68 PHYSIOLOGY OF ALIMENTATION. 



in an acid medium of the concentration found in the stomach. 

 A substance which is obtained as a coagulum from gastric 

 juice on boiling probably represents the combined ferments, 

 together with mucin and traces of organic material derived 

 from particles of digested food or the dead cells of the 

 stomach-wall itself. 



The wall of the stomach contains the antiproteinase (anti- 

 pepsin) discovered by WEINLAND. As its name indicates, 

 this substance, when present, prevents the proteolytic fer- 

 ments from acting. As it is probably due to the presence 

 of this substance in the wall of the stomach, and in the in- 

 testines, that the alimentary tract does not digest itself, it 

 will be discussed in some detail later. 1 



The inorganic constituents of the gastric juice exclusive of 

 the hydrochloric acid consist of the chlorides and traces 

 of the phosphates of sodium, potassium, magnesium, cal- 

 cium, iron, and ammonium. The only figures indicative 

 of the quantities in which these exist in the gastric juice 

 are based upon analyses of the impure secretion or such 

 as was obtained under other than physiological conditions. 

 As these are practically valueless, they will not be given 

 here. 



The action of the ferments of the gastric juice, and the 

 variations in its composition and quantity, will be discussed 

 further on. 



3. The Pancreatic Juice. The quantity of juice which 

 flows from the pancreas varies greatly in different animals 

 and in the same animal under different physiological con- 

 ditions. The observations of the older investigators are 

 probably very incorrect. PAWLOW and his coworkers state 

 that the amount of normal juice which can be obtained 

 from a dog possessing a permanent fistula 2 is 21.8 c.c. per 

 kilo ki twenty-four hours. The pancreatic juice from a 

 dog is a clear, colorless, odorless liquid, somewhat variable 



1 See p. 133. 2 See Chapter XII, Part 1. 



