DIGITI. 



41 



Fig. 24. 



Second^ is the longest, for the index finger ; has a notch at its 

 base for articulating with the trape- 

 zoid ; a lateral articular mark upon 

 one side only, and a mark upon its 

 dorsal surface for the extensor carpi 

 radialis longior. 



Tliird, has a triangular base, with 

 an articular mark on each side, and 

 on its dorsum, one for the extensor 

 carpi radialis brevior. 



Fourth, is much smaller. The ex- 

 ternal lateral surface of its base is 

 double. 



Fifth, the smallest. Its base has 

 but one lateral surface, and that is ex- 

 ternal and single. Internally a tuber- 

 cle at the base for the extensor carpi 

 ulnaris. 



DIGITI. 



The fingers contain three bones call- 

 ed phalanges: the thumb has but two. 



First row. — The phalanges of this row are the largest, convex on 

 their dorsal, and flat on the palmar surface. The superior extremity 

 has a single concavity for the head of the metacarpal bone. The 

 inferior has two convexities separated by a groove. A roughness 

 on either side of this extremity, indicates the attachment of the late- 

 ral ligament. The ridges extending from one extremity to the other, 

 are for the theca of the flexor tendons. 



Seco7td Toiv. — These are smaller. The superior extremity has 

 two concavities, separated by a ridge ; the inferior two convexities, 

 separated by a groove. The ridge on either side of the body has 

 the theca and tendon of the flexor sublimis attached to it. 



Third row. — These are the smallest, and differ much from the 

 other rows, having but one articular extremity, which is the superior, 

 having two concavities and a ridge. The inferior extremity is flat- 

 tened, thin, and rough. 



The middle finger {impudicus) is the longest. The ring finger 

 {annularis) is the next in size. The forefinger {indicato7') is 

 thicker than the last. The little finger {auricularis) is the smallest. 



Sesamoid hones. — These are four in number — two being placed 

 upon the palmar side of the lower extremity of the metacarpal bone 

 of the thumb, in connexion with the short flexor tendon. 



4* 



