No loan made by a private bank, directly or indirectly, to the owner or owners thereof, or to any person with whom the owner or any of the owners of such private bank is associated as partner or member of an unincorporated association, or to any corporation twenty-five percent or more of the capital of which is owned legally or equitably by the owners of the private bank, and no investment made in any business conducted by any such partnership, unincorporated association or corporation shall be included as an asset upon the books or other records or in any statement of the financial condition of the private bank, except to the extent of the value of a mortgage upon real property which complies with the requirements of this act or the market value of collateral which secures such loan.