THOEACIC LIMBS 



651 



is directed downward and to the radial side. It has a slightly concave 

 dorsal articular surface (a) for the cuneiform. To the rounded aspect 

 are attached the abductor minimi digiti and flexor carpi ulnaris 

 muscles. The pisiform does not articulate with the ulna. 



The trapezium (Fig. 512, 5) is not so strongly crescentic as in 

 the cat, and the palmar surface (5) is larger. It articulates by a 

 concave proximo-ulnar facet with the scaphoid, by a larger concave 

 ulnar surface (c) with the trapezoid, by a saddle-shaped radio-distal 

 surface (d) with the first metacarpal, and by a small ulno-distal facet 



FIG. 512. 



PALMAR ASPECT OF THE CARPAL BONES AND THE BASES OF THE METACARPALS. 



1, scaphoid: a, tuberosity; b, with radius; c, with magnum; d, with semilunar; e, with trapezium and 

 trapezoid. 2, semilunar: a, with radius ; b, with magnum ; c, with unciform ; d, with cuneiform. 3, cuneiform: 

 a, with interarticular cartilage; 6, with semilunar: c, with unciform; d, with pisiform. 4, pisiform: a, with 

 cuneiform. 5, trapezium : , ridge ; b, groove for the flexor carpi radialis muscle ; c, with trapezoid and second 

 metacarpal; d, with first metacarpal. 6, trapezoid: , with trapezium; b, with scaphoid; c, with magnum. 

 7, magnum: a, with semilunar; b, with scaphoid; c, with trapezoid and second metacarpal; d, with unciform; 

 f, for ligaments; /, with third and fourth metacarpals. 8, unciform: a, with cuneiform; b, with semilunar; 

 c, with fourth metacarpal ; d, with fifth metacarpal ; e, hook. 9, 10, 11, 12, and 13, first, second, third, fourth, ami 

 fifth metacarpals. 



with the second metacarpal. Its palmar surface is marked by a 

 deep groove (b) for the tendon of the flexor carpi radialis muscle 

 and a radial ridge (a) for the flexor brevis, opponens, and abductor 

 pollicis muscles. The opponens pollicis is attached also to the rough 

 radial aspect. 



The trapezoid (Fig. 512, 6) is crescent-shaped ; the sharp edge of 

 the crescent forms an ulno-distal border ; above this border is a con- 

 cave ulnar facet (c) for the magnum, and below it is a saddle-shaped 

 distal facet for the second metacarpal. The small proximal surface (b) 

 articulates with the scaphoid, and the larger radial surface (.) with the 

 trapezium. 



