2IO The Control of Mosquitoes 



them. The niunber of Anopheles caught in the 

 cars, which were surrounded by mosquito breed- 

 ing places, reached 1800 a week. The malaria 

 incidence in these camps was but slightly above 

 the incidence for the Canal Zone shown in the 

 table. It will be observed that in 1910 the 

 malaria incidence was two one hundredths of one 

 per cent, less for the camps, and in 191 1, three 

 tenths of one per cent, more, as gauged by admis- 

 sions to the hospital. It must be remembered, 

 however, that the percentages for the whole Zone 

 are based on the final diagnoses made by the exam- 

 ining physician. Experience has shown that the 

 examining physicians sometimes give a provisional 

 diagnosis of malaria in a somewhat larger number 

 of cases than the final diagnosis sustains. 



Another instance of the application of this 

 prophylactic measure under more favorable condi- 

 tions occurred near Corazal. In this case the 

 camps were remote from native habitations. In 

 June, 1908, several hundred United States marines 

 were quartered for two months on Diablo Hill. 

 During that period the malaria incidence among 

 them averaged fourteen per cent, a week. No 

 mosquito catching was done. Some cars in which 

 railroad laborers lived were located at the foot 

 of the same hill. Prom the early part of May to 



