94 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



nard) that the tissue is first killed by the acid, and that no 

 digestion takes place in the alkaline intestinal juice. But 

 why the stomach is not thus attacked when other living tissue 

 is remains obscure. The most plausible theory is that the 

 gastric epithelium is possessed of some power, mechanical 

 ^or physical, the nature of which is unknown, inhibiting the 

 action of the gastric juice, most probably by preventing its 

 absorption. 



"A nearer approach to an explanation seems to have been 

 attained in the discovery of an antipeptic and antitryptic ac- 

 tion of the stomach and intestinal mucosa. This action is 

 probably due to antienzymes which are found throughout 

 the whole animal scale and occur not only in the intestinal 

 tract, but also in cells of other organs. " (Tigerstadt.) 



Movements of the Stomach. Whether the exact details of 

 the muscular movements of the stomach be known or not, the 

 essential fact to be remembered is that the organ is in a more 

 or less continuous state of muscular activity for several 

 hours after the ingestion of an ordinary meal, and that this 

 activity results in the physical disintegration of most of the 

 solids introduced, in the thorough mixing of all classes of 

 foods with each other and with the gastric juice, and in the 

 passage from time to time of such parts as have been re- 

 duced to a pultaceous condition through the pylorus into the 

 duodenum, until finally the stomach is empty. 



In considering the mechanism of these movements a di- 

 vision of the organ into two segments, fundic and pyloric, by 

 the sphincter antri pylorici is to be kept in mind. When food 

 has entered the stomach the peristaltic wave of contraction 

 begins at the splenic end and passes toward the right. This 

 contraction is comparatively weak, is mainly evident along 

 the greater curvature, and increases in strength as it passes 

 toward the pylorus. Its wave-like character is due to the 

 contraction and subsequent relaxation of successive bands of 

 circular and oblique fibers. Regurgitation of food is pre- 

 vented by a rhythmical contraction of the lower end of the 



