CERVICAL PLEXUS. 411 



tebra. Each nerve, at its escape from the intervertebral foramen, divides 

 into an anterior and a posterior branch. The anterior branches of the four 

 upper cervical nerves form the cervical plexus ; the posterior branches, the 

 posterior cervical plexus. The anterior branches of the four inferior cer- 

 vical, together with the first dorsal, form the brachial plexus. 



ANTERIOR CERVICAL NERVES. The anterior branch of the fast cervical 

 nerve escapes from the vertebral canal through the groove upon the poste- 

 rior arch of the atlas which supports the vertebral artery, beneath which it 

 lies. It then descends in front of the transverse process of the atlas, sends 

 several twigs to the rectus lateralis and recti antici, and forms an anasto- 

 motic loop by communicating with an ascending branch of the second 

 nerve. 



The anterior branch of the second cervical nerve at its exit from the in- 

 tervertebral foramen between the atlas and the axis, gives twigs to the 

 rectus anticus major, scalenus posticus and levator anguli scapulae mus- 

 cles, and divides into three branches, viz. an ascending branch, w r hich 

 completes the arch of communication with the first nerve ; and two de- 

 scending branches, which communicate with the third nerve. 



The anterior branch of the third cervical nerve, double the size of the 

 preceding, divides at its exit from the intervertebral foramen into numer- 

 ous branches, some of which are distributed to the rectus major, longus 

 colli, and scalenus posticus muscles, while others communicate and form 

 loops and anastomoses with the second and fourth nerve. 



The anterior branch of the fourth cervical nerve, of the same size with 

 the preceding, sends twigs to the rectus major, longus colli, and levator 

 anguli scapulae, communicates by anastomosis with the third, and sends a 

 small branch downwards to the fifth nerve. Its principal branches pass 

 downwards and outwards across the posterior triangle of the neck, to- 

 wards the clavicle and acromion. 



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

 nerves will be described with the brachial plexus, of which they form a 

 part. 



CER VICAL PLEXUS. 



The cervical plexus is constituted by the loops of communication, and 

 by the anastomoses which take place between the anterior branches of the 

 four first cervical nerves. The plexus rests upon the levator anguli sca- 

 pulae, posterior scalenus, and splenius muscle, and is covered in by the 

 sterno-mastoid and platysma. 



The Branches of the cervical plexus may be arranged into three groups, 

 superficial ascending, superficial descending ; and deep 



( Superficial colli, 

 f Ascending, < Auricularis magnus, 

 Superficial J C Occipitalis minor. 



Descending, Acroroiales, 

 [ J I Claviculares. 



I Communicating branches, 

 Muscular, 

 Commumcans nom, 

 Phrenic. 



