Emily Hahn, a New Yorker contributor, went ape years ago after keeping a number of primates as household pets. Then she discovered that baboons were being used in research on atherosclerosis. Her subsequent investigations reveal a labyrinth of projects that started with a tenacious, dedicated Yale professor, one Robert Means Yerkes, who found unprecedented research material in man's unofficial cousins. Currently, there are seven Primate Centers throughout the U.S. Miss Hahn visited each one where she kept her sharp eyes open and developed an ability to dodge a well-aimed spittle from one of the inmates. She found experiments going on in pathology, neurochemistry, muscle diseases, psychobiology, immunology and even transplants, among others -- including the effects of marijuana and space travel. Social patterns are being studied and there are constant attempts at communication. However it took six months of dedication to teach one orangntan to say ""Papa"" and such attempts are fortunately being abandoned in favor of sign language (primates are just not equipped physiologically to speak). Perhaps most interesting are the experiments where small primates have been placed in homes to be brought up as normal children, both for their effect on the animal and on the adoptive parent. A heady combination of biography, research, anecdote and personal observation, this demonstrates that we have a lot to learn from our poor relations.