delivered the opinion of the Court:

Counsel for plaintiff in error contends that under our statute Miller, being a party to this suit, could not properly be allowed to testify for Combs upon this point, because the fact sworn to occurred before the death of Mrs. Morrison. He relies upon the provisions of the act of 1867 as to the competency of witnesses, which is now, with some additions and modifications not affecting this question, incorporated in the first eight sections of chapter 51 in the Revised Statutes of 1874, entitled “Evidence and Depositions.” Before the passage of that act, by the rules and usages of courts of chancery one defendant was held competent to testify in behalf of a co-defendant on any question in the decision of which he had no interest. The passage of that statute has in no manner impaired that rule. The first section (Rev. Stat. 1874, p. 488,) abolishes all disqualifications of a witness by reason of interest, as a party or otherwise, except as thereafter stated in the act. The qualifications thereafter-found are mere limitations upon the effect of that act in rendering witnesses competent in cases wherein they had been incompetent. Nothing in the act contained indicates an intention to render any witness incompetent in any case where, in the absence of the statute, he was, and had been, competent. We think Miller was properly held a competent witness.

It is also contended that parol evidence of the contract charged was rendered incompetent by a writing found upon the note. The note has indorsed upon it the following: “It is agreed by the parties to this note that the interest shall be at the rate of ten per cent until paid. ” This writing is signed by George A. Miller, the principal debtor, and bears date July 13, 1870. The testimony of Miller is, that at the time when this memorandum was signed by him it was agreed 'between himself and Brown, the agent of Mrs. Morrison, that the time of payment should be extended one year, and that this promise to pay ten per cent was made in consideration that the creditor agreed to forbear for one year. It is insisted that to receive this oral testimony is to vary the terms of a written agreement by parol proof of what was said at the making thereof, which the law forbids. We think not.- Had the parol proof offered been that the new rate of interest was to be nine per cent instead of ten, the rule in question would hake applied. Where parties reduce them agreement to writing they can not be allowed to vary its terms by parol; but where it is evident that the agreement is not reduced to writing, but only a part of it, and where that part reduced to writing is merely a partial execution of a part of an entire agreement between the parties, the whole agreement may be' proven. A man may buy a horse at $100, and agree to give his note, at one year, for $80 of the price, and to do labor at a given rate to the amount of $20, in payment for the horse. In such case the fact that he gives his note for the $80, and no other writing is made except the note, does not preclude the vendor of the horse from proving the promise to do the labor, nor would such fact prevent the purchaser of the'horse from proving the contract of sale, so as -to sustain his title to the horse. The case at bar is of that class of cases presented by this illustration. There was no valid objection to the proof on this ground.

Complaint is made that leading questions, and answers thereto, were permitted, and especially in the examination of Brown. After a careful examination of this suggestion we think no wrong was done. Brown was plainly a reluctant or unwilling witness. In such cases the purposes of truth and justice do not demand a strict and literal adherence to the general rule on the subject.

We think the proofs fully sustain the decree, and that the appropriate remedy for the relief of Combs, as surety, has been pursued in this case. High on Injunctions, (2d ed.) secs. 1375, 1376; Story’s Eq. Jur. secs. 324, 325.

Finding no error in the record, the judgment of the Appellate Court is affirmed.

Judgment affirmed.