DISEASES OF THE JOINTS 427 



commences, it is good treatment to smartly blister the whole 

 of the region of the coronet, the pastern, and the wound 

 itself with a mixed blister of cantharides and biniodide of 

 mercury, repeated at intervals of a fortnight. This prevents 

 to some extent further infection of the wound, and assists 

 also in promoting the changes that tend to anchylosis. 



((7) Anchylosis. 



The word anchylosis signifies the stiffening of a joint. 

 When one has read the serious changes occurring within 

 the joint in the more serious forms of arthritis, it is easy to 

 understand how it comes about. In suppurative arthritis, 

 for instance, we have the synovial membrane destroyed, the 

 articular cartilages partly or wholly obliterated, and the 

 former boundaries of the joint entirely lost. If the animal 

 lives, nature is bound to make repair of a sort. The synovial 

 membrane and the articular cartilages utterly destroyed, as 

 we have described, cannot again be replaced. Nature can 

 only build again from such materials as are left to her. In 

 this case the material is bone. 



It must be remembered, however, that often the bone 

 has been so diseased that spots of necrosis or caries within 

 it are bound to remain unless moved by operative inter- 

 ference. Such diseased portions, when dealing with the 

 foot, are beyond reach of the surgeon's knife, and we have 

 no alternative but to allow them to remain. We get, 

 therefore, in many cases, a condition of rarefactive ostitis 

 occurring side by side with a slowly progressive caries 

 within the bone, while outside is occurring an osteoj^lastic 

 periostitis. The concurrence of these conditions leads in 

 time to great increase in size of the parts, together with 

 increasing anchylosis and deformity. 



C. NAVICULAR DISEASE. 



Definition. — Chronic inflammatory changes occurring in 

 connection with the navicular bursa, affecting variously 

 the bursa itself, the perforans tendon, or the navicular 



