THE CAUSES OF DISEASE.
Daily observation demonstrates that the human structure, even in its most perfect formation is liable to lesions of organization and derangment of function, producing that state of the system in which its usual actions or perceptions are either interrupted or attended with pain—this state is called disease. Every animal carries within itself the germ of its own destruction, or, in other words, it is formed for a limited existence. Many diseases, therefore arise spontaneously, or without any assignable external cause; but many more are produced by causes, over which we have some control, and perhaps the chief source of the physical ills to which we are liable, is the deviation we make from the simplicity of nature. The injurious influence that domestication has upon the health of the lower animals is very strikingly apparent; and in proportion as their subjugation is more complete, and their manner of life differs more widely from that which is natural to them, so are their diseases more numerous and severe. The diseases of our more valuable domestic animals are sufficiently numerous and important to employ a particular class of men; and the horse alone has professional assistance appropriated to him. Men of education and talent have devoted themselves to the investigation of the diseases of this noble and useful creature. The poor little canary birds confined in their prisons, are very liable to disease, more especially inflammation of the bowels, asthma, epilepsy, and soreness of the bill. No animal deviates so far from the simplicity of nature in its habits, as man; none is placed under the influence of so many circumstances, calculated to act unfavourably upon the frame. His morbid affections are hence abundant and diversified, as may be seen by referring to the different nosological arrangements; these long catalogues of diseases affording strong evidence that man has not carefully followed that way of life which has been marked out for him by nature. The crowded state of the inhabitants of large cities; the injurious effects of an atmosphere loaded with impurities; sedentary occupations; various unwholesome avocations; intemperance in food; stimulating drinks; high-seasoned and indigestible viands (and these taken hastily in the short intervals allowed by the hurry and turmoil of business); the constant inordinate activity of the great central circulation, kept up by the double impulse of luxurious habits and high mental exertions; the violent passions by which we are agitated and enervated; the various disappointments and vexations to which all are liable, reacting upon and disturbing the whole frame; the delicacy and sensibility to external influences, caused by heated rooms, too warm clothing, and other indulgencies; are all contrary to the voice of nature, and they produce those morbid conditions of the system which a more simple and uniform mode of living would prevent. Our associates of the animal kingdom do not escape the influence of such causes: the mountain shepherd and his dog are equally hardy, and form an instructive contrast between a delicate lady and her lap-dog; the extreme point of degeneracy and imbecility of which each race is susceptible. In the early ages of society man enjoyed long life, his manner of living was simple, his food, habitation, and pursuits, were all calculated to fortify the body, and no anxious cares disturbed his mind.
Curtis's Essay on the Deaf and Dumb.