Fig. 6-5. A, mechanism for contralateral tonic deviation of eyes on irrigation of external auditory canal with hot water (horizontal canal in vertical position, see Fig. 6-4). B, ipsilateral tonic deviation of eyes on irrigation of external auditory canal with cold water. Increased temperature decreases endolymph specific gravity in the horizontal semicircular canal and endolymph flows ampulopetally - toward the crista - increasing its rate of firing. Cold water causes the opposite effect, essentially a temporary ablation of the irrigated apparatus.