General Anatomy, Applied to Physiology and Medicine, Vol. 3 (of 3)

by Xavier Bichat

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.