Then said I, Lo, I come: in the volume (megillah) of the book it is written of me, I delight to do thy will, O my God: yea, thy law is within my heart. — Psalm 40:7-8
The Lord Jesus Christ is the grand subject of all Scripture. The passage above contains His own words speaking of Himself, as it is written: “Wherefore when he [Christ] cometh into the world, he saith, … in the volume of the book it is written of me” (Heb 10:5ff). Christ fulfilled this Scripture, saying “For I came down from heaven, not to do mine own will, but the will of him that sent me” (John 6:38). He frequently spoke of the revelation of Himself in Scripture, as when he told the unbelieving Jews that “had ye believed Moses, ye would have believed me: for he wrote of me” (John 5:46), and again when He spoke with His disciples after His resurrection, saying “These are the words which I spake unto you, while I was yet with you, that all things must be fulfilled, which were written in the law of Moses, and in the prophets, and in the psalms, concerning me” (Luke 24:44ff). This is what the Bible is all about; it is the revelation of Jesus Christ.
The original manuscripts of the Old Testament were all written on scolls. This is the meaning of the Hebrew megillah, translated as “volume” in Psalm 40 above. It is from the root galal (to roll), since a scroll is something “rolled up.” This also is the root of galgal (wheel) which describes the geometric structure of the Bible. The same etymology is seen for the word “volume” which is from the Latin volumen (scroll) which in turn is based on the verb volvere (to roll). This is familiar to English speakers through other words such as revolve.
Scholars distinguish between a scroll and a book of bound pages by referring to the latter as a codex. The codex was invented around the time of Christ and popularized largely by Christians (see The Birth of the Codex) and data taken from it here This link takes you off the Bible Wheel site and opens a new window). Both Jews and Gentiles continued to use scrolls well into the fourth century especially for Sacred Scripture and important works of literature, but by that time Christians had moved to the codex format for nearly all of thier literature.
The codex was a huge technological advance over the scroll for two reasons. First, it was much more compact because its pages could be written on both sides. Scrolls were usually written on only on the inside since text on the unprotected outside would easily get smudged and effaced. Given the same amount of papyrus, a codex could hold twice as much text as a scroll. Second, the codex allowed quick random access to any of its content since one could simply turn to the appropriate page rather than having to “scroll” through the entire document. Imagine trying to compare Scripture with Scripture; first, you would have to retrieve both scrolls, and then scroll all the way through each until you found the passages you were looking for. Furthermore, it would be very difficult to travel with a huge satchet of rolled up documents. The freedom afforded by the codex is immortalized in the image from the Catacombs of Domitilla. It shows the a circular leather box – a capsa – with a big shoulder strap stuffed full of scrolls with a codex, presumably holding the same content, flying above it! The codex gave great freedom to the early Christian missionaries who could go forth with the Scriptures bound in a single Book. It seems likely that God inspired this invention to further His Gospel.
The invention of the codex had a third effect of great significance: it imposed a fixed order to the books it contained. A collection of scrolls contains no intrinsic order. Any order needs to be imposed by either written or oral tradition. A bound codex, on the other hand, has an intrinsic order by the mere fact of binding the books together. This ultimately led to the fixed order that we see in modern Bibles such as the King James Version, which is the foundation of the Bible Wheel.