The Mold That Healed the World

In September 1928, Alexander Fleming returned to his London laboratory at St. Mary's Hospital after a summer holiday and noticed something peculiar. A petri dish of Staphylococcus bacteria had been contaminated by a blue-green mold, and everywhere the mold touched, the bacteria had died. Most researchers would have discarded the ruined sample. Fleming looked closer. That moment of honest observation — of refusing to ignore what was plainly true — eventually gave the world penicillin.…