The Office is as on the Feast itself, but the antiphons and psalms come from the Psalter for Thursday. All hymns of Iambic metre are sung with the Doxology and tone of the Incarnation.
At Mattins in the first nocturn the lessons are taken as on the feast from the Canticle of Canticles with its exquisite poetry and symbolic language. The responsories of the feast are sung. A section of the third lesson illustrates the beauty of the texts:
Favus distillans labia tua, sponsa, mel et lac sub lingua tua; et odor vestimentorum tuorum sicut odor thuris. Hortus conclusus soror mea sponsa, hortus conclusus, fons signatus. Emissiones tuae paradisus malorum punicorum cum pomorum fructibus, cypri cum nardo.
Thy lips, my spouse, are as a dropping honey comb, honey and milk are under thy tongue; and the smell of thy garments, as the smell of frankincense. My sister, my spouse, is like a garden enclosed, a garden enclosed, a fountain sealed up. Thy plants are a paradise of pomegranates with the fruits of the orchard. Cypress with spikenard. (Translation by the nuns of Stanbrook Abbey)
In the second nocturn the lessons are taken from the Second Discourse of St. John Damascene on the Dormition of the Mother of God and are again beautiful and rich in their didactic content:
An ancient tradition has been handed down to us, that, at the time of the glorious falling-asleep of the blessed Virgin, all the Apostles, who were wandering throughout the world preaching salvation to the Gentiles, were caught up aloft in the twinkling of an eye, and met together in Jerusalem. And when they were all there, a vision of Angels appeared to them, and the chant of the heavenly powers was heard; and so with divine glory she gave up her soul into the hands of God. But her body, which bore God in an effable manner, being lifted up amid the hymns of Angels and Apostles was laid in a tomb in Gethsemane. There for three whole days the angelic song was heard. (Lesson IV)
But after three days, the chant of the Angels ceased, and the Apostles who were present (for Thomas, the only one who had been absent, came after the third day, and wished to adore the body which had borne God) opened the tomb; but they could by no means find her sacred body in any part of it. But when they only found those garments in which she had been buried, and were filled with indescribable fragrance which emanated from them, they closed the tomb. Amazed at this wonderful mystery they could only think that he, who had been pleased to take flesh from the Virgin Mary, to be made man, and to be born though he was God the Word, and the Lord of glory, he who had preserved her virginity without stain after childbirth, should also have been pleased to honour her pure body after her death, keeping it incorrupt, and translating it into Heaven before the general resurrection. (Lesson V)
In the sixth lesson St. John lists those present who had seen the body of the Virgin, including in addition to the Apostles, Timothy bishop of Ephesus (recipient of the Pauline Epistles), Dionysisus the Areopagite and Hierotheus. In the third nocturn the lessons are from the 27th Sermon of St. Augustine on the Words of the Lord. The ninth lesson is for St. Agapitus the Martyr. The Te Deum is sung.
At Lauds a commemoration of St. Agapitus is sung. At Prime Qui natus es is sung in the short responsory, the lectio brevis is In plateis as on the feast.
Mass is sung after Terce. In Mass, of the Octave, again the magnificent texts Gaudeamus etc are sung. The Gloria is sung, the second collect is of St. Agapitus, the third collect Deus, qui corda. The Creed is sung, the preface is of the BVM. [Note the error in the Ordo today - alas the consequence of 'cut & paste' - Ordo 2012 has just been double-checked!]
Vespers are of the following feast of St. John Eudes with a commemoration of the Octave.
In the 'liturgical books of 1962' of course the Octave has been done away with. No proper Doxology is sung at the hymns, no Qui natus es etc at Prime and neither Creed nor preface of the Assumption at Mass. The feast of St. Joachim remains a feast of nine lessons as a 'II class feast', the feasts of St. John Eudes and St. Bernard become 'III class' feasts of three lessons. Today St. Agapitus is commemorated in the 'IV class' feria and at private Masses.