In a suit to recover the reasonable value of services in effecting an exchange of real estate, when the defendant set up that plaintiff had agreed to aecept $500 for his services, but there was evidence tending to show that as an inducement for such agreement, defendant promised to pay plaintiff a further reasonable commission if he found the land satisfactory, it was proper to submit such issue to the jury. Blair v. Slosson, 27 Tex. Civ. App. 403, 66 S. W. 112.