Damon Knight 
Mind Switch [EPUB ebook] 

Time Switch at the Zoo.One day Martin Naumchik, reporter for Paris Soir, visited the Berlin Zoo. He was standing outside the spacious cage housing the newly-acquired Brecht Biped, Fritz, when the world seemed to lurch.Then he was no longer outside the cage looking in, but inside looking out. He was no longer Martin Naumchik. He was Fritz, the Biped, that strange celestial animal from a world eighteen light-years away.At the same time, Fritz, who had lived almost all his life in Hamburg Zoo, also felt the lurching motion. And found himself standing outside his cage in the body of Martin Naumchik, looking at the frantic Biped inside, who was beating with both hands on the glass.