1. An absolute and unconditional promissory note can not be so changed by evidence of a contemporaneous parol agreement as to engraft upon it a condition. Civil Code, §3675.

2. If, in the trial of a case; one party introduce immaterial and illegal evidence without objection, the other party is not thereby entitled to introduce, over objection, other illegal evidence in rebuttal. There can be no equation of errors in the trial of a case. Woolfolk v. State, 81 Ga. 552.

Judgment reversed.