Specialization of Schwann Cell Membranes

STACKS of desmosomes in successive layers of Schwann cell cytoplasm have been reported in the sheaths of nerve fibres in the earthworm Eisenia foetida1 and in the rat2 and also in the myelin sheath of the eighth nerve ganglion of the goldfish3. In each case the stacking occurred in loose myelin where narrow layers of Schwann cell cytoplasm were contained within the spiralling of the mesaxon. It was thought that the desmosomes in both nerve sheaths functioned as bonds between successive Schwann cell lamellae.