The fact that a loan broker negotiates a loan does not authorize him to collect either principal or interest, though the security be payable at his office; nor does the fact that he has authority to collect interest authorize him to collect the principal. Hefferman v. Botteler, 87 Mo. App. 316; Ortmeier v. Ivory, 208 I11. 577, 70 N. E. 665. See also Secs. 257, 352, 356, 566.