muscular contraction. What makes a muscle contract?

REFERENCES FOR CLASS READING

• Münsterberg: Psychology, General and Applied, Chapters I, II, and V.
• Pillsbury: Essentials of Psychology, Chapter I.
• Pyle: The Outlines of Educational Psychology, Chapter I.
• Titchener: A Beginner’s Psychology, Chapter I.

CHAPTER II
DEVELOPMENT OF THE RACE AND OF THE INDIVIDUAL

Racial Development. The purpose of this chapter is to make some inquiry concerning the origin of the race and of the individual. In doing this, it is necessary for us first of all to fix in our minds the idea of causality. According to the view of all modern science, everything has a cause. Nothing is uncaused. One event is the result of other previous events, and is in turn the cause of other events that follow. Yesterday flowed into to-day, and to-day flows into to-morrow. The world as it exists to-day is the result of the world as it existed yesterday. This is true not only of the inorganic world—the world of physics and chemistry—but it is true of living things as well. The animals and plants that exist to-day are the descendants of others that lived before. There is probably an unbroken line of descent from the first life that existed on the earth to the living forms of to-day.

Not only does the law of causality hold true in the case of our bodies, but of our minds as well. Our minds have doubtless developed from simpler minds just as our bodies have developed from simpler bodies. That different grades and types of minds are to be found among the various classes of animals now upon the earth, no one can doubt, for the different forms certainly show different degrees of mentality. According to the evidence of those scientists who have studied the remains of animals found in the earth’s crust, there is a gradual development of animal forms shown in successive epochs. In the very oldest parts of the earth’s crust, the remains of animal life found are very simple. In later formations, the remains show an animal life more complex. The highest forms of animals, the mammals, are found only in the more recent formations. The remains of man are found only in the latest formations.

Putting these two facts together—(1) that the higher types of mind are found to-day only in the higher types of animals, and (2) that a gradual development of animal forms is shown by the remains in the earth’s crust—the conclusion is forced upon us that mind has passed through many stages of development from the appearance of life upon the earth to the present time. Among the lower forms of animals to-day one sees evidence of very simple minds. In amœbas, worms, insects, and fishes, mind is very simple. In birds, it is higher. In mammals, it is higher still. Among the highest mammals below man, we see manifestations of mind somewhat like our own. These grades of mentality shown in the animals of to-day represent the steps in the development of mind in the animals of the past.

We cannot here go into the proof of the doctrine of development. For this proof, the reader must be referred to zoölogy. One further point, however, may be noted. If it is difficult for the reader to conceive of the development of mind on the earth similar to the development of animals in the past, let him think of the development of mind in the individual. There can certainly be no doubt of the development of mind in an individual human being. The infant, when born, shows little manifestation of mentality; but as its body grows, its mind develops, becoming more and more complex as the individual grows to maturity.

The World as Dynamic. The view of the world outlined above, and held by all scientific men of the present time, may be termed the dynamic view. Man formerly looked upon the world as static, a world where everything was fixed and final. Each thing existed in itself and for itself, and in large measure independent of all other things. We now look upon things and events as related and dependent. Each thing is dependent upon others, related to others.

Man not only lives in such a world, but is part of such a world. In this world of constant and ceaseless change, man is most sensitive and responsive. Everything may affect him. To all of the constant changes about him he must adjust himself. He has been produced by this world, and to live in it he must meet its every condition and change. We must, then, look upon human nature as something coming out of the past and as being influenced every moment by the things and forces of the present. Man is not an independent being, unaffected by everything that happens; on the contrary, he is affected by all influences that act upon him. Among these influences may be mentioned weather, climate, food, and social forces.

The condition of the various organs of a child’s body determine, to some extent, the effect which these various forces have upon it. If a child’s eyes are in any way defective, making vision poor, this tremendously influences his life. Not only is such a child unable to see the world as it really is, but the eyestrain resulting from poor vision has serious effects on the child, producing all sorts of disorders. If a child cannot hear well or is entirely deaf, many serious consequences follow. In fact, every condition or characteristic of a child that is in any way abnormal may lead on to other conditions and characteristics, often of a serious nature. The growth of adenoids, for example, may lead to a serious impairment of the mind. Poor vision may affect the whole life and character of the individual. The influence of a parent, teacher, or friend may determine the interest of a child and affect his whole life. The correct view of child life is that the child is affected, in greater or less degree, by every influence which acts upon him.

Significance of Development and Causality. What are the consequences of the view just set forth? What is the significance of the facts that have been enumerated? It is of great consequence to our thinking when we come to recognize fully the idea of causality. We then fully accept the fact that man’s body and mind are part of a causal and orderly world.

Let us consider, for example, the movement of a muscle. Every such movement must be caused. The physiologist has discovered what this cause is. Ordinarily and normally, a muscle contracts only when stimulated by a nerve current. Tiny nerve fibrils penetrate every muscle, ending in the muscle fibers. The nerve-impulse passing into the fibers of the muscles causes them to contract. The nerve stimulus itself has a cause; it ordinarily arises directly or indirectly from the stimulation of a sense organ. And the sense organs are stimulated by outside influences, as was explained previously.

Not only are our movements caused, but our sensations, our ideas, and our feelings follow