§ 25-c. Investment in bond and mortgage or note and mortgage. The term bond and mortgage or the term note and mortgage as heretofore or hereafter used in any statute which prescribes or authorizes investment therein, with or without a specified ratio of real property security, shall be deemed to include a share or part of a bond and mortgage or of a note and mortgage, as the case may be, prior in lien to all other shares and parts thereof and, for all purposes in connection with such an investment in a share or part, any specified ratio of real property security shall be determined on the basis of the investment in such share or part.