Canonical digits
As he begins the rite of consecration, the priest wipes the thumb and index of each hand making a sign of the cross on the corporal saying "qui pridie quam pateretur" (at the time he was betrayed).
Thus for example, it can be observed on a fresco in the lower church of San Clemente al Laterano in Rome that a priest at the altar at the end of the canon does not hold his finger and index with this caution.
According to the Cluniac Customary, written about 1068 by the monk Bernhard, the priest at the consecration should hold the host quattuor primis digitis ad hoc ipsum ablutis (with the four first fingers previously rinsed)."
[2] In the 13th century, for French liturgist Guillaume Durand, thumb and forefinger may be parted after the consecration only quando oportet hostiam tangi vel signa fieri, which means that the fingers can be disjoined when making the sign of the cross.
Similar provisions were made in the Ordo of Giacomo Gaetani Stefaneschi in 1311, in the Liber ordinarius of Liege as well as in the Dominican sources of the same, dated about 1256, all insisting that the liturgical digits be kept after the Lavabo.
"[4] The practise was made into a universal rubric by the Roman Missal promulgated by the Council of Trent which ended in 1563 insisting on the belief in the real presence in every particle of the Eucharist, in reply to doubts spread by the Protestant Reformation: "If anyone deny that Jesus Christ is contained whole and entire under each species in the adorable sacrament of the Eucharist, and also under each particle of these species, after they are divided, let him be anathema".
As Church law required the Blessed Sacrament be touched with the thumb and forefinger, he returned to France to implore Pope Urban VIII for an indult.
The last time the canonical digits were insisted upon as mandatory by the Sacred Congregation for the Discipline of the Sacraments was in 1962 in an answer to a dubia regarding the use of modern chalices with a node, explaining that "it suffices that the priest can satisfactorily hold the chaild with his thumb and index finger joined".
[11] With the Roman Instruction Inter ecumenici, published by this Congregation on September 26, 1964, a series of adaptations intended to be introduced into the sacred rites were decided.
