

CERVICAL PLEXUS. 563 



ANTERIOR BRANCHES OF THE CERVICAL NERVES. 



The anterior branch 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 Kectus 

 lateralis. As it crosses the foramen in the transverse process of the atlas, it 

 receives a filament from the sympathetic. It then descends, in front of this process, 

 to communicate with an ascending branch from the second cervical nerve. 



Communicating filaments from this nerve join the pneumogastric, the hypo- 

 glossal and sympathetic, and some branches are distributed to the Eectus lateralis 

 and the two Anterior recti. According to Valentin, it also distributes filaments 

 to the occipito-atloid articulation, and mastoid process of the temporal bone. 



The anterior branch 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 

 forwards on the outer side of the vertebral artery, divides in front of the Inter- 

 transverse muscle, into an ascending branch, which joins the first cervical, and 

 two descending branches which join the third. 



The anterior branch of the third cervical nerve is double the size of the preceding. 

 At its exit from the inter vertebral foramen, it passes downwards and outwards 

 beneath the Sterno-mastoid, and divides into two branches. The ascending branch 

 joins the anterior division of the second cervical, communicates with the sympa- 

 thetic and spinal accessory nerves, and subdivides into the superficial cervical, 

 and great auricular nerves. The descending branch passes down in front of the 

 Scalenus anticus, anastomoses with the fourth cervical nerve, and becomes con- 

 tinuous with the clavicular nerves. 



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

 It receives a branch from the third, sends a communicating branch to the fifth 

 cervical, and, passing downwards and outwards, divides into numerous filaments, 

 which cross the posterior triangle of the neck, towards the clavicle and acromion. 

 It usually gives a branch to the phrenic nerve whilst it is contained in the inter- 

 transverse space. 



The anterior branches of the fifth, sixth, seventh, and eighth cervical nerves are 

 remarkable for their large size. They are much larger than the preceding nerves, 

 and are all of equal size. They assist in the formation of the brachial plexus. 



CERVICAL PLEXUS. 



The cervical plexus (fig. 279) is formed by the anterior branches of the four 

 upper cervical nerves. It is situated in front of the four upper vertebra?, resting 

 upon the Levator anguli scapulae, and Scalenus medius muscles, and covered in by 

 the Sterno-mastoid. 



Its branches may be divided into two groups, superficial and deep, which may 

 be thus arranged : 



( Superficialis colli. 

 (" Ascending -! Auricularis magnus. 



cr /, . 7 ( Occipitalis minor. 



Superficial -{ } , , , 



( l Sternal. 



Descending \ Supra-clavicular < Clavicular. 

 ( ( Acromial. 



f Communicating. 

 Internal } Muscular. 



jy \ Communicans noni. 



Phrenic. 



TT, , i ( Communicating. 

 External < *, 



Muscular. 



