Transcriber's Notes

Obvious typographical errors have been silently corrected. Variations in spelling hyphenation and punctuation remain unchanged, but the use of ligatures has been standardised.

An analytical table of contents for all three volumes was included with volume III. The section for this volume has been linked to the relevant pages.

The outline Table of Contents was added by the transcriber.

GENERAL ANATOMY,
APPLIED TO
PHYSIOLOGY AND MEDICINE;

BY XAVIER BICHAT,

PHYSICIAN OF THE GREAT HOSPITAL OF HUMANITY AT PARIS, AND
PROFESSOR OF ANATOMY AND PHYSIOLOGY.

Translated from the French.

BY GEORGE HAYWARD, M.D.

FELLOW OF THE AMERICAN ACADEMY OF ARTS AND SCIENCES,
AND OF THE MASSACHUSETTS MEDICAL SOCIETY.

IN THREE VOLUMES.

VOLUME III.

BOSTON:
PUBLISHED BY RICHARDSON AND LORD.

J. H. A. FROST, PRINTER.
1822.

Table of Contents

DISTRICT OF MASSACHUSETTS, to wit:

District Clerk's Office.

Be it remembered, that on the seventeenth day of April, A. D. 1822, in the forty-sixth year of the Independence of the United States of America, Richardson & Lord, of the said District, have deposited in this office the title of a book, the right whereof they claim as proprietors, in the words following, to wit:

"General Anatomy, applied to Physiology and Medicine; by Xavier Bichat, Physician of the Great Hospital of Humanity at Paris, and Professor of Anatomy and Physiology. Translated from the French, by George Hayward, M. D. Fellow of the American Academy of Arts and Sciences, and of the Massachusetts Medical Society. In three Volumes. Volume III."

In conformity to the Act of the Congress of the United States, entitled, "An Act for the Encouragement of Learning, by securing the Copies of Maps, Charts and Books, to the Authors and Proprietors of such Copies, during the times therein mentioned:" and also to an Act entitled, "An Act supplementary to an Act, entitled, An Act for the encouragement of Learning, by securing the Copies of Maps, Charts and Books, to the Authors and Proprietors of such Copies during the times therein mentioned; and extending the Benefits thereof to the Arts of Designing, Engraving and Etching Historical and other Prints."

JOHN W. DAVIS,
Clerk of the District of Massachusetts.

[MUSCULAR SYSTEM OF ORGANIC LIFE.]

This system is not as abundantly spread out in the economy as the preceding. The whole mass which it forms, compared with the whole of the other, which is more than one third of the body, presents in this respect a very remarkable difference. Its position is also different; it is concentrated, 1st, in the thorax, where the heart and œsophagus belong to it; 2d, in the abdomen where the stomach and intestines are in part formed by it; 3d, in the pelvis where it contributes to form the bladder and even the womb, though this belongs to generation, which is a function distinct from organic life. This system then occupies the middle of the trunk, is foreign to the extremities, and is found far from the action of external bodies, whilst the other superficially situated, forming almost alone the extremities, seems, as we have said, almost as much destined in the trunk to protect the other organs, as to execute the different motions of the animal. The head contains no part of the organic muscular system; this region of the body is wholly devoted to the organs of animal life.

ARTICLE FIRST.
OF THE FORMS OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

All the muscles of the preceding system take in general a straight direction. These are all on the contrary curved upon themselves; all represent muscular cavities differently turned, sometimes cylindrical as in the intestines, sometimes conical as in the heart, sometimes rounded as in the bladder, and sometimes very irregular as in the stomach. No one is attached to the bones; all are destitute of tendinous fibres. The white fibres arising from the internal surface of the heart, and going to be attached to the valves of its ventricles, have by no means the nature of the tendons. Ebullition does not easily reduce them to gelatine; desiccation does not give them the yellowish appearance of these organs; they resist maceration longer than them.

It is in general a great character that distinguishes the muscular organic system from that of animal life, that it does not arise from, nor terminate in fibrous organs. All the fibres of this last are continuous either with tendons, or aponeuroses or fibrous membranes. Almost all those of the first go on the contrary from the cellular texture, and return to it after having run their course. I at first thought that the dense and compact texture which is between the mucous membrane and the fleshy fibres of the intestines, the bladder, the stomach, &c. was an assemblage and net-work of many small tendons corresponding to these fibres, and interwoven in the form of an aponeurosis; the density of this layer deceived me at first view. Ebullition, maceration, and desiccation have since taught me, that this layer, completely foreign to the fibrous system, should be referred, as Haller has said, to the cellular, which is only more dense and compact there than elsewhere. It is this layer, which I have designated, in the cellular system by the name of the sub-mucous texture. Many fibres of the system of which we are treating appear to form an entire curve, which is not crossed by any cellular intersection; some layers of the heart exhibit this arrangement, which is in general very rare; so that there is almost always an origin and termination of the fibres, upon an organ of a nature different from their own.

We can hardly consider in a general manner the forms of the system of which we are treating; each organ belonging to it is moulded upon the form of the viscus to the formation of which it contributes. In fact, the organic muscles do not exist in distinct fasciculi, like those of animal life; all, except the heart, form but a third, a quarter and often even less in the structure of a viscus.

The greatest number has a thin, flat and membranous form. There are layers more or less broad, and hardly ever distinct fasciculi. Placed at the side of each other, the fibres are rarely one above another; hence it happens that occupying a very great extent, these muscles form however a very small volume. The great gluteus alone would be larger than all the fibres of the stomach, the intestines and the bladder, if they were united like it into a thick and square muscle.

ARTICLE SECOND.
ORGANIZATION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

The organization of the involuntary muscles is not as uniform as that of the preceding. In these all is exactly similar excepting the differences of the proportion of the fleshy fibres to the tendinous, of the length of the first, of the prominence of the fasciculi, of their assemblage into flat, long or short muscles; in whatever place we examine them, their varieties are in their forms and not in their texture. Here on the contrary, there is in this texture marked differences; the heart compared with the stomach, the intestines with the bladder are sufficient to convince us of this. It is by virtue of these different textures, that the contractility and sensibility vary as we shall see in each muscle, that the force of the contraction is not the same, and that life is different in each, whilst it is uniform in all those of animal life. We shall now consider in a general manner the organization of the involuntary muscles.

I. Texture peculiar to the Organization of the Muscular System of Organic Life.

The organic muscular fibre is in general much finer and more delicate than that of the preceding system; it is not brought into as thick fasciculi. Very red in the heart, it is whitish in the gastric and urinary organs. Besides, this colour varies remarkably. I have observed that sometimes maceration renders it of a deep brown in the intestines.

This fibre never has one single direction, like that of the preceding muscles; it is interlaced always, or found in juxta-position in different directions; sometimes it is at a right angle that the fasciculi are cut, as in the longitudinal and circular fibres of the gastric tubes; sometimes it is with angles more or less obtuse or acute, as in the stomach, the bladder, &c. In the heart, this interlacing is such in the ventricles, that it is a true muscular net-work. From these varieties of direction, results an advantage in the motions of these sorts of muscles, which, being all hollow can by contracting diminish according to many diameters the extent of their cavity.

Every organic muscular fibre is in general short; those which, like the longitudinal of the œsophagus, the rectum, &c. appear to run a long course, are not continuous; they arise and terminate at short distances, and thus arise and terminate successively in the same direction or line; no one is comparable to those of the sartorius, the gracilis, &c. as it respects length.

We know the nature of their fibres no better than that of those of animal life; but they appear nearly the same under the action of the different reagents. Desiccation, putrefaction, maceration, ebullition, exhibit in them the same phenomena. I have observed upon the subject of this last, that once boiled, the fibres of both systems are much less alterable by the acids sufficiently weakened. After being some time in the sulphuric, the muriatic and nitric diluted with water, they soften a little, but keep their original form, and do not change into that pulp to which raw fibres are always reduced in the same experiment. The last of these acids turns them yellow as before ebullition.

I have also made an observation as it respects the horny hardening which is produced the instant ebullition commences; it is this, that it is always the same whatever may have been the antecedent dilatation or contraction of the fibres. The stomach which at death was so dilated as to contain many pints of fluid, is reduced to the same size, all other things being equal, as that which is contracted so as to be no larger than the cœcum. Diseases have a little influence on the horny hardening. The heart of a phthisical patient exhibited to me in the same experiment this phenomenon much less evidently, than that of an apoplectic.

The resistance of the organic muscular fibre is in proportion much greater than that of the fibres of the animal muscular system. Whatever may be the distension of the hollow muscles by the fluid which fills them during life, ruptures hardly ever take place in them.

The bladder alone sometimes exhibits this phenomenon, which is however very rare in it. In the great retentions of the urine, in which ruptures take place, it is almost always the urethra that is ruptured, and the bladder remains whole. We meet in practice with a hundred fistulas in the perineum, coming from the membranous portion, to one above the pubis. We find in authors many examples of rupture of the diaphragm; we know of but few of the rupture of the stomach, the intestines and the heart.

II. Common Parts in the Organization of the Muscular System of Organic Life.

The cellular texture is in general much more rare in the organic muscles than in the others. The fibres of the heart are in juxta-position, rather than united by this texture. It is a little more evident in the gastric and urinary muscles. It is almost wanting in the womb; thus these muscles are not infiltrated, like the preceding, in dropsies; they never exhibit that fatty state of which we have spoken, and which sometimes loads the fibres. I have not observed in these fibres the yellowish tinge which the others often take, especially in the vertebral depressions.

The blood vessels are very numerous in this system; they are found in it even in greater proportion than in the other; more blood consequently penetrates them. This fact is remarkable, especially in the intestines, in which the mesenteric arteries distribute numerous branches, over an extremely delicate fleshy surface. But I would remark that this appearance is to a certain degree deceptive, as many of these vessels only traverse the fleshy surface to go to the mucous membrane. In the ordinary state they give to the gastric viscera a reddish tinge, which I have rendered at will livid and afterwards brought back to its primitive state, by shutting and afterwards opening the stop-cock adapted to the wind pipe, in my experiments upon asphyxia.

The absorbents and exhalants have nothing peculiar in this system.

The nerves come to them from two sources; 1st, from the cerebral system; 2d, from that of the ganglions.

Except in the stomach in which the par vagum is distributed, the nerves of the ganglions predominate everywhere. In the heart, they are the principal; in the intestines, they are the only ones; at the extremity of the rectum and the bladder, their proportion is greater than that of the nerves coming from the spine.

The cerebral nerves intermix with them, in penetrating the organic muscles. The cardiac, solar, hypogastric, plexuses, &c. result from this intermixture which appears to have an influence upon the motions, though we are ignorant of the nature of this influence.

All the nerves of the ganglions which go to the organic muscles, do not appear to be exclusively destined to them. A great number of filaments belong only to the arteries; such is in fact their interlacing, that they form, as we have seen, around these vessels a real nervous membrane, superadded to their own, and exclusively destined to them. I would compare this nervous envelope to the cellular envelope which is also found around the arteries, and which is wholly distinct from the surrounding cellular texture; thus it only has communications with the nerves of the organic muscles, without being distributed to these muscles. Besides as the nerves of the ganglions are always the most numerous and essential in them, and as their tenuity is extreme, the nervous mass destined to each is infinitely inferior to that which is found in the voluntary muscles. The heart and the deltoid muscle compared together, exhibit in this respect a remarkable difference.

ARTICLE THIRD.
PROPERTIES OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

Under the relation of properties, this system is in part analogous to the preceding, and in part very different from it.

I. Properties of Texture. Extensibility.

Extensibility is very evident in the organic muscles. The dilatation of the intestines and the stomach by aliments, by the extrication of gas, by the fluids that are found there, that of the bladder by the urine, by injections that are forced in, &c. are essentially owing to this extensibility.

This property is characterized here by two remarkable attributes; 1st, by the rapidity with which it can be put into action; 2d, by the very great extent of which it is susceptible.

The stomach and intestines pass in an instant from complete vacuity to great extension. Artificially distended, the bladder becomes immediately of a size treble, quadruple even of that which is natural to it. It sometimes however resists, but this does not prove its defect of extensibility; it is because the fluid injected irritates it and makes it contract; the organic contractility in exercise, then prevents the development of extensibility, as it sometimes cannot be brought into action by stimulants in a muscle laid bare, because the animal contractility in exercise in the muscle, forms an obstacle to it. The muscles of animal life are never capable of this rapidity in their extensibility, whether because they are intersected by numerous aponeuroses which dilate but slowly, or whether because their layers of fibres are very thick, two circumstances that do not exist in the muscles of organic life. Hence a remarkable phenomenon that I have observed in all cases of tympanites. When we open the abdomen of subjects that have died in this state, without wounding the swelled intestines, these immediately burst out, swell more, and occupy twice as large a space as they were contained in in the abdomen; why? Because the parietes of the abdomen being unable to yield in proportion to the quantity of gas that is developed, this has been compressed in the intestines during life, and expands immediately by its elasticity when the cause of compression ceases. In dropsies in which the distension is slow, the abdominal parietes enlarge much more than in tympanites. The size of the abdomen would be double in this, if the extensibility of the parietes was in proportion to that of the intestines.

As to the extent of the extensibility of the organic muscles, we can form an idea of it by comparing the empty stomach which oftentimes is not larger than the cæcum in its ordinary state, with the stomach containing sometimes five, six and even eight pints of fluid; the bladder contracted and concealed behind the pubis, with the bladder full of urine from suppression, rising sometimes even above the umbilicus; the rectum empty, with the rectum filling a part of the pelvis in old people in whom the excrements have accumulated in it; the intestines contracted with the intestines greatly distended.

It is to the extent of extensibility of the organic muscles and to the limits placed to that of the abdominal parietes, that must be referred a constant phenomenon that is observed in the gastric viscera; viz. that in the natural series of their functions, they are never all distended at the same time; the intestines are filled when the matters contained in the stomach are evacuated; the bladder is not full of urine in the digestive order, until the other hollow organs are empty, &c. In general, that is an unnatural order in which all the organs are distended at once.

There is for the organic muscles a mode of extensibility wholly different from that of which I have just spoken; it is that of the heart in aneurisms, and the womb in pregnancy. The first, for example, acquires a size double, treble even sometimes in its left side, and yet it increases at the same time in thickness. This size is not owing to distension, but to a preternatural growth. The aneurismatic heart is to the ordinary heart, what this is to the heart of the infant; it is nutrition that makes the difference and not distension; for whenever it is owing to this it diminishes in thickness as it increases in extent; there is no addition of substance. Besides the aneurismatic heart has not often the cause that distends it, for commonly in this case the mitral valves allow a free passage to the blood; whilst when they are ossified the left ventricle often remains in a natural state. Moreover, the slow progress of the formation of aneurism proves that it is a preternatural nutrition that has presided over this increase of the heart. You would in vain then empty this organ of the blood it contains, it would not contract and resume its dimensions, as the inflated intestine does which we puncture to allow the air to escape.

In the womb there are two causes of distension; 1st, the sinuses greatly developed; 2d, an addition of substance, a real momentary increase of the fibres of the organ which remains as thick and even more so than in the natural state. At the time of accouchement, the sinuses immediately flatten by the contraction of the fibres; hence the sudden contraction of the organ. But as on the one hand nutrition alone can remove by decomposition the substances added to the fibres to enlarge them, and as on the other, this function is exerted slowly, after the womb has undergone the sudden contraction owing to the flattening of its sinuses, it returns but gradually and at the end of some time to its ordinary size. Extensibility is not then brought into action in the womb filled by the fœtus, and in the aneurismatic heart; these organs really become at that time the seat of a more active nutrition; they grow preternaturally, as they have grown naturally with the other organs; but these do not then experience an analogous phenomenon, they become monstrous in comparison. The womb decreases, because the motion of decomposition naturally predominates over that of composition after accouchement, whilst it was the reverse before this period. The aneurismatic heart remains always so.

These dilatations of the heart should be carefully distinguished from those really produced by extensibility, as in the right auricle and ventricle for example, which are found full of blood at the moment of death, because the lungs which are weakened, not allowing it to pass through them, compel it to flow back to the place from which it came. There are but few hearts which do not exhibit in very various degrees, these dilatations, which we have the power in a living animal of increasing or diminishing at will, according to the kind of death we produce. Two hearts are hardly ever of the same size after death; many varieties are met with, and these depend more or less on the difficulties which the blood experiences in the last moments, in passing through the lungs. Hence why in the diseases of the heart, there is no standard by which we can compare the morbid size, especially if we examine the organ as a whole. In fact the distension of the right side can give it an aneurismatic appearance, and a size even greater than that of some aneurisms. If we examine the left side separately, the error is more easily proved, because this side is subject to less variations. But the principal difference consists in the thickness. The power of contraction appears to increase in proportion to this thickness, which arises from the substance added by nutrition. It is this power which produces the great beating that is felt under the ribs, the strength of the pulse, &c.

Contractility.

It is in proportion to extensibility. It is often brought into action in the ordinary state. It is in virtue of this property, that the stomach, the bladder, the intestines, &c. contract, and acquire a size so small compared to what they have when they are full. In general, there is no muscle of animal life, which is capable of such extreme contractions as those of organic life.

It should be remarked, however, that life, without having contractility immediately dependant upon it, since the intestines, the stomach, and the bladder contract after death when their distension is removed, modifies it in a very evident manner. The causes even which alter or diminish the vital forces have an influence upon it; hence the following observation that all those accustomed to open dead bodies can make. When the subject has died suddenly, and the stomach is empty, it is much contracted; when, on the contrary, death has been preceded by a long disease which has weakened its forces, the stomach, though empty, remains flaccid, and is found but very little contracted.

We should consider the substances contained in the hollow muscles of organic life, as true antagonists of these muscles; for they have not muscles that act in a direction opposite to theirs. As long as these antagonists distend them, they do not obey their contractility of texture; when they are empty, this is brought into action. It is not, however, upon this property that the mechanism of the expulsion of matters from these organs turns, as aliments from the stomach and intestines, urine from the bladder, blood from the heart, &c. It is the organic contractility that presides over this mechanism. It is difficult to distinguish these properties in exercise. One occasions a slow and gradual contraction, which is without the alternation of relaxation; the other, quick and sudden, consisting in a series of relaxations and contractions, produces the peristaltic motion, those of systole, diastole, &c. It is after the organic contractility has procured the evacuation of the hollow muscles, that the contractility of texture closes them. In death from hemorrhage from a great artery, the left and even the right side of the heart send out all the blood they contain; afterwards empty, they contract powerfully, and the organ is very small. On the contrary, it is very large when much blood remaining in its cavities, distends it, as in asphyxia. These are the two extremes. There are, as I have said, many intermediate states.

The contractility of texture is, in the system of which we are treating, in proportion to the number of fleshy fibres. Thus, all things being equal, the rectum, when empty, contracts upon itself with much more force than the other large intestines; the contraction of the ventricles is much greater than that of the auricles, and that of the œsophagus is much greater than that of the duodenum, &c. &c.

II. Vital Properties.

They are almost in an inverse order of those of the preceding system.

Properties of Animal Life. Sensibility.

The animal sensibility is slight in the organic muscles. We know the observation related by Harvey upon a caries of the sternum that laid bare the heart; they irritated, without its being felt by the patient, this organ, which only contracted under the stimulant. Remove the peritoneum behind the bladder of a living dog, and irritate the subjacent muscular layer, the animal gives but few marks of pain. It is difficult to make these experiments upon the intestines and the stomach; their muscular coat is so delicate that we cannot act upon it without at the same time stimulating the subjacent nerves.

It appears that the organic muscles are much less susceptible of the feeling of lassitude, of which the preceding become the seat after great exercise. I do not know however if in those to which many cerebral nerves go, it does not take place; for example, when the stomach has been for a long time contracted, it is probable that the lassitude of its fibres, produces in part the painful sensation that we then have, and which we call hunger, a sensation that should be distinguished from the general affection that succeeds it, and which becomes truly a disease, when abstinence has been too much prolonged. We know that substances not nutritive then appease this sensation without remedying the disease, when the stomach is filled with them. I refer to the same kind of sensibility the anxiety and distress which patients experience, in whom we keep the bladder in permanent contraction by an open sound in the urethra, which transmits the urine as fast as it falls from the ureters. This sensation does not resemble that of hunger, because the sensibility of the bladder and that of the stomach being different, their modifications cannot be the same. Thus each of these two sensations is different from that of which the muscles of animal life, for a long time contracted, become the seat. I do not believe that the sensation of hunger belongs solely to the cause I have pointed out, and which others have not spoken of; but it cannot be denied that it has much part in it. Who knows if, after a fever in which the action of the heart has been for a long time accelerated, the weakness of the pulse which accompanies convalescence, is not a sign of the lassitude in which its fleshy fibres are, on account of the antecedent motion? We know the painful sensation of fatigue which the stomach experiences after the contractions of vomiting.

Contractility.

The animal contractility is foreign to the muscles of organic life. To be convinced of this, we must recollect that on the one hand this contractility always supposes the influence of the brain and the nerves, to bring in play the action of the muscle, and that on the other, the brain, in order to exert this influence, must be excited by the will, by stimulants or by sympathies. Now none of these causes acting upon the brain, the organic muscles cannot contract.

Every body knows that these muscles are essentially involuntary. If some men have had the faculty of arresting the motions of the heart, it is not upon this organ that the brain has acted; the action of the diaphragm and the intercostals has first been suspended; respiration has ceased for a time; then consequently the circulation.

If we irritate the brain with a scalpel or any other stimulant, the muscles of animal life become convulsed; they are paralyzed if we compress this organ. Those of organic life, on the contrary preserve in both cases their natural degree of motion. The heart still continues to beat, the intestines and stomach move some time after the cerebral mass and spinal marrow have been taken away. Who does not know that the circulation goes on very well in acephalous fœtuses; that after the blow that has knocked down an animal, and rendered his whole voluntary muscular system immoveable, the heart is still for a long time agitated, the bladder rejects the urine, the rectum expels the excrements, &c. the stomach even sometimes vomits up aliments? Opium, which benumbs the whole animal life, because it acts especially upon the brain which is the centre of it, which paralyzes all the voluntary muscles, leaves the others unaffected in their contractions. Intoxication produced by wine exhibits the same phenomenon. A man staggers after drinking; his limbs refuse to carry him, and yet his heart beats with force; his stomach often heaves and rejects the surplus fluids it contains. All narcotic substances also produce this effect.

