It might sound like something out of a creepy folk tale, but scientists have found evidence that injecting young human blood into older bodies does seem to offer powers of rejuvenation – even if those old bodies aren't human themselves.

In a new study, researchers took blood samples from a group of healthy, young 18-year-old human participants and injected them into 12-month-old mice – late middle age in mice years, or the equivalent of being about 50 years old in human terms.

For three weeks, the mice received twice-weekly injections of human blood plasma – blood's liquid component, which scientists think is responsible for its rejuvenating properties.

After this, scientists from California-based biopharmaceutical company Alkahest compared the injected animals' behaviour to young and old control groups of three-month-old and 12-month-old mice – neither of which had received the plasma injections.

The new blood made the old mice act young again, with the treated animals running around in open spaces much like their younger controls.

But there was also evidence that their powers of memory had improved.