THE BONES OF THE POSTERIOR LIMB 213 



anterior intercondyloid fossa lies in front of the intercondyloid 

 eminence, but is poorly differentiated. 



The fibula (Fig. 97) is the smaller, lateral bone of the leg, and 

 in the rabbit is so extensively fused with the tibia that scarcely more 

 than a third of it is distinguishable. The free portion forms a 

 flattened bony splint, the medial margin of which is firmly united 

 with the tibia by the interosseous ligament of the leg. Its proximal 

 extremity is connected with the lateral condyle of the tibia by an 

 elongated epiphysis, the latter, like those of the distal ends of 

 the radius and ulna, being distinguishable even in older animals. 



The combined distal extremities of the tibia and fibula bear 

 a roughly rectangular articular surface for the tarsus. The tibial 

 portion of this surface presents two grooves, separated by a ridge, 

 for articulation with the trochlea tali. On its medial side is a 

 small projection, the medial malleolus (malleolus medialis) round 

 which, in the intact animal, passes the insertion tendon of the 

 extensor hallucis longus muscle. 



The fibular portion of the distal extremity projects distad a 

 little further than the tibial portion, forming the lateral malleolus, 

 the end of which presents a broad, shallow, transverse depression 

 for the reception of the convex articular surface of the calcaneus, 

 while its medial surface articulates with the lateral side of the 

 trochlea tali. Immediately above it, on the lateral side of the bone, 

 a prominent projection forms the anterior and lateral boundaries 

 of a groove which in the natural condition lodges the insertion 

 tendons of the peroneal muscles. 



The Tarsus 

 The tarsus (Fig. 98) comprises six elements, the tarsal or ankle- 

 bones (ossa tarsi), which, like the corresponding bones of the 

 carpus, are arranged in proximal and distal rows. An exception 

 is to be made, however, for one element, the navicular, which 

 occupies an intermediate position. The proximal row contains two 

 elements, the talus and calcaneus.^ The talus is medial and also 

 slightly dorsal in position. It represents the tibial tarsal, or tibiale, 

 fused with the intermedium (Fig. 36, p. 63) of the primary limb 

 skeleton. Its proximal end, described as the body (corpus tali), 

 bears an extensive pulley-like surface, the trochlea tali, for 



