THE CARPUS. 



101 



Fig. 101. RIGHT SCAPHOID BONE : A, FROM OUTER SIDE 



AND BEHIND : B, FROM BEFORE AND INNER SIDE. (Gf. D. T. ) 



trapezium, trapezoid and os magnum bounding a cavity which lodges the external part 

 of the scaphoid, and the os magnum and unciform rising up in a convexity, which is 

 received into a hollow formed by the scaphoid, lunar, and pyramidal bones. 



The scaphoid bone, the largest and most external of the first row, lies with its 

 long axis directed outwards and downwards. It has a concave surface, which looks 

 downwards and inwards, and 

 rticulates with the os magnum ; 

 on the opposite side are two 

 convex articular surfaces, an 

 upper for the radius, and a 

 lower for the trapezium and 

 trapezoid bones of the second 

 row ; these approach so near to 

 one another behind, that the 

 dorsal free surface is reduced to 

 a narrow grooved transverse 

 strip, to which the posterior liga- 



ments of the wrist are attached. At the inner extremity is a small crescentic 

 surface for articulation with the lunar bone ; while the outer end is produced 

 into a stout conical tuberosity, which projects forwards and gives attachment to the 

 annular ligament. The scaphoid articulates with five bones, viz., the radius, lun&r, 

 trapezium, trapezoid, and os magnum. 



The lunar bone (semilunar), irregularly cubic, is characterized by the deep 

 concavity from before backwards of its inferior surface, which rests on the head of 

 the os magnum, and commonly also by a bevelled edge 

 slightly on the unciform bone. Its external surface is 

 crescentic and vertical, and articulates with the scaphoid 

 bone : its internal surface looks downwards and inwards, 

 is much deeper and narrower than the external, and 

 articulates with the pyramidal. The convex superior 

 surface, which articulates with the radius, extends like 

 that of the scaphoid farther backwards than forwards, 

 and hence the anterior free surface is deeper than 

 the posterior. The lunar articulates with five bones, 

 viz., the radius, scaphoid, pyramidal, os magnum, and 

 unciform. 



The pyramidal bone (cuneiform) is situated with 

 its blunted apex directed downwards and inwards : the 

 base has the shape of a half-oval, and articulates 

 with the lunar bone. There are three surfaces : the 

 inferior, concavo-convex from without inwards, articu- 

 lates with the unciform bone ; the anterior is dis- 

 tinguished by having a smooth circular facet on its 

 inner half for articulation with the pisiform bone ; and 

 the supero-posterior presents at the base a small articular 

 facet entering the wrist-joint, but is for the most part 

 rough for the attachment of ligaments. The pyramidal 

 articulates with three bones, viz., the lunar, pisiform, and 

 unciform. 



The pisiform bone lies on a plane anterior to the 

 other bones of the carpus. In form it is spheroidal, with 

 .its longest diameter directed vertically. On its posterior 

 aspect is an oval articular surface for the pyramidal AND BEHIND. (G. D. T.) 



Fig. 102. RIGHT LUNAR 



BONE, FROM THE INNER 

 SIDE AND BELOW. (G. 

 D. T.) 



Fig. 103. RIGHT PYRAMIDAL 



BONE, FROM BEFORE AND 

 OUTER SIDE. (Gr. D. T.) 



lg B ' ON ^ 

 AND BEHIND. 



