BONES OF THE HAND 



59 



of the trapezium, on the radial side; the pisiform bone and hook 

 of the unciform on the ulnar side. These mark the boundaries of 

 a deep groove where the long tendons of the ringers glide. 



THE METACARPUS OR PALM 



The five metacarpal bones (ossa metacarpalia) are long in 

 shape but have no medullary canal. Each has a base, a shaft, 

 and a head, the head being distal. The bases are articulated with 

 the second row of the carpus, the heads 

 with the first row of the phalanges. The 

 first corresponds to the thumb, the second 

 to the index finger, the third to the middle 

 finger, the fourth to the ring finger, and 

 the fifth to the little finger. 



The spaces between them are inter- 

 osseous spaces and are occupied by inter- 

 osseous muscles. 



Note. The third metacarpal bone (of 

 the middle finger) is the longest, and its 

 head is the most prominent when the hand 

 is clenched, as in making a "fist." 



FIG. 54. RIGHT HAND, PAL- 

 MAR OR VOLAR SURFACE. 



PHALANGES 



These are the bones of the fingers and for 

 thumb (digits). A finger has three, first, Carpus; 11-11, phalanges; 12, 

 second and third; the thumb has two, first phalanges; 14, 15, ist and 2d 

 and second. They are long in shape, but \sappey ^ of thumb -- 

 without a medullary canal. Each has a 



base, a shaft, and a head, the head being distal. The first row 

 of phalanges includes those which are next to the metacarpal 

 bones. The terminal phalanges (those of the third row) have 

 each a horse-shoe-shaped border on the anterior surface for the 

 support of the sensitive finger tip; because these bear the nails 

 they are called the ungual phalanges. 1 



1 This description of the metacarpal bones and phalanges follows that of standard 

 text-books. It would seem, however, more in accordance with the facts to con- 

 sider the palm as composed of four metacarpal bones one for each finger and to 

 give to the thumb three phalanges, since the bone commonly called the first metacarpal 

 (or the metacarpal of the thumb) resembles those of the first row of the phalanges in 

 both form and development. 