If from experiments we pass to observations on the sick, we see that all cerebral affections are foreign to the organic muscular system. Wounds of the head with depression, fungi of the brain, effusions of blood, pus and serum, apoplexy, &c. affect exclusively the voluntary muscles, the action of which they increase, weaken or destroy. In the midst of this general derangement of animal life, the organic remains unaffected. The paroxysm of mania and malignant fever likewise proves this fact. Who does not know that in this last the pulse is oftentimes scarcely altered, that sometimes even it is slower?

Frequently in diseases of the head, there are spasmodic vomitings; the action of the heart is accelerated in cerebral inflammations, &c. But these are sympathetic phenomena which happen in the organic muscles, as they do in all the other systems; they may not appear nor be developed; a thousand irregularities are observed in their progress. Whereas the contraction of the muscles of animal life by affections of the brain is a constant, invariable phenomenon, which nothing disturbs, and the development of which nothing prevents, because the means of communication are always the same between the affected organ and the one that moves.

If in the examination of the phenomena relative to the cerebral influence upon the organic muscles, we follow an inverse order, that is to say, that in the affections of these muscles we examine the state of the brain, we observe the same independence; consider most vomitings, the irregular motions of the intestines which take place in diarrhœas, those especially which form the iliac passion, &c.; observe the heart in the agitations of fevers, in the irregular palpitations of which it becomes frequently the seat, &c.; in these derangements of the organic muscles, you will very seldom find signs of lesions of the cerebral organ; it is calm, while every thing is disordered in organic life. Cullen thought that in syncope the action of the brain ceased first, and that that of the heart was afterwards consequently suspended. It is precisely the reverse in the greatest number of cases. The heart, at first affected, ceases to act; now its action being essential to that of the brain, whether from the motion it communicates to it, or from the red blood it sends, the functions of this last are suddenly suspended and the whole animal life ceases. This is remarkable especially in the syncopes that arise from the passions, in those from hemorrhages, polypi, great evacuations, &c. I refer upon this subject to my Treatise upon Life and Death.

If from the influence of the brain we pass to that of the nerves, we find new proofs of the absence of animal contractility in the organic muscles. The most of these muscles receive, as we have seen, two species of nerves, the one cerebral, the other from the ganglions.

The heart, the stomach, the rectum and the bladder are evidently entered by the first species of nerves; now by cutting, or irritating in any way the cardiac filaments of the par vagum, the heart experiences no alteration from it; its motion is neither retarded, nor accelerated. The division of both branches of the par vagum is fatal, it is true, but not until after some days; and I doubt whether it is by the heart that death commences in this case. The principal phenomena consequent upon this division show a great embarrassment in the lungs, a great difficulty of breathing; the circulation appears to be troubled only in consequence.

The same nerves going to the stomach, the same experiment serves to prove the cerebral influence upon this viscus. Now the division of that of one side is usually nothing upon it; that of both soon produces a remarkable derangement in it. But this derangement is wholly different from that which follows the section of the nerve of a muscle of animal life, which becomes suddenly immoveable, whilst that on the contrary the stomach not communicating with the brain except by the par vagum, seems to acquire in an instant an increase of power; it contracts and hence the spasmodic vomitings that are almost always observed during the two or three days that the animal survives the experiment, vomitings that I have constantly noticed in dogs, and which Haller and Cruikshank had before observed. It appears then from this, that though the brain has a real influence upon the stomach, this influence is of a nature wholly different from that which it exerts upon the voluntary muscles. I would observe however that the irritation of one branch of the par vagum, or of both, makes the stomach immediately contract, as happens in a voluntary muscle when we irritate its nerve. It is necessary, in order to make this experiment, to open the abdomen of a living animal, and afterwards to irritate the eighth pair in the region of the neck, so as to have in sight the organ that we make contract.

The bladder and the rectum appear to approximate the voluntary muscles, in their relation with the brain, more than the stomach and the heart. We know that falls on the sacrum, from which arises a shock of the inferior part of the spinal marrow, produce retention of urine; that they strike, as it were, this organ with the same paralysis as the inferior extremities, which then also cease to move. Yet as the bladder is very powerfully assisted in its functions by the abdominal muscles, by the levator ani and other voluntary muscles which surround it, the immobility of these muscles contributes much to the inability to evacuate the urine. That which makes me think so, is that, 1st, the irritation of the spinal marrow towards its inferior part which puts in motion all the voluntary muscles of the inferior extremities and of the pelvis, does not produce any effect upon this part. I have convinced myself of this fact many times upon dogs and guinea-pigs. 2d. By irritating the nerves coming from the sacral foramina and going to the bladder, nerves that it is often very difficult to find, on account of the blood in an animal recently killed, I have seen this muscle remain immoveable. On the contrary all these nerves having been cut, the injection of a fluid slightly stimulant makes it contract with force. 3d. In experiments upon living animals, as in surgical operations, the violence of the pain which sometimes produces spasmodic contractions of all the muscles of animal life, frequently occasions an involuntary discharge of urine. Now in these cases it is not the bladder that is convulsed; for if in an experiment this phenomenon takes place, open the abdominal parietes, in an instant the flow of urine ceases, because on the one hand the muscles of these parietes cannot act upon the intestines and press them against the bladder, and because on the other the levator ani which contracts and raises this organ, has no resisting point against which it can compress it above. Observe in fact that in strong jets of urine, the bladder is placed between two opposite efforts, one superior, which is the gastric viscera pressed by the diaphragm and the abdominal muscles, the other inferior, which is especially the levator ani which acts by contracting from below above, whilst the opposite effort acts from above below; now these two efforts are evidently under the cerebral influence. I have very frequently had occasion to observe the bladder full of urine in a living animal whose abdomen was opened; I have never seen it contract with sufficient violence to expel the fluid.

I do not deny but that the bladder, by the nerves it receives from the sacral plexuses, is to a certain extent a voluntary muscle; but I say that it is principally by forces accessory to its own and necessary to its functions, that it is subjected to the will; that the animal contractility is much greater in its functions than the sensible organic contractility. How then is the urine retained in this organ, or expelled from its cavity at will? In this way; when the urine falls into the bladder, and is there on the one hand but a short time, and on the other only in small quantity, it is not then an irritant sufficiently powerful to produce the exercise of the sensible organic contractility. The effort which the bladder makes is so small, that it cannot overcome the resistance of the urethra, which being shut by the contractility of texture, must be dilated by the impulse communicated to the urine. In order to void this fluid, there must then be added to the contraction of the bladder that of the surrounding voluntary muscles; now the least effort of these muscles is sufficient to overcome the resistance of the urethra. But if the urine is in great quantity in the bladder, and it has acquired by remaining in it a long time that deep colour which indicates the concentration of its principles, then the irritation that it produces on the organ brings powerfully into action the sensible organic contractility; the bladder contracts, and in spite of the animal, there is an evacuation of urine.

In the rectum, in which the excrements have not a long canal, but only a simple opening to pass, this is furnished with a sphincter which is wanting in the urethra. This sphincter habitually closed must be dilated by the impulse communicated to the excrements. When they are in the rectum a short time and in small quantity, the sensible organic contractility is not brought into action with sufficient power to expel them; it requires the action of the neighbouring voluntary muscles. If this action is not determined by the influx from the brain, the excrements remain in the intestines; hence how, for some time, we retain them at will. But as they increase in quantity, and become more acrid by remaining and consequently more irritating, then the sensible organic contractility strongly brought into action, empties the intestine involuntarily. If the sphincter, which is voluntary, is paralyzed, there will be incontinence, because no resistance is opposed to the tendency of the rectum to contract, a tendency which though feeble as long as it is but partly filled, is however always real.

From what we have said, it appears evidently that the bladder and rectum, though receiving cerebral nerves, are yet less influenced by the brain than it at first view appears, and that there is evidently between them and the voluntary muscles a very great difference. They are not mixt, as it is called; they approach the organic muscles infinitely nearer than the others; I doubt even whether if no accessory power acted with and compressed them, the mind could by the nerves which come from the sacral plexuses, make them contract at will. I have never seen an animal void his excrements when the abdomen was open.

Let us conclude from all that has been thus far said, that the cerebral nerves which go to the organic muscles have upon them an influence which by no means resembles that of the cerebral nerves going to the muscles of animal life. I am ignorant moreover of the nature of this influence.

All the organic muscles receive nerves from the ganglions, both the preceding ones which are also penetrated by the cerebral nerves, and the small intestines, and the cœcum, colour, &c. which are exclusively pervaded by them. Now by cutting, tying or irritating in any manner these nerves, by stimulating the ganglions from which they go, by destroying or burning them with a concentrated acid or alkali, the muscle remains in its natural state; its contractions are neither accelerated nor retarded.

I have not been contented with ordinary agents in convincing myself of the deficiency of real action of the nerves upon the organic muscles; a fact, which all good physiologists have always admitted, notwithstanding the opinions hazarded by some physicians who apply the vague term of nervous influence to organs which are not susceptible of it.

I have then employed galvanism, and I am convinced that it has very little, almost no power, in putting into action muscular contractions in organic life, whilst it is the most powerful agent in animal life. I shall not here relate my experiments upon this subject; they will be read in my Researches upon Death.

We can conclude from all that precedes, that the cerebral and nervous influence upon the organic muscles is not known to us; that it does not act as upon the voluntary muscles. It is however real to a certain extent, since it is necessary that the nerves which enter into the composition of these muscles should be of some use; but we are ignorant of this use.

Organic Properties.

The organic sensibility is strongly characterized in the muscles of which we are treating. Before the sensible organic contractility is developed in them, it is necessary that this should be put in action. But as these two properties are not separated, as in their exercise they always succeed each other, what we are going to say of sensible organic contractility will apply also to the sensibility of the same nature.

Insensible organic contractility or tone, exists in the muscular system, to a degree necessary for its nutrition; but it does not exhibit in it any thing peculiar.

It is the sensible organic contractility that is the predominant property in this system, all the functions of which rest almost entirely upon this contractility, as all the functions of the preceding muscular system are derived as it were from the animal contractility. We shall now examine more in detail this essential property, with regard to which physiology owes so much to the illustrious Haller. We can consider it in three relations; 1st, in the stimuli; 2d, in the organs; 3d, in the action of the first upon the second.

Of the Sensible Organic Contractility considered in relation to Stimuli.

Stimuli are natural or artificial. The action of the first is continual during life; upon them turn in part the organic phenomena; they place in action the muscles, which without them would be immoveable; they are as it were to these organs what pendulums are to our machines; they give the impulse. The second can hardly have effect until after death, or in our experiments.

Natural Stimuli.

These stimuli are blood for the heart, urine for the bladder, aliments and excrements for the gastric organs. Every organic muscle has a body, which, habitually in contact with it, supports its motions, as every animal muscle habitually in relation with the brain, borrows from it its power of motion. The natural stimuli support the organs at the same degree of mobility while they remain the same. All things being equal on the part of the organs, the pulse does not vary, the digestive periods continue for the same length of time, the intervals between the excretion of urine are equal, whilst the blood, the chyle or the urine exhibit no differences. But as these substances experience an infinite number of varieties, the organs preserving the same degree of sensibility, have yet frequent changes in their motion.

At the instant chyle enters the blood during digestion, the pulse changes, because the heart is differently irritated. We observe the same phenomenon under different circumstances; 1st, in re-absorptions in which pus goes into the mass of blood; 2d, in the injection of different fluids in the veins, injections that were so frequently made in the last age, at the period of experiments upon transfusion, and which I have also had occasion to make with other views which I shall mention; 3d, in inflammatory diseases in which the blood takes a peculiar character that is yet but little known, and which occasions the formation of the pleuritic buff; 4th, in various other affections, in which the nature of this fluid is remarkably altered; 5th, in the passage of the red blood into the system with black blood. I have observed that in putting a curved tube into the carotid of one side and the jugular of the opposite of a large dog, so that one forces blood into the other, the passage of the red blood into the veins is not fatal like that of the black blood into the arteries; but there is almost always at first an acceleration of the motions of the heart.

The influence of the degeneracy of the fluids in diseases has no doubt been exaggerated; too frequent a source of morbid derangements has been placed in this portion of the economy. But it cannot be denied, that according to the different alterations that the fluids exhibit, they may be capable of exciting differently the solids that contain them. We know that in the same individual, and with the same mass of aliments, digestion varies from one day to another in the duration of its periods; that some aliments prolong and others accelerate it; that some remain very long in the stomach, as it is said, and others as it were only pass through it. Now in all these cases the organ remains the same, the fluid only varies. According as the kidney secretes urine more or less acrid and consequently more or less irritating, the bladder retains it for a longer or shorter time. Such is oftentimes its stimulating qualities, that the moment it comes into this organ it is involuntarily rejected. Shall I speak of emetics and evacuants by the intestinal canal, the effects of which are so variable? We know that the words drastic, purgative, laxative, &c. indicate the different degrees of the stimulating qualities which certain substances introduced into the alimentary canal exhibit, degrees which are to be considered abstractedly from those of the sensibility of the organs; this in fact can be such, that a laxative may produce greater effects than a drastic purge.

Not only the quality, but also the quantity of the fluids contained in the organic muscles, has an influence upon their contractility. 1st. The word plethora is certainly employed too loosely in medicine; but we cannot doubt that the state which it expresses sometimes exists; now the more blood there is in the heart, the more are its contractions accelerated. 2d. I have many times made transfusion in dogs, whether with a view to that alone, or in researches relative to respiration and circulation. Now I have always observed, that by not opening a vein, to empty the blood as fast as the external jugular receives it (for I always choose this vein for the experiment) by thus producing consequently an artificial plethora, I have, I say, always observed that the motion of the heart was accelerated. I have even seen the eye of a dog become bright and as it were inflamed; in others this phenomenon has not been observed. 3d. We know that in running, in which all the muscles by contracting press out from all sides the venous blood contained in their texture, this which enters the heart in abundance, makes it palpitate powerfully. 4th. There is not doubt but that the quantity of urine and excrements as much and more than their quality, is for the bladder and the rectum, a cause of involuntary contraction. 5th. We know the serious consequences that arise from giving emetics and cathartics in too large doses. 6th. A glass of tepid water often does not produce vomiting when a pint will bring it on powerfully, &c. &c.

Artificial Stimuli.

The artificial stimuli are in general all the bodies in nature. Such is in fact the essence of organic contractility, that a muscle because it is in contact with a body to which it is not accustomed, instantly contracts. If the muscles are not irritated by the organs that surround them and with which they are in relation, it is because habit has blunted the sensation which arises from this relation. But when these organs change their modifications, when extracted from the body of the animal, they become cold, and are afterwards applied to the organic muscles laid bare, they will make them contract.

Caloric, by its absence which constitutes cold, as by its presence from which arises heat, can equally excite the muscles and in general all the organs. At the instant we open the thorax or the pericardium of a living animal, the heart is agitated with a suddenly increased force; it is because the air acts upon it, and it passes from the temperature of the body to another which is different. All the aeriform fluids, light, all fluids, &c. are stimuli of the muscles. If we see the heart emptied of blood, the stomach and intestines deprived of the substances that ordinarily enter them, contract with more or less force when they have been taken out of the body, it is because the surrounding medium, and the substances with which it is charged, contribute to produce this effect; they are then the stimuli of these organs.

In general the artificial stimuli act in different ways; 1st, by their simple contact; 2d, by tearing or cutting mechanically the fibres; 3d, by tending to combine with them; 4th, there are some of whose mode of action we are completely ignorant; such for example is electricity.

When the stimuli act only by simple contact, the fluids are, all things being equal, more efficacious than the solids, because they stimulate by a greater number of points; as they irritate not only the surfaces of the organ, but penetrate also into the interstices of the fibres. The solids produce an effect in proportion to the extent of their excitement, to the greater or less pressure that they exert, to their density, their softness, &c. They are almost always fluid substances that nature employs for stimuli in the ordinary state.

Tearing is a mode of excitement more active than contact. The heart, the intestines often inert when they are only touched by the scalpel, contract powerfully when the point of it excites them. Cutting produces a less sensible effect than tearing. Cut transversely, the fibres oscillate and are agitated only by the sensible organic contractility, whilst by the contractility of texture they experience an evident retraction.

Chemical excitement is, in the greatest number of cases, the most advantageous; but it is necessary here to distinguish that which belongs to the horny hardening, from that which is the effect of irritability brought into action. 1st. Plunge a frog without skin and alive into a concentrated acid; instantly every thing is disorganized; the reagent acts so strongly, that we can distinguish neither horny hardening nor contractility. 2d. Weaken the acid a little and plunge into it, the inferior extremities only of a frog; in an instant they stiffen by the contraction of the extensors, which overcome the flexors; for in this experiment, this is almost a constant phenomenon; withdraw the animal; its thighs remain immoveable, life has been extinguished in them; the contraction that has come on is a horny hardening, and not a vital phenomenon. A dead frog plunged into the same liquor experiences the same phenomenon. 3d. Weaken the acid still more; the instant the animal is plunged into it its limbs contract; but relaxation succeeds the contractions; these are alternate motions; it is the irritability that begins to be put into action. Yet if the acid is not very weak, some marks of the horny hardening still remain, and the animal has a stiffness in the motions of the inferior extremities, the evident result of the first degree of this horny hardening. 4th. Finally, if the acid is very weak, it becomes a simple irritant which puts in action the sensible organic contractility, without altering the texture of the fibres; the animal after coming out of the fluid preserves the same power of motion.

These experiments which it would be easy to multiply upon animals with warm blood, but which I have never attempted upon them, evidently show what belongs to the horny hardening, and what is the effect of vital contraction. Yet there is not an exact limit between them, and there is one degree of weakness of the acid in which these two causes of motions are confounded.

There is a mode of excitement to which authors have not paid attention; it may be called negative; it is that of which I spoke just now on the subject of caloric, the privation of which is oftentimes a very active stimulant. In the different experiments that I have had occasion to make, this has frequently struck me. Apply a stimulant to a muscle, it contracts; but at the end of some time the motion ceases, though the contact continues; remove the stimulant, the motion frequently returns in an instant. In general, nothing is more common in the heart, the intestines, &c. than their contractions ceasing under the continued action of a stimulant, and returning instantly upon its absence. I confess that this phenomenon is not as invariable and constant as that of the contraction produced by the application of the stimulus which succeeds a state of non-excitement; but this happens very often. We might say that the organic sensibility is in this case like the animal, that every new state affects it, whether it be positive or negative. The passage from non-excitement to excitement is more lively; but the opposite passage is not less when it is sudden. Moreover this manner of describing the sensible organic contractility in exercise, deserves some further experiments.

Of the Sensible Organic Contractility considered in relation to the Organs.

The sensible organic contractility, considered in the organ in which it has its seat, exhibits numerous varieties which are relative; 1st, to the diversity of texture; 2d, to age; 3d, to sex; 4th, to temperament, &c.

First Variety. Diversity of the Muscular Texture.

The animal contractility is everywhere the same in the voluntary muscles, because their organization is uniform. All things being equal as to the number and length of the fibres, the phenomena of contraction are exactly the same everywhere; here, on the contrary, the varieties of texture inevitably produce varieties in the vital properties.

Each involuntary muscle is at first especially in relation with the fluid which ordinarily acts as its stimulus. The blood alone can regularly support the motions of the heart. Let this fluid be altered in any manner, the contractions become irregular. All foreign substances forced into the veins produce this phenomenon. The urine, which supports with harmony the motions of the bladder, would disturb those of the heart, if it circulated in its cavities. The blood, more soft in appearance than the urine, can agitate convulsively the bladder, if it happens to be in it. I took care with Desault of a patient affected for a long time with retention of urine, and whom he had cut for a very large stone. After the operation, the urine remained stagnant in the bladder as long as it was alone, but when a little blood entered this organ, it contracted involuntarily and the bloody urine was evacuated. The excrements, which could continue for a long time in the rectum without making it contract, would make the stomach heave in an instant, &c. All these phenomena are to be referred to varieties of sensibility of the mucous membranes, varieties which we shall notice again. They prove evidently that each muscle has a degree of organic contractility which is peculiar to it, and that this or that fluid of the economy can exclusively, in a natural state, put it in exercise in a regular manner.

Foreign fluids exhibit the same result; the emetic which makes the stomach contract, is injected with impunity into the bladder; purgatives do not produce vomiting, &c. This relation of foreign fluids with the sensible organic contractility takes place, whether, as in the preceding case, these fluids are applied to the mucous surfaces corresponding to the muscles, or whether they come to the muscles by the circulation, as the experiments have proved which were made in the last age upon the introduction of medicinal substances into the veins; experiments of which Haller has collected a great number of results. We have seen in these experiments, the circulation present to all the organs sometimes an emetic, and the stomach alone contracts; sometimes a purgative, and the intestines only enter into action, &c. Taken in by cutaneous absorption, medicinal substances occasion the same phenomenon. Applied by friction, purgatives, emetics, &c. do not make all the organic muscles contract, though the circulation presents them to all, but only those with which their sensibility is in relation.

In the various affections of which they are the seat, we see the organic muscles having each a peculiar mode of irritation answer to each stimulus, and remaining deaf, if we may so say, to the voice of the others.

Second Variety. Age.

Age modifies wonderfully the sensible organic contractility. In infancy it is very evident; the muscles answer with extreme ease to the stimuli; the bladder retains the urine with difficulty; children void it in sleep involuntarily; the heart contracts with a rapidity of which the pulse is the measure; all the digestive phenomena are more prompt; hence there is less interval between the returns of hunger. It is a phenomenon analogous to that of the voluntary muscles, in which the rapidity of the motions is found, in the first age, connected with their small degree of force.

After infancy, the susceptibility of the muscles to answer to their stimuli, is constantly diminishing; thus all the great phenomena of organic life are continually becoming slower. The number of pulsations, the duration of digestion, the longer continuance of the urine, &c. are the thermometer of this slowness.

In old age the whole is weakened; the action of the organic muscles gradually diminishes. Those of the bladder and rectum are the most exposed to lose their contractile faculty; hence the retention of urine, which is a frequent companion of old age; hence also the accumulation of fecal matters above the anus, a disease almost as common as the first at this age of life, though it has received less attention from practitioners. Rich people and those accustomed to the luxury of the table are especially subject to it. I have seen much of it, as much even as of retention of urine, in the last year of the practice of Desault. The intestines and the stomach languish more slowly in their functions. It is the heart which resists the most; it is the ultimum moriens, as it has been the first in exercise; the duration of its pulsations measures exactly the duration of organic life.

Third Variety. Temperament.

