Originally published in 1938, this book presents a discussion regarding the nature of auditory and visual sensation. The text focuses mainly on the nature of the perceptual process. As Rawdon-Smith notes in the preface, 'I wish to be concerned more with the mechanism whereby our sensations arise than with what our sense organs can do.' Illustrative figures and a detailed bibliography are also contained. This book will be of value to anyone with an interest in sensory perception and the history of science.