722 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
peared. Havana, which was overrun with yellow fever, is to-day 
healthful. Entire regions of Italy where malaria was endemic, 
are entirely freed from it. One can thus judge of the enormous 
progress realized by the prophylaxis resulting from this single zo- 
ological discovery, the rdle of mosquitoes in the propagation of dis- 
eases. It is true that equally brilliant results have not been obtained 
in connection with diseases transmitted by other insects, but the 
example of the mosquitoes justifies great hopes, and it is only proper 
to remember that the biological study of tsetse flies and fleas is 
hardly more than begun. 
Much remains to be done in a branch of medicine where progress 
is necessarily slow, for it is specially concerned with exotic tropical 
diseases, which can only be well studied on the spot by the aid of 
missions, not only dangerous, but also very expensive. 
In closing, I can affirm that the friends of science can never put 
too much money at the disposal of those students who devote them- 
selves to the study of colonial medicine. 
= 
