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.

Why horses should be found in Europe, Asia, and Africa, and not in
America, is not obvious; the explanation that the conditions of life in
America are unfavourable to their existence, and that, therefore, they
had not been created there, evidently does not apply; for when the
invading Spaniards, or our own yeomen farmers, conveyed horses to these
countries for their own use, they were found to thrive well and
multiply very rapidly; and many are even now running wild in those
countries, and in a perfectly natural condition. Now, suppose we were
to do for every animal what we have here done for the Horse,--that is,
to mark off and distinguish the particular district or region to which
each belonged; and supposing we tabulated all these results, that would
be called the Geographical Distribution of animals, while a
corresponding study of plants would yield as a result the Geographical
Distribution of plants.