In response to a decree of the First Vatican Council (1870), Pope Pius X introduced in 1911 a new arrangement of the Psalter for use in the Breviary. In the bull "Divino afflatu", he described this change as "a first step towards a correction of the Roman Breviary and Missal". A Society of St. Pius X site states that this revision of the Breviary "significantly unsettled" clerics and encountered criticism. The laity would only have noticed the accompanying change whereby on Sundays the Mass liturgy ceased to be generally taken from the proper or common of the saint whose feast fell on that day, and began instead to be that of the Sunday.