An employee assumes the ordinary risks of his employment and is bound to exercise his own skill and diligence to protect himself. In actions for injuries arising from the negligence of the employer in failing to comply with the duties imposed by Code Section 34-7-20, in order that the employee may recover, it must appear that the employer knew or ought to have known of the incompetency of the other employee or of the defects or danger in the machinery supplied; and it must also appear that the employee injured did not know and had not equal means of knowing such fact and by the exercise of ordinary care could not have known thereof.