502 THE RABBIT CHAP. 



inner (preaxial) bone of the 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 concavities for the bones of the carpus : the shaft 

 is flattened where it abuts against the corresponding flat- 

 tened 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 pro- 

 duced to form a large olecranon 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 radiale 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 carpals. 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 con- 

 sisting 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 

 pollexis 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 having a conical form, its 



