Penicillin Past, Present and Future -- Here are the flasks containing Corn Steep medium and spores of Penicillium mould. There are 4,000 flasks in this lot ready for the mould to grow. It takes only a few days before the first white fluff will appear on top of the brown medium. The mould is delicate in its first stages and sudden jar will cause it to sink to the bottom of the flask. The room is kept at a temperature of 750 F. Fourteen years ago, Professor Fleming of the Chair, of Bacteriology at