634 SPINAL NERVES. 



tus 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 Kectus Late- 

 ralis, and the two Anterior Eecti. According to Valentin, the anterior branch 

 of the suboccipital 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 preced- 

 ing. At its exit from the intervertebral foramen, it passes downwards and out- 

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

 branch joins the anterior division of the second cervical, communicates with the 

 sympathetic and spinal accessory nerves, and subdivides into the superficial cer- 

 vical, and great auricular nerves. The descending branch passes down in front 

 of the Scalenus Anticus, anastomoses with the fourth cervical nerve, and be- 

 comes continuous 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 fila- 

 ments, 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 of equal size. They assist in the formation of the brachial 

 plexus. 



CERVICAL PLEXUS. 



The Cervical Plexus (Fig. 343) is formed by the anterior branches of the 

 four upper cervical nerves. It is situated in front of the four upper vertebrae, 

 resting upon the Levator Anguli Scapula, 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. 

 o . . 7 ( Occipitalis minor. 



Superficial ] (Sternal. 



[Descending. Supra-clavicular < Clavicular. 



( Acromial. 

 f Communicating. 

 J Muscular. 



f Internal } Communicans noni. 

 [ Phrenic. 



Deep 



( Communicating. 



External ( Muscular. 



SUPERFICIAL BRANCHES OF THE CERVICAL PLEXUS. 



The Superficialis Colli arises from the second and third cervical nerves, turns 

 round the posterior border of the Sterno-mastoid about its middle, and passing 



