The making of a controversy: The Hansen-Neisser debate revisited

Literature about the discovery of the leprosy bacterium Mycobacterium leprae usually mentions the Hansen-Neisser controversy. It is an established narrative that Neisser tried to present himself as the discoverer of the leprosy bacterium. However, Neisser's first publication on Mycobacterium leprae refers explicitly to Hansen's original discovery. How did the notion of Neisser trying to claim Hansen's discovery emerge? A thorough source-critical examination of Hansen's and Neisser's scientific and popular publications between 1874 and 1897 as well as of the literature dealing with the so-called controversy brought interesting new results. The notion that Neisser tried to steal Hansen's discovery is based on a misreading of Neisser's publications by Hansen's biographer. But Neisser tried indeed to bypass Hansen in trying to prove that Mycobacterium leprae was the contagion causing leprosy. The competition between the two scientists resulted in a personal enmity. This study shows how the history of modern science is prone to myths and underlines the importance of source criticism when dealing with established narratives.