1889.] 



Skatole in the Vegetable Kingdom. 



215 



recognised in very dilute solutions, but the production, under the 

 same conditions, of a reddish colour or precipitate is a sensitive test 

 for the presence of indole. 



By far the most delicate reaction for skatole consists in the deve- 

 lopment of a cherry-red colour when an aqueons solution is warmed 

 with a few drops of strong hydrochloric acid. This reaction has been 

 obtained with very dilute solutions. In moderately dilute solutions, 

 strongly acidified with hydrochloric acid, a saturated solution of 

 picric acid produces a red precipitate of skatole picrate. 



The occurrence of skatole in the vegetable kingdom is of especial 

 interest, and it is remarkable that the substance should make its 

 appearance, or, at any rate, that it should accumulate, at a late period 

 in the growth of the tree. The absence of indole is also significant. 

 Sometimes skatole, without indole, is observed to result from the 

 putrefaction of animal proteid, but usually both indole and skatole 

 are formed. The occasional absence of indole, as well as the incon- 

 stancy of the relation between the quantities of indole and skatole 

 formed duriug proteid putrefaction, has led Salkowski (' Zeits. fur 

 Physiol. Chem.,' vol. 8, p. 417) to regard the formation of each of these 

 substances as due to the intervention of a special ferment, which he 

 has called the indole ferment and the skatole ferment respectively. 

 It must be remembered, however, that indole is less stable than 

 skatole, and would be less likely to survive the effect of the various 

 chemical changes which are proceeding during the later stages of putre- 

 faction. Hoppe-Seyler (' Zeits. fur Physiol. Chem.,' vol. 8, p. 214) has 

 shown that if oxygen is freely supplied to a liquid in which proteid 

 putrefaction is taking place, neither indole nor skatole is formed. 

 The superior stability of skatole may possibly explain its survival in 

 the plant. It would be interesting to determine whether indole is 

 present in Geltis reticulosa at an earlier stage of its growth, as, for 

 example, at the period when the skatole first makes its appearance. 



It would also be of the highest biological and chemical interest to 

 discover if possible the exact source of the skatole in this plant, to 

 determine whether the vegetable proteid of Geltis reticulosa can be 

 made to yield skatole by the methods which are known to lead to its 

 production from animal proteid, or whether the skatole has been 

 formed from some intermediate substance, as, for example, an 

 amidated organic acid. The synthetical production of skatole from 

 nitrocumic acid furnishes us with a clue to one possible mode of 

 formation in the plant. 



This investigation has been conducted in the Research Laboratory 

 of the Pharmaceutical Society, and my thanks are due to Mr. W. A. 

 Salter for the assistance he has given me with some of the experi- 

 ments which are recorded in this paper. 



