‘ 
360 AGRICULTURAL REPORT. 
17,*) through which blood-vessels and nerves are abundantly distributed 
to ‘the soft and sensitive tissues that cover it. The wings extend directly 
backward from the body, and support the lateral cartilages. Upon its 
superior aspect is a smooth and concave surface, placed obliquely to the 
body of the bone for articulation with the middle phalanx or coronet- 
bone. Applied to the joint between the coronet and coffin bones, pos- 
teriorly, and lying in the concavity of the coffin-bone, is a small bone of 
peculiar shape—the navicular, (Fig. 14, “3.”) This is a sesamoid bone, 
being contained in, or attached to, the jeodea of the deep flexor. It is 
from two to two and one-half inches long, three-fourths of an inch in 
width at its widest part, and half an inch in thickness. Two surfaces 
of this bone, meeting in front at an acute angle, are covered with earti- 
lage and synovial membrane. The posterior surface is rough for the 
attachment of the tendon of the deep flexor. 
Attached to the upper edge of the wings of the coffin-bone are the 
two lateral cartilages. They are irregular in form, elastic, and ex- 
tend backward, giving form, substance, and elasticity to the heel upward 
as high as the pastern joint, and forward, so that only the width of the 
great extensor tendon of the foot separates them. In fact, the fibrous 
investment of the tendon is attached to these cartilages. 
This widely distributed cartilage may be observed passing d@ownward and surround- 
ing on every side the rough and knotty extremities of the heels of the coffin-bone, 
entering and filling up its si inuosities and taking strong attachment to these processes. 
It then extends horizontally inward, passing over the horny sole and bars, and, meet- 
ing the sides of the sensitive frog, intimately unites with ‘it, forming one inseparable 
mass and filling together the whole interior area described by the sides of the coffin- 
bone. The upright. or lateral portion of the cartilage forms with the horizontal por- 
tion passing inward a right angle, thus making together a hollow space or recepta- 
cle at the back of the coffin-bone that contains the spongy, elastic stuffing of the 
heels, together with the tendons, vessels, and nerves passing through the s sole of the 
foot. The upper surface of the horizontal process of cartilage is full of scabrous ele- 
vations and depressions that defy dissection, among which is found a quantity of gel- 
atino-ligamentous tissue. Beneath, or to the under surface of this horizontal layer, 
the sensitive sole and bar are adherent. As it approache s the frog or center of the foot, 
it loses its cartilaginous nature and becomes coriaceous, or rather ligamento- -coriaceous, 
in texture, agreeing in this with the internal frog.—(C yclop. Anat. and Phys.) 
The horizontal portion or process of the cartilage, known by veteri- 
nary writers as the stratiforin process, is of greater thickness and sub- 
stance than the other parts. It is also of coarser grain and more elas- 
tic nature. Both portions together communicate the general boundary 
of form to the lateral, posterior, and inferior parts of “the foot. When 
the bars and the frog are thrust upward by pressure from without, they 
are acting against this same horizontal flooring formed by the cartilage 
and the frog, and are met by the depression of the bones of the foot’ 
forced down by pressure of the weight of the animal. The whole can 
then dilate exteriorly along with the posterior and more elastie parts of 
the hoof. 
Several important purposes are answered by this extensive distribu- 
tion of elastic fibro-cartilage—tirst, the interposition of a layer of elas- 
tic tissue between the hard hoof and the hard bone prevents shock and 
jar to the body as the foot strikes the ground in walking or running; 
secondly, the coffin-bone not extending posteriorly much beyond the 
middle of the foot, except by its projecting wings, 2 large portion of the 
hinder part of the foot is made up of soft elastic earti lage instead of 
bone, materially breaking the force of the blow of the tre ead ; thirdly, 
the general distribution of elastic cartilage serves to equalize the pres- 
* Fig. 17.—Section of the coffin-bone showing the numerous canals for blood vessels 
and nerves. 
