Fig. 12. Occipital lobe and the corresponding projection of the visual field. A. Mesial aspect of left occipital lobe. The posterior pole (O) is flattened to illustrate the lateral surface (arrows), which is composed primarily of areas 18 and 19. The extension of striate cortex onto the lateral surface of the occipital pole is variable. The calcarine fissure (C) separates the striate or calcarine cortex into an upper and a larger lower strip, which also extends farther toward the splenium (SP) of the corpus callosum. The visual cortex is approximately 5 cm in horizontal diameter, and the macular projection (fine stippling) may occupy as much as the posterior 2.5 cm. The border zone between macular and peripheral retinal cortical projections is arbitrarily illustrated. B. The right hemifields. The upper field is represented in the inferior calcarine strip, and the lower field in the superior calcarine strip. The central field has a disproportionately large cortical representation. F, area of foveal projection. The temporal field of the right eye extends to 90 degrees as compared with the nasal 60-degree limit of the left eye. This 30-degree monocular temporal crescent is represented only in the contralateral hemisphere at the rostral extreme of the striate cortex.