It shall hereafter be unlawful for any county or township officer in any county to which sections 50.760 to 50.790 apply to purchase any supplies not contracted for as provided in sections 50.760 to 50.790 for his official use and for which payment is by law required to be made by the county unless he shall first apply to and obtain from the county commission an order in writing and under the official seal of the commission for the purchase of such supplies, and in all cases where the supplies requested by such officer have been contracted for by the county commission as provided in sections 50.760 to 50.790, the order shall be in the form of a requisition by said officer addressed to the person, firm, company or corporation with whom or which the county commission has made a contract for such supplies, and presented to the county commission for approval or disapproval; and unless approval be given such requisition shall not be filled and any such requisition filled without such approval shall not be paid for out of county funds. The county shall not be liable for any debts for supplies except debts contracted as provided in sections 50.760 to 50.790. The best price and the quality of supplies shall be considered and supplies of a higher price or quality than is reasonably required for the purposes to which they are to be applied shall not be purchased or contracted for. Preference to merchants and dealers within their counties may be given by such commissioners, provided the price offered is not above that offered elsewhere.

(RSMo 1939 § 2515)