Obj. 3: Further, as Augustine says (Tract. xxvi in Joan.), this is "the sacrament of unity." But multitude seems to be opposed to unity. Therefore it seems inconsistent with the sacrament for several priests to consecrate the same host.
On the contrary, It is the custom of some Churches for priests newly ordained to co-celebrate with the bishop ordaining them.
I answer that, As stated above (A. 1), when a priest is ordained he is placed on a level with those who received consecrating power from our Lord at the Supper. And therefore, according to the custom of some Churches, as the apostles supped when Christ supped, so the newly ordained co-celebrate with the ordaining bishop. Nor is the consecration, on that account, repeated over the same host, because as Innocent III says (De Sacr. Alt. Myst. iv), the intention of all should be directed to the same instant of the consecration.
Reply Obj. 1: We do not read of Christ baptizing with the apostles when He committed to them the duty of baptizing; consequently there is no parallel.
Reply Obj. 2: If each individual priest were acting in his own power, then other celebrants would be superfluous, since one would be sufficient. But whereas the priest does not consecrate except as in Christ's stead; and since many are "one in Christ" (Gal. 3:28); consequently it does not matter whether this sacrament be consecrated by one or by many, except that the rite of the Church must be observed.
Reply Obj. 3: The Eucharist is the sacrament of ecclesiastical unity, which is brought about by many being "one in Christ." _______________________
THIRD ARTICLE [III, Q. 82, Art. 3]
Whether Dispensing of This Sacrament Belongs to a Priest Alone?
Objection 1: It seems that the dispensing of this sacrament does not belong to a priest alone. For Christ's blood belongs to this sacrament no less than His body. But Christ's blood is dispensed by deacons: hence the blessed Lawrence said to the blessed Sixtus (Office of St. Lawrence, Resp. at Matins): "Try whether you have chosen a fit minister, to whom you have entrusted the dispensing of the Lord's blood." Therefore, with equal reason the dispensing of Christ's body does not belong to priests only.
Obj. 2: Further, priests are the appointed ministers of the sacraments. But this sacrament is completed in the consecration of the matter, and not in the use, to which the dispensing belongs. Therefore it seems that it does not belong to a priest to dispense the Lord's body.