Since the first English edition of this book appeared three years ago, the authors have received many useful comments from readers. In preparing this amended edition we have carefully examined each chapter, improving and expanding the text where necessary; in the process, we have been greatly helped by their remarks. Further commentary on this edition will be much appreciated. Again, I should like to express the gratitude of all the authors to the staff of Springer-Verlag for expediting the publication of the book. Kiel, Germany, July 1981 ROBERT F. SCHMIDT Preface to the First Edition In the field of sensory physiology we are concerned with what our sense organs and the associated central nervous structures - can do and how that perform ance is achieved. Research here is not limited to description of the physi cochemical reactions taking place in these structures; the conditions under which sensations and perceptions arise and the rules that govern them are also of fundamental interest. Sensory physiology thus demands the attention of everyone who wishes to - or must - delve into the potentialities and limitations of human experience.

The present volume covers the physiology of the visual system beyond the optic nerve. It is a continuation of the two preceding parts on the photochemistry and the physiology of the eye, and forms a bridge from them to the fourth part on visual psychophysics. These fields have all developed as independent speciali ties and need integrating with each other. The processing of visual information in the brain cannot be understood without some knowledge of the preceding mechanisms in the photoreceptor organs. There are two fundamental reasons, ontogenetic and functional, why this is so: 1) the retina of the vertebrate eye has developed from a specialized part of the brain; 2) in processing their data the eyes follow physiological principles similar to the visual brain centres. Peripheral and central functions should also be discussed in context with their final synthesis in subjective experience, i. e. visual perception. Microphysiology and ultramicroscopy have brought new insights into the neuronal basis of vision. These investigations began in the periphery: HARTLINE'S pioneering experiments on single visual elements of Limulus in 1932 started a successful period of neuronal recordings which ascended from the retina to the highest centres in the visual brain. In the last two decades modern electron microscopic techniques and photochemical investigations of single photoreceptors further contributed to vision research.