150 



Scientific Proceedings (53). 



thirty-six were found to be gram negative. This is in harmony 

 with most of the observations heretofore recorded, although a 

 contrary statement is made with reference to B. rhinoscleromatis 

 by McFarland 1 and by Page. 2 When studied by means of the 

 gentian violet agar plates, twenty-nine of the thirty-six cultures 

 were found to grow equally well on plain agar and on gentian 

 violet agar. Seven others, however, behaved differently. No 

 growth could be obtained on the gentian violet agar side of the 

 divided plates. Churchman has mentioned the fact that certain 

 bacteria when stained will not grow on one culture medium but 

 might grow on a more selective medium. The seven strains that 

 refused to grow on ordinary gentian violet agar were then planted 

 on serum agar violet, and three of them grew on serum agar violet, 

 although they had refused to grow on ordinary violet agar. The 

 other four did not grow even on the more favorable medium and 

 behaved in the same way as most of the gram positive bacteria. 

 Thinking the substitution of a selective culture medium for 

 ordinary medium in the case of certain of the gram positive bacteria 

 might result in a change in the action of gentian violet on their 

 growth, B. diphtheria and streptococcus were planted on serum 

 agar violet plates, and on agar violet plates. Both plates failed 

 to show a growth on the violet side. 



Of the three microorganisms that grew on serum agar violet, 

 two have remained constant, growing well on serum agar violet 

 but not at all on ordinary agar violet; the third one, however, 

 has shown a very interesting adaptation. The culture is one of 

 B. pneumonia Friedlander from the Krai collection. This bacillus 

 when grown on a plate containing serum violet and agar violet 

 can be induced to grow on agar violet once it has started to grow 

 on serum violet; if, however, the growth is started from the 

 opposite side of the plate on plain agar, it cannot be made to grow 

 on violet agar. The experiment was made by putting in one 

 plate culture, serum agar, serum agar violet, agar violet, and plain 

 agar, the different media merging into one another in a petri dish. 

 The behavior of the microorganism is thus shown to be inconstant 

 toward gentian violet, depending on the culture media on which 



1 McFarland, "Pathogenic Bacteria and rotozoa," 7th edition, 1912, p. 785. 



2 Page, Journal Medical Research, Vol. XXVI, No. 3, July, 1912, pp. 489-499. 



