This system, one of the most important in the animal economy, differs from most others in this, that the texture which is peculiar to it is not precisely the same in all the organs that compose it. The fibres of a muscle of animal life would as well serve for the structure of any other muscle of the same system. The tendinous fibres, the cartilaginous, osseous textures, &c. are everywhere the same. On the contrary, the texture of the liver would not serve to compose the kidney, nor that of this last the salivary glands. The glandular system then has a resemblance in its different parts only by certain general attributes which have many exceptions.
Authors have given the name of glands to organs to which it does not belong; such as the thyroid, the pineal, the lymphatic glands, those especially that are in the neighbourhood of the bronchia, the thymus, the suprarenal, &c. We should call by this name only a body from which flows, by one or many ducts, a fluid which this body separates from the blood which it receives by the vessels that go to it. 1st. On the head, the salivary, the lachrymal, the Meibomian and the ceruminous glands of the ear, and the amygdalÆ.; 2d, the mammÆ on the thorax; 3d, in the abdomen, the liver, the pancreas and the kidneys; 4th, in the pelvis, the prostate and the testicles; 5th, on the whole trunk and the face, the very numerous collection of mucous glands; these are nearly all that are dependant upon the glandular system; all the other organs which belong to it by this name, are foreign to it in their texture, their properties, their life and their functions. In this point of view, the division of Vicq d’Azyr is inaccurate.
The extremities contain nothing which belong to this system, no doubt because the fluids which it separates almost all serve for the functions of organic life, whilst in the extremities every thing is in relation to animal functions.
ARTICLE FIRST.
SITUATION, FORMS, DIVISION, &c. OF THE GLANDULAR SYSTEM.
The glands have two different positions. Some of them are sub-cutaneous, as the mammÆ, the salivary glands, &c.; the others deep seated, as the liver, the kidneys, the pancreas and almost all the mucous ones are removed from the action of external bodies. The greatest number occupy places where there is constantly much motion, as the salivary glands on account of the jaw, the mucous on account of the neighbouring fleshy layer, the liver on account of the diaphragm, &c. It is this which has made it believed that this motion, foreign to their functions, was destined to produce the excretion of their fluids. But, 1st, the glands of the palatine arch, the pancreas, the testicles, the kidneys even, can hardly borrow accessory aid on account of their position. 2d. We know that the sight alone of grateful food makes the saliva flow. 3d. Sialagogues produce the same effect. 4th. When the bladder is paralytic, the mucous juices pour into it as before, oftentimes more copiously. 5th. The semen flows involuntarily. 6th. The excretion of the mucous juices is as easy in the pituitary membrane as any where else, though the fleshy layer, almost everywhere spread under the mucous system, is wholly wanting here. A thousand other analogous facts prove this truth placed beyond a doubt by Bordeu, viz. that the vital action is the essential cause of every excretion.
Accessory aid should not however be entirely rejected. In fact, in salivary fistulas, there is evidently more fluid thrown out during mastication than at any other time. It is evident that in the excretion of urine, the abdominal muscles perform the principal part. When the gall-bladder is emptied, I believe that the neighbouring motions are much assistance to it. In general, whenever the fluids are found in considerable quantities, if the parietes of the organs which contain them are not very strong, like those of the heart, the motions of the neighbouring organs are necessary to overcome the resistance which they offer. On the contrary, in the capillary vessels in which the fluids are in small quantities, the organ that contains them is sufficient, by its reaction, for the motion.
There are single glands like the liver, the pancreas, &c.; and others in pairs, as the kidneys, the salivary, lachrymal glands, &c. These resemble each other in general on both sides; but their resemblance is not to be compared for precision to that of the organs in pairs of animal life. One of the kidneys is lower than the other; their arteries, veins and nerves are not analogous either in length or size; frequently fissures exist in one that are wanting in the other, &c. The same observation is true with respect to the salivary glands.
The glandular forms are not fixed and invariable; they exhibit a thousand different modifications in their size, direction and proportions; they have never the precise and exact conformation of the organs of animal life. This fact can be disputed by no one who has examined a number of dead bodies. The following are the means by which I have made this most evident to myself. We know that the organs vary much in size, in different individuals; now, in these varieties the proportions are always accurately kept in animal life, whilst it is rare that they are so in organic life. Let us take an organ for example in each of the two lives. I have always seen that in a small brain the corpus callosum, the thalami nervorum opticorum, the corpora striata, &c. are in proportion to the whole size of the organ. On the contrary, nothing is more common than to see a large lobe of Spigelius with a small liver, and vice versa a large liver with a small lobe. There is no anatomist who has not had frequent occasion to make this remarkable observation. A kidney is larger sometimes in its superior part, sometimes in its inferior, &c. It is in the whole of the organ that these varieties of size take place in animal life; it is oftentimes in insulated parts only in organic life. The reason of this appears to me to be that the harmony of action is necessary, as I have demonstrated, for the animal functions; so that if one side of the brain is more developed than the other, if one eye, one ear, one pituitary membrane, &c. are more developed than their corresponding organs, the perception, the sight, the hearing, the smell, &c. would be inevitably deranged; whilst the secretion of bile, of urine, &c. takes place equally well, though one part of these glands may be larger or smaller than the other parts.
There is a remark to be made respecting the glands with regard to these varieties of form, it is, that those which are covered by a membrane, as the liver, the kidneys, even the pancreas, are less exposed to them than those which are buried in cellular texture without having around them a membranous covering, as the salivary, the lachrymal, the mucous glands, &c. I have often examined these last in the mouth and in the course of the trachea; I never found them alike in two subjects. We know that the parotid sometimes extends upon the masseter, and sometimes does not, that it descends more or less into the neck, that it is of a greater or less size there, &c.
When one gland of a pair is wanting or becomes diseased, sometimes the other increases considerably in size, as I have seen in the kidneys. This takes place also in the treatment by compression of salivary fistulas, a treatment which does not however always succeed. In other cases, the sound gland increases its action and secretes more fluid, without increasing in size.
The exterior of the glands not covered by membranes is unequal and lobulated; it conforms to the muscles, the vessels, the nerves, and even the bones, as the parotid which is placed under the angle of the jaw. Less cellular texture is in general found around them, than around organs with great motion. That which is in contact with them is more dense and compact than that of the organic interstices. It closely resembles the sub-mucous texture, that exterior to the arteries, the veins, the excretories, &c. but it is not however so resisting. It receives fat with difficulty, and forms a kind of membrane, which, insulating to a certain extent the vitality of the gland, performs in great measure in this respect the functions of the peritoneum around the liver, of the peculiar membrane of the kidneys, the spleen, &c.
ARTICLE SECOND.
ORGANIZATION OF THE GLANDULAR SYSTEM.
I. Texture peculiar to the Organization of this System.
The glandular texture is distinct from most of the others in this, that the fibrous arrangement is wholly foreign to it. The elements that compose it are not placed at the side of each other, in longitudinal or oblique lines, as in the muscles, the fibrous bodies, the bones, the nerves, &c. They are found agglomerated, united by cellular texture, and adhere but very slightly. Thus whilst the organs with distinct fibres resist much, especially in the direction of their fibres, these are torn with the least effort, and break even with ease. Their rupture is unequal, full of prominences and depressions, a difference which distinguishes them from cartilage, the rupture of which is in general smooth. This rupture is not equally easy in all the glands. The prostate, the amygdalÆ, the mucous glands resist much more than the liver or the kidneys, which principally exhibit this phenomenon. The pancreas and salivary glands yield a little without breaking, when they are pulled; but it is not their texture which is the seat of this phenomenon, it is the abundant cellular texture that penetrates them; thus their different lobes are then separated, in proportion as the filaments which are between them become longer.
The glandular texture, which is very commonly called parenchyma, is in general arranged in three different ways. 1st. In the pancreas, the salivary and lachrymal glands, there are distinct lobes, separated by cellular texture, resulting from smaller lobes which are agglomerated together and which are composed of still less lobes, that are called glandular grains; the scalpel traces with ease the first, second, third and even fourth divisions. 2d. In the liver and the kidneys there is found no trace of the first of these divisions, of those into principal and even secondary lobes. The glandular grains all in juxta-position, having between them an equal quantity of cellular texture, a quantity which is very small, as we shall see, present an uniform texture without inequality, which is broken with ease, as I have said, and the rupture of which exhibits species of granulations. 3d. The prostate, the amygdalÆ and all the mucous glands have a soft parenchyma, like pulp, without the appearance of principal or secondary lobes, or even glandular grains, not breaking, yielding much more under the finger that compresses it, than that of the other glands. The simple inspection of the glandular system is sufficient to enable any one to perceive the triple difference which I have just pointed out, and which is essential. The testicles and the mammÆ have a peculiar texture which cannot be referred to these differences.
Authors have been much occupied with the intimate structure of the glands. Malpighi admitted that there were small bodies in them, which he believed were formed of a peculiar nature. Ruysch determined that they were all vascular. Let us neglect all these idle questions, in which neither inspection nor experiment can guide us. Let us begin to study anatomy where the organs can be subjected to our senses. The exact progress of the sciences in this age is not accommodated to all these hypotheses, which made general anatomy and physiology but a frivolous romance in the last.
There is no doubt that the excretories communicate with the arteries which penetrate the glands. Injections made in these escape with great ease by the first, without there being any trace of extravasation in the gland. The blood flows often naturally by the excretories, and produces sometimes bloody urine, saliva, &c. But do these facts prove that there are only vessels in the glands, that the peculiar parenchyma of which they are the result does not depend on a substance which is peculiar to them? The glands, like all the other organs, as the muscles, the bones, the mucous membranes, &c. have their peculiar texture which especially characterizes them, which belongs only to them, a texture in which the arteries communicate with the veins and the excretories. Let us not push our researches further; if we do, we shall be inevitably entangled in conjectures. Let us confine ourselves to examining what phenomena distinguish this texture from all the others when subjected to the different reagents. It is much to know the characteristic attributes of the glandular system, without seeking to understand its intimate nature, which, like that of all the other systems, is concealed by an impenetrable veil.
