Robert Koch demonstrates in 1876 that Bacillus anthracis is the exclusive causal agent of anthrax, establishing for the first time a direct causal relationship between a microorganism and a disease. In 1884 he formalizes the four postulates that define the criteria for causally attributing a pathogen to a disease: isolation, pure culture, reinoculation, and reisolation. He also identifies the tuberculosis bacillus (1882) and Vibrio cholerae (1883). The dispute with Pasteur over priority in bacteriology was real and documented; Koch's postulates are a methodological contribution with no equivalent in Pasteur's work.