"I arrived at the conclusion in the latter part of 1848, that cholera is communicated by the evacuations from the alimentary canal." --John Snow, On the Mode of Communication of Cholera, 1848 On the Mode of Communication of Cholera--Second Edition, Much Enlarged (1854) is the follow-up to an earlier short essay (also available from Cosimo Classics) by English physician John Snow, in which he stated his theory that diseases such as cholera and the plague were not caused by bad air, but by germs that were spread by contaminated water, dirty clothing, and fecal contact. At a time when the germ theory of disease was not yet known, Snow's theory was revolutionary and laid the groundwork for modern epidemiology. In this expanded edition, Snow adds his new findings, including his investigation of the role of the water supply in the cholera epidemic of 1854 in the Soho neighborhood of London.