452 
OBSERVATIONS ON SOUNDNESS. 
and is characterised for its lightness, being extremely porous, 
and forming an arch, which is so well adapted for the support 
of weight. From its situation and connection with the horny 
covering, it may be assumed that it remains almost in a passive 
state under all circumstances, if not, its movements must of 
necessity be extremely limited. It would appear that it more 
particularly serves the purposes of support, maintaining 
the form of the foot, and affording attachment to other as 
well as to more movable structures, situated within the hoof. 
The heels of this bone demand especial attention, as it is these 
parts of the bone which have so much influence in the produc¬ 
tion of corn. My conviction is that, as a general rule , some 
alteration must have taken place in the growth of the heels 
of the bone before corn is manifest, or undue pressure, which 
is so frequently observed, would cause the disease oftener than 
it is met with in our patients. I am fully aware, however, 
that th e first set of shoes placed upon a young animal is pro¬ 
ductive of extravasation of blood in the heel; this is more 
particularly the case when the subject is shod by a country 
shoer, or other inexperienced workman. The navicular bone 
is described as being something like a weaver’s shuttle; it is 
an irregular bone, divided into borders and extremities. It 
enters into the composition of the coffin-joint, as well as into 
that forming the important joint which gains its name from 
the bone. It is viewed as a sesamoid bone. It is the 
inferior surface of the bone, which more especially demands 
our attention in the examination of a horse as to soundness. 
I do not see that the coffm-joint is so entirely free from 
disease as some persons are desirous of making us believe : 
by some it is asserted that no such thing exists as lameness 
in the coffin-joint. I have dissected some well-marked cases 
of coffin-joint lameness, when I have found that the whole 
synovial surface has been extensively diseased. When we 
view the situation and position of the pedal and coronal bones, 
together with the solidity of the latter, and the constant 
pressure exerted upon the joint, we shall feel somewhat sur¬ 
prised (looking at it mechanically) that it so often escapes 
injury. We must feel convinced that its power of resistance 
resides in its vital properties chiefly. 
The navicular joint is a name in the mouth of every pos¬ 
sessor of anything in the shape of a horse. It owes its 
notoriety to the late Mr. James Turner, who, I believe, 
directed the profession to navicularthritis. The modern 
Babylon and other similarly paved cities are doubtless 
well supplied with cases of this sort. If concussion is 
the cause of navicular disease, we should look for it 
