"a large bundle of nerve fibers, running down the longitudinal axis of the body, that forms an important part of the central nervous system. Most invertebrates have a pair of solid nerve cords, situated ventrally and bearing segmentally arranged ganglia. All animals of the phylum Chordata have a dorsal hollow nerve cord; in vertebrates this is the spinal cord" (402).

Primary bundle of nerves in chordates, which connects the brain to the major muscles and organs of the body.

n. In chordate animals, a long, hollow tubular tract of neural tissue located above the notochord that develops into the spinal cord and the brain.