Roman Catechism 18.92

Chapter 18 — Part II: The Sacraments — The Holy Eucharist

Section 92. Christ Whole And Entire Present In Every Part Of Each Species — Nor should it be forgotten that Christ, whole and entire, is contained not only under either species, but also in each particle of either species. Each, says St. Augustine, receives Christ the Lord, and He is entire in each portion. He is not diminished by being given to many, but gives Himself whole and entire to each.