«LAUDA SION SALVATOREM». – Sequence of the Mass for Corpus Christi, composed by St. Thomas Aquinas, probably at Orvieto in 1264, on the occasion of the bull *Transitus*, by which Urban IV established the solemnity of the Eucharist for the whole Church, in imitation of the feast instituted at Liège in 1246 by Bishop Robert de Torote under the influence of the revelations of Bl. Juliana of Cornillon (v.).
The attribution of the Office and Mass (which contains the sequence) to St. Thomas was contested by the Bollandist D. Pabrechoc (*Acta SS. Aprilis*, I, Antwerp 1675, pp. 903 ff.), but was immediately vindicated by the Dominicans J. de Maison (*Dissertatio historica pro officio Corporis Christi Divi Thomae*, 2nd ed., Paris 1679) and A. Natalis (*Dissertationes historicae et criticae quibus officium ven. Sacramento s. Thomae vindicatur*, Paris 1680). This vindication was accepted even by Pabrechoc himself (*Conatus chronologico-historicus ad universam seriem Romanorum pontificum. Propylaeum ad Acta SS. Maii*, Antwerp 1688, pp. 374–376: here is found dissertation XLIII, alias XXIII: *De officio pro festo Corporis Christi Urbani IV iussu per s. Thomam composito*. Moreover, in the *Acta Sanctorum Bollandiana* the same vindication is reproduced in the apologetic books now first compiled into one volume (*ibid.* 1755, pp. 438–43), followed by an *Accusatio contra Pabrechocium* and a *Responsio*). Today, criticism is decidedly favorable to the Dominican thesis, since the precious testimony of St. Thomas’s contemporary and friend, Tolomeo da Lucca, cannot be diminished by the belated liturgical appearance of the Office; this delay is satisfactorily explained by special historical circumstances: after the death of Urban IV, the Holy See, entirely absorbed by the great difficulties of the moment, could not oversee the application of the bull *Transitus*; only after the Council of Vienne (1311), where Clement V revived the provisions of Urban IV, did the feast of Corpus Christi begin to spread, and it was therefore called the *nova sollemnitas*. Since neither Urban IV nor Clement V had imposed the Office composed by St. Thomas, it appeared only a few decades later and became almost universal, rapidly replacing, by reason of the superiority of its content and the growing prestige of its author, the Office and Mass that the Roman Curia had used before accepting the work of the Aquinate (cf. F. Baix–C. Lambot, *La dévotion à l'Eucharistie*, Gembloux–Namur 1946, p. 94).
The sequence, only verbally inspired by the hymns of Adam of Saint-Victor, is composed of 24 strophes arranged in tight logical succession: after the solemn exordium, consisting of an urgent invitation to praise and joy (1–5), the rhythm broadens in a swift evocation of the shadows of the Old Testament (6–8), fulfilled in the Eucharist (9–10), which, by multiplying in the mystery of Transubstantiation the presence of Christ “non concisus, non confractus, non divisus,” makes Him the food of all souls (11–15), from which souls draw fruits of life or death according to the dispositions with which they receive Him (16–20). A moved cry of admiration (“*Ecce panis Angelorum*”) and a tender prayer to the Divine Shepherd conclude this luminous and geometrically structured composition, suffused with the fervor of immense love.
The symmetry of *L. S.* is not artificial but arises from the inner logic of thought: it is the Gothic of poetry; as the cathedral of Cologne is a mighty bundle of spare lines reaching toward heaven, as if in prayerful arms, so the rhythm of St. Thomas ascends in the conceptual linearity of his diction toward the spaces of lofty speculation, only to burst forth with lyrical impetus into a warm supplication. These strophes, so limpid as to form as many articles of a perfect Eucharistic creed, so robust as to be deemed verses cast in bronze, constitute the pearl of Catholic liturgy and make their author the “Eucharistiae praeco et vates maximus” (Pius XI, enc. *Diurnum diem*, 29 Sept. 1923: in *AAS*, 15 [1923], p. 320).