The Classical Vertebrate Central Nervous System is a hierarchical model of gray matter structures that are common to the brain and spinal cord of all vertebrates. As in other classical models, structures are grouped by proximity as observed on dissection, and the upper levels correspond roughly to their organization in the embryo. The hierarchical organization is based on the Basic Partts List for Adult Nervous System in All Animals ( Swanson-2104 ), the nomenclature on NeuroNames ( Bowden-2012 ).