n8 Insects and Disease 



Stegomyia occurs in some of the South Sea islands 

 and yet there is no yellow fever there. 



EXPERIMENTS 



We may review, too, a few of the classic experi- 

 ments that have served to show that malaria can be 

 contracted in no other way than through the bite 

 of the mosquito. 



For many years Grassi, an Italian, devoted al- 

 most his whole time to the study of malaria. In 

 1900 he received permission from the government 

 to experiment on the employees of a piece of rail- 

 road that was being built through a malarial 

 region. This was divided for the purpose of the 

 experiment into three sections, a protected zone 

 in the middle and an unprotected zone at each end. 



Those working in the protected zone had their 

 houses completely screened and no one was al- 

 lowed out of doors after sunset except they were 

 protected with veils and gloves. Early in the 

 season they were all given doses of quinine to pre- 

 vent auto-infection. In the unprotected zone no 

 screens were used and every one was allowed to 

 go without special protection. The result for the 

 summer was that there were no new cases of fever 

 in the protected zone. In the unprotected zones 

 practically all had the fever as usual. 



