The white matter of the spinal cord is primarily composed of e) myelinated axons.
White matter gets its name from the myelin sheath that surrounds these axons, giving it a lighter appearance compared to the gray matter, which houses the cell bodies and unmyelinated portions of neurons.
Myelinated axons are crucial for the quick transmission of electrical signals between different parts of the nervous system. The myelin acts as an insulating layer, allowing impulses to jump between the nodes of Ranvier, which increases the speed of signal conduction. Therefore, while neuroglia, Schwann cells, and other components are important for overall spinal health and function, they are not the primary constituents of white matter itself.