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XI.

Dr. MACCULLOCH on the Propagation of Malaria.

In the leading article of our 15th Number, we gave a pretty full account of the first six chapters of Dr. M.'s, very interesting work. We now propose to dedicate a short article to an important chapter on the propagation of malaria, by which we shall render to the public a much more comprehensive analysis of Dr. M.'s researches, than has yet been offered in any other periodical publication.

We observed, in our former article, that, as Dr. M. had not travelled much himself, he had evidently made good use of his library, in the study of medical topography. We have since learnt that he is indebted to a gentleman, (who has made a comprehensive survey of the Mediterranean shores) for some very valuable information respecting malaria, and those places where that poison most commonly prevails. This circumstance, instead of detracting from the worth of the volume, very much enhances its value in our eyes, as giving a greater authenticity to certain details, than if they had been gathered from books.

CHAP. VII.-PROPAGATION OF MALARIA.

Next to a knowledge of those localities which give origin to malaria, is an acquaintance with the laws by which it is propagated. It is properly remarked, that whatever this miasma may be in its simple state, it is only as united with the atmosphere that we know it. It must indeed be considered as the very atmosphere itself, where it exists-and its propagation must, therefore, be primarily regulated by those laws which govern the motions of the air. Unfortunately, we do not know much of these laws. The union of malaria with air may be more or less perfect, according to the varying conditions of the latter, as to moisture, and other physical qualities -and it is very clear that its propagation is greatly influenced-perhaps totally suspended, or mightily accelerated, by the ever-varying atmospheric conditions. Though not so capable of becoming durably attached to bodies as the matter of contagion, yet there are not wanting sufficient proofs that malaria is attachable to certain solid substances, as vegetables, and, perhaps, to the soil.

The first fact which arrests our attention in the propagation of malaria, is PROXIMITY. While the atmosphere is quiescent, it may be taken as a general rule, that the place in which malaria is produced, or that which is nearest to it, suffers most. This was probably known to the Romans, from the earliest ages; and hence it may be, that so many of their ancient towns were situated on hills. Some fatality led to the site of Rome itself, in despite of this knowledge, if it did then exist. Dr. M, descants feelingly on

the want of attention to this fundamental fact in the propagation of malaria, by men in all ages, while selecting places for towns, encampments, or single mansions.

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"Rome perhaps became too gigantic during its period of ignorance, to be afterwards abandoned or transferred: but there was no apparent reason for perpetuating Calcutta, when, from the very hour almost, of its foundation by Charnock, its destructive situa tion had been demonstrated. That Holland should have persisted in inhabiting that Batavia which it had studied to render even more poisonous than nature had already done, by the model of its own pestiferous father-land, is a problem which Holland inust be allowed to explain as it best can."

Innumerable other examples might be pointed out, of the ignorance or obstinacy of our forefathers, in selecting places, that actually courted the grim king of terrors to visit them more frequently than he otherwise would have done. It is chiefly in military service that the ravages of malaria have been conspicuous, and that the want of knowledge, or the want of inclination to listen to the dictates of experience, has entombed thousands in a premature grave! The writings of Lancisi, Zimmerman, Pringle, Lind, Blane, Jackson, and many others, take away all excuse from some of our modern commanders, for the rash manner of proceeding which they have often adopted, and by which armies have been annihilated, expeditions frustrated, and the best laid political projects counteracted. In Walcheren, we lost 10,000 men, and the Antwerp fleet to boot-when the French army attempted Naples, in 1528, they were reduced from 28,000 to 4000 men, in a few days, by choosing an injudicious encampment at Baix! Ignorance, however, might have been better pleaded 300 years ago than now.

"It was a fortunate discovery in fortification, that a dry ditch was more defensible than a wet one; since the safety and efficiency of a garrison seem never to have entered the minds, even of the Vaubans, the Coehoorns, and the Cormontaignes; though far more intimate, it must be supposed, with Malaria than ourselves."

A whole regiment (says Dr. M.) was incapacitated at Malta, and many of our men destroyed, by persisting to occupy a village which the natives had abandoned. A party of 30 men were successively destroyed, by obstinate attempts to occupy, as a telegraph station, a rocky point in Sicily, between Rassaculmo and Spadafora, although we were warned by the natives of the deadly malaria there prevailing.

"Thus also was our hospital at Port Mahon fixed on the precise spot where it received the whole malaria of that pernicious valley, pestiferous during four months of the year; while by choosing the elevation of Cape Mola, at its north-eastern margin, these bad effects would have been entirely avoided."

