P^Sg ,f' . /*2r^ *■'*■■■-*".**■•.'- '..-'■■- ifr.-V *: / / • *j£f* Surgeon General's Offica 13 L «*« ?ffik w n^W? GC^crcr at? coo ^'^jooqct -.i*cn g< J* v**** „ * fr • 4 \ \Jjir\^^l±_ # /}/u+ OF BY A. RICHERAND, PROFESSOR OF THE FACULTY OF MEDICINE OF PARIS, SURGEON IN CHIEF OF THE HOSPITAL OF ST. LOUIS, MEMBER OF THE ACADEMIES OF TIENNA, PETEHSBURGH, MADRID, TURIN, &C. FAOMTHE FIFTHLOJYDOJVEDITION, REVISED, CORRECTED AJYD ENLARGED. WX-v/vxvw w»v\s\icra minora, 3 vol iv.< 11 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 giv^i in 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 beini is perfect in itself, each being is constructed most favorably for the purpose it is to fulfil; and all is equally admirable, in living and animated nature, from the lowest vegetation to the sublimity of thought. What does this plant present to us that springs up, and grows, and dies every year? A being whose existence is limited to the phenomena 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 tiie 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 projfcrtles direct the action of this smail 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; th stamina, or male organs, bow themselves over the female organ, the pistds, shrike on the stigma their fertilizing dust, then straighten, retire from it, and die with the flower, which is succeeded by the seed or fijtit. u This plant, divided into many parts, which are set in the •»arth with suitable precautions, is reproduced and multiplied by 12 slips, which proves that these parts are little enough dependent on each other ; that each of them contains the set of organs ne- cessary to life, and can exist alone. The different parts of a plant can live separately, because life, its simpler organs and proper- ties, 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 curious fact, which confirms what I have said.* A vine, trained against the eastern wall of a forge, shot into the building a few branches. These branches, which entered by-strait enough passages, wem covered with leaves in the middle of the hardest winters; and this premature but partial vegetation wrent 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 liquids, the contractile fibres, the tracheae, which gives 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 * Vegetable life, compared in its means and in its results, to the life of animals, .w.ould throw the greatest light on many phenomena, which it is still difficult for us to conceive and to explain. The treatment of disease in plants, for which as much would be gained by these inqui- ries, is almost entirely surgical. When, to make vegetation more fruitful, the gardener prunes a luxuria4i^,bfranch; when the peasants of the Cevennes, as M Chaptal has observed, burn the inside of their chesnut trees to stop the progress of a destructive caries; when the actual'cautery is applied to the really ichorous and foul ulcers of many trees, &c. it is to the organs of inward life (or that which carries on the process of assimilation,) the only life of vegetables, that surgery is applied; while, on the contrary, in man and animals, it is to the de- rangement of the external organs that the remedy is directed. I shall conclude this note with an observation on^he wounds of plants. Like those of the human body, they are much less da^erous when their surface is smooth, than when their edges are hacked, torn, or bruised Trees felled with the saw, will hardly shoot up from the stool, which always furnishes a better growth when an axe has been employed. * The saw lacerates the vegetable texture, and its violent and distress- ing action on the fibres, extending towards the roots, affects, more or less, the organization. The uneven surface of a tree felled in this man- ner, holds wet, as injurious to the trunk, which it rots, as#too|gireat quantity of pus, which bathes constantly the surface of a wound, checks the process ef granulation, and resists cicatrization.. 13 the.interual 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 re- sidue 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 gcmmiparous 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 fiom 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 lateral ramifications, a spinal marrow equally knotted, or compos- ed of a chain of ganglions, stigmas, and trachea?, analagous 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, 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, discovers 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 14 spinal marrow with bulgings, but, above all, a brain and a heatf. 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 im- pulses 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-blocded 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 tfsh, 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 ad<3ed to a heart, nor are less essential to life. However, the action of these chief organs is not so frequent, nor of momentary necessity for the continuance of life. The ser- pent passes long winters, torpid wjth 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 lie has intimation of whatever can affect him; muscles and hard parts, by the action of which he moves, and changes h\~ id 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 mammiferas and man. They are entirely alike, save some slight differences in the less essential organs. There is none that has not the vertebral column, four limbs, a brain which fills, exactly, the cavity of the skull, a spi- nal marrow, nerves of two sorts, five senses, muscles, partly obe- dient 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 part- ed from the body of the animal, and are in no way replaced; whatever some physiologists may have said on pretended regene? ration 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 saying, that all animals are essentially the same, and that their differences are in their external parts, and chiefly to be observed in their coverings and in their extremities. The human body, consisting of a collection of liquids and s^ids, contains of the former, about five-sixths of its weight. Tuis 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 glutaeus maximus, for exam- ple, becomes, by drying, no thicker than a sheet of paper. The liquids, which constitute the greatest weight of the body, exist before the solids: for, the embryo which is at first in a gelatinous state, may be considered as fluid; besides, it is from a liquid that all the organs receive their nourishment and repair their waste The solids, formed from the liquids, return to their former state, when, having for a sufficient length of time, formed a part of the animal, they become decomposed by the nutritive process. Even from this slight view of the subject, fluidity h seen to be essentia! to living matter, since the solids are uni- ;brmly formed from the fluids, and eventually return to their > 1(» former state. Solidity is then only a transient condition and ar: 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 easily 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 fibrine. 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 abuhdance in almost all the hu- mours; the fibrine of the blood is the cement which is employ- ed in repairing the waste of a system of organs, which, in point of bulk, hold the first rank among the constituent parts of the human body—I mean the muscular system. The chelnists sus- pect, and not without reason, that the animal matter passes successively through the different states, of gelatine, albumine and fibrins; that these different changes depend on the progres- sive animalization of the animal matter, which, at first gelati- nous, a hydro-carbonous oxide, containing no azote, and acidifia- ble by fermentation, becomes more closely combined with oxy- gen, takes up azote, so as to become albumen, subject to putre- faction, and finally fibrine, by a super-addition of the same prin- ciples. 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 systenL to a combination of parts which concur in the ^same uses, wf 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 »■ lands 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 grandular, 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 cap- sules; the vocal system, and the sexual or generative system, dif- ferent in the two sexes. Each of these organic systems contain* /" 17 m its structure several simple tissues, "or similar parts," as the ancients called them; these tissues in man, may be enumerated as follows: cellular tissue, nervous tissue, muscular tissue, besides that horny substance which constitutes the basis of the 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 snbstance 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 considerable, according to Bichat, whose happiest conception was this analysis of the human organization. This physiologist reckoned in the human eeonomy, no fewer than twenty-one general or generating tissues. But it is evident, that this analysis rs 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 seperate consideration of each organic tissue has furnished him with new ideas, ingenious ana- logies and useful results, and that his "Anatomie generale," in which those researches are contained, is his chief title to glory. That glory would be complete, if in that book, and yet more, in his other works, he had done his predecessors, as well as his con- temporaries, 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 phusiologo id r*f quod tinea gcQtnpfnr, ax qi'n nemnf 1 18 ftgurus 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, theie 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 nu- merous in man as in the other warm-blooded animals. None of them can act, unless the heart sends into the brain a certain quantity of blood, vivified by the contact of atmospherical air in the pulmonary tissue. Every serious wound of the brain or heart, every lasting interruption to the access of blood into the former of these organs, is invariably attended with death." The oxydalion of the blood, and its distribution into all the organs, is consequently the principal phenomenon, on which the life of man and of the most perfect beiugs depend. § VI 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 faiuler, 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 impression 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 reflection only, that we are induced to admit the existence of certain motions; of those, for instance, by which the humours, 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-lnn-id of a watch. The hour-hand appears motionless, and yet in twelve hours it describes the whole circumference of 19 the dial plate, round which the other hand moves in one minute, wi'h 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 poly- 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, tn- deed, and to be distinguished only by their effects. These two faculties appear to exist in the degree absolutely required for ena- bling 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 tho 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, overall 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, of such sensation, exerts motions that are easily perceptible, but over which we have no control. 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- -emblc him, obliged to keep up mul?if:irtO'i< intercourse wi'n 2'U e,very thing that surrounds them; thus they enjoy a very supe- rior kind of sensibility, by means of which tbe impressions which effect some of their organs are perceived, judged and compared. This mode of sensibility might be more properly called percepti- bility, or the faculty of accounting to oneself for the emotions which are experienced. It requires a centre to which the im- pressions 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, arc equally destitute of this faculty. The polypi, and some plants, as the sensitive, perform nevertheless certain spontaneous mo- tions, which seem to indicate the existence of volition, and con- sequently 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. TUe 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 tbe 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 faecal 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 systems of organs, very different in their uses and in their qualities, enter into the composition of the human body; ihey are as two living and united machines, the one, formed bV 2A \he 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- cretion.* The organs of generation in the two sexes form a separate class, which, as far as relates to the vital properties, partakes of the nature of the other two. By the organs of sense, and the nerves which form a 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 power, 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 Ihe 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 pro- perties, a division of the former is attended with a loss of senti- ment and voluntary motion in the parts to which they are dis- tributed. The other kind of sensibility is, on the contrary7, 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 ail essential to the life of nutrition; the bones, the arteries, the cartilages, and seve- ral other tissues, in which no nerves are seen to enter, are nour- ished equally well with the organs in which they exist in con- siderable 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; instead of that sudden, energetic and lasting decurtation which the will determines in them, they be- come 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 motiqn or of sensation: let him take his scalpej * This doctrine, which I believe originated with the celebrated Bichat, will be found more fully developed in his work, ) and dissect one of our limbs, the thigh, for instance; he will see the cords parting into numerous threads, most of wrhich disap- pear in the thickness of the muscles, whilst others, after creep- ing 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 papilla on its surface. The bones, the cartilages, the ligaments, the arte- ries, and the veins, all those parts whose action is not under the control 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 control, are yet endued with a sensibility and a contractility, which enables 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 properties, as bones, tendons, membranes, cartilages, and cellular membrane, &c. possess only that latent sensibility, and that obscure contractility, common to all living beings, and without which, it is impossible to conceive life to •xist. In a state of health, they are utterly incapable of trans. 2C6 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 entirely 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 nu- trition. 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. The solution of tartar emetic, causes no disa- greeable impression to the conjunctiva ; taken into the stomach, it excites convulsive motions, while an acid from which the sto- mach does not suffer, proves a cause of irritation to the conjunc- tiva, and brings en a violent inflammation of the eye. In the same manner, purgatives pass along the stomach, without produ- cing any effect on that viscus, but they stimulate the alimentary canal. Cantharides have a specific action on the bladder ; and mercury on the salivary glands. Each part feels, lives, moves, after its own way ; in each, the vital properties appear under such shades and modifications, that they may be looked upon as so separate members of the same family, concurring in one en- deavor, working for a common end, consentienlia 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 beings, similar to the fabulous Hamadryads, who, immoveably fixed in the trees of our forests, received, without any power to shun them, all the blows inflicted on their rustic abode. Dreams place us sometimes in situations which give us a just idea of their condition. A certain danger threatens our existence ; an enormous rock seems to detach itself, to roll and precipitate 24 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 repel it, but an irre- 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 contractibility, have remained in that, state of immobility, only for want of a stimulus fitted to their peculiar nature. Some physiologists say Chey have excited a distinct quivering, in themesentery of a frog and of a eat, 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- trusted, 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 from contraction, and the alveolar cavities disappear. These facts appear to me to prove, still belter 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 inirrifability of the serous membranes, and of 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 * The contraction of the membrane, formed by the expansion of the cremaster 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 o+" the same muscles corrugate the skin of the scrotum, when this part 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 procuring this effect. 25 t'o 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 action 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 pblar regions, as well as in the burning atmosphere of the torrid zone. It is by the exercise of sensibility and contractibility, 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 of a peculiar pro- perty to operate in producing other phenomena of no less im- portance. 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 contractibility 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 the 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 26 rery circumstance of their being endowed with life. The con- firm il 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 there- fore 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 duo- denum, from the admixture of the bile with the alimentary sub- stance, the vivificationofthe blood by respiration, the secretion of the fluids in the conglobate glands, nutrrn|n 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 perfect, according to the condition of these properties in the organs in which they occur. We have stated that there exist two great modifications of sen- sibility and contractility; that sensibility is divided into percipient sensibility and latent sensibility, that contractility is at times volun- tary, at others involuntary, and that the latter may be perceivable or insensible. Perceiving. (Cerebral, nervous, animal sensibili- ty, perceptibility.) With consciousness of impressions or perceptibili- ty; it requires a peculiar apparatus. sensibility. \ Latent. (JVutritive, organic sensibility.) Without consciousness of impressions; or, general sensibility, common to every thing that has life; it has no peculiar organ, and is found universal! v diffused in living parts, animal or vegetable. 27 J Voluntary and sentient, subordinate to pei- ceptibility. Involuntary and insensible, corresponding to latent sensibility. Tonicity. Involuntary and sentient. The cause of this last modification of contractility, appears to de- pend on tbe peculiar organization of the system of the great sym- pathetic nerves. From these nerves, the heart, the digestive ca- nal, &c. seem to receive the power of exerting sensible contrac- tion, an effect produced by the direct application 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 sick- ness, on the relative development of the lymphatic, cellular, 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 by use, re-supplied, or exhausted, equally distributed, or, occasion- ally 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, recovers its original delicacy, when the sentient organs have been long at rest. Thus, an epicure whose taste has grown dull with high living, will recover all its accuracy, if during several months, instead of spiced ragouts and 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 with- out pain. Domestic animals in that condition, are often ill treat- ed without appearing to feel what is done to them. If the hind legs of the toad are cutoff, at the time that he is holding the tv- 28 male 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 scarce- ly diverted from it by any means that can be employed. When during the influence of satyriasis, the vital power is carried to excess in the penis, patients have been known, (as we are told by Aetius,) to cut off both their testicles, without suffering the pain usually attending so severe an operation. It is by this law of sensibility, that we are to explain the observation of Hippocrates, that two parts of the body cannot be in pain at the same time. If two pains come on at once, the more violent prevents the slighter from being felt; Jlmbo partes non possunt dolere simul. Duobus doloribus, simul orientibus, vehementior obscurat alterum. (Hipp.) In cases of scrophulous swellings, the parts are observed to in- flame, to become painful, and suppuration occurs but rarely in every part at once, if the case is serious and attended with acute pain. The germ of a disease or of a slighter affection, may some- times remain dormant under a greater pain. I was once over- turned in a carriage, from the awkwardness of the coachman, the windows were broken and my wrists sprained. The right wrist, which had suffered most, swelled first; I employed the proper treatment, and when at the end of a week, the swelling and pain had almost completely ceased, and the right 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.* * John Hunter maintains from theory, the position that no two differ- ent 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 gentle- man'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 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 twemy-second, a considerable eruption appeared which was evidently the measles, and the sores on the arms appeared 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 da v. m The perfection of one sense is never obtained, but at the ex- pense 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 impres- sions of harmony. Fifthly. During sound sleep, the exercise of the percipient faculty, and that of voluntary contractility, are entirely suspended. During that state, it seems as if some covering were thrown over the sentient extremities. We know how hard the hearing becomes, how dull the senses of smell and taste become, how dim the sight, a cloud spreading before the eyes, the moment we are falling asleep. Vir quidam exquisitissima sensibilitate praiditus, §emi con- sopitus coibat; huic ut si velamento levi glans obduclus fuisset, sen- sus voluptatis referebatur. Sixthly. Sensibility is more lively, and more easily excited, in the inhabitants of warm climates, than in those of northern re- gions. What a prodigious difference there is, in that respect, be- tween the native of Germany and of the southern provinces of France. Travellers tell us, that there are in the neighbourhood of the poles, natives, so little endowed with sensibility, that they feel no pain from the deepest wounds. The inhabitants 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, without feeling the slightest uneasiness. On the contrary, the slightest prick from a thorn, for instance, in the foot, is in the strongest African, frequently followed by convul- sions and locked jaw. The impression of the air, is alone suffi- cient 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 birlh. " On the twenty-fifth, the measles began to disappear, on the twen- ty-sixth and twenty-seventh, the punctures began again to look a lit- tle 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 ■ourse, and terminated :V.\ ovvably." T. Hunter en Inflammation, p. 5, 30 Montesquieu* very justly observed this difference which exists in the sensibility of the southern and northern nations, and he says of the latter, that u if you would tickle you must flay them." 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 difficulty near the icy polar regions, unless the powerful influence of climate be counteracted by well directed moral and physical causes. Man is, of all beings, the one that most powerfully resists the influence of external causes; and although the influence of climate is sufficient to modify 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 cli- mate. Man is every where indigenous, and exists in all climates; wiiile the plants and animals of the equator languish and die whf n conveyed to the polar regions. From the flexibility of his nature, man enjoys the power of adapting himself to the most op-, posite situations, of establishing, between them and himself, re- lations 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 determines that of certain derangements, to which the animal economy is subject. The same diseases manifest them- selves under the influence of the same temperature, and, to use an ingenious comparison, resemole those birds of passage which visit us at slated seasons of tbe year. Thus, hemorrhages and eruptive affections come on with the return of the spring, sum- mer 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 * This philosopher has| borrowed from the father of physic, one of his most brilliant and paradoxical opinions In his conception, warm climates are the seat of despotism, and the cold, the seat of liberty This error is completely refuted in the profound and philosophical work of Volney on Egypt and Syria. He shows, that what Montesquieu has said of cold climates, applies to mountainous regions, while a champaign is more favourable to the establishment of tyranny. Hip- pocrates had said of the Asiatics, that their being less warlike than the Europeans, depended on the difference of climate, and likewise on the despotic form of their government. And he observes, that men who do not enjoy their natural rights, but whose affections are controlled bv masters, cannot feel the bold passion of war. See chap. XI. on the Varieties of the Human Species. ai body, does not show itself merely in occasioning epidemic dis- eases, the consideration of which leads to the establishing 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 to- wards the end of autumn, when the trees are shedding their leaves, the increase of growth is particularly 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 sensibility seems to decrease, in proportion as it has contributed to the develop- ment of the acts of life; and the power of being impressed by external objects, diminishes gradually with age, so that there is a period.of decrepid old age, at which death appears a necessary consequence of the complete exhaustion of that principle. In short, as I have said in describing the progress of death, at its approach, sensibility shows increase of activity and liveliness, as if its quantity required to be completely exhausted, before the termination of existence, or as if the organs made a last effort to oling to life. The development of the cellular and adipose substance, di- minishes the energy of sensibility; the extremities of the ucrves being more covered, and therefore not so immediately applied to the objects, the impressions which are felt, are more obscure. The fat op< rates on the nerves, as wool would do on vibrating chords, if wrapped round them, to fix them, to prevent their quiverings, and slop their vibrations. Very nervous women are very thin; persons of much sensibility have seldom much embonpoint. Sw>ne, in which the nerves are covered by a thick layer of fat, are the most insensible of all ani- mals. The susceptibility of the nerves may be diminished, and their sensibility blunted by pressure. The application of a ban- dage firmly rolled round the body and limbs of an hysterical wo- mf their activity, he. 68 of the functions into internal, which he likewise calls digcstive4 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- struments are solely employed on internal life or nutrition (JVlotus assimilationis. Bacon; hlas 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 them- selves, 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. 1 have, therefore, thought it right to include under two ge- neral 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 hu- man species would soon perish, from a loss of the power of re- production. In laying down these two great divisions, I have merely considered the object and end wrhich each function has to fulfil. Among the functions which are employed in the pre- servation of the individual, some fulfil this office by assimila- ting 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 require the concourse of two sexes; they constitute gene- ration properly 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 action of the digestive organs, which separate its nutri- tive 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 69 the secretory glands supply it with certain elements, and de- prive it of others, alter, modify, and animalize it; in fine, nu- trition, which may be considered as the complement of the assi- milating functions, whose object it is to provide for the main- tenance and growth of the organs, applies to them this annua- lized substance, assimilated by successive acts, when it has be- come quite similar to them. Several, however, of these functions, serve at once to pre- serve and to destroy. Absorption, which takes up extraneous molecules to be employed in the growth of the organs, takes up equally the organic molecules which are detached by motion, friction, heat, and all the other physical, chemical, and vital causes. The action of the heart and of the blood-vessels sends these fragments together with the parts truly recrementitious, towards the lungs, which, at the same time that they bring about a combination of the nutritive parts with the oxygen of the atmosphere, separate from the blood the materials which can no longer be employed in nourishing the organs; the same power sends them towards the secretory glands, which not only purify what is liquid, by separating from it that which cannot without danger remain in the animal economy, but which like- wise elabol&te 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 de- gree of animalization (as to the bile and saliva), while the others seem to be intermediate 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 of 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 kilter into all the parts of the body, by the action of the heart and arteries. But the advan- tage which would he obtained from a method so contrary to the common practice, which is to consider separately the functions of circulation and respiration, appeared to me too unimportant to justify its adoption. The external or relative functions, equally connected by their common destination, connect the individual to every thing that 70 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 be perceives relations of advantage or disadvantage, according as the opposite sensations of pain or pleasure result fr&m 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 nu- trition 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, secretion, 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 tbe 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 slightest changes, for example, by placing the history of the function of smell and taste before the account of the internal or 71 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 very 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 perfection; the eagle, whose sight is so piercing, has a very dull sense of touch, taste, and smell. The dog, whose smell is exquisite, has a very ordinary extent of sight; in him the taste and touch is equally imperfect. His touch, in the perfec- tion of which no animal comes up to man, has not been im- proved 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 impressions. 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 bis 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 increasing the number of their wheels, with a view of ob- taining more extensive or more varied effects. AH organized bodies are possessed of assimilating functions; but as assimilation requires means 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, at the same time, performs the functions of a circulatory organ, or ra/her, 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 » retrogade course, 1% from the brandies 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 manner, and produce a change in the atmospherical air, by depriving it of its carbonic acid gas, the result of com- bustion and of animal respiration, so that by a truly admi- rable reciprocity, plants, which decompose carbonic acid and allow oxygen to exhale, continually purify the air, which com- bustion 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 observe, that of all the acts of vegetable life, no one is more analogous to the animal economy, that that by which fecundation is affected. We shall not here explain tbe 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 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 * Especially in the account of living beings, § V of the prelimi" nary discourse ; articles sleep and foetus It is impossible at present to go over all th?se distinctions, without entering into useless and dis- agreeable repetitions. 73 that their food cannot be digested, unless it be composed of ma- terial analogous in composition to their 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 econo- my; the functions are linked together, and depend on one ano- ther, and are performed simultaneously; all represents a circle of which it is not possible to mark the beginning or the end. In circulum abeunt (Hippocrates). In man, while awake, di- gestion, 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 ex- ertions of the functions, would acquire but a very confused knowledge of them.t By becoming familiar with these abstractions, one might soon mistake them for realities; one might even go the length of seeing two distinct lives in the same individual; one would be apt to assign as the character of internal life, that it is car- ried on by organs independent of the will. Although this faculty of the soul presides over the phenomena of respiration, * In carnivorous animals, the power of digestion is extremely weak ; but their muscles are very powerful- This relative force of the muscles was necessary in carnivorous animals, as they live by depredations and slaughter, as their instinct, in unison with their or- ganization, 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. Grimacd, first Memoir on Nutrition. | 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 instituted among them All the acts of Nature are so connected, and are linked together in so close an union, and she passes from the one to the other, by such uniform mo- tions, 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. AH our methods of classing and ar- ranging the productions of nature, are mere abstractions of the mind, which does not consider things as they really are, but which attends to certain qualities, and neglects or rejects all the rest. Grimaud, Lectures on Physiology. 11 74 of mastication, of the expulsion of the urine and faeces, one might consider life as intrusted to unsymmetrical organs, al- though the heart, the lungs, and the kidneys, are evidently sym- metrical; 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 («/V7/ est in corpore viventi plane sincerum. Galen). Thus, respiration, which connects the external and assimilating func- tions, furnishes the blood with the principle which is to keep up the action of the brain, and to excite muscular contractions.— On the other hand, the mofion of the muscles is of use in the distribution of the humours, and concurs in the phenomena of assimilation. The brain, by means of the eighth pair of nerves, hoids 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 diges- tive 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 phycielogy. 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, between inorganized, and crganized 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 ob- ject 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 contractility, we have spoken of sympathies and habits, of the internal ner- vous apparatus, which unites, collects, and systematizes the or- gans of the assimilating functions; we have endeavoured to de- termine from facts, the existence of the cause which subjects living beings to a set of laws very different from those which 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 objects which this science considers, I have adopted a more simple and natural division, than any hitherto employed. 73 I shall close this preliminary discourse, by saying a few word^ 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 di- gestion. I have given precedence to the functions of assimila- tion, because of all others, they are the most essential to exist- ence, and their exercise is never interrupted, from the instant in which the embryo begins to live, lill death. In beginning with an account of them, we imitate nature therefore, who im- parts to man this mode of existence, before she has connected him with outward objects, and who does not deprive him of it, until the organs of sense, of motion, and of the voice, have com- pletely 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 us to depart from it. I have thought it right, that the consi- deration of the voice should immediately precede that of gene- ration, in order that the arrangement might, at a glance, show the connexion which exists between their phenomena. Seve- ral animals use their voice, only during the season of love; the birds which sing at all times, have, during that period, a more powerful and sonorous voice. When man becomes capable of reproduction, his vocal organs suddenly become evolved, as though nature had wished to inform him, that it is through them he is to express his desires to the gentle being who may sympa- thize in them. The voice, therefore, serves as a natural con- nexion, 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 exter- nal 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 be- 76 tween 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. FIRST CLASS. LIFE OF THE INDIVIDUAL. FIRST ORDER. FUNCTIONS OF ASSIMILATION, Or, Functions which are subservient to the preservation of the Individual, by assimilating to his substance the food by which he is nourished* 77 NEW ELEMENTS OF CHAPTER I. OF 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 or- gans, their qualities altered, and a new compound formed, fitted to their nourishment and growth. II. General considerations on the Digestive Organs. Ani- mals alone are provided with organs of digestion; all of them, from man down to the polypus, contain an alimentary cavity variously shaped. Tbe 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 animal- izmg the alimentary substance. The different parts of this di- gestive 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 tbe stomach, which again contracting, is continued down "n^r%^- name of intestine. This tube itself varies in size in diffeiuot parts of its extent; and it is by the consideration of these dif- ferences 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 78 OF DIGESTION. . 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 tbe 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 her- bivorous, nor carnivorous, but omnivorous or polyphagous. This question, of such easy solution, has long employed physi- cians, 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 if vari- ous iolds; lastly, a third coat is accidentally placed over the other two: and is furnished by the pleura to tbe oesopha- gus, by the peritoneum to the stomach, as well as to the intes- tinal 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 mo- tions of the two extremities, while the rest of its course is not under its control. In the cells of the tissue which unites its surfaces to the other coats, fat never accumulates, which might OF DIGESTION. 79 have impeded its contractions, and straitened and even obliter- ated 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 mi- neral 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 cer- tain degree, the power of 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 from among the poisonous 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 substances yield to these powers, and come under the class of aliments. What then is to be thought of our ptisans, of chicken and veal broth, and other such remedies? That they are employed to deceive the hunger and thirst of the patient, to prevent his receiving into his stomach, substances whose la- borious digestion would take up the strength required for the cure of the disease; 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 exciting 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? Because these substances contain many nutritious particles capable of being assimilated, so that strong constitu- tions digest them and completely neutralize their irritating or purgative qualities. An animal or vegetable substance, though essentially nutritious, may act as a medicine, or even as a poison, when, in consequence of the extreme debility of the digestive tube, or because it has not been sufficiently divided by the or- gans of mastication, it resists the digestive action. Thus sur- feits are brought on, because the stomach is debilitated, because it is oppressed by too great a mass of substances, or because sty OF DIGESTION. having been imperfectly triturated, 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 ap- pears that their elements require tbe elaboration of vegetable life; hence it has been justly observed, that plants are laborato- ries 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 sub- stance. Of all the parts of vegetables, the most nourishing is their amylaceous fecula, but it yields the more readily to the action of the digestive organs, from having already experienced an incipient fermentation; on that account, leavened bread is the best of vegetable aliments. The flesh of young animals is less nourishing than that of the full-grown, although, at an early age, the flesh of the former abounds more in gelatinous juices; for, this abundant gelatine wants the 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 substances, the internal composition of our organs does not al- ter; an evident proof, that the substance which we obtain from aliments, to incorporate with our own, is always the same, and this affords an explanation of 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 are all formed from hydrogen and carbon, are well known to differ chemically, only in the different proportions of oxygen which they contain. Thus, sugar is a kind of gum, containing a con- siderable quantity of oxygen; and which is reduced, in a cer- 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. Nothing, in fact, nourishes better, more quickly, and from a smaller bulk, than substances of this kind. The Arab crosses OF DIGESTION. 81 Uie vast plains of the desert, and supports himself by swallowing a small quantity of gum arabic. The nourishing quality of ani- mal and vegetable jellies is well known; saccharine substances soon cloy the appetite of those who are fondest of them. In de- crepid 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 sac- charine 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 casuitry, it may be seen, on what ridiculous grounds there was granted a dispensation in favour of plovers, of water hens, wild ducks, snipes, scoters, birds whose brown flesh, more animalized and more heating ought to have been proscribed from the. kitchen of monasteries, much more strictly than that of common poultry. Consider what is the alimentary regimen of the different 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 tbe contrary, are voracious from instinct and necessity. They swallow enormous quantities of 12 82 OF DIGESTION. 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 Samoides, 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 frebile action, prove plainly the necessity of balancing, by a vigorous inward excitement, tbe debiliating influence of powers that are ope- rating from without? The abuse of spiritous liquors is fatal to the European transported to the burning climate of tbe West Indies. The Russian drinks spiritous 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 practised. 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 practice in a climate such as that of Greece, may imitate this simplicity of the father of physic, Opium, bark, wine, spirits, aromalics, and the most active cor- dials are, on the other hand, the medicines suited to the inhabi- 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 by 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- OF DIGESTION. 85 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 pro- duce of a warmer climate, and as saccharine matter predomi- nates in its composition. Thus, Spanish wines are in them- selves nourishing, and are perhaps fitter 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 pos- sess, in a nearly equal degree, the treble advantage of diluting the fluids, of stimulating the organs, and of furnishing to the animal economy materials of nutrition. IV. Of hunger and thirst. By the words hunger and thirst, are meant two sensations, which warn us 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 fat, discoloration of the fluids, especially the blood, loss of strength, excessive sensibility, sleeplessness, with pain- ful sensations in the epigastric region. Death from inanition is most easily brought on, in those who are young and robust. Thus, the unfortunate father whose hor- rible story has been related by Dante, condemned to die of hunger and shut up with bis children in a dark dungeon, died the last, on the eighth day, after having witnessed, in the con- vulsions of rage and despair, the death of his four sons, unhap- py victims of the most execrable vengeance ever recorded in the history of man. Haller has related, in his great work on physiology, several instances of prolonged abstinence; if we are to give credit to these accounts, some of which are deficient in the degree of authenticity required to warrant belief, person6 8-1 OF DIGESTION. have been known to pass eighteen months, two, three, four- five, six, seven, and even ten years, without taking any nourish- ment. 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 ex- tinct, just showed itself, in an almost insensible pulse, an un- frequent 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 conceived that living, in a man- ner, on their own substance, the fluids in such persons, have been frequently subjected to the causes which produce assimi- lation and animalization, and have undergone the greatest al- teration 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, during that permanent constriction; on the dragging down of the diaphragm by the liver and spleen, when the stomach and intestines being empty, cease to support those viscera: a dragging which is the greater, as a new mode of circulation takes place in the viscera, which are supplied with blood by the cceliac artery, and while the slomach 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 stomach against each other, when brought together in an empty state, adduce the example of serpents, whose stomach is purely membranous, and who endure hunger a long time, while fowls whose powerful and muscular stomach is able to contract strongly on itself, endure it with difficulty. But to say nothing of the great difference of vitality, in the or- gans of a bird and of a reptile, the stomach which continues * JK'itidissima viscera sunt animaliumfame enectorum, et artrente phrarum fasciculi. Haller, Ulcm. Phys torn. VI. page 183. OP DIGESTION. 85 closing on itself as it is emptied, may contract to such a degree as scarcely to equal in size a small intestine, without its follow- ing, as a necessary consequence, that the parietes which are in contact, should exert on each other any friction, on which the sensation of hunger may depend. In fact, the presence of food is necessary to determine an action of the parieties 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 np, observe, that it may be appeased, for a time, by supporting the abdomin- al viscera by means of a wide girdle; that hunger ceases as soon as the stomach is full, before the food can have yielded to it any materials of nutrition. On this hypothesis, which is purely mechanical, as that which explains hunger by the irrita- tion of the gastric juice, by the lassitude of the contracted muscles, by the compression of the "nerves, how shall we ex- plain the fact, that when the hour of a meal is over, hunger ceases for a time? Ought not hunger, on the contrary, to be con- sidered as a nervous sensation which exists in the stomach, is communicated by sympathyr to all the other parts, and keeping up an active and continuous excitement in the organ in which it is principally seated, determines into it the fluids from all parts. This phenomenon, like all those which depend on nervous influence, is governed by the laws of habit, by the in- fluence of sleep, and of the passions of the mind, whose pow- er is so great, that literary men, absorbed 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 sympathetic manner, increases the appetite and occasions hunger. Thus, bulimia depends, sometimes, on the irritation of a tape worm in the organs of digestion. The ap- plication 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 stpmach is overfilled. Whatever, on the contrary, blunts or renders less acute the sensibility of the stomach, renders more endurable or suspends the sensation of hunger. Thus, we are told by travellers, that the Turkish dervises and the Indian faquirs, endure long fasts, because they 86 OF DIGESTION. are in the habit of using opium, and lull, in a manner, by this narcotic, the sensibility of the 6tomach. Tepid and relaxing drinks impair the appetite; the use of opiates suspends sudden- ly tbe 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 stimulating, from the concentration of the saline and other sub- stances 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 Cctses of hydrophobia. English sailors, who were becalmed, had exhausted all their stock of fresh water, and were at a dis- tance 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, they resolved to drink their own urine. This fluid, though very dis- gusting, allayed their thirst; but at the end of a few days, it be- came so thick and acrid, that they were incapable of swallow- ing 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 to- wards the seat of effusion. It is excessive in diabetes, and in proportion to the increased quantity of urine, in fever, it is increased, from the effect of perspiration, or because in some of these affections, for example, in bilious fevers, the blood seems to become more acrid. Hence the advantage of cooling, dilu- ting, and refreshing drinks, administered copiously, with a view to correct the temporary acrimony occasioned 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 OF DIGESTION. 87 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. On mastication. 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 moutb. The motions of the lips are extremely varied, and depend on the single or com- bined action of their muscles, by which the greater part of the face is,covered, and which may be enumerated as follow:— Elevators of tbe upper lip (caninus, incisivus, hvatores com- munes labiorum and nvyrtifornm). Depressors of the under lip (triangidaris labiorum, quadratus genes). Abductors (buccinator, zygomaticus major and minor, platysma myoides.) Constrictors (orbicularis oris). VII. The motions of the upper jaw are so confined, that some have denied that it has any motion; it nevertheless rises a little, when the lower jaw descends; but it is principally by the de- 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 tbe 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 motion! of the upper jaw is seen to increase, the further we descend from the human species; 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 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 differei.t bones of which the face is formed, if this unsteady 88 OF DIGESTION. 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 di- rection, while th zygomatic processes forcibly press the bones of the face against eachjiother, and powerfully resist separation out- wardly or laterally. The lower jaw falls by its own weight, when its elevators are relaxed; the external pterygoid 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- 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 scissors^ 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- OF DIGESTION. 89 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 tbe 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 fossae. 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 of view which we have just taken, man holds a middle station between carnivorous animals and those which feed on vegeta- ble substances; nothing, however, determines his nature better than tbe 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 kiniary* teeth are not to be met with, in the numerous class of * After the example of several naturalists, I have thought it right to give that name tp the canine teeth ; in the first place, be- cause 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 erroneous concep- tion, by leading to a belief that this kind of tooth belongs only to one kind of carnivorous animals, while they are stronger and more div tinct in the lion, the tiger, &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 sympton of barrenness of ideas. The teeth differ essentially from the other bones, by the 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 system ; 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 mu- cous membrane contained in the tooth, and which forms the most essential part of the bone; 4thly, by their not undergoing any change from exposure to the air, a property which they owe 10 the enamel which covers them externally. It has been said, with i i,- tice., that nature, in sheathing the tooth with this covering, ha» iaii- DO OF DIGESTION. rodentia. Some without incisors; the fonner appear mor# 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 grinding substances previously divided by the laniary teeth, which tear them, or by the incisors, which, in meeting as the blades of scissors, 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 crush a very hard substance, we instinctively place it between the last large grinders, and by thus shortening consid- erably the lever, between the resistance and the fulcrum, we improve on the lever of the third kind, which, though most em- ployed in the animal economy, acts the most unfavourable. The laniary teeth have very long fangs, which lying deeply buried in tbe alveolar processes, give them a degree of firmness to ena- ble them to act powerfully, without any danger of being loosen- ed from their situation. The enamel which covers the teeth, preserves the substance of the bone exposed to the contact of the air, from the injurious 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 conical 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 accidental causes, or in the progress of age, the teeth are gone, their alveoli contract, then disappear; the tatcd the process of tempering, by means of which we harden the cd^e of steel or iron tools. - OF DIGESTON. 91 gums, a reddish and dense membranous substance, which con- nects 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 di- vided. X. Salivary solution. The above mechanical trituration is not the only change which the food undergoes in the mouth. Subjected to tbe action of the organs of mastication, which overcome the force of cohesion of its molecules, it is at the same time imbued with the saliva. This fluid, secreted by the glands placed in the vicinity of the mouth, is poured, in con- siderable quantity, into that cavity during mastication. Th*e 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 albumin- ous 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 abun- dantly. 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 proportioned to the quan- tity of saliva which is secreted, and this is estimated at about six ounces duriug the average time of a meal. It flows in greater quantity, when the food that is used is acrid and stimu- lating: it mixes with the mucus copiously secreted by the mu- cous, 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 92 OF DIGESTION. 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 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-hyoideu 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 hvo-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 mucous substance which exudes from the surface of the amyg- dala further facilitates the passage of the food. When the food has thus dropped into the pharynx, the larynx which had risen, and had come forward, and which in that motion had drawn the pharynx along with it, descends and falls backwards. This last organ, stimulated by the presence of the food, contracts, and . OF DIGESTION. 93 terould in part send it back in a retrograde direction, by the nasal fossae, 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 Estachian tubes. Sometimes this obstacle is overcome, and the food returns, in part, by the nostrils. This 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 constric- tor isthmi faucium, and of the constrictor pharyngis 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 diffi- cult deglutition 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 precision the substance that is swal- lowed. Thus, it is observed, in those cases in which degluti- tion is prevented by some organic affection of the oesophagus, that the patients, though they have the power of swallowing so- lid food, find it difficult to swallow a few drops of a liquid, and are tortured with thirst, though they have still the power of •atisfy 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 cf air into the stomach. M. Gossee, of 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, be ascertained the digestibility of the articles of food in most com- mon use. 94 OF DIGESTION. The food descends into the oesophagus, propelled by the con- tractions of that musculo-membranous duct, situated along the vertebral column, from the pharynx to the stomach. Muljs is secreted, in considerable quantity, by the membrane which lines the inner part of the oesophagus; it sheathes the substances which pass along it, and renders their passage more free. Tbe 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 approach 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 tendency to get into the larynx, whose opening is not covered over by the epiglottis; and if it be insisted upon, that the pa- tient shall swallow some ptisan, the deglutition of which is im- practicable, 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 tilled 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 capacity 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 li- quid, and yet death has not followed as a consequence of so enormous an accumulation; while in consequence of the deli- OF DIGESTION. 95 cate texture of the brain, of the exact fulness of the skull, and especially of the inflexibility of its parieties, the slightest effu- sions 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, ca- pable of being easily increased, was required in a cavity whose viscera, for the most part hollow, and admitting of dilatation, contain substances varying in quality, and from which are dis- engaged gases occupying a considerable space. What a differ- ence is there not in the capacity of the abdomen of animals, according to the quality of the food on which they feed! Com- pare the slender body of the tyger, 01 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 deve- lopment, 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. r 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 com- pression of the pulmonary tissue; the heart, which adheres .to the diaphragm, drawn down by that muscle, when it descends, strikes against the parietes of the chest, every time its ventri- cles contract. The abdominal viscera are not less agitated by the motions of respiration; they experience from the diaphragm 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 alimentary canal is accelerated, the activity of digestion increased, and several ex- cretions, as of the urine and faeces, performed. XVI. 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- tention by the food, yields, without redacting. It is not, how- 9fj OF DIGESTION. ever, 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 omen- tum recede from each other, receive it between them, and em- brace its outer and dilated part. In man, the principal use of this fold of the peritoneum, appears to be to facilitate the dila- tion of the stomach, which expands chiefly at its forepart, as may be observed by inflating it in a dead body. As this viscus becomes distended with air, the two folds of the omentum ap- ply themselves 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 up- per portion of the omentum can alone be employed in this use, and the whole of this membranous fold is never entirely occu- pied by the stomach. Shall we say with Galen, that the omen- tum 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 contrac- tion, 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 omentum which may be considerered as a necessary result of the manner in which the peritoneum is disposed in relation to * The omentum is one of those parts, the use of which, in the ani- mal 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. James Rush, that the omentum is a reservoir, or depository of adipose matter, from which the system may derive nourishment in its extreme exigencies. This hypothesis is at least as plausible as any which has been advanced on the sub- ject, and is supported with considerable ingenuity. Vide his Inau- gural Thesis, Philadelphia, 1809.—Ed. OF DIGESTION. m 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, may besides, by the separation of the two laminae of which it is formed, favour the dilation of the hepatic vein, which is situated, 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 or- gan of digestion, yet its function in that process is but second- ary 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 pre- pared for this separation which is soon to be performed, it be- comes fluid, and undergoes a material alteration; it is convert- ed into a soft and homogeneous paste, known under the name of chyme. What is the ageat 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:—concoc- tion, 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 and 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 language of the ancients, concoction means the alteration, the maturation, the animalization of alimentary substances, as- similated 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 1* 98 OF DIGESTION-- changes. The experiments of Spallanzani on artificial digest- ion, 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 tbe 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 peristalic contractions of the stomach, and this viscus is shaken by the pulsations of the neighboring arteries; it is besides kept in continual motion by the act of respintion. In fermentation, gases are either ab- sorbed or extricated, neither of which circumstances takes place when (he stomach is not out of order. ft sb.»ul;l, however, be stated, in support of the opinion that accounts ior digestion on the principle of fermentation, that we can derive nourishment only from substances capable of under- going fermentation, and that the substanoes which have under- gone the panary and saccharine fermentation, are more easily digested, and in less time. This imperceptible fermentation, if it reaily 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, tbe 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 OF DIGESTION. 99 oar digestive organs have the power, as will be seen presently, of retarding, or of suspending, the putrefaction of the substances which are submitted to their action. Serpents, which in con- sequence of the greater dilatability 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 peristalic action of 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 improper to spend a little time in the refutation of the proofs which are adduced in its support. ; m 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 stomach; the first is called the cropj 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 thev are more easily ground by the gizzard, wnicb is a truly muscular stomach, that filnls ike office of organs of mas- 100 OF DIGESTION. 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 gravel, taken in with the food of those birds. Tie 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 tbe 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, 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 de- position 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 sto- mach, animals might be divided into three classes, the most numerous of which consists of those creatures, whose stomach is almost entirely membranous, and furnished with a muscular oat of very little thickness. In this class are contained, ma:;, OF DIGESTION. 101 quadrupeds, birds of prey, reptiles and fishes. Notwithstand- ing the weakness of that muscular coat, Pitcairn, by a misap- plied calculation, 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 alternate motions of respiration. What does so exagge- rated a calculation prove, except, as Garat observes, that this vain show of axioms, definitions, scholia, and corollaries with which works not belonging to mathematics have been disfigur- ed, have served only to protect vague, confused, and false no- tions, under the cover of imposing and respected forms. One need only introduce 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 o 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. 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 oesophagus. 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 moutb, by a truly antiperistaltic motion of the oesophagus. The alimentary bolus, after having been chewed over again by (he 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 which > 102 OF DIGESTION. 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 tbe paunch or the bonnet, which are useless, but at ouce 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 theA stomach, so favourable to Hal- ler's theory, is observed only in ruminating animals. But though animals are in general monogastric, 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 oesophagus is nearer to its left extremity, and the great fundus of that viscus is smaller, as animals feed more exclusive- ly on flesh, which is a substance of remarkably easy decompo- sition, and not requiring for its digestion a long stay in the sto- mach. 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 aliment. 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 des- tined to that organ; the pyloric, the right gastro-epiploic, given off by the hepatic artery. The greater part of the blood, there- fore, which passes from the aorta to the coeliac 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 they OF DIGESTION, i03 are more particularly allotted. One need only observe the great disproportion between tbe 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 tbe 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 in the vessels, as, in consequence 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, arid the liver, must receive a larger supply of blood, and again a smaller quan- tity, when the stomach is full. The gastric juice, the result of arterial exhalation, mixes with the mucus poured out by the mucous follicles of tbe 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, tbe 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 tbe 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 confirmed by an observation of Vesalius, who relates, that he found the ductus communis choledochus opening into the sto- mach, 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 tbe termination into the duodenum of the ductus communis 101 OF DIGESTION. choledochus, being very near to the pylorus, the bile easily ascends into the stomach, and is always found there in consid- erable 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 fast- ened 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 gat nic juice, in its natural state, is neither acidnor alka- line; it does not turn red or green, vegetable blue colours.* Its most remarkable quality is, its singularly powerful solvent faculty, the hardest bones cannot w-thstand its action; it acts on those on which the dog feeds, it combines with all their or- ganized and gelatinous parts, reduces them to a calcareous re- sidue, forming those excrementitious substances so absurdly called album graicum, 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 en- tirely membranous, it has most power and activity. In the numerous class of zoophytes, it alone suffices to effect decompo- sition of the food, always more prompt when accompanied by ■warmth of the atmosphere, as was observed by du Tretnbley, in tbe polypi, which in summer dissolve in twelve hours, what in colder weather it would take three day's to digest. In the actinia, in the hololhuria, the gastric juice destroys even the * There is some difference of opinion on this point. Carminati de- clares that in carnivorous animals the gastric fluid is acid, that ii; phytiferous it is alkaline, and that in those which live indiscriminate- ly on animal and vegetable food, it is neither acid nor alkaline. By Brugnatelli it is said that, in all animals, it is uniformly acid. That the gastric liquor is occasionally acid in the human species cannot be denied. It has indeed been found so both by Reaumur and Hun- ter, and in subjects where there was no reason to presume it had be- come 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 wc may appeal to the fact which has been verified by repeated experi- ments, that both carnivorous and phytiferous animals digest and thrive well on an exchange of food, the one being made to feed ex- clusively on vegetable and the other on animal matter. Vide Expc riments <.{" J. Hunter and Spallanzani.—Ed. OF DIGESTION. 105 shells in the muscles which they swallow. Are we not all ac- quainted with the peculiar flavour of oysters, how much they tend to whet the appetite? this sensation depends less on the salt water contained in the shell, than on the gastric juice which acts on the tongue, which softens its tissue and quickens its sensibility. This mucous substance, when received into the stomach, promotes the digestion of the food which is after- wards taken into it; for, the oyster itself is very little nutri- tious, and iawwlrrather as a condiment, than as affording nour- ishment, jjfywip&t/ The gastric juice not only pervades and dissolves the food received into the stomach, but it unites and intimately com- bines with it, completely alters its nature and changes its com- position. The gastric juice acts, in a manner peculiar to itself, on the food exposed to its action, and far from inducing a be- ginning of putrefaction, suspends on the contrary and corrects putrescency. This antiseptic quality of the gastric juict:, sug- gested the practice of moistening ulcers with it to accelerate their cure, and the experiments made at Geneva and in Italy, have, it is said, been fully successful. I have made similar experiments with saliva, which, there is every reason to con- sider, is similar to the gastric juice; and I have seen old and foul ulcers assume a better appearance, the granulations be- come healthy, and the affection rapidly advance towards a cure, from the use of that irritating fluid. I had under my care an obstinate sore on the inner ankle of the left leg of an adult; notwithstanding the external application of powdered bark, and of compresses soaked in the most detergent fluids, this sore was improving very slowly, when I bethought myself of moistening it every morning with my saliva, the secretion of which was increased by the hideous aspect of the sore. From that time, the patient evidently mended, and his wound contracting daily, at last became completely cicatrized. However powerful the efficacy of the gastric juice, to dis- solve 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 pow- er of vital resistance, that the polypus rejects unhurt its arms, 106 OF DIGESTION. 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 destroy- ed in several points in the body of a criminal, who for some time before his execution, had been prevailed upon, in consider- ation of a sum of money, to abstain from food.f The gastric juice is capable, even after dea^^o/. dissolving food introduced into the stomach, by a wcHDH^ajfc 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.:}: Every thing tends to show, that the stomach ought not to be considered as a chemical ves- sel, in which there takes place a mixture giving rise to new combinations. The tying the nerves of the eighth pair, the use of narcotics and of opium, intense thought, every powerful affection of the mind, trouble or even entirely suspend digestion in the stomach, which cannot take place independently of nervous influence. Yet this nervous influence may possibly not concur directly, and of itself, to stomachic digestion; it is perhaps mere- ly relative to the secretion of the gastric juice, which the liga- ture of the nerves, the action of narcotics or of other substan- ces may impede, alter, or even completely suspend. • It had been thought, that no animal could live on the flesh of its own kind, and this circumstance was explained on the same princi- ple ; but to refute it, we need only quote the instance of cannibals, and of several tribes of carnivorous animals, who, in the absence of other prey, devour one another. f The fact of the stomach itself, in some instances, being partly dissolved 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__Ed % In the experiments alluded to above, meat and bread mixed with the gastric fluid were reduced to a gelatinous pulp, resemliling in all its sensible properties, the natural chyme. By the artificial process however, a much longer time was found necessary to effect this end. Tt 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.—Ed. OF DIGESTON. 107 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 molecules, combines with it, alters it s inward composition, and imparts to it qualities very different from those which it possessed before the mixture. If, in fact, a mouthful of wine or of food is re- jected, a few minutes after being swallowed, the smell, the flavour, all the sensible and chemical qualities of such substances, are so completely altered, that they can scarcely be recognized: the vinous substances turned, to a certain degree, sour, are no longer capable 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 proba- ble, that its chemical composition varies at different times; that it is acid, alkaline or saponaceous, according to the nature of the food. Although the gastric juice be the most powerful agent of digestion, its solvent power requires to be aided by several secondary 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 fer- mentation which cannot be, strictly speaking, compared to the decomposition which substances subject to putrefaction and acescency undergo. The gentle and peristaltic action of the muscular fibres of the stomach, which press, in every direction, en the alimentary 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 digestion is at once chemical, mechanical, and vital; in that case, the authors of the theories that have been broach- ed, have been wrong, only in ascribing to one cause, such as heal, fermentation, putrefaction, trituration, maceration, and the action of the gastric juice, a process which is the result of a concurrence of these causes united. The food remains in the stomach, during a longer or shorter space of time, according as by its nature, it yields more or less readily to the changes which it has to undergo. Gosse of Ge- neva, ascertained, by experiments performed on himself, that the animal and vegetable fibre, concrete albumen, white and tendinous parts, paste containing fat or butler, substances which have either not undergone fermentation, or which do not readi- 108 OF DIGESTION. ly undergo that process, remain longer in the stomach, and of- fer more resistance to the gastric juice, than the gelatinous parts of animals or vegetables, fermented bread, &c ; that the latter required but an hour for their complete solution, while the for- mer were scarcely dissolved at the end of several hours. XXI. The following case throws, I think, some light on 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 wrrinkled 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 oblong tumour appeared on the injured spot: during the nausea and vomiting which came on afterwards, the tumour broke, and there escaped at the wound, which was left by this rupture, two pints of a fluid which the patient had just swallowed to obtain relief. From that time, the fistula, which at first would scarcely have admitted the tip of the little finger, increased daily; at first it allowed only the fluids to pass, but, on the eighth day, the so- lid food came away freely, and continued to do so till she died. When admitted into the hospital, she ate as much as three wo- men of her age, she voided about a pint of urine and went to stool only once in three days. Her faeces were yellowish, dry, rounded, and weighed more than a pound. Herpulse 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 OF DIGESTION. 109 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, and with a noise, a certain quantity of gases. The food thus evacuated, exhaled an insipid smell, was neither acid nor alka- line, 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 cmld not be recognized, and the bread form- ed a viscid, thick and soft substance, pretty similar to fibrine newly precipitated by the acetous acid, and it floated in a te- nacious 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 tbe 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 stomach, 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, show- ed 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 fore part of the abdomen, around the opening, that 110 OF DIGESTION. 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 tbe pylorus. It extended from the greater to the lesser curvature. In other respects, it. was the only organic affection of that viscus. It should be stated, that for several years, the patient had been thin and emaciated, and had led a languid life, which was terminated by a colliquative diarrhoea. She seemed to be sup- ported only by the small quantity of food which passed through the pylorous, into the duodenum, where it received the influ- ence of the bile, whose action on the chyme is, as we shall pre- sently state, absolutely essential to the separation of tbe nutri- tious parts. Not that there was any thing to prevent the absor- bents of the stomach from taking up a certain quantity of nu- tritious particles, but that small quantity of food, in an im- perfect condition, was of very little service in imparting nou- rishment, 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 contracted opening can no longer allow any food to pass* XXII. WThile 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 the pyloric orifice. Besides, its longitudinal fibres shorten it, in * Cases, in many respects, similar to the above, are recorded by different writers. Haller, in his " Chirurgical Dissertations," has the history of a woman with an aperture in her stomach, through which she was nourished for tiventy-seven years. For other ii stances of fistulous openings in this viscus, consult the " Irish Transactions," and " Me dical Facts and Observations."—Ed. OF D1GE9TION. lit the direction of its greatest diameter, and bring nearer to each other its own orifices. In these different motions, the stomach rises over the pylorouSj 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 tbe compression 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 natural obliquity of the stomach, from left to the right, be- ing increased, 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 place in the stomach, a sorting of the different substances which it contains. Those that are most readily dissolved, get near to the pylorus, which 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 tbey 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 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 admit? 112 OF DIGESTION. 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 by 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 fidlness 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 vigor of the stomach at the time, and to the activity of the gastric juices. Yet we may state from three to four hours, as tbe mean time of theiv remaining there. It is of consequence to know the time required for digestion in the stomach, that we may not disturb it by baths, bleeding, &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 ac- tion, all the other organs of the economy; if it summons to its aid, 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 diseases, and in all cases where Nature is engaged in an organic operation, which a little increase of irritation could not fail to disorder, or to break off. Those who have practised in great hospitals, know to !:^ w 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, at once overloaded with food, is changed into a centre of fluxion, toward; which the juices and humours all tend; and 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 OF DIGESTION. 113 felt in the lungs make 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 m 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 net 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 fluxionary motion*, a host of instances prove, what a close sympathy unites it to the stomach. Let us but call to mind pleurisies and bilious peripneumonies, 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 agastric 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. 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 affected with more force, more rapidly, and in a mariner 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 tbe contraction of the large muscles of the abdomen; the diaphragm rises up * Of all the organs it is that in which we most meet with organic injury ; and those who have opened many bodies, may have observ- ed, how rare it is to find the lungs completely sound in adults and in old men. 16 114 OF DIGESTION. 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, tipon 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 difficult to know, whether derangement of digestion did not proceed from the general disturbance brought upon all the functions: however, the brain does not appear to be in more immediate sympathy with tbe 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- 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 tbe 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 tbe other chylous or nutritious, the duodenum in which that separation * Dr Haighton has proved, in the most satisfactory manner, that a ligature on the eighth pair of nerves, far from inducing vomiting, renders the stomach incapable of rejecting its contents, even though excited by the most powerful emetics. T. See Memoirs of the London Medical Society, vol.11, page 512 OF DIGESTION. llg is performed, is its principal organ. In fact, however care- fully one may examine the grayish chyme which is sent out of the stomach, it will be discovered to be a mere slimy homoge- neous 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 ali- mentary tube In the stomach, the previously masticated food is reduced by the solvent quality ot the gastric liquor into that state which is denomi- nated chyme. This is the first step After reaching the duodenum, this pultacious mass is gradually 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 pan- creatic 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 pre- pared to abandon the hypothesis Before implicit confidence is re- posed in those experiments, we are, at least, entitled to demand that they be frequently repeated, and with the utmost caution and pre- cision, so as to leave no doubt of their entire accuracy. When chyle is formed, we have hitherto viewed the digestive pro- cess 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 chyle, 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: 1 One, which maintains its fluidity during life, but coagulates after death, or by exposure to the air. This may be compared to the 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.