Fear Page #10

THE learned and eloquent Professor of Physiology at Turin has given us in the book which he has entitled “Fear,” an analysis of this mental condition and its accompanying physical states, which, marked as it is by scientific accuracy and couched in charming and even in poetical diction, will take high rank as a popular exposition of our knowledge of the expression of one of the most interesting of the emotions of both men and animals.

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We have, therefore, in our nervous system mechanisms which work automatically, and produce a series of contractions directed to one object, which may, at first sight, appear voluntary, but is, in reality, mechanical and unconscious. Some of these mechanisms we bring into the world with us. If one puts a finger into the mouth of a new-born child it begins to suck. It is a machine working without discernment, as if one had touched the spring of an automatic doll; no one teaches the child, he need not learn it at all in fact, for the fœtus in the womb makes exactly the same movement. So it is with the chicken, which pecks when just escaped from the shell. In this case, what gives rise to the movement is no longer immediate contact as that of the finger in the mouth, but the impression of light and sight, which indeed is nothing else but contact with distant things by means of the rays of light. Scarcely has the image of the grain formed itself in the eye of the chicken but it pecks at it.

It suffices to observe our movements with a little attention, in order to be convinced that a greater number of them are automatic than one thinks. When we step out of bed in winter and thrust our naked feet into our slippers, the foot has scarcely touched the cold leather but it withdraws, and an effort is necessary in order to resist. We notice, too, that when the shoemaker measures us for a pair of shoes, it is somewhat difficult to keep our foot still even though he does not tickle us. When one touches iron, a cup, or any other object which is very hot, the hand lets go at once. This is a very useful circumstance, because we often let go of a thing which might injure us before we have even become aware that it burns or pricks. And when we have lost consciousness through illness or any accident, the body takes care of itself, as during sleep, by automatically removing itself from anything which pricks, burns, chills, stings, or presses, and so on. If the pain produced by burning is faint, only the one side of the body moves, if it spreads and grows stronger, it affects the opposite side also, and in the highest degrees, the whole body.

This law, which was established by Pflüger, holds good for normal and uninjured animals as well as for those from which the brain has been removed and which are unconscious. It shows us that the postures and movements of the body, so characteristic of a man responding to sudden pain, do not depend on his will. All that is most characteristic in the phenomena of fear: the palpitation, shortness of breath, pallor, screams, flight, trembling, are reflex movements. The more physiology advances, the more the domain of free-will is restricted, and the greater the increase of involuntary movements.

CHAPTER III

THE BRAIN

I

An animal deprived of the brain is a machine which requires external stimuli in order to move. An uninjured animal is also a machine, but it differs from the other by that power in itself which renders it capable of moving and acting.

When an animal with its brain removed is touched on any point of its body quite lightly, it does not respond at once to this external stimulus, and only when these light touches are often repeated is a reactionary movement excited. There are some very wonderful experiments which made a great impression on me, when I first saw them performed by my friends Kronecker and Stirling in the laboratory in Leipzig. They took a decapitated frog, and fastened between the toes of one of the hind-legs a pen, which made marks on the paper of a rotating cylinder whenever the frog moved. Between the toes of the other leg they fastened the wires of an electric current; a pendulum alternately opening and closing the current in such a manner that an interrupted stimulus was obtained. It was strange to see how the headless frog responded regularly for hours. When stimulated by a weak current (so weak that it could not be felt on the tongue) more numerous repetitions, perhaps thirty, were necessary before the frog responded by a spasmodic movement. If the stimulus were stronger a much smaller number was sufficient to cause reaction, and this continued until life was extinct.

Stimuli accumulate in the spinal cord. We all know it from experience; when we have something in the throat which tickles us, the slight, and at first scarcely perceptible, irritation becomes almost unbearable if it continues, compelling us to cough in order to remove it. As the Italian proverb says, one cannot disguise a cough. Even a slight tickling of the skin has the same effect, and in the functions of reproduction the repetition of slight stimuli produce greater and more ungovernable reflex movements.

There are, however, impressions which remain longer accumulated in the brain before their energy finds expression in muscular activity. Sometimes a part of the nervous system charges itself slowly, like a Leyden jar under the influence of weak electric sparks, the tension of the nerve-cells remaining, as it were, hidden, until suddenly discharged by a contact or some very slight impression. We are astonished; it seems an accidental explosion to us, an effect out of all proportion to the momentary cause, forgetting that fire glows under ashes, that the force had been slowly accumulating, and so we believe we have accomplished the act by means of the will.

The aptitude of the nerve-cells to accumulate and preserve external impressions is such a leading fact in physiology that I do not know any more important one.

If I were asked the difference between the brain and the spinal cord, I should say that the brain is more capable of accumulating impressions, not because of the difference of its substance, but because in it the nerve-cells serving this purpose are found in greater abundance.

The manner in which the brain has formed itself in the evolution of the animal world will render the comprehension of its activities easier. Let us consider the simplest creatures, those possessing, so to speak, only a spinal cord. The nerves branching off from the upper part to the nostrils, eyes, ears, mouth, and elsewhere, were subjected during the long series of generations to more continuous stimuli than other nerves. The cells placed at the roots of these nerves were constantly excited by impressions from the external world; chemical processes and combustion would be more rapid in them, hence the necessity of a more copious flow of blood to those parts which were in greater activity. These cells multiplied rapidly at the roots of the organs of sense, gradually covering a wider field. As the animal structure became more perfect during evolution, and the relations of the animal to the outer world increased, the more abundant and active the cells at the roots of these nerves would become. We must not think here of one individual, although individual exercise does strengthen an organ, but must fix our eyes on the interminable chain of generations, all working in this direction.
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