Q. 875. {241} How did our Lord institute the Holy Eucharist? A. Our Lord instituted the Holy Eucharist by taking bread, blessing, breaking, and giving to His Apostles, saying: "Take ye and eat. This is my body"; and then, by taking the cup of wine, blessing and giving it, saying to them: "Drink ye all of this. This is my blood which shall be shed for the remission of sins. Do this for a commemoration of me." Q. 876. {242} What happened when our Lord said, "This is my body; this is my blood"? A. When Our Lord said, "This is my body," the substance of the bread was changed into the substance of His body; when He said, "This is my blood," the substance of the wine was changed into the substance of His blood. Q. 877. How do we prove the Real Presence, that is, that Our Lord is really and truly present in the Holy Eucharist? A. We prove the Real Presence--that is, that Our Lord is really and truly present in the Holy Eucharist--(1) By showing that it is possible to change one substance into another; (2) By showing that Christ did change the substance of bread and wine into the substance of His body and blood; (3) By showing that He gave this power also to His Apostles and to the priests of His Church. Q. 878. How do we know that it is possible to change one substance into another? A. We know that it is possible to change one substance into another, because (1) God changed water into blood during the plagues of Egypt; (2) Christ changed water into wine at the marriage of Cana; (3) Our own food is daily changed into the substance of our flesh and blood; and what God does gradually, He can also do instantly by an act of His will. Q. 879. Are these changes exactly the same as the changes that take place in the Holy Eucharist? A. These changes are not exactly the same as the changes that take place in the Holy Eucharist, for in these changes the appearance also is changed, but in the Holy Eucharist only the substance is changed while the appearance remains the same. Q. 880. How do we show that Christ did change bread and wine into the substance of His body and blood? A. We show that Christ did change bread and wine into the substance of His body and blood: (1) From the words by which He promised the Holy Eucharist; (2) From the words by which He instituted the Holy Eucharist; (3) From the constant use of the Holy Eucharist in the Church since the time of the Apostles; (4) From the impossibility of denying the Real Presence in the Holy Eucharist, without likewise denying all that Christ has taught and done; for we have stronger proofs for the Holy Eucharist than for any other Christian truth. Q. 881. {243} Is Jesus Christ whole and entire both under the form of bread and under the form of wine? A. Jesus Christ is whole and entire both under the form of bread and under the form of wine.