"The story of penicillin is a lesson in serendipity and perseverance."

"The bacteriologist must be a patient man."

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

"The greatest joy of a scientist is to see his work used for the benefit of mankind."

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