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XIII. On the frequent occurrence of Indigo in Human Urine , and on its Chemical, 
Physiological, and Pathological Relations. By Arthur Hill Hassall, 
M.D. Lond., Member of the Royal College of Physicians, Physician to the Royal 
Free Hospital , 85c. Sfc. Communicated by Professor Sharpey, Sec. R.S. 
Received June 10, 1854, — Read June 15, 1854. 
SlNCE I had the honour of communicating to the Royal Society in June last*, the 
results of my investigations on the frequent presence of indigo in human urine, I 
have continued to follow up the subject, and this, I trust, with some interesting and 
important results. 
First. After some difficulty, I have succeeded in obtaining the blue pigment in 
question in considerable quantity, so as to allow of its being subjected to further 
experiment, with the view of furnishing additional proofs of its being really indigo ; 
and second, I have succeeded in determining the cases in which this pigment occurs 
most frequently and abundantly, and its probable source. 
The present communication comprises these additional particulars and observa- 
tions, together with the chief facts connected with the occurrence of indigo in the 
urine which have resulted from my previous investigations. 
Remarkable cases of variously-coloured urine have been described from time to 
time ; such instances have, however, hitherto been supposed to be of extremely rare 
occurrence, more than a single example of the kind but seldom falling under the 
observation of any one individual ; they have also been regarded rather as curiosities 
and extraordinary anomalies, than as physiological and pathological facts, which, if 
rightly understood, are full of the deepest interest and importance. 
Although several cases of coloured urine have been described, two only, in which 
the colouring matter has been at all satisfactorily proved to be indigo, have been 
recorded. 
The circumstances which led to the investigations recorded in this communication 
were the following : — Some four or five years ago, when examining urinary deposits 
under the microscope, I frequently noticed in the field of vision, particles of a deep 
blue colour. So often did this occur, that I could not even then help suspecting that 
their presence could scarcely be accidental ; however, no analysis of the blue colour- 
ing matter was at that time made, and the circumstance was in a fair way of being 
forgotten, until the recollection of it was renewed by another occurrence. 
In June 1852 , a sample of urine freely exposed to the air in an open vessel, was 
* See Proceedings of the Royal Society, June 16, 1853. 
2 Q 
MDCCCLIV. 
