520 LECTURE XXII. 



material as rich in caloric power as the fats will be quickly felt through the 

 entire organism. If the nourishment of the just-mentioned animals was 

 so chosen that they obtained sufficient calories from albumin or carbo- 

 hydrates, then there was no further loss in weight. The absorption of 

 the fat in such cases is not entirely prevented, but merely restricted. 

 That an excessive amount of fat in the nourishment can act injuriously 

 upon the absorption and digestion of albumin is clear, for the fat particles, 

 from their mechanical action, can prevent, or make more difficult, the 

 action of the digestive juice upon the proteins. 



The bile not only takes part in the solution of the fatty acids and their 

 alkali salts in the absorption of the fats, but its significance reaches much 

 farther. We must remember that the fat is hydrolyzed by the aid of a 

 particular ferment, called steapsin or lipase. This ferment is not present 

 originally in the pancreatic juice as such, but in the form of a zymogen. 

 The latter is activated by the bile. The bile also increases the fat-splitting 

 action of the pancreas-lipase in a way which has never been satisfactorily 

 explained. 1 Fiirth and Schiitz 2 have proved that the cholic acid com- 

 ponent of the bile salts is the cause of this marked acceleration in the 

 digestion of fats. 



An exact idea concerning the conditions governing the secretion of the 

 bile and its function was first made possible when Pawlow 3 instead of 

 making use of a biliary fistula placed the entrance of the bile-duct 

 into the duodenum on the outside of the body. He cut out the mouth 

 of the bile-duct together with a piece of the intestinal membrane and 

 sewed it into the wound in the body. He was then able to study the 

 secretion of the bile under normal conditions. The observations made 

 upon animals in which the bile flowed out of a fistula in the gall-bladder 

 naturally could not represent normal conditions, for the bladder repre- 

 sents a reservoir for the bile, so that when it is constantly being emptied 

 to the outside, the secretion of the bile must take place abnormally. 



Pawlow succeeded in showing at once from the amount of bile flowing 

 through this normal opening that the bile secretion depended upon the 

 taking of food. He also showed the influence of the nature of the food 

 upon the secretion. Thus we know that meat causes a particularly in- 

 tense flow of bile, while for the carbohydrates a slight amount suffices. 

 The fats stand intermediate between meat and carbohydrates. The 

 nature of the secretion is also regulated by that of the nourishment. The 

 maximum flow of bile does not correspond to the maximum amount of 

 food, and it appears that there are specific differences here. The purpose 



1 M. Nencki: Arch, exper. Path. Pharm. 20, 367 (1885). 



3 Zentr. Physiol. 20, 47 (1906); Hofmeister's Beitr. 9, 28 (1906) cf. A. S. Loeven- 

 hart and C. G. Soiiden: J. Biol. Chem. 2, 415, (1907). 



3 Pawlow: Le travail des glandes digestive (Pachon et Sabrazes). Paris, 1901. 



