BILE. 249 



product, and the function of the liver, so far as this substance is 

 concerned, is to eliminate it. It undergoes no changes in the 

 intestine, but is excreted as cholesterin in the feces. 



Lecithin. This is another of the constituents of the bile which, 

 like cholesterin, is derived from nervous tissue, and whose elimina- 

 tion from the blood is brought about by the liver-cells. 



Offices of the Bile. The amount of bile which is daily secreted, 

 being about 800 or 900 grams in the human subject, would 

 indicate that its offices in the body must be important. It is a 

 remarkable fact that a single anatomic element can perform so 

 many varied functions as does the liver-cell. (1) It secretes the 

 water of the bile; not alone, for the cells of the bile-ducts and 

 possibly those covering the lining of the gall-bladder aid in this 

 process. (2) It forms the bile-salts. (3) It forms the bile-pig- 

 ments. (4) It separates cholesterin and lecithin from the blood. 

 Besides these functions, all of which are related to the bile, it has 

 others no less important in connection with the formation of gly- 

 cogen and urea, both of which are discussed elsewhere. 



That the passage of bile into the intestine is not essential to 

 life, even in man, is conclusively proved by the results of the 

 establishment of fistulse of the gall-bladder through which all the 

 bile that is formed is removed ; indeed, under these circumstances 

 the health is not greatly impaired. 



If, however, the common bile-duct is tied, the bile which is 

 formed is absorbed by the lymphatics, an exit from the bile- 

 duct being due to rupture of their walls. That this absorption is 

 not into the blood-vessels is demonstrated by detecting the bile- 

 pigments and the bile-acids in the lymph as it is discharged from 

 the thoracic duct into the venous system at the junction of the 

 left internal jugular vein with the left subclavian vein; the result 

 of this absorption is to produce jaundice. 



Its most important office is probably the part which it plays in 

 serving as the medium through which cholesterin, lecithin, and 

 other results of katabolic metabolism are removed. Its bile-acids 

 are to a certain extent absorbed from the intestines and serve as 

 carriers of cholesterin. Its pigments are to a certain extent also 

 absorbed from the intestine, though what advantage results there- 

 from is not known. Its amylolytic action, if it possesses any, is 

 exceedingly slight, and it has no proteolytic power. It aids the 

 steapsin of the pancreatic juice in splitting up fat into its fatty 

 acids and glycerin, and it furnishes, as we have seen, alkaline salts 

 to unite with fatty acids in the small intestine and form soaps, 

 thereby assisting materially in the emulsification of the fats which 

 are not split up. 



The bile aids also, probably by virtue of the bile-salts, in the 

 absorption of fats. The theory that the bile-acids dissolve the fat 

 and that the intestinal walls moistened thereby absorb the fat more 



