^9 
Ehrlich and Bertheim have published the details of their chemical 
work, showing that the arsenic radicle is in the para position to the 
NH3 group. 
Moore, Nierenstein and Todd show that Atoxyl is not, as it was 
originally described, an anilide of metarsenious acid, but is an 
exceedingly stable chemical substance with the arsenical radicle 
directly attached to the benzene ring. It was shown that the aqueous 
solution is strongly dissociated electrolytically, giving in consequence 
an apparently low molecular weight by the freezing point method 
and possessing a high electrical conductivity. Except on standing 
in aqueous solution, it is a most stable compound, and neither aniline 
nor arsenic are easily detachable from its molecule by chemical 
means. 
Its toxic properties are neither those of arsenic nor of aniline even 
when pushed to excess, and its therapeutic action is rapid ; from this 
and its high conductivity, showing high dissociation, the conclusion 
was drawn that its activity must be ascribed, not to free inorganic 
ions or to free aniline, but to a complex organic ion containing both 
the arsenical and aniline radicles, 
Since the introduction of Atoxyl for the treatment of trypano¬ 
somiasis a large number of observers have tested it, and all are now 
united in giving it the premier position as a trypanocide. 
• The results of most observers upon the treatment of sleeping 
sickness by Atoxyl alone completely confirm the results stated above 
as having been obtained by Thomas and Breinl in the experimental 
trypanosomiasis of animals. Thus, cases have been described which 
were apparently permanently benefited and might be described as 
cured, but in a great many of them recurrences were observed, and 
finally the infection became persistent, the trypanosomes becoming 
‘ Atoxyl-fast ’ and being apparently no longer affected by the drug. 
Quite recently a second distinct advance has been made in the 
experimental therapeutics of trypanosomiases by workers of the 
Liverpool School. This consists in treating infected animals, from 
which the trypanosomes have primarily been driven out of the 
blood by the use of Atoxyl, by a second drug, so as to prevent the 
recurrences which so often follow Atoxyl treatment alone. 
The general principle underlying the combined method of treat¬ 
ment by two successive and quite different drugs is that when an 
