OF TNDIGO IN HUMAN URINE. 
307 
I have employed the phrases “altered hsematin ” or “urine-pigment,” because it 
does not appear that, by any treatment of the urine with reagents, indigo can be 
developed in healthy urine at will. I have made several attempts with this view, 
rendering various healthy urines alkaline (since the largest quantity of indigo was 
always found in alkaline urines) with potash, soda, lime-water, &c., but without 
obtaining any definite result. 
Reviewing the whole of the cases which have fallen under my observation in 
which indigo has become developed in the urine, there is every reason to believe that 
the occurrence of that substance in the urine is strictly pathological : that it is so 
when in large amount, no doubt whatever can be entertained. Looking to the 
composition of indigo, there is also no doubt that, like bile and urine pigments, 
it forms a vehicle for the elimination of carbon from the system ; and since it 
contains a much larger proportion of carbon than either hsematin, urine or bile 
pigments, we should be led to look for its occurrence in the urine in all those cases 
of functional derangement of any kind in which any impediment exists to decarboni- 
zation, as is the case especially in most diseases of the organs of respiration. 
From the facts which I have already succeeded in ascertaining, there is good 
reason for believing that the above view is, in the main, correct. Turning to the 
history of the three cases of blue urine which first attracted my attention, I find 
that one died phthisical ; the second, though living, has undoubtedly tubercular 
disease of the lungs, with greatly diminished capacity of respiration ; while in the 
third case there have been evidences, although less marked, of lung affection. 
Again, turning to the histories of the twenty cases in which samples of urine were 
set aside for observation, and in four of which samples indigo became developed in 
considerable quantity, I find that these were also cases of phthisis. These facts 
possess the greatest interest, and appear to point clearly to the causes which 
determine the presence of indigo in the urine. 
From other observations not yet completed, it appears, however, that indigo is not 
developed in the urine in all cases of phthisis. If the urine voided be very acid, 
or if the affection of the lungs be of but trifling extent, no great development of that 
substance will take place. Neither, on the other hand, is the occurrence of indigo in 
the urine by any means limited to cases of phthisis, as it may occur in abundance 
in any case, no matter from what cause it proceeds, in which there exists great 
impediment to the elimination of carbon from the system, as in scarlatina, Bright’s 
disease, cholera, &c. 
Indigo is not the only blue colouring matter which has been stated to occur in 
urine, since two or three others have been described by different observers, as 
ferrocyanide of iron or prussian blue, cyanourine and uroglaucin. I now propose to 
contrast the two last of these with blue indigo. 
Prussian blue may of course be readily distinguished from indigo, and it would 
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