490 DIGESTION 



with a test meal part of which was colored with carmine or charcoal, 

 has shown that none of the coloring material was present in the contents 

 of the pyloric end up to twenty minutes or so after the food had been 

 taken. It then appeared but at first only in traces. Another important 

 distinction between the food in the two portions of the stomach relates 

 to its consistency. In the pyloric end it is semifluid and homogeneous 

 in character; in the cardiac end, on the other hand, it is a lumpy, rather 

 incoherent mass. 



The gastric movements must greatly facilitate the digestive processes 

 in the stomach. In the cardiac part the undisturbed condition of the 

 food will, as we have seen, facilitate the digestive action of ptyalin, 

 whereas in the body of the stomach the peristaltic, waves, besides mov- 

 ing the food onward, will tend to bring fresh portions of mucous mem- 

 brane and food in contact, so that the latter becomes more thoroughly 

 mixed with the pepsin and hydrochloric acid. In the pyloric part, where 

 no hydrochloric acid is secreted, the contents, already sufficiently acid 

 in reaction, become more thoroughly churned up with the local pepsin 

 secretion, so that proteolytic action progresses very rapidly. 



The peristaltic waves also facilitate absorption from the stomach of such 

 substances as glucose in concentrated solution and, probably, of hydro- 

 lyzed protein; water, however, is not absorbed. One effect of such 

 absorption is the production of gastrin, which we have seen is the hor- 

 mone concerned in maintaining the gastric secretion after the psychic 

 flow. The fact that the mucosa of the vestibule has, relatively to the 

 cardiac end, few secreting glands is in harmony with the view that 

 absorption is an important function of this part of the stomach. 



The observations of Carlson, 17 Ginsburg 18 and others indicate that the 

 usually accepted explanation of the pains of gastric and duodenal ulcers, 

 namely, corrosion and irritation of exposed nerve endings in the gastric 

 and duodenal mucosae by highly acid stomach contents, is not correct. 

 The pains of ulcer may be present when the contents of the stomach are 

 alkaline and they may be absent when marked hyperacidity exists. Ac- 

 cording to these authors the pains are analogous in origin to those of 

 hunger, and are the result of contractions of the stomach and duodenum, 

 the nerves of which are in a hyperexcitable state. Hyperacidity then, 

 will affect the pain of ulcer in so far only as it increases the motility 

 of the stomach. 



THE EMPTYING OF THE STOMACH 



The Control of the Pyloric Sphincter 



When digestion has proceeded far enough in the stomach to bring the 

 food into a homogeneous, soup] ike fluid (chyme), portions of this, as they 



