Sir Alexander Fleming was a Scottish biologist, pharmacologist, and botanist. He wrote many articles on bacteriology, immunology, and chemotherapy. His best-known discoveries are the enzyme substance lysozyme in 1923 and the antibiotic substance penicillin from the mold Penicillium notatum in 1928, for which he shared the Nobel Prize in Physiology or Medicine in 1945 with Howard Florey and Ernst Boris Chain. This audiobook is from a 1950 talk he gave on the development of antibiotics. Download and start listening now!