144 THE SKELETON 



glenoid cavity is a wide, shallow, pyriform, articular surface for the head of the 

 humerus, directed forward and laterallj^, with the apex above and the broad end 

 below. Its margin is raised, and affords attachment to the glenoid ligament, 

 which deepens its concavity. The margin is not, however, of equal prominence 

 throughout, being somewhat defective where it is overarched by the acromion, 

 notched anteriorh', and emphasised above to form a small eminence, the supra- 

 glenoid tubercle, for the attachment of the long head of the biceps. 



The circumference and adjoining part of the neck give attachment to the articular capsule 

 of the shoulder-joint, and the anterior border to the three accessory ligaments of the capsule, 

 known as the superior, middle, and inferior gleno-humeral folds. The superior fold (Flood's 

 ligament) is attached above the notch near the upper end; of the two remaining folds, which 

 together constitute Schlemm's ligament, the middle is attached immediately above the notch 

 and the inferior below the notch. In the recent state the glenoid fossa is covered with hyaline 

 cartilage. The neck is more prominent behind than before and below than above, where it 

 supports the coracoid process. It is not separated by any definite boundary from the body. 



Processes. — The spine is a strong, triangular plate of bone attached obliquely 

 to the dorsum of the scapula and directed backward and upward. Its apex is 

 situated at the vertebral border; the base, corresponding to the middle of the neck, 

 is free, concave, and gives attachment to the inferior transverse ligament, which 

 arches over the transverse scapular (suprascapular) vessels and suprascapular 

 nerve. Of the two borders, one is joined to the body, whilst the other is free, 

 forming a prominent subcutaneous crest. The latter commences at the vertebral 

 border, in a smooth triangular area, over which the tendon of the trapezius glides, 

 usually without the intervention of a bursa, as it passes to its insertion into a 

 small tubercle on the crest beyond. Further laterally, this border is rough, and 

 presents two lips — a superior for the insertion of the trapezius and an inferior for 

 the origin of the deltoid. Laterally the crest is continued into the acromion. 



The spine has two surfaces, the superior, which also looks medialward and 

 forward, is concave, contributes to the formation of the supraspinous fossa, and 

 gives origin to the supraspinatus muscle; the inferior surface, also slightly concave, 

 is directed lateralward and backward, forms part of the infraspinous fossa, and 

 affords origin to the infraspinaius muscle. On both surfaces are one or more 

 prominent vascular foramina. 



The acromion, a process overhanging the glenoid cavity, springs from the 

 angle formed by the junction of the crest with the base of the spine. Somewhat 

 crescentic in shape, it forms the summit of the shoulder and is compressed from 

 above downward so as to present for examination two surfaces, two borders, and 

 two extremities. 



The posterior part sometimes terminates laterally in a prominent acromial angle (meta- 

 cromion) and the process then assumes a more or less triangular form. Of the two extremities, 

 the posterior is continuous with the spine, whilst the anterior forms the free tip. The upper 

 surface, directed upward, backward, and slightly lateralward, is rough and convex, and affords 

 origin at its lateral part to a portion of the deltoid; the remaining part of this surface is sub- 

 cutaneous. The lower surface, directed downward, forward, and slightly medialward, is con- 

 cave and smooth. The medial border, continuous with the upper lip of the crest, presents, 

 from behind forward, an area for the insertion of the trapezius; a small, oval, concave articular 

 facet for the lateral end of the clavicle^ the edges of which are rough for the acromio-clavicular 

 ligaments; and, beyond this, the anterior extremity or tip, to which is attached the apex of the 

 coraco-acromial ligament. The lateral border, continuous with the inferior lip of the crest, is 

 thick, convex, and presents three or four tubercles with intervening depressions; from the 

 tubercles the tendinous septa in the acromial part of the deltoid arise, and from the depressions, 

 some fle.shy fibres of the same muscle. 



Projecting upward from the neck of the scapula is the coracoid process, bent 

 finger-like,' pointing forward and laterally. It consists of two parts, ascending 

 and horizontal, arranged at almost a right angle to each other. 



The ascending pari arises by a wide root, extends upward and medially for a short distance, 

 and is compressed from before backward; it is continuous above with the horizontal part and 

 below with the neck of the scapula; tlie lateral border lies above the glenoid cavity and gives 

 attachment to the coraco-hurneral ligament; the medial border, which forms the lateral boundary 

 of the scapular notch, gives attachment to the conoid ligament above and the transverse liga- 

 ment below. Its anterior and posterior surfaces are in relation with the subscapularis and 

 supraspinaius respectively. The liorizonlal part of the process runs forward and lateralward; it 

 is compressed from above downward so as to present two borders, two surfaces, and a free 

 extremity. The medial border gives in.sertion along its anterior half to the pecloralis minor and 

 nearer the base to the costo-coracoid membrane; the lateral border is rough for the coraco- 

 acromial and coraco-humeral ligaments; the ui)r)er surface is irregular and gives insertion in 



