bloodhound, breed of large hound whose ancestors were known in the Mediterranean region before the Christian era. It stands about 25 in. (63.5 cm) high at the shoulder and weighs between 80 and 110 lb (36.3–49.9 kg). Its short, smooth coat may be black and tan, red and tan, or tawny. The skin is very loose and hangs in deep folds over the forehead and at the sides of the face, giving the dog its characteristically mournful expression. The oldest hound breed and probable progenitor of all the hounds, it was introduced into Europe long before the Crusades and became popular with the aristocracy and clergy. The latter, especially, were responsible for the dog's careful breeding and purity of strain, which led it to be called the "blooded hound," i.e., hound of noble ancestry. It was imported into the United States in the early 19th cent. Its sense of smell is second to no other breed and has earned it a singular reputation as a tracker of criminals and missing persons. Unlike the police dog, it does not attack the man or animal it is tracking. See dog.