around the end of the 13th century, and then only internally for unofficial administrative purposes. However, it had become official by the 15th century, when one of the offices of the Apostolic Chancery was named the "register of bulls" ("registrum bullarum").

By the accession of Pope Leo IX in 1048, a clear distinction developed between two classes of bulls of greater and less solemnity. The majority of the "great bulls" now in existence are in the nature