The laws which govern and control the universe,
are as definite and as wonderful among invisible atoms, as those which regulate the enormous masses floating in space; and the time will come when the advancing intellect of man will measure and weigh the morbid poisons, as he measures and weighs the stars. Why should the laws of Epidemics be less understood, than the laws which govern the course of comets? The aspirations of man have led him to penetrate the heavens, which charm and inspire him; he studies rather the more violent disturbing elements of nature, the thunder-cloud and the fire of heaven, than the silent pestilence which steals over the earth. I cannot conceive it possible that the Intellects, which are occupied in procuring means for the Majesty of this empire to issue her mandates with the velocity of a spirit to the nethermost parts of the earth, should be incapable of solving so deeply interesting a mystery as the causes and nature of pestilential diseases. It would seem that man prefers to issue a mandate of destruction many thousand miles distant, than to disarm the pestilence at his door. It is barely a century since Galvani observed the twitchings in the muscles of a frog's leg, and the battery, still named after him, has already become an agent of instantaneous communication between places many miles distant. But how many centuries have passed away, each one succeeding the other, with its millions of victims to epidemics? And where are the remedies for the evils? Drainage and cleanliness, with all their advantages, were better understood and more fully carried out by the ancient
Romans than by ourselves; there are monuments, though crumbling to decay, to tell us of the vast enterprise of these people and of the value they set upon a healthy and vigorous constitution, and how well they understood the means of warding of disease.
Cultivation and drainage are now fully understood to be the basis by which a healthy condition of air is to be obtained, next to that, cleanliness and ventilation; if either be neglected a sickly, mouldy, and unwholesome contamination of atmosphere ensues; the odour of a bog is proverbially mouldy, and so is that of an ill-ventilated house or cellar; dryness, or the fresh pleasant scent of clean water, are the antagonists of these; the aromatic odours of vegetation are opponents of putrefaction, and consequently of the development of the lower forms of life. All empyreumatic matters prevent mouldiness and decomposition; and odours arrest and prevent the growth of mouldiness. The oil of birch, with which the Russia leather is impregnated, and which gives it so pleasant an odour, effectually prevents mouldiness, and consequently decay.
Lindley says, "It is a most remarkable circumstance, and one which deserves particular enquiry, that the growth of the minute fungi, which constitute what is called mouldiness, is effectually prevented by any kind of perfume."[[71]] Cedar has
been used, from time immemorial, for a like purpose; and I doubt not the recommendation of Virgil, before quoted, in reference to the burning of cedar, was founded on some practical utility of this kind, though its modus operandi was unknown to him. Allied to these is a curious circumstance, and worthy attention. I copy the following from an old work on Pestilences. "It is remarkable that when the Plague raged in London, Bucklersbury, which stood in the very heart of the city, was free from that distemper; the reason given for it is, that it was chiefly inhabited by druggists and apothecaries, the scent of whose drugs kept away the infection, which were so unnatural to the pestilential insects, that they were killed or driven away by the strong smell of some sorts of them." "The smell of rue, and the smoke of tobacco, were prescribed as remedies against the infection; but especially tar and pitch barrels, which it was imagined preserved Limehouse, and some of the dock-yards from infection."[[72]]
Pitch and tar dealers are everywhere spoken of as being remarkably exempt from infectious diseases.
Cold infusion of tar was used in our colonies as a prophylactic against the Small Pox. Bishop
Berkeley was induced to try it when this disease raged in his neighbourhood. The trial fully answered expectation—for all those who took tar-water, either escaped the disease, or had it very slightly.
Tan yards and places in the immediate vicinity, are said to be free from pestilences. The tanners of Bermondsey are said to have escaped the Plague of London, and one person only died in Gutter Lane, where was a tan yard. The tanners of Rome are also stated to have been free from Plague. Dr. M‘Lean refers to the exemption of tanners at Cairo. Tannin is prejudicial to most vegetables,—but Dr. Lindley says it is not always so to fungi. "A species of Rhizomorpha is often developed in tan pits." I should imagine that neither plants nor insects would be found very abundantly, where tannin prevails; yet we find that the gall-nut is formed for the protection of an insect from injury by weather, and as a temporary means of sustenance.