66 DISSECTION OF THE NECK. 



Commonly there is not any branch connected with the artery in this 

 part of its course; but the posterior scapular branch (fig. 14) may take 

 origin from it at different distances from the scalenus, or there may be 

 more than one branch (Quain). 



The subclavian vein rises upwards not unfrequently as high as the 

 artery, or it may even lie with the artery beneath the anterior scalenus in 

 some rare instances. The position of the external jugular vein with 

 regard to the subclavian artery is very uncertain^ and the branches 

 connected with the lower end may form a kind of plexus over the arterial 

 trunk. 



The occipital part of the posterior triangle is larger than the other. Its 

 boundaries in front and behind are the sterno-mastoid and the trapezius ; 

 and it is separated from the clavicular portion by the omo-hyoid muscle. 



In it are contained chiefly the ramifications of the cervical plexus ; and a 

 chain of lymphatic glands lies along the sterno-mastoid muscle. The 

 spinal accessory nerve, ', is directed obliquely across this interval from 

 the sterno-mastoid muscle, which it pierces, to the under surface of the 

 trapezius ; and a communication takes place between this cranial and the 

 spinal nerves in the space. 



SUPERFICIAL BRANCHES OP THE CERVICAL PLEXUS. Behind the 

 sterno-mastoid muscle appear some of the ramifications of the cervical 

 nerves in the plexus of the same name ; and superficial branches are fur- 

 nished from these both upwards and downwards. 



The ASCENDING SET (fig. ] 4) are three in number, viz., small occipital, 

 great auricular, and superficial cervical. 



The small occipital branch (fig. 2, 2 ) comes from the second cervical 

 nerve, and is directed upwards to the head along the posterior border of 

 the sterno-mastoid muscle. At first the nerve is beneath the fascia ; but 

 near the occiput it becomes cutaneous, and is distributed between the ear 

 and the great occipital nerve (p. 24). Occasionally there is a second cuta- 

 neous nerve to the head. 



The great auricular nerve (fig. 2, J ) is a branch of the part of the 

 plexus formed by the second and third cervical nerves. Perforating the 

 deep fascia at the posterior border of the sterno-mastoid muscle, the nerve 

 is directed upwards beneath the platysma to the lobule of the ear, where 

 it ends in the following branches : 



The facial branches are sent forwards to the integuments over the 

 parotid, and a few slender filaments pass through the gland to join the 

 facial nerve. 



The auricular branches ascend to the external ear, and are chiefly dis- 

 tributed on its cranial aspect ; one or more reach the opposite surface by 

 piercing the pinna. On the ear they communicate with branches furnished 

 from the facial and pneumogastric nerves. 



The mastoid branch is directed backwards to the integuments between 

 the ear and the mastoid process ; and it joins the posterior auricular branch 

 of the facial nerve (p. 23). 



The superficial cervical nerve (fig. 2, u ) springs from the same source 

 as the preceding, and turns forwards round the sterno-mastoid muscle 

 about the middle. Afterwards it pierces the fascia and platysma, and 

 ramifies over the anterior triangular space (see p. 68). There may be 

 more than one branch to represent this nerve. 



The DESCENDING SET of branches (fig. 2) (supra-clavicular), are de- 

 rived from the third and fourth nerves of the plexus, and are directed 



