267 
because there are fewer parasites present, but also because 
developmental, resistant forms have not yet been produced ; we also 
suspect that it is to such resistant forms that recurrences are often 
due.*-*-® . , 
Control animals of the same species which remained untreated 
were inoculated at the same time as the treated animals in every 
instance where the therapeutic effect of any drug was tried ; and in 
experiments with Trypanosoma gamhiense, additional controls were 
inoculated from the experimental animal just before its treatment 
was commenced, to definitely prove for each experiment the \iru enc 
of the infecting parasite. u • u i; t 
The Atoxyl used came from the Charlottenburg firm which hrs 
manufactured the drug. Unless it is otherwise stated, it was us 
ma freshly-made five per cent, solution in water previously sterilized 
at 100° The Mercury bichloride was usually employed in a one 
per cent, solution in water. The poisonous dose of each substance 
for the species of animal employed was always ascertaine 
preliminary step to experimentation, and the largest possi e 
therapeutic dose was used in each instance. Save when 
stated, all drugs were given subcutaneously. 
The routine examination of the blood was made in res 
quarter inch square coverslip preparations of bloo rom 
ear according to the animal. The blood of important animals was 
centrifugalised whenever it seemed necessary, as, or examp , 
trypanosomes could not be found in the blood by the ordma y 
examination, althoug’h the temperature was elevate ■ ® ..Ipnt 
the first ten days or fortnight succeeding completion of the tt^titmen 
the animals were examined daily. As they lived 
examinations became less frequent, until they were 
mately weekly or, in the case of experiments made wi , 
twice weekly. The blood in the less successful 
ex-periments, for example, the donkeys, was examined ^ 
the whole time these animals were under observation. The blood 
of any animal evidently ill was, of course, immediately 
if trvpanosomes were not seen, subinoculations were a 
Subi'noculations of considerable quantities of blood 
at intervals from animals which had been apparently suc«ssMy 
treated. All such subinoculated animals were kept iindei observati 
