THE PREPARATION OF CULTURE MEDIA 171 



vestigations, differs from other bacteria in being able to grow in 

 the presence of quantities of violet which inhibit other Gram-positive 

 species. Dysentery bacilli show variations. They found, however 

 that, in addition to gentian violet, Hoffman violet, crystal violet, 

 dahlia violet, fuchsin, rosanilin and methyl violet will inhibit Gram- 

 positive but not Gram-negative bacteria in dilutions of from 1 to 

 5000 to 1 to 50,000. 



