Likely a sterile medium means an uncontaminated culture (food free of living organisms) that will grow only the new bacteria introduced for analysis. Source(s): http://www.thefreedictionary.com/sterile
Stonepelt was Bluestar's first mentor and a very well-respected senior warrior of ThunderClan. It is revealed in this book that he took her to the Gathering on her second day as an apprentice because she had caught a squirrel very well for a new apprentice, and the squirrel had been as big as she was.
Because cats could protect against the tiny monsters that made Egyptian homes unsafe, Mafdet was regarded as the protector of the home-- and of the kingdom itself! Later in Egyptian history, the goddess Bastet (sometimes just Bast) replaced Mafdet as the feline goddess of choice. Like Mafdet, she was regarded as a fierce protector of the home (and especially of children and royalty), largely because of cats' renowned ability to kill snakes, scorpions, and other vermin.