The trustees shall, after the passage of this act, and for three consecutive weeks, and yearly thereafter for the same length of time, commencing on the first Monday of September, advertise in three newspapers of general circulation for bids to furnish all needed supplies for the year beginning January first next ensuing. Said trustees shall furnish promptly on application, to all persons desiring to bid, an itemized list of the kind and probable amount required. The board of trustees shall at a stated meeting open such bids and award the contract for supplies to the lowest responsible bidder, taking such security for the faithful performance of such contract as they may deem necessary. The said appropriation to be paid monthly on the warrant of the Auditor General, on a settlement made by him and the State Treasurer, but no warrant shall be drawn on settlement made until the trustees of said institution shall have made, under oath, to the Auditor General, a report containing a specifically itemized statement of the cost of said improvements during the previous month, with the cash balance on hand, and the same is approved by him and the State Treasurer, nor until the treasurer shall have sufficient money in the treasury not otherwise appropriated to pay the monthly instalment due said institution. Unexpended balances of sums appropriated for specific purposes shall not be used for other purposes, whether specific or general, and shall revert to the State Treasury at the close of the two fiscal years.