Anilin Dyes and Bacterial Development. 177 



The inhibitory effect is referable to the underlying chromo- 

 phobe group, and the presence of the basic auxochromic groups. 

 If the basicity of the dye is diminished by the replacement of the 

 basic by acid auxochromic groups, or if such groups are introduced 

 in addition to the basic groups, the inhibitory effect is destroyed. 



Of the other classes of anilin dyes an inhibitory effect is pro- 

 duced only by those which contain the chromophonic radicles: 



N< N< R >0, N< R >S and 



I X R— N — , X R X X R X — N — 



and here also, only by those which contain basic auxochromic 

 radicles. Acid dyes possess no inhibitory properties. The most 

 active inhibitory dyes are the triamino triphenyl methanes, while 

 the indamins, the oxazins, the thiazins and azins are on the whole 

 less active in this respect. 



The inhibitory effect does not depend upon the color of the dye, 

 as there are violet acid dyes which are non-inhibitory, and red 

 basic dyes which are markedly inhibitory; similarly there are 

 green dyes which are active and others which are inactive in this 

 respect. The essential common factor evidently is the absence 

 of acid and the presence of basic auxochromic groups. Not all 

 representatives of the sensitive groups of organisms are equally 

 influenced by the dyes in question, nor even by a single dye, nor 

 are the different groups affected to the same extent. Certain 

 dyes will inhibit the growth of all the different sensitive groups, 

 while the effect of others is less extensive. 



The inhibitory action of the dyes in question is most readily 

 explained on the assumption that the susceptible organisms 

 combine with the dyes by means of corresponding nutriceptors, 

 but are unable to cause the cleavage of the anchored molecules, 

 the death of the organism resulting from interference with its 

 normal nutritional (sc. reproductive) functions. Upon this basis 

 a directly toxic effect on the part of the dye need not be assumed. 

 It is in accord with the validity of this hypothesis that dye-resistant 

 strains of susceptable groups exist in nature as such, or may be 

 produced artificially. This was accomplished in the case of 

 certain hay bacilli, staphylococci and streptococci. Upon this 



