Neuroanatomical asymmetry in the telencephalic hemispheres of the frog Rana esculenta.

The frog's brain postfixed with osmium tetroxide and stained with uranyl acetate was examined for asymmetries. Examination with the light microscope of serial semithin sections of the telencephalon revealed a nucleus of dark cells located in the lateral cortex of only the left hemisphere in a region close to the 'porcion arqueada' of Pedro Ramón y Cajal. Electron microscopy of ultrathin sections suggests that the cells of this asymmetric nucleus are neurons with a coarse cytoplasmic texture, where large inclusions occur, and with broad cisternae of endoplasmic reticulum.