830 THE NERVOUS SYSTEM. 



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 Com plexus 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, Avhich 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 

 of the atlas it receives a filament from the sympathetic on the vertebral artery. 

 It then descends, in front of this process, to j^in with the ascending branch from 

 the second cervical nerve. 



Communicating filaments from the loop between this nerve and the second 

 join the pneumogastric, the hypoglossal, and sympathetic' (superior_jcervical 

 ganglion), and some branches are distributed to the Rectus lateraTis~and the two 

 Anterior recti. The fibres communicating with the hypoglossal are mostly con- 

 tinued into its descendens hypoglossi branch (see page 825). l 



The anterior division of the second cervical nerve escapes from the spinal 

 canal, between the posterior arch of the atlas and the lamina of the axis, and, 

 passing forward on the outer side of the vertebral artery, divides in front of the 

 Intertransverse muscle into an ascending branch, which joins the first cervical, 

 and descending branches, which join branches from the third. These last-named 

 intercommunicating branches of the second and third cervical nerves, give off 

 the small occipital, the great auricular, and the superficial cervical nerves. . The 

 nerve also gives off one of the communicantes hypoglossi, and a filament to the 

 Sterno-mastoid which communicates in the substance of the muscle with the 

 spinal accessory. 



The anterior division of the third cervical nerve is double the size of the 

 preceding. At its exit from the intervertebral foramen it passes downward and 

 outward beneath the Sterno-mastoid, and divides into branches. The ascend- 

 ing ones join with branches of the second cervical, and this combination gives off, 

 as already stated, the small occipital, the great auricular, and the superficial 

 cervical nerves. The descending branches pass down in front of the Scalenus 

 anticus, and are as follows : One of the communicantes hypoglossi ; a branch to 

 the supraclavicular nerves ; a filament to assist in forming the phrenic ; and 

 muscular branches to the Levator anguli scapulae and Trapezius ; this latter 

 nerve communicates beneath the muscle with the spinal accessory. Sometimes ^ 

 the nerve to the Scaleuus medius is derived from this source. 



The anterior division of the fourth cervical is of the same size as the preceding. 

 It sends a communicating branch to the fifth cervical, and, passing downward 

 and outward^ unites with a branch from the third, and from this union are derived 

 numerous filaments which cross the posterior triangle of the neck, forming the 

 supraclavicular nerves. It also gives a branch to the phrenic nerve whilst it is 

 contained in the intertransverse space, and sometimes a branch to the Scalenus 

 medius muscle. It also gives a branch to the Levator anguli scapulae and to the 



1 According to Valentin, the anterior division of the suboccipital also distributes filaments to 

 the occipito-atlantal articulation and mastoid process of the temporal bone. 



