UROBILIN. UROBILINOIDS. 743 



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

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

 spectrum. Various investigators have prepared, from the urine, by dif- 

 ferent methods, pigments which differed slightly from each other but 

 behaved essentially like JAFFA'S urobilin. Thus different urobilins have 

 been suggested, such as normal, febrile, physiological, and pathological 

 urobilins. 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. 



In the perfectly fresh urine of healthy human beings no urobilin 

 occurs, as first suggested by SAiLLET, 3 but only the chromogen, uribilino- 

 gen, from which the urobilin is readily formed by the action of light 

 or by weak oxidizing agents. Pathological urines contain on the contrary 

 preformed urobilin. 



Urobilinoids, i.e., bodies which are similar to urobilin in that they fluoresce 

 and show the same absorption spectrum have been prepared from bile-pig- 

 ments (by MALY and STOKVIS) and from hsematin or haematoporphyrin (by 

 HOPPE-SEYLER, LE NOBEL, NENCKI and SIBBER, MAcMuNN 4 ) by reduction 

 as well as by oxidation. According to H. FISCHER and MEYER-BETZ 5 also non- 

 stable pyrrols, which contain a non-substituted hydrogen atom in a ring carbon 

 atom, pass readily in the animal body into substances which give the character- 

 istic urobilin reactions. These reactions are also given by bodies of different 

 constitution, but which probably contain the same chromophore groups, and it is 

 these conditions which cause the above-mentioned uncertainty as to the occur- 

 rence of different urobilins. 



That urobilin is identical with the hydrobilirubin of MALY (see page 

 428) has been considered for a long time. In opposition to this view 

 we find that both bodies, not to mention other small differences, have an 

 essentially different composition. While the hydrobilirubin contains 

 9.22 per cent nitrogen, according to MALY, the urobilin contains only 

 4.09 per cent nitrogen, according to HOPKINS and GARROD, and 5.93 per 

 cent nitrogen, according to FROMHOLDT. In the urobilin of the feces, 

 stercobilin, which is identical with urobilin. HOPKINS and GARROD found 



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, 1 7, 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 H. Fischer and Meyer-Betz, Zeitschr. f. physiol. Chem., 75. 



