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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 made up primarily of the cell bodies and dendrites of nerve cells rather than myelinated axons.
1. Brownish-gray nerve tissue, especially of the brain and spinal cord, composed of nerve cell bodies and their dendrites and some supportive tissue.
2. Informal Brains; intellect.