SANITARY PRECAUTIONS.

375

distinguish it from the endemic, which we cannot prevent, must also be contagiousunder the same circumstances. Here, however, I believe, in like manner, that theperson of the patient, independent of fomites, never gives out at any one time asufficiency of the typhoid poison to affect another healthy person; that the poisoncan only he made effective through contamination of atmosphere, under long-continued accumulation of morbific effluvia; and, in fine, that the atmosphere ofthe patient is infectious, and not his person, which if once cleansed and purified, andventilation restored, may be approached, however ill he may be, with perfectimpunity. In this belief I feel warranted, from the knowledge of several importantfacts, of a character so general as to warrant the greatest confidence in theirapplication. 1st, The Bristol Hospital, for a great many years, has received typhusfevers into its well-disciplined wards, without having ever spread the disease even tothe most contiguous beds. 2ndly, Several of the great hospitals in London havefollowed the same example with the same results. 3rdly, The most pestilentiallydangerous fevers to approach when single, in the confined dwellings of the poor,have almost everywhere been found devoid of every infectious principle whencollected together in numbers, and confined by the hundred within the walls ofa well-regulated fever hospital. Upon this point the question of contagion mustturn; for, if the evidence here given be not impugned, it will be impossible inhuman testimony to adduce anything more decisive and conclusive. Reasoningfrom single individual instances will generally deceive; but well-digested impartialobservation upon masses of men can never lead to an erroneous conclusion.

SECTION VII.-MARSH POISON.*

In this paper I propose submitting to the Society some observations on the natureand history of the marsh poison/ which, under the title of marsh miasmata, ormalaria, has ever been acknowledged as the undisputed source of intermittent fevers,and is believed, with good reason, to be the exciting cause of the whole tribe ofremittent fevers;—of endemic fever, in fact, in every form, and in every part ofthe world.

All authors who have treated of the nature of this poison (and they are mostnumerous) coincide in attributing its deleterious influence to the agency of vegetableor aqueous putrefaction. So universal a coincidence has caused these opinionsto be received with the authority of an established creed. It is my intentionto shew from a narrative of facts that they are unfounded, and that putrefaction,under any sensible or discoverable form, is not essential to the production ofpestiferous miasmata.

The marsh poison, happily so little knowm in this country and the colder regionsof the earth, is notwithstanding by far the most frequent and destructive source offever to the human race, as that form of fever to which it gives rise rages throughoutthe world wherever a marshy surface has been exposed for a sufficient length of timeto the action of a powerful sun. I have said for a sufficient length of time, because,as will presently be seen, the marsh must cease to be a marsh, in the commonacceptation of the word, and the sensible putrefaction of water and vegetables mustalike be impossible, before its surface can become deleterious. It will also be seenthat a healthy condition of soil in these pestiferous regions is infallibly regained bythe restoration of the marshy surface in its utmost vigour of vegetable growth and

From the ‘ Transactions of the Royal Society of Edinburgh.’