"It is not difficult to make microbes resistant to penicillin in the laboratory by exposing them to concentrations not sufficient to kill them, and the same thing has occasionally happened in the body."

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

"My own work was really quite simple. I just observed what was happening."

"It is the lone worker who makes the first advance in a subject; the details may be worked out by a team, but the prime idea is due to enterprise, thought, and perception of an individual."

"The mould was very interesting. I cultured it and found it produced a powerful antibacterial substance. It was very effective against staphylococci and other Gram-positive pathogenic bacteria."