There's a lot of nonsense in this thread, and it's not exclusively or even mostly on the RC side of the argument.
Both RC's and Orthodox believe that the Eucharist is the true body and blood of Christ. Christ is alive and not dead, so it cannot be that those who receive only the bread or only the wine are receiving only a part of Christ: they receive the one, whole, living Christ. If you're Orthodox and you don't get that, please put down the Philokalia and start reading the New Testament...and make an appointment to speak with your priest.
Some are asking the question why Christ offered the cup if the bread was sufficient. The Eucharist is both sign and reality. The separate blessing/"consecration" of the bread and the cup, following the example of the Lord, signify the separation of blood from flesh, which indicates death--the Eucharist is the memorial of the sacrificial death of Christ. But since Christ is risen from the dead, we unite the body and the blood to signify the living, risen Christ. When the gifts are transformed by the Holy Spirit's descent, they are not transformed into the dead body and dead blood of Christ, but into the body and blood of the Christ who was dead and now lives, never to die again. The act of mingling the gifts is a visible sign of this reality. As I wrote elsewhere:
For me, the most important "unification" of the Body and the Blood is in the ritual intinction. In the Byzantine rite, I think this happens after "Holies for the holy", when a particle of the Lamb is placed within the chalice. This precedes the Communion of the clergy. After this, the particles for the laity are placed in the chalice and most people receive from this mixture. But it is not so in all rites. The Roman rite practices this intinction at roughly the same moment in the Liturgy, but without necessarily communing the faithful under both species. In the Syriac and Coptic rites, a particle of the holy bread is placed in the chalice, and another particle is dipped into the Blood and is used to anoint the rest of the Body (which the Byzantine rite basically does when preparing the Presanctified Gifts). After this, they can either receive both separately (Coptic) or receive what basically looks like Communion under one species but is really not (Syriac). Whether a particular tradition habitually communes with one species or both, the gifts have been consecrated separately (death) and then reunited (resurrection), so that there is no longer two, but one. Again, for me, this is the most important consideration. All of our traditions allow communing under one species given specific reasons, and I think part of the reason this is acceptable is because of this rite.
Since we are speaking specifically of the Roman rite, this action takes place at (OF) or shortly before (EF) the Agnus Dei: the Host is broken, and a piece of it is dropped into the chalice. By the operation of the Holy Spirit and through ritual actions, the fact that the transformed gifts are really the body and blood of the living Christ has been signified. Whether you receive one or the other "species" or both, it is one and the same undivided Christ. Certainly, it is preferable and normative to receive "both species", separately or combined, because of the value of that sign. But even Orthodox will make exceptions to accommodate certain pastoral circumstances (e.g., communing of infants). These exceptions are not the norm in Orthodoxy, but neither is it the case that those communicants are "missing out" on half the sacrament.
So we cannot say that the centuries old RC practice of communion under one species is absolutely wrong: it does not deprive the faithful of a portion of the sacrament. In studying the history of how this practice came about, we might conclude that it was ill-advised, an overreaction, etc., and we might support a return to communion under both species, but there is no justification for some of the comments that appear in this thread. I think some are being intentionally obtuse in order to stick it to the RC's, and it just makes us look like idiots to criticise something we also practice from time to time (possible only because our underlying belief is the same) when there is plenty of substantial difference over which we ought to focus.