"I am often asked if I foresaw the impact of penicillin. My honest answer is no."

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

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

"I can only warn. It is up to others to heed the warning."

"It is not the man who first sees a thing who is the discoverer, but he who sees into a thing."