Every employee of any railroad corporation shall have the same right and remedies for any injury suffered by him from the act or omission of said corporation or its employees, as are allowed by law to other persons not employees where the injury results from the negligence of a superior agent or officer, or of a person having the right to control or direct the services of the party injured, and also when the injury results from the negligence of a fellow-servant engaged in another department of labor from that of the party injured, or of a fellow-servant on another train of cars, or one engaged about a different piece of work. Knowledge by any employee injured, of the defective or unsafe character or condition of any machinery, ways, or appliances, shall be no defense to an action for injury caused thereby, except as to conductors or engineers in charge of dangerous or unsafe cars, or engines voluntarily operated by them. Where death ensues from any injury to employees, the legal or personal representatives of the person injured shall have the same right and remedies as are allowed by law to such representatives of other persons. Any contract or agreement, express or implied, made by any employee to waive the benefit of this section shall be null and void; and this section shall not be construed to deprive any employee of a corporation or his legal or personal representative, of any right or remedy that he now has by the law of the land. The legislature may extend the remedies herein provided for to any other class of employees.