Cochleas were stripped and fixedby fixing solution. Light microscope observation:killedanimals,segregated otocyst from temporal bone quickly,exposedcochlea,bored apical cochlea,took stapes out,unpacked ovoidwindow and round window,poured cochlea with 4%Polyoxymethylene (4 ℃ ,PH=7.4) and fixed in it for oneday,washed with 0.1M PBS (PH=7.4),decalcificated with 10%Calcium Disodium Versenate for 20 days,washed withPBS;