Chapter 18 — Part II: The Sacraments — The Holy Eucharist
Section 23. It is one not because it is indivisible, but because it signifies a single thing. For as food and drink, which are two different things, are employed only for one purpose, namely, that the vigour of the body may be recruited; so also it was but natural that there should be an analogy to them in the two different species of the Sacrament, which should signify the spiritual food by which souls are supported and refreshed. Wherefore we have been assured by our Lord the Saviour: My flesh is meat indeed, and my blood is drink indeed.