UROBILIN. 705 



this solution has the same color and shade as a 0.1 per cent urochrome 

 solution. The urine must be diluted with water until it has the same 

 depth of color. The comparison is performed in vessels with parallel 

 walls. 



Urobilin is the pigment first isolated from the urine by JAFFE, 1 and 

 which is characterized by its strong fluorescence and by its absorption- 

 spectrum. Various investigators have prepared, from the urine, by different 

 methods, pigments which differed slightly from each other but behaved 

 essentially like JAFFE'S urobilin. Thus different urobilins have been 

 suggested, such as normal, febrile, physiological, and pathological uro- 

 bilins. 2 The possibility of the occurrence of different urobilins in the 

 urine cannot be denied; but as urobilin is a readily changeable body and 

 difficult to purify from other urinary pigments, the question *as to the 

 occurrence of different urobilins must still be considered open. According 

 to SAiLLET 3 no urobilin exists originally in human urine, but only the 

 mother-substance of the same, urobilinogen, from which the urobilin 

 is formed in the excreted urine by the influence of light. 



Urobilin-like bodies, so-called urobilinoids, have been prepared from 

 bile-pigments as well as blood-pigments, and indeed by oxidation as well 

 as by reduction. MALY obtained his hydrobilirubin by the reduction of 

 bilirubin with, sodium amalgam, and BISQUE obtained a product which is 

 still more similar to urobilin, while STOKVIS prepared, by the oxidation 

 of cholecyanin, with a little lead peroxide, a choletelin, which acted very 

 much like urobilin. HOPPE-SEYLER, LE NOBEL, NENCKI and SIEBER 

 have obtained urobilinoid bodies by the reduction of hsematin and hsema- 

 toporphyrin with tin or zinc and hydrochloric acid, while MACMUNN 4 

 obtained, by the oxidation of hsematin with hydrogen peroxide in alcohol 

 containing sulphuric acid a pigment, which seemed to be identical with 

 urinary urobilin. It is apparent that all these urobilins cannot be identical. 



Many investigators declare that urobilin is identical with hydrobilirubin, 

 but according to the researches of HOPKINS and GARROD 5 this view is not 

 correct, because, irrespective of other small differences, each body has an 

 essentially distinct composition. Hydrobilirubin contains C 64.68, H 6.93, 



1 Centralbl. f. d. med. Wissensch., 1868 and 1869, and Virchow's Arch., 47. 



2 See MacMunn, Proc. Roy. Soc., 31 and 35; Ber. d. deutsch. chem. Gesellsch., 14, 

 and Journ. of Physiol., 6 and 10; Bogomoloff, Maly's Jahresber., 22; Eichholz, Journ. 

 of Physiol., 14; Ad. Jolles, Pfluger's Arch., 61. 



3 Revue de medecine, 17, 1897. 



4 Maly, Ann. d. Chem. u. Pharm., 163; Disque, Zeitschr. f. physiol. Chem., 2; 

 Stokvis, Centralbl. f. d. med. Wissensch., 1873, 211 and 449; Hoppe-Seyler, Ber. d. 

 deutsch. chem. Gesellsch., 7; Le Nobel, Pfluger's Arch., 40; Nencki and Sieber, 

 Monatshefte f. Chem., 9, and Arch. f. exp. Path. u. Pharm., 24; MacMunn, Proc. Roy. 

 Soc., 31. 



5 Journ. of Physiol., 22. 



