189 
1888 - 89 .] Dr Haycraft on Chromatology of the Bile. 
it changes to green, and this finally to orange-brown. If some of 
the brown bile be then treated with a few drops of nitric acid, it is 
oxidised back into biliverdin, and further additions of acid develop 
the blue, violet, red, and yellow pigments. Here, then, without 
going any further, we have an instance of the reduction of the pig- 
ment. The reduction does not produce hydrobilirubin alone, as 
that substance cannot be reoxidised in the way we have described. 
If a bladder, fresh from the slaughter-house, be opened, one 
seldom or never fails to see signs of reduction within it. Blue or 
blue-green bile fills the cavity, but thick orange-brown bile is seen 
next the mucous membrane, which is itself brown in colour. It is 
not improbable, therefore, that during life, reduction of the biliverdin 
takes place, due perhaps to the action of the mucous membrane of 
the gall-bladder or to the mucus secreted by it. This is, indeed, 
almost certainly the case, and one can recall the fact that the pigment 
present in gall-stones from the ox consists, not of biliverdin, but of 
bilirubin. 
It was obviously a matter of some importance to investigate the 
reduction processes we have just described, in order, if possible, to 
ascertain their cause, and the influence of modifying conditions 
upon them. We have been greatly assisted in this inquiry by Dr 
MacMunn. We sent to him on several occasions solutions in which 
we had difficulty in determining whether definite absorption-bands 
were present, and we have very warmly to thank him for the courtesy 
with which he was ever willing to help us. 
Experiment I . — Temperature of the laboratory, 60°. Two test- 
tubes were filled with fresh green ox-bile, and watched from day to 
day. After three days the bile in the lower part of one of the tubes 
had become of a brown-green colour. The change in colour spread 
upwards, and in twelve hours the whole tube contained bile of a 
uniform brown tint. Putrefaction, indicated by an unpleasant 
odour, had set in by this time. In the other tube the bile did 
not change in colour, nor was there any sign of putrefaction until 
the following day, when both appeared simultaneously. Later on 
the bile became by degrees of a light amber colour, giving, how- 
ever, the play of colours for nearly four months, after which Gmelin’s 
test failed. The fluid was then examined with the spectroscope. 
There was slight shading at the violet end of the spectrum, and the 
