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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.
[L. substantia, essence, material, fr. sub- sto, to stand under, be present]
1. A specific type of substance.
2. Discharge or waste, such as pus or feces, from a living organism.
Material substance that occupies cavities.
Material substance that occupies space.
matterAnatomy Stuff that occupies cavities. See Gray matter, White matter.
[L. substantia, essence, material, fr. sub-sto, to stand under, be present]