The glandular parenchyma dried in the air after having been cut in slices, loses its original colour, takes a deep one, black even in the liver and the kidneys, in which it is owing especially to the blood which penetrates these glands, since if they are dried after having been deprived of it by repeated washing, they remain grey after their drying. No system becomes harder or more brittle than this by this preparation. It diminishes then less in size than most of the others. When immersed in water after being thus dried, it becomes soft, resumes in part its original appearance and its tendency to putrefaction, which takes place immediately if it is left in the open air.
The glandular texture, when exposed to the air so that it does not dry, becomes putrid very quickly, and gives out an odour more fetid than most of the others. More ammonia appears to be disengaged from it. The liver especially produces an insupportable odour when putrid. I do not know any organ, kept in a vessel full of water to macerate, which gives out more disagreeable emanations. The kidney becomes putrid much less quickly; this varies however a little.
When boiled, the glandular texture furnishes in the first moments of ebullition, a great quantity of grey substance, which mixes at first perfectly with the water which it renders turbid and then collects into a copious scum on the top of this fluid. It is this texture, the fleshy, the mucous and the cellular which give the most scum in boiling, as it is the cartilaginous, the tendinous, the aponeurotic, the fibro-cartilaginous, &c. which give the least of it. It should not be believed, moreover, that this first product of stewing is uniform in its nature; it varies in each system in quality as well as quantity. At least I have observed that its appearance is never the same, that it has nothing constant but its frothy state, which also varies much and which is even almost always nothing in the mucous system.
The liquor which results from the boiling is very much changed in colour, and appears to contain many more principles than that made with the white organs. An accurate analysis of the liquor in which each system had been boiled would be an interesting subject of research. I have found that in almost all the appearance, the taste and the colour were different.
The glands exhibit a phenomenon when cooking that especially distinguishes them. They harden at the moment of the first ebullition, and acquire the horny hardness like all the other systems; but whilst most of these soften again from long-continued stewing, so as to become pulpy, the glands uniformly become harder, so that after five or six hours boiling, they are three or four times as hard as they naturally are. I have very often made this experiment, which is also well known in our kitchens, in which when a gland is cooked, care is taken that the stewing should not continue too long. Beef kidney finally becomes soft; those of sheep and of man remain hard for a much longer time. They soften however more than the texture of the liver, which is of all the glands that which exhibits the hardness in the greatest degree.
Another phenomenon which especially distinguishes the ebullition of the glandular system, is that when it is taken out at the moment it has undergone the sudden horny hardening, common to almost all the animal solids plunged into boiling water, it has not like the others acquired elasticity. Draw in an opposite direction a tendon, a serous or mucous membrane or a muscle that have undergone the horny hardening, they stretch and afterwards suddenly contract the instant the extension ceases; on the contrary, a slice of liver that has the horny hardness breaks when it is drawn and never contracts. The texture of the prostate appears to be more capable of then acquiring a little elasticity. The non-fibrous disposition of the glands seems to have much influence upon this phenomenon.
Exposed to the sudden action of a very bright fire as in roasting, the texture of the liver and the other glands crisps and contracts on the exterior. There results from it on the surface a kind of covering impermeable in part to the juices contained in the organ, which in this way becomes cooked in these juices which soften it in the interior. This phenomenon is however common to all the solids. Hence why care is taken to expose what is roasting, whether it be muscular or glandular, at first to the action of a very quick fire; afterwards when the horny hardening of the surface has been produced, it is diminished, and the organ is cooked with a small fire.
The glands macerated in water yield differently to its action. The liver resists it longer than the kidney, which after an experiment of two months made in vessels placed in a cellar has been reduced to a reddish jelly swimming in the water; whilst the first preserved for the same time and a little longer, its form and density, and had only changed its red colour to a blueish brown, whereas the kidney retains its colour in maceration. The salivary glands contain much of this white, unctuous and hard substance, which all the cellular parts when long macerated exhibit. It is not the glandular texture that has changed, but only the fat contained in the cellular texture, which is here very abundant.
The acids act upon the glandular texture nearly the same as upon all the others. They reduce them to a pulp which varies in its colour and the rapidity of its formation, according to the acid employed. The sulphuric is uniformly the most efficacious in producing this pulp which it blackens, whilst the nitric yellows it. All the acids act with much more difficulty upon the glandular texture when stewed, than when raw. My experiments have convinced me that but few systems exhibit this difference in a more remarkable manner.
The glands are much less digestible than many other animal substances, especially when stewed, which produces in them in this respect an effect entirely different from what it does in the cartilages, the tendons, and all the fibrous organs, which by it lose their density, become soft, gelatinous, viscid even and are easier dissolved by the gastric juice. I believe in general that we should digest the glands much easier by eating them raw. Every one knows that the more the liver is cooked, the more indigestible it becomes. This induced me to make a comparative experiment upon this organ cooked and raw; when one portion in the second state was reduced to a pulp in the stomach of a dog, the other portion in the first state swallowed at the same time had just begun to be altered.
Of the Excretories, of their Origin, of their Divisions, &c. Of the Glandular Reservoirs.
All the glands have ducts destined to carry off the fluid which they secrete from the mass of blood; now as they are only found in the glands, they should be considered with the peculiar texture of these organs. The origin of these ducts is uniform in all the glands. They arise, like the veins, by an infinite number of capillaries, which form the last ramifications of a kind of tree, these ramifications appear to begin at each glandular grain, where these grains exist; so that for each there is one of these, an artery and a vein. Arising thus from the whole of the interior of the gland, these ducts soon unite and form larger ducts, which usually go in a straight line though the glandular texture, converge towards each other, unite with other ducts still larger and terminate differently.
In respect to this termination, glands should be divided into three classes. 1st. Some transmit their fluids by many ducts, each of which is the assemblage of smaller ducts, opening at the side of each other, but all entirely distinct and without communication. Sometimes at the place where these ducts terminate, a more or less considerable prominence is observed, as on the breast, as also on the prostate, of which the verumontanum is a kind of nipple. Sometimes there is a depression, a sort of cul-de-sac which is found at the place of these orifices, as in the amygdalÆ, upon the tongue, &c. Sometimes the surface on which the different ducts of a gland open, is smooth and even, as is the case with that on which those of the lachrymal, sublingual and almost all the mucous glands open. 2d. Other glands pour out their fluid by a single duct, as the parotids, the pancreas, the sublinguals, &c.; this arrangement is only a modification of the preceding; where the duct opens, no inequality is usually discovered, the surface is smooth. 3d. There are glands which, before throwing out their fluid by their excretories, deposit it for some time in a reservoir where it remains to be afterwards expelled; such as the kidneys, the liver, the testicles, &c. Here there are always two excretories, one which goes from the gland to the reservoir, the other from the reservoir outwards. These reservoirs are evidently a part of the same system to which their excretory ducts belong.
Though the first and second species of glands have no reservoir, yet the different ramifications of their excretories may to a certain extent be considered as such. In fact, these ramifications, as well as those of the excretories of the glands with a reservoir, are constantly full of the fluid which is secreted in these organs. Whatever may have been the kind of death, the fluid of the prostate may be always made to ooze out, by compressing the gland; I have often even by pressure produced a very evident jet. The papillÆ of the kidney also uniformly give out urine when pressed. The liver cut in slices allows natural bile to escape from the divisions of the hepatic duct. The semen is uniformly found in the windings of the vas deferens. The lactiferous vessels keep the milk in their cavity, till it is evacuated, and it has even no other reservoir. The greater or less size of the mammÆ during lactation is owing to the greater or less fulness of these vessels. It is also to this circumstance that must be referred the peculiar taste of each glandular texture, which always borrows some sapid particles from the fluid it secretes. We know that the kidney has always an urinous odour, especially in old animals. It is to this also that I refer the difference of putrefaction which I have observed between this organ and the liver. We know that the bile undergoes putrid fermentation sooner than the urine; this, when it is very acid, can even preserve it to a certain extent from putrefaction; expose then the liver and the kidney to it, the latter will almost always be the last to become putrid, as I have said.
It appears in general that the course of the fluids in the excretories is much less rapid than that of the blood in the veins and even than that of the lymph in the absorbents; the following considerations place this beyond a doubt. The urine flows continually by the ureters, as is evidently proved by fistulas in the loins; now, in the time taken to fill the bladder by this uninterrupted flowing, there would flow from a vein of a diameter equal to that of the ureter ten times as much blood, and much more lymph from the thoracic duct. Yet this rapidity of motion is subject to many varieties; during the period of inactivity of the glands, it is not half as great as during their activity; the salivary fistulas are a proof of this. We know how promptly the ureters transmit the urine from the drinks that are taken.
Size, Direction and Termination of the Excretories.
The size of the excretories varies. 1st. Those which go out in considerable number from a gland are very small, often hardly perceptible. They commonly run their course in a straight line, do not anastomose with each other and open immediately upon going out of the gland. 2d. Those that are single are larger, always in proportion to the size of their gland, except however the hepatic which is evidently very small in comparison with the liver. They run their course out of their glands, and arise from ducts as large as those of the preceding ones; so that if a single trunk arose from the excretories of these, they would resemble the others in every respect. They differ only in this, that their secondary excretories open directly on their surface, whereas they unite in a common trunk in the others. The pancreas is the only one in which this common trunk goes concealed in the gland itself. It is only in the testicles that it is tortuous, and in which, on this account, it is longer than the course which it has to run.
Whatever may be their arrangement, the excretories pour all their fluid either on the exterior, as the urethra, and ureters, the lactiferous tubes, and the ducts of the sebaceous glands; or on the interior of the mucous membranes, as the mucous, salivary, pancreatic, prostate and hepatic excretories. The cutaneous and mucous surfaces are the only ones then on which the excretories terminate, the only ones which their fluids moisten. These ducts are never seen opening upon the serous or synovial surfaces. The excretories of the pretended articular glands would be, if they existed, an exception to the laws of the general organization. The excretories never open in the cellular texture; if this happens preternaturally, either abscesses take place from the irritation which results from it, as in urinary fistulas, or a callus forms in the course of the excreted fluid, and thus defend the cellular system from a troublesome infiltration.
