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.