The exact number of dogs used in Vladimir Demikhov’s experiments is not well-documented, but it is estimated that he performed his groundbreaking organ transplantation procedures on dozens, possibly over 100 dogs, throughout his career. His most famous experiments involved creating two-headed dogs, of which he is known to have performed at least 20. Each of these experiments had a short survival time for the animals, with most lasting only days or weeks due to complications. These numbers reflect the scale of his work and the ethical debates surrounding it.