* * The proportion of the serum to the fibrine of the chyle is varied by circumstances. In healthy chyle there is a considerable quantity of fibrine. When the digestive organs are weak, it is less. 116 OF DIGESTtON. The duodenum may be considered as a second stomach, very distinct from tbe 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 valvulse 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 tbe situation of the duodenum and tbe 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 nu- merous 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; lastly, numerous valvulse 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, 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 contain- ing a great quantity of water, of albumen to which it owes its viscid condition, and oil to which the colouring and bitter prin- ciple is united; soda, to which the bile owes the property of turning vegetable blues to a green colour; phosphates, carbo- nates, and muriates of soda, phosphates of lime, and of ammo- nia; and, lastly, as some say, oxide of iron, and a saccharine 3. One, consisting of small globules analogous to those of the blood, with this difference, that they are considerably more minute —Ed. OF DIGESTION. 117 substance resembling the sugar of milk. This fluid, which the ancients looked upon as animal soap, fitted for effecting a more intimate mixture of the alimentary matter, by combining its watery with its fat and oily parts, is, therefore, extremely com- pound: it is at once watery, albuminous, oily, alkaline, and sa- line. The liver which secretes it, is a very bulky viscus, situ- ated in the upper part of the abdomen, and kept in its place chiefly by its attachment to the diaphragm, of which it follows all the motion. The hepatic artery, which the 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 portse. 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 ac- tion; and the vena porlae 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 ab- dominal venous ciiculation, is too speedily fatal, to justify any conclusive inference. It is on analogical proofs that the re- ceived hypothesis rests, touching the manner of the biliary secre- tion. The hepatic artery, remarkably lessened by the branches it has sent off in its way towards the liver, is to that organ what the bronchial arteries are to the lungs; and in tue 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 portse, 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 s|£prt, the supple- mentary organ of the lungs, and assists in clearing the blood of its hydrogen and carbon. % 118 OF DIGESTION, The name of vena porta is given to a particular venous system, inclosed in the abdominal cavity, and formed as follows: 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 biliary 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 ciit ulation, the blood which has not been employed in the for- mation of bile, and that which has not served to nourish the substance of the liver: for, they arise equally from the extremi- ties of the vena portse, and from the extremities of the ramifi- cations 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 prin- ciples are in superabundance. The blood acquires the venous qualities, as it passes aldng the eircuitious course of the circu- lation, and is supplied with hydrogen and carbon the more ful- 1\. ' e slower it flows. Now, it is easy to see, that all is na- ture si 'imposed for sickening the circulation of the hepatic blood, a >d 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 frequency anastomose, like the arteries of the in- testinal tube, which of oil that are in the body, abound most iti visible divisions and anastomoses. It will be seen in the chap- ter on circulation, 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 f the hollow viscera being collapsed 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 an<■! soft viscus, lodged in the left hypochondrium, and attached to the great fundus of the stomach, receive the blood into the # OP DIGESTION. ii«J minute cells of its spungy parenchyma, or does this fluid merely traverse, very slowly, the delicate and tortuous ramifications of the splenic vessels'1 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 . ■ Borne down by the weight of evidence against them, most of the advocates of the ancient hypothesis were indeed prepared to aban- don it, as no longer tenable, when about two years ago an experi- ment made by Dr. Massy again revived their faith in cuticular ab- sorption. This experimentalist very clearly proved that if the body be immersed in a decoction of madder, the colouring matter of this sub- stance 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 sub- sequently performed 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 effect the urine. The latter, of the two, the more OF ABSORPTION. 149 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 readily enters the system. Neither of these substances can be traced in any other of the secretions, or excretions, or in the serum of the blood. u-'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 substan- ces applied to the back, or abdomen, or sides, or shoulders, produc- ed no change in the urine, &c Equally ineffectual was the immer- sion of the feet and hands in a bath of the same materials. After be »g kept in it several hours, not the slightest proof of absorption was afforded. ^ Such is the state in ™ich this interesting subject is at present left. Though, perhaps^io^absolutely decided, enough surely has been done to demonjjB Hit cuticular absorption rarely happens, and whenever it rttfl Hnot be deemed the effort of a natural func- tion. Covered^Ws^Re whole surface o£ the body by the impervi- ous cuticle, it is manifest to us that absorption can only take place in one of two ways, either by forcing the spbstance under the scales of the epidermis, as in the instance of the application of frictions, or by long continued bathing, the cuticle becomes so changed in its or- ganization, as to admit of transudation, or the insinuation of the fluid under its squamous structure, so as to come in contact with the mouths of the lymphatics situated within. At all events, whatever difference 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 cuticu- lar 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 rationally accounted for on the principle of pulmonary absorption, and the law of sympathy-—E*. 150 OF ABSORPTION. 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.* 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 com- paring them to the puncta lachrymalia, which are larger and more easily discovered. Each orifice endowed with sensihility, and with a peculiar power of contraction, dilates or contracts, absorbs or rejects, according as it is affected by the substances which are applied to it. The variations of the absorbing pow- er, according to the age, tbe sex, the constitute n, and different periods 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 to- wards itself, and raises the surrounding membranous parts, and thus forms a small tubercle similar to the puncta lachrymalia. These little bulgings deceived Leiberkuhn. and led him to think, that the absorbents of the intestines originated from small ara- pullulae, or vesicular enlargements, which, as so many exhaust- ed receivers, pumped up the fluid extract^from the food. This physiologist may, further, have been led into error, by the nerv- ous papillae of the inner membrane of tUB ML swollen by the determination of blood attending irritatfl ■Natural conse- quence of the friction of the alimentary stibsnmces. The in- haling faculty belongs not only to the orifices at the extremity of each radicle, but likewise to the lateral pores, which are in- finitely numerous in the parietes of the vessels.! * Both hunger and thirst seem to be sensations, excited by the sto- mach'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 of- fice 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 in- stinct, far more certain in its operation. Besides these two sensa- tions the stomach has others equally specific, as satiety, longing, loathing, sickness, &c. 5cc—Ed. f As to the precise manner in which absorption is effected, physi- OF ABSORPTION. 151 XLI1I. After arising on the surface, and in the interior of the body, by radicles in close contact, the h mphatics 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 ologists are not agreed. By some it is contended that it is entirely the result of capillary 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 position. It is now perfectly well ascertained, that the operation goes on whether 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^vhicjydT they undoubtedly are, the hypothesis referring absorption to this principle does not, on first view, strike us as altogether ufl ble. When examined, however, more clearly, it will be fouH K to all the embarrassments enumerated in the text, and to othsiWt not less weight. Two additional objections at once occur to us : 1. Did the absorbents act mechanically, as is alledged, 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 at. traction requires. They frequently swell or bulge out in their course, and become of irregular capacities. Even at their orifices they as- sume the figure of the funnel, commencing with an exceedingly mi- nute opening, which suddenly expands. Aware of the unfavour .ble- ness of this structure to the progression of fluids, it has been main- tained by some other of the advocates of capillary attraction, that the fluid is simply imbibed by the power of this principle, and after- wards propelled by the united force of muscular pressure, and the action of the contiguous arteries. We do not think the hypothesis at all improved by this modifica- tion of it. We believe, that in absorption there is no capillary in- fluence, or, indeed, any sort of extrinsic agency t ;iiployed. It seems ** us to be owing altogether to the inherent contractile power of the 10 152 OF ABSORPTIONS. which line the internal parts of the alimentary canal, of the trachea and urethra. The Italian anatomist succeeded in fill- ing, with quicksilver, all the tissues which he'considered as lym- phatic; but Ruysch, in his admirable injections, reduced all the membranes, 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 microscope; and from his preparations he inferred, that ar- terial capillary vessels, singularly divided and convoluted,, form the basis of cellular and membranous tissues. To satisfy one- self that neither the pleura nor the peritoneum are formed as Mascagni or Ruysch imagiued, one need only consider, that ar- terial exhalation and lymphatic absorption take place from the whole extent of the internal surfaces, and that these two func- tions 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 absorbents, and the other by his beautiful injections of the most minute arteries, are to be attributed to the importance which we are pleased to assign to the objects which particularly en- gage our attention, and likewise to the distention of the minute vessels by the injection; these being distended beyond their na- * tural state, compress and conceal the neighbouring parts. '^Tjjj^y mphatics, after emerging from among the cellular sub- stanejHpiite into trunks sufficiently large to be distinguished fromJPe laminae of that tissue. These trunks proceed towards cemin parts of the body, there they become united to other trunks, follow a parallel course and frequently communicate to- gether. 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; vessel, and bears no very remote analogy to the peristaltic action of the intestines. We will, however, in a few words, explain our mean- ing more distinctly. When chyle, or any appropriate fluid, is applied to the mouth of an absorbent, 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 propels its contents iu succession along its course to the ultimate destination.— Ed. OF ABSORPTION. 153 iying 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 ca- vities contain, are likewise in two layers, the one superficial, the other deep sealed. The absorbents differ, likewise, from the blood vessels, in 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 com- pletely filled with quicksilver, appear to cover the whole sur- face of our organs: and the whole body seems enveloped in a net-work of close and small meshes. The metastatis of humours, from one part of the body to another at a distance, is easily understood by any one who has seen those numerous inoscula- tions rendered manifest by injection. Mestastasis ceases to be an inexplicable phenomenon; one has no difficulty in conceiving how, by means of the lymphatics, all the parts of the body com- municate freely; how, fluids absorbed by those vessels in one part, may be conveyed into another, and prevade the whole body, without following the circuitous route of the circulation, and that it is, therefore, not altogether impossible, however im- probable, 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 collected, and be conveyed to the place to which irritation calls it forth. All that Bordeu has said to the oscil- lations and currents of humours, through tbe cellular texture, in his " Recherches sur le Tissu muqueux,^ may be equally ex- plained by the anastomosis 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, ^he 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 tbe moutb, 154 OF ABSORPTION. along the left side of the body, without entering into the course of the circulation, and perhaps, without passing through any of the conglobate glands; for, that of the left groin, which alone was syvollen, did not sensibly diminish in size. Salivation may, therefore, take place in the cure of venereal disease, though none of the mercury enter tbe 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 inoculations, 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 tbe occiput, behind the sternum, alongthe internal mammary vessels, lastly, within the mesentery, in which their number and seize 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 " ajferentia," and the other extremity turned towards the tho- racic duct, which sends out vessels, fewer in number, but of a larger size, and called " efferentta" 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 1 give the name of gland to those coils of lymphatic vessels which are totally different from the real conglomerate or secretory glands It might be better, perhaps, to call them ganglions as has been done by my learned and respected colleague Chaussier thoueh that name is objectionable, from its association in the mind with the nervous ganglions, whose structure is not at all similar to that of the ly mphatic ganglions. OF ABSORPTION. 155 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 vessels enters the thoracic duct, without having previously pass- ed through these glands. It even frequently 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 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 me to explain, in a satisfactory manner, the transmission of the colouring matter of the bile, which, in jaundice, manifestly 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 valvular folds, arranged in pairs, like the valves of the veins, and like them preventing a retrograde 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 the lymph is far from being as rapid as * In some cases, the activity of the absorbents appears increased, in a singular degree. Thus, jaundice has been known to be the immediate consequence of a wound of the liver ; and on other oc- casions, metastasis of humours has taken place, with the utmost ra- rapidity. I suspect, that, in such cases, the substance that has been absorbed, circulates by means of the anastomoses, and pervades the lymphatics with which the whole Oody is covered, bat without passing through the glands, which would slacken its coarse, and, in a certain degree, alter its'nature. 156 OF ABSORPTIONS. that of the blood; it even frequently appears affected with irregular oscllations, such as are to be met with in the circu- lation of the blood through the capillary arteries. The nume- rous 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 anastomoses, and are most subdi- vided. 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 action of these vessels, naturally weaker in that situation, is still farther diminished by tbe 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 slackened in its passage through the glands, in order that it might undergo all the changes which those organs are to pro- duce upon it. Although we do not know precisely what those changes are, their object appears to consist in a more perfect union and combination of its elements, and in bestowing on it a certain degree of animalization, as is seen, by the greater tendency to coagulation of the fluid taken from the vasad efferen- tia. Another object of the passage of the lymph through the glands, appears to be to deprive it of its heterogeneous parti- cles, or at least to alter their nature, so that they may not be- come 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 co- lour of the mesenteric 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 effectu- ally prevent its transmission into the blood, it is because cer- tain colours, as indigo and madder, have too much tenacity, while other substances, as the bile, do not pass through a suffi- cient 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 dilutes 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. OF ABSORPTION. 157 enlarged and visible, in certain cases of disease. I have daily opportunities of observing in scrophulous patients, swollen glands, in situations in which anatomists have not pointed out any. The absorbent glands are, at no time, so large or numer- ous as in infancy. They very frequently disappear in old peo- ple, and it is difficult to say, whether they have been totally destroyed, or whether they are merely exceedingly reduced in bulk. XLVL 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 vessels in these parts. The influence of debilitating causes on the lymphatic system, acts most powerfully on the glands, which are the weaker 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 varioirs 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, de- ficient in preoision and accuracy, and it is to their fallacy that we are to attribute the number of contradictory opinions on the subject of its proper treatment. Too precise a distinctipn can- not 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 structure), and those cancers which affect the other parts'ofthe animal econon y, especially the lymphatic glands, the testicles and the breasts. In the cancerous ulcers peculiarly frequent in the face, the lips, the tongue, in the inner coat of the sto- mach, of the rectum, and of the uterus, the pails, affected with inllammation of a malignant kind, are destroyed, without any means of checking the progress of that, destructive action, the 158 OF ABSORPTION. cause of which is easily conceived; while in true cancer, the glandular tumefaction always precedes the cancerous diathesis. As long as the affection consists merely in the obstruction of the vessels by indurated 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 dif- ferent 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. Whenever 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 sur- gical 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 Ihe 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 prin- ciple of revulsion; and besides, what shall we oppose to experi- ence, which shows 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 required, and for which M. Pelletan removed, six years ago, the left breast, and, three years ago, a gland under the ax- illa 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 exists 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 OF ABSORPTION. 158 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 thoraic 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 tbe oesophagus and the trachea, and opens into the subclavian vein of the left sidet 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 absorbents of the right upper extremity, and those of the right side of the head and neck. Lastly, it unites with those vessels which are coming from the left 6ide of the head and neck, as well as from the left upper extremity, just before opening into the subsclavian vein. The thoracis 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 bead, and of the right upper extremity, unite to form a second duct^ which opens separately into the right subsclavian vein.* What- * In some rare cases, lymphatic vessels, in other parte of the bo- dy, 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 the meseraic veins, into which it had been poured by some lacteal. Mascagni was aware of this anatomical fact. The lym- phatic system is, however, the most subject- to deviations of am- \r 'he animal rconomv. isa OF ABSORPTION. 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 subsclavian vein, is furnished wtih 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 depending on the loss of equilibrium, between the processes of inhalation and exhalation, either from increased action of the exhalants, or from the absorbents refusing to take up the lymph, in consequence of obstruction in the glands, or of compression of the duct. XLVIII. The nature of the lymph is far from being as well understood, as that of the vessels along which it. circulates. Haller 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 co- agulate it; in short, that it possesses all the qualities of the al- buminous fluids. The serum of the blood exhaled, throughout the extent of the internal surfaces, and even within the substance of our organs, by the capillary arteries, is absorbed by the lym- phatics, and is one of the principal sources of the lymph, which resembles 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, al- most indiscriminately, 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 marked 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 persons, varying according to the quality of the different sub- stances on which we feed: indigo gives it a blue colour; it is reddened by madder and beet-root, and is changed to gieen, by the colouring matter of several vegetables, &c In a great num- OF ABSORPTION. 161 ber of experiments performed on living animals, it has always appeared to me, such as it is described by authors, white, with a slight viscidity, and very like milk containing a very small quantity of flour. It is easy to collect a certain quantity of chyle, by tying the thoracic duct of a large dog, of a sheep, or even of a horse, as was done several times at the veterinary school at Alfort. This fluid, when exposed to the air, on cooling, separates into two parts, tbe one forming a kind of gelatinous coagulum, ver. 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 cake on the surface of the fluid. Hence he concludes, contrary to the opinion of 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 trans- parent, 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 sub- stance which concretes 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 vesseU of white- blood animals. 22 162 ON THE CIRCULATION. 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 among the latter, some finish the work, while others prepare the materials, so tbe lungs and the secretory glands are continually occupied in separating from the blood whatever is too heterogeneous to our nature to become assimilated to our organs, or to afford them nourishment. To understand, thoroughly, the mechanism of this function, it is 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- ON THE CIRCULATION". 163 mg 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 circula- tion. IC, 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 threat- ened with immediate suffocation. In man, the heart is placed nearly towards the union of the upper third of the body, with 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 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 foetus 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 live- ly, and the better felt, when the heart is powerful. It is on that account that some passions, for example, anger, by in- creasing 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 164 ON THE CIRCULATION. animals, as the turkey cock and the ostrich, possess less courage than the least bird of prey; that the ox has less than the lion and other carnivorous animals. What has been said does not apply to the absolute, but to the relative size of the heart. Now, though the heart of a hawk be absolutely smaller than that of a turkey cock, it is nevertheless larger, in proportion to the other parts of the animal. Besides, the birds 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 facts, however, are only proofs of the influence of the mind on the body. In civilized man, the prejudices of honour, interest- ed considerations, and a thousand other circumstances, degrade the natural inclinations of man, so as to make a coward of one whose strength is such as would induce him to brave all kinds of 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 affections 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 accessary, 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 UN THE CIRCULATION. 165 point of death, the lungs expand with difficulty, arid the blood sent into them, by the contractions of the right ventricle, being no longer able to circulate through them, collects in that cavity, flows back in 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 cavities, 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 blood destined to the lungs, to a very short distance, and through a tissue easily penetrated, requires but a moderate impelling force. As will be shown, in speaking of respiration, a function of which the physiological history is not easily separated from that 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 ?-re 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 lithotomy. He was remarkable for the lividity of his compexion, the turgescence of the vessels of the conjunctiva, and the thickness of his lips, which, like the i>st of his face, wore of a dark colour: his respiration was laborious, his pulse 166 ON THE CIRCULATION. 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 natural simplicity, was such that he never had 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 bis dif- ficulty of breathing increased, was followed by syncope, and he died from suffocation. On opening his body, his heart was found filled with blood, and especially the right auricle, which was considerably distended; tbe pulmonary artery was aneurys- mal, and uniformly distended from the right ventricle to its division: none of its coats had yet given way. The two ven- tricles of the heart were of nearly the same capacity, and the relative thickness of their parietes did not vary so much as in health. The partition between them contained an opening of communication of an oblong shape, about half an inch in ex- tent, and directed obliquely from below upwards, from before backwards, and from left to right; so that not only the direc- tion 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 snowed, 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 al- ready vivified, and required less action from that organ to com- plete its oxydation; on the other hand, the right auricle emptied itself with difficulty, into the right ventricle, in part filled with the blood which the left ventricle sent into it with greater force: hence the extreme 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 in- activity might, likewise, depend on the flow of the venous blood into the aorta, along the ductus arteriosus. It is worthy of ON THE CIRCULATION. 167 observation, however, that this impure blood was not transmit- ted 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 prepara- tion was deposited by M. Deschamps, in the museum of the Ecole de Medecine of Paris, and was, by their desire, modelled in wax. M. Beauchene, junior, presented the same museum with a similar preparation, which he procured from a subject in the dissecting room. Several anatomists have paid attention to the structure of the heart; much has been said on the subject of the peculiar ar- rangement 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 various directions, form the two auricles; other and more numerous fibres form the parietes of the ventricles, reach from the apex to the base, extend into the septum which divides them, pass from the one to the other and are lost into each other, in several points. They are exceedingly red, short,close, and united by a cellular tissue, in which fat scarcely ever accu- mulates. V.-..'- These fibres, forcibly pressed against each other, from 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, whatever in other respects may be the direction of its fibres, tends to draw towards the centre of the cavities, every point of their parietes. Lastly, a very fine membrane lines the inner part of these cavities, facilitates the flow of the blood, and pre- vents the infiltration of that fluid. LI I If we suppose, for a moment, that all the cavities of the heart are perfectly emptied of blood, and that they fill in suc- cession, the following may be considered as tbe mechanism of the circulation through the heart. The blood brought back from every part of the body, and deposited into the right auri- cle, by the two vense cava?, and by the coronary vein, separates its parietes and dilates it in every direction. The irritation at- tending the presence of the blood, stimulates the auricle to con- traction; this fluid, which is incompressible, flows back, in part, into the veins, but it chiefly passes into the pulmonary ventricle, 168 ON THE CIRCULATION. through a large aperture, by means of which it communicates with the right auricle. The auricle after freeing itself of the blood with Which it is filled, relaxes and again dilates by the 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 tbe 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 edgeof the opening of communication, and the free edge of which is divided into three divisions, to which are attached small tendons terminating into the columnar carnese of tbe 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 carnese, 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 right, 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 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 ON THE CIRCULATION. 10U vailc, 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 wuich 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 •n 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 evi- dent, that the auricles could no't have emptied themselves into the ventricles. The alternate action is moreover absolutely ne- cessary, as the heart any more than the other organs, is unable to keep up a perpetual action; the principle of its motion, which is soon exhausted, being incapable of restoring itself, except during rest. But, as was observed at the beginning of this work, in speaking of the vital power and functions, the alter- nations of action and repose in organs which, like the heart, perform functions essential to life, must be extremely short in their duration and at very close intervals. 2$ 170 ON THE CIRCULATION. The cavities of the heart, however, are not entirely passive during dilatation, and the action of that organ docs 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 Ga'< n termed pulsivc; 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 dilatations 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. Tbe 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- lumnar, carneae 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 parietesof 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 tbe auricles are situated, rests against the vertebral column, and that these two cavities, by dilating at the same time, and by their inability to move the vertebreae, 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. * Both Haller and Senac found that, by injecting warm water into the heart, it could be made to contract for sometime after the death of the animal. En. ON THE CIRCULATION. 171 The quantity of blood which each contraction of the ven- tricles sends into the aorta and pulmonary artery, most proba- bly, 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 calculations by which it has been endeavoured to solve this physiological problem. In fact, from Keil, who estimates at a few ounces only, the force of the heart, to Borelli, who makes it amount to one hundred and eighty thousand pounds, we have the calculations of Michelot, Jurine, Robinson, Mor- gan, Hales, Sauvages, Cheselden, &c; but as Vicq-d'Azir ob- serves, 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 per- haps impossible to estimate it with mathematical 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 consi- derable 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 toul disagreement in the estimates of different writers Before we engage in any calculations respecting the matter, the following data should be clearly esta- blished. ' 1 The quantity of blood expelled from each ventricle at every contraction 2. The degree of velocity with which it is expelled. 3 The amount of resistance which each ventricle has to over- come before it can propel the blood into its corresponding arte- ries. r ° 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 con- tinue as heretofore, vague and conjectural. All we know with cer- tainty on the subject is, that the heart is a muscle of great streueth as is evinced by the phenomena of the circulation, and further? by the tact that, it 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 frequently asked, does not the heart become exhausted like other muscles, by exertion ? ' Three answers to this 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 involuntary muscles ; and hence he infers that the one set is thereby fitted for temporary, and the other for herma- nent, and uninterrupted action. 172 ON THE CIRCULATION. 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 ves- sels and causing an effusion of blood. The aortic arterial sys- tem may be compared to a tree, whose trunk, represented by the aorta, having its root in the left ventricle of the heart, ex- tends afar its branches, and throws out, on every side, its nu- merous ramifications. The size of the arteries decreases, the farther they are from the trunk by which they are given off. Their form, however, is not that of a cone, they are rather cy- linders 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 capa- city of the arterial system increases with the distance from the heart; hence it follows, that as the blood is continually flowing from a straiter to a wider channel, its course must slacken. The direction of the arteries is often tortuous, and it is observed, that the arteries which are sent to hollow viscera, as the sto- mach, 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 tis- sues into which they are distributed. Lastly, the arteries arise from one another, and form with the trunK or oranch from which they are given off, an angle varying in size, but which is always obtuse, and more or less acute towards the branch. 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 exceptions to this alledged distribution of the nerves 2. By Stahl, it is imputed altogether, to the intelligence of his ani- ma 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 irritability being possessed by the heart. It is to be recol- lected, that he judged of the degree of this property by the duration of the contractile power 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 voluntary mus- cles retain their irritability longer than the heart itself. The dif- ference, indeed, in this respect in any class of animals, is so slight. ON THE CIRCULATION. 173 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 sec 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 flowing in contrary directions, along the two branches, meet at the point of union, and mutually repel each other; their par- ticles 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 anasto- motic 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 calliber is smaller. The experiments of Clifton Wittringham prove, that the parietes are stronger in 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 collaspe, 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- that other objections aside, the hypothesis could not be entertained- —Ed. * If in man and the greater number of animals, the yellow fibres, which fbrm this coat differ greatly from muscular fibres, they in the elephant resemble that texture very completely, as I had an op- 174 ON THE CIRCULATION. 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 retrac- tion might depend on elasticity, it might likewise be occasioned by the contraction of fibres not absolutely circular nor longitu- dinal, but spiral and imperfectly surrounding the vessel, and crossing each other iu 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 ef- fort to which the external coat yields by stretching. Lastly, a third, thin, and epidermoid coat lines the inside of these ves- sels, and seems less calculated to give strength to the parietes of the arteries, than to facilitate the flow of the blood, by pre- senting to it a smooth, even, and slippery surface, continually moistened by a serous exudation from the minute arteries, or vassa vassorum, 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. Of the three coats which form the parieties of the arteries, the fibrous, though thicker than the other two, offers, however, the least resistance. If you take the carotid artery which, for a considerable space, does not send off any branches, and forci- bly inject into it a fluid, the internal and middle coat will be torn, before 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 experi- ment is attended with the same success, if performed with air or any other gas. In aneurism, tbe 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, portunity of observing, when I witnessed the dissection of the ele- phant that died in the year X. at the Museum of Natural History. Let men of judgment decide, whether the analogy is sufficient to warrant our admitting in the arteries of the human body, the exis- tence of muscular fibres. ON THE CIRCULATION. 175 it is ol.-.s.-rvcd, that the sac is entirely formed by the dilated ' :l!-i!ar coat. Take an artery of a certain caliber, for example, the carotid or humeral, apply a ligature around it and tighten it with some de^,\ce of force. Dissect and take out the vessel, then cut the thread, and examine the place to which it was ap- plied, you will observe, that the parietes of the artery are in that part thinners and formed merely by the cellular coat, which alone has withstood the constriction. Take hold fcf the two ends of an insulated arterial tube and stretch it, then examine its inner com, 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 theJ*nee, 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 in- ner coat is ruptured, or at least weakened, so as to occasion an aneurism, always rapid in its progresses 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 con- siderable number of aneurisms of the aorta have been occasion- ed by too forcible and too sudden an extension of the trunk in raising a heavy burthen. From the dryness, the frailty of the yellow 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 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 ;<>cs 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 176 ON THE CIRCULATION. of caries of the knee joint combined with a scorbutic affection, hemorhage attended the fall of the ligatures, which did not come away till nineteen days alter the operation; as if the fibrous coat of these arteries/partaking in the debility of the muscular organs, 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, con- tractility is very apparent in those of a smaller caliber, and is found complete in the capillary vessels.* It is owing to this that, in the 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 little influence on the motion of the blood sent in- to 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 ossification; 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 conclu- sive arguments in favour of those physiologists, who explain, on the principle of elasticity, the contraction of arteries. But however correct this explanation may be, with regard to the vessels near the heart, it does not apply to the capillaries; the influence of that organ does not operate on these vessels. One ♦This is not altogether correct. Every portion of the arterial system is unquestionably possessed of the property of contractility, In the larger vessels, muscular fibres are even demonstrable to the ^ye. Besides, mere elasticity will pot explain many of the phenome- na of arterial action Contrary to the doctrine of Mr Hunter, it was maintained by Baron Haller, and indeed by almost all the co- temporary 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 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.—Ed. ON THE CIRCULATION. f77 oiay 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, in- flexible, and consequently inert, on reaching the extremity Of these canals, is, in a manner, again taken up by the vital pow- er residing in the capillary vessels, and circulates from the in- fluence of the action belonging to these vessels. Besides, elas- ticity, 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, bow- ever 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, con- sider elasticity as the principal cause of the progression of the blood along the arteries.* * It has always been a matter of controversy among physiologists, whether the blood is propelled by the heart only, or whether the arteries co-operate to the same end. It is well known that. the illustrious Harvey, the discoverer of the circulation, was of the former opinion, and that he has since been supported by many followers. We admit, at once, that the heart is the chief organ con- cerned, but it seems to us equally true that the arteries also exer- cise a considerable agency, most commonly as auxiliary to the heart, yet sometimes to a certain extent independently of that organ These. two positions are demonstrable, 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 capillary extremities. 2. That the arteries contract with considerable force, the natural and unavoidable effect of which must bet the propulsion of the blood, and the quickening of the circulation. 3. That the circulation has been maintained in the foetus, though utterly destitute of a heart. Cases of this description are recorded in sufficient number, to put the fact beyond a doubt It may how- ever be alleged, that in these instances, as very 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 haemorr- hages, blushing, 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 consequently 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.—Ed. 24 178 ON THE CIRCULATION. 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 dimen- sions of the space in which it is contained;—the resistance from the curves of the vessels;—the friction which it under- goes, and which increases, as, at a distance from the heart, the canals along which it circulates increase in number; and last- ly, the deviations which the blood meets with in its course, from the trunks into the branches, which, coming off sometimes al- most at right angles, 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 to that of the animal economy, have, nevertheless, supported their opinion by a fact taken from hydraulics. To give any certainty to these calculations, respecting the impediments to the circulation of the blood in the arteries, it would, they say, be necessary, that the arteries should be empty at the instant when they receive the jet of blood sent into them by the con- traction of the ventricles. This, however, is not the case; the arteries are always full, the blood flows along all of them with the same degree of velocity. This system of vessels may be compared to a syringe, from which a number of straight 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 ON THE CIRCULATION. 179 contained in the arterial tube constantly enlarges, from the innu- merable divisions of the vessels. Since it is admitted, that the course of tbe 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 to only that set of vessels. A very remarkable difference is observable, between the blood which is sent to the toes, and that which goes to the 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 rc-action of tbe 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 contractility is almost the sole agent in producing the action of the minute arteries. If a finger is introduced into the artery of a living animal, its parietes compress it in every direction; if the blood is prevented from flowing in it, the canal becomes obliterated by the adhesion of its parietes, and the vessel is converted into a ligamentous cord, such as that formed in the adult, by the remains of the umbilical arteries and veins___ This contractility which, during life, is always in action, keeps the arteries, distended by the blood which fills them, of a smaller caliber than after death. In performing capital opera- tions, especially in the amputation of limbs, I have always found the arteries, whether filled with blood or empty, much smaller than I should have expected from their appearance in the dead body. It happens, however, sometimes, that the quantity of blood sent to an organ increases, in consequence of some cause of ir- ritation; the caliber of the arteries of the part, then becomes remarkably enlarged. Thus, the arteries of the uterus, which are very small in its unimpregnated state, acquire, towards the end of pregnancy, a caliber equal to that of the radial arterv: the 180 ON THE CIRCULATION. small arteries which are sent to the mamma?, 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 con- cerned in bringing to these glands the materials of their secre- tion. 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 precaution which need not be attended to, in a case of gangrene. Gangrene is attended with this peculiarity, tha the arteries of the mortified parts contract, so as to become obli- terated, when their caliber is inconsiderable. As the arteries are the canals which convey to all our organs tbe 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 if ON THE CIRCULATION. 181 lias 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 tbe parietes of these cavities, always filled with blood, to that which the heart sends into them. This dilatation 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 be- lieve, that another cause of this phenomenon is a slight dis- placement of the arteries, every time they dilate. These dis- placements are most easily observed at their curvatures, and where they adhere to surrounding parts, by a loose and yielding cellular 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 (he 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, afford the means of judging of the nature and danger of a disease, of the power of nature in bringing about a cure, of the organ that is most affected, of the time or period of the complaint, &c. No one has been more successful than Bordeu, in tbe consideration of the pulse, under these different points of view. Its modifications indicative of tbe 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 affection is situated above or below the diaphragm, hence the distinction of superior and inferior pulse. Lastly, peculiar 'haracters denote the lesion of peculiar organs: which consti- 182 ON THE CIRCULATION. tutes 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 pulsatory motion, by which all the parts of the body are agita- ted, 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 tbe impulse which it gives to the blood, dilate on receiving this fluid, and collapse when the effort of contraction is over. Every part vibrates, trembles, and palpitates within the body, the motions of the heart shake its whole mass, and these quiverings, which may be observed externally, are most manifest when the circulation is carried on with rapidity and force. In some head aches, the internal carotid arteries pulsate with such violence, that not only the ear is sensible to the noise made by the column of blood striking against the curvature of the 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 distinct, as the effect of which we are speaking is more marked. It is, likewise, from observing this phenomenon, that several physiologists have been led to conceive the idea of a double mo- tion, which dilates or condenses, which contracts or expands, alternately, all organs endowed with life; they have observed, that dilatation prevails in youth, in inflammation and erection, conditions of which all parts are capable, according to their difference of structure. LIX. At the moment when the left ventricle contracts, to send the blood into the aorta, the sigmoid valves of that artery 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 in the others. When the contraction of the ventricle is over, the aorta acts on the blood which it contains, and would send it back into the ventricle, if ON THE CIRCULATION. 183 the valves, by suddenly descending, did not present an insuper- able obstacle to the return of the blood, and did not yield a point of resistance to the action of the whole arterial system; only the small quantity of blood below the valves, at tbe moment of their descending, 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 pulsation is felt in all the arteries of a certain caliber, at the in- stant the ventricles are contracting. The reason that the pul- sations of the heart appear to take place at the same time as those of the arteries, ist that the columns of blood, in these ves- sels, receive an impulse from that which is issuing from tbe ven- tricles, and this concussion is felt in an instant of time, too short to be measured, such as that which is felt by the hand applied to the end of a piece of timber struck, at the other end, with a hammer. The blood which fills a main trunk, supplies to each of the branches which arise from it, columns proportionate to their caliber. This division of the principal column is effected by a kind of projection at the mouth of each artery. These in- ternal projections detach from the main stream the lesser ones, and these flow the more readily into the branches, according as these arise from the trunk at a more acute angle, as the projec- tion is more prominent and the deviation of the fluid less con- siderable. 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 admira- ble conformation, may be readily ascertained, by observing the aorta, in its passage through the cura of the diaphragm; tbe perforating arteries of the thigh, where they enter at the back part of the limb into the adductor muscles; the poplitieal, asit passes through the upper extremity of the soleus muscle. LX. Of tlie capillary of vessels. The arteries, after dividing into branches, these branches into lesser ones, and these into progressively smaller ramifications, terminate in the tissue of 184 OX THE CIRCULATION. 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 ofdivissions* 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 tissoe 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 retro- grade motion, is no longer red, because its globules are strain- ed, 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, thai the eye may discover their colour. We know, that grains of sand reduced to a very fine dust, appear colourless when ex- amined 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 lamina? 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 peri- toneum, the cartilages, the ligaments, &c. which naturally are whitish or transparent, become red, when affected with inflam- mation, whether from the increased impetus of the circulation, which forces and accumulates into the capillary vessels a grea- ter number of red globules, or that the sensibility of these small vessels is impaired by inflammation, so that they admit globu- les which they formerly rejected. * The arterial divisions which may be discerned by the aid of anatomy, do not exceed eighteen or twenty : nevertheless, they di- vide still further, when they are become so minute as not to be dis ■ cernable with the help of the most powerful microscope. ON THE CIRCULATION. 185 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 spongiosum of the urethra; the same ap- plies to the capillaries of the muscles of the mucous mem- branes ; there are, however, very few of those organs, in which the whole portion of the capillary tube, between the termina- tion 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 tbe capillary, and within this space ttie blood can- not 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 mucous 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, therefore, not to be wondered, that these organs should have a greater number of capillary vessels sent to them : since these vessels do not supply them merely with molecules to carry on nutrition and to repare the waste of the part, but impart to them the principle of their frequent contraction: the quantity of them is so considerable, in all these parts, employed in the twofold offices of nutrition and secretion, that Ruysch penetrated, with his injections, the whole thickness of their substance, to such a degree, that the organs which he had prepared were only a wonderful and inextricable network of capillary vessels ex- tremely minute. On these anatomical preparations, made with an art hitherto unrivalled, Ruysch grounded his hypothesis re- lative to tbe intimate structure of the body, in which, he ima- gined, all was capillary 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 conceive that the number of them must be re- ally prodigious. As long as tbe 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 subser- vient to these great functions, it must be diffused through the 25 186 ON THE CIRCULATION. very tissue of the organs, by means of the capillary divisions ; these little vessels exist then, in every part, where any organi- zed molecules are found united ; since tbe particle formed by their assemblage, must, at least, find, in the juices they bring to it, the materials of its reparation. Entering, in greater or less proportion, into the organization of all the tissues, the capilla- ries receive 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 the 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 excre- tory ducts of the organs, &c. are not openings like the pores common to all matter; each of them may be considered as an orifice, sensible, and, especially, contractile, of differing size, according to the state of the strength or of the vital powers. The size tben 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, tbe pores of the capillaries enlarge, and suffer the red blood to transude through their relaxed mouths. This phe- nomenon takes place, not only under the skin and on the vari- ous mucous surfaces, it is observed also in tbe very tissue of the organs. It is thus, that I have often seen, on opening the body 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 muscles into a kind of pulp; and the extravasated blood itself undergoes a beginning of decomposition. The bones themselves are liable to these scorbutic bloody infiltrations. I had an opportunity of ascertaining this in the hospital of St. ON THE CIRCULATION. 1-87 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 sysjtem, 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 di- visions, as false as they are useless. LXI. The sanguineous capillaries anastomose, and form, like the lymphatic capillaries, a net work that envelops all the or- gans. Their frequent communications do not allow obstruc- tions to take place and to produce inflammation, as Boerhaave thought, and as was long taught on the authority of that cele- brated physician. Haller, Spallanzani, all the microscopic ob- servers, have perceived threads of blood flowing in the capilla- ries, 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. 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 tbe inflamed part; for when death, which puts an end to all irritations, and relaxes all spasms (mors spasmos, solvit. Hipp.) ;r 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 tbe side. If lo 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 surprised, that the opening of the 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, 183 ON THE CIRCULATION. 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 maybe seen by the help of the microscope, in cold-blooded animals, in frogs and sa- lamanders. In some fisb, we may, even with the naked eye, ob- serve frequent and considerable inosculations between the arte- ries <,nd 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 terr minate, sometimes, in capillary vessels carrying serous fluid, such are the vessels of the sclerotic coat; these vessels become small veins whose caliber gradually increases, until they admit red globules in sufficient number to leflect that colour. At other times, the artery and vein are continuous, without 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 afford an explanation of the phenomena on which the belief of this termination of the arte- ries rests. There exists no parenchyma, no spongy 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, tbe retiform plexus, which surrounds the ori- fice of the vagina, and perhaps also the tissue of the spleen, though the experiments of anatomists (Mascagni andLobstein) seem to prove, that in these organs, the arteries and veins are immediately continuous. LXII. 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 OX THE CIRCULATION. 189 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 corresponding 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 thp arteries. In this calculation, one should con- sider as arterhd, the blood contained in the pulmonary veins and in the left cavities of the heart, while that which fills the cavi- ties in the right ride of the heart and the pulmonary artery, is truly venous, and has every character of such blood. Although the veins generally accompany the arteries, and are united to them by a common sheath of cellular membrane, this disposition of parts is not without exceptions. The veins which bring back the blood from the liver, do not, in any respect., fol- low the course of the branches of the hepatic artery; the sinuses of the brain are very different, in their arrangement, from the oerebral arteries; the veins of the bones, which are particular- ly 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 tbe bone, with the exception of those in the middle canal, and which pass through the nu- tritious foramen of the bone. The veins are not only more numerous than the arteries, but they are likewise more capa- cious, and dilate more readily: this structure was necessary, on account of the slowness with which the blood circulates, and of the readiness with which it stagnates, when the slightest obsta- cle impedes its circulation.* The force which carries on the circulation of the blood, along the arteries, is so great, that Na- •The arteries contain,at all thnes,nearly the same quantity of blood. The veins are always the seat of plethora, because the blood stag. nates in them more readily; and this condition brings on inflammato- ry fever (consisting merely in an increased action of the vascular system, as is expressed by the term angeiotenique applied to it by Professor Pinel) only when the venous congestion becoming exces- sive, 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, 8cc. 190 ON THE CIRCULATION. hire seems not to have availed herself of tbe mechanical ad* vantages which might have facilitated its flow. On the other hand, the power which determines the progression of the venous blood is so feeble, that she has sedulously removed every obsta- cle which might have impeded its course. And as the relation of the minute 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 rapidity of its course, must, therefore, be progressively in- creased. The veins are almost straight in their course; at least, they are much less tortuous than the arteries. The force which makes the blood flow along them, is consequently not taken up in straightening these curves; the anastomoses are, likewise, more frequent, and as the flow of the blood might have been 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 superficial 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 lympha- tics, 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 vessel, destroy the continuity of the column of blood returning to the heart, divide it into smaller columns, as numerous as the intervals between the valves, and the height of which is de- termined 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 advantageous- ly 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 tbe veins, is the combined action of the heart and arteries; but the impulse from those organs is lost ON THE CIRCULATION. 191 in the system of capillary vessels, and does not extend to the veins. The specific action of their own parietes, aided by aux- iliary means, such as the motion of the neighbouring arteries, is sufficient to carry the blood on to the heart.* 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 more extensible than that of the arteries and equally thin, adheres more closely to the other coals. 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 ossi- fied, as we advance in years. This internal coat is merely a continuation of that which lines the cavities of the heart; and as the origin 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 essential part of the venous system; it alone constitutes the veins within the bones, the sinuses of the dura mater, the he- patic veins, in a word, all the veins which are so firmly attach- ed externally to the neighbouring parts, that the blood flows along them, as along inert tubes, their parietes being, almost completely, incapable of contracting. * In the process of returning the blood to the heart, two causes are principally engaged, the most efficient of which, is undoubtedly the contractile power 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 shown by Haller that the vena cava, at least, is muscular, and Verschuyr and other respectable physiologists, have detected the same structure in the most minute veins. There is one act which we think ought alone to convince us of the contrac- tility of these vessels, which is, that they always adapt themselves to the quantity of blood they contain. Co-operating with the above cause is the action of the muscles, as may be illustrated by the familiar example of venisection When in this case the blood issues languidly from the orifice made in the vein, it is known, that nothing promotes its flow so effectually as pressing something hard in the hand. This operates simply by bringing into action the muscles of the fore-arm and humerus, there- by producing considerable compression of the veins.—Eb. 192 ON THE CIRCULATION 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 tbe 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. LXIV. As tbe inferior cava passes through the lower edge of the liver, whether along a deep fissure, or in a real canal in the 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 con- tents 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 finger; the termination downward of this vessel, in the right renal vein, and above in the superior cava, were most distinct, and by compressing it from above down- ward, 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 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 caviiy forces back the blood into the veins which open into it; this retrograde course is manifest in the superior ON THE CIRCULATION. 193 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 more marked in the inferior cava, the orifice of which is but imperfectly closed by the valve of Euslachius; it is felt in the abdominal veins, and extends even to the external iliacs, accord- ing 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 living 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, sut round- 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, tbe opinion which they entertained, that the chyle taken up by the mese- raic veins, was carried to the liver, in which its sanguification was effected, and lastly, that the arteries were filled with vital spirit, and contained only a few drops of blood which passed 194 ON THE CIRCULATION. through small holes, which, Galen says, perforate the septum of the ventiicles. The blood, however, continually urged on by tbe columns which follow each other in succession, by the action of the veins whose parietes become gradually stronger, and by the compres- sion which these vessels experience from the viscera, during the motions of respiration, reaches the heart, and enters the auri- cles with the greater facility, as the orifices of the cava? not be- ing directly opposed to each other, the columns of blood which they convey do not meet and do not oppose each other. LXV1. The blood, continually carried to all parts of the body by the arteries, returns, therefore, to the heart, by a motion which can never be interrupted, without considerable danger of life. We know, that the 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, compressed or tied, or when a fluid is injected into them. When an artery is wounded, the blood comes from the part of the vessel nearest the heart; it comes, on the contrary, from towards the extremi- ties, if it is a vein thai has been opened. By compressing or tying an artery, the course of the blood is suspended below the ligature, and the vessel swells above. The veins, on the con- trary, 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 micro- scope, 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. LXVII. The theory of Harvey, such as it is laid down in his work, entitled, De sanguinis circuitu, exercitationes anatomical, 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 hs completely inert tubes, while every thing tends to prove that the arteries and veins assist the motion of the blood, ON THE CIRCULATION. 195 by an action peculiar to themselves. He admits, that the blood flows, in every part of the circulatory system, with an uniform degree of speed; an opinion so manifestly contradicted by rea- soning and experience, which proves that the velocity of its course diminishes, the greater its distance from the heart, from the influence of a greater number of circumstances, which it would be useless to repeat (LVII.) This doctrine has yet, however, several abettors, and among the moderns, Spallanzani has endeavoured to support it, by a number of experiments so contradictory, that one is surprised that so judicious a physio- logist should have collected them to establish a theory com- pletely refuted by several of them. Nothing, for example, con- tradicts 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 possessed of that central organ, have nevertheless vessels along which the blood flows, and which contract and dilate by alternate motions. If the mere force of the heart propelled the blood to every part, the course of this fluid ought, at intervals, to be suspen- ded, its circulation, at least, ought to be slackened, when the ventricles cease to contract; but as the contraction of the arte- ries correspond to the relaxation ©f the ventricle, these two pow- ers whose action alternates, are continually employed in pro- pelling 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, form 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 general 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 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. 196 ON THE CIRCULATION. LXVIII. In what has been said of the circulation, no sepa- rate mention has been made of the course of tlje 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-hearl which belong to it, docs not represent a complete 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 enter tained 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, formingone half of the circle; tbe pulmonary veins, the left cavities of the heart, the aorta with all its branches, representing the other half.— The capillary vessels of the lungs form one of the points of in- tersection, and the capillaries of all the other organs represent the other point of intersection, by uniting together the arteries an'i veins of the whole body, in the same manner as those of the lungs establish 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 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 ves- sels that the blood receives its essential principles; and to un- derstand 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. OS THE CIRCULATION. 197 [here to combine with the atmospherical air, from which we ire 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 se- cretions; and supplies 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 or- gans 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 atmosphere, 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 re- paired; so that in supplying thus the different organs, the blood loses all the qualities which it had acquired by the union of the chyle and of the vital air, parts with the principles to which it owed its colour, and again becomes dark, to be repaired anew by combining with the lymph, and by the absorption of the vital part of the atmospherical air; this constitutes the principal phenomenon of the function, which will be considered in the fourth chapter. CHAPTER IV. ON RESPIRATION. LXIX. OF the different changes which the blood undergoes in the different organs, none are more essential or more remark- able than those it receives from the air, which, during respira- tion, 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 thirty degrees (Reaumur's thermometer; if laid by, it coagulates slowly, and there is separated from it a considerable quantity of serum. The blood which is brought by the pulmonary veins to the left 198 OP It F.Sri RATION. side of the heart, and which is conveyed to all parts of the body by means of the arteries, is, on the contrary, of a florid red co- lour; it is spumous, lighter, and warmer by two degrees. It likewise coagulates more readily, and contains a smaller quan- tity of serum. All these differences, which are so easily distin- guished, depend on the changes which it has undergone, by be- ing 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 very 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 panting, the pulse is quickened, and there is felt an univer- sal 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.! * The surface of the body is estimated at fifteen or sixteen square feet, in a man of middle size. •f Several travellers, whose reports on the subject I have consult- ed, agree in representing the corporeal, as well as some of the men- tal functions, to be very strangely influenced by a rarified condition of the atmosphere. But the celebrated De Saussure, a writer, who unites to the profundity of philosophical research, the polish of lite- rary refinement, has from personal experience described these af- fections with the most precision. To his description I shall, there- fore, principally adhere in the ensuing enquiry. He states, that at a certain height above the level of the sea, there uniformly 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 intolerable, indeed, is the fatigue induced in this- situ-uon, that the person suffering it. is rendered sometimes wholly incapable of motion. If he attempt to move, his legs sink ON RESPIRATION. 199 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 tinder 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 sum- mit of it, though his exertions were moderate, he was constrained frequently to desist altogether from them, and breath laboriously to recruit his strength * VVith this excessive degree of fatigue, accele- rated 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 re- novation, that he is persuaded he will be able to prosecute it unin- terruptedly. He, however, is soon disappointed On moving a short distance only, his former inability returns, and his progress is again arrested. An additional effect of this state of the atmosphere, is an almost irresistible propensity to sleep. We are told, that if the at- tention of the person be not engaged, and kept excited, he will, when pausing to rest, often fall to sleep almost instaueously, though an- noyed by the wind or cold, the light or heat of the sun, and in the most incommodious and disagueeable posture of his body Thi6 sleep, sometimes, approaches in soundness nearly to lethargy.f Nothing affords the least relief to any of the symptoms enumera- ted except rest and cold water. Cordials and spirituous liquors ag- gravate all the complaints. Now, in what manner are these singular affections to be explain- ed ? We believe with our author that they are in part owing to the diminished pressure of the atmosphere, but infinitely more to a de- ficiency of oxygen. It is clearly ascertained that respiration supports animal life, and all its actions. This process requires the presence of two principles. 11k e are oxygen and combustible matter. The former is supplied chiefly through the medium of the lungs, and the latter by the sto- + These effects are not peculiar to the human species. The same writer relates, that the mules which he employed to carry his bag- gage, became suddenly so weak and exhausted that they could hard- ly walk, even when the burden was removed from their backs. They staggered as they moved ; their respiration was panting and difficult, and seemingly attended with painful sensations of the chest, as they uttered plaintive and distressing cries ■j- It may also be observed, that aeronauts have generally men- tioned drowsiness as one of the consequences produced by the atte- nuated atmosphere of the exalted regions which they explore in their excursive flights, and some have even declared that they slept suundly, when atttie utmost pitch of their perilous adventures. 200 ON RESPIRATION. under its influence, it swells, the fluids are determined to it, in considerable quantity, 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. mach. Of the vital actions, none seems to be more immediately de- pendent and strikingly regulated by respiration than the muscular. ft is not, however, my design to dwell on the 1 elation between them. It is sufficient for my purpose to remark, that during exer- cise a greater quantity of oxygen is extracted from the atmospheie by thelungs, and that carbonic acid and water are formed, and ca- loric evolved in corresponding proportions. Hence it may be dedu- ced, that during muscular exertion, there is a greater demand for oxygen, and a larger consumption of combustible matter It also follows, if the pi'eceding premises be admitted, as a legitimate co- rollary, that the same effect would be produced, namely, an ex- haustion of the muscular 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 de- prives the body of its proper quantity of combustible matter until fatigue is finally induced. The body is afterwards gradually re- cruited by rest and feod, or, directly restored to momentary strength by the use of spirituous liquors, which are pure combustible mat- ter, 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 •want of oxygen. Here, of course, it is alleviated by rest, and deep inspirations, and exacerbated by exercise and spirituous liquors. It is suddenly induced, because the pulmonary system is so con- trived that the body at no instant receives more oxygen than what at the instant it requires.* It is speedhy removed, because, by the deep inspirations the ne- cessary quantity of oxygen is conveyed into the system. It is accompanied by sickness of stomach, and loathing of food, be- cause, digestion, like exercise, demands a copious supply of oxy- gen.f * We are instructed by experiments that animals placed in a ves- sel filled with oxygen, and respiring the gas in a state of puritv, do not consume more of it than when combined with irrespirable gas Thus it takes an animal nearly four times as long to consume the same quantity of oxygen as atmospheric air. f There are many facts to prove that oxygen is a principal agent m digestion and assimilation. The quantity employed in these pro- cesses seems, in some degree, to be regulated by the kind of food OF RESPIRATION. SOI 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 It is attended by excessive thirst, because, in a rare atmosphere, there will, of necessity, be a. profuse evaporation from the surface of the body The pulxations of the heart are more numerous, because they are performed less vigorously. Not altogether dissimilar in its nature, or origin, though milder in its symptoms, and slower in its occurrence is the fatigue occasioned by immoderate exercise under the ordinary constitution of the atmosphere. In this case, we observed an increased frequency of the pulse, and of respiration, &c. &c. The cure likewise is by rest. Cold water is touud more refreshing than spirituous li- no rs . There is another phenomenon connected with the present subject which deserves to he noticed. I allude to the propensity 1.0 sleep which has already been remarked. This too, can only be explained by ascribing it to a deficiency of oxygen. Sleep is a suspension of 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, ex- act 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 mus- cular exercise, he undertakes to show by calculation, * the quantity ot mechanical labour exerted by the philosopher who reflects, by the man of letters who writes, or the musician who composes!'1 These operations, he adds, though intelleccual, have a certain de- pendance on the physical and material part of man, which renders them susceptible of comparison with the labours of the mechanic- Whether these views be just as they are brilliant, 1 shall not pre- tend to decide. But, though we may never be competent to deter- mine with much accuracy the quantity of oxygen consumed by the operations of the mind, yet, that it is essentially necessary to tlie 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, and these contain no oxygen, is productive of hea- viness and sleep. Sleep is apt, moreover, to occur during the progress of digestion, used. An animal diet consumes more than a vegetable one. Mr. Spalding found that when he lived upon animal food, and drank spirituous liquors, he expen, led the oxygenous portion of the atmos- phere in his diving bell, in a much shorter time than when he sub- sisted on vegetable matter and water Dr Beddoes has also fur- nished some curious farts v. hicJi go to establish the same conclusion 27 302 OF RESPIRATION*. 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 tbe 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, notwithstand- ing the minute attention with whicb some writers note the state of the barometer, of the thermometer and hygrometer, and of tbe electrical state of the atmosphere, in giving an account of a disease or of an experiment, on which the above circumstances have no apparent or certain influence. The atmosphere, like every other fluid, has a perpetual tendency to a state of equili- brium; hence the rush of air into the lungs, or into other situa- 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 increases, and the latter diminishes as it grows cold; variations of tem- perature produce the same effect on solutions of salts in liquids. The formation of all the aqueous meteors, depends on the dif- ferent conditions of the solvent powers of the atmosphere; when considerable, the atmosphere is warm and dry and the air se- whenthe oxygen of the system is employed, in a considerable de- gree, in the assimilation of aliment, and the elaboration of chyle ; or, if the disposition to sleep be counteracted, the senses, at least, be- come 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 oxygen. It is from the combination of these causes, that among the inhabi- tants of hot climates, the custom of sleeping during the day, and es- pecially 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.—-Ed. OF RESPIRATION'. 20S rent; clouds form when it is saturated; dews, fogs, and rain, are the consequence of a diminution of its solvent power, as snow an I hail, of a degree of cold which precipitates the fluid. The different degrees of dryness or moisture, marked by the hygro- meter, 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 pro- portions 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- ral philosophy, which is called eudiometry, or the measurement •f the purity of the air, is far from accomplishing what its name indicates, and bas 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 atmos- phere; now its salubrity, its fitness for respiration, is not in pro- portion 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 Lom- bardy, there was found in each the same quantity of oxygen; and yet those who breathe the former enjoy robust health, while the inhabitants of the marshy plains of Lombardy are carried off by epidemic diseases, are pale, emaciated, and habitually lead a languid existence. Though at least 0,20 of oxygen are necessary to render the * This is pretty nearly the original estimate of Lavoisier, whose experiments have since been very frequently repeated, and with no material difference in the results. It is however proper to recollect in speaking of the relative proportion of the ingredients of the at- mosphere, that this estimate must be considered as having refer- ence to weight and not to measure. On this point Lavoisier is si- lent, as well as most other chemical writers. It is nevertheless a fact, as has been more particularly shown by Bertholet, that the at- mosphere contains only twenty-two parts of oxygen, in the hundred, by measure. By some chemists it has been supposed, from the circumstance of the carbonic acid being generally found in a larger quantity near the earth, that it .s 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 combination.—Eb 204 OF RESPIRATION. air fit for respiration, the proportion may be diminished to seven or eight parts in the hundred; but iu such cases the breathing is laborious, panting, and attended with a sense of suffocation; in short asphyxia conies on even while the air still contains a certain quantity of oxygen, of which the lungs cannot entirely deprive it. Whenever a number of persons are collected in a confined place, in which the air cannot be easily renewed, the quantity of oxygen diminishes rapidly, that of carbonic acid in; reases. The latter, in consequence of its specific gravity, sinks to the lowest part, and strikes with death every living be- ing 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 tbe most unhealthy part of a play-house, when a great num- ber of people, after remaining in it for several hours, have de- prived 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 composition by the combination of all the substances exhaled from their bodies. These volatilized animal emanations become putrid while in the atmosphere, and conveyed to the lungs during respiration, become the germ of the most fatal diseases. It is in this manner that the jail and hospital fever, so .fatal to al- most all whom it attacks, arises and spreads. A dry and tem- perate air, containing 0,27 of oxygen and 0,73 of azote, and free of other gases or other volatilized substances, is the fittest for respiration. In certain cases of disease, however, this func- tion 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 moun- tains; nervous women prefer that in which horn, feathers, op other animal substances are burning. An atmosphere highly electrical, at the approach of a storm, renders respiration very laborious in some cases of asthma. In short, the qualities of the *ir must be suited to tbe 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, Haiiy, Brisson, &c. to that of M. Guytan OF RESPIRATION. 