GASTRIC GLANDS 95 



esophagus, and the effect of this muscular wave (peristalsis) 

 in the fundus is to force the food toward the pylorus. But 

 when the right end is reached, the rather firm contraction of 

 the sphincter antri pylorici prevents the entrance into the an- 

 trum of all except the liquid or semi-liquid parts. The food, 

 thus denied admission to the antrum, takes a course along the 

 lesser curvature to the splenic end, then back along the 

 greater curvature, and such parts of it as have, during this 

 revolution, been sufficiently dissolved pass into the antrum. 

 These revolutions continue until the fundus has been emp- 

 tied. 



It is not to be supposed that food has been accumulating 

 meantime in the antrum. Indeed, it is certain that muscular 

 contractions are here much more active than in the fundus, 

 where the movements are slow and of a rather compressing 

 nature. It is thought that very soon after the entrance of 

 food from the fundus the entire muscular wall of the antrum 

 undergoes very strong contraction of a peristaltic nature, and 

 the pultaceous parts of its contents are sent with some force 

 into the duodenum. Those which are not sufficiently dis- 

 solved to pass the pyloric sphincter are said to excite an anti- 

 peristaltic movement, whereby they are thrown back into the 

 fundus for further digestion the sphincter antri pylorici 

 having now relaxed. However, substances which the gastric 

 juice and contractions cannot dissolve will finally pass the 

 pylorus, but they are probably delayed for a considerable 

 time. 



This succession of movements is continued with a rapidity 

 and regularity varying with the condition of the organ and 

 the nature of its contents. They last until the organ is emp- 

 tied in part by the absorption of its contents, but mainly by 

 their passage into the small intestine. Each circuit in the 

 fundus probably occupies about three minutes, and gastric 

 digestion as a whole lasts usually from two to five hours. 

 The contraction and relaxation of plain muscle is much 

 slower than that of striped. 



