Sometimes, our understanding of how the body works and how doctors should treat it comes from surprising places.
What happened to wounded soldiers treated in the Vietnam war during the 1960s revealed just how important the body's own defences are.
And made doctors rethink how they treat people with severe trauma.
Your blood has an in-built, automatic repair system that is activated almost instantly if there is any injury to a blood vessel.
Platelets are tiny cell-like particles in the blood, which have a sticky surface that helps them make a plug at the site of injury.
Proteins in the blood plasma then create fibrin strands to strengthen this plug. This forms the clot that seals the wound and prevents blood flowing away.
Platelets stick to torn vessels
Plug stops bleeding
Fibrin strands seal wound
Injuries in the Vietnam war were horrific. But medical support was rapid, with helicopters reaching the injured within minutes.
With such severe injuries, the amount of blood loss can be huge, which causes a massive and fast decrease in blood pressure.
In the 1960s, the standard treatment was to try to correct this by replacing blood as quickly as possible.
Blood transfusions were administered before soldiers were even lifted off the ground.
But many soldiers still went on to die.
Prof Jim Ryan, Trauma Surgeon – "Suddenly, they're pulled into a helicopter, lines are put in, blood pressure's driven up, they bleed. I think Mother Nature's built in a mechanism to take care of us, it's centuries old if not millennia old. We've got to be damn careful that any treatment we devise does not upset that."
That mechanism is the clotting of blood.
A blood clot is like a dam, if the blood pressure is low, there is less for the clot to hold back. Initially the clot is quite delicate, so increasing the pressure can burst the dam.
And that's what's thought to have happened to soldiers in Vietnam. Before the body was able to clot a wound of its own accord, increased blood pressure burst it open again.
It would be another 15 years before we discovered just how effective the body is at healing itself.