428 
ON BONY DISEASES OF THE HOCK. 
science it is believed to have only one cause, namely, the inter-os- 
seous disease, described by Mr. Percivall, pp. 302, 3, 4. This it is 
proposed to call the Inner hock disease. Now, assuming that the 
Inner hock disease, as described (pp. 302, 3, 4) by Goodwin and 
Percivall, is the cause of lameness, this is a totally different disease 
from spavin. 
Spavin may and probably does originate in the constitutional 
tendency of the horse to throw out bone, called by Mr. Percivall, 
p. 123, the ossific diathesis. It may be perfectly spontaneous like 
splint, and other bony swellings, in the fore leg. It may or may 
not be caused, or set in action, by extra work; or it may, when 
originating spontaneously, be encouraged in its growth by work. 
It may cease in its growth without doing any permanent mischief. 
On the other hand, the Inner hock disease commences in an in- 
flammation of the synovial membrane, proceeds tp ulceration, and 
then to caries of the bones : it is, in fact, a disease precisely simi- 
lar to the navicular joint disease, whereas spavin is very similar 
to ringbone. The navicular joint disease is allowed by veterinary 
surgeons to be almost incurable — certainly so, if it has proceeded 
to ulceration ; so the Inner hock disease would appear to be 
incurable after a certain stage. Ringbone, on the other hand, is 
manageable and within reach of cure by the iron. So is spavin. 
The Inner hock disease would obviously, like the navicular, be 
the result of over-exertion, call it concussion, or whatever else. 
If there be any truth in the philosophy of firing, it is obvious that 
it must be totally inapplicable to the navicular and the Inner hock 
diseases. Firing cures ringbone and spavin, by causing the 
taking up or stopping the growth of the bony deposit. When caries 
of the bone has commenced, firing can never replace lost bone. It 
is possible that, in the incipient stages, firing may be of use ; but 
inasmuch as the disease is not suspected until indicated by lame- 
ness, and that generally increasing, it is most likely that the disease 
will have got beyond the manageable point before surgical aid 
is required. How far these two diseases may run into each other, 
veterinary science, in its present state, does not clearly explain. 
It is remarkable that in all the cases described, pp. 304-5-6, there 
was no appearance of spavin either in the living or dead horse. 
But Mr. Percivall, after describing these two different diseases, 
p. 305, says that “ in the end both diseases change into one and 
the same morbid action of ossification,” without, as it would seem, 
adverting to the distinction of morbid deposits of bone and caries, 
or wasting of bone. In the specimens exhibited by Mr. Goodwin, 
p. 303, there was only caries. 
That a spavin affecting a joint may cause inflammation to the 
synovial membrane, which may spread inwards and proceed to 
