terminating at the lower one, gradually mixes together and pushes forwards the digesting materials into the intestine beneath it. At the same time the glands, that supply the gastric juices, vol. i. if 218 OF THE STOMACH Sect. XXV. .1. which are necessary to promote the chemical part of the process of digestion, are stimulated to discharge their continued fluids, and to separate a further supply from the blood-vessels: and the lacteals or lymphatics, which open their mouths into the stomach, are stimulated into action, and take up some part of the digest- ing materials. 3. The remainder of these digesting materials is carried for- wards into the upper intestines, and stimulates them into their peristaltic motion similar to that of the stomach; which continues gradually to mix the changing materials, and pass them along through the valve of the colon to the excretory end of this great gland, the sphincter ani. The digesting materials produce a flow of bile, and of pancre- atic juice, as they pass along the duodenum, by stimulating the excretory ducts of the liver and pancreas, which terminate in that intestine: and other branches of the absorbent or lymphatic system, called lacteals, are excited to drink up, as it passes, those parts of the digesting materials, that are proper for their purpose, by its stimulus on their mouths. 4. When the stomach and intestines are thus filled with their proper food, not only the motions of the gastric glands, the pan- creas, liver, and lacteal vessels, are excited into action; but at the same time the whole tribe of irritative motions are exerted with greater energy, a greater degree of warmth, colour, plump- ness, and moisture, is given to the skin from the increased action of those glands called capillary vessels; pleasurable sensation is excited, the voluntary motions are less easily exerted, and at length suspended; and sleep succeeds, unless it be prevented by the stimulus of surrounding objects, or by voluntary exertion, or by an acquired habit, which was originally produced by one or other of these circumstances, as is explained in Sect. XXI. on Drunkenness. At this time also, as the blood-vessels become replete with chyle, more urine is separated into the bladder, and less of it is reabsorbed; more mucus poured into the cellular membranes, and less of it reabsorbed: the pulse becomes fuller, and softer, and in general quicker. The reason why less urine and cellular mucus is absorbed after a full meal with sufficient drink, is owing to the blood-vessels being fuller; hence one means to promote absorption is to decrease the resistance by emptying the vessels by venesection. From this decreased absorption, the urine be- comes pale as well as copious, and the skin appears plump as well as florid. By daily repetition of these movements they all become con- nected together, and make a diurnal circle of irritative action. Sect. XXV. 5. AXD INTESTINES. 219 and if one of this chain be disturbed, the whole is liable to be put into disorder. See Sect. XX. on Vertigo. 5. When the stomach and intestines receive a quantity of food, whose stimulus is greater than usual, all their motions, and those of the glands and lymphatics, are stimulated into stronger action than usual, and perform their offices with greater vigour, and in less time: such are the effects of certain quantities of spice or of vinous spirit. 6. But if the quantity or duration of these stimuli are still further increased, the stomach and throat are stimulated into a motion, whose direction is contrary to the natural one above de- scribed; and they regurgitate the materials, vvhich they contain, instead of carrying them forwards. This retrogade motion of the stomach may be compared to the stretchings of wearied limbs the contrary way, and is well elucidated by the following experiment. Look earnestly for a minute or two on an area an inch square of pink silk, placed in a strong light, the eye becomes fatigued, the colour becomes faint, and at length vanishes, for the fatigued eye can no longer be stimulated into direct motions; then on closing the eye a green spectrum will appear in it, which is a colour directly contrary to pink, and vvhich will appear and dis- appear repeatedly, like the efforts in vomiting. See Section XXIX. 11. Hence all those drugs, which by their bitter or astringent sti- mulus increase the action of the stomach, as camomile and white vitriol, if their quantity is increased above a certain dose become emetics. These inverted motions of the stomach and throat are gene- rally produced from the stimulus of unnatural food, and are at- tended with the sensation of nausea or sickness: but as this sen- sation is again connected with an idea of the distasteful food, which induced it; so an idea of nauseous food will also sometimes excite the action of nausea; and that give rise by association to the inversion of the motions of the stomach and throat. As some, who have had horse-flesh or dogs-flesh given them for beef or mutton, are said to have vomited many hours afterwards, when they have been told of the imposition. 1 have been told of a person, who had gained a voluntary com- mand over these inverted motions of the stomach and throat, and supported himself by exhibiting this curiosity to the public. At these exhibitions he swallowed a pint of red rough gooseberries, and a pint of white smooth ones, brought them up in small par- cels into his mouth, and restored them separately to the specta- tors, who called for red or white as they pleased, till the whole wire redelivered. 220 OF THE STOMACH Skt. \XV. 7. 7. At the same time that these motions of the stomach and throat are stimulated into inversion, some of the other irritative motions that had acquired more immediate connexions with the stomach, as those of the gastric glands, are excited into stronger action by this association; and some other of these motions, which are more easily excited, as those of the gastric lymphatics, are inverted by their association with the retrograde motions of the stomach, and regurgitate their contents, and thus a greater quantity of mucus, and of lymph, or chyle, is poured into the stomach, and thrown up along with its contents. 8. These inversions of the motion of the stomach in vomiting are performed by intervals, for the same reason that many other motions are reciprocally exerted and relaxed; for during the time of exertion the stimulus, or sensation, vvhich caused this ex- ertion is not perceived; but begins to be perceived again, as soon as the exertion ceases, and is some time in again producing its effect. As explained in Sect. XXXIV. on Volition, where it is shewn, that the contractions of the fibres, and the sensation of pain, which occasioned that exertion, cannot exist at the same time. The exertion ceases from another cause also, which is the exhaustion of the sensorial power of the part, and these two causes frequently operate together. 9. At the times of these inverted efforts of the stomach not only the lymphatics, which open their mouths into the stomach, but those of the skin also, are for a time inverted: for sweats are sometines pushed out during the efforts of vomiting without an increase of heat. 10. But if by a greater stimulus the motions of the stomach are inverted still more violently or more permanently, the duode- num has its peristaltic motions inverted at the same time by their association with those of the stomach; and the bile and pancrea- tic juice, which it contains, are by the inverted motions brought up into the stomach, and discharged along with its contents; while a great quantity of bile and pancreatic juice is poured into this intestine; as the glands that secrete them, are by their asso- ciation with the motions of the intestine excited into stronger ac- tion than usual. 11. The other intestines are by association excited into more powerful action, while the lymphatics, that open their mouths into them suffer an invasion of their motions corresponding with the lymphatics of the stomach and duodenum; which with a part of the abundant secretion of bile is carried downwards, and contributes both to stimulate the bowels, and to increase the quan- tity of the evacuations. This inversion of the motion of the lym- phatics appears from the quantity of chyle, which comes away Sect. XXV. 12 AND INTESTINES. 221 by stools; which is otherwise absorbed as soon as produced, and by the immense quantity of thin fluid, which is evacuated along with it. 12. But if the stimulus, which inverts the stomach, be still more powerful, or more permanent, it sometimes happens, that the motions of the biliary glands, and of their excretory ducts, are at the same time inverted, and regurgitate their contained bile into the blood-vessels, as appears by the yellow colour of the skin, and of the urine; and it is probable the pancreatic secretion may suffer an inversion at the same time, though we have yet no mark by which this can be ascertained. 13. Mr.-------ate two putrid pigeons out of a cold pigeon- pye, and drank about a pint of beer and ale along with them, and immediately rode about five miles. He was then seized with vomiting, vvhich was after a few periods succeeded by purg- ing; these continued alternately for two hours; and the purg- ing continued by intervals for six or eight hours longer. Dur- ing this time he could not force himself to drink more than one pint in the whole; this great inability to drink was owing to the nausea, or inverted motions of the stomach, which the voluntary exertion of swallowing could seldom and with difficulty over- come; yet he discharged in the whole at least six quarts; whence caine this quantity of liquid? First, the contents of the stomach were emitted, then of the duodenum, gall-bladder, and pancreas, by vomiting. After this the contents of the lower bowels; then the chyle, that was in the lacteal vessels, and in the receptacle of chyle, was regurgitated into the intestines by a retrograde mo- tion of these vessels. And afterwards the mucus deposited in the cellular membrane, and on the surface of all the other mem- branes, seems to have been absorbed; and with the fluid absorb- ed from the air to have been carried by their respective lymphatic branches, by the increased energy of their natural motions, and down the visceral lymphatics, of lacteals, by the inversion of their motions. 14. It may be difficult to invent experiments to demonstrate the truth of this inversion of some branches of the absorbent sys- tem, and increased absorption of others; but the analogy of these vessels to the intestinal canal, and the symptoms of many diseases, render this opinion more probable than many other received opinions of the animal economy. In the above instance, after the yellow excrement was voided, the fluid ceased to have any smell, and appeared like curdled milk, and then thinner fluid, and some mucus, were evacuated: did not these seem to partake of the chyle, of the mucous fluid from all the cells of the body, and lastly, of the atmospheric mois- 222 OF THE STOMACH Sfxt. XXV. 15. ture? All these facts may be easily observed by any one, who takes a brisk purge. 15. Where the stimulus on the stomach, or on some other part of the intestinal canal, is still more permanent, not only the lac- teal vessels, but the whole canal itself, becomes inverted from its associations; this is the iliac passion, in which all the fluids mentioned above are thrown up by the mouth. At this time the valve in the colon, from the inverted motions of that bowel, and the inverted action of this living valve, does not prevent the re- gurgitation of its contents. The structure of this valve may be represented by a flexile leathern pipe standing up from the bottom of a vessel of water: its sides collapse by the pressure of the ambient fluid, as a small part of that fluid passes through it; but if it has a living power, and by its inverted action keeps itself open, it becomes like a rigid pipe, and will admit the whole liquid to pass. See Sect. XXXIX. 2. 5. In this case the patient is averse to drink, from the constant inversion of the motions of the stomach, and yet many quarts are daily ejected from the stomach, vvhich at length smell of ex- crement, and at last seem to be only a thin mucilaginous or aque- ous liquor. From whence is it possible, that this great quantity of fluid for many successive days can be supplied, after the cells of the body have given up their fluids, but from the atmosphere? When the cutaneous branch of absorbents acts with unnatural strength, it is probable the intestinal branch has its motions inverted, and thus a fluid is supplied without entering the arterial system. Could oiling or painting the skin give a check to this disease? So when the stomach has its motions inverted, the lymphatics of the stomach, which are most strictly associated with it, invert their motions at the same time. But the mere distant branches of lymphatics, vvhich are less strictly associated with it, act with increased energy; as the cutaneous lymphatics in the cholera, or iliac passion, above described. And other irritative motions be- come decreased, as the pulsations of the arteries, from the extra- derivation or exhaustion of the sensorial power. Sometimes when stronger vomiting takes place the more dis- tant branches of the lymphatic system invert their motions with those of the stomach, and loose stools are produced, and cold sweats. So when the lacteals have their motions inverted, as during the operation of strong purges, the urinary and cutaneous ab- sorbents have their motions increased to supply the want of fluid in the blood, as in great thirst; but after a meal with suffi Sect. XXV. 16. AND INTESTINE*. 223 cicnt potation of the urine is pale, that is, the urinary absorbents act weakly, no supply of water being wanted for the blood. And when the intestinal absorbents act too violently, as when too great quantities of fluid have been drunk, the urinary absorb- ents invert tluir motions to carry off the superfluity, which is a new circumstance of association, and a temporary diabetes su- pervenes. 16. I have had the opportunity of seeing four patients in the iliac passion, where the ejected material smelled and looked like excrement. Two of these were so exhausted at the time I saw them, that more blood could not be taken from them, and as their pain had ceased, and they continued to vomit up every thing which they drank, I suspected that a mortification of the bowel had already taken place, and as they were both women advanced in life, and a mortification is produced with less pre- ceding pain in old and weak people, these both died. The other two, who were both young men, had still pain and strength sufficient for further venesection, and they neither of them had any appearance of hernia, both recovered by repeated bleeding, and a scruple of calomel given to one, and a half a dram to the other, in very small pills: the usual means of clysters, and purges joined with opiates, had been in vain attempted. I have thought an ounce or two of crude mercury in less violent dis- eases of this kind has been of use, by contributing to restore its natural motion of some part of the intestinal canal, either by its weight or stimulus; and that hence the whole tube recovered its usual associations of progressive peristaltic motion. I have in three cases seen crude mercury given in small doses, as one or two ounces twice a day, have great effect in stopping pertinacious vomitings. 17. Besides the affections above described, the stomach is lia- ble, like many other membranes of the body, to torpor without consequent inflammation: as happens to the membranes about the head in some cases of hemicrania, or in general head-ach. This torpor of (he stomach is attended with indigestion, and con- sequent flatulency, and with pain, which is usually called the iramp of the stomach, and is relievable by aromatics, essential oils, alcohol, or opium. The -intrusion of a gall-stone into the common bile-duct from the gall-bladder is sometimes mistaken for a pain of the stomach, as neither of them is attended with fever; but in the passage of a gall-stone, the pain is confined to a less space, which is exact- ly where the common bile-duct enters the duodenum, as ex- plained in Section XXX. 3. Whereas in this gastrodynia the pain is diffused over the whole stomach; and, like other diseases 224 OF THE STOMACH Sect. XXV. 17. from torpor, the pulse is weaker, and the extremities colder, and the general debility greater, than in the passage of a gall-stone; for in the former the debility is the consequence of the pain, in the latter it is the cause of it. Though the first fits of the gout, I believe, commence with a torpor of the liver; and the ball of the toe becomes inflamed instead of the membranes of the liver in consequence of this tor- por, as a coryza or catarrh frequently succeeds a long exposure of the feet to cold, as in snow, or on a moist brick-floor; yet in old or exhausted constitutions, which have been long habituated to its attacks, it sometimes commences with a torpor of the sto- mach, and is transferable to every membrane of the body. When the gout begins with torpor of the stomach, a painful sensation of cold occurs, which the patient compares to ice, with weak pulse, cold extremities, and sickness; this in its slighter degree is relievable by spice, wine, or opium; in its greater degree it is succeeded by sudden death, which is owing to the sympathy of the stomach with the heart, as explained below. If the stomach becomes inflamed in consequence of this gouty torpor of it, or in consequence of its sympathy' with some other part, the danger is less. A sickness and vomiting continues many days, or even weeks, the stomach rejecting every thing stimulant, even opium or alcohol, together with much viscid mucus; till the inflammation at length ceases, as happens when other membranes, as those of the joints, are the seat of gouty inflammation; as observed in Sect. XXIV. 2. 8. The sympathy, or association of motions, between those of the stomach and those of the heart, is evinced in many diseases. First, many people are occasionally affected with an intermission of their pulse for a few days, which then ceases again. In this case there is a stop of the motion of the heart, and at the same time a tendency to eructation from the stomach. As soon as the pa- tient feels a tendency to the intermission of the motion of his heart, if he voluntarily brings up wind from his stomach, the stop of the heart does not occur. From hence I conclude that the stop of di- gestion is the primary disease; and that air is instantly generated from the aliment, which begins to ferment, if the digestive pro- cess is impeded for a moment, (see Sect. XXIII. 4.); and that the stop of the heart is in consequence of the association of the mo- tions of these viscera, as explained in Sect. XXXV. 1.4.; but if the little air, which is instantly generated during the temporary torpor of the stomach, be evacuated, the digestion recommences, and the temporary torpor of the heart does not follow. One pa- tient whom I lately saw, and who had been five or six days much troubled with this intermission of a pulsation of his heart, and Sect. XXV. 17. AND INTESTINES. 225 who had hemicrania with some fever, was immediately relieved from ihem all by losing ten ounces of blood, which had what is termed an inflammatory crust on it. Another instance of this association between the motions of the stomach and heart is evinced by the exhibition of an over dose of foxglove, which induces an incessant vomiting, which is attend- ed with very slow, and sometimes intermitting pulse.—Which continues in spite of the exhibition of wine and opium for two or three days. To the same association must be ascribed the weak pulse, which constantly attends the exhibition of emetics during their operation. And also the sudden deaths, which have been occasioned in boxing by a blow on the stomach; and lastly, the sudden death of those who have been long debilitated by the gnui. from the torpor of the stomach. See Sect. XXV. 1. 4. vol r. b 2 226 OF GLANDS. Sect. XXVI. 1. 1 SECT. XXVI. OF THE CAPILLARY GLANDS AND MEMBRANES. I. 1. The capillary vessels are glands. 2. Their excretory duct>\ Experiments on the mucus of the intestines, abdomen, cellular membrane, and on the humours of the eye. 3. Scurf on the head, cough, catarrh, diarrhoea, gonorrlicea. 4. Rheumatism. Gout. Leprosy. II. 1. The most minute membranes are unorganized. 2. Large membranes arc composed of the ducts of the capillaries, and the mouths of the absorbents. 3. Mucilaginous fluid is se- creted on their surface. III. Three kinds of rheumatism. I. 1. The capillary vessels are like all the other glands except the absorbent system, inasmuch as they receive blood from the arteries, separate a fluid from it, and return the remainder by the veins. 2. This series of glands is of the most extensive use, as their excretory ducts open on the whole external skin, forming its per- spirative pores, and on the internal surfaces of every cavity of the body. Their secretion on the skin is termed insensible per- spiration, which in health is in part reabsorbed by the mouths of the lymphatics, and in part evaporated in the air; the secre- tion on the membranes, which line the larger cavities of the body, which have external openings, as the mouth and intestinal canal, is termed mucus, but is not however coagulable by heat; and the secretion on the membranes of those cavities of the body, which have no external openings, is called lymph or water, as in the cavities of the cellular membrane, and of the abdomen; this lymph however is coagulable by the heat of boiling water. Some mucus nearly as viscid as the white of egg, which was dis- charged by stool, did not coagulate, though I evaporated it to one fourth of the quantity, nor did the aqueous and vitreous humours of a sheep's eye coagulate by the like experiment; but the se- rosity from an anasarcous leg, and that from the abdomen of a dropsical person, and the crystalline humour of a sheep's eye, coagulated in the same heat. 3. When any of these capillary glands are stimulated into greater irritative actions, than is natural, they secrete a more copious material; and as the mouths of the absorbent system, which open in their vicinity, are at the same time stimulated in- to greater action, the thinner and more saline part of the secret- ed fluid is taken up again: and the remainder is not only more copious but also more viscid than natural. This is more or less sect. XXVI. 1. 4. OF GLANDS. 227 troublesome or noxious according to the importance of the func- tions of the part affected; on the skin and bronchia?, where this secretion ought naturally to evaporate, it becomes so viscid as to adhere to the membrane; on the tongue it forms a pellicle, which can with difficulty be scraped off; produces the scurf on the heads of many people; and the mucus, which is spit up by others in coughing. On the nostrils and fauces, when the secretion of these capillary glands is increased, it is termed simple catarrh; when in the intestines, a mucous diarrhoea; and in the urethra, or vagina, it has the name of gonorrhoea, or fluor albus. 4. When these capillary glands become inflamed, a still more viscid or even cretaceous humour is produced upon the surfaces of the membranes, which is the cause or the effect of rheumatism, gout, leprosy, and of hard tumours of the legs, which are gene- rally termed scorbutic; all which will be treated of hereafter. II. 1. The whole surface of the body, with all its cavities and contents, are covered with membrane. It lines every vessel, forms every cell, and binds together all the muscular, and perhaps the osseous fibres of the body; and is itself therefore probably a simpler substance than those fibres. And as the containing ves- sels of the body, from the largest to the least, are thus lined and connected with membranes, it follows that these membranes themselves consist of unorganized materials. For however small we may conceive the diameters of the mi-. nutest vessels of the body, which escape our eyes and glasses, yet these vessels must consist of coats or sides, which are made up of an unorganized material, and which are probably produced from a gluten, which hardens after its production, like the silk or web of caterpillars and spiders. Of this material consist the memi branes, vvhich line the shells of eggs, and the shell itself, both which are unorganized, and are formed from mucus, which hard- ens after it is formed, either by the absorption of its more fluid part, or by its uniting with some part of the atmosphere. Such is also the production of the shells of snails, and of shell-fish, and I suppose of the enamel of the teeth. 2. But though the membranes, that compose the sides of the most minute vessels, are in truth unorganized materials, yet the larger membranes, vvhich are perceptible to the eye, seem to be composed of an intertexture of the mouths of the absorbent sys- tem, and of the excretory ducts of the capillaries, with their con- comitant arteries, veins and nerves: and from this construction it is evident, that these membranes must possess great irritability to peculiar stimuli, though they are incapable of any motions, that are visible to the naked eye: and daily experience shews us, that 228 OF GLANDS. Sect. XXVI. 2. 3. in their inflamed state they have the greatest sensibility to pain, as in the pleurisy and paronychia. 3. On all these membranes a mucilaginous or aqueous fluid is secreted, which moistens and lubricates their surfaces, as was ex- plained in Sect. XXIII. 2. Some have doubted, whether this mucus is separated from the blood by an appropriated set of glands, or exudes through the membranes, or is an abrasion or destruction of the surface of the membrane itself, which is con- tinually repaired on the other side of it, but the great analogy between the capillary vessels and the other glands, countenances the former opinion; and evinces, that these capillaries are the glands that secrete it; to which we must add, that the blood in passing these capillary vessels undergoes a change in its colour from florid to purple, and gives out a quantity of heat; from whence, as in other glands, we must conclude that something is secreted from it. III. The seat of rheumatism is in the membranes, or upon them; but there are three very distinct diseases, which commonly are confounded under this name. First, when a membrane be- comes affected with torpor or inactivity of the vessels vvhich com- pose it, pain and coldness succeed, as in the hemicrania, and other head-aches, which are generally termed nervous rheuma- tism; they exist whether the part be at rest or in motion, and are generally attended with other marks of debility. Another rheumatism is said to exist, when inflammation and swelling, as well as pain, affect some of the membranes of the joints, as of the ancles, wrists, knees, elbows, and sometimes of the ribs. This is accompanied with fever, is analogous to pleu- risy and other inflammations, and is termed the acute rheumatism. A third disease is called chronic rheumatism, which is distin- guished from that first mentioned, as in this the pain only affects the patient during the motion of the part, and from the second kind of rheumatism above described, as it is not attended with quick pulse or inflammation. It is generally believed to succeed the acute rheumatism of the same part, and that some coagulable lymph, or cretaceous, or calculous material, has been left on the membrane; vvhich gives pain, when the muscles move over it, as some extraneous body would do, which was too insoluble to be absorbed. Hence there is an analogy between this chronic rheu- matism and the diseases which produce gravel or gout stones; and it may perhaps receive relief from the same remedies, such as aerated sal soda. Sect. XXVII. 1. 1. OF HEMORRHAGES. 229 SECT. XXVII. OF HEMORRHAGES. I. Tlie veins are absorbent vessels. 1. Hemorrhages from inflam- mation. Case of hemorrhage from the kidney cured by cold bathing. Case of hemorrhage from the nose cured by cold im- mersion. II. Hemorrhage from venous paralysis. Of Piles. Black stools. Petechia. Consumption. Scurvy of the lungs. Blackness of the face and eyes in epileptic fits. Cure of he- morrhages from venous inability. I. As the imbibing mouths of the absorbent system already de- scribed open on the surface, and into the larger cavities of the body, so there is another system of absorbent vessels, which are not commonly esteemed such, I mean the veins, vvhich take up the blood from the various glands and capillaries, after their pro- per fluids or secretions have been separated from it. The veins resemble the other absorbent vessels; as the progres- sion of their contents is carried on in the same manner in both, they alike absorb their appropriated fluids, and have valves to prevent its regurgitation by the accidents of mechanical vio- lence. This appears first, because there is no pulsation in the very beginnings of the veins, as is seen by microscopes; which must happen, if the blood was carried into them by the actions of the arteries. For though the concurrence of various venous streams of blood from different distances must prevent any pul- sation in the larger branches, yet in the very beginnings of all these branches a pulsation must unavoidably exist, if the circula- tion in them was owing to the intermitted force of the arteries. Secondly, the venous absorption of blood from the penis, and from the teats of female animals after their erection, is still more similar to the lymphatic absorption, as it is previously poured in- to cells, where all arterial impulse must cease. There is an experiment, which seems to evince this venous absorption, which consists in the external application of a stimu- lus to the lips, as of vinegar, by which they become instantly pale; that is, the bibulous mouths of the veins by this stimulus are excited to absorb the blood faster, than it can be supplied by the usual arterial exertion. See Sect. XXIII. 5. 1. There are two kinds of haemorrhages frequent in diseases, one is where the glandular or capillary action is too powerfully ex- erted, and propels the blood forwards more hastily, than the veins can absorb it; and the other is, where the absorbent power 23U OF HEMORRHAGES. S«cr. XXYll. 1. 1. of the veins is diminished, or a branch of them is become totally paralytic. The former of these cases is known by the heat of the part, and the general fever or inflammation that accompanies the hae- morrhage. A hemorrhage from the nose or from the lungs is sometimes a crisis of inflammatory diseases, as of the hepatitis and gout, and generally ceases spontaneously, when the vessels are considerably emptied. Sometimes the haemorrhage recurs by daily periods accompanying the hot fits of fever, and ceasing in the cold fits, or in the intermissions; this is to be cured by re- moving the febrile paroxysms, which will be treated of in their place. Otherwise it is cured by venesection, by the internal or external preparations of lead, or by the application of cold, with an abstemious diet, and diluting liquids, like other inflammations. Which by inducing a quiescence on those glandular parts, that are affected, prevents a greater quantity of blood from being pro- truded forwards, than the veins are capable, of absorbing. Mr. B-------had a haemorrhage from his kidney, and parted with not less than a pint of blood a day (by conjecture) along with his urine for above a fortnight: venesections, mucilages, balsams, preparations of lead, the bark, alum, and dragon's blood, opiates, with a large blister on his loins, were separately tried, in large doses, to no purpose. He was then directed to bathe in a cold spring up to the middle of his body only, the up- per part being covered, and the haemorrhage diminished at the first, and ceased at the second immersion. In this case the external capillaries were rendered quiescent by the coldness of the water, and thence a less quantity of blood was circulated through them; and the internal capillaries, or other glands, became quiescent from their irritative associations with the external ones; and the haemorrhage was stopped a suf- ficient time for the ruptured vessels to contract their apertures, or for the blood in those apertures to coagulate. Mrs. K-------had a continued haemorrhage from her nose for some days; the ruptured vessel was. not to be reached by plugs up the nostrils, and the sensibility of her fauces was such that nothing could be borne behind the uvula. After repealed venesection, and other common applications, she was directed to immerse her whole head into a pail of water, which was made colder by the addition of several handfuls of salt, and the hae- morrhage immediately ceased, and returned no more; but her pulse continued hard, and she was necessitated to lose blood from the arm on the succeeding day. Query, might not the cold bath instantly stop haemorrhages from the lungs in inflammatory cases?—for the shortness of Sect XXVII. 2. 1. OF HEMORRHAGES. 231 breath of those who ?o suddenly into cold water, is not owing to the accumulation of blood in the lungs, but to the quiescence of the pulmonary capillaries from association, as explained in Section XXXII. 3. 2. II. The other kind of haemorrhage is known from its being at- tended with a weak pulse, and other symptoms of general de- bility, and very frequently occurs in those who have diseased livers, owing to intemperance in the use of fermented liquors. These constitutions are shewn to be liable to paralysis of the lym- phatic absorbents, producing the various kinds of dropsies in Sec- tion XXIX. 5. Now if any branch of the venous system loses its power of absorption, the part swells, and at length bursts and dis- charges the blood, which the capillaries or other glands circulate through them. It sometimes happens that the large external veins of the legs burst, and effuse their blood; but this occurs most frequently in the veins of the intestines, as the vena portarum is liable to suf- fer from a schirrus of the liver opposing the progression of the blood, vvhich is absorbed from the intestines. Hence the piles are a symptom of hepatic obstruction, and hence the copious discharges downwards or upwards of a black material, which has been called melancholia, or black bile; but is no other than the blood, which is probably discharged from the veins of the intestines. J. F. Meckel, in his Experiments de Finibus Vasorum, publish- ed at Berlin, 1772, mentions his discovery of a communication of a lymphatic vessel with the gastric branch of the vena portarum. It is possible, that when the motion of the lymphatic becomes re- trograde in some diseases, blood may obtain a passage into it, where it anastomoses with the vein, and thus be poured into the inlcs'.ines. A discharge of blood with the urine sometimes attends diabetes, and may have its source in the same manner. Mr. A-------, who had been a hard drinker, and had the gutta rosacea on his face and breast, after a stroke of the palsy voided near a quart of a black viscid material by stool: on di- luting it with water it did not become yellow, as it must have done if it had been inspissated bile, but continued black like the grounds of coffee. But any other part of the venous system may become quiescent or totally paralytic as well as the veins of the intestines: all which occur more frequently in those who have diseased livers, than in any others. lit nee troublesome bleedings of the nose, or from the lungs with a weak pulse; hence haemorrhages from the kidneys, too great menstruation; and hence the oozing of biood from •■very part of the body, and the petechia? in those fevers, which 232 OF HEMORRHAGES. Skct. XXVII. 2.1. are termed putrid, and vvhich is erroneously ascribed to the thin- ness of the blood: for the blood in inflammatory diseases is equally- fluid before it coagulates in the cold air. Is not that hereditary consumption, which occurs chiefly in dark-eyed people about the age of twenty, and commences with slight pulmonary haemorrhages without fever, a disease of this kind?—These haemorrhages frequently begin during sleep, when the irritability of the lungs is not sufficient in these patients to carry on the circulation without the assistance of volition; for in our waking hours, the motions of the lungs are in part volun- tary, especially if any difficulty of breathing renders the efforts of volition necessary. See Class I. 2. 1. 3. and Class III. 2. 1. 12. Another species of pulmonary consumption which seems more certainly of scrofulous origin is described in the next Sec- tion, No. 2. I have seen two cases of women, of about forty years of age, both of whom were seized with quick weak pulse, with difficult respiration, and who spit up by coughing much viscid mucus mixed with dark coloured blood. They had both large vibices on their limbs, and petechia;; in one the feet were in danger of mortification, in the other the legs were oedematous. To relieve the difficult respiration, about six ounces of blood were taken from one of them, which to my surprise was sizy, like inflamed blood: they had both palpitations or unequal pulsations of the heart. They continued four or five weeks with pale and bloated countenances, and did not cease spitting phlegm mixed with black blood, and the pulse seldom slower than 130 or 135 in a minute. This blood, from its dark colour, and from the many vibices and petechias, seems to have been venous blood; the quickness of the pulse, and the irregularity of the motion of the heart, are to be ascribed to debility of that part of the system; as the extravasa- tion of blood originated from the defect of venous absorption. The approximation of these two cases to sea-scurvy is peculiar, and may allow them to be called scorbutus pulmonalis. Had these been younger subjects, and the paralysis of the veins had only affected the lungs, it is probable the disease would have been a pulmonary consumption. Last week I saw a gentleman of Birmingham, who had for ten days laboured under great palpitation of his heart, which was so distinctly felt, by the hand, as to discountenance the idea of there being a fluid in the pericardium. He frequently spit up mucus stained with dark coloured blood, his pulse very un- equal and very weak, with cold hands and noise. He could not die down at all, and for about ten days past could not sleep a mi- nute together, but waked perpetually with great uueasiness. Sect. XXVII 2. 1. OF HEMORRHAGES. 23S Could those symptoms be owing to very extensive adhesions of the lungs? or is this a scorbutus pulmonalis? After a few days he suddenly got so much better as to be able to sleep many hours at a time, by the use of one grain of powder of foxglove twice a day, and a grain of opium at night. After a few days longer, the bark was exhibited, and the opium continued with some wine; and the palpitations of his heart became much relieved, and he recovered his usual degree of health, but died suddenly some months afterwards. In epileptic fits the patients frequently become black in the face, from the temporary paralysis of the venous system of this part. 1 have known two instances where the blackness has continued many days. M. P-----, who had drank intemperately, was seized with the epilepsy when he was in his fortieth year: in one of these fits the white part of his eyes was left totally black with effused blood; which was attended with no pain or heat, and was in a few weeks gradually absorbed, changing colour as is usual with vibices from bruises. The haemorrhages produced from the inability of the veins to absorb the refluent blood, are cured by opium, the preparations of steel, lead, the bark, vitriolic acid, and blisters; but these have the effect with much more certainty, if a venesection to a few ounces, and a moderate cathartic with four or six grains of ca- lomel be premised, where the patient is not already too much debilitated; as one great means of promoting the absorption of any fluid consists in previously emptying the vessels, which are to receive it. VOL. I. Hh 234 PAKALYSIS OF Sect. XXVIII. 1. SECT. XXVIII. OF THE PARALYSIS OF THE ABSORBENT SYSTEM. I. Paralysis of the lacteals, atrophy. Distaste to animal food. II. Cause of dropsy. Cause of herpes. Scrofula. ^Mesenteric consumption. Pulmonary consumption. Why ulcers in the lungs are so difficult to heal. The term paralysis has generally been used to express the loss of voluntary motion, as in the hemiplegia, but may with equal propriety be applied to express the disobediency of the muscular fibres to the other kinds of stimulus; as to those of irritation or sensation. I. There is a species of atrophy, which has not been well un- derstood; when the absorbent vessels of the stomach and intes- tines have been long inured to the stimulus of too much spiritu- ous liquor, they at length, either by the too sudden omission of fermented or spirituous potation, or from the gradual decay of nature, become in a certain degree paralytic; now it is observed in the larger muscles of the body, when one side is paralytic, the other is more frequently in motion, owing to the less expen- diture of sensorial power in the paralytic limbs; so in this case the other part of the absorbent system acts with greater force, or with greater perseverance, in consequence of the paralysis of the lacteals; and the body becomes greatly emaciated in a small time. I have seen several patients in this disease, of which the fol- lowing are the circumstances. 1. They were men about fifty years of age, and had lived freely in respect to fermented liquors. 2. They lost their appetite to animal food. 3. They became suddenly emaciated to a great degree. 4. Their skins were dry and rough. 5. They coughed and expectorated with difficulty a viscid phlegm. 6. The membrane of the tongue was dry and red, and liable to become ulcerous. The inability to digest animal food, and the consequent dis- taste to it, generally precede the dropsy, and other diseases, which originate from spirituous potation. I suppose, when the stomach becomes inirritable, that there is at the same time a de- ficiency of gastric acid: hence milk seldom agrees with these patients, unless it be previously curdled, as they have not suffi- cient gastric acid to curdle it; and hence vegetable food, which is itself acescent, will agree with their stomachs longer than ani- mal food, which requires more of the gastric acid for its digestion Sr.cT. XXVIII. 2. ABSORBENTS. 23J In this disease the skin is dry from the increased absorption of the cutaneous lymphatics, the fat is absorbed from the increased absorption of the cellular lymphatics, the mucus of the lungs is Joo viscid to be easily spit up by the increased absorption of the thinner parts of it, the membrana sneideriana becomes dry, co- vered with hardened mucus, and at length becomes inflamed and full of aphthae, and either these sloughs, or pulmonary ulcers, ter- minate the scene. II. The immediate cause of dropsy is the paralysis of some other branches of the absorbent system, which are called lym- phatics, and which open into the larger cavities of the body, or into the cells of the cellular membrane; whence those cavities or cells become distended with the fluid, which is hourly secreted into them for the purpose of lubricating their surfaces. As is more fully explained in No. 5. of the next Section. As those lymphatic vessels consist generally of a long neck or mouth, which drinks up its appropriated fluid, and of a conglobate gland, in which this fluid undergoes some change, it happens, that sometimes the mouth of the lymphatic, and sometimes the belly or glandular part of it, becomes totally or partially paralytic. In the former case, where the mouths of the cutaneous lympha- tics become torpid or quiescent, the fluid secreted on the skin ceases to be absorbed, and erodes the skin by its saline acri- mony, and produces eruptions termed herpes, the discharge from which is as salt as the tears, which are secreted too fast to be re- absorbed, as in grief, or when the puncta lacrymalia are obstruct- ed, and which, running down the cheek, redden and inflame the skin. When the mouths of the lymphatics, which open on the mucous membrane of the nostrils, become torpid, as on walking into the air in a frosty morning; the mucus, which continues to be secret- ed, has not its aqueous and saline part reabsorbed, which, run- ning over the upper lip, inflames it, and has a salt taste, if it falls on the tongue. When the belly, or glandular part of one of these lymphatics, becomes torpid, the fluid absorbed by its mouth stagnates, and forms a tumour in the gland. This disease is called the scro- fula. If these glands suppurate externally, they gradually heal, as those of the neck; if they suppurate without an opening on the external habit, as the mesenteric glands, a hectic fever ejisues, which destroys the patient; if they suppurate in the lungs, a pul- monary consumption ensues, vvhich is believed thus to differ from that described in the preceding Section, in respect to its seat or proximate cause. It is remarkable, that matter produced by suppuration will lie 236 PARALYSIS OF Sect. XXVIII. 2. concealed in the body many weeks, or even months, without pro- ducing hectic fever; but as soon as the wound is opened, so as to admit air to the surface of the ulcer, a hectic fever supervenes, even in very few hours, which I formerly conceived to be owingi to the azotic part of the atmosphere rather than to the oxygene; because those medicines which contain much oxygene, as the calces or oxydes of metals, externally applied, greatly contribute to heal ulcers; as these are the solutions of lead, and mercury, and copper in acids, or their precipitates; but have since believed it owing to the oxygene. See Class II. 1. 6. 7. in Vol. II. of this work. Hence when wounds are to be healed by the first intention, as it is called, it is necessary carefully to exclude the air from them. Hence we have one cause, vvhich prevents pulmonary ulcers from healing, which is their being perpetually exposed to the air. Another cause of the difficulty of healing pulmonary ulcers may arise from the inactivity of the vessels of the air-c; lis, which are covered with a membrane differing both from that of the mu- cous membranes of other cavities of the body, and from the ex- ternal skin. For it is probable, that the air-cells alone of the lungs constitute the organ of respiration, and not the internal sur- faces of the branching vessels of the trachea which lead to the air-cells. And, from a vegetable analogy mentioned below, they probably exhale or perspire either nothing, or much less than the surfaces of the pulmonary vessels, which lead to them. Hence the mucus, which in common coughs or superficial peripneumony is secreted on the surface of the branching vessels of the lungs, is forced up in coughing by the air behind it, which is hastily ex- cluded from the air-cells, and slowly inhaled into them. But if there was any mucus or matter formed in these air-cells, it is not easy to understand how it could be brought up by coughing, as no air could get admittance behind it; which may be one cause of the difficulty of healing pulmonary ulcers if they exist on the sur- face of the air-cells; but not so, if they exist in the vessels lead- ing to the air-cells, as after a wound with a sword, or when a vomica has burst after a peripneumony. In the vegetable system, I think, there can be no doubt, but that the upper surface of the leaves constitutes the organ of re- spiration; and M. Bonnet, in his Usages des Feuilles, shows by a curious experiment, that the upper surfaces of leaves do not ex- hale half so much as their under surfaces. He placed the stalks of many leaves fresh collected into glass tubes filled with water, of many of these the upper surfaces were smeared with oil, and the under surfaces of many others of them; and he uniformly Sect XXVIII. 2. ABSORBENTS. 237 found by the sinking of the water in the tubes, that the upper surfaces exhaled less by half than ihe under surfaces. Both the dark-eyed patients, which are affected with pulmo- nary ulcers from deficient venous absorption, as described in Sec- lion XXVII. 2. and the light-eyed patients from deficient lym- phatic absorption, which we are now treating of, have generally large apertures of the iris; these large pupils of the eyes are a common mark of want of irritability; and it generally happens, that an increase of sensibility, that is, of motions in consequence of sensation, attends these constitutions. See Sect. XXXI. 2. Whence inflammations may occur in these from stagnated fluids more frequently than in those constitutions, which possess more irritability and less sensibility. Great expectations in respect to the cure of consumptions, as well as of many other diseases, are produced by the very ingeni- ous exertions of Dr. Beddoes; who has established an apparatus for breathing various mixtures of airs or gases, at the hot-wells near Bristol, vvhich well deserves the attention of the public. Dr. Beddoes very ingeniously concludes, from the florid colour of the blood of consumptive patients, that it abounds in oxygene; and that the redness of their tongues, and lips, and the fine blush of their checks, shew the presence of the same principle, like flesh reddened by nitre. And adds, that the circumstance of the consumptions of pregnant women being stopped in their pro- gress during pregnancy, at which time their blood may be sup posed to be in part deprived of its oxygene, by oxygenating the blood of the foetus, is a forcible argument in favour of this theory vvhich must soon be confirmed or confuted by his experiments' See Essay on Scurvy, Consumption, &c. by Dr. Beddoes. Mum- London. Also Letter to Dr. Darwin by the same. MurrV' 2.36 RETROGRADE Sect. XXIX. 1. 1. SECT. XXIX. ON THE RETROGRADE MOTIONS OF THE ABSORBENT SYSTEM. I. Account of the absorbent system. II. The valves of the absorbent vessels may suffer their fluids to regurgitate in some diseases. HI. Communicationfrom the alimentary canal to the bladder by means of the absorbent vessels. IV. Tlie phenomena of diabetes ex- plained. V. 1. The phenomena of dropsies explained. 2. Cases of the use of foxglove. VI. Of cold sweats. VII. Translations of matter, of chyle, of milk, of urine, operation of purging drugs applied externally. VIII. Circumstances by which the fluids, that are effused by the retrograde motions of the absorb- ent vessels, are distinguished. IX. Retrograde motions of ve- getable juices. X. Objections answered. XI. The causes, which induce the retrograde motions of animal vessels, and tlie medi- cines by which the natural motions are restored. N. B. Thefollouing Section is a translation of a part of a Latin thesis written by the late Mr. Charles Darwin, which was printed with his prize-dissertation on a criterion between matter and mu- cus in 1780. Sold by Cadell, London. I. Account of the Absorbent System. 1. The absorbent system of vessels in animal bodies consists of several branches, differing in respect to their situations, and to the fluids, which they absorb. The intestinal absorbents open their mouths on the internal surfaces of the intestines; their office is to drink up the chyle and the other fluids from the alimentary canal; and they are termed lacteals, to distinguish them from the other absorbent vessels, which have been termed lymphatics. Those, whose mouths are dispersed on the external skin, im- bibe a great quantity of water from the atmosphere, and a part of the perspirable matter which does not evaporate, and are termed cutaneous absorbents. Those, which arise from the internal surface of the bronchia, and which imbibe moisture from the atmosphere, and a part of the bronchial mucus, are called pulmonary absorbents. Those, which open their innumerable mouths into the cells of the whole cellular membrane; and whose use is to take up the fluid, which is poured into those cells, after it has done its office there, may be called cellular absorbents. Those, which arise from the internal surfaces of the mem- Sect. XXIX. 1. % ABSORBENTS. 239 branes, which line the larger cavities of the body, as the thorax, abdomen, scrotum, pericardium, take up the mucus poured in- to those cavities; and are distinguished by the names of their re- spective cavities. r Whilst those, which arise from the internal surfaces o! the urinary bladder, gall-bladder, salivary ducts, or other receptacles of secreted fluids, may take their names from those fluids; the thinner parts of which it is their office to absorb: as urinary, bilious, or salivary absorbents. 2. Many of these absorbent vessels, both lacteals and lympha- tics, like some of the veins, are replete with valves: which seem designed to assist the progress of their fluids, or at least to pre- vent their regurgitation; where they are subjected to the inter- mitted pressure of the muscular, or arterial actions in their neighbourhood. These valves do not however appear to be necessary to all the absorbents, any more than to all the veins; since they are not found to exist in the absorbent system offish; according to the discoveries of the ingenious and much lamented Mr. Hewson. Philos. Trans, v. 59, Enquiries into the Lymph. Syst. p. 94. 3. These absorbent vessels are also furnished with glands, which are called conglobate glands; whose use is not at present sufficiently investigated; but it is probable that they resemble the conglomerate glands both in structure and in use, except that their absorbent mouths are for the conveniency of situation plac- ed at a greater distance from the body of the gland. The con- glomerate glands open their mouths immediately into the san- guiferous vessels, which bring the blood, from whence they ab- sorb their respective fluids, quite up to the gland; but these conglobate glands collect their adapted fluids from very distant membranes, or cysts, by means of mouths furnished with long necks for this purpose; and vvhich are called lacteals, or lym- phatics. 4. The fluids, thus collected from various parts of the body, pass by means of the thoracic duct into the left subclavian near the jugular vein; except indeed that those collected from the right side of the head and neck, and from the right arm, are car- ded into the right subclavian vein: and sometimes even the lym- phatics from the right side of the lungs are inserted into the ri' beco™^ker; and v hen the bowels or kidneys are stimulated by poison, a stone or inflammation, into more violent action; the stomach a\id cesopha g i ^^P^y invert their motions. P * 1. W hen any one drinks a moderate quantity of vinous snlrit the whole system acts with more energy by consent wi h it stomach and intestines, as is seen from the^lovv on the sk 1 he increase 0f strength and activity; but when a great r'a„ tj of this inebriating material is drunk, at the same timeTh»J the lacteals are excited into greater action to absorb it T ft 'luently happens, that the uriLry branch of ^J'Jhfa 246 RETROGRADE Sect. XXIX. 4. 2. connected with the lacteals by many anastomose*, inverts its mo- tions, and a great quantity of pale unanimalized urine is dis- charged. By this wise contrivance too much of an unnecessary fluid is prevented from entering the circulation. This may be called the drunken diabetes, to distinguish it from the other temporary diabetes, which occur in hysteric diseases, and from continued fear or anxiety. 2. If this idle ingurgitation of too much vinous spirit be daily practised, the urinary branch of absorbents at length gains a habit of inverting its motions, whenever the lacteals are much stimu- lated; and the whole, or a great part, of the chyle is thus daily carried to the bladder without entering the circulation, and the body becomes emaciated. This is one kind of chronic diabetes, and may be distinguished from the others by the taste and ap- pearance of the urine; which is sweet, and of the colour of whey, and may be termed the chyliferous diabetes. 5. Many children have a similar deposition of chyle in their urine, from the irritation of worms in their intestines, which stimulating the mouths of the lacteals into unnatural action, the urinary branch of the absorbents becomes inverted, and carries part of the chyle to the bladder: part of the chyle also has been carried to the iliac and lumber glands, of which instances are recorded by Haller, t. vii. 225. and which can be explained on no other theory: but the dissections of the lymphatic system of the human body, which have yet been published, are not suffi- ciently extensive for our purpose; yet, if we may reason from comparative anatomy, this translation of chyle to the bladder is much illustrated by the account given of this system of vessels in a turtle, by Mr. Hewson, who observed, u That the lacteals near the root of the mesentery anastomose, so as to form a net-work, from which several large branches go into some considerable lymphatics lying near the spine; and which can be traced almost to the anus, and particularly to the kidneys." Philos. Trans, v. 59. p. 199—Enquiries, p. 74. 4. At the same time that the urinary branch of absorbents, in the beginning of diabetes, is excited into inverted action, the celiular branch is excited by the sympathy above mentioned, in- to more energetic action; and the fat, that was before deposited, is reabsorbed and thrown into the blood vessels; where it floats, and was mistaken for chyle, till the late experiments of the in- genious Mr. Hewson demonstrated it to be fat. This appearance of what was mistaken for chyle in the blood, which was drawn from these patients, and the obstructed liver, which very frequently accompanies this disease, seems to have led Dr. Mead to suspect the diabetes was owing to a defect of Sect. XXIX 4.5. ABSORBENTS. 247 sanguification; and that the scirrhosity of the liver was the origi- nal cause of it: but as the scirrhus of the liver is most frequently owing to the same causes, that produce the diabetes and dropsies; namely, the great use of fermented liquors; there is no wonder they should exist together, without being the consequence of each other. . .. .. . 5. If the cutaneous branch of absorbents gains a habit ot being excited into stronger action, and imbibes greater quantities ot moisture from the atmosphere, at the same time that the urinary branch has its motions inverted, another kind of diabetes is form- ed, which-may be termed the aqueous diabetes. In this diabetes the cutaneous absorbents frequently imbibe an amazing quantity of atmospheric moisture; insomuch that there are authentic his- tories, where many gallons a day, for many weeks together, above the quantity that has been drunk, have been discharged by urine. Dr. Keil, in his Medicina Statica, found that he gained eighteen ounces from the moist air of one night; and Dr. Percival affirms, that one of his hands imbibed, after being well chafed, near an ounce and a half of water, in a quarter of an hour.— (Transact, of the College, London, vol. ii. p. 102.) Home's Medic. Facts, p. 2. sect. 3. Dr. Rollo, in his work on Diabetes, has shewn, that one pa- tient, whom he weighed after being ten minutes in the warm bath, did not weigh heavier on his leaving it. Dr Currie, I think, mentions a similar fact. I suspect, that if the bath be made very hot, perhaps much above animal heat, the bather may perspire more than he absorbs, and become in reality lighter. And that in a more moderate heat, if the patient has been previ- ously exhausted by abstinence or fatigue, that he will absorb much; but that if his system be already full of fluids, from the food and fluids which he has previously eaten and drunk, he may not absorb any thing. See Class I. 3! 2. 6. The pale urine in hysterical women, or which is produced by fea or anxiety, is a temporary complaint of this kind; and it wouM in reality be the same disease, if it was confirmed by habit. 6. The purging stools, and pale urine, occasioned by exposing tlie naked body to cold air, or sprinkling it with cold water, ori- ginate from a similar cause; for the mouths of the cutaneous lym- phatics being suddenly exposed to cold, become torpid, and cease, or nearly cease, to act; whilst, by the sympathy above described, not only the lymphatics of the bladder and intestines cease also to absorb the more aqueous and saline part of the fluids secreted into them; but it is probable that these lymphatics invert their motions, and return the fluids, which were previously absorbed 248 RETROGRADE Sect. XXIX. 4.7. into the intestines and bladder. At the very instant that the body is exposed naked to the cold air, an unusual movement is felt in the bowels; as is experienced by boys going into the cold balh: this could not occur from an obstruction of the perspirable mat- ter, since there is not time for that to be returned to the bowels by the course of the circulation. There is also a chronic aqueous diarrhoea, in which ihe atmos- pheric moisture, drunk up by the cutaneous and pulmonary lym- phatics, is poured into the intestines, by the retrograde motions of the lacteals. This disease is most similar to the aqueous diabetes, and is frequently exchanged for it: a distinct instance of this is recorded by Benningerus, Cent. v. Obs. 98. in which an aqueous diarrhoea succeeded an aqueous diabetes, and d<°s: roved the pa- tient. There is a curious example of this, described by Symp- son (De Re Medica)—" A young man (says he) was seized with a fever, upon which a diarrhoea came on, with great stupor; and he refused to drink any thing, though he was par' bed up with excessive heat: the better to supply him with moisture, I directed his feet to be immersed in cold water; immediately I observed a wonderful decrease of water in the vessel, and then an impetuous stream of a fluid, scarcely coloured, was discharged by stool, like a cataract." 7. There is another kind of diarrhoea, which has been called caeliaca; in this disease the chyle, drunk up by the lacteals of the small intestines, is probably poured into the large intes'ines by the retrograde motions of their lacteals: as in the chyliferous diabetes, the chyle is poured into the bladder by the retrograde motions of the urinary branch of absorbents. The chyliferous diabetes, like this chyliferous diarrhoea, pro- duces sudden atrophy; since the nourishment, which ought to supply the hourly waste of the body, is expelled by the bladder, or rectum: whilst the aqueous diabetes, and the aqueous diar- rhoea, produce excessive thirst; because the moisture, which is obtained from the atmosphere, is not conveyed to the thoracic receptacle, as it ought to be, but to the bladder, or lower intes- tines; whence the chyle, blood, and whole system of glands, are robbed of their proportion of humidity. 8. There is a third species of diabetes, in which the urine is mucilaginous, and appears ropy in pouring it from one vessel into another; and will sometimes coagulate over the fire. This disease appears by intervals, and ceases again, and seems to be occasioned by a previous dropsy in some part of the body.— When such a collection is reabsorbed, it is not always returned into the circulation; but the same irritation that stimulates one lymphatic branch to reabsorb the deposited fluid, inverts the Scct. XXIX. 4. 9. ABiORBENTS. 249 urinary branch, and pours it into the bladder. Hence this mu- cilaginous diabetes is a cure, or the consequence of a cure, of a worse disease, rather than a disease itself. Dr. Cotunnius gave half an ounce of cream of tartar, every morning, to a patient, who had the anasarca; and he voided a great quantity of urine; apart of vvhich, put over the fire, co- agulated, on the evaporation of half of it, so as to look like the white of an egg. De Ischiade Nervos. This kind of diabetes frequently precedes a dropsy, and has this remarkable circumstance attending it, that it generally hap- pens in the night; as during the recumbent state of the body, the fluid, that was accumulated in the cellular membrane, or in the lungs, is more readily absorbed, as it is less impeded by its gravity. I have seen more than one instance of this disease. Mr. I), a man in the decline of life, who had long accustomed himself to spirituous liquor, had swelled legs, and other symp- toms of approaching anasarca; about once in a week or ten days, for several months, he was seized, on going to bed, with great general uneasiness, which his attendants resembled to an hysteric fit; and which terminated in a great discharge of viscid urine; his legs became less swelled, and he continued in better health for some days afterwards. I had not the opportunity to try if this urine would coagulate over the fire, when part of it was evapo- rated, which I imagine would be the criterion of this kind of diabetes; as the mucilaginous fluid deposited in the cells and cysts of the body, which have no communication with the exter- nal air, seems to acquire, by stagnation, this property of coagu- lation by heat, which the secreted mucus of the intestines and bladder do not appear to possess; as I have found by experiment: and if any one should suppose this coagulable urine was separat- ed from the blood by the kidneys, he may recollect that in the most inflammatory diseases, in which the blood is most replete or most ready to part with the coagulable lymph, none of this ap- pears in the urine. 9. Different kinds of diabetes require different methods of cure. For the first kind, chyliferous diabetes, after clearing the stomach and intestines, by ipecacuanha and rhubarb, to evacuate any acid material, vvhich may too powerfully stimulate the mouths of the lacteals, repeated and large doses of tincture of cantharides have been much recommended. The specific stimulus of this medicine, on the neck of the bladder, is likely to excite the numerous absorbent vessels, which are spread on that part, into stronger natural actions, and by that means pre- vent their retrograde ones; till, by persisting in the use of the medicine, their natural habits of motions might again be estab- *oi,. i. k k 250 RETROGRADE Skct. XXIX. 4. 9. lished. Another indication of cure, requires such medicines, as by lining the intestines with mucilaginous substances, or with such as consist of smooth particles, or which chemically destroy the acrimony of their contents, may prevent the too great action of the intestinal absorbents. For this purpose I have found the earth precipitated from a solutioe of alum, by means of fixed alkali, given in the dose of half a dram every six hours, of great advantage, with a few grains of rhubarb, so as to produce a daily evacuation. The food should consist of materials that have the least stimulus, with calcareous water, as of Bristol and Matlock; that the mouths of the lacteals may be as little stimulated as is necessary for their proper absorption; lest with their greater exertions, should be con- nected by sympathy,the inverted motions of the urinary lymphatics. The same method may be employed with equal advantage in the aqueous diabetes, so great is the sympathy between the skin and the stomach. To which, however, some application to the skin might be usefully added; as rubbing the patient all over with oil, to prevent the too great action of the cutaneous absorb- ents. I knew an experiment of this kind made upon one patient with apparent advantage. The mucilaginous diabetes will require the same treatment, which is most efficacious in the dropsy, and will be described below. I must add, that the diet and medicines above mention- ed, are strongly recommended by various authors, as by Morgan, Willis, Harris, and Etmuller; but more histories of the success- ful treatment of these diseases are wanting to fully ascertain the most efficacious methods of cure. In a letter from Mr. Charles Darwin, dated April 21, 1778, Edinburgh, is the subsequent passage:—cc A man who had long laboured under a diabetes, died yesterday in the clinical ward. He had for some time drunk four, and passed twelve pounds of fluid daily; each pound of urine contained an ounce of sugar. He took, without considerable relief, gum kino, sanguis draconis melted with alum, tincture of cantharides, isinglass, gum arabic, crab's eyes, spirit of hartshorn, and ate ten or fifteen oysters thrice a day. Dr. Home, having read my thesis, bled him, and found that neither the fresh blood nor tlie serum tasted sweet. His body was opened this morning—every viscus appeared in a sound and natural state, except that the left kidney had a very small pelvis, and that there was a considerable enlargement of most of the mesenteric lymphatic glands. I intend to insert this in my thesis, as it coincides with the experiment, where some asparagus was eaten at the beginning of intoxication, and its smell perceived in the urine, though not in the blood." S*ct. XXIX. 4.9. ABSORBENTS. 251 The following case of chyliferous diabetes is extracted from some letters of Mr. Hughes, to whose unremitted care the infir- mary at Stafford for many years was much indebted. Dated October 10, 1778. Richard Davis, aged 33, a whitesmith by trade, had drunk hard by intervals; was much troubled with sweating of his hands, which incommoded him in his occupation, but which ceased on his frequently dipping them in lime. About seven months ago he began to make large quantities of water; his legs are cedematous, his belly tense, and he complains of a rising in his throat, like the globus hystericus; he eats twice as much as other people, drinks about fourteen pints of small beer a day, besides a pint of ale, some milk-porridge, and a bason of broth, and he makes about eighteen pints of water a day. He tried alum, dragon's blood, steel, blue vitriol, and cantha- rides in large quantities, and duly repeated, under the care of Dr. Underbill, but without any effect; except that on the day after he omitted the cantharides, he made but twelve pints of water, but on the next day this good effect ceased again* November 21.—He made eighteen pints of water, and he now, at Dr. Darwin's request, took a grain of opium every four hours, and five grains of aloes at night; and had a flannel shirt given him. 22.—Made sixteen pints. 23.—Thirteen pints: drinks less. 24.—Increased the opium to a grain and a quarter every four hours: he made twelve pints. 25.—Increased the opium to a grain and a half: he now rnake^ ten pints, and drinks eight pints in a day. The opium was gradually increased during the next fortnight, till he took three grains every four hours, but without any further diminution of his water. During the use of the opium he sweat much in the nights, so as to have large drops stand on his face and all over him. The quantity of opium was then gradually de- creased, but not totally omitted, as he continued to take about a grain morning and evening. January 17.—He makes fourteen pints of water a day. Dr. Underbill now directed him two scruples of common resin tritu- rated with as much sugar, every six hours; and three grains of opium every night. 19.—Makes fifteen pints of water; sweats at night. 21.—Makes seventeen pints of water; has twitchings of his limbs in a morning, and pains of his legs: he now takes a dram of resin for a dose, and continues the opium. 23.—Water more coloured, and reduced to sixteen pints, and he thinks has a brackish taste. >;i2 RETROGRADE Si ct. XXIX. 4.9. 26.—Water reduced to fourteen pints. 28.—Water thirteen pints: he continues the opium, and takes four scruples of the resin for a dose. February 1.—Water twelve pints. 4.—Water eleven pints: twitchings less; takes five scruples for a dose. 8.—Water ten pints: has had many stools. 12.—Appetite less: purges very much. After this the resin either purged him, or would not stay on bis stomach: and he gradually relapsed nearly to his former condi- tion, and in a few months sunk under the disease. October 3, Mr. Hughes evaporated two quarts of the water, and obtained from it four ounces and a half of hard and brittle saccharine mass, like treacle which had been some time boiled. Four ounces of blood which he took from his arm with design to examine it, had the common appearances, except that the serum resembled cheese-whey; and that on the evidence of four persons, two of whom did not know what it was they tasted, the serum had a saltish taste. From hence it appears, that the saccharine matter, with which the urine of these patients so much abounds, does not enter the blood-vessels like the nitre and asparagus mentioned above; but that the process of digestion resembles the process of the ger- mination of vegetables, or of making barley into malt; as the vast quantity of sugar found in the urine must be made from the food which he took, (vvhich was double that taken by others,) and from the fourteen pints of small beer which he drank. And, secondly, as the serum of the blood was not sweet, the chyle ap- pears to have been conveyed to the bladder without entering the circulation of the blood, since so large a quantity of sugar, as was found in the urine, namely, twenty ounces a day, could not have previously existed in the blood without being perceptible to the taste. November 1.—Mr. Hughes dissolved two drams of nitre in a pint of a decoction of the roots of asparagus, and added to it two ounces of tincture of rhubarb: the patient took a fourth part of this mixture every five minutes, till he had taken the whole.—In about half an hour he made eighteen ounces of water, which was very manifestly tinged with the rhubarb; the smell of asparagus was doubtful. He then lost four ounces of blood, the serum of which was not so opaque as that drawn before, but of a yellowish cast, as the serum of the blood usually appears. Paper dipped three or four times in the tinged urine and dri- ed agana, did not scintillate when it was set on fire: but when Sferr. XXIX. 5. 1. ABSORBENTS. 253 the flame was blown out, the fire ran along the paper for half an inch; which, when the same paper was unimpregnated, it would not do; nor when the same paper was dipped in urine made be- fore he took the nitre, and dried in the same manner. Paper, dipped in the serum of the blood and dried in the same manner as in the urine, did not scintillate when the flame was blown out, but burnt exactly in the same manner as the same pa- per dipped in the serum of blood drawn from another person. This experiment, which is copied from a letter of Mr. Hughes, as well as the former, seems to evince the existence of another passage from the intestines to the bladder, in this disease, besides that of the sanguiferous system; and coincides with the curious experiment related in section the third, except that the smell of the asparagus was not here perceived, owing perhaps to the roots having been made use of instead of the heads. The rising in the throat of this patient, and the twitchiugs of his limbs, seem to indicate some similarity between the diabetes and the hysteric disease, besides the great flow of pale urine, which is common to them both. Perhaps if the mesenteric glands were nicely inspected in the- dissections of these patients; and if the thoracic duct, and the larger branches of the lacteals; and if the lymphatics, which ^ arise from tlie bladder, were well examined by injection, or by 5^: the knife, the cause of diabetes might be more certainly under- stood. The opium alone, and the opium with the resin, seem much to have served this patient, and might probably have effected a cure, if the disease had been slighter, or the medicine had been exhi- bited before it had been confirmed by habit during the seven months it had continued. The increase of the quantity of water on beginning the large doses of resin was probably owing to his omitting the morning doses of opium. As the urine in chyliferous diabetes abounds so much with saccharine matter, as appears from the above case of Davis, Dr. Rollo has ingeniously recommended a diet of animal food alone; this, with a diminution of the quantity of fluid, which the patient was previously accustomed to, is said to have changed the quality of the urine, and to have diminished its quantity. See Part II. Class I. 3. 2. 6. of this work. V. The Phenomena of Dropsies explained. 1. Some inebriates have their paroxysms of inebriety termi- rtated by much pale urine, or profuse sweats, or vomiting, or 254 RETROGRADE Sect. XXIX. 5. 