Chapter 16

RELATION OF MIND AND BODY

We have found that mind is entirely dependent upon the bodily organs for its existence. Is the body in the same way dependent upon the mind? Can the mind die and the body go on?

Given a perfect body with unblocked sense channels, and put the mind to sleep, paralyze the _central nervous system_ with alcohol in sufficient quantity so that the undamaged _peripheral nervous system_--the senses--can obtain no response or recognition from it, and that perfect body is as useless for the time as if dead. But here comes proof of the remarkable hold of the body on life. The unconscious mind takes up the burden of directing the sympathetic nerves to stimulate the muscles of breathing. The unconscious sees to the beating of the heart. It directs the contraction of the blood-carrying vessels. It maintains certain vital processes of secretion. Thus automatically life goes on; the body still reacts to a limited field of stimuli, and consciousness recognizes it not. But when the unconscious mind ceases to function, then, indeed, does the body die. Yet the conscious mind may "die" and the body live on, so long as the unconscious continues its activity.

It is possible for the human body to live for years, utterly paralyzed, with many of the senses gone, with no consciousness of being--if cared for by other persons--a merely vegetable existence. The current of power is broken; but the spark is still glowing, though utterly useless because connected with nothing. And it may continue to glow for some time while properly stimulated from outside sources.

We might liken the mind to the boiler in which steam is generated, and the body to the engine which the steam runs. If the boiler bursts, the engine stops; but it may not be otherwise damaged. It simply cannot carry out its main function of motion any longer. The fires under the boiler are still burning and can be kept burning so long as fuel is provided, but the connection is broken and the great bulk of iron is a useless thing in that it can no longer fulfil its purpose.

In just such a way may the mind be paralyzed; but the spark of life, which has through all the years kindled the now lost mind to action, may still remain--a useless thing, which would die away if not tended from without by other bodies whose minds are still intact.

But in the demented mind consciousness still remains, the awareness of the young child or baby stage of life. The connection between the upper or conscious brain centers and the body has been tampered with; it no longer is direct, but breaks off into switch-lines. But the contact still holds between the lower or unconscious mind and the body; so the automatic body functions go on, directed as they were in babyhood before the independent mind assumed control. Hence, when all acute consciousness is finally gone, the unconscious mind, a perfect automaton, may still carry out the simplest vegetative activities of existence.

When body is dead, mind, so far as its reactions to the world we know are concerned, ceases to act. But when the conscious mind is "dead" the body may yet live as a vegetable lives, with all its distinctively human functions lost. Motionless, save for the beating of the heart and the reaction of the lungs to air, the body may still be alive, though the mind long since has ceased all earthly activity.

So we discover that an organ of mind is an essential, here, to life of mind, and that mind only can induce this organ to any action above the vegetative stage. But, on the other hand, we find that life can exist without conscious mind, even if untended by others, for a limited time.

If the direct nerve connections between the brain and the hand, the brain and the foot, or the brain and the trunk are cut off, the mind henceforth realizes nothing of that part except as the sense of sight reports upon it; for the optic nerves relate the hand and mind, through this sense, as truly as the motor nerves which carry the mind's message for motion to the hand, and the sensory nerves which carry back to the mind the hand's pain. But let the optic nerve be inert, the sensory and motor connections broken between brain and hand, or foot and trunk, or brain and trunk, and the hand or foot may be amputated and the mind never sense the fact; the trunk may be severely injured and the mind be serenely unconscious. So the brain in man is "the one immediate bodily condition of the mental operations." Take away all the brain and man's body is a useless mass of protoplasm.

The brain's varied and intricate nerve connections with all parts of the body, through nerves branching from the main trunks in the spinal cord, we shall not discuss, for you know them through your study of anatomy. For the purpose of our psychology we need consider only two of the main divisions of the brain--the _cerebrum_, which includes what we call the right and left hemispheres, and the _cerebellum_.

THE CEREBRUM OR FOREBRAIN

For convenience the various lobes of the cerebrum are known as frontal, temporal, parietal, and occipital, according to the parts of the brain referred to: as forehead, temples, crown, or occiput. The cerebellum, or hind brain, is also divided into two hemispheres, and is situated behind and below the hemispheres of the cerebrum.

A system of localization has been roughly mapped out, the result of careful laboratory work on animals and of studying the loss of various functions in human beings as related to the location of brain injuries.

From these experiments it seems proved that consciousness belongs only to the cortex or surface of the upper brain, and that the vast realm of the unconscious belongs to the lower brain centers. Hence the cortex is the organ of consciousness, and the lower centers are the repository of the unconscious until it again becomes conscious.

The motor zone of the cortex we now know to be situated in the convolutions bordering the fissure of Rolando. Vision is evidently excited from the occipital lobes, though not yet conclusively proved. Smell, presumably, is located in the temporal lobes. Considered action is directed from the upper hemispheres only. It is significant that the hemispheres of the cerebrum are also accepted as the seat of memory for man--that intellectual quality which makes him capable of acting from absent stimuli, stimuli only present to memory; which makes it possible for him to reason the present from the experiences of the past.

But in all animal life, except the higher forms, the control of action is from the lower brain centers, centers which respond only to present objects. With them memory, as man knows it, is lacking; but the reactions of the past are indelibly imprinted upon motor nerves and muscles, so that when the present object presses the button, as it were, calling forth the experience of the race, the animal instinctively reacts.

But of what use to man, then, are the lower brain centers?

In man, as in lower animals, they care for the vegetative functions of life, so that our blood continues to circulate, the air enters and leaves our lungs, digestion is carried on, with no assistance from the upper centers, the hemispheres of the cerebrum being thus left free for concentration on the external world of matter, which it can transform into a world of thought.

It is the lower or vegetative brain that may still exist and keep life intact when the functions of the cerebrum are destroyed. We can say, then, of the brain as a whole that it is the organ of the mind, the _sine qua non_ of the mind, the apparatus for the registration of sense impressions. The senses themselves are the rudiments of mind, are the means by which stimuli alighting on sense organs enter consciousness; for the nerves of special sense immediately carry the impetus to the brain, where it is recognized as the "not me," the _something_ definitely affecting the _me_, and demanding reaction from the _me_.

The functions of the cerebrum we find grouping themselves in three classes: _intellect_, _emotion_, and _volition_, more simply, thinking, feeling, and willing; and we find no mental activity of the normal or abnormal mind which will not fall into one of these groupings. This does not mean that one part of the brain thinks, another part wills, another part feels; for in the performance of any one of these functions the mind acts as a whole. Our thinking or our willing may be permeated with feeling, but the entire mind is simply reacting simultaneously upon various stimuli.