X BONES OF THE HIND-LIMB 487 



Close to the proximal end of the femur^ on its inner 

 (preaxial) border, is a rounded, projecting head for articulation 

 with the acetabulum ; the actual end of the bone is formed 

 by a strong process, the great trochanter, while just distal to 

 the head is a lesser trochanter, and opposite this, on the 

 outer (postaxial) side, a third trochanter. The distal end of 

 the bone bears two large condyles, separated from one 

 another by a notch, for articulation with the tibia . this 

 notch is continuous with a groove extending for a short 

 distance along the anterior (dorsal) surface of the femur in 

 which a large sesamoid bone, the knee-cap ox patella, slides : 

 the patella lies in the tendon of the extensor muscles of the 

 leg, and is connected by ligament with the tibia. Two other 

 sesamoid bones, the fabellce, occur on the opposite side of 

 the knee-joint. 



The tibia, or inner (preaxial) bone of the shank, is much 

 larger than thi: filn/la, the distal half of which in the adult 

 becomes completely fused with it. The proximal end of the 

 tibia bears two slightly concave articular surfaces for the 

 condyles of the femur, and distally it articulates with the 

 tarsus : a prominent ridge — the cneniial crest, extends along 

 the proximal end of its anterior (dorsal) surface. The 

 distinct part of the slender fibula is attached proximally to 

 the tibia. 



The tarsus consists of six bones arranged in three rows. 

 In the proximal row are two tarsals, of which the inner 

 (preaxial) or astragalns — probably corresponding to two 

 bones fused together, the tihiale and intermedium — has 

 a large pulley-like surface for articulation with the tibia : 

 while the outer (postaxial) — they?/'«/rt/-f or calcanenm — artic- 

 ulates with the fused end of the fibula, and is produced 

 into a strong heel or calcaneal process. In the middle 

 row is a single bone, the centrale of the tarsus, and the distal 



