With the experienced eye of a scientist, Alexander Fleming turned what appeared to be a spoiled experiment into the discovery of penicillin.

Fleming was born in 1881 to a farming family in Lochfield, Scotland. Following school, he worked as a shipping clerk in London and enlisted in the London Scottish Regiment. In 1901, he began his medical career, entering St. Mary's Hospital Medical School, where he was a prizewinning student. After graduation in 1906, he began working at that institution with Sir Almroth Edward Wright, a pathologist. From the start, Fleming was innovative and became one of the first to use Paul Ehrlich's arsenic compound, Salvarsan, to treat syphilis in Great Britain.

Wright and Fleming joined the Royal Army Medical Corps during World War I and they studied wounds and infection-causing bacteria at a hospital in Boulogne, France. At that time, antiseptics were used to treat bacterial infections, but Wright...