DIGESTION 34i 



precipitation of any unaltered native protein, acid-albumin, 

 albumose, and pepsin. The precipitate, which is a salt-like 

 compound of protein with taurocholic acid, is redissolved when the 

 liquid is rendered alkaline, and therefore in excess of bile, or of 

 a solution of bile-salts, but the pepsin has no longer any power 

 of digesting proteins. Part of the bile-acids and bile-mucin is 

 also thrown down by the acid of the digest. It has been sug- 

 gested that by thus precipitating the constituents of the chyme 

 which have not been carried to the peptone stage bile prepares 

 them for the action of the pancreatic juice. But it is difficult to 

 see how the precipitation of a substance can prepare the way for 

 its digestion, and it is more probable that if any physiological 

 value is to be given to this reaction, it has the function of pre- 

 venting the absorption of proteins which have not been suffi- 

 ciently split up. There is little doubt, however, that the ren- 

 dering of the pepsin inactive has physiological significance, for 

 pepsin exerts an injurious influence upon the ferments of the 

 pancreatic juice. In digestion, then, the bile has a twofold func- 

 tion, favouring greatly the activity of the pancreatic ferments, 

 especially the fat-splitting ferment, and aiding in establishing the 

 conditions necessary for the transition of gastric into intestinal 

 digestion. 



Succus entericus. This is the name given to the special 

 secretion of the small intestine, which is supposed to be a product 

 of the Lieberkiihn's crypts. In order to obtain it pure, it is 

 of course necessary to prevent admixture with the bile, the pan- 

 creatic juice, and the food. This can be done by dividing a loop 

 of intestine from the rest by two transverse cuts, the abdomen 

 having been opened in the linea alba. The continuity of the 

 digestive tube is restored by stitching the portion below the 

 isolated loop to the part above it. One end of the loop is sewed 

 into the lips of the wound in the linea alba, and the other being 

 closed by sutures, the whole forms a sort of test-tube opening ex- 

 ternally (Thiry's fistula). Or both ends are made to open through 

 the abdominal wound (Vella's fistula). Another method is to make 

 a single opening in the intestine, and by means of two indiarubber 

 balls, one of which is pushed down, and the other up through the 

 opening, and which are afterwards inflated, to block off a piece 

 of gut from communication with the rest. Or several openings 

 may be made at different levels in the intestine, each being allowed 

 to heal into a wound in the abdominal wall. When pure juice 

 is required it is collected from the lower fistula::, while the upper 

 fistulae are opened to permit the escape of the secretions which 

 enter the higher portions of the alimentary canal (gastric juice, 

 pancreatic juice, and bile). The intestinal juice so obtained is a 

 thin yellowish liquid of alkaline reaction, generally somewhat 



