Dogs HAVE BEEN INDISPENSABLE throughout history as helpers in human societies. Besides being used to herd other animals and for companionship,their principal function has been as guardians of the home and farm. Today the job of the guard dog has been extended to protection of factories and industrial estates. To shut up a dog on its own in an empty building or other enclosed space and expect it to live by itself, and to ward off intruders, goes against all the social behavioural patterns of the dog, and is cruel. Dogs that are trained by the police for protection and for detection of drugs and explosives are seldom alone and normally live well-balanced lives. Certain breeds are more innately aggressive than others, but nearly all dogs have to be specially trained to be aggressive to strangers and not to their handlers. Today there are innumerable other ways in which dogs help the sick, the disabled, and he lonely, and by insisting on a daily walk they keep their owners healthy.