INFECTIONS OF THE DIGESTIVE TRACT 273 



of cases the pigment which is separated from the urine 

 is blue in color. In the case of rabbits the substance 

 separated from the urine is red in color and represents 

 the presence of indirubin, a substance closely related to 

 indigo. It often happens in indigouria that both these 

 substances are present together. The onset of the indigo- 

 uria in dogs has been observed after three or four hours 

 from the time of the administration of the indol, but the 

 phenomenon is at its height after six or eight hours have 

 gone by. 



Porcher and Hervieux claim to have detected the 

 presence of indoxyl in the urine of dogs which had been 

 given experimental indigouria. It is thought by them 

 that the indoxyl-potassium-sulphate (which they call 

 the indigouria chromogen) is decomposed with the lib- 

 eration of indoxyl. In herbivorous animals, such as the 

 horse and the rabbit, the phenomenon of indigouria is 

 said not to be a rare occurrence. In the horse the pigment 

 consists of a mixture of indigo blue and indigo red, or 

 indirubin, whereas in the rabbit the coloring matter 

 is indigo red. It is stated that the occurrence of the 

 phenomenon of indigouria in these herbivorous animals 

 is not necessarily connected with any evidence of illness. 

 I believe there is at present not the slightest evidence that 

 the phenomenon of indigouria occurs in man in a state of 

 health. There seems to me no evidence that indigouria 

 depends on the presence of free indoxyl in the blood and 

 urine. It is much more likely that it is a phenomenon 

 dependent on the spontaneous oxidation of indoxyl- 

 potassium-sulphate in the urine in those cases in which 



