Structurally speaking, the ordinary form of the Mass follows the traditional Latin Mass in most respects, with most of the differences being the elimination of features unique to the latter. One of those eliminated features are the Prayers at the Foot of the Altar, which (in the Low Mass) immediately precede the reading of the Introit or (in a sung Mass) are altogether subdued and inaudible by the schola’s chanting of the Introit. The initial reform of 1965 saw the Prayers at the Foot of the Altar reduced, with the elimination of the Psalm Judica Me; the final reform of 1970 saw them completely eliminated, with only an amputated form of the Confiteor escaping the reformers’ red pens.
The Prayers at the Foot of the Altar proceed as follows. After processing out from the sacristy and situating the chalice on the altar, the priest genuflects while the servers kneel. The sign of the cross is followed by the antiphon Introíbo ad altáre Dei. / Ad Deum, qui lætíficat iuventútem meam. (“I will go in to the altar of God. / To God, who giveth joy to my youth”), then immediately by Psalm 42, the Judica Me, which is recited by priest and servers antiphonally:
V. Iúdica me, Deus, et discérne causam meam de gente non sancta: ab hómine iníquo et dolóso érue me. (Judge me, O God, and distinguish my cause from the nation that is not holy: deliver me from the unjust and deceitful man.)
R. Quia tu es, Deus, fortitudo mea: quare me repulísti, et quare tristis incédo, dum afflígit me inimícus? (For thou art God my strength: why hast thou cast me off? and why do I go sorrowful whilst the enemy afflicteth me?)
V. Emítte lucem tuam et veritátem tuam: ipsa me deduxérunt, et adduxérunt in montem sanctum tuum et in tabernácula tua. (Send forth thy light and thy truth: they have conducted me, and brought me unto thy holy hill, and into thy tabernacles.)
R. Et introíbo ad altáre Dei: ad Deum, qui lætíficat iuventútem meam. (And I will go in to the altar of God: to God who giveth joy to my youth.)
V. Confitébor tibi in cíthara, Deus, Deus meus: quare tristis es, ánima mea, et quare contúrbas me? (To thee, O God my God, I will give praise upon the harp: why art thou sad, O my soul? and why dost thou disquiet me?)
R. Spera in Deo, quóniam adhuc confitébor illi: salutáre vultus mei, et Deus meus. (Hope in God, for I will still give praise to him: the salvation of my countenance, and my God.)
V. Glória Patri, et Fílio, et Spirítui Sancto. (Glory be to the Father, and to the Son, and to the Holy Spirit.)
R. Sicut erat in princípio, et nunc, et semper: et in saecula sæculórum. Amen. (As it was in the beginning, is now, and ever shall be, world without end. Amen).
The antiphon is then repeated. From here, the priest prays the Confiteor, bowing moderately; the servers pronounce a prayer of absolution, then their own Confiteor, and are in turn absolved by the priest; and at last a general absolution is given. (These absolutions are not, of course, sacramental in character: they are akin to the Penitential Rite at the start of the reformed Mass). Notably, the traditional Latin Mass’ Confiteor is of a slightly different character than we find in its closest approximation in the reformed Mass (option A of the Penitential Rite); it includes the invocation of a number of saints. Where Mary is mentioned only in the second set of invocations in the reformed Mass’ Confiteor (where it is even said: option B, which adopts the Kyrie for penitential purposes, omits it entirely), she is mentioned in both sets in the traditional Latin Mass’ Confiteor, along with Sts. Michael, John the Baptist, Peter, and Paul.
Finally, a brief dialogue ensues, before the priest ascends to the altar and commences with the Mass proper:
V. Deus, tu convérsus vivificábis nos. (Thou wilt turn, O God, and bring us to life.)
R. Et plebs tua lætábitur in te. (And Thy people shall rejoice in Thee.)
V. Osténde nobis, Dómine, misericórdiam tuam. (Show us, O Lord, Thy mercy).
R. Et salutáre tuum da nobis. (And grant us Thy salvation.)
V. Dómine, exáudi oratiónem meam. (O Lord, hear my prayer.)
R. Et clamor meus ad te véniat. (And let my cry come unto Thee.)
V. Dóminus vobíscum. (The Lord be with you.)
R. Et cum spíritu tuo. (And with thy spirit.)
As you can see, the Prayers at the Foot of the Altar have a decidedly preparatory and penitential character to them, and in this sense mirror the extensive Old Testament regulations on preparation for entering the temple and offering the sacrifice. (Because of their penitential nature, they are abbreviated with the omission of the Psalm Judica Me on occasions that are already penitential, such as Requiem Masses or those during Passiontide). They are also more or less explicitly ministerial, in that their recitation is proper to the clerics and servers who are celebrating or assisting at Mass; for this reason, the faithful do not generally join in at their recitation at sung Masses.
The Prayers at the Foot of the Altar serve to immediately establish the Mass’ theocentric and sacrificial dimensions: theocentric in that the Mass’ opening words are directed exclusively toward God; sacrificial in that the initial action is oriented toward the altar. Compare this to the ordinary form of the Mass, where, after a brief reverencing of the altar, the celebrant proceeds immediately to the presider’s chair some distance away from the altar, and opens the Mass with a dialogue spoken to and with the people.
Why were these prayers cut from the reformed Mass? In the first place, there were some bitter polemics in the 50’s and 60’s against “medieval accretions,” i.e., later additions to the Mass not always present from the beginning; the Prayers at the Foot of the Altar date back to about the 11th century (making them a mere millennium or so old by the time of their elimination!). They most likely began earlier as sacristy devotions, further justifying the zeal for eliminating them as useless accretions (curiously, the fact that the Gloria in Excelsis Deo originally began as a Christmas hymn akin to Easter’s Exultet, and only found its way into the Missal around the beginning of the 6th century, is never used as an argument against its use).
In the second place, there were also some polemics at the time against the “clericalist” character of the old Mass, with its emphasis on the action of the priest, and as I alluded to earlier, the Prayers at the Foot of the Altar have a distinctly ministerial nature to them. Most of the Prayers at the Foot of the Altar couldn’t be salvaged in a way that reasonably includes the people: the people can of course join the servers in reciting the responses, but there is not much point. They are not the ones going “in to the altar of God,” at least in a bodily sense. Hence, they had to be eliminated in the name of inclusivity, with the exception of the Confiteor, which was rehabilitated to include the entire assembly.
Finally, there was a generalized animus against Romanitas, “Roman-ness,” among the reformers, and a consequent desire to eliminate or suppress those characteristics of the Mass unique to the Roman rite. The Prayers at the Foot of the Altar were one such feature, appearing in none of the other rites. So they had to go. Companion to the desire to eliminate Romanitas was an Orientalizing impulse, that is, an impulse to include or expand features unique to Eastern rites: more on that later.
Interesting to note is the fact that the Prayers at the Foot of the Altar are permitted at least as an option in the new Anglican Use of the Roman rite, which borrows many other features from the traditional Latin Mass, as well. It would appear, then, that Rome has largely repudiated her disdain for these venerable prayers, which serve to transition nicely into the primary action of the Mass. We may yet, in our lifetimes, see some interest in re-incorporating them into the reformed Mass.