[Illustration: FIG. 11. Typical appearance of a book, before it is sewn, with small trenches cut in the back in which the bands are to be laid; a bad method, but often used to produce a flat back.] This cutting of the back to make room for the bands was afterwards more easily effected by means of a saw--as it is done now--and in the eighteenth century was especially used by the French binder Derome le Jeune, who is usually made responsible for its invention. The existence of the sunken bands on early embroidered books probably marks the beginning of this vicious system, but here there is some excuse for it, whereas in the case of ordinary leather-bound books there is none, except from the commercial standpoint. In the case of vellum books there may be some reason for using the 'sawn in' bands, as it is certainly difficult to get vellum to fit comfortably over raised bands, although numerous early instances exist in which it has been successfully done. Again in the case of 'hollow backs,' the bands are kept flat with some reason. But for all valuable or finely bound books the system of 'sawing in' cannot be too strongly condemned. 'Sawing in' can be detected by looking at the threads in the centre of any section of a bound book from the inside. It will show as a small hole with a piece of hemp or leather lying transversely across it, under which the thread passes (Fig. 12). [Illustration: FIG. 12. Typical appearance of the sewing of a book with 'sawn in' bands, as seen from the inside of each section. The bands just visible.] In the case of a properly sewn book, the bands themselves cannot be seen at all from the inside of the sections, unless, indeed, the book is damaged (Fig. 13). If the covering of the back is off, or even loose, the method of sewing that has been used can very easily be seen; and if it appears that the bands are sunk in a small trench, that is the form of sewing that is called 'sawn in,' or analogous to it. [Illustration: FIG. 13. Typical appearance of the sewing of a book on raised bands, as seen from the inside of each section. The bands invisible. Known as 'flexible.']