Inner ear structure in the deaf and normally hearing Dalmatian dog.

Both cochleae of two 6-week-old Dalmatian dogs of the same litter were examined by means of surface specimens and histological section techniques. Basic quantitative data on the morphometry of the cochlear duct in the hearing (though hypopigmented) pup are presented. The cochlear ducts of the deaf (though normally coloured) pup exhibited in general the same alterations (collapse of the scala media) as described in the literature. In addition, we describe also the coalescence of membranous structures, projection of the tectorial membrane up to the spiral ligament and preservation of inner hair cells in the second (i.e. middle) cochlear coil. These new findings complement the previous data and indicate an alternative possible course of hereditary inner ear degeneration in the Dalmatian dog.