"The greatest discovery of my life was not penicillin, but the fact that I was wrong about something."

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

"The thoughtless person playing with penicillin treatment is morally responsible for the death of the man who succumbs to infection with the penicillin-resistant organism."

"I have been very lucky in my scientific career. I have stumbled on things by accident."