Instruction on Eucharistic Worship - Sacred Congregation of RItes 1967 - Pt.4

Consequently the Eucharistic sacrifice is the source and the summit of the whole of the Church's worship and of the Christian life."' The faithful participate more fully in this sacrament of thanksgiving, propitiation, petition, and praise, not only when they wholeheartedly offer the Sacred Victim, and in it themselves, to the Father with the priest, but also when they receive this same Victim sacramentally.

f) There should be no doubt in anyone's mind "that all the faithful ought to show to this most holy sacrament the worship which is due to the true God, as has always been the custom of the Catholic Church. Nor is it to be adored any the less because it was instituted by Christ to be eaten." 20 For even in the reserved sacrament He is to be adored 21 because He is substantially present there through that conversion of bread and wine which, as the Council of Trent tells us,22 is most aptly named transubstantiation.
g) The mystery of the Eucharist should therefore be considered in all its fullness, not only in the celebration of Mass but also in devotion to the sacred species which remain after Mass and are reserved to extend the grace of the sacrifice.23

These are the principles from which practical rules are to be drawn to govern devotion due to the sacrament outside Mass and its proper relation to the right ordering of the sacrifice of the Mass according to the mind of the Second Vatican Council and the other documents of the Apostolic See on this subject.24

4. The General Intention of This Instruction
 For this reason the Consilium set up to implement the Constitution on the Liturgy, on the instructions of His Holiness Pope Paul VI, has prepared an instruction setting out such practical rules of this nature as may be suitable for the present situation.

The particular purpose of these rules is not only to emphasize the general principles of how to instruct the people in the Eucharist, but also to make more readily intelligible the signs by which the Eucharist is celebrated as the memorial of the Lord and worshipped as a permanent sacrament in the Church.
For although this sacrament has this supreme and unique feature, that the author of holiness is Himself present in it, nevertheless, in common with the other sacraments, it is the symbol of a sacred reality and the visible form of an invisible grace.25 Consequently the more intelligible the signs by which it is celebrated and worshipped, the more firmly and effectively it will enter into the minds and lives of the faithful.26

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