HEAD AND NECK 



6. Nerves, 



Accessory. 

 Small occipital. 

 Great auricular. 

 Nervus cutaneus colli. 



,, scalenus medius. 



,, ,, posterior. 

 Supraclavicular. 

 To posterior belly of omo-hyoicl from ansa hypoglossi. 

 Trunks of brachial plexus. 

 The nervus dorsalis scapulae. \ 



[Branches of the brachial 



long thoracic, 

 suprascapular. 

 nerve to the subclavius. 



plexus. 



Some of the contents of the triangle which are now 

 displayed require further consideration. 



The Posterior Belly of the Omo-hyoid Muscle. The 

 posterior belly of the omo-hyoid muscle springs from the 

 upper border of the scapula and upper transverse scapular 

 ligament. It enters the posterior triangle, at its lower and 

 posterior angle, and runs upwards and anteriorly, at a 

 variable distance from the clavicle, to the posterior border 

 of the sterno-mastoid. Either immediately behind or 

 under cover of the posterior border of the sterno-mastoid it 

 joins the intermediate tendon which connects it with the 

 anterior belly. Its nerve has already been seen entering 

 its deep surface (p. 146) it divides the posterior triangle 

 into a lower or subclavian portion and an upper or occipital 

 portion. 



The Accessory Nerve (O.T. Spinal Accessory). The 

 portion of the accessory nerve which appears in the posterior 

 triangle consists of fibres which arise from the cervical part 

 of the spinal medulla and with them are incorporated some 

 filaments derived from the second cervical nerve. Before 

 appearing in their present situation the spinal fibres entered 

 the cranium through the foramen magnum and left it by pass- 

 ing through the jugular foramen ; then they passed downwards 

 and posteriorly, through the deeper fibres of sterno-mastoid, 

 where they received the communication from the second cervical 

 nerve. As already pointed out, the nerve usually enters the 

 posterior triangle at the level of the union of the upper third 

 with the lower two-thirds of the posterior border of the sterno- 

 mastoid. It runs downwards and posteriorly through the 

 triangle, along the line of the levator scapulae, and disappears 



