ON SPECIFIC THERAPEUTICS. 83 



a number of similar dyes belonging to the ben- 

 zidine series, some of which possess an even 

 more powerful action than trypan-red. In 

 several cases a blue dye belonging to the same 

 group, which was prepared by Nicolle and 

 Mesnil, has proved still more efficient. 



The value of arsenic acid which has for a 

 long time been employed in the treatment of 

 trypanosome diseases was first recognised by 

 Laveran. Later on it was discovered, at the 

 Liverpool School of Tropical Medicine, that 

 atoxyl was a far more powerful substance. It 

 is prepared by treating aniline with arsenic 

 acid. The makers believed it to be an anilide of 

 arsenic acid, i.e., a compound in which the 

 arsenic acid radical is supposed to be attached 

 to the amido group in a similar manner as the 

 acetic acid is present in acetanilide. Now, as 

 you all know, the ammonia radical, which in 

 aniline is very ready to react, has completely 

 lost this property in acetanilide. This latter 

 body is in fact almost an indifferent compound. 

 Similarly, by the view that atoxyl was the 

 anilide of arsenic acid, any further development 

 of this compound was rendered impossible. I 

 was, however, able to prove, together with 

 Dr. Bertheim, that this compound is to be 



G2 



