76 SCAPULA. 



tubercle and ridge, for the coraco-clavicular ligament. The opening 

 for the nutritious vessels is seen upon the under surface of the bone. 



Dei-elopment. By two centres ; one for the shaft and one for the 

 sternal extremity ; the former appearing before any other bone of the 

 skeleton, the latter between fifteen and eighteen. 



Articulations. With the sternum and scapula. 



Attachment of Muscles. To six; the sterno-mastoid, trapezius, pec- 

 toralis major, deltoid, subclavius, and sterno-hyoid. 



fl 



SCAPULA The scapula is a flat triangular bone, situated upon the 

 posterior aspect and side of the thorax occupying the space from the 

 second to the seventh rib. It is divisible into an anterior and poste- 

 rior surface, superior, inferior, and posterior border, anterior, superior, 

 and inferior angle, and processes. 



The anterior surface, or subscapular fossa, is concave and irregular, 

 and marked by several oblique ridges which have a direction upwards 

 and outwards. The whole concavity is occupied by the subscapularis 

 muscle, with the exception of a small triangular portion near the supe- 

 rior angle. The posterior surface or dorsum is convex, and unequally 

 divided into two portions by the spine ; that portion above the spine 

 is the supra-spinous fossa ; and that below, the infra-spinous fossa. 



The superior border is the shortest of the three ; it is thin and con- 

 cave, and terminated at one extremity by the superior angle, and at 

 the other by the coracoid process. At its inner termination, and 

 formed partly by the base of the coracoid process, is the supra- scapular 

 notch, for the transmission of the supra-scapular nerve. 



The inferior or axillary border is thick, and marked by several 

 grooves and depressions ; it terminates superiorly at the glenoid 

 cavity, and inferiorly at the inferior angle. Immediately below the 

 glenoid cavity is a rough ridge, which gives origin to the long head of 

 the triceps muscle. Upon the posterior surface of the border is a de- 

 pression for the teres minor ; and upon its anterior surface a deeper 

 groove for the teres major : near the inferior angle is a projecting lip, 

 which increases the surface of origin of the latter muscle. 



The posterior border or base, the longest of the three, is turned to- 

 wards the vertebral column. It is intermediate in thickness between 

 the superior and inferior, and convex, being considerably inflected out- 

 wards towards the superior angle. 



The anterior angle is the thickest part of the bone, and forms the 

 head of the scapula ; it is immediately surrounded by a constricted 

 portion, the neck. The head presents a shallow pyriform articular sur- 

 face, the glenoid cavity* having the pointed extremity upwards ; and at 

 its apex is a rough depression, which gives attachment to the long 

 tendon of the biceps. The superior angle is thin and pointed. The 

 inferior angle is thick, and smooth upon the external surface for the 

 origin of the teres major and for a large bursa over which the upper 

 border of the latissimus dorsi muscle plays. 



The spine of the scapula, triangular in form, crosses the upper part of 



