It was competent for the defendant to withhold delivery of the notes indorsed by him to plaintiff until plaintiff or Smith should procure the execution by Mrs. Robinson of the mortgage on the horses to secure such ■notes, and should file such mortgage in the proper office. Leaving the notes with Hawes, plaintiff’s agent, pending the execution and filing of such mortgage, was not necessarily a full delivery of the nofes to plaintiff. It may have been only a conditional delivery, which would be defeated by plaintiff’s failure to procure and file such mortgage, unless such failure was caused by defendant. Were there no proof except of the agreement that defendant should not be bound by his indorsements, or, what is the same thing, that the notes should not be fully delivered until the plaintiff procured the execution of the chattel mortgage by Mrs. Robinson, and filed the instalment so executed in the proper office, probably the direction of a verdict for the defendant would be upheld, for such agreement was not performed. But the testimony tends to prove that the defendant, without plaintiff’s consent, caused another, note executed by Robinson, and a mortgage executed by Robin*548son and his wife, and duly filed, to be substituted for the notes originally indorsed by defendant and the chattel mortgage stipulated for in the agreement between the parties. If defendant procured such substitution of securities without plaintiff’s consent, he prevented the execution of the agreement by plaintiff, and cannot now be permitted to escape liability on his indorsements for nonperformance by plaintiff of a condition precedent, the performance of which he prevented by his own unauthorized act. Under the testimony the jury might properly have found that the defendant caused such substitution, and thus prevented the performance by plaintiff of the agreement in respect to the mortgage. Such unauthorized substitution, when established either by conclusive proof or by verdict, is fatal to the defense. Hence, the plaintiff was at least entitled to have the question submitted to the jury, whether the defendant thus prevented the performance by plaintiff of the agreement.

For the above reasons the judgment of the circuit court must be reversed, and the cause will be remanded for a new trial.

By the Court.— Ordered accordingly.