DIGESTIVE ACTION OF BILE. 343 



does not break up fats, but to a limited extent emulsifies 

 them, though far less perfectly than the pancreatic secre- 

 tion. It is even doubtful if this action is exerted in the 

 intestines at all. In many animals, as in man, the bile and 

 pancreatic ducts open together into the duodenum, so that, 

 on killing them during digestion and finding emulsified 

 fats in the chyle, it is impossible to say whether or no the 

 bile had a share in the process. In the rabbit, however, the 

 pancreatic duct opens into the intestine about a foot farther 

 from the stomach than the bile-duct, and it is found that 

 if a rabbit be killed after being fed with oil, no milky chyle 

 is found down to the point where the pancreatic duct opens. 

 In this animal, therefore, the bile alone does not emulsify 

 fats, and, since the bile is pretty much the same in it and 

 other mammals, it probably does not emulsify fats in them 

 either. From the inertness of bile with respect to most 

 foodstuffs it has been doubted if it is of any digestive use 

 at all, and whether it should not be regarded merely as an. 

 excretion, poured into the alimentary canal to be got rid of. 

 But there are many reasons against such a view. In the 

 first place, the entry of the bile into the upper end of the 

 small intestine where it has to traverse a course of more 

 than twenty feet before getting out of the Body, instead of 

 its being sent into the rectum close to the final opening of 

 the alimentary canal, makes it probable that it has some 

 function to fulfill in the intestine. Moreover, a great part 

 of the bile poured into the intestines is again absorbed from 

 them, only a small part being pnssed out from the rectum; 

 this seems to show that part of the bile is secreted for 

 some other purpose than mere elimination from the Body. 

 One use is to assist, by its alkalinity, in overcoming the 

 acidity of the chyme, and so to allow the trypsin of the- 

 pancreatic secretion to act upon proteids. Constipation is, 

 also, apt to occur in cases where the bile-duct is temporarily 

 stopped, so that the bile probably helps to excite the con- 

 tractions of the muscular coats of the intestines; and it is 

 said that under similar circumstances putrefactive decom- 

 positions are extremely apt to occur in the intestinal con- 

 tents. Apart from such secondary actions, however, the 



