HEREDITARY PREDISPOSITION TO RING-BONE. 
607 
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 most 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, and may 
often be traced to small and badly-shaped joints, or defects in the forma¬ 
tion 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 con¬ 
demned 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 
on the ligaments. Peters says the process begins at the middle of the 
dorsal or anterior surface of the joint, as an inflammation of the capsular 
ligament. Percival believes, on the other hand, that upright pasterns 
favour formation of ring-bones, because of the greater shock to which 
the bones are subject in moving. The abnormal formation above 
noted is, however, of more importance. The predisposition to ring-bone 
in young animals is a result of the greater vulnerability of the bones 
and joints. 
The external causes are sprains and all influences favouring sprain, 
such as defective formation of the limb, unequal paring of the hoof, 
using animals at a rapid pace and on rough ground. Unskilful shoeing 
plays an important part. If one side of the foot-wall is left higher than 
the other, that side will first come in contact with the ground, the 
weight will be distributed unequally in the joints, and the external 
ligaments of the opposite side may be strained. The “camber” of 
modern roads acts in the same way. The causes of rliachitic ring-bone 
are little understood, and the same is true of the reported cases of ring¬ 
bone following strangles, and its greater frequency in certain breeds. 
It has not yet been shown that it is due to deficiency of calcium salts. 
Traumatic ring-bone is produced by inflammation extending from 
neighbouring parts to the periosteum. 