The next subject which we are to notice, and which is intimately connected with proximity, is CONDENSATION of malaria. It is natural to suppose, that the gradual production of this poison must occasion a gradual accumulation, unless decomposed or dispersed. Thus, we might anticipate that a marsh, confined within the walls of a forest, as in the pine swamps of America, or the marshy ground of a jungle, or even in our own moist woods, would accumulate malaria, and thereby render it unusually viru

lent. This is confirmed by experience. So also, a marsh, enclosed between high hills, or otherwise deprived of ventilation, is generally very insalubrious.

"How nearly this general rule may be applied to our own country residences, where uniting stagnant or still waters to the confinement of a woody lawn, it is quite superfluous to say. Those who cannot profit by general principles, but who must, at every minute, have the application made for them, are not of a capacity to profit by any thing."

And now for the MIGRATION or DISPERSION of malaria. If currents of air always moved horizontally, as weather-cocks or the sails of ships would indicate, the matter might be more easily investigated. But the fact is, that atmospheric currents are irregular and intricate in the highest degree -nay further, they scarcely in any instance, obey the common law of rarefaction, or unequal density, by which they are supposed to be regulated. If, therefore, we cannot explain how a current of malaria may be directed or limited, so, no movement can occur in this poison, however unexpected, that may not find its solution in the capricious currents of the atmosphere. If these currents move vertically upwards, so may malaria-if downwards the malaria may descend. Indeed, both these facts are ascertained. If there be curvilinear courses of malaria, there are curvilinear winds enough to justify such courses. But there are phenomena attendant on the propagation of malaria, which cannot, we fear, be explained, even by the capricious and intricate currents of the atmosphere. One of these is the fact, that a marshy spot of ground will produce disease at some distance, while the inhabitants of the marsh itself will be little affected, or escape altogether.

"In Italy, it has been ascertained that the poisonous exhalations of the Lake Agnano reach as far as the convent of Camaldoli, situated on a high hill at the distance of three miles: this instance further proving that, thus far at least, Malaria can be conveyed by the winds. In France, at Neuville les Dames, above Chatillon on the Indre, and at St. Paul near Villars, both situated on high grounds, there are found as many or more fevers than in the marshes beneath where the Malaria is produced, and the same is generally true all through Bresse in the Lyonnais. Thus also the plain of Trappes near Versailles is affected by the marshes of St. Cyr, though considerably elevated above them.

"I am also informed that a case of this nature occurs in Malta, of a very marked nature; the Malaria which is produced on the beach beneath a cliff, producing no effect on the spot itself, while it affects, even to occasional abandonment, the village situated above. Many more similar instances might be collected; but I must be content with adding a few from our own country coming under my own observation, and sufficiently well known to be easily verified.

"At Weymouth, where the back-water, as it is called, produces intermittents, and also autumnal fevers, commonly mistaken for typhus, these diseases scarcely affect the immediate inhabitants of its vicinity, but are found to range along the high grounds above; and the same, in Cornwall, is true of the vicinity of St. Austle, receiving its Malaria from the marshes of St. Blaisey. If I am not misinformed, it is equally true of the marsh of Marazion in the same county.

"The marshes about Erith in Kent, also, are less injurious to the inhabitants of the lower grounds near them than might be expected; while their effect on the houses which are situated high on the hill above, is such as, at different times, to have been very severely felt by the inhabitants. The same is true of Northfleet, if my information is correct; or, the fact as stated is, that at some distance, on the high ridge so well known, agues are more prevalent than below and near the point of

the introduction of the Malaria. If this is not to be explained by the flow of a current, so directed as to escape the low grounds beneath these cliffs and declivities, while it ranges across the hills in contact, I have no solution to offer."

Here our author introduces a statement from Captain Smyth's valuable statistical table of Sicily, which appears to generalize the whole of these facts and lead to the conclusion that, in nearly an equal number of cases, the higher grounds suffer as much as the lower-the locally healthy as much as those which are the very seats of the malaria !

"In this document, out of seventy-six unhealthy towns and villages enumerated, there are thirty-five situated on hills or declivities; while, from his personal inform ation, I may add that many of them are at considerable distances from the tracts which produce the disease. And I may add one remark as to the theory of this propagation, derived from a writer on the climate of Italy. It is that the southern winds in that country, propagate along the hills, upwards, that Malaria which the northern or mountain ones do not; such winds, independently of their superior power in producing the pernicious exhalations, tending, from their temperature, to ascend the acclivities, while the other winds, as is easily understood, have the opposite inclination."

