these substances, or detect such minute differences. We smell musk
and wine and tea; he smells footprints. One can’t say that either
has a better nose than the other. Really, a good deal of the
difference between us and the animals is that we depend on sight and
hearing, because we can use these two senses to handle words. We can
see words, and we can hear words; we cannot taste or smell them. So
we get to relying on eyes and ears. But the animals, which don’t use
words anyway, they think more about smells.
There is still another way in which we are apt, I think, to
overestimate the senses of animals. We know, for example, that a
horse will find his way home on a dark night, when everything is
pitch black, and the driver cannot see his hand before his face. We
say that the horse must have wonderful sight to make out his way
under such conditions.
The real fact is, however, that the horse goes straight home thru
darkness and storm, not because his eyesight is good, but because it
is poor. He is at home in the night, because he does not see
especially well by day. Those of you who have read _The Last Days of
Pompeii_ (as everybody should, for it is a famous old story) will
remember that when, during the eruption of Vesuvius, the city was
darkened under the shower of ashes, so that the inhabitants wandered
about in the streets completely lost and quite unable to find their
way out, the blind girl was able to lead her friends straight to
safety. She had always lived in the dark, and could find her way as
well one time as another.
So it is with horses and other animals. They seem to see in the
dark, when they really hear and smell. A horse especially depends
for finding his way, on his muscular sense. While his driver is
noticing houses and trees and sign-boards, the horse is noticing so
long a pull up one hill, so much holding back down another, so much
level stretch between. The man is lost when he cannot see his houses
and sign-boards; but the horse’s hills and levels are still there.
You remember the rats that, when the passage in their maze was
shortened, kept running full tilt against the end wall; and then
when the passage was lengthened, kept turning too soon and butting
into the side wall. The rats were depending on their muscular sense.
They remembered their way as so long a straight run, then a turn.
They could run as fast by night as by day, because they didn’t do
much seeing either time.
We also depend on our muscular sense far more than we commonly
realize. Doubtless we all know how to button our coats. But how do
we know? We certainly do not know how it tastes, smells or sounds. I
don’t think we often remember how it looks. What we do remember is
the feeling of the buttons and the movements we make. But if we try
buttoning with the other hand, or put on a coat that buttons on the
other side, we feel as awkward as can be. We can see as well as
before; the touch has not changed; there never was any taste,
hearing, or smell. The difference is in the movements. The muscular
sense is learning something new.
How hard it is to bat on the other side, to use any tool the other
way round, or make any change which is strange to the muscular
sense. That shows how much we all rely on it. If we play the piano,
and remember pieces without the notes, it is by this muscular sense
that we do it. Our fingers seem to know the tune; and in a sense,
they really do. Surely, if a musician can find his way back and
forth over the keyboard thru a long piece of music, by means of his
muscular sense, it is not so remarkable that a horse should find its
way home over the road, or a rat scamper thru its holes, guided by
the same means. They don’t really see in the dark, they simply turn
on another sense. We have it also; but mostly we trust to our eyes,
instead.
There is another sense, too, on which animals are more given to
depending than we are, and that is the sense of equilibrium and
direction, which, as I have explained, has its seat in a part of the
inner ear. You know the game where you are blindfolded, turn around
three times, and then try to blow out a candle. If your
direction-sense is at fault, as it generally is, you turn too far or
not far enough, blow where the candle isn’t, and make everybody
laugh. Men who have to find their way about over a wild country,
explorers and the like, sometimes have this direction sense trained
to a wonderful degree. They simply cannot get lost anywhere. The
rest of us, who depend on street numbers and the sign-boards on the
lamp posts, don’t have much use for this sense, and so never really
learn to use it. Many animals depend on it a good deal. They find
their way home in truly marvelous ways; and we say it is “instinct.”
It really isn’t instinct, but just plain sight, hearing, smell, and
direction sense. Men who have practiced their direction sense can
find their way quite as well.
