Physiological Researches on Life and Death

by Xavier Bichat

FOOTNOTES:

[18] Bichat often complains in his works of the injury that has been done to the physiological sciences, by the attempts that are made to facilitate the study of them by means of physics. He was not competent to decide the question, not having sufficient data in the sciences, the use of which he reprobated; the most that he should have said, was that a bad application had been made of them. Even this reproach was too general to be just. No doubt, mankind have been led into errors by attempting to support on slight foundations a science which was still in its infancy; but even in the time of Bichat it could not be denied that it was to the progress of these same sciences, that was owing the explanation of many very important phenomena; that by it was ascertained what takes place in respiration, and by what means a living body always supports itself between certain limits of temperature, &c.

[19] It must be remembered that the existence of such a sensibility is purely conjectural. As it is not transmitted to a common centre, we can recognize it only by its effects. In order to explain these effects, there is no need of admitting a similar faculty. This sensibility moreover, if its existence should be admitted, would be found continually in fault. The stomach, for example, allows a substance to go out of its cavity which could never serve for aliment, provided this substance exhibits a degree of fluidity approaching that of chyme. The absorbents take up the most noxious fluids, those even the action of which is sufficiently powerful to destroy the organization of their parietes; the heart contracts without the entrance of the blood into it, &c.

[20] This is altogether inaccurate; a nail in growing is not nourished, any more than the mucus is nourished in the nasal fossæ, or the urine in the bladder. The nails, the hair on the various parts of the body and the hair of the head, all in a word epidermoid productions, are the result of real secretions which do not differ from the secretions of which we have just spoken, only in this, that the product instead of remaining fluid like the urine, or viscid like the mucus, hardens as it comes out of the secretory organ, like the thread of the silk worm, or that of the spider. A certain number of these organs is commonly arranged in such a manner, that the matter secreted by each of them is found in a fluid state in contact with that of the neighbouring organs, with which it is agglomerated in hardening. Arranged in concentric circles around a small cone, they produce a hollow cylinder; extended in parallel lines upon a broad surface, they produce a flattened lamina. Such is the manner in which the nails and the hair are formed. We see from this that the epidermoid productions grow, but are not nourished. The hair exhibits, it is true, an internal cavity, filled with a coloured fluid, which appears to be necessary for its preservation; but we can easily conceive how an oily fluid may help to preserve it, by giving it suppleness and thus preventing it from breaking. This fluid is poured into the canal in which it is found, and it is not the hair which draws it in, any more at least, than a capillary tube draws in the fluid into which its extremity is plunged.

[21] The idea of endowing each texture with a peculiar kind of sensibility in relation with its uses is one which pleases the imagination. The ligaments are designed to oppose the separation of the bones; they should remain insensible to every kind of stimulus that does not tend to disunite these parts, and pain consequently, should not be produced but from distension or twisting. Unfortunately this supposition is not well founded, the facts on which it rests were not accurately observed. It is very true that in twisting these ligaments, the animal almost always cries out, but it is because we at the same time stretch some neighbouring parts endowed with sensibility. When this is prevented and the experiment is made with proper precaution, we can twist, distend or tear the ligament, without appearing to give the animal any pain.

[22] So, as long as the fluid is retained in the artery, which is easily done by means of ligatures, no pain is manifested; but when the irritating substance is carried by the vessels to the heart or to any other sensible part, we can easily conceive that the animal must experience pain, for the irritant always produces its effect, whether it be carried directly to the part or arrive there by means of the circulation.

[23] These expressions dose, sum, quantity of sensibility are incorrect, inasmuch as they exhibit this vital faculty under the same point of view as the physical forces, as attraction, for example; and as they present it to us as susceptible of calculation, &c.; but, from a want of words for one science, it is necessary, in order to make it understood, to borrow them from the other sciences. There are expressions, like the words to solder, to glue, to unglue, &c. that are used for the want of others in the osseous system, and which really give very inaccurate ideas, unless the mind corrects the sense.

[24] If the urine, during a perfect erection, does not go out of the bladder, it is because the contraction of the muscles of the perineum, and especially of the levator ani, prevents it. If these muscles are relaxed, though the turgescence of the corpus cavernosum and of the urethra remains the same, the urine flows out without any other obstacle than what arises from the contraction of the canal produced by the swelling of its parietes.

[25] These different excretory ducts do not exhibit in the mammalia any contractility. There is no stimulus which can produce it in them; I have tried them all in vain. In birds, on the contrary, the ureters and the pancreatic and biliary canals are contractile, and their motions, which return at intervals, are too well marked to be mistaken. It appears that the contractility of the excretory canals in the abdomen, is connected in these animals with the absence of the diaphragm. We know in fact that this muscle in the mammalia, assists by the pressure which it exerts, the course of the secreted fluids, and renders useless the existence of a peculiar motion in the canals which contain them. If it be however pretended that this motion exists in them, but that it is insensible, it must be allowed then, that it cannot perform the office which is attributed to it, viz. that of obliterating an opening often large enough to admit a quill. It is true, that if the orifice of one of these canals be irritated for a long time, a swelling of the membrane which lines it is sometimes produced, and the opening is then really lessened. But in these cases there is no occasion to be deceived; we see that this swelling is produced at that point by the afflux of the fluids, as it would be in any other part subjected to a similar excitement. Besides, it should be observed that the obliquity of insertion of the excretory ducts is alone sufficient to explain how the substances which pass in front of their orifices are not introduced into them. In fact these substances, at the moment of their passage, by the pressure which they exert, tend to obliterate the opening of the canal, by flattening its parietes against each other; it is thus that the pressure of the urine, upon the inferior extremity of the ureters, prevents this fluid from ascending towards the kidney. The obliteration of the opening is but an accidental thing, and most often is not even complete.

[26] It is not surprising, that a canal usually filled with the excreted fluids should refuse to admit another which runs in an opposite direction.

[27] All that is here said of the sensibility of the lymphatic vessels, which makes them sometimes admit and sometimes reject the effused fluids, is the more hypothetical, as it is not as yet proved that these vessels are the agents of absorption. It should be remarked, that the fluids that are supposed to be absorbed by them, differ essentially in their chemical composition, from the fluid that is usually found in their cavity. This fluid besides varies but very little in its composition, though its appearance is not uniformly the same; now, if it were the result of the absorption of fluids differing from each other, its composition ought also to vary as that of the chyle does, according to the nature of the aliments.

Before the lymphatic vessels were known, the principal phenomena of absorption were observed, and it was natural to attribute them to the action of the veins. This opinion was maintained for a long time after the discovery of the lymphatics. Finally, towards the middle of the last century, Hunter being engaged in examining these vessels, which he has done more to make known than any other man, thought that they should be considered as the agents of absorption, and this opinion was soon generally admitted. If we look for the means by which he overthrew the ancient theory, we are astonished to find that it was by five experiments only. Harvey did not with equal facility obtain the acknowledgment of the circulation, and perhaps there does not exist a second example of an opinion, which was for a long time established, being abandoned so readily. It should be remarked, that physiologists had not yet recovered from the surprise produced by the discovery of a system of vessels so extensive, and yet for so long a time unknown; they were impatient to know the use of them; the veins had already the function of returning to the heart the blood brought by the arteries; they thought it would not impoverish them too much to deprive them of the faculty of absorbing, in order to enrich the lymphatics with it. Of the five experiments of Hunter, two are designed to prove that the veins do not absorb, the object of the other three is to show that the lymphatics do.

In the first experiment he injected tepid water into a portion of intestine, and the blood which returned by the vein appeared to be neither more diluted nor lighter than before. We cannot conceive how by mere inspection, it is possible to judge if the blood contains a certain quantity of absorbed water, a quantity which must be proportionably very small, if we consider the whole amount of blood that passes through the mesentric veins during the period necessary for the absorption of the fluid. Hunter in the same experiment tied the artery which went to the portion of intestine, and examined the state of the vein. It did not swell, and its blood did not become aqueous. But after this ligature, did the absorption continue to go on in this portion of intestine, which still had no doubt lymphatic vessels? This the author does not say. How moreover should he think that the vein could continue its action when the artery was tied?

In the second experiment Hunter injected milk into a portion of intestine, and was unable to discover this fluid in the blood of the mesentric veins; but at the period in which this experiment was made, mankind were very far from being able to detect in the blood a very small quantity of milk, and at the present day, with all the aid derived from chemistry, we can hardly discover in it a small quantity which is mixed directly with it. These two experiments prove then nothing against the absorption of the veins; as to those which he brings forward in favour of absorption by the lymphatics, they are not more conclusive. I shall content myself with relating one of them. He injected, into a portion of intestine that was empty, a certain quantity of warm milk, and confined it there by two ligatures. The veins that came from this portion were emptied of their blood by several punctures made in their trunk. The corresponding arteries were tied. He then returned the parts into the abdomen, and drew them out again in half an hour. Having examined them with attention, he observed that the veins were almost empty, and that they contained no white fluid, whilst the lacteals were almost full of it. But was not this white fluid that filled them chyle rather than milk? Was it not there before the injection of this liquid? In order to ascertain what takes place in the lymphatic vessels during absorption, we must begin by examining the state of these vessels before the experiment. But this is what Hunter did not do, and it is this that renders his experiment of no value. It is not very astonishing that he mistook the chyle for the milk, since milk has for a long time been mistaken for chyle. Flandrin, Professor of the Veterinary School at Alfort, has several times repeated this experiment of Hunter; but he took care before the injection of the milk to ascertain that the lymphatics contained no white fluid; and he never found any in their cavity after the experiment. I have myself many times performed this experiment, with the same precaution, and I have uniformly obtained the same results as those of Flandrin.

It would occupy too much time to examine all the reasons that have been advanced for and against the absorption of the lymphatics; I shall only relate some experiments I have made myself; but I ought first to observe, that absorption undoubtedly takes place in parts such as the eye, the brain, and the placenta in which the most minute dissection has been unable to discover any lymphatic vessel.

First experiment.—Four ounces of the decoction of rhubarb was given to a dog, in half an hour after he was killed, and it was found that more than half of the liquid had disappeared; the urine evidently contained rhubarb, but the lymph in the thoracic duct exhibited no trace of it.

Second experiment.—A dog swallowed several ounces of alcohol diluted with water; at the end of a quarter of an hour, the blood of the animal had a very distinct odour of alcohol, but there was nothing of the kind in the lymph.

Flandrin made a similar experiment on a horse, to whom he gave half a pound of assafetida mixed with an equal quantity of honey. Six hours after, the horse was killed. The odour of the assafetida was very perceptible in the blood of the veins of the stomach, of the small intestines and the cœcum; but it could not be perceived in the lymph.

