« ПретходнаНастави »
tion over a surface from which they cannot be otherwise carried off, and a corresponding contamination of the air.
Much is said, in the work before us, of the danger of overlooking the more limited sources of Malaria, and this matter also deserves a serious examination. The play of chemical affinities exerted, while the process of vegetable decomposition is going on, will, under every variety of circumstances, determine the production of the same result. There are facts enough collected to prove the evolution of the same effluvia from the confined air of a moist cellar, in the dirty hold of an ill-ventilated ship, and from masses of vegetables or fruit heaped together in the market and store-houses. Nay, we are led by a reasonable analogy to infer that similar processes are productive of the same results in the stagnant water contained in a cask at sea, in the well-manured beds which supply our tables with esculents, beneath the trim herbage “of the green, smooth shaven lawn," within the very precincts of our ornamental gardens, from the fallen leaves and faded petals of their once beautiful inhabitants, and in the vases of flowers which decorate our apartments. “If," argues Dr. MacCullough, "the produce of a hundred square feet, or acres, or of any scale or number of parts can, under a dilution of one thousand or ten thousand times excite disease, then must, in the inverse ratio, the produce of the one thousandth or the ten thousandth portion of that space be capable, before dilution, of producing the same effects, or a single blade of grass, acting on water (if this be the cause) may be as efficacious as an acre, supposing, of course, that it is actually applied to that part of the body which can suffer from its action.'
We have already accused our author of exaggeration, and we think the above a striking example of it. Now, we deny his premises at once, and of course reject his conclusions. We do not believe that the noxious effluvia can or do retain their activity and energy when diluted as he has stated. All analogy is against such a supposition. A drop of strong prussic acid-or an atom rather--the smallest fraction of a drop, is instantly destructive to life when applied to the tongue or to the eye of an animal. But we use, with perfect impunity, the bay leaf, the oil of bitter almonds, and a great variety of other articles, in which it exists in a state of solution or diffusion. When most intensely concentrated, add to it a sufficient quantity of water, and you make it absolutely inert.
Dr. M. infers the retention of its energy by Malaria, notwithstanding the infinite dilution which he indicates, from the fact, that it will produce its deleterious effects, when wafted by winds, to a great distance from its sources. Allowing, as we have no
disposition to dispute the correctness of this statement, we, by no means, acknowledge the justness of his inference for the following reasons. Malaria seems totally innoxious (as shall be noticed hereafter) in a dry atmosphere; it has a remarkable affinity for moisture, and connects itself closely with mist, fog, vapour, or damp air. Thus combined, it will be carried by a moderate breeze a considerable number of miles, but such transportation does not necessarily imply dilution. We contend that it is carried on in its concentrated state. It must be observed that it does not diffuse itself in a calm state of the atmosphere that, as numerous writers affirm, it passes in narrow currents, the limits of which, on each side, are accurately defined—that opposing or oblique currents of dry air, dissolving the atmospheric moisture, put an end to its progress and effects—and, finally, a fact most in point, and directly to our present purpose, that storms, instead of spreading on all sides, in every direction, the diseases produced by it, disperse it entirely, and by diluting it abundantly, destroy, for a time, its capacity to do injury. Well may our author express his surprise at his own conclusion, “that after such a course, when it must have been diluted to a degree so incomprehensible, that we can only wonder how it should exist at all as a distinct substance or a chemical compound, it should still be capable of producing its peculiar diseases with an activity as great or often greater than it did at the very point of its birth-place.” “In reality,” he goes on to say, "this implies an activity on the part of Malaria, or what is the same thing, a power possessed by minute quantities of this poison to which that of all the contagions with which we are acquainted, bears not the most remote comparison, since it is notorious that the distance of but a few feet from the most active sources of these poisons, of the contagion of plague and typhus for example, is sufficient to render them innoxious, even when the presence of a crowd of living bodies, in the act of producing them, assures us that the quantity generated must be considerable, and when we have also reason to believe from the facility with which they unite to solid bodies, so as to retain their properties, even for years, that they are not destroyed in the cases alluded to, but merely diluted into inactivity.”
It would not be difficult to establish the position that the true and exclusive medium of conveyance of Malaria, is water in its several vaporous forms, either visible or invisible; these fogs, mists and dews being, in technical language, the “fomites” to which the noxious exhalations adhere in a manner analogous to the union of the contagions abovementioned with solid bodies. VOL. II.-NO. 3.
So tenacious is this adhesion, so close this union, that we might produce numerous examples from our author and others, in which the Malaria kept the exact width and level of the stratum of moist air, in which it had embodied itself, being thus wafted from hill to hill over intervening valleys, without depositing in these intervals one noxious atom, or going at all out of the line of the winds. It is equally well known, that when such a fog has been dispersed, or by any means the atmosphere has been robbed of its moisture (as by a change of wind or the heat of the sun on a clear day) Malaria exhibits no more of its influence. And here we can furnish a positive proof of its loss of energy and activity by dilution, for, as we have stated; it is so closely connected with vapour as to be exhaled with it, and again condensed with it, or at least re-united with it in its condensation ; now, we always observe the intensity of its effects to be inversely proportioned to the elevation at which the subject of its influence is placed, and we can, in no other way, account for the diminution of power here but by its dilution.
