remarkable animal; not least so in the fact
that it presents us with an example of one of the most perfect pieces of
machinery in the living world. In truth, among the works of human
ingenuity it cannot be said that there is any locomotive so perfectly
adapted to its purposes, doing so much work with so small a quantity of
fuel, as this machine of nature's manufacture--the horse. And, as a
necessary consequence of any sort of perfection, of mechanical
perfection as of others, you find that the horse is a beautiful
creature, one of the most beautiful of all land-animals. Look at the
perfect balance of its form, and the rhythm and force of its action. The
locomotive machinery is, as you are aware, resident in its slender fore
and hind limbs; they are flexible and elastic levers, capable of being
moved by very powerful muscles; and, in order to supply the engines
which work these levers with the force which they expend, the horse is
provided with a very perfect apparatus for grinding its food and
extracting therefrom the requisite fuel.

Without attempting to take you very far into the region of osteological
detail, I must nevertheless trouble you with some statements respecting
the anatomical structure of the horse; and, more especially, will it be
needful to obtain a general conception of the structure of its fore and
hind limbs, and of its teeth. But I shall only touch upon those points
which are absolutely essential to our inquiry.

Let us turn in the first place to the fore-limb. In most quadrupeds, as
in ourselves, the fore-arm contains distinct bones called the radius and
the ulna. The corresponding region in the Horse seem at first to possess
but one bone. Careful observation, however, enables us to distinguish in
this bone a part which clearly answers to the upper end of the ulna.
This is closely united with the chief mass of the bone which represents
the radius, and runs out into a slender shaft which may be traced for
some distance downwards upon the back of the radius, and then in most
cases thins out and vanishes. It takes still more trouble to make sure
of what is nevertheless the fact, that a small part of the lower end of
the bone of the horse's fore-arm, which is only distinct in a very young
foal, is really the lower extremity of the ulna.

What is commonly called the knee of a horse is its wrist. The "cannon
bone" answers to the middle bone of the five metacarpal bones, which
support the palm of the ha