THE PILGRIM PATH OF CHOLERA. 635 



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 dis- 

 semination 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 elimi- 

 nating 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 subse- 

 quent sufferers may be traced out, free from the interfering influ- 

 ence of possible infection from other sources covert and concealed 

 all around. Thus it happens that much of our most useful knowl- 

 edge 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 dis- 

 seminating cholera. His deductions to this effect, from his ob- 

 servations 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 1866, 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 pol- 

 luted 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 2d, seventy-eight deaths were 

 registered, in the next week there were two hundred and eighty- 