205 .Morveau on the method of purifying the air, when from differ- ent 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- ky 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 " circulation: it does not exist in some cold-blooded animals. In reptiles, for instance, the heart has but one auricle and one ventricle; the pulmonary artery, in them, arises from the aorta and conveys but a small proportion of the blood; hence the ha- bitual temperature of these animals is much lower than that of man. For the same reason too, there exists so small a differ- ence between their venous and arterial blood; the quantity of fluid vivified by exposure to the air, in the pulmonary tissue, be- ing too small to effect, by its union with the general mass, a ma- terial 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 emp- ty bladder, the neck of which, by being adapted to that of the bellows, should admit air on drawing asunder its sides. The air, in fact, enters the lungs only when the chest dilates, and enlarges, by the separation of its parietes. The agents of res- piration, are, therefore, the muscles which move tbe 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 organs which the chest contains, besides a capacity of motion required to carry on the functions intrusted to them. To carry on respiration, which may be defined the alternate ingress of air into the lungs and its egress from those organs, it is necessary that the dimensions 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 influence 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 206 OF RESPIRATION. aides 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 tbe thorax, and pass from the ribs to the neighbouring bones: as tbe subclavian muscles, the great and lesser pectorals, the serrati, the latissimi dorsi, the scaleni, the longissimi dorsi, tliesacro 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 other; it is attached to the cartilages of the false ribs, and to the lumbar vertebras, and has three openings to transmit the ossophagus 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 tbe descent of the dia- phragm. The curved fibres of that muscle, straightened in contraction, descend towards the abdomen, and compress the viscera. The descent of the viscera thrusts forward the ante- rior parietes of that cavity, and these recede, when on expiration taking place after inspiration, the diaphragm now relaxed, rises, pressed 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 n quired besides, that its dimensions should be increased in every direction. The intercostal mus- cles then contract, and tend to bring together tbe ribs between which they are situated. The intercostal spaces, however, be- come wider, especially at their anterior part, for whenever lines falling obliquely on a vertical 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. Besides, as the ribs are curv- ed 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 enlarged transversely, while the second curvature (in the direction of their edge) be* OF RESPIRATION". 207 mg increased by a real twisting of these bones, and which reaches to the cartilaginous parts, the sternum is heaved for- ward 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 extrem- ity is thrust forward The diameter of the chest from the fore to the back part increases, therefore, as well as the transverse diameter. This increase of dimensions has been estimated at two inches to each of these diameters; the dimensions of the vertical diameter, which are regulated by the depression of th.e 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 vertebrae, appear to him to favour these different motions, as the direction of the articulations of the upper ribs, is upward, 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 vertebrae 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 upper ribs, they oppose and neutralize this effort, and all the ribs are elevated at once. If this wen not the case, the ribs ought to be depressed whenever the intercostals contract, since the lowermost, fixed i08 OF RESPIRATION. by the diaphragm, would become the fixed point on which aU 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 physiolo- gists have thought, that these muscles were opposed to each Qther, that the internal intercostal muscles brought together the ribs, after they had been separated by the external intercostals, the one set being muscles of expiration, while the other set contracted during inspiration. It is well known with what pertinacity Hamberger, in other respects a physiologist of considerable merit, defended this er- roneous opinion, in his dispute with Haller; it is now, however, ascertained, that all the intercostal muscles concur in dilating the chest, and that they ought to be ranked among the agents of inspiration, because the unequal capacity of motion in the ribs, prevents the internal intercostals, the lower insertion of which is nearer to the articulation of these bones to the verte- bra?, from depressing the upper ribs. Of the very conclusive experiments by which Haller undertook to refute the arguments of his adversary, I shall relate only that which is performed by stripping the parietes of the chest, in a living animal, of all the muscles which cover it,.and by removing, in different parts of the thorax, some of the external intercostal muscles. The in- ternal intercostals are then seen to contract during inspiration, together with the remaining external intercostals. These mus- cles, therefore, have a common action, and are not in opposi- tion to each other. The same experiment serves to prove the increased dimensions of the space between the ribs. On hold- ing 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 fi- bres opposite directions. In answer to tins 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 RESPIRATION. 209 u 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 two muscular planes, united in their action of 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 difficult, and tbe 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 latissirai 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 suffoca- ting cough, will readily understand the importance and action of these auxiliary muscles. Inspiration is truly a state of action, an effort of contractile organs, which must cease when these are relaxed. The expira- fion which follows is passive, and assisted by very few muscles. 28 210 OF RESPIRATION. and depends chiefly on the re-action of the clastic parts entering into the structure of the parietes of the chest. We have v en that the cartlages 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 tbe 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 serra- tus 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 tw« viscera, soft, spungy, and of less specific gravity than water, covered by the pleura which is reflected over them, are dwiys in contact with the portion of that membrane which lint s 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 rarified, 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 pervious, except during deglutition. LXXV. The pulmonary tissue into which the air is thus drawn in, every time the capacity of the chest is increased, does not consist merely of air-vessels, which are but branches of different 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 greater quantity of lymphatics and OF RESPIRATION. 211 blood vessels, of glands and nerves. Cellular tissue unites to- gether 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 bronchia? and trachea, and every where in contact with the parietes of tbe 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 right ven- tricle, 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 ra- dicles of the pulmonary veins. These vessels, formed from the extremities of the artery, 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 bronchia] 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 auri- cle. 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 ar- tery 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 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 oxy- * It is well known that the right lung is larger than the left, that »t is divided intr three principal lobes, while the lattc- has only two. 212 OF- RESPIRATION. gen, it returns by the pulmonary veins into the left cavities ol 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 the stimulus is sufficient to de- termine their contraction, the action of the heart does not de- pend so closely as has been said on the impression of the blood on its substance, since it contracts though empty, and prolongs its contractions to relieve itself of the black blood which fills it, when as animal dies of asphyxia. Boerhaave, who admitted one sort of peripneumony depend- ing on the obstruction of the bronchial vessels, whilst another, according to tlie 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- cine. The anatomical analysis of the lungskor 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 pulmona- ry phlegmasias, the commonest and least serious catarrh consists in inflammation of the mucous membrane which lines the air passages, 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 • That the bronchial vessels exclusively nourish the lungs, is an opinion entertained certainly by a majority of physiologists. When, however we compare the size of these vessels with the magnitude of the office assigned to them, it seems very doubtful whether they are adequate to it. We are inclined to believe, notwithstanding what is alleged against it, that the pulmonary arteries also contri- bute to the nourishment of the lungs ; and indeed there is a fact which almost proves it We allude to the circumstance of the pul- monary adhesions, which are supposed to take place in consequence of inflammation, having been repeatedly injected from the trunk of the pulmonary arteries —E». OF RESPIRATION'. ^13 under the name of hepatization, because, in fact, the substance of the lung has acquired the hardness, the weight, and some- thing 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 sometimes leaves no trace, but which oftener exhibits, on the opening of bodies, the pleura thickened and opaque, eovered 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 sealed. The latter accompany the bronchial tubes and penetrate into the substance of the glan- dular bodies situated where those air vessels divide, but col- lected, in greatest number, towards the root of the lungs and at the angle formed by the bifurcation of the traches. 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, terminate 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- * These adhesions of the lung to the pleura Costalis are so com- mon, that the old anatomists considered them as a natural deposi- tion, and called them ligaments of the lungs. It has been believed till now, that these adhesions arose from the organization of a sub- stance 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 muscles, it is produced by the act of inflammation, that it is become cellular by the thinning of its tissue and the separation of its lamina. The pleura thus reduced to cellular texture, the adhesion is produced oy 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 innumerable ; 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: —dly. When it is red, thickened, and opaque:—3dly. When is is covered with coagulable lymph:—4thlv. W ien it adheres:—5thly. When, in consequence of chronic inflammation, hydrothorax has *aken place, &c. &o. 2ih OF INSPIRATION. nished by the great sympathetic, and especially by tbe 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 bronchia; 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 termi- nates 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 large lobes, and these together form the mass of the lungs. The tissue that connects together tbe different lobes, is very different from that in which the ramifications of the bronchise terminate; 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 lamina; of the air cells of that tissue, the lung loses its form, an'( becomes 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 distributed on these parietes, the blood is almost in immediate contict with the air. There can be no doubt, that the oxygen of the atmosphere acts on the blood, under such cir- cumstances, since it alters its qualities and communicates to it a florid red colour, when in a pig's bladder and placed under a vessel filled with oxygen gas. LXXVI. Every time the chest dilates, in an adult, there ente into the lungs between thirty and forty cubic inches of atmos. pherical air.* When the air has been exposed, for a few mo. * Some physiologsts think that the quantity of air inspired is much less considerable. Professor Gi'egory, 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 Mayow, at the expense of a certain quantity of air con- tained in a bladder, or by breathing into a vessel connected with a pneumatic apparatus, the air taken in by drawing a deep inspiration. Or else one may inflate the luns^s of a dead body, by adapting to the trachea a stop cock connected with a curved tube to receive the air under a vessel of the same apparatus Various means have been employed to measure the capacity of the chest. Boerhaave placed a man in a tub containing water above his shoulders, he then made him take a deep inspiration, and measured the height at which the fluid rose from the dilatation of the chest Keill injected water in- to the chest of a dead body. Lastly, it has been proposed toinjec- OF RESPIRATION. 215 ments, in the pulmonary tissue, it is expelled by the effort of expiration, but it is diminished in quantity and is reduced to thirty-eight inches. Its composition is no longer the same, it contains, it is true, 0,73 of azote, but the vital portion fit for respiration, the oxygen, has undergone a great diminution, its proportion 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 limes, clearly show a reciprocal action of this fluid and of the oxygen of the atmosphere. The dark venous blood which coagulates slowly and which then disengages a considerable quantity of serum abounding in hydrogen and carbon, and of a temperature of only thirty degrees, yields its hydrogen and carbon to the oxygen of the atmosphere, to form carbonic acid and the pul- monary 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 tbe more readily, aecor-ing to the ingeni- ous experiments of Crawford, as by parting with its hydrogen and carbon, its capacity for caloric increases in the proportion of 10 : 11.5. In parting with its carbon which, by uniting with oxygen, forms the carbonic acid that is thrown out during expiration, the blood looses 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 certain quantity of oxygen, it becomes spumous and light; its concrescibility 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 com- binations, and is converted into oxides of hydrogen and carbon, which, on receiving an additional quantity of oxygen, are 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. 216 OF RESPIRATION. 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 tbe 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, becomes venous after remaining in it some time. The changes, however, which the blood undergoes in its course through the arterial system, are not very remarkable, owing to the rapidity with which it flows along those vessels; there is less difference between the blood contained in an 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 very 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 qualities as of arterial, a phenomenon which, as is well obser- ved by the English writer already quoted, depends on the more easy and rapid flow of tbe blood of the arteries into tbe veins, in consequence of the evacuation of the venous system. This ob- servation 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. OF RESPIRATION. 317 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- 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 cha- racters. On reaching the lungs, which are real secretory or- gans, the water is exhaled, dissolved in tbe air, and lorms 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. 29 318 OF RESPIRATION. This theory of respiration, for which we are entirely indebt- ed 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 greaterthe warmth and vivacity of animals. Birds, whose lungs extend into the abdomen by vari- ous membranous sacs, and whose bones are hollow and commu- nicate with the lungs, consume a great deal of oxygen, either on account of the magnitude of this respiratory apparatus, or fiom their frequent, and, at times, hurried respiration. On that ac- count, the habitual temperature of their body exceeds lhat 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 tbe temperature or warmth of the body is 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 vita. Its digestion was, tbey 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; wbile 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 that 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 OF RESPIRATION. 210 animal remains 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 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-blood- ed 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 tbe lungs, in the same manner as in man the bladder empties itself of urine. In birds, whose diaphragm is equally membranous, and con- tains several openings to transmit the air into the pulmonary appendices, the parietes of the thorax are likewise more move- able 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 animals; 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 penniform laminae, generally four in number, situated on each side, at the posterior and lateral part of the head, covered over by a moveable lid, to which naturalists give the name of oper- culum. 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 gills and the pulmonary vessels which are distributed in them, then 220 OF RI.SPIRA.T10N. escapes at the auricular apertures, when the animal closes his mouth, and raises the opercula. It is not known, whether the water is decomposed and yields its oxygen to the blood which circulates in the gills, or whether the small quantity of air that is dissolved in the water, alone serves to vivify the pulmonary blood. The latter opinion seems the most probable, if it be considered that a fish may be suffocated by closing accurately the vessel of watrr in which it is enclosed., The same result might, I conceive, be obtained by placing the vessel under the receiver of an air pump, so as to exhaust it completely. Respiration, which is completely under the influence of the brain, as 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 ftw 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 conceives that all organs, for want of the stimulus which determines 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 phy- sician, 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 of respiration:. *Z t 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 blood, which is the principal phenomenon of respi- ration. 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- periments publicly in my presence, and at the society of the Ecole de Medecine of Paris. After dividing the two nerves of the eigth 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 the trachea at its anterior part. The blood of tbe 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? LXXVIf J. Of animal heat. The human body, which is habitually of a temperature between thirty-two and thirty-four degrees 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 Duhamel 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 sub- stances 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 inconve- nience. 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 222 OF RESPIRATION. 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 does a body which resists the influence of heat, withstand equally 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 bo- dies are a kind of laboratories, in which all these changes are perpetually 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 the chyle, abounding in nutritious particles; from respiration which im- parts to it an aeriform principle obtained from the atmosphere; and even, in some cases, from cutaneous absorption, through which different elements are received into it. All these dif- ferent substances carry along with them into the blood a cer- tain quantity of caloric, which is combined with them, and which is disengaged during the changes which they uudergo 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 communica- ting heat to the organs, none furnishes a greater quantity than oxygen, which, during respiration, combines with the blood is 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 bodies 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 tem- perature as in man; and such animals 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 abdomen, and communicate with the prin- cipal bones of the skeleton. The capacity of the pulmonary organ of birds, is not the only cause why their temperature is eight or ten dejgrees higher than that of man; this increase of OF RESPIRATION. S2S temperature depends, likewise, on the greater frequency of their respiration, and on the velocity of their pulse; on the quickness and multiplicity of their motions, and on the vital activity which animates them. In reptiles which have 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 supply- ing 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 vivified in the gills, on account of the small quantity of air which can be taken in during tbe 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 beat 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 con- tented himself with the quantity of food proportioned to his wants; for, as the digestive organs can extract only a certain quantity of the chyle, the quantity of recrementitious matter would only be greater, if more than the due quantity of food were received into the stomach. Hence the common saying, that nourishment comes from what we digest and not from what we eat. The pulmonary organ may, however, act on the air, with different 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 ef 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 ot the organs, which allow the blood to pass without affecting its component parts. It would be curious to ascertain whether tbe air expired from the lungs of a cataleptic, contains more oxygen, is less impaired, and con- tains a smaller quantity of carbonic acid than the breath of a 224 OF RESPIRATION. sound active adult. Perhaps it would be found, that in cata- lepsy and other similar affections, the blood does not part with its hydrogen and carbon, that it retains its colouring principles, and the different materials of the urine, whicb is voided in a co- lourless and limpid state, insipid and without smell, and in the condition of a mere serosity. The temperature of the body is produced not only by the pul- monary and circulatory combinations; it is besides developed in several organs, in which fluid or gasseous 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 tbe period of life, but young peo- ple, after death, preserve for a longer period the remains of vital heat; or rather, as tonicity does not so soon forsake the capillary vessels, life departing reluctantly, the combinations from which caloric is evoked, continue some time, even after it is extinct. For the same reason, the bodies of persons that have died suddenly retain their warmth long, while an icy cold- ness 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 belong- ing to all organs. It was of the utmost consequence that the internal temperature of the human body should be nearly the same at all times. For, let us for one moment suppose that the temperature of the blood should rise to fifty 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 combinations, a greater quantity of heat is disengaged, the ani- mal economy parts with it, and is taken up in a greater quanti- ty by the surrounding bodies. This accounts for tbe equality of the temperature of the internal parts of the body in old people OF RESPIRATIOX. 225 and in children, notwithstanding the difference of their tempe- rature externally. The difference consists in this: that where most caloric is produced, most is given out, and though the blood and urine in old people, as well as in the young, are at thirty- two degrees, what a difference is there not between the hot and penetrating 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 frozen breath of the latter! Hence tbe opinion so generally re- ceived and of such antiquity, that old people are benefited by cohabiting 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 bodies, from 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 re- sult of nutritive composition; and decomposition, merely keeps up an equilibrium and maintains the same degree of tempera- ture. The blood which becomes saturated with oxygen, in the ca- pillaries of the lungs, parts with that principle, and disengager 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 commu- nii ate a portion of it to the organs, which receive but a small quantity of blood, as the bones, the cartilages, &c It is easy to understand, why an inflamed part, through which the blood cir- culates with more rapidity, and whose sensibility and contrac- tility are much increased, is manifestly hotter to tbe 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, externallv, a considera- 30 £26 OF RESPIRATION. 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 »n it seems to him to be occasioned by an accu- mulation 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 pa- roxysm, 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 differ* nee 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 explanation 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 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 excess of heat, and retain the same temperature. Cutaneous perspiration, it is true, acts very powerfully in lowering the temperature, and as this evaporation increases with the tempe- rature, it should seem as if this function sufficed to moderate the heat of the body, and to restore the equilibrium. OF RESPIRATION. 221 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 power- ful means of cooling bodies, and that the mercury in the bulb of a thermometer, may be frozen merely by moistening it with asther, spirits of wine, or any other volatile substance, and then exposing it to a dry and warm air. This method is equally successful in its application to the human body, and the hands may be cooled to such a degree as to feel benumbed, by being frequently wetted with a spirituous fluid, and by being moved in a dry and renewed air. But though cutaneous perspiration operates in a somewhat similar manner, and though it may be ranked among the means which nature employs to preserve the anini;d temperature in a nearly uniform state, it must however be confessed, that it is not the only way in which this object is accomplished, and that it does not satisfactorily account for this phenomenon, for, the evaporation of the fluids contained in dead animal substances, does not prevent their being roasted on the application of heat; and besides, fishes and frogs have been known to live and retain their tempeiature in mineral waters, nearly of a boiling heal.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. 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 isnaturalto 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 * This celebrated physician made this discovery about forty years ago, which has thrown much light on several physico-chemi- cal phenomena, and he published it in a dissertation entitled: " Of the cold produced by evaporating fluids, and of some other means of producing cold, by Dr. W. Cullen." *" See So'inrrtrt's Voyage to the East Indie's. 228 OF RESPIRATION. famous instance of a Spaniard, who became so general a sub- ject of conversation in Paris- this young man, in making his way through a house on fire, perceived that the heat was less inconvenient to him than he had imagined. He applied him- self to bear, with impunity the action of fire, and was enabled to apply to bis 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 absur- dity and the exaggeration of the stories that were told of this man, except the ignorance 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 bis 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 com- municates a part of its heat, at the same time that it becomes moistened with saliva. This man having, in a public exhibi- tion, carried on, too long, the application of the spatula, the caustic effects of its heat showed themselves, the epidermis was detached, and found coiled, like the outer covering of an onion, in the cloth which he used to wipe his mouth He does not dip his hands and feet in boiling oil, he merely applies to the sur- face of the fluid his palms and his soles, and he repeats this fre- quently, with only a short interval between each application. When the experiment is carried on for a certain length of time, there is emitted a smell of burnt horn. No one has yet observ- ed, that though this man's hands are not callous, the palms of these, and the soles of his feet are cushioned with fat. A thick layer of fat, which is a bad conductor of heat, separates the skin from the subjacent aponeuroses and nerves; this cir- cumstance, to a certain degree, accounts for his imperfect sen- sibility. 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, maybe destroyed by the protracted appli- cation of caustic substances, and would be consumed by fire, if applied for a sufficient length of time, and nitric acid would infallibly destroy his tongue if he took any into his mouth, as it has been said he did. Tln^ man, therefore, in no one respect OF RESPIRATION. 229 departs 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 tbe body resists cold, and preserves its temperature, in the midst of a frozen at- mosphere. 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 tbe reason that in cold weather, di- gestion is more active (Hieme vero 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, shouid 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 ex- ertions do not appear to him laborious, 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 and the surrounding bodies. These general effects 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 incon- venient, caeteris 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 ef- fort of nature, which determines into the inflamed part an excess of the vital principle, so that the quantity of heat that is disen- gaged may correspond to that which has been abstracted. The effort of this conservatory principle is more marked, than if the whole surface of tbe body were at once exposed to cold, because acting wholly on a limited point, of small extent, it operates with more intensity. Beyond a certain degree, however, nature in vain struggles against cold; if severe, and if the creature exposed to it have 23U OF RESPIRATION. 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 in- fluence of cold, the person is benumbed, feels a stiffening of his limbs, stammers, and overpowered by an iriesistible propensity, 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 iro9. To resist the effects of cold, a certain degree of strength and vigour is therefore necessary; it is consequently very injudicious to recommend the cold bath to very young children, to delicate and nervous women, to persons whose constitution is not capa- ble of a sufficient reaction. The evil attending the injudicious use of this remedy in the cases that have just been enumerated, justifies the apparently singular terms in which Galen expressed himself: " Let the Germans (says this first of physiologists) 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." 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 debiliating, but on thexeaction 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, caculated 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 nutrition. Though we are without precise information respecting the manner in which a living body resists the admission of a de- OF RESPIRATION- 231 oree 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 equi- librium. 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 ven'ricle propels 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 tbe same quantity of blood returns by tne extremities of the pulmonary artery, and of all the other arte- ries 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, notwithstanding the collapse of the lungs and the creases of their vessels. The air which penetrates, at all times, into the lungs, supports their tissue and the vessels which are distributed to it, so that even during expiration, the vessels are much less creased than has been imagined by several physiologists. But the changes produced by the contact of the atmosphere, reno- vate this fluid, and fit it to re-excite and keep up the action of all the organs which require to be stimulated by arterial blood. If you make a living animal breathe de-oxygenated air, the blood undergoes no change by its pulmonary circulation: the 232 OF RESPIRATION. left cavities of the heart are no longer duly irritated by this fluid, which preserves all its venous qualities; their action be- comes 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 passsage 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- 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 re- duced, 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 pulmonary exhalation. It is scarcely possible to admit the combination of oxygen with the hydrogen of the venous blood, and that water is thus formed from its element, as happens when storms are gathering in the high regions of the atmosphere. If a similar process can be carried on in tbe 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 bronchi® and the OF RESPIRATION. 233 lobular tissue of the lungs. It is believed, that the quantity of (he 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 vice 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 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 bronchia, 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 bronchia? 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 submersicjwfrrangulation, the diminution of oxygen in the air inhaled, &'^ The only difference between real death, and asphyxia, is, that in this last state the principle of life may yet be re-animated, whilst, in the other, it is completely ex- tinct. Asphyxia takes place in drowning, because the lungs, depriv- ed 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 closing of the glottis prevents its getting into the trachea and its branches. Yet there is found a small quantity in the bronchia, after drowning, always frothy, because air has mixed with it, in the struggles which precede asphyxia. If the body remain long under water, the spasmodic state of the glottis ceases, water passes into the trachea and fills the lungs. The 2U OF RESPIRATION. anatomical examination of a drowned body, shows the lungs co!r lapsed, and in tbe state of expiration; the right cavities of the heart, the venous trunks which terminate in them, and gene- rally, all the veins, are gorged with blood,* whilst the left ca- vities and the 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 qualities necessary to their action; and per- haps also, because the venous blood that is accumulated in the tissues, affects them by its oppressive and deadly influ- ence. On that account, the best way of restoring the drowned to life, is to blow pure air into their lungs. This is done by means of bellows adapted to a canula introduced into the nos- tril; 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 al- ready 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 ef- ficacious remedies, such as friction, bronchotomy, glysters, fu- migations and suppositories, stimulating errhines, and espe- cially ammonia; stimulants taken into the mouth and sto- mach, 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 tbe in- terception of the air. To prove this, G.i*«-ory performed the following experiment; he opened the trac^ a 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 constriction 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 * Hence the dark and livid colour of the skin and conjunctiva. This last membrane is frequently injected with dark blood; the \ery delicate veins of the brain are considerably dilated, and this viscus ;s distended with venous blood. OF RESPIRATION, 235 of the cervical vertebrae, and from the injury done, at the same time, to the spinal marrow. Louis, it is well known, ascer- tained, that of the two executioners in Lyons and Paris, the one dispatched the criminals he executed, by dislocating the head at its articulation with the neck, while the other executioner- destroyed them by inducing asphyxia. 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 m ntion 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 occuring 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 uninjured; the right cavities of the heart and the venous system, are gorged with a dark but fluid blood. In the asphyxia, on the other hand, that is occasioned by sulphuretted or phosphuretted hydrogen, &c. or by certain vapours whose nature is not well understood, and which escape from privies, or from vaults in which a number of dead bodies undergo putrefaction; there are frequently found in the lungs, dark and gangrenous marks, and death seems the effect of a poison which is the more active, as its particles, exceedingly divided and in a gaseous state, are more insinuating, and affect throughout its whole extent the nervous and sensible surface of the lungs.* * 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 preclu- sion of oxygen. These writers however, are undoubtedlv mista- ken. Nothing is more clear than that this species of gas has a po- sitive 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 wheu expo- sed to the carbonic acid, than when placed in vacuo, or when a liga- ture is applied to the trachea. 2. It has been shown, that frogs may be kept, without injury, for tip wards 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.—En. 236 OF RESPIRATION- Inebriation seldom goes the length of bringing on asphyxia, it most commonly produces a stupor readily distinguished from the affection treated of in this article, by the perceptible, though obscure pulse, and by the motions of respiration, though these are rare and indistinct. On this account, M. Pinel, in his JVoso- graphie philosophique, has placed inebriation and the different kinds of asphyxia, in two separate genera of the class neuroses. It is conceivable, however, that the muscular irritability may be so far impaired by the use of spirituous liquors, that the heart and diaphragm might lose the power of contraction, which would bring vn complete asphyxia. The glottis, through which the atmospherical air passes in its ways 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 man- ner, 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 complete- ly 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 tbe delivery, that there has been no organic injury decidedly mortal, it must be con- sidered as a case of asphyxia from weakness; and all means em- ployed that are recommended in such cases, especially blowing in air into the Jungs, 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, yawning, 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 partake most in the affection of the mind. When a lover, in the midst of an agreeable reverie, sighs deeply, and at intervals, a physiologist perceives in that expression of desire, nothing but a long and deep inspiration, which, by fully distending the OF RESPIRATION. 237 lungs, enables the blood, collected in tbe right cavities of the heart, to flow readily into the left cavities of that organ. This deep inspiration, which is frequently accompanied by groans, becomes necessary, as the motions of respiration rendered progressively slower, are no longer sufficient to dilate the pulmo- nary 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 tbe expres- sion of Brown, may be considered as debilitating or asthenic. The fatigued inspiratory muscles have some difficulty in dila- ting 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 separation of both jaws. One yawns at the approach of sleep, because the agents of inspiration, being gradually debili- tated, require to be roused at intervals. One is likewise apt to yawn on waking, that the muscles of the chest may be set for respiration, 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 respiration require. The crowing of tbe 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 dis- tinct, the air, as it enters the mouth, rushes along the Eusta- chian tubes into the tympanum, and the membrane is acted upon in a different direction. The recollection of the relief at- tending the deep inspiration which constitutes gaping, the re- collection of the grateful sensation which follows the oppression that was felt 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 tgainst the tortuous nasal passages, and occasions a remarkable 238 OF Rt'.SPl RATION. noise. The irritation of the piluary membrane determines, by sympathy, 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 pituary 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 archaeus 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 tbe 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. Respii uion is besides employed in the formation of the voice; but tbe voice and the different modifications of which it is capa- ble, will form the subje( t 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 called 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 ^e atmosphere. The insensible p< rspiration is const.mtly escaping through the innumerable pores in the parietes of the OF RESPIRATION*. 239 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 cutaneous perspiration and the pulmonary exhalation; both are nitre arterial exhalations, and the mucous membrane, which lines the canals along which the air is transmitted, is a mere prolongation of the skin into those organs, and into the digestive tube. The surface from which the cutaneous per- spiration 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 generally attended with a sensible diminution of the other; lastly, the mucous membrane of the intestinal canal, be- sides secreting mucus, exhales likewise a fluid which increases much in quantity, 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 or- gans which 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 diskance from the surface. And if the body is placed be- fore a white wall, it is easy to distinguish the shadow of that emanation. We may, likewise, satisfy ourselves of the exis- tence of the cutaneous perspiration by the following experi- ment: hold the tip of the finger, at the distance of the twelfth part of an inch from a looking glass, or any other highly polish- ed surface; its surface will soon be dimmed by a vapour con- densed 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 look- ing glass, the latter will be covered by no tfapour. 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 240 OF RESPIRATION. under consideration. From the time of Sanctorius, who, 111 the beginning of the seventeenth century, published in his immortal work, uMedicina statica," 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 in- quiry, Dodart, who in 1668 communicated to the Academy of Sciences, which bad been founded but a shoit 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 se- cretions. According to Sanctorius, of eight pounds of solid and liquid aliments taken in twenty-four hours, five were carried off by the perspiration, and only three in excrement and urine. Haller conceives this calculation to be exaggerated; Dodart, however, carried it still further, and maintained that the relation of the perspiration to the solid excrements, was as seven to one. In France and in temperate climates, the quantity of the cutaneous perspiration and of the urine is nearly the same; it may 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 smaller quantity during sleep than while we are awake; in old age than during infancy; in weak persons, and in damp weather, than under the opposite circumstances. The perspiration may be said to be in a con pound ratio of the force with which the heart propels the blood into the mU 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, drv, and fre- quently renewed, cutaneous perspiration is greater, and the ne- cessity of taking liquid aliment is more urgent, and more fre- OF RESPIRATION". quently experienced; in summer, as every body knows, a pro- fuse 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 consider- able 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 a great measure aqueous. Like the urine, it holds in solu- tion several salts; also the volatilized recrementitious matter of animal substances, sometimes even acids, as in the case in which Berthollet detected the phosphoric acid in children affected with worms, in pregnant women, in nurses, from whom there exhales an odour manifestly acid. It may contain ammonia, and on certain occasions, the smell enables us to discover that alkali in the sweat or perspiration. The air which constantly surrounds our body does not mere- ly dissolve the aqueous vapour which arises from it, but several physiologists very reasonably conjecture, that the oxygen of the atmosphere may combine with the carbon of the blood brought to tbe 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 'o 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 fossa;, and in the intestinal c^.nal which they line. 32 S4& OF THE SECRETIONS. 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 exhaled 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 tbe membrane in which the sense of touch resides, should be habit- ually 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 at- tention. CHAPTER V. OF THE SECRETIONS. LXXXVTII. Of the animal fluids. The animal fluids were formerly divided into recrementitious, excrementitious, and excre- mento-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 with- in it without danger; such as the urine, the matter of insensi- ble perspiration and of sweat. Lastly, those of the third class partake of the nature of the two preceding, and are in part re- jected, while another part is retained and employed in the sup- OF THE SECRETIONS. 243 port and growth of the organ; this is the case with the saliva, the bile, the mucus of the intestines, &c. If one affected to be very minutely scrupulous, one might consider all the animal fluids as recremento-excrementitious. The chyle and the blood, which are so very nutritious, contain an abundance of hetero- geneous and excrementitious parts; the urine, which of all our fluids is that which may, with most propriety, be termed such, contains 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 by Haller, in his physiology. Fourcroy admits six classes of fluids: 1st, those which hold salts in solution, as the sweat and urine; he gives the name of saline to such fluids: 2d, inflammable oily fluids, all possessing a certain degree of consistence and con- crescibility, as fat, and the cerumen of the ears, &c: 3d, the saponaceous fluids, as the bile and tbe milk: 4th, the mucous fluids, as those which lubricate the internal coat of the intes- tinal canal: 5th, the albuminous fluids, among which one may rank the serum of the blood. The fibrinous 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 ab- sorbed by the lymphatics, and conveyed, with the chyle and lymph, into the circulatory system. Let us shortly attend to its nature, although this belongs more especially to the depart- ment of chemistry. The blood is red in man and in atl warm- blooded animals, and even in some whose temperature is not very different from that of the atmosphere, as in fishes and rep- tiles. This colour of a deeper or lighter shade, according as the blood is drawn from an artery or a vein, varies in its de- gree of intensity, according to the*state of health or weakness. It is of a deep red in strong and active persons, pale and colour- 244 OF THE SECRETIONS. less in dropsical patients, and whenever the health is weak. By its colour one may judge of all its other qualities. Its vis- cidity is greater, its saline taste more marked, its peculiar smell stronger, when its colour is deep. This colour is produ- ced oy a prodigious 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 dissolved in cachexia?. 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 tbe idea of their being so minute, by his calculation, that they were one millionth part of an inch in size, thought them spherical. Hewson soys they are annular and have an opening in their centre. Others compare them to 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 rea- dily 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 can not 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 pf soda, nitrate of potash, and muriate of lime. Serum, though bearing the same analogy to the albumen of egg, differs from it, in forming, on coagulating, a less solid and less homogenous mass. The Albumen is evidently mixed with a portion of transparent gelatine, not coagulable by heat. Albu- men has so great an atlr iction/or oxygen, that it is fair to pre- sume, that the serum absorbs oxygen and combines with if.- OF THE SECRETIONS. £45 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 oxydizement, 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 sufficient quantity of water; because the animal tem- perature, which never exceeds thirty-two or thirty four degrees, cannot give a solid form to albumen, which coagulates only at fifty degrees 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 al- cohol. 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 tha* 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 be- ing 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 fibrina, 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 coulante) 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 not agree m their accounts of the quantity of iron contained in the blood. Mcnghini says, there is one part in the hundred; others that it is in tbe proponion 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. 246 OF THE SECRETIONS. 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 phosphoric acid, and formed with that acid a phosphate of iron, with an excess of its base. This salt becomes decomposed by ■f calcination, the iron is set free and is acted upon by the magnet. Physiologists attribute the colour of the blood, to the 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 tbe presence of phosphate of iron, which beino- 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 by albumen, con- stitute, in an especial manner, hematosisor 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 co- louring 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. Tbe pale, aqueous, and colourless blood of a dropsical patient contains very little fibrina. In putrid or adynamic fever, in which bleeding, as is universally known, is improper, I have some- times seen the blood containing but a small portion of fibrina, and very slow of coagulating; 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 augmented; the fibrina is in greater quantity, even the albumen coagulates spontaneously and forms a crust above the serum, which is always in smaller quantity. XCII. Of the changes of tlie 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 u\> fl OF THE SECRETIONS. 247 pox, of syphilis, of the plague, &c. Thus, in time, the habitual use of the same aliment 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 hu- moral 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 takes up. This property of tlie absorbents is a provision of nature to pre- vent noxious substances from penetrating into the circulation un- changed. 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 pro- gress, as in the case of bubo. In this respect, therefore, th. conglo- bate glands may be considered as sentinels guarding the exterior ap- proaches of the body. We are not ignorant that some of the properties of certain sub- stance, when absorbed display themselves in the secretions and ex- cretions, as the odour of garlic, 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, not the other, can 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, or by the absorbent apparatus, com- pletely decomposes all substances subjected to its influence, and however various in their principles, reduces them to one homogene- ous 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 se- cretions, being removed beyond the sphere of the vital powers, che- mical action takes place, by which those substances are in part or entirely regenerated. Whether the particular explanation offered by this hypothesis be received or not, the fact at least must be acknowledged, that no sub- stam.* in its active condition does enter into the circulation, since ex- periments hav« shown that however mild the fluid may be, 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 substances 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 pans, we have a rationale far more consistent with those views de- rived from the present improved state of our knowledge. 248 UF THE SECRETIONS. 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 hunting, and who feed on raw, bloody, and palpitating flesh, 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 uniformly 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 Conformably to this theory, when a substance either medicinal or poisonous is applied to a susceptible portion of the body, externally or internally, an action is excited which is extended, more or less ac- cording to the diffusibility of the properties of the substance, or the degree of the sympathetic connexion which the part may have with the body generally. Thus a set of actions is raised, every one of which is precisely similar, provided they are confined tothe same sys- tem, by which is to be understood, parts of an identity of structure. If, however, the chain runs into other systems, it loses its homoge- neous 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 familiar case. By inserting a particle of variolous matter under the skin, local irritation is created: in a few days this action becomes diffused, and a fever ensues, which after a short con.inuauce 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 of virus as the primary or parent pustule. It is in this way, that morbid motion distributes itself. When diseases arise from a point, as in fact all diseases do, but more strikingly those occa- sioned by inoculation, the matter introduced is not infinitely divided and spread over the body, but the action which that matter had ori- ginally excited. These are general principles, which apply to the system iu every condition, and explain the modus operandi of medi- cines as well as of the causes of disease. Whatever, in short, ope- rates 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. QV THE SlEeRKTIONR. 249 physical cause, the daily and plentiful use of animal food, the breathing an air filled with emanations of the same kind, which •hey inhale, and which contribute to their embonpoint, which is sometimes excessive. As the plasticity and incresibilityof 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 scurvey, the tissue of the capillaries is relaxed, its meshesenlarged, 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. Petechia;, in putrid fever, are formed in the same manner, and depend, likewise, on the relaxation of the minute vessels, and on the greater fluidity of the blood, whose molecules are less coherent, and more readily separated from each other. In the summer 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 converted into 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 hu- moral pathology, have certainly gone too far; they have admit- ted that the animal fluids might be acid, alkalescent, acrimo- nious, while we have no proof whatever that they ever do un- dergo such changes. The solidists have, likewise, gone much beyond the truth, in saying, that every primitive change in the condition of the fluids is imaginary, and that the doctrine of humoral pathology is without foundation. Stahl relates* that * Theoria medica vera, page 678. 33 250 OF THE SECRETIONS. the blood of a young woman, who was bled during a fit of epi- lepsy, was absolutely coagulated, as if that fluid had partaken in the rigidity affecting the muscular organs. Some authors say that they have met with the same appearance; 1 have, however, never been able to discover any sensible differ- ence between the blood of an epileptic patient and of any other person of the same constitution of the same age, and living on the same regimen; and it should be considered, that to make a just comparison of our fluids, it is necessary that every thing should be alike in tbe 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 appearance, and does not coagu- late 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 under mercurial influence; the milky state of the se- rum which lubricates the parietes of the abdomen and of the viscera which it contains, after inflammation of the peritoneum; changes which, almost universally, depend on a derangement of action in the secretory 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, un- less the blood furnish it with the materials of secretion, and un- less it be in a state to bring about a due combination of their particles. When we come to the article of accidental secre- tions, we shall speak of those disorders of the fluids, depending on a depraved condition of the secretory organs. XC1II On the transfusion of blood. In the midst of the dis- putes to which the discovery of the circulation gave rise, some physicians 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 per- son in good health. Richard Lower, known by his work on the heart, first practised it on dogs, in 1665. Two years after- wards, transfusion was performed at Paris on men, and excited OF THE SECRETIONS. 251 the greatest expectations: it was thought that by this process, called transfusing surgery (chirurgie transfusoire), all remedies would be superseded, that henceforth, to cure tbe most serious and inveterate diseases, it would be necessary merely to trans- fuse the blood of a strong and healthy man into the veins of the diseased; nay, 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 brilliant chimeras soon vanished; some underwent the experi- ment without any remarkable effects from it, others were affect- ed 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 dan- gerous experiments. The experiments on the subject of the transfusion of blood were repeated, but without success, at tbe Academies of Scien- ces. 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 temper, &c.; that an extraneous fluid was thus introduced, which conveying to the organs an irritation to which they were not ac- customed, 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 nou- rishes another of a different kind, he would answer, that vege- tation does not depend on so complicated, nor on so delicate a mechanism as the nutrition of animals; that a hut may be form- ed of all kinds of stones taken at random, but that to build a palace, stones must be designedly shaped for the purpose, so that a stone destined for an arch, will not do for a wall, nor even for another arch.* It would be easy, by means of a curved tube, to transfuse the arterial blood of an animal, from a wound in its carotid artery, into the saphena vein of a man, into the internal jugular, or into some 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 difficult to 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 corru- * Academic royale des Sciences, 1667, page 37. 352 OF THE SECRETIONS. gated and refuse to transmit a fluid which doe? not act upon them, according to their wonted sensibility. Such was the re- sult of the experiments of Professor Buniva; he observed in a living calf, that the vessels did not transmit freely the fluid which was forced into them, till the instant when the animal was killed, by dividing the upper part of the spinal marrow. Attempts have been made to turn to useful purposes these ex- periments on transfusion, by limiting the process to the inject- ing 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 sufficiently authenticated to jus- tify their application to tbe 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 they separate from it. We have seen, that the liver ^s a remarkable excep- tion to this general rule; the same observation seems likewise applicable to the mamma); they appear to receive the elements of their milky secretion from the lymphatics, which are so very numerous in their structure. One is, therefore, justified in saying, that the elements of our fluids may be furnished by vessels of every kind, to the organs in which such fluids may be elaborated. The term secretion, whatever its etymology may be, denotes that function by which an organ separates from the blood the materials of a substance which does not exist in that fluid, with its characteristic quali- ties. By the term secretion, one should not, therefore, under- stand 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 OF THE SECRETIONS. 253 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 tbe other constituent parts of the fluid, which is in too much motion, and at loo high a tempera- ture, to allow of a spontaneous separation. The term exhala- tion, which is applied to this secretion, gives an incorrect idea of it; for exhalation, which is a purely physical phenomenon, and requiring the presence of air to dissolve the fluid that is exhaling, cannot take place from surfaces that are in absolute contact, and between which there is no interval The charac- ter of this mode of secretion is the absence of any intermediate substance between the vasa afferentia and the excretory ducts; the minute arteries and veins which enter into the structure of the membranes being, at once, vasa afftrentia and excretoiy ducts. The fluid secreted by the serous membranes, though bearing a considerable analogy to the serum of the blood, differs from it 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 by a serous membrane. XCVI. Next in order to the serous transudation, which re- quires a very simple organization, comes the secretion winch takes place in the cryptae, 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- dala?, 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'considera- ble number of vessels and nerves. The peculiar action of the 254 OF THE SECRETIONS, parietes of these different parts, determines the serretion of the mucus furnished by those glands. These mucous fluids, less liquid and more viscid than the serosity which is tbe 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 glandulae 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 uretha, at the base of the tongue, &c. Tbe albuminous fluid, which is poured within those glandular cryptse. remains some time within the cavity, becomes thicker from the absorption of its more fluid parts; for there are, likewise, lymphatics within the texture of their parietes. When the surfaces, on which they are situated, require to be moistened, this small pouch contracts, and throws up the fluid with which it is filled. The secretion and excretion are promoted by the irritation which the presence of the air, of the aliment, or of the urine occasions, by the compression exerted by those substances, and lastly, by the peristaltic contractions 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, re- quire, for their secretion, organs of a more complicated nature; such organs are called conglomerate glands, to distinguish them from the lymphatic glands, which have been termed conglobate. Those glands constitute the viscera, and are formed by a num- ber of nerves and vessels of all kinds, arranged in fasciculi and united by cellular membrane. A membrane peculiar to the or- gans, or supplied by those which line the cavities in which tbey 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 tbe veins and nerves, and the manner in which the lymphatics and ex- cretory ducts arise from them, have given rise to endless discus- sions, and formed the basis of former physiological theories. OF HIE SECRETIONS. 2o5 What follows may be considered as a correct abstract of what is known on the subject. The respective arrangement of the similar parts (parties sinulaires*) 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, 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 areolae 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 iu 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. XCVI1I. Oj accidental secretions. If one wished to extend the idea attached to the term secretion, one might say, that every thing, in tbe Kving economy, is performed by means of the secretions What is digestion, but the separation or se- cretion 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 con- tains the materials of the fluid to be elaborated? Respiration, as we have already seen, is but a double secretion which tbe lungs perform, on the one hand, of the oxygen contained in the * By parties similaires, the author means the simple elementary tissues.—See the preliminary discourse, page 19. f Do the different appearances of the substance of glandular bo- dies 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 rea- dily distinguish the substance ot 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 jlands to depend on the different proportions of those constitaen* jarts. in each of them, appears the most probable. 256 OF THE SECRETIONS. atmospherical air, and on the other hand, of the hydrogen and carbon, of the w.iter, and of tbe 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 un- dergo such a change of composition, as to render them fit for their growth and reparation. There is f very 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 bis existence, are tbe result of the secretions of which the blood furnishes the materials prepared by the brain, by the nerves, by the muscles, &c. A plant separates from the earth, in which its roots are buried, 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 gurns, 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 con- sidered 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 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 .fleeted. 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 mucus 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 l,he peritoneum, will allow a greater quantity of serum of a more albuminous quality, sometimes even coagulable lymph, to exude; at other times, inflammation causes an adhesion of their conti- guous surfaces, and as the inflammatory state varies in intensi- ty, 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, OF THE SECRETIONS. 257 uiid 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 bipod.* 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.f *To these examples of morbid secretions, others may be added, even more remarkable, as the virus in rabies canina, in syphilis, the small pox, 8cc By some animals the power is possessed of secret- ing naturally the most virulent 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 secretions pe- culiar 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 assailant.—Ed. f That the menstrual discharge results from a secretory action ot the uterus, is a doctrine which we early adopted, and have taught in our lectures for the last ten years. Every other hypothesis on the subject is totally irreconcileable with facts, and repugnant to the laws of the animal economy. The crude speculations of former times, respecting this operation, may, indeed, b considered as dis- carded. Does any one, for instance, whose knowledge has kept pace with the improvements of physiology, now entertain the no- tion of lunar influence, of fermentation of venereal appetite, of gen- eral plethora or local congestion, &c &c? The 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, can etr, &e, &c. 34 2o8 OF THE SECRETION*. The nerves, of which there is always a certain number in the structure of the secretory organs, and which are principally 2. That, like other secretory organs, blood is very copiously dif- fused through it . 3. That, by the arrangement of its vessels, it is evidently design- ed that the circulation should be retarded for the purpose of secre- tion. 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 vi'iation and derangement. In the beginning the discharge is commonly thin, colourless, and deficient, and recurs at protracted and irregular in- tervals. In some of these particulars, it is analogous to the seminal secretion 5. That, in many of the inferior animals, during the season of ve- nereal incalescence, there is an uterine effusion which is undoubtedly a secretion. This answers, seemingly, the same end as menstrua- tion, namely, giving to the uterus an aptitude for conception. Though this fluid generally differs from the menses in complexion, yet, m 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 re- lieves the symptoms of suppression. Do not these facts very un- equivocally proclaim the existence of a secretory function? Lastly, That the menses are a fluid sui generis, or at least vary- ing essentially from blood; having neither its colour, nor odour, nor coagulability, and, on chemical 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 com- plex apparatus Of what, indeed, does a gland consist, except a congeries of vessels? Even the most perfect of the secretions are ac- complished 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 struc- ture in 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* 8cc. No stronger proof can certainly be required of the extreme simplicity of the organs by ivhich 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 tiu OF THE SECRETIONS. 25'J 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, £nd 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 porta?, 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, tbe 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 celebrated Mr. Hunter ; but the evidence of his claims to it is ex- ceedingly slender. The only trace of it, which we can discover in his writings, is a vague expression in a paragraph of his Treatise on the Blood. Afterwards, however, he furnished an extract from his lectures to be published in Johnson's Midwifery, as exhibiting more fully his notion respecting this function. Speaking of the death of the blood from lightning, and other sudden causes, he in- cludes the catamenia among the illustrations of his reasonings. " The blood," says he, " discharged in menstruation is neither si- " milar 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 ** speciesof blood changed, separated, or thrown off from the com- " mon mass by an action of the vessels of the uterus, in a process " similar to 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, itre- " turns 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 maxillary nerve, from the fifth pair and from thecei vical nerves, a number of nerves that will appear very great, if tl e bulk of those glands is considered. 2M OF THE SECRETIONS. 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 considered as the effect, and at other times, as the cause. These changes in the condition of the bile (and what is now said ap- plies to almost all tbe secretions of the animal economy,) are never carried so far as to make the bile lose all its distinguish- ing characters, it never takes on the qualities belonging \a another fluid, it never resembles semen, urine, or saliva. The sfo real adeps is ever found within the skull, and the utility of this condition is v^ ry obvious. To how many dan- gers 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 of time, had been deposited into a cavity accurately filled by an organ which is affected by the slightest compres- sion ? 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 if it be considered that it is but imperfectly annualized, that it bears the most striking analogy to the oil extracted from plants; that it contains a very little azote and much hydrogen and carbon, like all other oily substances, since on distillation it is decomposed and yields water and carbonic acid, with a very small quantity of ammonia; that its proportions are very variable, and may be considerably increased or diminished, without manifestly impairing the order of the functions; that animals that spend a great part of their lives 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 * Marmots and dormice become prodigiously fat during the au- tumn, they then take to their holes and live in them during the six winter months, on the fat which is accomulated 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. 267 '.he nutritive matter extracted from the food, a kind of interme- diate state, through which it has to pass before it can be assi- milated to the animal whose waste it is destined to repair. Ani- mals which live on grain and vegetables, are always 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, sensi- bly becomes thinner in a very short time: the bulk and weight of his body diminishes from the absorption of the fat which supplies the deficient quantity of blood. Adeps may, there- fore, be considered as a substance in reserve, by means of which, notwithstanding the small quantity of food and its want of nutritive qualities, Nature finds wherewith to repair the daily ivaste. 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 combination 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 vege- table acid. Fat has a considerable affinity for oxygen, and by combining with it, turns rancid, after remaining some time ex- posed 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 os it absorbs oxygen, its density increases; thus oil becomes concrete by combining with oxygen, and fat acquires a consistence almost equal to that of wax, which is itself a fatty substance highly oxi- dized. 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-animalized 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 severe cold; the animals which inhabit northern climates, be- sides being clothed in a thick fur, are likewise provided with a considerable quantity of fat. The fishes of the frozen seas. the cetaceous animals which seldom go far from the polar re- 268 OF THE SECRETIONS. gions, all kinds of whales, are covered with fat, and have like- wise a considerable quantity within their body. By its unctu- ous qualities, fat promotes muscular contraction, the motion of the different organs, the free motion on each other of the dif- ferent 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 tbe 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 nervous people are exceedingly thin, and have an excessive de- gree 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 suffo- cation. Respiration in such persons is, at times, interrupted by deej) sighs, and their heart, probably overloaded with fat, expels, with difficulty, the blood within its cavities. CV. According to modern chemists, the use of fat is to take from the 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 inclination to action, by exerting the organs of digestion. Not- withstanding 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, many mutual- ly supply each other; but can we admit the chemical theory of the use of fal, when we recollect that frequently, in the most corpulent persons, respiration and the secretion of bile are per- formed with great freedom and with no difficulty; while the difficult respiration attending pulmonary consumption, and the OF THE SECRETIONS. 269 difficult flow of the bile from an obstruction of the liver, are always accompanied 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 tbe 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 merely a very liquid fat, whose consistence diminishes when animals become lean. Inclosed within the cells of the osse- ous tissue, in cavities whose sides cannot collapse, and whose dimensions must always remain tbe same, the mar- row, 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 con- sistence. CVI. The secretion of the marrow is, like that of the fat, a mere arterial transudation; it is performed by tbe 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 oc- casioned by the division of the skin and of the nerves, over- comes every other pain, and I have always seen patients im- pressed 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 270 ON NUTRITION. ease which follows the division %f the flesh, raise their head and look on, while the bone is being sawed through; at once ac- tors and spectators in this last part of a painful and bloody ope- ration. Vet 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 the organs of motion and on their action. CHAPTER VI. ON NUTRITION. CVII. ALL the functions which we have hitherto made the object of our study; digestion, by which tbe 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 essentia] function treated of in this chapter, and the consideration of which ter- minates 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 organs whose waste it is to repair; and this identification of the nutritive matter to our organs, which take it up and appro- priate ii to themselves, constitutes nutrition. Thus there is accomplished a real conversion of the aliment into our own sub- stance. 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 «N NUTRITION. 211 engaged in separating from it the fluids containing tbe recre- mentitious materials pf its substance worn by the combined ac- tion of tbe air and of ealoric, by inward friction and by a pulsa- tory motion that detaches its particles. Alike, therefore, to tbe 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 dyes red the bones of animals among whose food it is mixed, proves most unquestionably, this incessant decomposition of liv- ing 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 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 ye'ars 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 advanced 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 nnttcr is aninralized or assimilated to tbe bodv 27% ON NUTRITION. which it is to nourish, the parts which it moistens retain it and incorporate it to iheirown substance. This nutritive identifi- cation is not performed a ike 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 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 Iain suf- ficiently long in the cells of its tissue. The same happens to the muscles,wbich 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 of 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, eontain, 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 paralized, 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. ClX. 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, foim the basis of our food; on whatever part of tbe plant he may live, whether on the stem, on the leaves, on the blossoms, on the seeds, or on the root;.carbon, hydrogen, and ON NUTRITION. 273 oxygen enter into the composition of these vegetable substan- 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 nu- tritive matter undergo a more advanced state of composition, to deprive 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 con- stantly inundated by salt and brackish water.* Living bodies then, are real laboratories, in which there are carried on combinations and decompositions which art cannot imitate; bodies that appear to us simple, as soda and silex, seem to be formed by the union of their constituent particles; while * I am unacquainted with the details of the experiment referred to by the author; he quotes it, I conceive, to show that the power which, he says, is common to all living bodies, of producing a sub- stance 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 water- ed with distilled as with sea water. This, I apprehend, is the au- thor's meaning, though the text is somewhat obscure, and would al- most 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 soade, semee dans " une caisse pleine d'un terreau qui ne contient pas un seui atome "de cet alkali, arrocee avec l'eau distillee, ne lefournitplus com- " me si elle avoit pns sa croissance au milieu des marais toujours ' ir.ondes par leuis caux saumatres et muriatiques." 36 274 ON NUTRITION.' 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 decompo- sition 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 *£ of pure si- lex indissoluble in that acid, and 0,393 of phosphate of lime dissolved in it. The excrements of a ben, 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 con- tained in the oats, with a small deficiency in the quantity of silcx, which might have been employed in furnishing the excess of calcareous matter; a transmutation depending on the absorp- tion 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 decomposition 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 raucous substance; Cullen says it is saccharine; Professor 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 o. the oxalic acid. On analyzing the aninal sub- stance, by means of the nitric acid, it is reduced to this last base, * See the Annales de Chimie, and the Sytteme des Connaissances chimiques de Fourcroy, tome x. page 72. ON NUTRITION. 275 by depriving it of a considerable quantity of azote which con- stitutes 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 fluids; this gas comof 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 alimenta, into the digestive tube, or whether it is furnished by the decomposi- tion of the fluids within that cavity. The intestinal fluids ex- tricate azote, which combines with the alimentary mass, and occupies tbe 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 atmos- phere, this gas robs it of a portion of its carbon, and as it dis- engages 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 perhaps to the lymphatic system, what the pulmonary organ is to the sanguineous system. The animalization of the animal substance is therefore ef- fected, principally by the loss of its carbon, which is replaced by the excess of azote in the animal fluids. These maintain themselves, in this manner, in a due temperament; for con- tinually parting with the carbonous principle in the intestinal, pulmonary, and cutaneous combinations, they would be over animalized, if an additional quantity of chyle did not seize the azote, which is in excess. Still this theory does not ac- count for the formation of the phosphoric salts, of the adipo- ♦Thc late experiments of Messrs Allen and Pepys prove vidual, by establishing his relations with the beings that surround him. CHAPTER VII. OF SENSATIONS. CXIII. We have already seen, how the human body, es- sentially 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 tbe food it digests, and by the air it breathes. We shall now proceed to examine by what organs man is enabled to keep up with all nature, the relations on which his existence depends: by what means he is made aware of the presence of objects which concern him. what means he possesses to fit his connexion with them to his welfare, to draw them towards him or to re- pel them, to approach or to avoid and escape them, as he per- ceives in them danger, or the promise of enjoyment. Man possesses, in ail its plenitude, 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 OF SENSATIONS. 