The causal relation between the alleged negligence and the injury must be established by a preponderance of the evidence and with reasonable certainty. Rosenfeld v. Chicagoan, Inc., 318 Ill. App. 234, 47 N.E.2d 556; Lake Shore M.S.R. Co. v. Petersen, 86 Ill. App. 375. [4] Without further considering the question of negligence and the question of proximate cause, we are of the opinion that the judgment of the trial court should be reversed on the issue of contributory negligence of the plaintiff.