1288 THE BILE-ACIDS. 



slight difference being due to an admixture with another acid 

 either cholalic, as was first supposed, or fellic. 



Choleic acid, CjsH^C^ or 24114004. Is obtained in small amounts 

 mixed with cholalic acid during the preparation of the latter from 

 ox-bile. It differs from cholalic acid in the solubility of its salts 

 and the products of its oxidational decomposition. 



Fellic acid, 23114004 or 23113804. Obtained in small amounts from 

 human bile during the preparation of ordinary cholalic acid. It is 

 characterized by the extreme insolubility of its barium and magne- 

 sium salts. It also yields a less brilliant Pettenkofer reaction (see 

 below) than does cholalic acid. 



The bile-acids of the pig and goose when decomposed yield forms 

 of cholalic acid called respectively hyo-cholalic acid, C^H^O^ and 

 cheno-cholalic, 27114404. 



2. Dyslysin. C 24 H 36 O 3 . 



When cholalic acid is heated to 200 C. or boiled for some 

 time in solution with hydrochloric or sulphuric acid it loses 

 two molecules of water and yields a resinous anhydride called 

 dyslysin, from its insolubility in water, alcohol and alkalis. 

 As resulting from the dehydration of cholalic acid it is found 

 sometimes in small amount in the faeces. It is a non-crystal- 

 line substance which is soluble in an excess of ether, also in 

 solutions of cholalic acid or of its salts. By treatment with 

 boiling alkalis it may be reconverted by hydration into cholalic 

 acid. 



The various forms of cholalic acid which may be prepared 

 from the bile of different animals each yield a corresponding 

 form of dyslysin. 



3. Glycocholic acid. C 26 H 43 NO 6 . 



It is found as a sodium salt chiefly in ox-bile but also in 

 that of man, mixed in both cases with a much smaller and 

 variable amount of taurocholic acid, also present as a sodium 

 salt. In carnivora it occurs, if at all, in such minute traces 

 only, that it may be said to be absent from the bile of these 

 animals ; hence their bile-acid consists entirely of taurocholic 

 acid. In icterus the urine may contain small quantities of 

 glycocholic acid. 



Preparation. This may be effected as already described 

 in 207. 



The acid crystallizes in fine glistening needles which require 

 about 300 parts of cold but only 120 of hot water for their solu- 

 tion. They are also very soluble in alcohol but practically 

 insoluble in ether. The salts of this acid, more especially those 

 with the alkalis, are extremely soluble even in cold water, also 

 in alcohol, but very slightly so if at all in ether. Both the 



