... we ought to have saints' days to commemorate the great discoveries which have been made for all mankind, and perhaps for all time—or for whatever time may be left to us. Nature ... is a prodigal of pain. I should like to find a day when we can take a holiday, a day of jubilation when we can fête good Saint Anaesthesia and chaste and pure Saint Antiseptic. ... I should be bound to celebrate, among others, Saint Penicillin...

I doubt that Fleming could have obtained a grant for the discovery of penicillin on that basis [a requirement for highly detailed research plans] because he could not have said, 'I propose to have an accident in a culture so that it will be spoiled by a mould falling on it, and I propose to recognize the possibility of extracting an antibiotic from this mould.'

In my first publication I might have claimed that I had come to the conclusion, as a result of serious study of the literature and deep thought, that valuable antibacterial substances were made by moulds and that I set out to investigate the problem. That would have been untrue and I preferred to tell the truth that penicillin started as a chance observation. My only merit is that I did not neglect the observation and that I pursued the subject as a bacteriologist. My publication in 1929 was the starting-point of the work of others who developed penicillin especially in the chemical field.

It has been demonstrated that a species of penicillium produces in culture a very powerful antibacterial substance which affects different bacteria in different degrees. Generally speaking it may be said that the least sensitive bacteria are the Gram-negative bacilli, and the most susceptible are the pyogenic cocci ... In addition to its possible use in the treatment of bacterial infections penicillin is certainly useful... for its power of inhibiting unwanted microbes in bacterial cultures so that penicillin insensitive bacteria can readily be isolated.

It was astonishing that for some considerable distance around the mould growth the staphococcal colonies were undergoing lysis. What had formerly been a well-grown colony was now a faint shadow of its former self...I was sufficiently interested to pursue the subject.
[Sep 1928, the first observation of penicillin. Lysis is the dissolution or destruction of cells.]

Stay in college, get the knowledge. And stay there until you're through. If they can make penicillin out of moldy bread, they can sure make something out of you.
Advice to a young person to continue his education.

The genius of Man in our time has gone into jet-propulsion, atom-splitting, penicillin-curing, etc. There is left none over for works of imagination; of spiritual insight or mystical enlightenment. I asked for bread and was given a tranquilizer. It is important to recognize that in our time man has not written one word, thought one thought, put two notes or two bricks together, splashed color on to canvas or concrete into space, in a manner which will be of any conceivable imaginative interest to posterity.

While working with staphylococcus variants a number of culture-plates were set aside on the laboratory bench and examined from time to time. In the examinations these plates were necessarily exposed to the air and they became contaminated with various micro-organisms. It was noticed that around a large colony of a contaminating mould the staphylococcus colonies became transparent and were obviously undergoing lysis. Subcultures of this mould were made and experiments conducted with a view to ascertaining something of the properties of the bacteriolytic substance which had evidently been formed in the mould culture and which had diffused into the surrounding medium. It was found that broth in which the mould had been grown at room temperature for one or two weeks had acquired marked inhibitory, bacteriocidal and bacteriolytic properties to many of the more common pathogenic bacteria.