NAVICULAR DISEASE IN THE FEET OF HORSES. 25 
solidity, compactness of fibre, and an unusual appearance of 
strength, being its characteristics; the heels are high, the sole 
strong, and the crust thick, particularly at the toe : but it some¬ 
times loses its due proportion of obliquity, and becomes rather 
more upright than natural. There is, however, a more certain 
indication which usually presents itself; viz. a falling in of the 
inside quarter, or slight indentation about the middle of the 
crust towards the heel: this sometimes assumes the appearance 
of a stricture, in a slight degree, all round the crust, and occa¬ 
sionally two or three of these strictures or rings are apparent. 
Thus much may be observed without the removal of the shoe; 
but the protrusion of the frog within the foot (adverted to in my 
former paper), together with the morbid concavity of sole, may 
not be discoverable till the drawing-knife has been extensively 
employed, not only on the sole, but in excavating those channels 
or commissures on each side of the frog, between it and the bars. 
An inordinate growth of sole and other parts of the foot, by pre¬ 
senting prominent surfaces, too often conceal from our view the 
encroachments and consequent diminution of the horny cavity. 
This may be compared to the deceptive wine-bottle commonly 
used : while standing on its basis, it appears plausible enough as 
to its capacity; but when inverted, a most lamentable protrusion 
is discoverable in its breech, which proves to be a preparation of 
flint instead of the grape. The outer surface of the sole of such a 
foot sometimes resists the drawing-knife like a stone, from its 
excessive hardness. 
I contend, that the navicular joint disease is generally, though 
not always, preceded by one of these contractions of the horny 
box. It may be the general contraction first described, or this 
occult partial contraction. 
There will be found an ascent of the coffin bone within the hoof, 
occasioned by the contraction: it is the elevation of this larger 
foot bone which necessarily puts its small companion, the navicu¬ 
lar bone, in jeopardy. I say, necessarily; because they are so 
closely knit together by ligaments, that the smaller bone bears 
the resemblance of a process to the larger. 
The occult contraction is chiefly to be dreaded for these obvi¬ 
ous reasons : it occasions a more partial pressure, is frequently 
more- rapid in its progress, and, by operating principally from be¬ 
low upwards, has a greater tendency to elevate the coffin and 
navicular bones. 
On the contrary, the simple or general contraction is a more 
lateral compression, and so slow in its encroachment, that it 
affords, perhaps, one of the most striking instances in the animal 
creation of Nature’s resources, when contending against hostile 
VOL. III. k 
