20 



Scientific Proceedings (109). 



9 (1591) 



Relation of the gentian violet reaction to dilution of implanted 



suspension. 



By John W. Churchman. 



[From the Laboratory of Bacteriology, Cornell Medical School, New 



York City.] 



It has been stated above that if increasingly weak dilutions 

 of suspension of a Gram negative organism (B. coli) be stroked 

 on a divided gentian violet plate relatively few colonies appear on 

 the gentian violet side of the plate and, when very weak dilutions 

 are used, none at all. It has been shown that this is, in part, 

 due to the fact that in a suspension of a Gram negative organism 

 by no means all, indeed, only a small proportion of the organisms 

 may be gentian negative. 



This can hardly, however, be the whole explanation. For 

 if the experiment be repeated, using an emulsion of organisms 

 which have already grown in the presence of gentian violet and 

 have thus proven their resistance to the dye, a similar quantitative 

 phenomenon is observed; far fewer colonies appear on the gentian 

 violet agar than on the plain agar when weak dilutions of the 

 suspension are stroked across the plate. The explanation of this 

 fact is not clear; it may be due to some sort of communal property 

 which enables bacteria, instead of pursuing individual careers, 

 to aid each other in their growth and thus to accomplish in large 

 groups what they cannot accomplish singly. 



10 (1592) 



The effect of repeated re-inoculations of gentian violet agar with 

 gentian positive organisms. 



By John W. Churchman. 



[From the Laboratory of Bacteriology, Cornell Medical School, New 



York City.] 



If a divided gentian violet plate be stroked with a thick 

 suspension of the Gram positive and gentian positive B. subtilis no 



