206 



THE SKELETON. 



depression for the attachment of the conoid ligament, and, running frqpi it 

 obliquely forwards and outwards 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, it 

 is cellular in structure, of a dense compact tissue in the rest of its extent. The 

 centre and upper part of the dorsum, but especially the former, is usually so 

 thin as to be semi-transparent; occasionally the bone is found wanting in this 

 situation, and the adjacent muscles come into contact. 



Development (Fig. 153). By seven centres; one for the body, two for the cora- 

 coid process, two for the acromion, one for the posterior border, and one for 



Fig. 153 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. 



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 pos- 

 terior 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 appear- 

 ance. Between the fifteenth and seventeenth years, ossification of the remaining 

 centres takes place in quick succession, and in the following order : first, near 

 the base of the acromion, and in the root 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 



