64 DIGESTION 



glycerin and fatty acids by the action of lipase. The fatty 

 acids combining with sodium form soaps. There now simulta- 

 neously results a splitting up of the neutral fat, which remains 

 into minute globules which have no tendency to run together. 

 This process, known as the emulsification of the fat, is an obscure, 

 physical process. Although pancreatic juice is in itself suffi- 

 cient to emulsify fats, the process is greatly accelerated by 

 the presence of bile or bile salts. Possibly this is due to a well- 

 known characteristic of bile, that of diminishing surface tension 

 when added to aqueous solutions. Bile salts, furthermore, 

 have the capacity of dissolving soaps, and a solution of soaps 

 in bile salts, in turn, dissolve free fatty acids. Through this 

 interaction the amount of fat split is increased twofold or 

 threefold. 



In some diseases of the pancreas, fat and fatty acids appear 

 in the stools. The same may be true when bile is prevented 

 from entering the intestine through obstruction or in case of 

 biliary fistula, but in the. latter case, at least, the patient's 

 health is not affected. The offensive odor of the feces in the 

 latter cases is very likely due to a coating of the food with fat, 

 preventing the action of digestive enzymes and so giving free 

 reign to the activity of bacteria. 



When bile comes in contact with chyme a precipitate is 

 formed which is a salt-like compound of protein and tauro- 

 cholic acid. Bile acids and mucin are also thrown down. These 

 are redissolved by further additions of bile. 



Succus Entericus. The intestinal juice is supposed to be 

 the product mainly of Lieberkuhn's crypts. It is a thin, yel- 

 lowish liquid of alkaline reaction and generally turbid in 

 appearance. It contains the proteins, serum albumin and 

 serum globulin. The inorganic salts are chiefly sodium chloride 

 and sodium carbonate. The quantity formed per day has been 

 estimated to be two or three liters. It has little digestive 

 action except on starch. 



Extracts of the walls -of the small intestine, however, con- 

 tain four or five different enzymes which have a profound 

 influence upon intestinal digestion: 



1. Enterokinase, which activates trypsinogen. 



2. Erepsin, an enzyme which acts especially upon deutero- 

 proteoses and peptones, converting them to amino-acids. 



