What functions may an instituted acolyte perform in the Liturgy? Can he expose the Blessed Sacrament? Should he wear a cope?
In 1973, Pope Paul VI replaced the minor orders which were received by students training for the priesthood with admission to candidacy for Holy Orders, and the ministries of lector and acolyte. These are considered as lay ministries, though few dioceses institute lay people to these ministries except those who are in priestly formation. (One reason may be that Pope Paul reserved these ministries to men.)
The acolyte assists the priest and deacon especially in the celebration of Mass. He serves at Mass (a function that is normally carried out by others if there is no acolyte) and is an extraordinary minister of Holy Communion ex officio. If extraordinary ministers are required for the distribution of Holy Communion, the acolyte should be deputed to this function before others. He may also purify the sacred vessels after Holy Communion.
If there is no priest or deacon available, it is legitimate for an acolyte (or indeed a specially commissioned extraordinary minister) to expose the Blessed Sacrament for adoration. I have not found any particular instruction for what the acolyte ought to wear for this. According to the general practice of the Church, it would seem appropriate for him to wear an alb or a cassock and cotta. Although the cope is used by acolytes (and sometimes by lay people) for some functions at pontifical Mass in the extraordinary form, and for some processions and at the divine office in both forms, I doubt the suitability of an acolyte wearing a cope to expose the Blessed Sacrament since, in the absence of the priest this is not a solemn exposition.
Since Pope Paul decreed that the functions of the subdeacon are included in those of lector and acolyte, the Pontifical Commission Ecclesia Dei has confirmed that the practice of an acolyte carrying out the functions of the subdeacon at High Mass in the extraordinary form may be tolerated. This would be particularly appropriate if it made it possible to celebrate High Mass rather than simply a Missa Cantata.
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