Though most people understand more or less vaguely that the brain acts in some way during study, exact knowledge of the nature of this action is not general. As you will be greatly assisted in understanding mental processes by such knowledge, we shall briefly examine the brain and its connections. It will be manifestly impossible to inquire into its nature very minutely, but by means of a description you will be able to secure some conception of it and thus will be able better to control the mental processes which it underlies.
To the naked eye the brain is a large jelly-like mass enclosed in a bony covering, about one-fourth of an inch thick, called the skull. Inside the skull it is protected by a thick membrane. At its base emerges the spinal cord, a long strand of nerve fibers extending down the spine. For most of its length, the cord is about as large around as your little finger, but it tapers at the lower end. From it at right angles throughout its length branch out thirty-one pairs of fibrous nerves which radiate to all parts of the body. The brain and spinal cord, with all its ramifications, are known as the nervous system. You see now that, though we started with the statement that the mind is intimately connected with the brain, we must now enlarge our statement and say it is connected with the entire nervous system. It is therefore to the nervous system that we must turn our attention.
Although to the naked eye the nervous system is apparently made up of a number of different kinds of material, still we see, when we turn our microscopes upon it, that its parts are structurally the same. Reduced to lowest terms, the nervous system is found to be composed of minute units of structure called nerve-cells or neurones. Each of these looks like a string frayed out at both ends, with a bulge somewhere along its length. The nervous system is made up of millions of these little cells packed together in various combinations and distributed throughout the body. Some of the neurones are as long as three feet; others measure but a fraction of an inch in length.
We do not know exactly how the mind, that part of us which feels, reasons and wills, is connected with this mass of cells called the nervous system. We do know, however, that every time anything occurs in the mind, there is a change in some part of the nervous system. Applying this fact to study, it is obvious that when you are performing any of the operations of study, memorizing foreign vocabularies, making arithmetical calculations, reasoning out problems in geometry, you are making changes in your nervous system. The question before us, then, is, What is the nature of these changes? According to present knowledge, the action of the nervous system is best conceived as a form of chemical change that spreads among the nerve-cells. We call this commotion the nervous current. It is very rapid, moving faster than one hundred feet a second, and runs along the cells in much the same way as a "spark runs along a train of gunpowder." It is important to note that neurones never act singly; they always act in groups, the nervous current passing from neurone to neurone. It is thought that the most important changes in the nervous system do not occur within the individual neurones, but at the points where they join with each other. This point of connection is called the synapse and although we do not understand its exact nature, it may well be pictured as a valve that governs the passage of the nervous current from neurone to neurone. At time of birth, most of the valves are closed. Only a few are open, mainly those connected with the vegetative processes such as breathing and digestion. But as the individual is played upon by the objects of the environment, the valves open to the passage of the nervous current. With increased use they become more and more permeable, and thus learning is the process of making easier the passage of the nervous current from one neurone to another.
We shall secure further light upon the action of the nervous system if we examine some of the properties belonging to nerve-cells. The first one is impressibility. Nerve-cells are very sensitive to impressions from the outside. If you have ever had the dentist touch an exposed nerve, you know how extreme this sensitivity is. Naturally such a property is very important in education, for had we not the power to receive impressions from the outside world we should not be able to acquire knowledge. We should not even be able to perceive danger and remove ourselves from harm. "If we compare a man's body to a building, calling the steel frame-work his skeleton and the furnace and power station his digestive organs and lungs, the nervous system would include, with other things, the thermometers, heat regulators, electric buttons, door-bells, valve-openers,— the parts of the building, in short, which are specifically designed to respond to influences of the environment." The second property of nerve-cells which is important in study is conductivity. As soon as a neurone is stimulated at one end, it communicates its excitement, by means of the nervous current, to the next neurone or to neighboring neurones. Just as an electric current might pass along one wire, thence to another, and along it to a third, so the nervous current passes from neurone to neurone. As might be expected, the two functions of impressibility and conductivity are aided by such an arrangement of the nervecells that the nervous current may pass over definitely laid pathways. These systems of pathways will be described in a later paragraph.
The third property of nerve-cells which is important in study is modifiability.
That is, impressions made upon the nerve-cells are retained. Most living tissue is modifiable to some extent. The features of the face are modifiable, and if one habitually assumes a peevish expression, it becomes, after a time, permanently fixed. The nervous system, however, possesses the power of modifiability to a marked degree, even a single impression sufficing to make striking modification.