So in general, the animals haven’t different senses from ours, nor
on the whole better ones. But they use them differently; and
cultivate some senses which we let go to waste. For the most part,
the animals depend on smell far more than we. Smell is apt to be
their principal sense, as sight is ours. Because they don’t use
their eyes as much as we do, they notice and remember more of what
they learn thru their sense of direction and their muscular sense.
But a man who tries hard can usually beat any animal at his own
game.
The fact is, I suppose, that we, men and beasts and birds alike,
have all the senses there are, all that any sort of creature could
have anyway. Then each, according to his nature and habits, uses one
more than the rest, to think and remember with.
XXXIII
Seeing In The Mind’s Eye
Not all us human beings use our eyes, ears, and noses in the same
way, as a simple experiment will show.
Shut your eyes and think of the name of some familiar thing, like
BREAKFAST TABLE.
What did you see in your mind’s eye? Some people see that breakfast
table just as clearly as if they were in the dining room with the
table itself before them. They see the cloth and the plates and the
food, the people at their places, the walls of the room, the
furniture, all just as sharp and bright and natural as if they were
looking at the things themselves. Others, more commonly, see the
room and table dimly. They do indeed have an inner picture, but it
is more like the picture one gets of things far round at the side of
the head, out of the corner of the eye. They have a general
impression, right as far as it goes; but they can’t see the patterns
on the plates, nor the position of each fork and spoon. Still other
persons, though there are not many of these, and children are almost
never this way, cannot see any mental picture at all. They have no
mind’s eye. They cannot see anything unless it is actually there.
People who can make such inner pictures are said to be eye-minded.
Children are especially this way. Sometimes, indeed, they have
difficulty in telling the difference between what they actually see,
and what they dream or imagine. Then sometimes, they get punished
for telling fibs.
Some people have this gift for making mental pictures to an
extraordinary degree. If they have a lesson to learn, they see the
page of the book before their inner eyes, and simply read off what
it says. I knew of a type-setter in a printing office, who was a
crack speller. He could spell anything. Give him a hard word, and he
simply saw in his mind’s eye his composing stick with the word set
up in type in it, upside down and backwards, as type is set by hand.
Then he simply read off the letters, and always got it right.
Some musicians, as I have explained, remember their pieces as if in
their fingers; but some see the inner picture of the notes, and read
them off as if from a real score. There is a story of a public
speaker, who in the midst of his speech stopped, hesitated, went
back and said something different. He explained afterwards, that
while he never read his speeches from a real manuscript, he did
always read them from an imaginary one which he saw before his
mind’s eye. This time, the manuscript that wasn’t there had some
words written in between the lines, so that he could not read them
easily.
Possibly you have heard of the truly wonderful performances of some
champion chess players. Chess is played on a board like checkers,
only it is a vastly more complicated game, with six different sorts
of “men” all moved in different ways. Nevertheless, many players can
play about as well when they do not see the board at all, as when
they do. They make a mental picture of the board, sit blindfolded,
and as the game goes on, they keep track of every move, as they are
told what it is, by altering their inner picture. Some of the best
chess players have played ten, fifteen, and even twenty different
games, all at the same time, blindfolded, and won them all against
as many separate players, each playing one game and looking at the
board. Such a champion player has to carry in his head the picture
of ten, fifteen, or twenty different boards, each with sixteen men,
scattered about over sixty-four squares, and all continually
changing. Yet they do this without ever making a mistake; just by
these inner pictures in the mind’s eye.
Some eye-minded people can see a picture on a blank sheet of paper
so clearly that they can mark over it with a pencil, and in this way
make most accurate and effective drawings. Some can picture to
themselves all four sides of a room at once, and imagine what is
behind them as easily as what is in front. Some do not even hear
directly what is said to them; but as each word is uttered, see the
same word printed before their mind’s eye, and then read it off.
There are those who say that they cannot wake up in the night and
think of the bright sun, without having their eyes dazzled!
