ON HOCK LAMENESS. 
435 
discussion ; but now that I am only a nominal assistant, I have 
less scruple in entering on a debate, or rather, pointing out an 
error into which I am inclined to think Mr. Spooner has fallen, 
by describing what is a healthy structure as a diseased one. 
I do this the more readily, because Mr, Spooner has said that 
“the existence of this disease ought either to be acknowledged or 
denied and I now decidedly deny that what he describes is a 
diseased alteration of the structure. What is it, then ? will un- 
doubtedly be asked ; and my answer is — the natural and neces- 
sary construction of the joint. The cavities corresponding to 
each other, and having the appearance of excavations, are sulci, 
containing the synovia to supply the extended articular sur- 
faces, and which is rendered necessary by the peculiar sliding 
motion which the bones have on each other in that joint. 
They are, in fact, the “ oil wells or cisterns,” to retain a sup- 
ply of synovia, and to prevent the friction which Mr. Spooner 
supposes to be the cause of them, and are to be found in one 
form or another in all healthy hock joints, and in every true 
joint of the body. In many cases, however, they do not appear 
in the centre of the joint, but are placed at the side, and they 
have the appearance of a notch within the boundary of the syno* 
vial membrane on the edge of the articular surface, many of 
which never attract notice, but are, nevertheless, as important 
as a process is for the leverage of a muscle, or a foramen or notch 
for the transmission of a nerve or vessel, or any other organ. 
In other cases, the cavity formed by two bones forming one 
portion of a joint which is moved upon by another, produces the 
same effect — the coffin and pastern joints for example ; they are, 
in fact, as necessary in the animal machine, as similar cavities 
are in the bushes, or on the axle of the wheels of any well- 
formed machinery ; and if my observations are correct, are 
found commonly in the situation Mr. Spooner describes in the 
best formed hocks. 
It must not be supposed that I am contending that friction, 
or even ulceration, does not take place in the articulation formed 
by the tibia and astragalus ; quite the reverse : there, is perhaps, 
nothing more common than to observe the effects of friction on 
the articular surfaces of these bones ; but then it is quite dif- 
ferent from what has been described by Mr. Spooner, and is 
always attended by symptoms which sufficiently distinguish it 
even prior to death ; and those symptoms the reverse of what 
Mr. Spooner points out. In all cases of “ bog spavin” this exists 
in a greater or less degree. In those where there is but a slight 
enlargement or distention of the capsular ligament without ten- 
sion, there will merely be found slight grooves or semicircular 
