104 PHYSIOLOGY. 



body. Trypsin displays no digestive powers on nuclein, keratin, or 

 starches. There are vegetable trypsins like papain of Carica papaya, 

 and bromelin of pineapple juice. 



Hydrochloric acid quickly destroys trypsin unless there is great 

 excess of proteid substances present, which means that the acid is com- 

 bined with them and rendered less active. When a filled pancreas-cell 

 is examined, the little granules within are found not to be active 

 trypsin, but the precursor, or mother of the ferment. This zymogen, 

 trypsinogen, is readily converted into the ferment by the presence of 

 a trace of acid, since a great quantity will immediately kill the newly 

 formed ferment as soon as generated. 



Amylopsin, This starch-splitting ferment converts starch partly 

 into dextrin, but chiefly into isomaltose and maltose. During the 

 first month of life it is thought that no amylopsin is formed; hence 

 children of that age should not be fed starches. Amylopsin differs 

 from ptyalin in that it can digest cellulose, so that it is capable of 

 acting on unboiled starch. In many cases the failure of digestion of 

 the carbohydrates by the amylopsin is associated with drowsiness after 

 meals and slight headache. 



The Steapsin, or Fat-splitting Ferment, decomposes the neutral 

 fats into fatty acid and glycerin. It also emulsifies the fats: an 

 activity which is assisted by the bile. One part of the fatty acids set 

 free by the steapsin combines with alkalies in the intestine to form 

 soap. This soap favors the emulsification of the fats. Another part 

 of the fatty acid is absorbed as such and combines with glycerin in 

 the intestinal wall again to form a fat. Kastle and Loevenhart have 

 shown that lipase also has a reversible action : that is, it can make the 

 fatty acids and glycerin reunite after they have been separated by it. 

 The steapsin acts best in an alkaline medium, for acids stop it. 

 Glycerin does not dissolve' steapsin; so that a glycerin extract is not 

 suitable for an experiment. 



The Fourth Ferment present in the pancreatic juice is an un- 

 named one, which, like rennin, has the power to coagulate milk. It 

 is hardly possible that its powers are exercised extensively, if at all, 

 since the milk is probably coagulated in the stomach by the rennin 

 found there before it ever reaches the duodenum. The so-called 

 "peptonizing powders" are composed of pancreatin and sodium bicar- 

 bonate. 



From the nature of the resulting precipitates in the transforma- 

 tion of the caseinogen into casein, it is evident that the two ferments 

 rennin of the stomach and that found in pancreatic juice are 



