252 
MANUAL OF MODERN FARRIERY. 
as the ass, above all other animals, for the service of man, 
in short, had the hoof of the horse been cleft, he would 
have been incapacitated for many of the useful departments 
of his employment; and a correct knowledge of the struc¬ 
ture of every part of the foot is indispensably necessary to 
render us scientific overseers of the farrier’s art. 
The crust is that portion which reaches from the termi¬ 
nation of the hair to the ground. Its depth is greatest in 
front, and is denominated the toe ; it is more shallow at the 
sides, which are called the quarters, and still less behind, 
which is termed the heel. When the sole is placed on the 
ground, the front exhibits an angle of about forty-five 
degrees, differing, however, considerably in many horses to 
the extent of the angle. But a healthy and well-formed hoof 
very nearly approaches what we have stated, that is, a fourth 
part of a semicircle. With a greater degree of obliquity, it 
is said the crust has “ fallen in,” and when the sole is too 
flat, and is said to be pumiced, or convex ; and if the front be 
more upright than the above angle, it is the proof of a con¬ 
tracted foot with the sole too concave. When the crust is 
deep at the heel, it is a foot liable to contraction, thrush, 
sand-crack, and inflammation. The pastern will be found 
too upright, and the horse will have a bad and unpleasant 
action. If, on the other hand, the crust diminishes too 
rapidly from front to back, and the heels are low, this 
is always accompanied by too great obliquity of the pastern, 
producing a weakness in the joint, and liability to sprain of 
the back sinew, described at page 117. The foot itself will 
be weak, and have a general tendency to that hidden lame¬ 
ness called “the navicular-joint disease,” particularized at 
page 165. 
The general thickness of the crust in front is somewhat 
more than half-an-inch, becoming gradually thinner towards 
