1954-1959: The Two-Headed Dog Experiment
In 1954, the Soviet scientist named Vladimir Demikhov set out on a mission to graft the head of one dog onto the body of another fully-intact dog. He did transplant a lot of vital organs between dogs before this bizarre and horrifying experiment.
By 1959, him and his team had performed the surgery 23 times with varying degrees of success. The one they performed in 1959 attracted public attention. The host dog was an adult stray German Shepherd Dog named Brodyaga. The other dog was a smaller dog named Shavka.
The two-headed dog survived four days, but that wasn’t the longest. Demikhov created another two-headed dog that lived for 29 days.