Third experiment.—A dog was made to swallow six ounces of a solution of Prussiate of Potash in water. In a quarter of an hour, the urine very evidently contained some of the Prussiate; but the lymph taken from the thoracic duct showed no appearance of it.

Fourth experiment.—I gave to a dog, in whom I had tied the thoracic duct, two ounces of a decoction of nux vomica. The effects of absorption were as rapid as if the duct had been open. After the death of the animal I satisfied myself, that the duct had been well tied, and that there was no other branch, as there sometimes is, by which the lymph could get to the subclavian vein.

I have varied this experiment by putting the poisonous fluid, into the rectum, the sacs of the pleura and peritoneum. The results have been uniformly the same.

Fifth experiment.—M. Delille and myself made an incision into the abdominal parietes of a dog, who had been fed very heartily some hours before, so that the lacteals might be easily seen, and we then drew out a portion of the small intestine upon which we applied two ligatures three inches from each other. The lymphatics that went from this portion of intestine were full of chyle and very distinct. They were all tied and cut. The blood vessels were also tied and cut, with the exception of an artery and a vein; the portion of intestine also was cut off beyond the ligatures, and thus it had no communication with the rest of the animal except by the vein and artery which were left. These two vessels were dissected with the greatest care, and even stripped of their cellular coat, lest there might be some lymphatics concealed in it; we then injected into the cavity of this portion of intestine a decoction of nux vomica, and we retained it there by means of a new ligature. This portion of intestine, covered with fine linen, was restored to the abdomen; six minutes after, the effects of the poison were manifested with their usual intensity.

Sixth experiment.—M. Delille and myself separated the thigh of a dog from his body, leaving only the crural artery and vein, which kept up the communication between the two parts. These two vessels were dissected with care, insulated to an extent of from two to three inches, and even stripped of their cellular coat, for fear it might conceal some small lymphatic vessel. Two grains of a very active poison (the upas) were then inserted into the paw, and the effects were as sudden and as intense as if the thigh had not been separated from the body.

As it might be objected, that notwithstanding all the precautions taken, the parietes of the artery or vein might still contain some lymphatic, we varied our experiment so as to leave no doubt on this point. The artery was cut entirely off, the communication was reestablished between the two ends, by means of a leaden tube introduced into their cavity, and fixed by proper ligatures. The same was done for the vein. Thus there was no longer any communication between the thigh and the rest of the body, except by the arterial blood which came to the thigh, and by the venous blood which returned to the trunk: the poison afterwards introduced into the paw produced its effects in the ordinary time, that is in about four minutes.

From these different experiments, it is right to conclude that the minute branches of the veins possess the power of absorbing; that they exert it on the surface of the mucous and serous membranes, and in the interior of the organs; that the experiments that have been quoted in favour of the absorption of the lymphatics are inaccurate or incorrectly understood, and finally that there is no proof that these vessels absorb any thing but chyle.

Is it now necessary to refer to the venous branches this sensibility that has been attributed to the ultimate ramifications of the lymphatics? But this sensibility, as we have already said, would be constantly in error; the absorbent vessel does not select one fluid in preference to another; all are indiscriminately absorbed, even the most irritating, those in fact whose action is sufficiently powerful to destroy the vascular parietes. Besides, the phenomenon then continues, when it is no longer possible to suppose the existence of this sensibility. After death even, the venous branches absorb still as they do during life, if they are placed in analogous circumstances; and to do this it is evident, that an internal current must be established, which resembles the course of the blood. I shall now relate an experiment, which I made on this subject, and which I selected from many others, because it appeared to me to be very conclusive.

I took the heart of a dog that had died the day before; I injected into one of the coronary arteries some water of the temperature of 30 degrees of the centigrade thermometer. This water returned easily by the coronary vein to the right auricle, whence it flowed into a vessel or dish. I poured half an ounce of slightly acid water into the pericardium. At first the injected water exhibited no sign of acidity; but in five or six minutes it presented unequivocal marks of it.

Absorption then can take place without the assistance of this sensibility, as well as of this insensible organic mobility, which is supposed to be in the ultimate vascular extremities, in the absorbing mouths, as they are called. But do these mouths really exist? Do the last capillary branches terminate abruptly with a large opening on the surface of the membranes or in the texture of the organs? Can the absorbed fluids pass through their parietes as oxygen does in the lungs to arrive at the blood which it modifies? We are unable to make experiments on these small vessels, that are not cognizable by our senses; let us make them on the large ones, and if they permit fluids, in which they are immersed, to pass through them, for a stronger reason we may suppose that it takes place in the capillaries, whose parietes are so much more delicate and consequently more permeable. Now we have confirmed by experiments what we had suspected; the first attempts were made on dead vessels.

I took a portion of the external jugular vein of a dog; I stripped it of the surrounding cellular texture; I attached to each of its extremities a glass tube by means of which I established a current of warm water through its interior; I then immersed the vein into a liquor slightly acid.

It is seen by the arrangement of the apparatus that there could not be any communication between the internal current of warm water and the external acid liquor.

During the first minutes the liquid that I collected did not change its nature; but after five or six minutes the water became perceptibly acid; absorption had taken place.

The same experiment was repeated on veins taken from human subjects; the effect was the same; it was the same also with the arteries, but a little slower from the greater thickness of their coats.

It remained to be seen if in a living animal absorption thus took place through the parietes of a large vessel. I know that the textures that were permeable after death, are almost all so during life, though the contrary is generally believed. If we inject into the pleura of a living animal a certain quantity of ink, at the end of an hour, and often sooner, we shall find the pleura, the pericardium, the intercostal muscles, and the surface of the heart itself, evidently of a black colour. It is true that the signs of this exudation are not always apparent. Thus after death, the transudation of the gall bladder is rendered evident by the colouring of the neighbouring parts. During life, on the contrary, as fast as the colouring particles are deposited, they are absorbed by the serous membrane which covers the surrounding parts, and carried off by the sanguineous current which runs through this membrane and the subjacent organs.

From these considerations we must believe that absorption may take place through the parietes of the vessel during life as after death. To be satisfied of this I made the following experiment:

I took a young dog of about six weeks old. At this age the vascular parietes are delicate, and consequently more likely to render the experiment successful. I laid bare one of the jugular veins; I insulated it perfectly in its whole length; I stripped off carefully every thing which covered it, and especially the cellular texture and some small vessels that ramified on it; I placed it on a card, that it might not be in contact with the surrounding parts; I then let fall, on its surface and opposite the middle of the card, a thick aqueous solution of an alcoholic extract of nux vomica, a substance the action of which is very powerful on dogs; I took care that none of the poison could touch any thing but the vein and the card, and that the course of blood was free in the interior of the vessel. Before the fourth minute, the effects that I expected appeared, at first feeble, but afterwards with so much power as to render inflation of the lungs necessary to prevent the death of the animal. I repeated this experiment on an adult animal of a much larger size than the preceding one; the same effects appeared but slower, on account of the greater thickness of the parietes; they began to appear in fact after the tenth minute.

After satisfying myself with this result respecting the veins, I thought I would ascertain if the arteries exhibited analogous properties. These vessels are in a less favourable condition; their texture is less spongy than that of the veins and with an equal caliber, their parietes are much thicker. It was easy then to foresee, that if the phenomenon of absorption showed itself, it would appear much slower than in the veins; this was confirmed in an experiment on two large rabbits, in whom I dissected perfectly clean one of the carotid arteries. It was more than a quarter of an hour before the solution of nux vomica passed through the parietes of the artery. As soon as I saw the symptoms of poisoning distinctly, I stopped moistening the vessel; yet one of the rabbits died. In order then to convince myself that the poison had really passed through the arterial parietes, and that it had not been absorbed by small veins which might have escaped my dissection, I carefully detached the vessel that had been used in the experiment; I cut it open in its whole extent, and I made those who assisted me taste a little of the blood, that was still adhering to the internal surface; they all perceived in it, and I did myself, the extreme bitterness of the extract of the nux vomica.

To these experiments may be objected a fact that is observed, which is, that absorption does not take place the same under all circumstances; its activity is redoubled or diminished, according to the state of some other functions. Thus during a paroxysm of fever, a medicine, which would usually act with great effect, often produces, when given in a double or treble dose, no perceptible effect. Now if absorption, was a purely mechanical phenomenon, would it undergo modifications in relation with those of the vital functions? Without doubt it would; for these modifications of the functions may introduce new physical circumstances favourable or injurious to the production of a mechanical phenomenon. Thus in the present case, the state of fever, by accelerating the circulation distends with blood the arteries and the veins. The fluid that is to be absorbed must pass from the exterior to the interior of these vessels. Now it may be easily conceived, that the quantity of blood which they contain must have a great influence upon the production of the phenomenon by the greater or less degree of tension of their parietes. This is moreover completely confirmed by experiment.

We can, without producing a very great disturbance in the functions, increase at pleasure the quantity of fluid which passes through the blood-vessels, by carefully injecting into the veins water the temperature of which is near that of the blood. An artificial plethora is thus produced, followed by very curious phenomena, of which I shall have occasion hereafter to speak. One day while making this experiment, the idea occurred to me of seeing what influence the plethora thus produced would exert upon the phenomenon of absorption.

In consequence, after having injected into the veins of a dog of middle size about a quart of water, I placed in the pleura a small dose of a substance, the effects of which were well known to me. These effects did not show themselves till many minutes after the period in which they usually appear. I soon made the same experiment on another animal with the same result.

In many other trials the effects showed themselves at the period in which they ought to have appeared; but they were evidently weaker and prolonged much beyond the ordinary time.

Finally, in another experiment in which I had introduced as much water as the animal could bear and live, the effects did not appear at all. I waited nearly half an hour for effects which commonly show themselves in two or three minutes. Presuming then that the distension of the vessels prevented the absorption, I endeavoured to satisfy myself of it, by seeing if after the distension had ceased, absorption would be any longer prevented. In consequence, I bled the animal copiously from the jugular, and I saw, with the greatest satisfaction, the effects appearing as the blood flowed out.

It was proper to make the opposite experiment, that is to say to diminish the quantity of blood, in order to see if absorption would take place sooner. This took place in fact, as I thought it would; about half a pound of blood was taken from an animal; the effects, which did not usually appear till after the second minute, showed themselves in thirty seconds.

