Fleming is famous for his discovery of penicillin, possibly
the single biggest drug advance in the history of medicine,
but which came about by what he called a triumph of accident
and shrewd observation. He saw that a culture of staphylococcus
bacteria had accidentally become infected with mould, and the
mould, Penicillum notatum, which commonly grows on stale food,
was killing the bacteria. Tests showed it to have unprecedented
antibacterial properties while being harmless to human cells.
It took another 15 years to find a manufacturing process. Fleming
won the Nobel Prize in 1945. Displaying a morality sadly rare
in medical research today, Fleming never patented his discovery
so it could remain cheap and widely available to benefit as
many people as possible.