The following excerpts are taken from the document “Norms for the Distribution and Reception of Holy Communion under Both Kinds in the Dioceses of the U. S.:”

#5. While the heart of the celebration of the Eucharist is the Eucharistic Prayer, the consummation of the Mass is found in Holy Communion, whereby the people purchased for the Father by his beloved Son eat and drink the Body and Blood of Christ. They are hereby joined together as members of Christ’s mystical Body, sharing the one life of the Spirit. In the great sacrament of the altar, they are joined to Christ Jesus and to one another.
#6. The Lord himself gave us the Eucharist at the Last Supper. The Eucharistic sacrifice “is wholly directed toward the intimate union of the faithful with Christ through communion.” It is Christ himself who is received in Holy Communion, who said to his disciples, “Take and eat, this is my body.” Giving thanks, he then took the chalice and said: “Take and drink, this is the cup of my blood. Do this in remembrance of me” (Mt 26,26-27; 1 Cor 11,25).
#17. From the first days of the Church’s celebration of the Eucharist, Holy Communion consisted of the reception of both species in fulfillment of the Lord’s commandto “take and eat…take and drink.” The distribution of Holy Communion to the faithful under both kinds was thus the norm for more than a millennium of Catholic liturgical practice.
#18. The practice of Holy Communion under both kinds at Mass continued until the late eleventh century, when the custom of distributing the Eucharist to the faithful under the form of bread alone began to grow. This practice spread until the Council of Constance in 1415 decreed that Holy Communion under the form of bread alone would be distributed to the faithful.
#19. In 1963, the Fathers of the Second Vatican Council authorized the extension of the faculty for Holy Communion under both kinds in a document called Sacrosanctum Concilium.
#20. The Council’s decision to restore Holy Communion under both kinds at the bishop’s discretion took expression in the first edition of the Roman Missal and enjoys an even more generous application in the third edition:
“Holy Communion has a more complete form as a sign when it is received under both kinds. For in this manner of reception a fuller sign of the Eucharistic banquet shines forth. Moreover, there is a clearer expression of that will by which the new and everlasting covenant is ratified in the blood of the Lord and of the relationship of the Eucharistic banquet to the eschatological (heavenly)banquet in the Father’s kingdom.”
The General Instruction further states that “at the same time the faithful should be guided toward a desire to take part more intensely in a sacred rite in which the sign of the Eucharistic meal stands out more explicitly.”
#21. The extension of the faculty for the distribution of Holy Communion under both kinds does not represent a change in the Church’s beliefs concerning the Holy Eucharist. Rather, today the Church finds it salutary to restore a practice, when appropriate, that for various reasons was not opportune when the Council of Trent was convened in 1545.
But with the passing of time, and under the guidance of the Holy Spirit, the reform of the Second Vatican Council has resulted in the restoration of a practice by which the faithful are again able to e xperience “a fuller sign of the Eucharistic banquet.”