Fr. Dwyer's book, Mass Class may be ordered from the publisher

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Excerpt from Mass Class by Father Dave Dwyer, Copyright © 2022 by David P. Dwyer.

Published by Paulist Press, Inc., New York/Mahwah, NJ. Reprinted by permission of Paulist Press, Inc.

Paulist Press Website
Question (as it appears in Aug 18 Bulletin): 

Do We Really Believe that Communion is Christ's Flesh?

Answer:

The Catholic Church teaches that Christ is really and truly present in the Eucharist: body, blood, soul, and divinity. This is sometimes referred to as the “True Presence" or the “Real Presence." This term underscores that at Mass we are not merely mimicking what Jesus did at the Last Supper and using bread and wine as props as one would in a stage play.

During the worship services of many other Christian denominations, believers will often ritually enact the Last Supper because Jesus did say, aDo this in memory of me." In most cases, though, other Christians do not believe that any miraculous change occurs while they're doing that. 
In the Gospel of John, Jesus states emphatically, over and over again, that unless we eat his flesh and drink his blood, we will not have eternal life within us. He says, "My flesh is true food, and my blood is true drink" (John 6:55). So, yes, we believe that during communion we are really receiving the flesh and blood of Christ. How can that be, you may ask, since it doesn't look or taste like human flesh or blood, but rather seems much more like it's still bread and wine?

The Catechism of the Catholic Church describes it this way: "Because Christ our Redeemer said that it was truly his body that he was offering ... [we believe] that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the Body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change [we call] transubstantiation" (CCC 13 76).

What's important to focus on here is the word substance. The Church uses that term intentionally and in a somewhat technical sense. The substance of a thing is that which is most important in defining who or what it is. A good synonym might be the essence of something. In Greek philosophy, which Catholic theology builds upon, this essence or substance is distinct from the outer material form of something one of these can change without the other changing.

Let's use a real-world example. Imagine someone whom you had not seen in a long time had dyed his hair and lost a lot of weight. Your first impression might be that this person is now very different. But after talking with him for a few minutes, everything sounds familiar. “Yup, this is the same old guy that I used to know, even if he looks quite different on the outside." Now imagine the opposite. You encounter another old friend after several years and marvel at how she hasn't aged a day. “That’s amazing, you look the same!" Then she tells you about a life-changing event that happened to her.

You notice that her whole perspective on the world has shifted substantially. Maybe she had a brush with death but survived, and she is noticeably a more grateful or compassionate person. You think, "This is not the same person I used to know." On the outside, her looks are indistinguishable from before; her voice sounds the same. But on the inside, a fundamental change has taken place. And unlike the hair dye that will eventually grow out, the life-changing event has had a permanent effect; there's no going back to the way things used to be. This is most akin to what we Catholics call transubstantiation.

What we believe happens to the bread and wine during Mass is this kind of change. Our senses cannot perceive a difference. The little round wheat wafer still looks, smells, and tastes the same; it's the same size and shape. But that which is most fundamental to its existence, the very essence of it, has been changed into the True Presence of Christ's flesh. A cynic might counter, "Well, isn't it convenient that you believe in this miraculous change that cannot be measured by science?" To which I'd respond, "Don't humans believe in other imperceptible concepts like love and truth and beauty?" We do, and we take them for granted, or if you will, take them on faith. The great twelfth-century theologian St. Thomas Aquinas put it this way: "That in this sacrament are the true Body of Christ and his true Blood is something that 'cannot be apprehended by the senses, but only by faith, which relies on divine authority"' (CCC 1381).

So, yes, we are truly receiving Christ's flesh and blood in communion, fulfilling his command.
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Question (as it appears in Aug 18 Bulletin): 

Do We Really Believe that Communion is Christ's Flesh?

Answer:

The Catholic Church teaches that Christ is really and truly present in the Eucharist: body, blood, soul, and divinity. This is sometimes referred to as the “True Presence" or the “Real Presence." This term underscores that at Mass we are not merely mimicking what Jesus did at the Last Supper and using bread and wine as props as one would in a stage play.

During the worship services of many other Christian denominations, believers will often ritually enact the Last Supper because Jesus did say, aDo this in memory of me." In most cases, though, other Christians do not believe that any miraculous change occurs while they're doing that. 
In the Gospel of John, Jesus states emphatically, over and over again, that unless we eat his flesh and drink his blood, we will not have eternal life within us. He says, "My flesh is true food, and my blood is true drink" (John 6:55). So, yes, we believe that during communion we are really receiving the flesh and blood of Christ. How can that be, you may ask, since it doesn't look or taste like human flesh or blood, but rather seems much more like it's still bread and wine?

