130 
LAMENESS IN HORSES. 
BOG SPAVIN, although bog spavin, in the majority of instances, is 
unattended by thorough-pin. The pathology of thorough-pin will 
explain this seeming paradox. 
The Causes of Thorough-pin, so far as they are imme¬ 
diately exciting, may be said to be the same as produce bog 
spavin. A hock that is over-weighted or over-worked, over¬ 
stretched or strained in any way beyond its powers, will be likely 
to put out a bog spavin, and afterwards may shew thorough-pin. 
And, as was observed on another occasion, this may be expected 
to happen to young horses in particular at the time of breaking, 
and especially to such as have great frames with large bony 
joints. 
In respect to Predisposition, straight hocks are more liable 
to bog spavin and to thorough-pin than those of an opposite forma¬ 
tion. On this account, young horses with such predispositions 
should have attention paid to the shoeing of the hind feet. Since 
caulkings may be likely, by raising the heels and so still further 
straightening the hocks, to add to this susceptibility, it will gene¬ 
rally be found advisable to have such horses’ hind shoes made 
plain in the heels. Solleysell, who treats of these affections under 
the general heading of “ windgalls,” says, that “ this disease 
(seated between the great sinew of the hock and the thigh bone) 
is often hereditary , and derived from the stallion.” And, so far as 
conformation of hock goes towards predisposition to the disorder, 
we quite agree with Solleysell. 
The Pathology of Thorough-pin is analogous to that of 
bog-spavin. It consists in anormal accumulation of synovia in 
the joint of the hock, and consequent dilatation and bulging of the 
capsular ligament. The cavity of the hock joint may be said to 
be naturally divided into two compartments by the trochleated 
adaptation of the tibia to the astragalus. So long as the joint is 
at rest and the animal is bearing his weight upon it, all communi¬ 
cation between these two compartments of the joint is shut off; 
while, on the other hand, the joint is in motion, and especially so 
long as the hock is flexed, and all bearing is taken off it, it is pos¬ 
sible for fluid to pass from one compartment into the other. More¬ 
over, at the places where thorough-pin makes its appearance, viz., 
between the lateral processes of the lower head of the tibia and 
the os caleis, the capsular ligament of the hock joint is but com¬ 
paratively loosely attached, or rather, in the relaxed state, hags 
a little; and, being in those parts without any embrace outwardly 
from ligament or tendon, the moment accumulation takes place 
within the joint, the capsule at the said places bulges and pro¬ 
trudes at the sides, and so produces the tumours we denominate 
thorough-gin. This view of the pathology of thorough-pin ex- 
