THE SCAPULA. 143 



At birth a large part of the scapula is osseous, but the glenoid cavity, coracoid and 

 acromion processes, the posterior border, and inferior angle are cartilaginous. 

 From the fifteenth to the eighteenth month 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 Avhen the other centres make their appearance. Between the 

 fourteenth and twentieth years ossification of the remaining centres takes place in 

 quick succession, and in the following order : first, in the root of the coracoid proc- 

 ess, in the form of a broad scale ; secondly, near the base of the acromion process ; 

 thirdly, in the inferior angle and contiguous part of the posterior border ; fourthly, 

 near the extremity of the acromion ; fifthly, 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 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 

 bv fibrous tissue or by an imperfect articulation ; in some cases of supposed fracture 

 of the acromion with ligamentous union it is probable that the detached segment 

 was never united to the rest of the bone. The upper third of the glenoid cavity 

 is usually ossified from a separate centre (subcoracoid) which makes its appearance 

 between the tenth and eleventh years. Very often, in addition, an epiphysis 

 appears for the lower part of the glenoid cavity. 



Articulations. With the humerus arid clavicle. 



Attachment of Muscles. To seventeen : to the anterior surface, the Subscapu- 

 laris ; posterior surface, Supraspinatus, Infraspinatus ; spine, Trapezius, Deltoid ; 

 superior border, Omo-hyoid ; vertebral border, Serratus magnus, Levator anguli 

 scapulae, Rhomboideus minor and major ; axillary border, Triceps, Teres minor, 

 Teres major; apex of glenoid cavity, long head of the Biceps; coracoid process, 

 short head of the Biceps, Coraco-brachialis, Pectoralis minor ; and to the inferior 

 angle occasionally a few fibres of the Latissimus dorsi. 



Surface Form. The only parts of the scapula which are truly subcutaneous are the spine 

 and acromion process, but, in addition to these, the coracoid process, the internal or vertebral 

 border and inferior angle, and ; to a less extent, the axillary border, may be defined. The acro- 

 mion process and spine of the scapula are easily felt throughout their entire length, forming, 

 with the clavicle, the arch of the shoulder. The acromion can be ascertained to be connected 

 to the clavicle at the acromio-clavicular joint by running the finger along it, its position being 

 often indicated by an irregularity or bony outgrowth from the clavicle close to the joint. The 

 acromion can be felt forming the point of the shoulder, and from this can be traced backward 

 to join the spine of the scapula. The place of junction is usually denoted by a prominence, 

 which is sometimes called the angle. From here the spine can be felt as a prominent ridge of 

 bone, marked on the surface as an oblique depression, which becomes less and less distinct, and 

 terminates a little external to the spinous processes of the vertebrae. Its termination is usually 

 indicated by a slight dimple in the skin on a level with the interval between the third and fourth 

 dorsal spines. Below this point the vertebral border of the scapula may be traced, running 

 downward and outward, and thus diverging from the vertebral spines, to the inferior angle of 

 the bone, which can be recognized, although covered by the Latissimus dorsi muscle. From 

 this angle the axillary border can usually be traced through this thick muscular covering, form- 

 ing, with the muscles, the posterior fold of the axilla. The coracoid process may be felt about 

 an inch below the junction of the middle and outer third of the clavicle. Here it is covered by 

 the anterior border of the deltoid and lies a little to the outer side of a slight depression which 

 corresponds to the interval between the Pectoralis major and Deltoid muscles. When the arms 

 are hanging by the side, the upper angle of the scapula corresponds to the upper border of the 

 second rib or the interval between the first and second dorsal spines, the inferior angle to the 

 upper border of the eighth rib or the interval between the seventh and eighth dorsal spines. 



Surgical Anatomy. Fractures of the body of the scapula are rare, owing to the mobility 

 of the bone, the thick layer of muscles by which it is encased on both surfaces, and the elas- 

 ticity of the ribs on which it rests. Fracture of the neck of the bone is also uncommon. The 

 most frequent course of the fracture is from the suprascapular Blotch to the infraglenoid 

 tubercle, and it derives its principal interest from its simulation to a subglenoid dislocation of 

 the humerus. The diagnosis can be made by noting the alteration in the position of the 

 coracoid process. A fracture of the neck external to, and not including, the coracoid process is 

 said to occur, but it is exceedingly doubtful whether such an accident ever takes place. The 

 acromion process is more frequently broken than any other part of the bone, and there is some- 



