THE HIND-LIMB. 427 



2. The leg. 



i. The tibio-tarsus is a large stout nearly straight 

 bone, considerably longer than the femur : it 

 is formed by fusion of the tibia with the 

 proximal row of tarsals. The proximal ex- 

 tremity of the bone is much enlarged, and 

 bears at its end two surfaces which articulate 

 with the condyles of the femur ; on its ex- 

 tensor surface is the prominent cnemial crest, 

 into which the tendon of the extensor 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. The distal portion, corresponding 

 to the tarsal bones, is easily detached in the 

 young fowl. 



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 proxi- 

 mal 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 each 



other and with the distal tarsal row. The fifth or 



postaxial digit, corresponding to the little toe in man, 



is represented by a rudimentary metatarsal. 



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, 



fourth, and fifth metatarsals. Its proximal end 



is enlarged, and bears terminally two cup-shaped 