1. stools; others have their paroxysms terminated by stupor, or sleep, without the above evacuations. The former kind of these inebriates have been observed to be more liable to diabetes and dropsy; and the latter to gout, gravel, and leprosy. Evoe! attend, ye bacchanalians! stari at this dark train of evils, and amid your immodest jests, and idiot laughter, recollect, Qiem Deus vult perdere, prius dementat. In those who are subject to diabetes and dropsy, the absorbent vessels are naturally more irritable than in the latter; and by be- ing frequently disturbed or inverted by violent stimulus, and by their too great sympathy with each other, they become at length either entirely paralytic, or are only susceptible of motion from the stimulus of very acrid materials; as every part of the body, after having been used to great irritations, becomes less affected by smaller ones. Thus we cannot distinguish objects in the night, for some time after we come out of a strong light, though the iris is presently dilated; and the air of a summer evening appears cold, after we have been exposed to the heat of the day. There are no cells in the body, where dropsy may not be pro- duced, if the lymphatics cease to absorb that mucilaginous fluid, which is perpetually deposited in them, for the purpose of lubri- cating their surfaces. If the lymphatic branch, which opens into the cellular mem- brane, either does its office imperfectly, or not at all; these cells become replete with a mucilaginous fluid, which, after it has stagnated some time in the cells, will coagulate over the fire; and is erroneously called water. Wherever the seat of this disease is, (unless in the lungs or other pendent viscera,) the mucilagin- ous liquid above mentioned will subside to the most depending parts of the body, as the feet and legs, when those are lower than the head and trunk; for all these cells have communications with each other. When the cellular absorbents are become insensible to their usual irritations, it most frequently happens, but not always, that the cutaneous branch of absorbents, which is strictly asso- ciated with them, suffers the like inability. And then, as no wa- ter is absorbed from the atmosphere, the urine is not only less diluted at the time of its secretion, and consequently in less quantity and higher coloured: but great thirst is at the same time induced, for as no water is absorbed from the atmosphere to dilute the chyle and blood, the lacteals and other absorbent vessels, which have not lost their powers, are excited into more constant or more violent action, to supply this deficiency; Sect. XXIX. 5. I ABSORBENTS. 255 whence the urine becomes still less in quantity, and of a deeper colour, and turbid like the yolk of an egg, owing to a greater ab- sorption of its thinner parts. From this stronger action of those absorbents, which still retain their irritability, the fat is also ab- sorbed, and the whole body becomes emaciated. This increased exertion of some branches of the lymphatics, while others aw totally or partially paralytic, is resembled by what constantly oc- curs iu the hemiplegia; when the patient has lost the use of the limbs on one side, he is incessantly moving those of the other; for the moving power, not having access to the paralytic limbs, becomes redundant in those which are not diseased. The paucity of urine and thirst cannot be explained from a greater quantity of mucilaginous fluid being deposited in the cellular membrane: for though these symptoms have continued many weeks, or even months, this collection frequently does not amount to more than very few pints. Hence also the difficulty of promoting copious sweats in anasarca is accounted for, as well as the great thirst, paucity of urine, and loss of fat; since, when the cutaneous branch of absorbents is paralytic, or nearly so, there is already too small a quantity of aqueous fluid in the blood: nor can these torpid cutaneous lymphatics be readily ex- cited into retrograde motions. Hence likewise we understand, why in the ascites, and some other dropsies, there is often no thirst, and no paucity of urine; in these cases the cutaneous absorbents continue to do their office. Some have believed, that dropsies were occasioned by the in- ability of the kidneys, from having only observed the paucity of urine; and have thence laboured much to obtain diuretic medi- cines; but it is daily observable, that those who die of a total in- ability to make water, do not become dropsical in consequence of it: Fernelius mentions one, who laboured under a perfect sup- pression of urine during twenty days before his death, and yet had no symptoms of dropsy. Pathol. 1. vi. c. 8. From the same idea many physicians have restrained their patients from drinking, though their thirst has been very urgent; and some cases have been published, where this cruel regimen has been thought advantageous: but others of nicer observation are of opinion, that it has always aggravated the distresses of the patient; and though it has abated his swellings, yet by inducing a fever it has hastened his dissolution. See Transactions of the College, London, vol. ii. p. 235. Cases of Dropsy by Dr. G. Baker. The cure of anasarca, so far as respects the evacuation of the accumulated fluid, coincides with the idea of the retrograde ac- tion of the lymphatic system. It is well known that vomits, and other drugs, which induce sickness or nausea, at the same time 256 RETROGRADE Sect. XXIX. 5. 2. that they evacuate the stomach, produce a great absorption of the lymph accumulated in the cellular membrane. In the operation of a vomit, not only the motions of the stomach and duodenum become inverted, but also those of the lymphatics and lacteals, which belong to them; whence a great quantity of chyle and lymph is perpetually poured into the stomach and intestines, dur- ing the operation, and evacuated by the mouth. Now at the same time, other branches of the lymphatic system, viz. those which open on the cellular membrane, are brought into more energetic action, by the sympathy above mentioned, and an in- crease of their absorption is produced. Hence repeated vomits, and cupreous salts, and small doses of squill or foxglove, are so efficacious in this disease. And as dras- tic purges act also by inverting the motions of the lacteals; and thence the other branches of lymphatics are induced into more powerful natural action, by sympathy, and drink up the fluids from all the cells of the body; and by their anastomoses, pour them into the lacteal branches; which, by their inverted actions, return them into the intestines; and they are thus evacuated from the body:—these purges also are used with success in discharg- ing the accumulated fluid in anasarca. II. The following cases are related with design to ascertain the particular kinds of dropsy in which the digitalis purpurea, or common foxglove, is preferable to squill, or other evacuanls, and were first published in 1780, in a pamphlet entitled Experi- ments on mucilaginous and purulent Matter, &c. Cadell. Lon- don. Other cases of dropsy, treated with digitalis, were after- wards published by Dr. Darwin in the Medical Transactions, vol. iii. in which there is a mistake in respect to the dose of the powder of foxglove, which should have been from five grains to ene, instead of from five grains to ten. Anasarca of the Lungs. 1. A lady, between forty and fifty years of age, had been in- disposed some time, was then seized with cough and fever, and afterwards expectorated much digested mucus. This expecto- ration suddenly ceased, and a considerable difficulty of breathing supervened, with a pulse very irregular both in velocity and strength; she was much distressed at first lying down, and at first rising; but after a minute or two bore either of those atti- tudes with ease. She had no pain or numbness in her arms; she had no hectic fever, nor any cold shiverings, and the urine was in due quantity, and of the natural colour. The difficulty of breathing was twice considerably relieved by Sect. XXIX. 5. 2. ABSORBENTS. 257 small doses of ipecacuanha, which operated upwards and down- wards, but recurred in a few days: she was then directed a de- coction of foxglove, (digitalis purpurea) prepared by boiling four ounces of the fresh leaves from two pints of water to one pint; to which were added two ounces of vinous spirit; she took three large spoonfuls of this mixture every two hours, till she had taken it four times; a continued sickness supervened, with frequent vomiting, and a copious flow of urine: these evacuations conti- nued at intervals for two or three days, and relieved the difficulty of breathing. She had some relapses afterwards, which were again relieved by the repetition of the decoction of foxglove. 2. A gentleman, about sixty years of age, who had been ad- dicted to an immoderate use of fermented liquors, and had been very corpulent, gradually lost his strength and flesh, had great difficulty of breathing, with legs somewhat swelled, and a very irregular pulse. He was very much distressed at first lying down, and at first rising from his bed, yet in a minute or two was easy in both these attitudes. He made straw-coloured urine in due quantity, and had no pain or numbness of his arms. He took a large spoonful of the decoction of foxglove, as above, every hour, for ten or twelve successive hours, had incessant sickness for about two days, and passed a large quantity of urine; upon which his breath became quite easy, and the swelling of his legs subsided; but as his whole constitution was already sinking from the previous intemperance of his life, he did not survive more than three or four months. Hydrops Pericardii. 3. A gentleman of temperate life and sedulous application to business, between thirty and forty years of age, had long been subject, at intervals, to an irregular pulse: a few months ago he became weak, with difficulty of breathing, and dry cough. In this situation, a physician of eminence directed him to abstain from all animal food and fermented liquor, during which regimen all his complaints increased; he now became emaciated, and to- tally lost his appetite; his pulse very irregular both in velocity and strength; with great difficulty of breathing, and some swell- ing of his legs; yet he could lie down horizontally in his bed, though he got little sleep, and passed a due quantity of urine, and of the natural colour: no fulness or hardness could be perceived about the region of the liver; and he had no pain or numbness in his arms. One night he had a most profuse sweat all over his body and limbs, vvhich quite deluged his bed, and for a day or two some- vol. i. 1.1 258 RETROGRADE Sect. XXIX. 5. 2. what relieved his difficulty of breathing, and his pulse became less irregular: this copious sweat recurred three or four times at the intervals of five or six days, and repeatedly alleviated his symptoms. He was directed one large spoonful of the above decoction of foxglove every hour, till it procured some considerable evacua- tion: after he had taken it eleven successive hours he had a few liquid stools, attended with a great flow of urine, which last had a dark tinge, as if mixed with a few drops of blood: he continued sick at intervals for two days, but his breath became quite easy and his pulse quite regular, the swelling of his legs disappeared, and his appetite and sleep returned. He then took three grains of white vitriol twice a day, with some bitter medicines, and a grain of opium with five grains of rhubarb every night; was advised to eat flesh meat, and spice, as his stomach would bear it, with small beer, and a few glasses of wine; and had issues made in his thighs; and has suffered no relapse. 4. A lady, about fifty years of age, had for some weeks great difficulty of breathing, with very irregular pulse, and considerable general debility: she could lie down in bed, and the urine was in due quantity and of the natural colour, and she had no pain or numbness of her arms. She took one large spoonful of the above decoction of foxglove every hour, for ten or twelve successive hours; was sick, and made a quantity of pale urine for about two days, and was quite relieved both of the difficulty of breathing, and the irregularity of her pulse. She then took a grain of opium, and five grains of rhubarb, every night, for many weeks; with some slight chaly- beate and bitter medicines, and has suffered no relapse. Hydrops Thoracis. 5. A tradesman, about fifty years of age, became weak and short of breath, especially on increase of motion, with pain in one arm, about the insertion of the biceps muscle. He observed he sometimes in the night made an unusual quantity of pale water. He took calomel, alum, and peruvian bark, and all his symptoms increased: his legs began to swell considerably; his breath be- came more difficult, and he could not lie down in bed; but all this time he made a due quantity of straw-coloured water. The decoction of foxglove was given as in the preceding cases, which operated chiefly by purging, and seemed to relieve his breath for a day or two; but also seemed to contribute to Sect. XXIX. 5. 2. ABSORBENTS. 259 weaken him. He became after some weeks universally drop- sical, and died comatose. 6. A young lady of delicate constitution, with light eyes and hair, and who had perhaps lived too abstemiously, both in respect to the quantity and quality of what she ate and drank, was seiz- ed with great difficulty of breathing, so as to threaten immediate death. Her extremities were quite cold, and her breath felt cold to the back of one's hand. She had no sweat, nor could lie down for a single moment; and had previously, and at pre- sent, complained of great weakness and pain and numbness of both her arms; had no swelling of her legs, no thirst, water in due quantity and colour. Her sister, about a year before, was afflicted with similar symptoms, was repeatedly blooded, and died universally dropsical. A grain of opium was given immediately, and repeated every six hours with evident and amazing advantage; afterwards a blister, with chalybeates, bitters, and essential oils, were ex- hibited, but nothing had such eminent effect in relieving the dif- ficulty of breathing and coldness of her extremities as opium, by the use of which in a few weeks she perfectly regained her health, and has suffered no relape. Ascites. 7. A young lady of delicate constitution having been exposed to great fear, cold, and fatigue, by the overturn of a chaise in the night, began with pain and tumour in the right hypochon- drium: in a few months a fluctuation was felt throughout the whole abdomen, more distinctly perceptible indeed about the re- gion of the stomach; since the integuments of the lower part of the abdomen generally become thickened in this disease by a degree of anasarca. Her legs were not swelled, no thirst, water in due quantity and colour. She took the foxglove so as to in- duce sickness and stools, but without abating the swelling, and was obliged at length to submit to the operation of tapping. 8. A man about sixty-seven, who had long been accustomed to spirituous potation, had some time laboured under ascites; his legs somewhat swelled; his breath easy in all attitudes; no ap- petite; great thirst; urine in exceedingly small quantity, very deep coloured, and turbid; pulse equal. He took the foxglove in such quantity as vomited him, and induced sickness for two days; but procured no flow of urine, or diminution of his swell- ing; but was thought to leave him considerably weaker. 9. A corpulent man, accustomed to a large potation of fer- mented liquors, had vehement cough, difficult breathing, ana- 260 RETROGRADE Sect. XXIX. 6.3 sarca of his legs, thighs, and hands, and considerable tumour, with evident fluctuation of his abdomen; his pulse was equal; his urine in small quantity, of deep colour, and turbid. These swellings had been twice considerably abated by drastic cathar- tics. He took three ounces of a decoction of foxglove (made by boiling one ounce of the fresh leaves in a pint of water) every three hours, for two whole days; it then began to vomit and purge him violently, and promoted a great flow of urine; he was by these evacuations completely emptied in twelve hours. After two or three months all these symptoms returned; and were again relieved by the use of the foxglove: and thus in the space of about three years he was about ten times evacuated, and con- tinued all that time his usual potations: excepting at first, the medicine operated only by urine, and did not appear considerably to weaken him. The last time he took it, it had no effect; and a few weeks afterwards he vomited a great quantity of blood, and expired. QUERIES. 1. As the first six of these patients had a due discharge of urine, and of the natural colour, was not the seat of the disease confined to some part of the thorax, and the swelling of the legs rather a symptom of the obstructed circulation of the blood, than of a paralysis of the cellular lymphatics of those parts? 2. When the original disease is a general anasarca, do not the cutaneous lymphatics always become paralytic at the same time with the cellular ones, by their greater sympathy with each other? and hence the paucity of urine, and the great thirst distinguish this kind of dropsy? 3. In the anasarca of the lungs, when the disease is not very great, though the patients have considerable difficulty of breath- ing at their first lying down, yet after a minute or two their breath becomes easy again; and the same occurs at their first rising. Is not this owing to the time necessary for the fluid in the cells of the lungs to change its place, so as the least to incommode respi- ration in the new attitude? 4. In the dropsy of the pericardium does not the patient bear the horizontal or perpendicular attitude with equal ease? Does this circumstance distinguish the dropsy of the pericardium from that of the lungs and of the thorax? 5. Do the universal sweats distinguish the dropsy of the peri- cardium, or of the thorax? and those which cover the upper parts of the body only, the anasarca of the lungs? 6. When in the dropsy of the thorax, the patient endeavours Sfct.XXTX. 5. 2. ABSORBENTS. 261 to lie down, does not the extravasated fluid compress the upper parts of the bronchia, and totally preclude the access of air to every part of the lungs; whilst in the perpendicular attitude the inferior parts of the lungs only are compressed? Does not some- thing similar to this occur in the anasarca of the lungs, when the disease is very great, and thus prevent those patients also from lying down? 7. As a principal branch of the fourth cervical nerve of the left side, after having joined a branch of the third and of the se- cond cervical nerves, descending between the subclavian vein and artery, is received in a groove formed for it in the pericardium, and is obliged to make a considerable turn outwards to go over the prominent part of it where the point of the heart is lodged, in its course to the diaphragm; and as the other phrenic nerve of the right side has a straight course to the diaphragm; and as many other considerable branches of this fourth pair of cervical nerves are spread on the arms; does not a pain in the left arm distinguish a disease of the pericardium, as in the angino pecto- ris, or in the dropsy of the pericardium? and does not a pain or weakness in both arms distinguish the dropsy of the thorax? 8. Do not the dropsies of the thorax and pericardium fre- quently exist together, and thus add to the uncertainty and fa- tality of the disease? 9. Might not the foxglove be serviceable in hydrocephalus in- terims, in hydrocele, and in white swellings of the joints? VI. Of Cold Sweats. There have been histories given of chronical immoderate sweatings, vvhich bear some analogy to the diabetes. Dr. Willis mentions a lady then living, whose sweats were for many years so profuse, that all her bed-clothes were not only moistened, but deluged with them every night; and that many ounces, and some- times pints, of this sweat, were received in vessels properly placed, as it trickled down her body. He adds, that she had great thirst, had taken many medicines, and submitted to various rules of life, and changes of climate, but still continued to have these immoderate sweats. Pharmac. ration, de sudore anglico. Dr. Willis has also observed, that the sudor anglicanus which appeared in England, in 1483, and continued till 1551, was in some respects similar to the diabetes; and as Dr. Caius, who saw this disease, mentions the viscidity as well as the quantity of these sweats, and adds, that the extremities were often cold, when the internal parts were burnt up with heat and thirst with great and speedy emaciation and debility; there is great 2JH2 RETROGRADE Sect. XXIX. 6. I reason to believe, that the fluids were absorbed from the cells of the body by the cellular and cystic brain lies of the lymphatics, and poured on the skin by the retrograde motions of the cutaneous ones. Sydenham has recorded, in the stationary fever of the year 1685, the viscid sweats flowing from the head, which were pro- bably from the same source as those in the sweating plague above mentioned. It is very common in dropsies of the chest or lungs to have the difficulty of breathing relieved by copious sweats, flowing from the head and neck. Mr. P. about fifty years of age, had for many weeks been afflicted with anasarca of his legs and thighs, attended with difficulty of breathing; and had repeatedly been relieved by squill, oth-r bitters, and chalybeates. One night the difficulty of breathing became so great, that it was thought he must have expired; but so copious a sweat came out of his head and neck, that in a few hours, some pints, by estimation, were wiped off from those parts, and his breath was for a time relieved. This dyspncea and these sweats recurred at intervals, and after some weeks he ceased to exist. The skin of his head and neck felt cold to the hand, and appeared pale at the time these sweats flowed so abundantly; which is a proof, that they were produced by an inverted motion of the absorbents of those parts: for sweats, which are the consequence of an increased action of the sanguiferous system, are always attended with a warmth of the skin, greater than is natural, and a more florid colour; as the sweats from exercise, or those that succeed the cold fits of agues. Can any one explain how these partial sweats should re- lieve the difficulty of breathing in anasarca, but by supposing that the pulmonary branch of absorbents drank up the fluid in the cavity in the thorax, or in the cells of the lungs, and threw it on the skin, by the retrograde motions of the cutaneous branch? for, if we could suppose, that the increased action of the cuta- neous glands or capillaries poured upon the skin this fluid, pre- viously absorbed from the lungs; why is not the whole surface of the body covered with sweat? why is not the skin warm? Add to this, that the sweats above mentioned were clammy or gluti- nous, which the condensed perspirable matter is not; whence it would seem to have been a different fluid from that of common perspiration. Dr. Dobson of Liverpool, has given a very ingenious expla- nation of the acid sweats, which he observed in a diabetic patient —he thinks part of the chyle is secreted by the skin, and after- wards undergoes an acetous fermentation.—Can the chyle get thither, but by an inverted motion of the cutaneous lymphatics: Sect. X\1X. T. 1. ABSORBENTS. 263 in the same manner as it is carried to the bladder, by the inverted motions of the urinary lymphatics. Medic. Observat. and Enq. London, vol. v. Are not the cold sweats in some fainting fits, and in dying people, owing to an inverted motion of the cutaneous lymphatics; for in these there can be no increased arterial or glandular ac- tion'. Is the difficulty of breathing, arising from anasarca of the lungs, relieved by sweats from the head and neck; whilst that difficulty of breathing, which arises from a dropsy of the thorax, or peri- cardium, is never attended with these sweats of the head? and thence can these diseases be distinguished from each other? Do the periodic returns of nocturnal asthma rise from a temporary dropsy of the lungs, collected during their more torpid state in sound sleep, and then re-absovbed by the vehement efforts of the disordered organs of respiration, and carried off by the copious sweats about the head and neck? More extensive and accurate dissections of the Ivmphatic sys- tem are wanting to enable us to unravel these knots of science. VII. Translations of Mailer, of Chyle, of Milk, of Urine. Opera* lion of purging Drugs applied externally. 1. The translations of matter from one part of the body to another, can only receive an explanation from the doctrine of the occasioned retrograde motions of some branches of the lymphatic system: for how can matter absorbed and mixed with the whole mass of blood, be so hastily collected again in any one part? and is it not an immutable law, in animal bodies/that each gland can secrete no other, but its own proper fluid? which is, in part, fabricated in the very gland by an animal process, which it there Undergoes: of these purulent translations innumerable and very remarkable instances are recorded. 2. The chyle, which is seen among the materials thrown up by violent vomiting, or in purging stools, can only come thither by its having been poured into the bowels by the inverted motions of the lacteals: for our aliment is not converted into chyle in the stomach or intestines by a chemical process, but is made in the very mouths of the lacteals; .or in the mesenteric glands; in the same manner as other secreted fluids are made by an animal pro- cess in their adapted glands. lbre a curious phaenomenon in the exhibition of mercury is worth explaining:—If a moderate dose of calomel, as six or ten grains, be swallowed, and within one or two days a cathartic is given, a salivation is prevented: but after three*or four days, a 264 RETROGRADE Stcr. XXIX. 7. J. salivation having come on, repeated purges every day, for a week or two, are required to eliminate the mercury from the constitu- tion. For this acrid metallic preparation, being absorbed by the mouths of the lacteals, continues, for a time arrested by the mesen- teric glands, (as the variolous or venereal poisons swell the subaxillar or inguinal glands:) and, during the operation of a cathartic, is returned into the intestines by the inverted action of the lacteals, and thus carried out of the system. Hence we understand the use of vomits or purges, to those who have swallowed either contagious or poisonous materials, even though exhibited a day or even two days after such accidents; namely, that by the retrograde motions of the lacteals and lym- phatics, the material still arrested in the mesenteric, or other glands, may be eliminated from the body. 3. Many instances of milk and chyle found in ulcers are given by Haller, El. Physiol, t. vii. p. 12, 23, which admit of no other explanation than by supposing, that the chyle, imbibed by one branch of the absorbent system, was carried to the ulcer, by the inverted motions of another branch of the same system. 4. Mrs. P. on the second day after delivery, was seized with a violent purging, in which, though opiates mucilages, the bark, and testacea were profusely used, continued many days, till at length she recovered. During the time of this purging, no milk could be drawn from her breasts; but the stools appeared like the curd of milk broken into small pieces. In this case, was not the milk taken up from the follicles of the pectoral glands, and thrown on the intestines, by a retrogression of the intestinal ab- sorbents? for how can we for a moment suspect that the mucous glands of the intestines could separate pure milk from the blood? Dr. Smellie has observed, that loose stools, mixed with milk, which is curdled in the intestines, frequently relieves the turges- cency of the breasts of those who studiously repel their milk. Cases in Midwifery, 43, No. 2. 1. 5. J. F. Meckel observed in a patient, whose urine was in small quantity and high coloured, that a copious sweat under the arm- pits, of a perfectly urinous smell, stained the linen; which ceas- ed again when the usual quantity of urine was discharged by the urethra. Here we must believe from analogy, that the urine was first secreted in the kidneys, then re-absorbed by the increas- ed action of the urinary lymphatics, and lastly carried to the ax- illa? by the retrograde motions of the lymphatic branches of those parts. As in the jaundice it is necessary, that the bile should first be secreted by the liver, and re-absorbed into the cir- culation, to produce the yellowness of the skin; as was former- ly demonstrated by the late Dr. Munro, (Edin. Medical Es- hi t. XXIX. 7.6. ABSORBENTS. 265 says) and if in this patient the urine had been reabsorbed into the mass of blood, as the bile in the jaundice, why was it not de- tected in other parts of the body, as well as in the arm-pits ? 6. Cathartic and vermifuge medicines applied externally to the abdomen, seem to be taken up by the cutaneous branch of lymphatics, and poured on the intestines by the retrograde mo- tions of the lacteals without having passed the circulation. For when the drastic purges are taken by the mouth, they ex- cite the lacteals of the intestines into retrograde motions, as ap- pears from the chyle, which is found coagulated among the faeces, as was shewn above, (sect. 2 and 4.) And as the cutaneous lymphatics are joined with the lacteals of the intestines, by fre- quent anastomoses; it would be more extraordinary, when a strong purging drug, absorbed by the skin, is carried to the anas- tomosing branches of the lacteals unchanged, if it should not excite them into retrograde action as efficaciously, as if it was taken by the mouth, and mixed with the food of the stomach. VIII. Circumstances by which the Fluids, that are effused by the Retrograde Motions of the Absorbent Vessels, are distinguished. 1. We frequently observe an unusual quantity of mucus or other fluids in some diseases, although the action of the glands, by which those fluids are separated from the blood, is not un- usually increased; but when the power of absorption alone is di- minished. Thus the catarrhal humour from the nostrils of some who ride in frosty weather; and the tears which run down the cheeks of those, who have an obstruction of the punc- ta lacrymalia; and the ichor of those phagedenic ulcers, which are not attended with inflammation, are all instances of this cir- cumstance. These fluids however are easily distinguished from others by their abounding in ammoniacal or muriatic salts; whence they inflame the circumjacent skin: thus in the catarrh the upper lip becomes red and swelled from the acrimony of the mucus, and patients complain of the saltness of its taste. The eyes and cheeks are red with the corrosive tears, and the ichor of some herpetic eruptions erodes far and wide the contiguous parts, and is pungently salt to the taste, as some patients have informed me. Whilst, on the contrary, those fluids, which are effused by the retrograde action of the lymphatics, are for the most part mild and innocent; as water, chyle, and the natural mucus: or they take their properties from the materials previously ab- sorbed, as in the coloured or vinous urine, or that scented with asparagus, described before. vol. r. m m 266 RETROGRADE Stcr. XXlX. 8. 2 2. Whenever the secretion of any fluid is increased, there is at the same time an increased heat in the part; for the secreted fluid, as the bile, did not previously exist in the mass of blood, but a new combination is produced in the gland. Now as solu- tions are attended with cold, so combinations are attended with heat; and it is probable the sum of the heat given out by all the secreted fluids of animal bodies may be the cause of their ge- neral heat above that of the atmosphere. Hence the fluids derived from increased secretions are read- ily distinguished from those originating from the retrograde mo- tions of the lymphatics: thus an increase of heat of either in the diseased parts, or diffused over the whole body, is perceptible, when copious bilious stools are consequent to an inflamed liver; or a copious mucous salivation from the inflammatory angina. 3. When any secreted fluid is produced in an unusual quanti- ty, and at the same time the power of absorption is increased in equal proportion, not only the heat of the gland becomes more intense, but the secreted fluid becomes thicker and milder, its thinner and saline parts being reabsorbed: and these are dis- tinguishable both by their greater consistence, and by their heat, from the fluids, which are effused by the retrograde motions of the lymphatics; as is observable towards the termination of go- norrhoea, catarrh, chincough, and in those ulcers, which are said to abound with laudable pus. 4. When chyle is observed in stools, or among the materials ejected by vomit, we may be confident it must have been brought thither by the retrograde motions of the lacteals; for chyle does not previously exist amid the contents of the intes- tines, but is made in the very mouths of the lacteals, as was be- fore explained. 5. When chyle, milk, or other extraneous fluids are found in the urinary bladder, or in any other excretory receptacle of a gland; no one can for a moment believe that these have been collected from the mass of blood by a morbid secretion, as it con- tradicts all analogy. Aurea durx Mala ferant quercus ? Narcisco floreat alnus ? Pinguia corticibus sudent electra myricx ? VlBOIE. IX. Retrograde Motions of Vegetable Juices. There are besides some motions of the sap of vegetables, which bear analogy to our present subject; and as the vegeta- ble tribes are by many philosophers held to be inferior animals, Sect. XXIX. 10.1. ABSORBENTS. . 267 it may be a matter of curiosity at least to observe, that their ab- sorbent vessels seem evidently, at times, to be capable of a retro- grade motion. Mr. Perault cut off a forked branch of a tree, with the leaves on; and inverting one of the forks into a vessel of water, observed, that the leaves on the other branch continu- ed green much longer than those of a similar branch, cut off from the same tree: which shews, that the water from the ves- sel was carried up one part of the forked branch, by the retro- grade motion of its vessels, and supplied nutriment some time to the other part of the branch, which was out of the water. And the celebrated Dr. Hales found, by numerous very accurate ex- periments, that the sap of trees rose upwards during the warmer hours of the day, and in part descended again during the cooler ones. Vegetable Statics. It is well known that the branches of willows, and of many other trees, will either take root in the earth or ingraft on other trees, so as to have their natural direction inverted, and yet flourish with vigour. Dr. Hope has also made this pleasing experiment, after the manner of Hales—he has placed a forked branch, cut from one tree, erect between two others; then cutting off a part of the bark from one fork applied it to a similar branch of one of the trees in its vicinity; and the same of the other fork; so that a tree is seen to grow suspended in the air, between two other trees; which supply their foster friend with due nourishment. Mirantarque novas frondes, et nonsua poma. All these experiments clearly evince, that the juices of vegeta- bles can occasionally pass either upwards or downwards in their absorbent system of vessels. X. Objections answered. The following experiment, at first view, would seem to invali- date this opinion of the retrograde motions of the lymphatic ves- sels, in sonic diseases. About a gallon of milk having been given to a hungry swine, he was suffered to live about an hour, and was then killed by a stroke or (wo on his head with an axe. On opening his belly the lacteals were well seen filled with chyle; on irritating many of the branches of them with a knife, they did not appear to empty themselves hastily; but they did however carry forwards their contents in a little time. I then passed a ligature round several branches of lacteals, and irritated them much with a knife beneath the ligature, but 268 RETROGRADE Sfxt. XXIX. 11. 1. could not make them regurgitate their contained fluid into the bowels. I am not, indeed, certain, that the nerve was not at the same time included in the ligature, and thus the lymphatic rendered unirritable or lifeless; but this however is certain, that it is not any quantity of any stimulus, which induces the vessels of animal bodies to revert their motions: but a certain quantity of a cer- tain stimulus, as appears from wounds in the stomach, which do not produce vomiting; and wounds of the intestines, which do not produce the cholera morbus. At Nottingham, a few years ago, two shoemakers quarrelled, and one of them with a knife, which they use in their occupation, stabbed his companion about the region of the stomach. On opening.the abdomen of the wounded man after his death the food and medicines he had taken were in part found in the cavi- ty of the belly, on the outside of the bowels; and there was a wound about half an inch long at the bottom of the stomach; which I suppose was distended with liquor and food at the lime of the accident; and thence was more liable to be injured at its bottom: but during the whole time he lived, vvhich was about ten days, he had no efforts to vomit, nor ever even complained of be- ing sick at the stomach! Other cases similar to this are mention- ed in the Philosophical Transactions. t Thus, if you vellicate the throat with a feather, nausea is pro- duced; if you wound it with a penknife, pain is induced, but not sickness. So if the soles of the feet of children or their arm- pits are tickled, convulsive laughter is excited, vvhich ceases the moment the hand is applied, so as to rub them more forcibly. The experiment therefore above related upon the lacteals of a dead pig, which were included in a strict ligature, proves no- thing; as it is not the quantity, but the kind of stimulus, which excites the lymphatic vessels into retrograde motion. XI. The Causes which induce the Retrograde Motions of Animal Vessels; and the medicines by which the Natural Motions are restored. 1. Such is the construction of animal bodies, that all their parts, which are subjected to less stimuli than nature designed, perform their functions with less accuracy: thus, when too wa- tery or too acescent food is taken into the stomach, indigestion, and flatulency, and heartburn succeed. 2. Another law of irritation, connate with our existence, is, that all those parts of the body, which have previously been ex- posed to too great a quantity of such stimuli, as strongly affect them, become for some time afterwards disobedient to the na- Sect. XXIX. 11.3. ABSORBENTS. 269 lural quantity of their adapted stimuli. Thus the eye is incapable of seeing objects in an obscure room, though the iris is quite dilated, after having been exposed to-the meridian sun. 3. There is a third law of irritation, that all the parts of our bodies, which have been lately subjected to less stimulus than they have been accustomed to, when they are exposed to their usual quantity of stimulus, are excited into more energetic mo- tions; thus when we come from a dusky cavern into the glare of day-light, our eyes are dazzled; and after emerging from the cold bath, the skin becomes warm and red. 4. There is a fourth law of irritation, that all the parts of our bodies, which are subjected to still stronger stimuli for a length of time, become torpid, and refuse to obey even these stronger stimuli; and thence do their offices very imperfectly.—Thus, if any one looks earnestly for some minutes on an area, an inch di- ameter, of red silk, placed on a sheet of white paper, the image of the silk will gradually become pale, and at length totally vanish. 5. Nor is it the nerves of sense alone, as the optic and audi- tory nerves, that thus become torpid, when the stimulus is with- drawn or their irritability decreased; but the motive muscles, when they are deprived of their natural stimuli, or of their irrita- bility, become torpid and paralytic; as is seen in the tremulous hand of the drunkard in a morning; and in the awkward step of age. The hollow muscles also, of which the various vessels of the body are constructed, when they are deprived of their natural stimuli, or of their due degree of irritability, not only become tre- mulous, as the arterial pulsations of dying people; but also fre- quently invert their motions, as in vomiting, in hysteric suffoca- tions, and diabetes above described. I must beg your patient attention, for a few moments, whilst I endeavour to explain, how the retrograde actions of our hollow muscles are the consequence of their debility; as the tremulous actions of the solid muscles are the consequence of their debility. When, through fatigue, a muscle can act no longer, the antago- nist muscles, either by their inanimate elasticity, or by their ani- mal aclion, draw the limb into a contrary direction: in the solid muscles, as those of locomotion, their actions are associated in tribes, vvhich have been accustomed to synchronous action only; hence when they are fatigued, only a single contrary effort takes place; vvhich is either tremulous, when the fatigued muscles are again immediately brought into action; or it is a pandiculation, or stretching, where they are not immediately again brought into action. Now the motions of the hollow muscles, as they in general 270 RETROGRADE Sect. XXIX. U.S. propel a fluid along their cavities, are associated in trains, which have been accustomed to successive actions: hence when one ring of such a muscle is fatigued from its too great debility, and is brought into retrograde action, the next ring from its associa- tion falls successively into retrograde action; and so on through- out the whole caml. See Sect. XXV. 6. 6. But as the retrograde motions of the stomach, oesophagus, and fauces, in vomiting are, as it were, apparent to the eye; we shall consider this operation more minutely, that the similar ope- rations in the more recondite parts of our system may be easier understood. From certain nauseous ideas of the mind, from an ungrateful taste in the mouth, or from foetid smells, vomiting is sometimes instantly excited; or even from a stroke on the head, or from the vibratory motions of a ship; all which originate from association, or sympathy. See Sect. XX. on Vertigo. But when the stomach is subjected to a less stimulus than is natural, according to the first law of irritation mentioned above, its motions become disturbed, as in hunger; first pain is produced, then sickness, and at length vain efforts to vomit, as many authors inform us. But when a great quantity of wine, or of opium, is swallowed, the retrograde motions of the stomach do not occur till after se- veral minutes, or even hours; for when the power of so strong a stimulus ceases, according to the second law of irritation, men- tioned above, the peristaltic motions become tremulous, and at length retrograde; as is well known to the drunkard, who on the next morning has sickness and vomitings. When a still greater quantity of wine, or of opium, or when nauseous vegetables, or strong bitters, or metallic salts, are taken into the stomach, they quickly induce vomiting; though all these in less doses excite the stomach into more energetic action, and strengthen the digestion; as the flowers of chamomile, and the vitriol of zinc: for, according to the fourth law of irritation, the stomach will not long be obedient to a stimulus so much greater than is natural; but its action becomes first tremulous, and then retrograde. 7. When the motions of any vessels become retrograde, less heat of the body is produced; for in paroxysms of vomiting, of hysteric affections, of diabetes, of asthma, the extremities of the body are cold: hence we may conclude, that these symptoms arise from the debility of the parts in action; for an increase of muscular action is always attended with increase of heat. 8. But as animal debility is owing to defect of stimulus, or to defect of irritability, as shewn above, the method of cure is easily Sect. XXIX. 11. 3. ABSORBENTS. 271 deduced: when the vascular muscles are not excited into their due action by the natural stimuli, we should exhibit those medi- cines, which possess a still greater degree of stimulus; amongst these are the foetids, the volatiles, aromatics, bitters, metallic salts, opiates, wine, which indeed should be given in small doses, and frequently repeated. To these should be added constant, but moderate exercise, cheerfulness of mind, and change of coun- try to a warmer climate; and perhaps occasionally the external stimulus of blisters. It is also frequently useful to diminish the quantity of natural stimulus for a short time, by which afterwards the irritability of the system becomes increased; according to the third law of irri- tation above mentioned, hence the use of baths somewhat colder than animal heat, and of equitation in the open air. The catalogue of diseases owing to the retrograde motions of lym- phatics is here omitted, as it will appear in another place in this work. The following is the conclusion to this thesis of Mr. Charles Darwin. Thus have I endeavoured in a concise manner to explain the numerous diseases, which deduce their origin from the inverted motions of the hollow muscles of our bodies: and it is probable, that Saint Vitus's dance, and the stammering of speech, originate from a similar inverted order of the associated motions of some of the solid muscles; which, as it is foreign to my present pur- pose, I shall not here discuss. I beg, illustrious professors, and ingenious fellow-students, that ybu will recollect how difficult a task I have attempted, to evince the retrograde motions of the lymphatic vessels, when the vessels themselves for so many ages escaped the eyes and glasses of philosophers; and if you are not yet convinced of the truth •f this theory, hold, I entreat you, your minds in suspense, till Anatomy draws her sword with happier omens, cuts asunder the knots which entangle Physiology; and, like an augur in- specting the immolated victim, announces to mankind the wis- dom of HEAVEN. I'ARALVSiS Sect. XXX. 1. 1 SECT. XXX. PARALYSIS OF THE LIVER AND KIDNEYS. I. Bile-ducts less irritable after having been stimulated much. 2. Jaundice from paralysis of the bile-ducts cured by electric shocks. 3. From bile-stones. Experiments on bile-stones. Oil vomit. 4. Palsy of the liver, two cases. 5. Scirrhosity of the liver. 6. Large livers of geese. II. Paralysis of the kidneys. Ill Story of Prometheus. 1. From the ingurgitation of spirituous liquors into the sto- mach and duodenum, the termination of the common bile-duct in that bowel becomes stimulated into unnatural action, and a greater quantity of bile is produced from all the secretory vessels of the liver, by the association of their motions with those of their excretory ducts; as has been explained in Section XXIV. and XXV. but as all parts of the body, that have been affected with stronger stimuli for any length of time, become less sus- ceptible of motion, from their natural weaker stimuli, it follows that the motions of the secretory vessels, and in consequence the secretion of bile, is less than is natural during the intervals of sobriety. 2. If this ingurgitation of spirituous liquors has been daily continued in considerable quantity, and is then suddenly intermitted, a languor or paralysis of the common bile-duct is induced; the bile is prevented from being poured into the in- testines; and as the bilious absorbents are stimulated into strong- er action by its accumulation, and by the acrimony or viscidity, which it acquires by delay, it is absorbed, and carried to the receptacle of the chyle; or otherwise the secretory vessels in the liver, by the above-mentioned stimulus, invert their motions, and regurgitate their contents into the blood, as sometimes happens to the tears in the lacrymal sack, see Sect. XXIV. 2. 7. and one kind of jaundice is brought on. There is reason to believe, that the bile is most frequently re- turned into the circulation by the inverted motions of these he- patic glands, for the bile does not seem liable to be absorbed by the lymphatics, for it soaks through the gall-ducts, and is fre- quently found in the cellular membrane. This kind of jaundice is not generally attended with pain, neither at the extremity of the bile-duct, where it enters the duodenum, nor on the region of the gall-bladder. Mr. S. a gentleman between forty and fifty years of age, had had the jaundice about six weeks, without pain, sickness, or fe- Strr. XXX 1.3. OF THE LIVER. 273 ver; and had taken emetics, cathartics, mercurials, bitters, chalybeates, essential oil, and aether, without apparent advan- tage. On a supposition that the obstruction of the bile might be owing to the paralysis, or torpid action of the common bile-duct, and the stimulants taken into the stomach seeming to have no effect, I directed half a score smart electric shocks from a coated bottle, which held about a quart, to be passed through the liver, and along the course of the common gall-duct, as near as could be guessed, and on that very day the stools became yellow; he continued the electric shocks a few days more, and his skin gradually became clear. 3. The bilious vomiting and purging, that affect some peo- ple by intervals of a few weeks, is a less degree of this disease; the bile-duct is less irritable thin natural, and hence the bile be- comes accumulated in the gall-bladder, and hepatic ducts, till, by its quantity, acrimony or viscidity, a greater degree of irri- tation is produced, and it is suddenly evacuated, or lastly from the absorption of the more liquid parts of the bile, the remainder becomes inspissated, and crystallizes into masses too large to pass, and forms another kind of jaundice, where the bile-duct is not quite paralytic, or has regained its irritability. This disease is attended with much pain, which at first is fielt at the pit of the stomach, exactly in the centre of the body, where the bile-duct enters the duodenum; afterwards, when the size of the bile-stones increase, it is also felt on the right side, where the gall-bladder is situated. The former pain at the pit of the stomach recurs by intervals, as the bile-stone is pushed against the neck.of the duct; like the paroxysms of the stone in the uri- nary bladder, the other is a more dull and constant pain. Where these bile-stones are too large to pass, and the bile- ducts possess their sensibility, this becomes a very painful and hopeless disease. I made the following experiments with a view to their chemical solution. Some fragments of the same bile-stone were put into the weak spirit of marine salt, which is sold in the shops; and into solu- tion of mild alkali; and into a solution of caustic alkali; and into oil of turpentine; without their being dissolved. All these mix- tures were after some time put into a heat of boiling water, and then the oil of turpentine dissolved its fragments of bile-stone, but no alteration was produced upon those in the other liquids except some change of their colour. Some fragments of the same bile-stone were put into vitriolic aether, and were quickly dissolved without additional heat. Might not aether mixed with yolk of egg or with honey be given advantageously in bilious concretions? vol. i. n n 2"<1 PARALYSIS Sixt XXX. 1. 4. I have in two instances seen from thirty to fifty bile-stones come away by stool, about the size of large peas, after having given six grains of calomel in the evening, and four ounces of oil of almonds or olives on the succeeding morning. I have also given half a pint of good olive or almond oil as an emetic during the painful fit, and repeated it in half an hour, if the first did not operate, with frequent good effect. 4. Another disease of the liver, which I have several times observed, consists in the inability or paralysis of the secretory vessels. This disease has generally the same cause as the pre- ceding one, the too frequent potation of spirituous liquors, or the too sudden omission of them, after the habit is confirmed; and is greater or less in proportion, as the whole or a part of the liver is affected, and as the inability or paralysis is more or less com- plete. This palsy of the liver is known from these symptoms, the pa- tients have generally passed the meridian of life, have drunk fermented liquors daily, but perhaps not been opprobrious drunk- ards; they lose their appetite, then their flesh and strength di- minish in consequence, there appears no bile in their stools, nor in their urine, nor is any hardness or swelling perceptible in the region of the liver. But what is peculiar to this disease, and distinguishes it from all others at the first glance of the eye, is the bombycinous colour of the skin, vvhich, like that of full- grown silk worms, has a degree of transparency with a yellow tint not greater than is natural to the serum of the blood. Mr. C. and Mr. B. both very strong nun, between fifty and sixty years of age, who had drunk ale at their meals instead of small beer, but were not reputed hard drinkers, suddenly became weak, lost their appetite, flesh and strength, with all the symp- toms above enumerated, and died in about two months from the beginning of their malady. Mr. C. became anasarcous a few days before his death, and Mr. B. had frequent and great haemor- rhages from an issue, and some parts of his mouth, a few days before his death. In both these cases calomel, bitters, and chaly- beates were repeatedly used without effect. One of the patients described above, Mr. C. was by trade a plumber; both of them could digest no food, and died apparently for want of blood. Might not the transfusion of blood be used in these cases with advantage ? 5. When the paralysis of the hepatic glands is less complete, or less universal, a scirrhosity of some part of the liver is in- duced; for the secretory vessels retaining some of their living pow- er take up a fluid from the circulation, without being sufficient- ly irritable to carry it forwards to their excretory ducts; henct Sect. XXX. 1.6. OF THE LIVER 275 the body, or receptacle of each gland, becomes inflated, and this distention increases, till, by its very great stimulus, inflammation is produced, or till those parts of the viscus become totally para- lytic. This disease is distinguishable from the foregoing by the palpable hardness or largeness of the liver; and as the hepatic glands are not totally paralytic, or the whole liver not affected, some bile continues to be made. The inflammations of this vis- cus, consequent to the scirrhosity of it, belong to the diseases of the sensitive motions, and will be treated of hereafter. 6. The ancients are said to have possessed an art of increasing the livers of geese to a size greater than the remainder of the goose. Martial. 1. 13. epig. 58.—This is said to have been done by fat and figs. Horace. 1. 2. sat. 8.—Juvenal sets these large livers before an epicure as a great rarity. Sat. 5. 1. 114; and Persius, sat. 6. 1. 71. Pliny says, these large goose-livers were soaked in mulled milk, that is, I suppose milk mixed with honey and wine; and adds, "that it is uncertain whether Scipio Metellus, of consular dignity, or M. Sestius, a Roman knight, was the great discoverer of this excellent dish." A modern traveller, I believe Mr. Bry done, asserts that the art of enlarging the livers of geese still exists in Sicily; and it is to be lamented that he did not import it into his native country, as some method of affecting the human liver might psrhaps have been collected from it; besides the honour he might have acquired in improving our giblet pies. Our wiser caupones, I am told, know how to fatten their fowls, as well as their geese, for the London markets, by mix- ing gin, instead of figs and fat with their food; by which they are said to become sleepy, and to fatten apace, and probably ac- quired larger livers; as the swine are asserted to do, which are fed on the sediments of barrels in the distilleries; and which so frequently obtains in those, who ingurgitate much ale, or wine, or drams. II. The irritative diseases of the kidneys, pancreas, spleen, and other glands, are analagous to those of the liver above de- scribed, differing only in the consequences attending their ina- bility to action. For instance, when the secretory vessels of the kidneys become disobedient to the stimulus of the passing cur- rent of blood, no urine is separated or produced by them; their excretory mouths become filled with concreted mucus, or cal- culous matter, and in eight or ten days stupor and death super- vene in consequence of the retention of the feculent part of the blood. This disease in a slighter degree, or when only a part of the kidney is affected, is succeeded by partial inflammation of the 276 PARALYSIS, &c. Sect. XXX. o kidney in consequence of previous torpor. In that case greater actions of the secretory vessels occur, and the nucleus of gravel is formed by the inflamed mucous membranes of the tubuli uri- niferi, as farther explained in its place. This torpor, or paralysis of the secretory vessels of the kid- neys, like that of the liver, owes its origin to their being previous- ly habituated to too great stimulus; vvhich in this country is generally owing to the alcohol contained in ale or wine; and hence must be registered amongst the diseases owing to inebriety; though it may be caused by whatever occasionally inflames the kidney; as too violent riding on horseback, or the cold from a damp bed, or by sleeping on the cold ground; or perhaps by drinking in general too little aqueous fluids. III. I shall conclude this section on the diseases of the liver induced by spirituous liquors, with the well known story of Prometheus, which seems indeed to have been invented by phy- sicians in those ancient times, when all things were clothed in hieroglyphic, or in fable. Prometheus was painted as stealing fire from heaven, which might well represent the inflammable spirit produced by fermentation; which may be said to animate or enliven the man of clay: whence the conquests of Bacchus, as well as the temporary mirth and noise of his devotees. But the after punishment of those, who steal this accursed fire, is a vulture gnawing the liver; and well allegorizes the poor inebri- ate lingering for years under painful hepatic diseases. When the expediency of laying a further tax on the distillation of spiri- tuous liquors from grain was canvassed before the House of Commons some years ago, it was said of the distillers, with great truth, " They take the bread from the people, and convert it into poison!" Yet is this manufactory of disease permitted to con- tinue, as appears by its paying into the treasury above 900,000/. near a million of money annually. And thus, under the names of rum, brandy, gin, whiskey, usquebaugh, wine, cider, beer, and porter, alcohol has become the bane of the Christian world, as opium of the Mahometan. Evoe! parce, Liber, Parce, gravi metuende thyrso ! Hon. Skct. XXXI. 1. OF TEMPERAMENTS. 277 SECT. XXXI. OF TEMPERAMENTS. I. Tlie temperament of decreased irritability known by weak pulse, large pupils of the eyes, cold extremities. Are generally supposed to be too irritable. Bear pain better than labour. Natives of North America contrasted with those upon the coast of Africa. Narrow and broad-shouldered people. Irritable constitutions bear labour better than pain. II. Temperament of increased sensibility. Liable to intoxication, to inflammation, hemoploe, gutta serena, enthusiasm, delirium, reverie. These constitutions are indolent to voluntary exertions, and dull to irritations. The natives of South America, and brute animals of this temperament. III. Of increased voluntarily; these are subject to locked jaw, convulsions, epilepsy, mania. Are very active, bear cold, hunger, fatigue. Are suited to great exertions. This temperament distin- guishes mankind from other animals. IV. Of increased associ- ation. These have great memories, are liable to quartan agues, and stronger sympathies of parts with each other. V. Change of temperaments into one another. Ancient writers have spoken much of temperaments, but without sufficient precision. By temperament of the system, should be meant a permanent predisposition to certain classes of diseases: without this definition, a temporary predisposition to every distinct malady might be termed a temperament. There are four kinds of constitution, which permanently deviate from good health, and are perhaps sufficiently marked to be distin- guished from each other, and constitute the temperaments or pre- dispositions to the irritative, sensitive, voluntary, and associate classes of diseases. I. The Temperament of decreased Irritability. The diseases, vvhich are caused by irritation, most frequently originate from the defect of it; for those, which are immediately owing to the excess of it, as the hot fits of fever, are generally oc- casioned by an accumulation of sensorial power, in consequence of a previous defect of irritation, as in the preceding cold fits of fever. Whereas the diseases, which are caused by sensation and volition, most frequently originate from the excess of those sen- sorial powers, as will be explained below. The temperament of decreased irritability appears from the 27S OF TEMPERAMLXIS. Slct. X\XT. 1 following circumstances, which shew that the muscular fibres or organs of sense are liable to become torpid or quiescent, from less defect of stimulation than is productive of torpor or quiescence in other constitutions. 1. The first is the weak pulse, which in some constitutions is at the same time quick. 2. The next most marked criterion of this temperament, is the largeness of the aperture of the iris, or pupil of the eye, vvhich has been reckoned by some a beautiful feature in the female countenance, as an indication of delicacy, but to an experienced observer it is an indication of debility, and is therefore a defect, not an excellence. The third most marked circumstance in this constitution is, that the extremities, as the hands and feet, or nose and ears, are liable to become cold and pale in situations in respect to warmth, where those of greater strength are not affected. Those of this temperament are subject to hysteric affections, nervous fevers, hydrocephalus, scrofula, and consumption, and to all other diseases of debility. Those who possess this kind of constitution, are popularly sup- posed to be more irritable than is natural, but are in reality less so. This mistake has arisen from their generally having a greater quickness of pulse, as explained in Sect. XII. 1. 4. XII. 3. 3.; but this frequency of pulse is not necessary to the temperament, like the debility of it. Persons of this temperament are frequently found amongst the softer sex, and amongst narrow-shouldered men; who are said to bear labour worse, and pain better than others. This last cir- cumstance is supposed to have prevented the natives of North America from having been made slaves by the Europeans. They are a narrow-shouldered race of people, and will rather expire under the lash than be made to labour. Some nations of Asia have small hands, as may be seen by the handles of their scy me- tars; which, with their narrow shoulders, shew that they have not been accustomed to so great labour with their hands and arms, as the European nations in agriculture, and those on the coasts of Africa in swimming and rowing. Dr. Manningham, a popular accoucheur in the beginning of this century, observes in his aphorisms, that broad-shouldered men procreate broad-shoul- dered children. Now as labour strengthens the muscles cm- ployed, and increases their bulk, it would seem that a few gene- rations of labour or of indolence, may in this respect change the form and temperament of the body. On the contrary, those who are happily possessed of a great de- gree of irritability, bear labour better than pain; and are strong, active, and ingenious. But there is not properly a temperament Sect. XXXI. 1. OF TEMPERAMENTS. 279 of increased irritability tending to disease, because an increased quantity of irritative motions generally induces an increase of pleasure or pain, as intoxication, or inflammation; and then the new motions are the immediate consequences of increased sen- sation, not of increased irritation; which have hence been so per- petually confounded with each other. II. Temperament of Sensibility. There is not properly a temperament, or a predisposition to disease, from decreased sensibility, since irritability and not sensi- bility is immediately necessary to bodily heallh. Hence it is the excess of sensation alone, as it is the defect of irritation, that most frequently produces disease. This temperament of increased sen- sibility is known from the increased activity of all those motions of the organs of sense and muscles, which are exerted in conse- quence of pleasure or pain, as in the beginning of drunkenness, and in inflammatory fever. Hence those of this constitution are liable to inflammatory diseases, as hepatitis; and to that kind of consumption which is hereditary, and commences with slight re- peated haemoptoe. They have high-coloured lips, frequently dark hair and dark eyes with large pupils, and are in that cast subject to gutta serena. They are liable to enthusiasm, delirium, and reverie. In this last circumstance they are liable to start at the clapping of a door; because the more intent any one is on the passing current of his ideas, the greater surprise he experiences on their being dissevered by some external violence, as explained in Sect. XIX. on reverie. As in these constitutions more than the natural quantities of sensitive motions are produced by the increased quantity of sen- sation existing in the habit, it follows, that the irritative motions will be performed in some degree with less energy, owing to the great expenditure of sensorial power on the sensitive ones. Hence those of this temperament do not attend to slight stimulations, as explained in Sect. XIX. But when a stimulus is so great as to excite sensation, it produces greater sensitive actions of the sys- tem than in others: such as delirium or inflammation. Hence they are liable to be absent in company; sit or lie long in one posture; and in winter have the skin of their legs burnt into various colours by the fire. Hence also they are fearful of pain; covet music and sleep; and delight in poetry and romance. As the motions in consequence of sensation are more than na- tural, it also happens from the greater expenditure of sensorial power on thoin, thai the voluntary motions arc less easily exerted. 280 OF TEMPERAMENTS. Sect. XXXI. 3. Hence the subjects of this temperament are indolent in respect to all voluntary exertion, whether of mind or body. A race of people of this description seems to have been found by the Spaniards in the islands of America, where they first land- ed, ten of whom are said not to have consumed more food than one Spaniard, nor to have been capable of more than one-tenth of the exertion of a Spaniard. Robertson's History. In a state similar to this the greatest part of the animal world pass their lives, between sleep and inactive reverie, except when they are excited by the call of hunger. III. The Temperament of increased Voluntarily. Those of this constitution differ from both the last mentioned in this, that the pain, which gradually subsides in the first, and is productive of inflammation or delirium in the second, is in this succeeded by the exertion of the muscles or ideas, which are most frequently connected with volition; and they are thence subject to locked jaw, convulsions, epilepsy, and mania, as explained in Sect. XXXIV. Those of this temperament attend to the slightest irritations or sensations, and immediately exert themselves to ob- tain or avoid the objects of them; they can at the same time bear cold and hunger better than others, of vvhich Charles the Twelfth of Sweden was an instance. They are suited and generally prompted to all great exertions of genius or labour, as their desires are more extensive and more vehement, and their powers of at- tention and of labour greater. It is this facility of voluntary exer- tion, which distinguishes men from brutes, and which has made them lords of the creation. IV. The Temperament of increased Association. This constitution consists in the too great facility, with vvhich the fibrous motions acquire habits of association, and by which these associations become proportionably stronger than in those ol the other temperaments. Those of this temperament are slow in voluntary exertions, or in those dependent on sensation, or on irritation. Hence great memories have been said to be attended with less sense and less imagination from Aristotle down to the present time; for by the word memory these writers only under- stood the unmeaning repetition of words or numbers in the order they were received, without any voluntary efforts of the mind. In this temperament those associations of motions, which are t'ommonly termed sympathies, act with greater certainty and Sf.cT. XXXI. 5. OF TEMPERAMENTS. 281 energy as those between disturbed vision and the inversion of the motion of the stomach, as in sea-sickness; and the pains in the shoulder from hepatic inflammation. Add to this, that the catenated circles of actions are of greater extent than in the other constitutions. Thus if a strong vomit or cathartic be exhibited in this temperament, a smaller quantity will produce as great an effect, if it be given some weeks afterwards; whereas in other temperaments this is only to be expected, if it be exhibited in a few days after the first dose. Hence quartan agues are formed in those of this temperament, as explained in Section XXXII. on diseases from irritation, and other intermittents are liable to recur from slight causes many weeks after they have been cured by the bark. V. The first of these temperaments differs from the standard of health from defect, and the others from excess of sensorial power; but it sometimes happens that the same individual, from the changes introduced into his habit, by the different seasons of the year, modes or periods of life, or by accidental diseases, passes from one of these temperaments to another. Thus a long use of too much fermented liquor produces the temperament of increas- ed sensibility; great indolence and solitude that of decreased irri- tability; and want of the necessaries of life that of increased vol- untarily. vor.. f o ' 2"82 DISEASES Sfct. XXXII. 3 SECT. XXXII. DISEASES OF IRRITATION. I. Irritative fevers with strong pulse. With weak pulse. Symp- toms of fever. Their source. II. 1. Quick pulse is owing to decreased irritability. 2. Not in sleep or in apoplexy. 3. From inanition. Owing to deficiency of sensorial power. III. 1. Causes of fever. From defect of heat. Heat from secretions. Pain of cold in the loins and forehead. 2. Great expense of sensorial pern er in the vital motions. Immersion in cold water. Succeeding glow of heat. Difficult respiration in cold bathing explained. Why the cold bath invigorates. Bracing and relaxation are mechanical terms. 3. Uses of cold bathing. Uses of cold air in fevers. 4. Ague fits from cold air. Whence their periodical re- turns. IV. Defect of distention a cause of fever. Deficiency of blood. Transfusion of blood. V. 1. Defect of momentum of tlu blood from mechanic stimuli. 2. Air injected into the blood ves- sels. 3. Exercise increases the momentum of tlie blood. 4. Some- times bleeding increases the momentum of it. VI. Influence of the sun and moon on diseases. The chemical stimulus of the blood. Menstruation obeys the lunations. Queries. VII. Quiescence of large glands a cause of fever. Swelling of the precordia. VIII. Other causes of quiescence, as hunger, bad air, fear, anxiety. IX. 1. Symptoms of the cold fit. 2. Of the hot fit. 3. Second cold fit why. 4. Inflammation introduced, or delirium, or stupor. X. Recapitulation. Fever not an effort of nature to relieve herself Doctrine of spasm. I. When the contractile sides of the heart and arteries per- form a greater number of pulsations in a given time, and move through a greater area at each pulsation, whether these motions are occasioned by the stimulus of the acrimony, or quantity of the blood, or by their association with other irritative motions, or by the increased irritability of the arterial system, that is, by an in- creased quantity of sensorial, power, one kind of fever is produc- ed; which may be called synocha irritativa, or febris irrilativa pulsu forti, or irritative fever with strong pulse. When the contractile sides of the heart and arteries perform a greater number of pulsations in a given time, but move through a much less area at each pulsation, whether these motions are occasioned by defect of their natural stimuli, or by the defect of other irritative motions with which they are associated, or from the inirritability of the arterial system,, that is, from a, decreased skit. XXXII. 2. 1. OF IRRITATION, 283 quantity of sensorial power, another kind of fever arises; which may be termed typhus irritativus, or febris irrilativa pulsu de- bili, or irritative fever with weak pulse. The former of these fevers is the synocha of nosologists, and the latter the typhus mi- tior, or nervous fever. In the former there appears to be an increase of sensorial power, in the latter a deficiency of it; which is shewn to be the immediate cause of strength and weak- ness, as defined in Sect. XII. 1. 3. It should be added, that a temporary quantity of strength or debility may be induced by the defect or excess of stimulus above what is natural; and that in the same fever debility always exists during the cold Jit, though strength does not alio ays exist during the hot jit. These fevers are always connected with, and generally in- duced by, the disordered irritative motions of the organs of sense, or of the intestinal canal, or of the glandular system, or of the absorbent system; and hence are always complicated with some or many of these disordered motions, which are termed the symp- toms of the fever, and which compose the great variety of these diseases. The irritative fevers both with strong and with weak pulse, as well as the sensitive fevers with strong and with weak pulse, which are to be described in the next section, are liable to peri- odical remissions, and then they take the name of intermittent fevers, and are distinguished by the periodical times of their access. II. For the better illustration of the phenomena of irritative fevers, we must refer the reader to the circumstances of irritation explained in Sect. XII. and shall commence this intricate subject by speaking of the quick pulse, and proceed by considering many of the causes, vvhich either separately or in combination most frequently produce the cold fits of fevers. 1. If the arteries are dilated but to half their usual diameters, though they contract twice as frequently in a given time, they will circulate only half their usual quantity of blood: for as they are cylinders, the blood which they contain must be as the squares of their diameters. Hence when the pulse becomes quicker and smaller in the same proportion, the heart and arte- ries act with less energy than in their natural state. See Sect. XII. 1.4. That this quick small pulse is owing to want of irritability, appears, first, because it attends other symptoms of want of ir- ritability; and, secondly, because on the application of a stimu- lus greater than usual, it becomes slower and larger. Thus in cold fits of agues, in hysteric palpitations of the heart, and when 284 DISEASES sect. XXXII. 2. J. the body is much exhausted by haemorrhages, or by fatigue, as well as in nervous fevers, the pulse becomes quick and small; and, secondly, in all those cases if an increase of stimulus be add- ed, by giving a little wine or opium; the quick small pulse be- comes slower and larger, as any one may easily experience on himself, by counting his pulse after drinking one or two glasses of wine, when he is faint from hunger or fatigue. Now nothing can so strongly evince that this quick small pulse is owing to defect of irritability, as that an additional stimulus, above what is natural, makes it become slower and larger immediately; for what is meant by a defect of irritability, but that the arteries and heart are not excited into their usual exertions by their usual quantity of stimulus? but if you increase the quantity of stimulus, and they immediately act with their usual energy, this proves their previous want of their natural de- gree of irritability. Thus the trembling hands of drunkards in a morning become steady, and acquire strength to perform their usual offices, by the accustomed stimulus of a glass or two of brandy. 