636 MAMMALIAN ANATOMY 



near the base to the flexor brevis minimi digit!, or fourth palmar 

 interosseous ; it affords insertion distally to the opponens minimi 

 digiti. 



The Head is flattened on the radial side, and on the ulnar side 

 presents a prominence like that on the radial side of the head of the 

 second metacarpal. 



Determination. The rounded ulnar side of the bone distinguishes 

 this metacarpal from all others. When the bone is held with the 

 dorsal side upward and the proximal end toward the student, the 

 rough tuberosity on the base points to the side to which the bone 

 belongs. 



Articulation. The fifth metacarpal articulates with the unciforni 

 above, with the fourth metacarpal on the radial side, and with its own 

 phalanx below. 



Muscular Attachments. The fifth metacarpal affords attach- 

 ment at the ulnar side of the base to the extensor carpi ulnaris, and 

 on the palmar aspect to the fourth palmar interosseous, known as the 

 flexor brevis minimi digiti, and the opponens minimi digiti. 



Ossification. The fifth metacarpal is developed from two centres 

 of ossification, one for the shaft and one for the head. 



THE PHALANGES. 



General Description. The fourteen bones of the fingers or toes 

 are called the phalanges. Three belong to every digit, or finger, except 

 the thumb, which has but two. In every digit the phalanges are 

 placed end to end, the proximal phalanx articulating by its proximal 

 end with the head of the appropriate metacarpal, and by its distal end 

 with the proximal end of the middle phalanx, which in turn articulates 

 by its distal end with the terminal or distal phalanx. 



The phalanges lie in the long axes and form most of the substance 

 of the fingers. They are surrounded by tendons, blood-vessels, nerves, 

 and the skin, but are practically free from muscles. The phalanges 

 may be divided into three rows, the first including all the proximal, 

 the second all the middle, and the third all the distal phalanges. The 

 phalanges of any one row so closely resemble one another that they 

 can be distinguished only by slight differences in size and curvature. 

 The proximal phalanx of the thumb presents peculiarities of its 

 own. 



