I was watching a program on the Discorvery Channel about cats. They did one about where there purring motor was. It's kinda like (they had pictures duh so this si gonna be odd..... bear with me) where they breath in thru there nose the piping meet up with there (I'm haveing a blonde moment I can't think of it's name but where there food goes down.......~blonde~)

ANYWAY
they meet up & there a flapp thats controled by lil bitty muscels, so when they want to pur they'll flap the flap (thats adult tearmonology). but..... its that flap that moves quickly that makes them pur. & It's in the throught....... but that just what was on D.C. ~~