3. What rule should a priest follow when he finds in the Ordo a regulation which he believes to be certainly incorrect? * * * * * 1. It is beyond doubt, that the inclination ought to be made whilst the entire verses _Tantum ergo Sacramentum, Veneremur cernui_, are being sung; and if, in any church, custom has limited the inclination to the two last words, it has arisen from this, that whenever the celebrant intones the hymn, he makes the inclination only after the intonation. The ministers, however, are wrong in imitating him in this. "Tum in officio divino", says Cavalieri, t. iv., c. viii., _Inst. Clem._, § 33, n. 49, "quam in precibus omnibus coram SS. Sacramento, dum praedictus versus _Tantum ergo_ dicitur, ab omnibus omnino persistendum erit in inclinatione usque ad _cernui_. Haec est", says Gardellini (_Inst. cl. ibid._ n. 19), "praxis quae obtinet in majoribus Urbis basilicis". This doctrine is followed by modern authors. 2. Before we reply to the question, it will be useful to make two remarks. The first has reference to the difference between the functions of the deacon and those of the assistant priest. If the celebrant be assisted by a deacon and sub-deacon, the assistant need not do more than place the Blessed Sacrament on the throne, and lower it thence at the proper time. He may also extract the Blessed Sacrament from the tabernacle before the exposition, and replace it therein after the Benediction. The office of assistant appears to have been instituted as a measure of precaution against the danger which might result from the near approach of the deacon's vestments to the lights, in case he took down the ostensorium, or to guard against other inconveniences. But there is no reason why the assistant should present the ostensorium to the celebrant when the deacon and sub-deacon are present. We should remark, in the next place, that, according to the text of the _Ceremoniale Episcoporum_, and of the _Instructio Clementina_, the priest, after receiving the humeral veil, mounts the steps without the ministers, and himself takes the ostensorium. Authors prescribe that the deacon and sub-deacon should kneel on the highest step, and support the celebrant's cope during the benediction. In their absence, this is done by the master of ceremonies, or two clerks. When the benediction has been given, the priest having completed the circle, places the Blessed Sacrament in the corporal, genuflects, and descends with the sub-deacon, whilst the deacon restores the Blessed Sacrament to the tabernacle, unless this be done by the assistant priest, in which case the deacon descends with the celebrant and the sub-deacon. According to Baldeschi, the veil is removed from the celebrant when he genuflects in the predella, after having given the benediction.