External forces may modify a body, but they cannot develop it unless
there is something in the body waiting to be developed, craving
development, as it were. The warmth and moisture in the soil act alike
upon the grains of sand and upon the seed-germs; the germ changes into
something else, the sand does not. These agents liberate a force in the
germ that is not in the grain of sand. The warmth of the brooding fowl
does not spend itself upon mere passive, inert matter (unless there is a
china egg in the nest), but upon matter straining upon its leash, and in
a state of expectancy. We do not know how the activity of the molecules
of the egg differs from the activity of the molecules of the pebble,
under the influence of warmth, but we know there must be a difference
between the interior movements of organized and unorganized matter.

Life lifts inert matter up into a thousand varied and beautiful forms
and holds it there for a season,--holds it against gravity and chemical
affinity, though you may say, if you please, not without their aid,--and
then in due course lets go of it, or abandons it, and lets it fall back
into the great sea of the inorganic. Its constant tendency is to fall
back; indeed, in animal life it does fall back every moment; it rises on
the one hand, serves its purpose of life, and falls back on the other.
In going through the cycle of life the mineral elements experience some
change that chemical analysis does not disclose--they are the more
readily absorbed again by life. It is as if the elements had profited
in some way under the tutelage of life. Their experience has been a
unique and exceptional one. Only a small fraction of the sum total of
the inert matter of the globe can have this experience. It must first go
through the vegetable cycle before it can be taken up by the animal. The
only things we can take directly from the inorganic world are water and
air; and the function of water is largely a mechanical one, and the