OF INDIGO IN HUMAN URINE. 
.309 
singular that I should so frequently have met with indigo in urine, the occurrence of 
which has hitherto been deemed so rare, and not have fallen in with a single case 
of cyanourine or uroglaucin, the presence of which might be considered, from the 
inquiries of Braconnot, Scherer and Heller, to be so much more common. 
Taking into consideration then the whole of the facts and observations recorded 
in this communication, the following conclusions remain to be deduced : — 
1st. That blue indigo is frequently formed in human urine; the quantity being 
subject to the greatest variation. In some cases it is so considerable as to impart a 
deep green or bluish-green colour to the whole urine, and to form a pellicle of nearly 
pure indigo over the whole surface of the liquid. In others the blue scum is formed, 
but the urine itself does not become either blue or green ; and occasionally the 
quantity is so small, that it can only be detected by means of the microscope. 
2nd. That for the formation of this indigo, it is in general necessary that the urine 
should be exposed to the air for some days in an open vessel, when oxygen is absorbed 
and the blue indigo developed. Whatever facilitates therefore oxygenation, as free 
exposure to light, air, and warmth, hastens the development of the blue indigo ; 
hence in summer the changes described take place much more quickly than in 
winter. On the contrary, these changes are retarded, and even altogether prevented, 
by a more or less complete exclusion of oxygen. By this exclusion, blue indigo is 
deprived of its colour ; and it may be reduced or reformed, alternately, according as 
air or oxygen is excluded or admitted to urine containing it. From one or two 
cases elsewhere recorded, however, it would appear that blue indigo is occasionally 
formed in the system, and is voided as such in the urine. 
3rd. That there is usually, but not always, found with the blue indigo, where the 
amount of this is very considerable, a brown extractive, sometimes in large quantity, 
which closely resembles haematin in its chemical manifestations and elementary 
composition ; the aqueous solution of this, when exposed to the air, yields a further 
supply of coloured indigo. 
4th. That the urines in which the coloured indigo occurs in the largest quantities 
are usually of a pale straw-colour, readily becoming turbid ; they are alkaline, and of 
rather low specific gravity. Small quantities of indigo are, however, frequently found 
in urines possessing characters the very reverse, that is, in such as are high coloured 
and of high specific gravity ; but as a rule, the blue pigment is usually absent from 
these urines, and in only a few cases is it formed in them in any considerable amount. 
5th. That between haematin, urine-pigment, and indigo very close chemical and 
physiological relations exist, rendering it highly probable that the indigo formed in 
the urine is in many cases immediately derived from altered or modified haematin 
or urine-pigment. Urine-pigment is itself usually regarded as but a modification of 
haematin. 
6th. That the chemical composition of indigo would lead to the inference that 
when that substance is present in large quantities in the urine, it forms a vehicle for 
