Before issuing any warrant for the payment of a pension, it shall be the duty of the treasurer to examine under oath all applicants for such pensions with a view to ascertaining if they are at that time entitled to a pension as provided for herein. Whenever the said treasurer shall learn that any person has ceased to be entitled to a pension, he shall record the fact on the roll of pensioners, and promptly notify the council of such finding and such persons shall thereupon be dropped from the rolls.