THORACIC LIMBS 529 



above downward, but concave transversely on each side of the middle 

 line, which is elevated, often into a decided ridge. The scapula is so 

 thin, however, that in the process of drying it may be considerably 

 twisted out of shape; the surfaces will then assume abnormal con- 

 vexities and concavities. There is usually a vascular foramen at the 

 lower end. The supraspinatus muscle is attached in the supraspinous 

 fossa from the base almost down to the neck. 



The infraspinous fossa is larger than the supraspinous fossa. It is 

 triangular, wide above and very narrow below. It is nearly flat from 

 above downward, and at the same time concave from before backward, 

 but this is due more to the turning outward of the edges than to the 

 excavation of the surface itself. The fossa is overhung by the posterior 

 surface of the spine. With the exception of a small area below, near 

 the spine, its entire surface gives origin to the infraspinatus muscle. 

 The small area below is often pierced by one or more nutrient foramina. 



The inner surface of the body of the scapula (Fig. 419) is occupied 

 by the subscapular fossa. Its outline is the general outline of the 

 bone, except that a bevelled strip on the posterior edge belongs to the 

 axillary border. It is almost flat, slightly concave in the anterior 

 half, and marked by four or five ridges which begin at the upper end 

 and are directed downward and toward the middle line. The first and 

 more anterior of these ridges, also the best developed and the most con- 

 stant, begins at the superior angle ; the second begins at the vertebral 

 border not far above the superior angle and runs nearly parallel with 

 the first, but is bowed toward the axillary border. The area between 

 these lines is usually concave. The third ridge occupies the middle 

 line of the surface, and is often little more than a slight longitudinal 

 convexity, but sometimes it is a distinct elevated line, more marked 

 above the middle of the surface. On strongly developed bones the 

 upper part of this ridge divides at the level of the anterior angle ; 

 one branch runs upward and forward to join the vertebral border 

 near the beginning of the second ridge ; the other branch runs back- 

 ward and upward to the posterior third of the vertebral border. The 

 triangular flattened area included between these branches is part of 

 the area of origin of the serratus magnus and levator anguli scapuhe 

 muscles. A fourth ridge begins at or near the vertebral border not 

 far from the inferior angle and runs downward, close to the axillary 



border; which it sometimes joins below. 



34 



