or part of some
organisms is itself actually dead. The bones and hair and nails of such an
animal as a cat are almost entirely lifeless, even though they are
integral and necessary portions of the organism as a whole. They are
constructed by living protoplasm which has died in their making. Thus
without going beyond the boundaries of the individual body, these
substances have passed from the sphere of life, and are dead. The apparent
gap on the other side between the lifeless and living world is equally
imaginary, for our living substance is continually replenished and rebuilt
from the elements of our dead foods. So, as Huxley says, a living organism
is like a flame or a whirlpool, which is an ever changing though seemingly
constant individuality. We look at a gas flame, and we see in the flame
itself those particles of gas which have come through the pipe to be
agitated violently in the higher temperature of the flame as they are
oxidized or burnt. These particles immediately pass off as carbonic acid
gas and water vapor which are no longer parts of the flame. A fountain is
continually replenished by the water which is not-fountain, but which
becomes for the time a part of the graceful jet, falling out and away as
it leaves the fountain itself. Just so a living organism is an ever
changing, ever renewed, and ever destroyed mass of little particles--the
atoms of the inorganic world which combine and come to life for a time,
but which return inevitably to the world of lifeless things. This is one
of the most fundamental facts of biology. The independence of a living
thing like a human being or a crustacean is a product of the imagination.
How can we be independent of the environment when we are interlocked in so
many ways with inorganic nature? Our very substance with its energies has
been wrested from the environment; and as we, like all other living
things, must replenish our tissues as we wear out in the very act of
living, we cannot cease to maintain the closest possible relations with
the environment without surrendering our existence in the battle of life.

From the foregoing discussion, it will be evident, I am sure, that there
is ample justification for the biological dictum that a living individual
is a mechanism. Not only is the organism composed always of cell units
grouped mechanically in tissues and organs and organic systems; not only
are the operations which make up its life constant and regular under
simil