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46
THE POPULAR SCIENCE MONTHLY

are ill for years from malaria, and their capacity for work greatly reduced, and they may finally die from some other trouble.

 

Yellow Fever and Mosquitoes

As early as 1881, Dr. Charles Finlay, of Habaria, noticed a correspondence between the abundance of mosquitoes and the prevalence of yellow fever, but it was not until 1900, when our soldiers occupied the island of Cuba at the time of the Spanish War, that experiments were conducted proving that the disease is transmitted chiefly if not wholly by a mosquito, Stegomyia calopus. The investigating committee was appointed by Surgeon General Sternberg, and consisted of Messrs. Reed, Lazear, Carroll and Agramonte.

A small house was built and effectually screened against the entrance of all mosquitoes. A circulation of air was also prevented and all sunlight excluded. A temperature of 76.20° F., with a moist air, was maintained for sixty-three days—just the conditions favorable to the spread of bacterial diseases. Moreover, clothes, blankets and bedding which had been used by yellow fever patients and not cleaned were put into the building and used by the inmates. Seven non-immunes were kept in this house, two or three sleeping in one room with the contaminated bed-clothing, for about twenty nights, then shifts were made and other subjects placed under the same conditions. All seven were released from quarantine in excellent health at the end of sixty-three days, not a single case of yellow fever appearing. Formerly, contaminated clothing, bedding, etc., were regarded as a dangerous source of infection and were usually burned.

Another similar building was erected by these investigators and was divided into two large rooms, one admitting air and sunlight freely and containing the mosquitoes which had previously bitten yellow fever patients. In this room six out of seven persons bitten came down with yellow fever. From the other room mosquitoes were excluded, and the occupants remained in perfect health. These tests still more strongly confirmed previous experiments implicating the mosquito in transmitting yellow fever, and acting on this knowledge General Wood issued orders requiring the use of mosquito bars at the barracks and for the destruction of mosquito lame in the breeding pools by the use of petroleum. This work, in charge of Colonel Gorgas, was carried out thoroughly, and continued until Habana was a comparatively healthy city. Mosquito extermination has everywhere been practised-—fumigating buildings with tobacco or sulphur to kill the adults, and draining and filling the pools or applying oil to kill the larvæ or wigglers. Of 26,000 of these mosquito breeding places within the city limits in March, 1901, only 300 remained in January, 1902.[1] More-

  1. W. C. Gorgas, "A Few General Directions with Regard to Destroying Mosquitoes." Government Printing Office, Washington, D. C, 1904.