Section 21. The style of the laws of this state shall be: "Be it enacted by the General Assembly of the State of Missouri, as follows." No law shall be passed except by bill, and no bill shall be so amended in its passage through either house as to change its original purpose. Bills may originate in either house and may be amended or rejected by the other. Every bill shall be read by title on three different days in each house.
Source: Const. of 1875, Art. IV, §§ 24, 25, 26.