The membranous labyrinth is lodged within the bony labyrinth and has the same general form; it is, however, considerably smaller and is partly separated from the bony walls by a quantity of fluid, the perilymph. In certain places, it is fixed to the walls of the cavity. The membranous labyrinth contains fluid, the endolymph, and on its walls the ramifications of the acoustic nerve are distributed. Within the osseous vestibule, the membranous labyrinth does not quite preserve the form of the bony cavity, but consists of two membranous sacs, the utricle, and the saccule. The membranous labyrinth is also the location for the receptor cells found in the inner ear.