LITMIR.BIZ

Скачать книгу

Have you noticed a difference in the habit of attention in different pupils? Have you noticed the same thing for whole schools or rooms?

      7. Do you know of children too much given to daydreaming? Are you?

      8. Have you seen a teacher rap the desk for attention? What type of attention was secured? Does it pay?

      9. Have you observed any instance in which pupils' lack of attention should be blamed on the teacher? If so, what was the fault? The remedy?

      10. Visit a school room or a recitation, and then write an account of the types and degrees of attention you observed. Try to explain the factors responsible for any failures in attention, and also those responsible for the good attention shown.

CHAPTER III

       Table of Contents

THE BRAIN AND NERVOUS SYSTEM

       Table of Contents

      A fine brain, or a good mind. These terms are often used interchangeably, as if they stood for the same thing. Yet the brain is material substance—so many cells and fibers, a pulpy protoplasmic mass weighing some three pounds and shut away from the outside world in a casket of bone. The mind is a spiritual thing—the sum of the processes by which we think and feel and will, mastering our world and accomplishing our destiny.

      1. THE RELATIONS OF MIND AND BRAIN

      Interaction of Mind and Brain.—How, then, come these two widely different facts, mind and brain, to be so related in our speech? Why are the terms so commonly interchanged?—It is because mind and brain are so vitally related in their processes and so inseparably connected in their work. No movement of our thought, no bit of sensation, no memory, no feeling, no act of decision but is accompanied by its own particular activity in the cells of the brain. It is this that the psychologist has in mind when he says, no psychosis without its corresponding neurosis.

      So far as our present existence is concerned, then, no mind ever works except through some brain, and a brain without a mind becomes but a mass of dead matter, so much clay. Mind and brain are perfectly adapted to each other. Nor is this mere accident. For through the ages of man's past history each has grown up and developed into its present state of efficiency by working in conjunction with the other. Each has helped form the other and determine its qualities. Not only is this true for the race in its evolution, but for every individual as he passes from infancy to maturity.

      The Brain as the Mind's Machine.—In the first chapter we saw that the brain does not create the mind, but that the mind works through the brain. No one can believe that the brain secretes mind as the liver secretes bile, or that it grinds it out as a mill does flour. Indeed, just what their exact relation is has not yet been settled. Yet it is easy to see that if the mind must use the brain as a machine and work through it, then the mind must be subject to the limitations of its machine, or, in other words, the mind cannot be better than the brain through which it operates. A brain and nervous system that are poorly developed or insufficiently nourished mean low grade of efficiency in our mental processes, just as a poorly constructed or wrongly adjusted motor means loss of power in applying the electric current to its work. We will, then, look upon the mind and the brain as counterparts of each other, each performing activities which correspond to activities in the other, both inextricably bound together at least so far as this life is concerned, and each getting its significance by its union with the other. This view will lend interest to a brief study of the brain and nervous system.

      2. THE MIND'S DEPENDENCE ON THE EXTERNAL WORLD

      But can we first see how in a general way the brain and nervous system are primarily related to our thinking? Let us go back to the beginning and consider the babe when it first opens its eyes on the scenes of its new existence. What is in its mind? What does it think about? Nothing. Imagine, if you can, a person born blind and deaf, and without the sense of touch, taste, or smell. Let such a person live on for a year, for five years, for a lifetime. What would he know? What ray of intelligence would enter his mind? What would he think about? All would be dark to his eyes, all silent to his ears, all tasteless to his mouth, all odorless to his nostrils, all touchless to his skin. His mind would be a blank. He would have no mind. He could not get started to think. He could not get started to act. He would belong to a lower scale of life than the tiny animal that floats with the waves and the tide in the ocean without power to direct its own course. He would be but an inert mass of flesh without sense or intelligence.

      The Mind at Birth.—Yet this is the condition of the babe at birth. It is born practically blind and deaf, without definite sense of taste or smell. Born without anything to think about, and no way to get anything to think about until the senses wake up and furnish some material from the outside world. Born with all the mechanism of muscle and nerve ready to perform the countless complex movements of arms and legs and body which characterize every child, he could not successfully start these activities without a message from the senses to set them going. At birth the child probably has only the senses of contact and temperature present with any degree of clearness; taste soon follows; vision of an imperfect sort in a few days; hearing about the same time, and smell a little later. The senses are waking up and beginning their acquaintance with the outside world.

       Fig. 5.—A Neurone from a Human Spinal Cord. The central portion represents the cell body. N, the nucleus; P, a pigmented or colored spot; D, a dendrite, or relatively short fiber—which branches freely; A, an axon or long fiber, which branches but little.

      The Work of the Senses.—And what a problem the senses have to solve! On the one hand the great universe of sights and sounds, of tastes and smells, of contacts and temperatures, and whatever else may belong to the material world in which we live; and on the other hand the little shapeless mass of gray and white pulpy matter called the brain, incapable of sustaining its own shape, shut away in the darkness of a bony case with no possibility of contact with the outside world, and possessing no means of communicating with it except through the senses. And yet this universe of external things must be brought into communication with the seemingly insignificant but really wonderful brain, else the mind could never be. Here we discover, then, the two great factors which first require our study if we would understand the growth of the mind—the material world without, and the brain within. For it is the action and interaction of these which lie at the bottom of the mind's development. Let us first look a little more closely at the brain and the accompanying nervous system.

      3. STRUCTURAL ELEMENTS OF THE NERVOUS SYSTEM

      It will help in understanding both the structure and the working of the nervous system to keep in mind that it contains but one fundamental unit of structure. This is the neurone. Just as the house is built up by adding brick upon brick, so brain, cord, nerves and organs of sense are formed by the union of numberless neurones.

       Fig. 6.—Neurones in different stages of development, from a to e. In a, the elementary cell body alone is present; in c, a dendrite is shown projecting upward and an axon downward.—After Donaldson.

      The Neurone.—What, then, is a neurone? What is its structure, its function,

Скачать книгу