Insects and Human Health 529 



In Italy. With the opposition of medical practice to the 

 new theory advanced by Ross and others, a series of practical 

 tests was made to demonstrate its truth. A test undertaken by 

 an Italian scientist, Grassi, was to prove that the bite of the 

 Anopheles is the only way of transmission of the disease, and 

 also to formulate a set of rules which should banish malaria 

 from Italy. A group of railroad workers, about four hundred 

 men, women, and children, lived in a malarial district near 

 Salerno. Their cottages were equipped with screens, and the 

 people remained within doors from sunset until dawn, pursuing 

 their regular work during the day. The result was that all 

 individuals escaped infection, although three experienced a 

 recurrence of the disease. 



Another experiment made by four medical authorities of 

 London was carried out in a notorious malarial district, in the 

 Roman Campagna. In a house which they had built and made 

 mosquito-proof they remained from shortly before six o'clock 

 in the evening until broad daylight in the morning. A careful 

 observation showed that the female Anopheles appeared regu- 

 larly at sunset, and never during the day. By day they visited 

 the villages of the neighborhood, examining many cases of 

 malaria, and were exposed to bad weather. They kept the 

 windows of their house open day and night so as to admit the 

 miasmic air of the marsh ; but they developed not the slightest 

 trace of malaria. They exposed themselves to all possible 

 ways of infection except the bite of the mosquito, and took 

 no quinine or other drugs as preventives. This demonstra- 

 tion carried great weight with many medical men and others ; 

 but another test was made to establish the theory beyond any 

 doubt. 



In England. Dr. Manson, a son of Sir Patrick Manson 

 who had advanced the hypothesis that malaria is transmitted 

 by blood-sucking insects, and Dr. Warren, both London 

 physicians, undertook the crucial test. They allowed them- 

 selves to be bitten by Anopheles mosquitoes which had 



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