Digestion being, broadly speaking, the conversion of non-diffusible proteids and starch into highly diffusible peptones and sugar, and the emulsifying, or division into minute particles, of various fats, it is natural to suppose that the diffusible peptones and sugars pass by osmosis into the blood-vessels, and that the emulsified fats pass into the lacteals. That the great mass of the fat which enters the body from the intestines passes through the lacteals, there can be no doubt; and there is but little doubt that a considerable quantity of peptone and sugar does pass into the portal blood. Chyle is a white milky-looking fluid, which after its escape coagulates, forming a not very firm clot. The nature of the coagulation seems to be exactly the same as that of blood. Lymph seems to be blood minus red corpuscles, and chyle is lymph plus a very large quantity of minutely divided fats. It has been calculated that a quantity equal to that of the whole blood may pass through the thoracic duct in twenty-four hours, and of this it is supposed that about half comes from food through the lacteals, the remainder from the body at large; but these calculations are based on uncertain data. Entrance of chyle into the lacteals. The lacteals begin at a club-shaped lymphatic space lying in the center of the villus, and connected with the smaller lymphatic spaces of the adenoid tissue around it; it opens below into the submucous lymphatic plexus from which the lacteals spring. The thoracic duct is the common trunk which receives the absorbents from both the lower limbs, from the abdominal viscera, from the walls of the abdomen, from the left side of the thorax, left lung, left side of the heart, and left upper limbs, and from the left side of the head and neck. It is from fifteen to eighteen inches long in the adult, and extends from the second lumbar vertebra to the root of the neck. At the last dorsal vertebra there is usually a dilation of the duct, of variable size, which is called the receptaculum chyli, and is the common place of junction of the lymphatics of the lower limbs and the trunks of the lacteal vessels. There are two sets of absorbent vessels--the lacteals, which convey the chyle from the alimentary canal to the thoracic duct; and the lymphatics, which take up the lymph from all the other parts of the body and return it into the venous system. There is a right lymphatic duct, about a quarter to a half inch in length, which receives the lymph from the absorbents of the right upper limb, the right side of the head and neck, the right side of the chest, the right lung and the right half of the heart, and the upper surface of the liver. The thoracic duct terminates on the outer side of the internal jugular vein, in the angle formed by the union of that vein with the subclavian, and the subclavian empties itself in the superior vena cava.