Yet it might still be suspected, that it was less the distension of the blood-vessels than the change of the nature of the blood that opposed absorption. To remove this difficulty I made the following experiment; a dog was bled copiously; the place of the blood which he had lost was supplied by water at the temperature of 40 degrees of the centigrade thermometer, and a certain quantity of a solution of nux vomica was introduced into the pleura. The consequences of it were as prompt and as powerful, as if the nature of the blood had not been changed; it was then to the distension of the vessels that must be attributed the want or diminution of absorption.

The consequences that may be deduced from the experiments I have just related will acquire new force, if we connect with these facts a multitude of pathological ones, which are every day seen; such as the cure of dropsies, engorgements and inflammations by bleeding; the evident want of action of medicines at the moment of a violent fever, when the vascular system is powerfully distended; the practice of certain physicians who purge and bleed their patients before administering active medicines to them; the employment of cinchona at the period of remission for the cure of intermittent fevers; general or partial oedema from organic disease of the heart or lungs, and the application of a ligature upon the extremities after a puncture or a bite of a venomous animal, to prevent the deleterious effects which are the consequence of it.

On the whole, I think, it may be concluded from the preceding experiments that the capillary attraction of the small vessels is one of the principal causes of the absorption called venous. If the lymphatics do not appear to enjoy in the same manner the faculty of absorption, it probably arises not from the nature of the parietes, the physical properties of which are nearly the same as those of the veins, but from the want of a continuous current in their interior.

In this note I have brought together the absorption of the gases and that of fluids. This resemblance holds only as it relates to the permeability of the textures by these two orders of bodies. As to the cause of the absorption of the two, it cannot be the same, since gases are not subjected to capillary attraction.[28]

[28] Note by the Translator of Magendie’s Additions.—In the preceding note M. Magendie has not done justice to Mr. Hunter. Without entering at all into the examination of the question, whether absorption is performed by the lymphatics or the veins, it is due to Mr. Hunter to contradict the assertion, that “he overthrew the ancient theory by five experiments only.” He was not a man who adopted his opinions loosely or on slight grounds, and in the present case he performed between twenty and thirty judicious and satisfactory experiments, in the presence of several physicians and surgeons. It is true that these were performed on five different animals only, but if the result were uniform, this number was as good as five thousand or any other one that could be named.

G. H.

(See Hunter’s Commentaries and Cruikshank on the Absorbents.)

[29] Those theories no doubt are very incomplete that are borrowed from hydraulics, and probably will be so for a long time; but it arises from this, that the science on which it is founded, hydrodynamics, is still but little advanced. A great advance will unquestionably be made in physiology, when we shall arrive at a knowledge of the course of a fluid in a system of canals, which have the same physical conditions as the system of arterial and venous vessels. But it will be a long time before science will have arrived at that point. Is it necessary for this to make no use, in the explanation of the circulation, of the few facts which are known upon the course of the fluids? Is it necessary to enter entirely into the field of hypothesis, to suppose in the small vessels a sensibility and a contractility which evidently do not exist in the large ones? I cannot believe it, and I think even that if this hypothesis should be true, and if there should be demonstrated for the capillary vessels, those properties which are attributed to them, and which would have an influence on the course of the blood, we should then know but one of the conditions of this very complicated problem, and this would not in any degree do away the necessity of knowing all the mechanical conditions.

[30] Even in reasoning according to the hypothesis of Bichat, and admitting the existence of this organic sensibility, it would always be inaccurate to say, that the contraction is uniformly in proportion to the sensation. How is it to be known in fact? Since this sensibility is not transmitted to a common centre, it might very well be excited without our being informed of it by any apparent effect. Sometimes also a very evident contraction would correspond to the slightest excitement.

[31] The contractility in the different organs in which we can observe it does not exhibit characters so striking as those which Bichat here assigns to it, and the motions which he ranks in the same class have the greatest differences among them. To be convinced how little justice there is in this division, it will be sufficient to trace the progress of the food, along its whole course, to the interior of the digestive canal. The first act which is presented to our observation is entirely voluntary; this is mastication; the act which follows it is not so completely so. Deglutition in fact can sometimes take place against the will, if a body of a proper consistence is at the entrance of the pharynx. We have but an imperfect control over the muscles of the uvula and the velum palati, if we wish to move these parts separately; we have perhaps less power still over the contraction of the muscles of the pharynx, though they do not appear to differ from the locomotive muscles, either in their symmetry, or in the arrangement and colour of their fibres, or in the nerves which they receive; nor finally do they differ in the sudden, instantaneous contraction, wholly different from the slow contraction, the vermicular motion of the stomach and intestines.

After having passed the pharynx, the alimentary mass enters the œsophagus. The motions are there still under the influence of the nerves; but they are not at all under the influence of the will. The muscular layer which produces them has not the appearance, the red colour of the voluntary muscles; but it still preserves something of the sudden motion of their contraction. Hence we see, that the motions of the œsophagus cannot be ranked either among the motions of organic life, since they cease by the division of the nerves, or among those of animal life, as they are not under the influence of the will. It is remarkable also that Bichat, who, in this and the following paragraph, announces the characters of the different kinds of contractility, does not speak of the œsophagus, whilst he offers as an example the motions of the bladder, the heart, the stomach and the intestines.

When Bichat wrote this work, hardly any thing of the motions of the œsophagus was known, except from the writings of Haller, who made but four experiments on the subject. I wished to observe them myself, and I have discovered many facts which I think interesting; I shall relate them here as I described them in a memoir read to the Institute in 1813. Before attempting to ascertain what part the œsophagus took in the passage of the food, it was proper to ascertain its state when it was supposed to be at rest. In the first experiments, I noticed an important phenomenon, and which hitherto had escaped the observation of physiologists, viz., that the lower third of the œsophagus has constantly an alternate motion of contraction and relaxation, which appears to be independent of all foreign irritation. This motion appears to be confined to the portion of the tube which is surrounded by the plexus of nerves of the eighth pair, that is to say, to about its lower third; there is no trace of it in the neck nor in the superior part of the thorax. The contraction appears like a peristaltic motion, it begins at the junction of the superior two thirds with the inferior third, and is continued to the insertion of this tube in the stomach. When the contraction is once produced, it continues for an uncertain time; usually it is less than half an hour. The œsophagus contracted in this way in its lower third is hard like a cord powerfully stretched. Some persons whom I have made feel of it in this state have compared it to a rod. When the contraction has lasted the time I have just mentioned, the relaxation takes place suddenly and simultaneously in each of the contracted fibres; in some cases, however, the relaxation seems to take place from the superior fibres towards the inferior ones. The œsophagus examined during the state of relaxation exhibits a remarkable flaccidity, which contrasts wonderfully with the state of contraction.

This alternate motion is dependent on the nerves of the eighth pair. When these nerves are cut in an animal, this motion entirely ceases; the œsophagus contracts no more, but it is not in a state of relaxation; its fibres without the control of nervous influence shorten; it is this which produces, so far as the touch is concerned, an intermediate state between contraction and relaxation.

When the stomach is empty or half full of food, the contraction of the œsophagus recurs at much longer intervals; but if the stomach be powerfully distended by any cause, the contraction of the œsophagus is usually very powerful, and continues for a much longer time. I have seen it, in cases of this kind, continue more than ten minutes; under the same circumstances, that is to say, when the stomach is excessively full, the relaxation is always much shorter.

If during the time of contraction, we wished, by mechanical pressure made on the stomach, to make a part of the aliments which it contained pass into the œsophagus, it would be necessary, in order to accomplish it, to employ a very considerable force; and often even we should not succeed. It seems that pressure increases the intensity of the contraction, and prolongs its duration. If, on the contrary, the stomach is pressed during relaxation, it is very easy to make the substances it contains pass into the cavity of the œsophagus. If it be a liquid, the slightest pressure, sometimes even its own weight, or the tendency which the stomach itself has to contract, will bring about this result. When the stomach is laid bare and distended above measure, fluid does not usually enter into the œsophagus, because, as we have said, the distension of the stomach is a cause which prolongs the contraction of the œsophagus.

The passage of a fluid in the œsophagus is usually followed by its entrance into the stomach. Sometimes however the fluid is thrown out. When it goes into the stomach, the œsophagus contracts nearly the same as in deglutition, sometimes almost immediately after it has entered it; at other times the œsophagus allows itself to be considerably distended before it pushes it into the stomach.

It was at the moment of deglutition that Haller observed the motions of the œsophagus, and the description which he has given of them is very accurate for the two superior thirds of the canal; but the action of the inferior third is essentially different; and this distinction seems to have escaped him. Haller says that the relaxation of each circular fibre immediately follows the contraction; and this is true of the portion of the canal situated in the neck and in the superior part of the thorax; but it is not accurate for the inferior portion, in which we see that the contraction of all the circular fibres is continued long after the entrance of solids or fluids into the stomach. At this moment the mucous membrane of the cardiac extremity of the œsophagus, pushed by the contraction of the circular fibres, forms a very considerable projection into the cavity of the stomach. The contraction usually coincides with the period of inspiration, when the stomach is more strongly compressed; the relaxation takes place most often at the time of expiration. When the aliments have once entered the stomach, it is this contraction of the inferior part of the œsophagus which opposes their return. The resistance that is offered at the other orifice is not of the same species. In living animals, whether the stomach be empty or full, the pylorus is uniformly shut by the contraction of its fibrous ring and the contraction of its circular fibres. There is frequently seen in the stomach another contraction, at one or two inches distance, which appears to be designed to prevent the aliments from arriving at the pylorus. We perceive also irregular contractions, beginning at the duodenum, and extending to the pyloric portion of the stomach, the effect of which is to push back the aliments towards the splenic part.

The aliments remain in the stomach long enough to undergo no other modifications than those which result from their mixture with the perspiratory and mucous fluids, which are constantly found in it and renewed there. During this time the stomach remains uniformly distended; but afterwards the pyloric portion contracts in its whole extent, especially in the part nearest the splenic portion, towards which the aliments are carried. Then there is found, in the pyloric portion, only the chyle mixed with some unchanged aliments. When there is accumulated in this part a quantity of it, which is never very considerable, there is seen, after a moment of rest, a contraction at the extremity of the duodenum; the pylorus and the pyloric portion soon take part in this motion, and the chyle is forced towards the splenic portion; but afterwards the motion is in an inverse direction. The pyloric portion, which allowed itself to be distended, contracts from left to right, and directs the chyle towards the duodenum, which soon passes the pylorus and enters the intestine. The same phenomenon is repeated a certain number of times, then it ceases, and commences again after some time. This motion, when the stomach contains much food, is limited to that part of the organ nearest the pylorus; but as it becomes empty, the motion extends, and appears even in the splenic portion when the stomach is almost entirely evacuated. In general, it becomes more evident at the end of chylification.

