The pitbull is not a specific breed of dog but a name for a type of
dog that share common physical and behavioral traits. The classes of dog
breeds that constitute the pitbull are American pitbull terrier,
American bulldog, Staffordshire bull terrier, American Staffordshire
terrier and any other purebred or breed crossed with any of these
breeds.
Over 1,000 years ago in England, bull dogs were bred and
used in the blood sport of bull baiting, a British pastime that involves
tying a bull to the stake and setting these specially bred and trained
bull dogs to attack them with the primary objective of seizing and
holding the bulls by the nose as this was the most tender part of the
bull. The bull dog breed was selectively bred into a powerful muscular
breed with tremendous jaw power and the ability to bite and hold on with
unyielding tenacity that even when it was violently tossed in the air
by the bull it will not let go except its teeth got broken. The modern day pitbull blue exhibits similar tenacity and a powerful jaw as the bull dog.
http://www.aboutdogfacts.com/blue-nose-pitbull/
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