era, and who have had large experience of it, should hesitate to admit the fact that the way in which the infection parted with by the one sufferer gets round to another is by the water which the one man fouls and which the other drinks. But, as a fact, those who dwell in the midst of an endemic area, although they may have exceptional opportunities for studying the disease itself, its symptoms, its treatment, and its pathology, are not always so well placed for the investigation of its mode of dissemination as those whose lot is cast in places where the disease is but of exceptional occurrence. In an endemic area the chances of infection are so various and complicated, the difficulty of eliminating other modes of access so enormous, that it is often hard in the extreme to prove the particular route by which the malady has reached its billet. In non-endemic areas, however, things are very different. The disease may not have appeared in the district for months or years; the source of the infection, the first in-carrier of the disease, may usually be known at once, and all his previous doings may be ascertained. With patience every mode of contact or communication between the first and subsequent sufferers may be traced out, free from the interfering influence of possible infection from other sources covert and concealed all around. Thus it happens that much of our most useful knowledge on the subject comes from the investigation of the disease as it has appeared in isolated epidemics rather than in endemic areas.
For Dr. Snow, of London, I must once more claim the great honor of being the first to recognize water as a medium of disseminating cholera. His deductions to this effect, from his observations of cholera in England between 1848 and 1854, were, as I have elsewhere shown, confirmed by the elaborate investigation of Farr and Simon; and in I860, following in the same footsteps, I placed the corner stone of the edifice by tracing the disastrous cholera epidemic of that year in East London to the distribution of polluted and partially filtered water from the river Lee, by the East London Water Company—the poisonous sewage of one family distributed unfiltered for forty-eight miles. Since that startling experience, I have been convinced that specifically polluted water is not merely an occasional or adjuvant cause, but the causa causans of almost every great epidemic of Asiatic cholera.
The earliest important instance in which the agency of water as a disseminator of cholera was clearly demonstrated was that of the Broad Street pump in St. James's, Westminster. The first death in the parish was recorded early in August, 1854, and throughout that month a few deaths occurred each week, but during the week ending September 'id, seventy-eight deaths were registered, in the next week there were two hundred and eighty--
