New Morphological Aspects of the Bipolar Cell in the Chick Embryo: The Accessory Prolongation

Using the silver-staining techniques of Golgi Colonnier and Golgi-Stensaas, we have found a new morphological datum in the study and understanding of the structure of the bipolar cell in the chick retina. We describe the existence of a prolongation, possibly dendritic in nature, which sets out from the inner network and separates from its companions following a short path through the outer plexiform layer to terminate freely. It appears for the first time on the 10th day of incubation and always in bipolar cells whose outer branching has its dendritic pattern well-defined. We have named it the accessory prolongation.