256 
MANUAL OF MODERN FARRIERY. 
and deep, and of a triangular form, bounded on the sides by 
sloping prominences, which diverge from the convexity form¬ 
ing the toe of the frog, and terminate at the heels. This 
cavity is called the cleft of the frog, 
g. The frog, as also exhibited fig. 12, d , d. In its superior sur¬ 
face it is continuous, uniform, and porous, being the counter¬ 
part in form of the inferior surface, presenting only reverses, 
where the one is hollow, and the other swelling. Opposite to 
the cleft is the frog-stay , which is elevated and bounded on its 
sides by two deep channels, and a hollow of shallower dimen¬ 
sions in the front. This bold, horny elevation is admirably 
calculated to form that dove-tailed connexion with the sensitive 
foot, which greatly augments their surfaces of opposition, and 
establishes their union beyond all risk or possibility of dis¬ 
location. 
h , h The external crust, or wall; as also seen fig. 12, a , a., and 
fully described above. At the first h and i is the rounded 
portion of the heels belonging to the frog. 
/, Fig. 12, is the external surface of the sole, or the arched plate 
entering into the formation of the bottom of the hoof, and cover¬ 
ing the whole inferior surface of the foot, excepting the frog. 
No individual part requires such undivided attention as the 
sole, as regards shoeing; since the success of this mechanical 
operation chiefly depends upon the paring and defence of this 
arched horny plate. Viewed from below, the sole commonly 
presents an arch of more or less concavity. It is subject to 
vast variety in the degree of the arc; in some feet it is of 
surprising depth, and in others the arch is converted into a 
flattened surface, and yet both seem to perform equally well. 
In the hind feet the sole is generally more arched than in the 
fore, and approaches in figure more to the oval than the circle. 
Its thickness is about one-sixth of an inch. That portion 
most elevated from the ground—that which forms a union 
with the bars—is nearly double the thickness of the central or 
circumferent parts, and next to this in substance comes the 
heel. This is situate at the back part of the foot, at which 
point the crust of the hoof, instead of being continued round 
and forming a complete circle, is abruptly bent in, as will be 
seen by a reference to fig. 12, and at A, fig. 11 
