272 
MALARIA 
ceptible to this parasite, which would over¬ 
come the difficulties encountered with 
chicks. 
3. Human Malaria 
In testing a drug which has been found 
to be effective against one or more of the 
experimental malarial infections, field trials 
in endemic or epidemic areas, while difficult 
to control, are nevertheless probably more 
satisfactory than tests against induced in¬ 
fections in paretics. Induced infections are 
frequently more sensitive to the effect of 
drugs than are naturally occurring infec¬ 
tions. In addition, it seems unjustifiable to 
test a drug early in an induced infection in 
a paretic because if the malaria is inter¬ 
rupted the patient may be deprived of the 
beneficial effect of the malaria upon an 
otherwise fatal disease. If one waits until 
the paretic has completed the therapeutic 
course of the infection, it is difficult to 
evaluate the effect of a drug because of the 
possibility of spontaneous termination of 
the malaria. 
On the other hand, paretics are suitable 
for the testing of the prophylactic effect of 
drugs which are believed to have a direct 
effect on the sporozoite. If the drug is in¬ 
effective, the patient develops malaria with¬ 
out delay; if it proves effective and he is 
protected against the disease, he can be 
reinoculated with trophozoites. In addi¬ 
tion, when testing prophylactic effect on 
therapeutic malaria, all necessary controls 
such as reinoculation with sporozoites or 
trophozoites are possible. Field experi¬ 
ments could not, of course, be controlled in 
this manner, and such factors as immunity 
due to pre-existing infection could not 
always be ruled out. 
