DISEASES OF THE FOOT AND SHOEING 281 



CANKER 



Canker results from infection of the pododerm or foot-skin. 

 It is a disease with a slow course, during which a gradual under- 

 mining of the horn of the sole and frog takes place. Unless relief 

 is given these structures eventually loosen. Treatment is purely 

 local, and consists in providing dry quarters, removal of all in- 

 volved tissues, applying antiseptics, and in protecting the exposed 

 sensitive parts from external influences. Most cases of canker 

 require several weeks and often months of careful treatment for a 

 cure. 



CONTRACTED HEELS 



Contracted heels is a narrowing or "tied-in" condition most 

 often seen in the front feet. Lack of exercise, too little moisture, 

 thrush, or navicular disease may produce contraction. It is, 

 therefore, a symptom of some other affection rather than a dis- 

 ease itself. Remedial measures are given in connection with 

 these other diseases. 



NAVICULAR DISEASE 



Navicular disease is a chronic inflammation of one or more of 

 the following structures: the navicular bone, the navicular 

 joint, the navicular bursa, the perforans tendon. When the 

 disease first starts it is usually confined to the bone itself; later 

 the articular cartilage becomes roughened. At this stage pain is 

 pronounced with each and every movement of the joint. Many 

 observations show that navicular disease occurs almost ex- 

 clusively in harness horses. 



Causes. — The exact cause is often impossible to locate. 

 There seems to be a particular tendency for it to appear in ani- 

 mals subject to the so-called spavin group of lamenesses. 

 Whether or not this is an inherited tendency remains to be 

 definitely proved. 



Symptoms. — At first the symptoms are hardly noticeable. 

 Quite without warning the horse may limp, but after a few steps 

 recovers. When resting, the foot is advanced or "pointed" 

 and the toe is placed on the ground. The fetlock is flexed to 

 take pressure off the navicular apparatus. Later intermittent 

 lameness occurs. In more advanced cases of the disease the 



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