"We must be careful not to create a race of penicillin-resistant superbugs."

"The greatest tragedy is the misuse of a good thing."

"The purification of penicillin was a major triumph of chemistry."

"I had no idea at the time that I was making a discovery that would change the course of medicine."

"A good many people think that I deserve some credit for the discovery of penicillin. They are wrong. It was discovered by nature."