58 
THE NAVICULAR DISEASE, OR CHRONIC 
any other part of the internal foot, I am induced to consider them 
as mere effects arising out of the navicular disease ; and more par¬ 
ticularly, as there are far more groggy feet without the slightest 
ossification of the ligaments of the navicular bone than with 
them. In short, I think those who have called the navicular 
disease an ossification of the joint, have erred very much; foi it 
is any thing but an excrescence or exostosis, a great loss or ab¬ 
sorption of bone being, in fact, the malady : yet I must acknow¬ 
ledge that I have occasionally seen, in recent cases, a tew small 
eminences on the inferior surface of the centre of the bone, about 
the size of millet seeds; but, in the progress of the disease, not 
only would they have been absorbed by friction, but that poition 
of bone itself on which they appeared would also have been car¬ 
ried away by ulceration. . < . . , 1 
The first pernicious consequence of contraction 1 have invariably 
observed to have been a very gradual displacement of the navicu¬ 
lar and coffin bones : they ascend within the hoof; but more par¬ 
ticularly the navicular bone and heels of the coffin bone. is 
deviation from the natural position is not only observable on c is- 
section, but is quite as apparent in the living foot, by paring 
down to the quick those commissures or channels between the 
bars and frog which will be found so morbidly deep, and take so 
much time for the knife to reach the quick, that a by-stander, ig¬ 
norant of the nature of it, would be induced to remark that such 
a horse was devoid of blood in his foot. Exactly m proportion to 
this morbid concavity externally is the morbid convexity inter¬ 
nally ; and thus with a fixed ascent of the frog an unnatural arch 
is formed, which, by absorption of the soft elastic parts of the 
frocr, becomes a rigid protuberance, and is the rock oj dangei , 
on which I am daring enough to assert that more valuable horses 
have been struck with foot lameness than ships have been wrecked 
on the rocks of the ocean . This protrusion of frog within the foot 
is accompanied by an undue concavity of sole and rigidity of the 
bars. The navicular bone lies transversely across this projecting 
part of the frog, with the long flexor or perforans tendon passing 
under, and, by articulating with the bone, forms the navicular joint. 
The joint receives its share of the superincumbent weight from 
the small pastern bone, and with violence in the ratio of rapidity 
with which the animal moves, and is required to yield and de¬ 
scend in proportion to the impetus. It should also be lemem- 
bered, that it is placed immediately under the centre of weight, 
which is conveyed in a perpendicular direction. . 
The occult or partial contraction abruptly opposes the naviculaj 
bone in its descent, and thereby crushes or braises the delicate 
svnovial membrane lining the joint, which suffers a mechanical 
