the apostle of the Slavi, was born in Thessalonica about 820. His original name was Constantine. He was educated at Constantinople, where he became acquainted with Photius, and gave for some time lectures on philosophy. He therefore received and always retained the name "The Philosopher." After some time he took orders, became a monk, and soon, with his brother Methodius, withdrew into solitude. He now fell out with Photius, defended the veneration of images, and wrote against the Mohammedans. About 860 he was sent by the emperor Michael III as a missionary to a Tartar tribe, the Chazari, which at that time inhabited the northern shores of the Black Sea as far as the Lower Volga. Jews and Mohammedans vied with Christian missionaries to gain an influence upon this tribe, and the selection of Constantine by the emperor for this difficult mission indicates the high reputation which he enjoyed. He first went to Kherson, acquired a knowledge of the language, and put himself in possession of some relics of Clemens Romanus, which he seems to have always carried with him from this time. A portion of the tribe embraced Christianity, but there is no proof of a Christianization of the whole tribe and of the organization of a national Church. After his return to Constantinople he again lived with his brother Methodius in ascetic retirement until he was sent by the emperor as a missionary to the South Slavic tribes. Both Greek and Roman missionaries had for some time been at work among this people, which, anxious to preserve its independent nationality, mistrusted both. Constantine gained their confidence by convincing them that he sympathized with their national sentiments, and had in view nothing but their conversion to Christianity. He became the founder of a Slavic literature by translating into their language portions of the Scriptures and the most important liturgical books. For this purpose he used an alphabet which either had been invented by him or modified from one (the "Glagolitic") more ancient. The new alphabet, called after him the "Cyrillic," was adopted by most of the Eastern Slavi (Bulgarians, Servians, Bosnians, Slavonians, Russians, etc.), but subsequently underwent in the several countries a number of modifications. By prince Rastislav he was called as a missionary into the Slavic countries outside of the Greek empire. This Rastislav is probably the same whom the Germans call Rastices, the founder of a great Moravian empire whose exact limits cannot at present be defined. About 863 they arrived at the court of Rastislav, the seat of which we do not know, but which was probably at a point far to the south-east from the present Moravia. By disseminating the Scriptures and celebrating divine worship in the Slavic language, they soon founded a flourishing Slavic Church in the territory of Rastislav and other Pannonian princes. When pope Nicholas I heard of their successes he invited them to Rome. In 868 they followed this invitation, accompanied by many disciples. Their Slavic Bible and Slavic mass attracted great attention, and the successor of Nicholas (who in the meanwhile had died), Adrian II, received them with marks of great favor. They presented the pope with the relics of Clemens Romanus, and the pope approved their work, inclusive of the Slavic translation of the Bible and the Slavic liturgy, and declared his intention to organize the new churches in the Slavic provinces as an independent ecclesiastical province, under Constantine and Methodius as bishops. But Constantine, who felt the end of his life approaching, preferred to remain as a monk in Rome, assumed the name of Cyril, under which he has since been known in Church history, and died a few weeks later, Feb. 14, 869. The work of evangelization was continued by his brother Methodius. The works which were formerly ascribed to Cyril (Apologi Morales, Vienna, 1630; Opusculum de Diction. Venice, 1497) are spurious. —Herzog, Real-Encyklop. 3, 223; Schafarik, Slav. Alterthimer, 2:471; Wattenbach, Beitragie zur Geschichte der christl. Kirche in Mihren u. Bohmen (Vienna, 1849); Acta Sanctorum, Mart. 2:14; Dobrowsky, Cyrill und Method (Prague, 1823); Philaret (Russian bishop of Riga), Cyrillus und Methodius (German transl., Mittau, 1847); McLear, Missions in the Middle Ages, chap. 13.