a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers

[ Syn: myelin , myeline ]

lower or hindmost part of the brain; continuous with spinal cord; (`bulb is an old term for medulla oblongata); the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning

[ Syn: medulla oblongata , bulb ]

the inner part of an organ or structure in plant or animal