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

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

"The early days of penicillin were full of disappointments, but we never gave up."

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

"I am sometimes asked what I think of the future of penicillin. I think it has a great future, but it must be used wisely."