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

"The laboratory worker who is not prepared to meet with occasional failures will never achieve success."

"The impact of penicillin on modern medicine is immeasurable."

"It is a happy accident that the mold grew on my plate, but it was not an accident that I recognized it."

"It is a popular misconception that I was a brilliant chemist, but I was not. I was a bacteriologist."