DIGESTION. 49 



What is the daily secretion of gastric juice ? 

 From 10 to 20 pints. 



What is the source of the hydrochloric acid? 



It is probably secreted by the cubical parietal cells of the peptic 

 glands. Very little seems to be formed by the pyloric glands. 



What other acids are found in the stomach? 



Lactic, acetic, butyric, and some other fatty acids. They are 

 products of digestion or of abnormal processes due to decomposition 

 of food. 



What is the source of pepsin ? 



The globular cells in the peptic glands. These cells are supposed 

 to form a substance called pepsmogen, from which pepsin is derived. 

 Pepsin is derived for commercial or for experimental purposes from 

 fresh stomachs by scraping the surface and dissolving out the fer- 

 ment with cold water, or by mincing the mucous membrane and 

 extracting the ferment with glycerin after dehydrating with 

 alcohol. 



What is the function of gastric juice ? 



The principal function of the gastric juice is the transforming 

 of proteids into peptones. This action depends upon the presence 

 of both pepsin and acid. The first change which occurs is the for- 

 mation of acid albumin, but as the action of the ferment continues 

 the acid albumin is transformed to peptone. The presence of acid 

 albumin is demonstrated by the addition of an alkali, which precip- 

 itates it. 



What are the characteristics of peptone? 



(1) They are diffusible /. e. have the property of osmosis, or 

 passing through an animal membrane. This is of great importance 

 in digestion, for if this property were absent no animal food could 

 be absorbed from the intestines. (2) They are very freely soluble 

 in water and neutral solutions. (3) They do not respond to the 

 chemical tests for other proteid substances. They are not precip- 

 itated by heat and the mineral acids, but are precipitated by tanriic 

 acid, picric acid, or by the bichloride of mercury. 



What is the name given the food after digestion in the stomach ? 

 Chyme. The action of the pepsin in converting proteids to pep- 

 tones is called a proteolytic action, and chemically its action is to 

 cause a hydration of the proteid molecules. 

 4 Phy. 



