case of muscle, or in the
case of skin, or any of the organs I have mentioned, you will find that
they all come under the same condition. Every one of these microscopic
filaments and fibres (I now speak merely of the general character of the
whole process)--every one of these parts--could be traced down to
some modification of a tissue which can be readily divided into little
particles of fleshy matter, of that substance which is composed of the
chemical elements, carbon, hydrogen, oxygen, and nitrogen, having such
a shape as this (Fig. 2). These particles, into which all primitive
tissues break up, are called cells. If I were to make a section of a
piece of the skin of my hand, I should find that it was made up of these
cells. If I examine the fibres which form the various organs of all
living animals, I should find that all of them, at one time or other,
had been formed out of a substance consisting of similar elements; so
that you see, just as we reduced the whole body in the gross to that
sort of simple expression given in Fig. 1, so we may reduce the whole
of the microscopic structural elements to a form of even greater
simplicity; just as the plan of the whole body may be so represented
in a sense (Fig. 1), so the primary structure of every tissue may be
represented by a mass of cells (Fig. 2).

Having thus, in this sort of general way, sketched to you what I may
call, perhaps, the architecture of the body of the Horse (what we term
technically its Morphology), I must now turn to another aspect. A horse
is not a mere dead structure: it is an active, living, working machine.
Hitherto we have, as it were, been looking at a steam-engine with the
fires out, and nothing in the boiler; but the body of the living animal
is a beautifully-formed active machine, and every part has its different
work to do in the working of that machine, which is what we call
its life. The Horse, if you see him after his day's work is done, is
cropping the grass in the fields, as it may be, or munching the oats in
his stable. What is he doing? His jaws are working as a mill--and a very
complex mill too--grinding the corn, or crushing the grass to a pulp. As
soon as that operation has taken place, the food is passed down to
the stomach, and there it is mixed with the chemical fluid called the
gastric juice, a substance which has the peculiar property of making
soluble and dissolving out the nutritious matter in the grass, and
leaving behind