394 Dr. A. E. Garrod A Contribution to the Study [Apr. 



III. "A Contribution to the Study of the Yellow Colo 

 Matter of the Urine." By ARCHIBALD E. GARROD, M 

 M.D. Oxon., F.R.C.P. Communicated by Sir ALFRED 

 GARROD, M.D., F.R.S. Received February 5, 1894. 



The uncertainty which still surrounds the origin of a pheno: 

 BO familiar as the yellow coloration of the urine bears eloq 

 testimony to the difficulties which beset the investigation, by ordi 

 chemical methods, of such substances as the urinary pigments, and 

 the importance of the part which the spectroscope has played in 

 acquisition of such knowledge of them as we possess. 



Indeed, our acquaintance with the individual pigments is pro 

 tional to the distinctive character of their absorption spectra, rat! 

 than to the time which has elapsed since they first attracted a 

 tion ; and in not a few modern works doubt is thrown upon the 

 existence of a distinct yellow pigment, having negative spectra 

 properties, but to which normal urine owes its characteristic 

 the chief part in the coloration of the excretion being assigned 

 nrobilin. 



In this connexion the spectre-photometric researches of Viero: 

 are of much importance, for they appear to show conclusively 

 more than one pigment is present in normal urine. Vierordt fo 

 that with different specimens of the urine of a single healthy 

 vidual, examined at considerable intervals, the extinction coeffici 

 for different parts of the spectrum exhibited relative as well as 

 tive differences. 



The variations of positive value are of course dependent upon 

 depth of colour of the specimen, but the relative variations can o: 

 be explained by the presence, in varying proportions, of two or 

 distinct pigments. 



It must not, however, be forgotten that, as Vierordt himself poi 

 out, pigments which yield definite absorption bands may influe: 

 the extinction coefficients, even when present in such small quantiti 

 that their bands are not visible as such ; and it can be shown that 

 least three colouring matters, apart from a yellow pigment, may 

 present in any given specimen of the urine of a healthy individua 

 which may, nevertheless, exhibit no obvious selective absorption. 



Of these pigments, urobilin is certainly one, and when not seen a 

 direct examination of the untreated normal urine, its band not in 

 frequently appeal's on standing, or on the addition of a miner* 

 acid. 



Yet the quantity present is at best extremely minute, and wholl 



' Die Quantitative Spectralanalyse.' Tubingen, 1876, p. 78. 



