CHEMISTRY OF THE LIVER. 325 



FUNCTIONS AND BEHAVIOR OF BILE. 



The bile as a whole has a number of functions to perform in 

 the body, some of which have been referred to in the discus- 

 sion of digestive processes. It represents also the avenue of 

 escape of a number of by products formed by the katabolic 

 processes in the liver. Many of these processes are doubtless 

 very complex and in them a variety of secondary or side re- 

 actions occur which furnish matters of no further use appar- 

 ently in the body. These are collected in the gall bladder and 

 finally discharged into the small intestine, where escape from 

 the body with the feces is possible for the constituents having 

 no further value. 



In part, therefore, the bile must be regarded as an excretion 

 like the urine, but that the parallelism is not complete is shown 

 by the fact that a considerable absorption takes place from the 

 intestine, and products are returned which find further applica- 

 tion in the organism. There is evidence to show that this 

 portion returned from the intestine serves as a cholagogue to 

 stimulate new secretion in the liver. It is likely that this free 

 secretion and flow of bile in the liver is necessary for the suc- 

 cessful completion of certain metabolic processes going on 

 there, so that it may be regarded not merely as an end but 

 also as a means toward an end. 



The one digestive process in which the bile seems to play a 

 practically necessary part is in the absorption of fats ; here its 

 action is largely mechanical as in some way it aids the passage 

 of the finely divided fat through the intestinal walls. The 

 general behavior of bile in this respect may be illustrated by a 

 simple experiment. 



Ex. Moisten two similar filter papers in funnels, one with water and 

 the other with bile. Into each filter pour some fatty oil, such as cotton- 

 seed oil or olive oil. Note that while the oil will not pass through the 

 paper moistened with water a small amount passes slowly through the 

 bile-moistened filter. Similar experiments have been made with animal 

 membranes. 



A more important action with fat, however, is shown in the 

 power of bile to form fat emulsions. This is now looked upon 



