"Report on the mortality of cholera in England, 1848-49 "
Harvard University Libraries has digitized the Registrar-General's Report on the 1848-49 cholera epidemic in England.
The table of contents contains a section on "Causes of the Mortality in London" (v, sequence 9): The Thames and the mortality in each district served by a water company, as well as amount of evaporation from that river (lviii-lxi, sequence 74-77) [essential to his argument in the next section]; elevation and Farr's inverse mortality ratio (lxi-lxvi, sequence 77-82); density (lxvi, sequence 82; and wealth and poverty (lxvi-lxviii, sequence 82-84).
Thereafter Farr discusses eight theories and analogies: volcanic activity; electrical theory; bad water [from a variety of causes, mitigated by boiling it]; fungus theory; [Snow's] "theory that cholera is propagated by human intercourse, and that it is a local affection of the alimentary canal" (lxxvi-lxxviii, sequence 92-94); contagion (lxxviii-lxxix, sequence 94-95); spontaneous development; [Farr's own] zymotic theory (lxxx-lxxxiii, sequence 96-99.
With respect to Snow, Farr writes: "Dr. Snow, in a paper dated Aug. 29, 1849 [MCC], advanced a theory of the pathology of cholera; and it is in many respects the most important theory that has yet been propounded" (lxxxv). Farr quotes passages from Snow's May 5 1851 paper delivered at the Epidemiological Society (later published as MPC Part 1 and MPC Part 2), as well as MCC and PMCC Part 1 and PMCC Part 2, where Snow explains his hypothesis and some substantiating evidence, especially the contrast between cholera mortality at Exeter and Hull after changes in town water supplies.
"Dr. Snow's theory of the propagation of Asiatic cholera in London is very simple. The cholera matter was brought to London [in 1848] by patients from Hamburgh; it was multiplied in the intestines of infected people until the disease spread in this way all over the metropolis. It necessarily implies that the rice-water discharges of the cholera patients may, under the present system of water supply, be distributed unchanged to nearly every house in London, where water is used for drink, ablution, and washing. Dr. Snow is unfortunately able to show that this excremental distribution--almost too revolting and disgusting to write or read--is possible to a very considerable extent. The sewers of London run into the Thames and the Lea, from which a part of the water supply is derived. The water, which the inhabitants of London have but the repulsive alternative to discuss in words or to use in fact, is however baled from the ditches only by the wretched inhabitants of such parts as Jacob's Island. It is in one case before distribution pumped up to a distant reservoir at Brixton; in other cases it is taken higher up the rivers, largely diluted, or beyond the reach of any but casual contamination; filtration is employed; chemical action, as the chemists on behalf of their wealthy clients tell us, is incessantly going on, and converting impurities into simple elements; so that it is only in some places, or in rare circumstances, that the organic waste can reach and injure people. Still, in this mitigated form, the risk is too tremendous to be incurred by two millions and a half of people, who require and can obtain an abundance of sweet water.
. . . The experience of Paris . . . as well as of many of our own towns, lends some countenance to Dr. Snow's theory" (lxxviii).
Farr also mentions instances of local, or neighborhood, cholera outbreaks caused by contaminated well and ditch water: "Dr. Lloyd, on August 30, 1849, at a meeting of the South London Medical Society, adduced instances of the great mortality from cholera, of people in Silver-street and Charlotte-place, Rotherhithe, who got their water from a well and a ditch into which the privies discharged their contents. The disease was much more fatal in the parts of Rotherhithe where ditch-water was used, than it was in places which had their supply from the Water-works. Dr. Snow has collected examples in the South London districts, where the water being derived from deep wells, few cases of cholera occurred; and other instances of a great fatality among people living in houses, such as those in Wandsworth-road, where the contents of the water-closets found their way into the water" (lxxv).
Farr defined infection as atmospheric propagation: "The general argument in favour of the propagation of cholera by infection has been forcibly stated by Dr. Bryson, who brings facts from the experience of the navy to show that the existing virus may take effect at the distance of one or two miles, if not further; and, in contact with inanimate substances, may be conveyed to the distance of many hundred miles, provided the transit be accomplished within the space of about ten days. . . . [T]he hypothesis of infection, which assumes that 'an atmosphere charged with the specific virus emanating from a population labouring under cholera and choleraic diarrhœa may prove effective at the distance of several miles from an infected locality'" (lxxv).
Ordinary Contagion, or direct contact: "Instances are cited by writers on contagion of medical officers in attendance on cholera patients, suffering or escaping attacks of the disease; but they are seldom conclusive. . . .
The fact that the first cases of the epidemic appear in the sea-ports is not in itself a decisive proof of the importation of the disease; for if it is ever indigenous, as it was on the Delta of the Ganges, it will almost certainly break out in such low places and circumstances as are found in the neighbourhood of nearly all sea-ports" (lxxix).
Farr's description of his zymotic theory takes the form of an extended note in which he reprints his description from the appendix to the 4th Annual Report of the Registrar-General.
Although Farr believes that "elevation of the soil has a more constant relation with the mortality from cholera than any known element" (v), he is even-handed in his presentation of alternative theories and straight-forward about how much remains unknown about this epidemic disease. On page lxxx (sequence 96), Farr wrote: "It may, I think, be admitted that the disease Asiatic cholera is induced in man by a certain specific matter, and as it has been proposed to call the matter varioline which causes small-pox, so [Farr proposes] cholerine may designate the zymotic principle of cholera. A variety of that matter was produced in India in certain unfavourable circumstances; it had the property of propagating and multiplying itself in air, or water, or food, of of destroying men, by producing successive attacks the series of phenomena which constitute Asiatic cholera.
That cholerine is an organic matter, cannot, I think, be doubted by those who have studied the whole of its phenomena and the general laws of zymotic disease. The great questions remain--Is cholerine produced in the human organization alone and propagated by excreted matter? Is it produced and propagated in dead animal or vegetable matter or mixed infusions of excreta and other matter of the body? Is it propagated through water? through air? through contact? or through all these channels?"