Page:Popular Science Monthly Volume 23.djvu/669

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INSECTS AND DISEASE.

work. (See also p. 416 of Dr. Johnson's work, and p. 15 of Dr. W. J. Evans on "Endemic Fevers of West Indies," 1837.)

Dr. Oldham ("What is Malaria?" p. 172) tells us that the Jeevas of the Punjaub, employed in fishing and catching wild-fowl, spend the whole night in their boats, under the reeds of the marshes, "unharmed in the midst of malaria"; but they are wrapped from "head to foot" in a peculiar costume that completely envelops them, and which they always put on at sunset; and, moreover, a smoldering fire is kept up in the boat.

It is almost needless to add that, while these nets, curtains, etc., can hardly be conceived to intercept marsh-air, they certainly can and do intercept and protect from mosquitoes.

18. Malaria spares no age, but it affects infants much less frequently than adults.

The child in utero has even been alleged to suffer from ague when its mother was affected: she has felt it, as she supposed, shivering or executing spasmodic movements during the paroxysm, and such infants have been born with enlarged spleens. Nevertheless, it is a matter of daily observation that the sucking infant is less liable to malarial disease than older children and adults.

Young infants, however, be it remembered, are usually carefully housed, and in summer their beds or cradles are generally provided with mosquito-curtains to keep off house-flies, and they may thus be protected from mosquital inoculation. Furthermore, since the human infant, in savage life, and without the artificial protection of gnat-curtains, would be presumably helplessly exposed to mosquito-bites, it would not surprise us if Nature had given the infant some inbred eccentricity by which the inoculations would be rendered harmless; just as the bite of the African tsetse-fly, which will destroy cows and oxen, is perfectly harmless when inflicted upon the sucking calf, as attested by Burton, Livingstone, and Stanley.

19. "Of all human races the white is most susceptible to marsh fevers, the black least so."

The black man, however, is not entirely exempt, and is probably more secure in his native clime than in the United States and other civilized countries to which he has been imported. Acclimatization is alleged to be the proper explanation of this exemption. The negro, it is said, is born in a country where he is obliged almost incessantly and universally to breathe malarial emanations; he is descended from ancestors who, from prehistoric times, have lived in such poisoned air; he has thus become acclimatized to it more than any other race, and on this account is able to prosper in places where the white man would suffer for a long time (see Quatrefages's "Human Species," p. 223, Appletons' "International Scientific Series"). But we are not told in what this acclimatization consists. Will the mosquito theory furnish any probable explanation?