Deafness and vertigo are common complaints of the patient with head injury. By studying the clinical findings in human patients and correlating them with the findings of animal experiments, we have concluded that these symptoms are due, for the most part, to injury of the membranous labyrinth. I. CLINICAL MANIFESTATIONS The auditory and vestibular symptoms following head injury can be classified according to the following types of labyrinthine damage: A. longitudinal fracture of the temporal bone; B. transverse fracture of the temporal bone; C. labyrinthine concussion. A. Longitudinal Fracture of the Temporal Bone Typically, a longitudinal fracture of the temporal bone is a linear fracture through the floor of the middle cranial fossa, which lies parallel and adjacent to the anterior margin of the petrous pyramid. It extends medially from the region of the Gasserian ganglion to the middle ear and mastoid air cells laterally. On roentgenograms the fracture usually