252 DISEASES OF BONE. 



hock, the cuboid bone rests on the cannon bone, stands alongside the large 

 and middle cuneiform bones, and has a side bearing against the outer splint 

 bone, the top of which is free from downward pressure. 



NATURE OF THE DISEASE.— Spavin is a chronic ostitis (inflammation 

 of bone) which begins in the scaphoid, large cuneiform, and metatarsal 

 bones, and extends to the articular cartilages (p. 256) of the affected joint. 

 Hence the best treatment consists in hastening the bony union of the 

 diseased surfaces, which, as a rule, show little or no tendency to recover 

 their normal condition. . Rest, as complete as possible, is a very important 

 factor in obtaining the desired bony union. 



In bone spavin there is, as a result of inflammation, a deposition of bone 

 on the inner and lower part of the hock, commencing, usually, between the 

 middle cuneiform and the cannon bone, or between the middle and large 

 cuneiform bones. The higher this bony formation extends the more serious 

 is the disease. When the spavin is low down, being then confined to the 

 joint between the middle cuneiform and the cannon bone, it is of little 

 consequence ; as bony union of that joint does not affect the horse's action 

 to any appreciable extent. 



CAUSES. — It may be reasonably assumed that the usual cause 

 of spavin is unduly severe com pression of the bones of the jjock, 

 because work which entails this form of injury is specially liable 

 to bring on spavin ; and the more weight is put on the forehand, 

 tlie less susceptible are horses to this complaint. Hence, race- 

 horses do not suffer f rom spavin nearly so much as hunters, h igh 

 school horses, and £a£t-horsgs_^wliich have to drag heavy loads up 

 lijjls^ My experience is, tha t circus ho rges which, when in the 

 ring, ha,ve_ tn wa.lk a brait a. gmnH dftal on tJieir hind legs and to 

 perform such feats as cantering backwards and cantering with one 

 fore leg continually kept off the ground, are more inclined to 

 develop spavin than any other class of animal. The nearer to a 

 perpendicular direction the weight of a horse and rider falls on the 

 hocks while these joints are being straightened out during move- 

 ment, the more will the bones of the hooks be compressed. Sprain 

 of the short (interosseous) 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. 230). 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 



