codex

In the 3rd and 4th centuries A.D., the codex began to replace the older scroll as the preferred form for longer writings. Unlike the scroll, this wonderful invention permitted writing on both sides of a sheet, made it easy to locate a particular passage, and could contain a very long piece of writing. Codices (note this unusual plural form) were usually written on parchment, the specially prepared skin of a sheep or goat, or papyrus, the ancestor of paper. Because codices were handwritten, there were few copies of any single codex, and sometimes only a single copy. Today we no longer write our books in longhand, but the modern book has kept basically the same form as the original codices.