ANATOMY AND PHYSIOLOGY OF THE HORSE'S FOOT. 183 
tions in form and structure, as does likewise the front surface 
of the bone, which is disposed to become greatly modified 
with age and the influence of external causes. 
In youth, the wings, or, as they have been termed, the 
lateral angles of the pedal bone, are short, thick, and rounded, 
with the basilar process extending much beyond the retrossal 
process beneath it ; indeed, the latter is scarcely developed, 
and the preplantar fissure separating these two processes is 
in reality nothing but a simple groove throughout its course, 
whereas in the representation we have given of the pedal 
bone (fig. 4,/), it has become converted into a foramen at its 
posterior part. The alteration and development the wings 
of the bone gradually undergo would appear to be due, for 
the most part, to the progressive changes that take place in 
the texture of the complementary or lateral cartilages imme- 
diately surrounding them — changes which result in the more 
or less complete ossification of these bodies. 
The pedal bone of the hind foot only differs from that of 
the fore foot, which we have been describing, in its being 
generally smaller, less inclined laterally, and more particularly 
on its inner face ; the sole is more concave ; the narrowness and 
length of the bone, especially towards the toe, are very 
noticeable ; while its tissue is not so compact, the fore limb 
being the weight-sustaining column. 
Tig. 6. 
Navicular Bone. a. Inferior face with its transverse ridge, h. Supero- 
anterior face for articulation with the small pastern bone, showing on 
each side vascular canals for the passage of blood-vessels. 
The Navicular Bone (fig. 3, d ; 6, a, b ) . — The navicular 
bone is so named from its resemblance to a small boat 
[navicula) when laid on its lower border. It has also been 
designated the “ small sesamoid” from its supposed likeness to 
a sesamum seed ; “ nut bone” because of its being buried 
deeply within the foot; and “ shuttle bone,” as it not only 
looked like a weaver's shuttle, but lay across the axis of the 
limb. 
It derives very much of its importance from the part it 
