Calvin on the Real Presence in the Lord's Supper

And as they were eating, Jesus took bread, and after blessing it broke it and gave it to them, and said, “Take; this is my body.” And he took the chalice, and when he had given thanks he gave it to them, and they all drank of it. And he said to them, “This is my blood of the covenant, which is poured out for many.
~ Mark 14:22–24 ~

[It] is necessary, first of all, that [Jesus] be given us in the Supper, in order that the things which we have mentioned may be truly accomplished in us. For this reason I am wont to say, that the substance of the sacraments is the Lord Jesus, and the efficacy of them the graces and blessings which we have by his means. Now the efficacy of the Supper is to confirm to us the reconciliation which we have with God through our Saviour’s death and passion; the washing of our souls which we have in the shedding of his blood; the righteousness which we have in his obedience; in short, the hope of salvation which we have in all that he has done for us. It is necessary, then, that the substance should be conjoined with these, otherwise nothing would be firm or certain… For after commanding us to eat his body and drink his blood, he adds that his body was delivered for us, and his blood shed for the remission of our sins. Hereby he intimates, first, that we ought not simply to communicate in his body and blood, without any other consideration, but in order to receive the fruit derived to us from his death and passion; secondly, that we can attain the enjoyment of such fruit only by participating in his body and blood, from which it is derived.
~ John Calvin and Henry Beveridge (Translator), Tracts Relating to the Reformation, vol. 2 (Edinburgh: Calvin Translation Society, 1849), 169–170 ~

But if we give as much as we ought to Christ and his word, there is no doubt that as soon as these words are added to the bread and the wine, the bread and wine become the true body and true blood of Christ, so that the substance of bread and wine is transmuted into the true body and blood of Christ. He who denies this calls the omnipotence of Christ in question, and charges Christ himself with foolishness. 
~ John Calvin and Henry Beveridge (Translator), Tracts Relating to the Reformation, vol. 3 (Edinburgh: Calvin Translation Society, 1851), 214 ~