DIGESTION. 67 



muscles produces a movement of the contents of the stomach 

 like churning. In this way the food is thoroughly mixed 

 with the secretions from the inner walls of the stomach. 

 The mucous membrane, or lining of the stomach, is of a 

 pinkish hue, changing to red during digestion. It lies in 

 folds when the stomach is empty, but these folds disappear 

 when it is filled. Examined closely, the lining of the 

 stomach has a peculiar honeycomb appearance, owing to 

 its being dotted over with small shallow pits. At the 

 bottom of these little pits a number of ducts open. They 

 are the openings through which the juice from the gastric 

 glands situated in the lining reaches the food. 



The stomach is freely supplied with blood-vessels, and when 

 food is swallowed it excites the nerves of this organ, and 

 causes the small vessels to dilate. The increased flow of 

 blood, besides furnishing the glands with material from which 

 to extract the juice, stimulates them to action. 



The gastric juice is a thin, colorless fluid, with a distinctly 

 acid taste. Besides this free acid, it contains a peculiar 

 substance known as pepsin. The acid and the pepsin are 

 both necessary to the digestion of food in the stomach. 

 When the meal is completed the muscles begin to contract, 

 so as to roll the food over and over, until thoroughly mixed 

 with this juice, and reduced to a pulpy, soup-like mass. All 

 this time the outlet to the stomach is guarded so that no 

 food can pass until it has been properly changed. The flow 

 of gastric juice may be too free, and interfere with healthy 

 digestion. This increased flow may be caused by stimulating 

 articles, such as mustard or pepper, taken with the food, or 

 still worse, the use of ALCOHOL in any form, to stimulate 

 the appetite. On the other hand, the flow may be too 

 scanty. It is sometimes checked by a drink of cold water, 

 or by swallowing a piece of ice. If food is taken when a 

 person is much fatigued, the secretion of gastric juice is 



