ON HOCK LAMENESS. 
531 
work, and the lameness returns. What takes place in the hock? 
The synovial membrane on the borders of the cavity formed by 
the previous absorption becomes bruised and inflamed, ulceration 
again commences, and perhaps nearly the whole of the ridge of 
the tibia becomes denuded of its cartilage and synovial mem- 
brane. Now, I would ask, is there any thing incorrect in the 
external symptoms 1 have given of these obscure cases? and is 
there any thing irrational in the theory on which I have endea- 
voured to explain them ? It will be seen that I do not, by any 
means, contend that the degree of lameness manifested by the 
horse is in proportion to the extent of absorption or ulceration exist- 
ing in the joint; far from it. With an increase of absorption there 
may be a diminution of lameness, in consequence of the subsiding 
of the inflammation which, indeed, is the real cause of the pain 
that produces the lameness. Thus, we may examine a hock 
with very considerable abrasion of surface that had been attended 
by a much less degree of lameness than that of another hock 
presenting but a comparatively small abraded spot; but the 
latter would have been connected with a much greater degree of 
inflammation. 
Mr. Dick seems to dispute the theory of pathologists — that 
when a bone exposed to great friction presents a polished appear- 
ance, such appearance is occasioned by the deposition of a pecu- 
liar secretion to resist this friction. Mr. D. explains it mechan- 
ically, and says “ it is simply the effect of friction, as may be 
shewn by rubbing two bones against each other, when the same 
effect is produced.” Now, with all due deference to the 
authority of Mr. Dick, it appears to me that his explanation of 
the matter is not consistent with sound views of physiology in 
thus comparing together dead substances with living ones. 
The polishing the surfaces of wood or dead bone by friction 
is produced by rubbing down the irregularities and condensing 
the surface by pressure ; but if the living bones were exposed to 
the same degree of friction, irritation would be produced, the 
periosteum would be inflamed, and perhaps a sloughing of the 
bone would occur, as often takes place in the under jaw, when 
the bars are too severely pressed by the bit, or in other bones 
when a severe contusion has been received. A dead bone remains 
the same substance for hundreds of years ; but the living bone 
is perpetually changing its material ; it becomes harder or 
softer at different periods of life ; and is closely adapted to the 
wants of the animal. Whatever alteration, therefore, takes 
place in its substance arises from the absorption of one portion 
of its composition and the deposition of another, and not from 
the mechanical effects of friction, as in a dead substance. The 
