ACCESSORY OPTIC SYSTEM IN ERINACEUS (INSECTIVORA) AND GALAGO (PRIMATES)

After unilateral eye removal in Erinaceus and Galago, Nauta‐gygax and Fink‐Heimer silver impregnation methods were used to study the accessory optic system. In Erinaceus the accessory optic fibers terminate contralaterally in the dorsal lateral and medial terminal nuclei of the accessory optic system; in Galago only the dorsal and lateral terminal nuclei are seen. Hayhow's nomenclature of the accessory optic fibers in modified in such a way that they are now classified according to their terminations. The D‐fibers terminate in the dorsal terminal nucleus, the L‐fibers in the lateral terminal nucleus, and the M‐fibers in the medial terminal nucleus. Accordingly, D‐, L‐ and M‐fibers are found in Erinaceus, while only D‐ and L‐fibers are present in Galago. As in the two monkey species recently studied, but contrasting sharply with the findings in all non‐primate mammals, the M‐fibers and the medial terminal nucleus are absent in Galago. It is hypothetized that the accessory optic system is similarly reduced in all other primates. No retinal fibers terminate in the preoptic region, lamina terminalis, hypothalamus, subthalamic nucleus or substantia nigra. Copyright © 1969 The Wistar Institute Press