Definition of "white matter" []

• Whitish nerve tissue, especially of the brain and spinal cord, consisting chiefly of myelinated nerve fibers. (noun)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "“We found that if we just transplanted motor neurons into the spinal cord and did nothing else, then the surrounding neighborhood in the spinal cord—the white matter surrounding the spinal fluid, which is full of other, healthy myelinated axons—would see these motor neurons as foreign and reject them,” Kerr says."