The Holy Mass by St. Alphonsus Liguori, the priest receives the Sacred Host, p. 172:
"Then leaning his arms on the altar, and moderately inclining, he reverently receives Holy Communion, holding the paten under the Host. He should pay attention while taking the Host not to put his tongue out of his mouth, and not to chew the Host; and in order that it may not adhere to the roof of the mouth he should put it under his tongue, and there bend it. If it, however, adheres to the roof of the mouth, he should try to remove it with his tongue; but if some particle should remain, he should swallow it when taking the precious blood and the ablution."
Summa, III, q. 77, a. 7 Whether the sacramental species are broken in this sacrament?
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Objection 3. Further, breaking and mastication are seemingly of the same object. But it is Christ's true body that is eaten, according to John 6:57: "He that eateth My flesh, and drinketh My blood." Therefore it is Christ's body that is broken and masticated: and hence it is said in the confession of Berengarius
*: "I agree with the Holy Catholic Church, and with heart and lips I profess, that the bread and wine which are placed on the altar, are the true body and blood of Christ after consecration, and are truly handled and broken by the priest's hands,
broken and crushed by the teeth of believers." Consequently, the breaking ought not to be ascribed to the sacramental species.
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Reply to Objection 3. What is eaten under its own species, is also broken and masticated under its own species; but Christ's body is eaten not under its proper, but under the sacramental species. Hence in explaining John 6:64, "The flesh profiteth nothing," Augustine (Tract. xxvii in Joan.) says that this is to be taken as referring to those who understood carnally: "for they understood the flesh, thus, as it is divided piecemeal, in a dead body, or as sold in the shambles." Consequently, Christ's very body is not broken,
except according to its sacramental species. And
the confession made by Berengarius is to be understood in this sense, that the breaking and the crushing with the teeth is to be referred to the sacramental species, under which the body of Christ truly is.
*The Confession of Berengarius was apparently an oath, approved by the Church, that Berengarius was made to take to affirm his believe in the Real Presence
Our Lord literally says "eat/
chew/
gnaw/" My Flesh"