128 



OSTEOLOGY. 



seventeenth years, ossification of the remaining centres takes place in quick suc- 

 cession, and in the following order : first, near the base of the acromion, and in the 

 upper part of the coracoid process, the latter appearing in the form of a broad 

 scale ; secondly, in the inferior angle and contiguous part of the posterior border ; 

 thirdly, near the extremity of the acromion; fourthly, in the posterior border. 

 The acromion process, besides being formed of two separate nuclei, has its base 

 formed by an extension into it of the centre of ossification which belongs to the 

 spine, the extent of which varies in- different cases. The two separate nuclei 

 unite, and then join with the extension carried in from the spine. These various 

 epiphyses become joined to the bone between the ages of twenty-two and twenty- 

 five years. Sometimes failure of union between the acromion process and spine 

 occurs, the junction being effected by fibrous tissue, or by an imperfect articulation; 



Fig. 86. Plan of the Development of the Scapula. By Seven Centres. 



in some cases of supposed fracture of .the acromion with ligamentous union, it is 

 probable the detached segment was never united to the rest of the bone. 



Articulations. With the humerus and clavicle. 



Attachment of Muscles. To the anterior surface, the Subscapularis ; posterior 

 surface, Supra-spinatus, Infra-spinatus ; spine, Trapezius, Deltoid; superior border, 

 Omo-hyoid ; vertebral border, Serratus magnus, Levator anguli scapulae, Ehpm- 

 boideus minor and major ; axillary border, Triceps, Teres minor, Teres major ; 

 glenoid cavity, long head of the Biceps ; coracoid process, short head of Biceps, 

 Coraco-brach'ialis, Pectoralis minor ; and to the inferior angle, occasionally a few 

 fibres of the Latissimus dorsi. 



