THE HIND-LIMB 381 



muscle of the thigh is inserted, beyond the 

 patella. 



The distal end of the bone has a prominent 

 pulley-like articular surface for the tarso- 

 metatarsus. 



ii. The fibula is a slender bone, closely applied to 

 the outer or postaxial surface of the tibio- 

 tarsus, with which it is often fused. Its 

 proximal end is enlarged, and articulates with 

 the femur ; the rest of the bone is very slender, 

 and usually does not reach to the ankle. 



3. The ankle-joint is between the proximal and distal rows 



of tarsals : these at a very early age fuse with the 

 tibia and metatarsus respectively, so that in the 

 adult there are no free tarsal bones. 



4. The pes. The first four digits are present : the meta- 



tarsal of the first is small and imperfect ; those of 

 the next three are large, and are fused with one 

 another and with the distal tarsal row. The fifth or 

 postaxial digit, corresponding to the little toe in 

 man, is present in the embryo, but disappears early. 



a. The tarso-metatarsus is a stout straight bone, about 

 as long as the femur, and formed by the fusion of 

 the distal tarsal row with the second, third, and 

 fourth metatarsals. Its proximal end is enlarged, 

 and bears terminally two cup -shaped facets for 

 the tibio-tarsus : on its posterior surface is a 

 prominent ridge, deeply grooved behind, and tra- 

 versed at its base by a longitudinal canal, for the 

 passage of the tendons of the flexor muscles of 

 the toes. Behind the ridge, two sesamoid bones 

 are usually present. 



In the shaft of the bone, the three metatarsals 

 which compose it can readily be distinguished, 

 They do not lie quite parallel to one another, 

 the middle one being slightly posterior to the 



