Page:Popular Science Monthly Volume 23.djvu/674

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With regard to Tasmania, it may also be observed that the native inhabitants are universally of one color—absolutely black—which would suggest a previous history of malarial disease to which a prolonged succession of generations has finally secured complete adaptation and consequent exemption from symptoms. How far the eucalyptus-tree, which here abounds, Las been instrumental in correcting malarial disease, also deserves consideration. Possibly the sticky, pendent leaves, and camphoraceous odor of the plant are not conducive to the prosperity of the mosquito genus.

The Dismal Swamp, so far from being exempt from mosquitoes, is said to abound with them during the autumn. Alexander Hunter, writing in "Potter's American Monthly," July, 1881, page 15, says: "The mosquitoes were in uncounted millions; they came armies on armies, waves upon waves, clouds upon clouds, and charged in platoons and single file, and threw themselves with bloodthirsty voracity upon every living thing in reach." On the same page, however, his negro guide, "Bob," is made to say that he reckons he would be quite fat "but for the 'skeeters and chills." Another writer ("Harper's Magazine," vol. xiii, 1856, page 450) refers to an hotel having been erected for a summer resort in the "Dismals," but "before the month of August visitors, servants, and proprietors had all cleared out and left the place in full possession of the mosquitoes and yellow flies. These insects are said to be savage enough to worry the life out of a mule. . . . The hotel was taken down."

In so far, therefore, as regards the geographical relation between mosquitoes and malarial disease, it may be said: 1. The two often coexist; 2. There is no decided proof that localities alleged to be exempt from ague are also exempt from mosquitoes; 3. There is no locality noted for malarial disease where mosquitoes or other bloodsucking insects do not exist.

In those isolated cases of ague occurring during the winter or early spring, before inoculating insects have made their appearance, there may of course be other modes of inoculation. We have only to admit the production of the bacillus malariæ, its transmission in the air and its deposit upon the skin, to see how easily it may be inoculated into the body by accidental wounds, such as pin-scratches, the cut from a pocket-knife, or of a razor in shaving, etc. Furthermore, it is generally admitted by medical authorities that the period of inoculation after the poison is introduced into the system may, exceptionally, extend weeks and even months before symptoms are developed. In these, or in some other ways, the isolated winter cases referred to may therefore be explained without necessarily conflicting with the mosquito theory. Finally, it seems incredible that a function so necessary to life as respiration—a function that can not be suspended in any atmosphere—should be the means of infecting the body with a fatal disease. It was surely never designed that breath-