These transverse folds of the intestinal walls are called _valvulæ conniventes_. The villi are tiny finger-like projections of the mucous lining of the intestines, which stand out of the lining somewhat as the nap on plush. They have been called “sucking” villi, because during the movements of the intestines they seem to suck in the liquid food. As soon as the foodstuffs—proteins, carbohydrates, and fats—are put in an absorbable state called chyle, they are very promptly taken up by the villi. If for any reason the chyle remains unabsorbed, it is liable to be attacked by the bacteria always present in the intestines, and gases form. The peptones, sugars, and saponified fats are rapidly absorbed, while the undigested portion, together with the unabsorbed water, the bile, mucus, and bacterial products, are passed through the ileocecal valve into the large intestine. The mass passes up the ascending colon, on the right side of the abdomen, across the transverse, and down the descending colon, on the left side, losing, by absorption, the small amount of foodstuffs not absorbed in the stomach and small intestine. That the large intestine is to some extent adapted to absorption is shown by clinical experiments with patients who cannot retain food in the stomach, the food in such cases being given through rectal injections. While water and salt are absorbed in both the stomach and small intestine, the larger part of the water passes into the large intestine, that it may assist the passage of the intestinal contents. Water also stimulates peristaltic movements. As the food is absorbed through the walls of the alimentary canal, it is picked up by the rootlets of the mesenteric veins and by the lymph channels—the latter through the abdominal cavity are called lacteals. Nearly all of the fats are absorbed through the lacteals. The whitish color given to the contents of the lacteals, by the saponified fats, gives rise to the term “lacteal.” Nearly all of the proteins and sugars pass through the mesenteric veins and the portal veins to the liver. Here the sugars are at once attacked by the liver cells and built up into glycogen as described on pages 151 and 159. A small portion of the proteins, however, do not go to the liver, but are passed directly into the lymphatics and thus into the blood stream, where they are again carried to the liver, and the urea is separated. * * * * * To sum up, the larger part of the sugars, starches, proteins, and fats is absorbed through the small intestine, a small amount being absorbed in the stomach and a very little through the large intestine. While some water and salts are absorbed in the stomach and small intestine, these are largely absorbed in the large intestine. * * * * * [Sidenote: Economy in Food]