Rome’s approach to many aspects of liturgy has quite often been flexible. An ideal is set forth. Here, for example, the people receiving Communion consecrated at the Mass at which they are celebrating.
121. Now it is very fitting, as the liturgy otherwise lays down, that the people receive holy communion after the priest has partaken of the divine repast upon the altar; and, as we have written above, they should be commended who, when present at Mass, receive hosts consecrated at the same Mass, so that it is actually verified, “that as many of us, as, at this altar, shall partake of and receive the most holy body and blood of thy Son, may be filled with every heavenly blessing and grace.”[Roman Missal, Canon of the Mass]
The 1947 concession to practicality, and perhaps, long-standing local practice, was to remind bishops that the ideal set forth in MD 121 may not be met all the time:
122. Still sometimes there may be a reason, and that not infrequently, why holy communion should be distributed before or after Mass and even immediately after the priest receives the sacred species – and even though hosts consecrated at a previous Mass should be used. In these circumstances – as we have stated above – the people duly take part in the eucharistic sacrifice and not seldom they can in this way more conveniently receive holy communion. Still, though the Church with the kind heart of a mother strives to meet the spiritual needs of her children, they, for their part, should not readily neglect the directions of the liturgy and, as often as there is no reasonable difficulty, should aim that all their actions at the altar manifest more clearly the living unity of the Mystical Body.
When might the actions of the liturgy more closely suggest the living unity of the Church? That is the question any good bishop was to consider, and still must consider today.