279 filled with sensations, and that employs them with the most powerful combination, as tbe materials of thought, and the sources of intelligence: he is the best organized for feeling the action of all beings around bim, and re-acting on them in his turn. In tbe study which we are about to undertake, we shall see many instruments placed on the limits of existence, on the surface of tbe living being, ready to receive eve»y impression; conductors, stretching from these instruments to one common centre, to which all is carried: conductors through which this central organ regulates the actions which now transport tbe wbole body from one place to another (locomotion); now mere- ly 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- 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 bow 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 tbe eyes, of the nerves by which those organs com- municate with the brain, and of the brain itself, whither all sensations, or rather the motions in which they consist, are ulti- mately carried. CXV. Of light. At this day, the greater part of natural phi- losopners 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 obsersations of HerscheL* I shall not * This celebrated Astronomer has published, in the Philosophical f ransactions of the Royal Society for 1800. a series of experiments which show, theit the different coloured rays, heat, in different de- grees, 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 which Herschel concludes that rays are given out by the sun, too linle refrangible to 280 OF SENSATIONS. examine whether, as Pescartes and his followers imagine, light, consisting of globular molecules, exists 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, 1 st, 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; reflected, when it is thrown back to that organ by an opake body; refracted, when its direction has been changed by passing from one transparent medium to another of different density: 3dly, that the rays of light are reflected at an angle equal to that of incidence; that a ray, passing through a trans- parent 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 the combustibility of the diamond; and the existence of a com- bustible principle in water, since placed beyond doubt, by the beautiful experiments of modern chemistry; 4thly, that a ray of light refracted by a glass prism is 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 produces on the retina the liveliest impressions. The eagerness of savages for stuffs of this colour is well known. Among almost all nations it has dyed the mantle of kings: it is the most brilliant and splendid of all: there are animals whose eyes seem scarcely to sustain it: I have seen maniacs whose madness, after a long suspension, never failed to break out at the sight of a red cloth, or of one clothed in that colour. Green is, on the contrary, the softest of colours; the most permanently grateful; that which least fatigues the eyes, and on which they will longest and most willingly repose. Accordingly, nature has been profuse of green, in the colouring of all plants: she has dyed, in some sort, of this colour, the greater part of the produce the sensation of light, and of colours, but which produce the sensation of heat. OF SKNSATIONS. 281 surface of the globe. When the eyes bear uneasily the glare of too strong a light, glasses of this colour are used to soften the impression, which slightly tinge, with their own hue. all the objects seen through them. Lastly, the violet ray, last in the scale, of which the middle place is filled by the green, is of all the weakest, the most refrangible. Of all colours, violet has the least lustre; forms show to less advantage under it; their promim-nccs are lost: painters accordingly make but little use of it. When an enlightened body reflects all the rays, the sen- sations they might separately produce hlti,d into the sensation of white; if it reflect a few, it appears differently coloured, ac- cording to tbe rays it repels: finally, if all be absorbed, the sen- sation of black is produced, which is merely the negation of all colour. A black body is wrapped in utter darkness, and is vi- sible only by the lustre of those that surround it: 5lbly, that from every point in the surface of a luminous or enlightened body, there issues a multitude of rays, diverging according to their distance, with a proportionate 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. CX VI. 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 forward, and shaped obliquely outwards; so that their outward side uot being so long as the others, the ball of the eye supported, on that side, only by soft parts, maybe 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- come 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- 37 2S2 OF SENSATIONS. 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 tbe organ. Tbe eye-ball itself contains two parts answering very different purposes; the one, formed by nearly the.whole globe, is a real optical instrument, placed immediately in front of the retina, and destined to pro- duce on the luminous rays those changes which are indispensa- ble in the mechanism of vision; the other, formed by llie me- dullary expansion of the optic nerve, is the immediate organ of that function. It is the retina which alone is affected by the impression of light, and set in motion by the contact of that very subtle fluid. This impression, this motion, this sensation, is transmitted to the cerebral organ by the optic nerve, the ex- pansion of which forms the retina. CXVII. Of the Eye-brows, the eyelids, and the lachrymal apparatus (Tulamina oculi, Haller). The more or less dark colour of the hairs of the eye-brows, renders that projectiou very well adapted to diminish the effect of too livid 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 -rgan 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 eyfs, 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 they eye, one may still discern through their texture, light from darkness. On that account light may be considered as one of OF SENSATIONS. 283 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 luminous rays had continually excited their sensibility. The removal of the eye-lids is attended with loss of sleep. The fluids are determined to the affided organ, which suffers from incessant irritation. The eyes inflame, their inflammation spreads towards the brain, and the patient expires in the most dreadful agony. Thanks to an advanced state of civilization, these barbarous tortures have long been abolished; but what happens, when from ectropium of one or other of the eye-lids a small portion of the sclerotic coat or cornea remains unco- vered, 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 ophthal- mia, which can be cured only by bringing together, by means of a surgical operation, the divided edge 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 in- tended to prevent insects or other very light substances, float- ing 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, im bedded in fat, and supplied with pretty considerable vessels and nerves in proportion to its bulk, and pouring the fluid it secretes, by means of seven or eight ducts, which open on the internal surface of the upper eye-lid, by capillary orifices directed downward and inward. The tears are a muco-serous fluid, rather heavier than distilled water, saltish, changing to a green colour vegetable blues; and containing soda, muriate and car- bonate 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 qualities of the fluid that is secreted. The tears, which in those v 284 OF SENSATIONS. 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 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 this unites to the eye-lids From tbe whole extent of its surface, there oozs ■ n albuminous serority, 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 palpebral; 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 palpebral, prevents the tears from falling on the cheek, and answers the same purpose as the greasy substance with which one anoints the edges of a vessel, filled above its level, to prevent the over- flowing 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 move- able edge of the palpebrse, 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 I his course of the term is, likewise, promoted by the action of the palpebral * 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 part of the eye. The conjunctiva (if, however this portion of skin deserves that name) when opake, renders the globe of the eye, in otlier respects imperfect, absolutely useless. This is observed in the kind of eel, called in books of natural history, murena ctccilia: the gastrobranchus ctecus is blind from the same circumstance. (»!•• SENSATIONS. 285 portions of the orbicularis palpebrarum, whose fibres, hav'ng their fixed point at the inner angle of the orbit where the tendon is inserted, always draw in their external commissure. On reaching the intern d angle of the palpebral, the tear'- ac- cumulate in the lacus lachrymalis, a small space formed between the edges of the palpehrce, kept separated fron^ each other by the carunada lachrymalis. This last substance, long considered by the ancients as the secretory organ of the tears, is merelv a collection of mucuous cryptae. covered over by a loose fold of the conjunctiva. These follicles, alike in nature to the meibo- mian! glands, secrete like them an unctuous substance, which smears the moveable edges of the palpebrse near the internal commissure. Tbe edges of the eye-lids in this situation re- quired 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- pebr;e with the remaining five sixths, at the outer part, where their inlernal, 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 lachrymalia, and they are called superior and inferior, accord- ing to the palpebroe to which they belong. In the dead body the punctua do not appear tubecular; the small bulgings pro- duced, doubtless, by a state of orgasm and of vital erection, col- lapse at the approach of death. These small apertures, direct- ed inward and backward, are incessantly immersed in the ac- cumulated tears, absorb them, and convey them into the lach- rymal sac by means of the lachrymal ducts, of which they are the external orifices. The absorption of the tears, and their flow into a membranous reservoir lodged in the groove formed by the os unguis, do not depend on the capillary attraction of the lachrymal ducts; each of them, endowed with a peculiar vital action, takes up by a real process of suction, the tears ac- cumulated in the lacus lachrymalis, and determines their flow into the sac. The weight of the fluid, the effort of the columns which succeed each other, co-operate with the action of the parietes of the duct. The flow of the tears is further facilitated by the compression and slight concussions attending the con- tractions 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 readily discovered when we at- tempt to introduce into them Anel's syringe or Mejean's stylet, fo remove slight obstructions of the lachrymal passages. In a 28 Ij OF SENSATIONS. child now under my care for a mucous obstruction of tbe nasal due', I c ti Hf-e the puncta lachrymalia contract, when the ex- tremity of the syphon docs not at once enter tbe canal. One is then obliged to wait before it can be introduced for a cessa- tion of the spasmodic contraction, which lasts but a few mo- ments. The tears which flow into the lachrymal sac, by the common orifice of the united puncta lachrymalia, never accu- mulate within it, except in case of morbid obstruction; they, in that case, at once enter into the nasal duct, which is a con- tinuation of it, and fall into the nasal fossae, below the ante-; rior part of the inferior turbinated bones of these cavities. There they unite with the mucus of the nose, increase its quan- tity, render it more fluid, and change its composition. The use of the tears is to protect the eye-ball against the irritating impression of the immediate contact of the atmosphere. They, at the same time, favour the sliding of the palpebral, 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 cornea 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- branous capsule, inunoveably fixed in its situation by adhering to tbe capsule of the vitreous humour. Behii;!i t!'e crystalline lens, the posterior three-fourths of the cavity of the eye contain a viscid transparent humour, enclosed OF SENSATIONS. 287 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 op.ic nerve, the retina, is spread out on its surface, so as to be com entrical to the choroid and sclerotic coats. The eye-ball being nearly spherical, the length of its differ- ent diameters differs but little. The diameter of the eye, from the fore to the back part, is between ten and eleven lines; the transverse and verlical diameters are somewhat shorter. Within the space measured by tbe diameter from the fore to (he back part, there are situated, taking them in their or ler from the fore part, the cornea, the aqueous humour ronained in the an- terior chamber, the iris and its central opening or pupil; the aqueous humour of the posterior chamber, the crystalline lens, surrounded 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 per- pendicular, 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 sclero- tica, like the ghss 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 aque- ous 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 J.he iris, the posterior part of which, covered by a black pigment, is called the uvea.* The specific gravity of the aqueous hu- * Some anatomists have doubted the existence of the posterior chamber of the eye; but to be convinced of its existence, one need but freeze an eye, when there will be found a piece of ice, between the crystalline lens and the uvea The formation of this isicle is not owing to the admission, through the opening of the pupil, of the aque- ous humour, which, like all other fluids, expands considerably on freezing; for the expansion of fluids on their freezing being propor- tioned to their bulk, the vitreous humour which freezes at the same time as the aqueous, must prevent its retrograde flow through the pupil Lastly, the uvea or postei'ior part of the iris is covered with » black point which is easily detached from it; now, if the anterior 288 OF sllNSATIONf-. mourdoes not mucl) exceed that of distilled water; some have even thought it less; it is albuminous, and holds in solution several saline substances. Tlie crystalline, inclosed in its membranous and transparent 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 ap- proach 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 thickness at its centre, consists of an albuminous sub- stance coagulable by heat and alkohol. Extremely minute ar- teries 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 the continuity of its external covering is destroyed. The use of the choroid, is not so much to afford a covering to the other parts, as to present a dark surface, destined to absorb the luminous rays, when they have produced on the retina a sufficient im- pression. If if- 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, part of the crystalline luns had been in immediate contact with it, it would have been soiled b. some of this colouring matter, whicli would have tarnished its natural transparency, indispensable to perfect vi- sion. It is, therefore, undeniable that there does exist a posterior chamber, which is to the anterior in the proportion of two to five, and containing about two fifths of the aqueous humour, the whole of which is estimated at five grains, and that the iris forms a loose partition between 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 exhalation, it is soon reproduc- ed, as wc see after the operation for cataract. OF SENSATIONS. 289 and that the retina was only its epidermis. This hypothesis would never have obtained so much celebrity, if, besides the •bjections 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 glandu- lar body, opake and incapable of transmitting the luminous rays. The retina loses its form, as soon as it is separated from tbe vitreous humour, or from the choroid coat, between which it is spread out as a very thin capsule, so soft as to be almost fluid. A number of blood-vessels, from the central artery of Zinn, are distributed on the nervous substance of the retina, and give it a slight pink colour Ought we, with Boerhaave, to at- tribute 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 tbe sclerotica, to which the covering given to that nerve by the dura matter is connected; next penetrating through a very thin membrane perforated by a number of small holes and closing the opening left by the nerve, and which belongs as much to the choroid as to the sclerotic coats, it 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 philosophers, been exclusive- ly assigned to its central part, called the optical axis or porus opticus. This central part is easily recognized, in man, by a yellow spot discovered by Soemmering; in the middle of this spot, situated at the outer side of the entrance of the opric nerve into the globe of the eye, there is seen a dark spot and a light depression, the use of which is not understood This peculiar structure, recently discovered, is met with only in the eye of man and of monkeys. 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 area of the cornea on the eye-brows, the eye-lids and the sclerotica, are lost to vision. Those which strike the mirror of the eye pass through it, under a refraction proportioned to the density of the cornea, which much exceeds that of the atmosphere, and to 38 290 OF SENSATIONS. 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 iu different 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 enlarged or diminished, by the contraction or expansion of tbe iris. The motions of this membrane depend entirely on the man- ner in which light affects the retina. The iris itself is insensi- ble to the impression of the rays of light, as Fontana has proved, who always found it immoveable, when he directed on it alone the luminous rays. When the retina is disagreeably affected, by the lustre of too strong a light, the pupil contracts, to give passage only to a small number of rays: it dilates, on the con- tr.-ry, in gioom, to admit enough to make the requisite impres- sion on the retina. To explain the motions of the iris, it is not necessary to ad- mit 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 the membranous tissue. When the irritating cause ceases t« act, by our passing from light into darkness, the humours flew back into the neighbouring vessels, the membrane of the iris returns upon itself, and the pupil enlarges, the more as the darkness is greater.* The rays, admitted by the pupil, pass through the aqueous humour of the posterior chamber, and soon meet 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 * Habitual dilatation of the pupil is a symptom of weakness, o+' worms, &c- OF SENSATIONS. 291 produce the impression which gives us the idea of certain pro- perties of the boly which reflects them. As the retina em- braces the vitreous humour, it prevents a very extended surface to the contact of the rays, which enables us to behold, at once, a great diversily 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 therefore, in the interior of the organ, a cone, of which the hase cover the cornea, and applies to that of the external luminous cone, whilst its apex is on some point of the retina. It is conceived, generally, that the luminous cones issuing from all points of the object beheld, cross in their passage through the eye, so that the object is imaged on the retina reversed. Admitting this opinion, established on a physical experiment, we have to inquire, why we see objects upright, whilst their image is reversed on the retina. The best explanation we pos- sess 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 re- lative, 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- 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 them- selves to the distance and the smallness of objects, cannot de- pend, as has been fondly repeated, on the lengthening or shorten- ing 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 into 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 disputed. The eye which moves am1 rests on the adipose cush- ion 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 tbe circumference of the chrystalline 292 OF SENSATIONS. lens, cannot act on this transparent lens, compress Mormove it: for these little membranous folds, of which the aggregate com- poses the irradiated disk, known under the name of corpus ci- liare, possessing no sort of contractile power, are incapable of moving the chrystalline lens, with which their extremities lying in simple contiguity have no adherence, and which, besides, is immoveably fixed in the depression which it occupies, by the ad- hesions 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 explana- tion of this physiological problem. T!><- 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 ot the cone, and which need but a much smaller refraction for their re-union on a single point of the retina, are alone admitted by the straitened opening. When, on the contrary, we look at a distant object from which rays are given out, already very convergent, and which need but a small refraction to bring them towards the perpendicular, we dilate the pupil, in order to admit the 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 chrystalline, 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 OF SENSATIONS. 2m 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 chrystalline 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»chiI- dren get, of looking very close at objects which catch tbe'r at- tention. The pupil then becomes accustomed to great contric- tion, and dilates afterwards with difficulty. It is obvious, that, to correct this vicious disposition, you must show the child dist.nt 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 Nyctalopes, such is the name given to those affected with this disorder, distinguish objects amidst the deep- est darkness; a few rays are sufficient to impress their organ. It is related that an English gentleman, shut up in a dark dungeon, came gradually to distinguish all it contained: when he returned to the light of day, of which he had in some sort lost the habit, he could not endure its splendour; 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 stem of total paralysis of the optic nerve, or gutta serena. It may arise from any thing that can impair the sensibility of the retina. Saint-Yves relates, in his work on diseases of the eyes, many cases of hemeralopia. The subjects were chiefly workmen employed at the Hotel des Monnoies, in melting the * The author means " scarcely divergent." T. j I give to the 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 This acceptation is, however, a grammatical error, sinre 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 accord.! ingly in this sense that they are used by the father of physic. I owe this remark to Dr. Roussille Chamseru, who has carefully verified 'he text of Hippocrates in the MSS. of the Imperial library. 294 OF SENSATIONS. metals. The inhabitants of the northern regions, where tbe earth is covered with snow, great part of the year, become at an early age hcmeralopcs. Both contract this weakness, from their eyes being habitually fatigued by tbe spl ndour of too strong a light. Finally, in order to the completion of the mechanism of vi- sion, it is requisite that all parts of the eye be under certain conditions, the want of which is more or less troublesome. It is especially necessary, that the membranes and the humours which tbe rays of light are to pass through, should be perfectly transparent. Thus, specs of tbe cornea, the closing of tbe pu- pil by the preservation of the membrane which stops that opening during the first months of the life of the foetus; cata- ract, an affection which consists in the opacity of the crystal- line lens or its capsule; the glaucoma, or defect of transparen- cy in the vitreous humour, weaken or altogether destroy sight, by impeding the passage of the rays to the retina. This mem- brane itself must be of tempered sensibility to be suitably af- fected by their contact. The choroid, the concavity of which it fills, must present a coating black enough to absorb the rays that pass through it. It is to the sensible decay of the dye of tbe choroid in advancing years, as much as to the col- lapsing, induration, and discolouring of different parts of the eye, and the impaired sensibility of the retina from long use, that we ascribe the confusion and weakness of sight in old peo- ple. 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 hap- pens that the countenance of children, whose eyes are propor- tionally larger, is seldom disagreeable, because it is chiefly in these organs that physiogniony seeks expression. Might we not say, that if natuue 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 immovable in the place they occupy. Drawn into very various motions by four recti muscles and two oblique, they direct iheniselves towards all objects of which we wish to take corni/ance; and it is observed, that there is, be'ween the muscles which move the two eyes, such a correspondence of OF SENSATIONS. 21)5 action, that these organs turn at once the same wav, and are directed, at once, towards the same object, in such a manner that the visual axes are exactly parallel. It sometimes happens tiiat 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 possessed of a predominating power. Buffon has further as- signed, as a cause of squinting, the different aptitude of the eyes to be affected 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 usethe stronger, which is yet strengthened by exercise, whilst repose stid weakens the one which.remains in inaction. Tbe exami- nation of a great many young people, who had fallen un-'er military conscription, and claimed exemption on the score of infirmities, has shown me that squinting is constantly connect- ed with the unequal power of the eyes. Constantly* the inac- tive eye is the weakest, almest useless, and it was quite a in it- ter of necessity that the diverging globe should be thus neu- tralized, else the image it would have sent to the brain, lif- ferent from that which the sound eye gives, would have intro- duced confusion into the visual functions. The squinting eve being inactive, falls by degrees 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 md vari- ed, is liable to betray us into many errors. It may be doubted, whether it gives the notion of distance, since the boy couched by Cheselden, 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 dhnnce, 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 front the touch that we gain the correction of these errors which Condillac, in his Treatise on Sensation, has perhaps ex- aggsso-pharyngeal brunch 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 nerve6 of sensa- tion. Seveial 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 be knew a case in which the sense of taste was lost from tbe division of the nerve of the ninth pair, in removing a scirrhous gland- This case, however, ap- pears to me a very suspicious one. The patient might still nave tasted, by means of the lingual nerve, and the sense would only have been weakened. The division of one of tbe nerves of the ninth pair could render insensible only that half of the tongue to which it is distributed, the other half would continue fullv to possess the faculty of taste. The application of metals to the different nervous filaments distributed to the tongue, ought to inform us of their different use?, if, as Humboldt suspects, the galvanic excitement of the nerves of motion, alone produces contractions. To ascertain the truth of this conjecture, I placed a pl.ite of zinc within the skull, under the trunk of the nerve of the fifth pair, in a dog that had been killed a few minutes before, and that still retain- ed iis warmth; the muscles of the tongue, under which a piece of silver was placed, quivered very slightly; those of the fore- head 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 sensation of taste, which agrees with the opinion of most physiologists, and the same inference may be drawn from the * Especially the anterior part of the palatine membrane. The- naso-paiatine nerve, discovered by Scarpa, after arising from the ganglion of Mekel, and going for a pretty considerable distance in- to the nasal fossae, terminates in that thick and rugous portion of th- ^vlatice membrane situated behind the upper incisors, and wifli nhich the tip of the tongue is in such frequent contact. OF SENSATIONS. 311 anatomical knowledge of the situation of this nerve which, al- most entirely, terminates in the papilhc of the merrhrane of the tongue, and sends \e.ry few filaments to the muscles of that or- gan. But though the galvanic irritation applied to the hypo- glossal nerve affected the whole tongue,in a ronvulsive 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 (stylo, hyo, genio, glosso and Ungual); three nerves (lingual, glossopharyngeal, and hypoglossal); a ranine arterv and ve'n; and a set of lymphatic vessels precisely alike. All these parts, by their union, from a fleshy body of a close texture >nd not easily unravelled, similar to that of the ventricles of the heart, endowed with a considerable degree of mobility, in consequence of the numerous 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 tongue corresponding to the half of the body that is paralvzed, loses, likewise, the power of motion; the other retains its mobi- lity, and draws the tongue towards that side. In carcinom i of the tongue, one side remains unaffected by the affection which destroys the other half; lastly, the arteries and neves of the left side rarely anastomose with those on the right; injections forced along one of the ranine arteries, fill only the correspond- ing 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 preserva- 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 $12 OF SENSATIONS. that is not light, sound, smell or flavour is appreciated by the touch, whic'< 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 geoemetrical 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 yod have just touched ice, another body colder than yours, will ap- pear warm. It is fortius reason, that subterraneous places ap- pear warm to us during winter. They have kept their tempe- rature whilst all things else have changed theirs; and as we judge of the heat of an object by its relation not only to our own, but also to that of other bodies and of the air about us, we find the same places warm which had appeared cold to us in the middle of summer. The densest bodies being the best conductors of heat,* mar- ble, metals, &c. appear colder to us than they really are, be- cause, they carry it off so rapidly. Marble and metals, when polished, appear still colder, because, as they touch the skin ia many more points at once, they effect this abstraction more ef- fectually. Every one knows the experiment of placing a little ball between the two fingers crossed, and producing the sensa- tion of two different balls. * Woolly substances, &c. all felts, of which the crossing hairs con- fine, in some sort, a great quantity of air, a fluid which, from its gaseous state, is a very bad conductor of heat, retain heat well; and, of equal thickness, a stuff of fine wool, of which the hairs are more separated, the tissue softer, will be warmer than a stuffof coarse wool, of which the threads, too close, form a dense body, through which cold, as well as heat, will pass with ease It is by thus con- fining a certain mass of air, that snow keeps the soil it covers in a mild temperature, and preserves plants from the injury of exces- sive cold: a physical truth which is found figuratively expressed iu the words of the Psalmist, " M.t dedit illinivcm tanquam veetimen-1 turn." OF SENSATIONS. 313 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 carnosis envelopes, almost entirely, the body of some animals; its contractions wrinkle their skin covered with hairs, these rise, vibrate, and thus are cleared of the dust and dirt which may have gathered on them. It is by means of a cuta- neous muscle, of very complex structure, that the hedge hog is enabled to coil himself up, and to present to his enemy a sur- face studded with sharp points: only a few scattered rudiments of an analogous structure, are to be met with in the human body; the occipito-frontalis, the corrugator supercillii, several mus- cles of the face, the platysma jnyoides, the palmaris cutaneus, may be considered as forming part of this muscle. We may even include the cremaster, whose expanded fibres, surrounded by the dartos, have misled some anatomists to such a degree, that they have admitted the existence of a muscular texture in the latter. These fibres of the cremaster, produce distinct mo- tions in the skin of the scrotum, wrinkle it in a transverse di- rection, and at the same time, bring up the testicles. The pla- tysma myoides, acts, likewise, on the skin of the neck; lastly, tbe occipito-frontalis, in some men, performs so distinct a mo- tion of the hairy scalp, as to throw off a hat, a cap, or any other covering that may be on the head. One may compare to the panniculus carnosus, the muscular coat of the digestive tube, situated, throughout its whole length, below the mucous mem- brane, 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 4f 314 OF SENSATIONS. the latter its tension, its whiteness, its polish, its suppleness* favours its applying itself to tangible objects and thus renders the touch more delicate. Too hard or wrinkled a skin would have applied itself in a very incomplete manner, to bodies of a small size, and would not readily have accomodated 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 dis- cover 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 situa- tions, to the subjacent parts. The chemical analysis of the cutaneous tissue shows, that it does not exactly resemble that of the cellular and membranous tissue; it is gelatino-fibrous, and, with regard to its structure and to its share of contractility, it occupies a medium between the cellular tissues and the muscular flesh. There arise, from the surface 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 mi- nuteness. The papillae of the skin, which are more distinct in the fingers and lips than elsewhere, swell, when irritated, ele- vate, in a manner, the epidermis, and this kind of erection, which is useful when we wish to touch a substance with great precision, may be excited by friction or by moderate heaf. The nervous or sentient surface of the skin is covered with a mucous coating, colourless in Europeans, of dark colour, from the effects of light, among the natives of southern climates; of a gelatinous nature, destined to maintain the papillae in that state of moisture and softness favourable to the touch. This mucilaginous layer, known under the name of rcte mucosum of Malpighi, seems to contain the principle which causes the va- riety of colour in the skin of different nations, as will be obser- ved in speaking of the varieties of the human species. The reticular state of the rete mucosum may be explained in two ways; a thin and gelatinous layer, extending on the papil- lar surface of the skin, is perforated at each nervous papilla: and if it were possible to coagulate or detach this coating, we should have a real sieve, or reticulated mesh work, with a per- foration at every point, corresponding to a cutaneous papilla. The sanguineous and lymphatic capillaries which surround the OF 9ENSATIONS. 315 nervous papillae, form, besides, by their connexions, a net- work, the meshes of which are very mfnute, and adhere to the epidermis by a multitude of small vascular filaments that insi- nuate themselves between the icales of this last envelope. The skin would be unable to perform its functions, if an out- er, thin, and transparent membrane, the epidermis, did not pre- vent it from being over dried. This superficial covering is quite insensible, no nerves, and no vessels of any kind are found in it, and even in the present state of the science, we do not understand how it is formed, how it repairs and reproduces itself when destroyed. The most minute researches on its structure, merely show the existence of an infinite number of lamellae, lying over each other, and overlapping each other, like the tiles of a roof. This embrication of the epidermoid lamellae, is very obvious in fishes and reptiles, the scaly skin of which is merely an epidermis, whose parts are much more coarsely shaped. It was observed (XLII.), in the account of absorption, how much friction facilitates the absorption of substances applied to the surface of the skin, by raising the scales of the epidermis, so as to expose the orifices of the absorbents, whose activity, it in other respects, increases. Haller conceives that the epidermis is formed by the drying up of the outer layers of the rete mucosum. Morgagni thinks it is formed by the induration of the skin in consequence of the pressure of the atmosphere. In objection to these hypotheses, one may enquire, how it happens,that by the time the foetus, immersed in the liquor amnii, has attained its third month, it is covered with such an envelope. Pressure renders the skin hard and callous, increases considerably its thickness, as we see in the soles of the feet and in the palms of the hands of persons engaged in laborious employments. The epidermis reproduces itself with an incredible rapidity, after falling off in scales, after erysipelas or herpetic eruptions; or, when removed in large flakes, by blistering, it is renewed in the course of a very few days The cuticle, together with the hairs and the nails, 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 otlier respects, the chemical structure, of all these parts i> 31b' OF SENSATIONS. 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 prevented, and its suppleness maintained by an oily substance, which ex- udes through its pores, and is apparently secreted by the cuta- neous exhalants. This unctuous liniment should not be mis- • taken for that which is furnished by the sebaceous glands, in certain situations, as around the nostrils, in the hollow of the arm-pits, and in the groins. This adipose substance, with which the skin is anointed, is abundant and fetid in some persons, especially in those of a bilious temperament, with red hair. It is, likewise, more copious in the African negroes, as if nature had been anxious to guard against the too rapid de- siccation, by 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 Hottentots anoint their body, in the manner described under the name of tatooing, by the travellers* who have penetrated into tbe interior of the burning regions of Africa. The ancients had a somewhat similar practice, and the anointing with oil, so frequently used in ancient Rome, an- swered 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 transudation of this animal oil renders it necessary, occasionally, to clean the skin by bathing; the water removes the dust and the other impurities which may be attached to its surface by the fluid which lubricates it. It is this humour which soils our linen and obliges us so frequently to renew that in immediate contact with the skin, and which makes the water collect in drops when we come out of the bath, &c. ♦Among others Kolben, Description du Cap de Bonne-Esperance; Sj.armann, Voyage au Cap de Bonne-Esperance, et ehez les Hot- tentots. Vaillant, Voyage dans V interieur dePAfrique. 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 owned his long life to the use of wine inwardly, and to that of oil outwardly; intus vino, extusoleo. OF SENSATIONS. 31? 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, how- ever, a manifest influence on its quantity. I know several very corpulent persons in whom it appears to be evacuated by perspi- ration, on their being heated by the slightest exertion. They all grease their linen in less than twenty four hours. An ex- cess 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 hetero- geneous substauces 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 bo- dies are furnished with this covering, and, in all, in the seed of a plant, in its stem, and on the surface of the body, in man and animals, it bears to the skin the greatest analogy of function and nature. Incorruptibility is, in a manner, its essence, and is its peculiar character; and in tombs which contain merely the dust of the skeleton, it is not uncommon to find whole and in a state to be readily distinguished, thje thickened epidermis that forms the sole of the foot and especially the heel. However, this incorruptibility is possessed, as well as others of the qua- lities of the skin, by the nails and the hairs, which may be con- sidered as its appendages. CXXXII. Of the nails. The nails are, in fact, only a part of the epidermis: they are continuous with it, and after death, fall off along with it. They are thicker and harder: like it they are inorganic and lamellated; they grow rapidly from their root 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 tbe 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 pieces those which they have killed in hunting. The nails are • 318 OF SENSATIONS. 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 being sentient, any more than the growth of corn proves the sensibi- lity of the epidermis, of which they are but thickened parts, be- come 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 un- yielding substances; they likewise concur in improving the me- chanism of the touch.* CXXXI1I. 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 tbe touch, they interfere with it, or at least ren- der it less delicate. The skin, in man, is more bare than that of other animals; it is, likewise, least covered with insensible parts that might blunt the sense of touch. In almost all mammiferous animals, tbe whole body is covered with hair; only a small part of the hu- man body has any hair on it, and that in too small a quantity, and of too delicate a texture, to interfere with the touch. Some men, however, have a very hairy skin; and I have seen several who, when naked, looked as if covered over with the skin of an animal, so great was the quantity of hair over the whole body, ef which no part was bare, but a small proportion of the face, * The toe nails are favourable to the laying the foot to the sur- face on which the body is supported; they likewise improve the sense of touch in this part. The use of the feet is not merely to support the weight of the body, they are also intended to guide us in feeling for 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. I 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 frequently fell, in treading on uneven ground. Those who had lost one half of their feet, were obliged to use crutches. OF SENSATIONS. 319 the palms of the hands and the soles of the feet. This extra- ordinary growth of hair, is in general, a sure sign of vigour and strength. In childhood, there is no hair except on tbe bead, 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 pro- vide 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 to 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 spate 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 cbesnut, 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 fc 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 con- stitute a kind of root, comes out in a single trunk, passes through the skin and epidermis, receiving from the latter a sheath that covers it to its extremity, which terminates in a point. A hair may, therefore, be considered as an epidermoid tube filled with a peculiar kind of marrow. This spungy stem, which forms the centre of a hair, is a more essential part of 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 0 320 OF SENSATIONS. vjessels and nerves. Is the human hair nourished by the imbibi- tion of the gelatinous fluid contained in its bulbs, or is it nourish- ed on the fat in which the latter is embedded? Are vessels distributed along their axis, from the root to the extremity? In favour of this opinion, it was usual to mention the bleeding from the hair when cut, in the disease called plica polonica. But this disease, lately observed in Poland, by the French physicians, 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 oft* 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 bair one may take notice of the manner which it is affected by damp air, which>by relaxing its substance, increase its length. It is on that account, that hairs are used for the construction of the best hygrometers. Nor must we omit either the readiness with which they grow and are reproduced, even after being plucked out by the roots, as I have often seen after the cure of tinea by a painful method: nor their insulating property, with respect to the electric fluid, of which they are very bad conductors; a re- markable property, viewed with reference to the conjectured nature of the nervous fluid. The hairs possess no power of spontaneous motion by which tbey can rise on the head, when the soul shudders with horror or fear: but they do bristle at those times, by the contraction of the occipito-frontalis, 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 grow 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 * $ys!eme des connoissances chimtques, tome IX. page 263 %S SENSATIONS. 321 of very injurious consequence. A chartreux who, every month, had his head shaved, according to the rule of his order, qui'ting it at its destruction, went into the army, and let his hair grow. After a few months he was attacked with excruciating he id- 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 Gri.uaud,* 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 mo- tion 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 fizzing, and give out in an abundance a fetid ammoniacal oil. The ashes that remain from burning them, contain much phosphate of lime. The horns of mammiferae, the feathers of birds, give out 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: according- ly, all nations that cut the beard, first soften it by rubbing it with alkaline and soapy solutions. Is the use of the hair to evacuate the superabundant nutri- tious matter? The epoch cf 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 ef 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. Fi- nally, they have uses relative to the parts on which they grow. CXXXV. TheTaculty of taking cognizance of tangible quali- ties, belongs to all parts of the cutaneous o'rgan. 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, * Second Memoir on Nutrition, p. 49. >De Sedibus et Causis, epist. 8. No. T. 42 &22 OF SENSATIONS. of its weight, its consistence, and even its particular figure. But no part is better fitted to acquire exact motions, on all these properties, than the hand, which has ever been considered as the especial organ of touch. The great number of bones that lorm 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 confirmation is particularly manifest at the extremities of the fingers. Their anterior part, which is endued with the most delicate 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 fingci? wh'yh 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 is applied, is such, that they touch in the greastest number of points possible. The delicacy of the touch is kept up by the fineness of the epidermis: it increases by education, which has more power over this sense than over any of the others. It is known with what eagerness a child, allowed the free use of his limbs, stretches his little hands to all the objects within his reich; what pleasure he seems to take in touching them in all their parts, and running over all their surfaces. Blind men have been known to distinguish by touch the different colours, and even their different shades As the difference of colour depend' on tiie disposition, the arrangement, and number ef 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 voluptu- ous contact; a vital turgescence, explicable without the suppo- sition 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 OF SENSATIONS. $2$ horse, the dog, the ox, &c. want to judge of the tangible quali- ties 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, tbe an- tennae of butterflies, always set near the opening of the mouth, answer tbe same purpose. The tail of the beaver, the trunk of the elephant, are, in like manner, the parts of their body xvhere touch is most delicate. Observe that the perfection of the organ of touch, ensures to these two animals a degree of intelligence allotted to no other quadruped, and become, per- haps, the principle of their sociability. The books of travellers and naturalists swarm with facts attesting the wonderful saga- city of the elephant. Some Indian philosophers have gone the length of allowing bim an immortal soul. If birds, notwith- standing the prodigious activity of their life of nutrition, are yet of such confined intelligence, so little susceptible of durable at- tachment, so restive to education, is not the cause to be as- signed 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 endued, more remarka- bly, with all the qualities which characterize arterial bfood. In vain is their digestion rapid, their muscular power lively, and capable of long continued motion; certain of their senses, as those of sight and hearing, happily disposed; touch being al- most nothing with them, as also the greater number of impres- sions 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 manners much more remote than those of quadrupeds from the habits and manners of man. CXXXVI. Of all the senses, the touch is the most generally diffused among animals. All possess it, from man who, in the perfection of this sense, excels all vertebral animals, to the po- lypus, 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 co- ver so thickly the body of quadrupeds, the feathers which clothe that of birds, quite deaden it. The band of man, that admirable instrument of his intelligence, of which the etruc- 324 OF SENSATIONS. ture has appeared to some philosophers,* to explain sufficiency his superiority over all living species; the hand of man, naked, and divided into many moveable parts, capable of changing every moment its form, of exactly embracing the surface of bo- dies,'is much fitter for ascertaining their tangible qualities than the foot of the quadruped, enclosed in a horny substance, or than that of the biid, covered with scales too thick not to blunt a'l sensation. CXXXVU. Of the nerves. These whitish cords which arise from the base of the br in, and from the medulla oblongata, are distributed to all pprts 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 them merely as conductors of the power of sensation. We shall then see, in what manner they transmit the principle of mo- tion to the organs by which it is performed. The nerves arise,f 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 va- rieties 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 ' relation to tbe 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 tbe seventh pair, wholly deprived of its solid covering, and reduced to its medullary pulp, readily partakes in the sonorous motions transmitted to it by the fluid, in the midst of which its filaments are immersed. The nerves of smell and of taste, are more exposed than the nervous papillae of the skin, ♦See the work of Galen, de usu partium, cap. 4, 5, 6; and Buffon, Histoire Xaturelle, torn IV. et V. 12mo. ■\ In considering the nerves as conductors of sensation, it is correct s to say, that they arise from sentient parts, since it is the extremity most distant from the brain, which experiences the sensitive impres- sion, 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 trans- mitted 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 the union of the nerves. OF SENSATIONS. 335 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 iu speakingof the structure of these nervous cords. CXXXVIII. Every nerve is formed of a great number of filaments, extremely delicate, and which have two extremities, the one in the brain and the other from the part into which they terminate, or from which they originate. Each of these ner- vous 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 ex- treme minuteness; it is filled within with a whitish marrow, a kind of pulp, which Reil states he insulated from the small canal containing it, oy concreting it, by means of the litric acid, which dissolves the membranous sheath, and leaves un- covered the medullary pulp forming the essential part er basis of tbe nervous filament. This same physiologist discovered, by a different process, the internal structure of each nervous fibrilla; he dissolved the whitish or pulpy part, by a long continued so- lution in an alkaline ley, and he succeeded thus in separating it from the membranous tube which enclosed it and which was emptied. The membranous sheath is of cellular structure, and is remarkable only by its consistence and by the very consider- able number of vessels of all kinds that are distributed to its parietes; it ceases to cover the nerves near their two extremi- ties, 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 individual 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 pene- trating among them, and furnish the capillary ramifications which are distributed to the parietes of the sheath common to each filament. These small vessels, according to Reil, allow 3213 OF SENSATIONS. the nervous substance to exhale into each membranous tube; this, likewise, becomes the secretory organ of the medulla with wlvr1' it is filled. C XXXIX. 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 their mode of junction does not admit of being compared to that of the veins. It is, in the first instance, a mere separation; in the second, an approximation of filaments which had been separated, and which, though united in common sheaths, have, nevertheless, each a proper covering, are merely in juxta 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 to- wards a single muscle receiving its nerves from the same trunk as the otlier 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- tion 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 si- tuation. Thus, the medullary fibres of the optic nerve are not furnished with membranous coverings, the pia matter alone fur- nishing a sheath to the cord formed by the union of these fila- ments; the dura mater adds a second coat to it, on its leaving the skull. This coat, belonging, likewise, to the whole nerve, is not continued over it, after it has entered the eye ball, and is lost in tbe sclerotica. A minute artery passes through the centre of tbe optic nerve, and then dividing, forms a rete mirabile which supports tlie 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 con- sistence is always greater than that of the nerves which are sur- rounded 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 mem'jranous covering, whir h is los :o tlie pia mater, or immediate covering of these central parts oft tie brain. The medullory or white part of the brain is continued into their substance, which may be considered as principally fanned by the assemblage of these nervous extremities, which it is difii- OF SENSATION'S. 327 cult to distinguish in its tissue, from its want of consistence. It has long been known, that the origin of the nerves is not the spol 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 rig'it pass to the left, and vice versa. Soemmering thought, that the roots of the nerves, especially of the nerves of the organs of sense, reached to the prominences in the parietes of the ventricles of the brain, and that their furthest 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 tbe brain and nervous system, have completely overset tbese 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 very small, in proportion to the rest of the body, are, however, very large, if compared to the cerebral organ. In children, in women, and in individuals possessed of much sensibility, the nerves are very large, in proportion to the other parts of the body; they decrease in size and shrink in persons advanced in years; the cellular tissue which surrounds them, becomes more consistent, adheres to them more closely, and there exists a certain analogy be- tween 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 may judge of the importance of an organ by the care which na- ture has taken to protect it from external injury, no org in will appear of greater importance than the brain, for no one appears to have been protected with greater care. The substance of 32S OF SENSATIONS. this viscus has so little consistence, that the slightest injury would have altered its structure, and deranged its action; hence it is powerfully guarded by several envelopes, the most solid of which is the bony case in which it is contained. No part of anatomy is better understood than that of the many bones which, by their union, form the different parts of the human head. Every thing that relates to the place they occupy, to their respective size, to their projections and de- pressions, to the cavities whose parietes they form; everything that relates to their internal structure, to the different propor- tions of their component parts, the aggregation of some of these substances, in certain parts 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 appreciated 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 principal 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 surface 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 necessa- ry that the parts of which they are formed should be shaped obliquely, he explains the advantages of the squamous articula- tion between the temporal and parietal bones. When the arch of the cranium is loaded with a very heavy burthen, the temporal bones prevent the parietes on which the effort is immediately applied, from being forced inwardly, or from being separated outwardly. Hunauld very aptly compares them to buttresses, which are to the parietal bones of the same use as walls to the arches which they support. Bordeu* endeavoured to apply to the bones of the face, the principles by which Hunauld 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 upwaid, or to separate outwardly the bones ia which the teeth of that jaw are inserted. As the greatest stress * Academic des Sciences, Memories presentes par les savant etrangers, Tom. III. QF SENSATIONS. 339 of the effort determines them upward, it is, likewise, in that direction, that the bones of the upper jaw rest most powerfully on those of the skull. The author concludes this very ingenious memoir, by proposing to physiologists the solution of the fol- lowing problem: " When a man supports a great weight on his " head, and holds at the same time any thing very firmly be- 14 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 ef- forts 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 windings, and do not deserve to be attended to in this investigation. The vomer may, it is true, communicate to tlr? ethmoid, in an inferior degree, a part of the effort; for the an- terior part of its upper edge is articulated with the perpendicu- lar lamella of that bone; but this quantity is very small, as the vomer is thin, and transmits it almost wholly to the body of the sphenoid, with the lower face of which it is articulated. The effort exerted on the bones of the upper jaw, is trans- mitted, by means of the nasal processes of the upper maxillary bones, by the orbitar and zygomatic processes of the malar bones, and by the upper edge of the palate bones and 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 alae minores of the os sphenoides, which is shaped obliquely at the outer part of the bone. Tbe 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 hone is applied to them laterally. 330 dF SENSATIONS. 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 alae ini- 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 pressure. Lastly, the situation of ^V'body, placed between the dental arches, in front of the place7* 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 tbe lower on the upper jaw, is carried to the anterior, posterior, and inferior faces of the body of the sphenoid bone. The temporal bones which are affected by it, in a very slight degree, by me*ns of the zygomatic processes of the malar bones, support the greater weight of tbe effort acting from above down- ward, or from the arch of the skull towards its base. The weight laid on tbe head, tends to depress or to separate the pa- rietal 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 sphe- noid, by means of the alse majores of that bone, which are ar- ticulated, along the whole extent of their external edge, and along the posterior fourth of their internal edge, with the tem- porals. Besides, the upper extremity of the alae majores is sloped on the inner part of the bone, that it maybe 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 alse majores, which receive it themselves, either directly at the anterior and inferior angles of this bone, or (tlirough the medl- OF SENSATIONS. 331 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 tbe head, one should add that occasioned by tbe 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 tbe 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 eflbrt is transmitted: we may merely observe, that the least powerful of these muscles, the in- ternal pterygoid, tends to draw the sphenoid downward, and 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 sphenoid bone, support, therefore, the whole effort of the bones of the skull and face on one another, when the top of the head being loaded with a heavy burthen, one presses, at the same time, something very firmly between the dental arches. The anterior part of the body of the bone, containing the sphenoidal sinus, is thin and very frail; the posterior part, 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 tbey have to bear the greatest effort; hence the alse majores, by means of which the greatest part of * The sphenoidal sinus is prolonged, it is true, into this posterior part of the body of the bone, in persons considerably advancedfln years; but the parietes of this portion of its cavity are of considera- ble thickness. The anterior part of the basilary process of the oc- cipital bone, is then firmly united to the sphenoid, and may he con- sidered as forming a part of that bone, from which it cannot be de- tached. The cranium of an old man, in this respect, resembles 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 Se considered as forming but one. 832 OF SENSATIONS. 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 proctsses which arise from its lower part. I have, in this enquiry, 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 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 he equal, in every point of the parietes of the cranium, if the form of that cavity were completely spherical, and if the thickness of its parietes were, in every part of it, the same. In that case, no fractures by contre coup could occur, a kind of lesion occasioned by the unequal resistance of the bones of the head, to the force applied to their surface. The peri- cranium, 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 ca9e, there lies over OF SENSATIONS. 333 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 mater which adheres firmly to tbe 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 its folds, the falx, stretched between the crysta galli of the ethmoid bone, and the inner protuberance of the occipital bone, prevents the two hemispheres of the brain, between which it lies, from compressing each other, when the body is on tbe side; and maintains, on the other hand, the tentorium cerebelli in the state of tension necessary to enable it to support the weight of the posterior lobes of the brain. This fold of dura mater is of a semi-circular form, separates the portion of the skull which contains the brain, from that in which the cerebel- lum is situated. It is kept in a state of tension by the falx cere- bri, 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 transmits most of the weight which it has to support. The tentorium cerebelli, which thus divides the internal cavity of the skull into two parts of unequal dimen- sions, is bony in some animals that move by bounding and with rapid action; this is the case with tbe 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 pre- vented 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 secretory organ of the serum which moistens tbe internal surface of the dura mater, a fibrous mem- brane which serves as a periosteum to tbe 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 tbe brain is always of a size proportioned to that of the os- seous case which contains it, the, brain is also most bulky in man. This difference of size between the cranium and face, *Dissertatiodecontinuationibusmembranarum.48Lugdun Bat.l~63. 334 OF SENSATIONS may be taken as the measure of the human understanding and of the instinct of the lower animals; tbe 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 to another drawn in the direction of the base of the skull. He ban called the first of these lines facial, the second, palatine or mental It is easy te 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 fascial line meets the palatine at an angle neaily straight (of between 80 and 90 degrees). When the angle is quite straight, and the line which measures the height of the face is completely vertical, the head is of the most beautiful form possible, it approaches most to that conventional degree of perfection which is termed ideal beauty. If the facial line slopes backward, it forms with the palatine line, an angle more or less acute, and projecting forward, the inclination increases, and the sinus of tbe 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 tbe facial line to incline in a different direction, the angle then en- larges and becomes more or less obtuse. From this inclination forward of the facial line, there results an air of grandeur and majesty, a projecting forehead, indicating a voluminous brain and a divine intellect. To obtain with precision, by this means, tbe 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 oapacity. The relative size of the head, and consequently the propor- tionate bulk of tbe 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. 335 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 shoulder. The statues alone of the king of the gods, pre- sent the singular combination of an enormous head, resting on limbs of a proportionate size; but the Greek artists have trans- gressed 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 circumstance, 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 bead covered by few mus- cles, remains very small. Soemmering has stated, that the head in women is larger than in men, and that their brain is heavier; but it must be recollected, that this great anatomist obtained this result, by examining two bodies, male and female, of the same length. Now, the absolute size being the same, the proportionate magnitude was not so, and he was wrong in com- paring the head, the skull, and the 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, tbat 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 which bear to him a considerable resemblance both of organization and structure, is, likewise, the only animal in which tbe brain, properly so called, is largest ro proportion fo 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- 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- 336 OF SENSATIONS. tion, and rarely succeed in undertakings that require activity and perseverance.* CXL1II. 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 tbe 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 correspond- ing 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 prolongation known under the name ot 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 ot three or four cords or fasciculi of nerves, which, consisting of many filam« nts, tend obliquely from right to left, and vice versa. This crossing of nervous fibres, whi' h is not found in any other part of the brain, had been observed by several anatomists. It is not known bow it could be forgotten, so that the most exact and * See, in the article on Temperaments, an account of the influence of the physical organization on the moral disposition and on the in- tellectual faculties. OF SENSATIONS. 337 the latest among them, Boyer, for instance, says that the cross- ing of the nerves cannot be proved by anatomy. These nervous cords traced upwards, enlarge, strengthen, and forming pyra- midal eminence?, ascend towards the tuber annulare. Hnving 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 callsit 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 fasciculi which compose nearly the whole of the crura cerebri. The interior of these crura, contains a certain quantity of gray substance, 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 sensibly enlarged; and they pass from the thalami optici into new ganglions. These are the corpora striata, and the striae which are apparent on cutting these pyriform masses of gray substance, are only the same fibres, which, enlarged, multiplied, and radiating, 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, ali co- vered with the substance in which are terminated, in like manner, the extremities of the diverging fibres. Krom 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 callosuni, 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 train are a sort of duplicatures, susceptible of extension by the unfolding of two contiguous medullary la- mella? which form its base. The exterior surface of the brain, by means of this unfolding, offers then some relation to the skin, 44 338 OF SENSATIONS. a vast nervous expanse every where covered by a sort of pulpy substance, known by the name of tbe rete mucosum of Mal- pigni 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 tlie vertebral nerves arise from the grayish pulp of which the spinal marrow is full, as is best seen in animals without a brain, but not tbe less provided with a spinal marrow, or series of ganglions, from which the nerves arise. The ganglions, or rather the gray substance which they always show, produce the nervous fibres, and thicken the ner- vous 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 tbey are found, why do not the ganglions of the vertebral nerves fulfil the same function? All these nerves communicate by reciprocal anasto- moses. These communications in man, are equivalent to a real continuity. In truth, the brain acts upon the ner es that pro- ceed from the spinal marrow, as if this were one of its produc- tions, and all the nervous fibres, spread through the different organs, had an extremity terminating in this viscus. One thing well worthy of attention, and on which no anato- mist has dwelt, is that the brain of the foetus, and of the child just born, appears to consist, almost entirely, of a cineritious pulp, to such a degree that the medullary substance is difficult to perceive in if. 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 foetus, makes unnecessary there the existence of the medullary apparatus, to which the most important operations of intelligence seem entrusted. Its first rudiments are found in tbe foetus at its full time. That fibro-medullary apparatus will be strengthened by the exercise of thought as the muscles are seen to enlarge and perfect their growth by the effect of muscular action. CXL1V. Circulation of the brain. I have said that the blood; OF SENSATIONS. 339 iii 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 observation is not without foundation. Though the blood which the contractions of the left ventricle send into the vessels aris- ing from the arch of the aorta, does not undergo, at the place of this curvature, a mechanical separation carrying its lighter parts towards the head; it is not less true, that this blood, just passing from the contact of the air in the lungs, possesses, in the highest degree, all the peculiar qualities of arterial blood. So great a quantity of light, red, frothy blood, impregnated with caloric and oxygen, coming upon the brain, with all the force it has received from the action of the heart, would unavoidably have deranged its soft and delicate structure, if nature had not multiplied precautions to weaken its impulse. The fluid, compelled to ascend against its own weight, loses, from that alone, apart 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 temporal bone; and as this curvature, supported by hard parts, cannot streighten itself, the column of blood is vio- lently broken and turned out of its first direction, with consider- able loss of velocity. The artery immersed in the blood of the cavernous sinus, as it comes out from the carotid canal, is very easy dilated. Fi- nally, 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 340 OF SENSATIONS. 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 tbe heart, the blood reaches it then with an exceedingly slackened motion: it returns, on the contrary, with a motion progressively accelerat- ed. 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 nam? 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 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- wards 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 * In preventing this reflux, there is no use of valves, which the jugular vein is entirely without. 11 is sufficiently prevented, by the direction in which the blood flows, and the extensibility of its coats. This great size which the vein can acquire, would have made useless the valvular folds, insufficient to stop the canal, in that great aug-< mentation of its dimensions. f 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 visc-us. OF SENSATIONS. 341 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 brmin 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 medles, bent in a semi-circular form, passed into the flesh along the sides ©f the articulation of the cervical vertebra?, to apply ligatures to the arteries which ascend along their transverse processes. 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 arterial blood which the contractions of the heart determine towards the brain, that death is to be attributed? The latter opinion seems to be 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 t» life. The heart and brain are, therefore, united to each other by the strictest connexion; the continual access of the blood flow- ing along the arteries of the head is, therefore, absolutely neces- sary 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 34*3 OF SENSATIONS. flow without effort, and that his fruitful imagination traces, at pleasure, the most beautiful descriptions. Nothing is so favour- able to this condition as remaining long in a recumbent posture; in this horizontal posture, the determination of the fluids towards the head is the more easy, as the limbs, which are perfectly quiescent, do not divert its course. He can bring on this state by fixing his attention steadfastly on one object. May not the brain, which is the seat of 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 phy- sician, 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 tbe 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 consis- tence necessary to the exercise of its functions? What is to be thought of Ihe opinion of those chemists who consider the brain as a mere albuminous mass, concreted by oxygen, and of a con- sistence varying in different persons, according to the age, the sex, or tbe state of health or disease? Any answer that one might give to these premature questions, would be but simple con- jecture, to which it would be difficult to give any degree of pro- bability. CXLVI. Of the theory of Syncope. If we consider the action of tbe heart on the brain, we are naturally led to admit its ne- cessity to the maintenance of life, and to deduce from its mo-' OF SENSATIONS. 313 tnentary suspension, the theory of syncope. Several authors have attempted to explain the manner in which their proximate cause operates, but as not one of them has gone upon facts as- certained by experience, their explanations do not at all agree with what is learnt from observing the phenomena of their dis- eases. To satisfy oneself that the momentary cessation of the action of the heart on tbe 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 extreme debility, or on the entire cessation of the action of the heart and arteries. Their parietes, ossified, dilated, adhering to the neigh- bouring parts, or compressed by any fluid whatever, no longer act on the blood with sufficient force, or else this fluid is inter- rupted, in its progress, by some obstacle within its canal, as a polypous concretion, an ossified and immoveable valve. Cul- len, very justly, termed these, idiopathic or cardiac syncopes. To the above may be added plethoric syncope, depending on a congestion of blood in the cavities of the heart: tbe 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 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 (n 341 OF SENSATIONS. the vital functions, and involuntary motion; lastly, we may add asphyxia from strangulation, from drowning, and from the gases unfit for respiration; affections in which the blood being de- prived of the principle which enables it to determine the con- tractions of the heart, the circulation becomes interrupted. If tbe 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 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 substance has been taken into the stomach; when this viscus is much debilitated in consequence of long fasting, or when it contains indigestible substances; in colic, and in hysterical affections. This last class of occasional causes do not act directly, and produce syncope only at a distant period, but the result is OP SENSATIONS. Md 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 momentary cessation of the intellectual faculties, of the vital functions, and of voluntary motion. Morgagni, in treating of diseases, according to their anatomi- cal order, ranks lypothymia among the affections of the chest; be- cause 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 apopletic affections. When a man, on being exasperated, falls into a violent and sudden 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 apoplexy, occasioned by the mechanical pressure on the brain, towards which the blood is car- ried 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 a 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 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 depending parts, and on the difficulty in ascending of that which the contractions of the heart send towards the head? The phenomena of the cir- culation 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 in- dividual nature approaches the more to universal nature. y"\ CXLVII. Of the motions of the brain. Are the alternate motions of elevation and depression seen, when the brain is exposed, ex- clusively isochronous to the pulsations of the heart and arteries; or do thev correspond, at the same time, to those of respiration <• 346 OF SENSATIONS. Such is the physiological problem of which I am about to attempt the solution. Those authors who admit the existence of motions in tbe dura mater, do not agree as to the cause which produces them. Some, and among others, Willis and Baglivi, thought they had discover- ed muscular fibres, and ascribed these motions to their action: others, as Fallopius and Bauhinus, attributed these motions to the pulsations of the arteries of that membrane. The dura mater possesses no contractile power; its firm adhesion to the inside of the skull, would, besides, prevent any such motion. The motion observed in this membrane is not occasioned by the action of its vessels; for, as Lorry observes, the arteries of the stomach, of the intestines, and of the bladder, do not communicate any motion to the parietes of these hollow viscera, and yet in number and size, they at least equal the menyngeal arteries. The motion observed in the dura mater is communicated to it by the cerebral mass which this membrane covers; and this opi- nion of Galen, adopted by the greater number of anatomists, has been placed beyond a doubt by the experiments of Schlitting, of Lamure, Haller and Vicq-d'Azyr. They have all observed, that on removing the dura mater, the brain continued to rise and fall; and, with the exception of Schlitting, they agreed that the brain, absolutely passive, received from its vessels the motions in which the dura mater partook: but are these motions communicated bj the arteries or,by the cerebral veins, and by the sinuses in which these terminate? or, in other words, are they isochronous to the beats of the pulse, or to the contraction and successive dilatation of the chest during respiration? Galen, in his treatise on this function, says, that the air admit- ted into the pulmonary organ distends the diaphragm, and is con- veyed 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 presented to the Academy of Sciences, towards the middle of the last century, maintains that these motions take place in a different order; the elevation of the brain corresponding to expiration, and its depres- sion to inspiration. Conceiving that he has determined this fact by a sufficient number of experiments, he does not enter into any explanation, and concludes his inquiry, by asking whether the mo- tions 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- OF SENSATIONS. 347 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 per- formed. 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 the cavity. The lungs, pressed in every direction, collapse; the curvature of their Vessels increases, and the blood flows among 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 difficulty, into the right ventricle, whose blood is unable to penetrate through the pulmo- nary tissue On the other hand, as the lungs compress the vena cava, a regurgitation takes place of the blood which it was con- veying to the heart; forced back along the jugulars and vertebrals, it 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 inspira- tion succeeding expiration, and on the lungs dilating, the blood which fills the right cavities of the heart, can freely penetrate into the pulmonary substance, and make way for that which the vena eava is bringing 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 Lamure's expla- nation only in the forcible acts of respiration, as in coughing, laughing, and sneezing. He maintained that, in a slate 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 depending on the pulsations of its arteries, so that, according to Haller, the cerebral mass is in- cessantly affected by motions, some of which depend on respira- tion, while the others are quite independent of it. Lastly, according to Vicq-d'Azyr, the brain, on being exposed, presents a double motion, or rather two kinds of motion from without: tbe one from the arteries, and which is least remarkable, 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 re- peat the experiments which each of them brings in support of his 348 OF SENSAflQ&S- own opinion, and to perform further experiments on this subject. My investigation soon convinced me, that these authors 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 diastole of the arteries at its base. Tbe elevation of the brain corresponds to the dila- tation 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, the arrangement of the veins within the skull is such, that this stagnation or reflux could not produce alternate motions of the cerebral mass. The brain receives its arteries from the carotids and vertebrals, after they have entered the skull; the former along the carotid canals, the latter through the foramen magnum of the occipital bone. It would be useless to describe their numerous divisions, their frequent anastomoses, the arterial circle, or rather polvgon, 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 ex- cellent description of this part * The account of the internal ca- rotid published by that great anatomist is, according to Vicq- d'Azyr, a chef-d'oeuvre of learning and precision; the same enco- mium 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 di- vide, and the subdivisions of these branches, are, likewise, lodged at its base in a number of depressions; and that, in tbe 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 vascular, 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 convex surface and the arch of the cranium; each convolution contains a great vein, which opens into the superior longitudinal sinus. The Galeni, which deposits into the sinus the blood brought from the choroid plexus; small veins which open into the cavernous sinuses; others, likewise, very minute, which passing through the foramina in the alae majores of the sphenoid bone, contribute to form the ven ous plexus of the zygomatic fossa?, arc the only exceptions to this general rule. * Fasciculi janatomici. F. 7. tab. \ OF SENSATIONS. 