ASIATIC CHOLERA. Ill 



37. In impure cultures this reaction does not o<vur. 

 The FlNKLER-PllIOR bacillus cultures give after a longer 

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

 tui-K of many other bacilli were trie<l and failed to give 

 this reaction. 1 



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

 tive. In cholera cultures on albumins he obtained indol 

 by distillation with acetic acid. 



Bu.nvn> 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 l>e used 

 lor diagnostic purposes, and will give results before they 

 ean be obtained by plate cultures. 



(4) Impure cultures do not give this reaction. 



DI.MIAM finds the In-st 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 

 percent, tlrbly alkaline peptone solution with salt. JADAS- 

 SOHN finds that gelatin cultures give the reaction both 

 In-tiire and alter the liquefaction of the gelatin. The un- 

 dissolved gelatin, after the addition of hydrochloric or 

 sulphuric acid, Ix-comes rose-violet. 



OoHEH claims that cultures of other bacilli give a similar 

 coloration, but BUJWID explains that the results obtained 

 by Co i IK N were due to the use of impure acids, which con- 

 tained nitrous acid. SALKOWHKI agrees with Bu.iwin, and 

 -t:itis that, when acids wholly free from nitrous acid arc 

 used, the reaction is characteristic of the comma bacillus. 

 He explains the reaction by supposing that the germ pro- 



1 Poehl deserves 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. 



