198 Proceedings of Royal Society of Edinburgh. [sess. 
for in by far the greater number of cases of choluria there is 
diminution of bile entering the intestine, which should lead to less 
(and not more) urobilin, if the latter were derived from any pig- 
ment in the intestine. I do not here raise the question of the 
genetic relationship of biliary to urinary pigment, but shall be 
content to point out that even with the pocket spectroscope, the 
presence of bile-pigment in urine (even when not giving Gmelin’s 
test) may be detected. 
I examined a number of urines in cases of undoubted jaundice, 
with and without carcinoma of liver, none of which gave Gmelin’s 
test; and by comparing them spectroscopically with urine con- 
centrated to their tint, I was able to be certain that it was not 
urobilin that was the cause of their abnormal pigmentation. 
As to the band at F in these cases, close scrutiny reveals some 
degree of difference ; for, taking bilious and non-bilious urines of 
the same depth of colour to the eye, we notice — 
1. The left margin of the broad band at F in the case of 
urobilin is much more hazy than in the case of bilirubin. 
2. It does not extend so near to the red side as does the latter. 
3. Yery much more blue-violet light passes in the case of 
urobilin than in that of bilirubin; i.e ., while urobilin shows more 
blue, bilirubin shows more green. 
4. The darkest zone of the bilirubin band is slightly nearer to 
the left than that of the urobilin band. 
In other words, urine with a little bile-pigment resembles, both 
to the eye and with the spectroscope, non-bilious urine with an 
excessive amount of urobilin : given two urines, unsophisticated 
in any way, both with bands at F, the one in which the band is 
darker will probably contain bile-pigment, for the urinary pigment, 
in order to yield so dark a band, would either have to be present 
to a most unusual amount (such as is only reached by certain 
diseased urines), or have to be associated with a degree of con- 
centration much higher than we are supposing to exist. 
The spectroscope might be employed to distinguish the urine in 
carbolic-acid poisoning (carboluria) from that in choluria, for the 
former shows a distinct absorption in the orange region, coupled 
with a dimming of the entire green, features absent from the urine 
when containing either biliary or urinary pigment. 
