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OSTEOLOGY. 



often deficient. This marginal surface affords attachment throughout its entire 

 extent to the Serratus magnus muscle. The subscapular fossa presents a trans- 

 verse depression at its upper part, called the subscapular angle; it is in this situa- 

 tion that the fossa is deepest ; and consequently the thickest part of the Sub- 

 scapularis muscle lies in a line parallel with the glenoid cavity, and must conse- 

 quently operate most effectively on the humerus which is contained in it. 



The posterior surface or dorsum (fig. 85) is arched from above downwards, 

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



Fig. 84. Left Scapula. Anterior Surface or Venter. 



into two parts by the spine ; that portion above the spine is caned the supra- 

 apinous fossa, and that below it, the infra-spinous fossa. 



The supra-spinous fossa, the smaller of the two, is concave, smooth, and 

 broader at the vertebral than at the humeral extremity. It affords attachment by 

 its inner two-thirds to the Supra-spinatus muscle. 



The infra-spinous fossa is much larger than the preceding : towards its ver- 

 tebral margin a shallow concavity is seen at its upper part ; its centre presents a 



