Paul Ehrlich was a German bacteriologist and immunologist, the founder of chemotherapy and an early pioneer of hematology. His discoveries include: a method of staining (1882), and hence identifying, the tuberculosis bacillus (see also Robert Koch); the reasons for immunity in terms of the chemistry of antibodies and antigens, for which he was awarded, with Élie Metchnikoff, the 1908 Nobel Prize in Physiology or Medicine; and the use of the drug salvarsan to cure syphilis, the first drug to be used in treating the root causes of the disease (1911) and one of the earliest example of a 'magic bullet'.

 

A second era of expansion for the drug industry was based on the accidental discovery by Alexander Fleming that molds could produce antibacterial substances. Ernst Chain, who helped in the development of penicillin, took chemotherapy a stage further by suggesting that semi-synthetic drugs would prove useful.