THE CERVICAL PLEXUS. 



1289 



6. The supra acromial 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 shouldt- r 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.  



Fig. 1089. 



Small occipital 

 Complexus 



Muscular brs. to complexu 

 biveater from occip 

 Third occipita 



Fascial septum from ligamentum nucli:e 



Great occipital nerve 



Rectus capitis posticus major 



Branch to obliquus inferior 



Spine of II. cervical vertebra 



Cutaneous br. from III. cerviral 



Part of complexus and biventer 



Third occipital nerve 



Branch to complexus from II. cervical 



Branch to complexus from III. cervical 



Part of splenius 

 Trapezius, cut edge 



Cutaneous brs. from IV. cervical 



Internal br. dorsal division of 

 VI. cervical nerve 



VII. cervical, dorsal division 



VIII. cervical, dorsal division 



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



Spinous process of VII. cervical verteli > 



Obliquus superior 



Transverse process 

 of atlas 



Ant. division I. cervi- 

 cal, cutaneous br. of 

 dorsal division passing 



II. cervical nerve, dorsal division backward 



Levator anguli scapulae 

 Branch to trachelo-mastoid 



III. cervical nerve, dorsal di\ision 

 Communication between II. and III. dorsal division 

 External brs. of III. cervical, dorsal divisi-jn 



IV. cervical rerve, dorsal division 

 Ext. branch of dorsal di\ision V. cervical nerve 



V. cervical nerve, dorsal di\ision 

 Ext. brs. dorsal division \'l. cervical nerve 



VI. cervical nerve, dorsal division 



Transverse process I. thoracic vertebra 



Transverse process II. thoracic vertebra 

 Levator an^iili scapulae 



Trapezius 



\ 



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



b. The trapezius receives fibres from the thir.d 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. 108S). 



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 {b^ in the occipital 

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

 sterno-mastoid and subtrapezial plexuses. 



