THE DIGESTIVE PROCESS 27 



walls of the stomach is peculiar. In the first place it 

 mixes the food thoroughly with the gastric juice, then 

 as it forces the food forward some of it is squeezed 

 through the round (sphincter) muscle at the far end of 

 the stomach into the small intestines. The coarser parts 

 are left behind till they are softened down and rendered 

 capable of being squeezed through the round muscle 

 into the intestines. Some absorption of soluble 

 material takes place in the stomach, but most of it is 

 carried on into the intestines. 



Gastric juice of carnivorae (dogs, etc.) is more acid 

 in character than that of herbivorae (horses, cows, etc.), 

 which enables the former to swallow bones without 

 harm. Professor Pawlow found that food placed 

 directly in the stomach had little effect in stimulating 

 secretion, but sight, smell, and taste stimulated the flow 

 greatly even before any food had passed into the 

 stomach. The greater eagerness the dog showed for 

 the food, or the more appetising it was to the dog, the 

 more abundant was the flow of gastric juice, and the 

 richer it was in both acid and pepsin. It was also 

 found that in character and proportion the digestive 

 juices adapt themselves to the nature of the food. 



Small Intestines. The contents of the stomach 

 arrive at the small intestines in a semi-liquid state and 

 with an acid reaction. These nutrients are in various 

 stages of digestibility. Here it is attacked by the bile 

 and pancreatic juice, which change the food from an 

 acid to an alkaline reaction. 



The " bile," in the case of herbivorae, is a clear, 

 greenish-coloured liquid which is secreted by the liver, 

 and acts on the fats partly by emulsifying them, and 

 partly by splitting them up into fatty acids and 

 glycerine. These fatty acids then combine with the 



