MODEL RELEASED. Ranch owner fitting on and adjust- ing a myoelectric" prosthetic arm, before he begins a day of work. 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 as required. It gives the user fine control over the limb, and the ability to use the arm and hand slowly or quickly, with precision and varying strength. Here, the arm will be used for labour-intensive farm jobs. The "myoelectric" arm was developed at the University of Utah, USA. Photograph of Bob Goodman"