Rubrical Requirements
The "Instructio Clementina" for the Quarant' Ore aforementioned stands almost alone among rubrical documents in the minuteness of detail into which it enters. It has also been made the subject of an elaborate commentary by Gardellini. Only a few details can be given here. The Blessed Sacrament is always, except in the patriarchal basilicas, to be exposed upon the high altar. Statues, pictures and relics in the immediate neighbourhood are to be removed or covered. At least twenty candles are to be kept burning day and night. The altar of exposition is only to be tended by clerics wearing surplices.
Everything is to be done, e.g. by hanging curtains at the doorways, by prohibiting the solicitation of alms etc., to promote recollection and silence. There must be continuous relays of watchers before the Blessed Sacrament; and these, if possible, should include a priest or cleric in higher orders who alone is permitted to kneel within the sanctuary. At night the great doors of the church must be closed and women excluded. No Masses must be said at the altar at which the Blessed Sacrament is exposed.
Precise regulations are made as to the Masses to be said at the time of Exposition and Deposition. Except on greater feasts, this Mass must be a solemn votive Mass de Sanctissimo Sacramento. No bells are to be rung in the church at any private Masses which may be said there while the Blessed Sacrament is exposed. When a votive Mass de Sanctissimo Sacramento cannot be said, according to the rubrics, the collect of the Blessed Sacrament is at least to be added to the collects of the Mass. No Requiem Masses are permitted. The Mass pro pace is to be sung on the second day of the Exposition; and the litanies of the saints are to be chanted under conditions minutely specified, at the conclusion of the procession both at the opening and close of the Quarant' Ore.
Finally this "Instructio Clementina" is the foundation upon which is based the ritual for all ordinary Benedictions and Expositions. For example, the incensing of the Blessed Sacrament at the words "Genitori Genitoque" of the "Tantum Ergo", the use of the humeral veil, and the giving of the Blessing with the monstrance, etc., are all exactly prescribed in section thirty-one of the same document.
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