Freeze fracture and numerical analyses of the spiral ganglion cells.

The freeze-fracture technique was used to study the spiral ganglion cell population in the adult mouse. The majority of the ganglion cells (type I) had a smooth cell surface. Interspersed among these first ganglion cells, a small number of other ganglion cells (type II) showed considerable membrane specializations and were morphologically reminiscent of nerve terminals previously described only in human temporal bones. Calculations of the number of the two types of spiral ganglion cells in sectioned material showed that the adult mouse spiral ganglion comprises of 3%-4% unmyelinated type II ganglion cells.