LAMENESS IN HORSES. 
71 
but likewise from its being a dependent part, and one against which 
the accumulated fluid is thrust by the mere weight of the animal, 
is the inner and anterior part of the hock joint; the site, in fact, of 
bog spavin. 
The saccular dilatation of bog spavin once produced, there is no 
chance of the restoration of the capsule to its original contracted 
state ; on the contrary, Nature sets about making additions to it in 
order to guard against the consequences of its dilatation. Attenuated 
as the capsule has become through its extension, and immediately 
underneath the skin as the dilated sac now is, there seems dan¬ 
ger, not only of its giving way, but of the common integuments even 
doing so; and, therefore, is a process of thickening and strengthen¬ 
ing set up in the parietes of the sac, by which, in the course of 
time, they grow from less than an eighth to more than a quarter 
of an inch in thickness; nay—as we have witnessed them—to 
three-quarters of an inch in density. 
In the generality of cases this may be said to be the termination 
of bog spavin, little else than accumulation of synovia and thick¬ 
ening of the dilated sac appearing to take place. This accounts 
for lameness being unheard-of in bog spavin in its ordinary form : 
cases, however, occur in which disease proceeds further—or rather 
commences, for, so long as ordinary bog spavin continues in statu 
quo, it can hardly be accounted disease—renewing its attack on 
the joint as well in regard to its secretion as to its lining membrane. 
Mr. Pritchard (in his excellent remarks on the subject in The 
VETERINARIAN for last month) informs us he has discovered alter¬ 
ations to have taken place in the synovial fluid secreted under such 
circumstances, as well in thorough-pin as in bog spavin. “The 
fluid,” he says, “becomes highly charged (first) with cartilage, 
then with calcareous matter; and the whole tumour of the hock be¬ 
comes converted into ossific substance, of which I have a very large 
and excellent specimen. The first change in the synovia is in the 
increase of its albumen; then cartilage appears, most commonly in 
the form of cotton threads from one to two inches in length, per¬ 
fectly white, resembling fine needle-like worms, floating in the thick 
deep-coloured synovia. These threads increase in number and size; 
then comes the calcareous matter, and perfect ossification is effected 
in regular spherical masses; and in one case, of which I made a 
particular note, I was surprised at the early period of the disease at 
which these threads of cartilage appeared, and in considerable 
numbers.” 
In respect to the lining membrane of the joint, we have observed 
its smooth glistening surface to lose its transparency—to become, 
first opaque, then deadly yellow in aspect, and, finally, to present 
a surface uneven, rugged even, in consequence of being studded 
