1910.] Treatment of Animals infected with Trypanosomes. 229 
Small repeated doses of atoxyl in this strain of trypanosomes actually 
stimulate division of the parasites. This conclusion is arrived at by the 
fact that in Rats 35 and 36 the number of parasites increased with great 
rapidity in the peripheral blood, and examination of the smears showed 
numerous trypanosomes in process of division. Many were found dividing 
into four. | 
It is interesting to note that the animal which died of pneumonia was 
living in the animal house. Rats 35 and 36 were treated in the cold 
chamber. As an explanation of the above, namely, the prolonged life of the 
animal and the rapid multiplication of the trypanosomes, we would venture 
to suggest the well known tonic action of arsenic when given to man in 
small therapeutic doses. In small repeated doses arsenic in man, both 
in health and disease, increases the strength, weight, and appetite, and 
we would argue that small doses of atoxyl in rats raised the natural body 
resistance. 
In Rat 34, which lived 27 days, treated with small doses of atoxyl, we 
find that the period between the crests of the waves in a graph repre- 
senting the numbers of trypanosomes was certainly larger than in those of 
the untreated animals of this same strain. Here two high crests occurred 
in the graph corresponding to intervals of 5 days and 10 days respec- 
tively. | 
This may probably be explained by the action of the atoxyl in 
small repeated doses raising the resistance of the host. The doses given 
to this animal would represent in man approximately 8°38 grains, 16°76 grains, 
and 25:14 grains. 
We find that Gies* treated young rabbits with arsenic and found that 
those treated weighed more, had larger bones and more developed muscles 
than the untreated controls. These facts would explain the prolonged life 
of the animal, and we could at the same time attribute the increased activity 
in division of the trypanosomes to the small doses of atoxyl acting as a tonic 
to the trypanosome cells. 
(2) Large Doses of Atoxyl.—We now treated three rats with large doses of 
atoxyl. In this we were guided by the excellent work of Dr. Wolferstan 
Thomas in his investigations on the action of drugs in trypanosomiasis. 
We gave 0°5 c.c. of a 5-per-cent. solution of atoxyl subcutaneously, and we 
caused the trypanosomes to disappear from the blood of one rat in 24 hours. 
In this rat the weight was 202 grammes, and if we calculate this dose to 
the body weight of a man, it would be necessary to give over 130 grains of 
atoxyl to a patient weighing 70 kilogrammes. 
* Cushny’s ‘ Pharmacology.’ 
