ALIMENTATION AND DIGESTION 111 



upon the proteins of the food and especially upon those 

 proteins (albuminoids) which make up the connective tissue 

 of animal foods. By dissolving this connective tissue, which 

 holds together the muscle fibers, fat cells, etc., animal food 

 is considerably subdivided and made to present a greatly in- 

 creased surface to the further action of digestive juices. It 

 is also well to remember that the gastric juice dissolves con- 

 nective tissue much more rapidly than does, any other of the 

 digestive juices and that this action upon connective tissue 

 is really more important than that upon other proteins, al- 

 though the latter is usually more emphasized. Other proteins 

 not acted on in the stomach are rapidly digested by the 

 pancreatic juice in the intestine; connective tissue, on the 

 contrary, escaping solution in the stomach, is dissolved but 

 .slowly in the intestine. 



The student is, however, warned against supposing that 

 because gastric juice is able to transform the proteins of the 

 food to peptids, it actually does exert this action upon all 

 the protein eaten. In point of fact, as protein foods are 

 divided into smaller and smaller particles in the stomach, 

 they are discharged into the intestine, where their digestion 

 is completed by the pancreatic juice. In man the pancreatic, 

 and not the gastric, juice is the main agent of protein digestion. 



22. The stomach at work. Having now gained a general 

 idea of the chemical changes which occur in the stomach, we 

 may proceed to consider what actually happens when food 

 enters that organ. And here our knowledge has been gained 

 partly by examining the gastric contents at different periods 

 of digestion, partly by observing the movements of the 

 stomach by the aid of the Rbntgen rays, and partly by 

 other means. 



As soon as food enters the stomach, and even while it is 

 still in the mouth, the gastric glands begin to discharge the 

 gastric juice, and continue to do so during the four or more 

 hours of gastric digestion. When the meal is fluid or is small 



