The most important group of the Heidelberg manuscripts was collected by Ludwig III., who died in 1437.[256] His daughter Mechthild, whose first husband was the Count Ludwig of Wurtemberg, and whose second, the Archduke Albrich, retained in her widowhood in her castle at Rotenburg a collection of ninety-four volumes of the mediæval poets, whose works were written in the vernacular.[257] Ulbrich of Rappoldstein kept two scribes engaged for five years in transcribing the _Parsival_, and the cost of the work amounted to £200. It is apparent from the preceding sketch that the development of literature and the circulation of books during the Middle Ages were considerable, notwithstanding the serious difficulties there were to contend with during the ten centuries between the fall of the Roman Empire of the West and the time of the invention of printing. Under the “Peace of the World” secured by the imperial rule, there had come to be an active literary production and a development of literary interests throughout the community which called for a wide distribution and a general use of books. There was available for the use of publishers a great list of accepted classics, Greek and Latin, and there were also various epochs during which there came into existence works by contemporary writers of distinctive importance, many of which have been preserved as classics for future generations. The publishers of this period had a convenient and inexpensive material to use for the making of books, and they had available for book production the labour of skilled and inexpensive scribes,--chiefly slaves. The well established means of communication throughout the Empire enabled the publishers of Rome and Massilia and other literary centres to keep open connections with cities in the farthest districts of the realm, and there is adequate evidence of a well organised trade in the distribution of books over almost the entire civilised world, a trade which continued active until the latter part of the fourth century. With the fall of the Empire of the West and with the destruction of so much of the civilised organisation and machinery which had been dependent upon Roman rule, the book trade, or, at least, the trade outside of Italy, practically disappeared. There remained, however, with certain classes a knowledge of the classics and an interest in their preservation, and there remained also in the monasteries the knowledge and practice of writing and the collections of the works of the early Church Fathers, the multiplication of which, for the use of the increasing number of priests, called for continued labour on the part of the clerical scribes.