Mo. Rev. Stat. § 537.200

All persons engaged in the service of any railroad corporation doing business in this state or of any person, company or corporation operating a mine or mines in this state, who are entrusted by such railroad corporation, person, company or corporation, with the authority of superintendence, control or command of other persons in the employ or service of such railroad corporation, person, company or corporation, or with authority to direct any other servant in the performance of any duty of such servant, or with the duty of inspection or other duty owing by the master to the servant, are "vice-principals" of such corporation, and are not fellow servants with such employees.