2. In sleep and in apoplexy the pulse becomes slower, which is not owing to defect of irritability, for it is at the same time larger; and thence the quantity of the circulation is rather in- creased than diminished. In these cases the organs of sense are closed, and the voluntary power is suspended, while the motions dependent on internal irritations, as those of digestion and secre- tion, are carried on with more than their usual vigour; which has led superficial observers to confound these cases with those arising from want of irritability. Thus if you lift up the eyelid of an apoplectic patient, who is not actually dying, the iris will, as usual, contract itself, as this motion is associated with the stimulus of light; but it is not so in the last stages of nervous fevers, where the pupil of the eye continues expanded in the broad day light: in the former case there is a want of voluntary power, in the latter a want of irritability. Hence also those constitutions which are deficient in quantity of irritability, and which possess too great sensibility, as during the pain of hunger, of hysteric spasms, or nervous headaches, arc generally supposed to have too much irritability; and opium, which in its due dose is a most powerful stimulant, is errone- ously called a sedative; because by increasing the irritative mo- tions it decreases the pains arising from defect of them. Why the pulse should become quicker both from an increase of irritation, as in the synocha irritativa, or irritative fever with strong pulse; and from the decrease of it, as in the typhus irrita- tivus, or irritative fever with weak pulse; seems paradoxical. Sect. XXXII. J. 3. OF IRRITATION. 285 The former circumstance needs no illustration; since if the stimu- lus of the blood, or the irritability of the sanguiferous system be increased, and the strength of the patient not diminished, it is plain that the motions must be performed quicker and stronger. In the latter circumstance the weakness of the muscular power of the heart is soon over-balanced by the elasticity of the coats of the arteries, which they possess besides a muscular power of contraction; and hence the arteries are distended to less than their usual diameters. The heart being thus stopped, when it is but half emptied, begins sooner to dilate again; and the ar- teries being dilated to less than their usual diameters, begin so much sooner to contract themselves; insomuch, that in the last stages of fevers with weakness the frequency of pulsation of the heart and arteries become doubled; which, however, is never the case in fevers with strength, in which they seldom exceed 118 or 120 pulsations in a minute. It must be added, that in these cases, while the pulse is very small and very quick, the heart often feels large, and labouring to one's hand; which coincides with the above explanation, shewing that it does not completely empty itself. 3. In cases, however, of debility from paucity of blood, as in animals which are bleeding to death in the slaughter-house, the quick pulsations of the heart and arteries maybe owing to their not being distended to more than half their usual diastole; and in consequence they must contract sooner, or more frequently, in a given time. As weak people are liable to a deficient quantity of blood, this cause may occasionally contribute to quicken the pulse in fevers with debility, which may be known by applying one's hand upon the heart as above; but the principal cause I suppose to consist in the diminution of sensorial power. When a mus- cle contains, or is supplied with but little sensorial power, its contraction soon ceases, and in consequence may soon recur, as is seen in the trembling hands of people weakened by age or by drunkenness. See Sect. XII. 1. 4. XII. 3. 4. It may nevertheless frequently happen, that both the deficiency of stimulus, as where the quantity of blood is lessened, (as de- scribed in No. 4. of this section,) and the deficiency of sensorial power, as in (hose of the temperament of inirritability, described in Sect. XXXI. occur at the same time; which will thus add to the quickness of the pulse and to the danger of the disease. III. 1. A certain degree of heat is necessary to muscular mo- lion, and is, in consequence, essential to life. This is observed in those animals and insects which pass the cold season in a tor- pid state, and vvhich revive on being warmed by the fire. This necessary stimulus of heat has two sources: one from the fluid 2$b' DISEASES Sect. XXXII. 3.2. atmosphere of heat, in vvhich all things are immersed, and the other from the internal combinations of the particles, which form the various fluids, vvhich are produced in the extensive systems of the glands. When either the external heat, which surrounds us, or the internal production of it, becomes lessened to a certain degree, the pain of cold is perceived. This pain of cold is experienced most sensibly by our teeth, when ice is held in the mouth; or by our whole system, after having been previously accustomed to much warmth. It is pro- bable, that this pain does not arise from the mechanical or che- mical effects of a deficiency of heat; but that, like the organs of sense by which we perceive hunger and thirst, this sense of heat suffers pain, when the stimulus of its object is wanting to excite the irritative motions of the organ; that is, when the sensorial power becomes too much accumulated in the quiescent fibres.— S: j Sect. XII. 5. 3. For as the peristaltic motions of the sto- mach are lessened, when the pain of hunger is great, so the ac- tion of the cutaneous capillaries are lessened during the pain of cold; as appears by (he paleness of Ihe skin, as explained in Sect. XIV. 6. on the Production of Ideas. The pain in the small of the back and forehead in the cold fits of the ague, in nervous hemicrania, and in hysteric paroxysms, when all the irritative motions are much impaired, seems to arise from this cause: the vessels of these membranes, or muscles, be- come torpid by their irritative associations with other parts of the body, and thence produce less of their accustomed secretions, and in consequence less heat is evolved, and they experience the pain of cold; which coldness may often be felt by the hand applied upon the affected part. 2. The importance of a greater or less deduction of heat from the system, will be more easy to comprehend, if yve first consider the great expense of sensorial power used in carrying on the vital motions; that is, which circulates, absorbs, secretes, aerates, and elaborates the whole mass of fluids with unceasing assiduity. The sensorial power, or spirit of animation, used in giving perpetual and strong motion to the heart, which over- comes the elasticity and vis inertiae of the whole arterial system; next the expense of sensorial power in moving with great force and velocity the innumerable trunks and ramifications of the arterial system; the expense of sensorial power in circulating the whole mass of blood through the long and intricate intor- tions of the very fine vessels, which compose the glands and capillaries; then the expense of sensorial power in the exer- tions of the absorbent extremities of all the lacteals, and of all the lymphatics, which open their mouths on the external sur- Sect. XXXII. ., 2. OF IRRITATION. 287 face of the skin, and on the internal surfaces of every cell or interstice of the body; then the expense of sensorial power in^ the venous absorption, by which the blood is received from the capillary vessels, or glands, where the arterial power ceases, and is drunk up, and returned to the heart; next the expense of sensorial power used by the muscles of respiration in their of- fice of perpetually expanding the bronchia, or air-vessels, of the lungs; and lastly in the unceasing peristaltic motions of the stomach and whole system of intestines, and in all the secre- tions of bile, gastric juice, mucus, perspirable matter, and the various excretions from the system. If we consider the cease- less expense of sensorial power thus perpetually employed, it will appear to be much greater in a day than all the voluntary exer- tions of our muscles and organs of sense consume in a week; and all this without any sensible fatigue! Now, if but a part of these vital motions are impeded, or totally stopped for but a short time, we gain an idea that there must be a great accumulation of sensorial power; as its production in these organs, which are sub- ject to perpetual activity, is continued during their quiescence, and is in consequence accumulated. While, on the contrary, where those vital organs act too for- cibly by increase of stimulus without a proportionally increased production of sensorial power in the brain, it is evident, that a great deficiency of action, that is, torpor, must soon follow, as in fevers; whereas the locomotive muscles, which act only by in- tervals, are neither liable to so great accumulation of sensorial power during their times of inactivity, nor to so great an exhaus- tion of it during their times of action. Thus, on going into a very cold bath, suppose at 33 degrees of heat on Fahrenheit's scale, the action of the subcutaneous ca- pillaries, or glands, and of the mouths of the cutaneous absorb- ents is diminished, or ceases for a time. Hence less or no blood passes these capillaries, and paleness succeeds. But soon- after emerging from the bath, a more florid colour and a greater degree of heat are generated on the skin than were possessed be- fore immersion; for the capillary glands, after this quiescent state, occasioned by the want of stimulus, become more irritable than usual to their natural stimuli, owing to the accumulation of sei.sorial power, and hence a greater quantity of blood is trans- mitted through them, and a greater secretion of perspirable matter; and, in consequence, a greater degree of heat succeeds. During the continuance in cold water the breath is cold, and the act of respiration quick and laborious; which have gene- rally been ascribed to the obstruction of the circulating fluid by a- spasm of the cutaneous vessels, and by a consequent aecumu- 288 DISEASES Stct. XXXII 3. o. lation of blood in the lungs, occasioned by the pressure as well as by the coldness of the water. This is not a satisfactory account of this curious phenomenon, since at this time the whole circula- tion is less, as appears from the smallness of the pulse and cold- ness of the breath; which shew that less blood passes through the lungs in a given time; the same laborious breathing immediately occurs when the paleness of the skin is produced by fear, where no external cold or pressure are applied. The minute vessels of the bronchia, through which the blood passes from the arterial to the venal system, and which correspond with the cutaneous capillaries, have frequently been exposed to cold air, and become quiescent along with those of the skin; and hence their motions are so associated together, that when one is affected either with quiescence or exertion, the other sympathizes with it, according to the laws of irritative association. See Sect. XXVII. I. on haemorrhages. Besides the quiescence of the minute vessels of the lungs, there are many other systems of vessels which become torpid from their irritative associations with those of the skin, as the absorbents of the bladder and intestines; whence an evacuation of pale urine occurs, when the naked skin is exposed only to the coldness of the atmosphere; and sprinkling the naked body with cold water is known to remove even pertinacious constipation of the bowels. From the quiescence of such extensive systems of vessels as the glands and capillaries of the skin, and the minute vessels of the lungs, with their various absorbent series of vessels, a great ac- cumulation of sensorial powers is occasioned; part of which is again expended in the increased exertion of all these vessels, with an universal glow of heat in consequence of this exertion, and the remainder of it adds vigour to both the vital and voluntary exer- tions of the whole day. If the activity of the subcutaneous vessels, and of those with which their actions are associated, was too great before cold im- mersion, as in the hot days of summer, and by that means the sensorial power was previously diminished, we see the cause why the cold bath gives such present strength; namely, by stopping the unnecessary activity of the subcutaneous vessels, and thus preventing the too great exhaustion of sensorial power; which, in metaphorical language, has been called bracing the system; which is, however, a mechanical term, only applicable to drums, or musical strings: as on the contrary the word relaxation, when applied to living animal bodies, can only mean too small a quan- tity of stimulus, or too small a quantity of sensorial power; as explained in Sect. XII. 1. 3. This experiment of cold bathing presents us with a simple Sect XXXII 3. 4. OF IRRITATION. 289 fever-fit; for the pulse is weak, small, and quick during the cold immersion; and becomes strong, full, and quick during the sub- sequent glow of heat; till in a few minutes these symptoms sub- side, and the temporary fever ceases. In those constitutions where the degree of inirritability, or of debility, is greater than natural, the coldness and paleness of the skin with the quick and weak pulse continue a long time after the patient leaves the bath; and the subsequent heat approaches by unequal flushings,- and he feels himself disordered for many hours. Hence the bathing in a cold spring of water, where the heat is but forty-eight degrees on Fahrenheit's thermometer, much disagrees with those of weak or inirritable habits of body; who possess so little sensorial power, that they cannot without iujury bear to have it diminished eyeu for a short time; but who can nevertheless bear the more temperate coldness of Buxton bath, which is about eighty degrees of heat, and which strengthens them, and makes them by habit less liable to great quiescence from small variations of cold; and thence less liable to be disor- dered by the unavoidable accidents of life. Hence it appears, why people of these inirritable constitutions, vvhich is another ex- pression for sensorial deficiency, are often much injured by bath- ing in a cold spring of water; and why they should continue but a very short time in baths, which are colder than their bodies; and should gradually increase both the degree of the coldness of the water, and the time of their continuance in it, if they would obtain salutary effects from cold immersions. See Sect. XII. 2. 1. On the other hand, in all cases where the heat of the external surface of the body, or of the internal surface of the lungs, is greater than natural, the use of exposure to cool air may be de- duced. In fever fits attended with strength, that is, with great quantity of sensorial power, it removes the additional stimulus of heat from the surfaces above mentioned, and thus prevents their excess of useless motion; and in fever-fits attended with de- bility, that is, with a deficiency of the quantity of sensorial power, it prevents the great and dangerous waste of sensorial power ex- pended in the unnecessary increase of the actions of the glands and capillaries of the skin and lungs. 4. In the same manner when any one is long exposed to very cold air, a quiescence is produced of the cutaneous and pulmonary capillaries and absorbents, owing to the deficiency of their usual stimulus of heat; and this quiescence of so great a quantity of vessels affects, by irritative association, the whole absorbent and glandular system, which becomes in a greater or less degree quiescent, and a cold fit of fever is produced. TOT.. I. P p 290 DISEASES Sect. XXXII. 4. 1. If the deficiency of the stimulus of heat is very great, the quies- cence becomes so general as to extinguish life, as in those who are frozen to death. If the deficiency of heat be in less degree, but yet so great as in some measure to disorder the system, and should occur the suc- ceeding day, it will induce a greater degree of quiescence than before from its acting in concurrence with the period of the diurnal circle of actions, explained in Sect. XXXVI. Hence from a small beginning a greater and greater degree of quiescence may be induced, till a complete fever-fit is formed; and which will continue to recur at the periods bv which it was produced. See Sect. XVII. 3. 6. If the degree of quiescence occasioned by defect of the stimu- lus of heat be very great, it will recur a second time by a slighter cause, than that which first induced it. If the cause, which induces the second fit of quiescence, recurs the succeeding day, the quotidian fever is produced; if not till the alternate day, the tertian fever; and if not till after seventy-two hours from the first fit of quiescence, the quartan fever is formed. This last kind of fever recurs less frequently than the other, as it is a dis- ease only of those of the temperament of associability, as men- tioned in Sect. XXXI.; for in other constitutions ths capability of forming a habit ceases before the new cause of quiescence is again applied, if that does not occur sooner than in seventy-two hours. And hence those fevers, whose cause is from cold air of the night or morning, are more liable to observe the solar day in their periods; while those from other causes frequently observe the lunar day in their periods, their paroxysms returning near an hour later every day, as explained in Sect. XXXVI. IV. Another frequent cause of the cold fits of fever is the de- fect of the stimulus of distention. The whole arterial system would appear by the experiments of Haller, to be irritable by no other stimulus, and the motions of the heart and alimentary canal are certainly in some measure dependent on the same cause. See Sect. XIV. 7. Hence there can be no wonder, that the diminu- tion of distention should frequently induce the quiescence, which •constitutes the beginning of fever-fits. Monsieur Lieutaud has judiciously mentioned the deficiency of the quantity of blood amongst the causes of diseases, which he says is frequently evident in dissections; fevers are hence brought on by great haemorrhages, diarrhoeas, or other evacua- tions; or from the continued use of diet, which contains but little nourishment; or from the exhaustion occasioned by vio- lent fatigue, or by those chronic diseases in which the digestici s f.ct. XXXII. 5. 1. OF IRRITATION. 291 is much impaired; as where the stomach has been long affected with the gout or scirrhus; or in the paralysis of the liver, as de- scribed in Sect. XXX. Hence a paroxysm of gout is liable to recur on bleeding or purging; as the torpor of some viscus, vvhich precedes the inflammation of the foot, is thus induced by the want of the stimulus of distention. And hence the extremities of the body, as the nose and fingers, are more liable to become cold when we have long abstained from food; and hence the pulse is increased both in strength and velocity above the natural standard after a full meal by the stimulus of distention. However, this stimulus of distention, like the stimulus of heat above described, though it contributes much to the due action not only of the heart, arteries, and alimentary canal, but seems necessary to the proper secretion of all the various glands; yet perhaps it is not the sole cause of any of these numerous mo- tions: for as the lacteals, cutaneous absorbents, and the various glands appear to be stimulated into action by the peculiar pun- gency of the fluids they absorb, so in the intestinal canal the pungency of the digesting aliment, or the acrimony of the fasces, seems to contribute, as well as their bulk, to promote the peri- staltic motions; and in the arterial system, the momentum of the particles of the circulating blood, and their acrimony, stimulate the arteries, as well as the distention occasioned by it. Where the pulse is small this defect of distention is present, and con- tributes much to produce the febris irritativa pulsu debili, or irri- tative fever with weak pulse, called by modern writers nervous fever, as a predisponent cause. See Sect. XII. 1. 4. Might not the transfusion of blood, suppose of four ounces daily from a strong man, or other healthful animal, as a sheep or an ass, be used in the early state of nervous or putrid fevers with great prospect of success? V. The defect of the momentnm of the particles of the circu- lating blood is another cause of the quiescence, with vvhich the cold fits of fever commence. This stimulus of the momentum of the progressive particles of the blood does not act over the whole body like those of heat and distention above described, but is confined to the arterial system; and differs from the stimulus of the distention of the blood, as much as the vibra- tion of the air does from the currents of it. Thus are the dif- ferent organs of our bodies stimulated by four different mechanic properties of the external world: the sense of touch by the pressure of solid bodies so as to distinguish their figure; the muscular system by the distention, vvhich they occasion; the in- ternal surface of the arteries, by the momentum of their moving particles; and the auditory nerves, by the vibration of them: >Q0 DISEASES Sect. XXXII. 5. 2 and these four mechanic properties are as different from each other as the various chemical ones, which are adapted to the numerous glands, and to the other organs of sense. 2. The momentum of the progressive particles of blood is com- pounded of their velocity and their quantity of matter: hence whatever circumstances diminish either of these without propor- tionally increasing the other, and without superadding either of the general stimuli of heat or distention, will tend to produce a quiescence of the arterial system, and from thence of all the other irritative motions, which are connected with it. Hence in all those constitutions or diseases where the blood contains a greater proportion of serum, vvhich is the lightest part of its composition, the pulsations of the arteries are weaker, as in nervous fevers, chlorosis, and hysteric complaints; for in these cases the momentum of the progressive particles of blood is less; and hence, where the denser parts of its composition abound, as the red part of it, or the coagulable lymph, the arterial pulsations are stronger; as in those of robust health, and in inflammatory diseases. That this stimulus of the momentum of the particles of the circulating fluid is of the greatest consequence to the arterial action, appears from the experiment of injecting air into the blood vessels, which seems to destroy animal life from the want of this stimulus of momentum; for the distention of the arteries is not diminished by it, it possesses no corrosive acri- mony, and is less liable to repass the valves than the blood itself; since air-valves in all machinery require much less accuracy of construction than those which are opposed to water. 3. One method of increasing the velocity of the blood, and in consequence the momentum of its particles, is by the exercise of the body, or by the friction of its surface; so, on the contrary, too great indolence contributes to decrease this stimulus of the momentum of the particles of the circulating blood, and thus tends to induce quiescence; as is seen in hysteric cases, and chlorosis, and the other diseases of sedentary people. 4. The velocity of the particles of the blood in certain cir- cumstances is increased by venesection, which, by removing a part of it, diminishes the resistance to the motion of the other part, and hence the momentum of the particles of it is increas- ed. This maybe easily understood by considering it in the ex- treme, since, if the resistance was greatly increased, so as to over- come the propelling power, there could be no velocity, and in consequence no momentum at all. From this circumstance arises that curious phenomenon, the truth of vvhich I have been more than once witness to, that venesection will often instanta- Sect. XXXII. 6. 1. OF IRRITATION. 29,3 neously relieve those nervous pains, which attend the cold pe- riods of hysteric, asthmatic, or epileptic diseases; and that even where large doses of opium have been in vain exhibited. In these cases the pulse becomes stronger after the bleeding, and the extremities regain their natural warmth; and an opiate then given acts with much more certain effect. VI. There is another cause, which seems occasionally to in- duce quiescence into some part of our system, I mean the in- fluence of the sun and moon; the attraction of these luminaries, by decreasing the gravity of the particles of the blood, cannot af- fect their momentum, as their vis inertiae remains the same; but it may nevertheless produce some chemical change in them, because whatever affects the general attractions of the particles of matter may be supposed from analogy to affect their specific attractions or affinities: and thus the stimulus of the particles of blood may be diminished, though not their momentum. As the tides of the sea obey the southing and northing of the moon, (allowing for the time necessary for their motion, and the ob- structions of the shores,) it is probable, that there are also at- mospheric tides on both sides of the earth, which, to the inhabi- tants of another planet, might so deflect the light as to resemble the ring of Saturn. Now as these tides of water, or of air, are raised by the diminution of their gravity, it follows, that their pressure on the surface of the earth is no greater than the pressure of the other parts of the ocean, or of the atmosphere, where no such tides exist; and therefore that they cannot affect the mer- cury in the barometer. In the same manner, the gravity of all other terrestrial bodies is diminished at the times of the southing and northing of the moon, and that in a greater degree when this coincides with the southing and northing of the sun, and this in a still greater degree about the times of the equinoxes. This decrease of the gravity of all bodies during the time the moon passes our zenith or nadir might possibly be shewn by the slower vibrations of a pendulum, compared with a spring clock, or with astronomical observation. Since a pendulum of a cer- tain length moves slower at the line than near the poles, because the gravity being diminished and the vis inertia? continuing the same, the motive power is less, but the resistance to be overcome continues the same. The combined powers of the lunar and solar attraction are estimated by Sir Isaac Newton not to exceed one 7,868,850th part of the power of gravitation, which seems indeed but a small circumstance to produce any considerable ef- fect on the weight of sublunary bodies, and yet this is sufficient to raise the tides at the equator above ten feet high; and if it be considered, what small impulses of other bodies produce their 291 DISEASES Slct. XXXII. 6. I. effects on the organs of sense adapted to the perception of them, as of vibration on the auditory nerves, we shall cease to be sur- prised, that so minute a diminution in the gravity of the particles of blood should so far affect their chemical changes, or their stimulating quality, as, joined with other causes, sometimes to produce the beginnings of diseases. Add to this, that if the lunar influence produces a very small degree of quiescence at first, and if that recurs at certain periods even with less power to produce quiescence than at first, yet the quiescence will daily increase by the acquired habit acting at the same time, till at length so great a degree of quiescence is induced as to produce phrensy, canine madness, epilepsy, hysteric pains, or cold fits of fever, instances of many of which are to be found in Dr. Mead's work on this subject. The solar influence also ap- pears daily in several diseases; but as darkness, silence, sleep, and our periodical meals mark the parts of the solar circle of ac- tions, it is sometimes dubious to which of these the periodical returns of these diseases are to be ascribed. As far as I have been able to observe, the periods of inflam- matory diseases observe the solar day; as the gout and rheuma- tism have their greatest quiescence about noon and midnight, and their exacerbations some hours after; as they have more frequently their immediate cause from cold air, inanition, or fa- tigue, than from the effects of lunations: whilst the cold fits of hysteric patients, and those in nervous fevers, more frequently occur twice a day, later by near half an hour each time, accord- ing to the lunar day; whilst some fits of intermittents, which are undisturbed by medicines, return at regular solar periods, and others at lunar ones; which may, probably, be owing to the difference of the periods of those external circumstances of cold, inanition, or lunation, which immediately caused them. We must, however, observe, that the periods of quiescence and exacerbation in diseases do not always commence at the times of the syzygies or quadratures of the moon and sun, or at the times of their passing the zenith or nadir; but as it is probable, that the stimulus of the particles of the circumfluent blood is gradually diminished from the time of the quadratures to that of the syzygies, the quiescence may commence at any hour, when, co-operating with other causes of quiescence, it becomes great enough to produce a disease: afterwards it will continue to recur at the same period of the lunar or solar influence; the same cause operating conjointly with the acquired habit, that is, with the catenation of this new motion with the dissevered links of the lunar or solar circles of animal action. In this manner the periods of menstruation obey the lunar Sect. XXXII. 7.1. OF IRRITATION. 295 month with great exactness in healthy patients, (and perhaps the venereal orgasm in brute animals does the same,) yet these pe- riods do not commence either at the syzygies or quadratures of the lunations, but at whatever time of the lunar periods they be- gin, they observe the same in their returns till some greater cause disturbs them. Hence, though the best way to calculate the time of the ex- pected returns of the paroxysms of periodical diseases is to count the number of hours between the commencement of the two pre- ceding fits, yet the following observations may be worth attend- ing to, when we endeavour to prevent the returns of maniacal or epileptic diseases; whose periods (at the beginning of them es- pecially) frequently observe the syzygies of the moon and sun, and particularly about the equinox. The greatest of the two tides happening in every revolution of the moon, is that when the moon approaches nearest to the zenith or nadir; for this reason, while the sun is in the northern signs, that is, during the vernal and summer months, the greater of the two diurnal tides in our latitude is that, when the moon is above the horizon; and when the sun is in the southern signs, or during the autumnal and winter months, the greater tide is that, which arises when the moon is below the horizon; and as the sun approaches somewhat nearer the earth in winter than in summer, the greatest equinoctial tides are observed to be a little before the vernal equinox, and a little after the autumnal one. Do not the cold periods of lunar diseases commence a few hours before the southing of the moon during the vernal and summer months, and before the northing of the moon during the autumnal and winter months? Do not palsies and apoplexies, which occur about the equinoxes, happen a few days before the vernal equinoctial lunation, and after the autumnal one? Are not the periods of those diurnal diseases more obstinate, that commence many hours before the southing or northing of the moon, than of those which commence at those times? Are not those palsies and apoplexies more dangerous which commence many days before the syzygies of the moon, than those which happen at those times? See Sect. XXXVI. on the periods of diseases. VII. Another very frequent cause of the cold fit of fever is the quiescence of some of those large congeries of glands, vvhich compose the liver, spleen, or pancreas; one or more of vvhich are frequently so enlarged in the autumnal intermittents as to be perceptible to the touch externally, and are called by the vul- gar ague-cakes. As these glands are stimulated into action bv the specific pungency of the fluids, vvhich they absorb, the general 296 DISEASES Sect. XXXII. 8. t. cause of their quiescence seems to be too great insipidity of the fluids of the body, co-operating perhaps at the same time with other general causes of quiescence. Hence, in marshy countries at cold seasons, which have suc- ceeded hot ones, and amongst those, who have lived on innutri- tious and unstimulating diet, these agues are most frequent. The enlargement of these quiescent viscera, and the swelling of the praecordia in many other fevers, is, most probably, owing to the same cause; which may consist in a general deficiency of the production of sensorial power, as well as in the diminished sti- mulation of the fluids; and when the quiescence of so great a number of glands, as constitute one of those large viscera, com- mences, all the other irritative motions are affected by their con- nexion with it, and the cold fit of fever is produced. VIII. There are many other causes which produce quiescence of some part of the animal system, as fatigue, hunger, thirst, bad diet, disappointed love, unwholesome air, exhaustion from evacu- ations, and many others: but the last cause, that we shall men- tion, as frequently productive of cold fits of fever, is fear or anxiety of mind. The pains, which we are first and most generally acquainted with, have been produced by defect of some stimulus; thus, soon after our nativity we become acquainted with the pain from the coldness of the air, from the want of re- spiration, and from the want of food. Now all these pains oc- casioned by defect of stimulus are attended with quiescence of the organ, "and at the same time with a greater or less degree of quiescence of other parts of the system: thus, if we even endure the pain of hunger so as to miss one meal instead of our daily habit of repletion, not only the peristaltic motions of the stomach and bowels are diminished, but we are more liable to coldness of our extremities, as of our noses, and ears, and feet, than at other times. Now, as fear is originally excited by our having experienced pain, and is itself a painful affection, the same quiescence of other fibrous motions accompanies it, as has been most frequent- ly connected with this kind of pain, as explained in Sect. XVI. 8. 1. as the coldness and paleness of the skin, trembling, difficult respiration, indigestion, and other symptoms, which contribute to form the cold fit of fevers. Anxiety is fear continued through a longer time, and, by producing chronical torpor of the system, extinguishes life slowly, by what is commonly termed a broken heart. IX. 1. We now step forwards to consider the other symp- toms in consequence of the quiescence which begins the fits of fever. If by any of the circumstances before described, or by Sect. XXXII. 9. 1. OF IRRITATION. 297 two or more of them acting at the same time, a great degree of quiescence is induced on any considerable part of the circle of irritative motions, the whole class of them is more or less dis- turbed by their irritative associations. If this torpor be occa- sioned by a deficient supply of sensorial power, and happens to any of those parts of the system which are accustomed to per- petual activity, as the vital motions, the torpor increases rapidly, because of the great expenditure of sensorial power by the in- cessant activity of those parts of the system, as shewn in No. 3. 2. of this Section. Hence a deficiency of all the secretions suc- ceeds, and as animal heat is produced in proportion to the quan- tity of those secretions, the coldness of the skin is the first cir- cumstance which is attended to. Dr. Martin asserts, that some parts of his body were warmer than natural in the cold fit of fever; but it is certain, that those which are uncovered, as the fingers, and nose, and ears, are much colder to the touch, and paler in appearance. It is possible, that his experiments were made at the beginning of the subsequent hot fits; which com- mence with partial distributions of heat, owing to some parts of the body regaining their natural irritability sooner than others. From the quiescence of the anastomosing capillaries a pale- ness of the skin succeeds, and a less secretion of the perspirable matter; from the quiescence of the pulmonary capillaries a dif- ficulty of respiration arises; and from the quiescence of the other glands less bile, less gastric and pancreatic juice, are se- creted into the stomach and intestines, and less mucus and saliva are poured into the mouth; whence arises the dry tongue, cos- tiveness, dry ulcers, and paucity of urine. From the quiescence of the absorbent system arises the great thirst, as less moisture is absorbed from the atmosphere. The absorption from the atmo- sphere was observed by Dr. Lister to amount to eighteen ounces in one night, above what he had at the same time insensibly per- spired. See Langrish. On the same account the urine is pale, though in small quantity, for the thinner part is not absorbed from it; and when repeated ague fits continue long, the legs swell from the diminished absorption of the cellular absorbents. From the quiescence of the intestinal canal a loss of appetite and flatulencies proceed. From the partial quiescence of the glandular viscera a swelling and tension about the praecordia be- come sensible to the touch; which are occasioned by the delay of the fluids from the defect of venous or lymphatic absorption. The pain of the forehead, and of the limbs, and of the small of the back, arises from the quiescence of the membranous fascia or muscles of those parts, in the same manner as the skin be- comes painful, when the vessels, of vvhich it is composed, be- VOL. i. qq 298 DISEASES Sect. XXXII. 9,2 come quiescent from cold. The trembling in consequence of the pain of coldness, the restlessness, and the yawning, and stretching of the limbs, together with the shuddering, or rigors, are convulsive motions ; and will be explained amongst the dis- eases of volition; Sect. XXXIV. Sickness and vomiting are a frequent symptom in the begin- nings of fever fits, the muscular fibres of the stomach share the general torpor and debility of the system; their motions become first lessened, and stop, and then become retrograde; for the act of vomiting, like the globus hystericus and the borborigmi of hypochondriasis, is always a symptom of debility, either from want of stimulus, as in hunger; or from want of sensorial power, as after intoxication; or from sympathy with some other torpid ir- ritative motions, as in the cold fits of ague. See Sect. XII. 5. 5. XXIX. 11. and XXXV. 1. 3. where this act of vomiting is further explained. The small pulse, which is said by some writers to be slow at the commencement of ague-fits, and which is frequently trem- bling and intermittent, is owing to the quiescence of the heart and arterial system, and to the resistance opposed to the circu- lating fluid from the inactivity of all the glands and capillaries. The great weakness and inability to voluntary motions, with the insensibility of the extremities, are owing to the general quies- cence of the whole moving system; or, perhaps, simply to the deficient production of sensorial power. If all these symptoms are further increased, the quiescence of all the muscles, including the heart and arteries, becomes com- plete, and death ensues. This is, most probably, the case of those who are starved to death with cold, and of those who are said to die in Holland from long skating on their frozen canals. 2. As soon as this general quiescence of the system ceases, either by the diminution of the cause, or by the accumulation of sensorial power, (as in syncope, Sect. XII. 7. 1.) which is the natural consequence of previous quiescence, the hot fit com- mences. Every gland of the body is now stimulated into stronger action than is natural, as its irritability is increased by accumulation of sensorial power during its late quiescence, a superabundance of all the secretions is produced, and an increase of heat in consequence of the increase of these secretions. The skin becomes red, and the perspiration great, owing to the in- creased action of the capillaries during the hot part of the pa- roxysm. The secretion of perspirable matter is perhaps greater during the hot fit than in the sweating fit which follows; but as the absorption of it also is greater, it does not stand on the skin »n visible drops: add to this, that the evaporation of it also ■mxt. XXXII. 9. 2. OF IRRITATION. 299 is greater, from the increased heat of the skin. But at the de- cline of the hot fit, as the mouths of the absorbents of the skin are exposed to the cooler air, or bed-clothes, these vessels sooner lose their increased activity, and cease to absorb more than their natural quantity: but the secerning vessels for some time longer, being kept warm by the circulating blood, continue to pour out an increased quantity of perspirable matter, which now stands on the skin in large visible drops; the exhalation of it also being lessened by the greater coolness of the skin, as well as its ab- sorption by the diminished action of the lymphatics. See Class I. 1. 2. 3. The increased secretion of bile and of other fluids poured into the intestines frequently induces a purging at the decline of the hot fit; for as the external absorbent vessels have their mouths ex- posed to the cold air, as above mentioned, they cease to be ex- cited into unnatural activity sooner than the secretory vessels, whose mouths are exposed to the warmth of the blood: now, as the internal absorbents sympathize with the external ones, these also, which during the hot fit drank up the thinner part of the bile, or of other secreted fluids, lose their increased activity be- fore the gland loses its increased activity, at the decline of the hot fit; and the loose dejections are produced from the same cause that the increased perspiration stands on the surface of the skin, from the increased absorption ceasing sooner than the in- creased secretion. The urine during the cold fit is in small quantity and pale, both from a deficiency of the secretion and a deficiency of the absorption. During the hot fit it is in its usual quantity, but very high coloured and turbid, because a greater quantity had been secreted by the increased action of the kidneys, and also a greater quantity of its more aqueous part had been absorbed from it in the bladder by the increased action of the absorbents; and lastly, at the decline of the hot fit it is in large quantity and less coloured, or turbid, because the absorbent vessels of the bladder, as observed above, lose their increased action by sympathy with the cutaneous ones sooner than the secretory vessels of the kid- neys lose their increased activity. Hence the quantity of the sedi- ment, and the colour of the urine, in fevers, depend much on the quantity secreted by the kidneys, and the quantity absorbed from it again in the bladder: the kinds of sediment; as the lateritious, purulent, mucous, or bloody sediments, depend on other causes. It should be observed, that if the sweating be increased by the heat of the room, or of the bed-clothes, a paucity of turbid urine will continue to be produced, as the absorbents of the bladder will have their activity increased by their sympathy with the 300 DISEASES Sect. XXXII. 9. 3. vessels of the skin, for the purpose of supplying the fluid expend- ed in perspiration. The pulse becomes strong and full, owing to the increased irri- tability of the heart and arteries, from the accumulation of sen- sorial power during their quiescence, and to the quickness of the return of the blood from the various glands and capillaries. This increased action of all the secretory vessels does not occur very suddenly, nor universally at the same time. The heat seems to begin about the centre, and to be diffused from thence irregularly to the other parts of the system. This may be owing to the situation of the parts which first became quiescent and caused the fever-fit, especially when a hardness or tumour about the prae- cordia can be felt by ihe hand; and hence this part, in whatever viscus it is seated, might be the first to regain its natural or in- creased irritability. 3. It must be here noted, that, by the increased quantity of heat, and of the impulse of the blood at the commencement of the hot fit, a great increase of stimulus is induced, and is now added to the increased irritability of the system, which was occasioned by its previous quiescence. This additional stimulus of heat and momentum of the blood augments the violence of the movements of the arterial and glandular system in an increasing ratio. These violent exertions still producing more heat and greater momentum of the moving fluids, till at length the sensorial power becomes wasted by this great stimulus beneath its natural quantity, and predisposes the system to a second cold fit. At length all these unnatural exertions spontaneously subside with the increased irritability that produced them; and which was itself produced by the preceding quiescence, in the same manner as the eye, on coming from darkness into day-light, in a little time ceases to be dazzled and pained, and gradually recovers its natural degree of irritability. . 4. But if the increase of irritability, and the consequent in- crease of the stimulus of heat and momentum, produce more vio- lent exertions than those above described; great pain arises in some part of the moving system, as in the membranes of the brain, pleura, or joints; and new motions of the vessels are pro- duced in consequence of this pain, which are called inflamma- tion; or delirium or stupor arises; as explained in Sect. XXI. and XXXIII.: for the immediate effect is the same, whether the great energy of the moving organs arises from an increase of stimulus or an increase of irritability; though in the former case the waste of sensorial power leads to debility, and in the latter to health. Sect. XXXII. 10. 1. OF IRRITATION. 301 Recapitulation. X. Those muscles which are less frequently exerted, and whose actions are interrupted by sleep, acquire less accumulation of sen- sorial power, during their quiescent state, as the muscles of loco- motion. In these muscles after great exertion, that is, after great exhaustion of the sensorial power, the pain of fatigue ensues; and during rest there is a renovation of the natural quantity of senso- rial power; but where the rest, or quiescence of the muscle, is long continued, a quantity of sensorial power becomes accumu- lated beyond what is necessary; as appears by the uneasiness occasioned by want of exercise; and which in young animals is one cause exciting them into action, as is seen in the play of pup- pies and kittens. But when those muscles, vvhich are habituated to perpetual actions, as those of the stomach by the stimulus of food, those of the vessels of the skin by the stimulus of heat, and those which constitute the arteries and glands by the stimulus of the blood, become for a time quiescent, from the want of their appropriated stimuli, or by their association with other quiescent parts of the system; a greater accumulation of sensorial power is acquired during their quiescence, and a greater or quicker exhaustion of it is produced during their increased action. This accumulation of sensorial power from deficient action, if it happens to the stomach from want of food, occasions the pain of hunger; if it happens to the vessels of the skin from want of heat, it occasions the pain of cold; and if to the arterial system from the want of its adapted stimuli, many disagreeable sensa- tions are occasioned, such as are experienced in the cold fits of intermittent fevers, and are as various as there are glands or membranes in the system, and are generally termed universal uneasiness. When the quiescence of the arterial system is not owing to de- fect of stimulus as above, but to the defective quantity of senso- rial power, as in the commencement of nervous fever, or irrita- tive fever with weak pulse, a great torpor of this system is quickly induced; because both the irritation from the stimulus or the blood, and the associations of the vascular motions with each ether, continue to excite the arteries into action, and thence quickly exhaust the ill-supplied vascular muscles; for to rest is death; and therefore those vascular muscles continue to proceed, though with feebler action, to the extreme of weariness or faint- ness: while nothing similar to this affects the locomotive muscles, whose actions are generally caused by volition, and not much 302 DISEASES Sect. XXXII. 10. 1. subject either to irritation or to other kinds of associations besides the voluntary ones, except indeed when they are excited by the lash of slavery. In these vascular muscles, which are subject to perpetual ac- tion, and thence liable to great accumulation of sensorial power during their quiescence, from want of stimulus, a great increase of activity occurs, either from the renewal of their accustomed stimulus, or even from much less quantities of stimulus than usual. This increase of action constitutes the hot fit of fever, which is attended with various increased secretions, with great concomitant heat, and general uneasiness. The uneasiness at- tending this hot paroxysm of fever, or fit of exertion, is very dif- ferent from that which attends the previous cold fit, or fit of quiescence, and is frequently the cause of inflammation, as in pleurisy, which is treated of in the next section. A similar effect occurs after the quiescence of our organs of sense; those which are not subject to perpetual action, as the taste and smell, are less liable to an exuberant accumulation of senso- rial power after their having for a time been inactive; but the eye, vvhich is in perpetual action during the day, becomes daz- zled, and liable to inflammation after a temporary quiescence. Where the previous quiescence has been owing to a defect of sensorial power, and not to a defect of stimulus, as in the irrita- tive fever with weak pulse, a similar increase of activity of the arterial system succeeds, either from the usual stimulus of the blood, or from a stimulus less than usual; but as there is in gene- ral in these cases of fever with weak pulse a deficiency of the quantity of the blood, the pulse in the hot fit is weaker than in health, though it is stronger than in the cold fit, as explained in No. 2. of this Section. But at the same time, in those fevers where the defect of irritation is owing to the defect of the quan- tity of sensorial power, as well as to the defect of stimulus, ano- ther circumstance occurs; which consists in the partial distri- bution of it, as appears in partial flushings, as of the face or bosom, while the extremities are cold; and in the increase of particular secretions, as of bile, saliva, insensible perspiration, with great heat of the skin, or with partial sweats, or diarrhoea. There are also many uneasy sensations attending these increas- ed actions, which, like those belonging to the hot fit of fever with strong pulse, are frequently followed by inflammation, as in scar- let fever; which inflammation is nevertheless accompanied with a pulse weaker, though quicker, than the pulse during the re- mission or intermission of the paroxysms, though stronger than that of the previous cold fit. From hence I conclude, that both the cold and hot fits of fever Sect. XXXII 11. 1. OF IRRITATION. 303 are necessary Consequences of the perpetual and incessant action of the arterial and glandular system; since those muscu- lar fibres and those organs of sense, which are most frequently exerted, become necessarily most affected both with defect and accumulation of sensorial power: and that hence fever-fits are not an effort of nature to relieve herself, and that therefore they should always be prevented or diminished as much as possible, by any means which decrease the general or partial vascular ac- tions, when they are greater, or by increasing them when they are less than in health, as described in Sect. XII. 6. 1. Thus have I endeavoured to explain, and I hope to the satis- faction of the candid and patient reader, the principal symp- toms or circumstances of fever without the introduction of the supernatural power of spasm. To the arguments in favour of the doctrine of spasm it may be sufficient to reply, that, in the evolution of medical as well as of dramatic catastrophe, Nee Deus interfit, nisi dignus vindice nodus Incident. Hoh. XI. 1. Since I printed the above in the first edition of this work, I am told, that the spasmodic doctrine of fever has yet its advocates; who believe that the coldness at the beginning of in- termittent fevers is owing to a spasm of the cutaneous vessels. But as the skin is at that time lax and soft, the muscular fibres of those cutaneous vessels cannot be in action or contraction, which constitute spasm. Whence we have the evidence both of our sight and touch against this wild imagination. Others have advanced, that this spasmodic contraction of the cutaneous vessels or pores confines the heat, or drives it to the heart; which in the hot fit of fever repels the heat again to the skin by its reaction. Those who espouse this doctrine, seem to conceive, that the particles of heat are as large as shot-corns, or as the globules of blood; and not that it is an ethereal fluid, in which all things are immersed, and by which all things are penetrated; an opinion which originated from Galen, and must have been founded on a total ignorance of chemistry, and natu- ral philosophy. Others, I hear, still suppose cold to be a stimu- lus, not understanding that it is simply the absence of heat; and that darkness might as well be called a stimulus to the eye, or hunger a stimulus to the stomach, as cold to our sense, which perceives heat; which is commonly confounded with our sense of touch, which perceives figure. The pain, which we expe- rience on being exposed to a want of heat, vvhich is termed chil- ness, or coldness; and the pain we experience in our organs ol 304 DISEASES Sect. XXX11. 11. 1. digestion from the want of food, which is termed hunger; both arise from the inactivity of those vessels, which ought to be either perpetually, or at periodical times stimulated into action. See Sect. XIII. 3. 2. And the shivering or actions of the subcuta- neous muscles, when we are cold, are in consequence of the pain, or voluntary exertion to relieve that pain, and originate from the want of stimulus, not from the excess of it. In this age of reason it is not the opinions of others, but the natural phenomena, on which those opinions are founded, which deserve to be canvassed. And with the supposed existence of ghosts or apparitions, witchcraft, vampyrism, astrology, animal magnetism, and American tractors, such theories as the above must vanish like the scenery of a dream; as they consist of such combinations of ideas, as have no prototype or correspondent combinations of material objects existing in nature. Sect. XXXITI. 1. 1. OF SENSATION. 305 SECT. XXXIII. DISEASES OF SENSATION. I. 1. Motions excited by sensation. Digestion. Generation. Plea'- sure of existence. Hypochondriacism. 2. Pain introduced. Sen- sitive fevers of two kinds. 3. Two sensorial powers exerted in sensitive fevers. Size of the blood. Nervous fevers distinguished from putrid ones. The septic and antiseptic theory. 4. Two kinds of delirium. 5. Other animals are less liable to delirium, cannot receive our contagious diseases, and are less liable to mad- ness. II. 1. Sensative motions generated. 2. Inflammation ex- plained. 3. Its remote causes from excess of irritation, or of irri- tability, not from those pains which are owing to defect of irrita- tion. New vessels produced, and much heat. 4. Purulent matter secreted. 5. Contagion explained. 6. Received but once. 7. If common matter be contagious? 8. Why some contagions are re- ceived but once. 9. Why others may be received frequently. Con- tagions of small-pox and measles do not act at the same time. Two cases of such patients. 10. The blood from patients in the small-pox will not infect others. Cases of children thus inocu- lated. The variolous contagion is not received into the blood. It acts by sensitive association between the stomach and skin. III. 1. Absorption of solids and fluids. 2. Art of healing ulcers. 3. Mortification attended with less pain in weak people. I. 1. As many motions of the body are excited and continued by irritations, so others require either conjunctly with these, or separately, the pleasurable or painful sensations, for the purpose of producing them with due energy. Amongst these the business of digestion supplies us with an instance: if the food, which we swallow, is not attended with agreeable sensations, it digests less perfectly; and if very disagreeable sensation accompanies it, such as a nauseous idea, or very disgustful taste, the digestion becomes impeded; or retrograde motions of the stomach and oesophagus succeed, and the food is ejected. The business of generation depends so much on agreeable sen- sation, that, where the object is disgustful, neither voluntary ex- ertion nor irritation can effect the purpose: which is also liable to be interrupted by the pain of fear or bashfulness. Besides the pleasure, which attends the irritations produced by the objects of lust and hunger, there seems to be a sum of plea- surable affection accompanying the various secretions of the nu- merous glands, which constitute the pleasure of life, in contradis- vol. i. r r 306 DISEASES Ski XXXIII. 1.2. tinction to the tedium vitae. This quantity or sum of pleasur- able affection seems to contribute to the due or energetic per- formance of the whole moveable system, as well that of the heart and arteries, as of digestion and of absorption; since without the due quantity of pleasurable sensation, flatulency and hypochou- driacism affect the intestines, and a languor seizes the arterial pulsations and secretions; as occurs in great and continued anxiety of the mind. 2. Besides the febrile motions occasioned by irritation, de- scribed in Sect. XXXII. and termed irritative fever, it frequent- ly happens that pain is excited by the violence of the fibrous contractions; and other new motions are then superadded, in consequence of sensation, which we shall term febris sensitiva, or sensitive fever. It must be observed, that most irritative fe- vers begin with a decreased exertion of irritation owing to de- fect of stimulus; but that on the contrary the sensitive fevers or inflammations generally begin with the increased exertion of sensation, as mentioned in Sect. XXXI. on temperaments: for though the cold fit, which introduces inflammation, commences with decreased irritation, yet the inflammation itself commences in the hot fit during the increase of sensation. Thus a common pustule, or phlegmon, in a part of little sensibility, does not ex- cite an inflammatory fever; but if the stomach, intestines, or the tender substance beneath the nails, be injured, great sensa- tion is produced, and the whole system is thrown into that kind of exertion, which constitutes inflammation. These sensitive fevers, like the irritative ones, resolve them- selves into those with arterial strength, and those with arterial debility, that is, with excess or defect of sensorial power; these may be termed the febris sensitiva pulsu forti, sensitive fever with strong pulse, which is the synocha, or inflammatory fever; and the febris sensitiva pulsu debili, sensitive fever with weak pulse, which is the typhus gravior, or putrid fever of some writers. 3. The inflammatory fevers, which are here termed sensitive fevers with strong pulse, are generally attended with some topical inflammation, as pleurisy, peripneumony, or rheumatism, which distinguishes them from irritative fevers with strong pulse. The pulse is strong, quick, and full; for in this fever there is great irritation, as well as great sensation, employed in moving the arterial system. The size, or coagulable lymph, which appears on the blood, is probably an increased secretion from the in- flamed internal lining of the whole arterial system, the thinner part being taken away by the increased absorption of the inflamed lymphatics. Sect. XXXIII. 1.4. OF SENSATION. 307 The sensitive fevers with weak pulse, which are termed putrid or malignant fevers, are distinguished from irritative fevers with weak pulse, called nervous fevers, described in the last section, ;is the former consist of inflammation joined with debility, and the latter of debility alone. Hence there is greater heat and more florid colour of the skin in the former, with petechiae, or purple spots, and aphthae, or sloughs in the throat, and generally with previous contagion. When animal matter dies, as a slough in the throat, or the mor- tified part of a carbuncle, if it be kept moist and warm, as during its adhesion to a living body, it will soon putrify. This and the origin of contagion from putrid animal substances, seem to have given rise to the septic and antiseptic theory of these fevers. The mutter in pustules and ulcers is thus liable to become putrid, and to produce microscopic animalcula; the urine, if too long retained, may also gain a putrescent smell, as well as the alvine feces; but some writers have gone so far as to believe, that the blood itself in these fevers has smelt putrid, when drawn from the arm of the patient; but this seems not well founded; since a single particle of putrid matter taken into the blood can produce fever, how can we conceive that the whole mass could continue a minute in a putrid state without destroying life? Add to this, that putrid animal substances give up air, as in gan- grenes; and that hence, if the blood was putrid, air should be given out, vvhich in the blood vessels is known to occasion imme- diate death. In these sensitive fevers with strong pulse (or inflammations) there are two sensorial faculties concerned in producing the dis- ease, viz. irritation and sensation; and hence, as their combined action is more violent, the general quantity of sensorial power becomes further exhausted during the exacerbation, and the sys- tem more rapidly weakened than in irritative fever with strong pulse; where the spirit of animation is weakened by but one mode of its exertion: so that this febris sensitiva pulsu forti (or inflam- matory fever) may be considered as the febris irritativa pulsu forti, with the addition of inflammation; and the febris sensitiva pulsu debili (or malignant fever) may be considered as the febris irritativa pulsu debili (or nervous fever) with the addition of in- flammation. 4. In these putrid or malignant fevers a deficiency of irrita- bility accompanies the increase of sensibility; and by this waste of sensorial power by the excess of sensation, which was already too small, arise the delirium and stupor which so perpetually at- tend these inflammatory fevers with arterial debility. In these cases the voluntary power first ceases to act from deficiency of 308 DISEASES Sect. XXXIII. 1.4. sensorial spirit; and the stimuli from external bodies have no effect on the exhausted sensorial power, and a delirium like a dream is the consequence. At length the internal stimuli cease to excite sufficient irritation, and the secretions are either not produced at all, or too parsimonious in quantity. Amongst these the secretion of the brain, or production of the sensorial power, becomes deficient, till at last all sensorial power ceases, except what is just necessary to perform the vital motions, and a stupor succeeds; which is thus owing to the same cause as the preced- ing delirium exerted in a greater degree. This kind of delirium is owing to a suspension of volition, and to the disobedience of the senses to external stimuli, and is always occasioned by great debility, or paucity of sensorial power; it is therefore a bad sign at the end of inflammatory fevers, which had previous arterial strength, as rheumatism, or pleurisy, as it shews the presence of great exhaustion of sensorial power in a system, which having lately been exposed to great excitement, is not so liable to be stimulated into its healthy action, either by addi- tional stimulus of food and medicines, or by the accumulation of sensorial power during its present torpor. In inflammatory fevers with debility, as those termed putrid fevers, delirium is some- times, as well as stupor, rather a favourable sign; as less sen- sorial power is wasted during its continuance (see Class II. 1. 6. 8.), and the constitution not having been previously expos- ed to excess of stimulation, is more liable to be excited after pre- vious quiescence. When the sum of general pleasurable sensation becomes too great, another kind of delirium supervenes, and the ideas thus excited are mistaken for the irritations of external objects: such a delirium is produced for a time by intoxicating drugs, as fer- mented liquors, or opium: a permanent delirium of this kind is sometimes induced by the pleasures of inordinate vanity, or by the enthusiastic hopes of heaven. In these cases the power of volition is incapable of exertion, and in a great degree the exter- nal senses become incapable of perceiving their adapted stimuli, because the whole sensorial power is employed or expended on the ideas excited by pleasurable sensation. This kind of delirium is distinguished from that which at- tends the fevers above mentioned from its not being accompani- ed with general debility, but simply with excess of pleasurable sensation; and is therefore in some measure allied to madness or to reverie; it differs from the delirium of dreams, as in this the power of volition is not totally suspended, nor are the senses precluded from external stimulation; there is therefore a degree of consistency, in this kind of delirium, and a degree of attention Sect. XXXIII. 1. 5. OF SENSATION. 309 to external objects, neither of which exists in the delirium of fevers or in dreams. 5. It would appear, that the vascular systems of other animals are less liable to be put into action by their general sum of pleasurable or painful sensation; and that the trains of their ideas, and the muscular motions usually associated with them, are less powerfully connected than in the human system. For other animals neither weep, nor smile, nor laugh; and are hence seldom subject to delirium, as treated of in Sect. XVI. on In- stinct. Now as our epidemic and contagious diseases are pro- bably produced by disagreeable sensation, and not simply by irritation; there appears a reason why brute animals are less li- able to epidemic or contagious diseases; and secondly, why none of our contagions, as the small-pox or measles, can be commu- nicated to them, though one of theirs, viz. the hydrophobia, as well as many of their poisons, as those of snakes and of insects, communicate their deleterious or painful effects to mankind. Where the quantity of general painful sensation is too great in the system, inordinate voluntary exertions are produced either of our ideas, as in melancholy and madness, or of our muscles, as in convulsion. From these maladies also brute animals are much more exempt than mankind, owing to their greater inapti- tude to voluntary exertion, as mentioned in Sect. XVI. on Instinct. II. 1. When any moving organ is excited into such violent motions, that a quantity of pleasurable or painful sensation is produced, it frequently happens (but not always) that new mo- tions of the affected organ are generated in consequence of the pain or pleasure, vvhich are termed inflammation. These new motions are of a peculiar kind, tending to distend the old, and to produce new fibres, and thence to elongate the straight muscles, which serve locomotion, and to form new ves- sels at the extremities or sides of the vascular muscles. 2. Thus the pleasurable sensations produce an enlargement of the nipples of nurses, of the papillae of the tongue, of the penis, and probably produce the growth of the body from its embryon state to its maturity; whilst the new motions in consequence Ot painful sensation, with the growth of the fibres or vessels, which they occasion, are termed inflammation. Hence when the straight muscles are inflamed, part of their tendons at each extremity gain new life and sensibility, and thus the muscle is for a lime elongated; and inflamed bones become soft, vascular, and sensible. Thus new vessels shoot over the cornea of inflamed eyes, and into scirrhous tumours, when they become inflamed; and hence all inflamed parts grow together by intermixture, and inosculation of the new and old Vessels, 310 DISEASES Sect. XXXIII. U 3. The heat is occasioned from the increased secretions either of mucus, or of the fibres, vvhich produce or elongate the vessels. The red colour is owing to the pellucidity of the newly formed vessels, and as the arterial parts of them are probably formed be- fore their correspondent venous parts. 3. These new motions are excited either from the increased quantity of sensation in consequence of greater fibrous contrac- tions, or from increased sensibility, that is, from the increased quantity of sensorial power in the moving organ. Hence they are induced by great external stimuli, as by wounds, broken bones, and by acrid or infectious materials; or by common stimuli on those organs, vvhich have been some time quiescent; as the usual light of the day inflames the eyes of those, who have been confined in dungeons; and the warmth of a common fire inflames those, who have been previously exposed to much cold. But these new motions are never generated by that pain, which arises from defect of stimulus, as from hunger, thirst, cold, or inanitions, with all those pains which are termed ner- vous. Where these pains exist, the motions of the affected part are lessened; and if inflammation succeeds, it is in some distant parts; as coughs are caused by coldness and moisture being long applied to the feet; or it is in consequence of the renewal of the stimulus, as of heat or food, which excites our organs into stronger action after their temporary quiescence; as kibed heels after walking in snow. 4. But when these new motions of the vascular muscles are ex- erted with greater violence, and these vessels are either elongated too much or too hastily, a new material is secreted from their extremities, which is of various kinds according to the peculiar animal motions of this new kind of gland, which secretes it; such is the pus laudable or common matter, the variolous matter, venereal matter, catarrhous matter, and many others. 5. These matters are the product of an animal process; they are secreted or produced from the blood by certain diseased mo- tions of the extremities of the blood-vessels, and are on that ac- count all of them contagious; for if a portion of any of these is transmitted into the circulation, or perhaps only inserted into the skin, or beneath the cuticle of a healthy person, its stimulus in a certain time produces the same kind of morbid motions, by which itself was produced; and hence a similar kind is generated. See Sect. XXXIX. 6. 1. 6. It is remarkable, that many of these contagious matters are capable of producing a similar disease but once; as the small- pox and measles; and I suppose this is true of all those conta- gious diseases, which are spontaneously cured by nature in a cer- Sect. XXXIII 2.7. OF SENSATION. 311 tain time; for if the body was capable of receiving the disease a second time, the patient must perpetually infect himself by the very matter, which be has himself produced, and is lodged about him; and hence he could never become free from the disease. Something similar to this is seen in the secondary fever of the confluent small-pox; there is a great absorption of variolous matter, a very minute part of which would give the genuine small-pox to another person; but here it only stimulates the system into common fever; like that which common pus, or any other acrid material might occasion. 7. In the pulmonary consumption, where common matter is daily absorbed, an irritative fever only, without new inflam- mation is generally produced; which is terminated like other irritative fevers, by sweats or loose stools. Hence it does not appear, that this absorbed matter always acts as a contagious ma- terial producing fresh inflammation or new abscesses. Though there is reason to believe, that the first time any common matter is absorbed, it has this effect, but not the second time, like the variolous matter above mentioned. This accounts for the opinion, that the pulmonary consump- tion is sometimes infectious, which opinion was held by the an- cients, and continues in Italy at present; and I have myself seen three or four instances, where a husband and wife, who have slept together, and have thus much received each other's breath, who have infected each other, and both died in consequence of the original taint of only one of them. This also accounts for the abscesses in various parts of the body, that are sometimes produced after the inoculated small-pox is terminated; for this second absorption of variolous matter acts like common matter, and produces only irritative fever in those children whose consti- tutions have already experienced the absorption of common mat- ter; and inflammation with a tendency to produce new abscesses in those whose constitutions have not experienced the absorp- tions of common matter. It is probable that more certain proofs might have been found to shew, that common matter is infectious the first time it is absorbed, tending to produce similar abscesses, but not the se- cond time of its absorption, if this subject had been attended to. 8. These contagious diseases are very numerous, as the plague, small-pox, chicken-pox, measles, scarlet-fever, pemphi- gus, catarrh, chin-cough, venereal disease, itch, trichoma, tinea. The infectious material does not seem to be dissolved by the air, but only mixed with it perhaps in fine powder, which soon sub- sides; since many of these contagions can only be received by actual contact; and others of them only at small distances from 312 DISEASES. Sect. XXXIII. 2. 9. the infected person; as is evident from many persons having been near patients of the sinall-pox without acquiring the disease. The reason why many of these diseases are received but once, and others repeatedly, is not well understood; it appears to me that the constitution becomes so accustomed to the stimuli of these infectious materials, by having once experienced them, that though irritative motions, as hectic fevers, may again be produced by them, yet no sensation, and in consequence no general inflammation succeeds; as disagreeable smells or tastes by habit cease to be perceived; they continue indeed to excite irritative ideas on the organs of sense, but these are not succeed- ed by sensation. There are many irritative motions, which were at first suc- ceeded by sensation, but which by frequent repetition cease to ex- cite sensation, as explained in Sect. XX. on Vertigo. And, that this circumstance exists in respect to infectious matter appears from a known fact; that nurses, who have had the small-pox, are liable to experience small ulcers on their arms by the contact of variolous matter in lifting their patients; and that when pa- tients, who have formerly had the small-pox, have been inoculat- ed in the arm, a phlegmon, or inflamed sore, has succeeded, but no subsequent fever. Which shews, that the contagious matter of the small-pox has not lost its power of stimulating the part it is applied to, but that the general system is not affected in con- sequence. See Section XII. 7. 6. XIX. 10. 9. From the accounts of the plague, virulent catarrh, and putrid dysentery, it seems uncertain, whether these diseases are experienced more than once; but the venereal disease and itch are doubtless repeatedly infectious; and as these diseases are never cured spontaneously, but require medicines which act without apparent operation, some have suspected, that the con- tagious material produces similar matter rather by a chemical change of the fluids, than by an animal process; and that the spe- cific medicines destroy their virus by chemically combining with it. This opinion is successfully combatted by Mr. Hunter, in his Treatise on Venereal Disease, Part I.e. i. But this opinion wants the support of analogy, as there is no known process in animal bodies, which is purely chemical, not even digestion; nor can any of these matters be produced by chemical processes. Add to this, that it is probable, that the insects, observed in the pustules of the itch, and in the stools of dysenteric patients, are the consequences, and not the causes of these diseases. And that the specific medicines, which cure the itch, and lues venerea, as brimstone and mercury, act only by in- Si:< t. XXXTII.2. 9. OF SENSATION. 