forms, the diversity of the physiological functions which are exerted by
each.

If I were to take an oak tree as a specimen of the plant world, I should
find that it originated in an acorn, which, too, commenced in a cell;
the acorn is placed in the ground, and it very speedily begins to absorb
the inorganic matters I have named, adds enormously to its bulk, and we
can see it, year after year, extending itself upward and downward,
attracting and appropriating to itself inorganic materials, which it
vivifies, and eventually, as it ripens, gives off its own proper acorns,
which again run the same course. But I need not multiply examples,--from
the highest to the lowest the essential features of life are the same,
as I have described in each of these cases.

So much, then, for these particular features of the organic world, which
you can understand and comprehend, so long as you confine yourself to
one sort of living being, and study that only.

But, as you know, horses are not the only living creatures in the world;
and again, horses, like all other animals, have certain limits--are
confined to a certain area on the surface of the earth on which we
live,--and, as that is the simpler matter, I may take that first. In its
wild state, and before the discovery of America, when the natural state
of things was interfered with by the Spaniards, the Horse was only to be
found in parts of the earth which are known to geographers as the Old
World; that is to say, you might meet with horses in Europe, Asia, or
Africa; but there were none in Australia, and there were none whatsoever
in the whole continent of America, from Labrador down to Cape Horn. This
is an empirical fact, and it is what is called, stated in the way I have
given it you, the 'Geographical Distribution' of the Horse.