122 



form and relative proportions of diseased patches on the retina may 

 be determined, but their actual dimensions may probably be de- 

 duced. 



IX. " On the frequent occurrence of Indigo in Human Urine, 

 and on its Chemical, Physiological and Pathological 

 Relations." By ARTHUR HILL HASSALL, M.D., Member 

 of the Royal College of Physicians, Physician to the Royal 

 Free Hospital, &c. Communicated by Professor SHARPEY, 

 Sec. R.S. Received June 10, 1854. 



The present communication embraces some further observations 

 and experiments on the occurrence of indigo in human urine. 

 From these it appears that the presence of that substance is even 

 more common than the author was led to anticipate from his first 

 inquiries, the results of which were communicated to the Society in 

 June last. 



The author furnishes additional proofs of the blue colouring matter 

 in question being really indigo, by converting it into isatine and 

 aniline ; for this purpose it was necessary to obtain the pigment in 

 considerable quantity. 



Contrasting its chemical and physiological relations with hsema- 

 tine and urine pigment, he shows that indigo is closely allied in its 

 nature and origin to those substances, and he considers that when 

 indigo is met with in urine in considerable amount, it forms a vehicle 

 for the elimination of any excess of carbon contained in the system. 

 This view is borne out by the important fact, that the greater 

 number of cases in which indigo has been observed to be developed 

 in the urine in large amount have been cases of extensive tubercular 

 disease of the lungs, and in which the decarbonizing functions of 

 those organs are greatly impaired. 