Hence the mucous tube of the intestines should be considered as a kind of general excretory added to the pancreatic, hepatic excretories, &c. and which throws out all the fluids which are separately poured by these ducts into it. In fact, all the secreted fluids appear to be destined, as I have said, to be thrown out of the body. Separated from the mass of blood, they are foreign to it, and do not enter it in a natural state. Though still contained in cavities with mucous surfaces, they may be truly considered as being out of our parts. These surfaces are really true internal integuments, destined to defend the organs from the contact of the substances which they contain, a contact which would inevitably be injurious to them.
Remarks on the Secreted Fluids.
The fact that the secreted fluids are destined to be thrown out, a fact which is incontestable with regard to the urine, the bile which colours the excrements, the saliva, &c. has made me for a long time believe that the introduction of these fluids into the sanguineous system, would produce the most serious consequences. I was besides confirmed in this, 1st, by my experiments, in which I have always seen, as I have said, the urine, the bile, &c. injected into the cellular texture, remain without being absorbed, but producing abscesses; 2d, by the infiltration of the urine in the neighbourhood of the bladder, from which abscesses always arise; 3d, by the serious consequences from the effusions of this fluid in the peritoneum from the high operation for the stone, and of the bile on the same surface in certain penetrating wounds, in both these cases these fluids never re-enter the blood by way of absorption, like the peritoneal serum, but almost always occasion death; 4th, by an experiment in which I had seen a dog die shortly after the injection of urine into the jugular. All these considerations made me suspect that the secreted fluids, introduced again into the mass of blood, were always fatal at the end of some time, and that, as some physicians whose opinion is of great weight have thought, all that has been said of the bile’s being poured into the blood in bilious diseases, is but a consequence of vague ideas of the reality of which there is no proof. Yet the importance of this question, in regard to medical theories, has induced me to resolve it by experiments, so as to leave no doubt upon the subject.
I have then injected into the jugular veins of many dogs bile taken from the gall-bladder of other dogs which I opened at the same time. For the first few days they appeared to be weary, did not eat, were much altered, their eyes were heavy, and they were constantly lying down; but after some time they gradually regained their former vigour. I afterwards employed human bile in these experiments; the result was the same, except that many times, the animal had hiccough and vomiting some time after the injection. In one instance a dog died in three hours after the experiment; but it was because I made use of that extremely black fluid that is sometimes found in the gall-bladder instead of bile which resembles thick ink, and which appears to form a considerable part of those black vomitings that sometimes take place.
These experiments induced me to try some with the saliva, and I obtained the same result from them; only the languid state that succeeded the injection was less evident. I afterwards made use of nasal mucus suspended in a sufficient quantity of water, for it can hardly be dissolved in it. Finally urine itself was many times injected, not that which comes immediately from drink and is only aqueous, but that which is of slow formation. In this experiment the dogs have been sicker, but only one died, and that happened on the seventh day. I have many times repeated it, on account of that which I performed three years ago; the same result has always taken place, which makes me think that being but little used at that time to make experiments, I introduced by accident a bubble of air through the syringe, which is sufficient to produce the death of the animal.
A question then is evidently settled by the experiment. The secreted fluids, though destined to be thrown out in the natural state, can re-enter the circulation, without causing the death of the animal, which is only more or less affected according to the nature of the fluid injected. Whether the bile circulates or not with the blood in bilious fevers, I have not examined; but it certainly can circulate with it after having been absorbed in its canals. I do not doubt but that in purulent reabsorptions, the pus circulates in its natural state in the sanguineous system; I confess that I have not made experiments upon the injection of this fluid, but I intend to immediately.
We exaggerate every thing. No doubt the solids in which the vital forces are especially inherent, are particularly affected in diseases; but why should not the fluids be affected also? Why should we not seek in them causes of disease as well as in the solids?
There are cases in which these are primarily affected, and in which the fluids are so in consequence; thus in cancer, in the affections of the liver, the spleen, &c. in most organic lesions, the various yellowish, grey, brown and even greenish shades of the face, are an index of the consecutive alterations which the fluids experience in their colour and consequently in their nature.
In other cases the affection commences with them; as when the venom of the viper is introduced into the blood, as when reabsorption of pus takes place from external abscesses, or in phthisis, and as when there is absorption of various contagious principles. There is no doubt that the different substances which can be introduced with the chyle into the blood, may be the cause of various diseases. Is it not the blood which carries to the brain the narcotic principles which produce sleep? does it not carry turpentine and cantharides to the kidneys, mercury to the salivary glands, &c.? Inject opium, wine, &c. into the veins, and you will stupify the animal the same as if you had given them by the stomach.
Physiologists at one time were much engaged with the introduction of medicinal infusions into the veins of living animals. They circulated by these infusions purgatives, emetics and a thousand other foreign substances, the contact of which the blood bore, without occasioning any other accident to the animal than that of vomiting or alvine evacuations if they were emetics or purgatives, and a greater or less general derangement if they were other foreign substances which had no affinity with any particular organ.
The caustics, as the nitric and sulphuric acids and other very irritating substances, have alone caused death in these curious experiments of which Haller has given us a sketch, and which prove that various substances wholly foreign to the blood can circulate in it, and that it is a common mass in which are found many principles differing from each other, and which cannot be always essentially the same. In these experiments the most important part has been neglected, that of the infusion of the different animal fluids, particularly the secreted ones, and those also which are preternaturally produced in diseases. I think that the different reabsorptions would be much elucidated by the infusion of the various kinds of pus, sanies, &c. But we have already sufficient facts to convince us that the fluids and especially the blood can be diseased; that the various foreign substances mixed with it can act in a fatal manner upon the solids. In fact, every acrid, irritating matter, without being mortal, accelerates the action of the heart and produces a true fever, if injected into the veins. In all these cases, it is always necessary that the solids should act; for all the morbid phenomena suppose their alterations; but the principle of these alterations is in the fluids. They are the excitants, and the solids the organs excited. Now if there are no excitants, there is no excitement, and the solids remain unaffected.
Finally there are cases in which the whole economy both solids and fluids seem to be simultaneously affected; such are adynamic fevers, in which at the same time that there is a general prostration of the first, the second appear to be really decomposed.
Let us not exaggerate then medical theories; let us regard nature in diseases as she is in a state of health, in which the solids elaborate the fluids and are at the same time excited by them. There is a reciprocal action, every thing succeeds each other, every thing is connected together. Our abstractions hardly ever exist in nature. We usually adopt a certain number of general principles in medicine, and we accustom ourselves afterwards to deduce from these principles, as necessary consequences, all the explanations of diseases. There is in physical phenomena a regularity and uniformity which never deceive. In morals even, there is a certain number of principles acknowledged by all men, which direct them and regulate their actions; hence a constant uniformity in our manner of considering moral and physical phenomena; hence the habit of going always from the same principles in reasoning upon them. We have carried this habit into the study of the living economy, without considering that it incessantly varies its phenomena, that under the same circumstances they are hardly ever the same, that they are continually increased and diminished and have a thousand different modifications. Nature seems at every instant to be irregular, capricious and inconsequent in their production, because the essence of the laws which preside over these phenomena, is not the same as that of the physical laws.
I would observe that the experiments the result of which I have just given for the secreted fluids, differ from those which I published the last year, and in which these fluids have always been fatal, the instant they were forced towards the brain by the carotid. This is a phenomenon general to all the irritating fluids, whether drawn from the economy, or foreign to it; they destroy life when they arrive at the cerebral organ, by a direct injection and without having undergone any alteration, whilst we can inject them with impunity into the veins, as the experiments of the physicians of the last age have proved. We can even without danger, as I have observed, introduce them into the arterial system, on the side opposite to the brain, as in the crural artery, for example. Do the fluids mixed with the black blood rid themselves of some principles by respiration, before they arrive at the brain, or is the preceding phenomenon owing to other causes? I know not. I would only observe that every thing which is not arterial blood, as the black blood and even serum, produces death when forced into the carotid. Water alone is injected with impunity. When the irritating principles are much diluted in this fluid, their contact is less injurious. I have seen very light coloured urine not produce death.
Structure of the Excretories.
All the excretories have an internal membrane which is mucous, and which is a continuation of the mucous or cutaneous surfaces, upon which they terminate. But besides this, they all exhibit an external covering which forms the shell, as it were, of this mucous canal. This shell is very thick in the vas deferens, in which it exhibits a texture but little known. In the urethra it is of a spongy nature, containing much blood and analogous to the glans of which it is a continuation. In the ureters, in the hepatic, salivary ducts, &c. it is this extremely dense and compact cellular texture of which we have spoken, which, by its structure, resembles that of the arterial and venous cellular texture, and which differs essentially from the ordinary cellular texture, as from the intermuscular. It does not appear that there is in these ducts a membrane differing from this dense texture and the mucous surface.
Each excretory has its vessels. The ureters evidently receive branches from the renal, spermatic arteries, &c. &c. The hepatic gives them to the ductus choledochus; the transverse artery of the face supplies the duct of Steno. Various nerves coming from the ganglions accompany the corresponding arteries and veins. Yet I have uniformly observed that there is never around these ducts a plexus as evident as there is around most of the arteries.
The excretories have principally the vital properties of the mucous system which forms them in great part. Their sympathies are also nearly of the same nature.
II. Parts common to the Organization of the Glandular System. Cellular Texture.
The glands differ much in the cellular texture which enters into their structure. We may even, in this respect, divide them into two classes.
In all the salivary glands, in the lachrymal, in the pancreas, in all the glands with a granulated and white parenchyma, it is very abundant. Each glandular body is divided into lobes very distinctly separated by grooves which this texture fills, and which produce the lobulated appearance on the exterior of this species of gland; not only each lobe, but each lobule, each glandular grain even, has also the cellular texture for a boundary. In this respect, this sort of gland is truly an assemblage of small distinct bodies, which, separated from each other, would also perform well their functions. This is what is seen in the parotids, in which different accessory glands are often found in the course of the duct of Steno, and are perfectly independent of the principal gland. Sometimes there is a continuity, sometimes there is a separation between the sub-maxillary and the sub-lingual glands. The cellular texture is often loaded with much fat in this species of gland. This is especially remarkable in the mammÆ, the size of which is owing sometimes to the glandular texture, as in young people in whom this texture predominates over the fat; sometimes to the predominance of this fat, as we see after the fortieth year, when this gland preserves a considerable size. The difference is easily perceived by the touch by the softness and flaccidity of the organ in the second case, and by its resistance and firmness in the first. In the age of puberty often, it is also the fatty cellular texture which increases the size of this organ. Hence why there is often but little milk from a large breast, and a much greater quantity from a smaller one. In the voluptuous sensations which we experience at the sight of this organ, we distinguish very well, without being conscious of it, the breast whose prominence is real, from that which is not, and in which the fat only raises the skin of the breast. It is rare in the salivary glands, the pancreas, &c. that the cellular texture predominates so much, that the fat accumulates in them in so considerable a quantity. I have however seen cases in which the parotid resembled a fatty muscle; but there was no increase of size.
