THORACIC LIMBS 



629 



it fits into the depression under the dorsal part of the ridge on the 

 ulnar side of the base of the second metacarpal. 



The ulnar surface of the base (Fig. 495) presents on the proximal 

 edge a distinct convex ridge which is somewhat wider in front than 

 behind. The dorsal wider part presents an articular facet for the 



FIG. 495. 

 Proximal End. 



With Unciform. 

 With Fourth Metacarpal 



Dorsal Side. 



With Magnum. 



With Fourth Metacarpal. 



Palmar Side. 



THIRD LEFT METACARPAL, ULNAR SURFACE OF BASE AND 

 PART OF SHAFT. 



radial side of the unciform ; under this ridge is a rough depression 

 for a portion of the base of the fourth metacarpal, and below this 

 again a rougher area for the attachment of the interosseous ligament. 



The palmar surface (Fig. 496) begins on the palmar angle of the 

 proximal surface, is continued downward, and is lost on the palmar 

 border of the shaft. It is prominent, hook-like, narrow, and convex ; 



FIG. 496. 

 Proximal End. 



With Magnum. 



Ulnar Side. 



With Second Metacarpal. 



Radial Side. 



THIRD LEFT METACARPAL, PALMAR SURFACE OF BASE AND 



PART OF SHAFT. 



above, it affords attachment for the ligaments, and below gives origin 

 to the second palmar interosseous muscle. 



The radial surface (Fig. 497) presents on its dorsal third the pro- 

 jecting -part described above, behind which it is rough and concave 

 from before backward. This concavity is filled by the interosseous 

 ligament from the ulnar side of the base of the second metacarpal. 



