OPINION.
NIXON, P. J.I. The contract dated July 12th, but in fact executed and delivered August 11th, is complete and unambiguous on its face. It was executed subsequent to the memoranda and orders on which appellants rely as constituting the contract. Therefore, it superseded and merged into itself all the prior negotiations and became the sole and final authoritative expression of the intention of the parties. The defendants could not recover on their counterclaim, based on a breach of the prior negotiations; they are not entitled to damages for a breach of the *251prior contract after it has been superseded by a subsequent one. A written contract, complete and perfect in itself, and not ambiguous, will be held to supersede all prior negotiations, written or verbal, relating to the same subject-matter. [Howard v. Scott, 98 Mo. App. l. c. 514, 72 S. W. 709; Bignall & K. M. Co. v. Mfg. Co., 59 Mo. App. 673, 677, 678; Bethany Savings Bank v. Cushman, 66 Mo. App. 102, 105; Boggs v. Pacific Steam Laundry Co., 171 Mo. 282, 291, 70 S. W. 818.] And where the subsequent contract includes and goes beyond the first, the first is superseded and no action can be maintained thereon. [Munford v. Wilson, 15 Mo. 540, 562.] Upon respondent’s making proof of the subsequent contract, the ground under appellants’ counterclaim fell away and left» it no support in the pleadings.
II. Since appellants have based their case on a contract which has been superseded by a subsequent one, they must recover on the later contract or not at all. They cannot ask the appellate court for a reversal of this judgment on the ground that they should have been permitted to recover more than they did on a contract the validity of which they disputed at every turn in the court below. The position of the defendants at the trial was that the second contract was void. Their .position now is the exact opposite. They make no complaint here because the trial court held the second contract valid. Their sole contention is that their recovery under the second contract should have been greater. They present an entirely different ease here from the case they presented in the trial court. They relied on one contract below, and they rely on another contract here. That this is not permissible is too well settled for argument. A party cannot sue on one contract and recover on another. The trial court properly held against the defendants on the issue of the validity of the second contract, and *252therefore defendants should not be permitted to recover damages- at all. A litigant will not be permitted to play fast and loose with his antagonist, nor ■ to blow hot and cold. He must take his position and stand by it. [Koons v. St. Louis Car Co., 203 Mo. 227, 254, 101 S. W. 49; Cole v. Armour, 154 Mo. 333, 350, 55 S. W. 476; Smith v. Shell, 82 Mo. 215, 219, 220; Clements v. Yeates, 69 Mo. 623, 625.]
III. According to the contract under which the cement was to be shipped, a demand by the buyer was a condition precedent to delivery by the seller. The evidence showed that cement is perishable, and must be used soon after its manufacture, and that a dealer cannot keep large quantities of it in stock for any length of time as it deteriorates very rapidly. The dealer must therefore order it as he wants it. It was consequently necessary to have it delivered only on the buyer’s order. The seller could not safely ship any cement unless he knew the buyer was ready to use it. To meet this condition of things, the contract provided: “Buyer agrees^ to give seller shipping instructions a reasonable time before shipments are to be made.” The parties by the use of this language could have had but one intention and purpose and that was that until demand was made there should be no delivery. By the nature of the case, as well as by the terms of the contract, a demand by the buyer was clearly a condition precedent to delivery by the seller, and before the buyer can hold the seller hable for failure to deliver, he must show that he has demanded shipment of the cement. It was as much the duty of the defendants to give shipping instructions as it was. the duty of the plaintiff to ship.
Before there can be a breach of a contract, there must be a present duty to perform the conditions required by the contract. There could be no duty on the part of the plaintiff to deliver except on receipt *253of instructions from the buyer because it was so provided in the contract. All such instructions given by defendants were in fact honored by shipment except as to the 350 barrels which plaintiff delayed in shipping until defendants countermanded the order, and defendants were allowed damages for plaintiff’s failure to make this shipment. When goods sold are to be delivered on the buyer’s demand or at the buyer’s option, a demand by the buyer is a condition precedent to delivery by the seller; a demand is then necessary to render the contract absolute, and in an action for the- breach of such a contract, the demand must be alleged and proven. [Maddox v. Wagner (Ga.) 36 S. E. 609; Smith v. Watson (Iowa), 55 N. W. 68, 72; Holt v. Brown, 19 N. W. 235, 236.]
IV. Another respect in which appellants’ position here is inconsistent with their position below is that they now seek to show that they were excused from giving shipping instructions by the delay of plaintiff in filling their prior orders. The answer contains the following allegations in this connection: “Defendants further state that said plaintiff failed and refused to ship the remainder of the said 4000 barrels of cement so purchased, to-wit, 2260 barrels, although requested so to do by the defendants; that the defendants at all times complied with all the conditions of the contract between the said plaintiff and defendants, but that plaintiff, in violation of the terms of its said contract as aforesaid failed and refused to deliver said 2260 barrels of cement.”
This is a plea of performance of all the conditions precedent, and as under their contract the giving of shipping orders was a condition precedent, this allegation was a positive allegation that shipping orders were given for the whole amount of cement covered by the contract; and, having alleged it, they had no right of action on their counterclaim except by proof of performance. In this court appellants seek to ex*254plain why shipping orders were not given for the entire amount of cement contracted for. Under a plea of performance, evidence tending to show a waiver of performance is not admissible. And although appellants were permitted to introduce evidence tending to show an excuse for not ordering more cement, the admission of such evidence cannot enlarge the scope of their pleadings. The answer alleges performance and they are bound by that allegation. A party’s pleading is the only door through which he can introduce his evidence. A party suing for breach of a contract must allege and prove performance of all conditions precedent, or he must allege and prove an excuse for their nonperformance. He cannot rely on a waiver under a plea of performance. [Roy v. Boteler, 40 Mo. App. 213, 226; Brinkerhoff v. Elliott, 43 Mo. App. 185, 194; Kansas City ex rel. v. Walsh, 88 Mo. App. 271, 277, 278; Lanitz v. King, 93 Mo. 513, 6 S. W. 263; Mohney v. Reed, 40 Mo. App. 109.]
This action was carefully tried by the learned judge of the trial court; it is conceded that the finding of facts is supported by the evidence, the law was properly applied to the facts developed in the case and was as favorable to the appellants as they were entitled to. The judgment being for the right party is accordingly affirmed.
All concur.