Studies on the sensory hairs of receptor cells in the inner ear.

The crista ampullaris of the semicircular canal in the frog can be isolated and mounted in a chamber so that the sensory hairs can be observed under high magnification in interference-contrast. The cupula is removed and the sensory hairs can be manipulated and their mechanical properties investigated by a microprobe held in a micromanipulator. The hairs appear quite stiff and pivot around their base. When subjected to force they break as if they are brittle. All the cilia within a bundle move together as if joined to one another. Labelling for electron-microscopy with polycationic ferritin reveals that the membrane surrounding the cilia has a surface coat of negatively charged molecules. When the organ is incubated with polycationic ferritin before fixation the sensory hairs agglutinate. Fusion of the membrane surrounding individual sensory hairs also occurs.