It is relatively healthy for its size and tends to have far fewer problems than more popular breeds in its size range. It is relatively healthy for its size and tends to have far fewer problems than more popular breeds in its size range. Among the four Sennenhunde, or Swiss mountain dogs, this breed is considered the oldest, and is also the largest. There are several theories regarding the origin of the four Sennenhund breeds. The most popular theory states the dogs are descended from the Molosser, a large Mastiff-type dog, which accompanied the Roman Legions on their invasion of the Alps more than 2000 years ago. The hocks are well let down and straight when viewed from the rear. The hock joint corresponds to the human ankle and first short bones in the foot; the dog does not walk on the heel as people do. Feet are round and compact with well-arched toes; they turn neither in nor out.