A: Though Pope Saint Pius V, in his apostolic constitution Quo Primum, promised the wrath of Saints Peter and Paul upon anyone who would attempt to change the Missale Romanum of 1570, the Tridentine Missal did in fact undergo many minor (and sometimes even major) alterations before it reached the 1962 form in use today in the Extraordinary Form of the Roman Rite.
In 1605, Pope Clement VIII recognized that in the mere thirty-five years since the publication of the Missale Romanum many editorial changes were made by independent publishers without permission, particularly in relation to certain ancient scriptural citations from the Old Latin versions. Publishers were rendering these texts according to the official Vulgate edition. Pope Clement ordered that these texts be restored to their more ancient versions. However, in 1634 Pope Urban VIII reversed this decision by ordering that scriptural texts in the Missal reflect those of the Vulgate edition. Though no rubrical changes occurred, he also ordered some rubrics be re-worded to be more understandable.
No further changes were made to the Missal itself until 1884 when Pope Leo XIII ordered a revision of the calendar. By that time, the calendar was becoming so full of feasts that many saints were being omitted entirely—being superseded by other feasts on the same day. In addition to the removal of these feasts, Leo XIII also ordered a restoration of rubrics which, though never changed in the official versions, were being altered in local printings particularly in France and the surrounding regions. Leo XIII also established the custom of the traditional ‘Prayers after Low Mass’ which, though not part of the Missal itself, were nevertheless mandatory.
In 1920, Pope Benedict XV ordered a major revision of the Breviary and a sizable alteration of the Missal, which was envisioned by Pope St. Pius X, though never initiated before his death. This revision included the addition of several feasts, and a rubrical reform of the calendar, particularly relating to the practice of seasonal commemorations and the restoration of Lenten ferial days. Other feasts were added in the 20th century including Christ the King on the last Sunday of October (1925), the elevation of the Feast of the Sacred Heart to that of a first class (1932), and the Votive Mass of Our Lord Jesus Christ, Eternal High Priest (1935).
Pope Pius XII made perhaps the most significant changes with his reform of Holy Week in 1955, but he also introduced several other feasts including the Assumption, the Immaculate Heart of Mary, and St. Joseph the Worker. Permission was also given for the usage of vernacular hymns during low Mass, and the reading of the lections in the vernacular. And, of course, in 1962, Pope St. John XXIII issued a new edition of the missal which added the name of St. Joseph to the Roman Canon and removed the term ‘perfidious’ from the Good Friday intercession for the Jews.
—Answered by Father Aaron Williams,
Diocese of Jackson, MS