CORPUS CHRISTI - Thursday after Trinity Sunday

This feast is celebrated in the Latin Church on the Thursday after Trinity Sunday to solemnly commemorate the institution of the Holy Eucharist.

Of Maundy Thursday, which commemorates this great event, mention is made as Natalis Calicis (Birth of the Chalice) in the Calendar of Polemius (448) for the 24th of March, the 25th of March being in some places considered as the day of the death of Christ. This day, however, was in Holy Week, a season of sadness, during which the minds of the faithful are expected to be occupied with thoughts of the Lord's Passion. Moreover, so many other functions took place on this day that the principal event was almost lost sight of. This is mentioned as the chief reason for the introduction of the new feast, in the Bull "Transiturus." 

Read the rest at the Catholic Encyclopedia.

From the Collect (Oration) of the Feast:

Let us pray.

O God, under a marvelous sacrament you have left us the memorial of thy Passion; grant us, we beseech thee, so to venerate the sacred mysteries of thy Body and Blood, that we may ever perceive within us the fruit of thy Redemption. Who livest and reignest with God the Father in the unity of the Holy Spirit, one God, unto the ages of ages. Amen.

LAUDA SION (Sequence composed by St. Thomas Aquinas [English translation below])

Sion, lift up thy voice and sing:

Praise thy Savior and thy King,

Praise with hymns thy shepherd true.

All thou canst, do thou endeavour:

Yet thy praise can equal never

Such as merits thy great King.

See today before us laid

The living and life-giving Bread,

Theme for praise and joy profound.

The same which at the sacred board

Was, by our incarnate Lord,

Giv'n to His Apostles round.

Let the praise be loud and high:

Sweet and tranquil be the joy

Felt today in every breast.

On this festival divine

Which records the origin

Of the glorious Eucharist.

On this table of the King,

Our new Paschal offering

Brings to end the olden rite.

Here, for empty shadows fled,

Is reality instead,

Here, instead of darkness, light.

His own act, at supper seated

Christ ordain'd to be repeated

In His memory divine;

Wherefore now, with adoration,

We, the host of our salvation,

Consecrate from bread and wine.

Hear, what holy Church maintaineth,

That the bread its substance changeth

Into Flesh, the wine to Blood.

Doth it pass thy comprehending?

Faith, the law of sight transcending

Leaps to things not understood.

Here beneath these signs are hidden

Priceless things, to sense forbidden,

Signs, not things, are all we see.

Flesh from bread, and Blood from wine,

Yet is Christ in either sign,

All entire, confessed to be.

They, who of Him here partake,

Sever not, nor rend, nor break:

But, entire, their Lord receive.

Whether one or thousands eat:

All receive the self-same meat:

Nor the less for others leave.

Both the wicked and the good

Eat of this celestial Food:

But with ends how opposite!

Here 't is life: and there 't is death:

The same, yet issuing to each

In a difference infinite.

Nor a single doubt retain,

When they break the Host in twain,

But that in each part remains

What was in the whole before.

Since the simple sign alone

Suffers change in state or form:

The signified remaining one

And the same for evermore.

Lo! bread of the Angels broken,

For us pilgrims food, and token

Of the promise by Christ spoken,

Children’s meat, to dogs denied.

Shewn in Isaac's dedication,

In the manna's preparation:

In the Paschal immolation,

In old types pre-signified.

Jesu, shepherd of the sheep:

Thou thy flock in safety keep,

Living bread, thy life supply:

Strengthen us, or else we die,

Fill us with celestial grace.

Thou, who feedest us below:

Source of all we have or know:

Grant that with Thy Saints above,

Sitting at the feast of love,

We may see Thee face to face.

Amen. Alleluia.