But how does it happen that under the influence of a powerful emotion the empire of the will over the muscles ceases, and the energy for defence fails?
If we study the phenomena of sleep, we can easily imagine that there are links between the centres of the will and the muscles which may, in certain circumstances, be severed. We all know what nightmare is; we all remember the oppression we have suffered when, in a dream, we have felt ourselves suffocating under an immovable weight on the chest, or from a noose round the throat which we cannot unloose. These dreams, in which we feel ourselves paralysed, are a positive torture; the ground gives way under us and we are precipitated into an abyss; we fall while being pursued and cannot get up again; we find ourselves stretched out in the middle of the street and hear the approaching roll of wheels that will crush us, or see a horse gallop up to trample us with its hoofs. We cannot even scream, hands and feet try in vain to move, the oppression and despair increase until the nightmare passes and we awake with beating heart and laboured breath.
Women and children overcome by violent fear turn their back, cover their eyes with their hands, or creep into a corner without looking behind them. In terror even the most intrepid men do not think of flight; it seems as though the nerves of defence were severed and they were left to their fate. Even in slight emotions we notice a partial failure of the power of the will over the muscles of the hand. Anyone weeping bitterly or laughing heartily cannot steady the pen between the fingers, and the writing is altered.
Whytt noticed that after the head is cut off an animal, its excitability increases greatly after the lapse of a few minutes. The electric stimuli applied to the skin of the trunk immediately after decapitation do not produce any movement of reaction, but a few minutes later the same electric current causes vigorous movements of the legs.
This unexpected phenomena gave rise to the belief that there were mechanisms in the spinal cord which, when irritated by the violent blow of the axe, were capable of arresting the reflex movements. But there are many other experiments which lead us rather to suspect the existence in the nerve-centres of some mechanism which, in certain conditions, nullifies the power of the will over the muscles.
Anyone who has tritons in an aquarium can try the experiment of seizing hold of one by the leg with a pair of pincers; he will see that it remains motionless, almost rigid, for a few minutes. Frogs, when suffering a strong irritation of the sensory nerves, are no longer capable of making a single movement. There are also many other experiments which show us how, under the influence of violent and supernormal excitation, the molecular work of the cells of the spinal cord, requisite for the production of muscular movement through voluntary stimuli, is impeded.
II
Horses tremble when they see a tiger, and are no longer able to run. Even monkeys cannot move when in great fear. The gibbons, the most agile of all monkeys, when taken by surprise on the ground, passively allow themselves to be bound by man. Seals become so agitated when surprised and pursued on shore, that they fall at every step, snort, tremble, and cannot defend themselves.
I quote a passage taken from Brehm’s 'Animal Life,’ in order to show in what an ignoble way man makes use of the disastrous effects which fright produces. Seals are very intelligent animals, and so good-tempered, that on lonely islands they look with the utmost indifference at travellers arriving there, and such is their trust, that they tranquilly allow them to pass or stop in their midst, while they sun themselves on the shore. But as soon as they learn from sad experience to know this terrible destroyer of animals, they become so cautious that they are with difficulty approached or surprised out of the water.
'To the south of Santa Barbara, in California, there is a plateau, rising about thirty metres above the level of the sea, which is a favourite place of repose with the seals. As soon as the boats were lowered, the animals descended from the plateau and plunged into the sea, where they stayed till all danger was over and the crew reassembled on board. The attempt to surprise them was repeatedly made without success, until one day, when a fresh wind was blowing from the plateau towards the ship, and a thick fog afforded effectual concealment. The crew landed at a certain distance, and, keeping to leeward, crept cautiously up to the herd, then rushed suddenly upon them, shouting noisily and brandishing guns, clubs, and spears. Overwhelmed with fear, with staring eyes, their tongues hanging out of their open mouths, the poor animals remained motionless, petrified, until at last the oldest and most courageous males tried to break through the line of destroyers who closed the way towards the sea. But they were killed before they reached the water, the crew then slowly approaching the others, which retreated just as slowly. An attack of this kind soon becomes a butchery, because the poor animals lose all hope of escape, and abandon themselves helplessly to their fate. This herd numbered seventy-five seals, and when all had been killed with clubs and spears but one single animal, the crew thought to try whether it would allow itself to be driven on without resistance. Forced on by its cruel persecutors, the poor creature moved as well as it could over the thorns and undergrowth, until at last, wounded and bleeding, it stopped, stretched out its fins full of thorns to the sailors, as though to move them to pity and beg for mercy. A blow from a club on its head put an end to its sufferings.’[30]