4 It will also come about that all the officers in the mission army, and the privates too, if We may so speak, who shall visit this Museum, after having compared the conditions of their respective missions and their methods of work, will draw from it inspiration for even better and larger projects. The faithful who visit the Museum will, We believe, experience the self-same feelings as did those who attended the original Vatican Exhibition. Meanwhile, in order that the interest of the faithful in the missions, which has been aroused already, may be even further developed We make a special appeal for your assistance in this task, Venerable Brothers. If your assistance may rightly be employed in any undertaking, certainly the dignity of your station in life, to say nothing of your filial affection for Us, will impel you to tender such aid particularly in this work and that with all zeal and diligence. For Our part, so long as Divine Providence shall preserve Our life, this duty of Our Apostolic office will always be a special obligation to us, for when We ponder over the fact that the pagans number, even in our day, almost a billion, "We have no rest in our spirit" (II Cor . vii, 5) and seem to hear sounding in Our ears the words, "Cry, cease not, lift up thy voice like a trumpet." ( Isaias lviii, 1)
Source: Rerum Ecclesiae (Vatican.va)