After the dogma of the Holy Trinity, the Holy Spirit reminds us of the dogma of the Incarnation of our Lord, in celebrating with the Church the greatest of all sacraments, summing up the whole life of the Redeemer, giving infinite glory to God and applying the fruits of the Redemption at all times to ourselves (Collect).
It was on the cross that our Lord redeemed us and the Holy Eucharist, instituted on the night before our Lord's Passion, remains its memorial (Collect). The altar is the extension of Calvary; the Mass "shows the death of the Lord " (Epistle). (The celebration of the Mass has the same value as the death of Jesus Christ on the cross," St. John Chrysostom.)
Jesus is there in the state of a victim, for the words of the double consecration mean only that the bread is changed into the Body of Christ and the wine into His Blood. On account of this double action with different effects, which constitutes the sacrifice of the Mass, we are entitled to speak of our Lord's Presence under the appearance of bread as that of the Body of Christ, although, since He can die no more, the whole Christ is there contained; similarly we may speak of the Presence under the appearance of wine as that of His Blood, although He is contained there whole and entire.
Through His priests, our Lord Himself, the principal Priest of the Mass, offers in an unbloody manner His Body and Blood which were really separated on the Cross, but on the altar only in a representative or sacramental sense, the matter and words used and the effect produced being different in the two consecrations. Besides, the Eucharist was instituted under the form of food (Alleluia), that we may be united with the Victim of Calvary, so that the Sacred Host becomes the "wheat " which feeds our souls (Introit).
Moreover, Christ, as the Son of God, receives the eternal life of the Father; in the same way Christians share in that eternal life by uniting themselves to Christ through the Sacrament which is the symbol of unity (Secret), and this possession of the divine life, already realized on earth through the Eucharist, is the pledge and the beginning of that in which we shall fully rejoice in heaven (Postcommunion). As the Council of Trent puts it: "That same Heavenly Bread that we eat now under the sacred veils, we shall feed upon in heaven without veil."
We should regard the Mass as the centre of all Eucharistic worship, seeing in Holy Communion the means instituted by our Lord to enable us to share more fully in this divine Sacrifice. In this way our devotion to our Lord's Body and Blood will effectively obtain for us the fruits of His Redemption (Collect).
Concerning the procession which regularly should follow the Mass, we remember how the Israelites revered the Ark of the Covenant which was the Presence of God among them. When they carried on their victorious marches, the Ark went before, born by the Levites in the midst of a cloud of incense, accompanied by the sound of musical instruments and of the songs and shouts of the multitude
We Christians have a treasure far more precious, for in the Eucharist we possess God Himself. Let us feel a holy pride in forming His escort and extolling His triumphs, while He is in our midst.
Cibavit eos ex adipe frumenti, alleluia: et de petra, melle saturavit eos, alleluia, alleluia, alleluia. * Exsultate Deo adjutorio nostro; jubilate Deo Jacob.
He fed them with the fat of wheat, alleluia; and filled them with honey out of the rock, alleluia, alleluia, alleluia. * Rejoice unto God our helper; sing aloud to the God of Jacob.
(Psalm 80:17,2 from the Introit of Mass)
Deus, qui nobis sub Sacramento mirabili passionis tuae memoriam reliquisti: tribue, quaesumus, ita nos Corporis et Sanguinis tui sacra mysteria venerari; ut redemptionis tuae fructum in nobis jugiter sentiamus.
O God, who in this wonderful sacrament has left us a memorial of Thy passion, grant us, we beseech Thee, so to venerate the sacred mysteries of Thy Body and Blood, that we may ever perceive within us the fruit of Thy redemption.
Continuation of the holy Gospel according to St. John.
At that time Jesus said to the multitudes of the Jews: My Flesh is meat indeed, and My Blood is drink indeed. He that eateth My Flesh, and drinketh My Blood, abideth in Me, and I in him. As the living Father hath sent Me, and I live by the Father, so he that eateth Me, the same also shall live by Me. This is the bread that came down from Heaven. Not as your fathers did eat manna and are dead. He that eateth this Bread shall live for ever.
(St. John 6:56-59)
From the Catholic Encyclopaedia: http://www.newadvent.org/cathen/04390b.htm