THE METACARPUS. 



167 



long and narrow, for articulation with the os magnum. The fourth facet is on the 

 inner or ulnar side of the extremity of the bone, and is for articulation with the 

 third metacarpal bone. 



The side to which this bone belongs is indicated by the absence of the lateral 

 facet on the outer (radial) side of its base, so that if the bone is placed with its 

 base toward the student and the palmar surface upward, the side on which there 

 is no lateral facet will be that to which it belongs. 



Attachment of Muscles. To six : Flexor carpi radialis, Extensor carpi radialis 

 longior, Adductor obliquus pollicis, First and Second dorsal interosseous, and 

 First palmar interosseous. 



The metacarpal bone of the middle finger (Fig. 116) is a little smaller than the 

 preceding : it presents a pyramidal eminence (the styloid process) on the radial side 

 of its base (dorsal aspect) which extends upward behind the os magnum ; imme- 

 diately below this, on the dorsal aspect, is a rough surface for the attachment of 



, For trapezium. 

 For trapezoid. 



FIG. 115. The second metacarpal. (Left.) 



For third metacarpal. 

 For os magnum. 



.Styloid For secoi* 

 process, metacarpal. 



For os magnum. 



"W 



For fourth 

 metacarpal. 



FIG. 116. The third metacarpal. (Left.) 



the Extensor carpi radialis brevior. The carpal, articular facet is concave behind, 

 flat in front, and articulates with the os magnum. On the radial side is a smooth, 

 concave facet, for articulation with the second metacarpal bone, and on the ulnar 

 side two small, oval facets, for articulation with the fourth metacarpal. 



The side to which this bone belongs is easily recognized by the styloid proc- 

 ess on the radial side of its base. "With the palmar surface uppermost and the 

 base toward the student, this process points toward the side to which the bone 

 belongs. 



Attachment of Muscles. To six : Extensor carpi radialis brevior, Flexor carpi 

 radialis, Adductor trans versus pollicis, Adductor obliquus pollicis, and Second and 

 Third dorsal interosseous. 



The metacarpal bone of the ring finger (Fig. 117) is shorter and smaller than 

 the preceding, and its base small and quadrilateral ; the carpal surface of the base 

 presenting two facets, a large one externally, for articulation with the unciform, and 

 a small one internally, for the os magnum. On the radial side are two oval facets, 

 for articulation with the third metacarpal bone ; and on the ulnar side a single 

 concave facet, for the fifth metacarpal. 



If this bone is placed with the base toward the student and the palmar surface 



