ROSS, Circuit Judge,
after stating the facts as above, delivered the opinion of the court.
It is a mistake to say that the complaint is confined to cattle covered by the written contract. That embraced only one and two year old steers. The number contracted for by the written contract was 1,800, consisting of about 900 head of yearlings and 900 head of two year old steers at certain specified prices, and sub*229ject to certain conditions, with a provision that, should the vendors tender more than 1,800, they would'he accepted by the vendee to the number of 2,000 head, at the same prices, and upon similar conditions. But the complaint, in addition to its allegations respecting- the one and two year old steers, also alleged that on the 31st day of May, 1890, the plaintiffs sold and delivered to the defendant 88 three year old steers at $18 per head. This allegation is not denied by the answer. The denial in that regard, if denial at all, is only to the effect that none of the three year old steers were delivered to or accepted by the defendant under the terms of the written contract. Two causes of action are, therefore, indiscriminately jumbled together in the complaint. No objection thereto, however, appears to have been taken in the court below by demurrer or otherwise. The cause of action upon the written contract proceeds upon its part performance by the plaintiffs and the alleged prevention by the defendant of the plaintiffs’ complete performance ■thereof. Unless the allegations of the complaint in respect to the defendant's prevention can be treated as surplusage, the judgment must he reversed, since those allegations are denied by the answer, and there is no proof to sustain them. Whatever was necessary for the plaintiffs to allege,was necessary to be proved. We'are, therefore, to inquire whether the allegations of the complaint in regard to prevention by the defendant of the full performance by the plaintiffs of their written contract can be regarded as surplusage. The action being an action at law, the pleadings and proceedings in the federal court were required to conform, as near as practicable, to those of the courts of the state in which it was held. Rev. St. § 914. By statute, as well as by the constitution of Idaho, it is declared that: there shall be in that state but one form of action for the enforcement or protection of private rights or the redress of pri-va i e wrongs. Const, art. 5, § i; Rev. lit. Idaho, § 4020. Section 4168 of the same statutes provides that “the complaint must contain a statement of the facts constituting the cause of action in ordinary and concise language.” Probative facts, of course, should not be stated, but every ultimate fact-essential to the cause of action is required to be alleged in the complaint:, in respect to all such facts the defendant is entitled to take issue. But facts not entering into the constitution of a cause of action need not be alleged, and, if alleged, may be properly treated as surplusage. Re curring to the complaint in the case at bar, it is to be observed that the plaintiffs sue only for the balance due for the number of cattle actually delivered to and received by the defendant at the prices the defendant is alleged to have agreed to. In respect to the effect of the acceptance of a delivery of a part of personal property contracted for under an entire contract the American cases are conflicting. In some of the states it has been held that nothing-can be recovered for part performance of an entire contract unless full performance was waived or prevented. Champlin v. Rowley, 18 Wend. 194; Smith v. Brady, 17 N. Y. 173; Catlin v. Tobias, 26 N. Y. 217; Jennings v. Lyons, 39 Wis. 553; Mill Co. v. Westervelt, 67 Me. 449. In Avery v. Willson, 81 N. Y. 341, however, it was *230held that, if the vendee evinces,by his acts a waiver of a complete delivery, by the receipt and appropriation to his own use of a portion of the goods contracted for, he thereby becomes liable to pay for what was actually delivered. The modern American rule seems to be that a party who has failed to perform in full his contract for the sale and delivery of personal property may recover compensation for the part actually delivered and received thereunder, less the damages occasioned by his failure to make the complete delivery. Many of the casés establishing this principle will be found cited in note 19, § 1032, 2 Benj. Sales. In Richards v. Shaw, 67 Ill. 222, in which the contract was to deliver 500 bushels of corn at a specified price per bushel, and the seller delivered only 391 bushels, for which he brought suit, the court said that, if the vendee received part of the goods sold under an entire contract, and retained that part after breach, this was a severance, and a suit would lie for the price, but the buyer might deduct damages for. the failure to fulfill the residue of the contract. A contract for the sale and delivery of a certain number of cattle, unlike one for the building and completion of a house or other structure, is sev-erable in its nature, and there is no just reason why, if the vendee accepts and appropriates to his own use a portion of the property so contracted for, he should not pay the stipulated price for such portion, less the amount of damages sustained by him by reason of the vendor’s failure to make complete delivery. Under this rule,— in accordance with which are the instructions of the court below,— the allegation of prevention contained in the complaint may be properly disregarded as surplusage. The judgment is affirmed.