313 creasing the absorption of the matter in the ulcuscles of those diseases, and thence disposing them to heal; which would other- wise continue *o spread. Why the venereal disease, and itch, and tinea, or scald head, are repeatedly contagious, while those contagions attended with fever can be received but once, seems to depend on their being rather local diseases than universal ones, and are hence not at- tended with fever, except the purulent fever in their last stages, when the patient is destroyed by them. On this account the whole of the system does not become habituated to these morbid actions, so as to cease to be affected with sensation by a repetition of the contagion. Thus the contagious matter of the venereal disease, and of the tinea, affects the lymphatic glands, as the in- guinal glands, and those about the roots of the hair and neck, vv here it is arrested, but does not seem to affect the blood-vessels, since no fever ensues. Hence it would appear that these kinds of contagion are pro- pagated not by means of the circulation, but by sympathy of dis- tant parts with each other; since if a distant part, as the palate, should be excited by sensitive association into the same kind of motions, as the parts originally affected by the contact of infec- tious matter, that distant part will produce the same kind of infectious matter; for every secretion from the blood is formed from it by the peculiar motions of the fine extremities of the gland, which secretes it; the various secreted fluids, as the bile, saliva, gastric juice, not previously existing, as such, in the blood- vessels. And this peculiar sympathy between the genitals and the throat, owing to sensitive association, appears not only in the production of venereal ulcers in the throat, but in a variety of other instances, as in the mumps, in the hydrophobia, some coughs, strangulation, the production of the beard, change of voice at puberty, which are further described in Class IV. 1. 2. 7. To evince that the production of such large quantities of con- tagious matter, as are seen in some variolous patients, so as to cover the whole skin almost with pustules, does not arise from any chemical fermentation in the blood, but that it is owing to morbid motions of the fine extremities of the capillaries, or glands, whether these be ruptured or not, appears from the quan- tity of this matter always corresponding with the quantity of the fever; that is, with the violent exertions of those glands and capillaries, vvhich are the terminations of the arterial system. The truth of this theory is evinced further by a circumstance observed by Mr. J. Hunter, in his Treatise on Venereal Disease; that in a patient, who was inoculated for the small-pox, and vol. i. s s 314 DISEASES Sect. XXXIII. 2.9. who appeared afterwards to have been previously infected with the measles, the progress of the small-pox was delayed till the measles had run their course, and that then the small-pox went through its usual periods. Two similar cases fell under my care, which I shall here relate, as it confirms that of Mr. Hunter, and contributes to illustrate this part of the theory of contagious diseases. I have transcribed the particulars from a letter of Mr. Lightwood, of Yoxal, the surgeon who daily attended them, and at my request, after I had seen them, kept a kind of journal of their cases. Miss H. and Miss L. two sisters, the one about four, and the other about three years old, were inoculated Feb. 7, 1791. On the 10th there was a redness on both arms discernible by a glass. On the 11th their arms were so much inflamed, as to leave no doubt of the infection having taken place. On the 12th less appearance of inflammation on their arms. In the evening Miss L. had an eruption, which resembled the measles. On the 13th the eruption on Miss L. was very full on the face and breast, like the measles, with considerable fever. It was now known, that the measles were in a farm house in the neighbourhood. Miss H.'s arm less inflamed than yesterday. On the 14th Miss L.'s fever great, and the eruption universal. The arm appears to be healed. Miss H.'s arm somewhat redder. They were now put into separate rooms. On the 15th Miss L.'s arms as yesterday. Eruption continues. Miss H.'s arms have varied but little. 16th, the eruptions on Miss L. are dying away, her fever gone. Begins to have a little redness in one arm at the place of inoculation. Miss H.'s arms get redder, but she has no appearance of complaint. 20th, Miss L.'s arms have advanced slowly till this day, and now a few pustules appear. Miss H.'s arm has made little progress from the 16th to this day, and now she has some fever. 2lst, Miss L. as yesterday. Miss H. has much inflammation, and an increase of the red circle on one arm to the size of half-a-crown, and had much fever at night, with fetid breath. 22d, Miss L.'s pustules continue advancing. Miss H.'s inflammation of her arm and red circle increases. A few red spots appear in different parts, with some degree of fever this morning. 23d, Miss L. has a larger crop of pustules. Miss H. has small pustules and great inflammation of her arms, with but one pustule likely to suppurate. After this day they gradu- ally got well, and the pustules disappeared. In one of these cases 'the measles went through their common course, with milder symptoms than usual, and in the other the measly contagion seemed just sufficient to stop the progress of variolous contagion, but without itself throwing the constitution Sect. XXXIII. 2.10. OF SENSATION. 315 into any disorder. At the same time both the measles and small- pox seem to have been rendered milder. Does not this give an idea, that if they were both inoculated at the same time, that nei- ther of them might affect the patient? From these cases I contend, that the contagious matter of these diseases does not affect the constitution by a fermentation, or chemical change of the blood, because then they must have pro- ceeded together, and have produced a third something, not ex- actly similar to either of them: but that they produce new mo- tions of the cutaneous terminations of the blood vessels, which for a time proceed daily with increasing activity, like some pa- roxysms of fever, till they at length secrete or form a similar poison by these unnatural actions. Now, as in the measles one kind of unnatural motion takes place, and in the small-pox another kind, it is easy to conceive, that these different kinds of morbid motions cannot exist together; and therefore, that that which has first begun, will continue till the system becomes habituated to the stimulus which occasions it, and lias ceased to be thrown into action by it; and then the other kind of stimulus will in its turn produce fever, and new kinds of motions peculiar to itself. 10. On further considering the action of contagious matter, since the former part of this work was sent to the press; where I have asserted, in Sect. XXII. 4. 3. that it is probable, that the variolous matter is diffused through the blood; I prevailed on my friend Mr. Power, surgeon at Bosworth, in Leicestershire, to try whether the small-pox could be inoculated by using the blood of a variolous patient instead of the matter from the pustules; as I thought such an experiment might throw some light at least on this interesting subject. The following is an extract from his letter:— " March 11, 1793. I inoculated two children, who had not had the small-pox, with blood; which was taken from a patient on the second day after the eruption commenced, and before it was completed. And at the same time I inoculated myself with blood from the same person, in order to compare the appearance, which might arise in a person liable to receive the infection, and in one not liable to receive it. On the same day I inoculated from other children liable to receive the infection, with blood taken from another person on the fourth day after the commence- ment of the eruption. The patients from whom the blood was taken had the disease mildly, but had the most pustules of any I could select from twenty inoculated patients; and as much of the blood was insinuated under the cuticle, as I could introduce by elevating the skin without drawing blood; and three or four such 316 DISEASES Sect. XXXIII. 2.10. punctures were made in each of their arms, and the blood was used in its fluid state. " As the appearances in all these patients, as well as in my- self, were similar, I shall only mention them in general terms.— March 13. A slight subcuticular discoloration, with rather a livid appearance, without soreness or pain, was visible in them all, as well as in my own hand. 15. The discoloration somewhat less, without pain or soreness. Some patients inoculated on the same day with variolous matter, have considerable inflammation. 17. The discoloration is quite gone in them all, and from my own hand, a dry mark only remaining. And they were all inoculated on the 18th, with variolous matter, which produces the disease in them all." Mr. Power afterwards observes, that, as the patients from whom the blood was taken had the disease mildly, it may be sup- posed, that though the contagious matter might be mixed with the blood, it might still be in too dilute a state to convey the in- fection; but adds, at the same time, that he has diluted recent matter with at least five times its quantity of water, and which has still given the infection; though he has sometimes diluted it so far as to fail. The following experiments were instituted at my request by my friend Mr. Hadley, surgeon in Derby, to ascertain whether the blood of a person in the small-pox be capable of communicat- ing the disease. " Experiment 1st, October 18th, 1793. I took some blood from a vein in the arm of a person who had the small- pox, on the second day of the eruplion, and introduced a small quantity of it immediately with the point of a lancet between the scarf and true skin of the right arm of a boy nine years old, in two or three different places; the other arm was inoculated with variolous matter at the same time. " 19th. The punctured parts of the right arm were surrounded with some degree of subcuticular inflammation. 20th. The in- flammation more considerable, with a slight degree of itching, but no pain upon pressure. 21st. Upon examining the arm this day with a lens, I found the inflammation less extensive, and the redness changing to a deep yellow or orange-colour. 22d. In- flammation nearly gone. 23d. Nothing remained, except a slight discoloration and a little scurfy appearance on the punctures. At the same time, the inflammation of the arm inoculated with variolous matter was increasing fast, and he had the disease mild- ly at the usual time. " Experiment 2d. I inoculated another child at the same time and in the same manner, with blood taken on the first day of the eruption; but as the appearance and effects were similar Sect. XXXIII. 2.10. OF SENSATION. 317 to those in the preceding experiment, I shall not relate them minutely. " Experiment 3d. October 20th. Blood was taken from a person who had the small-pox, on the third day of the eruption, and on the sixth from the commencement of the eruptive fever. I introduced some of it in its fluid state into both arms of a boy seven years old. 21. There appeared to be some inflammation under the cuticle, where the punctures were made. 22d. In- flammation more considerable. 23d. On this day the inflamma- tion was somewhat greater, and the cuticle rather elevated. " 24th. Inflammation much less, and only a brown or orange- colour remained. 25th. Scarcely any discoloration left. On this day he was inoculated with variolous matter, the progress of the infection went on in the usual way, and he had the small- pox very favourably. " At this time I was requested to inoculate a young person, who was thought to have had the small-pox, but his parents were not quite certain; in one arm 1 introduced variolous matter, and in the other blood, taken as in experiment 3d. On the second day after the operation, the punctured parts were inflamed, though I think the arm in which I had inserted variolous matter was rather more so than the other. On the third the inflamma- tion was increased, and looked much the same as in the preced- ing experiment. 4th. The inflammation was much diminished, and on the 5th almost gone. He was exposed at the same time to the natural infection, but has continued perfectly well. " I have frequently observed, (and believe most practitioners have, done the same,) that if variolous matter be inserted in the arm of a person who has previously had the small-pox, the in- flammation on the second or third day is much greater, than if they had not had the disease, but on the fourth or fifth it dis- appears. u On the 23d I introduced blood into the arms of three more children, taken on the third and fourth days of the eruption. The appearances were much the same as mentioned in experiments first and third. They were afterwards inoculated with variolous matter, and had the disease in the regular way. " The above experiments were made with blood taken from a small vein in the hand or foot of three or four different patients, whom I had at that time under inoculation. They were selected from 160, as having the greatest number of pustules. The part was washed with warm water before the blood was taken, * to prevent the possibility of any matter being mixed with it from the surface." Shall we conclude from hence, that the variolous matter never 318 DISEASES Sect. XXXIII. 2. 10. enters the blood-vessels; but that the morbid motions of the ves- sels of the skin around the insertion of it continue to increase in a larger and larger circle for six or seven days; that then their quantity of morbid action becomes great enough to produce a fever-fit, and to affect the stomach by association of motions? and finally, that a second association of motions is produced be- tween the stomach and the other parts of the skin, inducing them into morbid actions similar to those of the circle round the inser- tion of the variolous matter? Many more experiments and obser- vations are required before this important question can be satis- factorily answered. It may be adduced, that as the matter inserted into the skin of the arm frequently swells the lymphatic in the axilla, that in that circumstance it seems to be there arrested in its progress, and cannot be imagined to enter the blood by that lymphatic gland till the swelling of it subsides. Some other phaenomena of the disease are more easily reconcileable to this theory of sympathetic motions than to that of absorption; as the time taken up be- tween the insertion of the matter, and the operation of it on the system, as mentioned above. For the circle round the insertion is seen to increase, and to inflame; and, I believe, undergoes a kind of diurnal paroxysm of torpor and paleness with a succeed- ing increase of action and colour, like a topical fever-fit. Whereas if the matter is conceived to circulate for six or seven days with the blood, without producing disorder, it ought to be rendered milder, or the blood vessels more familiarized to its acrimony. It is much easier to conceive from this doctrine of associated or sympathetic motions of distant parts of the system, how it happens, that the variolous infection may be received but once, as before explained; than by supposing, that a change is effected in the mass of blood by any kind of fermentative process. The curious circumstance of the two contagions of small-pox and measles not acting at the same time, but one of them resting or suspending its action till that of the other ceases, may be much easier explained from sympathetic or associated actions of the in- fected part with other parts of the system, than it can from sup- posing the two contagions to enter the circulation. The skin of the face is subject to more frequent vicissitudes of heat and cold, from its exposure to the open air, and is in con- sequence more liable to sensitive association with the stomach than any other part of the surface of the body, because their ac- tions have been more frequently thus associated. Thus in a surfeit from drinking cold water, when a person is very hot and fatigued, an eruption is liable to appear on the face in rouse- Sect. XXXIII. 3. 1. OF SENSATION. 319 qucnce of this sympathy. In the same mannr-r the rosy eruption on the faces of drunkards more probably arises from the sympathy of the face with the stomach, rather than between the face and the liver, as is generally supposed. This sympathy between the stomach and the skin of the face is apparent in the eruption of the small-pox; since, where the dis- ease is in considerable quantity, the eruption on the face first suc- ceeds the sickness of the stomach. In the natural disease the stomach seems to be frequently primarily affected, either alone or along with the tonsils, as the matter seems to be only diffused in the air, and by being mixed with the saliva, or mucus of the tonsils, to be swallowed into the stomach. After some days the irritative circles of motions become disor- dered by this new stimulus, which acts upon the mucous lining of the stomach; and sickness, vertigo, and diurnal fever succeed. These disordered irritative motions become daily increased for two or three (Jays, and then by their increased action certain sensitive motions, or inflammation, is produced, and at the next cold fit of fever, when the stomach recovers from its torpor, an inflammation of the external skin is formed in points (which afterwards suppurate) by sensitive association, in the same man- ner as a cough is produced in consequence of exposing the feet to cold, as described in Sect. XXV. 1. 1. and Class IV. 2. 1.7. If the inoculated skin of the arm, as far as it appears inflamed, was to be cut out, or destroyed by caustic, before the fever com- menced, as supposed on the fourth day after inoculation, would this prevent the disease? as it is supposed to prevent the hydro- phobia. III. 1. Where the new vessels, and enlarged old ones, which constitute inflammation, are not so hastily distended as to burst, and form a new kuid of gland for the secretion of matter, as above mentioned; if such circumstances happen as diminish the painful sensation, the tendency to growth ceases, and by and by an ab- sorption commences, not only of the superabundant quantity of fluids deposited in the inflamed part, but of the solids likewise, and this even of the hardest kind. Thus during the growth of the second set of teeth in children, the roots of the first set are totally absorbed, till at length no- thing of them remains but the crown; though a few weeks before, if they are drawn immaturely, their roots are found complete. Similar to this Mr. Hunter has observed, that where a dead piece of bone is to exfoliate, or to separate from a living one, the dead part does not putrify, but remains perfectly sound, while the surface of the living part of the bone, which is in con- tact with the dead part, becomes absorbed, and thus effects its 320 DISEASES Sect. XXXIII. 3 2. separation. Med. Comment. Edinb. V. 1. 425. In the same manner the calcareous matter*of gouty concretions, the coagulable lymph deposited on inflamed membranes in rheumatism and ex- travasated blood become absorbed; which are all as solid and as indissoluble materials as the new vessels produced in inflammation. This absorption of the new vessels and deposited fluids of in- flamed parts is called resolution: it is produced by first using such internal means as decrease the pain of the part, and in con- sequence its new motions, as repeated bleedings, cathartics, dilu- ent potations, and warm bath. After the vessels are thus emptied, and the absorption of the new vessels and deposited fluids is evidently begun, it is much promoted by stimulating the part externally by solutions of lead, or other metals, and internally by the bark, and small doses of opium. Hence when an ophthalmy begins to become paler, any acrid eye water, as a solution of six grains of white vitriol in an ounce of water, hastens the absorption, and clears the eye in a very short time. But the same application used a few days sooner would have increased the inflammation. Hence, after evacuation, opium in small doses may contribute to promote the absorption of fluids deposited on the brain, as observed by Mr. Bromfield in his treatise of surgery 2. Where an abscess is formed by the rupture of these new vessels, the violence of inflammation ceases, and a new gland separates a material called pus: at the same time a less degree of inflammation produces new vessels called vulgarly proud flesh; which, if no bandage confines its growth, nor any other circum- stance promotes absorption in the wound, would rise to a great height above the usual size of the part. Hence the art of healing ulcers consists in producing a ten- dency to absorption in the wound greater than the deposition. Thus when an ill-conditioned ulcer separates a copious and thin discharge, by the use of any stimulus, as of salts of lead, or mer- cury, or copper externally applied, the discbarge becomes dimin- ished in quantity, and becomes thicker, as the thinner parts are first absorbed. To which, in ulcerations of the lungs, and in some catarrhs, a pertinacious abstinence from fluids has been recommended, as well as in dropsies, and diabetes, which, in the former as well as in the latter, may have a tendency to increase absorption from the affected parts, and may thus be moderately employed with ad- vantage; but may have a dangerous tendency if used to an ex- treme, by inducing too great thirst, and consequent fever or in- flammation. Lower de Catarrhis. Davidson on Pulmonary Sys- tem. Rollo on Diabetes. Sect. XXXIII. 3.3. OF SENSATION. 321 But nothing so much contributes to increase the absorption in a wound as covering the whole limb above the sore with a band- age, which should be spread with some plaster, as with emplas-= trum de minio, to prevent it from slipping. By this artificial tightness of the skin, the arterial pulsations act with double their usual power in promoting the ascending current of the fluid in the valvular lymphatics. Internally the absorption from ulcers should be promoted first by evacuation, then by opium, bark, mercury, steel. 3. Where the inflammation proceeds with greater violence or rapidity, that is, when by the painful sensation a more inordi- nate activity of the organ is produced, and by this great activity an additional quantity of painful sensation follows in an increas- ing ratio, till the whole of the sensorial power, or spirit of ani- mation, in the part becomes exhausted, a mortification ensues, as in a carbuncle, in inflammations of the bowels, in the extremi- ties of old people, or in the limbs of those who are brought near a fire after having been much benumbed with cold. And from hence it appears, why weak people are more subject to mortifi- cation than strong ones, and why in weak persons less pain will produce mortification, namely, because the sensorial power is sooner exhausted by an excess of activity. I remember seeing a gentleman who had the preceding day travelled two stages in a chaise with what he termed a bearable pain in his bowels; which when I saw him had ceased rather suddenly, and without a passage through him; his pulse was then weak, though not very quick; but as nothing which he swallowed would continue in his stomach many minutes, I concluded that the bowel was mortified; he died on the next day. It is usual for patients sinking under the small-pox with mortified pustules, and with purple spots intermixed, to complain of no pain, but to say they are pretty well to the last moment. Recapitulation. IV. When the motions of any part of the system, in conse- quence of previous torpor, are performed with more energy than in the irritative fevers, a disagreeable sensation is produced, and new actions of some part of the system commence in conse- quence of this sensation conjointly with the irritation: which motions constitute inflammation. If the fever be attended with a strong pulse, as in pleurisy, or rheumatism, it is termed syno- cha sensitiva, or sensitive fever with strong pulse; which is usu- ally termed inflammatory fever. If it be attended with weak VOL. I. t t 322 DISEASES Sect. XXXIII. 1. :. pulse, it is termed typhus sensitivus, or sensitive fever with weak pulse, or typhus gravior, or putrid malignant fever. The synocha sensitiva, or sensitive fever with strong pulse, is generally attended with some topical inflammation, as in perip- neumony, hepatitis, and is accompanied with much coagulable lymph, or size; which rises to the surface of the blood, when taken into a basin, as it cools; and which is believed to be the increased mucous secretion from the coats of the arteries, inspis- sated by a greater absorption of its aqueous and saline part, and perhaps changed by its delay in the circulation. The typhus sensitivus, or sensitive fever with weak pulse, is frequently attended with delirium, which is caused by the de- ficiency of the quantity of sensorial power, and with variety of cutaneous eruptions. Inflammation is caused by the pains occasioned by excess of action, and not by those pains which are occasioned by defect of action. These morbid actions, which are thus produced by two sensorial powers, viz. by irritation and sensation, secrete new living fibres, which elongate the old vessels, or form new ones, and at the same time much heat is evolved from these com- binations. By the rupture of these vessels, or by a new con- struction of their apertures, purulent matters are secreted of various kinds; which are infectious the first time they are applied to the skin beneath the cuticle, or swallowed with the saliva into the stomach. This contagion acts not by its being absorbed into the circulation, but by the sympathies, or associated actions, be- tween the part first stimulated by the contagious matter and the other parts of the system. Thus in the natural small-pox the contagion is swallowed with the saliva, and by its stimulus in- flames the stomach; this variolous inflammation of the stomach increases every day, like the circle round the puncture of an in- oculated arm, till it becomes great enough to disorder the circles of irritative and sensitive motions, and thus produces fever-fits, with sickness and vomiting. Lastly, after the cold paroxysm, or fit of torpor, of the stomach has increased for two or three suc- cessive days, an inflammation of the skin commences in points; which generally first appear upon the face, as the associated ac- tions between the skin of the face and that of the stomach have been more frequently exerted together than those of any other parts of the external surface. Contagious matters, as those of the measles and small pox, do not act upon the system at the same time; but the progress of that which was last received is delayed, till the action of the former infection ceases. All kinds of matter, even that from common ulcers, are probably contagious the first time they are in- Sect. XXXIII. 4. 1. OF SENSATION. 323 serted beneath the cuticle or swallowed into the stomach; that is, as they were formed by certain morbid actions of the ex- tremities of the vessels, they have the power to excite similar morbid actions in the extremities of other vessels, to which they are applied; and these by sympathy, or associations of motion, excite similar morbid actions in distant parts of the system, with- out entering the circulation; and hence the blood of a patient in the small-pox will not give that disease by inoculation to others. When the new fibres or vessels become again absorbed into the circulation, the inflammation ceases; vvhich is promoted, after sufficient evacuations, by external stimulants and bandages: but where the action of the vessels is very great, a mortification of the part is liable to ensue, owing to the exhaustion of sensorial power; which however occurs in weak people without much pain, and without very violent previous inflammation; and, like partial paralysis, may be esteemed one mode of natural death of old people, a part dying before the whole. 324 DISEASES Sect. XXXIV 1. 1.. SECT. XXXIV. DISEASES OF VOLITION. I. 1. Volition defined. Motions termed involuntary are caused by volition. Desires opposed to each other. Deliberation. Ass be- tween two hay-cocks. Saliva sicallowed against one^s desire. Voluntary motions distinguished from those associated with sensi- tive motions. 2. Pains from excess, andfrom defect of motion. No pain is felt during vehement voluntary exertion; as in cold jits of ague, labour-pains, strangury, tenesmus, vomiting, restlessness in fevers, convulsion of a wounded muscle. 3. Of holding tlie breath and screaming in pain; why swine and dogs cry out in pain, and not sheep and horses. Of grinning and biting in pain; why mad animals bite others. 4. Epileptic convulsions explained, why the fits begin with quivering of the under jaw, biting the tongue, and setting the teeth; why the convulsive motions are alternately relax- ed. The phenomenon of laughter explained. Why children can- not tickle themselves. How some have died from immoderate laughter. 5. Of cataleptic spasms, of the locked jaw, of painful cramps. 6. Syncope explained. Why no external objects are perceived in syncope. 7. Of palsy and apoplexy from violent ex- ertions. Case of Mrs. Scott. From dancing, seating, swimming. Case of Mr. Nairne. Why palsies are not always immediately preceded by violent exertions. Palsy and epilepsy from diseased livers. Why the right arm more frequently paralytic than the left. How paralytic limbs regain their motions. II. Diseases of the sensual motions from excess or defect of voluntary exertion. I. Madness. 2. Distinguished from delirium. 3. Why man- kind more liable to insanity than brutes. Suspicion. Want of shame, and of cleanliness,. 5. They bear cold, hunger, and fatigue. Charles XII. of Sweden. 6. Pleasurable delirium, and insanity. Child riding on a slick. Pains of martyrdom not felt. 7. Drop- sy. 8. Inflammation cured by insanity. III. 1. Pain relieved by reverie. Reverie is an exertion of voluntary and sensitive mo- tions. 2. Case of reverie. 3. Lady supposed to have two souls. 4. Methods of relieving pain. I. 1. Before we commence this Section on Diseased Vo- luntary Motions, it may be necessary to premise, that the vviord volition is not used in this work exactly in its common accepta- tion. Volition is said in Section V. to bear the same analogy to desire and aversion, which sensation does to pleasure and pain. And hence that, when desire or aversion produces any action of Sf.ct. XXXIV. 1. 1. OF VOLITION. 325 the muscular fibres, or of the organs of sense, it is termed voli- tion; and the actions produced in consequence are termed volun- tary actions. Whence it appears, that motions of our mus- cles or ideas may be produced in consequence of desire or aver- sion without our having the power to prevent them, and yet these motions may be termed voluntary, according to our definition of the word; though in common language they would be called involuntary. The objects of desire and aversion are generally at a distance, whereas those of pleasure and pain are immediately acting upon our organs. Hence, before desire or aversion is exerted, so as to cause any actions, there is generally time for deliberation; which consists in discovering the means to obtain the object of desire, or to avoid the object of aversion; or in examining the good or bad consequences, which may result from them. In this case it is evident, that we have a power to delay the pro- posed action, or to perform it; and this power of choosing, whether we shall act or not, is in common language expressed by the word volition, or will. Whereas in this work the word volition means simply the active state of the sensorial faculty in producing motion in consequence of desire or aversion: whether we have the power of restraining that action, or not; that is, whether we exert any actions in consequence of opposite desires or aversions or not. For if the objects of desire or aversion are present, there is no necessity to investigate or compare the means of obtaining them, nor do we always deliberate about their consequences; that is, no deliberation necessarily intervenes, and in consequence the power of choosing to act or not is not exerted. It is probable, that this two-fold use of the word volition in all languages has confounded the metaphysicians, who have disputed about free will and necessity. Whereas from the above analysis it would appear, that during our sleep, we use no voluntary exertions at all; and in our waking hours, that they are the consequence of desire or aversion. To will is to act in consequence of desire; but to desire means to desire something, even if that something be only to be- come free from the pain which causes the desire; for to desire nothing is not to desire; the word desire, therefore, includes both the action and the object or motive; for the object and motive of desire are the same thing. Hence to desire without an object, that is, without a motive, is a solecism in language. As if one should ask, if you could eat without food, or breathe without air. ■From this account of volition it appears, that convulsions of 326 DISEASES Si-ct XXXIV. 1. 1. the muscles, as in epileptic fits, may in the common sense of that word be termed involuntary; because no deliberation is inter- posed between the desire or aversion and the consequent action; but in the sense of the word, as above defined, they belong to the class of voluntary motions, as delivered in Vol. I. Class III. If this use of the word be discordant to the ear of the reader, the term morbid voluntary motions, or motions in consequence of aversion, may be substituted in its stead. If a person has a desire to be cured of the ague, and has at the same time an aversion (or contrary desire) to swallowing an ounce of Peruvian bark; he balances desire against desire, or aversion against aversion; and thus he acquires the power of choosing, which is the common acceptation of the word willing. But in the cold fit of ague, after having discovered that the act of shuddering, or exerting the subcutaneous muscles, relieves the pain of cold; he immediately exerts this act of volition, and shudders, as soon as the pain and consequent aversion return, without any deliberation intervening; yet is this act, as well as that of swallowing an ounce of the bark, caused by volition; and that even though he endeavours in vain to prevent it by a weaker contrary volition. This recalls to our minds the story of the hun- gry ass between two hay-stacks, where the two desires are supposed so exactly to counteract each other, that he goes to neither of the stacks, but perishes by want. . Now as two equal and opposite desires are thus supposed to balance each other, and prevent all action, it follows, that if one of these hay-stacks was suddenly removed, the ass would irresistibly be hurried to the other, which in the common use of the word might be called an involuntary act; but which, in our acceptation of it, would be classed amongst voluntary actions, as above explained. Hence to deliberate is to compare opposing desires or aver- sions, and that which is the most interesting at length prevails, and produces action. Similar to this, where two pains oppose each other, the stronger or more interesting one produces ac- tion; as in pleurisy the pain from suffocation would produce expansion of the lungs, but the pain occasioned by extending the inflamed membrane, which lines the chest, opposes this ex- pansion, and one or the other alternately prevails. When any one moves his hand quickly near another person's eyes, the eyelids instantly close; this act in common language is termed involuntary, as we have not time to deliberate or to exert any contrary desire or aversion; but in this work it would be termed a voluntary act, because it is caused by the faculty of volition, and after a few trials the nictitation can be prevented by a contrary or opposing volition. Sect XXXIV. 1.1. OF VOLITION. 327 The power of opposing volitions is best exemplified in the story of Mutius Scaevola, who is said to have thrust his band into the fire before Porcenna, and to have suffered it to be consumed for having failed him in his attempt on the life of that general. Here the aversion for the loss of fame, or the unsatisfied desire to serve his country, the too prevalent enthusiasms at that time, were more powerful than the desire of withdrawing his hand, which must be occasioned by the pain of combustion; of these opposing volitions Vincit amor patriae, laudumque immensa cupido. If any one is told not to swallow his saliva for a minute, he soon swallows it contrary to his will, in the common sense of that word; but this also is a voluntary action, as it is performed by the faculty of volition, and is thus to be understood. When the power of volition is exerted on any of our senses, they become more acute, as in our attempts to hear small noises in the night. As explained in Section XIX. 6. Hence by our attention to the fauces from our desire not to swallow our saliva; the fauces be- come more sensible; and the stimulus of the saliva is followed by greater sensation, and consequent desire of swallowing it. So that the desire of volition in consequence of the increased sensa- tion of the saliva is more powerful, than the previous desire not to swallow it. See Vol. I. Deglutitio invita. In the same man- ner, if a modest man wishes not to want to make water, when he is confined with ladies in a coach or an assembly room, thit very act of volition induces the circumstance, which he wishes to avoid, as above explained; insomuch that I once saw a partial insanity, which might be called a voluntary diabetes, which was occasioned by the fear (and consequent aversion) of not being able to make water at all. It is further necessary to observe here, to prevent any confu- sion of voluntary, with sensitive, or associate motions, that in all the instances of violent efforts to relieve pain, those efforts are at first voluntary exertions; but after they have been frequently re- peated for the purpose of relieving certain pains, they become associated with those pains, and cease at those times to be sub- servient to the will; as in coughing, sneezing, and strangury. Of these motions, those which contribute to remove or dislodge the offending cause, as the actions of the abdominal muscles in partu- rition or in vomiting, though they were originally excited by vo- lition, are in this work termed sensitive motions; but those ac- tions of the muscles or organs of sense, which do not contribute to remove the offending cause, as in general convulsions or ii* madness, are in this work termed voluntary motions, or motions 328 DISEASES Sttr. XXX1V. 1 2 in consequence of aversion, though in common language they arc called involuntary ones. Those sensitive unrestrainable actions, which contribute to remove the cause of pain, are uniformly and invariably exerted, as in coughing or sneezing; but those motions which are exerted in consequence of aversion, without contribut- ing to remove the painful cause, but only to prevent the sensation of it, as in epileptic or cataleptic fits, are not uniformly and inva- riably exerted, but change from one set of muscles to another, as will be further explained; and may by this criterion also be dis- tinguished from the former. At the same time, those motions which are excited by perpe- tual stimulus, or by association with each other, or immediately by pleasurable or painful sensation, may properly be termed in- voluntary motions, as those of the heart and arteries; as the fa- culty of volition seldom affects those, except when it exists in un- natural quantity, as in maniacal people. 2. It was observed in Sect. XIV. on the Production of Ideas, that those parts of the system, which are usually termed the or- gans of sense, are liable to be excited into pain by the excess of the stimulus of those objects, which are by nature adapted to ef- fect them; as of too great light, sound, or pressure. But that these organs receive no pain from the defect or absence of these stimuli, as in darkness or silence. But that our other organs of perception, which have generally been called appetites, as of hunger, thirst, want of heat, want of fresh air, are liable to be affected with pain by the defect, as well as by the excess of their appropriated stimuli. This excess or defect of stimulus is, however, to be considered only as the remote cause of the pain, the immediate cause being the excess or defect of the natural action of the affected part, ac- cording to Sect. IV. 5. Hence all the pains of the body may be divided into those from excess of motion, and those from defect of motion, which distinction is of great importance in the know- ledge and the cure of many diseases. For as the pains from ex- cess of motion either gradually subside, or are in general suc- ceeded by inflammation; so those from defect of motion either gradually subside, or are in general succeeded by convulsion, or madness. These pains are easily distinguishable from each other by this circumstance, that the former are attended with heat of the pained part, or of the whole body; whereas the latter exist with- out increase of heat in the pained part, and are generally attended with coldness of the extremities of the body; which is the true criterion of what have been called nervous pains. Thus when any acrid material, as snuff or lime falls into the Sect. XXXIV. 1. 2. OF VOLITION. 329 eye, pain and inflammation and heat are produced from the ex- cess of stimulus; but violent hunger, hemicrania, or the clavus hystericus, are attended with coldness of the extremities, and de- fect of circulation. When we are exposed to great cold, the pain we experience from the deficiency of heat is attended with a quiescence of the motions of the vascular system; so that no inflammation is produced, but a great desire of heat, and a tremu- lous motion of the subcutaneous muscles, which is properly a con- vulsion in consequence of this pain from defect of the stimulus of heat. It was before mentioned, that as sensation consists in certain movements of the sensorium, beginning at some of the extremi- ties of it, and propagated to the central parts of it; so volition consists of certain other movements of the sensorium, commenc- ing in the central parts of it, and propagated to some of its extre- mities. This idea of these two great powers of motion in the ani- mal machine is confirmed from observing, that they never exist in a great degree or universally at the same time; for while we strongly exert our voluntary motions we cease to feel the pains or uneasinesses, which occasioned us to exert them. Hence during the time of fighting with fists or swords no pain is felt by the combatants, till they cease to exert themselves. Thus in the beginning of ague-fits the painful sensation of cold is di- minished, while the patient exerts himself in the shivering and gnashing of his teeth. He then ceases to exert himself, and the pain of cold returns; and he is thus perpetually induced to reite- rate these exertions, from which he experiences a temporary re- lief. The same occurs in labour-pains, the exertion of the par- turient woman relieves the violence of the pains for a time, which recur again soon after she has ceased to use those exertions. The same is true in many other painful diseases, as in the strangury, tenesmus, and the efforts of vomiting; all these disagreeable sen- sations are diminished or removed for a time by the various exer- tions they occasion, and recur alternately with those exertions. The restlessness in some fevers is an almost perpetual exertion of this kind, excited to relieve some disagreeable sensations; the reciprocal opposite exertions of a wounded worm, the alternate emprosthotonos and opisthotonos of some spasmodic diseases, and the intervals of all convulsions, from whatever cause, seem to be owing to this circumstance of the laws of animation; that great or universal exertion cannot exist at the same time with great or universal sensation, though they can exist reciprocally; which is probably resolvable into the more general law, that the whole sensorial power being expended in one mode of exertion, there vol. i. it n 330 DISEASES Sect. XXXIV. 1. 3. is none to spare fcr any other. Whence syncope, or temporary apoplexy, succeeds to epileptic convulsions. 3. Hence when any violentpain afflicts us, of which we can neither avoid nor remove the cause, we soon learn to endeavour to alleviate it, by exerting some violent voluntary effort, as mentioned above; and are naturally induced to use those muscles for this purpose, which have been in the earlyperiods of our lives most frequently or most powerfully exerted. Now the first muscles, which infants use most frequently, arc those of respiration; and on this account we gain a habit of hold- ing our breath, at the same time that we use great efforts to ex- clude it, for this purpose of alleviating unavoidable pain; or wc press out our breath through a small aperture of the larynx, and scream violently, when the pain is greater than is relievable by the former mode of exertion. Thus children scream to relieve any pain either of body or mind, as from anger, or fear of being beaten. Hence it is curious to observe, that those animals, who have more frequently exerted their muscles of respiration violently, as in talking, barking or grunting, as children, dogs, hogs, scream much more when they are in pain, than those other animals, who use little or no language in their common modes of life; as horses, sheep, and cows. The next most frequent or most powerful efforts, which in- fants are first tempted to produce, are those with the muscles in biting hard substances; indeed the exertion of these muscles is very powerful in common mastication, as appears from the pain we receive, if a bit of bone is unexpectedly found amongst our softer food; and further appears from their acting to so great me- chanical disadvantage, particularly when we bite with the inci- sores, or canine teeth; which are first formed, and thence are first used to violent exertion. Hence when a person is in great pain, the cause of which he cannot remove, he sets his teeth firmly together, or bites some sub- stance between them with great vehemence, as another mode of violent, exertion to produce a temporary relief. Thus we have a proverb where no help can be had in pain, " to grin and abide;" and the tortures of hell are said to be attended with " gnashing of teeth." Hence in violent spasmodic pains I have seen people bite not only their tongues, but their arms or fingers, or those of the at- tendants, or any object which was near them; and also strike, pinch, or tear, others or themselves, particularly the pari of their own body, which is painful at the time. Soldiers, who die of painful wounds in battle, are said in Homer to bite the Sect. XXXIV. 1.4. OF VOLITION. 331 ground. Thus also in the bellon, or colica saturnina, the pa- tients are said to bite their own flesh, and dogs in this disease to bite up the ground they lie upon. It is probable that the great endeavours to bite in mad dogs, and the violence of other mad animals, are owing to the same cause. 4. If the efforts of our voluntary motions are exerted with still greater energy for the relief of some disagreeable sensation, con- vulsions are produced; as the various kinds of epilesy, and in some hysteric paroxysms. In all these diseases a pain or dis- agreeable sensation is produced, frequently by worms, or acidity in the bowels, or by a diseased nerve in the side, or head, or by the pain of a diseased liver. In some constitutions a more intolerable degree of pain is pro- duced in some part at a distance from the cause by sensitive as- sociation, as before explained; these pains in such constitutions arise to so great a degree, that I verily believe no artificial tor- tures could equal some which I have witnessed; and am con- fident life would not have long been preserved, unless they had been soon diminished or removed by the universal convulsion of the voluntary motions, or by temporary madness. In some of the unfortunate patients I have observed, the pain bus risen to an inexpressible degree, as above described, before the convulsions have supervened; and which were preceded by screaming, and grinning; in others, as in the common epilepsy, the convulsion has immediately succeeded the commencement of the disagreeable sensations; and as a stupor frequently succeeds the convulsions, they only seemed to remember that a pain at the stomach preceded the fit, or some other uneasy feel; or more frequently retained no memory at all of the immediate cause of the paroxysm. But even in this kind of epilepsy, where the pa- tient does not recollect any preceding pain, the paroxysms gene- rally are preceded by a quivering motion of the under*jaw, with a biting of the tongue; the teeth afterwards become pressed to- gether with vehemence, and the eyes are then convulsed, before the commencement of the universal convulsion; which are all efforts to relieve pain. The reason why these convulsive motions are alternately exert-. ed and remitted was mentioned above, and in Sect. XII. 1. 3. when the exertions are such as give a temporary relief to the pain, which excites them, they cease for a time, till the pain is again perceived; and then new exertions are produced for its relief. We see daily examples of this in the loud reiterated laughter of some people; the pleasurable sensation, which ex- cites this laughter, arisesfor a time so high as to change its name, and become painful: the convulsive motions of the respiratory 332 DISEASES Slct. XXXIV. 1.4. muscles relieve the pain for a time; we are, however, unwil- ling to lose the pleasure, and presently put a stop to this exertion, and immediately the pleasure recurs, and again as instantly rises into pain. All of us have felt the pain of immoderate laughter; children have been tickled into convulsions of the whole body; and others have died in the act of laughing; probably from a paralysis succeeding the long continued actions of the muscles of respiration. Hence we learn the reason, why children, who are so easily excited to laugh by the tickling of other people's fingers, cannot tickle themselves into laughter. The exertion of their hands in the endeavour to tickle themselves prevents the necessity of any exertion of the respiratory muscles to relieve the excess of plea- surable affection. See Sect. XVII. 3. 5. Chrysippus is recorded to have died laughing, when an ass was invited to sup with him. The same is related of one of the popes, who, when he was ill, saw a tame monkey at his bed-side put on the holy tiara. Hall. Phys. T. III. p. 306. There are instances of epilepsy being produced by laughing recorded by Van Swietcn, T. III. 402 and 308. And it is well known, that many people have died instantaneously from the painful excess of joy, which probably might have been prevented by the exertions of laughter. Every combination of ideas, which we attend to, occasions pain or pleasure; those which occasion pleasure, furnish either social or selfish pleasure, either malicious or friendly, or lascivi- ous, or sublime pleasure; that is, they give us pleasure mixed with other emotions, or they give us unmixed pleasure, without occasioning any other emotions or exertions at the same time. This unmixed pleasure, if it be great, becomes painful, like all other animal motions from stimuli of every kind; and if no other exertions are occasioned at the same time, we use the ex- ertion of laughter to relieve this pain. Hence laughter is occa- sioned by such wit as excites simply pleasure without any other emotion, such as pity, love, reverence. For sublime ideas are mixed with admiration, beautiful ones with love, new ones, with surprise; and these exertions of our ideas prevent the action of laughter from being necessary to relieve the painful pleasure above described. Whence laughable wit consists of frivolous ideas, without connexions of any consequence, such as puns on words, or on phrases, incongruous junctions of ideas; on which account laughter is so frequent in children. Unmixed pleasure less than that, which causes laughter, causes sleep, as in singing children to sleep, or in slight intoxication from wine or food. See Sect. XV11I. 12. SrcT. XXXIV. 1. 5. OF VOLITION. 333 5. If the pains, or disagreeable sensations, above described, do uot obtain a temporary relief from these convulsive exertions of the muscles, those convulsive exertions continue without remis- sion, and one kind of catalepsy is produced. Thus when a nerve or tendon produces great pain by its being inflamed or wounded, the patient sets his teeth firmly together, and grins violently, to diminish the pain; and if the pain is not relieved by this exer- tion, no relaxation of the maxillary muscles takes place, as in the convulsions above described, but the jaws remain firmly fixed together. This locked jaw is the most frequent instance of cataleptic spasm, because we are most inclined to exert the muscles subservient to mastication from their early obedience to violent efforts of volition. But in the case related in Sect. XIX. on Reverie, the catalep- tic lady had pain in her upper teeth; and pressing one of her hands vehemently against her cheek bone to diminish this pain, it remained in that attitude for about half an hour twice a day, till the painful paroxysm was over. I have this very day seen a young lady in this disease, (with which she has frequently been afflicted;) she began to-day with violent pain shooting from one side of the forehead to the occi- put, and after various struggles lay on the bed with her fingers and wrists bent and stiff for about two hours; in other respects she seemed in a syncope with a natural pulse. She then had in- tervals of pain and of spasm, and took three grains of opium every hour till she had taken nine grains, before the pains and spasm ceased. There is, however, another species of fixed spasm, which dif- fers from the former, as the pain exists in the contracted muscle, and would seem rather to be the consequence than the cause of the contraction, as in the cramp in the calf of the leg, and in many other parts of the body. In these spasms it should" seem, that the muscle itself is first thrown into contraction by some disagreeable sensation, as of cold; and that then the violent pain is produced by the great contraction of the muscular fibres extending its own tendons, which are said to be sensible to extension only; and is further explained in Sect. XVIII. 15. 6. Many instances have been given in this work, where after violent motions excited by irritation, the organ has become qui- escent to less, and even to the great irritation, vvhich induced it into violent motion; as after looking long at the sun or any bright colour, they cease to be seen; and after removing from bright day-light into a gloomy room, the eye cannot at first per- ceive the objects, which stimulate it less. Similar to this is the 334 DISEASES Sect. XXXlN . 1. / syncope, which succeeds after the violent exertions of our vo- luntary motions, as after epileptic fits, for the power of volition acts in this case as the stimulus in the other. This syncope is a temporary palsy, or apoplexy, which ceases after a time, the mus- cles recovering their power of being excited into action by the efforts of volition; as the eye in the circumstance above men- tioned recovers in a little time its power of seeing objects in a gloomy room, which were invisible immediately after coming out of a stronger light. This is owing to an accumulation of sensorial power during the inaction of those fibres, vvhich were before accustomed to perpetual exertions, as explained in Sect. XII. 7. 1. A slighter degree of this disease is experienced by every one after great fatigue, when the muscles gain such ina- bility to further action, that we are obliged to rest them for a while, or to summon a greater power of volition to continue their motions. In all the syncopes, which I have seen induced after convul- sive fits, the pulse has coniinued natural, though the organs of sense, as well as the locomotive muscles, have ceased to perform their functions; for it is necessary for the perception of objects, that the external organs of sense should be properly excited by the voluntary power, as the eye-lids must be open, and perhaps the muscles of the eye put into action to distend, and thence give greater pellucidity to the cornea, which in syncope, as in death, appears flat and less transparent. The tympanum of the ear also seems to require a voluntary exertion of its muscles, to gain its due tension, and it is probable the other external organs of sense require a similar voluntary exertion to adapt them to the distinct perception of objects. Hence in syncope as in sleep, as the power of volition is suspended, no external objects are perceived. See Sect. XVIII. 5. During the time vvhich the patient lies in a fainting fit, the spirit of animation becomes ac- cumulated: and hence the muscles in a while become irritable by their usual stimulation, and the fainting fit ceases. See Sect. XII. 7. 1. 7. If the exertion of the voluntary motions has been still more energetic, the quiescence, which succeeds, is so complete, that they cannot again be excited into action by the efforts of the will. In this manner the palsy, and apoplexy (vvhich is an uni- versal palsy) are frequently produced after convulsions, or other violent exertions; of this I shall add a few instances. Platnerus mentions some, who have died apoplectic from vio- lent exertions in dancing; and Dr. Mead, in his essay on poi- sons, records a patient in the hydrophobia, who at one effort broke the cords which bound him, and at the same instant ex- Sect. XXXTV. 1.7. OF VOLITION. 335 pired. And it is probable, that those, who have expired from immoderate laughter, have died from this paralysis consequent to violent exertion. Mrs. Scott of Stafford was walking in her garden in perfect health with her neighbour Mrs.-----; the lat- ter accidentally fell into a muddy rivulet, and tried in vain to disengage herself by the assistance of Mrs. Scott's hand. Mrs. Scott exerted her utmost power for many minutes, first to assist her friend, and next to orevent herself from being pulled into the morass, as her distressed companion would not disengage her hand. After other assistance was procured hy their united screams, Mrs. Scott walked to a chair about twenty yards from the brook, and was seized with an apoplectic stroke: which continued many days, and terminated in a total loss of her right arm, and her speech; neither of which she ever after perfectly re- covered. It is said, that many people in Holland have died after skating too long or too violently on their frozen canals; it is probable the death of these, and of others, who have died suddenly in swim- ming, has been owing to this great quiescence or paralysis; which has succeeded very violent exertions, added to the concomitant cold, which has had greater effect after the sufferers had been heated and exhausted by previous exercise. 1 remember a young man of the name of Nairne, at Cambridge, who walking on the edge of a barge fell into the river. His cousin and fellow-student of the same name, knowing the other could not swim, plunged into the water after him, caught him by his clothes, and approaching the bank by a vehement exertion propelled him safe to the land, but that instant, seized, as was supposed, by the cramp, or paralysis, sunk to rise no more. The reason why the cramp of the muscles, which compose the calf of the leg, is so liable to affect swimmers, is, because these mus- cles have very weak antagonists, and are in walking generally elongated again after their contraction by the weight of the body on the ball of the toe, which is very much greater than the re- sistance of the water in swimming. See Section XVIII. 15. It does not follow that every apoplectic or paralytic attack is immediately preceded by vehement exertion; the quiescence, which succeeds exertion, and which is not so great as to be term- ed paralysis, frequently recurs afterwards at certain periods; and by other causes of quiescence, occurring with those periods, as was explained in treating of the paroxysms of intermitting fevers; the quiescence at length becomes so great as to be inca- pable of agiin being removed by the efforts of volition, and com- plete parnly .is is formed. See Section XXXII. 3.2. Many oi'jjie paralytic patients, whom I have seen, have evi- 336 DISEASES Sect. XXXIV. 2 1. dently had diseased livers from the too frequent potation of spirituous liquors; some of them have had the gutta rosea on their faces and breasts; which has in some degree receded either spontaneously, or by the use of external remedies, and the paraly- tic stroke has succeeded; and as in several persons, who have drunk much vinous spirits, I have observed epileptic fits to com- mence at about forty or fifty years of age, without any hereditary taint, from the stimulus, as I believed, of a diseased liver; I was induced to ascribe many paralytic cases to the same source; which were not evidently the effect of age, or of unacquired de- bility. And the account given before of dropsies, which very frequently are owing to a paralysis of the absorbent system, and are generally attendant on free drinkers of spirituous liquors, con- firmed me in this opinion. The disagreeable irritation of a diseased liver produces exer- tions and consequent quiescence; these by the accidental con- currence of other causes of quiescence, as cold, solar or lunar periods, inanition, the want of their usual portion of spirit of wine, at length produces paralysis. This is further confirmed by observing, that the muscles, we most frequently, or most powerfully exert, are most liable to palsy; as those of the voice and of articulation, and of those paralytics which I have seen, a much greater proportion have lost the use of their right arm; which is so much more generally ex- erted than the left. I cannot dismiss this subject without observing, that after a paralytic stroke, if the vital powers are not much injured, the patient has all the movements of the affected limb to learn over again, just as in early infancy; the limb is first moved by the irritation of its muscles, as in stretching, (of which a case was related in Section VII. 1. 3.) or by the electric concussion; afterwards it becomes obedient to sensation, as in violent danger or fear; and lastly, the muscles become again associated with volition, and gradually acquire their usual habits of acting to- gether. Another phenomenon in palsies is, that when the limbs of one side are disabled, those of the other are in perpetual motion. This can only be explained from conceiving that the power of motion, whatever it is, or wherever it resides, and which is capa- ble of being exhausted by fatigue, and accumulated in rest, is now less expended, whilst one half of the body is incapable of receiving its usual proportion of it, and is hence derived with greater ease or in greater abundance into the limbs, which remain unaffected. II. 1. The excess or defect of voluntary exertion produces Sect. XXXIV. 2. 2. OF VOLITION. 337 similar effects upon the sensual motions, or ideas of the mind, as those already mentioned upon the muscular fibres. Thus when any violent pain, arising from the defect of some peculiar stimu- lus, exists either in the muscular or sensual systems of fibres, and which cannot be removed by acquiring the defective stimulus; as in some constitutions convulsions of the muscles are produced to procure a temporary relief, so in other constitutions vehement voluntary exertions of the ideas of the mind are produced for the same purpose; for during this exertion, like that of the mus- cles, the pain either vanishes or is diminished: this violent ex- ertion constitutes madness; and in many cases I have seen the madness take place, and the convulsions cease, and reciprocally the madness cease, and the convulsions supervene. See Section III. 5. 8. 2. Madness is distinguishable from delirium, as in the latter the patient knows not the place where he resides, nor the per- sons of his friends or attendants, nor is conscious of any external objects, except when spoken to with a louder voice, or stimu- lated with unusual force, and even then he soon relapses into a state of inattention to every thing about him. Whilst in the former he is perfectly sensible to every thing external, but has the voluntary powers of his mind intensely exerted on some par- ticular object of his desire or aversion, he harbours in his thoughts a suspicion of all mankind, lest they should counteract his designs; and while he keeps his intentions, and the motives of his actions profoundly secret; he is perpetually studying the means of acquiring the object of his wish, or of preventing or revenging the injuries he suspects. 3. A late French philosopher, Mr. Helvetius, has deduced al- most all our actions from this principle of their relieving us from the ennui ortaedium vitae; and true it is, that our desires or aversions are the motives of all our voluntary actions; and human nature seems to excel other animals in the more facile use of this voluntary power, and on that account is more liable to in- sanity than other animals. But in mania this violent exertion of volition is expended on mistaken objects, and would not be relieved, though we were to gain or escape the objects that ex- cite it. Thus I have seen two instances of madmen, who con- ceived that they had the itch, and several have believed they had the venereal infection, without in reality having a symptom of either of them. They have been perpetually thinking upon this subject, and some of them were in vain salivated with design of convincing them to the contrary. 4. In the minds of mad people those volitions alone exist, which are unmixed with sensation; immoderate suspicion is VOL. I. xx 338 DISEASES Sect. XXXIV 2. 5. generally the first symptom, and want of shame, and want of delicacy about cleanliness. Suspicion is a voluntary exertion of the mind arising from the pain of fear, vvhich it is exerted to relieve: shame is the name of a peculiar disagreeable sensation, see Fable of the Bees, and delicacy about cleanliness arises from another disagreeable sensation. And therefore are not found in the minds of maniacs, which are employed solely in voluntary exertions. Hence the most modest women in this disease walk "naked amongst men without any kind of concern, use obscene discourse, and have no delicacy about their natural evacuations. 5. Nor are maniacal people more attentive to their natural appetites, or to the irritations which surround them, except as far as may respect their suspicions or designs; for the violent and perpetual exertions of their voluntary powers of mind prevent their perception of almost every other object, either of irritation or of sensation. Hence it is that they bear cold, hunger, and fa- tigue, with -much greater pertinacity than in their sober hours, and are less injured by them in respect to their general health. Thus it is asserted by historians, that Charles the Twelfth of Sweden slept on the snow, wrapped only in his cloak, at the siege of Frederickstadt, and bore extremes of cold and hunger, and fa- tigue, under which numbers of his soldiers perished; because the king was insane with ambition, but the soldier had no such power- ful stimulus to preserve his system from debility and death. 6. Besides the insanities arising from exertions in consequence of pain, there is also a pleasurable insanity, as well as a pleasura- ble delirium; as the insanity of personal vanity, and that of re- ligious fanaticism. When agreeable ideas excite into motion the sensorial power of sensation, and this again causes other trains of agreeable ideas, a constant stream of pleasurable ideas succeeds, and produces pleasurable delirium- So when the sensorial power of volition excites agreeable ideas, and the pleasure thus pro- duced excites more volition in its turn, a constant flow of agree- able voluntary ideas succeeds; which when thus exerted in the extreme constitutes insanity. Thus when our muscular actions are excited by our sensations of pleasure, it is termed play; when they are excited by our volition, it is termed work; and the former of these is attended with less fatigue, because the muscular actions in play produce in their turn more pleasurable sensation; which again has the property of producing more muscular action. An agreeable in- stance of this I saw this morning. A little boy, who was tired with walking, begged of his papa to carry him. " Here," says the reverend doctor, " ride upon my gold-headed cane;" and the pleased child, putting it between his legs, galloped away Sect. XXXIV. 2. 7. OF VOLITION. 339 with delight, and complained no more of his fatigue. Here the aid of another sensorial power, that of pleasurable sensation, su- peradded vigour to the exertion of exhausted volition. Which could otherwise only have been excited by additional pain, as by the lash of slavery. On this account where the whole sensorial power has been exerted on the contemplation of the promised joys of heaven, the saints of all persecuted religions have borne the .tortures of martyrdom with otherwise unaccountable firmness. 7. There are some diseases, which obtain at least a temporary relief from the exertions of insanity; many instances of dropsies being thus for a time cured are recorded. An elderly woman labouring with ascites, I twice saw relieved for some weeks by insanity, the dropsy ceased for several weeks, and recurred again alternating with the insanity. A man afflicted with difficult re- spiration on lying down, with very irregular pulse, and oedema- tous legs, whom I saw this day, has for above a week been much relieved in respect to all those symptoms by the accession of in- sanity, which is shewn by inordinate suspicion and great anger. In cases of common temporary anger the increased action of the arterial system is seon by the red skin, and increased pulse, with the immediate increase of muscular activity. A friend of mine, when he was painfully fatigued by riding on horseback, was accustomed to call up ideas into his mind which used to ex- cite his anger or indignation, and thus for a time at least relieved the pain of fatigue. By this temporary insanity, the effect of the voluntary power upon the whole of his system was increased; as in the cases of dropsy above mentioned it would appear, that the increased action of the voluntary faculty of the sensorium affected the absorbent system, as well as the secerning one. 8. In respect to relieving inflammatory pains, and removing fever, I have seen many instances, as mentioned in Sect. XII. 2. 4. One lady, whom I attended, had twice at some years in- terval a locked jaw, which relieved a pain on her sternum with peripneumony. Two other ladies I saw, who towards the end of violent peripneumony, in which they frequently lost blood, were at length cured by insanity supervening. In the former the increased voluntary exertion of the muscles of the jaw, in the latter that of the organs of sense, removed the disease; that is, the disagreeable sensation, which had produced the inflamma- tion, now excited the voluntary power, and these new voluntary exertions employed or expended the superabundant sensorial power, which had previously been exerted on the arterial system, and caused inflammation. Another case which I think worth relating, was of a young man about twenty; he had laboured under an irritative fever 340 DISEASES Sect. XXXIV. 3.1 with debility for three or four weeks, with very quick and very feeble pulse, and other usual symptoms of that species of typhus, but at this time complained much and frequently of pain of his legs and feet. When those who attended him were nearly in despair of his recovery, I observed with pleasure an insanity of mind supervene: which was totally different from delirium, as he knew his friends, calling them by their names, and the room in which he lay, but became violently suspicious of his attend- ants, and calumniated with vehement oaths his tender mother, who sat weeping by his bed. On this his pulse became slower and firmer, but the quickness did not for some time entirely cease, and he gradually recovered. In this case the introduction of an increased quantity of the power of volition gave vigour to those movements of the system, which are generally only actu- ated by the power of irritation, and of association. Another case I recollect of a young man, about twenty-five, who had the scarlet fever, with very quick pulse, and an univer- sal eruption on his skin, and was not without reason esteemed to be in great danger of his life. After a few days an insanity su- pervened, which his friends mistook for delirium, and he gradu- ally recovered, and the cuticle peeled off. From these and a few other cases I have always esteemed insanity to be a favour- able sign in fevers, and have cautiously distinguished it from de- lirium. III. Another mode of mental exertion to relieve pain, is by producing a train of ideas not only by the efforts of volition, as in insanity; but by those of sensation likewise, as in delirium and sleep. This mental effort is termed reverie, or somnambu- lation, and is described more at large in Sect. XIX. on that sub- ject. But I shall here relate another case of that wonderful dis- ease, which fell yesterday under my eye, and to which I have seen many analogous alienations of mind, though not exactly similar in all circumstances. But as all of them either began or terminated with pain or convulsion, there can be no doubt but that they are of epileptic origin, and constitute another mode of mental exertion to relieve some painful sensation. 1. Master A. about nine years old, had been seized at seven every morning for ten days with uncommon fits, and had had slight returns in the afternoon. They were supposed to origin- ate from worms, and had been in vain attempted to be removed by vermifuge purges. As his fit was expected at seven yester- day morning, I saw him before that hour; he was asleep, seemed free from pain, and his pulse natural. About seven he began to complain of pain about his navel, or more to the left side, and in a few minutes had exertions of his arms and legs like Sect. XXXIV. 3. 2. OF VOLITION. 341 swimming. He then for half an hour hunted a pack of hounds; as appeared by his hallooing, and calling the dogs by their names, and discoursing with the attendants of the chase, describing ex- actly a day of hnnting, which (I was informed) he had witnessed a year before, going through all the most minute circumstances of it; calling to people, who were then present, and lamenting the absence of others, who were then also absent. After this scene he imitated, as he lay in bed, some of the plays of boys, as swimming and jumping. lie then sung an English and then an Italian song; part of which with his eyes open, and part with them closed, but could not be awakened or excited by any vio- lence, which it was proper to use. After about an hour he came suddenly to himself with appa- rent surprise, and seemed quite ignorant of any part of what had passed, and after being apparently well for half an hour, he sud- denly fell into a great stupor, with slower pulse than natural, and a slow moaning respiration, in which he continued about another half hour, and then recovered. The sequel of this disease was favourable; he was directed one grain of opium at six every morning, and then to rise out of bed; at half past six he was directed fifteen drops of laudanum in a glass of wine and water. The first day, the paroxysm became shorter and less violent. The dose of opium was increased to one half more, and in three or four days the fits left him. The bark and filings of iron were also exhibited twice a day; and I believe the complaint returned no more. 2. In this paroxysm it must be observed, that he began with pain, and ended with stupor, in both circumstances resembling a fit of epilepsy. And that therefore the exertions both of mind and body, both the voluntary ones and those immediately excited by pleasurable sensation, were exertions to relieve pain. The hunting scene appeared to be rather an act of memory than ef imagination, and was therefore rather a voluntary exertion, though attended with the pleasurable eagerness, which was the consequence of those ideas recalled by recollection, and not the cause of them. These ideas thus voluntarily recollected, were succeeded by sensations of pleasure, though his senses were unaffected by the stimuli of visible or audible objects; or so weakly excited by them as not to produce sensation or attention. And the pleasure thus excited by volition, produced other ideas and other motions, in consequence of the sensorial power of sensation. Whence the mixed catenations of voluntary and sensitive ideas and muscular motions in reverie; which, like every other kind of vehement 342 DISEASES Sbct. XXXIV. 