Ultrastructural morphology of schwann cell—neuronal relationships in the spiral ganglia of cats

Electron microscopic study of the cat's spiral ganglia reveals that neuronal cytoplasmic extensions evaginate into the inner Schwann cell lamellae; some may become surrounded by the ensheathing Schwann cell. Inner lamellae of ensheathing Schwann cells penetrate the neuron and invest small portions of neuronal cytoplasm. Membrane‐bound neuronal regions, completely or partially bare of Schwann cell ensheathment, also are observed within neurons or adjacent to the neuronal plasmalemma. Some of these isolated neuronal regions might represent cytoplasmic extensions of the same or another neuron. Speculations are made as to the mechanism by which the observed relationships are formed.