Human guinea pig?

Life, Liberty and Pursuit on the Planet of the Apes

When fugitive human astronaut Virdon is shot, his chimp companion Galen must charm an old flame into accepting that a book on human surgery is no hoax. Meanwhile, their friend Burke is captured by the ape authorities and is to be brainwashed by a brilliant ape scientist named Wanda. [The fourth of five telefilms edited from episodes of the 1974 TV series; this film combines the episodes "The Surgeon" and "The Interrogation"]