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 PHILIP SYNG PHYSICK 
 LIBRARY. 
 

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PHYSIOLOGY; 
 
 BYA.RICHERAND, 
 
 PnOFESSOB. OF THE FACULTY OF MEDICIITE OP PARIS, SUESEON IN CHIEF OF 
 THE HOSPITAL OP ST. LOUIS, MEMBER OF THE ACADEMIES OF 
 VIENNA, PETEBSBURUH, MADRID, TURIN, &C. 
 
 FROM THE FIFTH LOJ\'DOJ\r EDITIOJV, REVISED, CORRECTED, 
 AJVD EJVLHRGED. 
 
 rvwfli ffixvrov. 
 
 VWVWWV 
 
 TRANSLATED FROM THE FRENCH, 
 
 BY 
 
 G. J. M. DE LYS, M. D. 
 
 MEMBER OF THE ROYAL COLLEGE OF SURGEONS IN LONDON, 
 
 WITH NOTES, 
 
 BY N. CHAPMAN, M. D. 
 
 Professor of the Materia Medica in the University of Pennsylvania: 
 
 PHILADELPHIA: 
 
 PUBLISHED BY THOMAS DOBSON, AT THE STONE HOUSE, 
 No. 41, SOUTH SECOND STREET. 
 
 William Fry, Printer. 
 
 1813. 
 
District of Pennsylvania, to wit: 
 
 ********* be it remembered, That on the first day of November, 
 * SEAL. I in the thirty-eighth year of the Independence of the United 
 ********* States of America, A. D. 1813, Thomas Dobson, of the said 
 district, hath deposited in this office, the title of a book, the right whereof 
 he claims as proprietor, in the words following, to wit: 
 
 " Elements of Physiology; by A. Richerand, Professor of the Faculty of 
 “ Medicine of Paris, Surgeon in Chief of the Hospital of St. Louis, 
 “Member of tlie Academies of Vienna, Petersburgh, Madrid, Turin, 
 “ &c. From the fifth London edition, revised, corrected, and enlarged. 
 “ rvo6; a-iauTov. Translated from the French, by G. J. M. De Lys, M. D. 
 “ Member of the Royal College of Surgeons in Lomlon. Wich Notes, 
 “ by N Chapman, M. D Professor of the Materia Medica in the Uni- 
 “ versity of Pennsylvania.” 
 
 In conformity to the act of the Congress of the United States, intituled, 
 “ An act for the encouragement of learning, by securing the copies of 
 maps, charts, and books, to the authors and proprietors of such copies dur- 
 ing the times therein mentioned.” — And also to the act, entitled, “An act 
 supplementary to an act, entitled, “ An act for the encouragennent of learn- 
 ing, by securing the copies of maps, charts, and books, to the authors and 
 proprietors of such copies during the time therein mentioned,” and extend- 
 ing the benefits thereof to the arts of designing, engraving, and etching 
 historical and other prints.” 
 
 D. CALDWELL, 
 
 Clerk of the District of Pennsylvania. 
 
TO 
 
 THOMAS T. HEWSON, M. D, 
 
 Mr Deaji Sir, 
 
 Confidently expecting to be called to teach the Insti> 
 tutesof Medicine in the University of Pennsylvania, I engag- 
 ed with much ardour, in the preparation of the ensuing work, 
 to serve as a Text Book to my lectures on Physiology. But I 
 had hardly commenced the undertaking, when my appointment 
 to another Chair took place, which gave a different direction 
 to my studies, and engrossed nearly all my leisure. Notwith- 
 standing however, these disadvantages, it may be perceived 
 that no slender contributions have been made to the work, 
 and I trust that some of the matter which I have added, will 
 not be deemed wholly superfluous. 
 
 Nor is my primary object entirely defeated. As I must ne- 
 cessarily introduce into my lectures on the Materia Medica a 
 variety of speculations relative to the laws of the animal eco- 
 nomy, the work will still be exceedingly useful to my class. 
 
 In submitting a new edition of this System of Physiology 
 to the public, I can not help believing that I am rendering an 
 acceptable service. No work is perhaps so generally desidera- 
 ted at this period, especially by the students of medicine in the 
 United States, as a Treatise on Physiology, which should con- 
 cisely exhibit the existing state of the science, enriched as it 
 has recently been, by new discoveries and improvements. 
 The present work, in this respect, is of great value. Compa- 
 red with the other Elementary Treatises on the same subject, 
 it has a decided superiority, as is evinced by the uncommonly 
 favourable reception which it has experienced in every coun- 
 try, where the science of which it treats, is cultivated to any 
 extent. Not only in France, but in Italy, Spain, Germany, 
 
IV 
 
 DEDICATION. 
 
 England, and the United States, it has passed, in the short 
 space of eight years, through repeated impressions. 
 
 I have printed from the fifth and latest edition of the au- 
 thor, which, to employ his own language, was “ carefully re- 
 vised and corrected in all its parts, so as to render the work 
 more worthy of the success it had already obtained.” It has 
 indeed been enlarged to nearly double the size of the original 
 copy, tiot as continues he, “■ by idle discourses or frivolous 
 hypotheses, but by an accumulation of facts, supporting the 
 opinions previously advanced, and by developing those por- 
 tions of the subject, which, from being heretofore explained in 
 too succinct a manner, might be involved in some degree of 
 obscurity.” 
 
 If my time had not been so much occupied, certain it is, that 
 I could have made the notes which I have attached to the 
 work far more extensive. Brief as they are, however, I am 
 sure with the usual urbanity of your disposition, you will ex- 
 cuse the liberty I have taken of inscribing the work to you. 
 I wished to prefix your name to it, because, in the circle of 
 my friends, there is no one who is better qualified to judge 
 of its merits, or from whom I could expect a more indulgent 
 and discriminating criticism. Nor was I less anxious to seize 
 the earliest occasion of tendering some tribute of respect to 
 the son of one of the most distinguished cultivators of Physio- 
 logy during the last century. 
 
 I am, my dear Hewson, 
 
 Yours very faithfully, 
 
 N. CHAPMAN. 
 
 Philadelphia, November 1 , 1813 . 
 
PREFACE. 
 
 These Elements of Physiology, which contain an abstract 
 of the doctrines I have taught for several years past in my 
 public lectures, are written on the model of the small work on 
 physiology of the great and immortal Haller. I am far, how- 
 ever, from presuming to say that I have equalled the merit of 
 a work, which, as is remarked by a man of the highest abili- 
 ty,# gave, when it appeared, a new aspect to the science, 
 and commanded universal approbation. If these Elements of 
 Physiology deserve any preference over that work, the ho- 
 nour is not due to the Author, but to the times in which he 
 writes, enriched by the progress of the physical sciences, with 
 a multitude of data and results which may be said to have ren- 
 dered Physiology altogether a new science. 
 
 It will be easily perceived that the plan I have adopted dif- 
 fers essentially from that followed by several respectable phy- 
 sicians; and that the treatises on Physiology most recently 
 published, resemble the present, only in their title. In com- 
 bining a great number of facts, in adding to those already 
 known, the result of my own observation and experience, and 
 in connecting them by a method that should unite accuracy 
 and simplicity, I have had it in view to keep a due measure be- 
 tween those elementary works, whose conciseness approaches 
 to obscurity and dryness, and those in which the authors, 
 omitting no detail, and exhausting in a manner their subject, 
 seem to have written only for those who have leisure or incli- 
 nation for the profoundest study. 
 
 * “When Haller published his Prime linee Physiohgie, which he valued 
 most of all his works, a considerable sensation was excited in the schools. 
 In works on the same subject, it was customary to find long dissertations, 
 almost always void of proof, extraordinary opinions, or brilliant fictions. It 
 was matter of wonder, that in Haller’s work, there should be found onl}' nu- 
 merous facts, precise details, and direct inferences, &c.” — Vicq.-D’Azyr. 
 
Vi 
 
 PREFACE. 
 
 Should any conceive that the present undertaking is above 
 the capacity of my age, I will say, even at the risk of a para- 
 dox, that young men are perhaps fittest to compose elementa- 
 ry works; because the difficulties they have encountered in 
 the study, are yet fresh in their memory, as well as the steps 
 which they have taken to overcome them; and further, be- 
 cause their recent experience points out to them the defects 
 and advantages of the different methods of other instructors;* 
 so that he, who in the shortest space of time, has carried to 
 the greatest extent his own acquisition of sound knowledge, 
 will, in some respects, be the best guide to his successors, in 
 the difficult and perplexing paths of elementary study. 
 
 In the composition of the work, I have borne constantly in 
 mind the necessity of sacrificing elegance to clearness, which 
 I know to be the most important merit of an elementary trea- 
 tise. Further, I have throughout followed, I believe, the same 
 arrangement in the succession of the subjects, and applied to 
 the science of living man, the principle of the Association of 
 ideas; a principle so well developed by Condillac, in his Trea- 
 tise on the Art of Writing, and to which that philosopher has 
 shown, that all the rules of the art are to be referred. Not- 
 withstanding the rigorous law to which I have subjected my- 
 self, I have, after the example of the ancients, and, among the 
 moderns, of Bordcu, and of several other physicians and phy- 
 siologists of equal celebrity, thought myself justified in em- 
 ploying, when I felt it necessary', metaphorical expressions; 
 because, as has been justly observed bv a writer who has been, 
 in our own times, an honour to her sex, if conciseness do not 
 consist in the art of reducing the number of words, still less 
 does it consist in depriving language of imagery. The con- 
 ciseness which is to be envied is that of Tacitus, at once elo- 
 quent and energetic; and, far from any fear that imagery should 
 injure that justly admired compression of style, figurative ex- 
 
 * “ Tlie best order in wliicli truth can be set forth, is that in which it might 
 naturally have been discovered; for, the surest method of instructing others, 
 is to lead them along the path which we ourselves have foll.iwed, in our own 
 instruction. In this way, we shall seem not so much to l:.y before them our 
 own knowdedge, as to set themselves on the search anddiseovery of unkiiowH 
 truths.” — Condillac. 
 
PREFACE. 
 
 VII 
 
 pressions are, indeed, those which comprise in fewest words 
 the greatest sum of ideas. ^ 
 
 Those who insist on meeting in a work on Physiology, with 
 a romance instead of the history of the animal economy, will, 
 no doubt, reproach me with having entirely neglected a great 
 number of hypotheses, ingenious or absurd, on the uses of 
 organs; with having omitted, for example, while speaking of 
 the spleen, to mention the opinion which considers that viscus 
 as the seat of mirth and laughter; with having said nothing of 
 the opinion of those authors, who conceive it to maintain, by 
 counterpoising the liver, the equilibrium of the two hypochon- 
 dria; nor even of the doctrine of the ancients who ascribed to 
 it the secretion of the atra bilis, &c. To recal such errors for 
 the sake of elaborate refutation, would be wasting much pre- 
 cious time in idle discussions, and possessing, as Bacon calls 
 it, the art of making one question bring forth a thousand, by 
 answers more and more unsatisfactory. I have chosen to forego 
 all such vain parade, from a clear conviction, that works of 
 merit are as often distinguished by some things that are not to 
 be found in them, as by those they do contain. 
 
 Several authors, in treating of the science of man, have in- 
 dulged themselves in frequent excursion into the vast field of 
 accessory sciences, and have, without necessity, incorporated 
 in their works whole chapters on air, on sound, on light and 
 other subjects, which belong to the department of natural 
 philosophy and chemistry. Haller himself is not intirely free 
 of blame, for having discredited physiology by this borrow- 
 ed display. I have introduced only such general ideas of the 
 subject, as were absolutely necessary to render my own intel- 
 ligible, and were, indeed, too closely connected with it, to 
 admit of separation. 
 
 One of the principal faults of writers on physiology is, that 
 they are apt to fall into frequent repetitions; and that fault is 
 often owing to the difficulty of settling, satisfactorily, the limits 
 of actions which are mutually connected and dependent among 
 
 / 
 
 * De la Literature considere dans ses rapports avec les Institutions So* 
 ciales par Madame de Stael-Holstein, tome ii 
 
Vlll 
 
 PREFACE. 
 
 themselves, and running into each other, like those that are 
 carried on in the animal economy. 
 
 “■ In composition, one should avoid prolixity, because it is 
 “fatiguing to the mind; digressions, because they divert the 
 “attention; frequent divisions and sub-divisions, because they 
 “ are perplexing; and repetitions, because they are oppressive. 
 “ What has been once said, and in its proper place, is clearer 
 “than if several times repeated elsewhere.”* In following 
 these precepts, and they cannot be too much attended to, one 
 may, it is true, incur the risk of being thought superficial, by 
 superficial readers, who form their opinion of a work from the 
 perusal of a single chapter; but a most ample compensation 
 will be found in the opinion of those, who choose to be 
 thoroughly acquainted with a work, before they pass on it 
 their final judgment. 
 
 After having stated in what spirit this work has been writ- 
 ten, I may say something of the motives which have led to its 
 publication. I would mention, in the first place, the advantage 
 which, it might be expected, would accrue to the science, and 
 to those who are engaged in its pursuit: and, in the next place, 
 the satisfaction which study has in store for him, who bestows 
 on it the time he can snatch from the laborious practice of our 
 art. In his short intervals of leisure from public instruc- 
 tion and from professional duty, left to himself and his own 
 thoughts, in the silence of study, and in the calm of medita- 
 tion, he looks down, with an eye of pity, on those who drag 
 on, through the lowest intrigues, a despicable existence, and 
 finds his consolation against the endless vexations that are 
 prepared for him by supercilious ignorance, and jealous me?- 
 diocrity. 
 
 • Condillac Essai sur I’Origine des Connoissances humaines, seconde 
 partie, sect. ii. chap. iv. 
 
PRELIMINARY DISCOURSE. 
 
 Physiology* is the science of life. The term life is 
 applied to an aggregate of phenomena, which manifest them- 
 selves in succession, for a limited time in organized bodies. 
 Combustion is likewise only a combination of phenomena; 
 oxygen unites with the substance which is burning, caloric is 
 disengaged from it; affinity is the cause of these chemical phe- 
 nomena, as attraction is the cause of the phenomena of astro- 
 nomy, and in the same manner as the sensibility and contractility 
 of living and organized bodies are the primary causes of all the 
 phenomena which such bodies exhibit — phenomena, which in 
 their union and aggregate succession constitute life. 
 
 The false notions which have been entertained on the subject 
 of life, and the vague definitions which have been given of it, 
 are to be accounted for, by considering that physiologists, 
 instead of regarding life as a simple result, have mistaken it for 
 the properties of life. These last are causes; the first is merely 
 an effect, more or less complex; and, as the spring of a watch, 
 or rather the elasticity of that spring, determines by the mere 
 action of the wheels, the motion of the hands and all the phe- 
 nomena of which the machine is capable; so the vital properties 
 acting by the organs produce all those effects, which in their 
 combination constitute life. These effects are more or less 
 numerous, according to the number of the organs; they become 
 more rapid too in their succession and life more active, with 
 the increase of energy in the vital properties. Precisely as the 
 motions of a watch become more complicated, stronger or 
 quicker, according to the greater tension of the spring, or the 
 increased number of the wheels. Sensibility and contractility, 
 are to be ranked among primary causes, of whose existence 
 and laws we acquire a knowledge from observation, but whose 
 
 * Anatomy is the science of organizaiioTi. 
 
 A 
 
2 
 
 essence eludes our investigation,* and will probably remain for 
 ever beyond its reach. 
 
 § I. OF NATURAL BEINGS. 
 
 The vast domain of nature is divided between two classes of 
 beings. Inorganic beings, possessing merely the common pro- 
 perties of matter; organic and living beings, obeying particular 
 laws, though subjected to the general laws which regulate the 
 universe. Each of these two grand divisions is naturally divid- 
 ed into two classes; we meet with inorganic bodies under the 
 form of elementary substances^ simple and not capable of ana- 
 lysis; or else under the form of mixed substances, compound, 
 and admitting of decomposition. Thus, too, organized beings 
 exist under two very different forms of life, which distinguish 
 them into vegetables and animals. 
 
 The first general conception with which we ought to enter 
 upon this comprehensive study of nature, is the mutual depen- 
 dence of those beings, which, in their co-ordinate whole, com- 
 pose the system of nature; a dependence which requires for 
 each die simultaneous existence of all. Thus a vegetable derives 
 its nourishment from inorganic bodies, and alters their inert 
 substance, which is unfit for the food of animals, unless it has 
 previously undergone the influence of vegetable life. 
 
 § II. OF THE ELEMENTS OF BODIES. 
 
 Another consideration, of equal importance with the former, 
 is the convertibility of all those substances so different from 
 one another, and their capacity of being reduced to a small 
 number of simple substances, called elements. The ancient 
 doctrine of Aristotle, relative to the four elements, still pre- 
 vailed in the schools, with a few modifications, which it had 
 received from the chemists, when the “ Pneumatistsf” demon- 
 
 * It would be wrong to infer, from our ignorance of the nature of the vital 
 properties, that physiology is an uncertain science. Its certainty in that point 
 of view, is equal to that of other parts of natural philosophy. The chemist, 
 who explains all his combinations by referring them to the princij)le of 
 affinity, and the astronomer, who finds in attraction the cause that rules the 
 universe, are absolutely ignorant of the nature of those properties. 
 
 f This is the name given to the school of modern cheraistrt', because it 
 originated from the discoveries made relative to the nature of air and elastic 
 
3 
 
 strated by their beautiful experiments, that three, at least, of 
 these pretended principles of bodies, air, water and earth, far 
 from being simple substances, were evidently formed by the 
 union and combination of several others; that atmospherical 
 air, for example, far from being an homogeneous fluid, was 
 composed of many different gases, and that in its purest state, 
 it contains at least two very distinct principles. Oxygen and 
 azote; that water is a compound of oxygen and hydrogen, and 
 that earth contains clay, lime, silex, &c. 
 
 We h&ve seen added in the present day, to the number of 
 the elements or simple substances, several which were not con- 
 sidered as such, at the time when natural philosophers, misled 
 by erroneous metaphysical doctrines, had created out of their 
 imaginations, beings of the existence of which they could find 
 no proof. There is every reason to believe, that the number of 
 substances not admitting of decomposition, limited at present 
 to forty-four, may hereafter be increased or diminished, by the 
 discovery of new principles in simple substances, or of new 
 elements in compound bodies, which have hitherto eluded the 
 investigation of chemists. Whatever may be the success of 
 their enquiries, of which it is impossible to. foresee the results, 
 or to fix the limits, there is reason to believe, that it will ever 
 be denied us, to arrive at a knowledge of the true elements of 
 bodies, and that many of those substances, which the imperfec- 
 tion of our means of decomposition or analysis obliges us to 
 consider as such, are frequently compound substances and sub- 
 ject to their laws. 
 
 After what has been stated on the elements or constituent 
 principles of substances, let us now see in what manner the 
 combination of these elements gives existence to all beings, and 
 what are the general differences existing among the great classes 
 into which they are divided. 
 
 fluids. It must be acknowledg’ed, to the credit of metaphysics, that the old 
 errors were forsaken, only at the period when chemists were thoroughly 
 convinced of this truth, that every idea is obtained through the medium of 
 the senses and that nothing is to be admitted beyond what they demonstrate 
 it} actual experiment. 
 
4 
 
 § III. DIFFERENCES BETWEEN ORGANIZED AND INOIIGANIZED 
 
 BODIES, 
 
 ' Much attention has been bestowed of late, on the diflFerence 
 %vhich exists between organized and inorganized bodies. The 
 latter have been observed to be very different from those which 
 are endowed with life, in the homogeneous nature of their 
 substance, in the complete independence of their molecules, 
 each of which, according to the observation of Kant, has in 
 itself causes to account for its peculiar mode of existence, in 
 that power of resisting decomposition which they owe to the 
 simplicity of their structure, and in the absence of those pe- 
 culiar powers which free organic bodies from the absolute 
 dominion of physical laws. The multiplicity, the volatility of 
 their elements, the necessary union of fluids and solids, the 
 nutrition and development from the diffusive combination, 
 while the growth of inanimate bodies takes place from the 
 mere juxta position of particles, the origin of living bodies 
 in generation, their destruction in death, such are the characters 
 which distinguish organized beings from inorganized substan- 
 ces. We are about to enter into a detail of those characters, to 
 appreciate all their differences, for knowledge is to be acquired 
 only by comparison; and the greater our accuracy in comparing, 
 the more precise and extensive will be the knowledgfe we ob- 
 tain. Several modern authors have proved, that it is impossible 
 to obtain an accurate idea of life, except by comparing those 
 bodies which are endowed with it, with those in which life 
 has never existed, or has ceased to exist. This comparison, 
 I hope, will be fruitful in interesting results, and will furnish 
 several useful considerations, immediately applicable to the 
 knowledge of man. 
 
 The first remarkable difference between organized and inor- 
 ganized bodies, is to be found in the homogeneousness of the 
 latter, and the compound nature of the former. Let a block of 
 marble be broken, each piece will be perfectly similar to the 
 rest, there will be no differences among them, but such as relate 
 to size or shape. Break down the fragments, each grain will 
 contain particles of carbonate of lime, which will be throughout 
 the same. On the other hand, the division of a vegetable or an 
 
5 
 
 animal, shews parts heterogeneous or dissimilar. In different 
 parts there will be found muscles, bones, arteries, blossoms, 
 leaves, bark, pith, &c. 
 
 Organized beings cannot live, or exist in their natural condi- 
 tion, unless solids and liquids enter at once into their composi- 
 tion. The co-existence of these two elements is necessary; and 
 living bodies always contain a liquid mass more or less con- 
 siderable, and incessantly agitated by the motion of the solid 
 and living parts. It is in fact impossible to conceive life exist- 
 ing, without a complicated combination of solids and fluids; 
 and without admitting in the former, the faculty of being affec- 
 ted by impressions from the latter, and the power of acting in 
 consequence of those impressions. The water which penetrates 
 into mineral substances, does not form a necessary part of 
 them, and one cannot adduce in proof of the existence of liquids 
 in that class of substances, the water of crystallization, though 
 intimately combined, and rendered solid in the crystallized 
 substances. 
 
 These inorganic and homogeneous substances, formed of 
 particles similar to one another, when resolved by decompo- 
 sition into their last elements, possess a great simplicity of 
 inward nature. Among them are ranked all the substances 
 which do not admit of analysis; the mineral compounds are 
 often binary, as the greater part of saline substances; some- 
 times they are ternary, but seldom quaternary; while the most 
 simple vegetable contains at least three constituent principles, 
 oxygen, hydrogen and carbon, and no being possessed of life, 
 consists of less than four, oxygen, hydrogen, carbon and azote. 
 In the degree of composition, nature appears therefore to rise 
 in gradations, from the mineral to the vegetable, and from the 
 latter to the animal kingdom. The complicated nature of the 
 latter, the multiplicity of their elements account for their ten- 
 dency to alteration. Minerals are not subject to change, unless 
 they are acted upon by external causes. Endowed with a vis 
 inertiae, they continue in one condition without change. The 
 state of organized bodies is incessantly varying. Their internal 
 parts contain an active laboratory, in which a number of instru- 
 ments are constantly transforming into their own substance, 
 nutritious particles. Besides that tendency to alteration in living 
 
6 
 
 animals and vegetables, when deprived of life, they become 
 decomposed, by a process of fermentation, which begins in 
 their internal parts, and by which their nature is changed in 
 proportion to the complication of their structure, and the greater 
 number and volatility of their constituent principles. 
 
 All the parts of a living body, whether of an animal or a 
 vegetable, have a natural tendency to a common object, the 
 preservation of the individual and of the species: each of the 
 organs, though provided for a peculiar action, concurs in this 
 object; and life in general, or life properly so called, is the 
 result of that series of concurring and harmonic actions. On 
 the contrary, each part of an inorganic mass, is independent of 
 the other parts, to which it is united, only by the force or 
 affinity of aggregation. When such a part is separated from the 
 rest, it maintains all its characteristic properties, and differs 
 only by its size, from the mass to which it no longer belongs. 
 
 Among animals and vegetables, all the individuals of the. 
 same class, appear to have been formed after the same model; 
 their parts are equal in number, and resemble each other in 
 colour; their differences are slight and evanescent. The forms 
 peculiar to organized beings are therefore invariably determin- 
 ed, and when nature departs from them, she never does so, to 
 such a degree, as in the shapes of minerals. The veins of mines 
 are never precisely alike, as the leaves of vegetables or the 
 limbs of animals. Crystals formed from similar substances, as- 
 sume very different shapes equally distinct and precise. Carbo- 
 nate of lime, for example, assumes according to circumstances 
 the shape of a rhomboid, that of a six sided regular prism, that 
 of a solid, terminated by twelve scaleni triangles, that of a 
 different dodecahedron with pentagonal faces, &c. as may be 
 seen at large in the writings of Haiiy. 
 
 A powerful inward cause, seems to arrange the constituent 
 parts of animal and vegetable bodies, by a determinate rule, in 
 s«ch a manner that they shall present a surface, more or less 
 completely rounded. Minerals often take their form, from ex- 
 ternal bodies, and when an especial force assigns it to them, as 
 in crystals, their surfaces are flat and angular. When the crys- 
 tallization is disturbed, and the molecules of the crystals are 
 driven tumultuously together, the geometrical form is impaired. 
 
7 
 
 the parts are rounded, which would have been ternninated 
 by angles, if a slow and tranquil crystallization had allowed 
 of regular aggregation: and as M. Haiiy has remarked, these 
 waving outlines, these roundings, so frequent in vegetables and 
 plants, where they belong to beauty of form, are, in minerals, 
 indication of defects. True beauty, in these beings, is characte- 
 rized by the straight line, and it is on good grounds that Rome 
 de Lisle* has said of this sort of line, that it seems to have an 
 especial determination to the mineral kingdom. 
 
 Amongst all the characteristics which distinguish the two 
 great divisions of natural bodies, the most absolute, and the 
 most palpable, is that which is drawn from the manner of 
 growth and of nourishment. Inorganic bodies grow only by 
 accretion, that is, by the accession of new layers to their 
 surface, whilst the organic, in virtue of its vital powers, re- 
 ceives into intimate combination, and is penetrated and per- 
 vaded, by the substance it assimilates to itself. In animals and 
 plants, nutrition is the effect of an internal mechanism: their 
 growth, is a development from within. In minerals, on the 
 contrary, growth cannot claim the name of development: it 
 goes on externally, by successive addition of new layers; it is 
 the same being, assuming other dimensions, whilst the organic 
 body is renewed in its growth. 
 
 Living bodies spring from a germ, which at first, was part of 
 another being, from which it detaches itself, for the sake of its 
 own development and growth. From the first, they are already 
 aggregates. Inorganic bodies have no germ: they are made up 
 of distinct parts brought together; they have no birth, but a 
 multitude of molecules, collecting into one, compose masses of 
 various bulk and figure. 
 
 Organized bodies alone can die; all have a duration, deter- 
 mined by their own nature; and this duration is not like that of 
 minerals, proportioned to the bulk and density: for, if man has 
 not the life of the oak, whose substance much exceeds his in 
 density, neither does he equal the life of many animals, such as 
 fishes, whose flesh is of inferior consistence to his own: and he 
 lives longer than the large quadrupeds, though his bulk is less.. 
 
 Crist allograph! e. Tom. I. p. 94. 
 
8 
 
 Finally, inorganic are essentially distinguished from organic 
 bodies, by the want of these peculiar powers or properties of 
 living nature; powers, which uphold the equilibrium of the 
 whole system of nature, as I shall explain more at large, when 
 I have considered the differences that mark the two divisions 
 of the organic kingdom, vegetables and animals. 
 
 § IV. DIFFERENCES BETWEEN VEGETABLES AND ANBIALS. 
 
 These are much fewer, less absolute, and therefore more 
 difficult to establish. There is, in fact, very little difference 
 between a zoophyte, and a plant, and there is a much wider 
 distance in their internal economy, between man, who stands at 
 the height of the animal scale, and the polypus on its lowest 
 line, than between the polypus and a plant. There lies between 
 organized and inorganic bodies, a space, which is not to be 
 filled up by figured stones, nor by lithophytes, nor by crystals, 
 in which some naturalists have thought, they saw a beginning 
 of organization. Whilst, at the extremity of the animal chain, 
 are found beings, fixed, like plants, on the spot of their birth, 
 sensitive and contractile, like the sensitive and some other 
 plants, and reproduced like them from slips. Yet we are able to 
 state some differences, sufficiently marked, to assign to the 
 vegetable kind, a character of their own, which will not suit the 
 individuals of either of the other kingdoms. 
 
 Their nature, more complex than that of minerals, is less so 
 than that of animals: the proportion of the solids to the liquids, 
 is greater than in these last: accordingly they retain, long after 
 death, their form and bulk, only that they grow lighter. The 
 solids are, in man, nearly a sixth of the whole body: his carcase, 
 decomposed by putrefaction, remains a little earth, and a light 
 skeleton, when the ground and the air have drawn from it all 
 its juices. A tree, on the contrary, is more than three parts of 
 its substance, solid wood. It has been dead for ages, and yet, in 
 our buildings, it preserves its form and size, though by drj'ing, 
 it has lost a little of its weight. 
 
 Their constituent principles, as they are less in number, are 
 also less diffusible. In fact, azote, which is predominant in 
 animal substances, is a gaseous, and volatile principle, whilst 
 carbon, the base of vegetable substance, is fixed and solid. This 
 
9 
 
 circumstance, added to the smaller quantity of their liquids, 
 explains the long duration after death, of vegetable substances. 
 
 But of all the characteristics which have been employed in 
 establishing the limits of animal and vegetable nature, there is 
 one quite sufficient to distinguish these two great classes of 
 beings, but which has not yet been allowed the weight it 
 deserves. 
 
 The zoophyte, which, fixed in his rocky habitation, cannot 
 change its place, confined to partial movements, which certain 
 plants are possessed of, which besides, has not that sensitive 
 unity, so remarkable in man, and in the animals, which nearest 
 resemble him in their organization; the zoophyte, whose name 
 indicates an animal-plant, is totally separated from all beings of 
 the vegetable kingdom, by the existence of a cavity, in which 
 alimentary digestion is carried on, a cavity by the surface of 
 which is an absorption, an imhihition, far more active than that 
 which takes place by the external surface of the body. From 
 this shapeless animal, up to man, nutrition is effected by two 
 surfaces, and especially the internal, whilst in the plant, nutri- 
 tion, or rather the absorption of nutritive principles, is only by 
 the external surface. 
 
 Every animal may be considered, in extreme abstraction, as 
 a nutritive tube, open at the extremities*; the whole existence 
 of the polypus seems reduced to the act of nutrition, as its en- 
 tire substance is employed in the formation of an alimentary 
 tube, of which the soft parietes, extremely sensible and contrac- 
 tile, are busied in appropriating to themselves, by a sort of 
 absorption, the substances which are brought into it. From the 
 worm up to man, the alimentary canal is a long tube, open at the 
 extremities; at first, only of the length of the body of the animal, 
 not bent at all in passing from the head to the tail, and carried 
 on towards the mouth, and towards the anus, with the external 
 covering of the body, but soon returning upon itself, and stretch- 
 ing out into length, far beyond that of the body which contains it. 
 
 * Lacepede, Histoire Naturelle des Poissons, tom. 1. There may be brought, 
 against this principle, the instance of some zoophytes, such as spunges, &c.; 
 but do these bodies really belong to the animal kingdom? and should not we 
 be warranted in rejecting them, by the want of the alimentary cavity, the 
 essential characteristic of animal existence? 
 
 B 
 
10 
 
 It is in the thickness of the parietes of this animated tube, be- 
 twixt the mucous membrane that lines it inwardly, and the skin 
 with which this membrane is continuous, that all the organs are 
 placed, which serve for the transmission and elaboration of 
 fluids, together with the nerves, the muscles, in short, all that 
 serves for the carrying on of life. As we rise, from the white- 
 blooded animals, to the red and cold-blooded, from these to the 
 warm-blooded, and from these to man, we see a progressive 
 multiplication of the organs that are contained within the thick- 
 ness of the parietes of the canal: — if we follow, on the other 
 hand, the descending scale, we see this structure gradually sim- 
 plified, till we arrive at last at the polypus, and find in it only 
 the essential part of animal existence. The simplicity of its or- 
 ganization is such, that it may be turned inside out, and the 
 external be made the internal surface; the phenomena of nutri- 
 tion, which are the whole life of the animal, go on, from the 
 close analogy between the two surfaces; unlike to man and the 
 greater part of animals, in whom the skin and the mucous mem- 
 branes, though growing into each other, though linked by close 
 sympathies, are far from possessing a complete analogy of 
 structure, or a capacity for the interchange of functions. 
 
 Man, then, and the whole animal kind carry about within 
 themselves, the supply of their subsistence; and absorption, by 
 an inward surface, is their distinguishing characteristic. It is in- 
 accurate to ascribe to Boerhaave the comparison of the diges- 
 tive system of animals, to the soil in which plants suck up the 
 juices that feed them, and the chylous vessels, to real internal 
 roots. I find the same thought well expressed in the work on 
 humours, which, justly or falsely, bears the name of Hippo- 
 crates. ^lemadmodum terra arbortbus^ ita animalibus ventricu- 
 lus. 
 
 The digestive tube, that essential part of every animal, is the 
 part of which the existence and action are the most independent 
 of the concurrence of the other organs, and to which the proper- 
 ties of life seem to adhere, if one may say so, with most force. 
 Haller,* who has made so manj'^ and such interesting inquiries 
 into the contractile power of the muscular organs, examining 
 
 opera minora, 3 vol. 4to. 
 
11 
 
 them under the tvva-fold relation of their irritability, as it is 
 more or less lively, or more or less lasting, looks on the heart, 
 as the one in which these two conditions are found in the highest 
 combination. He gives the second place to the intestines, the 
 stomach, the bladder, the uterus, and the diaphragm, and, after 
 these, all the muscles under the command of the will. I had at 
 first admitted, with every other writer, this classification of the 
 contractile parts; but more than a hundred experiments on 
 living animals have satisfied me, that the intestines are always 
 the last part in which the traces of life may be discovered. What- 
 ever may be the sort of death by which they are destroyed, 
 peristaltic motions, undulations, are still continued in this canal, 
 while the heart has already ceased to beat, and the rest of the 
 body is all an inanimate mass. M. Jurine had already observed 
 on the pulex monoculus, that, of all the parts of the body of 
 this little white-blooded animal, the intestines were the last to 
 die. 
 
 If the intestinal tube be the ultimum moriens, if it be the last 
 organ in which life lingers and goes out, it is to it we ought to 
 direct, in preference, the stimulants that are capable of recalling 
 it in case of asphyxia. I think that, after the blowing of pure air 
 into the lungs, the means that ought next to be attended to, is 
 the injection of acrid and irritating clysters, thrown in with 
 force. The large intestines are connected with the diaphragm 
 by a close sympathy, as is proved by the phenomena of fecal 
 evacuation; the irritation of them is the surest means of accele- 
 rating it; and this irritation is the easier, as the alimentary ca- 
 nal is the last part that is forsaken by life. 
 
 § V. OF LIFE, 
 
 After having thus laid down, between inorganic bodies and 
 organized living beings, and again between animal and vege- 
 table nature, a line of demarcation that cannot be mistaken, let 
 us endeavour to exalt ourselves to the conception of Life; and, 
 for accuracy of thought, let us, in some sort, analyse it, by stu- 
 dying it in all the beings of nature that are endowed with it. In 
 this study, of which I may be allowed to state, in advance, the 
 results, we shall see life composed at first of a small number of 
 phenomena, simple as the apparatus to which it is given in 
 
12 
 
 charge; but soon extending itself as its organs or instruments 
 are multiplied, and as the whole organic machines become more 
 complex; the properties which characterize it and bear witness 
 of its presence, at first obscure, becoming more and more mani- 
 fest, increasing in number as in development and energy; the 
 field of existence enlarging, as from the lower beings we re- 
 ascend to man, who, of all, is the most perfect: and observe, 
 that by this term of perfection, it is simply meant that the living 
 beings to which we apply it, possessed of more means, present 
 also more numerous results and multiply the acts of their exist- 
 ence; for in this wonderful order of the universe, every being 
 is perfect in itself, each being is constructed most favourably for 
 the purpose it is to fulfil; and all is equally admirable, in living 
 and animated nature, from the lowest vegetation to the subli- 
 mity of thought. 
 
 What does this plant present to us that springs up, and grows, 
 and dies every year? A being whose existence is limited to the 
 phenomena of nutrition and reproduction; a machine construct- 
 ed of a multitude of vessels, straight or winding, capillary tubes, 
 through which the sap is filtrated and other juices necessary to 
 vegetation; these vegetable liquors ascend, generally, from the 
 roots, where their materials are taken in, to the summit, where 
 what remains from nutrition is evaporated by the leaves, and 
 what the plant could not assimilate to itself is thrown off in 
 transudation. Two properties direct the action of this small 
 number of functions: a latent and faint sensibility, in virtue of 
 which, each vessel, every part of the plant, is affected in its own 
 way by the fluids with which it is in contact: a contractility as 
 little apparent, though the results prove irrefragably its exist- 
 ence; a contractility, in virtue of which, the vessels, sensible to 
 the impression of liquids, close or dilate themselves, to effect 
 their transmission and elaboration. The organs allotted to re- 
 production, animate, for a moment, this exhibition: more sen- 
 sible, more irritable, they are visibly in action; the stamina, or 
 male organs, bow themselves over the female organ, the pistil, 
 shake on the stigma their fertilizing dust, then straighten, retire 
 from it, and die with the flow'er, which is succeeded by the seed 
 or fruit. 
 
13 
 
 This plant, divided into many parts, which are set in the 
 . earth with suitable precautions, is reproduced and multiplied 
 by slips, which proves that these parts are little enough depend- 
 ent on each other; that each of them contains the set of organs 
 necessary to life, and can exist alone. The different parts of a 
 plant can live separately, because life, its simpler organs and 
 properties are diffused more equably, more uniformly, than in 
 ' animals like man, and its phenomena are connected in a less strict 
 and absolute dependance. I myself have witnessed a very curi- 
 ous fact, which confirms what I have said.* A vine, trained 
 against the eastern wall of a forge, shot into the building a few 
 branches. These branches, which entered by strait enough pas- 
 sages, were covered with leaves in the middle of the hardest 
 winters; and this premature but partial vegetation went through 
 all its periods, and was already in flower, when the part that 
 remained without, was beginning to bud with the spring. 
 
 If we pass from the plant to the polypus, which forms the last 
 link of the animal chain, we find a tube of soft substance, sensi- 
 ble and contractile in all its parts, a life and an organization at 
 least as simple as that of the plant. The vessels which carry the 
 
 * Vegetable life compared in its means and in its results, to the life of ani- 
 mals, would throw the greatest light on many phenomena, which it is stilt 
 difficult for us to conceive and to explain. The treatment of disease in plants, 
 for which as much would be gained by these enquiries, is almost entirely 
 surgical. When, to make vegetation more fi-uitful, the gardener prunes a 
 luxuriant branch; when the peasants of the Cevennes, as M. Chaptal has ob- 
 served, burn the inside of their chesnut trees to stop the progress of a destruc- 
 tive caries; when the actual cautery is applied to the really ichorous and foul 
 ulcers of many trees, &c. it is to the organs of inward life (or that which car- 
 ries on the process of assimilation,) the only life of vegetables, that surgery is 
 applied; while, on the contrary, in man and animals, it is to the derangement 
 of the external organs that the remedy is directed. 1 shall conclude this note 
 with an observation on the wounds of plants. Like those of the human body, 
 they are much less dangerous when their surface is smooth, than when their 
 edges are hacked, torn, or bruised. Trees felled with the saw, will hardly 
 shoot up from the stool, which always furnishes a better growth wdien an axe 
 has been employed. The saw lacerates the vegetable texture, and its violent 
 and distressing action on the fibres, extending towards the roots, affects, more 
 or less, the organization. The uneven surface of a tree felled in this manner, 
 holds w'et, as injurious to the trunk, wdiich it rots, as a too great quantity of 
 pus, which bathes constantly the surface of a wound, checks the process of 
 granulation, and resists cicatrization. 
 
14 
 
 liquids, the contractile fibres, the trachea^ which give access to 
 the atmospheric air, are no longer distinctly to be traced in this 
 almost homogeneous substance. There is no organ especially 
 allotted to the reproduction of the kind. Moisture oozes from 
 the internal surface of the tube, softens and digests the aliments 
 which it finds there; the whole mass draws in nourishment from 
 it; the tube then spontaneously contracts, and casts out the 
 residue of digestion. The mutual independence of parts is abso- 
 lute and perfect: cut the creature into many pieces, it is repro- 
 duced in every piece; for each becomes a new polypus, organiz- 
 ed and living, like that to which it originally belonged. These 
 gemmiparous animals enjoy, in a higher degree than plants, the 
 faculties of feeling and of self-motion; their substance dilates 
 and lengthens, and contracts, according to the impressions they 
 receive. Nevertheless, these spontaneous movements do not 
 suppose, any more than those of the mimosa, the existence of re- 
 flexion and will: like those of a muscle detached from the thigh 
 of a frog and exposed to galvanic excitation, they spring from 
 an impression which does not extend beyond the part that feels 
 it, and in which sensibility and contractility are blended and 
 lost in each other. 
 
 From this first degree of the animal scale, let us now ascend 
 to worms. We have no longer a mere animated pulp shaped 
 into an alimentary tube; parcels of contractile or muscular fibres, 
 a vessel divided by several constrictions into a series of vesicles, 
 which empty themselves one into another, by a movement of 
 contraction that begins from the head, or the entrance of the 
 alimentary canal, and proceeds towards the tail, which answers 
 to the anus, a vessel, from which, in all probability, are sent out la- 
 teral ramifications, a spinal marrow equally knotted, or compos- 
 ed of a chain of ganglions, stigmas, and tracheae, analogous to the 
 respiratory organs of plants, and in some, even gills: all shews 
 clearly an organization further advanced and more perfect: sen- 
 sibility and contractility are more distinct; the motions are no 
 longer absolutely automatic; there are some which seem to sup- 
 pose choice. The worm too, may be divided into many pieces; 
 each will become a separate and perfect worm, a head and tail 
 growing to each; but this division has its term, beyond which 
 there is no longer complete regeneration. It cannot, therefore. 
 
15 
 
 be pushed so far as in the polypi. The substance of the worm 
 being formed of elements more dissimilar, it may be that too 
 small a portion does not contain all that is necessary to consti- 
 tute the animal. 
 
 The crustaceous tribes, and among them the lobster, disco- 
 vers a more complex apparatus of organization. Here you will 
 find distinct muscles, an external articulated skeleton, of which 
 the separate parts are moveable upon each other, distinct nerves, 
 a spinal marrow with bulgings, but, above all, a brain and a 
 heart. These two organs, though imperfect, assign the animal to 
 an order much above that of worms. The first becomes the seat 
 of a sort of intelligence; and the lobster acts evidently under 
 impulses of will, when, attracted by a smell, it pursues a distant 
 prey^ or when it flies a danger discovered to it by its eyes. 
 There are viscera accompanying the intestinal tube, which give 
 out to it liquids that concur in alimentary digestion. Sensibility 
 and contractility present each two shades: in fact, the parts of 
 the animal are obedient to the internal stimuli, feel the impres- 
 sion of fluids, and contract to impel them; on the other hand, by 
 its nerves and locomotive muscles, the lobster places itself in 
 connexion with the objects that surround it. The phenomena of 
 life are linked together by a strict necessity: it is no longer pos- 
 sible to separate the creature into two parts, of which each may 
 continue to live; there are but few parts you may cut off without 
 injury, while you spare the central foci of life. So, if you take 
 off a claw, you observe soon a little granulation, which swells 
 and is developed, and which, soft at first, is soon clothed in a 
 calcareous covering, like that which encloses the rest of its body. 
 This partial regeneration is frequently to be seen. 
 
 If from white-blooded animals we go on to the red and cold- 
 blooded, such as fishes and reptiles, we see this power of repro- 
 duction becoming more and more limited, and life more involved 
 in organization. In fact, if you cut off a part of the body of a 
 fish, the tail of a serpent, or the foot of a frog, the separated 
 parts are either not supplied at all, or very imperfectly repro- 
 duced. All these creatures maintain, with the medium in which 
 they live, relations of more strict dependence. Gills in these, 
 lungs in others, are added to a heart, nor are less essential to life. 
 However, the action of these chief organs is not so frequent, 
 
16 
 
 nor of momentary necessity for the continuance of life. The ser- 
 pent passes long winters, torpid with cold, in holes where he has 
 no air, without breathing, without any motion of life, and in all 
 appearance dead. These creatures, like all reptiles, are able to 
 breathe only at long intervals, and to suspend, for a time, the 
 admission of air, without risking their existence. Here the vital 
 powers are distinct and strong, and differ from those of the more 
 perfect animals and of man, by very slight shades; the heart and 
 the vessels of the fish feel and act within him, without his con- 
 sciousness. Further, he has senses, nerves, and a brain, from 
 which he has intimation of whatever can affect him; muscles and 
 hard parts, by the action of which he moves, and changes his 
 place, adapting himself to the relations that subsist between the 
 substances around him and his own peculiar mode of existence. 
 
 We are come, at last, to the red and warm-blooded animals, 
 at the head of which are the mammiferse and man. They are en- 
 tirely alike, save some slight differences in the less essential 
 organs. There is none that has not the vertebral column, four 
 limbs, a brain which fills, exactly, the cavity of the skull, a 
 spinal marrow, nerves of two sorts, five senses, muscles, partly 
 obedient to the will, partly independent in their action; add to 
 these, a long digestive tube coiled upon itself, furnished at its 
 mouth with agents of saliva and mastication; vessels and lym- 
 phatic glands, arteries and veins, a heart with two auricles, and 
 two ventricles, lobular lungs, which must act incessantly in im- 
 pregnating the blood, that passes through them, with the vital 
 part of the atmosphere, which, if it fail, life is suspended, or 
 gone. None of their organs live but while they partake in the 
 general action of the system, and while they are under the in- 
 fluence of the heart. All die, irrecoverably, when they are parted 
 from the body of the animal, and are in no way replaced; what- 
 ever some physiologists may have said on pretended regenera- 
 tion of the nerves, and some other parts. 
 
 Every thing that is important to life, is to be found in these 
 animals; and as the most essential organs are within, and con- 
 cealed in deep cavities, a celebrated naturalist was correct in 
 sa}dng, that all animals are essentially the same, and that their 
 differences are in their external parts, and chiefly to be observed 
 n their coverings and in their extremities. 
 
17 
 
 The human body, consisting of a collection of liquids and 
 solids, contains of the former, about five-sixths of its weight. 
 This proportion of the liquids to the solids may, at first sight, 
 appear to you beyond the truth: but consider the excessive de- 
 crease of size of a dried limb: the glutseus maximus, for example, 
 becomes, by drying, no thicker than a sheet of paper. The li- 
 quids, which constitute the greatest weight of the body, exist 
 before the solids: for, the embryo which is at first in a gelatinous 
 state, may be considered as fluid; besides, it is from a liquid 
 that all the organs receive their nourishment and repair their 
 waste. The solids, formed from the liquids, return to their 
 former state, when, having for a sufficient length of time, form- 
 ed a part of the animal, they become decomposed by the nutri- 
 tive process. Even from this slight view of the subject, fluidity 
 is seen to be essential to living matter, since the solids are uni- 
 formly formed from the fluids, and eventually return to their 
 former state. Solidity is then only a transient condition and an 
 accidental state of organized and living matter, and this circum- 
 stance affords to the humoral pathologists ample opportunities 
 of embarrassing their opponents with many objections, not easi- 
 ly answered. Water forms the principal part and the common 
 vehicle of all the animal fluids, it contains saline substances in 
 a state of solution, and even animal matter itself is found in it 
 fluid, and that in three different conditions, under the form of 
 gelatine, of albumine, or Jibrine. The first of these substances, 
 solidified, forms the basis of all the organs of a white colour, to 
 which the ancients gave the name of spermatic organs, such as 
 the tendons, the aponeurosis, the cellular tissue, and the mem- 
 branes. Albumine exists in abundance in almost all the hu- 
 mours; the fibrine of the blood is the cement which is employed 
 in repairing the waste of a system of organs, which, in point of 
 bulk, hold the first rank among the constituent parts of the hu- 
 man body — I mean the muscular system. The chemists suspect, 
 and not without reason, that the animal matter passes succes- 
 sively through the different states of gelatine, albumine and 
 fibrine; that these different changes depend on the progressive 
 animalization of the animal matter, which, at first gelatinous, a 
 hydro-carbonous oxyde, containing no azote, and acidifiable by 
 fermentation, becomes more closely coaibined with oxygen, 
 
 C 
 
18 
 
 takes up azote, so as to become albumen, subject to putrefaction, 
 and finally fibrine, by a super-addition of the same principles. 
 
 The solid parts are formed into different systems, to each of 
 which is intrusted the exercise of a function of a certain degree 
 of importance. Limiting the term organic apparatus, or system, 
 to a combination of parts which concur in the same uses, we 
 reckon ten, viz. — the digestive apparatus, consisting essentially 
 of the canal which extends from the mouth to the anus; the ab- 
 sorbent^ or lymphatic system, which is formed of the vessels or 
 glands of that name; the circulatory system, which consists of 
 an union of the heart, the veins, the arteries and the capillary 
 vessels; the respiratory^ or pulmonary system; the glandular, or 
 secretory system; the sensitive system, including the organs of 
 sense, the brain and spinal marrow; the muscular system, or that 
 of motion, including not only the muscles, but their tendons and 
 aponeuroses; the osseous system, including the appendages of 
 the bones, the cartilages, the ligaments and the synovial capsules; 
 the vocal system, and the sexual or generative system, different 
 in the two sexes. Each of these organic systems contains in its 
 structure several simple tissues, “ or similar parts,” as the an- 
 cients called them; these tissues in man, may be enumerated as 
 follows: cellular tissue^ nervous tissue, muscular tissue, besides 
 that horny substance which constitutes the basis of the epidermis, 
 the nails and the hair. 
 
 These four substances may be considered as real organic ele- 
 ments, since with our means of analysis, we never can succeed 
 in converting any one of these substances into another. The 
 cerebral pulp is not convertible into a horny substance, into cel- 
 lular substance, or into muscular fibre, neither can any one of 
 these tissues ever be converted into cerebral pulp. The bones, 
 the cartilages, the ligaments, the tendons, the aponeuroses, may, 
 by long maceration, be decomposed into cellular substance. 
 Muscular fibres are not subject to that alteration, nor is the 
 nervous or cerebral pulp; the horny substance also resists that 
 change. Every thing, therefore, leads us to acknowledge these 
 four constituent principles in our organs. 
 
 The primitive or simple tissues, variously modified, and com- 
 bined in different quantities, and in various proportions, consti- 
 tute the substance of our organs. Their number is much more 
 
19 
 
 considerable, according to Bichat, whose happiest conception 
 was this analysis of the human organization. This physiologist 
 reckoned in the human economy, no fewer than twenty-one 
 general or generating tissues. But it is evident, that this analysis 
 is carried too far; that the tissues of which the skin and the hair 
 are formed, are exactly of the same nature, are analogous in 
 their properties, and are nourished in a similar manner; that the 
 cellular tissue is the common basis of the osseous, cartilaginous, 
 mucous, serous, synovial, dermoid, &c. 
 
 It must be confessed, that this separate consideration of each 
 organic tissue has furnished him with new ideas, ingenious ana- 
 logies and useful results, and that his “ Anatomic generale,” in 
 which those researches are contained, is his chief title to glory. 
 That glory would be complete, if in that book, and yet more, in 
 his other works, he had done his predecessors, as well as his 
 contemporaries, the justice they had a right to expect from him. 
 
 The simple, or elementary fibre, about which so much has 
 been written, may be considered as the philosopher’s stone of 
 physiologists. In vain, has Haller himself, in his pursuit of his 
 chimera, told us, that the elementary fibre is to the physiologist 
 what the line is to the geometer, and, that as all figures are form- 
 ed from the latter, so are all the tissues formed from this fibre; 
 Fibra enim physiologo id est quod linea geometr a ^ ex qua nempe 
 Jigurce omnes oriuntur. The mathematical line is imaginary, and 
 a mere abstraction of the mind, while the elementary fibre is al- 
 lowed a material or physical existence. Nothing, therefore, can 
 make us admit the existence of a simple, elementary, or primi- 
 tive fibre, since our senses shew us, in the human organization, 
 four very distinct materials. 
 
 Among the organs, whether single or combined in systems, 
 which enter into the human organization, there are some whose 
 action is so essential to life, that, with the cessation of that ac- 
 tion, life at once becomes extinct. These primary systems, whose 
 action regulates that of all secondary systems, are as numerous 
 in man as in the other warm-blooded animals. None of them 
 can act, unless the heart sends into the brain a certain quantity 
 of blood, vivified by the contact of atmospherical air in the pul- 
 monary tissue. Every serious wound of the brain or heart, every 
 lasting interruption to the access of blood into the former of 
 
20 
 
 these organs, Is invariably attended with death. The oxydation 
 of the blood, and its distribution into all the organs, is conse- 
 quently the principal phenomenon, on which the life of man and 
 of the most perfect beings depend. 
 
 § OF THE VITAL PROPERTIES; SENSIBILITY AND 
 CONTRACTILITY. 
 
 By sensibility is meant that faculty of living organs, which 
 renders them capable of receiving from the contact of other bo- 
 dies, an impression stronger, or fainter, that alters the order of 
 their motions, increases or diminishes their activity, suspends, 
 or directs them. Contractility is that other property by which 
 parts excited, that is, in which sensibility has been called into 
 action, contract or dilate, in a word, act, and execute motions. In 
 the same manner, as we have not always a consciousness of the 
 impressions received by our organs, and as, for example, no 
 sensation informs us of the stimulating impression by which the 
 blood calls the heart into action, so it is by reflexion only, that 
 we are induced to admit the existence of certain motions; of 
 those, for instance, by which the humors, when they have reach- 
 ed the smallest vessels, become incorporated into the tissue of 
 our organs. These motions, to make use of an ingenious com- 
 parison, resemble those of the hour-hand, compared with the 
 second-hand of a watch. The hour-hand appears motionless, and 
 yet in twelve hours it describes the whole circumference of the 
 dial plate, round which the other hand moves in one minute, 
 with a motion that is visible. 
 
 In considering life through the great series of beings that pos- 
 sess it, we have seen that those in which it is most limited, or 
 rather in which it consists of the least number of actions and 
 phenomena, vegetables, for instance, and animals like the polv 
 pus, which have no brain, no distinct nervous system, are at 
 once endowed with sensibility and contractility in all their 
 parts. All living beings, all the organs which enter into their 
 composition, are impregnated, if we may be allowed the expres- 
 sion, with these two faculties, necessarily co-existing, and which 
 shew themselves by internal and nutritive motions, obscure, in- 
 deed, and to be distinguished only by their effects. These two 
 faculties appear to exist in the degree absolutely required for 
 
21 
 
 enabling the fluids that pervade all the parts of a living body, to 
 induce the action by which these parts are to assimilate such 
 fluids. It is clear, that the two properties of feeling and of mo- 
 tion are indispensable to all the parts of the body. They are 
 properties universally diffused through organized and living 
 matter, but they exist without possessing any peculiar organ or 
 instrument of action. Were it not for these two faculties, how 
 would the different parts act on the blood, or on the fluid which 
 supplies its place, so as to obtain from it the materials subser- 
 vient to nutrition and the different secretions? These faculties 
 are therefore given to every thing that has life — to animals, to 
 vegetables, to man in his waking hours, or in his most profound 
 sleep, to the foetus, to the child that is born, to the organs of the 
 assimilating functions, and to those which connect us with sur- 
 rounding beings. Both these faculties, obscure, and inseparable, 
 preside over the circulation of the blood, of the fluids, and, in 
 short, over all the phenomena of nutrition. 
 
 Though this kind of sensibility is always latent or concealed, 
 it is otherwise with regard to contractility, which may be sensi- 
 ble or otherwise. The bone, which takes up the phosphate of 
 lime, to which it owes its solidity, exerts that action without our 
 being aware of its taking place, except by its effects: but the 
 heart which feels the presence of the blood, without any con- 
 sciousness, on our part, ©f such sensation, exerts motions that 
 are easily perceptible, but over which we have no controul, 
 either to suspend or accelerate them. 
 
 Vital properties in so weak a degree, would not have been 
 sufficient to the existence of man and of the animals which re- 
 semble him, obliged to keep up multifarious intercourse with 
 every thing that surrounds them; thus they enjoy a very supe- 
 rior kind of sensibility, by means of which the impressions 
 which affect some of their organs are perceived, judged and 
 compared. This mode of sensibility might be more properly call- 
 ed perceptibility^ or the faculty of accounting to oneself for the 
 emotions which are experienced. It requires a centre to which the 
 impressions may be referred, and therefore it exists only in the 
 animals which, like man, have a brain or some organ in its stead; 
 so that the zoophytes and vegetables, wanting that organ, are 
 
22 
 
 equally destitute of this faculty. The polypi, and some plants, as 
 the sensitive, perform nevertheless certain spontaneous motions, 
 which seem to indicate the existence of volition, and conse- 
 quently of perceptibility. But these motions are the result of an 
 impression, which does not extend beyond the part in which it 
 is experienced, and in which sensibility and contractility are 
 blended. 
 
 The almost latent sensibility of certain parts of the body, can- 
 not be absolutely compared to that of vegetables; since those 
 organs whose sensibility is so imperfect, manifest in disease a 
 percipient sensibility, which shews itself by acute pain, and it is 
 even sufficient to change the stimulus to which they are accus- 
 tomed, to determine the occurrence of that phenomenon. Thus 
 the stomach, on the parietes of which, the food does not in health 
 produce any perceptible impression, becomes the seat of very 
 distinct sensation, and of dreadful pain, when a small quantity 
 of poisonous matter is introduced into it. In like manner, we 
 are not conscious of the impressions excited in the parietes of the 
 bladder or rectum, by the collection of urine or fcecal substances, 
 except when their contents have become sufficiently irritating 
 by their presence, to excite, in a certain degree, those irritable 
 and sentient cavities, and to transform their obscure, into a very 
 distinct sensibility. Is there not reason to suspect, that our un- 
 consciousness, in health, of the impressions made on our organs 
 by the fluids which they contain, depends on our being accus- 
 tomed to the sensations which they incessantly excite? so that 
 there remains but a confused perception, which in time disap- 
 pears, and may we not, under that point of view, compare all 
 these organs to those of sight, hearing, smelling, tasting, and 
 touching, that are no longer irritable by stimulants, to which 
 they have long been habituated? 
 
 Two svstems of organs, very different in their uses and in 
 their qualities, enter into the composition of the human body; 
 they are as two living and united machines, the one, formed by 
 the organs of sense, the nerves, the brain, the muscles, and the 
 bones, serves to maintain its connexion with external objects; 
 the other, destined to internal life, consists in the digestive tube, 
 and the organs of absorption, circulation, respiration, and se- 
 
23 
 
 cretion.* The organs of generation in the two sexes form a se- 
 parate class, which, as far as relates to the vital properties, par- 
 takes of the nature of the other two. 
 
 By the organs of sense, and the nerves which form a commu- 
 nication between these organs and the brain, we are enabled to 
 perceive or to feel the impressions made on us by external ob- 
 jects; the brain, the true seat of that relative sensibility, which 
 might very justly be termed perceptibility^ or the perceptive 
 poxver^ when excited by these impressions, is able to irradiate 
 into the muscles the principle of motion, and to induce the ex- 
 ertion of their contractility. This property, which is under the 
 direction of the will, manifests itself by the sudden decurtation 
 of a muscle, which swells, hardens, and determines the motion 
 of those parts of the skeleton to which it is attached. The nerves 
 and the brain are essentially the organs of these two properties, 
 a division of the former is attended with a loss of sentiment and 
 voluntary motion in the parts to which they are distributed. The 
 other kind of sensibility is, on the contrary, quite independent 
 of the presence of nerves; it exists in all organs, although all do 
 not receive nervous filaments. It might even be asserted, that 
 the cerebral nerves are not at all essential to the life of nutrition; 
 the bones, the arteries, the cartilages, and several other tissues, 
 in which no nerves are seen to enter, are nourished equally well 
 with the organs in which they exist in considerable number; the 
 muscles themselves will carry on their own internal economy, 
 notwithstanding the division of their nerves; only, deprived of 
 those means of communication with the brain, they can no 
 longer receive from it the principle of voluntary contraction; in- 
 stead of that sudden, energetic and lasting decurtation which the 
 will determines in them, they become merely capable of those 
 quiverings called palpitations. 
 
 The anatomist who studies the nerves, with a view to ascer- 
 tain their termination, finds them all arising from the brain and 
 spinal marrow, and proceeding, by a longer or shorter course, 
 to the organs of motion or of sensation: let him take his scalpel 
 and dissect one of our limbs, the thigh, for instance, he will see 
 
 * This doctrine, which I believe ‘originated with the celebrated Bichat, will 
 be found more fully developed in his work, entitled “ Physiological Researches 
 on Life and Death.” Ed. 
 
24 
 
 the cords parting into numerous threads, most of which disap- 
 pear in the thickness of the muscles, whilst others, after creeping 
 for a time about the cellular tissue, which joins the skin to the 
 aponeurosis, end on the inward surface of the skin, of which 
 they compose the texture, and expand into sentient papillae on 
 its surface. The bones, the cartilages, the ligaments, the arte- 
 ries, and the veins, all those parts whose action is not under the 
 controul of the will, are without them. Nevertheless, all those 
 parts, which, in their natural state, send no perceptible impres- 
 sions to the brain, which, when once insulated, may be tied and 
 cut, without any sign of pain from the animal, and whose action 
 the will does not controul, are yet endued with a sensibility and 
 a contractility, which enable them, after their own manner, to 
 feel and to act, to recognize in the fluids that moisten them, 
 what is suited to their nourishment, and to separate that recre- 
 mentitious part which has suitably affected their particular mode 
 of sensibility. 
 
 In confining our attention then, to the consideration of a sin- 
 gle limb, we may easily satisfy ourselves of the existence of two 
 modes of feeling, as of two sorts of motion; a sensibility in virtue 
 of which, certain parts can send up to the brain, the impressions 
 they receive, to be there objects of consciousness; and another 
 sensibility belonging to all organs without exception, and all 
 that some of them possess, which is sufficient for the exercise of 
 the functions of nutrition, and by means of which they are 
 evolved, and are kept up in their natural state; two kinds of con- 
 tractility, appropriated to the two different kinds of sensibility: 
 The one, in virtue of which the muscles obedient to the will, ex- 
 ercise the contractions which it determines; the other, indepen- 
 dent of the will, manifests itself by actions, of which we have 
 no intimation, any more than of the impressions by which they 
 are determined- 
 
 The distinction being fairly laid down between sensibility 
 and contractility, it is easy to understand the origin of the end- 
 less disputes of Haller and his followers, about the parts of the 
 body, in man and animals, which are endowed with sensibility 
 and irritability. All the organs to which that learned physiolo- 
 gist has denied these propeities, as bones, tendons, membranes, 
 cartilages, and cellular membrane, &c. possess onh" that latent 
 
25 
 
 sensibility, and that obscure contractility, common to all living 
 beings, and without which, it is impossible to conceive life to 
 exist. In a state of health, they are utterly incapable of trans- 
 mitting to the brain perceptible impressions, and of receiving 
 from it the principle of manifest and sensible motion. It has 
 likewise been a matter of much dispute, whether sensibility and 
 contractility are qualities of nerves; if these parts are their only 
 instruments, and if their destruction is attended with a loss of 
 these two vital properties, in the parts to which they are trans- 
 mitted. We may answer in the affirmative, as far as relates to the 
 sensibility of perception, and the voluntary motion which is en- 
 tirely subservient to it, but that the existence of nerves is not at 
 all necessary to the exercise of the sensibility and contractility 
 which are indispensable to the assimilation of nutrition. 
 
 No part of the living body is absolutely insensible, but that 
 sensibility of every organ is so modified, that it is not affected 
 by the same stimuli. Thus, the eye is insensible to sound, and 
 the ear to light. A solution of tartar emetic, causes no disagree- 
 able impression to the conjunctiva; taken into the stomach, it ex- 
 cites convulsive motions, while an acid from which the stomach 
 does not suffer, proves a cause of irritation to the conjunctiva, and 
 brings on a violent inflammation of the eye. In the same manner, 
 purgatives pass along the stomach, without producing any effect 
 on that viscus, but they stimulate the alimentary canal. Can- 
 tharides have a specific action on the bladder; and mercury on 
 the salivary glands. Each part feels, lives, moves, after its own 
 way; in each, the vital properties appear under such shades and 
 modifications, that they may be looked upon as so many sepa- 
 rate members of the same family, concurring in one endeavour, 
 working for a common end, consentientia omnia (Hipp.) 
 
 The faculty of assigning a cause to the sensations, and that of 
 moving by volition, which man possesses in common with all 
 animals formed with a distinct nervous centre, are essentially 
 bound together. For suppose a living being, furnished with lo- 
 comotive organs, but without sensation, placed in the midst of 
 bodies, that every moment endanger its existence, without any 
 means of distinguishing them, it will hasten its own destruction. 
 If perceptibility could, on the other hand, exist independently 
 of motion, how dreadful would be the fate of such sentient be- 
 
 n 
 
26 
 
 ings, similar to the fabulous Hamadryads, ^vho, immoveably 
 fixed in the trees of our forests, received, without any power to 
 shun them, all the blows inflicted on their rustic abode. Dreams 
 place us sometimes in situations which give us a just idea of 
 their condition. A certain danger threatens our existence; an 
 enormous rock seems to detach itself, to roll and precipitate 
 itself on our frail machine; a frightful monster seems to pursue 
 us, and opens a yawning mouth to ingulf us. We struggle to 
 escape this imaginary danger, to avoid or to repel it, but an irre- 
 I sistible and unknown power, a mighty hand paralyses our 
 efforts, and keeps us rooted to the spot; it is a situation of horror 
 and despair, and we awaken overwhelmed with the uneasiness 
 which we have suffered. 
 
 As there is no part that does not feel, in a manner peculiar to 
 itself, so there is no one that does not act, move, or contract, in 
 a manner peculiar to itself; and the parts which have been found 
 without a power of motion analogous to muscular contractility, 
 have remained in that state of immobility, only for want of a 
 stimulus fitted to their peculiar nature. Some physiologists say 
 they have excited a distinct quivering, in the mesentery of a frog 
 and of a cat, by touching them, after they had been previously 
 moistened with alcohol, or muriatic acid. 
 
 In the operation for sarcocele,* I have often perceived that, 
 while with my left hand I supported the tumour, and with a 
 scalpel in the right, divided the spermatic chord, the tunica va- 
 ginalis shewed oscillatory contractions. It visibly contracts in 
 the operation for hydrocele. The injection of an irritating fluid 
 determines evident motions in the tunica vaginalis. The osseous 
 tissue, notwithstanding the phosphate of lime with which it is in- 
 crusted, is susceptible of a contraction, whose effects, though 
 slow, are nevertheless undeniable. After teeth have been shed 
 or extracted, the edges of the alveolar processes become thinned 
 
 • The contraction of the membrane, formed by the expansion of the cremas- 
 ter muscle, has doubtless assisted in rendering more distinct the appearance 
 in question. This effect must be particularly distinct, at the moment of dividing- 
 the spermatic chord. The contractions of the same muscle corrugate the skin 
 of the scrotum, when this pari is exposed to cold, and draw up the testicles 
 towards the inguinal rings. The contractility of the skin of the scrotum has 
 but little influence in producing this effect. 
 
27 
 
 from contraction, and the alveolar cavities disappear. These 
 facts appear to me to prove, still better than all the experiments 
 performed on living animals, (experiments of which, by the bye, 
 the results ought not too confidently to be applied to the economy 
 of man) what one should think of the assertions of Haller and 
 his followers, on the insensibility and inirritability of the serous 
 membranes, and of the organs of a structure analogous to their’s. 
 
 We will, at present, say nothing of the porosity, of the divisi- 
 bility, of the elasticity, and other properties which are common 
 to living bodies and inanimate substances. These properties are 
 never possessed in their whole extent, and in all their purity, if 
 that expression may be allowed. Their results are always influ- 
 enced by the vital power, which constantly modifies the effects 
 which seem to depend most immediately upon a physical, 
 chemical, or mechanical cause, or upon any other agent what- 
 soever. Not so with the truly vital extensibility, which is so 
 manifest in certain organs, as the penis and the clitoris. When 
 excited, they become turgid and dilated by the afflux of humours, 
 but that effect does not depend on a peculiar property, distinct 
 from sensibility and contractility. These parts dilate, their tissue 
 stretches under the actibn of these two properties, which would 
 occasion the same phenomenon in all other parts, if their struc- 
 ture were similar. 
 
 The same applies to caloricity, or that power inherent in all 
 living beings, of maintaining the same degree of heat, in vary- 
 ing temperatures. In consequence of which property, the human 
 body preserves its temperature, of from thirty to forty degrees 
 (of Reaumur’s scale) under the frozen climate of the polar 
 regions, as well as in the burning atmosphere of the torrid zone. 
 It is by the exercise of sensibility and of contractility, that is, by 
 the exercise of the functions over which these vital powers pre- 
 side, that the body resists the equally destructive influence of 
 excessive heat and cold. 
 
 If one were to admit caloricity as one of the vital properties, 
 because, according to Professor Chaussier, that power of pre- 
 serving a uniform warmth is a very remarkable phenomenon, 
 one might be led to suppose, a distinct cause or a peculiar pro- 
 perty to operate in producing other phenomena of no less im- 
 portance. 
 
28 
 
 Barthez and Professor Dumas have fallen Into the same error, 
 the former, in wishing to establish the existence of a power of 
 permanent situation in the molecules of muscular fibres; the 
 latter, in adding to sensibility and contractility a third property, 
 which he terms the power of vital resistance. Living muscles 
 are torn with much more difficulty than when dead, because the 
 contractility which these organs possess in the highest degree, 
 is incessantly tending to preserve the contact of the molecules, 
 the series of which forms the muscular fibre, and even to draw 
 them into closer connexion. This fact, which is brought forward 
 as a proof of the existence of a peculiar power, is easily ex- 
 plained, on the principle of contractility. 
 
 Organized and living bodies resist putrefaction, from the 
 very circumstance of their being endowed with life. The con- 
 tinual motion of the fluids, the re-action of the solids on the 
 fluids, the successive and continual renovation of the latter, by 
 the reception of new chyle, their constant purification by means 
 of the secretions, through which the products animalized in ex- 
 cess are parted with, such are the causes which prevent the pu- 
 trefactive action from taking place in bodies endowed with life, 
 notwithstanding the multiplicity and the volatility of their ele- 
 ments. Their preservation is therefore a secondary effect, and 
 depending on the exercise of the functions regulated by sensi- 
 bility and contractility. Nature is distinguished for deriving a 
 multitude of effects from a very small number of causes, it 
 therefore shews a very imperfect acquaintance with her laws, 
 to assign a separate cause to each fact. 
 
 The separation of the chyle, which takes place in the duode- 
 num, from the admixture of the bile with the alimentary sub- 
 stance, the vivification of the blood by respiration, the secretion 
 of the fluids in the conglobate glands, nutrition in the organs, 
 are so many acts of the living economy, to which one might 
 feel disposed to assign distinct causes; but these chemico-vital 
 processes, are so subordinate to sensibility and contractility, 
 that they are met with, only in organs endowed with these two 
 properties, and they take place, in a degree more or less per- 
 fect, according to the condition of these properties in the organs 
 in which they occur. 
 
 We have stated that there exist two great modifications of 
 
29 
 
 sensibility and contractility; that sensibility is divided into 
 percipient sensibility and latent sensibility^ that contractility 
 is at times voluntary, at others involuntary^ and that the latter 
 may be perceivable or insensible. 
 
 SENSIBILITY 
 
 ^Perceiving. {Cerebral^ nervous^ animal scnsu 
 bility^ perceptibility^ 
 
 With consciousness of impressions or percep- 
 tibility; it requires a peculiar apparatus. 
 Latent. {Nutritive^ organic sensibility.') 
 Without consciousness of impressions; or, ge- 
 neral sensibility, common to every thing that 
 has life; it has no peculiar organ, and is found 
 universally dilfused in living parts, animal or 
 vegetable. 
 
 V 
 
 p Voluntary and sentient, subordinate to per- 
 1 ceptibility. 
 
 CONTRACTILITY. y Involuntary and insensible, corresponding to 
 i latent sensibility. Tonicity. 
 ylnvoliintary and sentient. 
 
 The cause of this last modification of contractility, appears 
 to depend on the peculiar organization of the system of the 
 great sympathetic nerves. From these nerves, the heart, the 
 digestive canal, &c. seem to receive the power of exerting 
 sensible contraction, an effect produced by the direct appli- 
 cation of a stimulus, and over which volition has no controul, 
 as will be stated in speaking of those nerves. 
 
 Sensibility and contractility offer a vast number of differences, 
 the principal of which depend on the age, the sex, the regimen, 
 the climate, the state of waking or of sleep, of health or of 
 sickness, on the relative development of the lymphatic, cellu- 
 lar or adipose systems, and on the proportions which exist 
 between the nervous and muscular systems. 
 
 In the first place, the principle of sensibility and of contrac- 
 tility may, in its action, be likened to a fluid flowing from any 
 source whatsoever, which is consumed, repaired, and drained 
 
30 
 
 by use, resupplied, or exhausted, equally distributed, or, occa- 
 sionally concentrated on certain organs. 
 
 Secondly. Sensibility, like contractility, is very considerable 
 at the instant of birth, and seems to diminish more or less 
 rapidly till death. 
 
 Thirdly. The liveliness and frequency of impressions wear 
 it out very early. It, in a manner, repairs itself, that is, re- 
 covers its original delicacy, when the sentient organs have been 
 long at rest. Thus, an epicure whose taste has grown dull with 
 high living, will recover all its accuracy, if during several 
 months, instead of spiced ragouts and spirituous liquors, he 
 lives on dry bread and plain water. In like manner, contractility 
 becomes exhausted in the muscles which are too long employed, 
 and it is recovered during the repose of sleep. 
 
 Fourthly. The following is an instance of the manner in 
 which sensibility becomes concentrated on one organ, and 
 appears to forsake the others: when the venereal excitement 
 is in its highest degree, animals under its influence, receive 
 blows and stings without pain. Domestic animals in that condi- 
 tion, are often ill treated, without appearing to feel what is 
 done to them. If the hind legs of the toad are cut off, at the 
 time that he is holding the female firmly embraced, and is 
 pouring his prolific seminal fluid on the ova which are issuing 
 at her anus, he does not lose his hold, he seems insensible to 
 every other sensation; as a man who is taken up with one 
 thought, and absorbed in reflection, is scarcely diverted from 
 it by any means that can be employed. When during the influ- 
 ence of satyriasis, the vital power is carried to excess in the 
 penis, patients have been known, (as we are told by Aeiius) to 
 cut off both their testicles, without suffering the pain usually 
 attending so severe an operation. It is by this law of sensibility, 
 that we are to explain the observation of Hippocrates, that two 
 parts of the body cannot be in pain at the same time. If tw-o 
 pains come on at once, the more violent prevents the slighter 
 from being felt; Ambo partes non pcssunt dolere simul. Duobus 
 doloribus^ simul orientibus^vehementior obscurat alterum. (Hipp.) 
 In cases of scrophulous swellings, the parts arc observed to in- 
 flame, to become painful, and suppuration occurs but rarely in 
 every part at once, if the case is serious and attended with acute 
 
31 
 
 pain. The germ of a disease or of a slighter affection, may: 
 sometimes remain dormant under a greater pain. I was once 
 overturned in a carriage, from the awkwardness of the coach^ 
 man, the windows were broken and my wrists sprained. The 
 right wrist which had suffered most, swelled first; I employed 
 the proper treatment, and when at the end of a week, the sweh 
 ling and pain had almost completely ceased, and the right hand 
 was beginning to recover its suppleness and flexibility, the left 
 wrist swelled and in its turn became pained; two complaints, if 
 they may be called such, appeared in succession, and separately 
 went through their regular course.* 
 
 The perfection of one sense is never obtained, but at the 
 expense of another; the blind who bestow more attention on the 
 sensations communicated by the sense of touch and of hearing, 
 often astonish us by the delicacy of these organs, so that, as has 
 been observed, those who, to improve the human voice, have 
 dared to. mutilate their fellow creatures, by depriving them of 
 the organs of generation, might have bethought themselves of 
 putting out their eyes, to render them more sensible to the 
 sweet impressions of harmony. 
 
 Fifthly. During sound sleep, the exercise of the percipient 
 
 * John Hunter maintains from theory, the position that po two different 
 fevers can take place at the same time in the constitution, but that if the two 
 causes of disease exist together, the diseases themselves must be vicarious. 
 And he verifies his reasonings from experience. 
 
 “ On Thursday the sixteenth of May, 1775, I inoculated a gentleman’s 
 child, and it was observed that I made pretty large punctures. On the Sunday 
 following, viz. the nineteenth, he appeared to have received the infection, a 
 small inflammation or redness appearing round each puncture, and a small 
 tumour. On the twentieth and the twenty-first, the child was feverish, but I * 
 declared that it was not the variolous fever, as the inflammation had not at all 
 advanced since the nineteenth. On the twenty-second, a considerable eruption 
 appeared, which was evidently the measles, and the sores on the arms ap- 
 peared to go back, becoming less inflamed. 
 
 “ On the twenty-third he was very full of the measles; but the punctures on 
 the arms were in the same state as on the preceding day. 
 
 “ On the twenty-fifth, the measles began to disappear, on the twenty-sixth 
 and twenty-seventh, the punctures began again to look a little red. On the 
 twenty-ninth, the inflammation increased, and there was a little matter formed. 
 On the thirtieth, he was seized with fever. The small-pox appeared at the 
 regular time, went through its usual course, and terminated favourably.” 
 
 T. Hunter on Inflammation, p. 5: 
 
32 
 
 faculty, and that of voluntary contractility, are entirely suspend- 
 ed. During that state, it seems as if some covering were 
 thrown over the sentient extremities. We know how hard 
 the hearing becomes, how dull the senses of smell and taste 
 become, how dim the sight, a cloud spreading before the eyes, 
 the moment we are falling asleep. Fir quidam exquisitissima 
 sensibilitaie prceditus^ semi consopitus coibat; huic, ut si vcla- 
 mento levi glans obductus fuisset, sensus voluptatis referebatur. 
 
 Sixthly. Sensibility is more lively, and more easily excited, 
 in the inhabitants of warm climates, than in those of northern 
 regions. What a prodigious difference there is, in that respect, 
 between the native of Germany and of the southern provinces 
 of France. Travellers tell us, that there are in the neighbour- 
 hood of the poles, natives, so little endowed with sensibilitj', 
 that they feel no pain from the deepest wounds. The inhabitants 
 of the coast of North America, if we may believe the testimony 
 of Dixon and Vancouver, thrust into the soles of their feet, 
 sharp nails and pieces of glass, M'ithout feeling the slightest un- 
 easiness. On the contrary, the slightest prick from a thorn, for 
 instance, in the foot, is in the strongest African, frequently 
 followed by convulsions and locked jaw. The impression of the 
 air, is alone sufficient to produce the same accident in the negro 
 children in the colonies, the greater number of whom die of 
 locked jaw, a few days after birth. 
 
 Montesquieu"^ very justly observed this difference which 
 exists in the sensibility of the southern and northern nations, 
 and he says of the latter, that “ if you would tickle )’ou must 
 flay them.” 
 
 * This philosopher has borrowccl froin the fu-therof physic, one of his most 
 brilliant and paradoxical opinions. In his conception, warm climates are the 
 seat of despotism, and the cold, tlie seat of liberty. This error is completely 
 refuted in the profound and ]>hilosophical woi k of V'olney on Epypt and Syria. 
 He shews, that what Montesquieu lias said of cold climates, applies to 
 mountainous regions, while a champaign is more favourable to the establish- 
 ment of tyranny. Hippocrates had said of the Asiatics, that their being less 
 warlike than the Europeans, depended on the difl'erence of climate, and like- 
 wise on the despotic form of their government. And he observes, that men who 
 do not enjoy their natural rights, but whose affections arc controuled by masters, 
 cannot feel the bold passion of war. 
 
 See chap. XI. on the Varieties of the Human Species. 
 
33 
 
 Now, as the imagination is always proportioned to the sensi- 
 bility, all the arts that are cultivated and brought to perfection, 
 only by the exercise of that faculty, will flourish with difiiculty 
 near the icy polar regions, unless the powerful influence of 
 climate be counteracted by well directed moral and physical 
 causes. 
 
 Man is of all beings, the one that most powerfully resists the 
 influence of external causes; and although the influence of 
 climate is sufficient to modify his external appearance, so as 
 to lead to a division of the species into several distinct varieties 
 or kinds, this superficial impression is very different from the 
 great alterations to which other beings are exposed, from the 
 mere change of climate. Man is every where indigenous, and 
 exists in all climates; while the plants and animals of the 
 equator languish and die when conveyed to the polar regions. 
 From the flexibility of his nature, man enjoys the power of 
 adapting himself to the most opposite situations, of establish- 
 ing, between them and himself, relations compatible with the 
 preservation of life. Nevertheless, it is not without difficulty 
 that man undergoes these changes, and accustoms himself to 
 new impressions. The periodical return of the seasons deter- 
 mines that of certain derangements, to which the animal eco- 
 nomy is subject. The same diseases manifest themselves under 
 the influence of the same temperature, and to use an ingenious 
 comparison, resemble those birds of passage which visit us at 
 stated seasons of the year. Thus, hemorrhages and eruptive 
 affections come on with the return of the spring, summer 
 comes attended by bilious fevers, autumn brings on a return 
 of dysenteric affections, and winter abounds in inflammation of 
 the lungs and other parts. The influence of climate, on the 
 human body, does not shew itself merely in occasioning epi- 
 demic diseases, the consideration of which leads to the estab- 
 lishing what physicians call medical constitutions. This influence 
 operates on man in health, as well as in sickness; and to say 
 nothing of the alterations which our moral nature experiences 
 from the tendency to love, rendered more impetuous with the 
 return of spring, or of the melancholy to which nervous people 
 are often subject towards the end of autumn, when the trees are 
 shedding their leaves, the increase of growth is particularly 
 
 E 
 
34 
 
 remarkable at the time of the first growth of plants, as was 
 observed again and again, by a friend of mine, physician to a 
 large seminary. 
 
 Seventhly. Sensibility is greater in women and children; 
 their nerves are likewise larger and softer, in proportion to 
 the other parts of the body. In general, the principle of sen- 
 sibility seems to decrease, in proportion as it has contributed to 
 the development of the acts of life; and the pow'er of being im- 
 pressed by external objects, diminishes gradually with age, so 
 that there is a period of decrepid old age, at which death appears 
 a necessary consequence of the complete exhaustion of that 
 principle. In short, as I have said in describing the progress of 
 death, at its approach, sensibility shews increase of activity and 
 liveliness, as if its quantity required to be completely exhausted, 
 before the termination of existence, or as if the organs made a 
 last effort to cling to life. 
 
 The development of the cellular and adipose substance, di- 
 minishes the energy of sensibility, the extremities of the nerves 
 being more covered, and therefore not so immediately applied 
 to the objects, the impressions which are felt, are more obscure. 
 The fat operates on the nerves, as wool would do on vibrating 
 chords, if wrapped round them, to fix them, to prevent their 
 quiverings, and stop their vibrations. 
 
 Very nervous women are very thin; persons of much sensi- 
 bility have seldom much embonpoint. Swine, in which the nerves 
 are covered by a thick layer of fat, are the most insensible of all 
 animals. The susceptibility of the nerves may be diminished, 
 and their sensibility blunted by pressure. The application of a 
 bandage firmly rolled round the body and limbs of an hysteri- 
 cal woman, will diminish the violence of her fits. In dressing 
 wounds affected with what is called the hospital gangrene, I 
 have often relieved the pain, by desiring an assistant to apply 
 firm pressure above the sore. 
 
 Eighthly. There exists between the force of the muscles, and 
 the sensibility of the nerves, between the sensible energy and 
 the force of contraction, a constant opposition, so that the most 
 vigorous athlets, whose muscles are capable of the most prodi- 
 gious efforts, and of the most powerful contractions, are but 
 slightly affected by impressions, and are with difficulty roused 
 
35 
 
 into action, as w€ have explained in giving a history of the 
 nervous and museular temperaments, which are characterized 
 ' by this dilFerence. Hence, man has more sensibility than the 
 quadrupeds, although his nerves are smaller than theirs, which 
 seem destined to set the muscles into action, and to serve as 
 nerves of motion, rather than of sensation. 
 
 There is no muscular fibre, however minute, in which we are 
 not obliged to admit the existence of a small nervous filament, 
 to which it probably owes the power of contracting; contractility, 
 at least voluntary contractility, does not appear to be inherent 
 in the muscular fibre, nor independent of the nerves, through 
 the medium of which, the will determines the action of the 
 muscles; and if these last organs when insidated, contract on 
 the direct application of a stimulus, is there not reason to suspect, 
 that this stimulus acts on that portion of nerves which remains 
 in the muscle, after it has been insulated, and which is inti- 
 • mately united to its fibres? The animals which have no distinct 
 nervous system, possess at once in all their parts, sensibility and 
 contractility; these two properties become blended in the organs, 
 as well as in the phenomena of life, and can be perceived sepa- 
 rate, only by a pure abstraction of the mind, which considers in 
 succession the impression produced on these beings, and the 
 motion of their substance, which is an immediate consequence 
 of that impression. 
 
 We will not enter any farther into a consideration of the laws 
 and phenomena of the vital properties, for fear of being led into 
 useless repetitions, when we come to the history of the functions 
 over which they preside. We will conclude what relates to 
 them, by presenting the two most important features of their 
 history, I mean, sympathy and habit. 
 
 § VU. OF SYMPATHY. 
 
 There exist among all the parts of the living body, intimate 
 relations; all correspond to each other, and carry on a reciprocal 
 intercourse of sensations .and affections. These links which unite 
 together all the organs, by establishing a wonderful concurrence, 
 and a perfect harmony among all the actions that take place in 
 the animal economy, are known under the name of sympathies. 
 The nature of this phenomenon is yet unknown; we know not 
 
36 
 
 why, when a part is irritated, another very distant part partakes 
 in that irritation, or even contracts: we do not even understand 
 what are the instruments of sympathy, that is, what are the 
 organs which connect two parts, in such a manner, that when 
 one feels or acts, the other is affected. But though beyond 
 explanation, sympathy is not the less important in the economy 
 of living beings; and these connexions between remote parts, 
 constitute one of the most remarkable differences between those 
 beings and inorganic bodies. Nothing similar is observable in 
 dead or inanimate nature, in which all things are connected 
 together, only by palpable and material links; here the chain is 
 invisible, the connexion evident, the cause occult, and the effect 
 apparent. 
 
 Whytt has clearly shewn, that the nerves cannot be consider- 
 ed as the exclusive instruments of sympathy, since several 
 muscles of a limb which receive filaments from the same nerve, 
 do not sympathize together, while there may be a close and 
 manifest relation between two parts, of which the nerves have 
 no immediate connexion, since each nervous filament having 
 one of its extremities terminating in the brain, the other, in the 
 part to which it is sent, remains distinct from those of the same 
 trunk, and does not communicate with them. 
 
 Sympathies may be distinguished into different kinds. In the 
 first place, two organs, which execute similar functions; — the 
 kidnies may supply each other’s office. When the uterus is in a 
 state of pregnancy, the breasts participate in its condition, and 
 there is determined into them a flow of humours necessarj' to 
 the secretion which is to take place. Secondly. The continuity 
 of membranes is a powerful source of sympathy. The presence 
 of worms in the bowels, determines an uneasy pruritus around 
 the nostrils. When there is a stone in the bladder, a certain de- 
 gree of itching is felt at the extremity of the glans. The secre- 
 tion of several fluids is determined in the same manner; thus, 
 the presence of food in the mouth, brings at the extremity of 
 the parotid duct, an irritation which extends to the parotid 
 glands, calls them into action, and increases their secretion. 
 Thirdly. If the pituitary membrane is irritated, the diaphragm 
 with which it has no immediate organic connexion, nervous, 
 vascular, or membranous, contracts, and occasions sneezing. Is 
 
37 
 
 not this sympathy one of those which Haller ascribed to a re- 
 action of the sensortum commune? If the impression produced 
 on the olfactory nerves by snuff, is too powerful, the uneasy 
 sensation is transmitted to the brain, which determines towards 
 the diaphragm, a quantity of the principle of motion sufficient 
 to enable that muscle suddenly to contract the dimensions of the 
 chest, so as to expel a column of air, that may detach from the 
 pituitary membrane, the substances that are a cause of uneasi- 
 ness to it. Fourthly. Does not the principle of life seem to con- 
 troul at pleasure, the phenomena of sympathy? The rectum, 
 when irritated by the presence of the excrements, contracts; 
 what cause determines the accessory and simultaneous action of 
 the diaphragm and abdominal muscles? Does this connexion 
 depend on organic communications? Why, then, is not the sym- 
 pathy reciprocal, and why does not the rectum contract, when 
 the diaphragm is irritated? Fifthly. Can the repeated habit of 
 the same motions explain the harmony which is observed in 
 the symmetrical organs? Why, when our sight is directed to an 
 object, placed laterally, does the rectus externus of the eye on 
 that side, act at the same time as the rectus internus of the 
 other eye? The indispensable utility of this phenomenon, in 
 keeping a parallelism of the axis of vision is very obvious, but 
 who can assign the cause? Why are rotatory motions, in differ- 
 ent directions, performed with so much difficulty by the arm and 
 leg of the same side of the body. Can it be called a just idea of 
 the innumerable varieties of this phenomenon, and of its fre- 
 quent anomalies, to say, with Rega, that there are sympathies 
 of action or of contractility (consensus actionuni) sympathies of 
 sensibility (consensus passionum.") 
 
 All these difficulties render it pardonable in Whytt, to have 
 considered the soul as the sole cause of sympathy; which was, 
 in fact, a modest avowal of the difficulty of explaining the sub- 
 ject. We are not justified in considering sympathy as an ano- 
 malous action, as an aberration of the vital power. Can it be 
 said, that the natural order of sensibility and irritability is in- 
 verted, in the sympathetic erection of the clitoris and of the 
 nipple, or in the turgescence of the breast, determined by the 
 gravid state of the uterus? 
 
38 
 
 It is by means of sympathy that all the organs concur in the 
 same end, and yield each other mutual assistance. It affords us 
 the means of explaining, how an affection at first local or limited 
 in its extent, spreads, and extends to all the systems; it is thus 
 that every morbid process is carried on. The diseases termed 
 general, always originate, through the medium of association, 
 in the insulated affection of an organ or a system of organs. 
 
 In fact, the affections which appear to us most complex, in 
 the number, the variety and the dissimilarity of their symptoms, 
 consist of only one, or of a small number of primitive or es- 
 sential elements, all the rest are accessory, and depend on 
 numerous sympathies of the affected organ, with the other 
 organs of the animal economy. Thus, if the stomach is the seat 
 of irritation, from foulness of its contents, pains of all kinds 
 come on, but especially in the head and limbs, with a burning 
 heat, nausea, loss of appetite, anxiety, and these symptoms con- 
 stitute a disease which appears to affect the whole system. 
 
 To go on with the same illustration, the stomach, v/hen op- 
 pressed by irritating substances, contracts spontaneously to get 
 rid of them. The universal disturbance which their presence 
 occasions, seems directed towards the same end, as if the suffer- 
 ing organ called upon all the others to assist in relieving it. 
 
 These synergies, or aggregate motions, tending to one end, 
 and arising out of the laws of sympathy, constitute the diseases 
 termed general, as well as the greater part of those which are 
 called local. It is by means of them, and through these kinds of 
 organic insurrections, if we may be permitted to use that expres- 
 sion, which perfectly expresses our meaning, that nature strug- 
 gles with advantage, and rids herself of the morbific principle, 
 or of the cause of the disease; and the art of exciting arid direct- 
 ing these actions, furnishes the materials of the most important 
 doctrines of the practice of medicine. I have used the terms 
 excite and direct; for, it is necessary at times to increase, at 
 others to diminish their intensity and force, and on some occa- 
 sions to excite them, when nature, overwhelmed under disease, 
 is almost incapable of re-action. This last circumstance belongs 
 to the diseases of the most dangerous kind, if we include those 
 in v/hich the efforts of nature, though marked by a certain de- 
 gree of energy, are without connexion, or consent, and frus- 
 
39 
 
 trated by their want of coherence. The character of these affec- 
 tions was first well expressed by Selle, who substituted, for the 
 term malignant, which used to be applied to them without any 
 precise meaning, that of ataxic^ which points out very correct- 
 ly, the want of order, and the irregular succession of their 
 symptoms.* 
 
 A knowledge of synipathies is of the highest importance in 
 the practice of medicine. | When we wish to avert an irritation 
 fixed in a diseased organ, experience and observation prove, 
 that it is on the organ which bears to it the closest sympathetic 
 connexions, that it is useful to apply medicines intended to ex- 
 cite counter irritation. 
 
 This might perhaps be the fittest place to inquire into the 
 nature of those concealed relations which draw men together, 
 and of those aversions which prevent their union; to discover 
 the causes of those secret impulses which lead two beings 
 towards each other, and force them to yield to an irresistable 
 propensity. We might inquire into the reason of antipathy, and 
 in a word, establish the complete theory of moral sentiments 
 and affections. Such an undertaking is greatly above our strength, 
 and besides, does not absolutely belong to our subject. It would 
 require a considerable time, and whoever should undertake it, 
 would be in considerable danger of losing his way at every step, 
 in the extensive field of conjectures.^ 
 
 * Symptomata nervosa, nec inter se, neque causis manifestis respondentia. Ordo 
 tert. atactae, C. G. Selle. Rudimenta pyretologiae methodicae. 
 
 fThis information maybe obtained, by consulting' the works of the ac-- 
 cients, and especially of Hippocrates, who appears to have felt all the impor- 
 tance of this subject. Among the moderns. Van Helmont, Baglivi, Rega, 
 Whytt, Hunter, Barthez, and Bichat, have collected on this subject, a great 
 number of fiicts obtained from experiments on animals, and especially from 
 observations on diseases. 
 
 t That law of the animal economy termed “ sympathy or consent of parts,” 
 is a very important one, and has hitherto been too much overlooked in our 
 speculations as respects the phenomena of health and disease. There are 
 indeed, not wanting some, who have affected scepticism as to the very 
 existence of such a law. True it is that, at present, we have no very distinct 
 intelligence relative to the nature of the principle: but are we on this account 
 to question its existence? With equal reason might we doubt of the sensibility 
 or irritability of the body. By whom has the precise nature of either of these 
 qualities of vital matter been demonstrated? Yet we are persuaded of their 
 
40 
 
 § Vlll. OF HABIT. 
 
 It is easier to feel the meaning of this term than to define it.^ 
 Habit, however, may be said to consist in the frequent repeti- 
 tion of certain acts, of certain motions, in which the whole body 
 
 existence from the phenomena which they exhibit, and it is by the same de- 
 scription of evidence that we are, or ought to be, assured of the existence of 
 svTnpathy. 
 
 “ Causa latet, ms est notissima.” 
 
 Of the manner in which sympathetic impressions are extended, as well as 
 of the cause of the more intimate consent which exists between parts, we are 
 not accurately informed. It would seem, however, that in neither case is it to 
 be exclusively referred to the mediation of the nerves, as is commonly imagin- 
 ed. Those sympathies which prevail among the various viscera of the abdo- 
 men, and between them and the head, neck and contents of the thorax, may, 
 perhaps, be explained by the extensive anastomoses of the intercostals with 
 almost all the nerves which proceed from the spinal marrow. But there are 
 many other sympathies, equally^ conspicuous, between parts, the nerves of 
 which have not the slightest connection. Here it appears that, either by the 
 co-operation of different organs in tlie performance of a function, as in the 
 complex apparatus subservient to respiration, or from similarity of structure, 
 parts, though detached, being prone to be affected by the same cause, as the 
 parotid gland and testes in the male, and the same gland with the mammae in 
 the female, the habit of acting in unison is acquired, and sometimes confirmed. 
 This habit of concerted action is called association, and has been adopted as 
 a principle by Locke, by Hartley, and by Darwin to account for the connection 
 which is discernible in many of tlie motions of the body, as well as in the 
 operations of the mind. Both the sound and morbid states of the system pre- 
 sent numerous instances of these associated actions, some of which are con- 
 stant and uniform, while others are occasional, and anomalous, produced as it 
 were accidentally'. 
 
 The principle of sympathy extends throughout the body, every portion of it 
 being susceptible of associative actions, by which means the different parts 
 are linked togetlier so as to form one mhole. Certain organs however, are more 
 eminently endowed with the property, as the uterus, the brain, and especially 
 the stomach. This last viscus constitutes the chief medium of sympathetic 
 connection. With it, the brain, the organs of sense, and deglution, the whole 
 of the thoracic and abdominal viscera, the parts of generation in each sex, the 
 blood vessels, the joints, the exterior surface, and in short all the parts of the 
 system however minute, maintain a close and intimate sympathy. Placed in 
 the middle, the stomach is the centre of the greatest sphere of sympathy. 
 But, besides this great sphere, there are many subordinate ones, which our 
 narrow limits will not permit us particularly to designate; as for example, 
 the uterus with the different portions of its own system, the ovaries, the mam- 
 mx, &c. &c. It was on account of its vast dominion over the system, by its mul- 
 tiplied sympathies, that Van Helmont selected the stomach as the residence ol 
 his archceus, the anima medica, of Stahl and Nicholls. — E d. 
 
41 
 
 participates, or only some of Its parts. The most remarkable 
 effect of habit, is to weaken after a time the sensibility of organs. 
 Thus, a catheter introduced along the urethra, and allowed to 
 remain there, causes during the first day rather sharp pain, on 
 the second day it feels less uneasy; on the third day, it is onl)’’ 
 troublesome, and on the fourth, the patient scarcely feels it. 
 The use of snuff at first increases the secretion of mucus in the 
 nose, but if continued a certain time, it ceases to affect the pitui- 
 tary membrane, and the secretion would diminish considerably, 
 but for the practice of increasing daily the quantity of that acrid 
 powder; the presence of a canula in the nasal duct, after the 
 operation for fistula lachrymalis, increases at first the mucous 
 secretion of that canal; but in proportion as it becomes accus- 
 tomed to the extraneous body, the secretion returns to its natu- 
 ral condition. 
 
 It is only by our sensations that we are aware of our existence. 
 Life, to make use of the figurative language of system, of a 
 modern writer, consists in the action of stimuli on the vital 
 powers. (Tota vita^ quanta est^ consistit in stimulo^ et vi vitali. 
 Brown.) Sentient beings feel a continual necessity of renewed 
 emotions; all their actions tend to the obtaining agreeable or 
 disagreeable sensations; for, in the absence of other sensations, 
 pain is sometimes attended with enjoyment. Those who have 
 exhausted every kind of enjoyment, and who have had no plea- 
 sures ungratified, are led to suicide from a weariness of life; who 
 can live, when all power of feeling is gone? 
 
 The following is the most extraordinary and remarkable in- 
 stance known, of the manner In which habit and a frequent 
 repetition of the same impressions, wear out by degrees the 
 sensibility of organs. A shepherd, about the age of fifteen, 
 became addicted to onanism, and to such a degree, as to prac- 
 tise it seven or eight times in a day. Emission became at last so 
 difficult, that he would strive for an hour, and then discharge 
 only a few drops of blood. At the age of six and twenty, his 
 hand became insufficient, all he could do, was to keep the penis 
 in a continual state of priapism. He then bethought himself of 
 tickling the internal part of his urethra, by means of a bit of 
 wood six inches long, and he would spend in that occupation 
 several hours, while tending his flock in the solitude of the 
 
 F 
 
42 
 
 mountains. By a continuance of this titillation for sixteen years, 
 the canal of the urethra became hard, callous, and insensible. 
 The piece of wood then became as ineffectual as his hand; at 
 last, after much fruitless effort, G. one day in despair, drew from 
 his pocket a blunt knife, and made an incision into his glans, 
 along the course of the urethra; this operation, which would 
 have been painful to any one else, was in him attended with a 
 sensation of pleasure, followed by a copious emission. He had 
 recourse to his new discovery, every time his desires returned. 
 When after an incision into the cavernous bodies, the blood flow- 
 ed profusely, he stopped the hemorrhage, by applying around 
 the penis a pretty tight ligature. At last, after repeating the 
 same process perhaps a thousand times, he ended in splitting 
 his penis into two equal parts, from the meatus urinarius to the 
 scrotum, very near to the symphysis pubis. When he had got 
 so far, unable to carry his incision any farther, and again re- 
 duced to new privations, he had recourse to a piece of wood, 
 shorter than the former: he introduced it into what remained of 
 the urethra, and exciting at pleasure the extremities of the 
 ejaculatory ducts, he provoked easily the discharge of semen. 
 He continued this about ten years; after that long space of time, 
 he one day introduced his bit of wood so carelessly, that it slip- 
 ped from his fingers and dropped into the bladder. Excruciating^ 
 pain and serious symptoms came on. The patient was conveyed 
 to the Hospital at Narbonne. The surgeon, surprized at the 
 sight of two penes of ordinary size, both capable of erection, 
 and in that state diverging on both sides, and seeing besides 
 from the scars and from the callous edges of the division, that 
 this conformation was not congenital, obliged the patient to 
 give him an account of his life, which he did, with the details 
 which have been related. This wretch was cut as for the stone, 
 recovered of the operation, but died three months after, of an 
 abscess in the right side of the chest, his phthisical state having 
 been evidently brought on by the practice of onanism carried on 
 nearly forty years."^ 
 
 The habit of suffering, renders us in the end insensible to 
 pain; but every thing in this world is balanced, and if habit 
 
 Chopai’t, maladies des voles urinaires. Tome II. 
 
43 
 
 lightens our evils, by blunting sensibility, it on the other hand 
 drains the source of our sweetest enjoyments. Pleasure and 
 pain, these two extremes of sensation, in a manner, approximate 
 to each other, and become indifferent to him who is accustomed 
 to them. Hence arises inconstancy, or rather that insatiable de- 
 sire of varying the objects of our inclinations, that imperious 
 want of new emotions; hence we possess with indifference what 
 we pursued with the utmost ardour and perseverance, and even 
 cease to be impressed by those charms which once held us 
 captivated. 
 
 A striking instance of the powerful influence of habit on the 
 action of organs, is afforded by that criminal who, we are told 
 by Sanctorius, was taken ill on being removed from a noisome 
 dungeon, and did not recover till he was replaced in the impure 
 air to which he had been long accustomed. Mithridates, that for- 
 midable rival of the Roman power, dreading to be taken alive 
 by his enemies, tried in vain to put an end to his life, by taking 
 large doses of the most subtle poisons, because he had long 
 inured himself to their action.* It has, therefore, been justly 
 said of habit, that it is a second nature, whose laws ought to be 
 respected. 
 
 The organs of generation in women, in consequence of their 
 lively sensibility, are in an especial manner submitted to the 
 powerful influence of habit. The womb, after a miscarriage, has 
 a tendency to a renewal of the same occurrence, when the same 
 period of pregnancy recurs, so that the greatest precautions are 
 necessary to prevent abortion in women, who are subject to 
 it, when they have reached the month in which they before mis- 
 carried. 
 
 May not death be considered as a natural consequence of the 
 laws of sensibility? Life, depending on the continual excitement 
 of the living solids by the fluids which moisten them, ceases, 
 because the parts endowed with sensibility and contractility, 
 after long habitude of the impressions of those fluids, lose their 
 capacity of feeling them. Their action gradually extinguished, 
 
 * In some very rare cases, habit produces a quite contrary eiFect. Cullen 
 states, that he knew persons so accustomed to excite vomiting in themselves, 
 that the twentieth part of a grain of tartar emetic was suf&cient to excite a 
 convulsive action of the stomach. 
 
44f 
 
 Would perhaps revive, if the energ)’^ of the stimulating power 
 were increased. > 
 
 A knowledge of the power of habit, is a useful guide in the 
 application of remedies, the greatest part of which operate in 
 the cure of diseases, only by modifying sensibility. A wound in 
 which lint has kept up the degree of inflammation necessary to 
 cicatrization, becomes insensible to that application, the parts 
 become spungy and soft, and the cure is protracted. The lint 
 should then be covered with an irritating powder, and the 
 pledgits soaked in an active fluid: one may safely increase the 
 doses of a medicine which has been long employed. Thus, in the 
 treatment of the venereal disease by murcurials, the dose is to 
 be gradually increased; with the same view, Frederic HoflTman 
 recommended in the treatment of chronic diseases, that the re- 
 medies should be suspended for a time and then resumed, lest 
 the system should get accustomed to them and their influence 
 be lost. The same motive should lead one to vary the treatment, 
 and to employ, in succession, those medicines to which nearly 
 the same qualities are assigned, for, each of them calls forth the 
 sensibility in a peculiar manner. The nervous system may be 
 compared to an earth abounding in various juices, and for a full 
 display of whose fecundity, it is necessary that the husbandman 
 commit to it the germs of various plants. 
 
 It is very remarkable that habit, or the frequent repetition of 
 the same act, which uniformly, under all circumstances, and in 
 all organs, blunts physical sensibility, should improve the intel- 
 lect, and increase the facility, and activity of execution of all 
 the operations of the understanding, or of the actions which de- 
 pend on them. “ Habit impairs the sensitive pouoer^ and im- 
 proves the judgment^' Bichat was therefore incorrect, when in 
 his distinction of the organs which are subservient to the func- 
 tions of assimilation, from those which serve to keep up our 
 relation with the surrounding objects, he maintained that the 
 sensibility of the latter becomes more exquisite, while the sen- 
 sibility of the former becomes impaired from habit. 
 
 But can a painter, because he judges more correctly than the 
 ignorant, of the beauties of a picture, be said to see it better? 
 Surely not, for, he may with a sight far less penetrating, and 
 more infirm, form a more accurate analysis, from the habit 
 which he has acquired, and judge with a great deal mor« 
 
45 
 
 promptitude and certainty, of the several parts and of the whole; 
 just as the practised ear of the musician seizes, in a piece of 
 music, and during the most rapid execution, the expression and 
 the value of all the notes and tones. The error has arisen, from 
 its being forgotten, that, correctly speaking, it is not the eyes 
 that see, or the ears that hear; that the impressions produced by 
 the sounds on these organs, are but the occasional cause of the 
 sensation, or of the perception of which the brain is the exclu- 
 sive seat. Which has the more delicate sense of hearing, the 
 North American savage, who hears the noise of the step of his 
 enemies, at distances that astonish us, or the artist who does not 
 hear a person speaking at the distance of fifty paces from him, 
 but who directs with judgment, all the operations of a great or- 
 chestra, and who distinguishes skilfully, the effect of each part? 
 
 Bring down to a frugal Pythagorean regimen, one of our 
 modern epicures: his palate, exhausted of its sensibility by the 
 most savoury dishes, by ardent liquors and the most exquisite 
 ragouts, will discover no taste in dry bread. Let him, however, 
 live on bread, if he can, for some time, it will soon appear to 
 him to have a grateful taste, as it does to those who make it 
 their principal article of food, or who take it only with sub- 
 stances which have not a very distinct taste. Although with the 
 sense of smell, that of taste furnishes us only with ideas the 
 most directly connected with our preservation, those which 
 most turn upon the wants of our animal nature: although we 
 retain, with difficulty, the impressions of these senses, and that, 
 to enable us to retain them, they must be often repeated; the 
 epicure had so carefully analysed them, that he had attained to 
 the discernment of the faintest differences of taste, all those 
 delicacies of sensation, which, as Montesquieu said, are lost to 
 us vulgar eaters. 
 
 The motions, under the direction of the will, acquire by the 
 precision of the determinations, the same aptness, facility, and 
 readiness'; and the dancer, w'ho surprises us with his agility, has 
 reflected, more than might be imagined, on the very complicated 
 steps of which a ballet is composed. 
 
 Morbid sensibility, is equally under the influence of habit. I 
 have always observed, that discharges from the urethra become 
 less painful from their frequency. There is nothing down to 
 
46 
 
 disease itself, that is not made lighter by habit, as has been well 
 observed by the old man of Cos. 
 
 It remains then demonstrated, even as a general thesis, that 
 habit, or the frequent repetition of the same acts, whilst it regu- 
 larly reduces physical sensibility, improves intelligence, and 
 gives facility and promptness to all the motions that are under 
 the direction of the will. 
 
 § IX. OF THE VITAL PRINCIPLE. 
 
 The words vital principle^ vital force, &c. do not express a 
 being existing by itself, and independently of the actions by 
 which it is manifested: it must be used only as an abridged 
 formula, which serves to mark the total of the powers that ani- 
 mate living bodies, and distinguishes them from inert matter. 
 So that, whenever, in the course of this section, I shall use these 
 terms, or any equivalent, it is to be taken as if I had said, the 
 aggregate of the properties and laws that regulate the animal 
 economy. This explanation is become indispensable, now that 
 several writers, realizing a mere abstraction, have spoken of the 
 vital principle, as of something very distinct from the body, as 
 of a being altogether separable, which they have invested with 
 feeling, and thought, and even deliberate intentions. 
 
 From the farthest antiquity, the many and striking differences 
 of living, and inorganic bodies, have led some philosophers to 
 conceive in the former, a principle of particular actions, a force 
 which maintains the harmony of their functions, and directs 
 them all to a common end, the preservation of individuals and 
 of the species. This simple and luminous doctrine has remained, 
 even to our own days, only modified in its passage through 
 many years: and, no one now disputes the existence of a princi- 
 ple of life, which subjects the beings that enjoy it, to a system 
 of laws different from those which inanimate beings obey; a 
 force, which might be characterized, as withdrawing the bodies 
 it animates, from the absolute dominion of chemical affinities, 
 which would else, from the multiplicity of their elements, act 
 on them with great power; and, as maintaining them in a nearly 
 equal temperature, whatever may be that of the atmosphere. 
 Its essence is not in preserving the aggregation of constituent 
 molecules, but in drawing to it other molecules, which by as- 
 
 V 
 
47 
 
 similation to the organs it pervades, replace those that are car- 
 ried off in daily waste, and serve for their nourishment and 
 growth. 
 
 All the phenomena that are to be observed in the living hu- 
 man body, might be brought as proofs of the principle which 
 animates it. — The actions of the digestive organs on its food; 
 the absorption, by the chylous vessels, of its nutritious parts; 
 the circulation of these nutritious juices through the sangui- 
 neous system; the changes they undergo in their passage 
 through the lungs, and the secretory glands; the impressibility 
 by outward objects; the power of approaching or avoiding them; 
 in a word, all the functions that are carried on throughout the 
 animal economy, proclaim its existence. But it is customary to 
 take a proof of it yet more direct, from the properties with 
 which the organs of these functions are endowed. We have ex- 
 amined these properties, and we have seen that each of them 
 presents us with, at least, two great modifications; that the last 
 discovers three, which are, voluntary contractility, contractility 
 involuntary and insensible, Stahl’s tonic motion; and lastly, con- 
 tractility involuntary and sensible, as that of the heart and the 
 intestines. 
 
 If it is useful to analyse, in order to know, it is of equal im- 
 portance not to multiply causes, from misconceiving the nature 
 of effects. And if, on the one hand, the multitude of the pheno- 
 mena of life, inclines us to the belief of many causes to produce 
 them; the unfailing harmony that pervades all the actions, their 
 mutual connexions, and reciprocal dependencies, point much 
 more decisively to a sole agent, as causing, directing, and con- 
 trouling these phenomena. 
 
 The hypothesis of the vital principle, is to the philosophy of 
 living beings, what attraction is to astronomy. To calculate the 
 revolutions of the planets, this science is compelled to recognize 
 a force, which draws them constantly towards the sun, and con- 
 strains their tendency to fly from it, within the measured dis- 
 tance of those ellipses, which they describe around that common 
 centre of light and heat, which dispenses to them, as they roll, 
 the precious germs of life and of fertility. We are about to speak 
 of this force, to which all the powers that animate each separate 
 organ, join themselves, and in which all the vital powers are 
 
48 
 
 blended, but under the declaration, for the second time, of using 
 the term only in a metaphorical sense. Without this precaution, 
 I might lead you into all the false reasonings, which those have 
 fallen into, who have assigned to it a real and separate existence. 
 
 The vital power is in perpetual strife with the powers that 
 govern inanimate bodies. The laws of individual nature are, ac- 
 cording to the saying of antiquity, for ever struggling against 
 those of universal nature; and life, which is only this contest pro- 
 longed, in favour, altogether, of the vital powers, during health, 
 but with uncertain issue in disease, is at an end, the moment in 
 which the bodies endowed with it, fall again into the system of 
 lifeless being. This constant opposition of vital to physical laws, 
 both mechanical and chemical, does not withdraw, altogether, 
 living bodies from the controul of these laws. There are effects 
 always going on in the living being, chemical, physical, and me- 
 chanical: only these effects are constantly influenced, modified, 
 and altered by the powers of life. 
 
 Why, when we stand up, are hot all the humours carried down 
 to the lower parts, by the force of gravitation? The vital power 
 resists the completion of this hydrostatic phenomenon, and neu- 
 tralizes this tendency of the fluids, the more successfully as the 
 individual is more robust and vigorous. If it is one enfeebled 
 by previous disease, the propensity will be but imperfectly re- 
 pressed: the feet, after a certain time, swell: and this oedematous 
 swelling, can be ascribed only to the insufficient energy of the 
 vital powers, which determine the distribution of the fluids, &c. 
 
 When a tumbler throws himself backwards, the blood does 
 not flow altogether to his head, though this is become the lowfest 
 part; yet the natural tendency of fluids downwards is not alto- 
 gether overcome; it is only diminished; for if he preserves long 
 the same attitude, the struggle of the hydraulic and vital powers 
 becomes unequal; the former prevail; they accumulate the blood 
 upon the brain; and the man dies. 
 
 The following experiment proves incontestably, what has just 
 been said of the power of resistance, which, in the human body, 
 more or less, effectually counterbalances the force of physical 
 laws. I applied bags filled with very hot sand, along the leg and 
 foot of a man whose artery had been tied by two ligatures, in 
 the hollow of the ham, for popliteal aneurism. Not only the 
 
49 
 
 limb was not chilled, which is what happens when the course of 
 the blood is intercepted, but the extremity thus covered, ac- 
 quired a heat much above the ordinary temperature of the body. 
 The same apparatus applied to the sound leg, did not produce 
 this excess of heat, certainly, because the fulness of life, in that 
 limb, resisted the physical action. 
 
 The vital principle seems to act with the greater energy, as 
 the sphere of its activity is narrowed; which has led Pliny to 
 say, that it was chiefly in the smallest things that Nature has 
 shown the fulness of her power.* 
 
 The circulation is quicker, the pulse more frequent, the deter- 
 minations more prompt, in men of short stature. Such was the 
 great Alexander: never did man of colossal make, display great 
 activity of imagination: none of them have glowed with the fire 
 of genius. Slow in their actions, moderate in their desires, they 
 obey, without murmuring, the will that governs them, and seem 
 made for slavery. Agrippa (says Omilius Probus, in his History 
 of Augustvis) advised that they should disband the Spanish 
 guard, and that in its room, Caesar should choose one of German, 
 “ wotting well, that in these large bodies, there was little of 
 “ coverte malice, and yet lesse of subtiltie, and that it was a 
 “ people more minded to be ruled than to rule.” 
 
 To judge soundly of the remarkable difference which in- 
 equality of stature brings into the character, compare extremes; 
 set against a Colossus, a little man of diminutive stature; grant- 
 ing, nevertheless, to this last, full and vigorous health. You may 
 guess that he is talkative, stirring, always in action, always 
 changing his place: one would say that he is labouring to recover 
 in time, what he has lost in space. The probable reason of this 
 difference in the vital activity, following the difference of stature, 
 arises from the relative bulk of the primary organs of life. The 
 heart, the viscera of digestion, &c. are of nearly the same bulk 
 in all men; in all, the great cavities are nearly of the same ex- 
 tent, and it is principally in the length of the lower limbs, that 
 the difference of stature will be found to lie. It is easily con- 
 ceivable, that the viscera supplying the same quantity of nutri- 
 tious juices to a smaller bulk, that the heart giving the same 
 
 *Nns(ptam magis gtidm in minimis est tota Natnra. Hist. Nat. lib. II. cap. 2. 
 
 G 
 
50 
 
 impulse to blood which is to traverse a shorter course, all the 
 functions will be executed with greater rapidity and energy. 
 
 By an obvious consequence, the diseases of little men, have 
 a more acute character; they are more vehement, and tend more 
 rapidly to their crisis. They have in them something of the ve- 
 locity, I would even say the instability of morbid re-action dur- 
 ing infancy. There is nothing even to the duration of life, on 
 which the differences of stature have not some influence. With 
 this suspicion, and some curiosity to ascertain its justness, I 
 have made enquiries in the hospitals, where people in advanced 
 life are taken in, and I found them, for the most part, occupied 
 by old men above the middle size; so that reasoning and obser- 
 vation concur in showing that, all things else being equal, those 
 of superior stature have a grounded hope of prolonging their 
 life beyond the ordinary term. 
 
 I have observed, with many others, that the whole body un- 
 failingly receives an increase of vigour, from the amputation of 
 a limb. Frequently, after the loss of a part of the body, you will 
 see a manifest change take place in the temperament; those that 
 were weak, even before the disease which brings on the neces- 
 sity of the operation, becoming robust; affections, chronic from 
 debility, such as scrophula, tabes mesenterica, dissipated; glan- 
 dular swellings resolved; which indicates a very remarkable in- 
 crease in the actions of all the organs.* 
 
 The parts most remote from the centre of circulation are, in 
 general, less alive than those which are nearer. Wounds of the 
 legs and feet, are more liable to ulcerate, because, besides the 
 
 • The extraordinary development of an organ, never takes place but at the 
 expense of those about it, of which it draws off the juices. Aristotle observes, 
 that the lower extremities are almost always dry, and wasted in those who are 
 of ardent temperament, or in habits of frequent venery. Hippocrates relates in 
 his work {Be acre, lods, et aqms. Foes: fol. 293.) that the Scythian women seared 
 their right breast, that the arm on that side might grow in size and strength. 
 Galen speaks of Athletes, who, in his time, kept the sexual organs in the most 
 entire inaction, that withered, shrunk, and perished, in some sort, by this ab- 
 solute repose, they might not draw off the nutritious juices from the sole nou- 
 rishment of the muscular organs. A young man, who has several times carried 
 off the prize by running at the public fetes, abstains from venery for some 
 months, before entering the lists, in perfect certainty of victory, after this pri- 
 vation. 
 
51 
 
 circulation of the fluids, which the slightest weakness greatly re- 
 tards in them, their life is too feeble for their wounds to go quick- 
 ly through their periods, and readily cicatrize. The toes freeze 
 first, when we remain too long exposed to severe cold: it is in 
 them too that the mortification begins, which sometimes attacks 
 a limb after the ligature of its vessels.—-" 
 
 Thus, although we may say, that the principle of life is not 
 seated in any part of our being, that it animates every system of 
 organs, every separate organ, every living molecule, that it en- 
 dows them with different properties, and assigns to them, in some 
 sort, specific characters, it must be confessed, that there are in the 
 living body some parts more alive, from which all the others seem 
 to derive motion and life. We have already seen, that these cen- 
 tral organs, these foci of vitality, in whose life that of the whole 
 body is involved, diminish gradually in number in the animal 
 kinds, as they are more removed from man, whilst the fewer they 
 are, the more they are spread out over the body; so that life is 
 more generally diffused, and its phenomena less rigorously and 
 strictly connected, as we descend in the scale of being, from the 
 red and warm-blooded, to the red and cold-blooded animals, from 
 these to the mollusca, the Crustacea, worms andinsects,tothe poly- 
 pus, who forms the extreme link of the animal chain, and lastly, 
 to plants, of which not a few, like the zoophytes, so similar to 
 them in many respects, are endowed with the remarkable proper- 
 ty of reproduction by slips; which implies, that each part contains 
 the aggregate of organs necessary to life, and can exist alone. 
 
 The vital principle has by some been confounded with the 
 rational soul; but others have distinguished it from the emana- 
 tion of divinity, to which as much as to the perfection of his 
 organization, man owes his superiority to all the animal kinds. 
 What bond unites the material principle, whicfi receives impres- 
 sions and transmits them, to the intelligence which feels, per- 
 ceives, examines, compares, judges, and reasons on them? Were 
 man one, says Hippocrates, did his material principle make up 
 his whole nature, pleasure and pain would be as nothing to him; 
 he would be without sensation: for, how could he account to 
 himself for impressions? Si unus esset homo^ non doleret^ quia 
 non sciret unde doleret. Here we stand on the confines of phy- 
 siology and metaphysics: let us beware of setting foot in the 
 
52 
 
 dim paths that are before us: the torch of observation would 
 yield but ineffectual light, too faint to dispel the thick darkness 
 that lies over them. 
 
 The :vital power is merely the vis medicatrix nature, more 
 powerful than the physician, in the cure of many diseases; the 
 art of the physician consisting, in most cases, in awakening or 
 directing the action of that power. When a thorn is thrust into 
 a part endowed with sensibility, a sharp pain is felt, the fluids 
 rush in abundance to the part, it becomes red and swollen; all 
 the vital powers are excited, the sensibility becomes more acute, 
 the contractility greater, and the temperature rises. Does not 
 this increase of vital energy in the injured part, this process 
 which takes pi ce, around the substance that is the cause of the 
 disorder, those means which are provided to expel it, indicate 
 the existence of a preserving principle, incessantly watching 
 over the harmony of the functions, and struggling against all 
 the powers that may tend to interrupt its exercise, or to annihi- 
 late the vital motion? 
 
 Theory of injiammation. Inflammation may, I believe, be de- 
 fined, the increase of vital properties in the part -which it affects. 
 Sensibility becomes more acute in the part so affected, its con- 
 tractility greater; and from that increase of sensibility, and ac- 
 tion, arise all the symptoms characteristic of inflammation. Thus 
 the pain, the swelling, the redness, the heat, and the difference 
 in the state of the secretions, denote in the part, a more ener- 
 getic and active vitality. 
 
 Those who have objected to the definition which I have given 
 of inflammation, have evidently mistaken the functions of the 
 organs for their properties. It is very true, that inflammation 
 of the eye is attended with loss of sight, but that circumstance 
 depends on the opacity of the transparent parts which should 
 transmit the luminous rays of the retina. The sight is prevented 
 by a mechanical obstacle, but the sensibility of the organ is aug- 
 mented, to such a degree, that the faintest light reaching the 
 bottom of the eye, through the transparent cornea dimmed by 
 the congestion of the vessels, causes in it intolerable pain. On 
 this principle, darkness is universally recommended to patients 
 affected with ophthalmia. In like manner, when a muscle is in- 
 
53 
 
 flamed, the action of the fibre, its decurtation, is prevented by 
 the congestion in the cellular membrane, which covers it, and 
 fills its interstices. The cause preventing contraction, or the 
 exercise of contractility, is mechanical, and may be compared 
 to that, which, in an inflamed lung, opposes the admission of air, 
 and the passage of the blood, from the right to the left side of 
 the heart. Can anyone call in question, the increase of vital ac- 
 tion in peripneumony? I am therefore of opinion, that the above 
 definition is better than that proposed by Bichat, in his “ Ana- 
 tomic generale,” a work of later date than the first edition of 
 these elements of physiology, and in which he makes inflamma- 
 tion to consist in the increase of those vital properties, which 
 he terms insensible. 
 
 All the parts of the human body, with the exception of the 
 epidermis and its different productions, as the nails and the hair, 
 appear capable of inflammation. One might include among these 
 “epidermoid” parts, certain dry and slender tendons, as those of 
 the flexors of the fingers, which when pricked, lacerated and ir- 
 ritated in a thousand ways, are insensible to pain, and remain 
 uninjured in the midst of a whitlow, though attended with sup- 
 puration of all the neighbouring soft parts; and when exposed to 
 the air, they exfoliate instead of granulating. Organization is so 
 indistinct in all these parts, life so feeble and languid, that they 
 remain insensible to the impression of all those causes which 
 might tend to increase its activity'. 
 
 The degree of sensibility in a part, the number and size of the 
 nerves and vessels which are sent into it, determine the degree 
 of its aptitude to inflammation; thus the bones and cartilages in- 
 flame with considerable difficulty. When one of these parts is 
 laid bare, the first effect of the irritation to which it is exposed, is 
 a softening of its substance. When a bone is laid bare, it becomes 
 cartilaginous and softens, in consequence of the absorption of the 
 phosphate of lime which fills up the interstices of its tissue; and 
 it is only after this Js^ind of incarnation, that fleshy granulations 
 begins to sprout, aa^^may be observed on the extremities of bones 
 after amputation. The difficulty with which inflammation is set 
 up in the harder parts of the body, explains why, before the twelfth 
 or fifteenth day after a fracture, it is of little consequence towards 
 union of the bone, that the fractured ends should be placed in 
 
54 
 
 apposition; not that is it right to wait so long, before applying 
 the proper bandages, which are indispensable from the first, to 
 prevent the pain and laceration occasioned by the displaced 
 bones. The blood is determined, from all quarters, towards the 
 irritated and painful part, which swells and assumes a red colour, 
 from the presence of that fluid. The swelling would be unlimited, 
 if, at the same time that the arteries increase in power and cali- 
 ber, to occasion that determination, the veins and lymphatics did 
 not acquire a corresponding energy, to enable them to relieve 
 the part of the fluids which have accumulated in it, and which 
 irritation is constantly determining to it. The power of irrita- 
 bility and contractility increases with sensibility; the circulation 
 is more rapid, in the inflamed part; the pulsations of the capil- 
 lary vessels are manifest. The part is likewise hotter, because, 
 in a given time, there passes through its tissue more arterial 
 blood, from which a larger quantity of caloric is disengaged, 
 and the continued effects of the pulmonary respiration are bet- 
 ter marked in it than in any other organ. 
 
 It forms no part of our intention to treat of the varieties of 
 inflammation: they depend principally on the structure of the 
 organ \yhich is affected, on the violence and rapidity of the 
 symptoms, and on its effects. 
 
 Is not the turgescence of an inflamed part, occasioned in the 
 same manner, as in parts subject to erection, as the corpora 
 cavernosa of the penis and of the clitoris, the nipples, the iris, 
 &c.? In erection of the penis, as in inflammation, there is an ir- 
 ritation, a determination of fluids to the part, an increase of sen- 
 sibility and contractility; yet its condition is not that of inflam- 
 mation. Nature has so disposed the organization of these parts, 
 that they can sustain, without injury, those instantaneous aug- 
 mentations of vital energy, necessary to the exercise of the func- 
 tions performed by the organs to which they belong. As in 
 inflammation, these congestions disappear, when the cause of 
 irritation has ceased to act; thus, the pupil dilates, because the 
 iris recedes, when the eye is no longer exposed to the rays of a 
 vivid light. The penis returns to its naturally flaccid and soft 
 state, when no irritation operates to determine to it the fluids 
 whose presence, as long as the erection lasts, is easily explained 
 
55 
 
 by the continuance of the irritation, without its being necessary 
 to have recourse to mechanical explanations, to account for that 
 phenomenon. When the irritation, which produces the vital 
 turgescence of the penis or iris, is carried too far, or continues 
 too long, the natural congestion becomes morbid. It is well 
 known, that priapism is frequently attended with mortification 
 of the penis, and that the too long continued action of light on 
 the eye, brings on inflammation of that organ. 
 
 The preceding observations on inflammation, shew, that an 
 acquaintance with its phenomena is useful, even in a physio- 
 logical point of view. The vital processes, which in some organs 
 take place in so obscure a manner, that they are imperceptible, 
 acquire in inflammation a character of rapidity and intensity, 
 which renders it much easier to observe and recognize them. 
 Considered in a general and abstract point of view, and merely 
 with a reference to its object, inflammation may be considered 
 as a means employed by nature, to repel the influence of noxious 
 agents, which, when introduced within the body, or on Its sur- 
 face, she has no power of resisting, but by a more active deve- 
 lopment of the powers which animate it. 
 
 During the severe winter of 1793, the chemist Pelletier re- 
 peated the celebrated experiment of freezing mercury, and ob- 
 tained a solid ball in the bulb of a barometer, which he had for 
 a long while kept immersed in the midst of a quantity of ice, 
 continually moistened with nitric acid. When the metal had 
 attained a completely solid state, he drew the ball from the bulb, 
 and placed it on his hand. The heat of the part, joined to that 
 of the atmosphere, soon restored the quicksilver to its fluid 
 state: at the same instant, he experienced in his hand so intoler- 
 able a degree of cold, that he was obliged to drop the quicksilver 
 instantly. There soon came on, in the painful and chilled part, 
 a phlegmonous inflammation, which was cured by resolution. 
 Quicksilver, in a solid state, is one of the coldest bodies in na- 
 ture: how very rapid the caloric must have been carried off in 
 this case, and how deep the impression must have been in the 
 palm of the hand, doubly affected by the cold, and by the vital 
 re-action, which terminated in inflammation! I have produced 
 a similar effect, by endeavouring to melt a piece of ice in my 
 hand, during the heat of summer. In this experiment, the im- 
 
56 
 
 presslon of cold is soon succeeded bv a sensation of acute pain 
 and extraordinary throbbings, in the hand and fore arm. When 
 the two hands are afterwards compared, that which held the 
 piece of ice is extremely red, from the congestion of blood in 
 the cutaneous capillary tissue, and is very different in its ap- 
 pearance, from that which was not the subject of experiment. 
 
 Analogous facts, if seriously considered, should induce the 
 followers of Brown to apply to the effects of cold, the distinction 
 which he applied to debility, of direct and indirect. They 
 would have no difficulty in ascertaining, that in its medical ap- 
 plication, that negative state of caloric, which is directly debili- 
 tating, may, nevertheless, by the re-action which it excites, be 
 considered as an indirect tonic. 
 
 § X. OF THE SYSTEM OF THE GREAT SYMPATHETIC XERVES. 
 
 The great sympathetic nerves are to be considered as the bond 
 destined to unite the organs of the nutritive functions, by whose 
 action man grows, is evolved, and incessantly repairs the con- 
 tinual waste attending the vital motions. They form a nervous 
 system, very distinct from the system of the cerebral nerves; 
 and, as the latter are the instruments of the functions by which 
 we hold Intercourse with external objects, the great sympathetic 
 nerves supply motion and life to the organs of the inward, as- 
 similating, or nutritive functions. 
 
 In animals without vertebrse, may not the nervous system, 
 which floats in the great cavities with the viscera which they 
 contain, be considered as consisting entirely of the great sympa- 
 thetics? These nerves are principally distributed to the organs 
 of inward life, whose activity, in those animals, seems to grow, 
 in proportion as their external senses, and their faculty of loco- 
 motion, are imperfect. If the great sympathetics exist in all the 
 animals which have a distinct nervous system, do they not, in 
 an especial manner, contain the principle of vegetable life, essen- 
 tial to the existence of every organized body possessing the 
 power of digestion, absorption, circulation, secretion and nutri- 
 tion? Finally, is it not probable, that in man, the system of the 
 great sympathetic nerves has a very great share in occasioning 
 a number of diseases, and that the impressions with which pa- 
 
57 
 
 tients are affected, are referred to their numerous ganglions, 
 while the brain is exclusively the seat of intellect and thought?'*' 
 
 These suggestions will, doubtless, be answered in the affirma- 
 tive, if one consider the origin, the distribution and the peculiar 
 structure of these nerves, the acute sensibility of their branches, 
 as well as the disorders attending their injury. 
 
 Extended along the vertebral column, from the base of the 
 skull to the lower part of the sacrum, these great nerves, in 
 some measure parasitic, do not arise from the branches supplied 
 them by the fifth and sixth pairs arising from each side of the 
 brain: they live and are nourished, as it were, at the expense 
 of all the nerves of the spinal marrow, from which they receive 
 branches, so that there is not one of them, from which one can 
 say, that the great sympathetics arise exclusively. The nume- 
 rous ganglions which are distributed along their course, divide 
 them into so many small systems, from which arise the nerves 
 of the organs nearest to them. Amid these bulgings, consider- 
 ed by several physiologists, as so many little brains, in which 
 is performed the elaboration of the fluid which they transmit to 
 the nerves, no one is of more importance than the semi-lunar 
 ganglion, situated behind the organs which occupy the epigastric 
 region, and from which those nerves originate, which are dis- 
 tributed to the greater part of the viscera of the abdomen. It is 
 to the region occupied by that ganglion, in which the great sym- 
 pathetic nerves unite, and which may be considered as the cen- 
 tre of the system formed by their union, that we refer all our 
 agreeable sensations; there it is that we feel in sadness, a con- 
 striction which is commonly referred to the heart. Thence in 
 the sad emotions of the soul, seem to originate those painful 
 irradiations which trouble and disorder the exercise of all the 
 functions.! 
 
 * These opinions on the uses of the great sympathetic nerves, are explained 
 in my Essay on the connexion of Life with the circulation. This essay was 
 published before any thing that has appeared on the same subject.— Consult 
 the “ Memoires de la Societd M6dicale pour I’an VII.” 
 
 j- Consult on the subject of the epigastric centre, Van Helmont, who calls 
 it the archeus; Buffon, Bordeu, Barthez and Lacaze, who give it the name of 
 the phrenic centre, because they ascribe to the diaphragm, what belongs to the 
 nervous ganglions placed in front of its crura. 
 
 H 
 
58 
 
 The numerous filaments of the great sympathetic nerves are 
 finer, they are not of the same whitish colour, nor of the same 
 consistence as the filaments of the cerebral nerves. On that ac- 
 count, they are less easily dissected, the nervous fibrillae are less 
 distinct, their reddish chords are moister, and they appear form- 
 ed of a more homogeneous substance: their membranous cover- 
 ings are less considerable. They are likewise endowed with a 
 more acute and more delicate sensibility. Every one knows the 
 danger attending wounds of the mesentery, a membranous 
 duplicature, in itself insensible, but containing such numerous 
 nerves destined to the intestinal tube, that the most pointed in- 
 strument can scarcely wound the mesentery, without injuring 
 some of their branches. The pain attending affections of the 
 great sympathetic nerves, is of a very peculiar kind; it leads 
 directly to the extinction of the vital power. It is a well-known 
 fact, that a bruise of the testicles overpowers, in a moment, the 
 strongest man. Every one knows, that patients who die of 
 strangulated hernia, of volvulus, or of everj’^ other affection of 
 the same kind, die in the most distressing anguish, their heart 
 feels oppressed, and they are tormented with constant vomiting. 
 Intestinal and nephritic colics are attended with the same sort 
 of pain; that attending injection of the tunica vaginalis in hydro- 
 cele, is of the same kind. And one expects a favourable event 
 of the operation, only in those cases in which the patient has 
 felt pain along the spermatic chord, in the course of the sper- 
 matic nerves, which arise, as it is well known, from the renal 
 plexus. In three cases of wounds of the abdomen, I was led by 
 the nature of the pain which the patients suffered, to prognos- 
 ticate that the wounds had penetrated; the event justified my 
 prognostic. In all these affections of the great sympathetic 
 nerves, the pulse is frequent and hard, the face is covered with 
 a cold sweat, the features are sunk; all the symptoms are alarm- 
 ing and soon terminate fatally. 
 
 The use of the system of the great sympathetic nerves is, not 
 merely to establish a closer connexion and a greater union be- 
 tween all the organs which perform the functions of assimilation, 
 but likewise to free those parts from the influence of the will. 
 A power of the mind so fickle and so varying, that life would 
 be in constant danger, if we had it in our power to stop or 
 
59 
 
 suspend the exercise of functions with which life is essentially 
 connected. 
 
 If we consider what are the organs to which the functions of 
 assimilation are intrusted, and which receive their nervous in- 
 fluence from the great sympathetic nerves, we shall find, that 
 the action of the greater number, is wholly independent of the 
 controul of the will.* The heart, the stomach, the intestinal 
 canal, &c. do not obey the will, and seem to possess a more 
 insulated and more independent existence, and to act and rest, 
 without any influence. on our part. Some of these organs, as the 
 bladder, the rectum, and the muscles of respiration, which do 
 not receive their nerves exclusively from the great sympathetics, 
 are obedient to the will, and receive from the brain the principle 
 of motion, the former, from the branches which the sacral nerves 
 send to the hypogastric plexuses: the diaphragm, from the nerves 
 which it receives from the fifth and sixth cervical pairs. 
 
 The great sympathetic nerves supply the diaphragm, the 
 rectum, and bladder, only with nerves of sensation. This pro- 
 vision was a very necessary one, for, if, as is the case with the 
 heart, and the intestines, these parts had received their nerves 
 of motion from the great sympathetics, their action would have 
 been independent of the will, as is the case with all the parts 
 which these nerves supply with motion. The bladder and rectum, 
 placed at the extremities of the digestive apparatus, and destined 
 to serve as reservoirs to the excrementitious residue cf our solid 
 and liquid aliments, would have been constantly evacuating 
 their contents, as fast as the substances which are destined to 
 be retained within them for some time, reached their cavity. 
 
 On the other hand, if the diaphragm had received its nerves 
 of motion from the great sympathetics, respiration would have 
 ceased to be a voluntary function, of which we might at pleasure 
 
 * All those parts which receive their nerves from ganglions, are equally 
 independent. Professor Chaussier thinks, that the upper filaments of the 
 great sympathetic nerves, ascend along the internal carotid, and join the 
 sphenopalatine and lenticular ganglions. — M. Ribes thinks he has ascertained 
 by dissection, that several very long and slender filaments follow the course of 
 the branches of the internal carotid, and like them are sent to the base of the 
 brain, beyond which they cannot be traced. I have myself observed, in dissec- 
 tion, these filaments around the branches of the internal carotid artery, but I 
 had always considered them to be formed of cellular substance. 
 
60 
 
 accelerate, slacken, or even completely suspend the action. To 
 prove that the act of respiration is under the controul of the will, 
 we may have recourse to analogy, and adduce the instance of 
 reptiles, as lizards, frogs, serpents, salamanders, and toads, which 
 are cold-blooded animals, and in which this function is manifestly 
 voluntary. We may further mention those slaves, who, we are 
 told by Galen, put themselves to death, when summoned before 
 their executioners or judges. According to that physiologist, 
 and others, they choked themselves, by swallowing their tongue. 
 But it is sufficient to know how the muscles that bind down the 
 tongue are situated, and the degree of motion which they allow, 
 to see how little ground there is for that opinion. The action of 
 the brain would, in that case, have been no longer necessary to 
 the maintenance of life; in an animal without a brain, respira- 
 tion would have continued, and the circulation would not have 
 been interrupted. The death of that viscus would not have been 
 attended with the sudden death of all the rest. 
 
 The nerves which arise from the spinal marrow, and which 
 give to the diaphragm the power of contraction, a power which 
 that muscle loses suddenly, if these nerves be tied, appear to 
 me the chief links which unite the internal assimilating or nu- 
 tritive functions, to those which keep up the relation of the 
 animal with external objects. Without this bond of union, the 
 series of vital phenomena would have been less close, and their 
 dependence less necessary. Had it not been for the necessity 
 that the diaphragm should receive from the brain, by means of 
 the phrenic nerves, the principle which determines its contrac- 
 tions, acephalous animals, which are born without that organ, 
 might continue to live as they did before birth, when the organs 
 of nutritive life received blood, which had undergone, in the 
 lungs of the mother, the changes necessary to life. But where 
 the bond which united them to the mother is destroyed, obliged 
 themselves to produce in their fluids, the necessary changes, by 
 the inhalation of the vivifying principle contained in the atmo- 
 sphere, they no longer can obey that necessity; the organs 
 of respiration are deficient in the principle which should excite 
 them. 
 
61 
 
 When an internal inflammation is of small extent,* and is 
 seated in a part in which there are not, many nerves, and whose 
 tissue yields easily to the humours which irritation determines 
 into it, the whole morbid action takes place in the affected part, 
 and the general order of the functions is not sensibly deranged. 
 But when inflammation takes place in a part endowed with 
 much sensibility, or of a close texture, as the fingers and toes, 
 then fever comes on, because a sympathy in the morbid action 
 takes place, between the diseased part and the rest of the 
 system. This diffusion of the local action almost infallibly takes 
 place, when inflammation occurs in one of the organs of the 
 assimilating functions. This effect may be considered as uni- 
 form, though Morgagni mentions several instances of inflamma- 
 tion of the liver, marked by no peculiar symptoms. 
 
 A knowledge of the great sympathetic nerves accounts for 
 this difference. When an external part is affected with inflam- 
 mation, the irritation which it suffers, is by means of its nerves 
 propagated to the brain, which by a re-action, called by Vicq- 
 d’Azyr (who on this subject has only developed the opinions of 
 Van Helmont) internal nervous action, transmits that irritation 
 to the heart, to the organs of respiration, of digestion and 
 of secretion, in which the phenomena, denoting a febrile state, 
 are principally evolved. When, on the contrary, the heart, the 
 lungs, or any other internal organ is affected with acute in- 
 flammation, all the viscera partake in the derangement with 
 which any one of them is affected, and without the intervention 
 of the brain. They are all intimately connected by the filaments 
 which they receive from the great sympathetic nerves; and, by 
 means of that nervous system, which is in especial manner ap- 
 propriated to them, they carry on a more intimate intercourse 
 
 * A thousand pustules in the small pox occasion only a moderate degree of 
 fever, if they are at a distance from each other; but if the disease is confluent, 
 that is, if the pustules are close together and run into each other, the fevei’ 
 becomes considerable and the patient’s life is endangered. The fleshy granu- 
 lations which sprout inabundance from an ulcerated surface, are so many 
 small phlegmons unaccompanied by a febrile state, but if brought close to 
 each other by irritation, that condition will not fail to ensue. Vaccination is not, 
 i/i the greater number of cases, attended by the slightest febrile action, if, as 
 I have always done, the punctures are made at a certain distance from each 
 other, so that the inflammatory areolae may not run into each other. 
 
62 
 
 of sensations and affections. Besides, the derangement of the 
 important functions intrusted to the diseased organs, is neces- 
 sarily attended with proportionate changes in all the acts of the 
 animal economy, in the same manner, no doubt, as the defect 
 of one wheel interrupts or disturbs the mechanism of the whole 
 machine. 
 
 There exists in the stomach an union of the cerebral and 
 sympathetic nerves, which explains the manifest dependency, 
 in which that one of the three supports of life is found with the 
 brain; a dependency so marked, that every strong affection of 
 the soul, every violent agitation of the mind, weakens or even 
 totally suspends the action of digestion in the stomach.— This 
 combination of cerebral and sympathetic nerves likewise ac- 
 counts for a phenomenon, which was mentioned in speaking of 
 the influence of habit on the action of the organs. The stomach 
 differs essentially from the intestinal canal; for, far from getting 
 accustomed to the impression of emetics, so as to become by 
 degrees less sensible to their action, as the intestines to the 
 action of purgatives, though three grains of tartar emetic could, 
 at first, scarcely excite it, half a grain only of that salt is able to 
 bring on vomiting, when by frequent use, it has acquired the 
 habit of the motions excited by its action. Is it not in that case 
 with the stomach, as withalimb, whose muscles perform motions 
 with the greater ease and facility, when they have been often 
 practised. 
 
 § XI. OF THE RELATIONS OF PHYSIOLOGY TO SEVERAL OTHER 
 SCIENCES. 
 
 It would be entertaining a very incorrect notion of the science 
 of living man, to imagine with some authors, that it solely con- 
 sists in the application of the laws of natural philosophy, to the 
 explanation of the phenomena of the animal economy. Phy- 
 siology is an independent science; resting upon truths of its 
 own, which it draws from the observation of those actions, 
 which, in their aggregate succession and connexion, constitute 
 life. It is enriched, it is true, with facts furnished to it by 
 natural philosophy, chemistry, and mathematics; but what it 
 has borrowed from these, is accessory merely, and does not 
 form an essential part of the edifice of the science. Thus, the 
 
63 
 
 better to understand the mechanism of hearing and vision, 
 physiology borrows from acoustics and optics, elementary no- 
 tions on sound and light; and, in order to obtain a more correct 
 knowledge of the nature of our solids and fluids, and of the 
 manner in which animal substances are constantly passing from 
 the one to the other of, these two conditions, physiology calls in 
 the aid of chemistry. Thus, geometry and mechanism furnish it 
 with the means of better understanding the advantageous form 
 of the organs, and the perfection of their structure. 
 
 No study carries along with it a more lively interest, than 
 that of the admirable relations existing between the conforma- 
 tion of our parts, and the external objects, to which they are 
 applied. These relations are calculated with such precision, 
 and laid down with such accuracy, that the organs of sense and 
 of motion, considered in this point of view, may be regarded 
 as the model of the most ingenious productions of art. So true 
 it is, in the words of the great physician of Pergamus, that 
 nature did every thing before art, and better. 
 
 At the beginning of the last century, geometrical physicians, 
 deceived by an appearance of rigid precision, attempted to ex- 
 plain every thing by the calibre of vessels, their length, their 
 curvatures, the compound ratio of the action of solids and the 
 impulse of fluids. Hence were formed theories so very im- 
 perfect, that, as we shall see, in treating of several points of 
 physiology, and especially of the force with which the heart 
 acts, not one of those who proposed them, coincides with those 
 who have since followed their track. However, it does not 
 admit of a doubt, that there occur in the animal machine, 
 effects which are referable to the laws of hydraulics. The brain, 
 for example, required a large and constant supply of arterial 
 blood, vivified by recent circulation through the lungs; but the 
 too rapid and abrupt access of that fluid in the brain, might 
 have disordered its structure. Nature, therefore, has, as we 
 
 * ^lamJoquidem natura, ut arhilror, et prior tempore sit, et in operibus magis 
 sapiens qudm ars. — Galenus, dc vsu partium, lib. VII. cap. 13. 
 
 It was from observinsj the manner in which nature prevents the diffusion of 
 light in the globe of the eye, that Euler was led to the improvement of his 
 astronomical telescopes. 
 
64 
 
 shall mention in the article of the cerebral circulation, employ- 
 ed all the hydraulic resources in her power, to break the force 
 with which the blood enters the brain, and to slacken its course. 
 
 Has man ever applied the laws of hydraulics in a more 
 felicitous manner than nature, in the rete mirabile formed at 
 the base of the brain by the carotids of quadrupeds? An 
 arrangement truly remarkable, without which, the blood con- 
 veyed to the brain by those arteries, impelled by a force 
 superior to that of the human heart, and not having to over- 
 come the resistance of its own gravity, would infallibly have 
 occasioned a disorganization of that organ, whose consistence 
 is so soft. 
 
 As to the application which is allowable of mathematical 
 sciences, it may be said, that, as in physiology, but little is 
 absolutely certain,^ and much merely probable, we can reckon 
 only on probabilities, and seek our elements in facts deduced 
 from observation or experience: facts, which when collected 
 and multiplied to a certain degree, lead to results of equal value 
 with truths absolutely demonstrated. 
 
 The phenomena presented by living bodies vary incessantly, 
 in their activity, their intensity, and their velocity. How can 
 mathematical formulae apply to such variable elements? As well 
 might you inclose in a frail vessel, hermetically sealed, a fluid 
 subject to expansion, and of variable bulk. The motions of pro- 
 gression in man and in the animals, afford, nevertheless, sufii- 
 ciently correct applications of calculation. Calculation may 
 likewise be applied with advantage, to the measurement of the 
 results of our different secretions, to ascertain the quantity of 
 air, or of aliment, introduced into our organs, See. 
 
 Among the principal causes which have retarded, in a consi- 
 derable degree, the progress of ph)’^siology, may be enumerated 
 the mistake of those who have endeavoured to explain all the 
 phenomena of living bodies, by a single science, as chemistry, 
 hydraulics, &c., while the union of all these sciences will not 
 account for the sum of these phenomena. The abuse, however, 
 
 * This is to be understood, as applying only to the causes of the pheno- 
 mena, and not to the phenomena themselves; for physiology is perhaps richer 
 than any other science, in facts unquestionable, and easily ascertained by 
 observation. 
 
65 
 
 of these sciences, should not be a reason for setting them aside 
 altogether. The facts obtained from natural philosophy, che- 
 mistry, mechanics, and geometry, are so many means applicable 
 to the solution of the great problem of the vital economy; a 
 solution which, though as yet undiscovered, should not be con- 
 sidered as unattainable, and to which we shall approach the 
 nearer, as we attempt it with a greater number of data. But 
 it cannot be too often repeated, that he alone can hope for that 
 honour, who, in the application of the laws of natural philosophy 
 to living bodies, will take into account the powers inherent in 
 organized nature, which controul, with supreme influence, all 
 the acts of life, and modify the results that appear most to de- 
 pend on the laws by which inorganic bodies are governed. 
 
 Anatomy and physiology are united by such close relations, 
 tliat it has been an opinion with some, that they are absolutely 
 inseparable. If physiology, say they, has for its object, a know- 
 ledge of the functions carried on by our organs, how is one to 
 understand their mechanism, without knowing the instruments 
 by which they are performed? One might as well attempt to ex- 
 plain the manner in which the hand of a watch performs the circle 
 of its diurnal revolution, without understanding the springs and 
 tiuraerous wheels which set it In motion. Haller is the first who 
 established the connexion between anatomy and physiology, and 
 who illustrated it in his great work. Since Haller, a great num- 
 ber of anatomists, and among them Sosmmering,* in a work 
 recently published, have combined, as much as possible, these 
 two sciences; the latter. In treating separately of each system 
 of organs, explains what is best known of their uses and pro- 
 perties. 
 
 However close the connexion between anatomy and physio- 
 logy, they have, nevertheless, appeared perfectly distinct to the 
 greater number of authors, and we have several valuable works 
 on anatomy, of which physiology occupies but a small part. — 
 This manner of embracing the two sciences appears to me at- 
 tended with the greatest advantage; in fact, if the Insulated des- 
 cription of organs suffices to the physiologist who wishes to 
 
 * J. Ch. Soemmevlng', de corporis humani juiried. 6 vols. 8vo. 1804. 
 
 I 
 
66 
 
 study their functions, that method is attended with the disad- 
 vantage of furnishing few truly useful views, in the practice 
 of operative surgery. To render the knowledge of the human 
 body more especially applicable to the practice of surgery, it is 
 necessary, nOt only to consider separately the different parts, 
 but likewise to view them in their connexion, and to determine 
 precisely their relations. The anatomist, who knows that the 
 principal artery of the thigh is the crural, — that, continued un- 
 der the name of politeal, it passes behind the knee in its way to 
 the leg, — that, in its course, it supplies with branches different 
 parts of the limb, — even though he knew perfectly the name, 
 the number of these branches, the varieties to which they are 
 subject, the parts to which they are distributed, would never- 
 theless possess a knowledge of that branch of the system, almost 
 useless in the treatment of the diseases with which it may be 
 affected. The situation of the artery, its direction, the parts 
 which surround it, its precise relations to each of them, its su- 
 perficial or deep seated course, &c. are the only circumstances 
 from which he can derive any advantage. 
 
 He who, in this point of view, cultivates anatomy, may be 
 compared to the chemist; in the same manner as the latter is 
 never better acquainted with a substance, than when he is able 
 to decompose it, and to reproduce it from a combination of its 
 parts, so the anatomist is well acquainted with the body of man, 
 only, when having studied separately, and with the greatest care, 
 each of his organs and each of the systems, formed by the col- 
 lection of a certain number of similar organs, he is able to assign 
 to each of them its place, to determine its relations, and the pro- 
 portions which it bears in the structure of anyone of our limbs. 
 The study of the latter is much more difficult and extensive, than 
 that of the former: for, the chemist who decomposes and recom- 
 pounds a well-known substance, phosphat of lime, for instance, 
 attains only to the knowledge of its constituent principles, and 
 respective proportions: the phenomena of situation altogether 
 escape him. The anatomist, on the other hand, who knows that 
 such a part is composed of bones, of muscles, of nerves, of ves- 
 sels, must know, not only every one of these parts, their relative 
 bulk, but the exact place in which they are to be found. 
 
67 
 
 Anatomy, pursued in this spirit, offers a field of wide extent: 
 it is the art which Leibnitz called the analysis of situation, ana- 
 lysis situs; and the knowledge of it is too important not to re- 
 quire a separate place, among the departments of medical know- 
 ledge. I will not pass over the motives that are alleged for com- 
 bining anatomy and physiology in one course of instruction. 
 Anatomy, confined to the mere description of the organs, is too 
 dry and fatiguing: physiology throws over it interest and variety: 
 it helps to ensure the attention of the hearers, who will retain, 
 more permanently, what they have listened to with pleasure. 
 Would not one think that physiological details were, for an au- 
 dience, what is contrived for a sick and froward child, in the 
 honey that is rubbed on the edge of the cup, to disguise the 
 bitterness of the draught that is to recall him to life? In com- 
 bining two objects, of which one has no interest but that of use- 
 fulness, whilst the other is engaging as well, the attention will 
 be not merely divided, but altogether distracted, and the mind 
 of those who read or listen, will skim over dry details, to seize 
 with avidity what furnishes more to its activity of intelligence. 
 Anatomy is to physiology, what geography is to history. Gene- 
 ral considerations on the situation, the size, the form, the rela- 
 tions, the structure of an organ, are an indispensable preparation 
 to the perfect understanding of its functions: accordingly, you 
 shall find much anatomy in physiological treatises, as you find 
 much geographical detail in faithful historians. 
 
 I have said enough, I trust, to escape the reproach of not 
 having filled my book with anatomical descriptions, from the 
 multitude of excellent works we possess on the anatomy of the 
 human body. Let us now enquire what relation physiology 
 bears to Comparative Anatomy. 
 
 If a machine can be perfectly known, only after taking it to 
 pieces, down to its simplest elements; if the mechanism of the 
 whole action is conceived, only by separately studying the action 
 of each different part, comparative anatomy, by aid of which 
 we can study, in the great chain which the animal kinds com- 
 pose, the separate action of each organ, appreciate its absolute 
 or relative importance, consider it, at first, insulated and reduced, 
 so to speak, to its own powers, in order to determine what part 
 it bears in the carrying on o^a function; comparative anatomy 
 
68 
 
 is of absolute necessity to him who would make great progress 
 in the knowledge of man: it may be looked upon as a sort of 
 analytic method, by means of which we more completely attain 
 to the knowledge of ourselves. 
 
 In order to conceive rightly the operations of the human In- 
 tellect, and explain the generation of the faculties of the soul, 
 metaphysicians have imagined a statue, into which they have 
 infused a gradual animation, by investing it, one by one, with our 
 organs of sensation. Now, Nature has realized in some sort this 
 dream of philosophy. There are animals to which she has en- 
 tirely denied the organs of sight and hearing; in some, taste and 
 smell seem to have no separate existence from touch; in others, 
 she has exercised a sort of analysis on a system of parts which all 
 concur in one function. It is thus, that in some animals, divest- 
 ing the organ of hearing of the accessories allotted to collect, 
 transmit, and modify the rays of sound, she has reduced it to a 
 simple cavity, filled with glutinous fluid, in which float the ex- 
 tremities of the acoustic nerve, alone fitted to receive the im- 
 pression of sound; a fact which overthrows all the hypotheses 
 that had ascribed this sensation to other parts of the auditory 
 apparatus. 
 
 Of all the phj'sical sciences. Comparative Anatomy is that 
 which furnishes the most useful facts to physiolog)^ Like phy- 
 siology, it is concerned with organized living beings: there is, 
 therefore, no need of watching against the false applications, so 
 often made from the sciences, whose objects are matter inor- 
 ganic and dead, or which study, in living beings, only the gene- 
 ral properties of matter. Haller was so well aware of the utility' 
 of introducing this science into physiology, that he has brought 
 together the greater part of the facts known in his time, on the 
 anatomy of animals, at the head of each chapter of his immor- 
 tal work. 
 
 This general consideration of living and animated beings, so 
 well adapted to unveiling the secret of our organization, has 
 this further advantage, that it enlarges the sphere of ideas of 
 him who applies to it. Let him who aspires to that largeness of 
 conception, so requisite in medicine, where facts are so multi- 
 plied and various, explanations so contradictory, and rules of 
 
69 
 
 conduct so unfixed, cast a general glance on this great division 
 of organized beings, of which many, in their physical structure 
 so nearly resemble man; — he will see the sovereign Architect 
 of the world, distributing to all the element of life and activity 
 giving to some a less power of motion, to others more: so that 
 formed all on one model, they seem only the infinitely varied, 
 but gradual shades of the same form, if forms have shades like 
 colours: never passing abruptly from one to another, but rising 
 or falling by gentle and due degrees; covering the interval that 
 separates two different beings, with many species that serve as a 
 transition^ from one to the other, and which present a continuous 
 series of advancement or degradation: organization being con- 
 stantly simplified, in descending from man to the inferior crea- 
 tures; but rising in complexity, in re-ascending from those ani- 
 mals to man, who is the most complex being in nature, and was 
 justly considered, by ancient philosophy, as the master-piece of 
 the Creator. 
 
 If the intimate structure of our organs totally eludes our in- 
 vestigation, it is, that the finest and most delicate of their consti- 
 tuent parts are of such minute dimensions, that our senses have 
 no hold on them. It is then well to have recourse to analogy, 
 
 * The conception is noble and interesting of a scale of being, -which, as was 
 said by C. Bonnet, connecting all the worlds, embracing all the spheres, should 
 extend from the atom to the most exalted of cherubim. Without carrying it so 
 high or so low, if we confine it to the natural beings with which we are well 
 acquainted, and which can be brought under observation, it will be seen, that 
 the idea is not so chimerical as some writers of most respectable aulliority have 
 supposed it. The plan traced by C. Bonnet is evidently defective; we find in 
 it beings set beside each other, that have but faint lines of resemblance, or alto- 
 gether illusive. The present state of the natural sciences would allow of its 
 being better done: one might try at least for all bodies what Jussieu has ex- 
 ecuted with regard to vegetable productions; and if this undertaking, in the 
 hands of men the most able to bring it to a successful termination, left any thing 
 defective, would not that imperfection be an indication of the existence of 
 other worlds, or of lands yet unknown on the globe we inhabit; undiscovered 
 regions, where those animals, and plants, and minerals would be found wliich 
 were wanting to fill up the gaps in the immense series of co-ordinate ex- 
 istence? 
 
 Demonstratum fuit et hoc, nuUam rem contrarias, uel omnino multiim differentes 
 qualitates recipere posse, nisi per media prius iter fecerh. 
 
 Galenus, de usu partium, lib. 4, cap. 12. 
 
70 
 
 and to study the organization of animals that exhibit the same 
 organs on a larger scale. Thus, the cellular texture of the lungs, 
 which cannot be distinctly shewn in man, on account of the ex- 
 treme minuteness of the smallest bronchi*, may be satisfacto- 
 rily seen in the vesicular lungs of salamanders and frogs. In 
 like manner, the scales which cover the bodies of fishes and 
 reptiles, or tlje legs of birds, give us a just idea of the structure 
 of the epidermis, and of the arrangement of its small scales, 
 which lie over each other, in a part of their surface. 
 
 The human structure being more complicated, must produce 
 effects more numerous, and results more varied, and more diffi- 
 cult to understand. In commencing the study of the animal or- 
 ganization by that of man, we do not, therefore, follow the ana- 
 lytical method, we do not proceed from what is simple, to what 
 is more complex. It would perhaps be an easier and a more 
 natural way of arriving at a solution of the grand and difficult 
 problem of the animal economy, to begin by explaining its most 
 simple terms; to rise by degrees from plants to vegetating ani- 
 mals, as polypi; from these to white-blooded animals, then to 
 fishes and reptiles; from the latter to warm-blooded animals, 
 and lastly to man himself, placed at the head of that long series 
 of beings whose existence becomes complicated, in proportion 
 as they approach him. 
 
 The study of every part of natural history, and especially of 
 comparative anatomy, cannot fail, therefore, to prove of infinite 
 advantage to the physiologist; a truth well expressed by the 
 eloquent M. de Buffon,* who says, that if there existed no ani- 
 mals, the nature of man would be still more incomprehensible. 
 
 I shall say nothing of the well known relations of physiology 
 to medical science, of which it is justly considered as the base 
 or support. Medicine, called by some the art of healing, by 
 others more properly, the art of treating diseases, may be defined 
 the art of preserving health, or curing diseases, or of rendering 
 them more supportable; medicine, in all its parts, is enlightened 
 by physiology, and cannot have a surer guide. Owing to a neglect 
 of this auspicious guide, therapeutics and materia medica long 
 
 Histoire nat. tom. V. 12mo. p. 241. Discours sur la nature des animaux 
 
71 
 
 cemained involved in a mist of conjectures and hypothesis. Phy- 
 sicians should never for a moment forget, that as a great num- 
 ber* of diseases consist in a-derangement of the vital functions, 
 all their efforts should tend to bring hack sensibility and contrac- 
 tility to their natural condition; that the best classification of dis- 
 eases and of medicines, is that which is founded on a judicious 
 distinction of the vital powers. With this view it is that M. 
 Alibert, in his elements of materia medica, classes medicines 
 according to their effects on sensibility or contractility, and 
 according to the organs on which their action is particularly 
 exerted. 
 
 § XII. CLASSIFICATION OF THE VITAL FUNCTIONS. 
 
 After having treated separately of the vital powers or facili- 
 ties, nothing is easier than to arrange, in a clear and methodical 
 order, the functions carried on by the organs which these pow- 
 ers call into action. The term function might be defined, meaws 
 of existence. This definition would be the more just, as life is 
 only the exercise of these functions, and as it ceases, when any- 
 one of the more important can be no longer carried on. From 
 not distinguishing the faculties, from the functions which are 
 merely the acts of the faculties or powers, several modem 
 divisions, though far preferable to the old classification of the 
 functions into vital, animal and natural, are, nevertheless, defi- 
 cient in accuracy and simplicity. Thus Vicq-d’Azyr in the 
 classification of the phenomena of physiology, inserted in the 
 discourse which he has prefixed to his work on Anatomy, mis- 
 takes the cause for the effect, and places sensibility and irrita- 
 bility among the functions, and commits another mistake, by 
 ranking among the latter, ossification, which is but a peculiar 
 mode of nutrition, belonging to parts of a hard structure. 
 
 The best method of classing the actions which are performed 
 in the living human body is, doubtless, that by which they are 
 distributed and arranged according to the object which they 
 
 * All diseases consist in physical derangements, as solutions of continuity, dis- 
 j^lacements, organic alterations, as polypi, aneurisms, and other affections re- 
 sulting from organic affection and alteration of structure; ’vital lesions, as fevers_, 
 ataxice, adynamix, vesaniac, &c. see Nosographie Chirnrgicale. 
 
72 
 
 fulfil. — Aristotle, Buffon, and especially Grimaud, have laid oa 
 that base the foundation of a method which we shall adopt, with 
 the modifications which we are about to mention. 
 
 Aristotle and BuflTon had observed, that among the acts of the 
 living economy, some were common to all beings that have life, 
 to plants and animals during sleep and in waking, while others 
 seemed to belong exclusively to man, and to the animals which 
 more or less resemble him. Of these two modes of existence, 
 the one vegetative^ the other animal^ the former appeared to 
 them the more essential, as being more diffused and consisting 
 merely in the assimilation of nutritive molecules, in the nutrition 
 absolutely necessary to the preservation of the living being,* 
 who, as his substance is incessantly wasting, would soon cease to 
 exist, if these continual losses were not always repaired by the 
 act of nutrition. 
 
 Grimaud, Professor of Physiology at Montpellier, too soon 
 lost to the science which he cultivated as a philosopher truly de- 
 serving that name, adopted this simple and luminous division, 
 developed it better than had been done before him, and uniform- 
 ly followed it in his lectures and in his works.f This division of 
 the functions into internal^ which he likewise calls digestive., and 
 into external or loco-motive, lately brought forward under the 
 name of organic and animal, the former of which terms is quite 
 inaccurate and defective, since it leads to a belief, that the 
 animal life is not confided to organs, and that these vital in- 
 
 * Nam anima nutritlva etiam aliis inest, et prima et maxima, communis facultas 
 auinue, secwidUm quam omnibus visiere inest. Aristot. ile anim. lib. 2. cap. 4. 
 
 ■f In his MS. lectures on Physiolog’y, he .seems to feel a complacency in that 
 division which he had in a manner appropriated to himself, by his happy illus- 
 trations of it, and by the changes which he had introduced into it. In every 
 lecture, I might almost say in every page, he returns to this division, explains 
 it, dilates, and comments upon it. “ The functions,” says he, “ may be divided 
 “ into two great classes; some are performed in the interior of the body, and 
 “exclusively belong to it; others take place outwardly and belong to external 
 “ objects, &c.” The digestive power presides, in his opinion, over the internal 
 functions, whosp object is nutrition; the loco-motive power directs the external 
 functions. “It is by means of the organs of sense that the animal enlarges his 
 existence, that he applies and distributes it on the surrounding objects, tliat 
 he takes cognizance of the qualities in those objects which concern him; it is 
 by means of the muscles essentially obedient to the organs of sense, that he 
 adapts himself to those objects, that he places himself in a manner suited to 
 the mode of their activity, &c.” 
 
73 
 
 •jrtruments are solely employed on internal life or nutrition 
 (^Motus assimilationis. Bacon; Bias alterativum, Van Helmont): 
 This distinction does not comprehend the whole of the phe- 
 nomena, and does not embrace the sum of the functions 
 which are performed in the animal economy. In fact, there are 
 not found in the two great classes which it establishes, the acts 
 by which animals and vegetables re-produce and perpetuate 
 themselves, and immortalize the duration of their species. All 
 the functions destined to the preservation of the species are not 
 included; they merely relate to the functions subservient to the 
 preservation of individuals. 
 
 I have, therefore, thought it right to include under two gene- 
 ral classes, in the first place, the functions which belong to the 
 preservation of the species, functions without which man might 
 exist, as we see in eunuchs, but without which the human spe- 
 cies would soon perish, from a loss of the power of re-produc- 
 tion. In laying down these two great divisions, I have merely 
 considered the object and end which each function has to fulfil. 
 
 Among the functions which are employed in the preservation 
 of the individual, some fulfil this office by assimilating to his 
 own substance the food with which he is nourished; the others, 
 by establishing, in a manner suited to his existence, his relations 
 with the beings which surround him. 
 
 The functions destined to the preservation of the species, may 
 likewise be divided into two classes. Those of the first class re- 
 quire the concourse of two sexes; they constitute generation pro- 
 perly so called; those of the second order, exclusively belong to 
 the female, who, after conception, is alone destined to bear, to 
 nourish, to bring into the world, and suckle the new being, the 
 result of conception. 
 
 The internal, assimilating, or nutritive functions concur in the 
 same end, and all serve to the elaboration of the nutritive matter. 
 The aliment once admitted into the body, is subjected to the ac- 
 tion of the digestive organs, which separate its nutritive parts: 
 the absorbents take it up and convey it into the mass of fluids; 
 the circulatory system conveys it to all the parts of the body, 
 makes it flow towards the organs; the lungs and the secretory 
 glands supply it with certain elements, and deprive it of others, 
 alter, modify, and animalize it; in fine, nutrition, which may be 
 
 K 
 
74 
 
 considered as the complement of the assimilating functions, 
 whose object it is to provide for the maintenance and growth of 
 the organs, applies to them this animalized substance, assimila- 
 ted by successive acts, when it has become quite similar to them. 
 
 Several, however, of these functions, serve at once to preserve 
 and to destroy. Absorption, which takes up extraneous mole- 
 cules to be employed in’ the growth of the organs, takes up 
 equally the organic molecules which are detached by motion, 
 friction, heat, and all the other physical, chemical, and vital 
 causes. The action of the heart and of the blood-vessels sends 
 these fragments, together with the parts truly recrementitious, to- 
 wards the lungs, which, at the same time that they bring about 
 a combination of the nutritive parts with the oxygen of the at- 
 mosphere, separate from the blood the materials which can no 
 longer be employed in nourishing the organs; the same power 
 sends them towards the secretory glands, which not only purify 
 what is liquid, by separating from it that which cannot without 
 danger remain in the animal economy, but which likewise ela- 
 borate or prepare peculiar fluids, some of which are results of 
 the act of nutrition, are employed in that act, and impart to the 
 substances on which it is performed a certain degree of animali- 
 aation (as to the bile and saliva), while the others seem to be in- 
 termediate states, which the nutritive particles of the food are 
 obliged to undergo, before complete animalization; such are the 
 serous fluids and the fat. 
 
