90 THE UPPER EXTREMITY 



are stretched under it 3 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. 



Dissection, Detach the axillary vessels and brachial nerves from the 

 coracoid process to which they have been tied, and throw them distally. 

 Then proceed to remove the muscles. Divide the conjoined origin of the 

 short head of the biceps brachii and the coraco-brachialis close to the coracoid 

 process, the teres major about its middle, and the long head of the triceps 

 about an inch or two below its origin, and turn them aside. Next deal 

 with the muscles more immediately in relation to the joint, viz. the supra- 

 spinatus, the infraspinatus, the teres minor, and the subscapularis. These 

 must be removed with great care, because their tendons are closely con- 

 nected with the subjacent ligamentous capsule. They are not incorporated 

 with the capsule, however, although at first sight they appear to be so, 

 and thus they can be dissected from it. In the case of the subscapularis a 

 protrusion of the synovial membrane, forming a bursa mucosa, will be 

 found near its upper border, close to the root of the coracoid process. 

 The capsule of the shoulder-joint may now be cleaned, and its attachments 

 defined. 



The ligaments in connection with the shoulder- joint 

 are : 



1. The capsula articularis. 3. The lig. glenohumerale. 



2. The lig. coracohumerale. | 4. The labrum glenoidale. 



Capsula Articularis (Capsule). The capsule of the 

 shoulder-joint is a dense and strong ligamentous structure, 

 which envelops the articulation on all sides. It is attached 

 to the scapula around the glenoid cavity, but only above is it 

 directly fixed to the bone. Elsewhere it springs from the 

 fibrous ring or the labrum glenoidale, which serves to deepen 

 the articular cavity ; indeed, in its lower part it appears to 

 be continuous with the border of the labrum glenoidale. 

 Laterally it is fixed to the lateral part of the anatomical 

 neck of the humerus. The width of the capsule is not 

 uniform throughout. It expands as it passes over the en- 

 closed head of the humerus, and contracts as it reaches its 

 scapular and humeral attachments. The great laxity of the 

 capsule of the shoulder-joint will now be apparent. When 

 the muscles are removed, and air is admitted into the joint, 

 the bony surfaces fall away from each other the head of 

 the humerus sinking downwards, when the part is held by 

 the scapula, to the extent of an inch. 



The capsule of the shoulder-joint is not complete upon all 

 aspects. Its continuity is interrupted by two, and sometimes 

 three, apertures. The largest of these is an opening of some 

 size, which is placed upon its medial aspect, near the root 



