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THE NEKVOUS SYSTEM. 



gland, supply the skin of the cheek over the inferior part of the masseter muscle 

 and the parotid gland. They communicate with branches of the facial nerve in 

 the parotid gland. 



The nervus cutaneus colli arises from the second and third cervical nerves. 

 It winds round the posterior border of the sterno-mastoid muscle, and crosses 

 the muscle to reach the anterior triangle, under cover of the platysma muscle and 

 the external jugular vein. It divides near the anterior edge of the sterno-mastoid 

 muscle into superior and inferior branches, which are distributed through the 

 platysma to the skin covering the anterior triangle of the neck. The upper 

 branches communicate freely beneath the platysma with the cervical branch of 

 the facial nerve. 



Descending (supra-clavicular) Branches. By the union of two roots derived 



from the third and fourth 

 cervical nerves a considerable 

 trunk is formed, which emerges 

 from under cover of the sterno- 

 mastoid muscle and extends 

 obliquely downwards through 

 the inferior part of the posterior 

 triangle of the neck. It sub- 

 divides into radiating branches 

 anterior, middle, and posterior 

 which pierce the deep fascia 

 of the neck above the clavicle, 

 and are distributed to the skin 

 of the inferior part of the side 

 of the neck, to the front of the 

 chest, and the shoulder. The 

 anterior (O.T. supra - sternal) 

 branches are the smallest. Pass- 

 ing over the medial end of the 

 clavicle, they supply the skin 

 of the neck and chest as far 

 down as the synchondrosis 

 sternalis. The middle (O.T. 

 supra-clavicular) branches pass 

 over the intermediate third 

 of the clavicle, beneath the 

 platysma, and can be traced 

 as low as the third rib. The 

 posterior (O.T. supra-acromial] 

 branches pass over or through 

 the insertion of the trapezius 

 muscle, and over the lateral 

 third of the clavicle, to the 

 shoulder, where they supply the skin as far down as the distal third of the deltoid 

 muscle. 



Deep Branches. The deep branches of the cervical plexus are separated 

 into a lateral and a medial set by their relation to the sterno-mastoid muscle. 

 Beneath the muscle, the lateral branches are directed laterally towards the posterior 

 triangle, and the medial branches pass medially towards the anterior triangle. 



The lateral branches consist of muscular and communicating nerves, which 

 for the most part occupy the posterior triangle. 



The muscular branches are the following : (1) To the sterno-mastoid, from the 

 second cervical nerve. This enters the muscle on its deep surface and communicates 

 with the accessory nerve. (2) To the trapezius, from the third and fourth cervical 

 nerves. These nerves cross the posterior triangle and end in the trapezius, after 

 having communicated with the accessory nerve, both in the posterior triangle, and 

 under cover of the muscle. (3) To the levator scapulce, from the third and fourth 



FIG. 611. DISTRIBUTION OF CUTANEOUS NERVES TO THE HEAD 

 AND NECK. 



