Besredka's "antivirus" in relation to Fleming's initial views on the nature of penicillin.

Alexander Fleming's initial views on the nature and clinical use of penicillin have recently evoked a considerable amount of speculation.' It is clear that Fleming made a number of attempts to use crude penicillin (i.e., filtrates of cultures of Penicillium notatum) on surface wounds during the brief period following his chance discovery of the substance in September 1928.2 He also enlisted the help of a number of students and others in attempts to extract the active ingredient from the crude meat broths on which his penicillin-producing isolate grew. Although Lewis Holt used solvent transfer for the purification of penicillin in 1934,3 Fleming, with his limited knowledge of chemistry, did not appreciate the importance of this. Harold Raistrick's inability to isolate penicillin in the early 1930s no doubt increased Fleming's sense of the impossibility of the task.4 However, it seems that his own experiments had by that time convinced him that penicillin would be quickly inactivated when injected into the bloodstream, and that even if purified, it would be of limited medical use.5 Fleming did not discard penicillin altogether, but put it to good use as a component of selective bacterial culture media. There is also anecdotal evidence that he persisted with the view that it might one day find a use in medicine. For example, he is said to have commented to Douglas McLeod on leaving a talk on sulphonamides given by Gerhard Domagk in London in 1935 that in penicillin6 he had something much better than Prontosil, but nobody was interested and he was unable to find a chemist who would take the trouble to isolate this substance for him. My aim in this paper is to show that soon after discovering penicillin, Fleming's thoughts on the nature of penicillin were markedly altered by Besredka's "antivirus",