How much more interior can you get, after all, than the interior of bones? It's the center of the center of things. If marrow were a geological formation, it would be magma roiling under the earth's mantle. If it were a plant, it would be a delicate moss that grows only in the highest crags of Mount Everest, blooming with tiny white flowers for three days in the Nepalese spring. If it were a memory, it would be your first one, your most painful and repressed one, the one that has made you who you are.