THE AK.MY HORSE. 43 



Bones of the foot. 



The bones of the pastern region and foot form a cohimn 

 extending downward from the fetlock into the hoof, and, as 

 previously stated, are named as follows: Os snffraginls (long 

 pastern bone), os coronce (short pastern bone), os pedis (coffin 

 bone), and os navicularis (shuttle bone). 



The OS su-jfraginis is about one-third as long as the cannon 

 bone (the bone extending from the knee or hock to the fetlock) 

 and reaches from the fetlock joint above to the pastern joint 

 below; its superior extremity shows a shallow cavit}' on each 

 side, separated in the middle b}' a deep groove, and into this 

 surface fits the lower end of the cannon bone. The inferior 

 extremity is much smaller and narroAver than the upper; on 

 each side is a small convex surface, the two surfaces separated 

 in the middle by a shallow groove. This extremity meets the 

 upper end of the os corona? and forms the pastern joint. 



The OS coronm follows the direction of the os sulfraginis 

 downward and forward and lies between the pastern and coffin 

 joints, its loAver end being within the hoof. 



Its superior surface shows a shallow cavity on each side, with 

 a ridge between them to fit the lower end of the os sulfraginis. 

 The lower surface of this bone shows a convex part on each 

 side, separated b}'' a groove, to fit the upper surface of the coffin 

 bone in the coffin joint. 



The OS pedis is an irregular bone, situated within the hoof 

 and is similar to it in shape. 



The anterior surface is known as the wt/U si/rface; it shows 

 a number of small openings, called foramina, for the passage 

 of blood vessels and nerves, and is roughened to give attach- 

 ment to the soft parts {sensitive la?nina') covering it. At the 

 top of this surface, in front, is a ridge called the pyramidal 

 proeess, to which is attached the extensor pedis tendon. 



The lower surface, called the sole, is half-moon-shaped, con- 

 cave and smooth, and is covered by the sensitive sole. The 

 upper surface helps to form the coffin joint and is called the 

 articular surface; it shows two shallow cavities, separated by a 

 ridge. 



Just back of the articular surface is a small triangular sur- 

 face to fit the navicular bone behind. 



Just back of the sole is a rough surface, to which is attached 

 the flexor pedis perforans tendon ; it is called the tendinouH 

 surface. 



