In the 1950s, Soviet scientist Dr Vladimir Demikhov shocks the world with his two-headed dog experiments.

He grafts the head and paws of one dog onto the body of another. One of his creations lives for 29 days.

He wants to prove the possibilities of transplant surgery, which was a new field of medicine at the time.

Consultant cardiothoracic surgeon, Igor Konstantinov, tells Vicky Farncombe about the "difficult emotions" he experiences when he looks at photos of the creatures.

This programme includes a description of one of the experiments which some listeners may find upsetting.

(Photo: Vladimir Demikhov. Credit: Getty Images)