Centrifugal fibers to the retina in the rhesus monkey.

Abstract

In addition to the retinofugal fibers from theganglion cells of the retina and the supraoptic commissural fibers (Gudden''s commissure), the optic tracts, chiasm, and nerves of the rhesus monkey contain centrifugal (retinopetal, optic efferent) fibers to the retina. The centrifugal fibers were identified in the optic nerves, chiasm, and tracts of bilaterally enucleated monkeys on the basis of the principle that, following enucleation, the retinofugal fibers within the optic nerves, chiasm, and tracts degenerate and fragment months before the centrifugal fibers to the retina.Normally stained axons are present in the optic tracts; chiasm, and nerves of adult rhesus monkeys 5 or more months following bilateral enucleation. Many of these fibers, revealed by the Romanes silver technique, are present in those regions which exhibit the intense glial reactions associated with the axonal degeneration of the retinofugal fibers.The axons located centrally in the optic nerves appear to be centrifugal fibers to the retina. The cells of origin of these fibers are probably in the superior collicular region, from which their axons course successively through the midbrain reticular formation, crus cerebri (and capsule of the lateral geniculate body), optic tract, chiasm and optic nerve before terminating in the retina. Some of these fibers decussate and some remain uncrossed in their passage through the optic chiasm.