THE SCAPULA 41 



the coraco-humeralis muscle takes origin from the special tubercle which 

 has just been mentioned. The coracoid process forms a prominent pro- 

 jection at the point of the shoulder. It is particularly exposed to risk 

 of injury, and an important point to remember in connection with it is 

 that it has a special centre of ossification quite distinct from that from 

 which the body of the bone ossifies. 



The glenoid cavity is a shallow depression with a circumferent 

 edge approaching the elHptical in outline. It lies below the coracoid 

 process, from which it is distant about an inch. Inwardly, between 

 the process and the cavity, there is presented a well-marked notch, 

 which is overhung by the tubercle attached to the coracoid process. 

 Through this notch the tendon of the subscapularis muscle passes to 

 its insertion into the posterior division of the internal tuberosity of the 

 humerus. 



The glenoid cavity accommodates the articular head of the humerus. 

 It is circumscribed by a well-defined rim, which affords the superior attach- 

 ment to the capsular ligament of the shoulder joint. Supero-internally 

 the rim presents a notch through which the tendon of origin of the 

 coraco-humeralis muscle passes. This tendon is therefore in intimate 

 relationship to the capsular ligament. Outwardly the rim of the 

 glenoid cavity presents a small tubercle, from which some of the fibres of 

 the teres minor muscle arise. The glenoid cavity also ossifies from a 

 separate centre. 



Immediately above the glenoid cavity the bone is encircled by a 

 faintly defined neck, but at a distance of two inches above the cavity, and 

 therefore above the coracoid process also, there is a w^ell-marked con- 

 striction of the bone. On this constricted portion there are present on 

 the dorsal and ventral aspects of the bone a number of smooth, shallow 

 grooves, which are the impressions left by the blood-vessels which play 

 over this part. On the dorsal aspect in the inferior third of the infra- 

 spinous fossa we find the nutrient foramen, which is on a level with the 

 inferior extremity of the spine. 



