SHOULDER, ARM, FOREARM, HAND. POSTERIOR PART. 359 



tion. Cut this muscle at its insertion, turn it back (Fig. 254), and find the 

 vessels and nerves the suprascapular that supply this region. 



The suprascapular artery and nerve will come into view as you turn aside 

 the supraspinatus muscle. (Figs. 249254.) The nerve you will trace through 

 the suprascapular foramen under the transverse ligament. (Fig. 252.) The artery 

 crosses the transverse ligament. (Fig. 252.) Each structure divides into supra- 

 spinous and infraspinous branches. Trace these vessels and nerves out to their 

 respective localities of distribution. (Fig. 254.) 



The anastomosis between the suprascapular artery and the dorsal branch of 

 the subscapular takes place in the infraspinous fossa, on the bone. Find this. 

 (Fig. 249.) Anastomosis about the shoulder includes the following arteries, 

 which you may now demonstrate. (Fig. 254) : Circumflex, subscapular, dorsalis 



Transverse ligament 



Conoid ligament 



Acromio-clavicular 

 ligament 



Tendon of infra- 

 spinatus and tares 

 minor 



Inferior transverse 

 or spino-glenoid 

 ligament 

 Capsule of shoulder 



FIG. 252. POSTERIOR VIEW OF THE SHOULDER-JOINT, SHOWING ALSO THE ACROMIO- 

 CLAVICULAR JOINT AND THE PROPER LIGAMENTS OK THE SCAPULA. 



scapulae, suprascapular, posterior scapular artery, a continuation of the trans- 

 versalis colli, a branch of the thyroid axis of the subclavian. 



The triceps muscle (Fig. 253) has three heads. The longer scapular 

 head you will now very carefully trace to the axillary border of the scapula, 

 immediately below the glenoid fossa. As you have already observed, this head 

 assists in forming boundaries for the quadrangular space and also for the two 

 triangular spaces. The whole posterior surface of the humerus is occupied by 

 the inner and outer heads of the triceps muscle, and the musculo-spiral groove. 



Dissection. Locate the musculo-spiral nerve and the superior profuncla 

 artery in the second triangle. (Fig. 249.) Now the nerve will pass between the 

 bone and muscle. Cut the muscle in a line corresponding to the course of the 

 nerve, until you come to a point two inches above the outer condyle. The mus- 

 cular mass attached to the posterior surface of the humerus above the groove, in 



