Speed is vital in treating a violent head injury of the kind suffered by Phil Hughes, to minimise any further damage caused by bleeding, inflammation or reduced oxygen supply.
The brain is like a blancmange inside a wooden box and it is secured in the skull by veins no bigger than those on the back of your hand. A blow to the head can sever a blood vessel with relative ease.
After collapsing on the pitch yesterday, Hughes was given mouth-to-mouth resuscitation and was mechanically ventilated with oxygen in the ambulance on his way to hospital.
There he will have had a brain scan to identify the site of his injury and whether it had caused a bleed.
A major bleed creates a pool of blood between the meninges - the membranes that surround the brain - which presses on the brain, reducing the blood supply to the area affected. Unless this pressure is relieved it may lead to permanent brain damage, coma and death.