THOEACIC LIMBS 621 



The dorsal surface is flat or slightly convex, and passes into the 

 shaft without any distinct line of separation. It is roughened for the 

 attachment of ligaments. 



The radial surface or the ulnar surface, or both surfaces, may 

 have articular facets above for the contiguous metacarpal bones, and 

 in some cases for the carpal bones also. These surfaces are rough 

 below where strong ligaments are attached. 



The palmar surface is produced at its proximal end into a hook- 

 like process more or less marked, below which it is rough for the 

 insertion of ligaments. 



The Shaft comprises almost the entire bone. It is nearly cylin- 

 drical, and is six or eight times as long as wide. It is slightly convex 

 on its dorsal side from the base to the head, and concave on the palmar 

 side. On close examination it is seen to be not exactly cylindrical, 

 but slightly prismatic, presenting three surfaces, a dorsal, a radio- 

 palmar, and a palmo-ulnar, and three borders, a radial, an ulnar, and 



a palmar. 



FIG. 486. 



Proximal End. 



With Trapezoid. 



y- With Third Metacarpal. 



With Trapezium. I ll ^f Base. 



Insertion of EXTENSOR CARP, jTjJHr Groove for Radial Artery. 



BADIALIS LONQIOR. 



Radial Bonier. : ,1- Ulnar Border. 



Dorsal Surface of Shaft. 



Radial Tubercle. -jf^^OZI Vlnar Tubercle - 

 i.iciilnr Surface for Proximal H^lf Groove - 

 Phalanx of Second Digit. ~^vj" " Head. 



Distal End. 



SECOND LEFT METACARPAL, DORSAL SURFACE. 



r 



The dorsal surface (Fig. 486) is almost flat at the proximal and 

 distal ends, but for most of its length it is convex from side to side. 

 It passes without a break into the corresponding surface of the base, 

 and it widens out below and presents at each border a prominent 

 tubercle for the attachment of ligaments and the tendons of muscles. 



