MOVEMENTS OF THE STOMACH 167 



successive swallows only the last is followed by an effective 

 peristalsis. The glossopharyngeal also inhibits respiration 

 during deglutition an inhibition that is effective at any 

 stage of respiration and lasts for four or five seconds. It differs, 

 therefore, from the respiratory stoppage following stimulation 

 of other sensory nerves. Efferent fibers pass to the deglutition 

 mechanism, by way of fibers of the twelfth, tenth, ninth, 

 seventh, and fifth nerves. The vagus has a special relation to 

 the esophagus. Swallowing is interfered with after section, 

 and stimulation of the peripheral end causes movements of 

 the esophagus. 



Movements of the Stomach. From a physiological point of 

 view the stomach is divisible into two parts, the antrum pylori 

 and the fundus. The junction of these two parts is marked, 

 more or less, by a constriction which is the consequence of 

 a tonic contraction of the sphincter of the antrum. The latter 

 is little more than a physiological sphincter. A few minutes 

 after food is ingested a circular contraction, beginning at the 

 transverse band, runs in the direction of the pyloric sphincter. 

 Other constrictions follow and they become more pronounced 

 and energetic, involving the portion of the fundus which lies 

 next to the transverse band. Their direction is always toward 

 the pylorus. Two or three waves may be visible at any one 

 time. The effect upon the food is to drive that portion of 

 the stomach contents lying next to the stomach walls toward 

 the pylorus, and since the pyloric sphincter remains closed 

 there is a regurgitation of food backward through the centre 

 of the advancing wave of constriction. The effect is a churning 

 of the food in the antrum pylori where it gradually becomes 

 mixed with the secretions of the gastric glands. The semiliquid 

 food, called chyme, becomes acid in its reaction and thus 

 becomes the effective stimulus in a reflex inhibition of the 

 pyloric sphincter. With the relaxation of the sphincter a 

 portion of the liquid gastric contents makes its way into the 

 duodenum. 



The rapidity with which the passage of chyme from the 

 stomach to the duodenum takes place depends largely upon 

 the nature of the food. Carbohydrates leave the stomach 

 sooner than fats and fats sooner than proteins. The reason 

 for this lies in the quantity of acid formed during the digestion 



