Volume VII, Part 6 brings to a conclusion the Handbook of Sensory Physiology, the publication of which has spanned 9 years. In the General Preface of Volume I it was stated that: "The purpose of this handbook is not encyclopedic completeness, nor the sort of brief summaries provided by periodic annual reviews. " The Editorial Board and the editors hope that this golden mean has been achieved: An absorbing, thorough, but nevertheless exemplary presentation should, with the aid of relevant examples, enable the reader to become accustomed with the numerous facets of the sensory system without sacrificing an overview of the subject. The main issues of sensory physiology were formulated in the nineteenth and early twentieth centuries by JOHANNES MULLER, H. VON HELMHOLTZ, E. HERING, S. EXNER, 1. VON KRIES, W. TRENDELENBURG, and E. D. ADRIAN, to name but a few. Modern development in the field has been characterized by interdisciplinary cooperation, the foundation for which was laid in the second half of the nineteenth century by VON HELMHOLTZ, EXNER, MAXWELL, and others. Progress made in bio­ chemistry, physics, mathematics, and information theory has not only made pos­ sible unanticipated refinement of methods of measurement; it has above all per­ mitted the transformation of mere hypotheses into established, accepted theories as well as revealing new problems. However, at the same time such development has, in recent decades, resulted in the literature becoming dispersed in specialist journals; consequently, it has grown increasingly difficult to survey.