io8 CAUSES OF UNSOUNDNESS. 



are («) the navicular bone, (b) its cartilage, (c) the 

 navicular bursa, and (^) the tendon in the immediate 

 vicinity of the navicular bone. One or the whole 

 of these structures may be implicated in the morbid 

 process. Navicular disease affects the lighter 

 breeds of horses, and in them it is very common. 

 One or both fore feet are affected, and once the 

 disease starts it continues, so far as veterinarians 

 are aware, indefinitely. It is gradual at the onset, 

 and steadily progressive, rendering the subject of 

 it practically valueless. Let us suppose that a 

 horse was sold with a general warranty, and the 

 buyer subsequently found that he had, un- 

 fortunately, got hold of an animal that experts 

 declared to be suffering from this disease. He would, 

 of course, have a good claim against the seller ; 

 the only trouble that might arise, would be as to 

 whether the animal was, or was not, affected with 

 navicular disease. The short, cat-like step ; the 

 wasting of the muscles at the shoulder ; the wearing 

 of the shoe at the toe ; the pawing in the stable, 

 together with lameness following rest after exercise, 

 are the most significant signs of navicular arthritis. 

 Sometimes horses with this disease are "unnerved," 

 i.e., a portion of the nerve supplying the foot with 

 sensation is removed. Horses thus operated on 



