Answer to the Difficulty raised in respect of the Breaking of the Host

IT has been said above (Chap. LXIV) that the substance of the Body of Christ is in this Sacrament by virtue of the Sacrament [Sacramental words]: but the dimensions of the Body of Christ are there by the natural concomitance which they have with the substance. This is quite the opposite way to that in which a body naturally is in place.* A body is in place by means of its dimensions, by which it is made commensurate with its place.*

But substantial being and quantitative being do not stand in the same way related to that in which they are. Quantitative being is in a whole, but is not whole in each part: it is part in part, and whole in the whole.* But substantial being is whole in the whole, and whole in every part of the same, as the whole nature and species of water is in every drop of water, and the whole soul in every part of the body.* Since then the Body of Christ is in the Sacrament by reason of its substance, into which the substance of bread is changed, while the dimensions of bread remain, -- it follows that as the whole species of bread was under every part of its (visible) dimensions, so the whole Body of Christ is under every part of the same. The breaking then (of the Host) does not reach to the Body of Christ, as though the Body of Christ were subjected to that breaking: its subject is the dimensions of bread, which remain.*

4.66 : What happens when the Sacramental Species pass away
4.68 : The Explanation of a Text