heavens above and to the earth-fires beneath, to the ice-sheets that
ground down the mountains, and to the ocean currents. Just as we owe
a debt to the men and women in our line of descent, so we owe a debt
to the ruder primordial forces that shaped the planet to our use,
and took a hand in the game of animal life.

The gods of evolution had served a long apprenticeship; they had
gained proficiency and were master workmen. Or shall we say that the
elements of life had become more plastic and adaptable, or that the
life fund had accumulated, so to speak? Had the vast succession of
living beings, the long experience in organization, at last made the
problem of the origin of man easier to solve?

One fancies every living thing as not only returning its mineral
elements to the soil, but as in some subtle way leaving its vital
forces also, and thus contributing to the impalpable, invisible
store-house of vital energy of the globe.

At first among the mammalian tribes there was much muscle and little
brains. But in the middle Tertiary the mammal brain began suddenly
to enlarge, so that in our time the brain of the horse is more than
eight times the size of the brain of his progenitor, the dinoceras
of Eocene times.

Nature seems to have experimented with brains and nerve ganglia, as
she has with so many other things. The huge reptilian creatures of
Mesozoic time--the various dinosaurs--had ridiculously small heads
and brains, but they had what might be called supplementary brains
well toward the other end of the body,--great nervous masses near
the sacrum, many times the size of the ostensible brain, which no