170 MANUAL OF PHYSIOLOGY. 



from the ducts, before it has been modified by its sojourn in the 

 gall-bladder, it is necessary to make a biliary fistula, communi- 

 cating either with the gall-bladder or with the bile-duct. In this 

 way the rate, pressure, and other points concerning the mode of 

 secretion may be determined. 



Composition of Bile. The bile of man and carnivorous 

 animals is of a deep orange-red color, turning to greenish-brown 

 by decomposition of its coloring matter. In herbivorous animals 

 it has some shade of green when quite fresh, but turns to a muddy 

 brown after a time. It is transparent, and more or less viscid 

 according to the length of time it has remained in the gall- 

 bladder. It has a strong bitter taste, a peculiar aromatic odor, 

 and after remaining for some time in the gall-bladder it has an 

 alkaline reaction. Its specific gravity is about 1010 when taken 

 from the bile-ducts directly, but it rises to 1030 after prolonged 

 stay in the gall-bladder, owiug to the addition of mucus and the 

 absorption of some of its fluid. 



The following table gives approximately the proportions of the 

 chief constituents of the bile : 



Water, 85.0 per cent. 



Bile salts, 10.0 " 



Coloring matter and mucus, .... 3.0 " 



Fats, 1.0 



Cholesterin, 0.3 " 



Inorganic salts, 0.7 



100.0 



Bile contains no structural elements nor any trace of albumin- 

 ous bodies. 



I. The bile acids are two compound acids, glyco-cholic and 

 tauro-cholic, which exist in the bile in combination with sodium. 

 The amount of each varies in different animals and at different 

 times in the same animal. The bile of the dog and other carni- 

 vora contains only tauro-cholate of soda. In the ox the glyco- 

 cholate of soda is greatly in excess. In man both are present, 

 the proportion being variable, but the tauro-cholate is said to 

 preponderate. 



