i 189 



1894.] of the Yellow Colouring Matter of the Urine. 395 



inadequate to account for the coloration, and I am therefore con- 

 vinced that the statement that urobilin is the chief colouring matter 

 of normal urine is entirely incorrect. Indeed, as far as normal urine 

 is concerned, urobilin can hardly be reckoned as one of its colouring' 

 matters at all, for even a very faintly tinted solution of this pigment 

 yields a well-defined absorption band, far darker than is ever seen in 

 normal urine. In some morbid urines, on the other hand, it affects 

 the colour profoundly. 



The second pigment referred to is heematoporphyrin, which, as I 

 have elsewhere shown,* can usually be detected by appropriate means 

 even in normal urine ; but here, again, the amount present is so in- 

 finitesimal that it can have no appreciable effect upon the colour. 



The occasional deposition of pink urate sediments, apart from any 



i noticeable deviation from perfect health, shows that uroerythrin 



must also be reckoned among the pigments of normal urine ; and if 



1 further confirmation is needed, it is obtained, as Bivaf and Zoja have 



i shown, by the examination of the extracts obtained by shaking 



specimens of urine with araylic alcohol. 



Since, however, the above-mentioned pigments, with the possible 

 exception of uroerythrin, can have no material influence upon the 

 colour of normal urine, we are driven to the conclusion that there 

 must exist in the urine another much more abundant colouring 

 matter, of a yellow tint, which even in concentrated solution yields 

 no absorption bands, or that the colour is due to the presence of more 

 than one such substance. 



There are not wanting records of investigations directed to the 

 isolation of such a pigment, or mixture of pigments, and products 

 have been obtained by several observers, which they have looked 

 upon as the substance in question, but the various products have 

 differed in their properties, and no one of them has met with general 

 acceptance. 



The literature of the subject will be found admirably epitomized in 

 papers by ThudichumJ and Schunck, published in 1864 and 1867 

 respectively, and to these epitomes there remains little to be added, 

 seeing that during the twenty-seven years which have since elapsed, 

 no fresh observer has, as far as I am aware, published any investiga- 

 tions upon the subject. 



Referring my readers to these epitomes for records of the earlier 

 work of Proust, Berzelius, Lehmann, Harley, and others, I only 

 propose to allude here to the results obtained by Tichborne, Thudi- 

 chum, and Schunck. 



* ' Journal of Physiology,' 1892, vol. 13, p. 619. 

 t ' Gazzetta Medica di Torino,' 1892, vol. 43, p. 925. 

 I ' British Med. Journal,' 1864, vol. 2, p. 509. 

 ' Roy. Soc. Proc.,' 1867, vol. 16, p. 85. 



