Any state bank which has qualified under section 48.37 and obtained the certificate therein provided, and which has established and maintains a savings department, may use in its name or title, in addition to other words permitted by law, the words “savings” or “savings bank.” Savings deposits received by any such state bank using the words “savings” or “savings bank” in its corporate name or title, shall be invested only in authorized securities, as defined by law, and the bank shall keep in hand at all times, in addition to the securities required to be deposited under the provisions of section 48.37, such securities as deposits in savings banks may be invested in to an amount at least equal to the savings deposits, and these securities to the amount of these deposits shall be representative of and the fund for and applicable first and exclusively to the payment of the savings deposits. Deposits received by the bank subject to its right to require notice of withdrawal evidenced by pass books, shall be deemed savings deposits.