Lectures and Essays | Page 3

whole
of the plant world, and the whole of the animal world.
Few animals can be more familiar to you than that whose skeleton is
shown on our diagram. You need not bother yourselves with this
"Equus caballus" written under it; that is only the Latin name of it, and
does not make it any better. It simply means the common Horse.
Suppose we wish to understand all about the Horse. Our first object
must be to study the structure of the animal. The whole of his body is
inclosed within a hide, a skin covered with hair; and if that hide or skin
be taken off, we find a great mass of flesh, or what is technically called
muscle, being the substance which by its power of contraction enables
the animal to move. These muscles move the hard parts one upon the
other, and so give that strength and power of motion which renders the

Horse so useful to us in the performance of those services in which we
employ him.
And then, on separating and removing the whole of this skin and flesh,
you have a great series of bones, hard structures, bound together with
ligaments, and forming the skeleton which is represented here.
(FIGURE 1. Section through a horse.
FIGURE 2. Section through a cell.)
In that skeleton there are a number of parts to be recognized. The long
series of bones, beginning from the skull and ending in the tail, is
called the spine, and those in front are the ribs; and then there are two
pairs of limbs, one before and one behind; and there are what we all
know as the fore-legs and the hind-legs. If we pursue our researches
into the interior of this animal, we find within the framework of the
skeleton a great cavity, or rather, I should say, two great cavities,--one
cavity beginning in the skull and running through the neck-bones,
along the spine, and ending in the tail, containing the brain and the
spinal marrow, which are extremely important organs. The second great
cavity, commencing with the mouth, contains the gullet, the stomach,
the long intestine, and all the rest of those internal apparatus which are
essential for digestion; and then in the same great cavity, there are
lodged the heart and all the great vessels going from it; and, besides
that, the organs of respiration--the lungs: and then the kidneys, and the
organs of reproduction, and so on. Let us now endeavour to reduce this
notion of a horse that we now have, to some such kind of simple
expression as can be at once, and without difficulty, retained in the
mind, apart from all minor details. If I make a transverse section, that is,
if I were to saw a dead horse across, I should find that, if I left out the
details, and supposing I took my section through the anterior region,
and through the fore-limbs, I should have here this kind of section of
the body (Figure 1). Here would be the upper part of the animal--that
great mass of bones that we spoke of as the spine (a, Figure 1). Here I
should have the alimentary canal (b, Figure 1). Here I should have the
heart (c, Figure 1); and then you see, there would be a kind of double
tube, the whole being inclosed within the hide; the spinal marrow
would be placed in the upper tube (a, Figure 1), and in the lower tube (d
d, Figure 1), there would be the alimentary canal (b), and the heart (c);
and here I shall have the legs proceeding from each side. For

simplicity's sake, I represent them merely as stumps (e e, Figure 1).
Now that is a horse--as mathematicians would say--reduced to its most
simple expression. Carry that in your minds, if you please, as a
simplified idea of the structure of the Horse. The considerations which
I have now put before you belong to what we technically call the
'Anatomy' of the Horse. Now, suppose we go to work upon these
several parts,--flesh and hair, and skin and bone,--and lay open these
various organs with our scalpels, and examine them by means of our
magnifying-glasses, and see what we can make of them. We shall find
that the flesh is made up of bundles of strong fibres. The brain and
nerves, too, we shall find, are made up of fibres, and these
queer-looking things that are called ganglionic corpuscles. If we take a
slice of the bone and examine it, we shall find that it is very like this
diagram of a section of the bone of an ostrich, though differing, of
course, in some details; and if we take any part whatsoever of the tissue,
and examine it, we shall find it