I think there has been a confusion in this case between the doctrines of contributory negligence and proximate cause. My view is that the proximate cause of the plaintiff's injury was his attempt to close by manual force the cylindrical slide on door of the night deposit box maintained by the bank when ordinary prudence dictated that before he undertook to do so with his hand he should have assured himself that the box could have been closed by such means without injury to himself. See Quinn v. Smith 57 F.2d 784. Contributory negligence implies that the defendant was guilty of some negligence that was the proximate cause of the injury but that plaintiff's negligence contributed thereto.