Where, in an action on a written contract employing plaintiff as a broker to sell defendant's land, defendant pleaded that the contract had been altered and also denied that the plaintiff had secured a purchaser, an instruction that certain evidence was admissible as bearing on "the real testimony in this case," to-wit, whether plaintiff had furnished a buyer, was not objectionable as minimizing the issue of alteration in view of other instructions directly stating that if the jury find the contract has been altered they must find for defendant. McDermott v. Mahoney (Iowa Sup. '06), 106 N. W. 925. See also Sees. 55, 73, 293.