(2)The case stated by the. pleader in his "opening" must be in accordance with the party's pleadings, for no litigant can be allowed to make at the trial a case different from that which he has placed on record on which his adversary is prepared to meet. The failure of a party to open his case, and to state exactly the line which he proposes to take, provides an opportunity to him to change the case which he originally had in mind and to call not only the witnesses whom he had originally intended to call, but other witnesses on different points to support a different case, if he sees that the case which he had in his mind is not progressing as satisfactorily as he desires.
