ANATOMY. 41 



The OS sujfraginis is about ()iie-thii(l as long as the cannon bone 

 (the bone extenciing 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 nar- 

 rower 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 coronse and forms the pastern 

 joint. 



The OS coronse follows the direction of the os suffraginis downward 

 and forward and lies between the pastern and coffin joints, its lower 

 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 suffraginis. The 

 lower surface of this bone shows a convex part on each side, sepa- 

 rated 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 ipaU surface; it shows a num- 

 ber of small openings, called foramina, for the passage of blood vessels 

 and nerves, and is roughened to give attachment to the soft parts 

 {sensitive laminse) covering it. At the top of this surface, in front, is 

 a ridge called the pyramidal process, to which is attached the extensor 

 pedis tendon. 



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

 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 surface 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 tendinous surface. 



On each side of this surface is a groove running forward and termi- 

 nating in an opening, called the plantar foramen; an artery and a 

 nerve enter the bone and a vein leaves it through this opening. 



On each side of the os pedis, extending backward, is a prolongation, 

 called the wing. Each wing is divided by a notch and then by a 

 groove, which runs forward on the outside of the bone ; an artery lies 

 in the notch and groove. 



The OS navicularis is an irregular bone situated behind and below 

 the OS coronse and bohind the os pedis, articulating with both bones. 

 Its long axis is perpendicular to the axis of the foot. The extremi- 

 ties of the bone are attached to the wings of the os pedis ; the inferior 



