SURGICAL TREATMENT OF THE DISEASES OF THE HOCK JOINT. 
25 1 
ness is that produced by 3. mechanical interference with the 
function of the tendon, due to the presence of the bone tumor. 
In this case the animal may not warm entirely out of his lame¬ 
ness, but will improve on exercise. In addition to the bone 
tumor as a cause of lameness in chronic spavin, we may have an 
ulceration of the articular surface of the true hock joint, or the 
tibio-astragaloid articulation. With such a complication the 
lameness is permanent, persistent and continuous; the lameness 
is more severe than in what is known as inter-articular spavin, 
or arthritis of the cuneiform bones. The continuous severe 
lameness, with marked atrophy of the muscles of the croup, 
should enable us to make a diagnosis of this probable complica¬ 
tion, and permit us to avoid the mortification of failure, which 
would be the inevitable result of an attempt at treatment. 
This hurried and imperfect review of the different varieties of 
spavin lameness and lesions which cause them, brings us up to a 
consideration of the causes producing these lesions. 
Causes .—In a general way it may be said that any cause 
capable of producing an inflammation of the bones or other 
tissues of the hock may be the cause of spavin. These causes 
may act as forcibly on the articular surface of the bones as on 
the external or periosteal surface. The pressure sustained by 
the hock joint increases in proportion to a diminution of its 
width. When the hock is narrow, thin and clean, the cuneiform 
bones must sustain more weight to the given suiface area than 
when the hock is full, wide and well developed, from wnich it is 
seen that a narrow hock especially predisposes to inter-articular 
spavin. Certain kinds of work also predispose to this condition; 
animals used for running, jumping and saddle work generally 
are more prone to develop this disease, because in galloping 
the posterior extremity with which he leads caiiies the entire 
weight of the horse and rider at a certain period of the pace. 
Spavins developed under such an influence must be essentially 
articular, an arthritis always developing before the appeal ance 
of a bone tumor. 
A narrow hock, by the action of an entirely’ different median- 