Now it is a great advantage to be eye-minded. There is no easier way
of learning one’s lessons than by seeing books and maps and charts
and diagrams, whenever you want them, right in front of your eyes,
so that all you have to do is to look and see. The difference
between boys and girls who get their lessons almost without effort,
and those who get them only with the greatest labor, and then
promptly forget them again, is often in just this power of making
mental pictures. Some people can remember a page so clearly that
they can actually read off the first or last words of each line, or
read the printing backwards. Naturally, lessons come pretty easy to
such lucky people.
Then too, to be eye-minded is a great source of happiness. One sees
in the course of his lifetime, all sorts of beautiful and
interesting things. If he can, whenever he wishes, recall these as
mental pictures, almost as vivid as the reality, it is like seeing
the reality all over again. He always has with him a collection of
pictures, which though he cannot show to another, he can at any time
enjoy for himself.
The eye-minded person, moreover, has still another string to his
bow. Not only can he recall what he has seen; he can also imagine
things which he has not seen, and so tell in advance how they are
going to look. The engineer about to build a bridge, the architect
planning a house, the housekeeper deciding how she shall arrange a
room or set a table, the girl considering a new dress, the boy
laying out a ball field, all can work to vastly better advantage if
they can see exactly how everything is going to look, before they do
anything. It is a great deal easier to change things in one’s mind,
than after they get into wood and iron and cloth. No one can
possibly succeed as engineer, architect, designer, dress-maker,
milliner, and the like, unless he can make these pictures in his
mind’s eye, and see how things are going to be, before he wastes
time and material on the reality, Fortunately, this eye-mindedness
is easily cultivated. One has only to attend to his mental pictures,
and try to see all there is in them, to have them grow sharper and
more complete. In fact, children usually have so much of this
faculty that if they only kept what they have, instead of letting it
waste away from lack of use, they would be far better off when they
grew up than most grown-ups are. As we get older, we get to thinking
more in words, and we lose the knack of making pictures. All is, we
simply mustn’t.
XXXIV
Ear Minds and Others
Some persons are ear-minded. If you say to them
BREAKFAST TABLE.
they don’t see any breakfast table at all. Instead they hear in
their mind’s ear the sound of dishes, the murmur of conversation,
and the clatter of knives and forks. When they have learned their
lessons, and stand up to recite, they hear an inner voice telling
them what to say. They cannot easily remember how places look on the
map; but they remember the songs of birds, the different whistles
and bells of their neighborhood, they like lectures and readings,
and when they have heard a tune once, they know it again. Such
people may find it hard to learn to read a foreign language, but
they make it up by learning easily to understand it when spoken.
Musicians are apt to be ear-minded. Mozart, for example, could
listen to a long piece of music, then go home and hear it over again
as many times as he liked in his mind’s ear, and so write it down at
his leisure. Beethoven, after he became stone deaf, used still to
write his magnificent symphonies, that took hours to perform, making
them up in his head and hearing them in his soul’s ear—violins, and
trumpets and cymbals and drums, each in its proper place, long after
his bodily ears had ceased to hear any noise.
Not many people are ear-minded; not nearly so many are as
eye-minded. Those that are, can always hear sweet music and pleasant
sounds, whenever they will, and recall the words and voices of their
friends. Surely there is much happiness in being ear-minded.
Whatever ear-mindedness one has, is well worth hanging on to and
improving.
More people are muscle-minded. Think of a
BALL.
Do you see the ball in your mind’s eye? or do you hear the word ball
in your mind’s ear? or do you feel the ball in your fingers, and the
pull of your muscles as you throw? If the last, you are muscle, or
motor-minded, and you probably found yourself saying to yourself the
word ball.
Motor-mindedness, too, is a great convenience. It helps to make
games come easy, and dancing, and all sorts of gymnastics; it makes
it easy to carry oneself properly, to use tools, to be skillful with
one’s fingers, to play musical instruments. Motor-minded people are
apt to talk easily, and to learn readily to speak foreign languages.
