Page:Popular Science Monthly Volume 47.djvu/115

Rh. The poor man, by different forms of inanition, overwork, exposure, or uncleanliness, is liable to derangements of the lungs, liver, kidneys, bowels, etc. Like the rich man, he has a pathology special to certain organs, and different from that of the other, but which is due to his social sanitary situation.

The professions also entail their special maladies, which are liable to infect those who exercise them. Lead chemically poisons those who handle it—painters, printers, white-lead makers, etc.—and mercury is dangerous to silverers of glass and gilders; while each poison affects particular organs most directly—lead the kidneys, bowels, and brain, mercury the brain and nerves. Examples might be multiplied to show how the profession may injure the organs, create real diseases, or induce an imperfect condition of health which will facilitate the invasion of the microbe. It is not necessary to dwell here on the pathogenic effects of alcoholic intoxication—a condition which is in every feature the product of social influences. It ravages all classes of society, and is illustrated in the most various pathological modalities.

In short, we find that a great multiplicity of mechanisms, all of social origin, may affect the internal organs in their structure or their work, and bring the person into a condition of receptivity to microbes. A thousand social conditions may expose us to the invasion of microbes and thus make real the second term required to constitute an infectious disease. The hostile microbe is in fact everywhere—within and without us, seeking, we might say, what it may devour. All the natural cavities of the body—the nose, the mouth, and the digestive tube—having exterior openings are seeded with microbes brought from without by air or food, and afterward multiplied. The skin is similarly exposed. Among these microbes there are also others, the relics of infectious diseases, with which the subject, now well, has been formerly attacked. All these microbes live in the normal condition of a later life; they are sometimes useful, as we have seen in regard to digestion; more frequently inoffensive in the face of the resistance opposed to them by the cellular coverings of the organic cavities or by the activity of those zealous defenders of the organism, the white globules, or by the chemical action of the organic liquids. But when the texture of these coverings is modified by some of a variety of circumstances, whether of external or of internal origin, or when one or more of the microbes attain an unusual degree of virulence, then the protective barriers will be overcome, the microbe will penetrate to the interior of the tissues, and will be able to bring on some of a great variety of diseases, from pneumonia to erysipelas, meningitis, or liver disease.

The microbes living without the organism are likewise of