The subdeacons have no right to a place in the Diaconicum, nor to touch the Lords vessels.
Ancient Epitome of Canon XXI.
A subdeacon shall not touch the vessels.
The “Lords vessels” are the chalice and what we call the sacred vessels.
The ecclesiastical ministers shall not take into their hands the Lords vessels, but they shall be carried to the Table by the priests or deacons.
Both Balsamon and Zonaras agree that by ὑπέρεται is here meant subdeacons.
It is doubtful whether by diaconicum is here meant the place where the deacons stood during service, or the diaconicum generally so called, which answers to our sacristy of the present day. In this diaconicum the sacred vessels and vestments were kept; and as the last part of the canon especially mentions these, I have no doubt that the diaconicum must mean the sacristy. For the rest, this canon is only the concrete expression of the rule, that the subdeacons shall not assume the functions of the deacons.
With regard to the last words of this canon, Morinus and Van Espen are of opinion that the subdeacons were not altogether forbidden to touch the sacred vessels, for this had never been the case, but that it was intended that at the solemn entrance to the altar, peculiar to the Greek service, the sacred vessels which were then carried should not be borne by the subdeacons.
This canon is found in the Corpus Juris Canonici, Gratians Decretum, Pars I., Dist. xxiii., c. xxvj.