John Walvoord writes:
"Calvin held that the Lord's spiritual presence was in the elements but not his physical presence. Zwingli suggested that they were merely symbols and represented the body of Christ. The controversy cannot be settled, but many have concluded that Zwingli was probably right and that the bread and the cup become the body and blood of Christ no more than Jesus became a vine because of His words, 'I am the true vine.' These are figures of speech, although wonderfully eloquent in their meaning" (Matthew: Thy Kingdom Come, 215).
Schlatter adds this pertinent explanation:
"What we have to do with his flesh and blood is not chew and swallow, but recognize in his crucified body and poured out blood the ground of our life, that we hang our faith and hope on that body and blood, and draw from there our thinking and willing" (Das Evangelium nach Johannes. 4th Ed. Erlauterungen zum Neuen Testament, vol. 3, Stuttgart: Calwer, 1928, 116).