Development of the chick vestibular ganglion and its nerve terminating in the endorgan.

We investigated the morphological maturation of the vestibular ganglion and its dendrites terminating in the sacculus of the chick embryo. The cytoplasm of the ganglion cells had acquired a granular feature due to the abundance of ribosomal clusters and rER by the 13th day of incubation. The myelination of the dendrites occurred before that of the perikarya. Compact myelin of the dendrites was observed on the 13th day of incubation, while that of the perikarya was observed in the 20th day of incubation. Nerve endings of afferent and efferent character were observed first in the sacculus on the 13th day of incubation. Positive immunoreactvity of substance P was observed on the 13th day of incubation. It is suggested that the morphological basis of functional activity is present on or around the 13th day of incubation.