There is now one circumstance of importance, relating to the destruction or decomposition of malaria, which must not be passed over, from the interest of the facts depending on it: this is, that its propagation is checked by the streets of a crowded town, and apparently owing to this very cause, decomposition. Thus it is observed, that the fever never appears in the Judaicum of Rome, and, similarly, that the crowded streets and the poor people escape, when the opulent houses and open [p052] streets are attacked; and hence the Villa Borghese, among many other palaces and opulent houses in Rome, has been abandoned, while such desertion, being limited exclusively to houses where the air is most open and free, naturally excites wonder: the cause, however, is now plain; and thus it now appears why it was that the Penitentiary in Westminster suffered formerly from dysentery, originating in this cause, when no such disease appeared among the neighbouring inhabitants.
And if this fact is of value as it may relate to the erection of open streets in any place of this nature, it is most important to point out what has been the continuous effect at Rome, as the ultimate consequences threaten to be extremely serious.
It appears that from cutting down some forests which many years ago occupied the declivities of the hills to the southward of Rome, the malaria was let in upon that city from the Pontine marshes; and, further, that the extirpation of a similar wood to the eastward had let in the same poison upon another quarter. Thus it has been found to enter the city through the Porta del Popolo, while, for many years past, it has been gradually extending its influence through the streets; leading annually and successively to the abandonment of many houses and palaces, and still annually increasing and extending its ravages; so as, at length, as I understand, to have even become sensible at the Vatican. And the lines which it follows are distinctly traced out by the inhabitants; while, as I have already said, it is only the houses of the opulent which suffer, further than as the abandonment of these may also influence the inferior ones in their neighbourhood.
Whatever the original cause may be, and however the direction, abstractedly, may be regulated by the winds and the forms of the streets, or by local and fixed circumstances, it is plain that the annual extension is the consequence of desertion, and that as the inhabitants retire from before it, it acquires the means of making a new step and a further progress; because thus they withdraw those fires and smoke, or whatever else it be, dependent on human crowds, which decomposes and destroys this substance. And hence it must follow, that as Rome shall become still further abandoned and depopulated, from want of industry, or from political feebleness [p053] added to this cause, the effects must be expected to increase in a sort of geometrical ratio; almost leading to the fear that the whole city itself may, in time, fall a victim to it, or become abandoned to the wolves and mosquitoes.
If I dare not inquire more minutely into the remaining circumstances connected with the propagation of malaria, lest I should extend this article to an inconvenient length, it is necessary now to offer some remarks on prevention, and especially as it relates to this circumstance—the propagation of the poison; since the rules for prevention, as far as this relates to production, may be deduced from what was said in a former paper on this subject, and relate chiefly to the drainage of lands, and to other practices, more or less obvious, which a little reflection will, without much difficulty, deduce from what was there said.
It is plain, in the first place, that as far as the winds are concerned, it is by opposing obstacles to their course that we must attempt to counteract or divert their influence; and that, in this case, it is through the use of trees alone that we possess any power. Thus reversely, as in the case just stated, the cutting down of trees and forests has often been a serious cause of diseases in certain countries, by admitting a malaria to particular spots; though it is easy to see that where any given spot suffers from malaria, through condensation or confinement, the clearing away of these would be the remedy, by attaining a free ventilation. To detail the particular modes in which remedies may be applied through this species of aid, is obviously unnecessary, and not easy, as it must depend on local circumstances, differing for each place; but I may remark, as an example in illustration of my meaning, that where, as in many of the narrow and prolonged valleys of Greece, the sea shore is a marsh, the remedy would be to plant a screen of trees beyond it, and thus to prevent the sea winds from passing into the interior. And thus did the ancient Romans compel the planting of trees on the shores of Latium, to check the current from the Pontine marshes; rendering groves sacred, under heavy penalties, and enacting other laws with the same intentions.
