CHAPTER III.

Influence of Climate and Season in modifying the Diseases of Mankind.

"The time may come when, guided by yet undiscovered knowledge, new and more direct principles, the tendency to tubercular and other morbid formations, may be surely checked, chronic inflammations cured, and fever suspended in its first movements."

CONOLLY.

A COMPLETE history of the mode in which the diseases and mortality of the human race are modified by external temperature, regimen, clothing, habitations, employments, and the various modes of living, would afford more practical information in regard to the causes, prevention, and right method of treatment, than all the systems that have been invented within the last two thousand years; for it would enable us to reduce the heterogeneous and chaotic mass of facts that constitute the sum of Medical Literature, to the certainty of an exact science. And that such an important undertaking might be, to a great extent, accomplished in a short time, by the combined exertions of a few enlightened individuals, is manifest from what has been recently done in

Great Britain by the Reports of Major Tulloch, and those of the Registrar General, aided by the judicious researches of Mr. Farr and other statisticians.

The diseases of man are no less modified by climate and season, than the various mechanical, chemical, and physiological operations of our planet,—being as different in the tropical portions of Africa, India, South America, and the West Indies, from what they are in the temperate and higher latitudes, as are the botanical and zoological characters of those regions.

The following tables, constructed from the Reports of Tulloch, laid before both Houses of Parliament, exhibit the average annual ratio of mortality per 1000 mean strength of the British troops serving in different parts of the world, from 1817 to 1836, omitting epidemic cholera.

DISEASES OF MANKIND.

781

TABLE II.

Exhibiting the average annual ratio of Mortality per 1000 of Black Troops serving in the West Indies, Sierra Leone, and the South-east coast of Africa.

Thus we perceive, that in Great Britain, the Canadas, Nova Scotia, and New Brunswick, about one half of the mortality is from diseases of the respiratory organs; whereas in the warm climate of the Mediterranean, they form about of the whole, in the West Indies nearly 4,-and not 1 part among the white troops in tropical Africa. We are also informed by Tulloch, that in the East Indies, where the mean annual mortality varies from seventy to ninety per 1000, nearly the whole was from fever, dysentery, cholera, diarrhæa, and disease of the liver :-that among 74,850 native troops serving in Madras, the mean annual ratio was only one per 1000 from all diseases of the lungs; and but 24 in the Mauritius and at St. Helena. We further learn from the last edition of Dr. James Johnson's work on the Diseases of Tropical Climates, that from 1827 to 1836, the proportion of deaths from diseases of the respiratory organs was of

the whole at Calcutta,-at Chinsurah,-and at Berhampore. In north Africa, the mortality from phthisis is still less, according to M. Guyon, a medical officer of the French army, who states that from 1838 to 1841, it was only of the whole among the Moors at Algiers, among the Jews, and about among Europeans.

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But why is it, that the mortality from diseases of the lungs is so much greater among negroes of the West Indies, than among Europeans? And why are the latter so much more liable to fevers when removed to tropical climates, than the natives? The solution of these queries must be sought in the radical difference of organization of men and other animals in cold or temperate, and in hot climates. For example, we have seen that owing to the high temperature of tropical Africa, for the greater part of the year, during the heat of the day, respiration is proportionally diminished, and the lungs exercised less, than in colder climates, by which the size of the thorax is accommodated to the wants of the system; so that when removed to the West Indies, where the maximum temperature is from 10° to 20° lower, the natives of Africa are unable to obtain caloric from the atmosphere by respiration, as fast as it is abstracted by the surrounding media, especially in the high lands, or during the prevalence of northerly winds, and early in the morning when the air is damp.

DISEASES OF MANKIND.

783

The consequence is, that under such circumstances, they are often found shivering with cold; but never complain of the most intense heat of the sun, which is no less delightful to their feelings than conducive to health :-that during winter when northerly winds prevail, and the air is much cooler than at any other season, they are extremely liable to catarrh, influenza, pneumonia, pleurisy, and other diseases of the lungs, including rheumatism, eruptive fevers, dysentery, diarrhea, colic, and tenanus,—all of which are brought on by exposure to cold damp air, a shower of rain, and often by sleeping in damp clothes, by which the circulation through the lungs and general system is greatly diminished and perspiration checked, followed by congestion of the stomach and bowels, or of the pulmonary organs. Nor is it until several generations after his removal to a colder climate, that the thorax of the African is developed to the same extent as that of the European; so that, like the monkey, the lion, tiger, and leopard, he is proportionally subject to diseases of the lungs. On the other hand, as the lungs are more exercised in temperate and cold climates, the thorax is more highly developed among the whites, who therefore obtain a larger amount of caloric by respiration, ceteris paribus, by which they are enabled better to resist the influence of a low temperature. But for this very reason, when removed to the burning climate of