SHOULDER-JOINT 1 2 1 



there it is prolonged downwards, in the form of a fold, in the 

 ordinary dependent position of the limb (Figs. 50, 53). When, 

 however, the arm is abducted, the fold is obliterated, and the 

 head of the bone rests upon the inferior part of the capsule, 

 which now receives partial support from two muscles which 

 are stretched under it, viz. the long head of the triceps and 

 the teres major. Still, this must be regarded as the weakest 

 part of the joint, and consequently dislocation of the head of 

 the humerus downwards into the axilla, through the inferior 

 part of the capsule, is an occurrence of considerable frequency. 

 When the dislocation occurs, the axillary vessels and nerve 

 which lie close to the capsule may be injured. 



Dissection. The capsuie of the shoulder- joint has already 

 been exposed by the reflection of the muscles immediately 

 adjacent to its anterior, superior, and posterior aspects, and 

 the bursa between its anterior surface and the subscapularis 

 has been examined. To expose the capsule more fully, untie 

 the axillary vessels and nerves from the coracoid process ; cut 

 through the tendon of origin of the coraco-brachialis and the 

 short head of the biceps brachii and displace the muscles down- 

 wards. Cut through the teres major about its middle and the 

 long head of the triceps about 25 mm. (one inch) distal to its 

 origin and turn both muscles aside. Turn aside the divided sub- 

 scapularis, supraspinatus, infraspinatus and teres minor muscles. 

 Note that whilst the supraspinatus, infraspinatus and teres 

 minor completely cover the upper and posterior part of the 

 capsule, a small interval exists between the anterior border of 

 the supraspinatus and the upper border of the subscapularis. 

 In that interval the subacromial bursa is in relation with the 

 capsule, and occasionally, but very rarely, a communication 

 exists between the cavity of the bursa and the cavity of the 

 joint. Re-examine the bursa which lies between the sub- 

 scapularis and the front of the capsule, and note that its aperture 

 of communication with the joint is situated near the root of 

 the coracoid process. Thoroughly clean the outer surface of the 

 capsule. Note the laxity of the capsule, and define its attach- 

 ments to the margin of the glenoid cavity and to the lateral 

 border of the root of the coracoid process. 



The ligaments of the shoulder-joint are : 



Capsula articularis 



Lig. coracohumerale. 

 Lig. glenohumerale superius. 

 medium. 



inferius. 



Labrum glenoidale. 



Capsula Articularis. The fibrous stratum of the articular 

 capsule is a fairly dense and strong membrane which envelops 



