Quotes from Calvin's Commentary on I Corinthians 11:23-29:
"The Lord's Supper"
...But that participation in the body of Christ, which, I affirm, is presented to us in the Supper, does not require a local presence, nor the descent of Christ, nor infinite extension, nor anything of that nature, for the Supper being a heavenly action, there is no absurdity in saying, that Christ, while remaining in heaven, is received by us. For as to his communicating himself to us, that is effected through the secret virtue of his Holy Spirit, which can not merely bring together, but join in one, things that are separated by distance of place, and far remote.
But, in order that we may be capable of this participation, we must rise heavenward. Here, therefore, faith must be our resource, when all the bodily senses have failed. When I speak of faith, I do not mean any sort of opinion, resting on human contrivances, as many, boasting of faith on all occasions, run grievously wild on this point. What then? You see bread — nothing more — but you learn that it is a symbol of Christ’s body. Do not doubt that the Lord accomplishes what his words intimate — that the body, which thou dost not at all behold, is given to thee, as a spiritual repast. It seems incredible, that we should be nourished by Christ’s flesh, which is at so great a distance from us. Let us bear in mind, that it is a secret and wonderful work of the Holy Spirit, which it were criminal to measure by the standard of our understanding. In the meantime, however, drive away gross imaginations, which would keep thee from looking beyond the bread. Leave to Christ the true nature of flesh, and do not, by a mistaken apprehension, extend his body over heaven and earth: do not divide him into different parts by thy fancies, and do not adore him in this place and that, according to thy carnal apprehension. Allow him to remain in his heavenly glory, and aspire thou thither, that he may thence communicate himself to thee. These few things will satisfy those that are sound and modest. As for the curious, I would have them look somewhere else for the means of satisfying their appetite...
...Do this in remembrance of me. Hence the Supper is a memorial,(μνημόσυνον) appointed as a help to our weakness; for if we were sufficiently mindful of the death of Christ, this help would be unnecessary. This is common to all sacraments, for they are helps to our weakness. What is the nature of that remembrance which Christ would have us cherish with regard to him, we shall hear presently. As to the inference, however, which some draw from this — that Christ is not present in the Supper, because a remembrance applies to something that is absent; the answer is easy — that Christ is absent from it in the sense in which the Supper is a commemoration. For Christ is not visibly present, and is not beheld with our eyes, as the symbols are which excite our remembrance by representing him. In short, in order that he may be present with us, he does not change his place, but communicates to us from heaven the virtue of his flesh, as though it were present...
...Until he come As we always need a help of this kind, so long as we are in this world, Paul intimates that this commemoration has been given us in charge, until Christ come to judgment. For as he is not present with us in a visible form, it is necessary for us to have some symbol of his presence, by which our minds may exercise themselves.
The reader is encouraged to check out the context of these quotes by reading Calvin's complete commentary on this section of I Corinthians 11:23-29 at the CCEL library.
Side Note Regarding Zwingli:
Thomas Davis points out that Zwingli was killed at a realitively young age (47). As such, it is not clear how Zwingli's theology may have changed and matured if he had lived as long as Luther (62) or Calvin (54).
"Rather then a bare and simple memorialism, it appears that in Zwingli, Paul's admonition to "discern the body" took Zwingli along the path of theological development, one cut short, perhaps, by his untimely death at the Battle of Kappel." This Is My Body: The Presence of Christ in Reformation Thought; (page 159),