 It might perhaps seem more in conformity to the order of na- 
 ture, to have combined the account of respiration with that df 
 the circulation, by treating of the course of the venous blood, 
 after the action of the absorbent vessels, with which the veins 
 have so much analogy: then to have treated of the phenomena 
 of respiration, or of the conversion of the venous blood into ar- 
 terial, and of the course of the latter into all the parts of the 
 body, by the action of the heart and arteries. But the advantage 
 which would be obtained from a method so contrary to the com- 
 mon practice, which is to consider separately the functions of 
 circulation and respiration, appeared to me too unimportant to 
 justify its adoption. 
 
 The external or relative functions, equally connected by their 
 common destination, connect the individual to every thing that 
 
75 
 
 surrounds him; the sensations, by warning him of the presence 
 of objects which may be useful or injurious to him; motions, by 
 enabling him to approach, or avoid such objects, according as he 
 perceives relations of advantage or disadvantage, according as 
 the opposite sensations of pain or pleasure result from this ac- 
 tion on them, or from theirs on him. In fine, voice and speech 
 give him communication with beings enjoying the same means 
 of communication, and that without a necessity of motion. The 
 brain is the principal organ of these functions, as the system of 
 circulation is the centre of the assimilating functions. All the 
 impressions received by the organs of sense, are transmitted to 
 the brain, and from the brain, determinations arise, as well as 
 the voluntary motions and the voice. The sanguineous system 
 receives the molecules destined to nutrition, and those which 
 are to be thrown out of the body. The sensitive and circulatory 
 systems are the only systems provided with a centre (the brain 
 and the heart), which extend to all parts of the body, by emana- 
 tions originating from that organ, or terminating in it (the 
 nerves, the arteries, and veins): and, as the motions and the 
 voice depend on sensation, and are immediately connected with 
 it as necessary consequences, so respiration, secretion, and nutri- 
 tion are, in a manner, but consequences of the circulation which 
 distributes the blood to all the organs, in order that these may 
 produce on it various changes which constitute respiration, se- 
 cretion, and nutrition. They are, to anticipate what is to come 
 hereafter, only different kinds of secretion that take place at the 
 expense of the different principles contained in the blood. 
 
 The circulation which holds the functions of nutrition in a 
 kind of dependence, subjects the brain, which is the principal 
 organ of the external functions, to an influence still more imme- 
 diate and indispensable. The muscular motions are not less un- 
 der its influence. It is the first function that is apparent in the 
 embryo, whose evolution it brings about; in natural death, of 
 all the functions, it is the last to cease. These are many reasons 
 which justify Haller, for having placed it in the first order, and 
 for having begun by its history, his great work on physiology. 
 I enter into this digression, only to expose the absurdity of the 
 claims of some authors, who, because they have varied the me- 
 thodical order of the functions, broken the series, or made the 
 
76 
 
 slightest changes, for example, by placing the history of the 
 function of smell and taste before the account of the internal or 
 nutritive functions, think they have totally changed the aspect 
 of the science: pitiful sophists, who accumulate subtleties in- 
 stead of facts and ideas. 
 
 In warm and red-blooded animals, the nutritive functions, 
 digestion, absorption, circulation, respiration, the secretions 
 and digestion are performed as in man, and in that respect, 
 there exist between them verj’ slight differences; nay, in some 
 animals, these functions are performed with much more energy. 
 Thus several animals digest substances, on which our own or- 
 gans produce no effect, and others (birds) have a more rapid 
 circulation, a more active nutrition, and evolve more heat. But 
 not one of them is as well provided with organs to keep up in- 
 tercourse, as a living being, with surrounding objects. In no one 
 animal, are the senses possessed of the same degree of perfec- 
 tion; the eagle, whose sight is so piercing, has a very dull sense 
 of touch, taste, and smell. The dog, whose smell is exquisite, 
 has a very ordinary extent of sight; in him the taste and touch 
 are equally imperfect.— His touch, in the perfection of which 
 no animal comes up to man, has not been improved in delicacy, 
 at the expense of the other senses. The sight, the hearing, the 
 taste and smell, preserve a great delicacy, when their sensibility 
 has not been impaired, by injudicious or too frequent impres- 
 sions. The sensitive centre is in no one better developed, and 
 fitter to direct safely the use of the organs of motion. No other 
 animal can articulate vocal sounds, so as to acquire speech. 
 
 This greater extension of life in man, from the number and 
 perfection of his organs, makes him liable to many more dis- 
 eases than the other animals. It is with the human body, as with 
 those machines that become more liable to be deranged, by in- 
 creasing the number of their wheels, with a view of obtaining 
 more extensive or more varied effects. 
 
 All organized bodies are possessed of assimilating functions, »■ 
 but as assimilation requires nneans varying in number and power, 
 according to the nature of the being which performs it, the 
 series of assimilating phenomena commences in the plant by 
 absorption, since it draws immediately from the earth, the 
 juices which it is to appropriate to itself. Its absorbing system. 
 
77 
 
 at the same time performs the functions of a circulatory organ, 
 or rather, the circulation does not exist in plants, and the direct 
 and progressive motion of the sap which ascends from the root 
 towards the branches, and sometimes in a retrograde course, 
 from the branches towards the roots, cannot be compared to 
 the circulation of the fluids which takes place in man, and in 
 the animals which most resemble him, by means of a system of 
 vessels which every moment bring back the fluids to the same 
 spot, and convey them over the whole body, by making them 
 describe a complete circle, frequently, even a double rotation 
 (animals with a single or double circulation, that is, whose heart 
 has one or two ventricles.) Plants breathe after their own man- 
 ner, and produce a change in the atmospherical air, by depriv- 
 ing it of its carbonic acid gas, the result of combustion and of 
 animal respiration, so that -by a truly admirable reciprocity, 
 plants, which decompose carbonic acid and allow oxygen to ex- 
 hale, continually purify the air, which combustion and animal 
 respiration are incessantly contaminating. 
 
 The functions preservative of the species are common to 
 animals and plants. The organs by which these functions are 
 performed, when compared in these two kingdoms of nature, 
 offer a resemblance which has struck all naturalists, and has led 
 them to observe, that of all the acts of vegetable life, no one is 
 more analogous to the animal economy, than that by which 
 fecundation is effected. 
 
 We shall not here explain the general characters of the two 
 orders of functions which are subservient to the preservation of 
 the species: the differences which belong to them are pointed 
 out in several parts of this work.* I shall merely observe with 
 the authors who have considered them generally, that they are 
 in an inverse ratio to each other, so that, in proportion as the 
 activity of the assimilating functions increases, that of the ex- 
 ternal functions is abated. Grimaud has, in the most complete 
 manner, illustrated this idea of the constant opposition which 
 exists between those two series of actions, over which, in the 
 opinion of that physician, there preside two powers which he 
 
 • Especially in the account of living beings, § V. of the preliminary dis- 
 course; articles sleep and fetiis. It is impossible at present to go over all these 
 distinctions, without entering into useless and disagreeable repetitions. 
 
78 
 
 calls loco*motive and digestive. It is in no kind of animals 
 more distinct than in the carnivorous, which possess organs of 
 sense of the greatest delicacy, together with muscles capable of 
 prodigious efforts, and yet powers of assimilation so feeble, 
 that their food cannot be digested, unless it be composed of 
 materials analogous in composition to their own organs.* 
 
 Too much importance should not be attached to this classifi- 
 cation; like all other divisions, it is purely hypothetical. All is 
 connected together, all is co-ordinate in the animal economy; 
 the functions are linked together, and depend on one another, 
 and are performed simultaneously; all represent a circle of 
 which it is not possible to mark the beginning or the end. In 
 circulum aheunt (Hippocrates). In man, while awake, diges- 
 tion, absorption, circulation, respiration, secretion, nutrition, 
 sensation, motion, voice, and even generation, may be perform- 
 ed at the same time; but, whoever in the study of the animal 
 economy should bestow his attention on this simultaneous 
 exertion of the functions, would acquire but a very confused 
 knowledge of them.f 
 
 By becoming familiar with these abstractions, one might 
 soon mistake them for realities; one might even go the length 
 of seeing two distinct lives in the same individual; one would 
 
 * In carnivorous animals, the power of digestion is extremely weak; but 
 their muscles are very powerful. This relative force of the muscles was neces- 
 sary in carnivorous animals, as they live by depredations and slaughter, as 
 their instinct, in unison with their organization, sets them constantly at war 
 with every thing that has life, and as their subsistence depends on their being 
 victorious in the battles to which Nature incessantly calls them. 
 
 GiiiMAUD,^'r«i ^lemoir on Nutrition. 
 
 I The division which I lay down, is not to be strictly adopted, and as 
 being absolutely true. It is a mere hypothesis to be attended to, only in so far 
 as it assists in arranging one’s ideas in a more orderly manner. For, every 
 arrangement, even when arbitrary, is useful in laying before us a great 
 number of ideas, and in thereby facilitating the comparison that is to be insti- 
 tuted among them. All the acts of Nature are so connected, and are linked 
 together in so close an union, and she passes from the one to the other, by 
 such uniform motions, and by gradations so insensible and so adjusted, as to 
 leave no space for us to lay down the lines of separation, or demarcation, 
 which we may choose to draw. All our methods of classing and arranging the 
 productions of nature, are mere abstractions of the mind, which does not con- 
 sider things as they really are, but which attends to certain qualities, and 
 neglects or rejects all the rest. Grimaud, Lectures on Physiology. 
 
79 
 
 be apt to assign as the character of internal life, that it is carried 
 on by organs independent of the will. Although this faculty of 
 the soul presides over the phenomena of respiration, of masti* 
 cation, of the expulsion of the urine and faeces, one might con- 
 sider life as intrusted to unsymmetrical organs, although the 
 heart, the lungs, and the kidneys, are evidently symmetrical; one 
 might fancy it to exist in the foetus, which neither breathes, nor 
 digests, &c. Nothing in the animal economy, said Galen, is 
 ruled by invariable laws, or can be subject to the same accurate 
 results and calculations, as an inanimate machine {Nil est in 
 corpore viventi plane sincerum. Galen). Thus, respiration, 
 which connects the external and assimilating functions, fur- 
 nishes the blood with the principle which is to keep up the 
 action of the brain, and to excite muscular contractions. — On 
 the other hand, the motion of the muscles is of use in the dis- 
 tribution of the humours, and concurs in the phenomena of 
 assimilation. The brain, by means of the eighth pair of nerves, 
 holds influence over the stomach. The sensations of taste and 
 smell seem to preside, in an especial manner, over the choice 
 of food and of air, and to belong rather to the digestive and 
 respiratory functions, than to those of the intellect or of thought. 
 
 We have seen in this kind of general introduction to the 
 study of physiology, what idea is to be formed of that science 
 as well as of life, the study of which is its object; into how 
 many classes the beings in nature may be divided, and into how 
 many elements they are resolvable: what differences exist, be- 
 tween inorganized, and organized and living bodies; between 
 plants and animals; how life is complicated, modified, and 
 extended, in the immense series of beings which are endowed 
 with it, from the plant to man; and in further particularizing 
 the object under our consideration, we have examined, what 
 are the organs which, by their union, form the human machine; 
 what powers govern the exercise of their functions: Then, we 
 have laid down the fundamental laws of sensibility and contrac- 
 tility, we have spoken of sympathies and habits, of the internal 
 nervous apparatus, which unites, collects, and systematizes the 
 organs of the assimilating functions; we have endeavoured to 
 determine from facts, the existence of the cause which subjects 
 living beings to a set of laws very different from those which 
 
80 
 
 inorganic matter obeys. The knowledge of these laws, is the 
 light which is to guide us in the application to physiology of 
 the accessory sciences. Finally, in the arrangement of the olj- 
 jects which this science considers, I have adopted a more simple 
 and natural division, than any hitherto employed. 
 
 I shall close this preliminary discourse, by saying a few words 
 on the order adopted in the distribution of the chapters. I might 
 have begun by a view of the external functions, as well as of 
 those of assimilation or of nutrition, of sensation, or of diges- 
 tion. I have given precedence to the functions of assimilation, 
 because of all others, they are the most essential to existence, and 
 their exercise is never interrupted, from the instant in which the 
 embryo begins to live, till death. In beginning with an account 
 of them, we imitate nature therefore, who imparts to man 
 this mode of existence, before she has connected him with out- 
 ward objects, and who does not deprive him of it, until the 
 organs of sense, of motion, and of the voice have completely 
 ceased to act. 
 
 As to the course which has been followed in the arrangement 
 of the functions that belong to the same order, or which concur 
 in the same end, it was too well laid down by nature, to allow 
 VIS to depart from it. I have thought it right, that the conside- 
 ration of the voice should immediately precede that of genera- 
 tion, in order that the arrangement might, at a glance, shew the 
 connexion which exists between their phenomena. Several ani- 
 mals use their voice, only during the season of love; the birds 
 which sing at all times, have, during that period, a more 
 powerful and sonorous voice. When man becomes capable of 
 reproduction, his vocal organs suddenly become evolved, as 
 though nature had wished to inform him, that it is through 
 them he is to express his desires to the gentle being who may 
 sympathize in them. The voice, therefore, serves as a natural 
 connexion, between the external functions, and those which are 
 employed in the preservation of the human species. 
 
 The voice, which leads so naturally from the functions which 
 establish our external relations, to those whose end is the pre- 
 servation of the species, is still more intimately connected with 
 motion. It is, in a manner, the complement of the phenomena 
 of loco-motion; by means of it, our communication with external 
 
81 
 
 objects is rendered easier, more prompt, and more extensive: it 
 depends on muscular action, and is the result of voluntary mo- 
 tion. Finally, these motions sometimes supply the place of 
 speech, in pantomime, for example, and in the greater number 
 of cases, the language of action concurs in adding to its effect. 
 Every thing, therefore, justifies me in placing this function 
 after motion, in separating it from respiration, with which 
 every other author has joined it, without considering that the 
 relation between the voice and respiration is purely anatomical, 
 and can, therefore, in no wise apply to physiology. 
 
 I have placed after generation, an abridged account of life 
 and death, in which will be found whatever did not belong to 
 any of the preceding divisions. The necessity of this appendix, 
 containing the history of the different periods of life, that of the 
 temperaments and varieties of the human species, that of death 
 and putrefaction, arises from the impossibility of introducing 
 into the particular history of the functions, these general phe- 
 nomena in which they all participate. 
 
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FIRST CLASS. 
 
 LIFE OF THE INDIVIDUAL. 
 
 FIRST ORDER 
 
 FUNCTIONS OF ASSIMILATION, 
 
 Or, Functions ’luhich are subservient to the preservation 
 of the Individual, by assimilating to his substance 
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NEW ELEMENTS 
 
 OF 
 
 PHYSIOLOGY. 
 
 CHAPTER I. 
 
 OP DIGESTION. 
 
 I. Digestion is a function common to all animals, by which 
 substances extraneous to them, are introduced into their bodies, 
 and subjected to the action of a peculiar system of organs, their 
 qualities altered, and a new compound formed, fitted to their 
 nourishment and growth. 
 
 II. General considerations on the Digestive Organs. Animals 
 alone are provided with organs of digestion; all of them, from 
 man down to the polypus, contain an alimentary cavity variously 
 shaped. The existence of a digestive apparatus may, therefore, 
 be taken as the essential characteristic of the animal kind. In 
 man, this apparatus consists of a long tube extending from the 
 mouth to the anus: within this canal, there empty themselves 
 the excretory ducts of several neighbouring glands, that secrete 
 fluids fit for changing, for liquefying, and animalizing the ali- 
 mentary substance. The different parts of this digestive tube are 
 not of equal capacity; at first, enlarged in the part which forms 
 the mouth and pharynx, it becomes narrower in the oesophagus; 
 this last, dilating considerably, forms the stomach, which again 
 contracting, is continued down under the name of intestine. 
 This tube itself varies in size in different parts of its extent; 
 and it is by the consideration of these differences of size, that 
 anatomists have principally been guided in their divisions. 
 
 The length of the digestive tube is from five to six times the 
 length of the whole body, in an adult; it is greater in proportion 
 
OF DIGESTION. 
 
 86 
 
 in a child. At this age, likewise, digestion is more active, and 
 proportioned to the necessities of growth in the individual. The 
 digestive cavity is in man open at both extremities; in some 
 animals, in the zoophyte for example, one opening serves the 
 purpose of mouth and of anus, receives the food and ejects the 
 excrementitious remains. , 
 
 The extent of the digestive canal is according to the nature 
 of the aliments on which the animals feed: the less those ali- 
 ments are analogous in their nature, to the substance of the 
 animal which they are to nourish, the longer must they remain 
 in his body to undergo the necessary changes. Therefore, it is 
 observed, that the intestine of graminivorous animals is very 
 long, their stomach very capacious and often complex, while 
 carnivorous animals have their intestinal canal short and strait, 
 and so arranged, that the animal substances which are most 
 nourishing, in least bulk, of easy and rapid digestion, which, by 
 too long a stay in the intestines, might become putrid, pass 
 readily through it. In this respect, man holds a middle station 
 between those animals which feed on vegetables, and those 
 which feed on animal substances. He is, therefore, equally fitted 
 for these two kinds of food; he is neither exclusively herbivor- 
 ous, nor carnivorous, but omnivorous or polyphagous. This 
 question, of such easy solution, has long employed physicians, 
 naturalists, and philosophers; each bringing, in favour of his 
 opinion, very plausible arguments, drawn from the form and 
 number of the teeth, from the length of the intestinal canal, 
 from the force of its parietes, &c. 
 
 The parietes of the digestive tube are essentially muscular; a 
 mucous membrane lines its inside, forming within it various 
 folds; lastly, a third coat is accidentally placed over the other 
 two: and is furnished by the pleura to the oesophagus, by the 
 peritoneum to the stomach, as well as to the intestinal canal. 
 
 The characteristic of this third coat is, that it does not cover 
 the whole surface of the parts of the tube to which it is applied. 
 The muscular coat may be considered as a long hollow muscle, 
 extending from the mouth to the anus, and formed, throughout 
 almost the whole of its length, by two layers of fibres, the one 
 set longitudinal, the other circular. The will directs the motions 
 of the two extremities, while the rest of its course is not under 
 
OF DIGESTION. g7 
 
 Its controul. In the cells of the tissue which unites its surfaces 
 to the other coats, fat never accumulates, which might have 
 impeded its contractions, and straitened and even obliterated 
 the tube along which the food was to pass. 
 
 III. Of Food^ solid and liquid. The aliments which nourish 
 man, are obtained from vegetables or from animals. The mineral 
 kingdom furnishes only condiments, medicinal substances or 
 poisons. 
 
 By aliment is meant whatever substance affords nutrition, or 
 whatever is capable of being acted upon by the organs of diges- 
 tion. Substances which resist the digestive action, those which 
 the gastric juice cannot sheathe, whose asperities it cannot 
 soften down, whose nature it cannot change, possess, to a certain 
 degree, the power < f disturbing the action of the digestive tube, 
 which revolts from whatever it cannot overcome: there is no 
 essential difference between a medicinal substance and a poison. 
 Our most active remedies are obtained fiom among the poison- 
 ous substances: tartar emetic, corrosive sublimate, opium, all 
 of them remedies of so much efficacy in skilful hands, when 
 administered unseasonably or in too strong doses, act as most 
 violent poisons; they forcibly resist the digestive powers and 
 furnish them nothing to be acted upon, while mild and inert sub- 
 stances yield to these powers, and come under the class of ali- 
 ments. What then is to be thought of our ptisans, of chicken 
 and veal broth, and other such remedies? That they are employ- 
 ed to deceive the hunger and thirst of the patient, to prevent his 
 receiving into his stomach, substances whose laborious diges- 
 tion would take up the strength required for the cure of the dis- 
 ease; that they are mere precautions of regimen, that he who 
 most varies this kind of resource, can only be said to adopt a 
 treatment of expectation, leaving to nature alone, the care of ex- 
 citing those salutary motions which are to bring about a cure. 
 Why do certain vegetable purgatives, as manna and tamarinds, 
 produce so little effect, even though given in large doses? Be- 
 cause these substances contain many nutritious particles capable 
 of being assimilated, so that strong constitutions digest them 
 and completely neutralize their irritating or purgative qualities. 
 An animal or vegetable substance, though essentially nutritious, 
 may act as a medicine, or even as a poison, when, in consequence 
 
OF DIGESTION. 
 
 88 
 
 of the extreme debility of the digestive tube, or because it has 
 not been sufficiently divided by the organs of mastication, it re- 
 sists the digestive action. Thus surfeits are brought on, because 
 the stomach is debilitated, because it is oppressed by too great 
 a mass of substances, or because having been imperfectly tritu- 
 rated, they are insoluble. It is on considerations of this kind, 
 that the true foundations of materia medica are laid. 
 
 Mineral substances are of a nature too heterogeneous to our 
 own, to admit of being converted into our substance. It appears 
 that their elements require the elaboration of vegetable life; 
 hence it has been justly observed, that plants are laboratories 
 in which nature prepares the food of animals. 
 
 Aliments obtained from plants are less nutritious than those 
 furnished by the animal kingdom, because in a given bulk, they 
 contain fewer parts that can be assimilated to our own substance. 
 Of all the parts of vegetables, the most nourishing is their amy- 
 laceous fecula, but it yields the more readily to the action of 
 the digestive organs, from having already experienced an inci- 
 pient fermentation; on that account, leavened bread is the best 
 of vegetable aliments. The flesh of young animals is less nou- 
 rishing than that of the full-grown, although, at an early age, 
 the flesh of the former abounds more in gelatinous juices; for, 
 this abundant gelatine wants the necessary degree of consistence. 
 
 However various our aliments may be, the action of our or- 
 gans always separates from them the same nutritious principles; 
 in fact, whether we live exclusively on animal or vegetable sub- 
 stances, the internal composition of our organs does not alter; 
 an evident proof, that the substance which we obtain from ali- 
 ments, to incorporate with our own, is always the same, and 
 this affords an explanation of a saying of the father of physic. 
 “ There is but one food, but there exist several forms of food.” 
 
 Attempts have been made to ascertain the nature of this ali- 
 mentary principle, common to all nutritive substances, and it is 
 conjectured, with some probability, that it must be analogous 
 to gummy, mucilaginous, or saccharine substances; they arc all 
 formed from hydrogen and carbon, are well known to differ 
 chesnically, only in the different proportions of oxygen which 
 they contain. Thus, sugar is a kind of gum, containing a con- 
 siderable quantity of oxygen; and which is reduced, in a cer- 
 
OF DIGESTION. 
 
 S9 
 
 tain degree, to the state of starch, when brought to a very fine 
 powder by means of a rasp, for, the friction disengaging a por- 
 tion of its oxygen, deprives it in part of its flavour, and leaves it 
 an insipid taste, similar to that of farinaceous substances. No- 
 thing, in fact, nourishes better, more quickly, and from a smal- 
 ler bulk, than substances of this kind. The Arab crosses the 
 vast plains of the desert, and supports himself by swallowing a 
 small quantity of gum arabic. The nourishing quality of animal 
 and vegetable jellies is well known; saccharine substances soon 
 cloy the appetite of those who are fondest of them. In decrepid. 
 old age, some persons live exclusively on sugar; I know several 
 in that condition, who spend the day in chewing this substance, 
 which is a laborious employment for their feeble and toothless 
 jaws. Lastly, milk, the sole nourishment of the early periods of 
 life, contains a great proportion of gelatinous and saccharine 
 matter. 
 
 Though man, destined to live in all latitudes, is formed to 
 subsist on all kinds of food, it has been observed, that the in- 
 habitants of warm climates generally prefer a vegetable diet. 
 The Bramins in India, the inhabitants of the Canary Islands, 
 and of the Brazils, &c. who live almost exclusively on herbs, 
 grain, and roots, inhabit a climate, against the excessive heat of 
 which they have to seek means of protection; now, the digestion 
 of vegetables is attended with less heat and irritation. The 
 philosophical or religious sects, by which abstinence from ani- 
 mal food was considered as a meritorious act, were all insti- 
 tuted in warm climates. The school of Pythagoras flourished in 
 Greece, and the anchorites, who, in the beginning of the Chris- 
 tian religion, peopled the solitudes of Thebais, could not have 
 endured such long fastings, or supported themselves on dates 
 and water, in a more severe climate. So that the monks that 
 removed into different parts of Europe, were obliged to relax 
 from the excessive severity of such a regimen, and yielded to 
 the irresistible influence of the climate; the most austere came 
 to add to the vegetables, which formed the base of their food, 
 eggs, butter, fish, and even water fowl. In books of casuistrv, 
 it may be seen, on what ridiculous grounds there was granted a 
 dispensation in favour of plovers, of water hens, wild ducks, 
 snipes, scoters, birds whose brown flesh, more animalized and 
 
 M 
 
OF DIGESTION. 
 
 90 
 
 more heating, ought to have been proscribed from the kitchen 
 of monasteries, much more strictly than that of common poultry. 
 
 Consider what is the alimentary regimen of the different na- 
 tions on the face of the earth, and you will see, that a vegetable 
 diet is preferred by the inhabitants of warm countries: to them, 
 sobriety is an easy virtue; it is a happy consequence of the cli- 
 mate. Northern nations, on the contrary, are voracious from 
 instinct and necessity. They swallow enormous quantities of 
 food, and prefer those substances which in digestion produce 
 the most heat. Obliged to struggle incessantly against the action 
 of cold, which tends to benumb the vital powers, to suspend 
 every organic motion, their life is but a continual act of resist- 
 ance to external influences. Let us not reproach them with 
 their voracity, and their avidity for ardent spirits and fermented 
 liquors. Those nations that inhabit the confines of the habitable 
 world, in which man is scarcely able to withstand the severity 
 of the climate, the inhabitants of Kamtschatka, the Samoiedes, 
 live on fish, that in the heaps in which they are piled up, have 
 already undergone a certain degree of putrefactive fermentation. 
 Does not the use of a food so acrid and heating, that in our 
 climate it would inevitably be attended with a febrile action, 
 prove plainly the necessity of balancing, by a vigorous inward 
 excitement, the debilitating influence of powers that are ope- 
 rating from without? The abuse of spirituous liquors is fatal to 
 the European transported to the burning climate of the West 
 Indies. The Russian drinks spirituous liquors with a sort of im- 
 punity, and lives on to an advanced age, amidst excesses under 
 which an inhabitant of the south of Europe would sink. 
 
 This influence of climate affects alike the regimen of man in 
 health, and that of man in sickness, and, it has been justly ob- 
 served of medicine, that it ought to vary according to the places 
 in which it is practiced. Barley ptisan, honey, and a few other 
 substances, the greater part obtained from the vegetable king- 
 dom, sufficed to Hippocrates in the treatment of diseases; his 
 therapeutic treatment was, in almost every case, soothing and 
 refreshing. Physicians, who practise in a climate such as that of 
 Greece, may imitate this simplicity of the father of physic. 
 Opium, bark, wine, spirits, aromatics, and the most active cor- 
 dials are, on the other hand, the medicines sufted to the inhabi- 
 
OP DIGESTION. 
 
 91 
 
 tants of the north. The English physicians use,, freely and with- 
 out risk, these medicines, which elsewhere would be attended 
 with the utmost danger. 
 
 Simple aqueous drinks promote digestion, by facilitating the 
 solution of the solids; by serving as a vehicle to their divided 
 parts; and when rendered active by saline or other substances, 
 as spirituous liquors are bv alcohol, they are further useful in 
 stimulating the organs and exciting their action. 
 
 The least compound drinks are possessed, in different de« 
 grees, of this double property of dissolving solid aliments, and 
 of stimulating the digestive organs. The purest water is render- 
 ed stimulating by the air, and by the salts which it contains, in 
 different proportions; and, to the want of that stimulating qua- 
 lity, is to be attributed the difficult digestion of distilled water. 
 
 The drinks best suited to the wants of the animal economy, 
 are those in which the stimulating principles are blended, in 
 due proportions, with the water which holds them in solution. 
 But almost all the fluids which we drink, contain a certain pro- 
 portion of nutritious particles. Wine, for example, contains 
 these nutritive particles in greater quantity, as it is the produce 
 of a warmer climate, and as saccharine matter predominates in 
 its composition. Thus, Spanish wines are in themselves nou- 
 rishing, and are perhaps litter to satisfy hunger than to allay 
 thirst, while the acidulous Rhenish wines, which are merely 
 thirst-allaying, scarcely contain any cordial quality. Between 
 the two extremes are the French wines, which possess, in a 
 nearly equal degree, the treble advantage of diluting the fluids, 
 of stimulating the organs, and of furnishing to the animal eco- 
 nomy materials of nutrition. 
 
 IV. Of hunger and thirst. By the words hunger and thirsty 
 are meant two sensations, which warn us of the necessity 
 of repairing the loss which our body is continually undergoing 
 from the action of the vital principle. Their nature, as is well 
 observed by M. Gall, is not better known than that of thought. 
 Let us endeavour to explain the phenomena by which they are 
 attended. 
 
 The effects of a protracted abstinence are, a diminution of the 
 weight of the body, a diminution which becomes sensible in the 
 course of twenty-four hours; a wasting of the body, from the loss 
 
OF DIGESTION. 
 
 92 
 
 of fat, discoloration of the fluids, especially the blood, loss of 
 strength, excessive sensibility, sleeplessness, with painful sensa- 
 tions in the epigastric region. 
 
 Death from inanition is most easily brought on, in those who 
 are young and robust. Thus, the unfortunate father whose hor- 
 rible story has been related by Dante, condemned to die of hunger 
 and shut up with his children in a dark dungeon, died the last, 
 on the eighth day, after having witnessed, in the convulsions of 
 rage and despair, the death of his four sons, unhappy victims of 
 the most execrable vengeance ever recorded in the history of 
 man. Haller has related, in his great work on physiology, se- 
 veral instances of prolonged abstinence; if we are to give credit 
 to these accounts, some of which are deficient in the degree, of 
 authenticity required to warrant belief, persons have been known 
 to pass eighteen months, two, three, four, five, six, seven, and 
 even ten years, without taking any nourishment. In the memoirs 
 of the Edinburgh Society, is found the history of a woman who 
 lived on whey only, for fifty years. The subjects of these cases 
 are mostly weak, infirm women, living in obscurity and inaction, 
 and in whom life, nearly extinct, just showed itself, in an almost 
 insensible pulse, an unfrequent and indistinct respiration. It is a 
 fact well worthy of observation, that the muscles and viscera of 
 some of them when examined after death, shone with a light 
 evidently phosphoric.* Can it be that phosphorus is the result 
 of the lowest degree of animalization? It may be easily con- 
 ceived that living, in a manner, on their own substance, the fluids 
 in such persons, have been frequently subjected to the causes 
 which produce assimilation and animalization, and have under- 
 gone the greatest alteration of which they are capable.^ 
 
 The proximate cause of hunger has by some been conceived 
 to depend on the friction of the nervous papillae of the empty 
 stomach on each other; by others, it has been imputed to the 
 irritation produced on its parietes, by the accumulation of the 
 gastric juice. It has been thought to depend on the lassitude at- 
 tending the permanent contraction of the muscular fibres of the 
 stomach; and on the compression and creasing of the nerves, 
 
 * J^itidlssima •viscera sunt aniinalium fame enectormn,et argentei fibrarurnfasdculi. 
 
 Hai.ler, Elem. Phys. tom. VI. page 183. 
 
OF DIGESTION. 
 
 93 
 
 during that permanent constriction; on the dragging down of 
 the diaphragm by the liver and spleen, when the stomach and in- 
 testines being empty, cease to support those viscera: a dragging 
 which is the greater, as a new mode of circulation takes place 
 in the viscera, which are supplied with blood by the cseliac ar- 
 tery, and while the stomach receives less blood, the spleen and 
 liver increase in weight and size, because their supply is in- 
 creased. 
 
 Those who maintain, that hunger depends on the friction of 
 the parietes of the stojnach against each other, when brought 
 together in an empty state, adduce the example of serpents, 
 whose stomach is purely membranous, and who endure hunger 
 a long time, while fowls whose powerful and muscular stomach 
 is able to contract strongly on itself, endure it with difficulty. But 
 to say nothing of the great difference of vitalit5^,in the organs of a 
 bird and of a reptile, the stomach which continues closing on itself 
 as it is emptied, may contract to such a degree as scarcely to 
 equal in size a small intestine, without its following, as a neces- 
 sary consequence, that the parietes which are in contact should 
 exert on each other any friction, on which the sensation of hun- 
 ger may depend. In fact, the presence of food is necessary to 
 determine an action of the parietes of the stomach, and as long 
 as it is empty, there is nothing to call forth such action. 
 
 Those who think that hunger is mechanically produced by the 
 weight of the spleen and liver that keeps pulling down the dia- 
 phragm, which the empty stomach no longer bears up, observe, 
 that it may be appeased, for a time, by supporting the abdominal 
 viscera by means of a wide girdle; that hunger ceases as soon as 
 the stoihach is full, before the food can have yielded to it any 
 materials of nutrition. On this hypothesis, which is purely me- 
 chanical, as that which explains hunger by the irritation of the 
 gastric juice, by the lassitude of the contracted muscles, by the 
 compression of the nerves, how shall we explain the fact, that 
 when the hour of a meal is over, hunger ceases for a time? Ought 
 not hunger, on the contrary, to be considered as a nervous sen- 
 sation which exists in the stomach, is communicated by sympa- 
 thy to all the other parts, and keeping up an active and con- 
 tinuous excitement in the organ in which it is principally seated, 
 determines into it the fluids from all parts. This phenomenon. 
 
OF DIGESTION. 
 
 94 
 
 like all those which depend on nervous influence, is governed by 
 the laws of habit, by the influence of sleep, and of the passions 
 of the mind, whose power is so great, that literary men, ab- 
 sorbed in meditation and thought, have been known entirely to 
 forget that they required food. Every thing which awakens the 
 sensibility of the stomach, in a direct or sv mpathetic manner, in- 
 creases the appetite and occasions hunger. Thus, bulimia de- 
 pends, sometimes, on the irritation of a tape worm in the organs 
 of digestion. The application of cold to the skin, by increasing, 
 from sympathy, the action of the stomach, has been known to 
 occasion fames canina^ of which several instances are related by 
 Plutarch (Life of Brutus). Ardent spirits, and highly seasoned 
 food, excite the appetite, even when the stomach is overfilled. 
 Whatever, on the contrary, blunts or renders less acute the sen- 
 sibility of the stomach, renders more enduralde or suspends the 
 sensation of hunger. Thus, we are told by travellers, that the 
 Turkish dervises and the Indian faquirs, endure long fasts, be- 
 cause they are in the habit of using opium, and lull, in a manner, 
 by this narcotic, the sensibility of the stomach. Tepid and re- 
 laxing drinks impair the appetite; the use of opiates suspends 
 suddenly the action of the stomach. 
 
 V. Of thirst. The blood deprived of its serosity, by insensi- 
 ble perspiration and by internal exhalation, requires incessant 
 dilution, by the admixture of aqueous parts, to lessen its acri- 
 mony; and as the serosity is incessantly exhausting itself, the 
 necessity for repairing that loss is ever urgent. The calls of 
 thirst are still more absolute than those of hunger, and it is much 
 less patiently endured. If it be not satisfied, the blood, and the 
 fluids which are formed from it, become more and more stimu- 
 lating, from the concentration of the saline and other substances 
 which they contain. The general irritation gives rise to an acute 
 fever, with heat and parching of the fauces, which inflame and 
 may even become gangrenous, as happens in some cases of hy- 
 drophobia. English sailors, who were becalmed, had exhausted 
 all their stock of fresh water, and were at a distance from land; 
 not a drop of rain had for a long while cooled the atmosphere: 
 after having borne, for some time, the agonies of thirst, further 
 increased by the use of salt provisions, the}^ resolved to drink 
 their own urine. This fluid, though very disgusting, allayed 
 
OF DIGESTION. 
 
 95 
 
 their thirst; but at the end of a few days, it became so thick and 
 acrid, that they were incapable of swallowing a mouthful of it. 
 Reduced to despair, they expected a speedy death, when they 
 fell in with a ship which restored them to hope and life. Thirst 
 is increased every time that the aqueous secretions are increased; 
 thus, it becomes distressing to a dropsical patient, in whom the 
 fluids are determined towards the seat of effusion. It is exces- 
 sive in diabetes, and in proportion to the increased quantity of 
 urine. In fever, it is increased, from the effect of perspiration, 
 or because in some of these affections, for example, in bilious 
 fevers, the blood seems to become more acrid. Hence the ad- 
 vantage of cooling, diluting, and refreshing drinks, administered 
 copiously, with a view to correct the temporary acrimony occa- 
 sioned by the absence of a great quantity of the serous parts of 
 the blood, and to lessen the over excitement of a fluid become 
 too stimulating. 
 
 The use of aqueous drink is not the most effectual method of 
 allaying thirst. A traveller exposed to the scorching heat of sum- 
 mer, finds it advantageous to mix spirits to plain water, which 
 alone does not stimulate sufficiently the mucous and salivary 
 glands, whose secretion moistens the inside of the mouth and 
 pharynx, and covers these surfaces with the substance best cal- 
 culated to suspend, at least for a time, the erethism on which 
 thirst appears to depend. 
 
 VI. The organs employed in the mastication of 
 
 the food, are the lips, the jaws, and the teeth with which these are 
 furnished: the muscles by which they are moved, and those 
 which form the parietes of the mouth. The motions of the lips 
 are extremely varied, and depend on the single or combined ac- 
 tion of their muscles, by which the greater part of the face is 
 covered, and which may be enumerated as follow: — Elevators 
 of the upper lip incisivus, levator es communes labiorum 
 
 and myrtiformes). Depressors of the under lip (triangularis 
 labiorum, quadratus genoe). Abductors (buccinator, zygomaticus 
 major and minor, platysma myoides'). Constrictors (orbicularis 
 Gris'), 
 
 VII. The motions of the upper jaw are so confined, that some 
 have denied that it has any motion; it neverthless rises a little, 
 when the- lower jaw descends; but it is principally by the de- 
 
OF DIGESTION. 
 
 96 
 
 pression of the latter, and that the mouth is opened. The mus- 
 cles at the back of the neck, and that part of the digastric mus- 
 cle nearest the mastoid process, produce a slight elevation of 
 the upper jaw, which moves with the whole head, to the bones 
 of which it is firmly united. This connexion of the upper jaw 
 with the bones of the head, renders this jaw less moveable in 
 man than in the great number of animals, in which, freed from 
 the enormous weight of the skull, it stretches out in front of 
 that cavity, over the lower jaw. As we follow downwards the 
 scale of animal existence, the motions of the upper jaw is seen 
 to increase, the further we descend from the human speciesj it 
 is equal to that of the lower jaw, in the reptiles and in several 
 fishes; hence the enormous dimensions of the mouth of the 
 crocodile and shark; hence serpents frequently swallow a prey 
 of a bulk greater than their own, and would be suffocated, but 
 for the power they possess of suspending respiration for a long 
 time, and of waiting patiently till the gastric juice dissolves the 
 food, as it is swallowed. 
 
 In the act of mastication, the upper jaw may be considered 
 as an anvil, on which the lower jaw strikes as a moveable ham- 
 mer, and the motions of the under jaw, the pressure it exerts, 
 and its efforts, would soon have disturbed the connexion of the 
 different bones of which the face is formed, if this unsteady 
 edifice, merely formed of bones, in juxta position, or united by 
 sutures, were not supported, and did not transmit to the skull, 
 the double effort which presses on it from below upwards, and 
 pushes it out laterally. Six vertical columns, the ascending 
 apophyses of the superior maxillary bones, the orbitar processes 
 of the malar bones, and the vertical processes of the palate bones, 
 support and transmit the effort which takes place in the first direc- 
 tion, while the zygomatic processes forcibly press the bones of 
 the face against each other, and powerfully resist separation out- 
 wardly or laterally. The lower jaw falls bv its own weight, when 
 its elevators are relaxed; the external pterj goid muscles, and 
 those attached to the os hyoides, complete this motion, the centre 
 of which is not in the articulation of the jaw to the temporal 
 bones, but corresponds to a line that should cross the coronoid 
 processes, a little above the angles of the jaw. It is around this 
 axis, that, in falling, the lower jaw performs a motion of rota- 
 
OP DIGESTION. 
 
 97 
 
 tion, by which its condyles are turned forwards, while its angles 
 are carried backwards. In children, the coronoid processes stand- 
 ing off at a smaller distance from the body of the bone, of which 
 they have nearly the same direction, the centre of motion is 
 always in the glenoid cavities, which the condyles never quit, 
 however much the jaw may be depressed. By this arrangement, 
 nature has guarded against dislocation, which would have been 
 frequent at an early period of life, from crying, during which, 
 the jaw is depressed beyond measure, or when not knowing 
 the just proportion between the capacity of the mouth, and the 
 size of the bodies they would put into it, children endeavour 
 to introduce those which it cannot receive. The lower jaw 
 forms a double bended lever of the third kind, in which the 
 power, represented by the temporal, masseter and internal 
 pterygoid muscles, lies between the fulcrum and the resistance, 
 at a smaller or greater distance from the chin. 
 
 The mode of articulation of the jaw to the temporal bones, 
 allows it only a motion upwards and downwards, in which the 
 teeth of both jaws meet like the blades of scissars, and a lateral 
 motion, in which the teeth glide on each other, producing a fric- 
 tion well calculated to grind the food, which in the first part of 
 the act of mastication was torn or divided. 
 
 VIII. In carnivorous animals, the levator muscles of the 
 under jaw, especially the temporals and masseters, are prodi- 
 giously large and powerful. In them, the coronoid processes, 
 to which the temporal muscles are attached, are very promi- 
 nent; the condyles are received into a very deep cavity; while 
 in herbivorous animals, on the contrary, they are less strong 
 and bulky, and the pterygoid muscles, by whose action the late- 
 ral or grinding motion is performed, are stronger and more 
 marked. The glenoid cavities are also in them wide but shal- 
 low, so that they allow the condyles to move freely on their 
 surface. The comparative power of the levator and abductor 
 muscles of the lower jaw, may be easily appreciated, by view- 
 ing the temporal and zygomatic fossse. Their depth is always 
 in an inverse ratio, and proportioned to the bulk of the muscles 
 which they contain. In carnivorous animals, the zygomatic 
 arch, to which the masseter is attached, is depressed, and 
 seems to have yielded to the effort of the muscle. In the point 
 
 N 
 
OF DIGESTIOA. 
 
 98 
 
 of view which we have just taken, man holds a middle station 
 between carnivorous animals and those which feed on vegetable 
 substances; nothing, however, determines his nature better than 
 the composition of his dental arches. 
 
 IX. The small white and hard bones which form the dental 
 arches, are not alike in all the animals whose jaws are furnished 
 with them. All have not, as man, three kinds of teeth. The 
 laniary^ teeth are not to be met with, in the numerous class of 
 rodent ia Some are without incisors; the former appear more 
 fitted to tear fibrous tissues which offer much resistance. In 
 carnivorous animals, they are likewise very long, and bent like 
 curved pincers. The grinders are principally employed in grind- 
 ing substances previously divided by the laniary teeth, which 
 tear them, or by the incisors, which, in meeting as the blades of 
 scissars, fairly cut them through: the latter, of which each jaw 
 contains four, acting only on bodies which present but a slight 
 resistance, are placed at the extremity of the maxillary lever. 
 The grinders are brought nearer to the fulcrum, and it is on 
 them that the great stress of mastication rests. If we wish to 
 
 * After the example of several naturalists, I have thought it right to give 
 that name to the canine teeth; in the first place, because their principal use 
 being to lacerate or tear fibrous tissues, it is fit that they should have a name 
 from their manner of acting on the food, as is the case with the incisors and 
 molares: in the second place, because the word canine may lead to an errone- 
 ous conception, by leading to a belief that this kind of tooth belongs only to 
 one kind of carnivorous animals, while they are stronger and more distinct 
 in the lion, the tyger, &c. 
 
 Such an explanation is indispensable, at a period when every body aspires 
 to the easy glory of introducing innovations in language. The invention of 
 words is, however, in the opinion of a celebrated female writer, a decided 
 symptom of barrenness of ideas. 
 
 The teeth differ essentially from the other bones, by tlie acute sensibility 
 with which they are endowed; 2dly, by the nerves which may be traced into 
 them, while they seem to be wanting in every other part of the osseous sys- 
 tem; 3dly, by the mode of distribution of the blood vessels: these penetrate 
 into them at an aperture which is seen at the extremity of their root, and they 
 expand in the mucous membrane contained in the tooth, and which forms the 
 most essential part of the bone; 4thly, by their not undergoing an}' change from 
 exposure to the air, a property w'hich they owe to the enamel tvhich covers 
 them externally. It has been said, wdth justice, that Nature, in sheathing the 
 tooth with this covering, has imitated the process of tempering, by means of 
 which we harden the edge of steel or iron tools. 
 
OF DIGESTION. 
 
 9-9 
 
 crush a very hard substance, we instinctively place it between 
 the last large grinders, and by thus shortening considerably the 
 lever, between the resistance and the fulcrum, we improve on 
 the lever of the third kind, which, though most employed in 
 the animal economy, acts the most unfavourably. The laniary 
 teeth have very long fangs, which lying deeply buried in the 
 alveolar processes, give them a degree of firmness to enable 
 them to act powerfully, without any danger of being loosened 
 from their situation. 
 
 The enamel which covers the teeth, preserves the substance 
 of the bone exposed to the contact of the air, from the injuri- 
 ous effects which would not fail to result from direct exposure, 
 and as enamel is much harder than bone, it enables the teeth to 
 break the hardest bodies without injury. The concentrated acids 
 soften this substance and occasion a painful affection of the 
 teeth. The sensibility possessed by these bones is seated in 
 the mucous membrane which lines their inward cavity, through 
 which are distributed the vessels and nerves, which enter by 
 openings at their roots. This membrane is the seat of a great 
 number of diseases, to which the teeth are subject. The enamel, 
 incessantly worn by repeated friction, grows and repairs its 
 waste. The alveolar processes which receive the fangs of the 
 teeth, firmly embrace them, and all of them being exactly coni- 
 cal in form, every point of these small cavities, and not merely 
 their lower part at which the nerves and vessels enter, supports 
 the pressure which is applied to these bones. When from acci- 
 dental causes, or in the progress of age, the teeth are gone, their 
 alveoli contract, then disappear; the gums, a reddish and dense 
 membranous substance, which connects the teeth to the sockets, 
 harden and becomes callous over their thinned edges. Old men 
 who have lost all their teeth, masticate but imperfectly, and 
 this circumstance is one of the causes of their slow digestion, 
 as the gastric juice acts with difficulty on food, whose particles 
 are not sufficiently divided. 
 
 X. Salivary solution. The above mechanical trituration is not 
 the only change which the food undergoes in the mouth. Sub- 
 jected to the action of the organs of mastication, which over- 
 come the force of cohesion of its molecules, it is at the same 
 
OF DIGESTION. 
 
 100 
 
 time imbued with the saliva. This fluid, secreted by the glands 
 placed in the vicinity of the mouth, is poured, in considerable 
 quantity, into that cavity during mastication. 
 
 The saliva is a transparent and viscous fluid, formed of about 
 four parts of water and one of albumen, in which are dissolved, 
 phosphates of soda, of lime, and of ammonia, as well as a small 
 quantity of muriate of soda; like all other albuminous fluids, it 
 froths when agitated, by absorbing oxygen, for which it appears 
 to have a strong affinity. Its affinity for oxygen is such, that 
 one may oxydize gold and silver, by triturating in saliva thin 
 leaves of those metals which are of such difficult oxydizement. 
 
 The irritation occasioned by the presence or the desire of 
 food, excites the salivary glands, they swell and become so 
 many centres of fluxion^ towards which the humours flow 
 abundantly. Bordeu first called the attention of physiologists 
 to the great quantity of nerves and vessels received by the 
 parotid, maxillary and sublingual glands, from the carotid, 
 maxillary and lingual arteries, from the portio dura of the 
 seventh pair of nerves, from the lingual nerve of the fifth pair, 
 which penetrate their substance, or pass over a portion of their 
 surface. This great number of vessels and nerves is proportion- 
 ed to the quantity of saliva which is secreted, and this is esti- 
 mated at about six ounces during the average time of a meal. 
 It flows in greater quantity, when the food that is used is acrid 
 and stimulating: it mixes with the mucus copiously secreted 
 by the mucous, buccal, labial, palatine, and lingual glands, 
 and with the serous fluid exhaled by the exhalent arteries of 
 the mouth. The saliva moistens, imbues, and dissolves the ball 
 formed by the aliment, brings together its divided molecules, 
 and produces on them the first change. There can be no doubt, 
 that the saliva mixing with the food, by the motion of the jaws, 
 absorbs oxygen, and unites to the alimentary substances a 
 quantity of that gas fit to bring about the changes which they 
 are ultimately destined to undergo. 
 
 XI. The muscular parietes of the mouth are, during masti- 
 cation, in perpetual action. The tongue presses on the food, in 
 every direction, and brings it under the teeth; the muscles of 
 the cheek, especially the buccinator, against which the food is 
 pressed, force it back again under the teeth, that it may be duly 
 
OP DIGESTION. 
 
 101 
 
 triturated. When the food has been sufficiently divided, and 
 imbued with saliva, the tip of the tongue is carried to every 
 part of the mouth, and the food is collected on its upper surface. 
 The food having been thus completely gathered together, the 
 tongue presses it against the roof of the mouth, and turning its 
 tip upwards and backwards, at the same time that its base is 
 depressed, there is offered to the food an inclined plane, over 
 which the tongue presses it from before backwards, to make it 
 clear the isthmus of the fauces, and to thrust it into the oeso- 
 phagus. In this course of the food along the pharynx and into 
 the oesophagus, consists deglutition, a function which is assisted 
 by the co-operation of several organs whose mechanism is rather 
 complicated. — ^ 
 
 XII. Deglutition. In the process of deglutition, the mouth 
 closes by the approximation of both jaws; at the same time, the 
 submaxillary muscles, the digastrici^ the genio-hyoidei^ the 
 mylo-hyoidei, &c. elevate the larynx and pharynx, by drawing 
 down the os hyoides towards the lower jaw, which is fixed by 
 its levator muscles. The hyo-glossus muscle, at the same time 
 that it elevates the os hyoides, depresses and carries backwards 
 the base of the tongue. Then the epiglottis, situated between 
 these two parts, which are brought together, is pushed down- 
 wards and backwards by the base of the tongue, which lays 
 it over the opening of the larynx. The alimentary mass, pressed 
 between the palate and the upper surface of the tongue, slides 
 on the inclined plane formed by the latter, and pressed by its 
 tip, which bends back, clears the isthmus of the fauces. The mu- 
 cous substance which exudes from the surface of the amygdalae 
 further facilitates the passage of the food. When the food has 
 thus dropped into the pharynx, the larynx tvhich had risen, and 
 had come forward, and which in that motion had drawn the 
 pharnyx along with it, descends and falls backwards. This last 
 organ, stimulated by the presence of the food, contracts, and 
 would in part send it back in a retrograde direction, by the 
 nasal fossse, if the velum palati, elevated by the action of the 
 levatores palati, stretched transversely by the tensores palati, 
 was not applied to their posterior apertures, and towards the 
 openings of the Eustachian tubes. Sometimes this obstacle is 
 overcome, and the food returns, in part, by the nostrils. This 
 
OF DIGESTION. 
 
 102 
 
 happens, when during the act of deglutition, we attempt either 
 to laugh or speak. At such times, the air, expelled from the 
 lungs with a certain degree of force, elevates the epiglottis, and 
 meeting the alimentary mass, pushes it back towards the nos- 
 trils through which it is to pass. — The isthmus faucium is 
 closed against the return of the food into the mouth, by the 
 swelling of the base of the tongue, raised by the action of the 
 constrictor isthmi faucium, and of the constrictor pharvngis 
 superior, which are small muscles contained in the thickness of 
 the pillars of the velum. 
 
 The alimentary mass is directed towards the oesophagus, and 
 is thrust into that canal, by the peristaltic contractions of the 
 pharynx, which may be considered as the narrow part of a 
 funnel-like tube. The solid food passes behind the aperture of the 
 larynx, which is accurately covered over by the epiglottis. The 
 liquids flow along the sides of that opening, along two channels 
 easily distinguished. They are always of more difficult degluti- 
 tion than the solids; the molecules of a fluid have an incessant 
 tendency to separate from one another, and to prevent this 
 separation, the organs are obliged to use greater exertion, and 
 to embrace with more precission the substance that is swallow- 
 ed. Thus, it is observed, in those cases in which deglutition is 
 prevented by some organic affection of the oesophagus, that the 
 patients, though they have the power of swallowing solid food, 
 find it difficult to swallow a few drops of a liquid, and are 
 tortured with thirst, though they have still the power of satisfy- 
 ing their'hunger. 
 
 The deglutition of air and of gaseous substances is still 
 more difficult than that of liquids, because these elastic fluids 
 are much less coercible, and it requires considerable practice 
 to transmit a mouthful of air into the stomach. M. Gosse, ol 
 Geneva, had acquired that power from repeated experience, 
 and he made use of it to induce vomiting at pleasure, and by 
 the application of that faculty to the interests of science, he 
 ascertained the digestibility of the articles of food in most com- 
 mon use. 
 
 The food descends into the oesophagus, propelled by the 
 contractions of that musculo-membranous duct, situated along 
 the vertebral column, from the pharynx to the stomach. Mucus 
 
OF DIGESTION. 
 
 103 
 
 is secreted, in considerable quantity, by the membrane which 
 lines the inner part of the (Esophagus; it sheathes the substances 
 which pass along it, and renders their passage more free. The 
 longitudinal folds of the inner membrane, allow the oesophagus 
 to dilate; nevertheless, when it is stretched beyond measure, 
 severe pain is experienced, occasioned, no doubt, by the dis- 
 tention of the nervous plexuses, formed by the nerves of the 
 eighth pair which embrace the oesophagus, as they course along 
 its sides.— I purposely avoid speaking of the weight of the 
 food, as one of the causes which enable it to pass along the 
 oesophagus. Although, in man as in quadrupeds, that weight is 
 no obstacle to deglutition, it favours that function in so slight a 
 degree, that the diminution of muscular contractility at the ap- 
 proach of death, is sufficient, altogether to prevent it. The act 
 of drinking is then attended with a noise of unfavourable omen. 
 This noise consists in a gurgling of the fluid which has a tend- 
 ency to get into the larynx, whose opening is not covered over 
 by the epiglottis; and if it be insisted upon, that the patient shall 
 swallow some ptisan, the deglutition of which is impracticable, 
 it flows into the trachea, and the patient dies of suffocation. 
 
 XIII. Of the Abdomen. Before inquiring any further into the 
 phenomena of digestion, let us shortly attend to the cavity 
 which contains its principal organs. The abdomen is almost 
 entirely filled by the digestive apparatus, of which the urinary 
 passages form a part; its size, the structure of its parietes, are 
 evidently adapted to the functions of that apparatus. The ca- 
 pacity of the abdomen exceeds that of the other two great 
 cavities; its dimensions are not invariably fixed, as those of the 
 skull, whose size is determined by the extent of its osseous and 
 inelastic parietes. They are likewise more varying than those of 
 the chest, because, the degree of dilatation, of which the latter 
 is susceptible, is limited by the extent of motion of which the 
 ribs and sternum are capable. The abdomen, on the contrary, 
 enlarges in a sort of indefinite manner, by the yielding of its 
 soft and extensible parietes. In some cases of ascites, the abdo- 
 men has been known to contain as much as eighty pints of 
 liquid, and yet death has not followed as a consequence of so 
 enormous an accumulation; while in consequence of the deli- 
 cate texture of the brain, of the exact fulness of the skull, and 
 
OF DIGESTION. 
 
 104 
 
 especially of the inflexibility of its parietes, the slightest effusions 
 within that cavity are attended with so much danger; while the 
 collection of a few pints of fluid, within the chest, occasions 
 suffocation. This vast capacity of the abdomen, capable of being 
 easily increased, was required in a cavity whose viscera, for the 
 most part hollow, and admitting of dilatation, contain substances 
 varying in quantity, and from which are disengaged gases occu- 
 pying a considerable space. What a d’fference is there not in 
 the capacity of the abdomen of animals, according to the quality 
 of the food on which they feed! Compare the slender body of 
 the tyger, of the leopard and of all carnivorous animals, with the 
 heavy mass of the elephant, of the ox, and of all animals that 
 wholly or principally live on vegetable food. In the child, who, 
 for his growth and development, digests a considerable quantity 
 of food, the abdomen is much more capacious than in the adult 
 or the old man. In the child, the ensiform cartilage is situated 
 opposite to the body of the eighth or ninth dorsal vertebra. In 
 old men, it descends to the tenth or even the eleventh, so that the 
 capacity of the abdomen decreases with the want of food, and 
 with the activity of digestion. 
 
 The internal organs of the body are incessantly called into 
 action by different causes, and excited to different motions. 
 The action of the arterial system tends to raise the cerebral 
 mass, and to impart to it motions of elevation and depression. 
 The motion of the ribs brings about the expansion and the 
 compression of the pulmonary tissue; the heart, which adheres 
 to the diaphragm, drawn down by that muscle, when it de- 
 scends, strikes against the parietes of the chest, every time its 
 ventricles contract. The abdominal viscera are not less agitated 
 by the motions of respiration; they experience from the dia- 
 phragm and from the abdominal muscles a perpetual action and 
 re-action, by means of which the circulation of the fluids in 
 their vessels is promoted, the course of the food in the alimen- 
 tary canal is accelerated, the activity of digestion increased, and 
 several excretions, as of the urine and fseces, performed. 
 
 XIV. Of Digestion in the Stomach. The food which is taken 
 into the stomach, accumulates gradually within its cavity, and 
 separates its parietes, which are always in contact with each 
 other when it is empty. The stomach, in that mechanical dis- 
 
OP DIGESTION. 
 
 1Q5 
 
 tentlon by the food, yields without re-acting. It is not, however, 
 absolutely passive; its parietes apply themselves, by a general 
 contraction, by a kind of tonic motion, to the food which lies 
 within it, and to this action of the whole stomach, the ancients 
 gave the name of peristole. As the stomach dilates, its great 
 curvature is thrust forward, the two folds of the omentum re- 
 cede from each other, receive it between them, and embrace its 
 outer and dilated part. In man, the principal use of this fold of 
 the peritoneum, appears to be to facilitate the dilatation of the 
 stomach, which expands chiefly at its forepart, as may be ob- 
 erved by inflating it m a dead body. As this viscus becomese 
 distended with air, the two folds of the omentum apply them- 
 selves to its surface, and if this membrane is pierced with a pin, 
 at the distance of an inch from its great curvature, the pin is 
 observed to get nearer to this curvature; but the upper portion 
 of the omentum can alone be employed in this use, and the 
 whole of this membranous fold is never entirely occupied by 
 the stomach. Shall we say with Galen, that the omentum guards 
 the intestines against cold, and preserves in them a gentle 
 warmth, necessary to digestion; or shall we admit the opinion 
 of those who maintain, that it answers the purpose of a fluid, 
 filling up spaces, and lessening the effect of friction and pressure 
 from the anterior parietes of the abdomen; or shall we assert 
 with others, that the use of the omentum is to allow the blood 
 to flow into it, when the stomach, in a state of contraction, is 
 incapable of receiving it. May not the blood which flows so 
 slowly in its long and slender vessels, acquire some oleaginous 
 quality which renders it fitter to supply the materials of bile?* 
 
 The stomach likewise stretches, though in a less distinct 
 manner, towards its lesser curvature, and the laminae of the 
 gastro-hepatic omentum are separated from each other, as those 
 of the omentum majus. Such is the utility of the gastro-hepatic 
 
 * The omentum is one of those parts, the use of which, in the animal 
 economy, is not understood. The conjectures enumerated above are wholly 
 gratuitous, and seem to me abundantly absurd. Of late it has been suggested, 
 by Dr. Raines Hmh, that the omentum is a reservoir, or depository of adipose 
 matter, from which the system may derive nourishment in its extreme exi- 
 gences. This hypothesis is at least as plausible as any which has been ad- 
 vanced on the subject, and is supported wdth considerable ingenuity. Vide 
 his Inaugural Thesis, Philadelphia, 1809. — Ed. 
 
 0 
 
OF DIGESTIOX. 
 
 106 
 
 omentum, which may be considered as a necessary result of the 
 manner in which the peritoneum is disposed in relation to the 
 viscera of the abdomen. This membrane, which extends from 
 the stomach to the liver, so as to cover it, could not fill the 
 space which separates those organs, were it not for a kind of 
 membranous communication which connects them, and in which 
 are contained the vessels and nerves, which, from the lesser 
 curvature or the posterior edge of the stomach, course towards 
 the concave surface of the liver. This gastro-hepatic epiploon, 
 mav besides, bv the separation of the two laminae of which it is 
 formed, favour the dilatation of the hepatic vein, which is situa- 
 ted, as well as the vessels, the nerves and the excretory ducts of 
 the liver, in the thickness of its right border. 
 
 The stomach has ever been considered as the principal organ 
 of digestion, yet its function in that process is but secondary 
 and preparatory; it is not in the stomach, that the principal and 
 most essential phenomenon of digestion takes place, I mean the 
 separation of the nutritive from the excrementitious part of the 
 food. The food, when received into the stomach, is prepared 
 for this separation which is soon to be performed, it becomes 
 fluid, and undergoes a material alteration; it is converted into a 
 soft and homogeneous paste, known under the name of chyme. 
 What is the agent that brings about this change? or in other 
 words, in what does digestion in the stomach consist? 
 
 As it is frequently necessary to clear a spot on which one 
 means to build, we will bring forward and refute the hypotheses 
 that have been successively broached, to explain the mechanism 
 of digestion. They may be enumerated, as follows: — concoction^ 
 fermentation^ putrefaction^ trituration^ and maceration of the 
 food taken into the cavity of the stomach. 
 
 XV. The first of these opinions was that of the ancients and 
 of the father of physic; but, by the term concoction^ Hippocrates 
 did not mean, a phenomenon similar to that which takes place, 
 when food is put into a vessel an-d exposed to the influence of 
 heat. The temperature of the stomach, which does not exceed 
 that of the rest of the body (32 degrees of Reaumur’s scale) 
 would be insufficient. Cold-blooded animals digest equally with 
 the warm blooded, and, as Van Helmont observes, febrile heat 
 impairs instead of increasing the powers of digestion. In the 
 
OF DIGESTION. 
 
 107 
 
 language of the ancients, concoction means the alteration, the 
 maturation, the animalization of alimentary substances, assimi- 
 lated to our nature, by the changes which they undergo in the 
 cavity of the stomach. It is, however, a verified fact, that the 
 natural heat of the stomach promotes and facilitates those 
 changes. The experiments of Spallanzani on artificial digestion, 
 show, that the gastric juice is not of more efficacy than plain 
 water, in softening and dissolving alimentary substances, when 
 the heat is below seven degrees (of Reaumur’s scale); that its 
 activity, on the contrary, is greatly increased when the heat is 
 ten, twenty, thirty, or forty degrees above the freezing point. 
 The digestion in the cold-blooded animals is, besides, slower 
 than in the hot-blooded. 
 
 XVI. The abettors of the theory of fermentation admit, that 
 the food taken into the stomach undergoes an inward and spon- 
 taneous motion, in virtue of which it forms new combinations; 
 and as the process of fermentation is promoted, by adding to 
 the substance that is undergoing that change, a certain quan- 
 tity of the same that has already undergone the process, some 
 have supposed, that there continually exists in the stomach a 
 leaven, formed, according to Van Helmont, by a subtle acid, and 
 consisting, in the opinion of others, of a small quantity of the 
 food that remains from the former digestion. But indepen- 
 dently of the circumstance that the stomach empties itself com- 
 pletely, and presents no appearance of leaven, when examined 
 a few hours after digestion, substances undergoing fermentation 
 require to be kept perfectly at rest, whereas the food is exposed 
 to the oscillatory circulations and to the peristaltic contractions 
 of the stomach, and this viscus is shaken by the pulsations of the 
 neighbouring arteries; it is besides kept in continual motion by 
 the act of respiration. In fermentation, gases are either absorbed 
 or extricated, neither of which circumstances takes place when 
 the stomach is not out of order. 
 
 It should, however, be stated, in support of the opinion that 
 accounts for digestion on the principle of fermentation, that we 
 can derive nourishment only from substances capable of under- 
 going fermentation, and that the substances which have under- 
 gone the panary and saccharine fermentation, are more easily 
 digested, and in less time. This imperceptible fermentation, if 
 
OF DIGESTION. 
 
 108 
 
 it really take place, must bear a greater analogy to these two last 
 processes, than to those which are called vinous and acetous fer- 
 mentation, but no one can differ from it more than the putrid 
 fermentation. 
 
 XVII. There have been physiologists, however, from the 
 time of Plistonicus, the disciple of Praxagoras, who maintain, 
 that digestion is, in fact, the consequence of putrefaction. But, 
 not only is ammonia not disengaged during that process, but 
 our digestive organs have the power, as will be seen presenilj’, 
 of retarding, or of suspending, the putrefaction of the substances 
 which are submitted to their action. Se;pents, which in con- 
 sequence of the greater dilatabilitv of their oesophagus, and 
 from the power of holding asunder their jaws, both of which 
 are moveable nearly in an equal degree, frequently swal- 
 low larger animals than themselves, and take several days to 
 digest them; that part of the animal exposed to the action 
 of the stomach, is observed to be perfectly fresh, and dis- 
 solved to a certain extent, while the part which remains out, 
 exhibits signs of incipient putrefaction. In fine, notwithstand- 
 ing the heat and moisture of the stomach, the food does not re- 
 main in it long enough to allow putrefaction to come on, even 
 though every thing else should favour that process. Animals 
 which have by chance swallowed putrescent animal substances, 
 either reject them by vomiting, or, as Spallanzani has observed 
 in some birds, deprive them of their putridity. 
 
 XVIII. The system of fermentation was invented by the 
 chemists; that of trituration, by the mechanical philosophers, 
 who compare the changes which substances undergo in a mor- 
 tar from the action of the pestle, to the changes which the food 
 undergoes in the stomach. But how different is the triturating 
 action of a pestle, which crushes a substance softer than itself 
 against a resisting surface, to the gentle and peristaltic action of 
 the fibres of the stomach, on the substances which it contains. 
 Trituration, which is a mechanical effect, does not alter the 
 nature of the substance exposed to its action; but the food is 
 decomposed and no longer the same substance, after it has re- 
 mained some time in the stomach. As this evidently absurd 
 hypothesis has long been held in high estimation, it will not be 
 
OP DIGESTIOK*. 109 
 
 improper to spend a little time in the refutation of the proofs 
 which are adduced in its support. 
 
 The manner in which digestion is brought about in birds, 
 whose stomach is muscular, and especially in the gallinaceous 
 fowls, is the most specious argument adduced by the abettors of 
 mechanical digestion. Those granivorous birds all have a dou- 
 ble stomachj the first is called the crop, its sides are thin and 
 almost entirely membranous; a fluid is abundantly effused on its 
 inner surface, the seeds on which they feed get softened, and 
 undergo a kind of preliminary maceration in the crop, after 
 which they are more easily ground by the gizzard, which is a 
 truly muscular stomach, that fulfils the office of organs of mas- 
 tication, almost entirely deficient in that class of animals. The 
 gizzard acts so powerfully, that it crushes the solid substances 
 exposed to its action, reduces into dust balls of glass and crys- 
 tal, flattens tubes of tin, breaks pieces of metal, and what is 
 much more extraordinary, breaks with impunity the points of 
 the sharpest needles and lancets. Its internal part is lined with 
 a thick semi -cartilaginous membrane, incrusted with a number 
 of small stones and gra vel, taken in with the food of those birds. 
 The turkey cock is, of all other fowls, that in which this struc- 
 ture is most apparent; besides the small pebbles which line its 
 inner membrane, its cavity contains, almost in all cases, a num- 
 ber of them. The rubbing together of these hard substances, 
 exposed along with the seeds among which they are mixed, to 
 the action of the stomach, may assist in breaking them down. 
 The pieces of iron and the pebbles which the ostrich swallows, 
 some of which Valisnieri met with in the stomach of that bird, 
 are destined to the same use. But this mechanical division which 
 the gizzard performs in the absence of organs of mastication, 
 does not constitute digestion; the food, softened and divided by 
 the action of the crop and of the gizzard, passes into the duode- 
 num, and exposed in that intestine to the action of the biliary 
 juices, undergoes within it the changes most essential to the act 
 of digestion. 
 
 The singular structure of the lobster’s stomach is not more 
 favourable to the hypothesis of trituration. In that crustaceous 
 animal, the stomach is furnished with a real mandibular appa- 
 ratus, destined to break down the food. There are found in it, 
 
OF DIGESTION. 
 
 no 
 
 besides, at certain times of the year, two roundish concretions, 
 on each side, under its internal membrane. These concretions, 
 improperly termed crabs’ eyes, consist of carbonate of lime 
 joined to a small quantity of gelatinous animal matter; they dis- 
 appear, when, after the annual shedding of the shell, the exter- 
 nal covering, at first membranous, becomes solid from the depo- 
 sition of the calcareous matter of which they are formed. 
 
 The very great difference between the stomach of these ani- 
 mals and that of man, ought to have precluded every idea of 
 comparing them together. Spallanzani has justly observed, that 
 in regard to the muscular power of the parietes of the stomach, 
 animals might be divided into three classes, the most numerous 
 of wnich consists of those creatures, whose stomach is almost 
 entirely membranous, and furnished with a muscular coat of 
 very little thickness. In this class are contained, man, quadru- 
 peds, birds of prey, reptiles, and fishes. Notwithstanding the 
 weakness of that muscular coat, Pitcairn, by a misapplied cal- 
 culation, has estimated its power at 12,951 pounds; he reckons 
 at 248,335 pounds, that of the diaphragm and of the abdominal 
 muscles which act on the stomach and compress it in the alter- 
 nate motions of respiration. What does so exaggerated a calcu- 
 lation prove, except, as Garat observes, that this vain show of 
 axioms, definitions, scholia, and corollaries with which works 
 not belonging to mathematics have been disfigured, have served 
 only to protect vague, confused, and false notions, under the 
 cover of imposing and respected forms. One need only intro- 
 duce one’s hand into the abdomen of a living animal, or a finger 
 into a wound of the stomach, to ascertain that the force of that 
 viscus on its contents, does not exceed a few ounces. 
 
 XIX. The learned and indefatigable Haller thought, that the 
 food was merely softened and diluted by the gastric juice. This 
 maceration was, in his opinion, promoted and accelerated by the 
 warmth of the part, by the incipient putrefaction, by the gentle 
 but continual motions which the alimentary substance under- 
 goes. Maceration, in time, overcomes the force of cohesion of 
 the most solid substances; but by dilution it never changes their 
 nature. Haller rested on the experiments of Albinus, on the 
 conversion of membranous tissues into mucilage, by protracted 
 maceration. 
 
OF DIGESTION. 
 
 Ill 
 
 In ruminating animals, the cavity of the stomach is divided 
 into four parts, which open into one another, and of which the 
 three first communicate with the (Esophagus. When the grass, 
 after imperfect trituration by the organs of mastication, whose 
 power is inconsiderable, has reached the paunch, which is the 
 first and largest of the four stomachs, it undergoes a real mace- 
 ration, together with an incipient acid fermentation. The con- 
 tractions of the stomach propel the food, in small quantities at 
 a time, into the bonnet, which is smaller and more muscular 
 than the paunch; it coils on itself, covers with mucus the already 
 softened food, then forms it into a ball, which rises into the 
 mouth, by a truly antiperistaltic motion of the oesophagus. The 
 alimentary bolus, after having been chewed over again by the 
 animal, which seems to enjoy that process, descends along the 
 oesophagus into the third stomach, called the manyplus, on ac- 
 count of the large and numerous folds of its inner membrane. 
 From this cavity the food enters into the abomasum, in whkh 
 the stomachic digestion is completed. Such is the mechanism 
 of rumination, a function peculiar to animals that have four sto- 
 machs; they do not, however, ruminate at all periods of their 
 life. The sucking lamb does not ruminate: the half digested 
 milk does not pass along the paunch or the bonnet, which are 
 useless, but at once descends into the third stomach. Some men 
 have been capable of a kind of rumination; the alimentary ball, 
 after descending into the stomach, shortly after rose into the 
 mouth, to be there chewed a second time, and to be anew im- 
 bued with saliva. Conrad Peyer has made this morbid pheno- 
 menon the subject of a dissertation entitled, Mericologia^ sive 
 de Ruminantibus. 
 
 This fourfold division of the stomach, so favourable to Hal- 
 ler’s theory, is observed only in ruminating animals. But though 
 animals are in general raonogastric, as man, that is, provided 
 with only one stomach, this viscus offers a number of varieties, 
 the most remarkable of which refer to the relative facility which 
 the food meets, in remaining within its cavity. The insertion 
 of the (Esophagus is nearer to its left extremit}', and the great 
 fundus of that viscus is smaller, as animals feed more exclusively 
 on flesh, which is a substance of remarkably easy decomposition, 
 and not requiring for its digestion a long stay in the stomach. 
 
01-' mGEST10^'. 
 
 112 
 
 In herbivorous quadrupeds, which do not ruminate, this great 
 fundus forms nearly one half, sometimes even the greater part 
 of the stomach, as the oesophagus enters into it very near the 
 pylorus. In some, as in the hog, the stomach is divided into 
 two parts by a circular contraction. The food which is received 
 into the great fundus of the stomach, may remain longer in that 
 viscus, as this part of its cavity lies out of the course of the ali- 
 ment. 
 
 XX, Of the gastric juice. Of all the organs, the stomach 
 probably receives, in proportion to its bulk, the greatest number 
 of blood-vessels; in its membrano-muscular parietes, which are 
 little more than the twelfth part of an inch in thickness, there is 
 distributed the coronary artery of the stomach, entirely destined 
 to that organ; the pyloric, the right gastro-epiploic, given off by 
 the hepatic artery. The greater part of the blood, therefore, 
 which passes from the aorta to the caeliac artery goes to the 
 stomach, for, though, of the arteries into which that trunk is 
 divided, the coronary of the stomach is the least, the arteries 
 of the liver and spleen send to the stomach several pretty con- 
 siderable branches, before entering the viscera to which thev 
 are more particularly allotted. One need only observe the great 
 disproportion between the stomach and the quantity of blood 
 which it receives, to conclude, that this fluid is not merely sub- 
 servient to its nutrition, but is destined to furnish the materials 
 of some secretion. 
 
 The secretion in question, is that of the gastric juice, which 
 is most abundantly supplied by arterial exhalation, from the in- 
 ternal surface of the stomach; It is most active at the instant 
 when the food received within its cavity, excites irritation, 
 transforms it into a centre of fluxion towards which the fluids 
 flow from all directions. The state of fulness of the stomach, 
 favours the afflux of the fluids into the vessels, as, in conse- 
 quence of the extension of its parietes previously collapsed, the 
 vessels are no longer bent and creased. The arteries of the 
 stomach, of the spleen and liver, arising from a common trunk, 
 it may be easily understood how, when the stomach is empty, 
 little blood enters into it, in that state of contraction; how, at 
 the same time, the spleen which is less compressed, and the 
 liver, must receive a larger supply of blood, and again a smaller 
 quantity, when the stomach is full. 
 
<3F DIGESTION. • 
 
 113 
 
 The gastric juice, the result of arterial exhalation, mixes with, 
 the mucus poured out by the mucous follicles of the internal 
 membrane of the stomach. This mixture renders it viscous 
 and ropy like the saliva, to which in man, the gastric juice bears 
 a great analogy. It is very difficult to obtain it pure, so as to 
 analyze it, and even if by long fasting, the stomach should 
 be deprived of the alimentary residue, which might affect its 
 purity, one could not prevent its being mixed with a certain 
 quantity of liquid bile, which always flows back through the 
 pyloric orifice, turns yellow the inner surface of the stomach, 
 in the neighbourhood of that orifice, and even imparts a certain 
 degree of bitterness to the gastric juice. The passage of the bile 
 from the duodenum into the stomach, cannot be looked upon 
 as morbid; it occurs in the most perfect health, which has led 
 to a well founded opinion, that a small quantity of the biliary 
 fluid is a useful stimulus to the stomach. This opinion is con- 
 firmed by an observation of Vesalius, who relates, that he found 
 the ductus communis choledochus opening into the stomach, in 
 the body of a convict noted for his voracious appetite. It is 
 further confirmed by what is observed in birds of prey, in the 
 pike, &c. who digest easily and with great rapidity, because the 
 termination into the duodenum of the ductus communis chole- 
 dochus, being very near to the pylorus, the bile easily ascends 
 into the stomach, and is always found there in considerable 
 quantity. 
 
 To obtain some of this gastric juice, it is necessary either to 
 open a living animal under the influence of hunger, or to oblige 
 a night bird of prey, as an owl, to swallow small spunges fastened 
 to a long thread. When the spunge has remained for a short 
 time in the stomach, it is withdrawn soaked with gastric juice, 
 of which the secretion has been promoted by its presence in the 
 stomach. 
 
 The gastric juice, in its natural state, is neither acid nor alka- 
 line; it does not turn red or green, vegetable blue colours.* Its 
 
 * There is some difference of opinion on this point. Carminati declares that 
 in carnivorous animals the gastric fluid is acidf that in phytiferous it is alkaline, 
 and that in those whicli live indiscriminately on animal and vegetable food, it 
 is neither acid nor alkaline. By Brugnatelli it is said tliat, in all animals, it is 
 uniformly acid- That the gastric liquor is occasionally n«'c/ in the human species 
 
 P 
 
OF DIGESTION. 
 
 114 
 
 most remarkable quality is, its singularly powerful solvent fa- 
 culty; the hardest bones cannot withstand its action; it acts on 
 those on which the dog feeds; it combines with all their organ- 
 ized and gelatinous parts, reduces them to a calcareous residue, 
 forming those excrementitious substances so absurdly called 
 album grcecuniy by the older chemists. The solvent energy of 
 the gastric juice is in inverse ratio of the muscular strength of 
 the parietes of the stomach, and in those animals in which the 
 parietes of that viscus are very thin, and almost entirely mem- 
 branous, it has most power and activity. In the numerous class 
 of zoophytes, it alone suffices to effect decomposition of the 
 food, always more prompt when accompanied by warmth of 
 ^he atmosphere, as was observed by du Trembley,in the polypi, 
 which in summer dissolve in twelve hours, what in colder 
 weather it would take three days to digest. In the actinia, in 
 the holothuria, the gastric juice destroys even the shells of the 
 muscles which they swallow. Are we not all acquainted with 
 the peculiar flavour of oysters, how much they tend to whet the 
 appetite? this sensation depends less on the salt water contained 
 in the shell, than on the gastric juice which acts on the tongue, 
 which softens its tissue and quickens its sensibility. This mu- 
 cous substance, when received into the stomach, promotes the 
 digestion of the food which is afterwards taken into it; for, the 
 oyster itself is very little nutritious, and is used rather as a con- 
 diment, than as affording nourishment. 
 
 The gastric juice not only pervades and dissolves the food 
 received into the stomach, but it unites and intimately combines 
 with it, completely alters its nature and changes its composition. 
 The gastric juice acts, in a manner peculiar to itself, on the food 
 
 cannot be denied. It has Indeed been found so both by Reaumur and Hunter, 
 and in subjects wl>ere there was no reason to presume it liad become vitiated 
 by a disordered condition of the stomach. 
 
 We are inclined to believe that the .gastric fluid has pretty nearly the same 
 properties in all animals. In support of this conclusion we may appeal to the 
 fact which has been verified by repeated experiments, that both carnivorous 
 and phytiferous animals digest and thrive well on an exchange of food, the one 
 being made to feed exclusively on vegetable and the other on animal matter. 
 Vide Experiments of J. Hunter and Spallanzani. — E d. 
 
OF DIGESTION. 
 
 115 
 
 exposed to its action, and far from inducing a beginning of pu- 
 trefaction, suspends on the contrary and corrects putrescency. 
 This antiseptic quality of the gastric juice, suggested the prac- 
 tice of moistening ulcers with it to accelerate their cure, and the 
 experiments made at Geneva and in Italy, have, it is said, been 
 fully successful. I have made similar experinoents with saliva, 
 which, there is every reason to consider, is similar to the gas- 
 tric juice; and I have seen old and foul ulcers assume abetter 
 appearance, the granulations become healthy, and the affection 
 rapidly advance towards a cure, from the use of that irritating 
 iluid. I had under my care an obstinate sore on the inner ankle of 
 the left leg of an adult; notwithstanding the external application 
 of powdered bark, and of compresses soaked in the most deter- 
 gent fluids, this sore was improvingvery slowly, when I bethought 
 myself of moistening it every morning with my saliva, the secre- 
 tion of which was increased by the hideousa spect of the sore. 
 From that time, the patient evidently mended, and his wound 
 contracting daily, at last became completely cicatrized. 
 
 However powerful the efficacy of the gastric juice, to dissolve 
 the alimentary substances, it does not direct against the coats of 
 the stomach its active solvent faculty. These parietes endowed 
 with life, powerfully resist solution. The lumbrici so tender and 
 delicate, for the same reason, can exist within it, without being 
 in the least affected by it; and such is this power of vital resist- 
 ance, that the polypus rejects unhurt its arms, when it happens 
 to swallow them among its food.* But when the stomach and 
 the other organs have lost their vitality, its parietes yield to the 
 solvent power of the juices which it may contain, they become 
 softened, and even in part destroyed, if we may believe Hunter, 
 who found its inner membrane destroyed in several points in the 
 body of a criminal, who fbr some time before his execution, had 
 been prevailed upon, in consideration of a sum of money, to ab- 
 stain from food.f 
 
 * It had been thought, that no animal could live on the flesh of its own kind, 
 and this circumstance was explained on the same principle; but to refute it, 
 we need only quote the instance of cannibals, and of several tribes of carni- 
 vorous animals, who, in the absence of other prey, devour one another. 
 
 t The fact of the stomach itself, in some instances, being partly dissolved 
 
OP DIGESTION. 
 
 116 
 
 The gastric juice is capable, even after death, of dissolving 
 food introduced into the stomach, by a wound made into it, pro- 
 vided the animal still preserves some degree of animal heat. It 
 acts on vegetable and animal substances triturated and put 
 into a small vessel, such as those under which Spallanzani, in 
 his experiments on artificial digestion, kept up a moderate heat. 
 Let us not however consider as the same, this solution of the 
 food in the gastric juice, out of the stomach, and that which oc- 
 curs in digestion within the organ.f Every thing tends to shew, 
 that the stomach ought not to be considered as a chemical ves- 
 sel, in which there takes place a mixture giving rise to new com- 
 binations. The tying the nerves of the eighth pair, the use of 
 narcotics and of opium, intense thought, every powerful afifection 
 of the mind, trouble or even entirely suspend digestion in the 
 stomach, which cannot take place independently of nervous in- 
 fluence. Yet this nervous influence may possibly not concur di- 
 rectly, and of itself, to stomachic digestion; it is perhaps merely 
 relative to the secretion of the gastric juice,- which the ligature 
 of the nerves, the action of narcotics or of other substances may 
 impede, alter, or even completely suspend. 
 
 It is now pretty generally admitted, that digestion in the 
 stomach, consists In the solution of the food in the gastric juice. 
 This powerful solvent penetrates, in every direction, the ali- 
 mentary mass, removes from one another, or divides its mole- 
 cules, combines with it, alters its inward composition, and imparts 
 to it qualities very diflPerent from those which it possessed before 
 the mixture. If, in fact, a mouthful of wine or of food is re- 
 jected, a few minutes after being swallowed, the smell, the 
 flavour, all the sensible and chemical qualities of such substances, 
 
 by the operation of the gastric liquor after death, which was first noticed by 
 Mr. Hunter, has since been fully confirmed by the observations of Mr. Allan 
 Burns, and others. — E d. 
 
 f In the experiments alluded to above, meat and bread mixed with tlie gas- 
 tric fluid were reduced to a gelatinous pulp, resembling in all its sensible pro- 
 perties, the natural chyme. By the artificial process however, a much longer 
 time was found necessaiy to effect this end. It is to be regretted that these 
 experiments have not been made with greater accuracy. To determine with 
 precision the identity of the artificial and natural process, the same sort of food 
 should be used, and the two masses afterwards chemically analysed. — E d. 
 
OF DIGESTION. 
 
 117 
 
 are so completely altered, that they can scarcely be recognized; 
 the vinous substances turned, to a certain degree, sour, are no 
 longer capable of the acetous fermentation. The energy of the 
 solvent power of the gastric juice,. perhaps over-rated by some 
 physiologists, is sufficient to dissolve and reduce into a pulp, the 
 hardest bones on which some animals feed. It is highly probable, 
 that its chemical composition varies at difFei:<ent times; that it is 
 acid, alkaline or saponaceous, according to the nature of the 
 food. Although the gastric juice be the most powerful agent of 
 digestion, its solvent power requires to be aided by several se- 
 condary causes, as warmth, which seems to increase, and, in a 
 manner, to concentrate itself in the epigastric region, as long as 
 the stomach is engaged in digestion; a sort of inward fermenta- 
 tion which cannot be, strictly speaking, compared to the decom- 
 position which substances subject to putrefaction aud acescency 
 undergo. The gentle and peristaltic action of the muscular fibres 
 of the stomach, which press, in every direction, on the alimen- 
 tary substance, performs on it a slight trituration, while the 
 moisture of the stomach softens and macerates the food, before 
 it is dissolved; one might therefore say, that the process of di- 
 gestion is at once chemical, mechanical, and vital; in that case, 
 the authors of the theories that have been broached, have been 
 wrong, only in ascribing to one cause, such as heat, fermentation, 
 putrefaction, trituration, maceration, and the action of the gas- 
 tric juice, a process which is the result of a concurrence of these 
 causes united. 
 
 The food remains in the stomach, during a longer or shorter 
 space of time, according as by its nature, it yields more or less 
 readily to the changes which it has to undergo. Gosse of Ge- 
 neva, ascertained, by experiments performed on himself, that the 
 animal and vegetable fibre, concrete albumen, white and ten- 
 dinous parts, paste containing fat or butter, substances which 
 have either not undergone fermentation, or which do not readily 
 undergo that process,remain longer in the stomach, and offer more 
 resistance to the gastric juice, than the gelatinous parts of ani- 
 mals or vegetables, fermented bread, &c.; that the latter required 
 but an hour for their complete solution, while the former were 
 scarcely dissolved at the end of several hours. 
 
 XXI. The following case throws, I think, some light on 
 
OF DIGESTION. 
 
 118 
 
 the mechanism and importance of the action of the stomach in 
 digestion. The patient was a woman whom I had frequent op- 
 portunities of examining at the “Hopital de la Charite” at Paris, 
 in the clinical wards of Professor Corvisart, in which she died 
 on the ninth Nivose of the year X. after six months’ stay in the 
 hospital. 
 
 A fistulous opening of an oval form, an inch and an half in 
 length, and upwards of an inch in breadth, situated at the lower 
 part of the chest, at the upper and left side of the epigastric re- 
 gion, afforded an opportunity of viewing the inner part of the 
 stomach, which when empty of food, appeared of a vermilion 
 colour, was covered with mucus, its surface wrinkled over with 
 folds about half an inch deep, and enabled one to distinguish the 
 vermicular undulations of these folds, and of all the parts which 
 were in sight. The patient, who was then forty-seven years of 
 age, had had this fistula since she was in her thirty-eighth year. 
 Eighteen years before, she had fallen on the threshhold of a 
 door, and the blow had struck against her epigastric region. The 
 place remained affected with pain, and she became incapable of 
 walking or of sitting, otherwise than bent forward and to the left 
 side. At the end of this long interval, a phlegmonous and ob- 
 long tumour appeared on the injured spot; during the nausea 
 and vomiting which came on afterwards, the tumour broke, and 
 there escaped at the v/ound, which was left by this rupture, two 
 pints of a fluid which the patient had just swallowed to obtain 
 relief. From that time, the fistula, which at first would scarcely 
 have admitted the tip of the little finger, increased daily; at first 
 it allowed only the fluids to pass, but, on the eighth day, the solid 
 food came away freely, and continued to do so till she died. 
 When admitted into the hospital, she ate as much as three 
 women of her age, she voided about a pint of urine and went to 
 stool only once in three days. Her faeces were yellowish, drj% 
 rounded, and weighed more than a pound. Her pulse was very- 
 feeble and extremely slow, its pulsation scarcely^ exceeding forty- 
 five or forty-six beats in a minute. Three or four hours after a 
 meal, an irresistible desire obliged her to take off the lint and 
 compresses with which she covered the fistulous opening, and 
 to give vent to the food which her stomach might happen to con- 
 tain; it came out rapidly, and there escaped at the same time. 
 
OP DIGESTION. 
 
 119 
 
 and with a noise, a certain quantity of gases. The food thus eva^ 
 cuated, exhaled an insipid smell, was neither acid nor alkaline, 
 for, the chymous and grayish coloured pulp into which they 
 were reduced, when suspended in a certain quantity of distilled 
 water, did not affect vegetable blues. The digestion of the food 
 was far from being always complete, sometimes, however, the 
 smell of wine could not be recognized, and the bread formed a 
 viscid, thick and soft substance, pretty similar to fibrine newly 
 precipitated by the acetous acid, and it floated in a tenacious 
 liquid of the colour of common broth. 
 
 It follows, from the experiments performed at the Ecole de 
 Medicine, on these half digested substances, and on the same 
 before their admission into the stomach, that the changes which 
 they undergo, consist in the increase of gelatine, in the forma- 
 tion of a substance which has the appearance of fibrine, without 
 having all its qualities, in a greater proportion of muriate and 
 phosphate of soda, as well as of phosphate of lime. 
 
 This patient was unable to sleep, till she had emptied her sto- 
 mach, which she cleared by swallowing a pint of infusion of 
 chamomile. In the morning, there was seen in the empty sto- 
 mach, a small quantity of a ropy frothy fluid, like saliva. It did 
 not turn vegetable blues to a green or red colour, was not homo- 
 geneous, but exhibited particles of some degree of consistence, 
 among the more fluid parts, and even albuminous flakes com- 
 pletely opaque. The experiments performed on this fluid, showed 
 that it bore a considerable analogy to saliva, which, however, is 
 rather more liable to putrefaction. 
 
 The vermicular motion by which the stomach cleared itself 
 of its contents, took place in two different, but not in opposite 
 directions; the one pressing the food towards the fistulous open- 
 ing, the other towards the pylorus, through which the smaller 
 quantity was allowed to pass. 
 
 On opening the body, it was found, that the fistula extended 
 from the cartilage of the seventh left rib,, as high as the osseous 
 termination of the sixth; its edges were rounded and from three 
 to four lines in thickness; they were covered with a thin moist 
 skin, of a red colour, and similar to that of the lips. The peri- 
 toneal coat of the stomach adhered so firmly to the peritoneum 
 lining the force part of the abdomen, around the opening, that 
 
OF DIGESTION. 
 
 120 
 
 the line of adhesion would not be observed. The opening was 
 in the anterior part of the stomach, at the union of the two-thirds 
 on the left side, with the third on the right of that viscus; that 
 is, about eight fingers’ breadths from its greater extremity, and 
 only four from the pylorus. It extended from the greater to the 
 lesser curvature. In other respects, it was the only organic af- 
 ^fection of that viscus. 
 
 It should be stated, that for several years, the patient had 
 been thin and emaciated, and had led a languid life, which 
 was terminated by a colliquative diarrhcea. She seemed to be 
 supported only by the small quantity of food which passed 
 through the pylorus, into the duodenum, where it received the 
 influence of the bile, whose action on the chyme is, as we shall 
 presently state, absolutely essential to the separation of the nu- 
 tritious parts. Not that there was any thing to prevent the absor- 
 bents of the stomach from taking up a certain quantity of nutri- 
 tious particles, but that small quantity of food, in an imperfect 
 condition, was of very little service in imparting nourishment, 
 and, in that respect, she was in similar circumstances to patients 
 who are affected with obstruction of the pylorus, and reject the 
 greater part of their food, when, digestion being over, this con- 
 tracted opening can no longer allow any food to pass.* 
 
 XXII. While the alimentary solution is going on, the two 
 openings of the stomach remain perfectly closed; no gas disen- 
 gaged from the food, escapes along the oesophagus, except when 
 digestion is imperfect. A slight shivering is felt, the pulse be- 
 comes quicker, and more contracted, the vital power seems to 
 forsake the other organs, to concentrate itself on that which is 
 the seat of the digestive process. The parietes of the stomach 
 are soon called into action; its circular fibres contract in different 
 points; these peristaltic oscillations, at first irregular and uncer- 
 tain, acquire more regularity, and act from above downwards, 
 and from the left to the right, that is to say, from the cardiac to 
 
 • Cases, in many respects, similar to the above, are recorded by different 
 writers. 
 
 Haller, in his “ Chinirgical Dissertations,” has the history of a woman with 
 an aperture in her stomach, throug-h which she was nourished for tvientyseven 
 years. For other instances of fistulous openings in this viscus, consult the “ Irish 
 Transactions,” and “Medical Facts and Observations.” — Ed- 
 
OF DIGESTION". 
 
 121 
 
 the pyloric orifice. Besides, its longitudinal fibres shorten it, in 
 the direction of its greatest diameter, and bring nearer to each 
 other its two orifices. In these dilferent motions, the stomach 
 rises over the pylorus, so that the angle which it forms with the 
 duodenum, almost entirely ceases, and this facilitates the escape 
 of the food. It has been observed, that during sleep, digestion 
 takes place much more readily, when we lie on the right, than on 
 the left side, and this circumstance has been ascribed to the com- 
 pression of the liver on the stomach. It is much more likely to 
 depend on the circumstance, that when we lie on the right side, 
 the passage of the food is facilitated by its own weight, the na- 
 tural obliquity of the stomach, from left to the right, being in- 
 creased, by the changes attending the presence of the food. 
 
 XXIII. On the uses of the Pylorus. The pyloric orifice is 
 furnished with a muscular ring, covered over by a fold of the 
 mucous membrane of the stomach. This kind of sphincter keeps 
 it perfectly closed, while digestion is going on in the stomach, 
 and will not allow a free passage to the food which has not yet 
 undergone a sufficient change. The pylorus, which is endowed 
 with a peculiar and delicate sensibility, may be considered as a 
 vigilant guard, which prevents any thing from passing into the 
 intestinal canal, till it has undergone the necessary changes. 
 Several authors quoted by Haller, have very justly observed, 
 that the alimentary substances do not leave the stomach in the 
 same order that they were received into it, but that they are 
 evacuated according to their degree of digestibility. 
 
 One may say, that there really takes places in the stomach, a 
 sorting of the different substances which it contains. Those that 
 are most readily dissolved, get near to the pylorus, which ad- 
 mits them, rejecting those which, not yet sufficiently digested, 
 cannot produce on it the necessary affection. To this delicacy 
 of tact, which I ascribe to the pylorus, will be objected, per- 
 haps, the passage it allows to pieces of money and other foreign 
 indigestible substances. But these bodies, which have always 
 lain some time in the stomach before they make their way into 
 the intestines, repeatedly attempt the orifice of the pylorus, and 
 pass through, only when they have at last accustomed it to their 
 contact. The gastric system is under the laws of a secretory 
 
 Q 
 
OF DIGESTION. 
 
 122 
 
 gland: and as the roots of the excretory ducts, being endued 
 with a sort of elective sensibility, will not receive the secreted 
 fluid, until it has undergone the necessary preparation in the 
 glandular, parenchyma, in the same manner, the pylorus admits 
 aliments and gives them passage into the intestines, which may 
 be regarded as the excretory ducts of the stomach, only when 
 they have been sufficiently elaborated bj' the action of this organ. 
 
 XXIV. As the stomach empties itself, the spasm of the skin 
 goes off; the shivering is followed by a gentle warmth; the pulse 
 increases in fulness and frequency; the insensible perspiration is 
 augmented. Digestion brings on, therefore, a general action 
 analogous to a febrile paroxysm; and this fever of digestion, 
 noticed already by the ancients, is particularly observable in 
 women of great sensibility. Nothing positive can be said on the 
 duration of stomachic digestion; food passes sooner or slower 
 from the stomach, according as its nature is such as to resist, 
 more or less, the actions which tend to dissolve it; according 
 too to the strength and vigour of the stomach at the time, and to 
 the activity of the gastric juices. Yet we may state from three 
 to four hours, as the mean time of their remaining there. It is 
 of consequence to know the time required for digestion in the 
 stomach, that we may not disturb it by baths, bleedings, &c. 
 which would call off towards other organs, those powers which 
 ought, at that time, to be concentrated upon the stomach. 
 
 If,as is indisputable, the stomach carries with it,-into its action, 
 all the other organs of the economy; if it summons to its aid, the 
 so to say, the whole system of the vital powers; if this sort of 
 derivation is the more conspicuous, as the organization is more 
 delicate, the sensibility more lively, the susceptibility greater, 
 the importance is apparent of enforcing a strict diet in acute dis- 
 eases, and in all cases where Nature is engaged in an organic 
 operation, which a little increase of irritation could not fail to 
 disorder, or to break off. Those who have practised in great 
 hospitals, know to how many patients indigestions are fatal. I 
 have seen some with large ulcers; suppuration was copious and 
 healthy, the granulations florid, and all promising a happy issue 
 when ignorant friends bring them by stealth indigestible food, 
 with which they cram themselves, in spite of the utmost watch- 
 fulness. The stomach, used to a mild and moderate regimen. 
 
OF DIGESTION. 
 
 123 
 
 at once overloaded with food, is changed into ZiCentre of fluxion^ 
 towards which the juices and humours all tend; an irritation is 
 produced beyond that on the ulcerated surface, which, in a little 
 time, ceases to secrete pus, the fleshy granulations become flab- 
 by, extreme oppression is felt; with a difficulty of breathing 
 comes on a pungent pain in the side, the pain sympathetically 
 felt in the lungs makes this organ the seat of an inflammatory 
 and purulent congestion, a rattle ensues, and the patients die of 
 suffocation, at the end of two or three days, sometimes in twen- 
 ty-four hours; and this fatal termination is especially accelerated, 
 when, as I have often witnessed, a blister is applied to the seat 
 of the pain, instead of the ulcerated surface. 
 
 It will seem surprising, perhaps, that in the case of which I 
 have just been speaking, it should be in the lungs, and not the 
 stomach itself, that the congestion and the pain take place; but, 
 besides that the most permeable organ of the body, is the lungs, 
 as well as the weakest, and the most easily yielding to Jluxionary 
 motion^ ^ a host of instances prove, what a close sympathy unites 
 it to the stomach. Let us but call to mind pleurisies and bilious 
 peripneumonics, those acute pains of the side, which, since 
 Stahl, physicians have so successfully treated with vomits. The 
 rapidity with which their symptoms go off, on the evacuation of 
 the sordes which oppress the stomach, shows clearly that these 
 sympathetic diseases are not owing to the metastasis of bile 
 upon the lungs, and that they do not consist in the simultane- 
 ous existence of a gastric affection, and of an inflammatory state 
 of the pleura or of the lungs, but that they are simple gastric 
 affections, in which the lungs are, at the same time, the seat of 
 a sympathetic pain. 
 
 The action of the parietes of the stomach ceases, only when 
 this viscus is completely cleared of the food it contained. The 
 gastric juice, no longer secreted, ceases to be poured so freely 
 by its arteries; and the parietes, which close upon each other, 
 are chiefly lubricated by the mucus so plentifully secreted by 
 the inner coat. 
 
 * Of all the organs it is that in which we most meet with organic injury; and 
 those who have opened many bodies, may have observed, how rare it is to find 
 the lungs completely sound in adults and in old men. 
 
OF UIGESTIOM. 
 
 124 
 
 At times, the action of the muscular fibres of the stomach 
 is altogether inverted, they contract from the pylorus, towards 
 the cardia, and this anti-peristaltic motion, in which the con- 
 tractions are effected with more force, more rapidly, and in a 
 manner really convulsive, produces vomiting. Then, the action 
 of the abdominal muscles is added to that of the stomach; the 
 viscera are driven upwards and backwards, by the contraction 
 of the large muscles of the abdomen; the diaphragm rises up 
 towards the chest. If it sunk as it contracted, the oesophagus, 
 which passes in the interval of its two crura, would be com- 
 pressed, and the passage of the alimentary substances by the 
 cardiac orifice could not take place. Accordingly, it is ob- 
 served, that it is only during expiration that any thing passes 
 from the stomach into the oesophagus. Vomiting may depend 
 upon the obstruction of the pylorus, on the too irritating im- 
 pression of any substance on the coats of the stomach; it may 
 be produced by the irritation of some other organ with which 
 the stomach is in sympathy, &c. 
 
 Digestion in the stomach is essentially assisted by nervous 
 influence. Many physiologists, since Brunner, have found that 
 the tying of the eighth pair of nerves (the pneumo-gastriques) 
 provoked vomiting and retarded the work of digestion.* As it 
 is impossible to make this experiment without affecting respira- 
 tion, a function of very different importance, it becomes difiicult 
 to know, whether the derangement of digestion did not proceed 
 from the general disturbance brought upon all the functions: 
 however, the brain does appear to be in more immediate sym- 
 pathy with the stomach, than with any other part of the di- 
 gestive tube. Disgust from the recollection of loathed food ex- 
 cites vomiting. A more than ordinary exertion of the brain 
 relaxes, disorders, and will even suspend, altogether, the func- 
 tions of the stomach: an unexpected piece of news, a violent 
 emotion, are attended with a cessation of the strongest sensa- 
 
 * Dr. Haig-hton has proved, in the most satisfactorj- manner, that a ligature 
 on the eighth pa*ir of nerves, far from inducing vomiting, renders tlie stomach 
 incapable of rejecting its contents, even though excited by tlie most power- 
 ful emetics. T. 
 
 See Memoirs of the London Medical SocieW, vol. II. page 512. 
 
OP DIGESTION. 
 
 125 
 
 tion of hunger. It would be useless to bring together, in this 
 place, proofs of the intimate connexion subsisting between the 
 brain and the stomach, through the intervention of the pneumo- 
 gastric nerves, for the connexion is questioned by no one. 
 
 XXV. Of digestion in the duodenum. The food, on quitting 
 the stomach, enters the duodenum and there experiences new 
 changes, as essential as those; which were produced upon it by 
 digestion in the stomach. It might even be said, that as the 
 essence of digestion and its principal object is the separation of 
 the food into two parts, the one recrementitious and the other 
 chylous or nutritious, the duodenum in which that separation is 
 performed, is its principal organ. In fact, however carefully one 
 may examine the grayish chyme which is sent out of the sto- 
 mach, it will be discovered to be a mere slimy homogeneous 
 pulp; and in more than a hundred animals which I have opened 
 during the process of digestion, I never observed the absorbents 
 of the stomach filled with real chyle, like those of the intestines.* 
 
 * It is not very long, since an opinion universally prevailed that the chyle 
 was formed in the stomach. This error, however, has been completely exposed 
 by the well conducted experiments of Fordyce, Cruikshank, &c. &c. 
 
 Digestion is not a simple operation confined to the stomach only. It is, on 
 the contrary, a highly complicated function, consisting of a series of processes, 
 carried on chiefly in distinct portions of the alimentary tube. 
 
 In the stomach, the previously masticated food is reduced by the solvent 
 quality of the gastric liquor into tliat state which is denominated chyme. This 
 is the first step. After reaching the duodenum, this pultacious mass is gradu- 
 ally converted into chyle; but by what means so important a change is effected, 
 we do not exactly know. For some time, physiologists have been content to 
 impute it to a chemical action, resulting from a combination of the bile and 
 pancreatic juice with the chyme. But unfortunately for an hypothesis, which 
 so conveniently solved the problem, it has of late been shown by experiments, 
 that chyle may be produced, though the hepatic, cystic, and pancreatic ducts 
 be tied. We, nevertheless, are not prepared to abandon the hypothesis. Before 
 implicit confidence is reposed in those experiments, we are, at least, entitled 
 to demand that they be frequently repeated, and with the utmost caution 
 and precision, so as to leave no doubt of their entire accuracy. 
 
 When chyle is formed, we have hitherto viewed the digestive process as 
 completed. May not, however, some additional change, giving to the fluid 
 a more perfect character, take place in its passage through the lacteals to the 
 blood-vessels? Considering the number of conglobate glands, which in its 
 course act upon it, the supposition does not appear altogether unlikely. But 
 the change thus wrought, if any, must be slight, as the ch)de, prior to its 
 entering the lacteals, is well elaborated, as is evident from its having some 
 of the leading properties of blood. It is composed of three parts: 
 
 I. One 
 
OF DIGESTION. 
 
 126 
 
 The duodenum may be considered as a second stomach, very 
 distinct from the other small intestines, by its situation exterior 
 to the peritoneum, by its size and by its readiness of dilatation, 
 the size and regularity of its curvatures, the great number of 
 valvulae conniventes with which its inner part is furnished, the 
 prodigious quantity of chylous vessels which arise from it, and 
 especially by its receiving, within its cavity, the biliary and 
 pancreatic fluids. If the situation of the duodenum and the 
 peculiarities of its structure are attended to, it will be readily 
 observed, that every thing in that intestine tends to slacken 
 the course of the alimentary substance, and to prolong its stay 
 within it, that it may remain the longer exposed to the action of 
 these fluids. 
 
 The duodenum is, in fact, almost entirely uncovered by the 
 peritoneum, a serous membrane, which like all those that line 
 the inside of the great cavities, and reflect themselves over the 
 viscera which they contain, by furnishing them external cover- 
 ings, admits but of little extension, and seems to stretch, when 
 these viscera become dilated, only by the unfolding of its 
 numerous duplicatures. Fixed by a rather loose cellular tissue 
 to the posterior side of the abdomen, the duodenum is suscep- 
 tible of such dilatation, as to equal the stomach in size, as is 
 sometimes seen in opening dead bodies. Its curvatures depend 
 on the neighbouring organs, and seem almost invariably fixed j 
 lastly, numerous valvulae line its inner surface, so as to add to 
 the friction, and to increase the extent of surface, and thereby 
 the number of absorbents destined to take up the chyle separat- 
 ed in the duodenum from the excrementitious part of the food, 
 
 1. One, which maintains its fluidity during life, but coagulates after 
 death, or by exposure to the air. This may be compared to thb fibrine of 
 the blood. 
 
 2. One, which resembles the serum of the blood in continuing fluid when 
 exposed to the air, and in coagulating at the same degree of temperature as 
 the blood.* 
 
 3. One, consisting of small globules analogous to those of the blood, with 
 this difference, that they are considerably more minute. — Ed. 
 
 * The proportion of the serum to the fibrine of the chyle is varied by cir- 
 cumstances. In healthy chyle there is a considerable quantify of fibrine. When, 
 the digestive organs are weak, it is less. 
 
OF DIGESTIO>r. X2'7 
 
 by the action of the fluids poured into it from the united ducts 
 of the liver and pancreas. 
 
 XXVI. Of the bile and of the organs which serve for its secre- 
 tion. The bile is a viscous, bitter, and yellowish fluid, containing 
 a great quantity of water, of albumen to which it owes its viscid 
 condition, and oil to which the colouring and bitter principle is 
 united; soda, to which the bile owes the property of turning 
 vegetable blues to a green colour; phosphates, carbonates, and 
 muriates of soda, phosphates of lime, and of ammonia; and, 
 lastly, as some say, oxide of iron, and a saccharine substance 
 resembling the sugar of milk. This fluid, which the ancients 
 looked upon as animal soap, fitted for elfecting a more intimate 
 mixture of the alimentary matter, by combining its watery 
 with its fat and oily parts, is, therefore, extremely compound: 
 it is at once watery, albuminous, oily, alkaline, and saline. The 
 liver which secretes it, is a very bulky viscus, situated in the 
 upper part of the abdomen, and kept in its place chiefly by 
 its attachment to the diaphragm, of which it follows ^l the 
 motion. 
 
 The hepatic artery, which the coeliac sends off to the liver, 
 supplies it only with the blood requisite for its nutrition: the 
 materials of its secretion are brought by the blood of the vena 
 portae. 
 
 This opinion on the uses of the hepatic artery, which I take 
 up with Haller, cannot rest upon the experiments of those who 
 pretend to have seen the secretion of the bile going on, after it 
 was tied. Besides that the position of this vessel makes the 
 operation almost impossible, which gives me reason to doubt if 
 ever it was practised, — by intercepting the course of the arterial 
 blood carried to the liver, this viscus, even under the received 
 hypothesis, would remain deprived of nourishment and of 
 action; and the vena portae would supply it, in vain, with a 
 blood on which it could exert no influence. When this vein is 
 tied, which is far more easily done than the artery, the secretion 
 of bile is seen to stop: but the experiment which suspends the 
 abdominal venous circulation, is too speedily fatal, to justify 
 any conclusive inference. It is on analogical proofs that the 
 received hypothesis rests, touching the manner of the biliary se- 
 cretion. The hepatic artery, remarkablv lessened by the branches 
 
OF DIGESTION. 
 
 128 
 
 it has sent off in its way towards the liver, is to that organ what 
 the bronchial arteries are to the lungs; and in the same manner, 
 the branches of the vena portae, spread through its substance, 
 may be compared to the system of pulmonary vessels. It is still 
 to be confessed, however, that the enormous bulk of the liver, 
 its being found in almost all animals, and the quantity of blood 
 carried into it by the vena portae, compared to the small secre- 
 tion there is of bile, lead to the belief that the blood sent to it 
 from all the other organs of digestion, undergoes changes there, 
 on which science possesses, as yet, no certain data, though the 
 chemists maintain, that the liver is, in some sort, the supple- 
 mentary organ of the lungs, and assists in clearing the blood of 
 its hydrogen and carbon. 
 
 The name of vena porta: is given to a particular venous 
 system, inclosed in the abdominal cavity, and formed as fol- 
 lows: the veins which bring back the blood of the spleen and 
 the pancreas, of the stomach and intestinal canal, are united in 
 a very large trunk, which ascends towards the concave face of 
 the liver, and there divides into two branches. These lie in 
 a deep fissure in the substance of this viscus; they send out, 
 through all its thickness, a multitude of branches, which divide 
 like arterial vessels, and end, in part, by opening into the biliarv 
 ducts or pores, and, in part, by producing the simple hepatic 
 veins. These veins, situated chiefly towards the convex or 
 upper surface of the liver, bring back, into the course of the 
 circulation, the blood which has not been employed in the 
 formation of bile, and that which has not served to nourish 
 the substance of the liver; for, they arise equally from the ex- 
 tremities of the vena portte, and from the extremities of the 
 ramifications of the hepatic artery. 
 
 The liver differs from all organs of secretion, in this, that 
 the materials of the fluid it elaborates are not supplied to it by 
 its arteries. It should seem that the bile, a fat and oily fluid, in 
 which hydrogen and carbon predominate, could be drawn only 
 from venous blood, in which, as is known, these two principles 
 are in superabundance. The blood acquires the venous quali- 
 ties, as it passes along the circuitous course of the circulation, 
 and is supplied with hydrogen and carbon the more fully, the 
 slower it flows. Now, it is easy to see, that all is naturally 
 
OF DIGESTION. 
 
 129 
 
 disposed for slackening the circulation of the hepatic blood, and 
 to give it, eminently, the distinguishing properties of venous 
 blood. The arteries which furnish blood to the organs in which 
 the vena portae rises, are either very flexuous as the splenic, or 
 frequently anastomose, like the arteries of the intestinal tube, 
 which of all that are in the body, abound most in visible divi- 
 sions and anastomoses. It will be seen in the chapter on circu- 
 lation, how well these dispositions are adapted for retarding 
 the course of the arterial blood. Once carried into the organs 
 of digestion, the blood stays there, whether it be that the coats 
 of the hollow viscera being collasped or closed upon themselves, 
 hardly yield it passage, or that the organization of some one of 
 these viscera is favourable to its stagnation. 
 
 The spleen seems to serve this purpose. Does this dingy and 
 soft viscus, lodged in the left hypocondrium, and attached to 
 the great fundus of the stomach, receive the blood into the 
 minute cells of its spungy parenchyma, or does this fluid merely 
 traverse, very slowly, the delicate and tortuous ramifications of 
 the splenic vessels? In other respects, there is no organ that 
 exhibits more variety of number, of bulk, of figure, of colour, 
 and of consistence. Sometimes manifold, often divided into 
 several lobes by deep clefts; its bulk varies, not only in different 
 individuals, but even in the same, at different times of the day, 
 as the stomach, full or empty, admits’ or rejects the arterial 
 blood, and compresses the spleen between its large extremity 
 and the ribs under which it is situated, or leaves it free. 
 
 The blood which fills the tissue of the spleen, blacker, more 
 fluid, richer in oily principles, owes all these qualities, which 
 led the ancients to consider it as a peculiar substance, called by 
 them the atra bills or black bile, to its long protracted con- 
 tinuance within that viscus. The branches, which by their union 
 form the vena portae, have thinner parietes than the other veins 
 of the body, they are not furnished with valves, and they do 
 not readily free themselves of the blood which fills them. The 
 action of these veins is, in fact, so feeble, that it would not 
 suffice to enable them to carry the blood onward, if the gentle 
 and alternate compression of the diaphragm and abdominal 
 muscles on the viscera of the abdomen did not favour its circu- 
 lation. On reaching the liver, the blood, which is highly venous, 
 
 R 
 
OF DIGESTIOK. 
 
 130 
 
 is further slaclcened in its circulation, by the increased dimen- 
 sions of the space in which it is contained, the united caliber of 
 the branches of the hepatic vena portae exceeding considerably 
 that of the principal trunk. Besides, these vessels are enveloped 
 in the parenchymatous substance of the liver, and can act but 
 feebly. It, therefore, circulates slowly through that organ, and, 
 with difficulty, returns into the course of circulation. The 
 hepatic veins, which are of pretty considerable caliber, and 
 without valves, remain constantly open, their parietes cannot 
 close and contract on the blood which fills them, on account of 
 their adhesion to the parenchymatous substance of the liver. 
 They open int^ the vena cava, very near the place at which that 
 vein terminates into the right auricle. The regurgitation of the 
 blood, during the contraction of that cavity of the heart, is felt 
 in the veins, and the blood forced back tow-ards the liver, is 
 exposed for a longer time to its action. 
 
 The spleen, therefore, performs only preparatory functions, and 
 may be considered as the auxiliary of the liver, in the secretion 
 of the bile. It is observed, that the quantity of the latter in- 
 creases after the spleen has been extirpated, and that it is less 
 yellow, less bitter, and always imperfect. The blood which 
 circulates in the omentum, is very similar to that of the spleen; 
 I would even sa}', that it contains oily particles, if the drops 
 which I have clearly noticed on its surface, might not have come 
 from the adipose tissue of the omentum, which allows the fluid 
 contained in its cells to flow, when a small puncture is made into 
 it, in examining the blood contained in its veins. 
 
 The bile secreted in the tissue of the liver* Is absorbed by' 
 the biliary ducts, the union of which forms the hepatic duct. 
 The latter issues from the concave surface of the liver, and 
 conveys the bile, either immediately into the duodenum, by 
 means of the ductus communis choledochus, or into the gall 
 bladder. This small membranous pouch, which adheres by 
 means of cellular tissue to the lower surface of the liver, is in 
 some animals entirely distinct from that organ, and connected 
 to it onlv by the insertion of its duct into that which comes 
 from the liver. Its inner membrane is soft, fungous, plicated, 
 
 See, in the chapter on secretion, the laws which that function obeys. 
 
OF DIGESTION. 
 
 131 
 
 and always covered with the mucus secreted by the glandular 
 criptffi which it contains. This mucus defends the gall bladder 
 against the action of the bile which it contains. The almost 
 parallel course of the hepatic and cystic ducts, the acute angle 
 at which they meet, renders it difficult to account for the passage 
 of the bile into the gall bladder. It appears, that when the duo* 
 denum is empty, the bile regurgitates, in part, from the hepatic 
 duct into the gall bladder, collects within it, becomes thicker 
 and yellower, and acquires a greater degree of bitterness. Con- 
 sequently, the use of the gall bladder is to serve as a reservoir 
 to a portion of the bile, which, by remaining within it, is impr,dv- 
 ed in quality, acquires consistence and bitterness, and is height- 
 ened in colour, by the absorption of its fluid parts. 
 
 XXVII. The irritation produced on the parietes of the 
 duodenum, when distended by the chyme, is propagated to the 
 gall bladder, by the cystic and common ducts. Its parietes 
 then contract, and oblige the bile to flow along this cystic duct 
 into the ductus communis choledochus. I'he pressure of the 
 distended intestines on the gall bladder, favours the excretion 
 of bile. The hepatic bile is also more almndantly poured into 
 the duodenum during digestion, from being secreted in greater 
 quantity by the liver, which participates in the irritation affect- 
 ing the organs of digestion, and secretes a greater quantity. 
 The cystic and hepatic bile, mixed in the ductus communis 
 choledochus, undergoes a change before entering the duode- 
 num, by uniting with the fluid of the pancreas. The excretory 
 duct of the pancreas, a glandular organ, which, in structure, 
 bears so great an analogy to the parotid glands, that some phy- 
 siologists, assuming an identity of functions, have called it the 
 abdominal salivary gland, joins the biliary duct, before the 
 latter opens in the duodenum, after having insinuated itself 
 obliquely between the coats of that intestine. It arises within 
 the pancreas, from a great number of radicles which join it, 
 like the feathers of a quill to a common trunk. Its caliber 
 increases in size, as it approaches the large end of the pancreas, 
 situated on the right, in the concavity of the second curvature 
 of the duodenum. Nothing precise is known, with regard to 
 the nature of the pancreatic fluid; the striking resemblance of 
 the pancreas to the salivary glands leads to a presumption, that 
 
OF digestion; 
 
 132 
 
 this fluid bears considerable analogy to the saliva. The quantity 
 of fluid secreted by the pancreas is likewise unknown, but it 
 must be considerable, if one may judge from the great number 
 of nerves and vessels which pervade its glandular tissue, and its 
 quantity is, most probably, increased by the irritation of the 
 food in the duodenum. 
 
 This combination of the united pancreatic and biliary fluids 
 poured on the chyme, penetrates it, renders it fluid, animalizes 
 it, separates the chylous from the excrementitious part, and 
 precipitates whatever is not nutritious. In bringing about this 
 separation, the bile itself seems to be divided into two parts, its 
 oily, coloured, and bitter portion passes along with the excre- 
 ments, sheathes them, and imparts to them the stimulating 
 qualities necessary to excite the action of the digestive tube. 
 Its albuminous and saline particles combine with the chyle, 
 become incorporated to it, are absorbed along with it, and 
 return into the circulation. There may, in fact, be noticed in the 
 alimentary mass, after it has undergone this combination, two 
 very distinct parts: the one is a whitish milky substance, which 
 swims to the surface and is the least in quantity; the other is a 
 yellowish pulp, in which, when digestion is healthy, it is not 
 easy to recognize the nature of the food. When the liver is 
 obstructed, and the bile does not flow in sufficient quantity, the 
 feces are -dry and discoloured; the patients are troubled with 
 obstinate costiveness, the excrement, uncombined with the bitter 
 and colouring matter of the bile, not proving sufficiently irritat- 
 ing to the intestinal canal. 
 
 We have just mentioned how the separation of the chyle is 
 performed; but the mechanism of that separation and the process 
 of chylification are absolutely unknown. How does the union of 
 the bile to the chyme operate, in extracting from the latter the 
 recrementitious part, and in making it swim above the rest? Is 
 there any connexion between that process and the nature of the 
 constituent principles of the bile? The knowledge of the compo- 
 sition of the bile, affords as little assistance in the explanation, 
 as does the knowledge of the chemical properties of the semen, 
 in understanding the admirable function of generation. All 
 these acts of the animal economy, are as mysterious and inex- 
 plicable, as the action of the brain in producing thought; a 
 
OF DIGESTION. 
 
 133 
 
 phenomenon which so many physiologists have considered as 
 exceeding the power of matter, and for which they seem to 
 have reserved all their admiration, though nil mirari^ which 
 I would translate by zuondering at nothings ought to be the 
 motto of any one who has made some progress in the study of 
 the laws of life. 
 
 XXVIII. Of the action of the small intestines. After remain- 
 ing a certain time within the duodenum, the alimentary mass 
 decomposed by the bile, or rather by the pancreatico-biliary 
 fluid, separated into two parts, the one chylous, the other 
 excrementitious, passes into the jejunum and ileum, which are 
 not easily distinguished from each other, and which differ in 
 their relative length, according to the elements on which anato- 
 mists ground the distinction.* 
 
 The jejunum and the ileum alone occupy nearly three-fourths 
 of the whole length of the digestive canal; they are straiter 
 than the duodenum, and do not dilate so readily, because the 
 peritoneum, which forms their outer covering, lies over their 
 whole surface, with the exception of the posterior border at 
 which their vessels and nerves enter. It is along that border, 
 that they are fixed to the mesentery, a membranous band form- 
 ed by a duplicature of the peritoneum, which contains the 
 vessels and nerves going to the jejunum and ileum, which 
 prevents knots from forming in the intestines, and is a security 
 
 * The redness of the parietes of the jejunum, the empty condition of that 
 intestine, its situation in the umbilical region, the great number of its valvulse 
 conniventes, do not distinguish it from the ileum, for, tlie colour of the intes- 
 tinal canal varies in different parts of its extent, and the substances which fill 
 it are found in different parts of the canal, according to the progress of diges- 
 tion at the time the parts are examined; according as the convolutions are 
 situated within the cavity of the pelvis, or rise towards the epigastric region; 
 according to the full or empty state of the bladder and stomach; and the 
 number of circular folds, called valvule conniventes, diminishes as one gets 
 near to the termination of the ileum. Winslow got over the difficulty, by con- 
 sidering the upper two-fifths of the small intestines as jejunum, and the re- 
 maining three-fifths as ileum. This last division, from measurement, is wholly 
 arbitrary, and is besides useless, for there is not, perhaps, above one occasion 
 in which it would be interesting to distinguish the jejunum from the ileum. 
 In operating for hernia, when the intestine is mortified, one would decide the 
 more readily to leave an artificial anus, if one could be sure that the gangre- 
 nous portion belonged to the latter intestine; but of this ir is absolutely im- 
 possible to be certain. 
 
OP DIGESTION. 
 
 134 
 
 against the occurrence of intus-susceptlo. It is well known, 
 however, that in some rare cases, intus-susceptio does take 
 place, with the utmost danger of the patient’s life, who gene- 
 rally dies in the agonies of insufferable cholic pains, which 
 nothing can alleviate. The progress of the food, along the 
 small intestines, is retarded by its numerous curvatures, very 
 aptly compared by some physiologists to the windings of a 
 meandering stream which fertilizes the soil it waters. These 
 numerous convolutions of the intestinal canal favour the long 
 continued presence of the food within its cavity, so that the 
 chyle expressed from the excrementitious part by the peristaltic 
 contractions of the intestine, may present itself to the inhaling 
 mouths of the lacteals, by which it is to be absorbed. These 
 chylous absorbents are in greatest number on the surface of the 
 valvulae conniventes, which are circular folds of the inner mem- 
 brane, and these are at a greater distance from each other, the 
 nearer they are to the termination of the ileum. The valvulae 
 conniventes not only slacken the progress of the food, but by 
 their projections, they sink during the contraction of the bowels, 
 into the alimentary mass, and the lacteals on their surface take 
 up, from its inmost part, the chyle which they are destined to 
 absorb. 
 
 The number of the valvulae conniventes diminishes with that 
 of the lymphatics. The progress of the alimentary substance is 
 gradually accelerated, as it parts with its nutritive and rccremen- 
 titious particles. A quantity of mucus, secreted by the internal 
 membrane of the small intestines, envelops the chymous mass 
 and promotes its progress, by lubricating it; this intestinal mu- 
 cus thrown out by the exhalent arteries imbues it, renders it 
 liquid and adds to its bulk. “This fluid, which seems to partake 
 of the nature of albumen and gelatine, and to hold several sa- 
 line substances in solution, is, for the greater part, recrementi- 
 tious, and must be very considerable in quantity, if we may 
 judge from the caliber of the mesentric arteries, and from the 
 extent of the internal surface of the intestines. It is, however, 
 scarcely possible, that this exhalation should amount to eight 
 pounds in twenty-four hours, according to Haller’s calculation, 
 who, as we shall observe, when we treat of the secretions, has 
 generally over-rated their amount. 
 
OF DIGESTION. 
 
 135 
 
 The peristaltic contractions, by the assistance of which the 
 alimentary mass is sent along the whole course of the small intes- 
 tines, do not occur in a regular and uninterrupted succession, 
 from the stomach to the ccecum. This undulatory and vermicu- 
 lar motion manifests itself at once, in several points of the length 
 of the tube, whose curvatures straighten themselves at intervals. 
 In this action, the intestinal curves are decomposed into a great 
 number of short straight lines which meet so as to fofm obtuse 
 angles. The peristaltic motion which affects the muscular fibres 
 of the intestines, is caused by the irritation of the alimentary 
 substance on the sentient parietes of the canal along which it 
 descends towards the great intestines. The jejunum and the 
 ileum, covered by the peritoneum, except at the part which con- 
 nects them to the mesentery, at the time of dilatation, separate 
 the two peritoneal laminae, forming the mesentery. They occupy 
 the space between the branches of the mesentric vessels, whose 
 last division is always at some distance from the adhering edge 
 of the intestine. If this division of the vessels had taken place 
 nearer to the union of the intestine and mesentery, the intestinal 
 canal would not have admitted of dilatation, without stretching 
 the vessels situated at the angle of separation. It is likewise ob- 
 served, that in the portions of the digestive tube which are most 
 susceptible of dilatation, the last vascular divisions are most dis- 
 tant. Hence the left gastro epiploic artery is always at a greater 
 distance from the great curvature of the stomach than tlje right, 
 a circumstance of which no anatomist has hitherto taken notice. 
 
 XXJX. Of digestion in the great intestines. The alimentary 
 mass, after it has parted with nearly the whole of its nutritive 
 particles, passes from the ileum into the coscum; it then is re- 
 ceived into the great intestines, which are more spacious, though 
 shorter, than the small, forming scarcely a fifth of the whole 
 length of the digestive tube. 
 
 A musculo-membranous valvular ring is placed at the oblique 
 insertion of the ileum into the first of the great intestines. This 
 valve, called after Eustachius or Bauhinus, who are considered 
 as its discoverers, though the merit of the discovery belongs to 
 Fallopius, is formed of two semi-circular segments, the right 
 edge of which is free and floats towards the cavity of the coscum. 
 The more the parietes of that intestine are distended by the sub- 
 
OF DIGESTION. 
 
 136 
 
 stances which it contains, the greater is the difficulty to the re- 
 trograde flow of such substances, for under those circumstances, 
 the two extremities of the valve are at a distance from each 
 other, and its edges, which are free, close on each other, like 
 those of a button hole whose angles are drawn in opposite di- 
 rections; besides, the muscular fibres which enter into its struc- 
 ture render it capable of exerting constriction. It is, therefore, 
 calculated to permit the ready flow of matter from the ileum 
 into the coecum, and forcibly prevent their return into the small 
 intestines. There are facts which lead to a belief, that its resist- 
 ance is sometimes overcome, and that a clyster, thrown in with 
 violence, would force the valve and be thrown up by vomiting. 
 The great intestines may be considered as a kind of reservoir 
 destined to contain, for a certain time, the excrementitious re- 
 sidue of our solid aliments, so as to save us the disgusting 
 inconvenience of constantly parting with it. 
 
 As the peritoneum does not wholly cover the great intestines, 
 they are capable of considerable dilatation, and of extending 
 into the cellular substance which connects them to the posterior 
 part of the abdomen. Their muscular coat which, in a manner, 
 is the base of the intestinal tube, does not consist throughout 
 of circular and longitudinal fibres. The latter, collected into 
 fasciculi, form three narrow bands, in the intervals of which 
 the parietes of the gut are exceedingly weakened, and conse- 
 quently capable of greater extension. These longitudinal fibres 
 being, besides, shorter than the intestine, crease it transversely, 
 and form within it a number of cavities and cells, marked out- 
 wardly by prominences separated by depressions. If, in addi- 
 tion to these peculiarities of structure, it be considered, that in 
 the coscum and a great part of the colon, the contents of the 
 bowels have to ascend against their own weight; that the cur- 
 vature forming the sigmoid flexure of the colon is very conside- 
 rable, and that, in short, the rectum, before its outer termina- 
 tion in a narrow aperture, is considerably dilated, it will be 
 evident, that in the great intestines, every thing tends to pro- 
 tract the stay of the excrements. 
 
 The appendicula vermi-formis of the caecum is, in man, too 
 small to perform this office; in the herbivorous quadrupeds, in 
 which it is much larger, and sometimes not single, it may serve 
 
OF DIGESTION. 
 
 137 
 
 as a reservoir to the faecal matter. Its existence merely shews in 
 man, an analogy to those animals in which it is truly useful, and 
 it concurs in manifesting, that Nature, in the formation of par- 
 ticular organs, in certain kinds of animals, aims at a mere out- 
 line which she fills up in others, to shew, as it were, that there 
 are points of resemblance between all beings whom she has gifted 
 with life and motion. 
 
 While in the great intestines, the alimentary substance be- 
 comes merely fecal, by parting with the small quantity of chyle 
 which it may yet contain. The number of the absorbents decreases 
 progressively from the coecum to the rectum. The small number 
 of these vessels^ accounts for the difficulty of throwing in nou- 
 rishment by means of clysters, when there is an obstruction to 
 deglutition.* The excrements thicken, harden, and become 
 formed or moulded, in the cells of the colon, they are then 
 urged by the peristaltic action into the rectum, in the cavity of 
 which they accumulate, till they excite on its parietes an action 
 which determines their expulsion. 
 
 XXX. Of the evacuation of the faces. When a call to eva- 
 cuate the feces is experienced, the rectum contracts, while the 
 diaphragm descending, and the abdominal muscles receding 
 towards the spinef, thrust the viscera of the abdomen towards 
 the cavity of the pelvis, and compress the intestines which are 
 filled with fecal matter. During these efforts, the perineum per- 
 ceptibly descends, and the fibres of the lavator ani are somewhat 
 
 *'Tliis is one, but not the only reason, why the system cannot be sustained 
 for any length-of time by injections. For the formation of chyle, containing the 
 elements of blood, which it always does when genuine, it is indispensably ne- 
 cessary that the aliment should be previously converted into chyme, an opera- 
 tion which seems from experiments, cannot be effected in the great intes- 
 tines. — E d. 
 
 f Some physiologists have considered as unnecessary, this concurrent action 
 of the diaphragm and abdominal muscles; they ground their opinion on the 
 circumstance, that animals whose abdomen has been laid open are capable of 
 voiding their fieces. Astruc, one of the luminaries of Montpellier, denies the 
 action of the abdominal muscles, in the efforts which one makes at stool, and 
 in support of his opinion, he brings forward this geometrical proposition, “ that 
 a cord disposed in the form of a circle, can, by contracting, shorten itself in an 
 infinitely small degree, and, therefore, not perceptibly.” On which Pitcairn, 
 humorously enough observes, that Astruc had never practised what he rea- 
 sons upon: ‘' credo Astruccium nunqnam cacasse'’ 
 
 s 
 
Ot' DIGESTION. 
 
 1S8 
 
 elongated. The combined action of the rectum an'^ of the abdo- 
 minal muscles, overcomes the resistance of the sphincters, and 
 the alvin - evacuation takes place, and is facilitated by the secre- 
 tion of the mucous follicles of the rectum: these glands, squeez- 
 ed by the pressure of the faeces, pour out their contents and 
 lubricate the circumference of its lower aperture. When the 
 faeces have been voided, the diaphragm rises, the large muscles 
 of the abdomen cease to press backwards and downwards upon 
 the viscera of that cavity; the perineum ascends and the sphinc- 
 ters close, till a renewal of the same call, again brings on the 
 same action. 
 
 The call to void the faeces, is more frequent in children than 
 in adults, because, at an early period of life, the sensibilitv of 
 the intestinal canal is greater, the contents of the bowels more 
 fluid, and digestion more active. As we advance in years, sen- 
 sibility becoming impaired, and contractility experiencing a pro- 
 portionate loss of power; the secretions being, likewise, less 
 abundant, the bowels become sluggish, the stools more scanty 
 and indurated. They are, likewise, less frequent and copious in 
 women than in men, whether it be, that the digestive power ex- 
 tracts from the aliment, a greater proportion of nutritious mat- 
 ter, or that the menstrual evacuation being a kind of substitute 
 for the intestinal secretions, less remains to add to the bulk of 
 the excrementitious mass. The evacuation of the faeces, may be 
 brought on by throwing liquids into the rectum, which dilute 
 the faeces, detach them from the parietes of the intestines, and, 
 exciting on these parietes an irritation to which they are not ac- 
 customed, determine their contraction. 
 
 The fetor of the excrements depends on their incipient pu- 
 trefaction in the great intestines. This decomposition is, almost 
 always, attended with the extrication of gases, in which sul- 
 phuretted hydrogen prevails. This-gas, which at times escapes, 
 and which at others impregnates the faeces, is the cause of the 
 black colour which they give to silver exposed to their action. 
 One may recognize in the excrements, the colouring matter of 
 vegetables, such as the green colour of spinage, the red of beet 
 root; one may, likewise, find among them, the fibrous parts of 
 plants and animals, the indurated bark, and the seeds covered 
 with their husks. The digestive juices have so litde action on 
 
OF DIGESTION. 
 
 139 
 
 husks, that seeds which have not been broken down by the or- 
 gans of mastication, frequently continue capablfi of vegetation. 
 
 During the progress of digestion, the food contained in the 
 stomach and intestines absorbs or extricates different gases. M. 
 Jurine, of Geneva, opened the body of a maniac who had been 
 dead a few hours, and collected the gases which escaped; he ob* 
 served, that the proportion of ox}'gen and carbonic acid dimi- 
 nishes from the stomach towards the great intestines, while, on 
 the contrary, there is, in these, an increased proportion of azote; 
 that hydrogen is more abundant in the great than in the small in- 
 testines, that it is less in quantity in these than in the stomach. 
 Do the oxvgen and azote form a part of the atmospherical air 
 which is taken in with the food and with the saliva, and which 
 is disengaged by the heat of the intestinal canal? Or are these 
 gases the result of the decomposition of the food and of the in- 
 testinal fluids? Besides, may not the gas contained in the intes- 
 tines of a dead body, have been formed at the moment of death? 
 We know that, in several instances, at the moment contractility ^ 
 is forsaking our organs, the intestines become distended by gas 
 which hastens the approach of death, by impeding the descent of 
 the diaphragm. 
 
 Digestion, when healthy, is unaccompanied by the prodqction 
 of gases. In indigestion, there almost alwavs escapes carbonated 
 or sulphuretted hydrogen gas, which produces the offensiv e smell 
 of the air which escapes at the anus; this smell is different from 
 that of the flatus which are brought upwards; these contain pure 
 hydrogen or carbonic acid gas. The latter is, likewise, some- 
 times voided by the rectum, but less frequently than hydrogen 
 combined with carbon, sulphur, or even phosphorus. Is not am- 
 monia itself extricated, and does it not accompany the evacua- 
 tion of the faeces in certain putrid diarrhoeas, as in dysentery 
 combined with low fever? Though the formation of this gas im- 
 plies a putrefactive motion opposed to the vital principle, may 
 not this decomposition commence in substances lying in the 
 great intestines, when these are become almost inert from the 
 impaired condition of the vital power. This would not be the 
 only instance of a chemical process taking place in the intestinal 
 canal, notwithstanding the counteracting influence of vitality. 
 Thus, on some occasions, grapes eaten in too great quantity, fer- 
 
OP DIGESTIOJT. 
 
 140 
 
 ment and produce carbonic acid gas, in such abundance, that this 
 elastic fluid overcomes the resistance of the intestines. This is 
 the kind of distention from flatulence which is cured bv drinking 
 plentifully of cold water, which dissolves the gas naturally solu- 
 ble in that fluid.* 
 
 XXXI. Of the secretion and excretion of the urine. The fluids 
 absorbed with the chyle, and taken up by the lymphatics of the 
 intestinal tube, dilute the nutritive part extracted from the solid 
 aliment, and serve it as a vehicle. When they have reached the 
 mass of the blood, they increase its quantity, diminish its visci- 
 dity and render it more fluid; going along with it throughout 
 the whole course of the circulation, they supply moisture to all 
 the parts of the body, and become loaded with the molecules de- 
 tached from them by the vital motion. Then, conveyed to the 
 urinary organs, they become disengaged from the rest of the 
 fluids, carrying along with them a number of products of every 
 kind, which by a longer stay in the animal economy, would not 
 fail to occasion a manifest disturbance in the exercise of the 
 functions. 
 
 XXXII. The rapidity with which we void, with the urine, 
 certain diuretics, has induced several physiologists to think, that 
 there exists a direct communication between the stomach and 
 bladder; no one, however, has ever succeeded in pointing out 
 those peculiar ducts, which might serve to convey the urine from 
 the stomach to the urinary organs, without taking the circuitous 
 course of absorption and of the circulation; and, besides, the 
 learned Haller has proved, by accurate calculations, that the size 
 of the renal arteries, whose caliber amounts to an eighth of that 
 
 * It is now well ascertained, that no gas is extricated in healthy digestion. 
 In morbid conditions of this function, however, it does occasionally happen. 
 But I do not agree with the author in thinking “ its formation implies a putre- 
 factive motion opposed to the vital principle.” It may result from some chemi- 
 cal changes in the alimentary substances, but it is more probable that the gas, 
 in these instances, is the product of secretion. 
 
 By Mr. Hunter it has been shown very satisfactorily, that gas is often se 
 creted by the vessels of animal bodies, or in other words, as we suspect, 
 that a matter is eliminated, which has such an affinity for caloric as to as- 
 sume the gaseous state. This matter would seem to be carbon, as the gas 
 evolved, at least in colic, is carbonic acid, reddening the tincture of turnsole, 
 and making lime water turbid,— Ed. 
 
OP DIGESTION. 
 
 14i 
 
 of the aorta, and the quickness with which the blood flows, suf- 
 ficed to account for the shortness of the time in which certain 
 fluids reach the urinary organs. 
 
 A thousand ounces of blood pass through the renal tissue in 
 the space of an hour: supposing that this fluid contains only a 
 tenth of the materials fit for supplying urine, a hundred ounces, 
 or seven pounds and a quarter, may be given out in this short 
 time; and never, with the most copious and diuretic drinks, does 
 more of it pass in an hour. We shall see, however, in treating 
 of absorption, that it is not absolutely impossible, that by means 
 of the numerous anastomoses of the lymphatics, this set of vessels 
 may carry a liquid directly from the stomach into the bladder. 
 It would be superfluous to mention, in this place, the varieties 
 observable in the kidneys, in point of number, size, and situation. 
 These two lobular viscera, composed of the union of from twelve 
 to fifteen glandular bodies, divided in the foetus, and in some 
 quadrupeds, attached to the posterior part of the abdomen, be- 
 hind the peritoneum, are surrounded with a cellular covering of 
 different thickness, and particularly remarkable by the con- 
 sistence, approaching to that of tallow, of the fat which fills 
 its cells. 
 
 If ever the art of man shall penetrate into the mystery of the 
 intimate structure of our organs, it seems probable that the kid- 
 neys will furnish the first solution of the problem. Even coarse 
 injections pass readily from the renal arteries into the ureters, 
 or excretory ducts of the kidneys; a convincing proof of imme- 
 diate communication among the minute arteries, which, exceed- 
 ingly tortuous, form, with the minute veins, the cortical or out- 
 ward substance of the kidneys, and the straight urinary tubes, 
 which, distributed in conical fasciculi, in the interior of these 
 organs, constitute what has been called its tubuli and papillae. 
 The passage of injections from the arteries into the renal veins, 
 is as easy; and I have often seen the coarsest liquids flowing at 
 once by the ureters and by the emulgent veins. This free commu- 
 nication between the arteries, the veins, and excretory ducts of 
 the kidneys, gives an idea of the rapidity with which the blood 
 must flow through these organs, whose firm consistence allows 
 a very moderate dilatation to the vessels; and suggests the pos- 
 sibility of a sort of filtration of the urinary fluid, the secretion of 
 
OF DIGESTION 
 
 142 
 
 which would be only a succession of chemical or mechanical se- 
 parations from the blood, in its passage along very minute ducts, 
 of a bore progressively decreasing. This was the opinion, at 
 least, of Ruysch, whose sj'stem on the intimate composition of 
 our organs, and on the immediate continuation of the blood- 
 vessels with the excretory ducts, is chiefly founded on the facts 
 of structure, discovered to him by his beautiful injections of the 
 renal arteries. 
 
 The kidneys, are of duller sensibility and less energetic action 
 than the other glands. The force of life has less to do in their 
 secretion, and-their functions may be more readily explained on 
 the principles of chemistry or hydraulics. 
 
 XXXIII. If we attempt, indeed, to apply to the urinary or- 
 gans the fundamental laws on the mechanism of secretions,* it 
 is soon seen, that these organs are not under their absolute con- 
 - trol. Of all the animal fluids, urine is the one most complex in 
 its elements, and most variable in its qualities. Not only do fo- 
 reign substances sometimes appear in it, affect, and even change 
 its composition; other fluids may, at times, mix with it, and dis- 
 guise it altogether. Thus credible observers tell us of the ap- 
 pearance in urine, of bile, fat, milk, blood, pus, of which many 
 facts may be found collected in Haller’s great work on physio- 
 logy. The kidneys, then, have less sensibility than the other se- 
 cretory organs: they reason less, if I may venture on the ex- 
 pression, on the sensation produced by the various substances in 
 the blood: their action is also less powerful; it does not so inti- 
 mately affect the fluid subjected to it. It does not change the 
 heterogeneous qualities of those that are mixed with it, and al- 
 lows them to pass in a pure state. 
 
 This multitude of elements in the composition of urine, had 
 surely been understood by the ancients, before it was demon- 
 strated by modern chemistry; for they considered it as a sort of 
 extract of animal substance, as a real lixivium, carrying off all 
 that is impure in the economy, and gave it the name of lotium, 
 which indicates that destination. 
 
 Finally, the secretion of urine is more uniformly carried on: 
 it is continual, or at least, does not exhibit so prominently those 
 
 See the Chapter on Secretion. 
 
OP DIGESTION. 
 
 143 
 
 alterations of action and repose, so apparent in the work of the 
 other secretory organs. When, in a case of retention of urine, 
 we introduce a catheter into the urinary bladder, and leave it 
 there, the urine keeps dropping continually, and would wet the 
 patient’s bed, if the orifice of the catheter was not kept closed. 
 In the memoirs of the Academy of Sciences for the year 1761, 
 there is related a case of singular conformation of the urinary 
 bladder. This musculo-membranous viscus protruded through 
 an opening at the lower part of the linea alba, and was turned 
 inside out, so as to present, externally, its mucous membrane. 
 This case afforded an opportunity of observing the continual 
 flow of the urine through the orifices of the ureters, and of as- 
 certaining the different circumstances attending this process, 
 either with regard to the qualities of this fluid, or to the quan- 
 tity which might be voided, in a certain space of time, and in 
 this respect there was a good deal of difference, according to 
 the state of sleep and waking, to the quantity and to the diuretic 
 qualities of the drink. 
 
 The urine contained in the ureters is turbid and imperfect; its 
 constituent parts are not thoroughly blended together, as may 
 be observed, if made to flow’^, by compressing the kidneys in a 
 dead body. It improves by passing along those ducts, acquires 
 the characteristic qualities of urine, oozes at the surface of the 
 papillse, and flows into the membranous calices which embrace 
 the rounded terminations of the tubuli uriniferi. The union of 
 the calices forms the pelvis, or the expanded portion of the 
 ureters, or membranous ducts, along which the urine is inces- 
 santly flowing into the bladder. The urine flows into the bladder 
 by its own weight, and especially by the action of the parietes of 
 the ureters, which possess a certain degree of contractility. To 
 the above causes, may be added the concussions excited by the 
 pulsations of the renal arteries, behind which the pelvis of the 
 kidney is situated, and by the pulsations of the iliac arteries, in 
 front of which the ureter passes, before entering the cavity of the 
 pelvis; the alternate compression from the viscera of the abdo- 
 men, during the motions of respiration; the concussion attend- 
 ing bodily exercise, as riding on horseback, walking, running, 
 &c.; the pressure of the column of urine from the kidneys, and 
 the want of resistance towards the bladder. 
 
or DIGESTION. 
 
 144 
 
 XXXIV. The urine is continually passing, in drops, into the 
 bladder, it separatg^..4<5 parietes, without, however, exciting in 
 .them any perceptible impression, as they are accustomed to its 
 stimulus. The urine cannot accumulate in the musculo-membra- 
 nous cavity of the bladder,* which is situated, exterior to the 
 peritoneum, in the cavity of the pelvis, behind the pubis, above 
 which, in the adult, it never rises, except when excessivel dis- 
 tended, unless it is prevented from flowing along the urethra, or 
 from returning by the ureters. This retrograde flow is prevented 
 by the oblique insertion of these ducts, which pass, for some dis- 
 tance, between the muscular and mucous coats of the bladder, 
 before opening within it, towards the posterior angles of the 
 trigone vesical,f by openings of smaller dimensions than their 
 cavity. The inner coat of the bladder, raised over these aper- 
 tures, gives them the appearance of being provided with valves, 
 which fit the better these orifices, according as the urine con- 
 tained in the bladder, by separating its parietes, presses against 
 each other the coats by which they are formed, and between 
 which the ureters pass, along a space of from seven to eight lines. 
 
 The urine which flows into the bladder, requires a certain de- 
 gree of force to separate its parietes on which the weight of the 
 intestines presses. This is effected by no other power than by 
 that which causes the flow of the urine along the ureters, and 
 though inconsiderable, it will appear sufficient, if it be considered 
 
 * In the numerous tribe of birds, the bladder is wanting. In them, the ureters 
 open into the cloaca, a musculo membranous bag, whidi supplies the place of 
 the rectum, bladder, and uterus, and which serves as a reservoir to the solid 
 excrements, to the urine, and to the eggs detached from the ovaria. The.urine 
 of birds dilutes the fsepes and furnishes the carbonate of lime which forms 
 the basis of the egg shell. It has such a tendency to concretion, that I have 
 always observed, in dissecting various fowls of different kinds, an earthy, sa- 
 line or crystallized substance, forming white strix easily seen in the fluid of the 
 ureters, through their thin and transparent coats. Hence one may readily con- 
 ceive, how frequently calculi would form in these animals, if their urine accu- 
 mulated and remained, for any length of time, stationary in acavity destined to 
 contain it. 
 
 ■)• The French anatomists give the name of trigone vesical, to that portion of 
 the bladder included betw'een the openings of the ureters and the neck of the 
 bladder, and forming a triangle, whose base is represented by a line drawn 
 from the opening of one ureter to the other, and whose apte.x is situated at the 
 insertion of tlie urethra into the neck of the bladder. T 
 
OF DIGESTION. 
 
 145 
 
 that the fluids which pass from a strait channel into a larger ca- 
 vity, act on every superficial portion oHte^rietes equal to the 
 area of the channel, with a power equal to that which determines 
 their flow into the latter; so that if the urine descends along the 
 ureters, with a degree of force equal to one, and if the inner sur- 
 face of the bladder is a thousand times more extensive than the 
 area of the ureters the power will be multiplied a thousand fold. 
 
 This purely mathematical proposition is expressed by saying, 
 that the force with which the urinje passes along the ureters, is 
 to that by which the parietes of the bladder are distended, as the 
 caliber of the ureters is to the superficies of the bladder. 
 
 The pressure which the urine, accumulated within the bladder, 
 exerts on the lower part of the ureters, does not prevent the 
 force which determines its descent along the ureters, from car- 
 rying it into the bladder: — for, the column which descends along 
 the ureters, being higher than that contained in the bladder, 
 these two organs represent an inverted syphon, the longer branch 
 of which is represented by the ureter. 
 
 The following are the causes which enable the bladder to re- 
 tain the urine: the contraction of its sphincter, a muscular ring 
 surrounding the termination of the urethra into the bladder: the 
 angle formed by that canal, after it leaves the bladder: and lastly, 
 the action of the anterior fibres of the levator ani, which sur- 
 round the neck of that organ, surrounded besides and supported 
 by the, prostate gland. These fibres, which are calculated to com- 
 press the prostate over the neck of the bladder, and to raise the 
 latter against the pubis, have been called by Morgagni, pseudo 
 sphincteres vesica. 
 
 The urine, deposited by drops into the bladder, gradually se- 
 parates its parietes. This musculo-membranous organ rises, and 
 at the same time, carries upwards the convolutions of the ileum, 
 and the peritoneum before which it lies, behind the pubis and 
 the recti muscles with which it is in immediate contact. These 
 relations of the peritoneum to the distended bladder, account for 
 the possibility of puncturing it above the pubis, so as to let out 
 an accumulation of urine, without penetrating into the cavity of 
 the peritoneum. 
 
 The urine remains a certain time in the bladder, according to 
 the capacity of the latter, to the irritability and extensibility of 
 
 T 
 
OF DIGESTION. 
 
 146 
 
 its parietes, and according to the acrid or stimulating qualities 
 of the fluid itself. Thus in old men, in whom the bladder has but 
 a small degree of irritability and contractility, the urine is voided 
 less frequently; it accumulates in greater quantity, and is, at 
 times, evacuated with difficulty. The use of diuretics, especially 
 of cantharides, renders the urine more stimulating, it excites 
 powerfully the parietes of the bladder and incessantly stimulates 
 it to contraction. Every cause of irritation seated within the 
 bladder itself, or in its vicinity, renders more frequent the calls 
 to void urine. This is observed in cases of stone in the bladder, 
 of piles, gonorrhoea, &c. The urine, while in the bladder, be- 
 comes thicker from the absorption of its more fluid parts, its ele- 
 ments become more intimately blended, sometimes even it ap- 
 pears to undergo a certain degree of decomposition. 
 
 XXXV. When, either by the extension which the urine oc- 
 casions in the muscular fibres of the bladder, or by the irritation 
 which it excites in the nerves distributed on its inner membrane, 
 we experience in the pelvis a sensation of weight, together with 
 a kind of tenesmus, which, as it extends along the urethra, warns 
 us to void urine; then we bring on a contraction of the bladder, 
 and joining to its action that of the abdominal muscles and of 
 the diaphragm, we expel the urine by a process veiy similar to 
 that of the excretion of the feces (XXIX). It should be ob- 
 served, however, that in a healthy state of the parts, this assist- 
 ance is required, only to overcome the equilibrium between the 
 contractions of the bladder, and the resistance which the cause 
 of retention opposes to the evacuation of the urine. After the 
 simultaneous contraction of the diaphragm and abdominal mus- 
 cles, to press down the intestines on the bladder, and to deter- 
 mine the first flow of the urine, we cease that effort, and the 
 bladder alone, still supported by the weight of the surrounding 
 viscera, which compress it as it empties itself, completes the eva- 
 cuation. We repeat the first effort, only in case we wish to ac- 
 celerate the flow of the urine. In the evacuation of the feces, on 
 the contrary, the muscular coat of the rectum requires the in- 
 cessant co-operation of the respiratory powers, as these solid 
 substances are evacuated with more effort than the urine. To 
 prove, beyond a doubt, that the urine is evacuated, chiefly by 
 the action of the bladder, one need but observe the violent, but 
 
OF DIGESTION. 147 
 
 useless straining of patients affented with retention of urine, 
 from paralysis of the bladder.* 
 
 The urine is projected along the urethra with the greater force, 
 as it passes from a spacious cavity into a strait canal, and it is 
 expelled with a force proportioned to that of the muscular coat 
 of the bladder; we know, that in old men, this is so weak, that 
 the jet of urine is not projected more than a few inches beyond 
 the urethra. The urethra is not to be considered as inert in the 
 evacuation of the urine; it closes upon it and accelerates its flow, 
 aided in that action by the bulbo-cavernous muscles to which 
 several anatomists have given a name taken from their functions, 
 (acceleratores urina). 
 
 The action of these muscles expels the last drops of urine 
 which remain within the urethra, when the bladder is completely 
 emptied. The contractile and tonic action of the urethra is so 
 distinctly marked, that its spasmodic contraction may be enume- 
 rated among the causes which frequently occasion a difficulty 
 in introducing the catheter. If we attempt to inject fluids along 
 the urethra, the moment we remove the pipe of the syringe 
 which closes its external orifice, that instant, the parietes of 
 the canal contract on the fluid and expel it with a rapid jet. 
 
 The bladder and the canal of the urethra are lined internally 
 with a membrane, whose mucous follicles secrete a viscid hu- 
 mour calculated to protect the parietes of these organs against 
 the action of the urine, and to facilitate the evacuation of that 
 fluid. This membrane, whose surface is more extensive than 
 the cavities which it lines, forms a great number of folds, which 
 disappear when the bladder is distended with urine. This 
 mucus is secreted, in an unusual quantity, in catarrhal affections 
 of the bladder, and becomes, likewise, more ropy and more al- 
 buminous. The mucous secretion of the glands of the urethra 
 is altered in its quality, and becomes more abundant, from the 
 action of the venereal poison, and gives rise to the discharge of 
 
 * It is scarcely credible that some physiologists should have considered this 
 organ as inert and absolutely passive, in the evacuation of tlie urine, which, in 
 their opinion, is performed by the immediate pressure of the abdominal mus- 
 cles and diaphragm on that cavity. Amid this variety of opinions, if you wish to 
 come at the truth, you must take a medium, Iliaccs intrd muros peccatur, et 
 extrci. 
 
Of DIGESTION. 
 
 148 
 
 gonorrhoea; the orifices of these lacunae may stop the end of a 
 catheter, so as to add to the difficulty of introducing that in- 
 strument*. 
 
 The urine cannot be voided at the same time as the faeces, 
 when these, by their hardness, compress the prostatic and the 
 membranous part of the urethra, situated before the lower ex- 
 tremity of the rectum. It is difficult, and often impossible to 
 void urine, during a violent erection, as the parietes of the 
 canal are then closely applied to each other, by the turgescence 
 of the corpus spungiosum and of the corpora cavernosa of the 
 penis. The mode of sensibility of the urethra is besides chang- 
 ed in such a manner, that it is calculated to permit only the 
 emission of the seminal fluid. 
 
 When the bladder is completely emptied, it sinks behind the 
 pubis; the tumour which it formed above these bones, while in 
 a state of distention, collapses, the abdomen becomes less pro- 
 minent, respiration more free, and there is a general feeling of 
 lightness. The bladder cannot be completely evacuated, unless 
 the pelvis is gently inclined forward; its bas fond^ which is on a 
 lower level than its neck, would, in any other posture, retain a 
 certain quantity of urine. 
 
 XXXVI. Of the physical properties of urine. As this fluid 
 varies in quantity in a healthy man, according to the quantity 
 and diuretic qualities of the drink, the state of sleep or waking, 
 the condition of the secretions, and especially of the perspira- 
 tion, it is very difficult to determine, accurately, its proportions. 
 Nothing varies more than its quantity, as may be ascertained, 
 by comparing the different calculations on that subject, of a 
 great number of physiologists. At times, the urine is less in 
 quantity than the drink that has been taken in, at others, more. 
 
 * When this operation is performed in a case of simple paralysis of the 
 bladder, it is better to employ a very large catheter, which may stretch the 
 parietes of the urethra and prevent their forming into wrinkles, and whose 
 rounded beak may not get engaged in the lacunve of that canal. 
 
 When in a case of retention of urine, the bladder rises above the pubis, its 
 bas fund is carried upwards, and there is a period of excessive distention, at 
 which, like the uterus in an advanced stage of pregnancy, it seems to make 
 an effort to rise above the brim of the pelvis; under such circumstances in 
 women, it is impossible to introduce the catheter, except by fnereasing the 
 curve of the instrument. 
 
OF DIGESTION. 
 
 U9 
 
 It may be affirmed, however, that the quantity of urine voided 
 in twenty-four hours, is equal to that of the insensible perspira- 
 tion in the same time, and it may, therefore, be estimated at 
 between three and four pounds, in a healthy adult. Its colour 
 varies, from a light lemon yellow, to an orange, approaching to 
 red. Its smell and flavour are peculiar, and distinguish it from 
 every other animal fluid. Its colour is, in general, darker, its 
 smell and flavour stronger and more pungent, as it is less in 
 quantity, as the circulatory system is more active and powerful, 
 and as the substances of our food are more animalized. We all 
 know how fetid and how scanty is the urine of carnivorous ani- 
 mals; how offensive to the smell is that of the cat! The specific 
 gravity of urine is greater than that of distilled water, and 
 varies according to the quantity of saline and other substances 
 which it holds in solution; it is, likewise, slightly viscid, but not 
 ropy like the serum of the blood, the bile, the saliva, and other 
 albuminous fluids. 
 
 XXXVII. Of the chemical properties of urine. The peculiar 
 qualities of urine are always more marked in a powerful and 
 adult male, than in children, women, and weakly persons. By 
 chemical analysis, the urine is found to contain eleven substan- 
 ces, dissolved in a considerable quantity of water, viz. urea, a 
 gelatinous animal matter, muriates and phosphates of soda and 
 ammonia, in separate or in triple salts, phosphate of lime, phos- 
 phate of magnesia, phosphoric, uric, and benzoic acids. Be- 
 sides these substances which are constantly found in human 
 urine, this fluid may contain a great number of others; and if 
 it be true that the urinary system is to be considered as the 
 emunctory of the whole economy, one would expect to find in 
 it, in certain proportions and under different circumstances, the 
 whole of the constituent principles which analysis has hitherto 
 discovered in our solids and liquids. Hence, doubtless, the 
 difference in the results obtained by the chemists who have in- 
 vestigated the nature of the urine, by allowing it to run into 
 decomposition, or by applying to it various re-agents. 
 
 As the urine is, of ail our fluids, that which has the greatest 
 tendency to putrefaction, it should be examined shortly after 
 being voided; it is then distinctly acid, but in a very short time, 
 and especially if the heat of the atmosphere promotes and ac- 
 
OF DIGESTION. 
 
 150 
 
 celerates these changes, it becomes turbid, Its component parts 
 separate and form various precipitates. Urea and gelatine, 
 which alone of its constituent principles are capable of fermen- 
 tation and decomposition, give out ammonia, acetous and carbo- 
 nic acids, and from the chemical attraction between these newly 
 formed substances, and from the primitive elements, there are 
 produced new compounds the knowledge of which is of the 
 department of chemistry. 
 
 Of all the constituent parts of urine, the most essential is a 
 substance of the consistence of syrup, deliquescent, susceptible 
 of crystallization, to which -M. Fourcroy has given the name of 
 wea. This substance to which the urine owes its characteristic 
 properties, its peculiar colour, smell and flavour, which was 
 imperfectly known to several chemists who had sketched some 
 of its features, giving it different names, according to the notions 
 they entertained of its nature, was never well understood till 
 the late investigations of this celebrated professor*. It is a 
 compound in which azote prevails, as is shewn by the im- 
 mense quantity of carbonate of ammonia, which it gives out in 
 distillation; it may be considered as the most animalized pro- 
 duct, having such a tendency to the putrid fermentation, that, 
 even while in the animal economy, it is liable to that decompo- 
 sition, and might overcome the antiseptic influence of the vital 
 power, if nature did not get rid of it by the evacuation of the 
 tirine. 
 
 Sufficient attention has not hitherto been paid to the symp- 
 toms of urinary fever, an affection occasioned by the protracted 
 retention of the urine within the bladder. I have observed, on 
 several occasions, that no kind of fever is attended with more 
 marked signs of what physicians term putridity. The urinous 
 and ammoniacal smell exhaled from the body of the patients, 
 the yellowish and oily moisture of their skin, the parching thirst 
 with which they are tormented, the dryness and redness of their 
 tongue and throat, their frequent and irritable pulse, combined 
 with a flaccid and doughy feel of the cellular tissue, every thing 
 indicates that the animal frame is threatened with the most 
 speedy and dangerous decomposition. 
 
 * See his work entitled: Srsttme des connoissances Qhimiqiies . 8vo. tom. x. 
 page 153. 
 
OF DIGESTION. 
 
 151 
 
 I observed similar appearances in a cat and in a rabbit, in 
 which I tied the ureters. Nothing is easier than to find the ure- 
 ters and to perform this experiment. After a crucial incision of 
 the parietes of the abdomen, on the left side, the intestines are 
 pushed aside to the left, so as to apply a ligature on the right 
 uretur, they are then pushed to the right, while the left ureter 
 is tied. Both ureters are seen through the peritoneum, situated 
 behind that membrane, in the lumbar region. When the liga- 
 tures haye been applied to the ureters about their middle, 
 the divided edges of the abdomen are brought together and 
 united by sutures, and the body of the animal is wrapped round 
 with a cloth soaked in some emollient decoction. At the end of 
 six and thirty hours, the animals became exceedingly thirsty and 
 restless, their eyes glistening; their saliva, which flowed copi- 
 ously, exhaled a smell evidently urinous; on the third day, the 
 cat was seized with vomiting of a slimy substance, remarkable 
 by its having the same smell. This convulsive agitation was 
 followed by an excessive prostration of strength; it died on the 
 fifth day; the intestines were not inflamed, the bladder quite 
 empty, the ureters distended with urine between the ligatures 
 and the kidneys, and as large as the ring finger. The kidneys 
 themselves, gorged with urine, were turgid, softened, and as if 
 macerated. All the organs, all the fluids, the blood itself, par- 
 took of this urinous diathesis; putrefaction came on immediately 
 after death, and at the end of a few days, an almost complete 
 decomposition of the body had taken place. In the rabbit the 
 symptoms were less violent and rapid; it did not die till the 
 seventh day; the smell of its whole body, though evidently uri- 
 nous, was less offensive, and the putrefaction which succeeded 
 was less rapid. 
 
 These two experiments confirm, in the first instance, what 
 some authors have said of the absence of urine in the bladder, 
 when the ureters have been tied; an undeniable proof that these 
 are the only channels which convey the urine into the bladder; 
 they likewise concur in affording the most convincing proof, 
 that the kidneys are the emunctories by means of which the 
 blood clears itself of that part of it which is animalized in ex- 
 cess; finally, they prove, that the retention of this fluid is the 
 
OP DIGESTION. 
 
 152 
 
 more dangerous to the animal economy, as the urine is itself 
 more animalized. 
 
 Has nature the means of supplying the evacuation of urine 
 by other excretions? might this highly recrementitious fluid be, 
 without danger, evacuated by other emunctories? With a view 
 to answer this interesting question, the kidneys have been ex- 
 tirpated in dogs. The removal of one kidney, did not prevent 
 the secretion from being carried on; in every case in which 
 both kidneys were removed at once, the animal died in a few 
 days, and on opening the body, there was uniformly found a 
 considerable quantity of bile in the gall bladder, in the small 
 intestines, and even in the stomach, as if the urea had endea- 
 voured to make its escape in that direction, by combining with 
 the bile. These experiments were performed at the Hopital 
 Saint Louis, in the course of the year XI. 
 
 Urea, combined with a certain quantity of oxygen, appears to 
 form an acid peculiar to human urine, and which is the sub- 
 stance of the greater number of urinary calculi. It resembles 
 urea in this, that its crystals, exposed to heat, give out carbonate 
 of ammonia; but it differs essentially from it, by its ready con- 
 crescibility. It, in fact, crystallizes every time the urine grows 
 cold, and forms the greatest part of the urinary sediment.—. 
 This acid, so'weak that several chemists have considered it to 
 be a mere oxide, has been called by M. M. Fourcroy and 
 Vauquelin, the uric acid. Among its distinguishing characters, 
 may be mentioned its being insoluble in cold water; it is so fix- 
 ed, that several thousand times its own weight of boiling water 
 is required to dissolve it: hence it may be easy to account for 
 its so frequently giving rise to urinary calculi; we may, indeed, 
 wonder, that this complaint is not of more frequent occurrence, 
 since a slight cooling of the urine is sufiicient to cause a preci- 
 pitation and crystallization of the urine. Thus, every time an 
 extraneous substance drops into the bladder, it becomes the 
 nucleus of a calculus, formed by the uric acid becoming concrete 
 on the surface of this body, which is of a colder temperature. 
 Quadrupeds are less frequently affected with urinary calculi, 
 from the absence of the uric acid in their urine, and because car- 
 bonate of lime, of which, in those animals, such concretions are 
 
OP DIGESTION. 153 
 
 formed, is a salt decomposed with effervescence by the weaker 
 acids, and several such acids are found in the urine. 
 
 Phosphorus, which may be considered as the result of a high, 
 degree of animalization, enters, in considerable proportions, 
 into human urjne. Besides the phosphoric salts which it con- 
 tains, there is always found a certain quantity of disengaged 
 phosphoric acid, which holds in solution the calcareous phos- 
 phate, and gives to the urine its manifest acidity, when examin- 
 ed fresh, or shortly after it has been voided. It was from urine 
 that phosphorus was first obtained by those who originally dis- 
 covered it, and from that fluid it has long been procured for 
 the purposes of commerce. But it is seldom obtained from urine, 
 since the discovery of the phosphoric acid in the earth of bones 
 has rendered the manufacture of phosphorus easier and less ex- 
 pensive. In the urine of frugivorous mammiferous animals, phos- 
 phoric salts have their place supplied by calcareous carbonate, i 
 
 Certain substances impregnate the urine with a peculiar odour. 
 It is well known, that if one remain a few minutes in a room 
 newly painted with oil of turpentine, the urine, for some time 
 afterwards, gives out a smell of violets; asparagus gives to the 
 urine a very remarkable fetor. 
 
 XXXVIII. Besides the accidental varieties observed in the 
 urine, varieties which cannot be determined, since the urine is 
 never uniformly the same in its composition, and does not con- 
 tain the same ingredients in the same person, at different times 
 of the day, according to the quantity and quality of the food and 
 drink, the exercise which has been taken, the affections of the 
 mind which have been experienced, &c. ; it constantly varies, 
 according to the time which has elapsed since a meal, the age 
 of the subject and the diseases under which he may labour. 
 
 Physiologists have, for a long while, admitted two and even 
 three different kinds of urine, according to the time at which it 
 is voided; they are distinguished by the names of urine of the 
 drink, urine of the chyle, and urine of the blood. The first is a 
 limpid and nearly colourless fluid, which frequently retains, in 
 a remarkable manner, the qualities of the drink, and is voided 
 shortly after drinking, and has scarcely one of the characters of 
 perfect urine. The urine of the chyle or of digestion, voided 
 two or three hours after a meal, is more formed, still it is jiot 
 
 U 
 
OF DIGESTION. 
 
 154 
 
 perfect and does not contain all the component parts of this fluid. 
 Lastly, the urine of the blood, which is voided seven or eight 
 hours after a meal, and in the morning after the night’s rest, 
 contains, in an eminent degree, all the qualities of urine; hence 
 it is that which chemists prefer using in their analysis. The im- 
 perfect state of the two former kinds of urine, would prove 
 better than the rapidity of their secretion, the disputed existence 
 of a peculiar communication from the stomach and intestines 
 into the bladder. 
 
 The urine of children and that of nurses contains very little 
 phosphate of lime and phosphoric acid; it is only after the pro- 
 cess of ossification is completed, that these elements abound in 
 the urine. That of old men, on the other hand, contains a 
 considerable quantity of these substances; their osseous system 
 already containing phosphate of lime in excess, and incapable of 
 receiving more, this saline substance would ossify all the tissues, 
 as it sometimes does that of the arteries, the ligaments, the car- 
 tilages and membranes, if the urine did not carry off the greater 
 part. 
 
 In the rickets, it is by the urine that the phosphate of lime is 
 carried out of the system, and the absence of that substance is 
 the cause of mollities ossium; on the approach of fits of the gout, 
 the phosphoric ingredients of the urine diminish and seem to 
 be carried to the joints, to produce in their vicinity arthritic 
 concretions. 
 
