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

"The greatest reward for a scientist is the advancement of knowledge."

"It is not wise to be too dogmatic in science. One must always be prepared to change one's mind."

"The discovery of penicillin was a series of small observations, not a single eureka moment."

"It is a matter of great satisfaction to see penicillin saving so many lives."