146 INFECTIONS OF THE DIGESTIVE TRACT 



The explanation of the chemical basis of the Ehrlich 

 aldehyde reaction of the faeces is not yet wholly sat- 

 isfactory. Baumstark l thought it could be ascribed 

 to the indol of the faeces and based a quantitative 

 method for indol on the reaction. Bauer, 2 however, 

 showed that the faeces contain another substance which 

 reacts with the aldehyde, and claims that this substance 

 is urobilinogen. I reached a similar conclusion inde- 

 pendently, after noticing that the faeces in one instance 

 gave an intense red reaction after the indol had been 

 distilled off. In other cases a strong reaction was ob- 

 tained in spite of the fact that the faeces were free from 

 indol from the outset. That the reaction from this non- 

 volatile part of the faeces depends wholly on urobilino- 

 gen does not appear to me to have been convincingly 

 shown. It is true, however, that one may reduce 

 urobilin (Schuchardt's) with alkali and zinc dust and 

 thus obtain a substance which gives a stronger and 

 more characteristic Erhlich aldehyde reaction than 

 the urobilin itself. Probably both urobilinogen and 

 a skatol derivative are implicated in the Ehrlich 



1 " Bestimmungen der Faulniss Produkte im Urin und in dem 

 Faces mit Beniitzung der Ehrlichschen Aldehydreaktion," 

 Munch, med. Wochenschr., 1, p. 722, 1903; also Arch. f. Ver- 

 dauungskrankh., ix, p. 201, 1903. 



2 This distillation should be conducted in an atmosphere of 

 carbon dioxide in order to prevent oxidation of the reacting sub- 

 stance, which is sensitive both to air and to the action of sunlight. 



Bauer fell into error in claiming that the reaction from the 

 faeces is not due to indol and that the method does not serve 

 for the detection of this substance. I am confirmed in this 

 view by Ury ("Die Ehrlich'sche Reaction im Stuhl," Zentralbl. 

 f. innere Medizin, xxvii, p. 41, 1906). 



