The directors of any hospital corporation may, in their discretion, before the issuance of any securities, determine the authority of the hospital corporation to issue such securities, and the legality of all proceedings had or taken in connection therewith and the validity of the tax or other means provided for the payment thereof and the validity of all pledges of revenues and of all covenants and provisions contained in any resolution authorizing the securities in a proceeding instituted and conducted in accordance with Sections 6-6-750 through 6-6-757 as the same may be amended from time to time, or any similar proceeding prescribed by law, but such proceedings shall not be essential to the validity of such securities.