ning into remittents, and these latter into the continued form; both the one and the other being pure and uncomplicated in their character, on some occasions and under certain circumstances, and under others variously complicated, every important viscus of the body, in some case or other, becoming more particularly the seat of disease. Fever, however, is not the only effect produced by malaria upon the human constitution; other diseases of a most formidable description result from the same cause. The next in importance is dysentery. This disease, particularly when it occurs as an endemic or in an epidemic form, results as unequivocally from this cause as any of the types of fever which have been enumerated. When it is met with sporadically, and amongst soldiers, particularly in some situations, both in India and in temperate climates, it doubtless depends more upon the habits and conduct of the individual than upon any other cause. Vicissitudes of season and climate alone, with neglect of the state of the bowels and the immoderate use of spirits or intoxicating drinks, and of unwholesome articles of diet and acid fruits, will of themselves produce certain forms of dysentery. But these are, in warm climates, oftener only the predisposing and determining causes of that more efficient agent now under consideration. In all cases, however, their action very greatly assists its operation; and without which assistance, most probably no disease would have been induced by it. That terrestrial or marsh effluvia are efficient towards the production of dysentery, particularly when this disease is endemic or epidemic, is proved by its prevalence, chiefly or entirely, in situations where, and during seasons when, malaria or vegeto-animal miasms abound. There is not a province in India or its Archipelago that has not furnished instances of this fact. The expeditions to Batavia, and the capture of that colony in 1811, and the more recent expeditions to Ava, have shown it most satisfactorily. Sir John Pringle says that he has observed this disease to prevail in one part of an encampment, and intermittents and remittents in the other parts. Similar facts are recorded with respect to the French armies during their occupation of Italy and Germany, and are well illustrated by M. Vignes, in his work on dysentery.

There is no doubt that the scorbutic form of dysentery, which is well described by Mr. Bampfield, is chiefly dependent upon marshy effluvia, when this cause operates upon individuals imperfectly fed, or fed only upon salted provisions, and, at the same time, so thinly clothed as to allow the vicissitudes of weather, temperature, and season, to have their full effect upon the surface

of the body. The scorbutic dysentery which prevailed at Rangoon, and amongst the soldiers and troops engaged in the expedition to Ava, well illustrates this fact; and the endemic of the Milbank Penitentiary, according to every information which has been published, is also conclusive on the same point.

What the particular circumstances are which occasions marsh effluvia in the one case to produce fever, and in another dysentery, cannot always be precisely known. They are, however, very evident on many occasions, as will presently be shown: in this place it is sufficient to mention imperfect clothing, vicissitudes of temperature and weather, exposure to wet, night air, and cold dews, particularly after great heat or exposure to the sun's rays; whatever suddenly chills the surface of the body; the use of irritating food, of spirits, and unripe fruit, and of impure water, particularly if it be taken from places whence malaria is given off, or if it abound with animalculi or the infusoria, &c.

Besides those diseases, marsh miasmata seem also to be productive of disorders of the large viscera, more particularly the liver and spleen. The influence of this agent, in occasioning diseases of these organs, particularly when it acts conjointly with heat, is evident, although much less so than in the production of fevers and dysenteries; and its operation is much more difficult to explain in the former than in the latter. It is true that many of the instances of diseased liver and spleen, which occur in warm climates are induced consecutively upon intermittents and remittents; but they often occur primarily and endemically, evidently showing their chief dependance upon the exhalations proceeding from the soil. There is seldom seen, within the tropics, a case of disease in which, upon dissection, the liver and spleen are both sound. There seems also to be a tendency to determination to either one or other of these organs, in all cases of fever arising from marsh effluvia; for even in cold and temperate climates the liver or spleen is affected, or becomes so if fever from this source is prolonged; and the local affection is acute in proportion to the warmth of the climate or of the season in which the disorder supervened. From this it may be inferred that the habitual exposure to malaria, even when it fails of inducing fever or dysentery, and more readily if it gives rise to those diseases, will produce disorder of the liver or spleen, or of both. Whether the production of visceral disease in preference to fever depends upon the action of a weaker dose of the marsh poison relatively to the circumstances proper to the constitution of the individual affected by it, or rather upon the diet

and regimen usually adopted whilst exposed to its influence, it may be difficult to decide. It appears more conformable with the result of observation, to account for the circumstance by the latter supposition.

