Electron probe determination of relative ion distribution in the inner ear.

The relative amounts of potassium and chlorine present in various parts of the inner ear were studied by using an energy dispersive X-ray spectrometer in conjunction with a scanning electron microscope. Whereas the amount of chlorine was high in all compartments investigated, potassium was high in endolymphatic spaces and low in perilymphatic spaces. High contents of potassium and chlorine were also found in the tectorial membrane, in the inner sulcus and in the cupula of the semicircular canal. It is concluded that the tectorial membrane and the cupula do not present a barrier to ions and that therefore the sensory hairs in the inner ear are exposed to the ionic environment provided by the endolymph.