9. The Church's concern for its seminaries is therefore easy to understand. From the earliest years of the Church, the popes and the Catholic bishops took special care to establish centers for candidates to the priesthood. Here, either by themselves or with the help of suitable teachers (sometimes taken from the priests of the cathedral church), they taught the humanities, theology, and above all the conduct suitable to their vocation. The houses which the bishops and monks opened to receive clerics are celebrated up to this day. Among them shines the memory of the Lateran Patriarchate; from here, as from a fortress of wisdom and virtue, illustrious popes and bishops appeared, men remarkable for their holiness and for their teaching. The careful and diligent teaching of clerics seemed very important and necessary even from the beginning of the sixth century. The Council of Toledo, speaking about "those whom their parents forced to enter the clerical state as children," commands "that after having received tonsure or being ordained lector, they must be educated in the Church under the vigilance of the bishop." Thus we see why we must strive to organize and govern the seminaries of your dioceses according to the rules established by the fathers of the Council of Trent. That is also why in the previous agreements between the popes and the secular authorities from different periods, the Apostolic See-especially watched over the preservation of seminaries and reserved to the bishops the right to govern them, to the exclusion of all other powers. Among other documents, we have a clear example in the apostolic letter beginning De salute animarum. Pius VII published this encyclical on July 18, 1821, after reaching an agreement with the king of Prussia concerning a new delimitation of dioceses.