The Spinal Cord
The gray matter, substantia grisea (nerve cells), appears in transverse section of the spinal cord as a butterfly configuration sur-rounded by the white matter, substantia alba(fiber tracts). We distinguish on either side a dorsal horn (posterior horn) (AB1) and a ven-tral horn (anterior horn) (AB2). Both formcolumns in the longitudinal dimension of the spinal cord, the anterior column and the posterior column. Between them lies thecen-tral intermediate substance (A3) with theobliterated central canal (A4). In the thoracic spinal cord, the lateral horn (AB5) is interposed between the anterior and poste-rior horns. The lateral posterior sulcus (A6) is the site where the posterior root fibers (AB7) enter. The anterior root fibers (AB8) leave the anterior side of the spinal cord as fine bundles.
The posterior horn is derived from the alarplate (origin of sensory neurons) and con-tains neurons of the afferent system (B). The anterior horn is derived from the basal plate (origin of motor neurons) and contains the anterior horn cells, the efferent fibers of which run to the muscles. The lateral horn contains autonomic nerve cells of the sym-pathetic nervous system.
The white matter is subdivided into the dorsal column,or posterior funiculus(A9),which reaches from the posterior septum (A10) to the posterior horn, the lateralcolumn, orlateral funiculus(A11), whichreaches from the posterior horn to the ante-rior root, and the ventral column, or anteriorfuniculus (A12), which reaches from theanterior root to the anterior fissure (A13). The latter two form the anterolateral column. The white commissure (A14) connects the two halves of the spinal cord.