The distribution of primary afferents to the cochlear nuclei in the domestic hen (Gallus domesticus).

The normal anatomy of the three cochlear nuclei in the hen, the nucleus laminaris, the nucleus angularis and the nucleus magnocellularis is described. Following lesions of the cochlear nerve, all three nuclei are shown to receive primary cochlear fibers (silver impregnation methods). The part of nucleus laminaris which consists of a ventral convex sheet of cells is shown to receive cochlear nerve fibers from both ears, the nerve fibers from the ipsilateral ear terminating dorsal to the cell sheet while contralateral nerve fibers terminate ventral to the nerve cells. The cochlear ganglion cells projecting to the nucleus laminaris are apparently situated in other parts of the ganglion that the cells projecting to the nucleus angularis and magnocellularis. The findings are discussed in the light of known data on the organization and function of the cochlear nuclei in birds.