760 THE NERVOUS SYSTEM. 



accompanies the occipital artery and communicates with the occipitalis major and 

 minor nerves. 



The posterior division of the second cervical nerve is three or four times greater 

 than the anterior division, and the largest of all the posterior cervical divisions. 

 It emerges from the spinal canal between the posterior arch of the atlas and 

 lamina of the axis, below the Inferior oblique. It supplies a twig to this muscle, 

 and receives a communicating filament from the first cervical. It then divides 

 into an internal and an external branch. 



The internal branch, called, from its size and distribution, the occipitalis major, 

 ascends obliquely inward between the Obliquus inferior and Complexus, and 

 pierces the latter muscle and the Trapezius near their attachments to the 

 cranium. It is now joined by a filament from the posterior division of the third cer- 

 vical nerve, and, ascending on the back part of the head with the occipital artery, 

 divides into two branches, which supply the integument of the scalp as far forward 

 as the vertex, communicating with the occipitalis minor. It gives off an auricular 

 branch to the back part of the ear and muscular branches to the Complexus. 

 The external branch is often joined by the external branch of the posterior 

 division of the third, and supplies the Splenius, Trachelo-mastoid, and Complexus. 



The posterior division of the third cervical is smaller than the preceding, but 

 larger than the fourth ; it differs from the posterior divisions of the remaining 

 cervical nerves in its supplying an additional filament, the third occipital nerve, 

 to the integument of the occiput. The posterior division of the third nerve, like 

 the others, divides into an internal and external branch. The internal branch 

 passes between the Complexus and Semispinalis, and, piercing the Splenius and 

 Trapezius, supplies the skin over the latter muscle ; the external branch joins with 

 that of the posterior division of the second to supply the Splenius, Trachelo-mas- 

 toid, and Complexus. 



The third occipital nerve arises from the internal or cutaneous branch beneath 

 the Trapezius ; it then pierces that muscle, and supplies the skin on the lower and 

 back part of the head. It lies to the inner side of the occipitalis major, with 

 which it is connected. 



The posterior division of the suboccipital nerve and the internal branches of 

 the posterior divisions of the second and third cervical nerves are occasionally 

 joined beneath the Complexus by communicating branches. This communication 

 is described by Cruveilhier as the posterior cervical plexus. 



The posterior divisions of the fourth, fifth, sixth, seventh, and eighth cervical 

 nerves (Fig. 415) pass backward, and divide, behind the Intertransversales 

 muscles, into internal and external branches. The internal branches, the larger, 

 are distributed differently in the upper and lower part of the neck. Those 

 derived from the fourth and fifth nerves pass between the Complexus and Semi- 

 spinalis muscles, and, having reached the spinous processes, perforate the 

 aponeurosis of the Splenius and Trapezius, and are continued outward to the 

 integument over the Trapezius, whilst those derived from the three lowest cervical 

 nerves are the smallest, and are placed beneath the Semispinalis colli, which they 

 supply, and then pass into the Interspinales, Multifidus spinse, and Complexus, 

 and send twigs through this latter muscle to supply the integument near the 

 spinous processes (Hirschfeld). The external branches supply the muscles at the 

 side of the neck viz. the Cervicalis ascendens, Transversalis colli, and Trachelo- 

 mastoid. 



Anterior Divisions of the Cervical Nerves. 



The anterior division of the first or suboccipital nerve is of small size. It 

 escapes from the spinal canal through a groove upon the posterior arch of the 

 atlas. In this groove it lies beneath the vertebral artery, to the inner side of 

 the Rectus capitis lateralis. As it crosses the foramen in the transverse process 



