On the other hand, Northern Italy became known as a center for the study of Roman law. The cities here, in order to defend their independence, were led to study this subject, and endeavored to find some special charter, grant, or edict from the old Roman emperors upon which to base their claims. Several northern centers were renowned for their investigation of the Roman civil law, but early in the twelfth century Bologna became preëminent through the lectures of Irnerius. By him the entire _Corpus Juris Civilis_, a compilation of Roman law made by eminent jurists in the sixth century at the command of the emperor Justinian, was collected and critically discussed. Influenced by this example, a monk of Bologna, named Gratian, undertook to codify all edicts and formulations of popes and councils in a convenient text-book. The _Decree_ of Gratian, which resulted, was almost immediately recognized as the authority upon the subject, and canon law came to be studied here with the same thoroughness as civil law. The university at Bologna was regularly chartered by Frederick Barbarossa in 1158, probably as a recognition of the services of its masters in support of his imperial claims, and faculties of arts, medicine, and theology were established at various times. It was thus the first real university, and its reputation soon became widespread. [Sidenote: Development of liberal arts and theology at Paris.] Next in order of foundation came the university at Paris, which was by far the most famous of all. The special interest here, as in this part of Europe generally, was dialectic and scholasticism. The university grew out of the cathedral school at Notre Dame, which had acquired considerable reputation under the headship of William of Champeaux, Abelard, and Peter the Lombard, but it was not until 1200, after canon law and medicine had been added to the liberal arts and theology, that it received complete recognition by the charter of Philip Augustus. [Sidenote: ‘Master-universities’ in the North, but ‘student-universities’ in the South.]