[Structure of the neurons in the midbrain auditory center in the frog, Rana ridibunda].

Using rapid Coldgi technique, studies have been made on the structure of the nervous cells in torus semicircularis of the frog Rana ridibunda. 277 cells observed in frontal and sagittal sections were classified into 3 groups. 198 cells with an oval body had their basal dendrite spreading caudoventrally. The dendritic tree of these cells does not leave torus semicircularis. Nucleus laminaris and n. commisuralis usually contained simple cells of this type with one smooth basal dendrite. In the main nucleus of torus semicircularis, similar cells with additional horizontal or dorsal dendrites were found. Many cells of this type in the caudal part of the torus have spiny dendrites. 38 cells with large elongated bodies have one ventral dendrite which originates directly from the body and produces several ventro-lateral processes intersecting the efferent bundle in the tectum opticum. Long and thin dorsal dendrites pass through the laminar nucleus of the torus. These cells were found in the rostral part of the nucleus magnocellularis. In various parts of the torus, 17 multipolar cells were registered. It was not possible to classify 24 cells. Preliminary comparison of morphological and electrophysiological data showed that structural differentiation of the auditory center of amphibian midbrain reflects functional organization of this region.