It was customary in ancient times for princes who were at peace with one another to exchange messages of honor and good will. These messages were written on tablets, the backs of which were beautifully ornamented. Two tablets, one folding on the other, like the cover of a book, and bound by cords or hinges, were called "Diptychs", a Greek word meaning folded together or doubled. In Rome there were two officers known as Consuls, who during the republic held supreme power for one year. Even during the empire they were elected, although they ceased to have authority. At the beginning of the New Year those Consuls exchanged Diptychs, as we now send New Year cards. The custom was adopted by the other magistrates and by the Church. Diptychs were sent from one Bishop to another as a sign of friendship and communion, and the diptychs became part of the regular furniture of the altar. On them were inscribed the names of the Pope, Patriarchs and other Bishops; the names of those who died for the faith, the names of civil magistrates who had sent diptychs to the Church, the names of those for whose intention the Mass was offered, the names of those who had contributed to the support of the Church, and, finally, the names of the faithful departed, for whom prayers were asked. In the beginning all these names were read out during the Mass, but, as they became more numerous, and the reading would consume much time, the diptychs were laid on the altar, so that the priest could see the names. In course of time the custom ceased to be observed, and the diptychs were used as frames for pictures or sculptures representing sacred scenes.
The altar was originally shaped like a table or a tomb. It was set in the middle of the sanctuary, so that the ministers had free access to it from every side. It was not allowed to place anything on it except what was necessary for the sacrifice. About the eleventh century the canopies which were erected over the altars began to fall into disuse, and the altar itself was moved nearer and nearer to the back wall of the sanctuary. This change was accompanied by the practice of setting up perpendicularly the diptych now containing paintings and carvings at the back of the altar as an ornament on great feast days. From the position which it occupied it was called a "Retable," or "behind the table". In the course of time the retable was made a permanent fixture. It was enlarged and built of wood, stone, rare marbles, and even of precious metals. Sometimes it took the form of an arcade or of a succession of panels containing representations of sacred scenes. After the fifteenth century a second and a third story were added. The original retable appeared as a mere step, while the superstructure grew higher and higher with column, arch, pinnacle and niche. It was adorned with carvings, statues, relics and the like, and some times reached even to the roof. In some churches this superstructure on the retable took the shape of a great portico, the middle of which was occupied by a painting commonly known as an altar piece. The steps at the back of the altar proper, which represent the original retable, are used for candlesticks, flowers, relics and other decorations, as it is not lawful to place such things on the altar itself during the sacrifice. Table and retable are now commonly called the altar. But it is well to bear in mind that the retable is merely a piece of ornamentation, and that the real altar is the table. The retable is also called a reredos.
From the earliest times it was the practice of the Church to reserve the Blessed Eucharist for the communion of the sick. During the persecutions the Christians kept it in such places as they considered safe, even in private houses. After the persecutions it was reserved in the Church, but it had no fixed place. Sometimes there was a small room built for it, some times an elaborate tower; sometimes it was found in the sacristy, sometimes in a movable cupboard in the sanctuary, sometimes in a stationary cupboard set into the wall, either behind or on the north side of the altar, sometimes above the altar in a vessel hanging by a chain from a cross on the canopy or from an ornamental bracket, if there were no canopy. The vessel was in the shape of a dove, a cup, a box or a tower. It was covered with a small canopy from which hung miniature curtains, so that the vessel appeared to be set in a little tent. Hence the name "Tabernacle," from the Latin for tent. The vessel could be raised or lowered by means of a chain or pulley. It is easy to see that this method of preserving the Blessed Eucharist by means of a vessel suspended over the altar is one which is not safe in troublous times. It makes it easy for evil men to steal or profane the Sacrament. Hence it became necessary to reserve the Eucharist in a strong box which might offer some resistance to thieves. The growth of the retable, which offered a site almost on the altar itself, brought about an amalgamation of the two ancient methods. Accordingly, we find that since the reformation the cupboard is placed in the center of the retable and the custom of hanging the Eucharist over the altar or of preserving it in a different place is now observed only in a few localities. From the name of the little tent which covered the dove this cupboard is now called the "tabernacle." It is built in remembrance of the shape of some of the old Eucharistic vessels, either as a box, a little house or a tower. Our modern altar, therefore, contains three parts, which it is well to keep distinct first, the table or altar proper; secondly, the tabernacle, and thirdly, the retable, supporting the tabernacle and rising perpendicularly in the form of steps, arches and porticoes on either side of the tabernacle and sometimes like the Sacrament tower.
As the Mass is the same Sacrifice as that of the Cross we find that from the earliest times a Cross was used during the service. At first it was a plain Cross, without a figure, though often highly ornamented. From the sixth century onward the Crucifix or the Cross with the image of our Saviour affixed appears in use. It is a curious fact that up to the eleventh century Christ was represented as living on the Cross, but since then He is represented as dead. In keeping with the prohibition against placing anything on the altar except what was necessary for the Sacrifice, we find that in early times the Cross was placed on a stand on the floor to the right of the altar. Where ciboriums or canopies were in use it was suspended over the altar. After the introduction of retables, in the eleventh century, it was placed in the middle of the altar, and when Tabernacles came into use it was placed on top of the Tabernacle.