Temperament modifies in a remarkable manner organic contractility. We know that in some the pulsations are more frequent, the digestive and urinary phenomena more rapid; that in others, every thing is marked by more slowness in organic life; now these varieties have evidently their primitive source in the varieties of the contractility of the heart, the stomach, the intestines, &c. which have under this relation a great influence in the difference of the temperaments. With respect to this there are two essential observations to be made; 1st. The varieties of force of the organic muscles do not always coincide with those of the muscles of animal life. Thus we see an individual with feebly developed exterior forms, with an evident weakness of the muscles of the extremities, whilst the activity of digestion, of the urinary evacuations, &c. announces the greatest energy in the sensible organic contractility. I would remark with regard to this, that the heart is more frequently in relation of force with the external muscles than the stomach, the intestines and the bladder. A full pulse, well developed, is usually found with an athletic constitution; whilst often this constitution is united in the same subject to a feeble gastric system, and especially the force of this gastric system is frequently connected with external weakness. This fact, which the different temperaments demonstrate to us in man, is evident in the series of animals. Those who, like the carnivorous ones, have a very powerful animal muscular system, have the parietes of the gastric cavities like membranes. These parietes are strong in the herbivorous classes; they become very conspicuous in the gallinaceous. In general, mastication over which the animal contractility always presides, is in animals in an inverse ratio of the force of trituration of the stomach, over which the sensible organic contractility presides.

2d. The varieties of this property, relative to temperaments, exhibit another phenomenon almost always foreign to the animal muscular system. In fact in this the varieties are always general; we are able by exercise to strengthen this or that muscular region; but the differences of forces which are natural, always influence the whole system. The arms and the legs, the thorax and the abdomen are uniformly contractile in the different divisions of the muscles that belong to them. On the contrary, it is rare to see this uniformity in the involuntary muscles. One almost always predominates over the others; sometimes it is the heart, sometimes the stomach and sometimes the bladder. The gastric viscera even are frequently not all at the same level as to force. The stomach is feeble when the intestines preserve their ordinary action; and reciprocally the intestines too contractile expel immediately fecal matters and thus produce a diarrhœa, though the stomach may perform its functions well. This essential difference in the two muscular systems arises from the circumstance that the contractility of one depends upon a common centre, the brain; whilst that of the other on the contrary has its principle insulated in each organ in which it exists.

Fourth Variety. Sex.

Women in general resemble children in the phenomena of sensible organic contractility. The weakness of the motions coincides with their greater rapidity in this sex, all whose internal muscles, like the external, are more delicate and less strongly developed than in man. It might be said that the contractile power of the womb has been formed at the expense of the forces of all the other organs. In experiments, females give results much less decided and always less durable than males. The motions of the heart, the stomach, the intestines, &c. cease sooner; these motions are less; it requires stronger stimuli to produce them, &c.

Fifth Variety. Season and Climate.

In winter and in cold climates, in which the cutaneous organ contracted, and having as it were the horny hardness from the impression of the surrounding air, has but a feeble action, all the internal functions more active, require more energy in the forces that preside over them; all the digestive, urinary and circulatory phenomena are more evident. I do not know that there has yet been made any comparative experiments upon irritability in the different seasons; but I am persuaded that they would give different results.

Sensible Organic Contractility considered in relation to the Action of Stimuli upon the Organs.

We have just described separately the stimulant and the organ stimulated; each being separate there is no effect upon the sensible organic contractility; from their union alone results the exercise of this property. What happens in this union? We know not. To wish to know it, would be to wish to know how one body attracts another, how an acid combines with an alkali, &c. In attraction, affinity and irritability, we can only trace the phenomena to the action of bodies upon each other. This action is the utmost limit of our researches.

But that which ought not to escape us here is, that in this last property, the action is never immediate. There is always between the stimulus and the organ something intermediate which receives the irritation; this intermediate organ is a delicate membrane and continuous with that of the arteries for the heart; it is a mucous surface for the gastric viscera and the bladder. This intermediate organ is more susceptible of receiving excitement than the muscle itself. I have uniformly observed that by irritating the internal surface of the heart, its contractions are greater, than by laying its texture bare externally by removing its serous covering and afterwards stimulating it. The same is true with regard to the organic muscles of the abdomen.

Is there between the intermediate organ excited and the organ which contracts, any nervous communications that transmit the impression? I think not, the cellular texture is sufficient. In fact the serous surfaces and the organic muscles have only this texture as a means of union. The life of the first is in no way connected with that of the others, since they often leave them as we shall see, and yet they can transmit excitement to them. The pericardium and the peritoneum, irritated in their portion corresponding with the organ that we wish to move, produce a contraction in it. This fact is known to all those who have made the least experiment; it is almost always in this way that we stimulate the heart, the stomach, the intestines, the bladder, &c. By carrying the stimulus over the serous surface but very lightly, and so as not to communicate the motion to the fleshy fibres, we obtain a result. Yet simple contact is not sufficient to transmit the irritation; for example, by leaving the external layer of the pericardium applied to the heart and afterwards irritating it, the organ remains immoveable. If we separate the peritoneum from above the bladder, so as to break all the cellular adhesions, and afterwards reapply and stimulate it, the same immobility is observed.

When the intermediate organ that receives the excitement is diseased, the contractility is uniformly altered. The same stimulus produces slow or rapid contractions, according as the affection raises or diminishes the sensibility of this intermediate organ. A slight inflammation of the exterior of the bladder produces a kind of incontinence of urine; that of the intestines occasions diarrhœa, &c. &c. On the contrary, old catarrhs of the bladder, the affections in which weakness of the mucous surface of this organ predominates, are the frequent causes of retention.

I would observe that the existence of this intermediate organ is a remarkable difference between the sensible organic contractility and the insensible, for this organ does not exist in this last, in which the same system receives the impression and reacts upon the body that has produced it; for example, in the glandular, serous, cutaneous systems, &c. the fluid which enters them for secretion or exhalation produces in them the sensation, which is instantly followed by the reaction. In the sensible contractility on the contrary, one system feels and another is moved. This kind of mobility is less removed from that of animal life, in which the organs of the senses and those of the motion being wholly different, are very distant from each other.

Sensible Organic Contractility considered in relation to its duration after Death.

This duration is longer than that of the animal contractility. When the spinal marrow is irritated, the external muscles remain immoveable, whilst the internal ones are still in activity. There have been so many examples related of this duration, Haller has multiplied experiments so much upon this point, that there is no occasion for me to give proofs here of a fact of which no one can any longer doubt. To this duration are owing the evacuations of fecal matter and urine which often take place an instant after death; the vomitings that are observed in some subjects, if not in as evident a manner as during life, at least sufficient to raise the aliments into the mouth of the dead body, which is often completely filled with them, as I have frequently seen.

It is necessary, in relation to this duration, as in relation to that of the animal contractility, to distinguish two species of death; 1st, those that take place suddenly; 2d, those which are the consequence of long disease.

In every sudden death, produced either by a violent lesion of the brain, as in apoplexy, concussion, compression, effusion, &c. or by an affection of the heart, as in syncope, a wound, or a ruptured aneurism; or by a cessation of the action of the lungs, as in asphyxia from deleterious gases, a vacuum, submersion, &c. the duration of contractility is very evident; general death comes on first, then the organs die partially; each vital force is afterwards successively extinguished.

In every kind of death slowly produced, in all those especially which are preceded by a disease of weakness, it is the partial death of each organ that first takes place; each vital force is weakened and extinguished, gradually, before the cessation of them as a whole, which constitutes general death, comes on; when this death takes place, none of the lives peculiar to each organ remains, whilst most of these lives continue for a longer or shorter time after sudden death.

We cannot make these experiments upon dead bodies which we rarely have in the hospitals till fifteen hours or more after death; but by killing dogs by hunger, which, when long continued, becomes a real disease that lasts in these animals eight, ten and even twelve days, I have seen the contractility entirely extinguished at the moment of death. Dogs have been often brought to me affected with different diseases, especially three years since when there was a kind of epidemic among these animals; now by opening them at the instant of death, by killing them even some time before and thus producing a sudden death wholly different from that which happens in the sound state in which all the parts are uninjured in their functions and consequently in their vital forces, I have always seen a constant absence of contractility, or at least so greatly weakened that it appeared to be nothing.

Many physiologists have spoken of a general convulsion which comes on in the organic muscles at the instant of death, of a rising of the heart, the stomach, the intestines, &c. This excess of action is sometimes real in sudden deaths, in those especially that we produce for our experiments; it is very rare in deaths preceded by a long disease in which the patient is extinguished, as it were, insensibly, and passes gradually from life to death. It is a fault common to almost all authors, to generalize too much the facts observed under certain circumstances. Many false consequences are the results of it.

Sympathies.

No organ receives more easily the influence of others, than the organic muscles; all however are not equally susceptible of it. The heart occupies the first rank in this respect; then comes the stomach, then the intestines, and finally the bladder. It is in this order that we shall now examine this influence.

It is a remarkable phenomenon, that every kind of affection in any degree strong, arising in the economy, alters immediately the motions of the heart. The least wound, oftentimes the slightest pain are sufficient to produce derangements in it; now these derangements are of two kinds; sometimes its action is arrested for a moment; hence syncopes, a mode of derangement which happens especially in violent and sudden pains. The vulgar expression which is employed in these cases, viz. "my heart is failing," is perfectly true. Sometimes, and this is the most common case, this action is accelerated; hence the febrile motions so frequent in all the local affections, motions purely sympathetic and which cease when the affection disappears. In many local inflammations, the evil is too circumscribed to admit an obstacle to the course of the blood, an obstacle, which according to Boerhaave, forces the heart to redouble its action to surmount it; besides when there is no swelling, but only pain in the part, and the febrile motion comes on, it is there clearly a sympathetic phenomenon. The increase of the action of the heart may depend no doubt upon a foreign substance, which, mixed with the blood, alters and renders it more irritating; it may be owing to an affection of the substance of the organ which disposes it to be more irritable; but it is certainly very often sympathetic, and depends upon that unknown relation which connects all our organs, upon that consensus which links together all their actions, and places them in reciprocal dependance.

I shall say as much of the stomach; though its sympathetic reaction may not be altogether as frequent as that of the heart, yet it becomes very evident under many circumstances. Most local affections, especially inflammations are accompanied with sympathetic vomitings. Various fevers have in their commencement similar vomitings. It is in the hospitals especially that we frequently observe these phenomena. Many physicians have not considered these vomitings as merely sympathetic, but as the index of a bilious affection, founded on this, that bile is then almost always thrown up. But in all the animals that I have opened, I have almost always seen the stomach when empty containing a certain quantity of this fluid which had flowed back from the duodenum; other authors have also made similar observations; so that it appears that in the state of vacuity, the existence of bile in the stomach is a natural phenomenon. Hence it is not astonishing, that in the commencement of diseases, and even in their course, the stomach being sympathetically excited and thus becoming the seat of vomiting, more or less of this fluid should be thrown up. It would be brought up even in health if vomiting is then excited by an emetic; this is what sometimes happens in the morning when the stomach is empty, if any cause foreign to an affection of the liver, as the sight of a disgusting object, produces vomiting; the bile then comes out like every thing else that is contained in the stomach. I do not say that oftentimes the liver being sympathetically excited in the commencement of diseases, does not furnish more bile, that this superabundant bile flowing into the stomach, does not make this viscus contract; but certainly this is not most commonly the case; we vomit bile as we discharge it by the anus, because it is found in the stomach and intestines, and not because it is superabundant. If vomiting was a natural function, the bilious evacuations in this way would be as natural as the greenish tinge of the excrements, which is always found in a state of health. We see then, from this, that the bilious vomitings are, in many cases, purely accessory, and that the essential phenomenon is the sympathetic contraction of the stomach.

In the case of which I have just spoken there is no gastric difficulty; the sympathetic alteration of the stomach only extends to the fleshy fibres. But most frequently this gastric difficulty appears at the beginning of diseases in which there is local affection; sand-like substances are vomited up; it is because then the organ essentially affected, the lungs for example, if it is in a peripneumony, has acted sympathetically not only on the fleshy fibres, but also upon the mucous membrane. This excited increases its secretion; hence these sand-like substances, which are nothing but the mucous juices mixed with the gastric fluid and with the bile; now the presence of these substances is often sufficient to make the stomach contract, and produce vomiting which expels them.

From this it is evident that there can be sympathetic vomitings without gastric difficulty, and sympathetic gastric difficulty with a vomiting immediately produced. In the first case the fleshy fibres feel the sympathetic influence of the affected organ; in the second it is the mucous membrane. But how, when the lungs, the pleura, the skin, &c. being affected, does the stomach come into action? I have said that the word sympathy was only a veil for our ignorance in respect to the relations of the organs to each other. Vomitings produced by erysipelas, phlegmon, pleurisy, peripneumony, &c. are then most often an effect exactly analogous to the increase of the action of the heart, which produces fever. They resemble the cerebral derangement from which arises delirium, a derangement which is much more rare, &c. All these phenomena indicate that the other organs feel by reaction the state of that which is affected, &c. Physicians who have not viewed all these phenomena in a great and general manner, have confined their treatment to too narrow bounds. Much attention was formerly paid to the sympathetic derangement of the heart, and bleeding was much practised in the beginning of diseases; for some years past much regard has been had to the sympathetic derangement of the stomach, and emetics are frequently given; perhaps before long, more attention will be given to the weights of the head, pains in that part, watchfulness, drowsiness, &c. which are very common sympathetic symptoms, and the treatment will be directed to the brain. In these varieties judicious physicians will regard all these phenomena in a general manner; they will see in all a proof of that general agreement which disposes together all the functions, which connects all and thus connects their derangements; they will see each organ rise up, as it were against the evil which is introduced into the economy, and each react in its own way; they will see these reactions producing effects wholly different, according to the organ reacting, fever arising from the reaction of the heart, delirium, drowsiness, watchfulness, convulsions, &c. from that of the brain, vomiting from that of the stomach, diarrhœa from that of the intestines, gastric and intestinal derangements, foulness of the tongue from those of the mucous membranes, overflowings of bile from that of the liver, &c. Thus in a machine in which the whole is united and connected together, if one part is deranged all the others are so also. We should laugh at the mechanist who attempted to mend but one of these pieces, and neglected to repair the local derangement from which all those arose which the machine exhibits. Let us not laugh at the physician who attacks only a single symptom, without combating the disease, of which he oftentimes knows not the principle, though he knows that this principle exists; but let us laugh at him, if he attaches to his treatment an importance which is nothing compared with that of the disease.

The intestines next to the stomach are the most often sympathetically affected in diseases. The bladder is the organic muscle that is the last to feel the influences that go from the diseased organ; this sometimes however happens. In fevers, we know that retentions of urine from sympathetic and temporary paralysis, are not very rare; incontinence of urine is less often seen.

Character of the Vital Properties.

We see from what has been said, that the vital properties are very active in the organic muscles, especially as it respects contractility. These muscles are really during life, in constant action: they receive with great ease the influence of other organs. Their vital properties are altered with the greatest promptness, especially that which I have just pointed out; for the insensible contractility is rarely altered in them, because it does not perform an essential part. Observe in fact that the morbid derangements of an organ affect always the predominant vital force of that organ. Animal contractility is frequently altered in the preceding system; in this it is the sensible organic contractility. On the contrary, the insensible being very small, the phenomena over which it presides remain always nearly the same; nutrition is always uniform; lesions of the muscular texture are rare; when they take place, it is rather by communication, as in cancers of the stomach, in which the disease begins upon the mucous surface, and in which the fleshy fibres are only consequently affected. The heart and the womb are the muscles that are the most subject to these morbid alterations; yet in the first they belong oftener to the internal membrane than to the fleshy fibres themselves. On the contrary in the systems in which the sensible organic contractility is incessantly in action, as in the cutaneous, the serous, &c. in which it presides over nutrition and exhalation; in the glandular, the mucous, &c. in which it produces secretion and nutrition, it is this which is especially altered. From these derangements arise alterations of texture, organic diseases properly called, which are as common in these systems, as they are rare in those in which the insensible contractility, is so very obscure, as to be only at the degree necessary for nutrition.

It is to this that must be referred the infrequency of acute inflammations of this system. As this affection is frequent in the cutaneous, the serous, the mucous systems, &c. so this system, whose functions require but little insensible organic contractility, presents it rarely. Those who open many dead bodies know, that the texture of the heart is hardly ever found inflamed. Nothing is more common than phlegmasia of the external or serous membrane, and of the internal or mucous membrane of the stomach, the intestines, &c.; but nothing is more obscure and less frequently seen than that of their fleshy tunic. In rheumatism, there is sometimes when the pains cease around the joints, violent cholics, spasmodic vomitings even, indices perhaps of an acute affection of the fibres of the stomach or intestines; but we never find marks of these affections; we do not see the muscular texture exhibiting the bright red of the inflamed mucous, cutaneous and serous organs; or at least I have never observed it.

Physicians have not paid sufficient attention to the difference of inflammations according to the difference of systems; but especially they have not sufficiently observed that this difference accords perfectly with that of the insensible organic contractility; that where this vital force is most characterized, inflammations have the greatest tendency to take place, because it is this which presides over their formation; because these affections suppose its increase; as convulsions suppose the increase of animal contractility, as vomitings, accelerated pulsations of the heart, suppose that of organic contractility, &c. I cannot repeat it too much, that the most frequent diseases in each system, put always in action, raise or diminish the predominant vital force in that system. It is a new pathological view, that may be fruitful in results.

ARTICLE FOURTH.
PHENOMENA OF THE ACTION OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

These phenomena are, as in the preceding system, relative to the state of contraction or to that of relaxation.

I. Force of the Contractions.

It is never capable of being raised to the point which the force of the muscles of animal life sometimes attains. Between the strongest and the weakest pulse, between the feeble jet which precedes some retentions of urine, and the jet of the most vigorous man, there is much less difference than between the langour of the voluntary muscles of some women and the power of those of a maniac, or a man in anger. The heart and the deltoid muscle are nearly equal in respect to their fleshy mass; now what would become of the circulation, if the first sometimes sent the blood with the force which the second uses to raise the superior extremity? A fit of anger, mania, &c. is sufficient to produce aneurisms. On the other hand the organic muscles are not affected with those prostrations of forces so common in the others; paralysis is foreign to them, because they are not within the cerebral influence. There is something which answers to convulsions; it is the irregular agitations which produce so many varieties in the pulse of acute fevers, agitations which must be distinguished from those produced by an organic defect of the heart; but these agitations are wholly different from spasms of the voluntary muscles; there is even no analogy.

There is not in the force of the contraction of the muscles of which we are treating, the waste which is so remarkable in that of the other muscles; the effort is nearly proportionable to the acting cause, and the distinction of this force into absolute and effective, cannot be applied here; only there is required more or less contractile energy, according as the body to be expelled from a hollow muscle, is solid or fluid. Hence why the great intestines are provided with longitudinal fibres more characterized than those of the small intestines; why the rectum especially, in which the excrements have their greatest degree of solidity, exhibits these fibres in a more evident manner than the colon or the cæcum, though under a different form; why in diarrhœas the weakest contraction is sufficient to evacuate the intestines, whilst the sensible organic contractility of the rectum being insufficient to void very solid excrements, it is necessary that the abdominal muscle should aid the expulsion; why when a hard body is introduced into the stomach, and the gastric juices do not soften it, it remains there a long time before being expelled, and produces an inconvenient weight, &c. &c. We know with what rapidity the passage of liquids takes place from the stomach to the intestines, and how long on the contrary solid aliments remain in the first.

The force of the organic muscles is incomparably greater in the phenomena of life than in our experiments. Once laid bare, the heart communicates only feeble motions, and most often irregular ones. There is no proportion between the force necessary to produce the jet, sometimes from seven to eight feet, which the blood exhibits coming from the open carotid of a dog, and the force of the contractions which the strongest stimuli produce when applied to the heart extracted from the body. Nothing equals in our experiments the force of contraction necessary for vomiting, &c. &c.

Numerous calculations have been made upon the force of contraction, in the organic muscles as in the preceding, and there has been the same variety of results. Can we in fact calculate the degrees of a phenomenon which a thousand causes make vary every instant, not only in different individuals, but even in the same, which sleep, digestion, exercise, rest, tranquillity of mind, violence of the passions, day, night, every thing in a word, incessantly modifies? I do not know that we digest twice in exactly the same period, if the urine twice remains the same length of time in the bladder before being discharged, if its jet is twice exactly equal, &c.

The force of the organic muscles often remains in its ordinary degree, or is even increased; whilst a general weakness possesses the others. The force of the pulse, vomiting, diarrhœa, &c. coinciding with a general prostration of the muscles of animal life, are not rare phenomena in diseases.

II. Quickness of the Contractions.

It varies singularly; very rapid in experiments, when death is recent and the stimuli are very strong, the contractions are in general slower in the natural state; we might say that it is in the inverse ratio of the force; often at the instant we open the pericardium, the heart moves with a rapidity which the eye can hardly follow, especially if we inject an irritating fluid into this serous sac, a little before laying the organ bare. The contractions increase much in quickness in certain diseases; those of the heart, for example, then acquire in the adult a rapidity often much greater than they have in the first age; this rapidity is also in this case entirely distinct from the force of its contractions; it is rare even that these two things are found united at the highest point. In general when the force of the heart is increased, there is a little more quickness; but there is very often a diminution of force with an increase of quickness, or the force remains the same, the quickness being much increased.

We have seen that the voluntary muscles have in general a degree of quickness beyond which they cannot go, and that this quickness belongs to the original constitution. Is not the same phenomenon observed here? Often in two fevers whose symptoms are the same, whose degree of intensity seems to be exactly uniform, the pulse is infinitely more frequent in one individual than in the other. This does not always denote a difference in the disease, but in the primitive constitution, an aptitude of one of the two hearts to contract much quicker under the same stimulant. Who does not know that in experiments, the contractile rapidity is infinitely variable under the influence of the same causes?

Each organic muscle has its degree of quickness; the heart, the stomach, the intestines, the bladder, &c. differ remarkably in this respect.

III. Duration of the Contractions.

The heart never remains in permanent contraction, as often happens in the voluntary muscles. Though hunger seems to prove the contrary in the stomach and the intestines, yet this phenomenon is not contradictory; in fact, the permanent contraction of the empty gastric viscera is the result of the contractility of texture. Whenever the sensible organic contractility is in action, there is alternate contraction and dilatation; this alternation even characterizes essentially this last property, and distinguishes it from the animal contractility and from that of texture, in which the state of contraction is often permanent.

