PHALANGES. 113 



upon the radial side of its base, and two small circular facets upon its 

 ulnar lateral surface. The base of the metacarpal bone of the ring-finger 

 is small and square, and has two small circular facets to correspond with 

 those of the middle metacarpal. The metacarpal bone of the little finger 

 has only one lateral articular surface. 



Development. By two centres ; one for the shaft, and one for the digi- 

 tal extremity, with the exception of the metacarpal bone of the thumb, the 

 epiphysis of which, like that of the phalanges, occupies the carpal end of 

 the bone. Ossification of the metacarpal bones commences in the em- 

 bryo between the tenth and twelfth week, that is, soon after the bones of 

 the fore-arm. The epiphyses make their appearance at the end of the 

 second, or early in the third year, and the bones are completed at twenty. 



Articulations. The first with the trapezium ; second, with the trape- 

 zium, trapezoides, and os magnum, and with the middle metacarpal 

 bone ; third, or middle, with the os magnum, and adjoining metacarpal 

 bones ; fourth, with the os magnum and unciforme, and with the adjoin- 

 ing metacarpal bones ; and, fifth, with the unciforme, and with the meta- 

 carpal bone of the ring-finger. 



The figures resulting from the number of articulations which each 

 metacarpal bone possesses, taken from the radial to the ulnar side, are 

 13121. 



Attachment of Muscles. To the metacarpal bone of the thumb, three, 

 the flexor ossis metacarpi, extensor ossis metacarpi, and first dorsal inter- 

 osseous ; of the index finger, five, the extensor carpi radialis longior, 

 flexor carpi radialis, first and second dorsal interosseous, and first palmar 

 interosseous ; of the middle finger, four, the extensor carpi radialis bre- 

 vior, adductor pollicis, and second and third dorsal interosseous ; of the 

 ring finger, three, the third and fourth dorsal interosseous, and second 

 palmar; and of the little finger, four, extensor carpi ulnaris, adductor 

 minimi digiti, fourth dorsal, and third palmar interosseous. 



PHALANGES. The phalanges are the bones of the fingers ; they are 

 named from their arrangement in rows, and are fourteen in number, three 

 to each finger, and two to the thumb. In conformation they are long 

 bones, divisible into a shaft, and two extremities. 



The shaft is compressed from before backwards, convex on its poste- 

 rior surface, and flat with raised edges in front. The metacarpal ex- 

 tremity, or base, in the first row, is a simple concave articular surface, that 

 in the other two rows a double concavity, separated by a slight ridge. 

 The digital extremities of the first and second row present a pulley-like 

 surface, concave in the middle, and convex on each side. The imgual 

 extremity of the last phalanx is broad, rough, and expanded into a semi- 

 lunar crest. 



Development. By two centres ; one for the shaft, and one for the base. 

 Ossification commences first in the third phalanges, then in the first, and 

 lastly in the second. The period of commencement corresponds with 

 that of the metacarpal bones. The epiphyses of the first row appear dur- 

 ing the third or fourth year, those of the second row during the fourth or 

 fifth, and of the last during the sixth or seventh. The phalanges are per- 

 fected by the twentieth year. 



Articulations. The first row, with the metacarpal bones and second 



10* H 



