I3 2 HUMAN PHYSIOLOGY 



putrefactive micro-organisms, introduced into the stomach 

 with the food, are killed and rendered harmless by the 

 gastric juice. This action is especially due to the free 

 hydrochloric acid, but also to its acid compounds with 

 proteoses. 



Nutrition can go on normally after extirpation of the 

 stomach if small quantities of sterilized food are given at 

 frequent intervals. This has been proven in dogs and man. 



Hence it has been concluded that the chief functions of 

 the stomach are, first, to disinfect the food and, second, to 

 serve as a reservoir for large quantities of food, which is 

 given out, by the stomach to the intestine in such quantities 

 as can be quickly digested. The digestive function of the 

 stomach is, therefore, a secondary affair, seeing that the 

 pancreatic juice alone is sufficient for the digestion of pro- 

 teids. 



3. INTESTINAL DIGESTION 



i. The movements of the intestine. During digestion 

 the walls of the intestine make movements, called the peri- 

 staltic movements. These consist of periodic constrictions 

 of the intestine brought about by the contraction of the cir- 

 cular muscles. This constriction begins at the pylorus and 

 is propagated to the rectum in the form of a wave. By these 

 movements the chyme is forced from the pylorus towards 

 the rectum and at the same time mixed with the digestive 

 juices of the intestine. 



Besides the peristaltic movements, the individual loops of 

 the intestine make movements to and fro, causing the food 

 to be mixed with the digestive fluids. 



The cause of the peristaltic movements lies in the intestine 

 itself, for an excised loop of the intestine moves spon- 

 taneously. If the intestine is stimulated at a certain point, 

 the contraction begins at this point and spreads itself upward 

 and downward. The contractions are perhaps called forth 

 by the nervous plexures found in the walls of the intestine. 



