74 NUTRITIONAL PHYSIOLOGY 



tarily relaxes, under influences to be discussed presently, 

 the peristalsis of the antrum naturally drives more or less 

 of its contents into the duodenum. 



Nervous Control of the Gastric Movements. Muscular 

 elements of the order found in the stomach have been 

 said to have an automatic property. We have insisted, 

 however, that this fact does not exclude the influence of the 

 central nervous system. There is abundant evidence so 

 far as the stomach is concerned that the musculature of 

 the organ is played upon by efferent impulses. If it is 

 separated from the central nervous system many of its 

 reactions take place in a nearly normal manner, but we 

 cannot assume that its adjustments are as well timed and 

 decisive as they were before. Laboratory trials show that 

 the impulses which are sent to the stomach may either 

 accentuate or abate its spontaneous movements. In 

 other words, they may either excite or inhibit the contrac- 

 tile elements. 



Of the two types of nervous control, the inhibitory 

 seems to be of particular significance. Complete arrest of 

 the peristalsis of the antrum may be brought about. This 

 happens in the cat when the animal is enraged or terrified, 

 and, indeed, when it seems merely to be restless. Cannon 

 has again and again seen the peristaltic notches fading 

 away from the x-ray profile of the antrum when the animal 

 has wearied of being kept under restraint, and is manifest- 

 ing its feeling by switching its tail and struggling. He has 

 seen the regular activity resumed when the cat has been 

 pacified. Similar facts have been demonstrated for the 

 rabbit. Since we generally believe that the higher the 

 grade of an animal's development, the more extensive the 

 command of the nervous system over its organs, we have 

 every reason to think that unpleasant emotions may be 

 accompanied in man also by inhibition of the gastric move- 

 ments. We shall have occasion to enlarge upon this matter 

 in connection with the Hygiene of Nutrition. 



The Pyloric Sphincter. The regulation of the escape 

 of the stomach-contents to the intestine has long been a 



