La Roche, in a carefully prepared treatise on "Pneumonia; its Supposed Connection with Autumnal Fevers," recites[pg 213] 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:—
"All the above hypotheses failing to account for the effects 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 nothing 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 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:—
"In considering the circumstances external to the residence, which affect the sanitary condition of the population, the importance of a general land-drainage is developed by the inquiries as to the cause of the prevalent 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 effectual."
La Roche calls attention to these facts:—That the acclimated 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 atmosphere,—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 nothing else so interesting as the very ingenious article of Dr. J. H. 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[pg 215] low order of plant, which spores he claims to have invariably detected in the saliva, and in the urine, of fever patients, and in those of no other persons, and which he collected 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 unprofessional mind to be sufficient,) to show that the plant producing these spores is always found, in the form of a whitish, 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 foregoing 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 diseases.
The evidence of the effect of drainage in removing the cause of malarial diseases is complete and conclusive. Instances of such improvement in this country are not rare, but they are much less numerous and less conspicuous here than in England, where draining has been much more extensively carried out, and where greater pains have been taken to collect testimony as to its effects.
If there is any fact well established by satisfactory experience, it is that thorough and judicious draining will entirely remove the local source of the miasm which produces these diseases.
The voluminous reports of various Committees of the English Parliament, appointed to investigate sanitary questions, are replete with information concerning experience throughout the whole country, bearing directly on this question.