It shall be unlawful for any person to use or permit to be used a narcotic of any kind to stimulate or retard any horse that is to run in a race in this state to which the provisions of sections 2-1201 to 2-1218 apply, or for a person having the control of such horse and knowledge of such stimulation or retardation to allow it to run in any such race. The owners of such horse and their agents or employees shall permit any member of the commission or any person appointed by the commission for that purpose to make such tests as the commission deems proper in order to determine whether any such animal has been so stimulated or retarded. The findings of the commission that a horse has been stimulated or retarded by a narcotic or narcotics shall be prima facie evidence of such fact.