IV. State of the Muscle in Contraction.

All the phenomena described for the voluntary muscles, are almost applicable to these, such as the hardening, increase in thickness, diminution in length, expression of the blood, &c. &c. But there are some differences between the heart and the gastric muscles, in respect to the mode of contraction. In fact we see very sensibly in the first, 1st, contractions of the whole analogous to those of the voluntary muscles, contractions which take place in the state of health, which produce the projection of the blood, and which are easily made in experiments when the animals are still living; 2d, numerous oscillations which seize upon the fibres, which agitate the whole of them without producing any sensible effect, without contracting the cavity, without projecting the blood for example. These oscillations are observed at the instant of death, when the heart is ceasing to be contractile; we may then irritate it in vain, there are no more contractions of it as a whole; though there is a general and very evident vibration of its fibres, yet its cavity is not contracted; the blood stagnates in it. The heart perfectly resembles under this double relation the voluntary muscles; it is agitated as we see these muscles in the shuddering, that is called horripilatio, as we see it also in certain sub-cutaneous muscles in some individuals. I have already, for example, seen many persons affected with an habitual trembling of a portion of the solæus, a trembling very evident to the eye through the skin, and which had nothing in common with the contraction necessary to the extension of the foot.

The involuntary muscles of the abdomen never exhibit this double mode of contraction. Instead of the quick and sudden motions of the whole of the muscle, we see but a slow contraction in it, often but slightly apparent; it is a kind of creeping; there is not even to speak properly a contraction of the whole, like that of the heart in which all the fibres of an auricle or ventricle are moved at the same time; here each fleshy surface appears to act successively. Placed at the origin of the great vessels, the bladder and the stomach would be incapable of communicating to the blood those motions by jerks, which the jet of an artery exhibits at each contraction. On the other hand, at the instant the motion ends in the stomach, the intestines and the bladder, we never see in them those oscillations, those vibrations which are almost constant in the heart and the voluntary muscles, and which we can even create in them at will.

V. Motions imparted by the Organic Muscles.

There are hardly ever simple motions in these muscles; the different interlacing of their fleshy surface allows them to act almost always in three or four different directions upon the substances they contain. We can say nothing general upon those motions which compose the diastole of the heart, the peristaltic motion of the alimentary canal, the contraction of the bladder, &c. Each muscle has its mechanism which belongs to the physiological history of the function to which it contributes.

VI. Phenomena of the Relaxation of the Organic Muscles.

In the relaxation of the organic muscles, phenomena in general take place that are opposite to the preceding. It is then useless to enumerate them; but there is a question here that should be examined, that of knowing the nature of that state which succeeds contraction and alternates with it.

In the muscles of animal life, when the contraction ceases, the muscle does not in general go back itself to the state it was in antecedent to the contraction, but it is drawn back to it by its antagonist; for example, when the biceps is contracted to bend the fore-arm and its contraction ceases, it becomes passive; the triceps putting itself then in motion, extends it and draws it back to its natural position, by acting at first on the bones which communicate the motion to this muscle. Each muscular power of animal life finds then in that which is opposed to it a cause of return to the state it had left in order to contract. It is not so in organic life; its muscles, which are all hollow, have no antagonists. We have considered as such to a certain extent, the substances contained in the hollow muscles, substances which oppose the effect of contraction; but incapable most commonly of reacting after having been compressed, on account of their want of elasticity, these substances cannot perform the same offices as real antagonists.

Most physiologists have admitted as a cause of dilatation, the entrance of new substances, which replace, in the muscular cavities, those expelled by contraction; thus the entrance of new blood into the heart, aliments into the different portions of the alimentary canal, has been considered as proper to dilate these organs; so that according to this opinion the muscles would be purely passive when they enlarged. But the following considerations, many of which some authors, Grimaud in particular, have already stated, do not permit us to consider in this way the dilatation of the organic muscles, that of the heart in particular.

1st. When we lay bare a hollow muscle, the heart, the stomach, or the intestines, and empty it entirely of the substances that it contains, it contracts and dilates alternately as when it is full, if we apply an external stimulant to it. 2d. If we empty by punctures all the great vessels which go to the heart, or come from it, so as to evacuate it entirely, its alternate dilatations and contractions continue for some time. 3d. In order to judge comparatively of the degree of force of the contraction and the dilatation, we can extract two hearts nearly equal in size from two living animals; place immediately the fingers of one hand into the auricles or the ventricles of the first, and grasp with the other hand the exterior of the second; you will feel that one makes as great an effort in dilating as the other does in contracting. This fact already observed by Pechlin, is so much the more remarkable, as the effort of dilatation is often greater than that of contraction. I have even observed, in repeating this experiment, that whatever effort we make with the hand, we cannot prevent the organ from dilating. 4th. The alternate extension and contraction, from which arises the vermicular motion of the intestines, is seen during hunger when we open the abdomen of an animal. 5th. The hardness of the organic muscular texture is as evident during dilatation as during vacuity. 6th. I have many times observed that at the instant in which I irritated the heart with the point of a scalpel, that a dilatation was the first consequence of it, and that contraction was only consequent to it. It happens in general more often that contraction begins the motions in our experiments; but certainly, the muscle being at rest, it is frequently a dilatation that first manifests itself.

It appears then very probable that the dilatation of the organic muscles is a phenomenon as vital as their contraction; that these two states are united in a necessary manner; that both of them compose muscular motion, of which contraction is but one part. Who knows even if each may not be disturbed separately, if to a regular contraction may not succeed an irregular dilatation and vice versa? Who knows if certain alterations in the pulse do not belong to injuries of dilatation and others to those of contraction? I am far from being certain; for in medicine we must rest our belief on certainty and not on presumption; but we can make this point an object of research.

It appears that sometimes the voluntary muscles are also the seat of a true active dilatation. 1st. A muscle, laid bare and extracted from the body, contracts and afterwards dilates, without being drawn to this state of dilatation by any cause. 2d. In an amputation, we often see in the stump the end of the divided fibres alternately lengthen and contract; a double motion both of which appears to be equally vital. 3d. In many kinds of convulsions in which the extremities stiffen, in those, for example, which accompany most hysterical fits, it appears that there is a very evident active dilatation; by placing in fact the hand upon the muscles which should then be relaxed, from the disposition of the parts, we perceive a hardness as great as in feeling of the contracted muscles.

There are many researches to be made upon this mode of dilatation of our parts, a mode which undoubtedly is not exclusively confined to the muscular system, but which appears to belong also to the iris, to the spongy texture of the corpora cavernosa, to the nipples, &c. All these organs move by dilating very evidently; contraction succeeds in them expansion, as in the common muscles relaxation does contraction. Expansion is the principal phenomenon. Perhaps also, as some modern authors have thought, the sudden swellings of the cellular texture, which accompany contusions, bruises, &c. are the result of this mode of motion.

ARTICLE FIFTH.
DEVELOPMENT OF THE MUSCULAR SYSTEM OF ORGANIC LIFE.

The organic muscular system is wholly the reverse of the preceding, as it respects development. This is but slightly characterized in the early ages, whereas the growth of the other is precocious. Let us follow it in all the ages.

I. State of the Organic Muscular System in the Fœtus.

In the first days after conception, the heart is formed; it is the first point of motion, a punctum saliens, as it has been called. The researches of different authors, of Haller in particular, have rendered clear the successive progress of its increase in the early periods. Rather late in their formation, the muscles of the interior of the abdomen are yet developed before those that form the parietes of this cavity. It is the size of the intestines, the stomach, the bladder, &c. almost as much as that of the liver, which gives to the cavity in which these viscera are found, the remarkable capacity that it then exhibits.

Nearly uniform at this age, as it respects the proportion of their size, all the organic muscles are not as much so in regard to that of their texture. The heart is evidently firmer and more dense than all the others; its texture is very distinct. The fibres of the stomach, intestines and bladder are soft and loose and resemble exactly those of the muscles of animal life; but little blood goes to them in proportion to what they are afterwards to receive. The fibres of the heart, on the contrary, dense and compact, have a power of action in proportion to what they are afterwards to have. Their redness is as distinct; as much blood penetrates and consequently nourishes them. This redness of the heart, analogous in the adult to that of the voluntary muscles, forms at this period a contrast with the remarkable paleness of these muscles. Besides it has, as in all the other parts where it exists, a deep tinge, owing to the kind of blood that produces it.

We easily see the reason of the quantity of blood that penetrates the heart, as this organ then very active in its motions, has need of much force, whilst the others, almost immoveable, require but little.

Yet the sensible organic contractility of the heart in the fœtus and in the first age has been exaggerated, undoubtedly on account of the extreme rapidity that the circulation then exhibits. This rapidity depends as much on the activity of the tonic forces of the general capillary system, as on that of the heart; for the blood, when it has arrived in the capillary system, is wholly beyond the influence of the heart, as we have seen; the stay that it makes there is wholly dependant upon the forces of the system itself; now these forces, at that time very active, accelerate the course of the blood, and send it into the venous system, from which it goes to the heart. If the excitability of this were double and even treble, and the blood entered it but slowly, it would be unable to support a rapid and at the same time continuous pulse. Haller was drawn to this opinion by believing that the heart was the only agent of impulse of the blood circulating even in the small vessels. Besides, there is no doubt that the sensible organic contractility of the heart is less easily put into action by experiments in the fœtus, and that it is also much less durable. Then the strongest stimuli have less effect upon it an instant after death, than those of less power exhibit upon the heart of an animal that has been born. I have many times established this fact upon fœtuses of guinea-pigs. Compared with that of the voluntary muscles, the mobility of the heart is undoubtedly remarkable in the fœtus; but compared to what it will be after birth, it is but slight.

It is precisely the same with the contractility of the stomach, the bladder and the intestines; most commonly we can produce no motion in these muscles by stimuli. Mr. Léveillé has already made these important observations; he has also remarked that the urine remained in the bladder, and the meconium in the great intestines, without producing a contraction sufficient to expel them. I do not think however that there could be during life a complete immobility of the gastric viscera, and for this reason; most commonly the meconium is only met with in the great intestines; it must have been formed in them then, if there was complete immobility of the gastric muscles; now it is much more probable that it is the residuum of the bile, of all the mucous juices, &c.; that consequently it has been pushed successively by a slow action from the superior part towards the inferior of the alimentary canal.

The softness of the organic muscles renders their extensibility of texture very great at this period. I would observe however that the hearts of dead fœtuses do not exhibit those numberless varieties of size which those of adults do in the right side, according to the different kinds of death.

II. State of the Organic Muscular System during Growth.

The first days of existence are marked by an internal motion as quick in manifesting itself as the external of which we have spoken. The sucking of the milk, the evacuation of the urine and meconium, &c. are indices of this general internal motion, of this agitation almost sudden of all the involuntary muscles.

It is not the brain which, entering into action at birth, produces the contraction of these muscles, since as we have said they are not under its government; it appears to depend, 1st, on the sympathetic influence exerted upon their system, by the cutaneous organ, which is irritated by the new medium; 2d, on the excitement made upon the beginning of all the mucous surfaces, and upon the whole of that of the lungs, an excitement which afterwards reacts upon these muscles; 3d, on that produced by fluids introduced into the stomach; 4th, on the sudden entrance of the red blood into all these muscles, till then penetrated like the others with black; this cause is essential; irritability appears to be in part dependant on it, or at least to borrow from it a remarkable increase of force; 5th, the excretion of the meconium and the urine is also powerfully assisted by the abdominal muscles, which then enter into activity with the whole system to which they belong.

The general internal motion which takes place in the first moments of existence, and which is produced by the suddenly increased activity of the involuntary muscles, has an important use with respect to the mucous surfaces, which it relieves of the fluids that load them, and whose presence becomes painful. Where the mucous surfaces have not around them fleshy layers of the involuntary muscles, as in the bronchia, the nasal fossæ, &c. the muscles of animal life more or less distant, perform this function, as for example, the diaphragm and the intercostals, free the bronchial surface by coughing, and the pituitary by sneezing.

As we recede from the period of birth, the organic muscles grow in general much less in proportion than the others; it is this that gradually re-establishes the equilibrium between the two systems. I would remark however, as it respects the predominance of the first, that it is much less conspicuous in the fœtus than that of the nervous system. The brain, for example, is in proportion much larger than the heart.

It is probable that the muscles of which we are treating, exhibit, at this period, the same varieties of composition as the others, that gelatine especially predominates in them, that they have less fibrin, &c. This last substance perhaps exists, in the early periods, more abundantly in the heart than in the other muscles of this class.

We have observed two very distinct periods in the growth of the other muscles; one is finished when they have acquired their length; the other, when their thickness is complete. The first has not, in the organic system, a term as distinct; when the stature no longer increases, the gastric and urinary organs, and the heart still lengthen and grow.

We have considered growth in too general a manner. Each system has a different term in this great phenomenon. The osseous and muscular systems of animal life, and those which depend on them, as the fibrous, the cartilaginous, &c. have especially an influence upon the general stature of the body; it is these which produce this or that height; but this height has no influence upon the length of the intestines, or the capacity of the stomach, the heart, the bladder, &c. The glandular, serous, mucous systems, &c. are equally independent of stature; thus in these numerous varieties, it has much more influence upon the extremities, than upon the abdomen, the thorax, &c. A great height indicates the predominance of the apparatus of locomotion, but not of those of digestion, respiration, &c. The termination of the growth in height, which we consider in a general manner for the whole body, is only the termination of the growth of the muscles, the bones and their dependancies, and not of that of the internal viscera, which still lengthen and become thicker. It is easy to be convinced of this, by comparing the organic muscles of a young man of eighteen years, with those of a man of thirty or forty.

The organic muscles do not appear to be subject to those irregularities of growth which the other muscles and the bones frequently exhibit. We know that the stature often remains stationary for many years, and that suddenly it acquires very great dimensions in a very short time; this phenomenon is remarkable especially after long diseases. Now notwithstanding these inequalities, the heart and all the other analogous muscles grow in an uniform manner; the regularity of the internal functions to which these muscles especially contribute, could not adapt itself to those aberrations which would be unable to disturb the functions of the locomotive organs. Besides, if they took place, the circulation, digestion, excretion of urine, &c. would exhibit corresponding aberrations; now this is never observed. The heart and the gastric muscles, &c. always grow in an infant whose stature remains stationary; they do not grow suddenly in one who grows at once; hence why the thorax and the abdomen become large in the first case, and remain contracted in the second in proportion to the extremities.

Besides these two systems are never in precise relation of nutrition and power. I have already observed that very large organic muscles often exist with very small voluntary ones, and vice versa.

Let us consider neither the growth nor nutrition in an uniform manner; each system is developed and increases in its own way; all are never found at the same periods of this function. Why? because nutrition, like all the other acts over which life presides, is essentially dependant on the vital forces, and these forces vary in each system.

The growth of the involuntary muscular system is not uniform in all the organs which compose it. Each increases more or less, or is differently developed; one often predominates over the others in an evident manner; a bladder with strong, fleshy fibres, with columns as they are called, is often found in a subject with a debilitated stomach, with small intestines, &c.; reciprocally, the stomach, the heart, &c. have often an insulated predominance.

III. State of the Organic Muscular System after Growth.

It is from the twenty-fourth to the twenty-sixth year, that the organic muscles are completely developed. Then the thorax and the abdomen which contain them have their greatest capacity. These muscles are then as they are to remain through life; they have a density much greater than in youth; their power is increased and their colour is deeper. In general this is subject in the heart to frequent varieties, which coincide very nearly with the varieties of the preceding system. Acute and chronic diseases have nearly the same influence upon it. It is equally the index of the sanguineous, lymphatic temperaments, &c. by the different tinge it assumes. The colour of the gastric, intestinal and vesical fibres varies less; their whiteness, more uniform, is rarely influenced by diseases.

We cannot increase, by constant exercise, the nutrition of the organic muscles. Aliments taken beyond measure, making the stomach frequently contract, weaken it instead of developing its fibres more, as happens from constant exercise given to a superior or inferior extremity. The bladder incessantly in action in some cases of incontinence, is thus gradually weakened and loses its energy. We might say that these two systems were in this respect in an inverse order.

It appears that the nutrition of the organic muscles, like that of the others, is subject to frequent variations; that at some periods they are more developed and less so at others. Diseases have a great influence upon this phenomenon, which proves, like the softening of the bones and their return to the natural state, the constant composition and decomposition of which these organs are the seat. We find in the dissecting rooms many differences in different subjects, as it respects the colour, density and cohesion of the muscles. Now what many exhibit then at once, the same individual often experiences successively; the same man no doubt has, according to the different influences to which he is exposed, his heart red, dense, large and well nourished at one period of life, and feeble, pale and small at another; for the internal organs experience the same alterations as the exterior. Now we know that the external appearance often changes during life.

IV. State of the Organic Muscular System in Old Age.

As we advance in age, the muscular system of which we are treating becomes weak like all the others; yet its action is more durable; it survives, if we may so say, that of the other. When the old man, almost immoveable, crawls about but slowly and with pain, his pulse, digestion, &c. have vigour still. This difference of the two systems is so much the more remarkable, as the time of activity of the second is almost by half less than that of the first; sleep cuts off in fact almost half of the duration of the voluntary motions, whilst it leaves the involuntary wholly untouched. This phenomenon of the organic muscles as it were surviving the voluntary in the last periods of life, is derived on a great scale from the same principle from which arises on a small one the lassitude which follows the contraction in an insulated motion. A less durable motion is necessary to fatigue the voluntary muscles, than to fatigue the involuntary; the stomach empty remains for a long time contracted upon itself without producing any painful sensation, whilst if we hold a body strongly grasped between our fingers for a quarter of an hour, all the flexors are soon painfully affected. After a convulsion of half an hour, in which all the locomotive muscles have been stiff, the whole body is broken, as it is called; it cannot admit of any motion; whilst after a paroxysm of fever of six or eight hours in which the pulse has been violently agitated, the heart often preserves the natural type of its contractions; it requires repeated paroxysms to weaken it. All these phenomena of the two muscular systems evidently prove that that of animal life is fatigued much the soonest; it is this which occasions its intermission. Is it then astonishing that, although less often in exercise than the other, it exhausts sooner the quantum of force nature has given to it? is it astonishing that the other survives the longest? Life is a great exercise which gradually wears up the organs in motion, and which requires their rest; this rest is death; now each moveable organ arrives at it sooner or later, according to the different degree of the forces which it has to expend, and according to its greater or less disposition to be wearied by this great exercise.

Yet the organic muscles are gradually weakened. The pulse becomes slower, digestion is longer in old age; the bladder and rectum first cease to act; then the intestines remain inactive; the stomach and especially the heart die the last.

A long time before death, the muscular cohesion is weakened in this system as in the preceding; the fleshy texture becomes flaccid; the parietes of the heart support themselves in youth; they flatten in old age. The gastric system of a young animal suddenly killed during hunger is firm, dense and contracted upon itself; in an old one, under the same circumstance, it is but little contracted; the stomach and intestines remain much more dilated; they are loose and soft; it is the same phenomenon as in the preceding muscles, which vacillate under the skin, from want of cohesion. The bladder remains constantly large, though empty.

[MUCOUS SYSTEM.]

This system, the name of which I borrow from the fluid that constantly lubricates it, and which is furnished by small glands inherent in its structure, appears everywhere in a membranous form; that of fasciculi is wholly foreign to it. In speaking of the mucous organs we shall designate them almost always under the name of membranes. Their study is a new object of research. Pinel has been among the first, who has perceived the necessity of considering them in a general manner as it respects diseases. I believe that I am the first who has regarded them generally in an anatomical and physiological view. Few systems deserve more attention; upon it take place all the great phenomena of digestion, respiration, secretion, excretion, &c.; it is the seat of many diseases. It should alone, in a nosography in which diseases are distributed by systems, occupy a place equal to that of many.

ARTICLE FIRST.
OF THE DIVISIONS AND FORMS OF THE MUCOUS SYSTEM.

The mucous membranes occupy the interior of the cavities which communicate with the skin by the different openings this covering has on the surface of the body. Their number at first view is very considerable; for the organs in which they are reflected are very numerous. The mouth, the stomach, the intestines, the œsophagus, the bladder, the urethra, the womb, the ureters, all the excretories, &c. &c. derive from these membranes a part of their structure. Yet if we consider that wherever they are continuous, wherever we see them originate, by extending from each other, as they originated in the first instance from the skin, we shall perceive that this number must be wonderfully limited. In fact by thus describing them, not separately in each part, but at the same time in all those upon which they are continued, we see that they are reduced to two general surfaces, of which all the others are portions, and which, on account of the different parts to which they are distributed, can be called, the one gastro-pulmonary, the other genito-urinary. The first is found in the head, the neck and the abdomen. This last cavity and more especially the pelvis, contain the second.

There is also a small insulated mucous surface; it is that which enters by the openings of the nipples and lines the lactiferous tubes. But it is so small that it deserves but little attention; besides, what will be said of the two others will be equally applicable to it. It is then useless to examine it in a general manner.

I. Of the two General Mucous Membranes, the Gastro-Pulmonary and the Genito-Urinary.

The gastro-pulmonary surface penetrates into the interior by the mouth, the nose and the anterior face of the eye. 1st. It lines the first and second of these cavities, extends from the first to the excretory ducts of the parotid and sub-maxillary glands, from the other into all the sinuses, forms the conjunctiva, dips down into the puncta lachrymalia, the nasal duct, the sac of the same name, and is continued into the nose; 2d, it descends into the pharynx, furnishes an elongation to the Eustachian tube, then penetrates the internal ear and lines it, as we shall see; 3d, it dips down into the trachea and is spread upon all the air-tubes; 4th, it penetrates into the œsophagus and the stomach; 5th, it extends to the duodenum where it furnishes two elongations, one destined to the ductus choledochus, to the numerous branches of the hepatic and cystic ducts and the gall-bladder, the other to the pancreatic duct and its different branches; 6th, it is continued into the small and large intestines and finally terminates at the anus where we see it identified with the skin.

The second general mucous membrane, which we have called the genito-urinary, enters in man by the urethra, and thence is spread on the one hand upon the bladder, the ureters, the pelvis of the kidnies, the infundibula, the papillæ and the capillary tubes which open on their summit; on the other hand it goes into the excretory tubes of the prostate, into the seminal ducts, the vesiculæ seminales, the vasa deferentia and the branches with numberless windings that produce them.

