For trapezoid. 



THE CARPUS. 163 



Articulations. With one bone, the cuneiform. 



Attachment of Muscles. To two : the Flexor carpi ulnaris and Abductor 

 minimi digiti ; and to the anterior annular ligament. 



Bones of the Lower Row. 



TRAPEZIUM (Fig. 110). 



The Trapezium (rpdn^a, a table) is of very irregular form. It may be distin- 

 Groove. For scaphoid. 



mdge - ijJS^ 



BA ; ,l'<ir lritp,'z<iiil. 



For 2<L 



metacarpal. ' 



For 1st metacarpal. For2d metacarpal. 



FIG. 110. The left trapezium. 



guished by a deep groove, for the tendon of the Flexor carpi radialis muscle. 

 It is situated at the external and inferior part of the carpus, between the scaphoid 

 and first metacarpal bone. The superior surface, concave and smooth, is directed 

 upward and inward, and articulates with the scaphoid. The inferior surface, 

 directed downward and inward, is oval, concave from side to side, convex from 

 before backward, so as to form a saddle-shaped surface, for articulation with the 

 base of the first metacarpal bone. The anterior or palmar surface is narrow and 

 rough. At its upper part is a deep groove running from above obliquely down- 

 ward and inward ; it transmits the tendon of the Flexor carpi radialis, and is 

 bounded externally by a prominent ridge, the oblique ridge of the trapezium. 

 This surface gives attachment to the Abductor pollicis, Flexor ossis metacarpi 

 pollicis, and Flexor brevis pollicis muscles, and the anterior annular ligament. 

 The posterior or dorsal surface is rough. The external surface is also broad and 

 rough, for the attachment of ligaments. The internal surface presents two 

 articular facets : the upper one, large and concave, articulates with the trapezoid ; 

 the lower one, small and oval, with the base of the second metacarpal bone. 



Hold the bone with the saddle-shaped surface downward and the grooved 

 surface away from you. The prominent, rough, non-articular surface points to the 

 side to which the bone belongs. 



Articulations. With four bones : the scaphoid above, the trapezoid and second 

 metacarpal bones internally, the first metacarpal below. 



Attachment of Muscles. Abductor pollicis, Flexor ossis metacarpi pollicis, and 

 part of the Flexor brevis pollicis. 



TRAPEZOID (Fig. 111). 



The Trapezoid is the smallest bone in the second row. It may be known by 

 its wedge-shaped form, the broad end of the wedge forming the dorsal, the narrow 



Anterior surface. 

 For scaphoid. For trapezium. 



For os magnum. 

 Post, surface. 



For 2& metacarpal. 



FIG. 111. The left trapezoid. 



end the palmar, surface, and by its having four articular surfaces touching each 



