372 A MANUAL OF ANA TO MY. 



The Posterior Circumflex Artery and Circumflex 

 Nerve. Fig. 77. 



The artery is a branch from the third portion of the 

 axillary, the nerve comes from the posterior cord of the 

 brachial plexus. See pages 279 and 318. They are found 

 coming through a quadrilateral space bounded above (and 

 in front) by the subscapularis (behind by the teres minor), 

 below by the teres major, internally by the long head of the 

 triceps muscle, and externally by the humerus. 



The nerve supplies the teres minor and deltoid muscles 

 and sends branches to the shoulder-joint and the skin over 

 the deltoid and middle third of outer surface of the arm. 

 The artery supplies these muscles, the joint of the shoulder, 

 and anastomoses with the anterior circumflex, and by a 

 large branch with the superior profunda arteries. 



The Superior Profunda Artery and the Musculospiral 



Nerve. Fig. 77. 



These are found together as they course through the 

 musculospiral groove, from the inner to the outer side of 

 the arm, where the nerve terminates by dividing into its 

 radial and posterior interosseous branches (see page 3 1 8), 

 and the artery by anastomosing with the radial recurrent. 

 The artery also sends a branch upward to anastomose 

 with the posterior circumflex and one downward the 

 articular which, descending in the substance of the 

 triceps, supplies that muscle, and terminates in the anasto- 

 motic circle about the elbow-joint (for which see page 387). 



DISSECTION. 



Divide the levator anguli scapulae and rhomboid muscles. Clean the 

 inner surface of the serratus magnus, noting its attachments. 



Remove the serrati muscles and clean the fascia covering the extensor 

 muscles of the spine and note its attachments. 



