246 



THE SKELETON. 



smooth; its inner border is rough, and gives attachment to the Pectoralis minor; 

 its outer border is also rough for the coraco-acromial ligament, while the apex is 

 embraced by the conjoined tendon of origin of the short head of the Biceps and 

 of the Coraco-brachialis. At the inner side of the root of the coracoid process is 

 a rough impression for the attachment of the conoid ligament : and running from 

 it obliquely forward and outward on the upper surface of the horizontal portion, 

 an elevated ridge for the attachment of the trapezoid ligament. 



Structure. In the head, processes, and all the thickened parts of the bone 

 the scapula is composed of cancellous tissue, while in the rest of its extent it is 

 composed of a thin layer of dense, compact tissue. The centre and upper part of 

 the dorsum, but especially the former, are usually so thin as to be semitransparent ; 



FIG. 196. Plan of the development of the scapula. By seven centres. The epiphyses (except one for the 

 coracoid process) appear from fifteen to seventeen years, and unite between twenty-two and twenty-five years 

 of age. 



occasionally the bone is found wanting in this situation, and the adjacent muscles 

 come into contact. 



Development (Fig. 196). By seven centres : one for the body, two for the 

 coracoid process, two for the acromion, one for the vertebral border, and one for 

 the inferior angle. 



Ossification of the body of the scapula commences about the second month of 

 foetal life by the formation of an irregular quadrilateral plate of bone immediately 

 behind the glenoid cavity. This plate extends itself so as to form the chief part of 

 the bone, the spine growing up from its posterior surface about the third month. 

 At birth the chief part of the scapula is osseous, only the coracoid and acromion 

 processes, the posterior border, and inferior angle being cartilaginous. About 

 the first year after birth ossification takes place in the middle of the coracoid 

 process, which usually becomes joined with the rest of the bone at the time when 

 the other centres make their appearance. Between the fifteenth and seventeenth 

 years ossification of the remaining centres takes place in quick succession, and 