With respect to such temporary precautions in these cases [p054] as may concern armies in the field, or in camps, it is plain that they will depend on attention to the courses and seasons of the winds; while it would be abundantly easy to accumulate, from the histories of campaigns, the most fearful examples of mortality produced by neglect of these and similar precautions, and even down to almost the very date at which I am writing: and there can be no hesitation in saying, that an intimate and accurate knowledge of every thing which concerns the production and propagation of malaria, forms a most important branch in that information necessary to a soldier, and above all to the quarter-master-general’s department and the medical staff: while, did I dare to record but a very small portion of the mortality experienced, not only in our own armies, but in those of Europe at large, during even the last war, from ignorance or neglect on this subject, it would, I believe, be found that it almost equalled the mortality produced by the actual collision of war itself. Walcheren will not soon be forgotten; if we have ceased to think of our mortal Havannah expedition; and if a French army at Naples was diminished by twenty thousand men, out of twenty-four, in four days, from this cause; if Orloff lost nearly his entire army in Paros; if Hungary has more than once destroyed ten times the number of men by fever that it did by the sword,—these are but trifles in the mass of reasons for saying, that no subject can well be more important, and no knowledge much more necessary to the commander of an army.
Some other points relating to prevention may deserve a few words of notice, before I pass from this subject; if here, also, I must be brief. Not to repeat the cautions founded on what relates to the power of evening and morning, it has been asserted that the use of a gauze veil will prevent the effect of malaria; and it is not improbable that the air accumulated within that, may have the power of decomposing the poison: it is an opinion, at least, which is universal among the people in Malta, and very general in Spain and Portugal. It is also found that fires and smoke are useful, and especially on military service; the experiment having been tried on a very large scale by Napoleon before Mantua, and on a smaller one in Africa, with the most perfect success. With respect to [p055] personal precautions, it is universally recommended to use wine and a good diet, and especially never to leave the house in the evening in situations peculiarly insalubrious, without the previous use of wine or spirits; whence the universal practice of Holland in this respect. Thus, also, narcotics prevent its influence; whence the wide use of tobacco, of which the salutary effects appear to be most amply established.
As to the tropical countries, there is here also one important remark, which, from the great neglect of the fact, and its ruinous consequences, appear particularly to demand a statement in this place. It is the universal experience of the inhabitants, that the attack of malaria, or the production of fevers, is aided by the use of a full or animal diet; by the use of some particular articles of food, such as butter; by excess in eating, generally; and, above all, by eating in the heat of the day. This is not merely well known to the negroes, but the fact is distinctly stated to travellers, and the caution urged, however often it has been neglected, and especially by our own countrymen. Of this, in particular, Major Denham is a strong testimony; while he attributes his own exclusive preservation to his having rigidly followed the recommendations of the natives, which were always urged with the greatest earnestness. And if we examine the causes of death, in most cases, of our African travellers especially, I think there will be strong reasons for believing that their lives have often been sacrificed to this very negligence or obstinacy; while it is most evident that Niebuhr’s party, in particular, owed the loss of their lives to what may be safely called gluttony: and it is to be suspected that this will also explain the loss of Captain Tuckey’s party; while, with respect to nations, it has long been known that the English, the Dutch, and the northern voracious people in general, who habitually indulge themselves in the customs of their original country as tropical colonists, have always been greater sufferers from the effects of those climates than the French and the Spaniards, and apparently from this very difference. And there seems little doubt, generally, that the vegetable diet of Africa and Hindostan is the best security against the evil influence of those climates, and that the chief sufferings of our [p056] own colonists arise from transferring to those situations their ancient habits of full and free living.
As I must not prolong this subject much further, I shall now pass to a few remarks, but very brief ones, on the geography of malaria as it relates to those parts of the continent of Europe most frequented by English travellers; not daring to take room for actual and useful information on that head, but wishing to point out merely the importance of such geographical knowledge to those persons, on account of the hazards which they so universally incur from that ignorance or neglect, and of the great mass of suffering, and also of mortality, which has been the lot of persons who had resorted to those climates as travellers, or migrating residents, from various motives, and not unfrequently with views to health. How often health has been lost where it was sought, will be but too apparent to any one who has chanced to possess an extensive acquaintance of this nature.