5 HUMAN PHYSIOLOGY 



In human bile there are: 



(a) Glycocholic acid, C 26 H 43 NO 6 , a compound of glycocoll 

 and cholaiic acid. 



() Taurocholic acid, C 26 H 45 NSO 7 , a compound of taurin 

 and cholaiic acid. 



Cholaiic acid, C 24 R M O 5 , is a monobasic acid with three 

 -OH-groups (trioxy-acids). It is an unsaturated compound 

 since it unites directly with bromine. Its constitution is 

 unknown, as is also its origin in the body. Its high per- 

 centage of carbon makes it probable that it is first formed by 

 synthesis. 



Beside cholaiic acid, there is present in the human bile another 

 non-nitrogenous constituent of the bile acids-^/i?//zc acid, C 23 H 40 O 4 . 

 In animals there are still other non-nitrogenous constituents of 

 bile acids, closely related to cholaiic acid. 



Glycocoll (amido-acetic acid), NH 2 CH 2 .COOH, is a 

 decomposition product of proteids. It is especially present 

 among the products of the splitting up of gelatin. 



Taurin (amido-ethylsulphonic acid), NH 2 .C 2 H 4 .SO 2 OH 

 (the sulphur is directly united with the carbon, hence a 

 sulphonic acid), may also be regarded as a metabolic product 

 of proteid. 



The bile acids are formed in the liver and secreted in the 

 form of sodium salts. They are, in part, absorbed from the 

 intestine, in part they are transformed into their anhydrids 

 (dyslysins) by putrefaction in the intestine. The bile acids 

 aid the absorption of fats in the intestine (see Chapter X). 



8. Bile pigments. The most important are: 



(a) Bilirubin, a reddish-yellow pigment, C 32 H 36 N 4 O 6 . 

 (&) Biliverdin, a green pigment, C 32 H 36 N 4 O 8 . 



Biliverdin is an oxidation product of bilirubin. The bile 

 pigments are weak acids, forming soluble salts with the 

 alkalies and insoluble salts with calcium (this last is found 

 in the gall-stones). 



Bilirubin is slightly soluble in alcohol, readily in chloro- 

 form, and crystallizes in rhombic tables. Biliverdin is readily 



