St. Ireanaus was a pupil of Polycarp who was a disciple of St. John - the beloved disciple.  “If the Lord were from other than the Father, how could he rightly take bread, which is of the same creation as our own, and confess it to be his body and affirm that the mixture in the cup is his blood?” (Against Heresies 4:33–32 [A.D. 189]).

“He has declared the cup, a part of creation, to be his own blood, from which he causes our blood to flow; and the bread, a part of creation, he has established as his own body, from which he gives increase unto our bodies. When, therefore, the mixed cup [wine and water] and the baked bread receives the Word of God and becomes the Eucharist, the body of Christ, and from these the substance of our flesh is increased and supported, how can they say that the flesh is not capable of receiving the gift of God, which is eternal life—flesh which is nourished by the body and blood of the Lord, and is in fact a member of him?”(ibid., 5:2).

For not as common bread nor common drink do we receive these; but since Jesus Christ our Savior was made incarnate by the word of God and had both flesh and blood for our salvation, so too, as we have been taught, the food which has been made into the Eucharist by the Euscharistic prayer set down by Him, and by the change of which our blood and flesh is nourished, is both the flesh and blood of that incarnated Jesus.

 The Apostles in their memoirs which they produced, which are called Gospels, have thus passed on that which was enjoined upon them:  that Jesus took bread, and, having given thanks, said "Do this in remembrance of Me; this is My Body."  And in like manner, taking the cup and having given thanks, He said, "This is My Blood."

"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])

Our Lord Jesus took in His hands what in the beginning was only bread; and He blesses it and signed it and made it holy in the name of the Father and in the name of the Spirit; and He broke it and in His gracious kindness He distributed it to all His disciples one by one.  He called the bread His living Body, and did Himself fill it with Himself and the Spirit.

Do not, therefore, regard the Bread and Wine as simply that; for they are, according to the Master's declaration, the Body and Blood of Christ.  Even though the senses suggest to you the other, let faith make you firm.  Do not judge in this matter by taste, but-be fully assured by the faith, not doubting that you have been deemed worthy of the Body and Blood of Christ.

 Let us therefore in all respects put our faith in God and contradict Him in nothing, even if what is said seems to be contrary to our reasonings and to what we see.  Let His word be of superior authority to reason and sight.  This too be our practice in respect to the Mysteries, not looking only upon what is laid out before us, but taking heed also of His words.  For His word cannot deceive; but our senses are easily cheated.  His word has never failed; our senses err most of the time. 

“When [Christ] gave the bread he did not say, ‘This is the symbol of my body,’ but, ‘This is my body.’ In the same way, when he gave the cup of his blood he did not say, ‘This is the symbol of my blood,’ but, ‘This is my blood’; for he wanted us to look upon the [Eucharistic elements] after their reception of grace and the coming of the Holy Spirit not according to their nature, but receive them as they are, the body and blood of our Lord. We ought . . . not regard [the elements] merely as bread and cup, but as the body and blood of the Lord, into which they were transformed by the descent of the Holy Spirit” (Catechetical Homilies 5:1 [A.D. 405]).

“We will necessarily add this also. Proclaiming the death, according to the flesh, of the only-begotten Son of God, that is Jesus Christ, confessing his resurrection from the dead, and his ascension into heaven, we offer the unbloody sacrifice in the churches, and so go on to the mystical thanksgivings, and are sanctified, having received his holy flesh and the precious blood of Christ the Savior of us all. And not as common flesh do we receive it; God forbid: nor as of a man sanctified and associated with the Word according to the unity of worth, or as having a divine indwelling, but as truly the life-giving and very flesh of the Word himself. For he is the life according to his nature as God, and when he became united to his flesh, he made it also to be life-giving”

"You ought to know what you have received, what you are going to receive, and what you ought to receive daily. That Bread which you see on the altar, having been sanctified by the word of God, is the Body of Christ. The chalice, or rather, what is in that chalice, having been sanctified by the word of God, is the Blood of Christ." -Sermons 227, 21

"He who made you men, for your sakes was Himself made man; to ensure your adoption as many sons into an everlasting inheritance, the blood of the Only-Begotten has been shed for you. If in your own reckoning you have held yourselves cheap because of your earthly frailty, now assess yourselves by the price paid for you; meditate, as you should, upon what you eat, what you drink, to what you answer 'Amen'"-Second Discourse on Psalm 32. Ch. 4.

"The Holy Eucharist is called the “sacrament of sacraments” in the Orthodox tradition. It is also called the “sacrament of the Church.” The eucharist is the center of the Church’s life. Everything in the Church leads to the eucharist, and all things flow from it. It is the completion of all of the Church’s sacraments—the source and the goal of all of the Church’s doctrines and institutions.... It [the Eucharist] is strictly understood as being the real presence of Christ, His true Body and Blood mystically present in the bread and wine which are offered to the Father in his name and consecrated by the divine Spirit of God." 

“Perpetual adoration is the most beautiful thing you could ever think of doing. … Imagine for a moment that we are living in Jesus’ time and He has invited us to visit with Him and spend some quiet time getting to know Him better. Being aware who He was, we would be humbled and honored by such an invitation. The good news is that Jesus is here with us today — body, blood, soul and divinity — in the Holy Eucharist. Although Jesus comes to us under the appearance of bread and wine, his presence is as real to us now as He was flesh-and-blood-real to his disciples when he walked this earth. He can perform miracles, heal us, teach us and love us. We can talk to him and he can speak to us.”

She summarized, “The time you spend with Jesus in the Blessed Sacrament is the best time that you will spend on earth.”

1374:  The mode of Christ's presence under the Eucharistic species is unique. It raises the Eucharist above all the sacraments as "the perfection of the spiritual life and the end to which all the sacraments tend." In the most blessed sacrament of the Eucharist "the body and blood, together with the soul and divinity, of our Lord Jesus Christ and, therefore, the whole Christ is truly, really, and substantially contained." "This presence is called 'real' - by which is not intended to exclude the other types of presence as if they could not be 'real' too, but because it is presence in the fullest sense: that is to say, it is a substantial presence by which Christ, God and man, makes himself wholly and entirely present."