When Alexander Fleming began his work at St Mary's Hospital in London under the leadership of Sir Almroth Wright he was following the Listerian traditon and seeking new and more powerful antiseptics which could be used internally without damaging healthy tissues. It was in the course of this research that Felming noticed the accidental contamination of a culture plate of staphylococci by a mould which had floated through the window. The colonies of this common pus-forming bacterium adjacent to the mould appeared to be destroyed by it. The mould was identified as penicillium notatum and when cultures of it were developed it was found to produce a brown liquid substance which Fleming named 'penicillin' and which was shown to have a powerful destructive action on a wide range of microbes. -- PMM 420a.