BONES OF UPPER LIMB 13 



passes across the anterior surface of the bone to the middle o 

 the outer border. The lower end of the shaft is distinctly 

 triangular ; the edge of the narrow interosseous surface articu- 

 lates with the lower end of the ulna; the anterior surface is 

 smooth and concave, the posterior having a series of grooves for 

 the extensor tendons to work in. On the radial border is a 

 styloid process similar to that of the ulna. 



The radius articulates above by means of the upper surface of 

 its head with the capitellum of the humerus, and the lower end 

 articulates with the scaphoid and semilunar bones of the carpus ; 

 on its interosseous surface it articulates at both ends with the 

 ulna. 



Ossification. Similar to that of the ulna. 



The Carpus consists of eight bones arranged in two rows of 

 four. The proximal row beginning from the radial side are 

 scaphoid, semilunar, cuneiform, and pisiform.; the distal row, 

 beginning from the radial side, are trapezium, trapezoid, os mag- 

 num and unciform. They are all small irregular-shaped bones 

 articulating with one another. The bones are articulated so 

 that their united surface is convex backwards. 



The pisiform is the smallest of the bones and is a little round 

 bone resting entirely on the palmar surface of the cuneiform ; it,, 

 with the hook of the unciform, forms the projection on the 

 ulnar side of the wrist ; the tubercle of the scaphoid and ridge 

 of the trapezium form the projection on the radial side of the 

 wrist. 



The unciform is distinguished by having a hook-like process 

 on its palmar surface. 



The proximal row of bones articulates above with the radius 

 and triangular fibro-cartilage, and below with the distal row of 

 bones. The distal row of bones articulates below with the five 

 metatarsal bones; the first metatarsal with the trapezium; the 

 other four fitted into the trapezoid, os magnum, and unciform. 



Ossification. One centre for each bone appears after birth, 

 and the carpus is usually completely ossified at puberty. 



The Metacarpus consists of five bones; they are all long 

 bones, with a shaft and two extremities. The shafts are con- 

 stricted in the middle and curved so that they are slightly 