In the testicle, whose parenchymatous portions are separated as in the preceding glands, the cellular texture is not the medium of union. There is found between each grain species of threads which appear to be excretories, and not real cellular laminÆ.
In the glands with a compact parenchyma, as the liver, the kidney, the prostate, the mucous glands, &c. &c. there is very little cellular texture; by tearing them in different directions, they break without exhibiting intermediate laminÆ. Fat is never found accumulated in their parenchyma. The fatty state of the liver which takes place in many diseases, and which is not, as has been thought, an affection necessarily attendant upon phthisis, exhibits a phenomenon wholly different from the mammÆ and the salivary glands when they have become fatty. The fat enters then like an element into the texture of the organ; it is in this respect like the colouring substance, whose place it has as it were taken; it is not found in cells. Moreover much of it can be extracted by ebullition, and I have observed that much of it swims on the surface of the water in which livers of this kind are boiled. The kidney also has fat in its interior; but it is around the pelvis and not in its peculiar parenchyma. The amygdalÆ, the prostate, the mucous glands, &c. never have it. Serum is never effused into the texture of the glands with a compact parenchyma. The most complete leucophlegmasia leaves them sound in this respect.
Yet it cannot be doubted that the cellular texture exists in these glands; maceration demonstrates it in them. In the fungous tumours that grow out of them, there is much of it. It is principally around the vessels that it is found; the capsule of Glisson is an example of this. It often happens even, as I have been led to observe, that this texture becomes diseased, whilst that of the gland remains sound. Thus we see steatomatous tumours developed in the liver, serous cysts in the kidney, hydatids in both, and various productions in the other glands, without deranging the secretion in the least. It is upon the liver especially that these observations are best made; its size is trebled, even often quadrupled by internal tumours, without an increase of its texture; this texture dilated forms between these tumours, species of partitions in which the bile is secreted as usual. The same thing takes place in the kidney, in which serous cysts are found. Sometimes these cysts grow there till the whole glandular texture is destroyed, and there remains only a large sac separated by membranous partitions, and filled with serum. I have preserved three kidneys of this kind.
Blood Vessels.
All the glands not covered by a membrane, receive their arteries from all sides. Numerous branches coming from the neighbouring vessels, penetrate the whole surface of the pancreas, the salivary and lachrymal glands, &c. These arteries wind at first in the interstices between the lobes, ramify afterwards between the smaller lobes and finally penetrate the glandular grains. Each of them has its own artery; all communicate together; so that those of the sub-maxillary and the sub-lingual are filled by injection made by means of small tubes into the sub-mental, the external maxillary or the lingual, as well as by an injection of the trunk even of the external carotid.
In the glands surrounded by a membrane, as the liver, the kidney, the testicle, &c. the arteries enter only at one side, usually in a fissure, and by a single trunk which is very considerable, and which is sometimes divided into many branches more or less large. This part of the gland in which the artery enters is always the most distant from the action of external bodies, a remark common to all the important organs, as the lungs, the intestines, the spleen, &c. which always present externally their convex surface, that on which the vessels are the most ramified; so that the place where an injury can happen to them is that where hemorrhage is the least to be feared. The principal artery, after it has entered the gland, is soon divided into different branches which separate and are subdivided as they approach the convexity. They give off in their course many branches to the body of the gland and then terminate by a great number of capillaries on the convex part of the gland. They often even pierce the organ and ramify between it and the membrane which covers it. For example, by injecting the hepatic artery, if the liver is bare, many small blackish striÆ suddenly appear on its convexity, which are owing to this cause. The best means of seeing the glandular arterial system, is to inject a kidney with a solid substance, and afterwards destroy its parenchyma by maceration or something else. The arterial system is then bare and entirely by itself. Many of these preparations are found in anatomical museums.
The great arterial trunks winding in the glands, communicate to them an internal motion very favourable to their functions. This motion is so much the more evident, as almost all these organs very near the heart by their position in the trunk, are, if we may so say, under the immediate jar of its contractions. The salivary glands, the mucous ones of the mouth and the lachrymal on the one hand, the testicle, the prostate and the mucous ones of the genital parts on the other, exhibit the extremes of this position. Another cause which favours the jar of the glands by the entrance of the blood, is that almost all the arteries that go to them run but a very short course before they enter them. The spermatic alone is an exception to this rule; thus, every thing in the secretion of semen seems to be characterized by a remarkable slowness. To this constant motion imparted to the glands by the entrance of the blood, should be added that which is communicated to them by the neighbouring organs, and which keeps them in a constant excitement, which is more necessary to their secretion than to their excretion. In considering the action of organs, the constant motions with which they are agitated has been too much neglected. The example of the brain ought however to fix the attention of physiologists upon this point.
The veins, everywhere continuous with the arteries, follow the same distribution in the glandular system, and accompany them almost everywhere. We do not see superficial and deep-seated veins, as we do in many other organs. The liver is the only example in which the red blood enters at one side, and the black goes out at the opposite.
Most of the veins of the glandular system pour their blood into the general system of black blood, and as many glands are very near the heart, they feel the reflux which this system often experiences. This phenomenon is particularly remarkable in the liver, as the hepatic veins open but very little below the right auricle. Hence why whenever this auricle is considerably distended, as in asphyxia and in death in which the lungs being crowded present an obstacle to the blood, the liver has a much greater quantity than usual. I have uniformly made this observation. Weigh comparatively this organ when the auricle is full and when it is empty in the dead body, after having first tied all its vessels; you will find a very great difference. For the same reason, you will observe a constant relation between the weight of the liver and that of the lungs, provided a morbid alteration of texture of one of them be not the cause of death. The veins of many glands, as those of the mucous ones of the stomach and the intestines, as those of the prostate, &c. pour their blood into the system of abdominal black blood. There are hardly any in the system of which we are treating, but these veins, those especially of the glands situated in the pelvis, which become varicose. Varices of the prostate are frequent, as we know.
Of the Blood of the Glands.
The quantity of blood that is constantly found in the glands varies remarkably; they may even be divided in this respect into three classes. 1st. In the pancreas, the salivary, lachrymal glands, &c. there is found but very little. It does not furnish the colouring matter to these organs, which are white, and which, when macerated, tinge with red but two or three waters. 2d. In the mucous glands, the prostate, the testicles, and the amygdalÆ, there is found a little more. 3d. The liver and the kidneys contain so great a quantity of it, that there is not in this respect any proportion between them and the rest of the glandular system. This is owing in a small degree in the first to the cause pointed out above; thus it often contains more than the second, but it is not the essential cause. After death by hemorrhage in which there was no reflux, in the liver or the kidney suddenly taken from a living animal, &c. we observe the same thing. In macerating these glands, it is necessary to renew the water at least a dozen times before it ceases to be bloody. Hence why when they are preserved in alkohol on account of an organic disease of which they were the seat, they must be first macerated for a long time; if not, the liquor soon becomes turbid from the blood. It is this quantity of blood which gives to these glands a greater weight in proportion than that of the other parts. It is from this that their redness is derived, a colour which no other part exhibits to the same degree, but which is not more strongly inherent in their texture, than it is in the mucous surfaces or the muscles. In fact, we remove it with the same ease by repeated washing. Then the liver assumes a greyish appearance, which appears to be the colour inherent in its texture, as white is that of the fleshy fibre. The kidney seems a little less to derive its colour from the blood. It remains in part red when macerated; the pulp even which is the product of it, after remaining some months in water, that has been often changed, still exhibits in some degree this colour, much less however than in a natural state.
Does the state of the secretions make the quantity of the glandular blood vary? Does more of this fluid enter the kidney when it furnishes much urine, than when it secretes but little, or if the same quantity is brought by the arteries, is less returned by the veins in the first than the second case? This is an interesting subject for experiment.
Is the nature of the blood changed when it arrives at the glands? Has it a peculiar composition before entering each of them? Much has been said of this change necessary to secretion; but that this may take place, there must be a cause to produce it; now what is this cause here? Does not the blood circulate in the trunks which go to the glands, as in the others? It would be necessary then that the gland should be surrounded with an atmosphere which acts upon the blood at a certain distance from the place where it is; a vague idea, which has no solid foundation, and which is met with only in the books of those who have never made experiments. I have drawn blood from the carotid, spermatic, hepatic and renal arteries; it is equally red and coagulable. In the same animal, it is impossible for the senses to discover the least difference.
I would observe that secretion differs essentially from nutrition in this, that it always draws the materials of its fluids from the red blood, whereas the second often takes its own from the white fluids, as we see in the tendons, the cartilages, the hair, &c.
Nerves.
The glands receive two species of nerves. 1st. The cerebral are found almost exclusively in the salivary and lachrymal glands, the amygdalÆ, &c. 2d. The testicles, the prostate gland and the liver receive them in an almost equal proportion from the brain and the ganglions. 3d. The kidneys and most of the mucous glands receive scarcely any but those of the ganglions. What is now said of the nerves should be understood only of those that are free and independent of the arteries; for each arterial trunk that enters a gland, is surrounded by a nervous net-work belonging to the system of the ganglions, which is very evident in the great glands, as in the liver and the kidneys where this net-work comes from the semilunar ganglion, in the salivary glands where it comes from the superior cervical, in the testicles where it comes from the lumbar ganglions, &c.
Compared with the size of the glands, the nerves are in small proportion, notwithstanding what Bordeu has said. It is not necessary in fact to judge of this proportion by those of the parotid and sub-maxillary glands, which merely pass through these glands without stopping in them, and leave only some branches there. For example, there is certainly no organ in the economy, among those which receive nerves, that, in proportion to its size, has so few as the liver.
