When the vertebræ are bared the next step is the removal by saw, bone-forceps or chisel of the posterior bony wall of the spinal canal in such a manner as to expose the cord and permit of its removal without causing any damage to it, either from the instruments or from fragments of broken bone. A single-bladed saw with curved ends may be used to saw through the laminæ on both sides of the spinous processes; or even the small bone-saw (Fig. 9) may be used for this purpose. The blade of the saw should be held obliquely against the spinous processes with the sawing edge directed outward so as to cut the laminæ close to the medial borders of the ascending and descending transverse processes. The sawing is complete when the spinous processes become movable. The straight-edged chisel may be used to cut any adhesions left after sawing, and the bone-forceps may be used to cut the atlas and axis. When the laminæ have been cut through on both sides of the spinal column for its entire length, including the sacrum, the posterior ligament between the atlas and occiput is cut with the cartilage knife; and the strip of bone and ligaments loosened by sawing is torn off from above downward by grasping it in the upper cervical region with a pair of bone-nippers and jerking it off forcibly downward toward the sacrum, thus exposing the spinal canal. It may be taken off in the opposite direction by cutting the ligament between the last lumbar vertebra and the sacrum and stripping upward. The use of the single saw is not advised, however, as it is too time-consuming. The laminæ on both sides of the spinous processes may be cut at the same time by the use of _Luer’s rhachiotom_e (Fig. 11). The blades are separated according to the size of the vertebral arches and are set so as to include the spinous processes and cut the outer border of the laminæ close to the transverse processes in such a manner as not to injure the cord. Since the spinal canal is broader in the cervical and lumbar regions than in the dorsal, the distance between the saw-blades must be regulated accordingly. The dorsal portion is first sawed. The sawing should be in long cuts without too great pressure, the instrument being steadied by placing the left hand on the upright bar. As soon as the spinous processes become movable on slight pressure the sawing should be stopped. Should the blades become caught in the saw-cuts great care should be taken to avoid injuring the cord while releasing them. The straight-edged chisel may be inserted into the cuts and any parts still adherent may be carefully sprung apart. This is necessary particularly in the upper cervical region. The entire posterior wall of the canal may be loosened in this way, the sacrum being also sawed, when it is desired to open this part of the canal. When all the spinous processes are movable the attachments either above or below are cut with the cartilage-knife, and the spinous processes and laminæ torn off by the