156 ANATOMY AND PHYSIOLOGY OF THE HORSe’s FOOT. 
the points of the heels form an acute angle with the bars, 
leaving a cavity on each side known as the “ lateral lacunae.” 
The “ cleft,” or middle lacuna, is a wide space between the 
branches corresponding to the stay. In an unpared frog in a 
sound state this space is wide, firm, and rather shallow, and 
shows no narrow fissure at the bottom. 
The sides of the frog are flat and slightly oblique ; they 
are closely united to the bars and the indentation in the 
centre of the sole ; and so firm is this union that maceration 
in water for some months is necessary to dissolve it. The 
portions that are unattached aid in forming the angular 
spaces or commissures we have named the “ lateral 
lacunae.” 
What is termed the “ base of the frog” is formed by the 
branches becoming wider ajid more convex at their extremi- 
ties, so as to offer two prominences or bulbs, that expand on 
bending round or embracing the flexures of the wall, to 
constitute the “ glomes” of the frog. From these points 
they continue their course as a thin band around the upper 
part of the wall. 
The point of the frog reaches the centre of the sole, from 
which, in the unmutilated condition, it rises in an obtuse 
point. Around this point a narrow channel courses from the 
one commissure to the other. 
The frog, as a whole, is not so thick as the sole. Its 
thinnest parts are its sides, especially where it joins the bars. 
It is, too, composed of softer and more elastic horn than the 
sole, but this horn is much finer in texture. Like the sole 
and wall, its layers are harder and more resisting as they 
recede from the living tissues, and this hardness and resist- 
ance is increased in proportion as the organ is allowed to 
perform its natural function. The frog-stay is composed of 
denser horn than is found elsewhere in the frog. Its colour 
is usually darker than the other parts of the hoof when 
these are coloured ; even in white hoofs it has a yellowish 
tinge. Its structure is fibrous, like the sole and wall, and its 
fibres have in general the same direction, though they are 
much finer and more compact. 
The periople — The “ Periople” (7 repi, around, 07 tXjj, hoof), 
perhaps better known as the “ coronary frog-band,” from its 
being a continuation of the substance of the frog around the 
upper part of the hoof or coronet, completes our description 
of the external aspect of the hoof. Commencing our ex- 
amination at the heel, bulbs, or glomes of the frog, we see 
this body arising as a gradually narrowing band that encircles 
and covers the upper border of the wall around its sides and 
