"It is not wise to use penicillin as a prophylactic against every little infection."

"The mould grew, and then I saw the clear space around it."

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

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

"Many difficulties were encountered in the early attempts to isolate and purify penicillin."