At various periods, Western cultures have chosen to embody writing in vari­ ous technological forms, and these choices have in turn affected the organi­ zation, style, and genres of writing and our expectations as authors and as readers. The physical unit of a writing technology helps to define the con­ ceptual unit-what comes to be regarded as a written volume. For centuries in the ancient world, the papyrus roll, about 25 feet long, constituted a vol­ ume. (Our word “volume” comes from the Latin volumen, which means roll.) The codex, which replaced the roll, was more effective in enclosing, protecting, and delimiting the writing it contained. A whole work could be contained in a single codex, which was less often the case with the smaller papyrus roll, which might hold only segments or “chapters” of a work. The writer was and still is encouraged to think of his codex as a unit of meaning, a complete verbal structure. The codex has been associated with the idea that writing should be rounded into finite units of expression and that a writer or reader can and should close his text off from all other texts.