OX HOCK LAMENESS. 
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lines extending along the articular cartilage of both bones in the 
direction in which the bones move, the depression in one cor- 
responding to a ridge in the other, unless, as in some rare and 
severe cases, some portion of cartilaginous or bony matter has 
been detached, and given rise to deepened ridges in both; and 
these ridges may be multiplied in an indefinite degree, both in 
number, depth, and extent. In some cases the cartilage becomes 
abraded, and the bone polished by friction, like a piece of ena- 
mel; then pathologists say the “ porcelainous deposit” has 
taken place : that is, they suppose that a peculiar secretion 
has been deposited there to resist the friction. 
It will be found, however, that this is merely the effect of 
friction, which is alone proved by rubbing one bone with suffi- 
cient force against another, when the same appearance is readily 
produced; and further, if the diseased alteration of the direction 
of the motion of the joint is continued, it will be found that this 
polish of the bone becomes, at length, worn out, and the can- 
cellated structure is exposed ; yet all this goes on before ulcera- 
tion takes place, and it is only in the last stages, and in cases 
where there is great lameness, that ulceration does take place : 
indeed, so rare is it, that I am not satisfied that I have yet seen 
a case where ulceration could be said to have taken place in this 
joint, unaccompanied by an “open joint,” or some external 
injury. 
In all cases of “ bog spavin” I have stated that there are more or 
less marks of friction found on dissection ; but this is, in many 
cases, not attended by lameness, because what we are in the habit 
of considering as constituting the disease , is the means which 
nature has provided to diminish the friction, and to prevent bad 
consequences ; the accumulation of synovia serving to lubricate 
the joint more completely than the ordinary quantity would have 
done ; consequently in many cases we find a horse with “ bog 
spavins” and “ thoroughpins” going quite sound, and con- 
tinuing to do so for years. I should here distinguish (were I 
writing upon all the diseases of the hock) the occurrence of 
“ thoroughpin” without “ bog spavin,” from “ thoroughpin” 
occurring with “bog spavin;” because some may say, on ex- 
amining hocks with “ thoroughpin,” that they have not found 
what I have described; but it will be understood that, wherever 
there is “ bog spavin ” there we shall find friction. It will further be 
found that, as the friction is increased by increase of work, there 
will be a proportionate increase of synovia, until, as in some 
cases, where the labour is excessively severe, lameness takes 
place, and the capsular ligament is distended and thickened so 
as to produce pain and interruption of motion, in a great mea- 
