314 
ANATOMY OF THE HORSE. 
The solid wedge-like portion of horn in front of the cleft, ex¬ 
tending from it to the point of the toe, has been observed by 
Mr. Clark to exhibit, in the natural foot at its full growth, “ a 
considerable bulbous enlargement/’ which, by way of distinction, 
he calls the cushion of the frog. On making a perpendicular 
section of the foot, Mr. C. finds this part is situated “ nearly 
opposite or under the navicular bone.” It does not appear 
(according to this author) that this “ rotundity, or swell of the 
frog,” is ever reproduced, after it has once been annihilated by 
the knife of the smith. 
The superior Surface of the Frog, every where con¬ 
tinuous, uniform, and porous, being the counterpart in form of 
the inferior, presents us with nothing but reverses : wdiere the 
one is hollow or depressed the other rises into swells and emi¬ 
nences, and vice versa. This accounts for our finding the part 
opposite to the cleft elevated into a conspicuous eminence, 
bounded on its sides by two deep channels, and a hollow of 
broader but shallower dimensions in the front. To this central 
conical elevation Mr. Clark has given the name of frog-stay , 
from some novel notions he entertains of its physiology. Such 
a bold promontory of horn rising in the middle of broad and 
deep channels is well calculated to form that dovetailed sort of 
connexion with the sensitive foot, which greatly augments 
their surfaces of apposition, and establishes their union beyond 
all risk or possibility of dislocation. It is a part which (as far 
as my observations on it have extended) grows and becomes 
developed together with other parts of the foot; and one that is 
apt to vary in its relative volume in different feet. In front of 
the frog-stay, the lateral borders, bounding the hollow in the 
middle, describe a waving line, which, near half-way to the 
point of the toe, exhibits a dip or depression: this marks the 
impression of the navicular bone, and is the part immediately 
opposite to the “ cushion of the frog,”—a coincidence important 
to be borne in mind, as tending to throw some light on the nature 
of this new-christened structure. 
THE SIDES are the parts by which the frog establishes its 
union with the borders of the triangular vacuity in the hoof into 
which it is admitted. Along their superior borders they are 
transversely lamellated, or rather indentated, in order that they 
may be fitted to the internal surfaces of the bars, which exhibit 
a similar structure. 
The Commissures are the two deep triangular-shaped hollows 
between the bars and the sides of the frog, it being only the 
superior borders of these parts that are engaged in their union : 
their broad unattached parts, below, form the boundary walls 