 The great quantity of saline and crystallizable elements w’hich 
 enter into human urine, accounts for the frequency of the con- 
 cretions which form in that fluid. Urinary calculi were long con- 
 sidered as formed of a single substance, which the ancients 
 thought analogous to the earth of the bones, and which Scheele 
 took for uric acid. The late investigations of M. M. Fourcroy* 
 and Vauquelin have shown, that the component parts of urine 
 are too numerous and too complex to produce uniformly calculi 
 of one kind: that urinary concretions, most frequently formed 
 from uric acid, contain urate of ammonia, phosphate of lime, 
 phosphate of ammonia and magnesia, oxalate of lime, silex; and 
 that these substances, singly, or in binary and ternary combi- 
 nations, form the materials of nearly six hundred calculi which 
 they analysed. Notwithstanding the extent of these researches, 
 
OF DIGESTION. 
 
 155 
 
 there is reason to believe, that when carried further by the same 
 chemists, they will be attended with results still more varied. 
 For, as there is no integral molecule in the body which may not 
 be voided with the urine, and be found in the urine, so it is con- 
 ceivable, that under certain circumstances which it is impossible 
 to assign or to foresee, every thing in the human body that is 
 capable of concretion, might supply the materials of urinary 
 concretions. 
 
 This variety of elements in the composition of urinary calculi, 
 the absence of signs by which to ascertain their nature, the sen- 
 sibility of the parietes of the bladder which would be irritated 
 by agents capable of dissolving the concretions so frequently 
 formed in its cavity, must render it very difficult, not to say im- 
 possible, to discover a lithontriptic which should supersede the 
 necessity of a surgical operation, whose difficulties and danger 
 have been much over-rated. 
 
 XXXIX. The energy of the urinary system in the inhabi- 
 tants of temperate climates, has been considered as the cause of 
 the frequency of calculous affections in Holland, England, and 
 France, while they are very rare in more southern countries, in 
 which the cutaneous perspiration seems to be substituted, in 
 great measure, to the urinary secretion. There is no part of the 
 world in which cases of stone in the bladder are more frequent 
 than in England, and especially in Holland, in which a cold and 
 damp atmosphere is unfavourable to perspiration, which is, at 
 any rate, but scanty in persons of a leucophlegmatic tempera- 
 ment like that of the Dutch. In no other country, could a litho- 
 tomist (Raw) have operated on more than fifteen hundred 
 patients, it is said, successfully. Diabetes, or an immoderate 
 discharge of urine, a disease which appears to depend on an ex- 
 cessive relaxation of the renal tissue, is of frequent occurrence 
 only in cold and damp countries, as Holland, England, and Scot- 
 land; it is more rare in France and Germany, and is unknown 
 in warm climates. This relaxation of the renal tissue in diabetes, 
 depends on the exhaustion of the urinary organs called into too 
 frequent action, as is proved by the efficacy of tonics and astrin- 
 gents in the treatment of that complaint. 
 
 Cutaneous affections, on the contrary, seem to belong to the 
 inhabitants of southern countries. Lepra originated in Judea, 
 
OP DIGESTIOX. 
 
 
 156 
 
 the elephantiasis rubra of Cayenne, the framboesia of Java, the 
 yaws, elephantiasis, herpetic and psoric eruptions, are more fre- 
 quent among the inhabitants of southern latitudes, than among 
 those who live under the temperate zones. In countries near to 
 the equator, the surface of the body, habitually exposed to an ar- 
 dent atmosphere, is powerfully excited; the skin is irritated, and 
 its secretion increased; perspiration becomes so profuse, that it 
 weakens, in a short time, those who coming from distant coun- 
 tries, are not accustomed to so intense a heat. The activity of 
 the cutaneous system exceeds that of the urinary system, whose 
 action decreases in proportion. These differences in the energy 
 of the two systems, account readily for the difference of their 
 diseases: for, it is a law of nature, that the more an organ, or 
 system of organs, is called into action, the more it is liable to 
 disease, which is but a derangement of its action. 
 
 Calculous affections are more frequent in children and old 
 people, than in adults. In old age, the proportionate quantity of 
 the urine exceeds that of the perspiration. Phosphoric salts, the 
 base of a great number of urinary calculi, are more abundant in 
 old men, as is proved in them by the ossification of the arteries, 
 of the ligaments, of the cartilages, of the membranes, the solidi- 
 fication and the almost universal induration of the different parts. 
 In children, the activity of the urinar}'^ system is proportionate 
 to that of the digestive organs. Destined to throw out the re- 
 sidue of nutrition, which, at that period, is very active, the or- 
 gans by which the urine is secreted are likewise endowed with 
 considerable energy. Lastly, it is observed, that the greatest 
 number of calculous patients received into the hospitals of large 
 towns, come from low and damp streets near to rivers; every 
 thing, therefore, tends evidently to establish, that the frequency 
 of urinary calculi depends on an increase of activity. in the or- 
 gans destined to the secretion and excretion of urine. 
 
 r 
 
157 
 
 CHAPTER II. 
 
 OF ABSORPTION. 
 
 XL. In the history of the phenomena of life, a statement of 
 the functions of the absorbent system ought immediately to fol- 
 low that of the functions of the digestive organs. The vessels, 
 which take up the chyle separated from the food, by the action 
 of the organs of digestion, form 'a considerable part of the ab- 
 sorbent system, bear a perfect resemblance to the other lympha- 
 tics, and differ from them only in their origin. When digestion 
 is not going on, those vessels convey lymph absorbed in the in- 
 testinal canal, the inner part of which, even when in a state of 
 emptiness, is alway bedewed by an abundant quantity of serous 
 mucus. 
 
 There exist in all the parts of the human body, in the Interior, as 
 well as on the surface of our organs, vessels whose office it is to 
 absorb, and to carry into the mass of the blood, those substances 
 by which our machine is maintained and kept in repair, as well 
 as what comes off in the continual destruction of our parts; for, it 
 must not be forgotten, that the organized and living machine, 
 inwardly acted upon by a double impulse, is perpetually under- 
 going decay and renovation. 
 
 XLI. Absorption is effected on substances introduced from 
 without; such is the absorption from the skin, and the absorption 
 of the chyle, &c. At other times, absorption takes place in fluids 
 effused by arterial transudation; such is the serosity which mois- 
 tens the serous membranes, the fat, the marrow of the bones, 
 and this absorption, almost always, bears a proportion to transu- 
 dation, so -that the serosity, absorbed as fast as it is effused on 
 the surface of the membranes which lie in close contact, except 
 in cases of dropsy, never accumulates so as to separate those 
 membranes. Finally, there is a kind of absorption, which may 
 be termed nutritive or molecular, because it exerts its influence 
 on molecules, which, in the process of nutrition, are separated 
 from the organs and replaced by others. It is this absorption 
 which brings about the decomposition of organs, and to which 
 
OP absorption. 
 
 158 
 
 John Hunter gave the name of interstitial absorption. By means 
 of it, the thymus, so voluminous in the foetus, disappears entirely 
 in the adult. This absorption seems to be incessantly going on, 
 and to carry on decomposition, Avith a force that cannot be re- 
 sisted. It explains, in a satisfactory manner, the spontaneous 
 erosions of the living solids, of which ulceration* is the conse- 
 quence. This inward absorption is promoted by inflammation, 
 hence the advantage of applying heat to indolent tumours, and 
 of exciting a slight inflammation in swollen glands, in order to 
 bring about resolution. It is on that account, that in swelling 
 and induration of the testicle, unattended by cancer of the part, 
 the operation for hydrocele by injection, may be safely employ- 
 ed. — Of this I had a convincing proof, a few years ago: a gar- 
 dener, born deaf and dumb, had had for some years an hydrocele, 
 which he was in the habit of getting tapped every six months. 
 When I last tapped it, I found the testicle swollen and hard, and 
 three time larger than in its natural state; the patient, however, 
 was free from pain. A considerable quantity of a reddish serous 
 fluid was discharged; at the end of two days, inflammation of 
 the tunica vaginalis came on, the scrotum became enlarged and 
 was covered with emollient poultices. At the end of twenty 
 days, the testicle was a good deal lessened in size and adhered 
 to the inside of the tunica vaginalis: the cure was considered ra- 
 dical and proved such; for, though it is now ten years since the 
 operation was performed, the water has not collected and the 
 patient continues in the laborious employments of his business. 
 I frequently meet him, and he never fails, by inarticulate sounds 
 and signs of satisfaction, to express to me his gratitude. 
 
 The process of absorption, is very active in children, in 
 women, during sleep. In the morning when the body is refreshed 
 by the night’s rest. Is a state of weakness favourable or unfa- 
 vourable to that process? It is well known, that there are robust 
 men who have intercourse with women infected with the vene- 
 real virus, and who escape the contagion, unless they expose 
 themselves to it when debilitated by excesses. A mind free of 
 fear and anxiety, has ever been considered in the Eastern coun- 
 tries, a safe guard against the plague. A dog, ceteris paribus, is 
 
 Nosograplue Chinir^icale, tome I. art. Ulceres Jtoniqtiet- 
 
OF ABSORPTION, 
 
 159 
 
 in much less danger from the bite of a viper, when suddenly 
 bitten, than when he has been some time gazing at the reptile, 
 and more or less terrified by the sight. But in all these cases, 
 does debility favour the introduction of the contagious matter, 
 by increasing the force of absorption; or is it not more probable, 
 that by affecting the nervous system, it renders it more suscep- 
 tible of deleterious impressions?* 
 
 XL II. Absorption is much less active, on the external sur- 
 face of the body, than on the surface of its internal cavities, and 
 in the very substance of our organs. Cutaneous absorption, under 
 certain circumstances, has even so little activity, as to have led 
 some physiologists to doubt its existence. The absorbing orifices 
 of vessels which arise on the surface of the body, are covered 
 by the epidermis. This covering, which is insensible, and, as it 
 were, inorganic, forms a sort of separation, between the external 
 and internal part of our being, and opposes, or renders more 
 difficult, the absorption of substances in immediate contact with 
 our body; and if it be considered, that vve are frequently im- 
 mersed in the midst of gases and other substances, to a certain 
 degree, deleterious, it will be understood, how essential it was, 
 that the absorbing surface of the skin should not be entirely 
 exposed, and that cutaneous absorption should not be easily 
 carried on. 
 
 The increased weight of the body, after exercise in wet 
 weather; the abundant secretion of urine, after remaining long in 
 the bath; the manifest enlargement of the glands of the groin, 
 after keeping the feet immersed, for a considerable time, in 
 water, an experiment often performed by Mascagni on himself; 
 the effects of mercurial frictions, &c. show, however, in an un- 
 questionable manner, that absorption takes place through the 
 skin, with more or less rapidity, according to circumstances. It 
 must be taken into account, that the means which promote cuta- 
 neous absorption, operate, at least as much, by altering the struc- 
 ture of the epidermis, as by increasing the action of the ab- 
 sorbing orifices. In this manner, the bath appears to operate, by 
 softening the texture of the epidermis; and frictions, by dis- 
 placing and raising its scales. 
 
 The latter is undoubtedly the explanation. — E d. 
 
OF ABSORPTIOSr. 
 
 160 
 
 It is by means of frictions, that we succeed in introducing into 
 the lymphatic system, medicines possessing purgative, febrifuge, 
 sedative, or diuretic qualities, combined with the gastric juice, 
 or diluted in any other liquids; for, as has been shewn by the ex- 
 periments performed at the Salpetriere, by M. M. Dumeril 
 and AUbert, in the name of the Philomatic Society, the mixture 
 with saliva or gastric juice, of the medicines which are to be ad- 
 ministered by friction, is not necessary to insure their absorp- 
 tion. Extract of opium has soothed pain, bark has checked fits 
 of intermittent fever, rhubarb has procured alvine evacuations; 
 squills have stimulated powerfully the action of the urinary or- 
 gans, nor has the previous mixture, with gastric juice, of these 
 substances reduced into powder, seemed to increase or diminish 
 their efficacy. 
 
 Absorption takes place quickly and readily, wherever the epi- 
 dermis is thin, habitually moist, and the skin delicate, so as to 
 leave almost bear of covering, the subjacent parts, as on the lips, 
 in the inside of the mouth, on the surface of the glans, &c. The 
 complete removal of the epidermis, favours absorption from all 
 parts of the skin which it covered. Hence the least scratch on 
 the fingers of an accoucheur touching women infected with the 
 venereal virus, exposes him to this peculiar infection, which, in 
 such cases, is the more to be dreaded, from the admission of 
 the virus by an unusual course. The inoculation of variolous 
 and vaccine matter, equally furnishes proofs of the obstacle 
 which the epidermis presents to cutaneous absorption, and of 
 the facility with which that function takes place, from surfaces 
 denuded of that covering. Absorption goes on, likewise, with 
 great activity, from the surfaces of internal parts, but it no 
 where is so considerable as in the intestinal canal, and it would 
 perhaps be the most favourable part for introducing medicinal 
 substances into the animal economy, if when swallowed, they 
 did not undergo changes, by mixing with the gastric juices, or 
 with the intestinal fluids and fascal substances, when injected by 
 the rectum. From the evacuation by urine of clysters of warm 
 water, soon after they have been administered, it is to be pre- 
 sumed, that the great intestines absorb almost as powerfully as 
 the rest of the digestive canal. A pint of warm water injected 
 into the abdomen of a large dog or sheep, is often absorbed in 
 
OF ABSORPTION. 
 
 161 
 
 less than an hour, and the effusions which take place in those 
 cavities, would possibly not require an operation to let them out, 
 if such fluids were not subject to coagulation, and if the absorb- 
 ing surfaces were not diseased.* 
 
 * It is now thirteen years since the subject of cuticular absorption first en- 
 gag-ed the attention of the medical men of this city, during which time, it has 
 been prosecuted with an ardour and success highly honourable to those con- 
 cerned in the inquiry. As early as the year 1800, it was shown, or at least ren- 
 dered highly probable by Dr. Rousseau, that the pulmonary organs, and not 
 the skin, constitute the avenue through which certain substances enter the 
 system. By cutting off all communication with the lungs, which he easily 
 effected by breathing through a tube protruded into the external atmosphere, 
 he found that though the surface of his body were bathed with the juice of 
 garlick or the spirits of turpentine, none of the qualities of these fluids could 
 be detected, eitlier in the urine, or serum of the blood. Conducted nearly on. 
 the same principle, but with a greater diversity of substances, experiments ex- 
 ceedingly well devised and ably executed, have since been made, by persons of 
 opposite prepossessions, to an almost incredible extent. Contradictory as many 
 of these are, a candid examination of the whole will still lead to a pretty satis- 
 factory conviction, that absorption from the surface of the human body does 
 not exist as a natural and ordinary function. 
 
 Borne down by the weight of evidence against them, most of the advocates 
 of the ancient hypothesis were indeed prepared to abandon it, as no longer 
 tenable, when about two years ago an experiment made by Dr. Massy again 
 revived their faith in cuticular absorption. This experimentalist very clearly 
 proved that if the body be immersed in a decoction of madder, the colouring 
 matter of this substance will be taken in, and may be displayed in the urine, 
 by using any one of the alkalies as a test. 
 
 Determined, if possible, to put this long agitated question to rest. Dr. 
 Rousseau, assisted by his friend Dr. Samuel B. Smith, has subsequently per- 
 formed a series of experiments, many of which we witnessed, with every 
 variety of substance, mild and acrid, volatile and fixed, nutritive, medicinal, 
 and poisonous. 
 
 The result of these extensive researches is: 
 
 1. That of all the substances employed, madder and rhubarb are those only 
 which affect the urine. The latter, of the two, the more readily enters the 
 system. Neither of these substances can be traced in any other of the secre- 
 tions, or excretions, or in the serum of the blood. 
 
 2. That the power of absorption is limited to a very small portion of the 
 surface of the body. The only parts indeed which seem to possess it, are the 
 spaces between the middle of the thigh and hip, and between the middle of 
 the arm and shoulder. Topical bathing with a decoction of rhubarb or madder, 
 or poultices of these substances applied to the back, or abdomen, or sides, or 
 shoulders produced no change in the urine, &c. Equally ineffectual was the 
 immersion of the feet and hands in a bath of the same materials. After being 
 kept in it several hours, not the slightest proof of absorption was afforded. 
 
 Such is the state in which this interesting subject is at present left. Thouglt, 
 
 X 
 
OF ABSORPTION, 
 
 162 
 
 Besides absorption from surfaces, there exists, as we have 
 already stated, another which takes place in the living solid, and 
 in the internal substance of the organs. It is by this kind of ab- 
 sorption that the nutritive decomposition is effected; by means 
 of it, the living matter is incessantly renovated. Its vitiated ac- 
 tion accounts for the spontaneous formation of ulcers, the disap- 
 pearing of the thymus, the atrophy of parts in which nutrition 
 is carried on, in a sluggish manner; the resolution of certain 
 tumours, and many other phenomena, are dependent on the 
 same cause. I do not think, however, that it is possible to admit 
 the explanation of the sensation of hunger, adopted by Profes- 
 sor Dumas, who believes that it depends on the action of the 
 absorbing orifices directed against the organized substance of 
 the stomach, in the absence of aliment on which to act. The 
 sensation of hunger is felt only in the stomach, although its 
 effects extend to all parts of the body; it begins in a circum- 
 scribed spot, its seat is limited, yet absorption takes place every 
 where, so that if the hypothesis in question had any foundation, 
 the sensation of hunger ought to be felt at the heel, as well as 
 at the pit of the stomach.* 
 
 perhaps, not absolutely deckled, enough surely has been done to demonstrate 
 that cuticular absorption rarely happens, and that whenever it does, it can not 
 be deemed the effort of a natural function. Covered, as is the whole surface of 
 the body by the impervious cuticle, it is manifest to us that absorption can only 
 take place in one of two ways, either by forcing the substance under the 
 scales of the epidermis, as in tlie instance of the application of frictions, or by- 
 long continued bathing, the cuticle becomes so changed in its organization, as t* 
 admit of transudation, or the insinuation of the fluid under its squamous struc- 
 ture, so as to come in contact with the mouths of tlie lymphatics situated 
 within. 
 
 At all events, whatever dlfierence of opinion may be entertained as to the 
 degree of conclusiveness of the experiments to which I have alluded, it can 
 hardly be thought necessary to resort to cuticular absorption, to explain the 
 facts enumerated by our author as proofs of the existence of the function. 
 These, and, perhaps, all other phenomena, hitherto referred to the agency of 
 absorption by the skin, may be more ration.ally accounted for on the principle 
 of pulmonary absorption, and the law of sympatliy. — E d. 
 
 * Both hunger and thirst seem to be sensations, excited by the stomach’s 
 sympathising with the general exhaustion of the system, and are the means 
 employed by- nature to admonish us of the necessity of repairing the wastes 
 which it sustains from abstinence. An office so important to our well being, and 
 even existence, is not left to reason, which might often err, but is put under 
 the care of an instinct, fir more certain in its operation. Besides these two sen-. 
 
OF ABSORPTION. 
 
 163 
 
 The radicles from which the lymphatics arise, have orifices 
 so very minute, that they are imperceptible to the naked eye; a 
 tolerably accurate notion may be formed of them, by comparing 
 them to the puncta lachrymalia, which are larger and more 
 easily discovered. Each orifice endowed with sensibility, and 
 with a peculiar power of contraction, dilates or contracts, ab- 
 sorbs or rejects, according as it is affected by the substances 
 which are applied to it. The variations of the absorbing power, 
 according to the age, the sex, the constitution, and different pe- 
 riods of the day, show that it cannot be compared, as several 
 physiologists have done, to that principle which makes fluids 
 ascend, contrary to the laws of gravitation, in capillary tubes. 
 If absorption were a process merely mechanical, it would in no 
 case be accelerated or retarded, and would proceed with a re- 
 gularity never observed in the vital functions. The mouth of 
 every lymphatic, when about to absorb, erects itself, draws 
 towards itself, and raises the surrounding membranous parts, 
 and thus forms a small tubercle similar to the puncta lachry- 
 malia. These little bulgings deceived Leiberkuhn, and led him 
 to think, that the absorbents of the intestines originated from 
 small ampullulse, or vesicular enlargements, which, as so many 
 exhausted receivers, pumped up the fluid extracted from the 
 food. This physiologist may, further, have been led into error, 
 by the nervous papillae of the inner membrane of the canal, swol- 
 len by the determination of blood attending irritation, the natu- 
 ral consequence of the friction of the alimentary substances. 
 The inhaling faculty belongs not only to the orifices at the ex- 
 tremity of each radicle, but likewise to the lateral pores, which 
 are infinitely numerous in the parietes of the vessels.* 
 
 sations the stomach has others equally specific, as satiety, longing, loathing, 
 sickness, &c. &c. — E d. 
 
 * As to the precise manner in which absorption is effected, physiologists are 
 not agreed. By some it is contended that it is entirely the result of capillari} 
 attraction. To the exercise of this species of affinity, three circumstances seem 
 only to be demanded: 
 
 1. The tube must not exceed a certain size. 
 
 2. It must be of an equal caliber throughout. 
 
 3. One of its extremities must be immersed in a fluid. 
 
 Notwithstanding what has been urged to the contrary, capillary attraction 
 
 unquestionably is influenced neither by the flexibility of the tube, nor its posi.. 
 lion. It is now perfectly well ascertained, that the operation goes on whether 
 
OP ABSORPTION, 
 
 164 
 
 XLIII. After arising on the surface, and in the interior of 
 the body, by radicles in close contact, the lymphatics creep and 
 coil themselves, describe numerous curves, unite, then divide, 
 and presently unite again, and from these numerous inoscula- 
 tions, there results a net-work, with close meshes, forming, 
 with that of the blood vessels, the texture of the cellular tissue 
 and of the membranes. 
 
 Each lamina of cellular tissue is, in the opinion of Mascagni, 
 nothing but a mesh-work of lymphatics; the texture of the mem- 
 branous and transparent tissues, as the pleura and the perito- 
 neum, resembles that of the laminae of the cellular tissue; in 
 fine, the same vessels form the basis of the mucous membranes 
 
 the tube be soft or hard, or whether it be placed vertically,- horizontally, or 
 obliquely. 
 
 These facts being admitted, and also, that the lymphatic vessels are within 
 the dimensions necessary to capillary attraction, which they undoubtedly are, 
 the hypothesis referring absorption to this principle does not, on first view, 
 strike us as altogether unreasonable. When examined, however, more clear- 
 ly, it will be found liable to all the embarrassments enumerated in the text, 
 and to others of not less weight. 
 
 Two additional objections at once occur to us: 
 
 1. Did the absorbents act mechanically, as is alleged, they would take up 
 indiscriminately all fluids presented to their mouths, instead of which, they 
 exercise a degree of selection amounting almost to fastidiousness. 
 
 2. The absorbents have not that mechanism which capillary attraction re- 
 quires. They frequently swell or bulge out in their course, and become of 
 irregular capacities. Even at their orifices they assume the figure of the fun- 
 nel, commencing with an exceedingly minute opening, which suddenly expands. 
 Aware of the unfavourableness of this structure to the progression of fluids, 
 it has been maintained by some other of the advocates of capillary attraction, 
 that the fluid is simply imbibed by the power of this principle, and afterwards 
 propelled by the united force of muscular pressure, and the action of the con- 
 tiguous arteries. 
 
 We do not think the hypothesis at all improved by this modification of it. 
 We believe, that in absorption there is no capillary influence, or, indeed, any 
 sort of extrinsic agency employed. It seems to us to be owing altogether to 
 the inherent contractile power of the vessel, and bears no very remote analogy 
 to the peristaltic actioh of the intestines. We will, however, in a few words, 
 explain our meaning more distinctly. 
 
 When chyle, or any appropriate fluid, is applied to the mouth of an absor- 
 bent, it is excited by the stimulus of the fluid to an erection of its orifice, in 
 consequence of which, the latter is rendered pervious. The fluid being now 
 introduced, the vessel contracts, and propeb its contents in succession along 
 'its course to the ultimate destination. — £ d. 
 
OF ABSORPTION. 
 
 165 
 
 which line the Internal parts of the alimentary canal, of the 
 trachea and urethra. The Italian anatomist succeeded in filling, 
 with quicksilver, all the tissues which he considered as lymphatic; 
 but Ruysch, in his admirable injections, reduced all the mem- 
 branes, and the laminae of the adipose tissue, into a net-work 
 purely arterial, of which the meshes were so very closely united, 
 as to leave spaces that could scarcely be perceived by the mi- 
 croscope; and from his preparations he inferred, that arterial 
 capillary vessels, singularly divided and convoluted, form the 
 basis of cellular and membranous tissues. To satisfy oneself 
 that neither the pleura nor the peritoneum are formed as Mas- 
 cagni or Ruysch imagined, one need only consider, that arterial 
 exhalation and lymphatic absorption take place from the whole 
 extent of the internal surfaces, and that these two functions 
 prove the existence of both arteries and absorbents, in those 
 membranes and in the cellular tissue. The prejudices of those 
 two anatomists, so celebrated, the one by his study of the absor- 
 bents, and the other by his beautiful injections of the most mi- 
 nute arteries, are to be attributed to the importance which we 
 are pleased to assign to the objects which particularly engage 
 our attention, and likewise to the distention of the minute ves- 
 sels by the injection; these being distended beyond their natu- 
 ral state, compress and conceal the neighbouring parts. 
 
 The lymphatics, after emerging from among the cellular sub- 
 stance, unite into trunks sufficiently large to be distinguished 
 from the laminae of that tissue. These trunks proceed towards 
 certain parts of the body, there they become united to other 
 trunks, follow a parallel course and frequently communicate 
 together. The lymphatics are not single in their course, as the 
 arteries and veins; they collect together, form fasciculi of diffe- 
 rent sizes, some of which are deep seated and accompany the 
 blood vessels, while others of them are more superficial, corres- 
 ponding to the subcutaneous veins of the limbs, and, like them, 
 lying between the skin and the aponeuroses, and in greatest 
 number, on the inner side of the limbs, in which they are best 
 protected against external injuries. The lymphatics of the pa- 
 rietes of the great cavities, those of the viscera which these 
 cavities contain, are likewise in two layers, the one superficial, 
 the other deep seated. 
 
OF ABSORPTION. 
 
 166 
 
 The absorbents differ, likewise, from the blood vessels, iu 
 their singularly tortuous course, their frequent communications, 
 and especially in their unequal size in different parts of their 
 extent. An absorbent of very small dimensions, frequently en- 
 larges, so as to equal in size the thoracic duct, then contracts, 
 and again bulges out, though in the length of the vessel in which 
 these differences of size may have been noticed, it may have re- 
 ceived no collateral branches. The lymphatics, when completely 
 filled with quicksilver, appear to cover the whole surface of our 
 organs: and the whole body seems enveloped in a net-work of 
 close and small meshes. The metastasis of humours, from one 
 part of the body to another at a distance, is easily understood 
 by any one who has seen those numerous inosculations render- 
 ed manifest bj' injection. Metastasis ceases to be an inexplica- 
 ble phenomenon; one has no difficulty in conceiving how, by 
 means of the lymphatics, all the parts of the body coQamunicate 
 freely; how, fluids absorbed by those vessels in one part, may be 
 conveyed into another, and pervade the whole body, without 
 following the circuitous route of the circulation, and that it is, 
 therefore, not altogether impossible, however improbable, that 
 fluids taken into the stomach, may be conveyed directly from 
 the stomach to the bladder, and that in the same manner, the 
 milk of the intestinal canal may find its way into the breasts; 
 and that pus may be removed from the place in which it is col- 
 lected, and be conveyed to the place to which irritation calls it 
 forth. All that Bordeu has said of the oscillations and currents 
 of humours, through the cellular texture, in his “ Recherches 
 sur le Tissu muqueux^' may be equally explained by the anasto- 
 mosis of the lymphatics. 
 
 A young man whom I had ordered to rub in mercury along 
 the inner part of his left leg and thigh, for the cure of a pretty 
 large bubo, was affected, on the third day, with salivation, 
 though he used only half a dram of ointment at each friction. 
 The salivary glands of the left side were alone swollen, the left 
 side of the tongue was covered with aphthae, and the right side 
 of the body remained unaffected by the mercurial action; a clear 
 proof, that the mercury had been carried to the mouth, along the 
 left side of the body, without entering into the course of the cir- 
 culation, and perhaps, without passing through any of the con- 
 
OP ABSORPTION. 
 
 167 
 
 globate glands; for, that of the left groin, which alone was 
 swollen, did not sensibly diminish in size. Salivation may, there- 
 fore take place in the cure of venereal disease, though none of 
 the mercury enter the circulation, which warrants the opinion, 
 that the action of syphilis, as well as of the remedies which are 
 administered for its removal, operates chiefly on the lymphatic 
 system. 
 
 XLIV. If the fluids absorbed by these vessels can, in conse- 
 quence of their numerous inosculations, pervade all parts of the 
 body, without mixing with the blood, not a drop can enter the 
 course of the circulation, without having previously passed 
 through the glandular bodies that lie in the course of the lym- 
 phatics; dispersed like those vessels in all parts of the body, 
 seldom insulated, but in clusters in the hollows of the ham, the 
 arm-pit, in the bends of the groin and elbow, along the iliac ves- 
 sels, the aorta and the blood vessels of the neck, around the 
 base of the jaw and of the occiput, behind the sternum, along the 
 internal mammary vessels, lastly, within the mesentery, in which 
 their number and size bear a proportion to the quantity of ab- 
 sorbents which pass through them. These reddish glands,* vary- 
 ing in size of an oval or globular form, have two extremities, 
 the one at which the lymphatics enter, they are then called 
 “ afferentia^^ and the other extremity turned towards the tho- 
 racic duct, which sends out vessels, fewer in number, but of a 
 larger size, and called “ efferenticH'' from their use. 
 
 The lymphatics, on reaching the glands, divide, unite again 
 and inosculate, they likewise bend back on themselves, and thus 
 form the tissue of the conglobate glands, which are merely clus- 
 ters of coiled vessels, united by cellular tissue, in which blood 
 vessels are distributed, so as to occasion their reddish colour. 
 The coats of the lymphatics are thinner in the glands than else- 
 where; and their dilatations, their divisions, and their anasto- 
 moses are likewise more frequent, while they are in the glandu- 
 
 * It is with a view of conforming to the language in common use, that I give 
 the name of gland to those coils of lymphatic vessels, which are totally diffe- 
 rent from the real conglomerate or secretory glands. It might be better, per- 
 haps, to call them ganglions, as has been done by my learned and respected col- 
 league Chaussier, though that name is objectionable, from its association in 
 the mind with the nervous ganglions, whose structure is not at all similar ta 
 that of the lymphatic ganglions. 
 
OP ABSORPTION. 
 
 168 
 
 lar tissue. All the lymphatic vessels, whose course lies in the 
 direction of a gland, do not enter its substance; several pass by 
 the gland and embrace it, forming around it a sort of plexus, of 
 which the ramifications are directed towards other glands, more 
 in the vicinity of the thoracic duct. The lymphatic glands 
 form so essential a part of the absorbent system, they produce 
 on the lymph such indispensable changes, that no lymphatic 
 vessel enters the thoracic duct, without having previously pass- 
 ed through these glands. It even frequendy happens, that the 
 same vessel passes through several glands, before opening into 
 that common centre of the lymphatic system. Thus, the vessels 
 which absorb the chyle of the intestinal tube, pass several times 
 through the glands of the mesentery. — The lymphatics of the 
 liver, situated very near to the receptaculum of Pecquet, have 
 been thought, by some anatomists, not to follow that general 
 rule; but there are uniformly found, in the course of these ves- 
 sels, glands which they enter. As, however, the glands are few 
 in number, the lymph conveyed from the liver is only once sub- 
 jected to the action of the glands; and this circumstance appears 
 to ine to explain, in a satisfactory manner, the transmission of 
 the colouring matter of the bile, which, in jaundice, manifesdy 
 discolours the blood, in which M. Deyeux found it by chemical 
 analysis. 
 
 XLV. The parietes of the lymphatic vessels are formed of 
 two coats, both very thin and transparent, yet very strong, since 
 they support the weight of a column of mercury, which would 
 rupture the coats of arteries of the same caliber. The internal 
 coat, which is the thinner of the two, forms vahuilar folds, ar- 
 ranged in pairs, like the valves of the veins, and like them pre- 
 venting a retrogade circulation. — Although these coats are very 
 strong, and likewise very elastic and contractile, as they may be 
 seen to contract, and to expel the lymph with great impetus, when 
 the abdomen of a living animal* is laid open, yet the course of 
 
 * In some cases, the activity of the absorbents appears increased, in a singu- 
 lar degree. Thus, jaundice has been known to be the immediate consequence 
 of a wound of the lii'er; and on other occasions, a metastasis of humours lias 
 taken place, witli the utmost rapidity. I suspect, that, in such cases, the sub- 
 stance that has been absorbed, circulates by means of the anastomoses, and per- 
 vades the lymphatics with which the whole body is covered, but without pass- 
 ing through the gl.ands, which would slacken its course, and, to a certain de- 
 gree, alter its nature. 
 
OF ABSORPTION. 
 
 169 
 
 the lymph is far from being as rapid as that of the blood; it even 
 frequently appears affected with irregular oscillations, such as 
 are to be met with in the circulation of the blood through the 
 capillary arteries. The numerous dilatations, curvatures and 
 anastomoses of the absorbents must, in a. considerable degree, 
 impede the rapid progress of the lymph, but the circulation 
 must be retarded chiefly in the glands, as there the vessels are 
 most convoluted, dilated, and form the greatest number of anas- 
 tomoses, and are most subdivided. Besides, the parietes of the 
 absorbents are thinnest in their passage through the glands, for 
 these may be ruptured by the weight of a column of mercury 
 which the vessels themselves are able to support. And the ac- 
 tion of these vessels, naturally weaker in that situation, is still 
 farther diminished by the close cellular adhesion which unites 
 together the vessels whose union forms the glandular bodies. 
 
 It was necessary that the course of the lymph should be slack- 
 ened in its passage through the glands, in order that it might un- 
 dergo all the changes which those organs are to produce upon it. 
 Although we do not know precisely what those changes are, 
 their object appears to consist in a more perfect union and com- 
 bination of its elements, and in bestowing on it a certain degree 
 of animalization, as is seen, by the greater tendency to coagula- 
 tion of the fluid taken from the vasa efferentia. Another object 
 of the passage of the lymph through the glands, appears to be 
 to deprive it of its heterogeneous particles, or at least to alter 
 their nature, so that they may not become injurious, when they 
 get into the mass of the fluids. The yellow colour of the glands 
 through which the absorbents of the liver pass, the dark colour 
 of the bronchial glands, the red colour of the mesentric glands, 
 in animals which have been fed on madder or beet-root, the 
 whiteness of the same glands, while the chyle is passing through 
 them, are circumstances which show, that the glands separate, or 
 tend to separate, the colouring matter of the lymph, and that if 
 they do not effectually prevent its transmission into the blood, it 
 is because certain colours, as indigo and madder, have too much 
 tenacity, while other substances, as the bile, do not pass through 
 a sufficient number of glands, to lose their colour entirely. The 
 blood vessels, which are very numerous in the tissue of the con- 
 globate glands, pour into the lymphatics a serous fluid which di- 
 
 Y 
 
OF ABSORPTION. 
 
 170 
 
 lutes the lymph, increases its quantity, and at the same time, 
 animalizes it. The number of the lymphatic glands is very great; 
 many are so small as to escape the eye, but become enlarged and 
 visible, in certain cases of disease. I have daily opportunities of 
 observing in scrophuloiis patients, swollen glands, in situations 
 in which anatomists have not pointed out any. The absorbent 
 glands are, at no time, so large or numerous as in infancy. They 
 very frequently disappear in old people, and it is difficult to say, 
 whether they have been totally destroyed, or whether they are 
 merely exceedingly reduced in bulk. 
 
 XLVI. The frequent congestions of the conglobate glands, 
 depend on the stagnation of the lymphatic fluid in their sub- 
 stance, and on the comparative weakness of the sides of the ves- 
 sels in these parts. The influence of debilitating causes on the 
 lymphatic system, acts most powerfully on the glands, which 
 are the weakest part of that system. In such cases, the vessels 
 which enter into the composition of the glands, act feebly, or 
 cease to act altogether; the fluids, of which there is a continual 
 accession, accumulate; the most liquid part alone penetrates 
 through the glandular organ, the grosser particles remain, the 
 humour thickens, hardens, and forms congestions of various 
 kinds. If there is a tendency to cancer, such tumours, at first 
 indolent, become painful, the indurated matter being, in a man- 
 ner, out of the influence of the vital power, since its vessels are 
 in a state of complete atony, undergoes a sort of putrid fermen- 
 tation, the consequence of which is a destruction and erosion of 
 the cellular tissue, attended by inflammation of the skin and 
 neighbouring parts. The tumour becomes an abscess, and dis- 
 charges matter rendered liquid by the process of fermentation, 
 and so acrid and irritating, that it extends the affection towards 
 all the parts with which it comes in contact. 
 
 The notions entertained hitherto on cancer, are, at once, defi- 
 cient in precision and accuracy, and it is to their fallacy that we 
 are to attribute the number of contradictory opinions on the sub- 
 ject of its proper treatment. Too precise a distinction cannot be 
 laid down, between the cancerous or phagedenic ulcer, whose 
 seat is always in the skin, or in the mucous membranes (which 
 being mere prolongations of the skin, retain much of its struc- 
 ture), and those cancers which affect the other parts of the ani- 
 
OP ABSORPTION. 
 
 171 
 
 mal economy, especially the lymphatic glands, -Ae testicles and 
 the breasts. In the cancerous ulcers peculiarly^equent in the 
 face, the lips, the tongue; in the inner coat of the stomach, of the 
 rectum, and of the uterus, the parts, affected with inflammation 
 of a malignant kind, are destroyed, without any means of check- 
 ing the progress of that destructive action, the cause of which is 
 easily conceived; while in true cancer, the glandular tumefaction 
 always precedes the cancerous diathesis. As long as the affec- 
 tion consists merely in the obstruction of the vessels by indura- 
 ted lymph, the tumour is indolent, and is yet only a schirrus; but 
 soon all trace of organization is lost in the tumefied part, the 
 ruptured vessels are lost in the mass of different substances; the 
 process of fermentation which takes place, converts every part 
 into a grayish pulpy substance, in which the most expert eye can 
 discover no organization, and no distinction of parts. When- 
 ever this cancerous destruction of parts occurs, whether the 
 whole organ is affected, or whether the disease extends only to 
 a few points, extirpation is the only remedy to be employed; it 
 is absolutely necessary, that a surgical operation should rid the 
 constitution of a part, in which organization and life no longer 
 exist. 
 
 The lymphatic glands which swell in the vicinity of cancerous 
 tumours, have already received, by means of the absorbents, the 
 destructive germ, and must be removed with the rest of the 
 diseased part, that the operation may be attended with the 
 greater prospect of success. It is very true, that open cancers 
 of the breast may, for a long time, discharge putrid matter, 
 without inducing a cancerous affection of the glands of the ax- 
 illa. But may not the discharge, in this case, act on the princi- 
 ple of revulsion; and besides, what shall we oppose to experi- 
 ence, which shews that these glands, if not removed along with 
 the cancerous breast, soon become affected with cancer. If the 
 nature of this work did not circumscribe me within certain 
 limits, I should point out several other particulars relative to 
 the history of cancer; and among other cases, in my own prac- 
 tice, I should relate that of a woman, in whom I removed a 
 cancerous tumour situated on the left side of the chest: this case 
 is remarkable from the number of operations which her disease 
 
OF ABSORPTIOK. 
 
 172 
 
 required, and for which M. Pelletan removed, six years ago, 
 the left breast, and, three years ago, a gland under the axilla of 
 the same side. 
 
 The difference in the termination of glandular swellings and 
 those arising from cancer, scrophula or syphilis, makes it proba- 
 ble, that there exist ferments, or specific poisons, which dispose 
 the accumulated matter to undergo peculiar changes. 
 
 The venereal virus, absorbed by the lymphatics of the organs 
 of generation, remains, for some time, in the glands of the groin, 
 before it extends beyond, as is proved by the cure of the vene- 
 real disease, by extirpating the diseased glands. In short, the 
 impediment which the lymph meets with, in passing through 
 the glands, shows why these parts are so frequently the seat of 
 critical abscesses, by which we judge of the nature of several 
 fevers of a malignant kind. In the plague of eastern countries, 
 the virus that occasions this dreadful malady is disseminated 
 throughout the body, collects in the glands, is transmitted 
 through them with difficulty, brings on an irritation and gangre- 
 nous inflammation, terminating in pestilential buboes. 
 
 XLVII. The thoracic duct may be considered as the centre 
 in which the whole lymphatic system terminates; it arises at the 
 upper part of the abdomen, from the union of the chylous ves- 
 sels with the lymphatics coming from the inferior extremities. 
 At the part where all these vessels meet, there is a dilatation, a 
 sort of ampullula, called lumbar cistern, receptaculum chyli or 
 of Pecquet, which, in truth, is not always found, and the size of 
 which is very variable. The thoracic duct enters the chest 
 through the opening in the diaphragm which transmits the 
 aorta; it then ascends along the spine, on the right side of the 
 aorta, within the posterior mediastinum. At the upper part of 
 the chest, opposite to the seventh cervical vertebra, it inclines 
 from the right to the left side, passes behind the oesophagus and 
 the trachea, and opens into the subclavian vein of the left side, 
 at the back part of the insertion of the internal jugular into that 
 vein. While the thoracic duct is ascending along the spine, it 
 receives the lymphatics of the parietes of the chest; those of the 
 lungs enter it as it passes behind the root of these organs. In its 
 course from the right towards the left side, it receives the ab- 
 sorbents of the right upper extremity, and those of the right 
 side of the head and neck. Lastly, it unites with those vessels 
 
OF ABSORPTION. 
 
 173 
 
 which are coining from the left side of the head and neck, as 
 well as from the left upper extremity, just before opening into 
 the subclavian vein. The thoracic duct sometimes has its inser- 
 tion in the jugular vein of the same side, and not unfrequently 
 the lymphatics of the right side of the chest, neck, and head, 
 and of the right upper extremity, unite to form a second duct, 
 which opens separately into the right subclavian vein.=^ What- 
 ever be the vein into which the duct opens, its structure is the 
 same as that of the lymphatics, and its inner part is furnished 
 with valvular folds. Its increase of size is not progressive, as it 
 approaches towards its termination; on the contrary, there are 
 seen, here and there, dilatations of different sizes, separated by 
 proportionate contractions. Sometimes it divides into several 
 vessels which inosculate and form lymphatic plexuses. The 
 opening at which the thoracic duct enters the subclavian vein, 
 is furnished with a valve, better calculated to prevent the flow 
 of blood into the lymphatic system, than to moderate the too 
 rapid flow of the lymph into the torrent of circulation. Com- 
 pression of the thoracic duct, in aneurism of the heart and aorta, 
 gives rise to several kinds of dropsy, a disease always depend- 
 ing on the loss of equilibrium, between the processes of inhala- 
 tion and exhalation, either from increased action of the exha- 
 lants, or from the absorbents refusing to take up the lymph, in 
 consequence of obstruction in the glands, or of compression of 
 the duct. 
 
 XL VIII. The nature of the lymph is far from being as well 
 understood, as that of the vessels along which it circulates. Hal- 
 ler considers it as very analogous to the serum of the blood, and 
 says that this substance, to which he frequently gives the name 
 of lymph, is like the fluid contained in the absorbents, slightly 
 viscous and saltish; that heat, alcohol, and the acids coagulate 
 it; in short, that it possesses all the qualities of the albuminous 
 fluids. The serum of the blood exhaled, throughout the extent 
 
 * In some rare cases, lymphatic vessels, in other parts of the body, are seen 
 to open into neighbouring veins. This enables one to account for the presence 
 of the chyle which is said to have been found in tlie meseraic veins, into which 
 it had been poured by some lacteal. Mascagni was awai’e of this anatomical 
 fact. The lymphatic system is, however, the most subject to deviations of any 
 in the animal economy. 
 
OF ABSORPTION. 
 
 174 
 
 of the internal surfaces, and even within the substance of our 
 organs, by the capillary arteries, is absorbed by the lymphatics, 
 and is one of the principal sources of the lymph, which resem- 
 bles it much. It may be conceived, however, that the nature of 
 the lymph must be much more compound than that of the serum 
 of the blood, since the lymphatics which absorb, almost indiscri- 
 minately, every kind of substance, take up what comes off from 
 our organs, and the recrementitious parts of our fluids, and 
 these are sometimes recognisable in the absorbents, when mark- 
 ed by striking qualities, as fat by its not mixing with aqueous 
 fluids, and bile by its deep yellow colour. 
 
 The chyle, which is necessarily affected by the various kinds 
 of food which we use, has different appearances in the same per- 
 sons, varying according to the quality of the different substances 
 on which we feed; indigo gives it a blue colour; it is reddened 
 by madder and beet-root, and is changed to green, by the colour- 
 ing matter of several vegetables, &c. In a great number of ex- 
 periments performed on living animals, it has always appeared 
 to me, such as it is described by authors, white, with a slight 
 vicidity, and very like milk containing a very small quantity of 
 flour. It is easy to collect a certain quantity of ch\ le, by tying 
 the thoracic duct of a large dog, of a sheep, or even of a horse, 
 as was done several times at the veterinar)' school at Alfort. 
 
 This fluid, when exposed to the air, on cooling, separates 
 into two parts, the one forming a kind of gelatinous coagulum, 
 very thin and not unlike the buffy coat of inflammatory blood; 
 the other, in greater quantity and liquid, rising above the coagu- 
 lum, on its being detached from the sides of the cup to which 
 it adheres. The coagulated mass is semi transparent, of a light 
 pink colour, does not resemble the curd of milk, so that all that 
 has been said by a few modern physiologists, on the exact re- 
 semblance which they have pretended to discover between milk 
 and chyle, is totally void of foundation. 
 
 The lymph, which constantly unites with the chyle before 
 the latter enters the sanguiferous system, on being received into 
 a vessel by Mascagni, coagulated in the space of seven or ten 
 minutes, turned sour, and soon separated into two parts; the one 
 more abundant, serous, in the midst of which there floated a 
 fibrous coagulum, which by contracting, formed into a small 
 
OF ABSORPTION. 
 
 175 
 
 cake on the surface of the fluid. Hence he concludes, contrary 
 to the opinion uf Hewson, that lymph consists, for the greatest 
 part, of serum, and that fibrine constitutes its least part. 
 
 XLIX. The practice of surgery in a great hospital, has 
 afforded me frequent opportunities of examining the lymph 
 which is discharged, in abundance, from ulcerated scrophulous 
 tumours, in the groin, in the axilla, and in various other parts 
 of the body. I have always met with a liquid nearly transparent, 
 slightly saline, coagulable by heat, alcohol and the acids. Small 
 fibrous flocculi form, even on the surface of the cloths which 
 are wetted with it, and show the existence of two parts, the one 
 a gelatino albuminous fluid holding in solution several salts, the 
 other, in smaller quantity, is a fibrous substance which con- 
 cretes spontaneously. The lymph, in man and the warm-blooded 
 animals, appears to me, in every respect, similar to the fluid 
 which is contained in the vessels of white-blooded animals. 
 
 CHAPTER III. 
 
 ON THE CIRCULATION. 
 
 l.The term circulation is applied to that motion by which 
 the blood, setting out from the heart, is incessantly carried to all 
 parts of the body by means of the arteries, and returns, by the 
 veins, to the centre whence it began its circuit. 
 
 The uses of this circulatory motion are to expose the blood 
 changed by mixing with the lymph and the chyle, to the air in 
 the lungs (respiration)-, to convey it to several viscera in which 
 it passes through different steps of purification (secretions); and 
 to send it into the organs whose growth is to be promoted, or 
 whose losses are to be repaired, by the nutritive and animalized 
 part of the blood brought into a state of perfection by these 
 successive processes (nutrition). 
 
 The circulatory organs are less useful in elaborating, than in 
 conveying the fluids. To form a just conception of their uses, 
 one may compare them to those workmen in a large manufac- 
 tory in which various kinds of goods are made, who are employ- 
 ed in carrying the materials to those who are to work them ; and as 
 
ON THE CIRCULATION. 
 
 i / 6 
 
 among the latter, some finish the work, while others prepare 
 the materials, so the lungs and the secretory glands are continu- 
 ally occupied in separating from the blood whatever is too 
 heterogeneous to our nature to become assimilated to our or- 
 gans, or to afford them nourishment. 
 
 To understand, thoroughly, the mechanism of this function, 
 it is necessary to study separately the action of the heart, that 
 of the arteries which arise from it, and lastly that of the veins 
 which enter it. The union of these three classes of organs 
 forms the circle of the circulation. 
 
 LI. Of the action of the heart. In man and in all warm- 
 blooded animals, the heart is a hollow muscle, the inner part of 
 which is divided into four large cavities which communicate 
 with one another; from these, vessels arise which convey the 
 blood to all parts of the body, and the vessels which bring it 
 back from all those parts likewise terminate in these cavities. 
 
 The heart is placed in the chest, between the lungs, above 
 the diaphragm, whose motions it follows; it is surrounded by the 
 pericardium, a dense and fibrous membrane admitting of very 
 slight extension, closely united to the substance of the dia- 
 phragm, covering the heart and great vessels, without contain- 
 ing them in its cavity, furnishing an external covering to the 
 heart and bedewing its surface with a serous fluid, which never 
 accumulating, except in disease, facilitates its motion, and pre- 
 vents its adhering to the neighbouring parts. The principal use 
 of the pericardium, is to fix the heart in its place, to prevent its 
 being displaced into other parts of the chest, which could not 
 happen, without occasioning a fatal disorder in the circulation. 
 If, after having laid open the chest of a living animal, by raising 
 the sternum, an incision is made into the pericardium, the heart 
 protrudes through the opening, and moves to the right and left 
 by bending itself on the origin of the large vessels; the course of 
 the blood is then intercepted, and the animal threatened with 
 immediate suffocation. 
 
 In man, the heart is placed nearly towards the union of the 
 upper third of the body, widi the lower two thirds; it is, there- 
 fore, nearer to the upper parts; it holds them under a more im- 
 mediate control, and as that organ keeps up the action of all 
 the rest, by the blood which it sends into them, the parts above 
 
©N THE CIRCULATIO!Sr. 
 
 177 
 
 the diaphragm have much more vitality than the parts beneath. 
 The skin of the upper part of the body, and especially of the 
 face, has more colour and is warmer than that of the lower parts; 
 the phenomena of disease come on more rapidly in the upper 
 parts; they are, however, less liable to put on a chronic character. 
 
 The bulk of the heart, compared to that of other parts, is 
 larger in the fcetus than in the child that has breathed, in short 
 men, than in those of high stature. The heart is likewise larger, 
 stronger, and more powerful in courageous animals than in 
 weak and timid creatures. 
 
 This is the first instance of a moral quality depending on a 
 physical disposition of parts; it is one of the most striking proofs 
 of the influence of the moral character of man, on his physical 
 nature. Courage arises out of the consciousness of strength, and 
 the latter is in proportion to the activity with which the heart 
 propels the blood towards all the organs. The inward sensation 
 occasioned by the afflux of the blood, is the more lively, and the 
 better felt, when the heart is powerful. It is on that account that 
 some passions, for example, anger, by increasing the action of 
 the heart increase a hundred fold both the strength and courage, 
 while fear produces an opposite effect. Every being that is feeble, 
 is timorous, shuns danger, because an inward feeling warns him 
 that he does not possess sufficient strength to resist it. It may 
 perhaps be objected, that some animals, as the turkey cock and 
 the ostrich, possess less courage than the least bird of prey; that 
 the ox has less than the lion and other carnivorous animals. 
 What has been said does not apply to the absolute, but to the rec 
 lative size of the heart. Now, though the heart of a hawk be ab- 
 solutely smaller than that of a turkey cock, it is nevertheless 
 larger, in proportion to the other parts of the animal. Besides, 
 the bird of prey, like the other carnivorous animals, in part 
 owes his courage to the strength of his weapons of offence. 
 
 Another objection, more specious, but not better founded, is 
 drawn from the courage manifested, on certain occasions, by 
 the most timid animals; for example, by the hen in protecting 
 her young; from the courage with which other animals pressed 
 by hunger or lust, surmount all obstacles; but particularly from 
 the heroic valour of men of the most feeble bodies. All these 
 fects, however, are only proofs of the influence of the mind on 
 
 Z 
 
ON THE CIRCULATION. 
 
 178 
 
 the body. In civilized man, the prejudices of honour, interested 
 considerations, and a thousand other circumstances, degrade 
 the natural inclinations of man, so as to make a coward of one 
 whose strength is such as tvould induce him to brave all kinds 
 of dangers; while on the other hand, men whose organization 
 should render them most timid, are inspired to perform the 
 most daring actions. But all these passions, all these moral af- 
 fections operate, only by -increasing the action of the heart, by 
 increasing the frequency and the force of its pulsations, so that 
 it excites the brain or the muscular system by a more abundant 
 supply of blood. 
 
 The heart is not quite ovoid in man as it is in several animals, 
 nor is it parallel to the vertebral column, but it lies obliquely, 
 and is flattened towards the side next the diaphragm on which 
 it rests. 
 
 Of the four cavities which form the heart, two are in a mea- 
 sure accessory, viz. the auricles; they are small musculo-mem- 
 branous bags opposed to each other, receiving the blood of all 
 the veins, and pouring that fluid into the ventricles, at the base of 
 which the auricles are, as it were, applied. The ventricles are two 
 muscular bags separated by a partition of the same nature, and 
 belonging equally to both: they form the greatest part of the 
 heart and give origin to the arteries. 
 
 The auricle and ventricle on the right side, are larger than 
 those on the left. But that difference of size depends as much 
 on the manner in which the blood circulates, at the approach of 
 death, as on the original conformation of the heart. On the 
 point of death, the lungs expand with difficulty, and the blood 
 sent into them, by the contractions of the right ventricle, being 
 no longer able to circulate through them, collects in that cavit)’, 
 flows back into the right auricle, in which the veins continue to 
 deposit blood, stretches their parietes, and increases considera- 
 bly the dimensions of those cavities. The capacity of the right 
 cavities is, however, originally greater than that of the left, and is 
 proportioned to that of the venous system which opens into it. The 
 right cavities of the heart, which might be called its venous cavi- 
 ties, have likewise thinner parietes than the left or arterial, and, 
 in this respect, the same difference is observed, as in the parietes 
 of the arteries and veins. The right ventricle having to send the 
 
ON THE CIRCULATION, 
 
 179 
 
 blood destined to the lungS, to a very short distance, and through 
 a tissue easily penetrated, requires but a moderate impelling 
 force. 
 
 As will be shewn, in speaking of respiration, a function of 
 which the physiological history is not easily separated from that 
 of the circulation, the heart may further be considered, as form- 
 ed of two parts in contact, the one right or venous, the other 
 left or arterial. Notwithstanding the juxta position of these two 
 parts of the same organ, they are perfectly distinct, and the 
 blood in each cavity is very different from that in the other. 
 The blood, in the adult, can never pass immediately from the one 
 to the other; the right side of the heart receives the blood of the 
 whole body and transmits it to the lungs; the left side of the 
 heart, receives the blood of the lungs, and distributes it over the 
 whole body, so that, in a physiological point of view, the lungs 
 form a part of the circle of the circulation, and serve as an in- 
 dispensable medium between the two divisions of the heart, and 
 as will be seen hereafter, their part of the circle is by no means 
 the least important. 
 
 If there existed, between the ventricles, a direct communica- 
 tion, the venous blood would mix with the arterial, and the union 
 of these two fluids would mutually impair the qualities of each. 
 Recent observations have furnished an opportunity of judging 
 of the effects of such a communication between the ventricles, 
 which had been imagined by the ancients, but of which no case 
 had yet been met with. A man forty-one years of age, came to 
 the Hopital de la Charite, to undergo the operation of litho- 
 tomy. He was remarkable for the lividity of his complexion, the 
 turgescence of the vessels of the conjunctiva, and the thickness 
 of his lips, which, like the rest of his face, were of a dark colour; 
 his respiration was laborious, his pulse irregular, he could not 
 utter two words in succession, without taking breath; was obliged 
 to sleep in a sitting posture, and was particularly remarkable for 
 his indolence. This indolence, joined to great natur I simpli- 
 city, was such that he had never been able to maintain himself 
 without the assistance of his wife. A very small quantity of 
 blood was taken from his arm, in consequence of which his 
 pains were diminished, but his difficulty of breathing increased, 
 was followed by syncope, and he died from suffocation. On 
 
ON THE CIRCULATION. 
 
 180 
 
 opening his body, his heart was found filled with blood, and es- 
 pecially the right auricle, which was considerably distended; the 
 pulmonary artery was aneurismal, and uniformly distended from 
 the right ventricle to its division; none of its coats had yet 
 given way. The two ventricles of the heart were of nearly the 
 same capacity, and the relative thickness of their parietes did not 
 vary so much as in health. The partition between them contain- 
 ed an opening of communication of an oblong shape, about half 
 an inch in extent, and directed obliquely from below upwards, 
 from before backwards, and from left to right; so that not only 
 the direction of the opening, but likewise a kind of valve formed 
 in the right ventricle, by a fleshy column, so placed as to prevent 
 the return of the blood into the left ventricle, clearly showed, 
 that the blood flowed from the left into the right ventricle, and 
 thence into the pulmonary artery. The ductus arteriosus, an 
 inch in length, and large enough to admit a goose quill, allowed, 
 as in the foetus, a free passage to the blood from the pulmonary 
 artery into the aorta. The foramen ovale was closed. 
 
 This singular conformation explains, in the most satisfactory 
 manner, the phenomena observed during the life of the patient, 
 and the organic affection of the pulmonary artery. There was 
 necessarily, in this vessel, a mixture of venous and arterial 
 blood, and this blood was sent into it in part by the action of 
 the left ventricle, with an increased impetus, which accounts for 
 the aneurism. The blood which reached the lungs was already 
 vivified, and required less action from that organ to complete 
 its oxydation; on the other hand, the right auricle emptied 
 itself, with difficulty, into the right ventricle, in part filled with 
 the blood which the left ventricle sent into it with greater force; 
 hence the extreme difficulty in the venous circulation, the livi- 
 dity of the complexion, the colour and the puffiness of the face, 
 the habitual and general torpor. This state of languor and inac- 
 tivity might, likewise, depend on the flow of the venous blood 
 into the aorta, along the ductus arteriosus. It is worthy of ob- 
 servation, however, that this impure blood was not transmitted 
 to the brain, whose vital excitement it would not have been able 
 to maintain. The lower extremities bore no proportion to the 
 upper, and this inequality analogous to what is observed in the 
 foetus, depended on a similar cause. This morbid preparauon 
 
ON THE CIRCULATION, 
 
 181 
 
 was deposited by M. Deschamps, in the museum of the Ecole 
 de Medccine pf Paris, and was, by their desire, modelled in 
 wax. M. Beauchene, junior, presented the same museum with 
 a similar preparation, which he procured from a subject in the 
 dissecting room. 
 
 Several anatomists have paid attention to the structure of the 
 heart; much has been said on the subject of the peculiar arrange- 
 ment of the muscular fibres which form its parietes; yet the only 
 result that can be obtained from all these researches is, that it is 
 absolutely impossible to unravel the intricacy of these fibres. 
 Fibres of the ordinary structure, and crossing each other in va- 
 rious directions, form the two auricles; other and more nu- 
 merous fibres form the parietes of the ventricles, reach from the 
 apex to the base, extend into the septum which divides them, 
 pass from the one to the other and are lost into each other, in se- 
 veral points. They are exceedingly red, short, close, and united 
 by a cellular tissue, in which fat scarce!}' ever accumulates. 
 
 These fibres, forcibly pressed against each other, form a tis- 
 sue similar to the fleshy part of the tongue, endowed with but 
 little sensibility, but contractile in the highest degree. Vessels 
 and nerves, in considerable number, if compared to the bulk of 
 the heart, pervade this muscular tissue, whose contraction, what- 
 ever in other respects may be the direction of its fibres, tends to 
 draw towards the centre of the cavities, every point of their pa- 
 rietes. Lastly, a very fine membrane lines the inner part of these 
 cavities, facilitates the flow of the blood, and prevents the infil- 
 tration of that fluid. 
 
 LII. If we suppose, for a moment, that all the cavities of the 
 heart are perfectly emptied of blood, and that they fill in succes- 
 sion, the following may be considered as the mechanism of the 
 circulation through the heart. The blood brought back from 
 every part of the body, and deposited into the right auricle, by 
 the two venae cavae, and by the coronary vein, separates its pa- 
 rietes and dilates it in every direction. This irritation attending 
 the presence of the blood, stimulates the auricle to contraction; 
 this fluid, which is incompressible, flows back, in part, into the 
 veins, but it chiefly passes into the pulmonary ventricle, through 
 a large aperture, by means of which it communicates with the 
 right auricle. The auricle after freeing itself of the blood with 
 
182 circulatiok. 
 
 which it is filled, relaxes and again dilates by the accession of a 
 new supply of this fluid, continually brought by the veins which 
 open into it. 
 
 However, the right ventricle, filled with the blood which it has 
 received from the auricle, contracts in its turn on the fluid 
 whose presence excites its parietes, and tends, in part, to return 
 it into the right auricle, and to send it along the pulmonary ar- 
 tery. Regurgitation from the ventricle into the auricle, is pre- 
 vented by the tricuspid valve, a membranous ring surrounding 
 the edge of the opening of communication, and the free edge of 
 which is divided into three divisions, to which are attached 
 small tendons terminating into the columnae carneae of the heart. 
 These valves laid against the parietes of the ventricle, the in- 
 stant the blood passes into its cavity, recede from them when it 
 contracts, and rise towards the auricular opening. They cannot 
 be forced into the auricle, as their free and loose edge is kept in 
 its situation by the columnae carneae, which are like so many 
 little muscles whose tendons inserted into the loose edges of the 
 valves, bind them down, when the stream of blood tends to 
 force those membranous folds towards the auricles. The three 
 divisions, however, of the tricuspid valve, by rising towards the 
 auricular aperture, return into the auricle all the blood contain- 
 ed in the inverted cone which they form, immediately before 
 rising. Besides, these three portions of the tricuspid valve do 
 not close completely the aperture, around which they are placed; 
 they are perforated by a number of small holes: a part of the blood, 
 therefore, returns into the auricle, but the greatest portion is sent 
 into the pulmonary artery. The action of this vessel begins, when 
 the parietes of the ventricle are in a state of relaxation, and the 
 blood would be forced back into the ventricle, if the sygmoid 
 valves, by rising suddenly, did not prevent it. Supported on a 
 kind of floor formed by three valves which lie across the caliber 
 of the vessel, the blood pervades the tissue of the lungs, and 
 flows along the divisions of the pulmonary vessels; from the ar- 
 teries it passes into the veins, and these, four in number, deposit 
 it into the left auricle. This auricle, stimulated by the presence 
 of the blood, contracts in the same manner as the nght, part of 
 the blood flows back into the lungs, but the greatest part enters 
 the left ventricle, which sends it along the aorta, to every part of 
 
ON THE CIRCULATION. 
 
 18 S 
 
 the body, whence it returns to the heart by the veins. The re- 
 turn of the blood into the left auricle is prevented by the mitral 
 valve, which is similar to the tricuspid^ except that its loose edge 
 is divided only into two divisions. As soon as the blood has 
 reached the aorta, this vessel contracts, its sygmoid valves fall, 
 and the blood is sent to every part of the body which is supplied 
 by some of the innumerable branches of that great artery. 
 
 In a natural state, the circulation is not carried as has been 
 just stated; and we have supposed this successive action of the 
 four cavities of the heart, only to render more intelligible the 
 mechanism of the circulation in that organ. If we lay bare the 
 heart in a living animal, we observe, that the two auricles con- 
 tract at the same time, that the contraction of the ventricles is 
 likewise simultaneous, so that while the auricles are contracting, 
 to expel the blood which fills them, the ventricles are dilating to 
 receive it. This successive contraction of the auricles and ven- 
 tricles is readily explained, by the alternate application of the 
 stimulus which determines the action of these cavities. The 
 blood which the veins bring into the auricles, does not excite 
 their contraction, till a sufficient quantity has been collected. 
 While this accumulation is taking place, they yield, and the re- 
 sistance which is felt on touching them, during their diastole, de- 
 pends, almost entirely, on the presence of the blood which sepa- 
 rates and supports their parietes. The same applies to the ven- 
 tricles; they cannot contract, until a sufficient quantity of blood 
 is collected within them; that there remains some blood in these 
 cavities, for they are never completely emptied, is no objection 
 to the theory, since this small quantity is not sufficient to bring 
 on contraction of the heart, and is not worth taking into account. 
 
 If I am asked, why the four cavities of the heart do not all 
 contract at once, I answer, that it is easier to assign the final, than 
 the proximate cause. If the contraction of these cavities had been 
 simultaneous, instead of being successive, it is evident, that the 
 auricles could not have emptied themselves into the ventricles. 
 The alternate action is moreover absolutely necessary, as the 
 heart any more than the other organs, is unable to keep up a per- 
 petual action; the principle of its motion, which is soon ex- 
 hausted, being incapable of restoring itself, except during rest. 
 But, as was observed at the beginning of this work, in speaking 
 
ON THE CIRCULATION. 
 
 184 
 
 of the vital power and functions, the alternations of action and 
 repose in organs which, like the heart, perform functions essen* 
 tial to life, must be extremely short in their duration and at very 
 close intervals. 
 
 The cavities of the heart, however, are not entirely passive 
 during dilatation, and the action of that organ does not wholly 
 depend on the excitement of the blood on its parietes, since the 
 heart after it has been torn from the body of a living animal, pal- 
 pitates, its cavities contract and dilate, though quite emptied of 
 blood, and appear agitated by alternate motions, which become 
 fainter as the part gets cold.* If you attempt to check the dia- 
 stole of the heart, this organ resists the hand which compresses 
 it, and its cavities appear endowed with a power which Galen 
 termed pulsive; in virtue of which they dilate to receive the 
 blood, and not because they receive it. In that respect, the 
 heart differs essentially from the arteries, whose dilatation is oc- 
 casioned by the presence of the blood, whatever some physiolo- 
 gists may have said to the contrary. I have repeated, but unsuc- 
 cessfully, the famous experiment by which it is attempted to be 
 proved, that these vessels have the power of moving indepen- 
 dently of the presence of the blood. An artery tied and emptied 
 of blood, contracts between the two ligatures and is no longer 
 seen to move in alternate contractions. 
 
 LIII. The heart manifestly shortens itself, and the base ap- 
 proaches towards the apex, during the systole or contraction of 
 the ventricles. If it became elongated, as some anatomists have 
 thought, the tricuspid and mitral valves would be incapable of 
 fulfilling the functions to which they are destined, since the co- 
 lumnae carnese, whose tendons are inserted in the edges of these 
 valves, would keep them applied to the parietes of the ventri- 
 cles. The pulsations which are felt, in the interval between the 
 cartilages of the fifth and sixth true ribs, are occasioned by the 
 apex of the heart which strikes against the parietes of the chest. 
 In the explanation of this phenomenon, it is not necessary to ad- 
 mit the elongation of the heart during its systole; it is sufficient 
 to consider, that the base of the heart, in which the auricles are 
 situated, rests against the vertebral column, and that these two 
 
 • Both Haller and Senac found that, by injecting’ warm water into the heart, 
 it could be made to contract for some time after the death of the animal. Ed. 
 
ON THE CIRCULATION. 
 
 185 
 
 cavities, by dilating at the same time, and by their inability to 
 move the vertebrae, before which they are situated, displace the 
 heart, and thrust it downwards and forwards. This motion de- 
 pends likewise on the effort which the blood sent into the aorta 
 makes, to bring to a straight line the curvature of that artery, 
 which re-acts and carries downwards and forwards the whole 
 mass of the heart, as it were, suspended to it. 
 
 The quantity of blood which each contraction of the ventricles 
 sends into the aorta and pulmonary artery, most probably, does 
 not exceed two ounces in each of these vessels. The force with 
 which the heart acts on the blood which it sends into them, is but 
 imperfectly known, however numerous the caculations by which 
 it has been endeavoured to solve this physiological problem. la 
 fact, from Keil, who estimates at a few ounces only, the force of 
 the heart, to Borelli, who makes it amount to one hundred and 
 eighty thousand pounds, we have the calculations of Michelot, 
 Jurine, Robinson, Morgan, Hales, Sauvages, Cheselden, &c.; 
 but as Vicq-d’Azir observes, not one of these calculations is 
 without some error, either anatomical or arithmetical: hence we 
 may conclude with Haller, that the force of the heart is great, 
 but that it is perhaps impossible to estimate it with mathemati- 
 cal precision. If we open the chest of a living animal, and make 
 a puncture in his heart, and introduce a finger into the wound, 
 pretty considerable pressure is felt during the contraction of the 
 ventricles.* 
 
 * The difficulty of determining the exact degree of power exerted by the 
 heart is strikingly illustrated by the total disagreement in the estimates of dif- 
 ferent writers. Before we engage in any calculations respecting the matter, 
 the following data should be clearly established. 
 
 1. The quantity of blood expelled from each ventricle at every con- 
 traction. 
 
 2. The degree of velocity with which it is expelled. 
 
 3. The amount of resistance which each ventficle has to overcome before it 
 can propel the blood into its corresponding arteries. 
 
 4. The effects of the action of the heart on the blood. 
 
 But these are points which seem likely never to be ascertained with any sort 
 of precision, and of course our computations must continue as heretofore, 
 vague and conjectural. All we know with certainty on the subject is, that the 
 heart is a muscle of great strength, as is evinced by the phenomena of the cir- 
 
 2 A 
 
ON THE CinCULATlON. 
 
 186 
 
 LIV. Of the action of the arteries. There is no part of the 
 body to which the heart does not send blood by the arteries, for 
 it is impossible to make a puncture, with the finest needle, into 
 any of our organs, without wounding several of these vessels 
 and causing an effusion of blood. The aortic arterial systena 
 may be compared to a tree, whose trunk, represented by the 
 aorta, having its root in the left ventricle of the heart, extends 
 afar its branches, and throws out, on every side, its numerous ra- 
 mifications. The size of the arteries decreases, the farther they 
 are from the trunk by which they are given off. Their form, how- 
 ever, is not that of a cone, they are rather cylinders arising 
 from one another, and decreasing successively in size. As the 
 branches given off by a trunk, taken collectively, have a greater 
 diameter than that of the trunk itself, the capacity of the arterial 
 system increases with the distance from the heart; hence it fol- 
 lows, that as the blood is continually flowing from a straiter to 
 
 culation, and further, by the fact that, if the heart of a living animal be grasped, 
 no effort of the hand will repress its action. 
 
 An inquiry far more interesting here presents itself Why, as has been fre- 
 quently asked, does not the heart become exhausted, like other muscles, by 
 exertion? 
 
 Three answers to tills intricate question have been attempted, no one of 
 which however, is at all satisfactory. 
 
 1. By Willis it is maintained that the 'voluntary muscles derive their nerves 
 from the cerebrum, while the cerebellum supplies the heart and other involun- 
 tary muscles; and hence he infers that the one set is thereby fitted for tempora- 
 ry, and the other ior permanent, and uninterrupted action. 
 
 Admitting the statement to be anatomically correct, we do not perceive 
 that it leads to any such conclusion. But it is not so. There are many excep- 
 tions to this alleged distribution of the nerves. 
 
 2. By Stahl, it is imputed altogether, to the intelligence of his anima medica, 
 a guardian power, that foreseeing the danger to which the system would be 
 exposed by any remission in the action of the heart, ordains it otherwise. This 
 is all hypothesis and of the most wretched kind too: by the adoption of which 
 we only cut the knot that perplexed us to untie. 
 
 3. By Haller it is accounted for on the supposition of a larger share of irrita- 
 bility being possessed by the heart. It is to be recollected, that he judged of 
 the degree of this property by the duration of the contractile piower in a part, 
 after the death of the animal. Taking this as a just criterion, it will appear 
 from the experiments of Fowler, that in cold-blooded animals, at least, the vo- 
 luntary muscles retain their irritability longer than the heart itself The dif- 
 ference, indeed, in this respect in any class of animals, is so slight, that other 
 objections aside, the hypothesis could not be entertained. — E d. 
 
ON THE CIRCULATION. 
 
 187 
 
 a wider channel, Its course must slacken. The direction of the 
 arteries is often tortuous, and it is observed, that the arteries 
 which are sent to hollow viscera, as the stomach, the uterus and 
 the bladder, or other parts capable of contracting, of stretching, 
 and of changing their dimensions every moment, as the lips, are 
 much the most curved, no doubt, that they may by unfolding 
 give way to the extension of the tissues into which they are dis- 
 tributed. Lastly, the arteries arise from one another, and form 
 with the trunk or branch from which they are given off, an an- 
 gle varying in size, but which is always obtuse, and more or less 
 acute towards the branch. 
 
 As the arteries recede from their origin, they communicate 
 together, and these anastomoses form arches, two branches 
 bending towards each other, and joining at their extremities, as 
 we see in the vessels of the mesentery; sometimes two parallel 
 branches meet at an acute angle, and unite into one trunk, thus 
 the two vertebrals join to form the basilary artery; some com- 
 municate by transverse branches which pass from the one to the 
 other, as is seen within the skull. 
 
 In the anastomoses of the first kind, the columns of blood flow- 
 ing in contrary directions, along the two branches, meet at the 
 point of union, and mutually repel each other; their particles 
 mingle, and lose much of their motion in that reciprocal shock. 
 The blood then follows a middle direction, and enters the 
 branches which arise from the convexity of these anastomotic 
 arches. 
 
 When two branches unite to produce a new artery, of a 
 greater caliber than each taken separately, but not so large as 
 both together, the motion of the blood becomes accelerated, be- 
 cause it passes from a more capacious into a straiter channel, and 
 the forces which determined its progression are concentrated 
 into one. Lastly, the transverse anastomoses are well calculated 
 to promote the passage of the blood from the one branch into the 
 other, and to prevent congestion in the parts. 
 
 LV. The arteries are imbedded in a certain quantity of cel- 
 lular tissue, are almost universally accompanied by correspond- 
 ing veins, by lymphatics and nerves, and their coats are thicker 
 in proportion as their caliber is smaller. The experiments of 
 Clifton Whittringham prove, that the parietes are stronger in 
 
ON THE CIRCULATION. 
 
 188 
 
 the small than in the large arteries, hence it is observed, that 
 aneurisms are much less frequent in the former. Their parietes 
 have sufficient firmness not to collapse, when the tube of the ar- 
 tery is empty. They are formed of three coats; the external or 
 cellular admits of considerable extension, and appears to be 
 formed by the condensation of the laminae of the cellular tissue 
 which surrounds the artery and unites it to the neighbouring 
 parts. The second coat is thicker and firmer, of a yellow colour, 
 and fibrous, and is by some considered as muscular* and con- 
 tractile, while other physiologists merely allow it to possess a 
 considerable degree of elasticity. The longitudinal fibres, admit- 
 ted by some authors in the texture of this second coat, cannot be 
 distinguished, and their existence is not necessary to account 
 for the longitudinal retraction of arteries. In fact, this retraction 
 might depend on elasticity, it might likewise be occasioned by 
 the contraction of fibres not absolutely circular nor longitudinal, 
 but spiral and imperfectly surrounding the vessel, and crossing 
 each other in various directions. This yellow coat, thicker in 
 proportion in the smaller arterial twigs, than in the larger 
 branches, and thicker in these than in the trunks, is dry, hard, 
 not capable of much extension, and is ruptured by an effort to 
 which the external coat yields by stretching. Lastly, a third, 
 thin, and epidermoid coat lines the inside of these vessels, and 
 seems less calculated to give strength to the parietes of the arte- 
 ries, than to facilitate the flow of the blood, by presenting to it a 
 smooth, even, and slippery surface, continually moistened by a 
 serous exudation from the minute arteries, or vasa vasorum, 
 which are distributed between these coats. 
 
 Besides these three coats, the great arteries receive a fourth 
 from the membranes lining the great cavities; thus, the pericar- 
 dium and the pleura in the chest, the peritoneum in the abdo- 
 men, furnish to the different parts of the aorta, an adventitious 
 coat which does not completely surround the vessel. 
 
 * If in man and the greater number of animals, the yellow fibres which form 
 this coat differ greatly from muscular fibres, they in the elephant resemble 
 that texture very completely, as I, had an opportunity of observing, when 1 wit- 
 nessed the dissection of the elephant that died in the year X. at the Museum 
 of Natural History. Let men of judgment decide, whether the analog}’ is suffi- 
 cient to warrant our admitting, in the arteries of the human body, the exist- 
 ence of muscular fibres. 
 
ON THE CIRCULATION. 
 
 189 
 
 Of the three coats which form the parietes of the arteries, the 
 fibrous, though thicker than the other two, offers, however, the 
 least resistance. If you take the carotid artery which, for a con- 
 siderable space, does not send off any branches, and forcibly in- 
 ject into it a fluid, the internal and middle coat will be torn, be- 
 fore dilatation has increased, by one half, the caliber of the vessel. 
 The external coat resists the cause of rupture by dilating, and 
 forms a tumour, and it is only by applying a pretty considerable 
 force, that it can be ruptured. The experiment is attended with 
 the same success, if performed with air or any other gas. In 
 aneurism, the internal and fibrous coats of the arteries, but 
 more particularly the fibrous, are ruptured at an early stage of 
 the disease, which at that period increases suddenly, in a very 
 rapid manner; and on opening the tumour, it is observed, that 
 the sac is entirely formed by the dilated cellular coat. Take an 
 artery of a certain caliber, for example, the carotid or humeral, 
 apply a ligature around it and tighten it with some degree of 
 force. Dissect and take out the vessel, then cut the thread, and 
 examine the place to which it was applied, you will observe, that 
 the parietes of the artery are in that part thinner, and formed 
 merely by the cellular coat, which alone has withstood the con- 
 striction. Take hold of the two ends of an insulated arterial tube 
 and stretch it, then examine its inner coat, and you will find it 
 torn and cracked in several places, and the parietes of the artery 
 evidently weakened. 
 
 LVI. This want of extensibility in the coats of arteries, is the 
 principal cause of aneurism; hence the popliteal artery is so lia- 
 ble to that affection, from its situation behind the knee, whose 
 extension is limited merely by the resistance of the posterior 
 tendons and ligaments; this artery is affected by the jar which 
 takes place through all the soft parts, when the leg is violently 
 extended; and being less extensible than the other parts, its inner 
 coat is ruptured, or at least weakened, so as to occasion an aneu- 
 rism, always rapid in its progress. Of ten popliteal aneurisms 
 which I have seen in different hospitals, eight were ascribed to 
 a violent extension of the ham. In looking over the cases that 
 have been recorded, it will be seen, that a considerable number 
 of aneurisms of the aorta have been occasioned by too forcible 
 
ON THE CIRCULATION. 
 
 190 
 
 and too sudden an extension of the trunk in raising a heavy 
 burthen. 
 
 From the dryness, the frailty of the j’ellow or fibrous coat of 
 arteries, the application of ligatures to these vessels is attended 
 with a speedy laceration of their tissue; a moderate degree of 
 compression is sufficient to rupture that coat, the external and 
 internal remaining, at the same time, uninjured, provided the 
 constriction be not excessive. Why is the arterial tissue almost 
 the only one on which ligatures require to be applied, the least 
 fitted of all the organic tissues to bear them? This inconvenience 
 attending the ligature of arteries, led Pouteau to prefer tying 
 I arteries so as to include the surrounding soft parts within the 
 ligature, though this process is, in other respects, less eligible. 
 The objections will be obviated, by employing flat ligatures, 
 which, by acting on a greater surface of the artery, are less likely 
 to divide the coats of the vessel which will become obliterated 
 at the spot to which the ligature is applied, the more rapidly as 
 the patient is younger and stronger. 
 
 I once saw, in a man whose thigh was amputated, on account 
 of caries of the knee joint combined with a scorbutic affection, 
 hemorrhage attend the fall of the ligatures, which did not come 
 away till nineteen days after the operation; as if the fibrous coat 
 of these arteries, partaking in the debility of the muscular or- 
 gans, had not preserved a sufficient degree of contractile power 
 to close the cavity of the vessel." 
 
 LVII. The contractile power of the arteries is in their mid- 
 dle coat, it is greater, as this coat is thicker in proportion to the 
 caliber of the artery. Hence, as Hunter observes in his work on 
 the blood and inflammation, the larger arteries are endowed 
 with elasticity merely, while on the other hand, contractility is 
 very apparent in those of a smaller caliber, and is found com- 
 plete in the capillary vessels.* It is owing to this that, in the 
 
 • This is not altogether correct. Everj' portion of the arterial system is un- 
 questionally possessed of the property of contractili y. In the larger vessels, 
 muscular fibres are even demonstrable to the eye. Besides, mere elasticity wiH 
 not explain many of the phenomena of arterial action. Contrary to the doctrine 
 of Mr. Hunter, it was maintained by Bai-on Haller, and indeed by almost all 
 the cotemporary physiologists, that contractility belongs exclusively to the 
 large and middle sized arteries. In this however they were deceived. 
 
 It is now well ascertained, that muscularity increases exactly as the vessel 
 
ON THE CIRCULATION. 
 
 191 
 
 trunks near the heart, the progression of the blood is effected, 
 chiefly by the impulse which it receives from the heart, and as 
 Lazarus Riviere observed, the circulation of the blood in the 
 large vessels is more an hydraulic than a vital phenomenon. 
 The action of the main arterial trunks, near the heart, has so lit- 
 tle influence on the motion of the blood sent into them by that 
 organ, that the aorta is frequently ossified, without affecting the 
 circulation. The aorta is naturally bony in the sturgeon. J. L, 
 Petit, in the case of a bookseller whose leg he had taken off, 
 found all the arteries of a certain caliber in a state of ossifica- 
 tion; they were indurated, and, of course, incapable of acting, 
 in the slightest degree, on the column of blood which flowed 
 along them. All these facts seem conclusive arguments in favour 
 of those physiologists, who explain, on the principle of elasti- 
 city, the contraction of arteries. But however correct this ex- 
 planation may be, with regard to the vessels near the heart, it 
 does not apply to the capillaries; the influence of that organ does 
 not operate on these vessels. One may easily conceive, that the 
 column of blood which by the impulse it has received, in the 
 first instance, has been sent along the whole length of tubes 
 whose sides are ossified, inflexible, and consequently inert, on 
 reaching the extremity of these canals, is, in a manner, again 
 taken up by the vital power residing in the capillary vessels, and 
 circulates from the influence of the action belonging to these ves- 
 sels. Besides, elasticity, however considerable, merely restores 
 those tissues that have been stretched, to the condition in which 
 they were before extension. Elasticity is a kind of re-action, 
 proportionate or relative to the action which precedes it. Why 
 do arteries in the living body contract to such a degree, that 
 when empty, their canal becomes obliterated, while in the dead 
 body, however perfect the depletion of the arterial system may 
 have been, the cavity of the arteries remains perfectly open. 
 Several physiologists, however, and those among the most 
 modern, consider elasticity as the principal cause of the progres- 
 sion of the blood along the arteries.* 
 
 recedes from the heart, the capillaries having’ it in the greatest degree. As far 
 as I know, this opinion was originally taught by Cullen, and afterwards fully 
 confirmed by the experiments of Hunter. — E d. 
 
 * It has always been a matter of controversy among physiologists, whether 
 
ON THE CIRCULATION. 
 
 192 
 
 As the distance from the centre increases, the circulation 
 slackens, from several causes, and the blood could not reach all 
 the parts of the body, if the arteries, whose vitality increases 
 with their distance from the heart, and as they become smaller, 
 did not propel it to all the organs. The causes which retard the 
 circulation of the arterial blood, are, the increased dimensions 
 of the space in which it is contained; — the resistance from the 
 curves of the vessels; — the friction which it undergoes, and 
 which increases, as, at a distance from the heart, the canals along 
 which it circulates increase in number; and lastly, the deviations 
 which the blood meets with in its course, from the trunks into 
 the branches, which, coming off sometimes almost at right an- 
 gles, divert it from its original direction. 
 
 Several physiologists have called in question this progressive 
 slackening of the flow of arterial blood, and several among 
 them, who reject entirely the application of the physical sciences 
 
 the blood is propelled by the heart only, or whether the arteries co-operate to 
 to the same end. It is well known that the illustrious Harvey, the dii~overer 
 of the circulation, was of the former opinion, and that he has since been sup- 
 ported by many followers. We admit, at once, that the heart is the chief organ 
 concerned, but it seems to us equally true that the arteries also exercise a 
 considerable agency, most commonly as auxiliary' to the heart, yet sometimes 
 to a certain extent independently of that organ. These two positions are de- 
 monstrable, both by experiment and fact. 
 
 1. It has been proved that the muscular power is inherent in all the arteries 
 of the body, in the large and the small, in the main trunks as well as in the ca- 
 pillary extremities. 
 
 2. That the arteries contract with considerable force, the natural and un- 
 avoidable effect of which must be, the propulsion of the blood, and the quick- 
 ening of the circulation. 
 
 3. That the circulation has been maintained in the fcctus, though utterly 
 destitute of a heart. Cases of this description are recorded in sufficient num- 
 ber, to put the fact beyond a doubt. It may however be alleged, that in these 
 instances, as veiy often happens in the history of the animal economy, the 
 want of one organ is supplied by the assumption of new, or increased powers 
 by some other. We do not perceive much force in this objection, but as it might 
 be raised, we will appeal to other facts of a less disputable nature, such as are 
 afforded by the phenomena of local inflammation, active hjcmorrhages, blush- 
 ing, hectic suffusion, and many more which it would be easy to enumerate. 
 Enough however have been mentioned to show that the circulation may be 
 increased in a particular part without its being generally affected, and conse- 
 quently that the heart is not the only power which propels the blood, but that 
 this force also resides, in a limited degree, in the arteries. — E d. 
 
©N THE CIRCULATION. 
 
 19S 
 
 to that of the ' animal economy, have, nevertheless, supported 
 their opinion by a fact taken from hydraulics. To give any cer- 
 tainty to these calculations, respecting the impediments to the 
 circulation of the blood in the arteries, it would, they say, be ne- 
 cessary, that the arteries should be empty at the instant when 
 they receive the jet of blood sent into them by the contraction 
 of the ventricles. This, however, is not the case; the arteries are 
 always full, the blood flows along all of them with the same de- 
 gree of velocity. This system of vessels may be compared to a 
 syringe, from which a number of straight and tortuous tubes 
 should arise; each of these would throw out the fluid with an 
 equal degree of velocity, on applying pressure to the piston. 
 
 In refuting this doctrine, I must take notice of the manifest 
 contradiction of pretending to exclude, absolutely, all application 
 of the principles of mechanics to physiology, and the complete 
 application of these principles to the phenomena of the animal 
 economy. This contradiction, however, is not more surprising 
 than that of authors who exclaim against the abuse of modern 
 nomenclatures, and who, nevertheless, eagerly embrace every 
 opportunity of adding to it, by assigning new names to such 
 parts as may have escaped the attention of the new nomencla- 
 tors. What resemblance is there between a forcing pump whose 
 sides are unyielding, as well as those of the tubes which might 
 arise from it, and the aorta which dilates every time the blood is 
 sent into it; and again, what resemblance is there between tubes 
 which decrease towards their open extremities, while the space 
 contained in the arterial tube constantly enlarges, from the innu- 
 merable divisions of the vessels. Since it is admitted, that the 
 course of the blood is slower in the capillary vessels, must not 
 this resistance, opposed to the blood which fills the series of ves- 
 sels from the capillaries to the heart, be felt more at a greater 
 distance from that organ, &c.? Without this progressive increase 
 of resistance, as the arterial blood is at a greater distance from 
 the heart, this fluid would flow along the arteries, as it does 
 along the veins, without any pulsations; for this resistance, 
 which causes the lateral effort of dilatation effected by the blood 
 on the parietes of the arteries, is the principal cause of the pulse, 
 which belongs only to that set of vessels. A very remarkable dif- 
 ference is observable, between the blood which is sent to the 
 
 2 B 
 
ON THE CIRCULATION. 
 
 194 
 
 toes, and that which goes to the mammae, as I have several 
 times noticed in removing the carious bones of the toes, or in 
 extirpating cancerous breasts; the small arteries of these parts 
 are nearly of the same size, but the jet of blood is much more 
 rapid, the blood is sent to a much greater distance, when one of 
 the mammary arteries is divided. 
 
 The re-action of the arteries on the blood which dilates them, 
 depends not only on the great elasticity of their parietes, but 
 likewise on the contractility of the muscular coat. Elasticity has 
 a considerable share in the action of the larger trunks, while con- 
 tractility is almost the sole agent in producing the action of the 
 minute arteries. If a finger is introduced into the artery of a 
 living animal, its parietes compress it in every direction; if the 
 blood is prevented from flowing in it, the canal becomes obli- 
 terated by the adhesion of its parietes, and the vessel is con- 
 verted into a ligamentous cord, such as that formed in the 
 adult, by the remains of the umbilical arteries and veins. This 
 contractility which, during life, is always in action, keeps the 
 arteries, distended by the blood which fills them, of a smaller 
 caliber than after death. In performing capital operations, es- 
 pecially in the amputation of limbs, I have always found the 
 arteries, whether filled with blood or empty, much smaller than 
 I should have expected from their appearance in the dead body. 
 
 It happens, however, sometimes, that the quantity of blood 
 sent to an organ increases, in consequence of some cause of irri- 
 tation; the caliber of the arteries of the part, then becomes re- 
 markably enlarged. Thus, the arteries of the uterus, which are 
 very small in its unimpregnated state, acquire, towards the end 
 of pregnancy, a caliber equal to that of the radial artery: the 
 small arteries which are sent to the mammae, are not in the 
 same condition, as I have had an opportunity' of ascertaining in 
 a woman who had been suckling a child for two months before 
 her death; they retained their almost capillary minuteness, which 
 would seem to prove, that the lymphatics are alone concerned 
 in bringing to these glands the materials of their secretion. The 
 mammary arteries are evidently enlarged in open cancer of the 
 breast; in cancer of the penis, the blood-vessels likewise become 
 enlarged; hence in removing the penis for that affection, it is 
 absolutely' necessary to secure the arteries with ligatures, a pre- 
 
ON THE CIRCULATION. 
 
 195 
 
 caution which need not be attended to, in a case of gangrene. 
 Gangrene is attended with this peculiariu", that the arteries of 
 the mortified parts contract, so as to become obliterated, when 
 their caliber is inconsiderable. 
 
 As the arteries are the canals which convey to all our organs 
 the materials of growth and reparation, they are larger, in pro- 
 portion, in children, in whom nutrition is more active, and their 
 caliber is always proportionate to the natural or morbid de- 
 velopment of organs: hence the descending aorta and the iliac 
 arteries are larger in women than in men; hence the right sub- 
 clavian artery, which conveys blood to the larger and more 
 powerful of the two upper extremities, because the more em- 
 ployed, is larger than the left subclavian. But the effect should 
 not be mistaken for the cause, and it should not be imagined, 
 that the right upper extremity owes its superiority to the greater 
 caliber of its artery. In the new born child, this vessel is not 
 larger than the left subclavian; but the right arm being more 
 frequently employed, the distribution of the fluids takes place 
 more favourably, nutrition is carried on with more energy, it 
 acquires more bulk and strength, and therefore the right subcla- 
 vian artery conveys blood to it by a wider channel. If the left 
 upper extremity were employed in the same manner, and if the 
 right were kept in a state of inaction, the left subclavian would, 
 no doubt, exceed the right. I am warranted by two facts, in 
 forming this conjecture. In dissecting the bodies of two men 
 that were left-handed, I observed in the left subclavian arteries, 
 the same proportionate enlargement which is usually met with 
 in the same vessels on the right side. 
 
 LVIII. As the arteries are always full during life, and as 
 the blood flows along them with less velocity, the greater their 
 distance from the heart, the blood which the contractions of the 
 left ventricle send into the aorta, meeting the column of blood 
 already in that vessel, communicates to it the impulse which it 
 has received; but retarded in its direct progression by the re- 
 sistance of that column, it acts against the parietes of the vessels, 
 and removes them to a greater distance from their axis. This 
 lateral action which dilates the arteries, depends, therefore, on 
 the resistance of the parietes of these cavities, always filled with 
 blood, to that which the heart sends into them. This dilatation, 
 
ON THE CIUCULATION. 
 
 196 
 
 which is more considerable in the large arteries than in the 
 smaller ones, manifests itself by a beat, known under the name 
 of pulse. The experiments of Lamure would lead one to believe, 
 that another cause of this phenomenon is a slight displacement 
 of the arteries, every time they dilate. These displacements are 
 most easily observed at their curvatures, and where they adhere 
 to surrounding parts, by a loose and yielding cellular tissue. 
 
 The pulse is more frequent in women, in children, in persons 
 of small stature, during the influence of the passions, and under 
 violent bodily exercise, than in an adult man, of high stature, 
 and of a calm physical and moral nature. At an early period of 
 life, the pulse beats as often as a hundred and forty times in a 
 minute. But as the child gets older, the motion of the circula- 
 tion slackens, and at two years old, the pulse beats only a hun- 
 dred times in the same space of time. At the age of puberty, 
 the beats of the pulse are about eighty in a minute; in manhood, 
 seventy-five, and lastly, in old men of sixty, the pulse is not 
 above sixty. It is slower in the inhabitants of cold, than in those 
 of warm climates. 
 
 Since the time of Galen, the pulse has furnished physicians 
 with one of their principal sources of diagnosis. The force, the 
 regularity, the equality of its pulsations, opposed to their weak- 
 ness, inequality, irregularity, and intermittence, aflford the means 
 of judging of the nature and danger of a disease, of the power 
 of nature in bringing about a cure, of the organ that is most 
 affected, of the time or period of the complaint, &c. No one 
 has been more successful than Bordeu, in the consideration of 
 the pulse, under these diflFerent points of view. Its modifications 
 indicative of the periods of diseases, establish, according to that 
 celebrated physician, as may be seen in his Recherches sur le 
 pouls par rapport aux crises, the pulse of crudity, of irritation, 
 and of concoction. Certain general characters indicate, whether 
 the afiection is situated above or below the diaphragm, hence 
 the distinction of superior and inferior pulse. Lastly, peculiar 
 characters denote the lesion of peculiar organs; which constitutes 
 the nasal, guttural, pectoral, stomachic, hepatic, intestinal, renal, 
 uterine, &c. 
 
 Besides these sensible beats, which constitute the pheno- 
 menon of the pulse in the arteries, there is an inward and obscure 
 
ON THE CIRCULATION. 
 
 197 
 
 pulsatory motion, by which all the parts of the body are agitated, 
 every time that the ventricles of the heart contract. There is a 
 kind of antagonism between the heart and the other organs, they 
 yield to the impulse which it gives to the blood, dilate on re- 
 ceiving this fluid, and collapse when the effort of contraction is 
 over. Every part vibrates, trembles, and palpitates within the 
 body, the motions of the heart shake its whole mass, and these 
 quiverings, which may be observed externally, are most mani- 
 fest when the circulation is carried on with rapidity and force. 
 In some head aches, the internal carotid arteries pulsate with 
 such violence, that not only the ear is sensible to the noise made 
 by the column of blood striking against the curvature of the 
 osseous canal, but the head is evidently moved and raised, as it 
 were, at each pulsation. If you look at your hand or foot, when 
 the upper or lower extremity is quiescent and pendulous, you 
 will observe in it a slight motion corresponding to the beats of 
 the heart. This motion increases, and even makes the hand 
 shake, when, from the influence of the passions, or from violent 
 exercise, the circulation is accelerated; in every violent emotion 
 we feel, within ourselves, the effort by which the blood, at each 
 beat of the pulse, penetrates into our organs and fills every tissue. 
 And it is, in a great measure, from this inward tact, that we are 
 conscious of existence: a consciousness the more lively and dis- 
 tinct, as the effect of which we are speaking is more marked. It 
 is, likewise, from observing this phenomenon, that several phy- 
 siologists have been led to conceive the idea of a double motion, 
 which dilates or condenses, which contracts or expands, alter- 
 nately, all organs endowed with life; they have observed, that 
 dilatation prevails in youth, in inflammation and erection, con- 
 ditions of which all parts are capable, according to their differ- 
 ence of structure. 
 
 LIX. At the moment when the left ventricle contracts, to 
 send the blood into the aorta, the sigmoid valves of that artery 
 rise, and apply themselves to its parietes, without, nevertheless, 
 closing the orifices of the coronary arteries, which lie above the 
 loose edges of the valves; so that the blood is received into these 
 vessels, at the same time as into the others. When the contraction 
 of the ventricle is over, the aorta acts on the blood which it con- 
 tains, and would send it back into the ventricle, if the valves, by 
 
ON THE CIRCULATION. 
 
 198 
 
 suddenly descending, did not present an insuperable obstacle to 
 the reuirn of the blood, and did not yield a point of resistance 
 to the action of the whole arterial system; only the small quan- 
 tity of blood below the valves, at the moment of their descend- 
 ing, flows back towards the heart, and returns into the ventricle. 
 
 Though the rate at which the blood flows along the aorta, has 
 been estimated at only about eight inches in a second, a pulsa- 
 tion is felt in all the arteries of a certain caliber, at the instant 
 the ventricles are contracting. The reason that the pulsations of 
 the heart appear to take place at the same time as those of the 
 arteries, is, that the columns of blood, in these vessels, receive 
 an impulse from that which is issuing from the ventricles, and 
 this concussion is felt in an instant of time, too short to be mea- 
 sured, such as that which is felt by the hand applied to the end 
 of a piece of timber struck, at the other end, with a hammer. 
 The blood which fills a main trunk, supplies to each of the 
 branches which arise from it, columns proportionate to their cali- 
 ber. This division of the principal column is effected by a kind 
 of projection at the mouth of each artery. These internal projec- 
 tions detach from the main stream the lesser ones, and these flow 
 the more readily into the branches, according as these arise 
 from the trunk at a more acute angle, as the projection is more 
 prominent and the deviation of the fluid less considerable. If 
 the branches are given off at an almost right angle, the orifices 
 of the arteries scarcely project at all, and nothing but the effort 
 of lateral pressure determines the flow of the blood into them. 
 
 The flow of the blood into the arteries which are distributed 
 to muscles, is not interrupted when these muscles contract, for 
 whenever arteries, of a certain caliber, penetrate into muscles, 
 they are surrounded by a tendinous ring, which, during the con- 
 traction of the muscle, becomes enlarged, from the extension in 
 every direction, effected by the fibres which are attached to it, 
 around its circumference. The existence of this truly admirable 
 conformation, may be readily ascertained, by observing the 
 aorta, in its passage through the crura of the diaphragm; the 
 perforating arteries of the thigh, where they enter at the back 
 part of the limb into the adductor muscles; the popliteal, as it 
 passes through the upper extremity of the soleus muscle. 
 
ON THE CIRCULATION. 
 
 199 
 
 LX. Of the capillary vessels. The arteries, after dividing 
 into branches, these branches into lesser ones, and these into 
 progressively smaller ramifications, terminate in the tissue of 
 our organs, by becoming continuous with the veins. The ve- 
 nous system arises, therefore, from the arterial system, the ori- 
 gins of the veins being merely the more minute extremities of 
 the arteries, which becoming capillary from the great number 
 of divisions* they have undergone, bend in an opposite direc- 
 tion and become altered in their structure. 
 
 These minute capillary arteries form with the minute veins, 
 with which they are continuous, and with the lymphatics, won- 
 derful meshes in the tissue of our organs. 
 
 Several physiologists consider the capillary blood vessels, as 
 an intermediate system between the arteries and veins, in which 
 the blood, entirely out of the influence of the action of the heart, 
 flows slowly, with an oscillatory and sometimes retrograde mo- 
 tion, is no longer red, because its globules are strained, as it 
 were, and, in a manner, lost in a colourless serum, which serves 
 them as a vehicle. 
 
 It is, in fact, necessary, that bodies should be of a certain 
 bulk, to reflect the rays of light at an angle sufficiently obtuse, 
 that the eye may discover their colour. We know, that grains 
 of sand reduced to a very fine dust, appear colourless when 
 examined separately, and are seen to possess colour only when 
 in a state of aggregation: further, very thin laminae of a horny 
 substance, appear transparent, though the part from which they 
 have been detached be of a red or blue colour. But if several 
 of these transparent laminae be laid on one another, the red 
 colour becomes darker, in proportion as a greater number are 
 brought together. 
 
 Let irritation, from whatever cause, determine the blood to 
 flow into the serous capillary vessels, in greater quantity, and 
 with more force, these vessels will become apparent, the organs 
 in whose structure they circulate, will acquire a red colour, more 
 or less deep; thus the conjunctiva, the pleura, the peritoneum, the 
 
 * The arterial divisions which may be discerned by the aid of'anatomy, do 
 not exceed eighteen or twenty: nevertheless, they divide still further, when 
 they are become so minute as not to be discernible with the help of the most 
 powerful microscope. 
 
ON THE CIRCULATION. 
 
 !S00 
 
 cartilages, the ligaments, &c. which naturally are whitish or 
 transparent, become red, when affected with inflammation, 
 whether from the increased impetus of the circulation, which 
 forces and accumulates into the capillary vessels a greater num- 
 ber of red globules, or that the sensibility of these small vessels 
 is impaired by inflammation, so that they admit globules which 
 they formerly rejected. 
 
 Some capillary vessels transmit blood, at all times, and uni- 
 formly exhibit a red colour; this is the case with the capillary 
 vessels of the spleen, of the corpora cavernosa of the penis, of 
 the bulb and corpus spungiosum of the urethra; the same applies 
 to the capillaries of the muscles, of the mucous membranes; 
 there are, however, very few of those organs, in which the whole 
 portion of the capillary tube, between the termination of the 
 artery and the origin of the vein, is filled with red blood. There 
 is, almost always, a division in the tortuous line described by 
 the capillary, and within this space the blood cannot be detected 
 of its usual colour. 
 
 The number of the capillary vessels, as well as that of the 
 arteries, to which the former are as auxiliaries, is much more 
 considerable in the secretory organs, than in those in which life 
 carries on only the process of nutrition. It is on that account, 
 that the bones, the tendons, the ligaments, the cartilages, con- 
 tain so much smaller a quantity of blood, than the raucous and 
 serous membranes, and the skin. The capillary vessels are, 
 however, very numerous, in the muscles which owe that colour 
 to the great quantity of blood they contain; but, as we shall point 
 out, when we come to speak of motion, this fluid appears to 
 form an essential element in muscular contraction; it is, there- 
 fore, not to be wondered, that these organs should have a greater 
 number of capillary vessels sent to them: since these vessels do 
 not supply them merely with molecules to carry on nutrition and 
 to repair the waste of the part, but impart to them the principle 
 of their frequent contraction: the quantity of them is so consi- 
 derable, in all these parts, employed in the two fold oflices of 
 nutrition and secretion, that Ruysch penetrated, with his injec- 
 tions, the whole thickness of their substance, to such a degree, 
 that the organs which he had prepared were only a wonderful 
 and inextricable network of capillary vessels extremely minute. 
 
ON THE CIRCULATION. 
 
 201 
 
 On these anatomical preparations, made with an art hitherto 
 unrivalled, Ruysch grounded his hypothesis relative to the inti- 
 mate structure of the body, in which, he imagined, all was capil- 
 lary tubes; a hypothesis which has obtained the most favourable 
 reception, and has reigned, during more than a century, in the 
 schools. It is enough to reflect a moment on their uses, to con- 
 ceive that the number of them must be really prodigious. As 
 long as the blood is enclosed within the arteries, and flows 
 under the control of the heart, it fulfils no purpose either of 
 nutrition or secretion. To make it subservient to these great 
 functions, it must be diffused through the very tissue of the or- 
 gans, by means of the capillary divisions; these little vessels 
 exist then, in every part, where any organized molecules are 
 found united; since the particle formed by their assemblage, 
 must, at least, find, in the juices which they bring to it, the 
 materials of its reparation. Entering, in greater or less propor- 
 tion, into the organization of all the tissues, the capillaries re- 
 ceive certain modifications from the organs of which they are an 
 integral part; modifications which enable them to deposit the 
 serous part of the blood on the surface of the serous membranes, 
 admit the transudation of the fat into the cells of the cellular 
 tissue, furnish the urine to the kidneys, and the liver with the 
 materials of the bile; in a word, suffer to escape, through the 
 porosities with which their parietes are pierced, the principles 
 which the blood has to furnish to every organ. 
 
 It is by these lateral porosities, and not by extremities open 
 on all the surfaces, and in all the points of the organs, that the 
 capillaries transpire, in some sort, the elements of nutrition, and 
 of the various secretions. Mascagni was aware, that Nature, 
 skilful in deducing many effects from few causes, has not de- 
 viated, in the construction of the system of circulation, from the 
 invariable laws of her ordinary simplicity; but the lateral pores 
 of the capillaries, which are sufficient for the explanation of all 
 the phenomena ascribed to the exhaling mouths of the arteries, 
 and to the pretended continuity of these vessels with the excretory 
 ducts of the organs, &c. are not openings like the pores com- 
 mon to all matter;. each of them may be considered as an orifice, 
 sensible, and, especially, contractile, of differing size, according 
 to the state of the strength or of the vital powers. The size then 
 
 2 C 
 
ON THE CIRCULATION. 
 
 202 
 
 of these capillary pores is subject to frequent variations; and 
 this is the explanation given of the formation of scorbutic 
 ecchymoses, of petechise, and of passive or relaxed hemorrhages. 
 In all these affections, contractility being really diminished, the 
 pores of the capillaries enlarge, and suffer the red blood to tran- 
 sude through their relaxed mouths. This phenomenon takes 
 place, not only under the skin and on the various mucous sur- 
 faces, it is observed also in the very tissue of the organs. It is 
 thus, that I have often seen, on opening the bodies of those that 
 had died of scurvy, in its last stage, the muscles of the leg filled 
 with blood. This sort of interior hemorrhage, converts the mus- 
 cles into a kind of pulp; and the extravasated blood itself under- 
 goes a beginning of decomposition. The bones themselves are 
 liable to these scorbutic bloody infiltrations. I had an opportu- 
 nity of ascertaining this in the hospital of St. Louis, at the same 
 time that I learnt the difficulty of procuring a durable skeleton 
 from such bodies. The greatest number die in a very advanced 
 stage of the disease, and the bones dissolve in maceration, or 
 rot in a very little time. 
 
 The capillary vessels, whether the blood flow through them 
 red, or colourless, are not a system of vessels distinct from that 
 of the arteries, and from that of the veins; they belong essen- 
 tially to these two orders of vessels. Those which, ramifying in 
 the tissue of the skin, or of the serous membranes, suffer the 
 serum of the blood to transude, are not more entitled to the 
 name of exhalant system, which some authors have given them. 
 To consider as distinct and insulated systems, separate parts of 
 a system of organs, is to encumber science with a crowd of divi- 
 sions, as false as they are useless. 
 
 LX I. The sanguineous capillaries anastomose, and form, like 
 the lymphatic capillaries, a net work that envelopes all the organs. 
 Their frequent communications do not allow obstructions to 
 take place and to produce inflammation, as Boerhaave thought, 
 and as was long taught on the authority of that celebrated phy- 
 sician. Haller, Spallanzani, all the microscopic observers, have 
 perceived threads of blood flowing in the capillaries, offering 
 themselves at the various inosculations of these vessels, and 
 have seen them flow back, when they were not admitted, to 
 seek other easier entrances. 
 
ON THE CIRCULATION. 
 
 20S 
 
 I will not collect, in this place, superfluous arguments against 
 the theory of the Leyden professor, rejected at its birth by the 
 physicians of Montpellier, absolutely refuted, and now univer- 
 sally given up. Irritation alone keeps the blood in the inflamed 
 part; for when death, which puts an end to all irritations, and 
 relaxes all spasms (mors spasmos, solvit. Hipp.); when, I say, 
 death comes on, all slight inflammations are dissipated, and 
 whenever they have not been sufficiently intense to induce tran- 
 sudation of the blood through the parietes of the capillaries into 
 the areolce of the organic tissues, the blood flows back into the 
 large vessels, and there is no trace of it left. It is thus that ery- 
 sipelas of the skin disappears, that the pleura preserves its trans- 
 parency, in individuals affected, before death, with sharp pains 
 in the side. If to this we add our ignorance on the real organi- 
 zation of the nervous system, on the conditions absolutely re- 
 quired of the brain and nerves, for the maintenance of life, we 
 shall cease to be surprized, that the opening of bodies has 
 taught us no more on the real seat of disease, and we shall con- 
 fess with Morgagni, who however employed, with great success, 
 this means of improving the art of healing, that there are num- 
 berless diseases, of which, after death, no trace is left, and for 
 the fatal termination of which we are unable to account. 
 
 Contractility and sensibility exist, in a much higher degree, 
 in the capillary and serous vessels, than in the veins and arteries. 
 Life must needs be more active in the former, for the motion 
 given to the blood by the contractions of the heart being ex- 
 hausted, this fluid, no longer in the sphere of action of that 
 organ, can circulate but from the influence of the action of the 
 vessels themselves. 
 
 The termination of the arteries into veins, is the only well 
 ascertained termination of those vessels; it may be seen by the 
 help of the microscope, in cold-blooded animals, in frogs and sa- 
 lamanders. In some fish, we may, even with the naked eye, ob- 
 serve frequent and considerable inosculations between the arte- 
 ries and veins. In man, however, and in other warm-blooded 
 animals, these communications take place only at the extremi- 
 ties of the two systems of vessels. In this case, the arteries ter- 
 minate, sometimes, in capillary vessels carrying serous fluid, 
 such are the vessels of the sclerotic coat; these vessels become 
 
ON THE CmCULATIOJC. 
 
 204 
 
 small veins whose caliber gradually increases, until they admit 
 red globules in sufficient number to reflect that colour. At other 
 times, the artery and vein are continuous, vithout the interven- 
 tion of that extremely minute subdivision; the red blood then 
 passes readily and immediately from the artery into the vein. 
 
 It will be shown, in speaking of secretions, that the continua- 
 tion of the arteries into the excretory ducts of the conglomerate 
 glands, and their termination in exhaling orifices, cannot be ad- 
 mitted; and that the presence of small pores, in the sides of the 
 minute arteries and veins, would aflPord an explanation of the 
 phenomena on which the belief of this termination of the arte- 
 ries rests. There exists no parenchyma, no spungy tissue, be- 
 tween the extremities of the arteries and the origin of the veins, 
 with, perhaps, the exception of the substance of the cavernous 
 bodies of the penis and of the clitoris, of the bulb and spungy 
 part of the urethra, the retiforni plexis, which surrounds the ori- 
 fice of the vagina, and perhaps also the tissue of the spleen, 
 though the experiments of anatomists (Mascagni and Lobstein) 
 seem to prove, that in these organs, the arteries and veins are 
 immediately continuous. 
 
 LX II. Of the action of the veins. These vessels, whose func- 
 tion it is to carry back to the heart, the blood which the arte- 
 ries have sent to all the organs, are much more numerous than 
 the arteries themselves. It is observed, in fact, that arteries of a 
 middle size, as those of the leg and fore-arm, have each two cor- 
 responding veins, whose caliber at least equals theirs, and that 
 there is besides, a set of superficial veins, lying between the 
 skin which covers the limbs and the aponeuroses which envelop 
 the muscles; these have no corresponding arteries. The space 
 which the venous blood occupies is, therefore, much greater 
 than that taken up by the blood in the arteries. Hence also, it is 
 estimated, that of twenty-eight or thirty pounds of this fluid, 
 making about a fifth part of the whole weight of the body in an 
 adult man, nine parts are present in the veins, and only four in 
 the arteries. In this calculation, one should consider as arterial, 
 the blood contained in the pulmonary veins and in the left cavi- 
 ties of the heart, while that which fills the cavities in the right 
 side of the heart and the pulmonary arterj’, is truly venous, and 
 has every character of such blood. 
 
ON THE CIRCULATION. 
 
 205 
 
 Although the veins generally accompany the arteries, and are 
 united to them by a common sheath of cellular membrane, this 
 disposition of parts is not without exceptions. The veins which 
 bring back the blood from the liver, do not, in any respect, fol- 
 low the course of the branches of the hepatic artery; the sinuses 
 of the brain are very different, in their arrangement, from the 
 cerebral arteries; the veins of the bones, which are particularly 
 numerous, and of a much greater caliber than the arteries of the 
 same parts, from the slow circulation of the blood along them, 
 do not generally follow the direction of the arteries, and arise 
 singly from the substance of the bone, with the exception of 
 those in the middle canal, and which pass through the nutritious 
 foram.en of the bone. The veins are not only more numerous 
 than the arteries, but they are likewise more capacious, and di- 
 late more readily: this structure was necessary, on account of 
 the slowness with which the blood circulates, and of the readi- 
 ness with which it stagnates, when the slightest obstacle impedes 
 its circulation.* The force which carries on the circulation of 
 the blood, along the arteries, is so great, that Nature seems not 
 to have availed herself of the mechanical advantages which 
 might have facilitated its flow. On the other hand, the power 
 which determines the progression of the venous blood is so fee- 
 ble, that she has sedulously removed every obstable which 
 might have impeded its course. And as the relation of the mi- 
 nute to the larger branches, and of these to the trunk, is the same 
 as in the arteries, two branches unite to form a vein of greater 
 caliber than each separate vessel, but smaller than the two taken 
 together, the blood flows along a space which becomes narrower, 
 the nearer it approaches the heart;the rapidityof its course, must, 
 therefore, be progressively increased. 
 
 The veins are almost straight in their course; at least, they 
 are much less tortuous than the arteries. The force which 
 
 * Tlie arteries contain, at all times, nearly the same quantity of blood. The 
 veins are always the seat of plethora, because the blood stagnates in them more 
 readily; and this condition brings on inflammatory fever (consisting merely in 
 an Increased action of the vascular system, as is expressed by the term nn- 
 geiotenkiue applied to it by Professor Pine!) only when the venous congestion 
 becoming excessive, the blood passes with difficulty from the arteries into the 
 veins. The heart and the arteries then struggle, with considerable effort, to rid 
 themselves of the fluid which oppresses them, &c. 
 
ON THE CIRCUI ATION. 
 
 206 
 
 makes the Wood flow along them, is consequently not taken up 
 in straightening these curves; the anastomoses are, likewise, 
 more frequent, and as the flow of the blood might have been in- 
 tercepted in the deep seated veins of the limbs, when the mus- 
 cles, among which these vessels lie, during contraction, compress 
 them by their enlargement and induration, they communicate 
 freely with the superficia' veins, towards which the blood is car- 
 ried, and flows the more readily, as they are not liable to be 
 compressed. It is observed, and is to be accounted for on the 
 same principle, that the superficial veins are very large and dis- 
 tinct among the lower orders who are employed in laborious oc- 
 cupations, requiring an almost continual exertion of their limbs. 
 Lastly, the internal part of the veins, like that of the lymphatics 
 is furnished with valvular folds, formed by the duplicature of 
 their epidermoid coat. These valves, which are seldom single, 
 and almost always in pairs, are not found in the minute veins, 
 nor in the great trunks, nor in the veins which bring back the 
 blood from the viscera in the great cavities. 
 
 These valves, in falling, close completely the canal of the ves- 
 sel, destroy the continuity of the column of blood returning to 
 the heart, divide it into smaller columns, as numerous as the in- 
 tervals between the valves, and the height of which is determin- 
 ed by the distance between these folds. So that the power 
 which carries onward the venous blood, and which would be 
 incapable of propelling the whole mass, acts advantageously on 
 ^ each of the small portions into which it is divided. 
 
 LXIII. It has been thought, that the principal cause which 
 makes the blood flow into the veins, is the combined action of 
 the heart and arteries; but the impulse from those organs is lost 
 in the system of capillary vessels, and does not extend to the 
 veins. The specific action of their own parietes, aided by 
 auxiliary means, such as the motion of the neighbouring arteries, 
 is sufficient to carry the blood on to the heart.* 
 
 * In the process of returning' the blood to the heart, two causes are princi- 
 pally engaged, the most efficient of which, is undoubtedly, the contractile pomer 
 of the veins themselves. We are aware that this property is denied to them by 
 many who have speculated on the subject. It is however shewn by Haller that 
 the vena cava, at least, is muscular, and Verschuyr and other respectable phy- 
 siologists, have detected the same structure in the more minute veins. There 
 is one fact which we think ought alone to convince us of the contractUity of 
 
ON THE CIRCULATION. 
 
 207 
 
 These parietes, which are much thinner than those of the ar- 
 teries, are contained, like theirs, in a sheath common to all the 
 vessels. Three coats, likewise, enter into their structure; the 
 middle or fibrous coat is not very distinct, and consists merely 
 of a few longitudinal reddish fibres, which can be distinguished 
 only in the larger veins, near the heart. In' some of the larger 
 quadrupeds, as in the ox, these fibres form distinct fasciculi, and 
 their muscularity is much more manifest. 
 
 The internal coat, which is mere extensible than that of the 
 arteries and equally thin, adheres more closely to the other 
 coats. The cellular coat, which connects it to the middle one, is 
 less abundant, hence phosphate of lime is seldom deposited into 
 it, as happens to the arteries which frequently become ossified, 
 as we advance in years. This internal coat is merely a continua- 
 tion of that which lines the cavities of the heart; and as the orir 
 gin of the inner coat of the arteries is the same, there exists a 
 non-interrupted continuity in the membrane which lines all the 
 canals of the circulation. The inner coat forms the only essen- 
 tial part of the venous system; it alone constitutes the veins 
 within the bones, the sinuses of the dura mater, the hepatic 
 veins, in a word, all the veins which are so firmly attached ex- 
 ternally to the neighbouring parts, that the blood flows along 
 them, as along inert tubes, their parietes being, almost complete- 
 ly, incapable of contracting. 
 
 The veins, in their passage through muscles, are, like the ar- 
 teries, guarded by aponeurotic rings, than which none is more 
 remarkable than that which belongs to the aperture in the dia- 
 phragm, which transmits the ascending cava from the abdomen 
 into the thorax. This vessel is, therefore, not compressed by the 
 contraction of that muscle in inspiration. 
 
 LX IV. As the inferior cava passes through the lower edge 
 of the liver, whether along a deep fissure, or in a real canal in the 
 
 tliese vessels, which is, that they always adapt themselves to the quantity of 
 blood they contain. 
 
 Co-operatin,^ with the above cause is the action of the muscles, as may be 
 illustrated by the familiar example of vensesection. When in this case the blood 
 issues languidly from the orifice made in the vein, it is known, that nothing pro- 
 motes its flow so effectually as pressing sometliing hard in the hand. This ope- 
 rates simply by bringing into action the muscles of the fore arm and humerus, 
 thereby producing considerable compression of the veins. — Ed. 
 
ON THE CIRCULiVTION, 
 
 208 
 
 parenchymatous substance of that viscus, the course of the 
 blood must be impeded, when, from congestion of the paren- 
 chyma, the vessel is, in some sort, strangulated. 
 
 Obstruction of the liver, which is of such frequent occur- 
 rence, would be attended with fatal consequences^ by prevent- 
 ing the return of the blood from the inferior parts, along the 
 ascending cava, if this great venous trunk did not keep up, by 
 means of the vena azygos, an open and free communication with 
 the descending or superior cava. The use of this anastomosis of 
 the two great veins is, evidently, to facilitate the passage of the 
 blood from the one of these vessels into the other, when either, 
 especially the lower, does not readily evacuate its contents into 
 the right auricle. On this account, the vena azygos is capable of 
 considerable dilatation, and is entirely without valves. In the 
 body of a man opened this day in my presence, and whose liver 
 was twice as large as in health, I observed, that the vena azygos, 
 which was distended with blood, was of the size of the little fin- 
 ger; the termination downward of this vessel, in the right renal 
 vein, and above in the superior cava, were most distinct, and by 
 compressing it from above downward, or from below upward, 
 the blood flowed into the one or other of these vessels. 
 
 As the causes which determine the circulation of the venous 
 blood, communicate to it an impulse which is far from rapid, and 
 as this fluid meets with only trifling obstacles, and such as are 
 easily overcome, the pressure against the parietes of the veins is 
 very inconsiderable, and these vessels do not pulsate, as the ar- 
 teries. There is observed, however, near the heart, an undula- 
 tory motion which the blood communicates to the parietes of the 
 vessels. These kinds of alternate pulsations depend on the ra- 
 pidity with which the blood, whose course is progressively ac- 
 celerated, flows towards the heart, and on the reflux of the 
 blood, during the contraction of the right auricle. The contrac- 
 tion of this cavity forces back the blood into the veins which 
 open into it; this retrograde course is manifest in the superior 
 cava, and is the more readily occasioned, as the orifice of this 
 vein is not furnished with any valve that might prevent it. It 
 does not, however, extend very far towards the brain, the blood 
 having to ascend against its own weight, and the jugulars ad- 
 mitting of considerable dilatation. This regurgitation is still 
 
ON THE CIRCULATION. 
 
 <209 
 
 more marked in the inferior cava, the orifice of which is but im- 
 perfectly closed by the valve of Eustachius; it is felt in the ab- 
 dominal veins, and extends even to the external iliacs, according 
 to the testimony of Haller. 
 
 LXV. The orifice of the great coronary vein being exactly 
 covered over by its valve, the blood does not return into the 
 tissue of the heart, which being a contractile organ, would have 
 had its irritability impaired by the presence of venous blood. It 
 is of consequence to observe, that this reflux never extends to 
 the veins which bring back the blood from the muscles, and that 
 it is never felt in the veins of the limbs which are furnished in- 
 ternally with valvular folds. The case is very different between 
 our organs of motion and these secretory glands; towards these 
 the blood required to be sent back, so as to be the longer ex- 
 posed to their action: venous blood diminishes and even de- 
 stroys muscular irritability, and is truly oppressive, as may be 
 ascertained by injecting some, in the arteries of a li^4ng animal, 
 or else by tying the veins, so as to prevent its return, or by ob- 
 serving what happens, when the course of the blood is interrupt- 
 ed, either by applying firm ligatures round the limbs, or by 
 wearing confined clothes. 
 
 I am satisfied, that it was from observing the oscillatory un- 
 dulations of the venous blood, in the great vessels, that the an- 
 cients were led to the opinions they entertained on the course of 
 the blood, which they compared to the Euripus, whose waves 
 are represented by the poets, as uncertain in their course, and in 
 currents running in contrary directions. 
 
 The internal veins in which this reflux is observed, show this 
 motion of the blood most distinctly of any; their sides, which are 
 thin and semi-transparent, not being as in other parts, surround- 
 ed by an adipose cellular tissue. To give a complete notion of the 
 doctrine of the ancients, on the subject of the circulation, it will 
 merely be necessary to add to the above idea, the opinion which 
 they entertained, that the chyle taken up by the meseraic veins, 
 was carried to the liver, in which its sanguification was effected, 
 and lastly, that the arteries were filled with vital spirit, and con- 
 tained only a few drops of blood which passed through small 
 holes, which, Galen says, perforate the septum of the ventricles. 
 
 The blood, however, continually urged on by the columns 
 
 2 D V 
 
ON THE CIRCULATION. 
 
 210 
 
 which follow each other in succession, by the action of the veins 
 whose parii'tes become gradually stronger, and by the compres- 
 sion ..hich these vessels experience from the viscera, during the 
 motions of respiration, reaches the heart, and enters the auricles 
 with the greater facility, as the orifices of the cavae not being di- 
 rectly opposed to each other, the columns of blood which they 
 convey do not meet and do not oppose each other. 
 
 LX VI. The blood, continually carried to all parts of the 
 body by the arteries, returns, therefore, to the heart, by a mo- 
 tion which can never can be interrupted, without considerable 
 danger of life. We know, that the circulation is thus effected, 
 from the direction of the valves of the heart, of the arteries and 
 veins; by what happens when these vessels are opened, compress- 
 ed or tied, or when a fluid is injected into them. When an arte- 
 ry is wounded, the blood comes from the part of the vessel 
 nearest the heart; it comes, on the contrary, from towards the 
 extremities, if it is a vein that has been opened. By compress- 
 ing or tying an artery, the course of the blood is suspended be- 
 low the ligature, and the vessel swells above. The veins, on the 
 contrary, when tied or compressed, dilate below. Lastly, when 
 an acid fluid is injected into a vein, the blood is seen to coagu- 
 late in the direction of the heart. By the help of the microscope, 
 we may see in the semi-transparent vessels of frogs and other 
 cold-blooded animals, the blood flowing from the heart into the 
 arteries, and from these into the veins which return it to the 
 heart. It was on the strength of these convincing proofs, that 
 William Harvey established, towards the middle of the six- 
 teenth century, the theory of the circulation of the blood. Its 
 mechanism had been rather guessed at, than understood, by se- 
 veral authors: Servetus and Cesalpinus appear to have been ac- 
 quainted with it; but no one has more clearly explained it than 
 the English physiologist, who is justly considered the author of 
 that immortal discovery. 
 
 LX VI I. The theory of Harvey, such as it is laid down in his 
 work, entitled, De sanguinis circuitu^ exercitationes anatomica^ 
 does not appear to me entirely admissible. — He considers the 
 heart as the only agent which sets the blood in motion, and does 
 not take into account the action of the veins and arteries, which 
 he considers as completely inert tubes, while every thing tends 
 
ON THE CmCULATION, 
 
 211 
 
 to prove that the arteries and veins assist the motion of the blood, 
 by an action peculiar to themsel'^es. He admits, that the blood 
 flows, in every part of the circulatory system, with an uniform 
 degree of speed; an opinion so manifestly contradicted by rea- 
 soning and experience, which prove that the velocity of its 
 course diminishes, the greater its distance from the heart, from 
 the influence of a great number of circumstances, which it would 
 be useless to repeat (LVII.) This doctrine has yet, however, 
 several abettors, and among the moderns, Spallanzani has en- 
 deavoured to support it, by a number of experiments so contra- 
 dictory, that one is surprised that so judicious a physiologist 
 should have collected them to establish a theory completely re- 
 futed by several of them. Nothing, for example, contradicts it 
 more fully, than the continuation of the flow of the blood, in the 
 vessels of frogs and salamanders, after the heart of these reptiles 
 have been torn out; there are besides, animals which not pos- 
 sessed of that central organ, have nevertheless vessels along 
 which the blood flows, and which contract and dilate by alter- 
 nate motions. 
 
 If the mere force of the heart propelled the blood to every 
 part, the course of this fluid ought, at intervals, to be suspended, 
 its circulation, at least, ought to be slackened, when the ventri- 
 cles cease to contract; but as the contraction of the arteries cor- 
 responds to the relaxation of the ventricles, these two powers 
 whose action alternates, are continually employed in propelling 
 the blood along its innumerable channels. 
 
 Besides the general circulation of which the laws and pheno- 
 mena have just been mentioned, each part may be said to have 
 its peculiar mode of circulation, more or less rapid, according to 
 the arrangement and structure of its vessels. Each of these in, 
 dividual circulations forms a part of the machinery included in 
 the great circle of the general circulation, and in which the 
 course of the blood takes place in a different manner, may be ac- 
 celerated or retarded, without affecting the g. neral circulation. 
 Thus, in whitlow of a finger, the radial artery pulsates a hundred 
 times in a minute, while on the sound side, its beats are only se- 
 venty in number, and perfectly isochronous with the pulsations of 
 the heart. In the same manner, the blood of the intestines, which 
 
ON THE CIRCULATION. 
 
 212 
 
 is destined to furnish the materials of the bile, flows much more 
 slowly than that of other parts. 
 
 These modifications affecting the velocity of the circulatory 
 motion of the blood, account for the difference of its qualities 
 in different organs; all these differences form a part of the plan 
 of Nature, and it is not difficult to understand their utility. 
 
 LXVIII. In what has been said of the circulation, no sepa- 
 rate mention has been made of the course of the blood through 
 the lungs, called by authors the lesser or pulmonary circulation. 
 The vascular system of the lungs, with the addition even of the 
 cavities of the heart which belong to it, does not represent a com- 
 plete circle, it is only a segment, or rather an arch of the great 
 circle of the general circulation. ■ 
 
 The blood, in going along that great circle, meets with the or- 
 gans, situated like so many points of intersection in the course of 
 the vessels which form that circle. 
 
 To render still more simple, the idea which is to be entertain- 
 ed on the subject, one may reduce these intersections to two 
 principal ones; the one corresponding to the lungs, the other to 
 the rest of the body; the veins, the right cavities of the heart, 
 and the pulmonary artery with its divisions, forming one half of 
 the circle; the pulmonary veins, the left cavities of the heart, the 
 aorta with all its branches, representing the other half. The ca- 
 pillary vessels of the lungs form one of the points of intersection, 
 and the capillaries of all the other organs represent the other 
 point of intersection, by uniting together the arteries and veins 
 of the whole body, in the same manner as those of the lungs es- 
 tablish a communication between the veins and arteries of these 
 organs. 
 
 This division of the system of circulation into two parts, in 
 one of which there circulates a dark or venous blood, while the 
 other contains red or arterial blood, is at once more simple and 
 more accurate. As was already stated in the history of the cir- 
 culation, its organs are, in an especial manner, destined to the 
 mechanical act of conveying the fluids: the changes, the altera- 
 tions which the blood undergoes in passing through the organs, 
 are effected, only at the moment when in penetrating into their 
 tissue, it passes into the capillary vessels which are distributed 
 into them. The columns of blood are then sufficiently minute to 
 
ON THE CIRCULATION. 
 
 213 
 
 be operated upon by the vital action; till then, the columns of 
 blood are too large, and resist, by their bulk, if one may so speak, 
 any decomposition. It is, therefore, in the capillary vessels, that 
 the blood receives its essential principles; and to understand 
 how the nutritious lymph which is deposited by the thoracic duct 
 into the left subclavian vein, experiences in its course along the 
 sanguiferous system, the changes which are to assimilate it to 
 our own substance, it is necessary to follow it, along the venous 
 blood with which it unites, into the heart, through the right half 
 of which it passes in its way to the lungs, there to combine with 
 the atmospherical air, from which we are perpetually deriving 
 another aliment indispensable to life; then to examine, how, 
 when modified and conveyed with the red blood, from the 
 lungs to the whole body, it serves to the secretions, and sup- 
 plies nourishment to the whole body. 
 
 In considering, in this manner, the circulation of the blood, 
 with a reference to the changes which it undergoes in the organs 
 through which it passes, in describing that circle, we shall find, 
 that this fluid, already combined with the lymph and chyle, 
 parts, in the lungs, with some of its principles; at the same time 
 that it becomes impregnated with the vital portion of the atmos- 
 phere, which suddenly changes its colour and other qualities. 
 The blood will then be seen to flow into all the parts which it 
 stimulates, to keep up their energy, to awaken their action and 
 furnish them the materials of the fluids which they secrete, or 
 the molecules by which they grow or are repaired; so that in 
 supplying thus the different organs, the blood loses all the quali- 
 ties which it had acquired by the union of the chyle and of the 
 vital air, parts with the principles to which it owed its colour, 
 and again becomes dark, to be repaired anew by combining with 
 the lymph, and by the absorption of the vital part of the atmos- 
 pherical air; this constitutes the principal phenomenon of the 
 function, which will considered in the fourth chapter. 
 
2U 
 
 CHAPTER IV. 
 
 OF RESPIRATION. 
 
 Lxix. Of the different changes which the blood undergoes 
 in the different organs, none arc more essential or more remarka- 
 ble than those it receives from the air, which, during respiration, 
 is alternately received into the lungs and expelled from them. 
 The blood which the veins convey to the heart, and which the 
 right ventricle transmits to the lungs, is of a dark colour, and 
 heavy; its temperature is only thirtv degrees (Reaumur’s ther- 
 mometer); if laid by, it coagulates slowly, and there is separated 
 from it a considerable quantity of serum. The blood which is 
 brought by the pulmonary veins to the left side of the heart, and 
 which is conveyed to all parts of the body by means «>f the 
 arteries, is, on the contrary, of a florid red colour; it is spumous, 
 lighter, and warmer by two degrees. It likewise coagulates 
 more readily, and contains a smaller quantity of serum. All 
 these differences, which are so easily distinguished, depend on 
 the changes which it has undergone, by being in contact with 
 the atmospherical air. 
 
 LXX. Of the atmosphere. The mass of air which surrounds 
 the globe, and to which we give the name of atmosphere, bears on 
 all bodies with a pressure proportioned to their surface. That 
 of man* bears a weight of air amounting to about thirty-six 
 thousand pounds. Moreover, one of its constituent principles is 
 absolutely necessary to the keeping up of life, of which it- is a 
 principal agent. 
 
 The variations in the weight of the atmosphere have, in gene- 
 ral, but little influence on the exercise of the functions; never- 
 theless, when by ascending the tops of verj' high mountains, 
 man rises several thousand fathoms above the level of the sea, 
 the very remarkable diminution of the weight of the air, pro- 
 duces a very sensible effect. Respiration becomes laborious and 
 
 * The surface of the body is estimated at fifteen or sixteen square feet, in a 
 man of middle size. 
 
ep RF.SPraATlON. 
 
 215 
 
 panting, the pulse is quickened, and there is felt an universal 
 uneasiness, joined to excessive weakness, and hemorrhages 
 come on; these symptoms are occasioned both by the diminish- 
 ed pressure of the air, and by the smaller quantity of oxygen 
 contained in a rarer atmosphere.* 
 
 * Several travellers whose reports on the subject I have consulted, agree in 
 representing the corporeal, as well as some of the mental functions, to be very 
 strangely influenced by a rarificd condition of the atmosphere. Bi'.t the cele- 
 brated de Saussure, a writer, who unites to the profundity of philosophical re- 
 search, the polish of literary refinement, has from personal experience de- 
 scribed these affections with the most precision. To his description I shall, 
 therefore, principally adhere in the ensuing enquiry. 
 
 He states, that at a certain height above the level of the sea, there uniform- 
 ly takes place a sudden and uncommon exhaustion of the muscular power. 
 The natives of the Alps, who can climb for hours at the foot of the mountains 
 without being at all wearied, are forced to stop, and take breath every few 
 minutes, when they ascend the height of fourteen or fifteen hundred toises. 
 Those who are less accustomed to the air of the mountains are obliged to rest 
 much more frequently. So intoler.able, indeed, is the fatigue induced in this 
 situ.ation, that the person suffering it, is rendered sometimes wholly incapable 
 of motion. If he attempt to move, his legs sink under him, his heart palpitates, 
 his arteries throb, his head becomes giddy, his eyes are dazzled, and, to avoid 
 fainting, he is forced to sit down. Near the top of Mont Blanc our traveller 
 could not advance more than a few steps without stopping to respire, and on 
 the summit of it, though his exertions were moderate, he was constrained 
 frequently to desist altogether from them, and to breathe laboriously to recruit 
 his strength.* With this excessive degree of fatigue, accelerated pulse, and 
 difficult respiration, there is great thirst, sickness of stomach, a loathing of 
 food, and an aversion to every species of spirituous liquor. But what is very 
 extraordinary, these affections are as short in their duration, as they are 
 violent. 
 
 After resting a few minutes, the sense of fatigue is so completely dissipated, 
 that the person, in resuming his journey, feels such a renovation, that he is 
 persuaded he will be able to prosecute it uninterruptedly. He, however, is 
 soon disappointed. On moving a short distance only, his former inability re- 
 turns, and his progress is again arrested. An additional effect of this state of 
 the atmosphere, is an almost irresistable propensity to sleep. We are told, that 
 if the attention of the person be not engaged, and kept excited, he will, when 
 pausing to rest, often fall to sleep almost instantaneously, though annoyed by 
 the wind or cold, the light or heat of the sun, and in the most incommodious 
 
 * These effects are not peculiar to the human species. The same writer re, 
 jates, that the mules which he employed to cairy his baggage, became sud- 
 denly so weak and exhausted that they could hardly walk, even when the 
 burden was removed from their backs. They staggered as they moved; their 
 respiration was panting and difficult, and seemingly at: ended with painful sen- 
 sations of the chest, as they uttered plaintive and distressing cries. 
 
OF RESPraATION. 
 
 216 
 
 The human body resists, without any effort, the atmospherical 
 pressure, because it is applied, at all times, and in every direc- 
 tion. But if a part of its surface ceases, for a moment, to be 
 under its influence, it swells, the fluids are determined to it, in 
 
 and disagreeable posture of his body. This sleep, sometimes, approaches in 
 soundness nearly to lethargy .f 
 
 Nothing .ffords the least relief to any of the symptoms enumerated except 
 rest and cold laater. Cordials and spirituous liquors are found to aggravate all 
 the complaints. 
 
 Now, in what manner are these singular affections to be explained? AVe 
 believe with our author that they are in part owing to the diminished pressure 
 of the atmosphere, but infinitely more to a deficiency of oxygen. 
 
 It is clearly ascertained that respiration supports animal life, and all its actions. 
 This process requires the presence of two principles. These are oxygen and 
 combustible matter. The former is supplied chiefly through the medium of 
 the lungs, and the latter by the stomach. Of the vital actions, none seems to 
 be more immediately dependent and strikingly regulated by respiration than 
 the rnttscular. It is not, however, my design to dwell on the relation between 
 them. It is sufficient for my purpose to remark, that during exercise a greater 
 quantity of oxygen is extracted from the atmosphere by the lungs, and that 
 carbonic acid and water are formed, and caloric evolved in corresponding 
 proportions. Hence it may be deduced, that during muscular exertion, there 
 is a greater demand for oxygen, and a larger consumption of combustible matter 
 It also follows, if the preceding premises be admitted, as a legitimate corollan-, 
 that the same effect would be produced, namely, an exhaustion of the muscu- 
 lar vigour, by withholding the one or the other of these agents. In either case, 
 fatigue will be caused, and the body rendered incapable of muscular exertion. 
 But the incapacity in the two cases arises from different states of the system, 
 and will be distinguished by different appearances, and removed by different 
 methods of treatment. 
 
 Limited exercise in an atmosphere of sufficient density, slowly deprives the 
 body of its proper quantity of combustible matter until fatigue is finally in- 
 duced. The body is afterwards gradually recruited by rest and food, or, di- 
 rectly restored to momentary strength by the use of spirituous liquors, which 
 are pure combustible matter mixed with water. 
 
 But in the elevated regions of the atmosphere where there is a deficiency of 
 oxygen, the fatigue which comes on, is of an opposite kind. It arises from an 
 over-proportion of combustible matter, and a noant of oxvgen. Here, of course, it is 
 'alleviated by rest, and deep inspirations, and exacerbated by exercise and 
 spirituous liquors. 
 
 ■f It may also be observed, that aeronauts have generally mentioned drowsi- 
 ness as one of the consequences produced by the attenuated atmosphere of the 
 exalted regions which they explore in their excursive flights, and some have 
 even declared that they slept soimd/y, when at the utmost pitch of their peri- 
 lous adventures. ■' It 
 
OP RESPIRATION. 
 
 217 
 
 considerable quantity, the integuments become excessively dis- 
 tended, so as to be in danger of bursting; such are the pheno- 
 mena which attend the application of cupping glasses. 
 
 It is suddenly induced, because, the pulmonary system is so contrived that 
 the body at no instant receives more oxygen than what at the instant it 
 requires.* 
 
 It is speedily vemo'iedi, because, by the deep inspirations the necessary quan- 
 tity of oxygen is conveyed into the system. 
 
 It is accompanied by sickness of stomach, and loathing of food, because, di- 
 gestion, like exercise, demands a copious supply of oxygen.'\ 
 
 It is attended by excessive thirst, because, in a rare atmosphere, there will, of" 
 necessity, he a profuse evaporation from the surface of the body. 
 
 The pulsations of the heart are more numerous, because they are performed 
 less vigorously. 
 
 Not altogether dissimilar in its nature, or origin, though milder in its symp- 
 toms, and slower in its occurrence, is the fatigue occasioned by immoderate 
 exercise under the ordinary constitution of the atmosphere. In this case, we 
 observe an increased frequency of the pulse, and of respiration, &c. &c. The 
 cure likewise is by rest. Cold water is found more refreshing than spirituous 
 liquors. 
 
 There is another phenomenon connected with the present subject which de- 
 serves to he noticed. I allude to the propensity to sleep which has already been 
 remarked. This too, can only be explained by ascribing it to a deficiency of 
 oxygen. 
 
 Sleep is a suspension to all or a majority of the operations of the mind. We 
 have not, it is true, in our possession any direct evidence to prove that the 
 efforts of the intellect, like those of the body, exact a fixed and determinate 
 quantity of oxygen. We had, indeed, the promise of some experiments to 
 ascertain it by Lavoisier, in an essay, where after indicating the expenditure 
 of vital air by muscular exercise, he undertakes to show by calculation, “the 
 quantity of mechanical labour exerted by the philosopher who reflects, by the 
 man of letters who wn'fej, or the musician who composes'.” These operations, he 
 adds, though intellectual, have a certain dependance on the physical and ma- 
 
 * We are instructed by experiments that animals placed in a vessel filled 
 with oxygen, and respiring the gas in a state of purity, do not consume more 
 of it than when combined with an irrespirable gas. Thus it takes an animal 
 nearly four times as long to consume the same quantity of oxygen as atmos- 
 pheric air. 
 
 •j- There are many facts to prove that oxygen is a principal agent in diges- 
 tion and assimilation. The quantity employed in these processes seems, in 
 some degree, to be regulated by the kind of food used. An animal diet con- 
 sumes more than a vegetable one. Mr. Spalding found that when he lived 
 upon animal food, and drank spirituous liquors, he expended the oxygenous 
 portion of the atmosphere in his diving bell, in a much shorter time than when 
 he subsisted on vegetable matter and water. Dr. Beddoes has also furnished 
 some curious facts which go to establish the same conclusion. 
 
 2 E 
 
OF RESPIRATION. 
 
 218 
 
 The pressure of the air, on the surface of the globe, is neces- 
 sary to the existence of bodies in the condition in which we see 
 them. Several very volatile fluids, as alcohol and ether, would 
 become gaseous, under a less pressure of the atmosphere; water 
 would boil, under eighty degrees of temperature (Reaumur’s 
 scale); solid bodies themselves might become fluid. In a word, 
 a considerable diminution in the weight of the atmosphere would 
 have absolutely the same effect, as raising its temperature to a 
 very great height, which, changing the face of the universe, 
 would convert all liquids into elastic fluids, and would, doubt- 
 less, melt all solid bodies. 
 
 The variations in the weight of the atmosphere, distinguish- 
 able by the barometer, are of very little importance to the phy- 
 siologist, and I might even add to the physician, notwithstanding 
 the minute attention with which some writers note the state of 
 the barometer, of the thermometer and hygrometer, and of the 
 electrical state of the atmosphere, in giving an account of a dis- 
 ease or of an experiment, on which the above circumstances 
 have no apparent or certain influence. The atmosphere, like 
 every other fluid, has a perpetual tendency to a state of equili- 
 brium; hence the rush of air into the lungs, or into other situa- 
 
 tei-ial part of man, which renders them susceptible of comparison with the 
 labours of the mechanic. 
 
 Whether these views be as just as they are brilliant, I shall not pretend to 
 decide. But, thoucjh we may never be competent to determine with much 
 accuracy the quantity of oxygen consumed by the operations of the mind, yet, 
 that it is essentially necessai’y to the exertion of the intellectual faculties is 
 sufficiently probable. 
 
 With respect to the influence of a subtraction of oxygen in the production of 
 sleep, a few facts will be sufficient to attest it. 
 
 In the first place, we know, that the primary operation of all the irrespirable 
 gases, andtAeje contain 710 oxygen, 'i% productive of heaviness and sleep. 
 
 Sleep is apt, moreover, to occur during the process of digestion, when the 
 oxygen of the system is employed, in a considerable degree, in the assimilation 
 of aliment, and the elaboration of chyle; or, if the disposition to sleep be coun- 
 teracted, the senses, at least, become more dull, and the understanding less 
 acute and energetic. 
 
 The production of sleep is favoured too, as has been proved, by external 
 warmth, which lessens the supply of o.xygen. 
 
 It is from the combination of these causes, that among the inhabitants of 
 hot climates, the custom of sleeping during the day', and especially after eating, 
 universally prevails. We must acknowledge that the outline of this theory was 
 derived from the Lectures of Mr. Allen, of Edinburgh, on Physiology. — E d. 
 
OF RESPIRATION. 
 
 219 
 
 tions in which its quantity is diminished, by the combinations 
 which it forms, or by the effects of heat, which renders it lighter 
 by rarefaction: the same principle explains the formation of the 
 trade and other winds. 
 
 The atmospherical air combines with water and dissolves it, 
 as the latter dissolves saline substances. In this consists the 
 process of evaporation. The air becomes saturated with water 
 in the same manner as water becomes saturated with salt, to 
 such a degree as to be incapable of holding a greater quantity 
 in solution. As its temperature rises its solvent power in- 
 creases, and the latter diminishes as it grows cold; variations of 
 temperature produce the same effect on solutions of salts in 
 liquids. The formation of all the aqueous meteors, depends on 
 the different conditions of the solvent powers of the atmosphere; 
 when considerable, the atmosphere is warm and dry and the air 
 serene; clouds form when it is saturated; dews, fogs, and rain, 
 are the consequence of a diminution of its solvent power, as 
 snow and hail, of a degree of cold which precipitates the fluid. 
 The different degrees of dryness or moisture, marked by the 
 hygrometer, only sensibly affect the human body, when it has 
 been exposed for a considerable time to its influence. 
 
 Chemically considered, the atmospherical air, which was long 
 regarded as a simple body, is composed of about 0,27 of oxygen, 
 0,73 of azote, and of 0,01 or 0,02 of carbonic acid. The propor- 
 tions of oxygen, according to Humboldt, vary from 0,23, to 
 0,29; that of azote is almost always the same; carbonic acid is 
 the more abundant, as the air is less pure.* This part of natu- 
 
 * This is pretty nearly the original estimate of Lavoisier, whose experi- 
 ments have since been very frequently repeated, and with no material differ- 
 ence in the results. It is however proper to recollect in speaking of the rela- 
 tive proportion of the ingredients of the atmosphere, that this estimate must 
 be considered as having reference to weight and not to measure. On this point 
 Lavoisier is silent, as well as most other chemical writers. It is nevertheless 
 a fact, as has been more particularly shown by Bertholet, that the atmosphere 
 contains only twenty-two parts of oxygen, in the hundred, by measure. 
 
 By some chemists it has been supposed, from the circumstance of the cal’- 
 bonic acid being generally found in a larger quantity near the earth, that it is 
 an accidental, and not an essential constituent of the atmosphere. But by De 
 Saussure it was detected in the air, on the summit of Mont Blanc; and from 
 this, and a variety of other considerations, it would appear to be a uniform 
 part of atmospheric air, existing most probably in a state of chemical com. 
 bination, — Ed. 
 
»P RESPIRATION. 
 
 220 
 
 ral philosophy, which is called eudiometry, or the measurement 
 of the purity of the air, is far from accomplishing what its name 
 indicates, and has disappointed the hopes which had been enter- 
 tained on the subject. Eudiometrical instruments can inform us 
 only of the proportion of oxygen contained in the atmosphere; 
 now its salubrity, its fitness for respiration, is not in proportion 
 to the quantity of oxygen. The volatilized remains of putrid 
 animal or vegetable substances, various mephitic gases, combine 
 with it, and affect its purity. In the comparative analysis of air 
 procured on the Alps and in the marshes of Lombardy, there 
 was found in each the same quantity of oxygen; and yet those 
 who breathe the former enjoy robust health, while the inhabi- 
 tants of the marshy plains of Lombardy are carried oflF by epi- 
 demic diseases, are pale, emaciated, and habitually lead a languid 
 existence. 
 
 Though at least 0,20 of oxygen are necessary to render the 
 air fit for respiration, the proportion may be diminished to seven 
 or eight parts in the hundred; but in such cases the breathing is 
 laborious, panting, and attended with a sense of suffocation; in 
 short, asphyxia comes on even while the air still contains a cer- 
 tain quantity of oxygen, of which the lungs cannot entirely 
 deprive it. Whenever a number of persons are collected in a 
 confined place, in which the air cannot be easily renewed, the 
 quantity of oxygen diminishes rapidly, that of carbonic acid 
 increases. The latter, in consequence of its specific gravity, sinks 
 to the lowest part, and strikes with death every living being 
 which it envelops. When two lighted candles of different 
 lengths are placed under the same bell, the shorter candle goes 
 out first, because the carbonic acid formed during combustion, 
 sinks to the most depending part. For the same reason the pit 
 is the most unhealthy part of a play-house, when a great number 
 of people, after remaining in it for several hours, have deprived 
 the air of a considerable portion of its oxygen. 
 
 Persons collected together, and enclosed in a small space, 
 injure each other, not only by depriving the atmosphere of its 
 respirable element, but particularly by altering its composi- 
 tion by the combination of all the substances exhaled from 
 their bodies. These volatilized animal emanations become pu- 
 trid while in the atmosphere, and conveyed to the lungs during 
 
/ 
 
 OF RESPIRATION. 221 
 
 respiration, become the germ of the most fatal diseases. It is ia 
 this manner that the jail and hospital fever, so fatal to almost all 
 whom it attacks, arises and spreads. A dry and temperate air, 
 containing 0,27 of oxygen and 0,73 of azote, and free of other 
 gases or other volatilized substances, is the fittest for respira- 
 tion. In certain cases of disease, however, this function is most 
 freely performed in a less pure air. Thus patients labouring 
 under pulmonary consumption, prefer the thick and damp air 
 of low situations to the sharp and dry air of mountains; nervous 
 women prefer that in which horn, feathers, or other animal sub- 
 stances are burning. An atmosphere highly electrical, at the 
 approach of a storm, renders respiration very laborious in some 
 cases of asthma. In short, the qualities of the air must be suit- 
 ed to the condition of the vital power in the lungs, as those of 
 the food to the sensibility of the stomach. 
 
 Being obliged, on this subject, to content myself with the un- 
 gracious office of compiler, I hasten to bring this article to a 
 close, and to refer the reader for a fuller account of the air, con- 
 sidered in its physical and chemical relations, to the works of 
 M. M. Fourcroy, Hauy, Brisson, &c. to that of M. Guyton 
 Morveau on the method of purifying the air, when from different 
 combinations it is become unfit for respiration. 
 
 LXXI. In man and in all warm-blooded animals, with a 
 heart containing two auricles and two ventricles, the blood 
 which has been conveyed to all the organs by the arteries, and 
 which has been brought back by the veins to the heart, cannot 
 return to it, without having previously passed through the lungs, 
 which are viscera destined to the transmission of air; of a spun- 
 gy texture, and through which the blood must, of necessity, cir- 
 culate, to get from the right to the left cavities of the heart. This 
 course of the blood constitutes the pulmonary or lesser circula- 
 tion: it does not exist in some cold-blooded animals. In reptiles, 
 for instance, the heart has but one auricle and one ventricle; 
 the pulmonary artery, in them, arises from the aorta and con- 
 veys but a small proportion of the blood; hence the habitual 
 temperature of these animals is much lower than that of man. 
 For the same reason too, there exists so small a difference be- 
 tween their venous and arterial blood; the quantity of fluid vivi- 
 fied by exposure to the air, in the pulmonary tissue, being too 
 
OF RESPIRATION. 
 
 222 
 
 small to effect, by its union with the general mass, a material 
 change on its qualities. 
 
 Mayow has given the most accurate notion of the respiratory 
 organ, by comparing it to a pair of bellows containing an empty 
 bladder, the neck of which, by being adapted to that of the bel- 
 lows, should admit air on drawing asunder its sides. The air, in 
 fact, enters the lungs only when the chest dilates and enlarges, 
 by the separation of its parietes. The agents of respiration are, 
 therefore, the muscles which move the parietes of the chest, 
 these are formed of osseous and soft parts, in such a manner, as 
 to possess a solidity proportioned to the importance of the or- 
 gans which the chest contains, besides a capacity of motion re- 
 quired to carry on the functions intrusted to them. 
 
 To carry on respiration, which may be defined the alternate 
 ingress of air into the lungs, and its egress from those organs, it 
 is necessary that the dimensions of the chest should be enlarged 
 (this active dilatation of the cavity of the chest is called inspi- 
 ration), and that it should contract to expel the air which it had 
 received during the first process. This second action is called 
 expiration, it is always of shorter duration than the former, its 
 agents are more mechanical, and the muscles have much less in- 
 fluence upon it. 
 
 The parietes of the chest are formed, at the back part, by the 
 vertebral column, at the fore part by the sternum, and on the 
 sides by the ribs which are osseo-cartilaginous arches, situated 
 obliquely between the vertebral column which is fixed and be- 
 comes the point of support of their motions, and the sternum 
 which is somewhat moveable — the spaces between the ribs are 
 filled by muscular planes of inconsiderable thickness, the inter- 
 nal and external intercostal muscles, the fibres of which lie in 
 opposite directions. — Besides, several muscles cover the outer 
 part of the thorax, and pass from the ribs to the neighbouring 
 bones: as the subclavian muscles, the great and lesser pectorals, 
 the serrati, the latissimi dorsi, the scaleni, the longissimi dorsi, 
 the sacro lumbales, and the serrati minores, posterior, superior, 
 and inferior. But of all the muscles which form the anterior, pos- 
 terior, and lateral parietes of the chest, the most important is the 
 diaphragm, a fleshy and tendinous partition, lying horizontally 
 between the chest and the abdomen, which it divides from each 
 
OF RESPIRATION, 
 
 223 
 
 Other; it is attached to the cartilages of the false ribs, and to the 
 lumbar vertebrae, and has three openings to transmit the oesopha- 
 gus and the vessels which pass from the abdomen to the chest, 
 or from the latter into the abdomen. 
 
 In health, the chest dilates only by the descent of the dia- 
 phragm. The curved fibres of that muscle, straightened in con- 
 traction, descend towards the abdomen, and compress the vis- 
 cera. The descent of the viscera thrusts forward the anterior pa- 
 rietes of that cavity, and these recede, when on expiration taking 
 place after inspiration, the diaphragm now relaxed, rises, press- 
 ed upward by the abdominal viscera, compressed themselves by 
 the large muscles of the abdomen. But when it is necessary to 
 take into the chest a great quantity of air, it is not sufficient that 
 it should be enlarged merely by the descent of the diaphragm, 
 it is required besides, that its dimensions should be increased in 
 every direction. The intercostal muscles then contract, and 
 tend to bring together the ribs between which they are situated. 
 The intercostal spaces, however, become wider, especially at 
 their anterior part, for whenever lines falling obliquely on a ver- 
 tical line, change their direction, approaching to a right angle, 
 the intermediate spaces receive the greater increase, as the lines, 
 more oblique at first, become at last more nearly horizontal. Be- 
 sides, as the ribs are curved in the course of their length, in two 
 directions, and both in the direction of their faces, and edgewise, 
 the convexity of the first curvature is outwards, the ribs recede 
 to a distance from the axis of the chest, whose cavity is en- 
 larged transversely, while the second curvature (in the direc- 
 tion of their edge) being increased by a real twisting of these 
 bones, and which reaches to the cartilaginous parts, the sternum 
 is heaved forward and upward, so that the posterior extremity 
 of the ribs is removed from their sternal end. But as the ribs are 
 not all equally moveable, as the first is almost always invariably 
 fixed, and as the others are moveable in proportion to their 
 length, the sternum is tilted in such a way that the lowermost 
 extremity is thrust forward. The diameter of the chest from the 
 fore to the back part increases, therefore, as well as the trans- 
 verse diameter. This increase of dimensions has been estimated 
 at two inches to each of these diameters; the dimensions of the 
 
OP RESPIRATIOy. 
 
 224 
 
 vertical diameter, which are regulated by the depression of the 
 of the diaphragm, are much greater. 
 
 LXXII. Professor Sabatier, in his memoir on the motion of 
 the ribs, and on the action of the intercostal muscles, maintains, 
 that during the act of inspiration, the upper ribs alone rise, that 
 the lower ribs descend and slightly close on the chest, while the 
 middle ribs project outwardly; and that in expiration, the former 
 set of ribs descend, that the latter start a little outwardly, and 
 that the middle set encroach on the cavity of the chest. The 
 learned Professor adds, that the cartilaginous articulating sur- 
 faces, by which the ribs are connected to the transverse pro- 
 cesses of the vertebrse, appear to him to favour these different 
 motions, as the direction of the articulations of upper ribs, is 
 upwarct, and that of the lower, downward; but on considering 
 the subject with attention, it will be seen, that the surfaces by 
 which the transverse processes of the vertebrse are articulated to 
 the tuberosities of the ribs, are turned directly forward in the 
 greatest number, some of the lower ribs are, at the same time, 
 directed slightly upward. If we examine the action of the bones 
 of the chest, during inspiration, in a very thin person, for exam- 
 ple, in phthisical patients, whose bones are covered with little 
 else than skin, we shall find, that all the ribs rise and are carried 
 somewhat outwardly. It is not easy to conceive how the inter- 
 costal muscles, which Professor Sabatier considers as the agents 
 of expiration, should elevate the upper ribs and depress the 
 lower. The diaphragm, whose circumference is inserted in the 
 latter, might, by its contraction, produce this effect; but as the in- 
 tercostals have their fixed point of action in the upjjer ribs, they 
 oppose and neutralize this effort, and all the ribs are elevated at 
 once. If this were not the case, the ribs ought to be depressed 
 whenever the intercostals contract, since the lowermost, fixed by 
 the diaphragm, would become the fixed point on which all the 
 others should move. 
 
 As the fibres of the external and internal intercostal muscles 
 are in direct opposition to each other, those of the former set of 
 muscles having an oblique direction from above downward, and 
 from behind forward, and crossing the fibres of the other set 
 whose obliquity is in a different direction; several physiologists 
 have thought, that these muscles were opposed to each other. 
 
OF RESPIRATION. 
 
 225 
 
 that the internal intercostal muscles brought together the ribs, 
 after they had been separated by the external intercostals, the 
 one set being muscles of expiration, while the other set con- 
 tracted during inspiration. 
 
 It is well known with what pertinacity Hamberger, in other 
 respects a physiologist of considerable merit, defended this 
 "erroneous opinion, in his dispute with Haller; it is now, how- 
 ever, ascertained, that all the intercostal muscles concur in di- 
 lating the chest, and that they ought to be ranked among the 
 agents of inspiration, because the tjnequal capacity of motion in 
 the ribs, prevents the internal intercostals, the lower insertion of 
 which is nearer to the articulation of these bones to the vertebrae, 
 from depressing the upper ribs. Of the very conclusive experi- 
 ments by which Haller undertook to refute the arguments of his 
 adversary, I shall relate only that which is performed by strip- 
 ping the parietes of the chest, in a living animal, of all the mus- 
 cles which cover it, and by removing, in different parts of the 
 thorax, some of the external intercostal muscles. The internal 
 intercostals are then seen to contract during inspiration, to- 
 gether with the remaining external intercostals. These muscles, 
 therefore, have a common action, and are not in opposition to 
 each other. The same experiment serves to prove the increased 
 dimensions of the space between the ribs. On holding one’s 
 finger between two of the ribs, it feels less confined, when during 
 inspiration, these bones rise and thrust forward the sternum. 
 
 This question being at rest, although in the pursuit of science 
 one should inquire how things are effected, and not wherefore 
 they come to pass, one feels naturally desirous to know what 
 purpose is answered by the different direction of the fibres of 
 the two sets of intercostal muscles; and with what view Nature 
 has departed from her wonted simplicity, in giving to their 
 fibres opposite directions. In answer to this one may observe, 
 that the action of powers applied obliquely to a lever, being de- 
 composed in consequence of that obliquity, a part of the action 
 of the external intercostals would tend to draw the ribs towards 
 the vertebral column, which could not happen without forcing 
 back the sternum, if the internal intercostals did not tend to 
 bring forward the ribs, at the same time that they elevate them; 
 so that these fwo muscular planes, united in their action of 
 
 2 F 
 
OF RESPIRATION. 
 
 226 
 
 raising the ribs, antagonize and reciprocally neutralize each 
 other in the effort by which they tend to draw them in different 
 directions. 
 
 To this advantage of mutually correcting the effects that 
 would result from their respective obliquity, may be added the 
 benefit arising from a texture capable of a greater resistance; it 
 is clearly obvious that a tissue whose threads cross each other, 
 is firmer than one in which all the threads, merely in juxta posi- 
 tion or united by means of another substance, should all lie in 
 the same direction. Hence Nature has adopted this arrange- 
 ment in the formation of the muscular planes constituting the 
 anterior and lateral parietes of the abdomen, without which the 
 abdominal viscera would frequently have formed herniary tu- 
 mours by separating the fibres, and getting engaged between 
 them. In this respect, one may compare the tissue of the abdo- 
 minal parietes, in which the fibres of the external and internal 
 oblique muscles, which cross each other, are themselves crossed 
 by the fibres of the transversales, to the tissue of those stuffs 
 whose threads cross each other, or rather to wicker work, to 
 which basket-makers give so much strength, by interweaving the 
 osier in a variety of directions. 
 
 LXXIII. When from any cause respiration becomes diflS- 
 cult, and the diaphragm is prevented from descending towards 
 the abdomen, or the motion of inspiration impeded, in any way, 
 the intercostals are not alone employed in dilating the chest, 
 but are assisted by several other auxiliary muscles; the scaleni, 
 the subclavii, the pectorals, the serrati magni, and the latissimi 
 dorsi, by contracting elevate the ribs, and increase, in more di- 
 rections than one, the diameter of the chest. The fixed point of 
 these muscles then becomes their moveable point, the cervical 
 column, the clavicle, the scapula, and the humerus, being kept 
 fixed by other powers, which it is unnecessary to enumerate. 
 Whoever witnesses a fit of convulsive asthma, or of a suffocating 
 cough, will readily understand the importance and action of these 
 auxiliary muscles. 
 
 Inspiration is truly a state of action, an eflPort of contractile 
 organs, which must cease when these are relaxed. The expira- 
 tion which follows is passive, and assisted by very few muscles, 
 and depends chiefly on the re-action of the elastic parts entering 
 
OF RESPIRATION, 
 
 227 
 
 into the structure of the parietes of the chest. We have seen 
 that the cartilages of the ribs are pretty considerably twisted, 
 so as to carry outward and downward their upper edge: when 
 the cause which occasions this twisting ceases to act, these parts 
 return to their natural condition, and bring back the sternum 
 towards the vertebral column, towards which the ribs descend, 
 from their weight. The diaphragm is forced towards the chest 
 by the abdominal viscera, which are compressed by the broad 
 muscles of the abdomen. 
 
 In every effort of expiration, as in cough and vomiting, these 
 muscles re-act, not merely by their own elasticity, but they 
 besides contract and tend to approach towards the vertebral 
 column, by pressing upwards the abdominal viscera towards the 
 chest. The triangularis sterni, the subcostales, and the serratus 
 inferior posticus, may likewise be ranked among the agents of 
 expiration; but they appear to be seldom employed, and to be 
 too slender and weak to contribute much to the contraction of 
 the chest. 
 
 LXXIV. When the chest enlarges, the lungs dilate and fol- 
 low its parietes, as these recede from each other. These two 
 viscera, soft, spungy, and of less specific gravity than water, 
 covered by the pleura which is reflected over them, are always 
 in contact with the portion of that membrane which lines the 
 cavity of the thorax; no air is interposed between their surfaces 
 (which are habitually moistened by a serous fluid exuding from 
 the pleura) and that membrane, as may be seen by opening, 
 under water, the body of a living animal, when no air will be 
 seen to escape. As the lungs dilate, their vessels expand, and 
 the blood circulates through them more freely; the air contain- 
 ed in the innumerable cells of their tissue becomes ratified, in 
 proportion as the space in which it is contained is enlarged. 
 Besides, the warmth communicated to it by the surrounding 
 parts, enables it, in a very imperfect manner, to resist the pres- 
 sure of the atmosphere, rushing through the nostrils and mouth 
 into the lungs, by the opening in the larynx which is always per- 
 vious, except during deglutition. 
 
 LX XV. The pulmonary tissue into which the air isthus dra^vn 
 in, every time the capacity of the chest is increased, does not 
 consist merely of air-vessels, which are but branches of different 
 
OF RESPIRATION. 
 
 228 
 
 sizes of the two principal divisions of the trachea, but is formed 
 likewise by the lobular tissue into which those canals deposit 
 the air; it contains also a great quantity of lymphatics and blood 
 vessels, of glands and nerves. Cellular tissue unites together all 
 these parts, and forms them into two masses covered over by 
 the pleura, and of nearly the same bulk,'^*= suspended in the chest 
 from the bronchise and trachea, and every where in contact with 
 the parietes of the cavities of the chest, except towards their 
 root, at which they receive all their nerves and vessels. 
 
 The pulmonary artery arises from the base of the light ventri- 
 cle, and divides into two arteries, one to each lung. On reaching 
 the substance of these viscera, these vessels divide into as many 
 branches as there are principal lobes. From these branches there 
 arise others, which again subdivide into lesser ones, until they 
 become capillary, and continuous with the radicles of the pul- 
 monary veins. 
 
 These vessels, formed from the extremities of the aitery, 
 unite into trunks, which progressively enlarging, emerge from 
 the lungs, and open, four in number, into the left auricle. Be- 
 sides these large vessels, by means of which the cavities in both 
 sides of the heart communicate together, the lungs receive from 
 the aorta two or three arteries called bronchial arteries: these 
 penetrate into their tissue, and follow the direction of the other 
 vessels, and terminate in the bronchial veins, which open in the 
 superior cava, not far from its termination into the right auricle. 
 These bronchial vessels are sufficient for the nourishment of the 
 pulmonary organ, which, in reality, is not near so bulky as it 
 appears, as may be ascertained by examining the lungs, after all 
 the air has been extracted from them, by means of an air pump 
 applied to the trachea. 
 
 Physiologists, for the most part, consider the bronchial arte- 
 ries as the nutritious vessels of the lungs. They assert, that as 
 the blood which flows along the branches of the pulmonary- 
 artery resembles venous blood, it is unfit for the nutrition of the 
 lungs, and that it was necessary that these organs should be 
 supplied by arteries arising from the aorta, and containing blood 
 
 • It is well known tliat tlie right lung- is larger than the left, that it is divided 
 into three principal lobes, while the latter has only two. 
 
OF RESPIRATION. 
 
 229 
 
 analogous to that which is sent to every part of the body. But 
 though it be admitted, that this venous blood, brought from 
 every part of the body, and sent into the lungs by their principal 
 artery, may not be fit to maintain the organ in its natural eco- 
 nomy, this blood is fit for that use, when after being made hot, 
 spumous, and florid by the absorption of the atmospherical 
 oxygen, it returns by the pulmonary veins into the left cavities 
 of the heart.* 
 
 Some have thought that the blood which flows in the bron- 
 chial vessels, exposed to the action of the air, like the portion 
 of this fluid which traverses the pulmonary system, lost nothing 
 of its arterial qualities; and that, poured by the bronchial veins 
 into the superior or descending vena cava, it was a necessary 
 stimulus for the right cavities of the heart, of which blood en- 
 tirely dark and venous would not have awakened the contrac- 
 tility. But even if the experiments of Goodwin had not proved 
 that the parietes of these cavities have a sensibility relative to 
 dark blood, by virtue of which this stimulus is sufiicient to deter- 
 mine their contraction, the action of the heart does not depend so 
 closely as has been said on the impression of the blood on its sub- 
 stance, since it contracts though empty, and prolongs its contrac- 
 tions to relieve itself of the black blood which fills it, when an 
 animal dies of asphyxia. 
 
 Bocrhaave, who admitted one sort of peripneumony depend- 
 ing on the obstruction of the bronchial vessels, whilst another, 
 according to the same writer, depends on the obstruction of the 
 pulmonary vessels, seems to justify, in some measure, the re- 
 proach, exaggerated unquestionably, which some authors have 
 thrown out against anatomy, 'of having rather retarded than 
 accelerated the progress of the Hippocratic practice of medi- 
 
 * That tlie bronchial vessels exclusively nourish the lungs. Is an opinion, 
 entertained certainly by a majority of physiologists. When, however, we 
 compare the size of these vesssels with the magnitude of the office assigned 
 to them, it seems very doubtful whether they are adequate to it. We are in- 
 clined to believe, notwithstanding what is alleged against it, that the pulmo- 
 nary arteries also contribute to the nourishment of the lung.s; and Indeed there 
 is a fact which almost proves it. We allude to the circumstance of the pulmo- 
 nic adhesions, which are supposed to take place in consequence of inflainma- 
 mation, having been repeatedly injected from the trunk of the pulmonary 
 arteries. — Ed. 
 
OF RESPIRATION. 
 
