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) 

 terras 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 



NH2CI 



When parafuchsin is employed in doses large enough to affect the 

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

 kills it\ 



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

 nuclei intact. The strain was produced by acting upon normal T. brucei with increasingly 

 large doses of the dye. 



