THE CARPUS, OR WRIST. 119 



it is concave from before backward, strongly so from side 

 to side, and presents a slight ridge dividing the surface 

 into two articular facets, the outer for the scaphoid and 

 the inner for the semilunar. It is seen that the articula- 

 tion at the wrist is formed by the radius above and the 

 scaphoid and semilunar below, the ulna being blocked 

 out of the articulation by the interarticular fibro- 

 cartilage. 



The radius develops by three centres, one for the 

 upper extremity and head, one for the shaft, and one for 

 the lower extremity. 



THE CARPUS, OR WRIST. 



The carpus, or wrist, is made up of eight short bones, 

 arranged in two rows. The first or proximal row are 

 the scaphoid, semilunar, cuneiform, and pisiform. Those 

 of the second or distal row, the trapezium, trapezoid, os 

 magnum, and unciform. Each bone is cuboidal in form, 

 and presents six surfaces. The anterior or palmar and 

 the posterior or dorsal surfaces are rough, and serve for 

 the attachment of ligaments. Together they form a 

 series of close articulations, admitting of but little 

 movement. Each bone is developed by one centre, 

 except the unciform, which has two, one for the unci- 

 form process and one for the rest of the bone. The 

 pisiform is a sesamoid bone developed in the tendon of 

 the extensor carpi ulnaris. 



THE SCAPHOID 



The scaphoid articulates above with the radius, below 

 with the trapezium and trapezoid, and internally with the 

 semilunar and os magnum. The internal surface, small 

 and tuberculated, gives attachment to the external lateral 

 ligaments of the wrist-joint; the dorsal surface enters 

 into the formation of the dorsum of the wrist ; the 



