v.] VARIOUS SPECIES OF COMMA-BACILLI. in 



comma-bacilli in broth at 37 C. show already after twelve 

 hours' incubation, on the addition of the amount of 5 to 10 

 per cent, of common hydrochloric acid (also nitric or sulphuric 

 acid) a characteristic pink colouration which rapidly increases 

 in intensity during the first half hour ; it lasts for a few 

 days, and exposed to light changes into a brownish tint. 



Dr. E. K. Dunham has shown 1 that for this reaction the 

 presence of peptone is essential, and that the pink colour 

 becomes more pronounced and more rapidly evident if 

 instead of HC1, concentrated sulphuric acid be employed. 

 A previous addition of a drop of nitric acid enhances the 

 reaction, which under this condition can be obtained also 

 with Finkler's arid Deneke's comma-bacilli. Salkowski had 

 previously shown that this reaction is due to the formation 

 of indol and a trace of nitrite. 



Zeitschr. fur Hygiene, II. 2, p. 337. 



