VII 



DIGESTION 



folded up to form pocket-like glands over the entire 

 surface. 



The millions of these little glands pour a fluid into 

 the stomach, called gastric juice. This fluid is very im- 

 portant to digestion, as it contains an acid and a sub- 

 stance called pepsin, that together can digest proteids. 

 It is estimated that from ten to twenty pints of gastric 

 juice are made every 

 twenty-four hours. As 

 soon as the food enters 

 the stomach the gastric 

 juice begins to ooze 

 from the mouths of 

 these little glands, and 

 the muscles commence 

 to contract lengthwise, 

 then crosswise and 

 transversely. This vig- 

 orous churning motion, 

 which is kept up for 

 several hours after each 

 full meal, so completely 

 mixes the foods and gastric juice that the entire mass 

 becomes acid and of a uniform, thick soupy consistency, 

 having a grayish color. The proteids, like beefsteak, 

 cheese, and eggs, are changed into peptones by the 

 chemical action of the acid and the pepsin. The entire 

 mass is then known as chyme. 



If we chew the foods carefully, eat slowly, and do 

 not overload the stomach, it will do its work easily and 



Fio. 47. Inside of the stomach, front 

 view. (From Heitzmann's " Anatomy." 

 Becker.) 



