210 



Mutation in Micro-Organisms 



The orthoquinoid linkage appears to be the important thing in these 

 substances. Those drugs with it act upon the kinetonucleus : those 

 without it have no action. (Many dyes and other substances were tried 

 in this respect, e.g. atoxyl, arsenophenylglycin, trypan-red, etc.) It 

 must be noted, however, that dyes with a structure which Ehrlich (1909) 

 terms paraquinoid {e.g. parafuchsin) also have a slight action upon the 

 kinetonucleus. These dyes have the general structure : 



parafuchsin being a derivative of triphenylmethane with the structure : 



NH, 



NH^CI 



NH, 



When parafuchsin is employed in doses large enough to affect the 

 kinetonucleus, it also injures the rest of the Trypanosome, and finally 

 kills ii\ 



' The parafuchsin-resistant strain of Ehrlich, kept at the Speyer Haus, has its kineto- 

 nnclei intact. The strain was produced by acting upon normal T. briicei with increasingly 

 large doses of the dye. 



