Where defendant employed plaintiff as his agent to effect an exchange of defendant's property, plaintiff being given discretion as to the valuation to be placed on the property, and plaintiff and the agent of the owner with whom the exchange was made agreed to pool their commissions and divide the pool, the commissions being based on the valuation, plaintiff was not entitled to recover commissions. Quinn v. Burton, 195 Mass. 277, 81 N. E. 257; Levy v. Spencer, 18 Colo. 532, 23 P. 415; Norman v. Roseman, 59 Mo. App. 682; Armstrong v. O'Brien, 83 Tex. 635, 19 S. W. 268; Shepard v. Hill, 6 Wash. 605, 34 P. 159; Carder v. O'Neill, 207 Mo. 632, 106 S. W. 10; Plotner v. Chillian (Okla. Sup. '08), 95 P. 775; Peaden v. Marler, 189 P. 741, - Okl. Sup. -; Whittle v. Klipper, 165 N. W. 425, - Iowa Sup. - . If the principals have knowledge of the pool and do not object thereto, the broker is not barred recovery of commissions. Kurinsky v. Lynch (Mass. '09), 87 N. E. 70; Bearing v. Sears, 3 N. Y. S. 31. Compare Alvard v. Cook, 174 Mass. 120, 54 N. E. 499.