the eleventh pair of cranial nerves in the higher vertebrates. They originate from the spinal cord and pass forward into the skull, from which they emerge in company with the pneumogastrics.

the backbone, or connected series or vertebrae which forms the axis of the vertebrate skeleton; the spine; rachis; vertebral column.

the great nervous cord extending backward from the brain along the dorsal side of the spinal column of a vertebrate animal, and usually terminating in a threadlike appendage called the filum terminale; the spinal, or vertebral, marrow; the myelon. The nervous tissue consists of nerve fibers and nerve cells, the latter being confined to the so-called gray matter of the central portions of the cord, while the peripheral white matter is composed of nerve fibers only. The center of the cord is traversed by a slender canal connecting with the ventricles of the brain.