ORGANS OF CONSCIOUSNESS
Nothing is known to us until it has been transmitted to the mind by
the senses. The nerves of special sense, of sight, hearing, smell,
taste, touch, the temperature sense ("hot or cold" sense), the
muscular sense (sense of weight and position), these, and the nerves
controlling voluntary motion, form the peripheral, or surface, nervous
system. This acts as a connecting medium between the outside world and
the central nervous system, which is composed of the brain and spinal
cord. We might liken the nerves, singly, to wires, and all of them
together to a system of wires. The things of the external world tap at
the switchboard by using the organs of special sense; the nerves,
acting as wires, transmit their messages; at the switchboard is the
operator--consciousness--accepting and interpreting the jangle of
calls.
The recognition by the brain of the appeals coming by way of the
transmitting sense, and its interpretation of these appeals, is the
mind's function of consciousness, whether expressed by thinking,
feeling, or willing.
THE CENTRAL AND PERIPHERAL NERVOUS SYSTEMS IN ACTION
I am passing the open door of a bake-shop, and a pervading odor fills
the air. I think "hot rolls," because my organ of smell--the nose--has
received a stimulus which it transmits along my olfactory nerves to the
brain; and there the odor is given a name--"hot rolls." The recognition
of the stimulus as an odor and of that odor as "hot rolls" is
consciousness in the form of thinking. But the odor arouses desire to
eat--hunger; and this is consciousness in the form of feeling. The
something which makes me walk into the shop and buy the rolls is
consciousness in the form of willing. The sensory appeal from the
outside world gained admission through the sense of smell; this
transmitted the message, and consciousness recognized the stimulus,
which immediately appealed to my hunger and incited action to satisfy
that hunger.
The ear of the operator in the telegraph office, again, might illustrate
consciousness. It must be able to interpret mere clickings into terms of
sense. To the operator the sounds say words, and the words are the
expression of the object at the other end of the wire. The brain is the
receiving operator for all the senses, which bring their messages in
code, and which it interprets first as sound, vision, taste, touch,
feel, smell, temperature; then more accurately as words, trees, sweet,
soft, round, acrid, hot.
The mind can know nothing except as the stimulus is transmitted by
sense-channels over the nerves of sense, and received by a conscious
brain. A baby born without sight, hearing, taste, smell, or touch would
remain a mere bit of clay. He could have no awareness. But so long as
any one sense channel remains open the mind may acquire some knowledge.
Suppose I am paralyzed, blind, and deaf, and you put a tennis-ball into
my hand. I cannot tell you what it is, not even what it is like. It
means nothing whatever to me, for the sense channels of touch, sight,
and hearing, through which alone it could be impressed upon my brain,
are gone. Suppose I am blind and deaf, but have my sense of touch
intact; that I never saw or touched or heard of a tennis-ball before,
but I know "apple" and "orange." I can judge that the object is round,
that it is about the size of a small orange or apple. It is very light,
and has a feel of cloth. I know it to be something new in my experience.
You tell me in the language of touch that it is "tennis-ball"; and
thereafter I recognize it by its combination of size, feel, and weight,
and can soon name it as quickly as you, who see it.
Suppose I am blind and my hands are paralyzed, but I have my hearing.
You tell me this is a tennis-ball, and if I have known "tennis-ball" in
the past, I can describe it to you. It has been impressed upon my brain
through my sense of hearing; and memory immediately supplies the
qualities that go with "tennis-ball."
But if none of the senses has ever developed, my brain can receive no
impression whatever; it cannot have even the stimulus of memory. Hence
conscious mind cannot be, except as some sense-channel or channels have
been opened to carry thought material to the brain. So far as we know
today, in this world, mind is absolutely dependent upon the sense organs
and the brain--upon matter--for existence.
THE SYMPATHETIC NERVOUS SYSTEM
Associated with the central nervous system by connecting nerves--but
located outside of it in various parts of the body--are groups of
nerve-cells (gray matter) and their fibers, forming what we call the
_sympathetic nervous system_--the direct connecting link between mind
and body.
The _central nervous system_ is the director of all conscious action of
the body; the _sympathetic_ orders all unconscious action.
The beating of the heart, the contraction of the blood-vessels, hence
the flowing of the blood, the processes of digestion, the functioning of
the glands, are all directed by the sympathetic. In other words, the
_central nervous system_ normally controls the movements of the
voluntary muscles; the _sympathetic_ controls those of the involuntary
muscles.
The quick blush, the sudden paling of the cheeks, the start of fear, the
dilated pupils of fright are the direct result of the action of
involuntary muscles under control of the sympathetic system. The
stimulus is received by the central nervous system; the fibers
connecting the central and the sympathetic systems carry the message
quickly to the latter, which immediately respond by ordering contraction
or expansion of involuntary muscles. So tears flow, we breathe freely
again or we quake and tremble, our pupils widen or contract, the heart
beats suffocatingly, or seems almost to stop.
The _sympathetic system_, as the name implies, is influenced by
suggestions from the emotions rather than from the intellect. We might
say that it is controlled by the "feeling mind" rather than the thinking
mind, for intellect cannot influence it in the least.
The wise nurse, who knows something of the laws of the mind, soon
realizes that the _sympathetic nervous system_, rather than physical
disability, causes many indigestions, headaches, diarrheas, dry mouths,
chills; is responsible for much nausea, much "exhaustion," etc. When she
has had wider experience she finds that almost any known physical
disorder can be unconsciously imitated by the suggestible patient, whose
sympathetic nervous system causes physical reactions to respond to the
feelings of a sick mind. Let the nurse remember, however, that is it not
for her to decide whether the disorders from which her patient suffers
are of physical or nervous origin. It is for her, on the other hand, to
study her patient's mentality and reactions, and to become expert in
reporting symptoms of nervous as well as of physical significance.