Furthermore, the reservations[7] of benefices were another fruitful source of revenue. The policy of reserving benefices to the Holy See might be defended, on the ground that it was often necessary in order to counterbalance the interference of secular rulers in regard to ecclesiastical appointments, and that it afforded the Pope a convenient means of rewarding officials whose services were required for the government of the Church. But the right of the Pope to reserve benefices was abused during the fourteenth and fifteenth centuries, and gave rise to constant friction with the civil and ecclesiastical authorities in different countries of Europe. Reservations, instead of being the exception, became very general, and, as a result, the eyes of all ambitious clerics were turned towards Rome from which they hoped to receive promotion, whether their immediate superiors deemed them worthy or unworthy. Such a state of affairs opened the way to the most serious abuses, and not unfrequently to disedifying wrangles between rival candidates, all of whom claimed to have received their appointments from Roman officials. Intimately connected with papal reservations were expectancies or promises given to certain persons that they would be appointed to certain benefices as soon as a vacancy would occur. Such promises of appointment were unknown in the Church before the twelfth century, but later on they became very general, and led to most serious abuses during the residence of the Popes at Avignon and during the disturbances caused by the Great Western Schism. Expectancies were adopted as a means of raising money or of securing support. Various attempts were made to put an end to such a disastrous practice, as for example at the Councils of Constance and Basle, but it was reserved for the Council of Trent to effect this much needed reform.