As already indicated, ancient books were written on rolls of papyrus. The technical name of such a roll of papyrus was _volumen_ from which we get our word volume. With the increasing use of vellum as writing material came the book as we know it, originally called in Latin the codex, from _caudex_, meaning a pile of boards such as may be seen in any lumberyard. The other Latin word for book, _liber_, from which we get our word library and other allied terms, originally meant "bark" and is a curious preservation of the record of the use of bark as a writing material, a use, by the way, of which we have very little other knowledge. The origin of the book is rather interesting. One of its ancestors, as we have already seen, is the group of tablets bound together with thongs. Another was probably the roll itself. When the manuscript roll was read it was necessary in order to handle it properly and save it from damage to reroll the part of the roll which had been read as the student proceeded. The consequence was that when the reading was finished, the volume was left rolled up in reverse order. Consequently, before being replaced, the volume, if treated properly, had to be rolled back into its original position, a necessity which careless or lazy people found somewhat burdensome. It was discovered, however, that this could be avoided by folding the roll back and forth, creasing it in the spaces between the columns which were written at right angles to the length of the roll, the result being something like a book printed only on one side of the paper and with the edges uncut, like many Chinese and Japanese books of to-day. The real impulse, however, to the construction of books as distinguished from rolls came with the use of sheets of vellum. These could not be attached easily to make long rolls as could be done with the papyrus sheets, while even the single sheets were large enough to be unwieldy when spread out. Therefore, when long compositions were to be written, the vellum sheets were folded once and laid inside each other just as ordinary note paper is prepared for sale at the present time. In order to provide against the scattering of these leaves they were sewed together through the crease at the back. The result was called a quire. [Illustration: A Roman student at his books, showing the bookcase with a reading stand on top and the use of the roll.]