EXOSTOSES ON THE PASTERN BONES 71 



readily understood that in animals of such conformation much greater 

 strain is thrown upon the ligaments, with the result that the periosteum 

 near the insertion of the ligaments is rendered much more liable to 

 became injured and inflamed. These exostoses only in rare and 

 exceptional cases extend into the articulation, so that the movement of 

 the joint is not affected. In twenty-seven cases examined, only two 

 were found in which there were erosions on the articular surface, and in 

 these cases the body or main portion of the growth was placed on the 

 anterior aspect of the bone near its extremity ; and remembering that the 

 joint possesses no anterior common ligament, it will be understood how 

 readily this part of the periosteum might become inflamed as the result 

 of a blow or other injury, and the inflammation subsequently extend to 

 the articular cartilage. These two cases therefore come under the 

 category of what we describe as ringbones. Moreover, it was also found 

 that in those cases where the exostoses had a tendency to extend, they were 

 placed on the lateral aspect of the bone near the middle of the shaft, and 

 slightly in front of the oblique roughened areas to which the middle 

 divisions of the inferior sesamoidean ligament are attached. The 

 attachments of the lateral ligaments extend to these areas. The extension 

 of the growth was in the posterior direction, and in two cases the exostoses 

 met at the back of the tendons, and formed an osseous tube through which 

 the latter played. Yet even in these cases the articulation was not 

 affected, and the tubes simply played the part of a protective structure to 

 the tendons after the manner of the pisiform bone of the knee, the inner 

 aspect of the tube being perfectly smooth. Excepting in such cases where 

 their position or size causes them to interfere mechanically with the action 

 of the tendons, they rarely cause lameness. 



The treatment consists of pyro-puncturing the growth, and then 

 applying a blister of biniodide of mercury. A considerable reduction in 

 the size of the exostoses is a common result, but as a rule they are more 

 unsightly than injurious. 



