Penicillin for patients : stable ? pure ? or just 'safe enough' ? -- the essential disagreement between Fleming, Florey and Dawson

Alexander Fleming was famously known for his frugality : in speech, in the use of materials and in his physical exertions on his paid job.

Being too self confident in his own intellectual abilities (and perhaps also being too frugal cum lazy in the physical exertion department ?) fatally led him to avoid doing the needed series of experiments to prove up his claim that penicillin would never have time to do its work inside the body.

So he misled himself - and more importantly , the entire world,  for 14 years that penicillin would only work on the body,  never in the body - and tens of millions died premature deaths that could have/ should have been avoided.