THE NECK, ANTERIOR, 91 



united branch then passes downward and forward, usually 

 over the internal jugular vein to unite upon the common 

 carotid artery with the descendens hypoglossi. For the 

 distribution see (i). 



(6) The muscular branch to thetrapezius muscle appears 

 on the posterior border of the sternomastoid at its middle, 

 passes backward to the trapezius, and with the spinal acces- 

 sory, which courses at a higher level, is distributed to this 

 muscle. 



(7), (8), (9) The branches to the integument over the 

 sternum, clavicle, and acromial regions. They become 

 superficial at the posterior border of the sternomastoid 

 muscle and descend to their distribution. The supra- 

 sternal to the integument over the first piece of the sternum ; 

 the supraclavicular, to the skin over the front of the clavi- 

 cle (and chest as low as the fourth rib) ; and the supra- 

 acromial to the region of the shoulder. 



(10) The phrenic. For phrenic nerve, see page 100. 



The Spinal Accessory Nerve. Figs. 10, n, 12, 16, 



17- 



This will be found issuing under the posterior belly of 

 the digastric muscle. It continues downward through the 

 sternomastoid muscle, in the substance of which it forms 

 a plexiform junction with a branch from the second cervical 

 nerve for the supply of the muscle, then appears at the 

 posterior border of the sternomastoid and extends down- 

 ward and backward to the anterior surface of the trapezius, 

 to which (with branches from the third and fourth cervical 

 nerves) it is distributed. The deep course of the nerve 

 after it comes through the central compartment of the jugu- 

 lar foramen (with the ninth and the tenth nerves) is down- 

 ward and backward across the internal jugular vein and 



