Plain Facts for Old and Young | Page 6

life.
All nature teems with life. The practiced eye detects multitudes of
living forms at every glance.
The universe of life presents the most marvelous manifestations of the
infinite power and wisdom of the Creator to be found in all his works.
The student of biology sees life in myriad forms which are unnoticed
by the casual observer. The microscope reveals whole worlds of life
that were unknown before the discovery of this wonderful aid to human
vision,--whole tribes of living organisms, each of which, though
insignificant in size, possesses organs as perfect and as useful to it in its

sphere as do animals of greater magnitude. Under a powerful
magnifying glass, a drop of water from a stagnant pool is found to be
peopled with curious animated forms; slime from a damp rock, or a
speck of green scum from the surface of a pond, presents a museum of
living wonders. Through this instrument the student of nature learns
that life in its lowest form is represented by a mere atom of living
matter, an insignificant speck of trembling jelly, transparent and
structureless, having no organs of locomotion, yet able to move in any
direction; no nerves or organs of sense, yet possessing a high degree of
sensibility; no mouth, teeth, nor organs of digestion, yet capable of
taking food, growing, developing, producing other individuals like
itself, becoming aged, infirm, and dying,--such is the life history of a
living creature at the lower extreme of the scale of animated being. As
we rise higher in the scale, we find similar little atoms of life associated
together in a single individual, each doing its proper share of the work
necessary to maintain the life of the individual as a whole, yet retaining
at the same time its own individual life.
As we ascend to still higher forms, we find this association of minute
living creatures resulting in the production of forms of increasing
complicity. As the structure of the individual becomes more complex
and its functions more varied, the greater is the number of separate, yet
associated, organisms to do the work.
In man, at the very summit of the scale of animate existence, we find
the most delicate and wonderfully intricate living mechanism of all. In
him, as in lower, intermediate forms of life, the life of the individual is
but a summary of the lives of all numberless minute organisms of
which his body is composed. The individual life is but the aggregate
life of all the millions of distinct individuals which are associated
together in the human organism.
Animals and Vegetables.--The first classification of living creatures
separates them into two great kingdoms, animals and vegetables.
Although it is very easy to define the general characteristics of each of
these classes, it is impossible to fix upon any single peculiarity which
will be applicable in every case. Most vegetable organisms remain

stationary, while some possess organs of locomotion, and swim about
in the water in a manner much resembling the movements of certain
animals. Most vegetables obtain their nutriment from the earth and the
air, while animals subsist on living matter. A few plants seem to take
organic matter for food, some even catching and killing small insects.
It is found impossible to draw the precise line between animals and
vegetables, for the reason just mentioned. The two kingdoms blend so
intimately that in some cases it is impossible to tell whether a certain
microscopic speck of life is an animal or a vegetable. But since these
doubtful creatures are usually so minute that several millions of them
can exist in a single drop of water, it is usually of no practical
importance whether they are animal or vegetable, or sometimes one and
sometimes the other, as they have been supposed to be by some
biologists.
All living creatures are organized beings. Most possess a structure and
an organism more or less complicated; but some of the lowest forms
are merely little masses of a transparent, homogeneous jelly, known as
protoplasm. Some of the smallest of these are so minute that one
hundred millions of them could occupy the space of a cube
one-thousandth of an inch on each side; yet each one runs its course of
life as regularly as man himself, performing its proper functions even
more perfectly, perhaps.
Life Force.--To every thinking mind the question often recurs, What
makes the fragrant flower so different from the dead soil from which it
grows? the trilling bird, so vastly superior to the inert atmosphere in
which it flies? What subtle power paints the rose, and tunes the merry
songster's voice? To explain this mystery, philosophers of olden time
supposed the existence of a certain peculiar force which is called life,
or vital force, or vitality. This supposition does nothing