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.
prince of cats: In the folk tale, Reynard the Fox, the Prince of Cats is named Tybalt. 20. captain of compliments: master of ceremonies (in duelling). 21. as you sing prick-song: i.e., by the book. 22. proportion: rhythm.