344 Infectivity of G. palpalis Fed on Sleeping Sickness Patients. 
drug can render a patient non-infective to the fly. It will be seen that 
this case had been under treatment for one month, and had been injected 
with four doses of trypanocidal drugs. The tsetse flies were infected 25 days 
after the last of the four injections had been administered. 
Therefore, it may be said that to treat Sleeping Sickness patients with 
injections of soamin and perchloride of mercury, as specified, does not 
necessarily cause their blood to be incapable of infecting Glossina palpalis 
with Trypanosoma gambiense, and that flies so infected can transmit the 
disease to monkeys. 
The percentage of flies infected from untreated cases was not ascertained, 
as only 190 flies were dissected, at various intervals, after feeding on their 
patients, and none were found infected. 
A total of 857 flies were dissected; at different periods, after having fed 
upon treated cases, and four of these were found to be infected, 7.¢. a per- 
centage of 0-46. These four flies all came from a cage containing 100 
Glossina palpalis which had been fed on three occasions upon the only 
treated case that proved infective to the flies, vede Table IV, Experiment 2034. 
This patient therefore infected 4 per cent. of flies—an interesting and 
important fact. 
It was hoped that patients under the influence of trypanocidal drugs 
would be incapable of infecting tsetse flies. Unfortunately, this experiment 
(2034) is sufficient to show that Sleeping Sickness patients under treatment 
with arsenical compounds, etc., are not always innocuous to the fly, and 
should not be allowed their freedom to wander about the country during 
intervals of comparative good health, but must be kept completely and 
permanently isolated from all possible contact with the fly. 
Conclusions. 
1. Glossina paipalis fed on natives suffering from Sleeping Sickness, and 
untreated by drugs, may become infected and be capable of transferring the 
disease to healthy animals. 
2. Glossina palpatis fed on natives suffering from Sleeping Sickness, and 
treated by arsenic and other drugs, may also become infected and be capable 
of transferring the disease to healthy animals. 
