Part 2 (2/2)

1 THE RELATIONS OF MIND AND BRAIN

INTERACTION OF MIND AND BRAIN--How, then, come these tidely different facts, mind and brain, to be so related in our speech? Why are the tered?--It is because mind and brain are so vitally related in their processes and so inseparably connected in their work No ht, no bit of sensation, no , 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 inneurosis_

So far as our present existence is concerned, then, no h 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 es of rown 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 chapterthat the brain does not create the h the brain No one can believe that the brain secretes rinds 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 h it, then the mind must be subject to the limitations of its machine, or, in other words, the h which it operates A brain and nervous system that are poorly developed or insufficiently nourished rade of efficiency in our ly adjustedthe electric current to its work

We will, then, look upon the mind and the brain as counterparts of each other, each perfor 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 vieill 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 systeo 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 ine, 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 lifetience 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 et 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 ence

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 set 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 perfors and body which characterize every child, he could not successfully start these activities without aAt birth the child probably has only the senses of contact and teree of clearness; taste soon follows; vision of an i about the sa up and beginning their acquaintance with the outside world

[Illustration: 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 problereat universe of sights and sounds, of tastes and smells, of contacts and te to the material world in which we live; and on the other hand the little shapeless ray and white pulpyits own shape, shut away in the darkness of a bony case with no possibility of contact with the outside world, and possessing no h the senses

And yet this universe of external things nificant but really wonderful brain, else the reat factors which first require our study if ould 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 littlenervous 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

[Illustration: 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 doard--After DONALDSON]

THE NEURONE--What, then, is a neurone? What is its structure, its function, how does it act? A neurone is _a protoplas fibers_ The cell part of the neurone is of a variety of shapes, triangular, pyraular The cells vary in size froeneral the function of the cell is thought to be to generate the nervous energy responsible for our consciousness--sensation,and all the rest, and for our movements The cell also provides for the nutrition of the fibers

[Illustration: FIG 7--Longitudinal (a) and Transverse (b) section of nerve fiber The heavy border represents thesheath, which becoer fibers--After DONALDSON]

NEURONE FIBERS--The neurone fibers are of two kinds, _dendrites_ and _axons_ The dendrites are coe in diameter, branch freely, like the branches of a tree, and extend but a relatively short distance from the parent cell Axons are slender, and branch but little, and then approxireater distance froreatly in length Some of those found in the spinal cord and brain are not , while others which reach from the extremities to the cord, measure several feet Both dendrites and axons are of diameter so small as to be invisible except under the microscope

NEUROGLIA--Out of this simple structural element, the neurone, the entire nervous system is built True, the neurones are held in place, and perhaps insulated, by a kind of soft celia_ But this seems to possess no strictly nervous function The number of the microscopic neurones required to make up the mass of the brain, cord and peripheral nervous systerasp It is computed that the brain and cord contain some 3,000of the complexity of the brain structure can best be understood by an illustration Professor Stratton estimates that if ere tofor the neurone fibers wires so small as to be barely visible to the eye, in order to find room for all the wires the model would need to be the size of a city block on the base and correspondingly high I froray matter” of the brain and cord is made up of nerve cells and their dendrites, and the ter white ray lia which surrounds the nerve cells and fibers, and a network of blood vessels The ”white matter” of the central syste or lia The white matter contains no nerve cells or dendrites The difference in color of the gray and the white ray , thus revealing the ashen gray of the nerve threads In the white masses the medullary sheath is present

4 GROSS STRUCTURE OF THE NERVOUS SYSTEM

DIVISIONS OF THE NERVOUS SYSTEM--The nervous system may be considered in two divisions: (1) The _central_ system, which consists of the brain and spinal cord, and (2) the _peripheral_ syste the periphery and the internal organs with the central systeans of the senses The _sympathetic_ system, which is found as a double chain of nerve connections joining the roots of sensory and motor nerves just outside the spinal column, does not seem to be directly related to consciousness and so will not be discussed here A brief description of the nervous systeether in so wonderful a way to accoreat result