THE SCAPULA. 203 



rith each other round the 'free lateral concave border of the spine, where that 

 urves over the great scapular notch. The dorsal free border of the spine is 

 ubcutaneous throughout its entire length. Its upper and lower edges are 

 trongly lipped, and serve the superior, for the insertion of the trapezius; 

 he inferior, for the origin of the deltoid. The intervening surface varies in 

 ridth broad and triangular where it becomes confluent with the vertebral border, 

 ,b displays a smooth surface, over which the tendinous fibres of the trapezius play ; 

 .arrowing rapidly, it forms a surface of varying width which blends laterally with 

 I flattened process, the two forming a compressed plate of bone which arches across 

 She great scapular notch above and behind, and then curves, upwards, forwards, and 

 literally to overhang the glenoid cavity. The medial border of this process is con- 

 iinuous with the upper margin of the spine, and is gently curved. The lateral 

 order, more curved than the medial, with which it is united in front, is confluenj; 

 rith the inferior edge of the spine, with which it forms an abrupt bend, termed the 

 .cromial angle. The bone included between these two borders is called the acromion. 

 )f compressed form, it much resembles the acromial end of the clavicle, with which 

 b articulates by means of a surface (facies articularis acromii) which is placed on 

 bs medial border near its anterior extremity. The superior surface of the acromion, 

 rhich is broad and expanded, is subcutaneous, and is directed upwards and dorsally, 

 ,nd in the normal position of the bone laterally as well. Its medial edge, where 

 lot in contact with the clavicle, has attached to it the fibres of the trapezius, 

 whilst its lateral margin affords origin to the central part of the deltoid. At its 

 nterior extremity it is connected with the coracoid process by means of the coraco- 

 .cromial ligament. Its inferior surface is smooth and overhangs the shoulder-joint. 



The supra-spinous fossa, of much less extent than the infra-spinous, is placed 

 ,bove the spine, the upper surface of which assists in forming its curved floor ; in 

 b is lodged the supraspinatus muscle. The scapular notch opens into it above, 

 vhilst below and laterally it communicates with the infra-spinous fossa by the 

 ;reat scapular notch, through which the transverse scapular artery and supra- 

 capular nerve pass to reach the infra-spinous fossa. 



The infra-spinous fossa, overhung by the spine above, is of triangular form. The 

 .xillary margin of the bone limits it in front, whilst the vertebral margin bounds it 

 ehind ; the greater part of, this surface affords origin to the infraspinatus muscle, 

 xcepting a well-defined area which skirts the axillary margin and inferior angle of 

 he bone, and which affords an attachment to the fibres of origin of the teres minor, 

 ["his muscle extends along the dorsal surface of the axillary margin in its superior 

 wo-thirds, reaching nearly as high as the glenoid edge ; whilst a crescentic surface, 

 vhich occupies the inferior third of the axillary border and curves backward round 

 he dorsal aspect of the inferior angle, furnishes an origin for the teres major 

 nuscle. Here also, near the inferior angle, are occasionally attached some of the 

 ibres of the latissimus dorsi muscle. 



The facies costalis (costal aspect) of the body is hollow from above downwards 

 ind from side to side, the greatest depth being in correspondence with the spring of the 

 spine from the dorsal surface. Its medial boundary, which is formed by the anterior 

 ipped edge of the vertebral margin, affords attachment to the fibres of insertion of 

 ihe serratus anterior along the greater part of its extent. The area of insertion of 

 Ms muscle is, however, considerably increased over the ventral aspects of the 

 nedial and inferior angles respectively. Eunning down from the head and 

 jaeck above to the inferior angle below, there is a stout rounded ridge of bone, 

 vhich imparts a fulness to the costal aspect of the axillary margin and increases the 

 ! iepth of the costal hollow ; to this, as well as to the floor of the fossa, the sub- 

 ncapularis muscle is attached. The tendinous intersections of this muscle leave 

 it-heir imprint on this surface of the bone in a series of three or four rough lines 

 which converge towards the neck. 



Tie scapula of man is characterised by the greater proportionate length of its base 

 <Dr vertebral margin as compared with lower forms. This proportion is expressed 

 ;by what is termed the scapular index (Appendix D). -The greater' size of the 

 ; acromion is also a distinctive feature. The double ossification of the coracoid occurs 

 only in mammals. It is probable that the centre for the upper and anterior part of the 



