DIGESTION. 279 



The gall-bladder and all the main biliary ducts are provided with 

 mucous glands, which open on their internal surface. 



Functions of the Liver. The functions of the Liver may be 

 classified under the following heads : 1. The Secretion of Bile. 2. 

 The Elaboration of Blood ; under this head may be included the Glyco- 

 genic Function. 



1. THE SECRETION OF BILE. 



The Bile. Properties. The bile is a somewhat viscid fluid, of a 

 yellow or a reddish-yellow color, a strongly bitter taste, and, when 

 fresh, with a scarcely perceptible odor: it has a neutral or slightly alka- 

 line reaction, and its specific gravity is about 1020. Its color and degree 

 of consistence vary much, quite independent of disease; but, as a 

 rule, it becomes gradually more deeply colored and thicker as it ad- 

 vances along its ducts, or when it remains long in the gall-bladder, 

 wherein, at the same time, it becomes more viscid and ropy, of a 

 darker color, and more bitter taste, mainly from its greater degree of 

 concentration, on account of partial absorption of its water, but partly 

 also from being mixed with mucus. 



Chemical Composition of Human Bile. (Frerichs.) 



Water, . . . . . . . .859.2 



Solids Bile salts or Bilin, .... 91.5 



Fat, ... .... 9.2 



Cholesterin, . .... 2.6 



Mucus and coloring matters, . . .29.8 

 Salts, 7.7 



140.8 

 1000.0 



(a) Bile salts, or Bilin, can be obtained as colorless, exceedingly del- 

 iquescent crystals, soluble in water, alcohol, and alkaline solutions, 

 giving to the watery solution the taste and general characters of bile. 

 They consist of sodium salts of glycocholic and taurocholic acids. The 

 former salt is composed of cholic acid combined with glycin (see Ap- 

 pendix), the latter of the same acid combined with taurin. The pro- 

 portion of these two salts in the bile of different animals varies, e. g., 

 in ox bile the glycocholate is in great excess, whereas the bile of the dog, 

 cat, bear, and other carnivora contains taurocholate alone ; in human 

 bile both are present in about the same amount (glycocholate in excess?). 



Preparation of Bile Salts. Bile salts may be prepared in the fol- 

 lowing manner: mix bile which has been evaporated to a quarter of its 

 bulk with animal charcoal, and evaporate to perfect dryness in a water 

 bath. Next extract the mass whilst still warm with absolute alcohol. 



