anxiety as the image of a
Diatryma
, a bird of prey more than two metres in height without any wings to speak of, but consequently with far bigger thighs, claws and beak, surfaced in her mind. She raised her head and noticed in the reflection of the water how the hairs on her muzzle quivered, made static by the electricity in the air.
âWhat?â she wondered.
Convection wind caused the dayâs evaporation to rise until it was halted by the chill from the outer atmosphere and condensed into cumulonimbus clouds. The turbulence within the clouds shattered rain, hail and ice, producing smaller, electricallycharged particles. The disparity in voltage between the surface of the earth and the clouds rapidly approached the number of millions of volts per cubic metre that would trigger a spark. The hairs on our
Eohippus
âs little body stood on end as she sensed the electricity in the air. In an instant a bolt of lightning shot its plasma cord deep into the forest, barely one hundred metres away from the horses, and the resulting crash of thunder was so loud that they were temporarily struck deaf. The sudden silence in their heads contributed to their panic. Billions of synapses flashed in the horsesâ brains as their autonomous nervous system took control of their bodies and triggered an automatic fright-flee response. The direction of flight was initially diametrically opposite to the light and the sound.
The horseâs heart instantly obeyed the command from the sympathetic nervous system: noradrenaline in generous quantities stimulated the sinus node in order to increase the frequency of impulses that ran down through the atrioventricular node, then separated at the bundle of His into the right and left branches and caused, with appropriate delays in the right places, the muscle fibres to demand an ever-increasing working rate from the heart. The alternatingcontractions and relaxations of the heart muscles allowed blood in regulated quantities to flow into the right atrium, onwards to the right ventricle and from there out into the lungs, where it released carbon dioxide and absorbed oxygen; thereafter the blood flowed to the left atrium of the heart, down into the left ventricle and through the aorta out into the body. The heartâs rhythm accelerated; its muscles and the brain demanding fresh blood.
The horses ran along the lakeshore, but soon darted into the undergrowth of the forest, where the darkness was even denser now the clouds had compressed. Underneath her somewhat rasping breathing the mare could hear her blood pump through her ears.
Rain followed shortly afterwards, first as light showers, which they hardly noticed, growing heavier and then a sudden cloudburst. Gusts of wind swept curtains of heavy drops across the treetops and the surface of the lake. The horses continued their flight through the storm, until an element of indecision began to characterise their movements. Our mare chose the wrong path around a fallen tree and was lagging behind the herd; she could see the two horses in front of her jump over a swelling brook, whereasthe third one had halted. She hesitated: disorientated she was able neither to stop nor jump and consequently fell into the muddy water with a splash. For a while she fought to keep her head above water, but the current got hold of her and dragged her downwards. Then she banged her head against a rock and lost consciousness.
It would appear to be the shimmering sunlight creeping in under the rim of her eyelids which made the mare wake up, and not the crow sitting on her thigh pecking at a wound. Our mare, who was dazed but alive, jerked to scare the bird away, but experienced in the very same second a threatening loss of balance as a void opened up beneath her. It was not until now that she realised where she was: on a tangled mass of roots protruding from a steep slope that fell away down towards the lake a terrifying distance below her. A huge tree stooped