349 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. Tbe 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, the\ 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 6uch 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, ex- cept 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 arte- rial vessels. Does not this continued action of the heart on the brain, explain, in a satisfactory manner, the remarkable sympathy between those two organs, linked by such close connections? It is, besides, of very manifest utility, and connected with the re- turn of the blood, distributed to the cerebral mass and its enve- lopes. The veins which bring it back, alternately compressed against the arch of the skull, empty themselves more easily into the sinuses of the dura mater, towards which their course is re- trograde, 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 supe- rior vena caVa, the internal jugularis, and consequently the sinuses of the dura mater, and the veins of the brain which termi- nate in them, are gradually distended; and if this dilatation were carried to a certain degree, the veins of the brain, placed between it and tbe arch of the skull, would tend to depress it towards the base of that cavity. If this dilatation, at first slight, were car- ried beyond the extensibility of these vessels, their rupture would occasion fatal effusions. It is in this manner that some authors have explained sanguineous apoplexy. 350 OF SENSATIONS. 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 tbe 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, tbe 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 pa- rietes, formed chiefly by tbe 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 tbe disposition of parts, that the motions of the brain are communi- cated to it by the collection of arteries at its base; the fact musj 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, correspond perfectly to the beatings of the heart and arteries. B. A patient, trepanned for fracture, with effusion on the dura mater, enabled me to see the brain, alternately rising and falling. The rising corresponded with the diastole, the falling with Ihe systole of the arteries. C. Two dogs, trepanned, exhibited the same phenomenon, in the same relation to the dilatation and contraction of the ar- teries. 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, was 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 motion of rising, especially when the injection was forced at once along the two carotids. E. I have injected the internal jugular veins. The cerebral mass remained 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 and OF SENSATIONS. 351 the liquor flowed out. The same injection being made with watei 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 with 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- ton was pushed forward, the venous blood flowed with the greatest impetus; a clear proof ef the manifest influence of the motions of the brain on the course of the blood in its veins, and in the sinu- ses of the dura mater. This experiment had been already per- formed by other anatomists, ?nd amongst others by Ruysch, with a view of proving the immediate communication between the ar- teries and veins. This communication, which is, al present, uni- versally 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, ac- count 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. 1. The tying of the internal jugular veins, did not stop the mo- tions of the brain; but its veins dilated, and its surface, bared by the removal of a flap of the dura mater, was sensibly redder than in the natural state. The dog became affected with stupor, and expired in convulsions. The opening of these veins did not hinder the continuance ot 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, produces but a slight reflux in the jugular veins, especially if, during this compression, the trunk is kept raised. The reflux is greater when the trunk is laid flat. These experiments might be varied and multiplied; if, for in- 352 OF SENSATIONS; stance, the injection were thrown, at once, along the vertebral ar- teries, and the internal carotids: but those I have stated are suffi- cient for my purpose. Since the first publication of this enquiry in the Memoirs of the Medical Society,* I have had many opportunities of repeating the observations and experiments, which serve as h foundation to the theory there detailed. Among the facts which contain this theo- ry, there is one that appears to me worth stating: it would be suf- ficient by itself, if it were possible to establish a theory on the ob- servation 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 extent, and left uncover- ed 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 prejudi- cial observer, for the proper motions of that organ, and depending on the reflux of the 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 affect- ing the brain is experienced by the whole body, and that the effort of expiration in barking, causes a concussion more or less violent. The patient, mentioned in the preceding observation, died about about a month after I came to the Hospital of St. Louis, in which she had been for a considerable length of time. On opening the body, the left lobe of the brain was found softened and in a kind of putrid state; the ichor which was formed, in considerable quan- tity, flowed outwardly, by a fistulous opening in the dura mater,: whose tissue was rather thickened. CL. The slight consistence of the brain, which Lorry consi- ders as favourable to the communication of the motion which its arteries impart to it, appears to me to be against this transmis- sion. 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 * Me'moires de la Socie"te M^dicale de Paris, an VII. troiseme annee, ftage 197, ct sniv. OF SENSATIONS- 3^3 obseKe what happens when the posterior part of the knee rests on a pillow, or on any thing of.the same sort; then, tbe 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 re- sists 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 tbe internal carotid and the vertebral arteries, is not greater than that of the popliteal artery. This continual tendency of the brain to rise, produces in the end, on the bones of the skull which resist this motion, very mark- ed 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 action on the enclosing parietes. Sometimes it happens that, at a very advanced age, the bones of the skull are so thinned by this internal action, that the 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 si- multaneous to the beatings of the pulse, as Louis observes 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 regurgitation, could produce only a slow and gradual distention of tbe 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 (be 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 ofdinary ratio of 1 to 6-. On the contrary, it is easy to satisfy 46 354 OF SENSATIONS. 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 at- tempt at investigating the cause of our disagreement. For that purpose, I thought it necessary to examine scrupulously all the circumstances. Tbe 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 disciples. Lastly, Vicq d'Azyr attempted no confirming experiment, and seems to have had in view only the reconciling all opinions. No one of these anatomists has distinguished tbe motions of elevation impressed on ihe cerebral mass by the impulse of its arteries, from the swelling of the sinuses of the dura mater,Nof the veins distributed to it, and from the tumefaction of the brain which may be caused by difficult respiration. This mistake 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 experi- ments, appears especially to have confounded the motion of rising; the real displacement of the brain, with the turgescence of this viscus. At every expiration, he says, 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, cerebrum universum ascendere, id est intumescere; at que. in quavis inspiration illud descendere, id est detumescere.'>'> We may, therefore, consider as a truth strictly demonstrated by observation, experiment and reasoning,the following proposition:— The motions observable in the brain, when laid bare, are imparted to it solely by the pulsations of the arteries at its base, and are per- fectly simultaneous to the pulsations of these vessels: further, the reflux and stagnation of the venous blood, are able to swell its sub- stance. CLI. 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 circumference to the centre, (it is the motion of sensation which we are about more particularly to study iu this paragraph; the other, acting from OF SENSATIONS. 355 the centre to the circumference, and this motion, produced by the will, determines the action of the muscular organs, &c. In what manner are the impressions produced on the senses by the bodies which surround us, transmitted, along the nerves, to the brain? Is it through the intervention of a very subtle fluid; or can the nerves, as has been stated by some physiologists, be considered as vibrating cords? This last idea is so absurd, that one cannot help wondering it should so long have been in vogue. A cord, that it may vibrate, must be in a state of tension, along the whole of its length, and fixed at both extremities. The nerves are not in a state of tension; their extremities, in no degree fixed, approach towards each other or recede according to the difference of posi- tion, the tension, the turgescence, fhe fulness or collapse of parts, and vary constantly in their distance from each other. Besides, the nervous cords, situated between pulps, at their origin, and at their termination, cannot be extended between these two points, The nervous fibre is the softest, the least elastic of all the animal fibres; when a nerve is divided, its two extremities, far from re- ceding by contracting, project, on the contrary, beyond each other; the point of section shows a number of small granulations of medullary and nervous substance, which flows through its minute membranous canals. Surrounded by parts to which they are, to a certain degree, united, the nerves could not vibrate. Lastly, admitting the possibility of their being capabl ■ 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 nature, and to be judged of only by its effects, must be wonderfully minute, since it eludes all our means of investigation. Does it entirely proceed from the brain, or is it equally secreted by the membranous envelopes of each nervous filament? (Neunlemes, Reil.) To say tbe truth, one can bring no other proof of the existence of a ner- vous fluid, but the facility with which, by means of it, we are en- abled to explain the various phenomena of sensation, and its utility in explaining these phenomena These proofs, however, may not appear completely satisfactory to those who aie 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 conveyed, by means *>f it, to the brain or to the other organs? Docs not the vital ac- 354i OF SENSATIONS tion impart to them new qualities, by making them undergo un- known combinations? Do caloric and oxygen enter into these com- binations 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 philosophers of the present day, in Europe.f Tbe action of the nervous fluid takes place from the extremity of nerves towards the brain, so as to produce the phenomena of sensation; for, when the nerves are tied, the parts below the liga- ture 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 con- trary 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; alt sensations are carried to it; it is the spring of all voluntary mo- lion; this centre is to the functions of relation, as the heart to the functions of nutrition. One may say of the brain, as of the heart, omnibus dat et ab omnibus aceipit. It receives from all, and gives to all. The existence of a centre, 1o 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 tbe intellectual func- tions. But is this seat of the principle cf motion and of sensa- tion, circumscribed within the narrow limits of a mathematical point? or rather, should it not be considered as diffused over near- ly the whole brain? The latter appears to me the more probable opinion; were it otherwise, what could be the use of those divi- sions of the organ into several internal cavities? What could be the use of those prominences, all varying in their form, and of ths arrangement of the two substances which enter into their struc- * Were it not for these changes, electricity, magnetism, and gal- ^'anism, would suffice to restore life to an animal recently dead. j Galvanism, as yet, has not realized the expectations of physiolo-. prists. Chemistry has derived the greatest advantage from it.—It is, at present, with M M Davy.Thenard and Gay-Lussac. the mqst powf- e\i) a.gent in the analysis of certain, bodV«. OF SENSATIONS. 357 Cure? We may conjecture, with considerable probability, that each perception, each class of ideas, each faculty, is assigned to some peculiar part of the brain. It is, indeed, impossible to determine the peculiar functions of each part of the organ; to say what pur- pose is served by the ventricles, what is the use of tbe commis- sures, what takes place in the peduncles; but it is impossible to study an arrangement of such combination, and to believe that it is without design; and that this division of the cerebral mass into so many parts, so distinct, and of such various forms, is not rela- tive to the different functions which each has to fill in the process of thought. That ingenious comparison, mentioned in the pane- gyric of Mery, by Fontenelle, is very applicable in the brain. " We anatomists," he once said to me, " are like the porters in Paris, who are acquainted with the narrowest and most distant streets, but who know nothing of what takes place in the houses." What then are we to think of the system of Gall, and of his divi- sion of the outside of the skull into several compartments, which, according to the depression or projection of the osseous case, indi- cate the absence or the presence of certain faculties, moral or in- tellectual? I canftot help thinking, that this physiological doctrine of the functions of tbe brain, resting on too few well observed facts, is frivolous; while his anatomical discoveries on the anat- omy 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 organs of sense laid open to all impressions of surrounding objects; in vain were A their nerves fitted for their transmission: these impres- sions were us as if they had never been, were there not provided a seat of consciousness in the brain. For it is there that every sen- sation 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 bears, and smells, and tastes. You have only to interrupt by compression of the nerves, the communication between the organs and tbe brain, and all consciousness of the impressions of objects, all sensation is suspended. The torturing pains of 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 the experiment, suffers nothing from the most cruel laceration, if you have first cut the nerves of the parts which you are operating. To conclude, the organs of sense, and the nerves which communicate between them and the brain, shall have suffered no injury, shall be in a perfect state/or receiving and transmitting the sensitive impression, yet no phe- nomena of sensation can take place, if the brain be diseased: 358 OF SENSATIONS. when it is compressed, for instance, by a collection of fluid, "or by a splinter from the skull in a wound of the head. This organ is, therefore, the immediate instrument of sensations, of which im- pressions 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 without, would be correctly de- nominated cerebral sensibilily, but even in animals without brain, or distinct nervous system, that it is very manifest. Tiie sensi- bility, in virtue of which the polypus dilates its cavity, for the ad- mission of its prey, and contracts itself to retain it, is, in fact, quite distinct from that sensibility of nutrition, by which its sub- stance 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 ali- ments it receives by the oesophagus: it does, in its own way, di- gest them; set in motion by the impulse it receives, it begins to re act, and that reaction is the perceptive sensation, or perception. From that moment, the impression becomes an idea, it enters as an. element into thought, and becomes subject to the various com- binations that are necessary to the phenomena o£ understanding.* CLIII. Our sensations are nothing but modifications of our be- ing: they are not qualities of the objects: no body has colour to the blind from birth; the rose has lost its most precious quality to him who has lost his smell; he knows it from the anemone, only by its colour, its figure, &c. We perceive nothing but within our- selves. It is only by habit, only by applying different senses to the examination of the same object, that we are at last able to separate it from our own existence: to conceive of it as distinct from ourselves, and from other bodies with which we are ac- quainted; in a word, to refer to outward objects the sensations that take place within ourselves. Our ideas come to us only by tbe senses; there are none innate, as was imagined till the time of TiOrke. 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 suscepti- ble of impressions fom tbe 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 * T ought to observe that the the terms thought and understanding are, in my opinion synonimous; b >th are alike a abridged expi,e;«i sion of the whoL of the operation of the sensitive centre QF SENSATIONS. 35$ sensation came only from without, if the external senses were the only organs that could send impressions to tbe cerebral centre,the understanding, at the moment of birth, had indeed been nothing, and the comparison of its organs to a sheet of white paper, or to a slab of Parian marble, on which not a character were drawn, had been perfectly correct. B,ut we are compelled to acknow- ledge with Cabanis, two source of ideas quite distinct from each other: the external senses, and the internal organs. These in- ward 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 engaged iu the vagina, to seize upon the dug of their dam. Instinct, as the author just quoted has very justly observed, springs from impressions received by the interior organs, whilst reasoning is the produce of exter- nal sensations; and the etymology of the word instinct, composed of two Greek words, signifying "to prick," and " 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 tbe various determinations of mental action. But the part that each bears in the generation of ideas, is very different in animals, whose grosser external senses allow instinct to predominate; and in man, in whom the perfection of these senses, and the art of signs, which perpetuate the transient thought, augment the power of reason, while they enfeeble instinct. It is easy to conceive, that the brain, assailed by a crowd of impressions from without, will regard less attentively, and therefore suffer to escape, the greater part of those that result from internal excitation. Instinct is more vigorous in savage man, and its relative perfection is his compensation for the 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 the phenomena of understanding have their source. in physical sensibility, this sensibility being set in action by tw% sorts of impressions, the brain of an infant just born, has already the consciousness of those which spring from internal motion; and it is from these impressions that it executes certain spontane- ous movements, of which Loeke and his followers could find no explanatiou; accordingly, the partisans of innate ideas looked 360 OF SENSATIONS. upon them as the strongest confirmation of their system; but these ideas, anteriorto all action of outward objects on the senses, are sim- ple, 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 sen- sations, which have passed to the brain, combined themselves there, and entered into the action of the will with a velocity that equals, if it does not surpass, that of light. I* it only, after laying down between the sources of our know- ledge every exact line of demarcation; after scrupulously distinguish"- ing the rational from the instinctive determinations; acknowledg- ing that age, sex, temperament, health, disease, climate, and ha- bit, which modify our physical organization, must, by a secondary effect, modify these last; and 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 rea- son, of the sensations that spring from the habitual state of the internal organs, sees easily the origin of those everlasting disputes on the distinction between the sensitive and rational soul; why some philosophers have believed man solicited for ever by a good or evil geuius, spirits which they have personified under tbe names of Oromazes and Arimanes, betwixt whom they imagined eternal war; the contest of the soul with the senses, of the spirit with the flesh, of the concupiscent and irascible with the intellectual principle, that contradiction which St. Paul laboured under, when he said in his Epistle to the Romans, that his members were in open war with his reason. These phenomena, which suggeset the -conception of a two-fold being (Homo duplex, Buffon), are no- thing but a necessary strife betwixt the determinations of instinct and the determinations of reason; between the often times impe- rious wants of the organic nature, and the judgment which keeps under, or deliberates on the means of satisfying them, without of- fending 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 modern metaphysicians, is found dis- tinctly stated in the writings cf Aristotle,* and there is room for surprise that that father of phi?■>■-■•-fay should have merely recogtfi- * j\':.' esf in mtelleclu, y jd non prius fuerit in sensu, OF SENSATIONS. 361 zed 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 sensation the source of all our knowledge, that even the measure 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 intellectual nature; whilst the addition of a new sense to those we now possess, might lead us to a multitude of unknoivn sensations and ideas, would disclose to us in the beings we are concerned with, a vast variety of new relations, and would greatly enlarge the sphere of our intelligence The impression, produced on any organ, by the action of an outward body, does not constitute sensation; it is further requi- site, that the impression be transmitted to the brain, that it be there perceived, that is, felt by that organ; the sensation then be- comes perception, and this first modification supposes, as is ap- parent, a central organ, to which the impressions on tbe organs may be carried. The cerebral fibres are more or less disturbed by the sensations sent to them, at once, from all the organs of sense; and we should acquire but confused notions of the bodies from which they proceed, if one stronger perception did not si- lence, as it were, the rest, and fix the attention. In this concen- tration 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 sensations that were produced by the different colour of the paper and the letters. When a sensation is of short duration, our knowledge of it is so light, that soon there remains no remembrance of it. It is thus, that we do not perceive, every time we wink, that we pass from light to darkness, and from darkness to light. If we fix our at- tention 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 no- vel, 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 forgotten all but some of the principal actions. Time ought then to appear to us to have passed rapidly; for, as Locke has well said, in his Essay on the Human Understanding, " We conceive the succession of limes only by that of our thoughts." 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 V7 362 OF SENSATIONS. well supported attention, is found in greater or less strength in different minds: and some philosophers appear to me to have ex- plained, 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 examination 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 sensation, so as to receive it more deeply. To look, is to see with attention; to listen, is to hear attentively: the smell, the taste, in the same way, are fixed upon an odour, or a flavour, so as to receive from them the fullest impression. In all these cases, the sensation may be involuntary; but the attention by which it is heightened, is an act of the will. This distinction has already been well laid down with regard to the feeling, which is only the touch exerted under the 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 tbe recollection. Thus, we may have reminiscence of it, or recal faintly that we have been so affected; or memory, which is a representative 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 cicatrised. The stump has not more sensibility than any other part covered by integu- ments, 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 months ago. They recognize them by certain characters, for those of their disease, They, like all perceptions, 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. Finally, if the brain is easy of excitation, and at tbe same time, OF SENSATIONS. 363 faithful in preserving the impressions it has received, it will pos- sess the power of bringing up ideas with all their connected 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 imagination. If it sometimes produces monsters, it is that the brain, by its powers of associating, connecting, combining ideas, reproduces them in an order not according to nature, gathers them under capricious associations, and gives occasion to many erroneous 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 only to judge of the relations that exist among the ideas with which the senses supply us, or which are reproduced by im- agination. It is with the faculties of the soul, as with those of the body. When called into full exertion, the intellectual organ gains vigour; it languishes in too long repose. If we exereise certain faculties 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 extinction of ima- gination, 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 exclusively. CLV. Condillac has immortalized his name, by discovering, the first, and by demonstrating irrefragably, that signs are as ne- cessary to the formation as to the expression of ideas; that lan- guage 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 uncompleted, since we should have no power to associate and compare them, and to de- termine their relations. It is the imperfection 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 experi- ence is indeed, by the same cause, restrained within very narrow limits, and confined to a few simple notions, a few ideas resting merely on its wants and on its powers. If there were not signs to preserve ideas, and to connect them, memory would be nothing, all impressions would be effaced soon after they were felt, all col- lections of ideas would be dissolved as soon as formed, (if they could be formed at all) our ignorance would he indefinitely pro- 364 OF SENSATIONS. longed, and we should reach old age, with a mind still in its in- fancy. When we reflect on a subject, it is not directly on the ideas, but on the words expressing them, that th* 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 thou- sand, because the words of their language expressed nothing be- yond the number twenty. La. Condamine informs us, in his nar- rative, that there are some who count only to three, and the word they employ to express the number is so complicated, of a pro- nunciation 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 his reach, which an ordinary ca- " pacity will attain to without difficulty. Go on, and take from " him the use of speech, the lot of the dumb will show you, how " narrow are the limits within which you confine him. Finally, " take from him the use of all sorts of signs, let him be unable " to find the least sign for the most ordinary thought, and you have " an idiot."* We are made acquainted by travellers with certain tribes, so backward in the art of expressing their ideas by signs, that they seem to serve as a link between civilized nations and certain spe- cies of animals, whose instinct has been perfected by education. One might even assert, that there is less distance, in respect 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 powerful is their influence in the cultivation of the mind. But he shall speak himself, with that clearness of expression, which is the characteristic and the charm of his writings. u Languages are like the cyphers^of the geometricians; they present new views to the mind, and expand it as they are brought nearer to perfection. The discoveries of Newton had been prepared for him, by the signs that had been already contrived, and the methods of calcu- lation 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 departments." * Ess;>.i sur 1'origine des Connoissances humaines, sec. 4. OF SENSATIONS. 365 The most scanty languages have been formed in the most bar- ren countries. The savage who strays along the desert shores of New Zealand, needs but few signs to distinguish the small num- ber 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 number un- der this severe climate, are all that be has to name and to know; accordingly,his vocabulary is very small; it has been given to us by travellers in the compass of a few pages. A copious language, one capable of expressing a great variety of objects, of sensations and of ideas, supposes btgh civilization in the people among whom it is spoken. You hear complaints of the perpetual recurrence of of the same expressions, the same thoughts, tbe same images, in the poetry of Ossian; but living amidst the barren rocks of Scot- land, the bards could not speak of things of which nothing, on tbe soil they inhabited, could supply them with the idea. The monotony of their languages was involved in that of the impres- sions, always produced by rocks, mists, winds, the billows of the ireful ocean, the gloomy heath, and the silent pine, &c. The re- petition of same expressions in the Scriptures shows that civiliza- tion had not made the same progress among the Hebrews, as a- mong the Greeks and Romans. 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 man- ners on language, the reason why the great writers, in every de- partment, appear together, at the very time in which a language reaches its perfection and maturity, &c.; these are problems that suggest themselves, and would well merit our endeavours to ob- tain solution, did not the investigation manifestly lead beyond the limits of our enquiry. 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 uncer- tainty on tbe 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 ex- tract some of its main results, referring the reader for the rest to the work. • Elemens d'ldeologie, par M. Destutt Tracv, senateur, MembrerV 1'Institut. 366 OF SENSATIONS. To think is only to feel; and to feel is, for us, the same as to exist: for, it is by sensation we know of our existence. Ideas, or perceptions, are either sensations, properly so called, or rtcol- lections,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 sensibility, properly termed memory, judgment, and will. To feel, properly speaking, is to be conscious of an impression; to remember, is to be sensible of the remembrance of a past impression; to judge, is to feel re- lations among our perceptions; lastly, to will, is to desire some- thing. Of these four elements, sensations, recollections, judgments, and desires, are formed all compound ideas. Attention is but an act of the will; comparison cannot be separated from judgment, since we cannot compare two objects without judging them; rea- soning is only a repetition of the act of judging; to reflect,, to imagine, is to compose ideas, analyzable into sensations, recollec- tions, judgments, and desires. This sort of imagination, which is only certain and faithful memory, ought not to be distinguished from it. Finally, want, uneasiness, inquietude, desire, passions, &c. are either sensations or desires. There is room, therefore, to reproach Condillac with having divided the human mind into understand- ing and will only: because the first term includes actions too un- like, such as sensation, memory, judgment; and with having run into the opposite extreme, in the too great multiplication of secon- dary divisions. CLVI. Disorders of thought. Philosophers would undoubtedly attain to a much profounder knowledge of the intellectual facul- ties of man, if they joined to the study of their regular and tranquil action, that of tbe many disordered actions to which they are liable. It is not enougn, if we would understand them aright, to watch their operation when the soul is undisturbed and at ease: we must follow it in its pertubations and wanderings; we must see its powers, now separating themselves from those with which tbey ought to act, now combining with them under false perceptions; sometimes altogether drooping, and sometimes starting into an extreme violence of action, of wi icb 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 condition. The observation of mania is yet too imperfect in the number, -OF SENSATIONS. 367 varietv, 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, ven- tured to ground his distinctions of the species of mania, on the la- bours of modern psychologists, and shown that all might be refer- red to five kinds, which he marks by the names of melancholy, of mania without delirium, mania with delirium, dementia, and idiotcv.* In the four first kinds, there is perversion of the men- tal 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 puberty. It is agreed, among observers, that almost all maniacs have become so be- tween twenty and forty years old; that very few have lost their reason either before or after this stormy period of life, wherein men, yielding, by turns, to the torments of love and of ambition, of fear and of hope, to the sweet illusions of happiness, and the realities of suffering, consumed with passions for ever reviving, often repressed, and rarely satisfied, feel their intellectual powers impaired, annihilated, or abased by that tempest of the moral na- ture, which has well been compared to the storms which, in their violence, lay desolate the flourishing earth. We are compelled to grant, that our acquaintance with the structure of the brain and of the nerves is too imperfect, that dis- sections of the bodies of maniacs have been too few, and those of- ten by physiciansf too little familiar with the minute structure of the sensitive organ, to warrant us in asserting or denying, that de- rangement of intellect depends constantly on organic injury; though it is highly probable, many facts, at least, collected by ob- servers, who, like Morgagni, deserve the utmost confidence, au- thorize the belief, that the consistence of the brain is increased in some maniacs, who are distinguished by the most obstinate and unvarying adherence to their ruling ideas; that it is, on the other hand, soft, watery, and in a kind of incipient dissolution in some others, whose incoherent ideas, after their aptitude for association, and for transformation into judgments is gone, succeed one ano- ther rapidly, and seem to pass away without a trace, &c. If, in the multitude of maniacs, the organ of the understanding suffers only imperceptible injury, it is very remarkably changed in idiots. The almost entire obliteration of the intellectual facul- * For more ample explanation I must refer to the work. Traite me- dico/ihiloso/ihiquc sur V Alienation mentale ou la Manie, par P. Pinel. Pari*, 1800. f This censure is especially applicable to the researches of Pr. Gred- ing. 36S OF SENSATIONS. ties, which constitutes idiotcy, when it is not brought on by some strong and sudden shock, some unexpected and overwhelming emotion, breaking down at once all the springs of thought, when it is an original defect, is always connected with mal-conformation of the skull, with the constraint of the organs it encloses. These defects of organization lie, as M. Pinel observes, in the excessive smallness of the head, to the whole stature, or to the want of 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 on- ly tbe tenth of the whole height, whilst it should be something more than a seventh, if we taite tlie Apollo of Belvedere as the type of the ideal perfection of the human figure. An idiot, whom I occasionally see, has the occipital extremity of the bead so much contracted,that the large extremity of tbe oval formed by the upper face, instead of being placed at the back, as in other men, is, on the contrary, turned forwards and answers to the forehead, which itself slopes towards the sinciput. The vertical diameter of the skull is inconsiderable. 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 extremely large. In two other children, equally idiots, and now in the hospital of St. Louis, the skull, very large behind, ends in a very contracted extremity, and the forehead is very short, and not more than two inches and a half wide, measuring from the semi-circular process which terminates, at the upper part, the temporal fossa, to the commencement of the same process on the other side. The ex- cessive growth of the genitals is not less conspicuous; they are, in these fwo children, one ten, the other twelve years old, as well as in the first of whom I spoke, who is fourteen, of larger size than is commonly seen after the appearance of puberty. There is nothing to indicate that this season is attained by these three idiots. The same excess of growth is found more conspicuously among the cretins of the Valais, idiots who (in consequence of a weak and degraded organization) are prone to lasciviousness and tbe most frequent onanism. This sort of opposition in the relative energy of the intellectual organ, and of the system of reproduction, in the development of the brain, end that of the parts of generation, is a phenomenon which must strongly interest the curiosity and engage the attention of physiologists. Who is there unacquainted with that enervation of the understanding, that intellectual and physical debility, which indulgence in the pleasures of love brings on, if we exceed ever so little the bounds of scrupulous moderation? Castration modifies tfF SENSATIONS. 309 (he moral character of men and animals, 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 under a strict and necessary dependence; our vices and our virtues, some- times produced and often modified by social education, are fre- quently, too, results of organization. To the conclusive proofs which the philosopher I have just named, who is an honour to the profession, brings forward of the influence of thejihysical on the moral human being, I will only add a single observation. 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 bo 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 covered the dura mater, and I, at the same time, questioned the patient on her situation; as she felt no pain from the compression of the cerebral mass, I pressed down lightly the pledget of lint, and on a sudden the patient, who was answering my questions rationally, stopped in the midst of a sen- tence: but she went on breathing and her pulse continued to beat: I withdrew the pledget; she said nothing: I asked her if she re- membered my last question: she said not. Seeing that the experi- ment 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 faculties going, the consciousness of existence growing benumbed and threatening to cease, in the interval of each dressing, in proportion as the fluid collected. There are surgical observations on wounds of the head contain- ing several facts that may be connected with the preceding obser- vations. There is no one who has had syncope of more or less continuance, but knows that the state is without pain or uneasi- ness, 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 exam- ples of the strict connexieii which there is between the physical organization and the intellectual and moral faculties, to leave any necessity for dwelling longer on this truth, which no one questions, but which no philosopher has yet followed into its con- sequences CLVIII. An English writer, in a work on the history of me«- *8 370 OF SENSATIONS. tal 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 motion 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, there- fore, 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 phy- siologists, 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 oxyrgen,—to the impressions of excessive heat and cold,—to the troublesome sensation produced by the accumula- tion of urine and fecal matter,—to the feeling of weariness and fatigue that is left by 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 offthe possibility,—it is to satisfy all the factitious wants which society and civilization have created, that men con- demn themselves to those agitations, of which honour, reputation, wealth, and power, are the uncertain aim. Our passions have not yet been analyzed with the same care as our ideas: no one has yet duly stated the differences there are, in respect to their number and energy, betwixt savage man, and 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;—as every vivid sensation of joy or distress, of pleasure or pain, brings on a feeling of anxiety in the praecordia,—the ancients placed iu the viscera the seat of tbe passions of the soul: they placed cou- rage in the heart, anger in the liver, joy in the spleen, &c. Bacon and Van Helmonl seated them in the stomach; Lecat in the ner- vous plexures; 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, reside in the or- * An Inquriry into the Nature and Origin of Metal Derangement— Lon ion, 1798. 2 vols 8vo. OF SENSATIONS. 371 j-ans, they suppose only instinctive determinations, whilst passion carries with it the idea of intellectual exertion. Thus, the accu- mulation of semen in the vesiculas, 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 num- ber of philosophers. Of all the feelings of man, the most lasting, the most sacre'd, the most passionate, the least susceptible of in- jury from all the prejudices of the social state, maternal love, is surely not the result of any intellectual combination, of any cere- bral action: it is in the bowels (entrailles), its source lies; thence it springs, and all the efforts of imagination cannot attain it for those who have not been blessed with a mother's name. All passion springs from desire, and supposes a certain degree of 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 tbe lowest gradation, and maniacal rage the highest. A man, without passions, is as impos- sible to imagine, as a man without desires; yet we distinguish as passionate, those whose will rises powerfully towards one .ob- ject earnestly longed for. In the delirium of the passions, we are forever 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 pas- sion 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 hales, 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 • If we analysed the passions carefully, it would be right to distin- guish those which are common to all men, which appertain to our phy- sic d 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. 37S OF SENSATIONS. birth and growth, may be ranged in two classes, according t« 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 infinit variety of shades, according to the intensity of their causes, individual constitution, sex, age, &c. at times increase, at times abate the vital action, or depress or exalt the"power of the organs. The instances which establish the powerful influence of the passions on the animal economy, are too frequent to need reciting. Writers, in every department, furnish such as show, that excess of pleasure, like excess of pain, joy too lively or too sudden, or grief too deep and too unexpected, may bring on the most fatal accidents, and eveji death. Without collecting, in this place, all the observations of the sort with which books swarm, I shall con- tent myself with referring to those, who have brought together tbe greatest number of facts under one point of view; as Hal- ler, in this Physiology; Tissot, in his Treatise on Diseases of the Nerves; Lecamus, in his work on Diseases of the Mind; Bonne- foy, 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 tbe passions are not, for their uniformity, the less inexplicable. How, and why does anger give rise to madness, to suppression of urine, to sudden death? How does fear deter- mine paralysis, convulsions, epilepsy, &c? Why does excessive joy, a sense of pleasure carried to extremity, produce effects as fatal, as sad and afflicting impressions? In what way can violence of laughter lead to death ? Excess of laughter killed the painter Zeuxis and the philosopher Chrysippus, according to the relation of Pliny. The conversion of the reformed of the Cevennes, un- der Louis XIV, was effected by binding them on a bench, and tickling the soles of their feet, till, overpowered by this torture, they abjured their creed; many died in the convulsions and im- moderate laughter which the tickling excited. A hundred vo- lumes 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 tbe nobler parts of ourselves, of those wonderful faculties which OF SENSATIONS. 373 place our kind above all that have motion or life; in a word, the knowledge of moral and intellectual man, belongs to the science known by the name of metaphysics or psychology,of analysisof the understanding, but better described by that applied to it by the wri- ters of our days, ideology. On this science, you may consult, with advantage, the philosophical works of Plato and Aristotle among the ancients; of Bacon, Hobbes, Locke, Condillac, Bonnet, Smith, Cahanis, and Tracy among the moderns. CLIX. Of sleep and waking The causes of excitation to which our organs are exposed during waking, tend to increase progres- sively their action; the pulsations of the heart, for instance, are much more frequent in the evening than in the morning, and this motion, gradually accelerated, would soon be carried to a degree of activity incompatible with the continuance of life, did not sleep daily temper this energy, and bring it down to its due measure. Fever is occasioned by long continued want ef sleep, and in all acute diseases, the exacerbation comes on towards evening; the night's sleep abates again the high excitation of power; but this state of the animal economy, so salutary and so desirable in all sthenic aff ctions, is more injurious than useful in diseases, con- sisting chiefly in extreme debility Adynamy shows itself, al- most always, in the morning, in putrid fevers; and petechia, 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 pathological fact well ascertained. In all the cases I have mentioned, sleep does not improve the condi- tion 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, absorp- tion, circulation, respiration, secretion, nutrition, are carried on; some, as absorption and nutrition, with more energy than during waking; whilst others are evidently slackened. During sleep, the pulse is slower and weaker, inspiration is less frequent, insensible perspiration, urine, and all other humours derived from the blood, are separated in smaller quantity. Absorption is, on tbe contrary, very active: hence the danger of falling asleep in the midst of a noxious air. It is known, that the marshy effluvia, which make the Campngna di Roma so unhealthy, bring on, almost inevitably, intermittent fevers, when the night is passed there; whilst travel- lers who go through without stopping, arc not affected'by it. ■*74 OF SENSATIONS. The human body is a tolerable representation of the centripe- tal 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 se- cretory glands. Other actions, on the contrary, take their direc- tion 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 tbe in- terior of tbe lungs, and covers the surface of the body, the ele- ments of its growth and repair. These two motions, in opposite directions, continually balance each other, prevailing by turns, according to the age, the sex, the state of sleep or waking. Du- ring sleep, the motions tend from the periphery to the centre; (Hipp.) and if the organs that connect us with outward objects 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 Hos- pifal of St. Louis, for the cure of some scropbulous 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 digestion was always quick and easy; he kept up his plumpness, though the muscular action was extremely languid, the pulse very weak and very slow. In this man, who, to use the expression of Bordeu, lived under tbe dominion of the stomach, the moral affections were limited to the desire of food and of repose. Oppressed with irresistible sloth, it was never without great difficulty 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 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- ruption in the exercise 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 outward ob- jects, 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 imper- OP SENSATIONS. 375 fject relations, interrupted at every moment, would have been; their repose, which constitutes 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 child is 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 tbey are more in motion, 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 fbr their subsistence.* Sleep is a state essentially different from death, to which some authors have erroneously likened it.f 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 con- tinually awake; the removal of the material causes of our sensa- tions tends, therefore, to plunge us into the arms of sleep: where- fore we indulge in it more voluptuously in the gloom and the still - * 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 endurance of hunger. T. | To say that sleep is the image of death, that vegetables sleep al ways, is to use an inaccurate and unmeaning expression. How can plants, without brain or nerves, without organs of sense, motion, dv voice, sleep; when sleep is nothing bat the repose of these organs? 376 OF SENSATION'S. ness of night.* Our organs fall asleep one after tbe other; the smell, the taste, and the sight are already at rest, when the hear- ing and the touch still send up faint impressions. The perceptions, 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 erroneously 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 maintained, that to sleep required some measure of strength. Excessive fatigue hinders sleep, merely by a sense of pain in all the muscles, a pain that excites 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 lamina? of the cerebellum, which, as they conceive, are in a state of erf ction during waking; and they argue from the experiment in which by compressing the cerebellum of a living animal, sleep is immediately brought on. This sleep, like that produced by compression of any otber part of the cerebral mass, is really a state of disease; and no more natural than apoplexy. Others, conceiving sleep, no doubt, analagous 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 unsupported as the other. As long as the humours flow in abundance towards the brain, they keep up in it an excitement which is altogether 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 produee sleeplessness, by exciting the force of circulation, and de- termining 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, copu- lation, 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 * Tlie tissue of the eye-lids is not so opake, but we may distinguish through them light from darkness: accordingly a lighted torch, in the room, hinders us from sleeping. For ihe same reason, day succeeding to night awakens us. OF SENSATIONS. W while it lasts, the cerebral mass collapses; a sign that the flow of blood in:o 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 action, and begin to act, at the direction of the will. Tbe causes of wak- ing operate by determining a greater flow of blood into the brain: they include all that can affect the senses, as the return of light and of noise with the rising of the sun; at times, thty act within us. Thus, urine, fecal matter, other fluids accumulated in,their reservoirs, irritate them, and send up, towards the brain, an agita- tion which assists in dispelling slumber. Habit too, acts upon this phenomenon, as on all those of the nervous and sensitive sys- tem, 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 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. CLX. 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 betwixt sleep and waking, real mixed situations, which belong, more or less, to one or to tbe other. Let us suppose, for instance, that the imagination repro- duces, in the brain, sensations it has formerly known, the intellect works, associates and combines ideas, often discordant, and some- times natural, brings forth monsters, horrible, or fantastic, or ridi- culous; raises joy, hope, grief, surprise, or terror; and all these fancies, all these emotions are recollected more or less distinctly, 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 pheno- mena. 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 relative func- tions 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. Somnambti- 40 ms OF SENSATIONS. lists have been seen to get up, dress, go out of the house, opening 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 warning from their senses of the dangers they are near. Accordingly, they aie often seen throwing themselves out of a window, 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 rema;ns open to impression, and then you can direct, at pleasure, the intellectual action. 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 senses, and of the need there is to corr* ct 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. Tin hydropic dreams of waters and fountains, whilst he who is suffering with an in- flammatory 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 tbe falling of the diaphragm, tbe chest dilates with difficulty, the blood, which cannot flow through the lungs, stagnates in tlie right cavities of the heart, and a painful sensation 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, hydrothorax, for in- stance, but which always depends on the difficult 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 compass while awake. Thus mathematicians have accomplished in sleep, the most complex calculations, and resolved tbe 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 combination of ideas in which it must work with more energy. It is seldom that the action of imagination on the genital organs, during waking, OF SENSATIONS. 379 zoes 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 nature is most irritable and sensible. Thus the dog and horse dream more than the ruminating kin-Is; the one barks, the other neighs in sleep. Cows that are suckling their calves, utter faint low- irms: bulls and rams 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 imaginary 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, through the inter- vention of nerves, all centre in one, the chief and essential seat of the function of which this chapter treats. As the phenomena of the sensations are brought about by the intervention of an un- known agent, and as like those of electricity and magnetism, .they appear not to be subject to the ordinary laws of matter and motion, they have thown open the widest field to the conjectures of igno- ♦ ranee, and the inventions of quackery. It. is for their explana- tion, 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 employed 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 discovery. 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, bearing, smell, taste, sight and touch, were all there: the outivard senses, beiug, 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 bystanders, 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. BSO ON MOTION. or interposed any other non-conductor. Finally, to put to proof the whole power of faith in his readers, M. Petetin exclaims, 11 Oh prodigy beyond conception! was a 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 peiceful slumber, among the innumerable pamphlets, which Mesmerism has brought into the world, if a writer on physiology had not been the dupe of this mystification, and had not proceed- ed from it, to write a long chapter on the metastases of sensibility. If we should be so unfortunate as to be reproached by the loveis of the marvellous, with pushing scepticism too far, we must make answer: that. M. Petetin is the sole witness of his mi- racle: that it is impossible, from bis relation, to know when or on whom the prodigy took place; and that this zealot of magne- tism might have invented this story to confound the unbelievers who ventured to turn into ridicule his system on the electricity of the human body. CHAPTER VIII. ON MOTION. CLXI. THIS Chapter will treat enly of the motion performed 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 organic motions, by means of which each function is performed, have already been investigated separately. The organs of motion may be distinguished into active and pas- sive: the former are the muscles, the latter the bones, and all the parts by which they are articulated. In fact, when in consequence of an impression received by the organs of sense, we wish to ap- proach towards the object that produced it, or to withdraw from it, the muscular organs, called into action by the brain, contract: * Elect} kite animate, 1 vol. Svo. Lyons, 1808. ON MOTION. 381 while the bones, which obey this action, perform only a secon- dare part, are passive and may be looked upon as levers abso- lutely 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 blanched by ma- ceration or by repeated washing. Whatever may be the situation, the length, the breadth, the thickness, tin form or the direction of a muscle, it is formed of a collr lion of several fasciculi of fibres, enveloped in a cellular sheath similar to that which covers the muscle itself, and separates it from the surrounding parts. Each fasciculus is formed of the union ol a multitude of fibres, so delicate, that anatomy cannot reduce them to their ultimate division, and that the smallest dis- tinguishable fibre is still formed by the juxta position of numerous fibriilae of incalculable minuteness. As the last divisions of ihe muscular fibre completely elude our means of investigation, it wouid be 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 fibrillar progressively decreasing in size; with Leeuwenhoek, that the di- ameter of this elementary fibre is only the hundred thousandth part of a grain of sand; with Swanmerdam, 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 rami- fications of arteries; 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 mi- nuteness, eludes our most accurate investigations. To explain the phenomena of muscular action, it is sufficient to conceive each fibre as formed of a series of molecules of a peculiar nature, uni'ed together by some unknown medium, whether that be oil, gluten, or any otlier 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 very seldom ruptured. These fibres, which, when irritated, possess, in the highest de- gree, the power of shortening themselves, of contracting, however minute one may suppose them, are supplied with vessels and nerves. In fact, though they are neither vascular nor nervous, as may be readily ascertained by comparing the bulk of the vt ss< Is and nerves which enter into the structure of the muscles, with that of 382 ON MOTION. these organs, and by attending to the difference of their proper- ties; each fibre receives the power of contracting, from the blood brought to it by the arteries, and from fluid transmitted from the brain along the nerves. A cellular sheath surrounds these fibrillar (and the nerves and vessels perhaps terminate within it), others unile them together; the fasciculi of fiorts are inclosed in com- mon sheaths, and these unite, in the same manner, into masses varying in size, and the union of which lorms the muscles; fat sel- dom accumulates in the cellular tissue which connects together the smallest fasciculi; 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 va- pour fills these cells, maintains the suppleness of the tissue and promotes the action of the organ, which a fluid of more consis- tence would have impeded. The greater number of muscles terminate in bodies, in general round, of a brilliant white colour, that forms a striking contrast with the red colour of the muscular flesh, into which one of their exlr« mities are imbedded, while the other extremity is attached to the bone and is lost in the periosteum, though the tendons are quite distinct from it. The ttndons ait formed by a collection of longitudinal and parallel fibres; their structure is more com- pact than that of the muscles; they are harder, and apparently re- ceive neither nerves nor vessels; they consequently possess but a very inferior degree of vitality; hence they are frequently ruptur- ed by the action of the muscles. The muscular fibres are im- planted on the surface of the tendinous cords, without being con- tinuous with the filaments forming the latter; they join them in a different manner, and at angles more or less obtuse. The tendons, in penetrating into the fleshy part of tbe muscles, expand, become thinner, and form thus the internal aponeuroses. The external aponeuroses independent of the tendons, 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, furnishing points of in- sertion to the muscles; they prevent the muscles and their tendi- nous 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. ^ e cannot admit, with Pouteau, that the musclesof the limbs, though applied to the bones by aponeurotic coverings, can be- come displaced, so as to form herniac. When they contract in a wrong position, some fibrilke are torn, and this gives rise to most UN MOTION. 383 of those momentary and very sharp pains called cramp. I have at present before me, the case of a young girl, in whom the apo- neurosis of the \ez, exposed in consequence of an extensive ulce- ration, exfoliated from the middle and fore part of the limb to the instep This exfoliation was accompanied by a displacement of the tibialis anticus, and of tbe extensors of the toes; the leg is be- come deformed, the motions of extension of the foot and toes, are performed witn difficulty, and will soon become impossible, when the exfoliation of the tendons follows that of the aponeurosis which protected them from the air. CLXII When a muscle contracts, its fibres are corrugated transversely, its extremities are brought nearer to each other. These un lulatory oscilliations, 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 applica- tion of a stimulus. But these contractions, determined by exter- nal 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 swell sudden- ly, to stiffen, and to continue motionless in that state of contrac- tion, as long as the cerebral influence, or the act of the will, whicii determines if, 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 ex- periment, which consists in immersing tbe arm in a vessel filled with a fluid, which sinks when the muscles act. We cannot, how- ever, estimate the diminution of bulk, by the degree in which the fluid sinks, since that effect is, iu part, owing to the collapse of the layers of the adipose tissue, which is compressed in the mus- cular interstices. A sound state of the vessels and nerves, distributed to muscles, 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 com- pletely palsied. By dividing or trying the nerves, the action of the 384 Osi MOTION. mi sch s to which they are distributed, is suddenly interrupted. Tin- same effec may be produced by intercepting tbe course of the arterial blood, though in a less rapid and instantaneous manner; and it is very remarkable, that it is equally necessary that the veins should be as sound as the arteries, to enable muscular action to ta*e place. Kaaw Boerhaave ascertained, by actual experiment, that when a ligature is applied to the vena cava, above the iliacs, paralysis of the lower extremities is brought on, as when the aorta is tied, as was done by Steno in the same situation. And this is a ft.rther proof of what we h.tve 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 arteries which are distributed to their tissue. The tongue, which, of all the contractile organs, receives the greatest number of cerebral •nerves, is, likewise, that which, of all those under the control of the will, has most extent, most freedom, and most variety of mo- tions .* 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 to depend on the combinations of hydrogen, of carbon, of azote, and other combus- tible substances in the fleshy part of the muscle, with the oxygen conveyed 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 oxydize, but it is re- quired 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 formation of water, by the combination of the two gases of which it consists. Ac- cording to this theory, first proposed by Girtanner, all the changes which take place, during the contraction of a muscle, the turges- cence, the decurtation, and the induration of its tissue, its change of temperature, depend on the reciprocal action of the elements of the muscular fibre, and of the oxygen of arterial blood. * It s scarcely necessary to repeat, that I am not speaking of those motions., more or less involuntary, perfumed 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 distributed, we find that the general rule is almost without exceptions; for the ht-irtand diaphragm, whLh hold the hist rank among the |>;'.rts endowed with irritability, receive a cor« siderable number of vessels and nerves. ON MOTION". 383 Muscular flesh is harder, firmer, and more oxydized, according as the animal takes much exercise. We well know what a dif- ference there is, between the flesh of wild and of the domestic 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 ihe oxygen necessary to the contractions of the muscular fibre, is more complete, decomposes the greater quantity of atmospherical air, in those animals that are naturally destined 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 development of their muscular organs, and by the powerful efforts of which they are capable, all have a very ample chest, a powerful 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 extensors.^ 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 influx to the parts un- der its control, that in which we can continue longest without fatigue, is a medium between flexion and extension, a real state of semi flexion. Attempts have been made to discover the cause of this prepon- derance of the flexor muscles over their antagonists. According to Borelli, the flexors being shorter than the extensors of the same articulation, and contracting equally,! the former must occasion * I never saw a very strong man that had not broad shoulders, which indicates 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 frequent 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 em- ployed; as the arms, the legs, or the shoulders. t The theory of the preponderance of the flexors is intirely my own, and was first proposed by me, in the collection of memoirs ot the Me- dical Society of Paris, for the year VII. of the Republic (1799). t Musculi flexores ejusdem articuli breviores sunt extensoribus, er •itrimie rrrjuc contrahunter. Prop. 130, de motu animahu.m. 386 ON MOTION. a more extensive motion of the limbs, and determine them towards a state of flexion. But it is, in the first place, incorrect 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 include in the cal- culation, the tendinous cord which terminates it; but to consider the length of its fibres, on which depends entirely the extent of motion produced by its contractions. The degree of decurtation of which a muscle is capable, is al- ways 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 extensors, it follows as a necessary consequence, that the limbs will be brought into a state of flexion, when the principle of motion shall be distributed to them in an equal quantity; and even thongh 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 move through a greater •pace. If we examine the different parts of the body, the articulations of the limbs, and especially of the knee, the knowledge of which is of the highest importance in understanding the theory of stand- ing, it will be seen that the flexor muscles exceed the extensors, in tht" the muscles of tlie upper extremity. ass ON MOTIOM. elliptical shape of the uterus, concurs in giving to the muscles which produce it, the superiority which they retain during the re- mainder of life. The. new-born child preserves, in a very re- markable manner the habits of gestation; but, in proportion 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 stand- ing erect, abandoned to its own powers, all its parts are in a state of semi-flexion; it staggers, and is unsteady on its feet. Towards the middle of life, the preponderance of the flexors over tlie ex- tensors becomes less apparent; a man enjoys fully and complete- ly 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 con- sidered to be in a profound slumber. The cessation of sleep is at- tended in man, as well as in most animals, by frequent stretchings. We extend our limbs forcibly, to give the extensors the tone which they require during the state of waking.* Barthez ac- counts, in the same way, for the manner in which the cock an- nounces 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 exten- sion 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 the natural state, the greater the danger to be apprehended of the pa- tient's life. In certain nervous diseases, characterized by a mani- fest aberration in the distribution of the vital power, a continued state of extension must be considered a symptom highly dange- rous; 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 extension of the limbs during sleep, before a difficulty of moving the jaw could give rise to any apprehension of their approach. * Haller thinks that these extensions are intended to relieve the un- easy sensations occasioned by a long continued flexion. Nunc quidem homines et animalia extondunt artus, quod Us fere confiexis dormiant, et ex eoperpetuo situ, in musculis sensus incommodus ortatur, quern exiensione tollunt, (phenomena exptrghcentium J Elementu Physio,. 'vgia, torn. V. p. 62L ON MOTION. 389 Disease and excesses of all kinds, occasion in the extensor mus- cles, a relative weakness that is very remarkable; hence we see convalescents, and those who have been addicted to voluptuous- ness, walk with bending knees; the more so as their debility is greater, and as the force of the extensors is more completely ex- hausted. The flexion of the knees is then limited by that condi- tion, in which the tendons of the extensors of the leg act on the tibia, at an angle sufficiently great to make up for their diminish- ed energy. There exists a condition of the animal economy, iu 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- ly essential to life, a state to which physicians have given the name of prostration,* the limbs, if unsupported, fall of their own weight, * It is from a knowledge of the strength of his patient, that the phy- sician, in the treatment of disease, deduces the most instructive indica- tions. It seems to me that we ought to endeavour to characterize, by specific terms, the different states of animal adynamia in different diseases. Our language, less fruitful in imagery than the ancient lan- guages, will not easily furnish these characteristic 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 different kinds of fever, will prove its utility, and will, doubtless, be an inducement to extend it to all the classes of morbid derangements. In febrei nfiammatoria seu synocho simplici (aneeio 7 r\^^. ■ • tenicij J v \ * ^Opfiressiovmum. In febre biliosa seu ardente (meningo gastrica) Eractura virium. in febre pituitosa, seu morbo mucoso (adenomeningea) Languor virium. In febre putrida (adynamica) Prostratio varium. In febribus malignis sea atactis Ataxia virium. In febre pestilentiali (adeno nervosa) Sideratio virium. The first term, which is easily turned into French, expresses, with much precision, that condition in which the living system, far from be- ing 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 of general contusion and bruise, of which patients, labouring un- der bilious fever, (meningo-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 phle gma- tic temperament. The prostration, which is so remarkable a character of putrid fe- ff*rs, and in consequence of which they are called adynamic, ia easily 390 ON MOTION. as if they were palsied; the trunk is motionless and supine. Tbe patient is incapable of changing his attitude, and yielding to the weight of bis body, sinks on the inclined plane formed by the bed, and seems very heavy to those who may attempt to raise him, be- cause from his helplessness, he requires to be moved as an inert substance. CLXVI. Of the power of tlie 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 cel- lular tissue, fat, tendinous parts, and aponeuroses, without being the more powerful. Their 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, tbey are made shorter, by bring- ing near to each other their insertions, which occupy extensive surfaces, whether aponeurotic or osseous. We may, in general, judge of the power of a muscle by the extent of tbe surfaces to which its fleshy fibres are attached; thus, the gemelli and the so- leus have short compressed fibres, and lying obliquely between two large aponeuroses. 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 particu- lar muscular fibre; for, if the greater part of the long muscles of limbs lose little more than a third of their length in contracting, the circular fibres of the stomach, which in its greatest dilatation recognixed by the total cessation, or by an impaired condition of all the functions performed by muscular organs; as voluntary motion, re- spiration, circulation digestion, the excretion of urine, &c. The disordered condition of the vital powers characterizes ihe ata- xia; there is considerable irregularity in these fevers, with a very anomalous course of symptoms. In this point of view, one might com- pare it to several kinds of nervous disorders. Lastly, the word sideration appears to me to express, very forcibly, that sudden and deep stupor which overwhelms patients seized with the plague of the East. ON MOTION. 391 form circles nearly a foot in diameter, may contract to such a de- gree, when this organ has been long empty, as to form rings of scarcely an inch in circumference. In cases of extreme elonga- tion 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 or- gans of motion; the muscular powers, almost always parallel to the bones which they are to move, act with the more disadvan- tage 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 resis- tance move through a very considerable one. Besides, the fleshy fibres in shortening themselves, do not act directly on the tendon in which tbe muscle terminates; these fibres generally join, in an oblique direction, the aponeurotic expansion formed by the ten- dinous cord, as it penetrates into the muscular mass; now their action being exerted in a direction more or less oblique is decom- posed, and none is advantageously employed, but that which takes place in the direction of the tendon. Tbe 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 de- grees of motion on each other, of the parts on which the bone rests, into which Ihe muscles are inserted. All these organic im- perfections 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 muscle employs a power equal to 2568 pounds to overcome a resistance of 50. We are not to imagine, however, that there is a loss of 3^18 pounds; for the deltoid rail.* cle acting both on the shoulder and on the arm, about one half of its power is employed on each of these parts; hence it is said, that in estimating tbe 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 re- sistance which it overcomes, and on the fixed point to which its other extremity is inserted. 39# ON MOTION 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 re- moving, 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 tbey 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 internus. Nature has not, therefore, neglected mechanical advantages as much as one might be led to imagine, on a slight examination of the organs of motion. And if it be considered, that in the dif- ferent conditions of life, we do not require strength so much as rapidity of motion, that the power might be gained by increasing the number of fibres, while it was impossible to obtain velocity, by any other means than by employing a particular 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 arrangement of these organs, na- ture, in frequently sacrificing power to quickness of motion, has conciliated, as much as possible, these two almost irreconcileable elements. Though the lever of the third kind is that most frequently em- ployed in the animal economy, the two other kinds of levers are not altogether excluded from it; there are even limbs which re- present 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 continues at the heel, but the fulcrum is removed to the other extremity 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 standing on tip-toe, the muscles of the calf of the leg become prodigiously fatigued, though their action is ON MOTION 393 assisted by the most favourable lever,* adapted to the greatest re- sistance which nature can oppose to herself. Lastly, the foot moves as a lever of the third kind, when we bend it on the leg. CLXVII 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, Jhat the greater part of the muscles of the thigh have their fixed point in tbe 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 thigh is fixed by the action of other muscles, these move tbe pelvis on the thigh, and that which was the fixed point, becomes 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 performing 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 mas- toidei, whose office it is to perform this motion. Now, in order that the pieces forming this osseous structure may remain motion- less, it will be required, that the chest should be fixed by the ac- tion of the abdominal muscles, which, on the other hand, have their fixed point in tbe 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 horizontal 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 towards each otlier, 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 extensors, the adductors per- form motions different from those of the abductors. When two • 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. 3iH ON MOTION. antagonizing muscles of equal power act at the same time, on a part equally moveable, in every direction, the opposite powers neutralize each other, and the part remains motionless. If there is a difference in the degree of contraction, the part is directed towards the muscle whose contraction is the most powerful: if the opposition is not direct, the part follows a middle direction, be- tween the two powers which move it. Thus, the rectus externus muscle of the eye is not antagonized by the rectus inferior; hence when these two muscles come to contract, at the same time, the eye is not carried downward or inward, but at once downward and outward; it is then said to move in the diagonal of a parallelo- gram, of which the sides are represented by the muscles in action. CLXVIII. Of the nature of muscular flesh. 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 different parts. Haller first observed that most of the muscular arteries were very tortuous in their course to the muscles. This disposi- tion, 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 secretion. The muscles that are most in action, uniformly acquire the greatest size and strength; if left in a state of complete inaction, they become ex- ceedingly reduced in size, from the suspended secretion of the fi- brinous 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 desiring him to move it round in bis 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 * Nothing can prove, in a more complete manner, the essential dif- ference bet.veen the fleshy part of muscles and their tendinous and aponeurotic parts, than the chemical analysis of these organs. The ten- dons and aponeuroses may be completely resolved into gelatine, by long boiling, which, on the contrary, parches the muscular flesh, by expos- ing the fibrina, in tonsequerceot the i Kiting of the fat of the cellular ri(-s;ie, and of the albuminous juices in which it is enveloped. ON MOTION. 39j much animalized and exceedingly putrescent. It is from muscu- lar flesh, that M. Borthollet obtained, in considerable quantity, the peculiar animal acid, called by that chemist, the zoonic acid. Lastly, the element of the blood, by means of which the muscu- lar flesh is repaired, fibrina is already imbued with vital proper- ties, 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 qui- ver 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 organization 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 Bologna, 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, made it a subject of inqui- ry, and found that metals, applied to the nerves and to the mus- cles of these animals, determined quick and strong contractions, when they were disposed in a certain manner He gave the name of Animal Electricity to this set of new phenomena, from the ana- logy he thought he perceived between its effects and those of elec- tricity. 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 work of Professor Creve of Mentz, in which the term metallic ir- ritation (irritamentum metallorum) 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 produce them as well. The term of animal electricity has been also laid aside, notwithstanding the great analogy between the effects 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. To produce the galvanic phenomena, it is necessary to establish a communication between two points of a series of nervous and muscular organs. In this way, there is formed a circle, of which one are is composed of the animal parts that are subjected to the &>b* UN MOTION. experiment while thj2 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 communication 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 gal- vanic 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 tbe 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 under the nerve, and leaving the muscles without the galvanic circle; which proves, that the nerves essentially constitute the animal arc. To conclude, tbe galvanic circle may be entirely animal: for this purpose take a very lively frog, that it is to say, one enjoying 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 con- vulsed. 