PASSAGE OF FOOD FROM MOUTH TO STOMACH 763 



deglutition succeed one another, the cardiac sphincter shares in the 

 inhibition of the cesophageal walls, and offers no resistance to the 

 direct propulsion of food from the mouth to the stomach. 



B 



c 



FIG. 332. Curves obtained during swallowing by placing two rubber balloons, one 

 (the upper curve) in the pharynx, the other (lower curve) in the oesophagus. 



In A the second balloon was 4 cm. ; in B 12 cm. ; and in c 16 cm. from 

 the upper end of the oesophagus. In each curve it will be noticed that the 

 excursion of the upper lever is followed immediately by an excursion of the 

 lower lever (due to passage of the swallowed fluid and transmitted rise of 

 pressure), and then, after an interval of time varying with the distance between 

 the balloons, by another rise due to the peristaltic contraction of the wall of 

 the oesophagus. 



THE NERVOUS MECHANISM OF DEGLUTITION 



Deglutition is a reflex act. When we swallow voluntarily we 

 supply the necessary initial stimulus either by touching the fauces 

 with the tongue or by forcing a certain amount of saliva into the 

 fauces. The afferent channels of the reflex are contained in the 

 second division of the fifth nerve, the glossopharyngeal nerve, and 



