It was further found that in a normal stomach a meal of rice and potatoes gets out of the stomach rapidly, no trace being left in three hours, while a meal of protein and fat meat was much slower, some being present six hours after the meal. Indigestible substances are rejected by the sphincter and returned to the digestive cavity over and over again, but in the course of time the sphincter relaxes and the peristaltic contractions increase, until the force is sufficient to drive through the opening hard substances like peas, plum-stones, and coins. _The Absorption of Food from the Stomach._—A very wide-spread misconception prevails in regard to the amount of absorption that takes place through the gastric walls. This is very limited indeed; some sugar, alcohol and other fluids, and a small proportion of nitrogenous matter are taken up, but that is all. The legitimate rôle of the stomach is a peptonizer and grinder only. Absorption of nutrients is the special work of the intestines, and occupies but a subordinate place in the duties of the stomach. Proteins undergo peptonization, but that does not change them sufficiently. The mere splitting into peptones, formerly thought sufficient, is now known to be quite inadequate. Recent researches have shown that the complex protein molecule has to be quite crushed into a heterogeneous assemblage of fragments, from which those suitable for building up into the body protein are selected for that purpose, the remainder being used as fuel; that is, as a source of energy. In the case of the other food principles, fats and starches, the chemical processes are much simpler. =Intestinal Digestion.=—The chemical changes which food undergoes in the small and large intestines are exceedingly complex. Digestion in the intestine is due to the combined action of the bile, pancreatic juice, and succus entericus. The material which enters the duodenum from the stomach is known as the chyme. The acid chyme provokes a flow of bile and pancreatic juice. It acts upon the _prosecretin_ in the duodenal mucous membrane in such a manner that _secretin_, a hormone, is formed and carried by the blood to the cells of the pancreas which it stimulates. _Bile_ is a secretion of the cells of the liver and from the inner wall of the gall-bladder; after elaboration, bile is stored up in part at least in the gall-bladder. The secretion of bile is irregular in quantity, as is the case with the gastric juice, and appears to be induced by chemical excitants, of which acids, especially hydrochloric, seems to be especially effective. Of the nutrients, the proteins exert the most influence. Less secretion follows the ingestion of carbohydrates than of proteins. Formerly it was supposed that fatty foods checked the secretion of bile, but later experiments have proved that, to the contrary, they increase its secretion; and olive oil is a powerful cholagogue.