Brain Transplantation???
Here's my thought on this. If you take a brain out of one person and put it in the head of the other person (and the surgery is successful), there would be only ONE personality in the body, the personality of the brain.
So someone please explain to me what exactly was the surgery in this film? They talk of brain cells and brain transplantation but did he take one brain out and put it in his friend's head or did he take part of the brain? To me, this was never explicitly explained.