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

"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."

"It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them."

"If penicillin can cure those that are ill, Spanish sherry can bring the dead back to life."

"The most important thing in science is not to get discouraged by failures."