280 DIGESTION 



with the bile and food material at the same time. 

 It is alkaline in reaction, and contains three active 

 enzymes trypsin, amylopsin, and steapsin. 



Trypsin is a more active ferment than pepsin, and 

 continues the digestion of peptones into a more soluble 

 form than pepsin. It acts best in an alkaline medium. 

 The function of this ferment is to convert proteins 

 into peptones, as pepsin does in the gastric digestion. 



Amylopsin is the ferment in the pancreatic juice 

 which converts the undigested particles of starch 

 in the food into sugar maltose. It acts similarly to 

 the ferment ptyalin in the saliva. As starch digestion 

 ceases with the entrance of food into the stomach, the 

 action of the amylopsin ferment in the pancreatic 

 juice is important, in order that the starches are 

 completely digested, for they belong to the carbo- 

 hydrates which are essential as a food, to be used by 

 the tissues in the production of heat and energy. 



Steapsin is the ferment or enzyme which splits the 

 fats remaining in the partially digested food into 

 fatty acids and glycerin. The fatty acids coming 

 in contact with alkaline salts in the intestine are 

 saponified and form a soap, the products are absorbed 

 and combine again to form a neutral fat, which is 

 used by the tissues after absorption. This recombina- 

 tion may occur in the epithelial cells of the intestines. 

 Some of the fat is emulsified during the formation 

 of the soap, appearing as a creamy emulsion, before 

 being absorbed. 



Intestinal Juice. We have described or endeavored 

 to make clear how the food we eat has been gradually 

 reduced to a state in which it can be absorbed liquid 

 or semiliquid. There still remains, as has been proved 

 in animals and human beings, chyme in the intestines, 

 containing sugars, apparently non-absorbable without 

 undergoing further change. This is produced by the 

 action of the intestinal juice and the contained enzyme 

 or ferment invertin. The latter converts these sugars 



