Mo. Rev. Stat. § 509.120: Averments, how made.

All averments of claim or defense shall be made in numbered paragraphs, the contents of each of which shall be limited as far as practicable to a statement of a single set of circumstances; and a paragraph may be referred to by number in all succeeding pleadings. Each claim founded upon a separate transaction or occurrence and each defense other than denials shall be stated in a separate count or defense whenever a separation facilitates the clear presentation of the matters set forth.