312 
ANATOMY OF THE HORSE. 
part encircled by the toe of the wall, against which it abuts, and 
to which it is intimately united by horny matter, the two toge¬ 
ther forming a stout bulwark of defence to those parts of the 
internal foot included between them. The points or heels are 
the two posterior salient angles received into the angular inter¬ 
vals between the outer and inner walls or bars. Although, 
naturally, the least exposed, these are the parts most subject 
to injury or pressure from the shoe, being the seat of that disease 
mistakenly called corn. The middle or centre of the sole is 
the portion more immediately surrounding the fore parts of the 
frog, and would (were the sole a regular arch) be the most ele¬ 
vated part; but, in general, we find the sole flattened hereabouts; 
the highest parts of the arch being the angles alongside of the 
bars; the lowermost, those around the toes. 
Surfaces .—Of the surfaces, the superior (as was mentioned 
before) is unevenly convex; the inferior, correspondency con¬ 
cave. The former is every where pitted, particularly about the 
heels, with numerous circular pores, running in an oblique direc¬ 
tion, the marks of which remain evident upon the inferior surface 
likewise. These pores are the impressions made in the soft horn 
by the villi of the sensitive sole, from whose orifices the horny 
matter is produced. They also form the bond of union between 
the horny and the sensitive soles, which is of a nature so strong 
and resisting, that it requires the whole strength of a man's arm 
to effect their separation—an operation of a cruel description 
that was wont to be practised in times past, under the fallacious 
notion that “ drawing the sole" was extirpating the malady. 
Thickness .—The natural thickness of the sole may be estimated 
at about one-sixth of an inch. There will be found, however, 
variations from this standard in different horses; and it will 
also very much depend on the part selected for measurement. 
The portion of the sole most elevated from the ground—that 
which forms a union with the bars—is nearly double the thick¬ 
ness of the central or circumferent parts; and next to this, in 
substance, comes the heel. I do not find that the sole “ grows 
thinner from the circumference to the centre," as has been stated 
by an author of celebrity. 
[ The Frog. 
The frog is the prominent, triangular, spongy body, occupying 
the chasm left by the inflection of the bars. 
Situation and Connexion .—The frog is fitted into the interval 
between the bars ; the three, altogether, filling up the vacuity 
in the sole, and thereby completing the circle, and establishing 
the solidungulous character of the foot. The frog extends for- 
