"It is not often that one finds a substance that is both highly bactericidal and non-toxic to animal tissues."

"The purification of penicillin was a major triumph of chemistry."

"The public will probably never understand the difficulties that beset the path of the original investigator."

"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…"

"I have always been interested in the fight against disease."