Notes, accounts, bonds, mortgages, records, and all other written instruments, constituting, in whole or in part, the claim sued on, or the matter set up in defense, may be made a part of the pleadings by copies thereof, or the originals, being attached or filed and referred to as such, or by copying the same in the body of the pleading in aid and explanation of the allegations in the petition or answer made in reference to said instruments and shall be deemed a part thereof for all purposes. Such pleadings shall not be deemed defective because of the lack of any allegations which can be supplied from said exhibit. No other instrument of writing shall be made an exhibit in the pleading.