The motion which produces the progression of the chyle in the small intestines is very analogous to that of the pylorus; it is irregular, made at variable intervals, it is sometimes in one direction and sometimes in another, and sometimes appears in many parts at once; it is always more or less slow, it produces changes of relations in the intestinal circumvolutions, and it is entirely beyond the influence of the will.

We should form a very false idea of the motions of the small intestines during digestion, if we judged of them by those which these intestines exhibit in an animal recently killed. In this case, it is not the annular fibres only that enter into action, so as to exhibit, by their successive contractions, a vermicular motion. The longitudinal fibres act also in a very conspicuous manner, and produce a rolling of the intestinal circumvolutions, which change their relations at every instant. These motions are never more evident than when the whole mass of intestines is removed from a living animal.

The motions of the large intestines have nearly the same characters as those of the small intestines, like these last, they are not always in the same direction, but push the substances which are contained in their cavity, sometimes towards the ileum and sometimes towards the anus. But by means of this motion, these substances which have already the character of feces, can never re-enter the small intestines. The cause that prevents their return is different from that which prevents the return into the stomach of the substances contained in the duodenum. The obstacle in this case, we have said, is produced by the contraction of the contractile rings, which are found at the extremity of the two cavities; in the other, it is produced by a cause purely mechanical, by the arrangement of the ileo-cecal valve. Hence it follows, that if the mode of contraction of the different parts of the intestinal canal be perverted by any cause, it might happen that their contraction towards the pylorus would not take place when the duodenum was affected with its anti-peristaltic motion, and then the substances contained in it, pushed by the contraction of the annular fibres, would re-enter the stomach. At the coecum, on the contrary, as the obstacle is purely mechanical, so long as the ileo-cecal valve is not broken, it will present an insurmountable obstacle to the return of the feces into the small intestines.

The motions of the large intestines, sufficient to carry the feces into the rectum, would not, in a state of health, be powerful enough to expel them entirely, by overcoming the resistance which the sphincter constantly presents; in expelling the feces, the contraction of the intestine is assisted by the pressure which arises from the lowering of the diaphragm, and by the contraction of the abdominal muscles.

We have just pointed out the motions which carry the alimentary mass along the intestines. We may see that they have but little resemblance among them. The only character that is common to them is that of not being under the influence of the will. Yet there is an exception to this in some individuals who possess the faculty of ruminating. (The will is seen exerting itself on the production of other sensible organic motions. Bayle could stop at will the pulsation of his heart.) If we examine the motions of the digestive tube when it is free of aliments, we see their difference in a manner not less striking. The œsophagus exhibits those alternate motions that we have described; a very powerful contraction of its inferior third, and then suddenly the most complete relaxation. In the stomach we see only some undulations, that go irregularly from one orifice to another. In the intestines, these motions exhibit nearly the same regularity, but the groove formed by the contraction of the annular fibres is deeper, and the undulatory motion is not so slow. If a stimulating medicine is introduced into the stomach, these contractions become more evident, and the motions more rapid; but they always preserve the same character. The contraction takes place progressively, and never in the sudden manner of a muscle of locomotion. Of all the substances which can be used to ascertain these motions, there is no one whose action is more efficacious than veratrine, a new vegetable alkali extracted from the veratrum sabadilla. If the external parietes of the digestive tube be excited by any stimulus, by touching it with the finger, by a puncture, or by the galvanic fluid, there is in the œsophagus a sudden contraction of the longitudinal and circular fibres, which narrows the organ and shortens it at the same time; the relaxation takes place instantaneously and in as striking a manner. In the stomach, no motion is perceived in the direction of its length; we see only an annular contraction, which is developed slowly at the excited point, and which is usually not transmitted to the neighbouring parts. In the intestines, the excitement produces a very decided contraction, and very often in the neighbouring parts a kind of peristaltic motion; but this motion is always slow and does not at all resemble the sudden contraction of the œsophagus.

The difference between the motions of the œsophagus and those of the other parts of the intestinal canal is very remarkable in birds. In them the œsophagus appears to be entirely membranous; and yet it contracts like a muscle of locomotion; whilst the stomach, which has red muscles very similar to the locomotive muscles, has slow, gradual vermicular motions, like all the canal which is below it.

There exists finally between the motions of the intestinal canal a difference relative to the manner in which they terminate. Those of the intestines, but little sensible during life, acquire at the moment of death a very great intensity; whilst those of the œsophagus, before so distinct, cease immediately, and in the most complete manner.

[32] It is not the dartos that contracts in the motions of the scrotum, it is the skin itself that produces that vermicular motion that is observed in this part. This motion can be produced by stimuli of very different kinds; by the impression of cold, by pinching the skin or by fear. I have seen these motions so great in a man on whom I was about to operate for hydrocele, that I was obliged to wait for a long time for fear of wounding the testicle, which, by those motions, ascended and descended precipitately.

[33] It might be thought from this expression, that Bichat supposed that the great arteries influenced the course of the blood by an active contraction analogous to the muscular contraction; but this was not his opinion. He only wished to say, that the blood continued to move in the great arteries solely by the influence of the heart. This contraction of the great arterial trunks has been heretofore maintained by many anatomists, and is even at present by some. There are at the present day three principal theories relative to the circulation.

In the first, it is contended that all the parts of the arterial system are irritable, and that they contract like the muscular texture; many even add that they can dilate spontaneously, as takes place every instant in the heart. According to this supposition, the arteries alone would be able to continue the course of the blood.

In the second opinion, which is that of Harvey, and which is still adopted, more particularly by the English physiologists, it is affirmed on the contrary, that the arteries are not contractile in any point; that if they do contract in certain cases, it is in virtue of that property common to all the solids, by which they return upon themselves, when the cause that has distended them ceases to act. The partisans of this opinion conclude that the arteries have not and cannot have any influence upon the motion of the blood which runs through them, and that the heart is the principal, and as it were, the sole agent of the circulation.

Finally the third opinion, that which now prevails most generally in France, consists in a union of the two preceding ones; the trunks and principal arterial branches are considered as incapable of acting upon the blood; but this property is attributed to the small arteries, and it is thought to be very great in the last divisions of these vessels. Thus, in this mixed opinion, the blood is carried by the sole influence of the heart in all the arteries of a considerable size; it is moved in part by the influence of the heart and in part by that of the parietes in the smaller arteries, and finally it is moved by the sole action of the parietes in the last arterial divisions. This action of the small vessels is also described as the principal cause of the course of the blood in the veins.

In a question of this nature our opinion should be determined by experiments alone. This presents many points for elucidation.

The first and the easiest to be decided is to ascertain if the arteries are or are not irritable. The problem was in some measure resolved in relation to the great arteries by the experiments of Haller and his disciples, by Bichat himself, and by those which M. Nysten has made upon man. For the purpose of being more perfectly convinced, I have sought, by all the known means, to develop the irritability of the arterial parietes; I have successively subjected them to the action of pricking instruments, of caustics and of galvanism, and I have never perceived any thing which resembled a phenomenon of irritability; and as those who maintain the irritability of the arteries pretend that if we do not perceive the contractions, it is because the experiments are made on too small animals, in whom the effects are but slightly apparent in consequence of the small diameter of these canals, I have repeated the experiment on large animals, on horses and asses, and I have never observed any other motions than the communicated motions.

As the great arteries show no contraction, we ought to believe that the small ones would not; but as among the physiologists who reject the irritability of the arterial trunks, some like Haller, do not speak of the branches, others accord to them contractility, it becomes necessary to test this question by experiment; now these small vessels, like the larger ones, remain perfectly immoveable under the action of the scalpel, caustics and a stream of galvanic fluid.

Irritability does not exist then in the large or the small arteries. Respecting the last arterial divisions, as the vessels which form them are so small that they cannot come under the cognizance of the senses, at least in a state of health, no one can affirm or deny that they are irritable. Yet from analogy we ought to conclude, that they have no sensible motion. In cold-blooded animals, in fact, it is easy to see the blood circulating in these vessels, and even passing into the veins; now the vessels themselves appear to be completely immoveable.

As the arteries cannot act upon the blood by contracting in the manner of muscles, must we conclude that they have no action upon this fluid, and that they are in relation to it nearly like inflexible canals? I am very far from thinking so. If in fact the arteries had no influence upon the blood, this fluid, moved by the sole impulse of the heart, would, from its incompressibility, be alternately in motion and at rest. This is indeed what Bichat thought, and what he has advanced in his other works; it is what has been since maintained in a more formal manner by Dr. Johnson of London. It is however very easy to prove that it is not in this way that the blood is moved in these vessels. Open a large artery in a living animal, and the blood will escape in a continuous jet, but by jerks; open a small artery, and the blood will flow out in a continuous and uniform jet. The same phenomena take place in man if the arteries are opened, either by accident or in surgical operations. The heart being unable to produce a continuous flow, since its action is intermittent, it must be then that the arteries act upon the blood; this action can only be the disposition which they have to contract, and even to obliterate their cavity entirely. Bichat thought that his tendency to narrowing was not sufficient in the arteries to expel the blood contained in their cavity. He maintains that the vessel does not contract upon itself only when the blood has ceased to distend it. If it were so, the arteries would be equivalent to inflexible canals, and the course of the arterial blood would not be continuous; but we can easily demonstrate that the force with which the arteries contract is more than sufficient to drive out the blood that they contain.

When two ligatures are applied at the same time and at some centimetres distant upon two points of an artery which furnishes no branches, we have a portion of artery in which the blood is subjected only to the influence of the parietes. If we make in this portion of the vessel a small opening, almost all the blood that it contains is immediately thrown out, and the artery is much contracted. This experiment has been known for a long time, and uniformly succeeds. The following is one of my own, and places, it seems to me, the phenomenon in a very clear light. I laid bare the crural artery and vein of a dog to a certain extent; I passed under these vessels, near the trunk, a string, which I afterwards drew tightly at the posterior part of the thigh, so that all the arterial blood should come to the limb by the crural artery, and all the venous blood return to the trunk by the crural vein; I then applied a ligature upon the artery, and this vessel was very soon completely empty in the part below the ligature.

It is then satisfactorily proved that the force with which the arteries contract upon themselves is sufficient to expel the blood they contain. But what is the nature of this contraction? We have proved that it cannot be attributed to irritability. Every thing leads to the belief that it should be referred to the very great elasticity which the arterial parietes enjoy, an elasticity that is brought into action, when the heart forces a certain quantity of blood into the cavity of these vessels. This property of the arteries being known, it is easy to conceive how the principal agent of the arterial motion, being alternate, the course of fluid is yet continuous. The elasticity of the arterial parietes is similar to that of the reservoir of air in certain pumps with an alternate action, and which notwithstanding throw out the fluid in a continuous manner.

