*medullar*

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 medula oblongata. [ 1913 Webster ]

2. (Bot.) Filled with spongy pith; pithy. [ 1913 Webster ]

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. [ 1913 Webster ]