THE BILE 341 



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. 



CHEMICAL COMPOSITION OF HUMAN BILE. (FRERICHS.) 



Water 859.2 



Solids Bile salts 91.5 



Fat 9.2 



Cholesterin 2.6 



Mucus and coloring matters 29 .8 



Salts 7.7 



Bile salts can be obtained as colorless, exceedingly deliquescent 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 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 NO 6 + H 2 O = C 2 H 5 NO 2 -f C 24 H 4 oO6 

 Glycocholic Acid. Glycin. Cholic Acid. 



and C 26 H 45 NO 7 S + H 2 O = C 2 H 7 NO 3 S -f C 24 H 4 oO5 

 Taurocholic Acid. Taurin. Cholic Acid. 



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

 placed by the radical amidogen NH 2 C 2 H 3 (NH 2 )O 2 , C 2 H 5 NO 2 . Taurin likewise is 

 amido-isethionic acid. Isethionic acid is sulphurous acid H 2 SO 3 , in which an atom of 

 H is replaced by the monatomic radicle oxy-ethylene, C 2 H 4 OH, viz., H(C 2 H 4 OH)SO 3 , 

 and in amido-isethionic acid, the OH hydroxyl in this radicle is replaced by amidogen NH 2 , 

 thus H(C 2 H 4 NH 2 )SO 3 = C 2 H 7 NSO 3 . The proportion of these two salts in the bile of 

 different animals varies, e.g., in the 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 

 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 lg - 

 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 other 

 oxidizing agency, as by adding nitrous acid. Biliverdin is soluble in alcohol, 

 glacial acetic acid, and strong sulphuric acid, but insoluble in water, in chloro- 

 form, and ether. It is usually amorphous, but may sometimes crystallize in 

 green rhombic plates. 



There is a close relationship between the coloring matters of the blood 

 and of the bile, and it may be added, between these and that of the urine, 



