Section 841: The middle of the cochlea is visible, including the modiolus (m) containing the VIII nerve. The tensor tympani muscle (ttm) is still visible. The middle ear space has narrowed to form the beginning of the Eustachian (auditory) tube (et). The cochlear aqueduct (ca) can almost be followed to the medial surface of the temporal bone. ICA - Carotid artery; IAM - internal auditory meatus; VIIa - internal auditory canal segment of facial nerve.