Anything, in short, comes easy to them which involves doing
something.
Nearly all blind people are motor-minded. If they are also deaf,
then of course, they have to be so. I have seen a blind man get off
a street car, turn into his street, walk down the street as far as
his own gate, and there turn in without the least pause or
hesitation, any more than as if he could see. He couldn’t see. He
simply felt that he had walked just far enough. And he had.
Do you want to know which of the three possible sorts of minds your
mind happens to be? Then think of the street number of your house,
or the year in which Columbus discovered America. Did you look for
the figures, or listen for them, of try to say them to yourself? Did
you see 1492 printed out somewhere, or did you hear something say
it; or did you feel yourself saying it in your throat? In the first
case you are eye-minded; in the second, ear-minded; in the third,
motor-minded.
Most persons are mixed-minded. They have one principal sense, with
which they do most of their thinking; but where that is not
convenient to use, they employ another. Occasionally even, they use
the third. I am myself motor-minded. To learn anything, I say the
words over to myself. If anybody tells me anything, I cannot
remember it, unless I first say it over; and whenever I think of
anything, I say words about it to myself. I can Recognize tunes when
I hear them, but I cannot recall a tune, unless I fit it to some
words or sounds and think of myself as singing it. But I can think
of how things look, or imagine how things will look, much more
easily than I can think about how they sound; and I can, with some
effort, think how things look without starting to say anything about
them to myself in words. So I am also somewhat eye-minded.
Most of you will probably find yourselves, first eye-minded, then
motor-minded. That is, on the Whole, the most useful arrangement.
But the best sort of mind is one that can handle all three kinds of
ideas; and think about seeing, hearing, and doing all about equally
well. So you had better notice which you can’t do, and set about
learning to do it.
XXXV
Living Automobiles
If you will think back over what you have already learned in this
book, you will see that we began by finding out something about how
we men, the animals, and the plants come to have any such things as
bodies at all. We learned how the little chick forms inside the egg,
and the little plant inside the seed. We learned, too, about the
wonderful life-jelly or protoplasm of which all living things are
made; how it shapes itself into cells; how it builds these cells
into our various members, eyes and bones and hair and muscles; and
how the body changes, as we grow from youth to maturity, and from
maturity to old age.
Then, after we had learned something about this body of ours, we
turned to consider how we use it. We found about something of what
animals cannot do, and what they can do, and how they do it. We
learned how animals of various sorts, and plants as well, see and
feel and act; and we learned also something about how we ourselves
do our thinking, which is so very different, and so very much better
done, than that of any animal or plant.
Now we turn to a different matter. We have taken up being, and
doing, and thinking. Now we shall consider living. We shall learn
about how the body of the plant or animal feeds itself and keeps
alive, and how the different parts of it, the bones and skin and
leaves and bark, manage to get on with one another, and work
together like a well-made machine.
For, of course, the body is a machine. It is a vastly complex
machine, many, many times more complicated than any machine ever
made by hands; but still after all a machine. It has been likened to
a steam engine. But that was before we knew as much about the way it
works as we know now. It really is a gas engine; like the engine of
an automobile, a motorboat, or an airplane.
I don’t suppose that any boy, at least, needs to be told the
difference between a gas engine and a steam engine. In the one, we
build a fire under the boiler, and turn water to steam. Then the
steam goes thru a pipe to the cylinder, where it pushes the piston
back and forth, first on one side, then on the other, and so turns
the wheels.
In the gas engine, on the other hand, there is no boiler, no steam,
and no fire. A mixture of air and gasolene vapor flows into the
cylinder, cold. There it explodes, set off by an electric spark, and
the push of that explosion moves the piston and makes the wheels go
round.
