"The discovery of penicillin was a series of small observations, not a single eureka moment."

"It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them."

"I had no idea that I would be involved in such a great discovery. It was purely accidental."

"I can only warn. It is up to others to heed the warning."

"I never thought of myself as a genius. I just kept looking."