| Cervical, | 8 | pairs, |
| Dorsal, | 12 | “ |
| Lumbar, | 5 | “ |
| Sacral, | 6 | “ |
762. The four lower cervical and upper dorsal pass into each other and then separate to reunite. This is called the brach´i-al plex´us. From this plexus six nerves proceed, which ramify upon the muscles and skin of the upper extremities.
763. The last dorsal and the five lumbar nerves form a plexus called the lumbar, similar to that of the cervical. Six nerves pass from this plexus, which ramify upon the muscles and skin of the lower extremities.
764. The last lumbar and the four upper sacral unite to form the sacral plexus. From this plexus five nerves proceed, that are distributed to the muscles and skin of the hip and lower extremities.
765. The SYMPATHETIC NERVE[19] consists of a series of Gan´gli-a, or knots, extending each side of the spinal column, forming a chain its whole length. It communicates with both the cranial and spinal nerves. With the exception of the neck, there is a ganglion for each intervertebral space. These ganglia are composed of a mixture of cineritious and medullary matter, and are supposed to be productive of peculiar nervous power.
761. Give the division of the spinal nerves. 762. What nerves constitute the brachial plexus? How many nerves pass from this plexus? 763. How many nerves from the lumbar plexus, and where do they ramify? 764. How is the sacral plexus formed? 765. Of what does the sympathetic nerve consist? How is the sympathetic nerve distributed? What exception? Of what are the ganglia composed?
Fig. 131.
