"It is not an exaggeration to say that the discovery of penicillin has saved millions of lives."

"The greatest tragedy is the misuse of a good thing."

"I am very grateful for the recognition I have received, but the real credit belongs to the mould."

"My work was not a flash of genius, but a gradual unfolding of facts."

"I have been working for many years on the problem of finding substances which would destroy microbes in the body without injuring the cells of the body."