It is not enough to know the kind of influence which the contraction of the arteries has on the motion of the arterial blood; it is necessary to know if this contraction does not influence in a sensible manner the course of the blood in the veins. This is elucidated by the following experiment. Lay bare, as in the preceding experiment, the crural artery and vein of a dog; tie the limb strongly, taking care not to include these vessels; afterwards tie the crural vein, and make a small opening in it below the ligature, of one or two lines in length; the blood flows out in a continuous jet. If the artery be compressed, so as to intercept the course of blood in it, the jet still continues a short time; but it is seen sensibly to diminish, as the artery is becoming empty. It at length ceases entirely when the artery is completely emptied; and though the vein remains distended with blood along its whole extent, it does not flow out at the small wound. If the compression be taken off of the artery, the blood enters it with force, and almost at the same instant it begins again to flow from the opening in the vein, and the jet is reestablished as before. If we check the course of the blood in the artery, there is but a feeble jet from the vein; it is the same if the passage of this fluid is alternately intercepted and permitted.

I make the same phenomenon evident in another way; I introduce into the crural artery the extremity of a syringe filled with water at the temperature of 30 degrees of the centigrade thermometer; I push the piston slowly, and soon the blood goes out by the opening in the vein, at first alone and afterwards mixed with water, and it forms a jet the more considerable in proportion to the force with which the piston is pushed.

To prove, as we have done, that the heart maintains an evident influence on the course of the blood in the capillary vessels, is not to advance that these vessels have no action on the motion of this fluid. Many physiological phenomena, on the contrary, prove that the capillaries can aid with more or less facility the passage of the blood, and consequently sensibly influence its course.

[34] Under no circumstance does the stomach rise up, as Bichat calls it. We have, in a preceding note, explained the ordinary motions of this viscus, in a state of vacuity, during digestion and under the influence of an internal or external stimulus. None of these motions are sufficient to produce that sudden and energetic expulsion which characterizes vomiting. The opinion that the stomach rises up in vomiting originated in a time of ignorance, and we ought not to be astonished that it should find advocates even in our day. This has not however been uniformly adopted; Bayle and P. Chirac opposed it by experiments; Senac, Van Swieten and Duverney declared themselves against it; but Haller, by adopting it, suddenly changed the views and removed the uncertainty of a great number of physiologists, who, not taking the labour of making experiments for themselves, loved to repose on the faith of a celebrated name. In physiology the opinions of Haller are certainly entitled to very great weight; this is because this wise observer, before announcing them as a general proposition, was accustomed to repeat many times the experiments on which he founded them; but in this case he did not sufficiently question the use of the stomach in vomiting.

He has made four experiments only, less for the purpose of satisfying himself that the phenomenon existed, than to see it such as he supposed it. It is very difficult, even for the best mind, to divest itself in observing, of the ideas previously received without examination. It may then be believed, that Haller in this way saw but superficially. These considerations determined me some years since, to satisfy myself of what takes place in vomiting, and of the part which the stomach performs in it. I shall relate briefly the experiments which I tried on the subject. The first was made on a dog of middling size, whom I had made to swallow six grains of emetic. When this medicine had excited nausea, I cut through the linea alba opposite the stomach, and introduced my finger into the abdomen. At each nausea, I felt it very powerfully compressed above by the liver, which the diaphragm pushed down, and below by the intestines, which were compressed by the abdominal muscles. The stomach also appeared to me to be compressed; but instead of feeling it contract, it appeared to me, on the contrary, to increase in size. The nauseas became more frequent, and the more marked efforts, which precede vomiting, appeared. Vomiting finally took place, and then I felt my finger pressed with a force truly extraordinary. The stomach rid itself of a part of the aliments it contained; but I distinguished no sensible contraction in it. The nausea having ceased for a short time, I enlarged the opening in the linea alba, for the purpose of observing the stomach. As soon as the incision was enlarged, the stomach presented itself at it, and made an effort to come out of the abdomen; but I prevented it with my hand. The nauseas returned in a few minutes, and I was not a little surprized to see the stomach filled with air, as they came on. In a very little time the organ had become three times its former size; vomiting soon followed this dilatation, and it was evident to all who were present, that the stomach had been compressed without having experienced the least contraction in its fibres. This organ rid itself of air and of a portion of aliments; but, immediately after the exit of these substances, it was flaccid, and it was not till after some minutes, that gradually contracting, it became nearly of the same dimensions as it was before the vomiting. A third vomiting took place, and we saw again the same series of phenomena.

For the purpose of ascertaining whence the air came, which, during the nauseas, distended the stomach, I applied a ligature on the stomach near the pylorus, so as to close the communication which exists between this organ and the small intestines, and I made the dog swallow six grains more of emetic in powder. At the end of half an hour the vomiting returned, accompanied by the same phenomena. The distension of the stomach by air was at least as marked as in the preceding experiment; besides there was no appearance of contraction of the stomach, and we could not even clearly distinguish its peristaltic motion. The animal having been killed some moments after, in an experiment which had no relation to vomiting, we examined the abdomen. We saw that the stomach was of considerable size; its texture was flaccid and not all contracted; the ligature, at the pylorus, was not displaced, and the air had not been able to pass this way.

Having repeated this experiment and uniformly obtained the same results, I thought it right to conclude with Chirac and Duverney, that the mechanical pressure, exerted on the stomach by the diaphragm and the abdominal muscles, is much concerned in the production of vomiting; now, if it were so, by removing this pressure from the stomach, vomiting would be prevented; experiment confirmed this conjecture.

I injected into the vein of a dog four grains of an emetic dissolved in two ounces of common water, (in this way vomiting is produced quicker and more certainly;) I afterwards made an opening in the abdomen, and when the first efforts of vomiting began, I quickly drew out the whole of the stomach, which did not prevent the efforts of vomiting from continuing. The animal made precisely the same efforts as if he had vomited; but nothing came from the stomach; this organ remained completely immoveable. I wished then to see what would be the effect of pressure made on the stomach; for this purpose, I placed my right hand on the anterior face of this organ, and my left hand on the posterior face. The pressure was hardly commenced when the efforts of vomiting, that is to say, the contraction of the diaphragm and the abdominal muscles powerfully recommenced. I suspended the pressure; the abdominal muscles and diaphragm soon suspended their contractions. I renewed the pressure; the contractions of the muscles began again; then I suspended it; they ceased; and seven or eight times in succession. The last time, I made a strong and continued pressure; this produced a real vomiting. A part of the substances contained in the stomach was thrown off. I repeated this experiment on another dog; I observed the same facts; only I remarked moreover that the contractions of the diaphragm and the abdominal muscles can be produced by merely drawing by the œsophagus.

In the experiment just related, the emetic substance was introduced into the veins, and we have already remarked, that the effects were quicker and more certain than if the same substance had been introduced into the stomach. This alone should make us suspect that vomiting is not owing, as is generally believed, to the impression of the emetic on the mucous membrane of the stomach; for, in this case, its action ought to have been more prompt when it was placed directly in contact with this membrane, than when it arrived at it with the blood after having passed through the lungs and the four cavities of the heart. For the purpose of elucidating this question and of seeing if the contractions of the muscles were the result of the impression produced on the stomach, or if they were excited more directly by the emetic substance mixed with the blood, I made the following experiment:

I opened the abdomen of a dog, and having brought the stomach out at the opening, I tied with care the vessels that went to this viscus, and I removed the whole of it (I ascertained in some of the preceding experiments that a dog can live eight and forty hours after his stomach has been removed.) I made a suture in the abdominal parietes; then, having laid bare the crural vein, I injected into its cavity a solution of two grains of emetic in an ounce and a half of water. I had hardly finished the injection when the dog began to have nausea, and he soon made all the efforts that an animal does when he vomits. These efforts appeared to me to be even more violent and longer continued than in ordinary vomiting. The dog remained quiet about a quarter of an hour; I then renewed the injection, and I forced two grains more of emetic into the crural vein; this was followed with the same efforts of vomiting. I repeated the experiment many times and always with the same success; but this experiment suggested to me another, which I performed in the following way: I took a dog of good size, from whom I removed the stomach, as I had done in the preceding experiment; I introduced into the abdomen a hog’s bladder, to the neck of which I had fixed, by threads, a canula of gum elastic; I put the end of this canula into the extremity of the œsophagus, and I fixed it there also by threads, so that the bladder resembled somewhat the stomach, and was, like it, in communication with the œsophagus. I introduced into the bladder about a pint of common water; this distended it, but did not fill it completely. A suture was made in the wound of the abdomen, and four grains of emetic were injected into the jugular vein. Nausea soon appeared, and was followed with real efforts of vomiting; finally, after some minutes, the animal vomited up abundantly the water from the bladder.

It followed evidently from the preceding experiments, that the abdominal muscles and the diaphragm concurred to produce vomiting; but it remained to be ascertained, what was the part of the diaphragm in the production of this phenomenon, and what was that of the abdominal muscles.

If the diaphragm received only diaphragmatic nerves, it would be easy to resist the contraction of this muscle by dividing these nerves; but it also receives filaments from dorsal pairs, and these filaments are sufficient to support its contractions. Yet experiment shows us, that the diaphragmatic nerves being cut, the contraction of the diaphragm is very evidently diminished in power, and it may be said, without much hazard of mistake, that this muscle loses, by this division, three quarters of its contractile force. It was then useful to see what influence the division of these nerves would have on the production of this phenomenon. I made this division in the neck of a dog of three years old, and I afterwards injected into the jugular vein three grains of emetic; there was only a very feeble vomiting; another injection of emetic, a quarter of an hour after, excited no vomiting. I opened the abdomen and endeavoured to produce vomiting by compressing the stomach. The compression, though very powerful and long continued, excited no effort of vomiting; it did not even appear to produce nausea. I thought that this circumstance might be owing to the idiosyncrasy of the animal; but having many times since repeated this experiment, I have never obtained any other result.

