SCANNING ELECTRON-MICROSCOPY OF THE CELLOIDIN-EMBEDDED INNER-EAR SECTIONS

The nerve fibers running inside the organ of Corti were studied in cats by scanning electron microscopy (SEM). The fixed temporal bones were decalcified and embedded in celloidin according to the conventional method. Thick serial sections (100-150-mu-m) were cut parallel to the basilar membrane. After removing the celloidin, the sections were freeze-dried in t-butyl alcohol. Though some outer hair cells had been deformed, the nerve fibers were well preserved for analysis. Some new findings were observed in the present SEM study. The tunnel spiral bundle in a kitten took an atypical course on the floor of Corti's tunnel apart from the previously reported site. In the barely-patent tunnels of Corti in kittens, nerve fibers were stuck together into thick bundles and took different courses compared to those in the mature cochleas. Filiform projections of nerve fibers were climbing around the first row of the outer hair cells in the immature cochlea. These were thought to be growing ends of efferent nerves which would later grow into nerve endings.