Parasites, Pepsin, Pus, and Postulates: Jakob Henle's Essay on Miasma, Contagium, and Miasmatic-Contagious Diseases...

The German anatomist and pathologist Jakob Henle's essay on miasma and miasmatic-contagious diseases is considered a medical classic. Nevertheless, it has rarely been analyzed in depth. If at all, it has been read as foreshadowing Robert Koch's "postulates," the famous set of criteria for identifying pathogens. This reading has created misunderstandings of Henle's own work on miasma and miasmatic-contagious diseases and impeded our understanding of the broader experimental tradition on which later nineteenth-century medical research was grounded. I place Henle's work in the context of early nineteenth-century research on infectious diseases and disease causation. Moreover, I show how it resonates with experimental research on invisible causal agents in other fields, including chemistry, pharmacology, physiology, veterinary science, and natural history. The strategies encapsulated in Koch's "postulates" were commonly used in these fields; Koch and Henle were both part of a broader experimental tradition that was well established in the early 1800s.