"The therapeutic value of penicillin is enormous, but its indiscriminate use could lead to disaster."

"The thought that I might have discovered something which would be of value in treating disease was, of course, uppermost in my mind."

"It is a matter of great satisfaction to see penicillin saving so many lives."

"Nature makes penicillin; I just found it."

"I have been asked to say a few words about the discovery of penicillin. I must confess that I have been asked to do this so often that I am beginning to be a little tired of it."