CHAPTER VIII 

 THE PROCESS OF DIGESTION 



In order to understand how food is used in the Ixidy and 

 the part it pla3's in maintaining Ufe and producing results, 

 it is necessary to discuss briefly the simpler features of diges- 

 tion and more especially as applied to farm animals. 



The process of digestion begins with the mouth, where 

 the food is broken up and softened. The fluid called saliva 

 flows from small glands at the base of the tongue, and the 

 mixing of this with the food in the mouth is called insaliva- 

 tion. This fluid contains substances which act on the starch 

 in the food and help change it to a form of sugar, so that it 

 may be absorbed more readily. In swallowing, the food 

 passes from the mouth through the esophagus, or gullet, 

 into the stomach. The horse and hog have but one stomach, 

 but cattle, sheep, and other animals that chew the cud, have 

 four. The process of digestion, however, is similar in all 

 stomachs. The cow chews a mouthful of grass very imper- 

 fectly at first and swallows it into the paunch, which is the 

 largest of the four stomachs. From here, after more or less 

 mixing, the food is forced into a second and smaller stomach, 

 called the honeycomb. After it has been churned about and 

 softened in these two stomachs, the animal forces back into 

 the mouth as frequently as desired a small amount of food 

 called the "cud," for further chewing. The cattleman calls 

 this operation "chewing the cud." After a bit the cud is re- 

 turned, and by a special movement, passes into the many- 

 plies, or small third stomach, from which it passes on into 

 the fourth, or true, stomach. While in the true stomach the 

 food is churned about and mixed with gastric juice, which 

 contains a little acid. These juices act on the food, dissolv- 



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