248 
NAVICUL ARTHRITIS. 
bears us out in accounting for these apparently opposite localities 
of lameness. 
But why should not the coffin suffer as well as the navicular 
joint, that entering equally into the construction of the pedestal of 
the column of the fore limb ] This shews there must be something 
more, besides the circumstance of its nethermost situation in the 
column of support, to account for the navicular joint being so fre- 
quent a seat of injury, while the coffin is, in fact, a part rarely dis- 
eased. And I cannot, myself, satisfactorily account for this but on 
the principle of frog-pressure, or, rather, frog-contraction. The 
facts already stated, of navicularthritis having become so frequent 
a disease since frog-pressure became so fashionable in the practice 
of shoeing, compared to what we have reason to believe it was be- 
fore, and of its invariably happening in feet presenting sound pro- 
minent frogs, militate more strongly in favour of this opinion : at 
the same time, there may be something in causation ascribable to 
the circumstance of the navicular joint, as we denominate it, being 
one which owes its formation to the main tendon of the fore leg in 
connection with bone. We know that one of the uses of the frog 
is to serve as a stop or stay to the foot; and where horses in action 
are suddenly pulled up, or in their descent from leaps have to sus- 
tain themselves by firm footing upon the ground, they throw them- 
selves at once upon their heels and frogs, and in such efforts and 
shocks, no doubt, frequently do mischief to the navicular joints, 
and particularly when their hoofs, from standing in the stable or 
lack of moisture, have become hard and dry and inelastic. In the 
act of standing for any length of time, and in any efforts that may 
be required to sustain that posture, it would be the coffin-joints, 
were it not for the lamince, that would suffer; whereas, the former 
being relieved from pressure as well as concussion by the latter, we 
find horses that are compelled to fatiguing efforts of standing, par- 
ticularly in warm situations, not contracting disease of the coffin- 
joint, but of the laminae — laminitis, or “fever in the feet,” as the 
malady is called ; and this is a complaint which on many occasions 
has proved epidemic, and on board of ship in particular. 
Although predisposition may, and probably does, exist equally 
in either foot, it is a rare circumstance for a horse to be attacked 
with navicularthritis in both feet simultaneously, as rare as it is 
for laminitis to be known to confine its attack to one foot. This 
difference between two diseases affecting the foot admits of ready 
and satisfactory explanation in the fact of the one having the ex- 
citing cause applied equally to both feet, while in the other — navi- 
cularthritis — the excitant will rarely operate but in one, either 
from the circumstance of one foot being commonly made freer or 
stronger use of than the other, or from the application of the cause 
