ASIATIC OHOLEEA. Ill 



37°. In impure cultures tliis reaction does not occur. 

 The Finklee-Pkior bacillus cultures give after a longer 

 time a similar, but more of a brownish coloration. Cul- 

 tures of many other bacilli were tried and failed to give 

 this reaction.^ 



Briegee found that this color is due to an indol deriva- 

 tive. In cholera cultures on albumins he obtained indol 

 by distillation with acetic acid. 



BuJWiD has made a further contribution to our knowl- 

 edge of the " cholera-reaction." His conclusions are as 

 follows : 



(1) Five to ten per cent, of hydrochloric acid added to 

 cholera cultures produce a rose-violet coloration, which is 

 characteristic of the comma bacillus. 



(2) No other bacterium gives the same coloration under 

 the same conditions. 



(3) The coloration appears in such cultures which are 

 from ten to twelve hours old, so that this test can be used 

 for diagnostic purposes, and will give results before they 

 can be obtained by plate cultures. 



(4) Impure cultures do not give this reaction. 



Dunham finds the best medium for the " cholera-reac- 

 tion " to be a one per cent, alkaline peptone solution with 

 one-half per cent, of common salt. BuJWiD prefers a two 

 per cent, teebly alkaline peptone solution with salt. Jadas- 

 sohn finds that gelatin cultures give the reaction both 

 before and after the liquefaction of the gelatin. The un- 

 dissolved gelatin, after the addition of hydrochloric or 

 sulphuric acid, becomes rose-violet. 



Cohen claims that cultures of other bacilli give a similar 

 coloration, but Bujwid explains that the results obtained 

 by Cohen were due to the use of impure acids, which con- 

 tained nitrous acid. Salkowski agrees with BuJWiD, and 

 states that, when acids wholly free from nitrous acid are 

 used, the reaction is characteristic of the comma bacillus. 

 He explains the reaction by supposing that the germ pro- 



• Poehl deaeryee the credit of being the first to call attention to this 

 reaction, though his work was evidently unknown to Bujwid at the time 

 when the latter published his report. 



