No money shall be drawn from the treasury nor shall any obligation for the expenditure of money be incurred, except pursuant to appropriations made by the Council. No warrant for the payment of any claim shall be issued until such claim shall have been approved in writing by the head of the department for which the obligation was incurred. Each head of a department and his surety shall be liable to the City for all loss and damage sustained by the City by reason of the negligent or corrupt approval of any claim against the City in his Department. The Director of Finance shall have power to require evidence that the amount of the claim is justly due and is in conformity to law and ordinance, and for that purpose he may summon before him any officer, agent or employee of any department of this City, any claimant or other person, and examine him upon oath or affirmation relative thereto.