 Negri performed extensive research in the fields of histology, hematology, cytology, protozoology and hygiene.In 1903 he discovered the eponymous Negri bodies, defined as cytoplasmatic inclusion bodies located in the Purkinje cells of the cerebellum in cases of rabies in animals and humans.He documented his findings in an article titled "Contributo allo studio dell'eziologia della rabia", published in the journal "Bollettino della Societa medico-chirurgica".