380 SKELETON OF THE FOWL 



D. The Hind-Limb. 



In the bird's leg there is the same tendency to fusion of 

 the bones, which is characteristic of all parts of the skeleton. 

 There are no free tarsals, the proximal row having fused 

 with the tibia, and the distal row with the metatarsals. 



The position of the limb is the same as in the rabbit ; the 

 knee pointing forwards, and the preaxial border being internal 

 along the whole length of the limb. 



1. The thigh, has only a single bone. 



i. The femur has a cylindrical, slightly curved 

 shaft, and enlarged ends. The proximal end 

 is produced on its inner side into a rounded 

 head, articulating with the acetabulum. On 

 the outer or postaxial side of the head is an 

 irregular process, the great trochanter, be- 

 tween which and the head, at the proximal 

 end of the bone, is the articular surface for 

 the anti-tro chanter of the ilium. 



The distal end of the femur presents, in 

 front, a deeply grooved pulley-like surface for 

 the patella, a sesamoid bone in the tendon of 

 the extensor muscle of the leg : this surface is 

 bounded laterally by two prominent condylar 

 ridges, which articulate with the tibia; the 

 outer or postaxial condyle having on its pos- 

 terior surface a deeply grooved facet for the 

 upper end of the fibula. 

 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 

 extensor surface is the prominent cnemial 

 crest into which the tendon of the extensor 



