Lectures and Essays | Page 7

each of these complex structures that we have mentioned.
This embryo, as it is called, then passes into other conditions. I should
tell you that there is a time when the embryos of neither dog, nor horse,
nor porpoise, nor monkey, nor man, can be distinguished by any

essential feature one from the other; there is a time when they each and
all of them resemble this one of the Dog. But as development advances,
all the parts acquire their speciality, till at length you have the embryo
converted into the form of the parent from which it started. So that you
see, this living animal, this horse, begins its existence as a minute
particle of nitrogenous matter, which, being supplied with nutriment
(derived, as I have shown, from the inorganic world), grows up
according to the special type and construction of its parents, works and
undergoes a constant waste, and that waste is made good by nutriment
derived from the inorganic world; the waste given off in this way being
directly added to the inorganic world; and eventually the animal itself
dies, and, by the process of decomposition, its whole body is returned
to those conditions of inorganic matter in which its substance
originated.
This, then, is that which is true of every living form, from the lowest
plant to the highest animal--to man himself. You might define the life
of every one in exactly the same terms as those which I have now used;
the difference between the highest and the lowest being simply in the
complexity of the developmental changes, the variety of the structural
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.
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.
I pass on from that now, as I merely wished to explain to you what I
meant by the use of the term 'Geographical Distribution.' As I said,
there is another aspect, and a much more important one, and that is, the
relations of the various animals to one another. The Horse is a very
well-defined matter-of-fact