DISEASES AND INJURIES OF THE LEGS. 177 



It is generally conceded that hereditary influence has much to do 

 with the production of spavin. 



Symptoms. — During the formation of the exostosis, some degree of 

 abnormal heat and tenderness on pressure may be detected, but usually 

 the disease first makes its presence known by the jDrominence of the bony 

 growth, which destroys the symmetry of the hock. In well-developed 

 cases, the lameness arising from sprain causes the toe to be dragged 

 along the ground instead of being properly raised. 



In slighter cases, some stiffness of the hock and an occasional trip- 

 ping of the toe may be noticed; also a sort of vibration in the hock, 

 when the toe comes to the ground. These peculiarities will be most 

 observable if the horse is trotted on hard, smooth ground. The animal 

 should be especially vv^atched while turning, when a certain degree of 

 flinching will be detected. Exercise even for a few minutes greatly 

 diminishes the symjotoms; but when the horse, after exercise, is allowed 

 to stand till cool, the stiffness will recur, probably in an increased degree. 



In the stable, a horse, though only very slightly lame from spavin, 

 will often drop very much as the weight comes on the diseased leg, when 

 made to move to one side in the stall. In bad cases, in a state of rest, 

 the animal usually keeps the leg flexed. 



If the horse is worked during the formation of a spavin, the inflam- 

 mation will greatly increase, and an enormous deposit of bone may be 

 the result. 



In the examination for spavin, it is necessary, in the first place, to 

 compare the hocks with each other. Any difference in size is very sus- 

 picious, especially in the adult horse. A hock, however, which may at 

 first sight appear large on the inside, .may on closer examination prove 

 to be exactly similar to the other; and, if so, tlie formation must be re- 

 garded as natural, and generally is sound. It is true that there may be 

 sjxivins in both hocks; but it is very rarely, if ever, found that the two 

 abnormal growths are exactly similar. In long, coarse-coated horses, the 

 hock should be damped before examination, so as to make the hair lie 

 smooth. 



Allowance must be made in certain horses for the shape and promi- 

 nences of the bones at the inner and posterior half of the hock. In 

 sickle-hocked horses, for instance, there is often an apparent, but 

 natural, enlargement of the bones at the inner and posterior part of the 



hock, which is often mistaken for spavin. In other horses, there maybe 

 12 



