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June 13, 1908


JAMA. 1908;L(24):1959-1963. doi:10.1001/jama.1908.25310500007001a

In the course of investigations made on the urine of a child suffering from a chronic intestinal bacterial infection, it was noticed that the addition of concentrated hydrochloric acid to the urine led to the development of an intense rose color. The study of this color reaction showed it to be identical with the reaction described in 1882 by Nencki and Sieber as the urorosein reaction.1 Although there has been considerable discussion as to the nature of this reaction, its exact nature has, up to the present, been left in obscurity. In the course of my study of the patient just mentioned it was determined that the mother substance or chromogen from which the urorosein is derived is a definite substance arising in the intestinal tract from the breakdown of tryptophan by bacteria. This substance is indolacetic acid. Further study has shown that the occurrence of indolacetic acid in