Dr. M. makes many interesting remarks on the propagation of malaria along valleys, and on the opposite effects produced, in different places, by the same process-the cutting down or the planting of trees. Thus the cutting down of trees, in some places, would let in a stream of malaria-in others, it would keep it out. Hence the topography of places must be well studied, before we venture on any preventive or corrective measures. Thus a convent at St. Stephano, became unhealthy in consequence of cutting down some trees-and the extirpation of a wood brought on severe fevers at Veletri, during a space of three years, as also happened at Campo Salino, in the Pontine Marshes.

We had occasion, in our first article, to advert to the opinion entertained by many, that Rome was, in ancient times, protected from malaria, by groves that were held sacred. Lancisi remarks that, in later times, there was extirpated near Rome, a forest to the southward, reaching from the heights of Fracasti and Albano, to the Tiber, protecting it from malaria so abundantly generated in that quarter by marshes. Thus, says he, was destruction first let in upon the Campagna. Since that date, if Dr. M's information be correct, a similar proceeding seems to have opened Rome itself, in another quarter, to the malaria of that pernicious land. Dr. M. observes that there was formerly, in a situation interposed between the Campagna and the Porta del Popolo, a wood, cutting off the communication through the north-east winds-and it is, since the destruction of this wood, that the new progress of this pest has been noticed. If this be a fact, it will prove a valuable one, as the Papal government will thus acquire a remedy, as far as this point is concerned, which it has long sought for in vain by drainage. In whatever way the malaria is generated, or makes its way into the everlasting city, its progress seems to be determinate, if slow:-spreading, as it were from a fixed point, and making, in every year, a further step, so as

gradually to drive the inhabitants before it as far, at least, as they are opulent, and able to quit their unhealthy habitations. The progress and various windings of this malaria through the streets of Rome, are traced for Dr. M. by some hand, who was evidently well acquainted with the medical topography of that interesting city. Dr. M. speculates on the fate of Rome, in mournful accents; but the malaria may take another direction, or some revolution in the bowels of the earth may procrastinate the fall of this mistress of the world. Dr. M. thinks, and with great probability, that the decreasing population itself, is one cause of the accelerated march of the malaa, since nothing checks the generation of this poison so much as dense population and high cultivation. Among the mysterious circumstances connected with the generation and propagation of malaria is its partiality for one side of a street, and its repugnance to the other side.

"In Rome, it is pointed out, in more places than one, that the Malaria, which must there be transported, not generated, will occupy, even with some permanence, and in some instances also, perennially, one side of a garden or a street, while the opposite one remains exempt. If, in some cases, this is connected with that singular propagation just described, it is an explanation that will not solve every case of the difficulty. They who know Rome, and its tales on that subject, will remember the opposed churches were the porter or janitor on the one side, long and invariably suffering from fever, was cured by the mere transference of his office to the opposite side of the same street; and where, at the same time, the duty had been always as safe as it was invariably dangerous or destructive on the other. This is a circumstance indeed of very frequent occurrence in various parts of Italy, but I will only quote one more instance from that country, out of many, because it is well known to many officers then serving with our army in Sicily. The village, the name of which has escaped me, unless that be Faro, was situated above the Faro of Messina; and while one side of the street was in the highest degree pestiferous, producing mortal fevers among the troops, the opposed one was entirely exempt."

Dr. M. endeavours to throw some light on this apparent mystery, but with very doubtful success. It is probable, he observes, that the matter of malaria is often connected with vapour or mist-nay, that it is conducted and confined by this its vehicle. We find dews, mists, and hoar-frosts often oc cupying a certain extent, both as to height and depth, reaching, for example, a particular hedge in some valley, and then ceasing by a most definite and sudden line; while also terminating at a particular altitude on the trunks and branches of trees, as if suddenly cut off. This being the case, we may conceive how a malaria, thus united with a mist, may be as defined and local as it actually is found to be, in these singular cases. The following is a remarkable domestic instance of the transportation of this peculiar poison, for the accuracy of which our author pledges himself.

"This is the high road between Chatham and Feversham, involving an extent of about twenty miles; and it is here remarked by the inhabitants, that in every village and town, including also the detached houses, and comprising, from Chatham, Raynham, Newington, Sittingbourne, Bapchild, and Boughton, the ague occurs, on the left hand side of the road, generally, and is unknown on the right side; though the breadth of the road itself forms the only line of separation. If I were to repeat, in addition, some special facts, believed and related by the inhabitants of some of these places, and at Sittingbourne among others, this separation is even more

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