ON HOCK LAMENESS. 
535 
cartilage, and polished ; another part, with an open sulcus, and 
in other parts circumscribed, pale, opaque spots from absorption of 
the perichondrium, and which would, if the animal had lived, 
become sulci ; and in a specimen of these lesions now before me, 
the convex ridge of the tibia, and the corresponding furrow in 
the astragalus, possess a perfectly smooth covering of cartilage. 
Denusion and absorption of cartilage are occasionally found in 
the astragalus joint of those hocks possessing ossific spavin, con- 
sequent on the change of position of the joint; and they some- 
times take place in old subjects, as the only morbid condition of 
the hock, and unaccompanied by lameness. 
I agree with Mr. Spooner in the occurrence of these lesions ; 
but I differ with him in considering them the common cause of 
obscure lameness of the tarsus. I do not deny the possibility of 
it being so incidentally ; but from my own experience I believe 
it comparatively rare. When the lameness is in this joint, it is far 
from being obscure; it is the true hock-joint, and far the most 
extensive of the seven articulations of the tarsus : it possesses the 
greatest surface of synovial membrane, which, unlike the fibro- 
ligamentous and fibro-cartilaginous structures, readily inflames ; 
so that if inflammation occurs to the joint, if not primarily, it is 
secondarily and quickly, the seat of it : the increased secretion 
of synovia soon distends the capsular ligament, and the joint 
is enlarged. 
In reference to the true seat of occult lameness of the hock, 
we shall not trace it to any definite spot exclusively ; it may be 
in one or any of the six remaining articulations. If any of their 
synovial membranes are inflamed either primarily or secondarily, 
their capsular ligaments will not allow of sufficient distention to 
be detected externally, and in this membrane will be found the 
true seat of that pain which is the cause of the occult lameness of 
the tarsus. Fibro-ligamentous and fibro-cartilaginous structures 
of joints rarely take on acute inflammation: it is generally more 
tedious in its progress, and so indistinct in phenomena as to be 
easily overlooked. They are structures much less vascular, much 
less sensitive, than the synovial membrane ; and we have daily 
proofs of ossification and even anchylosis taking place in the 
minor articulations of the tarsus unaccompanied by lameness. 
In cases of acute lameness, without any enlargement, I have 
found, on dissection, excavations in the head of the metatarsus, 
and also in the cuneiform resting upon it ; but I have considered 
it a secondary lesion ; and in this case the synovial membrane, 
highly inflamed, was evidently and unequivocally the seat of pain. 
