Page:Popular Science Monthly Volume 23.djvu/675

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657
INSECTS AND DISEASE.

ing the indigenous air of any natural environment should be, and without warning of danger, a means of death. Such a supposition is inconsistent with that general beneficence of Nature as exhibited in the signals of danger, instinctively recognized by all living things, when contemplating their natural enemies, and when in the presence of conditions that are destructive to life.

Man naturally loves beautiful things—woman and the flowers. But the serpent also is beautiful—superficially smooth, tapering in form, elegantly elastic, absolute in symmetry, undulating in motion, every element of beauty in woman finds its counterpart in the snake; yet we love the one, loathe the other—loathe it because we have inherited the instinct that tells us it is one of our natural enemies, whose touch is destruction; and, when sight is not sufficient, the rattle is added, so that even in darkness we may hear the warning note of danger.

When man is prompted by Nature to invade a swamp in pursuit of fowl and fish, his natural foods, it can not be that the silent air he breathes shall, like a subtle enemy, and without any admonition, destroy his life. But when night comes, should he there lie down to rest, the annoying puncture of the mosquito and its siren-song, like the warning note of the serpent's rattle, would emphatically and persistently tell him, "This is no place to sleep!"

The mosquital origin of malarial disease is in this respect, therefore, more in accord with the beneficence of Nature's arrangements than is the conception of malarial fevers being produced by the respiration of a marsh-vapor.

I have before referred to "color-protection" as a means of defense' from natural enemies. Acuteness of audition is another well-known, means. It curiously happens that some forms of fever are followed in those who convalesce by a remarkable acuteness of hearing, which lasts for weeks and months, thus indicating another phase of adaptation to environment, an additional means of recognizing the warning note of the inoculating mosquito, or other insects inaudible to ordinary ears. Dr. J. B. Allan refers to this symptom in his description of a remittent fever prevailing on the African sea-coast ("Monthly Journal of the Medical Sciences," August, 1841, page 545). He says: "The acuteness of hearing sometimes came on during the second day in those who recovered. It was very distressing for the first six weeks or two months of convalescence; and every wave that burst on the distant reef was counted with pain and even dread."

If the mosquital origin of malarial fevers be correct—if protection from mosquital inoculation protects from ague the means of prophylaxis from malarial disease will not be difficult. It comprises the following items:

1. Personal protection from all winged insects, especially during evening and night, by gauze curtains, window-screens, or clothing im-