"It is a remarkable fact that this substance, which is so potent against bacteria, is almost harmless to animal tissues."

"It is not often that one finds a substance that is both highly bactericidal and non-toxic to animal tissues."

"The therapeutic value of penicillin is enormous, but its indiscriminate use could lead to disaster."

"I have been asked by many people how I came to discover penicillin. The answer is that I did not discover it. I just happened to notice it."

"It is a wonderful thing to be able to save lives with a simple substance."