CHEMICAL BASIS OF THE ANIMAL BODY. 253 



solvent &c., accounts with but little doubt not only for the extremely 

 numerous and insufficiently characterised pigments which have at one 

 time or another been obtained from urine, but also for much of the 

 conflict and confusion of opinion which exists as to the nature and 

 relationships of those pigments of which we can speak with most 

 confidence. 



1. Urobilin. C 32 H 40 N 4 7 . (?) 



This, the best known and most definitely characterised of the 

 urinary pigments, was first described by Jafie who regarded it as the 

 chief colouring-substance of normal urine, while present in much larger 

 amounts in the urine of fever 1 . He also obtained it occasionally from 

 bile, the name urobilin thus indicating its double source. In fresh 

 normal urine the amount was frequently extremely small, but was 

 observed to increase on standing exposed to the air (oxygen), a result 

 due to the probable presence in the urine of some chromogen or 

 mother-substance (urobilinogen) 2 of the urobilin. The amount of this 

 pigment in urine is too small to provide adequate material for an 

 elementary analysis, so that it was at first characterised by its solu- 

 bilities in various fluids, by the strongly-marked fluorescence of certain 

 of these solutions and more particularly by the absorption-spectrum 

 it exhibited. The subsequent preparation of hydrobilirubin from 

 bilirubin, and the establishment of its identity with urobilin (p. 247) 

 provided for the first time a mass of the substance sufficient to admit 

 of analysis, and upon this the formula given above for urobilin is 

 based. It must not however be forgotten that the identity of the two 

 pigments is disputed by several observers, although the balance of 

 belief seems as yet to support it. It will conduce to clearness if we 

 incline for the present to this belief and describe the preparation and 

 properties of urobilin as given by Jafie, on the assumption that it 

 is identical with hydrobilirubin, and then subsequently give a short 

 account of the opposing views. 



Preparation from urine. Several methods may be adopted ; of 

 these only the broader facts can here be given, but they suffice to 

 provide solutions which exhibit the characteristic spectra, (i) When 

 urine contained much urobilin Jaffe precipitated it by the addition 

 of chloride of zinc in presence of an excess of ammonia ; if but little, 

 then by the addition of basic lead acetate. These precipitates were 

 then worked up by processes which do not admit of a suitably brief 



1 Centralb. /. d. med. Wiss. 1868, S. 243 ; 1869, S. 177. Virchow's Arch. Ed. 

 XLVII. (1869), S. 405. 



2 For further references see Neubauer u. Vogel, Anal. d. Hams, 1890, Sn. 

 331, 336. 