Besides, the nerves enter the glands nearly in the same way as the blood-vessels, that is to say, 1st, on all sides, in those that have no membrane; 2d, by a groove only in those that are covered with one. They divide and subdivide after entering it, and are soon lost sight of. Ganglions never exist in the interior of the glands.
Have the nerves an influence upon secretion? It is probable they have, as every gland is provided with them; but they by no means exert so immediate an influence upon this function as many physicians have pretended. 1st. It is said that the nerves of the parotid glands have been cut, and that the secretion of the saliva has been suppressed. This division is evidently impossible, since the gland must be extirpated before removing its nerves. 2d. I have divided the nerves of the testicle of a dog, the only gland in which this experiment can be made. I could not obtain any result, because an inflammation of the gland came on and it suppurated; but this suppuration even supposes that the nervous influx is not actually necessary for secretion, since suppuration is accomplished by a mechanism analogous to that of this function. All physicians know that a paralyzed limb can inflame and suppurate. 3d. Erection and the ejection of semen take place in paralysis of the lower half of the body, in which at least the nerves of the prostate gland are completely paralyzed. Mr. Ivan related to me the case of a soldier who took gonorrhoea in this state. 4th. We know that when the bladder is perfectly paralyzed and its nerves have no longer any action, its mucous glands still continue to secrete their fluid so as even to produce a catarrh. 5th. The nostril of the affected side in hemiplegia is as moist as usual. The ear of this side has its ordinary quantity of wax. 6th. In paralysis of the uvula, the action of its glands continues. 7th. When the eighth pair of one side of a dog is cut, the bronchia is found some days after to contain as much mucus as common. 8th. During the convulsions of the different parts in which there are glands, and when consequently the nerves of these glands are more excited, their secretion is not increased. 9th. If we weigh the proofs given by Bordeu of the influence of the nerves on secretions, we shall see, that they either rest upon false facts, like those of the section of the nerve, of sleep, &c. or upon vague data. In general physicians attach no precise idea to the term nervous influence; the habit of experimenting shows how much they have abused it. When a nerve being cut, paralyzed or irritated in any manner, the organ which receives it undergoes no derangement in its functions, we certainly are unable to appreciate the nervous influence upon this organ. I do not say that it does not exist, but I maintain that we know nothing about it, and that we ought not to employ at hazard a word to which we cannot attach any precise idea. What word will you employ then to express the influence of the nerves upon the organs of the senses, upon the voluntary muscles, &c. if the same one is used to express an action which has no relation with this, and which perhaps even does not exist?
Exhalants and Absorbents.
This kind of vessels is but little known in the interior of the glands, where they perform only the purposes of nutrition.
ARTICLE THIRD.
PROPERTIES OF THE GLANDULAR SYSTEM.
I. Properties of Texture.
These properties are in general very inconsiderable in this system, which appears to me to be particularly owing to its non-fibrous texture. In fact, in order to be elongated and afterwards contracted and preserve their integrity, it is necessary that the particles of an organ should possess a certain degree of adhesion and cohesion; now, it is to the fibre that especially belongs this double attribute. Observe also that the glandular system is subjected to much less frequent causes of distension and contraction, than the systems with distinct fibres. It is scarcely ever found distended except when purulent deposits, serous, steatomatous collections, &c. are formed in its interior, as often happens in the middle of the liver, kidney, &c.; now in these cases it does not yield like the skin, the muscles, &c.; its particles are separated; it is the cellular texture with which they are surrounded that is uniformly dilated; the glandular texture is even soon destroyed. It is very evident when the collections are formed near the convexity of the glands; if the tumour be at all large the texture of the organ disappears; there remains only a cellular and membranous cyst. Hydatids so frequent on the exterior of the kidneys present us with examples of it. If it is in the middle of the gland that the cyst is formed, the destruction also takes place, but it is much less evident.
A strong proof of the small degree of extensibility of the glands, is what takes place in the liver in dead bodies. I have said above that it is more or less loaded with blood, according as the system with black blood had been more or less embarrassed in the last moments. Now whatever may be the quantity of blood it contains, its size remains nearly the same; only its texture is more or less compressed by the vessels, whilst on the contrary the greater or less size of the lungs, which is very apparent, always indicates its state of fulness or vacuity. It is probable even that it is this difference which has made all physicians neglect the infinitely various states of engorgement in which the liver may be found at death, whilst they have had a particular regard to the varieties of the lungs.
The veins of the kidneys, further from the heart, are less exposed than those of the liver to the reflux that takes place in the last moments in which the black blood is obstructed in the lungs. Yet it however takes place, and we see very great varieties in the quantity of blood in the great renal vessels, a quantity independent of that which is constantly found in the organ, and which, as I have said, is very considerable. Now the size of the kidney hardly corresponds to these varieties, because its extensibility is almost nothing.
As to the glands situated at the two extremities, as on the one hand the testicles, and on the other the salivary glands, we hardly observe in them the sanguineous stagnation, because the reflux is not sufficiently evident. We cannot then, in this way, judge but by analogy of their extensibility and contractility.
Yet the engorgements of the testicles, consequent upon gonorrhoea, and the various swellings of the parotid glands prove that these properties exist to a certain extent. Are the liver, the kidneys and other internal glands subject to those acute swellings that are often seen in the sub-cutaneous ones? It is very probable; perhaps even physicians have not paid sufficient regard to the accessory symptoms which may arise for a moment from the pressure of these swelled organs on the neighbouring parts. Besides, this swelling and the contraction that follows it, may take place especially in the cellular texture of the gland, and consequently suppose less extensibility of the glandular texture than they at first seem to.
II. Vital Properties. Properties of Animal Life.
The animal contractility is evidently nothing in the glandular texture. Does the sensibility of the same kind exist in it? The following facts are connected with this. 1st. A compression of the parotid is to a certain degree painful. I have even been obliged, in a particular case, to give up the method of compression that Desault had advised for a salivary fistula, on account of the pain the patient experienced; but the numerous nerves which traverse this gland may be the cause of these pains. 2d. We know that the instant the lithotome cuts the prostate, or the stone and forceps pass over it, the patient suffers very much. 3d. Stones lodged in the kidneys occasion horrible pains. 4th. Any considerable pressure of the testicle is very painful.
On the other hand we can cut the texture of the liver and the animal will give no signs of pain. Haller, after many experiments, ranked the glands among the insensible parts. What is to be concluded from this? That the animal sensibility, modified in a thousand ways, appears to exist in many organs in which certain agents cannot put it in action, and in which others develop it remarkably. We know that the various morbid alterations render it very evident in the glands. The inflammatory pain of these organs has even a peculiar character; it is obtuse and dull in the greatest number of cases. There is never experienced in them the acute sensation which characterises cellular inflammation, or the sharp and biting pain of which the skin is so often the seat.
Properties of Organic Life.
Of the properties of organic life, the sensible contractility is wanting in the glandular system. But the two other properties are developed in it to the highest degree. They are in constant activity; secretion, excretion and nutrition keep them in incessant action there. It is by its organic sensibility that the gland distinguishes, in the mass of blood, the materials which are proper for its secretion. It is by its insensible contractility, or its tonic forces, that it contracts to throw out those which are foreign to this secretion. The first is on a small scale in each gland, what the animal sensibility of the tongue and the nostrils is on a large one, which allows only aliments suitable for the stomach to be introduced into its cavity; the other does insensibly, what is effected in so evident a manner by the glottis, when it rises up convulsively against a foreign body that attempts to enter it. The blood contains the materials of all the secretions, of the nutrition of all the organs, and of all the exhalations. Each gland draws from this common reservoir what is necessary to its secretion, as each organ does what is proper for its nutrition, and as each serous surface does what is suitable for its exhalation. Now it is by its organic sensibility that each living part of the body distinguishes what its functions require.
When the fluids enter the small vessels of the gland, this sensibility is the sentinel that gives notice of it, and the insensible contractility is the agent which opens or closes the gates of the organ, according to the principles that are presented. This comparison, if I may be allowed the use of it, gives an idea of what then takes place. Every glandular action turns then especially upon these two properties, and as this action is almost permanent, they are then constantly in exercise.
From this it is evident, that all the glandular diseases ought to suppose a derangement in these properties; for, as we have often seen, they are the predominant properties of an organ, those, the exercise of which constitutes its peculiar life, which especially determine its diseases, by their alteration. This is in fact what observation shows us. Here we see these properties increased or diminished, sometimes produce an increase of secretion, as in diabetes, mercurial salivation, immoderate flow of bile, &c.; sometimes a diminution, a suspension even of this function, as in acute diseases in which all the ducts are closed as it were in a moment, as in the suppression of urine, dryness of the mouth, &c. It is the alteration in the nature of the glandular sensibility that puts it in relation with fluids foreign to the glands in a natural state; hence the innumerable varieties of the secreted fluids especially in diseases. I have spoken of these varieties as it regards the mucous fluids. The liver and the kidneys particularly do not experience less numerous ones. The taste, the colour, the consistence and odour of cystic bile appear in a thousand different states in dead bodies. Who is ignorant of the innumerable alterations of which the urine is susceptible? The saliva is less variable; but in diseases how different is it from its natural state. It is sufficient to have noticed for some time the various evacuations in diseases, to see of how many modifications they are capable. Nothing less resembles the urine and bile, than the fluids sometimes thrown out by the bladder and the liver; whence do these varieties arise? From this, that the variable organic sensibility places the organ in relation with substances to which it was foreign in a natural state; and from this, that the insensible contractility allows substances to enter the organ which it before excluded. The same gland without changing its texture, by a modification only of its vital forces, can then be a source of an infinite variety of different fluids; I believe even that the kidney, by taking a sensibility analogous to that of the liver, may secrete bile. Why may it not secrete it, if it can secrete other fluids so different from its own?
