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Page 4
Biology is the Science of Life. It seeks to explain the phenomena of all
life, whether animal or vegetable. Its methods are observation and
experiment. It observes the tiny cell on the surface of an egg yolk, and
watches it divide and multiply until it becomes a great mass of cells,
which group off or differentiate, and rearrange and alter their shapes.
It observes how little organs unfold themselves, or evolve out of these
little cell groups--how gradual, but how unvarying the change; how one
group becomes a bone, another a brain, another a muscle, to constitute
in three short weeks the body of a matured chick. Those little tendons
like silken threads, that run down those slender pink legs to each and
every toe, and move its little joints so swiftly that we hardly see
them--that little brain, no bigger than a tiny seed, in which is planted
a mysterious force that impels it to set all those brand-new muscles in
motion, and to dart after a fly with the swiftness of an arrow--all this
wondrous mechanism, all this beauteous structure, all this perfection of
function, all this adaptation to environment, have evolved from a few
microscopic cells in three short weeks.
Biology is the science that observes all this, and enunciates the law
that the life history of this animal cell, _i.e._, its history from a
simple unicellular state in the egg, to its complex multicellular state
in the matured chick, represents the history of the race to which the
chick belongs. If we could trace that chicken back through all its
ancestry, we would discover at different periods in the history of life
upon the globe (about 100 million years, according to Haeckel) exactly
the stages of development we found in the life history of the chick, and
arrive at last at a primordial cell.
What is true of the chick is true of all life. This is the law of
evolution. It is true of all plant and animal life; it is true of man as
an individual; it is true of his mind as well as of his body; it is true
of society as an aggregation of individuals. As men have evolved from a
lower to a higher, a simple to a complex state, so they are still
evolving and rising "on stepping stones of their dead selves to higher
things."
Natural selection, or the survival of the fittest, is one of the
processes by which evolution takes place. According to this law, only
the fittest survive in the struggle for life. Darwin was led to this
discovery on reading Malthus's thesis regarding the disproportion
between the rates of increase in population and food, and the consequent
struggle for existence.
All living organisms require food and space. The power of multiplication
in plants and animals is so great that food or space is sooner or later
entrenched upon, and then commences this inevitable struggle for
existence. In this struggle for life, the individuals best able to
conform to their environment, _i.e._, the best able to resist adverse
circumstances, to sustain hardships, to overcome difficulties, to defend
themselves, to outstrip their fellows, in short, to harmonise function
with environment, survive. These propagate their kind according to the
law of heredity. Variations exist in the progeny, and the individuals
whose variations best adapt them to their environment are the fittest
to, and do, survive.
In a state of nature the weaklings perish. If man interferes with this
state of nature in the lower animals, he may make a selection and
cultivate some particular attribute. This is artificial selection, and
is best exemplified in the experiments with pigeons. Pasteur saved the
silk industry of France, and perhaps of the whole world, by the
application of this law of artificial selection. The disease of
silkworms, known as Pebrine, was spreading with ruinous rapidity in
France. Pasteur demonstrated that the germ of the disease could be
detected in the blood of affected moths by the aid of the microscope. He
proved that the eggs of diseased moths produced unhealthy worms, and he
advised that the eggs of each moth be kept apart, until the moth was
examined for germs. If these were found, the eggs were to be burned.
Thus the eggs of unhealthy moths were never hatched, and artificial
selection of healthy stock stamped out a disease, and saved a great
industry.
Each individual plant in the struggle for life has only itself to
maintain. In the higher forms of animal life, each animal has its
offspring as well as itself to maintain. In a state of nature, that is
in a state unaffected by man's rational interference, defective
offspring and weaker brethren were the victims of the inexorable law of
natural selection. When Christ gave _his_ reply to the question, "Am I
my brother's keeper?" the defective and the weakling became the special
care of their stronger brother. They constituted thenceforth The Fit
Man's Burden. The work a man has to do during life, in order to support
himself, is the unit of measurement of the burden he has to bear. Many
factors in modern times have helped to reduce that work to a minimum.
The invention of machinery has multiplied his eyes, his hands, his feet;
and one man can now produce, for his own maintenance and comfort, what
it took perhaps a score of men to produce even a century ago. Man's
disabilities from incidental and epidemic disease have been immeasurably
reduced by modern sanitation, and the teaching and practice of
preventive medicine. Agricultural chemistry has made the soil more
productive, and manufacturing arts have aided distribution as well as
production.
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