The =internal ear= or =labyrinth= (Auris interna s. Labyrinthus)
consists of two parts, viz.: (1) a complex membranous sac, which
supports the auditory cells and the peripheral ramifications of the
auditory nerve; (2) a series of cavities in the petrous temporal bone,
which inclose the membranous part. The first is called the =membranous
labyrinth=, and contains a fluid, the =endolymph=. The second is the
=osseous labyrinth=. The two are separated by the =perilymphatic space=,
which is occupied by a fluid termed the =perilymph=.