254: DISEASES OF BONE. 



SPAVIN FROM A BREEDING POINT OF VIEW.— As in- 

 dividually acquired characters are not hereditary, it would be as 

 reasonable to reject an animal for breeding purposes, because he 

 had a spavin, as it would be, because he had lost an eye by a 

 gunshot wound. Here the point to consider, is that predisposition 

 in the form of defective conformation is hereditary. Hence, in 

 this case, rejection should depend on the nature of the conforma- 

 tion, and not on the presence of the spavin. When such a decision 

 is entrusted to a man who knows little or nothing of equine con- 

 formation, although his knowledge of anatomy and pathology may 

 be perfect, it will probably be safer for him to reject the animal 

 than to pass it. 



CAUSE OF BONY ENLARGEMENTS BEING FOUND MORE 

 FREQUENTLY ON THE INSIDE OF THE HOCK, THAN ON 

 THE OUTSIDE. — Although this question has not been definitely 

 decided, it seems probable that this predisposition is due to more 

 weight being put on the inside of the foot than on the outside. 

 Owing to the fact that the grooves on the bones (tibia and astraga- 

 lus) which form the true hock joint are directed obliquely outwards 

 as well as forwards, the toe of a hind foot is rotated slightly in- 

 wards, when the limb is straightened out to the rear, while the 

 foot is on the ground. The occasional occurrence of bony enlarge- 

 ments on the outside of the hock (p. 243), shows that excess of 

 strain is not always confined to the inside of that joint. 



COMPARATIVE GRAVITY OF SPAVINS.— Horses should not 

 be condemned indiscriminately on account of having a so-called 

 low spavin, which is in many cases a veritable splint, and has no 

 connection with the small bones of the hock, above the cannon bone 

 and splint bones. 



I believe that a splint, having the appearance of a low spavin, 

 rarely occurs on the head of a cannon bone without involving 

 the cuneiform medium also ; although union of these bones fre- 

 quently takes place without the action of the animal being affected 

 in any perceptible manner ; as there is very little motion in that 

 joint. The cuneiform medium, as the seat of spavin, has a natu- 

 rally well-marked bony ridge on its surface, which gives it ■ the 

 appearance of having a small splint (Fig. 129). 



The more to the front of the hock the bony deposit is situated, 

 the greater danger is there of its giving rise to lameness ; because 

 in that case it is more apt to interfere with the action of the joint, 

 than if it were at the side. 



The lameness of spavin in horses six years old and under is 