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 influence of nerves on muscular organs. There is no need that the nerves be untouched to allow the con- tractions, 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 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 in- terruption 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 jou will feel a sharp taste with ON MOTION. 39v 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 considerable shock: this has been carried the length of exciting a gentle purging, accompanied with slight colic Humboldt, after detaching the epidermis from the nape of the neck and the back, by two blisters, had metals applied to tbe parts laid bare, and felt in each sharp prickings, accompanied with a sero-sanguineous excretion, at the moment of communication. You may construct the arch 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, sliver, and tin, hold the first rank; then copper, lead, nickel, antimony, &c. without any apparent relation between their different degrees of exciting power and their physical properties, as their weight, malleability, &c. CLXX. Galvanic susceptibility i9 like muscular irritability: ft is exhausted by too long exertion; and returns when the parts are left for a time in repose. Dipping the nerves and muscles 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, benumbs and paralyzes the muscular action. Immersion in oxygenated muriatic acid re- stores 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 favourable 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 press- ing her sides, are more excitable than the hind feet; whilst in the other sex, it is tbe hind feet that are the most susceptible. M. Halle ascertained, by experiments made at the School of Medicine in Paris, that the muscles of animals killed by repeated shocks of an electrical battery, receive an increase of galvanic susceptibili- ty; that this property subsists, without alteration, in animali dead * f employed successfully, in the winter of the year Vlll, pieces of ice both as supports, and ns communicators. £98 ON MOTION. of asphyxia killed by immersion in mercury, pure hydrogen gas, carbonated hydrogen, oxygenated muriatic acid, ;md sulphureous acid gases, by strangulation, by privation of air in an exh- listed receiver; that it is weakened after suffbcation by drowning, by sulphureted 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 re- production of their kind. r 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 wire exhausted by the convulsions of death. In the cold-blooded, susceptibility is more permanent: long after se- p ration 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, too fleeting in the human body, to enable us to derive from galvanic 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 affections, than of those that die of inflammatory diseases, have suggested a pro* bable conjecture, which cannot, however, be established on ex- periment. Dr. Pfaff, Professor in the University of Kiel, who, next to Humboldt, is of all tbe 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, onlv 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 (he galvanic chain, according to the variations of tbe reciprocal situation of the associated metals. If the silver have been applied to the nerves and the- ON MOTION. 399 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 tbe 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 im- portance to be known, for the application of galvanism to the treatment of disease. Where the object is to revive enfeebled irritability, it is better to employ the tranquil and permanent in- fluence 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 ihe zinc upon the muscles of which it is wished to re-excite the torpid or suspended action, than to employ that sudden in- fluence, which, in an instant, exeitesand is gone. Professor Pfaff told me, he had treated successfully a hemiphlegia, 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 motions. To diminish, on the other hand, the irritable energy in many spasmodic affec- tions, you must invert the applications of the metals, place the zinc as near as possible to the central extremity of the nerves, and the silver on their superficial terminations. CLXXI1. 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 effects it produces, in a memoir presented by him to the Royal Society of London. These effects show the most striking analogy 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 zink, 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 in- stant 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 electrome- ter of M. Coulomb, the extremity of the pile, which answers to 400 ON MOTION. the zinc, appears positively electrified; that which is formed by the silver, gives, on the contrary, indications of negative elec- tricity. 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 unpleasant pricking. This effect may oe 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- vanism to those of electricity, it differs from it essentially in this, that tbe voltaic pile is constantly electrifying itself spontaneously; that its effects seem increased, the more they are excited, 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 tbe 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 hermetically 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, ami one with the base of the galvanic pile, these two ends, when brought within tbe distance of a few lines, undergo manifest changes, at the moment of touching the extremities of the pile. The wire in contact with the extremity which answers to the zinc, becomes covered with bubbles of hydrogen gas; that which touches the extremity formed by the silver, becomes oxydized. If the ends of the wire dipping into the water, are brought in'o con- tact, all effect ceases: there is no disengaging 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 au- thors might have fallen. Lastly, it has been attempted to explain the manner in which the apparatus acts in the production of hy- drogen gas and in oxydizement. M. Fourcroy ascribes this phenomenon to the decomposition of water by the galvanic fluid, which abandons the oxygen to the ON MOTION. 401 wire that touches the positive extremity of the apparatus, then conducts the other gas, in an invisible manner, to the extremity 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 hither- to been suggested. 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 holes or extremities of the pile, and insert into the rec- tum the conductor connected with the other extremity, you ob- serve contractions so strong, that the whole body of the animal quivers and is agitated, the eyes roll in their sockets, the jaws strike against each other,and the tongue is thurst out. The same effects take place after decapitation of the animal. These ex- periments have been repeated on the bodies of persons executed by tbe guillotine: by applying to the neck, the head that had been separated from it, and applying to both, conductors connect- ed with the pile, effects have been produced, which seemed at first miraculous. There are lew muscles that retain, longer than the diaphragm, their sensibility to the galvanic action; in the heart and the intestine it is the same. I know not why the in- ternal muscles have been held by many authors to be insensible to this kind of excitation. I have seen them constantly 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 galva- nism ended here. Since its publication, there has been an acces- sion of new facts to those already known. Volta came to Paris: he gave an exposition of his doctrine, in several memoirs read before a committee, the principal experiments on which it is found- ed. They have appeared so conclusive, that the theory of this il- lustrious philosopher has been unanimously adopted; and at this day, all men of science admit the entire identity of the phenome- na of galvanism, and those of electricity. Certain bodies, there- fore, in nature, and especially metals, possess the property of elec- trifying 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 philoso- phy: and in fact, in the present state of things, it belongs rather to the physico-chemical sciences, than to those of the. animal •*2 402 ON MOT I O.N. economy. However, the galvano-electric irritation produces on our organs, effects more decided than the ordinary effects of elec- tricity. It seems to have more intimate relations with them: ac- cordingly, 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 effect the nervous and muscular organs, more deeply than the com- mon 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 aciiou of a pile of fifty plates, by communications, through chains and metallic exciters, of the two extremities of the pile, with dif- ferent 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 ha-» applied galvanism with still more decided suc- cess, to a priest attacked with hemiplegia. This patient, who lay in the wards of the Hospital of St. Lewis, has recovered the use of the palsied side, sufficiently to walk, almost without as- sistance, and to use his right arm as he wants it. The treatment has gone on for several months: the pile employed consisted of fifty plates of zinc and copper. I am trying the same aparatua upon a Swedish officer, for incomplete deafness, which has hi« therto resisted all known applications, administered in different parts of Germany. Strong electrical shocks, recommended by Hufeland, had dispelled, in great measure, the hardness of hear- ing: but this amendment was only temporary: it ceased with the application of the remedy. The first trial of galvanism was at- tempted with the same effect. The extremity of a conductor be- ing placed in the exterior auditory duct of the right side (moisten- ed with a solution of muriate of ammonia, as well 3S the piece of cloth which made part of the pile) the left hand, dipped in the liquid, touched a conductor placed at the copper pole: immedi- ately an irritation, followed by painful prickings, was felt in the ear, the outer part of which became very red. The brain par- took in the excitement; the eyes flashed, and the effect was such, that after remaininga few minutes in the closed galvanic circle, the patient was taken with a sort of inebriation. I propose to di- rect, as has been done at Berlin, a more immediate irritation on the right ear, which is tbe deafest, by introducing behind the ve- lum palati, on the guttural orifice of the Eustachian tube, the ON MOTION. 403 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 behind tbe diseased ear. To use galvanism, in paralysis of the bladder, it would be ne- cessary 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 energetic stimulant of the vital powers; it may be employed, with great advantage, in all palsy both of sensation and of motion. It acts a? a stimu- lant, 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 scor- butic affection, &c. In all these cases, it acts as a resolvent and as a tonic. I shall communicate, 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 application 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 tbe 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 celebrated author of the discovery. CLXXIV. General view of the osseous system. Man, as well as the other red-blooded animals (the mammiferse, 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 animals have no in- ternal 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 internal structure of bones is com- posed of nearly the same materials in all animals: viz. gelatine and salts containing a calcareous basis. The external skeleton of ivhite-blooded animals bears a much greater resemblance to the epidermis than to the osseous system of the red-blooded animals. Like the epidermis, it undergoes changes of decomposition and re- *04 ON MOTION. novation. Thus, the lobster parts with its shell, every year, when the body of this crustaceous animal increases in size, and it is re- placed by a new envelope, which is at first veiy soft, and which gradually acquires the same consistence as the former. Lastly, the skeleton of birds differs from that of all other animals, in hav- ing its principal bones pierced by openings communicating with the lungs, and always filled with an air rarefied 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 ma- chine, 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 cal- careous earth to which they owe their hardness, these organs be- come soft, the limbs deformed, standing, and the different motions of progression, become after a time impossible. Such are the ef- fects of rachitis, a disease of which tbe nature is well understood, though we are not the better informed with regard to the manner In which its causes operate, or the medicines which it requires. The vertebral column forms tbe truly essential and fundamen- tal part of the skeleton; it may be considered as the base of the osseous edifice, as the point in which all their efforts terminate, as the centre on which all the bones rest in their various motions, since every effort or shock, in any way considerable, is felt there. Moreover, it contains in the canal with which it is perforated, the cerebral prolongation, which furnished most of the nerves in the body. In order that it may support all the different parts, and, at the same time, protect tbe 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, besides great solidity, a sufficient degree of mobility it possesses both these advantages, and owes the former to the breadth of the sur- faces by which its bones are articulated together, to the size, tbe length, the direction and the strength of tbeir processes, and to * The peculiar manner in which the vertebrae grow, is itself accom- modated to the delicacy of the spinal marrow; consisting, for a consider- able length of time, of several pieces divided by cartilages the circum- ference of the opening in these bones, becomes enlarged, with the en- largement of the spinal marrow, as we grow older. The circumfe- rence of the foramen of the occipital bone and that of the first verte- bra, which correspond to the thickest part of the spinal marrow, is, ou that account, formed of four distinct pieces separated by cartilages hi 1 h<: first of these bones, and of five pieces in the other. ON MOTION. 10.* the great number of muscles and ligaments connected with it: it owes its freedom of motion to the great number of bones of which it is formed. Each single vertebra has but a slight degree of mo- tion, but as they all have the power of moving at once, the sum of their individual motion added together, gives as the result a general motion which is considerable, and which is estimated by multiplying the single motion by the number ef 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 Me- moirs of the Academy of Sciences for the year 1730, nor in the intervertebral substance. The extension and flexion of the ver- tebrae 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 process perform, around this imaginary 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 interver- tebral substance are brought into close contact, and this substance is comprsssed, while the oblique processes move on one another, and tend to part from one another; this is what happens in bend- ing the trunk, while, in straightening it, the anterior surfaces are removed from each other, the posterior 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 vertebra;, is to limit the bending oi the trunk backwards, and to enable tbe 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 infan- cy, the tumblers who astonish us by the prodigious suppleness of their loins, in bending backward so as to change the natural di- rection of their spinal processes. It was of consequence, that the motions of the vertebral column should take place, at once, in a great number of articulations, as the curvatures are thus less sharp, and thus the organization of the spinal marrow, which is very delicate, is not injured. The fibro- cartilaginous substances which connect together the bodies of the 106 ON MOTION. vertebrre, between which they lie, possess a remarkable degree of elasticity, like all bodies of the same kind, and support, in a fa- vourable manner, the weight of the body. When tbe pressure which they experience is longcontinued, they somewhat yield, and diminish in thickness; and this effect taking place, at the same time, in all the intervertebral substances, 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 consid- erable, 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 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 outside of which it lies. It supports the foot, and prevents its starting 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, therefore, called into fre- quent action this force of resistance. Animals that climb, as tlie 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 * 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 thickness 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 asserted 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 Relvedere; 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 mi wards, the knees not being perfectly straight, and without any disproportion between the calf and the thin part of the leg. ON MOTION. 407 various motions of progression. In leaping from a height, we endeavour to fall on our toes, that tbe force of tbe fall may be broken, by being communicated to the numerous articulations of the tarsus and metatarsus, and may not affect the trunk 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 sufficient 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, becomes soft, flexible, and resembles a cartilage, which is resolvable, by long maceration, into a cellular tissue, similar to that of the other parts. This tissue contains a pretty considerable number of arteries, veins, and lymphatics. The bones are, therefore, mere cellular parenchymas, whose areolae contain a crystallized saline substance, which they separate from the blood, and with which they become incrusted, by a power inherent in their tissue and peculiar to it. The same result may be obtained by inverting the analysis. If a bone is exposed to boiling 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 calcining 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 vita- lity, and, when fractured, are more speedily and more easily con- solidated. In youth, the two constituent parts are nearly in equal quantities; in adults, the calcareous earth* alone forms two thirds * By chemical analyses of the bones, there have been discovered several other saline substances mixed with phosphate of lime; but as 408 ON MOTION. of the osseous substance. At last, gradually increasing in quan- tity, 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 consolidated, 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 great- est stress of the efforts applied to their f xtremities 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 tbe two extremities of the bone; in the same manner as the stalk and the roots press against the collet\ of 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 diffe- rent at their extremities, where tbey receive arteries equally large and more numerous? In the«process 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 os- sify 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 attend- ed with two advantages, that of giving to the bone, without in- creasing its weight, a considerable size, by which it may be arti- culated with the neighbouring bones, by wide surfaces, so as to give firmness to their connexions; this conformation is attended with another advantage, that of avoiding the parallelism 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 ac- tion. The mechanical hypotheses proposed by Haller and Duha- mel, 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 by the spungy substance, viz. the extremities of the long bones, of which the ru- tins 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 joins the root.—T. ON MOTION. 409 diments begin to appear, 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 num- ber and thinner; the spungy tissue expands in approaching the mid- dle part of the bones, and forms (within the medullary canal, of the compact substance) a reticular tissue, the use of which is to support the membranous tube containing the marrow. These three substances, notwithstanding their unequal density, 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 texture 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 hores, 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 anv other agent, by applying itself successively to the different layers of bone, produces between them a separation which did not exist in health, and determines their falling off in succession. Certain parts, in which this lamellated structure does not exist, may, in like man- ner, undergo the same kind of decomposition. Thus, Lassone saw a piece of human skin that had been preserved, for a consi- derable length offline, in a vault, separate into lasers 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 vessels 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, thev are all enveloped bv the periosteum 53 410 ON MOTION. a whitish, fibrous, dense and compact membrane, to which are distributed the vessels which penetrate into their substance. Tin 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 cellu- lar and vascular fibres which penetrate into the substance of the bone, establish a very close sympathetic connection between its periosteum and the very delicate membrane that lines its internal cavity, which secretes the marrow, and is called the internal pe- riosteum. On destroying the internal medullary membrane, by introducing a stylet within the cavity of the bone, its external lay- ers swell, are detached from the inner ones, and form, as it were, a new bone around tbe sequestra. The new bone is not formed by the ossification of tbe periosteum, as was maintained by Troja. This membrane has no more to do with the formation of the new bone, in necrosis, than with that of the callus in fracture. The periosteum, covering a bone affected with necrosis, does not be- come thicker, and does not acquire more consistence; nor is there formed around the ends of a fractured bone, a ring to keep them cemented, as was the opinion of Duhamel; an opinion recently brought forward in a work in which the author seems to delight in reviving errors that have been abandoned for ages. Destitute of nourishment, dead and dried up in this artificial necrosis, the sequestra moves in the centre of the new osseous production, 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 veneral affection, and which appear to have their seat in the centre of the .ong bones, occasion a swelling of these bones and of the periosteum. Tbe use of the periosteum is to regulate the distribution cf the nutritious juices of bones, since, whenever it is removed, granula- tions arise, in an irregular manner, on the spot that is bared. This quality is, besides,common to all fibrous membranes whose destruc- tion is followed by excrescenses from the organs which they cover. The same takes pi ce, w'.enever 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 successive induration of its internal laminse. The marrow which fills the central cavity of the long bones, and the medullary fluid contained in the cells of the spungy sub- stance, bear the greatest an dogy to adeps, both in their, chemical composition and in their uses (CVI.) The proportion of these ON MOTION. 411 two fluids is uniformly relative. In very thin people, the bones contain a marrow that is thin and watery, and though this* fluid always fills the internal cavities of these organs, whose solid pa- rietes cannot collapse, 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 exhalation, and does not serve to the immediate nutrition of the bone, as was thought by the ancients; at least, it does no* answer that purpose solely; for, in the numer- ous class of birds, the bones contain cavities for air, and are desti- tute of this fluid. It is difficult to determine the use of the maiv row 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? 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 tbe dif- ferent parts of tbe 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 account, termed synarthrosis. All the other articulations, whether the bones are in immediate contact (diarthrosis of contiguity), whether they are united by a substance interposed between them (diarthrosis of continuity or amphiarthrosis), are endowed with a certain degree of mobility. I shall speak merely of the moveable articulations; whether they allow of extensive motions and in every direction (diarthrosis orbicularis) or whether the bones move only in two opposite directions (alternate diarthrosis orginglymus) by forming an angle, (angular ginglymus), or by executing, on each other, motions of rotation (lateral ginglymus). In all the articulations, the osseous surfaces are covered by laminae of a substance less hard than that of the bone. These are the articulating cartilages, which answer the two purposes of wiving to the ends of the bones the degree of polish necessary 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 elasticity; their structure is very different from that of the bones, even when -hese are yet cartilaginous; for, these articulating cartilages do 412 UN MOTION. cot become ossified, even in persons greatly advanced in years.* They *re formed of very short fibres disposed 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, demonstrated by Lassone, is very favourable to their elastic re-action. The capsular ligament is reflected over them, becomes very thin, and is lost in their peri- chondrium, according to Bonn, Nesbith, and other anatomists. Besides the cartilages which surround the extremities of bones, there are found, in certain articulations, fibro-cartilaginous laminae lying between the articulating surfaces. These connecting liga- ments may be observed in the articulation of the lower jaw to the temporal bones, of the femur with the tibia, and of tbe sternum with the clavicle; and all such articulations perform a great num- ber 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 ap- paratus to lessen the effect on the trunk, the motion that is given being, in part, lost in tlie action of the articulating cartilage. I shall not repeat what has been already said of the secretion of the fluid that lubricates the articulating surfaces, that facilitates their motion and keeps them in contact. Its quantity is in direct ratio of the extent of these surfaces and of the membranous capsule in which tbey are contained; it is, likewise, proportioned to the frequency ot 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 tbem, and are reflected over tbe 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 viscera within that of the peritoneum. The synovia is heavier than common water, quite colourless, and more viscid than any other animal fluid. It contains a considerable quantity of albumine which, according to Margueron, who first gave a tolerably accurate analysis of syvo- via, is found in a particular state, and much disposed to concrete into filaments, on the addition of acids. Besides, it contains mu- * Sometimes, however, these cartilages are destroyed; the denuded bone then becomes polished by friction, and as hard as ivory. ON MOTION. 413 riate and carbonate of soda and phosphate of lime, the whole dis- solved in water, which forms about three fourths of its weight. CLXXVIII. Theory of Anchylosis. Motion may be considered as the proper stimulus of the synovial secretion; and a moveable joint, as is justly observed by Grimaud, is as a centre of fluxion towards 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 happen that the articulat- ing surfaces, remaining long absolutely motionless, lose their mois- ture, and from the want of the fluid which should lubricate tbem, 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 tbe congestion of the soft parts, and especially of the ligaments surrounding the articu- lations. In fact, when in a fracture of the thigh, or leg, about the middle of the length of one of these bones, and consequently, at the greatest possible distance from the knee joint, the circum- stances of the case require that the bandages should be kept on the limb a considerable time, the joint loses its power of motion, re- covers it with difficulty, and sometimes not at all. I have at pre- sent 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 tbe middle of the bone, that it has been found necessary to continue, for seven months, the use of splints. In the course of so long a state of inaction, the soft parts have lost the habit of moving, and the knee is, almost completely, anchylosed. Whenever on account of any complaint, one has been confined to bed, tbe first attempts to walk are painful, difficult, and attend- ed by a marked crepitus in the knee, denoting clearly the want of synovia. On the other hand, if the joint is examined in a per- son who before death has been long without motion, the articulat- ing surfaces will be found rough and dry, with evident marks of inflammation. Flajani mentions the case of a patient who died after having been three months in bed, in an almost motionless state. Externally, the knees did not appear to have been injured, and yet he could not bend his knee joint. On opening the joint, it was found that tbe articulating surfaces had grown together; the posterior part of the patella adhered to the condyles of the femur, 414 ON MOTION. and it was necessary to use a scalpel to defach these parts from each other. I have frequently observed the same appearance, in dissecting the knee joint of persons who died while labouring un- der 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 tbe case of the patient whose skeleton was presented by M. Larrey to the mu- seum of the School of Medicine at Paris. One of the most re- markable 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 mov- ing the lower extremity, when, after a fracture of the leg, the ends of the bone have become sufficiently united to prevent their being displaced. These motions, which are of indispensable necessity in all fractures of the femur, of the tibia, and especially of the pa- tella, are much better calculated to prevent anchylosis, than the various resolvent remedies which are commonly employed, as plasters of soap, vigo, cicuta, diabotanum, diachylon, pumping, bathing and fumigations, which, however, should be used in com- bination with a moderate exercise of the limb, in order to obtain the most complete success. - The gout affects those joints which are most subject to motion, and on which there is the greatest pressure. The first attacks, as Sydenham 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. The muscles which pass over the joints give them much great- er security than the lateral ligaments. In fact, if the muscles become palsied, the mere weight of the limb stretches the liga- ments, which give way, become elongated, and allow the head of the bone to escape from its glenoid cavity. It is, in this man- ner, that a loss of motion, and atrophy of the deltoid muscle, 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 co- ON MOTION. 415 lumn, when dissected and deprived of all but its ligamentous at- tachments, gives way under a weight much smaller than that which it would have supported, before being stripped of the mus- cles 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 faiis on the base of sustentation (I call thus the space defined by the feet, whether close or apart); but this line may tend to to exceed it, without our necessarily falling, the muscular action soon restoring the equilibrium which is deranged by the altered direction of this line. But if the lower extremity of the line, by being prolonged, should fall without the limits of the base of sustentation, a fall is unavoidable on the side towards which this line inclines.! If the body is inclined backwards, so that there is a danger of a fall on the occiput, the extensor muscles of the leg contract powerfully, to prevent the thigh from bending, while other powers bring forward the upper parts, and give to the prolong- ed line of the centre of gravity a different direction; and if, in proportion as the extensors of the leg are brought into action, its inclination be increased to such a degree, that nothing is capa- ble 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 th.>t bone. I think it useful to insist, more than has been dons hitherto, on the mechanism by which the human body is supported in the erect posture; for a knowledge of that mechanism facilitates the ♦ The centre of gravity, in the adult, is situated between the sacrum and pubis. f " Quotiescunque linea profiensionis corporis humani, cadit extra uniu* fiedis innixi plantain aut extra quadrilaterum, comprehensum a duubus plantis pedum, impediri ruina, a quocumque musculorum conutu 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 .v'nen we stand on one foot, and we are, under such circum- stances, obliged to be pe-rpe ua.iy struggling, to prevent the centre of gravity from falling out of the narrow limits of the base of sustentation, 416 ON MOTION. 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 supporting 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 superincumbent weight; but not one of these circumstances is to be observed in the human body: the articulation of the head does not correspond to its centre of gravity; tlie weight of the thoracic and abdominal viscera, and of the pa- rietes of the cavities in which they are contained, rests, almost entirely, on the anterior part of the vertebral column. The ver- tebral column is supported on an inclined base, and the bones of the inferior extremities, which are connected to each other by convex and slippery surfaces, are, more or less, inclined towards one another. It is therefore necessary, that an active power* watch incessantly, to prevent the fall which would be the natural consequence of their weight and direction. This power resides in tbe extensor muscles which keep the parts of our body in a state of extension, the more perfect, and which * An upright posture is ijpt, in all animals, as it is in man, the conse- quence of an effort. This is proved by the following fact observed by M Dumeril. The sea fowl, and especially the waders, (Grails, Linn.) as herons and storks, forced to live in the midst of marshes and mud- dy 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 confor- mation of the articulation between the leg and thigh. The articulat- ing surface of the thigh bone, as M. Dumeril had an opportunity of ob- serving in a stork, (Ardea ciconia, Linn.^ contains, in its centre, a de- pression, into which there is received a projection of the tibia. To en a>le the animal to bend its leg, that projection must be disengaged from the depression into which it is lodged, and this is resisted by several ligaments which keep the leg extended in standing, in flying, and other progressive motions, without the assistance of the extensor muscles. ON MOTION. 447 tender our erect posture the firmer, as they are endowed with a more considerable power of antagonism, and as our parts are natu- rally l°ss disposed to flexion; and,'besides, as we have seen (CLXVI.) these powers are not sufficient to balance those whose action is directlv opposed to theirs. The relative weakness of the extensor muscles is not the only obstacle which ren iers impossible an erect posture, at an early period of life. Other causes, into which we are about to enter, concur in unfitting the new born child for the exercise of that faculty. The articulation of the head to the vertebral column being nearer the occiput than the chin, and not corresponding to its centre of gravity, its own weight is sufficient to make it fall on the upper part of the chest. It is the more disposed to fall 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 tbe fore part of the chest, and in its fall draws the body after it. The weight of the thoracic and ab- dominal viscera tends to produce the same effect. 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 necessa- rily fall and bring them down with them. The relative weight of tbe thoracic and abdominal viscera, tends, therefore, to bring forwards the line in the direction of which all the parts of the body dress on the plane which supports it, and this line should be exactly perpendicular to that plane to enable the body to be perfectly erect: tbe following fact proves this assertion: I have observed, that children, whose head is very large, whose belly projects, and whose viscera are loaded with fat, have much difficulty in learning to stand; it is only about the end of their second year, that they dare trust to their own strength, and then they meet with frequent falls, and have a continual ten- dency to go on all fours. The vertebral column, in the child, does not describe, as in the adult, three curves alternately placed in opposite directions. It is almost straight, and yet presents in the direction of its length a slight curvature, the concavity of which looks forwards. This incurvation, whieh depends solely on the flexion of the trunk 54 418 ON MOTION. 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 considered as defined by two lines drawn from the anterior and posterior part of the first cervical vertebra, to the sacro lumbari symphysis. These two lines, very near to each other at their upper part, and below, at a distance from each other, would be the chords of arcs and the tangents of the curves, formed by the vertebral column. So that this column may be considered as having a fictitious thick- ness greatly exceeding its real bulk. In the new born child the want of alternate curvatures not only contracts the boundaries within which the centre of gravity may be varied, but the direction of the only curvature which exists, favours the flexion of the trunk, and consequently tbe inclination 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 qua- drupeds.* The disadvantage resulting from the want of alternate curva- tures in the vertebral column of the child is further increased by tbe total absence of spinous processes. It is well known, that tbe 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 lamina? of those bones are uni- ted, by means of a cartilaginous substance, which completes tlie posterior part of the vertebral canal. The muscles destined to keep the trunk erect, weakened by its constant flexion during gestation, lose, besides, a great deal of their power, from the un- * This curvature is very distinctly marked in swine. The back of these animals is remarkably prominent, and this form, necessary to enable the vertebral column to support the immense weight of their abdominal viscera, has a considerable influence on the 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 that their motion when rapid is effected by the alternate tension and relaxation of their spinal arch. ON MOTION. 419 favourable 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 con- siderable weight, but, likewise, on the want of spinous processes 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 up- per outlet very oblique. The viscera, which are afterwards to be contained within its cavity, are, for the greater part, situated above it. This obliquity of the pelvis would require a perpetual straightening of the vertebral column, to prevent the direction of the centre of gravity from obeying its natural tendency forward. On the other hand, the vertebral column, resting on a narrow pel- vis, 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 firm- ness to the knee joint, in front of which it is placed, and of in- creasing the power of the muscles of the leg, by placing them at a distance from the centre of motion in that articulation, and by increasing the angle at which they are inserted into the tibia, as yet does not exist in new born children. The tendinous portion of the extensors of the leg, where the patella is hereafter to be formed, is merely of a more condensed tissue, and of cartilaginous hardness. The want of a fulcrum is attended with a continual disposition in the leg to bend upon the thigh; and the parallel direction of its extensor muscles, occasions a complete loss of their effective pow- er. Then their antagonizing muscles induce a conflexion 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 pow?r 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, 420 ON MOTION. he, in great measure, owes tlie 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 mam- malia 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 does, of all ani- mals, rest on the broadest surface, 1 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 firmness to their peculiar mode of standing. The feet of the ourang outang, which, in the general structure of his organs, bears so striking an analogy to the human species, resemble a coarsely formed hand, better fitted to climb the trees on which that animal seeks his food, than to the purposes to which man applies his hands. Thus the erect postUre which he, at times, assumes, is neither the most convenient nor the most natural to him. And, according to a philosopher, who speaks on the authority of several travellers, if a sudden danger obliges him to make his escape, or to leap, he drops on all fours, and dis- covers his re.d origin; he is reduced to his own condition when he quits that unnatural attitude, and discovers in himself an animal, which, like many a man, has no better quality to recommend him than a specious disguise. The feet are the parts least developed in the new-born child; his body is insecure on that narrow basis; the prolongation of the line of his centre of gravity, which so many other causes tend to carry beyond that base, will be the more inclined to fall beyond it, from its small extent. The greater number of the differences which have just been examined, depend on the mode of nutrition in the feel us. 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 ex- tremities. Thus, the development, which almost uniformly bears a proportion to the quantity of blood sent into organs, is but im- perfect 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 arrangements of his organs. This analogy is the more marked, the nearer the foetus is to the period of his formation; and it might be laid down as a general proposition, that orga^ ON MOTION. 421 nized beings resemble one another more closely, the nearer to the period of incipient existence they are examined. The differences which characterize tl.em become apparent, in proportion 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 un- favourable disposition of the parts to which these powers are ap- plied, render it impossible for the infant to stand upright; that is, to keep the mean line of direction of its body n arly perpendicular to the plane which supports it. Bui in proportion as he advances in age, the preponderance of the flexors over the extensors ceases to be in excess. The proportionate size of tbe head, and of the thoracic and abdominal viscera, diminishes. The curvatures of the vertebral column begin to be distinguishable; the spinous pro- cesses of the vertebrae are evolved; tbe breadth of the pelvis is in- creased, and its obliquity lessened; the patella becomes ossified, the oscalcis juts out backwards, the relative smallnessof 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 perogative, 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 iu 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. CLXXX1. Though the articulation of the head to the cervical column, does not correspond either to its centre of magnitude, or to its centre of gravity; and though it is nearer to the occiput than to the chin, its distance from the latter is much smaller in man, than in the monkey and oilier animals, whose foramen mag- num is, according to Daubenton, placed nearest to the posterior extremity of the head, when they resemble man the least. The head, therefore, is very nearly in equilibrio on the column which supports it; at least to keep it in that position, a very slight power is 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 resistance. This purpose is * Os homini sublime dedit, celumque taeri Jussit, et credos ad sidera tollere vultus. These verses may be much more justly applied to the fish, called bv naturalists (Jranoscopus. Its eyes are turned upwards and con- -taivHv- look towards the heavens. 422 ON MOTION. answered by the posterior cervical ligament, so remarkable iu those animals, attached to the spinous processes of the vertebrae, and to the protuberance of the occipital bone, which projects much more in them than in the human species, in whom instead of 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 tbe feet, the great power of the extensors of the fool and thigh,* all these^avourable conditions observable in man, are wanting in animals-? but, as in the latter, every thing concurs to prevent their being capable of standing on two feet, in man every thing is so disposed, as to render it very difficult for him to rest on his four extremities. In fact, independently of the. great inequality which there is between his upper and lower limbs, a difference of length, which, being less sensible in early life, makes it less uneasy for a child to walk on its hamis 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 embrace a sufficient space. We cannot, therefore, agree with Barthez, that man, during infancy, is n turally 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. CLXXX1I. Very little has been added to what Galen has said in his admirable work on the structure of parts, relative to the re- spective advantages attending the peculiar conformation and struc- ture of the upper and lower limbs.. It is easy to see, that in com- bining, as much as possible, strength and facility of motion, Na- ture has made the former predominate in the structure of the in- ferior extremities; while she has sacrificed strength to facility, to precision, to extent, and rapidity of motion, in the upper extre- mities. To convince oneself of the truth of what has been stated, it is sufficient to compare, under the two relations! of the resistance of vvbich they are capable, and of the motions which they allow, the * These muscles form the calf of the leg and the buttocks; in no ani- mal are these masses of flesh more prominent than in man. | See the anatomical observations on the neck of the thigh bone, whi-h I »:ave prefixed to a memoir which bears the title of Disserta- tion anutomico-chirurtricale sur les fractures du col du femur. Paris, an. VII. ON MOTION. 42ei 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 cover- ed with the soft parts, will present the appearance of an inverted cone or pyramid, which, at first sight, appears contrary to the ob- ject which nature had in view; but if the bones be stripped of their fleshy coverings, these solid supports will be seen to repre- sent 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 co- lumns containing the same quantity of matter and of equal dia- meter, have each a solidity in inverse ratio of the squares of their height: in other words, of two columns, containing the same mate- rials, of equal diameter, and of unequal height, tbe smaller is the stronger. The long bones, which by their union form the inferior extremi- ty, contain a cavity which adds to their strength, for according 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 * Mcthodus inveniendi lineas curvas. \ Nature has, therefore, increased the number of these columns in the extremities of quadrupeds, by raising their heel and the different parts of the foot, whose bones she has lengthened, to make of them so many secondary legs. These numerous columns placed above one an- other, 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 hare and squirrel; while in the ox, and especially in the elephant, they are all placed vertically, so that the enormous mass of the latter rests on tour pillars, the different pieces of which are short, and so slightly moveable on one another, that, as Barthez ob- serves. Saint Basil has adopted the error of Pliny, rElian, and several other writers of antiquity, that there are no articulations in the legs of (hat monstrous animal. 424 ON MOTION. 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 innomi- natum, which receives that bone, come in contact in a surface of small extent. I am, on the contrary, of opinion that in no possi- ble 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 surface 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 thinh bone at a distance from the cavity of the pelvis, in- creases 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 absence of motion. It is, on the contrary, accompanied by a staggering 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 in- capacity of the extensors to keep up a conslant state of contrac- tion, so that they become relaxed for a short time, and the inter- vals of rest in the extensors are frequent, in proportion to the weaker state of the subject. Some physiologists have given a very inaccurate idea of stand- ing, by making that attitude depend on a general effort of the muscles; the exiensors only, are truly active. The flexors, far from assisting, tend, on the contrary, to disturb the relation be- tween the bones, necessary to render that stale 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 firmness to the attitude, we sometimes contract, in a moderate degree, 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 extremities; in keeping their surfaces firmly applied to each other, and in maintaining their ex- act super-position which is necessary to the erect posture of the body. No one that I know of, bad taken notice of this employ- ment 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 ON MOTION. 425 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 for- ward 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 protection 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 a dition to the ribs, protects the posterior part of the chest. Tbe 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 limbs are in an habitual state of flexion, are much less dangerous than those of a strong and powerful adult, whose body falls in one piece, if I may be allowed that expression. The falls which skaiters meet with, on the ice, are often fatal from fracture of the skull, which placed at the extremity of a long lever formed by the whole body, whose articulations are on the stretch, strikes the slippery and solid ice, with a momentum increased by the quick- ness of the fall. We have already seen, that wading fowls remain a long while standing, without effort, by means of a peculiar contrivance in the articulation of the tibia to the thigh bone; but all other birds are obliged to employ muscular action when standing, ex- cept 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 bis 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; * This tendency is much less distinct in tall slender men. it is ob- served, that they, 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 an4 easy understood reason. 426 ON MOTION. first who understood distinctly and explained stiusfaclorily 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, instead of rest- ing on the entire sole, we chuse to stand on the heel or on the toe: the base of support is then so small, thai no effort is suffi- cient 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 enclose a perfect square, that is, when, taking their length at nine inches, each side of the quadrilateral figure is of that measure, the stand is the firmest that can be conceived. Nevertheless, we are far from keeping or taking this posture to prevent falls. The wrestler, who wants to throw his antagonist, strides much more; but then he loses on one side what he gains on another; and if he stride 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 gymnastic art, is to bring back the feet to a moderate stride, in the line of the effort which is foreseen to require resistance. There is some resemblance to standing, in the attitudes of kneeling and sitting. In the first, the weight of the body bears upon the knees, and we must bring back the body, to throw ihe centre of gravity over the middle of the legs. Accordingly, if we have nothing before us to lean on, this posture is extremely distressing, and we cannot long keep it on. 1 have said, in another work, that genuflexion rendered monks very liable to hernia; the abdominal viscera be- ing pushed against the anterior and lower part of the abdomen by the throwing back of the body. In sitting, the weight of the body bearing on the tuberosities of the ischia, there is much less effort required than in standing on the feet. The base of support is much larger; and when the back leans, almost all the extensor muscles employed in standing are in action. i * De motu animalium, Prop. 150. Quseritur quare aves stando, ramis arhorum comprehensis, quiescunt et dormiunt absque ruina. Tab. II fig- 7- ON MOTION. 427 CLXXXV. Of the recumbent posture. Decubitus. All the authors who, like Borelli, have treated professedly of the animal mechanism; all the physiologists, who, like Haller, have set forth, in some detail, the mechanism of standing, and of progression, have completely passed over the 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 locomotive muscles recover the principle of their contractility, exhausted by exertion. Stand- ing without motion, has only the appearance of repose, and the unremitted contractions it require?, fatigue the muscular organs, more than the alternate contractions, by which the various mo- tions 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 organization, who lie on the other side. This depends on two causes; when the body lies on the left side, the liv.r, 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 pre- sents a canal in which the course of its contents is obliquely di- rected 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 de- scent of aliments, which, to pass into the intestines, are not obliged to ascend against their own weight, as they must, in lying on the left side These two anatomical causes exert their influence on the generality of men; and if there are any who fall into the habit ef lying on the left, one may safely conjecture some vicious orga- nizition, 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 parietiesof this cavity are not equally dis- tant from its axis; the pressure of the nody on the plane of support, 428 ON MOTION. prevents the separation of the ribs, whether as a mechanical hind- rance 10 the displacement of these bones, or in numbing the con- tractility of the muscles of inspiration, all more or less compressed: Now, as the healthy lun^ must supply the place of the diseased, nothing could be more in tbe way than to produce, on that side, by a bad posture, a constraint equal to that occasioned by disease on the other. It has long been imagined, and it is taught still, that, in thora- cic effusions, patients lie on the side of the effusion, to hinder the effused fluid from pressing on tbe mediastinum, and pushing it against the opposite lung, of which it will constrain the develop- ment. The following experiments show clearly enough the error of such a supposition: I have several times produced artificial hydrothorax, by inject- ing, 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 tbe 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 lungs displaced, gave room to see distinctly the septum of the mediastinum stretched from the vertebral co- lumn to tbe 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 effusion, lie constantly on the side of tbe effusion. It is for the same mo- tive, to which we may add that of not increasing the pain by drag- ging downward the inflamed pleura, that patients in pleurisy lie on the affected side. Tlie same thing happens in peripneumonies; 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 im- perfectly into effect this dilatation. Nevertheless, a determinate quantity of atmospherical air must be admitted, every moment, into the lungs, and the general weakness would be increased, if respiration did not impregnate the blood with a sufficiency of oxy- gen: patients choose, therefore, the posture which makes the di- latation of the lungs easiest for their weakened muscles. The pos- ON MOTION. 429 terior 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 articula- tion with the vertebral column, are almost immoveable backwards, and the moveableness of these bones, increases with the length of tbe lever which they represent; so that no where is it greater than at the anterior extremity terminating in the sternum. Thus, ly- ing on the back has the double advantage of not constraining any of the muscles of inspiration, and of not opposing the motion of the ribs, except at that part where these bones have the least play: lying on the back is one of the characteristic symptoms of putrid or adynamic fever, of scurvy, and of all the diseases of which de- bility of the contractile parts forms the principal characteristic. After the fatigue of a long march, or of any other continued exer- tion, 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 ex- pansion of the chest is hindered exactly where the bony structure is formed for the greatest play of motion: the abdominal viscera are besides pushed up on the diaphragm, of which they resist the depression, and tbe posture is accordingly unusual. The con- tinuance of it during sleep is possible only to the robust: others, even when they do fall asleep in this posture, soon awake from troubled and distressing dreams, under tbe agony known by tbe name of the night-mare. We sometimes seek this posture to con- strain respiration, and so abate inward excitation, in tbe ardour, for instance, of a febrile paroxysm. The different postures of lying having reference to the degrees of facility of respiration, very young children and persons advanced in years, prefer lying on the back; this posture being, as was already observed, the most favourable to the motions of respira- tion. Respiration, like all the other functions of the animal economy, with the exception of the circulation and of the pheno- mena which immediately depend on it, requires a kind of cultiva- tion; 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 re- spiration, at first small and weak, acquire strength from the very circumstance of being called into frequent action, that the chest dilates with facility, and that tbe lungs enjoy the full exercise of their faculties. Until that period, tbe enlargement of the cbest and the dilatation of the lungs took place in an imperfect manner; the child was unable, even by spitting, to free itself of the mucus with which its bronchitc are apt to get filled, and which render the pulmonary catarrh, called tbe hooping cough, so dangerous at an 430 ON MOTION. 4 early period 6f life. In like manner, in an old man, the muscles, debilitated, and returned to the relative weakness of infancy, in vain strive to clear the air cells of the mucus with which they be- come obstructed in the suffocating catarrh. The mechanical pro- cess of respiration is, therefore, equally difficult in the child, from the weakness of the muscles which have remained in a long con- tinued state of inactivity; in the old man, from the debility of the same organs and from th*- 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 sufficiently remarkable difference in that respect, and which may now be inquired into. In the foregoing observations, I have always spoken of the human body as stretched on a perfectly horizontal plane. It is seldom, however, that we rest on such a surface; almost every one, and especially 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 conges- tion of blood. Children, on the other hand, suffer no inconve- nience from a neglect of this precaution; whether it is that in them, ihe vital power has more energy, and thus balances better the laws of mechanics, by opposing more powerfully the effects of gravitation; or whether it is, that in very young children, the parietes of the arteries within the skull, have a proportionate thickness, and consequently greater power. The extreme dis- proportion observable in adults, in the thickness of the parietes, between the cerebral arteries and those of other parts of the body, is but trifling in children; and may not this difference of structure, which I have several times observed in the course of dissection, be considered as one of the principal causes which, in old age, bring on apoplexy, a disease to which the child is not liable. It is well known, that as the enlargement of the chest is pro- duced by the depression of the diaphragm, persons who have ta- ken a plentiful meal, dropsical patients, pregnant women, cannot rest without lying on a very inclined plane; so that the chest be- ing 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 de- pression of the diaphragm We might now inquire what is the posture in which the body rests with least fatigue; this investigation, unimportant to the phy- sician, would be of the highest value to the art?, which have for their object ihe imitation of nature. In consujuence of igno- rance on this subject, we often see, in the works of several of our ON MOTION. 431 sculptors, figures in attitudes of repose so incorreet 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 mechan- ism of running and leaping. In the most natural way ol walking, we, in the first instance, poise the body on one foot: then, bend- ing 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 per- forming the same motions with the limb which remained behind, we measure the space more rapidly, caeteris paribus, as the levers, on which the centre of gravity alternately bears, are longer. The weight of the body, compared to that of the lower extremi- ties, is as that-of a carriage^ which moves in succession, on the different spokes of its wheels. The centre of gravity does not move along a straight line, but between two parallels, in which place it describes oblique lines from the one parallel to the other, and forms zig-zags. The ob- lique direction of the neck of the thigh bones, accounts for the lateral oscillations of the body when we walk; the arms which move, in a different direction from that of the lower extremities, serve to balance us, preserve the equilibrium, and. correct the staggering, which would be much greater, if the neck of the thigh bone, instead of being oblique, bad been horizontal. The im- pulses communicated to the trunk, are reciprocally balanced, and the latter moves in tbe diagonal of a parallelogram, whose sides are lepresented by tbe line of these impulses. We constantly 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, be will, in his attempt to get out, and thinking that he is mov- ing in a straight line, make for one of the corners. It is, almost always, towards the left that we deviate; the right lower extremi- ty, which is the stronger, inclining the body towards the oposite side. Those who are lame depart much more from a straight line, and deviate towards the side of the shorter leg. The mo- tions which they are obliged to use, and render their gait so re- 432 ON MOTION. markable, are occasioned by the necessity of incessant and pow- erful 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 recognized by their gait. A sailor is unfit for active ser- vice, till he has acquired what is called, by seafaring people, a seaman's foot; that is till he is capable of stepping firmly on the deck of a vessel tossed by the tempest. The gait of a woman, from her having smaller feet, is less firm; but ought we, from that circumstance, to infer, with the most elo- quent writer of the eighteenth century, that this diminutive size of the foot, is connected with the necessity of her being overta- ken in flight? The concave form of the sole of the feet, by ena- bling them better to adapt themselves to the unevenness of the soil, concurs in giving a firmer footing in walking, and in,other motions of progression. There is, in walking, an intermediate 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 horizon- tal 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 arti- culations 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 ex- tends the articulations of the other extremity, carries thus the body upward, in a vertical direction, and completes this first step, by contracting the extensors of the leg that were first in action, so that they may bring forward and restore to it the centre of gra- vity, 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 tbe extensors of the foremost leg, bring back again upon it the centre of gravity, is more powerful than that ON MOTION. 433 by which the gemelli and the soleus impart to it, by extending the hindmost foot, a motion of vertical elevation. To relieve the extensors of the leg, we bend the body forward as much as possible; we lean back, on the contrary, in descending a flight of stairs, or a rapid si »pe, 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 longer within the base of sustentation, all the powers unite in action, that it may fall, as little as possible, from a vertical direction. The 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, when the slope is moderate, than in goinj^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 tbe 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 which he is loaded. The weight of an adult, of common stature and of moderate size, may be esti- mated 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 ef- forts must be, which are, as it were, unconsciously carried on, in tbe articulation of the foot with the leg. But how numerous the resources which nature has provided to overcome this great re- sistance; how many the circumstances she has happily combined to accomplish this without fatigue! In the first place, the foot in this action represents a lever of the second class, and this lever, it is well known, is the most advantageous, the resistance being al- ways 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 of the skeleton, you will no where find so powerful a lever applied in so favourable a manner. The os calcis, by carrying the foot beyond its articula- tion with the leg, adds likewise to the length of the lever by which the power acts. Its length has considerable influence on our 434 ON MOTION. v strength, on our power of taking, without fatigue, long walks, or engaging in exertions requiring considerable muscular force in the lower extremities The negroes, who excel in running, in danc- ing, and in all gymnastic exercises, have a longer and more pro- jecting 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 the leg; which implies, that its lower attachment is carried back, by the prolongation of the os calms. Those who have a short heel, have a long and flat foot; this conformation, which, when marked, is faulty, is not only unfavour- able to beauty of form, but is besides, remarkably injurious 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 (pieds 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 in the different motions of progression. We have seen that the tendons are generally inserted at a very acute angle, into the bones on which they act; in the present in- stance, 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 possible distance frcm the fulcrum and at the angle most favourable to their action; she has further in- creased the efficacy of this action, by adding extraordinarily to the number of muscular fibres. There is not, in the body, a stronger muscle than the soleus, whose short and oblique fibres between the two wide aponeuroses which cover its anterior and posterior surfaces, are more numerous than in any other muscle, as may be conceived, by considering the extensive surfaces to which they are attached. Besides, the tendo Achillis is kept in a due degree of straightness, by the aponeurosis of the leg behind it. Every thing, in the powers, as well as in the levers, is formed so as to overcome the resistance, without difficulty; that is, so as to raise the weight of the body, by the extension of the foot, ON MOTION. 435 the end of which rests on the ground, in every motion of pro- gression. This immense power with which the muscles of the calf of the leg act to raise the heel, and to support the whole weight of the body resting on the astragalus, 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 known to have been the case in several instances. This same arrangement of parts likewise accounts for an accident, which physiologists have long endeavoured to explain by a very unsatisfactory theory. It not unfrequently happens, that the mere effort of walking oc- casions 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 ec- chymosis, 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 al- together 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 appropriated remedies. 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 tbe force of projection, the action of which principally constitutes leaping. The mechanism of running is a compound of that of walking 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 transferred, with more rapidity, from one leg to the other, and falls are much more apt to take place. The quick repetition of the same motions, in running, requires a very lively contractility in the muscles which move the extremities, and as the energy of this vital property is proportioned to the extent of respiration, to the quantity of air which the blood acquires in passing through the lungs; in running we pant and breath frequently, and at short intervals, without any 436 ON MOTION. particular enlargement of the chest at each act of respiration.- It was necessary that the parietes of this cavity should, in running, be remarkably fixtd; for, it becomes the point on which those muscles are insered which steady the pelvis and loins, and pre- vent their yielding an unsteady basis to the lower extremities. Tiie best runners are those who have the strongest lungs; that is, who can give to the chest the greatest degree of permanent dila- tation. In contending for the prize in running, you may see them throw back their head and shoulders, not only to obviate the pro- pensity which there is in the line of the centre of gravity to fall towards the anterior plane, but. likewise, that the cervical column, the scapulae, the clavicles, and the humerus, being fixed, may furnish a firm attachment to the auxiliary muscles of respiration. We should run with much less speed, if we applied to the ground the whole sole of the foot; partly from the time which would be tak? n 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 slate of extension, tbe 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 follow each other in rapid succession, and never resting but on a basis of every limited extent. Another reason why the slightest uneven- ness of the ground is apt to occasion falls in running is, that the rapid motion communicated to the body by the sudden and per- petually recurring extensions of the posterior extremity, increases, at every step, so that it is impossible to stop suddenly, and with- out 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 run- ning we always throw back the head, and make use of our arms to balance the body, so that they may be in constant opposition to tfo- legs; that is, that the right lower extremity, for example, be- ing 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 account of the num- ber of the limbs on which he rests, if he had not tbe power of ON MOTION. 437 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 sudden 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 straightening is not limited to the lower limbs, in violent leaping; it likewise affects the vertebral column, which acts as a bow in unbending. Professor Barthez, who has the merit of having suggested this explanation, which Borelli and Muyow had very imperfectly un- derstood, 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 physiologists do not admit that, in leaping, there is a re-aclion from the ground, it is universally admitted, that there must be a certain resistance from the ground on which we tread. In fact, a moving sand, yielding to the pressure of the body, would, by giving way to a considera- ble degree, render it impossible to leap. The instantaneous con- traction of the extensor muscles is so powerful, in extending the lower extremities, and in communicating to the body a power of projection, so as to raise it, that frequently, during this effort, the tendons of these muscles, or even the bones into which they are inserted, break across. It is on this account, that dancers are very apt to fracture their patella. This accident happens at the moment when their body, in rising from the ground, is powerfully elevated to a certain height. If leaping consists merely in the sudden straightening of the lower extremities, whose articulations are bent in alternate direc- tions, it must be more considerable, according as these are longer, more bent on one another, and as the muscles which straighten them contract more powerfully. Hence, animals that move by leaps, as the hare, the squirrel, and the jerboa, have posterior ex- tremities of considerable length, in proportion to their fore legs. Their different parts are, besides, capableSff considerable flexion. All these animals, strictly speaking, are incapable of walking or running; and they move by leaps, or bounds, succeeding each other with different degrees of rapidity. Some, however, as the rabbit and the hare, are capable of running when climbing up a Bteep place, as the slope, in this case, lessens the effect of the im- pulse communicated by the extension of the posterior limbs; an impulse which, from the strength and length of these extremities, 438 ON MOTION. throws the whole weight of the body on the fore legs, which are weaker and shorter, with such a degree of force, tba* 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 fleas, between whose hind extremities and the rest of the body there is the greatest disproportion, astonish us by the very considerable space which they can clear at a leap; but the wonder ceases, when we consider 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 as200 to 1. A flea leaps still farther and more swiftly.* 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 mechanism, that the salmon, the trout, and other fishes, swim against rapid cur- rents 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, tbe leap is not effected solely by the straightening of the elastic curve, as is maintained by some au- thors, but that it is likewise occasioned by the resistance against the wrater, of the tail of the fish, which strikes it powerfully, at the moment of raising itself; in the same manner, as in the nor- thern seas, the enormous whale strikes, with so sudden and vio- lent 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. Lobsters leap by violently extending their tail, an elastic and contractile arch, which they had previ- ously kept bent under their body. This theory of leaping would seem to be contradicted by what * Barthez states, in his work on mechanics, that the Arabs call this lit lc insect the father of leaping; and that Roberval, a natural philoso- pher of considerable merit, had written a work entitled de saltu pu- .'ieis. Such a subject, thought by the ignorant to supply matter only fondle and fruitless speculation, may fun.ish results highly interesting, when treated by an able man. In tenui labor. > ON MOTION. 439 is related by Professor Dumas, of a man without thighs, and v,ho, nevertheless, performed surprising feats of dexterity and agility. But in this instance, might not the pelvis, the vertebral 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 form- ed by the lower extremity ? In the act of leaping, the body, which has received the impulse, ' may rise in one of two ways, perpendicularly to tbe 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 al- ways 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 mechanism 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 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 pro- duce 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 uniformly observed, that in the most celebrated public dancers, the trunk, and espe- cially the lower limbs, are very muscular, the calf of the legs, the buttocks, and the back indicate, by their bulk, a remarkable degree of energy in the extensors, by whose action 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 receiv- ed; his fall resembles that of a projectile in vertical motion: it takes place according to a descending line that is perfectly simi- lar, 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 440 ON MOTION. the body has described a curve which represents the half of a parabola; from that moment, the force of gravitation goes on in- creasing, 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, th.it corpulent men swim with less effort; but the weight is not equally distributed over every point of the supporting fluid. The head, whose relative weight is very considerable, 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 displace by pressing on it. In these various motions, there js 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 retain- ing, 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 Ihe 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 sufficient- ly 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 sa- lient angles, is well calculated to separate the columns of a fluid. A bladder filled with azote, which is expelled at pleasure, renders the specific gravity less than that of water, according to the quantify 0f gas it contains; lastly, their tail, moved by pow- erful 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 de- gree 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 * In saltu adhorizontem obliquo, motus fit per lineam parabolicam proxime. Borelli. op. cit. prop. 178.—Vide Galileo on the motion of projectiles. ON MOTION. 441 the animal, lying on his back, would be incapable of performing 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 oesophagus, when the animal wishes to sink. This expulsion becomes impracticable, if the gas undergoes considerable expansion, from the applicatiou of heat, and resists the compression that is applied to it. Hence, during the fry-time, fishes, after remaining 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 presents, on every side, an equal resistance, the velocity which he might have acquired, by striking the fluid behind with his tail, would b« lost, from the resistance of the water which he would havefo dis- place forward, if, immediately afler striking with his tail, he did not bring it back into a straight line, so as to present 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, tbe 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 tbe side be 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 tbe bottom of the water, unless they have a flat body and are furnished with horizontal fins, so as to enable them to strike a considerable sur- face 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-hut 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 flying. A bird, in rising, or in moving in the air, has to use much more force and with much greater velocity, than a fisb 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 be 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 57 442 ON MOTION. is, however, in their power to obtain a specific gravity, not much exceeding that of the atmosphere. Nature has rendered them 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 this 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, cloihtd in feathers almost as light as the air itself, requires 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, sufficiently 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 com- pass. What quadruped 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 defend 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 as- cending into the air, either by rising at once from the ground, or by allowing himself to fall from a height. If on the ground, and if his wings are too large to be freely spread, be has a difficulty in rising; in that case he goes to an elevated spot and throws him- self from it, that he may have sufficient room to extend his wings * Birds have three pectoral muscles; the great pectoral which is at- tached to their enormous sternum, and alone exceeds in weight 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 which it raises: by means of this mechanism, nature has placed an ele- vator 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 third, or lesser pectoral, is destined to draw the humerus towards the body. ON MOTION. 443 and strike in the air, the first stroke that is to raise him. The wings expand horizontally, the humerus which forms their prin- cipal part, standing off from the body; they then descend rapidly, and, as the air resists the sudden effort which tend to depress it, the body of tbe bird is elevated by a kind of elastic re-action, cor- responding to the leap of man and to the swimming of fishes; the impulse being given, the bird closes his wings, contracts his di- mensions, 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 parti- cularly 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 rapidly, but, on the contrary, descends, if this mo- tion is delayed. If he allow himself to fall only to the height whence he began to rise, he may, by a continuance of equal vi- brations, keep at the same height. A bird, sometimes, ceases al- together to move his wings, closes them against his sides and falls, with a precipitate 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 ground, 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 mo- tion, the resistance of the air always increases, as tbe squares of the velocity; be then rises anew and takes to flight. This pecu- liar act is called resource. The oblique motions differ from the vertical motion which 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 motion, so that in soaring, the curves which tbey describe are so slight, that the motion seems quite horizontal. Swimming, to many birds, is a more natural mode of progres- sion 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 tbe 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 444 ON MOTION. 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 suffered for their rashness. CXCI. Of crawling. All the motions of progression, of which man and animals are capable, may be referred to the theory of tbe lever of the third kind. The body, in leaping, as in walk- ing, may be compared to an elastic curve, since tbe point of sup* port, 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 body of the animal alternately bends and unbends, having its support on media of much less resistance than the ground, on which walk- ing, running, and leaping are generally performed? The mode of progression peculiar to serpents and soft reptiles, furnishes an ad- ditional 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 amphisbatnous, 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 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 destroys their union; hence, a blow with a very small stick is capable 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, some- times, 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 craw) on the ground, in as much i ON MOTION. 