_The Fundamental Aspect of Life_
I often think, when working over my plants, of what LinnŠus once said of
the unfolding of a blossom: "I saw God in His glory passing near me, and
bowed my head in worship," The scientific aspect of the same thought has
been put into words by Tennyson:--
"Flower in the crannied wall,
I pluck you out of the crannies,
I hold you here, root and all, in my hand,
Little flower,--but if I could understand
What you are, root and all, and all in all,
I should know what God and man is."
No deeper thought was ever uttered by poet. For in this world of plants,
which with its magician chlorophyll conjuring with sunbeams is
ceaselessly at work bringing life out of death,--in this quiet vegetable
world we may find the elementary principles of all life in almost
visible operation. It is one of these elementary principles--a very
simple and broad one--that here concerns us.
One of the greatest contributions ever made to scientific knowledge is
Herbert Spencer's profound and luminous exposition of Life as the
continuous adjustment of inner relations to outer relations. The extreme
simplicity of the subject in its earliest illustrations is such that the
student at first hardly suspects the wealth of knowledge toward which it
is pointing the way. The most fundamental characteristic of living
things is their response to external stimuli. If you come upon a dog
lying by the roadside and are in doubt whether he is alive or dead, you
poke him with a stick; if you get no response you presently conclude
that it is a dead dog. So if the tree fails to put forth leaves in
response to the rising vernal temperature, it is an indication of death.
Pour water on a drooping plant, and it shows its life by rearing its
head. The growth of a plant is in its ultimate analysis a group of
motions put forth in adjustment to a group of physical and chemical
conditions in the soil and atmosphere. A fine illustration is the spiral
distribution of leaves about the stem, at different angular intervals in
different kinds of plants, but always so arranged as to ensure the most
complete exposure of the chlorophyll to the sunbeams. Every feature of
the plant is explicable on similar principles. It is the result of a
continuous adjustment of relations within the plant to relations
existing outside of it. It is important that we should form a clear
conception of this, and a contrasted instance will help us. Take one of
those storm-glasses in which the approach of atmospheric disturbance
sets up a feathery crystallization that changes in shape and
distribution as the state of the air outside changes. Here is something
that simulates vegetable life, but there is a profound difference. In
every one of these changes the liquid in the storm-glass is passive; it
is changed and waits until it is changed again. But in the case of a
tree, when the increased supply of solar radiance in spring causes those
internal motions which result in the putting forth of leaves, it is
quite another affair. Here the external change sets up an internal
change which leads to a second internal change that anticipates a second
external change. It is this active response that is the mark of life.
All life upon the globe, whether physical or psychical, represents the
continuous adjustment of inner to outer relations. The degree of life is
low or high, according as the correspondence between internal and
external relations is simple or complex, limited or extensive, partial
or complete, perfect or imperfect. The relations established within a
plant answer only to the presence or absence of a certain quantity of
light and heat, and to sundry chemical and physical relations in
atmosphere and soil. In a polyp, besides general relations similar to
these, certain more special relations are established in correspondence
with the eternal existence of mechanical irritants; as when its
tentacles contract on being touched. The increase of extension acquired
by the correspondences as we ascend the animal scale may be seen by
contrasting the polyp, which can simply distinguish between soluble and
insoluble matter, or between opacity and translucence in its
environment, with the keen-scented bloodhound and the far-sighted
vulture. And the increase of complexity may be appreciated by comparing
the motions respectively gone through by the polyp on the one hand, and
by the dog and vulture on the other, while securing and disposing of
their prey. The more specific and accurate, the more complex and
extensive, is the response to environing relations, the higher and
richer, we say, is the life.
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