OF INDIGO IN HUMAN URINE. 
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rendered green and opalescent by boiling. These reactions show that the brown 
pigment was somewhat like hsematin in its chemical manifestations. 
While the aqueous solution of the colouring matter was undergoing evaporation, 
it gave a further supply of indigo, which was formed most freely at the edge of the 
liquid. The residue was made black by concentrated sulphuric acid and deep brown 
by potash. 
The blue colouring matter . — The two samples of this, when subjected to analysis, 
were in a dry state, and were mixed with a large quantity of earthy phosphates, 
Vibriones, mucus and epithelium ; one of them gave a dark brown solution with con- 
centrated sulphuric acid, and the other a dirty blue. Both of these solutions were de- 
composed by water, furnishing in the former case a dark brown deposit, and in the 
latter a dirty green. In their other reactions, however, they presented the charac- 
ters of indigo; and it is especially deserving of notice that they were reduced by 
lime and grape-sugar, giving a liquid from which hydrochloric acid threw down a 
greenish-blue precipitate. 
The cause of concentrated sulphuric acid giving with one of these samples a brown 
solution, and with the other only a dirty blue, was, no doubt, mainly owing to the 
large quantity of animal matter, mucus, Vibriones and epithelium with which the 
specimens were contaminated. The acid, from its charring effect on this, would 
produce a brown or blackish solution, thus obscuring the colour of the solution of 
sulphate of indigo. 
The brovm extractive . — The brown extractive yielded nearly the same results as 
on its first analysis, when deposited on the evaporation of the filtered urine ; and 
the aqueous solution, as before, furnished a few blue flocculi. A portion of the alco- 
holic extract was treated with potash, for the purpose of ascertaining whether it 
contained leucine ; and the product, on the addition of hydrochloric acid, gave off 
a powerful odour, which ^as somewhat like valerianic acid, but the result was too 
doubtful to be of much value. I have already referred to the peculiar smell of 
valerian emitted by the extractive of more than one of the samples. 
We have thus then obtained tolerably conclusive evidence that the blue colouring- 
matter in this case was indigo. 
It was not very long after the occurrence of the first case of blue urine that other 
cases fell under my observation. 
To the second case, as to the first, I was led by accident. A sample of urine left 
for some days exposed to the air gradually changed colour, the urine turning 
bluish-green, and its surface becoming covered with a bluish scum. As before, a 
series of samples of this urine was set aside, the changes which ensued being noticed 
from time to time. 
The specific gravity and reaction of the first sample of urine set aside, were not 
taken at the time it was passed. After it had been exposed to the air for about ten 
days, the following was found to be its condition. An irregular and broken scum 
