'Hæc est in gremio victos quæ sola recepit, Humanumque genus communi nomine fovit, Matris, non dominæ, ritu; civesque vocavit Quos domuit, nexuque pio longinqua revinxit. Hujus pacificis debemus moribus omnes Quod veluti patriis regionibus utitur hospes: Quod sedem mutare licet: quod cernere Thulen Lusus, et horrendos quondam penetrare recessus: Quod bibimus passim Rhodanum, potamus Oronten, Quod cuncti gens una sumus. Nec terminus unquam Romanæ ditionis erit.' [6] In the Roman jurisprudence, _ius sacrum_ is a branch of _ius publicum_. [7] Tertullian, writing circ. A.D. 200, says: 'Sed quid ego amplius de religione atque pietate Christiana in imperatorem quem necesse est suspiciamus ut eum quem Dominus noster elegerit. Et merito dixerim, noster est magis Cæsar, ut a nostro Deo constitutus.'--_Apologet._ cap. 34. [8] See the book of Optatus, bishop of Milevis, _Contra Donatistas_. 'Non enim respublica est in ecclesia, sed ecclesia in republica, id est, in imperio Romano, cum super imperatorem non sit nisi solus Deus:' (p. 999 of vol. ii. of Migne's _Patrologiæ Cursus completus_.) The treatise of Optatus is full of interest, as shewing the growth of the idea of the visible Church, and of the primacy of Peter's chair, as constituting its centre and representing its unity. CHAPTER III. THE BARBARIAN INVASIONS. [Sidenote: The Barbarians.] [Sidenote: Admitted to Roman titles and honours.] Upon a world so constituted did the barbarians of the North descend. From the dawn of history they shew as a dim background to the warmth and light of the Mediterranean coast, changing little while kingdoms rise and fall in the South: only thought on when some hungry swarm comes down to pillage or to settle. It is always as foes that they are known. The Romans never forgot the invasion of Brennus; and their fears, renewed by the irruption of the Cimbri and Teutones, could not let them rest till the extension of the frontier to the Rhine and the Danube removed Italy from immediate danger. A little more perseverance under Tiberius, or again under Hadrian, would probably have reduced all Germany as far as the Baltic and the Oder. But the politic or jealous advice of Augustus[9] was followed, and it was only along the frontiers that Roman arts and culture affected the Teutonic races. Commerce was brisk; Roman envoys penetrated the forests to the courts of rude chieftains; adventurous barbarians entered the provinces, sometimes to admire, oftener, like the brother of Arminius[10], to take service under the Roman flag, and rise to a distinction in the legion which some feud denied them at home. This was found even more convenient by the hirer than by the employed; till by degrees barbarian mercenaries came to form the largest, or at least the most effective, part of the Roman armies. The body-guard of Augustus had been so composed; the prætorians were generally selected from the