The flow of gastric juice is influenced by various circumstances. Cold water checks it for a time, and ice for a longer period. Anger, fatigue, and anxiety delay and even suspend the secretion. The gastric juice has no effect on the fats or the sugars of the food; its influence being mainly confined to the albuminous bodies, which it so changes that they become soluble in water. [Footnote: The question is often asked why the stomach itself is not digested by the gastric juice, since it belongs to the albuminous substances. Some have assigned as the probable reason that life protects that organ, and assert that living tissues can not be digested; but the fallacy of this has been clearly shown by experiments that have been made with living tissues in the course of scientific research. The latest opinion is that the blood which circulates so freely through the vessels of the lining of the stomach, being alkaline, protects the tissue against the acidity of the gastric juice.] The food, reduced by the action of the gastric juice to a grayish, soupy mass, called _chyme_ (kime), escapes through that jealously guarded door, the pylorus. Fig. 48. [Illustration: _A vertical Section of the Duodenum, highly magnified._ 1, _a fold-like villus;_ 2, epithelium, or cuticle;_ 3, _orifices of intestinal glands;_ 5, _orifice of duodenal glands;_ 4, 7, _more highly magnified sections of the cells of a duodenal gland._] III. INTESTINAL DIGESTION--The structure of the intestines is like that of the stomach. There is the same outer, smooth, serous membrane (peritoneum) to prevent friction, the lining of mucous membrane to secrete the digestive fluids, and the muscular coating to push the food forward. The intestines are divided into the _small_ and the _large_. The first part of the former opens out of the stomach, and is called the _du-o-de'-num_, as its length is equal to the breadth of twelve fingers. Here the chyme is acted upon by the _bile_, and the _pancreatic juice_. FIG. 49. [Illustration: _The Mucous Membrane of the Ilium, highly magnified._ 1, _cellular structure of the epithelium, or outer layer;_ 2, _a vein;_ 3, _fibrous layer;_ 4, _villi covered with epithelium;_ 5, _a villus in section, showing its lining of epithelium, with its blood vessels and lymphatics;_ 6, _a villus partially uncovered;_ 7, _a villus stripped of its epithelium;_ 8, _lymphatics or lacteals;_ 9, _orifices of the glands opening between the villi;_ 10, 11, 12, _glands;_ 13, _capillaries surrounding the orifices of the gland._]