254 DISEASES OF BONE. 



osseous) ligaments which bind the bones of the hock together, is 

 a possible cause of spavin. 



HEREDITY AND PREDISPOSITION.— As spavin is due to 

 causes which come into existence after birth, it cannot be regarded 

 as a hereditary disease. Hereditary predisposition, however, plays 

 a large part in its production. In the first place, the process of 

 evolution in the horse, which is a single-toed animal that has 

 descended from five-toed ancestors, predisposes him to suffer from 

 bony union of the bones of the hock, in the same way as it pre- 

 disposes him to splint (p. 232). Second, the weaker the bones of 

 the hock are in comparison to the weight of the body, the more 

 inclined will the animal naturally be to contract spavin. Third, 

 bad conformation of the hocks has undoubtedly a predisposing 

 influence. When a horse is "tied in below the hock" (namely, 

 when the width of the leg just below the hock, viewed sideways, 

 is small in comparison to the width of the fetlock), the bones of 

 the hock will present a comparatively small surface over which 

 compression has to be distributed. Also, " cow-hocked " horses 

 (the points of whose hocks are brought comparatively close to- 

 gether) are said to be predisposed to spavin ; the probable reason 

 being that the more the points of the hocks are turned in, the 

 more the toes are turned out, and, consequently, the more weight 

 is thrown on the inside of the leg. Fourth, impetuosity is evi- 

 dently a predisposing cause. Fifth, keeping the slope of the hind 

 feet at too acute an angle appears to predispose the animal to 

 spavin, apparently on account of the mechanical disadvantage 

 at which it places the muscles that straighten the hock. Dr. 

 Eberlein (" Journal of Comp. Path.", Sept. 1898) tells us that 

 " Olemm has experimentally shown that excessive cutting away of 

 the heels in shoeing is specially injurious in this way. Out of 

 fifteen horses that were shod with low heels, nine became affected 

 with spavin in from one to two months. I have myself had the 

 opportunity to verify G-lemm's views, and have obtained similar 

 results. Peters observed that spavin is specially frequent on soft 

 boggy land and uneven pavement." 



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 



