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.