6. Cut across the cord with fine scissors at the point where it is
freed from its membranes and examine the section. Note the arrangement
of gray and white matter and the fissures and grooves, particularly the
anterior or ventral. Demonstrate the central canal with the blowpipe.
7. Study the origin of the spinal nerves (p. 337). Count them.
Direction of exit? Carefully clean one in the thoracic region from dura
mater and connective tissue, with fine scissors, and study dorsal and
ventral roots and ganglion (see Fig. 135). Then follow it out and find
its dorsal ramus and ventral ramus and the communicating branch of the
latter with the sympathetic system. Do not trace the peripheral branches
of the nerve at present.