C. DOBELL 



209 



There is a point of considerable interest in connexion with the 

 dyes which bring about the disappearance of the kiuetonucleus in 

 Trypanosomes : for there appears to be a definite relation between 

 the chemical structure of the dye and its action upon the Trypanosome. 

 Werbitzki found that those dyes which destroy the kiuetonucleus are 

 substances belonging to the pyronin, oxazin, and acridin groups (" ani- 

 line " dyes with acid chromophores). These dyes all possess a structure 

 which Ehrlich (1909) calls an orthoquinoid structure. Orthoquinoid 

 substances possess a structure which is essentially thus: 



That is to say, they consist of two benzene rings united together as 

 shown. Dyes of the pyronin series have the general structure : 



Those of the acridin series have the structure : 



Both the pyronins and the acridins are derivatives of diphenylmethane. 

 This is not the case with the dyes of the oxazin group, however, which 

 have the general structure : 



and are diphenylamine derivatives. 