 230 
 
 cine. The anatomical analysis of the lungs, or the distinction of 
 the tissues which enter into their composition, furnishes juster 
 ideas on the difference of the inflammations by which they may 
 be attacked. It has been seen, that of these pulmonary phleg- 
 masias, the commonest and least serious catarrh consists in 
 inflammation of the mucous membrane which lines the air pas- 
 sages, whilst the real peripneumony has its seat in the paren- 
 chyma of the organ, which it converts into a hard and compact 
 mass. It is this state that anatomists have long designated under 
 the name of hepatization^ because, in fact, the substance of the 
 lung has acquired the hardness, the weight, and something of 
 the appearance of the liver. The same anatomical researches 
 have shown that pleurisy consists in inflammation of the pleura, 
 and of the surface of the lung; an inflammation which some- 
 times leaves no trace, but which oftener exhibits, on the opening 
 of bodies, the pleura thickened and opaque, covered with a 
 layer of coagulable lymph, whitish, more or less thick, or even 
 adhering to the lung.* 
 
 There arise from the surface and from the internal substance 
 of the lungs, a prodigious number of absorbents, which may be 
 divided into superficial and deep seated. The latter accompany 
 the bronchial tubes and penetrate into the substance of the glan- 
 dular bodies situated where those air vessels divide, but col- 
 
 * These adhesions of the lung to the pleura costalis are so common, that 
 the old anatomists considered them as a natural disposition, and called them 
 ligaments of the lungs. It has been believed till now, that these adhesions 
 arose from the organization of a substance transuding from the two surfaces 
 Numerous dissections have convinced me, that in all the points where they 
 are met with, the pleura has disappeared, that it is decomposed, and that 
 whether it be at the surface of the lungs, or within the ribs and their mus- 
 cles, it is produced by the act of inflammation, that it is become cellular 
 by the thinning of its tissue and the separation of its lamlnse. The pleura thus 
 reduced to cellular tissue, the adhesion is produced by the first intention, in 
 the same way as in simple wounds immediately united. There is no organ that 
 abounds more than the lungs in facts important to morbid anatomy. The 
 variety of appearances they exhibit, on the opening of bodies, are almost innu- 
 merable; and to give one instance, the pleura appears after pleurisy in five 
 perfectly distinct conditions. 1st. In its natural state, when the disease being 
 incipient and slight, the resolution is effected .at the moment of death. — 2dly. 
 When it is red, thickened, and opake: — 3dly. When it is covered with coagu- 
 lable lymph: — 4lhly. When it adheres: — 5thly. When, in consequence of 
 chronic inflamipation, hydrothorax has taken place, &c. &c. 
 
OF RESPIRATION. 
 
 231 
 
 lected, in greatest number, towards the root of the lungs and at 
 the angle formed by the bifurcation of the trachea. These bron- 
 chial glands, belonging to the lymphatic system, do not differ 
 from the glands of the same kind, and are remarkable only by 
 their number, their size, and their habitually darkish colour. 
 The absorbents of the lungs, after ramifying in these glands, ter- 
 minate in the upper part of the thoracic duct, at the distance of 
 a few inches from its termination into the subclavian vein. 
 Lastly, the lungs, though endowed with a very imperfect degree 
 of sensibility, have a pretty considerable number of nerves fur- 
 nished by the great sympathetic, and especially by the eighth 
 pair. 
 
 It was long believed, on the authority of Willis, that the aerial 
 tissue of the lungs is vesicular, that each ramification of the 
 bronchiae terminated in their substance, in the form of a small 
 ampullula; but at present, most anatomists adopt the opinion of 
 Helvetius, according to whom every air-vessel terminates in a 
 small lobe, or kind of spunge fitted for the reception of air and 
 formed of a number of cells communicating together. These 
 lobes, united by cellular tissue, form larger lobes, and these to- 
 gether form the mass of the lungs. 
 
 The tissue that connects together the different lobes, is very 
 different from that in which the ramifications of the bronchiae ter- 
 minate; air never penetrates in it, except when the tissue of the 
 air cells is ruptured. On such occasions, which are not of rare 
 occurrence, on account of the excessive thinness of the laminae 
 of the air cells of that tissue, the lung loses its form, and be- 
 comes emphysematous. Haller estimates at about the thousandth 
 part of an inch, the thickness of the parietes of the air cells, and 
 as the extreme ramifications of the pulmonary vessels are distri- 
 buted on these parietes, the blood is almost in immediate con- 
 tact with the air. There can be no doubt, that the oxygen of the 
 atmosphere acts on the blood, under such circumstances, since 
 it alters its qualities and communicates to it a florid red colour, 
 when inclosed in a pig’s bladder and placed under a vessel filled 
 with oxygen gas. 
 
 LXXVI. Every time the chest dilates, in an adult, there enter 
 into the lungs between thirty and forty cubic inches of atmos- 
 
OP RESPIRATION. 
 
 232 
 
 pherical air.^ When the air has been exposed, for a few mo- 
 ments, in the pulmonary tissue, it is expelled by the effort of ex- 
 piration, but it is diminished in quantity and is reduced to 
 thirty-eight inches. Its composition is no longer the same, it con- 
 tains, it is true, 0,73 of azote, but the vital portion fit for respi- 
 ration, the oxygen, has undergone a great diminution, its pro- 
 portion is only 0 , 14 : carbonic acid forms the remaining thirteen 
 hundredths, and there are sometimes found one or two parts of 
 hydrogen. It is besides affected by the addition of an aqueous 
 vapour, which is condensed in cold weather, as it escapes at the 
 mouth and nostrils. It is called the humour of the pulmonary 
 transpiration. These changes, compared to those which the 
 blood experiences in passing through the lungs, clearly xhow a 
 reciprocal action of this fluid and of the oxvgen of the atmos- 
 phere. The dark venous blood which coagulates slowly and 
 which then disengages a considerable quantity of serum abound- 
 ing in hydrogen and carbon, and of a temperature of only thirty 
 degrees, yields its hydrogen and carbon to the oxygen of the at- 
 mosphere, to form carbonic acid and the pulmonary vapour: and 
 as oxygen cannot enter into these new combinations, without 
 parting with a portion of the caloric which keeps it in a state of 
 gas, the blood acquires this warmth, which is disengaged the 
 more readily, according to the ingenious experiments of Craw- 
 ford, as by parting vvith its h}’drogen and carbon, its capacity for 
 caloric increases in the proportion of 10 : 11 . 5 . 
 
 * Some ph3 siologists think that the quantity of air inspired is much less con- 
 siderable. Professor Gregory, of Edinburgh, states, in his public lectures, that 
 scarcely two Inches of air enter into the lungs, at each inspiration. It may be 
 proved, however, that this calculation is inaccurate; either by drawing a full 
 inspiration, as was done by Ma3’ow, at the expense of a certain quantit3' of .air 
 contained in a bladder, or by breathing into a vessel connected with a pneuma- 
 tic apparatus, the air taken in by draw'ing a deep inspiration. Or else one 
 may inflate the lungs of a dead body, by adapting to the trachea a stop-cock 
 connected with a curved tube to receive the air under a vessel of the same ap- 
 paratus. Various means have been emplo3'ed to measure the capacity of the 
 chest. Boerhaave placed a man in a tub containing water above his shoulders, 
 Ite then made him take a deep inspiration, and measured the height at which 
 the fluid rose from the dilatation of the chest. Keill injected w'ater into the 
 chest of a dead body. Lastly, it has been proposed to inject the bronchial tubes 
 and the lobular tissue into which they terminate, with fusible metal consisting 
 of eight parts of pewter, five of lead, three of bismuth, to which may be added 
 one of mercury. 
 
OF RESPIRATION. 
 
 233 
 
 In parting with its carbon which, by uniting with oxygen, 
 forms the carbonic acid that is thrown out during expiration, the 
 blood loses its" dark and nearly purple colour, and becomes of a 
 florid red, and its consistence increases from the escape of its 
 hydrogen and of its aqueous parts. Besides, as it absorbs a cer- 
 ' tain quantity of oxygen, it becomes spumous and light; its con- 
 crescibility and plasticity increase, and on coagulating, there is 
 separated from it a smaller quantity of serum. 
 
 After parting with its hydrogen and carbon, and combining 
 with oxygen and caloric, in its passage through the lungs, the 
 blood, which is become arterial, parts with these two principles, 
 in proportion as in receding from the heart, it forms new combi- 
 nations, and is converted into oxides of hydrogen and carbon, 
 which, on receiving an additional quantity of oxygen, are 
 changed into water and carbonic acid, when on being carried 
 along with the venous blood. into the pulmonary tissue, they are 
 exposed to the influence of the atmospherical air. 
 
 The arterial blood becomes venous by yielding its oxygen, 
 when any cause whatever suspends or slackens its course, as is 
 proved by the following experiment of John Hunter. He tied 
 the carotid artery of a dog, with ligatures placed at the distance 
 of about four inches from each other; the blood contained in the 
 portion of artery included between the two ligatures, on laying 
 open this part of the vessel, at the end of a few hours, was found 
 coagulated and as dark as that in the veins. The blood contain- 
 ed in an aneurismal sac, and which is frequently found in a fluid 
 state, when the internal coats of the artery are but lately rup- 
 tured, becpmes venous after remaining in it some time. The 
 changes, however, which the blood undergoes in its course 
 through the arterial system, are not very remarkable, owing to 
 the rapidity with which it flows along those vessels; there is less 
 difference between the blood contained in an artery near the 
 heart, and that contained in an artery at a distance from that 
 organ, than in the blood taken from the veins near their extre- 
 mities, and from the great trunks which deposit it into the right 
 auricle. The blood in the small veins resembles arterial blood, 
 and frequently in a vpry copious bleeding the colour of the 
 blood, which, at first, is very dark, gradually becomes less dark, 
 till towards the end of the bleeding it shows nearly the same 
 
 2 G 
 
OP' RESPIRATION. 
 
 234 
 
 qualities as if arterial; a phenomenon which, as is well observed 
 by the English writer already quoted, depends on the more easy 
 and rapid flow of the blood of the arteries into the veins, in con- 
 sequence of the evacuation of the venous system. This observa- 
 tion is a complete refutation of the assertion of Bellini, who 
 maintains, that when a vein is wounded, the blood which comes 
 from it forms a double current which flows out at the wound. 
 The above opinion is maintained by highly distinguished phy- 
 siologists, as Haller and Spallanzani, who support it by experi- 
 ments performed on the vessels of cold-blooded animals or on 
 veins without valves. In bleeding at the bend of the arm, the 
 blood cannot come from that part of the vessel which is above 
 the wound: the valves oppose insuperable obstacles to its retro- 
 grade flow, hence it is very easy to distinguish the red blood 
 which comes from the lower extremity of the vein, from that 
 which flows from the upper end, and which is poured into the 
 vessel by the veins which open into it, between the puncture and 
 the nearest valve. 
 
 In its course to the parts among which the arteries are distri- 
 buted, the blood, vivified in its passage through the lungs, and 
 fitted, as M. Fourcroy says, for a new life, loses its oxygen and 
 caloric. Its capacity for the latter, diminishes, in proportion as 
 the oxygen, by combining with hydrogen and carbon, restores it 
 to the venous state. 
 
 This theory of the process by which the blood parts with its 
 oxygen, in its progress along the blood-vessels, is rendered still 
 more probable, by recent discoveries on the nature of the dia- 
 mond. This substance is the only pure carbon, and that which 
 is called so by chemists, is an oxide of carbon which owes its 
 dark colour to the oxygen with which it is combined. Before 
 these experiments, it was not easy to determine the particular 
 condition of the carbon which exists so plentifully in venous 
 blood. 
 
 No precise calculation has yet been made of the quantity of 
 oxygen absorbed by the venous blood, nor of the quantity em- 
 ployed in the combustion of hydrogen and carbon in the lungs, 
 so as to form water and carbonic acid. 
 
 Is the carbon, in venous blood, merely combined with oxygen, 
 or is it united with hydrogen, so as to form carburetted hydro- 
 
OF RESPIRATION. 
 
 235 
 
 gen? It appears to me more probable, that the oxygen which is 
 absorbed, by combining with hydrogen, in every part of the 
 body, produces the water which dilutes the venous blood, ren- 
 ders it more fluid, and richer in serum than arterial blood; while, 
 by its union with carbon, it forms an oxide that gives to the 
 blood the dark colour, which is one of its most remarkable 
 characters. On reaching the lungs, which are real secretory or- 
 gans, the water is exhaled, dissolved in the air, and forms the 
 pulmonary transpiration; the oxide of carbon, completely de- 
 composed by an additional quantity of oxygen, constitutes car- 
 bonic acid, which gives to the air that is expired, the power of 
 forming a precipitate in lime water. 
 
 The absorption of oxygen by the venous blood, explains how 
 the phenomena of respiration are continued into every part of the 
 body, and produce the warmth uniformly diffused over all our 
 organs. In proportion as the blood parts with its caloric, for 
 which its affinity diminishes as it becomes venous, the parts 
 which give out their hydrogen and carbon combine with it. If 
 the lungs were the only organs in which caloric might be disen- 
 gaged, the temperature of those viscera ought considerably to 
 exceed that of other parts: experience, however, shows that the 
 temperature of the lungs is not sensibly more elevated. 
 
 This theory of respiration, for which we are entirely indebted 
 to modern chemistry, is contradicted by no one phenomenon. 
 The greater the extent and capacity of the lungs, the more fre- 
 quent is respiration, and the greater the warmth and vivacity of 
 animals. Birds, whose lungs extend into the abdomen by vari- 
 ous membranous sacs, and whose bones are hollow and communi- 
 cate with the lungs, consume a great deal of oxygen, either on 
 account of the magnitude of this respiratory apparatus, or from 
 their frequent, and, at times, hurried respiration. On that ac- 
 count, the habitual temperature of their body exceeds that of 
 man and mammiferous animals. In reptiles, on the contrary, 
 whose vesicular lungs admit but a very small quantity of blood, 
 and present to the atmosphere a surface of very limited extent, 
 and in which respiration is performed with intervals of longer 
 duration, the body is at a temperature which, naturally, never 
 rises above seven or eight degrees. 
 
 LXXVII. Though the temperature or warmth of the body is 
 
OF RESPIRATION. 
 
 236 
 
 generally proportioned to the extent of respiration, to the quan- 
 tity of blood exposed, in a given time, to the action of the at- 
 mospherical air, it may be higher or lower, according to the de- 
 gree of the vital energy of the lungs. These organs should not 
 be considered as mere chemical receivers; they act on the air, 
 digest it, as the ancients said, and combine it with the blood, by 
 a power which is peculiar to them. If it were otherwise, there 
 would be nothing to prevent a dead body from being restored to 
 life, by Inflating with oxygen its pulmonary tissue. The ancients 
 alluded to this action of the lungs on the air we breathe, by call- 
 ing that air the pabulum vitce. Its digestion was, they thought, 
 effected in the lungs, in the same manner as the digestion in the 
 stomach of other aliments less essential to life, and whose priva- 
 tion may be borne for a certain time; while life is endangered, 
 when the aeriform nutriment ceases to be furnished to the lungs 
 for the short space of a few minutes. 
 
 In proof of the vitality of the lungs, and of the share which 
 they have in producing the changes which the blood undergoes 
 in passing through them, I may mention the experiment which 
 proves that an animal placed under a vessel filled with oxygen, 
 and breathing that gas in a pure state, consumes no more of it 
 than if it was received into the chest, mixed with other gases unfit 
 for respiration. A guinea-pig, placed under a vessel full of vital 
 air and of known capacity, will live four times longer than if the 
 vessel contained atmospherical air. No remarkable difference is 
 at first perceived in the act of respiration, but if the animal re- 
 mains long immersed in the oxygen, his respiration becomes 
 more frequent, his circulation more rapid, all the vital functions 
 are executed with more energy. The lungs separate by a power 
 inherent in themselves, the two atmospherical gases, and this 
 process is effected by a pretty considerable power; for oxygen, 
 in its combination with the blood, is, with difficulty, separated 
 from azote. In fact, the blood, though in thin layers, becomes 
 dark, when exposed to the atmospherical air. 
 
 It is observed, that the purity of the air contained in the re- 
 ceiver, is the more readily affected, as the animal placed under 
 it is younger, more robust, and as his lungs are more capacious. 
 Hence birds, whose lungs are very large, contaminate a consi- 
 derable quantity of air, and consume more quickly its respirable 
 
OF UESPIRATI03ST. 
 
 237 
 
 part. A frog, on the contrary, will remain a considerable time 
 in the same quantity of air, without depriving it of its oxygen. 
 
 The vesicular lungs of that reptile, as well as of all oviparous 
 quadrupeds, are much more irritable than those of warm- 
 blooded animals; they appear to contract at the will of the 
 animal. The frog is without a diaphragm, attracts the air into 
 its lungs, by swallowing it by a real process of deglutition, as 
 was proved by Professor Rafu, of Copenhagen, who killed those 
 animals by holding their jaws asunder for a certain time. They 
 reject the air by a contraction of the lungs, in the same manner 
 as in man the bladder empties itself of urine. 
 
 In birds, whose diaphragm is equalty membranous, and con- 
 tains several openings to transmit the air into the pulmonary ap- 
 pendices, the parietes of the thorax are likewise more moveable 
 than in man and quadrupeds. Their pectoral muscles are more 
 powerful, their ribs contain a joint situated in the middle of 
 those arches which are completely ossified In that class of ani- 
 mals; and those two portions move on each other, forming, at 
 their point of union, angles more or less acute, according to the 
 distance of the sternum from the vertebral column. 
 
 A numerous class of cold red-blooded animals, viz. fishes, 
 have no lungs; the gills, which supply their place, are small pen- 
 niform laminae, generally four In number, situated on each side, 
 at the posterior and lateral part of the head, covei-ed over by a 
 moveable lid, to which naturalistS^give the name of operculum. 
 The water which the animal swallows, passes, when he chooses, 
 through the parietes of the pharynx, which contain several pretty 
 considerable openings, is spread over the,^ills and the pulmo- 
 nary vessels which are distributed in them, then escapes at the 
 auricular apertures, when the animal closes his mouth, and 
 raises the opercula. It is not known, whether the water is de- 
 composed and yields its oxygen to the blood which circulates in 
 the gills, or whether the small quantity of air that is dissolved 
 in the water, alone serves to vivify the pulmonary blood. The 
 latter opinion seems the most probable, if it be considered that 
 a fish may be suffocated by closing accurately the vessel of water 
 in which it is enclosed. The same result might, I conceive, Jbe 
 obtained by placing the vessel under the receiver of an air pump, 
 so as to exhaust it completely. 
 
BF RESPIRAriON. 
 
 238 
 
 Respiration, which is completely under the influence of the 
 brain, as far as relates to its mechanism, is less dependent 
 upon it, in regard to the action of the lungs on the blood, and 
 the combination of that fluid with oxygen, which is the essen- 
 tial object of that function. The nerves, however, have some 
 influence on that function, as well as on the various secretions, 
 in which, according to Bordeu, they are of first-rate importance. 
 M. Dupuytren ascertained by his experiments, that the division 
 of the cervical portion of the eighth pair of nerves, did not sen- 
 sibly affect respiration; but the animal died with all the symp- 
 toms of asphyxia, when this nerve was divided on both sides. 
 Death took place in the course of a few minutes, when the ex- 
 periment was performed on horses. Other animals did not die 
 so soon after; dogs, for instance, have been known to live 
 several days after the experiment. By interrupting the com- 
 munication between the lungs and the brain, we paralyze the 
 former of these organs, and it ceases to convert the venous into 
 arterial blood. This fluid, conveyed by the pulmonary artery, 
 continues of a dark colour, when brought to the left cavities of 
 the heart; the arteries convey the blood without its having re- 
 ceived its vivifying principle, in passing through the lungs which 
 are paralyzed, by having their nerves tied or divided. It is easy 
 to conceive that all organs, for want of the stimulus which de- 
 termines their action, carry on their functions imperfectly, and 
 at last cease to act. The animal heat is likewise lowered a few 
 degrees, as was ascertained by the abovementioned physician, 
 who thinks he has established as a fact, that the ligature of the 
 nerves of the lungs does not destroy, but weakens the vital 
 power, which enables them to take up the oxygen and to give 
 out the carbonic acid. The brain, therefore, possesses a double 
 influence over the function of respiration; on the one hand, it 
 directs its mechanism by means of the nerves which it sends to 
 the diaphragm, and to the intercostal muscles; and on the other 
 hand, it is through the nerves which arise from the brain, that 
 the lungs have the power of converting dark blood into arterial 
 bipod, which is the principal phenomenon of respiration. 
 
 Experiments performed on the same subject by Dr. Gallois, 
 subsequent to those I just related, tend to throw some degree 
 of uncertainty on their results. Dr. Gallois repeated these ex- 
 
OF RESPIRATION. 
 
 239 
 
 periments publicly in my presence, and at the society of the 
 Ecole de Medecine of Paris. After dividing the two nerves of 
 the eighth pair in a guinea-pig, and after having by that process 
 brought on a state of asphyxia, he restored life and motion to 
 the animal by opening tbe trachea at its anterior part. The 
 blood of the carotids, which from red had become dark the 
 moment the nerves were divided, recovers immediately its red 
 colour, the motion of respiration is restored, and the animal 
 lives several days after the experiment. Whence does this 
 difference arise? Does the division of the eighth pair bring on 
 asphyxia by occasioning a spasmodic constriction of the glottis, 
 and by impeding, or even completely obstructing the admission 
 of the atmospherical air? 
 
 LXXVIII. Of animal heat. The human body, which is habi- 
 tually of a temperature between thirty-two and thirty-four de- 
 grees of Reaumur’s thermometer, preserves the same degree 
 of warmth under the frozen climate of the polar region, as well 
 as under the burning atmosphere of the torrid zone, during the 
 most severe winters and the hottest summers. Nay further, the 
 experiments of Blagden and Fordyce in England, and of Duha- 
 mel and Tillet in France, show that the human body is capable 
 of enduring a degree of heat sufficient to bake animal substances. 
 The Fellows of the Academy of Sciences saw two girls enter 
 into an oven, in which fruits and animal substances were being 
 baked; Reaumur’s thermometer which they took in with them, 
 stood at 150 degrees; they remained several minutes in the oven, 
 without suffering any inconvenience. 
 
 All living bodies have a temperature peculiar to themselves, 
 and independent of that of the atmosphere. The sap of plants 
 does not freeze, when the thermometer stands only at a few 
 degrees below zero; on placing the bulb of a thermometer in a 
 hole in the trunk of a tree during winter, the fluid sensibly 
 rises. Now, three circumstances remain to be investigated: in 
 the first place, what produces in living bodies this inherent and 
 independent temperature? In the second place, how do these 
 bodies resist the admission of a greater degree of heat than 
 that which is natural to them? What prevents caloric, which has 
 a perpetual tendency to a state of equilibrium, from passing 
 into a body surrounded by a burning atmosphere? Lastly, how 
 
OF RESPIRATION. 
 
 240 
 
 does a body which resists the influence of heat, withstand equal- 
 ly the destructive influence of an excessive degree of cold. 
 
 LXXIX. Caloric, in a latent state, or in combination with 
 bodies, is disengaged from them whenever they assume a dif- 
 ferent state; when from a gaseous form they become liquid; or 
 when from being liquid they become solid. Now, living bodies 
 nre a kind of laboratories, in which all these changes are perpetu- 
 ally going on; the blood which circulates in every part of the 
 human frame, is constantly receiving supplies of fresh materials; 
 from the thoracic duct which pours into it thp chyle, abounding 
 in nutritious particles; from respiration which imparts to it an 
 aeriform principle obtained from the atmosphere; and even, in 
 some cases, from cutaneous absorption, through which diflFerent 
 elements are received into it. All these different substances 
 carry along with them into the blood a certain quantity of 
 caloric, which is combined with them, and which is disengaged 
 during the changes which they undergo from the influence of 
 the action of the organs, and gives out its caloric to the parts 
 among which it is disengaged. Of all the principles in the blood, 
 which have the power of communicating heat to the organs, none 
 furnishes a greater quantity than oxygen, which, during respira- 
 tion, combines with the blood in the lungs. Gaseous substances, 
 it is well known, contain most combined caloric; their state 
 of elastic fluidity is entirely owing to the accumulation of that 
 principle, and they part with it, when, from any cause whatever, 
 they become liquid. It is on that account that the heat of bo- 
 dies is greater, the more they have the power of impregnating 
 their fluids with a considerable quantity of oxygen from the 
 atmosphere. For the same reason, as was already observed, in 
 animals that have cellular lungs, and a heart with two ventricles, 
 the blood is of the same temperature as in man; and such ani- 
 mals belong, as well as man, to the great class of warm red- 
 blooded animals; a class in which birds occupy the first place, 
 from the vast extent of their lungs, which reach into the abdo- 
 men, and communicate with the principal bones of the skeleton. 
 The capacity of the pulmonary organ of birds, is not the only 
 cause why their temperature is eight or ten degrees higher than 
 that of man; this increase of temperature depends, likewise, on 
 the greater frequency of tlxeir respiration, an4 on the velocity of 
 
OF RESPIRATION. 
 
 24 i 
 
 their pulse; on the quickness and multiplicity of their motions, 
 and on the vital activity which animates them. In reptiles which 
 have vesicular lungs, and a heart with a single ventricle; whose 
 respiration is slow, and performed at distant intervals, the blood, 
 though red, is of very inferior temperature to that of man. 
 They have, from that circumstance, been called cold red-blooded 
 animals; this numerous class includes fishes, which possess an 
 organ supplying but imperfectly the office of lungs. In fishes the 
 heart, which has but a single ventricle, sends, it is true, to the 
 gills (the organ supplying the place of lungs is so called) the 
 whole of the blood; that fluid, however, is but imperfectly vivi- 
 fied in the gills, on account of the small quantity of air which 
 can be taken in during the act of respiration. Lastly, in white- 
 blooded animals and in plants, the combinations with the air 
 being more difficult, the vital energy less marked, the tempera- 
 ture differs only by a few degrees from that of the atmosphere, 
 and they do not endure heat or cold so well as the more perfect 
 animals. 
 
 The lungs, as was before observed, consuming only a certain 
 quantity of air, there is no increase of temperature, however 
 great the quantity of oxygen contained in the atmosphere that 
 is breathed; as a man who should take a double quantity of 
 aliment could not receive more nourishment, than if he content- 
 ed himself with the quantity of food proportioned to his wants; 
 for, as the digestive organs can extract only a certain quantity 
 of chyle, the quantity of recrementitiops matter would only be 
 greater, if more than the due quantity of food were received 
 into the stomach. Hence the common saying, that nourishment 
 comes from what we digest and not from what we eat. 
 
 The pulmonary organ may, however, act on the air, with 
 different degrees of power, in robbing it of its oxygen; and when 
 the body becomes of an icy coldness, in certain nervous and 
 convulsive affections, this cold may depend as much on the atony 
 of the lungs, and on the spasmodic condition of the chest, which 
 dilating with difficulty does not admit the air readily, as on the 
 spasm and general insensibility of the organs, v. hich allow the 
 blood to pass without affecting its component parts. It would be 
 curious to ascertain whether the air expired from the lungs of a 
 cataleptic, contains more oxygen, is less impaired, and contains 
 
 2 H 
 
OP RESPIRATION. 
 
 242 
 
 a smaller quantity of carbonic acid than the breath of a sound 
 active adult. Perhaps it would be found, that in catalepsy and 
 other similar affections, the blood does not part with its hydro- 
 gen and carbon, that it retains its colouring principles, and the 
 different materials of the urine, which is voided in a colourless 
 and limpid state, insipid and without smell, and in the condi- 
 tion of a mere serosity. 
 
 The temperature of the body is produced not only by the pul- 
 monary and circulatory combinations; it is besides developed in 
 several organs, in which fluid or gaseous substances become 
 solid by parting with a portion of their caloric. Thus digestion, 
 particularly of certain kinds of food, is an abundant source of 
 caloric; the skin which is habitually in contact with the atmos- 
 phere, decomposes it and deprives it of its caloric. Lastly, ca- 
 loric is produced and evolved in all parts, whose molecules, 
 affected by a double motion, in consequence of which they are 
 incessantly being formed and decomposed, by changing their 
 condition and consistence, absorb or disengage more or less 
 caloric. The great activity of the power of assimilation in chil- 
 dren, is, no doubt, the cause of the habitually high temperature 
 at that period of life. The temperature of the body is not only one 
 or two degrees higher at that period of life; but young people, 
 after death, preserve for a longer period the remains of vital 
 heat; or rather, as tonicity does not so soon forsake the capillary 
 vessels, life departing reluctantly, the combinations from which 
 caloric is evolved, continue some time, even after it is extinct. 
 For the same reason, the bodies of persons that have died sud- 
 denly retain their warmth long, while an icy coldness seizes the 
 bodies of those who have died of a lingering disease, from the 
 slow, gradual, and total abolition of the powers of life. 
 
 Calorification, or the disengaging of animal heat, like nutri- 
 tion, takes place at all times, and may be considered as belonging 
 to all organs. It was of the utmost consequence that the inter- 
 nal temperature of the human body should be nearly the same 
 at all times. For, let us for one moment suppose that the tem- 
 perature of the blood should rise to fifty degrees of Reaumur’s 
 thermometer, its albuminous parts would suddenly coagulate, 
 obstruct all the vessels, interrupt the circulation and destroy 
 life. When, therefore, from an increased activity of the nutritive 
 
OF RESPraATION. 
 
 243 
 
 combinations, a greater quantity of heat is disengaged, the ani- 
 mal economy parts with it, and it is taken up in greater quantity 
 by the surrounding bodies. This accounts for the equality of the 
 temperature of the internal parts of the body in old people and 
 in children, notwithstanding the difference of their temperature 
 externally. The difference consists in this: that where most ca- 
 loric is produced, most is giv n out, and though the blood and 
 urine in old people, as well as in the young, are at thirty-two 
 degrees, what a difference is there not between the hot and pene- 
 trating perspiration which is poured in abundance from the 
 child, and the dryness and coldness of the skin in old people; 
 between the sweat and warm breath of the former, and the fro- 
 zen breath of the latter! Hence the opinion so generally received 
 and of such antiquity, that old people are benefited by cohabit- 
 ing with the young. Thus we are told that David had a young 
 virgin brought to him, that he might lie with her, and get heat 
 in his limbs that were stiffened with years. 
 
 If it be true, that in the very act of nutrition, which converts 
 our fluids into solids, there is disengaged a considerable quan- 
 tity of caloric; the motion of nutritive decomposition, by which 
 our solids are converted into liquids, must cause an equal quan- 
 tity of heat to be absorbed. The objection is a very strong one, 
 and not easily got over; it may be answered, by observing that all 
 living bodiesyfrom the instant of their formation, contain a certain 
 quantity of caloric which they retain, so that this double process 
 of acquiring heat and parting with it, the unavoidable result of 
 nutritive composition, and decomposition, merely keeps up an 
 equilibrium and maintains the same degree of temperature. 
 
 The blood which becomes saturated with oxygen, in the ca- 
 pillaries of the lungs, parts with that principle, and disengages 
 its caloric, throughout the capillary vessels of the whole body, 
 of which each organ must set free a greater quantity^in propor- 
 tion to the activity of the living principle, and to the rapidity of 
 the circulation. The parts through which the greatest number of 
 vessels circulate, perhaps give out most caloric, and communi- 
 cate a portion of it to the organs, which receive but a sm all 
 quantity of blood, as the bones, the cartilages, See. It is easy to 
 understand, why an inflamed part, through which the blood cir- 
 culates with more rapidity, and whose sensibility and contrac- 
 
OF RESPIRATION. 
 
 244 
 
 tility are much increased, is manifestly hotter to the feel of the 
 patient and of the physician, though, as was observed by John 
 Hunter, a thermometer applied to the inflamed part, shows a 
 scarcely perceptible increase of temperature. He injected into 
 the rectum of a dog, and into the vagina of an ass, a strong so- 
 lution of oxymuriate of mercury. Acute inflammation came on, 
 the swollen mucous membrane formed, externally, a considera- 
 ble projection. Blood flowed from the torn capillaries, yet the 
 thermometer rose very slightly, only one degree of Fahrenheit’s. 
 But however slight that increase of heat in the inflamed part, 
 it is very sensibly felt, on account of the extreme- sensibility of 
 the organ, whose vital properties are all increased. The liveli- 
 ness of impressions being proportionate to the degree of the 
 power of sensation, one need not wonder that the patient should 
 experience a sensation of burning heat, in a part in which the 
 thermometer indicates no increase of temperature, in which it 
 cannot be perceived even by the touch. I have just felt a young 
 man’s hand that is swollen from chilblains; though the pain 
 which he feels in it seems to him to be occasioned by an accumu- 
 lation of caloric, his hand is colder than mine, which is of the 
 same degree of warmth as the rest of my body, and in which 
 I have no peculiar sensation. It may, therefore, be laid down as 
 an axiom, that the real or thermometrical increase of heat is in- 
 considerable in inflammation, but that it is intensely felt, in con- 
 sequence of the increase of sensibility. 
 
 What is the reason, that during the cold fit of a febrile 
 paroxysm, a sensation of excessive cold is felt in a part in which 
 no diminution of heat can be discovered by the touch? Whence 
 comes the burning heat which attends inflammatory fever 
 (causos)? What is the cause of the difference of the sensations 
 attending the heat of erysipelas, bilious fevers and phlegmon, 
 &c.? These various sensations are owing to the different modi- 
 fications of sensibility in these different diseases. Should this ex- 
 planation appear unsatisfactory, let it be recollected, that how- 
 ever accurate the calculations may be, that have been made on 
 the subject of caloric or of the matter of heat, the existence of 
 caloric itself is hypothetical, and that it is not known, whether 
 caloric is a body, or whether heat is merely a property of matter. 
 LXXX. If we now inquire into the causes which enable the 
 
OP RESPIRATION. 
 
 245 
 
 body to resist the admission of a degree of heat superior to that 
 which habitually belongs to it, we shall be compelled to admit, 
 in all living bodies, a power by means of which they repel an ex- 
 cess of heat, and retain the same temperature. Cutaneous perspi- 
 ration, it is true, acts very powerfully in lowering the tempera- 
 ture, and as this evaporation increases with the temperature, it 
 should seem as if this function sufficed to moderate the heat of 
 the body, and to restore the equilibrium. 
 
 It is a fact known since the time of Cullen,* that the evapo- 
 ration of fluids, or their solution in the air, is the most powerful 
 means of cooling bodies, and that the mercury in the bulb of a 
 thermometer, may be frozen merely by moistening it with aether, 
 spirits of wine, or any other volatile substance, and then expos- 
 ing it to a dry and warm air. This method is equally successful 
 in its application to the human body, and the hands may be 
 cooled to such a degree as to feel benumbed, by being frequently 
 wetted with a spirituous fluid, and by being moved in k dry and 
 renewed air. But though cutaneous perspiration operates in a 
 somewhat similar manner, and though it may be ranked among 
 the means which nature employs to preserve the animal tem- 
 perature in a nearly uniform state, it must however be confess- 
 ed, that it is not the only way in which this object is accomplish- 
 ed, and that it does not satisfactorily account for this phenome- 
 non, for, the evaporation of the fluids contained in dead animal 
 substances, does not prevent their being roasted on the applica- 
 tion of heat; and besides, fishes and frogs have been known to 
 live and retain their temperature in mineral waters, nearly of a 
 boiling heat.f 
 
 I thought it right to repeat these experiments, and with this 
 view, I placed living frogs in a vessel containing water at fifty 
 degrees of temperature, and on taking them out, at the end of 
 ten minutes, I ascertained that they were not so hot as the 
 liquid, nor as pieces of flesh which had been put into it at the 
 same time. 
 
 * This celebrated physician made this discovery about forty years ago, which 
 has thrown much light on several physico-chemical phenomena, and he pub- 
 lished it in a dissertation entitled: “ Of the cold produced by evaporating fluids, 
 and of some other means of producing cold, by Dr. W. Cullen.” 
 
 t See Sonnerat's Voyage to the East Indies. 
 
Of BESPIltATlOK. 
 
 S46 
 
 We cannot admit the opinion of Grimaud, that living bodies 
 have the power of producing cold; for, as cold is merely the ab- 
 sence of heat, one cannot allow a positive existence to a nega- 
 tive being. 
 
 Habit has a remarkable influence on the faculty which the 
 body possesses of bearing a degree of heat, much exceeding that 
 which is natural to it. Cooks handle burning coals with impu- 
 nity; workmen employed in forges, leave the mark of their feet 
 on the burning and liquid metal, at the moment when it becomes 
 solid by cooling. Many, no doubt, recollect the too famous in- 
 stance of a Spaniard, who became so general a subject of con- 
 versation in Paris: this young man, in making his way through 
 a house on fire, perceived that the heat was less inconvenient to 
 him ihan he had imagined. He applied himself to bear, with im- 
 punity, the action of fire, and was enabled to apply to his tongue 
 a spatula heated red hot, and to apply the soles of his feet and 
 the palms of his hand on a red hot iron, or on the surface of 
 boiling oil. Nothing can equal the absurdity and the exaggera- 
 tion of the stories that were told of this man, except the igno- 
 rance and the want of veracity of those who invented them.— 
 The following is a correct statement of the feats of this man, who 
 was represented as incombustible and insensible. He passes 
 rapidly along the surface of his tongue, which is covered with 
 saliva, a red hot spatula, the action of which seems merely to 
 dry it, by bringing on an evaporation of the fluids with which 
 it is covered. After carrying the spatula from the base to the tip 
 of his tongue, he brings it back again into his mouth, and applies 
 it to his palate, to which it communicates a part of its heat, at 
 the same time that it becomes moistened with saliva. This man 
 having, in a public exhibition, carried on, too long, the applica- 
 tion of the spatula, the caustic effects of its heat showed them- 
 selves, the epidermis was detached, and found coiled, like the 
 outer covering of an onion, in the cloth which he used to wipe 
 his mouth. He does not dip his hands and feet in boiling oil, he 
 merely applies to the surface of the fluid his palms and his soles, 
 and he repeats this frequently, with only a short interval be- 
 tween each application. When the experiment ic carried on, for 
 a certain length of time, there is emitted a smell of burnt horn. 
 No one has yet observed, that though this tnan^s hands are not 
 
OF RESPIRATION. 
 
 247 
 
 callous, the palms of these, and the soles of his feet are cushion- 
 ed with fat. A thick layer of fat, which is a bad conductor of 
 heat, separates the skin from the subjacent aponeuroses and 
 nerves; this circumstance, to a certain degree, accounts for his 
 imperfect sensibility. 
 
 His pulse, during those experiments, was about a hundred 
 and twenty; the perspiration evidently increased, and some- 
 times copious. Every part of his body possesses the ordinary 
 degree of sensibility, may be destroyed by the protracted appli- 
 cation of caustic substances, and would be consumed by lire, if 
 applied for a sufficient length of time, and nitric acid would in- 
 fallibly destroy his tongue if he took any into his mouth, as it 
 has been said he did. This man, therefore, in no one respect de- 
 parts from the known laws of the animal economy, but, on the 
 contrary, affords an additional proof of the influence of habit on 
 our organs. 
 
 LXXXI. Before bringing to a conclusion this article on ani- 
 mal heat, it remains for me to explain how the body resists 
 cold, and preserves its temperature, in the midst of a frozen 
 atmosphere. This cannot be accomplished without an increase 
 of activity in the organs; it is only by augmenting the sum of 
 the combinations by which caloric is disengaged, that we can 
 succeed in making up for the loss of that principle so necessary 
 to our existence. — What is the reason that in cold weather, di- 
 gestion is more active (^Hieme verb ventres sunt calidiores, 
 Hipp.), the pulse stronger and more frequent, and the vital 
 energy greater? It is because heat comes from the same source, 
 and is produced by the same mechanism as the nutrition of the 
 organs; and that its evolution may go on increasing, it is neces- 
 sary that the secretions, nutrition, in a word, all the vital func- 
 tions, should increase in the same proportion. 
 
 Observe, for a moment, a man who is exposed to a moderate 
 degree of cold, he feels more activity, more strength, and is 
 more nimble, he walks and exerts himself, the most violent 
 exertions do not appear to him labourious, he struggles against 
 the disadvantages of the debilitating influence; and provided 
 the cold is not excessive and the body tolerably vigorous, there 
 is disengaged, within himself, a sufficient quantity of caloric 
 to make up for the loss of that which is carried off by the air 
 
OP RESPIRATION. 
 
 248 
 
 and the surrounding bodies. These general eiFects of cold are 
 not disproved by what happens, when only a part of the body 
 is exposed to it. Supposing the temperature a few degrees below 
 zero, there is felt, at first, a sensation of cold much more in- 
 convenient, cseteris paribus, than if it acted on a more extensive 
 surface. The spot on which the cold air acts, becomes affected 
 with a painful sense of pricking, reddens, then inflames; and in 
 this case, inflammation is evidently the result of a salutary eflFort 
 of nature which determines into the inflamed part, an excess of 
 the vital principle, so that the quantity of heat that is disengag- 
 ed may correspond to that which has been abstracted. The effort 
 of this conservatory principle is more marked, than if the whole 
 surface of the body were at once exposed to cold, because, act- 
 ing wholly on a limited point, of small extent, it operates with 
 more intensity. 
 
 Beyond a certain degree, however, nature in vain struggles 
 against cold; if severe, and if the creature exposed to it have 
 not the power of sufficient reaction, the part becomes purple 
 and benumbed from the loss of its caloric, vitality ceases, and 
 it mortifies; and if the whole body is equally exposed to the 
 influence of cold, the person is benumbed, feels a stiffening of 
 his limbs, stammers, and overpowered by an irresistible propen- 
 sity, yields to a sleep which inevitably ends in death. By yielding 
 thus to the illusive sweets of a perfidious sleep, many travellers 
 have perished after losing their way, in the mountains of the 
 old and of the new world. Thus, two thousand soldiers of 
 Charles the twelfth’s army perished, during a siege, in the 
 severe winter of 1709. 
 
 To resist the effects of cold, a certain degree of strength and 
 vigour is therefore necessary; it is consequently very injudicious 
 to recommend the cold bath to very young children, to deli- 
 cate and nervous women, to persons whose constitution is not 
 capable of a sufficient reaction. The evil attending the injudi- 
 cious use of this remedy in the cases that have just been enu- 
 merated, justifies the apparently singular terras in which Galen 
 expressed himself: “ Let the Germans (says this first of physio- 
 logists) let the Sarmatians, those northern nations as barbarous 
 as bears and lions, plunge their children in frozen water; what 
 I write is not intended for them.” 
 
OF RESPIRATION. 
 
 249 
 
 On the other hand, if it be recollected, that there is within 
 us a power of reaction which increases with use, that motion 
 strengthens our organs, it will be readily understood, that cold 
 acts as a tonic, whenever it is not applied to such a degree as to 
 extinguish the vital power. 
 
 The manner in which enlightened physicians have, at all 
 times, prescribed the cold bath, shows that they were acquaint- 
 ed with this tonic effect depending, not on the application of 
 cold, which in itself is debilitating, but on the reaction which it 
 occasions. Hence along with the cold bath, they are in the 
 habit of recommending exercise, a generous wine, bark, nutri- 
 tious food, and an analeptic regimen, calculated to excite a salu- 
 tary reaction. 
 
 LXXXII. Animal heat is, therefore, produced by the com- 
 binations of our fluids and solids in the process of nutrition; it 
 is a function common to all the organs, for, as they all nourish 
 themselves, so they all disengage, more or less, the caloric 
 combined with the substances which they apply to their nutri- 
 tion. 
 
 Though we are without precise information respecting the 
 manner in which a living body resists the admission of a degree 
 of heat exceeding that which is natural to it, one may consider 
 cutaneous exhalation, which is increased by the use of heating 
 substances, as the most powerful means employed by nature to 
 get rid of the excess of heat, and to restore the equilibrium. 
 
 Lastly, the body resists cold, because the organs being ren- 
 dered more active by cold, there is disengaged a quantity of 
 caloric equal to that which is carried off by the air, or by the 
 other substances with which the body happens to be in contact. 
 
 LXXXIII. The rapidity of the circulation of the blood 
 through the lungs, is equal to the velocity with which it flows 
 in the other organs. For, if on the one hand, the parietes of 
 the right ventricle and of the pulmonary artery, are weaker and 
 thinner than those of the left ventricle and aorta, the lungs, from 
 their soft, easily dilated, and spungy texture, are the most easily 
 penetrated by the fluids of all our organs. 
 
 The right ventricle sends into the lungs a quantity of blood, 
 equal to that which each contraction of the left ventricle propels 
 
 2 I 
 
OF RESPIRATION. 
 
 250 
 
 into the aorta; and it is not necessary to adopt the opinion of 
 M. Kruger, that each contraction of the heart sends into the 
 lungs and into the rest of the body an equal quantity of blood; 
 for, in that case, the circulation would have been much slower, 
 the length of the lungs being much shorter than the whole body. 
 Nor need we say, with Boerhaave, that this circulation is much 
 more rapid, because the same quantity of blood returns by the 
 extremities of the pulmonary artery, and of all the other arteries 
 of the body. 
 
 The extension of the pulmonary tissue, the straightening of its 
 vessels are, no doubt, favourable to the circulation of the blood; 
 but if the admission of air did not answer a different purpose, 
 the circulation would not be indispensably necessary. The blood 
 flows from the right into the left cavities of the heart, notwith- 
 standing the collapse of the lungs and the creases of their ves- 
 sels. The air which penetrates, at all times, into the lungs, 
 supports their tissue and the vessels which are distributed to 
 it, so that even during expiration, the vessels are much less 
 creased than has been imagined by several physiologists. But 
 the changes produced by the contact of the atmosphere, renovate 
 this fluid, and fit it to re-excite and keep up the action of all the 
 organs which require to be stimulated by arterial blood. If you 
 make a living animal breathe de-oxygenated air, the blood un- 
 dergoes no change by its pulmonary circulation: the left cavities 
 of the heart are no longer duly irritated by this fluid, which 
 preserves all its venous qualities; their action becomes languid, 
 and with it that of all the organs; and in a little while, it ceases 
 altogether. It is revived by introducing pure air, through a 
 tube fitted to the trachea; all the parts seem to awake out of a 
 sort of lethargic sleep: in which they are again immersed, by 
 depriving the lungs anew of the vital air. 
 
 The chyle, mixed in great quantity with the venous blood, 
 undergoes, in its passage through the heart and the sanguineous 
 system, a more violent agitation: its molecules are struck together, 
 break on each other, and, thus attenuated, become more per. 
 fectly intermingled: in its passage through the lungs, a great 
 part of this recrementitious fluid is deposited by a sort of inter- 
 nal perspiration, in the parenchymatous substance of these vis- 
 
OP RESPIRATION. 
 
 251 
 
 cera. Oxydated by the contact of the air, re-absorbed by a 
 multitude of inhalent vessels, it is carried into the bronchial 
 glands, which are found blackened by what it there deposits of 
 carbonic and fuliginous matter. Purified by this elaboration, it 
 returns into the thoracic duct, which pours it into the subclavian 
 vein, whence it soon returns to the lungs, to be there anew sub- 
 jected to the action of the atmosphere: so that there is effected, 
 through these organs, a real lymphatic circulation, of which the 
 object is to bring on the chyle to a higher degree of animaliza- 
 tion. 
 
 LXXXIV. Of pulmonary exhalation. It will be remembered, 
 that one of the great differences between the blood of the arte- 
 ries, and that of the veins, consists in the great quantity of se- 
 rum found in this last. It is in the lungs that the separation of 
 this aqueous part takes place, and that its proportion is reduced, 
 whether it be, that oxygen gives albumen and gelatine a greater 
 tendency to concrete, or that the serum, formed by the fixation 
 of oxygen throughout the whole extent of the circulatory system, 
 exhales from the arteries, and thus furnishes the matter of pul- 
 monary exhalation. It is scarcely possible to admit the combi- 
 nation of oxygen with the hydrogen of the venous blood, and 
 that water is thus formed from its elements, as happens when 
 storms are gathering in the high regions of the atmosphere. If 
 a similar process can be carried on in the lungs, without pro- 
 ducing deflagration and the various phenomena attending the 
 production of aqueous meteors, it is probable, that it furnishes 
 but a small part of the exhalation; and that this humour, analo- 
 gous to the serum of the blood, exhales, completely formed, 
 from the arterial capillaries ramified in the bronchise and the 
 lobular tissue of the lungs. It is believed, that the quantity of 
 the pulmonary exhalation is equal to that of the cutaneous ex- 
 halation (four pounds in twenty-four hours). These two secre- 
 tions are supplemental to one another: when much water passes 
 off by the pulmonary exhalation, the cutaneous is less, and mce 
 versa. 
 
 The surface, from which the pulmonary exhalation is given 
 out, is equal, if not superior in extent to that of the skin; exha- 
 lation and absorption are at once carried on from that surface, 
 many nerves are distributed to it, and are almost exposed in the 
 
OP HESPIRATION. 
 
 252 
 
 tissue of the membranes which are extremely thin. Are the mi- 
 asmata with which the atmosphere is sometimes loaded, absorb- 
 ed by the lymphatics, which, it is well known, have the power of 
 taking up gaseous substances; or do they merely produce on the 
 nervous and sensible membranes of the bronchiae, and of the 
 lobular tissue, the impression whence the diseases of which they 
 are the germ arise? 
 
 A part of the caloric which is disengaged in the combinations 
 which oxygen undergoes in the lungs, is taken up in dissolving 
 and reducing into vapour the pulmonary exhalation, which is the 
 more abundant, according as respiration is more complete. Pul- 
 monary exhalation should be carefully distinguished from the 
 mucous matter secreted within the bronchise and trachea, and 
 which is thrown up by a forcible expiration, and forms the mat- 
 ter of what we spit. 
 
 LXXXV. Of asphyxia. The term asphyxia, though merely 
 indicating a want of pulse, is applied to any kind of apparent 
 death occasioned by an external cause and suspending respira- 
 tion, as submersion, strangulation, the diminution of oxygen in 
 the air inhaled, &e. The only difference between real death, 
 and asphyxia, is, that iu this last state the principle of life may 
 yet be re-animated, whilst, in the other, it is completely extinct. 
 
 Asphyxia takes place in drowning, because the lungs, de- 
 prived of air, no longer impart to the blood which passes 
 through them, the qualities essential to the support of life. 
 The water does not find its way into these viscera: the spas- 
 modic cl<;>sing of the glottis prevents its getting into the trachea 
 and its branches. Yet there is found a small quantity in the 
 bronchiae, after drowning, always frothy, because air has mixed 
 with it, in the struggles which precede asphyxia. If the body re- 
 main long under wate: , the spasmodic state of the glottis ceases, 
 water passes into the trachea and fills the lungs. 7 he anatomical 
 examination of a drowned body, shows the lungs collapsed, and 
 in the state of expiration; the right cavities of the heart, the ve- 
 nous trunks which terminate in them, and generally, all the 
 veins, are gorged with blood,* whilst the left cavities and the 
 
 • Hence the dark and livid colour of the skin and conjunctiva This last 
 membrane is frequently injected with dark blood; the very delicate veins of 
 the brain are considerably dilated, and this viscus is distended with venous 
 blood. 
 
OF RESPIRATION. 
 
 253 
 
 arteries are almost entirely empty. Life ceases in this kind of 
 asphyxia, because the heart has sent to the different organs, and 
 especially to the lungs, no blood that is not deficient in the qua- 
 lities necessary to their action; and perhaps also, because the 
 venous blood that is accumulated in the tissues, affects them by 
 its oppressive and deadly influence. On that account, the best 
 way of restoring the drowned to life, is to blow pure air into 
 their lungs. This is done by means of bellows adapted to a ca- 
 nula introduced into the nostril; if a proper apparatus cannot be 
 procured, one might blow with one’s mouth into that of the 
 drowned person, or into his nostrils, by, means of a tube; but air 
 so expired, having already undergone the process of respiration, 
 contains a much smaller quantity of oxygen, and is much less 
 fitted to excite the action of the heart. There remain several 
 other less effieacious remedies, such as friction, bronchotomy, 
 glysters, fumigations and suppositories, stimulating errhines, 
 and especially ammonia; stimulants taken into the mouth and 
 stomach, the application of fire, bleeding, the bath, electricity, 
 and galvanism. 
 
 The redness and lividity of the face, in persons who are 
 hanged, had led to the opinion that death, in such cases, was 
 from apoplexy; but it appears that in the asphyxia from stran- 
 gulation, as in that from drowning, death is caused by the inter- 
 ception of the air. To prove this, Gregory performed the follow- 
 ing experiment; he opened the trachea of a dog, and passed a 
 noose round his neck, below the wound. The animal, though 
 hanged, continued to live and to breathe; the air entered and 
 came out alternately at the small opening. He died, when the con- 
 striction was applied below the wound. A respectable surgeon, 
 who served in the Austrian army, assured me, that he had saved 
 the life of a soldier, by performing upon him the operation of 
 laryngotomy, a few hours before his execution. 
 
 Persons who are hanged may die, however, from dislocation 
 of the cervical vertebrae, and from the injury done, at the same 
 time, to the spinal marrow. Louis, it is well known, ascertained, 
 that of the two executioners in Lyons and Paris, the one dispatch- 
 ed, the criminals he executed, by dislocating the head at its arti- 
 culation with the neck, while the other executioner destroyed 
 them by inducing asphyxia. 
 
eP RESPIRATION. 
 
 254 
 
 Of the different mephitic gases unfit for respiration, some ap- 
 pear to bring on asphyxia, merely by depriving the lungs of the 
 vital air necessary to the support of life, while others evidently 
 affect the organs and the blood which fills them, by their poison- 
 ous and deleterious influence. 
 
 One may mention among the former, carbonic acid. In the 
 asphyxia occasioned by this gas, and which of all others is the 
 most frequent, the blood preserves its fluidity, the limbs their 
 suppleness, and the body its natural warmth, or even a greater 
 degree of warmth, for some hours after death; for, this kind of 
 asphyxia occurring always in a very hot situation, the body, de- 
 prived of life, admits an excess of caloric, such as would have 
 been resisted if the vital power had not been suspended. How- 
 ever, in this asphyxia, as in the preceding, the lungs remain un- 
 injured; the right cavities of the heart and the venous system, 
 are gorged with a dark but fluid blood. In the asphyxia, on the 
 other hand, that is occasioned by sulphuretted or phosphuretted 
 hydrogen, &c. or by certain vapours whose nature is not well un- 
 derstood, and which escape from privies, or from vaults in 
 which a number of dead bodies undergo putrefaction; there are 
 frequently found in the lungs, dark and gangrenous marks, and 
 death seems the effect of a poison which is the more active, as its 
 particles, exceedingly divided and in a gaseous state, are more in- 
 sinuating, and affect throughout its whole extent the nervous and 
 sensible surface of the lungs.* 
 
 Inebriation seldom goes the length of bringing on asphyxia, it 
 most commonly produces a stupor readily distinguished from 
 
 • The celebrated Mr. Goodwin, not to mention others, concurs with our 
 author, in the opinion that the carbonic acid destroys life, and produces its 
 lesser mischievous effects merely by the preclusion of oxygen. These writers 
 however, are undoubtedly mistaken. Nothing is more clear than that this 
 species of gas has a positive operation on the animal economy. We will state 
 a few facts in proof of it. 
 
 1. It has been shown, that animals die much sooner when exposed to the 
 carbonic acid, than when placed in vacuo, or when a ligature is applied to the 
 trachea. 
 
 2. It has been shown, that frogs may be kept, without injury, for upwards of 
 an hour under water, but perish almost instantly if put into an atmosphere of 
 fixed air. 
 
 3. It has been shown, that when the carbonic acid is combined with water 
 it very speedily destroys fish. — E d. 
 
OF RESPIRATION. 
 
 255 
 
 the affection treated of in this article, by the perceptible, though 
 obscure pulse, and by the motions of respiration, though these 
 are rare and indistinct. On this account, M. Pinel, in his Noso- 
 graphte philosophique^ has placed inebriation and the different 
 kinds of asphyxia, in two separate genera of the class neuroses. 
 It is conceivable, however, that the muscular irritability may be 
 so far impaired bv the use of spirituous liquors, 'hat the heart 
 and diaphragm might lose the power of contraction, which would 
 bring on complete asphyxia. 
 
 The glottis, through which the atmospherical air passes in 
 its way to the lungs, is so small, that it may be readily ob- 
 structed, when the epiglottis rising at the moment of deglutition, 
 the substance that is swallowed stops at the orifice of the larynx; 
 a grape seed may produce this effect, and it was in this manner, 
 we are told, that Anacreon, that lovely poet of the graces and 
 of voluptuousness, came by his death. Gilbert, the poet, died in 
 the same way, after a long and painful agony. A great eater, in 
 the midst of a feast, went into an adjoining room, and did not 
 return, to the great surprise of all the guests. He was found 
 stretched on the floor, without any sign of life. Help, given by 
 ignorant people, was of no use. On opening the body, a piece of 
 mutton was found fixed in the larynx, and completely stopping 
 the passage of the air. 
 
 Sometimes a child is born and shows no signs of life. When 
 it is probable, from the circumstances of the delivery, that there 
 has been no organic injury decidedly mortal, it must be consi- 
 dered as a case of asphyxia from weakness; and all means em- 
 ployed that are recommended in such cases, especially blowing 
 in air into the lungs, by means of a tube introduced into the 
 mouth or nostrils. It is thus, that the Prophet Elisha restored to 
 life the son of the Shunammite, as we are informed in the 
 second book of Kings, chapter the fourth. 
 
 LXXXVI. Of certain phenomena of respiration^ as sighing^ 
 sobbing., yaxvning., sneezing, coughing, hiccup, laughing, &c. 
 When the imagination is strongly impressed with any object, 
 when the vital functions are languid, the vital principle seems to 
 forsake all the organs, to concentrate itself on those which par- 
 take most in the affection of the mind. When a lover, in the 
 midst of an agreeable reverie, sighs deeply, and at intervals, a 
 
OF RESPIRATION. 
 
 256 
 
 physiologist perceives in that expression of de'sire, nothing but 
 a long and deep inspiration, which, by fully distending the lungs, 
 enables the blood, collected in the right cavities of the heart, to 
 flow readily into the left cavities of that organ. This deep inspi- 
 ration, which is frequently accompanied by groans, becomes ne- 
 cessar)', as the motions of respiration rendered progressively 
 slower, are no longer sufficient to dilate the pulmonary tissue. 
 
 Sobbing differs from sighing merely in this, that though the 
 expiration is long, it is interrupted, that is, divided into distinct 
 periods. 
 
 Yawning is effected in the same manner; it is the certain sign 
 of ennui, a disagreeable affection, which, to use the expression 
 of Brown, may be considered as debilitating or asthenic. The 
 fatigued inspiratory muscles have some difficulty in dilating the 
 chest; the contracted lungs are not easily penetrated by the 
 blood, which stagnates in the right cavities of the heart, and 
 produces an uneasy sensation, which is put an end to by a long 
 and deep inspiration; the admission of a considerable quantity 
 of air is facilitated by opening the mouth widely by the separa- 
 tion of both jaws. One yawns at the approach of sleep, because 
 the agents of inspiration, being gradually debilitated, require to 
 be roused at internals. One is likewise apt to yawn on waking, 
 that the muscles of the chest may be set for respiration, which 
 is always slower and deeper during sleep. It is for the same 
 reason, that all animals yawn on waking, that the muscles may 
 be prepared for the contractions which the motions of respira- 
 tion require. The crowing of the cock and the flapping of his 
 wings seem to answer the same purpose. It is in consequence of 
 the same necessity, that the numerous tribes of birds in our 
 groves, on the rising of the sun, warble, and fill the air with 
 harmonious sounds. A poet then fancies he hears the joyous 
 hymn, by which the feathered throngs greet the return of the 
 God of light. 
 
 While gaping lasts, the perception of sounds is less distinct, 
 the air, as it enters the mouth, rushes along the Eustachian tubes 
 into the tympanum, and the membrane is acted upon in a dif- 
 ferent direction. The recollection of the relief attending the 
 deep inspiration which constitutes gaping, the recollection of 
 the grateful sensation which follows the oppression that tvas felt 
 
OF RESPIRATION, 257 
 
 before, involuntarily lead us to repeat this act whenever we see 
 any one yawning. 
 
 Sneezing consists in a violent and forcible expiration, during 
 which the air, expelled with considerable rapidity, strikes against 
 the tortuous nasal passages, and occasions a remarkable noise. 
 The irritation of the pituitary membrane determines, by sym- 
 pathy, this truly convulsive effort of the pectoral muscles, and 
 particularly of the diaphragm. 
 
 Coughing bears a considerable resemblance to sneezing, and 
 differs from it only in the shorter period of duration, and the 
 greater frequency of the expirations; and as in sneezing the air 
 sweeps along the surface of the pituitary membrane, and clears 
 it of the mucus which may be lying upon it, so the air, when we 
 cough, carries along with it the mucus contained in the bron- 
 chiae, in the trachea, and which we spit up. The violent cough 
 at the beginning of a pulmonary catarrh, the sneezing which 
 attends coryza, show that the functions of the animal economy 
 are not directed by an intelligent principle; for such an archseus 
 could not mistake, in such a manner, the means of putting a 
 stop to the disease, and would ,not call forth actions which, in- 
 stead of removing the irritation and inflammation already exist- 
 ing, can only aggravate them. 
 
 Laughing is but a succession of very short and very frequent 
 expirations. In hiccup the air is forcibly inspired, enters the 
 larynx with difficulty, on account of the spasmodic constriction 
 of the glottis; it is then expelled rapidly, and striking against 
 the sides of that aperture, occasions the particular noise attend- 
 ing it. 
 
 I shall, on another occasion, explain the mechanism of suck- 
 ing, of panting, and of the efforts by which the muscles of the 
 thorax fix the parietes of that cavity, so that it may serve as a 
 fixed point for the other muscles of the trunk and of the limbs. 
 
 Respiration is besides employed in the formation of the voice; 
 but the voice and the different modifications of which it is capa- 
 ble, will form the subject of a separate chapter. 
 
 LXXXVII. Of cutaneous perspiration. An abundant vapour 
 is continually exhaling from the whole surface of the body, and 
 is called the insensible perspiration, when in a state of gas in the 
 air which holds it in solution, it then eludes our sight; it is cal- 
 
 2 K 
 
OF RESPIRATION. 
 
 258 
 
 led sweat when in a greater quantity and in a liquid form. 
 Sweat differs, therefore, from insensible perspiration only by 
 the condition in which it appears; and it is sufficient for its pro- 
 duction, that the air should be incapable of reducing it into 
 vapour, whether from an increased secretion by the skin, or 
 from the dampness and consequent diminished solvent powers 
 of the atmosphere. The insensible perspiration is constantly 
 escaping through the innumerable pores in the parietes of the 
 minute arteries of the integuments; it oozes in the interstices of 
 the scales of the skin; the air which immediately surrounds our 
 body becomes saturated with it, and carries it off as soon as it 
 is renewed. There is the greatest resemblance between the cu- 
 taneous perspiration and the pulmonary exhalation; both are 
 mere arterial exhalations, and the mucous membrane, which 
 lines the canals along which the air is transmitted, is a mere pro- 
 longation of the skin into those organs, and into the digestive 
 tube. The surface from which the cutaneous perspiration is 
 exhaled, is not quite so considerable as that from which the 
 pulmonary exhalation arises, since it is reckoned at only fifteen 
 square feet in a man of middle size. These two secretions are 
 supplementary to each other; the increase of the one is general- 
 ly attended with a sensible diminution of the other; lastly, the 
 mucous membrane of the intestinal canal, besides secreting 
 mucus, exhales likewise a flu.d which increases much in quan- 
 tity, when the cutaneous perspiration is languid, as is proved by 
 the serous diarrhoeas, so frequently occasioned by a suppressed 
 perspiration. It must be owned, however, that notwithstanding 
 those analogies of structure and function in the skin and mucous 
 membranes, there exists perhaps a still more intimate connexion 
 between its action and that of the organs W'hich secrete the urine; 
 it has always been observed, that when this last fluid is scanty, 
 there is a greater cutaneous perspiration, and vice versa. 
 
 If we examine with a microscope the naked body, exposed 
 during summer to the rays of a burning sun, it appears sur- 
 rounded with a cloud of steam, which becomes invisible at a 
 little distance from the surface. And if the body is placed before 
 a white wall, it is easy to distinguish the shadow of that emana- 
 tion. We may, likewise, satisfy ourselves of the existence of 
 the cutaneous perspiration by the following experiment: hold 
 
OF RESPIRATION. 
 
 259 
 
 the tip of the finger, at the distance of the twelfth part of an 
 inch from a looking glass, or any other highly polished surface; 
 its surface will soon be dimmed by a vapour condensed in 
 very small drops, which disappear on removing the finger. One 
 may, in this manner, ascertain that the cutaneous perspiration 
 varies in quantity in different parts of the surface of the body; 
 for, on placing the back of the hand before a looking glass, the 
 latter will be covered by no vapour. 
 
 No function of the animal economy has been the subject of 
 more investigation, nor has any excited the attention of more 
 accurate and indefatigable physicians, than the secretion now 
 under consideration. From the time of Sanctorius, who, in the 
 beginning of the seventeenth century, published in his immortal 
 work, “ Medicina statical^'' the result of experiments carried on 
 for thirty years, with a patience which very few will imitate, to 
 that of Lavoisier, who jointly with Seguin, aided by the re- 
 sources of the improved state of chemistry, instituted an exami- 
 nation of the insensible perspiration, we find engaged in this 
 inquiry, Dodart, who in 1668 communicated to the Academy of 
 Sciences, which had been founded but a short time, the result 
 of his observations at Paris, under a climate different from that 
 of Venice, where Sanctorius lived; Keill, Robinson, and Rye, 
 who repeated the same experiments in England and Ireland; 
 Linnings who performed his in South Carolina; and several 
 physiologists of no less merit, as Gorter, Hartmann, Arbuthnot, 
 Takenius, Winslow, Haller, &c.; who all aimed at ascertaining, 
 with more precision than had been done by Sanctorius, the va- 
 riations in the cutaneous perspiration; according to the climate, 
 the season of the year, the age, the sex, the state of health 
 or disease, the hour of the day, and the quantity of the other 
 secretions. 
 
 According to Sanctorius, of eight pounds of solid and liquid 
 aliments taken in twenty-four hours, five were carried off by the 
 perspiration, and only three in excrement and urine. Haller con- 
 ceives this calcvilation to be exaggerated; Dodart, however, car- 
 ried it still further, and maintained that the relation of the per- 
 spiration to the solid excrements, was as seven to one. 
 
 In France and in temperate climates, the quantity of the cu- 
 taneous perspiration and of the urine is nearly the same; it may 
 
OF RESPIRATIOX. 
 
 260 
 
 be estimated at between two and four pounds in the twenty-four 
 hours. We perspire most in summer, and void most urine in 
 winter. The perspiration, like every other secretion, is in smal- 
 ler quantity during sleep than while we are awake; in old age 
 than during infancy; in weak persons, and in damp weather, 
 than under the opposite circumstances. 
 
 The perspiration may be said to be in a compound ratio of 
 the force with which the heart propels the blood into the mi- 
 nute capillary arteries, of the vital energy of the cutaneous or- 
 gan, and of the solvent powers of the atmosphere. The strongest 
 and most robust men perspire most; some parts of the skin per- 
 spire more than others, as the palms of the hands, the soles of 
 the feet, the arm-pits, &c. When the air is warm, dry, and fre- 
 quently renewed, cutaneous perspiration is greater, and the 
 necessity of taking liquid aliment is more urgent, and more 
 frequently experienced; in summer, as every body knows, a 
 profuse perspiration is brought on by passing from the heat of 
 the sun into the shade; and, on no occasion is a copious sweat 
 more easily brought on, than by taking exercise in summer, 
 when, on the approach of a storm, the atmosphere containing a 
 considerable quantity of vapours, and warm from the rays of the 
 sun, which shows itself now and then surrounded by the clouds, 
 is little capable of dissolving the insensible perspiration. 
 
 The skin may be covered with sweat without any increase of 
 the cutaneous perspiration; this may happen from dampness in 
 the air, or from its being imperfectly renewed. It must be 
 owned, however, that sweating is more frequently occasioned by 
 an increase of the insensible perspiration, and that the warmth 
 of the bed which excites it, acts by increasing the power of the 
 organs of circulation, and the energy of the cutaneous system. 
 The body is weakened by sweating, which is seldom the case 
 with the insensible perspiration. A profuse sweat is attended 
 with a very speedy exhaustion; thus, in hectic fever, in the suette 
 (sudor anglicus') and other affections equally dangerous, it is the 
 cause of a wasting almost universally fatal. 
 
 The matter of the insensible perspiration and of the sweat, is 
 in great measure aqueous. Like the urine, it holds in solution 
 several salts; also the volatilized recrementitious matter of ani- 
 mal substances, sometimes even acids, as in the case in which 
 
OF RESPIRATION, 
 
 261 
 
 Berthollet detected the phosphoric acid in children affected 
 with worms, in pregnant women, in nurses, from whom there 
 exhales an odour manifestly acid. It may contain ammonia, and 
 on certain occasions, the smell enables us to discover that alkali 
 in the sweat or perspiration. 
 
 The air which constantly surrounds our body does not merely 
 dissolve the aqueous vapour which arises from it, but several 
 physiologists very reasonably conjecture, thar the oxygen of the 
 atmosphere may combine with the carbon of the blood brought 
 to the skin by the numerous vessels which are sent to it, and 
 likewise with the gelatine, forming the substance of the rete 
 mucosum of Malpighi. 
 
 The experiments of Jurine, of Tingry, and of several other 
 naturalists, show that carbonic acid is constantly formed on the 
 surface of the skin, so that the skin may be considered as a 
 supplementary organ to that of respiration; and in that point of 
 view, one may compare to it the mucous membranes which are 
 in contact with the atmospherical air in the nasal fossse, and in 
 the intestinal canal which they line. 
 
 The cutaneous perspiration is, likewise, as was before men- 
 tioned, a powerful means of cooling the body, and of keeping it 
 while living, in a uniform temperature. The water which is ex- 
 haled from the whole surface of the body, carries off from it, in 
 passing into vapour, a considerable quantity of caloric; and it is 
 observed, that every thing which increases the production of 
 caloric, gives rise to a proportionate increase of the cutaneous 
 perspiration, and of the pulmonary exhalation; so that a constant 
 equilibrium being kept up between its production and escape, 
 the animal warmth always remains nearly the same. 
 
 To conclude, the extremities of the nerves of our organs of 
 sensation are all moistened by a fluid varying in quantity, and 
 which maintains them in a softened state, favourable to the exer- 
 cise of their functions. It was likewise necessary that the mem- 
 brane in which the sense of touch resides, should be habitually 
 kept moist by a fluid that should penetrate it throughout; this 
 use of the insensible perspiration is not less important than the 
 preceding, on which physiologists have bestowed most attention.. 
 
262 
 
 CHAPTER V. 
 
 OF THE SECRETIONS. 
 
 Lxxxviii. Of the animal Jluids. The animal fluids were 
 formerly divided into recrementitious^ excrementitious^ and ex- 
 cremento-recrementitious; this division, founded on the uses to 
 which the fluids are subservient, is preferable to any that has 
 since been adopted, and in which they are ranked according to 
 their nature. 
 
 The first class remain in the body and are employed in its 
 nutrition and growth; such as the chyle, the blood, the serosity 
 which lubricates the surface of the pleura, of the peritoneum, 
 and of the other membranes of the same kind. The second kind 
 are ejected from our body, and cannot remain long within it 
 without danger; such as the urine, the matter of insensible per- 
 spiration and of sweat. Lastly, those of the third class par- 
 take of the nature of the two preceding, and are in part rejected, 
 while another part is retained and employed in the support and 
 growth of the organ; this is the case wdth the saliva, the bile, 
 the mucus of the intestines, &c. If one affected to be very mi- 
 nutely scrupulous, one might consider all the animal fluids as 
 recremento-excrementitious. The chyle and the blood, which 
 are so very nutritious, contain an abundance of heterogeneous 
 and excrementitious parts; the urine, which of all our fluids 
 is that which may, with most propriety, be termed such, con- 
 tains likewise aqueous parts, which, while it remains in the 
 bladder, the lymphatics absorb, and carry into the mass of the 
 fluids. 
 
 Of all the modern divisions, Fourcroy’s is the best; Vicq-d’- 
 Azir acknowledged its superiority over that proposed b\ Haller, 
 in his Physiology. Fourcroy a^lmics six classes of flnid.s: 1st, 
 those which hold salts in solution, as the sweat and urine; he 
 gives the name of to such fluids: 2d, infla > mable oily 
 
 fluids, all possessing a certain degr-e of consistence and con- 
 crescibility, as fat, and the cerumen of the ears, &c.: 3. , tht sapo- 
 naceous fluids, as the bile and the milk; 4th, the mucous fluids. 
 
OF THE SECRETIONS. 263 
 
 as those which lubricate the internal coat of the intestinal canal: 
 5th, the albuminous fluids, among which one may rank the se- 
 rum of the blood. The Jibrinous fluids, containing fibrina, as 
 the fluid last mentioned. 
 
 In proportion as we advance in our knowledge of animal 
 chemistry, the defects of these divisions become more and more 
 evident. In short, the animal fluids are so compound, that there 
 is not one which does not, at once, belong to several of these 
 classes, and whose prevailing element is not sometimes exceed- 
 ed in quantity, by materials which commonly form but a small 
 part of them. 
 
 LXXXIX. The blood is the reservoir and the common source 
 of the fluids; these do not exist in the blood, with the qualities 
 which characterize them, unless, after having been previously 
 formed by the secretory organs, they have been absorbed by 
 the lymphatics, and conveyed, with the chyle and lymph, into 
 the circulatory system. Let us shortly attend to its nature, al- 
 though this belongs more especially to the department of che- 
 mistry. The blood is red in man and in all warm-blooded ani- 
 mals, and even in some whose temperature is not very different 
 from that of the atmosphere, as in fishes and reptiles. This 
 colour, of a deeper or lighter shade, according as the blood 
 is drawn from an artery or a vein, varies in its degree of in- 
 tensity, according to the state of health or weakness. It is of a 
 deep red in strong and active persons, pale and colourless in 
 dropsical patients, and whenever the health is weak. By its 
 colour, one may judge of all its other qualities. Its viscidity is 
 greater, its saline taste more marked, its peculiar smell stronger, 
 when its colour is deep. This colour is produced by a prodi- 
 gious number of globular molecules, which move and float in 
 an aqueous and very liquid fluid. When the blood is pale, the 
 number of these molecules diminishes, they seem to be dis- 
 solved in cachexiae. 
 
 The microscope, which affords the only method of perceiving 
 them, does not enable one to determine their bulk and their 
 figure. Leeuwenhoek, who brought forward the idea of their 
 being so minute, by his calculation, that they were one millionth 
 part of an inch in size, thought them spherical. Hewson says 
 
 I 
 
264 OP TE(E SECRETIONS. 
 
 they are annular and have an opening in their centre. Others 
 compare them to a flattened lentil, with a dark spot in the mid- 
 dle. They are solid, and formed by a nucleus or red point co- 
 vered over by a membranous vesicle, which appears to be readily 
 formed and destroyed. 
 
 XC. The blood, when no longer in the course of the circula- 
 tion, and on being received into a vessel, parts with its caloric 
 and exhales, at the same time, a powerful smell, a gas to which, 
 according to some physiologists (Moscati, Rosa, &c.), it owes 
 its vital properties, and the absence of which is attended with a 
 loss of its vitality; so that its analysis cannot furnish facts appli- 
 cable to the explanation of the phenomena of health and dis- 
 ease. This odour, extremely strong in carnivorous animals, is 
 very distinguishable in man, especially in arterial blood. I re- 
 member retaining it, a whole day, in my throat, after removing 
 the dressings, and suppressing a hemorrhage, occasioned by a 
 relaxation of the ligatures, a week after the operation for popli- 
 teal aneurism. Unless by agitation it is prevented from coagu- 
 lating, as it cools, its consistence increases, and, on being laid 
 by, it separates into two very different parts, the one aqueous, 
 more or less red, heavier than common water, and evidently 
 saltish; this is called the serum, consisting of water, in which 
 are dissolved albumen, gelatine, soda, phosphates, and muriates 
 of soda, nitrate of potash, and muriate of lime. 
 
 Serum, though bearing some analogy to the albumen of egg, 
 differs from it, in forming, on coagulating, a less solid and less 
 homogeneous mass. The albumen is evidently mixed with a 
 portion of transparent gelatine, not coagulable by heat. Albu- 
 men has so great an attraction for oxygen, that it is fair to pre- 
 sume, that the serum absorbs oxygen and combines with it, 
 through the very thin parietes of the air cells of the lungs, and 
 that it gives to arterial blood that spumous appearance which is 
 one of its distinguishing characters. This oxidiaement, and the 
 fixation of the caloric which accompanies it, equally increase 
 its consistence. It does not, however, coagulate; because it is 
 kept in perpetual motion by the circulatory action, and is dilu- 
 ted by a suflicient quantity of water; because the animal tem- 
 
OP THE SECRETIONS. 
 
 265 
 
 perature, which never exceeds thirty-two or thirty-four degrees, 
 cannot give a solid form to albumen, which coagulates only at 
 fifty '.kgr ees of Reaumur’s thermometer; and lastly, because as 
 serum contains a certain quantity of uncombined soda, which 
 enables it to turn green, vegetable blues; this alkali concurs in 
 keeping the albumen in a dissolved state, which it renders fluid, 
 when it has been coagulated by the acids, by heat, or by alcohol. 
 
 Amid the serum, and on its surface, there floats a red cake, 
 spungy, and solid (insula rubra') which, by repeated washing, 
 may be separated into two very distinct parts. The one is the 
 cruor or the colouring matter which mixes with the water; it is 
 a more highly oxygenated and more concrescible albumen than 
 that of the serum; it holds in solution soda, as well as phosphate 
 of iron, with an excess of iron. 
 
 The other is a solid and fibrous substance, which, after being 
 repeatedly washed has the appearance of felt, the filaments of 
 which cross each other, are extensible and very elastic. This 
 third part of the blood is called Jibrina, it is very similar in its 
 nature to muscular fibre, and like it, gives out, on distillation, a 
 considerable quantity of carbonate of ammonia. Fibrina does 
 not exist in the blood in a solid form, but in a state of solution 
 and combined with the other constituent parts of the fluid, as 
 is indicated by the appropriate expression of liquid flesh (chair 
 CGulante) first used by Bordeu, in speaking of the blood. 
 
 XCI. If the blood be exposed to the action of fire, if it be 
 calcined and reduced to powder, and if this pulverized sub- 
 stance be exposed to a magnet, the presence of iron will be 
 manifestly seen by the magnetic attraction. Authors do no,t 
 agree in their accounts of the quantity of iron contained in the 
 blood. Menghini s^ys, there is one part in the hundred; others 
 that it is in the proportion of 1 to 303; so that it is probable, 
 that this constituent principle of the blood, like all the materials 
 of our fluids, may vary in quantity, according to different cir- 
 cumstances. 
 
 Blumenbach justly observes, that iron is found only in cal- 
 cined blood; that none is to be found if it be slowly dried. This 
 peculiarity is no longer surprising, since M. Fourcroy has 
 shown that iron existed in the blood, in combination with the 
 
OF THE SECRETIONS. 
 
 266 
 
 phosphoric acid, and formed with that acid a phosphate of iron, 
 with an excess of its base. This salt becomes decomposed by- 
 calcination, the iron is set free and is acted upon by the magnet. 
 Ph)'siologists attribute the colour of the blood, to che presence 
 of the oxide of iron in that fluid. 
 
 It is, at present, the received opinion, that the red colour of 
 the blood is owing to the presence of phosphate of iron, which 
 being conveyed, of a white colour, into the blood, along with 
 the chyle, meets with the pure soda, by which it is dissolved, 
 and from which it receives its colour; the colour of the blood 
 is, likewise, owing to the oxidizement of the metallic portion, 
 which is in very considerable quantity in that salt. This solu- 
 tion of the phosphate of iron by soda, the oxidizement of the 
 excess of iron, and the absorption of oxygen bv albumen, con- 
 stitute, in an especial manner, hematosis or sanguification^ which 
 is principally carried on in the lungs. 
 
 The respective proportion of the three parts into which the 
 blood separates spontaneously, varies considerably. The serum 
 constitutes about one half or three fourths of the fluid; the colour- 
 ing matter and fibrina are in inverse ratio of the serum, and it is 
 observed, that the more brilliant and red the colour of the blood, 
 the greater the proportion of the fibrous part. The pale, aqueous, 
 and colourless blood of a dropsical patient contains very little 
 fibrina. In putrid or adynamic fever in which bleeding, as is uni- 
 versallv known, is improper, I have sometimes seen the blood 
 containing but a small portion of fibrina, and very slow of coagu- 
 lating; its texture seemed to suffer from the affection under which 
 the muscular organs were evidently labouring. In inflammatory 
 diseases, on the contrary, the plastic power of the blood is aug- 
 mented; the fibrina is in greater quantity, even the albumen 
 coagulates spontaneous!}' and forms a crust above the serum, 
 which is always in smaller quantity. 
 
 XCII. Of the changes of the blood. The fluids not only un- 
 dergo changes in their composition, in their qualities, and na- 
 ture, when the action of the solids is itself altered, but even the 
 absorbent system may introduce, into the mass of our fluids, 
 heterogeneous principles, evidently the cause of several dis- 
 eases. In this manner all contagions spread, the virus of small 
 pox, of syphilis, of the plague, &c. Thus, in time, the habitujd 
 
OF THE SECRETIONS. 
 
 267 
 
 use of the same aUment produces in our fluids a crasis or pecu- 
 liar constitution which has, on organized solids, an influence 
 acting even on the mind.* 
 
 • These opinions of our author are evidently borrowed from the humoral 
 pathology. Of this absurd system, much is still retained, and especially by the 
 French pathologists. We believe that the changes wrought in the fluids are 
 wholly produced through the intervention of the solids. Not the slightest 
 proof exists of their being vitiated by the introduction of “heterogeneous 
 principles” much less that this mixture is the “cause of several diseases ” It is 
 manifest that every portion of the absorbent system, has the power, in a very 
 great degree, of digesting and animalizing the substances which are taken up. 
 This property of the absorbents is a provision of nature to prevent noxious 
 substances from penetrating into the circulation unchanged. In most instances 
 they are fully adequate to this end. Where they are not, the substance passes 
 to the first lymphatic gland, which takes on inflammation and intercepts its 
 further progress, as in the case of bubo. In this respect therefore, the conglo- 
 bate glands maybe considered as centinels guarding the exterior approaches 
 of the body. 
 
 We are not ignorant that some of the properties of certain substances when 
 absorbed display themselves in the secretions and excretions, as the odour 
 of garlick, the colouring matter of madder, &c. &c. But it does not hence follow 
 that they entered the circulation unchanged. 
 
 Experiments indeed, prove quite the contrary, as neither one, nor the other, 
 ean be detected in the serum of the blood. It seems to us most probable, that 
 the process of assimilation, whether performed by the chylopoietic viscera, 
 ®r by the absorbent apparatus, completely decomposes all substances subject- 
 ed to its influence, and however various in their principles, reduces them to one 
 homogeneous fluid, bland and inoperative in its nature, or in other words ren- 
 ders it fit for the purpose of nutrition. But, in the excretions or secretions, being 
 removed beyond the sphere of the vital powers, chemical action takes place, 
 by which those substances are in part cr entirely regenerated. 
 
 Whether the particular explanation offered by this hypothesis be received 
 or not, the fact at least must be acknowledged, that no sub.stance in its active 
 condition does enter the circulation, since experiments have shown that how- 
 ever mild the fluid maybe, either milk or mucilage, oil or pus, it cannot even 
 in the smallest quantity be injected directly into the blood-vessels without 
 occasioning the most fatal consequences. As regards the operation of sub- 
 stances on the living system, we do not think it at all necessary to resort to 
 the circulation as a medium through which it is effected. By referring it to 
 that law of the animal economy termed sympathy or consent of parts, we ha\<e 
 a rationale far more consistent with those views derived from the present im- 
 proved state of our knowledge. 
 
 Conformably to this theory, when a substance either medicinal or poisonous fs 
 applied to a susceptible portion of the body, externally or internally, an action is 
 excited which is extended, more or less according to the diffusibility of the pro- 
 perties of the substance, or the degree of sympathetic connection which the part 
 
OF THE SECUETIONS. 
 
 268 
 
 A purely vegetable diet conveys into the blood, according to 
 Pythagoras, bland and mild principles. This fluid excites the 
 organs in a moderate degree, and this check over the physical 
 excitement, facilitates the observance of the laws of temperance, 
 the original source of all virtues. These observations of ancient 
 philosophy, on the influence of regimen, have, doubtless, led 
 their authors to exaggerated inferences, but they should not be 
 considered as altogether unsupported. The carnivorous species 
 are marked by their strength, their courage, and their ferocity; 
 savages who live by bunting, and who feed on raw, bloody, and 
 palpitating flesb, are the most ferocious of men; and, in our own 
 country, in the midst of those scenes of horror which we have 
 witnessed, and from which we have suffered, it was observed, 
 that butchers were foremost in the massacres, and in all the acts 
 of atrocity and barbarity. I know that this fact, which was uni- 
 formly noticed, has been explained by saying, that the habit of 
 slaying animals, had familiarized them to shed human blood. 
 But though I do not deny the existence of this moral cause, 
 which certainly operates, I think I may add to it as a physical 
 cause, the daily and plentiful use of animal food, the breathing 
 an air filled with emanations of the same kind, which they in- 
 
 may have with the body generally. Thus a set of actions is raised, every one of 
 which is precisely similar, provided they are confined to the same system, by 
 which is to be understood, parts of an identity of structure. If, however, the 
 chain runs into other systems, it loses its hemogeneous character, the actions 
 being modified according to the peculiar organization of the parts in which 
 they may take place. 
 
 To illustrate, the more distinctly, our meaning, we will state a very fami- 
 liar case. By inserting a particle of variolous matter under the skin, local irrita- 
 tion is created: in a few days this action becomes diffused, and a fever ensues, 
 which after a short continuance throws out an eruption, each pustule of which 
 is alike, because the surface of the body is of a uniform structure, containing 
 exactly the same sort ®f virus as the primary or parent pustule. It is in this 
 wa}', that morbid motion distributes itself When diseases arise from a pointy 
 as in fact all diseases do, but more strikingly those occasioned by inoculation, 
 the matter introduced is not infinitely divided and spread over the body, but 
 the action which that matter had originally excited. These are general prin- 
 ciples, which apply to the system in every condition, and explain the modus 
 operandi of medicines as well as of the causes of disease. Whatever, in short,- 
 operates on the living frame is obedient to the same laws. The spot first acted 
 upon, is the focus from which is irradiated the more diffused impressions. Ed 
 
OF THE SECRETIONS. 269 
 
 hale, and which contribute to their embonpoint^ which is some- 
 times excessive. 
 
 A s the plasticity and concresibility of the blood are diminish- 
 ed in asthenic diseases or of debility, as putrid fevers and scurvy, 
 two causes may be assigned for the hemorrhages which come on 
 in those diseases, viz. the relaxed state of the vessels and the 
 dissolution of the blood. In scurvy, the tissue of the capillaries 
 is relaxed, its meshes enlarged, red blood passes into them, tran- 
 sudes through their parietes, and forms scorbutic spots. I have 
 sometimes seen those ecchymoses or sanguineous cutaneous 
 transudations extend under the skin of the whole of one lower 
 extremity. Petechiae, in putrid fever, are formed in the same 
 manner, and depend, likewise, on the relaxation of the minute 
 vessels, and on the greater fluidity of the blood, whose mole- 
 cules are less coherent, and more readily separated from each 
 other. 
 
 In the summer of the year 1801 , I amputated the arm of an 
 old man of sixty, on account of a corroding and varicose ulcer, 
 which for thirty years had occupied a part of the forearm, and 
 extended to the elbow. All who were present at this operation, 
 observed that the blood which flowed from the arteries, was not 
 nearly so red as that from the arteries of a young man, whose 
 thigh had just been taken off, on account of a scrophulous caries 
 of the leg; that the venous blood was entirely dissolved, purple, 
 and similar to a weak dye of logwood. This blood did not co- 
 agulate like that of the young man, it became fluid and was con- 
 verted into a serum containing a few colourless clots. 
 
 Those who have endeavoured to find, in the changes undergone 
 by the blood and the other fluids, the cause of all diseases, have 
 fallen into as serious blunders as the determined solidists, who 
 maintain that all diseases arise from a deranged condition of the 
 solids, and that every change in the condition of the fluids is a 
 consequence of that derangement. The believers in the humoral 
 pathology, have certainly gone too far; they have admitted that 
 the animal fluids might be acid^ alkalescent^ acrimonious^ while 
 we have no proof whatever that they ever do undergo such 
 changes. The solidists have, likewise, gone much beyond the 
 truth, in saying, that every primitive change in the condition of 
 
OF THE SECRETIONS. 
 
 270 
 
 the fluids is imaginary, and that the doctrine of humoral patho- 
 logy is without foundation. Stahl relates* that the blood of a 
 ‘ young woman, who was bled during a fit of epilepsy, was abso- 
 lutely coagulated, as if that fluid had partaken in the rigidity af- 
 fecting the muscular organs. Some authors say they have met 
 with the same appearance; I have, however, never been able to 
 discover any sensible difference between the blood of an epilep- 
 tic patient and of any other person of the same constitution, of 
 the same age, and living on the same regimen; and it should be 
 considered, that to make a just comparison of our ffuids, it is ne- 
 cessary that every thing should be alike in the persons from 
 whom they are taken, with the exception of the difference of 
 which we are to judge. In fact, the blood has not the same ap- 
 pearance, and does not coagulate in the same manner when 
 taken from a child, a woman, or an old man; from a man who 
 lives abstemiously, or from one who lives on a full diet. 
 
 After enumerating the changes which the blood undergoes, 
 one might speak of those which affect the fluids that are formed 
 from it; one might attend to the greenish, leek colour, and some- 
 times even darkish appearance of the bile, which is not always 
 of the same degree of bitterness; the limpid state of the urine, 
 which is voided colourless, without smell or flavour,after a fright, 
 or during the convulsive fits of hysterical women; the fetid smell 
 and the viscidity of the saliva, when the salivary glands are un- 
 der mercurial influence; the milky state of the serum which lu- 
 bricates the parietes of the abdomen and of the viscera which it 
 contains, after inflammation of the peritoneum; changes which, 
 almost universally, depend on a derangement of action in the se- 
 cretory organs, and sometimes, likewise, on the general condition 
 of the fluids; for, a gland cannot secrete a fluid endowed with 
 the qualities which peculiarly belong to it, unless the blood fur- 
 nish it with the materials of secretion, and unless it be in a state 
 to bring about a due combination of their particles. When we 
 come to the article of accidental secretions, we shall speak of 
 some of those disorders of the fluids, depending on a depraved, 
 condition of the secretory organs. 
 
 XCIII. On the transfusion of blood. In the midst of the dis- 
 
 * T/ieoria medica •sera, page 678. 
 
OF THE SECRETIONS. 
 
 271 
 
 putes to which the discovery of the circulation gave rise, some 
 ph ysicians conceived the idea of renovating completely the whole 
 mass of the fluids, in persons in whom they might be vitiated, by 
 filling their vessels with the blood of an animal or of a person in 
 good health. Richard Lower, known by his work on the heart, 
 first practised it on dogs, in 1665. Two vears afterwards, trans- 
 fusion was performed at Paris on men, and excited the greatest 
 expectations: it was thought that bv this process, called trans- 
 fusing surgery (chirurgie transfusoire)^ all remedies would be 
 superseded, that henceforth, to cure the most serious and inve- 
 terate diseases, it would be necessary merely to transfuse the 
 blood of a strong and healthy man into the veins of the diseased; 
 nav, they went so far as actually to imagine they might realize 
 the fabulous fountain of Jouvence; they expected no less than 
 to restore youthful vigour to the old, by infusing into them the 
 blood of the young, and thus to perpetuate life. All these bril- 
 liant chimeras soon vanished; some underwent the experiment 
 without any remarkable effects from it, others were affected with 
 the most violent delirium; a lad of fifteen lost his senses, after 
 suffering two months from the most violent fever. The legislative 
 authority at last interfered, and prohibited those dangerous ex- 
 periments. 
 
 The experiments on the subject of the transfusion of blood 
 were repeated, but without success, at the Academy of Sciences. 
 Perrault opposed this new method, and showed that it was very 
 difficult for one animal to exist on the blood of another; that this 
 fluid, though apparently the same in animals of the same age, 
 was as different from it as the features of their face, their tem- 
 per, &c.; that an extraneous fluid was thus introduced, which con- 
 veying to the organs an irritation to which they were not accus- 
 tomed, must disorder their action in various ways; that if, as an 
 objection to what he had said, they should bring forward what 
 takes place in grafting, in which the sap of one tree nourishes 
 another of a different kind, he would answer, that vegetation 
 does not depend on so complicated, nor on so delicate a me- 
 chanism as the nutrition of animals; that a hut may be formed of 
 all kinds of stones taken at random, but that to build a palace, 
 stones must be designedly shaped for the purpose, so that a stone 
 
OF THE SECRETIONS. 
 
 272 
 
 destined for an arch, will not do for a wall, nor even for another 
 arch.* 
 
 It would be easy, by means of a curved tube, to tranfuse the 
 arterial blood of an animal, from a wound in its carotid artery, 
 into the saphena vein of a man, into the internal jugular, or into 
 some of the cutaneous veins of the fore arm; but it is to be pre- 
 sumed, from experiments on living animals, that it would be very 
 difEcultto transfuse blood into the arteries, as these vessels, filled 
 with blood, during life, do not yield to a greater distention. The 
 capillaries, in which the arteries terminate, become corrugated 
 and refuse to transmit a fluid which does not act upon them, ac- 
 cording to their wonted sensibility. Such was the result of the 
 experiments of Professor Buniva; he observed in a living calf, 
 that the vessels did not transmit freely the fluid which was 
 forced into them, till the instant when the animal was killed, by 
 dividingthe upper part of the spinal marrow. Attempts have been 
 made to turn to useful purposes these experiments on transfusion, 
 by limiting the process to the injecting of medicinal substances 
 into the veins. It is singular, that the moment a fluid is injected 
 into the veins of an animal, it endeavours to perform motions of 
 deglutition, as if the substance had been taken in at the mouth. 
 All these attempts have been too few in number, and are not suf- 
 ficiently authenticated to justify their application to the human 
 subject. But there is every reason to believe, that, even with 
 the utmost care, the life of those who should submit to them 
 would be endangered; so that it is at once humane and prudent 
 to abstain from them. 
 
 XCIV. Of the secretions. It has been said, in too general a 
 way, that the organs receive from the blood conveyed to them 
 by the arteries, the materials of the fluids which thev separate 
 from it. We have seen, that the liver is a remarkable exception 
 to this general rule; the same observation seems likewise appli- 
 cable to the mammae; they appear to receive the elements of 
 their milky secretion from the lymphatics, which are so very 
 numerous' in their structure. 
 
 One is, therefore, justified in saying, that the elements of 
 our fluids may be furnished by vessels of every kind, to the 
 
 * Academic royale des Sciences, 1667, page 37 
 
OF THE SECRETIONS. 
 
 273 
 
 organs in which such fluids may be elaborated. The term 
 secretion^ whatever its etymology may be, denotes that fiinction 
 by which an organ separates from the blood the materials of a 
 substance which does not exist in that fluid, with its characte- 
 ristic qualities. By the term secretion, one should not, therefore, 
 understand the mere separation of a fluid existing before the 
 action of the organ by which it is prepared. 
 
 XCV. The differences between the secreted fluids are evi- 
 dently connected with those of the organs employed in their 
 formation. Thus, the arterial exhalation which takes place, 
 throughout the whole extent of the internal surfaces, maintains 
 their contiguity, throws out an albuminous serosity which is 
 merely the serum of the blood, slightly changed, by the feeble 
 action of a very simple organization. The analysis of the fluid 
 of dropsy, which is merely the serosity constantly transuding 
 from the surface of the serous membranes, as the pleura and 
 peritoneum, shows, that it bears the strongest resemblance to 
 the serum of the blood, and that it differs from it, only in the 
 varying proportions of albumen and of the different salts which 
 it holds in solution. 
 
 This first kind of secretion, this perspiratory transudation, 
 would seem to be a mere filtration, through the pores of the 
 arteries, of a fluid already formed in the blood. There is, how- 
 ever, besides, an inherent action in the membranes whose sur- 
 face it continually lubricates. If it were not for this action, the 
 serum would remain united to the other constituent parts of the 
 fluid, which is in too much motion, and at too high a tempera- 
 ture, to allow of a spontaneous separation. The term exhalation, 
 which is applied to this secretion, gives an incorrect idea of it; 
 for exhalation, which is a purely physical phenomenon, and re- 
 quiring the presence of air to dissolve the fluid that is exhaling, 
 cannot take place from surfaces that are in absolute contact, and 
 between which there is no interval. The character of this mode 
 of secretion is the absence of any intermediate substance be- 
 tween the vasa afferentia and the excretory ducts; the minute 
 arteries and veins which enter into the structure of the mem- 
 branes being, at once, vasa afferentia and excretory ducts. The 
 fluid secreted by the serous membranes, though bearing a con- 
 siderable analogy to the serum of the blood, differs from it, 
 
 2 M 
 
OP THE SECRETIONS. 
 
 274 
 
 however, by being animalized in a greater degree. The most 
 important function of these organs is, therefore, that they concur 
 in the common process of assimilation; the office which has 
 been long assigned to them of facilitating the motion of the 
 organs which they envelop, by lubricating their surface, will 
 appear to be of very secondary importance, if it be considered, 
 that respiration is not impeded by adhesions between the lungs 
 and the pleura, and that, besides, the brain, which when the 
 cranium is whole, is completely motionless, is entirely surround- 
 ed bv a serous membrane. 
 
 XCVI. Next in order to the serous transudation, which 
 requires a very simple organization, comes the secretion which 
 takes place in the cryptas, in the glandular follicles and in the 
 mucous lacunae. Each of these small glands, contained within 
 the membranes lining the digestive canal, the air tubes, and the 
 urinary passages, and the collection of which forms the amyg- 
 dalae, the arytenoid glands, &c. may be compared to a small 
 bottle with a round bottom, and a very short neck; the mem- 
 branous parietes of these vesicular cryptae receive a considerable 
 number of vessels and nerves. The peculiar action of the parietes 
 of these different parts, determines the secretion of the mucus 
 furnished by those glands. These mucous fluids, less liquid and 
 more viscid than the serosity which is the product of the first 
 mode of secretion, contain more albumen and a greater number 
 of salts, differ still more from the serum of the blood, and are of 
 a more excrementitious nature. 
 
 The bottom of these utricular glandulse is turned towards the 
 parts to which the mucous membranes adhere; their mouth, or 
 neck, opens on the surface at which those membranes are in 
 contact. These kinds of excretory ducts, wider, or narrower, 
 and always very short, sometimes unite, run into each other, 
 and open within the cavities. These common orifices, at which 
 several mucous glands empty themselves, are easily seen on 
 the amygdalae, towards the mucous lacunae of the rectum and 
 of the urethra, at the base of the tongue, &c. The albuminous 
 fluid, which is poured within those glandular crj ptae, remains 
 some time within the cavity, becomes thicker from the absorp- 
 tion of its more fluid parts; for there are, likewise, lymphatics 
 within the texture of their parietes. When the surfaces, on 
 
OF THE SECRETIONS. 
 
 275 
 
 which they are situated, require to be moistened, this small 
 pouch contracts, and throws up the fluid with which it is filled. 
 The secretion and excretion are promoted by the irritation 
 which the presence of the air, of the aliment, or of the urine 
 occasions, by the compression exerted by those substances, and 
 lastly, by the peristaltic contractions of the muscular planes to 
 which the mucous membranes adhere, throughout the whole 
 extent of the digestive tube. 
 
 XCVII. Those fluids which differ much from the blood, 
 require, for their secretion, organs of a more complicated 
 nature; such organs are called conglomerate glands, to dis- 
 tinguish them from the lymphatic glands, which have been 
 termed conglobate. Those glands constitute the viscera, and are 
 formed by a number of nerves and vessels of all kinds, arrang- 
 ed in fasciculi and united by cellular membrane. A membrane 
 peculiar to the organs, or supplied by those which line the cavi- 
 ties in which they are contained, covers their outer part, and 
 insulates them from the neighbouring organs. 
 
 The intimate arrangement of the different parts which form 
 the secretory glands, the disposition of the arteries, of the 
 veins and nerves, and the manner in which the lymphatics and 
 excretory ducts arise from them, have given rise to endless dis- 
 cussions, and formed the basis of former physiological theories. 
 What follows may be considered as a correct abstract of what is 
 known on the subject. 
 
 The respective arrangement of the similar parts (^parties 
 similaires*') which enter into the structure of the glands and 
 which form their proper substance, or parenchyma,! is different 
 in each of them; this explains their differences, in the double 
 relation of their properties and their uses. The arteries are not, 
 
 * By parties similaires, the author means the simple elementary tissues. — 
 See the preliminary discourse, page 19. 
 
 t Do the different appearances of the substance of glandular bodies depend 
 on the different manner in which the similar parts cross each other, and on 
 their different proportions in every gland; or do these differences of colour, of 
 density, by means of which we so readily distinguish the substance of the 
 liver from that of the salivary glands, depend on the existence of a peculiar 
 tissue in each organ? This question cannot be answered, in the present state 
 of anatomy. The opinion, however, which supposes the different nature of the 
 glands to depend on the different proportions of those constituent parts, in 
 each of them, appears the most probable. 
 
OF THE SECRETIONS, 
 
 276 
 
 as Ruysch thought, immediately continuous with the excretory 
 ducts, nor are there intermediate glands between those vessels, 
 as Malpighi conceived; It seems more probable, that each 
 gland has its own peculiar cellular or parenchymatous tissue, 
 in the areolse of which the arteries pour the materials of the 
 fluid which the gland prepares, in virtue of a power which is 
 inherent to it, and which is its distinguishing character. The 
 lymphatics and the excretory ducts arise from the parietes 
 of those, cells; and these two kinds of vessels absorb — the one 
 set, the secreted fluid which they carry to the reservoirs in 
 which it accumulates; while the other set take up that part 
 of the fluid, on which the organ has not completed, its action; in 
 other words, the residue of secretion. 
 
 XCVIII. Of accidental secretions. If one wished to extend 
 the idea attached to the term secretion, one might say, that 
 every thing, in the living economy, is performed by means 
 of the secretions. What is digestion, but the separation or 
 secretion of the chylous or nutritive parts of aliments, from 
 their faecal or excrementitious portion? Do not the absorbents 
 concur in this secretion? May they not be considered as the 
 excretory ducts of the digestive organ which acts on the aliment, 
 in the same manner as a secretory gland acts on the blood that 
 contains the materials of the fluid to be elaborated? Respiration, 
 as we have already seen, is but a double secretion which the 
 lungs perform, on the one hand, of the oxvgen contained in the 
 atmospherical air, and on the other hand, of the hydrogen and 
 carbon, of the water, and of the other heterogeneous principles 
 contained in venous blood; and, as will be shown in the ensuing 
 chapter, nutrition is but a peculiar mode of secretion which is 
 different in every organ. It is, therefore, only after a series of 
 very delicate and very complicated separations and analyses, 
 that the organs are enabled to make extraneous substances 
 undergo such a change of composition, as to render them fit for 
 their growth and reparation. 
 
 There is every reason to believe, that the phenomena of sen- 
 sation and of motion, by means of which man keeps up, with 
 surrounding objects, the relations necessary to his existence, 
 are the result of the secretions of which the blood furnishes the 
 materials prepared by the brain, by the nerves, by the muscles, 
 
OF THE SECRETIONS. 
 
 277 
 
 &c. A plant separates from the earth, in which its roots are 
 huried, the juices which it requires; these juices constitute the 
 sap, which, after being filtered through a multitude of canals, 
 supplies the different secretions whose products are leaves, 
 blossoms and fruits, with gums, essential oils, and acids. All 
 organized bodies are, therefore, so many laboratories, in which 
 numerous instruments spontaneously perform various composi- 
 tions, decompositions, syntheses, analyses, which may be consi- 
 dered as so many secretions from the common fluid. 
 
 If we confine ourselves in our view of the subject, and limit 
 our attention to man, the principal and almost the sole object of 
 our study, we shall see that the different secretions that may 
 take place in him, are extremely numerous and varied, and that 
 a change in the condition of one of his organs, is sufficient to 
 enable it to secrete a new fluid. Hence inflammation in any 
 gland, is sufficient to alter the secretion of the organ that is 
 affected. A portion of adipose tissue, on being affected with 
 inflammation, shall secrete, instead of fat, a whitish fluid known 
 by the name of pus. The pituitary membrane, when inflamed, 
 furnishes a mucous more fluid and more abundant, and which, 
 by degrees, returns to its natural state, in proportion as the 
 coryza goes off; the serous membranes, as the pleura and the 
 peritoneum, will allow a greater quantity of serum of a more al- 
 buminous quality, sometimes even coagulable lymph, to exude; 
 at other times, inflammation causes an adhesion of their conti- 
 guous surfaces, and as the inflammatory state varies in intensity, 
 the accidental secretion will likewise vary as to its qualities; 
 thus, the phlegmonous inflammation which should furnish, on 
 terminating in suppuration, a whitish fluid, thick, consistent, 
 and almost without smell, will give out, if the process is not 
 sufficiently active, a serous pus, colourless, and without con- 
 sistence, &c. For the same reason, the blood vessels of the 
 uterus pour out, in some women, a dark coloured blood, while 
 in others, they give out a mere serosity, very slightly, if at all, 
 tinged with blood.* 
 
 * To these exampleis of morbid secretions, others may be added, even 
 more remarkable, as the virus in rabies canina, in syphilis, the small pox, &c. 
 By some animals the power is possessed of secreting naturally the most virulent 
 
 poisons. 
 
OP THE SECRETIOXS. 
 
 278 
 
 The menstrual discharge, in women, is the product of a real 
 secretion of the arterial capillaries of the uterus, in the same 
 manner as those vessels in the pituitary membrane, the mem- 
 brane which lines the bronchiae, the stomach, the intestines, the 
 bladder, &c. pour out blood abundantly, or allow its transuda- 
 tion, when irritation is determined to those parts; in hemorrhage 
 from the nose, in bleeding from the lungs, or from the stomach, 
 when the vessels are not ruptured by external violence. Apo- 
 plexy itself, whether sanguineous or serous, may, in several 
 instances, be ranked among those secretory evacuations, the 
 quality of which varies, according to the energy of the capilla- 
 ries which produce it. On opening dead bodies, one frequently 
 meets with a collection of blood in the ventricles of the brain, 
 in persons who have died from apoplexy, yet the most careful 
 examination does not enable one to detect the slightest lacera- 
 tion or rupture in the veins or in the arteries within the skull.'*' 
 
 poisons. Of this description are many of the reptiles, but especially the viper, 
 the rattle-snake, &c. There are others again, ■which are distinguished by secre- 
 tions peculiar to themselves. For instance, the ant pours out a fluid of a specific 
 acid nature, the scuttle fish a dark liquor, and the skunk a urine so offensive 
 as to become a means of protection, repelling, by its stench, many an as- 
 sailant. — Ed. 
 
 That the menstrual discharge results from a secretory action of the uterus, 
 is a doctrine which we early adopted, and have taught in our lectures for the 
 last ten years. Every other hy^po thesis on the subject is totally irreconcilcable 
 with facts, and repugnant to the laws of the animal economy. The crude 
 speculations of former times, respecting this operation, may, indeed, be 
 considered as discarded. Does any one, for instance, whose knowledge has 
 kept pace with the improvements of physiology, now entertain the notion 
 of lunar influence, of fermentation of venereal appetite, of general plethora or 
 local congestion, &c. &c.? Tlie leading arguments, in defence of this doctrine, 
 may be thus enumerated. 
 
 1. That the uterus, in its villous and vascular structure, resembles a gland, 
 and also in its diseases, being equally liable to scirrhus, cancer, &c. &c. 
 
 2. That, like other secretory organs, blood is very copiously diffused through 
 it. 
 
 S. That, by the arrangement of its vessels, it is evidently designed that the 
 circulation should be retarded for the purpose of secretion. The arteries are not 
 only exceedingly convoluted, but they are larger, and -with thinner coats than 
 their corresponding veins. 
 
 4. That, in common with other secretions, menstruation is often, at first, 
 imperfectly performed, and is subject afterwards to vitiation and derange- 
 ment. 
 
OB' THE SECRETIONS. 
 
 2,79 
 
 The nerves, of which there Is always a certain number in the 
 structure of the secretory organs, and which are principally 
 
 ment. In the beginning the discharge is commonly thin, colourless, and defi- 
 cient, and recurs at protracted and irregular intervals. In some of these par- 
 ticulars, .it is analogous to the seminal secretion. 
 
 5. That, in many of the inferior animals, during the season of venereal 
 incalescence, there is an uterine effusion which is undoubtedly a secretion. 
 This answers, seemingly, the same end as menstruation, namely, giving to the 
 uterus an aptitude for conception. Though this fluid generally differs from the 
 menses in complexion, yet, in some instances, they are precisely similar. 
 Whenever the venereal desire suffers a violent exacerbation from restraint or 
 other causes, the discharges in these animals become red. This has been 
 more especially remarked in bitches kept from the male. 
 
 6. That, when the menses are suppressed, they cannot be restored by 
 inducing plethora, nor the flow be checked by blood-letting, or any other 
 means of depletion. Besides, no vicarious discharge relieves the symptoms of 
 suppression. Do not these facts very unequivocally proclaim the existence of 
 a secretory function? 
 
 Lastly. That the menses are a fluid sui generis, or at least varying essentially 
 from blood; having neither its colour, nor odour, nor coagulability, and, on che- 
 mical analysis, present different results. Let us ask, if the menstrual fluid be 
 not blood, what is it? To the objection, which has sometimes been urged, that 
 the uterus is not sufficiently glandular for the office alleged, it may be, I 
 think, very satisfactorily replied, that there is hardly a viscus or surface of the 
 body which is not competent to this purpose. It would really seem that no 
 operation of the animal economy requires a less complex apparatus. Of what, 
 indeed, does a gland consist, except a congeries of vessels? Even the most 
 perfect of the secretions are accomplished by this simple contrivance. If a few 
 vessels, “ creeping through the coats of the stomach,” can secrete the gastric 
 liquor, why may not the infinitely more glandular organization of the uterus 
 elaborate the menstrual fluid? As yet we know of no glandular structure. ui 
 vegetables, they containing only tubes or vessels, through which the fluids 
 circulate. Notwithstanding, however, the want of glands, we find the sap of 
 plants converted into oil, mucilage, acids, &c. No stronger proof can certainly 
 be required of the extreme simplicity of the organs by which the secretory 
 transformations are effected. 
 
 Who originally suggested the theory of secretion we have not been able 
 to ascertain. It has very generally, been ascribed to the celebrated Mr. 
 Hunter; but the evidence of his claims to it is exceedingly slender. The only 
 trace of it, which we can discover in his ^vrltings, is a vague expression in 
 a paragraph of his Treatise on the Blood. Afterwards, however, he furnished 
 an extract fimm his lectures to be published in Johnson’s Midwifery, as exlii- 
 biting more fully his notion respecting this function. Speaking of the death of 
 the blood from lightning, and other sudden causes, he includes the catamenia 
 
 among 
 
OF THE SECRETIONS. 
 
 280 
 
 branches of the great symphathetic* nerves, terminating in 
 various ways, in their substance, give to each of them a peculiar 
 sensibility, by means of which they discover in the blood which 
 the vessels bring to them, the materials of the fluid which they 
 are destined to secrete, and these they appropriate to themselves 
 by a real selection. Besides, the nerves communicate to them a 
 peculiar mode of activity, the exercise of which makes those 
 separated elements undergo a peculiar composition, and bestows 
 on the fluid, which is the’product of it, specific qualities always 
 bearing a certain relation to the mode of action of which it is 
 the result. Thus, the liver seizes the materials of the bile con- 
 tained in the blood of the vena portae, elaborates, combines 
 those materials, and converts them into bile, an animal fluid, 
 distinguishable by peculiar characteristic properties subject to 
 certain variations, according as the blood contains, in different 
 proportions, the elements of which it is formed; according as 
 the gland is more or less disposed to retain them, and to blend 
 them together. The qualities of the bile depending on a con- 
 currence of all these circumstances, must present as many dif- 
 ferences as the blood which contains its elements, and the liver 
 may present varieties, with regard to the composition of the 
 former and to the activity of the latter. Hence the many 
 changes in the qualities of the fluid, the slightest of which, 
 not affecting the health, escape observation, while those changes 
 which are greater and which disorder the natural order of the 
 functions, show themselves in diseases of which they may be 
 
 among’ the illustrations of his reasonings. “The blood,” says he, “discharged 
 “ in menstruation is neither similai’ to blood taken from a vein of the same 
 “ person, nor to that extravasated by an accident in any other part of the 
 “ body: but is a species of blood changed, separated, or thrown off from the 
 “ common mass by an action of the vessels of the uterus, in a process similar 
 “ io secretion, by 'which action the blood, having lost its living principle, does 
 “ not coagulate,” &c. 
 
 “ The blood,” says Haller, “ is brought to the womb in greater quantity, 
 “ and more quickly, through its lax and ample arteries, and on account of the 
 
 rigidity and narrowness of the veins, it returns with difficulty.” — Ed. 
 
 * They are likewise given off, in great number, from the cerebral; thus, the 
 salivary glands receive from the seventh pair, from the maxillarj nerve, from 
 the fifth pair and from the cervical nerves, a number of nerves that will appear 
 very great, if the bulk of those glands is considered. 
 
OF THE SECRETIONS. 
 
 281 
 
 considered as the effect, and at other times, as the cause. These 
 changes in the condition of the bile (and v/hat is now said ap- 
 plies to almost all the secretions of the animal economy), are 
 never carried so far as to make the bile lose all its distinguishing 
 characters, it never takes on the qualities belonging to another 
 fluid, it never resembles semen, urine, or saliva. 
 
 The secretory glands do not carry on an uninterrupted action; 
 almost all of them are subject to alternate action and repose; all, 
 as Bordeu observed, sleep or waken when irritation affects them 
 or their neighbouring parts, and determines their immediate or 
 sympathetic action. Thus, the saliva is more plentifully secreted 
 during mastication; the gastric juice is poured within the sto- 
 mach only while digestion is going on; when the stomach is 
 emptied of food the secretion ceases, and is renewed when the 
 presence of food again excites a sufficient degree of irritation. 
 The bile flows more abundantly, and the gall bladder frees 
 itself of that which it contains, while the duodenum is filled by 
 the chymous mass. 
 
 When a secretory organ is in action, it determines the motion 
 of the parts in its vicinity, or, as Bordeu expresses it, within its 
 atmosphere. A part is said to belong to the department of a 
 certain gland, when it partakes in the motion affecting the latter, 
 during the process of secretion, or when it is employed in func- 
 tions subservient to that of the gland; these departments ara of 
 different extent, according to the importance of the action of the 
 gland. Thus, one may say, that the spleen and most of the viscera 
 of the abdomen are of the department of the liver, since they 
 receive from it the blood on which they are to act. The liver is 
 also comprised in the sphere of activity of the duodenum, since 
 the distention of that intestine irritates it, determines a more 
 copious flow of its fluids, and a more abundant secretion of bile. 
 
 C. The blood which is sent to a secretory gland, before 
 reaching it, undergoes preparatory changes, which dispose it to 
 furnish the materials of the fluid which is to be separated from 
 it. We have seen, in treating of digestion, how the blood, which 
 the vena portae sends to the liver, is fitted for the secretion of 
 bile. There can be no doubt that the portion of blood which is 
 carried to the testicles, by the long, slender, and tortuous sper- 
 
 2 N 
 
OF THE SECRETIONS. 
 
 282 - 
 
 tnatic arteries, undergoes changes which bring it nearer to the 
 seminal fluid. 
 
 The rapidity with which the blood flows into an organ, the 
 length, the diameter, the direction, the angles of its vessels, the 
 arrangement of their extreme ramifications, which may be stel- 
 lated, as in the liver; in fasciculi, as in the spleen; convoluted, 
 as in the testicles, &c.; are circumstances which should be taken 
 into account in the study of each secretion, since all have some 
 influence on the nature of the fluid secreted, and on the manner 
 in which the secretion is effected. 
 
 The fluid which lubricates the whole extent of the moveable 
 surfaces by which the bones of the skeleton are articulated to- 
 gether, is not exclusively prepared by the membranous capsules 
 which envelop the articulations. A number of reddish coloured 
 cellular substances, placed in their vicinity, co-operate in the 
 secretion. Though these parts, which were long considered as 
 synovial glands, do not completely resemble the conglomerate 
 glands, and although no glandular bodies nor excretory ducts 
 can be demonstrated in them, they cannot, however, but be con- 
 sidered as fulfilling, to a certain degree, the same functions; and 
 one must admit that they are of some utility in the secretion of 
 the synovia. They are always met with; their extent and bulk 
 are always proportioned to the extent of the articular surfaces, 
 and to the frequency of motion in the joints near which they are 
 situated. They are found in all animals; pale and light coloured 
 in those which have been long at rest; red, highly vascular, and 
 bearing the marks of a kind of inflammatory diathesis in those 
 which have been compelled to violent exercise; as the oxen 
 which are brought to Paris from distant provinces, and the wild 
 animals which have been hunted. In anchylosis they are less 
 red and of greater consistence than in a healthy state. 
 
 When, from the irritation attending friction, the fluids are 
 determined towards an articulation which is in motion, do they 
 not then, by passing through those glandulo- cellular bodies, un- 
 dergo a peculiar modification, which renders them fitter for the 
 secretion of synovia. This would not be the only instance in the 
 human body of parts whose action is but secondary, and con- 
 nected with that of other organs principally engaged in a secre- 
 tion, whose materials are contained in the blood which passes 
 
Of the secretions. 
 
 283 
 
 through them. It will be urged, no doubt, that this preparatory 
 apparatus is not met with in the neighbourhood of the great 
 cavities: but it should be recollected that the chemical composi- 
 tion and the uses of the synovia, are not precisely the same as 
 those of the fluids secreted by the pleura or the peritoneum; and 
 that, besides, the analogy between two objects does not consti- 
 tute their identity. The human mind being naturally indolent, 
 loves to discover analogies that support it in its weakness, and 
 that may save it the trouble of seeking points of difference. I am 
 aware that to prove that the mechanism of the synovial secre- 
 tion, which exactly resembles that of the fluid which moistens 
 the inside of the great cavities, and requires like it but a simple 
 membranous apparatus, it is customary to repeat in every pos- 
 sible way, that nature is scanty in her means, and lavish in her 
 results; that she produces from the same cause a variety of 
 different effects, &c. But without pointing out the manifest ab- 
 surdity of admitting metaphysical arguments in the natural 
 sciences, is it not much more reasonable to acknowledge with 
 philosophers, that the primitive cause may vary in many ways, 
 and that its innumerable modifications, whence arise the differ- 
 ence in the effects, exceed the limited powers of our under- 
 standing? 
 
 Cl. When a gland is irritated it becomes a centre of fluxion, 
 towards which the fluids are determined from every part; it 
 swells, hardens, contracts, is in a kind of state of erection, bends 
 on itself, and acts on the blood conveyed by its vessels. Secre- 
 tion, depending on the peculiar and inherent power of the glan- 
 dular organ, is promoted by the slight motion which it receives 
 from the neighbouring muscles. The gentle pressure of those 
 parts on the glandular organs, is sufficient to keep up their ex- 
 citement, and to assist in the separation and excretion of the 
 fluid. Bordeu, in his excellent work on the glands and on their 
 action, has shown that it is not in consequence of the compres- 
 sion which is produced on them by the neighbouring muscles, 
 that they part with the fluid they have prepared; that physio- 
 logists were therefore very much in the wrong in saying that 
 the excretion of a fluid consisted merely in its expression, 
 and in comparing, under that point of view, the glands to spunges 
 soaked with a fluid, which they give out on being squeezed. 
 
OF THE SECRETIONS. 
 
 284 
 
 The excretory ducts of organs absorb or reject the secreted 
 fluid, according as it affects their inhalent mouths; these canals 
 partake in the convulsive state of the gland, undergo a degree 
 of erection, and contract on the fluid to expel it. Thus, the saliva 
 starts from the parotid duct at the sight, or on the recollection 
 of food that has been longed for: thus, the vesiculae seminales 
 and the urethra, (for the reservoirs in which the fluids lie some 
 time before being expelled, may be considered as forming a 
 part of the excretory ducts), contract, become straighter, and 
 lengthen themselves to force to a distance the spermatic fluid. 
 
 The thin and transparent ureters of fowls have been seen to 
 contract on the urine, which in these animals concretes on the 
 slightest stagnation. 
 
 After remaining a certain length of time in that state of ex- 
 citement, the glands relax, their tissue collapses, the juices cease 
 to be conveyed to it as plentifully, they fall into a state of repose 
 or sleep, which restores their sensibility, exhausted by too much 
 action. It is well known that a gland over-stimulated, becomes, 
 like any other part, insensible to the stimulus, the continued 
 application of which parches and exhausts it. 
 
 From what has just been said relative to the mechanism of 
 the secretions, it will be seen that this function may' be divided 
 into three very' distinct periods: 1st, that of irritation, charac- 
 terized by the growth of the vital properties, and by the more 
 copious accession of the fluids, the necessary consequence of 
 that excitement; 2d, the action of the gland; that is, its secre- 
 tion, properly so called; 3d, lastly', the action by which the or- 
 gan parts with the fluid which it has prepared; this is the last 
 process: it is called excretion, and is promoted by the action of 
 the neighbouring parts. The determination of fluids to the part, 
 the secretion and excretion succeed each other; they are pre- 
 ceded by the excitement which is the primary cause of all the 
 subsequent phenomena. The circulation is at first excited, more 
 blood is sent into the part, and penetrates into the tissue of the 
 gland. Dr. Murat, who has had occasion to open a considerable 
 number of old men that died at the Bicetre, and who were 
 known to be great smokers of tobacco, has uniformly observed 
 that their parotid glands, continually' called into action by that 
 habit, were larger than in those who were not given to it, and 
 
OF THE SECRETIONS. 285 
 
 that they were remarkably red, in consequence of the blood with 
 which they were constantly injected. 
 
 What is the office of the nerves in the act of secretion? What 
 share has the nervous influence in the elaboration of the fluids 
 furnished by the glandular organs? All the glands which receive 
 their nerves from the system of animal life, such as the lachry- 
 mal and salivary glands, appear in certain cases to receive from 
 the brain the secretory excitation. The influence of the imagi- 
 nation is sufficient to determine it; thus, we shed involuntary 
 tears when the mind is taken up with painful thoughts; and the 
 mouth fills with saliva on the recollection of a grateful meal. In 
 such cases, the influence of the nerves on the process of secre- 
 tion is indisputable; it is not so, however, with the conglomerate 
 glands that receive their nerves from the great sympathetics. The 
 secretion of the kidneys, of the liver, and of the pancreas, appears 
 less influenced by affections of the mind; the brain, besides, has 
 no immediate connection with these glands; their nerves are 
 almost entirely given off by the great sympathetics; the kidneys 
 in particular, receive no nerves from the brain or from the spi- 
 nal marrow: hence the secretion of urine seems more than any 
 other to be independent of the nervous influence. 
 
 The great number of secretory organs, constantly engaged in 
 separating various secretions from the mass of the fluids, would 
 soon exhaust it if the calculations of physiologists of the amount 
 of what a gland is capable of secreting, were not manifestly ex- 
 aggerated. In fact, if we admit with Haller, that the mucous 
 glands of the intestinal canal secrete, in twenty four hours, eight* 
 pounds of mucus; that, in the same space of time, the kidneys 
 secrete four pounds of urine; that the same quantity is lost by' 
 the insensible perspiration; and again, as much by the pulmo- 
 nary exhalation; there will be lost, daily, twenty pounds of fluids, 
 almost entirely es^ementitious; for we do not include in that 
 calculation, the bile, the tears, nor the saliva and pancreatic 
 fluid, which, in part, returns into the blood after being separated 
 from it; nor the serum which moistens the internal surfaces, and 
 which is purely recrementitious. 
 
 This exaggeration in the calculation of the fluids which are 
 daily poured out by the different emunctories, is to be attributed 
 to the circumstance of having taken the maximum of each secre- 
 
OF THE SECRETIONS. 
 
 286 
 
 tion, without considering that they mutually supply each other; 
 so that, when less urine is voided, the quantity of perspiration 
 is greater, and vice versa. It is very well known, that a violent 
 diarrhoea is frequently the consequence of sudden cold applied 
 to the skin; the fluids, at once repelled towards the intestinal 
 canal, having to pass through the mucous glands whose action is 
 greatly increased. 
 
 CII. It has been customary to enumerate among the glands, 
 certain bodies which have truly a glandular appearance, but the 
 uses of which are yet unknown. Thus, the thyroid and thymus 
 glands, which are parenchymatous organs destitute of excretory 
 ducts, though receiving many vessels and some nerves, do not 
 appear to secrete any fluid. But may not the blood, which is con- 
 veyed so plentifully to the thyroid gland, undergo nevertheless 
 certain changes, though we may not be able to discover what 
 they are. Besides, may not the lymphatics perform the ofiice of 
 excretory ducts and convey back again immediately into the 
 mass of the blood, the fluid which has undergone changes in the 
 glandular body? The capsulae renales are in the same condition: 
 they have, however, in addition, an internal reservoir, a kind of 
 lacuna, whose parietes are smeared with a viscid and brown 
 coloured substance secreted by the capsule, and which, doubt- 
 less, is conveyed into the mass of the blood by the lymphatics 
 arising from the parietes of its internal cavity. 
 
 cm. Of the secretion of adeps xvithin the cellular tissue. 
 This soft tissue, which is diffused over the whole body, and af- 
 fords a covering to all our organs, is of use not merely in sepa- 
 rating them from one another, and in connecting together the 
 different parts; it is besides, the secretory organ of the adipose 
 substance, a semi-concrete oily animal substance which is found 
 in almost every part of the body, deposited in its innumerable 
 cells. The membranous parietes of these small cellular cavities 
 are supplied by numerous minute arteries, in which the adeps is 
 separated; it is conveyed by its specific light w'eight to the cir- 
 cumference of the column of blood in the vessels, and transudes 
 through the pores in their parietes. Its quantity and consistence 
 vary in different parts of the body, and in different persons: 
 there is situated below the skin a thick layer of cellular sub- 
 stance {pannicule graisseux); it is found, in considerable quan- 
 
OP THE SECRETIONS. 
 
 287 
 
 tity, between the interstices of the muscles, along the blood-ves- 
 sels, near the articulations and in the vicinity of certain organs, 
 as the eyes, the kidneys, and the breasts. That which fills the 
 bottom of the orbit, and which surrounds the eyeball, is softish 
 and almost fluid; that which envelops the kidneys and the great 
 joints is, on the contrary, of the consistence of suet. Between 
 these two extremes, there are many gradations, and it may b6 
 said, that the animal oil in question, is not exactly the same in 
 any two different parts of the body. The high temperature of the 
 human body maintains it in a state of semi-fluidity, as may be 
 observed in surgical operations. 
 
 In some parts, it is even absolutely fluid, but its nature is then 
 observed to be greatly changed; it no longer contains any oily 
 substance, and differs but little from a mere aqueous gelatine. 
 Thus, the fluid in the cellular tissue of the eye-lids, of the 
 scrotum. See. has been considered by several physiologists as ab- 
 solutely different from fat. It may not be amiss to observe, that 
 the laminae of the cellular tissue, in such circumstances, yield 
 more readily to extension, present a greater surface, form mem- 
 branous expansions, and circumscribe cells of a considerable 
 size, so that the differences in the secretion perfectly coincide 
 with the difference of structure. It may further be observed, 
 that the functions of the eyelids and of the penis required that 
 they should not contain any fat. Considerable deformity, when 
 the person grew fat, would have been the consequence of the 
 increased bulk of these parts, and besides, the folds of the skin 
 would not have that free motion which their functions require. 
 No real adeps is ever found within the skull, and the utility of 
 this condition is very obvious. To how many dangers would 
 not life have been exposed, if a fluid, so varying in quantity, 
 and the amount of which may be trebled, in a very short space 
 pf time, had been deposited into a cavity accurately filled by 
 an organ which is effected by the slighest compression? 
 
 In an adult male of moderate embonpoint ^ the proportion of 
 adeps is about one twentieth of the weight of the whole body; it 
 is greater, in proportion, in children and in females; for, its 
 quantity is always relative to the energy of the functions of as- 
 similation. When digestion and absorption are performed with 
 great activity, fat accumulates within the cellular substance; and 
 
OF THE SECRETIONS, 
 
 288 
 
 if it be considered that it is but imperfectly animalized, that it 
 bears the most striking analogy to the oils extracted from plants; 
 that it contains very little azote and much hydrogen and carbon, 
 like all other oily substances, since on distillation it is decom- 
 posed, and yields water and carbonic acid, with a very small 
 quantity of ammonia; that its proportions are very variable, and 
 may be considerably increased or diminished, without manifestly 
 impairing the order of the functions; that animals that spend a 
 great part of their life without eating, seem to exist during their 
 torpid state, on the fat which they have previously accumulated 
 in certain parts of their body;* one will be led to think, that the 
 state of fat is, to a portion of the nutritive matter extracted 
 from the food, a kind of intermediate state, through which it 
 has to pass before it can be assimilated to the animal whose 
 waste it is destined to repair. Animals which live on grain and 
 vegetables, are alwaj's fatter than those which live exclusively on 
 flesh. Their fat is consistent and firm, while that of carnivorous 
 animals is almost completely fluid. 
 
 A corpulent man, on having his diet suddenly reduced, sen- 
 sibly becomes thinner in a very short time: the bulk and weight 
 of his body diminishes from the absorption of the fat which sup- 
 plies the deficient quantity of blood. Adeps may, therefore, be 
 considered as a substance in reserve, by means of which, not- 
 withstanding the small quantity of food and its want of nutri- 
 tious qualities. Nature finds wherewith to repair the daily waste. 
 
 CIV. The use of adeps is not, as has been stated on the au- 
 thority of Macquer, to absorb the acids that are formed in the 
 animal economy; that which is obtained from it by distillation, 
 (the sebaceous acid) is a new product formed by the combina- 
 tion of the oxygen of the atmosphere with the hydrogen, the 
 carbon, and the small quantity of azote which it contains. The 
 small quantity of this last substance nearly constitutes it into a 
 vegetable acid. Fat has a considerable affinity for oxygen, and 
 
 * Marmots and dormice become prodigiously fat during the autumn, tliej' 
 then take to tlieir holes and live in them dunngthe six winter months, on the 
 fat which is accumulated in all their organs. There is most fat collected in the 
 abdomen, in which the epiploon forms masses of a considerable size. When, 
 in the spring, their torpor ceases, and they awaken from their sleep, they are, 
 for the most part, exceedingly emaciated. 
 
OF THE SECRETIONS. 
 
 289 
 
 by combining with It, turns rancid, after remaining some time 
 exposed to the air. It deprives metallic oxides of a part of their 
 oxygen, and likewise, on being triturated with metallic sub- 
 stances, promotes their oxidizement. In proportion as it absorbs 
 oxygen, its density increases; thus oil becomes concrete by com- 
 bining with oxygen, and fat acquires a consistence almost equal 
 to that of wax, which is itself a fatty substance highly oxidized. 
 
 Besides the principal use which we have assigned to adeps, 
 and according to which, the cellular system may be looked upon 
 as a vast reservoir in which there is deposited a considerable 
 quantity of nutritive and semi-animaliz,ed matter, this fluid an- 
 swers several purposes of secondary utility. It preserves the 
 body in its natural temperature, being as well as the tissue of 
 the cells in which it is contained, a very bad conductor of heat. 
 Persons who are excessively corpulent, scarcely feel the most se- 
 vere cold; the animals which inhabit northern climates, besides 
 being clothed in a thick fur, are likewise provided with a consi- 
 derable quantity of fat. The fishes of the frozen seas, the ceta- 
 ceous animals which seldom go far from the polar regions, all 
 kinds of whales, are covered with fat, and have likewise a con- 
 siderable quantity within their body. By its unctuous qualities, 
 fat promotes muscular contraction, the motion of the different 
 organs, the free motion ,on each other of the different surfaces; 
 it stretches and supports the skin, fills vacuities and gives to 
 our limbs those rounded outlines, those elegant and graceful 
 forms peculiar to the female body. Lastly, it envelops and 
 covers over the extremities of the nerves, diminishes their 
 susceptibility, which is always in an inverse ratio of the embon- 
 point^ which induced a physician of merit to say, that the ner- 
 vous tree, planted in the adipose and cellular substance, suffers, 
 when from the collapse and the removal of that tissue, its 
 branches are exposed, in an unprotected state, to the action of 
 external causes as injurious to them, as the rays of the sun to a 
 plant torn from its native soil. It is, in fact, observed, that ner- 
 vous people are exceedingly thin, and have an excessive degree of 
 sensibility. Too much fat, however, is as injurious as too small 
 a quantity of it. I have seen several persons whose obesity was 
 such, that besides being completely incapable of taking the 
 slightest exercise, they were in great danger of suffocation. Re- 
 
 20 
 
OF THE SECRETIONS. 
 
 290 
 
 spiration in such persons is, at times, interrupted by deep sighs, 
 and their heart, probably overloaded tvith fat, expels, with difB- 
 culty, the blood within its cavities. 
 
 C V. According to modern chemists, the use of fat is to take 
 from the system a part of its hydrogen. When the lungs or 
 liver are diseased, when respiration or the biliary secretion do 
 not carry out of the system a sufficient quantity of that oily and 
 inflammable principle, fat forms in a greater proportion. They 
 appeal to the result of the experiment of shutting up a goose, 
 whose liver is to be fattened, in a confined cage, placed in a hot 
 and dark situation, and in gorging it with paste, of which it eats 
 the more greedily, as being unabled to stir, it gratifies its incli- 
 nation to action, by exerting the organs of digestion. Notwith- 
 standing this quantity of food, the bird becomes emaciated, is 
 affected with a kind of marasmus, its liver softens, grows fatter, 
 more oily, and attains an enormous size. 
 
 This experiment, and many other facts, prove, that the secre- 
 tions from which analogous products are formed, may mutually 
 supply each other; but can we admit the chemical theory of the 
 use of fat, when we recollect that frequently, in the most corpu- 
 lent persons, respiration and the secretion of bile are performed 
 with great freedom and with no difficulty; while the difficult 
 respiration attending pulmonary consumption, and the difficult 
 flow of the bile from an obstruction of the liver, are always ac- 
 companied with complete marasmus. 
 
 Whatever moderates the activity of the circulatory system, 
 tends to bring on adipose plethora. Thus an inactive state of 
 the mind and body, profuse bleedings, castration, sometimes 
 induce obesity, an affection in which the cellular tissue appears 
 affected with atony and undergoes an actual adipose infiltra- 
 tion, which may be compared to that which gives rise to tu- 
 mours called steatomatous. If the energy of the heart and 
 arteries is too great, emaciation is always the consequence; 
 when, on the contrary, the sanguineous system is languid, there 
 is formed a merely gelatinous fat and the embonpoint is a mere 
 state of bloatedness. 
 
 This incompletely formed fluid, which distends the parts in 
 persons of a leucophlegmatic habit, is but an imperfect kind of 
 fat; it resembles the marrow or the medullary juice, which is 
 
OF THE SECRETIONS. 
 
 291 
 
 merely a very liquid fat, whose consistence diminishes when 
 animals become lean. Inclosed within the cells of the osseous 
 tissue, in cavities whose sides cannot collapse, and whose di- 
 mensions must always remain the same, the marrow, of which 
 they are never free, is of different degrees of density; and what 
 authors say of its diminished quantity, must be understood as 
 applying to the diminution of its consistence. 
 
 CVI. The secretion of the marrow is, like that of the fat, a 
 mere arterial transudation; it is performed by the medullary 
 membrane, which is thin, transparent, and cellular, which lines 
 the inside of the central cavity of the long bones, and extends 
 over all the cells of their spungy substance. The medullary 
 membrane, when in a healthy state, does not give any marks 
 of relative sensibility. In all the amputations I have perform- 
 ed, and they have not been few, in all the operations of the 
 same kind at which I have been present, whatever the bone 
 was, whether it was divided near a joint or in the middle of 
 its body, I never knew the patient complain of pain, provided 
 the limb was well supported by the assistants and provided no 
 jerk was given by the operator himself. In that operation, the 
 pain occasioned by the division of the skin and of the nerves, 
 overcomes every other pain, and I have always seen patients 
 impressed with the popular prejudice, and expecting anxiously 
 the division of the bone, feel quite free from pain, as soon as the 
 saw had begun to work. Nay, several, after expressing, by their 
 cries, the most acute pain, taking advantage of the kind of ease 
 which follows the division of the flesh, raise their head and look 
 on, while the bone is being sawed through; at once actors and 
 spectators in this last part of a painful and bloody operation. 
 
 Yet the medullary membrane, the injury of which is attend- 
 ed with no pain, while in a healthy state, becomes the seat of 
 the most exquisite sensibility in the pains in the bones which 
 mark the last stages of the venereal disease; in the kind of con- 
 version into flesh, of the solid bone, known by the name of 
 spina ventosa, as will be mentioned, in speaking of the uses of 
 the marrow, in the chapter on tire organs of motion and on theif 
 action. 
 
292 
 
 CHAPTER VI. 
 
 ON NUTRITION. 
 
 evil. All the functions which we have hitherto made the 
 object of our study; digestion, by which the alimentary substan- 
 ces received within the body are deprived of their nutritive 
 parts; absorption, which conveys that recrementitious extract 
 into the mass of the fluids; the circulation, by which it is carried 
 to the parts wherein it is to undergo different changes; diges- 
 tion, circulation, absorption, respiration, and the secretions, are 
 but preliminary acts, preparatory to the more essential function 
 treated of in this chapter, and the consideration of which termi- 
 nates the history of the phenomena of assimilation. 
 
 Nutrition may be considered as the complement of the func- 
 tions of assimilation. The aliment altered in its qualities by a 
 series of decompositions, animalized and rendered similar to the 
 substance of the being which it is to nourish, is applied to the or- 
 gans whose waste it is to repair; and this identification of the 
 nutritive matter to our organs, which take it up and appropriate 
 it to themselves, constitutes nutrition. Thus there is accomplish- 
 ed a real conversion of the aliment into our own substance. 
 
 There is incessantly going on a waste of the integrant parti- 
 cles of the living body, which a multiplicity of circumstances 
 tend to carry away from it; several of its organs are constantly 
 engaged in separating from it the fluids containing the recre- 
 mentitiouE materials of its substance worn by the combined 
 action of the air and of caloric, by inward friction and by a 
 pulsatory motion that detaches its particles. 
 
 Alike, therefore, to the vessel of the Argonauts, so often re- 
 paired in the course of a long and perilous navigation, that on 
 her return, no part of her former materials remained; an animal 
 is incessantly undergoing decay, and if examined at two differ- 
 ent periods of its duration, does not contain one of the same 
 molecules. The experiment performed with madder, which 
 
ON NUTRITION. 
 
 293 
 
 dyes red the bones of animals among whose food it is mixed, 
 proves most unquestionably, this incessant decomposition of 
 living matter. One has only to interrupt, for a sufficient length 
 of time, the use of that plant, to make the uniformly red colour 
 assumed by the bones, completely disappear. Now, if the hard- 
 est and most solid parts, most calculated to resist decay, are 
 undergoing a perpetual routine of decomposition and of regene- 
 ration, there can be no doubt, that this motion must be far more 
 I rapid in those whose power of cohesion is much inferior; for 
 example, in the fluids. 
 
 Attempts have been made to determine the period at which 
 the body is completely renovated; it has been said, that an inter- 
 val of seven years was required for one set of molecules to dis- 
 appear and be replaced by others; but this change must go on 
 more rapidly in childhood and in youth. It must be slower at a 
 mature age, and must require a considerable time, at a very ad- 
 vanced period of life, when all the parts of the body become, 
 in a remarkable degree, fixed and firm in their consistence, 
 while the vital powers become more languid. There can be no 
 doubt, that the sex, the habit, the climate in which we live, the 
 profession we follow, our mode of life, and a variety of other 
 circumstances, accelerate or retard it; so that it is absolutely 
 impossible to fix, with any degree of certainty, its absolute 
 duration. 
 
 CVIII. The parts of our body, in proportion as they under- 
 go decay, are repaired only by means of homogeneous particles 
 exactly like themselves: were it otherwise, their nature, which 
 always remains the same, would be undergoing perpetual 
 changes. 
 
 When, in consequence of the successive changes which it 
 has undergone from the action of the organs of digestion, of 
 absorption, of the circulation, of respiration, and of secretion, 
 the nutritive matter is animalized or assimilated to the body 
 which it is to nourish, the parts which it moistens retain it and 
 incorporate it to their own substance. This nutritive identifi- 
 cation is not performed alike in the brain, in the muscles, in the 
 bones, &c. Each of them appropriates to itself, by a real pro- 
 cess of secretion, whatever it meets with fitted for its nature, 
 in the fluids conveyed to it by the different kinds of vessels, but 
 
ox NUTKrnox. 
 
 294 
 
 especially by the arteries; leaving unaffected, the remaining 
 heterogeneous particles. A bone is a secretory organ, around 
 which phosphate of lime is deposited; the lymphatic vessels 
 which, in the process of nutrition, perform the office of excre- 
 tory ducts, remove that saline substance, when it has lain suf- 
 ficiently long in the cells of its tissue. The same happens, to 
 the muscles, with regard to fibrina, and to albumen with regard 
 to the brain: every part appropriates to itself, and converts into 
 a solid form, those fluids which are of the same nature, in vir- 
 tue of a power of which the term affinity of aggregation, used 
 in chemistry, gives an idea, and of which it is perhaps the em- 
 blem. 
 
 The nutrition of a part requires that it should be possessed 
 of sensibility and motion. By tying the arteries and nerves of a 
 part, it cannot be nourished nor can it live. The blood which 
 flows along the veins, the fluid conveyed by the absorbents, 
 contain, in a smaller proportion than arterial blood, vivifying 
 and reparatory particles. It is even commonly thought, that 
 the lymph and venous blood contain no directly nutritive parti- 
 cles. As to the share which the nerves take in the process of 
 nutrition, that is not yet completely determined. A limb that 
 is paralyzed, by the division or tying of its nerves, or by any 
 other affection, sometimes retains its original size and plump- 
 ness; most frequently, however, though perhaps for want of 
 motion, it becomes emaciated, and shrinks in a remarkable 
 degree. 
 
 CIX. We should be enabled to understand the process of 
 nutrition, if after having accurately determined the difference 
 of composition between our food, and the substance itself of 
 our organs, we could see how each function robs the aliments 
 of their qualities, to assimilate them to our own bodies; and 
 what share each function takes in the transmutation of the nu- 
 tritive particles into our own substance. To illustrate this point, 
 suppose a man to live exclusively on vegetable substances, which 
 in fact, form the basis of our food; on whatever part of the 
 plant he may live, whether on the stem, on the leaves, on the 
 blossoms, on the seeds, or on the root; carbon, hydrogen, and 
 oxygen enter into the composition of these vegetable substan- 
 
ON NUTRITION. 
 
 295 
 
 ces, which, by a complete analysis, may all be resolved into 
 water and carbonic acid. To these three constituent principles, 
 there is frequently united a small quantity of azote, of salts, and 
 of other materials, in different proportions. If then, we examine 
 the nature of the organs in this man, whose food is entirely 
 vegetable, it will be found that they are different in their com- 
 position, and far more animalized than that kind of food; that 
 azote predominates, though the vegetable substance contains 
 none or only a very small quantity; that new products, undis- 
 tinguishable in the aliments, exist, in considerable quantity, in 
 the body which is fed on them, and appear produced by the 
 very act of nutrition. 
 
 The essence of this function is, therefore, to make the nutritive 
 matter undergo a more advanced state of composition, to de- 
 prive it of a portion of its carbon and of its hydrogen, to make 
 azote predominate, and to produce several substances, which 
 did not exist in it before. All living bodies seem to possess the 
 faculty of composing and decomposing the substances by means 
 of which they are maintained, and to form new products; but 
 they possess it in various degrees of energy. The sea weed, 
 from the ashes of which soda is obtained, on being sown in a 
 box of soil, in which there is not a single particle of that alkali, 
 and watered with distilled water, will no longer contain it, as if it 
 had grown on the sea shore, in the midst of marshes constantly 
 inundated by salt and brackish water.* 
 
 Living bodies then, are real laboratories, in which there are 
 Carried on combinations and decompositions which art cannot 
 
 *I am unacquainted with the details of the experiment referred to by the 
 author: he quotes it, I conceive, to shew that the power which, he says, i& 
 common to all living bodies, of producing a substance not supplied to them 
 from without, is not possessed, in the same degree, by all bodies endowed with 
 life: since the sea weed here alluded to, does not possess it, in an equal degree, 
 when watered with distilled as with sea water. This, I apprehend, is the au- 
 thor’s meaning, though the text is somewhat obscure, and would almost lead 
 one to believe he meant, that no alkali whatever can be obtained from the sea 
 plant under the circumstances he states, “ L’algue marine dont les cendres 
 “ fournissent la soude, semee dans une caisse pleine d’un terreau qui ne conti- 
 “ ent pas un seul atome de cet alkali, arrocee avec I’eau distillee, ne le fournit 
 
 plus comme si elle avoit pris sa croissance au milieu des marais toujours in- 
 “ ondcs par leurs eaux sanmatres et muriatiques.” T.. 
 
ON NUTRITION. 
 
 296 
 
 imitate; bodies that appear to us simple, as Soda and silex, seem 
 to be formed by the union of their constituent particles; while 
 other bodies, whose composition we do not understand, under- 
 go an irresistible decomposition; hence, methinks, one may in- 
 fer, that the power of nature in the composition and decomposi- 
 tion of bodies, far exceeds that of chemistry. 
 
 Straw and cereal plants contain an enormous quantity of silex, 
 even when the earth in which they grow has been carefully de- 
 prived of its siliceous particles. Oats, particularly, contain a 
 considerable quantity of that vitrifiable earth; the ashes obtained 
 by burning its seed, on being analyzed by means of the nitric 
 acid, were found by M. Vauquelin, to contain jWV pure si- 
 lex indissoluble in that acid, and 0,393 of phosphate of lime 
 dissolved in it. 
 
 The excrements of a hen, fed, for ten days, on oats only, on 
 being calcined and analyzed by the same chemist, produced 
 twice as much phosphate and carbonate of lime as was contained 
 in the oats, with a small deficiency in the quantity of silex, 
 which might have been employed in furnishing the excess of 
 calcareous matter; a transmutation depending on the absorption 
 of an unknown principle, to the amount of nearly five times its 
 own weight.* 
 
 CX, A substance to be fit for our nourishment, should be ca- 
 pable of decompositon and fermentation; or in other words ca- 
 pable of undergoing an inward and spontaneous change, so that 
 its elements and relations may be altered. This spontaneous 
 susceptibility of decomposition, excludes from the class of ali- 
 ments whatever is not organized and is not a part of a living 
 body; thus, mineral substances absolutely resist the action of 
 our organs and are not convertible into their own substance. 
 The common principle extracted from alimentary substances, 
 however varied they may be, the aliment^ as Hippocrates terms 
 it, is, most probably, a compound highly subject to decomposi- 
 tion and fermentation; this is likewise the opinion of all those 
 who have endeavoured to determine its nature. Lorry thinks 
 it is a mucous substance; Cullen says it is saccharine; Professor 
 
 * See the Annaks de Cltimie, an<l tlie Srsttme des Cenmaissances cMmiqves de 
 Foiircroy, tome x. page 7?- 
 
ON NUTRITION. 
 
 297 
 
 Halle considers it as an hydro-carbonous oxide, which differs 
 from the oxalic acid, only in containing a smaller quantity of 
 oxygen. It is evident, that these three opinions are very much 
 alike, since oxygen, carbon, and hydrogen, combined in differ- 
 ent proportions, form the mucous and saccharine substances 
 and the base of the oxalic acid. On analyzing the animal sub- 
 stance, by means of the nitric acid, it is reduced to this last 
 base, by depriving it of a considerable quantity of azote which 
 constitutes its most remarkable character. 
 
 But whence comes this enormous quantity of azote? How 
 happens it, that the flesh of a man living exclusively on vege- 
 tables, contains as much azote and ammonia, and is as putres- 
 cent, as that of a man living on animal food? Respiration does 
 not introduce a single particle of azote into our fluidsj this gas 
 comes out of the lungs as it entered; the oxygen alone is dimi- 
 nished in quantity. Might not one suspect that this element of 
 animal substances is a product of the vital action, and that in- 
 stead of receiving it from our aliments, we form it within our- 
 selves, by an act that is hyper- chemical; that is, which chemis- 
 try cannot imitate?* 
 
 CXI. It has been maintained, that the hydro-carbonous oxide 
 combines in the stomach and intestinal canal with oxygen, 
 whether this last principle has entered, with the aliments, into 
 the digestive tube, or whether it is furnished by the decompo- 
 sition of the fluids within that cavity. The intestinal fluids extri- 
 cate azote, which combines with the alimentary mass, and occu- 
 pies the place of the carbon which the oxygen has taken from it, 
 to form carbonic acid. On reaching the lungs, and being again 
 exposed to the action of the oxygen of the atmosphere, this gas 
 robs it of a portion of its carbon, and as it disengages the azote 
 of the venous blood, it brings about a new combination of that 
 principle with the chyle: lastly, propelled with the blood to the 
 surface of the skin, the atmospherical oxygen disengages its 
 carbon, and completes its azotisation. The cutaneous organ is 
 
 * The late experiments of Messrs. Allen and Pepys prove that when an 
 animal is made to breathe pure oxygen, the blood disengages a certain quan- 
 tity of aaote and absorbs an equal quantity of oxygen. Philosophical Transac- 
 .tions, 1809. 
 
 2 P 
 
ON NUTRITION. 
 
 298 
 
 perhaps to the lymphatic system, what the pulmonary organ is 
 to the sanguineous system. 
 
 The animalization of the animal substance is therefore effect- 
 ed, principally by the loss of its carbon, which is replaced by"^the 
 excess of azote in the animal fluids. These maintain them- 
 selves, in this manner, in a due temperament; for, continually 
 parting with the carbonous principle in the intestinal, pulmon- 
 ary, and cutaneous combinations, they would be over animal- 
 ized, if an additional quantity of chyle did not seize the azote, 
 which is in excess. Still this theory does not account for the 
 formation of the phosphoric salts, of the adipocere, and a variety 
 of other products; but vvithout adopting it, to the full, one may 
 presume, from the experiments and facts on which it rests, that 
 the oxygen of the asmospherical air is one of the most power- 
 ful agents employed by nature, in the transformation of the 
 aliments we live upon, into our substance. 
 
 How are those animals nourished which live solely on more 
 animalized flesh, that is containing a greater quantity of azote, 
 and a greater proportion of ammonia than their own substance. 
 In such a case, the assimilation of the aliments, consists in their 
 desanimalization either by the co-operation of all the organs, 
 or by the sole action of the digestive organs, by the combination 
 of the gastric juice with the other fluids. 
 
 The constituent elements entering into the composition of our 
 organs, whether coming from the exterior, or formed by the 
 vital power itself, are thrown out of our body by the different 
 emunctories, and cease to form a part of it, after remaining 
 within it for a limited time. The urine carries along with it 
 an enorm.ous quantity of azote; the lungs and the liver rid us of 
 the carbon and of the hydrogen; the oxygen which contains 
 eighty-five parts in the hundred, in the composition of water, is 
 evacuated by means of the aqueous secretions, which carry off, 
 in a state of solution, the saline and other soluble principles. 
 
 Among those salts there is one, but little soluble, and which, 
 nevertheless, is of primary consequence among the constitu- 
 ent principles of the animal economy. Phosphate of lime, in 
 fact, forms the base of several organs; it, almost entirely, forms 
 the osseous svstem, at an advanced period of life; all the white 
 
ON NUTRITION. 
 
 299 
 
 organs; all our fluids contain a remarkable quantity of that sub- 
 stance, of which the economy rids itself by a kind of dry secre- 
 tion. The outer covering is, in all animals, the emunctory 
 destined for that purpose; the annual moulting of birds, the fall 
 of the hair of quadrupeds, the renovation of the scales of fishes 
 and reptiles, carry off, every year, a considerable quantity of 
 calcareous phosphate. Man is subject to the same laws, with 
 this difference, that the annual desquamation of the epidermic, 
 is not under the absolute influence of the seasons, as in the 
 brute creation. The human epidermis is renewed annually, as 
 well as the hair on the head and on the body; but this change 
 is brought about gradually, and is not completed in a season; 
 it does not take place in the spring, as in most animals, nor in 
 autumn with the fall of the leaf, though at these two periods, 
 the hair falls off in greatest quantity, and the desquamation of 
 the cuticle is most active. These two phenomena last through- 
 out the whole year, as, in southern climates, the fall of the leaves 
 and the renovation of vegetation are continually going on. As 
 will be mentioned, in speaking of the functions of generation, 
 man living in a state of society, and enjoying all the advantages 
 of civilization, is not as much under the influence of the seasons 
 as the inferior animals. One cannot, however, but observe, that 
 the successive shedding and renewing of the epidermoid parts, 
 as the cuticle, the nails, and the hair, are among the most 
 effective means which nature possesses of parting with the 
 phosphate of lime, so abundant in all animals, and which, 
 nevertheless, is so insoluble and consequently so unfit to be 
 carried out of the system, along with the excrementitious fluids. 
 This effect is very remarkable, on the termination of several 
 diseases, in the salutary renovation of the solids and fluids 
 which take place during convalescence. The hair ceases to 
 grow on the bald head of an old man; his perspiration dimin- 
 ishes: may not this be the cause of the great quantity of calca- 
 reous salts, of the ossification of the vessels, of the induration 
 of the membranes? 
 
 CXII. What is the ultimate result presented to us, by this 
 series of functions, linked together, growing out of one another, 
 and all acting on the matter of nutrition, from the moment it is 
 received within the body, till it is applied to the growth and 
 
ON NUTRITION. 
 
 300 
 
 reparation of its organs? It shows us man living within himself, 
 unremittingly employed in converting, into his own substance, 
 heterogeneous substances, and reduced to an existence purely 
 vegetative, inferior even to the greater part of organized beings, 
 in his powers of assimilation. But how high is he not placed 
 above them all, in the exercise of those functions we are now 
 about to contemplate; functions, which raise him above his own 
 nature, which enlarge the sphere of his existence, which serve 
 him to provide fur all his wants, and to keep up, with all nature, 
 those manifold relations which subject her to his empire! 
 
FIRST CLASS. 
 
 \ 
 
 SECOND ORDER. 
 
 Functions which tend to the preservation of the Individual, 
 by establishing his relations with the beings 
 that surround him. 
 

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 ^TA^V‘^' :s^\^ i\\ior ■^st\ •gnsA^'Ao’a^ij \tv^ 
 
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303 
 
 CHAPTER VII. 
 
 OP SENSATIONS. 
 
 cxiii. W E have already seen, how the human body, essen^ 
 tially changeable and perishable, maintains itself in its natural 
 economy, carries on its growth, and supplies its decay, by assi- 
 milating to its own substance, principles that are yielded to it by 
 the food it digests, and by the air it breathes. We shall now pro- 
 ceed to examine by what organs man is enabled to keep up with 
 all nature, the relations on which his existence depends: by what 
 means he is made aware of the presence of objects which con- 
 cern him, what means he possesses to fit his connexion with 
 them to his welfare, to draw them towards him or to repel 
 them, to approach or to avoid and escape them, as he perceives 
 in them danger, or the promise of enjoyment. 
 
 Man possesses, in all its plentitude, this new mode of existence, 
 which is denied to vegetable nature. Of all animals it is he that 
 receives impressions the most crowded and various, that is most 
 filled with sensations, and that employs them with the most pow- 
 erful combination, as the materials of thought, and the sources 
 of intelligence: he is the best organized for feeling the action of 
 all beings around him, and re-acting on them in his turn. In the 
 study which we are about to undertake, we shall see many in- 
 struments placed on the limits of existence, on the surface of the 
 living being, ready to Receive every impression; conductors, 
 stretching from these instruments to one common centre, to 
 which all is carried: conductors through which this central or- 
 gan regulates the actions which now transport the whole body 
 from one place to another (locomotiony, now merely change the 
 relative situation of its parts (^partial motion)-, and, at other 
 times, produce, in the organs, certain dispositions, of which 
 speech and language, in their various forms, are the result. 
 
 CXIV. If we are thoroughly to understand the mechanism 
 of this action of outward objects on our body, we must follow 
 the natural succession of the phenomena of sensation; studying 
 first the bodies which produce the sensitive impression; ex- 
 
OF SENSATIONS. 
 
 304 
 
 amining next the organs that receive it; and next the conduc- 
 tors which transmit it to a particular centre, whose office is per- 
 ception. To take the sense of sight, for instance, we can never 
 understand how it is that light procures us the knowledge of 
 certain qualities of bodies, if we have not learnt the laws to 
 which that fluid is subjected, if we know nothing of the confor- 
 mation of the eyes, of the nerves by which those organs commu- 
 nicate with the brain, and of the brain itself, whither all sensa- 
 tions, or rather the motions in which they consist, are ultimately 
 carried. 
 
 CXV. Of light. At this day, the greater part of natural phi- 
 losophers consider it as a fluid impalpable from its exceeding 
 tenuity. Many believe it to be only a modification of caloric, or 
 of the matter of heat; and this last opinion has received much 
 plausibility from the late observations of Herschel.* I shall not 
 examine whether, as Descartes and his followers imagine, light, 
 consisting of globular molecules, exist of itself, uniformly dif- 
 fused through space; or as Newton has taught us to believe, it 
 be but an emanation of the sun and fixed stars, which throw off, 
 from their whole surface, a part of their substance, without ever 
 exhausting themselves by this continual efflux: It is enough for 
 us to know, 1st, that the rays of this fluid move with such velo- 
 city, that light passes, in a second, through a distance of seventy- 
 two thousand leagues, since, according to the calculation of 
 Roemer and the tables of Cassini, it traverses in something less 
 than eight minutes the thirty-three millions of leagues that se- 
 parate us from the sun; 2dly, that light is called direct when it 
 passes from the luminous body to the eye, without meeting any 
 obstacle; refected^ when it is thrown back to that organ by an 
 opake body; refracted,, when its direction has been changed by 
 
 * This celebrated Astronomer has published, in the Philosophical Transac- 
 tions of the Ro3^al Society for 1800, a series of experiments which show, that 
 the different coloured rays, heat, in different degrees, the bodies on which they 
 fall, and that the red ray, which is the least refrangible, gives also the greatest 
 heat. 
 
 The thermometer placed out of the spectrum and towards the red ray, so 
 that it would receive any rays yet less refrangible, rises higher than when it 
 is placed in that colour: From wliich Herschel concludes that rays are given 
 out by the sun, too little refrangible to produce the sensation of light, and of 
 colours, but which produce the sensation of beat. 
 
OF SENSATIONS. 
 
 305 
 
 passing from one transparent medium to another of different den- 
 sity; 3dly, that the rays of light are reflected at an angle equal 
 to that of incidence; that a ray, passing through a transparent 
 body, is more strongly refracted as the body is more convex on 
 the furface, denser, or of more combustible elements. It was 
 from this last observation, that Newton conjectured the com- 
 bustibility of the diamond, and the existence of a combustible 
 principle in water, since placed beyond doubt, by the beautiful 
 experiments of modern chemistry: 4thly, that a ray of light re- 
 jracted by a glass prism is decomposed into seven rays, red, 
 orange, yellow, green, blue, indigo, and violet. Each of these 
 rays is less refrangible, as it is nearer to the red. This ray is of 
 all, that which strikes the eyes with the greatest force, and pro- 
 duces on the retina the liveliest impressions. The eagerness of 
 savages for stuffs of this colour is well known. Among almost 
 all nations it has dyed the mantle of kings: it is the most bril- 
 liant and splendid of all: there are animals whose eyes seem 
 scarcely to sustain it: I have seen maniacs whose madness, after 
 a long suspension, never failed to break out at the sight of a red 
 cloth, or of one clothed in that colour. Green is, on the con- 
 trary, the softest of colours; the most permanently grateful; that 
 which least fatigues the eyes, and on which they will longest and 
 most willingly repose. Accordingly, Nature has been profuse 
 of green, in the colouring of all plants; she has dyed, in some 
 sort, of this colour, the greater part of the surface of the globe. 
 When the eyes bear uneasily the glare of too strong a light, 
 glasses of this colour are used to soften the impression, which 
 slightly tinge, with their own hue, all the objects seen through 
 them. Lastly, the violet ray, last in the scale, of which the mid- 
 dle place is filled by the green, is of all the weakest, the most 
 refrangible. Of all colours, violet has the least lustre; forms 
 show to less advantage under it; their prominences are lost: 
 painters accordingly make but little use of it. When an en- 
 lightened body reflects all the rays, the sensations they might 
 separately produce blend into the sensation of white; if it re- 
 flect a few, it appears differently coloured, according to the rays 
 it repels; finally, if all be absorbed, the sensation of black is pro- 
 duced, which is merely the negation of all colour. A black body 
 is wrapped in utter darkness, and is visible only by the lustre of 
 
 2Q 
 
OF SENSATIONS. 
 
 306 
 
 those that surround it: 5thly, that from every point in the sur- 
 face of a luminous or enlightened body, there issue a niultitudc 
 of rays, diverging according to their distance, with a propor- 
 tionate diminution of their effect; so that the rays from each 
 visible point of the body, form a cone, of which the summit 
 is at that point, and the base, the surface of the eye on which 
 they fall. 
 
 CXVI. Sense of sight. The eyes, the seat of this sense, are 
 so placed as to command a great extent of objects at once, and 
 enclosed in two osseous cavities, known by the name of orbits. 
 The base of these cavities is forwards, and shaped obliquely 
 outwards; so that their outward side not being so long as the 
 others, the ball of the eye supported, on that side, only by soft 
 parts, may be directed outwards and take cognizance of objects 
 placed to a side, without its being necessary, at the same time, to 
 turn the head. In proportion as we descend from man in the 
 scale of animated beings, the shape of the base of the orbits be- 
 comes more and more oblique; the eyes cease to be directed for- 
 ward; in short, the external side of the socket disappears, and 
 the sight is entirely directed outward; and as the physiognomy 
 derives its principal character from the eyes, its expression is 
 absolutely changed. In certain animals very fleet in running, 
 such as the hare, the lateral situation of the organs of vision 
 prevents the animals from seeing small objects placed directly 
 before them; hence those animals, when closely pursued, are so 
 easily caught in the snares which are laid for them. 
 
 The organ of sight consists of three essentially distinct parts. 
 The one set intended to protect the eye-ball, to screen it, at 
 times, from the influence of light, and to maintain it in the con- 
 ditions necessary to the exercise of its functions; these parts are 
 the eye-brows, the eye-lids, and the lachrymal apparatus, and 
 they serve as appendages of the organ. The eye-ball itself con- 
 tains two parts answering very different purposes; the one, 
 formed by nearly the whole globe, is a real optical instrument, 
 placed immediately in front of the retina, and destined to pro- 
 duce on the luminous rays those changes which are indispensa- 
 ble in the mechanism of vision; the other, formed by the medul- 
 lary expansion of the optic nerve, is the immediate organ of that 
 function. It is the retina which alone is affected by the impres- 
 
OF SENSATIONS. 
 
 307 
 
 sion of light, and set in motion by the contact of that very subtle 
 fluid. This impression, this motion, this sensation, is transmit- 
 ted to the cerebral organ by the optic nerve, the expansion of 
 which forms the retina. 
 
 CXVII. Of the eye-brows^ the eye-lids^ and the lachrymal 
 apparatus {Tutamina oculi^ Haller). The more or less dark 
 colour of the hairs of the eye-brows, renders that projection 
 very well adapted to diminish the effect of too vivid a light, by 
 absorbing a part of its rays. The eye brows answer this pur- 
 pose the more completely, from being more projecting, and 
 from the darker colour of the hairs which cover them; hence 
 we depress the eye-brows, by knitting them transversely, in 
 passing from the dark into a place strongly illuminated, which 
 causes an uneasy sensation to the organ of sight. Hence, like- 
 wise, the custom that prevails with some southern nations, 
 whose eye-brows are shaded by thicker and darker hairs, to 
 blacken them, that they may still better answer the purpose 
 for which they are intended. 
 
 The eye-lids are two moveable curtains placed before the 
 eyes, which they alternately cover and uncover. It was re- 
 quisite that they should be on the stretch, and yet capable of 
 free motion ; now both these ends are obtained by the tarsal car- 
 tilages, which are situated along the whole of their free edges, 
 and of the muscles which enter into their structure. The cellu- 
 lar tissue which unites the thin and delicate skin of the eye-lids 
 to the muscular fibres, contains, instead of a consistent fat, 
 which would have impeded its motion, a gelatinous lymph, 
 which, when in excess, constitutes oedema of the eye-lids. The 
 tissue of the eye-lids is not absolutely opake, since even when 
 strongly drawn together, and completely covering the globe of 
 the eye, one may still discern through their texture, light from 
 darkness. On that account light may be considered as one of 
 the causes of awakening, and it is of consequence to keep in the 
 dark, patients fatigued by want of sleep. 
 
 The principal use of the eye-lids, is to shade the eyes from 
 the continual impression of light. Like all the other organs, the 
 eyes require to recruit themselves by repose; and they had not 
 been able to enjoy it, if the incessant impression of the lumi- 
 nous rays had continually excited their sensibility. The remo- 
 
OF SENSATIONS. 
 
 308 
 
 val of the eye-lids is attended with loss of sleep. The fluids are 
 determined to the affected organ, which suffers from incessant 
 irritation. The eyes inflame, the inflammation spreads towards 
 the brain, and the patient expires in the most dreadful agony. 
 Thanks to an advanced state of civilization, these barbarous tor- 
 tures have long been abolished; but what happens, when from 
 ectropium of one or other of the eye-lids a small portion of 
 the sclerotic coat or cornea remains uncovered, proves the 
 indispensable necessity of those parts. The spot exposed to the 
 continued action of the air and of the light, becomes irritated 
 and inflamed, and there comes on an ophthalmia, which can be 
 cured only by bringing together, by means of a surgical opera- 
 tion, the divided edges of the opening which is the cause of the 
 affection. From the moveable edges of both eye-lids there arise 
 short curved hairs, of the same colour as those of the eye-brow; 
 they are called eye-lashes, and are intended to prevent insects 
 or other very light substances, floating in the atmosphere, from 
 getting between the eye-ball and the eye-lids. 
 
 The anterior part of the eye thus defended against external 
 injuries, is continually moistened by the tears. The organ which 
 secretes this fluid, is a small gland situated in a depression at the 
 anterior and external part of the arch of the orbit, imbedded in 
 fat, and supplied with pretty considerable vessels and nen^es in 
 proportion to its bulk, and pouring the fluid it secretes, by 
 means of seven or eight ducts which open on the internal sur- 
 face of the upper eye-lid, by capillary orifices directed down- 
 ward and inw^ard. The tears are a muco-serous fluid, rather 
 heavier than distilled water, saltish, changing to a green colour 
 vegetable blues; and containing soda, muriate and carbonate of 
 soda, and a very small quantity of phosphate of soda and of 
 lime. 
 
 In ophthalmia, the irritation of the conjunctiva, transmitted 
 by sympathy to the lachrymal gland, not only augments the 
 quantity of its secretion, but appears, likewise, to alter the quali- 
 ties of the fluid that is secreted. The tears, which in those cases 
 flow in such profusion, bring on a sense of burning heat in the 
 inflamed part; do they not, perhaps, contain a greater quantity 
 of the fixed alkali than in the ordinary state of the parts; and 
 may not the painful sensation depend as much on the increased 
 
OF SENSATIONS. 3Q9 
 
 proportion of soda in the tears, as on the greater sensibility of 
 the conjunctiva? 
 
