The proposition stated in the foregoing headnote is too well settled to need discussion. Since the case is to be tried again, it may be proper and important to lay down a. further proposition concerning it. The contract sued on did not appear to be unilateral, especially so far as involved in the present case; but it did not purport to contain all the terms of the contract, so as to preclude resort to parol testimony to explain it. The agreement to pay “$45.00 commission on said purchase” may be explained by showing what service in connection with the purchase was to have been compensated under the head of “commission.” If the agreement set up by the defendant, as to the plaintiff’s arranging for the carrying of a mortgage on the property, was made contemporaneously with the execution of the written contract, and was, by the negotiations of the parties, a part of the trade, it would be binding on the plaintiff. However, if it was a voluntary undertaking *268on the plaintiff’s part after the contract had become complete, it would not be based on consideration, and, therefore, would not be enforceable. The written contract would not necessarily be complete with the physical signing of the paper, nor until it was delivered to, or left with, the plaintiff as the consummation of the agreement between the parties. Judgment affirmed.