The Mass is both a memorial and a sacrifice. Our Lord instituted the Holy Eucharist at the Last Supper on Holy Thursday, and the Mass gets its liturgical makeup from this event.
Holy Thursday was the night before Jesus died. He gave this sacrament to his apostles at the Last Supper: “Do this in memory of me.” By these words, Jesus ordained the twelve apostles priests. He did so to perpetuate the sacrament of the Holy Eucharist until the end of time.
In this way the Mass is a memorial. It makes new Christ’s sacrifice. The Holy Sacrifice of the Mass is not a new sacrifice or a sacrifice like the ones Jewish or pagan priests would perform. Rather, it is the sacrifice of Jesus on the cross. One big difference is in the unbloody manner that the sacrifice is made present.
The separate consecrations at the Mass denote the crucifixion of Christ. In the Jewish understanding, death is brought about by the separation of the blood from the body. At the Mass when the priest consecrates the bread, genuflects in adoration, and then consecrates the wine, and genuflects in adoration, this is signifying the separation of blood from the body, that is, death. The Holy Sacrifice of the Mass is also the resurrection.
After the consecration, but before Holy Communion, the priests place a small piece of the host into the Precious Blood in the chalice. This indicates resurrection. At the Mass, Catholics do not receive the dead Christ, but rather the risen and glorified savior. Every minute piece of the Host, every drop of the Precious Blood is the whole risen Savior. How this all happens is a mystery of faith.
Not only are parishioners receiving the Body and Blood of Christ, but also His soul and Divinity. Wherever the Son is, the Father and the Holy Spirit are as well. Therefore, Catholics receive the Triune God in Holy Communion but Christ remains present after the Sacrifice of the Mass. His presence remains as long as the appearance of bread is recognizable. Once the appearances of bread deteriorate beyond recognition, it is believed that the real presence of Jesus is gone.
This is especially true when a host drops to the floor and cannot be consumed. It is then placed in a glass of water. Once it is dissolved, it may be placed in the sacrarium, which is like a sink except that it drains into the ground.