132 papers are reviewed in some detail. They include: general surveys; apparatus and methods of stimulating, including rotational, surgical, galvanic, caloric, pressure, and drugs; perceptual functions, as auditory localization and perception of movements; modes of response, as ocular, general tonus, and postural reflexes; anatomical and physiological, the functions of the otoliths and of eye muscles; clinical and pathological studies of hereditary factors, syndromes, and special factors such as encephalitis.