92 PERISTALTIC ACTION. 



fauces. After section of the vagus, near its origin (vago- 

 accessorius), the muscles of the pharynx, as well as those 

 of the larynx and the cesophagus, are inactive, and the 

 reflex act of deglutition is prevented. The effect of 

 removal of the accessorius roots is scarcely different. 

 After section of both vagi in the neck, the first part of the 

 process is possible, but it cannot be completed. Food 

 collects in the relaxed cesophagus, being prevented from 

 entering the stomach by the permanently closed cardia ; 

 the glottis being inactive, portions of food are apt to enter 

 the trachea. The peristaltic action of the cesophagus 

 differs from that of the intestine in being much more 

 dependent on the intra-cranial centre which governs it. 



Regidation of the peristaltic action of the Stomach and 

 Intestine. Throughout the alimentary canal the motions 

 of its contents are produced by temporary constrictions of 

 its wall, which progress in the direction of its length. In 

 the intestine all that is observed is that the constriction 

 follows the mass in its progress and that, as a rule, every 

 peristaltic act begins at the pylorus and advances onwards. 

 In the stomach, the action is similar, but in consequence 

 of the form of the cavity, the effect is different ; for the 

 contents, instead of advancing, circulate along the smaller 

 curvature from pylorus to cardia, and along the larger, in 

 the opposite direction. In the inactive state, the stomach 

 is contracted and the pylorus closed, whereas the intestine 

 is (apparently) relaxed. When food is introduced into 

 the stomach its wall begins to relax and contract alter- 

 nately, each change beginning at the cardia. These 

 movements, at first feeble, become more and more 

 active towards the close of the process of gastric diges- 

 tion, the pylorus opening more and more at each relaxa- 

 tion, so as to allow of the gradual escape of chyme into 

 the duodenum. 



The motions of the stomach are in large measure influ- 

 enced by the vagus, for after section of both vagi the 



