BONE SPAVIN. 283 



BONE SPAVIN. 



A still more formidable disease ranks under the name of 

 Spavin, and is an affeotion of the bones of the hock-joint. It 

 has been stated that the bones of the leg, the shank-bone, g, 

 Fig. 45, and the two small splint-bones behind, h, support the lowei 

 layer of the bones of the hock. The cube-bone, d, rests prin- 

 cipally on the shank-hone, and in a slight degree on the outei 

 splint-bone. The middle wedge-bone, f, rests entirely upon tht 

 shank-bone, and the smaller wedge-bone presses (not' seen in 

 the cut) in a very slight degree on the shank-bone, but piinci 

 pally, or almost entirely, on the inner splint-bone. Then the 

 splint-bones sustain a very unequal degree of concussion and 

 weight. Not only is the inner one placed more under the body, 

 and nearer the centre of gravity, but it has almost the whole of 

 the weight and concussion communicated to the smaller cunei- 

 form bone carried on it. It is not therefore to be wondered at 

 that the inner splint-hone, or its ligaments, or the substance 

 which connects it with the shank-bone should receive injury, 

 particularly in young horses, before the limbs have become 

 properly knit. The smith frequently greatly increases this ten- 

 dency, by raising the outer heel higher than the inner one, to 

 prevent cutting (interfering). 



The weight and concussion being thrown principally on the 

 mner splint-bone, produce inflammation of the cartilaginous 

 substance that unites it to the shank-bone. In consequence of 

 it, the cartilage is absorbed, and bone deposited ; the union be- 

 tween the splint-hone and the shank becomes bony, instead of 

 cartilaginous ; the degree of elastic action between them is 

 destroyed, and there is formed a splint of the hind leg. As in 

 the fore leg, the disposition to form bony matter having com- 

 menced, and the cause which produced it continuing to act, 

 bone continues to be deposited, and it generally appears in the 

 form of a tumor, where the head of the splint-bone is united 

 with the shank, and in front of that union. It is seen at c, 

 Fig. 44. This is called bone spavin. Inflammation of the 

 ligaments of any of the small bones of the hock, proceeding to 

 bony tumor, would equally class under the name of spavin ; but, 

 commonly, the disease commences on the precise spot that has 

 been described. 



While spavin is forming, there is always .lameness, and that 

 frequently to a very great degree : but when the membrane of 

 the bone has accommodated itself to the tumor that extended it, 

 the lameness subsides or disappears, or depends, upon the degree 

 in which the bony deposit interferes with the motion of the 



