When ruling on negligence, should courts consider factors unrelated to the potential harm of an activity (such as the activity’s usefulness to society)? The defendant railroad company operated a turntable in the plaintiff child’s neighborhood. It was common practice for children of the neighborhood to revolve the turntable and ride on it. Defendant was aware of this practice. While playing on the turntable with his friends, the plaintiff’s foot was caught between the rails and severed at the ankle joint.