THE BONES. 87 



Structure, as in the long bones, spongy substance at the ends, compact in 

 the centre, medullary canal, but narrow, in the interior. 



Development; from two osseous points, one for the centre and 

 superior, one for the inferior extremity. The I. metacarpal at 

 the superior end like the phalanges, which it also resembles. At 

 birth the central piece is almost entirely ossified ; at the extre- 

 mities ossification commences between the second and third year, 

 and is only completed with the eighteenth to the twentieth year. 



101. 3. Digiti, fingers. 



On either hand there are five articulated pyramids, each of 

 which unites with one of the five metacarpal bones. 



I. Finger, thumb, has two, the rest three members, phalanges. 

 The first of the three, or two members, is united with the end of 

 the metacarpal bone, the third (second) is free, as the ungual. 

 Each phalanx has a superior, hollowed extremity, for the recep- 

 tion of the bone lying above it, an anterior concave body, and an 

 inferior roller-like end, for its junction with the phalanx below ; 

 only the ungual member, phalanx unguicularis, terminates in a 

 semilunar end. 



I. Thumb, pollex ; in it the centre Phalanx is wanting; on the base of the 

 first, at the metacarpal end in the hollow of the hand, lies an os sesamoideum 

 externum, for m. flexor pollicis brevis, and internum, for m. abductor pollicis. 



1. Phalanx sup. Extremity, for extens. et abd. brevis. 



2. for flex, et extern, long. 



II. Index finger. 



1. Phalanx, Radial side, for m. lumbricalis /., Interosseus. 



2. for m.flex. comm. subl., extens. comm. 



3. for m. flex. comm. prof., extens. prop. 



III. Middle finger, digitus med., muscles as in II. ; the last excepted. 



IV. Ring finger, dig. annularis, as in III. 

 V. Ear finger, dig. auricularis s. minimus. 



1. Phalanx, for abduct, etflex. brevis. 



2. for flex. comm. subl., opponens. 



3. for flex. comm. profundus. 



Development. Each of the phalanges is ossified from two 

 points, the body and the inferior extremity, in the third foetal 

 month. The extremity first unites with the body between the 

 eighteenth and twentieth year after birth. 



Abdominal Extremities. 

 B. Extremitates inferior es s. abdominales. 



102. I. Osfemoris, Thigh-bone. 



Position : close to and beneath the Pelvis, above the leg. 

 Shape: long, cylindrical, with thick extremities: the longest 

 bone in the body. 



