The Machinery of the Mind

CHAPTER I. The Physical Vehicle of Consciousness

THE PHYSICAL VEHICLE OF CONSCIOUSNESS

In order to arrive at an adequate understanding of mental processes it is necessary to have some idea of the machinery whereby the mind makes contact with the body.

Throughout every inch of our organism is a network of specialised fibres whose function it is to carry nervous impulses from the sense organs to the central nervous system of brain and spinal cord, and from thence out again to the muscles, glands, and other organs of reaction. The sense organs act as receivers of sensation, the nerve fibres as transmitters, the central nervous system as a general telephone exchange, and the muscles, glands, and organs as the executants of the impulses of the mind.

Sense organs consist of cells, or sets of cells, specialised for the reception of particular kinds of impressions. That is to say, if the particular kind of stimulus they are fitted to receive is administered to them, a change, probably of a chemical type, takes place in their substance, which, it is thought, gives rise to energy of an electrical nature, which runs along the nerve fibre as along a wire. At the present moment, however, our knowledge of the nature of the nervous impulse is tentative and hypothetical.

Like all other living tissue, the nervous system is built up of millions of specialised cells. These cells consist of a main cell body with prolongations, usually two in number. One of these has a mass of branching fibres like the root of a plant, and is called the DENDRON; the other consists of a long thread, the end of which is frayed out into strands as the end of a piece of worsted may be unravelled. This process is called the AXON.

The thread-like branches of the axon of one cell interlace with these of the dendron of another cell, and a nervous impulse, running down the nerve fibres, jumps the gap in the same way as the electric current jumps the space between the terminals of an arc lamp.

It will readily be seen that these interlacing fibrils, millions in number, ramifying throughout every portion of the body, form a most wonderful system of communication; the brain and spinal cord acting as a central telephone exchange.

Muscles are composed of long, spindle-shaped cells which are capable of contraction. Chemical changes are constantly going on in their substance. The blood and lymph which bathe them bring food materials and carry away the waste products of their activity.

These food substances, which are highly organised chemical compounds, are stored in the body of the cell. When a nervous impulse is received, these food globules, as it were, explode; that is to say, they break down into their component chemical parts, and the energy which went to build them up is set free in the process and performs the work for which the muscle is designed.

The glands are the chemists of the body, and in the crucibles of their minute cells carry out the wonderful processes of living chemistry upon which our vital functions are based. The quantity and quality of their output is controlled by the nervous system, which acts as regulator of every process of the body.

CHAPTER II. The Evolution of the Nervous System

THE EVOLUTION OF THE NERVOUS SYSTEM

The easiest way to grasp the organisation of our complex nervous structure is to study its evolution from its humble beginnings in the simplest forms of life.

In single-celled animalculæ, the most primitive type of living creatures, a single cell performs all the functions of life; it moves, breathes, assimilates, excretes, and feels. With the development of multi-cellular organisms, however, different cells are given different work to do, and made to do that, and nothing else.

It then becomes necessary that co-ordination should be maintained between the sense organs that perceive the prey and the muscles that move to its capture, and for this purpose other cells are told off to specialise in communication.

Thus it will be seen that the functional unit of the nervous system is not the nerve cell, but what is called the SENSORI-MOTOR ARC, consisting of a nerve carrying the incoming sensation from a sense organ and making contact with another nerve which carries the outgoing impulse to a muscle or organ.

When a multiplicity of muscles becomes available for movement, it is necessary to further link up the sensori-motor arcs, so that other parts of the structure may be brought into play, and the response not be confined to one muscle alone; so nerve cells form loops upon the arcs, and loops upon the loops, with further intercommunications among themselves, the organisation becoming more and more elaborate, admitting of more and more complex reactions to stimulus, till finally the wonderful complications of the human brain are achieved.

CHAPTER III. How an Idea Enters the Mind

HOW AN IDEA ENTERS THE MIND

When an impression is made on a sense organ, the sensation derived from it is telegraphed up the connecting nerve fibre to the brain, and there translated, by a process of which we know nothing, from a sensation to a thought.

We believe that the mind learns by experience to associate certain kinds of sensation with certain objects or conditions in the environment, and when it feels these particular sensations, deduces that certain objects are present, and forms mental images, or thought models, intended to represent these objects.

The truth of our percepts is determined by the closeness with which our thought model corresponds to its original. An exact copy is a true concept, an imperfect copy an inaccurate concept.

We “recognise” an object by a process of classification, noting its likeness or unlikeness to other objects already known. When an unfamiliar object attracts our attention, we put it through a process of comparison until we find to which compartment in our concept-pictures it should be assigned, and if we cannot find a perfect match, we put it in the most suitable compartment we can discover, and then partition off a little subclass for it, thus admitting its identity in essentials, but its difference in details from the other occupants of that compartment.

For example, supposing we were to land on an island and an object on the shore attracted our attention, we should try to see what class of things of which we already had experience it most closely resembled. We should observe its movements, and assign it to the class of living creatures; see its four limbs and hair, and conclude it was an animal. Note its upright attitude, clothes, and weapons, and recognise these as characteristic of humanity; but perceiving that its skin differed in colour from that of any human being we had ever seen before, we should partition off a fresh subdivision in the department of our mind in which our ideas connected with humanity were stored, place it there, and probably give it a distinguishing name by means of which we could indicate it to other human beings.

Supposing, however, we presently come across another object of the same nature, we should not have to make a fresh subdivision for it, but would classify it with the previously examined specimen, and thus we should feel this time that we “knew what it was.” In fact, the process of “knowing” is a process of classification, and we feel that we “know” a thing when we have assigned it to a satisfactory pigeon-hole among our concepts.

CHAPTER IV. The Organisation of the Upper Levels of the Mind

THE ORGANISATION OF THE UPPER LEVELS OF THE MIND

Those untrained in psychology generally conceive of the mind as a homogeneous whole; our first systematic examination reveals to us, however, that the mind is just as organic as the body.

The organisation of the mind may best be realised by thinking of it as a tank across which, at different heights, are placed sieves of varying coarseness of mesh. We must conceive of the mind as being composed of certain layers, and the layer in which our conscious life has its most permanent focus we will consider to be the outermost layer and name THE FOCUS OF CONSCIOUSNESS. Immediately behind the Focus of Consciousness lies the level which psychologists call THE FRINGE OF CONSCIOUSNESS, and the two are divided from one another by a sieve-like mechanism which is technically called a CENSOR.

The understanding of these two levels of the mind may be rendered clearer if we next consider the uses to which they are put. Supposing a person is sitting in a room listening to a lecture, of what will he be aware? Firstly, his attention will be concentrated upon the lecture, and, secondly, he will be dimly conscious of the sounds made by the traffic in the street outside. By an effort of will he will pay attention to those ideas only which are connected with the lecture, and exclude from consciousness those which are connected with the street traffic; or, to express the process in psychological terms, we may say that all the ideas connected with the lecture are admitted to the focus of consciousness, and all ideas connected with the street noises are kept in the fringe of consciousness, and that the censor-sieve is so adjusted that ideas in the fringe may not intrude upon the focus. Its meshes may be conceived as being of such a size that only the compact little ideas appertaining to the lecture can pass through them, and the undefined ideas connected with the street traffic are held back.

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