The instruments used in this operation are two frontal sinus rasps, two tapering curved chisels and three protectors.
The frontal sinus rasp (Fig. 1) is made on the same principle as the old-fashioned coarse horseshoe rasp, from which I derived the idea. It is slightly curved at the rasp end to fit into the frontal sinus and the teeth are on the longitudinally concave surface, pointing toward the handle, so that when traction is made on the rasp, the bone anterior to it is rasped away, as illustrated in Figure 5. The posterior surface of the rasp is perfectly smooth and flat.
The chisels (Fig. 2) are short, curved and tapering. The handle at the chisel end is very slender so that the chisel can be manipulated under the direct vision of the eye. The edges are tapering as well as blunt, so that if the edge should strike a