Maybe Dracula had a point. The term Young Blood - meaning an injection of youthful vigour - could have a medical origin.

Scientists at Stanford University found that wiring up an old mouse to the blood stream of a young one gave a major boost to muscle recovery time in the older one.

By contrast, when old blood was pumped round the body of a young mouse, muscle recovery time became more prolonged, they said in the science journal Nature.

It was not just muscles that benefited. The same was true of the livers of older mice.

Researchers said the results suggested that the ageing process lay less with the organs themselves than with the tired blood off which they fed.