© Science Museum/Science and Society Picture Library
This sample marks the transformation of penicillin from an interesting phenomenon to a potential drug.
Discovering in 1928 that a strain of penicillium mould exuded a substance which killed certain bacteria, Alexander Fleming did not immediately think of it as a medicine. However, when the German firm IG Farben announced the first general-purpose bacteria-killing drug, Prontosil, Fleming changed his views. He gave this sample of mould to a colleague at St Mary's Hospital after a conversation about Prontosil and its possible application to ward off infection.
Penicillin was eventually isolated in Oxford in 1939, and from 1942 became an important drug.