In health, each gland has a mode of sensibility nearly uniform, a mode which changes but little; thus each secreted fluid has an appearance, a consistence and a nature always nearly the same. But in diseases, a thousand causes change this mode at every instant. An hysterical paroxysm strikes the kidneys; in an instant they repulse all the principles that colour the urine, and this comes out limpid; the paroxysm passes off, the organ resumes its ordinary sensibility, and the urine returns to its usual state. The influence of the epileptic paroxysm extends to the sensibility of the salivary glands; in a moment, a thick, copious and frothy saliva, wholly different from the natural, comes from the mouth; after the paroxysm, the sympathetic storm is calmed in the gland, and the saliva returns to its ordinary state. If I may be allowed the comparison, the glands are in diseases like the atmosphere in the equinoxes. At these periods, the winds which succeed each other and incessantly change, often make rain, hail and snow succeed each other in a very short time; so the forces of the glandular life, constantly variable in diseases, make the different products of secretion vary with rapidity.
It is not only to secretion that the various alterations of the organic sensibility and the insensible contractility of the glands extend; these alterations when long continued, have an influence also upon their nutrition; they disturb the course of it; hence the changes of texture, the tumours of different kinds, the organic diseases, &c. that are so frequent in the glandular system, a system which presents the greatest field for morbid anatomy. The great number of organic diseases which it exhibits, in our dissecting rooms, compared with most of the other systems, is very striking. The glandular, the cutaneous, the mucous, the serous, the cellular systems, &c. hold the first rank in this respect. Observe also that it is in them that the organic sensibility and the insensible contractility are raised to the highest degree, because they are the only ones in which these properties are brought into action not only by nutrition, but also by various other functions that are going on in the insensible capillary system, viz. by exhalation, absorption and secretion.
Sympathies.
Few systems are more frequently the seat of sympathies than this. In examining them I shall adopt the same order as in the preceding system.
Passive Sympathies.
The glandular texture is affected with extreme ease by all the others. This constitutes its passive sympathies. They take place, 1st, in a natural state; 2d, in diseases.
I say first that there are certain cases in the natural state, in which the other organs being excited, the glandular is brought into action. This is especially remarkable in the mucous system. We have seen that almost all the excretory ducts terminate upon the mucous surfaces. Now when one of these surfaces is irritated in the neighbourhood of an excretory duct, the gland of this duct increases its action. 1st. The presence of aliments in the mouth produces an abundant flow of saliva. 2d. A sound in the bladder, irritating the ureters or their neighbourhood, increases the flow of urine. 3d. The irritation of the glans penis and the extremity of the urethra in coition, produces a kind of spasm in the testicle from which arises a copious secretion of the seminal fluid. 4th. Every irritating fluid applied either to the conjunctiva, or the pituitary membrane occasions a more or less considerable flow of tears. 5th. By making experiments upon the state of the gastric viscera during digestion and during hunger, I have observed that as long as the aliments are only in the stomach, the flow of bile is inconsiderable, but that this flow increases when they pass into the duodenum, so that much of it is then found in the intestines. During hunger, the gall-bladder is much distended; but little bile flows from it. At the end or even during digestion, it contains but half as much bile. Yet it might be emptied much more easily during abstinence, as the fluid which is then found in it is of a deep green, very bitter, very acrid and consequently very irritating. On the contrary, during or immediately after digestion, it is much milder, of a bright yellow and less irritating. There must then be another stimulus for it during digestion; this stimulus is the food that is passing by the extremity of the ductus choledochus. I have pointed out in a long note in my Treatise on the Membranes, the course of the cystic and hepatic bile.
Let us conclude from these numerous considerations, that one of the principal means which nature employs to increase the action of the glands, and to produce that of the excretory ducts is the sympathetic irritation of the extremity of these ducts or of the neighbourhood of the point of the mucous surface where they come out. It is to this also that must be referred the various catarrhs produced by an irritating body remaining upon one of these surfaces. The infant in sucking and irritating the nipple, produces a secretion of milk at the same time that he draws it out. In a morbid state the glands are also very frequently the seat of passive sympathies. It is almost always then the organic sensibility and the insensible contractility that are brought into action in them. It is rare, that the animal sensibility, excited by sympathies, occasions pains in the glands.
We have said that the varieties the glands exhibit in diseases are innumerable, either as it respects the quantity or the quality of the fluids they secrete. Now all these varieties are especially owing to sympathetic influence. Observe the salivary glands moistening the mouth or leaving it dry, filling it with a viscid or limpid fluid, frothy or thin, the mucous glands of the tongue furnishing sometimes a thick whitish substance, and sometimes a black crust. Physicians consider the state of the tongue as a constant index of that of the stomach; this is most often true. Nature has established such a sympathetic relation between these two parts, that when the mucous surface of the stomach is disordered, and is the seat of that kind of catarrh which is called derangement, fulness of the stomach, &c. that of the tongue is also affected and furnishes more mucous juices, which alter and destroy the appetite, and thus prevent the taking of aliments which the stomach could not digest, and which often even it would not bear. The tongue is then, as in a state of health, a kind of sentinel placed over the stomach, to refuse that which would injure, and to admit that which is suitable for it. This is no doubt the cause of this singular influence which the stomach exerts upon it in diseases. But let us also remark that sometimes the tongue is foul, when the stomach is in the ordinary state. This phenomenon is frequent in hospitals; it happens to me very often. And vice versa, nausea, &c. sometimes takes place without a catarrh of the tongue.
Shall I speak of the innumerable influences that the liver, the kidney and the pancreas receive? When an organ is diseased in the animal economy, these immediately perceive it; their secretion is increased, diminished or altered, and oftentimes even the sympathetic affection does not extend to these functions, but produces inflammation, suppuration, &c. We know that abscesses are formed in the liver from wounds in the head, &c. Shall I speak of the innumerable varieties of the flowing of tears in acute diseases, in inflammatory and malignant fevers, &c.? Who does not know that the eye is then more or less moist, that it is often constantly weeping? Now whence arise these varieties? from the sympathetic influence which the lachrymal gland receives. The disease itself is often foreign to it; but the unknown consensus which connects the glands with the diseased parts, makes them then enter into action. We weep from a variety of passions, from grief especially; how does this happen? Because the influence of the passion is first carried to the epigastric region, as the violent sensation experienced there, proves; and the affected organ reacts upon the lachrymal gland. We weep in the same way as we sweat from fear, or spit copiously in anger, a phenomenon which the vulgar express by these words, foaming with rage.
The testicles and the prostate are much less often sympathetically influenced in diseases than the other glands. Whilst every thing is disturbed in the glandular system, they most frequently remain calm and tranquil. Why? because they are insulated by their functions from the other glands. The salivary glands, the pancreas, the kidneys, the liver and almost all the mucous glands contribute to one common object, viz. digestion. This object is connected with the existence of most of the other organs. When these are diseased, it is not wonderful that the glands feel it. On the contrary, the testicles, destined only to the purpose of generation, entering later into action and ceasing to act sooner than the other glands, having great intermissions in their action, cannot in their affections be thus connected with the diseases of the other organs. Sometimes however they are. We know that some affections of the lungs dispose to venereal pleasures; that in a natural state, a lively excitement of certain parts of the skin, of that of the glutÆi muscles especially brings into activity the whole genital system, &c. &c.
We know the remarkable sympathy that renders the mammÆ dependant upon the womb. It is well known, that they swell a little every month, at the beginning of menstruation; that cancers are often formed in them at the cessation of this natural discharge; that the voluptuous sensation of coition sometimes extends even to them, &c. All physicians have observed this sympathetic relation which appears to be of a peculiar kind and to depend upon the analogy of the functions of the sympathizing organs.
After severe acute diseases, especially idiopathic fevers, the glandular action is oftentimes much increased; there are great evacuations; these are the crises; it is, according to the opinions of most, the morbific humour that is expelled. This is a phenomenon that should be examined, and which certainly in many cases does not depend, as I shall prove, on the cause to which it has been attributed.
Though I consider many of the secretory derangements in diseases as sympathetic, I am far from thinking that all are so. Certainly in many cases, there is a general affection of the whole system, an affection in which the glands, like all the other parts, participate; this is what takes place in idiopathic fevers. But when one system is especially affected, as the cutaneous in the small pox, the measles, scarlatina, &c. the serous in pleurisy, peritonitis, &c. the cellular in phlegmon, the nervous in convulsions, &c. I call the derangement which the others experience sympathetic, and which does not depend upon an injury of their texture.
Other ideas may be attached to the word sympathies, but these are what I have connected with it in diseases. The word is of but little consequence, provided what it expresses is understood.
Active Sympathies.
These sympathies are less frequent than the preceding. In the diseases of the glandular system, we see however examples of them. The history of inflammations of the kidneys, the salivary glands, the liver, &c. shows us many phenomena arising sympathetically in the other systems on account of the diseases of this. I do not speak of the derangement of digestion and the circulation, functions which, naturally connected with the secretions, are inevitably deranged when these are; I speak of the organs, which having no direct relation with the diseased glands, are yet affected, as we see in convulsions, spasms, wandering or fixed pains in different places, sweats, &c.
The testicles in health exert a remarkable influence upon the organs of the voice. We know that it becomes more harsh the moment they enter into action, and that it changes when they are removed by castration; this phenomenon is constant and invariable. Barthez believed that it arose from the ordinary sympathetic phenomena; in fact, it appears to be but a particular modification of that general influence which the testicles exert on all the vital forces, which are uniformly debilitated or strengthened, according as their action is feeble or strong. Yet some organs are more disposed than others to feel these affections. The pectoral mucous system is an example of this. Passive hemorrhage of this system is frequently the consequence of excessive excretion of semen; phthisis even is often the fatal effect of it.
Characters of the Vital Properties. First Character. Life peculiar to each Gland.
The glandular life, the result of the preceding forces considered in exercise, is not uniform in the whole system, no doubt because its texture differs in each gland, and because to each texture is given a peculiar modification of vitality. Many phenomena result from these differences which have been well observed by Bordeu.
1st. Each gland has certain substances with which it is exclusively in relation in the natural state. Hence why the salivary glands do not secrete bile, and the liver allows the materials of urine to pass in its vessels without separating them; from this results the diversity of secretions. Hence also why cantharides affect exclusively the kidneys; why mercury acts especially upon the salivary glands; why certain substances affect the testicles in a peculiar manner, increase their secretion and even promote the excretion of the semen; why some aliments give more milk than others. I am persuaded that certain substances act upon the mucous glands and dispose them to a greater secretion.
