The _solea_ was occupied by the sub-deacons and the minor clerks, whose duty it was to intone the psalmody. One or two sacristies (_secretaria_) were placed at the sides of the _solea_. The sanctuary (Figs. 180 and 181), in which the holy sacrifice took place, was surrounded with iron or wooden railings, and communicated through one or three doors with the naves. The farther end of the choir was semicircular in shape, and is now called the apse (in Greek, _kongche_, a muscle or cockle-shell; in Latin, _absida_; in French, _chevet_); around it were placed seats, amongst them that of the bishop, which was raised above the altar, and was visible to the whole congregation. The altar, which was draped and surmounted with the _ciborium_ (a canopy of a cupola shape--Italian, _baldacchino_), was always placed in the centre of the apse (Figs. 182 and 183). Such, was the material framework, the normal arrangement of the Greek and Latin liturgy towards the end of the sixth century. [Illustration: Fig. 182.--Altar-piece at Mareuil-en-Brie.] [Illustration: Fig. 183.--Altar-piece of the Church of Mareuil-en-Brie (Marne).--Latter half of the Thirteenth Century.] No pope was more capable than Gregory the Great (590–604) of uniting the different and scattered elements of which the liturgy was composed. To him is due the merit of having been the first to put forth a revised issue of the books of religious service, and who impressed the stamp of his genius on the Roman Catholic ceremonial. Before him, however, Pope Gelasius had collected the prayers used in the administration of the sacraments, and had prepared the first missal or book of masses. The latter was remodelled and corrected by Gregory. The same pope gave a more orthodox and popular form to the Antiphonary (_Antiphonarium_), sometimes called _Cantatorium_ and _Graduale_, a collection of anthems for every mass in the year; he amended and remodelled in the most skilful and learned manner the anthems that were badly selected and ill scored--endeavouring, after the example set by Solomon, to impart a harmonious and dignified character to sacred music which it did not previously possess. It is tolerably certain that the church chant dates from this period, and that notation by _neumes_, a method the present age does not understand, of marking the rhythm and the modulations of the voice, cannot be traced farther back than the pontificate of Gregory the Great. John Diacre, who has written the life of this illustrious pope, says that he has seen the school of choristers, founded at Rome by St. Gregory, officiating in full splendour. The founder of this famous school continued to give lessons to the pupils in spite of his old age, his attacks of gout, and his other infirmities, even when he was no longer able to stand or sit upright. Reclining on a narrow and very hard bed, he infused emulation into the minds of the idle and reproved the disobedient.