nstinct than the habit of
nest-building in birds. And yet there are numerous instances where
the structure and position of nests have been completely changed to
suit new circumstances. And the view that this habit is a pure
instinct, unmodified by intelligence, has been disproved by Mr.
Wallace. But while size of brain, keenness of sense-organs, and
length of life may be rightly emphasized as the most important
elements in the development of vertebrate intelligence, the
importance of the appendages should never be forgotten. Cats seem to
have acquired certain accomplishments--opening doors, ringing
door-bells, etc.--never attained by the more intelligent dog, mainly
because of the greater mobility and better powers of grasping of the
forepaws. The elephant has its trunk and the ape its hand. The power
of handling and the increased size of the brain aided each other in
a common advance.

The teachableness of mammals is also a sign of high intelligence.
The young are often taught by the parent, a dim foreshadowing of the
human family relation. And we notice this capacity in domestic
animals because of its practical value to man. And here, too, we
notice the difference between individuals, which fails in instinct.
All spiders of the same species build and hunt alike, although
differences caused by the moulding influence of intelligence will
probably be here discovered. But among individual dogs and horses we
find all degrees of intelligence from absolute stupidity to high
intelligence. And many mammals are slandered grievously by man. The
pig is not stupid, far from it.

Still only in man does intelligence reign supreme and clearly show
its innate powers. But even in man certain realms, like those of the
internal organs, are rarely invaded by consciousness, but are
normally left to the control of reflex action. These actions go on
better without the interference of consciousness.

But other lines of action are relegated as rapidly as possible to
the same control. We learn to walk by a conscious effort to take
each step; afterward we take each step automatically, and think only
whither we wish to go. We learn by conscious effort to talk and
write, to sing, or play the piano. Afterward we frame each letter or
note automatically, and think only of the idea and its expression.

So also in our moral and spiritual nature.[A]

[Footnote A: Mr. James Freeman Clarke has stated this better than I
can. "We may state the la