Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 46. Moreover, the body of the Church, which is one, consists of many members, and of this union nothing is more strikingly illustrative than the elements of bread and wine; for bread is made from many grains and wine is pressed from many clusters of grapes. Thus they signify that we, though many, are most closely bound together by the bond of this divine mystery and made, as it were, one body.