94 THE PHYSIOLOGY OF DIGESTION AND ABSORPTION 



tinal 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, inhibit- 

 ing 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 action 

 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 the 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 reduced to a pultaceous condition 

 through the pylorus into the duodenum, until finally the stomach 

 is empty. 



In considering the mechanism of these movements a division 

 of the organ into two segments, f undic and pyloric, by the sphinc- 

 ter 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 prevented by a rhythmical 

 contraction of the lower end of the esophagus, and the effect 



