Flasks growing penicillin culture, 1943.

Laboratory technician examining flasks of penicillin culture, taken by James Jarche for Illustrated magazine in 1943. As the penicillin mould grows in the glass flask it develops a distinctive appearance. It grows into a crinkled layer which is called a 'felt'. During this process of growth the mould exudes peniciliin into the growth solution. Each flask contains enough mould to produce a single dose of penicillin. However it takes another three weeks to extract and purify the drug.