Chyle

Chyle, CHYME. Food, having been partially digested and absorbed in the stomach, is then passed on into the small intestine. It is of a pulpy consistency, and is termed chyme. Both digestion and absorption continue in the small intestine (see DIGESTION). Of the digested chyme a portion finds its way directly into the blood-vessels of the intestine. Nearly all the fat, however, passes into a special system of Lymphatics (q.v.) termed lacteals. These lacteal vessels lie in the walls of the intestine, and, during the fasting condition, are filled with a watery-looking fluid called lymph, which exudes from the neighbouring blood-vessels. During absorption, however, the lacteals, in addition, become filled with the absorbed fat which is in a state of minute subdivision. This gives the chyle, as it is now termed, a milky appearance. The lacteals convey the chyle into a large vessel, the thoracic duct, which finally conducts it into the large veins at the root of the neck, where it mixes with the blood. One may observe the lacteals on opening the abdomen of an animal killed some few hours after a full meal containing fat. When filled with chyle they resemble white threads branching in the substance of the mesentery—a membrane stretching between the intestine and the back of the abdomen. Microscopically chyle consists of a fluid containing minute fat-globules and a few corpuscles, similar to white blood-corpuscles. Chyle is alkaline in reaction, and coagulates when withdrawn from the body. It may be looked upon as lymph plus the fat which has been absorbed. It contains (1) Proteids, such as serum-albumen, serum-globulin, and fibrinogen. Fibrin is formed during the process of coagulation. (2) Fats—palmitin, stearin, olein, and also cholesterol and lecithin. (3) Extractives, notably urea and grape-sugar. (4) Salts, especially sodium-chloride. See LYMPH, NUTRITION, DIGESTION.