For many years Grassi, an Italian, devoted almost 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 railroad 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 allowed 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 prevent 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.
Fig. 102—Salt-marsh mosquito (O. lativittatus) standing on a table.
Fig. 103—Anopheles hanging from the ceiling.
In the same year two English physicians, Sambon and Low, went to Italy where they built a cabin in one of the marshes noted as being a malaria pest-hole. The house was thoroughly screened so that no mosquitoes could enter, but the windows were always open so as to admit the air freely day and night. Here they lived for three months, out of doors as much as they pleased during the day but inside where they were protected from the mosquitoes at night. No quinine was used and no fever developed, although all about them other people were having the fever as usual.