In an action by a real estate broker for his commissions in securing a purchaser, an instruction is properly refused which ignores plaintiff's theory that the efficient cause of the sale was the vendor's representative acting with him and accepting his services, with knowledge of his occupation, although such representative may have acted with other agents in some matters respecting the sale. J. P. Watkins Land & Mtg. Co. v. Thetford (Tex. Civ. App. '06), 96 S. W. 72.