184 MANUAL OF PHYSIOLOGY. 



2. As a Stimulant, the bile is of considerable use, for it excites 

 the muscles of the intestine to increased action, and thereby aids 

 in absorption and promotes the forward movement of the food, 

 and more particularly of those insoluble materials which have to 

 be evacuated per anum ; this stimulation may amount to mild 

 purging. 



3. Moistening and Lubricating. The bile adds to the iugesta 

 an abundant supply of food and mucus, much of which passes 

 along the intestine to moisten arid lubricate the fseces and facili- 

 tate their evacuation. In cases of jaundice, or when the bile is 

 removed by a fistula, the fseces are hard and friable, and with 

 difficulty expelled, owing to the deficient fluid and mucus, as well 

 as to the weaker peristaltic movements. 



4. As an Aid to Absorption. The bile having some soap in 

 solution has a close relationship to both watery and oily fluids, and 

 possibly on this account, as well as owing to a peculiar power 

 possessed by the bile salts, a membrane saturated with bile allows 

 an emulsion of fat to pass through it much more readily than if 

 the same membrane were kept moistened with water. This can 

 be seen experimentally with filter paper. 



5. As Excrement. Although the great bulk of the bile is reab- 

 sorbed from the intestinal tract into the blood, and again used in 

 the economy, some of its constituents pass off with the fseces, and 

 are no doubt simply excrementitious matters that must be got 

 rid of. Thus all the cholesteriu, mucus and coloring matter are 

 normally eliminated, and a considerable quantity of the bile acids 

 are split up, the cholic acid being found in the fseces. 



6. As an Antiseptic, the bile is said to have an important func- 

 tion to perform. Possibly it restricts the formation of certain of 

 the by-products, such as the indol resulting from pancreatic 

 digestion, but it is not aseptic, since bacteria abound and thrive 

 in the intestine. 



7. Emulsification of Fats. The bile has no doubt some power of 

 forming an emulsion, but in a far less degree than the secretion 

 of the pancreas ; however, the mixed secretions are probably more 

 efficacious than either separately, from the presence of the free, 

 fatty acids which form soaps and aid in forming the emulsion. 



