370 



The cannon hone extends from tlie knee or liock to tlie fetlock is 

 cylindrical in shape, and stands nearly or quite perpendicular. 



The sesamoids occur in pairs, are small, shaped like a three-faced 

 pyramid, and are set behind the fetlock joint, at the upper end of the 

 suffraginis, with the base of the pyramid down. 



The suffraginis is a very compact bone, set in an oblique direction 

 doAvnward and forward, and extends from the cannon bone to the 

 coronet. 



The coronet is a short, cube-shaped bone, set between the suffraginis 

 and cof&n bone, in the same oblique direction. 



The coffin, hone forms the end of the foot and is shaped like the 

 horny box in which it is enclosed. 



The navicular hone is short, flattened above and below, and is 

 attached to the coffin bone behind. 



All of these bones are covered on the surfaces with a cartilage of 

 incrustation which goes to make up the joints, while the portions 

 between are covered with a fibrous membrane called the periosteum. 



The joints of the legs are of especial importance, since any inter- 

 ference Avith their function very largely impairs the value of the 

 animal for most purposes. As the joints of the foot and ankle are at 

 the point of greatest concussion they are the ones most subject to 

 injury and disease. 



There are three of these joints— the fetlock, pastern, and coflin. 

 They are made by the union of two or more bones, held together by 

 ligaments of fibrous tissue, and are lubricated by a thick viscid 

 fluid, called synovia, which is secreted by a special membrane inclos- 

 ing the joints. 



The fetlock joint is made by the union of the lower end of the 

 cannon and the upper end of the large pastern bones, supplemented 

 by the two sesamoids, so placed behind the upper end of the pastern 

 that the joint is capable of a very extensive motion. These bones 

 are held together by ligaments, only one of which— the suspensory- 

 demands special mention. 



The suspensory ligament of the fetlock starts from the knee, 

 extends down behind the cannon, Ij^ng behind the two splint bones, 

 until near the fetlock, where it divides and sends a branch on either 

 side of the joint, downward and forward, to become attached on the 

 sides of the extensor tendon at the lower end of the pastern bone. 

 As it crosses the sesamoids on the posterior borders of the fetlock it 

 throws out fibers, whieli hold it fast to these bones. (Plate XXXII, 

 Fig. 2.) 



Th.^ pastern joint is made by the union of the two pastern bones. 



The coffin joint is made by the union of the small pastern, coffin, 

 and small sesamoid or navicular bones, the latter being set behind 

 and beneath the joint surface of the coflin bone in such a way as to 

 largely receive the weight of the small pastern. 



