Question

What is the white matter of the spinal cord?

Answer 1

The outer portion of the spinal cord is termed as white matter.

Explanation:

Sometimes it is also referred to as superficial tissue because of it presence at the outer region of spinal cord and brain.
It contains glial cells and bundles of myelinated nerve fibers(axons) or tracts and not cell bodies. Because they are contained in gray matter.
These axons serve as a connection between white and gray matter and aid in transmitting the impulses.

https://www.quora.com/Why-does-grey-matter-position-change-between-brain-and-spinal-cord

Answer 2

White Matter is that portion of Spinal Cord or Brain which consists of Myleinated Nerve fibers only.

Mylein Sheath of nerve fibers are white in color so their aggregation forms White matter.

Grey Matter is that portion which consists of Non-Myleinated Nerve Fibers only