GASTRIC GLANDS 95 



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 pre- 

 vents the entrance into the antrum 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 emptied. 



It is not to be supposed that food has been accumulating 

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

 tractions 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 pultace- 

 ous parts of its contents are sent with some force into 

 the duodenum. Those which are not sufficiently dissolved 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 prob- 

 ably 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 emptied 

 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 contrac- 

 tion and relaxation of plain muscle is much slower than that of 

 striped. 



