124 CAUSES OF UNSOUNDNESS. 



hocks may be affected, as in the case of curb. The 

 swelling varies in its size, and is sometimes so small 

 as to be hardly noticeable. Thorough-pin comes on 

 gradually, being the result of a chronic inflammation. 

 It is due to the distension of the sheath of flexor 

 pedis perforatus tendon. 



Bog-spaYin. 



This term is employed for the purpose of indicat- 

 ing a soft or puffed condition of the hock, the 

 joint becoming swollen, through an over-secretion 

 of the lubricating material in connection with the 

 tendon, sheaths, and synovial membrane of the 

 hock joint. All classes of horses are liable to have 

 their hock — or hocks — enlarged in this manner. 

 The swelling may be sufficient to interfere 

 with the free play of the joint ; if so, it must be 

 looked upon as unsoundness. But a slight 

 over-filling of the joint, following active work, is 

 not usually of much significance. It is a very loose 

 term, and one that includes a variety of patho- 

 logical conditions. There are numerous bursae — 

 tendon sheaths in connection with the hock joint — 

 and a good deal of discretion must be exercised 

 when purchasing an animal with an enlargement 

 of this kind, because there is no knowing whether 



