Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 119. It will also be useful to consider attentively the nature of bread and wine, which are the symbols of this Sacrament. For what bread and wine are to the body, the Eucharist is to the health and delight of the soul, but in a higher and better way. This Sacrament is not, like bread and wine, changed into our substance; but we are, in some wise, changed into its nature, so that we may well apply here the words of St. Augustine: I am the food of the frown. Grow and thou shalt eat Me; nor shalt thou change Me into thee, as thy bodily food, but thou shalt be changed into Me.