There is one circumstance particularly worthy of attention, namely, the extreme disproportion between the number of those cases of disease which occur from malaria amongst Europeans and the natives of the country. It seems as if the European constitution had an inherent predisposition to be affected by this cause; and that the adaptation of the human frame to climate is especially manifested in the diseases which supervene among its exotic inhabitants comparatively with those which occur among indigenous

It has long been observed, in countries subject to marsh effluvia, particularly those which enjoy a warm climate, that, even when they do not act sensibly in the production of fevers, or even of any of the diseases I have particularised, they are very inimical to the duration of life in the white variety of the species, particularly in those who are born in the country. Dr. Jackson informs us that white females, born and residing in Lower Georgia, seldom reach the age of 40, and men scarcely ever attain to 50; while those who have arrived at manhood before they settle there, generally reach a good old age. In some places this influence upon the duration of life among white natives of a country abounding with malaria is still more remarkable. In Petersburgh, at Virginia, no white person born there has reached the age of 23. Dr. Jackson saw an individual of 21, who was the only one who had reached that age, and he was quite decrepid and worn down, although he had never been confined by severe sickness. Bruce records similar instances among the white natives of the banks of the Nile, in Abyssinia; and analogous proofs may be adduced from various authors, showing that the malaria of warm climates tends, according to its activity, to limit the extension of, or even entirely to cut off, a native white population, either by producing certain diseases, from some of which the indigenous races are in a great measure exempt, or by stunting their growth, or altogether blighting this variety of our species in their early youth, or in the course of their development, without causing any specific disease.* Individuals belong

* Children born of white or European parents in India require to be sent to Europe in order to attain due maturity and strength. If allowed to remain in India, they seldom present the appearance of health, even when they arrive at puberty. A greater proportion of them also die before they reach this epoch of existence: and it seems probable that children, whose parents have both been the

ing to the white families of mankind require to be previously brought to their full state of physical perfection, in order to enjoy their usually allotted span of existence, before they are removed to climates where the powerful agent of disease, now under consideration, is in full force.

In addition to the diseases already enumerated as being produced among Europeans by malaria, and in addition to its blighting effects in warm climates upon a native white population, even when it fails of inducing active and specific disorder, its influence in occasioning ulcers of the lower extremities, and foul sores, and even sphacelation and gangrene, must be mentioned. Every military surgeon has numerous opportunities of observing, in the East, the relation which subsists between unwholesome situations and these disorders, both among Europeans and natives. Indeed, it seems to be a general and necessary effect of malaria to diminish the powers of life throughout the whole body; and the phenomena accompanying and indicating this effect are various, according to numerous concurrent circumstances, to predisposing causes, and to concomitant influences.

Among those diseases which may be viewed as the consequence of terrestrial emanations in a more or less marked manner, it may be observed, that cholera, in its severer forms, and in that form more particularly which has lately ravaged all the countries in the East, is in some measure caused and influenced by this agent. Epizootics or epidemics amongst the lower animals generally prevail during warm seasons, and are more particularly severe towards the close of hot summers and autumns consequent upon heavy rains and inundations, and they frequently appear upon the occurrence of heavy rains immediately following a long hot, and dry summer and autumn; and it is a fact deserving of consideration, that the diseases which become epidemic amongst the lower animals, whether in warm climates or in temperate countries during hot seasons, generally present similar derangements and structural lesions of the internal viscera to those remarked in the human species. This is the case particularly in marshy situations, and in places subject to inundations.

It will naturally be inquired, in what manner does the marshy effluvium affect the human system, and how becomes it productive

offspring of Europeans, but born and constantly resident in India, would be still weaker, and less likely to arrive at maturity, or to reach the full physical development of the white variety of the species.

of disease? On these topics nothing positive or directly demonstrative can be adduced; inasmuch as the intrinsic nature of this agent has not yet been discovered. But observation has supplied data, which, when calmly considered, seem to show that terrestrial emanations, and all those causes of disease which float in the atmosphere, make an impression on those surfaces with which the air comes in contact: and this impression, when sufficiently strong, or frequently made, is productive of disease, either of the system generally, as in fever, or of some important viscus, as the liver or spleen. It is, therefore, chiefly to the internal surfaces of the lungs and air passages that we are to look as the channels through which malaria makes its hurtful impression upon the animal frame. But whether it acts by deranging the healthy condition of the nervous system of the organ, which derangement produces farther disorder until specific disease is fully formed; or whether the exhalations floating in the air are actually absorbed from the surfaces of the air passages and cells into the blood, vitiating this fluid, and, by its presence there, deranging the whole system, or some important viscus, it is impossible to decide. Both sides of the question have found supporters who have adduced arguments in behalf of their opinion, in the absence of positive proofs. On a subject where sufficient evidence has not been obtained, and where it scarcely can be obtained in the present state of our knowledge, it is almost impossible to come to a decision. As far, however, as circumstances serve either directly or indirectly to elucidate the subject, it seems most probable that the noxious impression of malaria upon the system may be made through the medium of both the nervous system and the blood.

That this agent is destructive to the powers of life admits not of a doubt, although pathologists differ as to the mode in which this effect is brought about. Dr. Cullen supposed it to be a direct sedative, by which the energy of the living system is diminished, and a spasm of the extreme capillaries produced; and that, if the power of the system, or the vis medcatrix naturæ, is not entirely overpowered by it, reaction supervenes in order to overcome this spasm, and the febrile action is fully formed. Other pathologists suppose that the marsh-effluvium acts as a stimulant, and that the debility which it obviously occasions, is a state of exhaustion consequent upon previous excitement. Neither of these theories accounts for the whole phenomena, which diseases arising from this cause evince throughout their course, and according to their varying manifestations; although either explains many of the symptoms which are