Mediator Dei §200

²⁰⁰ To attain this purpose, it will greatly help to select carefully good and upright young boys from all classes of citizens who will come generously and spontaneously to serve at the altar with careful zeal and exactness. Parents of higher social standing and culture should greatly esteem this office for their children. If these youths, under the watchful guidance of the priests, are properly trained and encouraged to fulfill the task committed to them punctually, reverently and constantly, then from their number will readily come fresh candidates for the priesthood. The clergy will not then complain - as, alas, sometimes happens even in Catholic places - that in the celebration of the august sacrifice they find no one to answer or serve them.