Medicine: The $40,000 Arm

In addition to his powerful mechanical legs and zoom-lens artificial eye, television's Six Million Dollar Man has an atomic-powered arm that can knock down walls, lift cars and pull out trees by the roots. Reid Hilton's new arm is only slightly less remarkable−and considerably less expensive. Hilton, 24, a Santa Ana, Calif., karate expert who lost his right arm below the elbow in an accident, will probably not risk smashing bricks with his experimental $40,000 replacement. But the prosthesis should enable him, with practice, to function like a man with two natural arms,...