Microbiology and evolutionary theories at the National Museum: João Baptista de Lacerda (1846-1915) between Pasteur and microbial polymorphis

Abstract

This article examines the role of João Baptista de Lacerda (1846–1915) in the consolidation of microbiology in Brazil, focusing on his theoretical influences, institutional contributions, and use of evolutionary concepts in studies of microorganisms. Drawing on the circulation of Pasteurian ideas in the late nineteenth century, it analyses the role of the National Museum’s Laboratory of Biology as a central site in the institutionalisation of bacteriology in the country. The article highlights Lacerda’s scientific production on human and veterinary diseases, the marked influence of Pasteur on his work, his institutional efforts to promote laboratory research, and his methodological and theoretical disputes with contemporaries, both national and international. It gives particular attention to the notion of microbial polymorphism in Lacerda’s writings, interpreted in some historiographical studies as neo-Lamarckism. An analysis of primary sources, however, suggests that Lacerda’s recurrent use of the term “evolution” primarily refers to ontogeny, linked to the life cycle of microorganisms and to environmental influences, rather than to hereditary transformations across generations.