Here it is plainly taught that by consecration the Bread and Wine have become the Flesh and Blood of Christ, and that as such they nourish our “blood and flesh” (observe the inverted order) by undergoing a change:  in other words, the Eucharistic Body and Blood of Christ are changed into nourishment of our blood and flesh, by being distributed (as Cyril says) to all our members, that is by being subjected to the natural processes of digestion and assimilation.  The unusual order of the words “our blood and flesh” is not accidental, but answers to the process of assimilation, in which the digested food first nourishes the blood and then the blood nourishes the flesh.