In order to understand what part the abdominal muscles by their contractions take in vomiting, we ought to observe what takes place when these muscles are unable to act. There is but one way of coming at this, which is, to separate these muscles from their attachments at the sides of the linea alba; this we have done on many animals; we have detached successively the external oblique, the internal oblique and the transversalis, leaving on the anterior face of the abdomen only the peritoneum. When these muscles are thus removed, we can see very distinctly through the peritoneum, all that takes place in this cavity; we distinguish, for example, perfectly the peristaltic motion of the stomach and the intestines; and if the stomach contracts it will be easy to see it. The abdominal muscles being thus detached, I injected three grains of emetic into the jugular vein, and also immediately nausea and vomiting took place by the contraction of the diaphragm alone. It was curious to see, in the convulsive contraction of this muscle, the whole intestinal mass pushed downwards, and pressing strongly against the peritoneum, which was ruptured in some places. In this case, the linea alba, formed by a very strong fibrous texture, is the only part which resists the pressure of the viscera; its existence then is indispensable to the action of vomiting; perhaps it performs an analogous office in the ordinary state. This experiment proves that vomiting can be produced by the efforts of the diaphragm alone; this is also confirmed by the following experiment:

I detached, as above, the abdominal muscles and laid bare the peritoneum; I afterwards divided the diaphragmatic nerves, and injected an emetic into the veins. The animal had some nausea, but nothing more. Though I repeated many times the injection of the emetic, I never was able to produce any sensible effort of vomiting.

From the different experiments that we have just related, and from the facts that we made known in a preceding note relative to the motions of the œsophagus, we may conclude, without any hazard,

1st. That vomiting can take place without any contraction of the stomach.

2d. That the pressure exerted immediately on the stomach by the diaphragm and abdominal muscles, appears to be sufficient to produce vomiting, when the occlusion of the inferior part of the œsophagus offers no obstacle to it.

3d. That the convulsive contraction of the diaphragm and abdominal muscles, in vomiting from tartarized antimony and emetic substances properly so called, is the result of a direct action of these substances on the nervous system and independent of the impression felt by the stomach.

[35] The motions of the iris cannot be attributed to an active expansion of an erectile texture; they are owing to the contractions of two muscular layers, one of which is radiated and enlarges the opening of the pupil, the other is orbicular and contracts it.

The motions of the iris, like all those which have muscular contraction for their cause, can be excited for a considerable time after death by the galvanic fluid. During life, the motions of the pupil are produced in man, by the more or less vivid impression of light on the retina. But they are beyond the influence of the will; in birds on the contrary, they appear to be entirely subjected to it. In these animals, we can even after death, and on an eye entirely detached from the body, produce the motions of the iris by pricking the optic nerve.

[36] When a patient dies after having for a long time been deprived of solid and liquid nourishment, it is not rare to find in him the stomach and intestines considerably lessened in their two dimensions, the internal cavity almost entirely effaced, the length being hardly a third of what it was before the disease. We truly say then with Bichat that is a contraction from a want of extension. But that this mode of contractility is as he says perfectly independent of life and owing only to the arrangement of parts, is what cannot be admitted. If it were so in fact, by emptying the stomach after death, we might produce a contraction similar to that which is produced during life. Now experiment shows us, that this does not take place. The stomach when emptied remains flaccid, and does not contract in any perceptible degree.

[37] We know that the organs are nourished, that the glands secrete, we know that certain vessels absorb (whether they be the lymphatics or not,) but we do not know, that all this is produced by a partial oscillatory movement in each fibre, in each molecule. No one can be certain that this movement takes place, because no one has seen it.

[38] Why invent a new word, when we have that of elasticity, which expresses for all bodies whether organic or inorganic, that tendency to resume their usual form and size, when the cause that made them change them is no longer in exercise?

[39] Bichat here unites three sorts of motion which have no relation between them; the systole of the cavities of the heart should be considered as a really active dilatation. The increase of size of the corpora cavernosa, which is an effect purely passive of the accumulation of blood in those parts, and which can be produced after death by artificially accelerating the circulation in them; and finally, the motion of the iris, a motion evidently produced by a muscular contraction, excitable by galvanism or pricking the nerve.

[40] Without denying the influence which the capillary systems of the different organs have on the circulation, we have shown that even in the veins the action of the heart is felt and modifies the course of the blood.

[CHAPTER VIII.]
OF THE ORIGIN AND DEVELOPMENT OF THE ANIMAL LIFE.

If there be any circumstance, which establishes a real line of demarcation between the two lives, this circumstance undoubtedly is the mode and epoch of their origin. The organic life is active from the very first moment of our existence; the animal life begins after birth only; for without external excitants the latter is as necessarily condemned to inaction, as without the fluids of the œconomy, which are its internal excitants, the former would become extinct. But the subject, on which we are now engaged deserves a more particular discussion, and in the first place let us examine, in what manner the animal life, which for some time is absolutely null, is born as it were and developed.

I. In the fœtus the first order of the functions of the animal life is not as yet in action.

The instant, at which the fœtus begins to exist, is nearly that of its conception; but this existence, the sphere of which is every day enlarged, is not the same as that, which the child is destined to enjoy after birth.

The state, in which the fœtus exists while in the womb, has been compared to that of a profound sleep. Such comparison is inexact. In a state of sleep the animal life is only in part suspended. In the fœtus it has not commenced. We have seen in fact, that this life is made up of the simultaneous or distinct exercise of the senses, of the nerves, of the brain, of the organs of locomotion, and the voice. Now in these different functions every thing in such state is inactive.

Every sensation supposes the action of external bodies upon our own, together with the perception of such action; a perception which takes place by virtue of the sensibility of the system, which is either general or particular, for the tact is the faculty of perceiving general impressions, and has for its object to warn us of the presence of bodies, together with their common attributes, such as heat, cold, dryness, or humidity, hardness or softness. To perceive the particular modifications of bodies is the business of the senses.

Has the fœtus in utero any general sensations? To decide this question, let us enquire whether any impressions are capable there of exercising its tact. The fœtus lives in a temperature at all times the same, swims in a fluid, and is thrown from time to time against the parietes of the womb: such are the three sources of its general sensations.

We shall now remark, that the two former are next to nothing, and that the fœtus cannot have a consciousness of the medium, in which it is nourished, nor of the heat, by which it is penetrated, for every sensation supposes a comparison between an actual and a past state of being. We are sensible of cold, only because we have experienced an antecedent heat; were the temperature of the atmosphere invariable, we should have no idea whatever of temperature. The Laplander enjoys himself in a climate, which would be pain, and death to the Negro, if suddenly transported thither. It is not at the time of the solstices, but at that of the equinoxes, that our sensations of heat, and cold are the most lively. The reason of which must be, that at the latter seasons, their varieties are more numerous, and occasion more frequent comparisons between that, which we feel and that which we have felt.

What we have now said of temperature, we may repeat with respect to the waters of the amnios: the fœtus cannot be sensible of their influence, because the contact of any other medium is unknown to it. Before bathing, we are not sensible of the air, after bathing, the impression made by it upon us is unpleasant. It then affects us because there has been an interruption of its action upon the cutaneous organ.

Is the shock of the parietes of the matrix a more real cause of excitement, than the waters of the amnios, or temperature? At first we might be inclined to answer this question in the affirmative, because the fœtus being only at intervals subject to such stimulus, there should appear to result from thence a sensation. But let us remark that the density[41] of the uterus in a state of pregnancy being little greater than that of its waters, the impression must be trifling. In fact the more the consistence of bodies resembles that of the medium in which we live, the less powerful will be their action upon us. Water for instance, when reduced into vapour in our common fogs, and mists, affects the tact but slightly; in proportion as it is condensed it is the cause of a livelier affection.

The air then, to the animal which breathes, is truly the general comparative term, to which he refers all the sensations of tact. If the hand be plunged into carbonic acid gas, such substance will not affect the tact because its density is little different from that of the air.

The variety then of these sensations is in proportion to the difference existing between the density of the air, and that of the bodies, which are the occasion of such sensations. In the same way, the measure of the sensation of the fœtus must be the excess of density in the matrix above that of its waters. Now such excess being very inconsiderable, the sensation of it must be very obtuse.

This assertion with respect to the fœtus will become more general if we add to it the following: namely, that the mucous membranes, which are the seat of an inward tact have not as yet begun to exercise their functions. These membranes, after birth, being continually in contact with extraneous substances, possess in these bodies so many causes of irritation, which being continually repeated, become excitants to the organs: but in the fœtus there is no succession in these causes. The same urine, the same meconium, the same mucus at all times exercise their action upon the bladder, the intestines, and pituitary membrane.

From all this we may conclude, that the general sensations of the fœtus are very inconsiderable, though it should appear that the child in this state is surrounded by many of the causes, which are hereafter to beget sensations. Neither are the particular sensations of the fœtus more active; indeed they cannot be so for their causes are absent.

The eye which is closed by the pupillary membrane, and the nostrils, which are scarcely indicated, would not be capable of receiving impressions, even in the supposition that light and odour could act upon them. Applied against the palate, the tongue is in contact with nothing capable of producing savour. Were it in contact with the waters of the amnios, the effect would be the same, because as we have said, there is no sensation, where there is no variety of impression. The saliva of one person to another person possesses savour, to the individual himself it is insipid.

The ear in like manner is awakened by no sound. All is calm, every thing reposes with the little individual.

Here then we have proved, that four of the gates of sensation are shut in the fœtus; and let us now observe that the nullity of action in the senses which we have mentioned, must occasion very nearly the same nullity with respect to that of the touch.[42]

In fact, this sense is especially destined to confirm the notions which are acquired by the others, and to rectify them, for the latter are frequently illusory—the touch is always the agent of truth.[43] In attributing to the touch such use, nature has submitted it directly to the will; light, odours, and sounds affect their respective organs independently of the will.

The exercise of the other senses precedes that of the touch, they are the occasion of it. If a man were born without sight, hearing, smell, or taste, can we conceive in what way, he would be possessed of the sense of touch?

The fœtus resembles such a man; it possesses wherewithal to exercise the touch in its hands, which are already developed, and in the parietes of the matrix. Nevertheless the fœtus is never in action, because in seeing, in hearing, in smelling, and in tasting nothing, it is not disposed to exercise the touch in any way. Its members are little better than what to the tree are its branches, which do not transmit the impression of the bodies, with which they are entangled.

I shall here notice a great difference between the tact and the touch; they were formerly confounded by physiologists; the impressions of the latter are always directed by the will, those of the former do not depend on it. We shall conclude that the portion of the animal life which constitutes sensation, does not exist in the fœtus.

This nullity of action in the senses supposes the same deficiency of action in the nerves, which belong to them, and in that of the brain from whence they issue; for the business of the former is to transmit, of the latter to receive. Now without objects for transmission and reception, the two functions cannot have place.