2d. Each gland has its peculiar mode of sympathies. We have seen that the testicles sympathize especially with the pectoral organs, and the liver with the brain. The kidneys, when affected with acute pain, have an influence peculiarly on the stomach, and occasion vomiting. The mammÆ and the womb are directly and particularly connected in sympathies.
3d. The inflammation of each gland has a particular character. That of the kidneys does not resemble that of the liver, the testicles, &c. The prostate gland when inflamed produces symptoms wholly different from those of the testicles, &c. I do not speak of the differences resulting from the diversity of the fluids, but only of those which arise from the difference of texture.
4th. Each gland has its peculiar diseases, or such at least to which it is disposed more than the others. Hydatids are very often found near the convexity of the liver; they are never seen in the salivary glands or the testicles. Though the parotid glands are as much exposed to the action of external bodies as the testicles, there are twenty sarcoceles to one scirrhus of these glands. The liver alone exhibits that peculiar state that is called fatty; no gland is more frequently the seat of steatomatous tumours. Physicians who have opened but few bodies, employ the vague and insignificant word obstruction, &c. for every kind of glandular swelling. But observe that most commonly these swellings have nothing in common among them but the increase in size; their nature is wholly different, and yet observe how ignorant many are in medicine; they perceive by the touch that there is a hardness of the liver, and immediately aperients, the acetate of potash, &c. are the common means which they oppose to hydatids, to steatomatous tumours, to scirrhi with granulations like marble, to fatty livers and to a hundred different alterations from which the increase of size may arise, as if it was this increase and not the kind of tumour that produced it, which they had to combat. Give then also aperients when the liver displaced by hydrothorax projects unnaturally, and you will act almost as rationally.
5th. Each gland exhibits peculiar modifications in those evacuations that are called critical, of which it is sometimes the seat after long diseases, &c. &c.
6th. It is also to the difference of vitality of the different parts of the glandular system, that must be referred the following phenomenon; certain glands enter suddenly into action, either from a direct irritation, or a sympathetic excitement, as the lachrymal for example, which from a state of remission passes suddenly from the influence of the passions, to that of copious secretion. On the contrary, it requires some time to excite the other glands, as for example the kidneys, pancreas, &c. which cannot suddenly pour out their fluids, whatever may be the excitement they experience. The same stimulus applied to the conjunctiva, produces a flow of tears, and at the same time increases the action of the Meibomian glands; but the first effect takes place before the other. The same stimuli applied to the mucous surfaces can never produce a catarrhal discharge till the expiration of some time.
Second Character. Remission of the Glandular Life.
The second character of the glandular life, is that of being subject to habitual alternations of increase and diminution. Sleep extends especially to the animal functions; they alone are completely suspended in the ordinary state, and it is this which constitutes sleep. But the glands sleep also to a certain extent, though there is never a complete suspension except in diseases. I would compare the sleep of animal life to the intermissions of intermittent fevers in which the apyrexia is complete, and the sleep of the glands to those of remitting fevers in which the paroxysm is only moderated, though it always continues.
The saliva is copiously poured out when aliments enter the mouth, at other times it only moistens this cavity. Whilst the chyme is passing through the duodenum, the pancreas and liver moisten it abundantly; they are also in action during hunger, but in an infinitely less degree. I have convinced myself of this by many experiments upon the comparative state of digestion and hunger; the substance of these experiments I have given elsewhere. We know that it is some time after eating before the kidneys commence their action. The intermissions of the action of the mammÆ are almost as real as those of the organs of animal life. Each mucous gland has its time of secretion; it is that in which the surfaces, to which the excretories go, are in contact with any substance that is remaining there, or that is only passing.
The glands then must be considered as continually separating a fluid from the blood, and as being at certain periods in greater activity, and consequently as furnishing more fluids.
This remission of the glands appears to be owing to a cause nearly analogous to that of sleep, which, in animal life, is produced by the weariness the sensitive and locomotive organs experience, after long continued action. The kind of weariness which the glands are capable of experiencing, is not in general attended with a painful sensation, as in animal life; its nature appears to be wholly different. Yet women, after nursing too long, feel a pain in the breast that warns them to leave off. The testicles become the seat of a painful sensation, when the emission of semen has been many times forced.
Third Character. The Glandular Life is never simultaneously raised in the whole system.
The vital properties of the glands are never simultaneously excited in all. When one is in action, the others are in remission. We might say, that there is but a determinate quantity of life for all, and that one cannot live more without the others living less. To this law is the digestive order accommodated. In the first period the salivary glands furnish at first a great quantity of fluid; in the second, the parietes of the stomach; in the third, in which the chyme passes into the small intestines, the liver and the pancreas are principally in action; in the fourth, it is the mucous glands of the great intestines which especially act; and finally the kidneys enter into a particular action in order to evacuate the residue of the fluids. All the glands cannot act at the same time; it is as in the external motions in which certain muscles always rest whilst the others contract. The most improper time for coition is that of digestion, because we then make the mucous, hepatic, pancreatic secretions, &c. coincide with that of the testicles. In diseases one gland increases its secretion only at the expense of the others. Observation proves this every day.
We might, as I have said, make use of this remark, by producing in various glandular and other affections, artificial catarrhs, a disease which we can always produce on the mucous surfaces by the introduction of a foreign body. I have for some time past made much use of ammonia respired by the nose. Pinel prescribes it before the paroxysms of epilepsy. There are an infinite number of other cases in which it is very efficacious, as in some kinds of cephalalgia, in ataxic fevers, in certain apoplexies, in various comatose affections, &c. A blister does not act till the expiration of some time; it requires four, five, six hours even for it to produce an irritation. Who does not know that oftentimes in diseases in which the forces are much prostrated, it has no action on the cutaneous system? On the contrary, the excitement of the pituitary membrane by ammonia is always sudden on the one hand and always efficacious on the other. Its effect, it is true, is only instantaneous, but this is precisely its advantage; for in many cases a blister is only useful the moment it irritates the skin; hence the use of drying it immediately and reapplying it. The employment of ammonia or of any other strong stimulant upon the pituitary membrane, can be repeated every quarter of an hour, every five or six minutes or even every minute. If habit renders the patient less sensible to its excitement, we can replace it by another irritating substance, whereas we cannot thus change the cutaneous excitement by a blister. What I have said of the pituitary surface is applicable to those of the rectum, the urethra and stomach, on which we can in many cases apply in diseases excitements in a more advantageous manner than is done upon the skin by means of blisters.
Moreover, the character of the glandular life of which we are treating, is only an insulated modification of a character general to all the vital properties, a character which consists in this, that they are weakened in one place when they are raised in another. Hence why the great collections of pus, large tumours and dropsies are always attended with a weakness in the glandular action. It is upon this character that rests the use of vesicatories, setons, moxa, cauteries, &c. which do not act, as has been said, by evacuating the morbific matter, but by making the irritation of the diseased part cease by that which is produced elsewhere.
Fourth Character. Influence of climate and season on Glandular Life.
Another phenomenon is also derived from the preceding character, and it is one that may be likewise considered as characteristic of the glandular system; viz. that in general it is in greater activity in winter than summer, in cold climates than in warm. In fact, heat which expands the cutaneous system increases the action of it at the expense of that of the glands, and reciprocally cold which contracts it, by preventing the constant exhalation that is going on there, forces the glandular system to supply this action. Hence why the same fluid, introduced into the economy, goes out with the urine in winter and with the sweat in summer; why, if we wish to produce an immediate discharge of urine in summer, it is necessary to suppress the perspiration by the sudden application of cold to the surface of the skin, by descending into a cellar, or some other subterraneous place; so that in summer we can, after digestion, make the product of the fluids pass off with the urine or the sweat, according to the temperature of the atmosphere in which we digest; why teas and diuretics forbid the use of each other, and why a physician who should employ them at the same time would know but little of the laws of our economy; why most of the diseases that are attended with an immoderate discharge of the secreted fluids, are almost always characterized by a diminution of the exhaled fluids; why in some seasons diseases have a greater tendency to be characterized by sweats, and in others by urinary, mucous evacuations, &c. It is to the greater degree of the vital activity of the glandular system in the winter, that must then be referred the frequency of catarrhs, diseases most of which suppose an unnatural increase of its action, the greater facility with which the kidneys are influenced by cantharides, &c. Physicians should have these considerations particularly in view in their treatment. It is necessary to act more upon the glandular system in winter, and the cutaneous in summer, because each system is as much more disposed to answer to the excitements made upon it, as it actually is in greater activity.
Fifth Character. Influence of Sex upon Glandular Life.
Is the life of the glandular system more active in man than in woman? As it respects the glands destined to digestion, the secretion of the tears, the evacuation of urine, &c. there is but little difference in the two sexes. As to genital glands, man has testicles and the prostate; woman has mammÆ, so that in this respect they seem to be equal. Observe however that the influence of the first upon the economy, is much greater than that of the second. It is from the womb that go forth in woman the irradiations which correspond with those which the testicles send to all the other organs.
ARTICLE FOURTH.
DEVELOPMENT OF THE GLANDULAR SYSTEM.
I. State of this System in the Foetus.
Though the secretions are not active in the foetus, the glandular system is in general much developed. All the salivary glands and the pancreas are larger in proportion than afterwards; the liver is enormous; and the kidneys have a size much greater in proportion than they have in the adult. The same probably is true of the mucous glands, though I have not made any very precise researches upon this point. The form is different in many; the kidney for example is evidently uneven, whilst afterwards its surface is almost smooth. The colour is not the same; this is particularly striking in the salivary and lachrymal glands. These glands which are white in the adult, have in the foetus an extreme redness which they lose by washing, which is not owing to the blood circulating in their vessels, though there is much of it in their vessels, but it is really inherent in their texture. This colour is never as great in the pancreas, though its texture is nearly the same. The texture of the glands is extremely soft and delicate at this age, which is the case with all the parts. They are divided and yield with great ease, and their vessels, which are large, carry into them a very great quantity of fluid.
