878 iii:i:i:i)IT.\i:v PREDISPOSITION to rtng-bone. 



seat of disease lies in its anatomical formation. To act as an 

 incomplete ginglymoid joint, its area must necessarily be limited, 

 and its articular surface flat. This, however, favours strain of the 

 ligaments and unequal distribution of weight over the articular 

 surface, circumstances which lie at the root of the morbid changes, 

 while they also explain why the periarticular form of ring-bone is 

 the tnosl frequent, and why the disease only occurs in solipeds. 



Considering the varied forms of ring-bone, it is not surprising 

 that equal variety exists in the immediate causes. The existence 

 of the disease in two or more feet suggests hereditary predisposition, 



Fig. 498. — The outside of the right coronet shows ring-bone formation ; 

 the left is normal. 



and may often be traced to small and badly-shaped joints, or defects 

 in the formation of the limbs. The greater weight borne by the 

 front limbs explains their so frequently becoming diseased. Turning 

 the toes in or out causes unequal distribution of weight in joints and 

 strain of ligaments, and therefore often produces periarticular ring- 

 bone. Such conformation being perpetuated in the progeny, renders 

 it easy to understand why the disease is often inherited. Havemann 

 drew attention to this, and condemned the use of animals with ring- 

 bone for breeding. There seems no reason for believing that 

 coarse-bred animals suffer oftener than others ; but if the statement 

 be true, the fact is probably due, in part at least, to the less care 

 taken in selecting mares for breeding. 



Both Peters and Williams state that ring-bones are commonest in 

 animals with long, weak pasterns, and refer this to the greater strain 



