Yoshiro Inoue

Morphological development of retinal ganglion cells in the chick embryo.

Abstract The morphological changes of the external shapes of the developing ganglion cells in the chicken retina were investigated by light microscopy and chiefly with Golgi methods. At stage 20, the neural retina revealed an almost pseudostratified type of arrangement of epithelial cells on routine staining. In silver-impregnation images, most cells in the neural retina showed bipolarly elongated shapes. The inner process of this cell extended toward the vitreous side and attached to the inner limiting membrane, and the outer process extended toward the scleral side and attached to the outer limiting membrane. At stage 25, the ganglion cells sprouted an axon from the inner process or sent an axon directly from the perikaryon of the vitreous side. Next, the original processes, which had attached at first to the inner and outer limiting membranes, disappeared. At stage 29, spine-like processes appeared, extending in every direction from the cell body. At stage 31, some of these spine-like processes grew more extensively to form the dendrites, but the others disappeared. At stage 34, the cells began to form the ganglion cell layer, and their dendrites extended into tertiary branches. At stage 39, the cells could be classified into six types according to the branching pattern of the dendrites, which was identical with the ganglion cells after hatching. This indicated that the fundamental differentiation of ganglion cells could be regarded as essentially completed at stage 39.