In woman, this membrane is introduced by the os externum and penetrating on the one hand by the urethra, goes as in man upon the urinary organs; on the other hand, we see it enter the vagina, lining it, the uterus and the fallopian tubes, and afterwards becoming continuous with the peritoneum by the opening of these tubes. It is the only example in the economy, of a communication established between the mucous and serous surfaces.

This manner of describing the course of the mucous surfaces, by saying that they are elongated, dip down, penetrate, &c. from one cavity to another, is no doubt not conformable to the progress of nature, which creates in each organ the membranes belonging to this organ, and does not thus extend them by degrees; but our manner of understanding it is better adapted to this language, the meaning of which the least reflection will show.

In thus referring to two general membranes all the mucous surfaces, I am not only supported by anatomical inspection, but pathological observation has also furnished me with points of demarcation between the two, and points of contact between the different portions of membranes of which each is the assemblage. In the different descriptions of catarrhal epidemics given by authors, we frequently see one of these membranes affected in all parts, the other remaining sound; it is especially not rare to observe a general affection of the first, of that which extends from the mouth, the nose, the surface of the eye, into the alimentary canal and the bronchial vessels. The last epidemic observed at Paris, with which Pinal himself was affected, was of this character; that of 1761, described by Razou, had it also; that of 1752, described in the memoirs of the Society of Edinburgh was remarkable for a similar phenomenon; now, we do not see at that time a corresponding affection in the mucous membrane that is spread upon the urinary organs and upon those of generation. There is then here, 1st, an analogy between the portions of the first, by the uniformity of affection; 2d, a demarcation between the two by the health of the one and the disease of the other.

We see also that the irritation of any one point of one of these membranes, frequently produces a pain in another point of the same membrane, which is not irritated. Thus a calculus in the bladder occasions a pain at the end of the glans penis, the presence of worms in the intestines causes an itching of the nose, &c. &c. Now, in these phenomena purely sympathetic, it is very rare that the partial irritation of one of these two membranes affects with pain one of the parts of the other; there are however examples of it; such is the singular relation that exists, in mucous hemorrhages, between the membrane of the womb and that of the bronchia. If the blood ceases accidentally to flow from one during menstruation, the other frequently exhales it and thus as it were supplies its functions.

We ought then, from inspection and observation, to consider the mucous surface, in general, as formed by two great membranes successively spread upon many organs, having between them no communication except by the skin, which serves them as an intermediate organ, and which, continuing with both, contributes thus with them to form a general membrane everywhere, continuous, covering the animal externally, and extending within upon most of its essential parts. We can conceive that there should exist important relations between the internal and external portion of this single membrane; and that they do will be proved by further researches.

II. Adhering Surface of the Mucous Membranes.

Every mucous membrane exhibits two surfaces, one adhering to the neighbouring organs, the other free, covered with villi, always moistened with a mucous fluid. Each deserves particular attention.

The adhering surface corresponds almost everywhere with the muscles, either of animal or organic life. The mouth, the pharynx, the whole alimentary canal, the bladder, the vagina, the womb, a portion of the urethra, &c. exhibit a muscular layer embracing on the outside their mucous tunic which is within. This arrangement coincides perfectly, in animals with a fleshy membrane, with that of the skin, which moreover approximates very near, as we shall see, the structure of the mucous membranes, and which, as we have seen, is everywhere continuous with them. This arrangement of the mucous membranes occasions them to be agitated by constant motions which favour wonderfully the secretion that takes place in them, the excretion which succeeds it, and the various other functions of which they are the seat. The insertion of this muscular layer exterior to the mucous system, is made, as we have seen, by this dense and compact texture which I have called the sub-mucous. It is from this texture, more compact than the rest of the cellular system, that the mucous surface derives its force. It is from it that the organ which it lines receives its form; it is this which supports and preserves this form; the following experiment proves it. Take a portion of the intestine; remove from any part of it this layer, as well as the serous and the muscular; then inflate it, after having tied it below; the air produces in this place a hernia of the mucous coat. Try afterwards another portion of intestine; deprive this, for a small space, of its mucous membrane and of this also; inflation will produce upon the serous and muscular tunics the same phenomenon that it did in the preceding on the mucous; then it is to this sub-mucous cellular layer that it owes the resistance with which it opposes substances that it contains. The same may be said of the stomach, the bladder, the œsophagus, &c.

III. Free Surface of the Mucous Membranes.

The free surface of the mucous membranes, that which is continually moistened by the fluid from which they borrow their name, exhibits three species of wrinkles or folds.

1st. One inherent in the structure of all the laminæ of these membranes, is constantly met with, whatever may be their state of dilatation or contraction; such are those of the pylorus and the valve of Bauhin. These folds are formed not only by the mucous membrane, but also by the intermediate tunic of which we have spoken, which here has a remarkable density and thickness, and gives them solidity. The fleshy tunic enters even into their composition, and we see on the exterior, upon the serous surface, a depression that indicates their presence.

2d. Other folds, only formed by the mucous surface, exist also always in a state of vacuity or fulness, less evident however than this; they are owing to the circumstance that the mucous surface is much more extensive than those upon which it is applied, so that it is folded that it may not run a longer course; such are the valvulæ conniventes of the small intestines, the structure of which we see very well by cutting longitudinally one of these intestines. The edge of the section exhibits the fleshy layer and the serous surface in a straight direction, whilst the mucous layer describes a line resembling a loose thread.

3d. The last species of folds is as it were accidental, and is only observed during the contraction of the organ which is lined by the mucous surface that is the seat of it; such are those of the interior of the stomach, the great intestines, &c. In the greatest number of subjects brought to the dissecting rooms, these folds of which so much has been said as it respects the stomach, cannot be perceived in it, because the subject has died after a disease that has so altered the vital forces, as to prevent all action of this viscus; so that though it is frequently found empty, its fibres are not contracted. In experiments upon living animals, on the contrary, these folds become very evident, and may be demonstrated in this way; make a dog eat or drink copiously, open him an instant after and cut the stomach in the length of its great curvature; no fold is then apparent; but soon the viscus contracts, its edges are turned over and the aliments escape; the whole mucous surface is covered with an infinite number of very prominent ridges, which have as it were the form of cerebral circumvolutions. We obtain the same result by taking out the stomach of an animal recently killed, distending it with air and opening it afterwards, or by cutting it immediately in its state of vacuity and drawing it in opposite directions by its edges; it stretches, its ridges disappear, and if we cease to distend it, they form again immediately in an evident manner. I would observe on the subject of the inflation of the stomach, that by distending it with oxygen, we do not produce by the contact of this gas, greater ridges and consequently a stronger contraction, than by using for the same purpose carbonic acid gas. This experiment furnishes a result very similar to what I have observed in rendering animals emphysematous by different aeriform fluids. It follows from all that we have said upon the folds of the mucous membranes, that in the ordinary contraction of the hollow organs which these membranes line they undergo but a very slight diminution of surface, that they contract scarcely at all, but fold within, so that by dissecting them on an organ in contraction we should have a surface almost equal in extent to that which they exhibit during its dilatation. This assertion, which is true as it respects the stomach, the œsophagus and the great intestines, is not perhaps as entirely so with regard to the bladder, the contraction of which makes the ridges within less evident; but they are not sufficient to destroy the general law. It is also nearly the same with the gall-bladder; yet here we find another cause. The gall-bladder, alternately observed in hunger and during digestion, contains double the bile in the first case that it does in the second, as I have had occasion to see very often indeed, in experiments made for this object or with other views. Now, when the bladder is in part empty, it does not contract upon the bile that remains, with the force of the stomach when it contains but few aliments, or with the power of the bladder when it contains but little urine. It is then flaccid; so that its being distended or not has but a slight influence upon the folds of its mucous membrane.

Besides, in saying that the mucous membranes always exhibit, with some slight difference, the same surface in the extension and contraction of their respective organs, I intend to speak only of the ordinary state of the functions, and not of those enormous dilatations of which we often see the stomach, the bladder, and more rarely the intestines become the seat. Then there is no doubt, a real extension and contraction, which coincide in the membrane with those of the organ.

A remarkable observation which the free surface of the mucous membranes exhibits, and which I have already pointed out, is, that this surface is everywhere in contact with bodies heterogenous to that of the animal, whether these bodies introduced from without to nourish it have not yet been assimilated to its substance, as we see in the alimentary canal and in the wind-pipe; or whether they come from within, as we observe in all the excretory ducts of the glands, which all open into cavities lined by the mucous membranes, and transmit without particles which, after having contributed for some time to the composition of the solids, become heterogeneous to them, and are separated from them by the constant motion of decomposition which takes place in living bodies. Hence we ought to regard the mucous membranes as limits, and barriers, which, placed between our organs and the bodies that are foreign to them, defend them from the mischievous impression of these bodies, and serve consequently within, the same functions which the skin performs without, with respect to the bodies which surround that of the animal, and which tend incessantly to act upon it.

The organization of the mucous system and its vital properties are accommodated to this habitual contact of substances heterogeneous to the living economy. That which is a foreign body to the other systems, the cellular, the muscular, &c. is not so to this. Solid substances, the metals, stones, wood, &c. which introduced into our parts excite in them inevitably suppuration and an antecedent inflammation by their simple contact, pass with impunity over this, provided that their angles and asperities do not tear it; they only augment a little the secretion, as I shall say. We can swallow a ball of lead, of wood, &c. and pass it by the anus without inconvenience. All the irritating fluids without being caustic, that we inject into the great intestines in enemas, or that we swallow, would produce abscesses, &c. if they were forced into the cellular system, &c. Surgeons employ the term foreign bodies in too general a manner; that which is so for one system, is not for another. Foreign is, in this respect, a term of comparison which we should employ only after a knowledge of the peculiar sensibility of each system, and not after that of this property described in a vague manner.

The mucous system not only bears without danger the presence of all bodies that are introduced into the economy, but also when it goes out, it can be exposed with impunity to the contact of external stimuli. Observe what takes place in prolapsus of the womb in which the whole membrane of the vagina sometimes becomes external, in those inversions of the intestinal tubes that take place through preternatural ani, in prolapsus of the rectum, &c.; then the mucous surfaces serve really as integuments; now in these cases the surrounding bodies produce hardly any more pain on them than upon the skin. On the contrary, the instant a serous surface is laid bare, as for example in the operation of hernia, in which the intestine is suffered to come out, on account of an opening unfortunately made by the point of a bistoury, this surface inevitably inflames. All the cellular, muscular, nervous, glandular systems, &c. laid bare, exhibit the same phenomenon. There is no danger in opening the bladder as it respects the contact of the air, whilst there is much in permitting this fluid to penetrate into an articular cavity, a tendinous groove, a serous sac, &c. We know how much in the high operation for the stone, we fear to wound the peritoneum, how uncertain are the results of empyema on account of the contact of the air upon the pleura, &c. The dangers of the action of this fluid upon these surfaces have been perhaps exaggerated, but they are notwithstanding real.

If a fistula extends from the exterior of the abdomen into the intestines, its whole course is lined with callous bodies; these defend the cellular texture and the muscles through which the fistula passes. On the contrary, nothing similar appears upon the intestinal mucous surface, because its organization alone is sufficient to protect it. The urinary, salivary and lacrymal fluids never escape externally by artificial ducts formed in the neighbouring organs, without there are similar callous bodies in the course of these ducts; on the contrary, they pass with impunity over the mucous surfaces. Make in a limb a long and straight opening with a pointed instrument, and fix in it for a time a sound; a callous canal will be produced by it. Let a sound on the contrary remain in the urethra, no alteration of texture will result from it.

Let us conclude from these different considerations, that the mucous system with the cutaneous alone, is organized so as to support the contact of all external bodies, and not to be affected by their presence, or at least experience only an increase of secretion, which is in no ways dangerous. Thus these two systems form two boundaries, the one internal and the other external, between which are placed the organs foreign, by their mode of sensibility and by that of their structure, to the external bodies. To these boundaries the excitement of these bodies is limited; their influence does not go beyond. So long as they do not pass these boundaries, the other organs do not feel them. We might say that the acute sensibility which each of them enjoys, is a kind of sentinel that nature has placed on the confines of the organic domain of the mind, to inform it of whatever can injure it.

ARTICLE SECOND.
ORGANIZATION OF THE MUCOUS SYSTEM.

I. Texture Peculiar to this Organization.

The mucous system presents two things to be considered in its peculiar texture, viz. 1st, a layer more or less thick which constitutes principally this texture, and which by analogy with the cutaneous corion, may be called the mucous corion; 2d, many small elongations which surmount it, and which are called villi or papillæ. As to the epidermis which covers it, I shall treat of it with the cutaneous epidermis. This texture has nothing similar to the substance that colours the skin, and which is between the papillæ and epidermis. We know in fact that negroes, as well as whites, have this texture of a bright red, which it derives from its vessels.

Mucous Corion.

This portion of the mucous texture, which is the most important, and which constitutes the thickness, form, and even the nature of it, has a soft and spongy appearance. We might say at first view that it was a consistent pulp, with which the extremely dense cellular texture that is subjacent to it had been covered. This softness is a character which distinguishes it from the cutaneous corion, which moreover has by its intimate nature but little resemblance to it.

The mucous corion is very various as to thickness; it differs in this respect in each organ. That of the gums and the palate is the thickest of all. Then come those of the nasal fossæ and the stomach, then those of the small intestines and the gall-bladder, then those of the large intestines, of the urinary bladder, the urethra and the other excretories, until it begins at length to become so fine as to appear transparent like a serous surface when it is removed with care. Finally, the finest and most delicate is that of the sinuses of the face and the interior of the ear; the arachnoides is often coarser.

I have called the texture within the ear mucous, though all anatomists call the membrane of the cavities of this organ periosteum. In fact, 1st, we see it evidently continued with the pituitary membrane, by means of the elongation of the Eustachian tube. 2d. We find it constantly moistened by a mucous fluid which this canal serves to convey out, a character foreign to the periosteum, which, like the fibrous membranes, always adheres by both its surfaces. 3d. No fibre can be distinguished in it. 4th. Its fungous appearance, though white and soft, and the ease with which it is torn, are evident attributes of the mucous membranes. Every thing proves that the membrane of the tympanum, that of the meatus, &c. belong to the system of which we are treating. Thus in catarrhs of the pituitary membrane, and of that of the fauces, we most often find that the ear is affected; thus the ear is, like the mucous surfaces, the seat of hemorrhage, thus polypi arise in it, as in the nose and on the surface of the womb. We consider as a sign of deposition of pus in the ear, every purulent discharge coming from that cavity. But how can we conceive of a purulent collection in a part in which there is hardly any cellular texture, in a part wholly osseous? Besides the fibrous system, to which the periosteum of the tympanum belongs, hardly ever suppurates, as we know. Every thing then induces us to believe that these discharges are only the effect of a catarrh of the ear, a catarrh which is sometimes acute and sometimes chronic. I have moreover a recent and decisive fact upon this point; the body of a man subject to these discharges during life exhibited a remarkable thickness and redness of the membrane of the tympanum, but without the least trace of erosion. The ear suppurates like the urethra, the vagina, &c. it is not a new fluid which is formed by suppuration; it is that which naturally comes from the meatus which increases in quantity and comes through a preternatural opening of the membrane of the tympanum.

Diseases make the thickness of all the mucous surfaces vary remarkably. I have seen them many lines thick in the maxillary sinus, and nearly half an inch in the bladder. In great extensions of the mucous sacs, this thickness diminishes very much; it increases in their contractions. The stomach especially exhibits this phenomenon in these two opposite states.

The softness of the mucous corion is also very variable; in the nasal fossæ, in the stomach and the intestines, it is really a kind of organized velvet. The name of villous membrane is perfectly suited to it. On the contrary, at the origins of the mucous system, as in the mouth, upon the glans penis, at the entrance of the nose, it is a more dense and compact texture, approximating nearer in its nature to the cutaneous corion. I am persuaded that like this it might be tanned and be useful in the arts if it were in larger pieces, whilst I doubt if the action of tanning could produce an analogous phenomenon upon the mucous texture of the deep-seated organs. The softness of this would render it incapable of serving for external integuments. The least cause would be in fact sufficient to break and tear it. Its structure being different from that of the cutaneous corion is the reason that the variolus pustules never appear on it, whilst we often see them on the mucous surfaces near the openings of the skin, especially upon the tongue, the palate and the internal surface of the cheeks.

Exposed to the action of dry air, so that it may come everywhere in contact with it, it becomes dry and very thin, but preserves some resistance. In bladders inflated and dried, in the stomach, the intestines, &c. thus prepared, it is this texture which supports these organs, and which prevents them from becoming flat, though we permit the air to escape; it offers even a resistance, from which arises a kind of crepitation when we wish to bend them in various directions. To be convinced of this, it is only necessary to dry the mucous surface separate from the serous and muscular that correspond with it; these when dried remain pliable like the cellular texture, whilst the first has a kind of rigidity.

In the organs in which the redness of the mucous texture is slight, as in the bladder, the rectum, &c. it becomes transparent by drying. Where it is very red as in the stomach, it takes a deep tinge, which becomes even almost black if there had been an antecedent inflammation in it by which much blood had been accumulated; hence it appears that this fluid is the cause of the colour.

Thus dried the mucous surfaces are smooth; they lose their viscidity at least in appearance; their folds are effaced by adhering to the surface from which they arise; thus the valvulæ conniventes are marked in a dried intestine, only by a red line, without any apparent prominence. But if we macerate the intestines in this state, the folds form again and become visible.

Exposed to a moist air, or left with other flesh that will not allow it to become dry, the mucous corion putrefies with great ease; the odour that it then sends out is very fetid. I think the reason why the abdomen of dead bodies becomes putrid so soon is in part because it contains substances already in putrefaction, and also because the surfaces, in contact with these substances, and which by their vitality resisted before their action, then readily yield to them. If these substances were contiguous to aponeuroses, putrefaction would be much less rapid. The mucous system when putrid takes a greyish colour; and as the dense, subjacent cellular texture putrefies much less easily, we can then remove from it by the least pressure, the mucous corion, reduced to a putrid pulp, in which every trace of organization has disappeared, and which forms a real pap.

During life, gangrene of the mucous texture takes place in general less frequently than that of the cutaneous. The consequences of catarrh, compared with those of erysipelas may convince us of this; there are however cases in which death appears in this texture, whilst the surrounding ones continue to live, as in gangrenous angina.

Exposed to maceration, the mucous texture yields to it promptly. I think that next to the brain it is altered quickest by the action of water. It is then reduced to a reddish pulp very different from that from putrefaction in the open air. When we put the whole stomach to macerate, this pulp is detached, when the sub-mucous texture and the serous membrane have as yet undergone but little alteration.

Ebullition at first extracts from the mucous texture a greenish scum, very different from that which the muscular and cellular textures give when boiled. This scum which mixed with the whole fluid in the beginning of the boiling, disturbs it and renders it green at first, afterwards rises upon the surface where it has small bubbles of air mixed with its substance; it often even falls to the bottom of the vessel by its weight. Sulphuric acid changes the colour of it to a dull brown.

A short time before the water begins to boil, the mucous texture crisps and acquires the horny hardness like the others, but in a less degree however; hence why it is then wrinkled almost always in different directions. In fact, the sub-mucous texture upon which it is applied, contracting at that time much more than it, it must fold on account of its length; thus during life, when the fleshy coat of the stomach contracts, its mucous surface not contracting in proportion, produces the numerous folds of which we have spoken. The action of a concentrated acid crisping the sub-mucous texture more than the mucous itself, produces an analogous phenomenon. After having been a long time dried, the mucous texture, like however almost all those of the animal economy, does not lose the faculty of acquiring the horny hardness when it is plunged into boiling water; it exhibits this phenomenon, whether we expose it to it dry, or whether we do it after having first softened it in cold water. It is a means by which all the valvulæ conniventes may be made suddenly to reappear, which had disappeared by drying, and which form again the instant the intestine contracts. This experiment is very curious to witness.

When the ebullition has been a long time continued, the mucous texture turns gradually to a very deep grey, from the white which it had first become. It is not softer than in the natural state, but it breaks much quicker; the following experiment is a proof of it. If we draw the mucous corion, boiled for some time with the subjacent cellular texture, this last resists the most; so that it remains entire, whilst the mucous corion is broken in many places. This never assumes the gelatinous appearance of the cutaneous corion or the fibrous and cartilaginous organs when boiled and of the others which yield much gelatine. However by mixing a solution of tannin with the water in which this system taken from an adult has been boiled, I have seen an evident precipitate.

The action of the acids reduces to a pulp the mucous texture much sooner than most of the others. During life, all the caustics act much more rapidly upon it than upon the cutaneous, of which the thick epidermis is an intermediate organ which checks their tendency of combining with its corion. Thus the instant the nitric acid, a substance which common people almost always choose for their poison, as the practice at the Hôtel Dieu proves, thus the instant I say, that the nitric acid is in contact with the alimentary canal, it disorganizes it, it forms there a whitish eschar, which, when death does not take place immediately, as most often happens, is slowly removed and detached in the form of a membrane. We know that the lips gently rubbed with weakened nitric acid, become the seat of a troublesome itching, whilst that oftentimes though this acid may have acted upon the skin sufficiently to make it yellow, it does not suffer from it.

The softness of the mucous corion makes me presume that it is easily altered by the digestive juices, not that I confide in the experiments of Hunter, who pretended that these juices could act upon the coat that secretes them, but because in general I have observed that the textures like it yield very easily to the action of water in maceration and are also very easily digested. I have not however any experiment upon the subject, and we know that in the animal economy analogy is not always a faithful guide.

All the mucous surfaces, but especially that of the stomach and intestines, have the property of curdling milk, as have many other substances, especially the acids. Is it to this property that must be attributed a phenomenon which is constant during life, viz. the coagulation of milk that enters the stomach for digestion? or is this phenomenon owing to the mixture of this fluid with those which are secreted by the surface of this organ? I think that both these causes contribute to it at the same time; both separate produce in fact this phenomenon. Spallanzani has proved it as it respects the gastric juices. Every body knows that the mucous membrane dried, and consequently deprived of these juices, preserves the property of coagulating milk. Spallanzani has convinced himself that the serous and organic muscular systems of the stomach are destitute of it.

Are aphthæ an affection of the mucous corion? do they belong to the papillæ? are they seated in the glands? are they a separate inflammation of these glands, whilst catarrhs are characterized by a general inflammation of a considerable extent of the mucous system? All these questions deserve to be examined. Pinel has perceived the void there is in morbid anatomy upon this point.