3. 3. exertion, contribute to relieve pain, by expending a large quan- tity of sensorial power. Those fits generally commence during sleep, from whence I suppose they have been thought to have some connexion with sleep, and have thence been termed Somnambulism; but their commencement during sleep is owing to our increased excitability by internal sensations at that time, as explained in Sect. XVIII. 14 and 15, and not to any similitude between reverie and sleep. 3. I was once concerned for a very elegant and ingenious young lady, who had a reverie on alternate days, which continued nearly the whole day; and as in her days of disease she took up the same kind of ideas, which she had conversed about on the alter- nate day before, and could recollect nothing of them on her well day, she appeared to her friends to possess two minds. This case also was of the epileptic kind, and was cured, with some relapses, by opium administered before the commencement of the paroxysm. 4. Whence it appears, that the methods of relieving inflamma- tory pains, is by removing all stimulus, as by venesection, cool air, mucilaginous diet, aqueous potation, silence, darkness. The methods of relieving pains from defect of stimulus, is by supplying the peculiar stimulus required, as of food or warmth. And the general method of relieving pain is by exciting into action some great part of the system, for the purpose of expending a part of the sensorial power. This is done either by exertion of the voluntary ideas and muscles, as in insanity and convulsion; or by exerting both voluntary and sensitive motions, as in reve- rie; or by exciting the irritative motions by wine or opium in- ternally, and by the warm bath or blisters externally; or lastly, by exciting the sensitive ideas by good news, affecting stories, or agreeable passions. Sect. XXXV. 1.1.. OF ASSOCIATION 343 SECT. XXXV. DISEASES OF ASSOCIATION. I. 1. Sympathy or consent of parts. Primary and secondary parts of an associated train of motions reciprocally affect each other. Parts of irritative trains of motion affect each other in four ways. Sympathies of the skin and stomach. Flushing of the face after a meal. Eruption of the small-pox on the face. Chilness after a meal. 2. Vertigo from intoxication. 3. Absorption from tlie lungs and pericardium by emetics. In vomiting the actions of the stomach are decreased, not increased. Digestion strength- ened after an emetic. Vomiting from deficiency of sensorial power. 4. Dyspnea from cold bathing. Slow pulse from di- gitalis. Death from gout in the stomach. II. 1. Primary and secondary parts of sensitive associations affect each other. Pain frmn gall-stone, from urinary stone. Hemicrania. Painful epilepsy. 2. Gout and red face from inflamed liver. Shingles from inflamed kidney. 3. Coryza from cold applied to tlie feet. Pleurisy. Hepatitis. 4. Pain of shoulders from inflamed liver. III. Diseases from the associations of ideas. I. 1. Many synchronous and successive motions of our mus- cular fibres, and of our organs of sense, or ideas, become asso- ciated so as to form indissoluble tribes or trains of action, as shewn in Section X. on Associate Motions. Some constitutions more easily establish these associations, whether by voluntary, sensi- tive, or irritative repetitions, and some more easily lose them again, as shewn in Section XXXI. on Temperaments. When the beginning of such a train of actions becomes by any means disordered, the succeeding part is liable to become dis- turbed in consequence, and this is commonly termed sympathy, or consent of parts by the writers of medicine. For the more clear understanding of these sympathies we must consider a tribe or train of actions as divided into two parts, and call one of them the primary or original motions, and the other the secondary or sympathetic ones. The primary and secondary parts of a train of irritative actions may reciprocally affect each other in four different manners. 1. They may both be exerted with greater energy than natural. 2. The former may act with greater, and the latter with less energy. 3. The former may act with less, and the latter with greater energy. 4. They may both act with less energy than natural. I shall now give an example of each kind of these 344 DISEASES Sbct.XXXV. 1.2. modes of action, and endeavour to shew, that though the pri- mary and secondary parts of these trains or tribes of motion are connected by irritative association, or their previous habits of act- ing together, as described in Sect. XX. on Vertigo; yet that their acting with similar or dissimilar degrees of energy, depends on the greater or less quantity of sensorial power, which the pri- mary part of the train expends in its exertions. The actions of the stomach constitute so important a part of the associations of both irritative and sensitive motions, that it is said to sympathize with almost every part of the body; the first ex-- ample, which I shall adduce to shew that both the primary and secondary parts of a train of irritative associations of motion act with increased energy, is taken from the consent of the skin with this organ. When the action of the fibres of the stomach is in- creased, as by the stimulus of a full meal, the exertions of the cutaneous arteries of the face become increased by their irritative associations with those of the stomach, and a glow or flushing of the face succeeds. For the small vessels of the skin of the face * having been more accustomed to the varieties of action, from their frequent exposure to various degrees of cold and heat, be- come more easily excited into increased action, than those of the covered parts of our bodies, and thus act with more energy from their irritative or sensitive associations with the stomach. On this account in small-pox the eruption in consequence of the pre- vious affection of the stomach breaks out a day sooner on the face than on the hands, and two days sooner than on the trunk, and recedes in similar times after maturation. But secondly, in weaker constitutions, that is, in those who possess less sensorial power, so much of it is expended in the in- creased actions of the fibres of the stomach excited by the stimu- lus of a meal, that a sense of chilness succeeds instead of the uni- versal glow above mentioned; and thus the secondary part of the associated train of motions is diminished in energy, in consequence of the increased activity of the primary part of it. 2. Another instance of a similar kind, where the secondary part of the train acts with less energy in consequence of the greater exertions of the primary part, is the vertigo attending in- toxication; in this circumstance so much sensorial power is ex- pended on the stomach, and on its nearest or more strongly asso- ciated motions, as those of the subcutaneous vessels, and proba- bly of the membranes of some internal viscera, that the irritative motions of the retina become imperfectly exerted from defi- ciency of sensorial power, as explained in Sect. XX. and XXI. 3. on Vertigo and on Drunkenness, and hence the staggering ine- briate cannot completely balance himself by such indistinct vision. Sect. XXXV. 1.]. OF ASSOCIATION. 345 3. An instance of the third circumstance, where the primary part of a train of irritative motions acts with less, and the second- ary part with greater energy, may be observed by making the following experiment. If a person lies with his arms and shoul- ders out of bed, till they become cold, a temporary coryza or catarrh is produced; so that the passage of the nostrils becomes totally obstructed; at least this happens to many people; and then on covering the arms and shoulders, till they become warm, the passage of the nostrils ceases again to be obstructed, and a quantity of mucus is discharged from them. In this case the quiescence of the vessels of the skin of the arms and shoulders, occasioned by exposure to cold air, produces by irritative asso- ciation an increased action of the vessels of the membrane of the nostrils; and ihe accumulation.of sensorial power during the torpor of the arms and shoulders is thus expended in producing a temporary coryza or catarrh. Another instance may be adduced from the sympathy or con- sent of the motions of the stomach with other more distant links of the very extensive tribes or trains of irritative motions associ-* ated with them, described in Sect. XX. on Vertigo. When the actions of the fibres of the stomach are diminished or inverted, Ihe actions of the absorbent vessels, vvhich take up the mucus from the lungs, pericardium, and other cells of the body, be- come increased, and absorb the fluids accumulated in them with greater avidity, as appears from the exhibition of foxglove, anti- mony, or other emetics, in cases of anasarca, attended with un- equal pulse and difficult respiration. That the act of nausea and vomiting is a decreased exertion of the fibres of the stomach may be thus deduced; when an emetic medicine is administered, it produces the pain of sickness, as a disagreeable taste in the mouth produces the pain of nausea; these pains, like that of hunger, or of cold, or like those, which are usually termed nervous, as the head-ach or hemicrania, do not excite the organ into greater action; but in this case I ima- gine the pains of sickness or of nausea counteract or destroy the pleasurable sensation, vvhich seems necessary to digestion, as shewn in Sect. XXXIII. 1.1. The peristaltic motions of the fibres of the stomach become enfeebled by the want of this stimulus of pleasurable sensation, and in consequence stop for a time, and then become inverted; for they cannot become invert- ed without being previously stopped. Now that this inversion of the trains of motion of the fibres of the stomach is owing to the deficiency of pleasurable sensation, is evinced from this cir- cumstance, that a nauseous idea excited by words will produce vomiting as effectually as a nauseous drug. vol. i. y v 346 DISEASES Sect. XXXV. 1.4. Hence it appears, that the act of nausea or vomiting expends less sensorial power than the usual peristaltic motions of the stomach in the digestion of our aliment; and that hence there is a greater quantity of sensorial power becomes accumulated in the fibres of the stomach, and more of it in consequence to spare for the action of those parts of the system, which are thus associated with the stomach, as of the whole absorbent series of vessels, and which are at the same time excited by their usual stimuli. From this we can understand, how after the operation of an emetic the stomach becomes more irritable and sensible to the stimulus, and the pleasure of food; since as the sensorial power becomes accumulated during the nausea and vomiting, the di- gestive power is afterwards exerted more forcibly for a time. It should, however, be here remarked, that though vomiting is in general produced by the defect of this stimulus of pleasurable sen- sation, as when a nauseous drug is administered; yet in long continued vomiting, as in sea-sickness, or from habitual dram- drinking, it arises from deficiency of sensorial power, which in the former case is exhausted by the increased exertion of the ir- ritative ideas of vision, and in the latter by the frequent applica- tion of an unnatural stimulus. 4. An example of the fourth circumstance above mentioned, where both the primary and secondary parts of a train of mo- tions proceed with energy less than natural, may be observed in the dyspnoea, which occurs on going into a very cold bath, and which has been described and explained in Sect. XXXII. 3. 2.; and by the increased debility of the pulsations of the heart and arteries during the operation of an emetic. Secondly, from the slowness and intermission of the pulsations of the heart from the incessant efforts to vomit occasioned by an over dose of digitalis. And thirdly, from the total stoppage of the motions of the heart, or death, in consequence of the torpor of the stomach, when af- fected with the commencement or cold paroxysm of the gout. See Sect. XXV. 17. II. 1. The primary and secondary parts of the trains of sen- sitive association reciprocally affect each other in different man- ners. 1. The increased sensation of the primary part may cease, when that of the secondary part commences. 2. The increased action of the primary part may cease, when that of the secondary part commences. 3. The primary part may have increased sensation, and the secondary part increased action. 4. The pri- mary part may have increased action, and the secondary part in- creased sensation. Examples of the first mode, where the increased sensation of Sict.XXXV. 2. 1. OF ASSOCIATION. 347 the primary part of a train of sensitive association ceases, when that of the secondary part commences, are not unfrequent; as this is the general origin of those pains, which continue some time without being attended with inflammation, such as the pain at the pit of the stomach from a stone at the neck of the gall- bladder, and the pain of strangury in the glans penis from a stone at the neck of the urinary bladder. In both these cases the part which is affected secondarily, is believed to be much more sen- sible than the part primarily affected, as described in the cata- logue of diseases, Class II. 1. 1. 11. and IV. 2. 2. 2. and IV. 2. 2. 4. The hemicrania, or nervous head-ach, as it is called, when it originates from a decaying tooth, is another disease of this kind; as the pain of the carious tooth always ceases when the pain over one eye and temple commences. And it is probable, that the violent pains, which induce convulsions in painful epilepsies, are produced in the same manner, from a more sensible part sympathizing with a diseased one of less sensibility. See Cata- logue of diseases, Class IV. 2. 2. 8. and III. 1. 1. 6. The last tooth, or dens sapientiae, of the upper jaw most fre- quently decays first, and is liable to produce pain over the eye and temple of that side. The last tooth of the under jaw is also liable to produce a similar hemicrania, when it begins to decay. When a tooth in the upper jaw is the cause of the head-ach, a slighter pain is sometimes perceived on the cheek bone. And when a tooth in the lower jaw is the cause of head-ach, a pain sometimes affects the tendons of the muscles of the neck, which are attached near the jaws. But the clavus hystericus, or pain about the middle of the parietal bone on one side of the head, I have seen produced by the second of the molares, or grinders, of the under jaw; of which I shall relate the following case. See Class IV. 2. 2. 8. Mrs.-----, about 30 years of age, was seized with great pain about the middle of the right parietal bone, which had continued a whole day before I saw her, and was so violent as to threaten to occasion convulsions. Not being able to detect a decaying tooth, or a tender one, by examination with my eye, or by strik- ing them with a tea-spoon, and fearing bad consequences from her tendency to convulsion, I advised her to extract the last tooth of the under jaw on the affected side; vvhich was done without any good effect. She was then directed to lose blood, and to take a brisk cathartic; and after that had operated, about 60 drops of laudanum were given her, with large doses of bark; by vvhich the pain was removed. In about a fortnight she took a cathartic medicine by ill advice, and the pain returned 348 DISEASES Sect. XXX\ . 2. 1. with greater violence in the same place; and, before I could ar- rive, as she lived 30 miles from me, she suffered a paralytic stroke; which affected her limbs and her face on one side, and relieved the pain of her head. About a year afterwards I was again called to her on account of a pain, as violent as before, exactly on the same part of the other parietal boue. On examining her mouth I found the second molaris of the under jaw on the side before affected was now decayed, and concluded that this tooth had occasioned the stroke of the palsy by the pain and consequent exertion it had caused. On this account I earnestly entreated her to allow the sound mo- laris of the same jaw opposite to the decayed one to be extract- ed; which was forthwith done, and the pain of her head imme- diately ceased, to the astonishment of her attendants. In the cases above related of the pain existing in a part dis- tant from the seat of the disease, the pain is owing to defect of the usual motions of the painful part. This appears from the coldness, paleness, and emptiness of the affected vessels, or of the extremities of the body in general, and from there being no tendency to inflammation. The increased action of the primary part of these associated motions, as of the hepatic termination of the bile-duct from the stimulus of a gall-stone, or of the inte- rior termination of the urethra from the stimulus of a stone in the bladder; or, lastly, of a decaying tooth in hemicrania, deprives the secondary part of these associated motions, namely, the exte- rior terminations of the bile-duct or urethra, or the pained mem- branes of the head in hemicrania, of their natural share of senso- rial power: and hence the secondary parts of these sensitive trains of association become pained from the deficiency of their usual motions, which is accompanied with deficiency of secretions and of heat. See Sect. IV. 5. XII. 5. 3. XXXIV." 1. Why does the pain of the primary part of the association cease, when that of the secondary part commences? This is a question of intricacy, but perhaps not inexplicable. The pain of the primary part of these associated trains of motion was owing to too great stimulus, as of the stone at the neck of the blad- der, and was consequently caused by too great action of the pained part. This greater action than natural of the primary part of these associated motions, by employing or expending the sensorial power of irritation belonging to the whole associated train of motions, occasioned torpor, and consequent pain in the secondary part of the associated train; which was possessed of greater sensibility than the primary part of it. Now the great pain of the secondary part of the train, as soon as it commences, employs or expends the sensorial power of sensation belonging Sect. XXXV. 2.2. OF ASSOCIATION. 349 to the whole associated train of motions; and in consequence the motions of the primary part, though increased by the stimulus of an extraneous body, cease to be accompanied with pain or sen- sation. If this mode of reasoning be just, it explains a curious fact, why when two parts of the body are strongly stimulated, the pain is felt only in one of them, though it is possible by voluntary at- tention it may be alternately perceived in them both. In the same manner, when two new ideas are presented to us from the stimulus of external bodies, we attend to but one of them at a time. In other words, when one set of fibres, whether of the muscles or organs of sense, contract so strongly as to excite much sensation; another set of fibres, contracting more weakly, do not excite sensation at all, because the sensorial power of sensation is pre-occupied by the first set of fibres. So we cannot will more than one effect at once, though by associations previously formed we can move many fibres in combination. Thus in the instances above related, the termination of the bile- duct in the duodenum, and the exterior extremity of the urethra, are more sensible than their other terminations. When these parts are deprived of iheir usual motions by deficiency of senso- rial power, as above explained, they become painful, according to law the fifth in Sect. IV. and the less pain originally excited by the stimulus of concreted bile, or of a stone at their other ex- tremities, ceases to be perceived. Afterwards, however, when the concretions of bile, or the stone in the urinary bladder, be- come more numerous or larger, the pain from their increased stimulus becomes greater than the associated pain; and is then felt at the neck of the gall-bladder or urinary bladder; and the pain of the glans penis, or at the pit of the stomach, ceases to be perceived. 2. Examples of the second mode, where the increased action of the primary part of a train of sensitive association ceases, when that of the secondary part commences, are also not unfrequent; as this is the usual manner of the translation of inflammations from internal to external parts of the system, such as when an inflammation of the liver or stomach is translated to the mem- branes of the foot, and forms the gout; or to the skin of the face, and forms the rosy drop; or when an inflammation of the mem- branes of the kidneys is translated to the skin of the loins, and forms one kind of herpes, called shingles; in these.cases, by whatever cause the original inflammation may have been pro- duced, as the secondary part of the train of sensitive association is more sensible, it becomes exerted with greater violence than the first part of it; and by both its increased pain, and the in- 350 DISEASES Sect. XXXV. 2. 3. creased motion of its fibres, so far diminishes or exhausts the sen- sorial power of sensation, that the primary part of the train be- ing iess sensible, ceases both to feel pain and to act with unna- tural energy. 3. Examples of the third mode, where the primary part of a train of sensitive association of motions may experience increased sensation, and the secondary part increased action, are likewise not unfrequent; as it is in this manner that most inflammations commence. Thus, after standing some time in snow, the feet become affected with the pain of cold, and a common coryza, or inflammation of the membrane of the nostrils, succeeds. It is probable that the internal inflammations, as pleurisies, or hepa- titis, which are produced after the cold paroxysm of fever, origi- nate in the same manner from the sympathy of those parts with some others, which were previously pained from quiescence; as happens to various parts of the system during the cold fits of fevers. In these cases, it would seem that the sensorial power of sensation becomes accumulated during the pain of cold, as the torpor of the vessels occasioned by the defect of heat contributes to the increase or accumulation of the sensorial power of irrita- tion, and that both these become exerted on some internal part, which was not rendered torpid by the cold which affected the ex- ternal parts, nor by its association with them; or which sooner recovered its sensibility. This requires further consideration. 4. An example of the fourth mode, or where the primary part of a sensitive association of motions may have increased action, and the secondary part increased sensation, may be taken from the pain of the shoulder, which attends inflammation of the membranes of the liver, see Class IV. 2. 2. 9.; in this circum- stance, so much sensorial power seems to be expended in the vio- lent actions and sensations of the inflamed membranes of the liver, that the membranes associated with them become quiescent to their usual stimuli, and painful in consequence. There may be other modes in which the primary and secondary parts of the trains of associated sensitive motions may recipro- cally affect each other, as may be seen by looking over Class IV. in the catalogue of diseases; all which may probably be resolved into the plus and minus of sensorial power, but we have not yet had sufficient observations made upon them with a view to this doctrine. III. The associated trains of our ideas may have sympathies, and their primary and secondary parts affect each other in some manner similar to those above described; and may thus occasion various curious phenomena not yet adverted to, besides those ex- Src t. XXXV. 3. 1. OF ASSOCIATION. 351 plained in the Sections on Dreams, Reveries, Vertigo, and Drunkenness; and may thus disturb the deductions of our rea- sonings, as well as the streams of our imaginations; present us with false degrees of fear; attach unfounded value to trivial cir- cumstances; give occasion to our early prejudices and antipa- thies; and thus embarrass the happiness of our lives. A copi- ous and curious harvest might be reaped from this province of science, in vvhich, however, I shall not at present wield my sickle. 352 PERIODS Sect. XXXVI. 1. 1 SECT. XXXVI. OF THE PERIODS OF DISEASES. I. Muscles excited by volition soon cease to contract, or by sensa- tion, or by irritation, oicing to the exhaustion of sensorial power. Muscles subjected to less stimulus have their sensorial power ac- cumulated. Hence the periods of some fevers. Want of irrita- bility after intoxication. II. 1. Natural actions catenated with daily habits of life. 2. With solar periods. Periods of sleep. Of evacuating the bowels. 3. Naturcd actions catenated irith lunar periods. Menstruation. Venereal orgasm of animals. Barrenness. III. Periods of diseased anient! actions from stated returns of nocturnal cold, from solar and lunar influence. Periods of diurnal fevir, hecticfever, quotidian, tertian, quar- tan fever. Periods of gout, pleurisy, of fevers with arterial de- bility, and with arterial strength. Periods of rhaphania, of nervous cough, hemicrania, arterial hemorrhages, hemorrhoids, ham opt oe, epilepsy, palsy, apoplexy, madness. IV. Critical days depend on lunar periods. Lunar periods in tlie small-pox. I. If any of our muscles be made to contract violently by the power of volition, as those of the fingers, when any one hangs by his hands on a swing, fatigue soon ensues; and the muscles cease to act owing to the temporary exhaustion of the spirit of animation; as soon as this is again accumulated in the muscles, they are ready to contract again by the efforts of volition. Those violent muscular actions induced by pain become in the same manner intermitted and recurrent; as in labour-pains, vomiting, tenesmus, strangury; owing likewise to the temporary exhaustion of the spirit of animation, as above mentioned. When any stimulus continues long to act with unnatural vio- lence, so as to produce too energetic action of any of our moving organs, those motions soon cease though the stimulus continues to act; as in looking long on a bright object, as on an inch-square of red silk laid on white paper in the sunshine. See Plate I. in Sect. III. 1. On the contrary, where less of the stimulus of volition, sensa- tion, or irritation, has been applied to a muscle than usual; there appears to be an accumulation of the spirit of animation in the moving organ; by which it is liable to act with greater energy from less quantity of stimulus, than was previously ne- cessary to excite it into so great action; as after having been im- mersed in snow the cutaneous vessels of our hands are excited SrcT. XXXVI. 2. 1. OF DISEASES. 353 into stronger action by the stimulus of a less degree of heat than would previously have produced that effect. From hence the periods of some fever-fits may take their ori- gin, either simply, or by their accidental coincidence with lunar and solar periods, or with the diurnal periods of heat and cold, to be treated of below; for during the cold fit at the commencement of a fever, from whatever cause that cold fit may have been in- duced, it follows, 1. That the spirit of animation must become accumulated in the parts, which exert during this cold fit less than their natural quantity of action. 2. If the cause producing the cold fit does not increase, or becomes diminished; the parts before benumbed or inactive become now excitable by smaller stimulus, and are thence thrown into more violent action than is natural; that is, a hot fit succeeds the cold one. 3. By the energetic action of the system during the hot fit, if it continues long, an exhaustion of the spirit of animation takes place; and another cold fit is liable to succeed, from the moving system not being excitable into action from its usual stimulus. This inirri- tability of the system from a too great previous stimulus, and consequent exhaustion of sensorial power, is the cause of the gene- ral debility, and sickness, and head-ach, some hours after intoxi- cation. And hence we see one of the causes of the periods of fever-fits; which however are frequently combined with the periods of our diurnal habits, or of heat and cold, or of solar or lunar periods. When besides the tendency to quiescence occasioned by the expenditure of sensorial power during the hot fit of fever, some other cause of torpor, as the solar or lunar periods, is necessary to the introduction of a second cold fit; the fever becomes of the intermittent kind; that is, there is a space of time intervenes be- tween the end of the hot fit, and the commencement of the next cold one. But where no exterior cause is necessary to the intro- duction of the second cold fit; no such interval of health inter- venes; but the second cold fit commences, as soon as the sen- sorial power is sufficiently exhausted by the hot fit; and the fever becomes continual. II. 1. The following are natural animal actions, which are frequently catenated with our daily habits of life, as well as ex- cited by their natural irritations. The periods of hunger and thirst become catenated with certain portions of time, or degrees of exhaustion, or other diurnal habits of life. And if the pain of hunger be not relieved by taking food at the usual time, it is liable to cease till the next period of time or other habits recur; this is not only true in respect to our general desire of food, but the kinds of it also are governed by this periodical habit; inso- vol. i. z z 354 PERIODS Si:ct. XXXVI. 2. 2. much that beer taken to breakfast will disturb the digestion of those, who have been accustomed to tea; and tea taken at dinner will disagree with those who have been accustomed to beer. Whence it happens, that those who have weak stomachs will be able to digest more food, if they take their meals at regular hours; because they have both the stimulus of the aliment they take, and the periodical habit, to assist their digestion. The periods of emptying the bladder are not only dependent on the acrimony or distention of the water in it, but are frequently catenated with external cold applied to the skin, as in cold bath- ing, or washing the hands; or with other habits of life, as many are accustomed to empty the bladder before going to bed, or into the house after a journey, and this whether it be full or not. Our times of respiration are not only governed by the stimulus of the blood in the lungs, or our desire of fresh air, but also by our attention to the hourly objects before us. Hence when a per- son is earnestly contemplating an idea of grief, he forgets to breathe, till the sensation in his lungs becomes very urgent; and then a sigh succeeds for the purpose of more forcibly pushing forwards the blood, which is accumulated in the lungs. Our times of respiration are also frequently governed in part by our want of a steady support for the actions of our arms and hands, as in threading a needle, or hewing wood, or in swimming; when we are intent upon these objects, we breathe at the intervals of the exertion of the pectoral muscles. 2. The following natural animal actions are influenced by solar periods. The periods of sleep and of waking depend much on the solar period, for we are inclined to sleep at a certain hour, and to awake at a certain hour, whether we have had more or less fatigue during the day, if within certain limits; and are liable to wake at a certain hour, whether we went to bed earlier or later, within certain limits. Hence it appears, that those who complain of want of sleep, will be liable to sleep better or longer, if they accustom themselves to go to rest, and to rise at certain hours. The periods of evacuating the bowels are generally connected with some part of the solar day, as well as with the acrimony or distention occasioned by the feces. Hence one method of cor- recting costiveness is by endeavouring to establish a habit of evacuation at a certain hour of the day, as recommended by Mr. Locke, which may be accomplished by using daily voluntary ef- forts at those times, joined with the usual stimulus of the material to be evacuated. 3. The following natural animal actions are connected wtth Sect. XXXVI. 3.1. OF DISEASES. 355 lunar periods. 1. The periods of female menstruation are con- nected with lunar periods to great exactness, in some instances even to a few hours. These do not commence or terminate at the full or change, or at any other particular part of the luna- tion, but after they have commenced at any part of it, they con- tinue to recur at that part with great regularity, unless disturbed by some violent circumstance, as explained in Sect. XXXII. No. 6. their return is immediately caused by deficient venous absorption, which is owing to the want of the stimulus designed by nature, of amatorial copulation, or of the growing fetus. When the catamenia returns sooner than the period of lunation, it shews a tendency of the constitution to irritability; that is to debility, or deficiency of sensorial power, and is to be relieved by small doses of steel and opium. The venereal orgasm of birds and quadrupeds seems to com- mence, or return about the most powerful lunations at the ver- nal or autumnal equinoxes; but if it be disappointed of its ob- ject, it is said to recur at monthly periods; in this respect re- sembling the female catamenia. Whence it is believed, that women are more liable to become pregnant at or about the time of their catamenia, than at the intermediate times; and on this account they are seldom much mistaken in their reckoning of nine lunar periods from the last menstruation; the inattention to this may sometimes have been the cause of supposed barrenness, and is therefore worth the observation of those, who wish to have children. III. We now come to the periods of diseased animal actions. The periods of fever-fits, which depend on the stated returns of nocturnal cold, are discussed in Sect. XXXII. 3. Those which originate or recur at solar or lunar periods, are also explained in Section XXXII. 6. These we shall here enumerate; observ- ing, however, that it is not more surprising, that the influence of the varying attractions of the sun and moon, should raise the ocean into mountains, than that it should affect the nice sensi- bilities of animal bodies; though the manner of its operation on them is difficult to be understood. It is probable, however, that as this influence gradually lessens during the course of the day, or of the lunation, or of the year, some actions of our system be- come less and less; till at length a total quiescence of some part is induced; which is the commencement of the paroxysms of fever, of menstruation, of pain with decreased action of the af- fected organ, and of consequent convulsion. 1. A diurnal fever in some weak people is distinctly observed to come on towards evening, and to cease with a moist skin early in the morning, obeying the solar periods. Persons of weak 356 PERIODS Sect. XXXVI. 3. 2 constitutions are liable to get into better spirits at the access of the hot fit of this evening fever; and are thence inclined to sit up late; which, by further enfeebling them, increases the dis- ease; whence they lose their strength and their colonr. Hence delicate ladies, who do not use rouge, are observed to become paler in the evening; which is probably owing to the circulation through the whole system being less frequently per- formed in a given time, though the pulse is quicker; and hence the mass of blood becomes less frequently oxygenated in the lungs, and in consequence has a less florid colour. This pale colour therefore arises from debility, which occurs to delicate people in the evening from the exhaustion of sensorial power during the day, and is generally attended with quickness of pulse; by which circumstance the debility may in some degree be measured. Another cause of the colour of the skin may occasionally de- pend on the increased action of the cutaneous capillaries, as in the hot fit of fever; or by the production of new blood vessels, as in topical inflammations. And paleness may arise from the contrary situations, as from inaction of the cutaneous capillaries in the cold paroxysm of fever, and from the concretion of the sides of the small cutaneous arteries, as in old age. 2. The periods of hectic fever, supposed to arise from ab- sorption of matter, obey the diurnal periods like the above, having the exacerbescence towards evening, and the remission early in the morning, with sweats, or diarrhoea, or urine with white sediment. 3. The periods of quotidian fever are either catenated with solar time, and return at the intervals of twenty-four hours; or with lunar time, recurring at the intervals of about twenty-five hours. There is great use in knowing with what circumstances the periodical return or new morbid motions are conjoined, as the most effectual times of exhibiting the proper medicines are thus determined. So if the torpor, which ushers in an ague fit, is catenated with the lunar day; it is known when the bark or opium must be given, so as to exert its principal effect about the time of the expected return. Solid opium should be given about an hour before the expected cold fit; liquid opium and wine about half an hour; the bark repeatedly for six or eight hours previous to the expected return. 4. The periods of tertian fevers, reckoned from the com- mencement of one cold fit to the commencement of the next cold fit, recur with solar intervals of forty-eight hours, or with lunar ones of about fifty hours. When the recurrence of these begins one or two hours earlier than the solar period, it shews, S£ct. XXXVI. 3. 5. OF DISEASES. 357 that the torpor or cold fit is produced by less external influence; and therefore that it is more liable to degenerate into a fever with only remissions; so when menstruation recurs sooner than the period of lunation, it shews a tendency of the habit to tor- por or inirritability. 5. The periods of quartan fevers return at solar intervals of seventy-two hours, or at lunar ones of about seventy-four hours and a half. This kind of ague appears most in moist cold au- tumns, and in cold countries replete with marshes. It is at- tended with greater debility, and its cold access more difficult to prevent. For where there is previously a deficiency of senso- rial power, the constitution is liable to run into greater torpor from any further diminution of it; two ounces of bark and some steel should be given on the day before the return of the cold pa- roxysm, and a pint of wine by degrees a few hours before its re- turn, and thirty drops of laudanum one hour before the expected cold fit. ' 6. The periods of the gout generally commence about an hour before sun-rise, which is usually the coldest part of the twenty- four hours. The greater periods of the gout seem also to ob- serve the solar influence, returning about the same season of the year. 7. The periods of the pleurisy recur with exacerbation of the pain and fever about sun-set, at which time venesection is of most service. The same may be observed of the inflammatory rheumatism, and other fevers with arterial strength, which seem to obey solar periods; and those with debility seem to obey lunar ones. 8. The periods of fevers with arterial debility seem to obey the lunar day, having their access daily nearly an hour later; and have sometimes two accesses in a day, resembling the lunar effects upon the tides. 9. The periods of rhaphania, or convulsions of the limbs from rheumatic pain, seem to be connected with solar influence, re- turning at nearly the same hour for weeks together, unless dis- turbed by the exhibition of powerful doses of opium. So the periods of tussis ferina, or violent cough with slow pulse, called nervous cough, recur by solar periods. Five grains of opium given at the time the cough commenced disturbed the period, from seven in the evening to eleven, at which time it re- gularly returned for some days, during vvhich time the opium was gradually omitted. Then 120 drops of laudanum were given an hour before the access of the cough, and it totally ceased. The laudanum was continued a fortnight, and then graduallv discon- tinued. 358 PERIODS S»:ct XXXM. 3. 10. 10. The periods of hemicrania, and of painful epilepsy, are liable to obey lunar periods, both in their diurnal returns, and in their greater periods of weeks, but are also induced by other ex- citing causes. 11. The periods of arterial haemorrhages seem to return at so- lar periods about the same hour of the evening or morning. Per- haps the venous haemorrhages obey the lunar periods, as the cata- menia, and haemorrhoids. 12. The periods of the haemorrhoids, or piles, in some recur monthly, in others only at the greater lunar influence about the equinoxes. 13. The periods of haemoptoe sometimes obey solar influence, recurring early in the morning for several days; and sometimes lunar periods, recurring monthly; and sometimes depend on our hours of sleep. See Class 1.2. 1. 9. 14. Many of the first periods of epileptic fits obey the monthly lunation with some degree of accuracy; others recur only at the most powerful lunations before the vernal equinox, and after the autumnal one; but when the constitution has gained a habit of re- lieving disagreeable sensations by this kind of exertion, the fit re- curs from any slight cause. 15. The attack of palsy and apoplexy are known to recur with great frequency about the equinoxes. 16. There are numerous instances of the effect of the lunations upon the periods of insanity, whence the name of lunatic has been given to those afflicted with this disease. IV. The critical days, in which fevers are supposed to termi- nate, have employed the attention of medical philosophers from the days of Hippocrates to the present time. In whatever part of a lunation a fever commences, which owes either its whole cause to solar and lunar influence, or to this in conjunction with other causes; it would seem that the effect would be the great- est at the full and new moon, as the tides rise highest at those times, and would be the least at the quadratures; thus if a fe- ver-fit should commence at the new or full moon, occasioned by the solar and lunar attraction diminishing some chemical af- finity of the particles of blood, and thence decreasing their stimu- lus on our sanguiferous system, as mentioned in Sect. XXXII. 6. this effect will daily decrease for the first seven days, and will then increase till about the fourteenth day, and will again decrease till about the twenty-first day, and increase again till the end of the lunation. If a fever-fit from the above cause should commence on the seventh day after either lunation, the reverse of the above circumstances would happen. Now it is probable, that those fevers, whose crisis or terminations are in- Sr.c-r. XXXVI. 4. 1. OF DISEASES. 359 fluenccd by lunations, may begin at one or other of the above times, namely, at the changes of quadratures; though sufficient observations have not been made to ascertain this circumstance. Hence I conclude, that the small-pox and measles have their cri- tical days, not governed by the times required for certain chemi- cal changes in the blood, vvhich affect or alter the stimulus of the contagious matter, but from the daily increasing or decreasing effect of this lunar link of catenation, as explained in Sect. XVII. 3. 3. And as other fevers terminate most frequently about the seventh, fourteenth, twenty-first, or about the end of four weeks, when no medical assistance has disturbed their periods, I con- clude, that these crises, or terminations, are governed by periods of the lunations, though we are still ignorant of their manner of operation. In the distinct small-pox, the vestiges of lunation are very ap- parent; after inoculation, a quarter of a lunation precedes the commencement of the fever, another quarter terminates with the complete eruption, another quarter with the complete maturation, and another quarter terminates the complete absorption of a ma- terial now rendered inoffensive to the constitution. 360 DIGESTION, Sect. XXXVII 1. 1 SECT. XXXVII. OF DIGESTION, SECRETION, NUTRITION. I. Crystals increase by tlie greater attraction of tlicir sides. Accre- tion by chemical precipitations, by welding, by pressure, by ag- glutination. II. Hunger, digestion, why it cannot be imitated out of the body. Lacteals absorb by animal selection, or appe- tency. III. The glands and pores absorb nutritious particles by animal selection. Organic particles of Buffon. Nutrition applied at the time of elongation of fibres. Like inflammation. IV. /( seems easier to have preserved animals than to reproduce them. Old age and death from inirritability. Three causes of this. Original fibres of the organs of sense and muscles unchanged. V. ,lrt of producing long life. I. The larger crystals of saline bodies may be conceived to arise from the combination of smaller crystals of the same form, owing to the greater attractions of their sides than of their angles. Thus if eight cubes were floating in a fluid, whose friction or re- sistance is nothing, it is certain the sides of these cubes would at- tract each other stronger than their angles; and hence that these eight smaller cubes would so arrange themselves as to produce one larger one. There are other means of chemical accretion, such as the depo- sitions of dissolved calcareous or siliceous particles, as are seen in the formation of the stalactites of limestone in Derbyshire, or of calcedone in Cornwall. Other means of adhesion are produced by heat and pressure, as in the welding of iron bars; and other means by simple pressure, as in forcing two pieces of caoutchouc, or elastic gum, to adhere; and lastly, by the agglutination of a third substance penetrating the pores of the other two, as in the agglutination of wood by means of animal gluten. Though the ultimate particles of animal bodies are held together during life, as well as after death, by their specific attraction of cohesion, like all other matter; yet it does not appear, that their original organization was produced by chemical laws, and their produc- tion and increase must therefore only be looked for from the laws of animation. II. When the pain of hunger requires relief, certain parts of the material world, which surround us, when applied to our palates, excite into action the muscles of deglutition; and the material is swallowed into the stomach. Here the new aliment becomes mixed with certain animal fluids, and undergoes a Sect. XXXVII. 3. 1. SECRETION, &c. 361 chemical process, termed digestion; which, however, chemistry has not yet learnt to imitate out of the bodies of living animals or vegetables. This process seems very similar to the saccharine process in the lobes of farinaceous seeds, as of barley, when it begins to germinate; except that, along with the sugar, oil and mucilage are also produced; which form the chyle of animals, which is very similar to their milk. The reason, I imagine, why this chyle-making, or saccharine process, has not yet been imitated by chemical operations, is owing to the materials being in such a situation in respect to warmth, moisture, and motion; that they will immediately change into the vinous or acetous fermentation; except the new sugar be absorbed by the numerous lacteal or lymphatic vessels, as soon as it is produced; which is not easy to imitate in the laboratory. These lacteal vessels have mouths, which are irritated into ac- tion by the stimulus of the fluid which surrounds them; and by- animal selection, or appetency, they absorb such part of the fluid as is agreeable to their palate; those parts, for instance, which are already converted into chyle, before they have time to undergo another change by a vinous or acetous fermentation. This animal absorption of fluid is almost visible to the naked eye in the action of the puncta lachrymalia; which imbibe the tears from the eye, and discharge them again into the nostrils. III. The arteries constitute another reservoir of a changeful fluid; from which, after its recent oxygenation in tlie lungs, a further animal selection of various fluids is absorbed by the nu- merous glands; these select their respective fluids from the blood, which is perpetually undergoing a chemical change; but the selection by these glands, like that of the lacteals, which open their mouths into the digesting aliment in the stomach, is from animal appetency, not from chemical affinity; secretion cannot therefore be imitated in the laboratory, as it consists in a selection of part of a fluid during the chemical change of that fluid. ct. XXXIX. 5. 2. GENERATION. 403 coloured. And thus, like the fable of the cameleon, all ani- mals may possess a tendency to be coloured somewhat like the colours they most frequently inspect, and finally, that colours may be thus given to the egg-shell by the imagination of the fe- male parent; which shell is previously a mucous membrane, in- dued with irritability, without which it could not circulate its fluids, and increase in its bulk. Nor is this more wonderful than that a single idea of imagination should in an instant colour the whole surface of the body of a bright scarlet, as in the blush of shame, though by a very different process. In this intricate sub- ject nothing but loose analogical conjectures can be had, which may however lead to future discoveries; but certain it is that both the change of the colour of animals to white in the winters of snowy countries, and the spots on birds' eggs, must have*some efficient cause; since the uniformity of their production shews it cannot arise from a fortuitous concurrence of circumstances; and how is this efficient cause to be detected, or explained, but from its analogy to other animal facts? 2. The nutriment supplied by the female parent in vivipa- rous animals to their young progeny may be divided into three kinds, corresponding with the age of the new creature. 1. The nutriment contained in the ovum as previously prepared for the embryon in the ovary. 2. The liquor amnii prepared for the fetus in the uterus, and in which it swims; and lastly, the milk prepared in the pectoral glands for the new-born child. There is reason to conclude that variety of changes may be produced in the new animal from all these sources of nutriment, but particu- larly from the first of them. The organs of digestion and of sanguification in adults, and afterwards those of secretion, prepare or separate the particles proper for nourishment from other combinations of matter, or recombine them into new kinds of matter, proper to excite into action the filaments, which absorb or attract them by animal ap- petency. In this process we must attend not only to the action of the living filament which receives a nutritive particle to its bosom, but also to the kind of particle, in respect to form, or size, or colour, or hardness, which is thus previously prepared for it by digestion, sanguification, and secretion. Now as the first filament of entity cannot be furnished with the preparative or- gans above mentioned, the nutritive particles which are at first to be received by it, are prepared by the mother, and deposited in the ovum ready for its reception. These nutritive particles must be supposed to differ in some respects, when thus prepared by different animals. They may differ in size, solidity, colour, and form; and yet may be sufficiently congenial to the living ](J4 GENERATION Sect. XXXIX. 5. 2. filament, to which they are applied, as to excite its activity by their stimulus, and its animal appetency to receive them, and to combine them with itself into organization. By this first nutriment thus prepared by the embryon is not meant the liquor amnii, which is produced afterwards, nor the larger exterior parts of the white of the egg; but the fluid pre- pared, I suppose, in the ovary of viviparous animals, and that which immediately surrounds the cicatricula of an impregnated egg, and is visible to the eye in a boiled one. Now these ultimate particles of animal matter prepared by the glands of the mother may be supposed to resemble the similar ultimate particles, which were prepared for her own nourish- ment; that is, to the ultimate particles of which her own or- ganization consists. And that hence when these become com- bined with a new embryon, which in its early state is not fur- nished with stomach, or glands, to alter them; that new embryon will bear some resemblance to the mother. This seems to be the origin of the compound forms of mules, which evidently partake of both parents, but principally of the male parent. In this production of chimeras the ancients seem to have indulged their fancies, whence the sphinxes, griffins, dragons, centaurs, and minotaurs, which are vanished from modern credulity. It would seem, that in these unnatural conjunctions, when the nutriment deposited by the female was so ill adapted to stimu- late the living filament derived from the male into action, and to be received, or embraced by it, and combined with it into organization, as not to produce the organs necessary to life, as the brain, or heart, or stomach, that no mule was produced. Where all the parts necessary to life in these compound animals were formed sufficiently perfect, except the parts of generation, those animals were produced which are now called mules. The formation of the organs of sexual generation, in contra- distinction to that by lateral buds, in vegetables, and in some animals, as the polypus, the taenia, and the volvox, seems the chef d'oeuvre, the master-piece of nature; as appears from ma- ny flying insects, as in moths and butterflies, who seem to un- dergo a general change of their forms solely for the purpose of sexual reproduction, and in all other animals this organ is not complete till the maturity of the creature. Whence it happens that, in the copulation of animals of different species, the parts necessary to life are frequently completely formed; but those for the purpose of generation are defective, as requiring a nicer organization; or more exact coincidence of the particles of nu- triment to the irritabilities or appetencies of the original living Sect. XXXIX. 5. 2. GENERATION. 405 filament. Whereas those mules, where all the parts could be perfectly formed, may have been produced in early periods of time, and may have added to the numbers of our various species of animals, as before observed. As this production of mules is a constant effect from the con- junction of different species of animals, those between the horse and the female ass always resembling the horse more than the ass; and those on the contrary, between the male ass and the mare, always resembling the ass more than the mare; it cannot be ascribed to the imagination of the male animal which cannot be supposed to operate so uniformly; but to the form of the first nutritive particles, and to their peculiar stimulus exciting the liv- ing filament to select and combine them with itself. There is a similar uniformity of effect in respect to the colour of the progeny produced between a white man, and a black woman, which, if I am well informed, is always of the mulatto kind, or a mixture of the two; which may perhaps be imputed to the peculiar form of the particles of nutriment supplied to the embryon by the mother at the early period of its existence, and their peculiar stimulus; as this effect, like that of the mule progeny above treated of, is uni- form and consistent, and cannot therefore be ascribed to the imagination of either of the parents. Dr. Thunberg observes, in his Journey to the Cape of Good Hope, that there are some families, which have descended from blacks in the female line for three generations. The first genera- tion proceeding from an European, who married a tawny slave, remains tawny, but approaches to a white complexion; but the children of the third generation, mixed with Europeans, become quite white, and are often remarkably beautiful. Vol. i. p. 112. When the embryon has produced a placenta, and furnished itself with vessels for selection of nutritious particles, and for oxygenation of them, no great change in its form or colour is likely to be produced by the particles of sustenance it now takes from the fluid, in which it is immersed; because it has now ac- quired organs to alter or new combine them. Hence it con- tinues to grow whether this fluid, in which it swims, be formed by the uterus or by any other cavity of the body, as in extra-uterine gestation; and which would seem to be produced by the stimulus of the fetus on the sides of the cavity, where it is found, as men- tioned before. And thirdly, there is still less reason to expect any unnatural change to happen to the child after its birth from the difference of the milk it now takes; because it has acquired a stomach, and lungs, and glands, of sufficient power to decom- pose and recombine the milk; and thus to prepare from it the various kinds of nutritious particles, which the appetencies of the various fibrils or nerves may require. 406 GEXERVriOX. Sect. XXXIX. 6.1. From all this reasoning 1 would conclude, that thougli the imagination of the female may be supposed to affect the embry- on by producing a difference in its early nutriment; yet that no such power can affect it after it has obtained a placenta, and other organs; which may select or change the food, which is presented to it either in the liquor amnii, or in the milk. Now as the eggs in pullets, like the seeds in vegetables, are produced gradually, long before they are impregnated, it does not appear how any sudden effect of imagination of the mother at the time of impregnation can produce any considerable change in the nu- triment already thus laid up for the expected or desired embryon. And that hence any changes of the embryon, except those uni- form ones in the production of mules and mulattoes, more probably depend on the imagination of the male parent. At the same time it seems manifest, that those monstrous birds, vvhich consist in some deficiencies only, or some redundancies of parts, originate from the deficiency or redundance of the first nutriment prepared in the ovary, or in the part of the egg im- mediately surrounding the cicatricula, as described above; and which continues some time to excite the first living filament into action, after the simple animal is completed; or ceases to excite it, before the complete form is accomplished. The form- er of these circumstances is evinced by the eggs with double yolks, which frequently happen to our domesticated poultry, and which, I believe, are so formed before impregnation, but which would be well worth attending to, both before and after impreg- nation; as it is probable, something valuable on this subject might be learnt from them. The latter circumstance, or that of deficiency of original nutriment, may be deduced from reverse analogy. There are, however, other kinds of monstrous births, which neither depend on deficiency of parts, or supernumerary ones; nor are owing to the conjunction of animals of different species; but which appear to be new conformations, or new dispositions of parts in respect to each other, and which, like the variation of colours and forms of our domesticated animals, and probably the sexual parts of all animals, may depend on the imagination of the male parent, which we now come to consider. VI. 1. The nice actions of the extremities of our various glands are exhibited in their various productions, vvhich are be- lieved to be made by the gland, and not previously to exist as such in the blood. Thus the glands, which constitute the liver, make bile; those of the stomach make gastric acid; those be- neath the jaw, saliva; those of the ears, ear-wax; and the like. Every kind of gland must possess a peculiar irritability, and Sect. XXXIX. 6. 1. GENERATION. 407 probably a sensibility, at the early state of its existence; and must be furnished with a nerve of sense, or of motion, to per- ceive, and to select, and to combine the particles, which com- pose the fluid it secretes. And this nerve of sense which per- ceives the different articles vvhich compose the blood, must at least be conceived to be as fine and subtile an organ, as the op- tic or auditory nerve, which perceives light or sound. See Sect. XIV. 9. But in nothing is this nice action of the extremities of the blood-vessels so wonderful, as in the production of contagious matter. A small drop of variolous contagion diffused in the blood, or perhaps only by being inserted beneath the cuticle, after a time, (as about a quarter of a lunation,) excites the ex- treme vessels of the skin into certain motions, vvhich produce a similar contagious material, filling with it a thousand pustules. So that by irritation, or by sensation in consequence of irritation, or by association of motions, a material is formed by the extremi- ties of certain cutaneous vessels, exactly similar to the stimulat- ing material, which caused the irritation, or consequent sensa- tion, or association. Many glands of the body have their motions, and in conse- quence their secreted fluids, affected by pleasurable or painful ideas, since they are in many instances influenced by sensitive associations, as well as by the irritations of the particles of ihe passing blood. Thus the idea of meat, excited in the minds of hungry dogs, by their sense of vision, or of smell, increases the discharge of saliva, both in quantity and viscidity; as is seen in its hanging down in threads from their mouths, as they stand round a dinner-table. The sensations of pleasure, or of pain, of peculiar kinds, excite in the same manner a great discharge of tears; which appear also to be more saline at the time of their secretion, from their inflaming the eyes and eye-lids. The pale- ness from fear, and the blush of shame, and of joy, are other in- stances of the effects of painful or pleasurable sensations, on the extremities of the arterial system. It is probable, that the pleasurable sensation excited in the stomach by food, as well as its irritation, contributes to excite into action the gastric glands, and to produce a greater secretion of their fluids. The same probably occurs in the secretion of bile; that is, that the pleasurable sensation excited in the stomach, af- fects this secretion by sensitive association, as well as by irrita- tive association. And lastly it would seem, that all the glands in the body have their secreted fluids affected, in quantity and quality, by the plea- surable or painful sensations, which produce or accompany those 408 GENERATION. Sect. XXXIX. 6. 2. secretions. And that the pleasurable sensations arising from these secretions may constitute the unnamed pleasure of existence, which is contrary to what is meant by taedium vita?, or ennui; and by which we sometimes feel ourselves happy, without being able to ascribe it to any mental cause, as after an agreeable meal, or in the beginning of intoxication. Now it would appear that no secretion or excretion of fluid is attended with so much agreeable sensation, as that of the semen; and it would thence follow, that the glands which perform this secretion, are more likely to be much affected by their catena- tions with pleasurable sensations. This circumstance is certain, that much more of this fluid is produced in a given time, when the object of its exclusion is agreeable to the mind. 2. A forcible argument, which shews the necessity of pleasura- ble sensation to copulation, is, that the act cannot be performed without it; it is easily interrupted by the pain of fear or bash- fulness; and no efforts of volition or of irritation can effect this process, except such as induce pleasurable ideas or sensations. See Sect. XXXIII. 1.1. A curious analogical circumstance attending hermaphrodite in- sects, as snails and worms, still further illusirates this theory; if the snail or worm could have impregnated itself, there might have been a saving of a large male apparatus; but as this is not so ordered by nature, but each snail and worm reciprocally receives and gives impregnation, it appears, that a pleasurable excitation seems also to have been required. This wonderful circumstance of many insects being her- maphrodites, and at the same time not having power to impreg- nate themselves, is attended to by Dr. Lister, in his Exercita- tiones Anatom. de Limacibus, p. 145; who, amongst many other final causes, which he adduces to account for it, adds, ut tam tristibus et frigidis animalibus majori cum voluptate perficia- tur venus. There is, however, another final cause, to which this circum- stance may be imputed: it was observed above, that vegetable buds and bulbs, which are produced without a mother, are al- ways exact resemblances of their parent, as appears in grafting fruit trees, and in the flower buds of the dioeceous plants, which are always of the same sex on the same tree; hence those hermaphrodite insects, if they could have produced young without a mother, would not have been capable of that change or improvement, which is seen in all other animals, and in those vegetables, which are procreated by the male embryon received and nourished by the female. And it is hence probable, that if vegetables could only have been produced by buds and bulbs, Sect. XXXIX. 6.3. GENERATION. 409 and not by sexual generation, that there would not at this time have existed one thousandth part of their present number of spe- cies; which have probably been originally mule-productions; nor could any kind of improvement or change have happened to them except by the difference of soil or climate. 3. 1 conclude that the imagination of the male at the time of copulation, or at the time of the secretion of the semen, may so affect this secretion by irritative or sensitive association, as described in No. V. 1. of this section, as to cause the produc- tion of similarity of form and of features, with the distinction of sex; as the motions of the chissel of the turner imitate or correspond with those of the ideas of the artist. It is not here to be understood, that the first living fibre, whieh is to form an animal, is produced with any similarity of form to the future animal; but with propensities, or appetencies, which shall pro- duce by accretion of parts the similarity of form, feature, or sex, corresponding to the imagination of the father. Our ideas are movements of the nerves of sense, as of the optic nerve in recollecting visible ideas, suppose of a triangular piece of ivory. The fine moving fibres of the retina act in a manner to which I give the name of white; and this action is confined to a defined part of it, to which figure I give the name of triangle. And it is a preceding pleasurable sensation existing in my mind, which occasions me to produce this par- ticular motion of the retina, when no triangle is present. Now it is probable, that the acting fibres of the ultimate termi- nations of the secreting apertures of the vessels of the testes, are as fine as those of the retina; and that they are liable to be thrown into that peculiar action, which marks the sex of the secreted embryon, by sympathy with the pleasurable motions of the nerves of vision or of touch; that is, with certain ideas of imagination. From hence it would appear, that the world has long been mistaken in ascribing great power to the imagination of the female, whereas from this account of it, the real power of imagination, in the act of generation, belongs solely to the male. See Sect. XII. 3. 3. It may be objected to this theory, that a man may be supposed to have in his mind, the idea of the form and features of the fe- male, rather than his own, and therefore there should be a greater number of female births. On the contrary, the general idea of our own form occurs to every one almost perpetually, and is termed consciousness of our existence, and thus may ef- fect, that the number of males surpasses that of females. See Sect. XV. 3. 4. and XVIII. 13. And what further con- firms this idea is, that the male children most frequently vol. i. 3 G 410 GENERATION. Sect. XXXIX 1. t resemble the father in form, or feature, as well as in sex; and the female most frequently resemble the mother, in feature, and form, as well as in sex. It may again be objected, if a female child sometimes resem- bles the father, and a male child the mother, the ideas of the father, at the time of procreation, must suddenly change from himself to the mother, at the very instant, when the embryon is secreted or formed. This difficulty ceases when we consider, that it is as easy to form an idea of feminine features with male organs of reproduction, or of male features with female ones, as the contrary; as we conceive the idea of a sphinx or mer- maid as easily and as distinctly as of a woman. Add to this, that at the time of procreation the idea of the male organs, and of the female features, are often both excited at the same time, by contact, or by vision. I ask, in my turn, is the sex of the embryon produced by ac- cident ? Certainly whatever is produced has a cause; but when this cause is too minute for our comprehension, the effect is said in common language to happen by chance, as in throwing a cer- tain number on dice. Now what cause can occasionally pro- duce the male or female character of the embryon, but the pe- culiar actions of those glands, which form the embryon? And what can influence or govern these actions of the gland, but its associations or catenations with other sensitive motions? Nor is this more extraordinary, than that the catenations of irritative motions with the apparent vibrations of objects at sea should produce sickness of the stomach; or that a nauseous story should occasion vomiting. 4. An argument which evinces the effect of imagination on the first rudiment of the embryon, may be deduced from the production of some peculiar monsters. Such, for instance, as those which have two heads joined to one body, and those which have two bodies joined to one head; of which frequent examples occur amongst our domesticated quadrupeds, and poultry. It is absurd to suppose, that such forms could exist in primordial germes, as explained in No. IV. 4. of this section. Nor is it possibler that such deformities could be produced by the growth of two embryons, or living filaments; which should afterwards adhere together; as the head and tail part of different polypi are said to do (Blumenbach on Generation. Cadell, London;) since in that case one embryon, or living filament, must have begun to form one part first, and the other another part first. But such monstrous conformations become less difficult to comprehend, when they are considered as an effect of the im- agination, as before explained, on the living filament at the time S*,.t. XXXIX. 6. 5. GENERATION. 411 of its secretion; and that such duplicature of limbs was produced by accretion of new parts, in consequence of propensities, or ani- mal appetencies, thus acquired from the male parent. For instance, I can conceive, if a turkey cock should behold a rabbit, or a frog, at the time of procreation, that it might happen, that a forcible or even a pleasurable idea of the form of a quad- ruped might so occupy his imagination, as to cause a tendency in the nascent filament to resemble such a form, by the apposition of a duplicature of limbs. Experiments on the production of mules and monsters would be worthy the attention of a Spallan- zani, and might throw much light upon the subject, which at present must be explained by conjectural analogies. The wonderful effect of imagination, both in the male and female parent, is shewn in the production of a kind of milk in the crops both of the male and female pigeons after the birth of their young, as observed by Mr. Hunter, and mentioned before. To this should be added, that there are some instances of men having had milk secreted in their breasts, and who have given suck to children, as recorded by Mr. Buffon. This effect of imagination, of both the male and female j.-urent, seems to have been attended to in very early times; Jacob is said not only to have placed rods of trees, in part stripped of their bark, so as to appear spotted, but also to have placed spotted lambs before the flocks, at the time of their copulation. Genesis, chap. xxx. verse 40. 5. In respect to the imagination of the mother, it is diffi- cult to comprehend, how this can produce any alteration in the fetus, except by affecting the nutriment laid up for its first re- ception, as described in No. V. 2. of this section, or by affect- ing the nourishment or oxygenation with which she supplies it afterwards. Perpetual anxiety may probably affect the secre- tion of the liquor amnii into the uterus, as it enfeebles the whole system; and sudden fear is a frequent cause of miscar- riage; for fear, contrary to joy, decreases for a time the action of the extremities of the arterial system; hence sudden pale- ness succeeds, and a shrinking or contraction of the vessels of the skin, and other membranes. By this circumstance, I ima- gine, the terminations of the placental vessels are detached from their adhesions, or insertions, into thev membrane of the uterus; and the death of the child succeeds, and consequent mis- carriage. Of this I recollect a remarkable instance, which could be ascribed to no other cause, and vvhich 1 shall therefore relate in few words. A healthy young woman, about twenty years of age, had been about five months pregnant, and going down into 412 GENERATION. Sect. XXXIX 6. 6. her cellar to draw some beer, was frighted by a servant boy starting up from behind the barrel where he had concealed him- self with design to alarm the maid servant, for whom he mistook his mistress. She came with difficulty up stairs, began to flood immediately, and miscarried in a few hours. She has since borne several children, nor ever had any tendency to miscarry of any of them. In respect to the power of the imagination of the male over the form, colour, and sex of the progeny, the following in- stances have fallen under my observation, and may perhaps be found not very unfrequent, if they were more attended to. I am acquainted with a gentleman who has one child with dark hair and eyes; though his lady and himself have light hair and eyes; and their other four children are like their parents. On observing this dissimilarity of one child to the others he assured me, that he believed it was his own imagination, that produced the difference; and related to me the following story. He said, that when his lady lay in of her third child, he became attached to a daughter of one of his inferior tenants, and offer- ed her a bribe for her favours in vain; and afterwards a greater bribe, and was equally unsuccessful; that the form of this girl dwelt much in his mind for some weeks, and that the next child, which was the dark-eyed young lady above mentioned, was ex- ceedingly like, in both features and colour, to the young woman who refused his addresses. To this instance I must add, that I have known two families, in which, on account of an entailed estate in expectation, a male heir was most eagerly desired by the father; and on the con- trary, girls were produced to the seventh in one, and to the ninth in another; and then they had each of them a son. I conclude, that the great desire of a male heir by the father produced rather a disagreeable than an agreeable sensation; and that his ideas dwelt more on the fear of generating a female, than on the plea- surable sensations or ideas of his own male form or organs at the time of copulation, or of the secretion of the semen; and that hence the idea of the female character was more present to his mind than that of the male one; till at length in despair of ge- nerating a male these ideas ceased, and those of the male cha- racter presided at the genial hour. 6. Hence I conclude, that the act of generation cannot exist without being accompanied with ideas, and that a man must have at that time either a general idea of his own male form, or of the form of his male organs; or an idea of the female form, or of her organs; and that this marks the sex, and the peculiar resemblances of the child to either parent. From whence it Skct. XXXIX 7. 1. GENERATION. 413 would appear, that the phalli, which where hung round the necks of the Roman ladies, or worn in their hair, might have effect in producing a greater proportion of male children ; and that the calipaedia, or art of begetting beautiful children, and of pro- creating either males or females, may be taught by affecting the imagination of the male-parent ; that is, by the fine extremities of the seminal glands imitating the actions of the organs of sense either of sight or touch. But the manner of accomplishing this cannot be unfolded with sufficient delicacy for the public eye ; but may be worth the attention of those, who are seriously in- terested in the procreation of a male or female child. Recapitulation. VII. 1. A certain quantity of nutritive particles are produc- ed by the female parent before impregnation, which require no further digestion, secretion, or oxygenation. Such are seen in the unimpregnated eggs of birds, and in the unimpregnated seed vessels of vegetables. 