Abstract: A prosthesis comprising:(a) a gripping member;(b) an operating lever mounted to pivot about a pivot axis and operatively connected to the gripping member;(c) a power unit including an electric motor, and a drive shaft rotatable by said electric motor;(d) means connecting the drive shaft to the operating lever at a region spaced from the said pivot axis of the operating lever, said connecting means being constructed so that when the drive shaft rotates the connecting means (and also the region of the operating lever connected to the shaft) travels axially along the shaft thereby causing the operating lever to pivot about its pivot axis; and(e) means pivotally mounting said power unit to allow the connecting means to move along an arcuate path about the pivot axis during pivoting of the operating lever.