X TABLE OF CONTENTS 



CHAPTER PAGE 



VII. ON THE SIGNIFICANCE OF PHOTOMECHANICAL 



MOVEMENTS 86 



Theoretical considerations 



VIIL THE RELATION OF RETINAL STRUCTURE TO 



VISUAL ACUITY 93 



Rod and cone thresholds 

 Area centralis retinae 

 The fovea centralis 



IX. ON THE SUPPOSED EVOLUTIONARY RELATION- 

 SHIPS AND FUNCTIONAL SIGNIFICANCE OF THE 

 FOVEA 108 



X. RETINAL PHOTOPIGMENTS 120 



Photochemical theory of Hecht 



The rhodopsin cycle 



The porphyropsin cycle 



Cone photopigment 



Kolmer's "droplets" and the rod visual cycle 



XL VITAMIN A-DEFICIENCY AND THE RETINA . 143 



Alteration of visual thresholds 

 Retinal damage and repair 



XII. RECAPITULATION 160 



BIBLIOGRAPHY 165 



AUTHOR INDEX 179 



SUBJECT INDEX 181 



