Source : Webster's Revised Unabridged Dictionary (1913)

Medulla \Me*dul"la\, n. [L.]
   1. Marrow; pith; hence, essence. [Obs.] --Milton.

   2. (Anat.) The marrow of bones; the deep or inner portion of
      an organ or part; as, the medulla, or medullary substance,
      of the kidney; specifically, the medula oblongata.

   3. (Bot.) A soft tissue, occupying the center of the stem or
      branch of a plant; pith.

   {Medulla oblongata}. [L., oblong medulla] (Anat.), the
      posterior part of the brain connected with the spinal
      cord. It includes all the hindbrain except the cerebellum
      and pons, and from it a large part of the cranial nerves
      arise. It controls very largely respiration, circulation,
      swallowing, and other functions, and is the most vital
      part of the brain; -- called also {bulb of the spinal
      cord}. See {Brain}.

Source : WordNet®

medulla
     n 1: a white fatty substance that forms a medullary sheath around
          the axis cylinder of some nerve fibers [syn: {myelin}, {myeline}]
     2: 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}]
     3: the inner part of an organ or structure in plant or animal
        [ant: {cortex}]
     [also: {medullae} (pl)]