766 



THE NERVOUS SYSTEM. 



fifth cervical, which joins that nerve on the Anterior scalenus muscle : the fifth 

 and sixth cervical nerves are joined by filaments to the middle cervical ganglion 

 of the sympathetic, the seventh and eighth cervical to its inferior ganglion, and 



FIG. 411. Cutaneous nerves of right upper 

 extremity. Anterior view. 



FIG. 412. Cutaneous nerves of right upper 

 extremity. Posterior view. 



the first dorsal nerve to its first thoracic ganglion, close to their exit from the 

 intervertebral foramina. 



Relations. In the neck, the brachial plexus lies in the posterior triangle, being 

 covered by the skin, Platysma, and deep fascia : it is crossed by the posterior belly 

 of the Omo-hyoid and by the Transversalis colli artery. When the posterior 

 scapular artery arises from the third part of the subclavian, it usually passes be- 

 tween the roots of the plexus. It lies at first between the Anterior and Middle 



