[Hansen versus Neisser: scientific controversies over the 'discovery' of the bacillus of leprosy].

This paper analyzes the turbulent scientific process that led to the 'discovery' of the bacillus that causes leprosy, which occurred in Europe in the second half of the nineteenth century and which involved some of the leading names in medical science of the period, such as Robert Koch, Rudolf Virchow and Armauer Hansen. Understood as a scientific paradigm, this 'discovery' is reexamined here based on primary sources as yet only partially researched in Latin America. The scope of this paper is to provide new instruments for analysis and reflection for the historiography of the sciences, as the cultural, social and even nationalist aspects are identified in the construction of this paradigm.