Page:The Scientific Monthly vol. 3.djvu/145

Rh it by experimental demonstrations. In 1895, he received the triennial Parkes Memorial Prize of 75 guineas and a gold medal for the best essay on "Malarial Fevers: their Cause and Prevention," Hanson and Sir Almworth Wright being among the judges of the eleven essays presented. This essay simply summed up what he had learned from Manson.

Lancisi and his succesors held that the malarial parasite or poison may somehow be carried from the marshes to man by mosquitoes. Manson, applying the analogy of his theory of the transmission of filariasis by the mosquito, thought that the insect carries the parasite from man to the marshes, laying her eggs on the surface of the water and dying in the act of doing so. He inferred that the embryos of the malarial parasite infect man by the digestive tract through the drinking of contaminated water. But long before Manson had taken up this hypothesis, it had been completely disproved by the Italians, Marchiafava (1885), Marino (1890) and Zeri (1890), whose careful experiments showed that it is impossible to infect healthy persons by the ingestion of water from the marshes. When Laveran investigated the malarial parasite in 1880, he found that certain large cells in the withdrawn blood give off long motile filaments, like the tentacles of the squid, which were supposed by Grassi, Bignami and other Italians to be the effect of the death agony of the parasite in vitro. Manson inferred that these filaments are in reality flagellate spores which escape from the parent parasites taken from the patient's blood by the mosquito and develop into the matured forms afterwards found in other malarial blood. So far, his theory explained how the parasites escape from the blood of an infected patient into the external world via the mosquito. But the important question was, how do they get into the body of a healthy patient and infect him with malarial fever? Boss soon found, like the Italians before him, that the hypothesis of the infection of the alimentary tract by drinking water falls to the ground completely. The real point of attack was obviously the motile filaments. He began his work at the malaria-ridden post of Secunderabad in 1895. In prosecuting his researches, he had first to devise methods for collecting, classifying, feeding, breeding and dissecting the mosquitoes themselves. He soon found that his Indian insects fall into three general classes, the brindled mosquitoes (Stegomyia), the gray (Culex) and the dappled or spotted-winged (Anopheles). He caused mosquitoes hatched from larvæ of these varieties to bite malarial patients and tried to find the parasites in the bodies of these insects, which were obviously free from malarial or other extraneous parasites of any kind. For two years, with constant improvement of technique, he labored at this problem without much success, his work being interrupted by a year and a half's detail to fight a cholera epidemic at Bangalore and by the Afridi War. At Bangalore, he made some inoculation experiments with mosquitoes upon Mr. Appia, assistant surgeon of the Bowring Civil