190 Proceedings of Royal Society of Edinburgh. [sess. 
bands of cholohsematin * were present. There was no distinct 
hydrobilirubin band. It is seen, therefore, that on exposure to the 
atmosphere the biliverdin is reduced ; the bilirubin disappears with- 
out forming hydrobilirubin. 
Experiment II. — Test-tubes were filled with ox-bile, and pieces 
of the mucous membrane of the gall-bladder were added. The 
changes observed were similar to those detailed in Experiment I. 
The mucous membrane seemed to hasten the reduction of the bile 
in its neighbourhood. The reduction of the pigment seemed 
remarkably to coincide in point of time with the establishment of 
putrefaction. The following experiments were conducted in order 
to eliminate putrefactive changes from the other conditions present. 
Experiment III. — Ox-bile was boiled in test-tubes which had 
previously been plugged with wool. No alteration in colour was 
produced by boiling, nor did any take place for seven days. It 
then became of a light brown colour, rapidly fading, until after a 
fortnight it was nearly colourless. Gmelin’s test failed after three 
weeks, and two weeks afterwards the fluid was examined with the 
spectroscope. Cholohsematin bands were absent; there w T as pos- 
sibly a trace of hydrobilirubin. This experiment indicates that 
reduction of the biliverdin takes place, and the bilirubin disappears 
in bile which has been prevented from putrefying. The reduction 
of the biliverdin seems to be hastened by putrefaction. 
Experiment IV. — Ox-bile was evaporated to dryness at 50°. It 
very slowly changed its colour, and only failed to give Gmelin’s test 
after several months’ exposure. 
Experiment V . — Some exhausted and sterilised glass tubes were 
drawn out into capillary points. The points were thrust through 
the wall of a fresh gall-bladder, and broken off by the fingers 'which 
grasped them from without the bladder. They instantly filled with 
bile, and after their withdrawal from the bladder their ends were at 
once sealed up in the blow-flame. No change of colour occurred 
for fourteen days ; the weather was cold and dull. By that time, 
however, they had become brown in colour. No further change 
occurred, and after a year they gave a distinct play of colours with 
nitric acid. 
* Cholohsematin is a pigment which gives absorption bands. It is present 
and often partially replaces biliverdin, in ox-bile. — MacMunn, loc. tit. 
