. The anatomy of the domestic animals . Veterinary anatomy. THE CARPUS 93 continued by a fibrous cord to the distal tuberosity of the radius, but this band may be replaced in part or entirely by bone. The proximal extremity (Extremitas proximalis) is the major part of the bone. It projects upward and somewhat backward behind the distal end of the humerus, and forms a lever arm for the extensor muscles of the elbow. The medial surface is concave and smooth. The lateral surface is convex and is roughened above. The dorsal border bears on its middle a pointefl projection, the processus anconeus o
. The anatomy of the domestic animals . Veterinary anatomy. THE CARPUS 93 continued by a fibrous cord to the distal tuberosity of the radius, but this band may be replaced in part or entirely by bone. The proximal extremity (Extremitas proximalis) is the major part of the bone. It projects upward and somewhat backward behind the distal end of the humerus, and forms a lever arm for the extensor muscles of the elbow. The medial surface is concave and smooth. The lateral surface is convex and is roughened above. The dorsal border bears on its middle a pointefl projection, the processus anconeus or "beak," which overhangs the semilimar notch (Incisura semilunaris).^ The latter is triangular in outline, concave from above downward, convex transversely, and articulates with the humerus; in ' \ its lower part there is an extensive synovial fossa. '' Just below the notch PTe two convex facets which ,J} articulate with those on the volar aspect of the proximal end of the radius. The volar border is nearly straight, and is thick and rounded. The free end or summit is a rough tuberosity, the ole- cranon, which gives attachment to the triceps brachii and other muscles. The primitive distal extremity has, as pre- viously stated, fused with the radius. Development.âThe ulna ossifies from three centers, of which one is for the main part of the ^ ^ bone, one for the olecranon, and one for the distal ;,' end. The cartilaginous embryonic ulna extends '^i, the entire length of the forearm. The distal part ' â [ of the shaft is usually reduced to a small fibrous band or may disappear entirely; in some cases a variable remnant of it ossifies. The distal ex- Vlf 'â >M ?. \ ^'g'f^f li !^.i Fig. 69.âDistal End of Left Radius and Ulna of Horse; End View. 1, 2, 3, 4, Facets which articulate with radial, intermediate, ulnar, and accessory carpal bones respectively; 5, groove for tendon of exten- sor carpi radialis; 6, groove for tendon of common digital extensor; 7, tubero
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