BONES OP THE THORACIC LIMB 



199 



line (Crista interossea) laterally for the attachment of the interosseous ligament. 

 The proximal end (Capitulum radii) is relatively small and is supported by a dis- 

 tinct neck (Collum radii). It bears a concave surface (Fovea capituli) for articu- 

 lation with the humerus, and a convex marginal area (Circumferentia articularis) 

 behind for the ulna. The radial tuberosity is small. There is a large lateral tuber- 

 osity and below this a rough eminence. The distal extremity is much wider. 

 It has an extensive concave carpal articular surface. Its medial border projects 

 downward, forming the styloid process of the radius. Laterally there is a concave 

 facet (Incisura ulnaris radii) for articulation with the ulna. Dorsally are three 

 distinct grooves for the extensor tendons. The ulna is well developed, but dimin- 



Lateral 

 tuherosity 



Cororwid fossa 



Medial 

 condyle 

 Lateral 

 condyle 



Medial Iritertuheral 

 tuberosity ^'""""^ 



Head 



Head 



Neck 

 Deltoid tuberosity 



Mu-ic u lo-spiral 

 groove 



Lateral condyloid 

 crest 



Olecranon fossa 



Medial epicondyle 



Lateral epicondyle 

 Fig. 218. — Left Humerus of Dog; Lateral View. 



Lateral tuber- 

 osity 



Medial condyle 



Fig. 219. — Left Humerus of Dog; Medial View. 



1, Attachment of medial ligament of elbow joint; 2, 



attachment of flexor muscles to medial epicondyle. 



ishes in size distally. It crosses the volar surface of the radius medio-laterall}^ 

 The shaft is large and three-sided in its proximal two-thirds, smaller and more 

 rounded below. Its dorsal surface is in general rough. The nutrient foramen is 

 near the proximal end. A vascular groove descends from it and indicates the course 

 of the interosseous artery. The proximal end is relatively short. It is concave 

 and smooth medially, convex and rough laterally. The olecranon is grooved and 

 bears three prominences, of which the posterior one is large and rounded. The 

 semilunar notch is wide below and completes the surface for articulation with the 

 trochlea of the humerus. Below it is a concave surface (Incisura radialis), which 

 articulates with the back of the head of the radius, and below this is a fossa, which 

 receives a tuberosity of the radius. The distal end (Capitulum ulnae) is small and 



