1897-98.] Dr D. F. Harris on Spectroscopy of Hcemoglobin. 197 
*0056 per cent, by the guiac method, the instrumental is twice as 
delicate a method as the chemical. 
The spectroscope could thus detect a loss of '3 c.c. of blood by 
the urine per twenty-four hours. 
X . — Urobilin and Bilirubin. 
I believe the spectroscope may be of service, clinically, in cases 
of suspected choluria, especially in those in which Gmelin’s re- 
action gives negative results. In urine, normal as to its depth of 
colour, its yellow pigment, urobilin, yields no absorption spectrum, 
nor, indeed, does an alcoholic solution of urobilin (prepared by 
M‘Munn’s method), if only no deeper than the tint of normal 
urine. With normal urine there is some haziness in the region of 
the F line, but it by no means amounts to a band. Urine evapo- 
rated to one-fifth its bulk, cooled and filtered ? from urates, does 
yield the broad, familiar band extending darkly over the F line 
and shading away into the green. How, it is quite true that the 
absorption-spectrum of bile from the greenish-yellow pigment 
bilirubin is, at a certain degree of dilution, remarkably similar 
to that of urobilin, and under certain conditions would be prac- 
tically indistinguishable from it ; nevertheless, I believe that in so 
far as pathological urines are concerned, we can say whether the 
abnormal pigmentation is due to an excessive amount of urobilin 
or to the presence of bilirubin. For, first of all, from the fact 
that unless specially concentrated or chemically treated, normal 
urine gives no spectroscopic evidence of urobilin, if one sees in a 
urine a band at F, and no other bands, the presumption is that 
that band is due to bile-pigment. All doubt is, of course, dispelled 
if this urine also yields Gmelin’s test, for urobilin does not give 
the play of colours. I am not forgetting that in choluria the 
urobilin may be itself increased, but as it is only in highly febrile 
urines that the urobilin band spontaneously appears (and when it 
does, is usually accompanied by bands more to the left), I am 
inclined to believe that the band at F in choluric urine is almost 
entirely due to bilirubin. If this increase of urobilin in choluria 
be anything like a common occurrence, it tends to confirm the 
contention emphasised in a former paper (9), that urinary pigment 
is not merely altered and reabsorbed intestinal biliary pigment,. 
