"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."

"A good gulp of hot whisky at bedtime—it's not very scientific, but it helps."

"The discovery of penicillin was a stroke of luck, but it was also the result of many years of hard work."

"I was not a great scientist, but I was a careful observer."

"My laboratory was always a bit chaotic, but I knew where everything was."