The debate between contagionists and anticontagionists over the transmission of infectious diseases played a major role in nineteenth-century medical discourse. On the one side were those who believed that diseases could be spread by infected material, perhaps including people and inanimate objects, and on the other those who subscribed to the more venerable miasmatic theory. Although the contagionist view would be substantially vindicated by Robert Koch’s germ theory of disease, it is important not to simply ignore the arguments put forward by the anticontagionists. Although these were based on science that has since been disproven, the concrete proposals put forward by scientists like Max von Pettenkofer marked a major step forward for public health policy. In particular, the anticontagionists' emphasis on the environmental factors of disease control continues to provide an important lesson.