THE FROG 31 



belonging to the ulnar and radial components respectively. 

 In ourselves the ulna and radius are separate ; the former 

 takes the main articulation with the humerus, the latter the 

 main articulation with the wrist. The radius can be crossed 

 over the ulna, carrying the wrist and hand with it, and thus we 

 are able to turn our hands palm upwards when the bones are 



C---. 



Fig. 3- 



A, Humerus of a female Frog, seen from below. A, head ; 

 jA, shaft ; ar, distal articular knot ; f, trochlea. B, 

 Radio-ulna of the right side. o, olecranon ; r, 

 radius ; , ulna. C, Forearm and hand of the right 

 side, seen from above, rit, radio-ulna; 7 V the five 

 digits; r, radiale; im, intermedium; u, ulnare ; a, 

 first distal carpal bone ; b, second distal ; c, third 

 distal. (All the figures after Ecker.) 



parallel (supination), or palm downwards when the bones are 

 crossed (pronation). In the frog the radius and ulna, though 

 fused together, are fixed half-way towards pronation. 



The wrist of the frog comprises six little carpal bones 

 arranged in two rows. In the proximal row there are three 

 bones : one corresponding to the radius, which we call the 

 radiale ; one corresponding to the ulna, the ulnare, and one 

 between the two, the intermedium. In the distal row we find, 



