134 EXAMINATION OF HORSES 
account no doubt of its puffy, boggy feel. Bog-spavin 
may be due to 
1. Habit of the secreting membrane. 
2. Formation of the hock. 
3. Disease in the joint. 
So that you see it may be an unsoundness, or it may 
not. When a joint works at a disadvantage, no matter 
from what cause, it requires more lubrication. If this 
disadvantage arises from conformation, it is evident that 
it is permanent, so that the hock will always require 
more lubrication; and as you know, there are few parts 
of the body which do’ not yield in response to extra 
calls upon their powers, whether it is a muscle that has 
to lift more weight, as the blacksmith’s biceps; a skin 
that has to stand more pressure, as a blacksmith’s hoofy 
hand ; or a membrane that has to endure more friction, 
as the synovial membrane in question. In this case 
then you have to determine upon the cause that is 
giving rise to the increased supply of oil, and if there 
be no actual disease present, which cannot fail to be in- 
dicated by lameness, but only mechanical disadvantage, 
he may be quite sound, however long he may remain so, 
with which you have nothing to do. 
Formation of hock has much to do with az appear- 
ance of bog-spavin. It is self-evident that, in a very 
straight hock, the ends of the bursa will be wider apart 
and the bursa stretched more than in a bent hock. In 
the bent hock there is, as you see by the diagram 
