THE FORE LIMB 



199 



fetlock joint. Behind they are covered with fibro- cartilage, and by 

 apposition form a groove over which the great flexor tendon of the foot 

 plays like a rope over a pulley. On the outer 

 sides, from the apex downward, a roughened 

 groove ojives attachment to the two l)ranche.s 

 of the suspensory ligament. The under sur- 

 face of the base is also roughened, and from 

 it proceed short strong ligaments [inferiof 

 sesamoid), which attach the bones to the pos- 

 terior surface of the large and small pasterns. 

 Os Coronas (fig. 305), small pastern, or 

 second phalanx, is a short bone placed be- 

 tween the large pastern and the os pedis, or 

 foot-bone. One-half of it is enclosed by the 



hoof, and the rest forms the region of the 



Fig. 305.- 



Os Coronse and Os Naviculare 

 (Anterior Aspect) 



coronet. Its upper extremity presents two 

 shallow depressions, with which the two con- 

 dyles of the lower end of the large pastern articulate. The lower end, 

 like that of the suflraginis, is divided by a shallow groove into two con- 

 dyles, by which the bone 

 articulates with the os pedis. 

 The tendon of the extensor 

 pedis muscle is attached to 

 the anterior surface, and that 

 of the flexor pedis perforatus 

 to the inner and outer part 

 of the superior border behind. 

 At the upper and posterior 

 part it is flattened and 

 covered by fibro - cartilage, 

 thus forming a smooth sur- 

 face over which the tendon 

 of the flexor perforans freely 

 plays in its course towards 

 the foot-bone. 



Os Pedis (figs 306, 



307), coffin -bone, or third 



phalanx. The coffin-bone is 



contained in the hoof, of the 



shape of which it in a large measure partakes. It is a porous bone, 



having a number of holes in its front and sides for the passage of blood- 



Fig. 306.— Os Pedis (Plantar Aspect) 



A, A Inferior Border. B Semilunar Crest. c Plantar Foramina. 

 D, D Retrossal Processes. 



