A passage which I selected from Fr. Nicholas Gihr's excellent work, The Sacrifice of the Mass. This particular segment demonstrates the continuity which always existed in the development of the Roman mass, that it was always preserved according to the ancient and venerable tradition of the Church.
Jesus Christ Himself offered the first Eucharistic Sacrifice in the Supper Room of Jerusalem, and this in close connection with the eating of the Paschal Lamb of the Old Testament. At the same time He ordered the celebration of this Sacrifice in His Church for all times, when He gave to the Apostles and their successors in the priestly office the command and the power to do the same as He had done. After the example and by the order of Christ, the Apostles celebrated everywhere on their missionary journeys the Eucharistic Sacrifice… Christ’s example was the norm for the Apostles; at the celebration of the Sacrifice they did, first, only that which Christ had done before. According to His directions and under the inspiration of the Holy Ghost they observed other things besides, namely, according to the circumstances of time and place, to the simple, essential act of sacrifice they added various prayers and observances, in order to celebrate the Holy Mysteries as worthily and edifyingly as possible. Those constituent portions of the sacrificial rite, which are found in all the ancient liturgies, have incontestably their origin from Apostolic times and tradition; such, for example, as the preparatory prayers, the readings from Holy Scripture, the Psalms, the offering of bread and wine mixed with water, the supplications for the living and the dead, the Offertory prayers and the words added to those of Consecration, the reference to the death and resurrection of Christ, the Lord’s Prayer, the sign of the Cross, the kiss of peace, the fraction and distribution of the Host, the thanksgiving after Communion… Already Pope Innocent I (402-417), in writing to Decentius, Bishop of Gubbio, about ritual matters, traces the origin of the Roman liturgy to the Prince of the Apostles: “Who does not know,” he writes, “that what has been handed down by Peter, the Prince of the Apostles, to the Roman Church, is still observed unto this day, and must be observed by all?” St. Peter, consequently, must be regarded (in a more general sense) as the founder of the Roman liturgy, for the method of celebration followed and introduced by him was, without doubt, the essential and permanent foundation for its later development and form… The most ancient written inventories of the Roman liturgy we possess in three Sacramentaries, which bear the names of Pope Leo I (440-461), Gelasius I (492-496), and Gregory 1 (590-604). The Sacramentaries contain a precious treasure of liturgical traditions, which date from the most ancient period of the Roman Church. The above named Popes deserve well of the liturgy, inasmuch as they faithfully preserved the ancient formulas, and, at the same time, enriched and perfected them with additions suitable to the times. Our Missal is principally derived from the Sacramentary of the St. Gregory the Great. Under him the Canon of the Mass received its last addition. The rest of the constituent parts of the Roman liturgy of the Mass (the Introit, the Kyrie, the Gloria, the Collect, the Epistle, the Gradual, the Gospel, the Secreta, the Preface, the Pater Nosted, the Communion and the Post-Communion) date back at least to the fifth or even the fourth century.