med'ullary

Relating to the medulla or marrow. m. sheath, (i) m. substance; (2) In botany, the sheath of protoxylem surrounding the pith of a stem. m. space, the central cavity and the cellular Intervals between the trabeculae of bone, filled with marrow, m. sub's tance, (i) myelin substance, white substance of Schwann; a soft material, composed of a network of neurokeratin enclosing in Its meshes the semifluid myelin, which suiTOunds the axis-cylinder of a medullated nerve-fiber, and is itself surrounded by a delicate membrane, the neurilemma; it Is interrupted at more or le regular intervals by constrictions of the neurilemma forming the nodes of Ranvler, the portion between two nodes being called an internode; (2) subs tanti a meduUaris [BNA].