"We must be careful not to create a race of penicillin-resistant superbugs."

"It is not the discovery of a new substance that is important, but the recognition of its properties."

"The mold was there, I just saw it."

"The discovery of penicillin was a matter of chance, but the application of it was a matter of hard work."

"It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them, and the same thing has occasionally happened in the body."