445 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 ihe same time, on the extremity of that which is nearest his tail; then, as I have several times ob- served, he describes the smallest possible number of curves, bends into three or four greater arehes than usual, but never into a single one, whatever the length of his body may be. Tortoises, frogs, lizards, salamanders, and all reptiles that have legs, drag themselves along on their belly, being ill supported 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 Itgs of the caterpillar, too feeble to support it, or, of themselves, to carry the body forward, are used by these crea- tures to obtain a hold on the surface on which they move, by bending, in arches, mostly vertical, the p.ills situated between the legs, that are in pairs, at a certain distance from one another. The caterpillars that ha.'e a scaly covering, crawl better, the elas- ticity of their scales assisting the contractile action of their mus- cular 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 form- ing 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 bis whole body towards 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 snail, loaded with his shell, adheres to the surface on which he moves, by a viscid and glutinous fluid, which coagulates, 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 it 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 oxhauster, 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 (round on which it crawls, bear some analogy to the tentacula 416 ON MOTION. which assist the progression of the sepia and other cephalopodoii* molusca. CXCII. Partial 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 animals. This idea simplifies and facilitates, in a remarkable manner, the study of animal mechanies; 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 par- ticularly 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 having a firm hold of a body, the action of the great pectorals draws the whole body, lying prone on a horizontal surface, or sus- pended. We experience a difficulty in climbing, because our hands alone enable us to grasp tbe body on which this mode of progression is to be effected, while the four extremities of the quadrumana and the sharp claws of cats, those of climbing birds, render this ac- tion 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 walking on all fours can never be natural to the human species; besides, as Daubenton observed, the situation of the foramen magnum of the occipital bone, in man, renders this attitude exceedingly un- easy. 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 perforin motions by which we act on the object 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 pushing, man places himself between the obstacle and the ground; be bends his body between these two points, by bringing * Dictionnaire d'Histoire Naturelle de l'Encyclop^die. m£thodiquek Introduction, page 21 et suiv. ON MOTION. 447 all his limbs into a state of flexion; he then extends them: bis whole bodv represents a spring which is released and recovers it- self, and the two extremities of which, meeting two obstacles, 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 slate 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 state of extension. It is in the same manner, and by a similar mechanism, that bv pushing against tbe shflre with an oar, we force a boat from it. The ver- tebral 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 tbe extensors: because the axes of the hones 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 performing a mere oscillatory motion, or by a whirling motion of the arm. This last action is much more pow- erful, because the muscles, which go from the trunk to the upper extremity, concur in it. In the former, the previous oscillations gives to the arm a motion that is peculiar to it, which is added to the force of mnscular contraction, and which augments its effects. Professor Barthez was aware that 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 opposed 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 communicated to it in leaping, by tbe abrupt extension of the lower extremities. The scapula is too moveable on the trunk, its articulation with the humerus is too unsteady, and the action of this bone is not directed, with re- Sard to the shoulder, in a sufficiently favourable manner, to ren- er the impulse equally great, even though the powers should be equal: and they are far from being so. In every repulsion, and in every attraction, whether we bring towards us an object or remove 418 ON MOTION. it from us, bv aeting upon it, with our superior extremities, these limbs represent an elastic arch, which is curved or streiglitenec] by tbe action of its flexors or extensors; and these motions, like the greater number of those which we have hitherto eonsidered, present a precise application cf the levers of the third kind. Tbe action of seizing a body, with the hand, is facilitated, 1st, by the action of the radiuson the ulna, which performs pronation and supination, motions which belong exclusively to the hands, and of which the feet are incapable; 2dly, by the mobility of ths wrist, which, properly speaki.iir, is capable of flexion and exten- sion in two directions; for the extension of the band does not con* sist in merely bringing it into a parallel line with tiie axis of th* limb, but it is, besides, capable of turning it round towards ths back part of the fore arm; a phenomenon not observable in any other articulation; 3diy, by the obscure motions, on one another, of the bones of the carpus, by which the palm of the hand be. comes more concave; ithly, by the motions of opposition arid cir- cumduction of the thumb and little finger; 5thly, by the great number of the phalanges; every thing, in this part of the upper extremity, prove 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, near* ly tbe whole weight of the body bears on one of the upper ex- tremities, which is powerfully extended, the shoulder resting on the arm, so that the glenoid cavity of the scapula maybe perpen- dicular to the head of the humerus. It would be a superfluous task, to endeavor to describe all th« motions which our parts may execute; ihese partial motions are exp'ained 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* of this important part of physiology, the only one iu which it is pos- sible to obtain, in the investigation of its objects, that degree of mathematical certainty, so much sought after by every man of precision and of sound judgment. CXCIII. Partial motions may yet further be studied assigns * Consult J. A Borelli, de motu animalliumy AX.^. The errors contain- ed in this work, depend on Hie circu—istan. t of the author's being more ©fa mathematician than of an anatomist. P. J. Barthez, nouvelle Mcchanique des mouvimcns de I'homme et 4cs animaux. ON MOTION. 449 expressive of ideas. They compose what is called the language of action, and are supplemental to speech. The language of ges- ture, in its perfection, is found 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 whicb he speaks: they contribute to tbe expo- sition 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 employed to move and sway the assembled multitude in the public 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 Ro- man people, the bloody corse of the first of the Caesars, 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 ad- dress 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 pas- sions, 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 Natural History of Man; Winkelmann's Treatise on Art; Lavater'S Essay on Physiognomy; with the important additions by M. Moreau (de fa Sarthe,) in the edition he has just published. 58 450 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, articulated by the motions of the tongue, the lips, and other parts of tlie mouth, is produced speech, which may be defined articulated 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 de- fect, 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 membranes, and moved on one another by many little muscles, called laryngeal. Of these five cartilages, three only are concerned in the produc- tion of voice, these are the arytenoid and the thyroid. The epi- glottis is of no other use than to close, to what we swallow, the entrance of the windpipe, whilst the cricoid, situated at the lower part of the organ, serves it for a base, on which the arytenoid and the thyroid execute the motions, by which the opening of the glottis is contracted or enlarged, for the formation of acute or grave tones. This slit, from ten to eleven lines long in an adult, and from two 1o three wide, where the width is greatest, is the most essential part of the larynx. It is really the organ of voice, which is gone at once, when, by opening the trachea, or the larnyx below it, the air is prevented from passing through it. Speech only is lost, when the wound is above the place of the glottis; 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 susceptible, 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 instrument, or with Ferrein, that it is a stringed instrument. OF VOICE AND SPEECH. 451 It is very true that the voice becomes stronger, fuller, and passes from the acute to the grave, as the glottis enlarges with the pro- gress 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 relation 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 manner, 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-aryten- oidei postici, which carry back the arytenoid cartilages to which the ligaments of the glottis are attached, whilst the thyroid car- tilage, 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-thy- roidei*) the voice will be shrill, that is clear and piercing; whereas it would be grave, if the arytenoid cartilages being brought for- wards by the action of the crico-arytenoidei obliqui, and the thyro-arytenoidei the vocal strings, relaxed, executed less frequent vibrations? 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 pro- duction of sound, in the instrunumts to which this anatomist has compared the larynx: but for aJ| the incompleteness of their re- semblance to strings, the ligaments of the glottis, similar to the vibratory bodies, serving as niouth-pieces to wind-instruments, 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 impos- sible to decide whether it be to the enlargement 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 con- sidered as serving at once the purposes of a wind and stringed in- strument, is, that the ligature or section of the recurrent nerves, which give to its muscles their contractility, takes away the * The arytenoid muscle is used in the formation of acute sounds, for bringing together the two arytenoid cartilages. 45$ OF VOI«E AND SPEECH. 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 them in its passage along the glottis, only relaxed parts, and little capable ot Vibration, the vocal sound is no longer produced. The permanent 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 ex- planation of Ferrein and Dodart, we are to consider the larynx as an instrument combining the advantages, and exhibiting the dou- ble 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 inexhaustible variety 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 instrument, 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 (be 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. The modifications of the voice depend, not only on the varied. sizes of the opening of the glottis, and of the tension of its liga- ments, 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 ascend- ing, be stretches them out. The force of the voice* depends on the volume of air that may be expelled from the lungs at once, and on the degree of aptness, in tbe 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 almost! 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 imper- ceptible. * Sailors, and those that live on the banks, of great rivers, have com- monly 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. 453 The hissing of serpents, and the croaking of frog*, are heard. '.o some distance, because these creatures can send out a largo quantity of air, at once, from their vesicular lungs; and in th,c last, because tlie vocal strings are 'completely insulated from the coats of the larynx, with which in other animals tbey are con-. tinuous. The voice of men is strong according to the capacity of the, chest. It is always weaker after meals, when tbe 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 mou.tb, and in the nasal cavities. It is weakened and disagreeaMf3i|^ paired, when a polypus of the nasal canals, or of the tlrM Wp the destruction of the roof of the mouth, prevents the arr^Wm 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 belong-* ing to the nose. CXCV. Of speech. Towhisper is to articulate very weak sounds, which, in truth, deserve not the name of voice, since they scarce- ly exceed the sound which always accompanies tbe passage of anj 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 impossible to quadrupeds. The. monkey, in whom these parts have the same conformation as iu 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 melancholy. Every time that th* animal would utter bis cry, these sacs swell, then empty them- selves, so that he is not able, at will, to supply to tbe 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 nature, when be 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 furnishes almost completely formed, and which need, for their articulation, nothing more than * In the ass, an analogous structure is observed. f----Graiis dedit ore rotundo Mum loqui.—?Hohat. 454 OF VOICE AND SPEECH. the more or less opening of the mouth, by the separation of the jaws and of the lips. We pronounce, 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 dif- ficult. Accordingly, it is observed, that the most harmonious lan- guages, the most grateful to the ear, are those which use fewest* consonants and most vowels. It is in this point especially, that the Greek tongue surpasses all, ancient and modern; that, of dead languages, Latin holds the second place; and lastly, that Russian, Italian, and Spanish, are more agreeable in pronunciation, than French, and still more than languages of Teutonic 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 pronunciation, no doubt, because it requires greater effort, and he who listens sym- pathizes in the difficulty which seems to be felt by him who speaks. Would it not seem that the inhabitants of cold countries have been led to use consonants rather than vowels, because the pro- nunciation, not requiring the same opening ot the mouth, does not give the same room to the continual admission of cold air into the lijngs. The gentle 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 rigor of their climate, the barrenness of their soil, and their fero- cious and warlike habits. The distinction of letters, into vowels and consonants, has not been thought sufficient: they have been further distinguished ac- cording to the parts which are more especially engaged in the me- chanism of their pronunciation. Thus we remark the labial, oral, nasal and lingual vowels, and semi-vowels, M, N, R, L, which bear different names, according as the tongue in articulating them, strikes the roof of the mouth, the teetb, or the lips: lastly, explo- sive consonants, K, T, 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 pronunciation. If information on this subject could be of real utility, I should explain the mechanism of the pronnnciation of every letter of the alphabet, at the risk of furnishing a new scene to the Bourgeois Gentilhomme. CXCVI. Singing, stammering, dumbness, ventriloquism. Sing- OF VOICE AND SPEECH. 455 iriff 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 to it. This action of tbe organs of the voice requires more efforts and motions than speech: the glottis enlarges or contracts, tbe larynx rises or descends, the neck stretches out or is drawn in; inspiration is ac- celerated, prolonged, or slackened; expiration 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 tbe 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 understanding, and the acts of the will.* Of all the instruments which this art employs, the vocal organ of man is indisputably the most perfect, that from which the most agreeable combinations 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 lan- guages?! I will observe, on the occasion of song, that it is especially consecrated to the expression of tender sentiments or movements of passion, and that it is turning it aside from its natural or primi- tive destination, to employ it in situations where no emotion can be supposed. It is this that makes the recitative of our operas so 'intolerably tiresome, and throws such ludicrousness over dialogues where the speakers converse singing, on the most indifferent mat- ters. Languages abounding in vowels, are thereby fitted to song, and favour tbe growth of musical genius. It is perhaps their smooth and sonorous language that has given to the music of the Italians, its superiority over that of other countries.^ The decla- * See G retry, Essais sur la Musique, &c. f See in the Aviceptologie Erancaise, or Art de prendre toutes tortes SOtseaux, the way in which they are drawn into snares by counter- feiting their song. :f This pre-eminence hasbecn strongly contested, especially in France, where towards the middle of the last century, a war arose on the sub- ject, in which her whole literature, split into two factions, fought for the superiority of Piccini and Gluck. Out of the heaps of writings in vcrsf -ird in prose, with which the contest was carried on, a few epi- 456 OF VOICE AND SPEECH. mation 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 different 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 un- equally developed to prevent precision and distinctness of voice Stammering is a vice of pronunciation too weli known to make it necessary to define it. A tongue loo bulky and thick,—a re- markable diminution of irritability, as in drunkenness, at the ap- proach of apoplexy, and in certain fevers of a malignant kind,— the too great length of the frsenum of the tongue,—by hindering the readiness and ease of its motions, become causes of stammer- ing. Or it may be produced by the want or bad arrangement of several teeth. The same causes, but especially the length of the fraenum of the tcnguc, keep down this organ against the lower parietes of the mouth, and hinder its point from striking the an- terior 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. *^**4 l\Jttdl As for dumbness, it may be either accidental or/from birtry 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 ap- ply itself to the different parts of the parietes of tbe mouth and combine its motions with those of the lips, then the person be- comes 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 of the mouth are perfect in their conformation, and yet the child cannot attain to speech. Such is tbe case of a little boy of three years and a half old, who has been brought to me, to divide his fraenum 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 grams will be remembered, the letter of Rousseau on French music, and the littie work of D'Alembert on the liberty of Music. Marmontel too has made these disputes the subject of an unpublished Poem, un- der the name of Voyages de Polymnie. OF VOICE AND SPEECH. 457 middle line of the inferior surface. In other cases, the edges of the tongue adhere to ihe 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 ab- solute ignorance of sounds, and of their force represented by the letters of the alphabet; the organs of voice show no trace of inju- ry: they are well fitted for fulfilling the purposes to which they were allotted by nature: but they remain inactive 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 endeavor to imitate. His eye must be made to watch the motionst 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 jind dumb by birth, as has enabled them to utter words, and con- nected discourse. Even something of inflexion of strong and weaker tones has been taught them, by using the arm as a regula- tor, as pedals are employed to modify the touches of the piano- forte. But instruction to the deaf and dumb must be given them by another language. Written language they learn, not as represen- tative of speech, but as hieroglyphic 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 convenient and rapid representation of that hieroglyphic language of written charac- ters. 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. * This is the author's solution of the story, not Herodotus's state- ment, who says expressly the boy was dnmb. But the conjecture is ingenious, and shows a possibiUty in the story, which, as Herodotus 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 wh# are speaking. 59 458 OF VOICE AND SPEECH* To conclude this chapter, I have still to speak of a phenome- non, well worthy, by its singularity, of the attention of physiolo- gists. 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 dia- logue 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 bis 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 great- est care, this curious phenomenon in M. Fitz-James, who exhib- its it in the highest perfection, I have satisfied myself that tbe name of ventriloquism no ways suits it; since its whole mechan- ism consists in a slow, gradual, attenuated expiration, whether for that purpose the artist employ the power of the will upon the mus- cles of the parietes of the chest, or whether he holds the epiglot- tis, slightly lowered, by means of tbe root of the tongue, of which he scarcely brings the point beyond the dental arches. I find this long expiration always preceded by a strong inspira- tion, by means of which he introduces into his lungs a large quan- tity of air of which he afterwards husbands the use. Accord- ingly, repletion of the stomach is a great hindrance to the action of M. Fitz-James, by preventing tbe 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 different voices, make it seem that the speakers, in a dialogue, which be carries on by himself, stand at different distances, and produce 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 ON GENERATION. 559 parts. But what completes the illusion, and especially 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. It is easy to discern the value of such a talent in the days of oracles. i' ' . . ■■■ i .i1,", ims SECOND CLASS. FUNCTIONS SUBSERVIENT TO THE PRESERVATION OF THE SPECIES. 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 (he power of reproduction; these functions, destined to preserve tbe 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 inimitable model. In woman, sensibility, is also more exquisite; and with less strength, her mobility is greater. The female skeleton even is easily dis- tinguished from that of the male, by striking differences. The asperities of the bones are les9 prominent; the clavicle is less 4fJ0 ON GENERATION. curved, the chest shorter but more expanded, the sternum shorter but wider; the pelvis more capacious, the thigh bones more obli- que,*^. In a dissertation on physical beauty, read by Camper to the Academy of design, at Amsterdam, this celebrated physio- logist showed, that, in tracing the forms of tbe 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 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 organization and character be ascribed to the influence of tbe sexual organs upon tbe rest ofclhe body? Does the uterus impress on the sex all its characteristic modifications, and is it just to say with Vanbelmont: Propter solum uteium mulier est, id quod est; the uterus alone makes woman what she is. Though this viscus, very evidently, redacts on the whole system of the female, and seems to draw under its control nearly the whole of the actions and affections of woman, 1 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 sys- tem is far from having attained its full activity. A very singular fact, recorded by Professor Cailliot, in the second volume of the Memoirs of the Medical Society of Paris, proves better than all the reasoning in the world, bow much the character of the sex is independent of the influence of tbe uterus. A female was born and grew up with all the external 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, occupied the place of the vagina, and ler- minated in a cul de sac, and was about an inch in deptb. The most accurate examinations, by introducing the sound into the bladder, and the finger up the rectum, discovered nothing like the uteru?. 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. * Compare the beautiful plates of the male and female skeleton by Albinus and Scemmering. ON GENERATION. 46i The young woman had never been subject to the periodical eva- cuation which accompanies or precedes the time of puberty. No hemorrhage supplied the place of this excretion. Sie experienced none of the indispositions that are occasioned by the absence of menstiuation; she enjoyed, on the contrary, 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 nventy- 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 impor- tant object of life; it is almost the only destination to which na- ture 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 bis wants, he dispenses with the services of woman, in obtaining from it means of subsistence; he releases her from tlie burthen of social obligations. The Asiatic expects from the women he maintains in his seraglio, in a state of inactivity, nothing but pleasuies 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 withdraws woman from this primitive desti- nation; whatever diverts her from this end, it is to her injury; it is the scope of all her actions and habits; every thing, in her phy- sical organization, has evident reference to it. Of all the passions in woman, love has the greatest sway; it lias 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 fhem from those of men.* We will enter no further into the examination of the general differences which characterize the two sexes; no one has entered • Fonlenelle used to say of the devotion of some women: One may ice that love has been here, it has been said in speaking of St. Theresa: To love God is still to love. Thomas maintains that, with woman, a ■nan is more than a nation. Love is but an episode in the life of man; it is the '.vh-)!e history of the life of woman. (Madame de Stael.) 462 UN GENERATION. more deeply into this subject, or has treated it in a more inter- esting manner, than M. Roussel, in au excellent work, intitled Systeme physique, et moral de lafemme. 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 re- cord, no well authenticated case of such a combination; and all the iiermaphrodites that have been hitherto met with, were beings imperfectly formed; in wrhom 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: tbe greater number were incapable of reproduc- tion; 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 Memors oi 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~lhis, that the male and female organs being combined in the same individual. it is still singly not capable of generation, but is obliged to copu-; late with another being likewise an bermaphodite, so as to receive from friction and other means of irritation, 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 perpetu- ated. The same vegetable species containing sometimes male and female individuals, the sexes may be at considerable 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 U*es, on which Gleditscb made his first observations on the gene- ration of plants; hemp, spinage, mercurialis, &c. CXC1X. It is a distinction of the human species that, in them, ON GENERATION. 463 the functions of generation are not under the influence cf the sea- sons. Tue lower animals, on the contrary, draw together, and pair at stated periods of the ye.ir, and seem afterwards to forget the enjoyments of love, that they may attend to their other ne- cessities. Thus, wolves and foxes copulate in the middle of win- ter; deer in autumn, most birds in spring. Man alone seeks his partm i at all seasons of the year, and impregnates her under all latitudes and in all temperatures. This privilege is not so much the consequence of his peculiar constitution, as a result which he derives from his industry; protected by the shelters which he con- structs against the inclemency of the seasons, and the variations of the atmosphere; always capable 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 do- mestic animals which we have, in gr^at measure, removed from the influence of external causes, bring forth almost indiscriminate- ly, 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 sea- son, and thus, a greater number of insects depend on the heat of the weather for their powers of reproduction, and for their exis- tence. 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 say- ing that they differ only in their position, being external in man, and internal in woman There is, in fact, a considerable resem- blance between the ovaria and the testicles, the fallopian tubes and the vasa deferentia, the uterus and the vesiculae seminales, the vagina, the external organs of generation in woman, and the male penis. The former secrete the seminal fluid, and furnish, iu man or in woman, a matter essential 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 suffi- cient length of time; lastly, the vagina and penis serve to expel them. However striking such analogies may be, we are not jus- tified in inferring a perfect resemblance between the organs of lb'4 ON GENERATION. generation in the two sexes. Each of them fulfils, in the act of reproduction, functions perfectly distinct, though of reciprocal ne- cessity. The prolific fluid is secreted by tbe testicles; these organs arc two iu number, covered by several coats, one of which, covered bv the skin, and known under the name of scrotum, resembles a ba<> containing both these organs; it contracts on the application of cold, is relaxed by heat, and possesses a degree 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 membrane, affords an immediate covering to them, and reflecting itself over their surface, is dis- posed with regard to them, as the peritoneum with regard to tlit abdominal viscera, that is, it does not contain them, within its ca- vity. Lastly, the testicles are covered by a fibrous, white, thick and very consistent membrane; it is termed tunica albuginea, from the inner surface of which there arise a considerable number of membranous laminae, which, crossing one another, within its ca vity, form cells containing a yellowish vascular substance. This substance contained within the tunica albuginea, has so little con- sistence, 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 about ten or twelve lubes which unite in a cord situated within tbe tunica albuginea, called the corpus Highmorianum. 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 convo- luted on itself, becomes less and less tortuous, as it approaches the lower extremity of the testicle; there it bends back and as- cends under the name of vas deferens, along the spermatic cord. as far as the inguinal ring, by which it enters the abdominal cavity. The vasa deferentia, though of tbe 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, slender, and very tortuous vessels, arising from tbe aorta, at a very acute angh ON GLNERATION. 465 This fluid is filtered through the seminiferous tubes, passes into those of the corpus, Highmorianum, and thence into vassa de- ferentia, which, after they have entered the abdomen, terminate into the vesiculte seminales, and deposit into them the spermatic fluid. The delicacy of the organization of the testicle, the deli- cacy 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. 1'he spermatic fluid passes from the vasa deferentia into the vesiculae 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 tbe ductus, chole- dochus is pressed by the coats of the duodenum, contracted on itself when empty; the semen, because tbe duct along which it is conveyed, penetrating through the prosttate gland, and opening into the urethra, by a very narrow orifice, this fluid flows back more readily into the vesiculae seminales, than from tbe vas defe- rens into the ejaculatory duct. The vesiculae 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 mucus mem- brane 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 seminales, between the rectum, the levatores ani, and the posterior part of the blad- der, promotes the excretion of their contents (which is chiefly brought about by the contraction of their parietes,) by the com- pression 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 considerable time in a state of copulation, the prolific fluid necessary to impregnation having to be secreted during the time that the copulation lasts, and flow- ing in drops. The ducts formed by the union of the vesiculfe seminales with (he vasa deferentia, pass through the prostate gland, and open, by separate orifices, into the urethra, at the bottom of a lacuna, near tbe verumontanum. The glandular body in which they are inclosed, and which contains both the neck of the bladder and the beginning of the urethra, does not exist in women. The mucous and whitish fluid, secreted by the prostate, is conveyed 6*0 466 ON GENERATION. 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 tbe 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 tbe 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 convey the prolific fluid into the female organs of generation, must be in a state of erec- tion to perform this function completely. Erection being a phe- nomenon of structure, that of the penis will be considered after the description of the female organs of generation. CCII. ()j the female organs of generation. I shall not adopt the anatomical arrangement generally followed in this description, but classing in three divisions, the different parts which, in wo- men, are subse vient to the genital functions, I shall speak first of the ovaria and fallopian tubes, then of the uterus, and in tbe 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 lat- ter, but are somewhat smaller. Do tbe ovaria secrete a fluid, which, by mixing with ;he male semen, produces the new being, or is there detached from them, at the moment of conception, an ovum which tbe semen vivifies? Whatever opinion is adopted, one is compelled 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 tbe 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 Ihe uterus. The external orifice of the fallopian tube, called corpus fimbriatum, has been found grasping thus the ovarium, in females opened immediately after coition. It may happen, from a mal- formation of the parts, that the fallopian tube may not be able to apply itself to the ovarium; I dissected at the Hospital de la Charitee", the body of a woman who had been barren; and found the corpefa fimbriata, or the expanded termination of the fallopian tubes, adhering to the lateral parietes of the pelvis, so that it OS-GENERATION. 467 was impossible they should perform the motions required for im- pregnation. The uterus, lying in the pelvis, between the rectum and blad- der, is a hollow viscus, in which the foetus grows till the period of birlh. Its internal part has been found separated into two cavities, opening, iu some cases, in the same vagina, and, at others, terminating in a vagina that was double, only in the im- mediate vicinity of the uterus. Valisnieri mentions the case of a woman who had a double uterus, the one opening in the vagina, and the other communicating with the rectum. Though the muscularity of the parietes of the uterus becomes manifest, in pro- portion as this or^an enlarges, during the progress of pregnancy, this hollow muscle may be said to differ from other muscular organs, by the arrangement of its fibres, which it is difficult to discover while its cavity is empty, and which it is even impossi- ble completely to unravel, while it contains the foetus; its most remarkable distinguishing character, is its singular property 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 spongy body, whose cells fill with blood and expel it, like the corpora cavernosa of tbe penis and clitoris. Il is ealled plexus retiforme; its turgescence, during erection, con- tracts the orifice of the vagint; the contraction of the constrictor muscle, which answers the purpose of the accelerator urinse in man, and which lies over this plexus retiforme, surrounds like it, the entrance of the vagina, and may, in the same manner, con- tract 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 bieadth, generally semicircular, raid called the hymen. Its exis- tence 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 equivocal.* The relaxed'stale of the parts, from a great quantity of mucus, in a woman subject to the fluor albus, or from the blood of the men- strual discharge, may make the bymen yield and not rupture, so that a woman might seem a virgin without being such; while hiioiiicr woman who has not lost her virginity, might, from illness, * "AtLuicii prima vcnus debut esse crueuta."— Haller. 46b ON GENERATION. have her hymen destroyed. There are in the last place, persons in whom the hymen is so indistinct, that several anatomists have doubted its existence. 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 utility. The folds of skin which form the labia and the nymphae, yield, during the delivery of the foetus. These duplicatures not only unfold themselves, but likewise undergo a degree of exten- sion, their tissue being moister, softer, and more extensible than thai of the skin. The mons veneris, the hairs which cover it, the clitoris which resembles an imperfect penis, seem merely or- gans of voluptuousness; but is not pleasure itself an element in the act by which the human species is reproduced? CC1II. Of conception. When a chemical, mechanical, or men- tal irritation excites the action of the genital organs, the penis elongates itself, becomes turgid and stiff, from the accumulation of blood within the cells of the corpus cavunosum, and within those of the corpus spongiosum of the urethra.* The turgescence of these two parts of the penis should be simultaneous, to render tbe erection complete. It has been thought that this phenomenon might be accounted for, by the compression of the pudic veins. which are situated between tbe symphysis pubis and the root of the penis, which, as long as the erection lasts, is compressed against the bone by tbe erector muscles. But far from elevating the penis, the muscles of the perineum, especially the ischio ca- verrois (erectoris penis,) tend to depress it. The blood which distends the corpora cavernosa of the penis, and the corpus spon- giosum of the urethra and glans, which is itself the expanded ex- tremity of the urethra, does hot stagnate in their cells, only there is a greater quantity of blood in them than usual; the irritation increasing, in a remarkable 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 brought into a state of erection, being put on the stretch by the * " Penis adest, ita constructs, ut stimulo corporeo sive menta'i ir- ritatus, turgeat et obrigescat, seque erigat, postca detumescat, et col- labatur "—Creve. f The animal heat is somewhat augmented, during erection, as well as in inflammation. The temperature of the blossoms of the arum rises several degrees above that of the atmosphere, at the moment of impregnation. ON GENERATION. 469 penis which is elongated, ils curves are straightened, the irritation is propagated from the external to the internal parts, to the vesi- culae seminales and the testicles. These swell, and their secretion is increased as they receive a gentle degree of motion from the action of the scrotum,nvbich becomes wrinkled and draws them up towards the abdomen, and by the action of the cremaster muscle, whose expansion forms between the tunica vaginalis and thedartos, what has been improperly called the tunica erythroidea: they emp- ty themselves with the greater ease along the vasa deferentia, which decrease in length as the testicles rise, and which partici- pate in the concussion affecting these organs. The concussions of the cremaster on the testicle, or on tbe vnsu deferentia, pre mote, in so important a manner, the secrelion and excretion of the semerij 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 Hun- ter in ihe hedge-hog and the ram. This fact of comparative anatomy shows, that the cremaster is cf use, not merely in suspend- ing the testicles as its name indicates, since in the animals above mentioned, they return into the abdomen 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 cavity, and they expel it by the spasmodic contraction of their membra- nous parietes, assisted, in this excretion, by the levatoris ani. (CCI.) The prostrate 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 purity, that is, such as it is prepared by the testicles; it is even conjec- tured, that the mucous fluid of the vesiculae seminales forms the greater part of jt. It is this mucus which eunuchs emit in con- siderable quantity. The fluid secreted by the prostate gland and by the mucous glands of the urethra, affect it, likewise, by uniting with it. 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 c'ots, 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 semen is more fre- quently 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 analyzed by M. Vauque- 470 ON GENERATION. lin, it was found to contain: of water 91* centimes—of aminal mucilage 6—phosphate of lime 3—soda 1. It is i » consequence of this last alkali, thai it is enabled to turn syrup of violents to a green colour. The animal mucilage is not pure albumine, but rather a gelatinous mucus, on vvbich 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 bead, a tapering tail, and moving with rapidity- Is the liquefaction of the glutinous and viscid parts of the semen, owing to the motion of these crea- tures? These microscopic animalcules are to be detected in the semen, only at the period of puberty, ll has been thought that they shunned the light; authors have even gone the length of de- scribing 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 explanations 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 par- ticipates 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 phy- sical lassitude is attended with a sensation of sadness which is not without enjoyment. Does this peculiar sensation, which, accord- ing 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 imagined, 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 tinea) offers too small a slit, and its thick edges are besides in contact. It would be difficult to conceive tlutt this strait pas- sage should admit even the seminal fluid, it it were not known, (lift in the moment of copulation, the uterus, from irritation, draws together, and inhales, by real suction, the semen which it craves. Plalo compared this organ to an animal living vu'.liin another ani- mal, controlling ali the actions of the living tconomy, burning to QN GENERATION. 471 sate itself with the liquor of the male, and digesting it to form a new individual. The great thickness of tie 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 th:d it was not this fluid itself that penetrated into the cavity of tbe uterus, but the subtlest of its parts, the most spiritualized, a prolific vapour, 1o which they have giv^n the name of aura semi- nalii; hut, besides that the semen has been found in the uterus, in animals opened immediately after copulation, Spallanzani, in his experiments on the fecundation of frogs, of salamanders, and toads, peiv..-i\ed that, to enable the eggs to produce, it was not enough to expose them to the vapour which rises from the seminal fluid of !h-' nvile; and that nothing was effected, unless ihe fluid semen aciinily touched them, though in ever so small a quantity. It b:is 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 preserve enough sing-froid to make observations in that situation, was the most undoubted sign that could be had of the success of the copu- lation. It is, no doubt, to insure this retention, that it is custo- mary to throw cold water on the females of some domestic ani- mais, when they go too eagerly to the male. The spasms of the skin, occasioned by the cold striking it, affects the uterus, and hinders the flowing back of the semen which has been thrown into its cavity. Ii 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, passes along the fdlopian 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, leis a fluid escape, or perhaps a little ovum, which passes into the uterus, the same way that the semen reached itself.* All * The account here given of the fecundation of the ovum, seems to us exceeding erroneous, and as this is a point of some interest, we will not too has:]) dismiss it. It is our intention, first, to show that the semen does not enter the cavity of th^ 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 472 OX GENERATION. that remains to be said, concerning the mechanism of generation, must not be delivered as real, but merely as probable, such is the darkness with which, nature has chosen to envelop this great mys- tery of the living economy. After distinguishing the true from the probable, an indispen- sable duty in every science of facts and observations like phy- some otlier modes have been suggested, but they are really so ridiculous, as to be wholly unworthy of criticism. That the male organ is endowed with a considerable projectile power, cannot be denied. It is very conspicuously evinced, by the impetus with which the urine is discharged. When engaged, however, in the art of coition, its capacity in this respect, is greatly diminished, or wholly suspended by the firmness with which it is embrassed. Grasped by the vagina, its ejaculatory muscles are crippled in their energies, and become passive. We see too, in the spissitude and tenacity of the se- men, an additional cause of resistance. 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. Tlie rugae 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 pro- jected as far as the uterus how couid 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 malts, and is not placed in the immediate axis of the vagina, but is inclined more or less to the one or the other side, or towards the sacrum. The ap ertures of the two organs, therefore, are not in apposition. But this is not all. The os tincse is for the most part fdled with a thick glutinous matter, capable of considerable resistance. Where it is wanting, as is generally the case in the virgin uterus, the hard, unyielding lips of the tine* 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 unini- pregnatcd state of the organ, probably not larger than a common size probe. That portion of the canal called the straight, is still more con- tracted. Besides, along the whole course of the canal, there are stria;, or wrinkles, and between which, glands, secreting mucus obviously calculated for the purpose of additional obstruction. Even the proper cavity of the uterus itself, is so extremely shallow that its two surfaces are nearly in contract. Such are the impediments incident to a perfectly natural and healthy condition 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 abridg- ed by 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 membranes of adventitious growth, or by tumors. 3. The os tinea is sometimes discovered impervious, either from ori- ginal imperfection, or by the process of inflammation, and is occasional- ON GENERATION. 473 siology, I shall proceed to state the hypothesis which appears to me the likeliest on the manner in which the two sexes concur in the production of the new being. ly rendered utterly inaccessible to the semen, by the obliquities, retro- versions, 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 almost 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 them- selves 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 Harvey, De Graaf. Luenhoeck, Haller, and Ilaighton. Different animals were the subjects of these experiments. The doe, the cow, the ass, the ewe, the bitch, the rabbit, were all in- spected immediately, or at remoter periods, after connexion with the male, and never except in one instance, could the semen be traced beyond the vagina. 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 observations both of himself and others and which can claim little consideration, especially when it is known, that such a result was essentially necessary to the mainten- ance 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 ob- servations have never been confirmed, and that under the circum- stances in which they were made, it is reduced almost to a moral cer- tainty that they mistook for semen what was in reality the mucus of the parts. But, conceding to these alleged facts all that can reasona- bly be required, what do they amount to? Contrasted with the vast mass of counter evidence, they dwindle into insignificance and will not weigh as the dust in the scale. It appearing, therefore, that the semen does not enter the uterus, it becomes superfluous to inquire respecting the practicability of its con- veyance by the fallopian tubes. The latter problem is merged in the former. But to silence all cavils, we will give the question a cursory •xamination. That the fallopian tubes are not subservient to this purpose, is very distinctly 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 pa- tulous 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 * Each of the above positions is supported by cases to be found in the writings of Harvey, Morgagni, Hildanus, Ruysh, Mauriceau, Simpson. GuiHemeau, Haller, and in the periodical journals. 61 474 ON GENERATION. CCV. The foetuses pre-exist in tbe ovaria of the females, not that they are there since the creation of the world, as Bonnet believed, and all who embraced the doctrine of that metaphysical 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 tbe lineaments of the new being: but it is only the sketch, or 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 ori- fice is fashioned accordingly. By assigning to the tube this function, we moreover invest it with the power of a tw o-fold action, precisely opposite, of which there is no an- alogy 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 ef- fect of violence and disease. It is useless, however, to protract this dis cussion, 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 whole process of conception is consummated in the ovary. "I found," says this eminent physiologist, "from a series of observa- tions made on different rabbits, at every hour between the 1st and 9th, that the fimbria 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 impregna- tion, and there appeared to be no action in the tubes, by which the se- men could be conveyed to them." Convinced that the hypothesis in its primitive shape was no longer tenable, some of the advocates of impregnation by contact, have con- tended that it is effected by the emission of subtle expalation from the semen, termed aura seminalis, and which is transmitted through the tubes to the ovary. But here they are again met by the whole body of facts, and chain of reasoning which drove them from their original po- sition. It has indeed been said, and with no want of plausibility, that the volatile vapours from the semen might penetrate through obstruc- tions which would resist the semen itself. Be it so: in many 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 amend- ed hypothesis. We are not disposed, however, to enter at present in- to any further 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 fecundation. As yet, no such proof has been exhibited. The experiments of Spallanzani, and Hunter, the only ones which have been made on the subject, prove indeed quite the contrary.—Ed. ON GENERATION. 475 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. inactivity, and with something of an electrical power waken it into life. The eggs laid by a maiden ben, 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 prevented, and themselves animated, by shedding on them the spermatic fluid, obtained by the process employed by Spallanzani, in his admirable experiments on arti- ficial 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 bis part is the least essential. It is not so difficult as may be imagined, to explain upon this system the striking resemblances which are frequently seen between fathers and sons. The imperceptible embryo has, at most, the consistency of slightly viscous glue. Such a body must be ex- ceedingly 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 tbe deeper, the resemblance the more striking, according to the spirit and energy with which the male performed the act of re- production. 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 inward changes. It is thus that we are able to explain, not only hereditary likeness, but also hereditary diseases. Nevertheless, it does ap- pear, 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, the mule resem- bles the sire outwardly, and the dam within. It is difficult to show good reason for the want of the generative faculty in mules. Why are their sexual parts, so well developed, altogether barren?— What secret defect frustrates their action? And why do certain mules, among birds, propagate; and in the same manner, hybrid plants, which are real mules, and not quadrupeds? 476 ON GENERATION. The impregnation of the ovum is effected in the ovariuai 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, de- taches itself from the organ which has produced it, and descends into tbe uterus, by the peristalic contractions of the fallopian tube. This canal is susceptible of a retrograde motion. It maybe con- ceived, by considering that having stretched itself by a real erec- tion to convey the semen to the ovarium, it must, in its return upon itself, cause a flow of the fluid its cavity contains, in a com- pletely inverted direction. This retrograde motion, as Nisbet ob- serves, is assisted by a sort of collapse succeeding the excitation which coition had produced: for, the experiments of Darwin prove that the weakness of the vessels is the cause of this mode of ac- tion in their parietes. Spungy as the urethra of man, the fallo- pian tube brings back the ovum, from the ovarium to the uterus. The extra-uterine fostations afford the proof, that matters are car- ried 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. Tbe ovaria, like the testicles, swell and enlarge at the time of * In extra-uterine abdominal conceptions, the ovum which the tube could not hold, or seize, rolls into the hypogastric region, and there adheres to some point of the peritoneum. It is found attached to the mesentery, ta the colon, to the rectum, to the external part of the uter- us, growing there, and developed, by the vascular communication which takes place at the adhesion: but the vessels of the peritoneum are in- sufficient for the entire development of the foetus, which dies for want of nourishment, in the first months of pregnancy. The adhesion of the ovum to the peritoneum, is easily accounted for, by the irritation it oc- casions: it may be considered as a foreign body, determining, by its pre- sence, inflammation of the membrane with which it lies in contact, and uniting with it, because it brings to this act its own share of vitality. 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 pul- monalis, and the pleura costalis, 8cc. 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, their vessels never develope themselves sufficiently to trans- mit to the ovum, which has adhered to them, a due supply of this fluid. The mucous membranes receiving more blood, are able to supply more: but the 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 communisation there is between the two kinds of membranes. ON GENERATION. 477 puberty. They shrink, and wither in some sort, when the woman is no longer tit for conception. On examination, a few days after r onception, one of the ovaria, larger than the other, shows a lit- tle yellowish vesicle, which dries up in the course of pregnancv, so that, towards the end, there remains nothing in its place, but a very small cicairix. Is this vesicule the outermost covering of the ovum, in which the germ is enclosed, and which is torn to al- low its escape? The observation of Haller prove that the corpus luteum is formed by the remains |of a vesicle that 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. Inflamma- tion comes on in the torn coats of the small vesicle, fleshy granu- lations appear, then sink, and a scar shows the place where it had been. The number of these cicatrices is proportioned to that of the foetuses. It is not known how long the germ detached fiom 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 distinctly in this viscus, before the seventeenth day. The obstruction of the tubes may, as well as the defect or dis- eased 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 parieties; the consequence, evidently of the habitual orgasm in tvhich they had been kept, by too frequent excitation. The structure of these parietes must make obstruction of the fallopian tubes very easy. Their tissue is spongy, vascular, and seems susceptible 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 mucous membrane, within the uterus) par- takes in the inflammation of both. I have often been consulted by young women on the cause of their sterility; by a close investiga- tion 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, afterobsti- nate suppression of the menses, exhibited all the symptoms of in- flammation of the peritoneum: a year afterwards she married; but never became pregnant. A woman recovered from pueperal fever ensuing from very difficult first labour; from that time, with all the appearances of the stoutest health, she has never been again a mother. Do tbe two testicles and the two ovaria, contain the seperate 478 ON GENERATION. germs of males and females? Are these, as has been guessed, co»- tained in the left ovarium, and males in the right? and may we procreate sexes at pleasure, by varying the attitude of copulation? This old opinion, lately revived, besides wanting all foundation, is formally confuted by facts: nothing is more common than to see men who have, from some accident, lost a testicle, procreating sexes indifferently. Women, with an ovarium deficient, or the fallopian tube obliterated on one side, have produced both boys and girls. Dr. .ladelot 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 mix- ture of the semen in the cavity of the uterus, set forth in the writings of Hippocrates and Galen, is still that of many physio- logists. 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 his hypothesis requires, and displayed its improbability. Each part, he says, furnishes molecules, which he calls organic, 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 tbe 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 ex- planation of the production of the placenta, and of the membranes covering the foetus: is is moreover directly disproved by the good conformation of children, born of parents, who not happening to have certain organs and limbs, could not certainly supply the pro- per molecules for their formation in the child. The system of the ovarists, which at this time stands highest in favour, numbers amongst its supporters, Harvey, Stenon, Mal- * All that Blnmenbach has said, on the force of formation, (nisus formative) applies to this generative faculty; it is only anew name given to an iold dea. ON GENERATION. 470 pighi, Valisnieri, Duhamel, Nuck, Littre, Swammerdam, Haller, Spallanzani, Bonnet, &c. 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, Harstoeker, Boerhaave, Mery, Werheyen, Covvper, &c have added to the opinion of the ovarists, that the seeds of the male contains a multitude of spermatic animalcules, all capable of becoming, by developement, beings similar to their father. These animalcules push forwards, along the tubes, upon the ovaria; there a general engagement takes place, in which all are slain, save only one, who, master of the field of battle, finds the triumph of his victory within the ovum that has been prepared for him. This system, which is not the most propable in the world, assigns to the male the greater part in the work of genera- tion, since the female is made to furnish merely the covering of 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 ob- served, that we have never so much to say, as when we set out from false principles.* CCVII. Of gestation. From the moment of conception, there begins in woman, both in the motion of the solids, aud the com- position of the fluids, a remarkable alteration. The change that has taken place shows itself in all her functions: she exhales a peculiar odour; the child she suckles refuses the breast, or takes it with reluctance, and soon falls away, if left in the hands of such a nurse. * Numerous as are the theories which have been advanced on the subject of generation, they may all, as mere varieties, (or at least such as are worthy of attention), be very properly reduced under two lead- ing heads or general divisions. 1. Doctrine of Palengenisis. 2. Doctrine of Epigenisis. The first of these doctrines suppose the pre-existence of germs. It is of great antiquity, and in its descent to us has undergone some slight modifications. By most of the early philosophers it was taught, "That these germs created with the beginning of things, were scattered throughout the world, but ultimately meeting with appropriate genital organs, effected a lodgment therein, and became fit for developement." As soon, however, as the moderns entered-into speculations of this nature, the hypothesis received a correction which, in part, divested it of its absurdity. Denying that these germs wandered about "in quest 480 ON GENERATION. Nature occupied over her work, seems to forget every thing else to bring it to perfection. It has been observed, that in time, of contagious diseases, even where the plague raged, pregnant women were least exposed to infection: but, at the same time, when tbey are seized with affections, which in other persons or at another season, would be without danger, they sink under them, because their diseases, though at first very slight, easily put on a malignant character. The progresss of mortal diseases is of an habitation and a home," it was now, nn the contrary, maintain- ed, "That all of the same species, were ab initio neatly incased, ont within another, so that the first parent, animal and vegetable, contain- ed 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, who urged their respective opinion^ with all the zeal, all the ar- dour, and all the pertinacity of party controversialists. They differ- ed, however, only on a single point. By the one side it was maintained, that the germs were furnished 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 as- certained as he thought, by a series of experiments on the egg, that it contained a preexisting embryon, he, with a numerous train of disci- ples, pushed their investigations, and finally detected, or pretended to detect, ova also in the viviparous animals. Enamoured" of this boasted discovery, the celebrated Harvey be- came one of the wannest and most strenuous supporters of the hypo- thesis to which it led. "Omnia ex ova." This brief aphorism, which escaped from him in the enthusiam ot his devotion, sufficiently marks his impressions on the subject. The only distinction, indeed, which he admits in the generative process of the two classes of animals, is, "That in the viviparous, the foetus be- gins to exist, increases, and completes its growth in the uterus; where- as, in the oviparous, the embryo exists in the egg in the body of the hen, but does not become a foetus till expelled, and is hatched into life by incubation." The ovular doctrine was first arranged by Luenhoeck, who made the pretended discovery of the spermatic animalcules in the male seed. By hiin and 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 ve- sicles of the ovary, which have no rescmblence to an egg, being mere- ly cup* 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 impregnation nothing like a germ could be found even in the real egg, but that there is placed on the vi- tellus, a small vesicle, the cicatricula, 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 the former has a single, while the latter has a cluster of vesicles. ON GENERATION. 481 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 Ky this doctrine of spermatic worms, which completely usurped the place of the ovular doctrine, and which acquired for a time an undisputed ascendency in the medical and philosophical schools, it was affirmed, that these seminal vermiculi are living miniatures of the animal from which they are derived, exacting only from the female a matrix for nourishment, evolu- tion and growth. Though the ovular doctrine was thus subverted by Luenhoeck and his auxiliaries, it after a while again revived, under the auspices of Hdler, so far atjeast, as to suppose the pre existence of a germ in the female, and soon receiTed the distinguished support of Bonnet, Spallanzani, Hunter, &c. Being restored in a more enlightened age, :l of c mrse 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 existence and de- velopment of the germs. Th«y all, however, maintained, " that the germ, as the exact miniature of the. animal or vegetable to which it belongs, exists in the female prior to fecundation, requiring only the stimulus of the male seed »o excite it into life," &c fee. By thus narrowing the definition of the doctrine, they presented it in a guise exceeding alluringly, 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 alarge number of distinguished physiologists have been induced, upon the most diligent scrutinies, to question altogether the pre- existence of germs. It would he wholly inconsistent with our limits to de- tail the arguments and reasonings which have been employed by the adverse parties in this interesting controversy \\ e proceed next, therefore, to the doctrine of Epigenisis Discarding, as we have already hinted, the notion of the pre-existence of germs, it presumes that " the prepared, but at the same time unorganized rudiments of fhe foetus fiist begin to be gradually organized when they ar- rive at tlu-ir place of destination, at a due time, and unuer the necessary cir- cumstances " This is the i efinition 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 matter which, after impregnation, becomes organized into an embryon by the ener- gies of the semen mascuiinum The primary traces of thi-doctrine are to Be met with in the writings of Aristotle. The prevailing opinion on the sub- ject of generation, in the time of this emine t philosopher was, that each sex furnishes semen, and that the embryon results from an admixture of the two fluids in the cavity . f the uterus. After confuting the popular idea of women having semen, he asserted that they contribute nothing towards con- ception, except the menstrual blood- that the rudiments of the embryon are derived from the menses, and are vivified and put together by a plastic pow- er, which he imputed to the semen With v 4Ui U.N i.i'.NI'.UATlOX. jiainful. Some days after he voided by stool, purulent, and fnu! matters; at the end of three months, he became wasted by maras- mus, he passed, by stool, a ball of hairs, and, in tbe course of 3 few weeks, died of consumption On opening his body, there was found, in a cavity in contact with the transverse arch of tbe colon, and communicating with it, some balls of hair and an organized mass. The cyst situated in the transverse mesocolon, near the colon, and externally to the di- gestive canal, communicated with the intestine. But this com- munication was recent and accidental, and one could plainly see the remains of the septum between these cavities. The organi- zed mass presented, in its forms, a great number of features of resemblance with the human fcetus, and, on dissection, no doubt could be entertained of its nature. There was discovered in it the trace of some of tbe organs of sense, a brain, a spinal marrow, very large nerves, muscles converted into a sort of fibrous matter, a skeleton consisting of a vertrebral column, a head and pelvis, and limbs in an imperfect state; lastly, a very short umbilical cord at- tached to the transverse mesocolon, at the outer part of the intes- tine, an artery and vein, ramifying at each of their extremities, where they were in contact with the fcetus and with the individual which contained it. This much is sufficient to establish the dis- tinct existence, as an individual, of this organized mass, though, in other respects, destitute of organs of digestion, of respiration, of the secretion of urine, and of generation. The absence, how- ever, of a great number of the organs necessary to the mainte- nance of life, should make ij be considered as one of those mon- strous foetuses, not destined to live beyond the moment of birth. This foetus was evidently contemporary with the boy to whose bo- dy it was attached. Similar to the product of exira-uterine con- ceptions, it received its nourishment from that which may be con- sidered 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 fcetus, returned after-. wards to the mesocolon of the boy who had so long been to bim as 3 mother. At last, the period fixed by nature for expulsion, be- ?ng arrived, and this expulsion being impracticable, the cyst be- came it.fiamed; the inflammation extended to the intestine, the part which separated these two cavities was destroyed, and the cyst opened into the colon; pus and hairs was voided by stool, and the patient died cf marasmus. The drawings of different parts of ON GENERATION. 495 riie body of this fcetus, taken by M. Cuvier and M. Jadelot, ren- der this interesting case most complete. They will be published in the first volume of the transactions of the Academical Society, near the faculty of Medicine at Paris.* We ought not to be too ready to place implicit coufidence in tbe extraordinary stories contained in tbe older writers, and even in some of the moderns. In reading the periodical publications of the seventeenth, and even of the eighteenth century, one is apt to wonder at the marvellous things which they contain. Among other strange, cases, is that of a girl that was born with a pig1* 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 prodigies in nature. CCXIV. Of the coverings of the fcetus. 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 fcetus, is formed by two membranes 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 secretory organ of the fluid which fills the ovum, is called the amnion. The third enveloped, admitted by Hunter, and called by that physiologist, tbe membrana decidua, is nothing more than the lanuginous tissue presented by the external part of the chorion, after tearing the multitude of cellular and vascular filaments 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 placenta, because it is there that the communication of the fcetus with tbe mother is established. The liquor amnii is a serous fluid, of a sweetish odour, of in- sipid 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, mu- riate of soda and phosphate of lime, discovered in it by MM. Buniva and Vauquelin, forming only 0,012 of the whole mass. It ♦ Mr, Young, of London, has communicated a case of the same kind, in a valuable paper inserted in the first volume of the Medico-Chirur- gical Transactions. In Mr. Young's case, the fcetus 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 organs and external organs of geueration.—Se** vol. 1st of the Medico-Chtrurpca! Transactions. T. t\ 496 ON GENERATION. turns of a green colour, tincture of violets, and reddens 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 separate stale. 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 tlie 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 proportion to the size of the fcetus, according as the latter is nearer the period of its formation. It is the product of arterial exhalation. Its materials are supplied by the blood conveyed by the 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 regi- men of the mother. In a woman who bad used mercurial friction, in the course of her pregnancy, the liquor amnii was observed to whiten copper. Thp fundus of the bladder in quadrupeds, is continous 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 fcetus 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 smallbore, in the part nearest the fundus of the bladoVer. The existance of these parts furnishes an additional proof of what was stated in speaking of the uses of the valve of the caecum, viz. that there are in the animal body, organs which answer no purpose, and which merely indicate the plan which nature has followed in the reproduction of beings, and tbe gra- ditions which she has uniformly observed in the divisions of the species; CCXV. Of the natural term of gestation. The fcetus may ex- ist without the maternal influence, when arrived at the period of seven or eight months from the instant of conception. All ac- coucheurs agree that it may be delivered alive at this period, and that it stays two months longer in the uterus,oniy that it may gain more strength, and be better fitted to resist the new impressions ON GENERATION. 497 which it is to experience on coming into the world. A child, however, has been known to live, though born 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 period; 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 Hnay prove afterwards, are very feeble when born, 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 fcetus 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 therefore 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. CCXV'I. Of parturition. When the foetus has remained suffi- ciently 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 enclosed 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 determine the com- ing on of labour; according to some, Fabrieius of Aquapendente for instance, it is the want of fresh air, which makes the foetus rupture its membranes; according to others, the foetus is determin- ed 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 fcetus was urged to it by the want of food, or that labour depends on the reaction of the fibres of tbe uterus, which distended beyond 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, atnd is the only one that is at present in any esteem, how conies it, that in a woman, whose uterus is of a de- terminate size, labour does not come on when they are twins, at the end of four months and a half, by which period the same degree of distention would be produced, as by one child at the full time? 49S ON GENERATION. It is very true, that for a fortnight, and even sometimes for a for a month before labour, the uterus seems to be preparing for the expulsion of the fcetus. 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 con- taining 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, readies a period at which it may exist, separated from the mother. When this period is arrived, the ovum in which it is contained, detaches itself from the uterus, by a mechanism, in every respect similar te that, by which the stalk of a ripe fruit drops from the bough or which it hung. Then, in all probability the foetus refuses to ad- mit the blood sent to it by the umbilical vein. The placenta be- comes affected with congestion; this stagnation of the fluids ex- tends gradually to the uterus, and to the neighbouring parts. Stim- ulated by their-presence, these organs are called into action, the woman feels wandering, irregular pains, similar to colic pains, which become more acute, are attented with a feeling of con- striction, 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 become more acute and frequent; ihe face red, the pulse full and frequent, the whole body seems to partake in the affection of the uterus, and is agitated with convulsive motions. The membranes, filled with the waters, force themselves like a wedge through the mouth of the uterus, whose edges are much weakened; the throes of labour increase 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 are violently compressed by the head of thefcetus; 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 a"i- rected backward towards one of the sacroiliac 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 dia- meter, which is from the fore to the back part. The bead de- ON GENERATION. *99 scends through tbe vagina, appears outwardly, soon disengages it- self, and is followed by the shoulders and the rest of tbe 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 fcetus 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 going 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 re- duced 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 relaxed towards the end of preg- nancy. During the progress of pregnancy, the fluids of the mother flow in every direction towards 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 between which they are placed. Hence, being softened and swollen, they do not force them asunder like a wedge, by in- creasing the diameters, but facilitate the separation of the bones, by the passage of the head through the pelvis. It is on the re- laxation of tbe 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 Le- roy. Analogy led very naturally to this operation, as is judicious- ly 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 tbe motion on one another of the osseous parts of the skull of the fat us, and of the pelvis of the mother; her care extends to tbe soft parts of the latter; these are soaked in mucus, so as to relax their tissue several days before parturition, and are so disposed, as was already observed (CCI,) that they may, 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 fcetus, it is customary to sepa- rate them by dividing the umbilical cord near the navel. It is uilnecessary to tie this cord, at the part near tbe mother, every communication being intercepted between the placenta and the uterus, so that no blood could flow but that of the placenta. Not 500 ON GENERATION. so, however, with the part nearest the fcetus; though the chauges which take place in the circulation, at the moment when the chest is dilated, and allows the air to distend the pulmonary tissue, di- vert the blood from the umbilical vessel; 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 t'1 bility. The human ovum is very seldom detached entire, and never so without considerable danger; that is, the fcetus 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 approx- imation of its sides; this organ contracted on itself, sinks behind the pubis, its cervix closes and this even impedes the delivery of the after-birth, when the latter is protracted too long. The pa- rietes 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 direc- ted by any irritation, and they flow towards the mammary glands. to supply the secretion of the fluid which is to nourish tbe new born child. CCXVIII. Of twins. Though in the human subject the off- spring is generally single, it is not uncommon for a woman to bring forth two children at once; it bas been even 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 chil- dren 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 chil- dren 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 having been born at a birth; Haller, therefore is guilty of exaggeration 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, terminating sometimes in a separate, and sometimes in a single placenta. Both foetuses are enveloped ON GENERATION. 501 in one chorion, but each has a distinct 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 cicatriculae, both in the same ovarium, or one in each. Twins are, generally, very like one other in features, and dispositions. The multiplicity of foetuses in the same pregnancy, is occasioned by the presence of several vesiculae, ready to be detached from the ovaria, and consequently ripe for fecundation. This multiplicity of offspring contributes very little to increase population, for they are, in general, less robust and strong, and not so capable of re- production; they, besides, exhaust the strength of the mother, and their birth is often fatal to her. The number of children which a woman might bring into the world, from the period of puberty to the cessation of the menstrual discharge, would be mm b 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 hun- dred and five survived her. It is now well known, that the number of male children who are born, exceeds in general, that of ihe females. The difference, in some countries, is estimated at one in twenty-one, at a four- teenth, a twelfth, and sometimes, though rarely, at a third. In all countries of ihe world, polygamy is therefore in direct opposi- tion to ihe intentions of nature, and to the multiplication of the species; this is proved in a most undeniable manner, by the loss of population in those countries in which this practice exists. The boys, more numerous than the girls during the early part of life, exposed afterwards to the dangers of war, of navigation, and oc- cupied in laborious occupations, lead a more laborious and anxious life, and die in greater numbers, so that the equilibrium is soon restored, and the least numerous portion of the human species at the cradle, forms about two thirds of it in old age, since we always see more women than men reach a very advanced age. CCXIX. Of superfcetations. The cases of foetuses born with unequal degrees of developement, are not to be considered, as su- perfcetations, but as twin cases. Thus, if in a case of twins, one fcetus is of its full size, while the other is an embryo whose size does not exceed that of a fcetus in the first month; it does not fol- low that their conception took place at different and distant pe- riods, but merely that for some reason or other, one of tbe germs has been incapable of growth and developement. To settle the question of superfoetations, one should know whe- ther a woman, with a single uterus, is capable of conceiving, two 502 OX GENERATION. months after effective copulation. Haller is of opinion, that tbe 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 se- parated by a short interval; thus, the American woman mentioned by Buffon, who, in the course of one morning, had connexion with her husband and with a negro slave, bore two children of diffe- rent 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 pos- sibility of such superfcetations is well proved; they are ascribed to septa, dividing the uterus, sometimes into two cavities, merely be- cause such an arrangement would explain, to a certain degree, how two conceptions might take place, at some interval from one an- other; for it has never been ascertained, by actual dissection, that any woman, in whom such superfcetations took place, had a double uterus.* * It seems to me, that a belief in superfcetations can hardly be en- tertained 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 tinea, as well as the internal apertures of the fallopian tubes, are closed by a deposition of a thick tenacious mucus. But to accomplish still more perfectly an end so important 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 bloody a membrane of some firmness of texure 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 al- ready 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 impediments arises to the frustration of a second conception. In this state of the organ, it is accurately ascertained, that the tubes lie parallel t° its sides, and subsequently in the progress of gestation, be- come bound in tbe same situation, instead of running in a transverse direction towards the ovaries, with their extremities loose and fluctua- ting. Were an embryon, therefore, to be generated by any anomalous combination of circumstances, the tubes could not possibly embrace the fecundated vesicle, and the embryon, of course, must remain in the nary, or fall into the abdomen, constituting an extra uterine concep- 'ion. * HaUer. | Dr. Hunter. % Mr. Hunter. ON GENERATION. 