An employer shall be responsible in damages for personal injury caused to an employee, who, was himself in the exercise of due care and diligence at the time he was injured, by reason of any defect in the condition of the machinery or appliances connected with or used in the business of the employer which arose, or had not been discovered or remedied owing to the negligence of the employer, or of any person entrusted by him with the duty of inspection, repair, or of seeing that the machinery or appliances were in proper condition.