Mucous Papillæ.

The peculiar kind of sensibility which the skin enjoys is attributed principally, as we know, to what is called the papillary body, which commonly is not easy to be demonstrated. The sensibility of the mucous membranes, somewhat analogous to that of the skin, appears to me to have the same kind of organization, which is perceived with infinitely less ease. The papillæ of this system cannot be called in question at its origin, where it dips into the cavities, in the commencement even of these cavities, as upon the tongue, the palate, the internal part of the alæ of the nose, upon the glans penis, in the fossa navicularis, within the lips, &c. Inspection is sufficient to demonstrate them there. But it is asked if the papillæ exist also in the deep-seated parts of this system. Analogy indicates it, since the sensibility is as great there as at their origin, though with varieties that we shall point out; but inspection proves it in a manner not less certain. I think that the villi with which we everywhere see them covered are nothing but these papillæ.

Very different ideas have been entertained of the nature of these villi; they have been considered in the stomach and the œsophagus as destined to the exhalation of the gastric juice, in the intestines as serving for the absorption of chyle, &c. But, 1st, it is difficult to conceive how an organ everywhere nearly similar, can perform in different parts functions so different; I say nearly similar, for we shall see that these papillæ exhibit differences of length, size, &c. without having any of texture or structure. 2d. What can be the functions of the villi of the pituitary membrane, of the internal coat of the urethra, the bladder, &c. if they have not relation to the sensibility of these membranes? 3d. The microscopical experiments of Leiberkuhn upon the vesicle of the intestinal villi have been contradicted by those of Hunter, of Cruikshank and especially of Hewson. I am certain that I have never seen any thing similar on the surface of the small intestines, at the time of chylous absorption; and yet it would appear that a thing of inspection could not vary. 4th. It is true that these intestinal villi are everywhere accompanied by a vascular net-work, which gives them a red colour very different from the colour of the cutaneous papillæ; but the non-appearance of the cutaneous net-work is owing to the pressure of the atmospheric air, and especially to the contraction which it occasions in the small vessels. Observe in fact the fœtus as it comes from the womb of its mother; its skin is as red as the mucous membranes, and if its papillæ were a little longer, it would resemble almost exactly the internal surface of the intestines. Who does not know moreover, that the vascular net-work surrounding the cutaneous papillæ, is rendered evident by fine injections, so as to change their colour entirely?

That in the stomach this vascular net-work continuous with the exhalants furnishes the gastric juice, and that in the intestines it intermixes with the origin of the absorbents, so that these embrace the villi, we cannot doubt after the experiments and observations of anatomists who have recently engaged themselves in investigating the lymphatic system. But this does not prevent the base of these villi from being nervous, and them from performing upon the mucous membranes the same functions that the papillæ do upon the cutaneous organ. This manner of regarding them by explaining their existence generally observed upon all the mucous surfaces, appears to me to be much more conformable to the plan of nature, than to suppose them in each place with different and often opposite functions.

Besides it is difficult to decide the question by ocular observation. The delicacy of these elongations conceals their structure, even from our microscopical instruments, agents from which anatomy and physiology do not appear to me to have derived much assistance, because when we see obscurely, each sees in his own way and according to his own wishes. It is then the observation of vital properties that should especially guide us; now, it is evident to judge by them, that the villi have the nature I have attributed to them. The following experiment served to demonstrate to me the influence of the papillary body upon the cutaneous sensibility; it succeeds also upon the mucous membranes. Remove the epidermis in any part and irritate the papillary body with a sharp stilet; the animal is agitated, cries out and gives marks of acute pain. Slide afterwards, through a small opening made in the skin, a pointed stilet into the sub-cutaneous cellular texture, and irritate the internal surface of the corion; the animal remains quiet and makes no noise, unless some nervous filaments accidentally struck make him suffer. Hence it follows very evidently, that it is upon the external surface of the skin that its sensibility resides, that the nerves pass through the corion without contributing to its texture, and that their expansion takes place on the papillary body. It is precisely so with the mucous surfaces. Observe that this circumstance coincides very well with the functions of the two surfaces, which receive by their free portion the action of external bodies, to which they are foreign by their adhering portion.

The papillæ exhibit very great varieties. On the tongue, in the small intestines, in the stomach and in the gall-bladder, they are remarkable for their length. The œsophagus, the large intestines, the bladder, all the excretory ducts have those that are less evident; these last especially and the urethra in particular, are almost smooth in their whole mucous surface. We can scarcely distinguish the papillæ in the frontal, sphenoidal, maxillary sinuses, &c.

These small nervous eminences are sufficiently distinct and separate upon the tongue. In the nasal fossæ, the stomach and the intestines, they are so near together and at the same time so delicate, that the membrane has at first view an uniform and smooth appearance, though it is covered with these elongations. Each papilla is simple; no bifurcation is ever observed at its extremity. All appear to have a pyramidal form, if we can judge at least by those which are the most evident.

Are they susceptible of a species of erection? It has been believed with regard to those of the tongue, which become erect, it is said, to perceive tastes, and with regard to those of the nose, which receive odours more efficaciously in this state of erection, which is in the sensitive phenomena on a small scale, what the erection of the corpora cavernosa is on a large one. I do not believe that any exact experiment can prove this fact. Moreover, it would be necessary then that the intestinal, vesical papillæ, &c. should be in permanent erection, since they are almost always in contact with foreign substances.

II. Parts common to the Organization of the Mucous System.

Besides the blood vessels, the exhalants and the absorbents which contribute to the structure of this system as to that of all the others, it exhibits also a common organ, which is found almost always separate elsewhere, but which is here especially designed for it. This common organ is of a glandular nature; we shall now examine it.

Of the Mucous Glands and of the Fluids which they secrete.

The mucous glands exist in all the system of this name. Situated beneath the corion or even in its thickness, they pour out incessantly through imperceptible openings a mucilaginous fluid which lubricates its free surface, and which defends it from the impression of the bodies with which it is in contact, and at the same time favours the course of these bodies.

These glands are very apparent in the bronchia, palate, the œsophagus and the intestines, in which they take the names of the anatomists who have accurately described them, and where they make in many places evident projections upon the mucous surface. They are less apparent in the bladder, the womb, the gall-bladder, the vesiculæ seminales, &c.; but the mucus that moistens them clearly demonstrates their existence. In fact, since on the one hand this fluid is analogous on all the mucous surfaces, and, on the other, in those in which the glands are apparent, it is evidently furnished by them, it must be secreted in the same way in those in which the glands are less evident. The identity of the secreted fluids supposes in fact the identity of the secretory organs. It appears that where these glands are hidden from our view, nature compensates for their delicacy by their number. Besides, there are animals in which, in the intestines especially, they form by their vast number, a kind of new layer, in addition to those of which we have spoken. In man this is remarkable in the palatine arch, in the pillars of the velum, on the internal surface of the lips, the cheeks, &c. &c. There is then this great difference between the mucous and the serous membranes, that the fluid which lubricates one is furnished by secretion, whilst that which moistens the others is from exhalation.

The size of the mucous glands varies; those of the velum of the palate, those of the mouth, &c. are the largest; they become insensible in the greatest number of mucous surfaces. I dissected two subjects that died of a pulmonary catarrh, and in them the glands of the trachea and bronchia, which are, as we know, very apparent, were not enlarged; the membrane alone appeared to be affected. Besides, we do not yet know the injuries of these glands, like those of the analogous organs, which are more apparent from their size. They are in general of a rounded form but with many varieties. No membrane appears to cover them. They have, like the salivary glands and the pancreas, only the cellular texture for an envelope. Their texture is more dense and compact than these last glands; but little cellular texture is found in them; they are soft, vascular, and appear when opened very much like the prostate gland. I cannot say whether nerves penetrate them; analogy indicates it, for all the principal glands receive them.

Mucous Fluids.

We know but little of the composition of the mucous fluids, because in the natural state, it is difficult to collect them, and in the morbid, in which their quantity increases as in catarrhs for example, this composition is probably changed. We know that in general they are unsavoury, insipid, and but slightly soluble in water, in that even which is raised to the highest temperature; they become putrid with difficulty. In fact they remain a long time unchanged in the nose, exposed to the contact of a moist air; in the intestines, they serve, without danger to them, as an envelope for putrid substances, &c.; taken from the body and subjected to different experiments, they give results conformable to these facts. All the acids act upon them and colour them differently; exposed to a dry air, they thicken by evaporation, and are often even reduced to small shining laminæ. The nasal mucus especially exhibits this phenomenon. Fourcroy has given in detail the analysis of this mucus; he has also given that of the tracheal mucus. But we must not apply rigorously to the analogous fluids our knowledge of the composition of these. It is sufficient in fact to examine a certain number of these fluids, to be convinced that they are not the same in any two places, that more or less thick, more or less uniform, different in their colour, their odour even, &c. they vary in the principles that constitute them, as the membranes which furnish them vary in their structure, in the number and size of their glands, in the thickness of their corion, the form of their papillæ, the state of their vascular and nervous systems, &c. I am far from being certain that the gastric juice is a mucous juice; it is even probable that exhalation furnishes it, the glands of the stomach throwing out a different fluid by the way of secretion. But this assertion is not accurately demonstrated, and perhaps hereafter it will be proved that this juice, so different from the other mucous juices, is however one of them, and that its properties are distinct only because the structure of the mucous surface of the stomach is not the same as that of the other analogous surfaces.

The functions of the mucous fluids in the animal economy are not ambiguous. The first of these functions is to defend the mucous membranes from the impression of the bodies with which they are in contact, and all which, as we have observed, are heterogeneous to that of the animal. These fluids form upon their respective surfaces a layer which supplies, to a certain extent, by its extreme tenuity, the absence of their epidermis. Thus where this membrane is very apparent, as upon the lips, the glans penis, at the entrance of the nose and in general at all the origins of the mucous system, these fluids are not very abundant. The skin has only an oily layer, infinitely less evident than the mucous of which we are treating, because its epidermis is very distinct.

This use of the mucous fluids explains why they are more abundant where heterogeneous bodies remain some time, as in the bladder, at the extremity of the rectum, &c. than where these bodies are only to pass, as in the ureters, and the excretory ducts generally.

Hence why when the impression of a body would be injurious, these fluids are poured out in greater quantity upon their surfaces. The sound which enters the urethra and remains in it, the instrument that is left in the vagina to compress a polypus, that which remains some time with the same view in the nasal fossæ, the canal fixed in the lachrymal sac to remove the obstruction, that which is introduced into the œsophagus to assist interrupted deglutition, always produce, upon the portions of the mucous surface that corresponds to them, a more abundant secretion of the fluid which is constantly poured out, a true catarrh. This is one of the principal reasons that renders it difficult to keep elastic sounds in the wind-pipe. The abundance of the mucus that is then secreted, by closing the openings in the instrument, renders frequent introductions necessary, and can even threaten the patient with suffocation, as Desault himself has observed, though however he obtained great advantage from this means, as I have shown in his surgical works. I ought even to say, that since the publication of the Treatise on the Membranes, I attempted to fix a sound in the air tube of a dog, and that the animal died at the end of some time, having the bronchia filled with a frothy fluid which appeared to have suffocated him.

It appears then that every considerable excitement of the mucous surfaces produces a remarkable increase of action. But how can this excitement, which does not take place immediately upon the gland, have so great an influence upon it? for, as we have said, these glands are always under the membrane, and consequently separated by it from the irritating bodies. It appears that it is owing to a general modification of the glandular sensibility, which is capable of being brought into action by any irritation upon the extremity of the excretory ducts, as I shall prove in the glandular system.

It is to the susceptibility that the mucous glands have of feeling the irritation made at the extremity of their ducts, that must be referred the artificial catarrhs with which Vauquelin has been affected by respiring the vapours of the oxy-muriatic acid, the mucous discharge that attends the presence of a polypus, of any tumour in the vagina, of a stone in the bladder, &c. the frequency of fluor albus in women who are immoderate in the use of sexual intercourse, the more abundant discharge of the mucus from the nostrils of those who take snuff, &c. In all these cases, there is evidently excitement at the extremity of the mucous ducts. I refer also to this excitement the mucous discharge that takes place, from stimulating the end of the nipple of a woman who does not give suck, the copious secretions which the presence of an irritating body produces in the intestines, secretions which especially furnish the matter of diarrhœas, the gastric derangements which succeed an indigestion that has allowed to remain on the mucous surface of the stomach substances not digested and consequently irritating; these derangements are in fact real catarrhs of the membrane of the stomach, catarrhs which most often are not connected with bilious turgescence. I could add many other examples of the mucous secretions increased by an irritation upon the surface of the membranes, at the extremity of the excretory ducts; these will be sufficient to give an idea of the others.

All these excitements produce a kind of inflammation, the peculiarity of which is to contract at first for some time the glandular ducts, and arrest the secretion, which they afterwards excite in great quantity. When the mucous fluids have flowed abundantly for some time, they gradually diminish though the cause continues; thus less mucus is discharged from the urethra in proportion after the sound has remained in it a month, than when first introduced; but almost always as long as the cause continues, the mucous discharge is greater than in a natural state.

Blisters are much employed in medicine on the cutaneous organ, to dispel, according to some, the morbific humour, and overcome, according to others, a natural irritation by an artificial one. Why should we not also in many cases irritate the mucous surfaces? why not act upon the pituitary membrane, upon the glans penis, upon the membrane of the urethra, upon the pharynx, &c. and especially upon the uvula which is so sensible? why, instead of epispastics upon the perineum and sacrum, should we not introduce a sound into the urethra for a paralysis of the bladder? Instead of acting in hemiplegia upon the cutaneous organ, I have already twice employed the following means; I have introduced a sound into the urethra, one in each nasal fossa, and at the same time, a surgeon irritated at intervals the uvula; the patients appeared to be much more excited than by blisters. Very strong purgative enemas and emetics prove the advantage of the excitement of the mucous membranes in this case. Would it not often be better in ophthalmia, to produce an artificial catarrh in the nostril of the diseased side, than to put a blister or seton in the neck? I have once tried it; it did not succeed; but the ophthalmia was of long standing; I propose to repeat these experiments at the Hôtel Dieu upon a great number of patients. I think that we might often in diseases make use of mucous excitements instead of cutaneous, with much more advantage, because in the mucous system the contact of a body is sufficient, and it is not necessary to produce, by removing the epidermis, a kind of ulcer.

The mucous membranes by the continual secretion of which they are the seat, enjoy a principal part in the animal economy. We ought to consider them as one of the great emunctories by which the residue of nutrition constantly escapes, and consequently as one of the principal agents of the habitual decomposition which removes from living bodies the particles that, having for some time contributed to the composition of the solids, are afterwards to become heterogeneous to them. Observe in fact that the mucous fluids do not enter the circulation, but go out of the body; that of the bladder, the ureters and the urethra, with the urine; that of the vesiculæ seminales and the different ducts with the semen; that of the nostrils by the act of blowing the nose; that of the mouth, in part by evaporation and in part by the anus with the excrements; that of the bronchia, by pulmonary exhalation, which arises principally, as I shall say, from the solution of this mucous fluid in the inspired air; those of the œsophagus, the stomach, the intestines, the gall-bladder, &c. with the excrements, of which they often form in the ordinary state a part almost as considerable as the residue of the aliments, and which they even compose almost entirely in some cases of dysentery and fever, in which the quantity of matter voided is evidently disproportioned to that taken in, &c. Let us observe upon this subject that there are always some errors in the analyses of the fluids in contact with the membranes of which we are speaking, as in that of the urine, the bile, the gastric juices, &c. because it is very difficult and even impossible to separate the mucous fluids from them.

If we recollect what has been previously said upon the extent of the two general mucous surfaces, which is equal and even superior to the extent of the cutaneous organ, and if we afterwards consider that these two great surfaces are constantly throwing out mucous fluids, we shall perceive how important this evacuation must be in the economy, and of what mischief its derangement must become the source. It is undoubtedly to this law of nature which wishes to have every mucous fluid thrown out, that must be attributed, in part in the fœtus, the presence of the unctuous fluid of which the gall-bladder is full, the meconium which loads the intestines, &c. fluids which appear to be but a mass of mucous juices, which being unable to pass off, remain until birth, without being absorbed, upon the respective organs on which they have been secreted.

The mucous fluids are not the only ones that are thrown out, and are in this way excrementitious substances to the economy; this is the case with almost all the fluids separated from the mass of blood by secretion; this is evident as it respects the greatest part of the bile; probably the saliva, the pancreatic juice and the tears are also thrown out with the excrements, and their colour alone prevents them from being distinguished like the bile. I do not even know if, by reflecting on many phenomena, we might not attempt to establish as a general principle, that every fluid separated by secretion does not enter the circulation again, that this phenomenon belongs only to the fluids separated by exhalation, as those of the serous cavities, of the articulations, of the cellular texture, of the medullary organ, &c.; that all the fluids are thus either excrementitious or recrementitious, and that no one is excremento recrementitious as the common division implies. The bile in the gall-bladder, the urine in the bladder, the semen in the vesiculæ seminales, are certainly absorbed; but it is not the fluid itself which re-enters the circulation; it is only its most delicate parts, some of its principles which we do not exactly know, probably the serous and lymphatic part; this does not resemble the absorption of the pleura and other analogous membranes, in which the fluid re-enters the blood as it came out of it.

That which is certain on the subject of the excretion of the secreted fluids is, that I have never been able to produce absorption of the bile by the lymphatics by injecting it into the cellular texture of an animal; it produces there inflammation and afterwards suppuration. We know that urine effused is not absorbed and that it destroys every part it touches, whilst that effusions of lymph and blood are easily discussed. There is as it respects the composition an essential difference between the blood and the secreted fluids. The exhaled fluids on the contrary, as the serum, in this respect resemble it very much.

Another very evident proof that all the mucous fluids are designed to be thrown out, is, that when they have continued for some time in any quantity upon their respective surfaces, they create there a painful sensation of which nature relieves us by various means. Thus the cough, which is the constant result of an accumulation of mucus in the bronchia, serves to expel it; thus vomiting in gastric derangements answers the same purpose as it respects the mucous juices accumulated in the stomach, whose presence produces a weight and even pain, though the membranes be not affected. We cough at will, because it is the diaphragm and intercostals by which this function is performed; we do not seek in medicine for any means to excite it. But as we cannot vomit at will, and as the presence of mucous juices often by fatiguing the stomach, does not irritate it sufficiently to produce a contraction, art has recourse to various emetics. We know what a painful sensation of weight the continuance of mucus accumulated in the frontal, maxillary, sinuses, &c. occasions, when there is a catarrh of a portion of the pituitary membrane. The region of the bladder is for the same reason, in catarrhs of this organ, the seat of a troublesome and even painful sensation.

In general, the sensation which arises from the presence of the mucous juices remaining too long and in too great quantity upon their respective surfaces, varies because, as we shall see, each part of the mucous system has its peculiar mode of sensibility; so that the pain is not the same in each, though produced by the same cause. I would only observe that this sensation does not resemble that which arises from the tearing or the acute irritation of our parts; it is an uneasy, inconvenient sensation, difficult to be borne. Every one knows that which arises from mucus accumulated in the nasal fossæ, when the nose has not been blown for a long time, that disagreeable one that accompanies gastric derangements, &c. Those who have a weakness of the lachrymal sac in which the tears, on account of this, accumulate during the night, wake up with a sensation of weight, of which they are relieved by evacuating the sac by pressure, if the puncta lachrymalia are open.

Blood Vessels.

The mucous membranes receive a very great number of vessels. The remarkable redness that distinguishes them would be sufficient to prove it, if injections did not demonstrate it; this redness is not everywhere uniform. It is almost nothing in the sinuses of the face, in the internal ear, of which the membranes are rather whitish, and which appear so especially, because their extreme delicacy allows the bone upon which they are applied to be seen very distinctly. In the bladder, in the great intestines, in the excretories, &c. this colour, though still very pale, is a little more evident; it becomes very much so in the stomach, the small intestines, the vagina and in the pituitary and palatine membranes. In the gall-bladder we cannot distinguish it, because the bile always covers the mucous surface in the dead body.

This colour depends upon a very extensive vascular net-work, the branches of which, after having passed through the mucous corion, and ramifying there, divide and spread ad infinitum on its surface, embracing the papillary body and covered only by the epidermis.

It is the superficial position of these vessels and consequently their want of support on one side, that exposes them frequently to ruptures from considerable shocks, as happens on the surface of the bronchia from a severe cough, on that of the ear and the nose from a violent blow on the head. We know that hemorrhage of the mucous system bordering on the brain, is a common accident from concussions and wounds of the head. Hence why the least gravel makes the ureters bleed; why one of the signs of stone in the bladder is the passing of blood; why a blunt sound carefully introduced is so often withdrawn bloody from the urethra; why the least effort made with instruments carried upon polypi, into a fistula lachrymalis or into the nostrils, produces hemorrhage. I have already observed that we must carefully distinguish these hemorrhages from those furnished by the exhalants, and which do not suppose any vascular rupture.

It is also the superficial position of the vessels of the mucous system, which makes its portions visible, as the red edge of the lips, the glans penis, &c. often serve to show us the state of the circulation. Thus in the different species of asphyxia, in submersion, strangulation, &c. these parts are remarkably livid, an effect of the passage of the venous blood, which has undergone no change from the want of respiration, into the extremities of the arterial system.

The long continued exposure of the mucous system to the air, often makes it lose the redness that characterizes it, and it then assumes the appearance of the skin, as has been observed by Sabatier in treating of prolapsus of the womb and vagina, which, from this circumstance, have sometimes so misled some people, as to make them believe it a case of hermaphrodism.

An important question presents itself in the history of the vascular system of the mucous membranes, viz. whether this system admits more or less blood according to different circumstances. As the organs within which these membranes are spread, are almost all susceptible of contraction and dilatation, as we see in the stomach, the intestines, the bladder, &c. it has been thought that during the dilatation, the vessels being more expanded, receive more blood, and that during the contraction on the contrary, being folded up, as it were choaked, they admit but a small quantity of this fluid which then flows into the neighbouring organs. Chaussier has made an application of these principles to the stomach, whose circulation he has considered as being alternately inverse of that of the omentum, which receives during the vacuity of this organ, the blood which this when it is contracted cannot admit. An analogous use has also been attributed to the spleen since the time of Lieutaud. The following is what the inspection of animals opened during abstinence and at different periods of digestion, has shown me upon this point.

