The third stage of book-production in Europe may be said to begin with the first years of the fifteenth century, when the manuscript trade of Venice and Florence became important, when the book-men or publishers of Paris, outside of the university, had developed a business in the collecting, manifolding, and selling of manuscripts, and when manuscripts first find place in the schedules of the goods sold at the fairs of Frankfort and Nordlingen. The costliness of the skilled labour required for the production of manuscripts, and the many obstacles and difficulties in the way of their distribution, caused the development of the book-trade to proceed but slowly. It was the case, nevertheless, and particularly in Germany, that a very considerable demand for literature of certain classes had been developed among the people before the close of the manuscript period, a demand which was being met with texts produced in constantly increasing quantities and at steadily lessening cost. When the printing-press arrived it found, therefore, already in existence a wide-spread literary interest and a popular demand for books, a demand which, with the immediate cheapening of books, was, of course, enormously increased. The production of books in manuscript came to a close, not with the invention of the printing-press in 1450, but with the time when printing had become generally introduced, about twenty-five years later. It was in the monasteries that were preserved such fragments of the classic literature as had escaped the general devastation of Italy; and it was to the labours of the monks of the West, and particularly to the labours of the monks of S. Benedict, that was due the preservation for the Middle Ages and for succeeding generations of the remembrance and the influence of the literature of classic times. For a period of more than six centuries, the safety of the literary heritage of Europe, one may say of the world, depended upon the scribes of a few dozen scattered monasteries.