THOEACIC LIMBS 545 



downward and backward to the posterior inferior angle. The anterior 

 triangular portion is flat, slightly roughened, and pierced by foramina 

 for veins. It faces outward and forward, and is free from muscular 

 attachment. The posterior smaller portion is ovoid in outline and 

 faces outward and backward. Its upper part is rough and depressed ; 

 it is the area of insertion of the tendon of the infraspinatus muscle. 

 The lower part is slightly elevated, particularly at the lower angle, for 

 the attachment of the teres minor muscle and the upper end of the 

 outer humeral head of the triceps muscle. 



The lesser tuberosity of the humerus (Figs. 429, 430) is closely 

 united with the head, so closely, indeed, that it appears little more than 

 its enlarged anterior internal portion. It is very much smaller than 

 the greater tuberosity, from which it is separated in front by the 

 bicipital groove and behind by the entire width of the head. It is 

 oblong, and the long diameter, which is twice as great as the trans- 

 verse diameter, is directed from above downward and backward. It 

 is divided by an internal border into anterior and posterior surfaces. 



The internal border begins above at the prominent superior angle 

 behind the bicipital groove ; it then arches downward and backward, 



c 



and at the inferior angle bends abruptly forward and outward to con- 

 tinue downward as the internal border of the shaft. 



The quadrate anterior surface of the lesser tuberosity is concave 

 from side to side, convex from above downward at the upper part, and 

 almost flat below. It faces forward, outward, and slightly downward. 

 It forms part of the floor and the inner wall of the bicipital groove; it 

 is limited below by the internal border. 



The posterior surface of the tuberosity is long and narrow ; it is 

 flattened from side to side, and is convex from above downward ; the 

 upper part faces upward, backward, and outward, and the lower part 

 faces outward and backward. It is limited in front by the inner 

 border of the tuberosity, and behind by a faint groove which separates 

 it from the articular surface of the head. It has a short, obscure 

 superior margin, directed inward and backward, and is defined clearly 

 below by a short arcuate line, below which, and behind the beginning 

 of the internal border of the shaft, is the outer part of the posterior 

 surface of the head, continuous below with the posterior surface of the 

 shaft. The subscapularis muscle is attached to the entire posterior 

 surface of the lesser tuberosity. 



35 



