A large part of the food is necessarily composed of albuminous substances. They form, as I have shown, the chief constituents of meat, cheese, milk, and eggs, and are found in many vegetable foods, such as peas, beans, lentils, and also in wheat and oats. In the condition in which albumen is introduced into the stomach it is incapable of being absorbed by the blood vessels. It must, therefore, first be brought into such a condition that it will pass easily through the coats of the veins and be introduced into the circulation. That albumen in its usual condition will not pass through an animal membrane may be proved by placing the white of an egg on a bladder tightly stretched over a vase quite full of water. The white of egg, which is pure albumen, will not pass through the bladder into the water. If, however, some pepsine and a free acid be added, and the whole allowed to stand at a temperature of about 100 deg., the albumen will undergo such changes that it will pass easily through the bladder, and will be found diffused in the water on the other side. The action of pepsine and the acids of the stomach is such that insoluble albumen is converted into soluble and diffusible albumose; and in this state it passes through the delicate walls of the blood vessels of the stomach, and is conveyed by the portal vein to the liver. Owing to the presence of hydrochloric acid in the stomach the digestion of starch is interrupted as long as the food remains in this organ, for the diastase which converts starch into sugar can only act in an alkaline medium. The digestion of cane sugar is, however, continued in the stomach, where it is converted by the action of the hydrochloric acid into glucose or grape sugar, in which state it is readily absorbed by the blood vessels.

The time occupied by gastric digestion varies from three to four hours. Some articles of food take much longer to digest than others. In arranging the diet of a dyspeptic, it is important to know which foods are most quickly and easily digested in the stomach.

The process of digestion in the stomach being completed, the albumen being turned into soluble albumose, the cane sugar into glucose, and a large part of these substances having been absorbed direct by the blood vessels which ramify on the surface of the stomach, the semi-fluid mass passes gradually, and in small quantities at a time, out of the stomach through the narrow opening of the "pylorus". The pylorus is a small circular passage or opening, which is closed by strong encircling muscular fibres during the process of gastric digestion. If the chyme, or partially digested mass, is thoroughly well mixed, and there are not any large undigested or irritating portions present, the food passes through the pylorus, without any feeling of discomfort. If, however, portions of food are undigested, the pylorus may refuse to let the chyme pass, and the muscles of the stomach, being then thrown sympathetically into a state of irritation, may contract spasmodically, and the food be ejected forcibly from the mouth by the act of vomiting. If, on the other hand, the stomach has performed its part well, the food passes into the duodenum.