1. An elongate disposable electrode for insertion into a surgical retractor blade, the electrode comprising: (a) a proximal end; (b) a distal end; (c) a generally flat electrode body; (d) a conducting trace extending through the electrode body such that the trace is only exposed at a first exposed area at about the proximal end and at a second exposed area at about the distal end; (e) a pair of flattened wings running along the electrode body between the first exposed area and the second exposed area, wherein said wings are generally coplanar; and (f) a ledge at the distal end, said ledge extending in a direction generally perpendicular to a plane defining the pair of flattened wings.