7O APPLIED PHYSIOLOGY 



present in the food. The gastric juice is more often deficient in acid 

 than in pepsin. 



Besides assisting the pepsin the acid alone can perform the first 

 stages of changing albumin to peptone. Living germs of fermentation 

 and disease are sometimes swallowed. The acid destroys them if it is 

 present in the gastric juice in its full amount. This is a provision of 

 nature to prevent fermentation from taking place in the stomach, which 

 might otherwise become sour at every meal. This explains why 

 diseases are more easily caught when the stomach is deranged. In 

 a healthy person the germs meet the destroying acid almost at the 

 entrance to the body. 



92. Amount of stomach digestion. The stomach digests 

 only albumin. The main uses of the stomach are, to act 

 as a storehouse for food, to mix it with the watery gastric 

 juice, and to reduce it to a form still more liquid than 

 when it left the mouth. The acid prevents the food from 

 spoiling, and, with the pepsin, begins the digestion of the 

 albumin. The stomach is not absolutely necessary for 

 digestion, but because of its capacity it enables us to carry 

 a store of food so that we do not need to eat every few 

 minutes. 



93. Passage of food into the intestine. Every minute 

 or two the pylorus opens, permitting a little of the chyme 

 to escape into the intestine, where the main work of diges- 

 tion is performed. 



Some food begins to pass out of the stomach within a 

 few moments after eating. The time required for the 

 stomach to empty itself completely is from two to five 

 hours, depending upon the amount of food and the ease 

 with which it is broken up. Thus we commonly say that 

 it takes from two to five hours for food to digest. 



When the stomach has been empty for some time, there 

 is a sense of hunger. Yet the intestine may still contain 

 enough undigested food to supply the body for hours. 



