THE SHOULDER-JOINT 



253 



The intermediate part, of variable extent, is thin and membranous, containing 

 but few ligamentous fibres; it is often incomplete near the coracoid process, 

 leaving a small gap (fig. 286). 



The superior surface of the Ugament looks upward and a little forward, and is covered by 

 the deltoid muscle; the inferior looks downward and a little backward, and is separated from 

 the capsule of the shoulder-joint by a bursa and the tendons of the supraspinalus and sub- 

 scapularis muscles. At the coracoid process it overlies the coraco-humeral ligament. It is 

 barely one-third of an inch (8 mm.) above the capsule of the shoulder, and in the undissected 

 state there is scarcely a quarter of an inch (6 mm.) interval. The anterior band projects over 

 the centre of the head of the humerus, and is continued into a tough fascia under the deltoid; 

 the posterior band is continuous with the fascia over the supraspinatus muscle. It binds the 



Fig. 287. — ^Posterior View of the Shoulder-joint, showing also the Acromio-cla- 

 vicuLAR Joint and the Special Ligaments of the Scapula. 



Superior transverse ligament 



Conoid ligament 



Acromio-clavicular 

 ligament 



Tendon of infra- 

 spinatus and ^--i?F 

 teres minor ^.^ //^^ 

 Inferior transverse j:^ f// 

 ligament '~ /, 



Capsule of shoulder 



two processes firmly together, and so strengthens each; it holds the deltoid off the capsule of 

 the shoulder, and protects the joint from shght injuries directed downward and backward 

 against it. 



The superior transverse (coracoid, or suprascapular) ligament (figs. 286, 

 287, and 288) is a small triangular band of fibrous tissue, the surfaces of which 

 look forward and backward; and its edges, which are thin and sharp, are turned 

 upward and downward. It continues the superior border of the scapula, bridging 

 over the scapular notch. 



It is broader medially, where it springs from the upper border of the scapula on its dorsal 

 surface; and narrow laterally, where it is attached to the base of the coracoid process; some of 

 its fibres are inserted under the edge of the trapezoid Ugament, and others pass upward with 

 the conoid to reach the clavicle. The transverse scapular (suprascapular) artery passes over it, 

 and the suprascapular nerve beneath it. Medially, some fibres of the omo-hyoid muscle arise 

 from it. 1. 1 1 



The inferior transverse (spino-glenoid) ligament (fig. 287) reaches from the lateral 

 border of the spine of the scapula to the margin of the glenoid cavity, and so forms a foramen 

 under which the transverse scapular (suprascapular) vessels and suprascapular nerve gain the 

 infraspinous fossa. It is usually a weak membranous structure with but few ligamentous 

 fibres. 



3. THE SHOULDER-JOINT 

 Class. — Diarthrosis. Subdivision. — Enarthrodia. 



The shoulder [articulatio humeri] is one of the most perfect and most movable 



