Observations on the Nissl’s substance, cytoplasmic filaments and the nuclear membrane of spinal ganglion cells

Abstract

Thin sections of spinal ganglia were examined with the electron microscope. The axon runs in the cytoplasm of the capsule cells which are separated from the nerve cell by a lipid sheath. Nissl’s substance occurs as discrete aggregates in ‘light’ cells, and dispersed throughout the cytoplasm in ‘dark’ cells. The unit structures of Nissl’s substance are granules of size range 50 to 200 Å. Both nerve-cell cytoplasm and axoplasm have small mitochondria and a background network of fine filaments of 20 to 50 Å diameter. The nuclear membrane consists of a multilayered structure. This membrane has distributed through it an arrangement of nodes, 850 Å in diameter. It is suggested that the nuclear membrane may undergo phasic alteration in structure and that the nodes are characteristically present during active nucleocytoplasmic transport.