Q. 1. What is "Communion by intinction?" I never heard this expression in the Catholic Church.
A. 1. The reason you never heard of "Communion by intinction" is because most Catholics have never experienced Communion by intinction. In this method of administering the Sacrament of the Holy Eucharist, the priest takes the Consecrated Host, dips it part way into the chalice (intincts it), and then places it on the tongue of the communicant.
The Fathers of the Second Vatican Council opened the way to a change in the practice of distributing the Holy Communion to the faithful under only one form of bread. They said, "Communion under both kinds may be granted when the bishops think fit, not only to clerics and religious but also to the laity, in cases to be determined by the Apostolic See" (Sacrosanctum Concilium §55).
In the "General Instruction of the Roman Missal(GIRM)" we read, "The Blood of the Lord may be received either by drinking from the chalice directly, or by intinction, or by means of a tube or a spoon." (GIRM §245)
It further states that this responsibility is left to the local Bishops. "The Diocesan Bishop may establish norms for Communion under both kinds for his own diocese, which are also to be observed in churches of religious and at celebrations with small groups. The Diocesan Bishop is also given the faculty to permit Communion under both kinds whenever it may seem appropriate to the priest to whom, as its own shepherd, a community has been entrusted, provided that the faithful have been well instructed and there is no danger of profanation of the Sacrament or of the rite’s becoming difficult because of the large number of participants or some other reason." (GIRM §283)
"Communion by intinction" is a rare practice because most liturgists oppose it. They oppose it in fear, especially in the United States, that this practice may lead to a form of "self-intinction". Such can never happen because the Church tradition has always been that the faithful must receive the Sacrament of Holy Communion from the priest.
In #104 of "Redemptionis Sacramentum" we read, "The communicant must not be permitted to intinct the host himself in the chalice, nor to receive the intincted host in the hand. As for the host to be used for the intinction, it should be made of valid matter, also consecrated; it is altogether forbidden to use non-consecrated bread or other matter."
Some claim that Communion by intinction is not practiced because it alludes to the betrayal of Judas, the follower of Jesus who is described in the Holy Bible as “dipping” the Bread in the Wine at the Last Supper.
A concern expressed by some priests is that by dipping the Consecrated Host into the Blood of Christ, there is always a risk that a drop of the Consecrated Blood may fall on the floor or the soaked Host may fall apart and It too fall on the floor.