If we could tell what determines the division of labor in the hive of
bees or a colony of ants, we could tell what determines the division of
labor among the cells in the body. A hive of bees and a colony of ants
is a unit--a single organism. The spirit of the body, that which
regulates all its economies, which directs all its functions, which
coördinates its powers, which brings about all its adaptations, which
adjusts it to its environment, which sees to its repairs, heals its
wounds, meets its demands, provides more force when more is needed,
which makes one organ help do the work of another, which wages war on
disease germs by specific ferments, which renders us immune to this or
that disease; in fact, which carries on all the processes of our
physical life without asking leave or seeking counsel of us,--all this
is on another plane from the mechanical or chemical--super-mechanical.
The human spirit, the brute spirit, the vegetable spirit--all are mere
names to fill a void. The spirit of the oak, the beech, the pine, the
palm--how different! how different the plan or idea or interior
economies of each, though the chemical and mechanical processes are the
same, the same mineral and gaseous elements build them up, the same sun
is their architect! But what physical principle can account for the
difference between a pine and an oak, or, for that matter, between a man
and his dog, or a bird and a fish, or a crow and a lark? What play and
action or interaction and reaction of purely chemical and mechanical
forces can throw any light on the course evolution has taken in the
animal life of the globe--why the camel is the camel, and the horse the
horse? or in the development of the nervous system, or the circulatory
system, or the digestive system, or of the eye, or of the ear?
A living body is never in a state of chemical repose, but inorganic
bodies usually are. Take away the organism and the environment remains
essentially the same; take away the environment and the organism changes
rapidly and perishes--it goes back to the inorganic. Now, what keeps up
the constant interchange--this seesaw? The environment is permanent; the
organism is transient. The spray of the falls is permanent; the bow
comes and goes. Life struggles to appropriate the environment; a rock,
for example, does not, in the same sense, struggle with its
surroundings, it weathers passively, but a tree struggles with the
winds, and to appropriate minerals and water from the soil, and the
leaves struggle to store up the sun's energy. The body struggles to
eliminate poisons or to neutralize them; it becomes immune to certain
diseases, learns to resist them; the thing is _alive_. Organisms
struggle with one another; inert bodies clash and pulverize one another,
but do not devour one another.
Life is a struggle between two forces, a force within and a force
without, but the force within does all the struggling. The air does not
struggle to get into the lungs, nor the lime and iron to get into our
blood. The body struggles to digest and assimilate the food; the
chlorophyll in the leaf struggles to store up the solar energy. The
environment is unaware of the organism; the light is indifferent to the
sensitized plate of the photographer. Something in the seed we plant
avails itself of the heat and the moisture. The relation is not that of
a thermometer or hygrometer to the warmth and moisture of the air; it is
a vital relation.
Life may be called an aquatic phenomenon, because there can be no life
without water. It may be called a thermal phenomenon, because there can
be no life below or above a certain degree of temperature. It may be
called a chemical phenomenon, because there can be no life without
chemical reactions. Yet none of these things define life. We may discuss
biological facts in terms of chemistry without throwing any light on the
nature of life itself. If we say the particular essence of life is
chemical, do we mean any more than that life is inseparable from
chemical reactions?
After we have mastered the chemistry of life, laid bare all its
processes, named all its transformations and transmutations, analyzed
the living cell, seen the inorganic pass into the organic, and beheld
chemical reaction, the chief priestess of this hidden rite, we shall
have to ask ourselves, Is chemistry the creator of life, or does life
create or use chemistry? These "chemical reaction complexes" in living
cells, as the biochemists call them, are they the cause of life, or only
the effect of life? We shall decide according to our temperaments or our
habits of thought.