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

"The bacteriologist is a detective. He must follow every clue, however small."

"The medical profession has a great responsibility in seeing that penicillin is used wisely."

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

"I did not invent penicillin. Nature did that. I only discovered it by accident."