Colouring-matter of Human Urine. 



29 



urobilin alone is present, and the neglect of this observation has led to 

 disappointment. 



Examination of the Bile- Spectra of various Animals. — If urobilin be 

 formed from bile, the question naturally arises, is urobilin present as 

 such in the bile of any animal ? If so, its biliary origin is made more 

 certain. To enable me to reply to this question, I proceeded to 

 examine this fluid in various animals, using in each instance fresh 

 bile, and examining the spectra by means of a Sorby-Browning micro- 

 spectroscope, and checking observations — when the amount of fluid at 

 my disposal was sufficient for the purpose — by means of a one-prism 

 chemical spectroscope. 



The bile of the following animals was examined : — man, pig, dog y 

 cat, guinea-pig, rabbit, mouse, sheep, hedge-hog, ox, crow, blackbird, 

 chicken, goose, wild duck, duck, frog. 



Among these animals, the bile of the f olio win g gave a characteristic 

 spectrum : — guinea-pig, rabbit, mouse, sheep, ox, crow. 



The darkest green or golden-red bile gave the least characteristic 

 spectrum. I have fully described, in the "Spectroscope in Medicine," 

 the colour and spectrum of each specimen, but I shall here merely 

 mention those facts which throw light upon the origin of urobilin,, 

 namely, that by careful dilution or by examination in a sufficiently 

 thin depth, a band at F is always visible, that this band is made 

 darker by acids, and is made to disappear by adding ammonia. This 

 is very striking in the case of the bile of the mouse (Chart II, 

 sp. 12*), which gives a black band, resembling exactly that seen in 

 febrile human urine. If Chart II be inspected, the most noticeable 

 appearance is the presence of this band in so many spectra. And one 

 cannot help also noticing the general resemblance between these bile- 

 spectra and those shown in the figure, which are the spectra of 

 urobilin in various solutions, and treated by various reagents. 



I also attempted to extract urobilin from the liver of the pig, by 

 means of various solvents, the pounded liver having been extracted 

 with water, alcohol, ether, chloroform, and acidulated alcohol re- 

 spectively, but without success. 



Separation of Urobilin from Httman Urine. — Before describing the 

 method which I adopted for the separation of urobilin, I may make one 

 or two preliminary observations. The reagents used were perfectly 

 pure, and pure ethyl alcohol was used in every instance ; this is a 

 matter of great importance, as methylated spirit is not suitable for the 

 separation of such easily decomposed bodies as urobilin. 



The readings of the spectra are those of a photographed scale 

 adapted to the micro-spectroscope ; and before taking the readings, the 

 precaution was always adopted of narrowing the slit until the sodium 



* The Chart II referred to above is reproduced in the " Spectroscope in Medi- 

 cine j" and accordingly does not accompany this paper. 



