THE LYMPHATIC VESSELS AND GLANDS Lacteal has been pointed out on pages 204 and 205 that the blood is regularly receiving fresh supplies of material to maintain its bulk and quality from food that has been taken into the alimentary canal. It has been seen that the nourishing portions of the food gain access to the current of blood by two channels, that watery parts of the food, containing sugar, salts, &c., dissolved in them, can pass directly through the walls of the blood-vessels of the mucous membrane of the intestine, and gain entrance to the blood, but that fatty matters cannot so pass. In the small intestine, how ever, fat is acted on by bile and pancreatic juice, and, as a result of that action, the fat no longer floats in large globules among the food, but is made into a milk-like mixture, and is broken up into a great number of very minute globules. The fat, being scattered through the food in this fine state of division, gives it a milky appearance, from which it is called chyle (Greek chuThs, juice). The chyle is separated from the contents of the intestinal canal by the villi (p. 199) of the small intestine, which pro ject from the surface of the bowel to suck up the juices it may contain. The sucked-up juices pass into a vessel in the villus. The vessel has been called a lacteal, from the Latin word lac, milk, because of the milky appearance of the juice it contains. So that the lacteals are the second channel by which nourishing material passes from the intestinal canal. The process that we thus see performed by blood-vessels and lacteals, by which materials are picked up to be used in the body, is called absorption (from Latin absorbere, to suck up), and it is a process, as we shall see, not confined to the intestinal canal, but going on in every tissue and organ of the body. The vessels by which the absorption process is carried on are called absorbents. We must now follow the course of the chyle in more detail than it was con venient to do on page 204. It appears that this milky fluid which fills the lacteals is not in a proper condition to be poured at once into the current of blood. It may be it is too raw material yet, and must undergo some measure of preparation. The bowel is suspended from the back wall of the belly by means of a double fold of membrane, the mesentery (p. 190). The
lacteal vessels are continued up from the bowel between the folds of the mesentery, and pass through glands which are also contained be tween the folds. [Refer to Fig. 124, and its description.] Glands of the glands are called the lymphatic glands of the mesentery, or, shortly, the mesenteric glands. There are about one hundred and fifty of them. In a healthy state each gland should be about the size of an almond, but in certain diseases they are enlarged, and, as has already been pointed out (p. 254), they are seriously affected in consump tion of the bowels. Fig. 125 represents the structure of one of these glands. The gland has an investing coat or capsule (a a), which com pletely surrounds it. From the capsule fibrous strands (b, b) pass into the gland, dividing it off like partitions into spaces. The spaces round the circumference (or cortex) of the gland are of considerable size, and are more or less oval (d, d, d), while the spaces towards the smaller (e, c). The spaces are almost coMpletely filled with masses of material, consisting of a net-work of very delicate connective tissue, in which white cells of various sizes are entangled. This sort of tissue is called adenoid, or gland tissue, from the Greek actin, a gland. But the masses of tissue do not quite fill the spaces. Between the outer surface of the mass and the wall of the space are channels, and the channel round one mass communicates with that of another, and those round the edge communi cate with those in the centre, so that the gland might be looked upon as a mass of gland tissue broken up into numerous little clumps by a series of irregularly winding and communicat ing channels. The channels, moreover, are not perfect fairways. They are crossed and re crossed by spans of the delicate tissue of the gland, so that the whole structure becomes not unlike that of a sponge. Now the lacteal vessels join the mesenteric gland at the margin or outside (as shown at f, f, Fig. 125), and pour their fluid contents into the channels there. From them the fltiid filters its way to the channels of the centre, bathing and penetrat ing the gland tissue in its course, and finally joins vessels, identical with f, f, at the centre, by which it is carried away from the gland. The outgoing vessel is represented by g, h.