40. Some have with reason feared that this practice would permanently prevent Latin priests from offering Mass in Greek Churches, since these have only one altar which cannot be used twice on the same day for the celebration of Mass. In that case, Latin priests could not use the oratories for saying Mass since these were built for Greeks only. But to dispel this fear, it can be seen that today Greek churches generally have a second altar at which Latin priests can celebrate Mass. Goarius describes three kinds of Greek churches in his Euchologium Graecorum. The third kind has a second altar built, as Goarius thinks, for Latin priests, and Schelestratus follows him in this view (p. 887).

In the Maronite and Greek churches in Rome, besides the main altar, there are other altars at which Latin priests say Mass. In Our constitution Etsi Pastoralis, sect. 6, no, 8-9, We deal with the best way of treating Italian Greeks, and in this passage We forbid Latin priests ever to celebrate Mass at the main altar in Greek churches except in a case of absolute necessity and then only with the consent of the Greek parish priest. We also allow the Greeks to build altars in their churches apart from the main altar and at these, Latin priests may, if they wish, celebrate Mass.