To return: to modern science, above all to Liebig, the practical chemist par excellence, we owe the discovery of the true office of ulmine or humus in vegetation; it nourishes the plant before it is in a position to draw its nourishment from the atmosphere. The vegetation called antediluvian had this peculiar character, that it enabled the plant to be greatly independent of roots and soil; its broad-leaved foliage sought everywhere for food in the carbonic acid of the atmosphere. Accordingly all the plants were remarkable for the smallness of their roots, which generally have disappeared, and are now no longer to be found.
Let me now consider briefly—keeping the same object in view, namely, its influence on man—what are the sources and results of that amount of hydrogen or azote which plays so important a part in the economy of all that lives.
An agricultural farmer at a distance from markets sufficiently remunerative, has a large field of turnips which he knows not how to dispose of. Not having cattle or sheep sufficient to consume these turnips, he addresses himself to drivers of sheep on the way to the markets, inviting them to turn their sheep into the field, and there remain until the turnips are consumed. Thus he hopes to restore to the field the azotized and other principles removed from it by previous crops, and to prepare the way for fresh and more productive and profitable crops. It is on the same principle that in many leases of farms (those called steel-bow) there is an express clause that the straw shall not quit the farm, but be consumed on it. The object of this is simply to restore to the soil what forced crops have removed from it. Man has taken on himself the task of growing on one acre the natural produce of many; to feed twenty men instead of one from off the same extent of soil; to live in crowded cities, drawing their provisions from the surrounding country, producing nothing of themselves; to feed millions where nature intended but a few thousands should exist; he has taken the task on himself and must carry it through, exposed to destruction at every false step, and at this moment exposed to the accusation by the medical authorities of England of deliberately rendering his farm-house, his homestead, his cottage, his mansion, his palace, a pesthouse, the propagator, if not the absolute generator, of all the wide-spread plagues and pestilences, from that which desolated Athens in the time of Thucydides; laid waste the Roman world when Justinian reigned; smote England in the most unhappy and disgraceful period of past history;[42] and now, appearing amidst the tents of an obscure Arab tribe, ignorant of agriculture, living with their flocks and herds on the desert, happily remote from the influences of boards of health, officers of health, and registrars-general, once more threatens Europe; he is accused, in fact, of being the involuntary but certain slaughterer of his little babes. So says the eloquent Registrar-General of England in one of his sanitary reports; he belongs, it is true, and this must not be forgotten, to the theory-loving fraternity,[43] a professor, in fact, of that conjectural art which heretofore despised statistics, and which now, by mistaking figures for facts, threatens to convert true science into a scheme of fictions anything but brilliant. To the Chadwicks, the Gavins, and a host of others still more potent, but who always act through the agency of employées, we owe the affair of Luton and of Birmingham, of the disgraceful condition of the Thames and of innumerable other localities; the deodorizing schemes of Leicester and Bristol, the intercepting scheme of the Thames, and the network of officers of health, amounting to 2600, now spread over England for the benefit of this tax-loving country.
If you hope to raise a crop you must replace in the soil certain elements which previous crops have removed from it. So says Liebig, and to some extent the experience of mankind supports the view.
The refuse of men and urinals which English speculators recommend you to throw into the nearest river, or into the sea if you can, or at least to deluge well with water before throwing it over your fields, the Belgian farmer places as nearly as may be under ground until required. Of it he forms a compost, seemingly inoffensive as being in some measure buried, trapped, and mixed with house refuse, and other materials. This compost, to which he looks in due time for the restoration to his well-managed farm of that which abundant crops had removed from it, he spreads at convenient and suitable times on his ground, into which it is speedily dug; thus at every step he reverses the theories of the would-be agriculturists of England, and should it be said that the measures he adopts are injurious to his health, destructive to his family, sources of pestilence to the country, we have the sure and trustworthy statistics of a true statistician[44] to oppose to the wild theories and bold assertions of the needy adventurers and hired officials who, clamouring so loudly for place and distinction, have chosen for the field of their tactics broad England and her colonies.
CHAPTER IX. ON POISONS, MIASMS AND CONTAGIONS.
§ 1. Although the amount of disease and mortality traceable to accidents, to the ordinary atmospheric changes of which the thermometer gives us due information, to the habits of life and the effects of hereditary influence, be sufficiently great, it yet seems nothing when compared with the terrible inflictions occasionally and at uncertain periods visiting man, whether shut up, as it were, within the confined haunts of cities, or living apart in the open country, in situations where it might be reasonably imagined no such influences could reach him. The poison of typhus, for example, if it be a poison, spares none: in certain epidemics the citizen and the peasant suffer alike: the strong robust man in the prime of life is its special victim; cholera attacked the inhabitants of the remote and isolated cottage as certainly as the careful wealthy citizen, and with the same results. No mode of life, nor sex, nor age was security against it; no race, no locality.[45] An inquiry into the origin of such influences is the most important to which man’s attention can be directed. These terrible epidemics appear under various forms; sometimes it is by typhus or influenza, cholera or plague; even those diseases which seem to be endemic, or confined to a locality, assume the form of epidemical raging pestilences, and then disappear for a time. Thus the remittents and yellow fevers of tropical climates do not always put out their whole strength; there is a lull, a season of repose, when man, deluded by the security of a few years, hopes that at last the evil influence has disappeared for ever. Vain hope! It moves in cycles, like the typhus of temperate climates, falsifying all predictions. Thus, in Jamaica, the grave of so many noble English regiments, the fever, sometimes called remittent, sometimes yellow fever, exhibited its fitful attacks during eighteen years, in the following capricious manner, at a station called Port Antonio, about eighty miles from Kingston. At Stoney Hill Barracks, the disease was still more capricious.[46] As the poison producing intermittents and remittents must be presumed to be always present, it is incomprehensible how it should at times cease its attacks on man, showing that another influence or element requires to be present to render its attack successful. Again, we find that within a limited range, a long residence in a land unhealthy to the stranger seems by acclimation to diminish if not entirely to eradicate the susceptibility to disease on the part of the latter; but this opinion must be received cautiously and with reserve, for the phenomenon may be partly due to the difference in race, respecting which we as yet know but little. The banks of the Scheldt, the Polders of Holland, and the mouths of the Rhine, the Danube, and the Indus, are healthy to the natives of these districts; graves to foreigners. In all inquiries of this kind, these well-established facts must not be overlooked.
§ 2. When a chemical substance is applied externally or internally to the living tissues of an animal sufficiently strong to dissolve the affinity between them and the vital force, and to substitute for it other stronger affinities, the explanation of the phenomena is easy, and the coarsest chemistry offers a solution. The action of caustic potass, of concentrated sulphuric acid, present the examples of this kind of dissolution. Other substances alone poisonous when given in concentrated doses, are known to pass, when sufficiently diluted, through the blood, and be eliminated by secretion and excretion from the body: after causing disturbances more or less grave, more or less important, the combinations they form, if any, with the living organic molecules are overcome by the vital force, which then resumes its usual influence. Of such substances some pass off unaltered, others are decomposed, and the bases only appear in the secretions or excretions. Whilst passing through the lungs, certain of these vegetable salts combine with the oxygen of the air, and the respiration in consequence becomes slower, or in other terms, they diminish the production of arterial blood.[47]