LM of the central canal of the spinal cord in transverse section. In life, CSF normally fills the lumen (*) of this canal. A single continuous layer of ependymal cells lines the lumen. A few isolated ependymal cell nests (arrows) are also seen nearby, and their presence is normal in the adult. The central canal of the spinal cord is usually patent in the child and young adult but with advancing age often becomes obliterated. Areas of white (WM) and gray (GM) matter of the spinal cord are indicated. 160×. H&E.