2. A living filament is produced by the male, which being inserted amidst these first nutritive particles, is stimulated into action by them ; and in consequence of this action, some of the nutritive particles are embraced, and added to the original liv- ing filament; in the same manner as common nutrition is per- formed in the adult animal. 3. Then this new organization, or additional part, becomes stimulated by the nutritive particles in its vicinity, and sensation is now superadded to irritation ; and other particles are in con- sequence embraced, and added to the living filament ; as is seen in the new granulations of flesh in ulcers. By the power of association, or by irritation, the parts already produced continue their motions, and new ones are added by sensation, as above mentioned ; and lastly by volition, vvhich last sensorial power is proved to exist in the fetus in its maturer age, because it has evidently periods of activity and of sleeping ; which last is another word for a temporary suspension of volition. The original living filament may be conceived to possess a power of repulsing the particles applied to certain parts of it, as well as of embracing others, which stimulate other parts of it; as these powers exist in different parts of the mature animal; thus the mouth of every gland embraces the particles of fluid, which suit its appetency ; and its excretory duct repulses those particles, vvhich are disagreeable to it. 4. Thus the outline or miniature of the new animal is pro- duced gradually, but in no great length of time; because the 414 GENERA! ION. Sict. XXXIV. 7. 5. original nutritive particles require no previous preparation by di- gestion, secretion, and oxygenation: but require simply the se- lection and apposition, which is performed by the living fila- ment. Mr. Blumenbach says, that he possesses a human fetus of only five weeks old, which is the size of a common bee, and has all the features of the face, every finger, and every toe com- plete ; and in which the organs of generation are distinctly seen. P. 76. In auother fetus, whose head was not larger than a pea, the whole of the basis of the skull with all its depressions, aper- tures, and processes, were marked in the most sharp and distinct manner, though without any ossification. Ib. 5. In some cases by the nutriment originally deposited by the mother the filament acquires parts not exactly similiar to those of the father, as in the production of mules and mulattoes. In other cases, the deficiency of this original nutriment causes defi- ciencies of the extreme parts of the fetus, vvhich are last form- ed, as the fingers, toes, lips. In other cases, a duplicature of limbs is caused by the superabundance of this original nutritive fluid, as in the double yolks of eggs, and the chickens from them with four legs and four wings. But the production of other monsters, as those with two heads, or with parts placed in wrong situations, seems to arise from the imagination of the father being in some manner imitated by the extreme vessels of the seminal glands ; as the colours of the spots on eggs, and the change of the colour of the hair and feathers of animals by do- mestication, may be caused in the same manner by the imagina- tion of the mother. 6. The living filament is a part of the father, and has there- fore certain propensities, or appetencies, which belong to him ; which may have been gradually acquired during a million of ge- nerations, even from the infancy of the habitable earth ; and which now possesses such properties, as would render, by the ap- position of nutritious particles, the new fetus exactly similar to the father ; as occurs in the buds and bulbs of vegetables, and in the polypus, and taenia or tape-worm. But as the first nutriment is supplied by the mother, and therefore resembles such nutritive particles, as have been used for her own nutriment or growth, the progeny takes in part the likeness of the mother. Other similarities of the excitability, or of the form of the male parent, such as the broad or narrow shoulders, or such as constitute certain hereditary diseases, as scrofula, epilepsy, in- sanity, have their origin produced in one or perhaps two gene- rations ; as in the progeny of those who drink much vinous spirits ; and those hereditary propensities cease again, as I have observed, if one or two sober generations succeed ; otherwise the family becomes extinct. SecT. XXXIX. 7. 5. GENERATION. 415 This living filament from the father, is also liable to have its propensities, or appetencies, altered at the time of its production by the imagination of (he male parent; the extremities of the seminal glands imitating the motions of the organs of sense; and thus the sex of the embryon is produced; vvhich may be thus made a male or a female, by affecting the imagination of the father at the time of impregnation. See Sect. XXXIX.6. 3. and 7. 7. After the fetus is thus completely formed together with its umbilical vessels and placenta, it is now supplied with a dif- ferent kind of food, as appears by the difference of consistency of the different parts of the white of the egg, and of the liquor amnii, for it has now acquired organs for digestion or secretion, and for oxygenation, though they are as yet feeble; which can in some degree change, as well as select the nutritive particles, vvhich are now presented fo it. But may yet be affected by the deficiency of the quantity of nutrition supplied by the mother, or by the degree of oxygenation supplied to its placenta by the maternal blood. The augmentation of the complete fetus by additional particles of nutriment is not accomplished by distention only, but by ap- position to every part both external and internal; each of which acquires by animal appetencies the new addition of the particles which it wants. And hence the enlarged parts are kept similar to their prototypes, and may be said to be extended; but their extension must be conceived only as a necessary consequence of the enlargement of all their pans by apposition of new particles. Hence the new apposition of parts is not produced by capilla- ry attraction, because the whole is extended; whereas capillary attraction would rather tend to bring the sides of flexible tubes together, and not to distend them. Nor is it produced by chemical affinities, for then a solution of continuity would suc- ceed, as when sugar is dissolved in water; but it is produced by an animal process, which is the consequence of irritation, or sensation: and which may be termed animal appetency. This is further evinced from experiments, which have been instituted to shew that a living muscle of an animal body re- quires greater force to break it, than a similar muscle of a dead body. Which evinces, that besides the attraction of cohesion, which all matter possesses, and besides the chemical attractions of affinities which hold many bodies together, there is an ani- mal adhesion, which adds vigour to these common laws of the inanimate world. 8. At the nativity of the child it deposits the placenta or gills, and by expanding its lungs acquires more plentiful oxyge- 416 GENERATION. Sect. XXXIX. 7.8. nation from the currents of air, which it must now continue perpetually to respire to the end of its life; as it now quits the liquid element, in vvhich it was produced, and like the tadpole, when it changes into a frog, becomes an aerial animal. 9. As the habitable parts of the earth have been, and con- tinue to be, perpetually increasing by the production of sea- shells and corallines, and by the recrements of other animals, and vegetables; so from the beginning of the existence of this terraqueous globe, the animals, which inhabit it, have constant- ly improved, and are still in a stale of progressive improvement. This idea of the gradual generation of all things seems to have been as familiar to the ancient philosophers as to the mo- dern ones; and to have given rise to the beautiful hieroglyphic figure of the tt^otov uov or first great egg, produced by night, that is, whose origin is involved in obscurity, and animated by ejos, that is, by Divine Love; from whence proceeded all things which exist. Appendix. VIII. 1. Since the former publication of the preceding Sec- tion on Generation, 1 have been induced, in my treatise on Phy- tologia, to give more attention to the lateral or solitary genera- tion of vegetables in the production of their buds, hoping from thence to throw some light on their sexual generation in the pro- duction of seeds; and in consequence on the propagation of more perfect animals, vvhich I shall here relate, believing that it may interest the philosophical reader, observing only, that by the vegetable facts here attended to, I am now induced to be- lieve that the embryons or complicate animal and vegetable bodies are not formed from a single filament as above delivered; but that their structure commences in many parts at the same time, though it is probable, that the most simple or first exordium of animation was begun by a single filament, and continues to do so in the spontaneous production of the smallest micro- scopic animals, which do not appear to have been generated by other animalcula similar to themselves, as further spoken of in No. 11. 5. of this Section. 1. It is shewn at large in the work above mentioned, that every bud of a tree is an individual vegetable, and consists of the plumula or leaf at its summit, of a long caudex extending from this summit downwards to the earth, forming a filament of the bark, and lastly of radicles beneath the soil: it is also shewn, that every bud possesses the power of germination or reproduc- tion, not only in the axilla of the leaf, which is most common, Sect. XXXIX. 8. 1. GENERATION. 417 but from any part of the long caudex gemma? above mentioned, as appears from new buds springing out from any part of the bark, when the top of a branch is cut off. Now if a scion of a nonpareil apple be ingrafted on a crab stock, and a golden pippin be ingrafted on the nonpareil, what happens?—The caudex of the bud of the golden-pippin consists of its proper absorbent vessels, arteries, and veins, till it reaches down to the nonpareil stock; and then the continuation of its caudex downwards consists of vessels similar to those of the non- pareil; and when its caudex descends still lower, it consists of vessels similar to those of the crab-stock. The truth of this is shewn by two circumstances; first, be- cause the lower parts of this compound tree will occasionally put forth buds similar to the original stock. And secondly, because in some ingrafted trees, where a quick-growing scion has been in- serted into a stock of slower growth, as is often seen in old cherry- trees, the upper part of the trunk of the tree has become of almost double the diameter of the lower part. Both which occurrences shew, that the lower part of the trunk of the tree continues to be of the same kind, though it must have been so repeatedly covered over with new circles of wood, bark, and cuticle. Now as the caudex of each bud, which passes the whole length of the trunk of the tree, and forms a communication from the upper part or plumula, to the lower part or radicle, must consist in these doubly ingrafted trees of three different kinds of caudexes, resembling those of the different stocks or scions; w7e acquire a knowledge of what may be termed a lateral or paternal mule, in contradistinction to a sexual mule. For as in these trees thus combined by ingraftment every bud has the upper part of its cau- dex that of a golden-pippin, the middle part of it that of a non- pareil, and the lower part of it that of a crab; if these caudexes, vvhich constitute the filaments of the bark, could be separated en- tire from the tree with their plumules and radicles, they would exhibit so many lateral or paternal mules, consisting of the con- nected parts of their three parents; the plumula belonging to the upper parent, and the radicle to the lower one, and the triple cau- dex to them all. A separation of these buds from the parent plant is said to have been observed by Mr. Blumenbach, in the conferva fonti- nalis, a vegetable vvhich consists of small short slender threads, which grow in our fountains, and fix their roots in the mud. He observed by magnifying glasses, that the extremities of the threads swell, and form small tubera or heads; which gradually separate from the parent threads, attach themselves to the vol. i. 3 H 418 GENERATION". Sect. XXXIX. 8. 2 ground, and become perfect vegetables; the whole progress of their formation can be observed in forty-eight hours. Observa- tions on Plants by Von Uslar. Creech, Edinb. 2. The lateral propagation of the polypus found in our ditches in July, but more particularly that of the hydra stentorea, is won- derfully analogous to the above idea of the lateral generation of vegetables. The hydra stentorea, according to the account of Mons. Trembly, multiplies itself by splitting lengthwise; and in twenty-four hours these divisions, which adhere to a common pedicle, re-split, and form four distinct animals. These four in an equal time split again, and thus double their number daily; till they acquire a figure somewhat resembling a nosegay. The young animals afterwards separate from the parent, attach themselves to aquatic plants, and give rise to new colonies. Another curious animal fact is related by Blumenbach in his Treatise on Generation concerning the fresh water polypus. He cut two of them in halves, vvhich were of different colours, and applying the upper part of one to the lower part of the other by means of a glass tube, and retaining them thus for some time in contact with each other, the two divided extremities united, and became one animal. The facile union of the divided halves of different polypi is also asserted by Mr. Adams. Treatise on Mi- croscopes. The intelligent reader has already anticipated me in applying these wonderful modes of lateral animal reproduction and con- junction, to the lateral propagation and ingraftment of vegetables. The junction of the head part of one polypus to the tail part of another is exactly represented by the ingraftment of a scion on the stock of another tree, the plumula or apex of each bud with the upper part of its caudex joins to the long caudex of the stock, which passing down the trunk terminates in the radicles of it. And if this compound vegetable could be separated longitudinally from the other long filaments of the bark in its vicinity, like the fibres of the bark of the mulberry tree prepared at Otaheite, or as the bark of hemp and flax are prepared in this country, as the young ones of the hydra stentorea separate from their parents, it might claim the name of a lateral or paternal mule, as above mentioned. 3. It hence appears, that every new bud of a tree, where two scions have been inserted over each other on a stock, if it could be separated from the plume to the radicle, must consist of three different kinds of caudex; and might therefore be called a triple lateral mule. And that hence it follows, that every part of this new triple caudex must have been separated or secreted laterally from the adjoining part of the trunk of the tree; and that it Sect. XXXIX. 8. 4- GENERATION. 419 could not be formed, as I formerly believed, from the roots of the plume of the bud descending from the upper part of the cau- dex of it to the earth. A circumstance of great importance in the investigation of the curious subject of the lateral generation of vegetables and of insects. One might hence suspect, that if Blumcnbach had attended to the propagation of the polypus, which he had composed of two half polypi, that the young progeny might have possessed two colours resembling the compound parent, like the different cau- dexes of ingrafted trees; an experiment well worthy repeated observation. 4. Another animal fact ought also to be here mentioned, that many insects, as common earth worms as well as the poly- pus, are said to possess so much life throughout a great part of their system; that they may be cut into two or more pieces without destroying them; as each piece will acquire a new head, or a new tail, or both, and the insect will thus become multi- plied! How exactly this is resembled by the long caudex of the buds of trees; which possess such vegetable life from one ex- tremity to the other, that when the head or plume is lopped off, it can produce a new plume, and when the lower part is cut off, it can produce new radicles; and may be thus wonderfully multiplied! This curious vegetable phenomenon is worthy our attention and remembrance; for as each filament of the new bark of a tree constitutes a caudex of an embryon bud; when the sum- mit of a twig is lopped off, vvhich contained the plumules or em- bryon leaves of many of them; each embryon caudex can gene- rate new plumules or embryon leaves; and new radicles, when the lower part of a twig is cut off, and the upper part planted; which demonstrates, that the primary parts of a vegetable em- bryon may produce secondary parts; and that hence it is not necessary, that the whole of an animal fetus should be formed at the same time. 5. Hence we acquire some new and important ideas con- cerning the lateral generation of vegetables, and which may probably contribute to elucidate their sexual generation. These are, first, that the parts of the long caudex of each new bud of an ingrafted tree, and consequently of all trees, are separated or secreted from the correspondent or adjoining parts of the long caudex of the last year's bud, vvhich was its parent. And not that it consists of the roots of each new bud shot down from the plumula or apex of it; as I formerly supposed. And lint these various molecules or fibrils secreted from the caudex of the last year's buds adjoin and grow together beneath the cuticle 420 GENERATION. Scct. XXNIX. 8. 6. of the trunk of the tree; the upper ones forming the plumula of the new bud, vvhich is its leaf or lungs to acquire oxygene from the atmosphere; and the lower ones forming the radivles of it, vvhich are absorbent vessels to acquire nutriment from the earth. Secondly, that every part of the caudex of an ingrafted tree, and consequently of all trees, can generate or produce a new plumula, when the upper part of it is strangulated with a wire or cut off; or otherwise when it is supplied more abundantly with nutriment, ventilation, and light. And that each of these new buds thus produced resembles that part of the stock in com- pound trees, where it arises. Thus in the triple tree above mentioned a bud from the upper part of the long caudexes, which form the filaments of the bark, would become a golden- pippin branch, a bud from the middle part of them would become a nonpareil branch, and a bud from the lower part a crab branch. Thirdly, another wonderful property of this lateral mule progeny of trees compounded by ingraftment consists in this, that the new mule may consist of parts from three or four or many parents; when so many different scions are ingrafted on each other, whence a question may arise, whether a mixture of two kinds of anther-dust previous to its application to the stig- ma of flowers might not produce a threefold mule partaking of the likeness of both the males? 6. On this nice subject of reproduction, so far removed from common apprehension, the patient reader will excuse a more prolix investigation. The attraction of all matter to the centres of the planets, or of the sun, is termed gravitation, that of par- ticular bodies to each other is generally called chemical affinity; to which the attractions belonging to electricity and magnetism appear to be allied. In these latter kinds of attraction two circumstances seem to be required, first, the power to attract possessed by one of the bodies, and secondly, the aptitude to be attracted possessed by the other. Thus when a magnet attracts iron, it may be said to possess a specific tendency to unite with iron; and the iron may be said to possess a specific aptitude to be united with the magnet. The former appears to reside in the magnet, because it can be deprived of its attractive power, which can also be re- stored to it. And the iron appears to possess a specific aptitude to be united with the magnet, because no other metal will approach it. In tlie same manner a rubbed glass tube or a rubbed stick of sealing wax may be said to possess a specific tendency to unite with a light straw, or hair, and the straw or hair to possess a Sect. XXXIX 8.7. GENERATION. 421 specific aptitude to unite with the rubbed glass or sealing wax; because the specific attraction to the rubbed glass or sealing wax can be withdrawn or restored; to vvhich may be added, that some chemical combinations may arise from the single attrac- tion of one body, and the aptitude to be attracted of another. Or they may be owing to reciprocal attractions of the two bodies, as in what is termed by the chemists double affinity, which is known to be so powerful as to separate those bodies, which are held together by the simple attraction probably of one of them to the other; which other possesses only an apti- tude to be attracted by the former. It is probable, that in some of tlie most simple combinations of the particles of inanimate matter, two of them may be strongly united by reciprocal attractions to each other; that in other simple combinations two particles may be held together, though less firmly, by the attraction of one and the aptitude to be attracted of the other. Thus I suspect that carbon and oxygen rush together by their reciprocal attractions producing explosion, and being afterwards not easily separable; while azote or nitro- gen is less firmly united with oxygen by the attraction of one of them, and only the aptitude to be attracted of the other. If this circumstance could be nicely ascertained, the theory of chemical affinities might possibly advance a step further in the explana- tion of some difficult phenomena, as of the heat generated in the explosion of various materials, with which oxygen is more loosely united, when applied to ignited carbon; as of the acid of nitre, and several metallic oxydes; as well as of the general circumstances of combustion and inflammation, as of phospho- rus in the atmosphere, and of oil of cloves with nitrous acid. 7. The above account of the tendencies to union of unor- ganized or inanimate matter is not given as a philosophical analogy, but to facilitate our conception of the adjunctions or concretions observable in organized or animated bodies; which constitute their formation, their nutrition, and their growth. These may be divided into two kinds; first, the junction or union of animated bodies with inanimate matter, as when fruit or flesh is swallowed into the stomach; and becomes absorbed by the lacteals; and the second, where living particles coalesce or concrete together; as in the formation, nutrition, or conjunc- tion of the parts of living animals. In respect to the former the animal parts, as the nostrils and palate, possess an appetency, when stimulated by the scent and flavour of agreeable food, to unite themselves with it; and the inanimate material possesses an aptitude to be thus united with the animal organ. The same occurs, when the food is swal- 422 GENERATION. Sect. XXXtX. 8. !!. lowed into the stomach; the mouths of the lacteal vessels be- ing agreeably stimulated possess an appetency to absorb the par- ticles of the digesting mass; which is in a situation of under- going chemical changes, and possesses at some period of them an aptitude to stimulate, and to be united with the mouths of the absorbent lacteals. But when these absorbed particles of inanimate matter have been circulated in the blood, they seem gradually to obtain a kind of vitality; whence Mr. John Hunter, and I believe some ancient philosophers, and the divine Moses, asserted, that the blood is alive; that is, that it possesses some degree of organi- zation, or other properties, different from those of inanimate matter; which are not producible by any chemical process, and which cease to exist along with the life of the animal. Hence for the purpose of nutrition there is reason to suspect, that two circumstances are necessary, both dependent upon life, and con- sequent activity; these are first an appetency of the fibrils of the fixed organization, which wants nutrition; and secondly a propensity of the fluid molecules existing in the blood, or se- creted from it, to unite with the organ now stimulated into ac- tion. So that nutrition may be said to be effected by the em- brace or coalescence of the fibrils, which possess nutritive appe- tencies, with the molecules, which possess nutritive propensities, or in other words of particles, which possess reciprocal appe- tencies to embrace each other. 8. If the philosopher, who thinks on this subject, should not be inclined to believe, that the whole of the blood is alive, he cannot easily deny life to that part of it, which is secreted by the organs of generation, and conveys vitality to the new em- bryon, which it produces. Hence though in the process of nu- trition the activity of two kinds of fibrils or molecules may be suspected, yet in the process of the generation of a new vegeta- ble or animal, there seems great reason to believe, that both the combining and combined particles are endued with vitality; that is, with some degree of organization or other properties not existing in inanimate matter, which we beg leave to denominate fibrils with formative appetencies, and molecules with formative propensities; as the former may seem to possess a greater degree of organization than the latter. And thus it appears, that though nutrition may be conceived to be produced by the animated fibrils of an organized part be- ing stimulated into action by inanimate molecules, which they then embrace; and may thus be popularly compared to the simple attractions of chemistry; yet that in the production of a new embryon, whether vegetable or animal, both the fibril? Sect. XXXIX. 8.9. GENERATION. 423 with formative appetencies and the molecules with formative pro- pensities reciprocally stimulate and embrace each other, and in- stantly coalesce ; and may thus popularly be compared to the re- ciprocal attractions of some of the atoms of inanimate matter, or to the double affinities of chemistry. But there are animal facts, which may be compared to both these, and are thence more philosophically analogous to them ; and these are the two great supports of animated nature, the passions of hunger and of love. In the former the appetency resides only in the stomach, or perhaps in the cardia ventriculi, but the object consists of in- animate matter; in the latter there exist reciprocal appetencies and propensities in the male and female, which mutually ex- cite them to embrace each other. Two other animal facts are equally analogous; the thirst, which resides at the upper end of the esophagus, and though it possesses appetency itself, its ob- ject is inanimate matters; but in lactescent females, when they give suck to their young, there exists a reciprocal appetency in the mother to part with her milk, and in the young offspring to receive it. This then finally I conceive to be the manner of the produc- tion of the lateral progeny of vegetables. The long caudex of an existing bud of a tree, vvhich constitutes a single filament of the present bark, is furnished with glands numerous as the per- spirative or mucous glands of animal bodies; and that these are of two kinds, the one secreting from the vegetable blood the fibrils with formative appetencies, correspondent to the masculine secretion of animals; and the other secreting from the vegeta- ble blood the molecules with formative propensities, correspon- dent to the feminine secretion of animals, and then that both these kinds of formative particles are deposited beneath the cu- ticle of the bark along the whole course of it, and instantly em- brace and coalesce, forming a new caudex along the side of its parent, with vegetable life, and with the additional powers of nutrition, and of growth. 9. This then is the great secret of nature. More living particles, some with appetencies, and some with propensities, are produced by the powers of vitality in the fabrication of the vegetable blood, than are necessary for nutrition, or for the re- storation of decomposing organs. These are secreted by differ- ent glands, and detruded externally, and produce by their com- bination a new vital organization beneath the cuticles of trees over the old one. These new combinations of vital fibrils and molecules acquire new appetencies, and fabricate molecules with new propensities ; and thus possess the power of forming the leaf or lungs at one extremity of the new caudex; and the 424 GENERATION. Sect. X^XXlX. 8. 10. radicles or absorbent vessels at the other end; and some of them, asinjthe central buds, which terminate the branches, finally form the sexual organs of reproduction, which constitute the flower; all which are secondary parts of the new embryon or fetus, as shewn in number 9. 4. of this section. That new organizations of the growing system acquire new appetencies appears from the production of the passion for ge- neration, as soon as the adapted organs are complete, and also from the variation of the palate, or desire for particular kinds of food, as we advance in life, as from milk to flesh; thus as a popular allusion, not as a philosophical analogy, we may again be allowed to apply to the combinations of chemistry. Where two different kinds of particles unite, as acids and alkalis, a third something is produced, vvhich possesses attractions dissimi- lar to those of either of them. And that new organizations form new molecules, appears from the secretions of the seminal and uterine glands, when they have acquired their maturity; and from the pectoral ones of lactescent females. 10. In the lateral propagation of vegetable buds, as the su- perfluous fibrils or molecules, which were fabricated in the blood, or detached from living organs, and possess nutritive or formative appetencies and propensities; and which were more abundant, than were required for the nutrition of the parent vegetable bud, when it had obtained its full growth, were se- creted by innumerable glands on the various parts of its surface beneath the general cuticle of the tree, and there embracing and coalescing, form a new embryon caudex, which gradually pro- duces a new plumula and radicles. And as the different parts of the new caudex of a compound tree resemble the parts of the parent caudex, to which it adheres, this important circum- stance is shewn beyond all doubt, that different fibrils or mole- cules were detached from different parts of the parent caudex to form the filial one. So in the sexual propagation of vegetables the superfluous liv- ing fibrils or molecules detached from various parts of the sys- tem, and floating in the blood, appear to be secreted from it by two kinds of glands only, those which constitute the anthers, and those which constitute the pericarp of flowers. By the for- mer I suppose the fibrils with formative appetencies and with nutritive appetencies to be secreted; and by the latter the mole- cules with formative and with nutritive propensities. After- wards, that these fibrils with formative and nutritive appeten- cies become mixed in the pericarp of the flower with the cor- respondent molecules with formative and nutritive propensities, Sect. XXXIX. 8. 11 GENERATION. 425 and that a new embryon is instantly produced by their reciprocal embrace and coalescence. And that parts of this new organization afterwards acquire new appetencies, and form new molecules, and thus gradually produce other parts of the growing seed, which do not at first appear, as the plumula, radicles, cuticle, and the glands of re- production in the pericarp and anthers, vvhich correspond in the animal fetus to the lungs, intestines, cuticle, and the organs, which distinguish the sexes, and are their parts of secondary formation. If secondary parts of a vegetable embryon were not fabricated from the primary parts, or first rudiments of it, the flowers of the class dicecia of Linnaeus could not produce both male and female seeds, as the male and female organs of reproduction reside on different plants. For as the male plants produce buds similar to themselves, which may be termed male buds; and the female plants produce buds similar to themselves, which may be termed female buds, it would seem impossible for the flowers to generate female seeds according to the theory of re- production above delivered. As the male, not being an her- maphrodite, cannot be supposed to secrete any fibrils with ap- petencies proper to produce female organs, as no such can exist in his blood, which must therefore be fabricated afterwards by the new appetencies acquired by the new organizations of the grow- ing embryon. 11. From this new doctrine of a three-fold vegetable mule by lateral propagation, as the new bud of a tree, which has had two scions ingrafted on it one above another; in which it is in- contestibly shewn, that different fibrils or molecules are detach- ed from different parts of the parent caudex to form the filial one, vvhich adheres to it; we may safely conclude, as it is de- ducible from the strongest analogy, that in the production of sexual mules, some parts of the new embryon were produced by, or detached from, similar parts of the parent, which they resemble. And that as these fibrils or molecules floated in the circulating blood of the parents, they were collected separately by appropriated glands of the male or female; and that final- ly on their mixture in the matrix the new embryon was gene- rated, resembling in some parts the form of the father, and in other parts the form of the mother, according to the quantity or activity of the fibrils or molecules at the time of their con- junction. And lastly, that various parts of the new organizations after- wards acquired new appetencies, and formed molecules with new propensities, and thus gradually produced other secondory VOL. I. 3 I 426 GENERATION. Sect. XXXIX. 9. 1. parts of the growing fetus, as the skin, nails, hair, and the organs which distinguish the sexes. If the molecules secreted by the female organ into the peri- carp of flowers, or into the ovary of animals, were supposed to consist of only unorganized or inanimate particles; and the fibrils secreted by the male organ only to possess formative appetencies to select and combine with them; the new embryon must proba- bly have always resembled the father, and no mules could have had existence. But by the theory above delivered it appears, that the new offspring, both in vegetable and animal reproduction, whether it be a mule or not, must sometimes more resemble the male pa- rent, and sometimes the female one, and sometimes to be a com- bination of them both, as in the Epigram of Ausonius. Dum dubitat Natura marem, faceretne puellam Factus es, O pulcher, pene puella, Puer ! IX. 1. The foregoing remarks on vegetable generation are chiefly transcribed from my work on Phytologia, Sect. VII. and may be applied to animal reproduction; since from this analogy to the lateral propagation of vegetable buds, if we suppose, that redundant fibrils with formative appetencies, are produced by, or detached from, various parts of the male animal, and circulating in his blood, are secreted by adapted glands, and constitute the seminal fluid; and that redundant molecules with formative apti- tudes or propensities are produced by, or detached from, various parts of the female, and circulating in her blood, are secreted by adapted glands, and form a reservoir in the ovary; and finally, that when these formative fibrils, and formative molecules, be- come mixed together in the uterus, that they coalesce or embrace each other, and form different parts of the new embryon, as in the cicatricula of the impregnated egg; we may more readily comprehend some circumstances, which are difficult to under- stand on any other system of generation. It must be observed that this theory differs from that of M. Buffon; as he conceives the same organized particles to exist in the generative secretions both of the male and female pa- rent; whereas in this theory it is supposed, that particles com- pletely organized are too large to pass the glands of either sex, and that those, which are seen in the semen by microscopes, are the consequence of the stagnation of the fluid, as in the pustules of the itch, and in the liquid feces of dysenteric patients. Hence the fibrils with formative appetencies, and the molecules with formative aptitudes or propensities, must coalesce to produce the first organization. Sect. XXXIX. 9. 1. GENERATION. 427 Secondly, in M. Buffon's theory the fetus is supposed to be instantaneously produced all at once; whereas in our theory there is believed to exist a primary, and secondary formation; that is, that many essential parts, as the brain and the heart, are pri- marily produced from the congress of the fibrils with formative appetencies, and the molecules with formative aptitudes or pro- pensities; and that these combinations acquire new appetencies, and produce or unite with molecules with new aptitudes, and thus generate other parts of secondary formation, as ribs, fingers, intestines, with the external form, and the glands, which consti- tute the difference of the sexes. One great objection to the theory delivered in the former par- of this section on generation is removed by this idea of the exist fence of formative fibrils, and formative molecules, which, by their coalescence generate various parts of the embryon at the same time; vvhich is, that in some monstrous or imperfect fetuses different parts only are produced, instead of the whole; and such parts as would not appear to be primary ones. Such are the teeth and hair, which have been found in moles or false conceptions, as they exist naturally at a distance from the brain and heart, which are esteemed to be the centre of vitality, and are first visi- ble in the embryon chick. Many other parts in monstrous births are said to have been completely formed, where no brain nor heart has existed; the production of which on other ideas of generation cannot be explained; unless it be supposed, that an entire embryon had been at first generated, all of which had perished, and had been absorbed, except the parts which con- stitute the monstrous or imperfect fetus at its birth, which would be difficult to explain. Many instances of very imperfect fetuses are recorded by Mons. J. J. Sue in his Recherches sur la Vitalite; and in the Comment, of Leipsic. I. 17. p. 528. M. Sue dissected a fetus of five months old, which had no head, nor chest, nor stomach, nor large intestines, and yet the inferior half of the lower belly was complete, with the umbilical cord, male organs of genera- tion, and one complete inferior limb, of which a print is given in Magazin. Encycloped. 1797. This monstrous fetus, which was only half of it formed, shews, that the embryon is not always produced from one beginning, but probably from many: as there was no brain or heart, the connection of nerves in the lower part of the spine must have served the purpose of the former; and a junction of the large arteries and veins must have served the purpose of a heart, producing a circulation like that in the liver, or in the aorta and vena cava of fish. For a previous production and reabsorption of the other more essential parts of 42S GENERATION. Sect. X\XIX. 9.2 the fetus, as the brain and heart, with all the upper parts of the body, and intestines, would seem to be attended with still greater difficulties. The mistake of conceiving the embryon to begin its formation in one point only, might more readily be fallen into from our habitually considering an animal as an individual entity; vvhich it seems not to be, till an union of the nerves from every part is formed in the common sensorium, and produces a general sensi- bility, which is thus distinguished from irritability, which may reside in parts even when detached from the system, as is seen in the contractions of the heart of a viper taken out of the body, or of limbs recently cut off. 2. Another thing difficult to conceive from those theories, which supposed the first rudiment to consist of a single entity, was to answer the curious question, whether the brain, or heart and arteries were first formed; as the motions of the arterial system previously exerted seem to have been necessary for the secretion of sensorial power in the brain, and conversely those motions of the arterial system seem previously to require the sensorial power derived from the brain. This difficulty vanishes, when we believe, that many parts of the young embryon can be begun at the same time, as various for- mative fibrils and formative molecules coalesce, as they come into contact with each other; and thus the rudiments of the brain and of the heart may be fabricated at the same instant of time. 3. If fibrils with formative appetencies, and molecules with formative aptitudes or propensities exist in the circulation both of males and females, why do they not coalesce there? This seems an unanswerable objection to M. Buffon's theory, who holds, that organic particles exist in the circulation; but in the system above delivered, no organic particles exist in the blood in their combin- ed state; and hence no microscopic animalcula are seen in blood recently drawn, though they may appear after some hours stagna- tion; but the formative fibrils only and formative molecules are believed to exist in the circulation; and that they do not produce combinations there, as they cannot rest; and as such combina- tions would be too large to pass the capillary vessels of the aorta, and of the pulmonary artery, and of all the glands, and must there be perpetually dissevered, if they could be previously formed in the larger vessels. 4. If similar organized particles were secreted by the sexual glands of the male and also of the female, why do they not pro- duce parts, or rudiments, of an embryon in the male or female reservoirs without a reciprocal commixture. This is another unanswerable objection to M. Buffon's theory, but not to that Sect. XXXIX. 9. 5. GENERATION. 429 above delivered; which latter supposes, that no organized parti- cles are secreted either by the glands of the male or female; but that the fibrils with formative appetencies are secreted by the glands of the male, and the molecules with formative aptitudes or propensities are secreted by those of the female; and that, when these combine, the organization commences. 5. If the whole of the embryon is supposed to be synchro- nously produced, which is said almost to be visible in the cicatri- cula of the egg even before incubation, how can this happen from a commixture of any kind of particles deduced from both the male and female parents, if those particles are previously de- tached from the various parts of their respective bodies; since no parts similar to the female organs can previously exist in the male, nor any of those of the male organs previously exist in the female? This synchronous production of all the parts of the em- bryon is supposed by M. Buffon, and militates against his the- ory; and if it was true, would equally militate against that above delivered; but from all the histories of the beginning and growing fetus given by anatomists, there are parts of secondary formation, as well as parts of primary formation; thus the head and spine of the back are first seen both in the oviparous and vi- viparous embryon, and afterwards the lungs, ribs, limbs, nails, hairs, and feathers, and last of all perhaps the glands vvhich dis- tinguish the sexes; as these are the last, which afterwards arrive at their maturity. This secondary formation of parts is evinced in the long cau- dexes of the buds of trees, vvhich form a filament of the bark; as from any part of this a new plumula or leaf, vvhich is the lungs of the embryon bud, can be produced, when the upper part of a branch is lopped off, as shewn in No. 9. 4. of this section; and is further evinced in some animals, as when a common earth-worm is cut in halves, the tail-part can produce a head-part, and the head-part can produce a tail-part; and lastly, it is evinced from the power, which crabs possess of gen- erating a new leg, when one of them is accidently broken off. This power is likewise possessed by the human body, as in the production of new teeth, and then of a second set, and there are some instances on record, that a third set of teeth have been fa- bricated in the jaw-bones of age. The power of formation of secondary parts in the human sys- tem is wonderfully shewn by the following case, which is related by Mr. White in the Manchester Memoirs, Vol. I. p. 338. " Sonic years ago 1 delivered a lady of rank of a fine boy, who had two thumbs on one hand, or rather one thumb double from the first joint, the outer one being rather less than the inner. 130 GENERATION. m. r. XXXIX. 10. 1. and each of them having a perfect nail. When he was about three years old, I was desired to take off the lesser one; which I did, but to iny great astonishment it grew again, and along with it the nail. The family afterwards went to reside in London, when the father shewed it to Mr. Bromfield; who said, that he supposed Mr. White, from fear of damaging the joint had not taken it wholly out, but that he would dissect it out entirely, and that then it would not return. He accordingly executed his plan, and turned the ball out of the socket. Notwithstanding this it grew again, a fresh nail was formed, and the thumb re- mains in this state." Recapitulation. X. On considering the production of v egetable buds and seeds, of some insects, and of more perfect animals, the modes of ge- neration may be divided into solitary and sexual. 1. The first consists either in solitary lateral generation, as in the reproduction of the buds or bulbs of vegetables, and of the young of the polypus, and of the hydra stentorea, or of the soli- tary internal generation, as of the aphis, vine-fretter, actinia, sea-anemone, tenia, tape-worm, and the volvox; all vvhich are properly a viviparous progeny, as they are not preceded by seeds, or spawn, or eggs. In these modes of reproduction I suppose, that fibrils with formative appetencies, and molecules with formative aptitudes or propensities, produced by, or detached from, various essential parts of their respective systems, float in the vegetable or insect blood. These may be termed animalized particles of primary combination, consisting of a solid particle adjoined to a peculiar appetency or propensity; which latter may be esteemed its ethe- real part, as magnetism or electricity may be added to iron or to other inanimate bodies. These fibrils with formative appetencies, and molecules with formative aptitudes or propensities, cannot unite, or continue united, in the circulating blood, as they are not at rest; and would be too large to pass the capillaries of the aorta, pulmonary artery, and glands, if they could be united in the larger vessels; they are therefore selected or secreted separately by adapted glands, and when mixed together combine, and form the primary parts of the new organization of an embryon. Those secreted from the long caudex of vegetable buds are deposited beneath the cuticle of the bark of trees, and there uniting form a new caudex gemmae along the side of the parent one; which has the property of producing secondary organiza- Sect XXXIX. 10. 2. GENERATION. 431 tions from the new powers it has acquired so as to form a leaf or lungs either at its summit or in the axilla of the parent leaf, or in any other part of its length; and also to form radicles below, or from any amputated part. This new caudex gemmae is proved to commence its forma- tion in several places at the same time from the triple caudex of the bud of a tree, which has been twice successively ingrafted, vvhich we have called a triple mule; but as the new vegetable consists in general of a combination of parts derived from one parent, it much more accurately resembles that parent in its form, growth, and diseases, than the progeny from sexual or seminal generation. The same circumstances occur to the vege- tables, which possess short and flat caudexes, which exist be- tween the radicles and the root-leaves, as in the bulbs of tulips and onions; which might possibly be ingrafted on each other like the buds of different trees, and form curious mule bulbs. This lateral or solitary mode of propagation belongs likewise to the polypus of our ditches, and to the hydra stentorea, and probably to many other insects. 2. There is also a solitary internal mode of generation, which occurs in the viviparous productions of the aphis, which are known to proceed for eight or nine successive generations with- out the congress of sexes; but what is extraordinary, a con- gress of sexes appears to be necessary in their production of an oviparous progeny in the autumn for the preservation of the spe- cies during winter; whence it would seem, that solitary genera- tion always produces a viviparous offspring. For the more par- ticular history of this wondeffuhand important insect see Phy- tologia, Sect. IX. and XIV. To which may be added, that a similar internal solitary mode of reproduction probably obtains in the tenia, or tape-worm, of the intestines, which afflicts va- riety of animals, and of the actinea, or sea-anemone, and of the volvox, as described in the Systema Naturae of Linnaeus. The essential difference between the solitary lateral generation and the solitary internal generation seems to consist in this; that in the former there are many glands, which secrete or pro- duce the fibrils with formative appetencies; and many other glands, which secrete or produce the molecules with formative aptitudes or propensities; and that these numerous secretions are mixed together and combine in one large receptacle beneath the cuticle of trees, and of some insects, and there combining gene- rate the organized particles, which constitute the rudiment of the new embryon, producing many of the essential parts of it at the same time; wdiereas in the latter, there probably exists but one set of glands, which secrete the fibrils with formative appe- 432 GENERATION. Sect. XXXIX. 10. 3. tencies; and another set of glands which secrete the molecules with formative propensities; and that these primary particles are received and mingled together in a less extensive reservoir; as an universal existence of procreative glands, as in the long caudexes of vegetable buds, might have been inconvenient to locomotive animals. These therefore seem to constitute a link of the chain of nature between her lateral production of buds, and the sexual hermaphrodites, which are next to be considered. 3. The sexual mode of propagation may be divided first into hermaphrodite or reciprocal sexual generation, as in the flowers of most vegetables, and in some large insects, as in dew-worms and shell-snails, and probably in many smaller ones. Secondly, into the simpler sexual generation, which occurs in the larger animals. The sexual modes of generation may also be divided into the seminal or oviparous modes, as the seeds of plants, the spawn of fish, and of insects, and the eggs of birds; and secondly, into the viviparous modes, as the summit-bulbs of some vegetables, as of polygonum viviparum, magical onions, and the cloves of garlic; as these summit-bulbs succeed the sexual congress of the male and female organs of flowers; and are not buds, as their roots or caudexes do not pass down the stem of the plant into the ground; and are therefore a sexual viviparous progeny of vegetables: but the principal viviparous sexual productions are those of quadrupeds and of mankind. Next to the internal solitary mode of propagation nature seems to have produced the hermaphrodite system of reproduction, as in most flowers; and in snails and dew-worms; in these the masculine and feminine organs arc generally external, and totally separated from each other, and consist of glands, which secrete the fibrils with formative appetencies, and the molecules with formative propensities from the same mass of blood. Hence in vegetable productions the trees from seed, as apple trees, sometimes exactly resemble the parent tree, like the buds and bulbs vvhich are produced without sexual intercourse; at other times they do not exactly resemble the parent tree, which seems to be owing to the anther-dust sometimes of the same flower, or sometimes of other flowers in its vicinity, causing the impregnation of the stigma. But in hermaphrodite insects, as the shell-snail, and dew-worm, I have frequently observed, that they impregnate each other reciprocally, though it is attended with much danger and inconvenience to them: and I thence conclude, that they have not the power to impregnate them- selves by the conjunction of their own organs of reproduction, since if that had happened, the progeny would probably, like the sect. XXXIX. 10. 4. GENERATION. 433 buds of trees, more exactly have resembled the parent; and no improvement of the species, or no new species from the same genus, could have been procreated; which latter circumstance has probably much increased the number both of animal and vegetable productions. 4. Lastly, the simple mode of sexual generation differs from the reciprocal or hermaphrodite mode of generation; as the glands, which constitute the masculine and feminine organs, se- crete the fibrils with formative appetencies and the molecules with formative propensities from different masses of blood; as a double system of organs might have been cumbersome, if they had existed together in larger and more active animals: though it is not improbable, that all animals were originally hermaphro- dite, according to the opinion of Plato in respect to human kind, as would appear from the teals or nipples, as well as the pecto- ral glands, which are still to be seen in men and in all male quadrupeds. In this mode of propagation the fibrils with formative appe- tencies detached from some or many essential parts of the male parent, or which were formed from the blood accordant to those essential parts, are secreted by the male organ into an adapted reservoir; and the molecules with formative propensities de- tached from some or many essential parts of the female parent, or which are formed from the blood accordant to those essen- tial parts, are secreted by the female organ into an adapted reser- voir: and in this circumstance secretion differs from nutrition; in the latter certain particles of the blood, vvhich were not pre- viously used in the system, are embraced and become a solid part of the animal; in the former certain particles, which had pre- viously been used in the system, and detached from it, are im- bibed by adapted glands, and deposited in reservoirs, or detruded See Sect. XXXVII. 3. Finally, when these are mixed together in the act of copula- tion, they embrace and coalesce, and form the essential parts of the new embryon; the production of which commences in more places than one; as the brain and heart, with some nerves, arteries, veins, and absorbent vessels, are probably formed at the same time, and almost instantaneously. These new fibrous combinations acquire new appetencies, and produce molecules by their vital activity with new aptitudes or propensities; and thus gradually fabricate other secondary parts either synchronous or successive ones, as the ribs, lungs, limbs, and finally the organs, which distinguish the sexes, with the general difference of the male and female form throughout the whole system, according to the prevailing or preponderant vol. i. 3 k 434 GENERATION. Sect. XXXTX. 10. 5. activity or quantity of the fibrils with appetencies derived from the male, or the molecules with propensities derived from the female. This idea differs from the theory of M. Buffon, which supposes the whole embryon to be formed at the same lime, or that the sexual organs are first produced, as a centre of animali- zation; but the secondary production of these organs is agree- able to all observations on the growing chick or fetus, and is strongly countenanced by the slow progress of these parts after birth, which are not complete till the maturity of the animal, which is termed its puberty. The power, which the primary or essential parts of the em- bryon possess, of producing secondary or less essential parts, is analogous to the production of a new plumula or new radicles by the vegetable embryon, or caudex gemmae mentioned in No. 8. 4. of this section; and to the power with which crabs are furnished to produce a new limb, when one is broken off; and to that of earth-worms, which, when cut in halves, can acquire a new head or a new tail; and to the power in a human infant of regenerating a supernumerary thumb, to the production of a new set of teeth, and the developement of the sexual glands at puberty. See No. 9. 5. of this section. 5. Some of these sexual reproductions consist of seeds, or eggs, in which the essential parts of the vegetable or of the chick are already formed, as may be seen in the corculum of many seeds, and in the cicatricula of an egg as soon as it leaves the body of the hen before incubation. In this state the embryon does not continue to grow, if exposed only to the usual degree of the warmth and moisture of the atmosphere, but may be long kept in its state of insensible life; though it will soon ferment or putrify, if it be deprived of life. Otherwise these sexual productions consist of spawn, which differs from eggs by the embryon not being included in a hard unyielding shell; so that the receptacle distends, as the fetus increases in size; which is seen in the spawn of fish and frogs, and in the eggs of spiders, snails, and many other insects. From this distensibility of the bag, which contains the embryons of fish and insects, it seems more to resemble the uterus of quad- rupeds than the eggs of birds; as in the former the receptacle increases in size along with the fetus, and supplies the liquor of the amnios, as it is wanted; but differs by its not continuing in the matrix of the mother, till the exclusion of the young animal into the cold and dry atmosphere. XI. 1. Finally, we conclude, that as the inanimate particles or atoms of matter unite into crystals of various forms by the various powers of attraction, which some kinds of them possess; Sect. XXXIX. 11. 1. GENERATION. 435 and the various aptitudes to be attracted, which other kinds possess; which may be termed the ethereal properties of inani- mate matter; so the animated fibrils or molecules, which possess appetencies to embrace and propensities to be embraced, which may be called their ethereal properties, coalesce, when they ap- proach each other, and form organized bodies. When this organization begins only in a single point, and only enlarges, as it acquires new kinds of appetencies, as ex- plained in the former part of this section on generation, I sup- pose an animated being commences; such as the animalcula, which are seen by the solar microscope in variety of fluids, which have for a time stagnated; as in infusions of the seeds of plants; in the semen of animals, and of all other vegetable and animal recrements diffused in water. These microscopic ani- mals I suppose are produced by the stagnation of the semen in the vesiculae seminales, and by the matter of the itch by stagna- tion in its pustules, and by the feces by their stagnation in the intestines; but I believe, that they do not exist in the blood, nor in fluids recently secreted. These microscopic animals consti- tute the primordium vitae, or first order of animal life, and pro- bably are not originally propagated, but simply arise from the dissolution of all vegetable or animal matter. This spontaneous production of microscopic animals appears from their being discovered in a few days in all solutions of de- composing vegetable and animal matters, as well after having been subjected to the heat of boiling water as before. Thus Mr. Reaumur put some boiling veal broth, and Mr. Baker put some boiling hot mashed potatoes into hot phials, vvhich were closed with glass-stopples; and both of them in three days be- came as full of animalcula, as the same materials put into other phials without being previously boiled. Baker on the Microscope. It is probable that there exist microscopic vegetable produc- tions, as well as microscopic animals, which may not have been attended to. owing to the quick evaporation of a drop of water in a microscope; and that these are first formed spontaneously from the decomposing recrements of vegetable or animal bodies; and that they afterwards generate others rather more perfect than themselves by lateral reproduction. From this kind of spontaneous microscopic vegetation, I suppose the green matter observed by Dr. Priestley, which gives up so much vital air in the sunshine, originates; and that it afterwards generates a suc- ceeding progeny. As it is at first slowly produced in water in any situation, and afterwards is propagated with great rapidity; and according to the observations of Senebier it is most quickly produced in water in which vegetable or animal substances are 43b' GENERATION. Sect. NXX1X. 11. 2- in a state of dissolution. Whence some philosophers have late- ly supposed this green matter to be of animal origin, as it changes from a globular form to that of a thread; which has occasioned much investigation by Fontana, Ingenhouz, and Sencbrer. Journal de Physique par Delametherie, T. 5. In the same manner the mucor, or mould, which grows on all decomposing vegetable and animal substances, which are at rest in a proper degree of moisture and warmth, and which thence appears to have no parent, is probably first produced by the spontaneous appetencies and aptitudes or propensities of the decomposed particles of organic bodies; and probably these new combinations are at first microscopic objects, which pro- duce others by lateral or solitary generation, more and more perfect and of greater magnitude than themselves, but which never acquire the organization necessary for sexual reproduc- tion. The fungi which grow only on decaying parts of trees or other vegetables, as well as the mushrooms from horse dung, which commence with small hair-like roots, and probably never produce seeds, seem to arise in a similar manner from spontane- ous microscopic organization, improved and magnified by suc- cessive solitary generations. 2. The second kind of animal production, which is properly generation, commences in more points than one; as in the pro- duction of the long caudexes of the buds of trees; and the ani- mated fibrils and molecules first combine, and form organized bodies; and these unite again, wlure they are in contact; and thus the new embryon commences in many points at once; and the solitary mode of generation is secondary to the produc- tion of the smallest microscopic animals, which I suppose com- mence their existence in one point only, that is, by the produc- tion first of a single living filament, which I formerly believed to be the general mode of propagation. This solitary mode of generation occurs in the production of the buds of all vegeta- bles; and perhaps the most imperfect vegetables, as truffles, and other fungi, are only propagated by buds to this day, not hav- ing yet acquired sexual organs, as seems also to occur in some imperfect animals, as the polypi, hydra, and tenia. 3. Other vegetables have acquired an hermaphrodite state, and possess external sexual organs, as in most flowers; but both the male and female organs acquire or produce their adapted fluids from the same mass of blood, and thus resemble herma- phrodite insects, as snails and worms. 4. Other vegetables have acquired a separation of the sexes, either on the same plant, as in the class of vegetables termed by Linnaeus, monoecia, or on different plants, as in the class dioe- Sect. XXXIX. 11. 5. GENERATION. 437 da; the buds of which may properly be called male or female vegetables, and differ in some degree in their form and colour, like male and female animals; and in this they resemble the larger animals, as their sexual glands acquire or produce their prolific fluids from different masses of blood; which is probably less cumbersome to the individual, than where both the sexual glands exist in one organized system. In all these vegetable and animal modes of reproduction, I sup- pose the new embryon to begin in many points, and in compli- cated animals in many more points probably than in the more sim- ple ones; and finally, that as these new organized parts, or rudi- ments of the embryon, acquire new appetencies, and produce or find molecules with new propensities, many secondary parts are afterwards fabricated. Thus it would appear, that all nature exists in a state of per- petual improvement by laws impressed on the atoms of matter by the great cause of causes; and that the world may still be in its infancy, and continue to improve for ever and ever. 5. Concerning the spontaneous production of microscopic ani- malcules, I beg leave to repeat, first, that I suppose the smallest ones to be formed by the coalescence or embrace of the animal fibrils, which possess appetencies, with the animal molecules, which possess correspondent propensities; and that the animal fibrils and molecules are found in all vegetable and animal mat- ter, as its organization becomes decomposed; if there exists along with it sufficient moisture and proper warmth. Secondly, that this kind of spontaneous reproduction resem- bles actual generation in its consisting of the coalescence of ani- mal fibrils with appetencies and animal molecules with corres- pondent propensities, that in the former they meet each other in the solution of animal matter, as it decomposes by stagnation; whereas in the latter these formative fibrils and molecules are secreted by different glands from the blood of the parent. Thirdly, that the first animalcules produce other ones by ac- tual generation, but without sexes, like the buds of trees, and that as many generations may occur in a day, perhaps in an hour, I conceive, that they may gradually acquire new organiza- tions, and improve by addition of new parts, as of fins, mouth, intestines, and finally, perhaps, sexual organs of reproduction. Thus the seed of a tulip produces a small root the size of a pea the first summer, with a summit like a blade of grass; this dies in autumn, having previously produced a successor larger than itself, and with a stronger leaf or summit; in the autumn this likewise perishes, and a third generation is produced, which is still larger and more perfect; till the fifth generation from the 438 GENERATION. Seh. XXXIX. 12. 1- seed becomes so much more perfect as to produce sexual organs of reproduction, as the flower with its anthers and stigma. This curious analogy is not only supported by the seedling buds of trees, which succeed each other for ten or twelve gene- rations, the parent buds dying in the autumn, before they become sufficiently perfect to form the sexual organs of reproduction in their flower, as occurs in apple-trees; but is also observable in a complete insect, as in the aphis, which continues to propagate for nine generations from the egg without sex; and then becomes so perfect as to form sexual organs, and to produce an oviparous pro- geny. Other insects, as the moths and butterflies, undergo a great change of form, before they acquire the property of sexual re- production; and probably innumerable other kinds of insects are subject to the same law. This idea of the production and changes of form of microsco- pic animalcules is countenanced by the smaller kinds, never, I believe, having been seen in their egg or infant state; and by some of them being capable of being revived in a few hours by warmth and moisture after having been dry and motionless for months, as the insect named vorticella. And lastly, from the changeful forms, which some of them assume, as that which is called proteus. See Baker and Adams on the Microscope. Thus as by the attractions, and aptitudes to be attracted, which exist in inanimate matter, various new bodies are produced from the decomposition of those, which previously existed; so by the appetencies to embrace, and the propensities to be embraced, in animalized matter, various new animalcules are formed from the decomposition of those, which previously existed; owing in both cases to the immutable laws impressed both on inanimate and on organized matter by the great first cause. XII. 1. Cause and effect may be considered as the pro- gression, or successive motions, of the parts of the great system of Nature. The state of things at this moment is the effect of the state of things, which existed in the preceding moment; and the cause of the state of things, which shall exist in the next mo- ment. These causes and effects may be more easily comprehended, if motion be considered as a change of the figure of a group of bodies, as proposed in Sect. XIV. 2. 2. inasmuch as our idea9 of visible or tangible objects are more distinct, than our ab- stracted ideas of their motions. Now the change of the con- figuration of the system of nature at this moment must be an effect of the preceding configuration, for a change of configura- tion cannot exist without a previous configuration; and the proximate cause of every effect must immediately precede that Sect. XXXIX. 12.2. GENERATION. 439 effect. For example a moving ivory ball could not proceed on- wards, unless it had previously begun to proceed; or unless an im- pulse had been previously given it; which previous motion or im- pulse constitutes a part of the last situation of things. As the effects produced in this moment of time become causes in the next, we may consider the progressive motions of objects as a chain of causes only; whose first link proceeded from the great Creator, and vvhich have existed from the beginning of the created universe, and are perpetually proceeding. 2. These causes may be conveniently divided into two kinds, efficient and inert causes, according with the two kinds of entity supposed to exist in the natural world, vvhich may be termed mat- ter and spirit, as proposed in Sect. I. and further treated of in Sect. XIV. The efficient causes of motion, or new configura- tion, consist either of the principle of general gravitation, which actuates the sun and planets; or of the principle of particular gravitation, as in electricity, magnetism, heat; or of the principle of chemical affinity, as in combustion, fermentation, combination; or of the principle of organic life, as in the contraction of vegeta- ble and animal fibres. The inert causes of motion, or new con- figuration, consist of the parts of matter, which are introduced within the spheres of activity of the principles above described. Thus, when an apple falls on the ground, the principle of gravi- tation is the efficient cause, and the matter of the apple-tree the inert cause. If a bar of iron be approximated to a magnet, it may be termed the inert cause of the motion, vvhich brings these two bodies into contact; while the magnetic principle may be termed the efficient cause. In the same manner the fibres, vvhich constitute the retina, may be called the inert cause of the motions of that organ in vision, while the sensorial power may be termed the efficient cause. 3. Another more common distribution of the perpetual chain of causes and effects, which constitute the motions, or changing configurations, of the natural world, is into active and passive. Thus, if a ball in motion impinges against another ball at rest, and communicates its motion to it, the former ball is said to act, and the latter to be acted upon. In this sense of the words a mag- net is said to attract iron; and the prick of a spur to stimulate a horse into exertion; so that in this view of the works of nature all things may be said either simply to exist, or to exist as causes, or to exist as effects; that is, to exist either in an active or pas- sive state. This distribution of objects and their motions, or changes of position, has been found so convenient for the purposes of common life, that on this foundation rests the whole construe- 440 GENERATION. Sect. XXXXIX. 12. 4. tion or theory of language. The names of the things themselves are termed by grammarians Nouns, and their modes of existence are termed Verbs. The nouns are divided into substantives, which denote the principal things spoken of; and into adjectives, which denote some circumstances, or less kinds of things, belong- ing to the former. The verbs are divided into three kinds, such as denote the existence of things simply, as, to be; or their ex- istence in an active state, as, to eat; or their existence in a pas- sive state, as, to be eaten. Whence it appears, that all languages consist only of nouns and verbs, with their abbreviations for the greater expedition of communicating our thoughts; as explained in the ingenious work of Mr. Home Tooke, who has unfolded by a single flash of light the whole theory of language, which had so long lain buried beneath the learned lumber of the schools. Di- versions of Purley. Johnson. London. 4. A third division of causes has been into proximate and re- mote; these have been much spoken of by the writers on medical subjects, but without sufficient precision. If to proximate and remote causes we add proximate and remote effects, we shall include four links of the perpetual chain of causation; which will be more convenient for the discussion of many philosophical subjects. Thus if a particle of chyle be applied to the mouth of a lac- teal vessel, it may be termed the remote cause of the motions of the fibres, which compose the mouth of that lacteal vessel; the sensorial power is the proximate cause; the contraction of the fibres of the mouth of the vessel is the proximate effect; and their embracing the particle of chyle is the remote effect; and these four links of causation constitute absorption. Thus when we attend to the rising sun, first the yellow rays of light stimulate the sensorial power residing in the extremities of the optic nerve, this is the remote cause. 2. The sensorial power is excited into a state of activity, this is the proximate cause. 3. The fibrous extremities of the optic nerve are con- tracted, this is the proximate effect. 4. A pleasurable or pain- ful sensation is produced in consequence of the contraction o' these fibres of the optic nerve, this is the remote effect; and these four links of the chain of causation constitute the sensi- tive idea, or what is commonly termed the sensation of the rising sun. 5. Other causes have been announced by medical writers under the names of causa procatarctica, and causa proegumina, and causa sine qua non. AH which are links more or less distant of the chain of remote causes. Sixt. XXXIX. 12.6. GENERATION. 44] To these must be added the final cause, so called by many au- thors, which means the motive, for the accomplishment of which the preceding chain of causes was put into action. The idea of a final cause, therefore, includes that of a rational mind, which employs means to effect its purposes; thus the desire of preserving himself from the pain of cold, which he has frequent- ly experienced, induces the savage to construct his hut; the fix- ing stakes into the ground for walls, branches of trees for rafters, and turf for a cover, are a series of successive voluntary exer- tions; which are so many means to produce a certain effect. This effect of preserving himself from cold, is termed the final cause; the construction of the hut is the remote effect; the ac- tion of the muscular fibres of the man, is the proximate effect; the volition, or activity of desire to preserve himself from cold, is the proximate cause; and the pain of cold, which excited that desire, is the remote cause. 