An inquiry into the propagation of contagious poisons, by the atmosphere

by Somerville Scott Alison

For those very reasons day-light is said to be the effect of the sun that comes with it, remains with it, and goes with it.

Let us see if the same connection holds with disease and those agencies and circumstances we have cursorily referred to.

Those agencies and circumstances, relating to food, drink, air, heat, contagious matter, &c. &c. are known to present themselves, and with them are presented diseases. They are known to remain, and with them are known to continue diseases. They are known to disappear, and with them all the world knows diseases disappear also.

These being the causes of epidemic or widely spread disease, as such a connection proves, it is altogether superfluous to admit the operation of atmospheric contagion, whose existence has never been known, but by the very circumstances which it is said to bring about.

It is surely most unwise, when we see disease arising with the existence of unwholesome circumstances, such as scarcity of food, unwholesome quality of it, great vicissitudes of weather, uncommon conditions of the atmosphere, want of sufficient clothing or incommensurate with the severities of the season, the operation of depressing passions, and the like,—growing with their intensity—extending where they extend—abating where they decrease—and finally disappearing when they disappear—to refuse to grant the relation as cause and effect, and to plunge into the tide of difficulties such ill-timed incredulity creates, with nothing but the appearance, nothing but the assurance, of an object to grasp at.

In general, such a connection can be made out between the existence of wide-spread disease and such circumstances.

If, in respect to some diseases, so intimate a connection cannot be observed, the probability is, that it is the obscurity connected with these subjects, the less direct way in which they operate and the remote time at which their effects may be experienced on the body, that are the occasion of the difficulty. The human body, unlike mere inanimate matter, has the power of withstanding, at least for a time, the operation of unwholesome influences, if not very virulent; and it is only natural to allow, that, in respect to a machine so complicated, affected by so many agencies, and standing in so many relations, there will be less complete directness of operation, than with simple or inanimate substances, and more variety in the amount and duration of the effect.

On these accounts, the indications of the case are less direct and obvious, and it should cause no great surprise, that being considered, and the fact of the imperfect state of our knowledge on the varieties of the agencies referred to, being kept in mind, that the causes of disease cannot at all times be completely and satisfactorily ascertained.

Our knowledge of the derangements of health, from the operation of these agencies, on some of which we are dependent, and with others of which we are constantly brought in contact, is fast increasing, and the relation between the former and the varieties in the latter is becoming clear and precise. There is, therefore, reason to hope that difficulties which now baffle us, will soon be explained away, and that much of that mist that has long overhung the causes of pestilence, will soon be dissipated.

Certain circumstances produce certain uniform effects, and in every instance where they are operating, their effects will be produced, provided no agency is acting adequate to neutralize them. Not one hill only, in northern latitudes, has its summit whitened with snow, nor does sterility mark a few spots only in the immense deserts of Africa and Asia.