Origins of Breed: A working dog, the mastiff was originally bred from the Tibetan Mastiff, perhaps a thousand years ago. It has been used as a guard dog in Great Britain for hundreds of years; it has also been used to fight other dogs and bait bulls.

Anatomy: The Mastiff is about 27 1/2 to 30 inches (70-76 cm) high at shoulders, and weighs 175 to 190 pounds (79-86 kg) - this is heavier than many adult humans. This huge dog has a short coat. The fur is dark brown, tan, or mixed; black fur surrounds the eyes, nose and muzzle. A wide, flat skull, a wrinkled brow, and droopy ears give this dog a distinctive look.