Then they are, if we may so say, in a state corresponding with that of remission in the adult; they secrete even less fluid, though they appear however to be in constant action. In fact, all the reservoirs would be insufficient to contain their fluids, if in a given time, as much flowed from them as after birth. Is this because the black blood, which then enters their parenchyma, is unfit to furnish the materials of the secretions? This may have an influence, and I have elsewhere imagined it, from the circumstance that this blood is unable to support many other functions. But the principal reason appears to me to be, that in the foetus the nutritive motion of composition predominates evidently over that of decomposition, which is very inconsiderable. Almost every thing which arrives in the organs remains in them and continues to furnish the materials of the rapid growth which is then taking place in the body; now, the secretions being principally destined to carry off the residue of nutrition, must then be very inactive.
Besides, digestion does not introduce into the blood any of those principles which, being useless to nutrition, must on this account go out as they entered, that is to say without making a part of our organs; such are for example most of the drinks, which only pass into the mass of blood, and go out immediately with the urine.
The glands of the foetus are then like the brain at that age; though much developed, they remain inactive; they are in the expectation of action.
II. State of the Glandular System during Growth.
At birth, the glandular system increases suddenly in energy; it takes a life which until then was foreign to it, and begins to pour out more fluid. It owes this change, 1st, to the difference of the blood which enters it, and which till then black and consequently venous, then becomes red and charged with principles that are new to it; 2d, to the general and sudden excitement carried to the extremity of all the excretories, by the aliments to those which open upon the canal that extends from the mouth to the anus, by the air to the mucous ducts of the bronchial and pituitary surfaces and to the lachrymal gland, by the various frictions of the extremity of the glans penis and even by the air which acts also upon it, to the kidneys and the bladder.
All the glands are so much the more sensible to this sudden excitement, as they are unaccustomed to it. Their sensibility, heretofore torpid, is roused; they feel the contact of the blood which enters them and which till then had made only a feeble impression upon them. This sensation is so much the more acute, as on the one hand the organic sensibility of the glands becomes more evident, and as on the other the red blood is a more powerful stimulus than the black; for, as I have already had occasion to observe, the blood that arrives in an organ produces two effects in it, one of which is to excite it, either by the motion it communicates, or by the contact of the principles it contains, and the other is to furnish materials for the different functions, as for exhalation, secretion, nutrition, &c. The first effect is common to all the organs which the blood enters; the second is peculiar to each.
I would observe however that many of the secretions are much less active during the first years, than they are afterwards; such are those of the salivary glands, the liver, &c. The kidneys being destined to throw out the residue of digestion, as much and more often than that of nutrition, are in a state of activity in proportion to that of the first function. The infant often passes urine, as he frequently voids excrements. It is not because many substances, returning from the organs which they have nourished, present themselves to the kidneys, to be thrown out by this part.
The affections of the glandular system are not the predominant ones in early age. 1st. It is not the parotids that are enlarged in the frequent swellings that take place in their neighbourhood, but it is almost always the lymphatic glands. 2d. We know that an excessive flow of bile, and the affections which arise from it, are then very rare. 3d. All the secretions relating to generation are absolutely nothing. 4th. In the same proportion in which the organic affections of the liver and the kidneys are common in the adult, are they rare in the infant. Then it is in what are improperly called lymphatic glands, in the brain, &c. that the morbid anatomist finds materials for his researches; for observe that the organs which are particularly in action in one age, are those which are most often attacked by acute and chronic diseases at that age, and that on the contrary they seem to forget those in which but little is done. 5th. Surgeons know that sarcoceles, hydroceles by effusion, varicoceles and all the diseases of the testicles are as rare before the period of puberty, when nutrition only is going on in these glands, as they are common in the subsequent years.
It appears that it is the mucous glands which are then the most commonly affected and are consequently in the greatest activity. The lachrymal glands are also very frequently in action. The infant weeps more often than the adult; we might say that all the passions which agitate this age have but one uniform mode of expression, and this mode is weeping. If the infant suffers, if he is jealous or frightened he weeps; if he is furious, he weeps because he is not very strong. This influence of the passions upon the lachrymal gland in the early years, seems to take place at the expense of the influence exerted upon the other glands. It is rare that fear or fright give to infants a sudden jaundice, or that they excite bilious secretions. At this age they do not pass water and void their excrements from fright as often as in the after ages; they have not the spasmodic vomitings that are so frequently occasioned by the passions of the adult; they do not become pale or red as much in anger; thus the countenance is not to the same extent the moveable picture upon which is painted the emotions of the mind. The eye does not sparkle in anger and is not expressive in friendship. It is the lachrymal gland which then most often serves in the face, for the expression of the passions. Observe that this expression is that of weakness and want of power, it is that of woman, who resembles the infant in so many phenomena. The feeble stag opposes his tears to the dogs, who seize upon him to devour him.
The glandular texture remains for a long time soft and delicate in the infant. At birth and in the foetus, neither the liver nor the kidneys have the singular property of hardening by boiling. They remain during this experiment very tender and yield easily to the least impression. If the boiling be ever so long continued, they do not lose this character, which is gradually weakened as we advance in age, and which at this period makes the glands fit for some uses in our kitchens to which they are not so proper in the adult.
III. State of the Glandular System after Growth.
Puberty commences about the period that growth finishes. A gland till then inactive in man, enters suddenly into activity. The prostate follows it in its development. In woman the breasts swell, separate, and acquire in a short time a size which they would not have done in many years, if they had grown according to the same laws as in the preceding state. The other glands, far from being weakened, in proportion as these become stronger, increase their action also; they become stronger, and gradually lose the softness that characterized them in infancy; they moreover grow harder.
Till then composition had predominated over decomposition in the general nutritive motion. Then almost as many substances are constantly thrown from each organ, as enter its interior to nourish it. Now as the glands are the great emunctories which throw out the residue of nutrition, they then pour out more fluids in proportion than before.
During youth it is the genital glands which predominate over the others; they seem to be a centre whence go irradiations that animate the whole machine. We might say most often that they are, in the mechanism of our moral actions, the spring which puts every thing in motion.
As we recede from youth, the influence of the genital glands becomes weaker, because they are in less activity. Towards the thirty-sixth or fortieth year, it is especially the glands destined to digestion which predominate over the others, and among these the liver in particular seems to be in activity. Then the bilious affections are predominant; then the passions to which the bilious temperament seems to dispose us, more frequently agitate the mind. Ambition, hatred and jealousy are often the sad attendants of this age. These passions are then more durable. The levity of youth and the passions arising from the influence of the genital glands, which predominate at this age, had for a time suppressed these, or rather had prevented them from being developed. Then they remain alone, the others having escaped in smoke with the fire of youth. Then also the influence of the lively emotions of the mind affects especially the glands and the abdominal viscera. Then is felt that contraction at the epigastric region, the painful effect of the bad passions; jaundice occasioned by sorrow is then more frequent.
This age is that of the organic affections of the glands, of all the numerous changes of texture, of all the excrescences which destroying as it were the nature of these organs, transform them into bodies of a different texture. In infancy, leucophlegmasia is most often produced by an engorgement of those lymphatic bunches that are called glands, which resembles tabes mesenterica, the engorgement of the bronchial glands, &c. In the adult on the contrary, it is with the diseases of the liver, of the spleen, of the kidneys, that it is most often seen.
IV. State of the Glandular System in Old Age.
In old age, the glands become more firm and hard. Before that period even, the glandular system of animals ceases to be used at our tables. The liver, the kidneys, the spleen, &c. are mixed with the fleshy texture in common boiled meat, only to communicate to it some salts, some savoury principles that are foreign to this texture. They are not eaten, or at least they are not agreeable to the taste. The lungs which contain so great a quantity of mucous glands, do not afford a very digestible aliment except those of the calf; those of the ox are not brought to our tables, especially when the animal is old. I would observe upon this subject that the muscular and glandular systems are in an inverse order as it respects digestion, at least in the stewed state to which they are reduced for nourishment. In fact, the glandular system has not an agreeable taste and is not very digestible except in young animals, whilst at this age the muscular is insipid, and does not become savoury food till towards the middle of life.
In extreme old age, the colour of the glands changes less than that of most of the other organs. We find the liver, the kidneys, &c. almost as full of blood as in the adult; they are as red, whilst the muscles pale and colourless announce by their appearance that but little blood enters them at the latter periods of life. We might say that this fluid first abandons the skin and the muscles of animal life which in the trunk are subjacent to it, and which in the extremities are found very distant from the heart, or at least that it diminishes much in the two systems, and is concentrated in the organs in the neighbourhood of the heart; thus the secretions are still very abundant in old people, whilst the muscular, nervous forces, &c. are considerably weakened. The kidneys still secrete much urine; the liver pours out much bile, though this gland loses in part the kind of predominance it exercised in the economy towards the fortieth year. We know that the very frequent catarrhs that then take place, indicate an increase of action in the mucous glands. The functions of the testicles and mammÆ have long since ceased.
The activity of the glands remaining in exercise, appears to be owing to two causes. 1st. The decomposition being very great at this age, many substances are presented to the glands to be thrown out. An old person decreases by a phenomenon opposite to the rapid growth of the foetus, in which the glandular system throws out scarcely any thing from the economy. 2d. The skin having the horny hardness and being contracted, ceasing in part to be an emunctory of the products of decomposition, the glands supply the place of these functions. The cutaneous and glandular systems are then in the same relation as in winter and in cold countries, in which, we have seen, that the second constantly supplies the place of the first.
In general, the glandular system is one of those in which life is the most slowly extinguished. In the dead bodies of old people we find the bile still filling the gall-bladder, the bladder full of urine, &c. All the glands when compressed, the prostate itself, permit a large quantity of fluid to escape from their excretories. I have even observed that in this compression, we uniformly press out more fluid in an old subject than in a young one. The older the animals are, the more their kidneys, as we know, preserve the urinous smell. The lungs, which abound so much in mucous surfaces and consequently in mucous glands, are not withered and have not the horny hardening in old age; they perform their functions as regularly as in youth.
In general it is a very remarkable phenomenon that all the principal internal organs, the liver, the kidneys, the spleen, the heart, the lungs, &c. still preserve a very considerable vital force, whilst the sensitive and locomotive organs already almost exhausted, have broken in part the communications which connect the individual with the objects which surround him.
