A large number of the manuscripts placed in these ducal family libraries were evidently originally prepared by scribes having knowledge only of plain script, and the addition of the initial letters and of the illuminated head and tail pieces was made later by illuminators and designers attached to the ducal families. It was to these latter that fell the responsibility of placing upon the manuscripts the arms of the owners of the libraries. In case manuscripts which had been inscribed with family arms came to change hands, it became necessary to replace these arms with those of the later purchaser, and many of the illuminated manuscripts of the period give evidence of such changing of the decorations, decorations which took the place of the book-plate of to-day. The taste for these elaborate illuminated manuscripts, each one of which, through the insertion of individual designs and of the family arms, became identified with the personality and taste of its owner, could not easily be set aside, after the middle of the fifteenth century, by the new art of printing. As a matter of fact, therefore, it not infrequently happened, towards the latter part of the fifteenth century, that these noble collectors caused elaborate transcripts to be made, by hand, of works which were already in print, rather than to place in their own collection books in the form in which ordinary buyers could secure them. By the year 1448, the number of certified _librarii_ in Paris had increased to twenty-four.[366] Kirchhoff is of opinion that a certain portion at least of these _librarii_ carried on also other trades, but it is evident that there had come to be in these years, immediately preceding the introduction of the printing-press, a very considerable development in the demand for literature and in the book-trade of the capital. In 1489, the list of book-dealers and of those connected with the manufacture of books who were exempt from taxation included twenty-four _librarii_, four dealers in parchment, four dealers in paper, seven paper manufacturers (having mills outside of Paris), two illuminators, two binders, and two licensed scribes. In the following year, the list of _librarii_ free from taxation was reduced to seventeen. It is probable that those _librarii_ whose names had been taken off the exemption list undertook a general book business carried on outside of the university regulations, and were probably able to secure returns more than sufficient to offset the loss caused by the curtailing of their freedom from taxation and of their university privileges. This reduction in the number of manuscript-dealers who remained members of the corporation was, however, very promptly made up by including in the corporation the newly introduced printers. As early as 1476, one of the four officials of the guild was the printer Pasquier Bonhomme.