STRUCTURE OF THE LIMBS OF THE HORSE 141 



attached by ligaments. The middle portion is constricted and 

 forms a neck. The inferior or posterior portion is flattened 

 from above to below, and directed inward to meet the border 

 of the opposite bone. Just below the neck and externally, there 

 is a cup-shaped cavity into which the head of the thigh bone 

 fits. The two coxa, together with the sacral ligaments (sacrum) 

 and the muscles of the quarter, enclose the pelvic cavity. 



The region of the thigh is formed by the femur, the largest 

 long bone in the body. The superior extremity is formed by a 

 rugged eminence, to which the heavy muscles of the quarter are 

 attached, and by an articular head. The inferior extremity is 

 formed by two convex articular surfaces that are separated by 

 a deep notch, and a third pulley-like articular surface, with which 

 the patella or knee-cap articulates. The pair of condyles articu- 

 lates with the superior extremity of the leg bone. The thigh 

 or femoral region is heavily muscled. 



The leg is formed by three bones. The patella, a short bone, 

 has already been mentioned as articulating with the thigh bone. 

 The tibia and fibula are the other two bones in the region. 



The tibia belongs to the class of long bones and the fibula 

 is quite rudimentary, being represented by a stylet-shaped bone 

 that lies posterior to, and along the outer border of the tibia. 

 The superior extremity of the tibia shows a central spine mar- 

 gined laterally by rather plain articular faces. It articulates 

 with the thigh bone. The muscles of this region are divided 

 into two sub-regions, anterior and posterior tibial. The muscles 

 originate from the lower extremity of the femur and the two 

 bones in this region, and terminate inferiorly in tendons that are 

 attached to the bones of the hock, cannon and digit. 



The hock or tarsal region is formed by six bones. They are 

 described as forming two rows. In the upper row there are two 

 bones and in the lower four. They form a series of articulations, 

 the same as the bones of the knee. Practically all of the move- 

 ment occurs in the articulation between one of the large bones 



