Copies of papal deeds were collected into registers or _bullaria_. Lists showing the chronological sequence of documents are catalogues of acts. When into such lists indications from narrative sources are introduced they become _regesta_ (_res gestae_): a term not to be confused with "register."
Clearness and conciseness have been recognized as attributes of early papal letters; but even in those of the 4th century certain rhythmical periods have been detected in their composition which became more marked under Leo the Great, A.D. 440-461, and which developed into the _cursus_ or prose rhythm of the pontifical chancery of the 11th and 12th centuries.
In the most ancient deeds the pope styles himself _Episcopus_, sometimes _Episcopus Catholicae Ecclesiae_, or _Episcopus Romanae Ecclesiae_, rarely _Papa_. Gregory I, A.D. 590, was the first to adopt the form _Episcopus, servus servorum Dei_, which became general in the 9th century, and thenceforth was invariable.
The second period of papal documents extends from Leo IX. to the accession of Innocent III., A.D. 1048-1198. At the beginning of the period formulae tended to take more definite shape and to become fixed. In the superscription of bulls a distinction arose: those which conferred lasting privileges employing the words _in perpetuum_ to close this clause; those whose benefaction was of a transitory character using the form of salutation, _salutem et apostolicam benedictionem_. But it was under Urban II., A.D. 1088-1099, that the principal formulae became stereotyped. Then the distinction between documents of lasting, and those of transitory, value became more exactly defined; the former class being known as greater bulls, _bullae majores_ (also called _privilegia_), the latter lesser bulls, _bullae minores_. The leading characteristics of the greater bulls were these: The first line containing the superscription and closing with the words _in perpetuum_ (or, sometimes, _ad perpetuam_, or _aeternam_, _rei memoriam_) was written in tall and slender ornamental letters, close packed; the final clauses of the text develop with tendency to fixity; the pope's subscription is accompanied with the _rota_ on the left and the _benevalete_ monogram on the right; and certain elaborate forms of dating are punctiliously observed. The introduction of subscriptions of cardinals as witnesses had gradually become a practice. Under Victor II., A.D. 1055-1057, the practice became more confirmed, and after the time of Innocent II., A.D. 1130-1145, the subscriptions of the three orders were arranged according to rank, those of the cardinal bishops being placed in the centre under the papal subscription, those of the priests under the _rota_ on the left, and those of the deacons under the _benevalete_ on the right. In the lesser bulls simpler forms were employed; there was no introductory line of stilted letters; the salutation, _salutem et apostolicam benedictionem_, closed the superscription; the final clauses were shortened; there was neither papal subscription, nor _rota_, nor _benevalete_; the date was simple.