503 CCXX. Of suckling. Nothing is more generally known in phy- siology, than the strict sympathy which subsists between the ute- rus and mammae; a connexion, in consequence of which, these two organs are called into action at the same period of life, are evol- Lct us, however, withdraw all the obstacles which have been enu- merated to the passage of the embryon, and admit the practicability of its reaching the uterine cavity. What in this event would happen? Disorganization f ital to each foetus must ensue. li is to be recollected, that the uterus had prepared, in the first in- stance, whatever was required for the reception, the nourishment, and evolution of the foetus. It had originally supplied it with a decidua, as a medium of attachment, and afterwards with a placenta for still more important purposes. For the second foetus, the same offices are to be rendered. These it could not execute, without suspending the action existing at tlie time, and taking on such as are necessary to the fabri- cation of an additional decidua and placenta. That actions so incompatible cannot co-exist, strikes me as suffi- ciently obvious. Were the utefus, therefore, to attempt this new pro- cess, 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 menstruation continuing during gestation. By all the very re- cent writers it is denied. Those who hold, or I might rather say, did hold the contrary opinion, have mistaken a hemorrhage from the va- gina, which sometimes recurs with considerable periodical regularity, for the catamenial flux. Several cases of this kind have come under my own observation, where I had an opportunity of inspecting the dis- charge accurately. In every instance, I found it pure coagulable 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 uteru*, we shall see that a suppression of the catamenia is exactly what ought to be ex- pected. The deciduous membrane is framed while the process of con- ception is proceeding in the ovary. The vessels which had secreted the catamenia are now engaged in a new operation. They form the membrane and then support it. While thus employed, their secretory function is suspended. They cannot at the same period, perform ac- tions so incongruous and inconsistent. The one must yield to the other. This is very strikingly illustrated by the fact which has not been suf- ficiently attended to, that in a large proportion of the cases of obstinate amenorrhea, the membrana decidua exists, and that 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 * Baillie, Burns, &r. &c. 501 ON CENEUATIOX. ved, 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 account for this sympathy, by ascribing it to the influence of the nervous system, or to the anastomosis of tbe epigastric with the internal mammary arteries; an anastomosis which is not uniform, for, instead of inosculating with each other, these vessels frequently terminate in the recti muscles of the 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 mamma; often receive no branches from the epigastric and mammary arte- ries, and when they do they are exceedinglv small. The new-born child, on being brought in contact with the breasts, applies his mouth to the nipple, and withdiawing his tongue, while with his lips he compresses the edges of the nipple, he draws in the fluid whose flow is facilitated by the erection of the lactiferous tubes. These ducts, from twelve to fifteen in num- ber, not only become enlarged, when the nipple, which almost en- tirely consists of them, is elongated by being drawn out by the child, but, besides, being excited by his touch, they become af- fected 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 the nurse's breasts. The use of these gentle compressions, is not so much to express the milk mechanically, as to excite of 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 suffi- cient to excite the secretion of milk, even under circumstances against the hypothesis which I am combating. It could, I think, in particular, be urged with great plausibility, that changed as is the whole uterine system by gestation, not only in the mechanical distinc- tion, but also in the structure and functions of its parts, it cannot pos- sibly assume that peculiar condition which seems indispensable to con- ception. Of all the operations of the animal economy, that of concep- tion undoubtedly requires the most harmoniously concerted action in the several organs by which it is commenced, carried on and consum- mated. Derangements in any one portion of this complex apparatus are confessedly productive of sterility. So essential, indeed to the generative process in the human species, is a perfect integrity in the functions of the uterine system, that by the suppression or even vitia- tion 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 1 have stated. If they be correct, it results that superfcetation cannot take place in the human species.—• Ed. ON GENERATION. 505 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, so as to furnish a pretty considerable quantify of this fluid. There have been known men, in whom a long continued titillation of the breasts had determined so considerable an afflux 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 mamma;, at first turgid, soon collapse, especially if care have been taken to de- termine the fluids downwards, by exhibiting gentle laxatives. The erection of the breasts, by titillation on the nipple, the spasmodic, and almost convulsive action which follows this kind of excitement, may be carried so far as to produce an emission of the fluid to some distance. While its excretion lasts, women experience in their breasts an agreeable sensation; these parts are tense and swollen; they feel, as they express it, the milk ris- ing; several feel a sensation of extension reaching to the axilla, to the arms and chest. The whole mass of cellular substance sur- rounding the breasts and extending to the neighbouring parts, partakes in their activity. The breasts, themselves, consist, in great measure, of cellular substance; an adipose and lymphatic layer, of a certain thickness, covers the gland, which is divided into several lobes, and incloses it within its substance. They receive a 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 enter in con- siderable numbers into the composition of the breasts, increase greatly in size, in nurses; and when injected in this condition, it has been ascertained, that several of them joined to form larger trunks, which going towards the nipple, contributed in forming what are called the lactiferous tubes. If the lymphatic vessels be immediately continuous with the excretory ducts of tbe 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 veastls and the quantity of 506 ON GENERATION. blood which the breasts supply. The opinion that the lymphatit vessels bring to the breasts the materials of the secretion of milk, is not in opposition to the laws of the circulation in the lympha- tics; 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 wot as apparent in the breasts, as in the other glandular organs, hence they bear 3 greater resemblance to the lymphatic, than to the conglomerate glands. The milk which they secrete, has always been con- sidered 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 tbe least effect, and that which preservei most the characteristic qualities of the food taken by the nurse. It is well known, that instead of giving medicines to infants at the breast, we, most frequently, administer the medicine to the nurse; thus, (be milk acquires purgative qualities, and acts on the bowels of tbe child, when the nurse has been purged. Tbe 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 ma- terials of their secretion, these vessels ought to increase in size, when these organs become twice, or even three or four times lar- ger than natural; in the same manner that, in open cancer, and in other similar affections, in which the determination off blood be- ing increased, the caliber of the vessels is proportioned to them. Nothing, however, of the same kind occurs, whatever size the breast may acquire from presence of milk; their arteries preserve tbeir almost capillary minuteness, as I bad an opportunity of as- certainining, by injecting the mammae of a woman twenty-nine years of age, who died in the second month of suckling, and whose breasts were remarkable by their size, and by the quantity of milk they were able to secrete. Notwithstanding all these reasons, which have long made me adopt the opinion of the celebrated Haller, who considers the milk as immediately extracted from the chyle, I own that it must be considered as hypothetical, and resting solely on probability. The impossibility of demonstrating, anatomically, the branches going from the messentary to the breasts, without communicating with the thoracic duct, gives still greater probability to the gene- rally received opinion which makes the milk, like all the other se- ON GENERATION. 507 creted fluids, with the exception of the bile, to be supplied by ar- terial 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 ac- tion is so evident, that, as Bordeu observes: u There are women who seem to have no milk in their breasts, which are flaccid and empty; but as soon as the child excites them, they become dis- tended, and the milk comes spontaneously." It is well known, and the same author has pointed it out, that women, cows, and the females of other animals, allow themselves more willingly to be sucked by a suckling that knows how to excite their sensibility, and to apply due irritation to the nipple; and that, on the contra- ry, they return 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 them- selves to be sucked by these reptiles. CCXXII. Of the physical properties of milk, and of the chemU cal nature of this fluid. The quantity of milk is in general, pro- portioned to that of the animals, to the degree of their nutritious qualities, to their moist and farinaceous nature. Though it e- quals 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 con- sistency. The latter quality is in an inferior degree in woman, but is greater in the cow, the goat, the ass and the ewe. Its flui- dity is intermediate between that of aqueous and oily liquids; its colour, its smell and flavour having something very peculiar, and by which it is easily recognized; in the last place, it is not ex- actly alike, at different periods of the same milking. This is proved by the work of MM. Deyeu\and Parmentier on milk, a work abounding in valuable observations, and which may be con- sidered as the complete history of this animal fluid. They ob- served 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 con- tained in the udder were affected by the laws of gravitation.! * " Lac utilis alimcnti est superfluum." Gal. De Usu part Lib. \ FI Cap. XXII. fThc author Sw*e.ns to fosgetthathe is speaking of the cow, and rhat her udder han^s in a sv ■iatiou unfavourable to to thish;^.-. thesis T ■ - *-c -. ■ y i.. * * '• * •.. 508 ON GENERATION. The milk, when exposed to the open air in a vessel, becomes de- composed like the blood, and separates into three parts; the serum, the curd, orcheezy part, and the fatty part or cream. The lat- ter, 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 tbe air; and this proves, as was first observed by Fourcroy, that tbe oxygen of the atmosphere has some influence on its separation. The caseous part, which coagulates spontaneously, appears albu- minous and abounds in oxygen. MM. Parmentier and Deyeux consider it as the colouring matter of milk, and as giving to it its most characteristic properties. Lastly, the serum or whey, which alone constitutes the greatest part of this fluid, contains besides a peculiar acid (tlie lactic acid) which is formed when this substance is allowed to remain for some time; a saccharine matter, which may be obtained by evaporation, and which, when chrystallized in rhomboidal parallepipeds, constitutes the sugar of milk, whose purity depends on the degree of care with which the process has been carried on. This sugar of milk contains, as Scheele first as- certained, while endeavouring by means of the nitric acid, to con- vert it into the oxalic, a peculiar acid in the form of a powder, difficult of solution, and to which he gave the name of saclactic acid. Milk may be considered as one of (he most compound of the animal fluids, whose qualities are very variable 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. Hydrogenj car- bon, and oxygen predominate in milk; in the last place, it con- tains several salts, amongst others muriate of soda, muriate of pot- ash, and phosphate of lime. The presence of the two last of these substances, leads to the following considerations. Muriate of potash, as is observed by Rouelle, does not exist in the blood; the probability is, therefore, that it is not tbe blood which supplies the mammse with the materials whence the milk is secreted, muriate of potash being found, in greater quantity in milk, than muriate of soda. These sails of potash, on the contrary, are found in considerable pro- portions, in the chyle, formed from vegetable substances; which would lead one to "think, that milk is furnished by the absorbent system. The phosphate of lime which is found, in smaller quan- tity, in the urine of nurses, and which is wholly determined towards the mammse, was absolutely necessary in a fluid which ON GENERATION. 509 ■mpplies nourishment to the now being, while the bones become indurated, and all the parts acquire solidity. If we now wish to inquire into the causes which render suc- tion necessary, and which subject the new-born child to this peculiar mode of nutrition, these causes will be found in the gene- ral weakness of its organs. The organs of digestion would nave 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, there- fore, 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 un- dergoing any change, into the vessels of the child; the child di- gests the milk, and obtains from it, in a short space of time, and without effort, a considerable quantity of nutritious particles, ner cessary 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 anirnalized, 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 en- trusted with a greater share of the process; it is then sufficient that the aliment should have undergone the first degree of elabo- ration, 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 cir- culates through them; the animal heat would be under what is required by the wants of life, if the mother did not make up for this 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 langua>;e; and this very interesting intercourse takes place, after the bonds of their physical communication ore loosened; but it does not tear them asunder. The infant is, therefore, detached from the mother *• / ar est cihus rroctr ronfectus. (ialer.us de usu partimr. Lib. VII. cap. XMI 510 ON GENERATION. 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 tlie breasts, may be prevented by ir- ritation in the uterus. If the labourhave 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 puer- peral fever; not that tbe milk flows back into the humours, and becomes the cause of the complaint, but that the inflammation ofthe uterus prevents tbe fluids from flowing in their natural direction. During the first few days afier 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 ofthe lungs are not distended with air, in the first inspirations ofthe child, after birth. Some ofthe lobes which are harder and more compact, take some time to ad- mit this fluid, and even sometimes altogether reject it. A child died twenty-one days after birth; the body was opened by Profes- sor Boyer. On examining the lungs, he found that the posterior part of these organs was as bard and compact as in the foetal state. The anterior part alone was distended, contained air, could be felt to crepitate, and floated in water. The heart was examined, to ascertain whether its structure was connected with this condi- tion ofthe lunga, which depended on the want of power in the respiratory functions. The foramen ovale was found'previous, so that the blood could pass from the right into the left cavities ofthe heart, without flowing through the lungs. The child had been exceedingly languid, during the whole of its short life; its skin was, at times pale, at others livid. It was very difficult to keep it worm. The child of Madame L**** died nine days after birth, with the same appearances. I opened the chest, and found the upper part of both lungs indurated and compact; the foramen ovale was quite pervious. This aperture is often closed very imperfectly, mi tli:d 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 tbe 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 vas purple and livid, all their moral and physical faculties feeble ON AGES. #11 and torpid. It would be interesting to ascertain, by dissection, whether in good divers, who can remain a long while underwater, without breathing, the foramen ovale is not imperfectly inclosed. CHAPTER XI. CONTAINING THE HISTORY OF THE AGES. THE TEMPERAMENTS AND THE V \RIETIES OF THE HU.VlAN SPECIES; OF DEATH, AND PUTREFACTION. CCXXIV. Of infancy. The epidermis of the new-born babe thickens, the redness of the skin grows paler, the wrinkles are effaced, the soft down, which covered the face, falls and disappears; the buttocks swell out and soon conceal the opening of the rectum. During the first month of life, it seems to need nothing but nourish- ment and sleep. In the meanwhile, the understanding is begin- ning to form, it looks fixedly at objects, and seeks to take cogni- zance of all the bodies that surround it. Confined, at first, to tbe uneasy sensations, which it expresses by almost continual cries, its existence becomes less painful, as it grows accustomed to the im- pressions 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 il begins to express them by laughing.* CCXXV. Detention. Towards the end of the seventh month,j the middle incisor teeth of the upper jaw, cut through the sub- * At Hercules risus prxcox ille et celerrimus, ante quadragesimum diem nulli datur.—Plin. Hist. Nat. Prsef. ad lib. Vtll f It would be very difficult to say, why a tertain fever often termi- nates of itself, when it has reached its seventh paroxysm, whilst a con- tinued fever is judged of by critical evacuations, in seven, fourteen, or twenty-one days; why delivery 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 towards the fourteenth year, and menstrua- tion is repeated at determinate periods. Nature appears to subject herself, in all her acts, to certain periods which observation may as- certain, without any possibility of arriving at a knowledge ofthe causes of these phenomena so easy to establish. Because their manifestation is correlative to certain numerical terms, we are not to put faith, like Pythagoras, in the power of numbers, and believe that the number 3 and the numbers f and 9 enslave all nature to their supreme influence. We find traces of this ancient error in all sciences, in all religion5;, even in those of enlightened nation's. 912 ON AGES. stance of tbe gums: a little while after, the corresponding incisors of the lower jaw show themselves: next, the lateral incisors of the upper jaw, those ofthe lower, then the cuspidati, in the same order. At tbe 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 ofthe child is more secure; it was before very uncertain, since the cal- culations 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. Convulsions 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 tbose^that pre- cede 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 teethy better formed, and larger, excepting the small grinders, and with longer and more perfect roots. Towards the ninth year, two new large grinders appear beyond the others. The child has then twenty-eight teeth, and dentition is complete, though between eighteen and thirty, and sometimes much later, the dentes sapien- tial, two 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 phenomena 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 fcetus. Each alveolar process, at that age of life, contains two membranous follicles, lying one over the other. That which is to form the primitive tooth swells the first, a calcareous matter covers its surface and forms the body of the tooth, which invades also the follicle by which the osseous part is secreted, so that the growth uf the little bone being completed, the membranous vesicle, in the parietes of which the dental vessels and nerves branch out, * See Erreurs populaires, sec: edit: Chap. A. dts Annees climaterigues c: a et j curs eritiuues da?is les maladies. ON AGES. 013 is found in the centre of its body, and adheres to the parietes ef Its internal cavity. It is difficult to say, why the growth of the dental germs is successive; why, in the seventh year, the primitive teeth are detached, and are replaced by others which have re- mained so long buried within the alveolar processes. Dentition is like all the other phenomena of the living economy; it is sub- ject to endless varieties in its period and duration, &c. Thus, teeth of a third set have been known to be cut in very old people. There are instances, but they are very scarce, of children that have come into the world with two incisors in the upper jaw; there are often supernumerary teeth, »\c. CCXXVI Ossification. The process which goes on in the osseous system, is not confined to the cutting and growth of the little bones which are attached to the two jaws. Ail other parts of tbe skeleton harden; osseous nuclei are formed in the centre ofthe cartilages, which hold tbe place of the short bones of tbe carpus and tarsus; the thickness of the cartilaginous substances, which separate the epiphyses of the bodies of the long bones, is diminished; the large bones grow, and acquire solidity, from the centre to the circumference. Those of the skull meet at their edges, their fibres cross and form tbe sutures; the cartilaginous spaces (fontanels) which were situated at the meeting of their edges and angles disappear. The urine contains exceedingly little phosphate of lime, that salt being entirely taken up in tbe solidifi- cation 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 burtben, and bend permanently in different directions. It is towards the bead, that the vital motions tend in infancy: accordingly, this part is the principal seat of the affections peculiar to this age, affections in which it is often of use to procure local evacuations. The organs of the senses, open to all sorts of impressions, re- ceive 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 extend- ed; but soon overpowered by imagination, roused up by the power- ful re-action of the sexual organs on the brain, it ceases to have the same exactness. 66 % 014 ON AGES. CCXXVII. Of puberty. Sex, climate, manner of life, have great influence on the earlier or later manifestation of the pheno- mena of puberty. Women reach it one or two years before men: the inhabitants of southern, long before those of northern coun- tries. 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 charac- teristic 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 tbey attain rapidly their full size. Tbe whole body grows; the general characters which distinguish the two sexes, and which are so obscure, before puberty, that they may often be mistaken, become very decided, and can no longei 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 developement of tbe vocal organs, which constantly accompanies that of tbe sexual parts. CCXXVIII. A boy, aged fourteen, died in the year VII. at the Hospital of la Charite. On opening the larynx, I was surprised to see it so small; and especially the glottis, which was not above five lines it its. anteroposterior diameter, and about a line and a half in its transverse diameter, where its dimensions are greatest; an observation that must not be omitted, is, that he was very tall; but that the developement of the genital organs was as backward as of the vocal. I have repeated the same observation on 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 ofthe 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 in- creases, 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 glot- tis increases, in the proportion only of about five to seven; that in ON AGES. 51£ I 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 lympb, tbe 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 employed to make my- self understood, is only the expression of the truth, since anatomi- cal inspection shows that the glottis, in adults, is double tbe size it is before puberty. CCXXIX. Menstruation. The symptoms by which puberty is known, in women, are not less remarkable. Tbe swelling of the genital organs straitens tbe 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 ofthe womb, and which is known by the name of the menstrual discharge, or menses. This periodical evacuation de- clares itself, in most women, by all tbe symptoms that indicate ful- ness of blood, as spontaneous lassitude, beat, and flushings in tbe face, and by others which show a direction ofthe humours towards the uterus, and a local plethora of that organ, as pains in the kid- neys, and a certain itching ofthe parts. The first eruption puts an end to this state; which, in many, may be considered as a 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, haemoptysis, melaena, some- times by unusual evacuations of blood, from the eyes, ears, the fore-finger, from ulcerated surfaces over different parts of the body. It it easily conceived, that the different parts ofthe sanguineous system may supply each others place, and that the bloody secretion, in which menstruation consists, in failure of the internal surface of tbe uterus, may be carried on by another part, equally provided with capillary vessels: but that similar deviations may take place for the fluids secreted by the conglomerate glands, as urine, bile, saliva, is difficult to believe, notwithstanding the many testimonies and authorities'bat m^y he brought in support of this opinion. 516 ON AGES. 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 prepar- ed by the peculiar action ofthe liver, may, is true, from absorp- tion, by the lymphatic vessels, be carried into the blood, and pro- duce there a diseased urinary or bilious diathesis; occasion an ir- ritation and derangement, after which, the humour of the cutaneous perspiration, and ofthe sweat, and the saliva itself will exhibit some of the qualities ofthe humour retained, and introduced by the absorbents into the circulation. The blood, contaminated by the admixture of a certain quantity of urine, may purify itself by va- rious emunctories, by urinous vomitings and sweats; but that urine may, like the menstrual blood, come out at the eyes, the ears, or.the naval, except in case of urinary umbilical fistula; that one whose urinary discharge, by the urethra, is not interrupted, may spontaneously vomit it, is what no man who has any sound notions on physiology will believe; and yet it is related, with full details, in a late work, where these errors are found, in the midst of many interesting researches, on various points of physiological chemistry. I have seen myself the woman, whose urine has been so well an- alysed by Dr. Nysten, when the clinical professor of medicine, at Paris, obliged her to submit to a severe but necessary examination, and I am astonished that well informed men should so long have given credit to such gros? impostures. The reader will, I hope, excuse this long digression, for the sake of its importance. Lite- rary criticism is now carried on with such partially, that no jour- nalist, 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 libidinous, 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 per- nicious qualities which have been ascribed to it. During the whole time of menstruation, women are weaker, more delicate, more susceptible of impressions; all their organs partake more or less, in the affection ofthe uterus; and it is not difficult to an observer, of any practice, to discern this state, not merely by the pulse, but by tbe change of the countenance and tone ofthe voice. Women then require very careful management. An improper blood letting, a purge, or any other remedy untime- ly administered, may suppress the discharge, and occasion the ON AGES. 517 most serious affections. Climate evidently influences the dura- tion and quantity of the discharge; since, in Africa, it flows al- most 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 oblique position ofthe uterus, without considering, that upon their princi- Sle, ^menstruation should take place from the soles of the feet. lich'ard 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 wbo have found the cause of it in ple- thora, general or local, have, if we admit their explanation, only changed the difficulty; for then, wt must ask what are the causes of this plethora? But, if this opinion had any ground, nervous wo- men, 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 *hat all the secretory or- gans of women are too weak to evacuate the superfluity of hu- mours, which would require for them a new emunctory? But is not this tatting the effect for the cause? Does not this smaller quantity of fluids, proceeding from the blood, arise from the puri- fication which the blood undergoes in the uterus? Let it be re- marked, in the mean time, that this periodical discharge 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 conception: does it not seem to dis- pose the uterus to that function?* (CCIV.) Was it not requi- site that this organ should be accustomed to receive a great quan- tity 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 ofthe vital functions? Menstruation is suspended during pregnancy; it is so during (he first months of suckling; though this rule admits of many ex- ceptions. Its cessation inour climate, is from the fortieth to the fiftieth year; some times before, seldom later: though I have now before me the instance of a woman of seventy, who has not yet ceased to menstruate-, a fact, which after all, is nothing more sur- prising, than that of menstruation beginning at an early period of life. When menstruation ceases, the breasts collapse, plumpness * The greater part of female quadrupeds have the parts of genera- ?'^r. bathed in a reddish lymph,during the vime of being in heat. 518 OF TEMPERAMENTS. goes off and the skin shrivels, and looses its softness, colour, and suppleness. This cessation is the cause of a great many diseases which break out, at this season of life, called the turn of life, and are fatal to many women: but then, it is observed, that when this period is past, their life is more secure, with more hope of prolong- ing it, than a man has at tbe same age. CCXXX. Of manhood. To youth succeeds manhood: which may be considered as beginning from the twenty-first to the twenty-fifth year. Then all increase of the body, in height, is at an end. The processes are completely united to the body of the bones. But still, growth goes on in other dimensions. All the organs require remarkable hardness, solidity, and consistency. It is the same with the intellectual and moral faculties. To tbe empire of imagination, succeeds that of judgment. Man is capa- ble of fulfilling all the duties of family and society. This period of life, to which we give the name of mature age, extends to the fiftieth or fifty-fifth year for men: it scarcely goes beyond the for- ty-fifth for women, with whom it begins also a little sooner. Du- ring this long interval, men enjoy the whole plentitude of their existence. Although, in general, it is not difficult to distinguish, at first sight, a man of twenty-five, from one of fifty,the differences which mark them depending on the quantity and colour of their hair, t and on their muscular strength, are neither manyVior very essential. Let us avail ourselves of this age, during which the character of the human species, merely sketched, in childhood and youth, take a more defined and lasting form, to trace the features of indi- viduals 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 distin- guishes bis temperament from that of any other, to whom, how- ever, he may bear great resemblance. We express by the term idiosyncrasy, these individual temperaments, the knowledge of which is of no small importance in the practice of medicine. The predominance of any particular system of organs, modifies the whole economy, impresses striking differences on the. results of the organization, and has no less influence on the moral and in- tellectual, than on the physical faculties. This predominance es- tablishes the temperament; it is the cause, and constitutes its essence. OF TEMPERAMENTS. 519 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 anima- ted, the shape good, the forms softened though distinct, the flesh of tolerable consistence, moderate plumpness, the hair fair and in- clining to chtsnut; the nervous susceptibility will be lively, and attended with rapid successibility, that is to say, that being easily affected by the impressions of outward objects, men of this tem- perament will pass rapidly from one idea to another; conception will be quick, memory prompt, the imagination 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 disases, and these slight, modified by the temperament, will have their seat principally in the circulatory system (inflammatory fever, or an- %eio-tenique; phlegmasia; acute haemorrhage;) and will terminate, when moderate, by the mere force of nature, and require the use of remedies, called antiphlogistic, among which bleeding is the chief. The ancients applied the name of sanguine to this dispo- sition 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 de- scribed, may show themselves, in all their truth, it is requisite that the moderate developement 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 Alcibiades. In Bacchus are found both the forms and the character. But why seek amongst the illustrious men of antiquity, or among its gods, the model of the temperament 1 have been describing, whilst it is so easy to find it among the moderns? No one, in my opinion, exhibits a more per- fect type of it than the Marshal Duke of Richelieu, that man, so amiable, fortunate and brave in war, light and inconstant, to the end of his long and brilliant career.* Inconstancy and levity are, in fact, the chief attribute of men ♦See his Memoirs, 6 vols 8vo. Voltaire has painted his character, with superior ability, in man} verses addressed to him. Rival du conquerant de l'lnde, Tu bois, tu plais, tu combats, &c 520 OX TEMPERAMENTS. 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 ofthe most intoxicated caresses, they make their escape from beauty, at the very moment she thought to have Oound tbem by indissoluble chains.* In vain he whom nature has endowed with a sanguine temperament, will think to renounce the pleasures ofthe senses, to take fixed and lasting likings, to attain, by profound meditation, to the most abstract truths; mastered by his physical dispositions, he will oe for ever driven back to the pleasures from which he flies, to the inconstancy which is his lot; more fitted to the bril- liant products of wit, than the sublime conceptions of genius.f His blood, which a vast lung impregnates, plentifully, with at- mospherical oxygen, flows freely in very dilatable canals, and this facility in the distribution and course ofthe humours is, at once, the cause and the image ofthe happy dispositions of his mind. CCXXX1I. 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 developement proportioned to that of the sanguinous system, increase in bulk: tbe sanguineous tempera- ment undergoes a great modification; and there results from it the muscular or athletic temperament, conspicuous by all the outward signs of vigour and strength. The head is very small, the neck sunk, especially backward, the shoulders broad, tbe chest large, the haunches solid, the intervals ofthe muscles deeply marked. The hands, the feet the knees, all the articulations not covered by muscles, seem very small, the tendons are marked through tbe skin which covers them: the susceptibility is not great: feeling * The history of Henry IV. of Lewis XIV. of Regnard, and of Mira- beau, proves that, to the extreme love of pleasure, sanguine men join, when circumstances require it, great elevation of thought and charac- ter; and can bring into action the highest talents, in every department. ■j- I have just met, in a gazette, wi h 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 biogra- phers have preserved on the physical temperament of this illustrious philosopher, lead us to believe that his temperament was the melan- cholic, which is very frequently met with in England. I will not dare to pronounce absolutely, on subjects on which we can attain only a cer- tain degree of probability; but if Newton had been sanguine, he would not have carried his maidenhead with him to the grave, at the age ef fourscore, as it was affirmed he did. ON TEMPERAMENTS. 53l dull and difficult to rouse, the athlete surmounts all resistance, when he has once broken from his habitual tranquillity. The Farnese Hercules exhibits the model ofthe physical attributes of this particular constitution of body, and what fabnlous antiquity relates ofthe exploits of this demi god, gives us the idea ofthe moral dispositions that accompany it. In the history of his twelve labours, without calculation, without 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 o#a man who has combin- ed, with the physical powers which this temperament implies, dis- tinguished strength of the intellectual faculties. For excelling in the fine'arts and in the sciences, there is need of exquisite sen- sibility, a condition absolutely at variance with much develope- ment of the muscular masses. CCXXXIII. If sensibility, which is vivid and easily excited, can dwell long upon one object; if the pulse is strong, hard, and frequent, the sub-cutaneous veins prominent, tbe skin of a brown, inclining towards yellow, the hair black, moderate ful- ness, of flesh, but firm, the muscles marked, the forms harshly expressed ; the passions will be violent, the movements of the soul often abrupt and impetuous, the character firm and inflexible. Bold in the conception of a project, constant and indefatigable in its execution, it is among men of this temperament we find those who in different ages have governed the destinies of the world ; full of courage, of boldness and activity, all have signalised them- selves by great virtues or great crimes, have been the terror or admiration of the universe. Such were Alexander and Julius Caesar, Brutus, Mahomet, Charles XII., the Czar Peter, Cromwell, Sixtus V., Cardinal Richelieu. As love in the sanguine, ambition is in the bilious, the govern- ing passion. Observe a man, who, born of an obscure family, long vegetates in the lower ranks: great shocks agitate and overthrow empires: actor, at first secondary, of these great revolutions, 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 posses- sed himself of it. This is, in two words, the history of Cromwell, and of all usurpers.* , To attain to results of such importance, the proioundest dis- * Vie d* Olivier Cromwell, par Jeudv Du^our, 2 vols 1 itin. fir 522 ON TEMPERAMENTS. 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 fa- mous Pope, who slowly travelling on towards the pontificate, went for twenty years, stooping, and talking for ever of bis 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.f 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 hemorrhoidal discharge.:); This temperament is further characterized by the premature developement of the moral faculties. Scarcely past their youth, the men I have named projected and carried into execution, en- terprises which would have been sufficient for their fame. An excessive developement of the liver, a remarkable superabundance Cf the biliary juices, most commonly accompanying this constitu- tion 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 circumstan- ces, or as complication, the derangement of the action of the hepatic organs, joined to changes of composition in the bile. Among the remedies directed against these sort of diseases, evacu- ants, 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 Achilles, and some others of his heroes. (CXXXIV. When, to tbe bilious temperament, is added dis- eased obstruction of any one of tbe organs of the abdomen, or * Vie de Sixte Quint, vol. in 12. | See his (haracter drawn, with as much truth as eloquence, by Thomas, in the last edition of his Essaisur les Eloge-i. X Memoires de Gourville. ON TEMPERAMENTS. 558 derangement of the functions of the nervous system, so that Ihe vital functions are feebly or irregularly performed, tlie skin takes a deeper hue, the look becomes uneasy and gloomy, the boweb sluggish, all the excretions difficult: the pulse hard and habitually contracted (serre.) The general uneasiness affects the mind; ihe imagination becomes gloomy, the disposition suspicious; the ex- ceedingly 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, excessive study, the abuse of pleasures, &c. justify the opinion which Clerc has pro- posed, in his natural history of man, in a state of disease, where he considers the melancholic temperament less as a primitive and natural constitution, than as a diseased affection hereditary or ac- quired. The characters of Lewis XI. and Tiberius, leave nothing wanting for the moral determination 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, mis- trustful, suspicious, seeking solitude by instinct, and polluting it by all the acts ofthe most savage atrocity, and the most ungoverned debauch. Distrust and fearfulness, joined to all the disorders of imagination, compose the moral character of this temperament. The passage in which Tacitus paints the artful conduct of Tibe- rius, when he refuses the empire, offered him after the death of Augustus, may be given as the most perfect model of it. Versa} inde ad Tiberium preces, Sfc. Corn. Tacit. Jlnnal. lib, i. As Professor Pinel very justly observes, in his treatise on insa- nity, ihe history of men celebrated in the sciences, letters, and arts, has shown us the melancholic under a different light: endow- ed with exquisite feeling, and the finest perception; devoured with an. ardent enthusiasm for the beautiful, capable of realizing it in rich conceptions, living with men in a state of reserve bordering upon distrust, analyzing with care, all their actions, catching in sentiment its most delicate shades, but ready in unfavourable in- terpretations, and seeing all things through the dingy glass of me- lancholy. It is extremely difficult to delineate this temperament in a gene- ral or abstract manner. Though the ground work ofthe 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, Zim- merman, are remarkable, among many others, and deserve, by their just celebrity, to fix our consideration. Tbe first, born in the happy climate of Italy, proscribed and unhappy from his child- 524 ON TEMPERAMENTS*. hood, author, at twenty-two years old, of th; 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 thcsister ofthe Duke de Ferrara, at whose court he lived: an extravagant passion, which was the pretext ofthe most cruel per- secutions, and which followed bim to his death; which took place towards the thirly-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, en- joying, like Tasso, a premature celebrity, almost on quitting child- hood was led to melancholy; not like him, by the crosses of un- happy 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 ac- cident.* No one, perhaps, has ever shown tbe melancholic temperament, in a higher degree of energy, than the philosopher of Geneva. To be convinced of it, it is enough to read, with attention, certain passages of his immortal works, and especially the two last parts of his Confessions, and Reveries in the Solitary Walker; torment- ed with continual distrusts and fears, his fruitful imagination re- presents to him all men as enemies. If you believe him, the whole human race is an leagueto do him mischief: "kings and nationshave conspired together, against the sonofapoor unUch-maker; "children and invalidsare brought in to execute these dreadful plots. But let us leave bim to speak for himself, the most eloquent and most un- fortunate man ofthe eighteenth century. "Here then I am, alone upon the earth, without brother, neighbour, friend, without so- ciety but myself; the most sociable and the most loving of men, has been proscribed by them with unanimous consent." This is the beginning ofthe first walk; further on he adds, "Could I be- lieve that I should be held, without, the smallest doubt, for a mons- ter, a poisoner, an assassin; that I should become the horror ofthe human race, and the game ofthe 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 ofthe 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 melancholies who have distinguished themselves in literature, shows us genius struggling with misfortune; a strong soul lodged in a feeble body, * He died at 39. See his life by Condorcet. ON TEMPERAMENTS. 525 at first gentle, affectionate, open, and tender, soured by the sense of an unhappy condition, and ofthe iujustice of men. Tillthetime when, impelled by the desire of fame, Rousseau sprang forward in the career of letters, we see him endowed with a sanguine tem- perament; acting with all the qualities belonging to it; gentle, loving, generous, feeling, though inconstanf; his fertile imagina- tion shows him nothing but gay images, and in this illusion of happiness, he lives oh agreeable chimera!1; but gradually undeceiv- ed by the hard lessons 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 bis moral nature changes, and he may be referred to as the most striking proof of tbe reciprocal influence ofthe moral on the physical, and the physical on the moral part ofour being.* His history is a proof, beyond reply, that the melancholic temperament is less a peculiar constitution of the body, than a real disease, of which the degrees may infinitely vary, from a mere originality of character, to the most decided mania. Gilbert arrives at Paris, with the germs of talents fitted for that great theatre. Poor and rebuffed by those on whom he had built his hopes, he 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 enemies enjoyed, and to which he believed himself called, led him on to a state of perfect madness. He believes himself persecuted by the philoso- * I have no doubt that the influence of the physical organization on the intellectual faculties is so decided, that we may regard as possible the solution of the following problem, analogous to that with which Condillac concludes his work on the origin of human knowledge. The physical man being given, to determine the character and ex- tent of his cafia'ity, and to assign, consequently, not only the talents he possesses, but those he is capable of acquiring. The profound meditation of the work of Galen (qnod animi mores corporis temperamehta seqnan'ur;) the perusal of Plutatvh'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-tl'Azyr, &c, and the study ofthe medico-philosophi- cal works of Haller, Cullen, Cabanis, Pinel, Halle, who have modified and enriched the ancient doctrine of temperaments, will be of great avail in the search of this solution. "Philosophy," cries an eloquent writer, in the noble enthusiasm which -eizes 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 out- ward man isonlv the shell of the man within."—Duflaty, 33d letter on I'afu. 526 ON TEMPERAMENTS. phers, who want to rob him of his papers; to save them from their imagined rapacity, he locks his manuscripts in a press, and swal- lows the key. It sticks at the entrance of the larynx, stops the passage ofthe air, and suffocates the patient, who dies, attheHo- tel-Dieu, after three days ofthe most cruel sufferings.* Zimmerman, early exhausted by study, already a physician of celebrity, at an early age lives in solitude, with an ardent imagina- tion; 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 So- litude, 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 sad- ness, 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.t CCXXXV. If the proportion of the fluids to the solids is too great, this superabundance of the humours, which is constantly in favour of the lymphatic system, gives to the whole body con- siderable bulk, determined by the developement and repletion of the cellular tissue. Tbe flesh is soft, the countenance pale, the hair fair, the pulse weak, slow, and soft, the forms rounded and without expression, all the vital actions more or less languid, the memory treacherous, the attention not continuous. Men of this temperament, to which the ancients gave the name of pituUous and which we should call lymphatic, because it depends really on excessive developement of this system, have in general, an insur- mountable inclination to sloth, averse alike to labours of the mind ♦ His life would have been preserved, if the cause of his illness had been understood, which he indicated himself 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 ofthe larynx; it would have been easy to draw it out, by putting a finger down the throat. This unfortunate young- man expressed, a few days before his death, the melancholy state of his soul, in stanzas most touchingly mournful^ this is one, full of interest and simplicity: ,*' Au banquet de la vie infortune convive, Je parusun jour, etje meurs; Je meurs et sur ma tombe ou lentement j'arrive Nul ne viendra verser des pleurs. t See his Eulogium by Tissot; it is at the beginning of the last edition of the Treaties on Experience in Medicine. It there appears how deep- ly he was affected by the French revolution, of which he foresaw, with a sortof prophetic spirit,the disastrous consequences to.his own country. ON TEMPERAMENTS. 527 and body : accordingly, we are not to wonder, if we find none of them among Plutarch's illustrious men. Little fitted for busi- ness, 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 ail the factions which tore the Roman re- public 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 ofthe lymphatic system was not carried so far, but that he joined to it a good deal of nervous susceptibility. In the pituitous, from the excess of watery particles in the fluid which should carry every where heat and life, the circulation goes on slowly, the imagination is weak, the passions languid; and, from this moderation of tbe 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, sen- sible to impressions on our organs, weak in the pituitous, almost nothing in athlets, moderate in those of sanguine temperament, rather quick in the bilious, constitutes, by its excess, the nervous temperament; seldom natural or primitive, but commonly acquir- ed, and depending on a sedentary and too inactive life, on habi- tual indulgence in sensuality, on tbe morbid action of the brain, promoted by reading works of imagination, &c. This tempera- ment shows itself in the emaciation, in the smallness ofthe muscles, soft, and as it were, in an atrophy, in the vivacity of the sensa- tions, in the suddenness and mutability of the determinations and judgments. Nervous women, whose wills are absolute, but changeable, with excess of sensibility, frequently exhibit it with all these characteristics. Often, however, they have something of good looks, tbe extreme preponderance of the nervous system still allowing a moderate developement of the lymphatic. Spas- modic affections are not uncommon among them; and when it is observed that, on the other hand, the atblectic constitution, direct- ly opposite to the nervous temperament, predisposes to tetanus, may we not say, that the two extremes meet, or produce the same effects? Antispamodics are employed, with success, in the treatment of their diseases, which partake always, more or less, of the tempera- ment. Stimulants, on the. contrary, are very suitable to those of 528 ON TEMPERAMENTS. 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 disease. This temperament, like the nervous affections which are the result of it, has never shown it- self but among societies brought to that state of civilization, in which man is the farthest possible from nature. The Roman la- dies 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 century, and in the times preceding the fall of the monarchy. Of tbat epoch, are the works of Wttt, Raulin, Lor- rey, Pomme, &c on nervous affections. Tronchin, a Genevese physician, acquired great wealth and reputation by the treatment of these diseases. His whole secret consisted in exercising to fatigue, women habitually inactive, keeping up their strength, at the same time, by simple, healthy, and plentiful food. The two most remarkable men ofthe eighteenth century Voltaire and the great Frederick, may be given as instances of the nervous tem- perament; and the history of their brilliant and agitated life, shows, sufficiently, how much the circumstances in which they lived, contributed to develope their native dispositions. I shall finish this article on temperaments by observing, that in truth, we bring with us into the world these particular disposi- tions of body; bnt that from education, manner of life, climate, acquired habits, they are altered, or altogether changed. Further, it is exceedingly rare to find individuals, who show, in their purity the characters assigned to the different temperaments: the descrip- tions 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 san- guine 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 perfections which he saw sepa- rate 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 happen that a man sanguir.e in youth, shall become melancholic after a lapse of time; for, as I haveiaid before, man never remains such as he came from the hjnds of nature; fashioned by all that sur- "* It is thus that, in the arts of imitation, the ideal grows up; now, from the exaggeration of features; now, from the union of qualities •viuch nature has produced separate. ON TEMPERAMENTS. 559 blinds him, his physical qualities, at different periods of his life, are as much changed as his character. Of all the causes that can modify the nature of man, and which will even change completely the nature of his native dispositions, there is none more powerful than the long continued action of air, water, and residence, as the father of medicine has said. Climate, in fact, exerts upon the temperament the most marked influence. Thus, the bilious temperament is that of the greater part of the inhabitants of southern countries; the sanguine that ofthe nations of the north; the lymphatic constitution reigns, on the contrjry, in cold and moist countries, like Holland. YVe have seen in what manner the athletic, melancholic, and nervous temperament grows out of our habits of life: let us now endeavour to appreciate the power of climate over the constitution of the greater part of man- kind. It is known, that the influence of heat, in the production of bilious diseases, is sucb, that after having been extremely preva- lent during the summer, they disappear, or at least become much less frequent in the autumn. A notable increase of perspiration never takes place without a proportioned diminution in the quan- tity of the liquids with which the alimentary surfaces are moist- ened. Now, when the gastric juice is less abundant, the bile, being mixed with a smaller quantity of serosities, irritates more tbe intestinal surfaces; the digestive powers languish, and there it an approaching disposition to meningo-gastric fevers. The same influences, continued during tbe whole year in hot countries, must necessarily increase, with the activity of the biliary system, its power over the other parts of the economy, and thus establish a predominance ofthe bilious constitution, through both health and disease. As for the sanguine temperament, so generally met with among northern nations, it is the necessary consequence ofthe continual and very energetic re-action ofthe powers of circulation, against the effects of external cold. It is only by the constant activity of the heart and vessels, that calorification can be effected with the necessary vigour. Now, the effects of this redoubled 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 of the nations ofthe north, ana- loguos to their temperament, have for the most part, their seat in the system of sanguineous vessels: tbeir character is eminently in- flammatory. Lastly, the lymphatic state of nations, living under a moist cli- mate, is nothing more surprising than the aqueous nature of plants, 68 bSQ ON TEMPERAMENTS. and small density of the wood, in trees growing under the influ- ence of a foggy air. Animal bodies, like plants, absorb by their surfaces, and become gorged with humours, the excess vf which always produces a remarkable slackening of activity in the orga- nic motions. The temperament of which ihe character is the predominance ✓of one organ or system of organs, departs from that ideal state, where all the powers are reciprocally balanced, so as to exhibit in the living economy,, a perfect equilibrium. This state, which has perhaps never been found, but in the imagination of physiolo- gists, and which was called by the ancients, the temperate tem- perament, 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 system is not in such excess as to destroy all equilibrium, and impede the action of life; but let the constitutional dispositions be much in- creased, the disease is begun, and this transition takes place in the conversion of the lymphatic temperament into scropbula.* In the scrophulous constitution, there is, at once, activity ofthe ab- sorbing mouths, great facility of absorption, inertness ofthe ves- sels and lymphatic glands, weakness of the absorbents, and con- sequently a thickening and stagnation of the liquids absorbed. The same thing is seen in the lymphatic temperament, charac- terized by the activity ofthe inhaling mouths, and the debility of tbe lymphatic system, as Professor Cabanis was aware,t when he refuted the opinion of .those who ascribe the lymphatic tempera- ment to the excess of activity in the absorbent system, though the only part of this system really quickened, is that which immedi- ately 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 natu- ralisls, as tbe 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, struc- ture, and manner of life. Men, then, are but one species, and the difference that appearsin thein, according to the region ofthe ♦ See .Vosografihie Chirurgicale, tome 1. for the history of scrophul- ous ulcers, from which this paragraph is taken entire. The author, in that work, has aimed at introdu ing physiology into surgery, till then exclusively abondoned to explanations of the grossest mechanism. f Ofthe relations ofthe physical and moral man, by G. Cabanis, Sen- ator, Professor in the School of Medicine, in Paris, &c. ON THE HUMAN RACE. 531 globe they inhabit, can only constitute varieties or races. I ad- mit, with M. Lacepede, the worthy continuator of Buffon, four principal races of the human species, which I shall call, like him, tbe European Arab, the Mogul, the Negro, and the Hyperborean. We might add a fifth, of tbe American, were it not most probable, that the new continent is peopled by inhabitants, who, coming from the old, either by land in the austral hemisphere, or along the immense Archipelago of the Pacific Ocean, have been altered by the influence of that climate, and the yet virgin soil, so that they are to be regarded less as a distinct race than a simple variety. There is, in truth, this difference between varieties and races, that, in these last, there are implied modifications more profound, more essential differences, changes not confined to the surface, but extending to the very structure ofthe body; whereas, to make a variety, nothing more is needed, than the superficial influence of climate on the integuments which it colours, and on the hairs which it makes longer or shorter, lank or curled, hard or soft. An Abyssinian, scorched by the heat of an almost tropical sky, is as black as the negro under the equator: yet they are by no means of one race, since the Abyssinian, a negro only in colour, resem- bles the European in the cast of his face, and the proportions of all his parts. The characteristics ofthe 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 funda- mental characteristics are no where more decided, than in the north of Europe. The inhabitants of Sweden, Finland, and Po- land, give the prototype of the race: their stature is tall, their skin of perfect whiteness, their hair long, lank, and of a light co- lour; the colour of the iris generally bluish. Tbe Russians, the English, the Danes, the Germans, are already somewhat removed from this primordial type: the colour of their skin is of less pure white, their hair of deeper hue. The French seem to stand midway betwixt the nations ofthe North and those of 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 Portu- guese, are browner, their hair, iu general, black. Lastly, the Arabs, the Moors, and the Abyssinians, have hair, in some mea- sure, black and crisp, the skin tawny, and might serve for the step from the European Arab to the Negro race: which is, however, dis- tinguished from them, by the flattening of (he forehead, tbe small- 532 ON THE HUM AX RAeE. ness of the skull, the slope of the line measuring the height of the face, the thickness of the lips, the projection of malar bones, and further, by a darker skin, thicker, greasy, and, as it were, oily, as well as by shorter, finer, curly, and woolly hair. The Mogul race has the forehead flat, the skull jutting but lit- tle, the eyes looking rather obliquely outwards; the cheeks are prominent, and the oval of tlie face, instead of extending from tbe forehead to the chin, is drawn between the two malar bones. The Chinese, the Tartars, the inhabitants of the Peninsuli, of the Ganges, and of the other countries of India, of Tonquin, Co- chin-China, Japan, of tlie kingdom of Siam, &c compose this race, more numerous than all the others* and apparently more ancient also, which is spread over a far greater extent than the European Arab race, and yet more, than the Negro race, 6ince it reaches from the fortieth to the sixtieth parallel of latitude, oc- cupying an arc ofthe meridan 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, between the tropics of Cancer and of Capricorn, is bounded within the limits of an arc of from 30 to 35°.* The Hvperborean race, situated in the north of the two con- tinents in the neighbourhood of the polar circles, composed of the Laplanders, the Ostiaks, tbe Samoiedes, and the Greenlanders, 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 cli-mate, its distinctive characteristics. Striving for ever with the inclemency of a severe climate, tbe destructive action of an icy temperature, nature, fettered in ber motions, shrunk in her dimensions, can produce only beings whose physical imperfections explain their almost barbarous condition. The small progress of the negroes in the study ofthe sciences, and in civilization, tbeir decided taste and singular aptitude for all the arts which require more taste and dexterity, than under- standing and reflection, as dancing, music, fencing, &c. the figure of the head, which is midway between that ofthe European and the ourang-ewtang,t the existence of the intermaxillary bones, at * Lacep£de, GeographieZnologique. f The black colour of the skin, in Negroes, seems owing, as 1 have already said, to the scorching of the gelatine, which is the base ofthe i>ete mucosum of Malpighi. This colour, acquired in a long succes- sion of ages, perpetuated and transmitted by generation, is become one of the characteristic feacures of the Negro race. M. Volney, in a work which should be a model to all travellers, grounds on the face of the blacks, a conjecture as ingenious as it is probable. He observes, that it cxiiibits, precisely, that state of contraction which our face takes when it is 6truck by light, and a strong reverberation of heat: then, says ON THE HUMAN RACE. 533 an age, when, with us, the traces of their separation are complete- ly effaced; the bigb situation and small developement of the calf ofthe 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 iniquitous traffic, and a cruel tyranny: re- proaches of civilized men, which they must wipe off by other means than a presumptuous assertion of their own digniiy, or a jpnxtd insult on tbe native character of those, whom tbey them- selves have cast into degradation. Without admitting this belief, which owes its origin to a thirst of riches, we cannot help acknowledging that the differences of organization draw after them a striking inequality in the deve- lopement ofthe 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: op- posing the activity, the versatility, the restlessness of tbe Euro- pean, to the indolence, the phlegm, tbe patience ofthe Asiatic; examining what is the power, on the character of nations, of fer- tility of soil, serenity of sky, tbe mildness of climate; showing by what catenation of physical and moral causes, the empire of cus- tom is so powerful over the people of tbe East, that we find in India and China the same laws, manners, and religion which pre- vailed there long before our era: inquiring by what singularity, well worthy the meditation of philosophers and politicians, these laws, this worship, and these manners have undergone no change, amidst the revolutions which have so often taken place among those nations, many times conquered by the warlike Tartars; showing how, by the irresistable ascendancy of wisdom and knowledge, ignorant and ferocious conquerors have adopted the Usages ofthe nations they had subjugated: and proving that tbe stationary condition ofthe sciences and arts among those who, so long before ourselves, were in possession ofthe advantages of ci- vilized society, is derived not so much from the imperfection of their organization as from the degrading yoke of a religion loaded with absurd practices, and which makes knowledge the exclusive birthright of a privileged cast.* But such an undertaking, besides this philosophical traveller, the brow contracts, the cheek-bones rise, the eye-fid contracts and the lips project. Must not this contraction of the moveable part have influenced, in course of time, tlie hard parts, and even moulded the structure of the bones? Voyage en Syrie et en Egypte, Tom. I. p. 70, 3ieme Edition. * See, concerning the religion of the Brainins, and the Indian customs, Jlaynai's Philosophical H.story. We must assign further as a main 534 ON OLD AGE. exceeding the limits I have prescribed myself, does not belong di- rectly to my subject. The Mbinoes of Africa, the Vagots of the Pyrenees, and the Cretins of the Valais, cannot be given as varietes of tbe 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 tbe existence of tribes of Giants, that have appeared on the Magella- nic 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 sufficient 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 of in the Book of Kings, Ch. xvii. v. 4. the King Og, Deut. Ch. iii. v. 2. and many others, whose sta- ture varies from six to ten feet high. CCXXXVIII. Of old age and decrepitude. The human body which, from the twentieth year of life, ceases to grow in height, increases in every other dimension, during the twenty succeeding years. After this period, far from growing, it begins to decay, and loses daily a part of its strength. The decay proceeds at the same rate as the growth, and is not more rapid; since man requires from thirty to forty years in reaching to his full growth, and takes about the same time in his progress to the grave, provided no ac- cident 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 grey, then cause of the want of progress of the Indians and Chinese, in the arts and sciences sprung from civilization, the imperfection of their alpha- bet, which, being composed of a multitude of characters, which do not, \:ke oars, represent sounds, but ideas. It is no part of my object to khow how much signs so defective must confine the sphere and fetter tiie combinations of the mind. ♦The duration of life may be estimated by that of the growth. A dog ceases to grow, at the end of two or three years, and lives only ten or twelve; Mnn. whose growth requires a space of from twenty to thirty years, attains to the aj^e of ninety or a hundred. Fishes live se- veral centuries, their developement requiring a considerable number of vear-. ON OLD AGE. 535 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 wiib greater danger. . Decay succeeds old age. The sensibility ofthe organs is blunt- ed; the physical and intellectual faculties undergo a gradual decay; man ceases to be impressed, in the same manner, by surrounding bodies. His judgments are incorrect, because self love prevent- ing him from being aware ofthe changes which he has undergone, he is more disposed to ascribe to an universal degeneracy, tbe dif- feu nee which exists between the sensations which he now expe- riences, and those which he experii need in his youth (laudator tem- poris acti). Tbe disgestion is bad, the pulse weak and slow; ab- sorption difficult, from the almost complete obliteration ofthe lym- phatics and the induration ofthe conglobate glands; the secretion languid and nutrition imperfect. The old man is slow in all his actions, and stiff in all his motions: his Jiair falls off, his teeth drop from their sockets, the cartilages ossify; the bones gr w irregular and become auchylosed, their interna! cavity enlarges; all the organs become indurated, and the fibres dried and shrivelled. The bones become heavier, from the gradual accumulation of phosphate of lime, and if those of the skull, as is justly observed by Soemmer- ing, on the contrary, become lighter, it is that they are, in a man- ner, worn out, by the continued motions ofthe brain, on their in- ternal surface. The ossification of some of tlie cartilages, for example, of those of the ribs and vertebrae, is productive of remarkable effects The ribs becoming soldered, in.a manner, to the sternum, perform very imperfectly, their natural motion of elevation and twisting,(LXXI.) which produces the enlargement ofthe chest This cavity dilat- ing less fully, the pulmonary combinations, which are the abund- ant sources of animal heat, take place in a less effectual manner, which, joined to a want of tone and energy in the lungs, and in all the organs, lowers the temperature of old people, as was observed by the father of physic,* a circumstance however, which has been denied by Dehaen. Those fibro-cartilaginous laminae, with oblique fibres crossing each other, which unite, so firmly, the bodies ofthe vertebrse, be- come 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, ihe weakened condition ofthe muscles, ♦ Senibus autem modicus est calor * * * * frigidum est enim iproru-n corpus.—Hippocr. Aph. 14. Sect- 2- 53G ON OLD Atue which raise the trunk, makes the weight ofthe viscera bend for- ward 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, however, 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, whieh enters into the composition of all the organs, converts into tssific matter the whole osseous sys'em, 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 weakened, 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 ligament! and other fibrous organs; these ligaments become softened and re- laxed, to a considerable degree, so that luxation 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 oxidized than in younger subjects: impressions are less easily made, and the motions necessary to the operations of the undersianding are performed with difficulty. Hence, in decrepitude, man returns, as far as relates to his intel- lectual faculties, to a state of second childhood, limited to certain recollections which are at first confused, and, in the end, complete- ly lost, incapable of judgment or will, or of new impressions; sleep resumes its influence; reduced to a mere vegetative existence, he sleeps the greatest p.irt of the day, and wakens only to satisfy his physical wants, and to take food, which be digests very im- perfectly. For, in the first place, the want of tr.eth prevents his being able to divide sufficiently the different substances, and, in the next place, the supply of saliva, of gastric and intestinal juices * Non ergo in sola rigiditate causam senii mortis oportet ponere; tvim ex defectu irritabilitatis, plurimi in sentbus musculi languent, mol- tsque pendent.—Elementa Pnysiol. torn. VII!. 4to. lib. SO. ON DEATH. 537 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 consider- ed that women, in whom the organs are naturally softer, are lon- ger in reaching that state, are more retentive of life than men, and, generally, live to a greater age. The body therefore, dies slowly and by degrees, says the elo- quent 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. CCXXX1X. 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 between life and death, the organs of sense first hecome insensible to all sorts of impressions; the eyes grow dim, the cornea fades, the eye-lids close, the voice becomes extinct, the limbs and the trunk motion- less; 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. Respira- tion, gradually slackened, being entirely suspended after a strong expiration,* the lungs no longer transmit the blood which the veins bring, from every quarter, to the heart. This fluid stag- nates in the right cavities of the heart, and these die last, (ulti- mum moriens,) and distended by the blood which collects within them, they attain a capacity exceeding greatly that of the left ca- vities, 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 circu- latory 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 tbe action of tbe heart and brain; for, the death of the lungs occasions that of tbe whole body, only by preventing the ac- tion of the heart, by interrupting its influence on the encephalic organ. In natural death, therefore, life becomes extinguished from the circumference to the centre; in accidental death, on the contrary, tbe centre is affected before tlie extremities. + Does this last and powerful expiration, often attended by sighing, depend on the spasmodic contraction of the muscles of expiration; or rather does it not depend on the re-action of the elastic parts which from the chest, a re-action which suddenly ceases to be counter-balan- ced by the vital properties. 69 538 ON DEATH* Bichat, in his work entitled, Recherches sur la vie et la mort, has given a very complete account ofthe manner in which the organs of the animal economy cease to act in articulato mortis; but like all the other authors yvho went before bim, he has limited his in- quiries 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 phe- nomena of nutrition to which tbe foetal existence is almost entirely limited, continue, even when the organs destined to establish a re- lation with the beings that surround us, have long been sunk into a slumber from which they are never to be roused. The following is the order in which the intellectual faculties cease and are decomposed.* Reason, the exclusive attribute of man, first forsakes him. He begins by losing the faculty of as- sociating judgments, and then of comparing, of bringing together, and of connecting a number of ideas, so as to judge of their rela- tions. The patient is then said to have lost his Consciousness, or to be delirious. This delirium has, generally, for ils subject, the ideas that are most familiar to the patient, and his prevailing pas- sions is easily recognized. The miser talks, in the most indiscreet manner, of his bidden treasures; the unbelievers dies haunted by religious apprehensions. Sweet recollections of a distant native land, then it is that ye return with your all powerful energy and delight! After reasoning and judgment, the faculty of associating ideas is next completely destroyed. The same occurs in fainting, as I once experienced in myself; I was conversing with one of my friends, when I experienced an insuperable difficulty in associa- ting two ideas, from the comparison of which I wished to form a judgment. Yet syncope was not complete, I still preserved me- mory and the faculty of feeling. I could distinctly hear those about me say, he is fainting, and exert themselves to relieve me from this condition, which was not without enjoyment. The memory then fails. The patient who, during the early part * I need not inform the reader, that I am not here speaking of the immortal soul, of that divine emanation which outlives matter, and which, freed from our perishable part, returns to the Almighty. I am speaking merely of the intellectual faculties common to man, and to those animals which, like him, are provided with a brain. OX DEATH. 539 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; tbe ear is yet sensible to sound and noise, and no doubt, it was on this account, that the ancients, to ascertain that death bad 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 arm's in various directions, and is perpetually changing his posture; he performs, as was already said, motions similar to those of the fcetus within the mother's womb. CCXL. Ofthe period of death. This period is nearly the same with all men, whether they live near the poles, or under the equa- tor, whether they live exclusively on animal or vegetable substan- ces, 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 philosophical transac- tions, one ef 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 du- ration of life, has, however, a remarkable inffuence on rapidity of growth. Puberty, manhood, and old age, come on much sooner in warm climates, than in northern countries; but this premature developement which shortens the duration ofthe 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 tbe hair be considered as the certain sign of old age? We daily see young men with gray hair. May we determine its accession, by the cessation ofthe 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 man very equivocal; the emission of seminal fluid is an uncertain sign, from tbe diffi- culty of distinguishing the mucus of the vesiculae 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, dis- 510 ON DEATH. fended with urine, on the vesicular seminales. It is more diffi- cult than is imagined, to determine, from observation, tbe period at which, in the human species, the male is entirely deprived of the power of sieneratiofl; and it may be said that, in establishing be 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 otlier 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 confirmed period of old age. Whatever regimen may have been followed, man, at that age, is truly old and cannot but be aware of it. CCXLI. Of the probabilities of human life. Man dies at all ages; and if the duration of bis life surpass that ofthe lower ani- mals, the great number of diseases to which be is liable, renders it much more uncertain, and is the cause why a much smaller number arrive at the natural term of existence. It has been at- tempted 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 tbe children that are born, die within the first eleven months of life; one third before twenty- three months; and one half before they reach the eighth year. Two thirds of mankind die before the thirty-ninth year, and three fourths before the fifty-first; so that, as Buffon observes, of nine children that are born, only one arrives at fihe age of seventy-three; of thirty, only one Jives 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 ninety- six, only one drags on a languid existence to the age of a hundred years. The mean term of life is, according to the same author, eight years, in a new-born child. As tbe child grows older, his exis- tence becomes more secure, and after the first year, be may rea- sonably be expected to live to the age of thirty-three. Life be- comes gradually firmer up to the age of seven, when the child, <\iU r going through the dangers of dentition, will probably live forty-two years and three months. After this period, ihe sum of probabilities which had gradually increased, undergoes a progres- sive decrease; so that a child of fourteen cannot expect to live be- yond 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 ON DEATH. 541 year only. From the eighty-fifth to the ninetieth year, probabili- ties remain stationary, but after this period, existence is most pre- carious and is painfully carried on to the end. Such is the result of ob?ervation, and of calculations on the different degrees of pro- bability 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 observa- tions, collected at Montpellier in the course of a great number .of years, and with the most scrupulous accuracy. ^J should enter more fully into this subject, but that it belongs more to the department of political economy than to that of phy- siology. The calculations irn the probabilities of human life, present re- sults 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 in the innocence of a pastoral life, breathing the pure air of his mountains, is, in this respect, subject to the same laws as the in- habitant of populous cities, exposed to the inconveniences attend- ing numerous collections of men; inconveniences, which viewed in a philosophical point of view, or which greatly overrated, have so often furnished a text to the meditation 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 preced- ing 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; among the Egyptians, the Hebrews, the Greeks, and Romans, there were very few instances of persons living to tbe age of a hundred years, and instances of longevity are perhaps more frequent among the moderns. The art of providing for the wants of life, making daily pro- gress, it is very probable, that far from being shortened, the term of human life may be lengthened a certain number of years be- yond its ordinary duration. This idea is, it is true, contrary to the commonly received opinion of the progressive depravity of man kind in all ages; but the golden age never existed, but in the ima- * The researches of Sir John Sinclair do not disprove this statement, though this author adhere faithfully to the practice generally adopted by his countrymen, of speaking most favourably of England and Scot- land. The statistical tables published in different parts of Europe show that the number of people who reach the age of a hundred is rujially great there. 512 ON PUTRBFACT1N. gination 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 different manner, by surrounding 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 an I colourless. But the cause of all these changes is within himself, every thing else remains as it was.. Always equally fruitful, nature exposes ever, thing to the action of her inexhaustible crucible; maintains every thing in a state of everlasting youth,, and preserves a freshness ever renewed. Individuals die, species are renovated; life every where arises in the midst of death. The materials of organized bodies, enter into new combinations and serve in forming new be- ings, when life ceasing to animate those to which tbey belonged, putrefaction seizes upon them, and effects their destruction. CCXL1I. 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 ac- company the decomposition of animal substances. And this investigation appears to me to belong to the department of physio- logy, 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 be- come subject to the laws of physics, operating on substances that are not organized. An iuwatd motion takes place within their substance, and their molecules have the greater tendency to be- come separated from one another, as their composition is more ad- vanced. Chemistry informs us that the tendency to decomposi- tion 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 iis 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 power- fully antiseptic, and one might say that life is a continual struggle against the laws of physics and chemistry. This vital resistance, ciludcd to by the ancients when tbey said, that the laws ofthe mi- rrocosm where 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: V-> ^