The lacertid ear. Eremias argus.

window membrane, a second bead electrode was placed on inactive tissues in the region of the incision, and a third (grounded) electrode in the form of a stainless steel needle was inserted beneath the skin of the throat. These electrodes led to the three input terminals of a balanced preamplifier, which provided about 80 db rejection of stray potentials, such as those from power lines, that might be picked up by the electrodes. The preamplifier produced a gain of 1000 times, and its output was led to a wave analyzer used as a selec-tive voltmeter. Cochlear potentials as small as 0.03-0.04 microvolts (rms) were measur- able for all but the lowest tones, the noise level for which was most disturbing. For these tones, the measurements were taken at higher levels up to 0.1 ,uv. Experience has shown that cochlear potential measurements in the lizard ear are best carried out at as low a level as possible, within the limit imposed by noise, because when exposed to strong sounds this ear becomes unstable and nonlinear and is particularly susceptible to damage.