SECTION 21 EXPRESS COMPANIES. Railroad companies now or hereafter organized or doing business in this state, shall allow all express companies organized or doing business in this state, transportation over all lines of railroad owned or operated by such railroad companies upon equal terms with any other express company, and no railroad corporation organized or doing business in this state shall allow any express corporation or company any facilities, privileges or rates for transportation of men or materials or property carried by them or for doing the business of such express companies not allowed to all express companies.