THOEACIC LIMBS 623 



outer of these parts is prominent and rounded for the attachment of 

 the tendon of the extensor ossis metacarpi pollicis. It passes into the 

 radial surface and the radial side of the dorsal surface. The inner 

 part is an articular surface for the radial surface of the trapezium ; 



FIG. 487. 



First. Second. Third. Fourth. Fifth. 



I 



With Trapezium. \ 



V^w ' jrr.'irt, aw?' 1 ' \ 11 



Vith Unciform. 



ii iii i mm\ \^ 



With Trapezoid.- 



With Magnum. With Unciform. 

 THE METACARPAL BONES, PROXIMAL ASPECT. 



it is longer than wide, saddle-shaped, deeply concave from side to 

 side, and convex from above downward. The palmar margin of this 

 surface is sharp and slightly emarginate. Its lateral margin is sharp 

 and elevated. Below, it is lost on the ulnar aspect of the dorsal sur- 



FIG. 488. 

 Proximal End. 



With Trapezium. 



Dorsal Side. Palmar Side. 



With Proximal Phalanx 

 of Thumb. 



Distal End. 



FIRST LEFT METACARPAL, ULNAR SURFACE. 



face of the shaft of the bone (Fig. 488) . When the bone is held with 

 its dorsal surface upward the articular surface faces upward and to the 

 ulnar side, but when the bone is in position, as the dorsal surface 

 looks radially, the facet faces toward the wrist and the back of the 

 hand. On the ulnar side of the base is a rough surface, in which 

 is inserted the ligament which binds the bone to the contiguous side 

 of the second metacarpal. 



The Shaft is flattened from above downward. 



Its dorsal surface (Fig. 489) is convex in both directions ; its radio- 

 palmar and palmo-ulnar surfaces are concave in the proximo-distal line 