During the persecutions the Roman Christians worshiped in the Catacombs. As those were all underground, it was necessary to use lights during the services. This use was continued after the persecutions had ceased, both in remembrance of the persecutions and for symbolical reasons. In the first place, Christ is the light of the world, and, as He is present on the altar, the candles symbolize that presence. Secondly, it appears to be a human instinct to use lights as a sign of joy. Towns and houses are illuminated on the occasion of great victories, and when people entertain visitors it is customary to decorate their apartments with many lights. For these reasons, the Church uses lights even during the day. Just as the altar is built in the shape of a tomb, so the lights recall the days of the Catacombs, and, just as people adorn their houses with lights to welcome their guests, so the Church adorns her altars to welcome our Lord. As we have seen, in early times the candles were not placed on the altar, but on the ground on each side or else were held by the ministers. After the eleventh century, like the Cross, they were placed on the retable, and sometimes at the corners of the altar itself. A lamp known as the Sanctuary Lamp burns day and night before the Blessed Sacrament. As the tabernacle is now placed on the high or chief altar, the lamp is usually suspended from the roof towards the front of the sanctuary.
The table at which our Lord ate the Last Supper was covered with a cloth after the custom of the Jews. Hence, whenever the Supper was celebrated afterwards in commemoration of Him, the same practice was observed. Up to the fifteenth century the cloth was not spread on the altar until before Mass began, so that the altar usually remained bare or had an ornamental cover to preserve it from the dust. Since the seventh century the Altar Cloths have always been of linen, and since the ninth century three layers of cloth have been prescribed. These three layers are obtained either by three distinct pieces of linen, or by two pieces, one of which is folded twice. The object of having three folds is no doubt to catch the Precious Blood, if by any chance it should happen to be spilled. But, added to this, is the fact that the Altar is a symbol of our Lord, and the various Altar Cloths correspond to the various cloths He was wrapped in when laid in the grave.
"Peter therefore went out and that other disciple and they went toward the tomb. And they both ran together, and that other disciple did outrun Peter and came first to the sepulcher. And when he stooped down he saw the linen cloths lying; yet he went not in. Then comes Simon Peter following him, and went into the sepulcher and saw the linen cloths lying, and the napkin that had been about his head, not lying with the linen cloths, but wrapped up in a place by itself." (John 20)
The two under cloths just cover the table, but the upper cloth hangs down at both ends almost to the ground. A fringe of lace or other ornamental work is often attached to the under cloth and is known as the "frontal". Wherever the altar is not made entirely of stone or is not closed in, it is the custom to hang in front of it a curtain or screen known as the "antependium". Formerly the antependium was of metal like the retable (see No. 83), but it now consists of cloth stretched on a frame. When employed it should agree in color with the vestments used at the Mass. The antependium is not in very general use in this country except at Masses for the dead.
As we have explained above, formerly the Liturgy was not written. The priests were compelled to rely on their memories. When peace was given to the Church by the conversion of Constantine, this old rule did not disappear suddenly, but very gradually, so that only portions of the Liturgy, or such as were too long or too complicated to be learned by rote, were committed to writing. Thus we have the "Lectionary", which contained the "Lessons" read in the service, the "Evangeliary", which contained the portions of the Gospel, the "Antiphonary", which contained the passages to be sung. "Antiphon" is a Greek word which originally meant a "reply," then a method of singing in which one choir or singer replied to or alternated with another choir or singer. All these books deal with the public prayer which preceded the Sacrifice. The Order of the Sacrifice itself, being most holy and mysterious, was not written until much later. It was called the "Book of Mysteries" or the "Sacramentary". It contained most of those portions of the Liturgy which the priest recited. In the Middle Ages all these books were collected into one, which was called a "Missal," or "Mass Book." The edition which we use today was revised by command of the Pope in the sixteenth century, and is known as the Roman Missal. Portions of the prayers to be said by the priest are printed on cards and are set up on the altar for convenience sake. They spare the trouble of turning over to various places in the Mass Book. These cards are called "Altar Cards," or "Altar Charts." One is placed in front of the Tabernacle and one at each end of the altar. They are not found in many of the churches in Spain and Italy, while in churches of other places only one is used.
It is the custom to place shrines containing the relics of the saints between the candlesticks on the steps of the retable. Moreover, the use of flowers is of very ancient date. In accordance with the law that nothing should be placed on the Table except what was necessary for the Sacrifice, the flowers, in early times, were hung in garlands or wreaths around the altar or on the walls of the sanctuary. Artificial flowers were first made in the thirteenth century by certain nuns of Flanders. The custom of placing flowers on the retable, begun in some convents of women, was adopted by the Mendicant Orders (Dominicans and Franciscans), then spread to the country churches, and came afterwards into general use. The Roman Basilicas, however, still proscribe them.
- taken from The Mass, by Father Peter Christopher Yorke