Since the advocates of this spurious dogma are not ashamed to honour it with the suffrages of the ancients, and especially of Augustine, how perverse they are in the attempt I will briefly explain. Pious and learned men have collected the passages, and therefore I am unwilling to plead a concluded cause: any one who wishes may consult their writings. I will not even collect from Augustine what might be pertinent to the matter,  but will be contented to show briefly, that without all controversy he is wholly ours. The pretence of our opponents, when they would wrest him from us, that throughout his works the flesh and blood of Christ are said to be dispensed in the Supper--namely, the victim once offered on the cross, is frivolous, seeing he, at the same time, calls it either the eucharist or sacrament of the body. But it is unnecessary to go far to find the sense in which he uses the terms flesh and blood, since he himself explains, saying (Ep. 23, ad Bonif.) that the sacraments receive names from their similarity to the things which they designate; and that, therefore, the sacrament of the body is after a certain manner the body. With this agrees another well-know passage, "The Lord hesitated not to say, This is my body, when he gave the sign" (Cont. Adimant. Manich. cap. 12). They again object that Augustine says distinctly that the body of Christ falls upon the earth, and enters the mouth. But this is in the same sense in which he affirms that it is consumed, for he conjoins both at the same time. There is nothing repugnant to this in his saying that the bread is consumed after the mystery is performed: for he had said a little before, "As these things are known to men, when they are done by men they may receive honour as being religious, but not as being wonderful" (De Trinit. Lib. 3 c. 10). His meaning is not different in the passage which our opponents too rashly appropriate to themselves--viz. that Christ in a manner carried himself in his own hands, when he held out the mystical bread to his disciples. For by interposing the expression, in a manner, he declares that he was not really or truly included under the bread. Nor is it strange, since he elsewhere plainly contends, that bodies could not be without particular localities, and being nowhere, would have no existence. It is a paltry cavil that he is not there treating of the Supper, in which God exerts a special power. The question had been raised as to the flesh of Christ, and the holy man professedly replying, says, "Christ gave immortality to his flesh, but did not destroy its nature. In regard to this form, we are not to suppose that it is everywhere diffused: for we must beware not to rear up the divinity of the man, so as to take away the reality of the body. It does not follow that that which is in God is everywhere as God" (Ep. ad Dardan.). He immediately subjoins the reason, "One person is God and man, and both one Christ, everywhere, inasmuch as he is God, and in heaven, inasmuch as he is man." How careless would it have been not to except the mystery of the Supper, a matter so grave and serious, if it was in any respect adverse to the doctrine which he was handling? And yet, if any one will attentively read what follows shortly after, he will find that under that general doctrine the Supper also is comprehended, that Christ, the only-begotten Son of God, and also Son of man, is everywhere wholly present as God, in the temple of God, that is, in the Church, as an inhabiting God, and in some place in heaven, because of the dimensions of his real body. We see how, in order to unite Christ with the Church, he does not bring his body out of heaven. This he certainly would have done had the body of Christ not been truly our food, unless when included under the bread. Elsewhere, explaining how believers now possess Christ, he says, "You have him by the sign of the cross, by the sacrament of baptism, by the meat and drink of the altar" (Tract. in Joann. 50). How rightly he enumerates a superstitious rite, among the symbols of Christ's presence, I dispute not; but in comparing the presence of the flesh to the sign of the cross, he sufficiently shows that he has no idea of a twofold body of Christ, one lurking concealed under the bread, and another sitting visible in heaven. If there is any need of explanation, it is immediately added, "In respect of the presence of his majesty, we have Christ always: in respect of the presence of his flesh, it is rightly said, Me ye have not always.'" They object that he also adds, "In respect of ineffable and invisible grace is fulfilled what was said by him, I am with you always, even to the end of the world.'" But this is nothing in their favour. For it is at length restricted to his majesty, which is always opposed to body, while the flesh is expressly distinguished from grace and virtue. The same antithesis elsewhere occurs, when he says that "Christ left the disciples in bodily presence, that he might be with them in spiritual presence." Here it is clear that the essence of the flesh is distinguished from the virtue of the Spirit, which conjoins us with Christ, when, in respect of space, we are at a great distance from him. He repeatedly uses the same mode of expression, as when he says, "He is to come to the quick and the dead in bodily presence, according to the rule of faith and sound doctrine: for in spiritual presence he was to come to them, and to be with the whole Church in the world until its consummation. Therefore, this discourse is directed to believers, whom he had begun already to save by corporeal presence, and whom he was to leave in coporeal absence, that by spiritual presence he might preserve them with the Father." By corporeal to understand visible is mere trifling, since he both opposes his body to his divine power, and by adding, that he might "preserve them with the Father," clearly expresses that he sends his grace to us from heaven by means of the Spirit.Calvin admits that Augustine does use realistic language in regards to the Eucharist--Augustine speaks of Christ's body falling on the earth and entering the mouth. However Calvin claims that Augustine only uses this verbiage because of the relationship between the sign and the thing signified. He then provides some quotes where according to Calvin, Augustine is teaching that Christ is spiritually present in the church but Christ's body is only in heaven. But in reality, Augustine ends up sounding very Lutheran when these passages are read in context at least in regards to the way that Christ is present. Lutherans of course, do not agree with Augustine in all of his teachings about the Eucharist being a sacrifice. Lutherans do not teach a local presence of Christ's body. Instead they teach that Christ is in fact in heaven but through the power of His Divinity Christ's flesh and blood are supernaturally present in the Lord's Supper. And this seems to be exactly what Augustine is actually saying. Calvin cites a portion of Augustine's book on the Trinity chapter 10 section 20 that says:
But in the VERY next section, Augustine says:
But because these things are known to men, in that they are done by men, they may well meet with reverence as being holy things, but they cannot cause wonder as being miracles.
