Chapter LXXXIX: Section 133: There are eight cervical (spinal) nerves, one in front of

the atlas, and one behind each of the cervical vertebrae. The last four and the first thoracic (spinal) contribute to a leash of nerves running out to the fore limb, the brachial plexus (plexus, literally network, but here meaning a plaited cord). The fourth cervical also sends down a phrenic nerve (p.n., Figure 1), along by the external jugular vein and the superior caval vein to the diaphragm. The last three lumbar and the sacral nerves form a sacral plexus, supplying the hind limb.