THE SCAPULA, OR SHOULDER BLADE 175 



above downward, its apex corresponding to the vertebral border, its base (which 

 is directed outward) to the neck of the scapula. It presents two surfaces and three 

 borders. Its superior surface is concave, assists in forming the supraspinous 

 fossa, and affords attachment to part of the Supraspinatus muscle. Its inferior 

 surfice forms part of the infraspinous fossa, gives origin to part of the Infraspi- 

 natus muscle, and presents near its centre the orifice of a nutrient canal. Of the 

 three borders, the anterior is attached to the dorsum of the bone; the posterior, 

 or crest of the spine, is broad, and presents two lips and an intervening rough 

 interval. To the superior lip is attached the Trapezius to the extent shown in 

 Fig. 139. A rough tubercle is generally seen occupying that portion of the spine 

 which receives the insertion of the middle and inferior fibres of this muscle. From 

 the inferior lip, throughout its whole length, arises the Deltoid. The interval 

 between the lips is also partly covered by the tendinous fibres of these muscles. 

 The external border, or base, the shortest of the three, is slightly concave, its edge 

 thick and round, continuous above with the under surface of theacromion process, 

 below with the neck of the scapula. The narrow portion of bone external to this 

 border, and separating it from the glenoid cavity, is called the great scapular notch, 

 and serves to connect the supra- and infraspinous fossa?. 



The acromion process (acromioii) is a large and somewhat triangular or oblong 

 process, flattened from behind forward, directed at first a little outward, and then 

 curving forward and upward, so as to overhang the glenoid cavity. Its upper 

 surface, directed upward, backward, and outward, is convex, rough, and gives 

 origin to some fibres of the Deltoid, and in the rest of its extent it is subcutaneous. 

 Its under surface is smooth and concave. Its outer border is thick and irregular, 

 and presents three or four tubercles for the tendinous origins of the Deltoid 

 muscle. Its inner margin, shorter than the outer, is concave, gives attachment 

 to a portion of the Trapezius muscle, and presents about its centre a small oval 

 surface for articulation with the acromial end of the clavicle. Its apex, which 

 corresponds to the point of meeting of these two borders in front, is thin, and has 

 attached to it the coracoacromial ligament. 



Margins, or Borders of the Scapula. The superior border (margo superior) is 

 the shortest and thinnest of the three borders; it is concave and extends from the 

 internal angle to the coracoid process. At its outer part is a deep, semicircular 

 notch, the suprascapular notch (incisura scapulae), formed partly by the base 

 of the coracoid process. The notch is converted into a foramen by the supra- 

 scapular ligament, and serves for the passage of the suprascapular nerve. Some- 

 times this foramen is entirely surrounded by bone. The adjacent margin of the 

 superior border affords attachment to the Omohyoid muscle. 



The external or axillary border (margo axillaris] is the thickest of the three. It 

 commences above at the lower margin of the glenoid cavity, and inclines obliquely 

 downward and backward to the inferior angle. Immediately below the glenoid 

 cavity is a rough impression, the infraglenoid tubercle (tuberositas infraglenoidalis), 

 about an inch in length, which affords origin to the long head of the Triceps muscle; 

 in front of this is a longitudinal groove, which extends as far as the lower third 

 of the external border and affords origin to part of the Subscapularis muscle. 

 The inferior third of this border, which is thin and sharp, serves for the origin 

 of a few fibres of the Teres major behind and the Subscapularis in front. 



The internal or vertebral border (margo vertebralis) is the longest of the three, 

 and extends from the internal to the inferior angle of the bone. It is arched, is 

 intermediate in thickness between the superior and the external borders, and the 

 portion of it above the spine is bent considerably outward; so as to form an obtuse 

 angle with the lower part. The internal border presents an anterior lip, a posterior 

 lip, and an intermediate space. The anterior lip affords attachment to the Serratus 

 magnus; the posterior lip, an origin to the Supraspinatus above the spine, the 



