How proud the Romans must be that their ancient accusation against the Christians is now repeated by Christians.
Yeah and in the gate and vine passages he clearly said it to prove a point as can be seen by his explanation of the words to his disciples afterwards. No such explanation is given for "This is my Body" and "This is my Blood".
Not sure where you're getting that. Heres just a few passages where Paul speaks of the Eucharist.
DRC: I Corinthians Chapter 10
[16] The chalice of benediction, which we bless, is it not the communion of the blood of Christ ? And the bread, which we break, is it not the partaking of the body of the Lord ?
[17] For we, being many, are one bread, one body, all that partake of one bread.
DRC: I Corinthians Chapter 11
[23] For I have received of the Lord that which also I delivered unto you, that the Lord Jesus, the same night in which he was betrayed, took bread.
[24] And giving thanks, broke, and said: Take ye, and eat: this is my body, which shall be delivered for you: this do for the commemoration of me.
[25] In like manner also the chalice, after he had supped, saying: This chalice is the new testament in my blood: this do ye, as often as you shall drink, for the commemoration of me.
[26] For as often as you shall eat this bread, and drink the chalice, you shall shew the death of the Lord, until he come.
[27]
Therefore whosoever shall eat this bread, or drink the chalice of the Lord unworthily, shall be guilty of the body and of the blood of the Lord.
[28] But let a man prove himself: and so let him eat of that bread, and drink of the chalice.
[29] For he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord.
Pay particular attention to the bold-faced verses.
Also there is the Early Church Fathers on the subject.
Ignatius of Antioch
"I have no taste for corruptible food nor for the pleasures of this life. I desire the bread of God, which is the flesh of Jesus Christ, who was of the seed of David; and for drink I desire his blood, which is love incorruptible" (Letter to the Romans 7:3 [A.D. 110]).
"Take note of those who hold heterodox opinions on the grace of Jesus Christ which has come to us, and see how contrary their opinions are to the mind of God. . . . They abstain from the Eucharist and from prayer because they do not confess that the Eucharist is the flesh of our Savior Jesus Christ, flesh which suffered for our sins and which that Father, in his goodness, raised up again. They who deny the gift of God are perishing in their disputes" (Letter to the Smyrnaeans 6:2–7:1 [A.D. 110]).
That is all the ECF quotes i'll post here but you can go to this website,
The Real Presence | Catholic Answers, to find some more.
Thats what the Eucharist is all about, Christ, and by extension that is what the Mass is all about as well.