318 
more purple in colour than usual, and with a slightly altered band, 
and it was only after considerable expenditure of time that I 
discovered that part of the urobilin was present as its mercury 
compound owing to the administration of calomel. 
Another variation which gave rise to great difficulty is that the 
urobilin, obtained by the extraction of the faeces with acidulated 
water, proves very refractory at different stages in the process of 
purification and separation, described by Garrod and Hopkins— 
indeed we have as yet failed to get a reasonably pure product from 
the faeces and so possibly the figures obtained may later require 
revision. 
1 he urobilin was extracted by repeated shaking with large 
amounts of water, acidulated with dilute sulphuric acid, and the 
filtrates were fully exposed to daylight for some time, before being 
estimated by the same method as was adopted for urinary urobilin; 
this solvent has the advantage that it does not take up bile pigment 
01 chlorophyll to any extent, and only on one occasion (later 
extracts of a case of blackwater fever) did I find any definite band 
other than that of urobilin, though other writers seem to have found 
such extra bands very frequently when using different solvents. 
Another point of interest is that in such literature as I have 
discovered on faecal urobilin, the writers seem to convey the 
impression that it is present in small amounts and requires somewhat 
delicate tests for its identification. Only in McMunn’s papers did 
I find descriptions of solutions comparable in colour and spectroscopic 
appearances to those with which I had become acquainted, and in 
which, as a general rule, a very high dilution was necessary before 
the general absorption was overcome ; and the urobilin band was the 
only one ever distinguished save in the instance referred to in the 
ast paragraph, when a band was also present embracing the D line, 
probably due to haematoporphyrin. 
From Case 23, lor example, nearly two litres of acidulated extract 
were obtained in which there were visible: — 
'• Acid Ur °bilin Band to a dilution of 
2 . Mercury ,, 
, !> 
3. Pink colour of mercury urobilin „ 
4- Fluorescence with Zinc Chloride „ ... 
100 volumes. 
120 „ 
800 
3°o „ 
