myelin(redirected from medullary sheath)
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a white tissue forming an insulating sheath (myelin sheath) around certain nerve fibres. Damage to the myelin sheath causes neurological disease, as in multiple sclerosis
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
A soft, white fatty substance that forms a sheath around certain nerve fibers.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.