Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 98. Proof From Scripture — The doctrine thus defined is a natural inference from the words of Scripture. When instituting this Sacrament, our Lord Himself said: This is my body. The word this expresses the entire substance of the thing present; and therefore if the substance of the bread remained, our Lord could not have truly said: This is my body.