No director, officer or employee shall, directly or indirectly, in any manner, use the funds of the bank, or any part thereof, except in its regular business transactions, and every loan made to any of its directors, officers, employees, or agents shall be upon the same security required of others and in strict conformity to its rules and regulations. No cashier or other officer or employee of a bank shall sell to the bank, directly or indirectly, any mortgage, bond, note, stock, or other security without the written approval of the board of directors, filed in the office of the bank or embodied in a resolution adopted by the board. A copy of this written approval or resolution shall immediately be sent to the commissioner of commerce.