6. This perpetual chain of causes and effects, the first link of which is rivetted to the throne of God, divides itself into innu- merable diverging branches, which, like the nerves arising from the brain, permeate the most minute and most remote extremi- ties of the system, diffusing motion and sensation to the whole. As every cause is superior in power to the effect, which it has produced, so our idea of the power of the Almighty Creator be- comes more elevated and sublime, as we trace the operations of nature from cause (o cause, climbing up the links of these chains of being, till we ascend to the Great Source of all things. Hence the modern discoveries in chemistry and in geology, by having traced the causes of the combinations of bodies to remoter origins, as well as those in astronomy, which dignify the present age, contribute to enlarge and amplify our ideas of the power of the Great First Cause. And had those ancient philosophers, who contended that the world was formed from atoms, ascribed their combinations to certain immutable pro- perties received from the hand of the Creator, such as general gravitation, chemical affinity, or animal appetency, instead of ascribing them to a blind chance; the doctrine of atoms, as con- stituting or composing the material world by the variety of their combinations, so far from leading the mind to atheism, would strengthen the demonstration of the existence of a Deity, as the first cause of all things; because the analogy resulting from our perpetual experience of cause and effect would have thus been exemplified through universal nature. The heavens declare the Glory of God, and the firmament shewcth his handy work! One day telleth another, and one night vol. i. 3l 44^ GENERATION. Sect. XXXIX. 12. 6. certifieth another; they have neither speech nor language, yet their voice is gone forth into all lands, and their words into the ends of tlie world. Manifold are thy works, 0 Lord! in wisdom hast thou made them all. Psal. xix. civ. Sect. XL. OCULAR SPECTRA. 443 SECT. XL. On the Ocular Spectra of Light and Colours, by Dr. R. W. Darwin, of Shrewsbury. Reprinted, by permission, from the Philosophical Transactions, Vol. LXXVI. p. 313. Spectra of four kinds. 1. Activity of the retina in vision. 2. Spec- tra from defect of sensibility. 3. Spectra from excess of sensibili- ty. 4. Of direct ocular spectra. 5. Greater stimulus excites the retina into spasmodic action. 6. Of reverse ocular spectra. 7. Greater stimulus excites the retina into various successive spas- modic actions. 8 Into fixed spasmodic action. 9. Into tempora- ry paralysis. 10. Miscellaneous remarks; 1. Direct and re- verse spectra at the same time. A spectral halo. Rule to prede- termine the colours of spectra. 2. Variation of spectra from ex- traneous light. 3. Variation of spectra in number, figure, and remission. 4. Circulation of the blood in the eye is visible. 5. A new way of magnifying objects. Conclusion. When any one has long and attentively looked at a bright ob- ject, as at the setting sun, on closing his eyes, or removing them, an image, which resembles in form the object he was attending to, continues some time to be visible; this appearance in the eye we shall call the ocular spectrum of that object. These ocular spectra are of four kinds: 1st, Such as are owing to a less sensibility of a defined part of the retina; or spectra from defect of sensibility. 2d, Such as are owing to a greater sensi- bility of a defined part of the retina; or spectra from excess of sen- sibility. 3d, Such as resemble their object in its colour as well as form; which may be termed direct ocular spectra. 4th, Such as are of a colour contrary to that of their object; which may be termed reverse ocular spectra. The laws of light have been most successfully explained by the great Newton, and the perception of visible objects has been ably investigated by the ingenious Dr. Berkeley and M. Malebranche; but these minute phenomena of vision have yet been thought re- ducible to no theory, though many philosophers have employed a considerable degree of attention upon them: among these are Dr. Jurin, at the end of Dr. Smith's Optics; M. jEpinus, in the Nov. Com. Petropol. V. 10.; M. Beguelin, in the Berlin Memoires, V. II. 1771; M. d'Arcy, in the Histoire de l'Acad. des Scienc. 1765; M. de la Hire; and, lastly, the celebrated M. de Buffon, in the Memoires de l'Acad. des Scien. who has termed them ac- 1J..-L OCULAR SPECTRA. Sect. XL. 1. 1. cidental colours, as if subjected to no established laws, Ac. Par. 1743. M. p. 215. 1 must here apprize the reader, that it is very difficult for dif- ferent people to give the same names to various shades of colours; whence, in the following pages, something must be allowed, if, on repeating the experiments, the colours here mentioned should not accurately correspond with his own names of them. I. Activity of the Retina in Vision. From the subsequent experiments it appears, that the retina is in an active not in a passive state during the existence of these ocular spectra; and it is thence to be concluded, that all vision is owing to the activity of this organ. 1. Place a piece of red silk, about an inch in diameter, as in plate 1, at Sect. III. 1, on a sheet of white paper, in a strong light; look steadily upon it from about the distance of half a yard for a minute; then closing your eyelids cover them with your hands, and a green spectrum will be seen in your eyes, resem- bling in form the piece of red silk: after some time, this spectrum will disappear and shortly reappear; and this alternately three or four times, if the experiment is well made, till at length it va- nishes entirely. 2. Place on a sheet of white paper a circular piece of blue silk, about four inches in diameter, in the sunshine; cover the centre of this with a circular piece of yellow silk, about three inches in diameter; and the centre of the yellow silk with a circle of pink silk, about two inches in diameter; and the centre of the pink silk with a circle of green silk, about one inch in diameter; and the centre of this with a circle of indigo, about half an inch in di- ameter; make a small speck with ink in the very centre of the whole, as in plate 3, at Sect. III. 3. 6.; look steadily for a minute on this central spot, and then closing your eyes, and applying your hand at about an inch distance before them, so as to pre- vent too much or too little light from passing through the eyelids, you will see the most beautiful circlesof colours that imagination can conceive, which are most resembled by the colours occasion- ed by pouring a drop or two of oil on a still lake in a bright day; but these circular irises of colours are not only different from the colours of the silks above mentioned, but are at the same time perpetually changing as long as they exist. 3. When any one in the dark presses either corner of his eye with his finger, and turns his eye away from his finger, he will see a circle of colours like those in a peacock's tail: and a Se. r. XL. 1.4. OCULAR SPECTRA. 415 sudden flash of light is excited in the eye by a stroke on it. (Newton's Opt. Q. 16.) 4. When any one turns round rapidly on one foot, till he be- comes dizzy, and falls upon the ground, the spectra of the am- bient objects continue to present themselves in rotation, or ap- pear to librate, and he seems to behold them for some time still in motion. From all these experiments it appears, that the spectra in the eye are not owing to the mechanical impulse of light impressed on the retina, nor to its chemical combination with that organ, nor to the absorption and emission of light, as is observed in many bodies; for in all these cases the spectra must either re- main uniformly, or gradually diminish; and neither their alter- nate presence and evanescence as in the first experiment, nor the perpetual changes of their colours as in the second, nor the flash of light or colours in the pressed eye as in the third, nor the rotation or libration of the spectra as in the fourth, could exist. It is not absurd to conceive, that the retina may be stimulated into motion, as well as the red and white muscles which form our limbs and vessels; since it consists of fibres, like those, inter- mixed with its medullary substance. To evince this structure, the retina of an ox's eye was suspended in a glass of warm water, and forcibly torn in a few places; the edges of these parts appeared jagged and hairy, and did not contract, and be- come smooth like simple mucus, when it is distended till it breaks; which shews that it consists of fibres; and its fibrous construction became still more distinct to the sight, by adding some caustic alkali to the water, as the adhering mucus was first eroded, and the hair-like fibres remained floating in the vessel. Nor does the degree of transparency of the retina invalidate the evidence of its fibrous structure, since Leeuwenhoek has shewn that the crystalline humour itself consists of fibres, (xvrcana Nature, Vol. I. p. 70.) Hence it appears, that as the muscles have larger fibres inter- mixed with a smaller quantity of nervous medulla, the organ of vision has a greater quantity of nervous medulla intermixed with smaller fibres; and it is probable that the locomotive muscles, as well as the vascular ones, of microscopic animals have much greater tenuity than those of the retina. And besides the similar laws, which will be shewn in this paper to govern alike the actions of the retina and of the mus- cles, there are many other analogies which exist between them. They are both originally excited into action by irritations, both act nearly in the same quantity of time, are alike strengthened or fatigued by exertion, arc alike painful if excited into action 446 OCULAR Sl'EGTRA Sect. XL. 2. 1 when they are in an inflamed state, are alike liable to paralysis, and to the torpor of old age. II. OF SPECTRA FROM DEFECT OF SENSIBILITY. The retina is not so easily excited into action by less irritation after having been lately subjected to greater. 1. When any one passes from the bright day-light into a dark- ened room, the irises of his eyes expand themselves to their ut- most extent in a few seconds of time; but it is very long before the optic nerve, after having been stimulated by the greater light of the day, becomes sensible of the less degree of it in the room; and if the room is not too obscure, the irises will again contract themselves in some degree, as the sensibility of the retina returns. 2. Place about half an inch square of white paper on a black hat, and looking steadily on the centre of it fior a minute, remove your eyes to a sheet of white paper; and after a second or two a dark square will be seen on the white paper, which will con- tinue some time. A similar dark square will be seen in the closed eye, if light be admitted through the eyelids. So after looking at any luminous object of a small size, as at the sun for a short time, so as not much to fatigue the eyes, this part of the retina becomes less sensible to smaller quantities of light; hence, when the eyes are turned on other less lumi- nous parts of the sky, a dark spot is seen resembling the shape of the sun, or other luminous object which we last beheld. This is the source of one kind of the dark-coloured musce volilantes. If this dark spot lies above the centre of the eye, we turn our eyes that way, expecting to bring it into the Centre of the eye, that we may view it more distinctly; and in this case the dark spectrum seems to move upwards. If the dark spectrum is found beneath the centre of the eye, we pursue it from the same motive, and it seems to move downwards. This has given rise to various conjectures of something floating in the aqueous humours of the eyes; but whoever, in attending to these spots, keeps his eyes unmoved by looking steadily at the corner of a cloud, at the same time that he observes the dark spectra, will be tho- roughly convinced, that they have no motion but what is given to them by the movement of our eyes in pursuit of them. Some- times the form of the spectrum, when it has been received from a circular luminous body, will become oblong; and sometimes it will be divided into two circular spectra, which is not owing to our changing the angle made by the two optic axises, accord- ing to the instance of the clouds or other bodies to which the Sect. XL. 2.3. OCULAR SPECTRA. 447 spectrum is supposed to be contiguous, but to other causes men- tioned in No. X. 3. of this section. The apparent size of it will also be variable according to its supposed distance. As these spectra are more easily observable when our eyes are a little weakened by fatigue, it has frequently happened, that peo- ple of delicate constitutions have been much alarmed at them, fearing a beginning decay of their sight, and have thence fallen into the hands of ignorant oculists; but I believe they never are a prelude to any other disease of the eye, and that it is from habit alone, and our want of attention to them, that we do not see them on all objects every hour of our lives. But as the nerves of very weak people lose their sensibility, in the same manner as their muscles lose their activity, by a small time of exertion, it frequently happens, that sick people in the extreme debility of fevers are perpetually employed in picking some- thing from the bed-clothes, occasioned by their mistaking the appearance of these musce volitantes in their eyes. Benvenuto Celini, an Italian artist, a man of strong abilities, relates, that having passed the whole night on a distant mountain with some companions and a conjurer, and performed many ceremonies to raise the Devil, on their return in the morning to Rome, and looking up when the sun began to rise, they saw numerous devils run on the tops of the houses, as they passed along; so much were the spectra of their weakened eyes magnified by fear, and made subservient to the purposes of fraud or superstition. (Life of Ben. Celini.) 3. Place a square inch of white paper on a large piece of straw-coloured silk; look steadily some time on the white paper, and then move the centre of your eyes on the silk, and a spec- trum of the form of the paper will appear on the silk, of a deeper yellow than the other part of it: for the central part of the re- tina, having been some time exposed to the stimulus of a greater quantity of white light, is become less sensible to a smaller quan- tity of it, and therefore sees only the yellow rays in that part of the straw-coloured silk. / Facts similar to these are observable in other parts of our system: thus, if one hand be made warm, and the other exposed to the cold, and then both of them immersed in subtepid water, the water is perceived warm to one hand, and cold to the other; and we are not able to hear weak sounds for some lime after we have been exposed to loud ones; and we feel a chilliness on com- ing into an atmosphere of temperate warmth, after having been some time confined in a very warm room: and hence the sto- mach, and other organs of digestion, of those who have been ha- bituated to the greater stimulus of spirituous liquor, are not ex- 448 OCULAR SPECTRA. Sect. XL. J. 1. cited into their due action by the less stimulus of common food alone; of vvhich the immediate consequence is, indigestion and hypochondriacism. III. OF SPECTRA FROM EXCESS OF SENSIBILITY. The retina is more easily excited into action by greater irritation after having been lately subjected to less. 1. If the eyes are closed, and covered perfectly with a hat, for a minute or two, in a bright day; on removing the hat a red or crimson light is seen through the eyelids. In this experi- ment the retina, after being some time kept in the dark, becomes so sensible to a small quantity of light, as to perceive distinctly the greater quantity of red rays than of others vvhich pass through the eyelids. A similar coloured light is seen to pass through the edges of the fingers, when the open hand is opposed to the flame of a candle. 2. If you look for some minutes steadily on a window in the beginning of the evening twilight, or in a dark day, and then move your eyes a little, so that those parts of the retina, on which the dark frame-work of the window was delineated, may now fall on the glass part of it, many luminous lines, repre- senting the frame-work, will appear to lie across the glass panes: for those parts of the retina, vvhich were before least stimulated, by the dark frame-work, are now more sensible to light than the other parts of the retina winch were exposed to the more lu- minous parts of the window. 3. Make with ink on white paper a very black spot, about half an inch in diameter, with a tail about an inch in length, so as to represent a tadpole, as in plate 2, at Sect. III. 8. 3; look steadily for a minute on this spot, and, on moving the eye a lit- tle, the figure of the tadpole will be seen on the white part of the paper, which figure of the tadpole will appear whiter or more luminous than the other parts of the white paper; for the part of the retina on wdiich the tadpole was delineated, is now more sensible to light than the other parts of it, vvhich were ex- posed to the white paper. This experiment is mentioned by Dr. Irwin, but is not by him ascribed to the true cause, namely, the greater sensibility of that part of the retina which has been exposed to the black spot, than of the other parts which had re- ceived the white field of paper, which is put beyond a doubt by the next experiment. 4. On closing the eyes after viewing the black spot on the white paper, as in the foregoing experiment, a red spot is seen Sm •, XL. 3. 5. OCULAR SPECTRA. 449 of the form of the black spot: for that part of the retina, on which the black spot was delineated, being now more sensible to light than the other parts of it, which were exposed to the white pa- per, is capable of perceiving the red rays vvhich penetrate the eyelids. If this experiment be made by the light of a tallow candle, the spot will be yellow instead of red; for tallow candles abound much with yellow light, which passes in greater quantity and force through the eyelids than blue light; hence the diffi- culty of distinguishing blue and green by this kind of candle light. The colour of the spectrum may possibly vary in the daylight, according to the different colour of the meridian or the morning or evening light. M. Beguelin, in the Berlin Memoires, V. II. 1771, observes, that when he held a book so that the sun shone upon his half- closed eyelids, the black letters, which he had long inspected, became red, which must have been thus occasioned. Those parts of the retina which had received for some time the black letters, were so much more sensible than those parts which had been opposed to the white paper, that to the former the red light, which passed through the eyelids, was perceptible. There is a similar story told, I think, in M. de Voltaire's Historical Works, of a Duke of Tuscany, who was playing at dice with the general of a foreign army, and, believing he saw bloody spots upon the dice, portended dreadful events, and retired in confusion. The observer, after looking for a minute on the black spots of a die, and carelessly closing his eyes, on a bright day, would see the image of a die with red spots upon it, as above explained. 5. On emerging from a dark cavern, where we have long continued, the light of a bright day becomes intolerable to the eye for a considerable time, owing to the excess of sensibility existing in the eye, after having been long exposed to little or no stimulus. This occasions us immediately to contract the iris to its smallest aperture, which becomes again gradually dilated, as the retina becomes accustomed to the greater stimulus of the daylight. The twinkling of a bright star, or of a distant candle in the night, is perhaps owing to the same cause. While we continue to look upon these luminous objects, their central parts gradu- ally appear paler, owing to the decreasing sensibility of the part of the retina exposed to their light; whilst, at the same time, by the unsteadiness of the eye, the edges of them are perpetually falling on parts of the retina that were just before exposed to the darkness of the night, and therefore tenfold more sensible to light than the part on which the star or candle had been for vol. i. 3 m 450 CELLAR SPEC IRA. Sect. XL. 4. I. some time delineated. This pains the eye in a similar manner as when we come suddenly from a dark room into bright daylight, and gives the appearance of bright scintillations. Hence the stars twinkle most when the night is darkest, and do not twinkle through telescopes, as observed by Muschenbroeck; and it will afterwards be seen why this twinkling is sometimes of different colours when the object is very bright, as Mr. Melvill observed in looking at Sirius.- For the opinions of others on this subject, see Dr. Priestley's valuable History of Light and Colours, p. 494. Many facts observable in the animal system are similar to these; as the hot glow occasioned by the usual warmth of the air,. or our clothes, on coming out of a cold bath; the pain of the fingers on approaching the fire after having handled snow; and the inflamed heels from walking in snow. Hence those who have been exposed to much cold have died on being brought to a fire, or their limbs have become so much inflamed as to mortify. Hence much food or wine given suddenly to those who have almost perished by hunger has destroyed them; for all the organs of the famished body are now become so much more irritable to the stimulus of food and wine, which they have long been de- prived of, that inflammation is excited, which terminates in gan- grene or fever. IV. OF DIRECT OCULAR SPECTRA. A quantity of stimulus somewhat greater than natural excites the retina into spasmodic action, which ceases in a few seconds. A certain duration and energy of the stimulus of light and eolours excites the perfect action of the retina in vision; for very quick motions are imperceptible to us, as well as very slow ones, as the whirling of a top, or the shadow on a sun-dial. So per- fect darkness does not affect the eye at all; and excess of light produces pain, not vision. I. When a fire-coal in whirled round in the dark, a lucid cir- ele remains a considerable time in the eye; and that with so much vivacity of light, that it is mistaken for a continuance of' the irritation of the object. In the same manner, when a fiery meteor shoots across the night, it appears to leave a long lucid train behind it, part of which, and perhaps sometimes the whole, is owing to the continuance of the action of the retina after having been thus vividly excited. This is beautifully illustrated by the following experiment: fix a paper sail, three or four inches in diameter, and made like that of a smoke jack, in a tube S-cct. XL. 4. 2. OCULAR SPECTRA. 451 of pasteboard; on looking through the tube at a distant pros- pect, some disjointed parts of it will be seen through the nar- row intervals between the sails; but as the fly begins to revolve these intervals appear larger; and when it revolves quicker, the whole prospect is seen quite as distinct as if nothing intervened, though less luminous. , 2. Look through a dark tube, about half a yard long, at the area of a yellow circle of half an inch diameter, lying upon a blue area of double that diameter, for half a minute; and on closing your eyes the colours of the spectrum will appear similar to the two areas, as in fig. 3.; but if the eye is kept too long upon them, the colours of the spectrum will be the reverse of those upon the paper, that is, the internal circle will become blue, and the external area yellow; hence some attention is re- quired in making this experiment. 3. Place the bright flame of a spermaceti candle before a black object in the night; look steadily at it for a short time, till it is observed to become somewhat paler; and on closing the eyes, and covering them carefully, but not so as to compress them, the image of the blazing candle will continue distinctly to be visible. Look steadily, for a short time, at a window in a dark day, as in Exp. 2. Sect. III. and then closing your eyes and covering them with your hands, an exact delineation of the window re- mains for some time visible in the eye. This experiment re- quires a little practice to make it succeed well; since, if the eyes are fatigued by looking too long on the window, or the day be too bright, the luminous parts of the window will appear dark in the spectrum, and the dark parts of the frame-work will appear luminous, as in Exp. 2. Sect. III. And it is even diffi- cult for many, who first try this experiment, to perceive the spectrum at all; for any hurry of mind, or even too great atten- tion to the spectrum itself, will disappoint them, till they have had a little experience in attending to such small sensations. The spectra described in this section, termed direct ocular spectra, are produced without much fatigue of the eye; the irri- tation of the luminous object being soon withdrawn, or its quan- tity of light being not so great as to produce any degree of un- easiness in the organ of vision; which distinguishes them from the next class of ocular spectra, which are the consequence of fatigue. These direct spectra are best observed in such circum- stances that no light, but what conies from the object, can fall upon the eye, as in looking through a tube, of half a yard long, and an inch wide, at a yellow paper on the side of a room, the direct spectrum was easily produced on closing the eye with- out taking it from the tube; but if the lateral light is admitted 452 OCULAR SPECTRA. Sect. XL. 5. 1. through the eyelids, or by throwing the spectrum on white paper, it becomes a reverse spectrum, as will be explained be- low. The other senses also retain for a time the impressions that have been made upon them, or the actions they have been ex- cited into. So if a hard body is pressed upon the palm of the hand, as is practised in tricks of legerdemain, it is not easy to distinguish for a few seconds whether it remains or is removed; and tastes continue long to exist vividly in the mouth, as the smoke of tobacco, or the taste of gentian, after the sapid mate- rial is withdrawn. V. A quantity of stimulus somewhat greater than tlie last mentioned excites the retina into spasmodic action, which ceases and recurs alternately. 1. On looking for a time on the setting sun, so as not greatly to fatigue the sight, a yellow spectrum is seen when the eyes are closed and covered, which continues for a time, and then dis- appears and recurs repeatedly before it entirely vanishes. This yellow spectrum of the sun when the eyelids are opened be- comes blue; and if it is made to fall on the green grass, or on other coloured objects, it varies its own colour by an intermix- ture of theirs, as will be explained in another place. 2. Place a lighted spermaceti candle in the night about one foot from your eye, and look steadily on the centre of the flame, till your eye becomes much more fatigued than in Sect. IV. Exp. 3.; and on closing your eyes a reddish spectrum will be perceived, which will cease and return alternately. The action of vomiting in like manner ceases, and is renewed by intervals, although the emetic drug is thrown up with the first effort; so after-pains continue some time after parturition; and the alternate pulsations of the heart of a viper are renewed for some time after it is cleared from its blood. VI. OF REVERSE OCULAR SPECTRA. The retina, after having been excited into action by a stimulus somewhat greater than the last mentioned, falls into opposite spasmodic action. The actions of every part of animal bodies may be advanta- geously compared with each other. This strict analogy con- tributes much to the investigation of truth; while those looser analogies, which compare the phenomena of animal life with Sect. XL. 6.1 OCULAR SPECTRA. 453 those of chemistry or mechanics, only serve to mislead our in- quiries. When any of our larger muscles have been in long or in vio- lent action, and their antagonists have been at the same time ex- tended, as soon as the action of the former ceases, the limb is stretched the contrary way for our ease, and a pandiculation or yawning takes place. By the following observations it appears, that a similar circum- stance obtains in the organ of vision; after it has been fatigued by one kind of action, it spontaneously falls into the opposite kind. 1. Place a piece of coloured silk, about an inch in diameter, on a sheet of white paper, about half a yard from your eyes; look steadily upon it for a minute; then remove your eyes upon another part of the white paper, and a spectrum will be seen of the form of the silk thus inspected, but of a colour opposite to it. A spec- trum nearly similar will appear if the eyes are closed, and the eyelids shaded by approaching the hand near them, so as to per- mit some, but to prevent too much light falling on them. Red silk produced a green spectrum. Green produced a red one. Orange produced blue. Blue produced orange. Yellow produced violet. Violet produced yellow. That in these experiments the colours of the spectra are the reverse of the colours which occasioned them, may be seen by examining the third figure in Sir Isaac Newton's Optics, L. II. p. 1. where those thin laminae of air, which reflected yellow, transmitted violet; those which reflected red, transmitted a blue green; and so of the rest, agreeing with the experiments above related. 2. These reverse spectra are similar to a colour, formed by a combination of all the primary colours except that with which the eye has been fatigued in making the experiment: thus the reverse spectrum of red must be such a green as would be pro- duced by a combination of all the other prismatic colours. To evince this fact, the following satisfactory experiment was made. The prismatic colours were laid on a circular pasteboard wheel, about four inches in diameter, in the proportions described in Dr. Priestley's history of Light and Colours, pi. 12. fig. 83. except that the red compartment was entirely left out, and the others pro- portionably extended so as to complete the circle. Then, as the orange is a mixture of red and yellow, and as the violet is a mix- 454 OCULAR SPEC Hi A. Sr.iT. XL. 6. S. ture of red and indigo, it became necessary to put yellow on the wheel instead of orange, and indigo instead of violet, that the ex- periment might more exactly quadrate with the theory it was designed to establish or confute; because in gaining a green spec- trum from a red object, the eye is supposed to have become in- sensible to red light. This wheel, by means of an axis, was made to whirl like a top; and on its being put in motion, a green colour was produced, corresponding with great exactness to the reverse spectrum of red. 3. In contemplating any one of these reverse spectra in the closed and covered eye, it disappears and reappears several times successively, till at length it entirely vanishes, like the direct spectra in Sect. V.; but with this additional circumstance, that when the spectrum becomes faint or evanescent, it is instantly revived by removing the hand from before the eyelids, so as to admit more light: because then not only the fatigued part of the retina is inclined spontaneously to fall into motions of a contrary direction, but being still sensible to all other rays of light, except that with vvhich it was lately fatigued, is by these rays at the same time stimulated into those motions which form the reverse spectrum. From these experiments there is reason to conclude, that the fatigued part of the retina throws itself into a contrary mode of action, like oscitation or pandiculation, as soon as the stimulus which has fatigued it is withdrawn; and that it still remains sensible, that is, liable to be excited into action by any other co- lours at the same time, except the colour with which it has been fatigued. VII. The retina, after having been excited into etclion by a stimulus somewhat greater than the last mentioned, falls into various successive spasmodic actions. 1. On looking at the meridian sun as long as the eyes can well bear its brightness, the disk first becomes pale, with a lu- minous crescent, which seems to librate from one edge of it to the other, owing to the unsteadiness of the eye; then the whole phasis of the sun becomes blue, surrounded with a white halo; and on closing the eyes, and covering them with the hands, a yellow spectrum is seen, which in a little time changes into a blue one. M. de la Hire observed, after looking at the bright sun, that the impression in his eye first assumed a yellow appearance, and then green, and then blue; and wishes to ascribe these appear- ances to some affection of the nerves. (Porterfield on the Eve, Vol. I. p. 343.) Sect:. XL. 7.2. OCULAR SPECTRA. 455 2. After looking steadily on about an inch square of pink silk, placed on white paper, in a bright sunshine, at the distance of a foot from my eyes, and closing and covering my eye-lids, the spectrum of the silk was at first a dark green, and the spectrum of the white paper became of a pink The spectra then both disappeared; and then the internal spectrum was blue; and then, after a second disappearance, became yellow, and lastly pink, whilst the spectrum of the field varied into red and green. These successions of different coloured spectra were not exact- ly the same in the different experiments, though observed, as near as could be, with the same quantity of light and other simi- lar circumstances; owing, I suppose to trying too many experi- ments at a time; so that the eye was not quite free from the spectra of the colours vvhich were previously attended to. The alternate exertions of the retina in the preceding section resembled the oscitation or pandiculation of the muscles, as they were performed in directions contrary to each other, and were the consequence of fatigue rather than of pain. And in this they differ from the successive dissimilar exertions of the retina, men- tioned in this section, which resemble in miniature the more violent agitations of the limbs in convulsive diseases, as epilepsy, chorea S. Viti. and opisthotonos; all which diseases are perhaps at first, the consequence of pain, and have their periods after- wards established by habit. VIII. The retina, after having been excited into action by a stimu- lus somewhat greater than the last mentioned, falls into a fixed spasmodic action, which continues for some days. 1. After having looked long at the meridian sun, in making some of the preceding experiments^ till the disk faded into a pale blue, I frequently observed a bright blue spectrum of the sun on other objects all the next and the succeeding day, which constantly occurred when I attended to it, and frequently when I did not previously attend to it. When I closed and covered my eyes, this appeared of a dull yellow; and at other times mix- ed with the colours of other objects on which it was thrown. It may be imagined, that this part of the retina was become in- sensible to white light, and thence a bluish spectrum became visi- ble on all luminous objects; but as a yellowish spectrum was also seen in the closed and covered eye, there can remain no doubt of this being the spectrum of the sun. A similar appearance was observed by M. TEpiuus, which he acknowledges he could give no account of. (Nov. Com. Petiop. V. 10. p. 2. and 6.) The locked jaw. and some cataleptic spasms, are resembled by 456 OCULAR SPECTRA. Sect. XL. 9. 1 this phenomenon; and from hence we may learn the danger to the eye by inspecting very luminous objects too long a time. IX. A quantity of stimulus greater than the preceding induces a temporary paralysis of the organ of vision. 1. Place a circular piece of bright red silk, about half an inch in diameter, on the middle of a sheet of white paper; lay them on the floor in a bright sunshine, and fixing your eyes steadily on the centre of the red circle, for three or four minutes, at the distance of four or six feet from the object, the red silk w ill gra- dually become paler, and finally cease to appear red at all. 2. Similar to these are many other animal facts; as purges, opiates, and even poisons, and contagious matter, cease to stimu- late our system, after we have been habituated to their use. So some people sleep undisturbed by a clock, or even by a forge hammer in their neighbourhood: and not only continued irrita- tions, but violent exertions of any kind, are succeeded by tem- porary paralysis. The arm drops down after violent action, and continues for a time useless; and it is probable, that those who have perished suddenly in swimming, or in seating on the ice, have owed their deaths to the paralysis, or extreme fatigue, which succeeds every violent and continued exertion. X. MISCELLANEOUS REMARKS. There were some circumstances occurred in making these experiments, which were liable to alter the results of them, and which I shall here mention for the assistance of others, who may wish to repeat them. 1. Of direct and inverse spectra existing at the same time; of recipro- cal direct spectra; of a combination of direct and inverse spectra; of a spectral halo; rules to pre-determine the colours of specira. a. When an area, about six inches square, of bright pink In- dian paper, had been viewed on an area, about a foot square, of white writing paper, the internal spectrum in the closed eye was green, being the reverse spectrum of the pink paper; and the external spectrum was pink, being the direct spectrum of the pink paper. The same circumstance happened when the inter- nal area was white and external one pink; that is, the internal spectrum was pink, and the external one green. All the same appearances occurred when the pink paper was laid on a black hat. Sb.-t. XL. 10. 1. OCULAR SPECTRA. 457 b. When six inches square of deep violet polished paper were viewed on a foot square of white writing paper, the internal spec- trum was yellow, being the reverse spectrum of the violet paper, and the external one was violet, being the direct spectrum of the violet paper. c. When six inches square of pink paper were viewed on a foot square of blue paper, the internal spectrum was blue, and the external spectrum was pink; that is, the internal one was the direct spectrum of the external object, and the external one was the direct spectrum of the internal object, instead of their being each the reverse spectrum of the objects they belong- ed to. d. When six inches square of blue paper were viewed on a foot square of yellow paper, the interior spectrum became a bril- liant yellow, and the exterior one a brilliant blue. The vivacity of the spectra was owing to their being excited both by the sti- mulus of the interior and exterior objects; so that the interior yellow spectrum was both the reverse spectrum of the blue paper, and the direct one of the yellow paper; and the exterior blue spectrum was both the reverse spectrum of the yellow paper, and the direct one of the blue paper. c. When the internal area was only a square half-inch of red paper, laid on a square foot of dark violet paper, the internal .spectrum was green, with a reddish-blue halo. When the red internal paper was two inches square, the internal spectrum was a deeper green, and the external one redder. When the internal paper was six inches square, the spectrum of it became blue, and the spectrum of the external paper was red. /. When a square half-inch of blue paper was laid on a six- inch square of yellow paper, the spectrum of the central paper in the closed eye was yellow, encircled with a blue halo.. On looking long on the meridian sun, the disk fades into a pale blue surrounded with a whitish halo. These circumstances, though they very much perplexed the experiments lill they were investigated, admit of a satisfactory explanation; for while the rays from the bright internal object in exp. a. fall with their full force on the centre of the retina, and, by fatiguing that part of it, induce the reverse spectrum, many scatlcml rays, from the same internal pink paper, fall on the more external parts of the retina, but not in such quantity as to occasion much fatigue, and hence induce the direct spectrum of the pink colour in those parts of the eye. The same reverse and direct spectra occur from the violet paper in exp. b.: and in cxp. c. the scattered rays from the central pink paper produce a direct spectrum of this colour on the external parts of the eye, VOL. I. 3 N 458 OCULAR M'EC'TRA. Skut. XL. 10. i while the scattered rays from the external blue pnpcr produce a direct spectrum of that colour on the central part of the t ye, in- stead of these parts of the retina falling reciprocally into their reverse spectra. In exp. d. the colours being the reverse of each other, the scattered rays from the exterior object falling on the central parts of the eye, and there exciting their direct spec- trum, at the same time that the retina was excited into a reverse spectrum by the central object, and this direct and revere spec- trum being of similar colour, the superior brilliancy of this spec- trum was produced. In exp. e. the effect of various quantities of stimulus on the retina, from the different respective sizes of the internal and external areas, induced a spectrum of the inter- nal area in the centre of the eye, combined of the reverse spec trum of that internal area and the direct one of the external area, in various shades of colour, from a pale green to a deep blur, with similar changes in the spectrum of the external area. For the same reasons, when an internal bright object was small, as in c\p. /., instead of the whole of the spectrum of the external object being reverse to the colour of the internal object, only a kind of halo, or radiation of colour, similar to that of the inter- nal object, was spread a little way on the external spectrum. For this internal blue area being so small, the scattered rays from it extended but a little way on the image of the external area of yellow paper, and could therefore produce only a blue halo round the yellow spectrum in the centre. If any one should suspect that the scattered rays from the ex- terior coloured object do not intermix with the rays from the interior coloured object, and thus affect the central part of the eye, let him look through an opaque tube, about two feet in length, and an inch in diameter, at a coloured wall of a room, with one eye, and with the other eye naked; and he will find that by shutting out the lateral light, the area of the wall seen through a tube appears as if illuminated by the sunshine, com- pared with the other parts of it; from whence arises the advan- tage of looking through a dark tube at distant paintings. Hence we may safely deduce the following rules to deter- mine before-hand the colours of all spectra. 1. The direct spectrum without any lateral light is an evanescent representa- tion of its object in the unfatigued eye. 2. With some lateral light it becomes of a colour combined of the direct spectrum of the central object, and of the circumjacent objects, in pro- portion to their respective quantity and brilliancy. 3. The re- verse spectrum without lateral light is a representation in the fatigued eye of the form of its objects, with such a colour as would be produced by all the primary colours, except that of the Sect. XL. 10. 2. OCULAR SPECTRA. 459 object. 4. With lateral light the colour is compounded of the reverse spectrum of the central object, and the direct spectrum of the circumjacent objects, in proportion to their respective quan- tity and brilliancy. ■2. Variation and vivacity of the spectra occasioned by extraneous light. The reverse spectrum, as has been before explained, is similar to a colour, formed by a combination of all the primary colours, except that with which the eye has been fatigued in making the experiment; so the reverse spectrum of red is such a green as would be produced by a combination of all the other prismatic colours. Now it must be observed, that this reverse spectrum of red is therefore the direct spectrum of a combination of all the other prismatic colours, except the red; whence on removing the eye from a piece of red silk to a sheet of white paper, the green spectrum which is perceived may either be called the re- verse spectrum of the red silk, or the direct spectrum of all the rays from the white paper, except the red; for in truth it is both. Hence we see the reason why it is not easy to gain a direct spec- trum of any coloured object in the day-time, where there is much lateral light, except of very bright objects, as of the setting sun, or by looking through an opaque tube; because the lateral ex- ternal light falling also on the central part of the retina, con- tributes to induce the reverse spectrum, vvhich is at the same time the direct spectrum of that lateral light, deducting only the colour of the central object which we have been viewing. And for the same reason, it is difficult to gain the reverse spectrum, where there is no lateral light to contribute to its formation. Thus, in looking through an opaque tube on a yellow wall, and closing my eye, without admitting any lateral light, the spectra were all at first yellow; but at length changed into blue. And on looking in the same manner on red paper, I did at length get a green spectrum; but they were all at first red ones: and the same after looking at a candle in the night. The reverse spectrum was formed with greater facility when the eye was thrown from the object on a sheet of white paper, or when light was admitted through the closed eyelids; because not only tlie fatigued part of the retina was inclined spontane- ously to fall into motions of a contrary direction; but being still sensible to all other rays of light except that with which it was lately fatigued, was by these rays stimulated at the same time into those motions which form the reverse spectrum. 46U OULLAIt Sl'ECTRA. Si-.-r. XL. 10 2 Hence when the reverse spectrum of any colour became faint, it w?s wcnderful'y revived by admitting more light through the eyelids, b- removing the hand from before them: and hence, on ccv.ring ihe closed eyelids, the spectrum would often cease for a tunc, till the retina became sensible to the stimulus of the smaller quantity oi light, and then it recurred. Nor was the spcctriur. only (hanged in vivacity, or in degree, bv this admis- sion :t li^hi tliiugh the eyelids; but it frequently happened, after having viewed bright objects, (hat the spectrum in the closed and covered t*ye was changed into a third spectrum, when light v/i-s admitted through the eyelids; which third spectrum was composed of such colours as could pass through the eyelids, ex- cept those of the object. Thus, when an area of half an inch diameter of pink paper was viewed on a sheet of white paper in the sunshine, the spectrum with closed and covered eyes was green; but on removing the hands from before the closed eye- lids, the sp.etrum became yellow, and returned instantly again to green, as often as the hands were applied to cover the eye- lids, or removed from them: for the retina being now insensible to red light, the yellow rays passing through the eyelids in greater quantity than tlie other colours, induced a yellow spectrum; whereas if the spectu'.m was thrown on white paper, with the eyes open, it became only a lighter green. Though a certain quantity of light facilitates the formation of the reverse spectrum, a greater quantity prevents its formation, as the more powerful stimulus excites even the fatigued parts of the eye into action; otherwise we should see the spectrum of the last viewed object as often as we turn our eyes. Hence the reverse spectra are best seen by gradually approaching the hand near the closed eyelids to a certain distance only, which must be varied with the brightness of the day, or the energy of the spectrum. Add to this, that ail dark spectra, as black, blue, or green, if light be admitted through the eyelids after they have been some time covered, give reddish spectra, for the reasons given in Sect. III. Exp. 1. From these circumstances of the extraneous light coinciding with the spontaneous effor'.s of the fatigued retina to produce a reverse spectrum, as was observed before, it is not easy to gain a .''irect spectrum, except of objects brighter than the ambient ligb.!-; such as a candle in the night, the setting sun, or viewing a bright object through an opaque tube; and then the reverse spectrum is instantaneously produced by the admission of some external light; and is as instantly converted again to the direct spectrum by the exclusion of it. Thus, on looking at the set- ting sun, on closing the eyes, and covering them, a yellow spec- $> Sect. XL. 10. J. OCULAR SPECTRA. 461 trum is seen, which is the direct spectrum of the setting sun; but on opening the eyes on the sky, the yellow spectrum is im- mediately changed into a blue one, which is the reverse spec- trum of the yellow sun, or the direct spectrum of the blue skv, or a combination of both. And this is again transformed into a yellow one on closing the eyes, and so reciprocally, as quick as the motions of the opening and closing eyelids. Hence, when Mr. Melvill observed the scintillations of the star Sirius to be sometimes coloured, these were probably the direct spectrum of the blue sky on the parts of the retina fatigued by the white light of the star. [Essays Physical and Literary, p. 81. V. 2.] When a direct spectrum is thrown on colours darker than it- self, it mixes with them; as the yellow spectrum of the setting sun, thrown on the green grass, becomes a greener yellow. But when a direct spectrum is thrown on colours brighter than itself, it becomes instantly changed into the reverse spectrum which mixes with those brighter colours. So the yellow spec- trum of the setting sun thrown on the luminous sky becomes blue, and changes with the colour or brightness of the clouds on which it appears. But the reverse spectrum mixes with eve- ry kind of colour on which it is thrown, whether brighter than itself or not; thus the reverse spectrum, obtained by viewing a piece of yellow silk, when thrown on white paper, was a lucid blue green; when thrown on black Turkey leather, becomes a deep violet. And the spectrum of blue silk, thrown on white paper, was a light yellow; on black silk was an obscure oramre; and the blue spectrum, obtained from orange-coloured silk' thrown on yellow, became a green. In these cases the retina is thrown into activity or sensation by the stimulus of external colours, at the same time that it con- tinues the activity or sensation which forms the spectra; in the same manner as the prismatic colours, painted on a whirling top, are seen to mix together. When these colours of external objects are brighter than the direct spectrum which is thrown upon them, they change it into the reverse spectrum, like the admission of external light on a direct spectrum, as explained above. When they are darker than the direct spectrum, they mix it, their weaker stimulus being insufficient to induce the re- verse spectrum. 3. Variation of spectra in respect to number, and figure, and remission. When we look long and attentively at any object, the eve can- not always be kept entirely motionless; hence, on inspecting a 462 OCULAR SPECTRA. Sect. XL. 10. :>' circular area of red silk placed on white paper, a lucid crescent or eoge is seen to librate on one side or other of the red circle: for the exterior parts of the retina sometimes falling on the edge of the central silk, and sometimes on the white paper, are less fatigued with red light than the central part of the retina, which is constantly exposed to it; and, therefore, when they fall on the edge of the red silk, they perceive it more vividly. Afterwards, when the eye becomes fatigued, a green spectrum in the form of a crescent is seen to librate on one side or other of the central circle, as by the unsteadiness of the eye a part of the fatigued retina falls on white paper; and as by the increasing fatigue of the eye the central part of the silk appears paler, the edge on which the unfatigued part of the retina occasionally falls will ap- pear of a deeper red than the original silk, because it is com- pared with the pale internal part of it. M. de Buffon, in mak- ing this experiment, observed, that the red edge of the silk was not only deeper coloured than the original silk; but, on his re- treating a little from it, it became oblong, and at length divided into two, which must have been owing to his observing it either before or behind the point of intersection of the two optic axises. Thus, if a pen is held up before a distant candle, when we look intensely at the pen, two candles are seen behind it; when we look intensely at the candle, two pens are seen. If the sight be unsteady at the time of beholding the sun, even though one eye only be used, many images of the sun will appear, or luminous lines, when the eye is closed. And as some parts of these will be more vivid than others, and some parts of them will be produced nearer the centre of the eye than others, these will disappear sooner than the others; and hence the number and shape of these spectra of the sun will continually vary, as long as they exist. The cause of some being more vivid than others, is the unsteadiness of the eye of the beholder, so that some parts of the retina have been longer exposed to the sun-beams. That some parts of a complicated spectrum fade and return before other parts of it, the following experiment evinces. Draw three concentric circles; the external one an inch and a half in diameter, the middle one an inch, and the internal one half an inch; colour the external and internal areas blue, and the remaining one yellow, as in Fig. 4; after having looked about a minute on the centre of these circles, in a bright light, the spectrum of the external area appears first in the closed eye, then the middle area, and lastly the central one; and then the central one disappears, and the others in inverted order. If con- centric circlesof more colours are added, it produces the beauti- ful ever changing spectrum in Sect. I. Exp. 2. Sbct. XL. 10. 4. OCULAR SPECTRA. 463 From hence it would seem, that the centre of the eye pro- duces quicker remissions of spectra, owing perhaps to its greater sensibility; that is, to its more energetic exertions. These re- missions of spectra bear some analogy to the tremors of the hands, and palpitations of the heart, of weak people: and per- haps a criterion of the strength of any muscle or nerve may be taken from the time it can be continued in exertion. 4. Variation of spectra in respect to brilliancy; the visibility of the circulation of the blood in the eye. 1. The meridian or evening light makes a difference in the colours of some spectra; for as the sun descends, the red rays, which are less refrangible by the convex atmosphere, abound in great quantity. Whence the spectrum of the light parts of a window at this time, or early in the morning, is red; and be- comes blue either a little later or earlier; and white in the me- ridian day; and is also variable from the colour of the clouds or sky which are opposed to the window. 2. All these experiments are liable to be confounded, if they are made too soon after each other, as the remaining spectrum will mix with the new ones. This is a very troublesome cir- cumstance to painters, who are obliged to look long upon the same colour; and in particular to those whose eyes, from natu- ral debility, cannot long continue the same kind of exertion. For the same reason, in making these experiments, the result be- comes much varied if the eyes, after viewing any object, are re- moved on other objects for but an instant of time, before we close them to view the spectrum; for the light from the object, of which we had only a transient view, in the very time of clos- ing our eyes acts as a stimulus on the fatigued retina; and for a time prevents the desired spectrum from appearing, or mixes its own spectrum with it. Whence, after the eyelids are closed, either a dark field, or some unexpected colours, are beheld for a few seconds, before the desired spectrum becomes distinctly visible. 3. The length of time taken up in viewing an object of which we are to observe the spectrum, makes a great difference in the appearance of the spectrum, not only in its vivacity, but in its colour; as the direct spectrum of the central object, or of the circumjacent ones, and also the reverse spectra of both, with their various combinations, as well as the time of their duration in the eye, and of their remissions or alterations, depend upon the degree of fatigue the retina is subject to. The Chevalier d'Arcy constructed a machine by which a coal of fire was whirled round in the dark, and found, that when a luminous 464 OCl EAR SPEC I U.K. Sect. XL. 10. 4. body made revolution in eight-thirds of time, is presented to the eye. a complete circle of fire; from whence he concludes, that the impression continues on the organ about the seventh part of a second. (Me'm. de l'Acad. des Sc. 1765.) This, however, is only to be considered as the shortest time of the duration ot these direct spectra; since in the fatigued eye both the direct and reverse spectra, with their intermissions, appear to take up many seconds of time, and seem very variable in proportion to the cir- cumstances of fatigue or energy. 1. It sometimes happens, if the eyeballs have been rubbed hard with the fingers, that lucid sparks are seen in quick mo- tion amidst the spectrum we are attending to. This is similar to the flashes of fire from a stroke on the eye in fighting, and is resembled by the warmth and glow, which appears upon the skin after friction, and is probably owing to an acceleration of the ar- terial blood into the vessels emptied by the previous pressure. By being accustomed to observe such small sensations in the eye, it is easy to see the circulation of the blood in this organ. 1 have attended to this frequently, when I have observed my eyes more than commonly sensible to other spectra. The circulation may be seen either in both eyes at a time, or only in one of them; for as a certain quantity of light is necessary to produce this curious phenomenon, if one hand be brought nearer the closed eyelids than the other, the circulation in that eye will for a time dis .ppear. For the easier viewing the circulation, it is some- times necessary to rub the eyes with a certain degree of force after they are closed, and to hold the breath rather longer than is agreeable, vvhich, by accumulating more blood in the eye, facili- tates the experiment; but in general it may be seen distinctly after having examined other spectra with your back to the light till the eyes become weary; then having covered your closed eyelids for half a minute, till the spectrum is faded away which you were examining, turn your face to the light, and removing your hands from the eyelids, by and by again shade them a little, and the circulation becomes curiously distinct. The streams of blood are however generally seen to unite, vvhich shews it to be the venous circulation, owing, I suppose, to the greater opacity of the colour of the blood in these vessels; for this venous cir- culation is also much more easily seen by the microscope in the tail of a tadpole. 5. Variation of spectra in respect to distinctness and size; with a new way of magnifying objects. 1. It was before observed, that when the two colours viewed BANKS. Sxct. XL. 10. 5. OCULAR SPECTRA 465 together were opposite to each other, as yellow and blue, red and green, &c. according to the table of reflections and transmis- sions of light in Sir Isaac Newton's Optics, B. II. Fig. 3. the spectra of those colours were of all others the most brilliant, and best defined; because they were combined of the reverse spec- trum of one colour, and of the direct spectrum of the other. Hence, in books printed with small types, or in the minute gra- duation of thermometers, or of clock-faces, which are to be seen at a distance, if the letters or figures are coloured with orange, and the ground with indigo; or the letters with red, and the ground with green; or any other lucid colour is used for the letters, the spectrum of which is similar to the colour of the ground; such letters will be seen much more distinctly, and with less confusion, than in black or white: for as the spectrum of the letter is the same colour with the ground on which they are seen, the unsteadiness of the eye in long attending to them will not produce coloured lines by the edges of the letters, which is the principal cause of their confusion. The beauty of colours lying in vicinity to each other, whose spectra are thus recipro- cally similar to each colour, is owing to this greater ease that the eye experiences in beholding them distinctly; and it is pro- bable, in the organ of hearing, a similar circumstance may con- stitute the pleasure of melody. Sir Isaac Newton observes, that gold and indigo were agreeable when viewed together; and thinks there may be some analogy between the sensations of light and sound. (Optics, qu. 14.) In viewing the spectra of bright objects, as of an area of red silk of half an inch diameter on white paper, it is easy to mag- nify it to tenfold its size: for if, when the spectrum is formed, you still keep your eye fixed on the silk area, and remove it a i\\\ inches further from you, a green circle is seen round the red silk; for the angle now subtended by the silk is less than it was when the spectrum was formed, but that of the spectrum continues the same, and our imagination places them at the same distance. Thus when you view a spectrum on a sheet of white paper, if you approach the paper to the eye, you may di- minish it to a point; and if the paper is made to recede from the eye, the spectrum will appear magnified in proportion to the dis- tance. I was surprised, and agreeably amused, with the following ex- periment. I covered a paper about four inches square with yellow, and with a pen filled with a blue colour wrote upon the middle of it the word BANKS in capitals, as in fig. 5, and sit- ting with my back to the sun, fixed my eyes for a minute exactly on the centre of the letter N in the middle of the word; after vol. i 3 o 466 OCULA SPECTRA. Sect. XL. 10. have been used as acc^rnf0"80^3"^0^ r°mit' PUr«e' 0r sweat> either h .vl g, V ^uantlty exhlblted' or as a l^t of what is given well 1 \. mUS 3 qUarter of a Sfain 0f tmetic terti (if !l# WI." Pro,m°te a ^Phoresi., if the skin be kept warm half a gram will procure a stool or two first, and sweat- ing afterward; and a grain will generally vomit, and then purge, and lastly sweat the patient. In less quantity it is pro- bable, that this medicine acts like other metallic salts, as steel zinc, or copper in small doses; that is, that it strengthens the system by its stimulus. As camomile and rhubarb in different doses vomit, or purge, or act as stimulants so as to strengthen the system. ° Some of the medicines of this class of sorbentia have been termed tonics by some authors, as giving due tone to the ani- mal fibre But it should be observed, that tone is a mechanical term, applicable only to musical strings, and like bracing and re- laxation, cannot be applied to animal life except metaphorically. Ihe same may be observed of the word reaction, used by some modern authors which in its proper signification is a mechanical term, inapplicable to the laws of life except metaphorically. II. OBSERVATIONS ON THE SORBENTIA. I. 1. As there is great difference in the apparent structure of the various glands, and of the fluids which they select from the blood, these glands must possess different kinds of irritabili- ty, and are therefore stimulated into stronger or unnatural ac- tions by different articles of the materia medica, as shewn in the secernentia. Now as the absorbent vessels are likewise glands and drink up or select different fluids, as chyle, water, mucus' with a part of every different secretion, as a part of the bile a part of the saliva, a part of the urine, &c. it appears, that these absorbent vessels must likewise possess different kinds of irrita- bility, and in consequence must require different articles of the materia medica to excite them into unusual action. This part of the subject has been so little attended to, that the candid reader will find in this article a great deal to excuse. It was observed that some of the secernentia did in a less de- gree increase absorption, from the combination of different pro- perties in the same vegetable body; for the same reason some of the class of sorbentia produce secretion in a less degree, as those bitters which have also an aroma in their composition; these 'ii SOKUENT1A. Aiit. IV. 2. 1.2. are known from their increasing the heat of the system above its usual degree. It must also be noted, that the actions of every part of the absorbent system are so associated with each other, that the drugs which stimulate one branch increase the action of the whole; and the torpor or quiescence of one branch weakens the exertions of the whole; or when one branch is excited into stronger action, some other branch has its actions weakened or inverted. Yet though peculiar branches of the absorbent sys- tem are stimulated into action by peculiar substances, there are other substances which seem to stimulate the whole system, and that without immediately increasing any of the secretions; as those bitters which possess no aromatic scent, at the head of which stands the famed Peruvian bark, or cinchona. 2. Cutaneous absorption. I have heard of some experi- ments, in which the body was kept cold, and was thought to absorb more moisture from the atmosphere than at any other time. This however cannot be determined by statical experi- ments: as the capillary vessels, which secrete the perspirable matter, must at the same Time have been benumbed by the cold; and from their inaction there could not have been the usual waste of the weight of the body; and as all other muscular ex- ertions are best performed, when the body possesses its usual de- gree of warmth, it is conclusive, that the absorbent system should likewise do its office best, when it is not benumbed by external cold. The austere acids, as of vitriol, lemon-juice, juice of crabs and sloes, strengthen digestion, and prevent that propensity to sweat so usual to weak convalescents, and diminish the colliquative sweats in hectic fevers; all which are owing to their increasing the action of the external and internal cutaneous absorption. Hence vitriolic acid is given in the small-pox to prevent the too hasty or too copious eruption, which it effects, by increasing the cutaneous absorption. Vinegar, from the quantity of alcohol which it contains, exerts a contrary effect, to that here describ- ed, and belongs to the incitantia; as an ounce of it promotes sweat and a flushing of the skin; at the same time externally it acts as a venous absorbent, as the lips become pale by moisten- ing them with it. And it is said when taken internally in great and continued quantity, to induce paleness of the skin and soft- ness of the bones. The sweet vegetable acids, as of several ripe fruits, are among the torpentia; as they are less stimulating than the general food of this climate, and are hence used in inflammatory diseases. Where the quantity of fluids in the system is much lessened, Art. IV. 2. 1.3. SORRENTIA. 45 as in hectic fever, which has been of some continuance, or in spurious peripneumony, a grain of opium given at night will sometimes prevent the appearance of sweats; which is owing to the stimulus of opium increasing the actions of the cutaneous absorbents, more than those of the secerning vessels of the skin. Whence the secretion of perspirable matter is not decreased, but its appearance on the skin is prevented by its more facile absorption. 3. There is one kind of itch, which seldom appears between the fingers, is the least infectious, and most difficult to eradicate, and which has ils cure much facilitated by the internal use of acid of vitriol. This disease consists of small ulcers in the skin, which are healed by whatever increases the cutaneous absorp- tion. The external application of sulphur, mercury, and acrid vegetables, acts on the same principle; for the animalcula, which are seen in these pustules, are the effect, not the cause, of them; as all other stagnating annual fluids, as the semen itself, abounds with similar microscopic animals. See Dysentery, Class II. 1. 3. 18. 4. Young children have sometimes an eruption upon the head called tinea, which discharges an acrimonious ichor inflaming the parts on which it falls. This eruption I have seen submit to the internal use of vitriolic acid, when only wheat-Hour was applied externally. This kind of eruption is likewise frequently cured by testaceous powders; two materials so widely different in their chemical properties, but agreeing in their power of promoting cutaneous absorption. II. Absorption from the mucous membrane is increased by applying to its surface the austere acids, as of vitriol, lemon-juice, crab-juice, sloes. When these are taken into the mouth, they immediately thicken, and at the same time lessen the quantity of the saliva; which last circumstance cannot be owing to their coagulating the saliva, but to their increasing the absorption of the thinner parts of it. So alum applied to the tip of the tongue does not stop in its action there, but independent of its diffusion it induces cohesion and corrugation over the whole mouth. (Cul- len's Mat. Med. Art. Astringentia.) Which is owing to the asso- ciation of the motions of the parts or branches of the absorbent system with each other. Absorption from the mucous membrane is increased by opium taken internally in small doses more than by any other medicine, as is seen in its thickening the expectoration in coughs, and the discharge from the nostrils in catarrh, and perhaps the discharge from the urethra in gonorrhoea. The bark seems next in power for all these purposes. 46 SORRENTIA. Aiit. IV. 2.3. 1 Externally slight solutions of blue vitriol, as two or three grains to an ounce of water, applied to ulcers of the mouth, or to chan- cres on the glans penis, more powerfully induce them to heal than any other material. Where the lungs or urethra are inflamed to a considerable degree, and the absorption is so great, that the mucus is already too thick, and adheres to the membrane from its viscidity, opiates and bitter vegetable and austere acids are improper; and muci- laginous diluents should be used in their stead with venesection and torpentia. III. 1. Absorption from the cellular membrane, and from all the other cavities of the body, is too slowly performed in some constitutions; hence the bloated pale complexion;, and when this occurs in its greatest degree, it becomes an universal dropsy. These habits are liable to intermittent fevers, hysteric paroxysms, cold extremities, indigestion, and all the symptoms of debility. The absorbent system is more subject to torpor or quiescence than the secerning system, both from the coldness of the fluids which are applied to it, as the moisture of the atmosphere, and from the coldness of the fluids which we drink; and also from its being stimulated only by intervals, as when we take our food; whereas the secerning system is perpetually excited into action by the warm circulating blood; as explained in Sect. XXXII. 2. The Peruvian bark, camomile flowers, and other bitter drugs, by stimulating this cellular branch of the absorbent system prevents it from becoming quiescent; hence the cold paroxysms of those agues, which arise from the torpor of the cellular lym- phatics, are prevented, and the hot fits in consequence. The pa- tient thence preserves his natural heat, regains his healthy colour, and his accustomed strength. Where the cold paroxysm of an ague originates in the absor- bents of the liver, spleen, or other internal viscus, the addition of steel to vegetable bitters, and especially after the use of one dos« of calomel, much advances the cure. And where it originates in any part of the secerning system, as is probably the case in some kinds of agues, the addition of opium in the dose of a grain and half, given about an hour be- fore the access of the paroxysm, or mixed with the chalybeate and bitter medicines, ensures the cure. Or the same may be effected by wine given instead of opium before the paroxysm, so as nearly to intoxicate. These three kinds of agues are thus distinguished; the first is not attended with any tumid or indurated viscus, which the peo- ple call an ague cake, and which is evident to the touch. The second is accompanied with a tumid viscus; and the last has Aut. IV. 2. S. 3. SORRENTIA. 47 generally, I believe, the quartan type, and is attended with some degree of arterial debility. The bark of the broad-leaved willow or salix caprea of Lin- neus, is much recommended as equal to the Peruvian bark given in the same or in greater quantity by Mr. White of Bath. Ob- serv. and Exper. on broad-leafed willow. Vernor and Hood, London. A Dr. Gunz in Germany recommends also as a sub- stitute for Peruvian bark, the bark of six species of willow, the salix alba, pentandra, fragilis, caprea, vitellina, and amygdalina. Dr. Gunz believes some of these barks to be more efficacious than the Peruvian. And as some of these willow-barks may be procured in great quantity, as they are stripped off from the wil- low twigs used by the basket-makers in many parts of the coun- try in the vernal months, it would seem to be an article worth at- tending to. The root of geum uibanum, avens, is recommended as a sub- stitute for Peruvian bark by Dr. Vogel, and said to cure the quartan ague given in the dose of half a dram every hour through the day. The datisca cannabina of Linnaeus is also said to equal the Peruvian bark in its febrifuge virtues. Medical and Physical Journal, Vol. I. p. 191. 3. This class of absorbent medicines are said to decrease irri- tability. After any part of our system has been torpid or quies- cent, by whatever cause that was produced, it becomes after- wards capable of being excited into greater motion by small stimuli; hence the hot fit of fever succeeds the cold one. As these medicines prevent torpor or quiescence of parts of the sys- tem, as cold hands or feet, which perpetually happen to weak constitutions, the subsequent increase of irritability of these parts is likewise prevented. 4. These absorbent medicines, including both the bitters, and metallic salts, and opiates, are of great use in the dropsy by their promoting universal absorption; but here evacuations are likewise to be produced, as will be treated of in the Invertentia. 5. The matter in ulcers is thickened, and thence rendered less corrosive, the saline part of it being reabsorbed by the use of bit- ter medicines; hence the bark is used with advantage in the cure of ulcers. 6. Bitter medicines strengthen digestion by promoting the ab- sorption of chyle; hence the introduction of hop into the potation used at our meals, which as a medicine maybe taken advantage- ously, but, like other unnecessary stimuli, must be injurious as an article of our daily diet. The hop may perhaps in some degree contribute to the pro- duction of gravel in the kidneys, as our intemperate wine-drinkers vol. i. 3 u 45 SORBENTIA. Airr. IV. 2. 3. 7. are more subject to the gout; and ale-drinkers to the gravel; in the formation of both which diseases, there can be no doubt, but that the alcohol is the principal, if not the only agent. 7. Vomits greatly increase the absorption from the cellular membrane, as squill, and foxglove. The squill should be given in the dose of a grain of the dried root every hour, till it operates upwards and downwards. Four ounces of the fresh leaves of the foxglove should be boiled from two pounds of water to one, and half an ounce of the decoction taken every two hours for four or more doses. This medicine, by stimulating into inverted action the absorbents of the stomach, increases the direct action of the cellular lymphatics. Another more convenient way of ascertaining the dose of fox- glove is by making a saturated tincture of it in proof spirit; which has the twofold advantage of being invariable in its original strength, and of keeping a long time as a shop-medicine without losing any of its virtue. Put two ounces of the leaves of purple foxglove, digitalis purpurea, nicely dried, and coarsely powdered, into a mixture of four ounces of rectified spirit of wine and four ounces of water; let the mixture stand by the fire-side twenty-four hours, frequently shaking the bottle, and thus making a saturated tincture of digitalis; which must be poured from the sediment or passed through filtering paper. Some person has lately objected to the quantity of the dried leaves of digitalis used in this tincture as an unnecessary ex- pense; not knowing that the plant grows spontaneously by cart- loads in all sandy situations, and not recollecting that the cer- tainty of procuring this medicine at all times of the year, and from all shops of the same degree of strength, is a circumstance of great importance. As the size of a drop is greater or less according to the size of the rim of the phial from which it is dropped, a part of this satu- rated tincture is then directed to be put into a two-ounce phial, for the purpose of ascertaining the size of the drop. Thirty drops of this tincture are directed to be put into an ounce of mint- water for a draught to be taken twice or thrice a day, till it re- duces the anasarca of the limbs, or removes the difficulty of breathing in hydrothorax, or till it induces sickness. And if these do not occur in two or three days, the dose must be gradually in- creased to forty or sixty drops, or further. A lady, who was 92 years of age, was seized suddenly, early in the morning, with great difficulty of respiration, which con- tinued in greater or less degree in spite of many medicines for two or three weeks. Her legs were then become oedematous, and she could not lie down horizontally. On taking thirty Aiit. IV. 2. 