The Eye: Volume 2, The Visual Process is a compendium of papers that describes the physiology of the eye, particularly the visual functions, the photobiology of the visual process, and the visual pathway. One paper describes the light stimuli used in physiological experiments concerning vision in terms of their spectral energy distribution, particularly the amounts of light absorbed by the photosensitive substances contained in the retinal receptors. Another paper explains the mosaic-like arrangement of the receptors and the variations of this mosaic in the different regions of the retina, including the Purkinje phenomenon which can cause errors in visual measurements. One paper examines the directional properties of the rods at long wavelengths and the theory of the Stiles-Crawford effect. Other papers investigate the limits of the visible spectrum, the scotopic luminous efficiency, theories of dark-adaptation, as well as the minimum retinal illumination, the minimum flux of energy, and the minimum amount necessary for vision. One paper notes that whereas one rod can be stimulated by one quantum (a discrete process involving one pigment molecule), it is not sufficient to make a human subject see a light stimulus. The compendium is invaluable for researchers and investigators involved in physiology, psychology, ophthalmology, and in all branches of ocular physiology.