462 © ANNUAL REPORT SMITHSONIAN INSTITUTION, 1944 
passed this over, but Fleming, an acute observer with a special inter- 
est in antiseptics, subcultured the mold for further investigation. 
From its descendants all the penicillin in the world was produced 
until recently. 
The mold was identified as Penicilliwm notatum. Fleming culti- 
vated it in a liquid medium, peptone broth, and found that it pro- 
duced in the broth a substance capable of inhibiting the growth of 
many dangerous germs, even when diluted 800 times. The active 
substance he named penicillin. He noted that broth containing 
penicillin was not more toxic when injected into rabbits and mice 
than pure broth and that it did not appear to be harmful to the white 
cells of the blood. 
As a result of this, he suggested that penicillin might be a good 
antiseptic to apply to septic wounds, and indeed a few cases were 
so treated. He concluded that it certainly appeared to be superior 
to dressings containing potent chemicals. The observations, how- 
ever, were not carried further, though Clutterbuck, Lovell, and Rais- 
trick made an attempt to extract the active material. As a result 
of their work they concluded that penicillin was extremely unstable, 
and they did not pursue the matter. 
In the succeeding years no further interest seems to have been taken 
in its chemical properties or its possible application to medicine, 
though Fleming continued to use the crude culture medium in the 
laboratory as a means of suppressing the growth of certain kinds of 
bacteria in mixed cultures. 
In 1929 one of the present authors, H. W. Florey, started work on 
the antibacterial substance lysozyme—another discovery of Fleming’s. 
This substance was first discovered in egg white but is widely distrib- 
uted in nature. It has the power of dissolving or killing certain spe- 
cies of air bacteria, though it has, unfortunately, no effect against 
bacteria causing disease in man. 
The work on lysozyme was carried on until its purification (by 
Roberts in 1936) and the elucidation of its mode of action as a carbo- 
hydrate-splitting enzyme (Meyer and associates, 1936; Epstein and 
Chain, 1940). During the later part of this work, in 1938, the present 
writers decided to undertake a systematic investigation of the anti- 
bacterial substances produced by bacteria and molds, about whose 
chemical and biologic properties little was known. 
Although the reports suggested that penicillin was an unstable sub- 
stance, it was among the first chosen for investigation, since it seemed 
likely to be of considerable biochemical and biologic interest. In 
particular, it was active against many organisms causing the most 
destructive lesions in man, including staphylococcus. Fleming, 
Clutterbuck, et al., reported that under suitable conditions penicillin 
