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

"The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantitie…"

"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."

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

"The greatest reward for a scientist is the advancement of knowledge."