614 MAMMALIAN ANATOMY 



the curved proximal border. It articulates with a corresponding facet 

 on the unciform. The posterior half of the proximal border is rounded 

 and continuous with the proximal surface. Between the palmar border 

 and these facets is a distinct pit, which is filled by a strong ligament 

 from the unciform. 



Nomenclature. Os magnum is the great bone of the human 

 carpus. Os capitatum, the bone with a head, is the European syn- 

 onym. The Germans have das Kopfbein, and the French le grand 

 os. In comparative anatomy the magnum is the carpale IIL 



Determination. If the proximal surface be held upward and the 

 dorsal surface toward the student, the produced radio-palmar angle will 

 point to the side to which the bone belongs. 



FIG. 478. 

 Proximal Side. 



With Scapho-lunar. 



Dorsal Side. Palmar Side. 



With Unciform. 



Distal Side. 



LEFT OS MAGNUM, ULNAR SURFACE. 



Articulation. The magnum articulates with the scapho-lunar on 

 the proximal side, with the trapezoid and second metacarpal on the 

 radial side, with the third and fourth metacarpal on the distal side, 

 and with the unciform on the ulnar side. It is connected by ligament 

 with the trapezium. 



Muscular Attachments. The palmar surface of the magnum 

 affords attachment indirectly to the flexor brevis pollicis and adductor 

 pollicis muscles. 



Ossification. The magnum has one centre of ossification. 



THE UNCIFORM. 



General Description. The Unciform is placed on the ulnar end 

 of the distal row (Fig. 479), and may be easily recognized by its 

 characteristic shape, that of a wedge. It is narrow from side to 

 side, and longer in its dorso-palmar and proximo-distal diameters. 

 The apex of the wedge is truncate and forms the proximal surface. 

 There are six surfaces. 



