Page:Popular Science Monthly Volume 23.djvu/671

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INSECTS AND DISEASE.

and inexplicable mystery; a mystery, however, that may be now possibly explained by man's geographical relations with his zoölogical tormentors, the proboscidean diptera.

That malarial diseases occur frequently without the development of malarial melanosis is not difficult of explanation. The disease is not permitted to pursue its natural course; it is interrupted by quinine. The individual, moreover, is clothed, or protected from the sun—an artificial appendage and addition to the organism which the ancestrally inherited powers of adaptation could scarcely anticipate would occur. Possibly, if every ague-patient were exposed to a broiling sun, naked, during the chill, and were then suffered to follow the bent of his successive inclinations during the remaining stages of the disease, the accumulated pigment enlarging the spleen would find its natural and more salutary destination in an even distribution over the cutaneous surface—a phase in the natural career of the disease which seems to be further indicated by the circumstances that the chills of ague only occur, in typical cases, between sunrise and sunset, the paroxysms getting of later and later occurrence, as they are wont to do, until reaching sunset, when the night is "skipped," and the attacks begin early next morning. It seems as if Nature required the sun during the chill, in order that her beneficent purpose of protective cutaneous pigmentation should be carried out.

Although the ethnological bearings of this subject hardly belong to a medical paper, I can not refrain from expressing the suggestion that it is not at all impossible that future study and observation may demonstrate that much of the difference in type between the lowest grade of negro and the most perfect Caucasian white may find its true explanation in the changes produced by an environment of inoculating gnats. Even the characteristic type of the negro skeleton and the capacity of his brain, it is not impossible, may be susceptible of explanation in this manner; for, when we remember that the spleen and its allies are not the only pigment-forming organs, this function being also performed by the marrow of bones, and when we recall, further, the aching of bones that so often attends an ague-chill, in some cases so severe as to have originated the term "break-bone fever," it is not difficult to conceive that the bone-marrow, like the spleen, may become congested during the chill, and in this way, in the course of time, so far lead to modified nutrition of the osseous structures as to set up, finally, a change of type in the embryological formation of the skeleton.

In certain tropical regions it has already been observed by ethnologists that tribes inhabiting elevated regions in the interior are superior to those dwelling on low tracts on the sea-coast, the superiority being manifest both in mental and bodily qualities. The lowlands and sea-coasts, however, are favorite habitats of the fever-producing and pigment-producing mosquito.