This may be done either before or after the abdominal and thoracic cavities have been examined.

The body is placed prone with the head over the edge of the table and a block under the abdomen so as to lessen the lumbar curve. An incision is made from the occiput to the sacrum along the spinous processes. The skin and muscles are dissected away on either side, exposing the laminae at the bottom of the groove, which should be thoroughly clean. By means of a double- or single-bladed saw the laminae should be divided so as to enter the spinal canal at its outside limits. The laminae of the cervical vertebrae are more easily bitten through with strong bone forceps.

Divide the spinous processes on either side, cut the ligaments in the lower lumbar region, and lift them up to the neck.

The dura over the cauda equina is picked up with forceps and the nerves are cut from below upward; if done carefully, the posterior root ganglia can be removed with the cord. At no time should the cord be pulled or bent.

The dura should be opened by a longitudinal incision, made with probe-pointed scissors, either along its anterior or posterior surface. Transverse sections of the cord, about 2 cm. in thickness, should be made; the incisions coming in between each two pair of nerves and leaving the segments attached to the pia.

A diagnosis is frequently made with difficulty from the fresh macroscopic appearance of the cord.