Like gap 74K, gap 74M allows the upper surface 30M, the lower surface 32M, and perimeter surface 34M of the arched bridge region 38M to be easily engaged by a cutting device such as surgical scissors 75, wire cutters or a cautery so as to permit the scissors 75, wire cutters or cautery to sever the bridge 38M. Consequently, elongated plate 28M permits physician access to the thoracic cavity 26 by