164 THE HORSE 



These are interposed between the lower end of the 

 radius (a) and the upper part of the cannon-bone {k) 

 and the splint-bones (j, I), six being placed in front, and 

 the seventh, the trapezium, behind. It will be seen on 

 examining Fig. 2, Plate V., that when the knee is bent there 

 would be a very large opening between the radius and the 

 cannon-bone were it not for the interpolation of the six 

 small bones, which reduces the wide opening to three 

 narrow ones ; these are, moreover, well protected with a 

 capsular ligament, extending from the radius to the shank- 

 bone, and therefore danger to the joint is very largely 

 minimised by this ingenious arrangement. 



The Cannon, or shank-bone (k), and the Splint bones (j, I), 

 which have just been mentioned, form the leg-bone, and 

 are termed the metacarpals, and all three articulate with 

 the lower row of the bones of the knee. The two splint- 

 bones are situated behind, and a little on one side of the 

 cannon-bone, and are probably the relics of the early period 

 in the history of the horse when it possessed three toes. 

 An interesting example of reversion to the primitive type 

 was that of a mare which was racing in 1822-23, and 

 ran in nine races, two of which she won. She was first 

 named Pincushion, which was afterwards changed to 

 Creeping Jenny. She suddenly commenced to throw out 

 a new set of limbs, which began half-way below the 

 hocks, on the hind legs, and from just above the fetlock 

 on the near fore-leg. The cannon-bone is very subject to 

 throwing out nodules of bone, especially in young horses, 

 though old horses are also subject to this annoyance, and 

 the writer has had cases when animals of fourteen and 

 sixteen years have thrown them out, who had never 

 previously suffered from them. These are termed splints, 

 and frequently become absorbed, and disappear as age 

 creeps on. During their formation they are very painful, 

 and make the animal lame, which is chiefly due to their 

 stretching the periosteum, a membrane that covers the 

 bones very closely, and is inelastic, and also to the in- 

 flammation inseparable from the growth of the exostosis. 



The splint-bones, which have nothing to do with the 