 This last membrane is merely a fold of the skin, which is ex- 
 ceedingly thin, covers the posterior surface of the eye lids, and 
 is then reflected over the anterior part of the eye which it thus 
 unites to the eyelids. From the whole extent of its surface, 
 there oozes an albuminous serosity, which mingles with the 
 tears, and adds to their quantity.* 
 
 The tears are equably diffused over the globe of the eye by 
 the alternate motions of the palpebrjje; they prevent the effects 
 of friction, and save the organ of sight from being dried at that 
 part which is exposed to the air. The air dissolves, and carries 
 off in evaporation a part of the lachrymal fluid. This evapora- 
 tion of the tears is proved by the weeping to which those, in 
 whom that secretion is very profuse, are subject, whenever the 
 atmospherical air from being damp does not carry off a sufficient 
 quantity of the fluid. The unctuous and oily fluid, secreted by the 
 meibomian glands, smears the loose edge of the palpebrae, pre- 
 vents the tears from falling on the cheek, and answers the same 
 purpose as the greasy substance with which one anoints the 
 edges of a vessel, filled above its level, to prevent the overflow- 
 ing of the contained fluid. 
 
 The greatest part of the tears, however, flow from without 
 inward, and towards the inner canthus of the eye; they take that 
 direction in consequence of the natural slope of the moveable 
 edge of the palpebrae, of the triangular groove, which is formed 
 behind the line of union of their edges, whose round and convex 
 surfaces touch each other only in a point; and this course of the 
 tears is, likewise, promoted by the action of the palpebral por- 
 tions of the orbicularis palpebrarum, whose fibres, having their 
 fixed point at the inner angle of the orbit where the tendon is 
 inserted, always draw in their external commissure. 
 
 * There is no opening in the part which corresponds to the globe of the eye; 
 it is exceedingly thin, and is continued under the name of conjunctiva over the 
 transparent cornea, to which it adheres so firmly that it is not easily separated 
 from it. In some animals that have no palpebrse, the skin is continued of the 
 same thickness over the fore pai-t of the eye. The conjunctiva (if, however, 
 this portion of skin deserves that name) when opake, renders the globe of 
 the eye, in other respects imperfect, absolutely useless. This is observed in 
 the'kind of eel, called in books of natural histor)’-, murena ccecUia: the gasm- 
 bronchus cacus is blind from the same circumstance. 
 
OF SENSATIONS. 
 
 310 
 
 On reaching the internal angle of the palpebrae, the tears accu- 
 mulate in the lacus lachrymalis^ a small space formed between 
 the edges of the palpebraj, kept separated from each other by 
 the caruncula lachrymalis. This last substance, long considered 
 by the ancients as the secretory organ of the tears, is merely a 
 collection of mucous cryptae, covered over by a loose fold of the 
 conjunctiva. These follicles, alike in nature to the meibomian 
 glands, secrete like them an unctuous substance, which smears 
 the moveable edges of the palpebrae near the internal commis- 
 sure. The edges of the eye-lids in this situation required a 
 thicker coating, as the tears accumulated in that spot have no 
 where a greater tendency to flow on the cheek. 
 
 Near the union of the inner sixth of the free edge of the pal- 
 pebrae with the remaining five sixths, at the outer part, where their 
 internal, straight, or horizontal portion unites with the curved 
 part, there are situated two small tubercles, at the top of each 
 of which there is a minute orifice. These are the puncta lachrj’- 
 malia, and they are called superior and inferior, according to 
 the palpebrse to which they belong. In the dead body the puncta 
 do not appear tubercular; the small bulgings produced, doubt- 
 less, by a state of orgasm and of vital erection, collapse at the 
 approach of death. These small apertures, directed inward and 
 backward, are incessantly immersed in the accumulated tears, 
 absorb them, and convey them into the lachrymal sac by means 
 of the lachrymal ducts, of which they are the external orifices. 
 The absorption of the tears, and their flow into a membranous 
 reservoir lodged in the groove formed by the os unguis, do not 
 depend on the capillary attraction of the lachrymal ducts; each 
 of them, endowed W'ith a peculiar vital action, takes up by a 
 real process of suction, the tears accumulated in the lacus lachry~ 
 ?nalisy and determines their flow Into the sac. The weight of the 
 fluid, the effort of the columns which succeed each other, co- 
 operate with the action of the parietes of the duct. The flow of 
 the tears is further facilitated by the compression and slight 
 concussions attending the contractions of the palpebral fibres of 
 the orbicularis, behind which the lachrymal ducts are situated. 
 This vitality of the puncta lachrymalia and of the ducts is rea- 
 dily discovered when we attempt to introduce into them Anel’s 
 syringe or Mejean’s stylet, to remove slight obstructions of the 
 
OF^SENS ATIONS. 5 1 ], 
 
 lachrymal passages. In a child now under my care for a mu- 
 cous obstruction of the nasal duct, I can see the puncta lachry- 
 malia contract, when the extremity of the syphon does not at 
 once enter the canal. One is then obliged to wait before it can 
 be introduced for a cessation of the spasmodic contraction, 
 which lasts but a few moments. The tears which flow into the 
 lachrymal sac, by the common orifice of the united puncta 
 lachrymalia, never accumulate within it, except in case of mor- 
 bid obstruction; they, in that case, at once enter into the nasal 
 duct, which is a continuation of it, and fall into the nasal fossae, 
 below the anterior part of the inferior turbinated bones of these 
 cavities. There they unite with the mucus of the nose, increase 
 its quantity, render it more fluid, and change its composition. 
 The use of the tears is to protect the eye-ball against the irri- 
 tating impression of the immediate contact of the atmosphere. 
 They, at the same time, favour the sliding of the palpebrae, 
 lessen the friction in those parts and in the eye-ball, and thus 
 promote their motion. 
 
 CXVIII. Of the globe of the eye. The eye-ball, as was al- 
 ready observed, may be considered as a dioptrical instrument 
 placed before the retina; whose office it is to refract the lumi- 
 nous rays, and to collect them into one fasciculus, that may 
 strike a single point of the nervous membrane exclusively cal- 
 culated to feel its impression. An outer, membranous, hard, 
 and consistent covering supports all its parts. Within the first 
 membrane called the sclerotic, lies the choroid, a darkish coat, 
 which lines the inside of the sclerotic, and forms the eye into a 
 real camera obscura. At the interior part of the globe, there is 
 a circular opening in the sclerotic in which the transparent cor- 
 nea is inserted. At about the distance of the twelfth part of an 
 inch from this convex segment, received in the anterior aper- 
 ture of the sclerotica, lies the iris, a membranous partition 
 placed perpendicularly, and containing a round opening (the 
 pupil), which dilates or contracts, according to the state of dila- 
 tation or contraction of the iris. 
 
 At the distance of about half a line from the back part of the 
 iris, towards the union of the anterior fourth of the globe of the 
 eye with the posterior three fourths, opposite to the opening of 
 the pupil, there is situated a lenticular body, inclosed in a mem- 
 
OF SENSATIONS. 
 
 312 
 
 branous capsule, immoveably fixed in its situation by adhering 
 to the capsule of the vitreous humour. 
 
 Behind the crystalline lens, the posterior three-fourths of the 
 cavity of the eye contain a viscid transparent humour, enclosed 
 in the cells of a remarkably fine capsule, called hyaloid. This 
 vitreous humour forms about two thirds of a sphere from which 
 the anterior segment had been taken out; the pulpous expan- 
 sion of the optic nerve, the retina, is spread out on its surface, 
 so as to be concentrical to the chorid and sclerotic coats. 
 
 The eye-ball being nearly spherical, the length of its different 
 diameters differs but little. The diameter of the eye, from the 
 fore to the back part, is between ten and eleven lines; the trans- 
 verse and vertical diameters are somewhat shorter. Within the 
 space measured by the diameter from the fore to the back part, 
 there are situated, taking them in their order from the fore 
 part, the cornea, the aqueous humour contained in the anterior 
 chamber, the iris and its central opening or pupil; the aqueous 
 humour of the posterior chamber, the crystalline lens, surround- 
 ed by the ciliary processes; then the vitreous humour in its 
 capsule; and behind those transparent parts of the eye, through 
 which the luminous rays pass in approaching to a perpendicu- 
 lar, are the retina which receive the impression, the choroid 
 whose black paint absorbs the rays that pass through the thin 
 and transparent retina, and the sclerotic in which there is an 
 opening for the passage of the optic nerve to the globe of the 
 eye. 
 
 The cornea, contained in the anterior aperture of the sclerotica, 
 like the glass of a watch case within its frame, is about the third 
 of a line in thickness; it forms, at the fore part of the eye, the 
 segment of a smaller sphere: behind it lies the aqueous humour 
 which fills what are called the chambers of the eye; these form 
 spaces divided into anterior and posterior; the former, which is 
 the larger of the two, bounded by the cornea at the fore part, 
 and by the iris at the back part; the latter, which is smaller 
 and separates the crystalline humour from the iris, the posterior 
 part of which, covered by a black pigment, is called the tivea*. 
 
 * Some anatomists have doubted the existence of the posterior chamber of 
 the eye; but to be convinced of its existence, one need but freeze an eye, 
 when there will be found a piece of ice, between the crystalline lens and the 
 
OF SENSATIONS. 
 
 313 
 
 The specific gravity of the aqueous humour does not much ex- 
 ceed that of distilled water; some have even thought it less; it 
 is albuminous, and holds in solution several saline substan- 
 ces. The crystalline, inclosed in its membranous and transpa- 
 rent capsule, is a lenticular body rather solid than fluid; its 
 consistence is particularly great towards its centre; it there 
 forms a kind of nucleus, on which are laid several concentric 
 layers whose density diminishes as they approach the surface, 
 where the external layers, truly fluid, form what Morgagni 
 considered as a peculiar liquid, on which the lens might be 
 nourished by a kind of imbibition. This body, composed of 
 two segments of unequal convexity, about two lines in thick- 
 ness at its centre, consists of an albuminous substance coagula- 
 ble by heat and alkohol. Extremely minute arteries given off 
 by the central artery of Zinn, pass through the vitreous humour, 
 and bring to it the materials of its growth and reparation. 
 
 The vitreous humour, so called from its resemblance to melted 
 glass, is less dense than the crystalline and more so than the 
 aqueous, and is in considerable quantity in the human eye; it ap- 
 pears to be secreted by the minute arteries which are distributed 
 to the parietes of the membrane of the vitreous humour; it is 
 heavier than common water, somewhat albuminous and saltish. 
 
 The sclerotica is a fibrous membrane to which the tendons 
 which move the globe of the eye are attached; it supports all 
 the parts of that organ, and these collapse and decay, whenever 
 
 uvea. The formation of this isicleis net owing to the admission, through the 
 opening of the pupil, of the aqueous humour, which, like all other fluids, ex- 
 pands considerably on freezing; for the expansion of fluids on their freezing 
 being proportioned to their bulk, the vitreous humour which freezes at the 
 same time as the aqueous, must prevent its retrograde flow through the pupil. 
 Lastl)', the uvea or posterior part of the iris is covered with a black point which 
 is easily detached from it; now, if the anterior part of the crystalline lens had 
 been in immediate contact with it, it would have been soiled by some of this 
 colouring matter, which would have tarnished its natural transparency, indis- 
 pensable to perfect vision. It is, therefore, undeniable that there does exist a 
 ]josterlor chamber, which is to the anterior in the proportion of two to five, 
 and containing about two fifths of the aqueous humour, the whole of which is 
 estimated at five grains, and that the iris forms a loose partition between the 
 two portions of the aqueous humour in which the dark pigment of the uvea 
 is insoluble. The aqueous humour appears to be the product of arterial exha- 
 lation; it is soon reproduced, as we see after the operation for cataract. 
 
 2 R 
 
0F SENSATIONS 
 
 314 
 
 the continuity of its external covering is destroyed. The use of 
 the choroid, is notAO much to afford a covering to the other parts, 
 as to present a dark surface, destined to absorb the luminous 
 rays, when they have produced on the retina a sufficient im- 
 pression. If it were not for the choroid, the light’would be re- 
 flected, and after having impinged on the nervous membrane, its 
 rays would cross, and produce only indistinct sensations. Ma- 
 riotte thought that the choroid was the immediate seat of vision, 
 and that the retina was only its epidermis. This hypothesis 
 would never have obtained so much celebrity, if, besides the 
 objections that analogy might have furnished against it, there 
 had been adduced, in opposition to it, the fact observed in 
 fishes, in which the choroid is separated from the retina, by a 
 glandular body, opake and incapable of transmitting the lumi- 
 nous rays. The retina loses its form, as soon as it is separated 
 from the vitreous humour, or from the choroid coat, between 
 which it is spread ouj: as a very thin capsule, so soft as to be 
 almost fluid. A number of blood-vessels, from the central ar- 
 tery of Zinn, are .distributed on the nervous substance of the 
 retina, aud give it a slight pink colour. Ought we, with Boer- 
 haave, to attribute to aneurismal or varicose enlargements of 
 those small vessels, the spots which are seen in objects, in the 
 disease to which Maitre Jean gave the name of imaginations? 
 In order to form the retina, the optic nerve enters into the 
 globe of the eye, by piercing the sclerotica, to which the cover- 
 ing given to that nerve by the dura mater is connected; next 
 penetrating through a very thin membrane’ perforated by a num- 
 ber of small holes and closing the opening left by the nerve, 
 and which belongs as much to the choroid as to the sclerotic 
 coats, it spreads out to furnish the expansion which lines the 
 concavity of the choroid and covers over the convex surface 
 of the vitreous humour. The whole extent of the retina, which 
 is equally nervous and sentient, may receive the impression 
 of the luminous rays, though this faculty has, by several philo- 
 sophers, been exclusively assigned to its central part, called 
 the optical axis or porus opticus. This central part Is easily 
 recognized, in man, by a yellow spot discovered by Soem- 
 mering; in the middle of this spot, situated at the outer side 
 of the entrance of the optic nerve into the globe of the eye, 
 
OF SENSATIONS. 
 
 315 
 
 there is seen a dark spot and a slight depression, the use of 
 which is not' understood. This peculiar structure, recently dis- 
 covered, is met with only in the eye of man and of monkeys. 
 
 CXIX. Mechanism and phenomena of- vision. The rays of 
 light passing from any point of an enlightened object, form a 
 cone of which the apex answers to the point of the object, and 
 of which the base covers the anterior part of the cornea. All 
 the rays, more diverging, which fall without the firea of the 
 cornea on the eye-brows, the eye-lids and the sclerotica, are lost 
 to vision. Those which strike the mirror of the eye pass 
 through it, under a refraction proportioned to the density of 
 the cornea, which much exceeds that of the atmosphere, and to 
 the convexity of that membrane; approaching the perpendicular, 
 they now pass through the aqueous humour, less dense, and fall 
 upon the membrane called the iris. All those that fall upon this 
 membrane are reflected, and show its colour, different in differ- 
 ent persons, and apparently depending on the organic texture, 
 and on the particular and very diversified arrangement of the 
 nerves, and of the vessels, and cellular tissue, which enter into 
 its structure. None but the most central traverse the pupil and 
 serve to sight. These will pass that opening, in greater or less 
 number, as it is more or less dilated. Now, the pupil is enlarg- 
 ed or diminished, by the contraction or expansion of the iris. 
 
 The motions of this membrane depend entirely on the man- 
 ner in which light affects the retina. The iris itself is insensible 
 to the impression of the rays of light, as Fontana has proved, 
 who always found it immoveable, when he directed on it alone 
 the luminous rays. When the retina is disagreeably affected, 
 by the lustre of two strong a light, the pupil contracts, to give 
 passage only to a smaller number of rays: it dilates, on the con- 
 trary, in gloom, to admit enough to make the requisite impres- 
 sion on the retina. 
 
 To explain the motions of the iris, it is not necessary to admit 
 that muscular fibres enter into its structure; it is enough to know 
 its vascular, spungy and nervous texture; the irritation of the 
 retina sympathetically transmitted to the iris, determines a more 
 copious afflux of humours; its tissue dilates and stretches, the 
 circumference of the pupil is pushed towards the axis of this 
 opening, which becomes contracted by this vital expansion of 
 
OP SENSATIONS. 
 
 316 
 
 the membi'anous tissue. When the irritating cause ceases- to 
 act, by our passing from light into darkness, the humours flow 
 back into the neighbouring vessels, the membrane of the iris 
 returns upon itself, and tlfe pupil enlarges, the more as the 
 darkness is greater^. 
 
 The rays, admitted by the pupil, pass through the aqueous 
 humour of the posterior chamber, and soon meet the crystalline, 
 which powerfully refracts them, both from its density, and its 
 lenticular form. Brought towards the perpendicular by this 
 body, they pass on towards the retina through the vitreous 
 humour, less dense, and which preserves, without increasing 
 it, the refraction produced by the crystalline lens. The rays, 
 gathered into one, strike on a single point of the retina, and 
 produce the impression which gives us the idea of certain pro- 
 perties of the body which reflects them. As the retina embraces 
 the vitreous humour, it presents a very extended surface to the 
 contact of the ra5^s, which enables us to behold, at once, a great 
 diversity of objects, variously situated towards us, even when 
 we or these objects change our relative situation. The luminous 
 rays, refracted by the transparent parts of the eye, form there- 
 fore, in the interior of the organ, a cone, of which the base 
 covers the cornea, and applies to that of the external luminous 
 cone, whilst its apex is on some point of the retina. It is con- 
 ceived, generally, that the luminous cones issuing from all 
 points of the object beheld, cross in their passage through the 
 eye, so that the object is imaged on the retina reversed. Admit- 
 ting this opinion, established on a physical experiment, we have 
 to inquire, why we see objects upright, whdst their image is 
 reversed on the retina. The best explanation we possess of this 
 phenomenon, we owe to the English philosopher Berkeley, who 
 proposed it in his work, entitled Theory of Vision^ &c. In his 
 opinion, there is no need of the touch to correct this error into 
 which sight ought to betray us. As we refer all our sensations 
 to ourselves, the uprightness of the object is only relative, and 
 its inversion really exists at the bottom of the eye. 
 
 By the point of distinct vision, is understood the distance at 
 which we can read a book of which the characters are of mid- 
 
 * Habitual dilatation of the pupil is a symptom of weakness, of womis^, kc. 
 
OF SENSATIONS. 
 
 317 
 
 dling size, or distinguish any other object equally small. This 
 distance is not confined within very narrow limits, since we can 
 read the same book at six inches from the eye, or at five or six 
 times the distance. This faculty of the eyes to adapt themselves 
 to the distance and the smallness of objects, cannot depend, as 
 has been fondly repeated, on the lengthening or shortening of the 
 globe of the eye by the muscles that move it. Its four recti 
 muscles are not, in any case, capable of compressing it on its 
 sides, nor of lengthening it by altering its spherical form; their 
 simultaneous action can only sink the ball in its socket, flatten 
 it from the fore to the back part, diminish its depth, and make 
 the refraction, consequently, less powerful when objects are 
 very distant or very small: this last effect, even, might be dis- 
 puted. The eye, which moves and rests on the_ adipose cushion 
 which fills the bottom of the socket, is never strongly enough 
 pressed to lose its spherical figure, which of all the forms in which 
 bodies can be invested, is that which, by its especial nature, 
 best resists alteration. The extremities of the ciliary processes, 
 which surround the circumference of the crystalline lens, can- 
 not act on this transparent lens, compress nor move it: for, these 
 little membranous folds, of which the aggregate composes the 
 irradiated disk, known under the name of corpus ciliare, possess- 
 ing no sort of contractile power, are incapable of moving the 
 crystalline lens, with which their extremities lying in simple 
 contiguity have no adherence, and which, besides, is immove- 
 ably fixed in the depression which it occupies, by the adhesions 
 of its capsule with the membrane of the vitreous humour. The 
 various degrees of contraction or dilatation of which the eye- 
 ball is susceptible, afford a much more satisfactory explanation 
 of this physiological problem. 
 
 The rays of light which come from a very near object, are 
 very divergent: the eye would want the refracting power neces- 
 sary to collect them into one, if the pupil, contracting by the 
 enlargement of the iris, did not throw off the more divergent 
 rays, or those which form the circumference of the luminous 
 cone. Then, those which form the centre of the cone, and which 
 need but a much smaller refraction for their re-union on a 
 single point of the retina, are alone admitted by the straitened 
 opening. When, on the contrary, we look at a distant object 
 
OF SENSATIONS. 
 
 318 
 
 from which rays are given out, already very convergent, and 
 which need but a small refraction to bring them towards the 
 perpendicular, we dilate the pupil, in order to admit the more 
 divergent rays, which, when collected, will give the image of 
 the object. In this respect, very small bodies are on the same 
 footing as those at a great distance. 
 
 Though the image of every object is traced at the same time 
 in both our eyes, we have but one sensation, because the two 
 sensations are in harmony and are blended and serve only, one 
 aiding the other, to make the impression stronger and more 
 durable. It has long been observed, that the sight is more pre- 
 cise and correct when we use only one eye, and Jurine thinks 
 that the power of the two eyes united exceeds only by one-thir- 
 teenth, that of a single eye. The correspondence of affection 
 requires the direction of the optical axes on the same objects, 
 and be that direction ever so little disturbed, we see really 
 double, which is what happens in squinting. 
 
 If the eyes are too powerfully refractive, either by the too 
 great convexity of the cornea and the crystalline, the greater 
 density of the humours, or the excessive depth of the ball, the 
 rays of light, too soon re-united, diverge anew, fall scattering 
 on the retina, and yield only a confused sensation. In this de- 
 fect of sight, called myopia^ the eye distinguishes only very 
 near objects, giving out rays of such extreme divergence as to 
 require a very powerful refractor. In presbytia^ on the other 
 hand, the cornea too much flattened, the crystalline little con- 
 vex, or set too deeply, the humours too scanty, are the cause 
 that the rays are not yet collected when they fall upon the re- 
 tina, so that none but very distant objects are distinctly seen, 
 because the very* convergent rays they give out, have no need 
 of much refraction. 
 
 Myopia is sometimes the effect of the habit which some chil- 
 dren get, of looking very close at objects which catch their at- 
 tention. The pupil then becomes accustomed to great constric- 
 tion, and dilates afterwards with difficulty. It is obvious, that, 
 to correct this vicious disposition, you must show the child 
 
 * The author means “scarcely divergent.” T. 
 
OF SENSATIONS. 
 
 distant objects which will strongly engage his curiosity, and 
 keep him at some distance from every thing he looks at. 
 
 The sensibility of the retina, on some occasions, arises to such 
 excess, that the eye can scarcely bear the impression of the 
 faintest light. Nyctaclopes, such is the name given to those af- 
 fected with this disorder, distinguish objects amidst the deep- 
 est darkness; a few rays are sufficient to impress their organ. 
 
 It is related than an English gentleman, shut up in a dark 
 dungeon, came gradually to distinguish all it contained: when 
 he returned to the light of day, of which he had in some sort 
 lost the habit, he could not endure its splendor; the edges of 
 the pupil, before extremely dilated, became contracted to such 
 a degree, as entirely to efface the opening. 
 
 When, on the other hand, the retina has little sensibility, strong 
 day light is requisite to sight. This injury of vision, known by 
 the name of hemeralopia*^ may be considered as the first step 
 of total paralysis of the optic nerve, or gutta serena. It may 
 arise from any thing that can impair the sensibility of the retina. 
 Saint-Yves relates, in his work bn diseases of the eyes, many 
 cases of hemeralopia. The subjects were chiefly workmen em- 
 ployed at the Hotel des Monnoies, in melting the metals. The 
 inhabitants of the northern regions, where the earth is covered 
 with snow, great part of the year, become at an early age he- 
 meralopes. Both contract this weakness, from their eyes being 
 habitually fatigued by the splendor of too strong a light. 
 
 Finally, in order to the completion of the mechanism of vision, 
 it is requisite that all parts of the eye be under certain condi- 
 tions, the want of which is more or less troublesome. It is espe- 
 cially necessary, that the membranes and the humours which the 
 rays of light are to pass through, should be perfectly transparent. 
 Thus, specks of the cornea, the closing of the pupil by the pre- 
 
 * I give to tile word nyctalopia and hemeralopia the same meaning as all other 
 writers down to Scarpa, who has published the latest treatise on diseases of 
 the eyes. Tiiis acceptation is, liowever, a grammatical error, since of the two 
 terms, nyctalopia, in its Greek roots, signifies an affection which takes away 
 sight during the night, and hemeralopia, one in which it is lost during the day. 
 It is accordingly in this sense that they are used by the father of physic. I owe 
 this I’emark to Dr. Roussille Chamseru, who has carefully verified the text of 
 Hippocrates in tlie MSS. of the Impei'ial library. 
 
OF SENSATIONS. 
 
 329 
 
 servation of the membrane which steps that opening during the 
 first months of the life of the feetus; cataract, an affection which 
 consists in the opacity of the crystalline lens or its capsule; the 
 glaucoma, or defect of transparency in the vitreous humour, 
 weaken or altogether destroy sight, by impeding the passage of 
 the rays to the retina. This membrane itself must be of tempered 
 sensibility to be suitably affected by their contact. The choroid, 
 the concavity of which it fills, must present a coating black 
 enough to absorb the rays that pass through it. It is to the sen- 
 sible decay of the dye of the choroid in advancing years, as 
 much as to the collapsing, induration, and discolouring of dif- 
 ferent parts of the eye, and the impaired sensibility of the retina 
 from long use, that we ascribe the confusion and weakness of 
 sight in old people. The extreme delicacy of the eyes of Albinos 
 proves equally the necessity of the absorption of light, by the 
 black coating which covers the choroid. 
 
 The eyes are, of all the organs of sense, those which are the 
 most developed in a new-born child. They have then nearly the 
 bulk which they are to retain during life. Hence it happens, 
 that the countenance of children, whose eyes are proportionally 
 larger, is seldom disagreeable, because it is chiefly in these 
 organs that physiognomy seeks expression. Might we not say, 
 that if nature sooner completes the organ of sight, it is because 
 the changes which it produces on the rays of light, arising purely 
 from a physical necessity, the perfection of the instrument was 
 required for the exercise of the sense? 
 
 The eyes are not immoveable in the place they^ occupy. Drawn 
 into very various motions by four recti muscles, and two oblique^ 
 they direct themselves towards all objects of which we wish to 
 take cognizance; and it is observed, that there is, between the 
 muscles which move the two eyes, such a correspondence of ac- 
 tion, that these organs turn at once the same way, and are di- 
 rected, at once, towards the same object, in such a manner, that 
 the visual axes are exactly parallel. It some times happens, 
 that this harmony of motion is disturbed; and thence squinting, 
 an affection, which depending, almost always, on the unequal 
 force of the muscles of the eye, may be distinguished into as 
 many species as there are muscles which can draw the globe of 
 the eye into their direction, when from any cause, they become 
 
 I 
 
OF SENSATIONS. 
 
 321 
 
 possessed of a predominating power. Buffon has further as- 
 signed, as a cause of squinting, the different aptitude of the 
 eyes to be aflFected by light. According to this celebrated na- 
 turalist, it may happen, that one of the eyes being originally of 
 greater sensibility, the child will close the weaker to use the 
 stronger, which is yet Strengthened by exercise, whilst repose 
 still weakens the one which remains in inaction. The examina- 
 ton of a great many young people, who had fallen under mili- 
 tary conscription, and claimed exemption on the score of infir- 
 mities, has shown me that squinting is constantly connected with 
 the unequal power of the eyes. Constantly, the inactive eye is 
 the weakest, almost useless, and it was quite a matter of neces- 
 sity that the diverging globe should be thus neutralized^ else tha 
 image it would have sent to the brain, different from that which 
 the sound eye gives, would have introduced confusion into the 
 visual functions. The squinting eye, being inactive, falls by de- 
 grees into that state of debility, from default of exercise, which 
 Brown has so well called indirect debility. 
 
 The sense of sight appears to me much rather to deserve the 
 name which J. J. Rousseau has given to that of smell, of sense 
 of the imagination. Like that brilliant faculty of the soul, the 
 sight, which furnishes us with ideas so rich and varied, is liable 
 to betray us into many errors. It may be doubted, whether it 
 gives the notion of distance, since the boy couched by Chesel- 
 den, conceived every thing he saw to touch his eye. It exposes 
 us to false judgments on the form and size of objects; since, 
 agreeably to the laws of optics, a square tower seen at a dis- 
 tance, appears to us round; and very lofty trees seen also very 
 far off, seem no taller than the shrubs near us. A body, moving 
 with great rapidity, appears to us motionless, &c. It is from the 
 touch that we gain the correction of these errors, which Con- 
 dillac, in his Treatise on Sensation, has perhaps exaggerated. 
 
 CXX. The organ of sight, in different animals, varies accord- 
 ing to the medium in which they live; thus, in birds which flv in 
 the higher regions of the air, there is an additional and verv re- 
 markable eye-lid; this is particularlv the case with the eafi^le, 
 which is thus enabled to look at the sun, and with night birds, 
 whose very delicate eve it seems to protect from the effects of 
 too strong a light. In birds, likewise, there is a copious secretion 
 
 as 
 
OF SENSATIONS. 
 
 322 
 
 of tears, the medium in which they live causing a considerable 
 evaporation. The greater part of fishes, on the contrary, have 
 no moveable eye-lid, and their eyes are not moistened by tears, 
 as the water in which they are immersed answers the same pur- 
 pose. In some fishes, however, the eyes are smeared with an 
 unctuous substance, calculated to prevent the action of the water 
 on the organ. 
 
 The globe of the eye in birds, is remarkable by the convexity 
 of the cornea which is sometimes a complete hemisphere; hence 
 it possesses a considerable power of refraction. This power of 
 refraction appears to be very weak in fishes, the fore part of 
 their eyes being very much flattened; but the water in which 
 they live made it unnecessary that they should have an aqueous 
 humour, for the density of this fluid being nearly the same as 
 that of water, it would not have produced any^ refraction: be- 
 sides, being, in sea fish, of inferior density to that of salt water, 
 it would have broken the rays of light, by making them diverge 
 from the perpendicular. In fact, the refractive power of a me- 
 dium is never but a relative quantity; the degree of refraction is 
 not determined by the density of the medium, but by the diflFer- 
 cnce of density between it and the medium that is next to it. To 
 make up for the flatness of the cornea occasioned by the small 
 quantity, or even by the absence of aqueous humour, fishes have 
 a very dense and spherical crystalline humour, the spherical 
 part of which forms a part of a small sphere. 
 
 The eyes of birds, whose cornea is thrust out by a very co- 
 pious aqueous humour, possess, in consequence of the presence 
 of this fluid, a very considerable power of refraction; the air, in 
 the higher regions of the air, owing to its extreme rarefaction, 
 being but little calculated to approximate the rays of light. 
 
 The pupil admits of greater dilatation in the cat, in the owl, 
 in night birds, and in general in all animals that see in the dark. 
 The sensibility of the retina appears, likewise, greater in those 
 animals; several of them appear incommoded by the light of day, 
 and never pursue their prey but in the most obscure darkness. 
 
 The crystalline humour of several aquatic fowls, as the cor- 
 morant’s, is spherical like that of fishes, and this is not, as will be 
 mentioned hereafter, the only peculiarity of structure in these 
 kind of amphibious animals. Lastly, the choroid of some ani- 
 
OF SENSATIONS. 
 
 323 
 
 xnals, more easily separated into two distinct laminse, than that 
 of man, presents, at the bottom of the eye, instead of a darkish 
 uniformly diffused coating, a pretty extensive spot of various 
 colours, and in some, most beautiful and brilliant. It is not easy 
 to say what is the use of this coloured spot, known by the name 
 of tapetum. 
 
 The rays of light, reflected by this opake substance, must, 
 in passing through the eye, cross those which are entering at the 
 same time; they must consequently prevent distinct vision, or 
 at least impair the impression, in a manner which it is impossi- 
 ble to determine. It has been said, that the lower animals, pro- 
 vided with less perfect and often less numerous senses than 
 those of man, must have different ideas of the universe; is it 
 not, likewise, probable, that in consequence of the indistinct 
 vision occasioned by the reflection from the tapetum, they may 
 entertain erroneous and exaggerated notions of the power of 
 man? And notwithstanding the power granted to naan by the 
 Creator over the lower animals, as we are told in the book of 
 Genesis, is it probable that those which nature has gifted with 
 prodigious strength or with offensive weapons, would obey the 
 Lord of the creation if they saw him in his feeble and destitute 
 condition, in a word, such as he is? 
 
 The head of insects with numerous eyes, is joined to their 
 body, and moves along with it; their existence is, besides, so 
 frail, that it was requisite that nature should furnish them abun- 
 dantly with the means of seeing those objects which may be in- 
 jurious to them. We shall not enter any farther into these re- 
 marks relative to the differences in the organ of sight, in the va- 
 rious kinds of animals. More ample details on this subject be- 
 long, in an especial manner, to comparative anatomy. 
 
 CXXI. Of the organ of hearing. Of sound, Sound is not, 
 like light, a body having a distinct existence; we give the name 
 of sound to a sensation which we experience whenever the vi- 
 brations of an elastic body strike our ears. All bodies are capa- 
 ble of producing it, provided their molecules are susceptible- of 
 a certain degree of re-action and resistance. When a sonorous 
 body is struck, its integrant particles experience a sudden con- 
 cussion, are displaced and oscillate with more or less rapidity. 
 This tremulous motion is communicated to the bodies applied 
 
324 SENSATIONS. 
 
 to its furface; if we lay our hand ou a bell that has been struck 
 by its clapper, we feel a certain degree of this trembling. The 
 air, which envelops the sonorous body, receives and transmits 
 its vibrations with the more effect from being more elastic. 
 Hence, it is observed that, caeteris paribus, the voice is heard at 
 a greater distance in winter, when the air is dry and condensed 
 by the cold. 
 
 The sonorous rays are merely series of particles of air, along 
 which' the vibration is transmitted from the sonorous body, to 
 the ear which perceives the noise occasioned by its percussion. 
 These molecules participate in the vibrations which are com- 
 municated to them; they change their form and situation, in 
 proportion as they are nearer to the body that is struck, and vice 
 versa; for sound becomes weaker in proportion to the increase 
 of distance. But this oscillatory motion of the aerial molecules, 
 should be well distinguished from that by which the atmosphere, 
 agitated by the winds, is transported and changes its situation. 
 And in the same manner as the balance of a pendulum moves 
 incessantly within the same limits, so this oscillatorv motion 
 affects the molecules of the air within the space which thev oc- 
 cupy, so that they move to and fro during the presence or 
 the absence of the vibration. The atmospherical air, when set 
 in motion in a considerable mass at a time, produces no sound, 
 unless in its course it meets with a body which vibrates from 
 the percussion which it experiences. 
 
 The force of sound depends, entirely, on the extent of the 
 vibrations experienced by the molecules of the sonorous body. 
 In a large bell struck violently, the agitation of the molecules is 
 such, that they are transmitted to considerable distances, and 
 that the form of the body is evidently changed by it. Acute or 
 grave sounds are produced by the greater or smaller number of 
 vibrations in a given time, and the vibrations will be more 
 numerous, the smaller the length and diameter of the body. 
 Two catgut strings, of the same length and thickness, and with 
 an equal degree of tension, will vibrate an equal number of 
 times in a given time, and produce the same sound. This in mu- 
 sic is called unison. If one of the strings is shortened by one 
 half, it vibrates as often again as the other, and gives out a 
 sound more acute, or higher by one octave. The same result may 
 
OF SENSATIONS. 
 
 325 
 
 be obtained by reducing the string one half of its original thick- 
 ness, without taking from its length. The vibrations will, in the 
 same manner, be accelerated by giving a greater degree of ten- 
 sion to the sonorous cord. The difference of the sounds pro- 
 duced by a bass, a harp, or any other stringed instrument, de- 
 pends on the unequal tension, length and size of the strings. 
 
 This division of the elementary sound is an act of the under- 
 standing, which distinguishes in a noise, apparently monotonous, 
 innumerable varieties, and shades expressed by signs of conven- 
 tion. But in the same manner as light, refracted by a prism, 
 presents innumerable intermediate shades between the seven 
 primitive colours, and as the transition is gradual from the one 
 to the other of these colours; so, the division of the primitive 
 sound into seven tones, expressed by notes, is not absolute, and 
 there are a number of intermediate sounds which augment or 
 dimmish their value, &c. 
 
 Sound has, therefore, been analysed as well as light; the use 
 of the ear with regard to sound, corresponds to that of the prism 
 with regard to light; and the modifications of which sound is 
 capable, are as numerous and as various as the shades between 
 the primitive colours. 
 
 Sound is propagated with less velocity than light. The report 
 of a cannon fired at a distance is heard only a moment after the 
 eye has perceived the flash of the explosion. Its rays diverge 
 and are reflected, like those of light, when they meet with an 
 obstacle at an angle equal to that of incidence. The force of 
 sound, like that of light, may be increased by collecting and con- 
 centrating its rays. The sonorous rays which strike a hard and 
 elastic body, when reflected by it, impart to it a vibratory mo- 
 tion, giving rise to a secondary sound, which increases the force 
 of the primitive sound. 
 
 When these secondary sounds, produced by the percussion 
 of a body at a certain distance, reach the ear, they give rise to 
 what is called an echo. Who is unacquainted with the ingenious 
 allegory, by which its nature is expressed in ancient mythology, 
 in which echo was called daughter of the air and of the earth? 
 
 CXXII. Of the organ and mechanism of hearing. The organ 
 of hearing in man, consists of three very distinct parts; the one 
 placed externally, is intended to collect and to transmit the sono- 
 
OF SENSATIONS. 
 
 326 
 
 rous rays which are modified in passing along an intermediate 
 cavity, between the external and internal ear. It is within the 
 cavities of this third part of the organ, excavated in the sub- 
 stance of the petrous portion of the bone, that the nerve destined 
 to the perception of sound exclusively resides. The external 
 ear and the meatus auditorius externus may be compared to an 
 acoustic trumpet, the broad part of which, represented by the 
 concha, collects the sonorous rays which are afterwards trans- 
 mitted along the contracted part, represented by the meatus ex- 
 ternus. The concha contains several prominences separated by 
 corresponding depressions; its concave part is not wholly turned 
 outward; in those who have not laid their ears flat against the 
 side of the head by tight bandages, it is turned slightly forward; 
 and this arrangement, favourable to the collecting of sound, is 
 particularly remarkable in savages, whose hearing, it is well 
 known, is remarkably delicate. The base of the concha consists 
 of a fibro-cartilaginous substance, thin, elastic, calculated to re- 
 flect sounds, and to increase their strength and intensity by the 
 vibrations to which it is liable. This cartilage is covered by a 
 very thin skin, under which no fat is collected that could impair 
 its elasticity; these prominences are connected together by small 
 muscles; these may relax it by drawing the projections together, 
 and thus place it in unison with the acute or grave sounds. 
 These small muscles within the external ear, as the musculi 
 helicis major and minor, the tragicus and anti-tragicus, and the 
 transversus auris, are like the muscles on the outer part of the 
 ear, stronger and more marked in timid animals with long ears. 
 In the hare, the fibres of these muscles are most distinctly 
 marked; their action is most apparent in this feeble and fearful 
 animal, which has no resource but in flight against the dangers 
 which incessantly threaten his existence, and which required 
 that he should receive early intimation of the approach of dan- 
 ger; hence hares have the power of making their ears assume 
 various forms, of shaping them into more advantageous trum- 
 pets, of moving them in every direction, of directing them 
 towards the quarter from which the noise proceeds, so as to 
 meet the sounds and collect the slightest. 
 
 The form of the external ear is not sufficiently advantageous 
 in man, whatever Boerhaave may have said to the contrary, to 
 
OF sensations. 
 
 327 
 
 enable all the sonorous rays, which in striking against it, are 
 reflected at an angle equal to that of their incidence, to be di- 
 rected towards the meatus auditorius externus. United, for the 
 most part, into a single fasciculus, and directed towards the 
 concha, they penetrate into the meatus auditorius externus, and 
 the tremulous motions which they excite in its osso-cartilagi- 
 nous parietes, contribute to increase their force. On reaching 
 the bottom of the meatus, they strike against the membrana 
 tympani, a thin and transparent septum, stretched between the 
 bottom of the meatus and the cavity in which the small bones 
 of the ear are lodged. These small bones form a chain of bone 
 which crosses the tympanum from without inward, and which 
 extends from the membrana tympani to that which connects the 
 base of the stapes to the edge of the fenestra ovalis. 
 
 An elastic air, continually renewed by the Eustachian tube, 
 fills the cavity of the tympanum; small muscles attached to the 
 malleus and stapes move these bones, or relax the membranes 
 to which they are attached, and thus institute a due relation 
 between the organ of hearing and the sounds which strike it. It 
 will be easily conceived, that the relaxation of the membrana 
 tympani, effected by the action of the anterior muscle of the 
 malleus, must weaken acute sounds, while the tension of the 
 same membrane, by the internal muscles of the same bone, must 
 increase the force of the grave sounds. In the same manner as 
 the eye, by the contraction or dilatation of the pupil, accomo- 
 dates itself to the light, so as to admit a greater or smaller num- 
 ber of its rays, according to the impression which they produce: 
 so by the relaxation or tension of the membrane of the tympa- 
 num, or of the fenestra ovalis, the ear reduces or increases the 
 strength of sounds whose violence would affect its sensibility in 
 a painful manner, or whose impression would be insufficient. 
 The iris, and the muscles of the stapes and of the malleus 
 are, therefore, the regulators of the auditory and visual impres- 
 sion; there is as close a sympathetic connexion between these 
 muscles and the auditory nerve, as between the iris and the 
 retina. The air which fills the tympanum is the true vehicle of 
 sound; this air diffuses itself over the mastoid cells, the use of 
 which is to augment the dimensions of the tympanum, and the 
 
OP SENSATIONS. 
 
 328 
 
 force and extent of the vibrations which the air experiences 
 within it. 
 
 These vibrations, transmitted by the membrana tympani, are 
 communicated to those membranes which cover the fenestra 
 ovalis and the fenestra rotunda; then, by means of these, to the 
 fluid which fills the different cavities of the internal car, and in 
 which lie the soft and delicate filaments of the auditory nerve, 
 or of the portio mollis of the seventh pair. 
 
 The agitation of the fluid affects these nerves, and determines 
 the sensation of grave or acute sounds, according as they are 
 slower or more rapid. It appears that the diversity of sounds 
 should rather be attributed to the more or less rapid oscillations, 
 and to the undulations of the lymph of Cotunni, than to the im- 
 pressions on filaments, of different lengths, of the auditory 
 nerve. These nervous filaments are too soft and too slender to 
 be traced to their extreme terminations. It is, however, proba- 
 ble, that the various forms of the internal ear, (the semi circular 
 canals, the vestibule, and the cochlea,') have something to do 
 with the diversity of sounds. It must also be observed, that the 
 cavities of the ear are contained in a bony part, harder than any 
 other substance of the same kind, and well fitted to maintain, or 
 even to augment by the re-action of which it is capable, the 
 force of the sonorous rays. 
 
 < The essential part of the organ of hearing, that which appears 
 exclusively employed in receiving the sensation of sounds is, 
 doubtless, that which exists in all animals endowed with the fa- 
 culty of hearing. This part is the soft pulp of the auditory- 
 nerve, floating in the midst of a gelatinous fluid, contained in a 
 thin and elastic membranous cavity. It is found in all animals, 
 from man to the sepiae. In no animal lower in the scale of ani- 
 mation, has an organ of hearing been met with, although some 
 of these inferior animals do not seem to be absolutely destitute 
 of that organ. This gelatinous pulp is, in the lobster, contained 
 in a hard and horny covering. In animals of a higher order, its 
 internal part is divided into various bony cavities. In birds, 
 there is interposed a cavity, between that which contains the 
 nerve of hearing and the outer part of the head; in man and in 
 quadrupeds, the organ of hearing is very complicated; it is en- 
 
OF SENSATION'S. 
 
 ■ 329 
 
 closed In an osseous cavity, extremely hard, situated at a consi- 
 derable depth, and separated from the outer part of the head, 
 by a cavity and a canal along which the sonorous rays are trans- 
 mitted, after having been collected into fasciculi by trumpets 
 situated on the outside. 
 
 This kind of natural analysis of the organ of hearing, is well 
 calculated to give accurate notions on the nature and Import- 
 ance of the functions fulfilled by each of its parts. But in the 
 investigation of the uses and of the relative importance of the 
 auditory apparatus, morbid anatomy furnishes data of an equal 
 value with those obtained from comparative anatom) . 
 
 CXXIII. The external ear may be removed, with impunity, 
 in man, and even in animals in which its form is more advan- 
 tageous; the hearing is at first impaired, but at the end of a few 
 day’s recovers its wonted delicacyu The complete obliteration 
 of the meatus auditorius externus, is attended with complete 
 deafness. It is not essentially necessary for the mechanism of 
 hearing, that the membrana tympani should be whole; persons 
 in whom it has been accidentally ruptured, can force out smoke 
 at their ears, without losing the power of hearing; it may be 
 conceived, however, that if instead of having merely a small 
 opening that would not prevent its receiving the impression of 
 the sonorous rays, nor its being acted upon by the handle of the 
 malleus, the membrana tympani were almost entirely destroyed, 
 deafness would be the almost unavoidable consequence. If, in 
 consequence of the obstruction of the Eustachian tube, the air in 
 the tympanum is not renewed, it loses its elasticity and com- 
 bines with the mucus within the tympanum. The cavity of the 
 tympanum is then in the same condition as an exhausted re- 
 ceiver, in which the sonorous ray’s are transmitted with diffi- 
 culty. It has been thought, that the use of the Eustachian tube 
 was, not only to renew the air contained in the ty’mpanum, but 
 also to transmit the sonorous tay’s into that cavity’. In listening 
 attentively, we slightly open our mouth, in order. It is said, that 
 the sound may pass from this cavity into the pharynx and thence 
 reach the organ of hearing. This explanation is far from satis- 
 factory, for the obliteration of the meatus auditorius externus 
 is attended with complete deafness, which would not happen, if 
 
 2 T 
 
OF SENSATIONS. 
 
 330 
 
 the Eustachian tubes transmitted the sonorous rays. When a 
 man listens attentively, and with his mouth open, the condyles 
 of the lower jaw, situated in front of the external auditory mea- 
 tus, being depressed and brought forward, the openings are 
 evidently enlarged, as may be ascertained by putting the little 
 finger into one’s ear, at the moment of depressing the lower 
 jaw. The luxation of the small bones of the ear, or even their 
 complete destruction does not occasion deafness, the only con- 
 sequence is a confusion in the perception of sounds. When, 
 however, the stapes, the base of which rests on the greatest part 
 of the fenestra ovalis, or when the thin membrane which closes 
 the fenestra ovalis, or when that which closes the fenestra ro- 
 tunda is destroyed, deafness takes place, in consequence of the 
 escape of the fluid which fills the cavities in which the auditory 
 nerve is distributed. 
 
 The existence of this fluid appears essential to the mechan- 
 ism of hearing, either from its keeping the nerves in the soft 
 and moist state required for the purpose of sensation, or from 
 its transmitting to them the undulatory motion with which it 
 is agitated. 
 
 The deafness of old people, which, according to authors, de- 
 pends on the impaired sensibility of the nerves, whose excita- 
 bility has been exhausted by impressions too frequently repeat- 
 ed, appears, sometimes, to be occasioned by a deficiency of this 
 humour, and by the want of moisture in the internal cavities of 
 the ear. During the severe winter of 1798, Professor Pinel open- 
 ed, at the Hospital of Salpetriere, the skull of several women 
 who died at a very advanced age, and who had been deaf for 
 several years. The cavities of the internal ear were found quite 
 empty; they contained an isicle in younger subjects who had 
 possessed the power of hearing. 
 
 Deafness may, likewise, be produced by a palsy of the portio 
 mollis of the seventh pair, or by a morbid condition of the part 
 of the brain from which this nerve arises. The mechanical ex- 
 planation applied by Willis to the anomalous affections of the 
 organ of hearing, is inadmissible, in those cases in which that 
 organ is sensible only to the impression of weak or strong 
 sounds acting together or separately. 
 
OF SENSATIONS. 
 
 331 
 
 This author relates the case of a woman who could not hear, 
 -unless a great noise was made near her, either by beating a drum 
 or by ringing a bell; because, says he, under such circumstances, 
 these loud noises determine in the membrana tympani, which 
 he supposes in a state of relaxation, the degree of tension re- 
 quired to enable it to vibrate under the impression of weaker 
 sounds. This, membrane, to present greater resistance, must be 
 put on the stretch by the internal muscle of the malleus, or by 
 its own contraction. The total absence of muscular fibres in the 
 membrani tympani, in man, renders very doubtful this sponta- 
 neous contraction. Mr. Home, however, has just ascertained 
 that the membrana tympani of the elephant is muscular and 
 contractile. Admitting all these suppositions, we only substi- 
 tute one difficulty for another, and it remains to be shown, why 
 the more powerful sounds merely increase the tone of the mem- 
 brana tympani; why they do not become objects of perception 
 of the organ of hearing, though they might be expected to ren- 
 der us insensible to the perception of weaker sounds. 
 
 CXXIV. Of odours. Chemists have long thought that the 
 odoriferous part of bodies formed a peculiar principle, distinct 
 from all the other substances entering into their composition; 
 they gave it the name of aroma; M. Fourcroy, however, has 
 clearly shown, that this pretended element consisted merely of 
 minute particles of bodies detached by heat and dissolved in the 
 atmosphere, which becomes loaded with them and conveys them 
 to the olfactory organs. According to this theory, all bodies are 
 odoriferous, since caloric may sublimate some of the particles of 
 those which are least volatile. Linnaeus and Lorry had endea- 
 voured to class odours, according to the sensations which they 
 produce*; M. Fourcroy has been guided by the chemical nature 
 
 * Llnnseus admit? seven classes of odours; 1st class, ambrosiac odours, those 
 of the rose and of musk belong" to this class; they are characterised by their 
 tenacity: 2d, fragrant; for example, the lily, the saffron, and jasmine; they 
 fly off readily: 3d, aromatic, as the smell of the laurel: 4lh, aliaceous, ap- 
 proaching to that of garlic: 5th, fwtid, as that of valerian and fungi: 6th,w>ows, 
 as of poppies and opium: 7th, nauseous, as that of gourds, melons, cucumbers, 
 and, in general, all cucurbitaceous plants. 
 
 Lorry admits only five kinds of odours, camphorated, narcotic, ethereal, 'volatile, 
 ncid, and alkatine. 
 
 M. Fourcrov 
 
OF SENSATIONS. 
 
 332 
 
 of substances; but however advantageous this last classification 
 mav be, it is difficult to include in it, the infinitely varied odours 
 which exhale from substances of all kinds, and it is perhaps as 
 difficult to arrange them in classes, as the bodies from which 
 they are produced. 
 
 This being laid down on the nature of odours, it is next ex- 
 plained, why the atmosphere becomes loaded with the greater 
 quantity, the warmer and the more moist it is. We know, that 
 in a flower garden, the air is at no time more loaded with frag- 
 rant odours, and the smell is never the source of greater enjoy- 
 ment, than in the morning, when the dew is evaporating by the 
 rays of the sun. It is, likewise, easily understood, why the most 
 pungent smells generally evaporate very readily, as ether, al- 
 cohol, the spirituous tinctures and essential volatile oils. 
 
 CXXV. Of the organ of smell. The nasal fosste, within 
 which this organ is situated, are two cavities in the depth of 
 the face and extending backward into other cavities, called 
 frontal, ethmoidal, sphenoidal, palatine, and maxillary sinues- 
 
 A pretty thick mucous membrane, always moist, and in the 
 tissue of which the olfactory nerves and a considerable number 
 of other nerves and vessels are distributed, lines the nostrils and 
 extends into the sinuses which communicate with them, and 
 covers their parietes, throughout their windings and promi- 
 nences. This membrane, called pituitary., is soft and fungous, 
 and is the organ which secretes the mucus of the nose; it is 
 thicker over the turbinated bones which lie within the olfactory 
 cavities; it grows thinner and firmer, in the different sinuses. 
 
 The smell appears more delicate, in proportion as the nasal 
 fossse being more capacious, the pituitary membrane covers a 
 greater space. The soft and moist condition of this membrane 
 is, likewise, essentially necessary to the perfection of this sense. 
 In the dog, and in all animals which have a very exquisite sense 
 of smell, the frontal, ethmoidal, sphenoidal, palatine, and max- 
 illary sinuses, are prodigiously capacious, and the parietes of the 
 skull are, in great measure, hollowed by these different parts of 
 the olfactor}- apparatus; the turbinated bones are, likewise, very 
 
 M. Fourcroy admits the Tmtcous aroma, belonging to plants improperly term- 
 ed inodorous: Oi/y and fugacious, oily and volatile, acid and hydro-sulphureous- 
 
OF SENSATIONS. 
 
 33S 
 
 prominent in them, and the grooves between them very deep; 
 lastly, the nerves of the first pair are large in proportion. Among 
 the animals possessed of great delicacy of smell, few are more 
 remarkable than the hog. This impure animal, accustomed to 
 live in the roost offensive smells, and in the most disgusting 
 filth, has, however, so very nice a smell, that it can detect cer- 
 tain roots, though buried in the earth at a considerable depth. 
 In some countries this quality is turned to advantage, and swine 
 are employed in looking for trufles. The animal is taken to 
 those places where they are sufipected to be, turns up the earth 
 in which they buried, and would feed on them greedily, if the 
 herdsman, satisfied with this indication, did not drive them 
 away from this substance intended for more delicate palates. 
 
 CXXVI. Of the sensation of odours. Co the nerves of the 
 first pair alone give to the pituitary membrane the power of re- 
 ceiving the impression of smell, and do the numerous filaments 
 of the fifth pair merely impart to it the general sensibility be- 
 longing to other parts? This question appears to require an 
 answer in the affirmative. The pituitary membrane in fact pos- 
 sesses two modes of sensibility, perfectly distinct, since the one 
 of the two may be almost completely destroyed, and the other 
 considerably increased. Thus, in violent catarrh, the sensibility 
 of the part as far as it relates to the touch is very acute, since 
 the pituitary membrane is affected with pain, while the patient 
 is insensible to the strongest smells. 
 
 It seems probable that the olfactory nerves do not extend into 
 the sinuses, and that these improve the sense of smell merely 
 by retaining, for a longer space of time, a considerable mass of 
 air loaded -with odoriferous particles. I have known detergent 
 injections, strongly scented, thrown into the antrum highmoria- 
 num by a fistula in the alveolar processes, produce no sensation 
 of smell. A phial filled with a spirituous liquor having been ap- 
 plied to a fistula in the frontal sinuses, gave no impression to 
 the patient. The true seat of the sense of smell is at the most 
 elevated part of the nostrils, which the nose covers over in the 
 form of a capital. There the pituitary membrane is moister, 
 receives into its tissue the numerous filaments of the first pair 
 of the nerves, v/hich arising by two roots from the anterior lobe 
 
OP SENSATIONS. 
 
 •334 
 
 of the brain, and from the fissure which separates it from the 
 posterior lobe, passes from the cranium through the openings 
 ol the cribriform plate of the ethmoid bone, and terminates, 
 forming, by the expansion of its filaments, a kind of parenchy- 
 matous tissue, not easily distinguished from that of the mem- 
 brane. The olfactory papillje would soon be destroyed by the 
 contact of the atmospherical air, if they were not covered over 
 by the mucus of the nose. The use of this mucus is not merely 
 to preserve the extremities of the nerves in a sentient state, by 
 preventing them from becoming dry, but, likewise, to lessen the 
 too strong impression that would arise from the immediate con- 
 tact of the odoriferous particles. It perhaps even combines with 
 the odours, and these affect the olfactory organs only when dis- 
 solved in mucus, as the food in saliva. 
 
 As the air is the vehicle of odours, these affect the pituitary 
 membrane only when we inhale it into the nostrils. Hence, 
 when any odour is grateful to us, we take in short and frequent 
 inspirations, that the whole of the air which is received into the 
 lungs, may pass through the nasal fossse. We, on the contrary', 
 breathe through the mouth, or we suspend respiration altogether, 
 when smells are disagreeable to us. 
 
 The sense of smell, like all the other senses, is readily im- 
 pressed on children, though the nasal fossie are in them much 
 contracted, and though the sinuses are not yet formed. The 
 general increase of sensibility at this period of life, makes up 
 for the imperfect state of the organization; and it is, in this re- 
 spect, with the nasal fossae as with the auditory apparatus, of 
 which an important part, the meatus externus, is then not com- 
 pletely evolved. The sense of smell is perfected by the loss of 
 some of the other senses; every body, for example, knows the 
 history of the blind man, whom that organ enabled to judge of 
 the continence of his daughter; it becomes blunted by the appli- 
 cation of strong and pungent odours. Thus, snuff changes the 
 quality of the mucus secreted by the membrane of the nose, 
 alters its tissue, dries its nerves, and in the course of time im- 
 pairs their sensibility. / 
 
 The shortness of the distance between the origin of the olfac- 
 tory nerves in the brain, and their termination in the nasal fossse^ 
 
OF SENSATIONS. 
 
 335 
 
 render very prompt and easy the transmission of the impres- 
 sions which they experience. This vicinity to the brain, induces 
 us to apply to those nerves, stimulants calculated to rouse the 
 sensibility when life is suspended, as in fainting and asphyxia. 
 The sympathetic connexions between the pituitary membrane 
 and the diaphragm, account for the good effects of sternuta- 
 tories, in cases of apparent death. 
 
 CXXVII. Of favours. Flavours are no less varied and no 
 less numerous than odours; and it is as difficult to reduce them 
 to general classes connected by analogies, and including the 
 whole.* Besides, there exists no element of flavour, any more 
 than an odoriferous principle. The flavour of fruits alters as they 
 ripen, and appears to depend on the inward composition of 
 bodies, on their peculiar nature, rather than on the form of 
 their molecules; since crystals of the same figure, but belonging 
 to different salts, do not produce similar sensations. 
 
 To affect the organ of taste, a body should be soluble at the 
 ordinary temperature of the saliva; all insoluble substances are 
 insipid, and one might apply to the organ of taste this celebrated 
 axiom in chemistry; corpora non agunt nisi soluta. If there is a 
 complete absence of saliva, and if the body that is chewed is 
 altogether without moisture, it will affect the parched tongue 
 only by its tactile, and not at all by its gustatory qualities. The 
 substances which have most flavour, are those which yield most 
 readily to chemical combinations and decompositions; as acids, 
 alkalies and neutral salts. When, in affections of the digestive 
 organs, the tongue is covered with a mucous or whitish fur, or 
 of a yellowish or bilious colour, we have only incorrect ideas 
 of flavours; the thinner or thicker coating prevents the immedi- 
 ate contact of the sapid particles; when they act, besides, on the 
 nervous papillae, the impression which they produce is lost in 
 that occasioned by the morbid contents of the stomach; hence 
 every aliment appears bitter while the bilious disposition exists, 
 and insipid in those diseases in which the mucous elements 
 prevail. 
 
 • This has been attempted, thoug’h \Vith indifferent success, by Boerliaave, 
 Haller, and Linnaeus. Acid, svieet, bitter, acrid, saltish, alkaline, rinotts,spiritttoiis, 
 aromatic, and acerb, were the terms empisyed by those physicians to express 
 the general characters of flavours. 
 
Ol’ SENSATIONS. 
 
 336 
 
 CXXVIII. Of the sense of taste. No sense is so much akin 
 to that of the touch, or resembles it more. The surface of the 
 organ of taste differs from the common integuments only in this 
 respect; — that the chorion, the mucous body, and the epidermis, 
 which envelop the fleshy part of the tongue, are softer, thinner, 
 and receive a greater quantity of nerves and vessels, and are 
 habitually moistened by the saliva and by the mucus, secreted 
 by the mucous glands contained in their substance. These mu- 
 cous cryptse, and the nerves of the cutaneous covering of the 
 tongue, raise the very thin epidermis which covers its upper 
 surface, and form a number of papillae, distinguished 6y their 
 form into fungous., conical., and villous. With the exception of 
 the first kind, these small prominences are formed by the ex- 
 tremities of nerves surrounded by blood-vessels, which give to 
 these papillae the power of becoming turgid and prominent, and 
 of being affected with a kind of erection when we eat highly 
 seasoned food, or when we long for a savoury dish. The fun- 
 gous papillae are mostly situated at the remotest part of the 
 upper surface of the tongue," towards its root, where it forms a 
 part of the isthmus faucium. The pressure with which they are 
 affected by the alimentary bolus, in its passage from the mouth 
 into the pharynx, squeezes out the mucus w'hich lubricates the 
 edges of the aperture, and serves to promote its passage; these 
 mucous follicles fulfil, in this respect, the same office as the 
 amygdalae. 
 
 The upper surface of the tongue is the seat of taste: it is un- 
 deniable, however, that the lips, the gums, the membrane lining 
 the arch of the palate, and the velum palati, may be affected by 
 the impression of certain flavours. 
 
 It is observed in the different animals, that the organ of taste 
 is more perfect, according as the nerves of the tongue are larger, 
 its skin thinner and moister, its tissue more flexible, its surface 
 more extensive, its motions easier and more varied. Hence the 
 bone in the tongue of birds, by diminishing its flexibility; the 
 osseous scales of the swan’s tongue, by reducing the extent of 
 the sentient surface; the adhesion of the tongue to the jaws in 
 frogs, in the salamander, and in the crocodile, by preventing 
 freedom of motion, — render in these animals, the sense of taste 
 duller, and less calculated to feel the impression of sapid bodies, 
 
OF SENSATIONS. 33 y 
 
 than in man, and the other mammiferous animals. Man would 
 probably excel all the other animals in delicacy of taste, if he 
 did not, at an early period, impair its sensibility by strong 
 drinks, and by the use of spices, and of all the luxuries that are 
 daily brought to our tables. The quadrupeds, whose tongue is 
 covered by a rougher skin, discover better than we can, by the 
 sense of taste, poisonous or noxious substances. We know that 
 in the variety of plants which cover the face of the earth, herbi- 
 vorous animals select a certain number of plants suited to their 
 nature, and uniformly reject those which would be injurious to 
 them 
 
 CXXIX. Is the lingual branch of the fifth pair of nerves 
 alone subservient to the sense of taste? Are not the ninth pair 
 (almost wholly distributed in the tissue of the tongue), and the 
 glosso-pharyngeal branch of the eighth, likewise subservient to 
 this function? Most anatomists, since Galen, have thought that 
 the eighth and ninth pair supplied the tongue with its nerves of 
 motion, and that it received from the fifth its nerves of sensa- 
 tion. Several filaments, however, of'the great hypoglossal nerve, 
 may be traced into the nervous papillae of the tongue.* This 
 nerve is larger than the lingual, and is more exclusively distri- 
 buted to this organ than the fifth pair, to which the other nerve 
 belongs. Hevermann states, that he knew a case in which the 
 sense of taste was lost from the division of the nerve of the ninth 
 pair, in removing a scirrhous gland. This case, however, appears 
 to me a very suspicious one. The patient might still have tasted, 
 by means of the lingual nerve, and the sense would only have been 
 weakened. The division of one of the nerves of the ninth pair 
 could render insensible only that half of the tongue to which it 
 is distributed, the other half would continue fully to possess the 
 faculty of taste. 
 
 The application of metals to the diflPerent nervous filaments dis- 
 tributed to the tongue, ought to inform us of their different uses, 
 if, as Humboldt suspects, the galvanic excitement of the nerves 
 
 * Especially the anterior part of the palatine membrane. The naso-palatine 
 nerve, discovered by Scarpa, after arising- from the g-anglion of Meke!, and 
 going for a pretty considerable distance into the nasal fossse, terminates in that 
 thick and rugous portion of the palatine membrane situated behind the upper 
 incisors, and with which the tip of the tongue is in such frequent contact. 
 
 2U 
 
OP SENSATIONS. 
 
 338 
 
 of motion, alone produces contractions. To ascertain the truth 
 of this conjecture, I placed a plate of zinc within the skuil, un- 
 der the trunk of the nerve of the fifth pair, in a tlog that had 
 been killed a few minutes before, and that still retained its 
 warmth; the muscles of the tongue, under which a piece of 
 silver was placed, quivered very slightly; those of the forehead 
 and temples in contact with the same metal, experienced very 
 sensible contractions, whenever a communication was made by 
 means of an iron rod. This experiment showed, that the lingual 
 branch of this nerve was, almost solely, subservient to the sen- 
 sation of taste, which agrees with the opinion of most physiolo- 
 gists, and the same inference may be drawn from the anatomical 
 knowledge of the situation of this nerve which, almost entirely, 
 terminates in the papillae of the membrane of the tongue, and 
 sends very few filaments to the muscles of that organ. But though 
 the galvanic irritation applied to the hypoglossal nerve affected 
 the whole tongue, in a convulsive manner, I did not think myself 
 justified to infer, that this nerve was solely destined to perform 
 its motions; as this nervous trunk might, in this part of the 
 body, as it does in others, contain filaments both of sensation 
 and motion. 
 
 The tongue, though an azygous organ, is formed of parts 
 completely symmetrical; there are, on each side, four muscles 
 (stylos hyo, genio^ glosso and lingual); three nerves {lingual^ 
 glosso-pharyngeal^ and hypoglossal); a ranine artery and vein; 
 and a set of lymphatic vessels precisely alike. All these parts, 
 by their union, form a fleshy body of a close texture and not 
 easily unravelled, similar to that of the ventricles of the heart, 
 endowed wit h a considerable degree of mobility, in consequence 
 of the nume ous vessels and nerves entering into its substance. 
 If we compare their number and size with the small bulk of the 
 organ, it will be readily understood, that, as no part of the body 
 can execute more frequent, more extensive, and more varied 
 motions, so no one receives more vessels and nerves. A middle 
 line separates and marks the limits of the two halves of the 
 tongue, which anatomically and physiologically considered, ap- 
 pears formed of two distinct organs in juxta-position. 
 
 This independence of the two parts of the tongue is confirm- 
 ed by the phenomena of disease; in hemiplegia, the side of the 
 
OF SENSATIONS. 
 
 339 
 
 tongue corresponding to the half of the body that is paralyzed, 
 loses, likewise, the power of motion; the other retains its mobi- 
 lity, and draws the tongue towards that side. In carcinoma of 
 the tongue, one side remains unaffected by the affection which 
 destroys the other half; lastly, the arteries and nerves of the left 
 side rarely anastomose with those on the right; injections forced 
 along one of the ranine arteries, fill only the corresponding half 
 of the organ, &c. 
 
 CXXX. Of the touch. No part of the surface of our body is 
 exposed to receive the touch of a foreign body, without our 
 being speedily informed of it. If the organs of sight, of hearing, 
 of smell and of taste, occupy only limited spaces, touch resides 
 in all the other parts and effectually watches over our preserv’a- 
 tion. The touch, distributed over the whole surface, appears to 
 be the elementary sense, and all the others are only modifica- 
 tions of it, accommodated to certain properties of bodies. All 
 that is not light, sound, smell, or flavour, is appreciated by the 
 touch, which thus instructs us in the greater part of the quali- 
 ties of bodies which it concerns us to know, as their tempera- 
 ture, their consistence, their state of dryness, or humidity, their 
 figure, their size, their distance, &c. It corrects the errors of 
 the sight and of all the other senses, of which it may justly be 
 called the regulator, and it furnishes us with the; most exact and 
 distinct ideas. 
 
 The touch, of which some authors have sought to consecrate 
 the excellence, by giving it the name of the geometrical sense, 
 is not, however, safe from all mistake. Whilst it is employed 
 on the geometrical properties, derived from space, and that it 
 appreciates the length, the breadth, the thickness, the form of 
 bodies, it transmits to the intellect, rigorous and mathematical 
 results; but the ideas we acquire by its means on the tempera- 
 ture of bodies, are far from being equally precise. For, if you 
 have just touched ice, another body colder thar yours, will ap- 
 pear warm. It is for this reason, that subterraueous places ap- 
 pear warm to us during winter. They have kept their tempera- 
 ture whilst all things else have changed theirs; and as we judge 
 of the heat of an object by its relation not only to our own, but 
 also to that of other bodies and of the air about us, we find the 
 
OF SENSATIONS. 
 
 340 
 
 same places warm which had appeared cold' to us in the middle 
 of summer. 
 
 The densest bodies being the best conductors of heat,* mar- 
 ble, metals, &c. appear colder to us than they really are, because 
 they carry it off so rapidly. Marble and metals, when polished, 
 appear still colder, because, as they touch the skin in many 
 more points at once, they effect this abstraction more effec- 
 tually. Every one knows the experiment of placing a little ball 
 between the two lingers crossed, and producing the sensation 
 of two different balls. 
 
 CXXXI. Of the integuments. The general covering of the 
 whole body is the organ of touch, which resides in the skin pro- 
 perly so called. The cellular tissue which connects together all 
 our parts, forms over the whole body, a layer varying in thick- 
 ness, which covers it in every part; it is called panniculus adi- 
 posus. As it approaches the surface, its laminae are more con- 
 densed, are in more immediate contact with each other, and are 
 no longer separated by adeps. It is by the closer juxta-position 
 of the laminae of the cellular tissue, that the skin or dermis is 
 formed, a dense and elastic membrane, into which numerous 
 vessels, of all kinds, are distributed, and into which so great a 
 quantity of nerves terminate, that the ancients did not hesitate 
 to consider the skin as purely nervous. 
 
 In certain parts of the body, a very thin muscular plane sepa- 
 rates the skin from the panniculus adiposus. This kind of pan- 
 niculus carnosus envelops, almost entirely, the body of some 
 animals; its contractions wrinkle their skin covered with hairs, 
 these rise, vibrate, and thus are cleared of the dust and dirt 
 which may have gathered on them. It is by means of a cuta- 
 neous muscle, of very complex structure, that the hedge hog is 
 
 • Woolly substances, &c. all felts, of which the crossing hairs confine, in 
 some sort, a great quantity of air, a fluid which, from its gaseous state, is a 
 very bad conductor of iieat, retain heat well; and, of equal thickness, a stuff of 
 fine wool, of which the hairs are more separated, tlte tissue softer, will be 
 warmer than a stufl'of coarse wool, of which the threads, too close, form a 
 dense body, througli which cold, as well as heat, will pass with ease. It is by 
 thus confining a certain muss of air, that snotv keeps the soil it covers in a 
 mild temperatui’e, and preserves plants from the injury of excessive cold: a 
 physical truth which is found figuratively e.xpressed in the words of the 
 Psalmist, “ Et dedit HU ni^em tanguam vesiimentiim.” 
 
OF SENSATIONS. 
 
 341 
 
 enabled to coil himself up, and to present to his enemy a surface 
 studded with sharp points: only a few scattered rudiments of an 
 analogous structure, are to be met with in the human body; the 
 occipito-froiitalis, the corrugator supercilii, several muscles of 
 the face, the platysma myoides, the palmaris cutaneous, may be 
 considered as forming part of this muscle. We may even in- 
 clude the cremaster, whose expanded fibres, surrounded by the 
 dartos, have misled some anatomists to such a degree, that they 
 have admitted the existence of a muscular texture in the latter. 
 These fibres of the cremaster, produce distinct motions in the 
 skin of the scrotum, wrinkle it in a transverse direction, and, at 
 the same time, bring up the testicles. The platysma myoides 
 acts, likewise, on the skin of the neck; lastly, the occipito-fron- 
 talis, in some men, performs so distinct a motion of the hairy 
 scalp, as to throw off a hat, a cap, or any other covering that 
 may be on the head. One may compare to the panniculus car- 
 nosus, the muscular coat of the digestive tube, situated, through- 
 out its whole length, below the mucous membrane, which is 
 merely a prolongation of the skin modified and softened. 
 
 But if, in man, the subcutaneous muscle, from its imperfect 
 state, answers purposes only of secondary importance, the layer 
 of cellular adipose substance, extended under the skin, gives to 
 the latter its tension, its whiteness, its polish, its suppleness, fa- 
 vours its appl3ong itself to tangible objects and thus renders the 
 touch more delicate. Too hard or wrinkled a skin would have 
 applied itself in a very incomplete manner, to bodies of a small 
 size, and would not readily have accommodated itself to the 
 small irregularities of those of inconsiderable bulk. Hence the 
 pulp of the fingers, which is the seat of a more delicate touch, 
 is furnished with a kind of adipose cushion supported by the 
 nails, ready to be applied to polished surfaces, and to discover 
 their slightest asperities. I have observed the sense of touch to 
 be very imperfect in men wasted by marasmus, and whose hard, 
 dry, and wrinkled skin adheres, in certain situations, to the sub- 
 jacent parts. 
 
 The chemical analysis of the cutaneous tissue shows, that it 
 does not exactly resemble that of the cellular and membranous 
 tissue; it is gelatino-fibrous, and, with regard to its structure 
 and to its share of contractility, it occupies a medium between 
 
OF SENSATIONS. 
 
 342 
 
 the cellular tissues and the muscular flesh. There arise, from 
 the surface of the skin, innumerable small papillae, fungous, 
 conical, pointed, obtuse and variously shaped, in the different 
 parts of the body. These papillae are merely the pulpous extre- 
 mities of the nerves which terminate into them, and around which 
 there are distributed vascular tissues of the utmost minuteness. 
 The papillae of the skin, which are more distinct in the fingers 
 and lips than elsewhere, swell, when irritated, elevate, in a man- 
 ner, the epidermis, and this kind of erection, which is useful 
 when we wish to touch a substance with great precision, may 
 be excited by friction or by moderate heat. 
 
 The nervous or sentient surface of the skin is covered with a 
 mucous coating, colourless in Europeans, of dark colour, from 
 the effects of light, among the natives of southern climates; of a 
 gelatinous nature, destined to maintain the papillae in that state 
 of moisture and softness favourable to the touch. This mucila- 
 ginous layer, known under the name of rete mucosum of Mal- 
 pighi, seems to contain the principle which causes the variety of 
 colour in the skin of different nations, as will be observed in 
 speaking of the varieties of the human species. 
 
 The reticular state of the rete mucosum may be explained in 
 two ways; a thin and gelatinous layer, extended on the papillar 
 surface of the skin, is perforated at each nervous papilla: aud if 
 it were possible to coagulate or to detach this coating, we should 
 have a real sieve, or reticulated mesh work, with a perforation 
 at every point, corresponding to a cutaneous papilla. The san- 
 guineous and lymphatic capillaries which surround the nervous 
 papillae, form, besides, by their connexions, a net-work, the 
 meshes of which are very minute, and adhere to the epidermis 
 by a multitude of small vascular filaments that insinuate them- 
 selves between the scales of this last envelope. 
 
 The skin would be unable to perform its functions, if an outer, 
 thin, and transparent membrane, the epidermis^ did not prevent 
 it from being over dried. This superficial covering is quite in- 
 sensible, no nerves and no vessels of any kind are found in it, 
 and even in the present state of the science, we do not under- 
 stand how it is formed, how it repairs and reproduces itself 
 when destroyed. The most minute researches on its structure, 
 merely show the existence of an infinite number of lamellae. 
 
OF SENSATIONS. 
 
 343 
 
 lying over each other, and overlapping each other, like the tiles 
 of a roof. This embrication of the epidermoid lamellae, is very 
 obvious in fishes and reptiles, the scalv skin of which is merely 
 an epidermis, whose parts are much more coarsely shaped. 
 
 It was observed (XLII.^, in the account of absorption, how 
 much friction facilitates the absorption of substances applied to 
 the surface of the skin, by raising the scales of the epidermis, so 
 as to expose the orifices of the absorbents, whose activity, it in 
 other respects, increases. 
 
 Haller conceives that the epidermis is formed by the drying 
 up of the outer layers of the rete mucosum. Morgagni thinks it 
 is formed by the induration of the skin in consequence of the 
 pressure of the atmosphere. In objection to these hj'potheses, 
 one may inquire, how it happens, that by the time the foetus, 
 immersed in the liquor amnii, has attained its third month, it 
 is covered with such an envelope. Pressure renders the skin 
 hard and callous, increases considerably its thickness, as we see 
 in the soles of the feet and in the palms of the hands of persons 
 engaged in laborious employments. The epidermis reproduces 
 itself with an incredible rapidity, after falling olF in scales, after 
 erysipelas or herpetic eruptions; or, when removed in large 
 flakes, by blistering, it is renewed in the course of a very few 
 days. The cuticle, together with the hairs and the nails, which 
 may be considered as productions of the same substance, are. 
 the only parts, in man, that are capable of reproducing them- 
 selves. The hairs and the horns of quadrupeds, the feathers of 
 birds, the calcareous matter of the lobster and of several mol- 
 lusca, the shell of the turtle, the solid sheaths of a number of 
 insects, possess, as well as the epidermis, this singular property. 
 In other respects, the chemical structure of all these parts is 
 the same; they all contain a considerable proportion of phos- 
 phate of lime, withstand decomposition, and give out a consi- 
 derable quantity of ammonia, on being exposed to heat. The 
 use of the epidermis is to cover the nervous papillae, in which 
 the faculty of the touch essentially resides, to moderate the too 
 vivid impression that would have been produced by an imme- 
 diate contact, and to prevent the air from drying the skin or 
 from impairing its sensibility. 
 
 This desiccation of the cutaneous tissue is further prev'ented. 
 
OF SENSATIONS. 
 
 344 
 
 and its suppleness maintained by an oily substance, which exudes 
 through its pores, and is apparently secreted by the cutaneous 
 exhalants. This unctuous liniment should not be mistaken for 
 that which is furnished by the sebaceous glands, in ceitain 
 situations, as around the nostrils, in the hollow of the arm pits, 
 and in the groins. This adipose substance, with which the skin 
 is anointed, is abundant and fetid in some persons, especially in 
 those of a bilious temperament, with red hair. It is, likewise, 
 more copious in the African negroes, as if nature had been 
 anxious to guard against the too rapid desiccation, bv the 
 burning atmosphere of tropical climates. This use of the oil 
 of the skin, is, likewise, answered by the tallow, the fat, and 
 the disgusting substances with which the Caffres and the Hot- 
 tentots anoint their body, in the manner described under the 
 name of tatooing, by the travellers* who have penetrated into 
 the interior of the burning regions of Africa. 
 
 The ancients had a somewhat similar practice, and the anoint- 
 ing with oil, so frequently used in ancient Rome, answered the 
 same purpose of softening the skin, of preventing its becoming 
 dry, or chapped. f The pomatums employed at the present day 
 at the toilet, possess the same advantages. The continual tran- 
 sudation of this animal oil renders it necessary, occasionally, to 
 clean the skin by bathing; the water removes the dust and the 
 other impurities which may be attached to its surface by the 
 fluid which lubricates it. It is this humour vhich soils our 
 linen and obliges us so frequently to renew that in immediate 
 contact with the skin, and which makes the water collect in 
 drops when we come out of the bath, &c. 
 
 Though the parts in which there is found the greatest quan- 
 tity of subcutaneous fat, are not always the most oily, and though 
 one cannot consider this secretion as a mere filtration of this 
 adeps through the tissue of the skin, corpulence has, however, 
 a manifest influence on its quantity. I know several very cor- 
 
 * Among others Kolben, Description da Cap de Bontie-Esp6rance; Sp.'irmann, 
 Voyage au Cap de Bonne-Espirance et chez les Hottentots. Vaillant, Voyage dans 
 I’Interieur de UMfrique. 
 
 f The reply of the old soldier is well known, who, on being asked by 
 Augustus, how he came to live so long, said, he owed his long life to the use 
 of wine inwardly, and to that of oil outwardly; intusvino, exths oleo. 
 
OF SENSATIONS. 
 
 345 
 
 pulent persons in whom it appears to be evacuated by perspira- 
 tion, on their being heated by the slightest exertion. They all 
 grease their linen in less than twenty-four hours. An excess of 
 the oily matter of perspiration is injurious, by preventing the 
 evacuation of the perspiration and its solution in the atmos- 
 phere. 
 
 We all know how, after the epidermis has been removed, the 
 slightest contact is painful: that of the air is sufficient to bring on 
 a painful inflammation of the skin exposed by the application of 
 a blister. The epidermis, as was likewise mentioned in speaking 
 of the absorption, placed on the limits of the animal economy, 
 and in a manner inorganic, serves to prevent heterogeneous sub- 
 stances from being too readily admitted into the body, and, at 
 the same time, it lessens the too vivid action of external objects 
 on our organs. All organized and living bodies are furnished 
 with this covering, and, in all, in the seed of a plant, in its stem, 
 and on the surface of the body, in man and animals, it bears to 
 the skin the greatest analogy of function and nature. Incor- 
 ruptibility is, in a manner, its essence, and is its peculiar charac- 
 ter; and in tombs which contain merely the dust of the skeleton, 
 it is not uncommon to find whole and in a state to be readily 
 distinguished, the thickened epidermis that forms the sole of 
 the foot and especially the heel. However, this incorruptibility 
 is possessed, as well as others of the qualities of the skin, by 
 the nails and the hairs, which may be considered as its ap- 
 pendages. 
 
 CXXXII. Of the nails. The nails are, in fact, only a part of 
 the epidermis: they are continuous with it, and after death, fall 
 off along with it. They are thicker and harder: like it they are 
 inorganic and lamellated; they grow rapidly from their root to- 
 wards their free extremity; they reproduce themselves rapidly 
 and acquire several inches in length, when the part beyond the 
 ends of the fingers and toes has not been removed; as is the 
 case with the Indian fakirs. In this state of development, they 
 bend over the tips of the fingers and toes, and impair the sense 
 of touch, whose free enjoyment is preferable to any advantages 
 which savages can derive from their long and crooked nails, in 
 defending themselves, or in attacking animals, or tearing to 
 
 2 X 
 
OP SENSATIONS. 
 
 / 
 
 346 
 
 pieces those which they have killed in hunting. The nails arc 
 quite insensible; and the reason that so much pain is felt, when 
 the nails run into the flesh, and that the operation of tearing 
 them out, which is sometimes necessary, is so painful, is, that 
 the nerves, over which the nail grows, are more or less in- 
 jured when it grows in a wrong direction. The pain from the 
 growing of the nails into the quick, is no proof of their beings 
 sentient, any more than the growth of corns proves the sensi- 
 bility of the epidermis, of which they are but thickened parts, 
 become hard and callous by pressure, and which, confined in 
 tight shoes, press painfully on the nerves below. The nail 
 itself may acquire a considerable degree of thickness; I have 
 seen that of the great toe nearly half an inch thick. The use of 
 the nails is to support the tips of the fingers, when they are 
 applied to unyielding substances; they likewise concur in im- 
 proving the mechanism of the touch*. 
 
 CXXXIII. Of the hair on the head and on other parts of 
 the body. These parts are treated of, in the present instance, 
 only in consequence of their connexion with the epidermis; as, 
 far from improving the touch, they interfere with it, or at least 
 render it less delicate. 
 
 The skin, in man, is more bare than that of other animals; 
 it is, likewise, least covered with insensibile parts that might 
 blunt the sense of touch. In almost all mammiferous animals, 
 the whole body is covered with hair, only a small part of the 
 human body has any hair; on it, and that in too small a quantity, 
 and of too delicate a texture, to interfere with the touch. Some 
 men, however, have a very hairy skin; and I have seen several 
 
 * The toe nails are favourable to the laying the foot to the surface on whlck 
 the body is supported; they likewise improve tlie sense of touch in this part 
 The use of the feet is not merely to support the weight of the body, tliey are 
 also intended to guide us in feeling for the plane on which we are to rest them, 
 to enable us to judge of the solidity, of the temperature, and of the inequalities 
 of the ground on which we tread. They, therefore, required rather a delicate 
 sense of touch. The division of the fore part of the foot, into several distinct 
 and separate parts, serves to enable us to stand more firmly, and facilitates the 
 action .of walking. 1 have seen several soldiers who lost, from severe cold, 
 the extremities of their feet, in crossing the Alps which separate France from 
 Italy. Those who had lost only their toes, did not walk so steadily, and fre- 
 quently fell, in treading on uneven ground. Those who had lost one half of 
 their feet, were obliged to use crutches. 
 
OF SENSATIONS. 
 
 347 
 
 who, when naked, looked as if covered over with the skin of an 
 animal, so great was the quantity of hair over the whole body, 
 of which no part was bare, but a small portion of the face, the 
 palms of the hands and the soles of the feet. This extraordinary 
 growth of hair, is in general, a sure sign of vigour and strength. 
 In childhood, there is no hair except on the head, the rest of 
 the body is covered with down. Women have no beard, and 
 there is in them, a smaller quantity of hair in the arm pits and 
 on the parts of generation, and scarcely any on the limbs and 
 trunk. But as though the matter which should provide for the 
 growth of the hair, were wholly applied to the hairy scalp, it is 
 observed, that their hair is longer and in greater quantity. 
 
 The colour of the hair varies from white to jet black; and, as 
 will be mentioned, in speaking of the temperaments and of the 
 varieties of the human species, this difference of colour is a test 
 by which we judge of those varieties. The colour of the hairs 
 enables us to judge of their thickness: Withof, who, with a 
 truly German patience, was at the pains to count how many 
 hairs were contained in the space of a square inch, states, in 
 his dissertation on the human hair, that there are five hundred 
 and seventy two black hairs, six hundred and eight chesnut, 
 and seven hundred and ninety light coloured; so that the diame- 
 ter of a hair, which is between the three and seven hundredth 
 part of an inch, is least in light hair, and these are finer the 
 lighter their shade. It is, likewise, observed, that men of a 
 bilious constitution, with dark hair and inhabiting warm cli- 
 mates, have more hair, in other parts of the body, and that it is 
 coarser and more greasy. 
 
 In whatever part of the body hairs may grow, they are, every 
 where, of the same structure, they all arise from a vesicular 
 bulb in the adipose cellular tissue; from this bulb containing a 
 gelatinous lymph, on which the hair seems to be nourished, 
 the latter, at first divided into two or three filaments which 
 constitute a kind of root, comes out in a single trunk, passes 
 through the skin and epidermis, receiving from the latter a 
 sheath that covers it to its extremity, which terminates in a 
 point. 
 
 A hair may, therefore, be considered as an epidermoid tube 
 filled with a peculiar kind of marrow. This spungy stem, which 
 
OP SENSATIONS. 
 
 348 
 
 forms the centre of a hair, is a more essential part cf it, than the 
 sheath supplied by the epidermis. Along this spungy and cellu- 
 lar filament, the animal oil of the hair and the juices on which 
 it is repaired flow. Though we see, in some animals, vascular 
 branches and very small nervous filaments directed towards the 
 root of certain kinds of hair, and lost in it, as is the case with 
 the long and stiff whiskers of some of the quadrupeds, it is im- 
 possible to say, whether in man, the hair or its bulbs receives 
 vessels and nerves. Is the human hair nourished by the imbibition 
 of the gelatinous fluid contained in its bulb, or is it nourished 
 on the fat in which the latter is imbedded? Are vessels distri- 
 buted along their axis, from the root to the extremity? In favour 
 of this opinion, it was usual to mention the bleeding from the 
 hair when cut, in the disease called plica polonica. But this dis- 
 ease, lately observed in Poland, by the French physicians, ap- 
 peared to them a mere entangling of hair, in consequence of 
 the filth of the Poles and of their habit of keeping their head 
 constantly covered with a woollen cap. The hairy scalp re- 
 mains perfectly sound beneath the entangled hair, and the only 
 way to cure the complaint is to cut off the hair. Fourcroy*^ 
 thinks that each hair has several short branches that stand off 
 from it, which, according to the explanation given by Monge, 
 favour the matting of the hairs that are to be converted into 
 tissues, by the process called felting. 
 
 CXXXIV. Among the most remarkable qualities of the hair 
 one may take notice of the manner in which it is affected by 
 damp air, which, by relaxing its substance, increases its length. 
 It is on that account, that hairs are used for the construction of 
 the best hygrometers. Nor must tve omit either the readiness 
 with which they grow and are reproduced, even after being 
 plucked out by the roots, as I have often seen after the cure of 
 tinea by a painful method; nor their insulating property, with 
 respect to the electric fluid, of which they are very bad con- 
 ductors; a remarkable property, viewed with reference to the 
 conjectured nature of the nervous fluid. 
 
 The hairs possess no power of spontaneous motion by whigh 
 
 Systeme des connoissances chimiques, tome IX. page 263. 
 
OF SENSATIONS. 
 
 349 
 
 they can rise on the head, when the soul shijdders with horror 
 or fear: but they do bristle at those times, by the contraction 
 of the occipito-frontales, which, intimately adhering to the hairy 
 scalp, carries it along in all its motions. 
 
 They appear totally without sensibility: nevertheless, the pas- 
 sions have over them such influence, that the heads of young 
 people have turned white the night before execution. The Re- 
 volution, which produced in abundance the extremes of hu- 
 man suffering, furnished many authentic instances of persons 
 that grew hoary, in the space of a few days. In this premature 
 hoariness, is the hair dried up, as in old people, when it seems 
 to die for want of moisture and its natural juices? 
 
 The following fact seems to show, that they are the excre- 
 tory organ of some principle, the retention of which might be ^ 
 of very injurious consequence. A chartreux who, every month, 
 had his head shaved, according to the rule of his order, quitting 
 it at its destruction, went into the army, and let his hair grow. 
 After a few months he was attacked with excruciating head- 
 aches, which nothing relieved. At last, some one advised him 
 to resume his old habit, and to have his head frequently shaved; 
 the head-aches went off, and never returned. 
 
 We know, says Grimaud*, that there are nervous head-aches, 
 which give way to frequent cropping the hair: when it is kept 
 close cut, the more active growth that takes place sets in motion 
 stagnating juices. A friend of Valsalva, as Morgagnif relates, 
 dispelled a maniacal affection, by having the head of the patient 
 shaved; Casimir Medicus cured obstinate gonorrhoea, by the 
 frequent shaving of the parts of generation. 
 
 The hairs partake of the inalterability, the almost indestructi- 
 bility of the epidermis. Like it they burn with a fizzing, and 
 give out in abundance a fetid ammoniacal oil. The ashes that 
 remain from burning them, contain much phosphate of lime. 
 The horns of mammiferse, the feathers of birds, give out the 
 same smell in burning, and yield the same products as the hair 
 on the head and other parts; which has led to the saying, that 
 these last were a sort of horny substance drawn out like wire. 
 Acids, but especially alkalies, dissolve them: accordingly, all 
 
 * Second Memoir on Nutrition, p. 49. tZIc Sedihns et CausU, epist. 8, No. T- 
 
OF SENSATIONS. 
 
 350 
 
 nations that cut the beard, fit^st soften it by rubbing it with alka^ 
 line and soapy solutions. 
 
 Is the use of the hair to ev'acuate the superabundant nutri- 
 tious matter? The epoch of puberty and of the termination of 
 growth, is that in which it first springs in many parts of the 
 body, which were before without it. They are, at the same time, 
 the emunctory by which nature gets rid of the phosphate of 
 lime, which is the residue of the work of nutrition. The hairs 
 of quadrupeds, whose urine abounds less in phosphoric salts 
 than that of man, seem especially to fulfil this destination. The 
 hairs have some analogy with the fat, which has not yet been 
 ascertained. They are often found accidentally developed in the 
 fatty tumours known under the name of steatomas. Finally, 
 they have uses relative to the parts on which they grow. 
 
 CXXX V. The faculty of taking cognizance of tangible quali- 
 ties, belongs to all parts of the cutaneous organ. We have only 
 to apply a substance to any part of the surface of our body, to 
 acquire the idea of its temperature, of its dryness or moisture, 
 of its weight, its consistence, and even its particular figure. But 
 no part is better fitted to acquire exact notions, on all these 
 properties, than the hand, which has ever been considered as the 
 especial organ of touch. The great number of bones that form 
 its structure, make it susceptible of very various motion, by 
 which it changes its form, adapts itself to the inequalities of the 
 surfaces of bodies, and exactly embraces them; this apt con- 
 formation is particularly manifest at the extremities of the fin- 
 gers. Their anterior part, which is endued with the most deli- 
 cate feeling, receives from the median and cubital nerves, 
 branches of some size, which end in rounded extremities, close, 
 and surrounded with a cellular tissue. The part of the fingers 
 which is called their pulp, is supported by the nails; vessels in 
 great number are spread through this nervo-cellular tissue, and 
 moisten it with abundant juices, that keep up its suppleness. 
 When perspiration is increased, it breaks out in small drops 
 over this extremity of the fingers, along the hollow of the con- 
 centric lines with which the epidermis is furrowed. 
 
 It has been attempted to explain the pleasure we feel in 
 touching rounded and smooth surfaces, by showing that the re- 
 ciprocal configuration of the hand and of the body to which it 
 
OF SENSATIONS. 
 
 351 
 
 is applied, Is such, that they touch In the greatest number of 
 points possible. The delicacy of the touch is kept up by the 
 fineness of the epidermis: it increases by education, which has 
 more power over this sense than over any of the others. It is 
 known with what eagerness a child, allowed the fiee use of his 
 limbs, stretches his little hands to all the objects within his 
 reach; what pleasure he seems to take in touching them in all 
 their parts, and running over all their surfaces. Blind men have 
 been known to distinguish by touch the dilferent colours, and 
 even their different shades. As the difference of colour depends 
 on the disposition, the arrangement, and number of the little 
 inequalities which roughen the surface of bodies that appear the 
 most polished, and fit them to reflect such or such a ray of light, 
 absorbing all the others, one does not refuse to believe facts of 
 this kind, related by Boyle and other natural philosophers. 
 
 Some parts appear endowed with a peculiar touch; such are 
 the lips, whose tissue swells, and spreads out under a volup- 
 tuous contact; a vital turgescence, explicable without the sup- 
 position of a spungy tissue in their structure: — such are those 
 organs which Buffon considers as the seat of a sixth sense. In 
 most animals the lips, and especially the lower one, without 
 feathers, scales, or hair, are the organ of a sort of touch, imper- 
 fect at best. When the domestic quadrupeds, such as the horse, 
 the dog, the ox, &c. want to judge of the tangible qualities of 
 bodies, you will see them apply to it the end of their nose, the 
 only part where the external covering is without hair: the fleshy 
 appendages of certain birds, and many fish, the antennae of butter- 
 flies, always set near the opening of the mouth, answer the same 
 purpose. The tail of the beaver, the trunk of the elephant, are, 
 in like manner, the parts of their body where touch is most deli- 
 cate. Observe that the perfection of the organ of touch, ensures 
 to these two animals a degree of intelligence allotted to no other 
 quadruped, and becomes, perhaps, the principle of their sociabi- 
 lity. The books of travellers and naturalists swarm with facts 
 attesting the wonderful sagacity of the elephant. Some Indian 
 . philosophers have gone the length of allowing him an immortal 
 soul. If birds, notwithstanding the prodigious activity of their 
 life of nutrition, are yet of such confined intelligence, so little sus- 
 ceptible of durable attachment, so restive to education, is not 
 
OF SENSATIONS. 
 
 352 
 
 the cause to be assigned in their imperfection of touch? In vain 
 the heart sends towards all their organs, with more force and 
 velocity than in any other animal, a warmer blood, and endu- 
 ed, more remarkably, with all the qualities which characterize 
 arterial blood. In vain is their digestion rapid, their muscular 
 pow’er lively, and capable of long continued motion; certain of 
 their senses, as those of sight and hearing, happily disposed; 
 touch being almost nothing with them, as also the greater num- 
 ber of impressions belonging to this sense, which informs us of 
 the greater part of the properties of bodies, the circle of their 
 ideas must be extremely narrow, and their habits and man- 
 ners, much more remote than those of quadrupeds from the 
 habits and manners of man. 
 
 CXXXVI. Of all the senses, the touch is the most generally 
 diffused among animals. All possess it, from man who, in the 
 perfection of this sense, excels all vertebral animals, to the 
 polypus, who, confined to the sense of touch only, has it in such 
 delicacy, that he appears, to use a happy expression of M. Du- 
 meril, to feel even light. The skin of man is more delicate, 
 fuller of nerves than that of the other mammiferae; its surface is 
 covered only by the epidermis, insensible indeed, but so thin 
 that it does not intercept sensation; whilst the hairs which cover 
 so thickly the body of quadrupeds, the feathers which clothe 
 that of birds, quite deaden it. The hand of man, that admirable 
 instrument of his intelligence, of which the structure has ap- 
 peared to some philosophers,* to explain sufficiently his supe- 
 riority over all living species; the hand of man, naked, and 
 divided into many moveable parts, capable of changing every 
 moment its form, of exactly embracing the surface of bodies, is 
 much fitter for ascertaining their tangible qualities than the foot 
 of the quadruped, enclosed in a horny substance, or than that of 
 the bird, covered with scales too thick not to blunt all sensation* 
 
 CXXXVI I. Of the nerves. These whitish cords which arise 
 from the base of the brain, and from the medulla oblongata, are 
 distributed to all parts of the body, and give them at once the 
 power of moving and feeling. In this analysis of the functions 
 of the nervous system, the most natural order is to consider 
 
 * See the work of Galen, de um partium, cap. 4, 5, 6; and BufTon, Histoire 
 Naturelle, tom. IV. et V. 12mo. 
 
OF SENSATIONS. 
 
 353 
 
 them merely as conductors of the power of sensation. We shall 
 then see, in what manner they transmit the principle of motion 
 to the organs by which it is performed. The nerves arise, from 
 all sentient parts, by extremities that are, in general, soft and 
 pulpy, but not alike in all in consistence and form; and it is to 
 these varieties of arrangement and structure, that the varieties 
 of sensation in the different organs are to be referred. 
 
 One may say that there exists, in the organs of sense, a cer- 
 tain relation between the softness of the nervous extremity, and 
 the nature of the bodies which produce an impression upon it. 
 Thus, the almost fluid state of the retina, bears an evident >re- 
 lation to the subtility of light. The contact of this fluid could 
 not produce a sufficient impression, unless the sentient part were 
 capable of being set in motion by the slightest impression. The 
 portio mollis of the seventh pair, wholly deprived of its solid 
 ©overing, and reduced to its medullary pulp, readily partakes in 
 the sonorous motions transmitted to it by the fluid, in the midst 
 of which its filaments are immersed. The nerves of smell and 
 of taste, are more exposed than the nervous papillse of the skin, 
 employed in receiving the impressions produced by the coarser 
 properties of bodies, &c. 
 
 From their origin, the nerves ascend towards the medulla 
 oblongata and the spinal marrow, in a line nearly straight, and 
 seldom tortuous, as most of the vessels. When they have reach- 
 ed these parts, they terminate in them, and are lost in their sub- 
 stance, as will be mentioned in speaking of the structure of these 
 nervous cords. 
 
 CXXX VIII. Every nerve is formed of a great number of fila- 
 ments, extremely delicate, and which have two extremities, the 
 one in the brain and the other from the part into which they 
 
 * In considering’ the nerves as conductors of sensation, it is correct to say, 
 that they arise from sentient parts, since it is the extremity most distant from 
 the brain, which experiences the sensitive impression, that is propagated to the 
 organ itself, along the course of the nerve. In attending, on the contrary, to 
 the phenomena of motion, the nerves are considered to arise from the brain; 
 for, it is from the centre to the circumference, that the principle of motion is 
 transmitted to the muscles called, by Cullen, moving extremities of the nerves. 
 Some anatomists have considered it as a doubtful point, whether the nerves 
 arise from the brain and spinal marrow, or whether these parts are formed by 
 theiunion of the nerves. 
 
 3 Y 
 
OF SENSATIONS, 
 
 354 
 
 terminate, or from which they originate. Each of these nervous 
 fibres, however minute, is composed of a membranous tube, 
 which is a production of the pia mater. Within the parietes of 
 this tube, there are distributed innumerable vessels of extreme 
 minuteness; it is filled within with a whitish marrow, a kind of 
 pulp, which Reil states he insulated from the small canal con- 
 taining it, by concreting it, by means of the nitric acid, which 
 dissolves the membranous sheath, and leaves uncovered the me- 
 dullary pulp forming the essential part or basis of the nervous 
 filament. This same physiologist discovered, by a different pro- 
 cess, the internal structure of each nervous fibrilla; he dissolved 
 the whitish or pulpy part, by a long continued solution in an al- 
 kaline ley, and he succeeded thus in separating it from the mem- 
 branous tube which inclosed it and which was emptied. The 
 membranous sheath is of cellular structure, and is remarkable 
 only by its consistence and by the very considerable number of 
 vessels of all kinds that are distributed to its parietes; it ceases 
 to cover the nerves near their two extremities, and protects 
 them only along their course. 
 
 Each nervous fibre, thus formed of two very distinct parts, 
 joins other fibres of a perfectly similar structure, to form a ner- 
 vous filament enveloped in a common sheath of cellular tissue. 
 These filaments, by their union, form small ramifications, and 
 these progressively larger branches, and lastly, trunks wrapped 
 in a common covering of cellular tissue; then other envelopes 
 to each fasciculus of filaments, and lastly, a sheath to each in- 
 dividual filament. When nervous cords are of a certain size, 
 veins and arteries of a pretty considerable caliber, may be seen 
 to insinuate themselves between the bundles of fibres of which 
 they are composed; these vessels then divide, after penetrating 
 among them, and furnish the capillary ramifications which are 
 distributed to the parietes of the sheath common to each fila- 
 ment. These small vessels, according to Reil, allow the nervous 
 substance to exhale into each membranous tube; this, likewise, 
 becomes the secretory organ of the medulla with which it is 
 filled. 
 
 CXXXIX. The nervous filaments unite, or are separated 
 from one another, but do not run into each other. The divi- 
 sions of the nerves are different from those of the arteries, and 
 
OF SENSATIONS. 
 
 355 
 
 their mode of junction does not admit of being compared to 
 that of the veins. It is, in the first instance, a mere separation; 
 in the second, an approximation of filaments which had been se- 
 parated, and which, though united in common sheaths, have, 
 nevertheless, each a proper covering, are merely in juxta posi- 
 tion and perfectly distinct. If that were not the case, one could 
 not say, that each fibre has one extremity in the brain, and the 
 other in some one point of the body; nor could one conceive 
 how the impressions which several sentient extremities receive 
 at once, reach the brain without running into each other; nor, in 
 what manner the principle of motion could be directed towards 
 a single muscle receiving its nerves from the same trunk as the 
 other muscles of the limb. 
 
 In general, the nerves divide from each other and unite at an 
 angle more or less acute, and equally favourable to the circula- 
 lation of a fluid, from the circumference to the centre, and from 
 the centre to the circumference. 
 
 The structure of the nerves is different according to their situa- 
 tion. Thus, the medullary fibres of the optic nerve are not fur- 
 nished with membranous coverings, the pia mater alone furnish- 
 ing a sheath to the cord formed by the union of these filaments; 
 the dura mater adds a second coat to it, on its leaving the skull. 
 This coat, belonging, likewise, to the whole nerve, is not con- 
 tinued over it, after it has entered the eye ball, and is lost in 
 the sclerotica. A minute artery passes through the centre of 
 the optic nerve, and then dividing, forms a rete mirabile which 
 supports the medullary pulp of the retina. The nerves which 
 pass along osseous canals, as the Vidian nerve of the fifth pair, 
 are not provided with a cellular covering, and their consistence 
 is always greater than that of the nerves which are surrounded 
 by soft parts. 
 
 CXL. On reaching the brain, the medulla oblongata, or the 
 spinal marrow, every nervous filament, as was already mention- 
 ed, parts with its membranous covering, which is lost in the pia 
 mater, or immediate covering of these central parts of the brain. 
 The medullary or white part of the brain is continued into their 
 substance, which may be considered as principally formed by 
 the assemblage of these nervous extremities, which it is difii- 
 cult to distinguish in its tissue, from its want of consistence. It 
 
OF SENSATIONS. 
 
 356 
 
 has long been known, that the origin of the nerves is not the 
 spot at which they are detached from the brain, that they sink 
 into the substance of this viscus, in which their fibres cross each 
 other, so that those on the right pass to the left, and vice versa. 
 Scemmering thought, that the roots of the nerves, especially of 
 the nerves of the organs of sense, reached to the prominences in 
 the parietes of the ventricles of the brain, and that their furthest 
 extremity was moistened by the serosity which keeps these in- 
 ward surfaces in contact. It has, likewise, long been thought, 
 that the cerebral extremities of the nerves all joined in a fixed 
 point of the brain, and that to this central point all sensations 
 were carried, and that from it, all the determinations producing 
 voluntary motion arose. But the inquiries of Gall on the struc- 
 ture of the brain and nervous system, have completely overset 
 these various hypotheses. 
 
 The spinal marrow and the nerves, in the different animals 
 furnished with them, are larger in proportion to the brain, ac- 
 cording as the animal is more distant from man in the scale of 
 animation. In carnivorous animals, the prodigious develop- 
 ment of the muscles required nerves of motion of a proportion- 
 ate size; hence, in them, the cerebral mass, compared to the 
 nerves and spinal marrow. Is very inconsiderable. It is ob- 
 served, that there exists the same relation in men of an athle- 
 tic disposition; the whole nervous power seems employed in 
 moving their large muscles, and the nerves, though verj' small, 
 in proportion to the rest of the body, are, however, v£ry large, 
 if compared to the cerebral organ. In children, in women, and 
 in individuals possessed of much sensibility, the nerves are verj" 
 large, in proportion to the other parts of the body; they de- 
 crease in size and shrink in persons advanced in years; the cel- 
 lular tissue which surrounds them, becomes more consistent, 
 adheres to them more closely, and there exists a certain analogy 
 betw'een the nerves of old men, enveloped by that yellowish 
 tissue which makes their dissection laborious, and the branches 
 of an old tree covered over by a destructive moss. 
 
 As the uses of the nerves cannot be explained independently 
 of those of the brain, I shall now go on to consider this impor- 
 tant viscus. 
 
 CXLI. Of the coverings of the brain. If it be true, that one 
 
GF SENSATIONS. 
 
 357 
 
 may judge of the importance of an organ by the care which na- 
 ture has taken to protect it from external injury, no organ will 
 appear of greater importance than the brain, for no one appears 
 to have been protected with greater care. The substance of this 
 viscus has so little consistence, that the slightest Injury would 
 have altered its structure, and deranged its action; hence it is 
 powerfully guarded bv several envelopes, the most solid of 
 which is the bony case in which it is contained. 
 
 No part of anatomy is better understood than that of the 
 many bones which, by their union, form the different parts of 
 the human head. Every thing that relates to the place they oc- 
 cupy, to their respective size, to their projections and depres- 
 sions, to the cavities whose parietes they form; every thing that 
 relates to their internal structure, to the different proportions of 
 their component parts, to the aggregation of some of these sub- 
 stances, in certain points of their extent; has been described by 
 several modern anatomists, with an accuracy which it would not 
 be easy to surpass. Several, however, have not sufficiently ap- 
 preciated the direct influence of their mode of action on the 
 functions which they are destined to fulfil; no one has insisted 
 sufficiently on the manner in which they all concur to a princi- 
 pal object; the preservation of the organs enclosed within the 
 skull. 
 
 Hunauld, in a memoir inserted among those of the Academy 
 of Sciences, for the year 1730, was the first that endeavoured to 
 account for the arrangement of the articulating surfaces of the 
 bones of the skull. After laying down a few principles on the 
 theory of arches, and after showing, that the difference of ex- 
 tent of their concave and convex surfaces, rendered it necessary 
 that the parts of which they are formed should be shaped ob- 
 liquely, he explains the advantages of the squamous articulation 
 ' between the temporal and parietal bones. 
 
 When the arch of the cranium is loaded with a very heavy 
 burthen, the temporal bones prevent the parietals on which the 
 effort is immediately applied, from being forced inwardly, or 
 from being separated outwardly. Hunauld very aptly compares 
 them to buttresses, which are to the parietal bones of the same 
 use as walls to the arches which they support. 
 
OF SENSATION& 
 
 ■358 
 
 Bordeu^ endeavoured to apply to the bones of che face, the 
 principles by which Hunauld had been guided in his investiga- 
 tion with regard to those of the skull. According to Bordeu, the 
 greater part of the bones of the upper jaw, but particularly the 
 superior maxillary bones, resist the effort of the lower jaw, 
 which, by acting on the upper dental arch, has a perpetual ten- 
 dency to force upward, or to separate outwardly the bones in 
 which the teeth of that jaw are inserted. As the greatest stress 
 of the effort determines them upward, it is, likewise, in that di- 
 rection, that the bones of the upper jaw rest most powerfully 
 on those of the skull. The author concludes this very ingenious 
 memoir, by proposing to physiologists the solution of the fol- 
 lowing problem: “ When a man supports a great weight on his 
 “ head, and holds at the same time any thing very firmly be- 
 ** tween his teeth, which is the bone of the head that is most 
 “ acted upon? Which supports the weight of the whole machine?” 
 
 The body of the sphenoid, and especially its posterior half, 
 appears to me to be the central point on which the united efforts 
 of the bones of the skull and of the face act, in the case supposed 
 by Bordeu. 
 
 The sphenoid is connected with all the other bones of the 
 skull; it is immediately connected with several of the bones of 
 the face: as with the malar bones, with the palatine bones, with 
 the vomer, and sometimes with the superior maxillary bones. 
 These bones of the face, in the case in question, alone support 
 the lower jaw against the upper. The ethmoid bone, the ossa 
 unguis, and the inferior turbinated bones are thin and frail, and 
 serve merely to form the nasal fossae, of which they increase the 
 tvindings, and do not deserve to be attended to in this investiga- 
 tion. The vomer may, it is true, communicate to the ethmoid, 
 in an inferior degree, a part of the effort; for the anterior part 
 of its upper edge is articulated with the perpendicular lamella 
 of that bone; but this quantity is very small, as the vomer is 
 thin, and transmits it almost v/holly to the body of the sphenoid, 
 with the lower face of which it is articulated. 
 
 The effort exerted on the bones of the upper jaw, is trans- 
 mitted, by means of the nasal processes of the upper maxillary 
 
 ifademiedes Sciences, Alemoires pr^srr.ti^s par ies suvan'i ^tran^ers. Tome III. 
 
OF SENSATIOiNS. 
 
 359 
 
 bones, by the orbitar and zygomatic processes of the malar 
 bones, and by the upper edge of the palate bones and of the vo- 
 mer, to the frontal, to the temporal, and sphenoidal bones. 
 
 If we wish to determine what becomes of the greater part of 
 the effort transmitted to the frontal bone by the maxillary and 
 malar bones, we may observe, in the first place, that it is arti- 
 culated with the sphenoid bone by the whole of its lower edge, 
 which is bevelled at its inner part, so that it is covered by the 
 alse minores of the os sphenoides, which is shaped obliquel)'" at 
 the outer part of the bone. The frontal bone is articulated, be- 
 sides, with the lateral and inferior parts of its upper edge. The 
 remainder of this upper part is united to the anterior edge of 
 the parietal bones, which, by means of a slope in a different di- 
 rection rest on the middle part of this edge, while the frontal 
 bone is applied to them laterally. 
 
 This bone, which the effort tends to force upward and back- 
 ward, cannot yield to this double impulse; for, on the one hand, 
 its mode of articulation with the anterior edge of the alas mi- 
 nores of the sphenoidal bone, and the internal part of the ante- 
 rior edge of the parietal bones, resist this tendency upward, 
 while the resistance from the latter prevents them from being- 
 forced backward. That share of the effort which affects the 
 parietal bones, follows the curved line described by these 
 bones, and extends along that formed by the occipital, and thus 
 reaches the posterior face of the body of the sphenoid bone. 
 
 The portion directly transmitted to the anterior and inferior 
 face of this bone, by the ossa palati, and by the vomer, is incon- 
 siderable, and proportioned to their thinness. The anterior half 
 of the body of the sphenoid bone, hollowed by the sphenoidal 
 sinus, would have been incapable of supporting greater pres- 
 sure. Lastly, the situation of the body, placed between the 
 dental arches, in front of the place occupied by the ossa palati, 
 explains why this transmission is chiefly effected by the upper 
 maxillary bones. 
 
 The above is the manner in which the effort exerted from 
 below upward, by the lower on the upper jaw, is carried to the 
 anterior, posterior, and inferior faces of the body of the sphenoid 
 bone. 
 
OF SENSATIONS. 
 
 360 
 
 The temporal bones which are affected by it, in a very slight 
 degree, by means of the zygomatic processes of the malar bones, 
 support the greater weight of the effort acting from above down- 
 ward, or from the arch of the skull towards its base. The weight 
 laid on the head, tends to depress or to separate the parietal 
 bones, which resist the pressure, in consequence of the support 
 afforded them by the temporals. These transmit the effort to 
 the lateral and posterior parts of the body of the sphenoid, by 
 means of the alse majores of that bone, which are articulated, 
 along the whole extent of their external edge, and along the pos- 
 terior fourth of their internal edge, with the temporals. Besides, 
 the upper extremity of the alae majores is sloped on the inner 
 part of the bone, that it may be articulated with the anterior 
 and inferior angles of the parietal bones, and answer the same 
 purpose to them as the squamous portion of the temporals. 
 
 The lateral and posterior parts of the body of the sphenoid 
 support, therefore, almost the whole effort of the pressure ap- 
 plied to the parietal bones. It is communicated to them by the 
 alae majores, which receive it themselves, either directly at the 
 anterior and inferior angles of this bone, or through the medi- 
 um of the temporals. The small portion of the effort trans- 
 mitted by the latter to the occipital, follows the curved line of 
 this bone, and is felt on the posterior face of the body of the 
 sphenoid. 
 
 To the effort resulting from the pressure exerted by the body 
 on the summit of the head, one should add that occasioned by 
 the contraction of the muscles, which elevate the lower jaw. 
 These tend to depress the temporal, the malar, and sphenoid 
 bones; and in this action they employ a power, equal to that by 
 which they raise the lower jaw, and press it firmly against the 
 upper. 
 
 The effort exerted from the arch to the base of the skull de- 
 pends, therefore, on two very different causes; the portion result- 
 ing from the action of the elevators of the lower jaw, is equal 
 to the effort exerted from below upward, by this bone. After 
 what has been stated, it would be useless to say any thing fur- 
 ther of the manner in which the effort is transmitted: we may 
 merely observe, that the least powerful of these muscles, the in- 
 ternal pterygoid, tends to draw the sphenoid downward, and 
 
0F SENSATIONS. 
 
 361 
 
 prevents this bone, fixed like a wedge with its base^turned up- 
 ward, from being disengaged by the effort applied to it by the 
 bones between which it is situated. 
 
 The posterior, anterior, inferior and lateral faces of the sphe- 
 noid bone, support, therefore, the whole effort of the bones of 
 the skull and face on one. another, when the top of the head 
 being loaded with a heavy burthen, one presses, at the same 
 time, something very firmly between the dental arches. 
 
 The anterior part of the body of the bone, containing the 
 sphenoidal sinus, is thin and very frail; the posterior part, cor- 
 responding to the sella turcica, is alone capable of resisting the 
 effort which, I believe, it is destined to sustain*; hence, it is at 
 this point, that ossification begins: and this confirms the obser- 
 vation of Kerkringius, that the spot at which bones begin to 
 ossify, is that on which they have to bear the greatest effort; 
 hence the alse majores, by means of which the greatest part of 
 the efforts which the body of the sphenoid has to support, arise 
 from the lateral parts of its posterior half, by an origin of con- 
 siderable size, and which is further increased by the base of the 
 pterygoid processes which arise from its lower part. 
 
 I have, in this inquiry, purposely avoided mentioning the 
 support which the head receives from the vertebral column, and 
 which, in the case under consideration, is of use merely in pre- 
 venting it from yielding to the law of gravitation. If the bones 
 of the skull and of the face had pressed, during the effort which 
 they sustain, on the circumference of the foramen magnum, 
 this /aperture would have been incapable of increasing its di- 
 mensions, and this would have been attended with the most 
 serious inconveniences. 
 
 The name given by the ancients to the bone whose principal 
 use has just been explained, is composed of sphenos, which 
 
 * The sphenoidal sinus is prolonged, it is true, into this posterior part of the 
 body of the bone, in persons considerably advanced in years; but the parietes 
 of this portion of its cavity are of considerable tliickness. The anterior 
 part of the basilary process of the occipital bone, is then firmly united to 
 the Sphenoid, and may be considered as forming a part of that bone, from 
 which it cannot be detached. The cranium of an old man, in this respect, re- 
 sembles that of several quadrupeds, in which the union of the sphenoid to the 
 occipital bone takes place so early, that these two bones might well be con- 
 sidered as forming but one. 
 
 2 Z 
 
OF SENSATIONS. 
 
 362 
 
 means a wedge, and eidos, which signifies resemblance, and 
 would lead one to think that they were not ignorant of its uses. 
 From its situation at the middle and inferior part of the skull, 
 and from its various connexions with the bones which form this 
 osseous case, it is to them of the same use as the key-stone of 
 arches, with regard to the different parts of which they are form- 
 ed. The numerous connexions required for this purpose, ac- 
 count for its strange and irregular form, and for the different 
 shapes of its articular surfaces, and the great number of its pro- 
 jections, which render the demonstration of this bone so com- 
 plicated, and a knowledge of it so difficult. 
 
 It is more advantageous, with regard to the brain, that the 
 skull should be formed of several bones, than if it had con- 
 sisted of a single bone. It resists, more effectually, the blows 
 it receives, their effect being lessened in passing from one 
 bone to the other, and being interrupted in the obscure motions 
 which they may experience at their sutures; its rounded form 
 increases, likewise, its power of resistance. This force would 
 be equal, in every point of the' parietes of the cranium, if the 
 form of that cavity were completely spherical, and if the thick- 
 ness of its parietes were, in every part of it, the same. In that 
 case, no fractures by contre coup' co\Ad occur, a kind of lesion 
 occasioned by the unequal resistance of the bones of the head, 
 to the force applied to their surface. The pericranium, the hairy 
 scalp, the muscles which cover it, and the great quantity of hair 
 on its surface, serve, besides, to defend the brain, and are well 
 calculated to break the force of blows applied to the cranium. 
 
 In addition to this hard and unyielding case, there lies over 
 the brain, a treble membranous covering, formed by the dura 
 mater, which owes its name to the erroneous opinion according 
 to which it was supposed to form all the other membranes of 
 the body; it is further covered by the tunica arachnoidea, so 
 called from the extreme minuteness of its tissue, and by the 
 pia matter which adheres firmly to the substance of the brain. 
 
 The dura mater lines, not only the inside of the skull and 
 of the vertebral canal, which may be considered as a prolonga- 
 tion of it, but, likewise, penetrates between the different parts of 
 the cerebral mass, supports them in the different positions of 
 the head, and prevents mutual compression. Thus, the greatest 
 
OF SENSATIONS. 
 
 36,3 
 
 of its folds, the falx, stretched between the crysta galli of the eth- 
 moid bone, and the inner protuberance of the occipital bone, pre- 
 vents the two hemispheres of the brain, between which it lies, 
 from compressing each other, when the body is on the side; and 
 maintains, on the other hand, the tentorium cerebelli in the state 
 of tension necessary to enable it to support the weight of the pos- 
 terior lobes of the brain. This fold of dura mater is of a semi- 
 circular form, separates the portion of the skull which contains 
 the brain, from that in which the cerebellum is situated. It is kept 
 in a state of tension by the falx cerebri, on which it also exerts 
 the same action: it does not present an horizontal plane to the 
 portion of brain which lies upon it, but one that slopes, in every 
 direction, towards the parietes of the skull, to which it trans- 
 mits most of the weight which it has to support. The tentorium 
 cerebelli, which thus divides the internal cavity of the skull 
 into two parts of unequal dimensions, is bony in some animals 
 that move by bounding and with rapid action; this is the case 
 with the cat, which can, without being stunned, take leaps from 
 a considerable height. By means of this complete partition, the 
 two portions of the brain are prevented from pressing on each 
 other, in the violent concussions which they experience. 
 
 The tunica arachnoides, according to Bonn^, who was tho- 
 roughly acquainted with its structure and who has given a very 
 beautiful plate of it, is the secretorj^ organ of the serum which 
 moistens the internal surface of the dura mater, a fibrous mem- 
 brane which serves as a periosteum to the bones it lines. 
 
 CXLII. Of the size of the brain. Of all animals, man has 
 the most capacious skull, in proportion to his face, and, as the 
 bulk of the brain is always of a size proportioned to that of the 
 osseous case which contains it, the brain is also most bulky in 
 man. This difference of size between the cranium and face, may 
 be taken as the measure of the human understanding and of the 
 instinct of the lower animals; the stupidity and ferocity of the 
 latter are greater, according as the proportions of these two 
 parts of their skull vary from those of the human head. 
 
 To express this difference of size, Camper imagined a verti- 
 cal line, drawn from the forehead to the chin, and perpendicular 
 
 * Dissertatio de continuationibus membranarum. 4® Liigdun. Bat. 1763., 
 
354 SENSA'noKs. 
 
 to another drawn in the direction of the base of the skull. He 
 has called the first of these lines facial^ the second, palatine or 
 mental. It is easy to understand, that, as the projection of the 
 forehead is determined by the size of the skull, the larger it is, 
 the more the angle at which the facial line meets that from the 
 base of the skull must be obtuse. In a well formed European 
 head, the facial line meets the palatine at an angle nearly straight 
 (of between 80 and 90 degrees). When the angle is quite 
 straight, and the line which measures the height of the face is 
 completely vertical, the head is of the most beautiful form pos- 
 sible, it approaches most to that conventional degree of perfec- 
 tion which is termed ideal beauty. If the facial line slopes 
 backward, it forms with the palatine line, an angle more or less 
 acute, and projecting forward, the inclination increases, and the 
 sinus of the angle is shorter; if, from man, we pass to monkeys, 
 then to quadrupeds, to birds, reptiles, and fishes, we find this 
 line slope more and more, and, at last, become almost parallel 
 to the mental, as in reptiles and in fishes, with flat heads. If, on 
 the contrary, we ascend from man to the gods, whose images 
 have been transmitted to us by the ancients, we find the facial 
 line to incline in a different direction, the angle then enlarges 
 and becomes more or less obtuse. From this inclination for- 
 ward of the facial line, there results an air of grandeur and 
 ^ majesty, a projecting forehead, indicating a voluminous brain 
 and a divine intellect. 
 
 To obtain with precision, by this means, the respective di- 
 mensions of the skull and face, one must measure, not only the 
 outside, but, likewise, draw the tangents on the internal sur- 
 faces, after dividing the head vertically. There are, in fact, 
 animals, in which the sinuses of the frontal bone are so large, 
 that a considerable portion of the parietes of the skull is pro- 
 truded by their cells. Thus, in the dog, in the elephant, in the 
 owl, &c. the apparent size of the skull exceeds much its real 
 capacity. 
 
 The relative size of the head, and consequently the propor- 
 tionate bulk of the brain, is inconsiderable in very tall and mus- 
 cular subjects; this fact will be confirmed by observing the pro- 
 portions of antique statues. In all those which represent heroes 
 or athlets gifted with a prodigious bodily power, the head is 
 
OF SENSATIONS. 
 
 365 
 
 very small, in proportion to the rest of the body. In the statues 
 of Hercules, the head scarcely equals in size the top of the shoul- 
 der. The statues alone of the king of the gods, present the sin- 
 gular combination of an enormous head, resting on limbs of a 
 proportionate size; but the Greek artists have transgressed 
 the laws of nature, only in favour of the god that rules over 
 her; as if a vast brain had been necessary to one whose intellect 
 carries him, at a glance, over the whole universe. The relative 
 small dimensions of the head, in athlets, depend on this circum- 
 stance, that in such men, the excessive development of the 
 organs of motion, gives to the body, and especially to the limbs, 
 an enormous size, while the head covered by few muscles, 
 remains very small. Sremmering has stated, that the head in 
 women is larger than in men, and that their brain is heavier; but 
 it must be recollected, that this great anatomist obtained this 
 result, by examining two bodies, male and female, of the same 
 length. Now, the absolute size being the same, the proportion- 
 ate magnitude was not so, and he was wrong in comparing the 
 head, the skull, and brain of a very tall woman, to that of a very 
 short man. 
 
 It has long been thought, that there exists a connexion be- 
 tween the bulk of the cerebral mass and the energy of the intel- 
 lectual faculties. It has been thought, that, in general, men 
 whose mind is most capacious, whose genius is most capable of 
 bold conceptions, had a large head supported on a short neck. 
 The exceptions to this general rule have been so numerous, 
 that many have doubted its truth; should it then be absolutely 
 rejected, and will it be allowed to be wholly without foundation, 
 when we consider that man, the only rational being out of so 
 great a number, and some of which bear to him a considerable 
 resemblance both of organization and structure, is, likewise, the 
 only animal in which the brain, properly so called, is largest in 
 proportion to the cerebellum, to the spinal marrow, to the nerves 
 and to the other parts of the body? Why may it not be with the 
 brain, as with the other organs, which fulfil their functions the 
 better, from being more completely developed? It should be re- 
 collected, in this comparison of the brain and of the intellectual 
 powers, that several causes may give to this viscus an unnatu- 
 ral degree of enlargement. Thus, in subjects of a leucophleg- 
 
OF SENSATIONS. 
 
 366 
 
 matic temperament, the tardy ossification of the bones of the 
 skull, causes the brain, gorged with aqueous fluids, to acquire 
 a considerable size, without its containing a greater quantity of 
 real medullary substance. Hence it is observed, that men of 
 this temperament are, most frequently, unfit for mental exer- 
 tion, and rarely succeed in undertakings that require activity 
 and perseverance^. 
 
 CXLIII. Structure of the cerebral mass. What we know of 
 the brain, serves only to show us that we are ignorant of much 
 more. All that we know of it consists of notions tolerably ex- 
 act of its external conformation, its colour, its density, and of 
 the different substances that enter into its composition; but the 
 knowledge of its intimate structure is yet a mystery, which will 
 not be soon unveiled to us. The brain, properly called, is divi- 
 ded by a longitudinal furrow, into two lobes of equal bulk. 
 Gunzius, however, imagined that he found the right lobe, or 
 hemisphere, a little larger than the left; but even were this fact 
 as certain as it is doubtful, we could not thereby explain the 
 predominant force of the right side of the body, since the nerves 
 which are distributed to this side, rise from the left lobe of the 
 brain, in the substance of which all the roots of these cords 
 cross. This fact of the crossing of the nerves, at their origin, is 
 proved by a multitude of pathological observations, in which 
 the injury of a lobe is always found to bring on paralysis, con- 
 vulsion, or any other symptomatic affection, on the opposite side 
 of the body. Unless you chuse to explain this phenomenon by 
 admitting a necessary equilibrium in the action of the two lobes; 
 an equilibrium, the disturbance of which is the occasion that the 
 sound lobe, acting with more force, compresses the origin of 
 the nerves on its side, and determines paralysis. May not the 
 want of judgment, the unevenness of humour and character, 
 depend on the want of harmony between the two corresponding 
 halves of the cerebral mass? 
 
 In order to disclose, better than had before been done, the 
 structure of the brain, M. Gall begins his dissection at the 
 lower part; examining, in the first place, the anterior part of the 
 
 * See, in the article on Temperaments, an account of the influence of the 
 physical organization on the moral disposition and on the intellectual faculties. 
 
OF SENSATIONS. 
 
 367 
 
 prolongation, known under the name of cauda of the medulla 
 oblongata, he finds the two pyramidal eminences. If you part 
 the two edges of the median line, below the furrow which sepa- 
 rates the two pyramids, you see distinctly the crossing of three 
 or four cords or fasciculi of nerves, which, consisting of many 
 filaments, tend obliquely from right to left, and vice versa. This 
 crossing of nervous fibres, which is not found in any other part 
 of the brain, had been observed by several anatomists. It is not 
 known how it came to be forgotten, so that the most exact and 
 the latest among them, Boyer, for instance, say that the cross- 
 ing of the nerves cannot be proved by anatomy. These nervous 
 cords, traced upwards, enlarge, strengthen, and forming pyra- 
 midal eminences, ascend towards the tuber annulare. Having 
 reached this ganglion, the fibres strike into it, and are lost in a 
 mass of pulpy or grayish substance, of the same nature as that, 
 which, under the name of cortical substance, covers the two 
 lobes of the brain. This grayish pulp, distributed in various 
 parts, may be considered, agreeably to the views of M. Gall, 
 who calls it the matrix of the nerves, as the source from which 
 the medullary fibres take their origin. These ascending fibres 
 cross other transverse fibres, which, on either side, proceed from 
 the crura of the cerebellum; enlarged and multiplied by means 
 of their passage through the gray substance which is found in 
 the tuber annulare, they rise from it at its upper part, in two fas- 
 ciculi which compose nearly the Avhole of the crura cerebri. The 
 interior of these crura, contains a certain quantity of gray sub- 
 stance, which is what nourishes the nervous fibre. On reaching 
 the ventricles, -these peduncles, or rather the two fasciculi of 
 fibres which form them, meet with large ganglions full of gray 
 substance; they have long been called thalami optici, though they 
 do not give origin to the optic nerves. There the fibres are sen- 
 sibly enlarged; and they pass from the thalami optici into new 
 ganglions. These are the corpora striata, and the striae which are 
 apparent on cutting these pyriform masses of gray substance, 
 are only the same fibres, which, enlarged, multiplied, and ra- 
 diating, spread out in the manner of a fan, towards the lobes of 
 the brain, where, after forming by their expansion a whitish and 
 fibrous substance, they terminate at the outer part of that viscus, 
 forming its convolutions all covered with the substance in which 
 
OF SENSATIONS. 
 
 368 
 
 are terminated, in like manner, the extremities of the diverging 
 fibres. From this gray substance proceed converging fibres, 
 tending from all parts of the periphery to the centre of the 
 brain, where they unite to form the different commissures, the 
 corpus callosum, and other productions, destined to facilitate 
 the communication of the two hemispheres. 
 
 The exterior of the brain may, therefore, be considered as a 
 vast nervous membrane, formed by the gray substance. To form 
 a due conception of its extent, it must be understood, that the 
 convolutions of the brain are a sort of duplicatures, susceptible 
 of extension by the unfolding of two contiguous medullary la- 
 minse, which forms its base. The exterior surface of the brain, 
 by means of this unfolding, offers then some relation to the skin, 
 a vast nervous expanse every where covered by a sort of pulpy 
 substance, known by the name of the rete mucosum of Mal- 
 pighi. M. Gall compares this cutaneous pulp to the cineritious 
 substance which forms the outer part of the brain, and, I must 
 confess, it is not every one that will admit the analogy. How- 
 ever, true it is, that the brain consists, principally, of a mass of 
 ganglions, that it produces neither the elongated medulla, nor 
 the spinal marrow; that this last may be considered as a series 
 of ganglions united together; that the vertebral nerves arise from 
 the greyish pulp of which the spinal marrow is full, as is best 
 seen in animals without a brain, but not the less provided with 
 a spinal marrow, or series of ganglions, from which the nerves 
 arise. The ganglions, or rather the gray substance which they 
 alway show, produce the nervous fibres, and thicken the nervous 
 cords that pass through them. 
 
 That is the only use that can be assigned to these parts of the 
 nervous system; for, if they were meant to withdraw from the 
 dominion of the will, the parts in which they are found, why do 
 not the ganglions of the vertebral nerves fulfil the same function? 
 All these nerves communicate by reciprocal anastomoses. These 
 communications in man, are equivalent to a real continuity. In 
 truth, the brain acts upon the nerves that proceed from the spinal 
 marrow, as if this were one of its productions, and all the ner- 
 vous fibres, spread through the different organs, had an extre- 
 mity terminating in this viscus. 
 
 One thing well worthy of attention, and on which no anato- 
 
OF SENSATIONS. 
 
 369 
 
 mist has dwelt, is that the brain of the fetus, and of the child 
 just born, appears to consist, almost entirely, of a cineritious 
 pulp, to such a degree that the medullary substance is difficult 
 to perceive in it. Would it be absurd to believe, that the me- 
 dullary part of the brain does not take its perfect organization 
 till after birth, by the development of the fasciculi of medul- 
 lary fibres, in the midst of these masses of cineritious substance, 
 which must be considered as the common source from which 
 the nerves have their origin, or, to use the language of Gall, as 
 the uterus which gives them birth. The almost total inactivity, 
 the passive state of the brain in the fetus, makes unnecessary 
 there the existence of. the medullary apparatus, to which the 
 most important operations of intelligence seem entrusted. Its 
 first rudiments are found in the fetus at its full time. That 
 fibro-medullary apparatus will be strengthened by the exercise 
 of thought, as the muscles are seen to enlarge and perfect their 
 growth by the effect of muscular action. 
 
 CXLIV. Circulation of the brain. I have said that the blood, 
 in its circular course, does not traverse the different parts of the 
 body with uniform velocity: that there are partial circulations 
 in the midst of the general circulation. In no organ are the 
 laws, to which this function is subjected, more remarkably mo- 
 dified than in the brain. There is none which receives, in pro- 
 portion to its bulk, larger arteries and more in number. The in- 
 ternal carotid and vertebral arteries, as we may satisfy ourselves 
 from the calculations of Haller, carry thither a great portion of 
 the whole quantity of blood that flows along the aorta; (from a 
 third to the half). 
 
 The blood which goes to the brain, said Boerhaave, is more 
 aerated than that which is distributed to the other parts: the ob- 
 servation is not without foundation. Though the blood which 
 the contractions of the left ventricle send into the vessels 
 arising from the arch of the aorta, does not undergo, at the 
 place of this curvature, a mechanical separation carrying its 
 lighter parts towards the head; it is not less true, that this 
 blood, just passing from the contact of the air in the lungs, 
 possesses, in the highest degree, all the peculiar qualities of 
 arterial blood. So great a quantity of light, red, frothy blood, 
 impregnated with caloric and oxygen, coming upon the brain, 
 
 3 A 
 
OF SENSATIONS. 
 
 370 • 
 
 with all the force it has received from the action of the heart, 
 would unavoidably have deranged its soft and delicate struc- 
 ture, if nature had not multiplied precautions to weaken its 
 impulse. 
 
 The fluid, compelled to ascend against its own weight, loses, 
 from that alone, a part of its motion. The vertical column must 
 strike against the angular curvature which the internal carotid 
 takes in its passage along the osseous canal of the petrous por- 
 tion of the tenaporal bone; and as this curvature, supported by 
 hard parts, cannot straighten itself, the column of blood is vio- 
 lently broken and turned out of its first direction, with conside- 
 rable loss of velocity. 
 
 The artery immersed in the blood of the cavernous sinus, 
 as it cpmes out from the carotid canal, is very easily dilated. 
 Finally, the branches into which it parts, on reaching the base 
 of the brain^ have coats exceedingly thin, and so weak that they 
 collapse, when they are'^empty, like those of the veins. This 
 weakness of the cerebral arteries, explains their frequent rup- 
 tures, when the heart sends the blood into them too violently; 
 and it is thus that the most part of sanguineous apoplexies are 
 occasioned, many of which, however, take effect without rup- 
 ture, and by the mere transudation of blood through the coats 
 of the arteries. These vessels, like the branches arising from 
 their divisions, are lodged in the depressions with which the 
 base of the brain is furrowed, and do not enter its substance 
 till they are reduced to a state of extreme tenuity, by the fur- 
 ther divisions they undergo in the tissue of the pia mater. 
 
 Notwithstanding the proximity of the brain to the heart, the 
 blood reaches it then with an exceedingly slackened motion: it 
 returns, on the contrary, with a motion progressively accelera- 
 ted. The position of the veins at the upper part of the brain, be- 
 tween its convex surface and the hollow of the skull, causes 
 these vessels, gently compressed by the alternate motions of 
 rising and falling of the cerebral mass, to disgorge their con- 
 tents readily into the membranous reservoirs of the dura mater, 
 known by the name of sinuses. These, all communicating to- 
 gether, offer to this fluid a sufficiently large receptacle, from 
 which it passes into the great jugular vein, which is to carry it 
 again into the general course of the circulation. Not only is the 
 
OF SENSATIONS. 
 
 ■ 371 
 
 caliber of this vein considerable, but its coats too, of little thick- 
 ness, are very extensible; so much so that it acquires, by injec- 
 tion, a caliber superior to that of the venae cavae. The flowing 
 of the blood is favoured by its own weight, which makes a re- 
 trograde course very difficult.* Thus, to sum up all that is pe- 
 culiar in the cerebral circulation, the brain receives, in great 
 quantity, a blood abounding in oxygen; the fluid finds, in its 
 course thither, many obstacles which impede and slacken its 
 impulse, whilst all, on the contrary, favours its return and pre- 
 vents venous congestion.! Let me observe, to conclude what 
 I have to say on the: circulation of the brain, that of the eye is 
 nearly allied to it, since the ophthalmic artery is given out by the 
 internal carotid, and the ophthalmic vein empties itself into the 
 cavernous sinus of the dura mater. Accordingly, the redness of 
 the conjunctiva, the prominence, the brightness, the moistness 
 of the eyes, indicate a stronger determination of the blood to^ 
 towards the brain. Thus the eyes are animated at the approach 
 of apoplexy, in the transport of a burning fever, during delirium, 
 a dangerous symptom of malignant or ataxic fevers. On this 
 connexion of the vessels of the eye and brain, depends the 
 lividity of the conjunctiva, whose veins, injected with a dark 
 coloured blood, indicate the fulness of the brain in the gene- 
 rality of cases of suffocation. 
 
 CXLV. Of the connexion between the action of the brain and 
 that of the heart. It is possible, as was done by Galen, to tie 
 both carotids, in a living animal, without his appearing sensibly 
 affected by it; but if, as has never yet been done, both the ver- 
 tebral arteries are tied, the animal drops instantly and dies at 
 the end of a few seconds. To perform this experiment, it is ne- 
 cessary, after tying the carotid arteries of a dog, to remove the 
 soft parts which cover the side of the neck, then with needles, 
 bent in a semi-circular form, passed into the flesh along the 
 
 * In preventing this reflux, there is no use of valves, which the jugular vein 
 is entirely without. It is sufiiciently prevented, by the direction in which the 
 blood flows, and the extensibility of its coats. This great size which the vein 
 can acquire, would have made useless the valvular folds, insufficient to stop 
 the canal, in that great augmentation of its dimensions. 
 
 ! The transverse anastomoses of the arteries, at the base of the brain, are 
 very proper for distributing the blood, in equal quantity, to all parts of this 
 viscus. 
 
OP SENSATIONS. 
 
 372 
 
 sides of the articulation of the cervical vertebrse, to apply liga- 
 tures to the arteries which ascend along their transverse pro- 
 cesses. The same effect, viz. the speedy death of the animal, 
 is produced by tying the ascending aorta in an herbivorous 
 quadruped. 
 
 These experiments, which have been repeated a number of 
 times, decidedly prove the necessity of the action of the heart 
 on the brain, in preserving life. But how does this action ope- 
 rate? Is it merely mechanical? Does it consist solely in the gen- 
 tle pressure which the arteries of the brain exert on the sub- 
 stance of this viscus; or is it merely to the intercepted arte- 
 rial blood which the contractions of heart determine towards 
 the brain, that death is to be attributed? The latter opinion 
 seems to me the most probable; for, if, the moment the verte- 
 brals have been tied, the carotids are laid open, and the pipe of 
 a syringe adapted to them, and any fluid whatever is then in- 
 jected with a moderate degree of force, and at nearly the same 
 intervals as those of the circulation, the animal will not be re- 
 stored to life. 
 
 The heart and brain are, therefore, united to each other by 
 the strictest connexion; the continual access of the blood flowing 
 along the arteries of the head is, therefore, absolutely necessary 
 to the preservation of life; if intercepted, for one moment, the 
 animal is infallibly destroyed. 
 
 The energy of the brain appears, in general, to bear a rela- 
 tion to the quantity of arterial blood which it receives. I know 
 a literary man, who, in the ardour of composition, exhibits all 
 the symptoms of a kind of brain fever. His face becomes red 
 and animated, his eyes sparkling; the carotids pulsate violently; 
 the jugular veins are swollen; every thing indicates that the 
 blood is carried to the brain with an impetus, and in a quantity 
 proportioned to its degree of excitement. It is, indeed, only 
 during this kind of erection of the cerebral organ, that his 
 ideas flow without eflbrt, and that his fruitful imagination 
 traces, at pleasure, the most beautiful descriptions. Nothing 
 is so favourable to this condition as remaining long in a re- 
 cumbent posture; in this horizontal posture, the determination 
 of the fluids towards the head is the more easy, as the limbs, 
 which are perfectly quiescent, do not divert its course. He can 
 
OP SENSATIONS. 
 
 373 
 
 bring on this state by fixing his attention steadfastly on one ob- 
 ject. May not the brain, which is the seat of this intellectual 
 action, be considered as a centre of fluxion; and may not the 
 stimulus of the mind be compared, as to its effects, to any other 
 stimulus, chemical or mechanical? 
 
 A young man of a sanguineous temperament, subject to in- 
 flammatory fevers which always terminate by a profuse bleed- 
 ing at the nose, experiences, during the febrile paroxysms, a re- 
 markable increase of his intellectual powers and of the activity 
 of his imagination. Authors had already observed, that in cer- 
 tain febrile affections, patients of very ordinary powers of mind, 
 would sometimes rise to ideas which, in a state of health, would 
 have exceeded the limits of their conception. May we not ad- 
 duce these facts in opposition to the theory of a celebrated 
 physician, who considers a diminution of the energy of the 
 brain to be the essential character of fever? 
 
 It is well known, that the difference of the length of the neck, 
 and, consequently, the greater or lesser degree of vicinity of the 
 heart and brain, give a tolerably just measure of the intellect of 
 man, and of the instinct of the lower animals; the dispropor- 
 tionate length of the neck has ever been considered as the em- 
 blem of stupidity. 
 
 In the actual state of our knowledge, is it possible to deter- 
 mine in what manner arterial blood acts on the brain? Are 
 oxygen or caloric, of which it is the vehicle, separated from it 
 by this viscus, so as to become the principle of sensation and 
 emotion; or do they merely preserve it in the degree of con- 
 sistence necessary to the exercise of its functions? What is to 
 be thought of the opinion of those chemists who consider the 
 brain as a mere albuminous mass, concreted by oxygen, and of 
 a consistence varying in different persons, according to the age, 
 the sex, or the state of health or disease? Any answer that one 
 might give to these premature questions, would be but a simple 
 conjecture, to which it would be difficult to give any degree of 
 probability. 
 
 CXLVI. Of the theory of syncope. If we consider the action 
 of the heart on the brain, we are naturally led to admit its ne- 
 cessity to the maintenance of life, and to deduce from its mo- 
 mentary suspension, the theory of syncope. Several authors 
 
OP SENSATIONS. 
 
 374 
 
 have attempted to explain the manner in which their proximate 
 cause operates, but as not one of them has gone upon facts as- 
 certained by experience, their explanations do not at all agree 
 with what is learnt from observing the phenomena of these 
 diseases. 
 
 To satisfy oneself that the momentary cessation of the action 
 of the heart on the brain, is the immediate cause of syncope, 
 one need but read, with attention, the chapter which Cullen, in 
 his work on the practice of physic, has devoted to the conside- 
 ration of this kind of affection. It will be readily understood, 
 that their occasional causes, the varieties of which determine 
 their different kinds, exist in the heart or great blood-vessels, 
 or act on the epigastric centre, and affect the brain only in a 
 secondary manner. Thus the kinds of syncope occasioned by 
 aneurismal dilatations of the heart and great vessels, by poly- 
 pous concretions formed in these passages, by ossification of 
 their parietes or of their valves, evidently depend on the ex- 
 treme debility, or on the entire cessation of the action of the 
 heart and arteries. Their parietes, ossified, dilated, adhering 
 to the neighbouring parts, or compressed by any fluid what- 
 ever, no longer act on the blood with sufficient force, or else 
 this fluid is interrupted, in its progress, by some obstacle with- 
 in its canal, as a polypous concretion, an ossified and immovea- 
 ble valve. Cullen, very justly, termed these, idiopathic or car- 
 diac syncopes. 
 
 To the above may be added plethoric syncope, depending on 
 a congestion of blood in the cavities of the heart: the contrac- 
 tions of this organ become more frequent; it struggles to part 
 with this excess of blood, which is injurious to the performance 
 of its functions; but to this unusual excitement by which the 
 contractility of its fibres is exhausted, there succeeds a kind of 
 paralysis necessarily accompanied by syncope. 
 
 One may, likewise, include the fainting attending copious 
 blood-letting; the rapid detraction of a certain quantity of the 
 vivifying principle deprives the heart of the stimulus necessary 
 to keep up its action. The same effect is produced by drawing off 
 the water contained in the abdomen, in ascites: a considerable 
 number of vessels cease to be compressed; the blood which they 
 before refused to transmit, is sent to them in profusion; the 
 
OF SENSATIONS. 
 
 375 
 
 quantity sent to the brain by the heart is lessened, in the same 
 proportion, and becomes insufficient for its excitement. Among 
 the syncopes, called idiopathic, one may enumerate those oc- 
 curring in the last stage of the scurvy, the principal character 
 of which is, an excessive debility of the muscles employed in 
 the vital functions, and in voluntary motion; lastly, we may 
 add asphvxia from strangulation, from drowning, and from the 
 gases unfit for respiration; affections in which the blood being 
 deprived of the principle which enables it to determine the 
 contractions of the heart, the circulation becomes interrupted. 
 If the blood loses, by slow degrees, its stimulating qualities, 
 the action of the heart gradually weakened, impels towards the 
 brain a blood which, by its qualities, partakes of the nature of 
 venous blood, and which, like it, cannot preserve the natural 
 economy of the brain. It was thought, that by injecting a few 
 bubbles of air into the jugular vein of a dog, one might occa- 
 sion in the animal immediate syncope, and that it was even 
 sufficient to deprive it of life; but the late experiments of M. 
 Nysten have proved, that the atmospherical air produces these 
 bad effects, only when injected in a quantity sufficient to dis- 
 tend, in excess, the cavities of the heart, or when by being in- 
 jected into the arteries, it compresses the brain. When injected 
 only in a small quantity, the gas, dissolved in the venous blood, 
 is conveyed along with it to the lungs, and is thence exhaled in 
 respiration. 
 
 A second class of occasional causes consists of those which, 
 by acting on the epigastric centre, determine, by sympathy, a 
 cessation of the pulsations of the heart and the syncope neces- 
 sarily attending this cessation. Such are the violent emotions of 
 the soul; terror, an excess of joy, an irresistible aversion to cer- 
 tain kinds of food, the dread which is felt on the unexpected 
 sight of an object, the disagreeable impression occasioned by 
 certain odours, &c. In all these cases, there is felt in the region 
 of the diaphragm an inward sensation of a certain degree of 
 emotion. From the solar plexus of the great sympathetic nerve, 
 which, according to the general opinion, is considered as the 
 seat of this sensation, its effects extend to the other abdominal 
 and thoracic plexuses. The heart, the greater part of whose nerves 
 arise from the great sympathetic, is particularly affected by this 
 
OF SENSATIONS. 
 
 376 
 
 sensation. Its action is, at times, merely disturbed by it, and at 
 others wholly suspended. The pulse becomes insensible, the 
 countenance pale, the extremities cold, and syncope ensues. 
 This is the course of things, when a narcotic or poisonous sub- 
 stance has been taken into the stomach; when this viscus is 
 much debilitated in consequence of long fasting, or when it 
 contains indigestible substances; in colic, and in hysterical 
 affections. 
 
 This last class of occasional causes do not act directly, and 
 produce syncope only at a distant period; but the result is 
 always the same. It happens, in all these cases, that as the arte- 
 ries of the head no longer receive as much blood as in health, 
 the brain falls into a kind of collapse, which occasions a mo- 
 mentary cessation of the intellectual faculties, of the vital func- 
 tions, and of voluntary motion. 
 
 Morgagni, in treating of diseases, according to their anatomi- 
 cal order, ranks lypothymia among the affections of the chest; 
 because the viscera contained in that cavity, show marks of 
 organic affection, in persons who, during life, were subject to 
 ' frequent fainting. 
 
 The compression of the brain, by a fluid effused on the dura 
 mater, in wounds of the head, does not produce real syncope, 
 but rather a state of stupor. All causes acting in this manner on 
 the brain, produce comatose and even apoplectic affections. 
 When a man, on being exasperated, falls into a violent and sud- 
 den fit of passion, his face becomes flushed, and he is affected 
 with vertigo and fainting. There is no loss of colour, no loss of 
 pulse; the latter, on the contrary, generally beats with more 
 force. This is not syncope, but the first stage of apoplrxy, oc- 
 casioned by the mechanical pressure on the brain, towards 
 which the blood is carried suddenly, and in too great a quantity. 
 
 I might support this theory of syncope, by additional proofs 
 drawn from the circumstances which favour the action of the 
 causes giving rise to affections of this kind. For instance, syn- 
 cope comes on, almost always, when we are in an erect posture, 
 and in such a case, it is right to lay the patient in an horizontal 
 posture. Patients debilitated by long diseases, faint the moment 
 they attempt to rise, and recover on returning to the recumbent 
 posture. Now, how are we to explain this effect of standing, in 
 
OF SENSATIONS. 
 
 377 
 
 persons in whom the mass of humours is much impoverished, 
 and whose organic action is extremely languid, unless by the 
 greater difficulty to the return of the blood from the more de- 
 pending parts, and on the difficulty in ascending of that which 
 the contractions of the heart send towards the head? The phe- 
 nomena of the circulation are, under such circumstances, more 
 subject to the laws of hydraulics, than when the body is in a 
 state of health; the living solid yields more easily to the laws of 
 physics and mechanics, and, according to the sublime idea of 
 the father of physic, our individual nature approaches the more 
 to universal nature. 
 
 CXLVII. Of the motions of the brain. Are the alternate mo- 
 tions of elevation and depression seen, when the brain is ex- 
 posed, exclusively isochronous to the pulsations of the heart and 
 arteries; or do they correspond, at the same time, to those of 
 respiration? Such is the physiological problem of which I am 
 about to attempt the solution. 
 
 Those authors who admit the existence of motions in the 
 dura mater, do not agree as to the cause which produces them. 
 Some, and among others, Willis and Baglivi, thought they had 
 discovered muscular fibres, and ascribed these motions to their 
 action: others, as Fallopius and Bauhinus, attributed these mo- 
 tions to the pulsations of the arteries of that membrane. The 
 dura mater possesses no contractile power; its firm adhesion to 
 the inside of the skull, would, besides, prevent any such motion. 
 The motion observed in this membrane is not occasioned by 
 the action of its vessels; for, as Lorry observes, the arteries of 
 the stomach, of the intestines, and of the bladder, do not com- 
 municate any motion to the parietes of these hollow viscera, 
 and yet in number and size, they at least equal the menyngeal 
 arteries. 
 
 The motion observed in the dura mater is communicated to 
 it by the cerebral mass which this membrane covers; and this 
 opinion of Galen, adopted by the greater number of anatomists, 
 has been placed beyond a doubt by the experiments of Schlitting, 
 of Lamure, Haller and Vicq-d’Azyr. They have all observed, 
 that on removing the dura mater, the brain continued to rise 
 and fall; and, with the exception of Schlitting, they agreed that 
 the brain, absolutely passive, received from its vessels the mo- 
 
 3 B 
 
OF SENSATIONS. 
 
 378 
 
 tions in which the dura mater partook: but are these motions 
 communicated by the arteries or by the cerebral veins, and by 
 the sinuses in which these terminate? or, in other words, arc 
 they isochronous to the beats of the pulse, or to the contraction 
 and successive dilatation of the chest during respiration? 
 
 Galen, in his treatise on this function, says, that the air ad- 
 mitted into the pulmonary organ distends the diaphragm, and is 
 Conveyed along the vertebral canal into the skull. According to 
 this writer, the brain rises during the enlargement of the chest, 
 and it sinks, on the contrary, when the parietes of this cavity 
 are brought nearer to its axis. Schlitting, in a memoir present- 
 ed to the Academy of Sciences, towards the middle of the last 
 century, maintains that these motions take place in a different 
 order; the elevation of the brain corresponding to expiration, 
 and its depression to inspiration. Conceiving that he has deter- 
 mined this fact by a sufficient number of experiments, he does 
 not enter into any explanation, and concludes his inquiry, by 
 asking whether the motions of the brain are occasioned by the 
 afflux of air, or of blood towards that organ. 
 
 Haller and Lamure attempted to answer this difficulty. They 
 both performed a number of experiments on living animals, ac- 
 knowledged the fact observed by Schlitting, and explained it in 
 the following manner. As well as this last anatomist, Lamure 
 believed that there is a vacuum between the dura and pia mater, 
 by means of which the motions of the brain might always be 
 performed. The existence of such a vacuum is disproved by the 
 close contact of the membranes between which it is supposed to 
 exist. 
 
 During expiration, continues Lamure, the parietes of the chest 
 close on themselves, and lessen the extent of this cavity. The 
 lungs, pressed in every direction, collapse; the curvature of 
 their vessels increases, and the blood flows along them with 
 difficulty. The heart and great vessels thus compressed, the 
 blood carried by the upper vena cava to the right auricle, cannot 
 be freely poured into this cavity, which empties itself, with dif- 
 ficulty, into the right ventricle, whose blood is unable to pene- 
 trate through the pulmonary tissue. On the other hand, as the 
 lungs compress the vena cava, a regurgitation takes place of the 
 blood which it was conveying to the heart; forced back along 
 
OF SENSATIONS. 
 
 37p 
 
 the jugulars and vertebrals, it distends these vessels, the sinus 
 of the dura mater which empty themselves into them, and the 
 veins of the brain which terminate into these sinuses. Their 
 distention accounts for the elevation of the cerebral mass, soon 
 followed by depression, when, on inspiration succeeding expi- 
 ration, and on the lungs dilating, the blood which fills the right 
 cavities of the heart, can freely penetrate into the pulmonary 
 substance, and make way for that which the vena cava is bring- 
 ing from the superior parts of the body. 
 
 Haller considered this reflux as very difficult, the blood 
 having to rise against its own gravity; and he admitted La- 
 mure’s explanation only in the forcible acts of respiration, as in 
 coughing, laughing, and sneezing. He maintained that, in a 
 state of health, there is to be observed during expiration a mere 
 stagnation of the blood, in the vessels which bring it from the 
 internal parts of the skull. He further admits, on the testimony 
 of a great number of authors, another order of motions depend- 
 ing on the pulsations of its arteries; so that, according to Hal- 
 ler, the cerebral mass is incessantly affected by motions, some 
 of which depend on respiration, while the others are quite in- 
 dependent of it. 
 
 Lastly, according to Vicq-d’Azyr, the brain, on being expos- 
 ed, presents a double motion, or rather two kinds of motion 
 from without: the one from the arteries, and which is least re- 
 markable, the other from the alternate motions of respiration. 
 
 CXLVIII. This opposition between authors of reputation, 
 and whose theories have in general been adopted, induced me 
 to repeat the experiments which each of them brings in support 
 of his own opinion, and to perform further experiments on this 
 subject. My investigation soon convinced me, that these au- 
 thors had given a statement of their opinions, and not of the fact 
 itself. In fact, the alternate motions of elevation and depression 
 observed in the brain, are isochronous to the systole and dias- 
 tole of the arteries at its base. The elevation of the brain cor- 
 responds to the dilatation of these vessels, its depression to their 
 contractions. The process of respiration has nothing to do with 
 this phenomenon; and even admitting the stagnation or the 
 regurgitation of the blood in the jugular veins, tfle arrangement 
 
OF SENSATIONS. 
 
 380 
 
 of the veins within the skull is such, that this stagnation or re- 
 flux could not produce alternate motions of the cerebral mass. 
 
 The brain receives its arteries from the carotids and verte- 
 brals, after they have entered the skull; the former along the 
 carotid canals, the latter through the foramen magnum of the oc- 
 cipital bone. It would be useless to describe their numerous 
 divisions, their frequent anastomoses, the arterial circle, or ra- 
 ther polygon, formed by these anastomoses, and by means of 
 which the carotid and vertebral arteries communicate together, 
 by the side of the sella turcica. Haller has given a very correct 
 view, and an excellent description of this part.* The account of 
 the internal carotid artery published by that great anatomist is, 
 according to Vicq-d’Azyr, a chef-d’oeuvre of learning and pre- 
 cision; the same encomium might be bestowed on the latter, 
 who gave a superb drawing of the same part. I shall content 
 myself with observing, that the principal arterial trunks going 
 to the brain, are situated at the base of this viscus; that the 
 branches into which these trunks divide, and the subdivisions of 
 these branches, are, likewise, lodged at its base in a number of 
 depressions; and that, in the last place, the arteries of the brain 
 do not penetrate into its substance, till after they have undergone 
 in the tissue of the pia mater, which appears completely vascu- 
 lar, very minute subdivisions. 
 
 The vessels which return the portion of blood which has not 
 been employed in the nutrition and growth of the brain, are, on 
 the contrary, situated towards its upper part, between its con- 
 vex surface and the arch of the cranium; each convolution con- 
 tains a great vein, which opens into the superior longitudinal 
 sinus. The vena Galeni, which deposits into the sinus the blood 
 brought from the choroid plexus; small veins which open into 
 the carvemous sinuses; others, likewise, very minute, which 
 passing through the foramina in the alae majores of the sphenoid 
 bone, contribute to form the venous plexus of the zygomatic 
 fossae, are the only exceptions to this general rule. 
 
 This being laid down on the arrangement of the arteries and 
 veins, let us examine what will be the effect of their action with 
 regard to this viscus. 
 
 * Fasciculi anatomici. F. 7 . tab. 1. 
 
OF SENSATIONS. 
 
 381 
 
 The contractions of the heart propel the blood into the arterial 
 tubes, which experience, especially at the place of their curva- 
 tures, a manifest displacement at the time of their dilatation. 
 All the arteries situated at the base of the brain, experience 
 both these effects at once. Their united efforts communicate to 
 it a motion of elevation, succeeded by depression, when, by their 
 contraction, they re-act on the blood which fills them. 
 
 These motions take place only as long as the skull remains 
 entire; this cavity is too accurately filled, and there is no void 
 space between the membranes of the brain. Lorry, who, with 
 good reason, denied the existence of such a space, committed 
 an equally serious anatomical mistake in asserting, that as no 
 motion could take place on account of the state of fulness of 
 the skull, it^ was effected in the ventricles, which he considers 
 as real cavities, but which, as Haller has shown, are, when in a 
 natural state, merely surfaces in contact. No motion actually 
 takes place, except in those cases in which there is a loss of 
 substance in the parietes of the skull. 
 
 It is easy to conceive, however, that the brain, which is soft 
 and of weak consistence, yields to the gentle pressure of its 
 arterial vessels. Does not this continued action of the heart on 
 the brain, explain, in a satisfactory manner, the remarkable sym- 
 pathy between those two organs, linked by such close connec- 
 tions? It is, besides, of very manifest utility, and connected with 
 the return of the blood, distributed to the cerebral mass and its 
 envelopes. The veins which bring it back, alternately compress- 
 ed against the arch of the skull, empty themselves more easily 
 into the sinuses of the dura mater, towards which their course 
 is retrograde, and unfavourable to the circulation of the blood 
 which they pour into them. 
 
 When any thing impedes the free passage of the blood through 
 the lungs, it stagnates in the right cavities of the heart; the su- 
 perior vena cava, the internal jugulars, and consequently the 
 sinuses of the dura mater, and the veins of the brain which ter- 
 minate in them, are gradually distended; and if this dilatation 
 were carried to a certain degree, the veins of the brain, placed 
 between it and the arch of the skull, would tend to depress it 
 towards the base of that cavity. If this dilatation, at first slight, 
 were carried beyond the extensibility of these vessels, their rup- 
 
382 SENSATIONS. 
 
 ture would occaslou fatal effusions. It is in this tnanner that 
 some authors have explained sanguineous apoplexy. 
 
 It will be objected, perhaps, that many of the sinuses of the 
 dura mater are at the base of the skull, and that, consequently, 
 their dilatation must tend to raise the cerebral mass. 
 
 But the greater part of these sinuses are connected only with 
 the cerebellum and the medulla oblongata, of which it has not 
 yet been possible to ascertain the motions. These sinuses are 
 almost all lodged in the edges of the falx and of the tentorium 
 cerebelli. The cavernous sinus in which the ophthalmic vein 
 disgorges itself, the communicating sinuses which allow the 
 blood of one of these sinuses to pass into the other, are too 
 insignificant to produce a raising of the cerebral mass. Lastly, 
 the resistance of their parietes, formed chiefly by the dura mater, 
 must set strait bounds to their dilatation; the spungy tissue 
 which fills the interior of the cavernous sinuses, still makes this 
 dilatation and the reflux of the blood more difficult. 
 
 CXLIX. It is not enough to prove, by reasons drawn from 
 the disposition of parts, that the motions of the brain are com- 
 municated to it by the collection of arteries at its base; the fact 
 must yet be established upon observation, and placed beyond 
 doubt by positive experiments. The following are what I have 
 attempted for .this purpose: 
 
 A. I have first repeated the observation of some authors, and 
 ascertained, as they did, that the pulsations felt on placing the 
 finger on the fontanels of the skulls of new-born infants, corres- 
 pond perfectly to the beatings of the heart and arteries. 
 
 B. A patient, trepanned for fracture, with effusion on the 
 dura mater, enabled me to see the brain, alternately rising and 
 falling. The rising corresponded with the diastole, the falling 
 with the systole of the arteries. 
 
 C. Two dogs, trepanned, exhibited the same phenomenon, 
 in the same relation to the dilatation and contraction of the 
 arteries. 
 
 D. I removed carefully the arch of the skull, on the body of 
 an adult. The dura mater, disengaged from its adhesions to the 
 bones which it lines, w’as preserved perfectly untouched. I after- 
 wards laid bare the main carotids, and injected them with water. 
 At every stroke of the piston, the brain showed a very sensible 
 
OF SENSATIONS. 383 
 
 motion of rising, especially when the injection was forced at 
 once along tht two carotids. 
 
 E. I have injected the internal jugular veine. The cerebral 
 mass reiTtained motionless. Only the veins of the brain, the si- 
 nuses of the dura mater dilated. The injection having been kept 
 up for some time, there resulted from it a slight swelling of the 
 brain: when driven with more force, some of the veins burst, anti 
 the liquor flowed out. The same injection being made with 
 water strongly reddened, the surface of the brain became colour- 
 ed with an intense red. To see clearly this effect, you ought, 
 after removing the arch of the skull, to divide on each side the 
 dura mater, on a level with the circular incision of the skull, 
 then turn back the flaps towards the upper longitudinal sinus. 
 
 F. The internal jugular veins having been laid open while the 
 injection was forced along the main carotids, each time the pis- 
 toiT was pushed forward, the venous blood flowed with the 
 greatest impetus; a clear proof of the manifest influence of the 
 motions of the brain on the course of the blood in its veins, and 
 in the sinuses of the dura mater. This experiment had been 
 already performed by other anatomists, and amongst others by 
 Ruysch, with a view of proving the immediate communication 
 between the arteries and veins. This communication, which is, 
 at present, universally acknowledged, may be proved by other 
 facts. This one is evidently any thing but conclusive. 
 
 G. In a trepanned dog, I tied successively the two carotids. 
 The motions of the brain abated, but did not cease. The anas- 
 tomoses of the vertebrals, with the branches of the carotids, 
 account for this phenomenon. 
 
 H. I took a rabbit, a gentle creature, easy to confine, and 
 very well adapted for difficult experiments: after laying bare the 
 brain, and observing that its motions were simultaneous to the 
 beats of the heart, I tied the trunk of the ascending aorta: the 
 moment the blood ceased rising to the head, the brain ceased 
 moving, and the animal died. 
 
 I. The tying of the internal jugular veins, did not stop the 
 motions of the brain; but its veins dilated, and its surface, bared 
 by the removal of a flap of the dura mater, was sensibly redder 
 than in the natural state. The dog became affected with stupor, 
 and expired in convulsions. 
 
OF SENSATIONS. 
 
 384 
 
 The opening of these veins did not hinder the continuance of 
 the motions; they grew fainter only when the animal was weak- 
 ened by loss of blood. 
 
 K. The opening of the superior longitudinal sinus, the only 
 one that could easily be opened, did not weaken the motions of 
 the brain. It is observed that the blood flows out more freely 
 from it during the elevation. 
 
 L. The compression of the thorax, on human bodies, pro- 
 duces but a slight reflux in the jugular veins, especially if, 
 during this compression, the trunk is kept raised. The reflux 
 is greater when the trunk is laid flat. 
 
 These experiments might be varied and multiplied; if, for 
 instance, the injection were thrown, at once, along the vertebral 
 arteries, and the internal carotids; but those I have stated are 
 sufficient for my purpose. 
 
 Since the first publication of this inquiry in the Memoirs of 
 the Medical Society,* I have had many opportunities of repeat- 
 ing the observations and experiments, which serve as a founda- 
 tion to the theory there detailed. Among the facts which con- 
 firm this theory, there is one that appears to me worth stating: 
 it would be sufficient by itself, if it were possible to establish a 
 theory on the observation of a single fact. A woman, about fifty 
 years of age, had an extensive carious affection of the skull; the 
 left parietal bone was destroyed, in the greatest part of its ex- 
 tent, and left uncovered a pretty considerable portion of the 
 dura mater. Nothing was easier than to ascertain the existence 
 of a complete correspondence between the motions of the brain 
 and the beats of the pulse. I desired the patient to cough, to 
 suspend her respiration suddenly; the motions continued in the 
 same relation to each other; when she coughed, the head was 
 shaken, and the general concussion, in which the brain partook, 
 might have been mistaken by a prejudiced observer, for the 
 proper motions of that organ, and depending on the reflux of 
 blood in the veins. 
 
 In experiments on dogs, the same motion takes place when 
 the animal barks; but it is easy to perceive, that the concussion 
 affecting the brain is experienced by the whole body, and that 
 
 • Mdinolres de la Societe M^dicale de Paris, an VII. troiseme annee, pa^e 
 197, et sifiv. 
 
OF SENSATIONS. 385 
 
 the effort of expiration, in barking, causes a concussion more 
 or less violent. 
 
 The patient, mentioned in the preceding observation, died 
 about a month after I came to the Hospital of St. Louis, in 
 which she had been for a considerable length of time. On open- 
 ing the body, the left lobe of the brain was found softened and 
 in a kind of putrid state; the ichor which was formed, in consi- 
 derable quantity, flowed outwardly, by a fistulous opening in 
 the dura mater, whose tissue was rather thickened. 
 
 CL. The slight consistence of the brain, which Lorry con- 
 siders as favourable to the communication of the motion which 
 its arteries impart to it, appears to me to be against this trans- 
 mission. In fact, the dilated vessels not being able to depress 
 the base of the skull on which they rest, make their effort 
 against the cerebral mass, and raise it the more easily (the 
 arch of the skull being removed) from its presenting a certain 
 resistance. If the brain were too soft, the artery would merely 
 swell into it, and would not lift it. To satisfy one’s self of this 
 truth, one need only observe what happens when the posterior 
 part of the knee rests on a pillow, or on any thing of the same 
 sort; then, the motions which the popliteal artery impresses on 
 the limb, are but little apparent; but they become very visible 
 if the ham rests on any thing that resists the action; on the other 
 knee, for instance: then the artery, which cannot depress it, 
 exerts its whole action in raising the lower extremity, which it 
 does the more easily, from acting against a bony, resisting, and 
 hard part. This experiment completely invalidates the opinion 
 of Lorry. The want of analogy will not be objected: it will not 
 be said that the brain is heavier than the lower extremity, nor 
 that the sum of the calibers of the internal carotid and the ver- 
 tebral arteries, is not greater than that of the popliteal artery. 
 
 This continual tendency of the brain to rise, produces in the 
 end, on the bones of the skull which resist this motion, very 
 marked effects. Thus, the interior surface of these bones, 
 smooth, in early life, becomes furrowed with depressions, the 
 deeper as we advance in age. The digital depressions and the 
 mammillary processes, corresponding to the convolutions and 
 windings of the brain, are very evidently the result of its ac- 
 tion on the enclosing parietes. Sometimes it happens that, at a 
 
 3 C 
 
OP SENSATIONS. 
 
 386 
 
 very advanced age, the bones of the skull are so thinned by 
 this internal action, that the pulsations of the brain become 
 perceptible through the hairy scalp. 
 
 No doubt, the same cause hastens the destruction of the skull 
 by the fungous tumours of the dura mater. The effort from ex- 
 pansion of the tumour, which develops itself, is further added, 
 and makes the waste of the bones more rapid. At the end of a 
 few months, the tumour projects outwardly, with pulsations 
 plainly simultaneous to the beatings of the pulse, as Louis ob- 
 serves in a memoir inserted among those of the Academy of 
 Surgery. 
 
