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Beginning with a short description of the eye as a whole in various vertebrates, the author goes on to a more detailed study of the vertebrate retina. With a careful digest of the literature is included a summary of his own studies, including measurement of the retina in twenty-seven different vertebrates with illustrations from his own photomicrographs. Various forms of the macular area are illustrated and adequate consideration is given to Polyak's work, which has necessitated a modification of our simple conception of the conduction pathways in the retina to a much more complex one. The minute histology of the rods and cones and their development are reviewed. The author estimates that there are about seven million cones in the human retina and from seventy-five to one hundred and seventy million rods. His review and personal studies have convinced him that the duplicity theory is valid; i. e., that the
Vertebrate Photoreceptors. JAMA. 1943;123(10):664-665. doi:10.1001/jama.1943.02840450066040