NATURE
OF
CONTAGION.
That the Reasonableness of any Method, which shall be proposed to prevent the spreading of Contagious Diseases, may the better appear, it is necessary to premise somewhat in general concerning Contagion, and the Manner, by which it acts.
Contagion is propagated by three Causes, the Air; Diseased Persons; and Goods transported from infected Places.
We shall therefore first enquire what alteration of the Air it is, that makes it infectious; and then, by what Means it communicates its noxious Quality to other Bodies.
The ancientest and best Authors of Physick, who lived in a Country more exposed to these Calamities than ours, observed the Constitution of the Air, which preceded Pestilential Fevers, to be great Heats attended with much Rain and Southerly Winds[[1]]: And one of Them takes particular Notice, that no other than a moist and hot Temperament of the Air brings the Plague; and that the Duration of this Constitution is the Measure of the Violence of the Distemper[[2]].
The Natural History of several Countries confirms this Observation; in Africa particularly, if Showers fall during the sultry Heats of July and August, the Plague ensues thereupon, with which whosoever is infected hardly escapes[[3]].
It has besides been remarked in all Times, that the Stinks of stagnating Waters in hot Weather, putrid Exhalations from the Earth; and above all, the Corruption of dead Carcasses lying unburied, have occasioned infectious Diseases.