BONES OF THE THORACIC LIMB 



163 



The neck is better marked than in the horse. The undivided external tuberosity 

 is placed well forward and extends little above the level of the head. The internal 

 tuberosity is small. The Ijicipital groove is undivided and is displaced to the inner 

 side by the extension forward of the external tuberosity. The distal end bears 

 an oblique trochlear articular surface for articulation with the radius and ulna, 

 the outer part of which is the more extensive and is faintly grooved. The epi- 

 condyles are prominent. Tlu^ coronoid and olecranon fossae often communicate 

 through a large supratrochlear foramen. 



The two bones of the forearm are relatively long and articulate with each 

 other at either end in such a manner as to allow of slight movement. A narrow 

 interosseous space separates their shafts. The radius is flattened from before 

 backward and increases in size from above downward. The shaft forms two 

 curves; one of these, an anterior convexity, involves the whole shaft; the other, 



Fig. 130. — Left Humerus of Dog, External View. 

 a. Head; h, neck; c, cre.st; d, external tuber- 

 osity; e, mark for in.sertion of infraspinatus tendon; 

 /, external condyle; g, e.xternal condyloid cre!?t; h, 

 coronoid fossa; i, olecranon fossa. (Ellenberger- 

 Bavnn, Anat. d. Hundes.) 



Fig. 131. — Left Radiits and Uln.a. of Dog, Antero- 



EXTERNAL ViEW. 



A, Radius; B, ulna; a, groove for tendon of 

 extensor carpi radialis; b, groove for common exten- 

 sor tendon; c, proximal articular surface of radius; 

 d, olecranon; e, beak (proc. anconeus) of ulna; /,. 

 semilunar notch; g, coronoid process; /(, facet for 

 radius; i, groove for lateral extensor tendon; k, 

 groove for tendon of extensor carpi obliquus. (Ellen- 

 berger-Baum, Anat. d. Hundes.) 



an inner convexity, affects the upper part. The anterior surface is convex in both 

 directions and is marked by a groove for the oblique extensor of the carpus. The 

 posterior surface presents the nutrient foramen in its upper third, and bears a 

 rough line (Crista interossea) externally for the attachment of the interosseous 

 ligament. The proximal end (Capitulum radii) is relatively small and is supported 

 by a distinct neck (Collum rachi). It bears a concave surface (Fovea capituli) 

 above for articulation with the humerus, and a convex marginal area (Circumfer- 

 entia articularis) behind for the ulna. The bicipital tuberosity is small. There 

 is a large external tuberosity and below this a rough eminence. The distal ex- 

 tremity is much wider. It has an extensive concave carpal articular surface. 

 Its inner border projects downward, forming the styloid process of the radius. 

 Externally there is a concave facet (Incisura ulnaris radii) for the ulna. In front 

 are three distinct grooves for the extensor tendons. The ulna is well developed, 



