Neither the State nor any city, county, town or other municipality in this State shall ever lend its credit for any purpose whatever; nor shall any county, city or town or municipality ever issue any interest bearing evidences of indebtedness, except such bonds as may be authorized by law to provide for and secure the payment of the indebtedness existing at the time of the adoption of the Constitution of 1874, and the State shall never issue any interest-bearing treasury warrants or scrip.