Fear Page #9

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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My friend Tiegel, professor of physiology in Japan, made another experiment. He took a snake and severed the head at a blow. While the trunk was writhing on the ground he touched it with a red-hot iron bar, and the snake wound itself round it and did not desist, although its flesh was burnt and skin charred. And so, in this case too, the spinal cord producing these movements is unreasoning.

But how to explain all the other apparently reasoning acts?

The structure of the nerve-centres can itself give an appearance of intelligence to results which are purely mechanical. Let us assume that the nerve-paths passing to the various muscles from one side or the other transmit more or less easily the stimuli given off from the spinal cord. A drop of vinegar having been put on the leg of a frog, as before mentioned, certain muscles will at once move--that is, those of which the nerves oppose the least resistance to the stimuli produced in the centre. But if the animal cannot remove the cause of the irritation, the latter accumulates in the spinal cord, so increasing in force that the nervous tension makes a way for itself along more resisting paths, thus giving rise to other less usual movements.

VI

During my medical career I had more than once an opportunity of seeing the human spinal cord injured or severed. The most interesting case was that of a peasant, who, in falling from a tree, had severed the spinal cord in the dorsal region a little below the shoulder-blades, with a pruning hook. He moved his arms, spoke, but did not feel the lower part of his body any longer, nor the pain which a wound he had on the shin-bone would otherwise have caused him, although the leg moved whenever we touched the sore in order to treat it.

Marshall Hall proved that all generative acts are dependent on the lower part of the spinal cord, and Brachet tells of a soldier who became the father of two children although the lower half of his body was paralysed and quite without feeling. The only thing we do not find in an animal with the spinal cord severed are those irregular movements of the part separated from the brain, corresponding by their spontaneity to those we call voluntary.

Frogs and other animals of which one has cut the spinal cord are in general motionless and paralysed in the parts separated from the brain; we must touch them in order to make them move. If one pinches or slightly presses the hind-paw of a dog with the spinal cord severed in the dorsal region, he moves it or draws it away, but does it unconsciously, as we do if we are touched while asleep. If the stimulus is strong, he moves the other leg and his tail; if stronger still, he moves his whole body and trembles.

Even when the brain is wanting, slight stimuli produce a wagging of the tail; strong stimuli the drawing of the tail between the legs. This proves that certain characteristic phenomena of fear are produced without any participation of the will or consciousness.

The liveliness and restlessness so characteristic of youth arise from the greater excitability of the nervous system, which one always notices in young animals. The age, race, and bodily condition render very dissimilar the reflex movements by which animals deprived of their brain respond, even when they are excited in the same manner. The differences observable in character correspond to anatomical and functional differences of the nerve-centres.

As it is impossible to find two men having all parts of their brain or spinal cord exactly alike, we infer that these differences in the structure of the nerve apparatus materially influence other functional differences which seem to depend on causes of a higher order known under the generic name of will. What many call free-will is only a fatal necessity, an indissoluble chain of causes and effects, of physical and mechanical actions, of automatic and unconscious reactions in the living machine.

VII

In order to understand certain phenomena of fear, we must first study a few peculiarities presented by the excitable portions of the nervous system. If one stimulates the nerve running through the frog’s leg by very slight electric currents which are incapable of producing a contraction of the muscles, the force of the current may be slowly and evenly increased without the leg moving or in any way responding. This experiment shows us that the motor nerves do not respond to the stimulus as such, because the latter may be very strong without producing any visible effect, but that it is the rapid variations and changes which cause the convulsive movements.

Any pain or fear assailing us unexpectedly causes a great disturbance in the organism, but have a less serious effect when slowly developed.

There is always a more energetic response during the first moments of a sensation. This fact is true of all phenomena of the nervous system, and it is therefore unnecessary to give examples of what everyone knows from experience. This depends also upon the fact that the nervous system discharges a part of its energy at every reaction, so that when the animal is very weak it responds no more after the first two or three times.

We now understand why slight, unexpected emotions produce such intense perturbations in the organism, while very serious events for which we are prepared have in proportion much less effect.

VIII

Pliny, in speaking of fear making one close the eyes, relates that amongst twenty gladiators scarcely two were found who did not wink when suddenly menaced.[8]

[8] Plinius: Historia naturalis, lib. xi., p. 480.

It is striking that such slight causes produce movements so pronounced that we are not capable of suppressing them. We know that our friend will certainly not poke his finger into our eye, but the conviction that it is a joke does not suffice. Even if a thick pane of glass were between us and the approaching hand, with all the force of reason and will, many would be unable to avoid shutting the eyes, as though there were in us two natures: one, animal and unreasoning which commands, and the other human and intelligent which succumbs.

Again, when a gnat or a grain of dust gets into our eye, the eye closes irresistibly by an automatic mechanism quite independent of our will. Sometimes there is not only one contraction, but a somewhat complicated series of movements excited in parts distant from the stimulus.

As a convincing example, I shall communicate what I observed in an investigation of deglutition. This act, performed unceasingly during eating, is by no means voluntary, for if we try to repeat it a few times in succession we notice at once that, as soon as we have no saliva in the mouth, every effort to swallow is in vain. In order to swallow it is necessary that a morsel of food or some fluid should touch the mucous membrane of the posterior portion of the mouth. The sensory nerves stimulated in this way communicate to the spinal cord that a body is at the entrance of the œsophagus which must be sent to the stomach. Immediately a succession of orders is issued, one after the other, by the spinal cord, so that first the upper part of the œsophagus contracts and propels the morsel a short way down, then a further order causes a contraction of the next part, then comes another order whereupon a part still lower down contracts, and so all the successive portions of the œsophagus transmit the morsel one to another by means of various separate orders until it reaches the stomach.
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