28 



Dr. C. A. MacMunn. Researches into the 



that lie can produce urobilin, or, as he called it, hydrobilirubin from 

 bilirubin, the red colouring matter of human bile ;* and, although his 

 researches have been called in question by some physiological chemists 

 who profess to have repeated his experiments with a negative result, 

 yet the conclusions drawn by him are practically correct, and have 

 led, in my hands, to the discovery of urobilin in the bile of various 

 animals, in human urine, and to its complete isolation from the latter 

 fluid. 



Most specimens of high-coloured urine, provided the high colour is 

 not due to blood or unchanged bilirubin or biliverdin, show, when 

 examined with the spectroscope, a dark band at F, which disappears 

 completely when the urine is treated with ammonia, and which is 

 moved towards the red end of the spectrum by treatment with solution 

 of caustic soda. The band can be made to reappear after the am- 

 monia treatment by the addition of nitric, hydrochloric, or acetic 

 ,acid. 



Since almost all specimens of urine which I examined showed 

 a band at F, I had concluded that this band was due to urobilin, but I 

 could not account for the fact that ammonia did not always cause its 

 disappearance. I now find that there are two pigments in urine ivhich 

 give a hand at F. This discovery was made while I was engaged in 

 studying urobilin, for, on treating normal human urine, which was of 

 a pale straw colour, in the same manner as that adopted for the 

 separation of urobilin, I found a pigment of a brownish colour, which, 

 when dissolved in ether, gave two faint bands, one of which was 

 placed over F, the other between b and D (see 18 of figure). The band 

 at F was not made to disappear by ammonia, nor did acids intensify it. 

 As a similar band is found in blood serum, in yelks of eggs, in butter, 

 cheese, &c, which is due to Thudichum's "lutein," I see no objection 

 in accepting that author's name, urolutein, for- this pigment. My 

 object in mentioning this is to call attention to the fact that urobilin 

 is not the only pigment which gives a band at F ; but urobilin appears 

 to be the only pigment which behaves on treatment with acids and 

 alkalies in the manner I have described. The presence of this 

 pigment urolutein in urine containing urobilin as well, has also led to 

 the statement which appears in some text-books of physiological 

 chemistry, that caustic soda, when added to urine containing urobilin, 

 causes two bands to appear. The reason is, that caustic soda moves 

 the urobilin band towards the red, but leaves untouched the band of 

 urolutein ; consequently, two bands are seen instead of one. "When 

 urobilin alone is present, ammonia causes the complete disappearance 

 of the band at F, and caustic soda moves it towards the red. Accord- 

 ingly, a preliminary examination will enable us to determine whether 



* By reduction with sodium amalgam and subsequent treatment with hydro- 

 chloric acid. 



