THE Ainrv horse. 43 



Bones of the foot. 



The bones of the pastern region aiul foot form a cohimn 

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

 previously stated, are named as follows: Os sii-ffrdgitds (long 

 pastern bone), os coroiuc (short pastern bone), os pedis (cotlin 

 bone), and os navicidaris (shuttle bone). 



The OS suffraginis 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 cavity on each 

 side, separated in the middle by a deep groove, and into this 

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

 extremity is much smaller and narrower 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 

 ujDper end of the os coronse and forms the pastern joint. 



The OS coronce follows the direction of the os suffraginis 

 downward and forward and lies betw^een the pastern and coffin 

 joints, its lower end being Avithin 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 suffraginis. 

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

 side, separated by 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 icaU surface; it shows 

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

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

 ment to the soft parts {sensitiee lamince) covering it. At the 

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

 process, to which is attached the extensor ])edis tendon. 



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

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

 upper sui"fac(> 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 triangulai- sur- 

 face to fit the navicular bone Ix'hind. 



Just back of the M)le i-- a rough sui-face. to which is attached 

 the fiexor pedis perforans tendon; it is called the tctuIinoKs 

 surface. 