What man, again, knows how the angels made or took those clouds and fires in order to signify the message they were bearing, even if we supposed that the Lord or the Holy Spirit was manifested in those corporeal forms? Just as infants do not know of that which is placed upon the altar and consumed after the performance of the holy celebration, whence or in what manner it is made, or whence it is taken for religious use. And if they were never to learn from their own experience or that of others, and never to see that species of thing except during the celebration of the sacrament, when it is being offered and given; and if it were told them by the most weighty authority whose body and blood it is; they will believe nothing else, except that the Lord absolutely appeared in this form to the eyes of mortals, and that that liquid actually flowed from the piercing of a side which resembled this.Augustine did in fact introduce the platonic vocabulary that the Calvinist position is so dependent upon but Augustine himself did not hold to the Calvinist position and it's really hard for me to believe that Calvin himself could have thought that Augustine did. It really seems to me that Calvin had already concluded what he thought must be happening in the sacrament and then went digging in the church fathers to find some phrases. It is also possible that Calvin was reading Augustine through some sort of faulty lens that Calvin learned from medieval scholasticism. But it does not seem to possible to read Augustine in such a way that he agrees with Calvin.
Augustine unfortunately introduces some Platonic philosophical language into the way that we speak of the Lord's Supper. The word "sacrament" finds its roots in Augustine and is itself problematic. Augustine also introduces the idea of distinguishing between the sign and the thing signified. But Augustine doesn't believe that one can be present without the other. It wasn't until the middle ages that some theologians began to talk about the sign being there but not the thing signified or the thing signified but not the sign. Augustine regards the Supper both as symbol and reality at the same time. For Calvin it is unthinkable that those without faith would receive Christ's body and blood but Augustine is certain that they do:
“For as Judas, to whom the Lord gave the sop, not by receiving what was evil, but receiving in an evil manner, afforded a place in himself to the devil, so each one who receives the Sacrament of the Lord unworthily does not bring it to pass that it is evil, because he is evil, or that he has received nothing because He has not received unto salvation. For it is the Body and Blood of the Lord no less even to those of whom the Apostle said, ‘Who eats and drinks unworthily, eats and drinks judgment to himself’.” (De Baptismo, V. 9)For Calvin it is unthinkable that we would receive Jesus' body and blood in our mouths but Augustine says that we do:
“We receive with a faithful heart and the mouth (ore) the Mediator of God and man, the Man Christ Jesus, who gives us His Body to be eaten, and His Blood to be drunk, although it may seem more horrible to eat human flesh than to destroy it, and to drink human blood than to shed it “ (Contra advers. leg. et prophet. 1-2, n. 34)Calvin tries to read the many passages in Augustine that make these kinds of statements as if they are just attributing something to the bread because of its relationship to the body of Christ in the sacrament but Augustine is saying much more than that. In his exposition of Psalm 34 Augustine says:
Or rather some spiritual Christian invites us to approach to our Lord Jesus Christ Himself. But let us approach to Him and be lightened; not as the Jews approached to Him, that they might be darkened; for they approached to Him that they might crucify Him: let us approach to Him that we may receive His Body and Blood. They by Him crucified were darkened; we by eating and drinking The Crucified are lightened. (9)