During a Mass when there are two or more priests concelebrating, and there is also a deacon present, why does the deacon elevate the Blood (while one of the priests elevates the Body) at the end of the Eucharistic Prayer, instead of another priest elevating the Blood?
The *General Instruction of the Roman Missal * instructs the deacon (when present) to do this. “At the final doxology of the Eucharistic Prayer, the deacon stands next to the priest, holding the chalice elevated while the priest elevates the paten with the host, until the people have responded with the acclamation, Amen.” (GIRM 180)
At a concelebrated Mass without a deacon, a concelebrating priest carries out this duty. “If a deacon is not present, his proper duties are to be carried out by some of the concelebrants.” (GIRM 208)