The Papers of Joseph Henry


44. TO JOHN KEARSLEY MITCHELL[1]

My dear Dr

I happened a few evening ago to have a conversation with Mr Walker secretary of the Treasury on the subject of the yellow fever and his remarkes struck me as being characterized with ↑so much↓ philosophical discrimination that knowing your interest in this matter I am induced to note them down for your inspection.
The following as far as I can recollect are ↑the conclusions↓ he has arrived at from his own observations of the phenomena as they have been exhibited for several years at Natchis and New Orleans.
1 Yellow fever occurs spontaneously in certain places under the predisposing causes of heat filth and moisture.
2 Yellow fever is sometimes ↑produced↓ from the pent up air brought in the hold of vessels from a distance and thence spreads by propogation, provided the necessary conditions are present.
3 The cause of the disease is destroyed by a single exposure of the air to a white frost. A case to illustrate this fell under Mr Walkers notice in which a house was closed at the time the fever was raging and not opened until after a frost; when three persons died who attempted[A] to live in it though there was no feave in any other part of the city at the time.
4 The cause of the yellow fever appears to require the presence of of collections of human beaings for its propagation; no instance has been known of the disease breaking out or spreading on an insulated plantation not in the vicinity of a city.
5 Yellow fever after having made its appearance from year to year in a certain place has entirely disappeared after the land has been drained, vegetabl and animal matter in a state of putrescence removed, and a more general attention ↑given↓ to the clenliness of the place grounds & buildings.
I do not suppose that any of these conclusions are new to you though they may serve to fortify some of your points and I doubt not that Mr Walker would readily communicate to you the details of facts on which he has founded his inductions.[2]

With my best wishes for your continued success in all that renders life plesant and profitable

I remn yours truly

Joseph Henry
Dr J. K. Mitchell
Draft, Henry Papers, Smithsonian Archives.
    [1] Mitchell was professor of medicine at Jefferson Medical College in Philadelphia. Henry Papers, 3:325n.
    [2] The cause of yellow fever was unknown. The dominant view in the medical profession was that it was caused by miasma, or poisons in the air produced by marshes. Others blamed atmospheric conditions, while a minority believed the disease was caused by tiny animal or vegetable creatures usually termed animalculae. Doctors also divided into contagionists, who believed the disease was spread by people or animals, and non-contagionists, who believed it could arise spontaneously and be spread by infected air. As with other fevers, disease theorists tried to determine the cause by a process of induction from everything known about the disease. Henry was undoubtedly aware of Mitchell's lectures on fevers, six of which from the 1846–1847 academic year became On the Cryptogamous Origin of Malarious and Epidemic Fevers (Philadelphia, 1849). Having hesitated to publish because he feared controversy and felt he lacked conclusive proof, Mitchell joined the organic theorists by proposing a "fungous theory of fevers," in which yellow fever was caused by fungus (pp. iv, 106). Although Mitchell did not mention Walker's observations, he did discuss some of the same phenomena Walker noticed (pp. 102–107). The true cause of yellow fever, a virus carried by mosquitoes, was not discovered until the turn of the century. Phyllis Allen, "Etiological Theory in America Prior to the Civil War," Journal of the History of Medicine and Allied Sciences, 1947, 2:489–520.
    [A] Altered from attemppted