BONES AND INTEGUMENTS OF PASTERN AND FOOT 2 19 



lower down they expand on both sides, and as they 

 approach the pasterns, separate, and are inserted 

 into two small sesamoid bones, situate at the back 

 of the upper pastern. These form a joint, both 

 with the lower termination of the shank bone and 

 the upper pastern bone, to both of which they are 

 united by ligaments, /, i, and k, but more firmly 

 united with the pastern than the shank. Between 

 them pass the flexor tendons, through a synovial 

 bag, which prevents the friction to which they would 

 otherwise be exposed in passing through so confined 

 a situation. This ligament is continued over the 

 sesamoid bones, and afterwards is directed obliquely 

 forward over the pastern, where it unites with the 

 long extensor tendon, and downward to the perforated 

 tendon, which it surrounds, and fixes in its position, 

 and likewise to the smaller pastern bone. 



a. The coffin bone. This bone is fitted to, and occupies the 

 fore part of, the hoof, filling about half of it. It nearly 

 resembles the hoof in form, being half-moon shaped ; it 

 is convex above and in front, and concave behind and 

 beneath. It varies, however, with the natural form of 

 the hoof, and also adapts itself to such changes in the 

 hoof as are induced by disease. Its structure is light and 

 spongy, and perforated with numerous holes. These 

 are adapted for the passage of the blood-vessels of 

 the foot, without which the circulation could not be so 

 safely and conveniently kept up, and affords another 

 striking example of those beautiful provisions of nature 

 for effecting certain ends. But for this, these vessels 

 would be frequently subjected to great pressure, which 

 would occasionally obstruct its free passage. The upper 

 surface, it will be seen, is concave, for the reception of 

 the rounded end of the lower pastern, b ; at the back, o, 

 is a depression for the perforating tendon, g. We have 

 described the diseases connected with this joint at page 

 104. 



b. The lower or smaller pastern bone. 



