Pathway systems (nerve fibre masses) that after passing down through the inner nerve fibre capsule make their way through the midbrain, bridge, semi-mortar and reach down into the spinal cord.
Parts of the wire mass find their target areas at different levels and then end there. A large part of the wires end in the bridge where the signals are forwarded to the small brain. The thread mass also contains the "Pyramidal System" that accomplishes the voluntary control of our movements.