432 MAMMALIA— PHYSIOLOGY 



greenish yellow In color and bitter to the taste. It is passed from 

 the bile duct to the duodenum, where it neutralizes chyme and thus 

 facilitates the action of the pancreatic juice. In higher vertebrates, 

 bile has a weak ferment that acts on fats, aiding in their emulsifica- 

 tion. It has slight amylotic and proteolytic ferments. American 

 packing houses sell gallstones from cattle to the Chinese and Japanese 

 who use them as medicine. 



The pancreas is a rather long narrow organ, pinkish-yellow in 

 color and situated at the posterior end of the stomach, extending 

 along its greater curvature. A duct traversing the gland enters the 

 duodenum via the common bile duct or quite close to it. The 

 pancreas secretes digestive enzymes and is also responsible for an 

 internal secretion which regulates the liberation of sugar from the 

 liver. (See p. 445.) 



Pancreatic juice is alkaline, its sodium carbonate neutralizing 

 the acid food from the stomach. The enzyme trypsin is at first 

 secreted in the form oi trypsinogen and converted into trypsin by the 

 action of enterokinase formed by the intestinal glands. Trypsin 

 converts proteins into amino-acids which are reconvertible into 

 proteins when needed. Amylopsin {diastase) digests carbohydrates, 

 thus continuing in an alkaline medium the action of the salivary 

 glands stopped by the acid gastric juice of the stomach. Steapsin 

 {lipase) splits fats into soaps, fatty acids and glycerine. Dissolved 

 fats are absorbed in the intestinal walls and later combined to form 

 fat in the cells. 



The human pancreas secretes about one pound of pancreatic 

 juice in twenty-four hours. In the pancreas of the cow, which 

 weighs but seventeen ounces, eleven pounds of fluid are secreted 

 per day. 



Digestive Action in the Small Intestine. — The change of starch 

 into sugar is resumed; proteins are largely dissolved by the action 

 of the bile, pancreatic juice, and the intestinal juices. Starch is 

 converted into sugar and the sugar is in part converted into lactic 

 and other acids. Fats are emulsified and to some extent saponified 

 by the steapsin of the pancreas. 



The Cecum. — x^t the point where the ileum joins the large 

 intestine there is a pouch, the cecum^ relatively small in the cat and 

 man, but large in herbivores, where cellulose is dissolved by bacterial 

 action. In man, the cecum has attached to it an attenuated vermi- 

 form appendix^ frequently the seat of inflammation. Foreign sub- 



