If at said election three-fifths of the voters voting thereon shall vote in favor of the issuance of hospital self-liquidating revenue and/or general obligation bonds, the Board of County Commissioners shall proceed at once to the issuing of same and shall deposit the bonds in the treasury of the county, the treasurer being responsible and chargeable therefor on his official bond. The Board of County Commissioners shall proceed to sell said bonds and deposit the proceeds from the sale thereof in the treasury of said county which money shall be paid out by the treasurer upon the orders of the Board of County Commissioners from time to time as the same shall be needed; provided, however, that said bonds shall not be sold for less than par value thereof and accrued interest thereon.