208 STOMACH DIGESTION. 



" 5. The food in the fundus is not moved by peristalsis, and 

 consequently is not mixed with the gastric juice ; salivary diges- 

 tion can therefore be carried on in this region for a considerable 

 period without being stopped by the acid gastric juice. 



" 6. The pylorus does not open at the approach of every wave, 

 but at irregular intervals. The arrival of a hard morsel causes 

 the sphincter to open less frequently than normally, thus mate- 

 rially interfering with the passage of the already liquefied food. 



" 7. The solid food remains in the antrum to be rubbed up by 

 the constrictions until triturated, or to be softened by the gastric 

 juice, or later it may be forced into the intestine in the solid 

 state. 



" 8. The constriction-waves have, therefore, three functions : 

 The mixing, trituration, and the expulsion of the food. 



" 9. At the beginning of vomiting the gastric cavity is separated 

 into two parts by a constriction at the entrance to the antrum ; 

 the cardiac portion is relaxed, and the spasmodic contractions of 

 the abdominal muscles force the food through the opened cardia 

 into the esophagus. 



" 10. The stomach movements are inhibited whenever the cat 

 shows signs of anxiety, rage, or distress." 



Excretory Function of the Stomach. The excretion of 

 morphin and the venom of snakes by the gastric and intestinal 

 mucous membrane, when they have been subcutaneously injected 

 into the body, suggests that this power of excretion may under 

 some circumstances be an important function of the gastro-intestinal 

 tract. Experiments with cesium and strontium have demonstrated 

 that they are eliminated by the same channel. Iron may also be 

 eliminated by the action of the intestinal epithelium. 



Effect of Nervous Disturbances upon Gastric Diges- 

 tion. It is a matter of common experience that fear, worry, 

 anger, the reception of unexpected news, either joyous or sorrowful, 

 will oftentimes seriously interrupt gastric digestion. In the case 

 of St. Martin, Dr. Beaumont observed that when his temper was 

 irritated the secretion of gastric juice was greatly interfered with 

 or even suspended. Unusual fear or a condition of fever would 

 produce the same results. Cannon observed that when the cats 

 that were the subjects of his experiments were angry, or when 

 their breathing was stopped by preventing the entrance of air 

 into the air-passages, there was a total suspension of the motor 

 activities of the stomach together with a relaxation of the antral 

 fibers. 



Self-digestion of the Stomach. One of the interesting 

 and still unexplained physiologic enigmas is : Why does not the 

 stomach, which is proteid in its nature, undergo self-digestion 

 during life? It is known that when death takes place during the 

 period of active stomach digestion, erosion of the mucous membrane, 

 and even perforation of the wall of the stomach, may occur. As 



