"The laboratory worker who is not prepared to meet with occasional failures will never achieve success."

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

"My only merit is that I did not discard the cultures at an early stage."

"The story of penicillin has been told so often that it is almost a cliché."

"It is not often that one finds a substance that is both highly bactericidal and non-toxic to animal tissues."