264 THE SKELETON. 



To ascertain to which side the bone belongs, hold it with the superior or 

 radial convex, articular, surface upward, and the posterior surface i. e. the narrow, 

 non-articular, grooved surface toward you. The tubercle on the outer surface 

 points to the side to which the bone belongs. 1 



Articulations. With five bones : the radius above, trapezium and trapezoid 

 below, os magnum and semilunar iivternally. 



The Lunar or Semilunar (semi, half; luna, moon) bone may be distinguished by 

 its deep concavity and crescentic outline. It is situated in the centre of the upper 

 row of the carpus, between the scaphoid and cuneiform. The superior surface, con- 

 vex, smooth, and bounded by four edges, articulates with the radius. The inferior 

 surface is deeply concave, and of greater extent from before backward than trans- 

 versely : it articulates with the head of the os magnum and by a long, narrow 

 facet (separated by a ridge from the general surface) with the unciform bone. 

 The anterior or palmar and posterior or dorsal surfaces are rough, for the attach- 

 ment of ligaments, the former being the broader and of somewhat rounded form. 

 The external surface presents a narrow, flattened, semilunar facet for articulation 

 with the scaphoid. The internal 'surface is marked by a smooth, quadrilateral 

 facet, for articulation with the cuneiform. 



Hold it with the convex articular surface for the radius upward, and the 

 narrowest non-articular surface toward you. The semilunar facet for the scaphoid 

 will be on the side to which the bone belongs. 



Articulations. With five bones : the radius above, os magnum and unciform 

 below, scaphoid and cuneiform on either side. 



The Cuneiform (cuneus, a wedge ; forma, likeness) may be distinguished by 

 its pyramidal shape (os pyramidale), and by its having an oval, isolated facet for 

 articulation with the pisiform bone. It is situated at the upper and inner side of 

 the carpus. The superior surface presents an internal, rough, non-articular por- 

 tion, and an external or articular portion, which is convex, smooth, and articulates 

 with the triangular interarticular fibro-cartilage of the wrist. The inferior sur- 

 face, directed outward, is concave, sinuously curved, and smooth for articu- 

 lation with the unciform. The posterior or dorsal surface is rough, for the attach- 

 ment of ligaments. The anterior or palmar surface presents, at its inner side, an 

 oval facet, for articulation with the pisiform ; and is rough externally, for liga- 

 mentous attachment. The external surface, the base of the pyramid, is marked 

 by a flat, quadrilateral, smooth facet, for articulation with the semilunar. The 

 internal surface, the summit of the pyramid, is pointed and roughened, for the 

 attachment of the internal lateral ligament of the wrist. 



Hold the bone with the surface supporting the pisiform facet away from 

 you, and the concavo-convex surface for the unciform downward. The base 

 of the wedge (i. e. the broad end of the bone) will be on the side to which it 

 belongs. 



Articulations. With three bones : the semilunar externally, the pisiform in 

 front, the unciform below ; and with the triangular, interarticular fibro-cartilage 

 which separates it from the lower end of the ulna. 



The Pisiform ( pisum, a pea ; forma, likeness) may be known by its small size 

 and by its presenting a single articular facet. It is situated at the anterior and 

 inner side of the carpus, is nearly circular in form, and presents on its posterior 

 surface a smooth, oval facet, for articulation with the cuneiform. This facet 

 approaches the superior, but not the inferior, border of the bone. The anterior 

 or palmar surface is rounded and rough, and gives attachment to the anterior 

 annular ligament and to the Flexor carpi ulnaris and Abductor minimi digit! 

 muscles. The outer and inner surfaces are also rough, the former being convex, 

 the latter usually concave. 



Hold the bone with the posterior surface that which presents the articular 



1 In these directions each bone is supposed to be placed in its natural position that is, such a 

 position as it would occupy when the arm is hanging by the side, the forearm in a position of supi- 

 nation, the thumb being directed outward, and the palm of the hand looking forward. 



