468 
W. J. MARTIN. 
horses running wild on the pampas of South America it is a 
very rare sight to see one affected with spavin. 
During the several years in which I have been engaged in 
the study of the osteology of fossil equidae I have examined the 
hock bones of fossil horses from nearly all parts of the world 
without being able to discover any trace of a disease among 
them similar to spavin in the domestic horse. It is true that 
these fossil horses are of a distinct genera to that of the domes¬ 
tic species, yet the bones of the hock are almost identical with 
those of the domestic animal. More especially is this true of 
Hipparion. 
From a close study of the pathology of spavin it will be 
seen that it often becomes a difficult matter to ascertain the true 
cause of spavin. In the idiopathic form, heredity undoubt¬ 
edly plays an important part, because there is probably no do¬ 
mestic animal so prone to morbid ossific enlargements as the 
horse. In my opinion the most common cause of spavin is a 
defective anatomical conformation of the bones of the entire 
limb as well as those of the tarsus, and in tracing the cause of 
spavin lameness we should view the limb as a whole rather 
than at any one point. We should note the formation of the 
muscles of the limb, the manner in which they perform their 
functions, as well as their relation to the bones of the limb. In 
a word, take a generalized view of the whole mechanical con¬ 
struction of the diseased lee. 
In examining a hock affected with spavin, we notice in the 
majority of cases a peculiar rounded form of the superior head 
of the large metatarsal bone ; this is anomalous, and gives to 
the scaphoid and cuneiform bones the appearance of being top- 
heavy. We almost invariably find such joints the seat of 
spavin. In the bent or “sickle hock,” the powerful action of 
the extensor muscles of the limb, when the animal is subjected 
to hard and fast work, will, by the great pressure and contrac¬ 
tion on the articulating surfaces of the bones and ligaments, 
excite ostitic inflammation. Some pathologists claim that 
spavin is due to incomplete formation of the bones of the hock, 
