The |myelin sheath| is a coat of white, |fatty tissue| which covers ~nerves~ of the peripheral nervous system. The white, myelinated |fibers| of the ~nerve~ bundles within the |brain| and |spine| account for the white matter found there. The grey matter also there is due to the inner structures of the ~nerve~ cell bodies. The |myelin sheath| is, in turn, covered by a membrane called the neurolemma (or the nucleated membrane).
