Does the bread cease to be bread and the wine cease to be wine?

Yes. In order for the whole Christ to be present—body, blood, soul, and divinity—the bread and wine cannot remain, but must give way so that his glorified Body and Blood may be present. Thus in the Eucharist the bread ceases to be bread in substance, and becomes the Body of Christ, while the wine ceases to be wine in substance, and becomes the Blood of Christ. As St. Thomas Aquinas observed, Christ is not quoted as saying, ” This bread is my body,” but ” This is my body” ( Summa Theologiae, III q. 78, a. 5).