502 THE RABBIT CHAP. 



fore-arm, and is slightly curved. Its head presents a 

 large double surface for articulation with the trochlea of 

 the humerus, and its distal extremity a pair of slight con- 

 cavities for the bones of the carpus : the shaft is flattened 

 where it abuts against the corresponding flattened 

 surface of the ulna. Near the proximal end of the last- 

 mentioned bone is a cavity for the articulation of the 

 humerus, and proximally to this, at the elbow, the ulna is 

 produced to form a large oleeranon process, which is 

 received into the fossa on the humerus when the limb is 

 extended : its small distal end articulates with the carpus. 

 The carpus, as in the frog (p. 50), consists of a 

 proximal and a distal row of small, nodular bones, 

 which articulate with one another where they are in 

 contact. The bones of the proximal row, beginning at 

 the inner (preaxial) side, are the radiate and intermedium, 

 articulating with the radius, and the ulnare, articulating 

 with the ulna. In the distal row are five bones, the 

 middle one of which is. distinctly proximal to the other 

 four, so as really to lie in the middle of the carpus : this 

 is the centrale, the others constituting a row of distal 

 car pals. Of these the first three articulate with the 

 corresponding digits, the fourth, on the outer (postaxial) 

 side, supporting the fourth and fifth digits and really 

 consisting of two carpals fused with one another. 



A small bone, the pisiform, articulating with the ulna and 

 ulnare on the ventral side, is usually looked upon as a 

 sesamoid bone, i.e., an ossification in the tendon of a muscle ; 

 but it probably represents the vestige of a sixth digit. 



The hand or manus consists of five digits, each made 

 up of a metacarpal and of phalanges, articulating with 

 one another. The innermost (preaxial) digit the 

 thumb or pollex is the shortest, and the third the 

 longest : the former has two phalanges, the others three 

 each, the distal or ungual phalanx of all the digits 