3. 8. SORBENTIA. 49 drops of the saturated tincture of digitalis from a two-ounce phial twice a day, she became free from the difficult respiration, and her legs became less swelled, in two or three days. She has repeated this medicine about once a month for more than a year, with tincture of bark at intervals, and half a grain of opium at night, and retains a tolerable state of health. From the great stimulus of this medicine the stomach is ren- dered torpid with consequent sickness, which continues many hours and even days, owing to the great exhaustion of its senso- rial power of irritation; and the action of the heart and arteries becomes feeble from the deficient excitement of the sensorial power of association; and lastly, the absorbents of the cellular membrane act more violently in consequence of the accumula- tion of the sensorial power of association in the torpid heart and arteries, as explained in Suppl. I. 12. A circumstance curiously similar to this occurs to some peo- ple on smoking tobacco for a short time, who have not been ac- customed to it. A degree of sickness is presently induced, and the pulsations of the heart and arteries become feeble for a short time, as in the approach to fainting, owing to the direct sym- pathy between these and the stomach, that is, from defect of the excitement of the power of association. Then there suc- ceed a tingling, and heat, and sometimes sweat, owing to the in- creased action of the capillaries, or perspirative and mucous glands; which are occasioned by the accumulation of the senso- rial power of association by the weaker action of the heart and arteries, which now increases the action of the capillaries. 8. Another method of increasing absorption from the cellu- lar membrane is by warm air, or by warm steam. If the swell- ed legs of a dropsical patient are enclosed in a box, the air of which is made warm by a lamp or two, copious sweats are soon produced by the increased action of the capillary glands, which are seen to stand on the skin, as it cannot readily exhale in so small a quantity of air, which is only changed so fast as may be necessary to permit the lamps to burn. At the same time the lymphatics of the cellular membrane are stimulated by the heat into greater action, as appears by the speedy reduction of the tu- mid legs. It would be well worth trying an experiment upon a person labouring under a general anasarca by putting him into a room filled with air heated to 120 or 130 degrees, which would pro- bably excite a great general diaphoresis, and a general cellular absorption both from the lungs and every other part. And that air of so great heat may be borne for many minutes without 50 SORHENTIA. Aiit. IV. 2. 3. 9. great inconvenience was shewn by the experiments made in heated rooms by Dr. Fordyce and others. Philos. Trans. Another experiment of using warmth in anasarca, or in other diseases, might be by immersing the patient in warm air, or in warm steam, received into an oil-skin bag, or bathing tub of tin, so managed, that the current of warm air or steam should pass round and cover the whole of the body except the head, which might not be exposed to it; and thus the absorbents of the lungs might be induced to act more powerfully by sympathy with the skin, and not by the stimulus of heat. See Uses of Warm Bath, Art. II. 2.2. 1. A warm saline pediluvium has often been used with success to remove swellings of the legs from deficient action of the ab- sorbents of the lower extremities; the quantity of sea-salt should be about one thirtieth part of the water, which with about one eightieth part of sulphuric magnesian salt, called magnesia vitri- olata, or bitter cathartic salt, constitutes the medium strength of the sea-water round this island, according to the experiments of Mr. Brownrig. In such a pediluvium the swelled legs should be immersed for half an hour every night for a fortnight, at the heat of about 96 or 98 degrees. Dr. Reid, in a Treatise on Sea-bathing; Cadell and Davis, London; recommends an universal warm-bath of sea-water, in (Edematous swellings, apparently with great success, and well advises friction to be diligently used in the bath on the tumid limbs, always rubbing them from their extremities towards the trunk of the body, and not the contrary way; as this must most facilitate the progress of the fluids in the absorbent system; though these vessels are furnished with valves to prevent its re- turn. In these baths the stimulus of the salt is added to that of the heat. See Art. II. 2.2. 1. 9. Another method of increasing absorption from the cellu- lar membrane, which has been used in dropsies, has been by the great or total abstinence from fluids. This may in some degree be used advantageously in subjects of too great corpulency, but if carried to excess may induce fevers, and greater evils than it is designed to counteract, besides the perpetual existence of a painful thirst. In most dropsies the thirst already existing shews, that too little diluent fluid, and not too much, is present in the circulation. IV. 1. Venous absorption. Cellery, water-cresses, cabbages, and many other vegetables of the class tetradynamia, do not in- crease the heat of the body, (except those, the acrimony of which approaches to corrosion,) and hence they seem alone, or princi- pally, to act on the venous system; the extremities of which we Aiit. IV. 2. 4. 2. SORBENTIA. 51 have shewn are absorbents of the red blood, after it has passed the capillaries and glands. 2. in the sea-scurvy and petechial fever the veins do not per- fectly perform this office of absorption; and hence the vibices are occasioned by blood stagnating at their extremities, or ex- travasated into the cellular membrane. And this class of vege- tables, stimulating the veins to perform their natural absorption, without increasing the energy of the arterial action, prevents future petechia;, and may assist the absorption of the blood al- ready stagnated, as soon as its chemical change renders it proper for tnat operation. 3. The fluids, which are extravasated, and received into the cells of the cellular membrane, seem to continue there for many days, so as to undergo some chemical change, and are then taken up again by the mouths of the cellular absorbents. But the new vessels produced in inflamed parts, as they communicate with the veins, are probably absorbed again by the veins along with the blood vvhich they contain in their cavities. Hence the blood which is extravasated in bruises of vibices, is gradually many days in disappearing; but after due evacuations the inflamed vessels on the white of the eye, if any stimulant lotion is applied, totally disappear in a few hours. Amongst absorbents affecting the veins we should therefore add the external application of stimulant materials; as of vinegar, which makes the lips pale on touching them. Friction and electricity. 4. Haemorrhages are of two kinds, either arterial, which are attended with inflammation; or venous, from a deficiency in the absorbent power of this set of vessels. In the former case thetorpentia are efficacious; in the latter steel, opium, alum, and all the tribe of sorbentia, are used with success. 5. Sydenham recommends vegetables of the class tetradyna- mia in rheumatic pains left after the cure of intermittents. These pains are perhaps similar to those of the sea-scurvy, and seem to arise from want of absorption in the affected part, and hence are relieved by the same medicines. V. 1. Intestinal absorption. Some astringent vegetables, as rhubarb, may be given in such doses as to prove cathartic; and after a part of it is evacuated from the body, the remaining part augments the absorption of the intestines; and acts, as if a similar dose had been exhibited after the operation of any other purgative. Hence 4 grains of rhubarb strengthen the bowels, 30 grains first empty them. 2. The earthy salts, as alum, increase the intestinal absorp- tion, and hence induce constipation in their usual dose; alum 52 SORBENTIA. A*r. IV. 2. 5. 3. is said sometimes to cure intcrmittents, perhaps when their seat is in the intestines, when other remedies have failed. It is use- ful in the diabetes, by exciting the absorbents of the bladder in- to their natural action; and combined with resin is esteemed in the fluor albus, and in gleets. Lime-stene, or chalk, and probably gypsum, possess effects in some degree similar, and in- crease the absorption of the intestines; and thus in certain doses restrain some diarrhoeas, but in greater doses, alum I sup- pose will act as a cathartic. Five or ten grains produce consti- pation, 20 or 30 grains are either emetic or cathartic. 3. Earth of alum, tobacco-pipe clay, marl, Armenian bole, lime, crab's eyes or claws, and calcined hartshorn, or bone ashes, restrain fluxes; either mechanically by supplying something like mucilage, or oil, or rollers to abate the friction of the ali- ment over inflamed membranes; or by increasing their absorption. The two last consist of calcareous earth united to phosphoric acid, and the Armenian bole and marl may contain iron. By the consent between the intestines and the skin 20 grains of Ar- menian bole, given at going into bed to hectic patients, will fre- quently check their tendency to sweat as well as to purge, and the more certainly if joined with one grain of opium. VI. 1. Absorption from the liver, stomach, and other viscera. When inflammations of the liver are subdued to a certain de- gree by venesection, with calomel and other gentle purges, so that the arterial energy becomes weakened,four or eight grains of iron filings, or of salt of steel, with the Peruvian bark, have won- derful effect in curing the cough, and restoring the liver to its usual size and sanity; which it seems to effect by increasing the absorption of this viscus. The same I suppose happens in res- pect to the tumours of other viscera, as of the spleen, or pan- creas, some of which are frequently enlarged in agues. 2. Haemorrhages from the nose, rectum, kidneys, uterus, and other parts, are frequently attendant on diseased livers; the blood being impeded in the vena portarum from the decreased powcr of absorption, and in consequence of the increased size of this viscus. These haemorrhages after venesection, and a mercurial cathartic, are most certainly restrained by steel alone, or joined with an opiate; which increase the absorption and diminish the size of the liver. Chalybeates may also restrain these haemorrhages by their pro- moting venous absorption, though they exert their principal effect upon the liver. Hence also opiates, and bitters, and vi- triolic acid are advantageously used along with them. It must be added that some haemorrhages recur by periods like the par- Aiit. IV. 2. 6. 3. SORBENTIA. 53 oxyms of intermittent fevers, and are thence cured by the same treatment. 3. The jaundice is frequently caused by the insipidity of the bile, which does not stimulate the gall-bladder and bile-ducts in- to their due action; hence it stagnates in the gall-bladder, and produces a kind of crystallization, which is too large to pass into the intestines, blocks up the bile-duct, and occasions a long and painful disease. A paralysis of the bile-duct produces a similar jaundice, but without pain. 4. Worms in sheep called flukes are owing to the dilute state of the bile; hence they originate in the intestines, and thence migrate into the biliary ducts, and corroding the liver produce ulcers, cough, and hectic fever, called the rot. In hu- man bodies it is probable the inert state of the bile is one cause of the production of worms; which insipid state of the bile is owing to deficient absorption of the thinner parts of it; hence the pale and bloated complexion, and swelled upper lip, of wormy children, is owing to the concomitant deficiency of absorption from the cellular membrane. Salt of steel, or the rust of it, or filings of it, with bitters, increase the acrimony of the bile by promoting the absorption of its aqueous part; and hence destroy worms, as well by their immediate action on the intestines, as on the wrorms themselves. The cure is facilitated by premising a purge with calomel. See Class I. 2. 3. 9. 5. The chlorosis is another disease owing to the deficient ac- tion of the absorbents of the liver, and perhaps in some degree also to that of the secretory vessels, or glands, which compose that viscus. Of this the want of the catamenia, which is gene- rally supposed to be a cause, is only a symptom or consequence. In this complaint the bile is deficient perhaps in quantity, but certainly in acrimony, the thinner parts not being absorbed from it. Now as the bile is probably of great consequence in the pro- cess of making the blood; it is on this account that the blood is so destitute of red globules; which is evinced by the great pale- ness of these patients. As this serous blood must exert less sti- mulus on the heart, and arteries, the pulse in consequence be- comes quick as well as weak, as explained in Sect. XII, 1. 4. The quickness of the pulse is frequently so great and perma- nent, that when attended by an accidental cough, the disease may be mistaken for hectic fever; but is cured by chalybeates, and bitters exhibited twice a day; with half a grain of opium, and a grain of aloe every night; and the expected catamenia appears in consequence of a restoration of the due quantity of red blood. This and the two former articles approach to the disease termed paralysis of the liver. Sect. XXX. -1. 54 SORBENTIA. Amt. IV. 2.6. 6. 6. It seems paradoxical, that the same treatment with chaly- beates, bitters, and opiates, which prodmes menstruation in chlo- rotic patients, should repress the too great or permanent men- struation, which occurs in weak constitutions at the time of life when it should cease. This complaint is a haemorrhage owing to the debility of the absorbent power of the veins, and belongs to the paragraph on venous absorption above described, and is thence curable by chalybeates, alum, bitters, and particularly by the exhibition of a grain of opium every night with five grains of rhubarb. As steel is soluble in the gastric acid, perhaps the best way of giving it may be in fine filings, or in a steel-powder prepared in the following manner: dissolve green vitriol in water, add a few bits of iron to the solution, to precipitate any copper which may be accidentally in it; precipitate this solution by salt of tartar, kali preparatum. Add to the precipitate two or three times its quantity of charcoal powder, mix and put them into a crucible covered with a tile, and give them a red heat for an hour. An impalpable powder of iron will be produced, which ought all of it to obey the magnet. 7. Metallic salts supply us with very powerful remedies for promoting absorption in dropsical cases; which frequently are caused by enlargement of the liver. First, as they may be giv- I en in such quantities as to prove strongly cathartic, of which more will be said in the article on invertentia; and then, when their purgative quality ceases, like the effect of rhubarb, their absorbent quality continues to act. The salts of mercury, silver, copper, iron, zinc, antimony, have all been used in the dropsy; either singly for the former purpose, or united with bitters for the latter, and occasionally with moderate but repeated opiates. 8. From a quarter of a grain to half a grain of blue vitriol given every four or six hours, is said to be very efficacious in ob- stinate intermittents; which also frequently arise from an en- larged viscus, as the liver or spleen, and are thence owing to the deficient absorption of the lymphatics of that viscus. A quarter of a grain of white arsenic, as I was informed by a surgeon of the army, cures a quartan ague with great certainty, if it be given an hour before the expected fit. This dose he said was for a ro- bust man, perhaps one eighth of a grain might be given and re- peated with greater safety and equal efficacy. Dr. Fowler has given many successful cases in his treatise on this subject. He prepares it by boiling sixty-four grains of white arsenic in a Florence flask along with as much pure vege- table fixed alkali in a pint of distilled water till they are dissolv- ed, and then adding as much distilled water as will make the Art 1Y. 2. 6. 9. SORUENTIA 55 whole exactly sixteen ounces. Hence there are four grains of arsenic in every ounce of the solution. This should be put into a phial of such a size of the edge of its aperture, that sixty drops may weigh one dram, which will contain half a grain of arsenic. To children from two years old to four, he gives from two to five drops three or four times a day. From five years old to seven, he directs seven or eight drops. From eight years old to twelve, he directs from seven to ten drops. From thirteen years old to eighteen, he directs from ten to twelve drops. From eighteen upwards, twelve drops. In so powerful a medicine it is always prudent to begin with smaller doses, and gradually to increase them. A saturated solution of arsenic in water, is preferable, I think, to the above operose preparation of it; as no error can happen in weighing the ingredients, and it more certainly therefore pos- sesses an uniform strength. Put much more white arsenic re- duced to powder into a given quantity of distilled water, than can be dissolved in it. Boil it for half an hour in a Florence flask, or in a tin sauce-pan; let it stand to subside, and filter it through paper. My friend Mr. Greene, a surgeon at Bree- wood in Staffordshire, assured me, that he had cured in one sea- son agues without number with this saturated solution; that he found ten drops from a two-ounce phial given thrice a day was a full dose for a grown person, but that he generally began with five. 9. The manner in which arsenic acts in curing intermittent fevers cannot be by its general stimulus, because no intoxication or heat follows the use of it; nor by its peculiar stimulus on any part of the secreting system, since it is not in small doses succeeded by any increased evacuation, or heat, and must therefore exert its power, like other articles of the sorbentia, on the absorbent sys- tem. In what manner it destroys life so suddenly is difficult to understand, as it does not intoxicate like many vegetable poisons, nor produce fevers like contagious matter. When applied ex- ternally it seems chemically to destroy the part like other caus- tics. Does it chemically destroy the stomach, and life in conse- quence? or does it destroy the action of the stomach by its great stimulus, and life in consequence of the sympathy between the stomach and the heart? This last appears to be the most pro- bable mode of its operation. The success of arsenic in the cure of intermittent fevers I sus- pect to depend on its stimulating the stomach into stronger ac- tion, and thus, by the association of this viscus w;th the heart and arteries, preventing the torpor of any part of the sanguiferous vol. i. 3 x 56 SORBENTIA Abt. IV. 2.6.9. system. I was led to this conclusion from the following con- siderations. First. The effects of arsenic given a long time internally in small doses, or when used in larger quantities externally, seem to be similar to those of other great stimuli, as of wine or alco- hol. These are a bloated countenance, swelled legs, hepatic tu- mours, and dropsy, and sometimes eruptions on the skin. The former of these I have seen, where arsenic has been used externally for curing the itch; and the latter appears on evidence in the famous trial of Miss Blandy at Chelmsford, about forty years ago. Secondly. I saw an ague cured by arsenic in a child, who had in vain previously taken a very large quantity of bark with great regularity. And another case of a young officer, who had lived intemperately, and laboured under an intermittent fever, and had taken the bark repeatedly in considerable quantities, with a grain of opium at night, and though the paroxysms had been thrice thus for a time prevented, they recurred in about a week. On taking five drops of a saturated solution of arsenic thrice a day the paroxysms ceased, and returned no more, and at the same time his appetite became much improved. Thirdly. A gentleman about sixty-five years of age had for about ten years been subject to an intermittent pulse, and to frequent palpitations of his heart. Lately the palpitations seemed to observe irregular periods, but the intermission of every third or fourth pulsation was almost perpetual. On giving him four drops of a saturated solution of arsenic from a two-ounce phial almost every four hours for one day, not only the palpita- tion did not return, but the. intermission ceased entirely, and did not return so long as he took the medicine, wliich was three or four days. Now as when the stomach has its action much weakened by an over-dose of digitalis, the pulse is liable to intermit, this evin- ces a direct sympathy between these parts of the system; and as I have repeatedly observed, that when the pulse begins to in- termit in elderly people, that an eructation from the stomach, voluntarily produced, will prevent the threatened stop of the heart; I am induced to think that the torpid state of the sto- mach, at the instant of the production of air occasioned by its weak action, caused the intermission of the pulse. And that arsenic in this case, as well as in the cases of agues above men- tioned, produced its effects by stimulating the stomach into more powerful action; and that the equality of the motions of the heart was thus restored by increasing the excitement of the sen- sorial power of association. See Sect. XXV. 17. Class IV. 2. 1. 18. Art. IV. 2. 7. 1. SORBEXTIA. 5"J Arsenic has lately been recommended in the hooping cough, tussis convulsiva, by Mr. Simmons, surgeon of Manchester, which he asserts to he attended with the most salutary effects, moderating the disease in a few days, and curing it generally in a fortnight. He has given it to children of a year old with safety, in the doses recommended by Dr. Fowler, whose solution he used, but seems to have used venesection and emetics occa- sionally, and recommends, after the solution has been omitted for a week, to repeat it, to prevent a relapse. Annals of Medi- cine, 1797. 10. Where arsenic has been given as a poison, it may be dis- covered in the contents of the stomach by the smell like garlic, when a few grains of it are thrown on red-hot iron. 2. If a few grains are placed between two plates of copper, and sub- jected to a red heat, the copper becomes whitened. 3. Dissolve arsenic in water along with vegetable alkali, add to this a solu- tion of blue vitriol in water, and the mixture becomes of a fine green, which gradually precipitates, as discovered by Bergman. 4. Where the quantity is sufficient, some wheat may be steeped in a solution of it, which given to sparrows or chickens will de- stroy them. VII. 1. Absorption of the matter from venereal ulcers. No ulcer can heal, unless the absorption from it is as great as the de- position in it. The preparations or oxydes of mercury in the cure of the venereal disease seem to act by their increasing the absorption of the matter in the ulcers it occasions; and that whether they are taken into the stomach, or applied on the skin, or on the surface of the ulcers. And this in the same manner as sugar of lead, or other metallic oxydes, promote so rapidly the healing of other ulcers by their external application; and probably when taken internally, as rust of iron given to children affected with scrofulous ulcers contributes to heal them, and solutions of lead were once famous in phthisis. The matter deposited in large abscesses does not occasion hec- tic fever, till it has become oxygenated by being exposed to the open air, or to the air through a moist membrane; the same seems to happen to other kinds of matter, which produce fever, or which occasion spreading ulcers, and are thence termed con- tagious. See Class II. 1. 3. II. 1. 5. II. 1. 6. 6. This may perhaps occur from these matters not being generally absorbed, till they become oxygenated; and that it is the stimulus of the acid thus formed by their union with oxygen, which occasions their absorption into the circulation, and the fever, which they then produce. For though collections of matter, and milk, and 58 SORBENTIA. Aht. IV. 2. 7. 2. mucus, are sometimes suddenly absorbed during the action of emetics or in sea-sickness, they are probably eliminated from the body without entering the circulation; that is, they are taken up by the increased action of one lymphatic branch, and evacuated by the inverted action of some other lymphatic branch, and thus carried off by stool or urine. 2. But as the matter in large abscesses is in general not ab- sorbed, till it becomes by some means exposed to air, there is reason to conclude, that the stimulus of this new combination of the matter with oxygen occasions its absorption; and that hence the absorption of matter in ulcers of all kinds, is still more power- fully affected by the external application or internal use of metal- lic oxydes; wliich are also acids consisting of the metal united with oxygen; and lastly, because venereal ulcers, and those of itch, and tinea, will not heal without some stimulant applica- tion; that is, the secretion of matter in them continues to be greater, than the absorption of it; and the ulcers at the same time continue to enlarge, by the contagion affecting the edges of them; that is, by the stimulus of the oxygenated matter stimulating the capillary vessels in its vicinity into actions similar to those of the ulcer, which produces it. This effect of the oxydes of mercury occurs, whether salivation attends its use or not. Salivation is much forwarded by external warmth, when mercury is given to promote this secretion; but as the cure of venereal complaints depends on its absorbent qua- lity, the act of salivation is not necessary or useful. A quarter of a grain of good corrosive sublimate twice a day will seldom fail of curing the most confirmed pox; and will as seldom salivate, if the patient be kept cool. A quarter of a grain thrice a day I believe to be infallible, if it be good sublimate. Mercury alone when swallowed does not act beyond the in- testines; its active preparations are the salts formed by its union with the various acids, as mentioned in the catalogue. Its union with the vegetable acid, when triturated with manna, is said to compose Keyser's Pill. Triturated with gum arabic it is much recommended by Plenck; and triturated with sugar and a little essential oil, as directed in a former Edinburgh Dispensatory, it probably forms some of the syrups sold as nostrums. United with sulphur it seldom enters the circulation, as when cinnabar, or aethiops mineral, is taken inwardly. But united with fat and rubbed on the skin, it is readily absorbed. I know not whether it can be united to charcoal, nor whether it has been given internally when united with animal fat; if six grains only of sulphur be added to two ounces of hog's fat and six Art. IV. 2. 8.1. SORBENTIA. 59 drachms of mercury, they are said to unite with much less labour. of trituration, than the hog's fat and mercury alone. \III. 1. Absorptions in general are increased by inanition; hence the use of evacuations in the cure of ulcers. Dr. Jurin absorbed in one night, after a day's abstinence and exercise, eighteen ounces from the atmosphere in his chamber; and every one must have observed, how soon his sheets became dry, after having been moistened by sweat, if he throws qff part of the bed- clothes to cool himself; which is owing to the increased cutane- ous absorption after the evacuation by previous sweat. 2. Now as opium is an universal stimulant, as explained in Ihe article of Incitantia, it must stimulate into increased action both the secretory system, and the absorbent one; but after re- peated evacuation by venesection, and cathartics, the absorbent system is already inclined to act more powerfully; as the blood- vessels being less distended, there is less resistance to the progress of the absorbed fluids into them. Hence after evacuations opium promotes absorption, if given in small doses, much more than it promotes secretion;-and is thus eminently of service at the end of inflammations, as in pleurisy, or peripnuemony, in the dose of four or five drops of the tincture, given before the access of the evening paroxysm; which I have seen succeed even when the risus sardonicus has existed. Some convulsions may originate in the want of the absorption of some acrid secre- tion, which occasions pain; hence these diseases are so much more certainly relieved by opium after venesection or other evacuations. IX. 1. Absorption is increased by the calces or solutions of mercury, lead, zinc, copper, iron, externally applied; and by arsenic, and by sulphur, and by the application of bitter vegeta- bles in fine powder. Thus an ointment consisting of mercury and hog's fat rubbed on the skin cures venereal ulcers; and ma- ny kinds of herpetic eruptions are removed by an ointment con- sisting of sixty grains of white precipitate of mercury and an ounce of hog's fat. 2. The tumours about the necks of young people are often produced by the absorption of a saline or acrid material, which has been deposited from eruptions behind the ears, otving to de- ficient absorption in the surface of the ulcer, but which on run- ning down on the skin below becomes absorbed, and swells the lymphatic glands of the neck; as the variolous matter, when inserted into the arm, swells the gland of the axilla. Some- times the perspiralive matter produced behind ihe ears becomes putrid from the want of daily washing them, and may also cause by its absorption the tumours of the lymphatics of the nrck. GO SORBENTIA. Aa*. IV. 2. 9. 3. In the former case the application of a cerate of lapis calamina- ris, or of cerussa in dry powder, or of rags dipped in a solution of sugar of lead, increases the absorption in the ulcers, and pre- vents the effusion of the saline part of the secreted material. The latter is to be prevented by cleanliness. After the eruptions or ulcers are healed, a solution of corrosive sublimate of one grain to an ounce of water applied for some weeks behind the ear, and amongst the roots of the hair on one side of the head, where the mouths of the lymphatics of the neck open themselves, frequently removes these tumours. 3. Linen rags moistened with a solution of half an ounce of sugar of lead to a pint of water applied on the erysipelas on ana- sarcous legs, which have a tendency to mortification, is more effi- cacious than other applications. White vitriol six grains dissolv- ed in one ounce of rose water removes inflammations of the eyes after evacuation more certainly than solutions of lead. Blue vitriol two or three grains dissolved in an ounce of water cures ulcers in the mouth, and other mucous membranes, and a solu- tion of arsenic externally applied cures the itch, but requires great caution in the use of it. See Class II. 1. 5. 6. A feeble old man with swelled legs had an erysipelas on both of them ; to one of these legs a fine powder of Peruvian bark was applied dry, and renewed twice a day ; on the other linen rags moistened with a solution of saccharum saturni were appli- ed, and renewed twice a day; and it was observed, that the lat- ter healed much sooner than the former. As the external application of calx of lead stimulates inflam- ed parts very violently, if it be applied too early, before the vessels are emptied by evacuations, or by the continuance of the disease, it is liable to increase the inflammation, or to induce mortification, as in ophthalmy; and in a case, which was re- lated to me of a person who much pricked his legs amongst gorse, which on the application of Goulard's solution of lead, mortified with extensive sloughs. But where the system is pre- viously emptied, there is less resistance to the progress of absorb- ed fluids; and the stimulus of lead then increases the action of the absorbent system more than of the secerning system, and the inflamed part presently disappears. 4. Bitter vegetables, as the Peruvian bark, quilted between two shirts, or strewed in their beds, will cure the ague in children sometimes. Iron in solution, and some bitter extract, as in the form of ink, will cure one kind of herpes called the ringworm. And I have seen seven parts of bark in fine powder mixed with one part of ceruse, or white lead, in fine powder, applied dry to scrofulous ulcers, and renewed daily, with great advantage. Art. IT. 2. 9. 5. SORBENTIA. 61 5. To these should be added electric sparks and shocks, which promote the absorption of the vessels in inflamed eyes of scrofulous children; and disperse, or bring to suppuration, scrofu- lous tumours about the neck. For this last purpose smart shocks should be passed through the tumours only, by enclosing them between two brass knobs communicating with the external and internal coating of a charged phial. See Art. II. 2. 2. 2. X. 1. Bandages increase absorption, if they are made to fit nicely on the part; for which purpose it is necessary to spread some moderately adhesive plaster on the bandage, and to cut it into tails, or into shreds two inches wide; the ends are to be wrapped over each other; and it must be applied when the part is least tumid, as in the morning before the patient rises, if on the lower extremities. The emplastrum de minio made to cover the whole of a swelled leg in this manner, whether the swell- ing is hard, which is usually termed scorbutic; or more easily compressible, as in anasarca, reduces the limb in two or three days to its natural size; for this purpose I have sometimes used carpenter's glue, mixed with one-twentieth part of honey to prevent its becoming too hard, instead of a resinous plaster; but the minium plaster of the shops is in general to be preferred. Nothing so much facilitates the cure of ulcers in the legs, as covering the whole limb from the toes to the knee with such a plaster bandage; which increases the power of absorption in the surface of the sore. 2. The lymph is carried along the absorbent vessels, which are replete with valves, by the intermitted pressure of the arteries in their neighbourhood. Now if the external skin of (he limb be lax, it rises, and gives way to the pressure of the arteries at every pul- sation; and thence the lymphatic vessels are subject to the pres- sure of but half the arterial force. But when the external skin is tightened by the surrounding bandage, and thence is not ele- vated by Ihe arterial diastole, the whole of this power is exerted in compressing the lymphatic vessels, and carrying on the lymph already absorbed; and thence the absorbent power is so amaz- ingly increased by bandage nicely applied. Pains are sometimes left in the fleshy parts of the thighs or arms, after the inflamma- tion is gone, in the acute rheumatism, or after the patient is too weak for further evacuation; in this case after internal absorbent medicines, as the bark, and opiates, have been used in vain, I have successfully applied a plaster-bandage, as above described, so as to compress the pained part. Since the above was written, Mr. Baynton, an ingenious sur- geon of Bristol, has published " A Method of Treating Ulcers of the Legs," sold by Robinson, London. In which he endeavours 62 SORBENTIA. Aht. IV. 2.11. 1 to bring the lips of those ulcers nearer together by means of slips of adhesive plaster, as above described; which seems to have been attended with great success, without confinement of the patient. See Sect. XXXIII. 3. 2. But when slips of adhesive plaster are put over a wound so as to bring the edges of it together nearly, or quite, into contact with each other, the part is at the same time covered, as the slips of adhesive plaster are applied, from the eye of the surgeon. 1 have therefore advised two tin plates a little longer than the wound, and about half an inch broad, to be fastened to the ends of the pieces of adhesive plaster, and applied one on each lip of the wound or ulcer; and then by a narrow slip of adhesive plas- ter applied at each end of these tins, they may be drawn together, and the whole lips of the wound may be seen at the same time by the surgeon; and then a compress of thin lead, or of linen, may be applied by other strips of plaster so as to heal recent wounds, and even ulcers, without scarcely any unevenness or width of the scar. XI. 1. We shall conclude by observing, that the sorbentia strenglhen the whole habit by preventing the escape of the fluid part of the secretions out of the body, before it has given up as much nourishment, as it is capable; as the liquid part of the se- cretion of urine, sweat, saliva, and of all other secretions, which are poured into receptacles. Hence they have been said to brace the body, and been called tonics, which are mechanical terms not applicable to the living bodies of animals; as explained in Sect. XXXII. 3. 2. 2. A continued use of bitter medicines for years together, as of Portland's powder, or of the bark, is supposed to induce apo- plexy, or other fatal diseases. Two cases of this kind have fallen under my observation; the patients wrere both rather intem- perate in respect to the use of fermented liquors, and one of them had been previously subject to the gout. As I believe the gout generally originates from a torpor of the liver, which, in- stead of being succeeded by an inflammation of it, is succeeded by an inflammation of some of the joints; or by a pimpled face, which is another mode, by which the disease of the liver is ter- minated: I conceive, that the daily use of bitter medicines had in these patients prevented the removal of a gouty inflammation from the liver"to the membranes of the joints of the extremities, or to the skin of the face, by preventing the necessary torpor of these parts previous to the inflammation of them; in the same manner as cold fits of fever are prevented by the same medicines; and, as I believe, the returns of the gout have sometimes for two or three years been prevented by them. Art. IV. 3.1. SORBENTIA. €8 One of these patients died of the apoplexy in a few hours; and the other of inflammation of the liver, which I believe was called the gout, and in consequence was not treated by venesection, and other evacuations. Hence it appears, that the daily use of hop in our malt liquor must add to the noxious quality of the spirit in it, when taken to excess, and contribute to the production of apoplexy, or inflammation of the liver. III. CATALOGUE OP THE SORBENTIA. I. Sorbentia affecting the skin. 1. Acid of vitriol, of sea-salt, lemons, sloes, prunus spi- nosa, crabs, pyrus, quince, pyrus cydonia, opium. 2. Externally calx of zinc, of lead, or of mercury. II. Sorbentia affecting the mucous membranes. 1. Juice of sloes, crabs, Peruvian bark, cinchona, opium. 2. Externally blue vitriol. III. Sorbentia affecting the cellular membrane. 1. Peruvian bark, wormwood, artemisia maritima, arte- misia absynthium, worm-seed, artemisia santonicum, chamomile, anthemis nobilis, tansey, tanacetum, bog- bean, menyanthes trifoliata, centaury, gentiana centau- rium, gentian, gentiana lutea, artichoke-leaves, cynara scolymus, hop, humulus lupulus, salix caprea, geum urbanum, datisca cannabina. 2. Orange-peel, cinnamon, nutmeg, mace. 3. Vomits, squill, digitalis, tobacco. 4. Bath of warm air, of steam. IV. Sorbentia affecting the veins. 1. Water-cress, sisymbrium nasturtium aquaticum, mus- tard, sinapis, scurvy-grass, cochlearia hortensis, horse- radish, cochlearia armoracia, cuckoo-flower, cardamine, dog's-grass, dandelion, leontodon, taraxacon, cellery, apium, cabbage, brassica. 2. Chalybeates, bitters, and opium, after sufficient evacua- tion. 3. Externally vinegar, friction, electricity. V. Sorbentia affecting the intestines. 1. Rhubarb, rheum palmatum, oak-galls, gallae quercinae, tormentilla erecta, cinquefoil, potentilla, red-roses, uva ursi, simarouba. 2. Logwood, haematoxylum, campechianum, succus aca- cias, dragon's blood, terra japonica, mimosa catechu. 3. Alum, earth of alum, Armenian bole, chalk, creta, crab's vol. i. 3 y 64 SORBENTIA. AnT. IV. 3.6. claws, chelae cancrorum, white clay, cimolia, calcined hartshorn, cornu cervi calcinatum, bone-ashes. VI. Sorbentia affecting the liver, stomach, and other viscera. Rust of iron, filings of iron, salt of steel, sal martis, blue vitriol, white vitriol, calomel, emetic tartar, sugar of lead, white arsenic. VII. Sorbentia affecting venereal ulcers. Mercury dissolved or corroded by the following acids: I. Dissolved in vitriolic acid, called turpeth mineral, or hydrargyrus vitriolatus. 2. Dissolved in nitrous acid, called hydrargyrus nitratus ruber. 3. Dissolved in muriatic acid, mercurius corrosivus sub- limatus, or hydrargyrus muriatus. 4. Corroded by muriatic acid. Calomel. 5. Precipitated from muriatic acid, mercurius precipitatus albus, calx hydrargyri alba. 6. Corroded by carbonic acid? The black powder on crude mercury. 7. Calcined, or united with oxygen. 8. United with animal fat, mercurial ointment. 9. United with sulphur. Cinnabar. 10. Partially united with sulphur, ^thiops mineral. 11. Divided by calcareous earth. Hydrargyrus cum creta. 12. Divided by vegetable mucilage, by sugar, by balsams. VIII. Sorbentia affecting the whole system. Evacuations by venesection and catharsis, and then the exhibition of opium. IX. Sorbentia externally applied. 1. Solutions of mercury, lead, zinc, copper, iron, arsenic; or metallic calces applied in dry powder, as cerussa, lapis calaminaris. 2. Bitter vegetables in decoctions and in dry powders, applied externally, as Peruvian bark, oak bark, leaves of wormwood, of tansey, chamomile flowers or leaves. 3. Electric sparks, or shocks. X. Bandage spread with emplastrum e minio, or with car- penter's glue mixed with one-twentieth part of honey. XL Portland's powder, its continued use pernicious, and of hops in beer. Anr. \. 1. 1 INVERTENTIA 65 Art. V. INVERTENTIA I. Those things which invert the natural order of the suc- cessive irritative motions, are termed invertentia. 1. Emetics invert the motions of the stomach, duodenum, and oesophagus. 2. Violent cathartics invert the motions of the lacteals, and in- testinal lymphatics. 3. Violent errhines invert the nasal lymphatics, and those of the frontal and maxillary sinuses. And medicines producing nausea, invert the motions of the lymphatics about the fauces. 4. Medicines producing much pale urine, as a certain quantity of alcohol, invert the motions of the urinary absorbents; if the dose of alcohol is greater, it inverts the stomach, producing the drunken sickness. 5. Medicines producing cold sweats, palpitation of the heart, globus hystericus; as violent evacuations, some poisons, fear, anxiety, act by inverting the natural order of the vascular motions. II. OBSERVATIONS ON THE INVERTENTIA. I. 1. The action of vomiting seems originally to have been occasioned by disagreeable sensation from the distention or acri- mony of the aliment; in the same manner as when any disgustful material is taken into the mouth, as a bitter drug, and is rejected by the retrograde motions of the tongue and lips; as explained in Class IV. 1.1.2. and mentioned in Sect. XXXV. 1.3. Or the disagreeable sensation may thus excite the power of volition, which may also contribute to the retrograde actions of the stomach and oesophagus, as when cows bring up the contents of their first stomach to remasticate it. To either of these is to be attributed the action of mild emetics, which soon cease to operate, and leave the stomach stronger, or more irritable, after their operation; ow'mg to the accumulation of the sensorial power of irritation dur- ing its torpid or inverted action. Such appears to be the operation of ipecacuanha, or of antimonium tartarizatum, in small doses. 2. But there is reason to believe, that the stronger emetics, as digitalis, firtt stimulate the absorbent vessels of the stomach into greater action; and that the inverted motions of these ab- sorbents next occur, pouring the lymph, lately taken up, or ob- tained from other lymphatic branches, into the stomach; the quantity of which in some diseases, as in the cholera morbus, is 66 INVERTENTIA. Art. V. 2. 1. 2. inconceivable. This inverted motion, first of the absorbents of the stomach, and afterwards of the stomach itself, seems to origi- nate from the exhaustion or debility, which succeeds the unna- tural degree of action, into which they had been previously sti- mulated. An unusual defect of stimulus, as of food without spice or wine in the stomachs of those, who have been much accustom- ed to spice or wine, will induce sickness of vomiting; in this case the defective energy of the stomach is owing to defect of accus- tomed stimulus; while the action of vomiting from digitalis is owing to a deficiency of sensorial power, which is previously ex- hausted by the excess of its stimulus. See Sect. XXXV. 1. 3. and Class IV. 1. 1. 2. For first, no increase of heat arises from this action of vomit- ing; which always occurs, when the secerning system is stimu- lated into action. Secondly, the motions of the absorbent ves- sels are as liable to inversion as the stomach itself; which last, with the oesophagus, may be considered as the absorbent mouth and belly of that great gland, the intestinal canal. Thirdly, the class of sorbentia, as bitters and metallic salts, given in large doses, become invertentia, and vomit, or purge. And lastly, the sick- ness and vomiting induced by large potations of wine, or opium, does not occur till next day in some people, in none till some time after their ingurgitation. And tincture of digitalis in the dose of 30 or 60 drops, though applied in solution, is a considerable time before it produces its effect; though vomiting is instantaneously induced by a nauseous idea, or a nauseous taste in the mouth. At the same time there seem to be some materials which can im- mediately stimulate the stomach into such powerful action, as to be immediately succeeded by paralysis of it, and consequent con- tinued fever, or immediate death; and this without exciting sen- sation, that is, without our perceiving it. Of these are the con- tagious matter of some fevers swallowed with the saliva, and pro- bably a few grains of arsenic taken in solution. See Suppl. I. 8.8. Art. IV. 2. 6. 9. 3. Some branches of the lymphatic system become inverted by their sympathy with other branches, which are only stimulated into too violent absorption. Thus, when the stomach and duode- num are much stimulated by alcohol, by nitre, or by worms, in some persons the urinary lymphatics have their motion inverted, and pour that material into the bladder, which is absorbed from the intestines. Hence the drunken diabetes is'fboduced; and hence chyle is seen in the urine in worm cases. When on the contrary some branches of the absorbent systems have their motions inverted in consequence of the previous ex- haustion of their sensorial power by any violent stimulus, other Art. V. 2. 1. 4. INVERTENTIA. 67 branches of it have their absorbent power greatly increased. Hence continued vomiting, or violent cathartics, produce great absorption iiom the cellular membrane in cases of dropsy; and the fluids thus absorbed are poured into the stomach and intes- tines by the inverted motions of the lacteals and lymphatics. See Sect. XXIX. 4. and 5. 4. The quantity of the dose of an emetic is not of so great consequence as of other medicines, as the greatest part of it is rejected with the first effort. All emetics are said to act with greater certainty when given in a morning, if an opiate had been given the night before. For the sensorial power of irritation of the stomach had thus been in some measure previously exhausted by the stimulus of the opium, which thus facilitates the action of the emetic; and which, when the dose of opium has been large, is frequently followed on the next day by spontaneous sickness and vomitings, as after violent intoxication. Ipecacuanha is the most certain in its effect from five grains to thirty; white vitriol is the most expeditious in its effect, from twenty grains to thirty dissolved in warm water; but emetic tartar, antimonium tartarizatum, from one grain to four to sane people, and from thence to twenty to insane patients, will answer most of the useful purposes of emetics; but nothing equals the di- gitalis purpurea for the purpose of absorbing water from the cel- lular membrane in the anasarca pulmonum, or hydrops pectoris. See Art. II. 3. 7. II. Violent cathartics. 1. Where violent cathartics are re- quired, as in dropsies, the squill in dried powder made into small pills of a grain, or a grain and a half, one to be given every hour till they operate briskly, is very efficacious; or half a grain of emetic tartar dissolved in an ounce of peppermint-water, and given every hour, till it operates. Scammony, and other strong purges, are liable to produce hypercatharsis, if they are not nicely prepared, and accurately weighed, and are thence dan- gerous in common practice. Gamboge is uncertain in its effects, it has otherwise the good property of being tasteless; and on that account some preparation of it might be useful for children, by which its dose could be ascertained, and its effects rendered more uniform. 2. In inflammations of the bowels with constipation, calomel, given in a dose from ten to twenty grains after due venesection, is most efficacious; and if made into very small pills is not lia- ble to be rejected by vomiting, which generally attends those cases. When this fails, a grain of aloes every hour will find ils way, if the bowel is not destroyed; aud sometimes, I believe, if it be, when the mortification is not extensive. If the vomiting 6S INVERTENTIA. Art. V. 2.3. 1. continues after the pain ceases, and especially if the bowels be- come tumid with air, which sounds on being struck with the" finger, these patients seldom recover. Opiates given along with the cathartics I believe to be frequently injurious in inflammation of the bowels, though they may thus be given with advantage in the saturnine colic; the pain and constipation in which disease are owing to torpor or inactivity, and not to too great action. See Class I. 2. 4. 8. III. Violent errhines and sialagogues. l.Turpeth mineral in the quantity of one grain mixed with ten grains of sugar answers every purpose to be expected from errhines. Their operation is by inverting the motions of the lymphatics of the membrane, which lines the nostrils, and the caverns of the forehead and cheeks; and may thence possibly be of service in the hydrocepha- lus internus. Some other violent errhines, as the powder of white hellebore, or Cayenne pepper, diluted with some less acrid powder, are said to cure some cold or nervous head-achs; which may be effected by inflaming the nostrils, and thus introducing the sensorial power of sensation, as well as increasing that of irritation; and thus to produce violent action of the membranes of the nostrils, and of the frontal and maxillary sinuses, which may by associa- tion excite into action the torpid membranes, which occasion the head-ach. They may be used on the same account in amaurosis and in deafness. 2. A copious salivation without any increase of heat often at- tends hysteric diseases, and fevers with debility, owing to an in- version of the lymphatics of the mouth, see Class 1. 1. 2. 6. The same occurs in the nausea, which precedes vomiting; and is also excitable by disagreeable tastes, as by squills, or by nause- ous smells, or by nauseous ideas. These are very similar to the occasional discharge of a thin fluid from the nostrils of some peo- ple, which recurs at certain periods, and differs from defective absorption. IV. Violent diuretics. 1. If nitre be given from a dram to half an ounce in a morning at repeated draughts, the patient lie- comes sickish, and much pale water is thrown into the bladder by the inverted action of the urinary lymphatics. Hence the ab- sorption in ulcers is increased and the cure forwarded, as observ- ed by Dr. Rowley. 2. Cantharides taken inwardly so stimulate the neck of the bladder as to increase the discharge of mucus, which appears in the urine; but 1 once saw a large dose taken by mistake, not less than half an ounce or an ounce of the tincture, by which I sup- pose the urinary lymphatics were thrown into violent inverted Art. V. 2. 4. 3. INVERTENTIA. 69 motions, for the patient drank repeated draughts of subtepid Vater to the quantity of a gallon or two in a few hours; and during the greatest part of that time he was not I believe two entire minutes together without making water. A little blood was seen in his water the next day, and a soreness continued a day longer without any other inconvenience. 3. The decoction of foxglove should also be mentioned here, as great effusions of urine frequently follow its exhibition. See Art. IV. 2. 3. 7. And an infusion or tincture of tobacco as recommended by Dr. Fowler of York. 4. Alcohol, and opium, if taken so as to induce slight intoxi- cation, and the body be kept cool, and much diluting liquids taken along with them, have similar effect in producing for a time a greater flow of urine, as most intemperate drinkers must occasionally have observed. This circumstance seems to have introduced the use of gin, and other vinous spirits, as a diuretic, unfortunately in the gravel, amongst ignorant people; which disease is generally produced by fermented or spirituous liquors, and always increased by them. 5. Fear and anxiety are well known to produce a great fre- quency of making water. A person who believed he had made a bad purchase concerning an estate, told me, that he made five or six pints of water during a sleepless night, which succeeded his bargain; and it is usual, where young men are waiting in an anti-room to be examined for college preferment, to see the chamber-pot often wanted. V. Cold sweats about the head, neck, and arms, frequently attend those, whose lungs are oppressed, as in some dropsies and asthma. A cold sweat is also frequently the harbinger of death. These are from the inverted motions of the cutaneous lymphatic branches of those parts. III. CATALOGUE OP INVERTENTIA. I. Emetics, ipecacuanha, emetic tartar, antimonium tartari- satum, squill, scilla maritima, carduus benedictus, cni- cusacarna, chamomile, anthemis nobilis, white vitriol, vitriolum zinci, foxglove, digitalis purpurea, clysters of tobacco. II. Violent cathartics, emetic tartar, squill, buckthorn, rham- nus catharticus, scammonium, convolvulus scammo- nia, gamboge, elaterium, colocynth, cucumis colocyn- this, veratrum. III. Violent errhines and sialagogues, turpeth mineral, hydra- 70 REVERTENTIA. Art. VI. 1. 1. gyrus vitriolatus, asarum europaeum, euphorbium, cap* sicum, veratrum, nauseous smells, nauseous ideas. IV. Violent diuretics, nitre, squill, seneka, cantharides, alco- hol, foxglove, tobacco, anxiety. V. Cold sudorifics, poisons, fear, approaching death. Art. VI. REVERTENTIA. I. Those things which restore the natural order of the invert- ed irritative motions, are termed Revertentia. 1. As musk, castor, asafoetida, valerian, essential oils. 2. Externally the vapour of burnt feathers, of volatile salts, or oils, blisters, sinapisms. These reclaim the inverted motions without increasing the heat of the body above its natural state, if given in their proper doses, as in the globus hystericus, and palpitation of the heart. The incitantia revert these morbid motions more certainly, as opium and alcohol; and restore the natural heat more; but if they induce any degree of intoxication, they are succeeded by debility, when their stimulus ceases. II. OBSERVATIONS ON THE REVERTENTIA. I. 1. The hysteric disease is attended with inverted motions feebly exerted of the oesophagus, intestinal canal, and lympha- tics of the bladder. Hence the borborigmi, or rumbling of the bowels, owing to their fluid contents descending as the air be- neath ascends. The globus hystericus consists in the retrograde motion of the oesophagus, and the great flow of urine from that of the lymphatics spread on the neck of the bladder; and a copious salivation sometimes happens to these patients from the inversion of the lymphatics of the mouth; and palpitation of the heart ow- ing to weak or incipient inversion of its motions; and syncope, when this occurs in its greatest degree. These hysteric affections are not necessarily attended with pain; though it sometimes happens, that pains, which originate from quiescence, afflict these patients, as the hemicrania, which has erroneously been termed the clavus hystericus; but which is owing solely to the inaction of the membranes of that part, like the pains attending the cold fits of intermittents, and which fre- quently returns like them at very regular periods of time. Vrt. VI. 2. 2. 1. REVERTENTIA. 71 Many of the above symptoms are relieved by musk, castor, the fcetid gums, valerian, oleum animale, oil of amber, which act in the usual dose without heating the body. The pains, which sometimes attend these constitutions, are relieved by the secernentia, as essential oils in common tooth-ach, and balsam of Peru, in the flatulent cholic. But the incitantia, as opium, or vinous spirit, reclaim these morbid inverted motions with more certainty than the fcetids; and remove the pains which attend these constitutions, with more certainty than the secernentia; but if given in large doses, a debility and return of the hysteric symptoms occur, when the effect of the opium or alcohol ceases. Opiates and fcetids joined seem best to answer the purpose of alleviating the present symptoms; and the sorbentia, by stimu- lating the lymphatics and lacteals into continued action, prevent a relapse of their inversion, as Peruvian bark, and the rust of iron. See Class I. 3. 1. 10. II. Vomiting consists in the inverted order of the motions of the stomach and oesophagus; and is also attended with the invert- ed motions of a part of the duodenum, when bile is ejected; and of the lymphatics of the stomach and fauces, when nausea at- tends, and when much lymph is evacuated. Permanent vomit- ing is for a time relieved by the incitantia, as opium or alcohol; but is liable to return when their action ceases. A blister on the back, or on the stomach, is more efficacious for restraining vomit- ing by their stimulating into action the external skin, and by sympathy affecting the membranes of the stomach. In some fevers attended with incessant vomiting, Sydenham advised the patient to put his head under the bed clothes, till a sweat appeared on the skin, as explained in Class IV. 1. 1.3. In chronical vomiting I have observed crude mercury of good effect in the dose of half an ounce twice a day. The vomitings, or vain efforts to vomit, which sometimes attend hysteric or epi- leptic patients, are frequently instantly relieved for a time by applying flour of mustard-seed and water to the small of the leg; and removing it, as soon as the pain becomes considerable. If sinapisms lie on too long, especially in paralytic cases, they are liable to produce troublesome ulcers. A plaster or cataplasm, with opium and camphor on the region of the stomach, will sometimes revert its retrograde motions. III. Violent catharsis, as in diarrhoea or dysentery, is attended with inverted motions of the lymphatics of the intestines, and is generally owing to some stimulating material. This is coun- teracted by plenty of mucilaginous liquids, as solutions of gum arabic, or small chicken broth, to wash away or dilute the stimu- lating material, which causes the disease. And then by the use vol. i. 3 z ■};j REVERTENTIA. Art. VI 2.4. 1. of the intestinal sorbentia, Art. IV. 2. 5, as rhubarb, decoction of logwood, calcined^iartshorn, Armenian bole; and lastly by the incitantia, as opium. IV. The diabcetes consists in the inverted motions of the urinary lymphatics, which is generally, I suppose, owing to the too great action of some other branch of the absorbent system. The urinary branch should be stimulated by cantharides, turpen- tine, resin, (which when taken in larger doses may possibly excite it into inverted action,) by the sorbentia and opium. The intes- tinal lymphatics should be rendered less active by torpentia, as calcareous earth, earth of alum; and those of the skin by oil externally applied over the whole body; and by the warm- bath, which should be of ninety-six or ninety-eight degrees of beat, and the patient should sit in it every day for half an hour. V. Inverted motions of the intestinal canal with all the lym- phatics, which open into it, constitute the ileus, or iliac passion; in which disease it sometimes happens, that clysters are returned by the mouth. After venesection from ten grains lo twenty of calomel made into very small pills; if these be rejected, a grain of aloe every hour; a blister, crude mercury; warm-bath; if a clyster of iced water? Many other inverted motions of different parts of the system are described in Class 1.3. and which are to be treated in a man- ner similar to those above described. It must be noted that the medicines mentioned under number one in the catalogue of rever- (entia are the true articles belonging to this class of medicines. Those enumerated in the other four divisions are chiefly such things as tend to remove the stimulating causes, which have in- duced the inversion of the motions of the part, as acrimonious contents, or inflammation, of the bowels in diarrhoea, diabetes, or in ileus. But it is probable after these remote causes are de- stroyed, that the fetid gums, musk, castor and balsams, might be given with advantage in all these cases. III. CATALOGUE OF REVERTENTIA. I. Inverted motions, which attend the hysteric disease, are re- claimed, 1. By musk, castor. 2. By asafoetida, galba- num, sagapenum, ammoniacum, valerian. ■>. Essential oils of cinnamon, nutmeg, cloves, infusion of penny-roy- al, mentha, pulegium, peppermint, mentha piperita, ether, camphor. 4. Spirit of hartshorn, oleum animale, sponge burnt to charcoal, black snuffs of candles, which consist principally of animal charcoal, wood-foot, oil of amber. 5. The incitantia, as opium, alcohol, vinegar. 6 Art. VII 1 1. TORPENTIA. 73 Externally the smoke of burnt feathers, oil of amber, vo- latile salt applied to the nostrils, blisters, sinapisms. II. Inverted motions of the stemach are reclaimed by opium, alcohol, blisters, crude mercury, sinapisms, camphor, and opium, externally, clysters with asafcetida. III. Inverted motions of the intestinal lymphatics are reclaim- ed by mucilaginous diluents, and by intestinal sorbentia, as rhubarb, logwood, calcined hartshorn, Armenian bole; and lastly by incitantia, as opium. IV. Inverted motions of the urinary lymphatics are reclaim- ed by cantharides, turpentine, resin, the sorbentia, and opium, with calcareous earth of alum, by oil externally, warm bath. V. Inverted motions of the intestinal canal are reclaimed by calomel, aloe, crude mercury, blisters, warm-bath, clys- ters with asafoetida, clysters of iced water? or of spring water further cooled by salt dissolved in water contained in an exterior vessel? Where there exists an introsus- ception of the bowel in children, could the patient be held up for a time by the feet with his head downwards, or be laid with his body on an inclined plane with his head downwards, and crude mercury be injected as a clyster to the quantity of two or three pounds? Art. VII. TORPENTIA. I. Those things which diminish the exertion of the irritative motions, are termed torpentia. 1. As mucus, mucilage, water, bland oils, and whatever possesses less stimulus than our usual food. Diminution of heat, light, sound, oxygene, and all other stimuli; venesection, nau- sea and anxiety. 2. Those things which chemically destroy acrimony; as calca- reous earth, soap, tin, alkalies, in cardialgia; or which prevent chemical acrimony, as acid of vitriol in cardialgia, which pre- vents the fermentation of the aliment in the stomach, and its consequent acidity. Secondly, which destroys worms, as calo- mel, iron filings or rust of iron, in the round worms; or amal- gama of quicksilver and tin, or tin in very large doses, in the tape-worms. Will either in clysters destroy ascarides? Thirdly, by chemically destroying extraneous bodies, as caustic alkali, lime, mild alkali in the stone. Fourthly, those things which lu- 74 TORrENTIA. Art. VII. 2. 1. 1. bricatc the vessels along with extraneous bodies slide, as oil in the stone in the urethra, and to expedite the expectoration of hardened mucus; or which lessen the friction of the contents in the intestinal canal in dysentery or aphtha, as calcined harts- horn, clay, Armenian bole, chalk, bone-ashes. Fifthly, such things as soften or extend the cuticle over tumours or phleg- mons, as warm water, poultices, fomentations, or by confining the perspirable matter on the part by cabbage-leaves, oil, fat, bees'-wax, plasters, oiled silk, externally applied. These decrease the natural heat, and remove pains occasioned by excess of irritative motions. II. OBSERVATIONS ON THE TORPENTIA. I. As the torpentia consist of such materials as are less stimu- lating than our usual diet, it is evident, that where this class of medicines is used, some regard must be had to the usual manner of living of the patient both in respect to quantity and quality. Hence wounds in those who have been accustomed to the use of much wine, are very liable to mortify, unless the usual pota- tion of wine be allowed the patient. And in these habits I have seen a delirium in a fever, cured almost immediately by wine; which was occasioned by the too mild regimen directed by the attendants. On the contrary, in great inflammation, the sub- duction of food, and of spirituous drink, contributes much to the cure of the disease. As by these means both the stimulus from distention of the vessels, as well as that from the acrimony of the fluids, is decreased; but in both these respects the previous habits of diet of the patients must be attended to. Thus if tea be made stronger than the patient has usually drunk it, it be- longs to the article sorbentia; if weaker, it belongs to the tor- pentia. II. 1. Water in a greater quantity than usual diminishes the action of the system not only by diluting our fluids, and thence lessening their stimulus, but by lubricating the solids; for not only parts of our solids have their sliding over each other facili- tated by the interposition of the aqueous particles; but the par- ticles of mucaginous or saccharine solutions slide easier over each other by being mixed with a greater portion of water, and thence stimulate the vessels less. At the same time it must be observed, that the particles of water themselves, and of animal gluten dissolved in water, as the glue used by carpenters, slide easier over each other by an additional quantity of the fluid matter of heat. These two fluids of heat and of water may be esteemed ihe Art. VII. 1.3. 1. TORPENTIA. 75 universal solvents or lubricants in respect to animal bodies, and thus facilitate the circulation, and the secretion of the various glands. At the same time it is possible that these two fluids may occasionally assume an. aerial form, as in the cavity of the chest, and by compressing the lungs may cause one kind of asth- ma, which is relieved by breathing colder air. An increased quantity of heat by adding stimulus to every part of the system belongs to the article Incitantia. III. 1. The application of cold to the skin, which is only another expression for the diminution of the degree of heat we are accustomed to, benumbs the cutaneous absorbents into inac- tion; and by sympathy the urinary and intestinal absorbents be- come also quiescent. The secerning vessels continuing their ac- tion somewhat longer, from the warmth of the blood. Hence the usual secretions are poured into the bladder and intestines, and no absorption is retaken from them. Hence sprinkling the skin with cold water increases the quantity of urine, which is pale; and of stool, which is fluid; these have erroneously been ascribed to increased secretion, or to obstructed perspiration. The thin discharge from the nostrils of some people in cold weather is owing to the torpid state of the absorbent vessels of the membrana schneideriana, which as above are benumbed sooner than those, which perform the secretion of the mucus. The quick anhelation, and palpitation of the heart, of those, who are immersed in cold water, depends on the quiescence of the external absorbent vessels and capillaries. Hence the cuta- neous circulation is diminished, and by association an almost universal torpor of the system is induced; thence the heart be- comes incapable to push forwards its blood through all the inac- tive capillaries and glands; and as the terminating vessels of the pulmonary artery suffer a similar inaction by association, the blood is with difficulty pushed through the lungs. Some have imagined, that a spasmodic constriction of the smaller vessels took place, and have thus accounted for their re- sistance to the force of the heart. But there seems no necessity to introduce this imaginary spasm; since those, who are conver- sant in injecting bodies, find it necessary first to put them into warm water to take away the stiffness of the cold dead vessels; which become inflexible like the other muscles of dead animals, and prevent the injected fluid from passing. Before the improved knowledge of chemistry, and of natural philosophy, and of the laws of organic life, some writers have spoken of cold as a stimulus to the system, instead of speaking of it as a diminution of the stimulus of heat. But the immedi- sto consequence of ptimultis is the exertion of the stimulated 7b' TORPENTIA. Aht. \ 11.2. 3.2. fibres; now an increased application of heat is followed by an increased action of the fibres exposed to it; but an increased ap- plication of cold is followed by a decreased action of the fibres exposed to it; as appears by the redness of our hands when warmed by the fire, and the paleness of them, when they have been a while covered with snow. A painful sensation succeeds the defect as well as the excess of the stimulus of heat, as mentioned in Vol. I. Sect. IV. 5. and the voluntary exertions of the subcutaneous muscles called shud- dering, are excited to relieve the pain occasioned by the torpor of the fibres exposed to cold; and those of the muscles subser- vient to respiration are voluntarily excited in screaming to re- lieve the pain occasioned by heat, which may have occasioned the error above mentioned. Others have spoken of a sedative quality of cold, which is cer- tainly an unphilosophical expression; as a sedative power, ii it has any distinct meaning, should express a power of di-ninishing any unnatural or excessive motions of the system; butthe applica- tion of cold diminishes the activity of the fibres in general, which may previously be less han natural, as well as greater. All the same symptoms occur in the coll (i, >. Opium, ii. 2. 1.2, iv. 1, 2. in nervous pains, ii- 2, 1, 5. in inflammatory pains, ii. 2, . 1,6. increases all secretions and absorptions, ii. 2, 1, 1. absorption after evacuation, iv. 2, 8. 2, ii. 2, 1, o. stops sweats, iv. 2, 1,2. intoxicates, ii 2,1, 1. Oranges, their peel, iv. 3, 3. Orch.s, vii. >, 3. Oxygen gas, ii. 2, 4, i 2, 5, iii. 2, 11, iv. 1, 4. produces and heals ul- cers, iv. 2, 7. P Pains, periodic, cured by opium, ii. 2, 1 Papin's digester, i.' 2,3, 5. Papaver somniferum, ii. 3,1, iv. 3, 2. See Opium. Pareira brava, iii. 3, 4, 4. Parsley, iii. 3, 4. Passions, ii. 2, 5. Pasturage, i. 2, 3, 7. Pepper, iii. 3, 1. Peripneumony, iv. 2, 8, 2. Perspiration in a morning, iii. 2, 1. not an excrement, iii 2, 1. Peru, balsam of, iii. 3, 5, 4. Petechiae, iv. 2, 4, 2. Pimento, iii. , 1. Piper indicum, iii. 3, 1. Pistacia lentiscus, iii. 3, 2. Pix liquida, iii. 3, 2. Phosphorus, iii. 2, 6. Plaster-bandage, iv. 2, 10. Pleurisy, iv. 2, 8, 2. Polygala seneka, iii. 3, 3, 2. Poppy. See Papaver. Portland's powder noxious, why, iv 2, 11, 2. Potatoe-bread, i 2, 3, 4. Potentilla, iv. 3, 5. Powder of iron, iv. 2, 6,6. Prunes, iii. 3,5, 1. Prunus domestica, iii. 3, 5,1. spinosa, iv 3,1. laurocerasus, ii. 3, 1. Pulegium, vi. 3, 3. Pulse, intermittent, relieved by ar senic, iv. 2, 6. INDEX OF THE ARTICLES—Part HI. 95 Pyrethrum, iii. 3, 2. Pyrus malus, vii. cydonia, iv. 3. Q Quassia, iv. 2, 2. Quince, iv. 3,1. Quinquefolium, iv. 3, 5. R Ritafia, why destructive, ii. 2,1. Reaction, iv. 1, 10. Resin diuretic, iii. 2, 4, vi. 2,4. Rhamnus catharticus, v. 3, 2. Rheumatism, iv- 2, 4, 5, iv. 2, 10, 2. Rheum palmatum. See Rhubarb. Rhubarb, iii. 2,1, iv. 2, 5,1, iii. 3,5,5. causes constipation, why, iii. 2, 1, 1. Rice, vii. Roses, iv. 3, 5. Rot in sheep, iv. 2, 6. S Sagapenum, vi. 3, 1. Sago, vii. 3. Salivation not necessary, iv. 2, 7. hysteric, v. 2, 3. Salt, common, unwholesome, iii. 1, 12. muriatic, iii. 3,1. in clysters, iii. 2, 7. Salts, why diuretic, iii. 2, 4. neutral, iii. 3, 5, 3, iii. 2,4. improper in coughs and go- norrhoea, iii. 2,4. Salt fish and salt meat increase per- spiration, iii. 2, 1. Sassafras, iii. 3, 1. Scammony, v. 2, 2. Scarcity, times of, i. 2, 3, 5 and 6. Scilla maritima, v. 2, 2, iv. 2, 3, iii. 3, 3, v. 2, 3. Scorbutic legs, iv. 2, 10. Scrofulous tumours, ii. 2, 4, iv. 2, 9. Sea-water, iii. 3, 5, 3. Secernentia, iii. Secretion of the bladder, iii. 2, 6. rectum, iii 2, 7. skin, iii. 2, 8. Seneca, iii. 3, 3, 2. Senna, iii. 3, 5, 5. Serpentaria virginiana, iii. 3,1. Sialagogues, iii. 2, 2, v. 2, 3. Siniarouba, iv. 3, 5. Sinapi, iv. 3, 4. VOL. I. Sinapisms, vi. 2, 2, iii. 2, 8. Sisymbrium nasturtium, iv. 3, 4. Sloes, iv. 2, 2. Snuff' in head-ach, v. 2,3,1. See errhines. Snuffs of candles, vi. 3, 4. Society, i. 2, 3, 7. Soot, vi. 3, 4. Sorbentia, various kinds, iv. 2,1. Spasmodic doctrine exploded, vji. Spermaceti, iii. 3, 3,3. Spice, noxious, iii. 1,12. Spirit of wine noxious, ii. 2,1. Sponge, burnt, vi. 3, 4. Squill. See Scilla. Starch, i. 2, 3, 1. from poisonous roots, i. 2, 3, 4. Steam, bath of, iv. 2, 3, 8. Steel, iv. 2, 6,1. forwards and represses men- struation, iv- 2, 6, 6. powder, iv. 2, 6, 6. Stizolobium siliqua hirsuta, iii. 2, 7, vii. 3, 11. Strychnos nux vomica, ii. 3, 1. Sublimate of mercury, iv. 2,7, iv. 2,9. Sugar nourishing, i. 2,3,1, and 5, iii. 3, 3, 3. formed after the death of the plant, i. 2, 3, 5. aperient, iii. 3, 5, 1. Sulphur, iii. 3, 5, 4. Sweats in a morning, iii. 2, 1,1. on waking, iii. 2, 1, 1. cold, v. 2, 5. stopped by opium, iv. 2,1, 2. T Taenia, vermes. See Worms. Tamarinds, iii. 3, 5, 1. Tansey, tanacetum, iv. 3, 3. Tar, iii. 3, 3. Tartar, crystals of, iii. 3, 5, 1. Class i. 2, 3, 13. vitriolate, iii. 3, 5, 3. emetic, v. 2, 1, v. 2, 2- Tea, vii. 2,1. Tears, iii. 2, 2. Testaceous powders, iv. 2, 2. Tetradynamia, plants of, iv. 2, 4. Tincture of digitalis, iv. 2, 3, 7. Tinea, herpes, iv. 2, 1, 4. Tobacco, ii 3,1, iii. 3, 9, iv. 2, 3, 8. injures digestion, iii. 2, 2,3. Tolu balsam, iii. 3, 3. 4C 96 INDEX OF THE ARTlCLES.-rPart IU. Tonics, iv. 1. 10. Tormentilla erecta, iv. 3, 5. Torpentia, vii. Tragacanth gum, iii. 3,3, 3. Turpentine, vi. 2, 4. spirit of, iii. 2, 6. Turpeth mineral, v. 2, 3. Tussilago farfara, iii. 3, 3, 3. U Ulcers cured by bandage, iv. 2,10,2. scrofulous, iv. 2, 9. of the mouth, iv. 2, 2. cured by absorption, ii. 2, 1, 4, iv. 2, 3, 5, iv. 2, 7. Uva ursi, iv. 3, 5. V Valerian, vi. 3, 3. Vegetable acids, iv. 2, 1. food, i. 2,1,2. Venereal ulcers, iv. 2, 7. Venesection, vii. 2, 4, iv. 2, 8. diminishes secretions, vii. 2, 4. increases absorptions, vii. 2,41 Veratrum, v. 3, 2. Vibices, iv. 2, 4,3. Vinegar, iv. 2, 1, 9, iv. 3, 4, 3, ii. 2, 1.9. Vitriol, blue, in agues, iv. 2,6, iv. 2,2. in ulcers, iv. 2, 9. white, iv. 3,6, v. 2, 1. acid of, iv. 2, 1. in sweats, iv. 1, 1. in small-pox, iv. 1, 1. Volatile salt, vi 3, 6. Vomiting, v. 2, 2. stopped by mercury, vi. 2,2. Vomits, iv. 2, 3, 7. W Warm bath, ii. 2, 2,1. saline, iv. 2, 3, 8. in diabetes, vi. 2, 4. Water, i. 2, 4. dilutes and lubricates, vii. 2> 2- cold, produces sweats, iii. 2, 1. iced, in ileus, vi. 2, 5. cresses, iv. 3, 4. Whey of milk, iii. 3, 5, 2, i. 2, 2,2. Willow bark, iv. 2, 3, 2. Wine, ii 3, 1. Worms, vii. 1, 2, iii. 2, 7, iv. 2, 6, 4. in sheep, iv. 2, 6, 4. Wounds cured by bandage, iv. 2, 15, 10. Z Zinc, vitriol of, v. 3, 1. Mwl. Hfst WZ ' 3J7fi ID Xliiz.