German bacteriologist who studied the life cycle of the anthrax bacterium, cultivating the bacteria outside the body using bloom serum at body temperature. He was invited to work in the laboratory of Cohn. Using his techniques, he isolated the tubercule bacillus, which was responsible for the disease of tuberculosis in 1882. He won the 1905 Nobel Prize primarily for these researches. Koch also showed that the plague was transmitted by fleas infesting rats.

Cohn