 I have shown (CXLVIII.) that the disposition of the veins of 
 the brain and of the sinuses of the dura mater was adverse to 
 the action ascribed to them on this viscus. Experiment (E. L.) 
 shows that the stagnation of the blood, or even its regurgita- 
 tion, could produce only a slow and gradual distention of the 
 sinuses of the dura mater, and veins terminating in it with a 
 slight turgescence of the cerebral mass, if the cause, producing 
 the stagnation of the blood or its reflux, prolonged its action to 
 a partial destruction of the skull. 
 
 Lastly, the alternate motions of the brain, said to correspond 
 to those of respiration, ought to be to the beats of the pulse, in 
 the ordinary ratio of 1 to 5. On the contrary, it is easy to sa- 
 tisfy one’s self that these motions are in an inverse ratio, and 
 perfectly simultaneous to the pulsations of the heart and arteries. 
 
 The results of the experiments I have stated in that memoir, 
 compared to those obtained by justly celebrated inquirers, are 
 too remarkably different not to have induced me to make some 
 attempt at investigating the cause of our disagreement. For 
 that purpose, I thought it necessary to examine scrupulously 
 all the circumstances. 
 
 The work of Lamure contains anatomical errors, which throw 
 suspicions upon his accuracy. Haller did not himself make the 
 experiments of which he speaks, in treating of the influence of 
 respiration on the circulation of venous blood. This article is 
 drawn from a thesis defended at Gottingen by one of his dis- 
 ciples. Lastly, Vicq-d’Azyr attempted no confirming experi- 
 ment, and seems to have had in view only the reconciling all 
 opinions. 
 
OF SENSATIONS. 
 
 387 
 
 No one of these anatomists has distinguished the motions of 
 elevation impressed on the cerebral mass by the impulse of its 
 arteries, from the swelling of the sinuses of the dura mater, of 
 the veins distributed to it, and from the tumefaction of the 
 brain which may be caused by 'difficult respiration. This mis- 
 take would be the more easy, as animals tortured by the knife 
 of the anatomist, breathe painfully, convulsively, and at shorter 
 intervals than in their natural state. Schlitting, the first author 
 of these experiments, appears especially to have confounded the 
 motion of rising, the real displacement of the brain, with the 
 turgescence of this viscus. At every expiration, he says, I have 
 seen the brain rise, that is to say, swell; and at every inspiration 
 I have seen it fall, that is to say, collapse. 
 
 “ Toties animadverti perspicue — in omni expiratione, cere- 
 brum universum ascendere, id est intumescere; at que in quavis 
 inspiratione illud descendere^ id est detumescere. ” 
 
 We may, therefore, consider as a truth strictly demonstrated 
 by observation, experiment, and reasoning, the following pro- 
 position; — 
 
 The motions observable in the brain^ when laid bare, are im- 
 parted to it solely by the pulsations of the arteries at its base, and 
 are perfectly simultaneous to the pulsations of these vessels: fur- 
 ther, the reflux and stagnation of the venous blood, are able to 
 sxvell its substance. 
 
 CL I. Action of the nerves and brain. It is undoubtedly, as 
 Vicq-d’Azyr has said, by a motion of some sort that the nerves 
 act. Setting out from this simple idea, one may admit several 
 kinds of nervous motions, the one operating from the circum- 
 ference to the centre, (it is the motion of sensation which we are 
 about more particularly to study in this paragraph;) the other, 
 acting from the centre to the circumference, and this motion, 
 produced by the will, determines the action of the muscular 
 organs, &c. 
 
 In what manner are the impressions produced on the senses 
 by the bodies which surround us, transmitted, along the nerves, 
 to the brain? Is it through the intervention of a very subtle fluid; 
 or can the nerves, as has been stated by some physiologists, be 
 considered as vibrating cords? This last idea is so absurd, that 
 one cannot help wondering it should so long have been in 
 
OF SENSATIONS. 
 
 3S8 
 
 vogue. A cord, that it may vibrate, must be in a state of ten- 
 sion, along the whole of its length, and fixed at both extre- 
 mities. The nerves are not in a state of tension; their extre- 
 mities, in no degree fixed, approach towards each other or re- 
 cede according to the difference of position, the tension, the 
 turgescence, the fulness or collapse of parts, and vary con- 
 stantly in their distance from each other. Besides, the nervous 
 cords, situated between pulps, at their origin, and at their ter- 
 mination, cannot be extended between these two points. The 
 nervous fibre is the softest, the least elastic of all the animal 
 fibres; when a nerve is divided, its two extremities, far from 
 receding by contracting, project, on the contrary, beyond each 
 other; the point of section shows a number of small granula- 
 tions of medullary and nervous substance, which flows through 
 its minute membranous canals. Surrounded by parts to which 
 they are, to a certain degree, united, the nerves could not 
 vibrate. Lastly, admitting the possibility of their being capa- 
 ble of vibrating, the vibration of a single filament ought to 
 bring on that of all the rest, and carry confusion and disorder 
 in every motion and sensation. 
 
 It is much more probable that the nerves act by means of a 
 subtle, invisible, and impalpable fluid, to which the ancients 
 gave the name of animal spirits; this fluid, unknown in its na- 
 ture, and to be judged of only b)^ its effects, must be wonder- 
 fully minute, since it eludes all our means of investigation. 
 Does it entirely proceed from the brain, or is it equally se- 
 creted by the membranous envelopes of each nervous filament? 
 {Neur'ilemes^ Reil.) To say the truth, one can bring no other 
 proof of the existence of a nervous fluid, but the facility w’ith 
 which, by means of it, we are enabled to explain the various 
 phenomena of sensation, and its utility in explaining these 
 phenomena. These proofs, however, may not appear com- 
 pletely satisfactory to those who are very strict, and who do 
 not consider as proved what is merely probable. 
 
 Among the constituent principles of the atmosphere, there 
 are generally diffused several fluids, such as the magnetic and 
 electric fluids. Might not these fluids, on entering with the air 
 into the lungs, combine with the arterial blood, and be convey- 
 ed, by means of it, to the brain or to the other organs? Does 
 
OF SENSATIONS. 
 
 389 
 
 not the vital action impart to them new qualities, by making 
 them undergo unknown combinations? Do caloric and oxygen 
 enter into these combinations which endow fluids with a certain 
 vitality, and produce on them important changes, and which 
 are not understood?* Have not these conjectures acquired a 
 certain degree of probability, since the analogy of galvanism 
 to electricity, at first supposed by the author of this discovery, 
 has been confirmed by the very curious experiments of Volta, 
 repeated, commented, and explained by all the natural philo- 
 sophers of the present day, in Europe.f 
 
 The action of the nervous fluid takes place from the extre- 
 mity of nerves towards the brain, so as to produce the pheno- 
 mena of sensation; for, when the nerves are tied, the parts be- 
 low the ligature lose the power of sensation, while, as will be 
 seen in the proper place, this action is propagated from the 
 brain towards the nervous extremities, and from the centre to 
 the circumference, in producing motions of every kind. This 
 double current, in contrary directions, may take place in the 
 same nerves, and it is not necessary to arrange the nerves into 
 two classes of sensation and of motion. 
 
 All the impressions received by the organs of sense, and by 
 the sentient extremities of nerves, are transmitted to the cere- 
 bral mass. The brain is, therefore, the centre of animal life; all 
 sensations are carried to it; it is the spring of all voluntary mo- 
 tion; this centre is to the functions of relation, as the heart to 
 the functions of nutrition. One may say of the brain, as of the 
 heart, omnibus dot et ab omnibus accipit. It receives from all, 
 and gives to all. 
 
 The existence of a centre, to which all the sensations are car- 
 ried, and from which all motions spring, is necessary to the 
 unity of a thinking being, and to the harmony of the intellectual 
 functions. But is this seat of the principle of motion and of sensa- 
 tion, circumscribed within the narrow limits of a mathematical 
 
 * Were it not for these changes, electricity, magnetism, and galvanism, 
 would suffice to restore life to an animal recently dead. 
 
 \ Galvanism, as yet, has not realized the expectations of physiologists. 
 Chemistry has derived the greatest advantages from it. — It is, at present, 
 with MM. Davy, Thenard and Gay-Lussac, the most powerful agent in the 
 analysis of certain bodies- 
 
OF SEXSATIOXS. 
 
 390 
 
 point? or rather, should it not be considered as diffused over 
 nearly the whole brain? The latter appears to me the more pro- 
 bable opinion; were it otherwise, what could be the use of those 
 divisions of the organ into several internal cavities? What could 
 be the use of those prominences, all varying in their form, and 
 of the arrangement of the two substances which enter into their 
 structure? We may conjecture, with considerable probability, 
 that each perception, each class of ideas, each faculty, is assign- 
 ed to some peculiar part of the brain. It is, indeed, impossible 
 to determine the peculiar functions of each part of the organ; to 
 say what purpose is served by the ventricles, what is the use of 
 the commissures, what takes place in the peduncles; but it is 
 impossible to study an arrangement of such combination, and to 
 believe that it is without design; and that this division of the 
 cerebral mass into so many parts, so distinct, and of such vari- 
 ous forms, is not relative to the different function which each 
 has to fill in the process of thought. That ingenious comparison, 
 mentioned in the panegyric of Mery, by Fontenelle, is very ap- 
 plicable to the brain. “We anatomists,” he once said to me, 
 “are like the porters in Paris, who are acquainted with the nar- 
 rowest and most distant streets, but who know nothing of what 
 takes place in the houses.” What then are we to think of the 
 system of Gall, and of his division of the outside of the skull 
 into several compartments, which, according to the depression 
 or projection of the osseous case, indicate the absence or the 
 presence of certain faculties, moral or intellectual? I cannot 
 help thinking, that this physiological doctrine of the functions of 
 the brain, resting on too few well observed facts, is frivolous; 
 while his anatomical discoveries on the anatomy of this organ, 
 and' on the nervous system, are of the highest importance, and 
 well founded. 
 
 CLII. Analysis of the Understanding. In vain were the or- 
 gans of sense laid open to all impressions of surrounding objects; 
 in vain were their nerves fitted for their transmission: these im- 
 pressions were to us as if they had never been, were there not 
 provided a seat of consciousness in the brain. For it is there 
 that every sensation is felt; light, and sound, and odour, and 
 taste, are not felt in the organs they impress; it is the sensitive 
 centre that sees, and hears, and smells, and tastes. You have 
 
OF SENSATIONS. 
 
 391 
 
 only to interrupt by compression of the nerves, the communi- 
 cation between the organs and the brain, and all consciousness 
 of the impressions of objects, all sensation is suspended. 
 
 The torturing pains of a whitlow cease, if you bind the arm 
 so strongly as to compress the nerve which carries the sensation 
 to the brain. A living animal, under experiment, suffers nothing 
 from the most cruel laceration, if you have first cut the nerves 
 of the parts on which you are operating. To conclude, the or- 
 gans of sense, and the nerves which communicate between them 
 and the brain, shall have suffered no injury, shall be in a perfect 
 state for receiving and transmitting the sensitive impression, yet 
 no phenomena of sensation can take place, if the brain be dis- 
 eased: when it is compressed, for instance, by a collection of 
 fluid, or by a splinter from the skull in a wound of the head. 
 This organ is, therefore, the immediate instrument of sensa- 
 tions, of which impressions made on the others are only the 
 occasional causes. This modification of sensibility, which serves 
 to establish the relations of the living being with objects with- 
 out, would be correctly denominated cerebral sensibility^ but 
 that even in animals without brain, or distinct nervous system, 
 it is very manifest. The sensibility, in virtue of which the poly- 
 pus dilates its cavity, for the admission of its prey, and con- 
 tracts itself to retain it, is, in fact, quite distinct from that sen- 
 sibility of nutrition^ by which its substance is enabled to take to 
 itself nutritious juices. 
 
 The brain, as Cabanis has well expressed it, acts upon the im- 
 pression transmitted by the nerves, as the stomach upon the 
 aliments it receives by the ossophagus: >it does, in its own way, 
 digest them; set in motion by the impulse it receives, it begins 
 to re-act, and that re-action is the perceptive sensation^ or per- 
 ception. From that moment, the impression becomes an idea, 
 it enters as an element into thought, and becomes subject to the 
 various combinations that are necessary to the phenomena of 
 understanding.* 
 
 CLIII. Our sensations are nothing but modifications of our 
 being; they are not qualities of the objects: no body has colour 
 
 * I ought to observe that the terms thouglit and understanding are, in my 
 opinion, synonimous; both are alike an abridged expression of the whole of 
 the operations of the sensitive centre. 
 
OP SENSATIONS* 
 
 392 
 
 to the blind from birth; the rose has lost its most precious 
 quality to him who has lost his smell; he knows it from the 
 anemone, only by its colour, its figure, &c. We perceive 
 nothing but within ourselves. It is only by habit, only by apply- 
 ing different senses to the examination of the same object, 
 that we are at last able to separate it from our own existence; 
 to conceive of it as distinct from ourselves, and from the other 
 bodies with which we are acquainted; in a word, to refer to out- 
 ward objects the sensations that take place within ourselves. 
 Our ideas come to us only by the senses; there are none innate, 
 as was imagined till the time of Locke, who has allotted to the 
 refutation of this error a large part of his valuable work on the 
 Human Understanding. The child that opens its eyes to the 
 light, is prepared for the acquisition of ideas by this merely, that 
 it has senses; that is, that it is susceptible of impressions from 
 the objects that surround it. 
 
 It is inaccurate, however, to compare, as some philosophers 
 have done, the brain of a child new-born to a blank tablet, on 
 which are to be figured all the future acts of his intelligence. If 
 sensation came only from without, if the external senses were 
 the only organs that could send impressions to the cerebral cen- 
 tre, the understanding, at the moment of birth, had indeed 
 been nothing, and the comparison of its organ to a sheet of 
 white paper, or to a slab of Parian marble, on which not a 
 character were drawn, had been perfectly correct. But we are 
 compelled to acknowledge with Cabanis, two sources of Ideas 
 quite distinct from each other: the external senses, and the inter- 
 nal organs. These inward sensations, springing from functions 
 that are carrying on within us, are the cause of those instinctive 
 determinations, by which the new-born child seizes the nipple of 
 its mother, and sucks the milk by a very complicated process; 
 which directs the young of animals the moment after birth, and 
 sometimes in the very act of birth, while their limbs are yet en- 
 gaged in the vagina, to seize upon the dug of their dam. In- 
 stinct, as the author just quoted has very justly observed, springs 
 from impressions received by the interior organs, whilst reason- 
 ing is the produce of external sensations; and the etymology of 
 the word instinct, composed of two Greek words, signifying 
 
OF SENSATIONS. 393 
 
 “ to prick,” &c. “ within,” agrees with the meaning we assign 
 to it. 
 
 These two parts of the understanding, reason and instinct, 
 unite and blend together, to produce the intellectual system, and 
 the various determinations of mental action. But the part that 
 each bears in the generation of ideas, is very different in ani- 
 mals, whose grosser external senses allow instinct to predomi- 
 nate; and in man, in whom the perfection of these senses, and 
 the art of signs, which perpetuate the transient thought, aug- 
 ment the power of reason, while they enfeeble instinct. It is easy 
 to conceive, that the brain, assailed by a crowd of impressions 
 from without, will regard less attentively, and therefore suffer 
 to escape, the greater part of those that result from internal ex- 
 citation. Instinct is more vigorous in savage man, and its rela- 
 tive perfection is his compensation for the advantages which 
 superior reason brings to man in civilization. The moral and 
 intellectual system of the individual, considered at different 
 periods of life, owes more to internal sensation the less it is 
 advanced; for, instinct declines as reason is strengthened and 
 enlarged. 
 
 Thus, though all the phenomena of understanding have their 
 source in physical sensibility, this sensibility being set in action 
 by two sorts of impressions, the brain of an infant just born, has 
 already the consciousness of those which spring from the inter- 
 nal motion; and it is from these impressions that it executes 
 certain spontaneous movetnents, of which Locke and his fol- 
 lowers could find no explanation; accordingly, the partisans of 
 innate ideas looked upon them as the strongest confirmation of 
 jtheir system; but these ideas, anterior to all action of outward 
 objects on the senses, are simple, few, and extending to a very 
 small number of wants; the child is but a few hours old, and 
 already it expresses a multitude of sensations, that throng upon 
 it from the instant of its birth; sensations, which have passed to 
 the brain, combined themselves there, and entered into the ac- 
 tion of the will with a velocity that equals, if it does not surpass, 
 that of light. 
 
 It is only, after laying down between the sources of our know- 
 ledge a very exact line of demarcation; after scrupulously dis- 
 tinguishing the rational from the instinctive determinations; 
 
 3 D 
 
OP SENSATIONS. 
 
 394 
 
 acknowledging that age, sex, temperament, health, disease, cli- 
 mate, and habit, which modify our physical organization, must, 
 by a secondary effect, modify these last; that we can possibly 
 understand the diversity of humours, of opinions, of characters, 
 and of genius. He who has well appreciated the effect, on the 
 judgment and reason, of the sensations that spring from the ha- 
 bitual state of the internal organs, sees easily the origin of those 
 everlasting disputes on the distinction between the sensitive and 
 the rational soul; why some philosophers have believed man 
 solicited for ever by a good or evil genius, spirits which they 
 have personified under the names of Oromazes and Arimanes, 
 betwixt whom they imagined eternal war; the contest of the 
 8oul with the senses, of the spirit with the flesh, of the concu- 
 piscent and irascible with the intellectual principle, that contra- 
 diction which St. Paul laboured under, when he said in his 
 Epistle to the Romans, that his members were in open war with 
 his reason. These phenomena, which suggest the conception of 
 a two-fold being (^Homo duplex^ Buffon), are nothing but a ne- 
 cessary strife betwixt the determinations of instinct and the de- 
 terminations of reason; between the often times imperious wants 
 of the organic nature, and the judgment which keeps them un- 
 der, or deliberates on the means of satisfying them, without 
 offending received ideas of fitness, of duty, of religion, &c. 
 
 CLIV. A being, absolutely destitute of sensitive organs, 
 would possess only the existence of vegetation: if one sense 
 were added, he would not yet possess understanding, because, 
 as Condillac has shown, the impressions produced on this only 
 sense, would not admit of comparison; it would all end in an 
 inward feeling, a perception of existence, and he would believe 
 the things which affected him to be a part of his being. The 
 fundamental truth, so completely made out by modem meta- 
 physicians, is found distinctly stated in the writings of Aris- 
 totle;* and there is room for surprise that that father of philo- 
 sophy should have merely recognized it, without conforming 
 to its doctrine: but still more that it should have been for so 
 many ages disregarded by his successors. So absolutely is sen- 
 sation the source of all our knowledge, that even the measure. 
 
 J^il est in intellectu, quod non priiis facrit in ftnai. 
 
OF SENSATIONS. 
 
 595 
 
 of understanding is according to the number and perfection of 
 the organs of sense; and that by successively depriving them of 
 the intelligent being, we should lower, at each step, his intel- 
 lectual nature; whilst the addition of a new sense to those we 
 now possess, might lead us to a multitude of unknown sensa- 
 tions and ideas, would disclose to us in the beings we are con- 
 cerned with, a vast variety of new relations, and would greatly 
 enlarge the sphere of our intelligence. 
 
 The impression, produced on any organ, by the action of an 
 outward body, does not constitute sensation; it is further requi- 
 site, that the impression be transmitted to the brain, that it be 
 there perceived^ that is, felt by that organ; the sensation then 
 becomes perception^ and this first modification supposes, as is 
 apparent, a central organ, to which the impressions on the or- 
 gans may be carried. The cerebral fibres are more or less dis- 
 turbed by the sensations sent to them, at once, from all the or- 
 gans of sense; and we should acquire but confused notions of the 
 bodies from which they proceed, if one stronger perception did 
 not silence, as it were, the rest, and fix the attention. In this 
 concentration of the soul upon a single object, the brain is 
 feebly stirred by many sensations that leave no trace; it is thus, 
 that after the attentive perusal of a book, we have lost the sen- 
 sations that were produced by the different colour of the paper 
 and the letters. 
 
 When a sensation is of short duration, our knowledge of it is 
 so light, that soon there remains no remembrance of it. It is 
 thus, that we do not perceive, every time we wink, that we 
 pass from light to darkness, and from darkness to light. If we fix 
 our attention on this sensation, it affects us more permanently. 
 After occupying oneself, for a given time, with a number of 
 things, with but moderate attention to each; after reading, for 
 instance, a novel, full of events, each of which in its turn has 
 interested us, we finish it without being tired of it, and are 
 surprized at the time it has taken up. It is because successive 
 and light impressions have effaced one another, till we have for- 
 gotten all but some of the principal actions. Time ought then 
 to appear to us to have passed rapidly; for, as Locke has well 
 said, in his Essay on the Human Understanding, “ We con- 
 ceive the succession of times only by that of our thoughts.” 
 
OF SENSATION'S. 
 
 396 
 
 This faculty of occupying oneself long and exclusively with 
 the same idea, of concentrating all the intellectual faculties on 
 one object, of bestowing on the contemplation of it alone, a 
 lively and well supported attention^ is found in greater or less 
 strength in different minds: and some philosophers appear to 
 me to have explained, very plausibly, the different capacity of 
 different minds, the various degrees of instruction of which we 
 are capable, by the degree of attention we are able to give to 
 the objects of our studies. 
 
 Who, more than the man of genius, pauses on the examina- 
 tion of a single idea; considers it with more profound reflexion, 
 under more aspects and relations; bestows on it, in short, more 
 entire attention? 
 
 Attention is to be considered as an act of the will, which 
 keeps the organ to one sensation, or prepares it for that sensa- 
 tion, so as to receive it more deeply. To look, is to see with at- 
 tention; to listen, is to hear attentively: the smell, the taste, in 
 the same way, are fixed upon an odour, or a flavour, so as to re- 
 ceive from them the fullest impression. In all these cases, the 
 , sensation may be involuntary; but the attention by which it is 
 heightened, is an act of the will. This distinction has already 
 been well laid down with regard to the feeling, which is only 
 the touch exerted under the direction of the will. 
 
 According to the strength or faintness of the impression that 
 a sensation, or an idea (which is but a sensation operated upon 
 by the cerebral organ), has produced on the fibres of that organ, 
 will be the liveliness and permanence of the recollection. Thus, 
 we may have reminiscence of it, or recal faintly that we have 
 been so affected; or memory^ which is a representation of the 
 object, with some of its characteristic attributes, as colour, 
 bulk, &c. 
 
 The pains that appear to be felt in limbs which we have lost, 
 have not their place in the part that is left; the brain is not de- 
 ceived when it refers to the foot, the cause of the sufferings of 
 which is in the stump, after the amputation of the leg or thigh. 
 I have at this moment before me, the case of a woman and of 
 a young man, whose leg and thigh I took off for scrophulous 
 caries, of many years standing, and incurable by any other 
 means. The wound, from the operation, is completely cica- 
 
0F SENSATIONS. 
 
 397 
 
 trised. The stump has not more sensibility than any other part 
 covered by integuments, since it may be handled without pain. 
 And yet, both, at intervals, and especially when the atmosphere 
 is highly electrified, complain of pains in the limbs which they 
 have lost some month^^ago. They recognize them bv certain 
 characters, for those of their disease. They, like all percep- 
 tions, are manifestly given in charge to the memory, which 
 reproduces them, when the cerebral organ repeats the action, 
 once occasioned by the impressions of the disease. 
 
 Finallj', if the brain is easy of excitation, and at the same 
 time, faithful in preserving the impressions it has received, it 
 will possess the power of bringing up ideas with all their con- 
 nected and collateral ideas; of reproducing them, in some sort, 
 by recalling the entire object, whilst memory presents us with 
 a few of its qualities only. This creative faculty is called ima- 
 gination. If it sometimes produces monsters, it is that the brain, 
 by its power of associating, connecting, combining ideas, repro- 
 duces them in an order not according to nature, gathers them 
 under capricious associations, and gives occasion to many erro- 
 neous judgments. 
 
 When the mind brings together two ideas, when it compares 
 
 them, and determines on their analogy, it judges, A certain 
 number of judgments^ in series, form a reasoning. To reason, 
 
 then, is onljr to judge of the relations that exist among the ideas 
 with which the senses supply us, or which are reproduced b}’- 
 imagination. 
 
 It is with the faculties of the soul, as with those of the body. 
 When called into full exertion, the intellectual organ gains vi- 
 gour; it languishes in too long repose. If we exercise certain fa- 
 culties only, they are greatly developed to the prejudice of the 
 rest. It is thus that, by the study of mathematics, soundness of 
 judgment is acquired, and precision of reasoning, to the extinc- 
 tion of imagination, which never rises to great strength without 
 injury to the judging and reasoning powers. The descriptive 
 sciences employ especially the memory, and it is seldom that 
 they much enlarge the minds of those who study them exclu- 
 sively. 
 
 CLV. Condillac has immortalized his name, by discovering, 
 the first, and by demonstrating irrefragably , that signs are as 
 
OP SENSATIONS. 
 
 398 
 
 necessary to the formation as to the expression of ideas; that 
 language is not less useful for thinking than for speaking; that 
 if we could not attach the notions once acquired to received 
 signs, they would remain always unconnected, and uncom- 
 pleted, since we should have no power to associate and com- 
 pare them, and to determine their relations. It is the imperfec- 
 tion or the total want of signs, for fixing their ideas, that makes 
 the infancy of the lower animals perpetual. It is this that makes 
 it impossible for them to transmit to another generation, or even 
 to communicate one with another, the acquisitions of individual 
 experience: which experience is indeed, by the same cause, re- 
 straixted within very narrow limits, and confined to a few sim- 
 ple notions, a few ideas resting merely on its wants and on its 
 powers. If there were not signs to preserve ideas, and to con- 
 nect them, memory would be nothing, all impressions would be 
 effaced soon after they were felt, all collections of ideas would 
 be dissolved as soon as formed, (if they could be formed at all) 
 our ignorance would be indefinitely prolonged, and we should 
 reach old age, with a mind still in its infancy. 
 
 When we reflect on a subject, it is not directly on the ideas, 
 but on the words expressing them, that the mind operates; we 
 should never have the idea of numbers, if we had not assigned 
 distinct names to numbers, whether single or collected. Locke 
 speaks of some Americans, who had no idea of the number 
 thousand, because the words of their language expressed no- 
 thing beyond the number twenty. La Condamine informs us, 
 in his narrative, that there are some who count only to three, 
 and the word they employ to express the number is so compli- 
 cated, of a pronunciation so long and difficult, that, as Condillac 
 observed, it is not surprising, that having begun with a method 
 so inconvenient, they have not been able to advance any further. 
 “ Deny, (says this writer), to a superior mind, the use of letters, 
 “ how much of knowledge you put out of his reach, which an 
 “ ordinary capacity will attain to without difficulty. Go on, and 
 “ take from him the use of speech, the lot of the dumb wdll 
 “show you, how narrow are the limits within which you con- 
 “fine him. Finally, take from him the use of all sorts of signs, 
 “let him be unable to find the least sign for the most ordinary 
 “ thought, and you have an idiot.”* 
 
 * Esaai sur I’origine des Connoissances humaines, sec. 4-. 
 
OF SENSATIONS. 
 
 399 
 
 We are made acquainted by travellers with certain tribes, so 
 backward in the art of expressing their ideas by signs, that they 
 aeem to serve as a link between civilized nations and certain 
 species of animals, whose instinct has been perfected by educa- 
 tion. One might even assert, that there is less distance, in re- 
 spect to intelligence, from man in that extreme abasement to 
 the higher animals, than there is to a man of superior genius, 
 such as Bacon, Newton, or Voltaire. 
 
 In another part of the same work, after having demonstrated 
 that languages are real analytic methods, that the sciences may 
 be reduced to well constructed languages, he shows how power- 
 ful is their influence in the cultivation of the mind. But he shall 
 speak himself, with that clearness of expression, which is the 
 characteristic and the charm of his writings. “ Languages are 
 like the cyphers of the geometricians; they present new views to 
 the mind, and expand it as they are brought nearer to perfec- 
 tion. The discoveries of Newton had been prepared for him, by 
 the signs that had been already contrived, and the methods of 
 Calculation that had been invented. If he had arisen sooner, he 
 might have been a great man to his own age, but he would not 
 have been the admiration of ours. It is the same in other de- 
 partments.” 
 
 The most scanty languages have been formed in the most 
 barren countries. The savage who strays along the desert shores 
 of New Zealand, needs but few signs to distinguish the small 
 number of objects that habitually impress his senses; the sky, 
 the earth, the sea, fire, shells, the fish, that form his chief food, 
 the quadrupeds, and the vegetables, which are but few in num- 
 ber under this severe climate, are all that he has to name and to 
 know; accordingly, his vocabulary is very small; it has been 
 given to us by travellers in the compass of a few pages. A co- 
 pious language, one capable of expressing a great variety oF ob- 
 jects, of sensations and of ideas, supposes high civilization in the 
 people among whom it is spoken. You hear complaints of the 
 perpetual recurrence of the same expressions, the same thoughts, 
 the same images, in the poetry of Ossian; but living amidst the 
 barren rocks of Scotland, the bards could not speak of things 
 of which nothing, on the soil they inhabited, could supply them 
 with the idea. The monotony of their languages was involved 
 
©F SENSATIONS. 
 
 400 
 
 in that of their Impressions, always produced by rocks, mists, 
 winds, the billows of the ireful ocean, the gloomy heath, and 
 the silent pine, 8zc. The repetition of the same expressions, 
 in the Scriptures, shows that civilization had not made the same 
 progress among the Hebrews, as among the Greeks and Ro- 
 mans. The connexion there is between the genius of a language, 
 and the character of the people that speak it; the influence of 
 climate, of government, and of manners on language; the reason 
 why the great writers, in every department, appear together, at 
 the very time in which a language reaches its perfection and ma- 
 turity, &c.; these are problems that suggest themselves, and 
 would well merit ur endeavours to obtain solution, did not the 
 investigation manifestly lead beyond the limits of our inquiry. 
 
 Though Condillac has said, repeatedly, in his works, that all 
 the operations of the soul are merely sensation, variously trans- 
 formed; that all its faculties are included in the single one of 
 sense; his analysis of thought leaves still much doubt and un- 
 certainty on the real character and relative importance of each 
 of her faculties. 
 
 The merit of dispersing the mist which covered this part of 
 metaphysics, remained for M. Tracy. His Elements of Ideolo- 
 gy,* leave nothing to be wished for on this subject. I shall 
 extract some of its main results, referring the reader for the rest 
 to the work. 
 
 To think is only to feel; and to feel is, for us, the same as t® 
 exist: for, it is by sensation we know of our existence. Ideas, 
 or perceptions, are either sensations, properly so called, or re- 
 collections, or relations which we perceive, or, lastly, the desire 
 that is occasioned in us by these relations. The faculty of 
 thought, therefore, falls into the natural subdivision of sensi- 
 bility, properly termed memory, judgment, and will. To feel, 
 properly speaking, is to be conscious of an impression; to re- 
 member, is to be sensible of the remembrance of a past impres- 
 sion; to judge, is to feel relations among our perceptions; lastly, 
 to will, is to desire something. Of these four elements, sensa- 
 tions^ recollections, judgments, and desires, are formed all com- 
 
 *Elemens dTd&logie, par M. Destutt Tracy, senateur, Membre de 
 ITnstitut. ' 
 
OI-' SENSATIONS. 
 
 401 
 
 pound ideas. Attention is but an act of the ‘will; comparison can- 
 not be separated from judgment, since we cannot compare two 
 objects without judging them; reasoning is only a repetition of 
 the act of judging; to reflect, to imagine, is to compose ideas, 
 analyzable into sensations, recollections, judgments, and desires. 
 This sort of imagination, which is only certain and faithful me- 
 mory, ought not to be distinguished from it. 
 
 Finally, want, uneasiness, inquietude, desire, passions, Scc.are 
 either sensations or desires. There is room, therefore, to re- 
 proach Condillac with having divided the human mind into 
 understanding and will only: because the first term includes 
 actions too unlike, such as sensation, memory, judgment; and 
 with having run into the opposite extreme, in the too great mul- 
 tiplication of secondary divisions. 
 
 CLVI. Disorders of thought. Philosophers would undoubt- 
 edly attain to a much profounder knowledge of the intellectual 
 faculties of man, if they joined to the study of their regular and 
 tranquil action, that of the many disordered actions to which 
 they are liable. It is not enough, if we would understand them 
 aright, to watch their operation when the soul is undisturbed 
 and at ease: we must follow it in its perturbations and wander- 
 ings; we must see its powers, now separating themselves from 
 those with which they ought to act, now combining with them 
 under false perceptions; sometimes altogether drooping, and 
 sometimes starting into an extreme violence of action, of which 
 we can neither mistake the importance nor the nature; and, as 
 the greater part of our ideas are derived from the analogies we 
 are able to discern among the objects that supply them, amidst 
 these troubles of human passion and human reason, we learn to 
 conceive more profoundly of their nature, than if we had been 
 satisfied with observing them in the calm of their natural con- 
 dition. 
 
 The observation of mania is yet too imperfect in the number, 
 variety, and precision of its facts, to fix the classification of the 
 species of mental alienation, according to the intellectual faculty 
 that is disordered in each. Professor Pinel has, nevertheless, 
 ventured to ground his distinctions of the species of mania, on 
 the labours of modern psychologists, and shown that all might 
 be referred to five kinds, which he marks by the names of 
 
 3 E 
 
OP SENSATIONS. 
 
 402 
 
 melancholy, of mania without delirium, mania with delirium, 
 dementia, and idiotcv.* In the first four kinds, there is perver- 
 sion of the mental faculties, which are in languid or excessive 
 action. We are not to look for the cause of these derangements 
 in vice of original conformation; for, melancholy, mania with or 
 without delirium, and madness, scarcely ever appear before pu- 
 berty. It is agreed, among observers, that almost all maniacs 
 have become so between twenty and forty years old; that very 
 few have lost their reason either before or after this stormy pe- 
 riod of life, wherein men, yielding, by turns, to the torments of 
 love and of ambition, of fear and of hope, to the sweet illusions 
 of happiness, and the realities of suffering, consumed with pas- 
 sions for ever reviving, often repressed, and rarely satisfied, feel 
 their intellectual powers impaired, annihilated, or abased by 
 that tempest of the moral nature, which has well been compared 
 to the storms which, in their violence, lay desolate the flourish- 
 ing earth. 
 
 We are compelled to grant, that our acquaintance with the 
 structure of the brain and of the nerves is too imperfect, that 
 dissections of the bodies of maniacs have been too few, and 
 those often by physiciansf too little familiar with the minute 
 structure of the sensitive organ, to warrant us in asserting or 
 denying, that derangement of intellect depends constantly on 
 organic injury; though it is highly probable, many facts at least, 
 collected by observers, who, like Morgagni, deserve the utmost 
 confidence, authorize the belief, that the consistence of the brain 
 is increased in some maniacs, who are distinguished by the 
 most obstinate and unvarying adherence to their ruling ideas; 
 that it is, on the other hand, soft, watery, and in a kind of inci- 
 pient dissolution in some others, whose incoherent ideas, after 
 their aptitude for association, and for transformation into judg- 
 ments is gone, succeed one another rapidly, and seem to pass 
 away without a trace, &c. 
 
 If, in the multitude of maniacs, the organ of the understand- 
 ing suffer only imperceptible injury, it is very remarkably 
 
 • For more ample ^.vptanafWhrl must refer to the work. Traits medico-phi- 
 Itsophique si(r i’.dliination mentate ou par P. Pinel. Paris, 1800. 
 
 This censure is especially applicable to the researches of Dr. Greding. 
 
OP SENSATIONS. 
 
 403 
 
 changed in idiots. The almost entire obliteration of the intel- 
 lectual faculties, which constitutes idiotcy, when it is not 
 brought on by some strong and sudden shock, some unex- 
 pected and overwhelming emotion, breaking down at once 
 all the springs of thought, when it is an original defect, is 
 always connected with mal-conformation of the skull, with 
 the constraint of the organs it encloses. These defects of or- 
 ganization lie, as M. Find observes, in the excessive small- 
 ness of the head, to the whole stature, or to the want of pro- 
 portion among the different parts of the skull. Thus in the 
 idiot, whose head is given in the work on mania, (pi. 2, fig. 6.) 
 it is only the tenth of the whole height, whilst it should be 
 something more than a seventh, if we take the Apollo of Bel- 
 vedere as the type of the ideal perfection of the human figure. 
 An idiot, whom I occasionally see, has the occipital extremity 
 of the head so much contracted, that the large extremity of 
 the oval formed by the upper face, instead of being placed 
 at the back, as in other men, is, on the contrary, turned for- 
 wards and answers to the forehead, which itself slopes towards 
 the sinciput. The vertical diameter of the skull is inconside- 
 rable. The head, thus shortened from above downwards, is 
 much flattened on the sides. The hands and feet are very 
 small, and often cold; the genitals, on the contrary, are ex- 
 tremely large. 
 
 In two other children, equally idiots, and now in the hospital 
 of St. Louis, the skull, very large behind, ends in a very con- 
 tracted extremity, and the forehead is very short, and not more 
 than two inches and a half wide, measuring from the semi-cir- 
 cular process which terminates, at the upper part, the temporal 
 fossa, to the commencement of the same process on the other 
 side. The excessive growth of the genitals is not less conspi- 
 cuous; they are, in these two children, one ten, the other twelve 
 years old, as well as in the first of whom I spoke, who is four- 
 teen, of larger size than is commonly seen after the appearance 
 of puberty. There is nothing to indicate that this season is at- 
 tained by these three idiots. • . 
 
 The same excess of growt^^s found more conspicuously 
 among the cretins of the Valais, idiots who (in consequence 
 
OF SENSATIONS; 
 
 404 
 
 of a weak and degraded organization) are prone to lascivious- 
 ness and the most frequent onanism. 
 
 This sort of opposition in the relative energy of the intellec- 
 tual organ, and of the system of reproduction, in the develop- 
 ment of the brain, and that of the parts of generation, is a phe- 
 nomenon which must stronglj' interest the curiosity and engage 
 the attention of physiologists. Who is there unacquainted with 
 that enervation of the understanding, that intellectual and phy- 
 sical debility, which indulgence in the pleasures of love brings 
 on, if we exceed ever so little the bounds of scrupulous mode- 
 ration? Castration modifies the moral character of men and ani- 
 mals, at least, as powerfully as their physical organization, as 
 M. Cabanis has shown, in treating of the influence of the sexes 
 on the origin and growth of the moral and intellectual powers. 
 
 CLVII. Our physical, therefore, holds our moral nature un- 
 der a strict and necessary dependance; our vices and our vir- 
 tues, sometimes produced and often modified by social educa- 
 tion, are frequently, too, results of organization. To the conclu- 
 sive proofs which the philosopher I have just named, who is an 
 honour to his profession, brings forward of the influence of the 
 physical on the moral human being, I will only add a single ob- 
 servation. It is not, certainly, the first that has been made of 
 the kind; but none such, I believe, has yet been published. The 
 reader recollects, I have no doubt, the old woman of whom 
 I have spoken in treating of the motions of the brain, which an 
 enormous caries of the bones of the skull gave an opportunity 
 of observing in her. I wiped off the sanious matter which co- 
 vered the dura mater, and I, at the same time, questioned the 
 patient on her situation; as she felt no pain from the compres- 
 sion of the cerebral mass, I pressed down lightly the pledget of 
 lint, and on a sudden the patient, who was answering my ques- 
 tions rationally, stopped in the midst of a sentence: but she went 
 on breathing and her pulse continued to beat: I withdrew the 
 pledget; she said nothing: I asked her if she remembered my 
 last question: she said not. Seeing that the experiment was 
 without pain or danger, I repeated it three times, and thrice 
 I suspended all feeling and all intellect. 
 
 A man trepanned for a fracture of the skull, with effusion of 
 blood and pus on the dura mater, perceived his intellectual fa- 
 
QF SENSATIONS. 
 
 405 
 
 culties going, the consciousness of existence growing benumbed 
 and threatening to cease, in the interval of each dressing, in pro- 
 portion as the fluid collected. 
 
 There are surgical observations on wounds of the head con- 
 taining several facts that may be connected with th<5 preceding 
 observations. There is no one who has had syncope of more or 
 less continuance, but knows that the state is without pain or un- 
 easiness, and leaves no consciousness of what passed whilst it 
 lasted. It is the same after an apoplexy, a fit of epilepsy, &c. 
 
 The history of temperaments supplies us with too many ex- 
 amples of the strict connexion which there is between the phy- 
 sical organization and the intellectual and moral faculties, to 
 leave any necessity for dwelling longer on this truth, which no 
 one questions, but which no philosopher has yet followed into 
 all its consequences. 
 
 CLVIII. An English writer, in a work on the history of 
 mental alienation,* has traced, better than had before been 
 done, the physiological history of the passions, which he looks 
 upon as mere results of organization, ranking them among the 
 phenomena of the animal economy, and with abstraction of any 
 moral notion that might attach to them. 
 
 All passion is directed to the preservation of the individual 
 or the reproduction of the species. They may be distinguished, 
 therefore, like the functions, into two classes. In the second, we 
 should find parental love, and all the affections that protect our 
 kind through the helplessness of its long infancy. 
 
 But Crichton, with the greater part of metaphysicians and 
 physiologists, appears to me not to, have settled correctly the 
 meaning that should belong to the word passion. When he 
 gives this name to hunger, an inward painful sensation, the 
 source of many determinations of many kinds, a powerful 
 mover of savage and civilized man,- — to the anxiety which 
 attends the breathing an air deficient in oxygen, — to the im- 
 pressions of excessive heat and cold, — to the troublesome sen- 
 sation produced by the accumulation of urine and fecal mat- 
 ter, — to the feeling of weariness and fatigue that is left b} 
 
 * An Inquiry into the Nature and Origin of Mental Derangement — London, 
 1798 . 2 vols. 8vo. 
 
OF SENSATIONS. 
 
 406 
 
 violent exertions,— -he confounds sensation with the passions 
 or desires which may spring from it. 
 
 It is to avoid extreme wants, of which a vigilant foresight 
 perceives afar off the possibility, — it is to satisfy all the facti- 
 tious wants which society and civilization have created, that 
 men condemn themselves to those agitations, of which honour, 
 reputation, wealth, and power, are the uncertain aim. Our pas- 
 sions have not yet been analyzed with the same care as our 
 ideas: no one has yet duly stated the diflFerences there are, in 
 respect to their number and energy, betwixt savage man, and 
 man in the midst of civilized and enlightened society. 
 
 As the habitual state of the stomach, of the lungs, of the liver 
 and internal organs, is connected with certain sets of ideas;— a» 
 every vivid sensation of joy or distress, of pleasure or pain, 
 brings on a feeling of anxiety in the praecordia,— the ancients 
 placed in the viscera the seat of the passions of the soul: they 
 placed courage in the heart, anger in the liver, joy in the spleen, 
 &c. Bacon and Van Helmont seated them in the stomach; Le- 
 cat in the nervous plexuses; other physiologists in the ganglions 
 of the great sympathetics, &c. But have they not confounded 
 the effect with the cause? the appetite with the passion to which 
 it disposes? The appetites, out of which the passions spring, re- 
 side in the organs, they suppose only instinctive determinations, 
 whilst passion carries with it the idea of intellectual exertion. 
 Thus, the accumulation of semen in the vesiculae, which serve 
 for its reservoirs, excites the venereal appetite, quite distinct 
 from the passion of love, though often its determining cause. 
 Animals have scarcely more than appetite, which differs as 
 much from passion as instinct from intelligence. However, 
 the brain is not to be considered as the primitive seat of the 
 passions,* as is done by the greater number of philosophers. 
 Of all the feelings of man, the most lasting, the most sacred, 
 the most passionate, the least susceptible of injury from all the 
 
 * If we analyzed the passions carefully, it would be right to distinguish 
 those which are connraon to all men, whicii appertain to our physical wants and 
 to our nature, from certain caprices of the mind which have been honoured 
 with the name of passions, as avarice, ambition, erroneous calculations which 
 should be referred to mental derangement, and classed among the different 
 kinds of insanity. 
 
OF SENSATIONS. 
 
 407 
 
 prejudices of the social state, maternal love, is surely not the re- 
 sult of any intellectual combination, of any cerebral action; it is 
 in the bowels (entrailles)^ its source lies; thence it springs, and 
 all the efforts of imagination cannot attain it for those who have 
 not been blessed with a mother’s name. 
 
 All passion springs from desire, and supposes a certain de- 
 gree of exaltation of the intellectual faculties. The shades of the 
 passions are infinite; they might be all arranged by a systematic 
 scale, of which indifference would be the lowest gradation, and 
 maniacal rage the highest. A man, without passions, is as im- 
 possible to imagine, as a man without desires; yet we distin- 
 guish as passionate, those whose will rises powerfully towards 
 one object earnestly longed for. In the delirium of the passions, 
 we are for ever making, unconsciously, false judgments, of which 
 the error is exaggeration. A man recovering from a seizure of 
 fear, laughs at the object of his terror. Look at the lover whose 
 passion is extinct: freed at last from the spell that enthralled him, 
 all the perfections with which his love had invested its object 
 are vanished; the illusion has passed away; and he can almost 
 believe that it is she who is no longer the same, while himself 
 alone is changed; like those maniacs who, on their return to rea- 
 son, wonder at the excesses of their delirium, and listen, incre- 
 dulously, to the relation of their own actions. The ambitious 
 man feeds on imaginations of wealth and power. He who hates, 
 exaggerates the defects of the object of his hatred, and sees 
 crimes in his lightest faults. 
 
 The affections of the soul, or the passions, whether they come 
 by the senses, or some disposition of the vital organs favour 
 their birth and growth, may be ranged in two classes, according 
 to their effects on the economy. Some heighten organic activity; 
 such are joy, courage, hope, and love: whilst others slacken the 
 motions of life; as fear, grief, and hatred. And others there are, 
 that produce the two effects alternately or together. So ambi- 
 tion, anger, despair, pity, assuming, like the other passions, an 
 infinite variety of shades, according to the intensity of their 
 causes, individual constitution, sex, age, &c. at times increase, 
 at times abate the vital action, and depress or exalt the power of 
 the organs. 
 
OF SENSATIONS. 
 
 408 
 
 The instances which establish the powerful influence of the 
 passions on the animal economy, are too frequent to need re- 
 citing. Writers, in every department, furnish such as show, 
 that excess of pleasure, like excess of pain, joy too lu'ely or too 
 sudden, as grief too deep and too unexpected, may bring on the 
 roost fatal accidents, and even death. Without collecting, in this 
 place, all the observations of the sort with which books swarm, 
 I shall content myself with referring to those, who have brought 
 together the greatest number of facts under one point of view; 
 as Haller, in his Physiology; Tissot, in his Treatise on Diseases 
 of the Nerves; Lecamus, in his work on Diseases of the Mind; 
 Bonnefoy, in a paper On the Passions of the Soul, inserted in 
 the fifth volume of the Collection of Prizes, adjudged by the 
 Academy of Surgery. 
 
 The effects of the passions are not, for their uniformity, the 
 less inexplicable. How, and why does anger give rise to mad- 
 ness, to suppression of urine, to sudden death? How does fear 
 determine paralysis, convulsions, epilepsy, 8tc.? Why does ex- 
 cessive joy, a sense of pleasure carried to extremity, produce 
 effects as fatal, as sad and afflicting impressions? In what way 
 can violence of laughter lead to death? Excess of laughter killed 
 the painter Zeuxis and the philosopher Chrvsippus, according 
 to the relation of Pliny. The conversion of the reformed of the 
 Cevennes, under Louis XIV, was effected by binding them on, 
 a bench, and tickling the soles of their feet, till, overpowered by 
 this torture, they abjured their creed; many died in the convul- 
 sions and immoderate laughter which the tickling excited. A 
 hundred volumes would be insufficient to detail all the effects 
 of the passions on physical man; how many would it take to tell 
 their history in moral man, from their dark origin, through all 
 their stages of growth, in the infinite variety of their characters, 
 and in all their evanescent shades! 
 
 The inquiries of physiology are directed to the functions that 
 are carried on in physical man, to the functions of life; the 
 study of the nobler parts of ourselves, of those wonderful facul- 
 ties which place our kind above all that hav'e motion or life; in 
 a word, the knowledge of moral and intellectual man, belongs to 
 the science known by the name of metaphysics or psychology, 
 of analysis of the understanding, but better described by that 
 
OF SENSATIONS. 
 
 409 
 
 applied to it by the writers of our days, ideology. On this sci- 
 ence, you may consult, with advantage, the philosophical works 
 of Plato and Aristotle among the ancients; of Bacon, Hobbes, 
 Locke, Condillac, Bonnet, Smith, Cabanis, and Tracy among 
 the moderns. 
 
 CL IX. Of sleep and -waking. The causes of excitation to 
 which our organs are exposed during waking, tend to increase 
 progressiyely their action; the pulsations of the heart, for in- 
 stance, are much more frequent in the eyening than in the 
 morning, and this motion, gradually accelerated, would soon be 
 carried to a degree of actiyity incompatible with the continuance 
 of life, did not sleep daily temper this energy, and bring it 
 down to its due measure. Feyer is occasioned by long continued 
 want of sleep, and in all acute diseases, the exacerbation comes 
 on towards evening; the night’s sleep abates again the high ex- 
 citation of power; but this state of the animal economy, so 
 salutary and so desirable in all sthenic affections, is more in- 
 jurious than useful in diseases, consisting chiefly in extreme 
 debility. Adynamy shows itself, almost always, in the morning, 
 in putrid fevers; and petechias, a symptom of extreme weakness, 
 break out during sleep. This state is, likewise, favourable to the 
 coming on and to the progress of gangrene, and this is a patho- 
 logical fact well ascertained. In all the cases I have mentioned, 
 sleep does not improve the condition of the patients; a thing 
 easy to conceive, since it only adds to accidental debility, the 
 essential characteristic of the disease, weakness, which is also 
 its principal characteristic. 
 
 Sleep, that momentary interruption in the communication of 
 the senses with outward objects, may be defined the repose of 
 the organs of sense, and of voluntary motion. During sleep, the 
 inward or assimilating functions are going on: digestion, ab- 
 sorption, circulation, respiration, secretion, nutrition, are carried 
 on; some, as absorption and nutrition, with more energy than 
 during waking, whilst others are evidently slackened. During 
 sleep, the pulse is slower and weaker, inspiration is less fre- 
 quent, insensible perspiration, urine, and all other humours de- 
 rived from the blood, are separated in smaller quantity. Ab- 
 sorption is, on the contrary, very active; hence the danger of 
 falling asleep in the midst of a noxious air. It is known, that the 
 
 3 F 
 
OP SENSATIONS. 
 
 410 
 
 marshy effluvia, which make the Campagna di Roma so un- 
 healthy, bring on, almost inevitably, intermittent fevers, when 
 the night is passed there; whilst travellers who go through with- 
 out stopping, are not affected by it. 
 
 The human body is a tolerable representation of the centri- 
 petal and centrifugal powers of ancient physics. The motion of 
 many of the systems which enter into its structure, is directed 
 from the centre to the circumference; it is a real exhalation that 
 carries out the result of the perpetual destruction of the organs; 
 such is the action of the heart, of the arteries, and of all the 
 secretory glands. Other actions, on the contrary, take their di- 
 rection from the circumference to the centre; and it is by their 
 means, that we are incessantly deriving from the food we take 
 into the digestive passages, from the air which penetrates the 
 interior of the lungs, and covers the surface of the body, the 
 elements of its growth and repair. These two motions, in oppo- 
 site directions, continually balance each other, prevailing by 
 turns, according to the age, the sex, the state of sleep or waking. 
 During sleep, the motions tend from the periphery to the cen- 
 tre. (Hipp.) and if the organs that connect us with outward ob- 
 jects are in repose, the inward parts are in stronger exertion. 
 Somnus labor visceribus, (^Hipp.') A man, aged forty years, 
 taken with a kind of imbecility, remained about a year and a 
 half at the Hospital of St. Louis, for the cure of some scrophu- 
 lous glands; all that long time he remained constantly in bed, 
 sleeping five sixths of the day, tortured with devouring hunger, 
 and passing his short moments of waking in eating; his diges- 
 tion was always quick and easy; he kept up his plumpness, though 
 the muscular action was extremely languid, the pulse very weak 
 and very slow. Irj this man, who, to use the expression of Bor- 
 deu, lived under the dominion of the stomach, the moral affec- 
 tions were limited to the desire of food and of repose. Oppres- 
 sed with irresistible sloth, it was never without great difiiculty 
 that he could be brought to take the slightest exercise. 
 
 Waking may be looked upon as a state of effort, and of consi- 
 derable expenditure of the sensitive and moving principle, by 
 the organs of sensation and of motion. This principle would 
 have been soon exhausted by this uninterrupted effusion, if long 
 intervals of repose had not favoured its restoration. This inter- 
 
OF SENSATIONS. 
 
 411 
 
 ruption in the exef else of the senses and of voluntary motion, is 
 of duration corresponding to that of their exertion. I have al- 
 ready said, that there are functions of such essential importance 
 to life, that their organs could be allowed but short moments of 
 repose: but that these intervals are brought so close "to each 
 other, that their time is equally divided between activity and 
 repose. The functions which keep up our connexion with out- 
 ward objects, could not be without the capacity of continuing, 
 for a certain time, in a state of equal activity; for it is easy to 
 see how imperfect relations, interrupted at every moment, would 
 have been; their repose, which constitues sleep, is of equal 
 duration. 
 
 The duration of sleep is from a fourth to a third of the day; 
 few sleep less than six hours, or more than eight. Children, how- 
 ever, require longer sleep, the more, the nearer they are to the 
 period of their birth. Old men, on the contrary, have short sleep, 
 light, and broken: as if, says Grimaud, according to Stahl’s no- 
 tions, children foresaw that in the long career before them, there 
 were time enough for performing, at leisure, all the acts of life, 
 while old men near to their end, felt the necessity of hurrying 
 the enjoyment of a good already about to escape. 
 
 If the sleep of a childis long, and deep, and still, it is the won- 
 derful activity of the assimilating functions that makes it so, and 
 perhaps the habit itself of sleep, in which he has passed the first 
 nine months of his life, or all the time before his birth. In ad- 
 vanced age, the internal functions grow languid; their organs no 
 longer engage the action of the principle of life; and the brain is 
 moreover so crowded with ideas, that it is almost always kept 
 awake by them. Carnivorous animals sleep longer than grami- 
 nivorous animals, because during waking they are more in mo- 
 tion, and perhaps, too, because the animal substances on which 
 they subsist, yielding them more nutritious particles, from the 
 same bulk, they have need of less time for devouring their food 
 and providing for their subsistence.* 
 
 * Probably their more powerful digestion of a more nutritious food, bringing 
 into the system a more sudden accession of blood, oppresses them with 
 sleep: — a sleep and a fulness of blood required to recruit the powers that have 
 been exhausted by the laborious quest of food, and by the long continued en- 
 durance of hunger. T. 
 
412 SENSATIONS. 
 
 Sleep is a state essentially different from death, to which some 
 authors have erroneously likened it.* It merely suspends that 
 portion of life, which serves to keep up with outward objects an 
 intercourse necessary to our existence. One may say that sleep 
 and waking call each other, and are of mutual necessity. The 
 organs of sense and motion, weary of acting, rest; but there are 
 many circumstances favouring this cessation of their activity. 
 A continual excitation of the organs of sense would keep them 
 continually awake; the removal of the material causes of our 
 sensations tends, therefore, to plunge us into the arms of sleep: 
 wherefore we indulge in it more voluptuously in the gloom and 
 the stillness of night.f Our organs fall asleep one after the other; 
 the smell, the taste, and the sight are already at rest, when the 
 hearing and the touch still send up faint impressions. The per* 
 ceptions, awhile confused, in the end disappear; the internal 
 senses cease acting, as well as the muscles allotted to voluntary 
 motion, whose action is entirely subject to that of the brain. 
 
 Sleep is a state, if not altogether passive, in which, at least, 
 the activity of most of the organs is remarkably diminished, 
 and that of some of them completely suspended. It is erro- 
 neously then, that some authors have viewed it as an active 
 phenomenon, and a function of the living economy: it is only a 
 mode or manner of being. It is to no purpose they have main- 
 tained, that to sleep required some measure of strength. Ex- 
 cessive fatigue hinders sleep, merely by a sense of pain in all 
 the muscles, a pain that excites anew the action of the brain, 
 which it keeps awake, till it is itself overpowered by sleep. 
 
 It has been attempted to show the proximate cause of sleep. 
 Some have said that it depends on the collapse of the laminae of 
 the cerebellum, which, as they conceive, are in a state of erection 
 during waking; and they argue from the experiment in which 
 by compressing the cerebellum of a living animal, sleep is im- 
 
 * To say that slee[) is the image of death, that vegetables sleep always, is 
 ito use an inaccurate and unmeaning expression. How can plants, without 
 brain or nerves, without organs of sense, motion, or voice, sleep; when sleep 
 is nothing but the repose of these organs? 
 
 t The tissue of the eye-lids is not so opake but we may distinguish through 
 them light from darkness; accordingly a lighted torcli, in the room, hinders us 
 from sleeping. For the same reason, day succeeding to night awakens us. 
 
OF SENSATIONS. 
 
 41S 
 
 mediately brought on. This sleep, like that produced by com- 
 pression of any other part of the cerebral mass, is really a state 
 of disease; and no more natural than apoplexy. Others, con- 
 ceiving sleep, no doubt, analogous to this affection, ascribe it to 
 the collection of humours upon the brain, during waking. This 
 organ, say they, compressed by the blood which obstructs its 
 vessels, falls into a state of real stupor. An opinion as unsup- 
 ported as the other. As long as the humours flow in abundance 
 towards the brain, they keep up in it an excitement which is al- 
 together unfavourable to sleep. Do we not know, that it is 
 enough that the brain be strongly occupied by its thoughts, or 
 vividly affected, in any way, to repel sleep? Coffee, spirituous 
 liquors, in small quantities, will produce sleeplessness, by ex- 
 citing the force of circulation, and determining towards the 
 brain, a more considerable afflux of blood. All, on the other 
 hand, that may divert this fluid towards another organ, as 
 copious bleedings, pediluvium, purges, digestion, copulation, 
 severe cold, or whatever diminishes the force with which it 
 is driven towards it, as inebriation, general debility, tends pow- 
 erfully to promote sleep. In like manner, is it observed, that 
 while it lasts, the cerebral mass collapses; a sign that the flow 
 of blood into it is remarkably lessened. 
 
 The organs of the senses, laid asleep, in succession, awake in 
 the same manner. Sounds and light produce impressions, con- 
 fused at first, on the eyes and ears; in a little time, these sensa- 
 tions grow distinct; we smell, we taste, we judge of bodies by 
 the touch. The organs of motion prepare for entering into ac- 
 tion, and begin to act, at the direction of the will. The causes 
 of waking operate by determining a greater flow of blood into 
 the brain: they include all that can affect the senses, as the re- 
 turn of light and of noise with the rising of the sun; at times, 
 they act within us. Thus, urine, fecal matter, other fluids accu- 
 mulated in their reservoirs, irritate them, and send up, towards 
 the brain, an agitation which assists in dispelling slumber. Ha- 
 bit too, acts upon this phenomenon, as on all those of the ner- 
 vous and sensitive system, with most remarkable influence. 
 There are many that sleep soundly amidst noises which, at 
 first, kept them painfully awake. Whatever need he may have 
 of longer repose, a man that has fixed the daily hour of his 
 
OP SENSATIONS. 
 
 414 
 
 awaking, will awake every morning to his hour. It is as much 
 under the control of the will. It is enough to will it strongly, 
 and we can awake at any hour we choose. 
 
 GLX. Of dreams and somnambulism. Although sleep implies 
 the perfect repose of the organs of sensation and of motion, some 
 of these organs persist in their activity; which obliges us to ac- 
 knowledge intermediate states between sleep and waking, real 
 mixed situations, which belong, more or less, to one or to the 
 other. Let us suppose, for instance, that the imagination repro- 
 duces, in the brain, sensations it has formerly known, the intel- 
 lect works, associates and combines ideas, often discordant, and 
 sometimes natural, brings forth monsters, horrible, or fantastic, 
 or ridiculous; raises joy, hope, grief, surprise or terror; and all 
 these fancies, all these emotions are recollected more or less dis- 
 tinctly, when we are again awake, so as to allow no doubt but 
 that the brain has been really in action, during the repose of the 
 organs of sense and motion. Dreams is the name given to these 
 phenomena. Sometimes we speak in sleep, and this brings us a 
 little nearer to the state of waking, since to the action of the 
 brain is added that of the organs of speech. Finally, all the re- 
 lative functions are capable of action, excepting the outward 
 senses. The brain acts, and determines the action of the organs 
 of motion or speech, only in consequence of former impressions, 
 and this state, which differs from waking, only by the inaction 
 of the senses, is called somnambulism. 
 
 On this head we meet with surprising relations. Somnambu- 
 lists have been seen to get up, dress, go out of the house, open- 
 ing and shutting carefully all the doors, dig, draw water, hold 
 rational and connected discourse, go to bed again, and awake 
 without any recollection of what they had said and done in their 
 sleep. This state is always very perilous. For as they proceed 
 entirely upon former impressions, somnambulists have no warn- 
 ing from their senses of the dangers they are near. Accord- 
 ingly, they are often seen throwing themselves out of a win- 
 dow, or falling from roofs, on which they have got up, without 
 being on that account more dexterous in balancing themselves 
 there, as the vulgar believe, in their fondness for the marvellous. 
 
 Sometimes, one organ of sense remains open to impression, 
 and then you can direct, at pleasure, the intellectual action. 
 
OP SENSATIONS. 
 
 415 
 
 Thus, you will make him that talks in his sleep, speak on what 
 subject you choose, and steal from him the confession of his 
 most secret thoughts. This fact may be cited in proof of the 
 errors of the sensed, and of the need there is to correct them 
 by one another. 
 
 The condition of the organs influences the subject of the 
 dreams. The superabundance of the seminal fluid provokes 
 libidinous dreams; those labouring under pituitary cachexies 
 will dream of objects of a hue like that of their humours. The 
 hydropic dreams of waters and fountains, whilst he who is suf- 
 fering with an inflammatory affection, sees all things tinged red, 
 that is, of the colour of blood, the predominant humour. 
 
 Difficult digestion disturbs sleep. If the stomach, over-filled 
 with food, hinders the falling of the diaphragm, the chest dilates 
 with difficulty, the blood, which cannot flow through the lungs, 
 stagnates in the right cavities of the heart, and a painful sensa- 
 tion comes on, as if an enormous weight lay upon the chest, 
 and were on the point of producing suffocation: we awake with 
 a start, to escape from such urgent danger: this is what we call 
 night- mare, an affection that may arise from other causes, hy- 
 drothorax, for instance, but which always depends on the diffi- 
 cult passage of blood through the lungs. 
 
 The intellectual faculties which act in dreams, may lead us 
 to certain orders of ideas, which we have not been able to com- 
 pass while awake. 
 
 Thus mathematicians have accomplished in sleep, the most 
 complex calculations, and resolved the most difficult problems. 
 It is easily understood, how, in the sleep of the outward senses, 
 the sensitive centre must be given up altogether to the combi- 
 nation of ideas in which it must work with more energy. It is 
 seldom that the action of imagination on the genital organs, 
 during waking, goes the length of producing emission: nothing 
 is more common in sleep. 
 
 The human species is not the only one, that in sleep is subject 
 to agitations, which are generally comprehended under the name 
 of dreams; they occur in animals, and most in those whose na- 
 ture is most irritable and sensible. Thus the dog and horse 
 dream more than the ruminating kinds; the one barks, the other 
 neighs in sleep. Cows that are suckling' their calves, utter faint 
 
OF SENSATIONS. 
 
 416 
 
 lowings: bulls and tarns seem goaded by desires, which they 
 express especially, by peculiar motions of their lips. 
 
 After what has been said of sleep and dreams, it will not be 
 difficult to explain, why there is so little refreshment of the 
 powers, from sleep that is harassed by uneasy dreams. We 
 often awake, exceedingly fatigued with the distress of imagi- 
 nary dangers, and the efforts we have made to escape them. 
 
 We have seen the relations of man, with the external world, 
 established by means of peculiar organs, which, throup;h the in- 
 tervention of nerves, all centre in one, the chief and essential 
 seat of the function of which this chapter treats. As the pheno- 
 mena of the sensations are brought about by the intervention of 
 an unknown agent, and as like those of electricity and magne- 
 tism, they appear not to be subject to the ordinary laws of mat- 
 ter and motion, they have thrown open the widest field to the 
 conjectures of ignorance, and the inventions of quackery. It is 
 for their explanation, that the greatest abundance of theories, 
 and the wildest, have been devised. 
 
 On the 23d of December, it is not said in what year, a physi- 
 cian of Lyons, M. Petetin, was called in to a young lady of nine- 
 teen, sanguine and robust. She was cataleptic. The Doctor em- 
 ployed various remedies; and among others, one day bethought 
 himself of pushing over the patient on her pillow; he himself 
 fell with her, half stooping upon the bed, and this led him to 
 the “ discovery of the transport of the senses in the epigastrium, 
 to the extremity of the fingers and of the toes.” I use his own 
 pompous and barbarous expressions, in announcing his disco- 
 very. Our Doctor goes on to tell with all gravity, how putting 
 a bun on the epigastrium of the patient, she perceived the taste, 
 which was followed by motions of deglutition: if his word is to 
 be taken, hearing, smell, taste, sight and touch, were all there: 
 the outward senses, being, for the time, completely laid asleep. 
 To give an air of credibility to the matter, he adds, that she saw 
 the inside of her body, guessed what was in the pockets of by- 
 standers, made no mistake in the money in their purses: but the 
 miracle was over, the moment they lapped the objects in a silk 
 stuff, a coat of wax, or interposed any other non-conductor. 
 Finally, to put to proof the whole power of faith in his readers, 
 M. Petetin exclaims, “ Oh prodigy beyond conception! was a 
 
OF SENSATIONS. 
 
 417 
 
 thought formed in the brain without any sign of it in words! 
 the patient was instantly acquainted with it.”* Further details 
 of so incredible a story would be altogether superfluous. 
 
 I should not have disturbed the book of M. Petetin from its 
 peaceful slumber, among the innumerable pamphlets, which 
 Mesmerism has brought into the world, if a writer c5n physio- 
 logy had not been the dupe of this mystification, and had not 
 proceeded from it, to write a long chapter on the metastases of 
 sensibility. 
 
 If we should be so unfortunate as to be reproached by the 
 lovers of the marvellous, with pushing scepticism too far, we 
 must make answer: that M. Petetin is the sole witness of his 
 miracle: that it is impossible, from his relation, to know when 
 or on whom the prodigy took place; and that this zealot of mag- 
 netism might have invented this story to confound the unbe- 
 lievers who ventured to turn into ridicule his system on the 
 electricity of the human body. 
 
 CHAPTER VIII. 
 
 ON MOTION. 
 
 CLXI. T HIS Chapter will treat only of the motions per- 
 formed by the muscles under the influence of the will; they are 
 called muscles of locomotion, as it is by means of them that the 
 body changes its situation, moves from one spot to another, 
 avoids or seeks surrounding objects, draws them towards itself, 
 grasps them, or repels them. The internal^ involuntary^ and or- 
 ganic motions, by means of which each function is performed, 
 have already been investigated separately. 
 
 The organs of motion may be distinguished into active and 
 passive: the former are the muscles, the latter the bones, and all 
 the parts by which they are articulated. In fact, when in con- 
 sequence of an impression received by the organs of sense, we 
 wish to approach towards the object that produced it, or to with- 
 draw from it, the muscular organs, called into action by the 
 
 * Electriciti animale, 1 vol. 8vo. Lyons, 1808. 
 3 G 
 
ON MOTION. 
 
 418 
 
 brain, contract; while the bones, which obey this action, per- 
 form only a secondary part, are passive and may be looked 
 upon as levers absolutely inert. 
 
 The muscles consist of bundles of fibres, always, to a certain 
 degree, red in man; this colour, however, is not essential to 
 them, since it may be removed and the muscular tissue blanch- 
 ed by maceration or by repeated washing. 
 
 Whatever may be the situation, the length, the breadth, the 
 thickness, the form or the direction of a muscle, it is formed of 
 a collection of several fasciculi of fibres, enveloped in a cellular 
 sheath similar to that which covers the muscle itself, and sepa- 
 rates it from the surrounding parts. Each fasciculus is formed 
 of the union of a multitude of fibres, so delicate, that anatomy 
 cannot reduce them to their ultimate division, and that the 
 smallest distinguishable fibre is still formed by the juxta posi- 
 tion of numerous fibrillae of incalculable minuteness. As the last 
 divisions of the muscular fibre completely elude our means of 
 investigation, it would very absurd to attempt to explain their 
 minute structure, and after the example of Muys to write a 
 voluminous work on this obscure part of physiology. Shall we 
 say, with the above author, that each distinguishable fibre is 
 composed of three fibrillse progressive!)’ decreasing in size; 
 with Leeuwenhoek, that the diameter of this elementarj’ fibre 
 is only the hundred thousandth part of a grain of sand; with 
 Swammerdam, de Heyde, Cowper, Ruysch, and Borelli, that 
 this primitive fibre consists of a series of globular, rhomboidal 
 molecules; with Lecat, that it is nervous; with Vieussens and 
 Willis, that it is formed by the extreme ramifications of arte- 
 ries; with others, that it is cellular, tomentous, &c. How is it 
 possible to speak, with any degree of certainty, of the nature of 
 the parts of a whole which, from its extreme minuteness, eludes 
 our most accurate investigations. To explain the phenomena of 
 muscular action, it is sufiicient to conceive each fibre as formed 
 of a series of molecules of a peculiar nature, united together by 
 some unknown medium, whether that be oil, gluten, or any 
 other substance, but whose cohesion is manifestly kept up by 
 the vital power, since the muscles yield,, after death, to efforts 
 by which, during life, they would not have been torn; and such 
 is their tenacity, that they are v’ery seldom ruptured. 
 
ON MOTION. 
 
 419 
 
 These fibres, which, when irritated, possess, in the highest 
 degree, the power of shortening themselves, of contracting, 
 however minute one may suppose them, are supplied with ves- 
 sels and nerves. In fact, though they are neither vascular nor 
 nervous, as may be readily ascertained by comparing the bulk 
 of the vessels and nerves which enter into the structure of the 
 muscles, with that of these organs, and by attending to the dif- 
 ference of their properties; each fibre receives the power of con- 
 tracting, from the blood brought to it by the arteries, and from 
 the fluid transmitted from the brain along the nerves. A cellu- 
 lar sheath surrounds these fibrillte (and the nerves and vessels 
 perhaps terminate within it), others unite them together; the 
 fasciculi of fibres are inclosed in common sheaths, and these 
 unite, in the same manner, into masses varying in size, and the 
 union of which forms the muscles; fat seldom accumulates in 
 the cellular tissue which connects together the smallest fasci- 
 culi; it collects, in small quantity, in the interstices of the more 
 considerable fasciculi; lastly, it is in rather greater quantity 
 around the muscle itself. A lymphatic and aqueous vapour 
 fills these cells, maintains the suppleness of the tissue and pro- 
 motes the action of the organ, which a fluid of more consistence 
 would have impeded. 
 
 The greater number of muscles terminate in bodies, in gene- 
 ral round, of a brilliant white colour, that forms a striking con- 
 trast with the red colour of the muscular flesh, into which one 
 of their extremities is imbedded, while the other extremity is 
 attached to the bone and is lost in the periosteum, though the 
 tendons are quite distinct from it. Tire tendons are formed by 
 a collection of longitudinal and parallel fibres; their structure is 
 more compact than that of the muscles; they are harder and ap- 
 parently receive neither nerves nor vessels; they consequently 
 possess but a very inferior degree of vitality; hence they are fre- 
 quently ruptured by the action of the muscles. The muscular 
 fibres are implanted on the surfac of the tendinous cords, 
 without being continuous with the filaments forming the lat- 
 ter; they join them in a different manner, and at angles more 
 or less obtuse. 
 
 The tendons, in penetrating into the fleshy part of the mus- 
 cles, expand, become thinner, and form thus the internal apo- 
 
ON MOTION. 
 
 420 
 
 neuroses. The external aponeuroses, independent of the ten- 
 dons, though the same in structure, differ from them only in 
 the thinness and greater surface of the planes formed by their 
 fibres. At one time they cover a portion of the muscle to which 
 they belong; at another, they surround the whole limb, furnish- 
 ing points of insertion to the muscles; they prevent the muscles 
 and their tendinous cords from being displaced; in a manner, 
 direct their action and increase their power, in the same way as 
 a moderately tight girdle adds to the power of an athlete. 
 
 We cannot admit, with Pouteau, that the muscles of the limbs, 
 though applied to the bones by aponeurotic coverings, can be- 
 come displaced, so as to form herniae. When they contract in a 
 wrong position, some fibrillae are torn, and this gives rise to 
 most of those momentary and very sharp pains called cramp. I 
 have at present before me, the case of a young girl, in whom 
 the aponeurosis of the leg, exposed in consequence of an exten- 
 sive ulceration, exfoliated from the middle and fore part of the 
 limb to the instep. This exfoliation was accompanied by a dis- 
 placement of the tibialis anticus, and of the extensors of the toes; 
 the leg is become deformed, the motions of extension of the foot 
 and toes, are performed with difficulty, and will soon become 
 impossible, when the exfoliation of the tendons follows that of 
 the aponeurosis which protected them from the air. 
 
 CLXll. When a muscle contracts, its fibres are corrugated 
 transversely, its extremities are brought nearer to each other, 
 then recede, and again approach towards one another. These 
 undulatory oscillations, which are very rapid, are followed by a 
 slighter degree of agitation; the body of the muscle, swollen and 
 hardened in its decurtation, has acted on the tendon in which it 
 terminates; the bone to which the latter is connected, is set in 
 motion, unless other agents, more powerful than the muscle 
 which is in action, prevent its yielding to that impulse. Such 
 are the phenomena exhibited by the muscles exposed in a living 
 animal or in man, when their contractions are brought on by the 
 application of a stimulus. But these contractions, determined by' 
 external causes, are never so strong or instantaneous, as those 
 which are determined by the will, in a powerful and sudden 
 manner. When an athletic man, reduced by illness, powerfully 
 contracts the biceps muscle of the arm, this muscle is seen to 
 
ON MOTION. 
 
 421 
 
 -swell suddenly^ to stiffen, and to continue motionless in that 
 state of contraction, as long as the cerebral influence, or the act 
 of the will, which determines it, lasts. 
 
 Though the muscles manifestly swell in contracting, and 
 though the limbs are confined by the ligatures applied round 
 them, the whole bulk of the contractile organ diminishes; it 
 loses in length, more than it gains in thickness. This is proved 
 by Glisson’s experiment, which consists in immersing the arm 
 in a vessel filled with a fluid, which sinks when the muscles act. 
 We cannot, however, estimate the diminution of bulk, by the 
 degree in which the fluid sinks, since that effect is, in part, 
 owing to the collapse of the layers of the adipose tissue, which 
 is compressed in the muscular interstices. 
 
 A sound state of the vessels and nerves, distributed to mus- 
 cles, is indispensable to their contraction. If the free circulation 
 of the blood or of the nervous fluid is prevented, by tying the 
 arteries or nerves; if the return of the blood, along the veins, is 
 prevented, by applying a ligature to these vessels, the muscles 
 will be completely palsied. By dividing or tying the nerves, the 
 action of the muscles to which they are distributed, is suddenly 
 interrupted. The same effect may be produced by intercepting 
 the course of the arterial blood, though in a less rapid and in- 
 stantaneous manner; and it is very remarkable, that it is equal- 
 ly necessary that the veins should be as sound as the arteries, to 
 enable muscular action to take place. Kaaw Boerhaave ascer- 
 tained, by actual experiment, that when a ligature is applied to 
 the vena cava, above the illiacs, paralysis of the lower extremi- 
 ties is brought on, as when the aorta is tied, as was done by 
 Steno in the same situation. And this is a further proof of what 
 we have said elsewhere, of the stupefying qualities of the blood 
 which flows in the veins. 
 
 The irritability of the muscles destined to voluntary motions, 
 is proportioned to the size and number of the nerves and arte- 
 ries which are distributed to their tissue. The tongue, which, of 
 all the contractile organs, receives the greatest number of cere- 
 bral nerves, is, likewise, that which, of all those under the con- 
 trol of the will, has most extent, most freedom, and most varie- 
 
ON MOTION. 
 
 422 
 
 ty of motions.* The muscles of the larynx, and the intercostals, 
 receive nearly as many, considering the smallness of these parts. 
 
 CLXIII. Of all the hypotheses applied to the explanation of 
 the phenomena of muscular contraction, that appears to me the 
 most ingenious and the most probable, which makes it fo de- 
 pend on the combinations of hydrogen, of carbon, of azote, and 
 other combustible substances in the fleshy part of the muscle, 
 with the oxygen conyeyed with the blood by the arteries. 
 
 To effect this combination, it is necessary not only that the 
 muscle be supplied with arterial blood, and that oxygen come 
 in contact with the substances which it is to oxvdize, but it is 
 required that a stream of nervous fluid should penetrate through 
 the tissue of the muscle, and determine the decompositions 
 which take place; as the electrical spark gives rise to the forma- 
 tion of water, by the combination of the two gasses of which it 
 consists. According to this theory, first proposed bv Girtanner, 
 all the changes which take place, during the contraction of a 
 muscle, the turgescence, the decurtation, and the induration of 
 its tissue, its change of temperature, depend on this reciprocal 
 action of the elements of the muscular fibre, and of the oxygen 
 of arterial blood. 
 
 Muscular flesh is harder, firmer, and more oxydized, accord- 
 ing as the animal takes much exercise. We well know what a 
 difference there is, between the flesh of wild and of the domes- 
 tic animals; between the flesh of our common fowl, and that of 
 birds accustomed to remain long on the wing; in the former it 
 is white, tender, and delicate; while, in the latter, it is tough, 
 stringy, dark-coloured, carbonaceous, and of a very strong smell. 
 Respiration, of which the principal use is to impregnate arterial 
 blood with the oxygen necessary to the contractions of the mus- 
 cular fibre, is more complete, decomposes the greater quantity 
 of atmospherical air, in those animals that are naturally destined 
 
 * It is scarcely necessary to repeat, that I am not speaking of those motions, 
 more or less involuntary, performed by muscles which receive, their nerves, in 
 part or wholly, from the great sympathetics. Though the particular nature of 
 these nerves has a remarkable influence on the organs to which they are dis- 
 tributed, we find that the general rule is almost without exceptions; for the 
 heart and diaphragm, which hold the first rank among the parts endowed with 
 irritability, receive a considerable number of vessels and nerves. 
 
ON MOTION. 
 
 423 
 
 to most exertion. Those birds which support themselves in the 
 air by powerful and frequent motions, have, likewise, the most 
 active respiration. Athletes, who astonish us by the develop- 
 ment of their muscular organs, and by the powerful efforts 
 of which they are capable, all have a very ample chest, a power- 
 ful voice, and very capacious lungs.* In running, as there is a 
 considerable consumption of the principle of motion, we pant; 
 that is, we breathe in a hurried manner, that there may be the 
 greatest possible quantity of blood oxydized, to perform the 
 contractions necessary to the exercise of running. 
 
 CLXIV. Of the preponderance of the flexors over the exten^ 
 sors.j The extensor muscles are, generally, weaker than the 
 flexors; hence the most natural position, that in which all the 
 powers are naturally in equilibrio, that which our limbs assume 
 during sleep, when the will ceases to determine the vital in- 
 flux to the parts under its control, that in which we can continue 
 longest without fatigue, is a medium between flexion and exten- 
 sion, a real state of semi-flexion. 
 
 Attempts have been made to discover the cause of this pre- 
 ponderance of the flexor muscles over their antagonists. Accord- 
 ing to Borelli, the flexors being shorter than the extensors of 
 the same articulation, and contracting equally,^ the former must 
 occasion a more extensive motion of the limbs, and determine 
 them towards a state of flexion. But it is, in the first place, in- 
 correct to say, that the flexors are shorter than the extensors; 
 and, in the next place, if we are to estimate, by the length of a 
 muscle, the extent of motion that may be produced by its action, 
 we ought not to measure the whole of the fleshy part, nor to in- 
 
 * I never saw a very strong man that had not broad shoulders, which indi- 
 cates a considerable development of the cavity of respiration. If there be 
 individuals that seem to be exceptions to this general law, it is that by fre- 
 quent exercise, and by a laborious life, they have increased the natural power 
 of their muscles. This increase is seldom universal, but almost always limited 
 to certain parts which have been most employed; as the arms, the legs, or the 
 shoulders. 
 
 ■j-The theory of the preponderance of the flexors is intirely my own, and 
 was first proposed by me, in the collection of memoirs of the Medical Society 
 of Paris, for the year VII. of the Republic (1799). 
 
 4; Musculi flexores ejusdem articuli breviores sunt extensoribus, et utrique 
 seque contrahuntur. Prop. 130, de motu animalium. 
 
424 
 
 ON MOTION. 
 
 elude in the calculation, the tendinous cord which terminates it,* 
 but to consider the length of its fibres, on which depends entire- 
 ly the extent of motion produced by its contractions. 
 
 The degree of decurtation of which a muscle is capable, is 
 always proportioned to the length of its fleshy fibres, as is the 
 power of contraction to the number of the fibres. Now, if the 
 fibres of the flexors are in greater number than those of the ex- 
 tensors, it follows as a necessary consequence, that the limbs 
 will be brought into a state of flexion, when the principle of mo- 
 tion shall be distributed to them in an equal quantity; and even 
 though the number of fibres should be the same in the flexors 
 and extensors, the limbs would still be in a state of flexion, if the 
 fibres of the former being longer, they made the parts more 
 through a greater space. 
 
 If we examine the different parts of the body, the articula- 
 tions of the limbs, and especially of the knee, the knowledge of 
 which is of the highest importance in understanding the theory 
 of standing, it will be seen that the flexor muscles exceed the 
 extensors, in the number and length of their fleshy fibres. If we 
 compare the biceps cruris, the semi-tendinosus, the semi-mem- 
 branosus, the rectus internus, the sartorius, the gemelli, the 
 plantaris, and the popliteus, which all concur in the flexion of 
 the leg, to the triceps cruris and to the rectus, which extend the 
 leg, we shall readily understand that the fibres of these last are 
 much shorter, and in smaller number. Those of the sartorius 
 and rectus internus, are the longest of all the muscles employed 
 in voluntary motion; the fibres of the posterior muscles of the 
 limb, are not inferior in length to the fibres of the muscles at the 
 fore part. 
 
 ^Besides, the flexor muscles are Inserted into the bones which 
 they are to move, farther from their centre of motion. In fact, 
 if the insertion of the semi-membranosus is situated nearly at 
 the same height, the sartorius, the rectus internus, the semi-ten- 
 dinosus, the biceps, and the popliteus, are inserted lower than 
 the extensors of the leg. But this difference is particularly ob- 
 servable in the plantaris and gemelli, which terminate at the 
 greatest possible distance from the centre of motion, and whidi 
 
ON MOTION. 
 
 425 
 
 act with a very long lever*; lastly, most of these muscles de- 
 part much more than the extensors, from a parallel direction to 
 the bones of the leg. We all know the curved line of the course 
 of the sartorius,of the rectus internus, and semi-tendinosus, by 
 which the angle of their insertion becomes more favourable. 
 
 The flexor muscles, which, on their being first called into 
 action, are nearly parallel to the levers which they are to move, 
 tend to become perpendicular to them, in proportion as the mo- 
 tion of flexion is carried on. Thus, the brachialis, the biceps 
 brachii, and the supinator longus, the mean line of direction of 
 which is nearly parallel to that of the bones of the fore arm, 
 when the flexion of this limb commences, become oblique, then 
 perpendicular to this bone, and at last form with it the angle 
 most favourable to their action. The same applies to the flexors 
 of the leg; the angle of their insertion becomes greater, the more 
 it bends on the thigh. The extensors, on the contrary, are in the 
 most favourable state for action, at the moment when their con- 
 traction begins; in proportion as the extension goes on, they 
 have a tendency to become parallel to the levers which they set 
 in motion; their action even ceases before the parallelism is 
 complete at the elbow, by the resistance of the olecranon, and 
 at the knee, by the numerous ligaments, and by the tendons 
 situated towards the posterior part of the articulation. 
 
 The flexor muscles have, therefore, fibres of greater length 
 and more numerous than those of the extensors. They are in- 
 serted into the bones, at a greater distance from the centre of 
 their motion, at an angle less acute, and which increases in size 
 as the limbs bend. The union of these causes gives to the limbs 
 their superior power, and the greater range of motion in these 
 muscles, is a consequence of the arrangement of the articulating 
 surfaces, which almost all incline towards the side of flexion. 
 
 This preponderance of the flexor muscles, varies according 
 to the different periods of life; in the foetus, the parts are all bent 
 very considerably; this convolution of the young animal, may 
 
 • We may, in this respect, compare the gemelli to the supinator longus, the 
 use of which is not limited, as was shown by Heister, to the supination of the 
 hand, but which fs, likewise, a flexor of the fore arm, and acts the more 
 powerfully, as its inferior insertion is at a greater distance from the elbow 
 joint, and as its fibres are the longest of all those of the muscles of the upper 
 extremity. 
 
 3 H 
 
ON MOTION. 
 
 426 
 
 be perceived from the earliest period of gestation, when the em- 
 bryo, of the size of a French bean, and suspended by the um- 
 bilical cord, floats in the midst of the liquor amnii, in a cavity 
 in which it is more and more confined, as it approaches to the 
 period of its birth. This excessive flexion of the parts, which 
 was required to enable the produce of conception to accomodate 
 itself to the elliptical shape of the uterus, concurs in giving to 
 the muscles which produce it, the superiority which they retain 
 during the remainder of life. The new-born child preserves, in 
 a very remarkable manner, the habits of gestation; but, in pro- 
 portion as it grows, it straightens its body, and, by frequent 
 attempts to stretch itself, shows that a just proportion is about 
 to take place between the muscular powers. When the child 
 becomes capable of standing erect, abandoned to its own powers, 
 all its parts are in a state of semi-flexion; it staggers, and is un- 
 steady on its feet. Towards the middle of life, the preponder- 
 ance of the flexors over the extensors becomes less apparent; a 
 man enjoys fully and completely his power of locomotion; but, 
 as he advances in years, this power forsakes him; the extensor 
 muscles gradually return to the state of comparative debility of 
 infancy, and become incapable of supporting the body in a fixed 
 and permanent manner. 
 
 CLXV. The state of our limbs, during sleep, approaches to 
 that of the foetus, which, according to Buffon, may be consider- 
 ed to be in a profound slumber. The cessation of sleep is at- 
 tended in man, as well as in most animals, by frequent stretch- 
 ings. We extend our limbs forcibly, to give to the extensors 
 the tone which they require during the state of waking*. Bar- 
 thez accounts, in the same way, for the manner in which the 
 cock announces his waking, by crowing and flapping his wings. 
 
 It may happen, in consequence of a morbid determination of 
 the vital principle, that our limbs may remain in a state of ex- 
 tension during sleep. Hence Hippocrates recommends, that the 
 state of the limbs be carefully attended to while the patient 
 sleeps; for, as he observes, the further that condition is from 
 
 * Haller thinks that these extensions are intended to relieve the uneasy sen- 
 sations occasioned by a long continued flexion. Ni«ic qitide^n homines et ani- 
 malia extendunt artus, quod its fere confiexis dormiant, ct ex eo perpetuo situ, in 
 muscnlh sensus incommodus oriatuv, quern extensione toUunt, {phsenomena exper- 
 giscentium,) Elementa Fhvsiologiie, tom. V. p. 621. 
 
ON MOTION. 
 
 427 
 
 the natural state, the greater the danger to be apprehended of 
 the patient’s life. In certain nervous diseases, characterized by 
 a manifest aberration in the distribution of the vital power, a 
 continued state of extension must be considered a symptom 
 highly dangerous; I have had several times occasion to observe, 
 that in cases of wounds attended with convulsions and tetanus, 
 
 these alarming affections were announced by the permanent ex- 
 tension of the limbs during sleep, before a difficulty of moving 
 the jaw could give rise to any apprehension of their approach. 
 
 Disease and excesses of all kinds, occasion in the extensor 
 muscles, a relative weakness that is very remarkable; hence we 
 see convalescents, and those who have been addicted to volup- 
 tuousness, walk with bending knees; the more so as their de- 
 bility is greater, and as the force of the extensors is more com- 
 pletely exhausted. The flexion of the knees is then limited by 
 that condition, in which the tendons of the extensors of the leg 
 act on the tibia, at an angle sufficiently great to make up for their 
 diminished energy. There exists a condition of the animal eco- 
 nomy, in which all the muscular organs appear wearied with 
 exertion, and the limbs assume indifferently any position. In 
 this state, which is always a very serious one, as it indicates an 
 almost complete want of action in a system of organs whose 
 functions are absolute essential to life, a state to which physi- 
 cians have given the name of prostration^ the limbs, if unsup- 
 
 * It is from a knowledge of the strength of his patient, that the physician, 
 in the treatment of disease, deduces the most instructive indications. It seems 
 to me that we ought to endeavour to characterize, by specific terms, the diffe- 
 rent states of animal adynamia in different diseases. Our language, less fruit- 
 ful in imagery than the ancient languages, will not easily furnish these charac- 
 teristic denominations, so useful in a science which should paint objects in 
 their truest colours, in terms most approaching to nature. It will, therefore, 
 be necessary to have recourse to the Greek and Latin languages, and, perhaps, 
 to give the preference to the latter, which is generally understood by those 
 who practice the art of healing. The application of this principle to the diffe- 
 rent kinds of fever, will prove its utility, and will, doubtless, be an inducement 
 to extend it to all the classes of morbid derangements. 
 
 In febre inflammatoria seu svnocho simplici (angeio-7 
 
 •' r \ a e Qppressio virium. 
 
 In febre biliosa seu ardente (meningo-gastrica) Fractnra virium. 
 
 In febre pituitosa, seu morbo mucoso (adenomeningea) Languor virium. 
 
 In febre putrida (adynamica) Prostratio virium. 
 
 In febribus malignis seu atactis Ataxia virium. 
 
 In febre pestilentiali (adeno-nervosa) Sideratio viriutn. 
 
 The 
 
ox MOTION. 
 
 428 
 
 ported, fall of their own weight, as if they were palsied; the 
 trunk is motionless and supine. The patient is incapable of 
 changing his attitude, and yielding to the weight of his body, 
 sinks on the inclined plane formed by the bed, and seems very 
 heavy to those who may attempt to raise him, because from his 
 helplessness, he requires to be moved as an inert substance. 
 
 CLXVI. Of the power of the muscles; of the mode of estimating 
 that power. The actual power of the muscles is immensely 
 great, seems to grow in proportion to the resistance which it 
 meets with, and can never be estimated with precision. Borelli 
 was guilty of a serious mistake, in estimating the force of a 
 muscle by its weight, compared to that of another muscle; for, 
 muscles may contain cellular tissue, fat, tendinous parts, and 
 aponeuroses, without being the more powerful. Thejr strength 
 is always proportioned to the number of their fleshy fibres; 
 hence, nature has multiplied those fibres in the muscles which 
 are intended for powerful action. And in order that this great 
 number of muscular fibres might not add too much to the bulk 
 of the limbs, they are made shorter, by bringing near to each 
 other their insertions, which occupy extensive surfaces, whether 
 
 The first term, which is easily turned into French, exi>resses, with muck 
 precision, that condition in which the living’ system, far from being deficient 
 in strength, is encumbered by its excess, and is oppressed by its own powers. 
 It might, with slight modifications, be applied to all the kinds of phlegmasias 
 and active hemorrhages. 
 
 The second denomination, not so easily translated, expresses the sense ol 
 general contusion and bruise, of which patients, labouring under bilious fever, 
 {nieningo-gastrica) complain all over their limbs. 
 
 This sensation is, likewise, it is true, experienced in pituitary fever; but this 
 is more particularly characterized by languor and loss of strength. The same 
 is to be observed in many patients of a phlegmatic temperament. 
 
 The prostration, which is so remarkable a character of putrid fevers, and in 
 consequence of which they are called ad)-namic, is easily recognized by the 
 total cessation, or by an impaired condition of all the functions performed by 
 muscular organs; as voluntary motion, respiration, circulation, digestion, the 
 excretion of urine, &c. 
 
 The disordered condition of the vital po’wers characterizes the ataxiae; tlicre 
 is considerable irregularity in these fevers, with a very anomalous course of 
 symptoms. In this point of vie'w, one might compare it to several kinds of ner- 
 vous disorders. 
 
 Lastly, the word slderation appears to me to express, very forcibly, tliat 
 sudden and deep stupor which overwhelms patients seized with the plague of 
 the East. 
 
ON MOTION. 
 
 429 
 
 aponeurotic or osseous. We may, in general, judge of the power 
 of a muscle by the extent of the surfaces to which its fleshy 
 fibres are attached; thus, the gemelli and the soleus have short 
 compressed fibres, and lying obliquely between two large apo- 
 neuroses. 
 
 If the force with which a muscle contracts, is proportioned to 
 the number of its fibres, the degree of decurtation of which it is 
 capable, and consequently, the range of motions which it can 
 communicate to the limbs, are proportioned to the length of the 
 same fibres. Thus, the sartorius, whose fibres are longer than 
 any in the human body, is also capable of most contraction, and 
 performs the most considerable motions of the leg. It is impos- 
 sible to fix any precise limits to the decurtation of every parti- 
 cular muscular fibre; for, if the greater part of the long muscles 
 of limbs lose little more than a third of their length in con- 
 tracting, the circular fibres of the stomach, which in its greatest 
 dilatation form circles nearly a foot in diameter, may contract 
 to such a degree, when this organ has been long empty, as to 
 form rings of scarcely an inch in circumference. In cases of ex- 
 treme elongation or constriction, does the change that takes 
 place, affect the molecules that form the muscular fibre, or the 
 substances which connect them together; or does it affect, at 
 once, both the fibre and the parts by which these fibres are 
 united together? 
 
 However great the power of the muscles may be, a great part 
 of this power is lost, from the unfavourable disposition of our 
 organs of motion; the muscular powers, almost always parallel 
 to the bones which they are to move, act with the more disad- 
 vantage on these levers, as the mean line of their direction is 
 further from the perpendicular, and is nearly parallel to them. 
 
 The greater part of muscles are, besides, inserted in the bones, 
 very near their articulations or the centre of motion, and move 
 them as levers of the third kind, that is, are always placed be- 
 tween the fulcrum and the resistance; by multiplying thus, in 
 the animal machine, the levers of the third kind, nature has lost 
 in power, but has gained in strength; for, in this kind of lever, 
 the power moves through a very small space, but makes the re- 
 sistance move through a very considerable one. Besides, the 
 fleshy fibres, in shortening themselves, do not act directly on 
 
ON MOTION. 
 
 430 
 
 the tendon in which the muscle terminates; these fibres gene- 
 rally join, in an oblique direction, the aponeurotic expansion 
 formed by the tendinous cord, as it penetrates into the muscu- 
 lar mass; now their action being exerted in a direction more or 
 less oblique, is decomposed, and none is advantageously em- 
 ployed, but that which takes place in the direction of the ten- 
 don. The muscles frequently pass over several articulations, in 
 their way to the bone which they are to move; a part of their 
 power is lost in the different degrees of motion on each other, 
 of the parts on which the bone rests, into which the muscles are 
 inserted. All these organic imperfections are attended with an 
 enormous misapplication of power, and with a waste of the 
 greater part of it. It has been reckoned, that the deltoid mus- 
 cle employs a power equal to 2568 pounds to overcome a re- 
 sistance of 50. We are not to imagine, however, that there is a 
 loss of 2518 pounds; for the deltoid muscle acting both on the 
 shoulder and on the arm, about one half of its power is employ- 
 ed on each of these parts; hence it is said, that in estimating the 
 whole power of a muscle, one should double the effect produced 
 by its contraction, its action being applied, at the same time, 
 both on the weight which it raises, or on the resistance which it 
 overcomes, and on the fixed point to which its other extremity 
 is inserted. 
 
 If the muscles were quite parallel to the bones, they would 
 be incapable of moving them in any direction. On this account, 
 nature has, as much as possible, corrected the parallelism, by 
 removing, as we shall see, in speaking of the osseous system, 
 the tendons from the middle line of direction of the bones, and 
 by augmenting the angles at which they are inserted into them, 
 either by placing, along their course, bones which alter their di- 
 rection, as the patella and the sesamoid bones; by increasing the 
 size of the articular extremities of the bones, or by pullies, over 
 which the tendons or the muscles themselves are reflected, more 
 or less completely, as is the case with the circumflexus palati 
 and the obturator iuternus. 
 
 Nature has not, therefore, neglected mechanical advantages 
 as much as one might be led to imagine, on a slight examina- 
 tion of the organs of motion. And if it be considered, that in 
 the different conditions of life, we do not require strength so 
 
ON MOTION. 
 
 431 
 
 much as rapidity of motion, that the power might be gained by 
 increasing the number of fibres, while it was impossible to ob- 
 tain velocity, by any other means than by employing a particu- 
 lar kind of lever, and that, in short, to give our limbs the most 
 advantageous form, it was necessary that the muscles should be 
 applied to the bones, it will be confessed, that in the arrange- 
 ment of these organs, nature, in frequently sacrificing power to 
 quickness of motion, has conciliated, as much as possible, these 
 two almost irreconcilable elements. 
 
 Though the lever of the third kind is that most frequently 
 employed in the animal economy, the two other kinds of lever 
 are not altogether excluded from it; there are even limbs which 
 represent different levers, according to the muscles which set 
 them in motion; thus, if we take the foot as an instance, it will 
 present us with levers of every kind. The foot, when raised 
 from the ground and held up and raised towards the leg, forms 
 a lever of the first kind; the fulcrum is in the articulation and 
 separates the power, which is at the heel, from the resistance 
 which is at the tip of the foot that points downwards; if this 
 end of the foot rest on the ground, and if we stand on tip-toe, 
 they are changed into levers of the second kind; the power con- 
 tinues at the heel, but the fulcrum is removed to the other ex- 
 tremity of the lever, and the resistance to the middle; and this 
 resistance is very considerable, since the whole weight of the 
 body rests on the articulation of the foot with the leg. In stand- 
 ing on tip-toe, the muscles of the calf of the leg become prodi- 
 giously fatigued, though their action is assisted by the most fa- 
 vourable lever,^ adapted to the greatest resistance which nature 
 can oppose to herself. Lastly, the foot moves as a lever of the 
 third kind, when we bend it on the leg. 
 
 CLX VII. What is called the fixed point in the action of mus- 
 cular organs, does not always deserve that name. Thus, though 
 it may be said very correctly, that the greater part of the mus- 
 cles of the thigh have their fixed point in the bones of the pelvis, 
 to which their upper extremity is attached, and though they 
 move the femur on the ilia, which are less moveable; when the 
 
 • Of levers with arms of unequal length, that of the second kind is the most 
 favourable, since the arm of the power is uniformly longer than that of the 
 resistance. 
 
(^N' MOTION. 
 
 432 
 
 thigh is fixed by the action of other muscles, these move the 
 pelvis on the thigh, and that which was the fixed point, be- 
 comes moveable. The same applies to the other muscles of the 
 body, so that the fixed point is merely that which, generally, is 
 a fulcrum to the muscular action. This necessary fixed state of 
 one of the bones, to which is attached one of the extremities of 
 a muscle which we wish to contract, renders it necessary, in per- 
 forming the slightest motion, that several muscles should be 
 called into action, which implies a very complicated mechanism. 
 Nothing is easier to prove. Suppose a man stretched on the 
 ground or lying on his back; if we wish to raise his head, it will 
 be necessary that his chest become the fixed point of action of 
 the sterno cleido mastoidci, whose office it is to perform this 
 motion. Now, in order that the pieces forming this osseous 
 structure may remain motionless, it will be required, that the 
 chest should be fixed by the action of the abdominal muscles, 
 which, on the other hand, have their fixed point in the pelvis, 
 that is itself fixed in its place by the contraction of the glutaei 
 muscles. It was on this principle that Winslow first suggested, 
 that in reducing a hernia, the patient should be laid in an hori- 
 zontal posture, with injunctions not to raise his head, that the 
 abdominal muscles being relaxed, their different openings might 
 yield more easily to the reduction of the parts. 
 
 In case the two opposite points to which the extremities of a 
 muscle are attached, are equally moveable, they approach to- 
 wards each other, during the contraction of the muscle, by 
 making them move through equal spaces. These spaces would 
 not be equal, if the mobility were different. Each muscle has 
 its antagonist, that is, another muscle whose action is directly 
 opposed to it. Thus, the flexors balance the action of the exten- 
 sors, the adductors perform motions different from those of the 
 abductors. When two antagonizing muscles of equal power act 
 at the same time, on a part equally moveable, in every direc- 
 tion, the opposite powers neutralize each other, and the part re- 
 mains motionless. If there is a difference in the degree of con- 
 traction, the part is directed towards the muscle whose contrac- 
 tion is the most powerful: if the opposition is not direct, the 
 part follows a middle direction, between the two powers which 
 move it. Thus, the rectus externus muscle of the eye is not an- 
 
ON MOTION. 
 
 433 
 
 tagonized by the rectus inferior; hence when these two muscles 
 come to contract, at the same time, the eye is not carried down- 
 ward or outward, but at once downward and outward; it is then 
 said to move in the diagonal of a parallelogram, of which the 
 sides are represented by the muscles in action. 
 
 CLX VIII. Of the nature of muscular fesh. I shall not speak, 
 at present, of the manner in which the muscles receive nourish - 
 ment, by retaining within the meshes of their tissue, the fibrina 
 which the blood conveys to them in such quantity, that several 
 among the ancients and moderns have called the blood, “liquid 
 flesh;” an expression at once forcible and correct, since all the 
 organs are repaired and grow, by the solidification of its diffe- 
 rent parts. Haller first observed that most of the muscular arte- 
 ries were very tortuous in their course to the muscles. This dis- 
 position, which cannot fail to slacken, very considerably, the 
 course of the blood, favours the formation and the secretion of 
 the fibrous element which the muscles appropriate to their own 
 substance, and to which it bears so strong an affinity. Motion 
 influences, in a very remarkable manner, this nutritive secre- 
 tion. The muscles that are most in action, uniformly acquire 
 the greatest size and strength; if left in a state of complete in- 
 action, they become exceedingly reduced in size, from the sus- 
 pended secretion of the fibrinous principle. Muscular motion 
 promotes, very remarkably, the circulation and the distribution 
 of all the fluids. The flow of venous blood, after bleeding, is 
 never copious, unless the muscles of the fore arm are made to 
 contract, by making the patient hold the lancet case, and de- 
 siring him to move it round in his hand. 
 
 The chemical nature of the muscular fibre is nearly the same 
 as that of the fibrina obtained from the blood.* Like the latter, 
 it contains a great quantity of azote, and is, consequently, very 
 much animalized and exceedingly putrescent. It is from mus- 
 cular flesh, that M. Berthollet obtained, in considerable quan- 
 
 * Nothing can prove, in a more complete manner, the essential difference 
 between the fleshy parts of muscles and their tendinous and aponeurotic parts, 
 than the chemical analysis of these organs. The tendons and aponeuroses may 
 be completely resolved into gelatine, by long boiling, which, on the contrary, 
 parches the muscular flesh, by exposing the fibrina, in consequence of the melt- 
 ing of the fat of the cellular tissue, and of the albuminous juices in which it is 
 enveloped. ' 
 
 .3 I 
 
ON MOTION. 
 
 434 
 
 tity, the peculiar animal acid, called by that chemist, the zoonic 
 acid. Lastly, the element of the blood, by means of which the 
 muscular flesh is repaired, fibrina is already imbued with vital 
 properties, even while it yet flows in a state of combination 
 with the other parts of the fluid. This fibrina, extracted from 
 the blood and subjected to the galvanic influence, is distinctly 
 seen to quiver and contract under that influence. At what 
 period does this substance acquire the power of contracting? It 
 is, doubtless, at the moment when it becomes organized, in 
 passing from the liquid to the solid state. What relation does 
 there exist between the organizatian of matter and the vital 
 properties with which it is endowed? This question cannot be 
 answered, in the present state of our physiological knowledge. 
 
 CLXIX. A professor of anatomy in the University of Bo- 
 logna, Galvani, was one day making experiments on electricity. 
 In the laboratory, not far from the machine, lay some skinned 
 frogs, of which the limbs were convulsed every time a spark 
 was taken. Galvani, struck with the phenomenon, m.ade it a 
 subject of inquiry, and found that metals, applied to the nerves 
 and to the muscles of these animals, determined quick and 
 strong contractions, when they were disposed in a certain man- 
 ner. He gave the name of Animal Electricy to this set of new 
 phenomena, from the analogy he thought he perceived between 
 its effects and those of electricity. The discovery was made 
 public: many scientific men, chiefly those of Italy, and Volta 
 among others, were eager to make additions to the labours of 
 the inventor. The Medical Society of Edinburgh thought it 
 right to take this point of physiology as the subject of one of its 
 annual prizes, which was adjudged to the w'ork of Professor 
 Creve of Mentz, in which the term metallic irritation (irrita- 
 mentum metallorwn) is substituted to that of animal electricity. 
 This new expression is essentially bad, since it implies that 
 irritation by metals can alone determine the galvanic pheno- 
 mena, when charcoal, water, and many other substances pro- 
 duce them as well. The term of animal electricity has been also 
 laid aside, notwithstanding the great analogy between the ef- 
 fects of electricity and those of galvanism, and this last name 
 has been preferred, which applying equally to the whole of 
 the phenomena, immortalizes the name of the first observer. 
 
ON MOTION. 
 
 435 
 
 To produce the galvanic phenomena, it is necessary to esta- 
 blish a communication between two points of a series of ner- 
 vous and muscular organs. In this way, there is formed a cir- 
 cle, of which one arc is composed of the animal parts that are 
 subjected to the experiment, while the other arc is represented 
 by the instruments of excitation, which consist commonly of 
 several pieces, some of them placed under the animal parts, 
 and called supports, and the others, by which the communica- 
 tion with these is established, called communicators. 
 
 To form a complete galvanic circle, take the thigh of a frog 
 stripped of its skin, detach the crural nerve down to the knee, 
 and apply it on a plate of zinc; let the muscles of the leg lie on 
 a plate of silver, then complete the arc of excitation and the 
 galvanic circle, by establishing a communication between the 
 two supports with an iron Wire, or copper, tin, or lead: at the 
 moment of touching the two supports with the conductor, a 
 part of the animal arc formed by the muscles of the leg, will be 
 convulsed. Although this arrangement of the animal parts, and 
 of the galvanic instruments, is the one most favourable to the 
 production of these phenomena, there is room for varying a good 
 deal the composition of the animal arc and the arc of excitation. 
 Thus, you obtain contractions, by placing the two supports un- 
 the nerve, and leaving the muscles without the galvanic circle; 
 which proves, that the nerves essentially constitute the animal 
 arc. To conclude, the galvanic circle may be entirely animal: 
 for this purpose take a very lively frog, that is to say, one en- 
 joying strong contractility: after insulating the lumbar nerves, 
 present these nerves to the thigh of the frog; at the moment of 
 contact, the limb will be convulsed. Professor Aldini is the 
 first author of this experiment, which is really one of the most 
 curious, as it leads more directly to the explanation of the in- 
 fluence of nerves on muscular organs. 
 
 There is no need that the nerves be untouched to allow the 
 contractions, they are observed when these organs are tied, or 
 cut, provided there be simple contiguity between the two ends 
 made by the section. This shows that no rigorous conclusion 
 must be drawn from what happens in galvanic phenomena, to 
 what takes place in muscular action, since it is enough that a 
 nerve in man be cut or compressed by a ligature, to take from 
 
ON MOTION. 
 
 436 
 
 the muscles to which it is sent, the faculty of moving. I have, 
 however, observed that disorganizing, by a strong contusion, 
 the nerve which forms the whole or merely a part of the animal 
 arc, interrupts, or at least greatly impedes the galvanic current. 
 
 The epidermis obstructs galvanic action, which always is 
 faint in parts so covered. When it is moist, thin, and delicate, 
 the interruption is not complete, and hence the possibility is 
 inferred of making on oneself the following experiments:-— 
 
 Lay upon the tongue a plate of silver, and a plate of zinc be- 
 neath; let their edges touch, and you will feel a sharp taste with 
 a slight quivering. Apply upon the eyes two pieces of different 
 metals: make them communicate and you will perceive sparks. 
 Put a piece of silver in your mouth, and a piece of tin into your 
 anus, or copper or any other metal: connect them with an iron 
 wire: the long hollow muscle which, reaching from the mouth 
 to the anus, forms the base of the digestive canal, feels a consi- 
 derable shock: this has been carried the length of exciting a 
 gentle purging, accompanied with slight cholic. Humboldt, af- 
 ter detaching the epidermis from the nape of the neck and the 
 back, by two blisters, had metals applied to the parts laid bare, 
 and felt in each sharp prickings, accompanied with a sero-san- 
 guineous excretion, at the moment of communication. 
 
 You may construct the arc of excitation with three kinds of 
 metal, or two, or even one; with alloys, amalgams or other me- 
 tallic and mineral combinations; with carbonaceous substances,"* 
 &c., and it is observed, that metals which are, in general, the 
 most powerful exciters, provoke contractions with the greater 
 success the larger surface they present. The metals have more 
 or less power of excitation: thus it is found that zinc, gold, 
 silver, and tin, hold the first rank; then copper, lead, nickel, 
 antimony, &c. without any apparent relation between their diffe- 
 rent degrees of exciting power and their physical properties, as 
 their weight, malleability, &c. 
 
 CLXX. Galvanic susceptibility is like muscular irritability: 
 it is exhausted by too long exertion; and returns when the parts 
 are left for a time in repose. Dipping the nerves and muscles 
 
 * I employed successfully, in tlie winter of the year VIII, pieces of ice both 
 as supports, and as commiuiicators. 
 
ox MOTION. 
 
 437 
 
 in alcohol or opiate solutions, weakens and even will extinguish 
 this susceptibility, in the same manner, no doubt, as in the 
 living man, the immoderate use of the same substances, be- 
 numbs and paralyzes the muscular action. Immersion in oxy- 
 genated muriatic acid restores to the exhausted parts the power 
 of being affected by the stimulus. Humboldt has observed that 
 the season of spring, as well as the youth of the frog, was fa- 
 vourable to the production of the phenomena, and that the fore- 
 feet of these creatures with which the male fixes himself on the 
 back of the female, by pressing her sides, are more excitable 
 than the hind feet; whilst in the other sex, it is the hind feet 
 that are the most susceptible. M. Halle ascertained, by experi- 
 ments made at the School of Medicine in Paris, that the mus- 
 cles of animals killed by repeated shocks of an electrical bat- 
 tery, receive an increase of galvanic susceptibility; that this 
 property subsists, without alteration, in animals dead of as- 
 phyxia or killed by immersion in mercury, pure hydrogen gas, 
 carbonated hydrogen, oxygenated muriatic acid, and sulphu- 
 reous acid gases, by strangulation, by privation of air in an ex- 
 hausted receiver; that it is weakened after suffocation by drown- 
 ing, by sulphuretted hydrogen, azote, and ammoniacal gas, and 
 absolutely destroyed by suffocation in the vapour of charcoal. 
 Spring is the season in which galvanic experiments succeed 
 best; an excess of life seems., at that time, to animate all beings: 
 it is accordingly at this epoch, that the greater part of them are 
 employed in the reproduction of their kind. 
 
 CLXXI. Galvanic susceptibility disappears in the muscles 
 of warm-blooded animals, as the vital warmth goes off. Some- 
 times even, when their life has ended in convulsions, their con- 
 tractility is gone, though there be still warmth, as if this vital 
 property Were exhausted by the convulsions of death. In the 
 cold-blooded, susceptibility is more permanent: long after se- 
 paration from the body, and even to the moment when putre- 
 faction begins, the thighs of frogs are affected by galvanic exci- 
 tation; no doubt, because, in these animals, irritability is less in- 
 timately connected with respiration, because life is less one, is 
 more divided among different organs which have less need of 
 action on each other to produce its phenomena. 
 
 Contractility is then, as I have shown in another work, to© 
 
ON MOTION. 
 
 458 
 
 fleeting in the human body, to enable us to derive from galva* 
 nic experiments on it, after death, any light on the greater or 
 less weakening of this vital property in different diseases. Those 
 authors who have maintained that galvanic susceptibility is 
 sooner extinct on the bodies of those that die of scorbutic af- 
 fections, than of those that die of inflammatory diseases, have 
 suggested a probable 'conjecture, which cannot, however, be 
 established on experiment. 
 
 Dr. Pfaff, Professor in the University of Kiel, who, next to 
 Humboldt, is of all the scientific men of Germany, he who has 
 attended most successfully' to experiments on galvanism, has 
 had the goodness to communicate to me the following facts: 
 
 The galvanic chain produces sensible actions, that is to say, 
 contractions, only at the moment in which it is completed, by 
 establishing a communication among its parts. After it is made, 
 that is, during the time that the communication remains, all ap- 
 pears tranquil; yet the galvanic action is not suspended. In fact, 
 excitability appears singularly increased or diminished in the 
 muscles that have been left long in the galvanic chain, accord- 
 ing to the variations of the reciprocal situation of the associated 
 metals. If the silver have been applied to the nerves and the 
 zinc to the muscles, the irritability of these is increased in pro- 
 portion to the time they have remained in the chain. By this 
 means, you may revivify, in some sort, frogs’ thighs, which will 
 afterwards obey an influence that was no longer sufficient to ex- 
 cite them. By allotting the metals differently, applying the zinc 
 to the nerves, and the silver to the muscles, the opposite effect 
 takes place; the muscles which were introduced into the chain 
 with the liveliest irritability, seem entirely paralyzed, if they 
 have remained long in that situation. 
 
 This difference depends, very evidently', on the direction of 
 the galvanic fluid, determined towards the nerves or towards 
 the muscles, according to the arrangement of the metals. It is 
 of importance to be known, for the application of galvanism to 
 the treatment of disease. Where the object is to revive enfee- 
 bled irritability, it is better to employ the tranquil and perma- 
 nent influence of the closed galvanic chain, by distributing the 
 silver and zinc, so that the silver shall be nearest to the origin 
 of the nerves, and the zinc upon the muscles of which it is wish- 
 
ON MOTION. 
 
 439 
 
 ed to re-excite the torpid or suspended action, than to employ 
 that sudden influence, which, in an instant, excites and is gorie. 
 Professor PfafF told me, he had treated successfully a hemi- 
 plegia, by placing silver within the mouth, and a plate of zinc 
 on the paralyzed arm; at the end of 24 hours of uninterrupted 
 communication, the limb could already exert some slight mo- 
 tions. To diminish, on the other hand, the irritable energy in 
 many spasmodic affections, you must invert the applications of 
 the metals, place the zinc as near as possible to the central ex- 
 tremity of the nerves, and the silver on their superficial termi- 
 nations. 
 
 CLXXII. Apparatus of Volta, or galvanic pile. Curious to 
 ascertain the relation apprehended by several natural philoso- 
 phers, between electricity and galvanism, M. Volta invented 
 the following apparatus, which is described, as well as the ef- 
 fects it produces, in a memoir presented by him to the Royal 
 Society of London. These effects show the most striking ana- 
 logy between these two orders of phenomena, as will be seen by 
 a succinct view of them. Raise a pile, by laying successively, one 
 above another, a plate of zinc, a piece of moistened paste-board, 
 a plate of silver; then a second plate of zinc, &c. till the pile is 
 several feet high: for, the effects are stronger the higher it is: 
 then, touch, at once, the two extremities of the pile with the 
 same iron wire: at the instant of contact, a spark is seen at the 
 extremities of the pile, and often, at the same time, luminous 
 points, at different heights, in places where the zinc and silver 
 touch. Tried by the electrometer of M. Coulomb, the extremity 
 of the pile, which answers to the zinc, appears positively elec- 
 trified; that which is formed by the silver, gives, on the con- 
 trary, indications of negative electricity. 
 
 If after wetting both hands, by dipping them in water, or still 
 better, in a saline solution, you touch the two extremities of the 
 pile, you feel, in the joints of the fingers and elbow, a shock fol- 
 lowed by an unpleasant pricking. 
 
 This effect may be felt by several persons holding hands, as 
 in the Leyden experiment; it is the more sensible, the composi- 
 tion of the chain being in other respects the same, as the chain 
 consists of fewer people, and as they are better insulated. 
 
 Notwithstanding this great resemblance of the effects of gal- 
 
ON MO'l'ION. 
 
 440 
 
 vanism to those of electricity, it differs from it essentially in 
 this, that the voltaic pile is constantly electrifying itself sponta- 
 neously; that its effects seem increased, the more thev are ex- 
 cited, and are speedily renewed in greater strength; whilst the 
 Leyden phial, once discharged, requires to be electrified anew. 
 This loses, moreover, by damp, its electrical properties, whilst 
 those of the pile remain the same, though water is running on 
 all sides, and are quenched only by entire immersion in that 
 fluid. 
 
 If you introduce into a tube filled with water, and hermeti- 
 cally closed with two corks, the extremities of two wires of the 
 same metal, which, at the other extremity are in contact, one 
 with the summit, and one with the base of the galvanic pile, these 
 two ends, when brought within the distance of a few lines, un^ 
 dergo manifest changes, at the moment of touching the extre- 
 mities of the pile. The wire in contact with the extremity w'hich 
 answers to the zinc, becomes covered with bubbles of hydrogen 
 gas; that which touches the extremity formed by the silver, be- 
 comes oxydized. If the ends of the wire dipping into the water, 
 are brought into contact, all effect ceases: there is no disen- 
 gaging of bubbles on one side, no oxydizement on the other. The 
 plates of zinc and silver become alike oxydized in the pile, but 
 only on the surfaces which touch the moistened paste-board, 
 and very little, or not at all, on the opposite surfaces, &c. 
 
 Facts so singular could not but awaken the attention of all 
 natural philosophers. Accordingly, there was great eagerness, 
 every where, to repeat and verify these first experiments, to 
 vary and to extend them, and to rectify the errors into which 
 their authors might have fallen. Lastly, it has been attempted 
 to explain the manner in which the apparatus acts in the pro- 
 duction of hydrogen gas and in oxydizement. 
 
 M. Fourcroy ascribes this phenomenon to the decomposition 
 of water by the galvanic fluid, which abandons the oxygen to 
 the wire that touches the positive extremity of the apparatus, 
 then conducts the other gas, in an invisible manner, to the ex- 
 tremity of the other wire, where it allows it to escape: and this, 
 opinion, supported by many experiments detailed in a Memoir 
 presented to the National Institute, is the most probable of all 
 that have hitherto been suggested. 
 
ON MOTION. 
 
 441 
 
 The galvanic pile has been employed, with effect, to produce 
 with more energy, muscular contraction. If you place in the 
 mouth of an animal, fresh killed, a conductor attached to one 
 of the poles or extremities of the pile, and insert into the rec- 
 tum the conductor connected with the other extremity, you 
 observe contractions so strong, that the whole body of the ani- 
 mal quivers and is agitated, thfe eyes roll in their sockets, the 
 jaws strike against each other, and the tongue is thrust out. 
 The same eflPects take place after decapitation of the animals 
 These experiments have been repeated on the bodies of persons 
 executed by the guillotine: by applying to the neck, the head 
 that had been separated from it, and applying to both, conduc- 
 tors connected with the pile, effects have been produced, which 
 seemed at first miraculous. There are few muscles that retain, 
 longer than the diaphragm, their sensibility to the galvanic ac- 
 tion; in the heart and the intestines it is the same. I know not 
 why the internal muscles have been held by many authors to be 
 insensible to this kind of excitation. 1 have seen them con- 
 stantly obey it, and many experiments made publicly in my 
 lectures, have always afforded me this result. 
 
 CLXXIII. In the first edition of this work the article gal- 
 vanism ended here. Since its publication, there has been an 
 accession of new facts to those already known. Volta came to 
 Paris; he gave an exposition of his doctrine, in several me- 
 moirs read before the National Institute of France, and he 
 repeated before a committee, the principal experiments on 
 which it is founded. They have appeared so conclusive, that 
 the theory of this illustrious philosopher has been unanimously 
 adopted; and at this day, all men of science admit the entire 
 identity of the phenomena of galvanism, and those of electri- 
 city. Certain bodies, therefore, in nature, and especially metals, 
 possess the property of electrifying themselves, that is to say, 
 of producing the greater part of the phenomena which denote 
 the accumulation of electricity in a body, such as shocks, sparks, 
 irritations, &c. merely by contact. 
 
 It may be thought that galvanism, being only a new form of 
 electrical action, ought to be confined to books of natural phi- 
 losophy: and in fact, in the present state of things, it belongs 
 rather to the physico-chemical sciences, than to those of the 
 
 3 K 
 
ON MOTION. 
 
 442 
 
 animal economy. However, the galvano-electric imtation pro- 
 duces on our organs, effects more decided than the ordinary 
 effects of electricity. It seems to have more intimate relations 
 with them: accordingly, it has been endeavoured to bring it 
 into use in the treatment of disease. The experiments made by 
 MM. Halle and Thillaye, prove that the effects of the pile 
 penetrate, and affect the nervous and muscular organs, more 
 deeply than the common electrical apparatus; that they provoke 
 lively contractions, strong sensations of pricking and burning, 
 in parts which disease renders insensible to electrical sparks, 
 or even shocks. A man whose muscles of the left side of his 
 face were all paralysed, found no effect from the electrical shock. 
 He was exposed to the action of a pile of fifty plates, by com- 
 munications, through chains and metallic exciters, of the two ex- 
 tremities of the pile, with different points of the cheek affected. 
 At the moment of contact, all the muscles of the face became 
 convulsed, with heat, pain, &c. These endeavours repeated, 
 during more than six months, have, by degrees, brought back 
 the parts to their natural state. 
 
 Dr. Alibert has applied galvanism with still more decided 
 success, to a priest attacked with hemiplegia. This patient, 
 who lay in the wards of the Hospital of St. Lewis, has reco- 
 vered the use of the palsied side, sufficientl)’^ to walk, almost 
 without assistance, and to use his right arm as he wants it. 
 The treatment has gone on for several months: the pile em- 
 ployed consisted of fifty plates of zinc and copper. I am trying 
 the same apparatus upon a Swedish officer, for incomplete deaf- 
 ness, which has hitherto resisted all known applications, ad- 
 ministered in different parts of Germany. Strong electrical 
 shacks, recommended by Hufeland, had dispelled, in great 
 measure the hardness of hearing: but this amendment was only 
 temporary: it ceased with the application of the remedy. The 
 first trial of galvanism was attempted with the same effect. The 
 extremity of a conductor being placed in the exterior auditory 
 duct of the right side (moistened with a solution of muriate of 
 ammonia, as well as the pieces of cloth which made part of the 
 pile) the left hand, dipped in the same liquid, touched a con- 
 ductor placed at the copper pole: immediately an irritation, fol- 
 lowed by painful prickings, was felt in the ear, the outer part of 
 
ON MOTION. 
 
 445 . 
 
 which became very red. The brain partook in the excitement; 
 the eyes flashed, and the effect was such, that after remaining a 
 few minutes in the closed galvanic circle, the patient was taken 
 with a sort of inebriation. I propose to direct, as has been done 
 at Berlin, a more, immediate irritation on the right ear, which 
 is the deafest, by introducing behind the velum palati, on the 
 guttural orifice of the eustachian tube, the button which is at 
 the end of the conductor of the zinc pole; or else to make this 
 extremity correspond with a denuded surface, by a blister be- 
 hind the diseased ear. 
 
 To use galvanism, in paralysis of the bladder, it would be 
 necessary to place the conductor of the zinc pole in the rectum, 
 that of the other pole answering to a blister applied above the 
 pubis, or else to the upper part of the thigh. In women, the 
 vagina would be preferable to the rectum; the soft parts which 
 perform the part of moist conductors fulfilling that office the 
 better, the thinner they are. Galvanism is therefore an ener- 
 getic stimulant of the vital powers; it may be employed, with 
 great advantage, in all palsy both of sensation and of motion. 
 It acts as stimulant, reddening the skin where it is applied, 
 by determining thither the flow of blood, with heat. Monro 
 could make his nose bleed at pleasure, by applying it to the 
 pituitary membrane. I have made various experiments having 
 in view to establish the efficacy of galvanism, in white swelling 
 of the joints, and in ulcers which require excitement; such as 
 those which are attended with a scorbutic affection, &c. In all 
 these cases, it acts as a resolvent and as a tonic. I shall com- 
 municate, in my Surgical Nosography, the results of these 
 attempts. Cases of asphyxia are those in which the greatest 
 good may be hoped for from galvanism, provided the applica- 
 tion be made before all the vital heat be extinct. 
 
 Those who would wish fuller details on galvanism, and on 
 its possible application to the treatment of disease, will do well 
 to consult the complete History of Galvanism, by Professor 
 Sue, the eulogium of Galvani, by Dr. Alibert, in the beginning 
 of the fourth volume of the Memoirs of the Medical Society of 
 Emulation, and the works of Dr. Aldini, nephew to the cele- 
 brated author of the discovery. 
 
©N MOTION. 
 
 444 
 
 CLXXIV. General view of the osseous systeM, Man, as 
 well as the other red-blooded animals (the maramiferae, birds, 
 reptiles, and fishes) has an internal skeleton, formed of a great 
 number of bones articulated together, and set in motion by the 
 muscles with which they are covered. The white-blooded ani- 
 mals have no internal skeleton, and are enveloped in hard, 
 scaly, or stony parts, forming what is called their outer skeleton. 
 Some animals are entirely destitute of hard parts; this is the 
 case with the zoophytes, some worms and insects. The inter- 
 nal structure of bones is composed of nearly the same materials 
 in all animals: viz. gelatine and salts containing a calcareous 
 basis. The external skeleton of white-blooded animals bears a 
 much greater resemblance to the epidermis than to the osseous 
 system of the red-blooded animals. Like the epidermis, it un- 
 dergoes changes of decomposition and renovation. Thus, the 
 lobster parts with its shell, every year, when the body of this 
 crustaceous animal increases in size, and it is replaced by a new 
 envelope, which is at first very soft, and which gradually ac- 
 quires the same consistence as the former. Lastly, the skeleton 
 of birds differs from that of all other animals, in having its 
 principal bones pierced by openings communicating with the 
 lungs, and always filled with an air rarified by the vital heat, 
 which greatly assists in giving to them that specific lightness so 
 essential to their peculiar mode of existence. 
 
 The osseous system serves as a foundation to the animal 
 machine, yields a firm support to all its parts, determines the 
 size of the body, its proportion, its form and attitude. Without 
 the bones, the body would have no permanent form, and could 
 not easily move from one place to another. When, from the 
 loss of the calcareous earth to which they owe their hardness, 
 these organs become soft, the limbs deformed, standing, and 
 the different motions of progression, become af'.er a time im- 
 possible. Such are the effects of rachitis, a disease of which 
 the nature is well understood, though we are not the better in- 
 formed with regard to the manner in which its causes operate, 
 or the medicines which it requires. 
 
 The vertebral column forms the truly essential and funda. 
 mental part of the skeleton; it may be considered as the base 
 of the osseous edifice, as the point in which all their efforts ter» 
 
ON MOTION. 
 
 445 
 
 minate, as the centre on which all the bones rest in their va- 
 rious motions, since every effort or shock, in any way conside- 
 rable, is felt there. Moreover, it contains in the canal with 
 which it is perforated, the cerebral prolongation, which furnishes 
 most of the nerves in the body. 
 
 In order that it may support all the different parts, and at the 
 same time, protect the delicate organ which it contains,* and 
 adapt itself to the various attitudes required by the wants of life, 
 it was necessary that the vertebral column should possess, be- 
 sides great solidity, a sufficient degree of mobility: it possesses 
 both these advantages, and owes the former to the breadth of 
 the surfaces by which its bones are articulated together, to the 
 size, the length, the direction and the strength of their pro- 
 cesses, and to the great number of muscles and ligaments con- 
 nected with it: it owes its freedom of motion to the great num- 
 ber of bones of which it is formed. Each single vertebra has 
 but a slight degree of motion, but as they all have the power of 
 moving at once, the sum of their individual motion added to- 
 gether, gives as the result a general motion which is considera- 
 ble, and which is estimated by multiplying the single motion by 
 the number of vertebrae. 
 
 The centre of the motions, by which the spine is extended or 
 bends forward or backward, is not situated in the articulation 
 of the oblique processes, as is maintained by Winslow, in the 
 Memoirs of the Academy of Sciences for the year 1730, nor in 
 the intervertebral substance. The extension and flexion of the 
 vertebrae are not performed on two centres of motion, the one 
 in the intervertebral substance, the other in the articulations of 
 the articulating processes, as was imagined by Cheselden and 
 Barthez, but on an axis crossing the bone between its body and 
 its great aperture. The anterior part of the bone and its spinous 
 
 * The peculiar manner in which the vertebrje grow, is itself accommodated 
 to the delicacy of the spinal marrow; consisting', for a considerable length of 
 time, of several pieces divided by cartilages, the circumference of the opening 
 in these bones, becomes enlarged, with the enlargement of the spinal marrow, 
 as we grow older. The circumference of the foramen of the occipital bone 
 and that of the first vertebrs which correspond to the thickest part of the 
 spinal marrow, is, on that account, formed of four distinct pieces separated bt' 
 cartilages in the first of these bones, and of five pieces in the other. 
 
ON MOTION. 
 
 446 
 
 process perform, around this imaginar)' axis, motions forming 
 part of a circle, and which though limited are not the less 
 marked; and in these motions the articulating surfaces separated 
 by the intervertebral substance are brought into close contact, 
 and this substance is compressed, while the oblique processes 
 move on one another, and tend to part from one another; this is 
 what happens in bending the trunk, while, in straightening it, 
 the anterior surfaces are removed from each other, the poste- 
 rior surfaces approach, come closer and closer together, and 
 finally touch throughout the whole of their extent, when the 
 extension of the trunk is carried as far as the spinous processes 
 will allow. 
 
 The use of the ridge of projections which arise from the pos- 
 terior part of the vertebree, is to limit the bending of the trunk 
 backwards, and to enable the muscles which straighten it, to act 
 with a more powerful lever. When, from the habit of an habi- 
 tually erect posture, these processes have been prevented from 
 growing in their natural direction, the trunk may be bent back- 
 ward to such a degree, that the body forms, in that direction, an 
 arc of a circle. It is thus that they train, from the earliest in- 
 fancy, the tumblers who astonish us by the prodigious supple- 
 ness of their loins, in bending backward so as to change the na- 
 tural direction of their spinal processes. 
 
 It was of consequence, that the motions of the vertebral co- 
 lumn should take place, at once, in a great number of articula- 
 tions, as the curvatures are thus less sharp, and thus the organi- 
 zation of the spinal marrow, which is very delicate, is not injur- 
 ed. The fibro-cartilaginous substances which connect together 
 the bodies of the vertebrae, between which they lie, possess a re- 
 markable degree of elasticity, like all bodies of the same kind, 
 and support, in a favourable manner, the weight of the body. 
 When the pressure which they experience is long continued, 
 they somewhat yield, and diminish in thickness; and this effect 
 taking place, at the same time, in all the intervertebral sub- 
 stances, our stature is sensibly lowered. The body is, on that 
 account, always shorter in the evening than in the morning, and 
 this difference may be considerable, as is mentioned by Buffon 
 to have been the case in several instances. The son of one of 
 his most zealous coadjutors (M. Gueneau de Montbeillard, to 
 
ON MOTION. 
 
 447 
 
 whom is due the greatest part of the natural history of birds), 
 a young man of tall stature, five feet nine inches when he had 
 reached his complete growth, once lost an inch and an half, 
 after spending a whole night at a ball. This difference in the 
 stature depends, likewise, on the condensation of the cellular 
 adipose 'tissue at the heel, which forms, along the whole of the 
 sole of the foot, a pretty thick layer. 
 
 The thigh bone is longer in man than in quadrupeds, and 
 this relative length of the thigh gives him exclusively the 
 power of resting his body by sitting. 
 
 The tibia is the only one of the bones of the leg which affords 
 ' a support to the body. The fibula, situated at its outer part, too 
 thin and slender to support the weight of the body, is of use 
 merely with regard to the articulation of the foot, on the out- 
 side of which it lies. It supports the foot, and prevents its start- 
 ing outward by too powerful an abduction. The foot, in this 
 motion, is forced against the fibula which is bent outwardly, the 
 more so when the person is advanced in years, and has, there- 
 fore, called into frequent action this force of resistance. Ani- 
 mals that climb, as the squirrels, whose feet are in a continual 
 state of abduction, have a very large and strongly curved 
 fibula.* 
 
 The number of the parts which form the feet, besides giving 
 to these parts a greater solidity, is further useful in preventing 
 the foot from being too violently shaken by striking the ground, 
 in our various motions of progression. In leaping from a height, 
 we endeavour to fall on our toes, that the force of the fall may 
 be broken, by being communicated to the numerous articula- 
 tions of the tarsus and metatarsus, and may not affect the trunk 
 
 • This curvature is well marked in the chefs-d’oeuvre of antique sculpture, 
 and gives to the lower part of the leg, in our most beautiful statues, a thick- 
 ness which does not at all agree with our present notions of elegance of form. 
 This seems to me to prove, that the beautiful is not invariable, as has been as- 
 serted by many philosophers; and that ideal perfection is not precisely the same 
 in all ages, in nations equally civilized. The truth of this observation may be 
 proved by the Apollo Belvedere; his knees are rather large and close together, 
 and this form is the most beautiful representation of nature, which gives to 
 the femur an obliquity inwards, the knees not being perfectly straight, and 
 without any disproportion between the calf and the thin part of the leg. 
 
oyr MOTION. 
 
 448 
 
 and head with a painful and even dangerous concussion. It is 
 well known, that when, in falls, the whole sole of the foot 
 strikes against the ground, fracture of the neck, of the thigh 
 bones, and concussion of the brain and other organs, is not an 
 unlikely consequence. 
 
 CLXXV. Structure of the bones. Whatever difference there 
 may, at first sight, seem to exist, between a bone and another 
 organ, their composition is the same. Its structure consists of 
 parts that are perfectly similar, with the exception of the saline 
 inorganic matter which is deposited in the cells of its tissue, 
 which gives it hardness and that solidity which constitutes the 
 most striking difference that distinguishes it from the soft parts.' 
 This earthy substance may be separated by immersing the bone 
 in nitric acid diluted in a sufiicient quantity of water. It is then 
 found, that it is a phosphate of lime which is decomposed, by 
 yielding to the nitric acid its calcareous base. The bone, thus 
 deprived of the principle to which it owes its consistence, be- 
 comes soft, flexible, and resembles a cartilage, which is re- 
 solvable, by long maceration, into a cellular tissue similar to 
 that of the other parts. This tissue contains a pretty considera- 
 ble number of arteries, veins, and lymphatics. The bones are, 
 therefore, mere cellular parenchymas, whose areolas contain a 
 crystallized saline substance, which they separate from the 
 blood, and with which they become incrusted, by a power inhe- 
 rent in their tissue and peculiar to it. The same result may be 
 obtained by inverting the analysis. If a bone is exposed to boil- 
 ing heat, for a few hours, in Papin’s digester, all its organized 
 parts become dissolved, melt, and furnish a quantity of gelatine, 
 after which there remains only an inorganic saline concretion; 
 which may, likewise, be obtained in a separate state by calcin- 
 ing the osseous part. The different proportions of the saline to 
 the organized part, vary' considerably at different periods of life; 
 the bones of the embryo are, at first, quite gelatinous. At the 
 period of birth, and during the first years of life, the organic 
 part of the bone is in greater proportion; the bones are less apt 
 to break, more flexible, possessed of more vitality, and, when 
 fractured, are more speedily and more easily consolidated. In 
 youth, the two constituent parts are nearly in equal quantities; 
 
ON motion: 
 
 in adults, the calcareous earth* alone forms two thirds of the . 
 osseous substance. At last, gradually increasing in quantity, it 
 displaces, in old people, the part that is organized; hence their 
 bones are weaker, more liable to fracture, and unite less readily. 
 One may therefore say, that the quantity of phosphate of lime 
 deposited in the bones, is in the direct ratio of the age; and that, 
 on the contrary, the energy of the vital faculties of these organs, 
 their flexibility, their elasticity, their aptitude to become conso- 
 lidated, when their continuity is destroyed by accidents, are in 
 an inverse ratio. 
 
 ■ Anatomists distinguish in bones three substances, which they 
 term compact, spungy, and reticular. The first, which is the 
 hardest, collected in the centre of the long bones, where the 
 greatest stress of the efforts applied to their extremities rests, 
 gives to the bone the strength which it required. Its formation 
 has been explained, in various ways; some have maintained that 
 it owed its hardness to the pressure applied to its middle part 
 by the two extremities of the bone; in the same manner as the 
 stalk and the roots press against the colietj^oi a plant. Haller 
 thinks it is caused by the pulsations of the nutritious arteries 
 which penetrate into the long bones, at their middle part; why 
 then is their structure different at their extremities, where they 
 receive arteries equally large and more numerous? In the pro- 
 cess of ossification, this substance appears first in the centre of 
 the long bones; and this confirms the assertion of Kerkringius, 
 who says, that our long bones begin to ossify in those points 
 where they have to resist the greatest pressure. 
 
 The spungy substance is found within the short bones, and 
 at the extremities of the long ones, where its accumulation is 
 attended with two advantages, that of giving to the bone, with-, 
 out increasing its weight, a considerable size, by which it may 
 be articulated with the neighbouring bones, by wide surfaces, 
 
 m 
 
 * By chemical analysis of the bones, there have been discovered several 
 other saline substances mixed with the phosphate of lime; but as this salt 
 alone constitutes the greatest part of the substance which gives to the bones 
 their hardness, I thought that it would be useless to enter into minute details, 
 in a work of this kind, by giving an account of the more recent chemical 
 analyses. 
 
 t The part where the stem foins the root — T. 
 
 3 L 
 
ox MOTIOX. 
 
 450 
 
 so as to give firmness to their connexions; this conformation is 
 attended with another advantage, that of avoiding the paral- 
 lelism of the tendons which pass over the joints, in order to 
 enlarge the angle of their insertion in the bones, and to give 
 more efficacy to muscular action. The mechanical hypotheses 
 proposed by Haller and Duhamel, to explain the formation of 
 this spungy substance, are very unsatisfactory, especially if it 
 be considered, that in the gelatinous bones of the embryo, the 
 place that is to be occupied bvthe spungy substance, viz. the ex- 
 tremities of the long bones, of which the rudiments begin to ap- 
 pear, are larger than any other part. All the cells of this spungy 
 substance communicate with one another, they are lined by a 
 very fine membrane, and contain the medullary^ fluid. The 
 laminae which cross each other, in various directions, and which 
 form the parietes of the cells, become fewer in number and 
 thinner; the spungy tissue expands in approaching the middle 
 part of the bones, and forms (within the medullary canal, of the 
 compact substance) a reticular tissue, the use of which is t* 
 support the membranous tube containing the marrow. 
 
 These three substances, notwithstanding their unequal den- 
 sity, are, in reality, but one and the same substance differently 
 modified. The reticular and spungy differ from the compact, 
 in containing less phosphate of lime, and in having a rarer and 
 more expanded tissue. In other respects, those changes in the 
 osseous tissue which constitute the laminated exostoses, the 
 conversion of the bones, by acids, into a flexible cartilage, 
 which, by maceration, may be reduced into cellular tissue, 
 prove that these three substances are truly identical, and differ 
 from each other, only by the degrees of closeness of their tex- 
 ture and the quantity of calcareous phosphate deposited in the 
 meshes of their tissue. 
 
 The compact substance appears to consist of concentric lami- 
 nae strongly united together, and to be formed of fibres, arranged 
 longitudinally, and in juxta position. In proof of this arrange- 
 ment, it is usual to mention the exfoliation of bones exposed to 
 the air; but these laminae detached from an exfoliating bone, 
 merely prove that the action of the disease, the air, heat, or 
 any other agent, by applying itself successively to the different 
 layers of bone, produces between them a separation which did 
 
ON MOTION. 
 
 451 
 
 not exist in health, and determines their falling off in succes- 
 sion. Certain parts, in which this lamelated structure does not 
 exist, may, in like manner, undergo the same kind of decompo- 
 sition. Thus, Lassone saw a piece of human skin that had been 
 preserved, fora considerable length of time, in a vault, separate 
 into layers of extreme minuteness. 
 
 The vital principle which exists, in a smaller degree, in the 
 bones than in other parts, seems to animate, to a certain degree, 
 their different substances. Proportioned to the number of ves- 
 sels which are distributed to it, life is more active in the spungy 
 tissue; hence, in fracture of this part, fleshy granulations and 
 callus form more quickly. Caries, likewise, advances more 
 rapidly, and it is more difficult to interrupt its progress. 
 
 CLXXVI. Of the uses of the periosteum and of the medullary 
 juices. Whatever be the situation, the size, the shape, and the 
 composition of bones, they are all enveloped by the periosteum, 
 a whitish, fibrous, dense and compact membrane, to which are 
 distributed the vessels which penetrate into their substance. 
 The periosteum is a membrane perfectly distinct from the 
 other soft parts, and from the bone itself, to which it adheres 
 by means of vessels and of cellular tissue which pass from the 
 one to the other, the more closely, as we are more advanced in 
 years. The cellular and vascular fibres which penetrate into 
 the substance of the bone, establish a very close sympathetic 
 connection between its periosteum and the very delicate mem- 
 brane that lines its internal cavity, which secretes the marrow, 
 and is called the internal periosteum. On destroying the inter- 
 nal medullary membrane, by introducing a stylet within the 
 cavity of the bone, its external layers swell, are detached from 
 the inner ones, and form, as it were, a new bone around the 
 sequestra. The new bone is not formed by the ossification of 
 the periosteum, as was maintained by Troja. This membrane 
 has no more to do with the formation of the new bone, in ne- 
 crosis, than with that of the callus in fracture. The periosteum, 
 covering a bone affected with necrosis, does not become thicker, 
 and does not acquire more consistence; nor is there formed 
 around the ends of a fractured bone, a ring to keep them ce- 
 mented, as was the opinion of Duhamel; an opinion recently 
 brought forward in a work in which the author seems to delight 
 
452 MOTION. 
 
 in reviving errors that have been abandoned for ages. Desti- 
 tute of nourishment, dead and dried up in this artificial necro- 
 sis, the sequestra moves in the centre of the new osseous pro- 
 duction, from which it may be extracted by a perforation made 
 for that purpose. It is owing to the same sympathy, that the 
 dull nocturnal pains which are occasioned by the warmth of the 
 bed, in patients in the last stages of the venereal affection, and 
 which appear to have their seat in the centre of the long bones, 
 occasion a swelling of these bones and of the periosteum. 
 
 The use of the periosteum is to regulate the distribution of 
 the nutritious juices of bones, since, whenever it is removed, 
 granulations arise, in an irregular manner, on the spot that is 
 bared. This quality is, besides, common to all fibrous mem- 
 branes whose destruction is followed by excrescences from the 
 organs which they cover. The same takes place, whenever trees 
 are partially stripped of their bark. It has been erroneously 
 believed, that the periosteum, in the same way as the bark of 
 plants, contributes to the growth of the bones, by the succes- 
 sive induration of its internal lamina. 
 
 The marrow which fills the central cavity of the long bones; 
 and the medullary fluid contained in the cells of the spungy 
 substance, bear the greatest analogy to adeps, both in their 
 chemical composition and in their uses (CVI). The propor- 
 tion of these two fluids is uniforml}^ relative. In very thin peo- 
 ple, the bones contain a marrow that is thin and watery, and 
 though this fluid always fills the internal cavities of these or- 
 gans, whose solid parietes cannot colapse, it contains much 
 fewer particles in the same bulk: and its quantity, like that of 
 the fat, is in fact diminished. It is the product of arterial exha- 
 lation, and does not serve to the immediate nutrition of the 
 bone, as was thought by the ancients; at least, it does not 
 answer that purpose solely; for, in the numerous class of birds, 
 the bones contain cavities for air, and are destitute of this fluid. 
 It is difficult to determine the use of the marrow and of the 
 medullary fluid; may they not answer the purpose of filling the 
 cavities which nature has formed in the bones, so as to render 
 them lighter? Does a part of these fluids exude through the 
 cartilages of the joints, and mix with the synovia to increase its 
 quantity, and to lessen the friction of the articulating surfaces? 
 
ON MOTION. 
 
 453 
 
 If this transudation may take place after death, why might 
 it not take place, when all the parts are in a state of vital warmth 
 and expansion? 
 
 CLXXVII. Of the articulations^ the articulating cartilages 
 and ligaments^ and the synovial fluid. The articulations of the 
 different parts of the skeleton are not all intended to allow of 
 motion; several, as the serrated and squamous sutures, and the 
 gomphosis, are entirely without motion, and are, on that ac- 
 count, termed synarthrosis. All the other articulations, whether 
 the bones are in immediate contact (diarthrosis of contiguity), 
 whether they are united by a substance interposed between them 
 (diarthrosis of continuity or amphiarthrosis), are endowed with 
 a certain degree of mobility. I shall speak merely of the move- 
 able ar ticulations; whether they allow of extensive motions and 
 in every direction (diarthrosis orbicularis) or whether the bones 
 move only in two opposite directions (alternate diarthrosis or 
 ginglymus) by forming an angle, (angular ginglymus), or by 
 executing, on each other, motions of rotation (lateral gin- 
 glymus). 
 
 In all the articulations, the osseous surfaces are covered by 
 laipinse of a substance less hard than that of the bone. These 
 are the articulating cartilages, which answer the two purposes 
 of giving to the ends of the bones the degree of polish neces- 
 sary to their slipping freely, and to facilitate motion, by the 
 considerable degree of elasticity which they possess. Morgagni 
 has shown, that of all animal substances, cartilages possess most 
 I elasticity; their structure is very different from that of the bones, 
 even when these are yet cartilaginous; for, these articulating 
 cartilages do not become ossified, even in persons greatly ad- 
 vanced in years.* They are formed of very short fibres dis- 
 posed according to the length of the bone, strongly compressed 
 against each other, and united by other fibres. This vertical 
 direction of the greatest part of the cartilaginous fibres, demon- 
 strated by Lassone, is very favourable to their elastic re-action. 
 The capsular ligament is reflected over them, becomes very 
 
 * Sometimes, however, these cartilages are destroyed, the denuded bone 
 then becomes polished by friction, and as hard as ivory. 
 
ON MOTION. 
 
 454 
 
 thin, and is lost in their perichondrium, according to Bonn, 
 Nesbith, and other anatomists. 
 
 Besides the cartilages which surround the extremities of 
 bones, there are found, in certain articulations, fibro -cartilagi- 
 nous laminae lying between the articulating surfaces. These 
 connecting ligaments may be observed in the articulation of the 
 lower jaw to the temporal bones, of the femur with the tibia, 
 and of the sternum with the clavicle; and all such articulations 
 perform a great number of motions, as is the case with the jaw, 
 or suffer considerable pressure, as the joints of the knee and 
 sternum. The latter, which has a very slight degree of motion, 
 being the point in which terminate all the efforts of the upper 
 extremity, required this apparatus to lessen the effect on the 
 trunk, the motion that is given being, in part, lost in the action 
 of the articulating cartilage. 
 
 I shall not repeat what has been already said of the secretion 
 of the fluid that lubricates the articulating surfaces, that facili- 
 tates their motion and keeps them in contact. Its quantity is in 
 direct ratio of the extent of these surfaces and of the membra- 
 nous capsule- in which they are contained; it is, likewise, pro- 
 portioned to the frequency of motion which each articulation 
 allows. 
 
 Synovia is the name that is given to the fluid prepared by the 
 glandulo-cellular bodies in the vicinity of the articulations, and 
 secreted by the membranous capsules which surround them, 
 and are reflected over the articulating extremities of the bones 
 whose cartilages they cover; so that, as was shown by Bonn, 
 about the middle of the last century, these extremities cannot 
 be said to be contained within the cavity of the capsule, which 
 is closed, in every direction, any more than the abdominal vis- 
 cera within that of the peritoneum. The synovia is heavier than 
 common water, quite colourless, and more viscid than any other 
 animal fluid. It contains a considerable quantity of albumine 
 which, according to Marguerou, who first gave a tolerably ac- 
 curate analysis of synovia, is found in a particular state, and 
 much disposed to concrete into filaments, on the addition of 
 acids. Besides, it contains muriate and carbonate of soda and 
 phosphate of lime, the whole dissolved in water, which forms 
 about three fourths of its weight. 
 
ON MOTION. 
 
 455 
 
 CLXXVIII. Theory of anchylosis. Motion may be con- 
 sidered as the proper stimulus of the synovial secretion; and a 
 moveable joint, as is justly observed by Grimaud, is as a centre 
 of fluxion towards which the fluids rush, in every direction, in 
 consequence of the irritation which friction determines. If the 
 joint remains long without motion, the synovia is secreted in 
 smaller quantity, and this lessens gradually; it may even hap- 
 pen that the articulating surfaces, remaining long absolutely 
 motionless, lose their moisture, and from the want of the fluid 
 which should lubricate them, bring on irritation and adhesive 
 inflammation in each other, either from increased action of the 
 vessels of the perichondrium, or as is believed by Nesbith, 
 Bonn, and others, from an inflammatory state of the fold, which 
 is reflected from the capsule of the joint over the ligament. 
 
 This is the manner in which the disease, termed anchylosis, 
 comes on; a disease improperly ascribed to the congestion of 
 the soft parts, and especially of the ligaments surrounding the 
 articulations. In fact, when in a fracture of the thigh, or leg, 
 about the middle of the length of one of these bones, and con- 
 sequently, at the greatest possible distance from the knee joint, 
 the circumstances of the case require that the bandages should 
 be kept on the limb a considerable time, the joint loses its 
 power of motion, recovers it with difficulty, and sometimes 
 not at all. I have at present before me, the case of a man in 
 whom a scorbutic affection has delayed, to such a degree, union 
 of the bone, after a simple fracture of the femur, about the mid- 
 dle of the bone, that it has been found necessary to continue, 
 for seven months, the use of splints. In the course of so long a 
 state of inaction, the soft parts have lost the habit of moving, 
 and the knee is, almost completely, anchylosed. 
 
 Whenever on account of any complaint, one has been confined 
 to bed, the first attempts to walk are painful, difficult, and at- 
 tended by a marked crepitus in the knee, denoting clearly the 
 want of synovia. On the other hand, if the joint is examined 
 in a person who before death has been long without motion, 
 the articulating surfaces will be found rough and dry, with evi- 
 dent marks of inflammation. Flajani mentions the case of a 
 patient who died after having been three months in bed, in an 
 almost motionless state. Externally, the knees did not appear 
 
ON MOTION. 
 
 456 
 
 to have been injured, and yet he could not bend his knee joint. 
 On opening the joint, it was found that the articulating surfaces 
 had grown together; the posterior part of the patella adhered to 
 the condyles of the femur, and it was necessary to use a scalpel 
 to detach these parts from each other. I have frequently ob- 
 served the same appearance, in dissecting the knee joint of per- 
 sons who died while labouring under white swelling, with or 
 without ulceration. The anchylosis which invariably attends 
 this affection, evidently arises from the absolute rest of the 
 diseased joint. 
 
 Anchylosis from want of motion, and consequently from want 
 of synovia, is not always a partial affection limited to one or 
 two joints; sometimes it affects several at once, as in the case 
 of the patient whose skeleton was presented by M. Larrey to 
 the museum of the School of Medicine at Paris. One of the 
 most remarkable cases of universal anchylosis of the joints, is 
 that lately communicated to the National Institute by M. Percy; 
 the patient was an old cavalry officer, who was subject to fits 
 of the gout, and whose articulations, even that of the lower jaw, 
 became stiff, and completely lost all power of motion, so that, 
 towards the latter end of his wretched existence, he could not 
 be moved without feeling severe pain in his anchylosed joints. 
 
 From this explanation may be conceived the advantage of 
 moving the lower extremity, when, after a fracture of the leg, 
 the ends of the bone have become sufficiently united to prevent 
 their being displaced. These motions, which are of indispen- 
 sable necessity in all fractures of the femur, of the tibia, and 
 especially of the patella, are much better calculated to prevent 
 anchylosis, than the various resolvent remedies which are com- 
 monly employed, as plasters of soap, vigo, cicuta, diabotanum^ 
 diachylon, pumping, bathing and fumigations, which, however, 
 should be used in combination with a moderate exercise of the 
 limb, in order to obtain the most complete success. 
 
 The gout affects those joints which are most subject to mo- 
 tion,^ and on which there is the greatest pressure. The first 
 attacks, as Sydenham observes, come on in the joint of the 
 great toe with the first metatarsal bone; an articulation which 
 bears the weight of the whole body, and which is most called 
 into action, in the various motions of progression. 
 
ON MOTION, 
 
 457 
 
 The muscles which pass over the joints give them much 
 greater security than the lateral ligaments. In fact, if the mus- 
 cles become palsied, the mere weight of the limb stretches the 
 ligaments, which give way, become elongated, and allow the 
 head of the bone to escape from its gltnoid cavity. It is, in this 
 manner, that a loss of motion, and atrophy of the deltoid mus- 
 cle, are attended with a luxation of the humerus; the orbicular 
 ligament of the articulation of this bone with the scapula, being 
 incapable of retaining its head within the glenoid cavity. The 
 spinal column, when dissected and deprived of all but its liga- 
 mentous attachments, gives way under a weight much smaller 
 than that which it would have supported, before being stripped 
 of the muscles which are connected with it. 
 
 CLXXIX. Of standing'. This is the name given to the 
 action by which man holds himself upright on a solid plane. 
 In this erect position of all our parts, the perpendicular line, 
 passing through the centre of gravity* of the body, must fall 
 on some point of the space measured by the soles of the feet. 
 Standing is most firm, when, on prolonging the line of the 
 centre of gravity of the body, it falls on the base of sustenta- 
 tion (I call thus the space defined by the feet, whether close 
 or apart); but this line may tend to exceed it, without our 
 necessarily falling, the muscular action soon restoring the equi- 
 librium which is deranged by the altered direction of this line. 
 But if the lower extremity of the line, by being prolonged, 
 should fall without the limits of the base of sustentation, a fall 
 is unavoidable on the side towards which this line inclinesf. 
 
 If the body is inclined backwards, so that there is a danger 
 of a fall on the occiput, the extensor muscles of the leg contract 
 
 * The centre of gravity, in the adult, is situated between the sacrum and 
 pubis. 
 
 f “ Quotiescunque linea propensionis corporis humani, cadit extra unius pedis 
 innixi plantain aut extra quadrilaterum, comprehensum d duabus plantis pedum, 
 iinpediri ruina, d quocumque musculorum conatu non potest.” Borelli, Prop. 140. 
 
 The firmness of the attitude, in standing, depends, therefore, in part, on the 
 breadth of the feet and on their distance; hence, it is much more tottering 
 when we stand on one foot, and we are, under such circu mstances, obliged to 
 be perpetually struggling, to prevent the centre of gravity from falling out of 
 the narrow limits of the base of sustentation. 
 
 3 M 
 
ON MOTION. 
 
 458 
 
 powerfully, to prevent the thigh from bending, while other 
 powers bring forward the upper parts, and give to the pro- 
 longed line of the centre of gravity a different direction; and 
 if, in proportion as the extensors of the leg are brought into ac- 
 tion, its inclination be increased to such a degree, that nothing 
 is capable of keeping up the body, which its own weight tends 
 to bring to the ground, these muscles, by a motion proportioned 
 to the quickness of the fall, will increase their efforts to prevent 
 it, and may be able, in that violent contraction, to snap asunder 
 the patella, as I have explained in a memoir on the fractures of 
 that bone. 
 
 I think it useful to insist, more than has been done hitherto, 
 on the mechanism by which the human bodv is supported in the 
 erect posture; for a knowledge of that mechanism facilitates the 
 explanation of the motions of progression. To walk, or to run, 
 the body must be upright; now, when it is known by what power 
 the centre of gravity of the body is maintained perpendicular 
 on the plane which supports it, it will be easy to understand the 
 different ways in which it changes its place, in the course of 
 locomotion. 
 
 Let us first inquire into the question so long agitated, whether 
 man is intended to support himself and to walk on his four limbs, 
 in the early period of his existence after birth? 
 
 CLXXX. An upright position would be to man a state of 
 rest, if his head were in a perfect equilibrium on the vertebral 
 column, and if the latter, forming the axis of the body and sup- 
 porting equally, in every direction, the weight of the abdominal 
 and thoracic viscera, fell perpendicularly on the pelvis placed 
 horizontally; and, in short, if the bones of the lower extremities 
 formed columns set perpendicularly under their superincum- 
 bent weight; but not one of these circumstances is to be observed 
 in the human body: the articulation of the head does not corres- 
 pond to its centre of gravity; the weight of the thoracic and ab- 
 dominal viscera, and of the parietes of the cavities in which 
 they are contained, rests, almost entirely, on the anterior part 
 of the vertebral column. The vertebral column is supported on 
 an inclined base, and the bones of the inferior extremities, 
 which are connected to each other by convex and slippery sur- 
 faces, are, more or less, inclined towards one another. It is 
 
ON MOTION. 
 
 459 
 
 therefore necessary, that an active power* watch incessantly, 
 to prevent the fall which would be the natural consequence of 
 their weight and direction. 
 
 This power resides in the extensor muscles which keep the 
 parts of our body in a state of extension, the more perfect, and 
 which render our erect posture the firmer, as they are endowed 
 with a more considerable power of antagonism, and as our parts 
 are nacurally less disposed to flexion; and, besides, as we have 
 seen (CLXVI.) these powers are not sufficient to balance those 
 whose action is directly opposed to theirs. 
 
 The relative weakness of the extensor muscles is not the only 
 obstacle which renders impossible an erect posture, at an early 
 period of life. Other causes, into which we are about to enter, 
 concur in unfitting the new born child for the exercise of that 
 faculty. 
 
 The articulation of the head to the vertebral column being 
 nearer the occiput than the chin, and not correponding to its 
 centre of gravity, its own weight is sufficient to make it fall on 
 the upper part of the chest. It is the more disposed to fall for- 
 ward, from its greater bulk, and, as in a new born child the head 
 is much larger in proportion than the other parts of the body, 
 and as its extensor muscles partake of the greater weakness of 
 that set of muscles, it falls on the fore part of the chest, and in 
 its fall draws the body after it. The weight of the thoracic and 
 abdominal viscera tends to produce the same effect. 
 
 * An upright posture is not, in all animals, as it is in man, the consequence 
 of an effort. This is proved by the following fact observed by M. Dumeril. 
 The sea fowl, and especially the waders, (Grallse, Linn ) as herons and storks, 
 forced to live in the midst of marshes and muddy waters, in which they find 
 the fishes and reptiles on which they feed, have long since afforded matter of 
 surprize to naturalists, by the length of time they can remain motionless in an 
 erect posture. This singular power, so necessary to animals obliged to expect 
 their prey, more from chance than from industry, they owe to a peculiar con- 
 formation of the articulation between the leg and thigh. The articulating sur- 
 face of the thigh bone, as M. Dumeril had an opportunity of observing in a 
 stork, {Jlrdea ciconia, Linn.) contains, in its centre, a depression, into which 
 there is received a projection of the tibia. To enable the animal to bend its leg, 
 that projection must be disengaged from the depression into which it is lodg- 
 ed, and this is resisted by several ligaments which keep the leg extended in 
 standing, in flying, and other progressive motions, without the assistance of 
 the extensor muscles. 
 
ON MOTION. 
 
 460 
 
 Growth always proceeds from the upper to the lower parts, 
 and this law, which operates uniformly, completely eludes every 
 kind of mechanical explanation. It is otherwise, with regard to 
 the effects which result from this unequal growth in respect to 
 the erect posture. The inferior limbs, which serve as a base to 
 the whole edifice, being imperfectly evolved at the period of 
 birth, the upper parts placed on these unsteady foundations, 
 must necessarily fall and bring them down with them. 
 
 The relative weight of the head, of the thoracic and abdomi- 
 nal viscera, tends, therefore, to bring forwards the line in the 
 direction of which all the parts of the body press on the plane 
 which supports it, and this line should be exactly perpendicular 
 to that plane to enable the body to be perfectly erect: the fol- 
 lowing fact proves this assertion: I have observed, that children, 
 whose head is very large, whose belly projects, and whose vis- 
 cera are loaded with fat, have much difficulty in learning to 
 stand; it is only about the end of their second year, that they 
 dare trust to their own strength, and then they meet with fre- 
 quent falls, and have a continual tendency to go on all fours. 
 
 The vertebral column, in the child, does not describe, as in 
 the adult, three curves alternately placed in opposite directions. 
 It is almost straight, and yet presents in the direction of its 
 length a slight curvature, the concavity of which looks for- 
 wards. This incurvation, which depends solely on the flexion 
 of the trunk while in the womb, is accordingly more marked, 
 the nearer the child is to the time of his birth. 
 
 It is well known that the curvatures, in opposite directions to 
 the vertebral column, add to the firmness of the erect posture, 
 by increasing the extent of the space within which the centre of 
 gravity may move, without being carried beyond its limits. 
 With regard to that use, the vertebral column may be consider- 
 ed as defined by two lines drawn from the anterior and poste- 
 rior part of the first cervical vertebra, to the sacro lumbari sym- 
 physis. These two lines, very near to each other at their upper 
 part, and below, at a distance from each other, would be the 
 chords of arcs and the tangents of the curves, formed by the 
 vertebral column. So that this column may be considered as 
 having a fictitious thickness greatly exceeding its real bulk. 
 
 In the new born child the want of alternate curvatures not 
 
ON MOTION. 
 
 461 
 
 only contracts the boundaries within which the centre of gravity 
 may be varied, but the direction of the only curvature which 
 exists, favours the flexion of the trunk, and consequently the in- 
 clination forward of the centre of gravity, and the tendency to 
 fall in that direction. This inflexion of the vertebral column in 
 the foetus and in the young child resembles that observed in 
 several quadrupeds.* 
 
 The disadvantage resulting from the want of alternate curva- 
 tures in the vertebral column of the child is further increased by 
 the total absence of spinous processes. It is well known, that 
 the principal use of these projections, is to place the power at a 
 distance from the centre of motion of the vertebrae, to increase 
 the length of the lever by which it acts in straightening the 
 trunk, and thereby to render its action more efficacious. At the 
 period of birth, the vertebrae have no spinous processes; they 
 afterwards grow from the place at which the laminae of those 
 bones are united, by means of a cartilaginous substance, which 
 completes the posterior part of the vertebral canal. The mus- 
 cles destined to keep the trunk erect, weakened by its constant 
 flexion during gestation, lose, besides, a great deal of their 
 power, from the unfavourable manner in which they are applied 
 to the part on which they are to act. 
 
 The flexion of the head does not depend merely on its very 
 considerable weight, but, likewise, on the want of spinous pro- 
 cesses in the cervical vertebrae; since the principal motions of 
 the neck are performed, not so much by articulation with the 
 atlas, as by the union of the other cervical vertebrae. 
 
 The pelvis of the child is but imperfectly evolved, and its 
 upper outlet very oblique. The viscera, which are afterwards to 
 be contained within its cavity, are, for the greater part, situated 
 above it. This obliquity of the pelvis would require a perpetual 
 straightening of the vertebral column, to prevent the direction of 
 
 * This curvature is very distinctly marked in swine. The back of these ani- 
 mals is remarkably prominent, and this form, necessary to enable the vertebral 
 column to support the immense weight of their abdominal viscera, has a con- 
 siderable influence on the mechanism of their motions of progression. When 
 frightened by any noise, they spring in bounds, and it is easy to perceive that, 
 at each spring, the spine becomes arched and then straightens itself, and tliat 
 their motion when rapid is effected by the alternate tension and relaxation of 
 their spinal ai’ch. 
 
ON MOTION. 
 
 462 
 
 the centre of gravity from obeying its natural tendency forward. 
 On the other hand, the vertebral column, resting on a narrow 
 pelvis, is less firmly fixed, and may more readily be drawn 
 beyond the limits of the base of sustentation. Lastly, the limited 
 extent of the pelvis, together with its obliquity, causes the ill 
 supported abdominal viscera to fall on the anterior and inferior 
 part of the parietes of the abdomen, and favours the fall of the 
 body in the same direction. 
 
 The patella, which answers the double purpose of giving 
 firmness to the knee joint, in front of which it is placed, and of 
 increasing the power of the muscles of the leg, by placing them 
 at a distance from the centre of motion in that articulation, and 
 by increasing the angle at which they are inserted into the tibia, 
 as yet does not exist in new born children. The tendinous por- 
 tion of the extensors of the leg, where the patella is hereafter to 
 be formed, is merely of a more condensed tissue, and of a car- 
 tilaginous hardness. 
 
 The want of a fulcrum is attended with a continual disposi- 
 tion in the leg to bend upon the thigh; and the parallel direc- 
 tion of its extensor muscles, occasions a complete loss of their 
 effective power. Then their antagonizing muscles induce a 
 flexion of that limb, which is the more considerable, as it is but 
 imperfectly limited by the tendon which is situated at the fore 
 part of the knee. 
 
 The length of the os calcis, the extent of its projection beyond 
 the inferior extremity of the bones of the leg, tend to give firm- 
 ness to the erect posture, by increasing the length of the lever 
 by which the extensors of the foot act on the heel; and, as in 
 the new born child, this bone is shorter and less projecting, the 
 power of these muscles, whose insertion is very near the centre 
 of motion of the articulation of the foot, is greatly diminished. 
 
 The feet, in man, are broader than those of any other animal; 
 and to this breadth of the surface of the base on which he rests, 
 he, in great measure, otves the advantage of being able to sup- 
 port, on one leg or on both, the weight of his body, in standing 
 and in the different motions of progression; while the other 
 mammalia cannot support themselves, at least only for a very 
 limited time, without resting on three of their extremities. 
 When I say that from the extent of his feet, the body of man 
 
ON MOTION. 
 
 463 
 
 does, of all animals, rest on the broadest surface, I do not take 
 into account the space which those parts include between them 
 when apart from each other. In fact, the space which is measured 
 by the feet, is much greater in quadrupeds than in man. Nature 
 has made up for the disadvantage arising out of the smallness 
 of their feet, by the distance at which they are placed; and if 
 that form disables them from standing on two feet, it gives firm- 
 ness to their peculiar mode of standing. 
 
 The feet of the ourang outang, which, in the general struc- 
 ture of his organs, bears so striking an analogy to the human 
 species, resemble a coarsely formed hand, better fitted to climb 
 the trees on which that animal seeks his food, than to the pur- 
 poses to which man applies his hands. Thus the erect posture 
 which he, at times, assumes, is neither the most convenient nor 
 the most natural to him. And, according to a philosopher, who 
 speaks on the authority of several travellers, if a sudden danger 
 obliges him to make his escape, or to leap, he drops on all fours, 
 and discovers his real origin; he is reduced to his own condi- 
 tion when he quits that unnatural attitude, and discovers in him- 
 self an animal, which, like many a man, has no better quality to 
 recommend him than a specious disguise. 
 
 The feet are the parts least developed in the new-born child; 
 his body is insecure on that narrow basis; the prolongation of 
 the line of his centre of gravity, which so many other causes 
 tend to carry beyond that base, will be the more inclined to fall 
 beyond it, from its small extent. The greater number of the 
 differences which have just been examined, depend on the mode 
 of nutrition in the fcetus. The umbilical arteries bring to the 
 mother the blood which the aorta carries towards the lower parts, 
 and only a few small branches are sent to the pelvis, and to the 
 lower extremities. Thus, the development, which almost uni- 
 formly bears a proportion to the quantity of blood sent into 
 organs, is but imperfect in those parts at the time of birth, 
 while the head of the trunk and upper extremities are evolved 
 much more considerably. 
 
 The new-born child, therefore, resembles quadrupeds in the 
 physical arrangement of his organs. This analogy is the more 
 marked, the nearer the fcetus is to the period of his formation; 
 and it might be laid down as a general proposition, that orga- 
 
ON MOTION. 
 
 464 
 
 nized beings resemble one another more closely, the nearer to 
 the period of incipient existence they are examined. The dif- 
 ferences which characterize them become apparent, in propor- 
 tion to the progress of evolution; and they are more and more 
 distinct, as the acts of life are repeated in the organs which it 
 animates. 
 