1st. During the fulness of the stomach the vessels are more apparent on the exterior of this viscus, than when it is empty. Within, the mucous surface is not more red, sometimes it has appeared to me to be less so. 2d. The omentum, less extended during the fulness of the stomach, exhibits nearly the same number of vessels, as long, but more tortuous, than when it is empty. If they contain less blood, the difference is hardly sensible. I would observe, that in order to distinguish this well, it is necessary to take care that in opening the animal, the blood does not fall on the omentum which presents itself, and thus prevent its state from being ascertained. This is besides a necessary consequence of the arrangement of the vascular system of the stomach. In fact the great stomachic coronary being situated transversely between it and the omentum, and furnishing branches to each, it is evident that when the stomach is lodged between the layers of the omentum by separating these layers, and this by applying itself upon it becomes shorter; it is evident, I say, that the branches which it receives from the coronary cannot be equally applied to it also. In order to do this, it would be necessary that they should go from one to the other without the intermediate trunk that cuts them at right angles; then, in distending, the stomach would separate them as it does the omentum, and would be lodged between them; whereas it pushes them before it with their common trunk, the stomachic coronary, and makes them fold. 3d. I am confident that there is no such constant relation between the size of the spleen and the emptiness or fulness of the stomach, and that these two circumstances coincide necessarily, and that if the first organ increases or diminishes under different circumstances, it is not always precisely the reverse of the stomach. I first made, like Lieutaud, experiments upon dogs to convince myself of it; but the inequality in the size and age of those that were brought to me, making me fear that I should not be able to compare their spleens correctly, I repeated them upon guinea-pigs of the same litter and size, and examined at the same time, some when the stomach was empty and others when it was full. I have almost always found the size of the spleen nearly equal, or at least the difference was not very sensible. Yet in other experiments, I have seen under various circumstances, inequalities in the size of the spleen and especially in the weight of this viscus; but it was indifferently during or after digestion.

It appears from all this, that if during the vacuity of the stomach, there is a reflux of blood towards the omentum and spleen, this reflux is less than it has been commonly said to be. Besides during this state of vacuity, the numerous folds of the mucous membrane of this viscus leaving it, as we have said above, almost as much surface and consequently as many vessels as during fulness, the blood can circulate in it almost as freely. It has no real obstacles but in the tortuous courses, and not in the obstruction, compression and choaking of these vessels by the contraction of the stomach; now this obstacle is easily surmounted, or rather it is not one as I have proved in my Researches upon Death. As to the other hollow organs, it is difficult to examine the circulation of the neighbouring parts during their fulness and vacuity, as the vessels of these are not superficial as in the omentum, and as they themselves are not insulated like the spleen. We can only then, to decide the question, see the state of the mucous membranes on their internal face; now this face has always appeared to me to be as red during the contraction as during the dilatation.

Besides I only give this as a fact without pretending to draw from it any consequence in opposition to the common opinion. It is possible in fact that though the quantity of blood may be nearly always the same, the rapidity of the circulation being increased, more of this fluid may consequently in a given time enter it when it is full; which appears to be necessary to the greater secretion that then takes place of the mucous fluids, a secretion excited by the presence of the substances in contact with the surfaces of the same name. For example, there is no doubt that there is three or even four times as much mucus secreted in the urethra, when a sound fills it, as when it is empty; now the blood must be in proportion.

The remarkable redness of the mucous system, the analogy of respiration in which the blood flows through the mucous surface of the bronchia the well known experiment of a bladder filled with blood and immersed in oxygen, by which means the blood becomes red, have induced a belief that the blood being separated from the atmospheric air only by a thin pellicle or some of the mucous surfaces, as upon the pituitary, the palatine, the glans penis, &c. assumed there a redder colour, either from getting rid of a portion of its carbonic acid gas, or by combining with the oxygen of the air, and that these membranes thus performed functions accessory to those of the lungs. The experiments of Jurine upon the cutaneous organ, experiments adopted by many celebrated philosophers, seem to strengthen this conjecture.

I tried the following experiment to ascertain this fact. I drew through a wound made in the abdomen a portion of intestine which I tied at one point, I afterwards reduced it, keeping out a small portion only which I opened and by which I introduced atmospheric air, which filled the whole portion situated on this side of the ligature. I afterwards tied the intestine below the opening, and reduced the whole of it. At the end of an hour, the animal being opened, I compared the blood of the mesenteric veins which arose from the portion of intestine distended with air, with the blood of the other mesenteric veins arising from the rest of the canal. No difference of colour was manifest; the internal surface of the distended portion of the intestine was not of a more brilliant red. I thought I should obtain a more evident effect, by repeating with oxygen the same experiment upon another animal; but I perceived no greater variety in the colour of the blood. As upon the mucous membranes which are ordinarily in contact with the air, this fluid is constantly changing and is agitated by a perpetual motion, and as in the preceding experiment it remained stagnant, I attempted to produce the same effect in the intestines. I made two openings in the abdomen, and drew out at each a portion of the intestinal canal; having opened these two portions, I fitted to one the tube of a bladder full of oxygen and to the other that of an empty bladder; I afterwards compressed the full bladder, so as to make the oxygen pass into the other, by going through this portion of intestine, left in the abdomen that the heat might support the circulation in it. The oxygen was thus many times sent from one bladder to another, taking its course through the intestine, which, on account of its contractility is more difficult than it at first seems to be. The abdomen being afterwards opened I found no difference between the venous blood returning from this portion of intestine, and that which flowed from the others. The superficial position of the mesenteric veins, covered only by a fine and transparent layer of peritoneum, their size, if the animal be rather large, render this sort of comparison very easy.

I perceive that we cannot infer from what takes place in the intestines, what happens in the pituitary, palatine membrane, &c. because though analogous, the organization may be different. We cannot here as in the intestines examine the venous blood returning from the part; but, 1st, if we consider that in animals who have respired oxygen for some time, we see the palatine and pituitary membranes more red; 2d, if we reflect that the lividity of the different parts of this membrane, in those destroyed by asphyxia by the carbonic acid gas, depends not on the immediate contact of this gas upon the membrane, but upon the passage of venous blood into the arterial system, as my experiments have, I think, demonstrated; 3d, if we remark finally that in these circumstances the contact of the air does not change, after death, the lividity which the venous blood gives to the mucous membranes, although the skin be then much more permeable to every kind of aeriform fluid; we shall see that it is at least necessary to suspend our judgment upon the colouring of the blood in the mucous membranes, until further observations have decided the question.

The following experiment may also throw some light upon the subject. I have inflated the peritoneal cavity of several guinea-pigs with carbonic acid gas, with hydrogen, oxygen and atmospheric air, to see if I could effect through a serous membrane what I could not make succeed in a mucous; I have not, after these experiments, found any difference in the colour of the blood of the abdominal system; it was always the same as in the common guinea-pig which I killed for comparison.

I think however that I have remarked many times, both in frogs and animals with red and warm blood, such as cats and guinea-pigs, that the infiltration of oxygen into the cellular texture gives, at the end of some time, a much brighter colour to the blood, than that which this fluid exhibits in artificial emphysemas produced by carbonic acid gas, hydrogen and atmospheric air, in all which the colour of the blood scarcely differs at all from what is natural. But in other cases oxygen has had no influence upon the colour of the blood; so that notwithstanding having made many experiments upon this point, I am unable to give any general result. It appears that the tonic forces of the cellular texture and of the parietes of the vessels which are spread upon this texture, receive a very variable influence from the contact of the gases, and that according to the nature of this influence, the fibres crisping and contracting more or less, render these parts more or less permeable, either to the aeriform fluids that tend to escape from the blood in order to unite with that of the emphysema, or to this last fluid, if it tends to combine with the blood, which no doubt produces the varieties I have observed.

The red colour of the mucous system is analogous to that of the muscular system. It does not depend essentially on the blood circulating in the small arteries of this system. It arises from the colouring portion of the blood combined with the mucous texture, especially in the deep part of the organs; for at the origin of the mucous surfaces, this colour appears to be principally owing to the blood in circulation; in fact asphyxia does not render so livid the deep mucous surfaces, as it does those which are superficial and in communication with the skin. The black blood arrives immediately to these by the last arteries, and tinges them as we see. In syncope in which the heart being affected no longer sends blood into the arteries, we know that this portion of the mucous system becomes instantly white.

Besides the red colour of the deeper portions, can, like that of the muscles, be removed by repeated washing and frequently changing the water. Yet the water in which they have been washed is not as red as that used for the muscles.

The instant a mucous surface is plunged into boiling water, however red it may be, as that of the intestines and the stomach, it instantly whitens. The action of the nitric, sulphuric and muriatic acids produces in it also a sudden whiteness.

This colour of the mucous surfaces acquires a remarkable intensity in inflammation. The redness becomes then extremely deep on account of the quantity of blood that is accumulated in the capillary system. It is particularly in dysentery that the internal surface of the intestines exhibits this phenomenon in a striking degree. I ought however to observe to those who open dead bodies, that they never should lose sight of the original tinge of the portion of the mucous system they examine, since each of the divisions of this system exhibits in its shades remarkable differences. If the membrane of the bladder, the rectum, &c. is found as red as that of the stomach in its natural state, then pronounce that there had been inflammation; if the redness of the sinuses equals that which is natural to the bladder and the rectum, decide that inflammation had existed in them. There is, as I have said, a scale of colour for the mucous system. It is then essential to have an accurate knowledge of this scale, a type to which we can refer the inflammatory state in the examination of dead bodies.

Exhalants.

Does exhalation take place upon the mucous surfaces? The analogy of the skin seems to indicate it; for it is well proved that the sweat is not a transudation through the inorganic pores of the cutaneous surface, but a real transmission by vessels of a peculiar nature and continuous with the arterial system.

It appears at first that the pulmonary perspiration which takes place upon the mucous surface of the bronchia, which has so much relation with that of the skin, which increases and diminishes according as this diminishes or increases, and the matter of which is probably of the same nature; it appears, I say, that the pulmonary perspiration is made at least in great part by the system of exhalant vessels, and that if the combination of the oxygen of the air with the hydrogen of the blood contributes to produce it, during the act of respiration, it is but in very small quantity, and it is the portion that is purely aqueous. Besides, this last hypothesis of modern chemists, contradictory to the production of all the other fluids thrown out by the mucous surfaces, appears to me ill adapted to explain the formation of this. When the same phenomenon is produced in many places, and the explanation that is given of it is applicable only to one, we should be suspicious of this explanation.

It should be observed in regard to the pulmonary perspiration, that the solution of the mucous fluid which lubricates the bronchia, in the air constantly inspired and expired, furnishes a considerable portion of this vapour which, insensible in summer, is very evident in winter, on account of the condensation of the air. The mucous juices are dissolved like every other fluid; for wherever there is atmospheric air, heat and moisture, there is evaporation. Here this evaporation is even a means which nature employs to rid herself, as I have said, of the mucous juices. If they are too abundant, as in a cold, then the quantity of air which serves as a vehicle to them, not increasing in proportion, it is necessary that there should be another mode of evacuation; this is expectoration which compensates for what the air cannot remove by solution.

The intestinal juice which Haller has especially considered, but which appears to be in much less quantity than he thought it, the œsophagean and gastric juices, particularly this last which has been supposed to be distinct from the mucous juices, are probably deposited by exhalation upon their respective mucous surfaces. But in general it is very difficult to distinguish with precision what belongs in these organs to the exhalant system, from that which is furnished by the system of mucous glands, which, as we have said, are everywhere subjacent to them. Thus we constantly see the mucous fluids of the œsophagus, the stomach and the intestines, mixing with the œsophagean, gastric and intestinal fluids.

As on the one hand the blood vessels ramify almost naked on the mucous surfaces, and as on the other these vessels are always the origin of the exhalants, it is evident, that these have but a short course to run to arrive at their surfaces; they are rather pores than distinct vessels. Hence why no doubt the blood has so great a tendency to escape by the exhalants; why consequently hemorrhages without rupture are so frequent in the mucous system; why this affection can be classed in the diseases of this system, &c. &c. No other, by the arrangement of the arteries, offers to the exhalants so short a course between their origin and termination. Often even, as I have said, we make the blood of these vessels ooze in the dead body through their exhalants.

Absorbents.

The absorption of the mucous membranes is evidently proved, 1st, by those of chyle and of drinks on the intestinal surfaces, of the venereal virus upon the glans penis and the canal of the urethra, of the variolous when the gums are rubbed with it, of the serous portion of the bile, the urine and the semen, when they remain in their respective reservoirs. 2d. When, in the paralysis of the fleshy fibres that terminate the rectum, substances are accumulated at the extremity of this intestine, these substances often become hard, an effect probably of an absorption of the soft parts. 3d. There have been various cases in which the urine has been almost wholly absorbed by the mucous surface of the bladder, where there have been insurmountable obstacles in the urethra. 4th. If we respire, by means of a tube, the air of a large vessel filled with the exhalations of turpentine, so that these vapours can only act upon the mucous surface of the bronchia, the urine has the peculiar odour that always arises from the use of this substance, the exhalations from which have been introduced into the blood by the means of absorption, &c.

Whatever may be the mode of this absorption, it appears that it does not take place in a constant and uninterrupted manner, like those of the serous membranes, in which the exhalant and absorbent systems are in a regular and continual alternation of action. There is scarcely any but the chylous absorption, that of drinks, and that of the aqueous portion of the secreted fluids remaining in a reservoir as they come from their glands, that constantly take place. Nothing is more variable than the other absorptions. Under the same influence, the glans takes up or leaves the venereal virus; the internal surface of the bronchia sometimes admits and sometimes refuses admittance to contagious miasmata. There are more cases of retention in which the urine is not absorbed entirely, than there are where this absorption takes place, &c. &c. The innumerable varieties of the vital forces of the mucous membranes, varieties produced by those of the stimuli with which they are in contact, explain these phenomena. If these forces are raised or diminished a little, the absorption is altered, even that which is natural, as that of the chyle. Take a purgative; it contracts, shuts even the mouth of the absorbents of the intestinal canal; as long as the irritation continues, all the drinks that are taken pass off by the anus; at the end of four or five hours, the absorbents gradually recover their natural tone and absorption recommences. In these cases, the first discharges are only the intestinal matters, the others are the copious drinks that have been taken. There are many diseases in which, the sensibility of the chylous absorbents being too much raised, they are no longer in relation with the aliments, they take up with difficulty the residue of them, &c. Deficiency of action produces the same phenomenon; in absorption in fact it is a middle degree of sensibility of the organ which produces it, a degree below or above which it cannot take place.

All the mucous absorbents appear to go to the thoracic duct.

Nerves.

I would remark that at all the origins of the mucous system, where the animal sensibility is very great and where it places us, like the skin, in relation with external bodies, cerebral nerves are distributed. The pituitary and palatine membranes, the conjunctiva, the mucous surface of the rectum, the glans penis, the prepuce, &c. exhibit this fact very evidently. There are hardly any nervous filaments coming from the ganglions in these different places.

On the contrary, this last species of nerves is the predominant one in the intestines, in all the excretories, in the reservoirs of the secreted fluids, &c. places where the organic sensibility is the most evident.

ARTICLE THIRD.
PROPERTIES OF THE MUCOUS SYSTEM.

I. Properties of Texture.

Extensibility and contractility are much less in this system than they at first appear to be, on account of the numerous folds which it exhibits in the hollow organs during their contraction, folds which are developed only during extension, as we have seen. Yet these two properties become very evident in some cases. The excretories are capable of taking a size much larger than is natural to them. This is seen in the ureters in particular, which are sometimes found as large as an intestine. The ductus choledochus and the pancreatic duct have often also these dilatations. The urethra and the salivary ducts appear to be less extensible than the others. If they have ever so little obstacles from strictures, contractions, &c. they break rather than stretch; hence various urinary and salivary fistulas.

Hence there is, as we see, many varieties in the degrees of the extensibility of the mucous system; it is the same with regard to the contractility of texture. These two properties are besides capable of being put rapidly into action. We know that the stomach, the intestines, the bladder, &c. pass in an instant from a great size to extreme contraction. Their functions even suppose this rapidity, without which they could not be performed. The palatine membrane which lines the cheeks, exhibits the same phenomenon when the mouth is filled with air, aliments, &c. which are afterwards expelled from it.

When the usual fluids cease to pass through the mucous ducts, they remain in permanent contraction; this is what takes place in the intestines below a preternatural anus. I have seen in this case the cæcum and the rectum reduced to the size of a large quill. Yet there is never then an obliteration of their parietes, on account of the presence of the mucous juices, of which the patient always passes a certain quantity. The urethra, after the operations for stone in which the urine passes for a long time through the wound, and in the great fistulas in the perineum or above the pubis, the salivary ducts in wounds which affect them and through which the whole saliva is discharged, the nasal canal in fistulæ lachrymales, contract also more or less, but are never obliterated. We know that the vas deferens is often a very long time without having semen pass through it, and yet it remains open. This phenomenon distinguishes the mucous ducts from the arterial, which, when the course of blood is interrupted in them, change into ligaments in which every thing like a canal disappears. We ought not to lose sight of this phenomenon of all the mucous ducts; it proves the incorrectness of the practice of those who, thinking that at the end of some time it is impossible to re-establish, in fistulas, the natural way, think it necessary to make an artificial one.

The mucous tubes are not only not obliterated when they are empty, but when inflamed they do not even contract adhesions of their parietes, as so often happens in the serous cavities, in the cellular texture, &c. Observe how important this fact is to the great functions of life; what would indeed become of these functions, if in catarrhs of the intestines, the bladder, the stomach, the œsophagus, the excretories, &c. these adhesions were as frequent as they are in pleurisy, peritonitis, pericarditis, &c.

II. Vital Properties.

Few systems live in a more active manner than this; few exhibit the vital forces in a higher degree.

Properties of Animal Life.

Constantly in relation, like the integuments, with external bodies, the mucous surfaces have occasion for a sensibility which would enable the mind to perceive these relations, especially at the origin of these surfaces. Thus the animal sensibility is very much developed there. It is even superior in it in many places to that of the cutaneous organ, in which no sensation is as acute as those which take place on the pituitary membrane from odours, upon the palatine from tastes, upon the surface of the vagina, the urethra, the glans penis during coition. But without speaking of these exaggerations of sensibility, if I may so express myself, all the natural phenomena of the mucous surfaces prove this property in an evident manner; it is unnecessary however to pause for these phenomena.

I would only observe that this sensibility, like that of the cutaneous organ, is essentially subjected to the powerful influence of habit, which tending constantly to blunt the acuteness of the sensation of which they are the seat, brings equally to indifference the pain and the pleasure they make us experience, and of which it is the medium, as we know. 1st. I say that habit brings to indifference the painful sensations arising upon the mucous membranes. The presence of a sound in the urethra for the first time, is distressing the first day, painful the second, inconvenient the third, and insensible the fourth. Pessaries introduced into the vagina, bougies into the rectum, tents fixed in the nasal fossæ, and a canula kept for a length of time in the nasal canal, exhibit in different degrees the same phenomena. It is upon this remark that is founded the possibility of the introduction of sounds into the wind-pipe to aid respiration, and into the œsophagus to produce an artificial deglutition. This law of habit can even transform into a pleasure an impression at first painful; the use of snuff for the pituitary membrane and different aliments for the palatine, furnish well known examples of this. 2d. I say that habit brings to indifference agreeable sensations arising on the mucous surfaces; the perfumer, placed in an odoriferous atmosphere, the cook, whose palate is constantly affected by delicious tastes, do not find in their professions the acute enjoyments they give to others. From habit can even arise the succession from pleasure to painful sensations, as in the preceding case it converts pain to pleasure.

I would however observe that this remarkable influence of habit is only exerted upon sensations produced by simple contact, and not upon those produced by real injuries, as the tearing, the forced stretching, the cutting or pinching of the mucous system; thus it does not mitigate the pains caused in the bladder by pressure and by the tearing a stone occasions, or on the surface of the womb, of the nasal fossæ, &c. by a polypus, on that of the œsophagus or the wind-pipe by a sharp and uneven body accidentally lodged there, &c. &c.

It is to this power of habit over the sensibility of the mucous system, that must be in part referred the gradual diminution of its functions, which accompanies age. Every thing is stimulant in infancy, every thing is blunted in old age. In one, the very active sensibility of the alimentary, biliary, urinary, salivary surfaces, &c. contributes principally to produce that rapidity with which the digestive and secretory phenomena succeed each other; in the other, this sensibility blunted by habitual contact, connects but slowly the same phenomena.

Is it not from the same cause that arises this remarkable modification of the sensibility of this system, viz. that at its origins, as upon the pituitary, the palatine membranes, the œsophagus, the glans penis, the opening of the rectum, &c. it gives us the sensation of the bodies with which it is in contact, and that it does not give this sensation in the very deep organs which it lines, as in the intestines, the excretories, the gall-bladder, &c.? In the interior of the organs, this contact is always uniform; the bladder only knows the contact of the urine, the gall-bladder that of the bile, the stomach that of the aliments masticated and reduced, whatever may be their diversity, to an uniform, pulpy mass. This uniformity of sensation produces no perception, because in order to perceive, it is necessary to compare, and here the two terms of comparison are wanting. Thus the fœtus has no sensation of the waters of the amnios; thus, the air, very irritating to a new born infant, becomes insensible to it. On the contrary, at the beginning of the mucous membranes, the stimulants vary every instant; the mind can then perceive the presence of them, because it can establish approximations between their different modes of action. What I say is so true, that if in the interior of the organs, the mucous membranes are in contact with a foreign body, different from that which they are accustomed to, they transmit the sensation of it to the mind. A catheter in the bladder, sounds introduced into the stomach, &c. are examples of this. Fresh air, in great heat of the atmosphere, suddenly introduced into the trachea, carries an agreeable sensation over the whole surface of the bronchia; but habit soon renders us insensible to it and we cease to have the perception of it. Yet it is to be observed that when the intestines come out in preternatural inversions of the anus, their sensibility never becomes so acute as that of the palatine, pituitary surfaces, &c. &c. The absence of cerebral nerves no doubt has an influence upon this phenomenon.

The sensibility of the mucous system is much raised in inflammations; acute catarrhs are, as we know, very painful. The contact of bodies is then not only felt, but is very disagreeable. I would observe however that the sensibility never rises so high as it does in the inflamed cellular, serous, fibrous systems, &c. A phlegmon, a pleurisy, &c. compared with a catarrh, are sufficient to convince us of this. We may say that the organs least accustomed to feel in the natural state, experience in diseases the most acute sensations.

