152 SHOULDER JOINT ELBOW JOINT. 



the notch in the upper border of the scapula, from the base of the cora 

 coid process, and converts it into a foramen. The supra-scapular nerve 

 passes through this foramen. 



4. Shoulder Joint. The scapulo-humeral articulation is an enarthrosis, 

 or ball-and-socket joint its ligaments are, the 



Capsular, 



Coraco-humeral, 



Glenoid. 



The capsular ligament completely encircles the articulating head of the 

 scapula and the head of the hurnerus, and is attached to the neck of each 

 bone. It is thick above, where resistance is most required, and is 

 strengthened by the tendons of the supra-spinatus, infra-spinatus, teres 

 minor, and subscapularis muscles : below it is thin and loose. The cap- 

 sule is incomplete at the point of contact with the tendons, so that they 

 obtain upon their inner surface a covering of synovial membrane. 



The coraco-humeral ligament is a broad band which descends obliquely 

 outwards from the border of the coracoid process to the greater tuberosity 

 of the humerus, and serves to strengthen the superior and anterior part of 

 the capsular ligament. 



The glenoid ligament is the prismoid band of fibre-cartilage, which is 

 attached around the margin of the glenoid cavity for the purposes of pro- 

 tecting its edges, and deepening its cavity. It divides superiorly into two 

 slips which are continuous with the long tendon of the biceps ; hence the 

 ligament is frequently described as being formed by the splitting of that 

 tendon. The cavity of the articulation is traversed by the long tendon 

 of the biceps, which is enclosed in a sheath of synovial membrane in its 

 passage through the joint. 



The synovial membrane of the shoulder joint is very extensive ; it com- 

 municates anteriorly through an opening in the capsular ligament with a 

 large bursal sac, which lines the under surface of the tendon of the sub- 

 scapularis muscle. Superiorly, it frequently communicates through another 

 opening in the capsular ligament w r ith a bursal sac belonging to the infra- 

 spinatus muscle ; and it moreover forms a sheath around that portion of 

 the tendon of the biceps, w T hich is included within the joint. 



The muscles immediately surrounding the shoulder joint are the sub- 

 scapularis, supra-spinatus, infra-spinatus, teres minor, long head of the 

 triceps and deltoid ; the long tendon of the biceps is within the capsular 

 ligament. 



Actions. The shoulder joint is capable of every variety of motion, viz. 

 of movement forwards and backwards, of abduction and adduction, of 

 circumduction and rotation. 



5. Elbow Joint. The elbow is a ginglymoid articulation ; its ligaments 

 are four in number, 



Anterior, Internal lateral, 



Posterior, External lateral. 



The anterior ligament is a broad and thin membranous layer, descend- 

 ing from the anterior surface of the humerus, immediately above the joint, 

 10 the coronoid process of the ulna and orbicular ligament. On each side 

 it is connected with the lateral ligaments. It is composed of fibres which 

 pass ih three different directions, vertical, transverse, and oblique, the lat- 



