Figure 4 Sum of specific death ratios of the eight leading causes of death (primarily infectious diseases) in London between 1750 and 1909. The initial decline in mortality--accompanying urbanization and development--was interrupted in the 1830s by a resurgence of tuberculosis, small pox, and cholera, associated with overcrowding and unsanitary conditions. Environmental and sanitary reform and the birth of modern public health principles led to the ensuing, dramatic decline. From Mary Matossian Kilbourne. Poisons of the Past: Molds, Epidemics and History. Yale Univ. Press, New Haven, 1989.