External Conditions of Plague. Sanitary Conditions and Plague.
External Conditions of Plague
The nature of the soil has little influence on plague. It may flourish in alluvial deltas, on calcareous ridges or granitic mountains. Moisture in the soil has generally been though to be an important factor in its production, but, though often found in marsh situations, such as the banks of the Nile, the Euphrates or even the Volga, it also occurs in India at elevations approaching 7000 feet, and in Kurdistan at 5000 to 6000 feet above the sea.
The temperature most favourable to plague is a moderately high one. The disease is unknown in the tropics. When prevalent in Egypt it was said never to penetrate farther south than Assouan. It has not crossed the plains of India within historic times. Where the disease does occur, a temperature of 80° to 85° or more, combined with absence of moisture, usually stops the epidemic. In Egypt it was observed to cease as an epidemic almost suddenly about the 22nd to 24th of June, and not be begin again till September. In Irak [Iraq] it dies out suddenly during the summer. When the temperature rises above 86° it begins to diminish; and it ceased abruptly at a temperature of 113°. In India it has been observed by Dr Francis when the temperature of his tent was 83° to 95°, or in a grass hut to 105°, while the air was moist ; but he thinks a lower temperature with dryness renders the poison inert.
On the other hand, in northern countries, the disease is usually checked by the cold of winter, starts up in the spring, and is most active in August and September. To this rule there have been remarkable exceptions, such as the epidemic on the Volga in 1878 79, which raged during severe winter weather, and the great plague of Moscow in 1770.
Sanitary Conditions and Plague
Of all the co-operating causes of the plague, uncleanliness is the most powerful, -- meaning by this the accumulation of decaying animals matter around human bodiels or dwellings. The saturation of the soil with filth is perhaps the most important point. A plague seat in Mesopotamia is thus described by Colvill:-- " The ground is so saturated with moisture that the refuse of the village is neither absorbed nor evaporated, but
acquires the form of a bluish-black oily fluid, which surrounds the huts and covers the paths, and stains the walls 2 feet from the ground ; and in fact that village is in such a state of filth that it requires to be seen to be believed." Of the people among whom the Pali plague of India raged it is said "they were filthy beyond conception" (Francis). There can be little doubt that European cities in the Middle Ages, and down to the 17th century, presented very similar conditions. These conditions maybe considered to act by supplying a suitable environment for the life and growth of the organized poison (or bacterium) outside the human body. Where these are wanting one of the main in the spread and permanence of the disease will be absent, a fact which makes it probable that increased cleanliness is the chief cause of the disappearance of plague from Europe.
Overcrowded dwellings, especially with deficient ventilation, greatly favour the spread of the disease; but this is not necessarily correlative with density of population, and plague may flourish in thinly-peopled countries.
Of social conditions poverty has by the most powerful influence on the spread and development of plague. Many plague epidemics have followed on years of famine, or been connected with destruction of crops and cattle. The races among which the disease is endemic are almost without exception under-nourished, if not destitute. In the villages on the Volga there appeared to the writer, in 1879, to be little destitution, though the diet of the people was very meager. In all city epidemics the poor are the chief or almost the only sufferers. This is as true of Baghdad in the 19th century as it was of London in the 17th. Those of the upper classes who have been attacked have been chiefly doctors, clergy, officials, and others whose occupations take them among the sick.
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