214 



ANATOMY OF THE RABBIT 



articulation with the tibia, and forming with the latter the 

 chief portion of the ankle-joint. Its distal end, termed the head 

 of the talus (caput tali), provides a convex articular surface 

 for the navicular bone, and is separated from the larger trochlear 

 portion by a slightly constricted intermediate portion or neck (collum 

 tali). Its ventrolateral border is extensively articulated with the 

 calcaneus. The latter represents the 

 ulnar tarsal, or ulnare, of the primary 

 limb skeleton and is a cylindrical 

 element, fully twice as long as the talus, 

 since it is extended backward behind the 

 ankle-joint as the tuber calcanei, or 

 bone of the heel. Its dorsal surface bears 

 a prominent elevation for articulation 

 with the fibular side of the tibiofibula. 

 Its medial surface bears a flat, shelf-like 

 process, the sustentaculum tali, which 

 forms a ventral support for the talus. 

 The distal extremity of the bone articu- 

 lates wdth the cuboid and also with the 

 navicular. 



The intermediate element, the na- 

 vicular bone comes between proximal 

 and distal tarsals and is the central bone 

 of the primary pattern. Thus it does 

 not correspond with the navicular bone 

 of the wrist, which is the radiale (p. 205). 

 It is a somewhat cubical bone, lying on 

 the medial side of the tarsus between the 

 talus, on the one hand, and the proximal 

 end of the second metatarsal bone and 

 the second and third cuneiform bones, on 

 the other. It represents the central bone 

 of the primitive tarsus (Fig. 36) and its 

 position is more nearly that of a central 

 element than is the case with the bone 

 called by this name in the rabbit's 

 carpus. In this connection it will be remembered that the carpus 



Fig. 98. The bones of the left 

 foot, viewed from the dorsal sur- 

 face: T, tarsus; M, metatarsus; 

 P, phalanges. II-V, the four 

 metatarsal bones. cb., cuboid; 

 cl., calcaneus; c.s., second cunei- 

 form; c.t., third cuneiform; f.a., 

 articular surface for fibular side 

 of the tibiofibula; n, navicular; 

 t, talus; t.c., tuber calcanei; t.t., 

 trochlea tali. 



