84 THE ANATOMY OF THE HORSE. 



part of the cannon bone always rests upon the sessamoids ; 

 and we can readily understand how such a formation must 

 contribute to weakness ; as well as to the grace of the 

 animal's paces, and the ease of the rider. Horses, with 

 very erect pasterns, hardly ever have the sessamoids de- 

 pressed by the cannon bone ; hence we can account for 

 their want of elasticity, as well as danger to themselves, 

 when put beyond a walk. 



The lesser pastern, or coronet hone (Shel. Z), receives the 

 great pastern ; its largest extremity being placed below. 

 The eminence on the top of this bone is received into the 

 depression at the bottom of the large pastern. Upon its 

 sides are two projections ; which are intended to receive the 

 ends of the perforatus tendon. Its lower articulating sur- 

 face is very large ; showing it has a vast extent of motion. 

 It rests upon the coflfin and navicular bones ; and as the last 

 is another moveable bone, yielding to weight ; and as the 

 coronet bones in horses with long pasterns have neces- 

 sarily greater motion than those with short ; we can further 

 understand the reason for those quahties which such a con- 

 formation would bestow. 



The coffin bone {Skel. P) is a very peculiar one. In shape 

 it corresponds with the hoof; which, with its appendages, it 

 almost fills : in structure it is very porous ; having its bony 

 fibres perpendicularly placed so as to give it a rough linear 

 appearance. When viewed in front, an eminence is seen at 

 the upper part ; to which the tendon of the extensor pedis 

 is attached : its lateral parts are not so high, but pro- 

 ject farther back ; and form two lateral processes, which are 

 always distinct, and are called its wings. Upon the inner 

 surface of these wings is a groove for an artery, which 

 forms a semicircle within the substance of the bone, and 

 sends off branches to the internal and external parts. 

 Above the wings are concavities which receive the two side 

 cartilages of the foot. Around the outer surface of the 

 coffin bone are placed the sensible laminse ; w'hich are very 

 firmly attached to the roughened exterior. The inferior 

 surface of the coffin bone is concave, for the reception of 

 the sensible sole ; and though this part is far from smooth, 

 yet it is by no means so rough as the other parts of the 

 same bone. The porous nature of the coffin bone answers 



