In celebrating the memorial of the Lord, the Church bears witness by means of the rite itself to its faith in and adoration of Christ, present in the sacrifice and given as food to those sharing in the table of the eucharist.
The Church therefore has an intense concern to ensure the worthy celebration and fruitful reception of the eucharist through exact fidelity to the tradition that has evolved and come down to us, enriching the Church's practice and life. The pages of history show that the manner of celebrating and receiving the eucharist has taken many forms. At the present, with a view to meeting the spiritual and psychological needs of today's people more effectively, many and major changes in the rite have been introduced into the eucharistic celebration. As for the discipline governing the way in which the faithful share the sacrament, communion under the form of both bread and wine, when certain circumstances obtain, has been brought back from the disuse into which it had fallen after once being quite general in the Latin rite. (The disuse had become universal at the time of the Council of Trent, which supported it with dogmatic teaching and defended it as suited to the conditions of that era. )
These measures of reform have made the sign value of the eucharistic meal and the full carrying out of Christ's command more explicit and striking. At the same time, however, the more complete sharing in the eucharistic celebration, of which sacramental communion is the sign, has prompted a desire in some quarters during the last several years to return to that usage whereby the eucharistic bread is placed in the hand of the faithful, who communicate by putting the host into their own mouth.
Moreover such a rite has even been put into practice in some communities and locales, even though the Apostolic See's approval has not been sought beforehand and in some cases the necessary preparation of the faithful has not been provided.
It is quite true that ancient usage at times allowed the faithful to receive this divine food in the hand and to put it into their own mouth. It is also true that in the earliest years they could take the blessed sacrament away with them from the place of worship, principally in order that they might use it as viaticum in case they had to face danger for the sake of professing their faith.
But it is also true that the laws of the Church and the writings of the Fathers give ample witness to a supreme reverence and utmost caution toward the eucharist. "No one . . . eats the flesh who has not first adored it";  everyone receiving it is warned: ". . . Receive it with care that nothing of it be lost to you";  "For it is the body of Christ." 
Further, the care and ministry of the Lord's body and blood were entrusted in a special way to the sacred ministers or to those deputed for this: "After the one presiding has completed the prayers and the people have all responded together, those whom it is our custom to call 'deacons' distribute for participation by all present the bread, wine, and water in which thanksgiving has been offered and they also bring them to those who are absent." 
Thus quite early the function of bringing the eucharist to those absent was assigned exclusively to sacred ministers as a precautionary measure to ensure the reverence due to Christ's body and to meet the needs of the faithful. With the passage of time as the truth of the eucharistic mystery, its power, and Christ's presence in it were more deeply understood, the usage adopted was that the minister himself placed the particle of the consecrated bread on the tongue of the communicant. This measure was prompted by a keen sense both of reverence toward the sacrament and of the humility with which it should be received.
In view of the overall contemporary situation of the Church, this manner of distributing communion must be retained. Not only is it based on a practice handed down over many centuries, but above all it signifies the faithful's reverence for the eucharist. Such a practice in no way takes away from the personal dignity of those coming for so great a sacrament and it is a part of the preparation that is a prerequisite for the fruitful reception of the Lord's body. 
The reverence involved is a sign of sharing not "in ordinary bread an wine"  but in the Lord's body and blood; in virtue of this communion "the people of God share the benefits of the paschal sacrifice, renew the new covenant made once and for all by God with humanity in the blood of Christ, and in the faith and hope foreshadow and anticipate the eschatological banquet in the Father's kingdom." 
Further, this way of distributing communion, which must now be regarded as the normal practice, more effectively ensures that communion is distributed with the required reverence, decorum, and dignity; that there is less danger of disrespect for the eucharistic elements, in which "in a unique way Christ is present, whole and entire, God and man, substantially and continuously",  finally, that the caution is exercised which the Church has always counseled regarding the particles of the consecrated bread: "What you might permit to fall, think of as being the loss of a part of your own body." 
When, therefore, a few conferences of bishops and some individual bishops petitioned that the practice of placing the consecrated bread in the hand of the faithful be allowed in their territories, Pope Paul VI decided that all the bishops of the Latin Church be asked individually for their opinion on the advisability of introducing this rite. A change in so important a matter has its basis in an ancient and honored tradition does not simply affect discipline, but can also bring with it dangers that, it is feared, may arise from the new way of administering communion. In particular, these dangers are both the possibility of a lessening of reverence toward the august sacrament of the altar, its profanation, and the watering down of the true doctrine of the eucharist.
Three questions, therefore, were presented to the bishops; their replies to them, received up to 12 March 1969, were as follows:
1. Do you think that a positive response should be given to the request to allow the rite of receiving communion in the hand?
In favor with reservations:
2. Are you in favor, provided the local Ordinary agrees, of prior experiments with this new rite in small communities?
3. Are you of the opinion that the faithful, after well-planned catechetical preparation would welcome this new rite?
The answers given show that by far the greater number of bishops think that the discipline currently in force should not at all be changed. And if it were to be changed, it would be an offence to the sensibilities and spiritual outlook of these bishops and a great many of the faithful.
In a way appropriate to the seriousness of the matter and the importance of the issue raised, Pope Paul VI has considered the thoughts and recommendations of the bishops, "whom the Holy Spirit has made the guardians over" the Churches.  His judgement is not to change the long-accepted manner of administering communion to the faithful.
The Apostolic See earnestly urges bishops, priests, and faithful, therefore, to obey conscientiously the prevailing law, now reconfirmed, in view of the judgement rendered by the majority of the Catholic episcopate, the form in use in the actual rite of the liturgy, and the general good of the Church itself.
Wherever the contrary practice, that is, of communion in the hand, has already come into use, the Apostolic See, in order to assist the conferences of bishops to fulfill a pastoral responsibility often made more difficult by the contemporary state of affairs, entrusts to the same conferences of bishops the duty and task of evaluating any possible special circumstances. This, however, is with the proviso both that they prevent any possible lack of reverence or false ideas about the eucharist from being engendered in the attitudes of the people and that they carefully eliminate anything else unacceptable.
In order that this usage will be rightly dealt with, the conferences of bishops in these cases will, after previous careful study, come to a decision by secret ballot. To carry, their decision must receive two-thirds of the votes cast. The conferences will then submit their decision to the Holy See for the requisite confirmation  and will also annex an accurate report of the reasons that led to the decision. Mindful of that bond existing between the various local Churches and between each of them and the universal Church, the Holy See will carefully weigh each case in the interest of the general good, the building up of all, and the increase in faith and devotion that comes from mutual example.
By apostolic authority Pope Paul VI, on 28 May 1969, duly approved this Instruction, prepared at his command. He directed also that it be brought to the attention of the bishops by the presidents of the conferences of bishops.
All things to the contrary notwithstanding.