In 1928, Sir Alexander Fleming was studying Staphylococcus bacteria to try to find a way to cure the fatal infections this bacteria was causing in soldiers wounded in battle. While growing samples of the bacteria in petri dishes for his experiments, he noticed that some of the dishes had been accidentally contaminated by spores from a species of Penicillium mold that had apparently been floating in the air in his lab. When he observed the petri dishes closely, he noticed clear areas around the spots where the mold was growing, indicating that all of the bacteria that had been growing in these clear areas had died. No clear areas existed in the petri dishes that had not been contaminated by the mold. Fleming hypothesized that the mold must be producing a chemical that was killing the bacteria. He thought that if he could separate this bacteria-killing chemical from the mold, it could be used as a medicine to cure Staphylococcus bacterial infections. In order to test this idea, he set up an experiment. First, in order to separate the chemical from the mold, he set up two beakers with nutrient broth (food). He added penicillium mold to one of the beakers and let it grow, allowing the mold to produce the chemical. He then filtered the Penicillum mold out of the substance, leaving behind a sample of nutrient broth and the mold chemical. The other beaker still held plain nutrient broth. He was then ready to begin his actual experiment.
Fleming set up two petri dishes with the same amount of agar (food). He swiped the inside of each dish with Staphylococcus bacteria and placed them into a 98°F incubator for one week to grow. When he took the petri dishes out, he added 10 drops of the plain nutrient broth to one dish and 10 drops of the nutrient broth with the mold chemical to the other dish. He put the petri dishes back into the 98°F incubator. After two days, he
observed that the bacteria in the first dish with the plain nutrient broth added had not died, but had actually increased in number. The second dish with the nutrient broth and mold chemical had almost killed off the bacteria completely. He concluded that the chemical taken from the Penicillium mold had indeed killed the Staphylococcus bacteria. This chemical is now known as the antibiotic medicine Penicillin, and versions of it are in widespread use today to cure a variety of bacterial infections,

List the "Constants" of the experiment (there are at least 8)