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substance; used in anatomic nomenclature in naming various components of body tissues or structures.
substantia al´ba white matter.
substantia gelatino´sa the substance sheathing the posterior horn of the spinal cord and lining its central canal.
substantia gri´sea gray matter.
substantia ni´gra a dark layer of gray matter separating the tegmentum of the midbrain from the crus cerebri.
those regions of the brain and spinal cord that are made up primarily of the cell bodies and dendrites of nerve cells rather than myelinated axons.