CHAP, iv.] THE SKELETON OF THE LIMBS. 93 



is placed on the inner side of the bicipital groove. Both tuberosities 

 serve for muscular attachments. 



The lower end of the humerus expands considerably, havino a 

 lateral prominence termed a condyle, on 

 each side, but the internal condyle (ci) pro- /-, 



jects further inwards than does the external 

 condyle (ce) outwards. 



Between these projections is placed the 

 lower articular surface for the bones of the 

 o rearm. 



This is irregularly concave and convex. 

 At its outer part is a rounded prominence 

 (convex transversely as well as from before 

 backwards) called the capitettum (c), which 

 joins the outer bone of the fore- arm or 

 radius. Internal to this is a pulley-like trans- 

 versely concave surface (a), the trochlea, 

 which joins the inner bone of the fore-arm 

 or ulna. The groove of this " pulley " ex- 

 tends completely round from the anterior to 

 the posterior surface of the humerus. The 

 capitellum and the trochlea run one into the 

 other without any distinct demarcation. 

 There is a shallow cavity in front of the 

 humerus immediately above the trochlea. 

 This is called the coronoid fossa, because it 

 receives the coronoid process of the ulna. 

 There is another much deeper fossa (o), also 

 above the trochlea, but on the hinder surface 

 of the humerus. This is called the okcranal 

 or anconeal fossa, from the part of the ulna 

 which it receives when the fore-leg is 

 straightened. The inner margin of the 

 distal articular surface of the humerus (), 

 descends much below its external margin. 



4. The RADIUS (which is slightly 

 shorter than the humerus) is also a long 

 cylindrical bone, expanded more or less at 

 each end, and flattened on that side which 

 is behind when the fore-leg is so placed 

 that the paw rests on the ground. At its 

 place of attachment above, it is the external 



bone of the fore-arm. The long middle part of the bone, or shaft, 

 is a little curved, with the convexity forwards and outwards. At 

 the upper part of its inner margin is a prominence called the 

 tuberosity (t) 9 into which is inserted the tendon of the biceps 

 muscle. Just above this bicipital tuberosity the bone is nar- 

 rowed into what is called the neck, from which rises the head (h) 

 of the bone. This head is oval in shape, with a smooth margin, 



Fig. 54. THE INNER ASPECT 



OF THE HUMEKUS. 



c. Capitellum. 



cf. Supra-condyloid foramen. 



ic. Infernal condyle. 



dr. Deltoid ridge. 



7i. Head. 



t. Inner margin of trochlea. 



t\ Great tuberosity. 



t 2 . Lesser tuberosity. 



