84 THE HORSE 



the ossification of the natui'ally elastic lateral 

 cartilages attached to the pedal bone, and is easily 

 felt as a hard, rough lump, which may vary from 

 the size of a pea upward. Usually only the fore 

 feet are affected, and cart horses rather than light 

 horses are liable to the complaint. Tliis is prob- 

 ably due to the fact that the disease is almost al- 

 ways brought on by external injury, and that farm 

 horses harnessed abreast are extremely liable to 

 tread on one another's feet when tm^ning in 

 ploughing, etc. That the disease is usually con- 

 tracted in this way is proved by the fact that it is 

 almost always an outside cartilage which is af- 

 fected. In cart horses, not much is thought of the 

 disease, as animals with it can perform a great 

 amount of work on soft ground at a walking pace. 

 It is a grave unsoundness, however, in light horses, 

 one, moreover, which may increase as time goes 

 on, and no horse should be purchased for trotting 

 road work which has a suspicion of the disease. 

 The pain of side-bone is caused by the nipping or 

 pressure, as it were, of soft tissues between the ab- 

 normal deposit of bone and the hoof, and this is 

 obviously likely to increase as the disease extends, 

 and to be worse after severe work on hard roads. 

 Cart horses with side-bones will often be lame for 