From perception are immediately derived the memory and imagination; from these the powers of the judgment and the will. All this series of faculties then has not had a beginning in the fœtus, because the fœtus has not perceived, or had sensation. The brain exists in a state of expectation, it possesses all that is requisite for action. It does not want excitability, but stimulus. The first division of the animal life in consequence, or that, which relates to the action of exterior bodies, on the animal, has scarcely an outline in the fœtus. Let us examine whether the same be true of the second division of the animal life, or that which relates to the reaction of the living body.

II. Locomotion exists, but belongs in the fœtus to the organic life.

When we see the strict connexion which exists in animals, between sensation and their voluntary efforts, we might be induced to believe, that voluntary motion increases or diminishes with the increase or diminution of sentiment; for as sentiment furnishes out the materials of the will, when it does not exist, volition cannot exist: from induction to induction, it might thus be proved that in the fœtus the muscles must be totally inactive.

Nevertheless the fœtus moves, and sometimes even very strong shocks are the result of its motions. The reason why it does not produce sound, is because the medium for the production of sound is wanting. But how can we ally the inertia of the first part of the animal life with the activity of the second. It is thus.

We have seen in speaking of the passions, that the muscles of locomotion are brought into action in two manners. 1st, by the will; 2dly, by sympathy. This last mode of action occurs, when from the affection of an inward organ the brain is affected also, and occasions a motion which, in such case, is involuntary. A passion, for instance, affects the liver, the liver the brain, the brain the voluntary muscles. Here it is the liver, not the brain, which is the principle of motion: so that the muscles, though always thrown into action, immediately from the irradiations of the brain, belong nevertheless, as to their functions, sometimes to the one life, sometimes to the other.

Hence it is easy to conceive in what way the fœtus moves: with the fœtus, locomotion is not a portion of the animal life; its exercise does not suppose a pre-existent will; it is purely a sympathetic effect.

In utero the phenomena of the organic life succeed each other with an extreme rapidity; a thousand different motions are incessantly connected in the organs of circulation and nutrition. In these, every thing is energetically in action. But this activity of the organic life supposes a frequent influence exerted upon the brain by the inward organs, and consequently as many reactions on the part of the brain by sympathy upon the muscles. Besides, the brain is at such time more susceptible of such sort of influence, being much more developed than the other organs, and entirely passive on the side of the sensations.

We may now conceive what the motions or the fœtus are. They belong to the same class as many of those of the adult, which have not been as yet sufficiently distinguished. They are the same as those which are produced in the voluntary muscles by the passions; they resemble those of the man who sleeps, and who moves without dreaming, for nothing is more common than violent agitation in sleep succeeding difficult digestion. The stomach is in strong action; it acts upon the brain; the brain upon the muscles.

I might find a number of other involuntary organic motions taking place in the voluntary muscles of the adult, and consequently adducible to my present purpose; but what I have said on this subject will suffice. Let us remark only, that the organic motions, as well as the sympathetic affection of the brain, which is the seat of them, must gradually dispose this organ, and the muscles of the fœtus, the one to the perception of sensations, and the other to the motions of the animal life, which are to commence after birth. But on this head I shall refer to the memoirs of Monsieur Cabanis.

From what has been said, then, I believe we may confidently assert, that in the fœtus the animal life does not exist, and that all the actions which take place at this age, depend upon the organic life. The fœtus, indeed, has nothing of the especial character of the animal. Its very existence is that of the vegetable; and its destruction can only be said to be that of a living body, not of an animated being. Thus, in the cruel alternative of sacrificing the life of the mother, or that of the child, the choice cannot be doubtful.

The crime of destroying a fellow-creature is much more relative to his animal, than to his organic life.—We regret the being who feels, who reflects, who wills, who acts accordingly, and not the being which breathes, which is nourished, which is the seat of the circulation and the secretions. It is the former, whose violent death is accompanied with those images of horror, under which we look on homicide. In proportion then as in the series of animals, their intellectual functions diminish, is diminished also the painful sentiment which we feel at sight of their destruction.

If the blow, which terminates by an assassination the life of a man, were to destroy his organic life only, and suffer the other to subsist without alteration, such blow would be regarded with indifference, would excite neither pity for the victim, nor horror against the aggressor.

III. Development of the animal life, education of its organs.

A new mode of existence commences for the infant after birth; a variety of functions are added to its organic life; their aggregate become more complicated; their results are multiplied. As for the animal life, it only begins; and at this period a number of relations are established between the little individual and what surrounds him. It is then that every thing assumes with him a different mode of being, but at this remarkable epoch of the two lives, where the one is augmented by almost the half, and where the other commences only, they take upon them both a distinct character, and the aggrandisement of the first by no means follows the same laws as the development of the second.

We shall soon remark, that the organs of the internal life attain at once their perfection, and that from the instant at which they begin to act, they act with as much precision as they ever will do. On the contrary, the organs of the external life require a species of education; they arrive only by degrees at the perfection which we afterwards see in them. This important difference should be thoroughly examined. Let us begin by appreciating of what the animal life at first consists.

In examining the different functions of this life, which start at once into existence, we shall observe in their development a slow and graduated progress.—We shall see, that it is insensibly and by means of a real education that the organs attain a precision of action.

The sensations are at first confused; they transmit only general images; the eye has only the sensation of light; the ear that of sound only; the nose only that of smell. As yet there is nothing distinct in these general affections of the senses; but from habit the strength of the first impression is lessened and the particular sensations take place. The great differences of colours, sounds, smells, and savours, become perceptible; by little and little their secondary differences also are perceived, and after a certain lapse of time the child has learnt to see, to hear, to smell, to taste, and to touch.

After successfully undergoing the operation for the cataract, the patient, who has previously been totally blind, is sensible of light only, and learns by gradation to distinguish the objects which reflect it. Another person, before whom, as I have said, for the first time is exhibited the magnificent spectacle of an opera, at the first glance, perceives only a whole, which delights him, and only by degrees is able to isolate the enjoyments of which the dance, the music, and the decorations are productive.

The education of the brain is similar to that of the senses. Whatever depends upon its action, acquires the perfection, to which it is destined, by degrees only. The powers of perception, memory and imagination, which are all of them preceded and occasioned by the sensations, increase and extend in proportion as by repeated excitement they are brought into exercise.—The judgment, of which they form the triple base, associates but irregularly at first its motions, which themselves are but irregular. In a short time a greater degree of perspicuity is observed in its operations, and lastly they become precise and rigorous.

The voice and the agents of locomotion exemplify the same phenomenon: the cries of young animals at first are only an unformed sound, which possesses no sort of character: by age they are gradually modified, and after long repeated exercise affect the peculiar consonances of the species, by which, and particularly during the season of their loves, the individual of the same species is never deceived.[44] I do not instance the speech of man, for this is evidently the fruit of education.

In examining the newly born animal, its muscles will be seen continually in action. As every thing is new to it, every thing is an excitant to it, and makes it move; it endeavours to touch every thing, but neither progression, nor the power of standing can have place when the contractions of the voluntary muscles are so numerous. It is necessary for such, that habit shall have taught it to combine particular contractions with other particular contractions; until then it stumbles and falls at every moment.

Undoubtedly the inclination of the pelvis in the fœtus, the disposition of the femora, and the want of curvature in the spine, adapt it but little for standing immediately after birth; but with these causes is certainly also combined the want of exercise.[45] Who does not know, that if a limb be suffered to remain immoveable for a length of time, it loses the habit of moving, and that when afterwards its service is required, it requires a new kind of education before it can exercise its movements with any regularity or precision. The man, who for a long time should condemn himself to silence, would experience in like manner the same embarrassment in his first attempt at utterance.

From these considerations we may conclude that our exterior life, to allow myself the expression, is learnt, and requires before it can be perfected, a sort of apprenticeship.

IV. Of the influence of society over the education of the organs of the animal life.

Over this sort of education, which the organs of the animal life receive, society exercises a very great influence; it enlarges the sphere of action of some of them, lessens it for others, and modifies it in them all.

I shall first remark, that it constantly gives to some of the organs a perfection greater than naturally should be their portion. Such in fact is the nature of our occupations as always to require the especial action of some one, or other of these organs. The ear of the musician, the palate of the cook, the brain of the philosopher, the muscles of the dancer, and the larynx of the singer, receive in addition to the general education of the exterior life, a particular education.

Under these considerations, the occupations of mankind might be divided into three classes. The first would comprehend all those, which especially regard the senses, such as painting, music, and sculpture, the acts of the perfumer and the cook, and in a word all those the results of which are productive of pleasure to the senses. In the second would be ranged the occupations, wherein the brain is chiefly called into action; such as poetry, the sciences of nomenclature, the mathematics and metaphysics. The occupations of dancing, equitation, and the mechanic acts would form the third class.[46]

Each several occupation then of the individual, brings into permanent activity, some one organ in particular, and gives it a peculiar perfection. The ear of the musician in a piece of harmony, and the eye of the painter in a picture, distinguish many things which entirely escape the vulgar. It frequently happens that this perfection of action, is accompanied in the more exercised organ with an excess of nutrition: this we may frequently observe in the muscles of the arm of the baker, in those of the inferior limbs of the dancer, and in those of the countenance of the player.

In the second place I have asserted that society contracts the sphere of action, which should naturally belong to many of the external organs. Indeed, for the sole reason that any one of them is the more occupied, the others must be less so, and lose in aptitude what is gained by the single organ. The most common observation will prove this truth at every moment.

Examine the philosopher, who in his abstract meditations, and in the silence of the closet condemns to inaction his external and locomotive powers. Examine him by chance attempting any exercise of the body, and you will laugh at his awkwardness and air of constraint; his sublime conceptions astonish, the heaviness of his movements is amusing.

Examine on the contrary the dancer, who by the lightness of his steps exhibits apparently to the eye whatever the graces of fable have set before the imagination. It might be imagined perhaps that the profoundest meditations, have been productive of such felicity of motion; but let him be conversed with, and nothing very surprising will be found in the man.

The observing mind, which analyses the different individuals of society at every moment, will be led to similar remarks. Perfection of action in the locomotive organs, concurring with a like perfection of intellect, will seldom be found.

V. Of the laws, which regulate the education of the organs of the animal life.

It is manifest then that society inverts the natural order of education in the animal life, and that it irregularly distributes to the different organs of this life, a perfection which they would otherwise enjoy in a more uniform proportion.

A determined sum of power, has been attributed to every individual, which sum must always remain the same, whether it be equally or unequally distributed, accordingly the activity of one organ must imply more or less inactivity in the others.

