The mechanical hound, a throwback to the firehouse dalmatian that rode on fire engines in the past, has one main purpose, and that is to kill people who have hidden or coveted books or have broken laws established by the government. The mechanical hound is so advanced that it can sniff out and trail its victims scent. It can also smell books. It looks more like a spider with eight legs, and it is swift in delivering a large four inch needle and injecting its victim with drugs. It is a scary creature and chases Montag at one point. Like many of Bradbury's stories that involve possible advanced technology in the future, the mechanical hound is a symbol of government control that has gotten out of hand.