THP: SCAPULA. 



243 



anterior third of the fossa, which is smooth, is covered by, but does not afford 

 attachment to. the fibres of this muscle. The venter is separated from the 

 posterior border by a smooth, triangular margin at the superior and inferior 

 angles, and in the interval between these by a narrow edge which is often deficient. 

 This marginal surface affords attachment throughout its entire extent to the 

 Serratus magnus muscle. The subscapular fossa presents a transverse depression 

 at its upper part, where the bone appears to be bent on itself, forming a consider- 

 able angle, called the subscapular angle, thus giving greater strength to the body 

 of the bone from its arched form, while the summit of the arch serves to support 

 the spine and acromion process. It is in this situation that the fossa is deepest, 

 so that the thickest part of the Subscapularis muscle lies in a line perpendicular 



Cora 



Grooce for Dorsalis 

 Scapulae Artery. 



FIG. 195. Left scapula. Posterior surface, or dorsum. 



to the plane of the glenoid cavity, and must consequently operate most effectively 

 on the head of the humerus. which is contained in that cavity. 



The posterior surface, or dorsum (Fig. 195), is arched from above downward, 

 alternately concave and convex from side to side. It is subdivided unequally into 



