Knowledge of
even a great emergency is of little use, if I can do nothing about
it. But when the muscles appeared, nerves and ganglion cells were
necessary to stimulate and control them. And this highest system
holds for a long time a position subordinate to that of the lower
muscular organ. Its development seems at first sight extraordinarily
slow. Only in insects and vertebrates has it become a centre of
instinct and thought. Through the sense-organs it is gaining an ever
clearer, deeper, and wider knowledge of its environment. First it is
affected only by the lower stimuli of touch, taste, and smell. Then
with the development of ear and eye it takes cognizance of ever
subtler forces and movements. Memory comes into activity very early.
The animal begins to learn by experience. The brain is becoming not
merely a steering but a thinking organ. More and more nervous
material is crowded into it and detailed for its work. Wits and
shrewdness are beginning to count for something in the battle. Not
only the animal with the strongest muscles, but the one with the
best brain survives. And thus at last the brain began to develop
with a rapidity as remarkable as its long delay. Thus each higher
function is called into activity by the next lower, serves this at
first, and only later attains its supremacy.
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