Thanks for that, very informing. The most vicious dog I ever saw was a PICKENESE, darn thing started biting everybody, including it's owner....had to run it down and throw a burlap sack over it. Turned out the little foo-foo dog had a tack stuck in the roof of it's mouth.....
Have you ever seen a Jack Russell racing trial?
It is the only dog event I have observed where the dogs are required to be muzzled. They regularly attack each other unprovoked during the race.
http://www.terrier.com/trial/racing.php3