 The unequal distribution of power in the muscles, and the 
 unfavourable disposition of the parts to which these powers are 
 applied, render it impossible for the infant to stand upright; that 
 is, to keep the mean line of direction of its body nearly perpen- 
 dicular to the plane which supports it. But in proportion as he 
 advances in age, the preponderance of the flexors over the ex- 
 tensors ceases to be in excess. The proportionate size of the 
 head, and of the thoracic and abdominal viscera, diminishes. 
 The curvatures of the vertebral column begin to be distinguish- 
 able; the spinous processes of the vertebrae are evolved; the 
 breadth of the pelvis is increased, and its obliquity lessened; the 
 patella becomes ossified, the os calcis juts out backwards, the 
 relative smallness of the feet ceases. By degrees the child learns 
 to stand, resting on both or only on one of his feet; his eyes 
 naturally directed towards heaven, a noble prerogative, which, 
 if one might believe Ovid,^ is possessed by man alone of all the 
 animals. 
 
 Man is, of all animals, the only one that can stand upright, 
 and walk in that attitude, when his organs are sufficiently 
 evolved. Let us now point out some of the principal causes to 
 which that privilege is to be ascribed. 
 
 CLXXXI. Though the articulation of the head to the cervi- 
 cal column, does not correspond either to its centre of magni- 
 tude, or to its centre of gravity; and though it is nearer to the 
 occiput than to the chin, its distance from the latter is much 
 smaller in man, than in the monkey and other animals, whose 
 foramen magnum is, according to Daubenton, placed nearest to 
 the posterior extremity of the head, when they resemble man 
 
 * Os homini sublime dedit, calunique tueri 
 Jussit, et evectos ad sidera tollere vullus. 
 
 These verses may be much more justly applied to the fish, called by natu- 
 ralists Uranoscobus. Its eyes are turned upwards, and constantly look towards 
 the heavens. 
 
ON MOTION. 
 
 465 
 
 the least. The head, therefore, is very nearly in equilibrio on the 
 column which supports it; at least to keep it in that position, a 
 very slight power is required; while the head of a quadruped, 
 which has a constant tendency towards the ground, requires to 
 be supported by a part capable of a great and continued resist- 
 ance. This purpose is answered by the posterior cervical liga- 
 ment, so remarkable in those animals, attached to the spinous 
 processes of the vertebrae, and to the protuberance of the occi- 
 pital bone, which projects much more in them than in the human 
 species, in whom instead of a posterior cervical ligament, there 
 is found a mere line of cellular substance, dividing the nape of 
 the neck into two equal parts. 
 
 The alternate curvatures of the vertebral column, the breadth 
 of the pelvis and of the feet, the great power of the extensors of 
 the foot and thigh,* all these favourable conditions observable 
 in man, are wanting in animals; but, as in the latter, every 
 thing concurs to prevent their being capable of standing on two 
 feet, in man every thing is so disposed, as to render it very diffi- 
 cult for him to rest on his four extremities. In fact, indepen- 
 dently of the great inequality which there is between his upper 
 and lower limbs, a difference of length, which, being less sensi- 
 ble in early life, makes it less uneasy for a child to walk on its 
 hands and feet, these four limbs are far from affording the body 
 an equally solid support. The eyes being naturally forwards, 
 are, in that attitude, directed towards the earth, and do not em- 
 brace a sufficient space. 
 
 We cannot, therefore, agree with Barthez, that man, during 
 infancy, is naturally a quadruped, since he is then but an imper- 
 fect biped (CLXXX); nor can we admit that man might walk 
 on all fours all his life, if he were not broken of the bad habit 
 which he learns in infancy. 
 
 CLXXXII. Very little has been added to what Galen has 
 said in his admirable work on the structure of parts, relative to 
 the respective advantages attending the peculiar conformation 
 and structure of the upper and lower limbs. It is easy to see, 
 that in combining, as much as possible, strength and facility 
 
 * These muscles form the calf of the leg and the buttocks; in no animal are 
 these masses of flesh more prominent than in man. 
 
 3 N 
 
ON MOTION. 
 
 466 
 
 of motion, Nature has made the former predominate in the 
 structure of the inferior extremities; while she has sacrificed 
 strength to facility, to precision, to extent, and rapidity of mo- 
 tion, in the upper extremities. 
 
 To convince oneself of the truth of what has been stated, it is 
 sufficient to compare, under the two relations* of the resistance 
 of which they are capable, and of the motions which they allow, 
 the pelvis to the shoulder, the thigh to the humerus, the leg to 
 the fore arm, and the foot to the hand. 
 
 The inferior extremities, if examined when the bones are 
 covered with the soft parts, will present the appearance of an 
 inverted cone or pyramid, which, at first sight, appears con- 
 trary to the object which nature had in view; but if the bones 
 be stripped of their fleshy coverings, these solid supports will 
 be seen to represent a pyramid, whose base is at the lowest 
 part and formed by the foot, and which decreases in breadth 
 upward from the leg, formed by the union of two bones, 
 towards the thigh, consisting of only one bone. 
 
 If it be asked why the inferior extremities are formed of 
 several pieces, detached and placed one above the other, it will 
 be found that they are thereby much more solid, than if formed 
 of one bone; since, according to a theorem, demonstrated by 
 Euler,! two columns containing the same quantity of matter 
 and of equal diameter, have each a solidity in inverse ratio of 
 the squares of their height: in other words, of two columns, 
 
 * See the anatomical observations on the neck of tlie thigh bone, which I 
 have prefixed to a memoir which bears tlie title of Dissertation analomico-ciii- 
 rurgicale sur les fractures clu cot du femur. Paris, an VII. 
 
 f J\'hthodus inveniendi linens curvas. 
 
 Nature has, therefore, increased the number of these columns in the ex- 
 tremities of quadrupeds, by raising their heel and the different parts of the 
 foot, whose bones she has lengthened, to make of them so many secondary- 
 legs. These numerous columns placed above one another, are alternately 
 inclined, and in a state of habitual flexion, in the quadrupeds remarkable 
 for swiftness in running or for their power in leaping, as in the bare and 
 squirrel: while in the ox, and especially in the elephant, they are all phsced 
 vertically, so that the enormous mass of the latter rests on four pillars, the 
 different pieces of which arc short, and so slightly moveable on one another, 
 that, as Barthez observes, Saint Basil has adopted the error of Pliny, .3Elian, 
 and several other writers of antiquity, that there are no articulations in the 
 legs of that monstrous animal. 
 
ON MOTION. 467 
 
 containing the same materials, of equal diameter, and of une- 
 qual height, the smaller is the stronger. 
 
 The long bones, which by their union form the inferior ex- 
 tremity, contain a cavity which adds to their strength, for ac- 
 cording to another theorem, explained by Galileo, two hollow 
 columns of the same quantity of matter, of the same weight and 
 length, bear to each other a proportion of strength measured by 
 the diameter of their internal excavations. 
 
 The breadth of surface of the articulations of the inferior ex- 
 tremities, assists, materially, in giving them additional strength, 
 when, in standing, these bones are in a vertical direction. No 
 articulation has a broader surface than that of the thigh with 
 the leg and knee pan. Among the orbicular articulations, no 
 one has more points of contact than the joint of the thigh bone 
 to those of the pelvis. Professor Barthez says, that when the 
 body is erect, the head of the thigh bone and the acetabulum 
 of the os innominatum, which receives that bone, come in con- 
 tact in a surface of small extent. I am, on the contrary, of 
 opinion that in no possible case can the contact of two bones 
 be more complete. The middle line of direction of the upper 
 part of the thigh bone, is then exactly perpendicular to the sur- 
 face of the condyloid cavity, which embraces and touches, in 
 nearly every point, the almost spherical head of that bone. 
 
 The cervix on which the head of the bone is placed, by keep- 
 ing the thigh bone at a distance from the cavity of the pelvis, 
 increases the extent of the space, in which the centre of gravity 
 may vary without being carried beyond its limits. 
 
 CLXXXIII. The erect posture does not imply a perfect ab- 
 sence of motion. It is, on the contrary, accompanied by a stag- 
 gering which is the more marked in proportion as the person 
 has less strength and vigour. These perpetual oscillations, 
 though but slightly distinct in a man who stands upright, depend 
 on the incapacity of the extensors to keep up a constant state of 
 contraction, so that they become relaxed for a short time, and 
 the intervals of rest in the extensors are frequent, in propor- 
 tion to the weaker state of the subject. 
 
 Some physiologists have given a very inaccurate idea of 
 standing, by making that attitude depend on a general effort of 
 the musclesj the extensors only, are truly active. The flexors. 
 
468 
 
 ON MOTION. 
 
 far from assisting, tend, on the contrary, to disturb the relation 
 between the bones, necessary to render that state permanent. 
 This explains, why standing is so much more fatiguing than 
 walking, in which the extensors and flexors of the limbs are 
 in alternate action and rest. 
 
 It may be said, nevertheless, that to give the greater firm- 
 ness to the attitude, we sometimes contract, in a moderate de- 
 gree, the flexors themselves; then, that great part of the real 
 force of the muscles, which acts according to the direction of 
 the levers which they are to set in motion (CLXV.) and which 
 is completely lost in the different motions which they produce, 
 is usefully employed in drawing together the articular extre- 
 mities; in keeping their surfaces firmly applied to each other, 
 and in maintaining their exact super-position which is neces- 
 sary to the erect posture of the body. No one that I know of, 
 had taken notice of this employment of the greater portion of 
 our muscular power, which was thought completely lost by the 
 unfavourable arrangement of our organs of motion. The line, 
 according to which all the parts of the body bear on the plane 
 which supports them, has much more tendency to fall forwards 
 than backwards;* and falls forward are the most common and 
 the easiest. Thus, nature has directed, in the same direction, 
 the motion of the hands, which we carry forward to break the 
 force of our falls, to prevent too violent shocks, and to lessen 
 their effect. At the same time, she has provided means of pro- 
 tection towards the sides which the hands could not guard. 
 She has given more thickness to the back part of the skull; the 
 skin which covers the neck and back, is much denser than that 
 which covers the fore part of the body. The scapula, in addi- 
 tion to the ribs, protects the posterior part of the chest. The 
 spinal column lies along the whole length of the back; the bones 
 of the pelvis have their whole breadth turned backward. 
 
 Falls are the more serious, as they occur in a more perfect 
 state of extension of the articulations; the falls of a child whose 
 
 * This tendency is much less distinct in tall slender men. It is observed, 
 that the}", for the most part, stoop in walking, less from the habit of bending 
 forward, than to prevent the centre of gravity from falling behind. Pregnant 
 women, dropsical patients, all persons who have much embonpoint, throw 
 their body back, from an opposite and easy understood reason. 
 
ON MOTION. 
 
 46d 
 
 limbs are in an habitual state of flexion, are much less danger- 
 ous than those of a strong and powerful adult, whose body falls 
 in one piece, if I may be allowed that expression. The falls 
 which skaiters meet with, on the ice, are often fatal from frac- 
 ture of the skull, which placed at the extremity of a long lever 
 formed by the whole body, whose articulations are on the 
 stretch, strikes the slippery and solid ice, with a momentum 
 increased by the quickness of the fall. 
 
 We have already seen, that wading fowls remain a long 
 while standing, without effort, by means of a peculiar contri- 
 vance in the articulation of the tibia to the thigh bone; but all 
 other birds are obliged to employ muscular action when stand- 
 ing, except during sleep. The greater part, it is well known, 
 roost on a branch which they grasp firmly with their claws. 
 Now, this constriction, by which they cling to their support, is 
 a necessary result of the manner in which the tendons of the 
 flexors of their feet descend along their legs. These tendons 
 pass behind the articulation of the heel; a muscle which arises 
 from the pubis joins them, as it passes in front of the knee, so 
 that the bird has but to give way to his weight, and the joints, 
 becoming salient on the side along which the tendons run, 
 stretch and pull them, and make them act upon the feet, so as 
 to draw in the claws to clasp tightly the branch on which he is 
 perched. Borelli was the first who understood distinctly and 
 explained satisfactorily this phenomenon.^ 
 
 CLXXXIV. Although standing on both feet is most natural 
 to man, he is able to stand on one; but the posture is fatiguing, 
 from the forced inclination of the body to the side of the leg 
 which supports him, and the effort of contraction required to 
 keep up this lateral inflexion. The difficulty increases if, in- 
 stead of resting on the entire sole, we chuse to stand on the 
 heel or on the toe: the base of support is then so small, that no 
 effort is sufficient to keep the centre of gravity, long together, 
 in the requisite situation. 
 
 As to the degree of separation of the feet, which gives the 
 firmest possible stand, it depends upon their length. When they 
 
 * De motu animallum, Prop. 150. Qiisritur quare aves stando, ramis arbo- 
 rum comprehensis, qiiiescunt et dormiunt absque ruina. Tab. II. fig’. 7 . 
 
ON MOTION. 
 
 470 
 
 enclose a perfect square, that is, when, taking their length at 
 nine inches, each side of the quadrilateral figure is of that 
 measure, the stand is the firmest that can be conceived. Never- 
 theless, we are far from keeping or taking this posture to pre- 
 vent falls. The wrestler, who wants to throw his antagonist, 
 strides much more; but then he loses on one side what he 
 gains on another; and if he stride 36 inches, on the transversal 
 line, it will need much greater force to overthrow him on that 
 side; but it will take much less to throw him forwards, or on 
 his back. Wherefore, one of the great principles of this gym- 
 nastic art, is to bring back the feet to a moderate stride, in the 
 line of the effort which is foreseen to require resistance. 
 
 There is some resemblance to standing, in the attitudes of 
 kneeling and sitting. 
 
 In the first, the weight of the body bears upon the knees, and 
 we must bring back the body, to throw the centre of gravity over 
 the middle of the legs. Accordingly, if we have nothing before 
 us to lean on, this posture is extremely distressing, and we can- 
 not long keep it on. I have said, in another work, that genu- 
 flexion rendered monks very liable to hernia; the abdominal vis- 
 cera being pushed against the anterior and lower part of the ab- 
 domen by the throwing back of the body. 
 
 In sitting, the weight of the body bearing on the tuberosities 
 of the ischia, there is much less effort required than in standing 
 on the feet. The base of support is much larger; and when the 
 back leans, almost all the extensor muscles employed in stand- 
 ing are in action. 
 
 CLXXXV. Of the recumbent posture. Decubitus. All the 
 authors who, like Borelli, have treated professedly of the ani- 
 mal mechanism; all the physiologists, who, like Haller, have set 
 forth, in some detail, the mechanism of standing, and of pro- 
 gression, have completely passed over the consideration of the 
 human body in repose, left to its own weight, in lying on an 
 horizontal plane. The intention of the following observations is 
 to fill up this gap. Let us consider, at setting out, that lying on 
 an horizontal plane, is the only posture in which all the locomo- 
 tive muscles recover the principle of their contractility, exhaust- 
 ed by exertion. Standing without motion, has only the appear- 
 ance of repose, and the unremitted contractions it requires, fa- 
 
ON MOTION. 
 
 47i 
 
 tigue the muscular organs, more than the alternate contractions, 
 by which the various motions of progression are carried into 
 effect. 
 
 The human body, stretched on an horizontal plane, reposes 
 in four positions, as it lies on the back, the belly, or one or other 
 of the sides. The Latin tongue expresses the first two situations, 
 by the terms supine and prone. It has no particular word for 
 lying upon the side. 
 
 Lying upon the right side is the most ordinary posture of 
 sleep, in which we rest most pleasantly, and longest together. 
 There are very few, except under constraint of some faulty or- 
 ganization, who lie on the other side. This depends on two 
 causes; when the body lies on the left side, the liver, a bulky 
 viscus, very heavy, and ill steadied in the right hypochondrium, 
 presses with all its weight on the stomach, and draws down the 
 diaphragm: thence ensues an uneasiness, which hinders long 
 continuance of sleep, or disturbs it with distressing dreams: then 
 the human stomach presents a canal in which the course of its 
 contents is obliquely directed from above downwards, and from 
 left to right: the right or pyloric orifice of the stomach is much 
 less raised than its left or cardiac orifice; lying on the right side 
 favours, therefore, the descent of aliments, which, to pass into 
 the intestines, are not obliged to ascend against their own 
 weight, as they must, in lying on the left side. These two ana- 
 tomical causes exert their influence on the generality of men; 
 and if there are any who fall into the habit of lying on the left, 
 one may safely conjecture some vicious organization, or some 
 accidental cause, that determines them, as by instinct, to this 
 posture. 
 
 Let us Suppose an effusion of blood, water, or pus in the sac 
 of the pleura of the right side. The patient lies on this side, 
 that the weight of his body may not oppose the dilatation of the 
 sound side of the chest. The parietes of this cavity are not 
 equally distant from its axis; the pressure of the body on the 
 plane of support, prevents the separation of the ribs, whether as 
 a mechanical hindrance to the displacement of these bones, or 
 in numbing the contractility of the muscles of inspiration, all 
 more or less compressed: Now, as the healthy lung must sup- 
 ply the place of the diseased, nothing could.be more in the way 
 
ON MOTION. 
 
 .472 
 
 than to produce, on that side, by a bad posture, a constraint 
 equal to that occasioned by disease on the other. 
 
 It has long been imagined, and it is taught still, that, in tho- 
 racic effusions, patients lie on the side of the effusion, to hinder 
 the effused fluid from pressing on the mediastinum, and pushing 
 it against the opposite lung, of which it will constrain the deve- 
 lopment. The following experiments show clearly enough the 
 error of such a supposition: 
 
 I have several times produced artificial hydrothorax, by in- 
 jecting, with water, the chest of several bodies, through a wound 
 in one of the sides. This experiment can be made only on bodies 
 in which the lungs are free from adhesion to the parietes of the 
 chest, and the number is smaller than might be imagined; you 
 may introduce in this way from three to four pints of water. I 
 afterwards opened carefully the opposite side of the chest: the 
 ribs removed and the lung displaced, gave room to see distinctly 
 the septum of the mediastinum stretched from the vertebral 
 column to the sternum, and supporting, without yielding, the 
 weight of the liquid, whatever might be the posture given to 
 the body. 
 
 It is for the sake then, evidently, of not preventing the dilata- 
 tion of the sound part of the respiratory apparatus, already con- 
 demned in one part to inaction, that patients, in thoracic effu- 
 sion, lie constantly on the side of the effusion. It is for the same 
 motive, to which we may add that of not increasing the pain by 
 dragging downward the inflamed pleura, that patients in pleu- 
 risy lie on the affected side. The same thing happens in perip- 
 neumonies; in a word, in all diseased affections of the lungs and 
 parietes of the chest. 
 
 Lying on the back, which is unusual in health, is natural in 
 many diseases. It commonly indicates more or less weakness of 
 the muscles of inspiration. The contractile powers which per- 
 form the dilatation of the chest, when affected with adynamia, 
 in fevers of a bad character, or after extreme fatigue, carry very 
 imperfectly into effect this dilatation. Nevertheless, a deter- 
 minate quantity of atmospherical air must be admitted, ever)- 
 moment, into the lungs, and the general weakness would be 
 increased, if respiration did not impregnate the blood with a 
 sufficiency of oxygen: patients choose, therefore, the posture 
 
ON MOTION. 
 
 473 
 
 which makes the dilatation of the lungs easiest for their weak- 
 ened muscles. The posterior parietes of the chest, on which the 
 body reposes, in lying upon the back, is almost useless in the 
 expansion of the cavity. The ribs, which have the centre of 
 their motions in their articulation with the vertebral column, 
 are almost immoveable backwards, and the moveableness of 
 these bones, increases with the length of the lever which they 
 represent; so that no whei-e is it greater than at the anterior 
 extremity terminating in the sternum. Thus, lying on the back 
 has the double advantage of not constraining any of the mus- 
 cles of inspiration, and of not opposing the motion of the ribs., 
 except at that part where these bones have the least play: lying 
 on the back is one of the characteristic symptoms of putrid or 
 adynamic fever, of scurvy, and of all the diseases of which de- 
 bility of the contractile parts forms the principal characteristic. 
 After the fatigue of a long march, or of any other continued 
 exertion, we take this position in lying, and change it only when 
 sleep has sufficiently replaced the loss of contractility. 
 
 Lying on the belly has effects directly the reverse. The 
 expansion of the chest is hindered exactly where the bony 
 structure is formed for the greatest play of motion; the abdo- 
 minal viscera are besides pushed up on the diaphragm, of which 
 they resist the depression, and the posture is accordingly un- 
 usual. The continuance of it during sleep is possible only to 
 the robust: others, even when they do fall asleep in this posture, 
 soon wake from troubled and distressing dreams, under the 
 agony known by the name of the night-mare. We sonoetimes 
 seek this posture to constrain respiration, and so abate inward 
 excitation, in the ardour, for instance, of a febrile paroxysm. 
 
 The different pos^tures of lying having reference to the de- 
 grees of facility of respiration, very young children and persons 
 advanced in years, prefer lying on the back; this posture being, 
 as was already observed, the most favourable to the motions of 
 respiration. Respiration, like all the other functions of the ani- 
 mal economy, with the exception of the circulation and of the 
 phenomena which immediately depend on it, requires a kind of 
 cultivation; it is but feebly performed at an early period of life. 
 It is only after a certain number of years, and when the muscles 
 of respiration, at first small and weak, acquire strength from 
 
 30 
 
ON MOTION. 
 
 474 
 
 the very circumstance of being called into frequent action, that 
 the chest dilates with facility, and that the lungs enjoy the full 
 exercise of their faculties. Until that period, the enlargement 
 of the chest and the dilatation of the lungs took place in an im- 
 perfect manner; the child was unable, even by spitting, to free 
 itself of the mucus with which its bronchiae are apt to get filled, 
 and which render the pulmonary catarrh, called the hooping 
 cough, so dangerous at an early period of life. In like manner, 
 in an old man, the muscles, debilitated, and returned to the re- 
 lative weakness of infancy, in vain strive to clear the air cells of 
 the mucus with which they become obstructed in the suffocating 
 catarrh. The mechanical process of respiration is, therefore, 
 equally difficult in the child, from the weakness of the muscles 
 which have remained in a long continued state of inactivity; in 
 the old man, from the debility of the same organs and from the- 
 induration of the cartilages. Thus, at those two distant periods 
 of life, it is most natural to lie on one’s back, but there is a suf- 
 ficiently remarkable difference in that respect, and which may 
 now be inquired into. 
 
 In the foregoing observations, I have always spoken of the 
 human body as stretched on a perfectly horizontal plane. It is 
 seldom, however, that we rest on such a surface; almost every 
 one, and especially persons advanced in life, require that the 
 plane should be inclined, and that the head should be raised, to 
 a certain degree, else the brain would become affected with a 
 fatal congestion of blood. Children, on the other hand, suflFer 
 no inconvenience from a neglect of this precaution; whether it 
 is that in them, the vital power has more energy, and thus ba- 
 lances better the laws of mechanics, by opposing more power- 
 fully the effects of gravitation; or whether it is, that in very 
 young children, the parietes of the arteries within the skull, 
 have a proportionate thickness, and consequently greater power. 
 The extreme disproportion observable in adults, in the thick- 
 ness of the parietes, between the cerebral arteries and those of 
 other parts of the body, is but trifling in children; and may not 
 this difference of structure, which I have several times observ- 
 ed in the course of dissection, be considered as one of the 
 principal causes which, in old age, bring on apoplexjq a disease 
 to which the child is not liable. 
 
ON MOTION. 
 
 475 
 
 It Is well known, that as the enlargement of the ch^st is pro- 
 duced by the depression of the diaphragm, persons who have 
 taken a plentiful meal, dropsical patients, pregnant women, can- 
 not rest without lying on aVery inclined plane; so that the' chest 
 being considerably raised, and the patient, as It were, seated, 
 the weight of the abdominal viscera draws them towards the 
 most depending part, that their bulk may not interfere with the 
 depression of the diaphragm. 
 
 We might now inquire what is the posture in which the body 
 rests with least fatigue; this investigation, unimportant to the 
 physician, would be of the highest value to the arts, which have 
 for their object the imitation of nature. In consequence of 
 ignorance on this subject, we often see, in the works of several 
 of our sculptors, figures in attitudes of repose so incorrect and 
 uneasy, that they could not maintain them without considerable 
 effort and fatigue. 
 
 CLXXXVI. Of the motions of progression. Of walking. 
 Walking, running, and leaping, are so closely connected, that it 
 is difficult to distinguish them. There is, in fact, very little dif- 
 ference between walking, in a certain manner, or running; and 
 running is most frequently produced by the complicated me- 
 chanism of running and leaping. In the most natural way of 
 walking, we, in the first instance, poise the body on one foot; 
 then, bending the opposite foot on the leg, the latter on the 
 thigh, and the thigh on the pelvis, we shorten that extremity; 
 we, at the same time, carry it forward, extend its articulations, 
 which were bent, and when firmly applied to the ground, we 
 bend the body forward, and carry back the centre of gravity in 
 that direction; and performing the same motions with the limb 
 which remained behind, we measure the space the more rapidly, 
 cseteris paribus, as the levers, on which the centre of gravity 
 alternately bears, are longer. The weight of the body, compared 
 to that of the lower extremities, is as that of a carriage, which 
 moves, in succession, on the different spokes of its wheels. 
 
 The centre of gravity does mot move along a straight line, but 
 between two parallels, in which space it describes oblique line# 
 from the one parallel to the other, and forms zig-zags. The 
 oblique direction of the neck of the thigh bones, accounts for the 
 lateral oscillations of the body when we walk; the arms which 
 
ON MOTION. 
 
 476 
 
 move, in a different direction from that of the lower extremi- 
 ties, serve to balance us, preserve the equilibrium, and correct 
 the staggering, which would be much greater, if the neck of the 
 thigh bone, instead of being oblique, had been horizontal. The 
 impulses communicated to the trunk, are reciprocally balanced, 
 and the latter moves in the diagonal of a parallelogram, whose 
 sides are represented by the line of these impulses. We con- 
 stantly deviate from the straight line in walking; and if the sight 
 did not enable us to see, at a distance, the object towards which 
 we are moving, we should go to a considerable distance from it. 
 If you place a man, with his eyes blind-folded, in the middle of 
 a square field, he will, in his attempt to get out, and thinking 
 that he is moving in a straight line, make for one of the corners. 
 It is, almost always, towards the left that we deviate; the right 
 lower extremity, which is the stronger, inclining the body 
 towards the opposite side. Those who are lame depart much 
 more from a straight line, and deviate towards the side of the 
 shorter leg. The motions which they are obliged to use, and 
 which render their gait so remarkable, are occasioned by the 
 necessity of incessant and powerful efforts, to prevent the body 
 from giving way to its own weight, and to the greater power of 
 the sound extremity, which inclines it towards the affected side. 
 
 The breadth of the feet, and a moderate separation of these 
 parts, give a much firmer support to the centre of gravity. Thus, 
 in walking on a moving and insecure surface, we hold apart 
 our feet, so as to include a greater base of sustentation. Those 
 who have long been at sea, acquire such a habit of holding their 
 feet asunder, in the way they are obliged to do during the 
 rolling of a ship, that they cannot lose the habit even when on 
 shore, and are easily recognised by their gait. A sailor is unfit 
 for active service, till he has acquired what is called, by sea- 
 faring people, a seaman’s foot; that is, till he is capable of step- 
 ping firmly on the deck of a vessel tossed by the tempest. 
 
 The gait of a woman, from her having smaller feet, is less 
 firm; but ought we, from that circumstance, to infer, with the 
 most eloquent writer of the eighteenth century^ that this dimi- 
 nutive size of the foot, is connected with the necessity of her 
 being overtaken in flight. The concave form of the sole of the 
 feet, by enabling them b^ter to adapt themselves to the tmeveh- 
 
ON MOTION. 
 
 477 
 
 ness of the soil, concurs in giving a firmer footing in walking, and 
 in other motions of progression. There is, in walking, an inter- 
 mediate moment, between the beginning and end of a step, 
 during which the centre of gravity is in the air; this lasts from 
 the moment when the centre of gravity is no longer in the foot 
 which remains behind, till it returns into the other foot which 
 is carried forward. 
 
 Walking is modified, according as it takes place on a hori- 
 zontal or an inclined plane; in the latter case, we ascend or 
 descend, and the exertion Is much more fatiguing. To explain 
 the action of ascending, let us suppose a man at the bottom of a 
 flight of stairs, which he wishes to go up; he begins by bending 
 the articulations of the limb which he is desirous of carrying 
 forward; he raises it thus, and shortens it to advance; and when 
 the foot, which is in a state of semi-extension, rests on the 
 ground, he extends the articulations of the other extremity, 
 carries thus the body upward, in a vertical direction, and com- 
 pletes this first step, by contracting the extensors of the leg that 
 were first in action, so that they may bring forward and restore 
 to it the centre of gravity, to which the posterior leg, whose 
 foot is extended, has given a vertical motion of elevation. 
 Hence, in ascending, the calves of the legs and knees, especially 
 the latter, are so much fatigued; for, the effort with which the 
 extensors of the foremost leg, bring back again upon it the centre 
 of gravity, is more powerful than that by which the gemelli and 
 the soleus impart to it, by extending the hindmost foot, a mo- 
 tion of vertical elevation. 
 
 To relieve the extensors of the leg, we bend the body for- 
 ward as much as possible; we lean back, on the contrary, in 
 descending a flight of stairs, or a rapid slope, in order to slacken 
 the motion by which the body, yielding to its own weight, falls 
 on the leg that is carried forward. 
 
 At the moment when the centre of gravity is no longei* 
 within the base of sustentation, all the powers unite in action, 
 that it may fall, as little as possible, from a vertical direction. 
 The glutaei steady the pelvis, and straighten the thigh: the 
 lumbar muscles extend the trunk on the pelvis; hence, in going 
 down a slope, the loins get so much fatigued. We are less 
 fatigued in going down hill, wh/jn the slope is moolerate, than 
 
ON MOTION. 
 
 478 
 
 in going up hill; as the force of gravitation, or the weight of the 
 body, assists considerably the descending vertical motion. The 
 motion of walking, when we take very long steps, resembles 
 that of going up hill, as the body being lowered, every time the 
 legs are much apart, requires to be elevated, at each step, 
 towards the foremost leg. 
 
 At every step we take, the articulation of the leg with the 
 foot is the principal seat of an effort, to which physiologists 
 have not paid any attention. The whole weight of the body is 
 supported by the action of the levator muscles of the heel, and 
 the astragalus supports this weight, which varies according to 
 the corpulence of the person, and the burthen with w'hich he is 
 loaded. The weight of an adult, of common stature and of 
 moderate size, may be estimated at about 150 pounds; but 
 which sometimes, in corpulent people, amounts to between four 
 and five hundred pounds. If, then, to the weight of the body 
 there be added that of the burthen which it may support, it 
 will be conceived how immense the efforts must be, which are, 
 as it were, unconsciously carried on, in the articulation of the 
 foot with the leg. But how numerous the resources w'hich 
 nature has provided to overcome this great resistance; how 
 many the circumstances she has happily combined to accom- 
 plish this without fatigue! In the first place, the foot in this 
 action represents a lever of the second class, and this lever, it 
 is well known, is the most advantageous, the resistance being 
 always nearer to the fulcrum than the power, and the arm, by 
 which the latter acts, consisting of the whole length of the lever. 
 If you attend to the mechanism of the different parts ot the 
 skeleton, you will no where find so powerful a lever applied in 
 so favourable a manner. The os calcis, by carrying the foot 
 beyond its articulation with the leg, adds likewise to the length 
 of the lever by which the power acts. Its length has consider- 
 able influence on our strength, on our power of taking, without 
 fatigue, long walks, or engaging in exertions requiring con- 
 siderable muscular force in the lower extremities. The negroes, 
 who excel in running, in dancing, and in all gymnastic exercises, 
 have a longer and more projecting heel than Europeans. They 
 dance best, whose tendo Achillis is most detached, that is to 
 say, projecting, and at the greatest distance from the axis of 
 
ON MOTION. 479 
 
 the leg; which implies, that its lower attachment is carried 
 back, by the prolongation of the os calcis. 
 
 Those who have a short heel, have a long and flat foot; this 
 conformation, which, when marked, is faulty, is not only un- 
 favourable to beauty of form, but is besides, remarkably injuri- 
 ous to the strength of the limb, as well as to freedom of motion. 
 Men with flat feet are always bad walkers; hence, this flattened 
 form, when very considerable, is considered as unfitting a man 
 for military service. Lastly, the term denoting this physical 
 imperfection (^piedn plats)^ is accounted insulting in the French 
 language, as well as in several others. But let us go on with 
 our inquiry into the advantageous disposition of the articulation 
 of the foot with the leg, for facility in walking, and m the dif- 
 ferent motions of progression. 
 
 We have seen that the tendons are generally inserted at a 
 very acute angle, into the bones on which they act; in the pres- 
 sent instance, however, the insertion takes place at a right angle, 
 the common tendon of the muscles of the calf of the leg joining 
 the os calcis, at the angle most favourable to their freedom of 
 action. With the exception of the muscles which move the 
 head and lower jaw, no others are so evidently disposed with 
 this purpose. Nature has not been contented with forming the 
 foot in such a manner as to afford the most advantageous lever, 
 to which the moving powers are applied, at the greatest pos- 
 sible distance from the fulcrcum and at the angle most favour- 
 able to their action; she has further increased the efiicacy of 
 this action, by adding extraordinarily to the number of muscu- 
 lar fibres. There is not, in the body, a stronger muscle than 
 the soleus, whose short and oblique fibres between the two wide 
 aponeuroses which cover its anterior and posterior surfaces, are 
 more numerous than in any other muscle, as may be conceived, 
 by considering the extensive surfaces to which they are attached. 
 Besides, the tendo Achillis is kept in a due degree of straight- 
 ness, by the aponeurosis of the leg behind it. 
 
 Every thing, in the powers, as well as in the levers, is formed 
 so as to overcome the resistance, without difiiculty; that is, so 
 as to raise the weight of the body, by the extension of the foot, 
 the end of which rests on the ground, in every motion of pro- 
 gression. 
 
ON' MOTION. 
 
 48 © 
 
 This immense power with which the muscles or the calf of 
 the leg act to raise the heel, and to support the whole weight of 
 the body resting on the alfetragalus, accounts for the possibility 
 of transverse fractures of the os calcis, and for the rupture of 
 the tendo Achillis, notwithstanding its great thickness; and 
 should lead one not to allow patients, after such accidents, to 
 walk freely, for several months; the substance which unites the 
 parts being liable to rupture as is known to have been the case 
 in several instances. This same arrangement of parts likewise 
 accounts for an accident, which physiologists have long endea- 
 voured to explain by a very unsatisfactory theory. 
 
 It not unfrequently happens, that the mere effort of walking 
 occasions a rupture of some of the fibres of the gemelli and of 
 the soleus, in consequence of which, there comes on pain, 
 attended with induration of the muscles, and with a certain 
 degree of ecchymosis, occasioned by the extravasation of blood. 
 Pathologists suppose these symptoms to depend on a rupture of 
 the plantaris muscle: this rupture, however, is hypothetical, has 
 never been proved by experience to exist, and its supposed 
 symptoms are altogether idle and fallacious. 
 
 I could, if it were not out of place, bring forward several 
 cases of this affection; in all the cases which have come under 
 my own observation, the use of the bath, of emollient and 
 slightly narcotic poultices, but above all, continued rest, while 
 the symptoms lasted, have appeared to me the most appropriate 
 i^medies. 
 
 CLXXXVII. Of running. In running, the foot that is hind- 
 most being raised before that which is foremost be firmly applied 
 to the ground, the centre of gravity is, for a moment, suspended, 
 and moves in the air, impelled by the force of projection, the 
 action of which principally constitutes leaping. 
 
 The mechanism of running is a compound of that of walk- 
 ing and leaping, but resembling most the latter; hence some 
 authors have defined it to consist of a succession of low leaps. 
 The steps are not longer than in walking, but merely succeed 
 each other with greater velocity. The centre of gravity is trans- 
 ferred, with more rapidity, from one leg to the other, and falls 
 are much more apt to take place. The quick repetition of the 
 same motions, in running, requires a very lively contractility in 
 
ON MOTION. 
 
 481 
 
 the muscles which move the extremities, and as the energy of 
 this vital property is proportioned to the extent of respiration, 
 to the quantity of air which the blood acquires in passing 
 through the lungs; in running we pant and breathe frequently, 
 and at short intervals, without any particular enlargement of 
 the chest at each act of respiration. It was necessary that the 
 parietes of this cavity should, in running, be remarkably fixed; 
 for, it becomes the point on which those muscles are inserted 
 which steady the pelvis and loins, and prevent their yielding an 
 unsteady basis to the lower extremities. The best runners are 
 those who have the strongest lungs; that is, who can give to the 
 chest the greatest degree of permanent dilatation. In contend- 
 ing for the prize in running, you may see them throw back their 
 head and shoulders, not only to obviate the propensity which 
 there is in the line of the centre of gravitj^o fall towards the 
 anterior plane, but, likewise, that the cervical column, the sca- 
 pulae, the clavicles, and the humerus, being fixed, may furnish a 
 firm attachment to the auxiliary muscles of respiration. 
 
 We should run with much less speed, if vve applied to the 
 ground the whole sole of the foot; partly from the time which 
 would be taken up in thus applying the foot to the ground, and 
 partly by the friction which would necessarily take place. Hence, 
 in running we generally touch the ground only with the end of 
 the foot. We run with most speed when the foot is in a state of 
 extension, the leg being moved rapidly by the extensors of the 
 knee. This accounts for the tendency which there is to fall 
 while we run, the centre of gravity obeying impulses which fol- 
 low each other in rapid succession, and never resting but on a 
 basis of very limited extent. Another reason why the slightest 
 unevenness of the ground is apt to occasion falls in running is, 
 that the rapid motion communicated to the body by the sudden 
 and perpetually recurring extensions of the posterior extremity, 
 increases, at every step, sp that it is impossible to stop sudden- 
 ly, and without having previously slackened one’s pace, and 
 moderated the impulse to which the body is subjected. 
 
 As it is mostly forward that falls are apt to take place, in 
 running we always throw back the head, and make use of our 
 arms to balance the body, so that they may be in constant oppo- 
 sition to the legs; that is, that the right lower extremity, for 
 
 3 P 
 
ON MOTION'. 
 
 482 
 
 example, being carried forward, the left arm may be balanced 
 backward. 
 
 Few animals are better formed than man to run with speed; 
 his lower limbs are in length equal to one half of the whole 
 length of the body, and the muscles which move them are very 
 powerful; hence, savages, who are in the constant habit of run- 
 ning, overtake the animals which they make their prey; and, 
 even in Europe, there are professed runners, who equal in 
 swiftness the fleetest horse. This animal, like every other swift 
 quadruped, would move much more slowly than man, on ac- 
 count of the number of the limbs on which he rests, if he had 
 not the power of moving them in pairs, and thus reducing his 
 legs to two, as in what is called full gallop. 
 
 CLXXXVIII. Of leaping. Leaping, in man, is performed, 
 principally, by the ^dden extension of the lower limbs, whose 
 articulations were in a previous state of flexion. The alternate 
 angles of the foot, of the knee and hip, disappear, and the exten- 
 sors contract in almost a convulsive manner. This straighten- 
 ing is not limited to the lower limbs, in violent leaping; it like- 
 wise affects the vertebral column, which acts as a bow in 
 unbending. Professor Barthez, who has the merit of having 
 suggested this explanation, which Borelli and Mayow had very 
 imperfectly understood, perhaps goes too far, in considering as 
 imaginary, a power of repulsion in the ground. This re-action, 
 admitted by Hamberger and by Haller, clearly operates when 
 we leap on an elastic floor; it enables tumblers to rise, without 
 much effort, on the rope which bears them. But though all phy- 
 siologists do not admit that, in leaping, there is a re-action from 
 the ground, it is universally admitted, that there must be a cer- 
 tain resistance from the ground on which we tread. In fact, a 
 moving sand, yielding to the pressure of the body, would, by 
 giving way to a considerable degree, render it impossible to 
 leap. The instantaneous contraction of the extensor muscles is 
 so powerful, in extending the lower extremities, and in com- 
 municating to the body a power of projection, so as to raise it, 
 that frequently, during this effort, the tendons of these muscles, 
 or even the bones into which they are inserted, break across. It 
 is on this account, that dancers are very apt to fracture their 
 patella. This accident happens at the moment when their body. 
 
ON MOTION, 4^3 
 
 in rising from the ground, is powerfully elevated to a certain 
 height. 
 
 If leaping consists merely in the sudden straightening of the 
 lower extremities, whose articulations are bent in alternate di- 
 rections, it must be more considerable, according as these ai-e 
 longer, more bent on one another, and as the muscles which 
 straighten them contract more powerfully. Hence, animals that 
 move by leaps, as the hare, the squirrel, and the jerboa, have pos- 
 terior extremities of considerable length, in proportion to their 
 fore legs. Their different parts are, besides, capable of conside- 
 rable flexion. All these animals, strictly speaking, are incapable 
 of walking or running; and they move by leaps, or bounds, suc- 
 ceeding each other with different degrees of rapidity. Some, 
 however, as the rabit and the hare, are capable of running when 
 climbing up a steep place, as the slope, in this case, lessens the 
 effect ©f the impulse communicated by the extension of the pos- 
 terior limbs; an impulse which, from the strength and length of 
 these extremities, throws the whole weight of the body on the 
 fore legs, which are weaker and shorter, with such a degree of 
 force, that the animal is obliged to stiffen these, and to keep them 
 straightened, and in a state of extension, to avoid striking the 
 ground with his head, while leaping on an horizontal plane^ 
 Frogs, but especially grasshoppers and ffeas, between whose hind 
 extremities and the rest of the body there is the greatest dis- 
 proportion, astonish us by the very considerable space which 
 they can clear at a leap; but the wonder ceases, when we consi- 
 der that powers communicate to the masses equal degrees of 
 velocity, when proportionate to one another; now, the space gone 
 over, depending entirely on the velocity, since the body that 
 leaps, loses, by a gradation which nothing can lessen, that which 
 it had acquired; these motions must be nearly alike in small and. 
 in large animals. 
 
 Swammerdam says, that the height to which grasshoppers 
 rise, in leaping, is to the length of their body as 200 to 1. A 
 flea leaps still farther and more swiftly.* 
 
 • Barthez states, in his work on mechanics, that the Arabs call this little in- 
 sect the father of leaping; and that Roberval, a natural philosopher of conside- 
 rable merit, had written a work entitled </e saltu pulicis. Such a subject, thought 
 by the ignorant to supply matter only for idle and fruitless speculation, may 
 furnish results highly interesting, when treated by an able man. In tenui labor- 
 
ON MOTION. 
 
 484 
 
 The larva, called the cheese maggot, forms itself into a circle, 
 by contracting, as much as possible, its abdominal muscular 
 fibres; after having, in this manner, brought near to each other 
 its head and tail, it suddenly extends and straightens itself, and 
 sends itself to a considerable distance. It is by a similar me- 
 chanism, that the salmon, the trout, and other fishes, swim 
 against rapid currents interrupted by water-falls. They bend 
 their body, to a considerable degree, straighten it powerfully, 
 and thus overcome the obstacle which opposes their progress. 
 I believe, however, that in this particular case, the leap is not 
 effected solely by the straightening of the elastic curve, as is 
 maintained by some authors, but that it is likewise occasioned 
 by the resistance against the water, of the tail of the fish, which 
 strikes it powerfully, at the moment of raising itself; in the same 
 manner, as in the northern seas, the enormous whale strikes, 
 with so sudden and violent a blow of her tail against the water, 
 as to receive from it a fixed point, and rise to the height of 
 fifteen or twenty feet, as we are informed by navigators. Lob- 
 sters leap by violently extending their tail, an elastic and con- 
 tractile arch, which they had previously kept bent under their 
 body. 
 
 ■ This theory of leaping would seem to be contradicted by 
 what is related by Professor Dumas, of a man without thighs, 
 and who, nevertheless, performed surprising feats of dexterity 
 and agility. But in this instance, might not the pelvis, the ver- 
 tebral column, and especially the lumbar portion of the latter, 
 make up, by a greater mobility, for the want of the longest of 
 the three levers formed by the lower extremity. 
 
 In the act of leaping, the body, which has received the im- 
 pulse, may rise in one of two ways, perpendicularly to the 
 horizon, which constitutes the vertical leap, or in a direction 
 more or less oblique. The vertical leap is always of less extent 
 than that which takes place in an inclined direction, and the 
 latter is always greater when it has been preceded by running. 
 In running before leaping, we have already acquired an impulse 
 which is added to that which the mechanisn of leaping may 
 produce. 
 
 To convince ourselves of the reality of this additional power, 
 let us recollect how difficult it is to stop suddenly, in the midst 
 
ON MOTION. 
 
 485 
 
 'of a race, if we have not previously slackened our pace. This 
 impulse is one of the causes which make runners fall forward, 
 when the slightest obstacle meets their feet; but whatever may 
 be the force, the direction of leaping, and the powers which 
 produce it, the body by which it is executed must be considered 
 as a real projectile that is impelled by a motion counteracted 
 by the force of gravitation. Whatever motions we may perform, 
 every thing depends on the first impulse; as soon as the feet 
 cease to be in contact with the plane which supports them, it is 
 no longer in our power to augment the force of the leap or its 
 swiftness. In dancing, it is impossible to excel in cutting capers, 
 unless one is capable of rising to a certain height; I have uni- 
 formly observed, that in the most celebrated public dancers, the 
 trunk, and especially the lower limbs, are very muscular, the 
 calf of the leg, the buttocks, and the back indicate, by their bulk, 
 a remarkable degree of energy in the extensors, by whose ac- 
 tion leaping is chiefly effected. 
 
 A dancer who rises vertically, falls back to the ground, when 
 the force of gravitation exceeds the impulse which he had re- 
 ceived; his fall resembles that of a projectile in vertical motion; 
 it takes place according to a descending line that is perfectly 
 similar, in direction and height, to the ascending line. 
 
 The same thing takes place in the oblique leap, except how- 
 ever, that the body, like a shell projected by the explosion of gun- 
 powder, describes a parabolic curve, ascending, as long as the 
 impelling power exceeds the force of gravitation; descending, 
 when the latter, which increases during the progress of the leap, 
 is equal to the force of impulse. This takes place, when the body 
 has described a curve which represents the half of a parabola; 
 from that moment, the force of gravitation goes on increasing, 
 and the body descends in a curve corresponding to the first.* 
 
 CLXXXIX. Of swimming. Few animals have more difficulty 
 than man, in supporting themselves on the surface of a fluid; yet 
 the weight of the human body exceeds but little that of the same 
 bulk of water; sometimes even when the body is loaded with 
 much fat, its specific gravity and that of water are the same. 
 Hence it is observed, that corpulent men swim with less effort; 
 
 * In saltu ad horizontem obliquo, motus fit per lineain parabolicam proxime. 
 Borelli. op. cit. prop. 17&. — Vide Galileo on the motion of projectiles. 
 
ON MOTION. 
 
 486 
 
 but the weight is not equally distributed over every point of the 
 supporting fluid. The head whose relative weight is very consi- 
 derable, is the principal difficulty in swimming, and it requires 
 some effort to keep it raised, so as to allow the air to enter freely 
 into the lungs, through the mouth and nostrils. The upper and 
 lower limbs act alternately against the water which they dis- 
 place by pressing on it. In these various motions, there is a 
 successive flexion, extension, abduction, and adduction of the 
 limbs; most of the muscles of the body are in motion, and 
 have their fixed point of action in the chest, which swimmers 
 keep expanded by retaining, by a constriction of the glottis, a 
 considerable quantity of air within the pulmonary tissue. This 
 continuous dilatation of the chest is attended with this further 
 advantage, that it renders the body specifically lighter. The 
 force with which the swimmer is obliged to strike the water, 
 the rapidity with which the motions must succeed each other, 
 that the fluid may yield him a sufficiently fixed point of action, 
 accounts for the fatigue with which this exertion is attended. 
 
 Fishes are adapted, by their structure, to the element in 
 which they live; the form of their body bounded, every where, 
 by salient angles, is well calculated to separate the columns of 
 a fluid. A bladder filled with azote, which is expelled at plea- 
 sure, renders their specific gravity less than that of water, accord- 
 ing to the quantity of gas it contains; lasdy, their tail, moved 
 by powerful muscles, may be considered as an oar of great 
 strength, the motions of which impel the fish forward, while 
 the fins, like so many secondary oars, facilitate and direct his 
 motions. 
 
 The air bladder of fishes gives to their back a sufficient 
 degree of lightness to enable it to remain upward, else this part 
 of the body, which is the heaviest, would draw after it the rest, 
 and the animal, lying on his back, would be incapable of per- 
 forming any motions of progression; this happens when this 
 bladder is burst or punctured. Constrictor muscles expel the 
 gas which it contains, and force it into the stomach, or oesopha- 
 gus, when the animal wishes to sink. This expulsion becomes 
 impracticable, if the gas undergoes considerable expansion, 
 from the application of heat, and resists the compression that 
 is applied to it. Hence, during the fry-time, fishes, after re- 
 
ON MOTION. 487 
 
 maining long on the surface of the water, exposed to the heat 
 of the sun, become unable to sink, and are easily caught. 
 
 As the fish is entirely surrounded by a medium which pre- 
 sents, on every side, an equal resistance, the velocity which he 
 might have acquired, by striking the fluid behind with his tail, 
 would be lost, from the resistance of the water which he would 
 have to displace forward, if, immediately after striking with his 
 tail, he did not bring it back into a straight line, so as to pre- 
 sent to the fluid, only the inconsiderable breadth of his body; 
 the velocity with which he moves is, besides, very inferior to 
 that with which he uses his tail. This part being brought into 
 a straight line, the fish contracts it to its smallest dimensions, 
 at the same time that he brings it to the other side; he then 
 expands it and strikes the fluid, in a contrary direction, in a line 
 between the two oblique impulses which both strokes have 
 given to it. The fish turns horizontally, and directs himself 
 towards the side he chooses, by striking more powerfully, or 
 with greater quickness, on one side than on the other, or by 
 striking only on one side. 
 
 Fishes without an air bladder, are reduced to live at the bot- 
 tom of the water, unless they have a flat body and are furnished 
 with horizontal fins, so as to enable them to strike a consider- 
 able surface of water, in a powerful manner, as is the case with 
 rays, whose wide fins are not inaptly termed wings; the motion 
 of these fishes, in the water, precisely resembling that of birds 
 in the air, with no other difference but that of the different 
 density of the medium in which they move, as will be shown 
 in treating of the motions of progression peculiar to this class 
 of animals. 
 
 CXC. Of fifing. A bird, in rising, or in moving in the air, 
 has to use much more force and with much greater velocity, 
 than a fish in swimming. He has not the power, like the latter, 
 of placing himself in equilibrio with the fluid in which he moves, 
 by means of an internal organ that renders his specific gravity 
 equal to that of the medium he is in. This medium, besides, 
 presents less resistance to the powers which strike it to obtain a 
 point of support. 
 
 Though birds are incapable of becoming as light as the air, it 
 is, however, in their power to obtain a specific gravity, not much 
 
ON MOTION. 
 
 488 
 
 exceeding that of the atmosphere. Nature has rendered them 
 very light, by providing them with very capacious lungs, capable 
 of great dilatation, from the remarkable mobility of the parietes 
 of the chest, and by extending the lungs into the abdomen, by 
 means of membranous sacs, and into the skeleton, by means of 
 canals which establish a communication of these abdominal and 
 Osseous aerial tubes with the pulmonary organ; so that the 
 whole body, distended by air rarefied by a considerable degree 
 of heat, since it is ten degrees above that of other warm-blooded 
 animals, clothed in feathers almost as light as the air itself, re- 
 quires but a moderate degree of force to support itself in that 
 medium. On the other hand, when the wings are expanded, 
 they present to the fluid a very extensive surface; the pectoral 
 muscles which set them in motion, are besides, sufliciently 
 strong to strike the air with a power, and to repeat the stroke 
 with a rapidity and continuousness of which no other animal 
 would be capable. We know how powerful* the muscles of the 
 wings are, even in the tame fowl, which make so very little 
 use of them. Lastly, the contractility of these very powerful 
 muscles, is greater in birds than in any other animal; no one 
 possesses so much strength in so small a compass. What quad- 
 ruped of the same weight as an eagle, could strike with his foot 
 so violent a blow as that bird, when to stun his prey or to de- 
 fend himself, he gives repeated blows with his pinion? This 
 muscular energy is, no doubt, connected with the extensive 
 respiratory organs, with the highly stimulating qualities of a 
 blood that is warmer, more oxydized, more concrescible, in a 
 word, more arterialized than that of any other animal. 
 
 Let us now Inquire how birds, endowed with an organization 
 so favourable to flying, perform that action. A bird begins by 
 ascending into the air, either by rising at once from the ground, 
 
 * Birds have three pectoral muscles; the great pectoral which is attached to 
 their enormous sternum, and alone exceeds in wei,^ht all the other muscles of 
 the bird together; the middle pectoral, whose tendon turns over a kind of pulley, 
 and is attached to the head of the humerus whicli it raises; by means of this 
 mechanism, nature has placed an elevator muscle at the lower part of the body, 
 so as to increase the weight of this part of the bird, which, without this kind 
 of ballast, might have been upset in the air. The tfiird, or lesser pectoral, is des- 
 tined to draw the humerus towards the body. 
 
ON MOTION. 
 
 485 
 
 or by allowing himself to fall from a height. If, on the ground^ 
 and if his wings are too large to be freely spread, he has a 
 difficulty in rising; in that case he goes to an elevated spot and 
 throws himself from it, that he may have 'sufficient room to ex- 
 tend his wings and strike in the air, the first stroke that is to 
 raise him. The wings expand horizontally, the humerus which 
 forms their principal part, standing off from the body; they then 
 descend rapidly, and, as the air resists the sudden effort which 
 tends to depress it, the body of the bird is elevated by a kind of 
 elastic re-action, corresponding to the leap of man and to the 
 swimming of fishes; the impulse being given, the bird closes his 
 wings, contracts his dimensions, as much as possible, that the 
 impulse may be almost entirely employed in raising his body, 
 and may not be counteracted by the resistance of the air. This 
 resistance of the air, but particularly the weight of the bird, 
 would soon overcome the velocity that has been obtained, and 
 he would drop, if, by again striking the air, he did not again 
 rise. If the bird strikes a second time with his wings before the 
 impulse communicated by the first stroke is over, he rises ra- 
 pidly, but, on the contrary, descends, if this motion is delayed. 
 If he allow himself to fall only to the height whence he began 
 to rise, he nlay, by a continuance of equal vibrations, keep at 
 the same height. A bird, sometimes, ceases altogether to move 
 his wings, closes them against his sides and falls, with a pre- 
 cipitate motion, like any other weighty body. The name of 
 pouncing is given to the rapid descent of predaceous birds on 
 their prey. Observe a falcon drop suddenly on a poultry yard; 
 if on the point of reaching the grotind, he perceive danger, he 
 immediately spreads his wings, and thus saves himself from fall- 
 ing; for, whatever velocity he may have acquired in this rapid 
 motion, the resistance of the air always increases, as the squares 
 of the velocity; he then rises anew and takes to flight. This 
 peculiar act is called resource. 
 
 The oblique motions differ from the vertical motion \vhich 
 has just been described, in this, that the bird rises by a series of 
 curves which are more or less extended, as the motion is more 
 horizontal or vertical. In consequence of the peculiar strength 
 of their wings, birds of prey have a very powerful horizontal 
 
 3 Q 
 
ON MOTION, 
 
 490 
 
 motion, so that in soaring, the curves which they describe are 
 so slight, that the motion seems quite horizontal. 
 
 Swimming, to many birds, is a more natural mode of pro- 
 gression than flying; these birds are very light, their body is 
 covered with a light down, and with feathers over which the 
 water glides very readily; their body is flattened, and rests on 
 the fluid by a broad surface. Their pelvis is shaped like the keel 
 of a ship; lastly, their toes united by webs, strike the water with 
 a very broad surface. This is the case with the numerous tribes 
 of web -footed or water-fowl. 
 
 They who have conceived it to be possible for man to support 
 himself in the air, by rendering his body specifically lighter, have 
 not considered, that it was impossible to give to the muscles 
 which move the arms a sufficient degree of strength, to enable 
 them to move the machines which are adapted to them; and all 
 who have ventured to try such machines, have suflFered for their 
 rashness. 
 
 CXCI. Of cratuiing. All the motions of progression, of which 
 man and animals are capable, may be referred to the theory of 
 the lever of the third kind. The body, in leaping, as in walk- 
 ing, may be compared to an elastic curve, since the point of 
 support, or fulcrum, is in the ground; the force, the spring or 
 power, in the extensor muscles, and the resistance in the weight 
 of the body. What is running, but a succession of short leaps, 
 and is not its mechanism intermediate between walking and 
 leaping? Are not flying and swimming real leaps, in which the 
 bodj" of the animal alternately bends and unbends, having its 
 support on media of much less resistance than the ground, on 
 which walking, running, and leaping are generally performed? 
 The mode of progression peculiar to serpents and soft reptiles, 
 furnishes an additional application of the lever of the theory of 
 the third kind. The snake, which moves' by forming with its 
 body horizontal and vertical undulations, forms, in the course 
 of its length, a series of curves and straight lines, in succession, 
 from the head towards the tail; but sometimes, likewise, from 
 the tail towards the head, in the serpents called amphisbanousy 
 in which the scales covering the belly are equally favourable to 
 a retrograde motion, as to a motion forward. 
 
 The crawling of serpents is facilitated by the length of their 
 
ON MOTION. 
 
 491 
 
 body, by the smoothness of their scales, the Immense power of 
 their muscles, and the flexibility of their vertebral column. The 
 bones which form this part of the skeleton, are articulated by 
 arthrodia, and loosely jointed, so that a very slight cause de- 
 stroys their union; hence, a blow with a very small stick is ca- 
 pable of killing the largest serpents, if applied on the back. The 
 lateral inflexions of this column are very considerable; the 
 degree of extension is limited by the spinous processes, and 
 these are, sometimes, of considerable size, as in the rattle 
 snake. Hence, notwithstanding what has been stated by several 
 authors, and although painters have represented serpents 
 moving in vertical curves; they move, in most instances, in 
 horizontal curves. 
 
 A serpent, to swim, is obliged to bend and unbend his body 
 in more rapid succession; this swimming consists merely in 
 crawling faster, and in moving on a less resisting plane. 
 
 The motions of reptiles, in swimming, surpass, in strength 
 and velocity, those of reptiles which crawl on the ground, in as 
 much as the latter yields a more fixed point than water. If the 
 serpent is desirous of leaping, he suddenly, and at once, brings 
 to a straight line all his curves, resting, at the same time, on the 
 extremity of that which is nearest his tail; then, as I have 
 several times observed, he describes the smallest possible num- 
 ber of carves, bends into three or four greater arches than usual, 
 but never into a single one, whatever the length of his bod|y 
 may be. 
 
 Tortoises, frogs, lizards, salamanders, and all reptiles that 
 have legs, drag themselves along on their belly, being ill sup- 
 ported by their weak limbs, which bear no proportion to the 
 bulk of their body, and can scarcely be said to crawl by a 
 mechanism similar to that which has just been explained. 
 
 Caterpillars and maggots crawl much in the same manner as 
 serpents. The legs of the caterpillar, too feeble to support it, 
 or, of themselves, to carry the body forward, are used by these 
 creatures to obtain a hold on the surface on which they move, 
 by bending, in arches, mostly vertical, the parts situated be- 
 tween the legs, that are in pairs, at a certain distance from one 
 another. The caterpillars that have a scaly covering, crawl 
 better, the elasticity of their scales assisting the contractile 
 
ON MOTION. 
 
 492 
 
 action of their muscular fibres. Earth worms move, at times, in 
 undulations, as the snake, and at others, by dragging themselves 
 like slugs. This last variety of crawling is performed as follows: 
 instead of forming distinct curves, the contractile fibres of the 
 reptile shorten themselves from the head, which is fixed, towards 
 the tail which is moveable, and the animal performs only slight 
 inflexions. We may compare the mode of crawling peculiar to 
 some animals, to the motion by which a man lying horizontally, 
 on his belly, moves forward, by drawing his whole body to- 
 wards his arms, which are in a state of extension, and with 
 which he has a hold of some fixed object. The motion of the 
 snail is performed almost entirely in the same manner. 
 
 The snailj loaded with his shell, adheres to the surface on 
 which he moves, by a viscid and glutinous fluid, which coagu- 
 lates, and forms on his track a shining varnish. This creature 
 fixes itself, likewise, on the ground, by forming a vacuum with 
 a part of its body on which its crawls, which is broad, fringed 
 and well adapted to answer the purpose of a cupping glass. It 
 is by this double resource of a viscid and glutinous fluid, and 
 of a contractile exhauster, that the snail fixes the fore part of 
 his body, and then draws towards this fixed part, the rest of his 
 body loaded with the shell. This part of the snail, by which it 
 fastens itself to the ground on which it crawls, bears some 
 analogy to the tentacula which assist the progression of the 
 sepia and other cephalopodous molusca. 
 
 CXCll. Partia/ motions performed by the upper extremities. 
 These motions will furnish us additional illustrations of the 
 elastic curve, or of the third lever, to the theory of which may 
 be referred almost all the motions of man and of the lower ani- 
 mals. This idea simplifies and facilitates, in a remarkable man- 
 ner, the study of animal mechanics; it may be considered as a 
 general formula, by the help of which we may obtain a solution 
 of all the problems of this interesting part of physical science. 
 Its application particularly distinguishes what has just been 
 stated on motion, from what had been, heretofore, written on 
 the same subject. 
 
 The upper extremities, in man, are not employed in motions 
 of progression, at least, not generally, except in a few instances, 
 as, for example, when the limbs being extended and the hands 
 
ON MOTION. 
 
 493 
 
 having a firm hold of a body, the action of the great pectorals 
 draws the whole body, lying prone on a horizontal surface, or 
 suspended. 
 
 We experience a difficulty in climbing, because our hands 
 alone enable us to grasp the body on which this mode of pro- 
 gression is to be effected, while the four extremities of the 
 quadrumana and the sharp claws of cats, those of climbing 
 birds, render this action easy and natural to all these animals. 
 
 There exists so great a disproportion, in point of length and 
 strength, between our upper and lower extremities, that walk- 
 ing on all fours can never be natural to the human species; be- 
 sides, as Daubenton observed, the situation of the foramen 
 magnum of the occipital bone, in man, renders this attitude 
 exceedingly uneasy. Its situation, near the centre of the base 
 of the skull, and nearly horizontal, prevents the head from being 
 raised sufficiently high to enable us to turn our face forward and 
 to see before us, and if we bring the head downward, it strikes 
 the ground with its summit, or with the forehead.* But our 
 upper or thoracic limbs, though of no use in conveying us 
 whither our wants require, are almost exclusively destined to 
 perform motions by which we act on the objects towards which 
 we have brought ourselves. 
 
 If we wish to push, or draw towards us, or to propel afar a 
 moveable body, to compress, to elevate, or to lower it, our 
 upper extremities are almost exclusively engaged in this office. 
 
 In pushings man places himself between the obstacle and the 
 ground; he bends his body between these two points, by bring- 
 ing all his limbs into a state of flexion; he then extends them; 
 his whole body represents a spring which is released and re- 
 covers itself, and the two extremities of which, meeting two ob- 
 stacles, the ground and the body to which the impulse is to be 
 communicated, exert their action on the one of the two which 
 is the more easily moved. The force is equal to the contraction 
 of the extensors, which elongate the body previously in a state 
 of decurtation, and advance the moveable obstacle by the whole 
 difference, in regard to length, of a man whose limbs are in a 
 state of flexion, and of the same man while these parts are in a 
 
 • Dictlonnaire d’Histoire naturelle de I’Encyciopedie methodique. Intro- 
 duction, page 21 et suiv. 
 
ON" MOTION. 
 
 494 
 
 state of extension. It is in the same manner, and by a similar 
 mechanism, that by pushing against the shore with an oar, we 
 force a boat from it. The vertebral column represents an elastic 
 curve which straightens itself, between the feet which rest 
 against the bottom of the boat and the end of the pole or oar, 
 pushed against the shore, or the bottom of the water. 
 
 If, on the contrary, we wish to draw towards us a body, we 
 seize it with extended arms: we then bend them forcibly; the 
 spring, which is in a state of tension, shortens itself: the effort is 
 wholly performed by the flexors; it is less fixed, and of less dura- 
 tion than that of the extensors: because the axes of the bones do 
 not correspond to one another in a straight line, and because the 
 action is generally partial. 
 
 We can throw, to a distance, a projectile, the arm remaining 
 pendulous, and perforniing a mere oscillatory motion, or by a 
 whirling motion of the arm. This last action Is much more 
 powerful, because the muscles, which go from the trunk to the 
 upper extremity, concur in it. In the former, the previous 
 oscillations give to the arm a motion that is peculiar to it, which 
 is added to the force of muscular contraction, and which aug- 
 ments its effects. 
 
 Professor Barthez was aware diat the motions, by which the 
 upper extremity stiffens itself, and assumes a state of extension 
 to project a moveable body, or to repel a resistance that is op- 
 posed to it, perfectly resemble leaping, and are attended, like 
 that action, with a sudden extension of the joints which were 
 previously bent. In motions applied to a resistance that cannot 
 be overcome, the body is not repelled with the force communi- 
 cated to it in leaping, by the abrupt extension of the lower ex- 
 tremities. The scapula is too moveable on the trunk, its articu- 
 lation with the humerus is too unsteady, and the action of this 
 bone is not directed, with regard to the shoulder, in a suflSciently 
 favourable manner, to render the impulse equally great, even 
 though the powers should be equal: and they are far from being 
 90 . In every repulsion, and in every attraction, whether we 
 bring towards us an object or remove it from us, by acting upon 
 it, with our superior extremities, these limbs represent an elas- 
 tic afch, which is curved or straightened by the action of its 
 flexors or extensors; and these motion^, like the greater number 
 
ON MOTION. 495 
 
 of those which we have hitherto considered, present a precise 
 application of the levers of the third kind. 
 
 The action of seizing a body, with the hand, is facilitated, 
 1st, by the action of the radius on the ulna, which performs pro- 
 nation and supination, motions which belong exclusively to the 
 hands, and of which the feet are incapablej 2dly, by the mobility 
 of the wrist, which, properly speakings is capable of flexion 
 and extension in two directions; for, the extension of the hand 
 does not consist in merely bringing it into a parallel line with 
 the axis of the limb, but it is, besides, capable of turning it 
 round towards the back part of the fore arm; a phenomenon not 
 observable in any other articulation; 3dly, by the obscure mo- 
 tions, on one another, of the bones of the carpus, by which the 
 palm of the hand becomes more concave; 4thly, by the motions 
 of opposition and circumduction of the thumb and little finger; 
 5thly, by the great number of the phalanges; every thing, in 
 this part of the uppet extremity, proves the excellence of its 
 structure, and justifies all that philosophers and naturalists 
 have said of its advantages. 
 
 In applying pressure, for instance, in pressing on a seal, 
 nearly the whole weight of the body bears on one of the upper 
 extremities, which is powerfully extended, the shoulder resting 
 on the arm, so that the glenoid cavity of the scapula may be 
 perpendicular to the head of the humerus. 
 
 It would be a superfluous task, to endeavour to describe all 
 the motions which our parts may execute; these partial motions 
 are explained in anatomical works, in treating of the muscles on 
 whose action they depend. I shall content myself with having 
 inquired into the principal phenomena of animal mechanism, 
 chiefly with a reference to the human structure. Fuller details, 
 on animal mechanism, would be out of place, in a work like this. 
 They will be found in those works which treat professedly* pf 
 this important part of physiology, the only one in which it is 
 possible to obtain, in the investigation of its objects, that degree 
 
 • Consult J. A. Borelli, de mota animaliuni, 4to. The errors contained in 
 this work depend on the circumstance of the author’s being' more of a mathe- 
 piatician than of an anatomist. 
 
 P. J. Barthez, nouvelle Mechanique <ks motivemens de I’ Somme et. des aniviaux. 
 
ON MOTION. 
 
 496 
 
 of mathematical certainty, so much sought after by every mam 
 of precision and of sound judgment. 
 
 CXCIII. Partial motions may yet further be studied as signs 
 expressive of ideas. They compose what is called the language 
 of action, and are supplemental to speech. The language of ges- 
 tures, in its perfection, is fcjund sufficient even to express the 
 most subtle ideas, and the finest feelings, in the mute scenes 
 known under the name of pantomimes. The gestures, with 
 which the man of most phlegm accompanies his discourse, are 
 a language superadded to that which he speaks: they contribute 
 to the exposition of the thought; but what force, in the man of 
 passion, do they not add to his expression! what power to his 
 language! This eloquence of gesture, which was so often em- 
 ployed to move and sway the assembled multitude in the pub- 
 lic place of Rome and Athens, was habitual to the orators of the 
 ancient republics; and the moment when Marc Antony uncovers 
 and shows to the Roman people, the bloody corse of the first of 
 the Csesars, is not the least eloquent passage of his harangue. 
 
 Thus although the organ of voice is that which offers us the 
 greatest abundance of resources for the expression of our ideas, 
 for communication with our fellow creatures, — though the hear- 
 ing be the sense to which we must address ourselves to produce 
 in them distinct, varied, and lasting impressions, — we do yet 
 address ourselves to their touch and their sight, when we would 
 strongly move them, by an energetic declaration of our desires. 
 These three different languages are employed at once, when 
 we lead a man towards an object, and at the same time point it 
 out to him, and bid him go there: touch and gesture are then 
 auxiliary to speech, and testify in him who makes use of them, 
 a strong and resolute will. The motions of the eyes, the eye- 
 brows, the eye-lids, the lips, and generally, of all the parts of 
 the face, those of the upper limbs, and of the trunk itself, serve 
 to express our passions, as well as our ideas, are supplemental 
 to the language of convention, and often betray it, by saying the 
 reverse of what it expresses. The study of gestures, of motions, 
 and of attitudes, considered as signs of ideas and passions, is 
 the department of metaphysicians, of painters, of sculptors, and 
 physiognomists.* 
 
 * See Condillac’s Essay on the Origin of Human Knowledge; Buffon’s Na- 
 
497 
 
 CHAPTER IX. 
 
 OF VOICE AND SPEECH. 
 
 cxciv. The voice is an appreciable sound, resulting from 
 the vibrations which the air, expelled from the lungs, meets 
 with, in passing through the glottis. From this sound, articu- 
 lated by the motions of the tongue, the lips, and other parts of 
 the mouth, is produced speech^ which may be defined articu- 
 lated voice. 
 
 All animals furnished with a pulmonary organ have a voice; 
 for it is sufficient, to the production of this sound, that air, col- 
 lected in any receiver, be driven out in a body, with a certain 
 force, and that it meet, on its passage, with elastic and vibratory 
 parts. Fish, that have only tracheae, utter no sound: but this 
 defect, which is certainly an impediment to the extent and 
 facility of their relations, is in part made up by the extreme 
 velocity of their progressive motion. 
 
 The instrument of voice is the larynx, a sort of cartilaginous 
 box, placed at the upper part of the trachea. The thin and 
 elastic cartilages which form its parietes are united by mem- 
 branes, and moved on one another by many little muscles, 
 called laryngeal. Of these five cartilages, three only are con- 
 cerned in the production of voice, these are the arytenoid and 
 the thyroid. The epiglottis is of no other use than to close, to 
 what we swallow, the entrance of the windpipe, whilst the cri- 
 coid, situated at the lower part of the organ, serves it for a 
 base, on which the arytenoid, and the thyroid execute the mo- 
 tions, by which the opening of the glottis is contracted or en- 
 larged, for the formation of acute or grave tones. 
 
 This slit, from ten to eleven lines long in an adult, and from 
 two to three wide, where the width is greatest, is the most es- 
 sential part of the larynx. It is really the organ of voice, which 
 is gone at once, when, by opening the trachea, or the larynx 
 
 tural History of Man; Winkelmann’s Treatise on Art; Lavatei-’s Essay on 
 Physiognomy; with the important additions by M. Moreau (de la Sarthe,) in 
 the edition he has just published. 
 
 3 R 
 
OF VOICE AND SPEECH. 
 
 498 
 
 below it, the air is prevented from passing through it. Speech 
 only is lost, when the wound is above the place of the glottisj 
 which shows that voice and speech are two distinct phenomena, 
 one taking place in the larynx, and the other resulting from the 
 action of divers parts of the mouth, and especially the lips. 
 
 Are the different modifications of which the voice is suscep- 
 tible, dependent on the width or straightness of the glottis, or 
 on the tension or relaxation of the ligaments forming its sides? 
 Must we believe, with Dodart, that the larynx is a wind instru- 
 ment, or with Ferrein, that it is a stringed instrument. 
 
 It is very true that the voice becomes stronger, fuller, and 
 passes from the acute to the grave, as the glottis enlarges with 
 the progress of age; — that it remains always weaker and sharper 
 in a woman, whose glottis is nearly a third smaller than a man’s; 
 —but the tension or relaxation of the ligaments which form the 
 sides of the glottis, (the vocal strings of Ferrein) may they not 
 enable these ligaments to execute, in a given time, vibrations 
 more or less prolonged, and more or less rapid, in such a man- 
 ner, that if the air expelled from the lungs by expiration strike 
 upon them in the state of tension produced by the action of 
 the crico-arytenoidei postici, which carry back the arytenoid 
 cartilages to which the ligaments of the glottis are attached^ 
 whilst the thyroid cartilage, to which are attached the other 
 extremities of the same ligaments, is carried forward by a sort 
 of tilting, occasioned by the muscles connecting it with the 
 cricoid cartilage, (crico-thyroidei*) the voice will be shrill, 
 that is clear and piercing; whereas it would be grave, if the 
 arytenoid cartilages being brought forwards by the action of 
 the crico-arytenoidei obliqui, and the thyro-arytenoidei mus- 
 cles, the vocal strings, relaxed, executed less frequent vibra- 
 tions? 
 
 It has been objected to Ferrein, that to perform the office of 
 vibrating strings, the ligaments of the glottis are neither dry, 
 nor tense, nor insulated, the three-fold condition required for 
 the production of sound, in the instruments to which this anato- 
 mist has compared the larynx: but for all the incompleteness of 
 their resemblance to strings, the ligaments of the glottis, similar 
 
 * The arytenoid muscle is used in the formation of acute sounds, for bring- 
 ing together the two arytenoid cartilages. 
 
OF VOICE AND SPEECH. 
 
 499 
 
 to the vibratory bodies, serving as mouth-pieces to wind-instru- 
 ments, such as the reed of the oboe, the mouth-hole of flutes, 
 the lips themselves in the horn, do not the less contribute to 
 the formation and varied inflexions of the vocal sound. It is the 
 more difficult to set aside their influence altogether, inasmuch 
 as their state of tension coincides always with the contraction 
 of the glottis, and the two conditions producing the same effect, 
 it is difficult to determine if it be due to one rather than the 
 other, as it is impossible to decide whether it be to the en- 
 largement of the opening, or the relaxation of the ligaments, 
 that the grave tones are owing. A last reason, which, I think, 
 should make the larynx be considered as serving at once the 
 purposes of a wind and stringed instrument, is, that the liga- 
 ture or section of the recurrent nerves, which give to its muscles 
 their contractility, takes away the voice: so that there is 
 evidently required some kind of action in the sides of the 
 opening. 
 
 When we wish to speak low, we contract but slightly, or not 
 at all, the muscles of the larynx, whose action is entirely under 
 the direction of the will. The column of air meeting then in its 
 passage along the glottis, only relaxed parts, and little capable 
 of vibration, the vocal sound is no longer produced. The perma- 
 nent extinction of the voice must depend, in most cases, on 
 palsy of the vocal or laryngeal muscles. 
 
 It appears then, that, rejecting the opposite and exclusive 
 explanations of Ferrein and Dodart, we are to consider the 
 larynx as an instrument combining the advantages, and exhibit- 
 ing the double mechanism of wind and stringed instruments; 
 it is on this account that it surpasses all musical instruments, 
 by the extent, the perfection, and above all, by the inexhaust- 
 able variet)’^ of its effects. There is no one, that has heard, at a 
 concert, a solo on the French horn by an able performer, but 
 has been struck by the resemblance of the effects of this instru- 
 ment, and those of the human voice. It is because the vibrating 
 body at the mouth-piece of the instrument is alive: it is because 
 the lips, like the sides of the glottis, are moveable; the opening 
 of the mouth dilates and contracts, and, at the same time, its 
 edges are relaxed or stiffened by the contraction of the muscles 
 of the lips. 
 
OF VOICE AND SPEECH. 
 
 500 
 
 The modifications of the voice depend, not only on the 
 varied sizes of the opening of the glottis, and of the tension of 
 its ligaments, but further on the degree of length of the trachea. 
 The singer who runs down the whole scale of sounds, from 
 highest to lowest, visibly shortens the neck and the trachea, 
 whilst in ascending, he stretches them out. 
 
 The force of the voiced depends on the volume of air that 
 may be expelled from the lungs at once, and on the degree of 
 aptness, in the parietes of the canals by which it is given out. 
 Birds, whose body is all aerial, have a voice very strong for 
 their bulk. Their trachea, furnished with a double larynx, is 
 almostf entirely cartilaginous. It is especially so in certain 
 screaming birds, as the jay, and some others: whilst it is nearly 
 all membranous in the hedge-hog, a small quadruped, whose 
 cries are almost imperceptible. 
 
 The hissing of serpents, and the croaking of frogs, are heard 
 to some distance, because these creatures can send out a large 
 quantity of air, at once, from their vesicular lungs; and in the 
 last, because the vocal strings are completely insulated from 
 the coats of the larynx, with which in other animals they are 
 continuous. 
 
 The voice of men is strong according to the capacity of the 
 chest. It is always weaker after meals, when the stomach and 
 intestines, distended with food, push up the diaphragm and 
 resist its descent. The voice, formed in the passage of the air 
 along the glottis, acquires much force and intensity, becomes 
 much more sonorous, by the reverberations of the sound in the 
 mouth and in the nasal cavities. It is weakened and disagree- 
 ably impaired, when a polypus of the nasal canals, or of the 
 throat, or the destruction of the roof of the mouth, prevents 
 the air from passing along the nasal canals, and their various 
 sinuses. The voice is then said to be nasal, though, in truth, it 
 suffers from want of the modifications it should receive in the 
 cavities belonging to the nose. 
 
 * Sailors, and those that live on the banks of great rivers, have commonly 
 strong voices from being obliged to overpower, with the voice, the noise of 
 the waves, which has constrained them to a great habitual exertion of its 
 organs. 
 
 f See the Memoirs of M. Cuvier on the double larynx, and on the voice of 
 birds. 
 
OF VOICE AND SPEECH. 
 
 501 
 
 CXCV. Of speech. To whisper is to articulate very weak 
 sounds, which, in truth, deserve not the name of voice, since 
 they scarcely exceed the sound which alway? accompanies the 
 passage of air in expiration. Man only can articulate sound, 
 and enjoys the gift of speech. The particular disposition of the 
 mouth, of the tongue, and lips, makes all pronunciation impos- 
 sible to quadrupeds. The monkey, in whom these parts have 
 the same conformation as in man, would speak like him, if the 
 air as it leaves the larynx, were not diffused into the hyo-thyroid 
 cavities, which are membranous in some, cartilaginous and even 
 bony in the howling monkey, whose cry is so hoarse and me- 
 lancholy. Every time that the animal would utter his cry, these 
 sacs swell, then empty themselves, so that he is not able, at will, 
 to supply to the different parts of his mouth the sounds they 
 might articulate.* 
 
 Articulated sounds are represented by letters which express 
 their whole force. One cannot reflect on this, without seeing 
 what an advance man made towards the perfection of his na- 
 ture, when he invented these signs for the preservation and 
 transmission of his thoughts. The vocal sounds are expressed 
 by the letters called vowels^ that is to say, which the voice fur- 
 nishes almost completely formed, and which need, for their 
 articulation, nothing more than the more or less opening of the 
 mouth, by the separation of the jaws and of the lips. We pro- 
 nounce, without effort, the letters A, E, I, O, U; they are the 
 first the child utters; they appear, besides, to cost him less study 
 than the consonants. These, which form the most numerous 
 class of the letters of the alphabet, serve only, as their name 
 indicates, to bind together the vowels. Their pronunciation is 
 always less natural, and consequently more difiicult. Accord- 
 ingly, it is observed, that the most harmonious languages, the 
 most grateful to the ear, are those which use fewest conso- 
 nants and most vowels. It is in this point especially, that 
 the Greek tongue surpasses all, ancient and modern;f that, of 
 dead languages, Latin holds the second place; and lastly, that 
 
 * In the ass, an analogous structure Is observed. 
 
 f Grails dedit ore rotundo 
 
 Musa loqui. — Houat. 
 
OP VOICE AND SPEECH. 
 
 502 
 
 Russian, Italian, and Spanish, are more agreeable in pronun- 
 ciation, than French, and still more than languages of Teuto- 
 nic origin, as English, German, Dutch, Swedish, Danish, &c. 
 Among some northern nations, all articulated sounds appear to 
 issue from the nose or the throat, and make a disagreeable pro- 
 nunciation, no doubt, because it requires greater effort, and he 
 who listens sympathizes in the difficulty which seems to be felt 
 b)’^ him who speaks. Would it not seem that the inhabitants of 
 cold countries have been led to use consonants rather than 
 vowels, because the pronunciation, not requiring the same 
 opening of the mouth, does not give the same room to the 
 continual admission of cold air into the lungs. The gende 
 pacific nature of the inhabitants of Otaheite, and of the other 
 Fortunate Isles of the South Sea, is shown in the words of 
 their language, in which are abundance of vowels; whilst the 
 hard and barbarous speech of the Esquimaux, of the people of 
 Labrador, and New Zealand, is the natural consequence of 
 the rigour of their climate, the barrenness of their soil, and 
 their ferocious and warlike habits. 
 
 The distinction of letters, into vowels and consonants, has 
 not been thought sufficient: they have been further distinguished 
 according to the parts which are more especially engaged in the 
 mechanism of their, pronunciation. Thus we remark the 
 oral^ nasal, and lingual vowels, and semi-vomels, M, N, R, L, 
 which bear different names, according as the tongue in articulat- 
 ing them, strikes the roof of the mouth, the teeth, or the lips: 
 lastly, explosive consonants, K, T, P, Q, G, D, B, P, and sibilant, 
 H, X, Z, S, J, V, F, C, which are more numerous and more 
 frequently employed in languages of more difficult pronuncia- 
 tion. If information on this subject could be of real utility, I 
 should explain the mechanism of the pronunciation of every 
 letter of the alphabet, at the risk of furnishing a new scene to 
 the Bourgeois Gentilhomme. 
 
 CXCVI. Singing, stammering, dumbness, ventriloquism. 
 Singing is nothing more than voice modulated, that is, running 
 over with varying rapidity, the different degrees of the harmonic 
 scale, passing from the grave to the acute, and from the acute 
 to the grave, with expression too of the intermediate tones. 
 Though, in general, our song is spoken, speech is not necessary 
 
OF VOICE AND SPEECH. 
 
 503 
 
 to it. This action of the organs of the voice requires more ef- 
 forts and motions than speech: the glottis enlarges or contracts, 
 the larynx rises or descends, the neck stretches out or is drawn 
 in; inspiration is accelerated, prolonged, or slackened; expira- 
 tion is long, or short and abrupt. Accordingly all these parts are 
 more fatigued than by speech, and it is impossible for us to sing 
 as long as we speak. 
 
 Whatever Rousseau may have said, in his Dictionary of 
 Music, singing may be regarded as the most natural expression 
 of the emotions of the soul, since the least civilized nations so 
 use it in their songs of war and love, of joy and mourning: and 
 as every affection of the mind modifies in some way the voice, 
 music, which is only imitated song, can by the aid of sounds, 
 paint love or rage, sadness or joy, fear or desire, can produce 
 the emotions of these different states, can thus sway the course 
 of our ideas, and direct at pleasure the operations of the un- 
 derstanding, and the acts of the will.f^ Of all the instruments 
 which this art employs, the vocal organ of man is indisputably 
 the most perfect, that from which the most agreeable combina- 
 tions and the most varied may be obtained. Who is there that 
 knows not the property of the human voice to lend itself to all 
 accents, and to imitate all languages?! ^ observe, on the 
 occasion of song, that it is especially consecrated to the expres- 
 sion of tender sentiments or movements of passion, and that it 
 is turning it aside from its natural or primitive destination, to 
 employ it in situations where no emotion can be supposed. It is 
 this that makes the recitative of our operas so intolerably tire- 
 some, and throws such ludicrousness over dialogues where the 
 speakers converse singing, on the most indifferent matters. 
 Languages abounding in vowels, are thereby fitted to song, and 
 favour the growth of musical genius. It is perhaps their smooth 
 and sonorous language that has given to the music of the Ita- 
 lians, its superiority over that of other countries.! The declama- 
 
 * See Gretry, Essais sur la Musique, &c. 
 
 t See in the Aviceptologie Francaise, or Art de prendre toutes sortes d’Oiseaux, 
 
 ' the way in which they are drawn into snares by counterfeiting their song. 
 
 f This pre-eminence has been strongly contested, especially in France, 
 where towards the middle of the last century a war arose on the subject, in 
 which her whole literature, split into two factions, fought for the superiority of 
 Piccini and Gluck. Out of the heaps of writings in verse and in prose, w’ith which 
 
OF VOICE AND SPEECH. 
 
 504 
 
 tion of the ancients was much more removed than our own, from 
 the common tone of conversation, approached nearer to music, 
 and might be noted like real song. 
 
 The pleasantness, the precision of the voice, the extent and 
 variety of inflexions of which it is capable, depend on the good 
 conformation of its organs, on the flexibility of the glottis, the 
 elasticity of the cartilages, the particular disposition of the dif- 
 ferent parts of the mouth and nasal canals, &c. It would be 
 enough that the two halves of the larynx, or the two nasal canals, 
 were unequally developed to prevent precision and distinctness 
 of voice. 
 
 Stammering' is a vice of pronunciation too well known to 
 make it necessary to define it. A tongue too bulky and thick, 
 — a remarkable diminution of irritability, as in drunkenness, at 
 the approach of apoplexy, and in certain fevers of a malignant 
 kind, — the too great length of the frasnum of the tongue, — by 
 hindering the readiness and ease of its motions, become causes 
 of stammering. Or it may be produced by the want or bad ar- 
 rangement of several teeth. The same causes, but especially the 
 length of the fraenum of the tongue, keep down this organ 
 against the lower parietes of the mouth, and hinder its point 
 from striking the anterior part of the roof of the mouth with 
 the quick stroke requisite for the pronunciation of the letter R. 
 The name of burr is given to this defect of speaking. 
 
 As for dumbness^ it may be either accidental or from birth. 
 When by any accident, as from a gun-shot wound, a cancerous 
 tumour which has rendered necessary the extirpation of part of 
 the tongue, that organ, so far destroyed, is no longer able to 
 apply itself to the different parts of the parietes of the mouth 
 and combine its motions with those of the lips, then the person 
 becomes dumb, that is to say, deprived of speech. He has still 
 voice, or the faculty of uttering sounds; he may even articulate, 
 if he supply, by mechanical means, the parts of the tongue, lips, 
 or roof, the want of which hinders his pronunciation. 
 
 It is not so with the dumb from birth. Frequently, all parts 
 
 the contest was carried on, a few epigrams will be remembeied, tne letter of 
 Rousseau on French music, and the little work of D’Alembert on the liberty 
 of Music. Marmontel too has made these disputes the subject of an unpublish- 
 ed Poem, under the name of Voyages de Polymnie, 
 
OF VOICE AND SPEECH. 
 
 505 
 
 of the mouth are perfect in their conformation, and yet the 
 child cannot attain to speech. Such is the case of a little boy of 
 three years and a half old, who has been brought to me, to 
 divide his frsenum linguae. Sometimes, however, the tongue 
 adheres to the lower part of the mouth, because the internal 
 membrane of that cavity is reflected over its upper surface, long 
 before it reaches the middle line of the inferior surface. In 
 other cases, the edges of the tongue adhere to the gums. 
 
 Sometimes, also, the tongue is really paralytic; such was the 
 case of the son of Croesus, whose wonderful story is related by 
 Herodotus.* 
 
 In the deaf and dumb from birth, the dumbness always arises 
 from the deafness: this at least is what M. Sicard has observed 
 in the great number of pupils committed to his care: which has 
 led him to say, that, in them, the want of speech should bear 
 the name not of dumbness, but of silence. It is owing entirely 
 to the absolute ignorance of sounds, and of their force repre- 
 sented by the letters of the alphabet; the organs of voice show 
 no trace of injury: they are well fitted for fulfilling the purposes 
 to which they were allotted by nature: but they remain in- 
 active because the deaf child cannot be taught to use them. 
 
 It was necessary, therefore, as the ear was closed, to address 
 to other senses the speech he must endeavour to imitate. His 
 eye must be made to watch the motionsf of the lips and tongue: 
 his hand to feel the vibrations and utterance of sound, and thence 
 he must learn to use his organs of speech: this has been done. 
 What Pereira had begun, Sicard has brought to perfection: 
 and such command of articulate sounds has been given to the 
 deaf and dumb by birth, as has enabled them to utter words, 
 and connected discourse. Even something of inflexion of strong 
 and weaker tones has been taught them, by using the arm as a 
 regulator, as pedals are employed to modify the touches of the 
 piano-forte. 
 
 * This is the author’s solution of the stoiy, not Herodotus’s statement, 
 who says expressly the boy was dumb. But the conjecture is ingenious, and 
 shows a possibility in the story, which, asHerodotus tells it, is impossible: 
 
 f It is known, that old men, grown deaf, fix their attention very closely on 
 the motions of the lips, as well as on the varying expressions of the face, to 
 see the words as well as the thoughts of those who are speaking. 
 
 3 S 
 
OF VOICE AND SPEECH. 
 
 506 
 
 But instruction to the deaf and dumb must be given them, 
 by another language. Written language they learn, not as a re- 
 presentative of speech, but as hieroglvphic characters for ideas: 
 and a manual language, in which each letter is expressed by 
 the position of the fingers or hands, is used as a more con- 
 venient and rapid representation of that hieroglvphic language 
 of written characters. It is by this that conversation with them 
 is best carried on; and it is with an ease and rapidity which 
 astonishes those, who for the first time, are witnesses to the 
 use of it. 
 
 To conclude this chapter, I have still to speak of a pheno- 
 menon, well worthy, by its singularity, of the attention of 
 physiologists. It is known under the name of ventriloquism^ 
 because the voice weak, and little sonorous, appears to issue 
 from the stomach. There is now living, at the quondam Palais- 
 Royal, at the Coffee-House de la Grotte, a man, who can carry 
 on a dialogue so naturally, that you would think you were 
 listening to the conversation of two people, at some distance 
 from one another, and quite different in voice and tone. I have 
 observed, that he is not inspiring while he speaks from his 
 belly, but that less air comes from his mouth and nostrils than 
 in his ordinary speaking. Every time that he does so, he finds 
 a swelling in the epigastric region; sometimes he feels wind 
 moving lower down, and cannot go on long together without 
 fatigue. 
 
 I had at first conjectured that, in this man, a great part of the 
 air driven out by expiration, did not issue from the mouth and 
 nasal fossae, but that, being swallowed and carried down into 
 the stomach, it struck against some part of the digestive tube, 
 and produced a real echo; but having since observed, with the 
 greatest care, this curious phenomenon in M. Fitz-James, who 
 exhibits it in the highest perfection, I have satisfied myself that 
 the name of ventriloquism no ways suits it; since its whole 
 mechanism consists in a slow, gradual, attenuated expiration, 
 whether for that purpose the artist employ the power of the will 
 upon the muscles of the parietes of the chest, or whether he 
 holds the epiglottis slightly lowered, bv means of the root of 
 the tongue, of which he scarcely brings the point beyond the 
 dental arches. 
 
OF VOICE AND SPEECH. 
 
 507 
 
 I find this long expiration always preceded by a strong in- 
 spiration, by means of which he introduces into his lungs a 
 large quantity of air of which he afterwards husbands the use. 
 Accordingly, repletion of the stomach is a great hinderance 
 to the action of M. Fitz- James, by preventing the descent of 
 the diaphragm which the chest would require, to dilate itself 
 for the full quantity of air the lungs should receive. 
 
 By accelerating or retarding expiration, he can imitate diffe- 
 rent voices, make it seem that the speakers, in a dialogue, which 
 he carries on by himself, stand at different distances, and pro- 
 duce illusion the more complete, the more perfect is his talent. 
 No one equals M. Fitz-James in the art of deceiving, in this 
 respect, the most wary and suspicious observer. 
 
 He can set his organ to five or six different tones, pass rapidly- 
 from one to the other, as he does when he represents a very 
 eager discussion, in a popular society of the people, imitate the 
 sound of a bell, and carry on, singly, a conversation, in which 
 one might think that several persons of different ages and sexes 
 were taking parts. But what completes the illusion, and especi- 
 ally distinguishes the art of the ventriloquist from that of the 
 mimic, who can only counterfeit, consists in the power of so 
 modulating his voice that one is deceived as to the distance of 
 the speaker, in such sort, that one voice comes from the street, 
 another from a neighbouring apartment, that from one that had 
 clambered up the roof of the house, &c. ft is easy to discern 
 the value of such a talent in the days of oracles. 
 
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SECOND CLASS. 
 
 FUNCTIONS 
 
 SUBSERVIENT TO THE PRESERVATION OF 
 THE SPECIES. 
 

 J -'-'f 
 
 ‘^C 
 
 ' U'/ 1 V 'f^ 
 
511 
 
 CHAPTER X. 
 
 ON GENERATION. 
 
 cxcvii. Differences of the sexes. The functions 
 
 treated of in this chapter are not necessary to the life of the 
 individual, but, without them, the human species would soon 
 perish, for want of the power of reproduction; these functions, 
 destined to preserve the species, are entrusted to two kinds of 
 organs, belonging to the two sexes, of which they constitute the 
 principal, though not the only difference. 
 
 Woman, in fact, does not differ from man, in her genital 
 organs merely, but likewise in her lower stature, in the delicacy 
 of her organization, in the predominance of the lymphatic and 
 cellular systems, which softens down the projections of the 
 muscles, and gives to all her limbs those rounded and graceful 
 forms, of which we see, in the Venus of Medicis, the inimita- 
 ble model. In woman, sensibility is also more exquisite; and 
 with less strength, her mobility is greater. The female skeleton 
 even is easily distinguished from that of the male, by striking 
 differences. The asperities of the bones are less prominent; the 
 clavicle is less curved, the chest shorter but more expanded, 
 the sternum shorter but wider; the pelvis more capacious, the 
 thigh bones more oblique,* &c. In a dissertation on physical 
 beauty, read by Camper to the Academy of design, at Amster- 
 dam, this celebrated physiologist showed, that, in tracing the 
 forms of the male and female body within two elliptical areas, 
 of equal size in both, the female pelvis would extend beyond 
 the ellipsis, and the shoulders be within; while, in man, the 
 shoulders would reach beyond their ellipsis, and the pelvis be 
 contained within its limits. 
 
 The general characters of the sexes are so marked, that it 
 
 * Compare the beautiful plates of the male and female skeleton by .^Ibinus 
 and Stsramering-. 
 
ON GENERATION. 
 
 512 
 
 would be possible to distinguish a male, merely by seeing a part 
 of his body naked, even though this part should not be covered 
 with hairs, and should have none of the principal attributes of 
 virility. Should this difference of organisation and character be 
 ascribed to the influence of the sexual organs upon the rest of 
 the body? Does the uterus impress on the sex all its charac- 
 teristic modifications, and is it just to say with Vanhelmont: 
 Propter solum uterum mulier est, id quod est; the uterus alone 
 makes woman what she is. Though this viscus, very evidently, 
 re-acts on the whole system of the female, and seems to draw 
 under its control nearly the whole of the actions and affections 
 of woman, I am, nevertheless, of opinion, that it is far from 
 being the only cause of her distinguishing characteristics, since 
 these may be recognized, from the earliest period of life, when 
 the uterine system is far from having attained its full activity. 
 A very singular fact, recorded by Professor Cailiiot, in the 
 second volume of the Memoirs of the Medical Society of 
 Paris, proves better than all the reasoning in the world, how 
 much the character of the sex is independent of the influence of 
 the uterus. A female was bom and grew up with all the exter- 
 nal characteristics of her sex. At the age of twenty-one, she 
 wished to yield to her desires, but found it impracticable; there 
 was nothing beyond the vulva, in other respects, well formed. 
 A small canal, between two and three lines in diameter, occu- 
 pied the place of the vagina, and terminated in a cul de sac, 
 and was about an inch in depth. The most accurate examina- 
 tions, by introducing a sound into the bladder, and the finger 
 up the rectum, discovered nothing like the uterus. With the 
 finger in the rectum, the convexity of the sound in the bladder 
 could be distinctly felt, so that it was evident that, between the 
 lower part of the bladder and the anterior part of the rectum, 
 there lay no organ corresponding to the uterus. The young 
 woman had never been subject to the periodical evacuation 
 which accompanies or precedes the time of puberty. No he- 
 morrhage supplied the place of this excretion. She experienced 
 none of the indispositions that are occasioned by the absence 
 of menstruation; she enjoyed, on the contrarj^, the most perfect 
 health: she was deficient in none of the other characteristics of 
 her sex, only that her breasts were small. At the age of twenty- 
 
ON GENERATION. 
 
 513 
 
 six or twenty-seven, she became subject to a pretty frequent 
 evacuation of bloody urine. May not this affection, which re- 
 curred at irregular periods, be considered as a means by which 
 nature supplied the deficiency of the menstrual evacuation? The 
 bladder, in that case, would fulfil the office of the uterus, and 
 its capillary vessels must have been considerably evolved. 
 
 The reproduction of the species is, in woman, the most im- 
 portant object of life; it is almost the only destination to which 
 nature has called her, and the only duty she has to fulfil in 
 human society. Wherever the earth is fruitful, and furnishes 
 man with abundant means of providing for his wants, he dis- 
 penses with the services of woman, in obtaining from it means 
 of subsistence; he releases her from the burthen of social obli- 
 gations. The Asiatic expects from the women he maintains in 
 his seraglio, in a state of inactivity, nothing but pleasures and 
 children to perpetuate his race. The women of Otaheite have 
 no employment but pleasure and the duties of mothers. Among 
 some of the savage tribes of America, man, abusing the odious 
 right of power, tyrannizes it is true, over woman, and reserving 
 to himself all the advantages of social life, makes her bear all 
 its weight; but this exception does not invalidate the general 
 law deduced from observation of all nations. Whatever with- 
 draws woman from this primitive destination; whatever diverts 
 her from this end, is to her injury; it is the scope of all her 
 actions and habits; every thing, in her physical organization, 
 has evident reference to it. Of all the passions in woman, love 
 has the greatest sway; it has even been said to be her only 
 passion. It is true, that all the others are modified by it, and 
 receive from it a peculiar cast, which distinguishes them from 
 those of man.* 
 
 We will enter no further into the examination of the general 
 differences which characterize the two sexes; no one has entered 
 more deeply into this subject, or has treated it in a more inter- 
 
 * Fontenelle used to say of the devotion of some women: One may seethat 
 love has been here. It has been said in speaking of St. Theresa: To love God 
 is still to love. Thomas maintains that, with -women, a man is more than a 
 nation. Love is but an episode in the life of man; it is the tohole history of the life 
 of woman. (Madame de Stael.) 
 
 3 T 
 
ON GENERATION. 
 
 514 
 
 esting manner, than M. Roussel, in an excellent work, intltled 
 Systeme physique et moral de la femme. 
 
 CXCVIII. Hermaphrodism. Hermaphrodism, or the union 
 of the two sexes in the same individual, is impossible in man, 
 and in the numerous class of red-blooded animals. There is on 
 record, no well authenticated case of such a combination; and 
 all the hermaphrodites that have been hitherto met with, were 
 beings imperfectly formed; in whom imperfect male organs, or 
 female organs unnaturally enlarged, rendered the sex dubious. 
 None was ever found that had the power, by itself, of begetting 
 a similar being to itself: the greater number were incapable of 
 reproduction; the imperfection, or the faulty conformation of 
 their organs, condemned them to barrenness. Such was the case 
 with the hermaphrodite mentioned by Petit of Namur, in the 
 Memoirs of the Academy of Sciences; with that one whose 
 case is related by Maret, in the Memoirs of the Academy of 
 Dijon, and with all those to be found in the records of the 
 Medical Society, which contain the greatest number of facts of 
 this kind. 
 
 But though, in man, and in all beings that most resemble 
 him, in their organization, complete hermaphrodism has never 
 been met with, it is a frequent occurrence among the white- 
 blooded animals, and especially among the plants that occupy 
 the lowest part of the scale of organized beings. The same is 
 observed in polypi, in several kinds of worms, in oysters, and 
 snails. The latter present a singular variety of hermaphrodism, 
 in this, that the male and female organs being combined in the 
 same individual, it is still singly not capable of generation, but 
 is obliged to copulate with another being likewise an herma- 
 phrodite, so as to receive from friction and other means of irri- 
 tation, the excitement to the act of reproduction. 
 
 In the immense tribe of moncecia plants, the male and female 
 organs are combined on one stalk, and even sometimes within 
 the same flower. A number of stamina surround one or more 
 pistils, shed on the stigma their fertilizing dust or pollen, which 
 is conveyed along the canal of the style, into the ovary, there 
 to impregnate the seeds, by means of which the species are 
 perpetuated. The same vegetable species containing sometimes 
 male and female individuals, the sexes may be at considerable 
 
ON GENEEATION. 
 
 515 
 
 distances from one another; the seminal dust is, in that case, 
 conveyed by the air, from the male to the female. This is the 
 case with palm trees, on which Gleditsch made his first obser- 
 vations on the generation of plants; hemp, spinage, mercuri- 
 alis, &c. 
 
 CXCIX. It is a distinction of the human species that, in 
 them, the functions of generation are not under the influence of 
 the seasons. The lower animals, on the contrary, draw together, 
 and pair at stated periods of the year, and seem afterwards to 
 forget the enjoyments of^ love, that they may attend to their 
 other necessities. Thus, wolves and foxes copulate in the mid- 
 dle of winter; deer in autumn, most birds in spring. Man 
 alone seeks his partner at all seasons of the year, and impreg- 
 nates her under all latitudes and in all temperatures. This pri- 
 vilege is not so much the consequence of his peculiar constitu- 
 tion, as a result which he derives from his industry; protected 
 by the shelters which he constructs against the inclemency of 
 the seasons, and the variations of the atmosphere; always capa- 
 ble of gratifying his physical wants by help of the stores which 
 his foresight has led him to collect, he can, at all times, indulge 
 in the enjoyments of love. The domestic animals which we 
 have, in great measure, removed from the influence of external 
 causes, bring forth almost indiscriminately, at all seasons of the 
 year. To prove still further, that it is from counteracting, by 
 the resources of his industry, the influence of nature, that man 
 has succeeded in resisting the influence of the seasons, in the 
 reproduction of his species, I may observe, that this effect of 
 temperature is more absolute, the farther the species is from 
 man; hence the spawn of fishes and frogs is productive sooner 
 or later, according to the earliness or lateness of the season, and 
 thus, a great number of insects depend on the heat of the 
 weather for their powers of reproduction, and for their ex- 
 istence. 
 
 CC. Of the organs of generation in man. Aristotle, Galen, 
 and their verbose commentators, have expressed the analogy 
 which subsists between the organs of generation, in the two 
 sexes, by saying that they differ only in their position, being 
 external in man, and internal in woman. There is, in fact, a 
 considerable resemblance between Che ovaria and the testicles, 
 
ON GENERATION. 
 
 516 
 
 the fallopian tubes and the vasa deferentia, the uterus and the 
 vesiculae seminales, the vagina, the external organs of genera- 
 tion in women, and the male penis. The former secrete the 
 seminal fluid, and furnish, in man or in woman, a matter essen- 
 tial to generation (ovaria and testicles). The fallopian tubes, 
 like the vasa deferentia, convey this fluid into receptacles where 
 it has to remain for some time (uterus and vesiculae seminales). 
 These contractile cavities, which serve as reservoirs to the 
 semen, or its product, part with these substances, when they 
 have remained within them a sufficient length of time; lastly, 
 the vagina and penis serve to expel them. However striking 
 such analogies may be, we are not justified in inferring a per- 
 fect resemblance between the organs of generation in the two 
 sexes. Each of them fulfils, in the act of reproduction, func- 
 tions perfectly distinct, though of reciprocal necessity. 
 
 The prolific fluid is secreted by the testicles; these organs 
 are two in number, covered by several coats, one of which, 
 covered by the skin, and known under the name of scrotum, 
 resembles a bag containing both these organs; it contracts on 
 the application of cold, is relaxed by heat, and possesses a de- 
 gree of contractility more evident than in the other parts of the 
 cutaneous tissue. The dartos forms a second cellular envelope 
 common to each testicle. The tunica vaginalis, a serous mem- 
 brane, affords an immediate covering to them, and reflecting 
 itself over their surface, is disposed with regard to them, as the 
 peritoneum with regard to the abdominal viscera, that is, it does 
 not contain them, within its cavity. Lastly, the testicles are 
 covered by a fibrous, white, thick, and very consistent mem- 
 brane; it is termed tunica albuginea, from the inner surface of 
 which there arise a considerable number of membranous laminse, 
 which, crossing one another, within its cavity, form cells con- 
 taining a yellowish vascular substance. This substance con- 
 tained within the tunica albuginea, has so litde consistence, 
 that it would very soon be dissolved, if the testicle were stripped 
 of its outer covering. It is formed by the seminiferous tubes, 
 which are small capillary vessels extremely tortuous and coiled 
 on themselves, arising probably from the extremities of the 
 spermatic arteries, all directed towards the upper part of the 
 oval formed by the testicles, joining in this place, and forming 
 
ON GENERATION. 51 ^ 
 
 about ten or twelve tubes which unite in a cord situated within 
 the tunica albuginea, called the corpus Htghmorianum. The ten 
 or twelve ducts which unite into a fasciculus, and form this 
 cord, pass through the membrane within which they are con- 
 tained, unite into a single canal which is convoluted, and forms 
 a substance called the epididymis. This canal, formed by the 
 union of the ducts of the corpus Highmorianum, at first con- 
 voluted on itself, becomes less and less tortuous, as it ap- 
 proaches the lower extremity of the testicle; there it bends 
 back and ascends under the name of vas deferens^ along tha 
 spermatic cord, as far as the inguinal ring, by which it enters 
 the abdominal cavity. The vasa deferentia, though of the size 
 of a quill, have nevertheless a very small cavity; and it is not 
 easy to say why a capillary tube should have such thick parietes 
 and nearly as hard as cartilage. 
 
 The semen, secreted by the testicles, is formed from the 
 blood conveyed to them by the spermatic arteries, long, slen- 
 der, and very tortuous vessels, arising from the abrta, at a very 
 acute angle. This fluid is filtered through the seminiferous 
 tubes, passes into those of the corpus Highmorianum, and 
 thence into the vasa deferentia, which, after they have entered 
 the abdomen, terminate into the vesiculae seminales, and deposit 
 into them the spermatic fluid. The delicacy of the organization 
 of the testicle, the delicacy of the vessels along which the 
 semen is conveyed, account for its tendency to congestion, and 
 for the difficulty with which a resolution of this affection is 
 obtained. 
 
 The spermatic fluid passes from the vasa deferentia into the 
 vesiculse seminales, notwithstanding the retrograde direction of 
 their course. The cavities serving as receptacles to the semen, 
 resemble in this respect, the gall-bladder. Notwithstanding the 
 unfavourable direction in which the ducts of the liver and of the 
 testicles join their respective receptacles, they nevertheless con- 
 vey their fluids into the latter; the bile, because the ductys chole- 
 dochus is pressed by the coats of the duodenum, contracted on 
 itself when empty; the semen, because the duct along which it 
 is conveyed, penetrating through the prostate gland, and open- 
 ing into the urethra, by a very narrow orifice, this fluid flows 
 
ON GENERATION. 
 
 518 
 
 back more readily into the vesiculae seminales, than from the 
 vas deferens into the ejaculatory duct. 
 
 ’The vesiculse seminales form two membranous receptacles of 
 different capacity, in different individuals; larger in young people 
 and adults, than in children and old people. Their cavity is 
 divided into a number of cells; they are lined with a mucous 
 membrane which secretes, in considerable quantity, a viscid 
 humour that mingles with the semen, increases its quantity and 
 serves as a vehicle to it. The situation of the vesiculse semi- 
 nales, between the rectum, the levatores ani, and the posterior 
 part of the bladder, promotes the excretion of their contents 
 (which is chiefly brought about by the contraction of their pa- 
 rietes), by the compression of the levatores ani, which are in a 
 state of convulsion at the moment of emission. Animals that 
 are not provided with these seminal receptacles, remain a con- 
 siderable time in a state of copulation, the prolific fluid neces- 
 sary to impregnation having to be secreted during the time that 
 the copulation lasts, and flowing in drops. 
 
 The ducts formed by the union of the vesiculse seminales 
 with the vasa deferentia, pass through the prostate gland, and 
 open, by separate orifices, into the urethra, at the bottom of a 
 lacuna, near the verumontanum. The glandular body in which 
 they are inclosed, and which contains both the neck of the blad- 
 der and the beginning of the urethra, does not exist in women. 
 The mucous and whitish fluid, secreted by the prostate, is con- 
 veyed by ten or twelve orifices into the urethra. This prostatic 
 fluid mingles with the semen, adds to its quantity, is perhaps 
 emitted first, in order to lubricate the internal surface of the 
 canal, and prepare it for the passage of the seminal fluid, by 
 rendering the internal surface of the urethra more slippery. 
 The use of the urethra is, not only to convey the semen out of 
 the body, but likewise to serve in the excretion of the urine, and 
 to form a part of the penis. The latter, destined to conve)’ the 
 prolific fluid into the female organs of generation, must be in a 
 state of erection to perform this function completely. Erection 
 being a phenomenon of structure, that of the penis will be con- 
 sidered, after the description of the female organs of generation. 
 
 CCil. Of the female organs of generation. I shall not adopt 
 the anatomical arrangement generally followed in this descrip- 
 
ON GENERATION. 
 
 519 
 
 t!on, but classing in three divisions, the dilFerent parts which, 
 in women, are subservient to the genital functions, I shall speak 
 first of the ovaria and fallopian tubes, then of the uterus, and 
 in the last place of the vagina and external parts. 
 
 The ovaria, situated in the female pelvis, connected to the 
 uterus by a ligament, receive the vessels and nerves which, in 
 the male, are sent to the testicles; they resemble in form the 
 latter, but are somewhat smaller. Do the ovaria secrete a fluid, 
 which, by mixing with the male semen, produces the new be- 
 ing, or is there detached from them, at the moment of concep- 
 tion, an ovum which the semen vivifies? Whatever opinion is 
 adopted, one is coitipeiled to admit, that the ovaria prepare a 
 substance essential to generation, since females, in whom these 
 parts have been extirpated, are rendered steril. 
 
 It is likewise, unquestionably, along these membranous tubes, 
 called fallopian, that this substance, whatever it may be, fur- 
 nished by the ovaria, passes into the uterus, into which one of 
 their extremities opens; while the other extremity, broad and 
 fringed, lies loose in the cavity of the pelvis, supported by a 
 small duplicature of the peritoneum, but undergoes a state of 
 erection and applies itself to the ovarium, during the act of 
 coition, and forms a continuous canal between that organ and 
 the cavity of the uterus. The external orifice of the fallopian 
 tube, called corpus Jimbriatum, has been found grasping thus 
 the ovarium, in females opened immediately after coition. It 
 may happen, from a malformation of the parts, that the fallo- 
 pian tube may not be able to apply itself to the ovarium; I dis- 
 sected at the Hospital de la Charite^ the body of a woman who 
 had been barren; and found the corpora fimbriata, or the ex- 
 panded termination of the fallopian tubes adhering to the lateral 
 parietes of the pelvis, so that it was impossible they should per- 
 form the motions required for impregnation. 
 
 The uterus, lying in the pelvis, between the rectum and blad- 
 der, is a hollow viscus, in which the fcetus grows till the period 
 of birth. Its internal part has been found separated into two 
 cavities, opening, in some cases, in the same vagina, and, at 
 others, terminating in a vagina that was double, only in the 
 immediate vicinity of the uterus. Valisnieri mentions the case 
 of a woman who had a double uterus, the one opening in the 
 
ON GENERATION. 
 
 520 
 
 vagina, and the other communicating with the rectum. Though 
 the muscularity of the parietes of the uterus hecomes manifest, 
 in proportion as this organ enlarges, during the progress of preg- 
 nancy, this hollow muscle may be said to differ from other mus- 
 cular organs, by the arrangement of its fibres, which it is diffi- 
 cult to discover while its cavity is empty, and which it is even 
 impossible completely to unravel, while it contains the foetus; its 
 most remarkable distinguishing character, is its singular proper- 
 ty of dilating and stretching itself; and, at the same time, of 
 gaining in thickness instead of becoming thinner. 
 
 The vagina is remarkable, only by the soft, wrinkled, and 
 easily dilated structure of its parietes. The upper extremity of 
 this oblique canal, which is directed upward and backward, em- 
 braces the cervix of the uterus, while its lower orifice is sur- 
 rounded by a spungy body, whose cells fill with blood and 
 expel it, like the corpora cavernosa of the penis and clitoris. 
 It is called plexus retiforme; its turgescence, during erection, 
 contracts the orifice of the vagina; the contraction of the con- 
 strictor muscle, which answers the purpose of the accelerator 
 urinae in man, and which lies over this plexus retiforme, sur- 
 rounds like it, the entrance of the vagina, and may, in the same 
 manner, contract the orifice of this canal. 
 
 Besides, this external orifice is furnished, in women who 
 have had no connexion with men, with a membranous fold, 
 varying in breadth, generally semicircular, and called the hymen. 
 Its existence is considered by many as the most certain sign 
 of virginity. But all the marks by which it has been attempted 
 to obtain a certainty of the presence of virginity are very equi- 
 vocal*. The relaxed state of the parts, from a great quantity 
 of mucus, in a woman subject to the fluor albus, or from the 
 blood of the menstrual discharge, may make the hymen yield 
 and not rupture, so that a woman might seem a virgin without 
 being such; while another woman who has not lost her virgini- 
 ty, might, from illness, have her h}'men destroyed. There are, 
 in the last place, persons in whom the hymen is so indistinct, 
 that several anatomists have doubted its existence. 
 
 * “ Attemen priir.a venus tie bet esse cruenta.” — Haller. 
 
ON GENERATION. 
 
 521 
 
 The other external parts of generation, which are easily dis- 
 covered, without the aid of dissection, cannot be considered as 
 merely ornamental; all are, as will be shown presently, of real 
 ptility. The folds of skin which form the labia and the nymphte, 
 yield, during the delivery of the foetus. These duplicatures not 
 only unfold themselves, but likewise undergo a degree of ex- 
 tension, their tissue being moister, softer, and more extensible 
 than that of the skin. The mons veneris, the hairs which cover 
 it, the clitoris which resembles an imperfect penis, seem merely 
 organs of voluptuousness; but is not pleasure itself an element 
 in the act by which the human species is reproduced? 
 
 CCIII. Of conception. When a chemical, mechanical, or 
 mental irritation excites the action of the genital organs, the 
 penis elongates itself, becomes turgid and stiff, from the accu- 
 mulation of blood within the cells of the corpus cavernosum, 
 and within those of the corpus spongiosum of the urethra.* 
 The turgescence of these two parts of the penis should be 
 simultaneous, to render the erection complete. It has been 
 thought that this phenomenon might be accounted for, by the 
 compression of the pudic veins, which are situated between the 
 symphysis pubis and the root of the penis, which, as long as the 
 erection lasts, is compressed against the bone by the erector 
 muscles. But far from elevating the penis, the muscles of the 
 perineum, especially the ischio cavernous (erectoris penis,') tend 
 to depress it. The blood which distends the corpora cavernosa 
 of the penis, and the corpus spongiosum of the urethra and 
 glans, which is itself the expanded extremity of the urethra, 
 does not stagnate in their cells, only there is a greater quantity 
 of blood in them than usual; the irritation increasing, in a re- 
 markable manner, the action of the arteries. Erection, always 
 proportioned to the degree of the stimulus, ceases, when the 
 cause of irritation no longer acts on the penis; in the same 
 manner that an inflammatory tumour is discussed, when the 
 cause is removed.f In this voluptuous dilatation, the urethra is 
 
 * “ Penis adest, ita constructus, ut stimulo corporeo sive mentali irritatus, 
 turgeat et obrigescat, seque erigat, postea detumescat, et collabatur.” — 
 Creve. 
 
 t The animal heat is somewhat augmented, during erection, as well as in 
 inflammation. The temperatui'e of the blossoms of the arum rises several 
 degrees above that of the atmosphere, at the mom.ent of impregnation. 
 
 3 U 
 
ON GENERATION. 
 
 522 
 
 brought into a state of erection, being put on the stretch by the 
 penis which is elongated, its curves are straightened, the irri- 
 tation is propagated from the external to the internal parts, to 
 the vesiculffi seminales and the testicles. These swell, and their 
 secretion is increased as they receive a gentle degree of motion 
 fVom the action of the scrotum, which becomes wrinkled and 
 draws them up towards the abdomen, and by the action of the cre- 
 master muscle, whose expansion forms between the tunica vagi- 
 nalis and the dartos, what has been improperly called the tunica 
 erythroidea; they empty themselves with the greater ease along 
 the vasa deferentia, which decrease in length as the testicles 
 rise, and which participate in the concussion affecting these 
 organs. 
 
 The concussions of the cremaster on the testicle, or on 
 the vasa deferentia, promote, in so important a manner, the 
 secretion and excretion of the semen, that this little muscle is 
 found in animals whose testicles never leave the abdomen, but 
 remain within that cavity on the sides of the lumbar region, as 
 was observed by Hunter in the hedge-hog and the ram. This 
 fact of comparative anatomy shows, that the cremaster is of use, 
 not merely in suspending the testicles as its name indicates, 
 since in the animals above mentioned, they return into the ab- 
 domen towards the organ on which they are to act. 
 
 When irritation is carried to a certain length, it acts on the 
 vesiculae seminales, and these on the fluid which fills their ca- 
 vity, and they expel it by the spasmodic contraction of their 
 membranous parietes, assisted, in this excretion, by the leva- 
 tores ani. (CCI.) The prostate gland and the mucous glands 
 of the urethra furnish a viscid substance, calculated to promote 
 the evacuation of the seminal fluid, which is emitted in jets, 
 more or less rapid. 
 
 CCIV. The human semen is never emitted in a state of pu- 
 rity, that is, such as it is prepared by the testicles; it is even 
 conjectured, that the mucous fluid of the vesiculse seminales 
 forms the greatest part of it. It is this mucus which eunuchs 
 emit in considerable quantity. The fluid secreted by the pros- 
 tate gland and by the mucous glands of the urethra, affect it, 
 likewise, by uniting with it. 
 
ON GENERATION. 
 
 523 
 
 On being received into a vessel, it exhales a peculiar smell 
 like that of the pollen of a great number of plants, for example, 
 of the chesnut tree. It consists of two parts, the one thick and 
 in clots, while the other is viscid, white and more fluid. The 
 proportion of the fluid to the semi-concrete part is greater, in 
 proportion as the person is weaker, and as the emission of se* 
 men is more frequently repeated. It soon liquefies, by losing 
 part of its weight, which always exceeds that of water, in which 
 it becomes soluble, though it was not so at first. On being ana- 
 lyzed by M. Vauquelin, it was found to contain: of water 90 
 centimes — of animal mucilage 6— phosphate of lime 3 — soda 1. 
 It is in consequence of this last alkali, that it is enabled to turn 
 syrup of violets to a green colour. The animal mucilage is not 
 pure albumine, but rather a gelatinous mucus, on which the 
 qualities of the semen appear particularly to depend, such as its 
 insolubility in water, its odour and spontaneous liquefaction. 
 
 On being examined with the microscope, the semen is seen 
 to contain small animalcules, with a rounded head, a tapering 
 tail, and moving with rapidity. Is the liquefaction of the gluti- 
 nous and viscid parts of the semen, owing to the motion of these 
 creatures? These microscopic animalcules are to be detected in 
 the semen, only at the period of puberty. It has been thought 
 that they shunned the light; authors have even gone the length 
 of describing their ways and their diseases. The imagination 
 has had much to do with all that naturalists have fancied they 
 saw in these creatures, which they made subservient to their ex- 
 planations of the mechanism of reproduction. However, it must 
 be confessed, that in all the animal fluids and in the juices of 
 many plants, a certain number of these animalcules may be 
 detected by means of the microscope. 
 
 A spasmodic contraction affects, during the expulsion of the 
 semen, not only the organs of generation, but the whole body 
 participates in the convulsive state, and the moment of emission 
 is accompanied by a commotion of all its parts; so that it should 
 seem, says Bordeu, that in that instant, nature forgot every 
 other function, and was solely engaged in collecting her strength 
 and directing it to one organ. This general spasm, this, as it 
 were, epileptic convulsion, is followed by universal depression; 
 this physical lassitude is attended with a sensation of sadness 
 
ON GENERATION. 
 
 524 
 
 which is not without enjoyment. Does this peculiar sensation, 
 which, according to Lucretius, mingles grief with the most 
 lively enjoyment of which we are capable, depend on the fatigue 
 of the organs; or, in truth, as some metaphysicians have ima- 
 gined, on the confused and distant notion that occurs to the 
 soul, of its own dissolution? 
 
 The penis does not enter the uterus, though the semen does. 
 The os tincse offers too small a slit, and its thick edges are be- 
 sides in contact. It would be difficult to conceive that this strait 
 passage should admit even the seminal fluid, if it were not 
 known, that in the moment of copulation, the uterus, from ir- 
 ritation, draws together, and inhales, by real suction, the semen 
 which it craves. Plato compared this organ to an animal living 
 within another animal, controlling all the actions of the living 
 economy, burning to sate itself with the liquor of the male, and 
 digesting it to form a new individual. 
 
 The great thickness of the cervix of the uterus has given 
 room for reasonable doubt, if its orifice could dilate sufficiently 
 to admit a fluid of the consistency of semen. Some, therefore, 
 have thought that it was not this fluid itself that penetrated into 
 the cavity of the uterus, but the subtlest of its parts, the most 
 spiritualized, a prolific vapour, to which they have given the 
 name of aura seminalis; but, besides that the semen has been 
 found in the uterus, in animals opened immediately after copu- 
 lation, Spallanzani, in his experiments on the fecundation of 
 frogs, of salamanders, and toads, perceived that, to enable the 
 eggs to produce, it was not enough to expose them to the va- 
 pour which rises from the seminal fluid of the male; and that 
 nothing was effected, unless the fluid semen actually touched 
 them, though in ever so small a quantity. 
 
 It has been said, that the uterus dilates to receive the semen, 
 constricts itself to retain it, and that this spasmodic contraction 
 of the uterus, felt, as Galen assures us, by women, who pre- 
 serve enough sang-froid to make observations in that situation, 
 was the most undoubted sign that could be had of the success 
 of the copulation. It is, no doubt, to ensure this retention, that 
 it is customary to throw cold water on the females of some do- 
 mestic animals, when they go too eagerly to the male. The 
 spasm of the skin, occasioned by the cold striking it, affects the 
 
ON GENERATION. 525 
 
 uterus, and hinders the flowing back of the semen which has 
 been thrown into its cavity. 
 
 It has also seemed, that women conceived more easily, for a 
 little time, after menstruation; when the mouth of the uterus is 
 less exactly closed than usual. 
 
 The seminal fluid, thrown into the cavity of the uterus, pas- 
 ses along the fallopian tubes to the ovaria. It does not diffuse 
 itself in the cavity of the abdomen, because the membranous 
 duct seizes the ovarium, which corresponds to it, grasps it closely, 
 and establishes an uninterrupted canal, from this organ to the 
 uterus. The ovarium, bedewed by the semen, irritated by its 
 contact, lets a fluid escape, or perhaps a little ovum, whicifi 
 passes into the uterus, the same way that the semen reached 
 itself.^ All that remains to be said, concerning the mechanism 
 
 * The account here given of the fecundation of the ovum, seems to us 
 exceedingly erroneous, and as this is a point of some interest, we will not 
 too hastily dismiss it. 
 
 It is our intention, first, to show that the semen does not enter the cavity 
 of the uterus, much less that it reaches the ovary. Those who differ from 
 us on this subject, have mostly Insisted that the .semen is thrown into the 
 uterus, by injection from the penis. True it is, that some other modes have 
 been suggested, but they are really so ridiculous, as to be wholly unw'orthy 
 of criticism. 
 
 That the male organ is endowed with a considerable projectile power, 
 ©annot be denied. It is very conspicuously evinced, by the impetus with 
 which the urine is discharged. When engaged, however, in the act of coi- 
 tion, its capacity in this respect, is greatly diminished, or wholly suspended 
 by ihe firmness with which it is embraced. Grasped by the vagina, its ejacu- 
 latory muscles are crippled in their energies, and become passive. We see 
 too, in the spissitude and tenacity of the semen, an additional cause of re- 
 sistance. So heavy and glutinous a fluid, it is plain, cannot be thrown to any 
 distance. There is moreover a structure in the vagina, co-operating to the 
 same end. The rugs of its inner surface seem, indeed, evidently designed as 
 so many barriers, to arrest the progress of the semen. 
 
 But admitting, that by an unusually vigorous impulse it were projected as 
 far as the uterus, how could it enter into the cavity of that viscus? Let it be 
 recollected that the os tines, at least, in the virgin state, is nearly as small 
 as the opening of the urethra in the male, and is not placed in the im- 
 mediate axis of the vagina, but is inclined more or less to the one or the 
 other side, or towards the sacrum. The apertures of the two organs, there- 
 fore, are not in apposition. But this is not all. The os tines is for the most 
 part filled with a thick glutinous matter, capable of considerable resistance. 
 Where it is ivanting, as is generally the case in the virgin uterus, the hard. 
 
ON GENERATION. 
 
 526 
 
 of generation, must not be delivered as real, but merely as pro- 
 bable, such is the darkness with which nature has chosen to 
 envelop this great mystery of the living economy. 
 
 unyielding lips of the tincze are so closely approximated as to be nearly- 
 closed. 
 
 Nor are these the only obstacles to the passage of the semen. The canal 
 leading through the neck and body of the uterus, is, in the unimpregnated 
 state of the organ, probably not larger than a common size probe. That por- 
 tion of the canal called the straight, is still more contracted. Besides, along 
 the whole course of the canal, there are strise, or wrinkles, and between 
 which, glands, secreting mucus obviously calculated for the purpose of ad- 
 ^itional obstruction. Even the proper cavity of the uterus itself, is so ex- 
 tremely shallow that its two surfaces are nearly in contact. 
 
 Such are the impediments incident to a perfectly natural, and healthy con- 
 dition of the parts. To these may be added others resulting from morbid 
 derangements, or congenital deformities, and which are found to exist as 
 well in the male as the female organs. 
 
 1. The penis has its power of ejecting the semen, destroyed or abridged 
 fey truncation, by strictures, by anomalous openings along the course of the 
 urethra, or by debility and relaxation. 
 
 2. The vagina is obstructed or shut up by cohesion of its sides, by mem- 
 branes of adventitious growth, or by tumors. 
 
 3. The os tincse is sometimes discovered impervious, either from original 
 imperfection, or by the process of inflammation, and is occasionally render- 
 ed utterly inaccessible to the semen, by the obliquities, retroversions, or 
 prolapsions of the womb.* 
 
 These facts very clearly demonstrate, that conception can take place, 
 though the semen may be deposited merely within the vulva, and seem al- 
 most to warrant the conclusion, that it never does, as a natural event, reach 
 the cavity of the uterus. Lest, however, they may not appear to others in the 
 same strong light, in which they present themselves to us, we will bring to 
 their aid some further evidence. 
 
 Experiments have been resorted to in order to decide this point. They 
 have been made by Haney, De Graaf, Luenhoeck, Haller, and Haighton. 
 DiflTerent animals were the subjects of these experiments. .The doe, the cow, 
 the ass, the ewe, the bitch, the rabbit, were all inspected immediately, or at 
 remoter periods, after connection w-ith the male, and nev-er except in one in- 
 stance, could the semen be traced beyond the ’cagina. By Haller it is stated, 
 that he once detected the semen in the uterus of a sheep forty-five minutes 
 post coitu. But this is a solitary exception, to the numerous obsen ations both 
 of himself and others, and which can claim little consideration, especially 
 
 * Each of the above positions is supported by cases to be found in the 
 ivritings of Harvey, Morgagni, Hildanus, Ruysh, Mauriceau, Simpson, 
 Guillemeau, Haller, and in the periodical journals 
 
ON GENERATION. 
 
 527 
 
 After distinguishing the true from the probable, an indispen- 
 sable duty in every science of facts and observations like phy- 
 siology, I shall proceed to state the hypothesis which appears 
 
 when it is known, that such a result was essentially necessary to the main- 
 tenance of a favourite hypothesis. 
 
 As auxiliary to this single experiment of Haller, it is, however, urged that 
 Morgagni saw the semen in the uterus, and Ruysh in the fallopian tube of 
 the human species. Without impeaching the veracity of either of these 
 illustrious men, we may be permitted to remark, that their observations 
 have never been confirmed, and that under the circumstances in which 
 they were made, it is reduced almost to a moral certainty that they mis- 
 took for semen what was in reality the mucus of the parts. But, conceding 
 to these alleged facts all that can reasonably be required, what do they 
 amount to? Contrasted with the vast mass of counter evidence, they dwin- 
 dle into insignificance and will not weigh as the dust in the scale. 
 
 It appearing, therefore, that the semen does not enter the uterus, it be- 
 comes superfluous to inquire respecting the practicability of its conveyance 
 by the fallopian tubes. The latter problem is merged in the former. But to 
 silence all cavils, we will give the question a cursory examination. 
 
 That the fallopian tubes are not subservient to this purpose, is very dis- 
 tinctly indicated by the peculiarity of their structure. Commencing with 
 an aperture so very minute, as hardly to admit a common bristle, the canal 
 gradually enlarges, and finally terminates in a wide and patulous mouth. 
 Now, were they destined to convey from instead of to the uterus, would 
 not the construction be directly the reverse of what it is? We know that 
 they conduct the product of the ovary to the womb, and we see that the 
 extremity is adapted to this office. It is almost as well ascertained that they 
 convey nothing from the uterus, and the orifice is fashioned accordingly. 
 
 By assigning to the tube this function, we moreover invest it with the 
 power of a two-fold action, precisely opposite, of which there is no analogy 
 in the animal economy. The inverted peristaltic motion of the intestines, 
 comes nearest to an example, but it will not hold. The cases are not parallel, 
 the action of the intestine being preternatural, the effect of violence and dis- 
 ease. It is useless, however, to protract this discussion, as we have proof at 
 hand which is absolutely conclusive. By the experiments of Mr. Haighton, 
 it is ascertained that the tubes do not change their position to grasp the 
 matured vesicle till the v/hole process of conception is consummated in the 
 ovary. 
 
 “ I found,” says this eminent physiologist, “ from a series of observations 
 made on different rabbits, at every hour between the 1st and 9th, that the 
 fimbris remained nearly in their usual situation, and the only difference I 
 found in the last hour, was a greater turgescency’of vessels, as if preparatory 
 to some important action. I desisted from this inquiry at the 9th hour, because 
 the ovaries bore evident marks of impregnation, and there appeared to be 
 no action in the tubes, by which the semen could be conveyed to them.” 
 
 Convinced 
 
528 GENERATIOJC, 
 
 to me the likeliest on the manner in which the two sexes concur 
 in the production of the new being. 
 
 CCV. The foetuses pre-exist in the ovaria of the females, 
 not that they are there since the creation of the world, as Bon- 
 net believed, and all who embraced the doctrine of that meta- 
 physical naturalist: but the ovaria containing his germs are 
 formed by the proper action of the ovarium which secretes 
 them, a fresh proof that all the phenomena of organized bodies, 
 whether for the preservation of the species or of the individual, 
 are effected in the way of secretions. This ovum, produced by 
 the elaboration of the blood which the spermatic vessels carry 
 to the ovaria, contains the lineaments of the new being: but it 
 is only the sketch, or carcass of it, if this may be applied to 
 what has not yet lived. The seminal fluid must bring it out of 
 this state of inactivitt’, and with something of an electrical power 
 waken it into life. The eggs laid by a maiden hen, will never 
 hatch, though there are in them the rudiments of the chick. 
 The eggs of a frog that has been kept apart from the male, 
 during the whole time of spawning, putrefy in the vessel of 
 water they are kept in; if the male on the contrary, sprinkled 
 them with his semen, as they quitted her, they will speedily show 
 some development of life. Their putrefaction may be prevent- 
 ed, and themselves animated, by shedding on them the sper- 
 
 Convinced that the hypothesis in its primitive shape was no lon^^er tenable, 
 some of the advocates of impregnation by contact, have contended that it is 
 effected by the emission of subtle exhalation from the semen, termed aura 
 aejninalis, and which is transmitted through the tubes to the ovary. But here 
 they are ac:ain met by tlie whole body of facts, and chain of reasoning which 
 drove them from tlieir original position. It has indeed been said, and with no 
 want of plausibility, that the volatile vapours from the semen might penetrate 
 through obstructions vvliich would resist the semen itself. Be it so: in man)’ 
 instances, it might happen undoubtedly. But still, how can the cases formerly 
 referred to, be got over, where from organic derangement, the passages were 
 so entirely occluded, as to be impervious even to air? 
 
 Nor are these the only difficulties that stand in the way of this amended 
 liypothesis. We are not disposed, how’ever, to enter at present into any fur. 
 ther detail. Before we engage in a lengthened investigation of this sort, we 
 require it to be shown that the aura seminalis has the property of fecunda- 
 tion. As yet, no such proof has been exhibited. The e.xperiments of Spallan- 
 zani, and Hunter, the only ones which have been made on the subject, prove 
 indeed quite the contrary. —Ed. 
 
ON GENERATION. 
 
 529 
 
 matic fluid, obtained by the process employed by Spallanzani, 
 in his admirable experiments on artificial impregnation. 
 
 It is especially to the labours of this able observer, that we 
 owe what has been unveiled of the mystery of generation, and 
 of the part which each sex bears in this function. It is almost 
 proved, that the male co-operates in it only by supplying the 
 vivifying principle that must animate the individuals, of which 
 the female furnishes the germs; that thus his part is the least 
 essential. It is not so difficult as may be imagined, to explain 
 upon this system the striking resemblances which are frequendy 
 seen between fathers and sons. The imperceptible embryo has, 
 at most, the consistency of a slightly viscous glue. Such a body 
 must be exceedingly impressible, and the semen of the male, 
 applied to its surface, must impress on it powerful modifications. 
 The action of the fluid on this yet tender embryo must be like 
 that of a seal which stamps on the soft wax its own image. The 
 impression is the deeper, the resemblance the more striking, 
 according to the spirit and energy with which the male perform- 
 ed the act of reproduction. 
 
 The seminal fluid may not merely act on the surface of the 
 gelatinous and nearly liquid germ, and modify it externally, 
 but it may penetrate so soft a substance, and impress on it in- 
 ward changes. It is thus that we are able to explain, not only 
 hereditary likeness, but also hereditary diseases. Nevertheless, 
 it does appear, that the interior parts are derived chiefly from 
 the female, while the outward parts are especially influenced by 
 the male; for, when two animals of different species copulate, 
 their mule resembles the sire outwardly, and the dam within. 
 It is difficult to S(how good reason for the want of the genera^ 
 tive faculty in mules. Why are their sexual parts, so well deve- 
 loped, altogether barren? — What secret defect frustrates their' 
 action? And why do certain mules, among birds, propagate; 
 and in the same manner, hybrid plants, which afe real mules, 
 and not quadrupeds? 
 
 The impregnation of the ovum is effected in the ovarium 
 itself, to which the semen is conveyed, as has been said. The 
 ovum, stirred by the action of the semen, and of the fallopian 
 tube, detaches itself from the organ which has produced it, and 
 descends into the uterus, by the peristaltic contractions of the 
 
ON GENERATION. 
 
 530 
 
 fallopian tube. This canal is susceptible of a retrograde motion. 
 It may be conceived, by considering that having stretched itself 
 by a real erection to convey the semen to the ovarium, it must, 
 in its return upon itself, cause a flow of the fluid its cavity con- 
 tains, in a completely inverted direction. This retrograde mo- 
 tion, as Nisbet observes, is assisted by a sort of collapse suc- 
 ceeding the excitation which coition had produced: for, the 
 experiments of Darwin prove that the weakness of the ves- 
 sels is the cause of this mode of action in their parietes. Spungy 
 as the urethra of man, the fallopian tube brings back the ovum, 
 from the ovarium to the uterus. The extra-uterine fcetations 
 afford the proof, that matters are carried on in the manner we 
 have stated. Since foetuses have been found developed in the 
 ovarium, in the fallopian tube, and even in the cavity of the 
 abdomen, when the detached ovum has escaped from the grasp 
 of the corpus fimbriatum,* one must admit that it follows the 
 course which has been described. 
 
 The ovaria, like the testicles, swell and enlarge at the time 
 of puberty. They shrink, and wither in some sort, when the 
 
 • In extra uterine abdominal conceptions, the ovum which the tube could 
 not hold, or seize, rolls into the hypogastric region, and there adheres t» 
 some point of the peritoneum. It is found attached to the mesentery, to the 
 colon, to the rectum, to the external part of the uterus, growing there, and 
 developed, by the vascular communication which takes place at the adhe- 
 sion; but the vessels of the peritoneum are insufficient for the entire deve- 
 lopment of the fcetus, which dies, for want of nourishment, in the first months 
 of pregnancy. The adhesion of the ovum to the peritoneum, is easily account- 
 ed for, by the irritation it occasions; it may be considered as a foreign body, 
 determining, by its presence, inflammation of the membrane with which it 
 lies in contact, and uniting with it, because it brings to this act its own share 
 of vimlity It is really a union of two living parts, not unlike to that which 
 takes place between the bleeding lips of a wound, between the pleura pulmo- 
 nalis, and the pleura costalis, &c. 
 
 But as the serous membranes contain, in their tissue, capillaries so fine, 
 that when in a healthy state, the blood does not show its colour in them, 
 tlieir vessels never develope themselves sufficiently to ti-ansmit to the ovum, 
 which has adhered to them, a due supply of tliis fluid. The mucous mem- 
 branes receiving more blood, are able to supply more: but tire placenta never 
 adheres to them in extra-uterine conception. The membrane which lines the 
 tube belongs, in fact, as much to the serous as to the mucous membranes; it 
 establishes, as is well known, the only point of communication thene is be- 
 tween the two kinds of membntnes. 
 
ON GENERATION. 
 
 531 
 
 woman is no longer fit for conception. On examination, a few 
 days after conception, one of the ovaria, larger than the other, 
 shows a little yellowish vesicle, which dries up in the course of 
 pregnancy, so that, towards the end, there remains nothing in 
 its place, but a very small cicatrix. Is this vesicle the outermost 
 covering of the ovum, in which the germ is enclosed, and whicl> 
 is torn to allow its escape? The observations of Haller prove 
 that the corpus luteum is formed by the remains of a vesicle 
 thsit has burst at the moment of conception, and allowed the 
 fluid it contained to escape. In a ewe opened a few minutes 
 after coition, you may see, in one of the ovaria, a vesicle larger 
 than the others, torn with a little wound, of which the lips are 
 still bloody. Inflammation comes on in the torn coats of the 
 small vesicle, fleshy granulations appear, then sink, and a scar 
 shows’ the place where it had been. The number of these cica- 
 trices is proportioned to that of the fetuses. It is not known 
 how long the germ detached from the ovarium remains within 
 the fallopian tube, before it reaches the cavity of the uterus. 
 Valisnieri and Haller had never been able to perceive it dis- 
 tinctly in this viscus, before the seventeenth day. 
 
 The obstruction of the tubes may, as well as the defect or 
 diseased affection of the ovaria, cause barrenness. Morgagni 
 speaks, on this head, of certain courtezans in whom the tubes 
 were entirely obliterated by the thickening of their parietes; the 
 consequence, evidently, of the habitual orgasm in which they 
 had been kept, by too frequent excitation. The structure of 
 these parietes must make obstructions of the fallopian tubes 
 very easy. Their tissue is spungy, vascular, and seems suscep- 
 tible of erection, like the corpus cavernosum of the penis and 
 of the clitoris. Their internal coat (the point of union between 
 the serous membrane which lines the abdomen, and the mu- 
 cous membrane within the uterus) partakes in the inflammation 
 of both. I have often been consulted by young women on the 
 cause of their sterility; by a close investigation of the causes 
 from which it might have arisen, I have always found that they 
 had had, at different periods of life, inflammation of the lower 
 part of the abdomen. A young woman, after obstinate suppres- 
 sion of the menses, exhibited all the symptoms of inflammation 
 of the peritoneum; a year afterwards she married, but never 
 
ON GENERATION. 
 
 532 
 
 became pregnant. A woman recovered from puerperal fever, 
 ensuing upon a very difficult first labour; from that time, with 
 all the appearances of the stoutest health, she has never been 
 again a mother. 
 
 Do the two testicles and the two ovaria, contain the separate 
 germs of males and females? Are these, as has been guessed, 
 contained in the left ovarium, and males in the right? and may 
 we procreate sexes at pleasure, by varying the attitude of co- 
 pulation? This old opinion, lately revived, besides wanting all 
 foundation, is formally confuted by facts: nothing is more com- 
 mon than to see men who have, from some accident, lost a tes- 
 ticle, procreating sexes indifferently. Women, with an ovarium 
 deficient, or the fallopian tube obliterated on one side, have pro- 
 duced both boys and girls. Dr. Jadelot has presented to the 
 society of the School of Medicine in Paris, a uterus, wanting 
 the right tube and ovarium: and nothing indicated that they had 
 ever existed. On inquiry concerning this woman, it appeared 
 that she had been delivered of a boy and two girls: Haller 
 quotes similar cases. The cause, then, which determines the 
 sex, altogether eludes our investigation. Does that one of the 
 two, who exerts most energy in the act of coition, impress its 
 sex on the offspring? I cannot tell; but I think I have observed 
 that the marriage of young people, where both are glowing with 
 love and youth, most frequently produces daughters, whilst 
 boys are ordinarily the consequence of the union of a middle 
 aged, or elderly man, with a younger woman. 
 
 CCVI. Systems on generation. The antique system of the 
 mixture of the semen in the cavity of the uterus, set forth in the 
 writings of Hippocrates and Galen, is still that of many physio- 
 ogists. In this system, the mixed fluids may be considered as 
 an extract from all parts of the body, male or female. A gene- 
 rative faculty *= disposes them suitably for the formation of the 
 new individual. Buffon has further particularized the facts 
 which this hypothesis requires, and displayed its improbability. 
 Each part, he says, furnishes molecules, which he calls organic, 
 
 * All that Blumenbach has said, on the force of formation, {nisus fonnati- 
 ’ius) applies to this generative faculty; it is only a new name given to an old 
 
ON GENERATION. 
 
 533 
 
 and these molecules, coming from the eyes, the ears, &c. of the 
 man and the woman, arrange themselves round an internal 
 mould, of which he admits the existence, which mould forms 
 the basis of the edifice, and comes from the male probably, if it 
 be a boy, from the female, if a girl. Reason rejects a theory 
 which gives no explanation of the production of the placenta, 
 and of the membranes covering the foetus: it is moreover di- 
 rectly disproved by the good conformation of children, born of 
 parents, who not happening to have certain organs and limbs, 
 could not certainly supply the proper molecules for their forma- 
 tion in the child. 
 
 The system of the ovarists, which at this time stands highest 
 in favour, numbers amongst its supporters, Harvey, Stenon, 
 Malpighi, Vallsnieri, Duhamel, Nuck, Littre, Swammerdam, 
 Haller, Spallanzani, Bonnet, Stc. These admit the distinction 
 of animals into oviparous and viviparous, in this sense only, 
 that these last hatch within, and break their shell before they 
 are brought forth. Lastly, Lewenhoek, Hartsoeker, Boer- 
 haave, Mery, Werheyen, Cowper, &c, have added to the 
 opinion of the ovarists, that the seed of the male contains a 
 multitude of spermatic animalcules, all capable of becoming, by 
 development, beings similar to their father. These animalcules 
 push forwards, along the tubes, upon the ovafia; there a gene- 
 ral engagement takes place, in which all are slain, save only 
 one, who, master of the field of battle, finds the triumph of bis 
 victory within the ovum that has been prepared for him. This 
 system, which is not the most probable in the world, assigns to 
 the male the greater part in the work of generation, since the 
 female is made to furnish merely the coverings of the foetus. 
 
 It would be to no purpose to unfold, more at large, opinions 
 hazarded on a subject so obscure. What I have said is enough 
 to show that those parts of nature which most obstinately elude 
 our curiosity and afford most scope to our imagination, are 
 those which men believe they know the best, and on which 
 they speak with most confidence and prolixity: — so true is it, 
 as Condillac has observed, that we have never so much to say, 
 as when we set out from false principles.* 
 
 * Numerous as are tlie theories which have been advanced on the subject 
 of generation, they may all, as mere varieties, (or at least such as are 
 
ON GENERATION. 
 
 534 
 
 CCVII. Of gestation. From the moment of conception, there 
 begins in woman, both in the motion of the solids, and the com- 
 position of the fluids, a remarkable alteration. The change that 
 has taken place shows itself in all her functions: she exhales a 
 
 worthy of attention), be very properly reduced under two leading heads or 
 general divisions. 
 
 1. Doctrine of Palengenisis. 
 
 2. Doctrine of Epigenisis. 
 
 The first of these doctrines supposes the pre-existence of germs. It is of 
 great antiquity, and in its descent to us has undergone some slight modifi- 
 cations. By most of the early philosophers it was taught, “ That these 
 germs created with the beginning of things, were scattered throughout the 
 world, b^t ultimately meeting with appropriate genital organs, effected a 
 lodgment therein, and became fit for development.” 
 
 As soon, however, as the moderns entered into speculations of this nature, 
 the hypothesis received a con-ection which, in part, divested it of its absur- 
 dity. Denying that tliese germs wandered about “ in quest of an habitation 
 and a home,” it was now, on the contrary, maintained, “ That all of the 
 same species, were ab initio neatly incased, one w'ithin another, so that the 
 first parent, animal and vegetate, contained the germs of each succeeding 
 generation, and which to be evolved required only the seminal impulse of the 
 male.” 
 
 This doctrine of evolution had been hardly revived, when two sects arose, 
 wlio urged their respective opinions with all the zeal, all the ardour, and all 
 the pertinacity of party controversialists. They difiered, however, only on 
 a single point. By the one side it was maintained, that the germs were fur- 
 nished by the female, and by the other that they proceeded from the male. 
 
 The former of these opinions was brought into repute by Fabricius ab 
 Aquapendente, so called from the place of his nativity. Having ascertained, 
 as he thought, by a series of experiments on the egg, that it contained a pre- 
 existing embryon, he, w’ith a numerous train of disciples, pushed their inves- 
 tigations, and finally detected, or pretended to detect, ova also in the ovi- 
 parous animals. 
 
 Enamoured of this boasted discovery, the celebrated Harvey became one 
 of the warmest and most strenuous supporters of the hypothesis to which it . 
 led. 
 
 “ Omnia ex ova.” 
 
 This brief aphorism, which escaped from him in the enthusiasm of his de- 
 votion, sufficiently marks his impressions on the subject The only dis- 
 tinction, Indeed, wliich he admits in the generative process of the two 
 classes of animals, is, “ That in the viviparous, the fcrtus begins to exist, 
 increases, and com|)letes its growth in the uterus; whereas, in the ovipa- 
 rous, the embryo exists in the egg in the body of tlie hen, but does not be- 
 come a foetus till expelled, and is hatclied into life by incubation. 
 
 The ovular doctrine vvas first arraigned by Luenhoeck, who made the pre- 
 tended discovery of the- spermatic animalcules in the male seed. By him and 
 
ON GENERATION, 
 
 335 
 
 peculiar odour; the child she suckles refuses the breast, or takes 
 it with reluctance, and soon falls away, if left in the hands df 
 such a nurse. 
 
 Nature, occupied over her work, seems to forget every thing 
 
 his followers, the existence of ova in viviparous animals was speedily and 
 satisfactorily confuted. They demonstrated to entire conviction, that what 
 had been taken for true ova were the mere vesioles of the ovary, which 
 have no resemblance to an egg, being merely cups or reservoirs of a fluid, 
 which after fecundation is discharged and conveyed by the fallopian tube 
 to the cavity of the uterus. They further proved, that previously to im- 
 pregnation nothing like a germ could be found even in the real egg, but that 
 there is placed on the vitellns, a small vesicle, the cicatricu^j, containing a 
 fluid of the same nature, and destined for the same end as that in the vesicle 
 of the ovary. The only difference, therefore, in this respect, between the 
 egg and ovary, according to this sect, is, that that the former has a single, 
 while the latter has a cluster of vesicles. 
 
 By this doctrine of spermatic worms, which completely usurped the place 
 of the ovular doctrine, and which acquired for a tirtie an undisputed ascen- 
 dency in the medical and philosophical schools, it was aflirmed, that these 
 seminal vermlculi are living miniatures of the animal from which they are 
 derived, exacting only from the female a matrix for nourishment, evolution 
 and growth. 
 
 Though the ovular doctrine was thus subverted by Luenhoeck and his 
 auxiliaries, it after a while again revived, under the auspices of Haller, so 
 fer at least, as to suppose the pre-existence of a germ in the female, and 
 soon received the distinguished support of Bonnet, Spallanzani, Hunter, &c. 
 Being restored in a more enlightened age, it of course was stripped of most 
 of those extravagancies which had before detracted so much from its merit- 
 Agreeing in the fundamental principle of the doctrine, these physiologists 
 entertained some difference of opinion as to the origin, the e.xistence and de- 
 velopment of the germs. They all, however, maintained, “ that the germ, 
 as the exact miniature of the animal or vegetable to which it belongs, exists 
 in tile female prior to fecundation, requiring only the stimulus of the male 
 seed to excite it into life,” &c. &c. 
 
 By thus narrowing the definition of the doctrine, they presented it in a 
 guise exceedingly alluring, and rested its vindication on a collection of ex- 
 periments and observations, in appearance, the most definite and conclusive. 
 These, however, on a closer examination, exhibit a very different aspect, so 
 much so indeed that a large number of distinguished physiologists have been 
 induced, upon the most diligent scrutinies, to question altogether the pre- 
 existence of germs. It would be wholly inconsistent with our limits to detail 
 the arguments and reasonings which have been employed bj' the adverse 
 parties in this interesting controversy. We proceed next, therefore, to the 
 doctrine of Epigenisis. 
 
 Discarding, as we have already hinted, the notion of the pre-existence of 
 germs, it presumes th^t “ the prepared, but at the same time unorganized 
 
OJf GENERATIOX. 
 
 536 
 
 else, to bring it to perfection. It has been obsea-ved, that in 
 times of contagious diseases, even where the plague raged, 
 pregnant women were least exposed to infection: but, at the 
 same time, when they are seized with affections, which in 
 other persons or at another season, would be without danger, 
 they sink under them, because these diseases, though at first 
 very slight, easily put on a malignant character. The progress 
 of mortal diseases is retarded: a phthisical woman, and who 
 has only a few months to live, shall prolong her life through 
 the whole term of gestation. The consolidation of fractures is 
 nothing slower, though Fabricius Hildanus, pretends that the 
 state of pregnancy puts a complete stop to it, 
 
 I have never been able to find any difference in the time of 
 formation of callus, between pregnant women and others. M. 
 Boyer avows the same opinion.* Among the authors who have 
 asserted that fractures could not consolidate during pregnancy, 
 some have conjectured that this depends on nature, who is 
 
 * Lecons de M. Bo3'er, stir les Maladies des os, redlg’^es en un Traite com- 
 plet de ces Maladies, par A. Richerand, 2 vol. 8vo. 
 
 rudiments of the foetus, first begin to be gradually organized when they 
 arrive at their place of destination, at a.due time, and under the necessary 
 circumstances.” This is the definition of a learned writer. The doctrine, how- 
 ever, may be more distinctly enunciated. We would say, that, denying the 
 pre-existence of germs in either parent, the doctrine of Epigenisis supposes, 
 that the fluid contained in the ovarian vesicle is the rude elementary mat- 
 ter which, after impregnation, becomes organized into an embryon bytlie 
 energies of the semen masculinum. The primaiy traces of this doctrine are to 
 be met with in the writings of Aristotle. The prevailing opinion on the 
 subject of generation, in the time of this eminent philosopher was, that each 
 sex furnishes semen, and that the embryon residts from an admixture of 
 the two fluids in the cavity of the uterus. After confuting the popular 
 idea of women having semen, he asserted that they contribute nothing 
 towards conception, except the menstrual blood: that the rudiments of tlie 
 embryon are derived from the menses, and are vivified and put together 
 by a plastic power, which lie imputed to the semen. With various modifi- 
 cations this hypothesis has been handed down to us. It would be tedious and 
 impossible to point out all the shapes which at different times it has as- 
 sumed. Of late, its most able and determined supporter is Blumenbach, to 
 whose system of Physiology, and Essay on Generation, we must refer such 
 of our readers as are desirous of further information on this subject — En. 
 
ON GENERATION. 
 
 537 
 
 busy in directing the humours to the uterus, forgetting, in some 
 sort, every other function, and omitting to institute the process 
 necessary to the cure. But as we shall see, whatever may be 
 the importance of the uterus, charged during pregnancy with 
 the fruit of conception, the f ^tus is merely an organ added to 
 the organs of the mother, and assimilating to itself the juices 
 it receives fi'om the uterine vessels. It does not hinder the 
 other parts from getting their nourishment; they all go on 
 living, and separating to themselves the juices their existence 
 or their functions require. Haller ascribes the difficulty with 
 which the broken ends unite, in pregnant women, to the great 
 quantity of earthy matter which the foetus draws off from the 
 mother. This opinion will not stand: for, as I have shown 
 in my preliminary discourse, the phosphate of lime has but lit- 
 tle to do in the work of re-union, which chiefly goes on by 
 changes in that part of the bone which is really organic. Be- 
 sides, this hypothesis would imply that consolidation were as 
 difficult in nurses, whose milk carries off a large quantity of 
 phosphate of lime. Yet it has not been observed that the for- 
 mation of callus is more difficult during suckling. Lastly, on 
 this, as on all occasions, experience is more' effectual than 
 reasoning; now, experience shows, that the tim.e required for 
 the formation of callus, in pregnant women, is not sensibly 
 longer than in their ordinary state. 
 
 Meanwhile, the uterus, imbued with prolific fluid, swells, to 
 avail myself of the expression of a modern, like a lip stung by 
 a bee: it becomes a centre of fluxion towards which the humours 
 tend from all quarters. The diameter of its vessels increases 
 with the thickness of its parietes: these soften, and their mus- 
 cular nature becomes more marked. Till the end of the third 
 month, the only appearance of pregnancy is in the suspension 
 of menstruation; the uterus, of which the cei'vix has yet under- 
 gone no change, has concentrated itself behind the -pubis, but 
 very soon it rises above the upper outlet of the pelvis, pushing 
 upwards the intestines and the rest of the abdominal viscera. 
 Towards the end of pregnancy, it rises above the umbilicus, 
 its fundus comes in contact with the arch of the colon, and 
 reaches sometimes to the epigastric region. The compression 
 it exerts on the organs of digestion, explains the loathings, and 
 
 3 Y 
 
ON GENERATION. 
 
 538 
 
 the nausea which belong to the s.ate of pregnane}'. The ^de- 
 rangement of sensibility, by the affection of the great sympa- 
 thetics, accounts equally fur those depraved tastes, those fan- 
 tastic appetites, which the ignorant think it so important to 
 gratify. When the term of pregnancy draws near, respiration 
 is oppressed, the diaphragm forced upward by the abdominal 
 viscera, descends with difficulty; accordingly, nature has, as 
 much as possible, delayed this moment of oppression, by giving 
 the lower part of the abdomen a great capacity, at the expense 
 of the chest, which in woman, is much shorter than in man. 
 
 If the growth of the foetus, its size, the quantity of liquor 
 amnii, the development of the uterus, were always the same, 
 we might settle the height to which this last organ must rise, 
 at each stage of pregnancy; but these conditions vary so much, 
 in every individual, that the terms one might assign would suit 
 but a small number: let it suffice to have spoken of the ex- 
 tremes. The uterus tends to rise directly upwards: while in- 
 closed within the pelvis, it preserves this direction; but, as soon 
 as it has passed the upper outlet of the pelvis, it is no longer 
 supported, and inclines forwards, backwards, or to the sides. 
 These inclinations, if they go a certain length, constitute those 
 vices of situation which accoucheurs call obliquities of the 
 uterus. Their direction is determined by the disposition of the 
 parts: accordingly, they almost always lie forwards; either be- 
 cause the upper outlet of the pelvis is naturally so inclined, and 
 forms with the horizon an angle of 45 degrees, or because the 
 lumbar column, being convex, pushes the uterus, which cannot 
 depress it, upon the anterior parietes, which yields the easier, 
 the more frequent pregnancy has been. 
 
 The dilatation of the uterus is not the effect of a simple dis- 
 tention of its parietes, since these, far from stretching thinner 
 as the vise us grows in size, thicken progressively, on the con- 
 trary, by the dilatation of vessels of all sorts, and the afflux of 
 humours. In this sort of vegetation, the uterus is really active, 
 and does not give way to any efforts of the foetus. The cervix 
 of this viscus, which from its greater consistency had at first 
 resisted dilatation, ends by yielding to the efforts of the fibres 
 of the fundus, on the edges of the os tincse; the edges of that 
 opening are attenuated, the cervix effaced, the orifice enlarges. 
 
ON GENERATION. 539 
 
 and you may feel through its parietes, the fojtus plunged in the 
 waters which its membranes contain. 
 
 Towards the term of gestation, the discharge of urine is more 
 frequent, because the bladder, under compression, cannot con- 
 tain it in any quantity. The lower extremities are cedematous; 
 the veins of the legs varicose: women are also more exposed 
 to haemorrhoids; and these effects depend on the compression 
 of the vessels, which bring back the blood and the lymph of the 
 inferior parts, as the cramps, to which pregnant women are 
 subject, depend on that of the sacral nerves. The groins are 
 alike painful, and there are felt in them twitchings which must 
 be ascribed to congestion in the round ligaments of the uterus. 
 Lastly, the skin of the anterior parietes of the lower part of the 
 abdomen, distended beyond measure, cracks, when that of the 
 neighbouring parts has yielded as much as it could. 
 
 Before explaining how the uterus expels the fcetus and its 
 coverings, at the term of gestation, let us consider a little, this 
 fruit of conception: let us study its development; let us examine 
 the nature of the relations which it holds with its mother. 
 
 CCVIII. History of the foetus and its coverings , — The inte- 
 rior of the uterus, for a short period after the instant of concep- 
 tion, shows nothing that leads to a knowledge of the existence 
 of its product. But, at the end of a few days, there appears a 
 membranous transparent vesicle, filled with a liquid trembling 
 jelly; discovering no trace of organization and life. But the 
 little ovum begins to grow, parts of the gelatinous fluid assume 
 more consistence, losing at the same time their transparency: 
 one may then distinguish the first rudiments of parts, an im- 
 perfect appearance of the head, trunk, and limbs. The small 
 ovum, free at first in the cavity of the uterus, contracts adhe- 
 sions to this viscus: its v/hole exterior surface becomes shaggy, 
 and this sort of vegetation is no where more marked, than in 
 the situation to be occupied by the placenta. Meantime, to- 
 wards the seventeenth day, the parts which showed merely a 
 homogeneous semi-transparent mass, discover a more determi- 
 nate structure. A red point appears in the spot of the heart, it 
 is the heart itself, distinguishable by the pulsations of its cavi- 
 ties, and the motions of the molecules of the red liquid that 
 fills them. Because the heart is the punctum saliens, it is not 
 
ON GENERATION, 
 
 540 
 
 therefore to be concluded that it is the primum vivens. All our 
 parts are formed together, all are coeval, as Charles Bonnet 
 has said; only they discover themselves earlier or later to the 
 eye of the observer, according as the nature of their organiza- 
 tion is adapted to the reflection of light. Were we to admit a 
 successive order in the formation of our organs, the brain and 
 the nervous system might exist before the heart, without being 
 perceptible from their transparency. 
 
 Meanwhile, red lines, setting off from the heart, sketch the 
 course of the larger vessels, and seem agitated by the action of 
 these tubes, whose parietes are still semi-transparent. As the 
 blood, or rather its red part, extends from the centre to the 
 circumference, the forms become more determinate, the parts 
 unfold and grow rapidly: points quite opake are seen, and the 
 form of the foetus may be distinguished. Bent upon itself, the 
 foetus is not unlike a French bean, suspended by the umbilical 
 cord, which, as I shall mention by and by, formed with the 
 foetus and its coverings, proceeds in growth with them: it 
 swims amidst the liquor amnii, changes its position the more 
 easily, as the space in which it is inclosed is greater, compared 
 to its size. As it grows, it stretches out a little, without ceas- 
 ing however to retain its bent posture (CLXV): the head com- 
 poses the greater part of its body: the upper limbs, like little 
 buds, pullulate first, then the lower limbs: the feet and the 
 hands appear immediately attached to the trunk; the fingers 
 and toes show themselves like little papill . Of all the organs 
 of sense, the eyes are the first apparent: they are discernible, 
 as two little black spots, by the end of the first month; the eye- 
 lids are produced and cover them. The mouth, at first gaping, 
 closes by the drawing together of the lips, towards the end of 
 the third month. During the fourth, a reddish coloured fat be- 
 gins to be deposited in the cells of the mucous tissue, and the 
 muscles already exert some action. The growth is ever more 
 rapid, as the foetus draws nearer to its birth. It is impossible to 
 assign the weight and the length of the foetus, at the different 
 stages of pregnancy, since the time of conception is never very 
 certain; and further, the progress of growth varying much, one 
 foetus at six months shall be as large as another at the full term. 
 
ON GENERATION. 54 ^ 
 
 Nevertheless, at the time of birth, the body is commonly 18 
 inches long, and weighs from seven to eight pounds. 
 
 The secretion of bile, like that of the fat, seems to begin, 
 towards the middle of gestation, and tinges the meconium yel- 
 low, a mucus previously colourless, which fills the digestive 
 tube: a little while after, the hairs grow; the nails are formed 
 about the sixth or seventh month; a very thin membrane, which 
 closed the pupil, tears, by what mechanism is unknown, and 
 the pupil is seen. The kidneys at first manifold, that is to say, 
 formed each of from seventeen to eighteen separate glandular 
 lobules, unite, and form on each side a single viscus. Lastly, the 
 testicles, placed at first at the side of the lumbar column and 
 aorta, near the origin of the spermatic arteries and veins, then 
 carried along the iliac vessels to the inguinal rings, directed by 
 a cellular cord, which Hunter calls the (^gubernaciilum testis^ 
 clear this opening, carrying along with them the portion of the 
 peritoneum, which is to form their tunica vaginalis. 
 
 This covering of the testicles, furnished by the peritoneum, 
 not only covers these organs, and is reflected again over them, 
 but also rises, in adults, about half an inch high, along the 
 lower part of the spermatic cord. If it do not reach, it is said, 
 to the inguinal ring, it is because the whole portion which, 
 after birth, extended from this opening to near the testicle, has 
 been decomposed, and is reduced to cellular tissue. Upon re- 
 flecting on the causes of the spontaneous decomposition of a 
 portion of this peritoneal prolongation, it occurred to me, that 
 nothing was less proved, or more improbable; in fact, in ear- 
 liest life, the testicles, which have' passed out from the abdo- 
 men by the inguinal rings, are very little removed from this 
 opening. The portion of tunica vaginalis, which is carried on 
 upon the cord of the spermatic vessels, rises up to the ring, and 
 even extends beyond; communicating with the peritoneum, as 
 is sometimes seen in congenital bubonocele. It is only in the 
 progress of life, that the testicles descend into the scrotum, still 
 departing from the opening which gave them passage: so that, 
 in adults, the prolongation, which at first covered the whole 
 cord, (which, just after birth, was not more than a few lines 
 long,) is found to cover only its lower part, when it is lengthened 
 some inches, without any necessity of decomposition; a pheno- 
 
ON GENERATION. 
 
 542 
 
 menon, which it is as difficult to conceive as to explain. This 
 opinion suggested, for the first time in the first edition of this 
 work, is now almost universally received. 
 
 CCIX. Of the circulation in the foetus^ The principal differ- 
 ence that is found between the foetus and the new-born child, 
 besides the inactivity of the senses, and the repose of the mus- 
 cles subject to volition, lies in the manner in which the circu- 
 lation is carried on. Too feeble to assimilate to its own sub- 
 stance foreign substances, the fcstus receives from its mother 
 aliments ready prepared. The arteries of the uterus receive a 
 large supply of blood; this is not all employed for the nourish- 
 ment of the organ itself, but passes in great part from the mo- 
 ther to the child, being poured by the uterine vessels into the 
 cells of a spungy substance, adhering on one side to the uterus, 
 and on the other to the ovum which contains the fcetus. 
 
 This cellulo-vascular body, known under the name of placenta, 
 is, as well as the coverings of the foetus and the foetus itself, a 
 product of the act of generation. Though it adheres commonly 
 to the fundus of the uterus, it may adhere to any other point 
 of its parietes; sometimes even it is placed on its orifice, a 
 circumstance which always makes delivery difficult. The side 
 by which it is united to the internal face of the uterus is uneven, 
 covered with mammillary projections (cotyledons)^ which are 
 sunk in corresponding cells of the parietes of the uterus, the 
 internal surface of which loses as it develops itself, the smooth- 
 ness which it had while empty, is furrowed with depressions 
 destined to receive the placenta, and studded with projections 
 which penetrate into the cells of the latter. 
 
 The uterine arteries, and perhaps likewise the absorbents 
 which are so large and numerous in the gravid uterus, that 
 Cruickshank, who succeeded in injecting them, compares them 
 to quills, throw out on the surface of the placenta and within 
 its spungy tissue the arterial blood of the mother; according to 
 some, these vessels exhale only the serous part of the blood, 
 and according to others a chylous, lymphatic, whitish, or milky 
 substance.* These fluids, effused within the cells of the placenta, 
 
 * A German physician, Schreger, has suggested a very ingenious opinion 
 on the mode of circulation between the mother and child. He believes that 
 the uterine arteries pours out nothing but serum, into the cells of the pla- 
 
ON GENERATION. 543 
 
 are absorbed by the numerous minute divisions of the umbilical 
 vein, which by their union form the trunk of this vessel. 
 
 The umbilical vein, arising from the interior of the placenta 
 by numerous branches, detaches itself from it and goes towards 
 the umbilicus of the child, enters his body at that aperture, 
 ascends, in a fold of the peritoneum, behind the recti muscles, 
 to the anterior extremity of the sulcus of the liver, goes along 
 the anterior half of this fissure, sending a number of branches 
 to the lobes of that viscus, especially to the left lobe. On reach- 
 ing the right extremity of the transverse fissure, where this last 
 meets the antero-posterior, it unites in part with the sinus of 
 the vena portse hepatica, while the remainder of the vessel, 
 called ductus venosus, follows the original direction, and opens 
 into the ascending or inferior vena cava, very near to the spot 
 where this vein pours its contents into the right auricle of the 
 heart. 
 
