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seem to be sustained by such knowledge as exists on the subject.

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Dr. Bartlett, in his work on the Fevers of the United States, says: "The essential, efficient, producing cause "of periodical fever, the poison whose action on "the system gives rise to the disease,--is a substance or 66 agent which has received the names of malaria, or marsh "miasm. The nature and composition of this poison are "wholly unknown to us. Like most other analagous 66 agents, like the contagious principle of small-pox and of "typhus, and like the epidemic poison of scarletina and "cholera, they are too subtle to be recognized by any "of our senses, they are too fugitive to be caught by any "of our contrivances.

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"As always happens in such cases and under similar "circumstances, in the absence of positive knowledge, we "have been abundantly supplied with conjecture and spec "ulation; what observation has failed to discover, hy"pothesis has endeavored and professed to supply. It is quite unncessary even to enumerate the different sub66 stances to which malaria has been referred. Amongst "them are all of the chemical products and compounds "possible in wet and marshy localities; moisture alone; "the products of animal and vegetable decomposition; "and invisible living organisms. * * * * Inscruta"ble, however, as the intimate nature of the substances or agents may be, there are some few of its laws and "relations which are very well ascertained. One of these "consists in its connection with low, or wet, or marshy

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localities. This connection is not invariable and exclu "sive, that is, there are marshy localities which are not "malarious, and there are malarious localities which are "not marshy; but there is no doubt whatever that it gen"erally exists."

In a report to the United States Sanitary Commission, Dr. Metcalfe states, that all hypotheses, even the most

plausible, are entirely unsupported by positive knowledge

and he says:

"This confession of ignorance still leaves us in posses ❝sion of certain knowledge concerning malaria, from which "much practical good may be derived.

"1st. It affects, by preference, low and moist localities "2d. It is almost never developed at a lower tempera'ture than 60° Fahrenheit.

"3d. Its evolution or active agency is checked by a 66 temperature of 32°.

"4th. It is most abundant and most virulent as we ap "proach the equator and the sea-coast.

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"5th. It has an affinity for dense foliage, which has the 'power of accumulating it, when lying in the course of 'winds blowing from malarious localities.

"6th. Forests, or even woods, have the power of ob structing and preventing its transmission, under these circumstances.

"7th. By atmospheric currents it is capable of being "transported to considerable distances-probably as far as "five miles.

"8th. It may be developed, in previously healthy places, "by turning up the soil; as in making excavations for "foundations of houses, tracks for railroads, and beds for "canals.

"9th. In certain cases it seems to be attracted and ab"sorbed by bodies of water lying in the course of such "winds as waft it from the miasmatic source.

"10th. Experience alone can enable us to decide as to "the presence or absence of malaria, in any given locality. "11th. In proportion as countries, previously malarious, "are cleared up and thickly settled, periodical fevers disappear-in many instances to be replaced by the typhoid 66 or typhus."

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La Roche, in a carefully prepared treatise on "Pneumonia; its Supposed Connection with Autumnal Fevers," re

cites various theories concerning the mode of action of marsh miasm, and finds them insufficient to account for the phenomena which they produce. He continues as follows:

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"All the aoove hypotheses failing to account for the ef "fects in question, we are naturally led to the admission "that they are produced by the morbific influence of some "special agent; and when we take into consideration all "the circumstances attending the appearance of febrile "diseases, the circumscribed sphere of their prevalence, "the suddenness of their attack, the character of their "phenomena, etc., we may safely say that there is noth66 ing left but to attribute them to the action of some "poison dissolved or suspended in the air of the infected "locality; which poison, while doubtless requiring for its "development and dissemination a certain degree of heat. "and terrestrial and atmospheric moisture, a certain "amount of nightly condensation after evaporation, and 'the presence of fermenting or decomposing materials "cannot be produced by either of these agencies alone, "and though not indicated by the chemist, betrays its "presence by producing on those exposed to its influence "the peculiar morbid changes characterizing fever."

He quotes the following from the Researches of Dr. Chadwick:

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"In considering the circumstances external to the resi"dence, which affect the sanitary condition of the popula tion, the importance of a general land-drainage is developed by the inquiries as to the cause of the prevalent 66 diseases, to be of a magnitude of which no conception had "been formed at the commencement of the investigation "Its importance is manifested by the severe consequences "of its neglect in every part of the country, as well as by "its advantages in the increasing salubrity and productiveness wherever the drainage has been skillful and effee "tual."

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La Roche calls attention to these facts:-That the ac climated residents of a malarious locality, while they are less subject than strangers to active fever, show, in their physical and even in their mental organization, evident indications of the ill effects of living in a poisonous atmos. phere, an evil which increases with successive generations, often resulting in a positive deterioration of the race; that the lower animals are affected, though in a less degree than man; that deposits of organic matter which are entirely covered with water, (as at the bottom of a pond,) are not productive of malaria; that this condition of saturation is infinitely preferable to imperfect drainage that swamps which are shaded from the sun's heat by trees, are not supposed to produce disease; and that marshes which are exposed to constant winds are not especially deleterious to persons living in their immediate vicinity,—while winds frequently carry the emanations of miasmatic districts to points some miles distant, where they produce their worst effects. This latter statement is substantiated by the fact that houses situated some miles to the leeward of low, wet lands, have been especially insalubrious until the windows and doors on the side toward the source of the miasm were closed up, and openings made on the other side, and thenceforth remained free from the disease, although other houses with openings on the exposed sides continued unhealthy.

The literature relating to periodical fevers contains noth. ing else so interesting as the very ingenious article of Dr. J. II. Salisbury, on the "Cause of Malarious Fevers," contributed to the "American Journal of Medical Science," for January, 1866. Unfortunately, while there is no evidence to controvert the statements of this article, they do not seem to be honored with the confidence of the profession,not being regarded as sufficiently authenticated to form a basis for scientific deductions. Dr. Salisbury claims to have discovered the cause of malarial fever in the spores of a very

low order of plant, which spores he claims to have invariably detected in the saliva, and in the urine, of fever pa tients, and in those of no other persons, and which he col lected on plates of glass suspended over all marshes and other lands of a malarious character, which he examined, and which he was never able to obtain from lands which were not malarious. Starting from this point, he proceeds, (with circumstantial statements that seem to the unprofes sional mind to be sufficient,) to show that the plant producing these spores is always found, in the form of a whit ish, green, or brick-colored incrustation, on the surface of fever producing lands; that the spores, when detached from the parent plant, are carried in suspension only in the moist exhalations of wet lands, never rising higher (usually from 35 to 60 feet,) nor being carried farther, than the humid air itself; that they most accumulate in the upper strata of the fogs, producing more disease on lands slightly elevated above the level of the marsh than at its very edge; that fever-and-ague are never to be found where this plant does not grow; that it may be at once introduced into the healthiest locality by transporting moist earth on which the incrustation is forming; that the plant, being introduced into the human system through the lungs, continues to grow there and causes disease; and that quinia arrests its growth, (as it checks the multiplication of yeast plants in fermentation,) and thus suspends the action of the disease.

Probably it would be impossible to prove that the fore going theory is correct, though it is not improbable that it contains the germ from which a fuller knowledge of the disease and its causes will be obtained. It is sufficient for the purposes of this work to say that, so far as Dr. Salisbury's opinion is valuable, it is,-like the opinion of all other writers on the subject,-fully in favor of perfect drainage as the one great preventive of all malarial dis

eases.

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