In other words, the discovery of erepsin in the succus entericus and its effects has led to the now almost generally accepted view that the digestion of the proteins is carried further than the stage of proteoses and peptones; in fact, that this enzyme hydrolyzes them into amino-acids, in which form they are taken up by the cells of the intestinal mucous membrane. _The Absorption of Food from the Intestines._—It was formerly believed that the main stream of the nutrient passed out of the intestines through the lacteals and thoracic duct into the circulation. But it is now known that only the fats take this course, and that the dissolved proteins, carbohydrates, some fats and salts find their way into the circulation through the portal system and the liver. The blood contains a constant proportion of serum-albumin and serum-globulin, which are constructed out of the amino-acids resulting from the digestion of protein foods. The reconstruction of proteins takes place chiefly in the cells. Fuchs believes that the amino-acids from the food are carried to all the tissues; and that the cells of the muscles and glands pick out from the blood the “building stones” necessary for the construction of their special proteins. Fat is absorbed for the most part in the form of an emulsion and as a solution of soap. Only about 60 per cent. of the fat in the food is absorbed by the lacteals; the remaining 40 per cent. gets directly into the blood. The fat is carried directly by the blood-stream to the tissues all over the body; it is oxidized in the tissues to produce heat and energy; what is not immediately used for this purpose is stored up in the cells for future use. _Carbohydrates._—Practically all of the carbohydrates digested are absorbed in the form of sugar. The absorption takes place more rapidly in the upper than in the lower bowel. A portion of the ingested carbohydrates is destroyed in the alimentary canal by bacteria, whose enzymes transform them into various acids and gases.