Skins and scrapsFor much of the Middle Ages dead cows were the main ingredient for books. What was frolicking in the meadow one month, may have been a page in a Bible the next. The skin of animals - calfs, goats, sheep - was turned into parchment, which was subsequently cut into sheets. Parchment was introduced in late Antiquity, when the codex, the book made of double leaves, was born and started to replace the papyrus scroll. In the 12th century another material appeared in Europe: paper.