The stomach is lined with mucous membrane, filled with countless glands and ducts. These microspic organs both secrete and absorb fluids. The gastric glands secrete the gastric juice. Like the salivary glands, these are excited to activity by the presence of food, in this case, in the stomach. The gastric juice contains the ferments, pepsin and rennin, and free hydrochloric acid. The rennin curdles milk and the pepsin acts upon proteid matters and, in conjunction with hydrochloric acid, dissolves and converts them into albumose and finally into peptone. Peptone, compared with albumen in its first estate, is very diffusible and passes at once into the blood vessels of the stomach.

Results Of Gastric Digestion

The results of gastric digestion may be summed up as follows: Proteids are changed into albumose, then into peptone. Fats are liberated by solution of the cell walls. Starch is not affected. Sugar is partly changed into dextrose and partly into lactic acid. During the process all soluble matter - i.e., water, soluble salts, and peptones - are being absorbed by the walls of the stomach, and the rest of the proteids, together with the fats and starches and the greater bulk of the sugars, pass into the upper bowel, or small intestine.

Besides the pancreatic juice, before referred to, bile from the liver and the intestinal juice itself are active in carrying on the digestive process in the small intestine: absorption takes place chiefly here. This is made possible by the finger-like projections, called villi, into which the inner surface of the intestine is thrown. These projections dip into the fluid mass of food, absorbing digestible materials, peptones, fats, etc., which are carried, thus, into the blood and lymphatic vessels.