497 
in small doses, and there were greater numbers of red blood 
corpuscles. 
Is it not possible, therefore, that atoxyl in small doses, such as 
given to these rats acted not only upon the cells of the body of 
the host, but on the trypanosomes themselves, and acted as a tonic 
to both, so stimulating increased division of the parasites.-' I his 
would explain both the extraordinary division forms of the 
trypanosomes and also the prolonged life of the host without 
attributing to the atoxyl any trypanocidal action whatever. 
It must be remembered, however, that we are working with a 
specially virulent strain of trypanosomes, and that, therefore, it may 
be peculiarly resistant to the action of atoxyl, which drug m 
many cases of human sleeping sickness seems undoubtedly to have 
a favourable influence on the disease. 
Rats 35 and 36 were treated in the cold chamber and received 
atoxyl as well. In our experience, however, we hnd that although 
the cold tends to prolong the life of animals infected witi 
trypanosomiasis to a slight extent it has not, as a rule, any marked 
effect upon the numbers of trypanosomes in the perip aera 
circulation, and thus we attribute the numerous division forms to 
the atoxyl. 
(b) Large doses of Atoxyl. 
We now tried the effect of a large dose of atoxyl on three rats, 
all heavily infected with T. rhodesiense. 
Here wc were guided in our experiments by the wor< 0 0 
and Breinl*, who pointed out that if a cure was to be expectc m 
animals a large dose of atoxyl was necessary. 
fa> 38 .—Piebald, eight p«m. <*. Chart.) Do* ot ! ^ 
panosomes. T. rhodesiense _ 
Day 
Number of Trypanosomes per 
c.mm. ‘...I 
Atoxyl 5 per cent, solution ... — 
Leucocvtes . — 
6,162 
1005. 
IT 
* Memoir XVI, Trypanosomiasis research, pp 
, n _ Sch. of Trop. Med., Liverpool, October, 
lasts research, pp- ^ 5/1 * 
