This chapter discusses the origin of the spinal cord, including the spinal canal, the several layers of the wall of the spinal cord, and its white and gray matter, and describes the origin of the spinal nerves. The peripheral nervous system (PNS) is the portion of the nervous system outside the brain and spinal cord. The PNS has another component composed of autonomic nerves and ganglia, which arise from neural crest cells. The chapter also discusses the origin of the three-vesicle and the five-vesicle brain, including the ventricles and cerebrospinal fluid. It presents some of the parts of the adult brain derived from the parts of the five-vesicle brain, and explores the origin of spinal and cranial ganglia and nerves. In the brains of studied mammals, adult neurogenesis occurs in two regions of the adult brain: the subgranular zone of the dentate gyrus of the hippocampus and the subventricular zone of the striatum.