Epidemics considered with relation to their common nature, and to climate and civilization : in two lectures delivered at the Philosophical Institution, Edinburgh, November 1855 / by Southwood Smith.

  • Thomas Southwood Smith
Date:
1856
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Licence: Public Domain Mark

Credit: Epidemics considered with relation to their common nature, and to climate and civilization : in two lectures delivered at the Philosophical Institution, Edinburgh, November 1855 / by Southwood Smith. Source: Wellcome Collection.

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    Elevated temperature and excessive moisture are combined in tropica] countries ; and they are concentrated in those parts of the tropics in which there are extensive forests having an undergrowth of luxuriant vegetation ; in which the tides of the ocean penetrate deeply into the interior of the land, and mix with the waters of the rivers ; and in which the rivers con- stantly overflow their banks and form marshes and swamps. In tropical countries there are tracts such as these that extend in unbroken continuity hundreds of leagues. The western coast of Africa (the Bight of Benin) presents an un- broken area of upwards of 100,000 square miles, consisting of one vast alluvial and densely wooded forest, irrigated by Atlantic tides, and intersected by numerous rivers and creeks, whose muddy banks are constantly overflowed. In describing a tropical forest, Humboldt says, Under the bushy, deep, green verdure of trees of stupendous height and size, there reigns constantly a kind of half day-light, a sort of obscurity, of which our forests of pines, oaks, and beech trees afford no example ; forming a carpet of verdure, the dark tint of which augments the splendour of the aerial light. With this luxuriance of vegetation is combined a corre- sponding abundance of animal life. The earth and air teem with living creatures. The mould, observes the same distinguished traveller, contains the spoils of innumerable quantities of reptiles, worms, and insects. Wherever the soil is turned up we are struck with a mass of organic substances, which by turns are developed, transformed, and decomposed. Nature in these climates appears more active, more fruitful, we might say more prodigal of life. The air is still more alive than the land. Insects fill the lower strata of the atmosphere to the height of fifteen or twenty feet, like a condensed vapor. It is estimated that a cubic foot of air is often peopled by a million of winged insects, which contain a caustic and venomous liquid, several species being nearly two lines (1.8) long.
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