■318 VETERINARY PHYSIOLOGY 



C. Absorption from the Stomach. 



By ligaturing of the pyloric end, it has been found that 

 the stomach plays a very small part in the absorption of 

 food ; water is not absorbed, altliough alcohol and many 

 ■drugs are rapidly taken up. There is a slight absorption of 

 peptones and of sugars. 



While the stomach 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. 

 It has been shown, however, that the splitting of 

 proteins is somewhat different if peptic precedes trj-ptic 

 digestion. 



Its main function is to act as a reservoir, and probabl}' the 

 .antiseptic action of its secretion is of considerable importance. 



D. Regurgitation of Gastric Contents. 



1. Regurgitation into the Gullet. — Normally, the contents 

 of the stomach are prevented from passing back into the 

 gullet by the cardiac sphincter. The tone of this sphincter 

 is easily overcome, and it is relaxed b\^ repeated SAvallowing, 

 so that no sound is heard as the contents pass into the 

 stomach. Since adrenalin inhibits it, it is probably 

 relaxed by the sympathetic nerves. Stimulation of the 

 vagus first inhibits and then causes it to contract. It tends 

 to undergo rhythmic relaxations, during which the gastric 

 contents pass back into the oesophagus, even up to the 

 mouth, and then, by oesophageal peristalsis, are again 

 passed down. The tone of the muscle is increased b}' the 

 presence of hydrochloric acid in the stomach, and thus 

 regurgitation does not take place in normal digestion, but 

 is associated with a neutral reaction of the stomach con- 

 tents which is well marked in some forms of atonic 

 dyspepsia that occur in man. 



2. 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, 



