60 VETERINARY STUDIES 



horse's stomach hokis about 31/2 gallons, and the cow's stomachs 

 about 45 gallons. The cow's stomach is compound with four 

 cavities. 



The first cavity, the paunch or rumen, is much the largest, and 

 acts as a sort of storage vat where a certain amount of fermenta- 

 tion occurs, probably as a process of digestion. It holds about 

 36 gallons and is partly divided into two sacs, right and left. 

 Its lining mucous membrane is more or less covered with a 

 coarse moss-like mass of papillaj. 



The second cavity, the reticulum (tripe), is smaller than the 

 first and connects freely with the rumen and with the third 

 cavity. Its mucous lining is built into a coarse, heayj^, honey- 

 comb-like structure commonly called tripe. Its function is ap- 

 parently storage, particularly of water, thereby aiding the ru- 

 men in its work of rumination by holding a needed reserve 

 supply of water. Its capacity is about 2.5 gallons. 



The third cavity, the omasum (manyplies), holds about 3 gal- 

 lons and its interior is almost filled with a mass of flat, leaf-like 

 folds of the mucous membrane. The surface of these folds is 

 covered with small, hard papillie, which are believed to complete 

 the work of the teeth by further reducing the food particles. 

 The thin cakes of food between the folds are normally rather 

 dry. 



The fourth stomach, abomasium, is the true stomach. Its lin- 

 ing is a soft, pink mucous membrane containing the gastric 

 glands, which produce the gastric juice for the work of diges- 

 tion. Anatomically, the first three cavities or stomachs are 

 really bulges in the esophagus. The abomasum receives food 

 and water from the omasum and discharges them into the first 

 section of the small intestine. Its digestive fluid (gastric juice) 

 is largely water, and contains pepsin, hydrochloric acid, and 

 rennin ferment, and aids in digestion of proteid food materials. 



Gastric juice is furnished by glands in the right side of the 

 horse's stomach, and by the cow's fourth stomach. The effect 

 of gastric juice is to make proteid matters soluble. It does this 

 by the action of its pepsin ferment, which is very active. 



Small intestine. — This begins at the stomach, the common 

 opening being guarded by the pylon^s, a strong spliincter muscle 

 like a purse string. The small intestine is divided into three 

 parts: duodenum, jejunum, and ileum. The small intestine is 

 about 72 feet long in the horse and 140 feet long in the cow, and 



