ROSS AND MALARIAL FEVER 141
the gray mosquitoes (Cvlex fatigans), which, as he says, "practically proved the mosquito theory of malaria/' He confirmed his results hy a long series of differential experiments, which he transmitted to Laveran and Manson in letters of April 22, 1898, and after some interruptions, he discovered at Calcutta, on July 8, 1898, that the spores of the parasites were concentrated, not in the intestine, as he and Manson had supposed, but in what proved to be the salivary gla/nd of the mosquito.
The exaet route of infection of this great disease, which annuaUj" slajs its millions of human beings and keeps whole continents in darkness, was re- vealed. These minute spores enter the salivary gland of the mosquito, and pass with its poisonous saliva directly into the blood of men. Never in our dreams had we imagined so wonderful a tale as tliis.s
In confirmation of this, he infected a large number of sparrows with Proteosoma from gorged mosquitoes and his results were communicated by Manson to the British Medical Association in July, 1898. They at- tracted wide attention among the scientific experts but were absolutely ignored by the governmental and military authorities. Colonel Boss, his financial resources exhausted by these investigations, determined upon leaving India and returned to England in Februaiy, 1899. Shortly afterward, he was appointed fiist lecturer on tropical medicine at the newly created Liverpool School of Tropical Medicine, and here a new phase of his life work began.
In this year (1899), the Italians B. Orassi and A. Bignami gave con- clusive evidence that the malarial parasites develop only in the Anopheles mosquito^ and the causal relation was now definitely established. The next step lay in the direction of preventing the disease.
In August, 1899, Eoss was sent out by the Liverpool school to inves- tigate the West African coast fevers at Sierra Leone. Landing there on August 10, he soon found that two species of dapple-winged Anopheles (A. costalis and A. funestas) are the agents of transmission, and he im- mediately proceeded to establish for the first time the fundamental prin- ciples of the prevention of tropical malaria, viz., the culicidal treatment of the stagnant pools which were found to be the breeding places of Anopheles, scrupulous drainage of the soil, screening of buildings with wire gauze, isolation of the sick, and the habitual employment of mos- quito nets and punkahs by individuals. In 1901, he fitted out another West African expedition to Lagos, which, owing to the unscientific, un- practical and unenthusiastic attitude of the government, was paid for by private philanthropy. At Lagos, the marshes were filled up with sand from the lagoons, wire netting for houses and cinchonization of individ- uals were instituted, and an annual subscription of £150 was obtained from the leading merchants for the organization of a mosquito brigade,
sBoes, op. dt,, p. 572.
• B. Grassi and A. Bignami, Ann, dHg. sper,, Boma, 1899, N. S., IX., 258-264.
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