I've been having an ongoing discussion with my parents lately about penicillin's constitution. They firmly believe that it is, or at least was at some point in its history, made with pregnant mare's urine, despite my research on the subject yielding no results corroborating their story. Wikipedia tells me that penicillin comes from fungi. The only thing that I have found about urine is this quote:
[...] during the early penicillin era, the drug was so scarce and so highly valued that it became common to collect the urine from patients being treated, so that the penicillin in the urine could be isolated and reused.
Does anyone know if there is some truth to the use of pregnant mare's urine in penicillin? If this is absolutely false, where would this thought come from?