THE CERVICAL PLEXUS. 831 



Trapezius, which unites with the branch given off from the third nerve, and 

 communicates beneath the muscle with the spinal accessory. 



The anterior divisions 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. 



The Cervical Plexus. 



The cervical plexus (Fig. 496) is formed, as above described, by the anterior 

 divisions of the four upper cervical nerves. It is situated opposite the four upper 

 cervical vertebrae, 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 : 



( Occipitalis minor, 

 f Ascending . < Auricularis magnus. 

 (^ Superficialis colli. 



Superficial \ 



( Suprasternal. 



^Descending . Supraclavicular -I Supraclavicular. 



( Supra-acromial. 

 C Communicating. 

 rT , J Muscular. 



1 Communicans hypoglossi. 

 Deep . . . -< ^Phrenic. 



( Communicating. 

 ^External . . j Musculai , 



Superficial Branches of the Cervical Plexus, 



The Occipitalis minor (Fig. 502) arises from the second and third cervical 

 nerves ; it curves round the posterior border of the Sterno-mastoid, and ascends, 

 running parallel to the posterior border of the muscle, to the back part of the 

 side of the head. Xear the cranium it perforates the deep fascia, and is continued 

 upward along the side of the head behind the ear, supplying the integument, and 

 communicating with the occipitalis major, the auricularis magnus, and with the 

 posterior auricular branch of the facial. 



This nerve gives off an auricular branch, which supplies the integument of 

 the upper and back part of the auricle, communicating with the mastoid branch 

 of the auricularis magnus. This branch is occasionally derived from the great 

 occipital nerve. The occipitalis minor varies in size ; it is occasionally double. 



The Auricularis Magnus is the largest of the ascending branches. It arises 

 from the second and third cervical nerves, winds round the posterior border of 

 the Sterno-mastoid, and. after perforating the deep fascia, ascends upon that 

 muscle beneath the Platysma to the parotid gland, where it divides into facial, 

 auricular, and mastoid branches. 



The/'/'-/'// branches pass across the parotid, and are distributed to the integ- 

 ument of the face over the parotid gland ; others penetrate the substance of the 

 gland and communicate with the facial nerve. 



The auricular branches ascend to supply the integument of the back part of 

 the pinna, except at its upper part, communicating with the auricular branches 

 of the facial and pneumogastric nerves. 



The rnastoii.l branch communicates with the occipitalis minor and the posterior 

 auricular branch of the facial, and is distributed to the integument behind the ear. 



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 

 obliquely forward beneath the external jugular vein to the anterior border of that 



