Communicatio in sacris

 

http://liturgicalnotes.blogspot.com/2010/10/communicatio-in-sacris.html

St. Pope Pius X (1835-1914):

“But where a deplorable schism tore a
great number of Eastern Christians from
the center of Catholic unity, it was no
longer possible to continue such a
praiseworthy custom [that is, communion
with the Greeks prior to 1054 A.D.].
Michael Cerularius, who was not satisfied
with uttering poisonous calumnies against
the customs and ceremonies of the Latins,
openly declared that the consecration of
the unleavened bread was null and void [in
the Latin church]. It was then that the
Roman Pontiffs, careful of their Apostolic
duty, to prevent the Latins from falling
into error, forbade them to consecrate or
receive the Blessed Eucharist under the
species of leavened bread.

As for the Greeks [converts] who returned
to the faith and Catholic unity, they [the
Popes] allowed them to communicate with
unleavened bread in Latin churches, a
measure which, considering the times and
places [the Greek converts had to use Latin
churches], was certainly not fitting but
necessary.

In fact, as at that time it was not
easy to find Greek bishops who
were united to St. Peter’s Chair
and very few Catholic churches
of the Eastern rite existed, it was
to be greatly feared that
Catholics of the Eastern rite, if
not allowed to communicate in
Latin churches, would frequent
schismatic [so-called Orthodox
churches] and Pastors and would
run the risk of losing their faith.”

(Apostolic Constitution Tradita ad antiquis, Sept. 14, 1912. See also: Papal Teachings: The Liturgy, Selected and Arranged by the Benedictine Monks of Solesmes, Translated by the Daughters of St. Paul, Boston, Mass. 1962, p. 222).