OBSERVATIONS IN MYELIN STRUCTURE: INCISURES AND NODAL REGIONS

Abstract

The layered structure of the myelin sheath of frog nerves is discussed, with particular reference to the region of the Schmidt-Lantermann incisures. In the incisure the membrane doublets peel off from one side of the compact myelin, transverse the open space, and join the compact myelin on the other side. The incisure is thus not a diffusion channel from the axolemma to the extracellular space and is unlikely to be involved in current flow during impulse propagation. The structure of the myelin near the node is briefly described. The histological appearances of these structures are consistent with Geren''s membrane theory of the origin of nerve myelin (Geren, B. B., Exptl. Cell Research 1:558, 1954).