The Lateral Geniculate Complex in the Spider Monkey, Ateles Ater *

The lateral geniculate body of both primates and subprimates has in recent years been the subject of many valuable studies which have led to a darification of the manner of termination of the retinal optic fibers and the cortical projection of the geniculo-clcarine fibers. These studies were based on experimental lesions of the retina, section of the optic tract and optic radiation, and cortical extirpation in the case of animals; and on the study of degeneration following pathological lesions of various portions of the visual system in man. However, while much progress has been made in this direction, very little has been contributed toward a thorough and careful anatomical study of this nudeus. Thus, while the lateral geniculate body of the old world monkey Macaca has been the subject of various excellent experimental studies, there is still wanting a complete study of its anatomical structure. In the case of the new world monkeys, the anatomical literature is even more scanty. Although Clark82 has recently published an account of the lateral geniculate body in several platyrrhine or new world monkeys, including Cebus and Ateles, his descriptions are incomplete and, in the case of Ateles, misleading. There is even less definite information available in the anatomical literature about the nucleus pregeniculatus and intergeniculatus which are related morphologically to the primate lateral geniculate body. These two nuclei have not been subjected to a careful anatomical analysis nor have they usually been studied in conjunction with the lateral geniculate body, although such studies offered a good opportunity to elucidate their functional relationship to the visual system. To fill these gaps in our anatomical knowledge of the lateral geniculate body and its related nuclei, a series of studies is now in progress, the first of which forms the subject matter of the present paper. It is our purpose in these investigations to examine thoroughly within the limits imposed by normal cell and fiber material,