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.
The warrior Clans were just a lot of cats with 5 different atributes such as swimming for RiverClan, or hunting in the trees for SkyClan... or running quickly for WindClan, and that kind of stuff. So when there was this prey shortage the groups of cats ( including Sky, Thunder, River, Shadow, and WInd,) had a big battle, this wasn't jsut a skirmish!