NAVICULAR DISEASE. 907 



disease almost invariably occurs in well-bred horses, especially in 

 those with narrow, high feet. In coarsely-bred animals it is only 

 seen exceptionally. 



Only two cases are reported of the disease also affecting the hind 

 feet. In both cases the investigators (Rainsford and Fambach) 

 confirmed their diagnosis by post-mortem examination, and there 

 is no doubt that chronic inflammation of the gliding surface of the 

 navicular bone and of the perforans tendon had occurred, but no 

 explanation of the cause is given. In Fambach's case the horse 

 was lame for nine months ; as much as possible it avoided placing 

 weight on the limb, and both during movement and at rest kept the 

 limb flexed. 



The almost constant occurrence of navicular disease in the flexor 

 apparatus of the fore limb is partly due to the greater weight borne 

 by the front feet and to the violent strains thrown on the perforans 

 tendon during rapid movement on hard ground or under the weight 

 of the rider. Under these circumstances the navicular bone is exposed 

 to severe pressure on the one side from the coronet bone, on the other 

 from the flexor tendon ; and though disease of the bursa is seldom 

 caused by bruises from below when moving over uneven ground, 

 yet such an accident is conceivable. It is still very doubtful how 

 strains, &c, act in producing the disease. The variety of opinion 

 on this point is to some extent due to confusing cause and effect. 

 In no lameness are errors of diagnosis so common as in navicular 

 disease. 



The older English authors considered that a small, narrow formation 

 of the hoof often caused this disease, the strongly arched sole pressing 

 on the navicular bone. This view is due to confusing navicular 

 disease with contracted sole, as Brauell has pointed out. Williams 

 regards the upright position of the fetlock as a predisposing factor, 

 a view which is pertinent, so far as the position of the fetlock is in 

 some degree referable to that of the hoof. 



Peters and Fambach first explained the connection between this 

 conformation and the disease. Excessive lowering of the heels 

 causes the axis of the hoof to become more oblique than that of the 

 pedal bone, and throws excessive strain on the flexor perforans at 

 every movement. The pressure on the navicular bone thus produced 

 is increased by the flexor tendon describing a sharper curve in its 

 passage over the navicular bone. 



Leaving the toe too long may similarly cause the disease, or induce 

 inflammation of the flexor tendon. The upright position of the pastern 

 is not the sole factor, but acts in conjunction with faulty trimming 



