THE CERVICAL PLEXUS. 



1289 



6. The supraacromial branches (rr. supraclaviculares posteriores) cross the cla- 

 vicular insertion of the trapezius and are distributed to the skin over the anterior, external 

 and posterior aspects of the shoulder as far down as the lower portion of the deltoid. 



II. The deep branches are divided into two sets, an external and an internal. 

 Both arising- beneath the sterno-mastoid, the former pass away from and the latter 

 toward the median line of the neck. 



7. The external muscular branches are distributed as follows: 



a. The sterno-mastoid receives a branch from the second cervical which enters the deep 

 surface of the muscle and interlaces with a branch of the spinal accessory nerve to form the 

 sterno-mastoid plexus. 



f FIG. 1089. - \ 



/ V 



Muscular brs. to compfexus 

 biventer from occip. m 



Third occipital nerve -iVK'' 



Fascial septum from ligamentum nuchae 



Great occipital nerve 



Rectus capitis posticus major 



Branch to obliquus inferior 



Spine of II. cervical vertebra 



Cutaneous br. from III. cervical 



Part of complexus and biventer 



Third occipital nerve 



Branch to complexus from II. cervical 



Branch to complexus from III. cervical 



Internal br. dorsal division of 



VI. cervical nerve 



VII. cervical, dorsal di 



VIII. cervical, dorsal division 



Internal br. of post. div. of V. cervical nerve 



Spinous process of VII. cervical vertebra 



yg^fcjy Ant. division I. cervi- 



dorsal division passing 



II. cervical nerve, . orsal division backward 

 Levator anguli scapulae 



Branch to trachelo-mastoid 



III. cervical nerve, dorsal division 

 Communication between II. and III. dorsal division 

 External brs. of III. cervical, dorsal division 



IV. cervical rerve, dorsal division 



Ext. branch of dorsal division V. cervical nerve 



V. cervical nerve, dorsal division 



Ext. brs. dorsal division VI. cervical nerve 



VI. cervical nerve, dorsal division 



Transverse process I. thoracic vertebra 



Transverse process II. thoracic vertebra 



Levator anguli scapulas 



Trapezius 



Dissection of right side of neck, showing deeper relations of cervical nerves. 



b. The trapezius receives fibres from the third and fourth cervical nerves which arise with 

 and accompany the descending branches of the superficial set through the occipital triangle. 

 They dip under the anterior margin of the trapezius, before and after which they form a more 

 or less complex inosculation with the spinal accessory, called the subtrapezial plexus, from 

 which filaments are distributed to the trapezius muscle (Fig. 1088). 



c. The levator anguli scapulae receives two branches which take their origin from the third 

 and fourth nerves. 



d. The scalenus medius and ( e ) scalenus posticus also receive fibres from the third and fourth. 



8. The communicating branches form points of contact and union with 

 'the spinal accessory nerve (a) under the sterno-mastoid and (d~) in the occipital 

 triangle and under the trapezius. By means of these inosculations are formed the 

 sterno-mastoid and subtrapezial plexuses. 



