Med"ul*la*ry (?), a. [L.
medullaris, fr. medulla marrow: cf. F.
médullaire.] 1. (Anat.)
(a) Pertaining to, consisting of, or resembling,
marrow or medulla. (b) Pertaining to the
2. (Bot.) Filled with spongy pith;
Medullary groove (Anat.), a groove,
in the epiblast of the vertebrate blastoderm, the edges of which
unite, making a tube (the medullary canal) from which the brain and
spinal cord are developed. -- Medullary rays
(Bot.), the rays of cellular tissue seen in a transverse
section of exogenous wood, which pass from the pith to the bark.
-- Medullary sheath (Anat.), the layer
of white semifluid substance (myelin), between the primitive sheath
and axis cylinder of a medullated nerve fiber.