The priest breaks a bit of the host over the paten and drops a small piece into the chalice, saying quietly: “May this mingling of the Body and Blood of our Lord Jesus Christ bring eternal life to us who receive it.” These words are already used in the text of an eighth century papal mass. Meanwhile the Lamb of God acclamations are recited or sung.
There is testimony that very early on a fraction of the host would sometimes be added from another day or even from the papal or bishop’s Mass to that of another location. This becomes another sign of unity between the churches or between the bishop and his priests but it is a practice that eventually disappears.
Josef Jungmann (The Mass of The Roman Rite, Vol. 2, p. 312) states that this second commingling is employed for distant or outlying churches.
By an acolyte, the bishop sent the priests of the vicinity a particle of the Eucharist as an expression of ecclesiastical unity, as a token that they belonged to his “communio.” This particle was called the “fermentum.” The priests dropped it into the chalice at this part of the Mass!
Extending to the sixth century, the fraction would symbolize the passion and death while the commingling would signify the resurrection. The action itself would go back to the beginning in that it is reflective of all four New Testament accounts. Our Lord “took the bread, broke it and gave it to His disciples.” The “Breaking of the Bread” becomes the oldest title for the Eucharist and is designated in the story of the men on the road to Emmaus, as our encounter with the risen Christ. The fraction begins its trajectory in the development of the liturgy as a practical necessity— dividing the bread for the distribution in Holy Communion. A particle is retained for the commingling that follows.
After the Protestant Reformation, the formula or words are modified to make clear to critics that the commingling is symbolic and has no invisible operation apart from the consecration. It only expresses a desire or wish that this commingling may avail us of eternal life or salvation. Both species constitute one sacrament. The consecrated BODY of Christ and the BLOOD of Christ may be combined as a fuller sign but either constitutes the totality of the risen Christ— in every drop and in every particle. This is the case when Communion is given out as the host alone or with the chalice or as combined within intinction.
Just as the two-fold consecration of bread and wine signifies the death of Jesus (separation of the body and blood), the commingling symbolizes resurrection (wholeness between the body and blood). We are invited to have a share in our Lord’s new life. The power of grace can divinize us and grant us immortality— if we are properly disposed.