cles 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.

And yet the advance of the different functions is not altogether
successive. Muscle and nerve do not wait for digestion and
reproduction to show signs of halting before they begin to advance.
They all advance at once. But the progress of reproduction and
digestion is most rapid at first, and it appears as if they would
outrun the others. But in the ascending series the others follow
after, and soon overtake and pass by them. And these lower
functions, when out-marched, do not lag behind, but keep in touch
with the others, forming the rear-guard and supply-train of the
army. And notice that each organ holds the predominance about as
long as it shows the power of rapid improvement. The length of its
reign is pretty closely proportional to its capacity of development.
The digestive system reaches that limit early, the muscular system
is capable of indefinitely higher complexity, as we see in our hand.
But the muscular system has nearly or quite reached its limit. The
body had seen its day of dominance before man arrived on the globe.

But where is the limit to man's mental or moral powers? Every
upward step in knowledge, wisdom, and righteousness only opens our
eyes to greater heights, before unperceived and still to be
atta