370 BUREAU OF ANIMAL INDUSTRY. 



The sesa7)u)/(7s occur in pairs, are small, shaped like a three-faced 

 P3'ramid, and are set behind the fetlock joint, at the upper end of the 

 ^uffraginis, with the base of the pyramid down. 



The svffragmis is a verj'- compact bone, set in an oblicuie direction 

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

 coronet. 



The cm'Miet is a short, cube-shaped })one, set between the suffraginis 

 and coffinbone, in the same oblique direction. 



The co-ffinhone forms the end of the foot and is shaped like the horny 

 box in which it is enclosed. 



The iiavieuhir ho7ie is short, flattened above and below, and is 

 attached to the coffinbone behind. 



All of these bones are covered on the surfaces which go to make up 

 the joints, with a cartilage of incrustation, while the portions between 

 arc covered with a fibrous membrane called the periosteum. 



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

 ference with their function yg,yj 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 coffin. 

 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 mem))rane inclosing the 

 joints. 



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

 non and the upper end of the largo pastern bones, supplemented by 

 the two sesamoids, so placed behind the upper end of the i^astern that 

 the joint is capable of a verj- extensive motion. Those bones are held 

 together b}' ligaments, only one of which — the suspensory — demands 

 special mention. 



The susjpensory ligament of the fetlock starts from the knee, extends 

 down behind the cannon, lying behind the two splint bones, until near 

 the fetlock, where it divides and sends a branch on either side of the 

 joint, downward and foi-ward, 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 

 fi])ors which hold it fast to those bones. .(i*late XXXII, fig. 2.) 



The i^astern joint is made b}" the imion of the two pastern bones. 



The coffin joint is made hy tlye union of the small pastern, coffin, 

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

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

 receive largely the weight of the small pastern. 



Three tend/ms serve to move the bones of the foot one on another. 

 Two of these flex, or bend, the joints, while the other extends, or 

 straightens, the column of bones. (Plate XXX, fig. 5.) 



