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Related to white matter: gray matter
1. physical material having form and weight under ordinary conditions; called also substance.
gray matter areas of the nervous system where the nerve fibers are unmyelinated (not enveloped by a myelin sheath); it contains the bodies of the nerve cells. Tissue composed of myelinated fibers is called white matter. The cerebral cortex is entirely composed of gray matter and the cerebellum also contains some deep-seated masses of it. The spinal cord has a central core of gray matter surrounded by white matter; in cross section, its gray matter is shaped approximately like the letter H. Called also substantia grisea and gray substance.
those regions of the brain and spinal cord that are largely or entirely composed of nerve fibers and contain few or no neuronal cell bodies or dendrites.
Whitish nerve tissue, especially of the brain and spinal cord, consisting chiefly of myelinated nerve fibers.