"I play with microbes. There are, of course, many rules to this play...but when you have acquired knowledge and experience it is very pleasant to break the rules and to be able to find something nobody…"

"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…"

"The mold was a lucky accident, but the observation was not."

"The impact of penicillin on modern medicine is immeasurable."

"The accidental contamination of my cultures by a mold was not an unusual event in a bacteriological laboratory. What was unusual was my decision to investigate the mold."