endeavour to put before you a sort of broad notion of our knowledge of
the condition of the living world. There are many ways of doing this. I
might deal with it pictorially and graphically. Following the example of
Humboldt in his "Aspects of Nature", I might endeavour to point out the
infinite variety of organic life in every mode of its existence, with
reference to the variations of climate and the like; and such an attempt
would be fraught with interest to us all; but considering the subject
before us, such a course would not be that best calculated to assist us.
In an argument of this kind we must go further and dig deeper into the
matter; we must endeavour to look into the foundations of living Nature,
if I may so say, and discover the principles involved in some of her
most secret operations. I propose, therefore, in the first place, to
take some ordinary animal with which you are all familiar, and, by
easily comprehensible and obvious examples drawn from it, to show what
are the kind of problems which living beings in general lay before us;
and I shall then show you that the same problems are laid open to us by
all kinds of living beings. But first, let me say in what sense I have
used the words "organic nature." In speaking of the causes which lead to
our present knowledge of organic nature, I have used it almost as an
equivalent of the word "living," and for this reason,--that in almost
all living beings you can distinguish several distinct portions set
apart to do particular things and work in a particular way. These are
termed "organs," and the whole together is called "organic." And as it
is universally characteristic of them, this term "organic" has been very
conveniently employed to denote the whole of living nature,--the 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