156 
ON THE NAVICULAR DISEASE AND SPAVIN. 
small metatarsal to that of the cannon bone, without any ac¬ 
companying disease of the bones of the hock; and this, termi¬ 
nating in ossification, may be a splent as to its nature, but is a 
spavin as to its situation. If, however, the inflammation extends 
from this cartilago-ligamentous substance to the ligaments and 
bones of the hock, and terminates there in the effusion of bony 
matter; or if the exostosis of the inner metatarsal bone itself is so 
placed as to disturb the motions of this joint, then does a spavin 
differ essentially from a splent. To elucidate this point still far¬ 
ther:—if the exostosis, instead of making its appearance just be¬ 
neath the hock, is seated about the body or lower extremity of 
the cannon, it constitutes a splent of the hind leg,—a disease, 
however, of but rare occurrence, owing to the bony deposit com¬ 
monly appearing at that part where inflammation is first ex¬ 
cited. 
u Although a spavin, at the commencement, may be confined 
to the metatarsal bones, it seldom happens that those of the hock 
do not ultimately partake of the disease ; and this will account 
for the various degrees of lameness and stiffness observable in 
that joint: indeed, we have little doubt but the internal parts,— 
the vascular lining of the joint,—become eventually diseased ; so 
that the synovia is unnatural either in quantity or quality, or, per¬ 
haps, both, to which is chiefly referable the explanation of the fact 
of spavined horses improving in their action during work. In 
almost all cases of inveterate spavin, the cuneiform bones are 
united together by a layer of ossific matter, extending upwards 
from the inside of the large and inner small metatarsals; so that 
there is no longer any motion whatever between the small bones 
of the hock and those of the leg : very commonly, also, the same 
sort of union renders the os calcis, as well as the os cuboides, fixed 
in their places.’’ 
I now proceed to Heurtrel D’ArbovaFs definition of the same dis¬ 
ease : — u We give the title of spavin to the exostosis that occurs at 
the superior internal and lateral part of the cannon bone of the 
hind leg; and we call it the osseous or callous spavin, to distin¬ 
guish it from that which is denominated the eparvin sec , or (what 
X should construe as) the imperceptible spavin . The latter 
consists in a convulsive and precipitate catch of the limb at the 
moment it is put in motion; but where no swelling is observable, 
this irregular and disagreeable action is called, in French, by two 
names, ‘ harper’ and i trousser.’ It is perceptible from the mo¬ 
ment the horse starts till he becomes, as it is commonly called, 
excited and heated by exercise, .when this catching becomes 
no longer perceptible, unless it has already existed such a length 
