Abstract: A functional prosthesis for a hand comprises an opening and closing mechanism for articulated fingers. A worm gear coupled to a DC actuator-motor provides linear movement to a displacement mobile which is coupled to articulated fingers of the artificial hand. When the actuator rotates in one direction, the displacement mobile moves in one direction, causing the fingers to open or close, depending upon the direction of rotation. Rotation of the actuator in the opposite direction will cause the fingers to move in the opposite direction.