Two important encyclicals have been issued dealing with mis sionary work. Pope Benedict XV. in 1919 issued the encyclical Maximum Iliad in which extensive directions were given for the conduct of missionary work, exaggerated expressions of national ism were severely condemned and great emphasis was laid on the importance of developing a native clergy. Following upon this in 1926 six Chinese priests were consecrated bishops and in 1927 one Japanese priest. In 1926 Pope Pius XI. issued the encyclical Rerum Ecclesiae in which he developed the subject matter of Maximum Iliad, pointing out the paucity of missionaries, the lack of native ministers and the urgent need for training colleges being established with a view to the equipment of native clergy including bishops. The Pope further urged all Catholics to sup port the Society of the Propagation of the Faith, the Society of Holy Childhood (for the supporting of orphans, etc.) and the Society of S. Peter (for training native priests), and all priests to join the Unio cleri pro missionibus (Missionary Clergy Union). He emphasized also the annual day of prayer appointed for the penultimate Sunday in October. A great missionary exhibition was held at the Vatican during the Holy Year of 1925, and at the close of the Exhibition a museum of missions was established.