In all actions brought against any such common carrier to recover damages for personal injuries to any employee or when such injuries have resulted in his death, the fact that such employee may have been guilty of contributory negligence shall not bar a recovery, but the damages shall be diminished by the jury in proportion to the amount of negligence attributable to such employee; and no such employee, who may be injured or killed, shall be held to have been guilty of contributory negligence in any case when the violation by such common carrier of any statute enacted for the safety of employees contributed to the injury or death of such employee.