340 HUMAN PHYSIOLOGY 



Speaking generally, the vagus seems to increase the move- 

 ments, while the sympathetic fibres check them ; but the 

 vagus seems to inhibit the cardiac sphincter. 



Absorption from the Stomach. 



The stomach appears to play a small part in the absorp- 

 tion of food. Very little water is absorbed, fats are not 

 absorbed, but sugar and peptones seem to be absorbed to a 

 considerable extent. 



Importance of the Stomach in Digestion. 



The chief function of the stomach is as a reservoir for the 

 food. While it plays a certain part in digestion its action 

 is by no means indispensable, for it has been removed in 

 animals and in men without disturbance of the health. Pro- 

 bably the antiseptic action of its secretion is of very consider- 

 able practical importance. 



Vomiting. 



Sometimes the stomach is emptied upwards through the 

 gullet instead of downwards through the pylorus. This act 

 of vomiting is generally a reflex one, resulting from irritation 

 of the gastric mucous membrane and more rarely from 

 stimulation of other nerves. Usually the act is preceded by 

 a feeling of nausea and by a free secretion of saliva. In 

 vomiting, the glottis is closed, and, after a forced inspiratory 

 effort by which air is drawn down into the gullet, a forced 

 and spasmodic expiration presses on the stomach, while at 

 the same time the cardiac sphincter is relaxed through the 

 action of the vagus, and the contents of the stomach are 

 sent upwards. They are at first prevented from passing into 

 the nares by the contraction of the soft palate ; but, as the 

 act continues, these muscles are overcome, and the vomited 

 matter escapes through mouth and nose. The wall of the 

 stomach also seems to act, but its action is non-essential, 

 since vomiting may be produced in an animal in which a 

 bladder has been made to replace the stomach. 



