THE BILE 367 



perceptible odor; it has a neutral or slightly alkaline reaction, and its specific 

 gravity is about 1.020. Its color and consistency vary much, quite inde- 

 pendent of disease; but, as a rule, bile becomes gradually more deeply colored 

 and thicker as it advances along its ducts, or when it remains long in the gall- 

 bladder where it becomes more viscid and ropy, darker, and more bitter. 

 This is on account of its greater degree of concentration, from resorption of 

 its water, and also from being mixed with mucus, lipoids, and phosphatid 

 proteins secreted by the lining membrane of the gall-bladder. 



CHEMICAL COMPOSITION OF HUMAN BILE. (FRERICHS.) 



Water 859.2 



Solids Bile salts 91 . 5 



Fat 9.2 



Cholesterol 2.6 



Proteins and coloring matters 29.8 



Salts 7.7 



140. 



Bile salts can be obtained as colorless, exceedingly deliquescent crystals, 

 soluble in w T ater, alcohol, and alkaline solutions, giving to the watery solution 

 the taste and general characters of bile. They consist of sodium salts of gly- 

 cocholic and taurocholic acids; the formula of the former being C 26 H 42 NaNO 6 , 

 and of the latter C 26 H 44 NaNO 7 S. 



The bile acids are easily decomposed by the action of dilute acids or alkalies 

 thus: 



C 26 H 43 N0 6 + H 2 0=C 2 H 5 N0 2 +C 24 H 40 5 

 Glycocholic acid. Glycocoll. Cholic acid, 

 and C 26 H 45 NO 7 S + H 2 O =C 2 H 7 NO 3 S +C 24 H 40 O 5 

 Taurocholic acid. Taurin. Cholic acid. 



Glycocoll is amido-acetic acid, i.e., acetic acid C 2 H 4 O 2 , with one of the 

 atoms of H replaced by the radical amidogen NH 2 C 2 H,(NH,) O 2 , C 2 H 5 NO 2 . 

 Taurin likewise is amino-ethyl-sulphonic acid. Accordingly, it has the for- 

 mula CH 2 NH 2 CH 2 SO 2 OH. The proportion of these two salts in the bile of 

 different animals varies, e.g., in the ox bile the glycholate is in great excess, 

 whereas the bile of the dog, cat, bear, and other carnivora contains taurocho- 

 late alone. In human bile the glycocholate is in excess (4 . 8 to 1.5). 



The yellow coloring matter of the bile of man and the carnivora is termed 

 bilirubin, C 16 H 18 N 2 O 3 , is crystallizable and insoluble in water, and soluble in 

 chloroform or carbon disulphide. A green coloring matter, biliverdin, 

 C 16 H 18 N 2 O 4 , which always exists in large amount in the bile of herbivora, is 

 formed from bilirubin on exposure to the air or by subjecting the bile to any 



