Toward the end of the Middle Ages the number of the Frankfurt Jews was considerably increased by emigrants from Nuremberg (1498); and Frankfurt replaces Nuremberg as the leading Jewish community in the empire. This is seen in the numerous requests made by other cities to the magistrates of Frankfurt for information concerning their method of procedure in cases affecting Jews. Civil cases were decided by a commission of twelve, with the chief rabbi at its head. The reports of this commission from 1645 to 1808 are in the archives of the community. In 1509 the Jews were threatened with confiscation of their Hebrew books by Pfefferkorn, who arrived in the city with an imperial edict; on April 10, 1510, they were obliged to surrender all their books, which were not restored to them until June 6, after they had sent a special embassy to the emperor. In 1525 the impending danger of expulsion was averted by the municipal council; but the Jews were restricted in their commerce and were forbidden to build their houses higher than three stories. Although this measure crowded them more closely, there were 43 Jewish families in Frankfurt in 1543, and 454 in 1612.