portions of the nervous system made up of nerve fibers which are encaged in a myelin sheath, that renders a white coloration to an otherwise grayish neural structures. The sheaths cover only the fibers, so areas containing primary cell bodies are gray.

WHITE MATTER: "White matter are nerve fibers closed within a myelin sheath. "
Cite this page: N., Pam M.S., "WHITE MATTER," in PsychologyDictionary.org, April 29, 2013, https://psychologydictionary.org/white-matter/ (accessed October 18, 2021).