Me·dul·la n.
 1. Marrow; pith; hence, essence. [Obs.]
 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.  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.

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 Bulb n.
 1. Bot. A spheroidal body growing from a plant either above or below the ground (usually below), which is strictly a bud, consisting of a cluster of partially developed leaves, and producing, as it grows, a stem above, and roots below, as in the onion, tulip, etc. It differs from a corm in not being solid.
 2. Anat. A name given to some parts that resemble in shape certain bulbous roots; as, the bulb of the aorta.
 Bulb of the eye, the eyeball.
 Bulb of a hair, the “root,” or part whence the hair originates.
 Bulb of the spinal cord, the medulla oblongata, often called simply bulb.
 Bulb of a tooth, the vascular and nervous papilla contained in the cavity of the tooth.
 3. An expansion or protuberance on a stem or tube, as the bulb of a thermometer, which may be of any form, as spherical, cylindrical, curved, etc.
 3. a light bulb.