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 



Fig. 3- 



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

 s/i, shaft ; ar, distal articular knob ; /, trochlea. B, 

 Radio-ulna of the right side. 0, olecranpn ; r, radius ; 

 M, ulna. C, Forearm and hand of the right side, seen 

 from above, ru, radio-ulna; IV, the five digits; 

 r, radiale ; it, intermedium ; , 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 

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

 iised 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, 



