The white matter surrounds the central column of the grey mater in the spinal cord.  The white color is due to the presence of myelin, a white fatty insulating protein, which surrounds the nerve fibers.

Many of these nerve fibers lie longitudinally and are arranged into columns or funiculi, located dorsally, laterally and ventrally.

The white matter is active in communication between the various areas of grey matter and between the grey matter and the rest of the body.