THE CARPUS AND I\LETACARPUS 



381 



Fig. 28.— Os Pisifokme. 



1. Body of OS pisiforme. 



2. Surface articulating 



with inferior ex- 

 tremity of the ra- 

 dius. 



3. Surface articulating 



with the cuneiform 

 bone. 



presents two smooth ovoid surfaces : the superioi' one articulates with the 

 radius ; the inferior with a corresponding surface, mentioned as occurring 

 on the posterior surface of the os cuneiforme. The 

 three other borders, namely, the superior, posterior, 

 the inferior, are unevenly convex, and roughened 

 for the attachment of ligaments. 



The bones of the inferior row, viz. the Os Trape- 

 zoiDES (rpdireCa, a table), Os Magnum (the large 

 bone), and Os Unciforme (uncus, a hook), articulate 

 laterally one with the other, superiorly with the 

 top row of bones, and inferiorly with the three 

 metacarpal bones. 



The Metacarpal Bones, answering to the bones 

 in the palm of the hand of man, are three. One 

 (metacarpus magnus) is much larger than the other 

 two, which, from thus supporting, are sometimes 

 called splint-bones. 



The Metacarpus Magnus, or cannon-bone, has a 

 body and two extremities, the superior of which 

 articulates with the carpus while the inferior rests 

 upon the next phalanx, or great posterior bone (see 

 Fig. 26). 



The body is convex and smooth, anteriorly and 

 laterally ; thus forming two-thirds of a cylinder. 

 Posteriorly it is flattened ; its sides, extending from 

 above, downwards, to about three inches above its 

 inferior extremity, present two triangular scabrous 

 surfaces, on the upper parts of which two smooth 

 articulatory spots occur, to which the small meta- 

 carpal bones are attached. 



The superior extremity presents a smooth ar- 

 ticulatory surface which is, for the most part, flat; 

 it slopes ofi", however, on its outer side for articulation 

 with the OS unciforme. There is also another small 

 spot which slightly declines, situated at the outer 

 side of the head of the inner small metacarpal bone. 

 This spot articulates with the postero-inferior surface 

 of the OS trapezoides. The flat surface articulates 

 with the OS magnum, to which it corresponds in 

 figure. Its anterior and lateral edges are somewhat 

 roughened. 



The inferior extremity presents two smooth 

 condyloid surfaces, separated by a smooth semicircular 

 eminence, which articulate with a corresponding for- 

 mation on the superior extremity of the os suffraginis. 

 On the sides of each of the condyles a depression 

 occurs. 



Ossa Metacarpi Parva are in number, two ; external and internal. In 

 form they are pyramidal, presenting bases turned upwards, apices down- 

 wards, and bodies or middles. 



Fio. 2'^t —Back View of 

 THE Large and Small 

 Metacarpal Bones. 



2. Metacarpus magnus. 



3. The surfaces above ar- 



ticulate with the lower 

 carpal bones. 



■i. 4. External and internal 

 small metacarpal bones. 



5. 5. Condyloid surfaces ar- 

 ticulating witli corre- 

 sponding ones on tlio 

 upper extremity of tlie 

 OS suffraginis. 



0. Eminence articulating 

 with a corresponding 

 depression on the upper 

 extremity of the os suf- 

 fraginis. 



