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substantia gelatinosa substantia ge·lat·i·no·sa (jə-lāt'n-ō'sə, jěl'ə-tn-ō'sə)
The apical part of the posterior horn of the gray matter of the spinal cord, composed largely of very small nerve cells and whose gelatinous appearance is due to its very low content of myelinated nerve fibers. It functions in the integration of sensory stimuli that give rise to the sensations of heat and pain. Also called Rolando's gelatinous substance.