This is very important in study, being the basis for the retentive powers of the mind.
Having examined the action of the nervous system in its simplicity, we have now to examine the ways in which the parts of the nervous system are combined. We shall be helped if we keep to the conception of it as an aggregation of systems or groups of pathways. Some of these we shall attempt to trace out. Beginning with those at the outermost parts of the body, we find them located in the senseorgans, not only within the traditional five, but also within the muscles, tendons, joints, and internal organs of the body such as the heart, and digestive organs. In all these places we find ends of neurones which converge at the spinal cord and travel to the brain. They are called sensory neurones and their function is to carry messages inward to the brain. Thus, the brain represents, in great part, a central receiving station for impressions from the outside world. The nerve-cells carrying messages from the various parts of the body terminate in particular areas. Thus an area in the back part of the brain receives messages from the eyes; another area near the top of the brain receives messages from the skin. These areas are quite clearly marked out and may be studied in detail by means of the accompanying diagram.
There is another large group of nerve-cells which, when traced out, are found to have one terminal in the brain and the other in the muscles throughout the body.
The area in the brain, where these neurones emerge, is near the top of the brain in the area marked Motor on the diagram. From here the fibers travel down through the spinal cord and out to the muscles. The nerve-cells in this group are called motor neurones and their function is to carry messages from the brain out to the muscles, for a muscle ordinarily does not act without a nervous current to set it off.
So far we have seen that the brain has the two functions of receiving impressions from the sense-organs and of sending out orders to the muscles. There is a further mechanism that must now be described. When messages are received in the sensory areas, it is necessary that there be some means within the brain of transmitting them over to the motor area so that they may be acted upon. Such an arrangement is provided by another group of nerve-cells in the brain, having as their function the transmission of the nervous current from one area to another.
They are called association neurones and transmit the nervous current from sensory areas to motor areas or from one sensory area to another. For example, suppose you see a brick falling from above and you dodge quickly back. The neural action accompanying this occurrence consists of an impression upon the nerve-cells in the eye, the conduction of the nervous current back to the visual area of the brain, the transmission of the current over association neurones to the motor area, then its transmission over the motor neurones, down the spinal cord, to the muscles that enable you to dodge the missile. The association neurones have the further function of connecting one sensory area in the brain with another. For example, when you see, smell, taste and touch an orange, the corresponding areas in the brain act in conjunction and are associated by means of the association neurones connecting them. The association neurones play a large part in the securing and organizing of knowledge. They are very important in study, for all learning consists in building up associations.
From the foregoing description we see that the nervous system consists merely of a mechanism for the reception and transmission of incoming messages and their transformation into outgoing messages which produce movement. The brain is the center where such transformations are made, being a sort of central switchboard which permits the sense-organs to come into communication with muscles. It is also the instrument by means of which the impressions from the various senses can be united and experience can be unified. The brain serves further as the medium whereby impressions once made can be retained. That is, it is the great organ of memory. Hence we see that it is to this organ we must look for the performance of the activities necessary to study. Everything that enters it produces some modification within it. Education consists in a process of undergoing a selected group of experiences of such a nature as to leave beneficial results in the brain. By means of the changes made there, the individual is able better to adjust himself to new situations. For when the individual enters the world, he is not prepared to meet many situations; only a few of the neural connections are made and he is able to perform only a meagre number of simple acts, such as breathing, crying, digestion. The pathways for complex acts, such as speaking English or French, or writing, are not formed at birth but must be built up within the life-time of the individual. It is the process of building them up that we call education. This process is a physical feat involving the production of changes in physical material in the brain. Study involves the overcoming of resistance in the nervous system. That is why it is so hard. In your early school-days, when you set about laboriously learning the multiplication table, your unwilling protests were wrung because you were being compelled to force the nervous current through new pathways, and to overcome the inertia of physical matter. Today, when you begin a train of reasoning, the task is difficult because you are opening hitherto untravelled pathways. There is a comforting thought, however, which is derived from the factor of modifiability, in that with each succeeding repetition, the task becomes easier, because the path becomes worn smoothly and the nervous current seeks it of its own accord; in other words, each act and each thought tends to become habitualized. Education is then a process of forming habits, and the rest of the book will be devoted to the description and discussion of habits which a student should form.
READING AND EXERCISE Reading: Herrick (7) Exercise 1. Draw a picture of the brain, showing roughly what takes place there (a) when you read a book, (6) listen to a lecture, (c) take notes.
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