This truth will conduct us to the fundamental principles of all social education whatever; namely, that no individual at the same time, should be applied to many studies, even if it be wished that he should succeed in all of them. Philosophers have long insisted upon this maxim, but I doubt whether the moral reasons on which they have founded it, are all of them together worth this single and beautiful physiological observation by which it is demonstrated, that for the purpose of augmenting the powers of one organ, there are no other means than those of diminishing the powers of the others. On this account I shall dwell upon this observation, and prove its truth by a variety of facts.

The ear, and especially the touch, acquire in the blind man, a perfection which would hardly be credited, were not its reality proved by daily observation. The deaf and dumb possess in the eye an accuracy of sight, which is unknown to those, with whom the powers of the ear and utterance are unfolded. Little connexion with external objects, enfeebles the senses of persons who are subject to ecstasy, but gives the brain a power of contemplation, such as to make it appear, that every part of the animal life, excepting that organ, during such affection is in a state of sleep.

But what occasion is there for seeking in extraordinary facts, the proof of a law which the animal in its healthy state exemplifies at every moment. Let us consider in the series of animals the relative perfection of each organ, and it will be seen at once, that where any one of them is excellent, the others are less perfect. The eagle, which has a very piercing sight, has but a very obtuse sense of smell; in the dog, the latter sense is extremely fine, the former dull. The sense of hearing is particularly acute in the hare, that of touch in the bat; the cerebral action predominates in the monkey, and vigour of motion in the feræ.

Every species then possesses some particular division of its animal life, in a degree of excellence superior to that of the others. Not a single instance will be found, where the perfection of one organ does not appear to be acquired at the expense of the others. Man in general, abstraction being made of every other consideration, has the ear particularly good, and in the natural order of things, this must be so; because his speech, which exercises the ear incessantly, is for this organ a permanent cause of activity, and therefore of perfection. And not only in the animal life is this law remarkable; but it appears to have place also, in all the phenomena of the organic life. The morbid affection of one of the kidneys, of one of the parotid glands, will double the secretion of the other.

Let us now examine what happens in the process of digestion. Each system at such time is the seat of an exaltation of the vital powers. Immediately after the entry of the aliments into the stomach, the action of all the gastric viscera is augmented, the powers of life are concentrated about the epigastrium, and abandon the organs of the external life; from thence arise, as authors have observed, the lassitude, the inaptitude of the senses to the reception of external impressions, the tendency of the individual to sleep, and the cold which is so frequently felt in the integuments.

The gastric digestion being completed, the vascular succeeds, and the chyle is introduced into the circulatory torrent, for the purpose of undergoing the influence of this system, and that of respiration; accordingly the blood-vessels and lungs become in their turn, the focus of an increased action, the pulse rises, and the movements of the thorax are precipitated.[47]

It is then the glandular, then the nutritive system which enjoy a marked superiority in the state of their vital powers. Lastly, when these powers have been successively developed, over all the system, they return to the organs of the animal life, the senses resume their activity, the functions of the brain their energy, the muscles their vigour. Whoever reflects upon what he has experienced after a somewhat copious repast, will be easily convinced of the truth of these remarks.

In this way, the whole of the functions represent a species of circle, of which the one half belongs to the organic, the other to the animal life, the vital powers seem successively to traverse these two halves. When they are found in one half, the other is proportionably deprived of them, nearly in the same manner as every thing appears to languish and be reanimated in the two portions of the globe, accordingly as the sun refuses, or sheds down his beneficent influence.

Should any farther proof be required of this inequality of distribution with regard to the vital powers, we may find it in the process of nutrition. This process has always an excess of action in some one of the organs, which at such time may be said to live more than the others do. In the fœtus, the brain and the nerves, the inferior members after birth, and at the age of puberty, the genital parts and breast appear to grow at the expense of the others.

From such a variety of considerations, we may establish the following to be a fundamental law of the distribution of the vital powers, namely, that when they increase in one part, they decrease in the rest of the living œconomy, that the sum of them can never be augmented, and that they only transfer themselves successively from one organ to another. By the help of these general data, it is easy to perceive why we cannot at the same time attain to perfection in the various parts of our animal life, why we cannot at the same time excel in all the sciences.

Universality of knowledge in the same individual is a chimera; it is repugnant to the laws of our organization, and if history afford us some few instances of extraordinary men, who have thrown an equal light upon many of the sciences, such instances are but so many exceptions to the common laws of nature; for who are we, that we should venture on the pursuit of many things at once, and hope to attain in all of them a perfection, which for the most part, even when we have but a single object in view, escapes us?

Were we capable of following at once a number of occupations, such occupations would be those which have the greatest analogy among themselves with respect to the organs which they bring into exercise: and by restraining ourselves in this way within a narrow circle, we may, indeed, with a greater degree of facility excel in many parts; but even here the great secret of being superior in any one of them, is that of possessing but a mediocrity in the others.

Let us take, for example, the sciences, which bring into action the functions of the brain. We have seen that these functions relate especially to the memory, which presides over nomenclature; to the imagination, under the empire of which, is poetry; to the attention, which is chiefly excited by the details of calculation; and to the judgment, whose dominion embraces the whole of the sciences of reasoning. Now it is manifest from daily observation, that not one of these different operations of the mind is to be developed but at the expense of the others.

The habits of reciting the beauties of Corneille or Racine, we might naturally suppose would enlarge the mind of the actor; what can be the reason that from such habit he does not acquire an energy of conception beyond that of the vulgar? The reason depends in part, no doubt, upon the natural disposition of the man, but at the same time may be deduced from the greater efforts of memory, and the faculty of imitation, which such a person is obliged to exert: for the purpose of enriching these, the other parts of the brain are in a manner plundered.

Accordingly, when I perceive an individual, desirous at the same time of excelling by address of hand, in the operations of surgery, by depth of judgment in the practice of medicine, by extent of memory in botany, and by force of attention in metaphysical contemplation, methinks I see a physician, who, for healing a disease, for the purpose of expelling, according to the old expression, the morbific humour, at the same time undertakes to augment the whole of the secretions by the simultaneous use of sialagogues, diuretics, sudorifics, emmenagogues, &c. &c.

But would not the slightest acquaintance with the laws of the economy, suffice for hinting to such physician, that one gland pours forth a greater quantity of fluid, only because the others secrete a less? Should he not know that such a variety of medicines can operate in no decided way, and that to exact too much of nature, is frequently the means of obtaining nothing? The same may be asked of the individual who is desirous of simultaneous perfection, both in the bodily and mental exercises, who should pretend to double or triple his relative life, when nature has willed that he should only have the power of detaching from some few of his organs, some few degrees of force, which may be added to one or more of his other organs, and by no means that of increasing the sum of these powers.

Do we wish that any one organ in particular shall attain to perfection, we must condemn the others to inaction. We castrate men to change their voices; it is astonishing that the barbarous idea of depriving them of sight has not been found out also for the purpose of rendering them musicians, since it is well known how acute the sense of hearing is in the blind. The child, who should be destined to music, ceteris paribus, would make a much more rapid progress, were his ears to be assailed by harmonious sounds only, and every thing removed which might be capable of exercising his other senses.

It is a truth, then, that our superiority in such or such an art and science, may almost always be measured by our inferiority in other respects; and that this general maxim which the greater number of the ancient philosophers have insisted on, but which many of our modern ones would willingly overturn, has for its foundation one of the great laws of the animal economy, and will ever be as immutable as the base on which it rests.

VI. Of the education of the animal life as to duration.

The education of the organs of the animal life, is prolonged for a time which we cannot determine, as it is influenced by such a variety of circumstances; but the peculiarity of this education consists in its being the business of each age, to bring to perfection certain organs in particular.

In childhood, the senses more especially are educated; every thing seems to relate to the development of their functions. Environed with bodies which are new to him, the little individual seeks to know them all; he maintains in a sort of perpetual expectation those organs by which his connexions with what is near him are established, and undoubtedly his sensibility is excessively developed. His nervous compared with his muscular system, is proportionally very great; accordingly for the dissection of the nerves, we always prefer the bodies of children.

With the education of the senses, the improvement of the functions of the brain which relate to sensation is necessarily connected. In proportion, then, as the sum of the sensations becomes enlarged, the memory and imagination begin to come into play. The age which follows infancy, is that of the education of those parts of the brain in which these faculties are seated.—It is then, that there have existed a sufficient number of antecedent sensations for the exercise of the memory, and for the discovery of the type of those illusory sensations which it is the business of the imagination to assemble. On the other hand, the little activity of the judgment at this epoch is much in favour of the energy of these two faculties; and then the revolution which puberty brings on, the taste which it develops, and the desires which it creates, contribute very much to extend the sphere of the latter of them.

When perception, memory, and the imagination have been perfected, when their education is finished, that of the judgment commences, or rather becomes more active, for the judgment begins to be exercised upon the very first materials, with which it is presented. At this epoch the functions of the senses, and partly those of the brain have nothing more to acquire, and all the powers of the individual, are concentrated upon the education of the judgment.

Hence it is manifest, that the first portion of the animal life, or that by means of which we are acted on from without, and reflect such action, has at each age a division, which is then particularly unfolded. The first age is that of the education of the senses, the second that of the enlargement of the imagination, the third that of the development of the judgment.

We should never then prescribe the study of the sciences, which exact the exercise of the judgment, at an age when the senses are especially in action; but follow in our artificial methods of education, the same laws which preside over the natural education of the organs. The child should be applied to music and design; the adolescent, to the sciences of nomenclature, and the belles lettres; the adult, to the exacter sciences, where facts are connected by a process of reasoning. The study of logic and the mathematics, terminated our ancient plan of education; it was one advantage at least among its numerous imperfections.

As to the second portion of the animal life, or that by means of which the animal reacts upon external bodies, the state of infancy is characterized by the number, the frequency, and feebleness of its motions; adult age by their vigour; and adolescence by a mixture of the two. The voice, however, does not appear to follow these proportions, but is subject to an influence which proceeds especially from the organs of generation.

I shall not dwell upon the different modifications, which with respect to the animal life are derived from sex, climate, and season. So many have treated of these questions, that it would be difficult to add to what has been said upon them.

In speaking of the laws of education, as they affect the organs of the external life, I have supposed these organs to be in a state of complete integrity, and possessed of whatever is necessary to their perfection.—If they be feeble or delicate, if any defect of conformation exist in them, these laws will only be applicable more or less; for it is manifest that the habit of judging will not rectify the judgment, if the brain be badly constituted; and that the frequent exercise of the larynx and voluntary muscles, will never make up for the irregularity of action occasioned by irregularity of conformation.