 CCX. The arterial blood which flows along the umbilical 
 vein acquires the properties of venous blood, and combines 
 with hydrogen and carbon, andparts with its vivifying qualities, 
 
 eenta. This serum is absorbed by the lymphatics, whose existence he infers 
 from analogy, in this organ and in the umbilical cord, in which, however, no 
 one has yet succeeded in injecting them. These vessels convey it to the 
 thoracic duct, whence it is poured into the left subclavian vein, and at last 
 reaches the heart which sends it along the aorta. It returns to the placenta 
 by the umbilical arteries, after being converted into blood by the action of 
 the organs of the fetus. This serosity after undergoing the process of san- 
 guification, returns to the fetus by the umbilical vein, and following the well 
 known course of the fetal circulation, is subservient to the nourishment of its 
 organs. The branches of the umbilical arteries and vein, ramified in the pla- 
 centa and communicating together in this spungy tissue, reject through their 
 lateral pores that which can no longer serve to the maintenance of the fetus. 
 This residue of nutrition, deposited in the cells of the placenta, is absorbed 
 by the lymphatics of the uterus, which carry it back into the mass of the 
 fluids of the mother. Not to mention the impossibility of demonstrating the 
 presence of lymphatics, in the placenta, or in the umbilical cord, Schreger’s 
 hypothesis is attended with two objections. How does the nutritious fluid, 
 coming from the mother and sent along the aorta of the fetus to every part 
 of its body, return to the placenta, to be brought back again by the umbilical 
 vein? Absorption scarcely goes on in the fetus: the unctuous substance with 
 which the body of the fetus is covered, prevents that function from taking 
 place on the surface of the body. It goes on, with very little more activity, 
 within the body; the excrementitious secretions scarcely exist before birth; 
 whatever is conveyed to the fetus is emplot'ed in the development of its or- 
 gans; hence its growth is so rapid. 
 
ON GENERATION. 
 
 544 
 
 in flowing along the vessels of the mother and the tortuous 
 vessels of the placenta. It parts with these principles, and again 
 becomes vivified, by circulating through the liver which at this 
 period of life fulfils the functions, which after birth is committed 
 to the lungs. Hence the liver and brain form the greatest part 
 of the Weight of a new born child. The former alone occupies 
 the greatest part of the abdomen. It acquires this bulk, by as- 
 similating to itself the hydrogen and carbon of the umbilical 
 blood. Its substance is adipose, oily, and contains these two 
 principles in a considerable proportion. The secretion of the 
 bile and that of the fat, the only secretions that are manifesdy 
 carried on in the foetus, may besides supply very well the want 
 of respiration. 
 
 The blood conveyed by the umbilical vein into the lower vena 
 cava, and deposited by that vein into the right auricle, does not 
 unite with that which is brought by the descending cava, from 
 the upper parts; for, as was observed elsewhere, the orifices of 
 these two vessels not being directly opposed to each other, the 
 columns of blood which flow in them do not meet each other. 
 That which is brought by the lower cava, passes through the 
 foramen ovale, towards which the mouth of that vessel is turn- 
 ed; it passes into the left auricle, thence into the left ventricle, 
 without circulating through the lungs, which containing no air 
 and being dense and indurated, could not have received it; the 
 contractions of the left ventricle send it into the aorta, the force 
 of its impetus is broken, by striking against the great arch of 
 this artery. It enters into the vessels which arise from it, and 
 these convey it directly to the brain and upper parts. This blood 
 is the most pure, the most oxygenated, and that which comes 
 most immediately from the placenta; it has not yet circulated 
 in the body of the foetus, with the exception of a very small 
 quantity brought from the pelvis and lower parts, for the blood 
 which comes from the abdominal viscera, is purified in passing 
 through the liver. The other parts of the body receive, on the 
 contrary, blood very imperfecdy oxygenated, since the very in- 
 considerable quantity which the contractions of the left ventri- 
 cle and of the aorta hav^e not been able to send into the vessels 
 arising from the arch of this vessel, mixes with the venous 
 blood which is brought by the ductus arteriosus, immediately 
 
ON GENERATION. 
 
 545 
 
 below this curvature. Hence the growth which is always rela- 
 tive, not only in respect to the quantity, but likewise to the 
 vivifying qualities of arterial blood, is much more rapid, before 
 birth, in the upper parts, so that the brain alone constitutes the 
 greatest part of the body, and the shoulders, the chest and 
 the upper -extremities are developed in a much greater degree 
 than the abdomen, and especially than the pelvis and lower ex- 
 tremities. 
 
 The blood which is brought by the descending cava, from 
 the upper parts of the body of the foetus, passes into the right 
 ventricle which forces it into the pulmonary artery; this vessel 
 sends only two small branches to the lungs, and terminates by 
 a vessel called the ductus arteriosus, into the aorta immediately 
 below the origin of the left subclavian artery. The aorta, at its 
 origin, is therefore filled with arterial blood, sent towards the 
 upper parts of the body by the contraction of the left ventricle, 
 while the remainder of this artery contains venous blood, which 
 is expelled by the combined action of both ventricles. 
 
 It is impossible in this arrangement, not to recognize an evi- 
 dent design. In fact, if the whole force of the heart had been 
 exerted to send the blood towards the brain, the delicate texture 
 of this viscus would have been injured by it; the combined ac- 
 tion of the two ventricles was, on the contrary, required to 
 enable the blood to circulate along the extensive and tortuous 
 channels of the umbilical cord and placenta. The aorta on reach- 
 ing the body of the fourth or fifth lumbar vertebra, divides into 
 the two umbilical arteries; these send to the pelvis and to the 
 lowerparts only very insignificant branches, which convey blood 
 that contains a very small quantity of oxygen, they then bend 
 along the sides of the bladder, incline inwards, approach to- 
 wards the urachus, pass out of the abdomen at the umbilicus, 
 and joining the umbilical vein v/hich had entered through the 
 same opening into the body of the foetus, form with it the um- 
 bilical cord. 
 
 CCXI. The length of the umbilical cord, measured froih the 
 umbilicus to the placenta, is from twenty to twenty-four inches. 
 It may be not above six inches long, or may greatly exceed that 
 length, as is proved by a case of M. Baudelocque, in which 
 the umbilical cord was fifty-seven inches in length, and passed 
 
 3 Z 
 
ON GENERATION. 
 
 546 
 
 seven times round the child’s neck, which circumstance by the 
 way, shows that the foetus moves in its mother’s womi>. Of the 
 three vessels which form the umbilical cord, two which are the 
 smallest H-.ve an arterial structure, though they convey blood 
 that is truly venous, while the umbilical vein carries arterial 
 blood to the foetus. The umbilical arteries on reaching the pla- 
 centa, divide and are lost in its substance in a multitude of 
 vessels whose extremities deposit into the areolae of its tissue 
 the blood coming from the foetus, and which is to be returned 
 to the mother. Does the course of injection from the umbilical 
 vein into the arteries, prove that there exists an anastomosis 
 between the extremities of these vessels? 
 
 The foetus is connected to the mother, by the umbilical cord 
 and placenta; the veins, or the lymphatics of the uterus, and 
 perhaps both these sets of vessels, take up in the spungy tissue 
 of the placenta, the blood that has been employed in the nutri- 
 tion of the focms, and return it to the mother, that after undergo- 
 ing a change by the action of her organs, and especially by that 
 of the atmospherical air, by means of the pulmonary circula- 
 tion, it may become lit for the nourishment of the foetus. Whe- 
 ther we inject the uterine vessels, or whether we force the wax 
 along the umbilical vein, it never fills but a part of the placenta, 
 which has led to the division of this substance into two parts, 
 the one belonging to the mother, which has been called uterine, 
 the other called the foetal portion, which forms a part of the 
 umbilical cord. 
 
 The vessels of the mother do not, therefore, anastomose with 
 those of the foetus within the placenta; tlie circulation is not con- 
 tinued from the one to the other. If the communication were 
 immediate, the beats of the pulse of the child, ought to be 
 simultaneous with those of the mother, whereas they are much 
 more frequent, as may be observed, at the time of birth, before 
 the division of the umbilical cord. If the veins of a bitch, rea- 
 dy to whelp, are opened, the animal dies of hemorrhage, and 
 her bod}' remains bloodless. The placenta, however, is empty, 
 only in the part that adheres to the uterus; the rest of the pla- 
 centa, as well as the foetus, are filled with blood, as usual. It is 
 obvious, that if the vessels of the uterus had been direcdy con- 
 tinuous with those of the placenta, delivery would not have taken 
 
ON GENERATION. 
 
 547 
 
 place, without their being torn; alarming hemorrhage, inflam- 
 mation, and even suppuration of the uterus would have been 
 the consequence. Lastly, the force with which the heart and 
 arteries of the mother impel the blood along her vessels, would 
 have been attended with danger to the organs of the foetus, 
 which are too soft to sustain, without injury, so violent a shock. 
 Though the placenta and the umbilical cord form the bond of 
 union between the foetus and the mother, it must be confessed, 
 that they belong chiefly to the former, and may be considered 
 as a continuation of its body. 
 
 CCXII. The existence of the foetus is solely vegetative; he 
 is continually drawing from the juices, which the vessels of the 
 mother send to the placenta, what is to serve to his nourish- 
 ment and growth. He may be considered as a new organ, the 
 product of conception, participating in general life, but having 
 a peculiar life, and, to a certain degree, independent of that of 
 the mother. Bent on himself, so as to occupy the least possible 
 space, he cannot be considered as asleep; for, not only are the 
 organs of sense and of motion in a perfectly quiescent state, 
 but besides, several of the functions of assimilation are inactive, 
 as digestion, respiration, and most of the secretions. The foetus 
 performs, in the midst of the liquor amnii, spontaneous motions, 
 which accoucheurs reckon among the signs of pregnancy. The 
 existence of these phenomena has been denied, and the dis- 
 placement of the fetus has been ascribed to a mere shaking of 
 the body; this was asserted on the ground of the intimate con- 
 nexion between respiration and muscular motion. It was said, 
 that the blood of the fetus, not being impregnated with oxygen 
 in its passage through the lungs, contractility would not exist. 
 But besides that a fact may be certain, without being easily 
 explained, it may be answered, that the mother fulfils this office 
 for the fetus, and sends it arterial blood, fitted to maintain the 
 contractility of the muscles. 
 
 As we perform no motion, but in virtue of impressions pre- 
 viously received, and as the organs of sense, in the fetus, are 
 completely inactive, it is not easy to say, why it should move 
 in the womb. The touch, however, is exerted, when any part 
 of the surface of the body of the fetus comes in contact with 
 the internal part of the cavity in which it is contained. Lastly, 
 
ON GENERATION. 
 
 548 
 
 the internal impressions experienced by the great sympathetics, 
 may act as an occasional cause of such motions. 
 
 The foetus is nourished, like every other organ, by appro- 
 priating to itself whatever is suited to its nature, in the blood 
 brought to it by the vessels of the uterus. The interception of 
 this fluid, by a ligature, or by compression of the umbilical 
 cord, would occasion death, though not, as has been imagined, 
 by a sudden and quick suffocation, but the action of the organs 
 would become gradually weakened, and at last cease, when the 
 fluids of the foetus, being no longer vivified by the mixture of 
 new juices from the mother, would be completely deprived of 
 their nutritive parts. It is now well ascertained, that the liquor 
 amnii does not serve to the nutrition of the foetus, whose mouth 
 is closed, whose head is bent on his breast, and whose intesti- 
 nal canal is filled with a fluid different from that in which the 
 whole body is immersed. Besides, may not the unctuous sub- 
 stance with which the surface of the skin is covered, prevent 
 the absorption which might otherwise take place from the outer 
 part of the body? 
 
 It was long believed that the foetus was in an upright position, 
 during the first months of life, but that, towards the end of 
 pregnancy, it fell into a different position and lay with its head 
 downwards. This erroneous opinion, believed from its antiqui- 
 ty, and because it was admitted by several physiologists, is com- 
 pletely refuted in Professor Baudelocque’s work on Midwifery. 
 The absurdity of this hypothesis is manifest, if it be considered 
 that the head of the embryo, the most bulky and weighty part 
 of the body, must necessarily occupy the most depending part. 
 
 The plumpness and strength of the foetus do not altogether 
 depend on the strength of the mother. Corpulent and strong 
 women often bring forth puny children, while others who are 
 thin and feeble, bring forth children plump and healthy. Such 
 instances, however, are exceptions to the general rule, as, caete- 
 ris paribus, the healthy state of the fostus is to be estimated by 
 that of the mother. The morbid condition of the fluids of the 
 mother has a considerable influence on the health of the foetus, 
 and is perhaps the way in which hereditary diseases are trans- 
 mitted, which, by others, are ascribed to a diseased state of the 
 semen. 
 
ON GENERATION. 
 
 549 
 
 The foetus is subject to affections of various kinds, whether 
 of spontaneous origin or arising from a germ received from the 
 mother. Foetuses have been seen with cicatrices, which clearly 
 showed that solutions of continuity, of various kinds, had taken 
 place. A child, born with the loss of some limb, has met with 
 the accident, in consequence of some affection experienced in the 
 womb. Professor Chaussier having been called in to a case of 
 this kind, found the hand and a portion of the fore-arm among 
 the membranes. 
 
 CCXIII. Of monsters. As it is useful to study nature, even 
 in her irregularities, I shall say a few words on the subject of 
 monsters, adopting the arrangement proposed by Buffon, of 
 dividing them into three classes: the first including monsters 
 from excess; the second, monsters from defect; the third in- 
 cluding those in which there is a misplacement of organs. In 
 the first, are included those which have supernumerary limbs 
 or fingers, or even two bodies joined in various ways. In the 
 second, children bom with a harelip, or who are deficient in some 
 one part. In the last place, those monsters belong to the third 
 class, in which there is a general transposition of organs; when, 
 for example, the heart, the spleen and the sigmoid flexure of 
 the colon are on the right side, and the liver and caecum on the 
 left; those born with hernias of different kinds, likewise belong 
 to this class. One may reckon among those monstrous confor- 
 mations, spots in the skin, the colour of which always resembles 
 that of some of our fluids, but whose various forms are purely 
 accidental, though, from prejudice, one is apt to imagine some 
 likeness to objects longed for by pregnant women accustomed 
 to those fantastic appetites and longings, so frequsnt during 
 pregnancy. 
 
 Various attempts have been made to account for these unna- 
 tural formations: some, as Mallebranche, attributed them to the 
 influence of the mother’s imagination on the foetus in the womb; 
 others, as Maupertuis, thought that her passions communicated 
 to her humours irregular motions, which, acting with violence 
 on the delicate body of the embryo, disturbed its structure. 
 Disease, while the child is in utero, is a much more probable 
 cause of such affections. 
 
ON GENERATION 
 
 550 
 
 If two foetuses, contained in one ovum He back to back, and 
 if the surfaces at which they are in contact become affected 
 with inflammation, it is easy to conceive that adhesion may take 
 place between them. By placing, in a confined vessel, the fecun- 
 dated ova of a tench or any other fish, the numerous young 
 ones, which are formed, not having space sufficient for their 
 growth, adhere to each other, and fishes truly monstrous in their 
 formation are produced. 
 
 When, from disease, or from an original malformation, the 
 body of the foetus is deficient in some of its parts, the others 
 are better nourished and grow to a large size. Hence, in ace- 
 phalous monsters, as there is no brain, the blood which should 
 be sent to that viscus, going to the face, it acquires a remarka- 
 ble enlargement. 
 
 One of the most curious of all the cases of monstrosities de- 
 pending on an original defect in the organization of the germs, 
 is that which was sent, a few years ago, by the Minister of the 
 Interior to the School of Medicine at Paris. I shall give an 
 abstract of it, from a more detailed account, drawn up with 
 much accuracy and sagacity by M. Dupuytren. 
 
 A young man, thirteen years of age, had complained, from 
 his earliest infancy, of pain in the left side and lowe'r part of 
 the abdomen. This side had been prominent and contained a 
 tumour, from the earliest period of life. At the age of thirteen, 
 he was seized with fever, the tumour increased in bulk, and 
 became very painful. Some days after, he voided by stool, pu- 
 rulent and fetid matters; at the end of three months, he became 
 wasted by marasmus, he passed, by stool, a ball of hairs, and, 
 in the course of a few weeks, died of consumption. 
 
 On opening his body, there was found, in a cavity in contact 
 with the transverse arch of the colon, and communicating with 
 it, some balls of hairs and an organized mass. The cyst, situa- 
 ted in the transverse mesocolon, near the colon, and externally 
 to the digestive canal, communicated with the intestine. But 
 this communication was recent and accidental, and one could 
 plainly see the remains of the septum between these cavities. 
 The organized mass presented, in its forms, a great number of 
 features of resemblance with the human foetus, and, on dissec- 
 tion, no doubt could be entertained of its nature. There was 
 
ON GENERATION. 
 
 551 
 
 discovered in it the trace of some of the organs of sense, a brain, 
 a spinal marrow, very large nerves, muscles converted into a 
 sort of fibrous matter, a skeleton consisting of a vertebral co- 
 lumn, a head and pelvis, and limbs in an imperfect state; lastly, 
 a very short umbilical cord attached to the transverse mesoco- 
 lon, at the outer part of the intestine, an artery and vein, rami- 
 fying at each of their extremities, where they were in contact 
 with the foetus and with the individual which contained it. This 
 much is sufficient to establish the distinct existence, as an indi- 
 vidual, of this organized mass, though, in other respects, desti- 
 tute of organs of digestion, of respiration, of the secretion of 
 urine, and of generation. The absence, however, of a great num- 
 ber of the organs necessary to the maintenance of life, should 
 make it be considered as one of those monstrous foetuses, not 
 destined to live beyond the moment of birth. This foetus was 
 evidently contemporary with the boy to whose body it was 
 attached. Similar to the product of extra-uterine conceptions, it 
 received its nourishment from that which may be considered 
 as its brother, and whose germ had originally enclosed its own. 
 During the thirteen years of the life of Bissieu (this was the 
 name of the subject of this singular case), the organized mass 
 obtained from the mesocolon, by means of vessels of its own, 
 the blood necessary for its existence; this blood, propelled by 
 the organs of circulation into the body of the foetus, returned 
 afterwards to the mesocolon of the boy who had so long been 
 to him as a mother. At last, the period fixed by nature for 
 expulsion, being arrived, and this expulsion being impractica- 
 ble, the cyst became inflamed; the inflammation extended to the 
 intestine, the part which separated these two cavities was de- 
 stroyed, and the cyst opened into the colon; pus and hairs were 
 voided by stool, and the patient died of marasmus. The draw- 
 ings of different parts of the body of this fcetus, taken by M. 
 Cuvier and M. Jadelot, render this interesting case most com- 
 plete. They will be published in the first volume of the trans- 
 actions of the Academical Society, near the Faculty of Medi- 
 cine at Paris.* 
 
 * Mr. Young, of London, has communicated a case of the same kind, in a 
 valuable paper inserted in the first volume of the Medico Chirurgical Trans- 
 
ON GENERATION. 
 
 552 
 
 We ought not to be too ready to place implicit confidence in 
 the extraordinary stories contained in the older writers, and 
 even in some of the moderns. In reading the periodical publi- 
 cations of the seventeenth, and even of the eighteenth century, 
 one is apt to wonder at the marvellous things which they con- 
 tain. Among other strange cases, is that of a girl that was born 
 with a pig’s head; another of a woman who was delivered of 
 an animal, in every respect like a pike. There was a time, says 
 a philosopher, when philosophy consisted merely in seeing pro- 
 digies in nature. 
 
 CCXIV. Of the coverings of the foetus. The name of after- 
 birth is given to the envelopes of the foetus, because they are not 
 expelled from the uterus, till after the birth of the child. The 
 ovoid sac, which contains the foetus, is formed by two mem- 
 branes in contact with each other. The name of chorion is given 
 to that which, by its external and shaggy surface, adheres to the 
 inside of the uterus: the other, a concentric membrane to the 
 former, but of less thickness, and to be considered as the secre- 
 tory organ of the fluid which fills the ovum, is called the am- 
 nion. The third envelope, admitted by Hunter, and called by 
 that physiologist, the membrana decidua, is nothing more than 
 the lanuginous tissue presented by the external part of the cho- 
 rion, after tearing the multitude of cellular and vascular fila- 
 ments by means of which the ovum adheres to the uterus. 
 The placenta is itself merely a thicker portion of nearly the 
 same tissue, in which the umbilical vessels are ramified. The 
 uterus is also thicker at the part which corresponds to the pla- 
 centa, because it is there that the communication of the foetus 
 with the mother is established. 
 
 The liquor amnii is a serous fluid, of a sweetish odour, of 
 insipid taste, rendered slightly turbid by a milky substance 
 which it holds suspended, and somewhat heavier than distilled 
 water, 1,004. It is almost completely aqueous; albumine, soda, 
 muriate of soda and phosphate of lime, discovered in it by 
 
 actions. In Mr. Young’s case, the foetus was contained in a cyst that seemed 
 to answer the purpose of membranes and placenta; it was without a brain, 
 but had imperfectly formed digestive oi gans and external organs of genera- 
 tion.— See vol. 1st of the Medico Chirurgical Transactions. T. 
 
ON GENERATION. 
 
 553 
 
 MM. Buniva and Vauquelin, forming only 0,012 of the whole 
 mass. It turns of a green colour, tincture of violets, and red- 
 dens that of turnsol; a very remarkable circumstance, as is 
 observed by the last mentioned philosophers, and indicating the 
 co-existence of an alkali and of an acid in a separate state. The 
 latter is, in so small a quantity, so volatile, and so soluble in the 
 liquor amnii of woman, that it has never yet been obtained by 
 itself; there is found, however, in the liquor amnii of the cow, 
 a peculiar acid, called by MM. Buniva and Vauquelin, the 
 amniotic acid. The liquor amnii is in greater quantity, in pro- 
 portion to the size of the foetus, according as the latter is nearer 
 the period of its formation. It is the product of arterial exhala- 
 tion. Its materials are supplied by the blood conveyed by th<?- 
 vessels of the uterus. This is proved, not merely by analogy, 
 but likewise by observing the connection between the qualities 
 of the liquor amnii and the regimen of the mother. In a woman 
 who had used mercurial friction, in the course of her preg- 
 nancy, the liquor amnii was observed to whiten copper. 
 
 The fundus of the bladder in quadrupeds, is continuous with 
 a canal, of which the rudiments are observed in man, and which 
 is called the urachus. This canal joins the umbilical vessels, 
 passes out with them at the umbilicus, and terminates in a 
 membranous sac, between the chorion and the amnion; it is 
 called the allantois; it is always found in the foetus of the lower 
 animals, but it is very indistinct, and often does not exist in 
 man. Some anatomists say they have seen the urachus arising 
 from the human bladder, and which is commonly ligamentous, 
 terminate in a small vesicle which some of them compare to a 
 melon seed; while others say its bulk does not exceed a millet 
 or hemp seed. So small a vesicle can certainly answer no pur- 
 pose; the urachus always forming a solid cord, seldom pervious,, 
 and even of very small bore, in the part nearest the fundus of 
 the bladder. The existence of these parts furnishes an addi- 
 tional proof of what was stated in speaking of the uses of the 
 valve of the caecum, viz. that there are in the animal body, or- 
 gans which answer no purpose, and which merely indicate the 
 plan which nature has followed in the reproduction of beings, 
 and the gradations which she has uniformly observed in the 
 divisions of the species. 
 
 4 A 
 
ON GENERATION. 
 
 554 
 
 CCXV. Of the natural term of geatation. The fcctus may 
 exist without the maternal influence, when arrived at the period 
 of seven or eight months from the instant of conception. All 
 accoucheurs agree that it may be delivered alive at this period, 
 and that it stays two months longer in the uterus, only that it 
 may gain more strength, and be better fitted to resist the new 
 impressions which it is to experience on coming into the world. 
 A child, however, has been known to live, though bom at the 
 sixth month of pregnancy, in premature labour; but, in general 
 the child is the more likely to live when born at the usual pe- 
 riod; that is, towards the end of the ninth solar month, or of 
 the tenth lunar. It is observed, that children born at seven 
 months, however robust they may prove afterwards, are very 
 feeble when bom, have their eyes closed, and are in a state of 
 extreme debility and suffering, during the two months which 
 they ought to have spent in their mother’s womb; this proves 
 how necessary it is that gestation should be carried on to the 
 end of the ninth solar month. 
 
 If the fffitus may live, though separated from its mother, 
 before the natural period, may it not likewise remain longer 
 within the womb, grow with less rapidity, and be expelled 
 some days, weeks, and even months later? How difficult there- 
 fore will it not be to assign a precise term, beyond which we 
 shall not be able to admit the possibility of a late birth! 
 
 There are said to be authentic cases of children born more 
 than ten months after conception; yet the laws, which cannot be 
 founded on rare exceptions, do not allow of so long a period in 
 deciding of the legitimacy of children born after the dissolution 
 of matrimony. 
 
 CCXVI. Of parturition. When the fetus has remained suf- 
 ficiently long within its mother’s womb, to acquire the degree 
 of strength required for its insulated existence, it becomes 
 separated from her, carrying along with it the parts which enclos- 
 ed it, and by which it was connected to the uterus. Its expulsion 
 from the uterus is called delivery. The most ridiculous opinions 
 have been entertained, with regard to the causes which deter- 
 mine the coming on of labour; according to some, Fabricius 
 of Aquapendente for instance, it is the want of fresh air, which 
 makes the fostus rupture its membranes; according to others, 
 
ON GENERATION. 
 
 , 555 
 
 the foetus is determined to the same process, by the necessity 
 of voiding the meconium, an excrementitious fluid, which fills 
 the intestinal canal. It has been said that the foetus was urged 
 to it by the want of food, or that labour depends on the re- 
 action of the fibres of the uterus, which distended bev'ond 
 measure, towards the end of pregnancy, close on themselves, 
 and overcome the resistance of the cervix uteri, which is thinned 
 and gradually dilated. But, if this last hypothesis be correct, 
 and is the only one that is at present in any esteem, how comes 
 it, that in a woman, whose uterus is of a determinate size, la- 
 bour does not come on when there are twins, at the end of four 
 months and a half, by which period the same degree of disten- 
 tion would be produced, as by one child at the full time. 
 
 It is very true, that for a fortnight, and even sometimes for 
 a month before labour, the uterus seems to be preparing for 
 the expulsion of the foetus. This at least, may be inferred from 
 the prominence of the cervix of the uterus, which may then 
 sometimes be felt; and which is evidently produced by the 
 membranes containing the waters, which insinuate themselves 
 within the orifice of the uterus, when this organ contracts, and 
 which collapse and recede, when the uterus is relaxed. 
 
 The product of conception after a certain time, reaches a 
 period at which it may exist, separated from the mother. When 
 this period is arrived, the ovum in w'hich it is contained, de- 
 taches itself from the uterus, by a mechanism, in every respect 
 similar to that, by which the stalk of a ripe fruit drops from the 
 bough on which it hung. Then, in all probability the foetus re- 
 fuses to admit the blood sent to it by the umbilical vein. The 
 placenta becomes affected with congestion; this stagnation of 
 the fluids extends gradually to the uterus, and to the neighbour- 
 ing parts. Stimulated by their presence, these organs are called 
 into action, the woman feels wandering, irregular pains, similar 
 to cholic pains, which become more acute, are attended with a 
 feeling of constriction, and act from above downwards, that is, 
 from the fundus to the cervix of the uterus. — This contractile 
 cavity assisted by the diaphragm and abdominal muscles, then 
 acts with redoubled effort to expel its contents. The pains be- 
 come more acute and frequent; the face red, the pulse full and 
 frequent, the whole body seems to partake in the affection of 
 
ON GENERATION. 
 
 556 
 
 the uterus, and is agitated with convulsive motions. The mem- 
 branes, filled with the waters, force themselves like a wedge 
 through the mouth of the uterus, whose edges are much weak- 
 ened; the throes of labour increases in strength and number, 
 the membranes rupture, the liquor amnii escapes, the head of 
 the child follows, and it soon clears the mouth of the uterus 
 with most excruciating pains. 
 
 These pains are particularly severe, when the sacrum not 
 being sufficiently concave, the nerves of the sacral plexus arc 
 violently compressed by the head of the foetus; this part of the 
 body almost always presents first; it passes through the upper 
 outlet of the pelvis, in an oblique direction, the occiput being 
 turned forward, and corresponding to one of the acetabula, 
 while the face is directed backward towards one of the sacro- 
 iliac junctions. It passes thus along the greatest diameter of the 
 pelvis, but in descending lower down in the pelvis, it describes 
 a portion of a circle, and passes through the lower outlet of the 
 pelvis, at its greatest diameter, which is from the fore to the 
 back part. The head descends through the vagina, appears out- 
 wardly, soon disengages itself, and is followed by the shoulders 
 and the rest of the body. Thus it is that nature, after having 
 produced fecundation by an act attended with pleasure, expels 
 the product of conception in the midst of pain. 
 
 CCXVII. The passages along which the foetus is carried out 
 of the body, would be too confined, in their ordinary state, to 
 allow expulsion to take place without laceration, if, as I am go- 
 ing to explain, nature had not disposed every thing to facilitate 
 labour. In fact, nature has not only formed the foetal skull of 
 several flexible pieces, separated by membranous unossified 
 spaces, so as to allow the bones to move over one another, and 
 the whole head to be reduced in size, in passing through the 
 female pelvis, but she has besides united the bones of the pelvis, 
 in such a manner, that their articulations become evidently re- 
 laxed towards the end of pregnancy. During the progress of 
 pregnancy, the fluids of the mother flow in every direction to- 
 wards the pelvis and the parts which it contains; the ligamento- 
 cartilaginous articulations of the pubis, of the sacrum and 
 coccyx, soaked in fluids, unite with less firmness the bones be- 
 tween which they are placed. Hence, being softened and swoUcr, 
 
ON GENERATION. 
 
 557 
 
 they do not force them asunder like a wedge, by increasing the 
 diameters,, but facilitate the separation of the bones, by the 
 passage of the head through the pelvis. It is on the relaxation 
 of the articulations of the pelvis, that the indication for the 
 operation of dividing the symphysis pubis, rests; an operation 
 performed successfully by Sigault and by Professor Alphonse 
 Leroy. Analogy led very naturally to this operation, as is judi- 
 ciously observed by M. Thouret, in the same manner that the 
 invention and application of the forceps were founded on a 
 consideration of the means employed by nature, to lessen the 
 bulk of the child’s head, during the progress of labour. 
 
 The foresight of nature is not limited to the facilitating the 
 motion on one another of the osseous parts of the skull of the 
 foetus, and of the pelvis of the mother; her care extends to the 
 soft parts of the latter; these are soaked in mucus, so as to re- 
 lax their tissue several days before parturition, and are so dis- 
 posed, as was already'^ observed (CCI), that they ma)^, without 
 rupture or violence, and by the mere unfolding of the folds of 
 the skin, yield to a considerable degree. As the placenta and 
 membranes are not expelled, immediately after the foetus, it is 
 customary to separate them by dividing the umbilical cord near 
 the navel. It is unnecessary to tie this cord, at the part near 
 the mother, every communication being intercepted between 
 the placenta and the uterus, so that no blood could flow but 
 that of the placenta. Not so, however, with the part nearest 
 the fffitus; though the changes which take place in the circula- 
 tion, at the moment when the chest is dilated, and allows the 
 air to distend the pulmonary tissue, divert the blood from the 
 umbilical vessels; these changes, however, in the circulation of 
 the fluids might come on slowly from the weakness of the new 
 born child; hence it is always prudent to prevent by a ligature 
 a loss of blood that would increase the debility. 
 
 The human ovum is very seldom detached entire, and never 
 so without considerable danger; that is, the foetus is not expelled 
 with its membranes and in the liquor amnii, for these are not in 
 general expelled till a quarter of an hour, half an hour, or even 
 a full hour after the delivery of the foetus. When the uterus is 
 completely emptied, its cavity becomes obliterated by the ap- 
 proximation of its sides; this organ contracted on itself, sinks 
 
ON GENERATION, 
 
 558 
 
 behind the pubis, its cervix closes and this even impedes the 
 delivery of the after-birth, when the latter is protracted too 
 long. The parietes of the uterus, imbued with fluids are thicker 
 than in their natural condition: but they decrease in size, in 
 consequence of the lochial discharge, and return to their wonted 
 thickness. 
 
 When the labour is over, the uterus falls as it were asleep, 
 and enjoys repose after painful exertion. The humours cease to 
 be determined to that organ, towards which they are no longer 
 directed by any irritation, and they flow towards the mammary 
 glands, to supply the secretion of the fluid which is to nourish 
 the new born child. 
 
 CCXVIII. Of tivins. Though, in the human subject the 
 offspring is generally single, it is not uncommon for a woman 
 to bring forth two children at once; it has even been calculated, 
 that the proportion of twin cases to single births, was as one to 
 eighty. Indeed, there are cases of women who have brought 
 three children at a birth. Haller calculates that the number of 
 these last, to those of single births, is as one to seven thousand. 
 The cases of four children at a birth, are still less frequent, and 
 if three children born at once, seldom live long, the others which 
 when born, are of the size of children at five months, cannot 
 live. Only one or two instances are known of five children hav- 
 ing been born at a birth; Haller, therefore is guilty of exaggera- 
 tion in saying that these cases are to the ordinary cases, in the 
 proportion of one to a million. I take no notice of the instances 
 in which a greater number are said to have been delivered at 
 once, because those cases are not well authenticated. In the 
 case of twins, each child has its own umbilical cord, terminat- 
 ing sometimes in a separate, and sometimes in a single placenta. 
 Both foetuses are enveloped in one chorion, but each has a dis- 
 tinct amnion, and floats in a separate liquor amnii. It would be 
 curious to know whether in women who have had twins, as 
 well as in animals, one should find two cicatriculse, both in the 
 same ovarium, or one in each. Twins are, generally, very like 
 one another in features and dispositions. 
 
 The multiplicity of foetuses, in the same pregnancy, is occa- 
 sioned by the presence of several vesiculae, ready to be detached 
 fropi the ovaria, and consequently ripe for fecundation. This 
 
ON GENERATION. 
 
 559 
 
 mukiplicity of offspring contributes very little to increase popu- 
 lation, for they are, in general, less robust and strong, and not 
 so capable of reproduction; they, besides, exhaust the strength 
 of the mother, and their birth is often fatal to her. The num- 
 ber of children which a woman might bring into the world, 
 from the period of puberty to the cessation of the menstrual 
 discharge, would be much greater than it generally is, if no 
 time were lost. Some women have been known to have twenty- 
 four, thirty, thirty-nine, and even fifty-three children. A woman 
 died in North America, after having had five hundred children 
 and grand-children, of whom two hundred and five survived 
 her. 
 
 It is now well known, that the number of male children who 
 are bom, exceeds in general, that of the females. The differ- 
 ence, in some countries, is estimated at one in twenty-one, at a 
 fourteenth, a twelfth, and sometimes, though rarely, at a third. 
 In all countries of the world, polygamy is therefore in direct 
 opposition to the intentions of nature, and to the multiplica- 
 tion of the species; this is proved in a most undeniable manner, 
 by the loss of population in those countries in which this prac- 
 tice exists. The boys, more numerous than the girls during 
 the early part of life, exposed afterwards to the dangers of war, 
 of navigation, and occupied in laborious occupations, lead a 
 more laborious and anxious life, and die in greater numbers, 
 so that the eqilibrium is soon restored, and the least numerous 
 portion of the human species at the cradle, forms about two 
 thirds of it in old age, since we always see more women than 
 men reach a very advanced age. 
 
 CCXIX. Of superfcetations. The cases of foetuses born with 
 unequal degrees of development, are not to be considered as 
 superfcetations, but as twin cases. Thus, if in a case of twins, one 
 fcBtus is of its full size, while the other is an embryo whose 
 size does not exceed that of a foetus in the first month; it does 
 not follow that their conception took place at different and dis-, 
 tant periods, but merely that for some reason or other, one of 
 the germs has been incapable of growth and development. 
 
 To settle the question of superfcetations, one should know 
 whether a woman, with a single uterus, is capable of conceiv- 
 ing, two months alter effective copulation. Haller is of opinion, 
 
ON GENERATION. 
 
 560 
 
 that the cervix of the uterus is always open to the semen; but 
 how is the latter to reach the ovaria, through the adhesions of 
 the chorion to the uterus? It appears easier, where the two 
 conceptions are separated by a short interval; thus, the Ameri- 
 can woman mentioned by BufFon, who, in the course of one 
 morning, had connexion with her husband and with a negro 
 slave, bore two children of different colours. Hence, likewise, 
 it sometimes happens, that one of two twins is, by its features, 
 a living testimony of adultery. 
 
 Two children, born with an interval of some months between 
 their births, cannot be considered as twins, though they may 
 have existed some time together within the mother’s womb. 
 The possibility of such superfoctations is well proved; they are 
 ascribed to septa, dividing the uterus, sometimes into two cavi- 
 ties, merely because such an arrangement would explain, to a 
 certain degree, how two conceptions might take place, at some 
 interval from one another; for it has never been ascertained, by- 
 actual dissection, that any woman, in whom such superfoctations 
 took place, had a double uterus?* 
 
 * It seems to me, that a belief in superfcctatlon can hardly be entertained 
 by any one who is conversant with the human economy, and particularly 
 with the changes which the uterine system undergoes in consequence of 
 pregnancy. We know that soon after conception, the os tines, as well as 
 the internal apertures of the fallopian tubes, are closed by a deposition of s 
 thick tenacious mucus. But to accomplish still more perfectly an end so im- 
 portant to the scheme of generation as the occlusion of the uterus, nature 
 resorts to another provision. 
 
 By the sprouting forth of minute blood-vessels,* or by the effusion of a 
 species of lymph,f or out of coagulated blood,f a membrane of some firmness 
 of texture is quickly formed. This membrane, which is called decidua, or 
 caduca, from its being shed at the period of delivery, lines completely the 
 uterus, and thus co-operates -with the dense mucus already alluded to, in . 
 -obliterating the three openings into its cavity. 
 
 Such too, is the enlargement of the gravid uterus, and the change thereby 
 produced in the relative position of its appendages, that a new series of im- 
 pediments arises to the frustration of a second conception. 
 
 In this state of the organ, it is accurately ascertained, that the tubes lie 
 parallel to its sides, and subsequently in the progress of gestation, become 
 bound in the same situation. Instead of running in a transverse direction 
 towards the ovaries, with their extremities loose and fluctuating. 
 
 Were 
 
 Haller. 
 
 •{■Dr. Hunter. 
 
 Mr. Hunter. 
 
ON GENERATION. 
 
 561 
 
 CCXX. Of suckling. Nothing is more generally known in 
 physiology, than the strict sympathy which subsists between 
 the uterus and mammae; a connexion, in consequence of which, 
 these two organs are called into action at the same period of 
 
 Were an embryon, therefore, to be g'enerated by any anomalous combina- 
 tion of circumstances, the tubes could not possibly embrace tlie fecundated 
 vesicle, and the embryon, of course, must remain in tlie ovary, or fall into 
 the abdomen, constitutini^ an extra uterine conception. 
 
 Let us, however, withdrawal! the obstacles wdiich have been enumerated 
 to the passage of the embryon, and admit the practicability of its reaching 
 the uterine cavity. What in this event would happen! Disorganization fatal 
 to each fetus must ensue. 
 
 It is to be recollected, that the uterus had prepared, in the first instance, 
 whatever was required for the reception, the nourishment, and evolution of 
 the fetus. It had originally supplied it witli a decidua, as a medium of 
 attachment, and afterwards with a placenta for still more important pur- 
 poses. For the second fetus, the same offices are to be rendered. These 
 it could not execute, without suspending the action existing at the time, 
 and taking on such as are necessary to the fabrication of an additional deci- 
 dua and placenta. 
 
 That actions so incompatible cannot co-exist, strikes me as sufficiently 
 obvious. Were the uterus, therefore, to attempt this new process, the result 
 would be, the separation of the primary decidua and placenta, occasioning 
 an abortion, accompanied with hemorrhage, which would sweep out the 
 whole of its contents. 
 
 It is probably, on this account, that menstruation uniformly ceases with 
 the accession of pregnancy. I am aware, that this is a point not altogether 
 conceded. The weight of authority is, however, decidedly against menstru- 
 ation continuing during gestation. By all the verj' recent writers it is de- 
 nied. Those who hold, or 1 might rather say, did hold the contrary opinion, 
 have mistaken a hemorrhagy from the vagina, which sometimes recurs with 
 considerable periodical regularity, for the catamenial flux. Several cases of 
 this kind have come under my owm observation, where I had an opportunity 
 of inspecting the discharge accurately. In every instance, I found it pure 
 .^oagulable blood, having neither the colour, nor odour, nor any other of the 
 peculiar properties of the genuine menstrual fluid. 
 
 By again adverting to the condition of the pregnant uterus, we shall see 
 that a suppression of the catamenia is exactly what ought to be expected. 
 The deciduous membrane is framed while the process of conception is pro- 
 ceeding in the ovary. The vessels which had secreted the catamenia are 
 now engaged in a new operation. They form the membrane and then sup- 
 port it. While thus employed, their secretory function is suspended. They 
 cannot at the same period, perform actions so incongruous and inconsistent. 
 The one must yield to the other. This is very strikingly illustrated by the 
 fact which has not been sufficiently attended to, that in a large proportion of 
 the cases of obstinate amenorrhea, the membrana decidua exists, and that 
 
 4 B 
 
ON GENERATION. 
 
 562 
 
 life, are evolved, and cease to perform their functions, at the 
 same time, when woman becomes incapable of co-operating in 
 the reproduction of the species. I shall not endeavour to ac- 
 count for this sympathy, by ascribing it to the influence of the 
 nervous system, or to the anastomosis of the epigastric with 
 the internal mammary arteries; an anastomosis which is not 
 uniform, for, instead of inosculating with each other, these ves- 
 sels frequently terminate in the recti muscles of the abdomen. 
 But even though this anastomosis should exist, as distinctly as 
 it is often met with in some subjects, it would not account for 
 this sympathy, since the uterus and the mammse often receive 
 no branches from the epigastric and mammary arteries, and 
 when they do they are exceedingly small. 
 
 The new-born child, on being brought in contact with the 
 breasts, applies his mouth to the nipple, and withdrawing his 
 tongue, while with his lips he compresses the edges of the nip- 
 ple, he draws in the fluid whose flow is facilitated by the erec- 
 tion of the lactiferous tubes. These ducts, from twelve to fif- 
 teen in number, not only become enlarged, when the nipple, 
 which almost entirely consists -of them, is elongated by being 
 
 the first symptom of the return of the discharge is the coming away of the 
 membrane. Of the identity of the two membranes, there can be no doubt 
 It has been determined by very competent judges.* 
 
 By one less averse than myself to speculative reasonings in matters of 
 science, a variety of considerations of this nature, might be pressed against 
 the hypothesis which I am combating. It could, I think, in particular, be 
 urged with great plausibiUty, that changed as is the whole uterine system 
 by gestation, not only in the mechanical distribution, but also in the struc- 
 ture and functions of its parts, it cannot possibly assume that peculiar con- 
 dition which seems indispensable to conception. Of all the operations of tlie 
 animal economy, that of conception undoubtedly requires the most harmo- 
 niously concerted action in the several organs by which it is commenced, 
 carried on and consummated. Derangements in any one portion of this com- 
 plex apparatus are confessedly productive of sterility. So essential, indeed, 
 to tlie generative process in the human species, is a perfect integrity in the 
 functions of the uterine system, that by the suppression or even vitiation of 
 the catamenia, the aptitude to conception is lost or diminished. But enough 
 of these speculations; I am content to rest the defence of the question on the 
 facts which I have stated. If they be correct, it results that superfoetation 
 cannot take place in the human species. — Ed. 
 
 Baillie, Burns, kc. kc. 
 
ON GENERATION. 
 
 563 
 
 drawn out by the child, but, besides, being excited by his 
 touch, they become affected with a certain degree of erection, 
 and emit their fluid. This excretion, like that of other glands, 
 is excited by the touch and the motion of the hands of the 
 child on his nurse’s breasts. The use of these gentle compres- 
 sions, is not so much to express the milk mechanically, as to 
 excite the organ to excretion. 
 
 The irritation, produced by the child on the nipple, is the 
 most powerful exciting cause of the determination of milk into 
 the breasts; this irritation, or any other of the same kind, is 
 sufficient to excite the secretion of milk, even under circum- 
 stances not provided for by nature. It is thus that virgins 
 have been enabled to suckle another mother’s child; that 
 young girls, under the age of puberty, have had so complete a 
 secretion of milk, as to furnish a pretty considerable quantity 
 of this fluid. There have been known men, in whom a long 
 continued titillation of the breasts had determined so consi- 
 derable an afilux of the humours, that there oozed from them, 
 a whitish, milky, and saccharine fluid, not unlike the milk of a 
 woman. The sucking of the new born child is necessary to 
 keep up the secretion of milk in the mammae. It ceases to be 
 formed in them, when the child is committed to the care of a 
 different nurse; the mammae, at first turgid, soon collapse, 
 especially if care have been taken to determine the fluids 
 downwards, by exhibiting gentle laxatives. 
 
 The erection of the breasts, by titillation on the nipple, the 
 spasmodic, and almost convulsive action which follows this 
 kind of excitement, may be carried so far as to produce an 
 emission of the fluid to some distance. While its excretion 
 lasts, women experience in their breasts an agreeable sensa- 
 tion; these parts are tense and swollen; they feel, as they ex- 
 press it, the milk rising; several feel a sensation of extension 
 reaching to the axilla, to the arms and chest. The whole mass 
 of cellular substance surrounding the breasts and extending to 
 the neighbouring parts, partakes in their activity. 
 
 The breasts, themselves, consist, in great measure, of cellu- 
 lar substance; an adipose and lymphatic layer, of a certain 
 thickness, covers the gland, which is divided into several 
 
ON GENERATION. 
 
 564 
 
 lobes, and incloses it within its substance. They receive n 
 number of nerves, but very few blood-vessels for their bulk. 
 
 Their structure appears almost wholly lymphatic; the vessels 
 of this kind, after being distributed to the neighbouring glands, 
 and especially to those of the axilla, penetrate into the breasts, 
 in which their proportion, compared to that of the sanguineous 
 vessels, is as eight to one. These lymphatic vessels, which en- 
 ter in considerable numbers into the composition of the breasts, 
 increase greatly in size, in nurses; and when injefcted in this 
 condition, it has been ascertained, that several of them joined 
 to form larger trunks, which going towards the nipple, contri- 
 buted in forming what are called the lactiferous tubes. If the 
 lymphatic vessels be immediately continuous with the excretory 
 ducts of the breasts, there is reason to believe, that it is these 
 vessels which convey the materials of the fluid which they 
 separate, especially if it be considered how small the number 
 of minute arteries which are distributed into their tissue, and 
 what a disproportion there is between the caliber of these 
 small vessels and the quantity of blood which the breasts sup- 
 ply. The opinion that the lymphatic vessels bring to the 
 breasts the materials of the secretion of milk, is not in oppo- 
 sition to the laws of the circulation in the lymphatics; all who 
 are acquainted with these laws, know that the course of the 
 lymph, though in general, from the circumference to the centre, 
 is naturally liable to a number of aberrations or deviations, 
 facilitated by the numberless anastomoses of these vessels. 
 (XLV). 
 
 CCXXI. The granulated structure is not as apparent in the 
 breasts, as in the other glandular organs, hence they bear a 
 greater resemblance to the lymphatic, than to the conglome- 
 rate glands. The milk which they secrete, has always been 
 considered as very like the chyle, which it resembles, in its 
 white colour, its smell, and its saccharine taste. Like the chyle, 
 it is the least animalized fluid, the sweetest, that on which the 
 action of the organs produces the least effect, and that which 
 preserves most the characteristic qualities of the food taken bv 
 the nurse. 
 
 It is well known, that instead of giving medicines to infants 
 at the breast, we, most frequently, administer the medicine to 
 
ON GENERATION. 
 
 565 
 
 the nurse; thus, the milk acquires purgative qualities and acts 
 on the bowels of the child, when the nurse has been purged. 
 The chyle is white and opake, only in those animals which 
 suckle their young; in the others, it is as transparent as lymph. 
 (Cuvier). 
 
 In the last place, if the arteries carried to the breasts the 
 materials of their secretion, these vessels ought to increase in 
 size, when these organs become twice, or even three or four 
 times larger than natural; in the same manner that, in open can- 
 cer, and in other similar affections, in which the determination 
 of blood being increased, the caliber of the vessels is propor- 
 tioned to them. Nothing, however, of the same kind occurs, 
 whatever size the breasts may acquire from the presence of 
 milk; their arteries preserve their almost capillary minuteness, 
 as I had an opportunity of ascertaining, by injecting the mam- 
 mae of a woman twenty-nine years of age, who died in the 
 second month of suckling, and whose breasts were remarka- 
 ble by their size, and by the quantity of milk they were able to 
 secrete. 
 
 Notwithstanding all these reasons, which have long made 
 me adopt the opinion of the celebrated Haller, who considers 
 the milk as immediately extracted from the chyle, I own that 
 it must be considered as hypothetical, and resting solely on 
 probability. The impossibility of demonstrating, anatomically, 
 the branches going from the mesentery to the breasts, without 
 communicating with the thoracic duct, gives still greater pro- 
 bability to the generally received opinion, which makes the 
 milk, like all the other secreted fluids, with the exception of 
 the bile, to be supplied by arterial blood. 
 
 The milk does not resemble chyle, in every respect, though 
 it may be considered as extracted from the food*, changed in 
 its way to the mammae, by the glands through which it has 
 passed, and especially by the action of the organs themselves. 
 This action is so evident, that, as Bordeu observes: “ There 
 are women who seem to have no milk in their breasts, which 
 are flaccid and empty; but as soon as the child excites them, 
 
 * “Lac utilis alimenti est superfluum.” Gal. De Usu part. Lib. VII. Cap. 
 XXII. 
 
ON GENERATION. 
 
 566 
 
 they become distended, and the milk comes spontaneously.” 
 It is well known, and the same author has pointed it out, that 
 women, cows, and the females of other animals, allow them- 
 selves more willingly to be sucked by a suckling that knows 
 how to excite their sensibility, and to apply due irritation to 
 the nipple; and that, on the contrary, they retain their milk, 
 when the suckling does not excite the sensation in which they 
 feel pleasure. It is thought, in some countries, that serpents 
 know how to tickle the teats of cows, and that these animals 
 enjoy this excitement and allow themselves to be sucked by 
 these reptiles. 
 
 CCXXII. Of the physical properties of milk and of the 
 chemical nature of this fiuid. The quantity of milk is in general, 
 proportioned to that of the aliments, to the degree of their 
 nutritious qualities, to their moist and farinaceous nature. 
 Though it equals in weight about one third of the quantity of 
 food taken by the nurse, it may exceed that proportion, or may 
 not come up to it. Its specific gravity, even when the milk is 
 lightest, is greater than that of distilled water, and is always 
 proportioned to its consistency. The latter quality is in an in- 
 ferior degree in woman, but is greater in the cow, the goat, 
 the ass, and the ewe. Its fluidity is intermediate between that 
 of aqueous and oily liquids; its colour, its smell and flavour 
 have something very peculiar, and by which it is easily recog- 
 nized; in the last place, it is not exactly alike, at different 
 periods of the same milking. This is proved by the work of 
 MM. Deyeux and Parmentier on milk, a work abounding in 
 valuable observations, and which may be considered as the 
 complete history of this animal fluid. They observed that the 
 milk first drawn from the cow is serous, that its consistency 
 gradually increases, and that the richest milk is that which is 
 obtained towards the end of milking, as if the fluid contained 
 in the udder were affected by the laws of gravitation.* 
 
 The milk, when exposed to the open air in a vessel, becomes 
 decomposed like the blood, and separates into three parts; the 
 serum, the curd or cheesy part, and the fatty part or cream. 
 
 • The author seems to forget that he is speaking of the cow, and that her 
 udder hangs in a situation unfavourable to this hypothesis. T. 
 
ON GENERATION. 
 
 567 
 
 The latter, which is lighter than the others, is always on the 
 surface, and its quantity depends, not only on the richness of 
 the milk, but also on the extent of the surface by which it is 
 in contact with the air; and this proves, as was first observed 
 by Fourcroy, that the oxygen of the atmosphere has some in- 
 fluence on its separation. The caseous part, which coagulates 
 spontaneously, appears albuminous and abounds in oxygen. 
 MM. Parmentier and Deyeux consider it as the colouring- 
 matter of milk, and as giving to it its most characteristic pro- 
 perties. Lastly, the serum or whey, which alone constitutes the 
 greatest part of this fluid, contains besides a peculiar acid 
 \the lactic acid} which is formed when this substance is allow- 
 ed to remain for some time; a saccharine matter, which may 
 be obtained by evaporation, and which, when crystallized in 
 rhomboidal parallepipeds, constitutes the sugar of milk, whose 
 purity depends on the degree of care with which the process 
 has been carried on. This sugar of milk contains, as Scheele 
 first ascertained, while endeavouring by means of the nitric 
 acid, to convert it into the oxalic, a peculiar acid in the form of 
 a powder, difiicult of solution, and to which he gave the name 
 of saclactic acid. Milk may be considered as one of the most 
 compound of the animal fluids, whose qualities are very va- 
 riable and whose parts have but an imperfect affinity to each 
 other. So that it is liable to spontaneous decomposition, and 
 this takes place very easily. This kind of emulsion contains 
 but a small quantity of azote, so that it retains its vegetable 
 character. Hydrogen, carbon, and oxygen predominate in 
 milk; in the last place, it contains several salts, amongst others 
 muriate of soda, muriate of potash, and phosphate of lime. 
 
 The presence of the two last of these substances, leads to 
 the following considerations. Muriate of potash, as is observ- 
 ed by Rouelle, does not exist in the blood; the probability is, 
 therefore, that it is not the blood which supplies the mammae 
 with the materials whence the milk is secreted, muriate of 
 potash being found, in greater quantity in milk, than muriate 
 of soda. These salts of potash, on the contrary, are found in 
 considerable proportions, in the chyle, formed from vegetable 
 substances; which would lead one to think, that milk is fur- 
 nished by the absorbent system. The phosphate of lime which 
 
ON GENERATION. 
 
 568 
 
 is found, in smaller quantity, in the urine of nurses, and which 
 is wholly determined towards the mammse, was absolutely 
 necessary in a fluid which supplies nourishment to the new 
 being, while the bones become indurated, and all the parts 
 acquire solidity. 
 
 If we now wish to inquire into the causes which render 
 suction necessary, and which subject the new-born child to 
 this peculiar mode of nutrition, these causes will be found in 
 the general weakness of its organs. The organs of digestion 
 would have been incapable of extracting, from the aliments, 
 their nutritive parts, these substances not having undergone 
 the due degree of trituration, from the want of teeth, and from 
 the imperfect state of the other organs of mastication. It was 
 of consequence, therefore, that the mother should perform 
 this preliminary function, and that she should transmit the 
 aliment ready digested.* It is not, however, to be imagined, 
 that the milk passes, without undergoing any change, into the 
 vessels of the child; the child digests the milk, and obtains 
 from it, in a short space of time, and without effort, a conside- 
 rable quantity of nutritious particles, necessary to the rapidity 
 of its growth. 
 
 The connexion between the mother and child is far from 
 being broken, at the period of birth; the relations between 
 them, though not so close, are not less indispensable. Before 
 birth, the vital -power was so limited in the child, that it was 
 necessary it should receive a fluid already animalized, and in 
 a state to yield to the function of assimilation and nutrition. 
 When the child has breathed, when its strength is increased, 
 it may be entrusted with a greater share of the process; it is 
 then suflicient that the aliment should have undergone the first 
 degree of elaboration, within the digestive canal. But it is not 
 merely to assist in preparing its food, that the new-born child 
 requires the aid of the mother; its lungs, which are delicate and 
 Imperfectly evolved, do not supply a due quantity of oxygen 
 to the blood which circulates through them; the animal heat 
 would be under what is required by the wants of life, if the 
 
 * Lac est cibvs exacte covftctus. Galenus de usu partium. 
 
 Lib. VII, cap. XXII. 
 
ON GENERATION. 
 
 569 
 
 mother did not make up for this deficiency, by transmitting 
 some of her own warmth. She folds her infant gently to her 
 bosom, warms it with her breath, and by this kind of maternal 
 incubation continues to cherish it with that calorific influence 
 to which it was fully exposed, while forming a part of herself. 
 Besides, she feels for it, keeps it from danger, foresees its 
 wants, and understands its language; and this very interesting 
 intercourse takes place, after the bonds of their physical com- 
 munication are loosened;- but it does not tear them asunder. 
 The infant is, therefore, detached from the mother only by 
 degrees, since it is only in proportion as it grows older, that 
 it acquires the means of living independent. 
 
 The secretion of milk, in the breasts, may be prevented by 
 irritation in the uterus. If the labour have been difficult, if the 
 woman have suffered a certain degree of injury, the irritation, 
 in the parts so affected, prevents the determination of the fluids 
 towards the mammae. Hence these organs collapse, during 
 puerperal fever; not that the milk flows back into the hu- 
 mours, and becomes the cause of the complaint, but that the 
 inflammation of the uterus prevents the fluids from flowing in 
 their natural direction. 
 
 During the first few days after delivery, the parietes of the 
 uterus discharge a fluid, at first bloody, then of a reddish co- 
 lour, and, in the last place, mucous and whitish, termed the 
 lochia. 
 
 CCXXIII. All the parts of the lungs are not distended 
 with air, in the first inspirations of the child, after birth. Some 
 of the lobes which are harder and more compact, take some 
 time to admit this fluid, and even sometimes altogether re- 
 ject it. A child died twenty-one days after birth; the body was 
 opened by Professor Boyer. On examining the lungs, he found 
 that the posterior part of these organs was as hard and com- 
 pact as in the fcetal state. The anterior part alone was distend- 
 ed, contained air, could be felt to crepitate, and floated in 
 water. The heart was examined, to ascertain whether its struc- 
 ture was connected with this condition of the lungs, which 
 depended on the want of power in the respiratory functions. 
 The foramen ovale was found pervious, so that the blood 
 could pass from the right into the left cavities of the heart, 
 
 4 C 
 
ON GENERATION. 
 
 570 
 
 without flowing through the lungs. The child had been exceed- 
 ingly languid, during the whole of its short life; its skin was, 
 at times pale, at others livid. It was very difHcult to keep it 
 warm. 
 
 The child of Madame L**** died nine da)’’s after birth, 
 with the same appearances. I opened the chest, and found the 
 upper part of both lungs indurated and compact; the foramen 
 ovale was quite pervious. This aperture is often closed very 
 imperfectly, so that there remains, at the upper part of it, an 
 opening, varying in size, which would enable a small quantity 
 of venous blood to pass from the right into the left auricle, if 
 these cavities did not contract at the same moment, and if the 
 fluid which they contain, did not present equal resistance on 
 both sides. There are cases of persons, in whom the foramen 
 ovale remained pervious, and who, nevertheless, lived to a 
 pretty advanced age. Their skin was purple and livid, all their 
 moral and physical faculties feeble and torpid. It would be 
 interesting to ascertain, by dissection, whether in good divers, 
 who can remain a long while under water, without breathing, 
 the foramen ovale is not imperfectly closed. 
 
571 
 
 CHAPTER XL 
 
 CONTAINING THE HISTORY OF THE AGES, THE TEMPERAMENTS 
 
 AND THE VARIETIES OF THE HUMAN SPECIES; OF DEATH, AND 
 
 PUTREFACTION. 
 
 CCXXIV. Of infancy. The epidermis of the new-born babe 
 thickens, the redness of the skin grows paler, the wrinkles are 
 effaced, the soft down, which covered the face, falls and dis- 
 appears; the buttocks swell out and soon conceal the opening 
 of the rectum. During the first month of life, it seems to need 
 nothing but nourishment and sleep. In the meanwhile, the 
 understanding is beginning to form, it looks fixedly at objects, 
 and seeks to take cognizance of all the bodies that surround it. 
 Confined, at first, to the uneasy sensations, which it expresses 
 by almost continual cries, its existence becomes less painful, 
 as it grows accustomed to the impressions of outward things 
 upon its delicate organs. Towards the middle of the second 
 month, it becomes capable of agreeable sensations. If it feels 
 them before that time, at least it is only then that it begins to 
 express them by laughing.* 
 
 CCXXV. Dentition. Towards the end of the seventh month,f 
 the middle incisor teeth of the upper jaw, cut through the 
 
 • At Hercules risus praecox ille et celerrimus, ante quadragesimum diem 
 nulli datur. — Plin. Hist. Nat. Praef. ad lib. VIII. 
 
 ■(■ It would be very difficult to say, why a tertian fever often terminates of 
 itself, when it has reached its seventh paroxysm, whilst a continued fever is 
 judged of by critical evacuations, in seven, fourteen, or twenty-one days; why 
 deliveiy happens at the end of nine months; why the first teething begins at 
 seven months old, the second, at seven years; why puberty shows itself to- 
 wards the fourteenth year, and menstruation is repeated at determinate periods. 
 Nature appears to subject herself, in all her acts, to certain periods, which ob- 
 servation may ascertain, without any possibility of arriving at a knowledge of 
 the causes of these phenomena so easy to establish. Because their manifesta- 
 tion is correlative to certain numerical terms, we are not to put faith, like 
 Pythagoras, in the power of numbers, and believe that the number 3 and the 
 numbers 7 and 9 enslave all nature to their supreme influence. We find traces 
 of this ancient error in all sciences, in all religions, even in those of enlightened 
 nations. 
 
ON AGES. 
 
 572 
 
 substance of the gums: a little while after, the corresponding 
 incisors of the lower jaw show themselves: next, the lateral 
 incisors of the upper jaw, those of the lower, then the cuspidati, 
 in the same order. At the age of between eighteen months and 
 two years, the small molar teeth appear, but in reversed order; 
 those of the lower preceding those of the upper jaw. When 
 these molar teeth have come through, the first dentition is 
 complete; the life of the child is more secure: it was before 
 very uncertain, since the calculations of the probable duration 
 of human life show, that a third of the children born at any 
 given time, die before the age of twenty-three months. Con- 
 vulsions and diarrhoeas are the most fatal accidents attending 
 difficult dentition. To these twenty teeth are added two new 
 grinders in each jaw, when the child has reached the end of his 
 fourth year. These last will afterwards become the first large 
 grinders. They differ from those that precede them in this, that 
 they are to remain all life long, whilst the primitive or milk 
 teeth are lost at seven years old, in the same order in which 
 they appeared, and are replaced by new teeth, better formed, 
 and larger, excepting the small grinders, and with longer and 
 more perfect roots. Towards the ninth year, tw’O new large 
 grinders appear beyond the others. The child has then twenty- 
 eight teeth, and dentition is complete, though between eighteen 
 and thirty, and sometimes much later, the dentes sapientiae, ttvo 
 to each jaw, show themselves at the extremities of the alveolar 
 processes. 
 
 The order observed in the successive cutting of the teeth, is 
 not so invariable, but it is frequently inverted. A child ten years 
 old, now under my care, cut the four first small grinders before 
 the canine teeth. Dentition is, in this respect, like all other acts 
 of the living economy: instability is its principal character. An 
 attentive examination soon shows how irregularly those phe- 
 nomena proceed, whether physiological or pathological, which 
 appear the most to be subjected to calculable and determinate 
 periods.* 
 
 This double range of successive teeth existed in the jaws of 
 the foetus. Each alveolar process, at that age of life, contains 
 
 * See Erreul's populaires, sec; edit: Chap. 4, des Annies cUmaterinur’i, et de-’ 
 Jours critiques dans les maladies. 
 
ON AGES. 
 
 573 
 
 two membranous follicles, lying one over the other. That 
 which is to form the primitive tooth swells the first, a calcare- 
 ous matter covers its surface and forms the body of the tooth, 
 which invades also the follicle by which the osseous part is 
 secreted, so that the growth of the little bone being completed, 
 the membranous vesicle, in the parietes of which the dental 
 vessels and nerves branch out, is found in the centre of its 
 body, and adheres to the parietes of its internal cavity. It is 
 difficult to say, why the growth of the dental germs is succes- 
 sive; why, in the seventh year, the primitive teeth are detach- 
 ed, and are replaced by others which have remained so long 
 buried within the alveolar processes. Dentition is like all the 
 other phenomena of the living economy; it is subject to end- 
 less varietes in its period and duration, &c. Thus, teeth of a 
 third set have been known to be cut in very old people. There 
 are instances, but they are very scarce, of children that have 
 come into the world with two incisors in the upper jaw; there 
 are often supernumerary teeth, &c. 
 
 CCXXVJ. Ossification. The process which goes on in the 
 osseous system, is not confined to the cutting and growth of 
 the little bones which are attached to the two jaws. All other 
 parts of the skeleton harden; osseous nuclei are formed in the 
 centre of the cartilages, which hold the place of the short bones 
 of the carpus and tarsus; the thickness of the cartilaginous sub- 
 stances, which separate the epiphyses of the bodies of the long 
 bones, is diminished; the large bones grow, and acquire soli- 
 dity, from the centre to the circumference. Those of the skull 
 meet at their edges, their fibres cross and form the sutures; 
 the cartilaginous spaces (^fontanels') which were situated at the 
 meeting of their edges and angles disappear. The urine con- 
 tains exceedingly little phosphate of lime, that salt being entire- 
 ly taken up in the solidification of the bones. About the middle 
 of the second year, these have already acquired substance and 
 solidity enough to support the weight of the body; the child can 
 stand and walk. Before this time, it would be dangerous for 
 him to try it; the pillars of support, yet too flexible, would yield 
 under the burthen, and bend permanently in different directions. 
 It is towards the head, that the vital motions tend in infancy: 
 accordingly, this part is the principal seat of the affections pe- 
 
ON AGES. 
 
 574 
 
 culiar to this age, affections in which it is often of use to procure 
 local evacuations. 
 
 The organs of the senses, open to all sorts of. impressions, 
 receive them with ease; but if, in early infancy, sensation is 
 easy, it is very transient; no doubt from the want of consistence 
 in the cerebral organ. As it grows older, the mobility of the 
 child is lessened, without diminution of susceptibility; and it is 
 during the years that precede the boisterous season of puberty, 
 that he enjoys, in the highest degree, the faculty of recalling 
 things that have affected him, that his memory is most distinct 
 and extended; but soon overpowered by imagination, rouzcd 
 up by the powerful re-action of the sexual organs on the brain, 
 it ceases to have the same exactness. 
 
 CCXXVII. Of puberty. Sex, climate, manner of life, have 
 great influence on the earlier or later manifestation of the phe- 
 nomena of puberty. Women reach it one or two years before 
 men: the inhabitants of southern, long before those of northern 
 countries. Thus, in the hottest climates of Africa, Asia, and 
 America, girls arrive at puberty at ten, even at nine years old, 
 but in France, not till twelve, fourteen, or fifteen; whilst in 
 Sweden, Russia, and Denmark, the menstrual discharge, the 
 most characteristic mark of puberty, is from two to three years 
 later. 
 
 The male is known to be capable of generation, and that he 
 begins to live the life of the species, by the emission of prolific 
 semen, and the change of voice, which becomes fuller, more 
 grave, and sonorous: the chin becomes covered with beard, the 
 genitals with hair, and they attain rapidly their full size. The 
 whole body grows; the general characters which distinguish the 
 two sexes, and which are so obscure, before puberty, that thfey 
 may often be mistaken, become very decided, and can no longer 
 be confounded. 
 
 By all these signs of strength and virility, woman, urged by 
 desires which may be termed wants, recognizes the being capa- 
 ble of gratifying them. The change of voice is the most certain 
 of the indications of male puberty. It depends, as the following 
 observations show, on the development of the vocal organs, 
 which constantly accompanies that of the sexual parts. 
 
ON AGES. 
 
 575 
 
 CCXXVIII. A boy, aged fourteen, died in the year VII. at 
 the Hospital of la Charite. On opening the larynx, I was sur- 
 prized to see it so small; and especially the glottis, which was 
 not above five lines in its antero-posterior diameter, and about 
 a line and a half in its transverse diameter, where its dimen- 
 sions are greatest; an observation that must not be omitted, is, 
 that he was very tall; but that the development of the genital 
 organs was as backward as of the vocal. I have repeated the 
 same observation on subjects further from the age of puberty; 
 have extended my researches to those who had passed it, and I 
 have obtained as a general result, that between the larynx and 
 the glottis of a child of three or of twelve, the difference of size 
 is very inconsiderable, and cannot be estimated by the height of 
 the figure:-— 
 
 That, at the epoch of puberty, the organ of the voice enlarges 
 rapidly, and that in less than a year, the opening of the glottis 
 increases, in the proportion of five to ten, that its extent is thus 
 doubled both in length and breadth. 
 
 That these changes are less remarkable in women, whose 
 glottis increases, in the proportion only of about five to seven; 
 that in this respect, they still resemble children, as the tone of 
 their voice would lead us to suppose. 
 
 These differences, in the size of the glottis, account for the 
 danger which, in children, accompanies the croup. For, sup- 
 pose an opening of a line and a half in width, of which the 
 edges are covered with a membrane of coagulable lymph, the 
 opening will be entirely stopped: it would be only narrowed if 
 its width were double; a sufficient space would remain free for 
 the passage of the air. This supposition, which I have em- 
 ployed to make myself understood, is only the expression of the 
 truth, since anatomical inspection shows that the glottis, in 
 adults, is double the size it is before puberty. 
 
 CCXXIX. Menstruation, The symptoms by which puberty 
 is known, in women, are not less remarkable. The swelling of 
 the genital organs straitens the opening of the canals that make 
 part of them. The breasts become enlarged, and form, at the 
 fore part of the thorax, marked projections. Further, there 
 comes on a discharge of blood, which takes place every month, 
 from the vessels of the womb, and which is known by the name 
 
ON A6ES. 
 
 576 
 
 of the menstrual discharge, or menses. This periodical evacua- 
 tion declares itself, in most women, bv all the symptoms that 
 indicate fulness of blood, as spontaneous lassitude, heat, and 
 flushings in the face, and by others which show a direction of 
 the humours towards the uterus, and a local plethora of that 
 organ, as pains in the kidneys, and a certain itching of the parts. 
 The first eruption puts an end to this state; which, in many, 
 may be considered as real disease. A pure red blood flows in 
 more or less abundance, for some days; the general heaviness 
 goes off, and the woman feels herself relieved. 
 
 I shall not now speak of the many deviations incident to the 
 menstrual discharge, and which must be considered as real dis- 
 eases. Thus, the uterine discharge has been known to be sup- 
 plied by bleeding from the nose, haemoptt sis, melsena, some- 
 times by unusual evacuations of blood, from the eves, ears, the 
 fore-finger, from ulcerated surfaces over different parts of the 
 body. 
 
 It is easily conceived, that the different parts of the sanguine- 
 ous system may supply each others place, and that the bloody 
 secretion, in which menstruation consists, in failure of the inter- 
 nal surface of the uterus, may be carried on by another part, 
 equally provided with capillary vessels: but that similar devia- 
 tions may take place for the fluids secreted bt^ the conglomerate 
 glands, as urine, bile, saliva, is difficult to believe, notwithstand- 
 ing the many testimonies and authorities that may be brought 
 in support of this opinion. 
 
 The fluids are not in existence before the work of secretion; 
 the urine, retained in the bladder and in the ureters, the bile 
 stopped in the gall-bladder and the hepatic ducts, after it has 
 been prepared by the peculiar action of the liver, may, it is true, 
 from absorption, by the lymphatic vessels, be carried into the 
 blood, and produce there a diseased urinary or bilious diathe- 
 sis; occasion an irritation and derangement, after which, the 
 humour of the cutaneous perspiration, and of the sweat, and the 
 saliva itself will exhibit some of the qualities of the humour re- 
 tained, and introduced by the absorbents into the circulation. 
 The blood, contaminated by the admixture of a certain quantity 
 of urine, ma}’ purify itself by various emunctories, by urinous 
 vomitings and sweats; but that urine may, like the menstrual 
 
ON AGES. 
 
 577 
 
 blood, come out at the eyes, the ears, or the navel, except in 
 case of urinary umbilical fistula; that one whose urinary dis- 
 charge, by the urethra, is not interrupted, may spontaneously 
 vomit it, is what no man who has any sound notions on phy- 
 siology will believe; and yet it is related, with full details, in a 
 late work, where these errors are found, in the midst of many 
 interesting researches, on various points of physiological chem- 
 istry. I have seen myself the woman, whose urine has been 
 so well analyzed by Dr. Nysten, when the clinical professor of 
 medicine^ at Paris, obliged her to submit to a severe but neces- 
 sary examination, and I am astonished that well-informed men 
 should so long have given credit to such gross impostures. The 
 reader will, I hope, excuse this long digression, for the sake of 
 its importance. Literary criticism is now carried on with such 
 partially, that no journalist, in praising justly what is praise- 
 worthy, in the valuable work of Dr. Nysten, has pointed out 
 the imposture of which he was the dupe. 
 
 At first irregular, the menstrual discharge assumes regularity, 
 is repeated every month, and lasts from two days to a week, 
 with evacuation of from three ounces to a pound of blood, 
 every time. Women of sanguine temperament, robust and libi- 
 dinous, are those whose menses last longest, and flow most 
 copiously. The blood is arterial, red, and has not, in a healthy 
 woman, any of the pernicious qualities which have been ascrib- 
 ed to it. 
 
 During the whole time of menstruation, women are weaker, 
 more delicate, more susceptible of impressions; all their organs 
 partake more or less, in the affection of the uterus; and it is not 
 difficult to an observer, of any practice, to discern this state, 
 not merely by the pulse, but by the change of the countenance 
 and tone of the voice. Women then require very careful ma- 
 nagement. An improper blood letting, a purge, or any other 
 remedy untimely administered, may suppress the discharge, 
 and occasion the most serious affections. Climate evidently 
 influences the duration and quantity of the discharge, since, in 
 Africa, it flows almost continually, whilst in Lapland, it takes 
 place only two or three times a year. 
 
 I shall not dwell upon the different explanations that have 
 been given of this phenomenon. Some have ascribed it to the 
 
 4 D 
 
ON AGES. 
 
 578 
 
 oblique position of the uterus, without considering, that upon 
 their principle, menstruation should take place from the soles 
 of the feet. Richard Mead believed that it depended on the 
 influence of the moon over the female system; but why is it not 
 then subjected to the lunar phases? Those who have found the 
 cause of it in plethora, general or local, have, if we admit their 
 explanation, only changed the difficulty; for then, we must ask 
 what are the causes of this plethora? But, if this opinion had 
 any ground, nervous women, with a small quantity of blood in 
 their system, ought not to menstruate; and yet they do so, 
 plentifully. Must we ascribe menstruation to an acquired habit? 
 
 Is the problem resolved, by saying that all the secretory 
 organs of women are too weak to evacuate the superfluity of 
 humours, which would require for them a new emunctory? 
 But is not this taking the effect for the cause? Does not this 
 smaller quantity of fluids, proceeding from the blood, arise 
 from the purification which the blood undergoes in the uterus? 
 Let it be remarked, in the mean time, that this periodical dis- 
 charge seems to exempt the sex from many inconveniences, 
 from which ours suffers; such as gout, stone and gravel, so 
 unfrequent with them, and so common with us. Nor can we 
 avoid recognizing, in this discharge, a utility relative to con- 
 ception: does it not seem to dispose the uterus to that func- 
 tion?* (CCIV). Was it not requisite that this organ should be 
 accustomed to receive a great quantity of blood, that pregnancy, 
 which calls for this afflux, might not be injured, by bringing on 
 a sudden change in the system, and the whole of the vital func- 
 tions. 
 
 Menstruation is suspended during pregnancy; it is so during 
 the first months of suckling; though this rule admits of many 
 exceptions. Its cessation, in our climate, is from the fortieth to 
 the fiftieth year; sometimes before, seldom later: though I have 
 now before me the instance of a woman of seventy, who has not 
 yet ceased to menstruate; a fact, which, after all, is nothing 
 more surprising, than that of menstruation beginning at an 
 early period of life. When menstruation ceases, the breasts 
 collapse, plumpness goes off and the skin shrivels, and loses its 
 softness, colour, and suppleness. This cessation is the cause of 
 
 * The greater part of female quadrupeds have the parts of generation bathed 
 in a reddish lymph, during the time of being in heat. 
 
ON AGES. 
 
 579 
 
 a great many diseases which break out, at this season of life, 
 called the turn of life, and are fatal to many women: but then, 
 it is observed, that when this period is past, their life is more 
 secure, with more hope of prolonging it, than a man has, at the 
 same age. 
 
 CCXXX. Of manhood. To youth succeeds manhood: which 
 may be considered as beginning from the twent)'^-first to the 
 twenty-fifth year. Then, all increase of the body, in height, is 
 at an end. The processes are completely united to the body of 
 the bones. But still, growth goes on in other dimensions. All 
 the organs acquire remarkable hardness, solidity, and consist- 
 ency. It is the same with the intellectual and moral faculties. 
 To the empire of imagination, succeeds that of judgment. Man 
 is capable of fulfilling all the duties of family and society. This 
 period of life, to which we give the name of mature age, ex- 
 tends to the fiftieth or the fifty-fifth year for men: it scarcely 
 goes beyond the forty-fifth for women, with whom it begins 
 also a little sooner. During this long interval, men enjoy the 
 whole plenitude of their existence. 
 
 Although, in general, it is not difficult to distinguish, at first 
 sight, a man of twenty-five, from one of fifty, the differences 
 which mark them, depending on the quantity and colour of 
 their hair, and on their muscular strength, are neither many 
 nor very essential. 
 
 Let us avail ourselves of this age, during which the charac- 
 ters of the human species, merely sketched, in childhood and 
 youth, take a more defined and lasting form, to trace the fea- 
 tures of individuals and of races. 
 
 CCXXXI. Of temperaments and idiosyncrasies. We give the 
 name of temperaments to certain physical and moral differences 
 in men, which depend on the various proportions and relations 
 among the parts that make up their organization, as well as 
 upon different degrees in the relative energy of certain organs. 
 There is, besides, in each individual, a mode of existence which 
 distinguishes his temperament from that of any other, to whom, 
 however, he may bear great resemblance. We express by the 
 term idiosyncrasy^ these individual temperaments, the know- 
 ledge of which is of no small importance in the practice of 
 medicine. 
 
ON TEMPERAMENTS. 
 
 580 
 
 The predominance of any particular system of organs, modi- 
 fies the whole economy, impresses striking differences on the 
 results of the organization, and has no less influence on the 
 moral and intellectual, than on the physical faculties. This 
 predominance establishes the temperament; it is the cause, and 
 constitutes its essence. 
 
 If the heart and the vessels which carry the blood, through 
 every part, are of predominant activity, the pulse will be sharp, 
 frequent, regular, the complexion ruddy, the countenance ani- 
 mated, the shape good, the forms softened though distinct, the 
 flesh of tolerable consistence, moderate plumpness, the hair fair 
 and inclining to chesnut; the nervous susceptibility will be 
 lively, and attending with rapid successibility^ that is to say, 
 that being easily affected by the impressions of outward objects, 
 men of this temperament will pass rapidly from one idea to 
 another; conception will be quick, memory prompt, the imagi- 
 nation lively; they will be addicted to the pleasures of the table 
 and of love; will enjoy a health seldom interrupted by disease; 
 and all their diseases, and these slight, modified by the tem- 
 perament, will have their seat principally in the circulatory- 
 system (injlammatory fever^ or angeio-temque; phlegmasia; 
 acute haemorrhage') and will terminate, when moderate, by the 
 mere force of nature, and require the use of the remedies, cal- 
 led antiphlogistic, among which bleeding is the chief. The 
 ancients applied the name of sanguine to this disposition of 
 body; they considered it as produced by the combination of 
 warmth and moisture, and had very correctly perceived that it 
 existed in the young of both sexes, was heightened by the 
 spring, the season which has been justly compared to youth, 
 calling that age the spring time of life. 
 
 That the specific characters of the temperament I have just 
 described, may show themselves, in all their truth, it is requi- 
 site that the moderated development of the lymphatic system, 
 coincide with the energy of the sanguineous system, so that 
 these two sects of vascular organs may be in true equipoise. 
 The physical traits of this temperament are to be found in the 
 statues of Antinous and the Apollo of Belvedere. Its moral 
 physiognomy is drawn in the lives of Mark Antony and Alci- 
 biades. In Bacchus are found both the forms and the character^ 
 
ON TEMPERAMENTS. 
 
 581 
 
 But why seek amongst the illustrious men of antiquity, or 
 among its gods, the model of the temperament I have been 
 describing, whilst it is so easy to find it among the moderns? 
 No one, in my opinion, exhibits a more perfect type of it than 
 the Marshal Duke of Richelieu, that man, so amiable, fortu- 
 nate and brave in war, light and inconstant, to the end of his 
 long and brilliant career.* 
 
 Inconstancy and levity are, in fact, the chief attribute of men 
 of this temperament: excessive variety appears to be, to them, 
 a necessity as much as an enjoyment; good, generous, feeling, 
 quick, impassioned, delicate in love, but fickle, disgust, in them, 
 follows close upon enjoyment: meditating desertion, in the 
 midst of the most intoxicating caresses, they make their escape 
 from beauty, at the very moment she thought to have bound 
 them by indissoluble chains. f In vain he whom nature has 
 endowed with a sanguine temperament, will think to renounce 
 the pleasures of the senses, to take fixed and lasting likings, to 
 attain, by profound meditation, to the most abstract truths; 
 mastered by his physical dispositions, he will be for ever driven 
 back to the pleasures from which he flies, to the inconstancy 
 which is his lot; more fitted to the brilliant productions of wit, 
 than the sublime conceptions of genius, j; His blood, which a 
 vast lung impregnates, plentifully, with atmospherical oxygen, 
 flows freely in very dilatable canals, and this facility in the dis- 
 tribution and course of the humours is, at once, the cause and 
 the image of the happy dispositions of his mind. , 
 
 * See his Memoirs, 6 vols. Svo. 
 
 Voltaire has painted his character, with superior ability, >n many verses 
 addressed to him. 
 
 Rival du conqudrant de I’Inde, 
 
 Tu hois, tu plais, tu combats, &c. 
 
 t The history of Henry IV. of Lewis XIV. of Regnard, and of Mirabeau 
 proves that, to the extreme love of pleasure, sanguine men join, when cir- 
 cumstances require it, great elevation of thought and character; and can bring 
 into action the highest talents, in every department. 
 
 1 1 have just met, in a gazette, with an assertion at least singular. All the 
 world knows, says the journalist, that Newton was sanguine, and this proves 
 clearly, he adds, that temperaments have no influence on the intellectual 
 powers. I would ask the journalist where he has discovered that Newton was 
 sanguine. The few details which biographers have preserved on the physical 
 temperament of this illustrious philosopher, lead us to believe that his tempera- 
 
ON temperaments. 
 
 582 
 
 CCXXXII. If men of this temperament apply themselves, 
 from circumstances, to labours which greatly exert the organs 
 of motion, the muscles, plentifully supplied with nourishment 
 and disposed to acquire a development proportioned to that of 
 the sanguinous system, increase in bulk: the sanguineous tem- 
 perament undergoes a great modification; and there results from 
 it the muscular or athletic temperament, conspicuous by all the 
 outward signs of vigour and strength. The head is ver}' small, 
 the neck sunk, especially backward, the shoulders broad, the 
 chest large, the haunches solid, the intervals of the muscles 
 deeply marked. 
 
 The hands, the feet, the knees, all the articulations not 
 covered by muscles, seem very small, the tendons are marked 
 through the skin which covers them: the susceptibility is not 
 great: feeling dull and difficult to rouse, the athlete surmounts 
 all resistance, when he has once broken from his habitual tran- 
 quillity. The Farnese Hercules exhibits the model of the 
 physical attributes of this particular constitution of body, and 
 what fabulous antiquity relates of the exploits of this demi-god, 
 gives us the idea of the moral dispositions that accompany it. 
 In the history of his twelve labours, without calculation, with- 
 out reflection, and as by instinct, we see him courageous, 
 because he is strong, seeking obstacles to conquer them, certain 
 of overwhelming whatever resists him: but joining to such 
 strength so little subtlety, that he is cheated by all the kings he 
 serves, and all the women he loves. It would be difficult to find 
 in history the example of a man who has combined, with the 
 physical powers which this temperament implies, distinguished 
 strength of the intellectual faculties. For excelling in the fine 
 arts and in the sciences, there is need of exquisite sensibility, a 
 condition absolutely at variance with much development of the 
 muscular masses. 
 
 CCXXXIII. If sensibility, which is vivid and easily ex- 
 cited, can dwell long upon one object; if the pulse is strong, 
 
 ment was the melancholic, which is very frequently met with in England. I will 
 not dare to pronounce absolutely, on subjects on which we can attain onl)' a 
 certain degree of probability; but if Newton had been sanguine, he would not 
 have carried his maidenhead with him to the grave, at the age of fourscore; 
 as it is affirmed he did. 
 
ON TEMPERAMENTS. 
 
 583 
 
 hal'd, and frequent, the sub-cutaneous veins prominent, the skin 
 of a brown, inclining towards yellow, the hair black, moderate 
 fulness of flesh, but firm, the muscles marked, the forms harshly 
 expressed^ the passions will be violent, the movements of the 
 soul often abrupt and impetuous, the character firm and inflexi- 
 ble. Bold in the conception of a project, constant and indefati- 
 gable in its execution, it is among men of this temperament we 
 find those who in different ages have governed the destinies of 
 the word; full of courage, of boldness and activity, all have 
 signalised themselves by great virtues or great crimes, have 
 been the terror or admiration of the universe. Such were Alex- 
 ander and Julius Csesar, Brutus, Mahomet, Charles XII., the 
 Czar Peter, Cromwell, Sixtus V., Cardinal Richelieu. 
 
 - As love in the sanguine, ambition is in the bilious the govern- 
 ing passion. Observe a man, who, born of an obscure family, 
 long vegetates in the lower ranks: great shocks agitate and over- 
 throw empires: actor, at first secondary, of these great revolu- 
 tions, which are to change its destiny, the ambitious hides from 
 all his designs, and, by degrees, raises himself to the sovereign 
 power, employing to preserve it the same address with which 
 he possessed himself of it. This is, in two words, the history of 
 Cromwell, and of all usurpers.* 
 
 To attain to results of such importance, the profoundest dis- 
 simulation, and the most obstinate constancy are equally neces- 
 sary; these are, further, the most eminent qualities of the bilious. 
 No one ever combined them in higher perfection, than that 
 famous Pope, who slowly travelling on towards the pontificate, 
 went for twenty years, stooping, and talking for ever of his ap- 
 proaching death, and who, at once proudly rearing himself, cries 
 out “ I am Pope!”| petrifying with astonishment and mortifica- 
 tion, those whom his artifice had deceived into his party. 
 
 Such too was Cardinal Richelieu, who raised himself to a 
 rank so near to the highest, and was able to maintain himself in 
 it; feared by a king whose authority he established, hated by 
 the great, whose power he destroyed, haughty and implacable 
 towards his enemies, ambitious of every sort of glory, &c.J 
 
 • vie d’Olivier Cromwell, par Jeudy Dugour, 2 vols.lSmo. 
 
 f Vie de Sixte Quint, 2 vol. in 12. 
 
 \ See his character drawn, with as much truth as eloquence, by Thomas, in 
 the last edition of his Essai sur ks Elopes. 
 
ON TEMPERAMENTS. 
 
 584 
 
 The historians of the time inform us, that this celebrated 
 minister showed all the customary signs of the bilious tempera- 
 ment. Gourville tells us that he was all his life, subject to a 
 very troublesome heemorrhoidal discharge.* 
 
 This temperament is further characterized by the premature 
 development of the moral faculties. Scarcely past their youth, 
 the men I have named projected and carried into execution, 
 enterprizes which would have been sufficient for their fame. An 
 excessive development of the liver, a remarkable superabun- 
 dance of the biliary juices, most commonly accompanying this 
 constitution of body, in which the vascular sanguineous system 
 enjoys the greatest energy, to the prejudice of the cellular and 
 lymphatic system, the ancients gave it the name of bilious. The 
 diseases to which those distinguished by it are subject, involve 
 in fact, either as their principal characteristic, or as accessary 
 circumstances, or as complication, the derangement of the ac- 
 tion of the hepatic organs, joined to changes of composition in 
 the bile. Among the remedies directed against these sort of 
 diseases, evacuants, and especially emetics, are the best. 
 
 If all the characteristics assigned to the bilious temperament 
 are carried to the highest degree of intensity, and to this state 
 is added great susceptibility, men are irrascible, impetuous, 
 violent, on the lightest occasions. Such, Homer describes Achil- 
 les, and some others of his heroes. 
 
 CCXXXIV. When, to the bilious temperament, is added 
 diseased obstruction of any one of the organs of the abdomen, 
 or derangement of the functions of the nervous system, so that 
 the vital functions are feebly or irregularly performed, the skin 
 takes a deeper hue, the look becomes uneasy and gloomy, the 
 bowels sluggish, all the excretions difficult: the pulse hard and 
 habitually contracted (serve). The general uneasiness affects the 
 mind; the imagination becomes gloomy, the disposition suspi- 
 cious; the exceedingly multiplied varieties of this temperament, 
 called by the ancients the melancholic., the diversity of accidents 
 that may bring it on, such as hereditary disease, long grief, ex- 
 cessive^ study, the abuse of pleasures, &c. justify the opinion 
 which Clerc has proposed, in his natural history of man, in a 
 
 ^ Memoires de Gourville. 
 
ON TEMPERAMENTS. 
 
 585 
 
 state of disease, where he considers the melancholic tempera- 
 ment less as a primitive and natural constitution, than as a dis- 
 eased affection hereditary or acquired. The characters of Lewis 
 XI. and Tiberius, leave nothing wanting for the moral deter- 
 mination of this temperament. Read, in the Memoirs of Philip 
 de Commines, and in the Annals of Tacitus, the history of 
 these two tyrants; fearful, perfidious, mistrustful, suspicious, 
 seeking solitude by instinct, and polluting it by all the acts of 
 the most savage atrocity, and the most ungoverned debauch. 
 Distrust and fearfulness, joined to all the disorders of imagi- 
 nation, compose the moral character of this temperament. The 
 passage in which Tacitus paints the artful conduct of Tiberius, 
 when he refuses the empire, offered him, after the death of 
 Augustus, may be given as the most perfect mod'll of it. Versoe 
 tnde ad Tiberium preces^ Corn. Tacit. Annul, lib. i. 
 
 As Professor Pinel very justly observes, in his treatise on 
 insanity, the history of men celebrated in the sciences, letters, 
 and arts, has shown us the melancholic under a different light: 
 endowed with exquisite feeling, and the finest perception; de- 
 voured with an ardent enthusiasm for the beautiful, capable of 
 realizing it in rich conceptions, living with men in a state of re- 
 serve bordering upon distrust, analyzing with care, all their 
 actions, catching in sentiment its most drlicate shades, but ready 
 in unfavourable interpretations, and seeing all things through 
 the dingv glass of melancholy. 
 
 It is extremely difficult to delineate this temperament in a 
 general or abstract manner. Though the ground-work of the 
 picture remains always the same, its numerous circumstances 
 give room for an infinite number of variations. It is better, 
 therefore, to have recourse to the lives of illustrious men, who 
 have exhibited it in all its force. Tasso, Pascal, J. J. Rousseau, 
 Gilbert, Zimmerman, are remarkable, among manv others, and 
 deserve, by their just celebrity, to fix our consideration. The 
 first, born in the happy climate of Italy, proscribed and unhappy 
 from his childhood, author, at twenty-two years old, of the 
 finest epic poem the moderns can boast of, seized in the midst 
 of the enjoyments of premature glory, with the most violent and 
 most inauspicious love for the sister of the Duke of Ferrara, at 
 whose court he lived; an extravagant passion, which was the 
 
 4 E 
 
ON TEMPERAMENTS, 
 
 586 
 
 pretext of the most cruel persecutions, and which followed him 
 to his death; which took place towards the thirty-second year 
 of his age, on the eve of a triumphal pomp, which was prepared 
 for him in the capitol. 
 
 The author of the Provincial Letters, and of the Thoughts, 
 enjoying, like Tasso, a premature celebrity, almost on quitting 
 childhood was led to melancholy; not like him, by the crosses 
 of unhappy love, but by a violent and overpowering terror, 
 which left, in his imagination, the sight of a gulf for ever open 
 at his side; an illusion which left him only at his death, eight 
 years after the accident.* 
 
 No one, perhaps, has ever shown the melancholic tempera- 
 ment, in a higher degree of energy, than the philosopher of 
 Geneva. To be convinced of it, it is enough to read, with atten- 
 tion, certain passages of his immortal works, and especially the 
 two last parts of his Confessions, and the Reveries in the Soli- 
 tary Walker; tormented with continual distrusts and fears, his 
 fruitful imagination represents to him all men as enemies. If you 
 believe him, the whole human race is in league to do him rais" 
 chief: kings and 7iations have conspired together^ against the 
 
 son of a poor watch-makerf children and invalids are brought in 
 to execute these dreadful plots. But let us leave him to speak 
 for himself, the most eloquent and most unfortunate man of the 
 eighteenth century: “ Here then I am, alone upon the earth, 
 without brother, neighbour, friend, without society but myself; 
 the most sociable and the most loving of men, has been pro- 
 scribed by them with unanimous consent.” This is the begin- 
 ning of the first walk; further on he adds, “ Could I believe that 
 I should be held, without the smallest doubt, for a monster, a 
 poisoner, an assasin; that I should become the horror of the hu- 
 man race, and the game of the rabble; that all the salutation of 
 those that passed by me, would be to spit upon me; that a whole 
 generation would amuse itself, with unanimous consent, in bury- 
 ing me alive?” It is idle to multiply quotations, in speaking of 
 the works of a philosopher, who, in spite of his errors, will for- 
 ever be the delight of all those who love to read and to think. 
 
 The history of J. J. Rousseau, like that of all the melancho- 
 
 He died .it 39. See his life by Coudorcet. 
 
ON TEMPERAMENTS, 
 
 587 
 
 lies who have distinguished themselves in literature, shows us 
 genius struggling with misfortune; a strong soul lodged in a 
 feeble body, at first gentle, affectionate, open, and tender, soured 
 by the sense of an unhappy condition, and of the injustice of 
 men. Till the time when, impelled by the desire of fame, 
 Rousseau sprang forward in the career of letters, we see him 
 endowed with a sanguine temperament; acting with all the 
 qualities belonging to it; gentle, loving, generous, feeling, 
 though inconstant; his fertile imagination shows him nothing 
 but gay images, and in this illusion of happiness, he lives on 
 agreeable chimeras; but gradually undeceived by the hard les- 
 sons of experience, afflicted, in the depth of his heart, with his 
 own wretchedness, and the wrongs of his fellow creatures, 
 his bodily vigour wastes and decays; with it his moral nature 
 changes, and he may l)e referred to as the most striking proof 
 of the reciprocal influence of the moral on the physical, and the 
 physical on the moral part of our being.^ His history is a proof, 
 be5^ond reply, that the melancholic temperament is less a pecu- 
 liar constitution of the body, than a real disease, of which the 
 degrees may infinitely vary, from a mere originality of charac- 
 ter, to the most decided mania. 
 
 Gilbert arrives at Paris, with the germs of talents fitted for 
 that great theatre. Poor and rebuffed by those on whom he had 
 
 * I have no doubt that the influence of the physical organization on the intel- 
 lectual faculties is so decided, that we may regard as possible the solution of 
 the following problem, analogous to that with which Condillac concludes his 
 ■work on the origin of human knowledge. 
 
 The physical man being given, to determine the character and extent of his capa- 
 city, and to assign, consequently, not only the talents Ag possesses, but those he is 
 capable of acquiring. 
 
 The profound meditation of the work of Galen {quod animi mores corporis 
 temperamenta sequantur,-) the perusal of Plutarch’s lives of Illustrious Men, 
 and of the other biographers and historians of ancient and modern times; of 
 the Eulogies of Fontenelle, Thomas, D’Alembert, Condorcet, Vicq-d’Azyr, 
 &c., and the study of the medico-philosophical works of Haller, Cullen, Caba- 
 nis. Pine], Halle, who have modified and enriched the ancient doctrine of tem- 
 peraments, will be of great avail in the search of this solution. “ Philosophy,” 
 cries an eloquent writer, in the noble enthusiasm which seizes him at the 
 sight of the riches accumulated by Fontana, in the anatomical museum at 
 Florence, “ Philosophy has been in the wrong, not to descend more deeply 
 into physical man; there it is that the moral man lies concealed; the outward 
 man is only the shell of the man within.” — Dupaty, 23d letter on Italy. 
 
ON TEMPERAMENTS. 
 
 588 
 
 built his hopes, he mixes in the ranks of their detractors, and 
 soon signalizes himself, among the most formidable, by a 
 vigour worthy of a better cause. Persecuted, without respite, 
 by want, the mortifying sight of the happiness which his ene- 
 mies enjoyed, and to which he believed himself called, led him 
 on to a state of perfect jnadness. He believes himself perse- 
 cuted by the philosophers, who want to rob him of his papers; 
 to save them from their imagined rapacity, he locks his manu- 
 scripts in a press, and swallows the key. It sticks at the entrance 
 of the larynx, stops the passage of the air, and suffocates the 
 patient, who dies, at the Hotel-Dieu, after three days of the 
 most cruel sufferings.* 
 
 Zimmerman, early exhausted by study, already a physician 
 of celebrity, at an early age lives in solitude, with an ardent 
 imagination, joined to the highest susceptibility; abandoned to 
 himself, devoured with the thirst of glory, he gives himself up 
 to labour in excess, publishes his Treatise on Experience, and 
 the work on Solitude, so deeply imbued with the colouring of 
 his soul. Forced from the solitude he loves, he carries into the 
 courts to which his reputation calls him, an inexhaustible store 
 of bitterness and sadness, which political events supervening, 
 brought to greater excess; arrived at length gradually at the last 
 term of hypochondria, he dies beset with pusillanimous fears, 
 worthy of all eulogium and all regret.f 
 
 * His life would have been preserved, if the cause of his illness had been 
 understood, which he indicated him elf by repeating’, “the key chokes 
 me.” His state of madness made this pass for the words of a madman; but on 
 opening the body, the key was found, of which the ward part was fixed at the 
 entrance of the larynx; it would have been easy to draw it out, by putting a 
 finger down the throat. 
 
 This unfortunate young man expressed, a few days before his death, the 
 melancholy state of his soul, in stanzas most touchingly mournful; this is one, 
 full of interest and simplicity: 
 
 Au banquet de lu vie infortun^ convive, 
 
 Je parus un jour, et je meurs; 
 
 Je meurs et sur ina tombe oii lentement j’arri ve 
 Nul ne viendra verser des pleurs. 
 
 I See his Eulogium by Tissot; it is at the beginning of the last edition of the 
 the Treatise on Experience in Medicine. It there appears how deeply he vas 
 affected by the French revolution, of w hich he foresaw, witli a sort of prophetic 
 spirit, the disastrous consequences to his own country. 
 
ON TEMPERAMENTS. 
 
 589 
 
 CCXXXV. If the proportion of the fluids to the solids is 
 too great, this superabundance of the humours, which is con- 
 stantly in favour of the lymphatic system, gives to the whole 
 body considerable bulk, determined by the development and 
 repletion of the cellular tissue. The flesh is soft, the counte- 
 nance pale, the hair fair, the pulse weak, slow, and soft, the 
 forms rounded and without expression, all the vital actions 
 more or less languid, the memory treacherous, the attention not 
 continuous. Men of this temperament, to which the ancients 
 gave the name oi pituitous, and which we should call lymphatic^ 
 because it depends really on the excessive development of this 
 system, have, in general, an insurmountable inclination to sloth, 
 averse alike to labours of the mind and body; accordingly, we 
 are not to wonder, if we find none of them among Plutarch’s 
 illustrious men. Little fitted for business, they have never 
 exercised great empire over their fellow creatures, they have 
 never changed the face of the globe, by their negociations or 
 their conquests. One of the friends of Cicero, Pomponius 
 Atticus, whose history Cornelius Nepos has left us, conciliating 
 to himself all the factions which tore the Roman republic to 
 pieces, in the civil wars of Caesar and Pompey, may be given 
 as the model of it. Among the moderns, the easy Michel 
 Montaigne, all whose passions were so moderate, who reasoned 
 on every thing, even on feeling, was truly pituitous. But, in 
 him, the predominance of the lymphatic system was not carried 
 so far, but that he joined to it a good deal of nervous suscepti- 
 bility. In the pituitous, from the excess of watery particles in 
 the fluid which should carry every where heat and life, the cir- 
 culation goes on slowly, the imagination is weak, the passions 
 languid; and, from this moderation of the desires, spring, on 
 many occasions, those virtues of temperament^ which, to say it, 
 by the by, should not supply their possessors^ with matter of 
 quite so much self-complacency. 
 
 CCXXXVI. This property by which we are, more or less, 
 sensible to impressions on our organs, weak in the pituitous, 
 almost nothing in athletes, moderate in those of sanguine tem- 
 perament, rather quick in the bilious, constitutes, by its excess, 
 the nervous temperament; seldom natural or primitive, but 
 commonly acquired, and depending on a sedentary and too 
 
ON TEMPERAMENTS. 
 
 590 
 
 inactive life, on habitual indulgence in sensualitv, on the mor- 
 bid action of the brain, promoted by reading works of imagina- 
 tion, &c. This temperament shows itself in the emaciation, in 
 the smallness of the muscles, soft, and as it were, in an atrophy, 
 in the vivacity of the sensations, in the suddenness and muta- 
 bility of the determinations and judgments. Nervous women, 
 whose wills are absolute, but changeable, with excess of sensi- 
 bility, frequently exhibit it with all these characteristics. Often, 
 however, they have something of good looks, the extreme pre- 
 ponderance of the nervous system still allowing a moderate 
 development of the lymphatic. Spasmodic affections are not 
 uncommon among them; and when it is observed that, on the 
 other hand, the athletic constitution, directly opposite to the 
 nervous temperament, predisposes to tetanus, may we not say, 
 that the two extremes meet, or produce the same effects? 
 
 Anti-spasmodics are employed, with success, in the treatment 
 of their diseases, which partake always, more or less, of the 
 temperament. Stimulants, on the contrary, are very suitable to 
 those of a pituitous or lymphatic temperament. The nervous 
 temperament, like the melancholic, is not so much a natural 
 constitution of the body, as the first stage of a disease. This 
 temperament, like the nervous affections which are the result of 
 it, has never shown Itself but among societies brought to that 
 state of civilization, in which man is the farthest possible from 
 nature. The Roman ladies became subject to nervous affections, 
 only in consequence of those depraved manners which marked 
 the decline of the Empire. These affections were extremely 
 common in France, during the eighteenth centurj*, and in the 
 times preceding the fall of the monarchy. Of that epoch, are 
 the works of Wytt, Raulin, Lorrj'^, Pomme, &c. on nervous 
 affections. Tronchin, a Genevese physician, acquired great 
 wealth and reputation by the treatment of these diseases. His 
 whole secret consisted in exercising to fatigue, women ha- 
 bitually' inactive, keeping up their strength, at the same time, 
 by simple, healthy, and plentiful food. The two most re- 
 markable men of the eighteenth century', Voltaire and the 
 great Frederick, may' be given as instances of the nervous 
 temperament; and the history of their brilliant and agitated 
 
ON TEMPERAMENTS. 59]^ 
 
 life, shows, sufficiently, how much the circumstances in which 
 they lived, contributed to develop their native dispositions. 
 
 I shall finish this article on temperaments by observing, that 
 in truth, we bring with us into the world these particular dispo- 
 sitions of body; but that from education, manner of life, climate, 
 acquired habits, they are altered, or altogether changed. Fur- 
 ther, it is exceedingly rare to find individuals, who show, in 
 their purity, the characters assigned to the different tempera- 
 ments: the descriptions given are drawn from an assemblage of 
 individuals, much resembling one another. Their characters 
 are pure abstractions, which it is difficult to realize, because all 
 men are at once sanguine and bilious, sanguine and lymphatic, 
 &c. In this instance, physiologists have imitated the artist, who 
 united in the image of the goddess of beauty, a thousand per- 
 fections which he saw separate in the most beautiful women of 
 Greece.* 
 
 It is an observation that the sanguine constitution is directly 
 opposed to the melancholic, and never combines with it; that it 
 is the same with the bilious and lymphatic: though it may hap- 
 pen that a man, sanguine in youth, shall become melancholic 
 after a lapse of time; for, as I have said before, man never re- 
 mains such as he came from the hands of nature; fashioned by 
 all that surrounds him, his physical qualities, at different periods 
 of his life, are as much changed as his character. 
 
 Of all the causes that can modify the nature of man, and 
 which will even change completely the nature of his native 
 dispositions, there is none more powerful than the long con- 
 tinued action of air, water, and residence, as the father of 
 medicine has said. Climate, in fact, exerts upon the tempera- 
 ment the most marked influence. Thus, the bilious temperament 
 is that of the greater part of the inhabitants of southern coun- 
 tries; the sanguine that of the nations of the north; the lympha- 
 tic constitution reigns, on the contrary, in cold and moist coun- 
 tries, like Holland. We have seen in what manner the athletic, 
 melancholic, and nervous temperament grows out of our habits 
 
 * It is thus that, in the arts of imitation, the ideal growsup; now, from the ex- 
 aggeration of features; now, from the union of qualities which nature has pro- 
 duced separate. 
 
ON TEMPERAMENTS. 
 
 592 
 
 of life: let us now endeavour to appreciate the power of climate 
 over the constitution of the greater part of mankin .. 
 
 It is known, that the influence of heat, in the production of 
 bilious diseases, is such, that after having been extremely pre- 
 valent during the summer, they disappear, or at least become 
 much less frequent in the autumn. A notable increase of per- 
 spiration never takes place without a proportional diminution 
 in the quantity of the liquids with which the alimentary surfaces 
 are moistened. Now, when the gastric juice is less abundant, 
 the bile, being mixed with a smaller quantity of serosities, irri- 
 tates more the intestinal surfaces; the digestive powers languish, 
 and there is an approaching disposition to meningo-gastric 
 fevers. The same influences, continued during the whole year 
 in hot countries, must necessarily increase, with the activity of 
 the biliary system, its power over the other parts of the eco- 
 nomy, and thus establish a predominance of the bilious consti- 
 tution, through both health and'disease. 
 
 As for the sanguine temperament, so generally met with 
 among northern nations, it is the necessary consequence of the 
 continual and very energetic re actirin of the powers of circula- 
 tion, against the effects of external cold. It is only by the con- 
 stant activity of the heart and vessels, that calorification can be 
 effecteil with the necessary vigour. Now, the eff cts of this re- 
 doubled action are the same to the organs of circulation, as to 
 the muscles under the influence of volition: in both, exertion 
 increases the power of the organs exerted. The diseases ol the 
 nations of the north, analogous to their temperament, have, for 
 the most part, their seat in the svstem of sanguineous vessels: 
 their character is eminently inflammatory. 
 
 Lastly, the lymphatic state of nations, living under a moist 
 climate, is nothing more surprising than the aqueous nature of 
 plants, and small densitv of the wood, in trees growing under 
 the influence of a foggy air. Animal bodies, like plants, absorb 
 bv their surfaces, and become gorged with humours, the excess 
 of which always produces a remarkable slackening of activity in 
 the organic motions. 
 
 The temperament of which the character is the predominance 
 of one organ or svstem of organs, departs from that ideal state, 
 where all the powers are reciprocally balanced, so as to exhibit 
 
ON TEMPERATURES. 
 
 593 
 
 in the living economy, a perfect equilibrium. This state, which 
 has perhaps never been found, but in the imaginations of phy- 
 siologists, and which was called by the ancients, the temperate 
 temperament, temperamentum temperatum^ being taken as the 
 type of health, it follows that this temperament is already a step 
 made towards disease. Yet the action of the predominant sys- 
 tem is not in such excess as to destroy all equilibrium, and im- 
 pede the action of life: but let the constitutional dispositions be 
 much increased, the disease is begun, and this transition takes 
 place in the conversion of the lymphatic temperament into 
 scrophula.* In the scrophulous constitution, there is, at once, 
 activity of the absorbing mouths, great facility of absorption, 
 inertness of the vessels and lymphatic glands, weakness of the 
 absorbents, and consequently a thickening and stagnation of the 
 liquids absorbed. The same thing is seen in the lymphatic tem- 
 perament, characterized by the activity of the inhaling mouths, 
 and the debility of the lymphatic system, as Professor Cabanis 
 was aware,! when he refuted the opinion of those who ascribe the 
 lymphatic temperament to the excess of activity in the absorbent 
 system, though the only part of this system really quickened, is 
 that which immediately performs absorption, whilst the rest is 
 in a state of perfect atony. 
 
 CCXXXVII. Varieties of the human species. The power of 
 producing, by copulation, like individuals, is considered, by 
 naturalists, as the most certain test for fixing the species in red 
 and warm-blooded animals. This power of self-perpetuation, 
 by a constant succession of similar beings, is found in all the 
 races composing the human species, however different in colour, 
 structure, and manner of life. Men, then, are but one species, 
 and the difference that appears in them, according to the region 
 of the globe they inhabit, can only constitute varieties or races. 
 I admit, with M. Lacepede, the worthy continuator of Buffon, 
 four principal races of the human species, which I shall call, 
 
 * See Nosographie Chirurgicale, tome I. for the history of scrophulous ulcers, 
 from which this paragraph is taken entire. The author, in that work, has 
 aimed at introducing physiology into surgery, till then exclusively abandoned 
 to explanations of the grossest mechanism. 
 
 f Of the relations of the physical and moral man, by G. Cabanis, Senator, 
 Professor in the School of Medicine, in Paris, &c. 
 
 4 F 
 
ON THE HUMAN RACE. 
 
 594 
 
 like him, the European, Arab, the Mogul, the Negro, and the 
 Hyperborean. We might add a fifth, of the American, were it 
 not most probable, that the new continent is peopled by inhabi- 
 tants, who, coming from the old, either by land in the austral 
 hemisphere, or along the immense Archipelago of the Pacific 
 Ocean, have been altered by the influence of that climate, and 
 the yet virgin soil, so that they are to be regarded less as a 
 distinct race than a simple variety. 
 
 There is, in truth, this difference between varieties and races, 
 that, in these last, there are implied modifications more pro- 
 found, more essential differences, changes not confined to the 
 surface, but extending to the very structure of the body; where- 
 as, to make a variety, nothing more is needed, than the superficitd 
 influence of climate on the integuments which it colours, and 
 on the hairs which it makes longer or shorter, lank or curled, 
 hard or soft. An Abyssinian, scorched by the heat of an almost 
 tropical sky, is as black as the negro under the equator: yet they 
 are by no means of one race, since the Abyssinian, a negro 
 only in colour, resembles the European in the cast of his face, 
 and the proportions of all his parts. 
 
 The characteristics of the European Arab race, which takes in 
 the inhabitants, not of Europe only, but of Egypt also, Arabia, 
 Syria, Barbary, and Ethiopia, are an oval, or almost oval 
 face, in the vertical direction, a long nose, a prominent skull, 
 long and commonly lank hair, a skin more or less white. These 
 fundamental characteristicts are nowhere more decided than in 
 the north of Europe. The inhabitants of Sweden, Finland, and 
 Poland, give the prototype of the race; their stature is tall, their 
 skin of perfect whiteness, their hair long, lank, and of a light 
 colour; the colour of the iris generally bluish. The Russians, the 
 English, the Danes, the Germans, are already somewhat re- 
 moved from this primordial type: the colour of their skin is of 
 less pure white, their hair of a deeper hue. The French seem 
 to stand midway betwixt the nations of the North and those of 
 the South of Europe. Their skin is shaded with a deeper dye, 
 their hair less straight, and more of a chesnut and brown 
 colour. The Spaniards, the Italians, the Greeks, the European 
 Turks, and the Pprcuguese, are browner, their hair, in general, 
 black. Lastly, the Arabs, the Moors, and the Abyssinians, have 
 hair, in some measure, black and crisp, the skin tawny, and 
 
ON THE HUMAN RACE, 
 
 595 
 
 might serve for the step from the European Arab to the Negro 
 race: which is, however, distinguished from them, by the flat- 
 tening of the forehead, the smallness of the skull, the slope of 
 the line measuring the height of the face, the thickness of the 
 lips, the projection of the malar bones, and further, by a darkeif 
 skin, thicker, greasy, and, as it were, oily, as well as by shorter, 
 finer, curly, and woolly hair. 
 
 The Mogul race has the forehead flat, the skull jutting but 
 little, the eyes looking rather obliquely outwards; the cheeks 
 are prominent, and the oval of the face, instead of extending 
 from the forehead to the chin, is drawn between the two malar 
 bones. The Chinese, the Tartars, the inhabitants of the Penin- 
 sula, of the Ganges, and of the other countries of India, of 
 Tonquin, Cochin-China, Japan, of the kingdom of Siam, &c. 
 compose this race, more numerous than all the others, and ap- 
 parently more ancient also, which is spread over a far greater 
 extent than the European Arab race, and yet more, than the 
 Negro race, since it reaches from the fortieth to the sixtieth 
 parallel of latitude, occupying an arc of the meridian of nearly 
 75°, whilst that which measures the countries of the European 
 race is only of 50°, and the Negro race lying under the equator, 
 betiveen the tropics of Cancer and of Capricorn, is bounded 
 within the limits of an arc of from 30 to 33 °.* 
 
 The Hyperborean race, situated in the north of the two con- 
 tinents, in the neighbourhood of the polar circles, composed of 
 the' Laplanders, the Ostiaks, the Samoiedes, and the Greens 
 landers, is characterised by a flat face, a squat body, and a very 
 short stature. This degraded portion of the human species 
 derives, evidently, from the climate, its distinctive characteris- 
 tics. Striving for ever with the inclemency of a severe climate, 
 the destructive action of an icy temperature, nature, fettered 
 in her motions, shrunk in her dimensions, can produce only 
 beings whose physical imperfections explain their almost bar- 
 barous condition. 
 
 The small progress of the negroes in the study' of the sciences, 
 and in civilization, their decided taste and singular aptitude for 
 all the arts which require more taste and dexterity, than un- 
 derstanding and reflection, as dancing, music, fencing, &c. the 
 
 Lacepede, Geographic Zoologique. 
 
ON THE HUMAN RACE. 
 
 §96 
 
 figure of the head, which is midway between that of the 
 European and the ourang-outang,* the existence of the inter- 
 maxillary bones, at an age, when, with us, the traces of their 
 separation are completely eflfaced; the high situation and small 
 development of the calf of the leg, have been arguments more 
 specious than solid to those who have endeavoured to abase 
 this portion of the human species in order to justify an iniqui- 
 tous traffic, and a cruel tyranny: reproaches of civilized men, 
 which they must wipe off by other means than a presumptuous 
 assertion of their own dignity, or a proud insult on the native 
 character of those, whom they themselves have cast into de- 
 gradation. 
 
 Without admitting this belief, which owes its origin to a thirst 
 of riches, we cannot help acknowledging that the differences of 
 organization draw after them a striking inequality in the deve- 
 lopment of the moral and intellectual faculties. This truth would 
 appear in its full light if, after summarily indicating, as I have 
 just done, the physical characteristics of the races of men, I could 
 unfold their moral differences, as real and not less marked; 
 opposing the activity, the versatility, the restlessness of the Eu- 
 ropean, to the indolence, the phlegm, the patience of the Asiatic; 
 examining what is the power, on the character of nations, of 
 fertility of soil, serenity of sky, mildness of climate; showing 
 by what catenation of physical and moral causes, the empire 
 of custom is so powerful over the people of the East, that we 
 find in India and China the same laws, manners, and religion 
 which prevailed there long before our era: inquiring by what 
 
 * The black colour of the skin, in Negroes, seems owing, as I have already 
 said, to the scorching of the gelatine, which is the base of the rete mucosum 
 of Malpighi. This colour, acquired in a long succession of ages, perpetuated 
 and transmitted by generation, is become one of the characteristic features 
 of the Negro race. M. Volney, in a work which should be a model to all tra- 
 vellers, grounds on the face of the blacks, a conjecture as ingenious as it is 
 probable. He observes, that it exhibits, precisely, that state of contraction 
 which our face takes when it is struck by light, and a strong reverberation of 
 heat: then, says this philosophical traveller, the brow contracts, the cheek- 
 bones rise, the eye-lid contracts, and the lips project. Must not this contrac- 
 tion of the moveable part have influenced, in course of lime, the hard parts 
 and even moulded the structure of the bones? Voyage en Syrie et en Egypte, 
 Tom. I. p. 70, Sieme Edition. 
 
ON THE HUMAN RACE. 
 
 597 
 
 singularity, well worthy the meditation of philosophers and 
 politic ans, these laws, this worship, and these manners have 
 undergone no change, amidst the revolutions which have so 
 often taken place among those nations, many times conquered, 
 by the warlike Tartars; showing how, by the irresistible 
 ascendancy of wisdom and knowledge, ignorant and ferocious 
 conquerers have adopted the usages of the nations they had sub- 
 jugated: and proving that the stationary condition of the 
 sciences and arts among those who, so long before ourselves, 
 were in possession of the advantages of civilized society, is 
 derived not so much from the imperfection of their organiza- 
 tion, as from the degrading yoke of a religion loaded with 
 absurd practices, and which makes knowledge the exclusive 
 birthright of a privileged cast.* But such an undertaking, 
 besides exceeding the limits I have prescribed myself, does not 
 belong directly to my subject. 
 
 The Albinoes of Africa, the Cagots of the Pyrenees, and the 
 Cretins of the Valais, cannot be given as varieties of the human 
 species. They are infirm, feeble, degraded beings, incapable of 
 reproducing an existence, which has fallen to them, in the 
 midst of a healthy, vigorous, and robust population. 
 
 We are not to believe what some travellers have written on 
 the existence of tribes of Giants, that have appeared on the 
 Magellanic coasts. The Patagonians, concerning whose stature 
 there is so little agreement in relations, are men very well 
 formed, and whose stature does not exceed ours more than 
 nine or ten inches. The Laplanders, whose stature is the 
 smallest, are as much below, as the Patagonians are above; it 
 does not exceed from four feet to four and a half. In the midst of 
 ourselves, individuals reach from time to time, a stature suffi- 
 cient to intitle them to the name of giants, whilst others, shrunk 
 in all their proportions, are a renewal of the pygmies. Such was 
 Bebe, the dwarf of Stanislaus, king of Poland; Goliah, spoken 
 
 • See, concerning the religion of the Bramins, and the Indian customs, 
 Raynal’s Philosophical History. We must assign further as a main cause of the 
 want of progress of the Indians and Chinese, in the arts and sciences sprung 
 from civilization, the imperfection of their alpjiabet, which, being composed 
 of a multitude of characters, wdrich do not, like ours, represent sounds, but 
 ideas. It is no part of my object to show how much signs so defective must 
 confine the sphere and fetter the combinations of the mind. 
 
ON THE HUMAN nACB. 
 
 598 
 
 of in the Book of Kings, Ch. xvii. v. 4. the King Og, Deut. 
 Ch. iii. V. 2. and many others, whose stature varies from six to 
 ten feet high. 4 
 
 CCXXXVIII. Of old age and decrepitude. The human body 
 which, from the twentieth year of life, ceases to grow in height, 
 increases in every other dimension, during the twenty suceeuing 
 years. After this period, far from growing, it begins to decay, 
 and loses daily a part of its strength. The decay proceeds at 
 the same rate as the growth, and is not more rapid, since man 
 requires from thirty to forty years in reaching to his full growth, 
 and takes about the same time in his progress to the grave, 
 provided no accident hurries him to an untimely end.* The 
 whole bulk of the body diminishes, the cellular tissue becomes 
 collapsed, and the skin wrinkled, especially that of the forehead 
 and face. The hairs of the head and over the rest of the body 
 turn gray, then white; the organic action becomes languid; the 
 fluids become more disposed to putrefaction (Hunter); hence, 
 at this period of life, all diseases of debility are more frequent, 
 and attended with greater danger. 
 
 Decay succeeds old age. The sensibility of the organs is 
 blunted; the physical and intellectual faculties undergo a gra- 
 dual decay; man ceases to be impressed, in the same manner, 
 by surrounding bodies His judgments are incorrect, because 
 self-love preventing him from being aware of the changes which 
 he has undergone, he is more disposed to ascribe to an univer- 
 sal degeneracy, the difference which exists between the sensa- 
 tions which he now experiences, and those which he experienced 
 in his youth (laudator temporis acti). The digestion is bad, the 
 pulse weak and slow; absorption difficult, from the almost com- 
 plete obliteration of the lymphatics and the induration of the 
 conglobate glands; the secretion languid and nutrition imper- 
 fect. The old man is slow in all his actions, and stiff in all his 
 motions; his hair falls off, his teeth drop from their sockets; the 
 cartilages ossify; the bones grow irregularly and become anchy- 
 
 * The duration of life may be estimated by that of the growth. A dog 
 ceases to grow, at the end of two or tliree years, and lives only ten or twelve; 
 Man, whose growth requires a space of from twenty to thirty years, attains 
 to the age of ninety or a hundred. Fishes live several centuries, their develop- 
 TT\Cnt requiring a considerable number of years. 
 
ON OLD AGE. 
 
 599 
 
 losed, their internal cavity enlarges; all the organs become indu- 
 rated, and the fibres dried and shrivelled. The bones become 
 heavier, from the gradual accumulation of phosphate of lime, 
 and if those of the skull, as is justly observed by Scemmering, 
 on the contrary, become lighter, it is that they are, in a manner 
 worn out, by the continued motions of the brain, on their inter- 
 nal surface. 
 
 The ossification of some of the cartilages, for example, of 
 those of- the ribs and vertebrae, is productive of remarkable ef- 
 fects. The ribs becoming soldered, in a manner, to the sternum, 
 perform very imperfectly, their natural motion of elevation and 
 V twisting, (LXXI) which produces the enlargement of the chest. 
 This cavity dilating less fully, the pulmonary combinations, 
 which are the abundant sources of animal heat, take place in a 
 less effectual manner, which, joined to a want of tone and ener- 
 gy in the lungs, and in all the organs, lowers the temperature 
 of old people, as was observed by the father of physic,* a cir- 
 cumstance, however, which has been denied by Dehaen. 
 
 Those fibro-cartilaginous laminse, with oblique fibres crossing 
 each other, which unite, so firmly, the bodies of the vertebrae, 
 become indurated, dried and shrivelled, sink under the weight 
 of the body, and do not recover their former thickness, so that 
 the stature is really reduced; besides, the weakened condition 
 of the muscles, which raise the trunk, makes the weight of the 
 viscera bend forward the vertebral column, whose different parts 
 may remain fixed in this attitude, so that the whole column, 
 consisting of twenty-four vertebrae, may come to consist of only 
 seven or eight distinct bones. It should not be imagined, how- 
 ever, that all the soft parts become more compact, for several, 
 as Haller observes, the muscles, for instance, become softer,! 
 and seem, in losing a part of their vital properties, to draw 
 towards a speedy dissolution; not that death is entirely owing 
 to the accumulation of phosphate of lime, which enters into the 
 composition of all the organs, converts into ossific matter the 
 
 * Senibus autem modicus est calor * * » * frigidum est enlm ipsorum cor- 
 pus. — Hippocr. Aph. 14, Sect. 2. 
 
 ! Non ergo in sola rigiditate causam send mortis oportet ponere; nam ex 
 defectu irritabilitatis, plurimi in senibus musculi languent, mollesque pendent 
 — Elementa Physiol, tom. VIII. 4‘^. lib. 30. 
 
ON OLD AGE. 
 
 600 
 
 whole osseous system, and interrupts the action of the animal 
 machine. If this ossific matter invade every part of the animal 
 system, it is because the digestive powers, gradually weal^ed, 
 cease to affect, in a suitable manner, the alimentary substances. 
 The exuberance of calcareous salts is, therefore, not so much 
 the cause as the effect of the successive destruction of the vital 
 powers. 
 
 The slowness, the rigidity, and the difficulty of moving do 
 not depend so much, as is thought, on the induration of the 
 ligaments and other fibrous organs; these ligaments become 
 softened and relaxed, to a considerable degree, so that luxatiou 
 is more easily performed, after death, in old people. In them, 
 likewise, organs, which, in youth, have a degree of consistency, 
 become flaccid and soft; this is the case with the heart, which 
 becomes collapsed in old people, its cavities remaining entire, 
 while, in young persons and in adults, their parietes are not in 
 close contact. 
 
 The brain becomes harder and firmer, less soluble in alkalies; 
 its albumen appears less completely oxydized than in younger 
 subjects: impressions are less easily made, and the motions ne- 
 cessary to the operations of the understanding are performed 
 with difficulty. Hence, in decrepitude, man returns, as far as 
 relates to his intellectual faculties, to a state of second child- 
 hood, limited to certain recollections which are at first confused, 
 and, in the end, completely lost, incapable of judgment or will, 
 or of new impressions; sleep resumes its influence; reduced to 
 a mere vegetative existence, he sleeps the greatest part of the 
 day, and wakens only to satisfy his physical wants, and to take 
 food, which he digests very imperfectly. For, in the first place, 
 the want of teeth prevents his being able to divide sufficiendy 
 the different substances, and, in the next place, the supply of 
 saliva, of gastric and intestinal juices is almost interrupted; the 
 bile and other fluids are less active, and the intestinal tube is 
 without energy. Universal rigidity will be admitted as one of 
 the principal causes of death, if it be considered that women, in 
 whom the organs are naturally softer, are longer in reaching 
 that state, are more retentive of life than men, and, generally, 
 live to a greater age. 
 
ON DEATH. 
 
 601 
 
 The body, therefore, dies slowly and by degrees, says the 
 eloquent M. De BufFon; life gradually becomes extinguished, 
 and death is but the last term of this series of degrees, the last 
 shade (nuance) of life. 
 
 CCXXXIX. Of death. Long, in fact, before the close of life, 
 man loses the power of reproduction; and, in the course of the 
 agony which serves as a passage betvveen life and death, the 
 organs of sense first become insensible to all sorts of impres- 
 sions; the eyes grow dim, the cornea fades, the eye-lids close, 
 the voice becomes extinct, the limbs and the trunk motionless; 
 yet the circulation and respiration continue to be carried on, 
 but at last cease, first in the vessels furthest from the heart; and 
 then, gradually, in the vessels nearest that organ. Respiration, 
 gradually slackened, being entirely suspended after a strong ex- 
 piration,* the lungs no longer transmit the blood which the 
 veins bring, from every quarter, to the heart. This fluid stag- 
 nates in the right cavities of the heart, and these die last, (w/ti- 
 mum moriens) and distended bj' the blood which collects withia 
 them, they attain a capacity exceeding greatly that of the left 
 cavities, which are, to a certain degree, emptied. 
 
 Such is the course of natural death; the brain ceases to'receive 
 from the weakened heart, a sufficient quantity of blood to keep 
 up sensibility; there remains still some degree of contractility 
 in the respiratory muscles; it is soon exhausted, however, and 
 the circulatory motion of the blood ceases with the life of all 
 the organs, of which this fluid is one of the principal movers. 
 
 As to accidental death, it is always determined by the cessa- 
 tion of the action of the heart and brain; for, the death of the 
 lungs occasions that of the whole body, only by preventing the 
 action of the heart, by interrupting its influence on the encepha- 
 lic organ. In natural death, therefore, life becomes extinguished 
 from the circumference to the centre; in accidental death, on 
 the contrary, the centre is affected before the extremities. 
 
 Bichat, in his work entitled, Recherches sur la vie et la mort^ 
 has given a very complete account of the manner in which the 
 
 • Does this last and powerful expiration, often attended by sighing, depend 
 on the spasmodic contraction of the muscles of expiration; or ratlier does it 
 not depend on the re-action of the elastic parts which form the chest, a re- 
 action which suddenly ceases to be counter-balance^ by the vital properties. 
 
 4 G 
 
ON DEATH. 
 
 602 
 
 organs of the animal economy cease to act in articulo mortis; 
 but like all the other authors who went before him, he has 
 limited his inquiries to certain functions. No one has attempted 
 to extend them to the phenomena of the action of the brain, nor 
 has any one traced the order in which the various faculties of 
 thought and of sensation vanish. I shall endeavour faithfully to 
 mention the results of several hundred observations of my own 
 on this subject. 
 
 The close of life is marked by phenomena similar to those 
 with which it began. The circulation first manifested itself, and 
 ceases last. The right auricle is the part first seen to pulsate in 
 the embryo, and, in death, is the last to retain its motion. The 
 phenomena of nutrition to which the foetal existence is almost 
 entirely limited, continue, even when the organs destined to 
 establish a relation with the beings that surround us, have long 
 been sunk into a slumber from which they are never to be 
 rouzed. 
 
 The following is the order in which the intellectual faculties 
 cease and are decomposed.* Reason, the exclusive attribute of 
 man, first forsakes him. He begins by losing the faculty of 
 associating judgments, and then of comparing, of bringing to- 
 gether, and of connecting a number of ideas, so as to judge of 
 their relations. The patient is then said to have lost his con- 
 sciousness, or to be delirious. This delirium has, generally, for 
 its subject, the ideas that are most familiar to the patient, and 
 his prevailing passion is easily recognized. The miser talks, in 
 the most indiscreet manner, of his hidden treasures; the unbe- 
 liever dies haunted by religious apprehensions. Sweet recollec- 
 tions of a distant native land, then it is that ye return with your 
 all powerful energy and delight! 
 
 After reasoning and judgment, the faculty of associating 
 ideas is next completely destroyed. The same occurs in faint- 
 ing, as I once experienced in myself; I was conversing with 
 one of my friends, when I experienced an insuperable difficulty 
 
 * I need not inform the reader, that I am not liere speaking of the immor- 
 tal soul, of that divine emanation which outlives matter, and which, freed 
 from our perishable part, retu”ns to the Alinighty. I am speaking merely of 
 the intellectual fatuities common to man, and to those animals which, like him, 
 are provided witli a brain. 
 
OK DEATH. 
 
 693 
 
 -in associating two ideas, from the comparison of which I wished 
 to form a judgment. Yet syncope was not complete, I still pre- 
 served memory and the faculty of feeling. I could distinctly 
 hear those about me say, he is fainting, and exert themselves 
 to relieve me from this* condition, which was not without en- 
 joyment. 
 
 The memory then fails. The patient who, during the early 
 part of his delirium, recognized the persons about him, no 
 longer knows his nearest and most intimate friends. 
 
 At last, he ceases to feel, but his senses vanish in succession 
 and in a determinate order; the taste and smell cease to give 
 any sign of existence; the eyes become obscured by a dark and 
 gloomy cloud; the ear is yet sensible to sound and noise, and 
 no doubt, it was, on this account, that the ancients, to ascertain 
 that death had really taken place, were in the habit of calling 
 loudly to the deceased. 
 
 A dying man, though no longer capable of smelling, tasting, 
 hearing, and seeing, still retains the sense of touch; he tosses 
 about in his bed, moves his arms in various directions, and is 
 perpetually changing his posture; he performs, as was already 
 said, motions similar to those of the foetus within the mother’s 
 womb. 
 
 eeXL. Of the period of death. This period is nearly the 
 same with all men, whether they live near the poles, or under 
 the equator, whether they live exclusively on animal or vegetable 
 substances, whether they lead an active life, or consume their 
 existence in disgraceful sloth: few live beyond a hundred years. 
 There are, however, cases of men who have lived far beyond 
 that period; as, for example, those men mentioned in the phi- 
 losophical transactions, one of whom lived to a hundred and 
 sixty-five. 
 
 Few men, however, attain a hundred years; and death, even 
 when natural, overtakes us from the age of seventy-five to a 
 hundred. 
 
 Difference of climate though producing no difference in the ' 
 duration of life, has, however, a remarkable influence on rapi- 
 dity of growth. Puberty, manhood, and old age, come on much 
 sooner in warm climates, than in northern countries; but this 
 premature development which shortens the duration of the. 
 
ON DEATH. 
 
 604 
 
 periods of life, augments, in the same proportion, that of old 
 age. 
 
 It is, however, difficult to say, at what precise period old 
 age begins. Is it towards the fortieth year, when the body 
 begins to decrease and to decay? Can the change of the colour 
 of the hair be considered as the certain sign of old age? We 
 daily see young men with gray hair. May we determine its ac- 
 cession, by the cessation of the functions of generation and 
 the incapacity of reproduction? Fecundity, whose term is so 
 easily determined in woman by the cessation of the menses, is, 
 in m :,n, ve-y equivocal; the emission of seminal fluid is an 
 uncertain sign, from the difficulty of distinguishing the mucus 
 of the vesiculse seminales and of the prostate, from the truly 
 prolific semen. Erection is likewise a sign not to be relied 
 upon; this state may be occasioned by sympathetic irritation, 
 by the compression of the bladder, distended with urine, on 
 the vesiculae seminales. It is more difficult than is imagined, to 
 determine, from observation, the period at which, in the human 
 species, the male is entirely deprived of the power of genera- 
 tion; and it may be said that, in establishing the period of from 
 forty-five to fifty-five, as the beginning of old age in our climate, 
 there will be found men arrived at that state, before having 
 reached that age; as, on the other hand, others will be found 
 after the age of fifty-five, with all the characters of manhood. 
 The climacterical period of sixty-three is the decided and con- 
 firmed period of old age. Whatever regimen may have been 
 followed, man, at that age, is truly old and cannot but be aware 
 of it. 
 
 CCXLI. Of the probabilities of human life. Man dies at all 
 ages; and if the duration of his life surpass that of the lower 
 animals, the great number of diseases to which he is liable, ren- 
 ders it much more uncertain, and is the cause why a much 
 smaller number arrive at the natural term of existence. It has 
 been attempted to discover what are the probabilities of life, 
 that is, to ascertain, from observation, how long a man may 
 expect to live, who has already reached a determinate age. 
 From late accurate observations of the age at which a number 
 of persons have died, and from a comparison of the deaths 
 with the births, it has been ascertained, that about one fourth 
 of the children that are born, die within the first eleven months 
 
ON DEATH. 
 
 605 
 
 of life; one third before twenty-three months; and one half 
 before they reach the eightn year. Two thirds of mankind die 
 before the thirty-ninth year, and three fourths before the fifty- 
 first; so that as Buffon observes, of nine children that are born, 
 only one arrives at the age of seventy-three; of thirty, only one 
 lives to the age of eighty; while out of two hundred and ninety 
 one, only one lives to the age of ninety; and in the last place, 
 out of eleven thousand nine hundred and ninetv-six, only one 
 drags on a languid existence to the age of a hundred years. 
 
 The mean term of life is, according to the same author, eight 
 years, in a new-born child. As the child grows older, his exis- 
 tence becomes more secure, and after the first year, he may 
 reasonably be expected to live to the age of thirty-three. Life 
 becomes gradually firmer up to the age of seven, when the child 
 after going through the dangers of dentition, will probably live 
 forty-two years and three months. After this period, the sura 
 of probabilities which had gradually increased, undergoes a 
 progressive decrease; so that a child of fourteen cannot expect 
 to live beyond thirty-seven years and five months; a man of 
 thirty, twenty-eight years more; and, in the last place, a man 
 of eighty-four, one year only. From the eighty-fifth to the nine- 
 tieth year, probabilities remain stationary, but after this period, 
 existence is most precarious and is painfully carried on to the 
 end. Such is the result of observation, and of calculations on 
 the different degrees of probability of human life, by Halley, 
 Graunt, Kersboom, Wargentin, Simson, Deparcieux, Dupre 
 de St. Maur, Buffon, d’Alembert, Barthez, and M. Mourgues, 
 who has just published his observations, collected at Montpellier 
 in the course of a great number of years, and with the most 
 scrupulous accuracy. 
 
 I should enter more fully into this subject, but that it belongs 
 more to the department of political economy than to that of 
 physiology. 
 
 The calculations on the probabilities of human life, present 
 results applicable to the generality of cases, since the mean dura- 
 tion of existence is nearly the same with all men, in all countries 
 and climates.* The shepherd of the Pyrenees, who lives happy 
 
 * The researches of Sir John Sinclair do not disprove this statement, though 
 this autlior adheres faithfully to the practice generally adopted by his couiiuy- 
 inen, of speaking most favourably of England and Scotland. The statistical 
 
ON DEATH. 
 
 606 
 
 is the innocence of a pastoral life, breathing the pure air of his 
 mountains, is, in this respect, subject to the same laws as the 
 inhabitant of populous cities, exposed to the inconveniences at- 
 tending numerous collections of men; inconveniences, which 
 viewed in a philosophical point of view, or which greatly over- 
 rated, have so often furnished a text to the meditations of 
 philosophy, and to the idle declamations of oratory. 
 
 Does life experience a progressive diminution, in proportion 
 to the duration of the world, and to say nothing of the time 
 preceding the flood, when, according to the book of Genesis, 
 men lived several hundred years, did the men of former times 
 live longer than those of our own? This is very improbable; 
 4imong the Egyptians, the Hebrews, the Greeks, and Romans, 
 there were ver)’ few instances of persons living to the age of a 
 hundred years, and instances of longevity are perhaps more fre- 
 quent among the moderns. 
 
 The art of providing for the wants of life, making daily 
 progress, it is very probable, that far from being shortened, the 
 term of human life may be lengthened a certain number of 
 years beyond its ordinary duration. This idea is, it is true, con- 
 trary to the commonly received opinion of the progressive de- 
 pravity of mankind in all ages; but the golden age never exist- 
 ed, but in the imagination of poets; and the daily complaints of 
 morose old age have their origin in motives easily understood 
 by the physiologist. He whose sentiment is blunted by a long 
 course of years, is affected, in a very different manner, by sur- 
 rounding objects. As to the old man, flowers have lost their 
 scent and beauty, fruits no longer retain their flavour. The 
 whole of nature seems dull and colourless. But the cause of all 
 these changes is within himself, every thing else remains as it 
 was. Always equally fruitful, nature exposes every thing to the 
 action of her inexhaustible crucible; maintains every thing in a 
 state of everlasting youth, and preserves a freshness ever re- 
 newed. Individuals die, species are renovated; life every where 
 arises in the midst of death. The materials of organized bodies, 
 enter into new combinations and serve in forming new beings, 
 ^hen life ceasing to animate those to which they belonged, 
 putrefaction seizes upon them, and effects their destruction. 
 
 tables published in difFerent parts of Europe, show that the number of people 
 who reach the aje of a hundred is equally great there. 
 
ON PUTREFACTION. 
 
 607 
 
 CCXLII. Of putrefaction. Here the history of life ought to 
 terminate; if, however, it be considered that the changes which 
 bodies experience after death, throw a considerable light on its 
 means, its ends, and its nature, there will be an obvious neces- 
 sity for shortly inquiring into the different phenomena which 
 accompany the decomposition of animal substances. And this 
 investigation appears to me to belong to the department of phy- 
 siology, until the aspect of the body ceases to recal the idea of 
 its former state, and until the last lineaments of organization are 
 completely effaced. As soon as life forsakes our organs, they 
 become subject to the laws of physics, operating on substances 
 that are not organized. An inward motion takes place within 
 their substance, and their molecules have the greater tendency 
 to become separated from one another, as their composition is 
 more advanced. Chemistry informs us that the tendency to de- 
 composition of bodies is in direct ratio to the number of their 
 elements, and that a dead animal body is capable of remaining 
 unchanged, in proportion as its composition is more simple, and 
 its constituent principles less numerous and less volatile. 
 
 Before putrefaction can come on in the human body, it must 
 be entirely deprived of life, for the vital powers are most 
 powerfully antisepic, and one might say that life is a continual 
 struggle against the laws of physics and chemistry. This vital 
 resistance, alluded to by the ancients when they said, that the 
 laws of the microcosm were in perpetual opposition to those of 
 the universal world, and that these in the end prevailed; this 
 power which is in a state of perpetual re-action, manifests 
 itself in life: the latter, considering only the results, might, 
 therefore, be defined as follows: the resistance opposed by or- 
 ganic bodies to the causes incessantly tending to their destruction. 
 By attending to all these phenomena, it will be seen that all of 
 them tend to one end, the preservation of the bod}', and that 
 they obtain it, only by keeping up a perpetual struggle with 
 the laws which govern inorganic substances. 
 
 It might appear singular, that death should furnish a just 
 idea of life, did we not know, that it is by comparing that we 
 are enabled lo distinguish, to judge, and to arrive at knowledge. 
 
 Putrefaction takes place and is completed, only in substances 
 deprived of life. A mortified limb loses its vitality before putre- 
 faction com^s on, and if nature preserve sufficient energy to re- 
 
ON PUTREFACTION. 
 
 608 
 
 sist this destructive process, she draws, by a line of inflammation, 
 the separation between the dead and the living part. Life and 
 putrefaction are, therefore, two absolutely contradictory ideas; 
 and when, in some diseases, there is observed a tendency in the 
 solids and fluids to spontaneous decomposition, this tendency 
 to putrefaction should not be mistaken for putrefaction itself. 
 
 Several conditions. are required to enable putrefaction to 
 affect the human body after death. In the first place, a mild 
 temperature, that is, above ten degrees of Reaumur’s thermo- 
 meter; in the next place a certain degree of moisture, and, 
 lastly, the presence of air. This last condition, however, is not 
 so necessary as the two former, since substances undergo 
 putrefaction, in a vacuum, though more slowly. The air conse- 
 quently promotes decomposition, only by carrying oflF the ele- 
 ments which rise in vapours. On the other hand, an icy cold, 
 or a degree of heat approaching to boiling, prevent it; the 
 former, by condensing the parts; the second, by depriving them 
 of moisture, the complete absence of which, accounts lor the 
 preservation of the Egyptian mummies. 
 
 The phenomena of putrefaction, resulting from a series of pe- 
 culiar attractions, are modified in various waj's, according to the 
 nature of the animal substances which are subjected to it,' to 
 the media in which it takes place, to the different degrees of 
 moisture and temperature, and even according to its different 
 periods. Notwithstanding these innumerable varieties, one may 
 say, that all exhale a certain cadaverous smell, are softened, 
 increase in bulk, acquire heat, change colour, assume a green- 
 ish, then a livid and dark brown colour; there at the same time 
 disengaged, a great number of gaseous substances, of which 
 ammonia is the most remarkable, either from its quantity, or 
 from being given out by animal substances, from the moment 
 when decomposition begins, to the period of the most complete 
 dissolution. This gas produces the pungent and putrid smell 
 which exhales from dead bodies. 
 
 Towards the termination of putrefaction, there is disengaged 
 carbonic acid gas, which combining with ammonia, forms a fixed 
 ^nd crystallizable salt. Besides these products, there are given 
 out sulphuretted and phosphuretted hydrogen, or combined with 
 azote, carbonic acid, and all the substances that may be produced 
 
ON PUTREFACTION. 
 
 6Q9 
 
 by their respective combinations. In the last place, animal sub- 
 stances, when reduced to a residue containing oils and salts of 
 different kinds, form a mould, from which plants draw the prin- 
 ciples of a luxuriant and vigorous vegetation. The bones, those 
 least alterable parts of the organized machine, in time, become 
 dried by the slow combustion of their fibrous part, and by the 
 evaporation of their medullary juices. At last, reduced to an 
 earthy skeleton, they crumble into dust, and this dust is dissi- 
 pated, on opening the tombs in which they were laid. 
 
 Thus, in course of time, is effaced all that could recal the idea 
 of our physical existence. 
 
 Putrefaction, considered in a philosophical point of view, is 
 but a means employed by nature, to restore our organs, deprived 
 of life, to a more simple composition, in order that their ele- 
 ments may be applied to new creations. (Circulus oeterni motics,*') 
 Nothing, therefore, is better proved, than the metempsychosis of 
 matter;! which warrants the belief that this religious dogma, like 
 most of the fabulous worships and imaginations of antiquity, is 
 but a veil ingeniously thrown by philosophy, between nature and 
 the ignorant. i 
 
 * Beecher, Physica subterranea. 
 
 f Matter is eternal, in this sense, that the molecules of bodies merely pas^ 
 from the one into the other; they survive the destruction, or rather the disso- 
 lution of organic and inorganic beings, when the former, ceasing to live, re- 
 store to the inexhaustible fund of nature, those elements which she lends 
 witfiput ever parting with tlienj. 
 
 Mancipio nulli datur, omnibus usu. 
 
 Lucret. lib. III. 
 
 FINIS. 
 
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ANALYTICAL INDEX. 
 
 Preface — P reliminary discourse. Physiology— the ScicRce 
 of Life. Definition of life. 
 
 § I. Of Natural Beings. 
 
 They are inorganic or organized — The former are simple or 
 complex; the latter always complex, and distinguished into 
 vegetable and animal. Reciprocal dependance of all these be- 
 ings, 2. 
 
 § II. Of the Elements of Bodies. 
 
 The elements of Bodies. Their number forty-four; but it is 
 probable that several appear to us simple, from the imperfection 
 of our means of analysis, 3. 
 
 § III. Differences between Organized and Inorganized Bodies. 
 
 Differences between organized and inorganized bodies, 4. 
 Homogeneousness of the latter; complex nature of the former; 
 necessary co-existence of fluids and solids in all organized and 
 living beings; simplicity of inanimate matter; complex nature 
 and tendency to decomposition of organized bodies, 5. 
 
 § IV. Differences between Animals and Plants. 
 
 Differences between animals and plants, 8. The great distance 
 between the mineral and vegetable kingdom. A considerable 
 approximation, on the contrary, between animals and plants, 9. 
 Of all the characters which mark the differences between these 
 substances, the most remarkable is the presence of an alimen- 
 tary tube, which is found in every animal from man down to the 
 polypus, 9. In all animals, nutrition is performed by two sur- 
 faces, especially by the internal; the alimentary canal is the most 
 
INDEX. 
 
 612 
 
 essential part of their body, 9. It retains life longer than any 
 other part. — Experiments disproving Haller’s opinion on this 
 subject, 11. 
 
 § V. Of Life. 
 
 Consists of a number of phenomena proportioned to the com- 
 plication of the organization, 11. Simple in plants, in which its 
 actions are limited to nutrition and reproduction, 12. Of life in 
 the polypus; this animal, consisting merely of a sentient and con- 
 tractile pulp, shaped into an alimentary cavity, 13. Of life in 
 worms, 14 — in crustaceous animals, its apparatus more perfect, 
 15. Of life in cold-blooded animals, 15. In warm-blooded animals 
 and in man, 16. General view of the human organization, 17. Of 
 the elementary fibre, 19. Dependance of life on the oxydation of 
 the blood in the lungs, and on the distribution of this vivified 
 blood, throughou^t the organs, 19. 
 
 § VI. Of the Vital Projiertiesi Sensibility and Contractility. 
 
 These two properties not possessed, in an equal degree, by all 
 living bodies, 21. Modifications of sensibility in different organs, 
 26. Observations on the contractility of serous membranes, 27. 
 Caloricity, 27. Laws of sensibility, 29. Influence of sleep, of cli- 
 mate, of the seasons, of the age, &c. on the vital properties, 
 33—35. 
 
 § VII. Of Symfiathies. 
 
 Of sympathy, 35. Diseases arising from association; Syner- 
 gies, 38. 
 
 § VIII. Of Habit. 
 
 Of habit, 40. It uniformly lessens physical sensibility — A cu- 
 rious fact showing the effects of habit, 41. Habit impairs the 
 I sensitive power but improves the judgment, 44. 
 
 § IX. Of the Vital Princi/ile. 
 
 The vital pi’inciple, not a being existing by itself, andindepenr 
 dently of the actions by which it manifests itself, 46. A perpe- 
 tual struggle in organized bodies, between the laws of the vital 
 principle and those of universal nature, 48. The vital principle 
 resists the laws of chemistry, of physics and mechanics, 48. 
 There takes place, however, in the animal economy, chemical, 
 physical and mechanical phenomena, but they are always modi-. 
 
INDEX. 
 
 613 
 
 fied by the vital principle, 48. Influence of the stature on the 
 energy of the vital powers and even on longevity, 49. Vis medi- 
 catrix naturae, 52. Theory of inflammation, 52. Analogy between 
 the turgescence of an inflamed part, and of one in a state of erec- 
 tion, as the penis, &c. 54. Indirectly tonic influence of cold, 56,. 
 
 § X. Of the System of the Great Symfiathetic J\ferves. 
 
 These nerves are to be considered as connecting the organs of 
 the functions of assimilation, as the cerebral nerves unite that of 
 the external functions, 56. They are the only nerves found in 
 several animals without vertebrae. They arise from all the verte- 
 bral nerves, from which they receive filaments, as well as from 
 the fifth and sixth cerebral pairs, 57. Ganglions of the sympa- 
 thetic nerves; the semi-lunar ganglion, the principal, 57. The 
 great sympathetics render the internal organs independent of 
 the will, 58. 
 
 § XI. Of the relations of Physiology to several other Sciences. 
 
 The relation of physiology to physics, chemistry, and mecha- 
 nics. Connexion of physiology with human and comparative ana- 
 tomy, 63, 68. Its connexion with medicine, 70. 
 
 § XII. Classification of the Vital Functions. 
 
 The best divisions of the vital functions is that which was first 
 pointed but by Aristotle, adopted by Buffbn, and completely de- 
 veloped by Grimaud, 71. Modifications of which this division is 
 susceptible; preservative functions of the individual or of the 
 species, 73. These two great divisions further divided into two 
 orders, 73. Why man is subject to more diseases than ani- 
 mals, 7 6. 
 
 Of the arrangement of this work, 79. The voice is a natural 
 connexion between the preservative functions of the individual 
 and those of the species, 80. The history of the ages and tempe- 
 raments, and of the varieties of the human species; the account 
 ®f death and putrefaction forms a separate appendix, 81. 
 
614 
 
 INDEX. 
 
 FIRST CLASS. 
 
 Functions subservient to the fireser-vation of the Individual. 
 
 , ORDER FIRST. 
 
 Functions of Assimilation, 
 
 CHAPTER I. 
 
 On Digestion. 
 
 Definition of this function) 85. General considerations on the 
 digestive apparatus, 85. Connexion between the nature of the 
 aliment and the extent of the digestive tube, 86. Of aliments, 87. 
 The nutrient principle obtained from the aliment, by our organs, 
 is always the same, 88. Of the nature of the alimentary princi- 
 ple, 88. Differences of regimen, according to the climate, 89. 
 Hunger and thirst, 91 — 94. Mastication, 95. Action of the lips, 
 of the cheeks, of the tongue, of the teeth, of the jaws, 95 — 99. 
 The salivary solution, 99. Deglutition, its mechanism, 101. De- 
 glutition of fluids and of gaseous substances, 102. Of the abdo- 
 men, 103. Of digestion in the stomach, 104. Different systems of 
 digestion; of concoction, fermentation, 106. Of putrefaction, 108. 
 Of trituration; of digestion in granivorous fowls, 109. Of mace- 
 ration, 1 10. Phenomena of rumination. 111. Of the gastric juice, 
 112. Its source, its quantity, and solvent qualities, 114 — 115. 
 Digestion chiefly consists in the solution of the aliment in this 
 fluid, 1 16. Singular case of a fistula of the stomach, 1 17. Action 
 of the stomach, 120. Functions of the pylorus, 121. Of vomiting, 
 124. Digestion in the duodenum, 125. Of the bile and its secre- 
 tory organs, 127. Circulation of the blood in the liver, 128. Uses 
 of the spleen, 130. Of the pancreas and pancreatic juice, 131. 
 Separation of the alimentary matter into two substances, the one 
 chylous, the other excrementitious, 132. Of the action in the 
 small intestines, 133. The uses of their curvatures and valvulae 
 conniventes; of the peristaltic motion, 134. Of digestion in the 
 great intestines, 135. Uses of the appendicula vermiformis of the 
 osecum. Of the evacuation ot the faeces, 136, 137. Intestinal 
 gases, 139. 
 
 Of the secretion and excretion of the urine, 140. Of the cali- 
 ber of the renal arteries, structure of the kidneys, 140, 141. 
 Action of the kidneys and ureters, 143. Accumulation of the 
 
INDEX 
 
 615 
 
 urine within the bladder, 144. In what manner it is expelled, 
 146. Physical qualities of the urine, 148. Chemical analysis of 
 this fluid, urea, 149. Its retention produces urinous fever, 150. 
 Experiments on the effects attending retention of urine by tying 
 the ureters, in living animals, 151. Urinary calculi, why most 
 frequent in cold and damp climates, 155. 
 
 CHAPTER II. 
 
 Of Absorption. 
 
 Absorption takes place, in every part of the body, both on its 
 surface and in its internal parts, 157. Absorption more or less 
 active in different circumstances, 159. Its activity is very slight 
 on the external surface, except where the skin is thin and the 
 epidermis moists 1 60. 
 
 Absorbing mouths, 163. Their mode of action, in absorption, 
 163. Of the lymphatics, 164. Their innumerable anastomoses, 
 from the union of which there is formed a mesh work enveloping 
 the whole body, 166. Pathological inferences. 
 
 Of the conglobate glands, 167. Their action, 168. Circulation 
 of the lymph, 168. Observations on cancer, 170. 
 
 Of the thoracic duct, 172. Of the physical and chemical pro- 
 perties of the lymph, 173. 
 
 CHAPTER III. 
 
 Of the Circulation. 
 
 Definition and general idea of this function, 175. Of the action 
 of the heart; uses of the peric;irdium, 176. Connexion between 
 the bulk of the heart, and strength, and courage, 177. Singular 
 case of communication between the two ventricles, 179. Struc- 
 ture of the heart, 181. Action of the heart, in circulation, 181. 
 Decurtation and pulsation of the heart, every time the ventricles 
 contract, 182 — 184. The quantity of blood which these cavities 
 send out, along the arteries, 185. 
 
 Action of the arteries, 186; their arrangement and anasto- 
 moses, 187. Of the structure of the arteries, the force and con- 
 tractility of their different coats, 188. Dilatation of the arteries, 
 194. Of the pulse and its varieties, 196. Velocity of the circula- 
 tion along the arteries. 
 
 Of the capillary vessels, 199. Those which convey a colourless 
 fluid, 199. Of the manner in which the blood flows along these 
 vessels, 200. Terminations of the arterial system, 203. 
 
INDEX. 
 
 616 
 
 Of the action of the veins, 204. Proportion of the arterial to 
 the venous blood; difference of arrangement and structuie be- 
 tween the arteries and veins, 204 — 205. Of the use of the valves 
 of the veins, 206. Gradual increase of velocity in the venous cir- 
 culation. Of the use of the vena azygos, 208. Reflux of the blood 
 in the great venous trunks, 208, 209. Theory of the circulation, 
 
 210. Partial circulations in the midst of the general circulation, 
 
 211. Of the two divisions, venous and arterial, of the circle of 
 circulation, 212. Organs situated on the two points of intersec- 
 tion of this great circle, 2 12, 2 1 3. 
 
 CHAPTER IV. 
 
 Of Resfiration. 
 
 Of all the changes which the blood undergoes, in penetrating 
 through the organs placed in the course of the circulation, the 
 most remarkable are those it receives from respiration, 214. 
 Differences of arterial and venous blood, 214. Of the atmosphere, 
 214. Action by which respiration is performed, 222. Motions of 
 the ribs, 224. Difficult respiration, 226. Structure of the lungs, 
 2'27, 228. Use of the bronchial arteries. 228 Pulmonary inflam- 
 mations, 229. Changes pn the air and on the blood by respira- 
 tion, 231, 232. Vitality of the lungs, 236. Respiration of cer- 
 tain animals, 236. Division or ligature of the eighth pair of 
 nerves, 238. 
 
 Of animal heat, 239. Animal heat is independent of the media 
 in which animated beings live, 239. The heat of the animal body 
 thirty-two degrees, 239. The lungs not the only parts in which 
 caloric is disengaged, 242. Caloric evolved, to a certain degree, 
 in all organs receiving arterial blood, 243. Cutaneous evapora- 
 tion, the most powerful means of lowering the temperature. 245. 
 It does not explain however, why the animal temperature re- 
 mains the same, in a medium hotter than the body; case of a man 
 said to be incombustible, 245, 246. Effects of cold, 247, 248. 
 
 Phenomena of the circulation of the blood through the lungs, 
 249. Pulmonary exhalation, 250. Of asphyxia, from drowning 
 and from strangulation, 252. From noxious gases and from in- 
 toxication, 254. From obstruction of the glottis; of the asphyxia 
 of new born children, 255. 
 
 Of several phenomena of respiration, as sighing, yawning, 
 sneezing, coughing, hiccup, and laughter, 256. Cutaneous per- 
 spiration, 257. Its connection with the other functions, 258. Its 
 
INDEX. 
 
 617 
 
 quantity, 259. Of the sweat; of the formation of carbonic acid 
 gas on the surface of the skin, 261. Of the uses of the cutaneous 
 perspiration, 261. 
 
 CHAPTER V. 
 
 Of the Secretions. 
 
 Classification of the animal fluids, 262. Chemical classification 
 of the fluids by Fourcroy, the best, 262. Of the blood. Of its phy- 
 sical, chemical, and vital properties, 264 — 266. Of sanguifica- 
 tion, 266. Of the effects of regimen on the blood, 268. The 
 transfusion of blood, 270. 
 
 Of the secretory apparatus, 272. Serous transudation, 273. 
 Secretion in the mucous follicles, 274. In the conglomerate 
 glands, 275. Of accidental secretions, 276. Influence of the 
 nervous energy on the secretions, 279, 280. Influence of the 
 imagination on the secretions, 285. Quantity of fluids secreted, 
 285. 
 
 Secretion of adeps within the cellular tissue, 286. Difference 
 of quantity and quality of this fluid, in the different parts of the 
 body, 286. Of the uses of adeps, 288. Circumstances which in- 
 crease or lessen its secretion, 290. Analogy of the marrow of the 
 bones to adeps, 291. Of the insensibity of the medullary mem- 
 brane, 291. 
 
 CHAPTER VI. 
 
 Of J^utrition, 
 
 Nutrition is the complement of assimilation, 292. Period of 
 the complete renovation of the body, 293. Mechanism of nutri- 
 tion; from arterial blood only, 293. Difference of vegetable and 
 animal substances, 294. New products, 295. Of the emunctories, 
 298. General view of the functions of nutrition, 299. 
 
 CHAPTER VII. 
 
 «ii 
 
 Of Sensations. 
 
 Functions that are subservient to the preservation of the indivi- 
 dual, by connecting him with surrounding beings. Of sensations, 
 303. Natural succession of the phenomena of sense, 304. 
 
 Of light and of colours, 304. Organ of sight, 306 — formed of 
 three distinct parts, 306. Use of the eye-lids, eye-lashes, and 
 lachrymal ducts, 307, 309. Eye-ball, its structure, 311. Media- 
 
INDEX. 
 
 618 
 
 nism and phenomena of vision, 315. Motions of the iris, 315. Re- 
 fraction of the rays of light by the membrane, 316, and by the 
 fluids of the eye; inversion of objects on the retina; point of dis- 
 tinct vision, 3 1 6 . Defects of vision, 318. Development of the eyes, 
 and their motions, 319. Errors of vision, 321. Its difference in 
 different animals, 322. 
 
 Organ of hearing, 323. Of sound, 324. Structure of the ear, 
 and mechanism of hearing, 325. Differences in animals, 328. 
 Defects of hearing, 329. 
 
 Of odours, 331. Organ of smell, 332. Sensation of smell, 333. 
 
 Of taste, 336. Of the tastes of different substances, organ of 
 taste, 336. In different animals, 336, 337. Uses of the nerves of 
 the tongue, 338. Galvanic experiments on this subject, 338. 
 
 Of touch, 339. Its certainty and errors, 339. Of the integu- 
 ments, 340. Of the nails, 345. Of the hair, 346. Of the hand, 350. 
 Touch in different animals, 352. 
 
 Of the nerves, 352. Of their origin in sensible parts, 353. Of 
 their structure, 353, 354. Opinion of Reil on this subject, 354. 
 Of the manner they arise from each other, 355. Of their termi- 
 nation in the brain, 355. Of their comparative size, in different 
 animals, and in man at different ages, 356, 357. 
 
 Of the coverings of the brain, 356. Mechanism of the bones of 
 the skull and face, 358. Uses of the sphenoid, 358. Rounded 
 form of the skull, 362. Uses of the dura mater, of the arachnoid, 
 and the pia mater, 362, 363. Size of the brain, 363. Form of the 
 head, 364. Connexion with the intellectual powers, 365. Nerves 
 crossing, 366. Divergent and convergent fibres, 367, 368. Cere- 
 bral circulation, 369. Arterial blood retarded, 370. Jugular veins, 
 370. Connexion of the actions of the brain and heart, 371. Theory 
 of syncope, 373. Motions of the brain, 377. Experiments, 378, 
 384. Action of the nerves and brain, 387. Principle of motion and 
 sensation, 389. Different intellectual functions of different parts 
 of the brain, 390. Not yet perfectly understood, 390. 
 
 Analysis of the understanding, 390. Perception, 391. Reason- 
 ing and instinct, 392. Generation of the faculties, 392, 393. Sen- 
 sation, perception, attention, memory, imagination, association 
 of ideas, comparison, judgment, reasoning, 394, 396. Influence 
 of signs on the faculties of thought, 397. Analysis of ideas, by 
 M. Destutt Tracy, 400. Derangements of the mind, 401. Mania, 
 402. Idiotcy, 403. 
 
 Of the passions, 407. State of the intellectual powers connect- 
 ed with them, 407. Effects on the animal economy, 408. Of sleep 
 
INDEX. 
 
 619 
 
 and waking, 409. Repose of the functions which connect us with 
 surrounding objects; condition of the functions of assimilation, 
 during sleep, 409. Proximate cause of sleep, 412. Of dreams and 
 somnambulism, 414. Animals are also subject to dreams, 415. 
 
 CHAPTER VIII. 
 
 Of Motions. 
 
 This chapter treats only of voluntary motions, whose organs 
 may be distinguished into active and passive (the bones and the 
 muscles), 417. Structure and properties of muscular fibres, 418. 
 Of the tendons and aponeuroses, 419, 420. Phenomena of mus- 
 cular contraction determined by an act of the will, 421. A sound 
 state of the nerves, arteries, and veins belonging to a muscle, is 
 necessary to its action, 42 1 . Theory of this action, 422. Prepon- 
 derance of the flexor muscles over the extensors, 423. This pre- 
 ponderance varies, according to the age, the state of health or 
 disease, 425. Of the power of the muscles; it bears a proportion 
 to the number of their fibres, 428. The degree of decurtation 
 of which they are capable is proportioned to the length of their 
 fibres, 429. Direction of the motions performed by the action of 
 the muscles, 429, 430. Of muscular flesh, 433. Galvanism, 434. 
 Volta’s apparatus or galvanic pile, 439. Effects of galvanism, in 
 the treatment of disease, 442. General view of the osseous sys- 
 tem, 444. Of the vertebral column; it forms the most essential 
 part of the skeleton, 444. Difference of the stature, at different 
 times of the day, 446. Of the lower limbs, 447. Structure of the 
 bones, 448. Uses of the periosteum, and of the marrow, 451. 
 Theory of necrosis, 451, 452. Of the articulations, 453. Of the 
 articulating cartilages, 454. Of the synovia, 454. Theory of an- 
 chylosis, 455. 
 
 Of animal mechanics; of standing, 457. Of the centre of gra- 
 vity, 457. Tendency of the body to fall, 458. Standing is per- 
 formed by an effort of the extensor muscles, 459. Reasons why 
 it is impossible for a new born child to stand, 461. Man is the 
 only animal that can stand upright, 464. Of falls, 468. Of stand- 
 ing on one foot, 469. A degree of separation of the feet necessary 
 in standing, 469. Of kneeling; of sitting; of the recumbent pos- 
 ture, 470. Of lying ©n the sides, 471. Of the prone and supine 
 postures, 472, 473. The different modes of the recumbent pos- 
 ture have a reference to the degrees of facility of respiration and 
 to the period of life, 473, 474. Recumbent posture, on an inclined 
 
INDEX. 
 
 620 
 
 plane, necessary, especially to old people, 474. Of motions of 
 progression; of walking, 475. Of walking up or down an inclined 
 surface, 477. Mechanism of the articulation between the leg and 
 foot, 478. Of running, 480. Of leaping, 482. Leaping is per- 
 formed by the sudden extension of the lower extremities, pre- 
 viously in a state of flexion, 482. Of the vertical and oblique leap, 
 484, 485 Of swimming; man swims with difficulty, 485. Swim- 
 ming natural and easy to fishes; its mechanism, 486. Of flying, 
 487. The structure of the body in birds favourable to this action; 
 how performed, 487, 488. Of crawling, 490. All the phenomena 
 of animal mechanics may be referred to the theory of the lever 
 of the third kind, 490. Partial motions performed by the upper 
 extremities, 492. Of climbing; of pushing, 493. Of throwing a 
 projectile, 494. Partial motions, as signs expressive of ideas, 
 496. Of gestures and attitudes, 496. 
 
 CHAPTER IX. 
 
 Of Voice and Sfieech. 
 
 Definition of the voice and of speech; circumstances necessary 
 to the formation of the voice; its organs, 497. Opinions of Fer- 
 rein and Dodart, on the uses of the glottis, 498. The larynx is, 
 at once, a wind and a stringed instrument, 499. Of the power of 
 the voice; of speech; man alone is capable of speech, 501. Of the 
 vowels and consonants, 501, 502. Of song and music, 503. Of 
 stammering, burr, and dumbness, 504. Instruction of the deaf 
 and dumb, 506. Ventriloquism, 506. 
 
 SECOND CLASS. 
 
 CHAPTER X. 
 
 Fwictions subservient to the fireservation of the S/iecies. 
 
 Differences of the sexes, 511. Case in which the sexual organs 
 did not exist, 512. Hermaphrodism is never met with in the hu- 
 man species. Man, in the exercise of the functions of generation, 
 not under the control of the seasons, 515. Of the organs of gene- 
 ration, in man, 515. Of the female organs of generation, 518. Of 
 the signs of virginity, 520. 
 
 Of erection, 521. Of the human semen, 522. Of the ovaria, 
 525. Of the impregnation of the ovum. 529. Of barrenness, 531. 
 Systems of generation, 532. Gestation, 534. Of the foetus and its 
 coverings, 539. Of the development of its organs, 540. Of the 
 
INDEX. 
 
 621 
 
 circulation of the blood, in the foetus, 542. Of the placenta, 542. 
 The umbilical cord, 545. Mode of existence of the foetus, 547. 
 Morbid affections to which it is subject while in the womb, 549. 
 Of monsters, 549. Their different kinds, and the causes which 
 produce them, 550. History of a remarkable case, 550. Of the 
 chorion, of the amnion and liquor amnii, 552. Of the allantois 
 and urachus, 553. Of the natural term of gestation, 554. Of par- 
 turition, 554. Of the mechanism of parturition, 555. Of twins, 
 
 558. The number of male children born exceeds that of female, 
 
 559. Of superfoetations, 559. Of suckling, 561. Sympathy between 
 the uterus and mammae; structure of the latter, 561, 562. The 
 milk appears to be brought to the breasts by the lymphatics, 564. 
 Chemical qualities of the milk, 566. Connexion between the new 
 born child and the mother, 568. Imperfect development of the 
 foetal lungs, 569. 
 
 CHAPTER XI. 
 
 Containing the History of the ^ges, the Temperaments^ and the 
 Varieties of the Human Species; of Death and Putrefaction. 
 
 Of infancy; of dentition, 571. Ossification, 573. Phenomena of 
 puberty, 574. Connexion between the development of the sexual 
 organs and the voice, 575. Of menstruation, 575. Of the cause 
 of menstruation, 577, 578. Of the cessation of this evacuation, 
 578. Of manhood, 579. Of temperaments and idiosyncrasies, 579. 
 Of the sanguine temperament, 580. Of the muscular or athletic 
 temperament, 582. Of the bilious temperament, produced by an 
 increased energy of the hepatic system, joined to considerable 
 activity of the sanguineous system, 583. Of the melancholic 
 temperament, 584. Lymphatic temperament, 589. Nervous, 589. 
 Mixed and acquired temperaments, 591. Influence of climate on 
 temperaments, 591. 
 
 Varieties of the human species, 593. European Arab race, 594. 
 Negro, 595. Mogul, 595. Hyperborean, 595. Moral characte- 
 ristics of the different races, 596. Giants and dwarfs, 597. 
 
 Of old age and decrepitude, 598. Decay, 598. Death, 601. 
 Gradual extinction of bodily and mental powers, in the reversed 
 order of their production, 602 Period of death, 603. Probabilities 
 of human life, 604. Putrefaction, 607. 
 
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THOMAS DOBSON 
 
 Has in press and will shortly publish, 
 
 THE 
 
 SURGICAL WORKS 
 
 OF 
 
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 Surgeon in Chief of the Great Hospital of Humanity at Paris, 
 
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 VOL. I. 
 
 On Diseases^ of the Soft Parts. 
 
 VOL. II. 
 
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 TRANSLATED FROM THE ORIGINAL, 
 
 BT 
 
 EDWARD DARRELL SMITH, M. D. 
 
 Professor of Chemistry, See. in the South Carolina College. 
 
r 
 
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