ELEMENTARY BIOLOGY. [XIIL 



a. A somewhat cylindrical bone, with an articular 

 expansion at each end and a shaft uniting 

 them. 



fi. The great ridge (deltoid crest) on its antero- 

 internal surface, to which a muscle was at- 

 tached. 



The development of this crest is greater in the 

 males than in the females, 



b. The lone of the forearm. 



a. Hollowed out above to fit the lower end of the 

 humerus. 



/3. Shewing below a tendency to divide into the 

 two bones of which it is made up ; viz. the 

 radius and the ulna. When the limb is 

 stretched out at right angles to the body with 

 the pollex forwards, the radius is on the 

 anterior, and the ulna on the posterior side of 

 the axis of the limb. 



c. The carpus. Two bones (a, 6) articulate with the 

 ankylosed radius and ulna. A third bone (c), on 

 the radial side of the carpus, articulates only with 

 the carpal bones on the proximal and distal sides 

 of it. A large bone (d) occupies two-thirds of the 

 ulnar side of the carpus, and articulates with 

 a, 6 and c on one side, and with the third, fourth 

 and fifth metacarpals on the other. Two small 

 ossicles articulate with the distal face of c and 

 bear the first and second metacarpals. 



d. The digits. 



Five in number, the first (radial one) being, how- 

 ever, rudimentary: beginning at the ulnar side 

 we find 