Our author is one of those who maintain “that putrefaction, in the proper sense of the term, is not necessary to the production of Malaria, but that the stage or mode of vegetable decomposition required, for the production of that poison is different from that which generates a fetid gas.” Yet, it cannot be denied, that the two are almost always, if not invariably, produced together; in fact, if they form, as his expression implies, two successive stages of decay, the interval of time between them in so warm and moist a climate as ours will never be perceptible. It is a curious question, but one of great difficulty, whether there is any difference between the results of the decomposition of different vegetables. Few observations seem to have been made by physicians upon this point, and it is only by observation that we can here learn any thing. It is certainly worthy of more attention than it has yet obtained.*
We have spoken hitherto of Malaria, or the poisonous contamination of atmospheric air, as derived only from the decay and decomposition of vegetable matters, but we have more than hinted that this is not, in all probability, the exclusive source of
* We have heard some strong statements and ingenious speculations on this subject. The plants, however, which have, generally, been considered as suspicious, are those which grow spontaneously in rich, damp soils. They may, perhaps, rather indicate than produce exclusively, or, in any peculiar degree, these noxious exhalations. The strong objection to this opinion, is, that in every part of the globe where climate, and soil, and local circumstances favour the generation of Ma. laria, this evil principle is felt, however dissimilar may be the productions of the vegetable kingdom, however much, not only species and genera, but even tribes and natural families may be found to differ.
such contamination. We find the miasm existing in a state of powerful concentration, and exerting its deadly influences wherever marshes and bogs are spread out under a hot sun, but we further ascertain its presence by the production of similar effects in places where the same combination of circumstances is by no means present. It is certain that many of the districts of Italy, notoriously subject to the Malaria fevers, as they are there termed, do not offer the peculiarities of soil and surface which we have been considering as connected with the developement of this noxious effluvium. With regard to the Campagna of Rome, now a mere waste, deserted, except by the herdsman and his flock, it is a territory of volcanic formation, broken into gentle undulations, and quite dry, and elevated considerably above the level of the sea. On its surface, there is little or no water, nor is the vegetation by any means abundant. Yet, this is the very throne of the pestilential destroyer, to the influence of which is attributable the comparative desolation of the ancient mistress of the world--the queen of nations—the eternal city. The Malaria, arising from the whole surface of this dreary region, annually extends its encroachments through her streets and noble squares, and threatens the entire depopulation of her seven hills. Within the district, of which Rome may be considered the geographical centre, its influence is remarked to become, every year, more intense and universal, so as to offer sufficient ground for the melancholy anticipation, that the period is not far distant when her palaces will be heaps of solitary ruins, and her very site a wilderness.
Shall we ascribe the production of this vast mass of Malaria with all its concentration and malignity, to the same sources from whence it is poured forth in the Jungles of India-on the borders of the great Northern Lakes, and among the rice fields of Carolina, or shall we not rather be under the necessity of admitting its possible evolution in full energy and abundant quantity, from sources not yet contemplated. It is not only “a popular prejudice” in Italy, as our author scornfully terms it, but the settled and deliberate opinion of many of their best informed and most scientific men, that volcanic soils are especially productive of Malaria--that they are, intrinsically capable of producing it, as some believe, by giving out at a certain stage of the decay, and decomposition of the volcanic materials, the principles which go to form this poison; or, as others maintain, that the subdued or quiescent fires of the volcanos which burn beneath, generate gases or mephitic airs, capable of producing these dire effects. We know that such vapours are thrown out
in great abundance in volcanic districts before and during the eruptions, and sometimes, also, during earthquakes.
In support of this doctrine or hypothesis, we may mention the well-known fact, that in a remarkable number of instances, the sites of old and extinguished volcanos are peculiarly unhealthy. It does not appear that volcanic soils are of course unusually fertile, but we may infer that they contain certain ingredients not commonly met with from the nature of the vegetation which they supply; the grape which gives forth, the exquisite Lachryma Christi, grows no where but on the sides of Vesuvius.
In the month of June, we found more Malaria fevers prevailing at Civita Castellana (the ancient Veii) than in any other part of Italy, the Pontine Marshes not excepted. This town is situated on a high hill, or rather mountain of volcanic formation. The surrounding rocks are particularly porous and soft, insomuch, that the shepherds have, in many places, made deep and extensive excavations in the hill-sides to receive their flocks and cattle. In its environs there can be no stagnant water from the very nature of the soil, as well as from the abruptness and irregularity of the face of the country. To enter the gate on the side farthest from Rome, you pass over à bridge which crosses a glen or ravine more than a hundred feet in depth, down whose hollow track a mountain stream pours its varying torrent. Our author, who finds abundant source, "ample verge and room enough” in a water cask for the production of Malaria, would, by no means, imagine this locality to be exempt-yet, even he would not, we think, select it as peculiarly adapted to the dominion of this poison. Civita Castellana, however, suffers most miserably from it. At the very inn we were warned of the danger of remaining there a single night, and urged to proceed with the emphatic declaration that “every body in town had the fever."
There is a certain degree of coincidence between some of the views of our author, and those of a very respectable writer, Dr. Ferguson, lately of the British army. This gentleman lays down the doctrine, and has supported it with no little weight of fact and argument—"that putrefaction, under any sensible or discoverable form, is not essential to the production of pestiferous miasmata." He declares that he saw remittent and intermittent feyers become epidemic in the encampments of Rosendall and Oosterhout, in Dutch Brabant, upon level plains of sand, with a perfectly dry surface, where no vegetation existed, or could exist, but stunted heath plants, and where the water, obtained by digging a slight depth below the surface, so far from