MODEL RELEASED. Ranch owner mending a barbed-wire fence, with the aid of a myoelectric" prosthetic arm. This artificial right arm worn with a hand, is battery powered. Small electrodes placed on the skin at the site of amputation, sense the electrical activity of the remaining arm muscle. These muscle signals are electronically amplified and are used to move the prosthetic arm and hand as required. It gives the user fine control over the limb, and the ability to use the arm slowly or quickly, with precision and varying strength. Here, the hand copes well under a precision labour intensive job. The "myoelectric" arm was developed at the University of Utah, USA. Photograph of Bob Goodman."