126 SURGICAL ANATOMY OF 



scapular, which becomes greatly developed after ligature 

 of the subclavian in the third part of its course, playing 

 a chief part in the maintenance of the collateral circula- 

 tion for the supply of the arm. In front of the scapula, 

 between it and the ribs, is the subscapularis, a multi- 

 penniform muscle, the full development of which gives 

 such an appearance of depth to the thorax in muscular 

 persons. Beneath the tendons of the muscles inserted 

 into the greater and lesser tuberosities, are large bursse, 

 occasionally communicating with that beneath the del- 

 toid, and with the synovial membrane of the shoulder- 

 joint; inflammation or suppuration of which may be 

 mistaken for glandular inflammation or for axillary 

 aneurism. 



Articulation of the Shoulder-joint. The ellipsoidal ar- 

 ticular extremity of the humerus is very large in com- 

 parison with the glenoid cavity, which is ovoid in shape, 

 larger below than above ; and it is surgically of impor- 

 tance to note that, not only are the articular surfaces of 

 the humerus and scapula here in contact, but that the 

 head of the bone is in immediate relation with the arch 

 formed by the coracoid and acromion processes and the 

 coraco-acromial ligaments an approximation which is 

 due to the action of the deltoid, in atrophy of which 

 muscle there is a considerable interspace between these 

 points. The capsule of the joint is materially strength- 

 ened by fibrous expansion from the tendons of those 

 muscles which are in immediate contact with the articu- 

 lation viz., the supra- and infra-spinati, teres minor, 

 subscapularis, and long head of biceps and triceps, and 

 by bands passing from the coracoid process. The syno- 

 vial membrane lining the capsule is prolonged beneath 

 the subscapularis muscle, and into the bicipital groove. 