The Catechism of the Catholic Church describes it this way: "Because Christ our Redeemer said that it was truly his body that he was offering ... [we believe] that by the consecration of the bread and wine there takes place a change of the whole substance of the bread into the substance of the Body of Christ our Lord and of the whole substance of the wine into the substance of his blood. This change [we call] transubstantiation" (CCC 13 76).

What's important to focus on here is the word substance. The Church uses that term intentionally and in a somewhat technical sense. The substance of a thing is that which is most important in defining who or what it is. A good synonym might be the essence of something. In Greek philosophy, which Catholic theology builds upon, this essence or substance is distinct from the outer material form of something one of these can change without the other changing.

Let's use a real-world example. Imagine someone whom you had not seen in a long time had dyed his hair and lost a lot of weight. Your first impression might be that this person is now very different. But after talking with him for a few minutes, everything sounds familiar. “Yup, this is the same old guy that I used to know, even if he looks quite different on the outside." Now imagine the opposite. You encounter another old friend after several years and marvel at how she hasn't aged a day. “That’s amazing, you look the same!" Then she tells you about a life-changing event that happened to her.

You notice that her whole perspective on the world has shifted substantially. Maybe she had a brush with death but survived, and she is noticeably a more grateful or compassionate person. You think, "This is not the same person I used to know." On the outside, her looks are indistinguishable from before; her voice sounds the same. But on the inside, a fundamental change has taken place. And unlike the hair dye that will eventually grow out, the life-changing event has had a permanent effect; there's no going back to the way things used to be. This is most akin to what we Catholics call transubstantiation.

What we believe happens to the bread and wine during Mass is this kind of change. Our senses cannot perceive a difference. The little round wheat wafer still looks, smells, and tastes the same; it's the same size and shape. But that which is most fundamental to its existence, the very essence of it, has been changed into the True Presence of Christ's flesh. A cynic might counter, "Well, isn't it convenient that you believe in this miraculous change that cannot be measured by science?" To which I'd respond, "Don't humans believe in other imperceptible concepts like love and truth and beauty?" We do, and we take them for granted, or if you will, take them on faith. The great twelfth-century theologian St. Thomas Aquinas put it this way: "That in this sacrament are the true Body of Christ and his true Blood is something that 'cannot be apprehended by the senses, but only by faith, which relies on divine authority"' (CCC 1381).

So, yes, we are truly receiving Christ's flesh and blood in communion, fulfilling his command.

Fr. Dwyer's book, Mass Class may be ordered from the publisher

Order Mass Class
Question: 

How should we bow during the communion rite?  Do we bow our head or bow from the waist?

Short answer:

“When receiving Holy Communion, the communicant bows his or her head before the Sacrament as a gesture of reverence and receives the Body of the Lord from the minister" (General Instructions of the Roman Missal (GIRM) 160).

More Details:

Prior to 1970, when American Catholics received communion, they would almost always be kneeling at an altar rail and extending their tongue. Since then, though, "the norm for reception of Holy Communion in the dioceses of the United States is standing.... The consecrated host may be received either on the tongue or in the hand, at the discretion of each communicant" (GIRM 160). After living into this new practice for a few decades, it was felt that what was missing was an appropriate expression of reverence on the part of the communicant that is rightly due Christ's True Presence in the Eucharist.  After all, it used to be "built in": upon reception of the sacrament, one would already be kneeling, a posture from time immemorial expressing humility, reverence, and honor. Without that, one could more easily succumb to the temptation to move through the line expediently as if lining up to grab free samples at Costco.

Thus, when the Roman Missal was updated in 2003, the Vatican left it up to the bishops of each country to determine an appropriate sign of reverence to be made by the communicant before receiving the Eucharist (GIRM 390). After considering various options, the U.S. Bishops settled on this: "When receiving Holy Communion, the communicant bows his or her head before the Sacrament as a gesture of reverence and receives the Body of the Lord from the minister" (GIRM 160).

Now we can address your question more specifically, Frannie. In Catholic ritual, there are two types of bows; simple and pro-found. A profound bow, also called a bow "of the body," is bowing from your waist. A simple bow is a bow of the head (see GIRM
275). Remember the term fulcrum from high school physics class?
Its the bend point (like an elbow or knee). In a profound bow, the fulcrum is your waist. For a simple bow, the fulcrum is your neck. Why am I being so specific? Because so many people get this wrong, particularly in the communion line. The sign of reverence all American Catholics are asked to perform before receiving communion is a simple bow of the head.

Excerpt from Mass Class by Father Dave Dwyer, Copyright © 2022 by David P. Dwyer.

Published by Paulist Press, Inc., New York/Mahwah, NJ. Reprinted by permission of Paulist Press, Inc.

Paulist Press Website