MOST medical students have probably felt that current physiological teaching provided them with only a hazy conception of the mechanism for hearing in the cochlea. Helmholtz put forward the view that this organ contained a series of resonators, which were differentiated like a set of piano strings, so that each string vibrated only in response to one particular note. It will be remembered that the cochlea forms a spiral, which when unwound consists of two chambers, placed one above the other, and separated by the basilar membrane. At one end (the base) of the cochlea, in the wall of the upper chamber, is the window which is set in vibration by the middle ear, while in the wall of the lower chamber is a similar window whose function is to prevent the pressure from changing inside the cochlea when the upper window moves. Both chambers contain fluid, and, at the other end (the apex) of the cochlea, the chambers unite, for the basilar membrane ceases just short of the apex.