There is no animal contractility in the mucous system.

Properties of Organic Life.

Organic sensibility and insensible contractility are very evident in the mucous system. They are constantly put in action in it by four different causes; 1st, by the nutrition of this system; 2d, by the absorption that takes place in it, either naturally or accidentally; 3d, by its exhalation; 4th, by the constant secretion of its glands. These two properties are the original causes of all these functions, the increase and diminution of which are truly the indices of the state of these glands. As a thousand causes continually act upon the mucous surfaces, as a thousand different stimuli continually excite them, especially at their origin, this state is incessantly varying like the functions that result from it.

The mucous system differs then from most of the others; 1st, in this, that the organic sensibility and the insensible contractility are habitually more exalted in it, on account of the more numerous functions over which they preside; 2d, in this, that they incessantly vary, on account of the variety of the stimuli. Observe in fact that, in the osseous, fibrous, cartilaginous, muscular, nervous systems, &c. on the one hand, these properties are put in action only by nutrition; and on the other, no stimulant being in contact with these systems, they always remain at the same degree.

Hence it is not astonishing that the diseases which especially put in action the organic sensibility and the insensible contractility of the same species, should be so frequent in the mucous organs. All the catarrhal affections, both acute and chronic, all the hemorrhages, various and numerous tumours, polypi, fungi, &c. all kinds of excoriations, ulcers, &c. of which they are the seat, are derived from the various alterations of which their organic properties are susceptible.

It is also to these alterations that must be attributed a remarkable phenomenon, viz. the innumerable varieties the mucous fluids exhibit in diseases. Take for example those that are thrown off from the internal surface of the bronchia, those that are brought up by expectoration, and which we can examine better than others, because they are mixed with no foreign substance; observe how they differ, in the different affections of the chest; sometimes they have a yellowish and as it were bilious tinge; sometimes they are frothy in the vessel which receives them; sometimes they adhere to it with tenacity, and at others they are easily detached from it. Viscid or liquid, fetid or without odour, grey, white, green or even black in the morning, they have a thousand external appearances which evidently denote differences in their composition, differences which chemists have not yet explained to us. I do not speak of the cases where as in phthisis, hemoptysis, &c. foreign substances are mixed with these mucous juices. Now it is evident that all these varieties depend only upon the varieties of the organic sensibility of the bronchial glands or of the membrane upon which they pour out their fluids. According as the property is differently altered in the mucous system, it is in relation with different substances, admits some and rejects others. The same organ, the same vessels can there, according to the state of the forces that animate them, separate from the mass of blood many different substances, rejecting one to-day and admitting it to-morrow, &c.

Do you wish for other proofs of the innumerable varieties which the different modifications of the organic sensibility of the mucous membranes produce in their functions? Observe the urethra; in the ordinary state it lets the urine pass freely; in the excitement in which its forces are in erection, its sensibility repels it and admits only the semen. Who does not know that in one species of epiphora, the mucous passages for the tears are open, and that the diminution only of their vital forces prevents this fluid from flowing in them? The sensibility of the mucous surfaces is oftentimes so altered that their glands refuse to admit every kind of fluid; this happens in the beginning of some peripneumonies, in which expectoration is entirely suppressed, it is always a serious beginning, and even an indication of death, if the state of the sensibility does not change, unless a relaxation, as it is commonly called, takes place.

In general, I think that there are but few systems which deserve, more than this of which we are treating, to fix the attention of physicians, on account of the innumerable alterations of which it is susceptible, alterations which almost always suppose those of the predominant vital properties of this system, as the alterations of the muscular, nervous systems, &c. most often put in action the properties which more particularly belong to them, viz. animal contractility for one, and the sensibility of the same species for the other.

The sensible organic contractility does not appear to be the attribute of the mucous system; yet there is often in it something more than the insensible oscillations which compose the other organic contractility. For example, in the emission of semen, in which there is no agent of impulse at the extremity of the urethra, as in the evacuation of urine, it is very probable that this is spasmodically contracted to produce the jet, oftentimes very strong, which then takes place. The following phenomenon which I have observed in myself appears to belong to the same cause. In gaping, there sometimes escapes from the mouth then wide open, a small jet of fluid, which coming from the lateral parts of this cavity that it passes over, is thrown at some distance; if a surface is then before the mouth, as when we read a book, this fluid is spread in small drops upon this surface; it is the saliva which the excretory duct of Steno throws out with force. Now on the one hand this duct is almost wholly mucous, and on the other it has not at its posterior part a muscular agent of impulse. Perhaps the excretories which pour out their fluids in the deep parts of the organs, exhibit the same phenomenon. We know that the milk is also sometimes subject to a kind of ejection, when it is very abundant, an ejection which supposes a powerful contraction of the lactiferous ducts. In general, these different motions analogous to that of the dartos, of the cellular texture, &c. appear to hold a middle place between those of tone and those of irritability.

Sympathies.

There are few systems that sympathize more frequently with the others than this. Now in its sympathies, it sometimes influences and sometimes is influenced. The first Tissot calls the active mode of sympathy, the second the passive. Let us make use of this classification.

Active Sympathies.

One point of the mucous system being inflamed, irritated or stimulated in any way, all the vital forces can enter separately into action in the other systems.

Sometimes it is the animal contractility that is brought sympathetically into action; thus the diaphragm, the intercostal and abdominal muscles contract to produce sneezing from irritation of the pituitary membrane, or cough from the irritation of the membrane of the bronchia, or from that even of the surface of the stomach, which produces stomachic coughs, which, as we know, have nothing to do with affections of the chest. We know the general spasm that seizes all the muscles the instant a foreign body passes between the mucous edges of the epiglottis. Stones of the bladder and the urethra, by making the cremaster contract sympathetically, produce retraction of the testicle. Physicians might, I think, profit by the knowledge of these mucous sympathies. In apoplexy, in which the bronchia is sometimes filled with mucus that the patient cannot evacuate, the action of ammonia upon the pituitary membrane produces the double effect, 1st, of stimulating the brain as blisters do; 2d, of freeing, by the cough it occasions, the surface of the bronchia, which being obstructed, is an obstacle to the passage of the air.

Sometimes it is the animal sensibility that is put into action by an affection of the mucous surfaces. The stone, that irritates that of the bladder, causes an itching at the end of the glans penis. That of the intestines being irritated by worms, an inconvenient itching is felt at the end of the nose. Whytt has seen a foreign body introduced into the ear, affect painfully the whole corresponding side of the head; an ulcer of the bladder, produce every time the patient passed water, a pain on the superior part of the thigh, &c. &c.

The sensible organic contractility is often sympathetically excited by the affections of the mucous system. I might at first refer to this subject what I have observed respecting the organic muscles, almost all of which move from an excitement of a contiguous mucous surface; but that is a natural phenomenon; there are many others that are preternatural. A stone that irritates the internal surface of the pelvis of the kidney produces vomiting, which is, as we know, produced any time at will by an irritation of the uvula. The instant the semen passes the urethra in coition, the action of the heart is commonly accelerated. Tissot speaks of a stone which, being entangled in the duct of Warton, produced a sympathetic discharge from the bowels. I saw at the Hôtel Dieu two women, who, whenever they menstruated, and the mucous surface of the womb was consequently in activity, could retain the urine but a short time in the bladder, which contracted involuntarily to expel it the moment it entered it. At ordinary times, there was nothing peculiar in the evacuation of this fluid.

As to the sympathies of insensible contractility and of organic sensibility, they take place when a mucous surface being irritated towards the extremity of an excretory duct, the gland of this duct is brought into action, when, for example, the saliva flows in greater abundance by the action of sialagogues upon the extremity of the Stenonian duct. Whenever there is a gastric derangement and the mucous surface of the stomach consequently suffers, the surface of the tongue is sympathetically affected; the glands situated under this surface increase their action and hence that white mucous coat, that is commonly called a foul tongue, which is a real sympathetic catarrh, but which can however exist idiopathically. Here also is to be referred the remarkable influence of the mucous system upon the cutaneous; thus during digestion, in which the mucous juices pour out abundantly from all sides into the stomach and the intestines, and in which the mucous membranes of the gastric viscera are consequently in great action, the fluid of insensible transpiration is lessened remarkably, according to the observation of Sanctorius; it is in very small quantity three hours after the meal, so that the action of the cutaneous organ is evidently less energetic. Thus during sleep, in which all the internal functions become more evident and are exerted to their utmost, and in which the sensibility of the mucous membranes is consequently strongly developed, the skin seems to be struck with a species of atony; it becomes cold more easily, it allows less substances to escape from it, &c. To these sympathies also can be referred many phenomena of hemorrhages. We know with what facility the mucous surface ceasing, from any accidental cause, to throw out blood, as happens so often on that of the womb, another is immediately affected and discharges this fluid; hence hemorrhages from the nose, the stomach, the chest, &c. from the suppression of those of the uterus, &c.

Passive Sympathies.

In many cases, the other systems being irritated, the animal sensibility of this is brought into action. Among the numerous examples of this fact, the following is a remarkable one. In many diseases in which organs foreign to the mucous system are affected, we experience a sensation of burning heat in the mouth, the stomach, the intestines, &c. and yet the mucous surface, the seat of this sensation, does not disengage more caloric than usual; we may be convinced of this by placing the fingers in the mouth. This sensation is of the same nature as that which we refer to the glans penis when there is a stone in the bladder, as that which is experienced at the end of the nose from worms in the intestines, &c. There is no material cause of pain, and yet there is suffering. Thus in intermittent fevers we experience a cutaneous shivering, though the skin may be as warm as usual; I would observe in respect to this, that the mucous membranes are hardly ever the seat of an analogous sensation of sympathetic cold, but it is almost always a sensation of heat that the aberrations of the vital forces produce in them. Whence arises this difference between them and the cutaneous organs? I know not. I attribute also to a sympathy of animal sensibility the great thirst which takes place in all the severe affections of any part. In all great wounds, after severe operations, in experiments on living animals, &c. we observe this thirst which depends upon a sympathetic affection of the whole mucous surface that extends into the mouth, the stomach and the œsophagus.

Animal contractility cannot be put sympathetically into action in the mucous system, since it does not exist in it.

The same is true of the sensible organic contractility. It is possible that sometimes the kind of motion we have noticed, and which resembles this property, may be sympathetically excited; I know no example of it.

The insensible organic contractility is here very frequently in sympathetic activity. It is the skin especially which exercises by means of this property, a great influence upon the mucous system. 1st. In hemorrhages of the mucous surface of the womb, the nostrils, &c. a cold body applied to the skin in the neighbourhood, contracts this surface and stops the blood. 2d. Who does not know that the production of most catarrhs is often the sudden consequence of the action of cold on the cutaneous organ? 3d. In various affections of the mucous membranes, baths which relax and expand the skin, frequently produce happy effects. 4th. When the temperature of the atmosphere benumbs the cutaneous tone, that of the mucous system receives a remarkable increase of energy. Hence why in winter and in cold climates, in which the functions of the skin are very much diminished, all those of this system increase in proportion. Hence the more evident pulmonary exhalation, the more abundant internal secretions, a more active digestion, more quickly performed and consequently an appetite more easily excited. 5th. When on the contrary the heat of the climate and the season relax and expand the cutaneous surface, the mucous surface is in proportion contracted; in summer, at noon, &c. there is a diminution of the secretions, of that of the urine especially, a slowness in the digestive phenomena from a defect in the action of the stomach and intestines, an appetite slow to return, &c. 6th. In various general affections of the skin, certain portions of the mucous membranes are almost always affected. In scarlet fever, the throat most usually suffers sympathetically. This phenomenon is very common in small pox. 7th. In the latter periods of organic affections of the viscera, as in phthisis, diseases of the heart, enlargements of the liver, cancers of the womb, &c. the mucous membranes are affected like the serous surfaces. The kind of atony in which they then are, produces a more copious flow of mucous juices in them which are altered, become more fluid, &c.; hence the diarrhœas that are called colliquative, which are then to the mucous surfaces, what dropsies are to the serous ones; 8th. It is also to this atony that must be attributed the pectoral hemorrhages which so frequently take place in the last periods of organic diseases, in those of the heart especially. During the short time that I have been at the Hôtel Dieu, there has already died more than twenty patients whom I have opened, of these affections almost forgotten by all practitioners before the time of Corvisart; I have only observed four examples in which passive hemorrhage of the lungs was not the precursor of death.

Character of the Vital Properties.

From what we have thus far said, it is evident that the mucous system is one of those of the whole economy, in which life is the most active. Always in contact with substances that stimulate and irritate it, it is as it were like the skin, in continual action. Yet the life is not the same in all its parts; it undergoes in each remarkable modifications, which no doubt depend on those we have pointed out in the organization of this system, in the nature of its corion, in the arrangement of its papillæ, in the distribution of its vessels and its nerves, in that of its glands, &c.; for as we have seen, none of these essential bases of the mucous system is everywhere arranged in the same manner. There is an organization common to the system, and one peculiar to each of its divisions. It is the same in regard to its life; there is a life common to the system, and as many peculiar ones as there are parts to which it is extended. We know how much the animal sensibility of the pituitary membrane differs from that of the palatine, how powerfully the membrane of the glans penis and the urethra is stimulated by the passage of the semen which makes no impression upon any other mucous surface. The same is true in regard to the organic sensibility and the contractility of the same species. Each mucous surface, in relation with the fluid it is accustomed to, would bear the others with difficulty. The urine would be a stimulant for the stomach and the gastric juice for the bladder; the bile that remains in the gall-bladder would produce a catarrh upon the membrane of the nose, in the vesiculæ seminales, &c.

From these varieties in the vital forces of each division of the mucous system, it is not astonishing that the diseases of this system should also be very variable. Each has a general character, but this is modified in each mucous surface. There is an order of symptoms common to all catarrhs; but each has its peculiar signs, each has its different products. The fluid from a pulmonary catarrh does not resemble that from a nasal one; that coming from a urethral, vesical catarrh, &c. is wholly different from that from an intestinal one. These fluids exhibit in their morbid changes the same differences that we have pointed out in their natural composition, differences which are derived like them, from the different vitality of each portion of the mucous system.

It is to these varieties of life and the vital forces that must be referred also those of the sympathies. Each portion of this system has a peculiar sympathetic action upon the other organs. The pituitary alone being irritated produces sneezing. You would excite in vain the extremity of the glans penis, the rectum, &c. you would never produce vomiting as you do by stimulating the uvula.

An important remark should here be made in regard to the stomach. We know that there is no organ which performs a more important part in the sympathies than this. The least affection of this important viscus, the least gastric derangement, spread over the whole animal economy a painful influence; all the other parts feel it. I do not believe even that there is any uneasiness more fatiguing and general than that which we then experience in certain cases. The general weakness which takes place in hunger almost instantaneously, is sympathetic; the alteration of nutrition has not had time to produce it. The same is true with regard to the sudden increase of the forces which results from the contact of the aliments upon the mucous surface of this viscus, an increase which cannot be attributed to the passage of the chyle into the blood, which has not yet had time to take place.

I think the stomach owes this important part in the sympathies principally to its mucous surface. In fact, 1st, its serous surface has no connexion with it, since it is there of the same nature as in all the rest of the peritoneum, besides in what is called inflammation of the abdomen, and in which this serous surface is especially affected, we do not observe such numerous sympathetic relations. 2d. The fleshy coat appears to be the same as that of the whole intestinal canal; why then should it have different influences? 3d. As it respects blood-vessels and nerves of the ganglions, the stomach is nearly organized like the rest of the alimentary tube. 4th. It has besides the par vagum; but is this nerve alone capable of producing such numerous phenomena? It can contribute to them; but certainly the peculiar modifications which it experiences in the mucous surface, the peculiar nature of this membrane contribute also much to it. No membrane is organized like that of the stomach. Though we do not see perfectly at first view its organic differences, reflection is sufficient to convince us of them; thus on the one hand no one separates so great a quantity of fluid, and on the other none furnishes one of a nature analogous to that of the gastric juice.

ARTICLE FOURTH.
DEVELOPMENT OF THE MUCOUS SYSTEM.

I. State of the Mucous System in the First Age.

The development of the mucous system follows in general the laws of that of the organs to which it belongs. Early in the gastric apparatus, later in the pulmonary and that of generation, it seems in its growth rather to obey the impulse it receives, than to give one to what surrounds it, an arrangement common to almost all the systems which contribute to form the different apparatus. Observe in fact that there is always in the growth certain parts to which all the others refer; thus in the cerebral apparatus, the early size of the brain produces that of the bones of the cranium, of the dura-mater, the pia-mater, the arachnoides and the vessels; thus it is on account of the spinal marrow, that the vertebral canal is so evident in the fœtus; thus all the serous surfaces have a growth in proportion to that of their respective organs, &c. &c. I would remark however that the early growth of the systems which are only to follow that of the parts to which they are destined, is only in the dimensions of length, breadth, &c. The thickness most commonly does not correspond with these dimensions. Thus the bones of the cranium though broader in proportion than those of the pelvis in the fœtus, are not thicker. The extent of the dura-mater is in proportion greater than that of the albuginea which belongs to the same system; but the organization is no further advanced.

In the fœtus, the delicacy of the mucous texture is extreme, the papillæ are hardly perceptible. But by carrying the hand over a mucous surface, we feel there an extremely delicate velvet and such as is not equalled by the finest velvet. The redness of this system is not then as evident, because no doubt less blood penetrates it, as the various functions which are afterwards to take place upon these surfaces, as digestion, the excretions, respiration, &c. are but feeble or entirely wanting. At this age, the quantity of blood seems to be in an inverse ratio in the skin and in these surfaces. The mucous red is then like the muscular, of a very deep tinge, often even livid, on account of the nature of the blood circulating in the arteries. Then the adhesions of the mucous texture to the subjacent cellular are less; those especially of this last with the surrounding parts are very slight; thus it is very easy to draw out whole the internal portion of the intestines of the fœtus, from the external covering that contains it, so as to see two cylindrical canals, one of which is muscular and serous, the other cellular and mucous. The stretching destroys in this experiment all the valvulæ conniventes, and the small intestines are as smooth on the interior as the large, in the canal artificially extracted. If we subject this canal to ebullition, much more scum arises from it than in the adult; this scum is white and never green. The crisping that takes place a little before the first boiling, diminishes more in proportion the length of the canal, and consequently appears to be stronger.

At birth, when respiration and digestion suddenly commence, the secretions increase, the mucous system acquires a remarkable degree of activity. It is instantly excited powerfully by the many new substances with which it is in contact. It is by it and by the cutaneous system that bodies foreign to ours then immediately stimulate it, and so much the more efficaciously, as the double surface which receives the excitement is not accustomed to it. Then the red blood which penetrates the mucous system, gives it an increase of energy and sensibility, which renders it still more proper to receive impressions. Thus the mucous juices which till then stagnated upon their respective surfaces, without fatiguing and irritating them, are suddenly for them, on account of their increase of sensibility, stimulants which excite them, and force the subjacent muscles to contract. Then the urine becomes for the bladder a cause that promotes the contraction of it. A few instants after birth, all the openings in which the mucous membranes begin, open and permit to escape the meconium, the urine and all the mucous juices. This internal and general shock that empties all the mucous cavities, renders them fit to become the seat of the great functions which are soon to take place in them.

When all the internal functions are in activity, the mucous surfaces experience no more sudden changes, analogous to that of which I have spoken. They grow like the other viscera in a slow and insensible manner; they preserve for a long time their original softness, which is remarkable, especially in the nose, the stomach, &c. and which during lactation, is not adapted in the infant, to the solid substances with which the adult is nourished. Is this softness the cause of the mucous affections which are in general so common at that age? We know that then the mucous juices abound; the pituitary membrane is more moist; the stomach and intestines are frequently affected with a species of catarrh which is the cause of the looseness that we have so often to combat in infancy. The membrane of the bronchia is also frequently diseased. The two extreme ages of life resemble each other by the abundance of the mucous juices secreted upon their respective mucous surfaces.

In youth the mucous system is in very powerful action. The active hemorrhages of this system are very frequent at this age; those of the nose, the bronchia and even the stomach often take place; those of the portions of this system, subjacent to the diaphragm, are then less common. Observe that in man, hemorrhages of the gastro-pulmonary surface are infinitely more frequent than those of the genito-urinary surface, which on the contrary, are much more numerous in woman in whom one of them is natural to a part of this surface, viz. menstruation.

At the period of puberty, the development of the genital parts in both sexes, gives much activity to a part of the genito-urinary surface; then menstruation begins upon that of the womb; then the sensibility of the urethra is raised in order to feel acutely the passage of the semen. Observe that this increase of energy is not attended with a weakness of the other parts, as happens in many cases; on the contrary, all the systems, all the apparatus seem to borrow, from the force which the genital parts acquire, an increase of action.

II. State of the Mucous System in the subsequent Ages.

In the years which succeed youth, the mucous system continues to grow, thicken and become firmer. Its vital energy seems still to predominate for some time, in the superior surfaces, as in the pituitary, the membrane of the bronchia, &c.; thus the affections of these parts are more frequent until the thirtieth year. But as we advance in age, the abdominal mucous surfaces appear to predominate over the others, as in general all the organs of this region do.

Besides, a thousand causes in the course of life, make the state of the mucous system vary. We do not find it in two subjects, with the same shade of colour, with the same density, with the same external appearance. By taking any surface upon many subjects, that of the stomach, for example, we easily see these differences, with which we must be struck if we have opened dead bodies but ever so little.

The redness of the mucous texture is very bright until the thirtieth year; after that, it begins to alter. This texture becomes more and more pale in old age; the blood enters it but in small quantity; it acquires more consistence and density. The fingers carried over it no longer perceive that softness, that velvet so remarkable in the first age. Its forces, which grow languid, render difficult, in the excretories, the exit of the fluids which pass through these tubes to be thrown out. Yet the mucous glands still secrete their fluids in very great abundance. Often even these fluids increase in proportion which constitutes the catarrhal affections, so common in old age. But these affections then have the same character as the functions of the whole system; secretion takes place slowly; the disease is always chronic; most often it terminates only with life.

The mucous absorption is, at this age, slow and difficult, like all the others; the various contagions are taken much less easily, either by the respiratory surfaces, or by the contact of contagious miasmata upon the neighbouring surfaces of the skin. The chyle slowly absorbed, makes the digestive periods longer.