90 THE BONES OF THE UPPER LIMB. 



muscle glides, as it passes to be inserted into a rough thickening beyond. In the 

 rest of its extent this border is rough, broad, and serpentine, giving attachment by 

 its superior margin to the trapezius, and by its inferior to the deltoid muscle. The 

 external border, short, smooth, and concave, arises near the neck of the scapula, and 

 is continuous with the under surface of the acromion, enclosing tlie great scapular 

 notch between it and the neck of the bone. 



The acromion process, projecting outwards and forwards from the extremity of the 

 spine over the glenoid cavity, forms the summit of the shoulder. It is an expanded 

 process, compressed from above downwards. Its superior surface, rough and 

 subcutaneous, is continuous with the prominent border of the spine ; while the 

 inferior surface, smooth and concave, is continuous with the superior surface and 

 external border of the spine. On its internal border anteriorly is a narrow oval sur- 

 face for articulation with the clavicle. Its outer border gives origin to the acromial 

 portion of the deltoid, and is marked by three or four tubercles from which tendinous 

 processes of this part of the muscle spring : posteriorly it terminates in the pro- 

 minent acromial angle, which overhangs the hinder margin of the glenoid cavity. 

 The apex of the acromion projects beyond the end of the clavicle, and gives attach- 

 ment to the coraco-acromial ligament. 



The head bears the articular surface for thehumerus, known as the glenoid cavity. 

 This is a slightly concave surface, looking outwards, forwards, and slightly upwards. 

 It is pyriform in shape, with the narrow end uppermost, and gently incurved in 

 front. Its rim is flattened, and in the recent state is covered by a fibrous baud, the 

 glenoid ligament, which deepens its concavity; at its upper extremity is a small mark 

 indicating the attachment of the long head of the biceps muscle. 



The neck, supporting the head, is most distinct behind, where it forms with the 

 spine the great scapular or acromio-scapular notch, leading from the supraspinous to 

 the infraspinous fossa ; its position is also marked above by the notch in the upper 

 border of the bone. 



The coracoid process, thick, strong, and hook-like, rises for a short distance almost 

 vertically from the upper border of the head, and then bending at a right angle, is 

 directed forwards and slightly outwards. Its superior surface, towards the base, is 

 rough and uneven, giving origin to the coraco-clavicular ligament ; on its outer 

 border is attached the coraco-acromial ligament, at its extremity the coraco-brachialis 

 muscle and short head of the biceps, and on the inner edge the pectoralis minor. 



The superior border of the scapula is the shortest ; it extends from the superior 

 angle outwards and downwards to the coracoid process, at the base of which it presents 

 a rounded suprascapular or coraco-scapular notch, which is converted into a foramen 

 by a ligament, or occasionally by a spiculum of bone, and is traversed by the supra- 

 scapular nerve. The axillary border is the thickest ; at the upper end, below the 

 glenoid cavity, it presents a strong rough mark, above an inch long, to which the 

 long head of the triceps muscle is attached ; and below this there is usually a slight 

 groove, where the dorsal branch of the subscapular artery passes backwards ; on the 

 ventral aspect of this edge in the greater part of its length is a marked groove in which 

 a considerable part of the subscapularis muscle arises. The vertebral border, called 

 also the base, is the longest of the three, and is divisible into three parts, viz., a short 

 one opposite the triangular surface of origin of the prominent border of the spine, 

 and the portions above and below that space, both of which incline outwards as they 

 recede from the spine. The upper part gives attachment to the levator anguli 

 scapulas muscle, the middle to the rhomboideus minor, and the lower to the rhom- 

 boideus major muscle. 



The subcutaneous parts of the scapula are the free border of the spine in nearly 

 the whole of its length, the upper surface of the acromion, and a small part of the 

 vertebral border in its lower half ; the superior and axillary borders are entirely 



