CERVICAL NERVES. 503 



known as the spinal nerves. They consist of forty-two or forty- 

 three pairs, and are divided, according to the regions, into eight 

 cervical, seventeen dorsal, six lumbar, five sacral, and six or seven 

 coccygeal pairs. The whole of the spinal nerves originate by two 

 orders of roots, superior or sensory, and inferior or motor ; the 

 former, which are larger and more numerous, arising from the 

 superior lateral fissure, and the latter from the inferior lateral 

 fissure of the cord. In the intervertebral foramina there is a 

 ganglion on each of the superior roots, underneath which the 

 inferior root passes. The .union of the two roots constitutes the 

 spinal nerve, which, almost immediately after it passes through 

 the foramen, divides into two branches ; ' a superior, distributed 

 to the spinal muscles and the integument which covers them ; 

 and an inferior, longer and larger, distributed to the inferior 

 and lateral parts of the trunk, and in some cases the extremities. 

 The spinal nerve sends various communicating branches to the 

 sympathetic system. 



CERVICAL NERVES (8 pairs). 



The first cervical nerve, the suboccipital of Willis, leaves the 

 spinal canal through the internal foramen of .the atlas ; the 

 second through a foramen in the anterior part of the axis, the 

 succeeding five through the corresponding intervertebral fora- 

 mina, and the eighth between the last cervical and first dorsal 

 vertebra. 



Superior Branches. — The superior division of the first 

 nerve, after reaching the interstice between the anterior oblique 

 and the posterior straight muscles of the head, divides into 

 numerous branches, which are distributed to the muscles at the 

 back of the poll and to the retrahentes muscles of the ear ; . one 

 long branch, which anastomoses with the posterior auricular 

 branch of the seventh cranial nerve, to form the auricular plexus, 

 is sent to the concha, and the skin covering it. 



The superior division of the second nerve, situated under the 

 obliquus capitis posticus muscle, to which and the anterior 

 oblique it gives branches, is distributed in a similar manner to 

 the superior branches of the remaining cervical nerves. These, 

 gradually diminishing in size as they proceed backward, pierce 

 the intertransversalis muscle, and divide into superficial branches, 

 distributed to the superficial muscles and skin, and the deejy 

 branches, larger than the others, which cross the transverse pro- 



