dian ridge. The median
ridge widens out as it passes backwards, forming the larger part of the
posterior portion of the frog. This median ridge fits into the cleft of the
plantar cushion. It serves to prevent displacement of the sensitive from
the horny frog, and has been rather aptly termed the '_Frog-stay_.'

_The Inferior Surface_ is an exact reverse of the superior. The triangular
depression of the superior surface is represented in the inferior surface
by a triangular projection, and the ridge-like frog-stay of the upper
surface is represented below by a median cleft, the _Median Lacuna_ of the
frog. The triangular projection in front of the median lacuna is the
body or cushion of the frog. It is continued backwards as two ridge-like
branches, which, at the points of the heels, form acute angles with the
bars. On the outer side of each lateral ridge is a fissure. These are known
as the Lateral Lacunae.

_The Sides_ of the frog are flat and slightly oblique. They are closely
united to the bars and to the triangular indentation in the posterior
border of the sole.

_The Base_ of the frog is formed by the extremities of its branches, which,
becoming wider and more convex as they pass backwards, form two rounded,
flexible, and elastic masses separated from each other by the median
lacuna. These constitute the 'glomes' of the frog. They are continuous with
the periople.

_The Point of the Frog_ is situated, wedge-like, within the triangular
notch in the posterior border of the sole.

4. THE PERIOPLE, OR CORONARY FROG BAND.--This is a continuation of the
substance of the frog around the extreme upper surface of the hoof. It is
widest at the heels over the bulbs or glomes of the frog, and gradually
narrows as it reaches the front of the hoof. It is, in reality, a thin
pellicle of semi-transparent horn secreted by the cells of the perioplic
ring. When left untouched by the farrier's rasp it serves the purpose, by
acting as a natural varnish, of protecting the horn of the wall from the
effects of undue heat or moisture.

CHAPTER III

GENERAL PHYSIOLOGICAL AND ANATOMICAL OBSERVATIONS

The matter embraced by the heading of this chapter will offer for
discussion many subjects of great interest to the veterinary surgeon.
Around some of them debate has for many years waxed more than keen. Of the
points in dispute, some of them may be regarded as satisfactorily settled,
while others offer still further room for inv