We, I say, are not steam engines. We have neither boiler nor steam
nor fire. But each little working cell is like a little cylinder,
which takes up from the blood air and food, mixes them together
inside itself, waits with everything ready to go off, gets the
proper signal thru a nerve, then explodes and does something.
That’s the way a muscle does its work. It is a many-thousand-cylindered
engine. Each little fiber of the muscle is a cylinder; and each time you
lift your hand or move your foot there is a perfect battery of minute
explosions. You cannot hear them, for there is no pop—the muffling is
vastly better than any engine-builder ever devised. But you do feel the
heat; and if you move fast and hard enough, you have to stop to cool off
and get a drink.
The plants also are many-cylindered gas engines. They do not do so
much work as animals do, not so much running round and moving
things. But they do move, and certainly grow and lift themselves
high in the air. This much work they do by exploding their cells,
just as animals or automobiles do theirs. The growing plants take
their food out of the air thru their leaves; and they take also the
air itself in the same way. They mix these together inside their
cells; and when there is work to be done, growing, moving, or any
other sort, they explode a little of the mixture and do it.
[Illustration: The leaves take in air through breathing holes.]
Don’t think then that animals and plants and human beings are merely
like automobiles. They are automobiles. Their fuel is their food.
They mix it with air. They explode the mixture, and move. Anything
that does that is an automobile, and runs with a gas engine.
XXXVI
Air and Fuel
We are, then, gas engines. So we have to have air to mix with our
gasoline. The simpler water animals, such as sponges, which are
mostly holes, and all minute creatures, both animals and plants,
simply take it in directly into their cells where they are going to
use it. There is plenty of air in water—you can see it fizzle out
from the water in a drinking glass when you draw water from a faucet
in cold weather. The water creatures breathe this out of the water,
and die of suffocation if you put them in boiled water from which
the boiling has driven out the air.
Most animals which have blood, use this to carry the air to their
cells. For blood, whatever else it is, is nine-tenths water, and
will dissolve air like any other water. The insects, however, though
they have blood, do not use it to carry air. Instead, they have a
system of branching pipes running all over their bodies, and opening
at various points on the surface. You can often make these out
easily, a pair of openings for each joint, on the sides of
caterpillar’s body. These pipes carry the air everywhere over the
insect’s body, even to the feet, so that wherever there is a working
muscle, there also is the air for it to work with. Thus the insect
has no need of lungs, and has none; and therefore, I suppose never
gets out of breath, no matter how hard it works.
[Illustration: In place of lungs, insects have breathing holes like
a leaf.]
We human beings, and our four-footed cousins, all backboned animals
in fact, do not manage in any of these ways. We breathe the air into
our lungs. There, instead of dissolving it in the watery part of the
blood, we turn it over to the red corpuscles, which are especially
made to do this very thing and do it particularly well. These
minute, coin-like corpuscles carry the air all over the body, and
deliver it over to the cells as they need it. But of course, as you
must have already learned in school, the body handles only the part
of the air that it can use, the oxygen. The rest it lets go and
doesn’t bother with. That is where we have the advantage over other
automobiles, which can’t pick out the part they want but have to
take the air as it comes. Still it all comes to the same thing in
the end. With all animals the oxygen gets mixed with the fuel and
explodes.
Our fuel, moreover, is a good deal like gasoline. Gasoline, as you
know, is related to kerosene, benzine, paraffine, and the rest,
which are all products of rock oil. They are, then, themselves oils;
and gasoline is an oil.
We, too, eat oils; not, to be sure, mineral oils, but animal and
vegetable oils, olive oil and butter and cream and all sorts of
fats; for fats are merely oils that freeze at common living
temperatures and melt only after we get them stowed away.
We, then, burn many sorts of oil. We also burn bread and potatoes
and the like, starch and sugar and gums, which though not oils, are
much like them; really in a way, oils that are already about half
burned. These we finish up in our engines. On the whole, it’s much
more convenient than depending on one sort of fuel, and exploding
only gasoline.